Reuben Chayoth

Regulation of protein kinases activity by quercetin in Ehrlich ascites tumor cells

Cyclic AMP-independent protein kinase activities from Ehrlich ascites tumor cells, partially purified by DEAE-cellulose and phosphocellulose chromatography were inhibited by quercetin. The cyclic AMP in the tumor ascites cells and the cyclic AMP-dependent protein activity from this tumor and from bovine and mouse tissues were unaffected by this drug. Since we reported that quercetin elevates cyclic AMP level in Ehrlich ascites tumor cells, this bioflavonoid may have a dual effect on the protein kinase activities in these cells, thus, increasing the cyclic AMP-dependent and decreasing the cyclic AMP-independent protein kinase activities.

Regulation of cyclic amp level and synthesis of dna, rna and protein by quercetin in ehrlich ascites tumor cells.

Abstract Quercetin (3.3, 4′, 5.7-pentahydroxy flavone) at the concentration of 10 −4 M as well as 10 −2 M theophylline and 10 −3 M dibutyryl cyclic AMP caused at least 85 per cent inhibition of [ 3 H]thymidine incorporation in Ehrlich ascites tumor cells. At the same concentrations, these drugs decreased [ 3 H]uridine and [ 3 H]- L -leucine incorporation by 50–60 per cent and 35–45 per cent respectively. Ouabain (10 −3 M), the specific inhibitor of Na + -K + pump system, did not alter the incorporation of [ 3 H]thymidine and [ 3 ]uridine, but decreased the incorporation of [ 3 H]- L -leucine in these cells. Treatment of Ehrlich ascites tumor cells with the polyanion dextran sulfate did not change the inhibitory effect of quercetin, theophylline and dibutyrlyl cyclic AMP on [ 3 H]thymidine incorporation. On the other hand, this polyanion decreased the inhibitory effect of these drugs on incorporation of [ 3 H]uridine and abolished completely their effect on incorporation of [ 3 H]-L-leucine.

Elevation of cyclic AMP level in Ehrlich ascites tumor cells by quercetin

Abstract Quercetin, a flavonoid known to cause inhibition of ATPase activity and cell growth in vitro , increases cyclic AMP levels in Ehrlich ascites tumor cells. The possibility of interrelationship between cyclic AMP metabolism and (Na + + K + )ATPase activity is discussed.

COMPARATIVE STUDY OF EFFECTS OF PROSTAGLANDIN E2 ON cAMP LEVELS IN GONADS OF THE PRAWN MACROBRACHIUM ROSENBERGII AND THE CRAYFISH CHERAX QUADRICARINATUS

We compared the effects of prostaglandin E2 (PGE2) in vitro, as reflected by cAMP levels, on ovaries and testes of the giant prawn Macrobrachium rosenbergii (Decapoda, Caridea) and the redclaw crayfish Cherax quadricarinatus (Decapoda, Astacidea). These decapods differ in their reproductive physiology, representing distinct reproductive strategies. In both ovaries and testes of M. rosenbergii, PGE2 (10 p9g/ml) significantly stimulated cAMP synthesis, the reaction being augmented by IBMX. In contrast, in both ovaries and testes of C. quadricarinatus, PGE2 had no effect on cAMP levels. In muscular tissue, which served as the control for both species, cAMP levels were unaffected by PGE2. This comparative study suggests a case of different responses to PGE2 in the gonads of 2 decapod species that have distinctly different reproductive biologies. The giant prawn Macrobrachium rosenbergii (de Man) (Decapoda, Caridea) and the red-claw crayfish Cherax quadricarinatus (von Martens) (Decapoda, Astacidea) exhibit two distinct reproductive strategies, illustrating the great diversity of life cycles that have evolved during the evolution and diversifi

A Simulation Game for the Study of Enzyme Kinetics and Inhibition.

The subject of enzymes appears in high school biology curriculum as an independent topic and as a thread that connects various topics. Students have difficulty understanding concepts concerning enzyme kinetics and enzyme inhibition due to the abstract nature of molecules in general and of enzymes in particular. Several approaches that are commonly used to explain different patterns of enzyme kinetics indude laboratory experiments (Barbaric & Ries 1988; Bucholtz 1988; Meador 1988; Palmer 1986) and mathematical analysis (Bamsley 1990; Laidler 1988; Serra et al. 1986; Splittgerber 1983). In this artide, we suggest a simulation game which might facdlitate understanding of aspects concerning enzyme kinetics and inhibition. The first part of the game deals with the relationship between enzyme activity and substrate concentration. The second part concerns characterization of competitive and noncompetitive inhibition of enzyme activity. In competitive inhibition, the inhibitor resembles the substrate and carries out reversible binding, but the reaction actually does not occur once the inhibitor is bound. While the inhibitor occupies the active site, it prevents binding by the substrate until the release of the inhibitor from the enzyme takes place. In noncompetitive inhibition, the inhibitor binds to the enzyme a form that causes changes in the enzyme configuration

The effect of prolonged exposure of pregnant rats to high ambient temperature on several constituents of the genital tract's fluids

1. Various constituents of the genital tracts (GT) fluids were measured in heat-exposed rats (kept for at least 30 days at 35 +/- 1 degree C) and control rats (maintained at 22 +/- 2 degrees C). 2. There were no differences between the groups in the GT fluid volume, protein, free amino acids and glucose contents. 3. Arterial and venous blood glucose levels, pO2 and pH values were similar in both groups. 4. GT fluid protein hydrolysate from heat-exposed rats showed significantly reduced contents of glycine and alanine and elevated contents of valine and lysine as compared with controls. 5. The GT fluids free amino acid components showed reduced glycine and elevated valine and isoleucine in the heat-exposed group as compared with controls. 6. Progesterone levels in GT fluid of heat-exposed rats was 60% higher than that of controls. 7. It is suggested that the higher progesterone concentration and the altered relative contents of several free amino acids with a possible change in the proteins of the GT fluid may affect the development of the embryo in heat-exposed rats.