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Biomedical subjects

L C Harrison

Publications and source records attributed to L C Harrison.

At least 199 records · Page 11Linked to original sources
PubMed1986

Rapid improvement in visual field defects following bromocriptine treatment of patients with non-functioning pituitary adenomas.

The role of bromocriptine in the treatment of non-functioning pituitary tumours is not yet defined. Patients with these tumours who present with visual field defects usually undergo immediate surgery. Three consecutive patients are reported: each had rapid improvement in their visual field defects following bromocriptine 7.5 mg/d before surgery. Histological and immunohistochemical examination confirmed that their tumours were non-functioning chromophobe adenomas. Their responses indicate that bromocriptine may have a role in the management of some patients with non-functioning pituitary tumours.

Adenoma, Chromophobe↗
PubMed1986

The effects of weight change on the dexamethasone suppression test in depressed and anorexic patients.

Prior studies on weight change and hypothalamic-pituitary-adrenal (HPA) axis functioning are reviewed. Data on 58 depressed and eight anorexic patients is presented. No significant difference in the frequency of cortisol non-suppression in the dexamethasone suppression test (DST) was found between depressed patients with a history of weight loss and those without, nor between depressed patients who lost weight during their first week in hospital and those who did not. Mean weight loss of suppressors did not significantly differ from that of non-suppressors. Of 12 patients whose DST normalised during their stay in hospital, only four gained weight. Five anorexics who were non-suppressors were less than 70% of their ideal body weight (IBW), while three suppressor anorexics were greater than or equal to 70% IBW. These results indicate that mild to moderate weight change is not a significant influence on DST response in depression.

Anorexia Nervosa↗
PubMed1986

Interferon-gamma induces the expression of HLA-A,B,C but not HLA-DR on human pancreatic beta-cells.

We examined the effect of interferon-gamma (IFN gamma) on expression of the major histocompatibility proteins on cultured human islet cells isolated from adult and fetal pancreas and from an insulinoma. While the pancreatic beta-cells from different sources varied in their responses to IFN gamma, in all instances the expression of HLA-A,B,C protein was increased. Pancreatic beta-cells did not express HLA-DR protein, before or after culture of the islets in IFN gamma, although HLA-DR protein expression was induced on some non-beta-cells. These findings are at variance with those reported with thyroid follicular cells, in which IFN gamma induced expression of HLA-DR. We, therefore, conclude that the interaction between the immune and the endocrine systems may be endocrine cell specific. The up-regulation of HLA-A,B,C protein on beta-cells by IFN gamma provides a mechanism for enhanced targetting to the beta-cells of autoreactive cytotoxic T-lymphocytes and, hence, for amplifying beta-cell destruction.

Adult↗
PubMed1986

Structure of the human erythrocyte insulin receptor.

The structure of the insulin receptor in intact human erythrocytes was defined using the techniques of disuccinimidyl suberate (DSS) cross-linking of 125I-insulin and surface [125I]iodination followed by receptor immunoprecipitation. In contrast to a recent report, we found the erythrocyte insulin receptor to be similar in structure to that in classic target tissues for insulin, consisting of at least three species of molecular weight approximately 295,000, 265,000, and 245,000, containing disulfide-linked subunits of molecular weight approximately 130,000 and 95,000. The interconversion of the three oligomeric forms could mediate changes in receptor affinity as postulated in other tissues. The 95,000 subunit was detected by immunoprecipitation only if surface iodination was performed in a Tris/Hepes buffer using lodogen and not if phosphate-buffered saline or lactoperoxidase iodination was used. These findings indicate that the lack of a bioeffect of insulin in erythrocytes is not explained by a gross defect in the structure of their insulin receptors. The apparent identity of the insulin receptor structure in erythrocytes and insulin target tissues provides a firmer basis for the use of erythrocytes in some circumstances to reflect insulin receptor status.

Adult↗
PubMed1986

Expression of class I MHC proteins on RIN-m5F cells is increased by interferon-gamma and lymphokine-conditioned medium.

To examine whether products of the immune system interact with the pancreatic beta-cell, rat insulinoma cells (RIN-m5F line) were cultured in the presence of conditioned medium from concanavalin A-activated mouse spleen cells (CAS medium). Indirect immunofluorescence and flow cytometry revealed that after culture in CAS medium, RIN-m5F cells had an 8- to 10-fold increase in class I major histocompatibility complex (MHC) proteins, whereas class II MHC proteins remained undetectable, and the level of insulin and/or insulin-like growth factor 1 receptors was unchanged. The stimulation of class I MHC expression on RIN-m5F cells by CAS medium could be mimicked by recombinant interferon-gamma. Analysis of 125I-surface-labeled cells by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography revealed that in the presence of CAS medium, there was a major increase in the expression of proteins of 48,000, 32,000, and 12,000 Mr and a minor increase in proteins of 17,000 and 9,000 Mr. Precipitation with monoclonal antibody identified the 48,000- and 12,000-Mr proteins as the class I MHC protein and beta 2-microglobulin, respectively. The ability of lymphokine-conditioned medium to increase the expression of RIN-m5F cell surface proteins, including the class I MHC proteins, provides a potential mechanism for enhancing the immune-mediated destruction of the beta-cell.

Adenoma, Islet Cell↗
PubMed1986

Thyrotrophin (TSH) binding sites on Yersinia enterocolitica recognized by immunoglobulins from humans with Graves' disease.

Antibodies against the gram negative enteric bacterium Yersinia enterocolitica have been found in a high proportion of persons with autoimmune thyroid disorders, especially in those with Graves' disease or hyperthyroidism (Shenkman & Bottone, 1981). There is strong evidence that Graves' disease is caused by receptor autoantibodies which mimic the bioeffects of thyroid stimulating hormone (TSH) on the thyroid (Manley, Knight & Adams, 1982). Recently, saturable binding sites for TSH were demonstrated in Y. enterocolitica under non-physiological conditions (Weiss et al., 1983). We have characterized TSH binding sites on Y. enterocolitica under physiological conditions and studied their interaction with Graves' immunoglobulins (Ig's). Saturable and specific binding of receptor-purified 125I-TSH to lysozyme/EDTA-treated Y. enterocolitica (serotype 03) was demonstrated under both non-physiological and physiological conditions. Scatchard binding plots were linear indicating a single class of binding site (Kd 1 X 10(-7) M, maximum of 30,000 binding sites per cell). In the presence of Graves' Ig's the binding of 125I-TSH to Y. enterocolitica was significantly inhibited. Graves' Ig's also precipitated a protein of relative molecular mass (Mr) 64,000 from Triton-solubilized, 125I-labelled Y. enterocolitica, similar in size to one of the proteins precipitated by Graves' Ig's from human thyroid membranes. These findings are consistent with the hypothesis that thyroid autoimmunity may be triggered by bacterial infection via a mechanism involving crossreactivity at the level of the TSH receptor. They also suggest that elements of mammalian endocrine systems are highly conserved and have a function in prokaryotes.

Antibodies, Bacterial↗
PubMed1985

Homogeneous bivalent insulin receptor: purification using insulin coupled to 1,1'-carbonyldiimidazole activated-agarose.

A novel affinity gel, consisting of insulin coupled to 1,1'-carbonyldiimidazole-activated agarose (CDI-agarose), was used to purify insulin receptors from human placenta to homogeneity. This affinity gel is reproducibly prepared and is reported to have a number of advantages over the standard cyanogen bromide activated supports, such as ease and simplicity of coupling and minimal ligand leakage and non-specific binding. Insulin receptors in Triton X-100-solubilized microsomal membranes were purified 2,000-fold by sequential affinity chromatography on wheat germ lectin-agarose and insulin-CDI-activated agarose. They have one of the highest specific insulin-binding capacities (6 nmol/mg protein) reported and can be calculated to have a binding valence of two on the basis that the molecular weight of the oligomeric receptor is 300-350,000.

Chromatography, Affinity↗
PubMed1985

Structure of covalent insulin-receptor complexes (I-S-S-R) in isolated rat adipocytes and human placental membranes.

The structure of naturally-formed covalent disulphide-linked complexes between insulin and its receptor was examined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. To prevent destabilization of disulphide bonds at alkaline pH the standard discontinuous electrophoresis conditions were changed to a continuous buffer system at pH 7.0. 125I-insulin was first bound to either rat adipocytes or human placental membranes for 10 min at 37 degrees C. After washing, non-dissociable radioactivity was extracted from cells or membranes in Triton X-100 and immunoprecipitated with an antiserum (B-2) to the insulin receptor. Electrophoresis of the immune precipitate revealed the two smaller of the three reported species of native insulin receptor (Mr values approx. 350 000, 290 000 and 260 000); in addition, a species of Mr 200 000 was also frequently observed in adipocytes. When non-dissociable 125I-insulin was chemically crosslinked to adipocytes or placental membranes, prior to solubilization and immunoprecipitation, all three species of the native receptor were labelled; after reduction, only a single species of Mr 130000 was observed. These findings indicate that disulphide exchange of insulin occurs with the Mr 130000 (alpha) binding subunit within partially reduced species of the native, oligomeric receptor. The degree of disulphide binding of insulin could therefore depend on the relative abundance of partially reduced receptor species and on the redox state of the cell membrane.

Adipose Tissue↗
PubMed1985

The human placenta contains two distinct binding and immunoreactive species of insulin-like growth factor-I receptors.

Two species of insulin-like growth factor-I (IGF-I) receptors in human placenta have been delineated on the basis of their immunoreactivity with an autoantiserum (B-2) to the insulin receptor. When all the IGF-I binding sites in solubilized human placenta were assayed by polyethylene glycol precipitation, a curvilinear Scatchard plot was obtained which could be resolved into two single classes of binding sites: one immunoprecipitable by B-2 IgG and the other, nonimmunoprecipitable. The B-2 reactive sites bound IGF-I with lower affinity (Kd = 7.1 X 10(-10) M) than the B-2 nonreactive sites (Kd = 2.1 X 10(-10) M) and cross-reacted more readily with insulin, the IGF-I/insulin-binding potencies being congruent to 120 and congruent to 1100, respectively. Both receptor subtypes bound IGF-I with congruent to 30-fold higher affinity than multiplication-stimulating activity, and, after affinity cross-linking with 125I-IGF-I, migrated as specific reduced bands of Mr = 138,000 during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The subunit sizes of the B-2 reactive IGF-I receptor were similar to those of the insulin receptor. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of 125I-labeled receptors immunoprecipitated by autoantiserum B-2 or autoantiserum B-10 (which recognizes only insulin receptors) revealed, in both cases, specific reduced bands of Mr = 130,000 and 90,000; the same bands were also seen after sequential precipitation with B-10 and B-2 antisera to enrich the proportion of IGF-I receptors recovered. The presence of two distinct binding and immunoreactive species of IGF-I receptors in human placenta raises the possibility that cell- or tissue-specific isotypes of the IGF-I receptor could mediate the different biological actions of IGF-I.

Chemical Precipitation↗
PubMed1985

Nesidioblastosis and multifocal pancreatic islet cell hyperplasia in an adult. Clinicopathologic features and in vitro pancreatic studies.

The clinicopathologic features of an adult with insulinoma and pancreatic islet cell hyperplasia, who presented with hyperinsulinemic hypoglycemia are reported, together with in vitro studies on the patient's pancreatic islets. Islet cell hyperplasia with ductal proliferation and budding and beta cell degranulation was demonstrated by immunochemical means. The in vitro studies of cultured hyperplastic islet cells support the clinicopathologic features. Thus, in comparison with control islets maintained in culture for up to 14 days, hyperplastic islets could be cultured for up to 60 days, during which time cell overgrowth required subculture on three occasions. Furthermore, in contrast to control islets the release of both insulin and somatostatin from cultured hyperplastic islets was refractory to glucose, glucagon, and tolbutamide; theophylline was the only secretagogue to stimulate insulin and somatostatin release from hyperplastic islets in vitro. Indirect immunofluorescence revealed the presence of islet cell surface autoantibodies in the plasma of this patient reactive with both normal human islets and a rat insulinoma line (RIN-m5F). These studies demonstrate the proliferative capacity and relatively undifferentiated functional state of hyperplastic islets in vitro. They provide further evidence that islet cell division is capable of being stimulated in adult life. The pathogenic significance of islet cell surface autoantibodies in hyperplastic islet cell disease and insulinoma warrants further investigation.

Adult↗
PubMed1985

Insulin secretion and immuno-genetic markers in diabetics with 'secondary failure' of oral hypoglycemic agents.

'Secondary failure' of oral hypoglycemics, in non-insulin dependent diabetics, has been attributed to dietary non-compliance, inadequate drug dosage, metabolic stress, or true drug failure. Progressive loss of beta cell function is a suggested mechanism for true drug failure but on the basis of little documented evidence. In view of this, we have measured basal and glucagon-stimulated C-peptide levels, human leukocyte antigen (HLA) types, and islet cell antibodies in 20 non-insulin dependent diabetics with 'secondary failure' of oral agents. There were 16 females and four males with a mean ideal body weight of 1.30 units and mean duration of diabetes of 9.5 years. Fasting insulin (mean +/- SD: 15.1 +/- 10.6 mU/l) and fasting C-peptide (2.3 +/- 1.2 micrograms/l) were normal or slightly elevated in all but one patient. Mean C-peptide increased from 2.3 +/- 1.2 micrograms/l to 3.5 +/- 2.2 micrograms/l (152% over basal) 6 minutes after 1 mg i.v. glucagon. In 15 patients the C-peptide response was greater than 130% of basal. Islet cell cytoplasmic antibodies were detected in only two patients. The distribution of HLA types was not significantly different from a control population, with no increase in DR3 or DR4. Thus, absolute insulin deficiency is uncommon in non-insulin dependent diabetics with 'secondary failure' of oral hypoglycemic agents and such patients do not exhibit the immuno-genetic markers of insulin-dependent diabetes.

Administration, Oral↗
PubMed1985

Insulin resistance, acanthosis nigricans, and polycystic ovaries associated with a circulating inhibitor of postbinding insulin action.

A 21-yr-old moderately obese woman with hirsutism, acanthosis nigricans, and oligomenorrhoea was diagnosed as having polycystic ovary syndrome. Despite hyperinsulinemia, binding of insulin to her red cells was within the range for normal, young adult subjects. Her serum did not bind or degrade [125I]insulin or alter its binding to fat cells, and was negative for insulin receptor antibodies. However, her serum caused a dose-dependent inhibition of insulin-stimulated lipogenesis (conversion of [3-3H]glucose to [3H]lipid) in rat fat cells significantly greater than that produced with control serum (relative potency, 3.5:1) and (at a 1:20 dilution) markedly impaired the response of both lipogenesis and 2-deoxy-D-glucose uptake to maximum concentrations of insulin. After the patient was treated with clomiphene for 4 months, her menses resumed, hair growth slowed, fasting blood glucose and plasma insulin concentrations decreased, and serum inhibitory activity decreased to the control range. Serum inhibitory activity was stable to freezing and thawing and to heating at 56 C for 30 min, and could be extracted into acid-ethanol. By dialysis, its mol wt was below 1000, whereas by ultracentrifugation, it was above 3500; both high and low mol wt forms were detected after Sephadex G-50 gel chromatography of serum, suggesting that the inhibitor was of low mol wt but loosely bound to a higher mol wt component in serum. These findings indicate that insulin resistance in this patient with acanthosis nigricans and polycystic ovaries could be attributed to a circulating low mol wt inhibitor of postbinding insulin action.

Acanthosis Nigricans↗
PubMed1985

Adult human pancreatic islet cells in tissue culture: function and immunoreactivity.

In order to obtain an appropriate tissue model to study human diabetes we isolated islet cells from pancreata obtained from brain-dead, heart-beating kidney donor subjects by collagenase dispersion and tissue culture. The presence of viable islet cells was confirmed by both immunofluorescence staining and hormone release experiments. Insulin and somatostatin release were determined on culture day 3 or 4 when amylase measurements indicated an absence of functional exocrine cells. Glucose, alpha-ketoisocaproic acid, theophylline, glucagon, and tolbutamide each stimulated insulin release 2- to 3-fold and somatostatin release 1.5- to 2-fold. Epinephrine and somatostatin both inhibited glucose-stimulated insulin release. Successful subculture of islet cells was achieved after dispersion of primary cultures with dispase. Subcultured islet cells released insulin into the medium during a subsequent 8-day period and when challenged with glucose responded with a 1.6-fold increase in insulin output. Cells cultured on glass coverslips were used to detect, by indirect immunofluorescence, islet cell surface antibodies (ICSA) in the sera of patients with insulin-dependent diabetes mellitus. Of 15 sera from patients with newly diagnosed insulin-dependent diabetes mellitus 9 were ICSA positive, whereas all of 10 control sera were negative; in contrast, using rat insulinoma cells only 4 diabetic sera were positive, as well as 2 control sera. These findings demonstrate the functional viability of adult human islet cells in primary and secondary culture. Cultured human islet cells are a novel, sensitive, and specific system for detecting ICSA and for studying autoimmune effects, and provide a potential source of islet cells for transplantation.

Adolescent↗
PubMed1985

Interferon-gamma enhances the expression of the major histocompatibility class I antigens on mouse pancreatic beta cells.

Cell surface antigens of the major histocompatibility complex (MHC) play a crucial role in the initiation of immune reactions. To investigate whether the expression of MHC antigens on pancreatic islet cells could be altered, we have cultured mouse islets in the presence of interferon-gamma (IFN-gamma) and subsequently examined the levels of MHC antigen by indirect immunofluorescence using monoclonal antibodies. IFN-gamma induced a 10-fold increase in H-2K antigen expression on islet cells, the percentage of cells with detectable H-2K expression increasing from 24% to 98%. The effects of IFN-gamma on H-2D and la antigen expression were less marked, with only a twofold increase in mean fluorescence levels, the percentage of cells with detectable levels of expression increasing from 10% to 48% and 5% to 16%, respectively. Using double-indirect immunofluorescence, it was demonstrated that IFN-gamma enhanced expression of H-2K and H-2D antigens on beta-cells. However la-positive beta-cells were undetectable in the presence or absence of IFN-gamma. The ability of IFN-gamma to induce increased expression of H-2 antigens on beta-cells may represent a mechanism for targeting immune (cytotoxic) reactions to beta-cells, e.g., in autoimmune insulitis or allograft rejection.

Animals↗
PubMed1985

Increase in remission rate in newly diagnosed type I diabetic subjects treated with azathioprine.

Azathioprine (2 mg/kg) was given, in addition to routine insulin treatment, to alternate patients presenting with recent-onset type I diabetes. Treated (N = 13) and untreated (N = 11) patients did not differ significantly at diagnosis with respect to age, duration of symptoms, body weight, blood glucose, hemoglobin A1c, or presence of ketosis. Eight patients were treated for 12 mo, three elected to stop treatment at 6 mo, and treatment was stopped in two because of side effects. Seven treated patients had a remission compared with one untreated patient. At 12 mo these seven patients were distinguished by significantly higher basal and glucagon-stimulated levels of C-peptide (1.98 +/- 0.52 and 3.88 +/- 0.34 micrograms/L, respectively) compared with the other six treated patients (0.93 +/- 0.52 and 1.32 +/- 0.85 microgram/L, respectively), and by the persistence of islet cell cytoplasmic antibodies. Remissions were not sustained in the 1-2 yr after treatment, although relapsed patients required less insulin for control. These results corroborate those from nonrandomized trials using cyclosporine and suggest that protracted treatment with nonspecific immunosuppressive drugs may be necessary to avert insulin dependence.

Adolescent↗
PubMed1985

Gliclazide therapy is associated with potentiation of postbinding insulin action in obese, non-insulin-dependent diabetic subjects.

Six obese, non-insulin-dependent diabetic subjects were studied before and 3 mo after treatment with the sulfonylurea gliclazide, 40-80 mg b.i.d. Fasting plasma glucose fell significantly from 13.4 +/- 1.6 (SEM) to 8.6 +/- 1.2 mmol/L, accompanied by a significant reduction from 40.6 +/- 3.7 to 29.8 +/- 2.8 mM X h of the plasma glucose response to 75 g oral glucose. Fasting plasma insulin showed a nonsignificant increase from 24.8 +/- 2.0 to 31.3 +/- 2.3 mU/L. The percent specific binding of tracer 125I-insulin to erythrocytes and monocytes did not change significantly (from 9.8 +/- 1.7 to 8.5 +/- 0.7 for erythrocytes and 1.7 +/- 0.3 to 1.6 +/- 0.4 for monocytes). Glucose utilization was measured at three levels of insulin infusion (40, 100, and 300 mU/kg/h) by the euglycemic clamp technique. Overall there was a significant (P less than 0.05) increase in the disappearance rate (Rd) and metabolic clearance rate (MCRg) for glucose at the two higher insulin infusion rates (MCRg: 3.3 +/- 0.7 to 5.1 +/- 0.7 and 5.9 +/- 0.9 to 7.9 +/- 0.9 ml/kg/min), but not at the lowest infusion rate (MCRg: 3.6 +/- 0.8 to 3.3 +/- 0.6). Thus, the chronic hypoglycemic effect of gliclazide in obese diabetic subjects was associated with an improvement in insulin-mediated glucose utilization at high plasma insulin concentrations. This enhanced effect of insulin after gliclazide treatment was not accompanied by increased monocyte or erythrocyte insulin binding, which suggests that it was due to potentiation of postbinding insulin-sensitive pathways.

Aged↗
PubMed1984

Structure of insulin/insulin-like growth factor-1 receptors on the insulinoma cell, RIN-m5F.

The subunit structure of receptors for insulin and insulin-like growth factor-1 has been demonstrated on a rat insulinoma cell, RIN-m5F, grown in continuous culture. The specific binding of [125-I]-insulin-like growth factor-1 (2.9 +/- 0.42%; mean +/- SEM) to the RIN-m5F cell was significantly greater than of [125I]-insulin (0.7 +/- 0.2%). Immunoprecipitation of receptors from [125I]-surface labeled cells and analysis by sodium dodecyl sulfate polyacrylamide gel electrophoresis and autoradiography revealed reduced subunits of Mr 130,000 and 90,000, identical to those for both insulin and insulin-like growth factor-1 receptors on classic target tissues. An apparent abundance of insulin-like growth factor-1 over insulin receptors could be due to downregulation of the latter by secreted insulin. These findings support a role for insulin and insulin-like growth factor-1 receptors in regulating metabolic or growth functions in the beta cell.

Adenoma, Islet Cell↗