Vitamin thromboxane

Rats fed a purified nonlipid diet containing vitamins A and D exhibit a reduced growth rate and reproductive deficiency which may be cured by the addition of linoleic, a-linolenic, and arachidonic acids to the diet. These fatty acids are found in high concentrations in vegetable oils (Table 14-2) and in small amounts in animal carcasses. These essential fatty acids are required for prostaglandin, thromboxane, leukotriene, and lipoxin formation (see below), and they also have various other functions which are less well defined. Essential fatty acids are found in the stmctural lipids of the cell, often in the 2 position of phospholipids, and are concerned with the structural integrity of the mitochondrial membrane. 

Hall and Wolf [217] have proposed a hypothesis, concerning the pathogenesis of post-traumatic central nervous system ischaemia, which integrates an injury-induced rise in intracellular Ca2+, the increased synthesis of vasoactive prostanoids and progressive microvascular lipid peroxidation. The model used anaesthetised cats with a contusion injury to the lumbar spinal cord. Antioxidants, vitamin E and selenium, were compared with various Ca2 + antagonists, cyclo-oxygenase inhibitors, a thromboxane synthetase inhibitor and the stable prostacyclin analogue. The most impressive preservation of post-traumatic spinal cord blood flow was provided by the antioxidants. 

Coagulopathy is a common complication of liver disease. Synthesis of vitamin K and clotting factors is impaired in patients with cirrhosis and acute liver failure. Cirrhosis can also cause a reduced platelet synthesis of thromboxane-2, and a platelet adhesion defect is sometimes seen [8]. Cholestatic patients may have deranged clotting due to vitamin K malabsorption. 

Only niacin offers benefits in regard to newly determined, independent risk factors for the development and progression of heart disease and the incidence of heart attacks and strokes. It lowers levels of a particularly nasty variant of LDL termed lipoprotein(a). The vitamin improves the balance of the hormonelike substances called prostaglandins, with the detrimental thromboxane falling and the protective prostacycline going up. Activity of blood platelets, cells involved in the clotting process, decrease, resulting in fewer clots that can lead to heart attacks. 

Dietary fat serves several important nutritional functions. It is the source of essential fatty acids. Members of the n-6 and n-3 (also known as the co-6 and co-3) families of fatty acids are important constituents of cell membranes and serve as precursors of eicosanoids (biologically active compounds such as prostaglandins, thromboxanes, prostacyclins, and leukotrienes). Fat also serves as a carrier for the fat-soluble vitamins, and it is important source of energy. In addition, it has important culinary properties and contributes to the palatability of food. 

The stimulation of platelets to form a blood dot involves thromboxane production. The sequence of events resulting in the aggregation of platelets is summarized in Figure 9.100. The initial event of cell stimulation is the reaction of thrombin with the platelet surface, which provokes the release of arachidonic acid, as mentioned in the Vitamin K section. Arachidonic acid is converted to thromboxane A2. The TXAj, in turn, is released from the platelet. It travels a short distance, within the bloodstream, and binds to its receptor on the surface of nearby platelets. 

Embryemic development, see also Pregnancy cretinism, 737 neural tube defects, 314 prostaglandin F, 646 taurine, 103 thromboxane A, 646 transcription factors, 589 vitamin A. 565,5S9 zinc and, 813-814 Encephalocele, 514 Endocrine cells, 63,163 Endocytosis, 83,335 Endonuclease, 897 Endoplasmic nettculum (ER) alcohol catabolism in, 247 choline deficiency, 317 lipid digestion, 96 membrane-bound proteins, 40 polypeptide synthrais and transportation, 39-40... 

Thromboxane A2 Vitamin D Dietary Extreme cerebral vasoconstriction Cerebrovascular ischemia... 

The influence of fluorine on the physical, chemical and biological properties of molecules is described. A discussion of the effect of fluorination on bond lengths and bond strengths is presented in the course of an analysis of the steric demand of fluorinated substituents. These steric effects as well as electronic interactions are illustrated in a discussion of fluorinated vitamin D3 and prostaglandin and thromboxane analogs. 

Toivanen, J. L., 1987, Effects of selenium, vitamin E and vitamin C on human prostacyclin and thromboxane synthesis in vitro. Prostaglandins Leukotrienes Med. 26 265-280. 

Karpen, C. W., Cataland, S. D., Orisio, T. M., and Panakamala, R., 1984, Interaction of platelet vitamin E and thromboxane synthesis in type 1 diabetes mellitus. Diabetes 33 239-243. 

Patrignani, P, Panara, MR, Tacconelb, S, Seta, F, Bucciarelb, T, Ciabattoni, G, Alessandrini, P, Mezzetti, A, Santini, G, Sciulli, MG, Cipollone, F, Davi, G, Galbna, P, Bon, GB and Patrono, C (2000) Effects of vitamin E supplementation on Fj-isoprostane and thromboxane biosynthesis in healthy subjects. Circulation, 102, 539-545. 

Attempts to demonstrate disease-reduction benefit with respect to cardiovascular disease by selenium intervention have proven disappointing, despite the theoretical benefit of lipid peroxide removal by GPx and apparently beneficial changes in intermediate markers such as platelet aggregation, vasoconstriction, and thromboxane prostacyclin ratios following supplementation. Further studies of high-risk populations are needed, including a focus on the concerted action by combinations of selenium and vitamin E. 

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