Effects of ophiobolin B on cell enlargement and H+/K+ exchange in maize coleoptile tissues

Ophiobolin B (OPH B), a sesterpene metabolite of Helminthosporium oryzae, inhibits proton extrusion from maize coleoptiles. Moreover OPH B counteracts the biological activity of fusicoccin (FC), another terpenoid toxin produced by Fusicoccum amygdali having a similar basic chemical structure: OPH B inhibits FC-promoted proton extrusion, potassium uptake and cell enlargement.The findings suggest that the effect of OPH B in stimulating electrolites, glucose and aminoacid leakage, reported in a previous paper, can be explained by the capacity of the toxin to inhibit proton extrusion.Abbreviations FC fusicoccin - OPH B ophiobolin B     

Oogenesis in the egg-brooding frog Gastrotheca riobambae produces large oocytes with fewer nucleoli and low RNA content in comparison to Xenopus laevis

Abstract. The dissimilarities between oocytes of the eggbrooding frog, Gastrotheca riobambae , and Xenopus laevis suggest that oogenesis is modified according to the mode of reproduction. Oocytes of G. riobambae are large, yolky, and measure about 3 mm in diameter. In spite of the large oocyte size of Gastrotheca , the amplification of ribosomal genes, the number of nucleoli, and the amount of 18S and 28S rRNA are lower than in Xenopus oocytes. In Gastrotheca , the lower RNA content of oocytes is associated with a slow rate of development. A prolonged period of development is possible due to the protection given by the maternal pouch.     

Ryanodine does not affect the potassium channel from the sarcoplasmic reticulum of skeletal muscle

Single K channels from skeletal muscle sarcoplasmic reticulum were incorporated into artificial membranes. Ryanodine applied to either side of the membrane did not affect the gating nor the conductance properties of those channels. These results suggest that the site of action of ryanodine is limited only to the calcium channels present in the membrane of sarcoplasmic reticulum (1).     

Contrasting continental patterns and drivers of taxonomic and functional turnover among fish assemblages across Brazilian reservoirs

Hydrobiologia - In this paper, we investigated composition and trait turnover among fish assemblages in reservoirs distributed across major Brazilian basins, in order to contrast taxonomic and...     

Factors affecting searcher efficiency and scavenger removal of bat carcasses in Neotropical wind facilities

Bat fatalities at wind facilities have been reported worldwide, and environmental impact assessments depend on searches for carcasses around wind turbines to quantify impacts. Some of the carcasses may go undetected by search teams or be removed by scavengers during search intervals, so these biases must be evaluated and taken into account in fatality estimation. We investigated the influence of different factors on searcher efficiency and scavenger removal in a dry forest area in northeastern Brazil, one of the regions with the highest density of wind turbines in the Neotropics. We conducted searcher efficiency and scavenger removal trials around 34 wind turbines from January 2017 to January 2018. Searcher efficiency was influenced by cover type, season, and carcass size, ranging between 12% for small bats in shrub vegetation during the rainy season and 96% for large bats in absent or sparse vegetation during the dry season. Carcass type and season affected scavenger removal; carcass persistence time was shorter for chicks (1.2 days) than for bats and mice (2.1 days), and the probability of a carcass persisting for a whole day was higher in the rainy season, while the probability of carcass persistence for 7, 14, and 28 days was higher in the dry season. The scavenger community was composed of canids, birds of prey, and insects, with systematic removal of carcasses by the crab-eating fox (Cerdocyon thous) throughout the year and by dung beetles in the rainy season. Based on our findings, impact assessments of wind facilities on bats should conduct searcher efficiency trials in all seasons and cover types around wind turbines, using bat carcasses or models of different sizes. Scavenger removal trials should cover all seasons as well, and use mouse carcasses (but not chick carcasses) as surrogates for bats.     

Species Climatic Suitability Explains Insect–Host Dynamics in the Southern Rocky Mountains,USA

Ecosystems - Recent extreme events of drought and heat have been associated with insect-driven tree mortality. However, there is substantial uncertainty about the impact of climate variability and...     

Does dissolved organic carbon from Amazon black water (Brazil) help a native species,the tambaqui Colossoma macropomum to maintain ionic homeostasis in acidic water?

To assess how the quality and properties of the natural dissolved organic carbon (DOC) could drive different effects on gill physiology, we analysed the ionoregulatory responses of a native Amazonian fish species, the tambaqui Colossoma macropomum, to the presence of dissolved organic carbon (DOC; 10 mg l⁻¹) at both pH 7.0 and pH 4.0 in ion-poor water. The DOC was isolated from black water from São Gabriel da Cachoeira (SGC) in the upper Rio Negro of the Amazon (Brazil) that earlier been shown to protect a non-native species, zebrafish Danio rerio against low pH under similar conditions. Transepithelial potential (TEP), net flux rates of Na⁺, Cl⁻ and ammonia and their concentrations in plasma and Na⁺, K⁺ ATPase; v-type H⁺ ATPase and carbonic anhydrase activities in gills were measured. The presence of DOC had negligible effects at pH 7.0 apart from lowering the TEP, but it prevented the depolarization of TEP that occurred at pH 4.0 in the absence of DOC. However, contrary to our initial hypothesis, SGC DOC was not protective against the effects of low pH. Colossoma macropomum exposed to SGC DOC at pH 4.0 experienced greater net Na⁺ and Cl⁻ losses, decreases of Na⁺ and Cl⁻ concentrations in plasma and elevated plasma ammonia levels and excretion rates, relative to those exposed in the absence of DOC. Species-specific differences and changes in DOC properties during storage are discussed as possible factors influencing the effectiveness of SGC DOC in ameliorating the effects of the acid exposure.     

Characterization of chromate-resistant and -reducing bacteria by traditional means and by a high-throughput phenomic technique for bioremediation purposes

To select strains for the bioremediation of Cr(VI)-polluted environments, four highly Cr(VI)-resistant bacterial isolates were identified and characterized using both traditional techniques and a novel approach called phenotype microarrays. The isolates were identified as members of Pseudomonas mendocina (strains 34 and 56) and members of Pseudomonas corrugata (strains 22 and 28). Results showed that it was possible, by varying the carbon/energy source, to decouple bacterial growth and Cr(VI) reduction, inasmuch as some carbon/energy sources were more effective electron donors for chromate reduction, whereas other sources supported growth but not an effective chromate reduction. The isolates were characterized by a novel high-throughput technique, phenotype microarrays (PM)-Biolog, which can test up to 2000 cellular phenotypes simultaneously. The isolates belonging to P. corrugata had PM profiles different from those of the isolates belonging to P. mendocina. Such differences were related to the capacity of the isolates to resist various chemicals, pH values, and osmolytic substances. With the PM technique a very large amount of information about the fitness of isolates in the presence of different stressors could be obtained.     

A sex-ratio meiotic drive system in Drosophila simulans. I: an autosomal suppressor

Sex ratio distortion (sex-ratio for short) has been reported in numerous species such as Drosophila, where distortion can readily be detected in experimental crosses, but the molecular mechanisms remain elusive. Here we characterize an autosomal sex-ratio suppressor from D. simulans that we designate as not much yang (nmy, polytene chromosome position 87F3). Nmy suppresses an X-linked sex-ratio distorter, contains a pair of near-perfect inverted repeats of 345 bp, and evidently originated through retrotransposition from the distorter itself. The suppression is likely mediated by sequence homology between the suppressor and distorter. The strength of sex-ratio is greatly enhanced by lower temperature. This temperature sensitivity was used to assign the sex-ratio etiology to the maturation process of the Y-bearing sperm, a hypothesis corroborated by both light microscope observations and ultrastructural studies. It has long been suggested that an X-linked sex-ratio distorter can evolve by exploiting loopholes in the meiotic machinery for its own transmission advantage, which may be offset by other changes in the genome that control the selfish distorter. Data obtained in this study help to understand this evolutionary mechanism in molecular detail and provide insight regarding its evolutionary impact on genomic architecture and speciation.