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Biomedical subjects

G K Weiss

Publications and source records attributed to G K Weiss.

35 records · Page 2Linked to original sources
PubMed1982

Evidence for direct neural control of ovarian steroidogenesis in rats.

Electrical stimulation of the superior ovarian nerve of intact anaesthetized dioestrous rats for 30 min reduced ovarian progesterone levels, even when papaverine and propranolol were also given. The administration of phentolamine (an alpha receptor antagonist) before stimulation reversed this effect. The results suggest that a neural control of ovarian steroidogenesis may be either excitatory through the stimulation of beta receptors or inhibitory through the stimulation of alpha receptors.

Animals↗
PubMed1980

Stimulation by beta 2-adrenergic receptors of the production of cyclic AMP and progesterone in rat ovarian tissue.

Ovarian tissue from immature rats treated with pregnant mare serum gonadotrophin (PMSG) or PMSG and human chorionic gonadotrophin was incubated in Medium 199. Stimulation of the formation of cyclic AMP in follicular and luteal tissue by terbutaline (10(-5) mol/l), a selective beta 2-agonist, was blocked by butoxamine (10(-5) mol/l), a selective beta 2-antagonist, whereas practolol (10(-5) mol/l), a selective beta 1-antagonist, was ineffective. Propranolol (10(-5) mol/l) a non-selective beta-antagonist, butoxamine nor practolol affected the increase in cyclic AMP promoted by the addition of 1 microgram LH. Stimulation of the production of progesterone in both follicular and luteal tissue by terbutaline was blocked by butoxamine, but not by practolol. These findings indicated that beta-adrenergic stimulation of ovarian cyclic AMP and progesterone is mediated by beta 2-adrenergic receptors.

Adrenergic beta-Antagonists↗
PubMed1978

The efficacy of practolol-induced beta1 adrenergic blockade in the canine heart.

The efficacy of adrenergic blockade with practolol was assessed by subjecting 6 adult mongrel dogs in a closed-chest procedure to bolus injections of isoproterenol (0.5 mcg/kg, i.v.) before and after practolol (2.0 mg/kg, i.v.). Following practolol both heart rate and pulse pressure responses were significantly reduced. It is suggested that significant beta1 receptor adrenergic blockade is achieved by practolol.

Animals↗
PubMed1978

Vagal stabilization of the ischemic canine ventricle.

To determine whether vagal activity during myocardial ischemia functions to stabilize the heart, the left anterior descending coronary artery in dogs was occluded for periods of 3 1/2 minutes with and without concurrent vagal stimulation. Bipolar electrograms were measured from the surface of the canine left ventricle within and outside the regions of intended ischemia. Ischemia in the absence of vagal stimulation depressed both the electrogram amplitude and the upstroke velocity of the electrogram signal. Vagal stimulation significantly decreased the absolute magnitude of the ischemia-induced decrease of the electrogram signal, which indicates that it tended to stabilize the insulted heart. This stabilizing influence however, was seen only in the presence of adrenergic blockade with practolol. The vagal response was only partially blocked by atropine, whereas it was abolished by lidocaine. These results suggest that a vagally mediated stabilization of the ischemic canine ventricle can occur and is unmasked only in the absence of sympathetic neural activity.

Animals↗