(1/4953) Prediction of genetic contributions and generation intervals in populations with overlapping generations under selection.
A method to predict long-term genetic contributions of ancestors to future generations is studied in detail for a population with overlapping generations under mass or sib index selection. An existing method provides insight into the mechanisms determining the flow of genes through selected populations, and takes account of selection by modeling the long-term genetic contribution as a linear regression on breeding value. Total genetic contributions of age classes are modeled using a modified gene flow approach and long-term predictions are obtained assuming equilibrium genetic parameters. Generation interval was defined as the time in which genetic contributions sum to unity, which is equal to the turnover time of genes. Accurate predictions of long-term genetic contributions of individual animals, as well as total contributions of age classes were obtained. Due to selection, offspring of young parents had an above-average breeding value. Long-term genetic contributions of youngest age classes were therefore higher than expected from the age class distribution of parents, and generation interval was shorter than the average age of parents at birth of their offspring. Due to an increased selective advantage of offspring of young parents, generation interval decreased with increasing heritability and selection intensity. The method was compared to conventional gene flow and showed more accurate predictions of long-term genetic contributions. (+info)
(2/4953) Ancestral Asian source(s) of new world Y-chromosome founder haplotypes.
Haplotypes constructed from Y-chromosome markers were used to trace the origins of Native Americans. Our sample consisted of 2,198 males from 60 global populations, including 19 Native American and 15 indigenous North Asian groups. A set of 12 biallelic polymorphisms gave rise to 14 unique Y-chromosome haplotypes that were unevenly distributed among the populations. Combining multiallelic variation at two Y-linked microsatellites (DYS19 and DXYS156Y) with the unique haplotypes results in a total of 95 combination haplotypes. Contra previous findings based on Y- chromosome data, our new results suggest the possibility of more than one Native American paternal founder haplotype. We postulate that, of the nine unique haplotypes found in Native Americans, haplotypes 1C and 1F are the best candidates for major New World founder haplotypes, whereas haplotypes 1B, 1I, and 1U may either be founder haplotypes and/or have arrived in the New World via recent admixture. Two of the other four haplotypes (YAP+ haplotypes 4 and 5) are probably present because of post-Columbian admixture, whereas haplotype 1G may have originated in the New World, and the Old World source of the final New World haplotype (1D) remains unresolved. The contrasting distribution patterns of the two major candidate founder haplotypes in Asia and the New World, as well as the results of a nested cladistic analysis, suggest the possibility of more than one paternal migration from the general region of Lake Baikal to the Americas. (+info)
(3/4953) Long-term studies of hantavirus reservoir populations in the southwestern United States: rationale, potential, and methods.
Hantaviruses are rodent-borne zoonotic agents that cause hemorrhagic fever with renal syndrome in Asia and Europe and hantavirus pulmonary syndrome (HPS) in North and South America. The epidemiology of human diseases caused by these viruses is tied to the ecology of the rodent hosts, and effective control and prevention relies on a through understanding of host ecology. After the 1993 HPS outbreak in the southwestern United States, the Centers for Disease Control and Prevention initiated long-term studies of the temporal dynamics of hantavirus infection in host populations. These studies, which used mark-recapture techniques on 24 trapping webs at nine sites in the southwestern United States, were designed to monitor changes in reservoir population densities and in the prevalence and incidence of infection; quantify environmental factors associated with these changes; and when linked to surveillance databases for HPS, lead to predictive models of human risk to be used in the design and implementation of control and prevention measures for human hantavirus disease. (+info)
(4/4953) Long-term hantavirus persistence in rodent populations in central Arizona.
For 35 months, we monitored hantavirus activity in rodent populations in central Arizona. The most frequently captured hantavirus antibody-positive rodents were Peromyscus boylii and P. truei. Antibody-positive P. boylii were more frequently male (84%), older, and heavier, and they survived longer on trapping web sites than antibody-negative mice. The number of antibody-positive P. boylii was greater during high population densities than during low densities, while antibody prevalence was greater during low population densities. Virus transmission and incidence rates, also related to population densities, varied by trapping site. The spatial distribution of antibody-positive P. boylii varied by population density and reflected the species preference for dense chaparral habitats. The focal ranges of antibody-positive P. boylii also demonstrated a patchy distribution of hantavirus. (+info)
(5/4953) A longitudinal study of Sin Nombre virus prevalence in rodents, southeastern Arizona.
We determined the prevalence of Sin Nombre virus antibodies in small mammals in southeastern Arizona. Of 1,234 rodents (from 13 species) captured each month from May through December 1995, only mice in the genus Peromyscus were seropositive. Antibody prevalence was 14.3% in 21 white-footed mice (P. leucopus), 13.3% in 98 brush mice (P. boylii), 0.8% in 118 cactus mice (P. eremicus), and 0% in 2 deer mice (P. maniculatus). Most antibody-positive mice were adult male Peromyscus captured close to one another early in the study. Population dynamics of brush mice suggest a correlation between population size and hantavirus-antibody prevalence. (+info)
(6/4953) The changing elderly population and future health care needs.
The impending growth of the elderly population requires both fiscal and substantive changes in Medicare and Medicaid that are responsive to cost issues and to changing patterns of need. More emphasis is required on chronic disease management, on meaningful integration between acute and long-term care services, and on improved coordination between Medicare and Medicaid initiatives. This paper reviews various trends, including the growth in managed-care approaches, experience with social health maintenance organizations and Program of All-Inclusive Care for the Elderly demonstrations, and the need for a coherent long-term care policy. Such policies, however, transcend health care and require a broad range of community initiatives. (+info)
(7/4953) Sex-biased dispersal in sperm whales: contrasting mitochondrial and nuclear genetic structure of global populations.
The social organization of most mammals is characterized by female philopatry and male dispersal. Such sex-biased dispersal can cause the genetic structure of populations to differ between the maternally inherited mitochondrial DNA (mtDNA) and the bi-parental nuclear genome. Here we report on the global genetic structure of oceanic populations of the sperm whale, one of the most widely distributed mammalian species. Groups of females and juveniles are mainly found at low latitudes, while males reach polar waters, returning to tropical and subtropical waters to breed. In comparisons between oceans, we did not find significant heterogeneity in allele frequencies of microsatellite loci (exact test; p = 0.23). Estimates of GST = 0.001 and RST = 0.005 also indicated negligible if any nuclear DNA differentiation. We have previously reported significant differentiation between oceans in mtDNA sequences. These contrasting patterns suggest that interoceanic movements have been more prevalent among males than among females, consistent with observations of females being the philopatric sex and having a more limited latitudinal distribution than males. Consequently, the typical mammalian dispersal pattern may have operated on a global scale in sperm whales. (+info)
(8/4953) Patient health management: a promising paradigm in Canadian healthcare.
Disease management, or the focused application of resources to achieve desired health outcomes, began in Canada in 1971 with the introduction of a universal healthcare program and a single government payor. Although relatively unfocused and nonrestrictive by contemporary standards, this program was successful in terms of outcomes. However, it is expensive, and Canada's rapidly aging population is fueling a growing demand for more efficacious medical therapies. As a result, isolated services are being restricted in an effort to reduce costs. As a result of these changes and low prescription and patient compliance rates for efficacious therapies, total system costs have risen, there is a growing concern about deterioration of health outcomes, and stakeholders are dissatisfied. To optimize healthcare outcomes and reduce costs, a new paradigm--patient health management (PHM)--has emerged. With PHM, clinical and cost outcomes are continually measured and communicated to providers in an attempt to promote more efficacious care. PHM also seeks to avoid restrictive practices that are now associated with detrimental health outcomes and increased costs. PHM has proved successful when applied to acute and chronic cardiac disease treatment. It remains untested for most other diseases, but available data suggest that the comprehensive, evidence-based disease and systems management that characterizes PHM is likely to achieve the best health outcomes for the most people at the lowest possible costs. (+info)