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Biomedical subjects

L C Harrison

Publications and source records attributed to L C Harrison.

At least 235 records · Page 13Linked to original sources
PubMed1981

Biosynthetic labeling of insulin receptor: studies of subunits in cultured human IM-9 lymphocytes.

We have identified the subunits of the insulin receptor in cultured human lymphocytes (IM-9 line) by biosynthetic labeling with [35S]methionine and specific precipitation with autoantibodies against the insulin receptor. IM-9 lymphocytes were cultured with [35S]methionine and extracted with Triton X-100. Insulin receptors were concentrated and purified 20-fold by chromatography of the cell extract on wheat germ agglutinin-agarose, and then specifically precipitated by receptor antibodies after addition of a second antibody. Analysis of the immunoprecipitates by sodium dodecyl sulfate/polyacrylamide gel electrophoresis under reducing conditions followed by autoradiography revealed specific precipitation of two major bands with molecular weights of 130,000 and 90,000. Both species were precipitated by receptor antibodies from four different patients with the syndrome of extreme insulin resistance and acanthosis nigricans. In accord with previous data that insulin bound to receptor reduces the affinity of receptor for anti-receptor antibody, we found that preincubation of the wheat germ-purified cell extract with insulin (1.7 microM) prior to immunoprecipitation caused a decrease in the appearance of both species. The decrease in insulin binding seen after incubation of the lymphocytes with insulin for 12 hr ("down regulation") was associated with a decrease in the labeling of both the 130,000 and 90,000 bands. The apparent molecular weight of both subunits was decreased after pretreatment with mixed glycosidases. In conclusion, we have biosynthetically labeled the insulin receptor with [35S]methionine and showed that the receptor consists of two major glycoprotein subunits with apparent molecular weights of 130,000 and 90,000.

Cell Line↗
PubMed1981

Heterogeneity of the insulin-receptor interaction in lipoatropic diabetes.

[125] Insulin binding to its receptors was studied on circulating cells from 11 patients (8 females and 3 males) with lipoatropic diabetes. The patients ranged in age from 9-54 yr. All were insulin resistant, as evidenced by fasting hyperinsulinemia and insulin tolerance tests. Nine patients were evaluated by specific [125] insulin binding to monocytes. Three different patterns of receptor abnormalities were observed: 3 patients demonstrated decreased binding due to decreased binding capacity, 2 patients revealed normal tracer binding with decreased receptor affinity,, and 4 patients had normal or increased insulin binding. [125] Insulin binding to erythrocytes in 9 cases demonstrated similar heterogeneities of initial binding. In most cases there was a good correlation between the binding with erythrocytes and monocytes, although decreased affinity was not observed in the red blood cells. There was no obvious correlations between the nature of the receptor defect and the clinical patterns in these patients. Heterogeneity in insulin binding was even observed among affected members of the same family. Antibodies to the insulin receptor were not detected in any of these patients by either binding inhibition or immunoprecipitation assays. These data suggest that the pathogenesis of the insulin resistance in lipoatropic diabetes is heterogeneous and may involve both receptor and postreceptor abnormalities.

Adolescent↗
PubMed1981

Autoantibodies against the insulin receptor recognize the insulin binding subunits of an oligomeric receptor.

125I-insulin was specifically cross-linked to membranes of human cultured lymphocytes (IM-9 line) using disuccinimidyl suberate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions and autoradiography of this preparation revealed a major 125I-labeled band with an apparent mol wt of 130,000 and minor bands of about 300,000 and 95,000. Labeling of these bands was inhibited by incubation of membranes with either unlabeled insulin or autoantibodies to the insulin receptor. The bands were also observed after the 125I-insulin cross-linked preparation was solubilized and immunoprecipitated with a panel of autoantibodies to the insulin receptor. However, immunoprecipitation of the 125I-insulin-receptor complex was inhibited by preincubation with excess unlabeled insulin. Finally, 125I-Fab fragments of mol wt 50,000 prepared from anti-receptor antibodies and cross-linked to membranes were resolved into a major complex of mol wt 180,000 and a minor band of 125,000. Neither band was observed when 125I-Fab fragments were cross-linked to membranes in the presence of an excess of unlabeled insulin. These findings indicate that autoantibodies to the insulin receptor are directed against the insulin binding subunits of an oligomeric receptor.

Autoantibodies↗
PubMed1980

Autoantibodies to beta 2-adrenergic receptors: a possible cause of adrenergic hyporesponsiveness in allergic rhinitis and asthma.

Autoantibodies to beta 2-adrenergic receptors have been identified in the serum of one patient with allergic rhinitis ("hay fever") and two patients with asthma. The antibodies precipitate solubilized dog lung beta receptors in an indirect immunoprecipitation assay and inhibit the specific binding of iodine-125-labeled iodohydroxybenzylpindolol to membrane-associated receptors from dog lung, calf lung, and human placenta. Ligand binding to canine heart beta 1 receptors is not affected by the antibodies.

Asthma↗
PubMed1980

Diabetes is associated with autoimmunity in the New Zealand obese (NZO) mouse.

The New Zealand Obese (NZO) mouse was studied as a potential model for autoimmune diabetes. NZO mice develop obesity, glucose intolerance, and insulin resistance, and have low-titer IgM antibodies to the insulin receptor. It is shown that they have circulating antibodies to both native DNA and denatured, single-stranded DNA. The antibody levels are higher in females, and, up to 6 mo of age, are comparable to those found in the related NZB X NZW F1 (NZB/W) mouse, a model for systemic lupus erythematosus. After 6 mo of age the antibody levels in NZO mice fall toward normal, in contrast to the persistently elevated levels in NZB/W mice. NZB/W mice are known to succumb to immune complex-mediated proliferative glomerulonephritis before 1 yr of age, whereas NZO mice survive. NZO kidneys exhibit light microscopic features of both diabetic and lupus nephropathies: glomerular proliferation, mesangial deposits, mild basement membrane thickening, glomerulosclerosis, eosinophilic nodules in some glomeruli, occasional hyalinization of the glomerular arterioles, and healing arteriolar inflammation. These changes are associated with glomerular deposition of immunoglobulin, especially IgM, in a granular pattern on fluorescent staining. The NZO mouse, therefore, has evidence of a generalized immune disorder and provides a model for studying the relationship between autoimmunity, obesity, and diabetes.

Animals↗
PubMed1979

Radioimmunoassay of the insulin receptor: a new probe of receptor structure and function.

A sensitive and specific radioimmunoassay for the insulin receptor has been developed employing receptor autoantibodies from the serum of a patient with insulin-resistant diabetes. The assay detects insulin binding sites at concentrations as low as 0.1 nanomolar; distinguishes between receptors originating from human placental membranes, human lymphoblastoid cells, and mouse liver membranes; and measures the receptor independently of its binding function. Down-regulation, or loss of binding after exposure to insulin, is associated with loss of immunoreactive receptor.

Animals↗