Antirachitic

Antirachitic vitamin Antiredeposition agents Antirust additives Antiscaling additives Antiscorbutic vitamin Antiseize material Antisense agents Antisense DNA... 

In 1919, Huldschinski (8) realized that uv light cured rickets and impacted on its etiology. The uv light and codHver oil were found to be usehil in the treatment of the disease, and irradiation of food produced the same effect as irradiation of the animal. The link between irradiation and plant materials led to the conclusion that ergosterol was an antirachitic substance, and an extensive effort was made to characterize the chemistry of irradiated ergosterol. 

The observation that the uv spectmm of provitamin D changed with uv inradiation and also produced antirachitic activity led to the conclusion that vitamin D was derived from the provitamin. Windaus found the vitamin D2 formula to be isomeric with the provitamins. 

Irradiated ergosterol was found not to be as antirachitic in the chick as in the rat, whereas the chick could be protected by direct kradiation. The provitamin in cholesterol was shown not to be ergosterol. Rygh (14) in 1935 found that 1 rat unit of cod Hver oil was 100 times more potent in chicks than 1 rat unit of vitamin D2. Brockmann (15) in 1936, prepared the pure crystalline 3,5-dinitrobenzoate derivative of vitamin D obtained from tuna Hver oil... 

Ergosterol occurs in plants and yeast and is important as a precursor of vitamin D (Figure 14—18). When irradiated with ultraviolet Hght, it acquires antirachitic properties consequent to the opening of ring B. 

Edward Mellanby and the Antirachitic Factor. (With John Parascandola). Bull. Hist. Med., 51, 507-15 (1977). 

The vitamin and metabolic derivatives of a fat-soluble substance calciferol. These antirachitic vitamins are produced from A -unsaturated sterols upon irradiation with ultraviolet light. Population biologists have adduced strong evidence for the hypothesis that lighter skin color, the primary characteristic of race, is related to the lower solar radiance in northern climes. Vitamin D plays a central role in calcium metabolism, both in terms of... 

In 1918, Mellanby produced experimental rickets in dogs. In 1919, Huldschinsky ameliorated rachitic symptoms in children with ultraviolet radiation. Hess, in 1922, showed that liver oils contain the same antirachitic factor as sunlight In that same year, McCollum increased calcium deposition in rachitic rats with cod liver oil factor. In 1924. Steenbook and Hess demonstrated irradiated foods have antirachitic properties, It was in 1925 that McCollum named antirachitic factor as vitamin D. In 1931, Angus isolated crystalline vitamin D (calciferol). In 1936, Windaus isolated vitamin D3 (activated 7-dehydrocholesterol). 

Bioassay techniques involve testing rats on antirachitic qualities. An important physicochemical method involves reaction with antimony trichloride. 

On the positive side, there are photochemical reactions that are essential for human health. One of these is the formation of vitamin D (the antirachitic vitamin) by irradiation of ergosterol. This photochemical reaction is an electro-cyclic ring opening of the cyclohexadiene ring of ergosterol of the type described in Section 28-2D. The product, previtamin D2, subsequently rearranges thermally to vitamin D2 ... 

The stability of vitamin D in fats and oils corresponds to the stability of the fat itself, as described previously for vitamin A. Vitamin D is, however, more stable than vitamin A under comparable conditions. Once freed from the protection of the food matrix, vitamin D is susceptible to decomposition by oxygen and light. The vitamin is stable towards alkali, but under conditions of even mild acidity the molecule isomerizes to form the 5,6-trans and isotachysterol isomers, neither of which possesses any significant antirachitic activity (42). 

The chicken egg yolk, as deduced from its antirachitic activity, contains 1-2 pg of cholecal-ciferol and this can be raised further by increasing the intake of vitamin D3 of the laying hen (94). The concentration in yolk is 5-10 times higher than that of total vitamin D3 plus its metabolites in blood plasma of normal chickens and 50-100 times higher than the concentration in any other tissue (95). Consequently, the chicken egg yolk is a potent source of vitamin D3. 

Because several of the metabolites of vitamin D3 are biologically active, the molecular species of vitamin D3 which passes into the yolk cannot be determined just from measurement of antirachitic activity. Consequently, a reliable and sensitive method for determining the amount of the unchanged form of vitamin D3 would be extremely beneficial to those interested in the metabolism and other factors that influence the chicken to deposit vitamin D3 in... 

Sontag LW. 1938. Acute phosphorus poisoning in an infant resulting from an antirachitic preparation. Am J Dis Child 566 114-118. 

Vitamin D has been known for more than half a century to be a powerful antirachitic agent, necessary for the development of normal bone. However, and oddly enough, its primary and most direct effect in this tissue is the stimulation of bone resorption [36] leading to an increase in the circulating levels of calcium and phos-... 

Antioestrogenic at oestrogen response element level (VITD-R agonist) [antirachitic, promotes intestinal Ca2+ transport]... 

Hydroxylation yields VITD-R agonist 1,25-Dihydroxyvitamin D3 [antirachitic]... 

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