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PubMed2002

[Fur color gene profiles and length of hair of several cat populations in Cuba, Costa Rica, Colombia, Paraguay, Chile and Argentina, and possible genetic origins of these cat populations].

Until the present moment, only a scarce number of Latin American domestic cat populations have been studied from a population genetic standpoint. For this reason, the cat populations of La Havana (Cuba), San José (Costa Rica), Bogota and Ibagué (Colombia), Asuncion (Paraguay), Santiago (Chile) and Buenos Aires (Argentina) were sampled for several coat genes. The results obtained were as follows: (1) there was a strong genetic resemblance between several Hispanic American cat populations (especially, those of Buenos Aires, San José and the two Colombian populations studied) and those from South Western United States (California, Texas and Colorado), which adds support to the suspicion that these populations probably have a common origin; (2) The cat population of Santiago (Chile), contrarily to the other Hispanic American populations studied, showed a strong genetic resemblance with some Anglo North American populations; and (3) The l (long hair) and d (dilution) alleles showed systematic higher frequencies in the Hispanic American populations than those observed in Spain. Although the Hispanic American populations were not identical to the current Spanish populations (with the exception of Asuncion), this historic genetic experiment was very different to that found for the British populations and their overseas colonies.

Animals↗
PubMed2002

Among- and within-population variability in tolerance to cadmium stress in natural populations of Daphnia magna: implications for ecological risk assessment.

Previous attempts to test the hypothesis that laboratory selection of isogenetic populations can produce test organisms with a significantly increased mean tolerance to toxic substances have failed. One possible explanation for such failure is that the tolerance of laboratory populations is largely constrained by their origins (were the source populations composed of tolerant genotypes?). To address this question, among- and within-population variability in stress tolerance was assessed by calculating the variance in individual fitness and longevity across a cadmium gradient (0-10 microg/L). The study employed Daphnia magna clones from four geographically separate European populations. Results revealed significant differences in tolerance to lethal levels of toxic stress among populations. The distribution of tolerances within two of the studied populations showed high amounts of genetic variation in tolerance. Genetic relationships between tolerance traits and life history performance under nonstressful environments differed among the studied populations. One population showed significant but low costs associated with tolerance, whereas no costs were associated with tolerance in the other population. These results suggest that laboratory selection will favor individuals with high fitness or reproductive performance under optimal laboratory conditions resulting in laboratory populations with similar or lower tolerance to toxic stress than their original field populations. Given that populations can exhibit high levels of genetic variability in tolerance to toxic stress, minimizing genetic diversity in toxicity tests will increase the uncertainty attendant in extrapolating from the lab to the field.

Adaptation, Physiological↗
PubMed1995

Democratic People's Republic of Korea. Population programme paves the way for better flow of and use of population information.

The population program of DPRK is currently generating census data, a number of demographic and contraceptive research studies, and various IEC materials. However, these have not been widely disseminated. At the same time, policymakers and professionals engaged in population and development activities expressed the need for more information and materials to assist them in their tasks. To address these needs, the government represented by the National Coordinating Committee for Population Programs, proposed the establishment of a Population Information Center that will facilitate the collection, processing, dissemination, and use of population information and materials in order to support the work of the population personnel. In a fact-finding and project development mission undertaken with the assistance of the UNFPA (UN Population Fund), Beijing, UNDP (UN Development Programme) Pyongyang, and CST for East and Southeast Asia Adviser on Population Information, it was agreed upon that a Population Information Center be set up at the Grand People's Study House which serves as the central document information center in the country as well as correspondence university rendering re-education programs for the working people. The project document basically lays the foundation for a nationwide population information networking by building first the centerpiece of the network. It will develop the capability of the Grand People's Study House in collecting, organizing, analyzing, repackaging and disseminating population information as well as in managing a nationwide network. Four activities will be envisaged to achieve this goal. The first requires the establishment of the Population Information Center structure and organization. The rest necessitate the collection of materials and creation of a bibliographic database, the training of personnel in various information-handling tools and techniques and service provision, and facilitating dissemination of information through a repackaging and lecture series program.

Asia↗
PubMed2003

Side population keratinocytes resembling bone marrow side population stem cells are distinct from label-retaining keratinocyte stem cells.

Very primitive hematopoietic stem cells have been identified as side population cells based on their ability to efflux a fluorescent vital dye, Hoechst 33342. In this study we show that keratinocytes with the same side population phenotype are also present in the human epidermis. Although side population keratinocytes have the same dye-effluxing phenotype as bone marrow side population cells and can be blocked by verapamil, they do not express increased levels of the ABCG2 transporter that is believed to be responsible for the bone marrow side population phenotype. Because bone marrow side population cells have stem cell characteristics, we sought to determine if side population keratinocytes represent a keratinocyte stem cell population by comparing side population keratinocytes with a traditional keratinocyte stem cell candidate, label-retaining keratinocytes. Flow cytometric analyses demonstrated that side population keratinocytes have a different cell surface phenotype (low beta1 integrin and low alpha6 integrin expression) than label-retaining keratinocytes and represent a unique population of keratinocytes distinctly different from the traditional keratinocyte stem cell candidate. Future in vivo studies will be required to analyze the function of side population keratinocytes in epidermal homeostasis and to determine if side population keratinocytes have characteristics of keratinocyte stem cells.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2000

Genetic structure and AFLP variation of remnant populations in the rare plant Pedicularis palustris (Scrophulariaceae) and its relation to population size and reproductive components.

We investigated plant reproduction in relation to genetic structure, population size, and habitat quality in 13 populations of the rare biennial plant Pedicularis palustris with 3-28500 flowering individuals. We used AFLP (amplified fragment length polymorphism) profiles to analyze genetic similarities among 129 individuals (3-15 per population). In a cluster analysis of genetic similarities most individuals (67%) were arranged in population-specific clusters. Analysis of molecular variance indicated significant genetic differentiation among populations and among and within subpopulations (P < 0.001). Gene flow (N(e) m) was low (0.298). On average, plants produced 55 capsules, 17 seeds per fruit, and 42 seedlings in the following growing season. The number of seeds per capsule was independent of population size and of genetic variability. In contrast, the number of capsules per plant (P < 0.05) and the number of seedlings per plant (P < 0.05) were positively correlated with population size. The relation between population size and the number of seeds per plant was not significant (P = 0.075). The number of capsules and of seeds and seedlings per plant (P < 0.01) were positively correlated with genetic variability. Genetic variability was independent of actual population size, suggesting that historical population processes have to be taken into account, too. Stepwise multiple regressions revealed additional significant relationships of habitat parameters (soil pH, C:N ratio), vegetation composition, and standing crop on reproductive components. We conclude that populations of P. palustris are genetically isolated and that reproductive success most likely is influenced by population size, genetic variability, and habitat quality. Management strategies such as moderate grazing, mowing, and artificial gene flow should endeavor to increase population size as well as genetic variation.

Journal Article↗
PubMed2006

Generalizability of relative risk estimates from a well-defined population to a general population.

We investigated the degree of generalizability of relative risk (RR) estimates for a sample from a well-defined population to a general population using actual data. A total of 45,452 men aged 40-69 years who completed a self-administered questionnaire were followed from 1990-1994 to the end of 1999-2000 in the Japan Public Health Center-based Prospective Study. We considered those who responded to the self-administered questionnaire (45,452 men) as representing the general population (population), and those who underwent a health check-up as representing a sample from a well- defined population (sample) (12,162 men). Exposure distributions, mortality rates, and the confounder-adjusted RRs of all-cause mortality according to cigarette smoking or body mass index (BMI) were compared between the sample and the population using empirical sampling distributions from the population. The sample had significantly different prevalences of exposures and lower mortality rates than the population. Adjusted RRs were significantly higher in current smokers (RR = 1.83) and in subjects who smoked > or =40 cigarettes per day (RR = 2.67) in the sample than the respective values in the corresponding categories (RR = 1.48 and 1.62, respectively) of the population. The adjusted RR of those with the lowest BMI in the sample (RR = 1.30) were also significantly lower than those of the corresponding category in the population (RR = 2.06). Our results suggest that even for RRs, the extrapolation of estimates for a sample from a well-defined population to a general population may not be possible.

Adult↗
PubMed1987

Genetic differentiation of quantitative characters between populations or species. II: Optimal selection in infinite populations.

Using a new and more general genetic model called the discrete-allelic state model and assuming discrete-time process, the evolutionary changes of genetic variation of quantitative characters, controlled by a few loci, within and between populations during the process of genetic differentiation of populations or species, are studied under the effects of mutation and centripetal selection in infinitely large populations. While in a finite population and ignoring selection, the rate of change of additive genetic variance depends on mutation and effective population size, traits under optimal selection in infinitely large populations go through the dynamics of a rather complicated form depending on the relative intensities of selection and mutation. When a population, which has reached steady-state by mutation-selection balance, splits into two, in one of which the same optimum genotype holds but in the other the optimum shifts a few standard deviations away from the original optimum, the corresponding daughter population starts differentiating from its sister population by favouring certain class of mutant alleles and discarding others which were originally favoured. During this process of turn over of genes, both the intra- and inter-populational variances undergo a complicated change, and the ratio of the former to the latter is a non-linear function of time of divergence. This pattern is qualitatively very different from the case when selection is absent. The intra-population distribution of genotypic values, during this transition, is shown to deviate considerably from normality. The presence of linkage seems to retard the accumulation of intra-populational genetic variance. The implications of these results are discussed in comparison with the earlier findings of evolutionary models of quantitative traits.

Alleles↗
PubMed2004

Population genetic structure in European populations of Spiranthes romanzoffiana set in the context of other genetic studies on orchids.

Spiranthes romanzoffiana Cham. is restricted in Europe to the British Isles, where it is recognised as a conservation priority species due to frequent extirpation of populations along with no evidence of seed set; vegetative reproduction has been invoked as the sole means of perpetuation and dispersal. To investigate the reproductive ecology of this species, 17 populations have been sampled for chloroplast microsatellites and amplified fragment length polymorphisms (AFLPs). These markers revealed a previously unsuspected genetic-geographic split in the species, which correlates with differences in patterns of within-population variation. Northern populations were fixed for one chloroplast haplotype but showed high levels of AFLP genotypic diversity consistent with sexual reproduction (proportion of genotypes distinguishable, PD = 0.98). More southerly populations showed fixed differences from the northern populations in their chloroplast haplotype and for 10 AFLP markers. They harboured only 12 unique multilocus genotypes among 113 individuals from six populations (PD = 0.11). These genotypes differed mostly by single bands, and none by more than 4/138 loci, with identical multilocus genotypes occurring in widely separated populations. This uniformity in southern populations is consistent with agamospermous or autogamous reproduction, and/or an extreme population bottleneck. Finally, the observed patterns of population differentiation in S. romanzoffiana are compared with other studies of orchids, revealing a wide range of values that belie recent contrasting published generalisations that claim that orchids show either higher, or lower, levels of population differentiation than other plant families.

Chloroplasts↗
PubMed2000

Microsatellite analysis of population structure and genetic differentiation within and between populations of the root vole, Microtus oeconomus in the Netherlands.

Eight microsatellite markers for the root vole (Microtus oeconomus) were developed to assess the amount of genetic variation for nine Dutch root vole populations from four different regions, and to evaluate the degree of differentiation and isolation. All eight microsatellite loci were found to be highly variable with observed heterozygosity values ranging from 0.61 to 0.82. These values are similar to those observed for more distant populations from Norway, Finland and Germany. Therefore, the populations seem not particularly depauperate of genetic variation at the microsatellite level. Genetically, the Dutch populations were found to have diverged considerably. Pairwise comparisons of all populations studied revealed FST values significantly greater than zero for most comparisons. However, the magnitude of these values considerably depends on the compared population pair. The level of differentiation between local populations within Dutch regions is generally significantly lower than the differentiation between Dutch regions. The level of differentiation between Dutch regions, however, is not significantly different from that between populations of larger geographical distance. This implies that the regional Dutch populations are both isolated from each other and from other European populations. The observation that even local populations show low but significant genetic differentiation may be indicative for progressive isolation of these populations.

Animals↗
PubMed2005

Molecular analysis reveals tighter social regulation of immigration in patrilocal populations than in matrilocal populations.

Human social organization can deeply affect levels of genetic diversity. This fact implies that genetic information can be used to study social structures, which is the basis of ethnogenetics. Recently, methods have been developed to extract this information from genetic data gathered from subdivided populations that have gone through recent spatial expansions, which is typical of most human populations. Here, we perform a Bayesian analysis of mitochondrial and Y chromosome diversity in three matrilocal and three patrilocal groups from northern Thailand to infer the number of males and females arriving in these populations each generation and to estimate the age of their range expansion. We find that the number of male immigrants is 8 times smaller in patrilocal populations than in matrilocal populations, whereas women move 2.5 times more in patrilocal populations than in matrilocal populations. In addition to providing genetic quantification of sex-specific dispersal rates in human populations, we show that although men and women are exchanged at a similar rate between matrilocal populations, there are far fewer men than women moving into patrilocal populations. This finding is compatible with the hypothesis that men are strictly controlling male immigration and promoting female immigration in patrilocal populations and that immigration is much less regulated in matrilocal populations.

Bayes Theorem↗
PubMed2003

[The genetic characteristic of HLA-DRB1 locus in the Jiangsu-Zhejiang-Shanghai Han population and a comparison of its frequency distribution with that of other populations].

OBJECTIVE: To investigate the genetic polymorphism of HLA-DRB1 locus in Jiangsu-Zhejiang-Shanghai Han population and analyze the characteristic of the allele frequency distribution in comparison with that of other populations. METHODS: The technique of polymerase chain reaction-sequence specific primers (PCR-SSP) and reverse polymerase chain reaction-sequence specific oligonucleotide probe (PCR-SSOP) was adopted in genotyping a sample of 626 unrelated healthy individuals collected from a Chinese Han population in Jiangsu-Zhejiang-Shanghai area. HLA-DRB1*0101-1001, DRB3, DRB4 and DRB5 were detected. The allele frequency of HLA-DRB1 was calculated, and the allele frequency distribution of HLA-DRB1 in this population was compared with the results from other populations. RESULTS: HLA-DRB1*0101, 0301, 0701, 09012, 1001, 1201, 1202, 1301/02, 1303/04, 1401/04/05, 1402/03/1305, 1501/02, 16021 and 04xx, 08xx were detected in Jiangsu-Zhejiang-Shanghai Han population. The common HLA-DRB1*allele included 09012(17.97%), 04xx(12.53%), 1202(11.42%) and 1501/02(11.02%). The polymorphism information content is 0.9024, and expected heterozygosity is 0.9634 in Jiangsu-Zhejiang-Shanghai Han population. CONCLUSION: The HLA-DRB1 distribution of Jiangsu-Zhejiang-Shanghai Han population shares some genetic characteristic with other Han populations, but it exhibits its own characteristic, suggesting the intermediate state of this population between the southern and northern Han populations. The polymorphism of HLA-DRB1 of Jiangsu-Zhejiang-Shanghai Han population is the most abundant one in this study.

China↗
PubMed1980

Canine population dynamics: a study of the Manhattan, Kansas, canine population.

Analysis of the age distribution in the pet population of dogs in the community of Manhattan, Kansas from 1968 to 1979 revealed that the distribution was stationary and the rate of population change (lambda1) was close to 1, which means, that if present conditions do not change, the population probably would remain stable in size in the future. The number of females spayed in the Manhattan population reached a frequency of 66% in 1979. Considering only present age-dependent birth and survival rates, the population could not maintain itself and would decrease rapidly in size. It was found, however, that the population is maintained by a high net rate of immigration, with about 75% of all dogs under 6 months old coming from outside the Manhattan population. The ratio of people to dogs in Manhattan was estimated to be 4.14:1; about 41% of all dogs under 6 months of age were acquired through breeders. Roaming animals in 1 year represented about 12% of the canine population in Manhattan; of those, 36% were stray (not claimed by owner) and the rest were owned and redeemed. The data represented only a portion of the population (dogs with responsible owners) and for a complete understanding of the dynamics of the entire population, one should analyze roaming dogs in a similar way. The methods described in this study should be useful for collecting data to be used by veterinarians and municipal authorities confronted with proposals for regulation dealing with reproduction and pet population.

Age Factors↗
PubMed2005

A model of underlying socioeconomic vulnerability in human populations: evidence from variability in population health and implications for public health.

Drawing from insights into the variability of complex biologic systems we propose that the health of human populations reflects the interrelationship between underlying vulnerabilities (determined by population-level social and economic factors; e.g., income distribution) and capacities (determined by population-level salutary resources, e.g., social capital) and how populations, shaped by these vulnerabilities and capacities, respond to intermittent stressors (e.g., economic downturns) and protective events (e.g., introduction of a school). Monitoring this dynamic at the population-level can be accomplished by examining not only rates of illness and mortality, but variability in rates, either between populations or within populations over time. We used mortality data from New York City neighborhoods between 1990 and 2001 to test two related hypotheses consistent with this model of population health: (a) There is greater variability in mortality rates at a point in time between neighborhoods that are characterized by socioeconomic vulnerability; and (b) there is greater variability in mortality rates over time within neighborhoods that are characterized by socioeconomic vulnerability. We found that neighborhoods characterized by social and economic vulnerability displayed substantial variability in particular mortality rates. Mortality rates displaying the greatest variability were from causes that may be sensitive to social conditions (e.g., homicide or HIV/AIDS rates). Variability in population health existed both between neighborhoods with underlying vulnerability at one point in time and within vulnerable neighborhoods over time. The results of this analysis are consistent with a theory of underlying socioeconomic vulnerabilities of human populations and suggest that variability in population health may be an important consideration in population health assessment.

Health Status Indicators↗
PubMed2004

Short-period heart rate variability in the general population as compared to patients with acute myocardial infarction from the same source population.

BACKGROUND: Our aim was to compare the distribution and determinants of heart rate variability (HRV) measures in a middle-aged population with patients of the same sex and age after an acute myocardial infarction (AMI), and to show, whether HRV values defined as abnormal from the general population are indicative for a worse prognosis even in AMI patients. METHODS: HRV was studied in a random sample of 149 middle-aged men and 137 women from the general population (45-65 years) as well as 129 consecutive AMI patients (25-74 years). Spectral analysis was used to compute low frequency (LF), high frequency (HF), and total frequency power. To the AMI population of age 45-65 years (N = 85) a sample out of the general population was matched by age and sex by 2:1 matching (N = 149). All AMI patients were followed for a median of 43 months (range 1-47) for death or malignant arrhythmia. RESULTS: All measures of HRV were significantly and substantially lower in AMI patients than the general population (P < 0.001). Expression in relative terms revealed that the proportionate contributions of HF and LF to total power were significantly different in the two populations with relatively lower LF power in AMI patients (P < 0.01). The negative correlation with heart rate and HRV measures was significantly more pronounced in AMI patients (P < 0.01). The 2.5th percentile of the LF power distribution in the general population (3.08 ln ms2) corresponds to the 25th percentile in the AMI population. Subjects of the whole AMI population with values below this LF cutpoint revealed a significant increased risk of death or malignant arrhythmia during follow-up (odds ratio 5.1; 95% confidence interval: 1.3; 23). CONCLUSIONS: AMI patients had strongly diminished HRV compared to the general population. The relatively lower LF power indicates an alteration of the sympathico-vagal balance, and the significantly stronger correlation of heart rate with HRV may be indicative for a more pronounced effect of sympathetic activation on autonomic modulation in the case of myocardial infarction. Finally, a value below the 2.5th percentile of the population LF power distribution may identify subjects at risk and warrant further testing.

Adrenergic beta-Antagonists↗
PubMed2004

Population differentiation and recombination in wheat scab populations of Gibberella zeae from the United States.

In limited previous studies of the Ascomycete fungus Gibberella zeae in North America, the populations examined were genetically and phenotypically diverse and could be viewed as subsamples of a larger population. Our objective in this study was to test the hypothesis that a homogeneous, randomly mating population of G. zeae is contiguous throughout the central and eastern United States across a span of several years. We analysed presence/absence alleles based on amplified fragment length polymorphisms (AFLPs) at 30 loci, 24 of which are defined genetically on a linkage map of G. zeae, from > 500 isolates in eight field populations from seven states collected during the 1998, 1999 and 2000 cropping seasons. All these strains had AFLP profiles similar to those of standard isolates of G. zeae phylogenetic lineage 7. All the populations are genetically similar, have high genotypic diversity and little or no detectable genetic disequilibrium, and show evidence of extensive interpopulation genetic exchange. Allele frequencies in some of the populations examined are not statistically different from one another, but others are. Thus, the populations examined are not mere subsamples from a single, large, randomly mating population. Geographic distance and genetic distance between populations are correlated significantly. The observed differences are relatively small, however, indicating that while genetic isolation by distance may occur, genetic exchange has occurred at a relatively high frequency among US populations of G. zeae. We think that these differences reflect the time required for the alleles to diffuse across the distances that separate them, because relatively little linkage disequilibrium is detected either in the population as a whole or in any of the individual subpopulations.

Gene Frequency↗
PubMed1973

Population growth in planaria Dugesia tigrina (gerard). Regulation by the absolute number in the population.

Planaria reproduce by transverse fission. Isolated worms increase in number exponentially, while social animals at the same density are inhibited in terms of numerical increase, but over a 25 day period undergo a larger increase in mass. Isolated posterior fission products reproduce faster than isolated anterior fission products. Regulation of population growth is independent of density over a 16-fold range and regulatory factors cannot be demonstrated in the medium. Regulation of population growth depends on direct contact between animals. Fission period varies from individual to individual and from period to period for a given individual. Doubling time is related to the absolute number of individuals comprising the population as follows: P(N) = (P(M) . N)/(K + N), where P(N) is the doubling period of a population of N individuals, P(M) is the doubling time of an infinitely large population, N is the number of individuals in the population, and K is the number of individuals in a population the period of which is one-half P(M). At 22 degrees -24 degrees C P(M) is estimated to be 43.3 days and K is 1.87 individuals. A model system assumes that inhibitor flows through the population from animal to animal from the slowest to the fastest animal in the population thus acting to synchronize population increase as well as to determine the rate of population growth. A possible source of the inhibitor is discussed.

Animals↗
PubMed2005

Seeing ghosts: the effect of unsampled populations on migration rates estimated for sampled populations.

In 2004, the term 'ghost population' was introduced to summarize the effect of unsampled subpopulations that exchange migrants with other subpopulations that have been sampled. Estimated long-term migration rates among populations sampled will be affected by ghost populations. Although it would be convenient to be able to define an apparent migration matrix among sampled populations that incorporate the exchange of migrants with ghost populations, no such matrix can be defined in a way that predicts all features of the coalescent process for the true migration matrix. This paper shows that if the underlying migration matrix is symmetric, it is possible to define an apparent migration matrix among sampled subpopulations that predicts the same within-population and between-population homozygosities among sampled populations as is predicted by the true migration matrix. Application of this method shows that there is no simple relationship between true and apparent migration rates, nor is there a way to place an upper bound on the effect of ghost populations. In general, ghost populations can create the appearance of migration between subpopulations that do not actually exchange migrants. Comparison with published results from the application of the program, MIGRATE, shows that the apparent migration rates inferred with that program in a three-subpopulation model differ from those based on pairwise homozygosities. The apparent migration matrix determined by the method described in this paper probably represents the upper bound on the effect of ghost populations.

Homozygote↗