共查询到20条相似文献，搜索用时 15 毫秒
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John H. Relethford 《American journal of physical anthropology》1997,104(4):449-457
Previous studies of human skin color have shown a strong relationship between skin color and distance from the equator, which has been interpreted as a link between skin color, latitude, and the intensity of ultraviolet radiation. The underlying assumptions are that UV radiation is greatest at the equator and that it diminishes with increasing latitude to the same extent in both the Northern and Southern Hemispheres. The standard analysis of human skin color is based on these assumptions, such that skin color is assumed to be darkest at the equator, and the decrease of skin color with latitude is assumed to be the same in both hemispheres. A nonlinear piecewise regression model was developed to test these assumptions and applied to mean skin reflectance data from 102 male samples and 65 female samples from across the Old World. For both males and females, skin reflectance (%) is lowest at the equator (darkest skin). Among males, skin reflectance increases roughly 8.2% for every 10 degrees of latitude in the Northern Hemisphere but only 3.3% for every 10 degrees of latitude in the Southern Hemisphere. Among females, the corresponding numbers are 8.1% in the Northern Hemisphere and 4.7% in the Southern Hemisphere. These results indicate that human skin color is darker in the Southern Hemisphere than in the Northern Hemisphere at equivalent latitude. Recent research shows that UV radiation is higher in the Southern Hemisphere than in the Northern Hemisphere at similar latitude. This difference, relating to astronomical and climatic conditions, may have existed in the past at different times and perhaps influenced the evolution of human skin color. Am J Phys Anthropol 104:449–457, 1997. © 1997 Wiley-Liss, Inc. 相似文献
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Mark D. Lucock 《American journal of physical anthropology》2023,180(2):252-271
This review examines putative, yet likely critical evolutionary pressures contributing to human skin pigmentation and subsequently, depigmentation phenotypes. To achieve this, it provides a synthesis of ideas that frame contemporary thinking, without limiting the narrative to pigmentation genes alone. It examines how geography and hence the quality and quantity of UV exposure, pigmentation genes, diet-related genes, vitamins, anti-oxidant nutrients, and cultural practices intersect and interact to facilitate the evolution of human skin color. The article has a strong focus on the vitamin D-folate evolutionary model, with updates on the latest biophysical research findings to support this paradigm. This model is examined within a broad canvas that takes human expansion out of Africa and genetic architecture into account. A thorough discourse on the biology of melanization is provided (includes relationship to BH4 and DNA damage repair), with the relevance of this to the UV sensitivity of folate and UV photosynthesis of vitamin D explained in detail, including the relevance of these vitamins to reproductive success. It explores whether we might be able to predict vitamin-related gene polymorphisms that pivot metabolism to the prevailing UVR exposome within the vitamin D-folate evolutionary hypothesis context. This is discussed in terms of a primary adaptive phenotype (pigmentation/depigmentation), a secondary adaptive phenotype (flexible metabolic phenotype based on vitamin-related gene polymorphism profile), and a tertiary adaptive strategy (dietary anti-oxidants to support the secondary adaptive phenotype). Finally, alternative evolutionary models for pigmentation are discussed, as are challenges to future research in this area. 相似文献
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Janet Y. Uriu‐Adams Sarah G. Obican Carl L. Keen 《Birth defects research. Part C, Embryo today : reviews》2013,99(1):24-44
The essentiality of vitamin D for normal growth and development has been recognized for over 80 years, and vitamin D fortification programs have been in place in the United States for more than 70 years. Despite the above, vitamin D deficiency continues to be a common finding in certain population groups. Vitamin D deficiency has been suggested as a potential risk factor for the development of preeclampsia, and vitamin D deficiency during infancy and early childhood is associated with an increased risk for numerous skeletal disorders, as well as immunological and vascular abnormalities. Vitamin D deficiency can occur through multiple mechanisms including the consumption of diets low in this vitamin and inadequate exposure to environmental ultraviolet B rays. The potential value of vitamin D supplementation in high‐risk pregnancies and during infancy and early childhood is discussed. Currently, there is vigorous debate concerning what constitutes appropriate vitamin D intakes during early development as exemplified by differing recommendations from the Institute of Medicine Dietary Reference Intake report and recent recommendations by the Endocrine Society. As is discussed, a major issue that needs to be resolved is what key biological endpoint should be used when making vitamin D recommendations for the pregnant woman and her offspring. Birth Defects Research (Part C) 99:24–44, 2013. © 2013 Wiley Periodicals, Inc. 相似文献
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Kappelman J Alçiçek MC Kazanci N Schultz M Ozkul M Sen S 《American journal of physical anthropology》2008,135(1):110-116
Remains of fossil hominins from temperate regions of the Old World are rare across both time and space, but such specimens are necessary for understanding basic issues in human evolution including linkages between their adaptations and early migration patterns. We report here the remarkable circumstances surrounding the discovery of the first fossil hominin calvaria from Turkey. The specimen was found in the Denizli province of western Turkey and recovered from within a solid block of travertine stone as it was being sawed into tile-sized slabs for the commercial natural stone building market. The new specimen fills an important geographical and temporal gap and displays several anatomical features that are shared with other Middle Pleistocene hominins from both Africa and Asia attributed to Homo erectus. It also preserves an unusual pathology on the endocranial surface of the frontal bone that is consistent with a diagnosis of Leptomeningitis tuberculosa (TB), and this evidence represents the most ancient example of this disease known for a fossil human. TB is exacerbated in dark-skinned peoples living in northern latitudes by a vitamin D deficiency because of reduced levels of ultraviolet radiation (UVR). Evidence for TB in the new specimen supports the thesis that reduced UVR was one of the many climatic variables presenting an adaptive challenge to ancient hominins during their migration into the temperate regions of Europe and Asia. 相似文献
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Shinji Kakuda Kazuhisa Okada Hiroshi Eguchi Kazuya Takenouchi Wataru Hakamata Masaaki Kurihara Midori Takimoto‐Kamimura 《Acta Crystallographica. Section F, Structural Biology Communications》2008,64(11):970-973
Vitamin D receptor (VDR) is a ligand‐inducible hormone receptor that mediates 1α,25(OH)2D3 action, regulating calcium and phosphate metabolism, induces potent cell differentiation activity and has immunosuppressive effects. Analogues of 1α,25(OH)2D3 have been used clinically for some years. However, the risk of potential side effects limits the use of these substances. LG190178 is a novel nonsecosteroidal ligand for VDR. (2S)‐3‐[4‐(3‐{4‐[(2R)‐2‐hydroxy‐3,3‐dimethylbutoxy]‐3‐methylphenyl}pentan‐3‐yl)‐2‐methylphenoxy] propane‐1,2‐diol (YR301) is the only one of the four evaluated stereoisomers of LG190178 to have strong activity. To understand the strong activity of YR301, the crystal structure of YR301 complexed with the rat VDR ligand‐binding domain (VDR LBD) was solved at 2.0 Å resolution and compared with the structure of the VDR LBD–1α,25(OH)2D3 complex. YR301 and 1α,25(OH)2D3 share the same position and the diethylmethyl group occupies a similar space to the C and D rings of 1α,25(OH)2D3. YR301 has two characteristic hydroxyl groups which contribute to its potent activity. The first is 2′‐OH, which forms hydrogen bonds to the NE2 atoms of both His301 and His393. The other is 2‐OH, which interacts with Ser233 OG and Arg270 NH1. These two hydroxyl groups of YR301 correspond exactly to 25‐OH and 1‐OH, respectively, of 1α,25(OH)2D3. The terminal hydroxyl group (3‐OH) of YR301 is directly hydrogen bonded to Arg270 and also interacts indirectly with Tyr232 OH and the backbone NH of Asp144 via water molecules. Additional derivatization of the terminal hydroxyl group using the positions of the water molecules might be useful for the design of more potent compounds. 相似文献
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Shinji Kakuda Seiichi Ishizuka Hiroshi Eguchi Mathew T. Mizwicki Anthony W. Norman Midori Takimoto‐Kamimura 《Acta Crystallographica. Section D, Structural Biology》2010,66(8):918-926
TEI‐9647 antagonizes vitamin D receptor (VDR) mediated genomic actions of 1α,25(OH)2D3 in human cells but is agonistic in rodent cells. The presence of Cys403, Cys410 or of both residues in the C‐terminal region of human VDR (hVDR) results in antagonistic action of this compound. In the complexes of TEI‐9647 with wild‐type hVDR (hVDRwt) and H397F hVDR, TEI‐9647 functions as an antagonist and forms a covalent adduct with hVDR according to MALDI–TOF MS. The crystal structures of complexes of TEI‐9647 with rat VDR (rVDR), H305F hVDR and H305F/H397F hVDR showed that the agonistic activity of TEI‐9647 is caused by a hydrogen‐bond interaction with His397 or Phe397 located in helix 11. Both biological activity assays and the crystal structure of H305F hVDR complexed with TEI‐9647 showed that the interaction between His305 and TEI‐9647 is crucial for antagonist activity. This study indicates the following stepwise mechanism for TEI‐9647 antagonism. Firstly, TEI‐9647 forms hydrogen bonds to His305, which promote conformational changes in hVDR and draw Cys403 or Cys410 towards the ligand. This is followed by the formation of a 1,4‐Michael addition adduct between the thiol (–SH) group of Cys403 or Cys410 and the exo‐methylene group of TEI‐9647. 相似文献
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Although many studies have examined the mechanisms of 1,25-dihydroxyvitamin D(3) (calcitriol or 1,25 D) action in different prostate cancer cell lines, little is known regarding the influence of this steroid on the normal prostate. The presence of both VDR and AR in normal prostatic tissues raises the distinct possibility of an important role for this hormone in the normal gland. In order to ascertain the possible role of 1,25 D on both AR and VDR in the normal prostate, the effects of calcitriol and dihydrotestosterone (DHT) on the normal human neonatal prostatic epithelial cell line, 267B-1, were examined. These studies were approached by focusing on how 1,25 D in the presence or absence of DHT affects the distribution of AR and VDR in the cytoplasmic and nuclear compartments of the cells in terms of their protein levels and DNA binding activities. Immunoblot analyses show that 1,25 D increases the AR protein level in both the cytoplasmic and nuclear fractions but not the VDR protein level. On the other hand, the gel shift assays demonstrate that 1,25 D increases both the AR- and VDR-DNA binding activities in the nuclear fraction, whereas there is no increase in DNA binding activities in the cytoplasmic fraction. Addition of DHT along with 1,25 D does not affect the DNA binding activities of both AR and VDR. Overall, these studies suggest that 1,25 D actions on the normal prostate cells may be mediated independently through AR and VDR, respectively. 相似文献
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Ali Assi;Rime Michael-Jubeli;Hélène Duplan;Arlette Baillet-Guffroy;Ali Tfayli;Carine Jacques-Jamin; 《Journal of biophotonics》2024,17(8):e202400107
The skin surface lipids (SSLs) film, composed of sebum and keratinocyte membrane lipids, is crucial to the barrier function of the stratum corneum (SC). The first part of this study investigated the impact of solar radiation on the SC based on a novel hydration and dehydration approach using Raman spectroscopy. The SSLs were found to absorb solar light, and thus participate to the protection of the skin surface. However, the protective function of the SSLs may be limited and is dependent to the heterogenous distribution of SSLs over the body surface. To ensure comprehensive protection, synergistic measures such as the application of solar filters are necessary. In this second part of the study, we have evaluated the limits of the protection capacity of SSLs and explored the protective action of a solar filters on both SSLs composition and the water hydration and dehydration kinetics in the SC. 相似文献
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Indolyl-3-butyric acid and vitamin D3 enhance adventitious root formation in green cuttings of Populus tremula L. A significant synergistic effect is observed between these two substances. The number of roots formed on application of the individual substances and on simultaneous application depends on the growth substance concentration, the timing of application, the age of the cuttings and the number of leaves. Of the vitamin D3 animal metabolites tested, only 1,25-dihydroxyvitamin D3 markedly promoted adventitious rooting, and this to a lesser extent than vitamin D3 itself. The 3-O-glucopyranosides of vitamin D3 and the vitamin D3 animal metabolites, promoted rooting to the same extent as the parent compounds. 相似文献
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Eldecalcitol [1α,25‐dihydroxy‐2β‐(3‐hydroxypropyloxy)vitamin D3], a vitamin D analog with enhanced efficacy for treatment of osteoporosis, has been found to be less potent than 1,25‐dihydroxyvitamin D3 (calcitriol) in suppressing PTH in vivo. To define the mechanism for the latter observation, we compared the effects of eldecalcitol and calcitriol on PTH secretion by bovine parathyroid cells. While the two compounds showed similar potency when the cells were cultured in medium containing 15% newborn calf serum, eldecalcitol was 100 times more potent than calcitriol in the absence of serum. Eldecalcitol has a higher affinity for the serum vitamin D‐binding protein (DBP), and therefore binding to DBP, and possibly other serum components, appears to limit the uptake and activity of eldecalcitol in parathyroid cells, providing an explanation for the lower PTH suppressing activity in vivo (100% serum). However, the 100‐fold higher activity of eldecalcitol in the absence of serum was unexpected since the VDR affinity for eldecalcitol is eightfold lower than for calcitriol. The enhanced activity was not due to preferential uptake, but to a resistance to metabolism. While 1 nM [3H]calcitriol was completely degraded within 24 h, [3H]eldecalcitol was not metabolized, despite the induction of the vitamin D catabolic enzyme, 24‐hydroxylase (CYP24A). The resistance to metabolism is the likely explanation for the higher potency of eldecalcitol in suppressing PTH in cell culture lacking serum. Thus, the unique properties of eldecalcitol in vivo can be attributed, at least in part, to its high‐DBP affinity which increases the half‐life, but limits the uptake of eldecalcitol, and to its reduced metabolism, which prolongs the activity of this analog in target tissues. J. Cell. Biochem. 112: 1348–1352, 2011. © 2011 Wiley‐Liss, Inc. 相似文献
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John H. Relethford 《American journal of physical anthropology》2009,139(1):16-22
Phenotypic traits have been used for centuries for the purpose of racial classification. Developments in quantitative population genetics have allowed global comparison of patterns of phenotypic variation with patterns of variation in classical genetic markers and DNA markers. Human skin color shows a high degree of variation among geographic regions, typical of traits that show extensive natural selection. Even given this high level of geographic differentiation, skin color variation is clinal and is not well described by discrete racial categories. Craniometric traits show a level of among-region differentiation comparable to genetic markers, with high levels of variation within populations as well as a correlation between phenotypic and geographic distance. Craniometric variation is geographically structured, allowing high levels of classification accuracy when comparing crania from different parts of the world. Nonetheless, the boundaries in global variation are not abrupt and do not fit a strict view of the race concept; the number of races and the cutoffs used to define them are arbitrary. The race concept is at best a crude first-order approximation to the geographically structured phenotypic variation in the human species. Am J Phys Anthropol 2009. © 2009 Wiley-Liss, Inc. 相似文献