Search PubMed⌕ Search

Biomedical subjects

L C Harrison

Publications and source records attributed to L C Harrison.

At least 181 records · Page 10Linked to original sources
PubMed1988

Regulation of MHC protein expression in pancreatic beta-cells by interferon-gamma and tumor necrosis factor-alpha.

Isolated human and mouse pancreatic islet cells and the rat insulinoma cell line RIN-m5F were used to examine the ability of recombinant interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) to regulate the expression of the class I and class II major histocompatibility (MHC) surface proteins and mRNA in beta-cells. Each cytokine increased significantly the expression of class I MHC proteins as determined by double indirect immunofluorescence microscopy and flow cytofluorimetric analysis. In the RIN-m5F cells, this increase in surface expressed class I MHC proteins was mirrored by an increase in the level of class I MHC mRNA. The order of potency of the cytokines on class I MHC expression was TNF-alpha plus IFN-gamma greater than or equal to IFN-gamma greater than or equal to TNF-alpha. While IFN-gamma or TNF-alpha alone were without effect, in combination they were found to induce class II MHC proteins on 30-40% of human or murine beta-cells. In contrast, IFN-gamma plus TNF-alpha did not induce detectable class II MHC proteins or mRNA in the RIN-m5F cells. These findings indicate that 1) TNF-alpha, in addition to IFN-gamma, upregulates the expression of beta-cell class I MHC proteins and mRNA, and 2) more than one signal is required for the induction of class II MHC proteins on beta-cells. The ability of IFN-gamma plus TNF-alpha to induce class II MHC proteins on only a fraction of the normal beta-cell population and not on RIN-m5F cells suggests that this response is related to the differentiation state of the beta-cell.

Animals↗
PubMed1988

Reovirus infection enhances expression of class I MHC proteins on human beta-cell and rat RINm5F cell.

Viruses are implicated in the pathogenesis of beta-cell destruction in type I (insulin-dependent) diabetes. The aim of our study was to investigate whether reovirus 1 or reovirus 3, which are known to infect beta-cells and induce autoimmunity in susceptible mice, could alter the expression of the major histocompatibility complex (MHC) proteins by human beta-cells and rat insulinoma RINm5F cells. Forty-eight hours after infection of either human beta-cells or RINm5F cells with reovirus 1 or reovirus 3, cytopathic effects were noted. By flow-cytofluorometric analysis, infected RINm5F cells exhibited a seven- to eightfold increase in the surface expression of class I MHC proteins. Upregulation of class I MHC proteins on reovirus 3-infected RINm5F cells was inhibited by 80% after preexposure of the virus to reovirus 3 antiserum. When analyzed by double-indirect immunofluorescence microscopy, human beta-cells infected with reoviruses 1 or 3 also exhibited markedly increased levels of class I MHC proteins. Reovirus infection of human beta-cells or RINm5F cells was not accompanied by the induction of class II MHC proteins. These findings suggest that 1) in addition to direct cytopathic effects, reovirus infection may contribute to beta-cell destruction by increasing expression of class I MHC proteins and therefore reactivity with cytotoxic T-lymphocytes; and 2) some viruses may increase MHC protein expression independent of and before the action of cytokines (e.g., interferon-gamma and tumor necrosis factor) released by immunoinflammatory cells.

Adenoma, Islet Cell↗
PubMed1988

Association of HLA-DQw3 (TA10-) with type I diabetes occurs with DR3/4 but not DR1/4 patients.

We have shown in previous studies that the TA10-subtype of HLA-DQw3 is significantly increased in HLA-DR4 type I (insulin-dependent) diabetic patients. Data presented in this article indicate that this association only occurs in heterozygous DR3/4 patients and not in DR1/4 patients. Because there is an interactive effect of both DR3/4 and DR1/4 in type I diabetes, the data indicate that the contribution of DR4 haplotypes varies depending on the haplotype borne on the homologous chromosome. In addition, the frequency of the B44-DR4 haplotype was shown to be decreased in DQw3 (TA10-) diabetic subjects who were DR3/4 compared with those who were DR1/4 or DR4/x (a pooled group of patients with different DR alleles). This finding suggests that the decrease in the B44-DR4 haplotype in type I diabetes is not solely dependent on its linkage disequilibrium with the DQw3 (TA10+) allele but suggests there is an additional effect exerted independently.

Alleles↗
PubMed1987

Production of IGF-binding proteins by vascular endothelial cells.

Conditioned serum-free media from cultured human, bovine and rodent endothelial cells contained binding proteins with high affinity for the insulin-like growth factors (IGFs). After partial purifications on heparin or Multiplication Stimulating Activity (MSA)-affinity columns, 2 species of binding protein were identified, a major protein having Mr approximately 35,000 and a minor 22-28,000 protein. The binding proteins had greater affinity for IGF-I than IGF-II with no affinity for insulin or proinsulin. Substantial amounts of the binding proteins remained cell-associated, loosely bound to the outer cell surface of the endothelial cell. Binding protein(s) from human endothelial cells cross-reacted with antibodies to the 53,000 dalton acid-stable human serum binding protein. Production of endothelial binding proteins was not stimulated by growth hormone or insulin. We conclude that endothelial cells in culture produce large quantities of specific IGF binding proteins. Such binding proteins should be relevant in understanding the complex metabolism and function of the IGFs in the intact host.

Animals↗
PubMed1987

Interferon-gamma: pleiotropic effects on a rat pancreatic beta cell line.

We have recently shown that interferon-gamma (IFN-gamma) markedly upregulates the expression of the class I major histocompatibility proteins on pancreatic beta cells and have therefore postulated that interferon-gamma may enhance cytotoxic lymphocyte-mediated beta cell damage in insulin-dependent diabetes mellitus. To further explore the interaction between interferon-gamma and the pancreatic beta cell we have used the RIN-m5F insulinoma line to define the effects of interferon-gamma on major histocompatibility protein expression, (pro)insulin and protein synthesis and cell growth. Interferon-gamma induced a dose-dependent increase in the expression of the class I major histocompatibility proteins on the RIN-m5F cells, the maximal increase (10-fold) being seen at an interferon-gamma concentration of 1 U/ml. The induction of class I proteins by interferon-gamma was nearly completely abolished by cycloheximide. Expression of class II (Ia) proteins was not detected either in the presence or absence of interferon-gamma. (Pro)insulin and protein synthesis were decreased by 60% and 40%, respectively, in RIN-m5F cells cultured with interferon-gamma (10 U/ml). Furthermore, the growth of RIN-m5F cells was significantly inhibited, and corresponding changes in cell morphology were evident, after 3 days of exposure to interferon-gamma (10 U/ml). These findings indicate that, in addition to its potential role in amplifying cytotoxic T cell activity against the pancreatic beta cell, IFN-gamma may also directly inhibit beta cell function and growth. Several mechanisms could therefore account for an ability of IFN-gamma to compromise beta cell function and contribute to the pathogenesis of insulin-dependent diabetes.

Adenoma, Islet Cell↗
PubMed1987

Evidence against an immunogenetic basis for diabetes in chronic pancreatitis.

A possible immunogenetic basis for diabetes in chronic pancreatitis was explored by studying 19 patients with both disorders, most of whom required treatment with insulin. In contrast to patients with insulin-dependent (Type 1) diabetes, patients with diabetes and chronic pancreatitis had residual beta cell function but blunted C-peptide responses to intravenous glucagon, absence of circulating islet cell antibodies, and HLA-DR types similar to control subjects and patients with chronic pancreatitis without diabetes. Diabetes complicating chronic pancreatitis is therefore not associated with the biochemical or immunogenetic markers characteristic of Type 1 diabetes.

Adult↗
PubMed1987

64,000-Mr autoantigen in type I diabetes. Evidence against its surface location on human islets.

The sera of type I (insulin-dependent) diabetic subjects are reported to contain autoantibodies against a 64,000-Mr protein identified in [35S]methionine biosynthetically labeled pancreatic islet cells. We have attempted to localize this autoantigen to the surface of the beta-cell and to define its properties. Sera from 10 newly diagnosed type I diabetic subjects, including five of the index sera originally used to identify the autoantigen, were shown to specifically precipitate a reduced protein of 67,000 Mr from Triton-solubilized, surface 125I-labeled cultured adult human islet and rat insulinoma (RINm5F) cells but not from fresh rat spleen cells. Further characterization revealed that this protein was bovine serum albumin (BSA) adsorbed to cells from fetal calf serum (FCS)-supplemented culture medium and precipitated by BSA antibodies present in many diabetic sera. No labeled proteins were specifically precipitated when surface 125I-labeled and solubilized human islet or RINm5F cells were precleared with anti-BSA immunoglobulins or when cells were first cultured in human serum. In contrast, a 64,000-Mr protein, clearly not BSA, was precipitated by diabetic globulins from human islets but not from RINm5F cells labeled with [35S]methionine. In addition, a protein of the same size as well as proteins of approximately 35,000, 43,000, 140,000, and 200,000 Mr were specifically precipitated by diabetic globulins from freshly isolated human islets solubilized in Triton X-100 and then labeled with 125I. These findings suggest that the 64,000-Mr antigen is not expressed on the surface of human islet cells, at least in culture, and therefore question its relevance as a target for islet cell surface antibodies in initiating beta-cell damage.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1987

Detection of insulin antibodies in newly-diagnosed type 1 diabetic children after "acid-stripping" of sera.

A sensitive microassay using sera from which endogenous bound insulin was removed by acid-stripping was employed to screen for insulin antibodies in 48 newly-diagnosed Type 1 diabetic children and 20 age-matched controls. Using intact diabetic sera, the binding of 125I-insulin exceeded the upper control range in 16/48 (33%); when the sera were acid-stripped at pH 4.2 for 30 minutes at 4 degrees C, binding to the 16 positive sera increased further and in another five sera became significant, making a total of 21/48 positive (44%). Children 5 years of age or less had a higher prevalence of insulin antibodies. Islet cell antibodies, assayed by indirect immunofluorescence, were detected in equal fractions of insulin antibody-positive and -negative sera (76% versus 77%). Assay of insulin antibodies using acid-stripped sera under the conditions described significantly increases the sensitivity of insulin antibody detection. Insulin antibodies appear to be a specific marker of islet autoimmunity, but compared to islet cell antibodies are relatively insensitive, and may be a marker for a particular subgroup of diabetics.

Adolescent↗
PubMed1987

Isolation of a post-binding inhibitor of insulin action from the sera of non-insulin-dependent diabetics.

We have reported that sera from a majority of patients with non-insulin-dependent diabetes mellitus (NIDDM) inhibit insulin-stimulated lipogenesis (3-3H-glucose conversion to 3H-lipid) in rat adipocytes to a greater extent than control sera or sera from patients with insulin-dependent diabetes mellitus (IDDM). This effect was apparently due to a circulating, low molecular weight (Mr) substance soluble in acid/ethanol and resistant to proteases. We now describe the further characterization of this inhibitor isolated uniquely from NIDDM sera. Size exclusion chromatography of acid/ethanol extracts of sera on a Bio-Rad P2 column revealed the presence of a Mr 300-400 inhibitor of insulin-stimulated lipogenesis in 32 (70%) of 46 NIDDM sera but not in 9 IDDM or 12 control sera. NIDDM sera that contained the low Mr inhibitor had significantly elevated haemoglobin A1c levels compared with those without the inhibitor (14.1 +/- 2.6% vs 11.5 +/- 2.7%, p less than 0.001). In rat adipocytes, the low Mr inhibitor at a dilution equivalent to 1:40 unextracted serum, reduced maximal insulin-stimulated lipogenesis by 33%, 14C-6-glucose oxidation by 70% and 14C-1-glucose oxidation by 25%. In contrast, insulin-stimulated 2-deoxy-D-(1-3H) glucose uptake was unaffected. In the presence of the inhibitor, insulin sensitivity (insulin dose required for half-maximal response) was unchanged for lipogenesis but decreased for 14C-6-glucose oxidation and increased for 14C-1-glucose oxidation. In the presence of control sera, the low Mr inhibitor decreased basal lipogenesis (a measure of serum insulin-like activity) and its effect on insulin-stimulated lipogenesis was unaltered.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1986

Disulphide reduction alters the immunoreactivity and increases the affinity of insulin-like growth-factor-I receptors in human placenta.

We previously identified two forms of the insulin-like growth-factor-I (IGF-I) receptor in human placenta: a lower-affinity form reactive with an autoantiserum (B-2) to the insulin receptor and a higher-affinity non-immunoreactive form [Jonas & Harrison (1985) J. Biol. Chem. 260, 2288-2294]. Evidence is now presented that the lower-affinity immunoreactive forms are convertible into higher-affinity non-immunoreactive forms via reduction of receptor disulphide bonds. Treatment of placental membranes with increasing concentrations of dithiothreitol (DTT): (1) converted native Mr-290 000 heterotetrameric IGF-I receptors into Mr-180 000 dimers (determined by chemical cross-linking of 125I-IGF-I with disuccinimidyl suberate); (2) increased 125I-IGF-I binding, owing to an increase in receptor affinity; and (3) abolished the reactivity of Triton-solubilized IGF-I receptors with antiserum B-2 and transformed the curvilinear plot of IGF-I binding to a linear form. In isolated complexes between receptor and B-2 antibody, DTT increased 125I-IGF-I binding and released a single class of higher affinity IGF-I receptors of Mr 180,000. Thus DTT-treated IGF-I receptors have similar properties to the higher-affinity non-immunoreactive forms of the native receptor, except that reduced dimeric forms are not detected by cross-linking of 125I-IGF-I to native membranes. Cleavage of the inter-dimeric disulphide bonds is therefore not a prerequisite for higher-affinity binding or loss of immunoreactivity. These observations suggest that the thiol redox state of the IGF-I receptor in vivo is an important determinant of receptor conformation and therefore of the biological responses to IGF-I.

Cell Membrane↗
PubMed1986

Cardiovascular, biochemical, and hormonal responses to intravenous sedation with local analgesia versus general anesthesia in patients undergoing oral surgery.

The effects of intravenous conscious sedation and general anesthesia on a number of stress variables were compared in healthy patients undergoing oral surgery. In the intravenous sedation group only the levels of plasma growth hormone and prolactin rose significantly. In the general anesthesia group significant rises were seen in heart rate; systolic blood pressure; mean arterial pressure; levels of plasma adrenaline, adrenocorticotropic hormone, cortisol, and prolactin; and levels of blood glucose, all indicative of a stress response. This study demonstrates that oral surgery under intravenous conscious sedation with local analgesia is associated with less patient stress than is oral surgery under general anesthesia.

Adolescent↗
PubMed1986

An atypical insulin receptor with high affinity for insulin-like growth factors copurified with placental insulin receptors.

Insulin receptors purified from human placenta by sequential affinity chromatography on wheat germ lectin-agarose and insulin coupled to 1,1'-carbonyldiimidazole-activated agarose (CDI-agarose) retained full binding activity but bound a greater than predicted amount of 125I-labeled insulin-like growth factor I (IGF-I). IGF-I and multiplication-stimulating activity (MSA; the rat homologue of IGF-II) were equipotent in displacing either 125I-labeled IGF-I or 125I-labeled MSA from the purified receptors; insulin was 5-15 times more potent. Competitive binding studies indicated that this IGF binding activity could not be explained by cross-reaction with classical insulin receptors or by coelution of IGF-I or IGF-II receptors. Instead, it was due to a minor population of discrete atypical insulin receptors (6-18% total insulin receptors) with moderately high affinity (Kd = 2-4 X 10(-9) M) for IGF-I and MSA. These receptors were not an artifact of insulin-CDI-agarose chromatography, since they were present in wheat germ lectin-agarose-purified preparations and could also be purified from insulin-succinyldiaminodipropylamino-agarose. Affinity labeling with 125I-labeled MSA revealed that these atypical receptors had the same binding subunit (Mr 140,000) as classical insulin and IGF-I receptors. They displayed intermediate reactivity with polyclonal and monoclonal antibodies to the insulin and IGF-I receptors. It is therefore likely that insulin receptors purified by immunoadsorption would also contain atypical insulin receptors. The finding of more than one type of insulin receptor might relate to the slight variations in the cDNA nucleotide sequences and the multiple mRNA species reported for the insulin receptor [Ebina, Y., Ellis, L., Jarnagin, K., Edery, M., Graf, L., Clauser, E., Ou, J.-H., Masiarz, F., Kan, Y. W., Goldfine, I. D., Roth, R. A. & Rutter, W. J. (1985) Cell 40, 747-758].

Affinity Labels↗
PubMed1986

An anomalous postprandial increase in erythrocyte insulin receptor affinity associated with hyperinsulinemia.

Whereas the expected decrease in the binding of 125I-insulin to erythrocytes 4.5 h after a standard mixed breakfast was seen in six young nonobese normoglycemic controls (delta % bound/free = 2.0 +/- 0.5 SEM), 10 obese hyperglycemic subjects showed an increase (0.54 +/- 0.43) and eight obese normoglycemic subjects of similar age and weight, no change in binding (0 +/- 0.31), both being significantly different from the controls (p less than 0.05) but not from each other. Of the total 18 obese subjects, the 11 with fasting hyperinsulinemia (23 +/- 1.4 mU/l) showed an increase in binding of 0.82 +/- 0.40, significantly different (p less than 0.05) from the decrease of 0.30 +/- 0.25 shown by the seven normoinsulinemic (11 +/- 1.4 mU/l) subjects, despite their similar age, weight, and blood glucose concentrations. These changes in binding were explained by alterations in receptor affinity. Thus, an anomalous postprandial increase in erythrocyte insulin receptor affinity occurs in some obese subjects with or without diabetes, and is related to hyperinsulinemia rather than hyperglycemia.

Adult↗