previtamin

previtamin

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26) Oystercatchers may also display various physiologic mechanisms for controlling vitamin D metabolism, including inadequate cutaneous production, enhanced cutaneous destruction of previtamin [D.
Solar ultraviolet B photons are absorbed by 7-dehydrocholesterol in the skin, leading to its transformation to previtamin D3, which is rapidly converted to vitamin D3.
Solar radiation in the UVB waveband (wavelength, 290 to 315 nm) converts 7-dehydrocholesterol to previtamin D3 which is converted to vitamin D3 (1-5).
3] production occurs in human skin when ultraviolet B (UVB; 290-33 5 nrn) photons convert 7-dehydro-cholesterol, or provitamin D3, made by kera-tinocytes to previtamin [D.
The cutaneous photosynthesis of previtamin D3: A unique photoendocrine system.
Photosynthesis of previtamin D3 in human skin and the physiologic consequences.
Regulation of cutaneous previtamin D3 photosynthesis in man: skin pigment is not an essential regulator.
Under the influence of ultraviolet B (UVB) radiation, 7-dehydroxycholesterol in the skin is photoconverted to previtamin D3 (cholecalciferol).
Latitude: Sunlight converts 7-dehydocholesterol into previtamin D3, a precursor of vitamin D3 on the skin.
Given the increasing prevalence of diseases and health problems linked with low vitamin D levels, concern has been expressed in recent years that the widespread use of sunscreens, particularly those with high sun protection factors, may be one of the causative factors in this pattern, by leading to a significant decrease in solar induced previtamin D3 in the skin.
In the skin, sunlight converts a precursor of vitamin D to previtamin [D.