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1.
Tarun K. Dam Manju Sarkar Jharna Ghosal Amalesh Choudhury 《Molecular and cellular biochemistry》1992,117(1):1-9
Control Analysis has been carried out in the first steps of a rat liver glycolytic system. Attention has been focused on the effect of several glucose concentrations on the control, particularly regarding the role of glucokinase. From kinetic studies of the whole metabolic system we have obtained information on the flux variation under different glucose concentrations. This information together with the kinetics of glucokinase has allowed us to calculate Flux Control and Elasticity Coefficients for glucokinase and the Response Coefficient of the system with respect to glucose. The changes in of the value of Flux Control Coefficients demonstrates that in conditions of low glucose concentration, glucokinase is the main enzyme in controlling the flux through the pathway, but at high glucose concentration the control moves to phosphofructokinase. Next, we have compared our results with those obtained with the shortening and titration method, previously described (Torres, N.V., Mateo, F., Mélendez-Hevia, E. and Kacser, H., (1986) Biochem. J. 234, 169–174; Torres, N.V. and Meléndez-Hevia, E. 1991. Molec. Cell. Biochem. 101, 1–10). Furthermore, from knowledge of the enzyme kinetics of the system we have been able to build a model of the pathway that allows us computer similation of its behavior and calculation of the Flux Control Coefficient profile at different glucose concentrations. By the three methods the results correlate, supporting the use of the pathway substrate as external modulator of the metabolic system as a tool for practical application of Control Analysis. 相似文献
2.
3.
Experimental infection of hamsters with Leishmania donovani caused visceral leishmaniasis in which hematological changes occurred. The infected hamsters were anemic and reticulocyte counts were high. No significant change in the serum erythropoietin level was noted. Red cell membrane Na(+)-K(+)-ATPase and acetylcholinesterase activities increased. Osmotic fragility of the erythrocytes from infected animals increased. The level of 2,3-diphosphoglycerate of the red cells increased with the degree of anemia. 相似文献
4.
Dipak Kumar Banerjee 《Journal of biosciences》1987,11(1-4):311-319
Radio-labelled amphomycin (3H-amphomycin) forms a complex with dolichylmonophosphate in presence of Ca2+. Complex formation has also been documented with retinylmonophosphate and perhydromonoeneretinylmonophosphate. Analysis of
the space-filling model suggested both fatty acylated aspartic acid residue at the N-terminus of the lipopeptide and phosphate
head group of dolichylmonophosphate are necessary for the complex formation. The binding ability of amphomycin is then utilized
to localize dolichylmonophosphate in the microsomal membrane. Studies with microsomal membranes from hen oviduct suggested
that dolichylmonophosphate is located in the cytoplasmic side of the membrane. 相似文献
5.
Effect of erythropoietin on the glucose transport of rat erythrocytes and bone marrow cells 总被引:1,自引:0,他引:1
J Ghosal M Chakraborty T Biswas C K Ganguly A G Datta 《Biochemical medicine and metabolic biology》1987,38(2):134-141
The effect of Ep on radioactive glucose and methyl-alpha-D-glucoside transport by rat erythrocytes and bone marrow cells were studied. There is initial linearity followed by saturation kinetics of [14C]glucose transport by the erythrocytes of starved and starved plus Ep-treated rats at different concentrations of glucose. Starvation caused slight inhibition of glucose transport which increased markedly on Ep administration to starved rats. Normal animals failed to show any significant change in glucose transport after Ep treatment. Methyl-alpha-D-glucoside inhibited the Ep-stimulated glucose transport significantly. Ep also stimulated the transport of radioactive methyl-alpha-D-glucoside which was competitively inhibited in presence of D-glucose. Glucose transport in erythrocytes was found to be sensitive to metabolic inhibitors like azide and DNP. A sulfhydryl reagent and ouabain also inhibited the transport process. Ep stimulated glucose and methyl-alpha-D-glucoside transport in the bone marrow cells of starved rats. The sugar analog competitively inhibited the glucose transport in bone marrow cells and vice versa. 相似文献
6.
Hajime Otani Hitomi Otan Masao Morita Dipak K. Das 《Molecular and cellular biochemistry》1989,90(2):111-120
We investigated the effect of Ca2+ overload on the phospholipase C-catalyzed hydrolysis of phosphoinositides in the rat left ventricular papillary muscle. Ca2+ overload on the papillary muscle was induced by treatment with 0.3 mM ouabain in Ca2+-containing medium following either Ca2+-containing or Ca2+-free superfusion. The phosphoinositide breakdown was evaluated by determining accumulations of [3H]inositol phosphates ([3H]IPs) in the tissues prelabeled with [3H]inositol. Ca2+ repletion following Ca2+-free superfusion resulted in a rapid but small increase in resting tension that was not followed by contracture, nor was it associated with a significant increase in [3H]IPs accumulations. Treatment with ouabain following Ca2+-containing superfusion increased resting tension after a lag period of several minutes and produced contracture associated with an increase in [3H]IPs accumulations. The ouabain induced increases in resting tension, and accumulations of [3H]IPs were significantly potentiated by prior Ca2+-free superfusion instead of Ca2+-containing superfusion. There was a significant positive correlation between increases in resting tension and the phosphoinositide breakdown. The increased resting tension and the accumulations of [3H]IPs were not antagonized by treatments with prazosin plus atropine or indomethacin, but were abolished by superfusion with Ca2+-free buffer solution. Although the enhanced phospholipase C-catalyzed hydrolysis of phosphoinositides appears to be a consequence rather than a cause of increased intracellular Ca2+, such a biochemical change may provoke a positive feedback mechanism to develop the muscle contracture through the putative intracellular messenger action of inositol triphosphate and diacylglycerol.Abbreviations [3H]IPs
[3H]Inositol Phosphates
- IP
Inositol Phosphate
- IP2
Inositol Bisphosphate
- IP3
Inositol Trisphosphate
- PI
Phosphatidylinositol
- PI-4-P
Phosphatidylinositol-4-phosphate
- PI-4,5-P2
Phosphatidylinositol 4,5-bisphosphate
- PRZ
Prazosin
- ATR
Atropine
- INDO
Indomethacin
- min
Minutes 相似文献
7.
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
8.
Tuli Biswas Munmun Chakraborty Chayan K. Ganguly Jharna Ghosal 《Molecular and cellular biochemistry》1991,106(2):109-116
Effect of Erythropoietin (Ep) on the interaction of Concanavalin A (Con A) with rat erythrocytes was studied using 125I-labelled Con A. Binding of Con A to erythrocytes was dependent on time and cell concentration. Starvation caused an elevation of the lectin binding capacity of red cells which again came down towards the normal level on Ep administration to starved rats. Binding of Con A to erythrocytes decreased linearly with increasing concentration of Ep. Specificity of binding was confirmed by inhibition studies with -methyl-D-mannopyranoside (Me Man) Cells from the starved rats compared to those from normal and Ep treated animals were less prone to inhibition by this sugar analog. Positive cooperative binding of Con A to rat erythrocyte was observed at low concentration of Con A but was absent at higher lectin concentrations. Starvation caused an increase in the number of binding sites per cell which returned to normal level after Ep treatment. Under identical conditions, binding affinities were not much changed in these cells. Cells from the starved animals were more susceptible to agglutination compared to those from normal and Ep-treated rats. Microviscosity and cholesterol/phospholipid ratio of red cell membrane decreased in the starved animals which retraced its way back towards the normal level after Ep treatment. 相似文献
9.
Sunil Palchaudhuri Ranajit Kumar Dipak Sen Ruma Pal Sajal Ghosh Banwarilal Sarkar Sujit K. Bhattacharya Sudhir C. Pal 《FEMS microbiology letters》1985,30(1-2):187-191
Abstract Multiple antibiotic-resistant Shigella dysenteriae type 1 isolates from a recent epidemic in West Bengal (India) showed identical plasmid patterns. All isolates were resistant to ampicillin (Am), chloramphenicol (Cm), tetracycline (Tc), streptomycin (Sm) and trimethoprim (Tp) and contained 6 plasmids, ranging from 2.5–120 kb. The Am resistance determinant was located on the 120 kb plasmid. This plasmid was unstable when the S. dysenteriae strains were grown above 37°C. The Bangladesh strains of S. dysenteriae type 1 showed identical plasmid patterns, except that many isolates were Am-sensitive and lacked the 120 kb plasmid. In strains from both Bangladesh and West Bengal, predominantly group-B plasmids conferred resistance to Cm and Tc. Comparisons of Eco R1 fragments generated from the total plasmid DNA content of each strain support the view that the plasmids present in the S. dysenteriae type 1 strains isolated from all recent epidemics in India and Bangladesh were identical. 相似文献
10.