Showing papers by "Robert A. Levine published in 1968"

Effects of oral chromium supplementation on the glucose tolerance of elderly human subjects

Abstract: The possible role of Cr deficiency in the impairment of glucose tolerance in elderly subjects has been studied. Chromium supplements, 150 μg. daily, were given to 10 apparently healthy inmates of an old-age home, whose oral glucose tolerance tests (G.T.T.'s) were abnormal. Mean GTT became normal in 4 subjects (“Cr responders”) but remained abnormal in the other 6 subjects (“Cr non-responders”) during Cr administration. The beneficial effect of Cr in the “Cr responders” did not result from an increased release of insulin, since plasma ILA and immuno-reactive insulin levels were normal and rose normally after the glucose load both before and during Cr supplementation. Serum Cr concentration was found to rise significantly after the glucose load in old and young subjects but to a lower level in the elderly “Cr non-responders”, suggesting that an adequate rise in serum Cr might be necessary for normality of the G.T.T. The data support the possibility that Cr deficiency may lead to the impairment of the GTT in some elderly subjects.

Effects of exogenous adenosine 3′,5′-monophosphate in man

Abstract: The metabolic responses to administration of exogenous cyclic adenosine 3′,5′-monophosphate (3′,5′-AMP) were studied in 22 human volunteers, including a subject with anterior pituitary insufficiency. In relatively large doses (10 mg./Kg. or 0.5 mg./Kg./min.), 3′,5′-AMP induced prompt hyperglycemia and latent steroidogenesis. The plasma non-esterified fatty acid (FFA) response was biphasic, with an initial fall and subsequent rise in concentration. The possible mechanism by which 3′,5′-AMP stimulated these diverse processes was also investigated. Responses to 3′,5′-AMP were demonstrated in the presence of pharmacologic blockade of the beta-adrenergic receptor site by dl-propranolol and in the absence of efferent pathways of the pituitary gland. The actions of the cyclic nucleotide demonstrated in man support its role as the mediator of a variety of hormonal actions.

Relaxant effect of cyclic adenosine 3',5'-monophosphate on the isolated rabbit ileum.

Abstract: The effects of epinephrine, cyclic adenosine 3', 5' -AMP and other adenine nucleotides were investigated in segments of isolated rabbit ileum before and after adrenergic blockade by phentolamine and MJ 1999. 3', 5' -AMP, adenosine, 5' -AMP, 2', 3'-AMP and ATP all inhibited spontaneous motility of the isolated ileum within seconds, before and after adrenergic receptor blockade. The concentration of 3', 5'-AMP used to decrease the amplitude of contraction was between 10-6 and 10-4 M. There was evidence of tachyphylaxis. The depression of motility by 3', 5' -AMP was qualitatively similar to that observed with epinephrine and the other adenine nucleotides. Alpha and beta receptors did not appear to be involved in the function of intestinal relaxation induced by 3', 5' -AMP or other adenine nucleotides. The data obtained with the adenine nucleotides suggest a nonspecific role of 3', 5' -AMP on intestinal motility. The adenosine moiety may be the active inhibitory agent.

Steatorrhea induced by para-aminosalicylic acid.

Abstract: The effects of abnormally high (12 g) and normal (6 g) daily doses of para-aminosalicylic acid (PAS) recrystallized with ascorbic acid (PAS-C) on absorptive function was investigated in se...

Effects of exogenous adenosine 3',5'-monophosphate in man. I. Cardiovascular responses.

Abstract: The cardiovascular response to administration of cyclic adenosine 3',5'‐monophosphate (3',5'‐AMP) was studied in 26 human volunteers. In relatively large doses (10 mg. per kilogram or 0.5 mg. per kilogram per minute), 3',5'‐AMP induced prompt cardioacceleration and increased cardiac output. In contrast to those receiving rapid 3',5'‐AMP iniection, all subiects receiving a constant infusion of the nucleotide showed a progressive and sustained elevation of systolic blood pressure. Responses to 3',5'‐AMP were demonstrated in the presence of attempts at pharmacologic blockade of beta adrenergic and cholinergic receptor sites by dl‐propranolol and atropine, respectively. Following production of marked hypotension by trimethaphan (Arfonad) and glyceryl trinitrate, with consequent blockade of sympathetically induced cardioacceleration, administration of 3',5'‐AMP promptly increased heart rate without any change in blood pressure. These findings suggested a direct cardiac action of the nucleotide rather than reflex alterations of the heart due to arterial pressure changes. The cardiac findings in man support in vitro data that 3',5'‐AMP may represent part of the biochemical basis for the myocardial response to catecholamines.