Growth hormones, description

The classical theory of electrophoretic migration has also been successfully applied to the description of the behaviour of human growth hormone peptides. According to the classical theory, the mobility (ju) of a peptide can be described by... 

EPO is used in blood doping to generate more red blood cells for carrying oxygen. It is particularly favored by endurance athletes to enhance their performance. Human growth hormone (hGH, see description in Section 4.5.2) is used to build up muscle and bone strength. Both EPO and hGH are banned in sports. 

The difficulties encountered in the analysis of short peptides are reflected by the paucity of publications describing the elucidation of the amino acid sequence of short peptides with the aid of volatile buffers. Such buffers have been employed by Niall et al. 3,54) for their investigations on lactogenic and growth hormone. However, a detailed description of the experimental conditions and the results obtained has yet to be awaited. 

Ilias, I., Vgontzas, A., Provata, A., and Mastorakos, G., Complexity and non-linear description of diurnal cortisol and growth hormone secretory patterns before and after sleep deprivation., Endocrine Regulations, Vol. 36, No. 2, 2002, pp. 63-72. 

Membrane-bound hormone receptors were detected in the late 1960s. The binding of insulin, glucagon, and epinephrine to isolated plasma membranes of the rat liver or to isolated fat cells and fat cell membranes has been reported (Tomasi et al., 1970 Rodbell et al., 1971 Cuatrecasas, 1971a,b Freychet et al., 1971 Dunnick and Marinetti, 1971). Species-specific interaction between growth hormones and erythrocyte membranes has been shown by Cambiaso et al. (1971). Lef-kowitz et al. (1971) have published a detailed description of the interaction of adrenocorticotropic hormone with its receptors in the adrenal cortex, which appears to be a membrane-associated interaction (Finn et al., 1972). The modes of action for polypeptide hormones and their receptors have been the subject of intense investigation, and a number of reviews on this subject have been published (Cuatrecasas, 1974 Kahn, 1975 Catt and Dufau, 1977). 

There are many natural and biological macromolecules that possess anticancer activity. Cytokines, topoisomerase inhibitors, monoclonal antibodies, thymic hormones, cell growth inhibitors, and enzymes have been used [68], They have been recently reviewed [59,69] and their detailed description is beyond the scope of this article. The main problems connected with the administration of such natural macromolecules is their short intravascular half-life, immunogenicity, and sometimes poor solubility. Their modification with synthetic macromolecules can dramatically increase their therapeutic potential as described below. 

The physiological functions of hormones have been broadly categorized into those that (1) affect growth and development, (2) exert homeostatic control of metabolic pathways, and (3) regulate the production, use, and storage of energy. The descriptions below illustrate examples of these functions and mechanisms of control of hormone secretion. 

Control of physiological responses often involves several hormones. In some systems, two or more hormones act in opposition to each other (e.g., insulin and glucagon in the regulation of blood glucose). In other control systems, several hormones act in information hierarchies. Section 16.4 begins with a description of the best-researched example of such a hierarchy, referred to as a hormone cascade mechanism. This is followed by a discussion of growth factors, specialized proteins that stimulate cell division in susceptible cells. 

The word hormone comes from the Greek word hormone, which means to spur on, to set in motion, or to excite to action. These phrases are all very descriptive of a hormone. Released by the endocrine glands, hormones are chemical messengers which travel via the blood to specific organs or tissues and direct such processes as growth, reproduction, metabolism and behavior. In the blood they exist in extremely small quantities millionths and billionths of a gram. Yet, their effects upon the body are profound, tis demonstrated by diseased conditions where there is an over-or under-secretion of some hormone. 

Apart from the mechanisms of coarse and fine control discussed above there occur in plants and animals rhythms of metabolic activity and extrinsic control mechanisms involving, in both plant and animals, hormones and, in animals only, nervous system control. The role of plant hormones in the control of growth and differentiation in plants is discussed in the next chapter. The present chapter concludes with a brief description of circadian rhythms of metabolic activity in plants and of a particular example of a timing reaction. 

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