Genetic variation among world populations: inferences from 100 Alu insertion polymorphisms.
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We examine the distribution and structure of human genetic diversity for 710 individuals representing 31 populations from Africa, East Asia, Europe, and India using 100 Alu insertion polymorphisms from all 22 autosomes. Alu diversity is highest in Africans (0.349) and lowest in Europeans (0.297). Alu insertion frequency is lowest in Africans (0.463) and higher in Indians (0.544), E. Asians (0.557), and Europeans (0.559). Large genetic distances are observed among African populations and between African and non-African populations. The root of a neighbor-joining network is located closest to the African populations. These findings are consistent with an African origin of modern humans and with a bottleneck effect in the human populations that left Africa to colonize the rest of the world. Genetic distances among all pairs of populations show a significant product-moment correlation with geographic distances (r = 0.69, P < 0.00001). F(ST), the proportion of genetic diversity attributable to population subdivision is 0.141 for Africans/E. Asians/Europeans, 0.047 for E. Asians/Indians/Europeans, and 0.090 for all 31 populations. Resampling analyses show that approximately 50 Alu polymorphisms are sufficient to obtain accurate and reliable genetic distance estimates. These analyses also demonstrate that markers with higher F(ST) values have greater resolving power and produce more consistent genetic distance estimates. (+info)
Intercontinental genetic divergence of Castanea species in eastern Asia and eastern North America.
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Castanea is one of the many plant genera with a disjunct distribution pattern between eastern Asia and eastern North America. Five species from three sections of the genus were investigated to examine genetic divergence between eastern Asian and eastern North American species. A total of 62 native populations were sampled for allelic variation at isozyme loci. The Chinese chestnut C. mollissima had the highest genetic variability, while the American C. dentata had the lowest genetic variability. The highest intracontinental genetic identities were observed between the Allegheny and Ozark chinkapins (0.931) and between C. mollissima and C. seguinii (0.870), while lower identities were detected between the American C. pumila and C. dentata (0.720-0.729). In intercontinental comparisons, genetic identities of 0.505, 0.495 and 0.507 were observed between the American chestnut and the Chinese C. mollissima, C. seguinii and C. henryi, respectively, whereas the Ozark chinkapin C. pumila var. ozarkensis had lower identities of 0.469, and 0.435 with C. mollissima and C. seguinii, respectively, but a slightly higher identity of 0.520 with C. henryi, the Chinese chinkapin. Divergence times were estimated at 10-13 million years before present between C. dentata and C. mollissima, and C. pumila var. ozarkensis and C. henryi. (+info)
An international survey of indoor air quality, ventilation, and smoking activity in restaurants: a pilot study.
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During a pilot study of indoor air quality in restaurants, a survey was performed in 34 medium-priced restaurants in six countries in Asia, Europe, and North America using a uniform protocol. The concentration of selected constituents of environmental tobacco smoke (ETS) present in occupied areas was determined during lunch and dinner periods by measuring the levels of four particulate-phase markers and two gas-phase markers. The particulate-phase markers determined were respirable suspended particles, ultraviolet particulate matter, fluorescing particulate matter, and solanesol particulate matter. The gas-phase markers were nicotine and 3-ethenylpyridine (3-EP). Correlation between the markers was investigated to explore an improved monitoring approach. It was concluded that at least one marker in each phase was necessary to describe adequately the ETS load. An assessment was made of the ventilation system in each restaurant, and effective ventilation rates were determined based on CO(2) measurements. Smoking activity was also monitored. These data were used to model nicotine and 3-EP concentrations that resulted in a satisfactory prediction of their levels, especially at the higher concentrations. A total number of 1370 questionnaires were returned by the restaurant patrons in five countries. In some countries, dissatisfaction rates above 20% were observed for draft, freshness of air, and noise. The dissatisfaction rates related to tobacco smoke were less than 20%, which is lower than would be predicted based on measured ETS levels. Based on the results of this international pilot study, recommendations are given for future studies of this type. (+info)
Population genetic structure of Titanotrichum oldhamii (Gesneriaceae), a subtropical bulbiliferous plant with mixed sexual and asexual reproduction.
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BACKGROUND AND AIMS: Titanotrichum oldhamii is a monotypic genus distributed in Taiwan, adjacent regions of China and the Ryukyu Isands of Japan. Its conservation status is vulnerable as most populations are small and widely scattered. Titanotrichum has a mixed system of reproduction with vegetative bulbils and seeds. The aim of this study was to understand the population genetic structure of Titanotrichum in relation to its specific reproductive behaviour and to determine possible implications for conservation strategies. METHODS: After an extensive inventory of most wild populations of Titanotrichum in East Asia, samples from 25 populations within its major distribution were carried out utilizing RAPD and inter-SSR molecular fingerprinting analysis. KEY RESULTS: The findings support the conclusion that many populations reproduce predominantly asexually but that some genetic variation still exists within populations. However, significant amounts of variation exist between populations, perhaps reflecting population differentiation by drift. This partitioning of genetic diversity indicates that the level of inter-population gene exchange is extremely low. These findings are consistent with field observations of very limited seed production. The Chinese populations are similar to those of Northern Taiwan, while the Ryukyu populations fall within the range of variation of the north-central Taiwan populations. The Taiwanese populations are relatively variable and differentiation between north, east and south Taiwan is evident. CONCLUSIONS: The distribution of Titanotrichum seems to be consistent with a former land connection between China, Taiwan and the Ryukyu Islands at a glacial maximum during the Quaternary, followed by progressive fragmentation of the populations. North-central Taiwan is the centre of genetic diversity, possibly due to the proximity of the former land bridge between the regions, together with the variety of suitable habitats in north Taiwan. The significance of these findings for conservation is discussed. (+info)
Evidence for an "epidemic" of myopia.
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INTRODUCTION: It has been widely suggested that the prevalence of myopia is growing worldwide, and that the increases observed in East Asia, in particular, are sufficiently severe as to warrant the term "epidemic". Data in favour of a cohort effect in myopia prevalence are reviewed, with attention to significant shortcomings in the quality of available evidence. Additional factors contributing to myopia prevalence, including near work, genetics and socioeconomic status, are detailed. MATERIALS AND METHODS: Medline search of articles regarding myopia prevalence, trends and mechanisms. RESULTS: Age-related changes in myopia prevalence (increase during childhood, and regression in the fifth and sixth decades) are discussed as an alternative explanation for cross-sectional patterns in myopia prevalence. There have only been a handful of studies that have examined the relative contribution of longitudinal changes in refraction over life and birth cohort differences on age-specific myopia prevalence as measured in cross-sectional studies. Available data suggest that both longitudinal changes and cohort effects may be present, and that their relative contribution may differ in different racial groups. CONCLUSIONS: In view of the relatively weak evidence in favour of a large cohort effect for myopia in East Asia, and the even greater lack of evidence for increased prevalence of secondary ocular pathology, there appears to be inadequate support for large-scale interventions to prevent or delay myopia at the present time. (+info)
Shift in Japanese encephalitis virus (JEV) genotype circulating in northern Vietnam: implications for frequent introductions of JEV from Southeast Asia to East Asia.
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This study analyses the evolutionary relatedness of 16 Japanese encephalitis virus (JEV) isolates (nine from Vietnam and seven from Japan) to previously published JEV strains using E gene sequence data. Vietnamese and Japanese strains isolated between 1986 and 1990 were found to cluster in genotype 3. However, more recent Vietnamese and Japanese strains isolated between 1995 and 2002 grouped within genotype 1, now a dominant though previously unreported genotype in Vietnam. In addition, in this study, strains isolated between 1995 and 2002 were more closely related to those isolated in the 1990s than to the older genotype 1 strains. Recently, the introduction of JEV genotype 1 into Japan and Korea has also been reported. Hence this genotype shift phenomenon may be occurring throughout all East Asia. Further studies on JEV ecology are needed to clarify the mechanism of JEV genotype 1 spread to new territories. (+info)
Cancer burden and trends in the Asian Pacific Rim region.
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This paper describes the current cancer burden and time trends, discusses dominant risk factors and prevention and control strategies, and makes future projections for the top eight cancers (stomach, lung, liver, colon/rectum, esophagus, breast, cervix, and leukemia) in the Asian Pacific Rim region. The future cancer trends through to the year 2050 are projected based on population dynamics, including population growth and ageing. In 2000, the Asian Pacific Rim had over 3 million new cancer cases, over 2 million cancer deaths, and 5.4 million people living with cancer. In 2050, 7.8 million new cancer cases and 5.7 million deaths from cancer are projected. The current cancer burden and the future projection provide facts that cancer is and will be a very serious public health problem in the Asian Pacific Rim region and will assist public health officers and cancer researchers in the design and establishment of public health policies, prioritization of future research, and application of current knowledge in the prevention and control of cancer. (+info)
Mitochondrial genome variation in eastern Asia and the peopling of Japan.
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To construct an East Asia mitochondrial DNA (mtDNA) phylogeny, we sequenced the complete mitochondrial genomes of 672 Japanese individuals (http://www.giib.or.jp/mtsnp/index_e.html). This allowed us to perform a phylogenetic analysis with a pool of 942 Asiatic sequences. New clades and subclades emerged from the Japanese data. On the basis of this unequivocal phylogeny, we classified 4713 Asian partial mitochondrial sequences, with <10% ambiguity. Applying population and phylogeographic methods, we used these sequences to shed light on the controversial issue of the peopling of Japan. Population-based comparisons confirmed that present-day Japanese have their closest genetic affinity to northern Asian populations, especially to Koreans, which finding is congruent with the proposed Continental gene flow to Japan after the Yayoi period. This phylogeographic approach unraveled a high degree of differentiation in Paleolithic Japanese. Ancient southern and northern migrations were detected based on the existence of basic M and N lineages in Ryukyuans and Ainu. Direct connections with Tibet, parallel to those found for the Y-chromosome, were also apparent. Furthermore, the highest diversity found in Japan for some derived clades suggests that Japan could be included in an area of migratory expansion to Continental Asia. All the theories that have been proposed up to now to explain the peopling of Japan seem insufficient to accommodate fully this complex picture. (+info)