Variation in human hair ultrastructure among three biogeographic populations

Human scalp hairs are often examined microscopically to study the variation and diversity among a range of visible morphological traits. In this study, we focused on the ultrastructure of human scalp hair within its keratinized matrix, emphasizing, the density and distribution of melanosomes, variation in cuticle thickness within populations, and the relationship of hair fiber ultrastructure with biogeographic ancestry. We used transmission electron microscopy (TEM) to visualize hair cross-sections and generate micron-scale resolution images for analysis of particle morphology and the layered hair matrix. Our results revealed considerable variation in all parameters examined, including the relationship of ultrastructure to biogeographic ancestry. Among the three metapopulations studied (European, African, and East Asian), we identified hair cross-sectional shape, cuticle dimensions, and melanosome distribution as traits that reveal statistically significant ancestry-related patterns. This study establishes trait patterns in hair morphology and ultrastructure among three biogeographically defined metapopulations to improve the current understanding of human variation in hair form and establish a foundation for future studies on the genetic and developmental bases of phenotypic variation in hair ultrastructure related to genotype.     

Biochemical variation of hair keratins in man and non-human primates

Human hair from various racial groups was investigated using the following techniques: amino acid analysis, acrylamide gel electrophoresis, x-ray diffraction studies, stress-strain analysis. Each of these techniques yielded identical results for all samples, indicating that the variables producing phenotypic differences in human hair form are probably not on the level of primary or secondary biochemical structure. Hair samples of a variety of primates were examined electrophoretically, with each taxonomic family investigated exhibiting a different pattern. These biochemical results are consistent with accepted primate phylogeny.     

Flavonoids variation in seven tetraploid populations of Dactylis glomerata

133 individual plants representing seven tetraploid populations of Dactytis glomerata were examined for their flavonoid pattern by using HPLC. The chemical results expressed quantitatively as peak heights were submitted to multivariate analysis. This data treatment suggested an obvious discrimination between Eurasian and Mediterranean types, lending support to the taxonomic status of the species. This segregation is based on the distribution of C-glycosylluteolins and methylated derivatives. Moreover among the Mediterranean collections, a Coraica population was conspicuously separated from the other three in regard to the distributionof di-C-glycosylflavones. This chemical approach was compared with an electrophoretic assay concerning seven enzyme systems; their respective conclusions were in good agreement.     

Craniofacial variation in Australasian and Pacific populations

Stepwise discriminant function analysis and Mahalanobis's generalized distance are applied to 36 measurements recorded in crania from Australasia and Oceania for assessing biological relationships and possible origins of these populations. Craniofacial variation in Australia is found to be clinal. There is extreme diversity in the Murray River Valley and southern Queensland cranial series. Multiple origins of the Australians are not supported by these results. Although selection and other processes cannot be completely ruled out, gene flow and restrictions to the exchange of genes can explain most of the morphological patterning observed. Breadth and length dimensions of the vault, interorbital breadth, biorbital breadth, palate length, and upper facial height are among the most important discriminators. Viewed within the broader context of Asia and the Pacific, Australians represent a biologically distinct population, one sharing ancestral ties with Melanesians but not with the recent populations of Asia and the rest of the Pacific. The latter represent a second major population complex.     

Skin and hair pigmentation variation in Island Melanesia

Skin and hair pigmentation are two of the most easily visible examples of human phenotypic variation. Selection-based explanations for pigmentation variation in humans have focused on the relationship between melanin and ultraviolet radiation, which is largely dependent on latitude. In this study, skin and hair pigmentation were measured as the melanin (M) index, using narrow-band reflectance spectroscopy for 1,135 individuals from Island Melanesia. Overall, the results show remarkable pigmentation variation, given the small geographic region surveyed. This variation is discussed in terms of differences between males and females, among islands, and among neighborhoods within those islands. The relationship of pigmentation to age, latitude, and longitude is also examined. We found that male skin pigmentation was significantly darker than females in 5 of 6 islands examined. Hair pigmentation showed a negative, but weak, correlation with age, while skin pigmentation showed a positive, but also weak, correlation with age. Skin and hair pigmentation varied significantly between islands as well as between neighborhoods within those islands. Bougainvilleans showed significantly darker skin than individuals from any other island considered, and are darker than a previously described African-American population. These findings are discussed in relation to prevailing hypotheses about the role of natural selection in shaping pigmentation variation in the human species, as well as the role of demographic processes such as admixture and drift in Island Melanesia.     

Analysis of hair samples of mummies from Semna South (Sudanese Nubia)

Hair samples from 76 burials at Semna South (Sudanese Nubia) were examined using a variety of techniques. Electrophoresis and fluorescence microscopy indicated some oxidation of the cuticule and keratin protein had taken place. However, the cuticular structure and the lack of fluorescence of the cortex indicate that the low humidity and non-alkaline conditions preserved the physical and chemical properties of the hair well. Pigmentation, even allowing for oxidation of melanin, showed a higher proportion of lighter samples than is currently associated with the Nubian area. Hair form analysis showed medium diameter and scale count; the curling variables were intermediate between European and African samples. There was a high ratio of maximum to minimum curvature (a measure of irregularity), approached only by Melanesian samples. Meroitic and X-group burial types were not statistically significantly different (largely due to sample sizes), but the X-group, especially males, showed more African elements than the Meroitic in the curling variables. Principal components analysis showed the Semna sample to be significantly different from seven populations examined earlier.     

Craniometric variation among modern human populations

Previous studies of genetic markers and mitochondrial DNA have found that the amount of variation among major geographic groupings of Homo sapiens is relatively low, accounting for roughly 10% of total variation. This conclusion has had implications for the study of human variation and consideration of alternative models for the origin of modern humans. By contrast, it has often been assumed that the level of among-group variation for morphological traits is much higher. This study examines the level of among-group variation based on Craniometric data from a large sample of modern humans originally collected by W. W. Howells. A multivariate method based on quantitative genetics theory was used to provide an estimate of F_ST — a measure of among-group variation that can be compared with results from studies of genetic markers. Data for 57 Craniometric variables on 1,734 crania were analyzed. These data represent six core areas: Europe, Sub-Saharan Africa, Australasia, Polynesia, the Americas, and the Far East. An additional set of analyses was performed using a three-region subset (Europe, Sub-Saharan Africa, and the Far East) to provide comparability with several genetic studies. The minimum F_ST (assuming complete heritability) for the three-region analysis is 0.065, and the minimum F_ST for the six-region analysis is 0.085. Both of these are less than the average F_ST from genetic studies (average estimates of 0.10–0.11). The smaller value of the minimum F_ST estimates is expected since it provides an estimate of F_ST expected under complete heritability. Using an estimate of average craniometric heritability from the literature provides an estimate of F_ST of 0.112 for the three-region analysis and 0.144 for the six-region analysis. These results show that genetic and craniometric data are in agreement, qualitatively and quantitatively, and that there is limited variation in modern humans among major geographic regions. © 1994 Wiley-Liss, Inc.     

高原鼢鼠(Myospalax baileyi) 不同地理种群的形态变异

本文采用主成分分析和聚类分析两种方法,分析了高原鼢鼠(Myospalax baileyi)12 个地理种群17 项形态特征的变异。主成分分析结果显示,分析构建的雄性前3 个主成分累积贡献率为78.483% ,而雌性前4 个主成分累积贡献率为79.587% 。对种群间形态差异分析贡献最大的指标为颅全长、基长、后头宽等反映头骨大小性状,以及顶嵴、额嵴最小间距体现的颧弓扩张程度指标。主成分分析结果与聚类分析结果一致,12 个地理种群分化构成两个大的地域性群体:一个由甘肃种群构成的甘肃群体;另一个由四川种群和青海种群构成的混合群体。两个地域性群体实际上反映出两个不同的分化方向:一个方向表现为头骨较小,顶嵴、额嵴相对分开即颧弓扩张程度小,如甘肃群体;另一个则表现为头骨较大,顶嵴、额嵴相对靠拢即颧弓扩张程度大,如混合群体。这种地域群体的形态变异可以解释为,地下洞道系统中环境因子选择作用对高原鼢鼠形态变化产生了重要影响。     

Physical variation and history in Melanesia and Australia

Local biological variation is marked in Melanesia. Some of it may result from gene flow from Micronesia, but the essential variation appears to result from isolation due to social fragmentation, and to genetic drift in place. In different regions, the variation may correspond well with language relationships, and probably constitutes differentiation which has been preserved over a considerable period, especially since the arrival of horticulture and development of village farming. However, none of this patterning suggests distinct waves of migration into Melanesia. Variation among Australian aboriginal groups is smaller, though far from absent. It may reflect a hunting culture together with social customs allowing more intertribal marriage than is typical of Melanesia. While phenotypically Australians and Melanesians differ, cranially they are closely allied, as against other major human groups. It is suggested that the genetic and phenotypic variety is old, that it existed in the previous home of the Australo-Melanesians (Old Melanesia, comprising present Indonesia and the Phillipines) at least back to 40,000 years ago, and that much of the variation in Melanesia and Australia, including their differences, results from the sampling process involved when different groups out of the original populations made early crossings of the water barriers from Old Melanesia.     

Patterns of genetic variation in anthropogenically impacted populations

Genetic variation is considered critical for allowing natural populations to adapt to their changing environment, and yet the effects of human disturbance on genetic variation in the wild are poorly understood. Different types of human disturbances may genetically impact natural populations in a predictable manner and so the aim of this study was to provide an overview of these changes using a quantitative literature review approach. I examined both allozyme and microsatellite estimates of genetic variation from peer-reviewed journals, using the mean number of alleles per locus and expected heterozygosity as standardized metrics. Populations within each study were categorized according to the type of human disturbance experienced (“hunting/harvest”, “habitat fragmentation”, or “pollution”), and taxon-specific, as well as time- and context-dependent disturbance effects were considered. I found that human disturbances are associated with weak, but consistent changes in neutral genetic variation within natural populations. The direction of change was dependent on the type of human disturbance experienced, with some forms of anthropogenic challenges consistently decreasing genetic variation from background patterns (e.g., habitat fragmentation), whereas others had no effect (e.g., hunting/harvest) or even slightly increased genetic variation (e.g., pollution). These same measures appeared sensitive to both the time of origin and duration of the disturbance as well. This suggests that the presence or absence, strength, type, as well as the spatial and temporal scale of human disturbance experienced may warrant careful consideration when conservation management plans are formulated for natural populations, with particular attention paid to the effects of habitat fragmentation.     

Morphological variability among seven populations of brown trout, Salmo trutta L., in Greece

Morphological variation in five meristic and 21 morphometric characters was examined in the brown trout, Salmo trutta L., from seven distinct streams and rivers from N and NW Greece. Variation within each sample, estimated as the multivariate generalization of the coefficient of variation, did not vary substantially among the populations. The phenetic relationships of these populations were examined using the stepwise discriminant analysis. The taxonomic implications of these results are discussed.     

Genetic variation and population structure of interleukin genes among seven ethnic populations from Karnataka,India

The extent of genetic variation and the degree of genetic differentiation among seven ethnic populations from Karnataka, India (Bunt, Havyak, Iyengar, Lingayath, Smartha, Vaishya, Vokkaliga), was investigated using four single nucleotide polymorphisms (SNPs: IL-1A 4845, IL-1B 3954, IL-1B 511 and IL-1RA 2018) of the interleukin gene cluster. Allele frequencies varied by threefold among these populations, which also differed for gene diversity and heterozygosity levels. The average degree of population subdivision among these castes was low (F _ST = 0.02). However, pair-wise interpopulation differentiation ranged from 0–7%, indicating no detectable differentiation to moderate differentiation between specific populations. The results of phylogenetic analysis based on genetic distances between populations agreed with known social and cultural data on these ethnic groups. Variation in the allele frequencies, as well as differentiation, may be attributed to differential selection and demographic factors including consanguinity among the ethnic groups. Information on the distribution of functionally relevant polymorphisms among ethnic populations may be important towards developing community medicine and public health policies.     

常见毛囊细胞角蛋白在毛囊周期中的表达研究

目的探讨常见毛囊细胞角蛋白在毛囊周期中的表达特征。 方法取毛囊发育期、生长期启动、生长期、退化期和静止期的小鼠皮肤,石蜡切片后通过免疫荧光的方法,检测细胞角蛋白Krt5、Krt6、Krt10、Krt14、Krt15和Krt19的表达情况。 结果Krt5在静止期和生长期启动表达于所有毛囊上皮细胞,在其他时期表达不一致;Krt6表达于所有时期的外根鞘细胞和内根鞘细胞;Krt10表达于生长期和退化期的毛母质和内根鞘细胞,在其他时期表达不一致;Krt14在生长期和退化期表达于所有毛囊上皮细胞,在其他时期表达不一致;Krt15和Krt19表达于毛囊发育期、生长期启动和静止期的毛囊隆突区细胞,在生长期和退化期表达不一致。 结论角蛋白作为毛囊结构或毛囊干细胞标记物仅适用于特定的毛囊周期。研究者在使用毛囊角蛋白作为标记物时,应首先明确其在毛囊周期中的表达情况。     

大花栀子植物挥发物成分测定及其日变化分析

为探究大花栀子植物挥发物成分组成及其一天内早、中、晚的差异,采用热脱附气质联用技术对其进行香气成分的分析。结果表明:全天从其花朵中共鉴定出62种成分,主要为萜烯类、酯类、醇类物质,且不同时间其成分差异显著,如早、中、晚3个时间段,β-蒎烯相对含量分别为1.93%、1.69%、8.81%,顺式-β-罗勒烯分别为28.22%、4.35%、16.47%。3-蒈烯(3.45%)、异丁子香酚(0.21%)等只在早上检出;月桂烯(0.38%)、伞花烃(2.46%)等只在晚上检出;芳樟醇、金合欢烯等在早上和午间两个时间段相对含量较高,而在晚上却未检测出。从植物VOCs角度结合其日变化动态,为大花栀子园林配置及其综合开发利用提供理论依据。     

Genetic variation in North Amerindian populations: the geography of gene frequencies

Ten-level synthetic gene frequency maps derived from a principal component analysis of seven polymorphic loci are displayed for a large sample of North Amerindian populations. These maps are useful for assessing population affinities over broad geographical regions and perhaps, as others have argued, for inferring recent migrations. The influence of European admixture is investigated by deleting highly admixed populations and regenerating the maps. In broad outline the resultant geographic patterning, while appearing more homogeneous, preserves many features of the maps that include the highly admixed samples--especially with respect to the Eskimo/non-Eskimo dichotomy. Further, in an effort to evaluate how varying the number of display levels affects patterning as well as interpretation, the maps were replotted at 5 and 20 levels. The 5-level maps are found to accentuate differences between the full data set and the less admixed data set, while the 20-level maps tend to obscure these differences.     

Quantitative flavonoid variation in Lupinus sericeus

One hundred and eighty-one plants representing 32 individual populations of Lupinus sericeus were collected from throughout the range of the species. Quantitative analyses of flavonoid derivatives were performed using high performance liquid chromatography. Peak height data were subjected to multivariate analysis. Principal components analysis suggested the existence of a north-south cline based upon differences in orientin concentration. Canonical variates analysis suggested that southerly, central and northerly populations were distinguishable. Simple statistical tests on orientin concentration, the major flavonoid seen in the study, clearly distinguished southerly populations from all others. Seeds were collected from representative populations from the range of L. sericeus and the plants obtained therefrom were grown under uniform conditions. Analysis of orientin concentration in these plants showed no significant differences between populations. We conclude from these studies that all L. sericeus plants appear to have similar capacities to accumulate orientin, and that differences in concentration of this compound seen in naturally occurring plants are a reflection of environmental influences and cannot be used as support for any infrageneric taxonomic distinctions.