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Biomedical subjects

U Smith

Publications and source records attributed to U Smith.

At least 235 records · Page 13Linked to original sources
PubMed1975

Regional adipose tissue cellularity in relation to metabolism in young and middle-aged women.

Body composition and total number of fat cells were investigated in 31 randomly selected women 52 yr of age and in 13 young women (mean age 22 yr) whose body weights were within plus or minus 10% of the ideal weight. Two of the 52-year-old women were obviously obese and excluded. Regional determinations of adipose tissue thickness, fat cell size, and number were also determined. Middle-aged women had more body fat (BF) but a lower body cell mass (BCM) than the younger group. The increased BF in the middle-aged women was exclusively explained by larger fat cells, since the younger women had a significantly higher total number of fat cells. This increase was also found when differences in height, body weight, and body fat were matched out. Local fat cell number was also increased in the younger group. Local fat cell size was increased in all regions investigated in the middle-aged women, but the increase was particularly pronounced in the abdominal region. The highest degrees of correlation between fat cell sizes of different regions were found between the epigastric and hypogastric regions and between femoral and gluteal regions. Furthermore, the plasma insulin levels correlated with the fat cell sizes of the abdominal region but not with those of the femoral or gluteal regions. In conclusion, the data might indicate that the fat cells of the abdominal region are more sensitive to nutritional and/or hormonal factors than those of other regions. This may in turn indicate the existence of different fat cell populations.

Abdomen↗
PubMed1975

Adipocyte metabolism in endogenous hypertriglyceridemia.

In order to define specific metabolic abnormalities of adipose tissue metabolism in endogenous hypertriglyceridemia (EH) patients with this condition were compared with normolipidemic controls matched for body fat and fat cell size. In vitro the enlarged fat cells of EH were found to have an increased basal and noradrenaline-stimulated lipolysis in comparison with cells of the same size from normolipidemic controls. The insulin inhibition of noradrenaline-stimulated lipolysis was blunted. Lipoprotein lipase activity in these cells was clearly depressed. Basal triglyceride synthesis from labeled glucose was low in relation to plasma insulin. The reduction of insulin tolerance in vivo suggested that the depression of plasma glycerol and free fatty acid concentration was small in EH, suggesting that the more detailed findings in vitro were of relevance for in vivo conditions. It was suggested that the hyperinsulinemia and decreased glucose tolerance of EH may well be responsible for some of the aberrations of adipocyte metabolism in EH. The decreased responsiveness of lipolysis to insulin and the low lipoprotein lipase activity are, however, findings not typical for enlarged fat cells exposed chronically to insulin and might be characteristic for the fat cells of EH. It seems of importance to further define the factor(s) responsible for these metabolic aberrations, because the abnormalities of the acipocyte metabolism in EH may well offer a possible explanation to the pathogenesis of that condition.

Adipose Tissue↗
PubMed1975

Effects of age and cell size on rat adipose tissue metabolism.

In order to analyze separately the effects of cell size and age on the metabolism of rat adipose tissue, fat cells of different sizes were obtained from the same animals. The rats were 4 or 15 wk old. The results show that age as well as cell size influences the metabolic rates. At a given cell size, the basal lipolysis, the lipolytic effects of glucagon and noradrenaline, the rate of glucose incorporation into the triglycerides, and the effect of insulin on glucose metabolism were considerably increased in the young animals. Furthermore, irrespective of fat cell size the lipolytic action of glucagon was reduced in old animals. The data thus show that experiments with large fat cells from old rats and with small cells from young animals cannot be directly compared because both variables may influence metabolic reactions.

Adipose Tissue↗
PubMed1974

Studies of human adipose tissue in culture. 3. Influence of insulin and medium glucose concentration on cellular metabolism.

Explants of human adipose tissue were maintained in culture for 1 wk in different glucose concentrations with or without the addition of insulin. After this period of time the explants were carefully washed and then subjected to short-term incubations in the same glucose concentration and in the absence of insulin. With this experimental design the influence of long-term exposure to insulin and different glucose concentrations on adipose tissue metabolism could be studied. The results of these studies show that an increase in the glucose concentration of the culture medium enhanced the basal as well as the catecholamine-stimulated lipolysis in the short-term incubations. The presence of insulin in the culture medium enhanced the lipolytic process as well. Analogous results were obtained with the cellular rate of glucose conversion to triglycerides in the short-term incubations. The stimulating effects of insulin and glucose were most pronounced in the larger adipose cells possibly due to their enlarged surface areas. The data suggest that the metabolism of adipose tissue as revealed by short-term studies may be profoundly influenced by the antecedent biochemical environment.

Adipose Tissue↗
PubMed1973

Exocytosis in the adrenal medulla demonstrated by freeze-etching.

Replicas of fractured chromaffin cells are indicative of a range of activities thought to characterize exocytosis, including attachment of secretory vesicles to the plasma membrane, fusion, extrusion of contents, and membrane retrieval. Exocytosis sites are abundant on stimulated cells but are infrequent when calcium is omitted from the system.

Adrenal Medulla↗
PubMed1973

Freeze-etch studies of the plasma membrane of pulmonary endothelial cells.

Pulmonary endothelial cells are capable of metabolizing a variety of circulating hormonal substances. Indirect evidence indicates that some of the relevant enzymes are located on the plasma membrane. The associated caveolae are of special interest as globular subunits, possibly enzyme clusters, are evident in their membranes. In the present study, freeze-etch techniques were used to improve understanding of the fine structure of endothelial cells and to extend our investigations of possible sites of enzymes capable of metabolizing circulating vasoactive agents. As in other cells studied by freeze-etching, intramembranous particles are found on both inner aspects of the plasma membrane. In undifferentiated areas of plasma membrane, the particles appear to have a random distribution. These areas fracture such that approximately equal proportions of the particles adhere to the cytoplasmic aspect of the outer leaflet and the extracellular aspect of the inner leaflet. However, the particles organize into rosettes and plaques at the base of caveolae, and, after fracture, the rosettes and plaques adhere predominantly to the cytoplasmic aspect of the outer leaflet. The peculiar organization of particles in association with caveolae supports the concept that caveolae have a stomal skeletal structure and raises the possibility that the organization may be in some way related to pinocytosis.

Animals↗