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Biomedical subjects

S B Roberts

Publications and source records attributed to S B Roberts.

141 records · Page 8Linked to original sources
PubMed1980

Effect of rat age on blood levels of somatomedin-like growth factors.

Age-related changes in serum levels of somatomedin-like growth factors were measured using a bioassay based on myoblast proliferation in culture. The correspondence of this assay to thymidine incorporation and sulfation factor assays for somatomedins was demonstrated. Comparisons involved individual serum samples from a total of 28 rats at each of three age ranges (young = 2 to 6 month, middle-aged = 12 to 16 month, and old = 24 to 28 month) in five separate experiments. A small (10%) decrease in levels of somatomedin-like activity was observed between young and middle-aged animals, with a greater (20 to 40%) subsequent decrease in old rats. Assays of mixed samples indicated that the age-related decreases in somatomedin-like activity could not be attributed to increases in circulating levels of a dissociable inhibitor of this activity. Paired comparisons of amino acid uptake by isolated omohyoideus muscles from rats of the specified ages suggested that there were no significant age-related changes in response of these muscles to a somatomedin analog.

Aging↗
PubMed1979

A serum-free medium for the growth of muscle cells in culture.

Rates of cell proliferation essentially equal to those in 10% serum were obtained when Yaffe's L6 myoblasts were incubated in Ham's F-12 medium containing 10(-5) M fetuin, 10(-6) M insulin, and 10(-7) M dexamethasone; we have designated this mixture muscle medium-1 (MM-1). Addition of other growth factors and hormones in various combinations did not increase the proliferation of myoblasts above the rate in MM-1, and neither fetuin nor insulin could be replaced by other growth factors. All glucocorticoids tested (but no other steroid hormones) were active. Fetuins prepared by the rather different procedures of Pedersen, Deutsch, and Spiro were all active, and the active material was heat labile and nondialyzable; this is the first cell culture system in which highly purified Spiro fetuin has been found active. Primary rat myoblasts proliferated more rapidly that fibroblasts in parallel cultures when incubated in MM-1. This simple medium, composed of relatively inexpensive and readily available components, should be useful for the study of muscle cell growth and differentiation.

Adrenal Cortex Hormones↗
PubMed1976

Experimental stabilization of segmental defects in the human femur. A torsional study.

One of each of thirty-five pairs of fresh intact femora were tested to failure in torsion, recording the dynamic torque, the absorbed energy, and the angle of rotation. These results were compared with the results obtained with the contralateral femur, reconstituted after removal of a segment. Intramedullary nails with polymethylmethacrylate cement, strips of titanium mesh with cement, bone plates with and without cement, and multiple Steinmann pins with cement were the reconstituting configurations. Bone plates were the strongest configuration; the failure torques in all cases were limited by the stress concentration effects of the holes in the bone used for screw fixation. The use of cement as an adjunct to single-plate fixation provided some additional strength. The torsional strength of femora fixed with Küntscher and Schneider nails was limited by failure of the cement and bone. The use of titanium mesh with polymethylmethacrylate was less effective, because this composite has a low torsional rigidity. The use of multiple Steinmann pins packed with polymethylmethacrylate in the medullary cavity should be discouraged because severe twisting and fragmentation of the surrounding acrylic will occur at low levels of torque.

Bone Cements↗
PubMed1976

Studies of the metabolism of 5,5-diphenylhydantoin relating principally to the stereoselectivity of the hydroxylation reactions in man and the dog.

The hydroxylated metabolites of 5,5-diphenylhydantoin (DPH) in dog and human urine, after release by beta-glucuronidase, have been isolated and purified by procedures entailing only solvent partitioning without crystallization or any other procedure that could change the proportions of optical isomers. Dogs produced both the meta- and para-5-hydroxyphenyl-5-phenylhydantoins (m-HPPH and p-HPPH) from DPH, the former in approximately 6 times the amount of the latter. The m-HPPH from dog urine was dextrorotatory and had the properties of a pure optical isomer. The p-HPPH from dog urine was a mixture of optical isomers with approximately a 2:1 preponderance of the levorotatory isomer. When dog urine was heated with acid rather than treated with beta-glucuronidase, the isolated p-HPPH contained a small preponderance of the dextrorotatory isomer, probably owing to production of d-p-HPPH from the dihydrodiol metabolite. No o-HPPH was found in dog urine. When racemic p-HPPH and m-HPPH were administered to dogs, there was little if any preponderance of either optical isomer in the materials isolated from urine. Enzymatically released p-HPPH isolated from urine of human patients receiving DPH was a mixture of optical isomers with approximarely a 10:1 preponderance of the levorotatory isomer. Crystallization of this material readily yields pure l-p-HPPH. Human urine contained only very small amounts of m-HPPH, which was detectable by gas chromatography but insufficient in amount to permit isolation. Hypotheses are discussed that could account for the differences in the metabolism of DPH in man and dog. Small amounts of 2,2-diphenylhydantoic acid were found in urine of dogs but not of human patients receiving DPH.

Animals↗
PubMedDate not supplied

Control of food intake in older men.

OBJECTIVE: To investigate the effects of aging on mechanisms of body energy regulation and thereby determine the causes of unexplained weight loss in older persons, a factor predisposing to premature death and disability. DESIGN: Dietary intervention study. SETTING: Metabolic ward and outpatient. PARTICIPANTS: The subjects were 35 healthy younger and older men of normal body weight consuming a diet of typical composition and performing usual activities. MAIN OUTCOME MEASURES: Subjects were either overfed by a mean (+/- SD) of 4.09 (+/- 0.26) MJ/d (n = 17) or underfed by 3.17 (+/- 0.68) MJ/d (n = 18) for 21 days. Measurements were made of changes in body weight, body composition, and energy expenditure during overfeeding or underfeeding, and of subsequent voluntary nutrient intakes and changes in body weight. RESULTS: There was no significant effect of aging on changes in body composition, body weight, or energy expenditure with overfeeding or underfeeding. However, following overfeeding, younger men exhibited spontaneous hypophagia, whereas the older men did not (mean [+/- SD] changes in energy intake relative to control values were -2.11 [+/- 2.18] and 1.55 [+/- 2.11] MJ/d, respectively; P = .006). As a result, the younger men lost the excess body weight gained during overfeeding but the older men did not. Similarly, following underfeeding, the younger men exhibited hyperphagia while the older men did not (mean [+/- SD] changes in energy intake relative to control values were 1.88 [+/- 2.31] and -0.52 [+/- 1.54] MJ/d, respectively; P = .02), and as a result the older men failed to regain the weight lost during underfeeding. CONCLUSIONS: These results in 35 men suggest that aging may be associated with a significant impairment in the ability to control food intake following overeating or undereating. Since overeating and undereating occur routinely as part of the normal pattern of energy regulation, the findings reported herein may help to explain the vulnerability of older persons to unexplained weight gain and weight loss.

Adult↗
PubMedDate not supplied

Nonsurgical factors that influence the outcome of bariatric surgery: a review.

OBJECTIVE: Severe obesity (ie, at least 100% overweight or body mass index > or =40 kg/m2) is associated with significant morbidity and increased mortality. It is apparently becoming more common in this country. Conventional weight-loss treatments are usually ineffective for severe obesity and bariatric surgery is recommended as a treatment option. However, longitudinal data on the long-term outcome of bariatric surgery are sparse. Available data indicate that the outcome of bariatric surgery, although usually favorable in the short term, is variable and weight regain sometimes occurs at 2 years after surgery. The objective of this study is to present a review of the outcome of bariatric surgery in three areas: weight loss and improvement in health status, changes in eating behavior, and psychosocial adjustment. The study will also review how eating behavior, energy metabolism, and psychosocial functioning may affect the outcome of bariatric surgery. Suggestions for additional research in these areas are made. METHOD: Literature review. RESULTS: On average, most patients lose 60% of excess weight after gastric bypass and 40% after vertical banded gastroplasty. In about 30% of patients, weight regain occurs at 18 months to 2 years after surgery. Binge eating behavior, which is common among the morbidly obese, may recur after surgery and is associated with weight regain. Energy metabolism may affect the outcome of bariatric surgery, but it has not been systematically studied in this population. Presurgery psychosocial functioning does not seem to affect the outcome of surgery, and psychosocial outcome is generally encouraging over the short term, but there are reports of poor adjustment after weight loss, including alcohol abuse and suicide. CONCLUSIONS: Factors leading to poor outcome of bariatric surgery, such as binge eating and lowered energy metabolism, should be studied to improve patient selection and outcome. Long-term outcome data on psychosocial functioning are lacking. Longitudinal studies to examine the long-term outcome of bariatric surgery and the prognostic indicators are needed.

Feeding Behavior↗
PubMedDate not supplied

The measurement of milk intake in the neonatal guinea pig.

Study of the effects of enteral nutrition on neonatal growth and development has been hindered by lack of a suitable model. An isotope dilution method for the measurement of milk intake in suckling rodents was evaluated in 13 hand-fed neonatal guinea pigs, by comparing milk intakes determined using 3H20 with intakes determined by difference in weight before and after feeding. The effects of two experimental durations (1 or 2-3 days) on the accuracy and precision of the method was assessed. Weighted milk intakes were 18 -26 g/day, and body weight changes were -7% - +12% of initial weight. There was no significant difference between milk intakes determined using the two methods for both 1 and 2-3 day comparisons. However, the coefficients of variation for 1 and 2-3 day measurements were 24.4% and 5.5%, respectively. These values are equivalent to precisions of approximately 10% and 2% for estimates of total milk output in a rodent suckling 8 pups. It is concluded that the 3H20 method is no less accurate or precise than the weighing method for 2-3 day measurements of milk intake in individual pups and milk production of dams. These findings strengthen the use of the precocial guinea pig as a model for the study of the effects of early feeding on growth, development and aging.

Animal Nutritional Physiological Phenomena↗
PubMedDate not supplied

Dihydropyrimidinase. Stereochemistry of the metabolism of some 5-alkylhydantoins.

The (R)- and (S)-isomers of 5-methylhydantoin (5-MH) and of 5-isopropylhydantoin (5-IPH) were synthesized, and incubations of the individual isomers with a rat liver dihydropyrimidinase preparation (100,000g supernatant fraction) were carried out. Only the (R)-isomer of 5-MH or 5-IPH was ring-opened by the enzyme. Reversibility of the enzymatic ring-opening reaction could be demonstrated with only the (R)-isomer of 2-methylhydantoic acid (2-MHA) or 2-isopropylhydantoic acid (2-IPHA). The results of the present investigation show that the replacement in 5-phenylhydantoin of the phenyl group with an alkyl group does not alter the stereospecificity of the hydantoin substrates in the ring-opening reaction. The results are used to form the concept that (R)-dihydrothymine, the optical isomer previously postulated as the natural substrate to the enzyme, may have a different type of binding at the active site of the enzyme.

Amidohydrolases↗