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21.
K. Prasad J. B. Gupta J. Kalra B. Bharadwaj 《Molecular and cellular biochemistry》1992,111(1-2):55-59
It has been suggested that oxygen free radicals (OFR) depress the excitation-contraction coupling in cardiac muscle. It is possible that a decrease in the cardiac contractility in the failing heart may be due to an increased OFR producing activity of polymorphonuclear (PMN) leukocytes. We studied the OFR producing activity (chemiluminescence) of PMN leukocytes from blood in dogs with heart failure due to chronic volume overload. The animals were divided into two groups: I) normal, (n = 10): II) dogs with mitral insufficiency (MI) of 6 to 9 months duration, (n = 10). Hemodynamic studies were done to establish the presence of heart failure. Blood samples were collected to measure PMN leukocyte chemiluminescence. There was a decrease in the cardiac index and index of myocardial contractility (dp/dt/IIP) and an increase in the left ventricular end-diastolic pressure in dogs with MI indicating left ventricular failure. The peak chemiluminescent activity of the PMN leukocytes in blood of dogs with failure was about four folds greater than that in the blood from normal dogs. These results suggest that there may be an increased OFR generation in dogs with volume overload heart failure. The decrease in the myocardial contractility in the failing heart might be due to an increase in the OFR produced by the PMN leukocytes. 相似文献
22.
Dipak K. Das Richard M. Engelman Xuekun Liu Swapna Maity John A. Rousou Joseph Flack Jitendra Laksmipati Randall M. Jones M. Renuka Prasad David W. Deaton 《Molecular and cellular biochemistry》1992,111(1-2):77-86
Reperfusion injury occurs during open-heart surgery after prolonged cardioplegic arrest. Cardiopulmonary bypass also is known to cause hemolysis. Since reperfusion of ischemic myocardium is associated with the generation of oxygen free radicals, and since free radicals can attack a protein molecule, it seems reasonable to assume that hemolysis might be the consequence of free radical attack on hemoglobin protein. The results of this study demonstrated that reperfusion following ischemic arrest caused an increase in free hemoglobin and free heme concentrations, simultaneously releasing free iron and generating hydroxyl radicals. In vitro studies using pure hemoglobin indicated that superoxide anion generated by the action of xanthine oxidase on xanthine could release iron from the heme ring and cause deoxygenation of oxyhemoglobin into ferrihemoglobin. This study further demonstrated that before the release of iron from the heme nucleus, oxyhemoglobin underwent deoxygenation to ferrihemoglobin. The released iron can catalyze the Fenton reaction, leading to the formation of cytotoxic hydroxyl radical (OH·). In fact, the formation of OH. in conjunction with hemolysis occurs during cardiac surgery, and when viewed in the light of the in vitro results, it seems likely that oxygen-derived free radicals may cause hemolysis during cardiopulmonary bypass and simultaneously release iron from the heme ring, which can catalyze the formation of OH·. 相似文献
23.
The impact of atrazine, a triazine herbicide, on the lipid metabolism of fish, Sarotherodon mossambica was studied. Significant changes were reported in the lipid profiles of liver and muscle as a function of exposure period. 相似文献
24.
The growth of mustard was increased significantly when treated with up to 80 kg N ha–1 (N80). Spraying with (2-chloroethyl) trimethylammoniumchloride (chlormequat chloride) increased seed yield and seed protein content. Spraying nitrogen fertilized plots with chlormequat chloride, increased leaf area, leaf area ratio, leaf area duration, number of siliquae plant–1, number of seeds siliqua–1 and length of siliqua. Reducing, non-reducing and total sugars in the leaves at 80 days after sowing were also affected significantly. Chlorophyll a, b and total chlorophyll were little affected. The number of siliquae plant–1 was highly correlated with seed yield in both the seasons of experimentation. The correlation coefficient value () was 0.586 in 1982/83 and 0.912 in 1983/84.The total accumulation of nutrients, i.e. nitrogen, phosphorus and potassium in seed and straw was significantly affected by N80 × chlormequat chloride interaction. 相似文献
25.
U. Brand L. Brandes V. Koch T. Kullik B. Reinhardt F. Rüther T. Scheper K. Schügerl S. Wang X. Wu R. Ferretti S. Prasad D. Wilhelm 《Applied microbiology and biotechnology》1991,36(2):167-172
Summary Single and multisensor field effect transistors (FET) with a pH-sensitive Si/SiO2/Si3N4/Ta2O5-gate and reference electrode (for single sensor) were developed and used for manufacturing the following biological (Bio)-FETs: for glucose analysis, glucose oxidase-FET (GOD-FET); for urea analysis, urease-FET; and for cephalosporin C analysis, cephalosporinase-FET. The GOD-FETs were integrated into flow injection analysis (FIA) of the Eppendorf variables analyser (EVA) system and used for monitoring the glucose concentration in microbial cultivation and production processes with recombinant Escherichia coli K12 MF, recombinant E. coli JM103, Saccharomyces cerevisiae H620, and Candida boidinii. Urease-FET-FIA was used to monitor the urea concentration in a simulated cultivation of Cephalosporium acremonium and urease-FET-FIA and GOD-FET-FIA for the monitoring of urea and glucose concentrations in simulated S. cerevisiae cultivations. 相似文献
26.
A. Seetharama Acharya Rajendra Prasad Roy Bhuvaneshwari Dorai 《Journal of Protein Chemistry》1991,10(3):345-358
The relative roles of the two structural aspects of nonenzymic glycation sites of hemoglobin A, namely the ease with which the amino groups could form the aldimine adducts and the propensity of the microenvironments of the respective aldimines to facilitate the Amadori rearrangement, in dictating the site selectivity of nonenzymic glycation with aldotriose has been investigated. The chemical reactivity of the amino groups of hemoglobin A forin vitro reductive glycation with aldotriose is distinct from that in the nonreductive mode. The reactivity of amino groups of hemoglobin A toward reductive glycation (i.e., propensity for aldimine formation) decreases in the order Val-1(), Val-1(), Lys-66(), Lys-61(), and Lys-16(). The overall reactivity of hemoglobin A toward nonreductive glycation decreased in the order Lys-16(), Val-1(), Lys-66(), Lys-82(), Lys-61(), and Val-1(). Since the aldimine is the common intermediate for both the reductive and nonreductive modification, the differential selectivity of protein for the two modes of glycation is clearly a reflection of the propensity of the microenvironments of nonenzymic glycation sites to facilitate the isomerization reaction (i.e., Amadori rearrangement). A semiquantitative estimate of this propensity of the microenvironment of the nonenzymic glycation sites has been obtained by comparing the nonreductive (nonenzymic) and reductive modification at individual glycation sites. The microenvironment of Lys-16() is very efficient in facilitating the rearrangement and the relative efficiency decreases in the order Lys-16(), Lys-82(), Lys-66(), Lys-61(), Val-1(), and Val-1(). The propensity of the microenvironment of Lys-16() to facilitate the Amadori rearrangement of the aldimine is about three orders of magnitude higher than that of Val-1() and is about 50 times higher than that of Val-1(). The extent of nonenzymic glycation at the individual sites is modulated by various factors, such as thepH, concentration of aldotriose, and the concentration of the protein. The nucleophiles—such as tris, glycine ethyl ester, and amino guanidine—inhibit the glycation by trapping the aldotriose. The nonenzymic glycation inhibitory power of nucleophile is directly related to its propensity to form aldimine. Thus, the extent of inhibition of nonenzymic glycation at a given site by a nucleophile directly reflects the relative role ofpK
a
of the site in dictating the glycation at that site. The nonenzymic glycation of an amino group of a protein is an additive/synergestic consequence of the propensity of the site to form aldimine adducts on one hand, and the propensity of its microenvironment to facilitate the isomerization of the aldimines to ketoamines on the other. The isomerization potential of microenvironment plays the dominant role in dictating the site specificity of the nonenzymic glycation of proteins. 相似文献
27.
K K Caldwell M K Newell J C Cambier K N Prasad J M Masserano W Schlegel D M Cooper 《Analytical biochemistry》1988,175(1):177-190
The GTP-dependence for stimulatory and inhibitory regulation of plasma membrane adenylate cyclase activity was measured in plasma membrane fractions isolated from a variety of cell types (platelets, lymphocytes, PC12 cells, GH3 cells, NBP2 cells, and hepatocytes). This report shows that the isolation of plasma membranes for the study of GTP-dependent adenylate cyclase activity was, for some cells, enhanced by the exposure of the cells to glycerol prior to cell lysis. The isolation of plasma membranes from other cells, which did not appear to be sensitive to glycerol pretreatment, was enhanced by the removal of heavy particulate matter prior to fractionation of the cell lysate. The regulation of enzyme activity by various agents was found to be dependent upon the presence of (exogenous) GTP to varying degrees, indicating variable contamination of membrane preparations with GTP. It is concluded that (i) exposure of platelets and lymphocytes to glycerol prior to cell lysis decreases subsequent contamination of the plasma membrane preparation with GTP, and (ii) although glycerol pretreatment of other cells does not ensure the subsequent isolation of plasma membrane adenylate cyclase activity displaying high requirements for (exogenous) GTP, it is a reasonable first approach to be used during the development of procedures for the isolation of plasma membranes. 相似文献
28.
Mutations That Improve the Binding of Yeast Flp Recombinase to Its Substrate 总被引:6,自引:0,他引:6
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When yeast FLP recombinase is expressed from the phage lambda PR promoter in a Salmonella host, it cannot efficiently repress an operon controlled by an operator/promoter region that includes a synthetic, target FLP site. On the basis of this phenotype, we have identified four mutant FLP proteins that function as more efficient repressors of such an operon. At least two of these mutant FLP proteins bind better to the FLP site in vivo and in vitro. One mutant changes the presumed active site tyrosine residue of FLP protein to phenylalanine, is blocked in recombination, and binds the FLP site about five-fold better than the wild-type protein. A second mutant protein that functions as a more efficient repressor retains catalytic activity. We conclude that the eukaryotic yeast FLP recombinase, when expressed in a heterologous prokaryotic host, can function as a repressor, and that mutant FLP proteins that bind DNA more tightly may be selected as more efficient repressors. 相似文献
29.
Tetraphenylphosphonium is an indicator of negative membrane potential in Candida albicans 总被引:1,自引:0,他引:1
The characteristics of the uptake of lipophilic cations tetraphenylphosphonium (TPP+) into Candida albicans have been investigated to establish whether TPP+ can be used as a membrane potential probe for this yeast. A membrane potential (delta psi, negative inside) across the plasma membrane of C. albicans was indicated by the intracellular accumulation of TPP+. The steady-state distribution of TPP+ was reached within 60 min and varied according to the expected changes of delta psi. Agents known to depolarize membrane potential caused a rapid and complete efflux of accumulated TPP+. The initial influx of TPP+ was linear over a wide range of TPP+ concentrations (2.5-600 microM), indicating a non mediated uptake. Thus, TPP+ is a suitable delta psi probe for this yeast. 相似文献
30.