Drastic changes in aquatic bacterial populations from the Cuatro Cienegas Basin (Mexico) in response to long-term environmental stress

Understanding the changes of aquatic microbial community composition in response to changes in temperature and ultraviolet irradiation is relevant for predicting biogeochemical modifications in the functioning of natural microbial communities under global climate change scenarios. Herein we investigate shifts in the bacterioplankton composition in response to long-term changes in temperature and UV radiation. For this purpose, 15 mesocosms were seeded with composite aquatic microbial communities from natural pools within the Cuatro Cienegas Basin (Mexican Chihuahuan desert) and were subject to different temperatures and UV conditions. 16S rRNA gene clone libraries were obtained from water samples at the mid-point (4 months) and the end of the experiment (8 months). An increase in bacterial diversity over time was found in the treatment of constant temperature and UV protection, which suggests that stable environments promote the establishment of complex and diverse bacterial community. Drastic changes in the phylogenetic bacterioplankton composition and structure were observed in response to fluctuating temperature and increasing UV radiation and temperature. Fluctuating temperature induced the largest decrease of bacterial richness during the experiment, indicating that frequent temperature changes drive the reduction in abundance of several species, most notably autotrophs. The long-term impact of these environmental stresses reduced diversity and selected for generalist aquatic bacterial populations, such as Porphyrobacter. These changes at the community level occur at an ecological time scale, suggesting that under global warming scenarios cascade effects on the food web are possible if the microbial diversity is modified.     

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification

The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition—Control; after 60 h—PES Day 2.5 of embryo culture; and after 96 h—PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification (Control: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts (Control: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.     

Manipulation of Very Few Receptor Discriminator Residues Greatly Enhances Receptor Specificity of Non-visual Arrestins

Based on the identification of residues that determine receptor selectivity of arrestins and the analysis of the evolution in the arrestin family, we introduced 10 mutations of "receptor discriminator" residues in arrestin-3. The recruitment of these mutants to M2 muscarinic (M2R), D1 (D1R) and D2 (D2R) dopamine, and β(2)-adrenergic receptors (β(2)AR) was assessed using bioluminescence resonance energy transfer-based assays in cells. Seven of 10 mutations differentially affected arrestin-3 binding to individual receptors. D260K and Q262P reduced the binding to β(2)AR, much more than to other receptors. The combination D260K/Q262P virtually eliminated β(2)AR binding while preserving the interactions with M2R, D1R, and D2R. Conversely, Y239T enhanced arrestin-3 binding to β(2)AR and reduced the binding to M2R, D1R, and D2R, whereas Q256Y selectively reduced recruitment to D2R. The Y239T/Q256Y combination virtually eliminated the binding to D2R and reduced the binding to β(2)AR and M2R, yielding a mutant with high selectivity for D1R. Eleven of 12 mutations significantly changed the binding to light-activated phosphorhodopsin. Thus, manipulation of key residues on the receptor-binding surface modifies receptor preference, enabling the construction of non-visual arrestins specific for particular receptor subtypes. These findings pave the way to the construction of signaling-biased arrestins targeting the receptor of choice for research or therapeutic purposes.     

A BASIC microcomputer program to calculate the secondary structure of proteins from their circular dichroism spectrum

A BASIC program (CDPROT) has been developed to calculate thesecondary structure of proteins from their far UV circular dichroismspectrum. This implementation can use different reference spectra,calculated either from model polypeptides or proteins of knowntertiary structure. Apart from obtaining the a-helical, ß-structure,ß-turns or random percentages which would generatethe spectrum of best fit with respect to the experimental measures,CDPROT represents on screen both theoretical and experimentalspectra indicating the root-mean-square error. The provisionof additional reference spectra by the user is also considered,and another program (STOREREF) performs the editing in an adequateformat for CDPROT. Received on March 8, 1988; accepted on June 3, 1988     

Relationships between leaf morphological traits, nutrient concentrations and isotopic signatures for Mediterranean woody plant species and communities

Background and aims

Soil factors are driving forces that influence spatial distribution and functional traits of plant species. We test whether two anchor morphological traits—leaf mass per area (LMA) and leaf dry matter content (LDMC)—are significantly related to a broad range of leaf nutrient concentrations in Mediterranean woody plant species. We also explore the main environmental filters (light availability, soil moisture and soil nutrients) that determine the patterns of these functional traits in a forest stand.

Methods

Four morphological and 19 chemical leaf traits (macronutrients and trace elements and δ¹³C and δ¹⁵N signatures) were analysed in 17 woody plant species. Community-weighted leaf traits were calculated for 57 plots within the forest. Links between LMA, LDMC and other leaf traits were analysed at the species and the community level using standardised major axis (SMA) regressions

Results

LMA and LDMC were significantly related to many leaf nutrient concentrations, but only when using abundance-weighted values at community level. Among-traits links were much weaker for the cross-species analysis. Nitrogen isotopic signatures were useful to understand different resource-use strategies. Community-weighted LMA and LDMC were negatively related to light availability, contrary to what was expected.

Conclusion

Community leaf traits have parallel shifts along the environmental factors that determine the community assembly, even though they are weakly related across individual taxa. Light availability is the main environmental factor determining this convergence of the community leaf traits.     

Robo4 maintains vessel integrity and inhibits angiogenesis by interacting with UNC5B

Robo4 is an endothelial cell-specific member of the Roundabout axon guidance receptor family. To identify Robo4 binding partners, we performed a protein-protein interaction screen with the Robo4 extracellular domain. We find that Robo4 specifically binds to UNC5B, a vascular Netrin receptor, revealing unexpected interactions between two endothelial guidance receptors. We show that Robo4 maintains vessel integrity by activating UNC5B, which inhibits signaling downstream of vascular endothelial growth factor (VEGF). Function-blocking monoclonal antibodies against Robo4 and UNC5B increase angiogenesis and disrupt vessel integrity. Soluble Robo4 protein inhibits VEGF-induced vessel permeability and rescues barrier defects in Robo4(-/-) mice, but not in mice treated with anti-UNC5B. Thus, Robo4-UNC5B signaling maintains vascular integrity by counteracting VEGF signaling in endothelial cells, identifying a novel function of guidance receptor interactions in the vasculature.     

Osteopontin and systemic lupus erythematosus association: a probable gene-gender interaction

Osteopontin (SPP1) is an important bone matrix mediator found to have key roles in inflammation and immunity. SPP1 genetic polymorphisms and increased osteopontin protein levels have been reported to be associated with SLE in small patient collections. The present study evaluates association between SPP1 polymorphisms and SLE in a large cohort of 1141 unrelated SLE patients [707 European-American (EA) and 434 African-American (AA)], and 2009 unrelated controls (1309 EA and 700 AA). Population-based case-control association analyses were performed. To control for potential population stratification, admixture adjusted logistic regression, genomic control (GC), structured association (STRAT), and principal components analysis (PCA) were applied. Combined analysis of 2 ethnic groups, showed the minor allele of 2 SNPs (rs1126616T and rs9138C) significantly associated with higher risk of SLE in males (P = 0.0005, OR = 1.73, 95% CI = 1.28-2.33), but not in females. Indeed, significant gene-gender interactions in the 2 SNPs, rs1126772 and rs9138, were detected (P = 0.001 and P = 0.0006, respectively). Further, haplotype analysis identified rs1126616T-rs1126772A-rs9138C which demonstrated significant association with SLE in general (P = 0.02, OR = 1.30, 95%CI 1.08-1.57), especially in males (P = 0.0003, OR = 2.42, 95%CI 1.51-3.89). Subgroup analysis with single SNPs and haplotypes also identified a similar pattern of gender-specific association in AA and EA. GC, STRAT, and PCA results within each group showed consistent associations. Our data suggest SPP1 is associated with SLE, and this association is especially stronger in males. To our knowledge, this report serves as the first association of a specific autosomal gene with human male lupus.     

Capsaicin Modulates Proliferation,Migration, and Activation of Hepatic Stellate Cells

Capsaicin, the active component of chili pepper, has been reported to have antiproliferative and anti-inflammatory effects on a variety of cell lines. In the current study, we aimed to investigate the effects of capsaicin during HSC activation and maintenance. Activated and freshly isolated HSCs were treated with capsaicin. Proliferation was measured by incorporation of EdU. Cell cycle arrest and apoptosis were investigated using flow cytometry. The migratory response to chemotactic stimuli was evaluated by a modified Boyden chamber assay. Activation markers and inflammatory cytokines were determined by qPCR, immunocytochemistry, and flow cytometry. Our results show that capsaicin reduces HSC proliferation, migration, and expression of profibrogenic markers of activated and primary mouse HSCs. In conclusion, the present study shows that capsaicin modulates proliferation, migration, and activation of HSC in vitro.