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Biomedical subjects

M Verosky

Publications and source records attributed to M Verosky.

35 records · Page 2Linked to original sources
PubMed1977

Adenylate cyclase and phosphodiesterase activity in rabbit ureter.

Adenylate cyclase and phosphodiesterase enzyme activities were demonstrated in rabbit ureter. NaF, 10 mM, caused a 60.9 per cent increase in adenylate cyclase activity. Isoproterenol, 5 X 10-7 to 10-5 M induced a statistically significant dose-dependent increase in adenylate cyclase activity which was suppressed by propranolol, 10-7 M. Theophylline, 5 X 10-5 to 10-2 M, significantly inhibited phosphodiesterase activity. Thus, isoproterenol and theophylline, two agents that can relax ureteral segments previously contracted by a depolarizing concentration of potassium, could presumably increase cyclic AMP levels, isoproterenol by increasing synthesis and theophylline by decreasing degradation.

Adenylyl Cyclases↗
PubMed1975

Ouabain-induced changes in electrophysiologic properties of neonatal, young and adult canine cardiac Purkinje Fibers.

Young patients frequently require higher concentrations of digitalis per kilogram of body weight or per square meter of surface area than adults to induce digitalis effect or toxicity. In order to investigate the electrophysiologic basis for this observation, we used standard microelectrode techniques to study the effects of ouabain on action potential characteristics of cardiac Purkinje fibers of neonatal (1-7 day), 4 to 7 week and adult dogs. Purkinje fibers were stimulated at a 500-msec cycle length. Action potentials were recorded during control Tyrode's perfusion and 23.5 minutes after onset of superfusion with ouabain, 2 X 10(-7) M (10% ouabain-3H). The Purkinje fibers were then assayed for ouabain uptake. Ouabain accelerated repolarization and decreased action potential amplitude, resting membrane potential and maximum upstroke velocity of phase O. Changes were greatest in the adults, least in the neonates. Ouabain increased the slope of phase 4 depolarization in 10 to 12 adults, 7 of 16- 4 to 7-week puppies and 0 of 12 neonates. Hence, ouabain induced lesser changes in the action potentials of Purkinje fibers taken from young animals. These results suggest that Purkinje fiber sensitivity to ouabain effects increases with age.

Action Potentials↗
PubMed1975

Effect of albuterol and terbutaline, synthetic beta adrenergic stimulants, on the cyclic 3',5'-adenosine monophosphate system in smooth muscle.

The effect of albuterol and terbutaline on the cyclic 3',5'-adenosine monophosphate (cAMP) system was studied in rat uterus, aorta and myocardium and in dog bronchus, and was compared to that of isoproterenol in order to determine whether the tissue specificity observed in their functional effects is reflected in their effect on the cAMP system. Tissue specimens were either homogenized in Tris buffer for enzyme activity measurements or incubated in Krebs-Ringer-bicarbonate medium with the test drugs. Both albuterol and terbutaline produce an increase in cAMP content in the tissues due to a direct effect on adenylate cyclase. This effect can be potentiated by a phosphodiesterase inhibitor and antagonized by a beta adrenergic blocking compound. The cAMP response to each beta adrenergic agonist differs in the tissues examined: in uterus and aorta where the maximal effects are idenitcal, the ED50 values may reflect differences in affinity which may account for the different cAMP response to the compounds at the lower concentrations. In bronchus and myocardium, both the maximum effect and ED50 values of the compounds are different. Albuterol and terbutaline increases cAMP content in bronchus significantly and have only a small effect on cAMP cont in myocardium, whereas isoproterenol increases cAMP level significantly in both tissues. The results indicate that the tissue specificity of albuterol and terbutaline may have its origin at the level of the cAMP system.

Adenosine Triphosphate↗
PubMedDate not supplied

Plasma retention and metabolic fate of hemoglobin modified with an interdimeric covalent cross link.

Hemoglobin (Hb) modified with an interdimeric bicovalent cross link using 2-nor-2-formylpyridoxal 5'-phosphate (NFPLP) as the cross-linking agent has an exceptionally low O2 affinity (P50 = 47 torr), enabling it to deliver more oxygen at tissue pO2 than blood. In addition, the covalent cross link prevents dissociation of the HbXL tetramers. By using 3H-labeled HbXL, the present study investigated intravascular retention time of cross linked Hb (HbXL), organ distribution, and routes by which HbXL is metabolized and eliminated from the body. The rats were injected with an i.v. bolus (125-200 mg Hb/kg body weight) of either 3H-labeled HbXL or noncross-linked pyridoxal 5'-phosphate modified Hb (diPLPHb) as a control. Urine and feces were collected daily for up to 9 days. Organs and tissues were harvested either at 9 hr or 9 days and assayed for 3H-label content by standard liquid scintillation counting. Plasma retention of HbXL at this dose was about three times longer than diPLPHb, and no HbXL as such was recovered in the urine. HbXL did undergo metabolic degradation in the body, with labeled fragments (mol. wt. less than 10,000) being excreted by the kidneys and gastrointestinal tract. Total body clearance of the label by 9 days amounted to approximately 83% of the injected dose.

Adrenal Glands↗