Biochemical and morphological changes in the chorion of the carp (Cyprinus carpio) oocyte, following the cortical reaction

Following oviposition and/or fertilization in fieshwater, the soft vitelline membrane surrounding the carp oocyte elevates and becomes tough (fertilization envelope). We have studied the biochemical (protease digestion) and morphological (analysis scanning electron microscopy) changes associated with this transformation. The vitelline envelope is easily digested by most proteolytic enzymes; following elevation, the chorion becomes very resistant to proteolyse. This chorion is much thinner and smoother than the vitelline membrane, but retains a characteristic porous appearance. These results are compared with previous observations obtained by transmission electron microscopy and are discussed in relation to the blockage to polyspermy.     

The Contribution of Occult Precipitation to Nutrient Deposition on the West Coast of South Africa

The Strandveld mediterranean-ecosystem of the west coast of South Africa supports floristically diverse vegetation growing on mostly nutrient-poor aeolian sands and extending from the Atlantic Ocean tens of kilometers inland. The cold Benguela current upwelling interacts with warm onshore southerly winds in summer causing coastal fogs in this region. We hypothesized that fog and other forms of occult precipitation contribute moisture and nutrients to the vegetation. We measured occult precipitation over one year along a transect running inland in the direction of the prevailing wind and compared the nutrient concentrations with those in rainwater. Occult deposition rates of P, N, K, Mg, Ca, Na, Al and Fe all decreased with distance from the ocean. Furthermore, ratios of cations to Na were similar to those of seawater, suggesting a marine origin for these. In contrast, N and P ratios in occult precipitation were higher than in seawater. We speculate that this is due to marine foam contributing to occult precipitation. Nutrient loss in leaf litter from dominant shrub species was measured to indicate nutrient demand. We estimated that occult precipitation could meet the demand of the dominant shrubby species for annual N, P, K and Ca. Of these species, those with small leaves intercepted more moisture and nutrients than those with larger leaves and could take up foliar deposits of glycine, NO₃-, NH₄⁺ and Li (as tracer for K) through leaf surfaces. We conclude that occult deposition together with rainfall deposition are potentially important nutrient and moisture sources for the Strandveld vegetation that contribute to this vegetation being floristically distinct from neighbouring nutrient-poor Fynbos vegetation.     

“I Spent a Full Month Bleeding,I Thought I Was Going to Die…” A Qualitative Study of Experiences of Women Using Modern Contraception in Wakiso District,Uganda

Introduction

There is high unmet need for family planning (FP) in Uganda as well as high contraceptive discontinuation rates. These contribute to the high fertility rates that in part are due to unplanned pregnancies. There are gaps in knowledge about experiences that couples go through while using contraceptives in their lives. This study explored women’s experiences during the course of their contraceptive use.

Methods

We conducted a qualitative study involving 30 women who had used modern contraception for at least one year in Wakiso district, central Uganda. We used in-depth interviews to obtain their personal accounts. Index women were approached through health officers at four health centres in the district. All ethical approvals and informed consent were obtained. We used conventional content analysis; identifying codes through open coding, on which basis categories were developed and grouped into overarching themes.

Results

Women’s accounts were summarised in the following themes: negative experiences with modern contraceptive use, motivation to continue using FP in spite of these negative experiences, the role of influential people, and discontinuation of use. Negative accounts dominated the experiences of most women but they expressed strong desire to continue using modern contraception even amidst all challenges. Health workers emerged as the most influential people that played a vital role in women’s decisions.

Conclusion

Varied negative experiences with modern contraception and misperceptions exist amidst a determination to continue use. Partner engagement, health service strengthening to improve side effects management and health worker skills, and engaging older women that have successfully used contraception as community champions, are potential strategies to support women’s contraceptive decisions.     

Endogenous Murine BST-2/Tetherin Is Not a Major Restriction Factor of Influenza A Virus Infection

BST-2 (tetherin, CD317, HM1.24) restricts virus growth by tethering enveloped viruses to the cell surface. The role of BST-2 during influenza A virus infection (IAV) is controversial. Here, we assessed the capacity of endogenous BST-2 to restrict IAV in primary murine cells. IAV infection increased BST-2 surface expression by primary macrophages, but not alveolar epithelial cells (AEC). BST-2-deficient AEC and macrophages displayed no difference in susceptibility to IAV infection relative to wild type cells. Furthermore, BST-2 played little role in infectious IAV release from either AEC or macrophages. To examine BST-2 during IAV infection in vivo, we infected BST-2-deficient mice. No difference in weight loss or in viral loads in the lungs and/or nasal tissues were detected between BST-2-deficient and wild type animals. This study rules out a major role for endogenous BST-2 in modulating IAV in the mouse model of infection.     

Assessment of the Incremental Benefit of Computer-Aided Detection (CAD) for Interpretation of CT Colonography by Experienced and Inexperienced Readers

Objectives

To quantify the incremental benefit of computer-assisted-detection (CAD) for polyps, for inexperienced readers versus experienced readers of CT colonography.

Methods

10 inexperienced and 16 experienced radiologists interpreted 102 colonography studies unassisted and with CAD utilised in a concurrent paradigm. They indicated any polyps detected on a study sheet. Readers’ interpretations were compared against a ground-truth reference standard: 46 studies were normal and 56 had at least one polyp (132 polyps in total). The primary study outcome was the difference in CAD net benefit (a combination of change in sensitivity and change in specificity with CAD, weighted towards sensitivity) for detection of patients with polyps.

Results

Inexperienced readers’ per-patient sensitivity rose from 39.1% to 53.2% with CAD and specificity fell from 94.1% to 88.0%, both statistically significant. Experienced readers’ sensitivity rose from 57.5% to 62.1% and specificity fell from 91.0% to 88.3%, both non-significant. Net benefit with CAD assistance was significant for inexperienced readers but not for experienced readers: 11.2% (95%CI 3.1% to 18.9%) versus 3.2% (95%CI -1.9% to 8.3%) respectively.

Conclusions

Concurrent CAD resulted in a significant net benefit when used by inexperienced readers to identify patients with polyps by CT colonography. The net benefit was nearly four times the magnitude of that observed for experienced readers. Experienced readers did not benefit significantly from concurrent CAD.     

Predominant Leptospiral Serogroups Circulating among Humans,Livestock and Wildlife in Katavi-Rukwa Ecosystem,Tanzania

BackgroundLeptospirosis is a worldwide zoonotic disease and a serious, under-reported public health problem, particularly in rural areas of Tanzania. In the Katavi-Rukwa ecosystem, humans, livestock and wildlife live in close proximity, which exposes them to the risk of a number of zoonotic infectious diseases, including leptospirosis.ConclusionsThe results of this study demonstrate that leptospiral antibodies are widely prevalent in humans, livestock and wildlife from the Katavi-Rukwa ecosystem. The disease poses a serious economic and public health threat in the study area. This epidemiological study provides information on circulating serogroups, which will be essential in designing intervention measures to reduce the risk of disease transmission.     

Higher Trophic Levels Overwhelm Climate Change Impacts on Terrestrial Ecosystem Functioning

Forest floor food webs play pivotal roles in carbon cycling, but they are rarely considered in models of carbon fluxes, including soil carbon dioxide emissions (respiration), under climatic warming. The indirect effects of invertebrates on heterotrophic (microbial and invertebrate) respiration through interactions with microbial communities are significant and will be altered by warming. However, the interactive effects of invertebrates and warming on heterotrophic respiration in the field are poorly understood. In this study we combined field and common garden laboratory approaches to examine relationships between warming, forest floor food web structure, and heterotrophic respiration. We found that soil animals can overwhelm the effects of warming (to 5 degrees Celsius above ambient) on heterotrophic respiration. In particular, the presence of higher trophic levels and burrowing detritivores strongly determined heterotrophic respiration rates in temperate forest soils. These effects were, however, context-dependent, with greater effects in a lower-latitude site. Without isolating and including the significant impact of invertebrates, climate models will be incomplete, hindering well-informed policy decisions.     

A new factor stimulating peptidoglycan hydrolysis to separate daughter cells in Caulobacter crescentus

Cell division in Gram‐negative bacteria involves the co‐ordinated invagination of the three cell envelope layers to form two new daughter cell poles. This complex process starts with the polymerization of the tubulin‐like protein FtsZ into a Z‐ring at mid‐cell, which drives cytokinesis and recruits numerous other proteins to the division site. These proteins are involved in Z‐ring constriction, inner‐ and outer‐membrane invagination, peptidoglycan remodelling and daughter cell separation. Three papers in this issue of Molecular Microbiology, from the teams of Lucy Shapiro, Martin Thanbichler and Christine Jacobs‐Wagner, describe a novel protein, called DipM for Division Involved Protein with LysM domains, that is required for cell division in Caulobacter crescentus. DipM localizes to the mid‐cell during cell division, where it is necessary for the hydrolysis of the septal peptidoglycan to remodel the cell wall. Loss of DipM results in severe defects in cell envelope constriction, which is deleterious under fast‐growth conditions. State‐of‐the‐art microscopy experiments reveal that the peptidoglycan is thicker and that the cell wall is incorrectly organized in DipM‐depleted cells compared with wild‐type cells, demonstrating that DipM is essential for reorganizing the cell wall at the division site, for envelope invagination and cell separation in Caulobacter.     

A link between the accumulation of DNA damage and loss of multi‐potency of human mesenchymal stromal cells

Human mesenchymal stromal cells (hMSCs) represent an attractive cell source for clinic applications. Besides being multi‐potent, recent clinical trials suggest that they secrete both trophic and immunomodulatory factors, allowing allogenic MSCs to be used in a wider variety of clinical situations. The yield of prospective isolation is however very low, making expansion a required step toward clinical applications. Unfortunately, this leads to a significant decrease in their stemness. To identify the mechanism behind loss of multi‐potency, hMSCs were expanded until replicative senescence and the concomitant molecular changes were characterized at regular intervals. We observed that, with time of culture, loss of multi‐potency was associated with both the accumulation of DNA damage and the respective activation of the DNA damage response pathway, suggesting a correlation between both phenomena. Indeed, exposing hMSCs to DNA damage agents led to a significant decrease in the differentiation potential. We also showed that hMSCs are susceptible to accumulate DNA damage upon in vitro expansion, and that although hMSCs maintained an effective nucleotide excision repair activity, there was a progressive accumulation of DNA damage. We propose a model in which DNA damage accumulation contributes to the loss of differentiation potential of hMSCs, which might not only compromise their potential for clinical applications but also contribute to the characteristics of tissue ageing.