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1.
Satish K. Srivastava Naseem H. Ansari Siqi Liu Anja Izban Ballabh Das Gabor Szabo Aruni Bhatnagar 《Molecular and cellular biochemistry》1989,91(1-2):149-157
During the reductive process in the tissues, the aerobes generate a number of oxidants. Unless these oxidants are reduced, oxidative damage and cell death would occur. Oxidation of plasma membrane lipids leads to autocatalytic chain reactions which eventually alter the permeability of the cell. The role of oxidative damage in the pathophysiology of diabetic complications and ischemic reperfusion injury of myocardium, especially the changes in the channel activity which may lead to arrhythmia have been studied. Hyperglycemia activates aldose reductase which could efficiently reduce glucose to sorbitol in the presence of NADPH. Since NADPH is also aldose required by glutathione reductase for reducing oxidants, its diversion would lead to membrane lipid oxidation and permeability changes which are probably responsible for diabetic complications such as cataractogenesis, retinopathy, neuropathy etc. Antioxidants such as butylated hydroxy toluene (BHT) and also reductase inhibitors prevent or delay some of these complications. By using patch-clamp technique in isolated frog myocytes, we have shown that hydroxy radicals generated by ferrous sulfate and ascorbate as well as lipid peroxides such as t-butyl hydroperoxide facilitate the entry of Na+ by oxidizing Na+-channels. Increased intracellular Na+ leads to an increase in Na+/Ca2+ exchange. The increased Na+ concentration by itself may produce electrical disturbance which would result in arrhythmia. Increased Ca2+ may affect proteases and may help in the conversion of xanthine dehydrogenase to xanthine oxidase, consequently increased production of super oxide radicals. Increased membrane lipid peroxidation and other oxygen free-radical associated membrane damage in myocytes has been demonstrated. 相似文献
2.
Superoxide anion (O
2
.–
) was photogenerated upon illumination of riboflavin in fluorescent light. The rate of O
2
.–
formation was stimulated by double stranded DNA but not by denatured DNA or RNA. Depurinated DNA, which was predominantly depleted in guanine residues, did not exhibit the stimulatory effect, indicating an interaction of riboflavin, or active oxygen species derived from it, with guanine bases. Also, the stimulation of O
2
.–
photogeneration was not observed with ethidium bromide but was seen with proflavin-intercalated DNA. Since ethidium bromide intercalates preferentially between purines and pyrimidines, and proflavin prefers dA-dT rich sites, these results were interpreted to suggest that the interaction of riboflavin with DNA is mainly with GC or CG base pairs. 相似文献
3.
Summary The occurrence of cells resembling mammalian Langerhans cells in the avian epidermis was studied by ATPase histochemistry, Ia immunoreactivity and electron microscopy. The existence of MHC class II antigen-(Ia) expressing, ATPase-positive dendritic cells, which are ultrastructurally similar to mammalian Langerhans cells except for the absence of Birbeck granules, was demonstrated. These cells may be a basic component of the immune system of birds. 相似文献
4.
Alkali extracted mycelial biomass from Aspergillus niger, referred to as Biosorb, was found to sequester metal ions (Cd2+, Cu2+, Zn2+, Ni2+ and Co2+) efficiently both from dilute and concentrated solutions upto 10% of its weight (w/w). Sequestration of metal ions from a mixture was also efficient but with attendant antagonisms. The kinetics of metal binding by Biosorb indicated that it is a rapid process and about 70–80% of the metal is removed from solution in 5 min followed by a slower rate. The mechanism of metal binding is shown to be due to exchange of calcium and magnesium ions of the Biosorb during which equimolar concentrations of both the ions were released into the medium. Following this an efficient procedure for the regeneration and reuse of Biosorb was standardized by washing the biosorbent with calcium and magnesium solution (0.1 m). Biosorbents prepared from Neurospora, Fusarium and Penicillium also exhibited similar mechanisms for metal ion binding, though they had a lower metal binding capacity when compared with Biosorb. Chemical modification of carboxylic acid functional groups of the Biosorb resulted in loss of 90% of metal binding capacity which could not be restored even on regeneration. The significance of this finding on the metal sequestration mechanisms of microbial biosorbents is discussed. 相似文献
5.
The study compares the 3 years of birth control practice of 1172 women who underwent early menstrual regulation (MR) and 499 others who accepted contraceptives only (nonMR) from an urban clinic in Bangladesh. About 60% of the women in the sample were followed-up and their all-method continuation rate was analyzed by life-table technique. The 3-year overall continuation rate in the MR group (64%) did not differ from that of the nonMR group (62%). In the age groups 25 and over, the continuation rate was higher in the MR group. Among the women who did not desire any more children, the continuation rate in the MR group was significantly higher than that of the nonMR group (80% versus 68%, P0.05). Of women with parity greater than 2, the MR group had significantly higher continuation rates than the nonMR group. The MR group had higher extended use-effectiveness for IUDs, conventional contraceptives (condom and foam), injectables, and oral contraceptives than the nonMR group. These findings indicated effective contraceptive practice following MR for this urban population. Easy availability of a multimethod service after MR seemed to be important in promoting effective contraception. 相似文献
6.
7.
Linda J. Chan John D. Wade Frances Separovic Ross A. D. Bathgate Mohammed Akhter Hossain 《International journal of peptide research and therapeutics》2013,19(1):55-60
H2 relaxin (relaxin) is a member of the insulin–relaxin superfamily and exhibits several non-reproductive functions in addition to its well-known properties as a pregnancy hormone. Over the years, the therapeutic potential of relaxin has been examined for a number of conditions. It is currently in phase III clinical trials for the treatment of acute heart failure. The 53 amino acid peptide hormone consists of two polypeptide chains (A and B) which are cross-linked by two inter-chains and one intra-A chain disulfide bridge. Although its cognate receptor is relaxin family peptide receptor (RXFP) 1, relaxin is also able to cross-react with RXFP2, for which the native ligand is INSL3. The “RXXXRXXI” motif in the B-chain of H2 relaxin is responsible for primary binding to LRR of the RXFP1 receptor (Büllesbach and Schwabe, J Biol Chem 280:14051–14056, 2005). Previous RXFP2 receptor mutation and molecular modelling studies strongly suggest that, in addition to this motif, the Trp-B28 residue in the B-chain is responsible for H2–RXFP2 interaction. To confirm this finding, here we have mutated H2 relaxin in which Trp-B28 was replaced with alanine. The synthetic relaxin analogue was then tested on cells expressing either RXFP1 or 2 to determine the affinity and potency for the respective receptors. Our results confirm that Trp-B28 in the B-chain is crucial for binding and activating RXFP2, but not for RXFP1. 相似文献
8.
Alessia Belgi Ross A. D. Bathgate Geoffrey W. Tregear John D. Wade Mohammed Akhter Hossain 《International journal of peptide research and therapeutics》2013,19(1):71-79
Insulin-like peptide 5 (INSL5) is a two-chain, three-disulfide bonded member of insulin/relaxin superfamily of peptides that includes insulin, insulin-like growth factor I and II (IGFI and IGFII), insulin-like peptide 3, 4, 5 and 6 (INSL3, 4, 5 and 6), relaxin-1 (H1 relaxin), -2 (H2 relaxin) and -3 (H3 relaxin). Although it is expressed in relatively high levels in the gut, its biological function remains unclear. However, recent reports suggest a significant orexigenic action and a role in the regulation of insulin secretion and β-cell homeostasis, which implies that both agonists and antagonists of the peptide may have significant therapeutic applications. Modern solid phase synthesis techniques together with regioselective disulfide bond formation were employed for a preliminary structure–function relationship study of mouse INSL5. Two point mutated analogues, mouse INSL5 A-B(R24A, W25A) and mouse INSL5 A-B(K6A, R14A, Y18A) were chemically prepared, where the residues in the B-chain that may be involved in receptor activation and affinity binding, were respectively mutated. Synthetic mouse INSL5 A-B(R24A, W25A) analogue was inactive on RXFP4, the native receptor for INSL5, suggesting ArgB24 and TrpB25 are probably directly involved in INSL5 receptor activation. Mouse INSL5 A-B(K6A, R14A, Y18A) analogue had both decreased affinity and potency on RXFP4 (pIC50 7.7 ± 0.2, pEC50 7.87 ± 0.18) which indicated that one or more of these residues are critical for the binding to the receptor. 相似文献
9.
Tijjani Salihu Shinkafi Abhinav Kaushik Amena Mahmood Ambrish Kumar Tiwari Mohammad Mumtaz Alam Mymoona Akhter 《Journal of biomolecular structure & dynamics》2020,38(10):2976-2987
AbstractThis study identifies and validates hexokinase type 4 (HK4), an isozyme of hexokinase in the liver and pancreas, as an important target of C2-β-D-glucopyranosyl-1,3,6,7-tetrahydroxyxanthone (βdGT), a xanthone glucoside suggested to have antidiabetic property. In the study, we applied the computational pipeline of molecular docking followed by the molecular dynamics simulations to shortlist potential βdGT protein targets. The analysis of protein dynamics and the binding free energy (ΔG) led us to the identification of HK4 as a key βdGT target, whereby the binding mode and domain dynamics suggested the activator function of βdGT. βdGT bound to the allosteric site of the isozyme ~13?Å away from the substrate (glucose)-binding site. The binding free energy of the ligand-protein complex was energetically feasible (ΔG, –41.61?kcal/mol) and the cleft angle deviation between the two (small and large) domains of HK4 revealed differential HK4 dynamics in response to βdGT binding. 3D structure analysis of the isozyme-ligand complex highlighted the role of Arg63, Glu67 and Lys458 in ligand stabilization and hydrophobic interactions mediated by Tyr214 and Met235. Experimental validation of the results of computational analysis confirmed the activator function of βdGT on HK4. The study has implication in diabetes as βdGT may be used to lower the blood glucose level by activating hepatic and pancreatic hexokinase without the risk of hypoglycemia.Communicated by Ramaswamy H. Sarma 相似文献
10.
Gulwaiz Akhter Aiman Zafar Waseem Khan Mohmmad Jamshed 《Archives Of Phytopathology And Plant Protection》2013,46(7-8):399-407
AbstractAqueous leaf extracts of four commonly growing weeds namely Ageratum conyzoides, Elephantopus scaber, Lantana camara and Xanthium strumarium were used to evaluate their nematicidal activity on second stage juvenile of Meloidogyne incognita race-3. The juveniles were exposed to various concentration of leaf extract namely 250, 500, 1000 and 2000?ppm for 12, 24 and 48?h, respectively. All leaf extracts showed the nematicidal property in concentration and time-dependent manner. The maximum juvenile mortality was recorded in E. scaber throughout the incubation period followed by X. strumarium, L. camara and A. conyzoides. The regression and correlation of regression revealed the best concentration-dependent effect of aqueous leaf extracts on nematode mortality in E. scaber (R2?=?.751) followed by X. strumarium (R2?=?.749), A. conyzoides (R2?=?.687) and L. camara (R2?=?.756). Aqueous leaves extracts of these aforementioned weeds showed nematicidal properties, therefore, may be used as a key component of integrated disease management programme. 相似文献