Biochemistry and Physiology

Cholesterol is the major sterol in the body and occurs mainly as the nonesterified free form, which is a fundamental component of cell membranes and the precursor for steroid hormones and bile acids. Cholesteryl esters present in the tissues and plasma are mainly formed by cholesterol esterification with long chain fatty acids these cholesterol esters act as a storage pool. Most of the requirements for cholesterol are met by endogenous synthesis, mainly in the liver, with the exogenous supplementation from the diet. 

Fatty acids have a basic structure, R-COOH, and the important fatty acids have long chains with an even number of carbon atoms (C12-C20), which may be described as saturated (e.g., stearic acid, C18 l), monounsaturated (e.g., oleic acid, C18 2), and polysaturated (e.g., linoleic, C18 2, and linolenic, C18 3, acids). These long chain fatty acids are used to provide energy by beta-oxidation, which shortens the fatty acid by two carbon atoms with the production of acetyl CoA (known as the fatty acid spiral). 

Phospholipids have a glycerol backbone where one hydroxyl group is linked by a phosphodiester bond to an alcohol the other two hydroxyl groups are esterified with fatty acids. These phospholipids are a structural component of cell membranes with both a hydrophobic fatty acid domain and the hydrophilic domain of the phosphate group. 

Apolipoproteins are structural components of plasma lipoproteins, and they maintain the integrity of the lipoproteins through the interactions with the hydrophilic core and the surrounding aqueous environments. These apolipoproteins act as ligands for specific cell receptors and activators or inhibitors for enzymes involved in lipoprotein metabolism. There are at least 11 apolipoproteins, which differ in molecular mass (from 6.5 to 600 kDa) and amino-acid composition, and they form less than 2 g/L of normal plasma protein. The apolipoprotein classes are designated by letters of the alphabet—A, B, C, D, and E—and numerals for subclasses (e.g., apo C-II). 

The lipoproteins are macromolecules with varying complexes of lipids where the hydrophobic lipid portions—cholesterol esters and triglycerides—are localized at the core of the molecules. The amphipathic surface layers surrounding the core contain the apolipoproteins and phospholipids. The lipoproteins vary in size, density, lipid composition, and apolipoprotein constituents, and they ean be classihed by size, the flotation rate determined by ultracentrifugation, or their electrophoretic mobilities. Put simply, the density of a lipoprotein particle is determined by the relative amounts of lipid and protein contained in the particle. Chylomicrons and very low density lipoproteins have the highest lipid content and the lowest protein content thus, very excessive amounts of chylomicrons float on the surface of plasma. In descending order of size, the broad lipoprotein fractions (with their electrophoretic mobility) are 

Creatine is synthesized in the kidneys, liver, and pancreas by two enzymatically mediated reactions. In the first, transami-dation of arginine and glycine forms guanidinoacetic acid in the second, methylation of guanidinoacetic acid occurs with S-adenosylmethionine as the methyl donor. Creatine is then transported in blood to other organs, such as muscle and brain, where it is phosphorylated to phosphocreatine, a high-energy compound. 

Interconversion of phosphocreatine and creatine is a particular feature of the metabolic processes of muscle contraction. A proportion of the free creatine in muscle (thought to be between 1% and 2%/day) spontaneously and irreversibly converts to its anhydride waste product, creatinine. Thus the amount of creatinine produced each day is fairly constant and is related to the muscle mass (and body weight). In 

The clinical utility of creatinine measurement is discussed later in this chapter. 

Plasma creatinine is measured as a test of kidney function both chemical and enzymatic methods are used to measure 45,164,205 laboratories use adaptations of the same assay for measurements in both plasma and urine. 

Chemical Methods the Jaffe Reaction Most chemical methods for measuring creatinine are primarily based on the reaction with alkaline picrate. In this reaction, first described by Jaffe in 1886, creatinine reacts with picrate ion in an alkaline medium to yield an orange-red complex. Despite considerable literature on the subject, the reaction mechanism and the structure of the product remain unclear. 

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Inositol Phosphates Their Chemistry, Biochemistry and Physiology, by D.J. Cosgrove... 

C. R dSR, Biochemistry and Physiology of Herbicide Action, Spriuger-Vedag, New York, 1982. 

L. J. Eilet, Jr. and co-wotkets. Glutamic Acid Advances in Biochemistry and Physiology, Raven Press, New York, 1979. 

Rosenthal, H.L., Eves, M.M. and Cochran, O.A. 1970 Common strontium of mineralized tissues from marine and sweet water animals. Comparative Biochemistry and Physiology 32 445 50. 

Cannes, L.Z., Martinez del Rio, C., Koch, P. (1998). Natural abundance variations in stable isotopes and their potential uses in animal physiological ecology. Comparative Biochemistry and Physiology - Part A Molecular Integrative Physiology, Vol. 119, No. 3, pp. 725-737. (http //dx.doi.org/10.1016/S1095-6433(98)01016-2)... 

Walton, D.C. (1980). The biochemistry and physiology of abscisic acid. Annual Review of Plant Physiology, 31, 453-89. 

Abalis, I.M., Eldefrawi, M.E., and Eldefrawi, A.T. (1985). High affinity stereospecific binding of cyclodiene insecticides and gamma HCH to GABA receptors in rat brain. Pesticide Biochemistry and Physiology, 24, 95-102. 

Barse, A.V., Chakrabarti, T., Ghosh, T.K. et al. (2007). Endocrine disruption and metabolic changes following exposure of Cyprinus carpio to diethyl phthalate. Pesticide Biochemistry and Physiology 88, 36-42. 

Fleming, W.J. and Grue, C.E. (1981). Recovery of cholinesterase activity in 5 avian species exposed to dicrotophos, an organo-phosphorus pesticide. Pesticide Biochemistry and Physiology 16,129-135. 

Founmer, F., Karasow, W.H., and Kenow, K.P. et al. (2002). The oral availability and toxicokinetics of methyl mercury in common loon chicks. Comparative Biochemistry and Physiology, Part A 133, 703-714. 

Hetherington, L.H., Livingstone, D.R., and Walker, C.H. (1996). Two and one-electron dependant reductive metabolism of nitroaromatics by Mytilus edulis, Carcinus maenas and Asterias rubens. Comparative Biochemistry and Physiology 113, 231-239. 

Johnston, G.O, Walker, C.H., and Dawson, A. (1994). Potentiation of carbaryl toxicity to the hybrid red-legged partridge following exposure to malathion. Pesticide Biochemistry and Physiology 49, 198-208. 

Kadous, A.A, Ghiasuddin, S.M., and Matsumura, E. (1983). Differences in the picrotoxinin receptor between cyclodiene-resistant and susceptible strains of the German cockroach. Pesticide Biochemistry and Physiology 19, 157. 

Livingstone, D.R. and Stegeman, J.J. (Eds.) (1998). Forms and Functions of Cytochrome P450. Comparative Biochemistry and Physiology 121C (special issue), 1 12. 

Lundholm, E. (1987). Thinning of eggshells in birds by DDE mode of action on the eggshell gland. Comparative Biochemistry and Physiology 88C, 1-22. 

Mackness, M.I., Walker, C.H, Rowlands, D.G. et al. (1982). Esterase activity in homogenates of 3 strains of rust red flour beetle. Comparative Biochemistry and Physiology 74C, 65-68. 

Oppenoorth, E.J. and Welling, W. (1976). Biochemistry and Physiology of Resistance. In C.E. Wilkinson (Ed.) Pesticide Biochemistry and Physiology. London Heyden 507-554. 

Pilling, E.D., Bromley-ChaUenor, K.A.C., and Walker, C.H. et al. (1995). Mechanism of synergism between the pyrethroid insecticide lambda cyhalothrin and the imidazole fungicide prochloraz in the honeybee. Pesticide Biochemistry and Physiology 51, 1-11. 

Walker, C.H. and Jefferies, D.J. (1978). The post mortem reductive dechlorination of p,p -DDT in avian tissues. Pesticide Biochemistry and Physiology 9, 203-210. 

Watanuki, H., Yamaguchi, T., and Sakai, M. (2002). Suppression in function of phagocytic cells in common carp Cyprinus carpio L. injected with estradiol, progesterone or 11-ketotestosterone. Comparative Biochemistry and Physiology C—Toxicology and Pharmacology 132, 407 13. 

Takahama, U. Oniki, T. Enhancement of peroxidase-dependent oxidation of sinapyl alcohol hy esters of 4-coumaric and ferulic acid. In Plant Peroxidases, Biochemistry and Physiology Ohinger, C. Burner, U. Ebermann, R. Penel, C. Greppin, H., Eds. Universite de Geneve, Geneve Switzerland, 1996 pp. 118-123. 

Kushinsky, S. and Chen, V.L. (1967) The inhibition of/3-glucuronidase from bovine liver by 1,4-saccharolactone. Comparative Biochemistry and Physiology, 20, 535—542. 

Barrett, J., Ward, C.W. and Fairbairn, D. (1970) The glyoxylate cycle and the conversion of triglycerides to carbohydrates in developing eggs of Ascaris lumbricoides. Comparative Biochemistry and Physiology 35, 577-586. 

Saz, H.J. (1971) Anaerobic phosphorylation in Ascaris mitochondria and the effects of anthelmintics. Comparative Biochemistry and Physiology 39B, 627-637. 

Saz, H.J. and Lescure, O.L. (1966) Interrelationships between the carbohydrate and lipid metabolism of Ascaris lumbricoides egg and adult stages. Comparative Biochemistry and Physiology 18, 845-857. 

Smart, D.S., Shaw, C., Johnston, C.F., Halton, D.W., Fairweather, I. and Buchanan, K.D. (1992a) Chromatographic and immunological characterisation of immunoreactivity towards pancreatic polypeptide and neuropeptide Y in the nematode Ascaris suum. Comparative Biochemistry and Physiology 102C, 477—481. 

All-Union Scientific-Research Institute of Antibiotics Institute of Biochemistry and Physiology of Microorganisms, Academy of Sciences, Jpn. Kokai Pat. 80-102,580 (1980) [CA 94, 84156 (1981)]. 

Field P. A. (2001). Review Protein function at thermal extremes balancing stability and flexibility, Comparative Biochemistry and Physiology Part A 129 417-431. 

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