Human Social Behavior and Demography Drive Patterns of Fine-Scale Dengue Transmission in Endemic Areas of Colombia

Dengue is known to transmit between humans and A. aegypti mosquitoes living in neighboring houses. Although transmission is thought to be highly heterogeneous in both space and time, little is known about the patterns and drivers of transmission in groups of houses in endemic settings. We carried out surveys of PCR positivity in children residing in 2-block patches of highly endemic cities of Colombia. We found high levels of heterogeneity in PCR positivity, varying from less than 30% in 8 of the 10 patches to 56 and 96%, with the latter patch containing 22 children simultaneously PCR positive (PCR22) for DEN2. We then used an agent-based model to assess the likely eco-epidemiological context of this observation. Our model, simulating daily dengue dynamics over a 20 year period in a single two block patch, suggests that the observed heterogeneity most likely derived from variation in the density of susceptible people. Two aspects of human adaptive behavior were critical to determining this density: external social relationships favoring viral introduction (by susceptible residents or infectious visitors) and immigration of households from non-endemic areas. External social relationships generating frequent viral introduction constituted a particularly strong constraint on susceptible densities, thereby limiting the potential for explosive outbreaks and dampening the impact of heightened vectorial capacity. Dengue transmission can be highly explosive locally, even in neighborhoods with significant immunity in the human population. Variation among neighborhoods in the density of local social networks and rural-to-urban migration is likely to produce significant fine-scale heterogeneity in dengue dynamics, constraining or amplifying the impacts of changes in mosquito populations and cross immunity between serotypes.     

Deficit in DNA content relative to histones in X-irradiated HeLa cells.

The DNA and histone content of HeLa S-3 cell cultures was measured by direct mass assays 21 hours after 1000 rad of X-irradiation, when the cells were arrested in G2 phase. The nuclear DNA content of such cultures was found to be deficient (73% of control values). In contrast, the synthesis of nuclear histones persisted, and the total histone content was close to 100% of control values. When synchronously-growing cultures were irradiated in mid-S phase and examined 3-5 hours later in G2 phase, both DNA and histone content were equal to control values.     

Concurrent levels of 11-ketotestosterone in fish surface mucus, muscle tissue and blood

A rapid, reproducible method is described for extracting and comparing levels of the ether‐soluble fish androgen 11‐ketotestosterone (11‐KT) in blood serum, muscle tissue and surface mucus. Because widely different volumes of extract were recovered after centrifugation from the three sources, it was important to express androgen levels as pg 11‐KT/mg of total soluble protein (TSP). For six male and four female sexually‐staged freshwater Koi (Cyprinus carpio), the method yielded similar pg 11‐KT/mg TSP ratios in blood serum and extracts of muscle tissue and surface mucus, with the strongest correlation between blood serum and surface mucus. While male Koi were distinguishable from females based on the magnitude of 11‐KT levels, reproductive stage and gonadosomatic index levels were not correlated with the 11‐KT levels of either sex. Similar pg 11‐KT/mg TSP ratios were also found for autologous muscle tissue and surface mucus extracts of 37 captured and sexed wild marine fishes representing seven genera. However, high 11‐KT levels were not restricted to mature males. Collectively, results suggest that surface mucus collection (followed by 11‐KT assay) is a useful alternative to more invasive methods of determining systemic hormone levels in fish. Without knowledge of seasonal variation in levels of this and other sex hormones, however, reliance on 11‐KT levels alone may lead to spurious identification of gender, let alone reproductive stage.     

Vimentin Enhances Cell Elastic Behavior and Protects against Compressive Stress

Vimentin intermediate filament expression is a hallmark of epithelial-to-mesenchymal transitions, and vimentin is involved in the maintenance of cell mechanical properties, cell motility, adhesion, and other signaling pathways. A common feature of vimentin-expressing cells is their routine exposure to mechanical stress. Intermediate filaments are unique among cytoskeletal polymers in resisting large deformations in vitro, yet vimentin’s mechanical role in the cell is not clearly understood. We use atomic force microscopy to compare the viscoelastic properties of normal and vimentin-null (vim^−/−) mouse embryo fibroblasts (mEFs) on substrates of different stiffnesses, spread to different areas, and subjected to different compression patterns. In minimally perturbed mEF, vimentin contributes little to the elastic modulus at any indentation depth in cells spread to average areas. On a hard substrate however, the elastic moduli of maximally spread mEFs are greater than those of vim^−/−mEF. Comparison of the plastic deformation resulting from controlled compression of the cell cortex shows that vimentin’s enhancement of elastic behavior increases with substrate stiffness. The elastic moduli of normal mEFs are more stable over time than those of vim^−/−mEFs when cells are subject to ongoing oscillatory compression, particularly on a soft substrate. In contrast, increasing compressive strain over time shows a greater role for vimentin on a hard substrate. Under both conditions, vim^−/−mEFs exhibit more variable responses, indicating a loss of regulation. Finally, normal mEFs are more contractile in three-dimensional collagen gels when seeded at low density, when cell-matrix contacts dominate, whereas contractility of vim^−/−mEF is greater at higher densities when cell-cell contacts are abundant. Addition of fibronectin to gel constructs equalizes the contractility of the two cell types. These results show that the Young’s moduli of normal and vim^−/−mEFs are substrate stiffness dependent even when the spread area is similar, and that vimentin protects against compressive stress and preserves mechanical integrity by enhancing cell elastic behavior.     

Location and the primary structure around the disulfide bonds in cholera toxin.

The sequence of the four tryptic peptides containing cysteine from cholera toxin has been determined. The cysteine residue in peptide A₂, forms a disulfide bridge with the cysteine in the A₁ chain located near the NH₂-terminus. The region around the latter cysteine residue is characterized by a high content of proline. One of the cysteine residues that form the intrachain disulfide bond in subunit B has been located at position 9 in this subunit.     

Population structure and gene flow of the yellow anaconda (Eunectes notaeus) in northern Argentina

Yellow anacondas (Eunectes notaeus) are large, semiaquatic boid snakes found in wetland systems in South America. These snakes are commercially harvested under a sustainable management plan in Argentina, so information regarding population structuring can be helpful for determination of management units. We evaluated genetic structure and migration using partial sequences from the mitochondrial control region and mitochondrial genes cyt-b and ND4 for 183 samples collected within northern Argentina. A group of landscape features and environmental variables including several treatments of temperature and precipitation were explored as potential drivers of observed genetic patterns. We found significant population structure between most putative population comparisons and bidirectional but asymmetric migration in several cases. The configuration of rivers and wetlands was found to be significantly associated with yellow anaconda population structure (IBD), and important for gene flow, although genetic distances were not significantly correlated with the environmental variables used here. More in-depth analyses of environmental data may be needed to fully understand the importance of environmental conditions on population structure and migration. These analyses indicate that our putative populations are demographically distinct and should be treated as such in Argentina's management plan for the harvesting of yellow anacondas.