Alleviation of sodicity stress on rice genotypes by Phosphorus fertilization

Rice seedlings transplanted into sodic soil are exposed to an excess of potentially toxic ions as well as nutritional imbalance, both of which adversely affect their growth and yield. The present study was aimed to investigate the beneficial effects of fertilization with phosphorus and potassium on the plants at varying sodicity levels and also the response of genotypes with known variability in their tolerance to sodicity. In pot-house experiments during two seasons, the alleviating effects of P and K fertilization on three rice genotypes were examined at four sodicity levels. Seedlings of CSR13 and Jaya (both moderately tolerant to sodicity), died by 25–35 days after transplanting in sodic soils of pH 9.7–9.9 where Olsen's P was 12.5 and 14.8 kg/ha, respectively. However, there was no problem of survival or growth in these soils when Olsen's P was 17.6 and 20.8 kg/ha. Depletion in P from 12.0 kg to 10 kg resulted in some mortality of the seedlings even at pH 9.1. Sodicity tolerant genotype CSR10, did show some survival and growth even at pH 9.9 with Olsen's P at 14.8 kg/ha (without P fertilization) which suggests that differences in tolerance to sodicity which exist at genotypic level are not masked by low P. None of the three genotypes showed any survival problem at pH 8.0 and 8.1 with Olsen's P at 8.5 and 8.7 kg/ha, respectively. Seedlings in P fertilized sodic soils not only produced significantly more new roots but also higher root biomass than those in unfertilized sodic soils and these roots seem to have some control on Na uptake as reflected by low Na concentration in the shoots. Thus, P fertilization not only improved P and K status of plants but also reduced the concentration of potentially toxic Na ions in shoots, resulting in better survival, growth and yield. Although fertilization with K alone did improve shoot K content, it had no significant effect on reducing Na. So the mortality of the seedlings or grain yield in K fertilized sodic soils was as good as in control and this could be explained on the basis of lack of any significant difference in Na concentrations in shoots between these two treatments.     

Effect of hyperoxidized guanine on DNA primer-template structures: Spiroiminodihydantoin leads to strand slippage

Oxidation of guanine in DNA can lead to mutagenic lesions such as 7-hydro-8-oxoguanine (oG). Upon further oxidation, a more mutagenic lesion, spirominodihydantoin (Sp), can occur. In this study, nuclear magnetic resonance (NMR) investigations were performed to determine the structural features of DNA primer-template models with 5′-GG, 5′-G(oG), 5′-G(Sp) and 5′-T(Sp) templates, that mimic the situation in which the downstream G of the template has been oxidized to oG or hyperoxidized to Sp. Our results show that misalignment occurs only in the 5′-G(Sp) and 5′-T(Sp) templates, providing structural insights into the observed differences in mutagenicity of Sp and oG during DNA replication.     

Dietary salt intake and its relevance to ionic regulation in freshwater salmonids

Dietary sodium intake for freshwater salmonids feeding in the wild (invertebrate diet) or in captivity (pellet diet) was calculated and compared with published branchial sodium influx values. Dietary sodium intake (mmol kg⁻¹ per month) increases from winter minimum values of 5 and 30-40 to reach maximum values in summer of 175 and 240 for invertebrate and pellet diet, respectively. In summer, dietary sodium intake for fish feeding in the wild was of the same magnitude as branchial sodium influx. The implications of dietary sodium intake for sodium balance in freshwater fish are discussed.     

Novel insights into ATP-Stimulated Cleavage of branched DNA and RNA Substrates through Structure-Guided Studies of the Holliday Junction Resolvase RuvX

Much of our understanding of the homologous recombination (HR) machinery hinges on studies using Escherichia coli as a model organism. Interestingly enough, studies on the HR machinery in different bacterial species casts doubt on the universality of the E. coli paradigm. The human pathogen Mycobacterium tuberculosis encodes two Holliday junction (HJ)‐resolvase paralogues, namely RuvC and RuvX; however, insights into their structural features and functional relevance is still limited. Here, we report on structure-guided functional studies of the M. tuberculosis RuvX HJ resolvase (MtRuvX). The crystalline MtRuvX is a dimer in the asymmetric unit, and each monomer has a RNAse H fold vis-à-vis RuvC-like nucleases. Interestingly, MtRuvX also contains some unique features, including the residues essential for ATP binding/coordination of Mg²⁺ ions. Indeed, MtRuvX exhibited an intrinsic, robust ATPase activity, which was further accentuated by DNA cofactors. Structure-guided substitutions of single residues at the ATP binding/Mg²⁺coordination sites while markedly attenuating the ATPase activity completely abrogated HJ cleavage, indicating an unanticipated relationship between ATP hydrolysis and DNA cleavage. However, the affinity of ATPase-deficient mutants for the HJ was not impaired. Contrary to RuvC, MtRuvX exhibits relaxed substrate specificity, cleaving a variety of branched DNA/RNA substrates. Notably, ATP hydrolysis plays a regulatory role, rendering MtRuvX from a canonical HJ resolvase to a DNA/RNA non-sequence specific endonuclease, indicating a link between HJ resolvase and nucleic acid metabolism. These findings provide novel insights into the structure and dual-functional activities of MtRuvX, and suggest that it may play an important role in DNA/RNA metabolism.     

Structural insights into the Switching Off of the Interaction between the Archaeal Ribosomal Stalk and aEF1A by Nucleotide Exchange Factor aEF1B

The ribosomal stalk protein plays a crucial role in functional interactions with translational GTPase factors. It has been shown that the archaeal stalk aP1 binds to both GDP- and GTP-bound conformations of aEF1A through its C-terminal region in two different modes. To obtain an insight into how the aP1•aEF1A binding mode changes during the process of nucleotide exchange from GDP to GTP on aEF1A, we have analyzed structural changes in aEF1A upon binding of the nucleotide exchange factor aEF1B. The isolated archaeal aEF1B has nucleotide exchange ability in the presence of aa-tRNA but not deacylated tRNA, and increases activity of polyphenylalanine synthesis 4-fold. The aEF1B mutation, R90A, results in loss of its original nucleotide exchange activity but retains a remarkable ability to enhance polyphenylalanine synthesis. These results suggest an additional functional role for aEF1B other than in nucleotide exchange. The crystal structure of the aEF1A•aEF1B complex, resolved at 2.0 Å resolution, shows marked rotational movement of domain 1 of aEF1A compared to the structure of aEF1A•GDP•aP1, and this conformational change results in disruption of the original aP1 binding site between domains 1 and 3 of aEF1A. The loss of aP1 binding to the aEF1A•aEF1B complex was confirmed by native gel analysis. The results suggest that aEF1B plays a role in switching off the interaction between aP1 and aEF1A•GDP, as well as in nucleotide exchange, and promote translation elongation.     

反毒为药：精准控制河鲀毒素用作局部麻醉药的新进展

钠离子通道阻断剂河鲀毒素(TTX)是致命的毒素之一,却是极具价值的神经生物学和生理学等生命科学研究领域的工具药.近年来,越来越多的研究指出,TTX具有强大的局部麻醉潜能,有望成为替代氨基酯类和氨基酰胺类局部麻醉药、避免阿片类药物滥用的新型麻醉药物.本文综述TTX局部麻醉应用的辅助药物、TTX缓释及控释给药系统等相关研究,旨在为局部麻醉新药研发提供参考并探讨新的思路.     

Effects of Orally Administered Bovine Lactoperoxidase on Dextran Sulfate Sodium-Induced Colitis in Mice

The effect of lactoperoxidase (LPO) on dextran sulfate sodium-induced colitis was examined in mice. After 9 d of colitis induction, weight loss, colon shortening, and the histological score were significantly suppressed in mice orally administered LPO (62.5 mg/body/d) as compared to a group administered bovine serum albumin. These results suggest that LPO exhibits anti-inflammatory effects in the gastrointestinal tract.     

Isolation and Identification of Sodium 2-Propenyl Thiosulfate from Boiled Garlic (Allium sativum) That Oxidizes Canine Erythrocytes

Sodium 2-propenyl thiosulfate was identified in boiled garlic (Allium sativum). When canine erythrocytes were incubated with sodium 2-propenyl thiosulfate, the methemoglobin concentration and Heinz body percentage in erythrocytes were both increased, indicating that the compound induced oxidative damage in canine erythrocytes. It seems that this compound is one of the causative agents of garlic-induced hemolysis in dogs.