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Biomedical subjects

G B Forbes

Publications and source records attributed to G B Forbes.

At least 19 recordsLinked to original sources
PubMed1992

Sequence of changes in body composition induced by testosterone and reversal of changes after drug is stopped.

OBJECTIVE: --To study the changes in body composition produced by large doses of testosterone and reversal of changes when the drug is discontinued. DESIGN: --Weekly injections of testosterone enanthate were given to young adult male volunteers for 12 weeks. Repeated assays of lean body mass (LBM) by potassium 40 counting were made during this period and at intervals during the ensuing 5 to 6 months. PARTICIPANTS AND SETTING: --Subjects who were living on their own, who were known to be free of significant disease, and who volunteered as controls for a study of patients with neuromuscular disease. Assays were done in the Clinical Research Center. MAIN OUTCOME MEASURES: --Changes in body weight, LBM, and (by subtraction) body fat. RESULTS: --Testosterone treatment produced a progressive increase in LBM and a progressive decrease in body fat. Body composition reverted slowly toward normal when the injections were stopped; thus, the effects of testosterone lingered for some time. The magnitude of the observed changes in LBM was in keeping with the change in urinary creatinine excretion reported for these same subjects. CONCLUSION: --Testosterone is a powerful anabolic agent that also serves to reduce body fat content.

Adipose Tissue↗
PubMed1992

Body size and composition of perimenarchal girls.

A number of measurements are reported on a cross-sectional sample of girls who were studied at times ranging from 54 months prior to menarche to 82 months after menarche. Included are anthropometric measurements, lean weight, body fat, abdomen-hip ratio, skeletal size, bone age, muscle strength, and urinary hydroxyproline excretion. The years preceding menarche are associated with an array of physiological and anatomical changes, making it difficult to assign a causative role to any one of them.

Adipose Tissue↗
PubMed1992

Energy expenditure under free-living conditions in normal-weight and overweight women.

Total energy expenditure under free-living conditions of 12 normal-weight and 26 overweight women was determined with the 2H2(18)O method. Overweight women tended to expend more energy (mean +/- SD, 11.20 +/- 1.79 MJ/d) than normal-weight women (9.46 +/- 0.87 MJ/d, P less than 0.005). Approximately half of this effect was explained by an increase in basal metabolic rate (BMR) in the overweight group compared with the normal-weight group (6.47 +/- 0.74 vs 5.68 +/- 0.39 MJ/d, respectively, P less than 0.005) and the other half by an increase in above-basal energy expenditure (4.73 +/- 1.49 vs 3.78 +/- 0.94 MJ/d, P less than 0.05). Total energy expenditure was approximately 1.7 times the BMR in both groups. After adjusting energy expenditure for weight or lean body mass by analysis of covariance, there was no significant difference between normal-weight and overweight groups. We conclude that most overweight subjects must consume more energy than lean subjects to maintain their excess weight, although some could maintain their obesity without eating more than lean subjects.

Adult↗
PubMed1992

Exercise and lean weight: the influence of body weight.

Exercise can produce a modest gain of lean body mass (LBM) and loss of fat in weight-stable individuals, but it is important to realize that if much weight is lost during exercise there is a risk of some erosion of the LBM. Data from both human and animal experiments show that exercise cannot conserve lean weight in the face of significant energy deficit, although moderate obesity affords a modicum of protection in this respect.

Adipose Tissue↗
PubMed1991

Science, Volume 133, 1961: Estimation of total body fat from potassium-40 content.

On the assumption that the potassium content of the lean body mass is constant, it should be possible to estimate fat content in living man from a measurement of potassium-40 activity in the whole-body scintillation counter. A series of such measurements on children and young adults shows good correlations with skin-fold thickness and weight/height ratio as indices of fatness.

Adipose Tissue↗
PubMed1991

Exercise and body composition.

We assessed changes in body composition in 41 young adults who engaged in various exercise and/or training programs on ad libitum diets. Most of those who gained weight sustained an increase in lean body mass (LBM), and most of those who lost weight lost LBM as well as fat. The change in LBM was directly related to the change in weight, with a regression slope of 0.500. An analysis of published data confirms these findings and, in concert with our data, provides the additional information that the magnitude of the change in body composition in exercising individuals is influenced by body fat content, just as it is for nonexercising individuals.

Adipose Tissue↗
PubMed1990

Do obese individuals gain weight more easily than nonobese individuals?

A review of studies done on human subjects who were overfed under controlled conditions for periods ranging from 2 to 12 wk shows that the energy cost of induced weight gain is a function of initial body weight and of lean body mass, body fat, and percent body fat. Therefore, bigger and fatter people need to eat more to gain a given amount of weight than do those who are thin. A likely explanation is that obese individuals tend to put on a large proportion of fat, a high-energy tissue, whereas thin people tend to gain more lean, which is a low-energy tissue.

Adipose Tissue↗
PubMed1979

Iron absorption in the thalassemia syndromes and its inhibition by tea.

To determine the hemoglobin concentration at which iron absorption is minimal, five subjects with thalassemia major and one with thalassemia intermedia underwent a series of iron-absorption studies. The effect of tea as an inhibitor of non-heme iron absorption was also tested. Iron absorption increased as the hemoglobin concentration decreased, although iron absorption was much higher at any given hemoglobin level in the subject with thalassemia intermedia. In the subjects with thalassemia major, iron absorption averaged 10 per cent at hemoglobin concentrations between 9 and 10 and 2.7 per cent between 11 and 13 g per deciliter. The percentage of iron absorbed could be accurately predicted from the nucleated red-cell count (r = 0.91, P less than 0.001). Tea produced a 41 to 95 per cent inhibition of iron absorption. Since patients with thalassemia intermedia may absorb a large percentage of dietary iron, inhibitors of iron absorption, such as tea, may be useful in their management.

Adolescent↗
PubMed1979

Steroid hormone toxicity in human fibroblasts does not correlate with high affinity receptor content.

Human diploid skin fibroblasts derived from normal individuals and those with the testicular feminization syndrome (TFM) have been shown to be killed to the same degree by dihydrotestosterone in spite of the absence of high affinity cellular androgen receptors in the TFM fibroblasts. Furthermore, several different normal fibroblast strains from various anatomical sites all showed similar amounts of androgen-induced cytotoxicity even though their respective receptor contents differed by as much as ten-fold. These results suggest that steroid-induced cytotoxicity in human fibroblasts is not correlated with receptor content, unlike murine lymphoid cells in which the receptor content has been shown to be closely related to their ability to survive hormone exposure.

Androgen-Insensitivity Syndrome↗
PubMed1979

Loss of body nitrogen on fasting.

An analysis of the change in total body nitrogen during fasting shows that it declines exponentially, a small fraction being lost rapidly (t 1/2 of a few days), and the remainder being lost slowly (t 1/2 of many months). The obese faster loses N, and weight, at a slower relative rate than the nonobese; and the ratio of N loss to weight loss during an extended fast is inversely related to body fat content, being about 20 g/kg in the nonobese and about 10 g/kg in those with body fat burdens of 50 kg or more. The loss of body N on a low protein-calorie adequate diet can also be described in exponential terms, and this function allows an estimate to be made of the N requirement.

Adult↗
PubMed1979

Liver damage due to perhexiline maleate.

Two middle-aged men, who had received perhexiline in recommended dosage, showed clinical and histological evidence of severe hepatic damage, and one of them died. Histological study of the livers showed a striking resemblance to alcoholic hepatitis.

Chemical and Drug Induced Liver Injury↗
PubMed1978

Bone mineral turnover in a patient with osteogenesis imperfecta estimated by fluoride excretion.

A child with severe osteogenesis imperfecta was treated with NaF for 8 years, at the end of which time his iliac bone contained 29 mg F/g Ca. Urine F was assayed at intervals for 4.5 years after discontinuing treatment. After the first few days the decline in urinary F excretion can be described by a two component exponential function, with half-times of 5.4 months (10%) and 8.9 years (90%). The latter half-time value is of the same order of magnitude as those observed for F and other "bone-seeking" elements in normal subjects, which suggests that the turnover rate of bone mineral is normal in this disease. Three methods for estimating the attained body F burden at the end of NaF treatment--namely, metabolic balance, bone biopsy, and integration of the exponential function--yielded comparable values.

Bone and Bones↗
PubMed1978

Enhanced dexamethasone resistance in cystic fibrosis cells: potential use for heterozygote detection and prenatal diagnosis.

Cultured skin fibroblasts from patients with cystic fibrosis (CF) are more resistant to dexamethasone toxicity than are normal cells. We now report that, when fibroblasts cultured from obligate CF heterozygotes are exposed to dexamethasone, they have an intermediate survival compared to normal and homozygous CF cells. When dexamethasone survival was tested on cells from four patients undergoing amniocentesis, cells from a woman at risk of producing a child with CF showed significant dexamethasone resistance, similar to that of fibroblasts derived from lnown CF homozygotes; the other amniotic cell specimens showed dexamethasone sensitivity similar to that of normal skin fibroblasts. These data suggest that the dexamethasone resistance previously observed in skin fibroblasts may also be useful in the prenatal diagnosis of CF.

Amniotic Fluid↗