Steroidogenesis pathway in fish

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The seven enzymes involved in the shikimate pathway are DAHP synthase , 3-dehydroquinate synthase , 3-dehydroquinate dehydratase , shikimate dehydrogenase , shikimate kinase , EPSP synthase , and chorismate synthase . The pathway starts with two substrates , phosphoenol pyruvate and erythrose-4-phosphate and ends with chorismate , a substrate for the three aromatic amino acids. The fifth enzyme involved is the shikimate kinase , an enzyme that catalyzes the ATP -dependent phosphorylation of shikimate to form shikimate 3-phosphate (shown in the figure below). [1] Shikimate 3-phosphate is then coupled with phosphoenol pyruvate to give 5-enolpyruvylshikimate-3-phosphate via the enzyme 5-enolpyruvylshikimate-3-phosphate (EPSP) synthase .

Reproductive status is regulated by nutritional feedback to the hypothalamus that controls GnRH and hence LH pulsatile output ( Miller et al ., 2007 ). Both leptin and insulin have been shown to be involved in the long-and short-term control of reproductive neuroendocrine function in several species, including sheep. Both insulin and leptin stimulates LH secretion ( Cunningham et al ., 1999 ; Adam et al ., 2003 ; Miller et al ., 2007 ). Miller et al . (2007) further hypothesized that GnRH/LH stimulation by increasing nutritional status is mediated by increased amounts of circulating leptin and insulin entering the brain, down-regulating hypothalamic expression of neuropeptide Y (NPY) and agouti-related peptide (AgRP) and up-regulating expression of proopiomelanocortin (POMC) and amphetamine-regulated transcript (CART). whereas GnRH/LH inhibition by decreasing nutritional status is mediated by decreased amounts of circulating leptin and insulin entering the brain, up-regulating hypothalamic NPY and AgRP expression and down-regulating POMC and CART expression. The GnRH/LH response to an increasing plane of nutrition appears to be mediated by changes in circulating insulin, which enters the hypothalamic CSF and stimulates reproductive neuroendocrine output by inhibiting NPY expression. The GnRH/LH response to a decreasing plane of nutrition appears to be mediated by changes in leptin signaling via increased leptin receptor expression, which inhibits reproductive neuroendocrine output by inhibiting melanocortin activity ( Miller et al ., 2007 ).

Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more [38] or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram. [39] [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography . [2] : 10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. [39]

Steroidogenesis pathway in fish

steroidogenesis pathway in fish

Steroid isolation , depending on context, is the isolation of chemical matter required for chemical structure elucidation, derivitzation or degradation chemistry, biological testing, and other research needs (generally milligrams to grams, but often more [38] or the isolation of "analytical quantities" of the substance of interest (where the focus is on identifying and quantifying the substance (for example, in biological tissue or fluid). The amount isolated depends on the analytical method, but is generally less than one microgram. [39] [ page needed ] The methods of isolation to achieve the two scales of product are distinct, but include extraction , precipitation, adsorption , chromatography , and crystallization . In both cases, the isolated substance is purified to chemical homogeneity; combined separation and analytical methods, such as LC-MS , are chosen to be "orthogonal"—achieving their separations based on distinct modes of interaction between substance and isolating matrix—to detect a single species in the pure sample. Structure determination refers to the methods to determine the chemical structure of an isolated pure steroid, using an evolving array of chemical and physical methods which have included NMR and small-molecule crystallography . [2] : 10–19 Methods of analysis overlap both of the above areas, emphasizing analytical methods to determining if a steroid is present in a mixture and determining its quantity. [39]

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