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Biomedical subjects

P Webb

Publications and source records attributed to P Webb.

At least 127 records · Page 7Linked to original sources
PubMed1984

Five-day comparison of the doubly labeled water method with respiratory gas exchange.

Previous studies have indicated that the doubly labeled water method can be used to measure energy expenditure in free-living humans. In this study, we compare the doubly labeled water method with nearly continuous respiratory gas exchange in five healthy adults. Total body water and isotope elimination rates were determined by mass spectrometric analysis of urinary water after the administration of 2H2 18O. Respiratory gas exchange was measured 22 to 23 h/day for 5 consecutive days. Energy expenditures from the doubly labeled water method averaged 6% more than those from respiratory gas exchange with an 8% coefficient of variation.

Adolescent↗
PubMed1984

Ontogeny of cardiac ornithine decarboxylase and its beta adrenergic responsiveness in the rat.

Ornithine decarboxylase (ODC) is a marker of tissue growth and development and, because sympathetic stimulation of beta adrenergic receptors acutely increases ODC in the adult rat heart, measurement of this enzyme can be used to indicate the functional intactness of the beta adrenergic receptor system in the heart. Changes in the postnatal ontogenetic pattern of this enzymatic activity may also indicate abnormal development and ODC appears to be particularly useful in evaluating the effects of prenatal insult on cardiac development. The present study examines the pattern of basal ODC activity and its developing sensitivity to beta adrenergic stimulation during the perinatal period in order to establish a data base for studies on the effect of various environmental agents on the developing cardiovascular system. ODC activity was measured in rat hearts on gestation day (GD) 20 through postnatal day (PND) 28 under saturating conditions of L-ornithine and pyridoxal 5-phosphate. Basal ODC activity fell from 3 nmol of CO2/hr/mg of protein at GD 20 to less than 0.5 nmol of CO2/hr/mg of protein at PND 18, rising again to nearly 1 nmol of CO2/hr/mg of protein at PND 22. The beta adrenergic agonist isoproterenol (10 mg/kg s.c.) resulted in peak ODC stimulation at 4 hr postinjection on PNDs 6, 14 and 21; however, no response was seen at PND 1 at this dose or at GD 20 (300 micrograms/kg s.c.). In dose-response studies, isoproterenol produced a maximal response at 10 mg/kg s.c., resulting in increases from control of 67, 230 and 1700% at PNDs 6, 14 and 21, respectively, indicating that the sensitivity of the heart to beta adrenergic stimulation increases with age, during the perinatal period.

Animals↗
PubMed1984

Body size, subcutaneous fatness and total body fat in older adults.

In a sample of healthy adults (24 men, 21 women; 54 to 85 years of age) anthropometry was collected and body density measured by underwater weighing. Estimates of body fat were computed from body density. The men were significantly larger than the women in body size and have significantly less percent body fat and less subcutaneous fat on their arms and legs. There were no sex differences in measures of subcutaneous fat on the trunk or in estimates of total body fat. Chest and abdominal circumferences were the measurements most highly correlated with total and percent body fat in the men. In the women, abdominal circumference and subscapular skinfolds were highly correlated with percent body fat, as were subscapular and midaxillary skinfold with total body fat.

Adipose Tissue↗
PubMed1983

Calorimetry with heat flux transducers: comparison with a suit calorimeter.

Regional and total body heat loss rates of human subjects at rest were measured simultaneously by means of an array of heat flux transducers and with a tube suit calorimeter. Conditions ranged from thermal comfort to strong cooling. A high degree of correlation was found between heat loss rates determined by the two independent techniques. For the head and arms, the transducer array system measured less heat loss than the suit. For the torso and legs, measurements by the two methods were equivalent. For the whole body, the transducer system yielded a heat loss rate 87% of the suit calorimeter value.

Adult↗
PubMed1983

Hooked on radio.

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Adolescent↗
PubMed1983

Evaluation of a Reverse Gradient Garment for prevention of bed-rest deconditioning.

A Reverse Gradient Garment (RGG) was used to intermittently induce venous pooling in the extremities of a magnitude similar to that seen in going from a lying to standing position during the course of a 15-d period of horizontal bed rest. Venous pooling failed to improve bed-rest-induced losses in +2.5 Gz and +3.0 Gz centrifugation tolerance or to prevent increased heart-rate responses to lower-body negative pressure (LBNP). Four subjects served as controls, four were treated. Tests during the 7-d recovery period showed fluid/electrolyte and body composition values to have returned to pre-bed-rest levels with continued depression of acceleration tolerance times (56% decreased at +2.5 Gz and 74% decreased at +3.0 Gz compared to pre-bed-rest levels) and exaggerated blood insulin response on glucose tolerance testing (blood insulin for treated group increased 95% at 1 h before bed rest and 465% during recovery). This study demonstrates that the physiologic changes after bed rest persist for significant periods of time. Acceleration tolerance time proved to be a sensitive test for the deconditioning process.

Acceleration↗
PubMed1983

Adaptation to overeating in lean and overweight men and women.

In groups of four, men and women in their 40s and 50s, some of them lean and some overweight, overate for 30 d by 1000 kcal/d (4186 kJ/d) more than they needed to maintain weight. On an average dietary mixture for Americans they gained a mean of 2.68 kg, and on a diet high in carbohydrate (60 per cent of energy) they gained 2.73 kg. However, on a diet high in protein and fat (70 per cent of energy), they gained significantly less, 1.75 kg. On all three diets the subjects should have gained 5 kg, if adipose tissue has an energy density of 6 kcal/g, and had there been no adaptation. There was adaptation, as evidenced by an average 7 per cent increase in thermogenesis, which was measured by 24-h direct and indirect calorimetry. Energy balances were calculated from: bomb calorimeter values for food and body waste; change in fuel stores from body composition measured by densitometry; and daily expenditure estimated from the net food intake needed to maintain body weight during a 30-d control period. During overeating, energy intake matched energy losses (including fuel storage) for the average diet and the high-carbohydrate diet, but on the diet high in protein and fat energy intake exceeded losses by more than 500 kcal/d (2093 kJ/d). Thus smaller than expected weight gains from overeating (luxuskonsumption) were largely explained by increased thermogenesis, except when the diet was high in protein and fat. Lean and overweight subjects did not differ in weight gain, loss of energy in urine and faeces, or thermogenesis from overeating.

Adaptation, Physiological↗
PubMed1983

Loss of fat stores and reduction in sedentary energy expenditure from undereating.

Undereating for 6 weeks by 1000 kcal/d (4186 kJ/d) was studied in four women and five men following a 3-week control period when food intake was adjusted to expenditure. Sedentary energy expenditure was measured by direct and indirect calorimetry, food and waste by bomb calorimetry, and loss of body stores was calculated from body density and total body water. All nine subjects lost weight fairly steadily for the 6 weeks, reducing fat stores by 4.4 kg and body water by 1.0 kg on average. Sedentary energy expenditure declined by 12 per cent; energy losses in body waste decreased a little. Energy balance calculations from the quantities measured accounted for all but 362 kcal/d (1515 kJ/d) during undereating; the imbalance was thought to be the result of a smaller reduction in the expenditures of free activity, which was not measured, than in the measured reduction of sedentary expenditure.

Adipose Tissue↗
PubMed1982

Induced venous pooling and cardiorespiratory responses to exercise after bed rest.

The purpose of this study was to deliberately induce venous pooling the lower extremities of bed-rested subjects to determine whether such distention may reverse the reduction in maximal O2 uptake that has regularly been observed. Bed-rest deconditioning was assessed in eight healthy male subjects by measuring submaximal and maximal O2 uptake (VO2 max), ventilation, and heart rate (HRmax) before and after 15 days of bed rest. During bed rest four subjects in the experimental group received daily treatments of venous pooling for 210 min/day with a reverse gradient garment (RGG), whereas the four subjects in the control group received no treatment. Compared with prebed-rest values, VO2max was reduced by 14.0 (P less than 0.05), HRmax was increased by 4.2 (P less than 0.05), and endurance time for the exercise test was decreased by 9.2% (P less than 0.05) in the control group. In the RGG group, VO2max, HRmax, and endurance time were essentially unchanged after bed rest. The plasma volume (PV) of the control group decreased by 16.7 (P less than 0.05) after bed rest compared with a 10.3% (not significant) reduction in the RGG group. The percent delta PV was related to the percent delta VO2 max (r = 0.75, P less than 0.05) and percent delta HR max (r = 0.65, P less than 0.05). The data support the hypothesis that the lack of venous pooling and associated fluid shifts contribute the decrement in VO2 max associated with bed-rest deconditioning.

Adult↗
PubMed1982

Intake of phosphatase-active plasma membrane into the cytoplasm of oocytes from sexually immature hamsters.

When thiamine pyrophosphate is used as substrate, heavily stained complexly branching cytoplasmic structures are seen in developing oocytes of the hamster between 8 and 12 days after birth. This coincides with the onset of the dictyate stage of first meiotic prophase. The structures appear to arise from the oocyte plasma membrane in two ways: (1) by proliferation and infolding of the membrane, and (2) by membrane being pushed into the cytoplasm by invaginating follicle cell processes. This appears to be followed by proliferation of the invaginated plasma membrane within the oocyte cytoplasm. Incubations with ATP or beta-glycerophosphate, with and without the inhibitor L-p-bromotetramisole, indicate that the staining is not due to the action of either ATPase or alkaline phosphatases. The origin and possible developmental significance of the reactive structures are discussed.

Adenosine Triphosphatases↗
PubMed1982

Changes in adipocyte cellularity in children ten to 18 years of age.

Adipocyte size and number, and total body fat were collected serially from boys and girls living in South-western Ohio. Sex-specific annual increments were computed across age for each of these variables. During adolescence, the boys had a near zero mean increment in total body fat, but the girls had a positive mean increment in total body fat. In both the boys and girls, there were negative mean increments in adipocyte size and positive mean increments in adipocyte number. Sex-specific age-to-age correlations are statistically significant for adipocyte number and total body fat but not for adipocyte size. These data indicate that increases in total body fat during adolescence may be due to increases in adipocyte number and that annual increments in adipocyte size may provide little information in regard to changes in total body fat.

Adipose Tissue↗
PubMed1981

Cytochemistry of the Golgi apparatus in developing ovarian germ cells of the Syrian hamster.

A cytochemical study of the Golgi apparatus in the developing oocyte of the golden hamster was carried out using the TPPase, AcPase and zinc iodide-osmium tetroxide (ZnOs) techniques. Tissue from both immature and sexually mature animals was investigated. Peak TPPase activity was found in pre-growth oocytes in ovaries from sexually mature adults. Some activity was also present in SER in the peripheral cytoplasm of growing oocytes. AcPase activity was found only after the onset of oocyte growth. It was present in Golgi cisternae and associated vesicles and in some profiles of peripheral SER. No structures corresponding to GERL were identified. Strong staining with ZnOs was seen, at all stages studied, in certain Golgi vesicles and short tubules but not in the cisternae unless the oocyte was atretic. Weaker ZnOs staining was characteristic of ER throughout the oocyte. With all techniques there was a falling off of reactivity as oocyte size increased. Within a single oocyte some Golgi bodies were negative while others were positive, with both TPPase and AcPase techniques. This suggests that two or more functional types of this organelle are present within the developing oocytes.

Acid Phosphatase↗