Can hypertension be prevented? Applications of risk modifications in black populations: U.S. populations.
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Adult↗
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Results for “POPULATION”
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[Urgent issues of nutrition improvement and public health of Russian population: concept of state policy in the field of healthy nutrition of Russian population for the period up to the year 2005].
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Diet Therapy↗
[Radiation exposure of the population by roentgen diagnosis. II. The collective effective dosage of the population in former East Germany caused by 1987/1988 roentgen diagnosis].
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Adolescent↗
Frequency of mutations for glycogen storage disease type II in different populations: the delta525T and deltaexon 18 mutations are not generally "common" in white populations.
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Alleles↗
[The parasite capacity of the host population].
The estimation of parasitic pressure on the host populations is frequently required in parasitological investigations. The empirical values of prevalence of infection are used for this, however the latter one as an estimation of parasitic pressure on the host population is insufficient. For example, the same prevalence of infection can be insignificant for the population with high reproductive potential and excessive for the population with the low reproductive potential. Therefore the development of methods of an estimation of the parasitic pressure on the population, which take into account the features the host population, is necessary. Appropriate parameters are to be independent on view of the researcher, have a clear biological sense and be based on easily available characteristics. The methods of estimation of parasitic pressure on the host at the organism level are based on various individual viability parameters: longevity, resistance to difficult environment etc. The natural development of this approach for population level is the analysis of viability parameters of groups, namely, the changing of extinction probability of host population under the influence of parasites. Obviously, some critical values of prevalence of infection should exist; above theme the host population dies out. Therefore the heaviest prevalence of infection, at which the probability of host population size decreases during the some period is less than probability of that increases or preserves, can serve as an indicator of permissible parasitic pressure on the host population. For its designation the term "parasite capacity of the host population" is proposed. The real parasitic pressure on the host population should be estimated on the comparison with its parasite capacity. Parasite capacity of the host population is the heaviest possible prevalence of infection, at which, with the generation number T approaching infinity, there exists at least one initial population size ni(0) for which the probability of size decrease through T generations is less than the probability of its increase. [formula: see text] The estimation of the probabilities of host population size changes is necessary for the parasite capacity determination. The classical methods for the estimation of extinction probability of population are unsuitable in this case, as these methods require the knowledge of population growth rates and their variances for all possible population sizes. Thus, the development methods of estimate of extinction probability of population, based on the using of available parameters (sex ratio, fecundity, mortality, prevalence of infection PI) is necessary. The population size change can be considered as the Markov process. The probabilities of all changes of population size for a generation in this case are described by a matrix of transition probabilities of Markov process (pi) with dimensions Nmax x Nmax (maximum population size). The probabilities of all possible size changes for T generations can be calculated as pi T. Analyzing the behaviour matrix of transition at various prevalence of infection, it is possible to determine the parasite capacity of the host population. In constructing of the matrix of transition probabilities, should to be taken into account the features the host population and the influence of parasites on its reproductive potential. The set of the possible population size at a generation corresponds to each initial population size. The transition probabilities for the possible population sizes at a generation can be approximated to the binomial distribution. The possible population sizes at a generation nj(t + 1) can be calculated as sums of the number of survived parents N1 and posterities N2; their probabilities--as P(N1) x P(N2). The probabilities of equal sums N1 + N2 and nj(t + 1) > or = Nmax are added. The number of survived parents N1 may range from 0 to (1-PI) x ni(t). The survival probabilities can be estimated for each N1 as [formula: see text] The number of survived posterities N2 may range from 0 to N2max (the maximum number of posterities). N2max is [formula: see text] and the survival probabilities for each N2, is defined as [formula: see text] where [formula: see text], ni(t) is the initial population size (including of males and infected specimens of host), PI is the prevalence of infection, Q1 is the survival probabilities of parents, Pfemales is the frequency of females in the host population, K is the number of posterities per a female, and Q2 is the survival probabilities of posterities. When constructing matrix of transition probabilities of Markov process (pi), the procedure outlined above should be repeated for all possible initial population size. Matrix of transition probabilities for T generations is defined as pi T. This matrix (pi T) embodies all possible transition probabilities from the initial population sizes to the final population sizes and contains a wealth of information by itself. From the practical point of view, however, the plots of the probability of population size decrease are more suitable for analysis. They can be received by summing the probabilities within of lines of matrix from 0 to ni--1 (ni--the population size, which corresponds to the line of the matrix). Offered parameter has the number of advantages. Firstly, it is independent on a view of researcher. Secondly, it has a clear biological sense--this is a limit of prevalence, which is safe for host population. Thirdly, only available parameters are used in the calculation of parasite capacity: population size, sex ratio, fecundity, mortality. Lastly, with the availability of modern computers calculations do not make large labour. Drawbacks of this parameter: 1. The assumption that prevalence of infection, mortality, fecundity and sex ratio are constant in time (the situations are possible when the variability of this parameters can not be neglected); 2. The term "maximum population size" has no clear biological sense; 3. Objective restrictions exist for applications of this mathematical approach for populations with size, which exceeds 1000 specimens (huge quantity of computing operations--order Nmax 3*(T-1), work with very low probabilities). The further evolution of the proposed approach will allow to transfer from the probabilities of size changes of individual populations to be probabilities of size changes of population systems under the influence of parasites. This approach can be used at the epidemiology and in the conservation biology.
Animals↗
Population cycles in small rodents.
We conclude that population fluctuations in Microtus in southern Indiana are produced by a syndrome of changes in birth and death rates similar to that found in other species of voles and lemmings. The mechanisms which cause the changes in birth and death rates are demolished by fencing the population so that no dispersal can occur. Dispersal thus seems critical for population regulation in Microtus. Because most dispersal occurs during the increase phase of the population cycle and there is little dispersal during the decline phase, dispersal is not directly related to population density. Hence the quality of dispersing animals must be important, and we have found one case of increased dispersal tendency by one genotype. The failure of population regulation of Microtus in enclosed areas requires an explanation by any hypothesis attempting to explain population cycles in small rodents. It might be suggested that the fence changed the predation pressure on the enclosed populations. However, the fence was only 2 feet (0.6 meter) high and did not stop the entrance of foxes, weasels, shrews, or avian predators. A striking feature was that the habitat in the enclosures quickly recovered from complete devastation by the start of the spring growing season. Obviously the habitat and food quality were sufficient to support Microtus populations of abnormally high densities, and recovery of the habitat was sufficiently quick that the introduction of new animals to these enclosed areas resulted in another population explosion. Finally, hypotheses of population regulation by social stress must account for the finding that Microtus can exist at densities several times greater than normal without "stress" taking an obvious toll. We hypothesize that the prevention of dispersal changes the quality of the populations in the enclosures in comparison to those outside the fence. Voles forced to remain in an overcrowded fenced population do not suffer high mortality rates and continue to reproduce at abnormally high densities until starvation overtakes them. The initial behavioral interactions associated with crowding do not seem sufficient to cause voles to die in situ. What happens to animals during the population decline? Our studies have not answered this question. The animals did not appear to disperse, but it is possible that the method we used to measure dispersal (movement into a vacant habitat) missed a large segment of dispersing voles which did not remain in the vacant area but kept on moving. Perhaps the dispersal during the increase phase of the population cycle is a colonization type of dispersal, and the animals taking part in it are likely to stay in a new habitat, while during the population decline dispersal is a pathological response to high density, and the animals are not attracted to settling even in a vacant habitat. The alternative to this suggestion is that animals are dying in situ during the decline because of physiological or genetically determined behavioral stress. Thus the fencing of a population prevents the change in rates of survival and reproduction, from high rates in the increase phase to low rates in the decline phase, and the fenced populations resemble "mouse plagues." A possible explanation is that the differential dispersal of animals during the phase of increase causes the quality of the voles remaining at peak densities in wild populations to be different from the quality of voles at much higher densities in enclosures. Increased sensitivity to density in Microtus could cause the decline of wild populations at densities lower than those reached by fenced populations in which selection through dispersal has been prevented. Fencing might also alter the social interactions among Microtus in other ways that are not understood. The analysis of colonizing species by MacArthur and Wilson (27) can be applied to our studies of dispersal in populations of Microtus. Groups of organisms with good dispersal and colonizing ability are called r strategists because they have high reproductive potential and are able to exploit a new environment rapidly. Dispersing voles seem to be r strategists. Young females in breeding condition were over-represented in dispersing female Microtus (17). The Tf(C)/Tf(E) females, which were more common among dispersers during the phase of population increase (Fig. 6), also have a slight reproductive advantage over the other Tf genotypes (19). Thus in Microtus populations the animals with the highest reproductive potential, the r strategists, are dispersing. The segment of the population which remains behind after the selection-via-dispersal are those individuals which are less influenced by increasing population densities. These are the individuals which maximize use of the habitat, the K strategists in MacArthur and Wilson's terminology, or voles selected for spacing behavior. Thus we can describe population cycles in Microtus in the same theoretical framework as colonizing species on islands. Our work on Microtus is consistent with the hypothesis of genetic and behavioral effects proposed by Chitty (6) (Fig. 7) in that it shows both behavioral differences in males during the phases of population fluctuation and periods of strong genetic selection. The greatest gaps in our knowledge are in the area of genetic-behavioral interactions which are most difficult to measure. We have no information on the heritability of aggressive behavior in voles. The pathways by which behavioral events are translated into physiological changes which affect reproduction and growth have been carefully analyzed by Christian and his associates (28) for rodents in laboratory situations, but the application of these findings to the complex field events described above remains to be done. Several experiments are suggested by our work. First, other populations of other rodent species should increase to abnormal densities if enclosed in a large fenced area (29). We need to find situations in which this prediction is not fulfilled. Island populations may be an important source of material for such an experiment (30). Second, if one-way exit doors were provided from a fenced area, normal population regulation through dispersal should occur. This experiment would provide another method by which dispersers could be identified. Third, if dispersal were prevented after a population reached peak densities, a normal decline phase should occur. This prediction is based on the assumption that dispersal during the increase phase is sufficient to ensure the decline phase 1 or 2 years later. All these experiments are concerned with the dispersal factor, and our work on Microtus can be summarized by the admonition: study dispersal.
Aggression↗
Population growth rate and its determinants: an overview.
We argue that population growth rate is the key unifying variable linking the various facets of population ecology. The importance of population growth rate lies partly in its central role in forecasting future population trends; indeed if the form of density dependence were constant and known, then the future population dynamics could to some degree be predicted. We argue that population growth rate is also central to our understanding of environmental stress: environmental stressors should be defined as factors which when first applied to a population reduce population growth rate. The joint action of such stressors determines an organism's ecological niche, which should be defined as the set of environmental conditions where population growth rate is greater than zero (where population growth rate = r = log(e)(N(t+1)/N(t))). While environmental stressors have negative effects on population growth rate, the same is true of population density, the case of negative linear effects corresponding to the well-known logistic equation. Following Sinclair, we recognize population regulation as occurring when population growth rate is negatively density dependent. Surprisingly, given its fundamental importance in population ecology, only 25 studies were discovered in the literature in which population growth rate has been plotted against population density. In 12 of these the effects of density were linear; in all but two of the remainder the relationship was concave viewed from above. Alternative approaches to establishing the determinants of population growth rate are reviewed, paying special attention to the demographic and mechanistic approaches. The effects of population density on population growth rate may act through their effects on food availability and associated effects on somatic growth, fecundity and survival, according to a 'numerical response', the evidence for which is briefly reviewed. Alternatively, there may be effects on population growth rate of population density in addition to those that arise through the partitioning of food between competitors; this is 'interference competition'. The distinction is illustrated using a replicated laboratory experiment on a marine copepod, Tisbe battagliae. Application of these approaches in conservation biology, ecotoxicology and human demography is briefly considered. We conclude that population regulation, density dependence, resource and interference competition, the effects of environmental stress and the form of the ecological niche, are all best defined and analysed in terms of population growth rate.
Conservation of Natural Resources↗
The effect of revised populations on mortality statistics for the United States, 2000.
OBJECTIVES: This report presents revised mortality statistics for the year 2000 based on April 1, 2000, population figures from the 2000 census. Death rates are presented by race, Hispanic origin, sex, age, and cause of death. Life expectancies are presented by race (white and black), sex, and age. The revised statistics are compared with previously published statistics that used July 1, 2000, postcensal population estimates based on the 1990 census. METHODS: Data in this report are based on information from all death certificates filed in the 50 States and the District of Columbia. The statistics presented in this report are computed on the basis of two sets of population figures provided by the U.S. Census Bureau. The first set includes July 1, 2000, postcensal population estimates based on the 1990 decennial census. The second set includes April 1, 2000, populations from the 2000 decennial census bridged to single race categories. RESULTS: Crude death rates were lower for all groups using the April 1, 2000, populations. Age-specific death rates were generally lower for most age groups, except for infants and the very old for which death rates were higher. Age-specific death rates for males were lower for most age groups, except infants and those 75 years and over. For females, with the exception of infants, age-specific death rates were lower. Race-specific pattems by age for the white and black populations were similar to all races combined. For the American Indian population, age-specific death rates were substantially lower for ages under 75 years. For ages 75 years and over, American Indian death rates were dramatically higher. Age-specific death rates for the Asian or Pacific Islander (API) population were higher for ages under 15 years; lower for ages 15-84 years, especially for the 15-34 year age group; and higher for those 85 years and over. For the Hispanic population, age-specific death rates were substantially lower for those age 15-34 years and higher for those age 55 years and over, especially for those age 85 years and over. For the total white and total black populations, the age-adjusted death rate was somewhat higher for males and lower for females. For API the pattern was reversed. For the American Indian and Hispanic populations, age-adjusted death rates were higher for both males and females. For the 15 leading causes of death, age-adjusted death rates based on the April 1, 2000, population figures were lower for heart disease, cancer, chronic liver disease, septicemia, diabetes, chronic lower respiratory diseases, unintentional injuries, homicide, suicide, and hypertension. Age-adjusted death rates were higher for pneumonitis, Alzheimer's disease, and stroke. Rates were unchanged for influenza and pneumonia and nephritis, nephrotic syndrome and nephrosis. Life expectancy at birth was higher for the entire population and both the white and black populations using the April 1, 2000, population figures. It was 0.1 year higher for the whole population as well as for the total white and total black populations. For the total male population, life expectancy at birth was 0.1 year higher while it was 0.2 years higher for the female population. The increase in life expectancy at birth was 0.1 year for both sexes within the white and black populations. This observed gain in life expectancy at birth based on the revised population figures is reversed for life expectancy at the oldest age groups for the whole population and for males. A similar pattern is observed for both white and black males; however, the magnitude of the decline in life expectancy at older ages is much greater among black males. Among females of both race groups and the total population, there is either no change or an increase in life expectancy in the oldest age groups. CONCLUSIONS: Revised death rates and life expectancies are, in many cases, significantly different from previously published mortality statistics calculated using 1990-based postcensal estimates for 2000. Thus, previously published mortality statistics for 2000 using the 1990-based populations will not be comparable to the corresponding statistics that will be published for 2001. The data in this report will provide comparable 2000 data. Efforts are also underway to revise previously published mortality tables for 2000 as well as previously published data for 1991-99.
Adolescent↗
A microsatellite-based estimation of clonal diversity and population subdivision in Zostera marina, a marine flowering plant.
We examined the genetic population structure in eelgrass (Zostera marina L.), the dominant seagrass species of the northern hemisphere, over spatial scales from 12 km to 10 000 km using the polymorphism of DNA microsatellites. Twelve populations were genotyped for six loci representing a total of 67 alleles. Populations sampled included the North Sea (four), the Baltic Sea (three), the western Atlantic (two), the eastern Atlantic (one), the Mediterranean Sea (one) and the eastern Pacific (one). Microsatellites revealed substantial genetic variation in a plant group with low allozyme diversity. Average expected heterozygosities per population (monoclonal populations excluded) ranged from 0.32 to 0.61 (mean = 0. 48) and allele numbers varied between 3.3 and 6.7 (mean = 4.7). Using the expected frequency of multilocus genotypes within populations, we distinguished ramets from genetic individuals (i.e. equivalent to clones). Differences in clonal diversity among populations varied widely and ranged from maximal diversity (i.e. all ramets with different genotype) to near or total monoclonality (two populations). All multiple sampled ramets were excluded from further analysis of genetic differentiation within and between populations. All but one population were in Hardy-Weinberg equilibrium, indicating that Zostera marina is predominantly outcrossing. From a regression of the pairwise population differentiation with distance, we obtained an effective population size Ne of 2440-5000. The overall genetic differentiation among eelgrass populations, assessed as rho (a standardized estimate of Slatkin's RST) was 0.384 (95% CI 0.34-0.44, P < 0.001). Genetic differentiation was weak among three North Sea populations situated 12-42 km distant from one another, suggesting that tidal currents result in an efficient exchange of propagules. In the Baltic and in Nova Scotia, a small but statistically significant fraction of the genetic variance was distributed between populations (rho = 0.029-0. 053) at scales of 15-35 km. Pairwise genetic differentiation between European populations were correlated with distance between populations up to a distance of 4500 km (linear differentiation-by-distance model, R2 = 0.67). In contrast, both Nova Scotian populations were genetically much closer to North Sea and Baltic populations than expected from their geographical distance (pairwise rho = 0.03-0.08, P < 0.01). A biogeographical cluster of Canadian with Baltic/North Sea populations was also supported using a neighbour-joining tree based on Cavalli-Sforza's chord distance. Relatedness between populations may be very different from predictions based on geographical vicinity.
Gene Frequency↗
Evolution of Pacific/Asian populations inferred from HLA class II allele frequency distributions.
The allele frequency distributions for the HLA class II loci, DRB1, DQB1 and DPB1, in eight Pacific/Asian populations: Hawaiian, Samoan, Malay, Papua New Guinea (PNG) Highlands, and two Indonesian and PNG Lowland groups, were determined using high-resolution polymerase chain reaction/sequence-specific oligonucleotide probe (PCR/SSOP) typing methods. The allele frequency distributions for the HLA-DRB1 locus were determined for a third Indonesian population as well as for an additional Filipino population. DRB1 alleles in the DR2 serogroup (or allelic lineage) are very common in this region; in some populations, more than 50% of the alleles belong to this serogroup. The DRB1*1502 allele is frequent in nine of the ten populations studied, reaching a frequency of 0.48 in one Indonesian population and among Filipinos. Extensive DR-DQ haplotype diversity was detected in these populations. Seven different DR2-DQB1 haplotypes were observed in the Indonesian and PNG Lowland populations, eight in the PNG Highlands and ten in Malays and Filipinos. The DRB1*0410 allele, commonly observed in Australia, is observed in the PNG Highlands at a low frequency (f=0.03) and is absent in the other populations. Two additional DRB1 alleles commonly observed in Australia, DRB1*0405 and *1407, are also observed in the PNG Highlands at high frequencies (f=0.132 and 0.126), while they are rare in the PNG Lowlands (f=0.039 and 0.013). These alleles are generally rare or absent in the other populations. The DPB1*0501 allele, common in Chinese and Japanese populations, is most frequent in the Samoan, Hawaiian, Indonesian, and Malay populations, and the *0401 allele is the most frequent DPB1 allele in the PNG Lowlands. Both of these alleles have the same very high frequency (f=0.34) in the PNG Highlands. Analyses of homozygosity (the Ewens-Watterson F statistic) in these and other populations indicate that, while most allele frequency distributions are consistent with balancing selection, values of F for the Indonesian and Javan populations may reflect positive directional selection. Phylogenetic trees constructed using the allele frequencies at the DRB1 locus of the populations reported here, as well as those for additional Pacific, Asian, and Australian populations, indicate that the PNG Highland population is more closely related to Australian populations than to PNG Lowland populations, while the PNG Lowlands are more closely related to other Melanesian populations.
Alleles↗
Genetic divergence between cave and surface populations of Astyanax in Mexico (Characidae, Teleostei).
A study of genetic diversity at microsatellite loci and the mitochondrial DNA (mtDNA) cytochrome b gene was carried out to assess genetic relationships among four Mexican cave (Pachon, Sabinos, Tinaja, Chica) and four surface populations of Astyanax fasciatus (Characidae) from northeast Mexico and the Yucatan. With the exception of Chica, the cave populations were all characterized by extremely low microsatellite variability, which most likely resulted from bottleneck events. Population analyses of the microsatellite data indicated no measurable levels of gene flow between all cave and surface populations (F(ST) > 0.0707). Phylogenetic analyses of mtDNA data showed that only two cave populations - Sabinos and Tinaja - group together to the exclusion of surface populations. From the microsatellite data these cave populations cluster with the Pachon cave fish population. The mtDNA thus appears to have been replaced in Pachon because of introgressive hybridization. It is likely that these three cave populations have descended from a surface ancestor in common with current surface populations, rather than evolving recently from one of the extant surface populations. Like Pachon, the Chica population clustered with the surface populations according to mtDNA data, but was not clearly associated with either the surface or the other cave populations according to the microsatellite data. Our data indicate that the Chica population evolved recently from a surface population, and subsequently hybridized with a phylogenetically older cave population. In conclusion, both the microsatellite and mtDNA data suggest multiple origins of cave populations and the Chica and Sabinos/Tinaja/Pachon were founded after at least two independent invasions from surface populations.
Animals↗
Genetic differentiation among geographic populations of Gonatocerus ashmeadi, the predominant egg parasitoid of the glassy-winged sharpshooter, Homalodisca coagulata.
The aim of genetically comparing different populations of the same species of natural enemies is to identify the strain that is most adapted to the environment where it will be released. In the present study, Inter-Simple Sequence Repeat-Polymerase Chain Reaction (ISSR-PCR) was utilized to estimate the population genetic structure of Gonatocerus ashmeadi (Girault) (Hymenoptera: Mymaridae), the predominant egg parasitoid of Homalodisca coagulata (Say) (Homoptera:Cicadellidae), the glassy-winged sharpshooter. Six populations from throughout the U.S. and a population from Argentina identified as near G. ashmeadi were analyzed. Four populations (California; San Antonio, Texas; Weslaco, Texas [WTX-2]; and Florida) were field collected and two (Louisiana and Weslaco, Texas [WTX-1]) were reared. Three ISSR-PCR reactions were pooled to generate 41 polymorphic markers among the six U.S. populations. Nei's expected heterozygosity values (h), including the reared population from Louisiana, were high (9.01-14.3%) for all populations, except for a reared population from WTX-1 (2.9%). The total genetic diversity value (Ht) for the field populations was high (23%). Interestingly, the Florida population that was collected from one egg mass (siblings) generated the greatest number of polymorphic markers (20) and was observed with the highest gene diversity value (14.3%). All populations, except WTX-2 generated population-specific markers. Comparison of genetic differentiation estimates, which evaluate the degree of genetic subdivision, demonstrated good agreement between G(ST) and theta values, 0.38 and 0.50, respectively for field populations, and 0.44 and 0.50, respectively for all populations. Genetic divergence (D) indicated that the WTX-1 population was the most differentiated. Average D results from the Argentina population support the taxonomic data that it is a different species. The present results estimate the population genetic structure of G. ashmeadi, demonstrating genetic divergence and restricted gene flow (Nm = 0.83) among populations. These results are of interest to the Pierce's disease/glassy-winged sharpshooter biological control program because the key to successful biological control may not be in another species, but instead in different geographic races or biotypes.
Animals↗
Differentiation between African populations is evidenced by the diversity of alleles and haplotypes of HLA class I loci.
The allelic and haplotypic diversity of the HLA-A, HLA-B, and HLA-C loci was investigated in 852 subjects from five sub-Saharan populations from Kenya (Nandi and Luo), Mali (Dogon), Uganda, and Zambia. Distributions of genotypes at all loci and in all populations fit Hardy-Weinberg equilibrium expectations. There was not a single allele predominant at any of the loci in these populations, with the exception of A*3002 [allele frequency (AF) = 0.233] in Zambians and Cw*1601 (AF = 0.283) in Malians. This distribution was consistent with balancing selection for all class I loci in all populations, which was evidenced by the homozygosity F statistic that was less than that expected under neutrality. Only in the A locus in Zambians and the C locus in Malians, the AF distribution was very close to neutrality expectations. There were six instances in which there were significant deviations of allele distributions from neutrality in the direction of balancing selection. All allelic lineages from each of the class I loci were found in all the African populations. Several alleles of these loci have intermediate frequencies (AF = 0.020-0.150) and seem to appear only in the African populations. Most of these alleles are widely distributed in the African continent and their origin may predate the separation of linguistic groups. In contrast to native American and other populations, the African populations do not seem to show extensive allelic diversification within lineages, with the exception of the groups of alleles A*02, A*30, B*57, and B*58. The alleles of human leukocyte antigen (HLA)-B are in strong linkage disequilibrium (LD) with alleles of the C locus, and the sets of B/C haplotypes are found in several populations. The associations between A alleles with C-blocks are weaker, and only a few A/B/C haplotypes (A*0201-B*4501-Cw*1601; A*2301-B*1503-Cw*0202; A*7401-B* 1503-Cw*0202; A*2902-B*4201-Cw*1701; A*3001-B*4201-Cw*1701; and A*3601-B*5301-Cw*0401) are found in multiple populations with intermediate frequencies [haplotype frequency (HF) = 0.010-0.100]. The strength of the LD associations between alleles of HLA-A and HLA-B loci and those of HLA-B and HLA-C loci was on average of the same or higher magnitude as those observed in other non-African populations for the same pairs of loci. Comparison of the genetic distances measured by the distribution of alleles at the HLA class I loci in the sub-Saharan populations included in this and other studies indicate that the Luo population from western Kenya has the closest distance with virtually all sub-Saharan population so far studied for HLA-A, a finding consistent with the putative origin of modern humans in East Africa. In all African populations, the genetic distances between each other are greater than those observed between European populations. The remarkable current allelic and haplotypic diversity in the HLA system as well as their variable distribution in different sub-Saharan populations is probably the result of evolutionary forces and environments that have acted on each individual population or in their ancestors. In this regard, the genetic diversity of the HLA system in African populations poses practical challenges for the design of T-cell vaccines and for the transplantation medical community to find HLA-matched unrelated donors for patients in need of an allogeneic transplant.
Africa South of the Sahara↗
[Analysis of three Y-STR loci polymorphism in isolated populations].
OBJECTIVE: To figure out the polymorphism of three Y-STR loci in isolated populations and explore the consanguinity of the populations with the use of Y-STR. METHODS: Male samples were selected from two isolated populations(80 and 60 males) in Zhejiang province and one open population (36 males), genescan was performed with males' DNA by genescan technology with ABI PRISM 377 sequencer at Y chromosome loci DYS388, DYS390 and DYS395. RESULTS: DYS388, DYS390, DYS395 allele counts in Yushan island population, Taohua island population and open population were 8, 9, 7, 5, 6, 7 and 6, 6, 5 respectively. Gene diversity was between 0.70-0.80 in the three populations. There was no difference in distribution of allele frequency and shared genotypes between the isolated populations and the open population by statistical test. Genetic distance is long between Taohua island population and open population, short between Yushan island population and open population, and moderate between Yushan island population and Taohua island population. CONCLUSION: The main allele is 129 at DYS388; 215 at DYS390; and 119 at DYS395. The distribution of allele frequency and gene diversity at DYS388, DYS390, DYS395 loci, and the shared genotypes between populations as well as the genetic distance are unable to explain the blood relationship between the isolated and open populations, suggesting the additional studies in large sample size will be necessary to use Y-STR for exploring the blood relationship between populations.
Alleles↗
Patterns of gene variation in central and marginal populations of Drosophila robusta.
The central and marginal populations of D. robusta differ greatly in the level of inversion polymorphism; the marginal populations are monomorphic or nearly so and the central populations are highly polymorphic. This paper presents the frequencies of alleles at forty gene loci in various populations of D. robusta, studied by electrophoresis of proteins and enzymes. Population samples were obtained from eight widely separated populations of D. robusta which included the central, the extreme marginal and the intervening populations between the center and the margins. We find that the proportion of polymorphic loci and average heterozygosity per individual is slightly higher in the marginal populations than the central populations. In D. robusta on an average, 39% of the loci are polymorphic and the average proportion of loci heterozygous per individual is 11%. A breakdown of loci in three categories, viz, hydrolytic enzymes and some other enzymes, larval proteins and glycolytic and Kreb's cycle enzymes, shows that in all populations the level of polymorphism is highest in the hydrolytic enzymes, intermediate in larval proteins and least in the glycolytic and Kreb's cycle enzymes. On the average, the proportion of loci heterozygous per individual for three groups of loci is: hydrolytic enzymes and others (.164), larval proteins (.115) and glycolytic and Kreb's cycle enzymes (.037). We also observe that in all populations the level of polymorphism on the X chromosome is far less than the expected 38%; in salivary gland cells the euchromatic length of the X chromosome is 38% of the entire genome. Lower levels of polymorphism for the X chromosome loci are explained due to low probability of balanced polymorphisms for the X-linked loci since the conditions for establishment of balanced polymorphism for X-linked loci are more restrictive than for the autosomal loci.-The polymorphic loci can be grouped according to pattern of allele frequencies in different populations as follows: (1) The allele frequencies are similar in all populations at the XDH, Pep-1 and Hex-1 loci. (2) The alleles at the Est-1, Est-2, Amy loci and the AP-4(1.0) and the LAP-1(.90) alleles show north south clinal change in frequency. (3) There is north south and east west differentiation at the Pt-5, Pt-8 and Pt-9 loci and the allele AP-4(.81). (4) Polymorphism at loci such as Fum, B.Ox, Hex-8, Pep-2 and Pep-3 are restricted to only one or two of the populations. (5) Allele frequencies at the MDH and ODH loci fluctuate between populations. (6) Allele frequencies at many polymorphic loci such as Est-1, Est-2, LAP-1, AP-4, Pt-5, Pt-8, Pt-9, Pt-16, MDH, Fum change clinally within a gene arrangement. The pattern of gene variation in D. robusta is very complex and cannot be easily explained due to migration of neutral alleles between once-isolated populations or to semi-isolation of neutral alleles. The observations of the pattern of allele variation in different populations, high levels of polymorphism in the marginal populations which have small population size and low levels of polymorphism of the X chromosome loci all support the argument in favor of balancing selection as the main mechanism for the maintenance of these polymorphisms. Environmental factors must play a role in the maintenance of a great deal of these polymorphisms, since we observe clinal allele frequency changes even within a given inversion type.
Acid Phosphatase↗
Genetic changeover in Drosophila populations.
Three populations of Drosophila melanogaster that were daughter populations of two others with histories of high, continuous radiation exposure [population 5 (irradiated, small population size) gave rise to populations 17 (small) and 18 (large); population 6 (irradiated, large population size) gave rise to population 19 (large)] were maintained for 1 year with no radiation exposure. The frequency with which random combinations of second chromosomes taken from population 19 proved to be lethal changed abruptly after about 8 months, thus revealing the origin of a selectively favored element in that population. (This "element" may or may not have been the cause of the lethality.) A comparison of the loss of lethals in populations 17 and 18 with a loss that occurred concurrently in the still-irradiated population 5 suggests that a second, selectively favored element had arisen in that population just before populations 17 and 18 were split off. This element was on a nonlethal chromosome. The result in population 5 was the elimination of many lethals from that population, followed by a subsequent increase as mutations occurred in the favored nonlethal chromosome. Populations 17 and 18, with no radiation exposure, underwent a loss of lethals with no subsequent increase. The events described here, as well as others to be described elsewhere, suggest that populations may be subject to episodic periods of rapid gene frequency changes that occur under intense selection pressure. In the instances in which the changeover was revealed by the elimination of preexisting lethals, earlier lethal frequencies were reduced by approximately one-half; the selectively favored elements appear, then, to be favored in the heterozygous--not homozygous--condition.
Animals↗
Three challenges of China's population in the 1990s.
China will encounter 3 challenges of its population problem in the 1990s. The 1st is the huge number of people born or population increase each year. The 3rd baby boom, which started at the mid-1980s, will last until abound 1997. The women entering into the age of peak childbearing (23 years old) exceed 11 million each year with an upper range of about 13 million. IN 1992, the number of women of fecund ages (22-29) in the whole country will reach 124 million, the largest number of fertile women in history. The net increase of population will be from 15.5 to 17.0 million for each hear. What is more serious is that the momentum of population increase will continue, instead of being checked by the year 2000. The next are the continuous increase of the aged population of 65 and over and the growing tendency of population aging ahead of economic development. China is a developing socialist country, huge in population, weak in economic development, with less-developed science, culture, and education. However, as a result of the decline in the proportion of children to the total population due to the decline in the birth rate in the 1970s, China's population has become an adult population from a young one in terms of the age structure, and will be an aged one very soon. China is facing the challenge of aging under economically less developed conditions. For developed countries, it took 80 years for the proportion of the aged population of 65 and over to increase from 7% to 17%; for China, it has taken only 40 years. It will certainly bring about a series of problems and difficulties upon the society to cope with such a huge number of elderly in an underdeveloped economy. The 3rd challenge is the increasing pressure on employment due to the continuous growth of working-age population (15-64). It is estimated that the working-age population will increase to 858 million by 2000, 20 million more than the sum of working-age population in all of the developed countries; and to 977 million by 2020. Since in a short period of time it is difficult to change the situation of labor supply greater than demand, the pressure on employment will continue to increase, with more than 15 million people entering the labor force or waiting for jobs each year. In particular, the rural surplus labor force will reach 233 million by 2000. This is signaled by the huge number of farmers who have rushed into big cities for work in recent years. It is far beyond the capability of the government to employ such a huge number of laborers because it would require an investment of at least 3600 billion yuan for fixed assets. It seems to me that the 3 population challenges stated above are not isolated but interact to restrict the process of China's economic and social development. The way out lies in developing production and doing a better job of economic construction, while also adopting comprehensive measures to make further efforts in practicing family planning to better control the overrapid growth of population and improve the quality of human resources.
Adult↗
Importance of population structure at the time of toxicant exposure.
Populations in nature often consist of a mixture of stages and ages, yet toxicological studies even demographic studies, usually evaluate one starting life stage. In this study it was asked whether the starting age/stage structure of a population at the time of initial pesticide exposure influenced the impact that pesticides have on population growth rates. This question was answered by exposing differently structured populations of two terrestrial arthropod species, the two-spotted spider mite, Tetranychus urticae (Koch), and the pea aphid, Acrythosiphon pisum (Harris), to pesticides. The three structured populations tested were (1) eggs or neonates for A. pisum and T. urticae, respectively, (2) stable age distribution, and (3) young adult females only. Instantaneous rates of population increase (ri) for the three structured populations were determined over time without exposure to pesticides (control) and after exposure to pesticides. Populations of T. urticae were exposed to 100 ppm of the pesticide dicofol; populations of A. pisum were exposed to 200 ppm Neemix. The ri for the three control populations of T. urticae and A. pisum converged in a closed system 16 and 17 days after the start of the study, respectively. Unlike the control populations, the ri of the three treated populations did not converge by Day 16 for the mite species or Day 17 for the aphid species after exposure to pesticides. Growth rates of populations started as eggs (mites) or neonates (aphids) remained significantly lower than those of the adult or mixed-age populations (P</=0.05). Acute mortality data indicated that exposure to 100 ppm dicofol was equivalent to the LC21 for the egg stage, the LC59 for immatures, and the LC69 for adult T. urticae. Thus, even though the egg stage was the least susceptible stage of T. urticae, populations started as eggs were significantly more susceptible than populations started as the stable age distribution or as adults. It was concluded that the initial structure of a population does have an influence on the impact that pesticides will have on populations and that age/stage structure should be given serious consideration when evaluating toxicant effects.
Age Factors↗