The Variety of Animal Forms

The aesthetic satisfaction to be derived from contemplating the mere variety of animal forms, and from tracing the order that runs through all its diversity, appeals to a very deep instinct in human nature. 

The pentose phosphate pathway is also known as the hexose monophosphate shunt and the phos-phogluconate pathway because of the variety of intermediates formed by the pathway under different conditons. The pathway which occurs in a wide variety of organisms including animals, plants and microorganisms is classihable as secondary metabolism (Section 10.5) due to the relatively small quantity of glucose catabolized by this route. In mammalian tissues, the pathway yields a number of important products, in particular, reduced nicotinamide adenine dinucleotide phosphate (NADPH) and pentose sugars. 

Heliantholysin. The major form of heliantholysin is a basic polypeptide chain (pi in the region of 9.8) having a molecular weight of 16,600. Its amino acid sequence has been determined (11). It is powerfully hemolytic for washed erythrocytes derived from a variety of animals, those of the cat being the most sensitive, and those of the guinea pig the most resistant (10). As is true of most hemolytic systems, the biochemical basis for the very large differences in sensitivity of erythrocytes from different animal species is unknown. 

This epoxidation of AFB has been associated with aldrin epoxidase (AE) activity in trout (30). As with other epoxide carcinogens, OAFB may be a substrate 7or epoxide metabolizing enzyme systems such as epoxide hydrase (EH) (EC4.2.1.63) and glutathione-S-epoxide transferase (GTr) (EC4.4.1.7) found in mammals and fish (31, 32, 33, 34). AFB also undergoes a variety of other reactions, generally to less toxic metabolites depending on the species of animal involved (35, 36). The primary AFB metabolite in rainbow trout has been shown to be a reduced form of AFB, aflatoxicol (AFL) (24). 

The malarial parasite is a single-cell protozoan (plas-modium). Although more than 100 species of plasmodia have been identified, only four are capable of infecting humans Plasmodium malariae, P. ovale, P. vivax, and P. falciparum) the rest attack a variety of animal hosts. P. falciparum and P. vivax malaria are the two most common forms. 

Valdes completed a variety of animal experiments in order to determine the psychoactivity of A divinorum, particularly salvinorin A. Homo sapiens were excluded as test subjects. Since salvinorin A is insoluble in water, he dissolved it in com oil and Tween-80, a surfactant. He then added water to form an emulsion which settled easily (23). 

Biological calcification processes are widely distributed in nature. They can be found in microorganisms, in plants, in the animal kingdom and in humans. Under physiological conditions, the results of mineral deposition in biological systems can be represented by the formation of bones, teeth and shell material as well as coccoliths, corals, pearls etc. The variety of biomineralisates can best be expressed by the fact that approximately 128,000 species of molluscs636 are known. The majority of them (Conchifera) form shells of different kinds of size and shape as well as of color. 

Little is known as to the biosynthesis and metabolism of plant dolichols. Nevertheless, this is an interesting field if the variety of polyprenols synthesized by plants (see Table I and Scheme 1), as compared with animals, is considered. The early knowledge on the stereochemistry of E, Z-polyprenol biosynthesis was obtained by Gough and Hemming63 with a plant system. They found that the 4-5 hydrogen atom of mevalonate is retained when a Z- double bond is formed, whereas this hydrogen atom is lost in the biosynthesis of an -double bond. The same authors found similar results for rat-liver dolichol.64 With this technique, [3H]dolichol was found in rat-liver mitochondria when the animals were injected with65 4-(S)-[3H]meval-... 

Because of the possible transmission of infectious diseases during the use of human blood samples, it is recommended that students use bovine, porcine, or other animal serum samples. Sera from a wide variety of animals, including humans, are available in a lyophilized form from Sigma Chemical Co. When reconstituted with water, these provide convenient unknowns. 

Among the variety of sulfate esters formed by living cells are the sulfate esters of phenolic and steroid compounds excreted by animals, sulfate polysaccharides, and simple esters, such as choline sulfate. The key intermediate in the formation of all of these compounds lias been shown to be 3 -phosphoadenosine-5/-phosphosulfate (PAPS). This nucleotide also serves as an intermediate in sulfate reduction. 

Phospholipids are found in all living cells and typically constitute about half of the mass of animal cell plasma membranes (Cevc, 1992). The reason forthe variety of membrane lipids might simply be that these amphiphilic structures have in common the ability to arrange as bilayers in an aqueous environment (Paltauf and Hermetter, 1990). Thus, the use of endogenous phospholipids to form vesicles as drug carriers may have much less adverse effects in patients compared to synthetic drui carrier molecules. 

Saponins appear to lower plasma LDL cholesterol concentration by interfering with cholesterol absorption. Studies in rats and monkeys fed naturally occurring saponins exhibited significant reductions in cholesterol absorption efficiency and an increase in fecal cholesterol excretion (Malinow et al., 1981 Nakamura et al., 1999 Sidhu et al., 1987). Decreased bile acid absorption and increased excretion has also been reported in animals fed saponins (Malinow et al., 1981 Nakamura et al., 1999 Stark and Madar, 1993). One possible mechanism of action for decreased cholesterol absorption is the ability of saponins to form insoluble complexes with cholesterol (Gestetner et al., 1972 Malinow et al., 1977). In an effort to isolate the specific properties of saponins, Malinow (1985) prepared a variety of synthetic saponins in which the complex carbohydrate moieties of native plant saponins were replaced with simplified carbohydrates such as glucose or cellobiose. One of these synthetic saponins, tiqueside (Pfizer, Inc.), can effectively precipitate cholesterol from micelle solutions in vitro and inhibit cholesterol absorption in a variety of animals (Harwood et al., 1993) and in humans (Harris et al., 1997). But despite ample data showing the formation of a saponin/cholesterol complex in vitro, there is essentially no definitive evidence that complexation occurs in the intestinal lumen (Morehouse et al., 1999). 

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