Reduced fertility of female mice lacking CD81

In somatic cells, the tetraspanins CD81 and CD9 associate with each other, with additional tetraspanins and with non-tetraspanin molecules to form proteolipidic complexes. Here we show that CD81 is expressed on the surface of oocytes where it associates with tetraspanin-enriched membrane structures. A major CD9 and CD81 partner, CD9P-1, is also expressed by oocytes. Deletion of CD81 gene in mice results in a 40% reduction of female fertility. In vitro insemination indicated that this infertility is due to a deficiency of oocytes to fuse with sperm. While the fertility of CD9-/- mice is severely but not completely impaired, double knock-out CD9-/- CD81-/- mice were completely infertile indicating that CD9 and CD81 play complementary roles in sperm-egg fusion. Finally, a fraction of CD9 was transferred from CD81-/- oocytes to sperm present in the perivitelline space indicating that the defect of fusion of CD81-/- oocytes does not result from an impaired initial gamete interaction.     

Ecosystem productivity can be predicted from potential relative growth rate and species abundance

We show that ecosystem-specific aboveground net primary productivity (SANPP, g g⁻¹ day⁻¹, productivity on a per gram basis) can be predicted from species-level measures of potential relative growth rate (RGR_max), but only if RGR_max is weighted according to the species' relative abundance. This is in agreement with Grime's mass-ratio hypothesis. Productivity was measured in 12 sites in a French Mediterranean post-agricultural succession, while RGR_max was measured on 26 of the most abundant species from this successional sere, grown hydroponically. RGR_max was only weakly correlated ( r ² = 0.12, P  < 0.05) with field age when species abundance was not considered, but the two variables were strongly correlated ( r ² = 0.81, P  < 0.001) when the relative abundance of species in each field was taken into account. SANPP also decreased significantly with field age. This resulted in a tight relationship ( r ² = 0.77, P  < 0.001) between productivity and RGR_max weighted according to species relative biomass contribution. Our study shows that scaling-up from the potential properties of individual species is possible, and that information on potential and realized species traits can be integrated to predict ecosystem functioning.     

Hydrology shapes microbial communities and microbiome-mediated growth of an Everglades tree island species

Plant-associated microbiomes can improve plant fitness by ameliorating environmental stress, providing a promising avenue for improving outplantings during restoration. However, the effects of water management on these microbial communities and their cascading effects on primary producers are unresolved for many imperiled ecosystems. One such habitat, Everglades tree islands, has declined by 54% in some areas, releasing excess nutrients into surrounding wetlands and exacerbating nutrient pollution. We conducted a factorial experiment, manipulating the soil microbiome and hydrological regime experienced by a tree island native, Ficus aurea, to determine how microbiomes impact growth under two hydrological management plans. All plants were watered to simulate natural precipitation, but plants in the “unconstrained” management treatment were allowed to accumulate water above the soil surface, while the “constrained” treatment had a reduced stage to avoid soil submersion. We found significant effects of the microbiomes on overall plant performance and aboveground versus belowground investment; however, these effects depended on hydrological treatment. For instance, microbiomes increased investment in roots relative to aboveground tissues, but these effects were 142% stronger in the constrained compared to unconstrained water regime. Changes in hydrology also resulted in changes in the prokaryotic community composition, including a >20 log₂fold increase in the relative abundance of Rhizobiaceae, and hydrology-shifted microbial composition was linked to changes in plant performance. Our results suggest that differences in hydrological management can have important effects on microbial communities, including taxa often involved in nitrogen cycling, which can in turn impact plant performance.     

A temperature‐dependent conformational change of NADH oxidase from Thermus thermophilus HB8

Using molecular dynamics simulations and steady‐state fluorescence spectroscopy, we have identified a conformational change in the active site of a thermophilic flavoenzyme, NADH oxidase from Thermus thermophilus HB8 (NOX). The enzyme's far‐UV circular dichroism spectrum, intrinsic tryptophan fluorescence, and apparent molecular weight measured by dynamic light scattering varied little between 25 and 75°C. However, the fluorescence of the tightly bound FAD cofactor increased approximately fourfold over this temperature range. This effect appears not to be due to aggregation, unfolding, cofactor dissociation, or changes in quaternary structure. We therefore attribute the change in flavin fluorescence to a temperature‐dependent conformational change involving the NOX active site. Molecular dynamics simulations and the effects of mutating aromatic residues near the flavin suggest that the change in fluorescence results from a decrease in quenching by electron transfer from tyrosine 137 to the flavin. Proteins 2012. © 2011 Wiley Periodicals, Inc.     

Intracellular Calcium Dynamics and Cellular Energetics in Ischemic NG108-15 Cells Studied by Concurrent 31P/19F and 23Na Double-Quantum Filtered NMR Spectroscopy

Abstract: The role of voltage-sensitive Ca²⁺ channels in mediating Ca²⁺ influx during ischemia was investigated in NG108-15 cells, a neuronal cell line that does not express glutamate-sensitive receptor-mediated Ca²⁺ channels. Concurrent ³¹P/¹⁹F and ²³Na double-quantum filtered (DQF) NMR spectra were used to monitor cellular energy status, intracellular [Ca²⁺] ([Ca²⁺]_i), and intracellular Na⁺ content in cells loaded with the calcium indicator 1,2-bis-(2-amino-5-fluorophenoxy)ethane-N,N,N′,N′-tetraacetic acid (5FBAPTA) during ischemia and reperfusion. Cells loaded with 5FBAPTA were indistinguishable from unloaded cells except for small immediate decreases in levels of phosphocreatine (PCr) and ATP. Ischemia induced a steady decrease in intracellular pH and PCr and ATP levels, and a steady increase in intracellular Na⁺ content; however, a substantial increase in [Ca²⁺]_i (about threefold) was seen only following marked impairment of cellular energy status, when PCr was undetectable and ATP content was reduced to 55% of control levels. A depolarization-induced increase in [Ca²⁺]_i could be completely blocked by 1 µM nifedipine, whereas up to 20 µM nifedipine had no effect on the increase in [Ca²⁺]_i seen during ischemia. These data demonstrate that voltage-gated Ca²⁺ channels do not mediate significant Ca²⁺ flux during ischemia in this cell line and suggest an important role for Ca²⁺_i stores, the Na⁺/Ca²⁺ antiporter, or other processes linked to cellular energy status in the increase in cytosolic Ca²⁺ level during ischemia.     

Assessing the effectiveness of a community intervention for monkeypox prevention in the Congo basin

Background

In areas where health resources are limited, community participation in the recognition and reporting of disease hazards is critical for the identification of outbreaks. This is particularly true for zoonotic diseases such as monkeypox that principally affect people living in remote areas with few health services. Here we report the findings of an evaluation measuring the effectiveness of a film-based community outreach program designed to improve the understanding of monkeypox symptoms, transmission and prevention, by residents of the Republic of the Congo (ROC) who are at risk for disease acquisition.

Methodology/Principal Findings

During 90 days, monkeypox outreach was conducted for ∼23,860 people in northern ROC. Two hundred seventy-one attendees (selected via a structured sample) were interviewed before and after participating in a small-group outreach session. The proportion of interviewees demonstrating monkeypox-specific knowledge before and after was compared. Significant gains were measured in areas of disease recognition, transmission, and mitigation of risk. The ability to recognize at least one disease symptom and a willingness to take a family member with monkeypox to the hospital increased from 49 and 45% to 95 and 87%, respectively (p<0.001, both). Willingness to deter behaviors associated with zoonotic risk, such as eating the carcass of a primate found dead in the forest, remained fundamentally unchanged however, suggesting additional messaging may be needed.

Conclusions/Significance

These results suggest that our current program of film-based educational activities is effective in improving disease-specific knowledge and may encourage individuals to seek out the advice of health workers when monkeypox is suspected.     

Nitrogen fertilizer and landscape position impacts on CO2 and CH4 fluxes from a landscape seeded to switchgrass

This study was conducted to evaluate the impacts of N fertilizer and landscape position on carbon dioxide (CO₂) and methane (CH₄) fluxes from a US Northern Great Plains landscape seeded to switchgrass (Panicum virgatum L.). The experimental design included three N levels (low, 0 kg N ha⁻¹; medium, 56 kg N ha⁻¹; and high, 112 kg N ha⁻¹) replicated four times. The experiment was repeated at shoulder and footslope positions. Soil CO₂ and CH₄ fluxes were monitored once every 2 weeks from May 2010 to October 2012. The CO₂ fluxes were 40% higher at the footslope than the shoulder landscape position, and CH₄ fluxes were similar in both landscape positions. Soil CO₂ and CH₄ fluxes averaged over the sampling dates were not impacted by N rates. Seasonal variations showed highest CO₂ release and CH₄ uptake in summer and fall, likely due to warmer and moist soil conditions. Higher CH₄ release was observed in winter possibly due to increased anaerobic conditions. However, year to year (2010–2012) variations in soil CO₂ and CH₄ fluxes were more pronounced than the variations due to the impact of landscape positions and N rates. Drought conditions reported in 2012, with higher annual temperature and lower soil moisture than long-term average, resulted in higher summer and fall CO₂ fluxes (between 1.3 and 3 times) than in 2011 and 2010. These conditions also promoted a net CH₄ uptake in 2012 in comparison to 2010 when there was net CH₄ release. Results from this study conclude that landscape positions, air temperature, and soil moisture content strongly influenced soil CO₂ fluxes, whereas soil moisture impacted the direction of CH₄ fluxes (uptake or release). However, a comprehensive life cycle analysis would be appropriate to evaluate environmental impacts associated with switchgrass production under local environmental conditions.