Environment and sex ratios among alaska natives: An historical perspective

Human-environment interactions can affect the sex ratios of resource-dependent societies in a variety of ways. Historical and contemporary data on Alaska Native populations illustrate such effects. Some eighteenth and early nineteenth century observers noted an excess of females, which they attributed to high mortality among hunters. Population counts in the later nineteenth century and well into the twentieth found instead an excess of men in many communities. Female infanticide was credited as the explanation: since family survival depended upon hunting success, males were more valued. Although infanticide explanations for the excess of males have been widely believed, available demographic data point to something else: higher adult female mortality. Finally, in the postwar years, the importance of mortality differentials seems to have faded-and also changed direction. Female outmigration from villages accounts for much of the gender imbalance among Native populations today. Natural-resource development, particularly North Slope oil, indirectly drives this migration. In Alaska\u27s transcultural communities, the present gender imbalances raise issues of individual and cultural survival

Prenatal Exposures to Environmental Chemicals and Children's Neurodevelopment: An Update

This review surveys the recent literature on the neurodevelopmental impacts of chemical exposures during pregnancy. The review focuses primarily on chemicals of recent concern, including phthalates, bisphenol-A, polybrominated diphenyl ethers, and perfluorinated compounds, but also addresses chemicals with longer histories of investigation, including air pollutants, lead, methylmercury, manganese, arsenic, and organophosphate pesticides. For some chemicals of more recent concern, the available literature does not yet afford strong conclusions about neurodevelopment toxicity. In such cases, points of disagreement among studies are identified and suggestions provided for approaches to resolution of the inconsistencies, including greater standardization of methods for expressing exposure and assessing outcomes

A Strategy for Comparing the Contributions of Environmental Chemicals and Other Risk Factors to Neurodevelopment of Children

Background: The impact of environmental chemicals on children’s neurodevelopment is sometimes dismissed as unimportant because the magnitude of the impairments are considered to be clinically insignificant. Such a judgment reflects a failure to distinguish between individual and population risk. The population impact of a risk factor depends on both its effect size and its distribution (or incidence/prevalence)

Mitigating the mass dependence in the Δν\Delta\nu scaling relation of red-giant stars

The masses and radii of solar-like oscillators can be estimated through the asteroseismic scaling relations. These relations provide a direct link between observables, i.e. effective temperature and characteristics of the oscillation spectra, and stellar properties, i.e. mean density and surface gravity (thus mass and radius). These scaling relations are commonly used to characterize large samples of stars. Usually, the Sun is used as a reference from which the structure is scaled. However, for stars that do not have a similar structure as the Sun, using the Sun as a reference introduces systematic errors as large as 10\% in mass and 5\% in radius. Several alternatives for the reference of the scaling relation involving the large frequency separation (typical frequency difference between modes of the same degree and consecutive radial order) have been suggested in the literature. In a previous paper, we presented a reference function with a dependence on both effective temperature and metallicity. The accuracy of predicted masses and radii improved considerably when using reference values calculated from our reference function. However, the residuals indicated that stars on the red-giant branch possess a mass dependence that was not accounted for. Here, we present a reference function for the scaling relation involving the large frequency separation that includes the mass dependence. This new reference function improves the derived masses and radii significantly by removing the systematic differences and mitigates the trend with $\nu_{\rm max}$ (frequency of maximum oscillation power) that exists when using the solar value as a reference.Comment: 12 pages, 7 figures, accepted for publication in MNRA

Social Ecology of Children’s Vulnerability to Environmental Pollutants

BACKGROUND: The outcomes of exposure to neurotoxic chemicals early in life depend on the properties of both the chemical and the host’s environment. When our questions focus on the toxicant, the environmental properties tend to be regarded as marginal and designated as covariates or confounders. Such approaches blur the reality of how the early environment establishes enduring biologic substrates. OBJECTIVES: In this commentary, we describe another perspective, based on decades of biopsychological research on animals, that shows how the early, even prenatal, environment creates permanent changes in brain structure and chemistry and behavior. Aspects of the early environment—encompassing enrichment, deprivation, and maternal and neonatal stress—all help determine the functional responses later in life that derive from the biologic substrate imparted by that environment. Their effects then become biologically embedded. Human data, particularly those connected to economically disadvantaged populations, yield equivalent conclusions. DISCUSSION: In this commentary, we argue that treating such environmental conditions as confounders is equivalent to defining genetic differences as confounders, a tactic that laboratory research, such as that based on transgenic manipulations, clearly rejects. The implications extend from laboratory experiments that, implicitly, assume that the early environment can be standardized to risk assessments based on epidemiologic investigations. CONCLUSIONS: The biologic properties implanted by the early social environment should be regarded as crucial elements of the translation from laboratory research to human health and, in fact, should be incorporated into human health research. The methods for doing so are not clearly defined and present many challenges to investigators

Prenatal Lead Levels, Plasma Amyloid β Levels, and Gene Expression in Young Adulthood

Background: Animal studies suggest that early-life lead exposure influences gene expression and production of proteins associated with Alzheimer’s disease (AD)

Studies on the Occurrence and Elemental Composition of Bacteria in Freshwater Plankton

The occurrence and cation content of bacteria in a eutrophic freshwater lake (Rostherne Mere, Cheshire, UK) were investigated over a one year sampling period in relation to cation changes in the lake surface water and phytoplankton. Scanning electron microscope examination of trawl-net and filtered samples demonstrated bacterial association with Anabaena, Aphanizomenon and diatoms. Direct counts of associated and unassociated bacteria showed that increases in bacterial population relate to population decline of major algal constituents. Spectrophotometric determination of selected cation levels in the lake water demonstrated wide fluctuations throughout the sampling period, with elevated levels of transition metals before and at the end of Summer stratification. Zn and Pb also showed increased levels in relation to episodic events. Mass fractions of spectrophotometrically-determined selected cations (Fe, Cu, Zn and Pb) in phytoplankton also varied considerably during the sampling period, with major increases apparently following peaks in water level. X-ray microanalysis of whole, unassociated bacterial eel ls demonstrated high levels of soluble and bound cations, including K, Ca, Fe, Cu, Ni, Zn and Pb. Changes in the cation levels of bacteria did not follow a similar pattern to the general phytoplankton - probably due to differences in uptake or adsorption or to cycling of bacterial cells in the water column