Genetic structure of the world's polar bear populations.

We studied genetic structure in polar bear (Ursus maritimus) populations by typing a sample of 473 individuals spanning the species distribution at 16 highly variable microsatellite loci. No genetic discontinuities were found that would be consistent with evolutionarily significant periods of isolation between groups. Direct comparison of movement data and genetic data from the Canadian Arctic revealed a highly significant correlation. Genetic data generally supported existing population (management unit) designations, although there were two cases where genetic data failed to differentiate between pairs of populations previously resolved by movement data. A sharp contrast was found between the minimal genetic structure observed among populations surrounding the polar basin and the presence of several marked genetic discontinuities in the Canadian Arctic. The discontinuities in the Canadian Arctic caused the appearance of four genetic clusters of polar bear populations. These clusters vary in total estimated population size from 100 to over 10 000, and the smallest may merit a relatively conservative management strategy in consideration of its apparent isolation. We suggest that the observed pattern of genetic discontinuities has developed in response to differences in the seasonal distribution and pattern of sea ice habitat and the effects of these differences on the distribution and abundance of seals.

Integrated literature review on effects of exposure to violence upon adolescents.

Violence has reached epidemic proportions in the Unites States. The past decade has seen professionals in public health, law enforcement, social sciences, and health care commit more attention to this area. Research and anecdotal articles read by the researcher indicated adolescents exposed to chronic community violence may experience a myriad of problems including; academic failure, the tendency to engage in violent behavior, depression, and a nihilistic, fatalistic orientation to the future, which often leads to increased risk-taking behaviors. The purpose of this integrative literature review is to discover what is known about exposure to violence among adolescents. While the review did find various negative effects of being exposed to violence, a cross-sectional design was often used, with self-reported data. Instruments with established validity and reliability were used to gather the data were often appropriate to the population. Aspects of the methodologies used by the researchers should be replicated in order to add to the knowledge of this topic.

Protective factors within the family, and their role in fostering resiliency in African American adolescents.

Violence has reached epidemic proportions in the United States, with African American males residing in urban areas bearing the brunt of this epidemic. The violence permeating our society emanates from a variety of societal ills, including poverty, racism, substance abuse and exposure to violence. Traditionally, methods of research on adolescent violence have focused on an identification of associated risk factors. The majority of African American adolescents living in communities with widespread and chronic violence grow up to be law-abiding citizens. The reason for this may be due to resiliency within these adolescents. Resiliency has been defined as the ability to experience adverse circumstances and successfully overcome them. Resiliency is enhanced through three mechanisms identified as protective factors: individual characteristics/traits; familial traits; and extrafamilial relationships. The risks faced may be altered, and even ameliorated, through the presence of these protective factors. The purpose of this paper is to identify protective factors within the family that foster resiliency. Protective factors within the family may be categorized as having three broad characteristics: caring and support, high expectations, and encouragement of participation and involvement for the adolescent.

Microsatellite analysis of population structure in Canadian polar bears.

Attempts to study the genetic population structure of large mammals are often hampered by the low levels of genetic variation observed in these species. Polar bears have particularly low levels of genetic variation with the result that their genetic population structure has been intractable. We describe the use of eight hypervariable microsatellite loci to study the genetic relationships between four Canadian polar bear populations: the northern Beaufort Sea, southern Beaufort Sea, western Hudson Bay, and Davis Strait-Labrador Sea. These markers detected considerable genetic variation, with average heterozygosity near 60% within each population. Interpopulation differences in allele frequency distribution were significant between all pairs of populations, including two adjacent populations in the Beaufort Sea. Measures of genetic distance reflect the geographic distribution of populations, but also suggest patterns of gene flow which are not obvious from geography and may reflect movement patterns of these animals. Distribution of variation is sufficiently different between the Beaufort Sea populations and the two more eastern ones that the region of origin for a given sample can be predicted based on its expected genotype frequency using an assignment test. These data indicate that gene flow between local populations is restricted despite the long-distance seasonal movements undertaken by polar bears.

Identificación de embarazos de alto riesgo de bajo peso al nacer en zonas urbanas de América Latina: II. Indice simplificado de detección precoz en la Ciudad de Guatemala / Epidemiologic identification of infants with low birth weight in urban areas of Latin America: II. A simplified risk score for early prenatal identification in an urban area of Guatemala City

En los países en desarrollo hace falta un instrumento empírico sencillo para identificar a embarazadas en alto riesgo de dar a luz un hijo de bajo peso. Tal instrumento ayudaría a reducir la incidencia de bajo peso al nacer, ya que permitiría brindar a estas madres cuidados prenatales apropiados. El propósito del presente estudio fue crear un instrumento de este tipo a partir de datos obtenidos antes de la 26a. semana de gestación en una población compuesta de 17 135 embarazadas de la Ciudad de Guatemala. El instrumento al parecer, podría servir para detectar el riesgo de bajo peso al nacer en las poblaciones urbanas de otros países en desarrollo

Epidemiologic identification of infants with low birth weight in urban areas of Latin America: II. A simplified risk score for early prenatal identification in Guatemala City.

A simple, empirically derived instrument is needed in developing countries to identify mothers at risk of delivering low birth weight (LBW) infants, in order to help reduce the incidence of LBW deliveries and provide mothers at high risk with appropriate health care. The study reported here was devoted to developing an instrument of this kind using data obtained before the twenty-sixth week of gestation from an urban study population of 17,135 Guatemalan women. It appears that this instrument could be appropriately applied to urban populations in other developing countries.

Identificación de embarazos de alto riesgo de bajo peso al nacer en zonas urbanas de América Latina: II. Indice simplificado de detección precoz en la Ciudad de Guatemala / Epidemiologic identification of infants with low birth weight in urban areas of Latin America: II. A simplified risk score for early prenatal identification in an urban area of Guatemala City

En los países en desarrollo hace falta un instrumento empírico sencillo para identificar a embarazadas en alto riesgo de dar a luz un hijo de bajo peso. Tal instrumento ayudaría a reducir la incidencia de bajo peso al nacer, ya que permitiría brindar a estas madres cuidados prenatales apropiados. El propósito del presente estudio fue crear un instrumento de este tipo a partir de datos obtenidos antes de la 26a. semana de gestación en una población compuesta de 17 135 embarazadas de la Ciudad de Guatemala. El instrumento al parecer, podría servir para detectar el riesgo de bajo peso al nacer en las poblaciones urbanas de otros países en desarrollo

Epidemiologic identification of infants with low birth weight in urban areas of Latin America:: II A simplified risk score for early prenatal

A simple, empirically derived instrument is needed in developing countries to identify mothers at risk of delivering low birth weight (LBW) infants, in order to help reduce the incidence of LBW deliveries and provide mothers at high risk with appropriate health care. The study reported here was devoted to developing an instrument of this kind using data obtained before the twenty-sixth week of gestation from an urban study population of 17,135 Guatemalan women. It appears that this instrument could be appropriately applied to urban populations in other developing countries

Epidemiologic identification of infants with low birth weight in urban areas of Latin America:: II A simplified risk score for early prenatal

A simple, empirically derived instrument is needed in developing countries to identify mothers at risk of delivering low birth weight (LBW) infants, in order to help reduce the incidence of LBW deliveries and provide mothers at high risk with appropriate health care. The study reported here was devoted to developing an instrument of this kind using data obtained before the twenty-sixth week of gestation from an urban study population of 17,135 Guatemalan women. It appears that this instrument could be appropriately applied to urban populations in other developing countries

The measuring of blood pressure during pregnancy.

This is an evaluation of the methodology of blood pressure measurement in a high-risk obstetric clinic. Blood pressure values were obtained from 149 patients by the clinic staff and the research project coordinator. The project coordinator using the random-zero sphygmomanometer measured lower systolic and higher diastolic values. The diastolic and systolic values increased after 30 weeks of pregnancy up to term. Agreement among observers is low for diastolic blood pressure. The clinic staff measured about 50% of the values with a zero terminal digit as compared with only 14% by the project coordinator. The fourth Korotkoff sound can be recorded in 83% of the patients. The mean diastolic blood pressures obtained with the fourth sound are significantly higher than when the fifth sound is used. Recommendations are offered for blood pressure measuring during pregnancy, and it is strongly suggested that the same methodologic rigor be used as in any other medical procedure.

Mortality of the Monarch Butterfly (Danaus plexippus L.): Avian Predation at Five Overwintering Sites in Mexico.

Analyses of predated butterflies on the forest floor at five monarch overwintering sites in Mexico and observations of birds foraging in mixed flocks indicate that individual birds of several species have learned to penetrate the monarch's cardenolide-based chemical defense. Predation is inversely proportional to colony size and appears to be one evolutionary explanation of the dense aggregations.

Social indicators in black and white: some ethnic considerations in delivery of service to the elderly.

A random sample of older persons who contacted the Central Intake Referral and Information Service (CIRIS) of the Houston Areawide Model Project for the Elderly responded to the Social Indicators Index for the Aged. The scores obtained from this instrument were analyzed with respect to ethnicity. Comparisons were made with data from an independent city-wide sample to which the same instrument was administered. When ethnicity was controlled, consistent differences emerged both between the two samples and within each sample. Significant differences found in the CIRIS sample on measures of income, health, and life satisfaction were combined with differences between the two samples to provide indications of cultural factors involved in utilization of services by the elderly. Our findings support other literature which has stressed the necessity of considering ethnic differences in developing theories on aging and in designing and delivering services to the aged--regardless of whether one is dealing with minority or majority individuals.

Ionospheric topside sounding.

Over the past few years, the satellite topside sounders have significantly contributed to the understanding of the upper ionosphere. A great quantity of radio echo data has been accumulated, from which the ionospheric electrondensity distribution can be determined. The topside measurements of electron density essentially agree with similar measurements from the ground, except for an occasional 10-percent discrepancy near the peak of the ionosphere. While horizontal non-uniformity is a likely cause, this discrepancy has not yet been adequately explained. The electron-density scale heights measured at a constant altitude indicate both a higher temperature and a heavier mean ion mass at high latitudes. At low latitudes the topside measurements have shown the detailed latitudinal structure of the equatorial anomaly, demonstrating control by the geomagnetic field. A variety of electron-density irregularities have been studied. Most are greatly elongated along the magnetic field, and produce echoes either by lateral scattering, if they are thin, or by longitudinal ducting, if they are thick. Some of the thick irregularities are continuous between the hemispheres and support conjugate echo propagation. The topside sounders have revealed the complex structure of the ionosphere near the auroral zone and at higher latitudes. At night an east-west trough of greatly reduced electron density occurs equatorward of the auroral zone. At the auroral zone itself the electron density is high and quite variable, both in space and time. The electron density at the polar cap within the auroral zone is often uniform and smooth. Ionospheric irregularities are common in the area of the trough and the auroral zone. Among other satellites, the topside sounders have been used in various plasma studies involving the excitation and propagation of waves. These studies suggest that the ionosphere is an appropriate region for future plasma physics investigations, especially with rocket and satellite payloads designed specifically for that purpose.