| This contest is fueled by the following news: |
| | Four Oakland Raiders football players - defensive tackle Dana Stubblefield, center Barret Robbins, linebacker Bill Romanowski and defensive tackle Chris Cooper - have tested positive for the newly discovered steroid THG (tetrahydrogestrinone) and face four-game suspensions.
Steroids are substances of animal or more often of plants, possessing high biological activity. Steroids are formed in nature from isoprenoid predecessors. Specialty of steroid structure is the presence of condensed tetracyclic system of gonane (former name - sterane). Nucleus of gonane in steroids can be saturated or partially unsaturated and contain alkyl and some functional groups – hydroxyl, carbonyl or carboxyl.
Steroid hormones participate in metabolic control of substances and several physiological functions of organism. Series of synthetic hormones, for example, prednisolone, due to the action of which on organism, natural analogues excel. Sterols of cholesterol and also bile acids – compounds, having carboxyl group in side chain, for example, cholic acid, which are present in the human organism, belong to steroids group.
Cardiac glycosides – vegetable substances (from digitalis, strophanthus, lily of the valley), regulating cardiac activity, belong to steroids. In glycosides, steroid fragment is connected by glycoside connection with oligosaccharide.
STEROIDS is a group of natural and synthetic chemical compounds – derivatives of partially or completely hydrogenated 1,2-cyclo pentene phenantrene type
Four articulated rings A, B, C, D are formed from 17 carbon atoms in molecular structure. Steroids occur widely in nature and they participate in realization of diversified biological functions. Sexual hormones, vitamin D, hormones of adrenal glands, bilious acids, molting hormone and metamorphosis of arthropods, repellents of insects, frightening off the predators and poison in skin of toads have steroid nature. Both natural and synthetic steroids, at similar structure, reveal highly distinguishing physiological action, therefore, they are widely used in medicine as anti-inflammatory, cardiac, contraceptives and other means.
Steroids are divided into sterols, bile acid, steroid hormones, steroidal saponins, cardiac glycosides and steroidal alkaloids (Also refer “ALKALOIDS”).
More often, steroids occur in the form of sterols, found practically in all plants, mushrooms and animals. Particularly, cholesterol, which is known to all, serves as initial substance for synthesis of all steroid hormones in organism. Cholesterol can be used for industrial manufacture of many steroids, however, it is more economically viable to use some readily available vegetative sterols (for example, stigmasterol from soybeans), having structural similarity with target steroids instead of cholesterol.
Steroidal sexual hormones are steroids, produced by sexual glands (testicles and ovaries) or influencing them. Androgens or male hormones, main of which is testosterone and female sexual hormones – estrogens and progestines (gestogens) belong to steroidal sexual hormones. Progestin, including progesterone, participates in preparation of uterus for pregnancy and help in maintenance of pregnancy. Synthetic progestines and estrogen are part of contraceptive tablets (Also refer “HORMONES”).
Thanks to its anabolic activity (occurring particularly in growth of muscular and bone tissues), all the androgens acquired bad popularity amongst sportsmen, for which, the word "steroid" began to mean male sexual hormones. However, ability of androgens, taken in large doses to improve the sports shape by increasing the force, endurance and muscular weight, remains subject of dispute. Moreover,excessive use of these steroids can lead to liver diseases and also other harmful side effects.
|
|
| | 10 Contest Pictures Page 1 - View All
|
|
