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Biomedical subjects

M Greenfield

Publications and source records attributed to M Greenfield.

36 records · Page 2Linked to original sources
PubMed1979

Effect of a high carbohydrate diet on insulin binding to adipocytes and on insulin action in vivo in man.

We studied the effects of short-term (5 days) and long-term (2 wk) high carbohydrate (75%) feedings on insulin binding to isolated adipocytes and insulin sensitivity in vivo in normal subjects. Ingestion of the high carbohydrate diet led to daylong hyperinsulinemia in both short- and long-term groups. Insulin binding to isolated adipocytes was decreased in both groups; in the short-term groups this decrease in insulin binding was caused by a decrease in the receptor affinity, whereas in the long-term group it was caused by a decrease in receptor number. On the other hand, despite this decrease in insulin binding, total in vivo insulin sensitivity was markedly improved in both groups. In conclusion, (1) the short-term adaptive response of the insulin receptor is a decrease in binding affinity whereas the long-term response is a decrease in receptor number, (2) sustained and chronic hyperinsulinemia can lead to a decrease in the number of cellular insulin receptors, (3) high carbohydrate diets lead to a general increase in insulin's ability to promote glucose removal from plasma, and (4) the paradox of enhanced insulin sensitivity in the face of decreased insulin binding can be explained if high carbohydrate diets also lead to an increase in the activity of steps in glucose metabolism distal to the insulin receptor.

Adipose Tissue↗
PubMed1978

The effect of ten days of fasting on various aspects of carbohydrate metabolism in obese diabetic subjects with significant fasting hyperglycemia.

Patients with nonketotic diabetes mellitus, who were both obese and had significant fasting hyperglycemia (mean plasma glucose = 310 mg/100 ml), were fasted for 10 days. There was a prompt drop of plasma glucose levels as the result of the caloric deprivation with a mean fall of approximately 200 mg/dl at the end of the fast. The drop in plasma glucose level that occurred during the fast was associated with a drop in plasma insulin level. Fasting plasma glucose concentration rose immediately after food intake was resumed and stabilized within 3--4 days at levels halfway between the initial and the lowest value. At this time, the patients also seemed capable of disposing of an oral glucose load more efficiently. The apparent improvement in carbohydrate homeostasis observed after the fast could not be attributed to an increase in insulin response, but was associated with some amelioration of the insulin resistance that characterizes these patients. Unfortunately, the beneficial effects of the 10-day period of caloric deprivation were transitory and fasting plasma glucose values had returned to prefast levels in most patients within a few months.

Adult↗
PubMed1977

Effect of simultaneous potassium and saline loading on plasma aldosterone levels.

To assess the relative importance of the renin-antiotensin system and potassium in the acute regulation of aldosterone secretion in the salt depleted state, normal subjects were infused with an asotonic saline solution containing potassium chloride (KCl) and the responses compared to the infusions of isotonic saline (500 ml/h) and KCl alone (20 mEq K+/h). Subjects were studied recumbent in balance on a 10 mEq sodium/100 mEq potassium diet. The rates of infusing saline and potassium were selected to produce comparable but opposite effects on the levels of plasma aldosterone. As plasma renin activity (PRA) declined and plama potassium increased during the combined saline-KCl infusions, plasma aldosterone levels appeared to be the arithmetic sum of the changes in these parameters. In fact, the calculated changes in aldosterone levels per unit change in PRA or potassium from each infusion alone, correlated well with the observed levels, further supporting an additive relationship. These data support the concept that in the salt depleted state the renin-angiotensin system and potassium are equally important in the acute regulation of plasma levels of aldosterone.

Aldosterone↗
PubMed1976

A delayed suppression of the renin-aldosterone axis following saline infusion in human hypertension.

The purpose of this study was to compare the acute suppressibility of the renin-angiotensin-aldosterone (RAA) axis in normotensive (n = 23) and essential hypertensive (n = 62) subjects. Only those hypertensive subjects with normal plasma renin activity (PRA) levels (sodium restricted, upright) were included in the study. Acute suppression of the RAA axis was determined by measuring PRA, plasma angiotensin II (A II), and plasma aldosterone (PA) at frequent intervals during the infusion of isotonic saline (500 ml/hour for 6 hours). Although all parameters fell significantly from control levels by 20-30 minutes in the normotensive subjects, we found that 60% of the hypertensive subjects showed no significant decline in PRA or PA until 120-240 minutes after beginning the infusion. The other hypertensive subjects showed normal RAA suppression. In addition, while there were no significant differences between the three groups in control PRA or PA levels, we found that the PA levels from 30 to 240 minutes during the saline were significantly higher (P less than 0.01) in the hypertensive subjects with delayed suppression. That there were two distinct populations in the hypertensive group was suggested by the bimodality of the frequency response curve, with peaks occurring at 30 and 240 minutes. These studies indicate an abnormality in the acute suppression of the RAA axis in a substantial proportion of subjects with normal renin essential hypertension. Since previous studies in normal subjects have reported that the early phase of response to saline infusion is related to the sodium ion per se and not to intravascular volume expansion, we have come to the conclusion that the present data are consistent with the hypothesis that the delayed suppression hypertensive group has a diminished ability to respond to the sodium ion.

Adult↗
PubMed1970

Hospital libraries: focal point in the continuing education crisis.

The Proposed Requirements for Professional Libraries in Hospitals to be Licensed in the Commonweath of Pennsylvania are presented and discussed. Indication is given of current trends in the development of hospital libraries as the single most important factor in continuing medical education and as the least-developed factor.

Education, Medical, Continuing↗
PubMed1916

A New Ice Sampler.

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Journal Article↗
PubMedDate not supplied

Development of Bragg diffraction imaging for medical use.

Experience gained in developing a real-time acoustical imaging system using Bragg diffraction is presented. Particular emphasis has been placed on medical applications. We have studied the difficulties in assembling a system capable of producing high-quality images. Engineering data on the optical mounting and on the design of the transducer along with representative images are presented and discussed.

Bone and Bones↗
PubMedDate not supplied

Comparison of fixed-ratio versus variable-ratio regular and NPH semisynthetic human insulin in insulin-requiring diabetic patients.

The efficacy and safety of a fixed combination of semisynthetic human insulin (Novolin) providing a 70:30 ratio of NPH to regular insulin versus a varying ratio of semisynthetic human insulin, regular and NPH (control group), were compared in adult insulin-dependent and noninsulin-dependent diabetic patients whose glycemic control had been stable on customized split-mix regimens of animal insulin. Seventy-eight patients were enrolled, of whom 72 were evaluated for efficacy of the respective regimens. Although the baseline fasting serum glucose concentrations were significantly higher in the fixed-ratio group than in the control group, mean serum glucose and glycosylated hemoglobin values throughout the 12 weeks of experimental treatment were not significantly different between groups. The mean serum glucose and glycosylated hemoglobin values in the fixed-ratio group also did not differ significantly from baseline; however, statistically significant increases were observed in the control group at weeks 4 and 8, but not at week 12. Total daily insulin dosages were comparable between the two groups, and body weight did not change significantly in either group. At the end of the study, the investigators judged 90% of the patients in the fixed-ratio group and 88% of the patients in the control group to be either improved or unchanged with respect to glycemic control. The frequency of hypoglycemic episodes and other clinical events did not change significantly from baseline in either group or differ significantly between the two groups at any time. The results of this study suggest that stable diabetic patients receiving animal insulin can safely be transferred to semisynthetic human insulin and that the majority of patients can maintain acceptable glycemic control with a fixed 70:30 ratio of NPH to regular semisynthetic human insulin.

Adult↗
PubMedDate not supplied

Pheochromocytoma.

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Adrenal Gland Neoplasms↗