HIV Status Awareness,Partnership Dissolution and HIV Transmission in Generalized Epidemics

Objectives

HIV status aware couples with at least one HIV positive partner are characterized by high separation and divorce rates. This phenomenon is often described as a corollary of couples HIV Testing and Counseling (HTC) that ought to be minimized. In this contribution, we demonstrate the implications of partnership dissolution in serodiscordant couples for the propagation of HIV.

Methods

We develop a compartmental model to study epidemic outcomes of elevated partnership dissolution rates in serodiscordant couples and parameterize it with estimates from population-based data (Rakai, Uganda).

Results

Via its effect on partnership dissolution, every percentage point increase in HIV status awareness reduces HIV incidence in monogamous populations by 0.27 percent for women and 0.63 percent for men. These effects are even larger when the assumption of monogamy can be relaxed, but are moderated by other behavior changes (e.g., increased condom use) in HIV status aware serodiscordant partnerships. When these behavior changes are taken into account, each percentage point increase in HIV status awareness reduces HIV incidence by 0.13 and 0.32 percent for women and men, respectively (assuming monogamy). The partnership dissolution effect exists because it decreases the fraction of serodiscordant couples in the population and prolongs the time that individuals spend outside partnerships.

Conclusion

Our model predicts that elevated partnership dissolution rates in HIV status aware serodiscordant couples reduce the spread of HIV. As a consequence, the full impact of couples HTC for HIV prevention is probably larger than recognized to date. Particularly high partnership dissolution rates in female positive serodiscordant couples contribute to the gender imbalance in HIV infections.     

Measuring Parathyroid Hormone (PTH) in Patients with Oxidative Stress – Do We Need a Fourth Generation Parathyroid Hormone Assay?

Oxidation of PTH at methionine residues results in loss of biological activity. PTH may be oxidized in patients with renal disease. The aim of this study was to develop an assay considering oxidation of PTH. Oxidized hPTH was analyzed by high resolution nano-liquid chromatography coupled to ESI-FTT tandem mass spectrometry (nanoLC-ESI-FT-MS/MS) directly and after proteolytic cleavage. The oxidized hPTH(1-84) sample shows TIC-peaks at 18-20 min and several mass peaks due to mass shifts caused by oxidations. No significant signal for oxidized hPTH(1-84) species after removal of oxidized PTH molecules by a specific column with monoclonal antibodies (MAB) raised against the oxidized hPTH was detectable. By using this column in samples from 18 patients on dialysis we could demonstrate that measured PTH concentrations were substantially lower when considering oxidized forms of PTH. The relationship between PTH concentrations determined directly and those concentrations measured after removal of the oxidized PTH forms varies substantially. In some patients only 7% of traditionally measured PTH was free of oxidation, whereas in other patients 34% of the traditionally measured PTH was real intact PTH. In conclusion, a huge but not constant proportion of PTH molecules are oxidized in patients requiring dialysis. Since oxidized PTH is biologically inactive, the currently used methods to detect PTH in daily clinical practice may not adequately reflect PTH-related bone and cardiovascular abnormalities in patients on dialysis.     

AP-1 is required for the maintenance of apico-basal polarity in the C. elegans intestine

Epithelial tubes perform functions that are essential for the survival of multicellular organisms. Understanding how their polarised features are maintained is therefore crucial. By analysing the function of the clathrin adaptor AP-1 in the C. elegans intestine, we found that AP-1 is required for epithelial polarity maintenance. Depletion of AP-1 subunits does not affect epithelial polarity establishment or the formation of the intestinal lumen. However, the loss of AP-1 affects the polarised distribution of both apical and basolateral transmembrane proteins. Moreover, it triggers de novo formation of ectopic apical lumens between intestinal cells along the lateral membranes later during embryogenesis. We also found that AP-1 is specifically required for the apical localisation of the small GTPase CDC-42 and the polarity determinant PAR-6. Our results demonstrate that AP-1 controls an apical trafficking pathway required for the maintenance of epithelial polarity in vivo in a tubular epithelium.     

Rapid adaptive evolution of photoperiodic response during invasion and range expansion across a climatic gradient

Abstract Understanding the mechanisms of adaptation to spatiotemporal environmental variation is a fundamental goal of evolutionary biology. This issue also has important implications for anticipating biological responses to contemporary climate warming and determining the processes by which invasive species are able to spread rapidly across broad geographic ranges. Here, we compare data from a historical study of latitudinal variation in photoperiodic response among Japanese and U.S. populations of the invasive Asian tiger mosquito Aedes albopictus with contemporary data obtained using comparable methods. Our results demonstrated rapid adaptive evolution of the photoperiodic response during invasion and range expansion across ～15° of latitude in the United States. In contrast to the photoperiodic response, size-based morphological traits implicated in climatic adaptation in a wide range of other insects did not show evidence of adaptive variation in Ae. albopictus across either the U.S. (invasive) or Japanese (native) range. These results show that photoperiodism has been an important adaptation to climatic variation across the U.S. range of Ae. albopictus and, in conjunction with previous studies, strongly implicate the photoperiodic control of seasonal development as a critical evolutionary response to ongoing contemporary climate change. These results also emphasize that photoperiodism warrants increased attention in studies of the evolution of invasive species.     

Factors influencing community structure in a South American tank bromeliad fauna

We examined factors influencing the structure of naturally replicated, taxonomically unrestricted communities inhabiting South American tank bromeliads. We measured aspects of plant physical structure and collected the entire macroscopic fauna of 209 bromeliads from the Yasuní Scientific Reserve in lowland eastern Ecuador. We collected a total of 11 219 individuals of 354 morphospecies. The morphospecies abundance distribution of our sample was approximated by a log-series distribution dominated by rare morphospecies (57% of the morphospecies were represented by a single individual). Six methods for estimating the total number of bromeliad associated morphospecies in our study area gave results which varied by a factor of three, illustrating that caution should be exercised in interpreting the results of any single estimator. Variation in plant volume, number of leaves, detritus content, and water volume explained 62% of the variation in morphospecies richness among plants. Finally, there was a quadratic relationship between body mass and both individual abundance and morphospecies richness in our sample. These results illustrate an important role of both biotic and abiotic factors influencing the structure of taxonomically unrestricted, ecologically defined natural communities.     

Evaluation of the phosphorus status of P-deficient podzols in temperate pine stands: combining isotopic dilution and extraction methods

Phosphorus (P) is often a limiting factor of forest growth but our knowledge of the processes governing P availability in forest soils is rather limited. In the present work, we combined a isotopic dilution method with extraction methods to evaluate the P status in Pinus pinaster plantation forests on highly P-deficient soils. Total, organic, and inorganic P, dissolved and diffusive P, i.e. ionic P species that can be transferred from the solid phase to the soil solution due a gradient of concentration, were determined to a soil depth of 120 cm in a gradient of 18 forest sites (seven humid sites, five mesic sites, and six dry sites). Our objective was to assess the potential contribution of organic and inorganic P to plant available P. Based on results and our original assumptions, we observed that the contribution of organic P fractions (mineralization of soil organic P) to P availability related to the contribution of inorganic P fractions (diffusive P for durations up to 1 year) was predominant in litter, less important in top soil horizons, and negligible at depths below 30 cm. This was partly due to a decreasing proportion of organic P and an increasing proportion of diffusive P with soil depth. Owing to a very low amount of diffusive P in the top soils in dry sites, the relative contribution of organic P was actually higher in these sites than in humid and mesic sites, despite a lower overall organic P fraction. The combination of extraction and isotopic dilution methods in our study shed new light on P status in this forest range. In particular, these methods enable assessment of both the size of the pools and their dynamic fractions.     

MOLECULAR CLOCKS PROVIDE NEW INSIGHTS INTO THE EVOLUTIONARY HISTORY OF GALEICHTHYINE SEA CATFISHES

Intercontinental distributions in the southern hemisphere can either be the result of Gondwanan vicariance or more recent transoceanic dispersal. Transoceanic dispersal has come into vogue for explaining many intercontinental distributions; however, it has been used mainly for organisms that can float or raft between the continents. Despite their name, the Sea Catfishes (Ariidae) have limited dispersal ability, and there are no examples of nearshore ariid genera with a transoceanic distribution except for Galeichthys where three species occur in southern Africa and one in the Peruvian coast. A previous study suggested that the group originated in Gondwana, and that the species arrived at their current range after the breakup of the supercontinent in the Early Cretaceous. To test this hypothesis, we infer molecular phylogenies (mitochondrial cytochrome b , ATP synthase 8/6, 12S, and 16S; nuclear rag2 ; total ∼4 kb) and estimate intercontinental divergence via molecular clocks (penalized-likelihood, Bayesian relaxed clock, and universal clock rates in fishes). Age ranges for cladogenesis of African and South American lineages are 15.4–2.5 my, far more recent than would be suggested by Gondwanan vicariance; thus, the distribution of galeichthyines must be explained by dispersal or more recent vicariant events. The nested position of the Peruvian species ( Galeichthys peruvianus ) within the African taxa is robust, suggesting that the direction of the dispersal was from Africa to South America. The progenitor of the Peruvian species likely arrived at its current distribution with the aid of ocean currents, and several scenarios are discussed.     

Competition drives specialization in pollination systems through costs to male fitness

Specialization in pollination systems played a central role in angiosperm diversification, yet the evolution of specialization remains poorly understood. Competition through interspecific pollen transfer may select for specialization through costs to male fitness (pollen lost to heterospecific flowers) or female fitness (heterospecific pollen deposited on stigmas). Previous theoretical treatments of pollination focused solely on seed set, thus overlooking male fitness. Here we use individual-based models that explicitly track pollen fates to explore how competition affects the evolution of specialization. Results show that plants specialize on different pollinators when visit rates are high enough to remove most pollen from anthers; this increases male fitness by minimizing pollen loss to foreign flowers. At low visitation, plants generalize, which minimizes pollen left undispersed in anthers. A model variant in which plants can also evolve differences in sex allocation (pollen/ovule production) produces similar patterns of specialization. At low visitation, plants generalize and allocate more to female function. At high visitation, plants specialize and allocate equally to both sexes (in line with sex-allocation theory). This study demonstrates that floral specialization can be driven by selection through male function alone and more generally highlights the importance of community context in the ecology and evolution of pollination systems.     

Patterns of asymmetry in the twining vine Dalechampia scandens (Euphorbiaceae): ontogenetic and hierarchical perspectives

We studied patterns of fluctuating asymmetry (FA) in leaves of four populations of the neotropical vine Dalechampia scandens to obtain insight into the origin of leaf FA and the level at which it is controlled. We analysed correlations in signed and unsigned asymmetry at different organizational levels. We also analysed the ontogeny of FA during leaf expansion to test whether asymmetry is regulated during cell expansion, and whether fast-expanding leaves are more or less asymmetrical. Signed asymmetry was negatively correlated between successive leaves, that is, when the right side of a leaf was larger than the left side, the next leaf on the shoot tended to show the opposite pattern. The magnitude of FA, however, was very weakly correlated among successive leaves or among leaves measured on different shoots. The direction of asymmetry did not change during leaf expansion, but the relative asymmetry, that is, asymmetry corrected for difference in trait size, decreased during expansion. We found a weak negative relationship between leaf expansion rate and relative asymmetry on the fully expanded leaves. These results suggest that leaf asymmetry in Dalechampia originates from perturbations in cell proliferation in the stem, creating asymmetries in opposite directions in successive leaves. These asymmetries persist during leaf expansion, but tend to be reduced by unknown mechanisms.     

Three-dimensional reciprocity of floral morphs in wild flax (Linum suffruticosum): a new twist on heterostyly

Here, we studied the floral morphology and pollination of the distylous plant Linum suffruticosum (Linaceae) in southern Spain.We observed a previously unreported form of distyly that involved twisting and bending of styles and stamens during floral development to achieve three-dimensional reciprocity of anthers and stigmas in the long-styled (pin) and short-styled (thrum) morphs. This developmental pattern causes pin pollen to be placed on the underside of pollinating Usia flies (Bombyliidae), and thrum pollen to be placed on the top of the thorax and abdomen. The pin stigmas contact the flies on the dorsum, apparently picking up predominantly thrum pollen, and the thrum stigmas contact the flies on the ventral surface, apparently picking up predominantly pin pollen.This form of heterostyly would appear on morphological grounds to be far more efficient in dispersing pollen between compatible morphs than the typical pin-thrum system. If so, this plant fits Darwin's prediction of efficient pollen flow between heterostylous morphs more closely than anything Darwin himself reported.Molecular phylogenetic analyses indicate that this form of heterostyly evolved in a lineage that already had typical heterostyly. The analyses also indicate that there have been several independent origins of heterostyly in Linum and at least one reversal to stylar monomorphism.