Effects of acidosis on ventricular myocyte shortening and intracellular Ca2+ in streptozotocin-induced diabetic rats

We have investigated the effects of acute acidosis on ventricular myocyte shortening and intracellular Ca²⁺ in streptozotocin (STZ)-induced diabetic rat. Shortening and intracellular Ca²⁺ were measured in electrically stimulated myocytes superfused with either normal Tyrode solution pH adjusted to either 7.4 (control solution) or 6.4 (acid solution). Experiments were performed at 35–36°C. At 8–12 weeks after treatment, the rats that received STZ had lower body and heart weights compared to controls, and blood glucose was characteristically increased. Contractile defects in myocytes from diabetic rat were characterized by prolonged time to peak shortening. Superfusion of myocytes from control and diabetic rats with acid solution caused a significant reduction in the amplitude of shortening; however, the magnitude of the response was not altered by STZ treatment. Acid solution also caused significant and quantitatively similar reductions in the amplitude of Ca²⁺ transients in myocytes from control and diabetic rats. Effects of acute acidosis on amplitude of myocyte contraction and Ca²⁺ transient were not significantly altered by STZ treatment. Altered myofilament sensitivity to Ca²⁺ and altered mechanisms of sarcoplasmic reticulum Ca²⁺ transport might partly underlie the acidosis-evoked reduction in amplitude of shortening in myocytes from control and STZ-induced diabetic rat. (Mol Cell Biochem 261: 227–233, 2004)     

A nuclease‐toxin and immunity system for kin discrimination in Myxococcus xanthus

The use of toxin to attack neighbours and immunity proteins to protect against toxin has been observed in bacterial conflicts, including kin discrimination. Here, we report a novel nuclease‐toxin and its immunity protein function in the colony‐merger incompatibility, a kind of bacterial kin discrimination, in Myxococcus xanthus DK1622. The MXAN_0049 gene was determined to be a genetic determinant for colony‐merger incompatibility, and the incompatibility could be eliminated by deletion of the upstream co‐transcribed MXAN_0050 gene. We demonstrated that the MXAN_0050 protein was a nuclease, and MXAN_0049 protein was able to bind to MXAN_0050 to block nuclease activity in vitro. Expression of MXAN_0050 in Escherichia coli inhibited cellular growth, and the inhibition effect could be recovered by co‐expression of MXAN_0049. We found that deletion of the PAAR‐encoding gene (MXAN_0044) or the type VI secretion system led to the colony‐merger and co‐existence with the ΔMXAN_0049 mutant, suggesting that they were associated with colony‐merger incompatibility. Homologues of the nuclease‐toxin and cognate immunity pair are widely distributed in bacteria. We propose a simplified model to explain the kin discrimination mechanism mediated by the nuclease‐toxin and immunity protein.© 2018 Society for Applied Microbiology and John Wiley & Sons Ltd     

Different Profile of mRNA Expression in Sinoatrial Node from Streptozotocin-Induced Diabetic Rat

BackgroundExperiments in isolated perfused heart have shown that heart rate is lower and sinoatrial node (SAN) action potential duration is longer in streptozotocin (STZ)–induced diabetic rat compared to controls. In sino-atrial preparations the pacemaker cycle length and sino-atrial conduction time are prolonged in STZ heart. To further clarify the molecular basis of electrical disturbances in the diabetic heart the profile of mRNA encoding a wide variety of proteins associated with the generation and transmission of electrical activity has been evaluated in the SAN of STZ-induced diabetic rat heart.Conclusions/SignificanceCollectively, this study has demonstrated differences in the profile of mRNA encoding a variety of proteins that are associated with the generation, conduction and regulation of electrical signals in the SAN of STZ-induced diabetic rat heart. Data from this study will provide a basis for a substantial range of future studies to investigate whether these changes in mRNA translate into changes in electrophysiological function.     

Investigations of anticholinestrase and antioxidant potentials of methanolic extract,subsequent fractions,crude saponins and flavonoids isolated from Isodon rugosus

Background

Based on the ethnomedicinal uses and the effective outcomes of natural products in various diseases, this study was designed to evaluate Isodon rugosus as possible remedy in oxidative stress, alzheimer’s and other neurodegenerative diseases. Acetylecholinestrase (AChE) and butyrylcholinesterase (BChE) inhibitory activities of crude methanolic extract (Ir.Cr), resultant fractions (n-hexane (Ir.Hex), chloroform (Ir.Cf), ethyl acetate (Ir.EtAc), aqueous (Ir.Aq)), flavonoids (Ir.Flv) and crude saponins (Ir.Sp) of I. rugosus were investigated using Ellman’s spectrophotometric method. Antioxidant potential of I. rugosus was determined using DPPH, H₂O₂ and ABTS free radicals scavenging assays. Total phenolic and flavonoids contents of plant extracts were determined and expressed in mg GAE/g dry weight and mg RTE/g of dry sample respectively.

Results

Among different fractions Ir.Flv and Ir.Cf exhibited highest inhibitory activity against AChE (87.44 ± 0.51, 83.73 ± 0.64%) and BChE (82.53 ± 0.71, 88.55 ± 0.77%) enzymes at 1 mg/ml with IC₅₀ values of 45, 50 for AChE and 40, 70 μg/ml for BChE respectively. Activity of these fractions were comparable to galanthamine causing 96.00 ± 0.30 and 88.61 ± 0.43% inhibition of AChE and BChE at 1 mg/ml concentration with IC₅₀ values of 20 and 47 μg/ml respectively. In antioxidant assays, Ir.Flv, Ir.Cf, and Ir.EtAc demonstrated highest radicals scavenging activities in DPPH and H₂O₂ assays which were comparable to ascorbic acid. Ir.Flv was found most potent with IC₅₀ of 19 and 24 μg/ml against DPPH and H₂O₂ radicals respectively. Whereas antioxidant activates of plant samples against ABTS free radicals was moderate. Ir.Cf, Ir.EtAc and Ir.Cr showed high phenolic and flavonoid contents and concentrations of these compounds in different fractions correlated well to their antioxidant and anticholinestrase activities.

Conclusion

It may be inferred from the current investigations that the Ir.Sp, Ir.Flv and various fractions of I. rugosus are good sources of anticholinesterase and antioxidant compounds. Different fractions can be subjected to activity guided isolation of bioactive compounds effective in neurological disorders.     

Sequential Application of Ligand and Structure Based Modeling Approaches to Index Chemicals for Their hH4R Antagonism

The human histamine H₄ receptor (hH₄R), a member of the G-protein coupled receptors (GPCR) family, is an increasingly attractive drug target. It plays a key role in many cell pathways and many hH₄R ligands are studied for the treatment of several inflammatory, allergic and autoimmune disorders, as well as for analgesic activity. Due to the challenging difficulties in the experimental elucidation of hH₄R structure, virtual screening campaigns are normally run on homology based models. However, a wealth of information about the chemical properties of GPCR ligands has also accumulated over the last few years and an appropriate combination of these ligand-based knowledge with structure-based molecular modeling studies emerges as a promising strategy for computer-assisted drug design. Here, two chemoinformatics techniques, the Intelligent Learning Engine (ILE) and Iterative Stochastic Elimination (ISE) approach, were used to index chemicals for their hH₄R bioactivity. An application of the prediction model on external test set composed of more than 160 hH₄R antagonists picked from the chEMBL database gave enrichment factor of 16.4. A virtual high throughput screening on ZINC database was carried out, picking ∼4000 chemicals highly indexed as H₄R antagonists'' candidates. Next, a series of 3D models of hH₄R were generated by molecular modeling and molecular dynamics simulations performed in fully atomistic lipid membranes. The efficacy of the hH₄R 3D models in discrimination between actives and non-actives were checked and the 3D model with the best performance was chosen for further docking studies performed on the focused library. The output of these docking studies was a consensus library of 11 highly active scored drug candidates. Our findings suggest that a sequential combination of ligand-based chemoinformatics approaches with structure-based ones has the potential to improve the success rate in discovering new biologically active GPCR drugs and increase the enrichment factors in a synergistic manner.     

乌鲁木齐达坂城山区地衣生态位特征的研究

为揭示达坂城山区地衣对生境资源的利用状况及竞争程度,该研究在野外设置30个样方并调查其物种盖度数据,利用生态位宽度、生态位重叠指数及排序分析,探讨达坂城山区地衣的生态位特征及环境影响因子。结果表明:(1)达坂城山区生态位最宽的为丽黄鳞衣(Rusavskia elegans)和内卷野粮衣(Circinaria contorta),对不同环境具有较强的适应性,其他地衣物种生态位宽度较窄,对环境资源利用程度低。(2)物种间生态位重叠值整体偏低,生态位重叠值较高的物种对极少,地衣物种生态位分化程度高,物种间竞争不激烈。(3)生态位较宽的物种与多数物种之间都存在生态位重叠,但重叠值较低; 一些生态位较窄的物种与其他物种之间的生态位重叠值较高; 生态位重叠和生态位宽度之间并无直接的线性关系。(4)地衣物种沿海拔梯度分布具有差异,海拔、光照强度、湿度、风速和人为干扰是本地区地衣群落物种生态位特征差异的主导环境因子。综上所述,达坂城山区地衣物种由于生境资源的竞争占据各自独特的生态位,形成了生态位的分化,群落较为稳定,沿海拔梯度的生境条件差异是物种差异分布的重要原因。该研究可为地衣群落构建研究提供理论依据,并对该地区地衣物种的多样性和生境保护具有重要意义。     

Influence of sodium ion on heavy metal-induced inhibition of light-regulatd proton efflux and active carbon uptake in the cyanobacterium Anabaena flos-aquae

The light-induced proton efflux and active carbon uptake are inhibited by mercury and cadmium ions in Anabaena flos-aquae. The inhibitory effects of these heavy metal ions are reversed by 40 mM concentration of sodium. Here we report that light-induced proton efflux is sodium-dependent which leads to a characteristic enhancement in the rate of photosynthetic oxygen generation and carbon fixation. A low concentration (10 M) of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) significantly inhibited the rate of oxygen generation while 10 M carbonyl cyanide-m-chlorophenylhydrazone (CCCP) completely blocked the oxygen generation activity in the organism. The chlorophyll-a fluorescence yield indicates that little fluorescence quenching occurred in the absence of sodium ion. Increasing the extracellular sodium ion accelerated both the initial rate and the extent of fluorescence quenching. These results support the assumption that metal-induced inhibition of the photosynthetic machinery may be mediated by the movement of protons.     

Developmental regulation of the mRNAs for elastins a, b and c in foetal-calf nuchal ligament and aorta.

The data presented clearly suggest that relative amounts of mRNAs for elastins a, b and c are developmentally regulated in foetal-calf nuchal ligament and aorta and that this regulation is tissue-specific. In nuchal ligament, at earlier stages of foetal development, the relative amounts of mRNAs for elastins a and b are very low. After the foetal age of about 6 months the relative amount of mRNA for elastin b begins to increase. This is followed by an increase in the relative amount of mRNA for elastin a. In aorta, with increasing foetal age, the relative amounts of mRNAs for elastins b and c increase and decrease alternately. The relative amounts of mRNA for elastin a remain low, with only marginal increases with foetal age. A possible self-aggregation role of elastin a in elastogenesis is proposed.