Regulation of the Oxidative Processes in the Organs of Mice under the Effects of Chemical and Physical Factors at Low Doses

Biophysics - The effects of the separate and combined action of lead nitrate in a wide range of doses, uranyl nitrate, and chronic low-dose gamma irradiation on the formation of oxidative stress in...     

The Gut–Brain Axis and Peroxisome Proliferator-Activated Receptors in the Regulation of Epileptogenesis

Journal of Evolutionary Biochemistry and Physiology - A large proportion of patients with epilepsy suffer from pharmacoresistant forms of the disease, and this makes the search for new treatments...     

Effect of TNF-α, IL-2, IL-5 and IL-6 on Rat Tracheal and Bronchial Smooth Muscle Contractions

Journal of Evolutionary Biochemistry and Physiology - The article addresses the role of TNF-α, IL-2, IL-5 and IL-6 in the contractile activity of rat tracheal and bronchial smooth muscle...     

Environment versus dispersal in the assembly of western Amazonian palm communities

Aim It is a central issue in ecology and biogeography to understand what governs community assembly and the maintenance of biodiversity in tropical rain forest ecosystems. A key question is the relative importance of environmental species sorting (niche assembly) and dispersal limitation (dispersal assembly), which we investigate using a large dataset from diverse palm communities. Location Lowland rain forest, western Amazon River Basin, Peru. Methods We inventoried palm communities, registering all palm individuals and recording environmental conditions in 149 transects of 5 m × 500 m. We used ordination, Mantel tests and indicator species analysis (ISA) to assess compositional patterns, species responses to geographical location and environmental factors. Mantel tests were used to assess the relative importance of geographical distance (as a proxy for dispersal limitation) and environmental differences as possible drivers of dissimilarity in palm species composition. We repeated the Mantel tests for subsets of species that differ in traits of likely importance for habitat specialization and dispersal (height and range size). Results We found a strong relationship between compositional dissimilarity and environmental distance and a weaker but also significant relationship between compositional dissimilarity and geographical distance. Consistent with expectations, relationships with environmental and geographical distance were stronger for understorey species than for canopy species. Geographical distance had a higher correlation with compositional dissimilarity for small‐ranged species compared with large‐ranged species, whereas the opposite was true for environmental distance. The main environmental correlates were inundation and soil nutrient levels. Main conclusions The assembly of palm communities in the western Amazon appears to be driven primarily by species sorting according to hydrology and soil, but with dispersal limitation also playing an important role. The importance of environmental characteristics and geographical distance varies depending on plant height and geographical range size in agreement with functional predictions, increasing our confidence in the inferred assembly mechanisms.     

Linoleic acid hydroperoxide favours hypochlorite- and myeloperoxidase-induced lipid peroxidation

Liposomes composed of soybean phosphatidylcholine were peroxidized using the reagent sodium hypochlorite or the myeloperoxidase-hydrogen peroxide-Cl^- system. Linoleic acid hydroperoxide previously prepared from linoleic acid by means of lipoxidase was incorporated into liposomes. The yield of thiobarbituric acid reactive substances (TBARS) continuously increased with higher amounts of hydroperoxide groups after the initiation of lipid peroxidation by hypochlorous acid producing systems. The accumulation of TBARS was inhibited by scavengers of free radicals such as butylated hydroxytoluene and by the scavengers of hypochlorous acid, taurine and methionine. Lipid peroxidation was also prevented by sodium azide or chloride free medium in the myeloperoxidase-hydrogen peroxide-Cl^- system. Here we show for the first time that the reaction of hypochlorous acid with a biologically relevant hydroperoxide yields free radicals able to cause further oxidation of lipid molecules.     

Steady-state kinetics of F1-ATPase. Mechanism of anion activation

The kinetic behaviour of the ATPase activity of beef heart F1 depends largely on the exposure of the enzyme to some anionic ligands such as sulphate and/or EDTA. F1 prepared in the presence of such anions exhibited a triphasic kinetic pattern whereas F1 from which those anions were removed by dialysis exhibited only two Km values for ATP. Conversely to what has been previously reported, bicarbonate did not linearize F1-ATPase kinetics. Moreover, anion activation cannot be simply explained by promotion of ADP release but mainly by an increase in affinity of the third catalytic site for ATP.     

The synthesis of 15N- and deuterium-substituted, spin-labeled analogues of NAD+ and their use in EPR studies of dehydrogenases

Calcium efflux and EGTA-induced calcium release from an internal platelet membrane fraction have been studied after the oxalate-supported calcium uptake had reached steady state. Increasing external calcium concentrations stimulate the calcium efflux velocity, with an apparent half-maximal stimulation at about 5 microM outside calcium concentration and a maximal velocity of calcium efflux of 4.66 +/- 2.32 nmol X min-1 X mg-1. Moreover, the ratio of the liberated calcium on the loaded calcium seems to be independent of the increasing external calcium concentration. Increasing the calculated internal calcium concentration by varying the oxalate potassium concentration from 10 mM to 1 mM results in an increase of the liberated calcium from the membrane vesicles from 7.4% to 63%, respectively, without changing the calcium efflux velocity. Similar conclusions can be drawn from the observation of results from the calcium efflux and EGTA-induced calcium release methods. Moreover, calcium pump reversal does not seem to be responsible for the calcium efflux or calcium release. All these different points added to the previously described regulation of calcium efflux by the catalytic subunit of cAMP protein kinase suggest us that the mechanism of calcium liberation by the platelet membranes is different from the calcium uptake.     

Biosynthesis of various types of collagen by human hepatoma cells in vitro

A cloned human hepatoma cell line (HH2-1) produced and formed collagen fibers in vitro. The relative rate of collagen synthesis by the cells was increased with an enhancement of the cell density. An analysis of the components of the collagen using sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that the cells synthesized interstitial collagen, types I and III, and other collagenous proteins. Thus, human hepatoma cells may play an important role in the formation of stromal collagen in the tumor.     

Role of methyl groups in dynamics and evolution of biomolecules

Recent studies have discovered strong differences between the dynamics of nucleic acids (RNA and DNA) and proteins, especially at low hydration and low temperatures. This difference is caused primarily by dynamics of methyl groups that are abundant in proteins, but are absent or very rare in RNA and DNA. In this paper, we present a hypothesis regarding the role of methyl groups as intrinsic plasticizers in proteins and their evolutionary selection to facilitate protein dynamics and activity. We demonstrate the profound effect methyl groups have on protein dynamics relative to nucleic acid dynamics, and note the apparent correlation of methyl group content in protein classes and their need for molecular flexibility. Moreover, we note the fastest methyl groups of some enzymes appear around dynamical centers such as hinges or active sites. Methyl groups are also of tremendous importance from a hydrophobicity/folding/entropy perspective. These significant roles, however, complement our hypothesis rather than preclude the recognition of methyl groups in the dynamics and evolution of biomolecules.