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Matti Narkia

Vitamin D effective ultraviolet wavelengths due to scattering in shade - ScienceDirect ... - 0 views

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    Vitamin D effective ultraviolet wavelengths due to scattering in shade.
    Turnbull DJ, Parisi AV, Kimlin MG.
    J Steroid Biochem Mol Biol. 2005 Sep;96(5):431-6. Epub 2005 Jul 6.
    PMID: 16005208
Matti Narkia

RANK ligand and TNF-{alpha} mediate acid-induced bone calcium efflux in vitro -- Frick ... - 0 views

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    Frick KK, LaPlante K, Bushinsky DA.
    RANK ligand and TNF-alpha mediate acid-induced bone calcium efflux in vitro.
    Am J Physiol Renal Physiol. 2005 Nov;289(5):F1005-11. Epub 2005 Jun 21.
    PMID: 15972386 [PubMed - indexed for MEDLINE
Matti Narkia

In vivo threshold for cutaneous synthesis of vitamin D3. - [J Lab Clin Med. 1989] - Pub... - 0 views

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    In vivo threshold for cutaneous synthesis of vitamin D3.
    Matsuoka LY, Wortsman J, Haddad JG, Hollis BW.
    J Lab Clin Med. 1989 Sep;114(3):301-5.
    PMID: 2549141
Matti Narkia

Regulation of cutaneous previtamin D3 photosynthesis in man: skin pigment is not an ess... - 0 views

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    Holick, M. F., MacLaughlin, J. A. & Doppelt, S. H. (1981)
    Factors that influence the cutaneous photosynthesis of previtamin D3. Science 211:590-593

    When human skin was exposed to simulated solar ultraviolet radiation, epidermal 7-dehydrocholesterol was converted to previtamin D3. During prolonged exposure to simulated solar ultraviolet radiation, the synthesis of previtamin D3 reached a plateau at about 10 to 15 percent of the original 7-dehydrocholesterol content, and previtamin D3 was photoisomerized to two biologically inert isomers, lumisterol3 and tachysterol3. Increases either in skin melanin concentration or in latitude necessitated increases in the exposure time to simulated solar ultraviolet radiation required to maximize the formation, but not the total content, of previtamin D3. In order of importance, the significant determinants limiting the cutaneous production of previtamin D3 are (i) photochemical regulation, (ii) pigmentation, and (iii) latitude.
Matti Narkia

Aging decreases the capacity of human skin to produce vitamin D3. - Journal of Clinical... - 0 views

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    Aging decreases the capacity of human skin to produce vitamin D3.
    MacLaughlin J, Holick MF.
    J Clin Invest. 1985 Oct;76(4):1536-8.
    PMID: 2997282
    doi:10.1172/JCI112134

    An evaluation of surgically obtained skin (age range, 8-92 yr) revealed that there is an age-dependent decrease in the epidermal concentrations of provitamin D3 (7-dehydrocholesterol). To ascertain that aging indeed decreased the capacity of human skin to produce vitamin D3, some of the skin samples were exposed to ultraviolet radiation and the content of previtamin D3 was determined in the epidermis and dermis. The epidermis in the young and older subjects was the major site for the formation of previtamin D3, accounting for greater than 80% of the total previtamin D3 that was produced in the skin. A comparison of the amount of previtamin D3 produced in the skin from the 8- and 18-yr-old subjects with the amount produced in the skin from the 77- and 82-yr-old subjects revealed that aging can decrease by greater than twofold the capacity of the skin to produce previtamin D3. Recognition of this difference may be extremely important for the elderly, who infrequently expose a small area of skin to sunlight and who depend on this exposure for their vitamin D nutritional needs.
Matti Narkia

Factors that Influence the Cutaneous Synthesis and Dietary Sources of Vitamin D - 0 views

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    Factors that influence the cutaneous synthesis and dietary sources of vitamin D.
    Chen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF.
    Arch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8.
    PMID: 17254541
    doi: 10.1016/j.abb.2006.12.017

    Vitamin D is rare in food. Among the vitamin D-rich food, oily fish are considered to be one of the best sources. Therefore, we analyzed the vitamin D content in several commonly consumed oily and non-oily fish. The data showed that farmed salmon had a mean content of vitamin D that was ~25% of the mean content found in wild caught salmon from Alaska, and that vitamin D2 was found in farmed salmon, but not in wild caught salmon. The results provide useful global guidelines for obtaining sufficient vitamin D3 by cutaneous synthesis and from dietary intake to prevent vitamin D deficiency and its health consequences.ensuing illness, especially, bone fractures in the elderly.
Matti Narkia

Vitamin D and skin physiology: a D-lightful story - JBMR Online - Journal of Bone and M... - 0 views

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    Vitamin D and skin physiology: a D-lightful story.
    Holick MF, Chen TC, Lu Z, Sauter E.
    J Bone Miner Res. 2007 Dec;22 Suppl 2:V28-33.
    PMID: 18290718
    doi: 10.1359/jbmr.07s211

    Very few foods naturally contain vitamin D, and those that do have a very variable vitamin D content. Recently it was observed that wild caught salmon had between 75% and 90% more vitamin D(3) compared with farmed salmon. The associations regarding increased risk of common deadly cancers, autoimmune diseases, infectious diseases, and cardiovascular disease with living at higher latitudes and being prone to vitamin D deficiency should alert all health care professionals about the importance of vitamin D for overall health and well being.

    Humans have depended on sunlight for their vitamin D requirement. The impact of season, time of day, and latitude on vitamin D synthesis is well documented.(2,3) We now report that altitude also has a dramatic influence on vitamin D3 production and that living at altitudes above 3500 m permits previtamin D3 production at a time when very little is produced at latitudes below 3400 m. It was surprising that, at 27° N in Agra (169 M), little previtamin D3 production was observed. However, there was significant air pollution that caused a haze over the city. It is likely the ozone and other UVB-absorbing pollutants in the air prevented the solar UVB photons from reaching the earth's surface to produce previtamin D3.
Matti Narkia

White Europeans evolved only '5,500 years ago' - Times Online - 0 views

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    White Europeans could have evolved as recently as 5,500 years ago, according to research which suggests that the early humans who populated Britain and Scandinavia had dark skins for millenniums.

    It was only when early humans gave up hunter-gathering and switched to farming about 5,500 years ago that white skin began to be favoured, say the researchers.

    This is because farmed food was deficient in vitamin D, a vital nutrient. Humans can make this in their skin when exposed to sunlight, but dark skin is much less efficient at it.
Matti Narkia

Factors that influence the cutaneous synthesis and dietary sources of vitamin D. - Scie... - 0 views

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    Factors that influence the cutaneous synthesis and dietary sources of vitamin D.\nChen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF.\nArch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8.\nPMID: 17254541\ndoi:10.1016/j.abb.2006.12.017\n
Matti Narkia

Factors that influence the cutaneous synthesis and dietary sources of vitamin D - Scien... - 0 views

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    Chen TC, Chimeh F, Lu Z, Mathieu J, Person KS, Zhang A, Kohn N, Martinello S, Berkowitz R, Holick MF.
    Factors that influence the cutaneous synthesis and dietary sources of vitamin D.
    Arch Biochem Biophys. 2007 Apr 15;460(2):213-7. Epub 2007 Jan 8.
    PMI
Matti Narkia

Vitamin D (Cholecalciferol, Calcitriol) - 0 views

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    Bioactive vitamin D or calcitriol is a steroid hormone that has long been known for its important role in regulating body levels of calcium and phosphorus, and in mineralization of bone. More recently, it has become clear that receptors for vitamin D are present in a wide variety of cells, and that this hormone has biologic effects which extend far beyond control of mineral metabolism.

    The active form of vitamin D binds to intracellular receptors that then function as transcription factors to modulate gene expression. Like the receptors for other steroid hormones and thyroid hormones, the vitamin D receptor has hormone-binding and DNA-binding domains. The vitamin D receptor forms a complex with another intracellular receptor, the retinoid-X receptor, and that heterodimer is what binds to DNA. In most cases studied, the effect is to activate transcription, but situations are also known in which vitamin D suppresses transcription.

    Each of the forms of vitamin D is hydrophobic, and is transported in blood bound to carrier proteins. The major carrier is called, appropriately, vitamin D-binding protein. The halflife of 25-hydroxycholecalciferol is several weeks, while that of 1,25-dihydroxycholecalciferol is only a few hours.

    The vitamin D receptor binds several forms of cholecalciferol. Its affinity for 1,25-dihydroxycholecalciferol is roughly 1000 times that for 25-hydroxycholecalciferol, which explains their relative biological potencies
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