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Biomedical subjects

C K Silbert

Publications and source records attributed to C K Silbert.

27 records · Page 2Linked to original sources
PubMed1979

Studies of cultured human fibroblasts in diabetes mellitus: changes in heparan sulfate.

The incorporation of [35S]sulfate into glycosaminoglycans was studied in cultures of normal and diabetic skin fibroblasts. Heparan sulfate was determined by column chromatography after enzymatic degradation of chondroitin sulfates and dermatan sulfate by chondroitinase ABE. Cultured skin fibroblasts from both insulin-dependent and noninsulin-dependent diabetics were found to have increased proportions of heparan sulfate in the media relative to the other sulfated glycosaminoglycans.

Adult↗
PubMed1976

Tumor hypoglycemia: deficient splanchnic glucose output and deficient glucagon secretion.

Fasting hypoglycemia occurred in a patient with a histologically benign mesothelioma; the serum insulin was low (2-4 muU./ml.), as was the glucose utilization rate. Splanchnic glucose output was markedly decreased on direct measurement (21 mg./min.; normal: 108-180 mg./min.). Splanchnic uptake of gluconeogenic substrates plasma glucagon was low normal during hypoglycemia and responded poorly to oral and intravenous alanine. The nonsuppressible insulin-like (NSILA-s) and somatomedin-like activities of the serum were not elevated, and the tumor did not release insulin-like activity on incubation nor did it contain somatostatin. The marked decrease in splanchnic glucose output was the principal cause of hypoglycemia, was associated with an apparent decrease in glycogenolysis, and was at least partly due to deficient glucagon secretion. The relationship of the tumor to these defects is unclear. The tumor may have secreted an unknown insulin-like material affecting primarily the liver and/or pancreatic alpha cell. The approach used here may serve as a paradigm for the analysis of hypoglycemia not caused by excessive insulin.

Glucagon↗
PubMed1975

The effect of glucose on the growth hormone response to glucagon and propranolol-glucagon in normal subjects.

UNLABELLED: The mean (+/- SE) peak level of serum growth hormone (GH) after intramuscular injection of glucagon in ten normal adult men was 15.1 +/- 2.1 ng/ml; glucose infusion suppressed the mean peak GH to 9.6 +/- 3.7 ug/ml (p less than 0.05). Pretreatment of eight of these subjects with propranolol caused a modest increase in the mean peak GH after glucagon (19.4 +/- 2.8 ng/ml) but did not improve the mean peak GH after glucagon when glucose was infused (8.7 +/- 2.8 ng/ml). Individual analysis of the peak GH showed that glucose infusion did not uniformly suppress the peak GH after glucagon; in seven subjects the peak GH was suppressed but in three it was not. CONCLUSIONS: (1) The GH response after glucagon is usually due to a fall in serum glucose after the initial rise in serum glucose induced by glucagon. (2) Nevertheless, since glucose does not consistently inhibit the GH response after glucagon, a second mechanism probably exists by which glucagon stimulates GH secretion. (3) Glucose completely suppresses the propranolol-induced increase in the GH response to glucagon; an adrenergic mechanism may be involved in the control of GH secretion by glucose.

Adolescent↗
PubMed1975

Heparan sulfate of skin fibroblasts grown in culture.

Primary cultures of normal human skin fibroblasts were examined for glycosaminoglycan content. Heparan sulfate was found in the growth medium of these cells, in fractions obtained by sequential collagenase and trypsin treatments, and in the remaining intact cells. Heparan sulfate was found to be the major sulfated glycosaminoglycan of the trypsin fraction but appeared as a smaller proportion of the collagenase fraction. The heparan sulfate of the growth medium, the collagenase fraction, and the trypsin fraction appeared to be proteoglycan while intracellular material appeared to be mainly free polysaccharide. The collagenase fraction is thought to be representative of "matrix" material produced by the cells, while the trypsin fraction may represent external cell surface material. The trypsin fraction heparan sulfate polysaccharide was relatively homogeneous in size with an average molecular weight of approximately 40,000 relative to a chondroitin sulfate standard. It was also relatively homogeneous in sulfate content, containing an average of 0.8 sulfate groups per disaccharide repeating unit. Approximately 50% of this was N-sulfate.

Cells, Cultured↗
PubMed1975

Double-antibody radioimmunoassay of serum insulin: effect of use of hormone-depleted human serum.

Human serum can be depleted of insulin and growth hormone by treatment with dextran-coated charcoal or by dialysis, or both. Inclusion of such hormone-depleted serum in the standard curve of a double-antibody radioimmunoassay for immunoreactive insulin more nearly mimics the conditions under which an unknown human serum sample is assayed. Compared to the usual standard curve in which serum albumin is the only protein, the addition of hormone-depleted serum can cause an increase (by an average 64% under the conditions we used) in the absolute value for apparent insulin in serum. The effect of hormone-depleted serum should be tested in the standard curves of double-antibody radioimmunoassays and included routinely in these standard curves if it changes the results. When used in conjunction with an eventual reference standard for human insulin, this modification of the insulin assay may make the measured values of human serum insulin from different laboratories more comparable.

Blood↗