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Biomedical subjects

P C Butler

Publications and source records attributed to P C Butler.

67 records · Page 4Linked to original sources
PubMed1990

Pattern of postprandial carbohydrate metabolism and effects of portal and peripheral insulin delivery.

The importance of portal insulin delivery in the regulation of postprandial carbohydrate metabolism is uncertain. To address this question, three groups of dogs were studied: one group in which pancreatic venous drainage was transected and reanastomosed (portal insulin delivery), one in which the pancreatic drainage was transected and anastomosed to the inferior vena cava (peripheral insulin delivery), and one that received only a sham operation. Plasma insulin was greater (P less than 0.05) during peripheral insulin delivery than in either the portal or sham groups, respectively, before and after meal ingestion. On the other hand, C-peptide concentrations did not differ between groups, resulting in a higher (P less than 0.001) insulin to C-peptide ratio in the peripheral group. This indicated that the hyperinsulinemia in the peripheral group was due to decreased insulin clearance rather than increased insulin secretion. Isotopically determined splanchnic uptake of ingested glucose, postprandial suppression of hepatic glucose release, incorporation of CO2 into glucose (a qualitative measure of gluconeogenesis), and total-body glucose uptake were virtually identical in all groups. Similarly, plasma lipid, beta-hydroxybutyrate, and lactate concentrations did not differ between groups. Our data indicate that, despite differences in systemic insulin concentration, portal and peripheral insulin delivery comparably regulate hepatic and extrahepatic carbohydrate metabolism after meal ingestion.

Animals↗
PubMed1990

Hepatic and extrahepatic responses to insulin in NIDDM and nondiabetic humans. Assessment in absence of artifact introduced by tritiated nonglucose contaminants.

It is well established that patients with non-insulin-dependent diabetes mellitus (NIDDM) are resistant to insulin. However, the contribution of hepatic and extrahepatic tissues to insulin resistance remains controversial. The uncertainty may be at least in part due to errors introduced by the unknowing use in previous studies of impure isotopes to measure glucose turnover. To determine hepatic and extrahepatic responses to insulin in the absence of these errors, steady-state glucose turnover was measured simultaneously with [6-3H]- and [6-14C]glucose during sequential 5- and 4-h infusions of insulin at rates of 0.4 and 10 mU.kg-1.min-1 in diabetic and nondiabetic subjects. At low insulin concentrations, [6-3H]- and [6-14C]glucose gave similar estimates of glucose turnover. Hepatic glucose release was equal to but not below zero in the nondiabetic subjects, but persistent glucose release (P less than 0.001) and decreased glucose uptake (P less than 0.001) was observed in the diabetic patients. At high insulin concentrations, both isotopes underestimated glucose turnover during the 1st h after initiation of the high-dose insulin infusion. More time (P less than 0.05) was required to reachieve steady state in NIDDM than nondiabetic subjects. At steady state, [6-3H]- but not [6-14C]glucose systematically underestimated (P less than 0.05) glucose turnover in both groups due to the presence of a tritiated nonglucose contaminant. The percentage of radioactivity in plasma due to tritiated contaminants was linearly related to turnover.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1990

Effects of meal ingestion on plasma amylin concentration in NIDDM and nondiabetic humans.

Recent interest has focused on the potential role of amylin in the pathogenesis of non-insulin-dependent diabetes mellitus (NIDDM). This 37-amino acid peptide is found in extracellular amyloid deposits in approximately 50% of pancreatic islets of patients with NIDDM and has been shown to inhibit skeletal muscle glycogen synthesis in vitro. Immunocytochemical studies have colocalized amylin and insulin within beta-cell secretory granules in nondiabetic humans, provoking the following questions. Is amylin cosecreted with insulin? Are circulating amylin concentrations higher in patients with NIDDM either before or after food ingestion? To answer these questions, we developed a sensitive and specific immunoassay to measure plasma concentrations of amylin in humans. Use of this assay indicated that, in lean nondiabetic subjects, glucose ingestion resulted in an increase (P less than 0.001) in the plasma concentration of amylin (from 2.03 +/- 0.22 to 3.78 +/- 0.39 pM) and insulin (from 48.3 +/- 3.1 to 265 +/- 44 pM). There was a significant correlation between the concentrations of insulin and amylin (r = 0.74, P less than 0.001) and the increase in insulin and amylin concentration (r = 0.65, P less than 0.005). Fasting concentrations of amylin did not differ in diabetic and weight-matched nondiabetic subjects and showed a similar pattern of change after ingestion of a mixed meal. We conclude that amylin is secreted in response to ingestion of either glucose or a mixed meal and circulates at concentrations that do not differ in patients with NIDDM and nondiabetic subjects. It remains to be determined whether amylin at physiological concentrations influences carbohydrate metabolism and if so whether its effects differ in diabetic and nondiabetic humans.

Adult↗
PubMed1989

Diversion of the gastroduodenal vein: an in situ model of systemic insulin drainage.

A technique of diversion of the gastroduodenal vein in a canine model is described to compare long-term metabolic effects of systemic versus portal pancreatic endocrine drainage. The vein was transected at its entrance into the portal vein and either diverted to the inferior vena cava (systemic group) or reanastomosed to the portal vein (portal group). All remaining venous drainage of the pancreas was interrupted. An additional group of animals underwent laparotomy without manipulation of pancreatic vasculature (sham group). Fasting peripheral insulin and glucose values were determined 3 months postoperatively. Fasting insulin values were significantly higher in the systemic group (mean 10.7 +/- 1.06 U/ml) than in the portal (5.8 +/- 0.70, P = 0.002) and sham (6.4 +/- 0.68, P = 0.01) groups. Fasting glucose values were not significantly different in the three groups. At sacrifice, venous thrombosis was noted in one systemically diverted dog (6.7%). All other anastomoses were patent. No significant collateralization was apparent in any group. No significant complications were noted. This procedure simulates the hormonal milieu created by heterotopic pancreatic transplantation while preserving pancreatic innervation and exocrine function, and serves as an excellent model for investigating the effects of systemic hyperinsulinemia on protein, carbohydrate, and lipid metabolism.

Animals↗
PubMed1989

Effects of growth hormone on insulin sensitivity and forearm metabolism in normal man.

To elucidate the short-term actions of growth hormone on insulin sensitivity and forearm metabolism, we have studied six normal male subjects receiving a 6-h hyperinsulinaemic euglycemic clamp with and without a concomitant 4-h growth hormone infusion. When infused, serum growth hormone rose to 25 +/- 4 mU/l and during administration of insulin serum insulin increased by 11 +/- 1 mU/l. During euglycemic clamp, administration of growth hormone decreased forearm glucose uptake after 180 min and onward (240 min 0.216 +/- 0.031 vs 0.530 +/- 0.090 mg/100 ml/min, p less than 0.05). Glucose infusion rate (240 min 2.83 +/- 0.24 vs 4.35 +/- 0.28 mg.kg-1.min-1, p less than 0.05) and glucose disposal rate (240 min 3.57 +/- 0.17 vs 4.00 +/- 0.15 mg.kg-1.min-1, p less than 0.05) also decreased. Growth hormone persistently increased hepatic glucose production after 120 min. After 210 min, all circulating lipid intermediates increased slightly. The decrease in forearm glucose uptake and glucose infusion rate and the increase in hepatic glucose production was observed before there was any detectable increase in circulating levels and forearm uptake of lipid intermediates. These data suggest that growth hormone induces insensitivity to insulin in liver, muscle and fat after 120, 180 and 210 min respectively. The early effects of growth hormone on glucose metabolism seems independent of changes in the rate of lipolysis.

Adult↗
PubMed1989

Human forearm arteriovenous differences of carnitine, short-chain acylcarnitine and long-chain acylcarnitine.

1. Forearm arterial and venous concentrations of free carnitine, short-chain acylcarnitine, long-chain acylcarnitine, glucose, lactate, pyruvate, alanine, non-esterified fatty acids, glycerol, 3-hydroxybutyrate and acetoacetate were measured in fasted adult subjects. 2. In all subjects there was net uptake of short-chain acylcarnitine, 3-hydroxybutyrate and acetoacetate and net release of free carnitine and non-esterified fatty acids. The arteriovenous differences of the other metabolites were not consistent. 3. These observations support the concept that short-chain acylcarnitine (largely acetylcarnitine) contributes to the flux of metabolic fuels from the liver to muscle in the fasted state, although to a limited extent in comparison with 3-hydroxybutyrate (less than 5% on a molar basis).

3-Hydroxybutyric Acid↗
PubMed1989

Metabolic and hormonal responses to exogenous hyperthermia in man.

To study whether hyperthermia reproduces hormonal and metabolic responses seen in stress states such as mild infections, six normal male subjects underwent (i) a 3-h hot bath and (ii) a 3-h thermoneutral control period. During the hot bath body temperature rose by 1.2 +/- 0.03 degrees C (mean +/- SEM) and significant peaks of circulating growth hormone (56 +/- 9 vs 7 +/- 4 mU/l), adrenaline (310 +/- 34 vs 152 +/- 39 pmol/l), glucagon (19.2 +/- 4.3 vs 11.8 +/- 2.3 pmol/l) and cortisol were recorded together with slight hyperinsulinaemia (6.5 +/- 1.3 vs 5.3 +/- 1.0 mU/l, P less than 0.05). Hyperthermia was also accompanied by significant increases in circulating levels of free fatty acids (0.93 +/- 0.1 vs 0.46 +/- 0.1 mmol/l), 3-hydroxybutyrate (196 +/- 67 vs 50 +/- 18 mumol/l), glycerol (102 +/- 10 vs 48 +/- 5 mumol/l) and lactate. Blood alanine decreased and blood glucose remained constant. When an intravenous glucose tolerance test was performed during the last hour of hyperthermia signs of impaired first phase and enhanced second phase insulin responses were recorded. Calculated values for glucose disappearance also deteriorated (1.34 +/- 0.19 vs 2.04 +/- 0.50 %/min, P less than 0.05). We conclude that hyperthermia mimics most major metabolic and hormonal changes observed during mild infection and could provide a model to study these conditions.

Adult↗
PubMed1989

Heterogeneity of hepatocyte antigen expression in rat liver carcinogenesis: concordance between neoplastic nodules and tumours.

Fischer F344 rats were given a cyclical diet of 0.06% 2-acetylaminofluorene (AAF), which progressively induced oval cell proliferation, cirrhosis and hyperplastic (or neoplastic) nodules. Primary liver tumours developed from 7 months after ceasing the diet. Liver samples taken during and after AAF administration and specimens of primary tumours were processed into frozen sections and examined microscopically for morphological changes in cell populations, stained histochemically for gamma-glutamyl transpeptidase (GGTase) and four phosphatases, and stained by the immunoperoxidase technique for the presence of antigens detected by seven anti-liver cell monoclonal antibodies and monoclonal antibodies to six oncoproteins. During and after AAF treatment several of the anti-liver antibodies revealed foci of aberrantly or heterogeneously-stained cells, although anti-oncoprotein antibodies showed no consistent changes. Foci of cells positive for GGTase and heterogeneous for adenosine triphosphatase (ATPase) were also seen. Nodules invariably showed heterogeneous antigenicity, raised GGTase and abnormal ATPase expression. Primary tumours exhibited varying degrees of positivity, negativity and heterogeneity with the anti-liver monoclonal antibodies, and all were positive for GGTase. Comparison between various parameters and different lesions showed the greatest concordance between nodules and tumours, suggesting that nodules are probably the precursors of malignant tumours in this system.

2-Acetylaminofluorene↗
PubMed1989

Regulation of carbohydrate metabolism and response to hypoglycemia.

Postabsorptive and postprandial glucose concentrations are regulated by the interaction of insulin and the counterinsulin hormones. Either an excess of insulin or insulin-like activity or a deficiency of counterregulatory hormone secretion can cause hypoglycemia. Impairment of glycogen storage or breakdown is likely to lead to a relatively rapid fall in glucose, whereas hypoglycemia caused by alterations in gluconeogenesis are generally observed with a more prolonged fast. Although glucagon, epinephrine, cortisol, and growth hormone all possess biologic activity capable of opposing insulin action, glucagon appears to be the primary hormone responsible for defense against hypoglycemia. In the absence of glucagon, epinephrine becomes important. Cortisol and growth hormone appear to serve a permissive role during recovery from acute hypoglycemia. Whether they have a more important role during recovery from chronic hypoglycemia remains to be determined.

Acute Disease↗
PubMed1988

Reactivity of monoclonal antibodies to oncoproteins with normal rat liver, carcinogen-induced tumours, and premalignant liver lesions.

Monoclonal antibodies to proteins encoded by the ras, myb, myc, erb-B, src and PDGF-2 genes were tested for reactivity with normal rat liver, livers from rats fed with 0.06% 2-acetylaminofluorene (AAF), and premalignant lesions and primary liver tumours from rats given AAF alone or a combined treatment with diethylnitrosamine and AAF. Radioimmunoassays were performed with plasma membrane fractions and total soluble subcellular extracts of the tissues, and immunoperoxidase staining was carried out on frozen tissue sections. All of the antibodies were positive in radioimmunoassays, some more strongly than others, and each antibody bound equally to extracts of different kinds of tissue. Immunohistology revealed significant staining of normal liver by 5 of the 6 antibodies, and only minor qualitative differences of the staining pattern in some tumours and hyperplastic nodules. It was concluded that these antibodies were not able to discriminate sufficiently well between normal, premalignant and malignant rat liver to be of value in identifying the precursor cells of malignant tumours.

2-Acetylaminofluorene↗
PubMed1988

Osmoregulation of thirst and vasopressin secretion in insulin-dependent diabetes mellitus.

1. Osmotically stimulated thirst and vasopressin release were studied during infusions of hypertonic sodium chloride and hypertonic D-glucose in euglycaemic clamped diabetic patients and healthy controls. 2. Infusion of hypertonic sodium chloride caused similar elevations of plasma osmolality in diabetic patients (288.0 +/- 1.0 to 304.1 +/- 1.6 mosmol/kg, mean +/- SEM, P less than 0.001) and controls (288.6 +/- 0.9 to 305.7 +/- 0.6 mosmol/kg, P less than 0.001), accompanied by progressive increases in plasma vasopressin (diabetic patients, 0.9 +/- 0.3 to 7.7 +/- 1.5 pmol/l, P less than 0.001; controls 0.5 +/- 0.1 to 6.5 +/- 1.0 pmol/l, P less than 0.001) and thirst ratings (diabetic patients 1.0 +/- 0.2 to 7.1 +/- 0.5 cm, P less than 0.001; controls 1.8 +/- 0.4 to 8.0 +/- 0.5 cm, P less than 0.001) in both groups. 3. Drinking rapidly abolished thirst and vasopressin secretion before major changes in plasma osmolality occurred in both diabetic patients and healthy controls. 4. There were close and significant correlations between plasma vasopressin and plasma osmolality (diabetic patients, r = +0.89, controls r = +0.93) and between thirst and plasma osmolality (diabetic patients r = +0.95, controls r = +0.97) in both diabetic patients and healthy controls during hypertonic saline infusion. 5. Hypertonic D-glucose infusion caused similar elevations in blood glucose in diabetic patients (4.0 +/- 0.2 to 20.1 +/- 1.2 mmol/l, P less than 0.001) and healthy controls (4.3 +/- 0.1 to 19.3 +/- 1.2 mmol/l, P less than 0.001) but did not change plasma vasopressin or thirst ratings.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗