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Biomedical subjects

M I Friedman

Publications and source records attributed to M I Friedman.

At least 109 records · Page 6Linked to original sources
PubMed1983

Suppression of food intake by intragastric glucose in rats with impaired glucose tolerance.

Three experiments were performed to examine the relationship between impaired glucose tolerance and food intake. In the first experiment, normal rats that were given long-term insulin treatment, which was then withdrawn, ate less than controls when refed after food deprivation. Despite reduced intakes, rats previously treated with insulin became more hyperglycemic than controls during refeeding. In the second experiment, intragastric glucose injections reduced food intakes to a similar degree in control rats and in rats experiencing insulin withdrawal even though glucose loading produced a much greater increase in plasma glucose level in previously insulin-treated rats. In the third experiment, intragastric loads of a glucose polymer, Polycose, reduced food intake to the same degree in normal rats and in streptozotocin-diabetic rats both two and sixteen days after insulin withdrawal when diabetic rats were, respectively, hypo- and hyperphagic. The results show that impaired glucose tolerance does not appreciably alter the suppressive effects of glucose loading on food intake. Other effects of glucose administration, besides those on insulin-dependent glucose utilization, appear to reduce food intake after glucose loading.

Animals↗
PubMed1983

Food intake and blood fuels after oil consumption: differential effects in normal and diabetic rats.

The mechanisms by which fat feeding suppresses the hyperphagia of diabetic rats were examined. Rats that were allowed to consume a small amount (1.5 ml) of corn oil decreased subsequent food intake within 6 hr after ingesting. Diabetic rats decreased food intake much more than normal rats. Similar results were obtained when oil was given intragastrically. Analysis of blood samples revealed that diabetic rats showed greater increases in plasma ketones and triglycerides and smaller increases in plasma glycerol than normal rats following consumption of 1.5 ml corn oil. This difference between diabetic and normal rats appeared when rats were allowed to eat after oil ingestion as well as when they were fasted. Brief periods of food deprivation (2.5-4.5 hr) substantially increased plasma ketones and glycerol and decreased plasma triglycerides in both diabetic and normal rats. The results indicate that diabetic rats decrease food intake more than normal rats after fat feeding because they oxidize more of the ingested fat.

Animals↗
PubMed1983

Differential effects of medium- and long-chain triglycerides on food intake of normal and diabetic rats.

Three experiments were performed to examine the effect of ingestion of medium- (MCT) and long-chain (LCT) triglyceride oils at the beginning of the normal feeding period on subsequent food intake of normal and diabetic rats. In the first experiment, diabetic rats reduced food intake more than normal animals in the first 6 hr after ingestion of 2.0 ml of MCT or LCT oil. In the second experiment, diabetic rats reduced food intake to a similar extent by 6 hr after ingestion of 1.5 ml of MCT or LCT oil, but the time course of this effect depended on the oil ingested. Ingestion of MCT oil produced a decrease in food intake within 2 hr, whereas ingestion of LCT oil reduced food intake 2-4 hr later. In the third experiment, a direct comparison was made of the differential time course of food intake suppression by MCT or LCT oil in both normal and diabetic rats. Diabetic rats decreased food intake after ingestion of 1.5 ml MCT or LCT oil, whereas normal rats did not. Again, in diabetic rats, ingestion of MCT oil produced a more rapid reduction in food intake than ingestion of LCT oil. It is proposed that the more pronounced reduction in food intake of diabetic rats after oil ingestion is due to a greater degree of hepatic oxidation of ingested fat, whereas the differential effect of MCT and LCT oil ingestion in diabetic rats is due to a differential rate of delivery of the ingested lipid substrate to the liver.

Animals↗
PubMed1983

Metabolic concomitants of hypophagia during recovery from insulin-induced obesity in rats.

Rats were given daily injections of protamine-zinc insulin (PZI) that increased food intake and body weight. Termination of insulin treatment resulted in transient hypophagia and weight loss. Simultaneously with the weight loss, plasma levels of glycerol, free fatty acids, glucose, and ketones increased, whereas adipose tissue lipoprotein lipase activity and liver glycogen decreased. These changes in food intake and metabolism after termination of PZI treatment were accentuated in streptozotocin-diabetic rats. Two antilipolytic drugs (nicotinic acid and 3,5-dimethylpyrazole) blocked the elevation in plasma glycerol while having no effect on food intake. A 1-day fast after termination of insulin treatment equalized insulin-treated and control groups for plasma glycerol and ketones and reversed group differences in free fatty acids; the elevation in plasma glucose persisted despite starvation. Following starvation, previously PZI-treated rats ate less than controls on refeeding. The results show that enhanced lipolysis does not invariably accompany hypophagia during excess weight loss and suggest that a disturbance in carbohydrate metabolism or an increase in hepatic fatty acid oxidation may underlie this decrease in food intake.

Animals↗
PubMed1983

Food intake and peripheral factors after recovery from insulin-induced hypoglycemia.

Rats increased food intake after plasma glucose returned to normal in the wake of an insulin-induced hypoglycemic episode. Whereas increased eating 6-8 h after insulin occurred only when plasma glucose levels fell below 70 mg/dl, intakes were not related to the degree of prior hypoglycemia. Administration of glucose in the first 3 h after insulin prevented increased eating, whereas glucose given 4-6 h after insulin was less effective. Intravenous infusions of fructose given in the first 3 h after insulin injection prevented increased food intake in normal but not hepatic-vagotomized rats. Determination of various metabolic variables in parallel experiments showed that insulin treatment resulted in changes in peripheral metabolism, which persisted at the time feeding tests were conducted, and that administration of glucose or fructose tended to reverse these changes. The results suggest that increased food intake after recovery from hypoglycemia is associated with peripheral metabolic consequences of ongoing or previous counterregulatory responses which occur during hypoglycemia and that alterations in hepatic metabolism are sufficient to inhibit this insulin-induced eating.

Animals↗
PubMed1983

Feeding after recovery from 2-deoxyglucose injection: cerebral and peripheral factors.

Rats increased food intake 6 h after peripheral and intracerebroventricular injections of 2-deoxy-D-glucose (2-DG) when plasma glucose concentrations had returned to normal from elevated levels. Rats with adrenal demedullation did not become hyperglycemic after injection of 2-DG and increased food intake more than normal animals after peripheral, but not ventricular, injections of 2-DG. Peripheral injections of 2-DG inhibited gastric emptying in normal, but not adrenal demedullated, rats. Intravenous infusions of epinephrine into normal rats, which mimicked some of the physiological effects of peripheral 2-DG injection, did not increase food intake. The results indicate that a prior disruption of cerebral metabolism is sufficient to elicit feeding in the absence of an adrenomedullary response and that increased gastric fill may restrain the increase in food intake produced by a previous cerebral emergency.

Adrenal Medulla↗
PubMed1982

Obesity and adipocyte abnormalities in offspring of rats undernourished during pregnancy.

Pregnant rats underfed in the first 2 weeks of gestation had offspring with normal body weight at birth and weaning. However, starting at about 5 weeks of age the male offspring became hyperphagic and gained more weight than the controls. The female offspring did not overeat and did not become obese. Both male and female progeny showed increased fat cell size as adults. In males the epididymal and retroperitoneal fat pads were significantly enlarged nd adipocytes in these pads were hypertrophied. In females and fat pads were not enlarged, but adipocytes in the parametrial pads were hypertrophied.

Adipose Tissue↗
PubMed1982

Metabolic and physiologic effects of a hunger-inducing injection of insulin.

Rats injected subcutaneously with 5 U/kg of regular insulin increased food intake above control levels in a 2 hr test and showed a median latency to eat of 59 min. One week later, rats were injected again with saline or insulin (5 U/kg), deprived of food and killed 60 +/- 10 min later. Insulin treatment produced a marked reduction in plasma glucose, plasma ketone bodies and liver glycogen, as well as a marked acceleration of gastric emptying. The results indicate that a variety of changes in peripheral metabolism and physiology may underlie the increase in food intake observed after insulin injection and that it is premature to ascribe the hunger-inducing effect of insulin treatment solely to a decline in blood glucose.

Animals↗
PubMed1982

Caloric compensation following insulin administration in rats.

Caloric intakes following injections of insulin were examined in male rats maintained on diets of different caloric densities. Following saline or insulin injections, food intake was measured every two hours for six hours or food was withheld for six hours until recovery of normo-glycemia and total intake was measured at seven and eight hours post-injection. Additionally, levels of plasma metabolic fuels, liver glycogen and stomach contents were measured following saline and insulin injections. Animals in both the continuous and delayed access conditions consumed the same number of calories following injections of insulin. Similarly, the increases in intake relative to saline baseline conditions were comparable across diet groups in both conditions although animals tested in the delayed access paradigm were less variable in their response. Changes in levels of metabolic fuels, stomach contents and liver glycogen were found to be consistent with the known effects of insulin and counter-regulatory responses to the induced hypoglycemia.

Animals↗
PubMed1982

Glycerol is not a physiologic signal in the control of food intake in rats.

Rats were given two daily subcutaneous injections of either 40, 80 or 160 mg/kg of glycerol or control injections of glucose. Glycerol injections did not reliably affect body weight gain at any dose tested whether animals were maintained in constant light or a 12 hr light/dark cycle. Only injections of 160 mg/kg of glycerol given twice daily significantly reduced daily food intake; however, this dose also raised plasma glycerol concentrations briefly to an unphysiologic level. Continuous intravenous infusions of 390 or 780 mg/rat/day of glycerol had no effect on food intake, even though plasma glycerol levels increased markedly within the normal range. These findings indicate that reductions of food intake and body weight after administration of glycerol are probably responses to a treatment which is not physiologic.

Animals↗
PubMed1981

Physiological and behavioral consequences in rats of water recycling during lactation.

Radioactive water injected into 10-day-old rats were recovered the following day from their mothers' blood. This transfer of water was nearly eliminated by ligating the injected pups' urethras, a result indicating that mother rats consume their offspring's urine. Preventing urine consumption by ligating urethras of all pups in a litter doubled the plasma volume deficit in dams produced by 24 hr of water deprivation alone and led to increased isotonic saline, but not water, intakes following after water deprivation. Mother rats' daily water intakes increased after they were deprived of pup urine, and their pup-licking behavior increased following water deprivation. These findings indicate that urine consumption by mother rats has both physiological and behavioral consequences and suggest that pup licking is, in part, an ingestive behavior.

Animals↗
PubMed1980

Hepatic modulation of insulin-induced gastric acid secretion and EMG activity in rats.

Intravenous infusions of fructose, a hexose that does not cross the blood-brain barrier, suppressed insulin-induced gastric acid secretion and electromyographic (EMG) activity despite continuing hypoglycemia. Hepatic portal vein infusions of 0.15 M fructose inhibited acid output while the same concentration delivered via the jugular vein did not, suggesting a hepatic site of action of the hexose. Only infusions of fructose that began before onset of the insulin-induced gastric responses were effective, whereas glucose infusions, which elevated plasma glucose levels, readily reversed ongoing gastric activity. The suppressive effects of fructose on gastric activity were prevented by prior section of the hepatic branch of the vagus nerve. In contrast, hepatic vagotomy did not prevent suppression of gastric responses by infusions of glucose, a hexose utilized by both brain and liver. These results suggest that receptors in the brain may initiate and terminate insulin-induced gastric acid secretion and motor activity, whereas sensors in the liver may inhibit these responses.

Animals↗
PubMed1979

Cardiovascular nuclear medicine: an overview.

Some of the available cardiovascular nuclear medicine methods are incompletely validated, and others are incompletely developed. They are, however, of very great potential in diagnostic cardiology, and in patient management. A new era of clinical research and acute care monitoring has been opened by serial, noninvasive, hemodynamic measurements of right ventricular as well as left ventricular function. Stress testing has become more specific, and should, with future developments, become more specific, and should, with future developments, become more sensitive, using radionuclide procedures. Serious quality control and validation questions concerning thallium stress testing must be addressed. Intracoronary injection of radiogases has great potential, although minimal present application. Emission computerized tomography will be an important research tool. Compartmental analysis modeling of first pass tracer injections has much to offer, but is not yet validated. Present growth rate of these procedures is very rapid. Fully developed, cardiovascular nuclear medicine may become the largest component of clinical nuclear medicine practice.

Adult↗
PubMed1979

Sensory functions of the liver--a review.

In this paper we critically review anatomic, electrophysiological, physiological, and behavioral evidence for neural receptors in the liver. Several lines of evidence suggest that the afferent innervation of the liver may be substantial, although few anatomic studies have directly addressed the question of an hepatic sensory supply. On the other hand, there is convincing functional evidence for a variety of hepatic sensory receptors. Hepatic osmo-, ion, and baroreceptors, sensitive to changes in the osmolarity and electrolyte concentrations in blood and to variations in portal venous pressure, modulate diuresis and natriuresis. Metabolic receptors, for which the adequate stimuli have not yet been specified, influence feeding behavior and gastric acid secretion in response to alterations in hepatic metabolism associated with changes in the supply of metabolic fuels. Directions for future research are suggested and general conclusions about the role of hepatic receptors in homeostasis are discussed.

Afferent Pathways↗