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M M Rechler

Publications and source records attributed to M M Rechler.

At least 145 records · Page 8Linked to original sources
PubMed1979

Primary defect of insulin receptors in skin fibroblasts cultured from an infant with leprechaunism and insulin resistance.

Insulin binding to insulin receptors, on skin fibroblasts established in culture from an infant with insulin resistance and clinical features of leprechaunism was markedly decreased in comparison with cultures from an age-matched control. By contrast, the binding of epidermal growth factor, a polypeptide growth factor chemically unrelated to insulin, to patient's and control fibroblasts was indistinguishable. The selective defect in insulin binding to patient's fibroblasts was reflected in an impaired ability of insulin to stimulate 2-deoxyglucose uptake. These results most likely indicate a primary genetic defect of insulin receptors.

Biological Transport↗
PubMed1978

Extreme insulin resistance in ataxia telangiectasia: defect in affinity of insulin receptors.

The syndrome of ataxia telangiectasia is associated with glucose intolerance and insulin resistance. We examined the status of insulin receptors on circulating monocytes and on cultured fibroblasts from two siblings with ataxia telangiectasia and severe insulin resistance. 125I-insulin binding to monocytes of the two patients consistently demonstrated an 80 to 85 per cent decrease in receptor affinity. In contrast, the defect in receptor affinity was not expressed on the patients' cultured fibroblasts or on monocytes or fibroblasts obtained from unaffected family members. Whole plasma and immunoglobulin-enriched fractions of plasma from the patients inhibited the normal binding of insulin to its receptors on cultured human lymphocytes (IM -9 line) and on human placental membranes. We conclude that the insulin resistance in the two siblings with ataxia telangiectasia was associated with defects in the affinity of the receptors for insulin, probably caused by circulating inhibitors of insulin binding.

Acanthosis Nigricans↗
PubMed1978

Multiplication-stimulating activity (MSA): a somatomedin-like polypeptide from cultured rat liver cells.

Multiplication-stimulating activity (MSA) has been purified to homogeneity with the use of Dowex chromatography. Sephadex gel filtration, and preparative disc gel electrophoresis. A molecular weight of 8,700 was determined for both native and reduced and alkylated MSA by chromatography on a 6% agarose column in 6 M guanidine HCl. Amino acid analysis of performic acid-oxidized MSA revealed 2--3 cysteic acid residues, and reduction and alkylation resulted in loss of biologic residues, and reduction and alkylation resulted in loss of biologic activity. These results suggested the presence on one intrachain disulfide bond, which is required for biologic activity. Specific receptors for MSA have been identified on chick embryo fibroblasts, human skin fibroblasts, a rat liver cell line, and purified rat liver plasma membranes. The closely related peptides, acid ethanol-soluble nonsuppressible insulin-like activity (NSILA-S) and somatomedin-A, competed for MSA tracer binding to these MSA receptors, whereas unrelated peptides did not compete. MSA receptors were divided into two types based on their reactivity with insulin and proinsulin. Insulin and proinsulin competed potently for MSA binding to chick embryo and human skin fibroblasts (type II) but did not compete for MSA tracer binding to rat liver cells and purified rat liver membranes (type I). In chick embryo fibroblasts, the concentrations of MSA, insulin, proinsulin, and somatomedin-A, which inhibited [125I]MSA binding by 50%, also gave half-maximal stimulation of DNA synthesis, consistent with the MSA receptor being a mediator of DNA synthesis. MSA tracer has also been shown to bind specifically to rat serum proteins. The MSA binding profile on Sephadex G-200 was shown to be growth hormone dependent. Since the serum half-life of somatomedin activity in the rat was also growth hormone dependent, these results suggest that growth hormone induces the binding protein for somatomedin and thereby governs the half-life of somatomedin. Finally, the ability of two rat liver cells lines to multiply in serum-free medium did not depend upon the level of MSA in the conditioned medium.

Animals↗
PubMed1977

Proliferation of Buffalo rat liver cells in serum-free medium does not depend upon multiplication-stimulating activity (MSA).

A line of Buffalo rat liver cells (BRL 3A) that multiplies in the absence of serum produces a family of polypeptides termed MSA that can partially satisfy the serum requirement for growth of chick embryo fibroblasts. Temin, Pierson and Dulak (1972) proposed that BRL cells multiply in serum-free medium because they produce MSA. This does not appear to be the case. We have studied three BRL cell lines: 3A2 and 3A have diverged from the same original isolate from normal liver; 61t is a spontaneous transformant of a different isolate. All three cell lines showed a 10 fold increase in cell number during 5 days in serum-free medium. However, 3A-conditioned medium stimulated 3H-thymidine incorporation into DNA in chick embryo fibroblasts and human skin fibroblasts; 3A2- and 61t-conditioned media did not. After ion-exchange chromatography or gel filtration of the conditioned media and measurement of MSA by 3H-thymidine incorporation or radioreceptor assay, MSA again was found in the 3A medium but not in the 3A2 or 61t media. The absence of MSA in the 3A2 and 61t media was not due to inactivation of MSA by these two cell lines. Addition of partially purified MSA to 3A2 cells did not increase their multiplication rate in serum-free medium. We conclude that the ability of the BRL cells to multiply in serum-free medium is independent of the level of MSA in the medium.

Animals↗
PubMed1977

Identification of a receptor for somatomedin-like polypeptides in human fibroblasts.

We have demonstrated a specific receptor for somatomedin-like growth polypeptides in human fibroblasts in culture using the closely related polypeptide, multiplication stimulating activity (MSA), as the radioligand. Polypeptides purified from human plasma, somatomedin A and acid soluble nonsuppressible insulin-like activity (NSILA-s), competed potently for 125I-MSA binding, as did unlabeled MSA. Although insulin and proinsulin also strongly inhibited MSA binding, the properties of the growth peptide receptor differed from those of the human fibroblasts insulin receptor. Somatomedin A, NSILA-s, MSA, insulin and proinsulin all stimulated the incorporation of [3H]thymidine into DNA in human fibroblasts. We propose that these polypeptides induce DNA synthesis through their interaction with the growth peptide receptor.

Cells, Cultured↗
PubMed1976

DNA synthesis in cultured human fibroblasts: regulation by 3':5'-cyclic AMP.

The addition of serum to density-inhibited human fibroblast cultures induced a wave of DNA synthesis, measured as [3H] thymidine incorporation into acid-precipitable material, beginning after 8-12 hr and reaching maximum levels of 16-24 hr. Addition of dibutyryl-3':5'-cyclic AMP (DBcAMP) together with serum inhibited [3H] thymidine incorporation by 75-95%. When DBcAMP was added for the first 4 hr of serum stimulation and then removed, the wave of DNA synthesis was not delayed. This suggested that serum could induce DNA synthesis even though cyclic AMP concentrations were maintained at high levels by DBcAMP during this initial period. These results are inconsistent with the hypothesis that it is the immediate transient reduction in 3':5'-cyclic AMP concentration following the addition of serum that triggers DNA synthesis. By contrast, DBcAMP added 8 hr after serum inhibited [3H] thymidine incorporation to the same extent as DBcAMP added at the same time as serum. This indicated that a step essential for DNA synthesis and occurring late in G1 was inhibited by high concentrations of 3':5'-cyclic AMP.

Bucladesine↗
PubMed1976

Insulin receptors in cultured human fibroblasts.

In order to study human insulin resistance, we have first characterized the interaction of insulin with specific insulin receptors in cultures of normal human fibroblasts. 125 I-insulin bound rapidly to human fibroblasts in suspension at 15 degrees, achieving steady state between one and three hours. Insulin was not degraded during the binding assays. In competitive binding experiments, 2 ng/ml. (3.3 X 10(-10) M) of unlabeled insulin reduced 125 I-insulin binding by 50 per cent. Insulin analogues competed for binding in proportion to their biologic potencies. A curvilinear Scatchard plot was obtained, suggesting the existence of negatively cooperative site-site interactions among the insulin receptors. This was confirmed directly by studies of the dissociation kinetics. The high affinity, specificity, and negative cooperativity of the fibroblast insulin receptor closely resembles the properties of other human insulin receptors. The cultuted human fibroblast should prove a useful tissue for the study of insulin-resistant states in man.

Cells, Cultured↗