Whole-body Counting Of 40K Research Articles

Body fat and adipose tissue cellularity in infants: A longitudinal study

Body fat, fat cell size, and fat cell number were determined in a longitudinal study on 16 normal-weight infants during the age period 1–18 mo. The methods used included whole-body counting of 40K for determination of body fat and adipose tissue biopsies. A new method of calculation of body fat in infants is presented. No sex differences were found. Body fat expressed as per cent of body weight increased from 16.2% to 28.1%. From 1 to 12 mo of age the expansion of body fat was explained by an increase in fat cell size, while in the age period 12–18 mo it was mainly due to an increase in fat cell number. At 18 mo the fat cell size was the same as in 8-yr-old girls and 22-yr-old women (normal-weight females previously studied). The fat cell number at 18 mo, however, was far below the number at 8 yr of age, as well as the still higher number of the 22-yr-old women.

Comparative skeletal mass and radial bone mineral content in black and white women

The age-related changes in both skeletal mass and muscle mass were directly measured in normal black women ages 30–80 yr. The levels of total-body calcium (TBCa) were determined with the use of in vivo neutron activation. The muscle mass was measured by whole-body counting of 40K. In the same population, the bone mineral content of the radius was measured using a photon absorptiometric technique. Although there was no significant difference in stature, black women had a greater skeletal mass and bone mineral content of the radius than age-matched white female subjects. When the TBCa values were normalized for body size (i.e., corrected for height and lean body mass), the TBCa was still higher for the black women but not as high as the absolute TBCa values. Clearly, it is the larger muscle mass (as reflected by the 40K measure) in relation to weight and height that accounts for this difference. The lower prevalence of fracture and osteoporosis observed in black women relative to white women is due in part to this greater quantity of skeleton. American black women with a higher bone density (i.e., skeletal mass) maintain mechanical integrity of the skeleton longer than individuals with a lower bone density. It is suggested that the larger muscle mass in black women is, in part, a determinant of their increased skeletal mass and is partly responsible for their apparent resistance to osteoporosis and fracture of the skeleton.

Body composition in Cushing's disease.

Lean body mass and body fat mass were estimated in 12 patients with Cushing's disease before treatment, in 5 of these after correction of the adrenal hyperfunction, and in 23 patients with simple obesity. The methods used, whole-body counting of 40K and tritiated water dilution, may in Cushing's disease over- and underestimate, respectively, the body fat mass and may therefore be considered to give upper and lower limits of that entity. By a comparison with the results in simple obesity, we conclude that the total body fat mass generally is increased in patients with Cushing's disease.

Estimation of body fat in rats by whole-body counting.

A method for determining body fat in vivo in rats by whole-body counting of 40K is described. The technique utilizes a Nuclear Chicago Corporation TOBOR system with 5-in thallium-activated sodium iodide crystals. To test the method a regression equation was developed using the 40K counts and body weight of young adult rats weighing 333-788 g; the results were compared with those obtained from the gravimetric determination of fat in the carcass. The correlation coefficient between the two methods was 0.945.

Whole Body 40K Loss as a Predictor of Heat Tolerance in Cattle

Eleven nonlactating Holstein cows were exposed for 3 days at 18.3C and 50% relative humidity followed by 3 days at 32.2C and 50% relative humidity in the climatic laboratory. Feed and water were provided ad libitum. Liquid scintillation whole body counting of 40K was performed at the end of each climatic exposure. Heat caused an increase in rectal temperature (P<0.01) and decreases in whole body 40K (P<0.01), nitrogen retention (P<0.01), and body weight (P<0.05). Predicted heat tolerance was measured by subtracting the percentage decrease in body potassium, due to heat exposure, from 100. The coefficient ranged from 75 to 102 among the cows studied. It was possible to arrange the animals arbitrarily into 6 classes of predicted heat tolerance in the ascending order of: 70 to 75, 76 to 80, 81 to 85, 86 to 90, 91 to 95, and 96 to 100. The 40K of the rumen contents decreased insignificantly with heat exposure and such a decrease was too low compared to the whole body 40K loss; thus, it did not interfere with accuracy of the test. There was no significant correlation (P>0.05) between the final rise in rectal temperature and the percentage decrease in 40K or in body weight caused by heat exposure. The percentage decreases in body weight and in 40K due to heat also were not correlated (P>0.05).

Turnover rate of plasma FFA and rate of esterification of plasma FFA to plasma triglycerides in obese humans before and after weight reduction

With a constant microinfusion technique for administration of palmitate-1- 14C, a FFA flux rate of 286–654μEq./min. (average 533) was found in 5 control subjects as against a flux rate of 663–959 μEq./min. (average 837) in 5 untreated obese patients. When expressed per kilogram lean body mass (LBM) (obtained by whole body counting of 40K) the FFA flux rate was considerably higher in the obese people (16.98–24.78 μEq./min. Kg. LBM, average 20.49) than in the controls (9.17–14.31, average 11.55). Treatment by intermittent starvation did not directly affect this high rate of lipolysis. 1.5 months after having reached a normal body weight, one patient, treated by calorie-restriction only, exhibited normalization of the previously high FFA turnover rate. A comparative study of the mentioned parameters was made in 2 patients with a pheochromocytoma (with a high lipolysis rate, corrected after operation) and 1 patient suffering from anorexia nervosa (with a depleted body fat mass). It is considered probable that in the pathogenesis of human “exogenous” obesity, impairment of lipolysis is not primarily involved. The plasma triglyceride influx rate in the obese patients was high as compared to that in the controls, when expressed as μmole/min./L.plasma. This high rate of esterification, too, showed no diminishment shortly after starvation treatment.