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| | Judging and jury scandals in gymnastics and equestrian, as well as the doping issue - featuring prominently again on Wednesday - leading to 'wrong' medal ceremonies are not doing the Olympic image good.
Although the doping issue has been prominent throughout the Games, International Olympic Committee spokeswoman Giselle Davies warned not to blow the doping issue out of proportion.
Steroids - a class of organic compounds, belonging to isoprenoids with respect to chemical nature. Various kinds of steroids are widely spread in wildlife and are also found in microorganisms, plants and animals; one of the basic directions of the chemical evolution of steroids is their specialization as biological regulators — hormones etc.
Formally, all the steroids are derivatives of the hypothetical hydrocarbon of sterane (I, R =H) and bio-genetically occur from squalene, which transforms into the closest polycyclic predecessors of steroids— lanosterol (in animals) or cycloartenol (plants), containing 30 atoms of carbon (C30). Almost all the steroids are crystallic substances, possessing an optic activity and are better soluble in organic solvents than in water.
The classification of steroids is based on their chemical structure and nature of the physiological effect or function, which allows dividing them into the following groups. 1) Sterols, containing branched sided chains of R from 8—10 atoms of carbon. Sterols are part of animal and vegetative lipids; important steroids amongst sterols are cholesterol, which participates in the biosynthesis of steroids and hormones. 2) D Vitamins: Unsaturated isomers of sterols (with the open ring B) and participate in the regulation of calcium metabolism and the formation of the skeleton in vertebrates.3) Bile alcohols and bile acids, containing hydroxyl or the carboxyl group in the side ring (of 8 or 5 carbon atoms); Help in food digestion in the intestines in vertebrates. 4) Aglycones (Genins) are the steroid saponins and steroid glycoalkaloids. Diosgenin (II, Х=О) and solasodin (II, Х == NH) are typical representatives of aglycones; both groups are characteristic for plants of the lily, figwort and solanaceous family and possess surface active and hemolytic properties in the form of glycosides. 5) Steroid alkaloids of other types: С27-alkaloids with a modified steroid skeleton, stimulating the reduction of cross-striated muscles; vegetative С21-alkaloids, possessing bactericidal and amebicidal effects and modified С21-alkaloids from the glands of amphibians (samandaron, batrachotoxin, etc.), being strong poisons of the central nervous system and cardio toxins. 6) Cardiac genins, containing the side ring in the form of unsaturated pentamerous (С23-cardenolides) or hexamerous (C24-bufadienolides) lactone cycle; possess the ability to bolster the reduction of the cardiac muscle by inhibiting the enzyme LTF-elements in the membranes of heart cells; cardenolides are found in many plants, bufadienolides — predominantly in the poison from the skin glands of toads. 7) Steroidal sexual hormones and their transformation products, defining the development and functioning of sexual system in animals. Progesterone and its related C-21 compounds, in which the side ring R contains two carbon atoms and also male sexual hormones — androgens, containing 19 carbon atoms and female sexual hormones —oestrogens, containing 18 carbon atoms; hydroxyl or carbonyl group is found inside the ring for androgens and oestrogens. All these belong to steroidal sexual hormones. 8) Hormones of the cortex of adrenal glands — corticosteroids (R = СОСН2ОН); regulate the balance of electrolytes and carbohydrate metabolism in the organism of vertebrates. They are close to steroids, some oxylisine antibiotics fusidic acid, cephalosporin P1 and other oxylisines.
The biosynthesis ability of steroids is most brightly expressed in higher vertebrates. Insects do not produce steroids and receive them through food, however, the molting function, which is vital for the insects, is controlled by a special variety of С27-sterols — ecdysones, the derivatives of progesterone that serve for a number of insect types as a means of chemical protection. In some lower-order mushrooms (Achlya, etc.), sexual reproduction is also induced by steroids. It can be possible that steroids take part in morphogenesis in vascular plants. The inhibitors of the biosynthesis of steroids disturb the reproduction of some mushrooms and flowering in higher-order plants.
The chemistry, biochemistry and physiological activity of steroids are intensively studied due to the great value of steroids in medicine, veterinary science and animal husbandry. The chemical and microbiological methods of the partial synthesis of steroid hormones from accessible natural raw materials (sterols, bile acids, saponins) and in the 60s and 70s of the 20th century, also methods of their full chemical synthesis from elementary initial substances are mastered in industry. The synthesis of “artificial” steroid hormones with specialized physiological actions (contraceptive, anabolic, etc.), in particular, fluorine-containing and nitrogen-containing analogues, acquire huge importance.
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