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R Zivković

Publications and source records attributed to R Zivković.

At least 19 recordsLinked to original sources
PubMed1989

[Evaluation of disorders of portal and total hepatic blood flow in patients with chronic diffuse liver diseases].

The total hepatic blood flow measured with radioactive colloidal gold and the portal blood flow with the echo-Doppler method were investigated in 19 healthy examinees and 63 patients with chronic diffuse liver diseases. In the group of healthy examinees, the average values of the total hepatic blood flow was 1254 +/- 231 ml/min and of the portal one 1104 +/- 227 ml/min. The lowest blood flow values were obtained in patients with decompensated cirrhosis, especially in the hepatic (704 +/- 186 ml/min) and the portal blood flow (562 +/- 198 ml/min). In all the groups of examinees, registered values of the total hepatic blood flow were significantly higher than the values of the portal blood flow. The relations of the values obtained by both methods, among groups, were similar. By both methods decreased values are not obtained in liver steatosis and chronic persistent hepatitis in relation to the normal values. In patients with more serious forms of chronic diffuse liver diseases (cirrhosis and chronic active hepatitis) significantly lower blood flow values than the normal ones were obtained. Both methods contribute to the investigation of liver circulation disturbances, liver function damages, and to the follow-up of the liver disease course. The possibility of an indirect evaluation of the arterial hepatic blood flow from the difference of hepatic and portal blood flows may mean a new approach to the investigation of pathophysiological liver occurrences.

Adult↗
PubMed1987

Activation and desensitization of glycolysis by stimulation of adenylate cyclase in rat reticulocytes.

Isoproterenol or forskolin induce a 10-15-fold increase in concentration of cyclic AMP in rat reticulocytes as compared with the basal level of 2.3 +/- 0.3 microM. Glycolysis is stimulated by both compounds transiently more than 2-fold with a peak after 7.5 min followed by an exponential decline. The glycolytic rate in the presence of 10 microM isoproterenol or 10 microM forskolin did not return to basal levels within 60 min of incubation, but was depressed by as much as 50% under the influence of 100 microM forskolin. This phenomenon is designated as metabolic desensitization. The stimulation of glycolysis is probably due to activation of phosphofructokinase as well as to stimulation of Na+,K+-ATPase. The diminished glycolytic flux during the period of metabolic desensitization is accompanied by a decline of glucose 6-phosphate and in the presence of high concentrations of forskolin also by a decrease in glucose 1,6-bisphosphate. A lower rate of influx of glucose is postulated.

1-Methyl-3-isobutylxanthine↗
PubMed1981

Effects of dibutyryl-cANP on glycolysis in washed human erythrocytes.

The experiments were carried out with washed human erythrocytes in order to study the effects of dibutyryl-cAMP (DB-cAMP) on glycolysis. 5 mM DB-cAMP significantly increases glucose consumption and lactate production in incubated erythrocytes. The cross-over plot of glycolytic intermediates shows that increased glycolysis is probably the result of activation of phosphofructokinase by DB-cAMP. Under the same condition DB-cAMP significantly protects the 2,3-diphosphoglycerate level in incubated erythrocytes.

2,3-Diphosphoglycerate↗
PubMed1981

[The role of cAMP in the energy metabolism of human erythrocytes].

In human red blood cell there is complete adenyl cyclase--cAMP system. However, the role of this system and its connection with energy metabolism in red cell is not known. Hence, we studied the effects of cAMP and DB-cAMP on energy metabolism in human red cell. Blood was taken out from haematologically healthy volunteers. Red cells were isolated by differential centrifugation and washed three times in Tris-Ringer buffer (pH 7.4). The red cells suspensions (in the above buffer) were simultaneously incubated without additions (control) and with cAMP or DB-cAMP (5 mmol/L). Incubation temperature was 37 degrees C. The samples of suspensions for the extraction of metabolites and cofactors were taken at 0 and 180 minutes of incubation. The lactate, glucose, G6P, F6P, TP, ATP, ADP and AMP were determined in neutralized perchloric acid extracts by specific enzymatic methods. Results of our experiments show that cAMP and DB-cAMP significantly increase red cell glycolysis. Under the same conditions these nucleotides induce positive "cros-over" point at the phosphofructokinase (PFK) step of the glycolysis. The levels of adenine nucleotides (ATP, ADP, AMP) were unchanged through a whole period of incubation. We concluded that cAMP and DB-cAMP stimulates glycolytic process in red cells probably by allosteric activation of PFK.

Adenine Nucleotides↗
PubMed1981

[The effect of thrombin on glycolysis in human thrombocytes].

The experiments were carried out in order to study the mechanism of thrombin--induced stimulation of glycolysis in washed human platelets. The platelets, isolated from human blood and resuspended in Krebs-Ringer-phosphate buffer (pH 7.4), were incubated in water bath (37 degrees C) either without (control) or with thrombin (1 NIH U/ml platelet suspension). Lactate, glycolytic intermediates and adenine nucleotides were measured in the neutralized perchloric acid extracts of platelets by enzymatic analysis and using the fluorimetric methods. The results of this study show that thrombin significantly increases the rate of lactate production in washed human platelets. At the same time thrombin induces the profound changes in the levels of platelet glycolytic intermediates with the "crossover" point at phosphofructokinase step of glycolysis. The results are interpreted as indicating that thrombin stimulates platelet glycolysis through allosteric phosphofructokinase activation due to the changes in adenine nucleotides energy charge.

Adenine Nucleotides↗