Columnar grouping preserves synchronization in neuronal networks with distance-dependent time delays.

Neuronal connectivity at the cellular level in the cerebral cortex is far from random, with characteristics that point to a hierarchical design with intricately connected neuronal clusters. Here we investigate computationally the effects of varying neuronal cluster connectivity on network synchronization for two different spatial distributions of clusters: one where clusters are arranged in columns in a grid and the other where neurons from different clusters are spatially intermixed. We characterize each case by measuring the degree of neuronal spiking synchrony as a function of the number of connections per neuron and the degree of intercluster connectivity. We find that in both cases as the number of connections per neuron increases, there is an asynchronous to synchronous transition dependent only on intrinsic parameters of the biophysical model. We also observe in both cases that with very low intercluster connectivity clusters have independent firing dynamics yielding a low degree of synchrony. More importantly, we find that for a high number of connections per neuron but intermediate intercluster connectivity, the two spatial distributions of clusters differ in their response where the clusters in a grid have a higher degree of synchrony than the clusters that are intermixed.

A closer look at the rural-urban health disparities: Insights from four major diseases in the Commonwealth of Virginia.

Health disparities are increasingly recorded in literature, but are much less understood in a rural-urban context. This study help bridges this gap through investigation of four major diseases in the Commonwealth of Virginia: cancer, stroke, cardiovascular disease and chronic obstructive pulmonary disease. We utilize a unique inpatient hospital discharge billing dataset, and construct average patient counts at ZIP-code level over 2006-2008 where covariates from alternative sources are merged (806 ZIP-code areas, 190 urban, 616 rural). Count data regressions are first fitted to identify possible regional-level factors that affect disease incidences. A system of equations with rural-urban specification are then estimated via seemingly unrelated regression techniques to account for possible associations among these diseases and correlations of errors, which is followed by disease-specific nonlinear Blinder-Oaxaca decompositions that compare the respective explanatory powers of observed characteristics and unobserved mechanisms. Results suggest that regional-level factors are significantly correlated with health outcomes in both rural and urban areas. The unknown mechanisms behind these linkages are different between rural and urban areas, and explain even larger proportions of the observed disparities. These findings confirm the role of regional-level factors in generating rural-urban health disparities, and call for further investigations of the causal mechanisms of such disparities that remain largely unknown.

Integrating service-learning into an MPH curriculum for future public health practitioners: strengthening community-campus partnerships.

Through a 3-year grant from the Community-Campus Partnerships for Health, the Virginia Commonwealth University MPH program adopted an incremental approach to implement service-learning focused on health disparities into its curriculum. We first incorporated service-learning into an elective course and then a required internship. We then worked with the Virginia Department of Health to develop a plan for first-year students to engage in additional experiential learning through a practicum. Students also were encouraged to organize community service events, such as health fairs. Service-learning was fully incorporated into the internship. The first-year student practicum, followed by the internship, has strengthened collaborations among faculty, students, and the Virginia Department of Health and expanded student service in the community. The number of student-supported community service events more than doubled. An incremental approach to incorporating service-learning led to successful implementation of the pedagogy. Service-learning benefits community partners, enriches student learning, and is well-suited for studies in public health.

Understanding African American men's perceptions of racism, male gender socialization, and social capital through photovoice.

In this study we used a participatory qualitative research approach--photovoice--to collect information about African American men's perceptions of the factors that influenced their own health and the health of their communities. Photovoice was conducted as part of the "Men as Navigators (MAN) for Health" project, an evaluation of a male lay health advisor (LHA) intervention in central North Carolina. Twelve African American men living in both urban and rural communities took photographs and discussed the photos in six photo discussion sessions. Analysis involved identifying recurring themes from the photos and transcriptions of photo discussions. The results suggest that race and racism, male gender socialization, and social networks and social capital all have important influences on African American men's health. The implications for further research and public health practice are discussed.

Biological monitoring of uranium exposure in south central Virginia.

In May 2004, two groundwater wells in Dinwiddie County, Virginia were found to have natural uranium levels either at or above the EPA recommended limit of 30 microg/l. As a result, a stop drinking water advisory was issued until a water treatment system could be installed to remove the uranium. In response to residents' concerns, and uncertainty of exposures, affected individuals were asked to participate in a voluntary epidemiological investigation of uranium uptake and 1-year uranium retention study. This study had two primary objectives: quantification of the uranium load on the participants, as expressed by their urine uranium concentration, and retention after 1 year of no exposure. A first-morning void urine specimen, along with survey information, was collected from 156 participants in May 2004, with a second collection occurring 12 months later of 91 participants. The samples were analyzed for uranium by ICP/MS, pH, creatinine by the Jaffe method, and RBP by LIA after both collections. A reduction of one order of magnitude for the geometric mean urine uranium concentration was observed, from 0.100 microg/g creatinine to 0.011 microg/g creatinine in 1 year. Comparatively, NHANES has reported that the geometric mean for all participants, ages 6 years and older, is 0.008 microg/g creatinine, with the 95th percentile being 0.040 microg/g creatinine. None of the second round specimens showed a urine uranium concentration higher than baseline for an individual.

A structural approach to examining prostate cancer risk for rural southern African American men.

Physical, cultural, and social factors influence health risk and behavior, but few have explored how the environmental context affects African American men's prostate cancer screening and treatment. This paper describes a structural analysis of data from eight focus groups of rural, southern African American men (n=66). A structural approach highlights the interrelationships between individuals, the health service system, and community factors that directly and indirectly affect screening and treatment for prostate cancer. The availability of accurate and timely health information and health services, social norms regarding health and professional help-seeking, and the sociopolitical context shaped men's screening and treatment behaviors. These proximal and distal health factors affected men's prostate cancer knowledge, perceived risk, willingness to seek care and trust in the health service system. The findings suggest that prostate cancer screening and treatment occurs in a larger structural context that has important implications for help-seeking and health promotion.

A pilot study of global positioning system/geographical information system measurement of residential proximity to agricultural fields and urinary organophosphate metabolite concentrations in toddlers.

This pilot study enrolled 20 children between the ages of 11 and 17 months in Imperial County, California to assess children's pesticide exposure and residential proximity to agricultural fields. We compared parental self-report of residential proximity to agricultural fields to measurements using global positioning system/geographical information system (GPS/GIS) technology, and we assessed the relationship between residential proximity to agricultural fields and a biomarker of organophosphate (OP) pesticide exposure. Questionnaires were administered twice, 4 weeks apart, to determine self-reported residential proximity to agricultural fields. Urine samples were collected at each contact to measure OP metabolites. Actual residential proximity to the closest agricultural field and number of fields was within 1 mile to the west were measured using GPS/GIS. Self-report of living proximity to agricultural fields agreed with GPS/GIS measurement 75% of the time during the initial interview, compared to 66% agreement during the second interview. Presence of urinary metabolites suggests that OP exposure was ubiquitous: creatinine-adjusted total urinary dimethyl values ranged from 1.60 to 516.00 microg/g creatinine, and total diethyl ranged from 2.70 to 134.84 microg/g creatinine. No association was found between urinary OP metabolites and residential to field proximity. These results suggest that initial self-report of living proximity to agricultural fields may be more accurate than follow-up self-report. Limitations in this pilot study prevent determination of whether self-report is an accurate measure of proximity.