View allAll Photos Tagged Injectables
The energy injector is like 4000 microwave ovens, another innovative design element of this reactor.
They use a process called radio-frequency heating to ignite the nuclear fuel. These antennae outside the tokamak reactor use a specific frequency of radio waves to excite the particles. The radio waves are calibrated to target just the less abundant material, in this case hydrogen ions. Because the hydrogen accounts for a small fraction of the fuel's total density, focusing the radio-frequency heating on the minority ions allows them to reach extreme energy levels. The excited hydrogen ions then slam into the more abundant deuterium ions, and resulting particles fly into the reactor's outer shell, generating heat and electricity.
And then... "Researchers improved the efficiency of this process by adding helium-3 ions to the mix. The new fuel contains less than one percent helium-3. By focusing all the radio-frequency heating on this trace amount of helium-3, the researchers raised the ions to megaelectronvolt (MeV) energies. An electronvolt is the amount of energy gained or lost when a single electron jumps from a point of electric potential to a point one volt higher, a common unit of measurement for fusion experiments. The new results with helium-3 fuel, generating ions that reach megaelectronvolt energies, has never been achieved before, and the increase in ion energy is a full order of magnitude higher than previous efforts." — Popular Mechanics
Before testing the 3-D printed rocket injector, materials engineers at NASA's Marshall Space Flight Center in Huntsville, Ala., performed a computer tomography scan to ensure the part was fabricated according to the design.
Image credit: NASA/MSFC
Read more:
www.nasa.gov/exploration/systems/sls/multimedia/gallery/3...
www.nasa.gov/exploration/systems/sls/3dprinting.html
More about SLS:
www.nasa.gov/exploration/systems/sls/index.html
Space Launch System Flickr photoset:
www.flickr.com/photos/28634332@N05/sets/72157627559536895/
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These official NASA photographs are being made available for publication by news organizations and/or for personal use printing by the subject(s) of the photographs. The photographs may not be used in materials, advertisements, products, or promotions that in any way suggest approval or endorsement by NASA. All Images used must be credited. For information on usage rights please visit: www.nasa.gov/audience/formedia/features/MP_Photo_Guidelin...
This section of wall shows the semi circular Davies Tower, built c1160 - 1230. The castle sits on top of a layer of rock known as black crags, similar to that at Lindisfarne. It's part of the Whin Sill, and is a mixture of sedimentary rock injected with a plug of molten rock.
Bamburgh has been a Border stronghold throughout history, so there has been a castle here for hundreds of years. Originally a motte and baily castle, the castle was replaced with stone and the oldest surviving part, the Keep, dates to the C12th.
It was visited by a succession of kings, as well as serving as a prison. Having ceased to be a royal residence, in 1610 James I gave it to Claudius Forster, but he couldn't afford the upkeep, and together with the Civil War destroying parts of the castle, it fell into disrepair.
In 1704 it was bought by Lord Crewe, Bishop of Durham. On his death the Crewe Trust was set up to restore and manage it, and it was used as a library, hospital and school. It was eventually put up for sale again in 1894 and William Armstrong bought it. He was an inventor and engineer and he envisaged it as a home for retired gentlemen. (he also owned Cragside).
Today it is still privately owned by descendants of Armstrong.
Clio started injecting her hormones 3 months ago... But never had an injection as bloody as this one!
After doing this twice in a row, she later started moving the injection site slightly to the outside of the thigh muscle. This put an end to the blood. Nowadays she injects in the butt, anyway.
(1.0" needle for intramuscular thigh injection. Works VERY well, levels-wise, even if they recommend a 1.5" needle for this situation.)
Transition Progress at this point: On hormones since 8/1 (7.5 months); injections since 12/22 (3 months) [18 so far]. Full-time female since 9/15 (6.5 months). Publicly out as trans since 10/11 (5.5 months). Legally female since 12/21 (3 months). 4 transgender group speech therapy classes taken at GW Speech Clinic (since 2/22). Plastic surgery consults continuing. Have seen endo/primary therapist 6X, and 4 other therapists 10X. Weight down to 144lbs (53 down from 197). Hair removal includes 34 electrolysis treatments totaling 26hours; 30 laser hair removal sessions (51 area treatments: 16/15/13/12/8 mouth/goatee/face/neck/armpits, 7 legs/chest, 6 ears/Brazilian); and bi-weekly at-home IPL on arms since 6/17 (9 months). Latisse for eyelash lengthening since 4/17 (11 months). 2 dental implants, Zoom teeth whitening, pierced ears, dyed/layered hair, hypertrophic scars on arms removed. Female wardrobe replacement up to more than 700 items. Total transition expenditures now over $17,800 at this point.
Clio.
injecting estrogen.
bandage, bandaid, blood, hormones, leg, needle, prep pad, syringe, thigh.
upstairs, Clio and Carolyn's house, Alexandria, Virginia.
March 27, 2018.
... Read my blog at clintjcl at wordpress dot com
... Read Carolyn's blog at CarolynCASL at wordpress dot com
Having a new lens to play with, no one to photograph and a pretty flower garland. I headed in to my garden and attempted taking a self portrait.
Spiders (order Araneae) are air-breathing arthropods that have eight legs and chelicerae with fangs that inject venom. They are the largest order of arachnids and rank seventh in total species diversity among all other orders of organisms. Spiders are found worldwide on every continent except for Antarctica, and have become established in nearly every habitat with the exceptions of air and sea colonization. As of November 2015, at least 45,700 spider species, and 114 families have been recorded by taxonomists. However, there has been dissension within the scientific community as to how all these families should be classified, as evidenced by the over 20 different classifications that have been proposed since 1900.
Anatomically, spiders differ from other arthropods in that the usual body segments are fused into two tagmata, the cephalothorax and abdomen, and joined by a small, cylindrical pedicel. Unlike insects, spiders do not have antennae. In all except the most primitive group, the Mesothelae, spiders have the most centralized nervous systems of all arthropods, as all their ganglia are fused into one mass in the cephalothorax. Unlike most arthropods, spiders have no extensor muscles in their limbs and instead extend them by hydraulic pressure.
Their abdomens bear appendages that have been modified into spinnerets that extrude silk from up to six types of glands. Spider webs vary widely in size, shape and the amount of sticky thread used. It now appears that the spiral orb web may be one of the earliest forms, and spiders that produce tangled cobwebs are more abundant and diverse than orb-web spiders. Spider-like arachnids with silk-producing spigots appeared in the Devonian period about 386 million years ago, but these animals apparently lacked spinnerets. True spiders have been found in Carboniferous rocks from 318 to 299 million years ago, and are very similar to the most primitive surviving suborder, the Mesothelae. The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appeared in the Triassic period, before 200 million years ago.
A herbivorous species, Bagheera kiplingi, was described in 2008,[5] but all other known species are predators, mostly preying on insects and on other spiders, although a few large species also take birds and lizards. Spiders use a wide range of strategies to capture prey: trapping it in sticky webs, lassoing it with sticky bolas, mimicking the prey to avoid detection, or running it down. Most detect prey mainly by sensing vibrations, but the active hunters have acute vision, and hunters of the genus Portia show signs of intelligence in their choice of tactics and ability to develop new ones. Spiders' guts are too narrow to take solids, and they liquefy their food by flooding it with digestive enzymes and grinding it with the bases of their pedipalps, as they do not have true jaws.
Male spiders identify themselves by a variety of complex courtship rituals to avoid being eaten by the females. Males of most species survive a few matings, limited mainly by their short life spans. Females weave silk egg-cases, each of which may contain hundreds of eggs. Females of many species care for their young, for example by carrying them around or by sharing food with them. A minority of species are social, building communal webs that may house anywhere from a few to 50,000 individuals. Social behavior ranges from precarious toleration, as in the widow spiders, to co-operative hunting and food-sharing. Although most spiders live for at most two years, tarantulas and other mygalomorph spiders can live up to 25 years in captivity.
While the venom of a few species is dangerous to humans, scientists are now researching the use of spider venom in medicine and as non-polluting pesticides. Spider silk provides a combination of lightness, strength and elasticity that is superior to that of synthetic materials, and spider silk genes have been inserted into mammals and plants to see if these can be used as silk factories. As a result of their wide range of behaviors, spiders have become common symbols in art and mythology symbolizing various combinations of patience, cruelty and creative powers. An abnormal fear of spiders is called arachnophobia.
BODY PLAN
Spiders are chelicerates and therefore arthropods.[6] As arthropods they have: segmented bodies with jointed limbs, all covered in a cuticle made of chitin and proteins; heads that are composed of several segments that fuse during the development of the embryo. Being chelicerates, their bodies consist of two tagmata, sets of segments that serve similar functions: the foremost one, called the cephalothorax or prosoma, is a complete fusion of the segments that in an insect would form two separate tagmata, the head and thorax; the rear tagma is called the abdomen or opisthosoma. In spiders, the cephalothorax and abdomen are connected by a small cylindrical section, the pedicel. The pattern of segment fusion that forms chelicerates' heads is unique among arthropods, and what would normally be the first head segment disappears at an early stage of development, so that chelicerates lack the antennae typical of most arthropods. In fact, chelicerates' only appendages ahead of the mouth are a pair of chelicerae, and they lack anything that would function directly as "jaws". The first appendages behind the mouth are called pedipalps, and serve different functions within different groups of chelicerates.
Spiders and scorpions are members of one chelicerate group, the arachnids. Scorpions' chelicerae have three sections and are used in feeding. Spiders' chelicerae have two sections and terminate in fangs that are generally venomous, and fold away behind the upper sections while not in use. The upper sections generally have thick "beards" that filter solid lumps out of their food, as spiders can take only liquid food.[8] Scorpions' pedipalps generally form large claws for capturing prey, while those of spiders are fairly small appendages whose bases also act as an extension of the mouth; in addition, those of male spiders have enlarged last sections used for sperm transfer.
In spiders, the cephalothorax and abdomen are joined by a small, cylindrical pedicel, which enables the abdomen to move independently when producing silk. The upper surface of the cephalothorax is covered by a single, convex carapace, while the underside is covered by two rather flat plates. The abdomen is soft and egg-shaped. It shows no sign of segmentation, except that the primitive Mesothelae, whose living members are the Liphistiidae, have segmented plates on the upper surface.
CIRCULATION AND RESPIRATION
Like other arthropods, spiders are coelomates in which the coelom is reduced to small areas round the reproductive and excretory systems. Its place is largely taken by a hemocoel, a cavity that runs most of the length of the body and through which blood flows. The heart is a tube in the upper part of the body, with a few ostia that act as non-return valves allowing blood to enter the heart from the hemocoel but prevent it from leaving before it reaches the front end. However, in spiders, it occupies only the upper part of the abdomen, and blood is discharged into the hemocoel by one artery that opens at the rear end of the abdomen and by branching arteries that pass through the pedicle and open into several parts of the cephalothorax. Hence spiders have open circulatory systems. The blood of many spiders that have book lungs contains the respiratory pigment hemocyanin to make oxygen transport more efficient.
Spiders have developed several different respiratory anatomies, based on book lungs, a tracheal system, or both. Mygalomorph and Mesothelae spiders have two pairs of book lungs filled with haemolymph, where openings on the ventral surface of the abdomen allow air to enter and diffuse oxygen. This is also the case for some basal araneomorph spiders, like the family Hypochilidae, but the remaining members of this group have just the anterior pair of book lungs intact while the posterior pair of breathing organs are partly or fully modified into tracheae, through which oxygen is diffused into the haemolymph or directly to the tissue and organs. The trachea system has most likely evolved in small ancestors to help resist desiccation. The trachea were originally connected to the surroundings through a pair of openings called spiracles, but in the majority of spiders this pair of spiracles has fused into a single one in the middle, and moved backwards close to the spinnerets. Spiders that have tracheae generally have higher metabolic rates and better water conservation. Spiders are ectotherms, so environmental temperatures affect their activity.
FEEDING, DIGESTION AND EXCRETION
Uniquely among chelicerates, the final sections of spiders' chelicerae are fangs, and the great majority of spiders can use them to inject venom into prey from venom glands in the roots of the chelicerae. The family Uloboridae has lost its venom glands, and kills its prey with silk instead. Like most arachnids, including scorpions, spiders have a narrow gut that can only cope with liquid food and spiders have two sets of filters to keep solids out. They use one of two different systems of external digestion. Some pump digestive enzymes from the midgut into the prey and then suck the liquified tissues of the prey into the gut, eventually leaving behind the empty husk of the prey. Others grind the prey to pulp using the chelicerae and the bases of the pedipalps, while flooding it with enzymes; in these species, the chelicerae and the bases of the pedipalps form a preoral cavity that holds the food they are processing.
The stomach in the cephalothorax acts as a pump that sends the food deeper into the digestive system. The mid gut bears many digestive ceca, compartments with no other exit, that extract nutrients from the food; most are in the abdomen, which is dominated by the digestive system, but a few are found in the cephalothorax.
Most spiders convert nitrogenous waste products into uric acid, which can be excreted as a dry material. Malphigian tubules ("little tubes") extract these wastes from the blood in the hemocoel and dump them into the cloacal chamber, from which they are expelled through the anus. Production of uric acid and its removal via Malphigian tubules are a water-conserving feature that has evolved independently in several arthropod lineages that can live far away from water, for example the tubules of insects and arachnids develop from completely different parts of the embryo. However, a few primitive spiders, the sub-order Mesothelae and infra-order Mygalomorphae, retain the ancestral arthropod nephridia ("little kidneys"), which use large amounts of water to excrete nitrogenous waste products as ammonia.
CENTRAL NERVOUS SYSTEM
The basic arthropod central nervous system consists of a pair of nerve cords running below the gut, with paired ganglia as local control centers in all segments; a brain formed by fusion of the ganglia for the head segments ahead of and behind the mouth, so that the esophagus is encircled by this conglomeration of ganglia. Except for the primitive Mesothelae, of which the Liphistiidae are the sole surviving family, spiders have the much more centralized nervous system that is typical of arachnids: all the ganglia of all segments behind the esophagus are fused, so that the cephalothorax is largely filled with nervous tissue and there are no ganglia in the abdomen; in the Mesothelae, the ganglia of the abdomen and the rear part of the cephalothorax remain unfused.
Despite the relatively small central nervous system, some spiders (like Portia) exhibit complex behaviour, including the ability to use a trial-and-error approach.
Sense organs
EYES
Most spiders have four pairs of eyes on the top-front area of the cephalothorax, arranged in patterns that vary from one family to another. The pair at the front are of the type called pigment-cup ocelli ("little eyes"), which in most arthropods are only capable of detecting the direction from which light is coming, using the shadow cast by the walls of the cup. However, the main eyes at the front of spiders' heads are pigment-cup ocelli that are capable of forming images. The other eyes are thought to be derived from the compound eyes of the ancestral chelicerates, but no longer have the separate facets typical of compound eyes. Unlike the main eyes, in many spiders these secondary eyes detect light reflected from a reflective tapetum lucidum, and wolf spiders can be spotted by torch light reflected from the tapeta. On the other hand, jumping spiders' secondary eyes have no tapeta. Some jumping spiders' visual acuity exceeds by a factor of ten that of dragonflies, which have by far the best vision among insects; in fact the human eye is only about five times sharper than a jumping spider's. They achieve this by a telephoto-like series of lenses, a four-layer retina and the ability to swivel their eyes and integrate images from different stages in the scan. The downside is that the scanning and integrating processes are relatively slow.
There are spiders with a reduced number of eyes, of these those with six-eyes are the most numerous and are missing a pair of eyes on the anterior median line, others species have four-eyes and some just two. Cave dwelling species have no eyes, or possess vestigial eyes incapable of sight.
OTHER SENSES
As with other arthropods, spiders' cuticles would block out information about the outside world, except that they are penetrated by many sensors or connections from sensors to the nervous system. In fact, spiders and other arthropods have modified their cuticles into elaborate arrays of sensors. Various touch sensors, mostly bristles called setae, respond to different levels of force, from strong contact to very weak air currents. Chemical sensors provide equivalents of taste and smell, often by means of setae. Pedipalps carry a large number of such setae sensitive to contact chemicals and air-borne smells, such as female pheromones. Spiders also have in the joints of their limbs slit sensillae that detect forces and vibrations. In web-building spiders, all these mechanical and chemical sensors are more important than the eyes, while the eyes are most important to spiders that hunt actively.
Like most arthropods, spiders lack balance and acceleration sensors and rely on their eyes to tell them which way is up. Arthropods' proprioceptors, sensors that report the force exerted by muscles and the degree of bending in the body and joints, are well understood. On the other hand, little is known about what other internal sensors spiders or other arthropods may have.
LOCMOTION
Each of the eight legs of a spider consists of seven distinct parts. The part closest to and attaching the leg to the cephalothorax is the coxa; the next segment is the short trochanter that works as a hinge for the following long segment, the femur; next is the spider's knee, the patella, which acts as the hinge for the tibia; the metatarsus is next, and it connects the tibia to the tarsus (which may be thought of as a foot of sorts); the tarsus ends in a claw made up of either two or three points, depending on the family to which the spider belongs. Although all arthropods use muscles attached to the inside of the exoskeleton to flex their limbs, spiders and a few other groups still use hydraulic pressure to extend them, a system inherited from their pre-arthropod ancestors. The only extensor muscles in spider legs are located in the three hip joints (bordering the coxa and the trochanter). As a result, a spider with a punctured cephalothorax cannot extend its legs, and the legs of dead spiders curl up. Spiders can generate pressures up to eight times their resting level to extend their legs, and jumping spiders can jump up to 50 times their own length by suddenly increasing the blood pressure in the third or fourth pair of legs. Although larger spiders use hydraulics to straighten their legs, unlike smaller jumping spiders they depend on their flexor muscles to generate the propulsive force for their jumps.
Most spiders that hunt actively, rather than relying on webs, have dense tufts of fine hairs between the paired claws at the tips of their legs. These tufts, known as scopulae, consist of bristles whose ends are split into as many as 1,000 branches, and enable spiders with scopulae to walk up vertical glass and upside down on ceilings. It appears that scopulae get their grip from contact with extremely thin layers of water on surfaces.[8] Spiders, like most other arachnids, keep at least four legs on the surface while walking or running.
SILK PRODUCTION
The abdomen has no appendages except those that have been modified to form one to four (usually three) pairs of short, movable spinnerets, which emit silk. Each spinneret has many spigots, each of which is connected to one silk gland. There are at least six types of silk gland, each producing a different type of silk.
Silk is mainly composed of a protein very similar to that used in insect silk. It is initially a liquid, and hardens not by exposure to air but as a result of being drawn out, which changes the internal structure of the protein. It is similar in tensile strength to nylon and biological materials such as chitin, collagen and cellulose, but is much more elastic. In other words, it can stretch much further before breaking or losing shape.
Some spiders have a cribellum, a modified spinneret with up to 40,000 spigots, each of which produces a single very fine fiber. The fibers are pulled out by the calamistrum, a comb-like set of bristles on the jointed tip of the cribellum, and combined into a composite woolly thread that is very effective in snagging the bristles of insects. The earliest spiders had cribella, which produced the first silk capable of capturing insects, before spiders developed silk coated with sticky droplets. However, most modern groups of spiders have lost the cribellum.
Tarantulas also have silk glands in their feet.
Even species that do not build webs to catch prey use silk in several ways: as wrappers for sperm and for fertilized eggs; as a "safety rope"; for nest-building; and as "parachutes" by the young of some species.
REPRODUCTION AND LIFE CYCLE
Spiders reproduce sexually and fertilization is internal but indirect, in other words the sperm is not inserted into the female's body by the male's genitals but by an intermediate stage. Unlike many land-living arthropods, male spiders do not produce ready-made spermatophores (packages of sperm), but spin small sperm webs on to which they ejaculate and then transfer the sperm to special syringe-like structures, palpal bulbs or palpal organs, borne on the tips of the pedipalps of mature males. When a male detects signs of a female nearby he checks whether she is of the same species and whether she is ready to mate; for example in species that produce webs or "safety ropes", the male can identify the species and sex of these objects by "smell".
Spiders generally use elaborate courtship rituals to prevent the large females from eating the small males before fertilization, except where the male is so much smaller that he is not worth eating. In web-weaving species, precise patterns of vibrations in the web are a major part of the rituals, while patterns of touches on the female's body are important in many spiders that hunt actively, and may "hypnotize" the female. Gestures and dances by the male are important for jumping spiders, which have excellent eyesight. If courtship is successful, the male injects his sperm from the palpal bulbs into the female's genital opening, known as the epigyne, on the underside of her abdomen. Female's reproductive tracts vary from simple tubes to systems that include seminal receptacles in which females store sperm and release it when they are ready.
Males of the genus Tidarren amputate one of their palps before maturation and enter adult life with one palp only. The palps are 20% of male's body mass in this species, and detaching one of the two improves mobility. In the Yemeni species Tidarren argo, the remaining palp is then torn off by the female. The separated palp remains attached to the female's epigynum for about four hours and apparently continues to function independently. In the meantime, the female feeds on the palpless male. In over 60% of cases, the female of the Australian redback spider kills and eats the male after it inserts its second palp into the female's genital opening; in fact, the males co-operate by trying to impale themselves on the females' fangs. Observation shows that most male redbacks never get an opportunity to mate, and the "lucky" ones increase the likely number of offspring by ensuring that the females are well-fed. However, males of most species survive a few matings, limited mainly by their short life spans. Some even live for a while in their mates' webs.
Females lay up to 3,000 eggs in one or more silk egg sacs, which maintain a fairly constant humidity level. In some species, the females die afterwards, but females of other species protect the sacs by attaching them to their webs, hiding them in nests, carrying them in the chelicerae or attaching them to the spinnerets and dragging them along.
Baby spiders pass all their larval stages inside the egg and hatch as spiderlings, very small and sexually immature but similar in shape to adults. Some spiders care for their young, for example a wolf spider's brood cling to rough bristles on the mother's back, and females of some species respond to the "begging" behaviour of their young by giving them their prey, provided it is no longer struggling, or even regurgitate food.
Like other arthropods, spiders have to molt to grow as their cuticle ("skin") cannot stretch. In some species males mate with newly molted females, which are too weak to be dangerous to the males. Most spiders live for only one to two years, although some tarantulas can live in captivity for over 20 years.
SIZE
Spiders occur in a large range of sizes. The smallest, Patu digua from Colombia, are less than 0.37 mm in body length. The largest and heaviest spiders occur among tarantulas, which can have body lengths up to 90 mm and leg spans up to 250 mm.
COLORATION
Only three classes of pigment (ommochromes, bilins and guanine) have been identified in spiders, although other pigments have been detected but not yet characterized. Melanins, carotenoids and pterins, very common in other animals, are apparently absent. In some species, the exocuticle of the legs and prosoma is modified by a tanning process, resulting in brown coloration. Bilins are found, for example, in Micrommata virescens, resulting in its green color. Guanine is responsible for the white markings of the European garden spider Araneus diadematus. It is in many species accumulated in specialized cells called guanocytes. In genera such as Tetragnatha, Leucauge, Argyrodes or Theridiosoma, guanine creates their silvery appearance. While guanine is originally an end-product of protein metabolism, its excretion can be blocked in spiders, leading to an increase in its storage. Structural colors occur in some species, which are the result of the diffraction, scattering or interference of light, for example by modified setae or scales. The white prosoma of Argiope results from hairs reflecting the light, Lycosa and Josa both have areas of modified cuticle that act as light reflectors.
ECOGOGY AND BEHAVIOR
NON-PREDATORY FEEDING
Although spiders are generally regarded as predatory, the jumping spider Bagheera kiplingi gets over 90% of its food from fairly solid plant material produced by acacias as part of a mutually beneficial relationship with a species of ant.
Juveniles of some spiders in the families Anyphaenidae, Corinnidae, Clubionidae, Thomisidae and Salticidae feed on plant nectar. Laboratory studies show that they do so deliberately and over extended periods, and periodically clean themselves while feeding. These spiders also prefer sugar solutions to plain water, which indicates that they are seeking nutrients. Since many spiders are nocturnal, the extent of nectar consumption by spiders may have been underestimated. Nectar contains amino acids, lipids, vitamins and minerals in addition to sugars, and studies have shown that other spider species live longer when nectar is available. Feeding on nectar avoids the risks of struggles with prey, and the costs of producing venom and digestive enzymes.
Various species are known to feed on dead arthropods (scavenging), web silk, and their own shed exoskeletons. Pollen caught in webs may also be eaten, and studies have shown that young spiders have a better chance of survival if they have the opportunity to eat pollen. In captivity, several spider species are also known to feed on bananas, marmalade, milk, egg yolk and sausages.
METHODS OF CAPTURING PREY
The best-known method of prey capture is by means of sticky webs. Varying placement of webs allows different species of spider to trap different insects in the same area, for example flat horizontal webs trap insects that fly up from vegetation underneath while flat vertical webs trap insects in horizontal flight. Web-building spiders have poor vision, but are extremely sensitive to vibrations.
Females of the water spider Argyroneta aquatica build underwater "diving bell" webs that they fill with air and use for digesting prey, molting, mating and raising offspring. They live almost entirely within the bells, darting out to catch prey animals that touch the bell or the threads that anchor it. A few spiders use the surfaces of lakes and ponds as "webs", detecting trapped insects by the vibrations that these cause while struggling.
Net-casting spiders weave only small webs, but then manipulate them to trap prey. Those of the genus Hyptiotes and the family Theridiosomatidae stretch their webs and then release them when prey strike them, but do not actively move their webs. Those of the family Deinopidae weave even smaller webs, hold them outstretched between their first two pairs of legs, and lunge and push the webs as much as twice their own body length to trap prey, and this move may increase the webs' area by a factor of up to ten. Experiments have shown that Deinopis spinosus has two different techniques for trapping prey: backwards strikes to catch flying insects, whose vibrations it detects; and forward strikes to catch ground-walking prey that it sees. These two techniques have also been observed in other deinopids. Walking insects form most of the prey of most deinopids, but one population of Deinopis subrufa appears to live mainly on tipulid flies that they catch with the backwards strike.
Mature female bolas spiders of the genus Mastophora build "webs" that consist of only a single "trapeze line", which they patrol. They also construct a bolas made of a single thread, tipped with a large ball of very wet sticky silk. They emit chemicals that resemble the pheromones of moths, and then swing the bolas at the moths. Although they miss on about 50% of strikes, they catch about the same weight of insects per night as web-weaving spiders of similar size. The spiders eat the bolas if they have not made a kill in about 30 minutes, rest for a while, and then make new bolas. Juveniles and adult males are much smaller and do not make bolas. Instead they release different pheromones that attract moth flies, and catch them with their front pairs of legs.
The primitive Liphistiidae, the "trapdoor spiders" of the family Ctenizidae and many tarantulas are ambush predators that lurk in burrows, often closed by trapdoors and often surrounded by networks of silk threads that alert these spiders to the presence of prey. Other ambush predators do without such aids, including many crab spiders, and a few species that prey on bees, which see ultraviolet, can adjust their ultraviolet reflectance to match the flowers in which they are lurking. Wolf spiders, jumping spiders, fishing spiders and some crab spiders capture prey by chasing it, and rely mainly on vision to locate prey.Some jumping spiders of the genus Portia hunt other spiders in ways that seem intelligent, outflanking their victims or luring them from their webs. Laboratory studies show that Portia's instinctive tactics are only starting points for a trial-and-error approach from which these spiders learn very quickly how to overcome new prey species. However, they seem to be relatively slow "thinkers", which is not surprising, as their brains are vastly smaller than those of mammalian predators.Ant-mimicking spiders face several challenges: they generally develop slimmer abdomens and false "waists" in the cephalothorax to mimic the three distinct regions (tagmata) of an ant's body; they wave the first pair of legs in front of their heads to mimic antennae, which spiders lack, and to conceal the fact that they have eight legs rather than six; they develop large color patches round one pair of eyes to disguise the fact that they generally have eight simple eyes, while ants have two compound eyes; they cover their bodies with reflective hairs to resemble the shiny bodies of ants. In some spider species, males and females mimic different ant species, as female spiders are usually much larger than males. Ant-mimicking spiders also modify their behavior to resemble that of the target species of ant; for example, many adopt a zig-zag pattern of movement, ant-mimicking jumping spiders avoid jumping, and spiders of the genus Synemosyna walk on the outer edges of leaves in the same way as Pseudomyrmex. Ant-mimicry in many spiders and other arthropods may be for protection from predators that hunt by sight, including birds, lizards and spiders. However, several ant-mimicking spiders prey either on ants or on the ants' "livestock", such as aphids. When at rest, the ant-mimicking crab spider Amyciaea does not closely resemble Oecophylla, but while hunting it imitates the behavior of a dying ant to attract worker ants. After a kill, some ant-mimicking spiders hold their victims between themselves and large groups of ants to avoid being attacked.
DEFENSE
There is strong evidence that spiders' coloration is camouflage that helps them to evade their major predators, birds and parasitic wasps, both of which have good color vision. Many spider species are colored so as to merge with their most common backgrounds, and some have disruptive coloration, stripes and blotches that break up their outlines. In a few species, such as the Hawaiian happy-face spider, Theridion grallator, several coloration schemes are present in a ratio that appears to remain constant, and this may make it more difficult for predators to recognize the species. Most spiders are insufficiently dangerous or unpleasant-tasting for warning coloration to offer much benefit. However, a few species with powerful venoms, large jaws or irritant hairs have patches of warning colors, and some actively display these colors when threatened.
Many of the family Theraphosidae, which includes tarantulas and baboon spiders, have urticating hairs on their abdomens and use their legs to flick them at attackers. These hairs are fine setae (bristles) with fragile bases and a row of barbs on the tip. The barbs cause intense irritation but there is no evidence that they carry any kind of venom. A few defend themselves against wasps by including networks of very robust threads in their webs, giving the spider time to flee while the wasps are struggling with the obstacles. The golden wheeling spider, Carparachne aureoflava, of the Namibian desert escapes parasitic wasps by flipping onto its side and cartwheeling down sand dunes.
SOCIAL SPIDERS
A few spider species that build webs live together in large colonies and show social behavior, although not as complex as in social insects. Anelosimus eximius (in the family Theridiidae) can form colonies of up to 50,000 individuals. The genus Anelosimus has a strong tendency towards sociality: all known American species are social, and species in Madagascar are at least somewhat social. Members of other species in the same family but several different genera have independently developed social behavior. For example, although Theridion nigroannulatum belongs to a genus with no other social species, T. nigroannulatum build colonies that may contain several thousand individuals that co-operate in prey capture and share food. Other communal spiders include several Philoponella species (family Uloboridae), Agelena consociata (family Agelenidae) and Mallos gregalis (family Dictynidae). Social predatory spiders need to defend their prey against kleptoparasites ("thieves"), and larger colonies are more successful in this. The herbivorous spider Bagheera kiplingi lives in small colonies which help to protect eggs and spiderlings. Even widow spiders (genus Latrodectus), which are notoriously cannibalistic, have formed small colonies in captivity, sharing webs and feeding together.
WEB TYPES
There is no consistent relationship between the classification of spiders and the types of web they build: species in the same genus may build very similar or significantly different webs. Nor is there much correspondence between spiders' classification and the chemical composition of their silks. Convergent evolution in web construction, in other words use of similar techniques by remotely related species, is rampant. Orb web designs and the spinning behaviors that produce them are the best understood. The basic radial-then-spiral sequence visible in orb webs and the sense of direction required to build them may have been inherited from the common ancestors of most spider groups. However, the majority of spiders build non-orb webs. It used to be thought that the sticky orb web was an evolutionary innovation resulting in the diversification of the Orbiculariae. Now, however, it appears that non-orb spiders are a sub-group that evolved from orb-web spiders, and non-orb spiders have over 40% more species and are four times as abundant as orb-web spiders. Their greater success may be because sphecid wasps, which are often the dominant predators of spiders, much prefer to attack spiders that have flat webs.
ORB WEBS
About half the potential prey that hit orb webs escape. A web has to perform three functions: intercepting the prey (intersection), absorbing its momentum without breaking (stopping), and trapping the prey by entangling it or sticking to it (retention). No single design is best for all prey. For example: wider spacing of lines will increase the web's area and hence its ability to intercept prey, but reduce its stopping power and retention; closer spacing, larger sticky droplets and thicker lines would improve retention, but would make it easier for potential prey to see and avoid the web, at least during the day. However, there are no consistent differences between orb webs built for use during the day and those built for use at night. In fact, there is no simple relationship between orb web design features and the prey they capture, as each orb-weaving species takes a wide range of prey.
The hubs of orb webs, where the spiders lurk, are usually above the center, as the spiders can move downwards faster than upwards. If there is an obvious direction in which the spider can retreat to avoid its own predators, the hub is usually offset towards that direction.
Horizontal orb webs are fairly common, despite being less effective at intercepting and retaining prey and more vulnerable to damage by rain and falling debris. Various researchers have suggested that horizontal webs offer compensating advantages, such as reduced vulnerability to wind damage; reduced visibility to prey flying upwards, because of the back-lighting from the sky; enabling oscillations to catch insects in slow horizontal flight. However, there is no single explanation for the common use of horizontal orb webs.
Spiders often attach highly visible silk bands, called decorations or stabilimenta, to their webs. Field research suggests that webs with more decorative bands captured more prey per hour. However, a laboratory study showed that spiders reduce the building of these decorations if they sense the presence of predators.
There are several unusual variants of orb web, many of them convergently evolved, including: attachment of lines to the surface of water, possibly to trap insects in or on the surface; webs with twigs through their centers, possibly to hide the spiders from predators; "ladder-like" webs that appear most effective in catching moths. However, the significance of many variations is unclear.
In 1973, Skylab 3 took two orb-web spiders into space to test their web-spinning capabilities in zero gravity. At first, both produced rather sloppy webs, but they adapted quickly.
TANGLEWEB SPIDERS (COBWEB SPIDERS)
Members of the family Theridiidae weave irregular, tangled, three-dimensional webs, popularly known as cobwebs. There seems to be an evolutionary trend towards a reduction in the amount of sticky silk used, leading to its total absence in some species. The construction of cobwebs is less stereotyped than that of orb-webs, and may take several days.
OTHER TYPES OF WEBS
The Linyphiidae generally make horizontal but uneven sheets, with tangles of stopping threads above. Insects that hit the stopping threads fall onto the sheet or are shaken onto it by the spider, and are held by sticky threads on the sheet until the spider can attack from below.
EVOLUTION
FOSSIL RECORD
Although the fossil record of spiders is considered poor, almost 1000 species have been described from fossils. Because spiders' bodies are quite soft, the vast majority of fossil spiders have been found preserved in amber. The oldest known amber that contains fossil arthropods dates from 130 million years ago in the Early Cretaceous period. In addition to preserving spiders' anatomy in very fine detail, pieces of amber show spiders mating, killing prey, producing silk and possibly caring for their young. In a few cases, amber has preserved spiders' egg sacs and webs, occasionally with prey attached; the oldest fossil web found so far is 100 million years old. Earlier spider fossils come from a few lagerstätten, places where conditions were exceptionally suited to preserving fairly soft tissues.
The oldest known exclusively terrestrial arachnid is the trigonotarbid Palaeotarbus jerami, from about 420 million years ago in the Silurian period, and had a triangular cephalothorax and segmented abdomen, as well as eight legs and a pair of pedipalps. Attercopus fimbriunguis, from 386 million years ago in the Devonian period, bears the earliest known silk-producing spigots, and was therefore hailed as a spider at the time of its discovery. However, these spigots may have been mounted on the underside of the abdomen rather than on spinnerets, which are modified appendages and whose mobility is important in the building of webs. Hence Attercopus and the similar Permian arachnid Permarachne may not have been true spiders, and probably used silk for lining nests or producing egg-cases rather than for building webs. The largest known fossil spider as of 2011 is the araneid Nephila jurassica, from about 165 million years ago, recorded from Daohuogo, Inner Mongolia in China. Its body length is almost 25 mm.
Several Carboniferous spiders were members of the Mesothelae, a primitive group now represented only by the Liphistiidae. The mesothelid Paleothele montceauensis, from the Late Carboniferous over 299 million years ago, had five spinnerets. Although the Permian period 299 to 251 million years ago saw rapid diversification of flying insects, there are very few fossil spiders from this period.
The main groups of modern spiders, Mygalomorphae and Araneomorphae, first appear in the Triassic well before 200 million years ago. Some Triassic mygalomorphs appear to be members of the family Hexathelidae, whose modern members include the notorious Sydney funnel-web spider, and their spinnerets appear adapted for building funnel-shaped webs to catch jumping insects. Araneomorphae account for the great majority of modern spiders, including those that weave the familiar orb-shaped webs. The Jurassic and Cretaceous periods provide a large number of fossil spiders, including representatives of many modern families.
WIKIPEDIA
Injecting technology into our universe.
A wise operation?
Shot in MIlano looking at north towards the Alps, with Rubinar 1000mm and Canon 5D Mark II (video mode)
Music by John Zorn: The Dreamer - Raksasa.
St Martin, Nacton, Suffolk
Nacton is one of a number of lovely villages in close proximity to Ipswich. And it really is close to town - I live near the centre of Ipswich and I can cycle out to Nacton church in twenty minutes. The village is scattered in a valley, with two great houses, Broke Hall and Orwell Park.
There are a couple of exciting 1960s modernist buildings as well, although the village does have the unenviable reputation of not having had a pub for a couple of centuries, thanks to the temperance tendencies of not just one but two major landowning families in the parish. Technically, the vast Shepherd and Dog on Felixstowe Road is within the bounds of Nacton parish, but it is not the kind of pub I expect many villagers would make the effort to get to when the smashing Ship Inn at neighbouring Levington is closer and more convivial.
The two great families were the Vernons and the Brokes. St Martin is in the grounds of Orwell Park, and a gateway in the wall shows where the Vernons used to come to divine service, but the Brokes must have arrived by road. Orwell Park today is a private school, and Broke Hall has been divided into flats, but St Martin still retains the memory of the great and the good of both families.
Externally, St Martin gives no indication of the early 20th Century treasures in store within. It only takes the sun to go in, and that rendered tower ends up looking like a grain silo, the colour of cold porridge. This is a pity, because on a sunny day there is something grand and imposing about it, especially with that pretty dormer window halfway along the nave roof. It gives a pleasing Arts and Crafts touch to the austerity of a building which was almost entirely rebuilt between 1906 and 1908 by Charles Hodgson Fowler. They'd actually been two dormers, and Fowler retained that on the south side. They had been installed in the 1870s by a budding medievalist, but there had been an earlier going-over by Diocesan architect Richard Phipson in 1859. Mortlock tells us that Fowler added the aisle, the organ chamber and vestry, the porch and the east window. The roofs and floors were also replaced. The small south transept survived from the earlier restoration, largely because it forms a memorial chapel to the Broke family of Broke Hall. Grand memorials record their miltary deeds, including captaining the Shannon when it captured the Chespeake during the American War of Independence.
The medieval font also survives, and is a good one, although perhaps a bit recut. Around the bowl, angels bearing carved shields alternate with symbols of the four evangelists.The wild men are striking, and the smiling lions are reminiscent of those you often find on Norfolk fonts of this type.
There are two image niches in one of the window embrasures, but otherwise this is almost entirely a Victorian and Edwardian interior, full of Brokes and Vernons. Their greatest legacy to St Martin has been the large range of stained glass which ultimately gives St Martin its character. It is interesting to compare the church to St Peter at Levington, a mile or so off. There, the church is simple and rustic; the difference that the money spent here has made is accentuated by a visit to both. But St Martin has been given a sober gravitas, a self-confidence that falls short of triumphalism.
There are some fragments of medieval glass surviving, including a fine shield of the Instruments of the Passion which may or may not have come from this church originally, But the glass in Fowler's north aisle is the star of the show. At the west end is a finely drawn 1913 Adoration of the Shepherds and Magi by Burlison & Grylls. The shepherds are lifted directly from the late 15th Century Portinari altarpiece by Hugo van der Goes, today in the Uffizi gallery in Florence. The use of images from Northern European old masters was common practice for the workshop. To the east of it is a rather less successful window by By Christopher Powell, and believed to be his only work in Suffolk, depicting the three figures of the Sower, the Good Shepherd and St Martin. It is interesting to compare it with his similar window at Dersingham in Norfolk.
Next along is a memorial to the Pretyman family. Herbert Pretyman died in 1891, and when Fowler's aisle was complete in 1906 his widow installed the central light, a typically predestrian image of St George by Clayton & Bell. However, the two figures that flank it, St Michael as Victory and St Raphaeil (but actually St Gabriel, surely?) as Peace are something else again, tremendous images installed in 1920 to give thanks for the safe return of two Pretyman sons from the horror of the First World War. The angels are wise and triumphant, their feathered wings flamboyant. No one seems to know who they are by (it certainly isn't Clayton & Bell) and it would be interesting to know.
To the east again is a lancet of the Blessed Virgin and child by Kempe under the guiding hand of Walter Tower, and the Kempe/Tower partnership was also responsible for the east window, a not entirely successful collection of workshop cartoons of the crucifixion and Old Testament prophets. Beside it on the south side of the chancel is the earliest modern glass in the church, two post-resurrection scenes by William Wailes. The only other 19th Century window is on the south side of the nave, a chaotic assemblage of heraldic symbols from Broke family marriages, showing arms and crests over the generations. It dates from the 1860s, and is by Clayton & Bell.
When the church reopened in 1908, people were said to be delighted by the Anglo-catholic mood of the time which had been injected into the building. Outside, their ancestors lie beneath headstones that have been eroded and smoothed clean by the salty air that comes from the great river beyond the school. Hardly any of the 18th and early 19th century inscriptions are legible now. One exception is to a man who died in the middle years of the 19th century who fought at Traffalgar. This is as clearly read now as it was when Arthur Mee came this way in the 1930s.
Der Mercedes R107 ist ein zweisitziger Roadster mit auf Wunsch lieferbaren hinteren Notsitzen. Das Schwestermodell Mercedes C107 verfügt gegenüber dem Roadster über einen verlängerten Radstand und ist ein fünfsitziges Coupé mit vollwertigen hinteren Sitzen. Die Wagen gehören zur SL-Baureihe von Mercedes-Benz.
Die SL-Baureihe 107, die 1971 als Nachfolger der sogenannten Pagoden-SL (Baureihe W113) debütierte, begründete mit den Breitband H4-Scheinwerfern und den großen geriffelten Rückleuchten eine neue Designlinie bei Mercedes-Benz. Eine leichte Keilform deutete auf eine verbesserte Aerodynamik hin. Verantwortlicher Designer dieser Serie war erneut Friedrich Geiger, der bereits für die zeitlosen Schöpfungen des 300 SL (einschließlich Roadster) und des vom W111 abgeleiteten Coupés verantwortlich zeichnete. [1]
Mit den Typen 450 SLC und 450 SLC 5.0 bzw. 500 SLC nahm Daimler-Benz Ende der siebziger Jahre an großen Rallyes wie der 30.000 km langen Vuelta à la America del Sud (1977), der Safari-Rallye (1979) und der Bandama-Rallye (1979/1980) teil.
Mittlerweile befindet sich der älteste noch erhaltene R107, ein 350 SL mit der Chassis-Nummer 107043-12-000008 und der Motor-Nummer 116982-12-000001, in der Hand eines Arztes aus Erlangen. Der Wagen ist sandbeigemetallic und wurde am 21. April 1971 in Italien zum ersten Mal zugelassen.
(Wikipedia)
---
The Mercedes-Benz R107 automobiles were produced from 1971 through 1989, being the longest single series ever produced by the firm, besides the G-Class. They were sold under the SL-Class and SLC-Class model names. The R107 replaced the W113 SL-Class in 1972 and was replaced by the R129 SL-Class in 1989.
The R107 took the chassis components of the mid size Mercedes-Benz W114 model and mated them to the larger engines from the S-Class. The W 107 chassis is also referred to as "R 107" for "Reihe" (series). The series comprised SL and SLC models.
The SL variant was a 2-seat convertible/roadster with standard soft top and hardtop. The SLC (technically C107) derivative was a 2 door hardtop coupe, with usable rear seats and in effect an SL stretched 10 inches (254 mm) with a fixed roof. Although some may air this car as an 'SL coupe'- though technically it might be, but in the real world it was an S-class coupe (modern day CL), replacing the former saloon-based 280/300SE coupé in Mercedes` lineup. The SLC was replaced earlier than the SL, in 1981, with a much larger model, the 380SEC. It was aimed at the same market as more exotic machines like the Jaguar E-Type and Citroën SM.
The 107 chassis had the longest run of any Mercedes chassis, 18 years from 1971 to 1989. Some 237,000 107 chassis SL's were built. About two thirds were sold in the US. These 107 cars are larger, heavier and more costly than the previous generation W113 SL cars.
Volume production of the first R107 car, the 350 SL, started in April, 1971 alongside the last of the W 113 cars; the 350 SLC followed in October. Early North American cars wore the name 350 SL, but had a larger 4.5L V8 (and were renamed 450 SL/SLC for model year 1973); the big V8 became available on other markets with the official introduction of the 450 SL/SLC on non-North American markets in March, 1973.
From July, 1974 both SL and SLC could also be ordered with a fuel-injected 2.8L straight-6 as 280 SL and SLC.
In September, 1977 the 450 SLC 5.0 joined the line. This was a special version of the big coupé featuring a bored five-liter version of the 4.5L V8, some light alloy body panels and a black plastic rear spoiler.
The 350, 450 and 450 SLC 5.0 models (like the 350 and 450 SL) were discontinued in 1980 with the introduction of the 380 and 500 SLC in March, 1980. At the same time, the cars received a very mild make-over; the 3-speed automatic was replaced by a four-speed unit, the 280 models came with a standard 5-speed (formerly a 4-speed) manual and all five-liter cars gained a black rear spoiler lip.
The 280, 380 and 500SLC were discontinued in 1981 with the introduction of the 126 series 380 and 500SEC coupes. A total of 62,888 SLCs had been manufactured over a ten year period of which just 1,636 were the 450SLC-5.0 and 1,133 were the 500SLC. Both these models are sought by collectors today. The SLC remains the only fixed roof Mercedes-Benz coupe based on a roadster rather than a sedan. Even today, an SLC in good mechanical condition still gives a mix of good performance, superb handling, comfort and safety, making it is easy to realise why they were a successful rally car.
Following the discontinuation of the SLC in September, 1981, the 107 series continued initially as the 280, 380 and 500SL. At this time, the V8 engines were re-tuned for greater efficiency, lost a few hp and consumed less fuel, helped by substantially numerically shorter axle ratios (that went from 3.27:1 to 2.47:1 for the 380 SL and from 2.72:1 to 2.27:1 for the 500 SL). From September, 1985 the 280SL was replaced by a new 300 SL, and the 380 SL by a 420 SL; the 500 SL continued and a 560SL was introduced for certain extra-European markets, most notably the USA. The final R107 SL was built on August 4, 1989. This eighteen-year run makes the 107 series the longest running series produced by Daimler-Benz.
The last 107 made, a 1989 500SL painted Astral Silver, resides in the Mercedes-Benz museum in Stuttgart, Germany. The W107 series today is prized by classic car collectors; almost all usable examples are worth £5000+ apiece, with the highest-range models sometimes worth £10,000 or more.
(Wikipedia)
Testosterone
The chemical structure of testosterone.
A ball-and-stick model of testosterone.
Names
IUPAC name
17β-Hydroxyandrost-4-en-3-one
Systematic IUPAC name
(8R,9S,10R,13S,14S,17S)-17-Hydroxy-10,13-dimethyl-1,2,6,7,8,9,11,12,14,15,16,17-dodecahydrocyclopenta[a]phenanthren-3-one
Other names
Androst-4-en-17β-ol-3-one
Identifiers
CAS Number
58-22-0 ☑
3D model (JSmol)
Interactive image
ChEBI
CHEBI:17347 ☑
ChEMBL
ChEMBL386630 ☑
ChemSpider
5791 ☑
DrugBank
DB00624 ☑
ECHA InfoCard100.000.336
KEGG
D00075 ☑
PubChem CID
6013
UNII
3XMK78S47O ☑
InChI[show]
SMILES[show]
Properties
Chemical formula
C19H28O2
Molar mass288.431 g·mol−1
Melting point155 °C
Pharmacology
ATC code
G03BA03 (WHO)
License data
EU EMA: by INN
Routes of
administration
Transdermal (gel, cream, solution, patch), by mouth (as testosterone undecanoate), in the cheek, intranasal (gel), intramuscular injection (as esters), subcutaneous pellets
Pharmacokinetics:
Bioavailability
Oral: very low (due to extensive first pass metabolism)
Protein binding
97.0–99.5% (to SHBG and albumin)[1]
Metabolism
Liver (mainly reduction and conjugation)
Biological half-life
2–4 hours[citation needed]
Excretion
Urine (90%), feces (6%)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references
Testosterone is the primary male sex hormone and an anabolic steroid. In male humans, testosterone plays a key role in the development of male reproductive tissues such as testes and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair.[2] In addition, testosterone is involved in health and well-being,[3] and the prevention of osteoporosis.[4] Insufficient levels of testosterone in men may lead to abnormalities including frailty and bone loss.
Testosterone is a steroid from the androstane class containing a keto and hydroxyl groups at the three and seventeen positions respectively. It is biosynthesized in several steps from cholesterol and is converted in the liver to inactive metabolites.[5] It exerts its action through binding to and activation of the androgen receptor.[5] In humans and most other vertebrates, testosterone is secreted primarily by the testicles of males and, to a lesser extent, the ovaries of females. On average, in adult males, levels of testosterone are about 7 to 8 times as great as in adult females.[6] As the metabolism of testosterone in males is more pronounced, the daily production is about 20 times greater in men.[7][8] Females are also more sensitive to the hormone.[9]
In addition to its role as a natural hormone, testosterone is used as a medication, for instance in the treatment of low testosterone levels in men and breast cancer in women.[10] Since testosterone levels decrease as men age, testosterone is sometimes used in older men to counteract this deficiency. It is also used illicitly to enhance physique and performance, for instance in athletes.
Contents
1Biological effects
1.1Before birth
1.2Early infancy
1.3Before puberty
1.4Pubertal
1.5Adult
1.6Aggression and criminality
1.7Brain
2Medical use
3Biological activity
3.1Steroid hormone activity
3.2Neurosteroid activity
4Biochemistry
4.1Biosynthesis
4.2Distribution
4.3Metabolism
4.4Levels
5Measurement
6History
7Other animals
8See also
9References
10Further reading
Biological effects[edit]
In general, androgens such as testosterone promote protein synthesis and thus growth of tissues with androgen receptors.[11] Testosterone can be described as having virilising and anabolic effects (though these categorical descriptions are somewhat arbitrary, as there is a great deal of mutual overlap between them).[12]
Anabolic effects include growth of muscle mass and strength, increased bone density and strength, and stimulation of linear growth and bone maturation.
Androgenic effects include maturation of the sex organs, particularly the penis and the formation of the scrotum in the fetus, and after birth (usually at puberty) a deepening of the voice, growth of facial hair (such as the beard) and axillary (underarm) hair. Many of these fall into the category of male secondary sex characteristics.
Testosterone effects can also be classified by the age of usual occurrence. For postnatal effects in both males and females, these are mostly dependent on the levels and duration of circulating free testosterone.
Before birth[edit]
Effects before birth are divided into two categories, classified in relation to the stages of development.
The first period occurs between 4 and 6 weeks of the gestation. Examples include genital virilisation such as midline fusion, phallic urethra, scrotal thinning and rugation, and phallic enlargement; although the role of testosterone is far smaller than that of dihydrotestosterone. There is also development of the prostate gland and seminal vesicles.
During the second trimester, androgen level is associated with sex formation.[13] This period affects the femininization or masculinization of the fetus and can be a better predictor of feminine or masculine behaviours such as sex typed behaviour than an adult's own levels. A mother's testosterone level during pregnancy is correlated with her daughter's sex-typical behavior as an adult, and the correlation is even stronger than with the daughter's own adult testosterone level.[14]
Early infancy[edit]
Early infancy androgen effects are the least understood. In the first weeks of life for male infants, testosterone levels rise. The levels remain in a pubertal range for a few months, but usually reach the barely detectable levels of childhood by 4–7 months of age.[15][16] The function of this rise in humans is unknown. It has been theorized that brain masculinization is occurring since no significant changes have been identified in other parts of the body.[17] The male brain is masculinized by the aromatization of testosterone into estrogen, which crosses the blood–brain barrier and enters the male brain, whereas female fetuses have α-fetoprotein, which binds the estrogen so that female brains are not affected.[18]
Before puberty[edit]
Before puberty effects of rising androgen levels occur in both boys and girls. These include adult-type body odor, increased oiliness of skin and hair, acne, pubarche (appearance of pubic hair), axillary hair (armpit hair), growth spurt, accelerated bone maturation, and facial hair.[19]
Pubertal[edit]
Pubertal effects begin to occur when androgen has been higher than normal adult female levels for months or years. In males, these are usual late pubertal effects, and occur in women after prolonged periods of heightened levels of free testosterone in the blood. The effects include:[19][20]
Growth of spermatogenic tissue in testicles, male fertility, penis or clitoris enlargement, increased libido and frequency of erection or clitoral engorgement occurs. Growth of jaw, brow, chin, and nose and remodeling of facial bone contours, in conjunction with human growth hormone occurs.[21] Completion of bone maturation and termination of growth. This occurs indirectly via estradiol metabolites and hence more gradually in men than women. Increased muscle strength and mass, shoulders become broader and rib cage expands, deepening of voice, growth of the Adam's apple. Enlargement of sebaceous glands. This might cause acne, subcutaneous fat in face decreases. Pubic hair extends to thighs and up toward umbilicus, development of facial hair (sideburns, beard, moustache), loss of scalp hair (androgenetic alopecia), increase in chest hair, periareolar hair, perianal hair, leg hair, armpit hair.
Adult[edit]
Testosterone is necessary for normal sperm development. It activates genes in Sertoli cells, which promote differentiation of spermatogonia. It regulates acute HPA (hypothalamic–pituitary–adrenal axis) response under dominance challenge.[22] Androgen including testosterone enhances muscle growth. Testosterone also regulates the population of thromboxane A2 receptors on megakaryocytes and platelets and hence platelet aggregation in humans.[23][24]
Adult testosterone effects are more clearly demonstrable in males than in females, but are likely important to both sexes. Some of these effects may decline as testosterone levels might decrease in the later decades of adult life.[25]
Health risks[edit]
Testosterone does not appear to increase the risk of developing prostate cancer. In people who have undergone testosterone deprivation therapy, testosterone increases beyond the castrate level have been shown to increase the rate of spread of an existing prostate cancer.[26][27][28]
Conflicting results have been obtained concerning the importance of testosterone in maintaining cardiovascular health.[29][30] Nevertheless, maintaining normal testosterone levels in elderly men has been shown to improve many parameters that are thought to reduce cardiovascular disease risk, such as increased lean body mass, decreased visceral fat mass, decreased total cholesterol, and glycemic control.[31]
High androgen levels are associated with menstrual cycle irregularities in both clinical populations and healthy women.[32]
Sexual arousal[edit]
See also: Hormones and sexual arousal
When testosterone and endorphins in ejaculated semen meet the cervical wall after sexual intercourse, females receive a spike in testosterone, endorphin, and oxytocin levels, and males after orgasm during copulation experience an increase in endorphins and a marked increase in oxytocin levels. This adds to the hospitable physiological environment in the female internal reproductive tract for conceiving, and later for nurturing the conceptus in the pre-embryonic stages, and stimulates feelings of love, desire, and paternal care in the male (this is the only time male oxytocin levels rival a female's).[citation needed]
Testosterone levels follow a nyctohemeral rhythm that peaks early each day, regardless of sexual activity.[33]
There are positive correlations between positive orgasm experience in women and testosterone levels where relaxation was a key perception of the experience. There is no correlation between testosterone and men's perceptions of their orgasm experience, and also no correlation between higher testosterone levels and greater sexual assertiveness in either sex.[34]
Sexual arousal and masturbation in women produce small increases in testosterone concentrations.[35] The plasma levels of various steroids significantly increase after masturbation in men and the testosterone levels correlate to those levels.[36]
Mammalian studies[edit]
Studies conducted in rats have indicated that their degree of sexual arousal is sensitive to reductions in testosterone. When testosterone-deprived rats were given medium levels of testosterone, their sexual behaviors (copulation, partner preference, etc.) resumed, but not when given low amounts of the same hormone. Therefore, these mammals may provide a model for studying clinical populations among humans suffering from sexual arousal deficits such as hypoactive sexual desire disorder.[37]
In every mammalian species examined demonstrated a marked increase in a male's testosterone level upon encountering a novel female. The reflexive testosterone increases in male mice is related to the male's initial level of sexual arousal.[38]
In non-human primates, it may be that testosterone in puberty stimulates sexual arousal, which allows the primate to increasingly seek out sexual experiences with females and thus creates a sexual preference for females.[39] Some research has also indicated that if testosterone is eliminated in an adult male human or other adult male primate's system, its sexual motivation decreases, but there is no corresponding decrease in ability to engage in sexual activity (mounting, ejaculating, etc.).[39]
In accordance with sperm competition theory, testosterone levels are shown to increase as a response to previously neutral stimuli when conditioned to become sexual in male rats.[40] This reaction engages penile reflexes (such as erection and ejaculation) that aid in sperm competition when more than one male is present in mating encounters, allowing for more production of successful sperm and a higher chance of reproduction.
Males[edit]
In men, higher levels of testosterone are associated with periods of sexual activity.[41][42]
Men who watch a sexually explicit movie have an average increase of 35% in testosterone, peaking at 60–90 minutes after the end of the film, but no increase is seen in men who watch sexually neutral films.[43] Men who watch sexually explicit films also report increased motivation, competitiveness, and decreased exhaustion.[44] A link has also been found between relaxation following sexual arousal and testosterone levels.[45]
Men's levels of testosterone, a hormone known to affect men's mating behaviour, changes depending on whether they are exposed to an ovulating or nonovulating woman's body odour. Men who are exposed to scents of ovulating women maintained a stable testosterone level that was higher than the testosterone level of men exposed to nonovulation cues. Testosterone levels and sexual arousal in men are heavily aware of hormone cycles in females.[46] This may be linked to the ovulatory shift hypothesis,[47] where males are adapted to respond to the ovulation cycles of females by sensing when they are most fertile and whereby females look for preferred male mates when they are the most fertile; both actions may be driven by hormones.
Females[edit]
Androgens may modulate the physiology of vaginal tissue and contribute to female genital sexual arousal.[48] Women's level of testosterone is higher when measured pre-intercourse vs pre-cuddling, as well as post-intercourse vs post-cuddling.[49] There is a time lag effect when testosterone is administered, on genital arousal in women. In addition, a continuous increase in vaginal sexual arousal may result in higher genital sensations and sexual appetitive behaviors.[50]
When females have a higher baseline level of testosterone, they have higher increases in sexual arousal levels but smaller increases in testosterone, indicating a ceiling effect on testosterone levels in females. Sexual thoughts also change the level of testosterone but not level of cortisol in the female body, and hormonal contraceptives may affect the variation in testosterone response to sexual thoughts.[51]
Testosterone may prove to be an effective treatment in female sexual arousal disorders,[52] and is available as a dermal patch. There is no FDA approved androgen preparation for the treatment of androgen insufficiency; however, it has been used off-label to treat low libido and sexual dysfunction in older women. Testosterone may be a treatment for postmenopausal women as long as they are effectively estrogenized.[52]
Romantic relationships[edit]
Falling in love decreases men's testosterone levels while increasing women's testosterone levels. There has been speculation that these changes in testosterone result in the temporary reduction of differences in behavior between the sexes.[53] However, it is suggested that after the "honeymoon phase" ends—about four years into a relationship—this change in testosterone levels is no longer apparent.[53] Men who produce less testosterone are more likely to be in a relationship[54] or married,[55] and men who produce more testosterone are more likely to divorce;[55] however, causality cannot be determined in this correlation. Marriage or commitment could cause a decrease in testosterone levels.[56] Single men who have not had relationship experience have lower testosterone levels than single men with experience. It is suggested that these single men with prior experience are in a more competitive state than their non-experienced counterparts.[57] Married men who engage in bond-maintenance activities such as spending the day with their spouse/and or child have no different testosterone levels compared to times when they do not engage in such activities. Collectively, these results suggest that the presence of competitive activities rather than bond-maintenance activities are more relevant to changes in testosterone levels.[58]
Men who produce more testosterone are more likely to engage in extramarital sex.[55] Testosterone levels do not rely on physical presence of a partner; testosterone levels of men engaging in same-city and long-distance relationships are similar.[54] Physical presence may be required for women who are in relationships for the testosterone–partner interaction, where same-city partnered women have lower testosterone levels than long-distance partnered women.[59]
Fatherhood[edit]
Fatherhood decreases testosterone levels in men, suggesting that the emotions and behavior tied to decreased testosterone promote paternal care. In humans and other species that utilize allomaternal care, paternal investment in offspring is beneficial to said offspring's survival because it allows the parental dyad to raise multiple children simultaneously. This increases the reproductive fitness of the parents, because their offspring are more likely to survive and reproduce. Paternal care increases offspring survival due to increased access to higher quality food and reduced physical and immunological threats.[60] This is particularly beneficial for humans since offspring are dependent on parents for extended periods of time and mothers have relatively short inter-birth intervals.[61] While extent of paternal care varies between cultures, higher investment in direct child care has been seen to be correlated with lower average testosterone levels as well as temporary fluctuations.[62] For instance, fluctuation in testosterone levels when a child is in distress has been found to be indicative of fathering styles. If a father's testosterone levels decrease in response to hearing their baby cry, it is an indication of empathizing with the baby. This is associated with increased nurturing behavior and better outcomes for the infant.[63]
Motivation[edit]
Testosterone levels play a major role in risk-taking during financial decisions.[64][65]
Aggression and criminality [edit]
See also: Aggression § Testosterone, and Biosocial criminology
Most studies support a link between adult criminality and testosterone, although the relationship is modest if examined separately for each sex. Nearly all studies of juvenile delinquency and testosterone are not significant. Most studies have also found testosterone to be associated with behaviors or personality traits linked with criminality such as antisocial behavior and alcoholism. Many studies have also been done on the relationship between more general aggressive behavior/feelings and testosterone. About half the studies have found a relationship and about half no relationship.[66]
Testosterone is only one of many factors that influence aggression and the effects of previous experience and environmental stimuli have been found to correlate more strongly. A few studies indicate that the testosterone derivative estradiol (one form of estrogen) might play an important role in male aggression.[66][67][68][69] Studies have also found that testosterone facilitates aggression by modulating vasopressin receptors in the hypothalamus.[70]
The sexual hormone can encourage fair behavior. For the study, subjects took part in a behavioral experiment where the distribution of a real amount of money was decided. The rules allowed both fair and unfair offers. The negotiating partner could subsequently accept or decline the offer. The fairer the offer, the less probable a refusal by the negotiating partner. If no agreement was reached, neither party earned anything. Test subjects with an artificially enhanced testosterone level generally made better, fairer offers than those who received placebos, thus reducing the risk of a rejection of their offer to a minimum. Two later studies have empirically confirmed these results.[71][72][73] However men with high testosterone were significantly 27% less generous in an ultimatum game.[74] The Annual NY Academy of Sciences has also found anabolic steroid use which increase testosterone to be higher in teenagers, and this was associated with increased violence.[75] Studies have also found administered testosterone to increase verbal aggression and anger in some participants.[76]
Testosterone is significantly correlated with aggression and competitive behaviour and is directly facilitated by the latter. There are two theories on the role of testosterone in aggression and competition.[77] The first one is the challenge hypothesis which states that testosterone would increase during puberty thus facilitating reproductive and competitive behaviour which would include aggression.[77] Thus it is the challenge of competition among males of the species that facilitates aggression and violence.[77] Studies conducted have found direct correlation between testosterone and dominance especially among the most violent criminals in prison who had the highest testosterone levels.[77] The same research also found fathers (those outside competitive environments) had the lowest testosterone levels compared to other males.[77]
The second theory is similar and is known as "evolutionary neuroandrogenic (ENA) theory of male aggression".[78][79] Testosterone and other androgens have evolved to masculinize a brain in order to be competitive even to the point of risking harm to the person and others. By doing so, individuals with masculinized brains as a result of pre-natal and adult life testosterone and androgens enhance their resource acquiring abilities in order to survive, attract and copulate with mates as much as possible.[78] The masculinization of the brain is not just mediated by testosterone levels at the adult stage, but also testosterone exposure in the womb as a fetus. Higher pre-natal testosterone indicated by a low digit ratio as well as adult testosterone levels increased risk of fouls or aggression among male players in a soccer game.[80] Studies have also found higher pre-natal testosterone or lower digit ratio to be correlated with higher aggression in males.[81][82][83][84][85]
The rise in testosterone levels during competition predicted aggression in males but not in females.[86] Subjects who interacted with hand guns and an experimental game showed rise in testosterone and aggression.[87] Natural selection might have evolved males to be more sensitive to competitive and status challenge situations and that the interacting roles of testosterone are the essential ingredient for aggressive behaviour in these situations.[88] Testosterone produces aggression by activating subcortical areas in the brain, which may also be inhibited or suppressed by social norms or familial situations while still manifesting in diverse intensities and ways through thoughts, anger, verbal aggression, competition, dominance and physical violence.[89] Testosterone mediates attraction to cruel and violent cues in men by promoting extended viewing of violent stimuli.[90] Testosterone specific structural brain characteristic can predict aggressive behaviour in individuals.[91]
Estradiol is known to correlate with aggression in male mice.[92] Moreover, the conversion of testosterone to estradiol regulates male aggression in sparrows during breeding season.[93] Rats who were given anabolic steroids that increase testosterone were also more physically aggressive to provocation as a result of "threat sensitivity".[94]
Brain[edit]
The brain is also affected by this sexual differentiation;[13] the enzyme aromatase converts testosterone into estradiol that is responsible for masculinization of the brain in male mice. In humans, masculinization of the fetal brain appears, by observation of gender preference in patients with congenital diseases of androgen formation or androgen receptor function, to be associated with functional androgen receptors.[95]
There are some differences between a male and female brain (possibly the result of different testosterone levels), one of them being size: the male human brain is, on average, larger.[96] Men were found to have a total myelinated fiber length of 176 000 km at the age of 20, whereas in women the total length was 149 000 km (approx. 15% less).[97]
No immediate short term effects on mood or behavior were found from the administration of supraphysiologic doses of testosterone for 10 weeks on 43 healthy men.[98] A correlation between testosterone and risk tolerance in career choice exists among women.[64][99]
Attention, memory, and spatial ability are key cognitive functions affected by testosterone in humans. Preliminary evidence suggests that low testosterone levels may be a risk factor for cognitive decline and possibly for dementia of the Alzheimer's type,[100][101][102][103] a key argument in life extension medicine for the use of testosterone in anti-aging therapies. Much of the literature, however, suggests a curvilinear or even quadratic relationship between spatial performance and circulating testosterone,[104] where both hypo- and hypersecretion (deficient- and excessive-secretion) of circulating androgens have negative effects on cognition.
Medical use[edit]
Main article: Testosterone (medication)
Testosterone is used as a medication for the treatment of males with too little or no natural testosterone production, certain forms of breast cancer,[10] and gender dysphoria in transgender men. This is known as hormone replacement therapy (HRT) or testosterone replacement therapy (TRT), which maintains serum testosterone levels in the normal range. Decline of testosterone production with age has led to interest in androgen replacement therapy.[105] It is unclear if the use of testosterone for low levels due to aging is beneficial or harmful.[106]
Testosterone is included in the World Health Organization's list of essential medicines, which are the most important medications needed in a basic health system.[107] It is available as a generic medication.[10] The price depends on the form of testosterone used.[108] It can be administered as a cream or transdermal patch that is applied to the skin, by injection into a muscle, as a tablet that is placed in the cheek, or by ingestion.[10]
Common side effects from testosterone medication include acne, swelling, and breast enlargement in males.[10] Serious side effects may include liver toxicity, heart disease, and behavioral changes.[10] Women and children who are exposed may develop virilization.[10] It is recommended that individuals with prostate cancer not use the medication.[10] It can cause harm if used during pregnancy or breastfeeding.[10]
Biological activity[edit]
Steroid hormone activity[edit]
The effects of testosterone in humans and other vertebrates occur by way of multiple mechanisms: by activation of the androgen receptor (directly or as DHT), and by conversion to estradiol and activation of certain estrogen receptors.[109][110] Androgens such as testosterone have also been found to bind to and activate membrane androgen receptors.[111][112][113]
Free testosterone (T) is transported into the cytoplasm of target tissue cells, where it can bind to the androgen receptor, or can be reduced to 5α-dihydrotestosterone (DHT) by the cytoplasmic enzyme 5α-reductase. DHT binds to the same androgen receptor even more strongly than testosterone, so that its androgenic potency is about 5 times that of T.[114] The T-receptor or DHT-receptor complex undergoes a structural change that allows it to move into the cell nucleus and bind directly to specific nucleotide sequences of the chromosomal DNA. The areas of binding are called hormone response elements (HREs), and influence transcriptional activity of certain genes, producing the androgen effects.
Androgen receptors occur in many different vertebrate body system tissues, and both males and females respond similarly to similar levels. Greatly differing amounts of testosterone prenatally, at puberty, and throughout life account for a share of biological differences between males and females.
The bones and the brain are two important tissues in humans where the primary effect of testosterone is by way of aromatization to estradiol. In the bones, estradiol accelerates ossification of cartilage into bone, leading to closure of the epiphyses and conclusion of growth. In the central nervous system, testosterone is aromatized to estradiol. Estradiol rather than testosterone serves as the most important feedback signal to the hypothalamus (especially affecting LH secretion).[115] In many mammals, prenatal or perinatal "masculinization" of the sexually dimorphic areas of the brain by estradiol derived from testosterone programs later male sexual behavior.[116]
Neurosteroid activity[edit]
Testosterone, via its active metabolite 3α-androstanediol, is a potent positive allosteric modulator of the GABAA receptor.[117]
Testosterone has been found to act as an antagonist of the TrkA and p75NTR, receptors for the neurotrophin nerve growth factor (NGF), with high affinity (around 5 nM).[118][119][120] In contrast to testosterone, DHEA and DHEA sulfate have been found to act as high-affinity agonists of these receptors.[118][119][120]
Testosterone is an antagonist of the sigma σ1 receptor (Ki = 1,014 or 201 nM).[121] However, the concentrations of testosterone required for binding the receptor are far above even total circulating concentrations of testosterone in adult males (which range between 10 and 35 nM).[122]
Biochemistry[edit]
Human steroidogenesis, showing testosterone near bottom.[123]
Biosynthesis[edit]
Like other steroid hormones, testosterone is derived from cholesterol (see figure).[124] The first step in the biosynthesis involves the oxidative cleavage of the side-chain of cholesterol by cholesterol side-chain cleavage enzyme (P450scc, CYP11A1), a mitochondrial cytochrome P450 oxidase with the loss of six carbon atoms to give pregnenolone. In the next step, two additional carbon atoms are removed by the CYP17A1 (17α-hydroxylase/17,20-lyase) enzyme in the endoplasmic reticulum to yield a variety of C19 steroids.[125] In addition, the 3β-hydroxyl group is oxidized by 3β-hydroxysteroid dehydrogenase to produce androstenedione. In the final and rate limiting step, the C17 keto group androstenedione is reduced by 17β-hydroxysteroid dehydrogenase to yield testosterone.
The largest amounts of testosterone (>95%) are produced by the testes in men,[2] while the adrenal glands account for most of the remainder. Testosterone is also synthesized in far smaller total quantities in women by the adrenal glands, thecal cells of the ovaries, and, during pregnancy, by the placenta.[126] In the testes, testosterone is produced by the Leydig cells.[127] The male generative glands also contain Sertoli cells, which require testosterone for spermatogenesis. Like most hormones, testosterone is supplied to target tissues in the blood where much of it is transported bound to a specific plasma protein, sex hormone-binding globulin (SHBG).
Regulation[edit]
Hypothalamic–pituitary–testicular axis
In males, testosterone is synthesized primarily in Leydig cells. The number of Leydig cells in turn is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In addition, the amount of testosterone produced by existing Leydig cells is under the control of LH, which regulates the expression of 17β-hydroxysteroid dehydrogenase.[128]
The amount of testosterone synthesized is regulated by the hypothalamic–pituitary–testicular axis (see figure to the right).[129] When testosterone levels are low, gonadotropin-releasing hormone (GnRH) is released by the hypothalamus, which in turn stimulates the pituitary gland to release FSH and LH. These latter two hormones stimulate the testis to synthesize testosterone. Finally, increasing levels of testosterone through a negative feedback loop act on the hypothalamus and pituitary to inhibit the release of GnRH and FSH/LH, respectively.
Factors affecting testosterone levels may include:
Age: Testosterone levels gradually reduce as men age.[130][131] This effect is sometimes referred to as andropause or late-onset hypogonadism.[132]
Exercise: Resistance training increases testosterone levels,[133] however, in older men, that increase can be avoided by protein ingestion.[134] Endurance training in men may lead to lower testosterone levels.[135]
Nutrients: Vitamin A deficiency may lead to sub-optimal plasma testosterone levels.[136] The secosteroid vitamin D in levels of 400–1000 IU/d (10–25 µg/d) raises testosterone levels.[137] Zinc deficiency lowers testosterone levels[138] but over-supplementation has no effect on serum testosterone.[139]
Weight loss: Reduction in weight may result in an increase in testosterone levels. Fat cells synthesize the enzyme aromatase, which converts testosterone, the male sex hormone, into estradiol, the female sex hormone.[140] However no clear association between body mass index and testosterone levels has been found.[141]
Miscellaneous: Sleep: (REM sleep) increases nocturnal testosterone levels.[142] Behavior: Dominance challenges can, in some cases, stimulate increased testosterone release in men.[143] Drugs: Natural or man-made antiandrogens including spearmint tea reduce testosterone levels.[144][145][146] Licorice can decrease the production of testosterone and this effect is greater in females.[147]
Distribution[edit]
The plasma protein binding of testosterone is 98.0 to 98.5%, with 1.5 to 2.0% free or unbound.[148] It is bound 65% to sex hormone-binding globulin (SHBG) and 33% bound weakly to albumin.[149]
Plasma protein binding of testosterone and dihydrotestosterone show
Metabolism[edit]
vte Testosterone metabolism in humans
Testosterone structures
The image above contains clickable linksTestosterone metabolism in humans. Conjugation (sulfation and glucuronidation) occurs both with testosterone and with all of the other steroids that have one or more available hydroxyl (-OH) groups in this diagram.
Both testosterone and 5α-DHT are metabolized mainly in the liver.[1][151] Approximately 50% of testosterone is metabolized via conjugation into testosterone glucuronide and to a lesser extent testosterone sulfate by glucuronosyltransferases and sulfotransferases, respectively.[1] An additional 40% of testosterone is metabolized in equal proportions into the 17-ketosteroids androsterone and etiocholanolone via the combined actions of 5α- and 5β-reductases, 3α-hydroxysteroid dehydrogenase, and 17β-HSD, in that order.[1][151][152] Androsterone and etiocholanolone are then glucuronidated and to a lesser extent sulfated similarly to testosterone.[1][151] The conjugates of testosterone and its hepatic metabolites are released from the liver into circulation and excreted in the urine and bile.[1][151][152] Only a small fraction (2%) of testosterone is excreted unchanged in the urine.[151]
In the hepatic 17-ketosteroid pathway of testosterone metabolism, testosterone is converted in the liver by 5α-reductase and 5β-reductase into 5α-DHT and the inactive 5β-DHT, respectively.[1][151] Then, 5α-DHT and 5β-DHT are converted by 3α-HSD into 3α-androstanediol and 3α-etiocholanediol, respectively.[1][151] Subsequently, 3α-androstanediol and 3α-etiocholanediol are converted by 17β-HSD into androsterone and etiocholanolone, which is followed by their conjugation and excretion.[1][151] 3β-Androstanediol and 3β-etiocholanediol can also be formed in this pathway when 5α-DHT and 5β-DHT are acted upon by 3β-HSD instead of 3α-HSD, respectively, and they can then be transformed into epiandrosterone and epietiocholanolone, respectively.[153][154] A small portion of approximately 3% of testosterone is reversibly converted in the liver into androstenedione by 17β-HSD.[152]
In addition to conjugation and the 17-ketosteroid pathway, testosterone can also be hydroxylated and oxidized in the liver by cytochrome P450 enzymes, including CYP3A4, CYP3A5, CYP2C9, CYP2C19, and CYP2D6.[155] 6β-Hydroxylation and to a lesser extent 16β-hydroxylation are the major transformations.[155] The 6β-hydroxylation of testosterone is catalyzed mainly by CYP3A4 and to a lesser extent CYP3A5 and is responsible for 75 to 80% of cytochrome P450-mediated testosterone metabolism.[155] In addition to 6β- and 16β-hydroxytestosterone, 1β-, 2α/β-, 11β-, and 15β-hydroxytestosterone are also formed as minor metabolites.[155][156] Certain cytochrome P450 enzymes such as CYP2C9 and CYP2C19 can also oxidize testosterone at the C17 position to form androstenedione.[155]
Two of the immediate metabolites of testosterone, 5α-DHT and estradiol, are biologically important and can be formed both in the liver and in extrahepatic tissues.[151] Approximately 5 to 7% of testosterone is converted by 5α-reductase into 5α-DHT, with circulating levels of 5α-DHT about 10% of those of testosterone, and approximately 0.3% of testosterone is converted into estradiol by aromatase.[2][151][157][158] 5α-Reductase is highly expressed in the male reproductive organs (including the prostate gland, seminal vesicles, and epididymides),[159] skin, hair follicles, and brain[160] and aromatase is highly expressed in adipose tissue, bone, and the brain.[161][162] As much as 90% of testosterone is converted into 5α-DHT in so-called androgenic tissues with high 5α-reductase expression,[152] and due to the several-fold greater potency of 5α-DHT as an AR agonist relative to testosterone,[163] it has been estimated that the effects of testosterone are potentiated 2- to 3-fold in such tissues.[164]
Levels[edit]
Total levels of testosterone in the body are 264 to 916 ng/dL in men age 19 to 39 years,[165] while mean testosterone levels in adult men have been reported as 630 ng/dL.[166] Levels of testosterone in men decline with age.[165] In women, mean levels of total testosterone have been reported to be 32.6 ng/dL.[167][168] In women with hyperandrogenism, mean levels of total testosterone have been reported to be 62.1 ng/dL.[167][168]
Testosterone levels in males and females show
Total testosterone levels in males throughout life show
Reference ranges for blood tests, showing adult male testosterone levels in light blue at center-left.
Measurement[edit]
Testosterone’s bioavailable concentration is commonly determined using the Vermeulen calculation or more precisely using the modified Vermeulen method,[174][175] which considers the dimeric form of sex-hormone-binding-globulin.[176]
Both methods use chemical equilibrium to derive the concentration of bioavailable testosterone: in circulation testosterone has two major binding partners, albumin (weakly bound) and sex-hormone-binding-globulin (strongly bound). These methods are described in detail in the accompanying figure.
Dimeric sex-hormone-binding-globulin with its testosterone ligands
Two methods for determining concentration of bioavailable testosterone.
History[edit]
A testicular action was linked to circulating blood fractions – now understood to be a family of androgenic hormones – in the early work on castration and testicular transplantation in fowl by Arnold Adolph Berthold (1803–1861).[177] Research on the action of testosterone received a brief boost in 1889, when the Harvard professor Charles-Édouard Brown-Séquard (1817–1894), then in Paris, self-injected subcutaneously a "rejuvenating elixir" consisting of an extract of dog and guinea pig testicle. He reported in The Lancet that his vigor and feeling of well-being were markedly restored but the effects were transient,[178] and Brown-Séquard's hopes for the compound were dashed. Suffering the ridicule of his colleagues, he abandoned his work on the mechanisms and effects of androgens in human beings.
In 1927, the University of Chicago's Professor of Physiologic Chemistry, Fred C. Koch, established easy access to a large source of bovine testicles — the Chicago stockyards — and recruited students willing to endure the tedious work of extracting their isolates. In that year, Koch and his student, Lemuel McGee, derived 20 mg of a substance from a supply of 40 pounds of bovine testicles that, when administered to castrated roosters, pigs and rats, remasculinized them.[179] The group of Ernst Laqueur at the University of Amsterdam purified testosterone from bovine testicles in a similar manner in 1934, but isolation of the hormone from animal tissues in amounts permitting serious study in humans was not feasible until three European pharmaceutical giants—Schering (Berlin, Germany), Organon (Oss, Netherlands) and Ciba (Basel, Switzerland)—began full-scale steroid research and development programs in the 1930s.
Nobel Prize winner, Leopold Ruzicka of Ciba, a pharmaceutical industry giant that synthesized testosterone.
The Organon group in the Netherlands were the first to isolate the hormone, identified in a May 1935 paper "On Crystalline Male Hormone from Testicles (Testosterone)".[180] They named the hormone testosterone, from the stems of testicle and sterol, and the suffix of ketone. The structure was worked out by Schering's Adolf Butenandt, at the Chemisches Institut of Technical University in Gdańsk.[181][182]
The chemical synthesis of testosterone from cholesterol was achieved in August that year by Butenandt and Hanisch.[183] Only a week later, the Ciba group in Zurich, Leopold Ruzicka (1887–1976) and A. Wettstein, published their synthesis of testosterone.[184] These independent partial syntheses of testosterone from a cholesterol base earned both Butenandt and Ruzicka the joint 1939 Nobel Prize in Chemistry.[182][185] Testosterone was identified as 17β-hydroxyandrost-4-en-3-one (C19H28O2), a solid polycyclic alcohol with a hydroxyl group at the 17th carbon atom. This also made it obvious that additional modifications on the synthesized testosterone could be made, i.e., esterification and alkylation.
The partial synthesis in the 1930s of abundant, potent testosterone esters permitted the characterization of the hormone's effects, so that Kochakian and Murlin (1936) were able to show that testosterone raised nitrogen retention (a mechanism central to anabolism) in the dog, after which Allan Kenyon's group[186] was able to demonstrate both anabolic and androgenic effects of testosterone propionate in eunuchoidal men, boys, and women. The period of the early 1930s to the 1950s has been called "The Golden Age of Steroid Chemistry",[187] and work during this period progressed quickly. Research in this golden age proved that this newly synthesized compound—testosterone—or rather family of compounds (for many derivatives were developed from 1940 to 1960), was a potent multiplier of muscle, strength, and well-being.[188]
Other animals[edit]
Testosterone is observed in most vertebrates. Testosterone and the classical nuclear androgen receptor first appeared in gnathostomes (jawed vertebrates).[189] Agnathans (jawless vertebrates) such as lampreys do not produce testosterone but instead use androstenedione as a male sex hormone.[190] Fish make a slightly different form called 11-ketotestosterone.[191] Its counterpart in insects is ecdysone.[192] The presence of these ubiquitous steroids in a wide range of animals suggest that sex hormones have an ancient evolutionary history.[193]
This series of 4 photos show basically how to fry a turkey. This one is the raw turkey injected with butter and cajun seasoning.
21st Annual Gilmore Heritage Auto Show
A few cars from the Odd Squad CC & friends crashed the Gilmore Heritage show injecting a dose of much needed low-brow aesthetic to the event.
A Leopard 2A4 tank from Lord Strathcona’s Horse (Royal Canadians) drives on a black track during EXERCISE MAPLE RESOLVE 21 in the 3rd Canadian Division Support Base Garrison Wainwright Training Area, Alberta on May 6, 2021.
Photo By: Sailor First Class Camden Scott,
Directorate of Army Public Affairs
20210506LFC0010D47
From May 1 to 11, 2021, about 2500 Canadian Armed Forces members are participating in Exercise MAPLE RESOLVE 21 in Wainwright, Alberta. As the premier annual Canadian Army field training event, Ex MAPLE RESOLVE tests soldier skills and abilities within a realistic, complex, and challenging combat environment.
Du 1er au 11 mai 2021, environ 2 500 membres des Forces armées canadiennes participent à l'exercice MAPLE RESOLVE 21 à Wainwright, en Alberta. En tant que principal événement d'entraînement annuel sur le terrain de l'Armée canadienne, l'exercice MAPLE RESOLVE teste les capacités des soldats dans un environnement de combat réaliste, complexe et stimulant.
In a rare glint of light, The fireman of Riddles BR Standard 5 73156 get the injector on as its train rounds Kinchley Lane bound for Leicester North
ma79lt topic loool ,,
ALL BY : ME
[ without edit bs el nickname oOo el border]
Hope you like it =)
* seen on EXPLORE
A Leopard 2A4 tank from Lord Strathcona’s Horse (Royal Canadians) drives on a black track during EXERCISE MAPLE RESOLVE 21 in the 3rd Canadian Division Support Base Garrison Wainwright Training Area, Alberta on May 6, 2021.
Photo By: Sailor First Class Camden Scott,
Directorate of Army Public Affairs
20210506LFC0010D46
From May 1 to 11, 2021, about 2500 Canadian Armed Forces members are participating in Exercise MAPLE RESOLVE 21 in Wainwright, Alberta. As the premier annual Canadian Army field training event, Ex MAPLE RESOLVE tests soldier skills and abilities within a realistic, complex, and challenging combat environment.
Du 1er au 11 mai 2021, environ 2 500 membres des Forces armées canadiennes participent à l'exercice MAPLE RESOLVE 21 à Wainwright, en Alberta. En tant que principal événement d'entraînement annuel sur le terrain de l'Armée canadienne, l'exercice MAPLE RESOLVE teste les capacités des soldats dans un environnement de combat réaliste, complexe et stimulant.
injecting myself into the scene a la hitchcock... the henna is real - i layered a sepia tone copy over a full color copy then erased where the henna was.
Here is a link to a very good information source on Schick injector razors - www.safetyrazors.net/schick/schicktech.htm
The 1957 Chevrolet got a more elaborate grille, twin spears were set in the hood, tail fins and tail lights were more pronounced.
2 and 4 door pillared sedans, 2 and 4 door hardtops, 2 and 4 door wagons and convertible.
Base 150 (single stainless steel side trim).
Mid spec 210 (dual stainless wedge at the rear, two tone cars got a contrasting colour within the wedge, along with the roof)
Delray; an upscale trim option on the 210.
Top spec Bel Air (same stainless steel trim as the 210 but a ribbed aluminium insert)
Nomad; 2 door wagon Bel Air
Up until 1968, Chevrolet Sedans were exported from Canada in Semi-Knock-down form and assembled at General Motors Holden in Australia and at Todd Motors in New Zealand.
Engine; 140hp 235 cu in 6 cyl, 162hp 265 cu in V8 and 185, 220, 270 or 283hp 283 cu in V8 (283hp was fuel injected)
Playing around with a syringe and needle with the macro lens. I'm used to being on the giving end for these, so seeing it like this is always a concern!
Bonhams , les grandes marques du monde au Grand Palais 2019
Châssis N° 30837S111365
Moteur N° 3111365 F0305RF
•V8 culbuté à soupapes en tête, 327 cid (5 358 cm3)
•Injection mécanique Rochester
•arbre à cames à culbuteurs
•Rare et recherché modèle « Fuelie »
•360 ch à 6 000 tr/min
•Transmission manuelle à 4 rapports
•Suspension indépendante à ressorts hélicoïdaux
•Suspension arrière indépendante à ressort à lames transversal
•Freins à tambour aux quatre roues
Le directeur du style GM, Bill Mitchell, avait engagé Peter Brock et Larry Shinoda pour l'habiller d'une carrosserie Sting Ray spécifique et immédiatement reconnaissable. Avec une ceinture de caisse profondément marquée sous les ailes joliment courbées, elle avait des phares escamotables actionnés électriquement qui préservait ses qualités aérodynamiques.
doté du moteur à culbuteurs L84 327/360 ch, de la transmission manuelle à 4 rapports M20, des roues en alliage à blocage central, d'une radio AM à chercheur de fréquence et du différentiel Posi-Traction 3,73:1.
Le bloc moteur est estampillé des numéros de châssis et de moteur conformes à la configuration du 327/360 ch à injection mécanique Rochester alimentée en air par un collecteur d'admission Winters « snowflake » (un flocon est gravé dans la fonte).
Malgré un surcoût de 430,40 $, les clients de Corvette 1963 achetèrent 2 610 L84, soit 12,1% de la production totale de la Corvette 1963, en principe équipée de la transmission manuelle à 4 rapports facturée, elle, 180,30 $.
A Leopard 2A4 tank from Lord Strathcona’s Horse (Royal Canadians) drives across a road during EXERCISE MAPLE RESOLVE 21 in the 3rd Canadian Division Support Base Garrison Wainwright Training Area, Alberta on May 6, 2021.
Photo By: Sailor First Class Camden Scott,
Directorate of Army Public Affairs
20210506LFC0010D43
From May 1 to 11, 2021, about 2500 Canadian Armed Forces members are participating in Exercise MAPLE RESOLVE 21 in Wainwright, Alberta. As the premier annual Canadian Army field training event, Ex MAPLE RESOLVE tests soldier skills and abilities within a realistic, complex, and challenging combat environment.
Du 1er au 11 mai 2021, environ 2 500 membres des Forces armées canadiennes participent à l'exercice MAPLE RESOLVE 21 à Wainwright, en Alberta. En tant que principal événement d'entraînement annuel sur le terrain de l'Armée canadienne, l'exercice MAPLE RESOLVE teste les capacités des soldats dans un environnement de combat réaliste, complexe et stimulant.
The latest Injector Dynamics "test mule" is this 2007 Ford Mustang Shelby GT500 in Grabber Orange. This 800+ HP beast is boosted by a Whipple supercharger, supported by Eibach remote-reservoir coilovers, and fitted with 19 inch Forgeline one piece forged monoblock GA1R wheels finished in Silver. See more at: www.forgeline.com/customer_gallery_view.php?cvk=792
The Main Injector tunnel, from a proton's perspective.
Initial blurring effect achieved with low ISO, an ND filter, and zooming the lens during a slow shutter speed. Additional radial blur added in Photoshop CS6.
Black.
The 1953-62 C1 Corvette, (often referred to as the solid-axle models), featured a fibreglass body and was available as a roadster only.
The '58 Corvette received a styling update, it was slightly longer and wider. Single headlights were replaced with quad, bumpers were larger front and rear, different tail lights and the side coves revised. The interior got a new dash with the instruments now in front of the driver, and a new console.
The 1958-60 Corvettes were very similar, exclusive to the 1958 model were hood louvers and the trunk had chrome strips running down its length, these items disappearing for the 1959/60 cars.
1958 engines; 245 or 270hp 283 cu in V8, fuel injected option (250 or 290hp)
This 1958 Roadster has the Auxillary Hardtop option, it was removable and came in the same colour as the body.
Bonhams , les grandes marques du monde au Grand Palais 2019
Châssis N° 30837S111365
Moteur N° 3111365 F0305RF
•V8 culbuté à soupapes en tête, 327 cid (5 358 cm3)
•Injection mécanique Rochester
•arbre à cames à culbuteurs
•Rare et recherché modèle « Fuelie »
•360 ch à 6 000 tr/min
•Transmission manuelle à 4 rapports
•Suspension indépendante à ressorts hélicoïdaux
•Suspension arrière indépendante à ressort à lames transversal
•Freins à tambour aux quatre roues
Le directeur du style GM, Bill Mitchell, avait engagé Peter Brock et Larry Shinoda pour l'habiller d'une carrosserie Sting Ray spécifique et immédiatement reconnaissable. Avec une ceinture de caisse profondément marquée sous les ailes joliment courbées, elle avait des phares escamotables actionnés électriquement qui préservait ses qualités aérodynamiques.
doté du moteur à culbuteurs L84 327/360 ch, de la transmission manuelle à 4 rapports M20, des roues en alliage à blocage central, d'une radio AM à chercheur de fréquence et du différentiel Posi-Traction 3,73:1.
Le bloc moteur est estampillé des numéros de châssis et de moteur conformes à la configuration du 327/360 ch à injection mécanique Rochester alimentée en air par un collecteur d'admission Winters « snowflake » (un flocon est gravé dans la fonte).
Malgré un surcoût de 430,40 $, les clients de Corvette 1963 achetèrent 2 610 L84, soit 12,1% de la production totale de la Corvette 1963, en principe équipée de la transmission manuelle à 4 rapports facturée, elle, 180,30 $.
Flower urchin -
The pedicellariae inject venom, not the spines. It's extremely painful and irritating
Learn more about the hazardous marine life of Okinawa.
okinawanaturephotography.com/hazardous-marine-life-in-oki...
Equipment: Nikon D500 60.0 mm f/2.8
Nauticam underwater housing
2 Sea & Sea YS-D2J Underwater Strobe
- -custom diffusor -
Light&Motion
- - - Sola red light 1200 and Sola 3800