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Biomedical subjects

U Smith

Publications and source records attributed to U Smith.

At least 253 records · Page 14Linked to original sources
PubMed1972

Angiotensin I: metabolism by plasma membrane of lung.

(8-L-[(14)C] phenylalanine) angiotensin I is metabolized in one passage through blood-free lungs. Approximately 20 percent of the radioactivity emerges as angiotensin 11, the remainder as lower homologs. Radioactivity is not retained by the lungs but has the same volume of distribution and mean transit time as blue dextran, a compound unlikely to leave the intravascular space. Plasma membrane fractions of lung are capable of converting angiotensin I to angiotensin II. These data, taken together, indicate the circulating angiotensin I is metabolized by enzymes of the luminal surface of pulmonary endothelial cells.

Angiotensin II↗
PubMed1972

Comparison of two methods for determining human adipose cell size.

The mean cell sizes of specimens of human adipose tissue were determined on sectioned slices according to the method described by Sjöström et al. (J. Lipid Res. 1971. 12: 521-530) and on adipocytes isolated after treatment of the tissue with collagenase. The average mean cell sizes from 11 biopsy specimens were 94.4 and 94.0 micro m, respectively (r = 0.964; P(t(b)) < 0.001; y = 0.90x + 9.74), for the two methods. There was no indication of an increased rupture of isolated large human adipose cells. Thus, with precautions (freshly siliconized glassware and omitting the centrifugation of the isolated cells), the collagenase method may be used for metabolic as well as morphologic studies of human adipose tissue.

Adipose Tissue↗
PubMed1972

Effect of cell size on lipolysis and antilipolytic action of insulin in human fat cells.

The lipolytic response to catecholamines and the antilipolytic effect of $$Word$$ were studied as a function of adipose cell size and number. The results show that cellular enlargement is associated with an increase in the basal lipolysis as well as the release of glycerol induced by salbutamol (a beta(2)-receptor agonist), noradrenaline, adrenaline, and isopropyl-noradrenaline. The glycerol release induced by all these agents seems to be more favorably correlated with cell surface area than with cell volume or diameter. Under the incubation conditions used with glucose in the medium, the antilipolytic effect of insulin on the basal as well as on the adrenaline- and isopropylnoradrenaline-stimulated lipolysis was not consistent at any cell size studied. However, in the presence of noradrenaline and salbutamol, insulin exerted a consistent antilipolytic effect. The results show that the larger adipose cells are at least as sensitive to the antilipolytic effect of insulin as the smaller cells. The results imply that the previously reported diminished responsiveness to insulin shown by large adipose cells is exerted only on the side of lipid accumulation. It is suggested that the negative correlation between cell size and responsiveness to insulin on the side of lipid accumulation may be one way to control adipose cell enlargement.

Adipose Tissue↗
PubMed1971

Endothelial projections as revealed by scanning electron microscopy.

Scanning electron micrographs of the endothelium of the pulmonary artery reveal that the entire surface is covered by a meshwork of irregular projections which vastly increase the surface area. The size and density of the projections suggest that they may function to direct an eddying flow of plasma along the endothelial surface.

Animals↗
PubMed1971

Effect of cell size on lipid synthesis by human adipose tissue in vitro.

When adipose tissue cells were incubated with collagenase for different periods of time, cell populations with different mean cell sizes were obtained from the same tissue sample. Lipid synthesis from glucose was studied as a function of adipose cell size and number. The incubations were performed in Parker medium 199, which is suitable for tissue culture of human adipose tissue. The results show that the larger cells of a specimen have a greater rate of lipid synthesis than the smaller cells of the same specimen. This is mainly due to an increase in the synthesis of glyceride-glycerol. Addition of insulin stimulated lipid synthesis. However, the larger adipose cells were less sensitive to the stimulating effect of insulin than the smaller cells.

Adipose Tissue↗
PubMed1970

The toxicity of streptolysin O for beating mammalian heart cells in tissue culture.

Pulsating mammalian myocardial cells were found to be highly susceptible in tissue culture to rapid destruction by streptolysin O. Cessation of beating occurred almost immediately, followed within minutes by multiple cell membrane bleb formation. Parallel with these changes, the cytoplasm became intensely granular and the nuclear membrane apparently thickened when viewed by phase microscopy. At the ultrastructural level, the cell membrane blebs were found to contain relatively small numbers of granular fragments. The endoplasmic reticulum of damaged heart cells was quite swollen, and its contents were considerably condensed. The myofibers were not strikingly altered, but cytoplasmic and mitochondria vacuoles were rather abundant. Cardiac endothelial, kidney epithelial, and fibroblast cells were also susceptible to lysis by this toxin, but the reactions occurred more slowly or bleb formation was less evident. An antiserotonin drug known to be protective against streptolysin-O in vivo (UML-491), did not protect against killing of cardiac cells at the tissue culture level. Serotonin could not be detected in the culture fluid after lysis of cardiac cells by streptolysin O.

Animals↗