The role of environmental factors in the composition of anuran species in several ponds under the influence of coal mining in southern Brazil

Environmental pollution caused by the disposal of chemicals or toxins into the environment represent a great threat to amphibians. In this study, it was evaluated which environmental factors of ponds under the influence of coal-mining influence the composition of anuran species. For this purpose, anuran samples were performed in ponds in coal extraction areas in southern Brazil. Physical and chemical characteristics of water, sediment and structural characteristics of the ponds were determined. The content of copper in the sediments of the ponds was the main variable to explain the composition of pond species. Besides copper, it is evident the relevance of number of vegetation strata at pond border and pond area on the composition of anurans. It is shown that the composition of species in ponds under the influence of mineral coal mining activity may be a result of historical perturbations, remaining only the most tolerant towards colonization. From the results obtained in this work it can be suggested that there is a synergistic interaction between environmental factors and the coal mining effects on the anurans fauna of impacted ponds. Thus, efforts should be directed to elucidate the effects of pollutants exposure levels on the species, the understanding of sub-lethal and lethal effects of each pollutant on each species, as well as how local populations can be maintained through recruiting rates of larvae and anurans of the impacted ponds.     

Structure of the carboxypeptidase B complex with N-sulfamoyl-L-phenylalanine – a transition state analog of non-specific substrate

Carboxypeptidase B (EC 3.4.17.2) (CPB) is commonly used in the industrial insulin production and as a template for drug design. However, its ability to discriminate substrates with hydrophobic, hydrophilic, and charged side chains is not well understood. We report structure of CPB complex with a transition state analog N-sulfamoyl-L-phenylalanine solved at 1.74Å. The study provided an insight into structural basis of CPB substrate specificity. Ligand binding is affected by structure-depended conformational changes of Asp255 in S1’-subsite, interactions with Asn144 and Arg145 in C-terminal binding subsite, and Glu270 in the catalytic center. Side chain of the non-specific substrate analog SPhe in comparison with that of specific substrate analog SArg (reported earlier) not only loses favorable electrostatic interactions and two hydrogen bonds with Asp255 and three fixed water molecules, but is forced to be in the unfavorable hydrophilic environment. Thus, Ser207, Gly253, Tyr248, and Asp255 residues play major role in the substrate recognition by S1’-subsite.     

Natural Killer Cells Control Tumor Growth by Sensing a Growth Factor

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Differentiation ofCorynebacterium diphtheriae of theMitis type found in diphtheria and ozaena

Summary The purpose of this study was to find out whether there existed any difference betweenC. diphtheriae typemitis always present in the nasal cavity of ozaena patients (the so-calledC. belfanti) andC. diphtheriae of themitis type found in diphtheria patients or carriers. Studying in details all the morphological, cultural and biochemical properties, a difference was found to exist in the reduction of nitrates. This test was investigated in 55 strains ofC. belfanti and 45 strains of themitis type ofC. diphtheriae. All the strains ofC. belfanti yielded negative results in the reduction of nitrates, while all strains ofC. diphtheriae typemitis reduced nitrates within 24 hours. The value of this observation was shorty discussed.     

Engineered silver nanoparticles are sensed at the plasma membrane and dramatically modify the physiology of Arabidopsis thaliana plants

Silver nanoparticles (Ag NPs) are the world's most important nanomaterial and nanotoxicant. The aim of this study was to determine the early stages of interactions between Ag NPs and plant cells, and to investigate their physiological roles. We have shown that the addition of Ag NPs to cultivation medium, at levels above 300 mg L^?1, inhibited Arabidopsis thaliana root elongation and leaf expansion. This also resulted in decreased photosynthetic efficiency and the extreme accumulation of Ag in tissues. Acute application of Ag NPs induced a transient elevation of [Ca²⁺]_cyt and the accumulation of reactive oxygen species (ROS; partially generated by NADPH oxidase). Whole‐cell patch‐clamp measurements on root cell protoplasts demonstrated that Ag NPs slightly inhibited plasma membrane K⁺ efflux and Ca²⁺ influx currents, or caused membrane breakdown; however, in excised outside‐out patches, Ag NPs activated Gd³⁺‐sensitive Ca²⁺ influx channels with unitary conductance of approximately 56 pS. Bulk particles did not modify the plasma membrane currents. Tests with electron paramagnetic resonance spectroscopy showed that Ag NPs were not able to catalyse hydroxyl radical generation, but that they directly oxidized the major plant antioxidant, l ‐ascorbic acid. Overall, the data presented shed light on mechanisms of the impact of nanosilver on plant cells, and show that these include the induction of classical stress signalling reactions (mediated by [Ca²⁺]_cyt and ROS) and a specific effect on the plasma membrane conductance and the reduced ascorbate.     

Effects of lipophilic dications on planar bilayer phospholipid membrane and mitochondria

In this paper, we studied effects of phosphonium dications P2C5 and P2C10 on bilayer planar phospholipid membrane (BLM) and rat liver mitochondria. In line with our previous observations [M.F. Ross, T. Da Ros, F.H. Blaikie, T.A. Prime, C.M. Porteous, I.I. Severina, V.P. Skulachev, H.G. Kjaergaard, R.A. Smith, M.P. Murphy, Accumulation of lipophilic dications by mitochondria and cells, Biochem. J. 400 (2006) 199-208], we showed both P2C5 and P2C10 are cationic penetrants for BLM. They generated transmembrane diffusion potential (Delta Psi), the compartment with a lower dication concentration positive. However, the Delta Psi values measured proved to be lower that the Nernstian. This fact could be explained by rather low BLM conductance for the cations at their small concentrations and by induction of some BLM damage at their large concentrations. The damage in question consisted in appearance of non-Ohmic current/voltage relationships which increased in time. Such a non-Ohmicity was especially strong at Delta Psi >100 mV. Addition of penetrating lipophilic anion TPB, which increases the BLM conductance for lipophilic cations, yielded the Nernstian Delta Psi, i.e. 30 mV per ten-fold dication gradient. In the State 4 mitochondria, dications stimulated respiration and lowered Delta Psi. Moreover, they inhibited the State 3 respiration with succinate or glutamate and malate (but not with TMPD and ascorbate) in an uncoupler-sensitive fashion. Effect on the in State 4 mitochondria, similarly to that on BLM, was accounted for by a time-dependent membrane damage. On the other hand, the State 3 effect was most probably due to inhibition of the respiratory chain Complex I and/or Complex III. The damaging and inhibitory activities of lipophilic dications should be taken into account when one considers a possibility to use them as a vehicle to target antioxidants or other compounds to mitochondria.