Effect of <Emphasis Type="Italic">Gymnema montanum</Emphasis> leaves on red blood cell resistance to oxidative stress in experimental diabetes

The aim of the present study was to evaluate the protective effect of Gymnema montanum on red blood cell (RBC) membrane in diabetic rats during lipid peroxidation. Ethanol extract of G. montanum leaves (GLEt) was administered orally to alloxan-induced diabetic rats for 3 weeks, and the effects on blood glucose, insulin, lipid peroxidation markers, thiobarbituric acid reactive substances, hydroperoxides in plasma and antioxidant enzymes including superoxide dismutase, catalase and glutathione peroxidase activities in erythrocytes were studied. Administration of GLEt to diabetic animals at doses of 50, 100, and 200 mg/kg body weight lowered elevated blood glucose levels by 24, 35, and 66%, respectively, relative to untreated diabetic rats. In comparison, treatment with the known antidiabetic drug, glibenclamide (600 μg/kg body weight) decreased blood glucose concentrations by 51%. Plasma insulin concentrations were increased in the diabetic rat by 73% with GLEt (200 mg/kg body weight) and 45% with glibenclamide (600 μg/kg body weight). Although a significant decrease in the lipid peroxidation markers was observed in plasma on treatment with GLEt and glibenclamide, the RBC antioxidant levels were increased significantly in diabetic rats. Furthermore, erythrocytes from the GLEt-treated animals were found to be more resistant to H₂O₂-induced peroxidation than that of untreated diabetic animals. The chemical characterization of the polyphenolics of the extract showed the presence of gallic acid (5.29% w/w), resveratrol (2.2% w/w), and quercetin (16.6% w/w). The results of this study suggest that G. montanum may be useful for the control, management, and prevention of oxidative stress associated with diabetes.     

C-Terminal truncation affects subunit exchange of human αA-crystallin with αB-crystallin

In human lenses, C-terminal cleavage of αA-crystallin at residues 172,168, and 162 have been reported. The effect of C-terminal truncation of αA-crystallin on subunit exchange and heterooligomer formation with αB-crystallin and homooligomer formation with native αA-crystallin is not known. We have conducted fluorescence resonance energy transfer studies which have shown that the rates of subunit exchange of αA_1–172 and αA_1–168 with αB-wt were two-fold lower than for αA-wt interacting with αB-wt. The subunit exchange rate between αA_1–162 and αB-wt was six-fold lower. These data suggest that cleavage of the C-terminal residues could significantly affect heterooligomerization. On the other hand, the subunit exchange rates between αA-wt and the truncated αA-crystallins were either unchanged or only slightly decreased, which suggest that homooligomerization may not be significantly influenced by C-terminal truncation. The main conclusion from this study is that cleavage of C-terminal residues of αA-crystallin including the nine residues of the flexible tail is expected to significantly affect the formation of heteroaggregates. Reconstitution experiments showed that the presence of an intact C-terminus is essential for the formation of fully integrated heteroaggregates with equal proportion of αA and αB subunits.     

Functionalized hydroxyethylamine based peptide nanostructures as potential inhibitors of falcipain-3, an essential proteases of Plasmodium falciparum

Self-assembled peptide based nanostructures gained enough popularity due to their easy biocompatibility and numerous potential applications. An excellent model of self-assembly of hydroxyethylamine based peptide nanostructures was synthesized and characterized by DLS and TEM. Spherical nano structures of I and III were observed with particle size ～50 and ～80 nm, respectively. Further, I and III were screened against anti-malarial target, falcipain-3 (FP3), a crucial cysteine protease involved as a major hemoglobinase of Plasmodium falciparum. Interestingly, compound III completely inhibited the activity of FP3. The effective concentration (1.5 μM) of III found to be more potent than I. This biochemical result was substantiated by molecular-docking studies indicating III to be best inhibitor of FP3. This is the first report showing that bis hydroxethylamine based peptide nanostructures could be very effective inhibitor of malarial cysteine proteases.     

Cell-wall-bound metal ions are not taken up in Neurospora crassa

To establish the relevance of the cell wall in metal ion transport, cobalt uptake was examined in Neurospora crassa. Cobalt taken up was largely surface bound (>90%), resulting in a release of calcium and magnesium. Surface-bound cobalt could not enter intracellular locations upon further incubation of mycelia in a metal-free medium. Saturation of the surface with one metal augured subsequent dose-dependent entry of a different metal into intracellular locations. In comparison with the cobalt-resistant mutant, the cobalt-sensitive strain of N. crassa bound less cobalt on the surface but with significant intracellular accumulation. Our results demonstrate the importance of the cell wall in metal transport, toxicity, and resistance in fungi.     

Survivin inhibition induces human neural tumor cell death through caspase-independent and -dependent pathways

Survivin inhibits apoptosis during development and carcinogenesis and is absent in differentiated cells. To determine whether survivin inhibition induces cell death in neural tumor cells, survivin antisense oligonucleotides (SAO) were administered to a human neuroblastoma (MSN) and an oligodendroglioma (TC620) resulting in a dose-dependent reduction in survivin protein. Although 74% of the SAO-treated MSN cells were trypan blue(+), PARP cleavage or activated caspase-3 was not observed. However nuclear translocation of AIF occurred and XIAP increased dramatically. Co-administration of z-Val-Ala-Asp(OMe)-fluoromethyl ketone (zVAD-fmk) with SAO did not inhibit cell death suggesting a caspase-independent mechanism of cell death. Propidium iodide (PI) staining revealed multiple large macronuclei with no apoptotic bodies supporting a role for survivin in cell division. By contrast, while 70% of the SAO-treated TC620 cells were trypan blue(+), PARP was cleaved, cells were TUNEL(+) and PI-staining revealed macronuclei and numerous apoptotic bodies. Co-treatment of the TC620 cells with SAO and zVAD-fmk blocked cell death. While no macronuclei or apoptotic bodies were observed there was a two-fold increase in metaphase cells. Our results suggest that survivin inhibition decreases the viability of human neural tumor cells and as a result of mitotic catastrophe, cell death can be initiated by either a classic apoptotic mechanism or a caspase-independent mechanism.     

Effect of nicotine on glycosaminoglycan metabolism in rats.

Cigarette smoking has been established as a major risk factor for atherosclerosis and also for lung cancer. Nicotine is one of the major components of cigarette smoke which is believed to be partly responsible for the deleterious effect of cigarette smoke. There was significant alteration in the concentration of glycosaminoglycans (GAG) in rats exposed to cigarette smoke. Administration of nicotine to rats has been found to decrease many of GAG fractions in the aorta, liver and heart and increase in the lungs. The increase in GAG now observed in lung tissue in rats administered nicotine and those exposed to cigarette smoke may be involved in the increased incidence of lung cancer in smokers. Increased activity of many of GAG hydrolysing enzymes indicates increased degradation of GAG. Sulphate metabolism in the liver is also significantly altered by nicotine. Thus administration of nicotine to rats caused alteration in the metabolism of GAG which are similar to those observed on exposure of rats to cigarette smoke, indicating that nicotine content of the tobacco smoke may partly be responsible for the effect on GAG observed on exposure to cigarette smoke.