Secretion by glucagonomas of a possible glucagon precursor

Five patients with glucagonomas had elevated plasma levels of total glucagon immunoreactivity. Gel filtrations of these plasma samples on Bio-Gel P30 columns showed that most of the immunoreactivity eluted in the 3,500-(true glucagon) and 9,000-dalton fractions. After the administration of alpha cell effectors, changes in total glucagon immunoreactivity were seen which were accounted for primarily by the 3,500-dalton species, but there were also changes in the 9,000-dalton moiety. Venous effluent plasma from tumors of two subjects contained elevated concentrations of glucagon immunoreactivity in both fractions. When material from both the 3,500- and 9,000-dalton peaks were serially diluted in a glucagon immunoassay, parallel displacement curves were found, suggesting that both have similar or identical antigenic determinants. Thus, with conversion to a neoplastic state, alpha cells of glucagonomas, much like beta cells of insulinomas, may secrete an increased amount of a larger, 9,000-mol wt glucagon species which may be a prohormone.

Nitrogen washout studies in acute mountain sickness

We assessed the severity of Acute Mountain Sickness (A.M.S.), indices of pulmonary gas exchange and nitrogen washout curves in healthy volunteers acutely exposed to high altitude. Symptoms of A.M.S. ranged from malaise to vomiting with intractable headache. The slope of phase III of the nitrogen washout curve increased most in those subjects with the most severe A.M.S. and who were most hypoxemic. The sickest subject also had the greatest increase in (A-a)DO2 and the largest increase in the slope of phase III. These abnormalities in gas exchange and nitrogen washout curves in the subjects with the most marked A.M.S. suggest that the manifestations of cerebral and pulmonary dysfunction at altitude develop simultaneously, although not necessarily by identical mechanisms.

Pulmonary gas exchange in acute mountain sickness

The severity of acute mountain sickness (AMS) was investigated in healthy volunteers, airlifted to high altitude (5,360 m). Blood gases were measured at 2,990 m and 5,360 m. Symptoms of AMS were found in all subjects, but ranged from malaise to vomiting with intractable headache. The clinical severity of AMS was directly related to the arterial PCO2 and inversely to pH, but unrelated to the PO2 on arrival at high altitude. However, PO2 fell and was lowest 48 h after arrival at high altitude in those subjects with the most severe AMS. These were the only subjects to show an increase in the alveolar-arterial PO2 difference and in the venous admixture ratio during the first 48 h. These abnormalities in gas exchange, which developed in the subjects with the most marked cerebral symptoms, suggest that the manifestations of cerebral and pulmonary dysfunction at altitude develop simultaneously, a finding that suggests coexisting cerebral and pulmonary edema.

Interrelationships of insulin, glucose, lipid and anthropometric data in a natural population

A population sample of 142 men and 148 women aged 40-69 was drawn in Chittenden County, Vermont, and studied for interrelationships among several parameters of obesity, fasting serum cholesterol, triglycerides, glucose and insulin concentrations, and 2-hour post-Glucola glucose and insulin concentrations. No significant sex differences were observed with regard to mean fasting concentrations of glucose, insulin, cholesterol, or triglyceride. Post-Glucola insulin concentrations were higher in women, particularly in the older age groups. Positive correlations were observed between mean log fasting insulin concentration and all parameters of obesity except log triceps skinfold thickness in men. In addition, a positive correlation was present between mean log fasting insulin and fasting triglycerides. There was a positive correlation between fasting triglycerides and ponderal index and estimated percent body fat. Fasting triglycerides correlated with percent ideal weight in women but not in men and with log subscapular skinfold thickness in men but not in women. There was no correlation with either log triceps skinfold thickness or with combined triceps and subscapular skinfold thickness in either men or women. No positive correlations were observed with regard to serum cholesterol. The measurement of glucose and insulin concentrations 2 hours post-Glucola or the calculation of insulin-to-glucose ratios did not provide additional correlations to those observed from the fasting data alone and in some instances correlations which existed in the fasting state were largely obscured following carbohydrate administration.

Glucose metabolism and the response to insulin by human adipose tissue in spontaneous and experimental obesity. Effects of dietary composition and adipose cell size

[1-(14)C]glucose oxidation to CO(2) and conversion into glyceride by adipose tissue from nonobese and obese subjects has been studied in vitro in the presence of varying medium glucose and insulin concentrations as functions of adipose cell size, the composition of the diet, and antecedent weight gain or loss. Increasing medium glucose concentrations enhance the incorporation of glucose carbons by human adipose tissue into CO(2) and glyceride-glycerol. Insulin further stimulates the conversion of glucose carbons into CO(2), but not into glyceride-glycerol. Incorporation of [1-(14)C]glucose into glyceride-fatty acids by these tissues could not be demonstrated under any of the conditions tested. Both adipose cell size and dietary composition influence the in vitro metabolism of glucose in, and the response to insulin by, human adipose tissue. During periods of ingestion of weight-maintenance isocaloric diets of similar carbohydrate, fat, and protein composition, increasing adipose cell size is associated with (a) unchanging rates of glucose oxidation and increasing rates of glucose carbon incorporation into glyceride-glycerol in the absence of insulin, but (b) decreasing stimulation of glucose oxidation by insulin. On the other hand, when cell size is kept constant, increasing dietary carbohydrate intake is associated with an increased basal rate of glucose metabolism and response to insulin by both small and large adipose cells. Thus, the rate of glucose oxidation and the magnitude of the insulin response of large adipose cells from individuals ingesting a high carbohydrate diet may be similar to or greater than that in smaller cells from individuals ingesting an isocaloric lower carbohydrate diet.The alterations in basal glucose metabolism and insulin response observed in adipose tissue from patients with spontaneous obesity are reproduced by weight gain induced experimentally in nonobese volunteers; these metabolic changes are reversible with weight loss. The relationships among adipose cell size, dietary composition, and the metabolism of adipose tissue are similar in spontaneous and in experimental obesity.

Experimental obesity in man: cellular character of the adipose tissue

Studies of adipose tissue cellularity were carried out in a group of nonobese adult male volunteers who gained 15-25% of their body weight as the result of prolonged high caloric intake. Adipose cell size (lipid content per cell) was determined in tissue obtained from three subcutaneous sites (gluteal, anterior abdominal wall, and triceps) and total adipose cell number estimated from measurement of total body fat. Five experimental subjects gained an average of 16.2 kg of body weight, of which 10.4 kg was determined to be fat. Expansion of the adipose mass was accompanied by a significant and relatively uniform increase in fat cell size in each subcutaneous site tested. Total adipose cell number did not change as a result of weight gain and expansion of the adipose depot in adult life. Subsequent loss of weight and restoration of original body fat was associated with a reduction in adipose cell size at each subcutaneous site, but no change in total number. In two control subjects who neither gained nor lost weight there were no changes in total adipose cell number or cell size. These observations suggest that expansion and retraction of the adipose depot in adult life is accompanied by changes in adipose cell size only. Significant differences in both the size and total number of adipose cells were observed between subjects in both the experimental and control groups. In addition, within individuals of both groups there were significant differences in cell size when adipose cells from the three subcutaneous sites were compared. These findings indicate that wide variations in adipose cell size and number exist in nonobese individuals having similar adipose depot sizes.