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Biomedical subjects

W A Scherbaum

Publications and source records attributed to W A Scherbaum.

At least 91 records · Page 5Linked to original sources
PubMed2000

Regulation of the diabetes-associated autoantigen IA-2 in INS-1 pancreatic beta-cells.

IA-2, a member of the protein tyrosine phosphatase family, represents a major target autoantigen in type 1 diabetes. To study the regulation of IA-2 gene expression, we used INS-1 insulinoma cells to analyze beta-cell signal transduction pathways as well as the effect of metabolic and hormonal factors involved in the regulation of the insulin secretory pathway. Quantitative competitive reverse transcriptase-polymerase chain reaction revealed that an increase of cellular cAMP mediated by forskolin (10 micromol/l, 24 h) or 3-isobutyl-1-methylxanthine (100 micromol/l, 24 h) induced maximal stimulation of IA-2 mRNA levels (451 +/- 85 and 338 +/- 86% compared with basal conditions; P < 0.001). In contrast, activation of protein kinase C (PKC) by short-term treatment with phorbol 12-myristate 13-acetate (PMA) (1 micromol/l, 6 h) did not alter IA-2 expression, whereas depletion of PKC by prolonged culturing (24 h) exerted a significant inhibition (57 +/- 24%; P < 0.05). cAMP-dependent upregulation was confirmed by the findings that glucagon (10 micromol/l, 24-48 h) increased levels of IA-2 mRNA (190 +/- 35%; P < 0.05), whereas short-term incubation with high glucose concentration showed no effect. However, prolonged incubation in high glucose (21 mmol/l) induced a time- and dose-dependent increase of IA-2 mRNA expression, reaching maximal values after 144 h (285 +/- 68%; P < 0.05). These studies demonstrate that stimuli of insulin secretion that operate by activation of adenylate cyclase generating cAMP significantly increase IA-2 gene expression. In contrast, activation of PKC by high glucose concentration or PMA exerted no effect, suggesting that IA-2 gene expression is not simply coupled to insulin secretion, but may be involved in the fine regulation of beta-cell function. These findings may be important to clarify the function of IA-2 in beta-cells and elucidate mechanisms involved in the induction of autoimmunity to IA-2.

1-Methyl-3-isobutylxanthine↗
PubMed1999

[Model trial: use and evaluation of a problem-oriented learning program in internal medicine].

BACKGROUND: Problem-based training is a new approach in medical education. It is in particular essential that students work actively with authentic medical cases. Modern software is appropriate for developing interactive case-based training systems and the use in teaching environments. This method is still rarely integrated within medical curricula. METHOD: In an educational trial with 287 students the conceptual background, feasibility and evaluation are discussed. The learning program CASUS was used to present the case of a macroprolactinoma for interactive training. A questionnaire with a return rate of 78% was used for evaluation. RESULTS: 96% of the students had no problems in learning how to handle and use the program. A major problem was to focus the contents of the program exactly to the students' needs. The students' judgement was independent of the individual computer skills. 82% of the students would like to use the program in the future. CONCLUSION: Case-based and computer-assisted learning increases motivation and probably improves the quality in medical education. Controlled trials have to be implemented in future to show the effectiveness and the long-term output of these learning systems.

Computer-Assisted Instruction↗
PubMed1999

[The heart and metabolic syndrome].

Most people with the Metabolic Syndrome die from thrombotic complications superimposed to degenerative arterial vascular lesions, mostly myocardial infarction. Type-2-Diabetes is a risk factor per se for such complications, but often clusters with dyslipoproteinemia, hypertension and obesity. This is referred to as "Metabolic Syndrome" and often operates on a genetically programmed susceptibility which accelerates the pathogenesis of coronary artery disease in front of a much wider diabetes specific cardiopathy. From a pathophysiological point of view none of these associated risk factors explains the pathogenetic series of events leading to the precipitation of an occlusive thrombus at sites of complicated coronary plaques. In patients with the Metabolic Syndrome the coagulation system is switched towards a prethrombotic state, involving increased plasmatic coagulation, diminished fibrinolysis, decreased endothelial thromboresistance and predominantly platelet hyperreactivity ("diabetic thrombocytopathy"). Some of these factors are associated with an increased coronary risk (e.g. fibrinogen, PAI-1, platelets), but are also directly linked to the pathogenesis of "atherothrombosis". Altered cardiac remodelling together with adhesion and coagulation mechanisms appears suitable to explain decreased functional performance of infarcted organs, decreased success of acute (reduced fibrinolytic response, no reflow phenomenon) and longterm intervention strategies for vessel patency (PTCA, CABG) in Diabetes. Glucose adjustment alone will not adequately neutralize these complex mechanisms, but in the situation of myocardial infarction eumetabolization with parenteral glucose-insulin-potassium infusion appears mandatory similar to non-diabetics. On the longterm a multidimensional interventional repertoire is required particularly in patients with the Metabolic Syndrome including antihypertensive, antidyslipoproteinemic and antithrombotic drugs, customized according to the individual patients needs as assessed by early diagnostic measures ("early secondary prevention").

Blood Glucose↗
PubMed1999

Comparative analysis of epitope recognition of glutamic acid decarboxylase (GAD) by autoantibodies from different autoimmune disorders.

Autoantibodies to GAD, an important marker of the autoimmune process in type I or insulin-dependent diabetes mellitus (IDDM), are also found in non-diabetic individuals with autoimmune polyendocrine syndrome type 1 (APS1), APS2, and stiff man syndrome (SMS). Most IDDM sera contain two distinct GAD antibody specificities, one of which targets an epitope region in the middle-third of GAD65 (IDDM-E1; amino acids 221-359) and one of which targets the carboxy-third of GAD65 (IDDM-E2; amino acids 453-569). Using 11 chimeric GAD65/GAD67 proteins to maintain conformation-dependent epitopes of GAD65, we compared the humoral repertoire of IgG antibodies from an individual with APS2-like disease (b35, b78, and b96) and MoAbs from an IDDM patient (MICA-2, MICA-3, and MICA-4). Neither the APS2 IgG antibodies nor the IDDM MoAbs bind the amino-terminal third of GAD65, but instead target the carboxy-terminal two-thirds of GAD65. Amino acids 270-359 (IDDM-E1) are targeted by one APS2 IgG antibody and MICA-4, while two other APS2 IgG antibodies, MICA-2 and MICA-3, target amino acids 443-585 (IDDM-E2). Using GAD65/67 chimera that span the IDDM-E2 region, we found that MICA-2 binds amino acids 514-528 of GAD65, but two APS2 IgG antibodies require this region and amino acids 529-570. In contrast, the binding of MICA-3 requires two discontinuous amino acid segments of GAD65 (452-513 and 528-569), but not amino acids 514-528. These results indicate that there are both similarities and differences in the humoral response to GAD65 in APS2 and IDDM.

Amino Acid Sequence↗
PubMed1999

Incidentally discovered pituitary lesions: high frequency of macroadenomas and hormone-secreting adenomas - results of a prospective study.

OBJECTIVE: With increasing use of computed tomography and magnetic resonance imaging, pituitary adenomas are being discovered incidentally with increasing frequency. However, limited data are available concerning the clinical importance and natural history of such 'incicentalomas'. We have undertaken a prospective study to investigate changes in adenoma size and endocrine and visual function in patients with incidentally discovered intrasellar masses. PATIENTS AND METHODS: Our study included 67 patients with incidentalomas of the pituitary gland during a 5-year period (1992-96). 50 of these patients were followed up prospectively over a mean period of 2.7 years. Initially, all patients underwent endocrine testing and ophthalmological examinations as well as magnetic resonance imaging or computed tomography scans. These investigations were repeated after 3 months and then annually. RESULTS: 42 (62.7%) out of 67 patients with incidentalomas had microadenomas whereas 37.3% had macroadenomas. Macroadenomas were found more frequently in men (52.2%). Visual field defects could be documented in 4.5% of the patients. Partial deficiency of anterior pituitary function was present in 14.9%. Eight patients (11.9%) had prolactinomas. An increase in adenoma size was detected in 3.2% of the microadenomas and in 26.3% of the macroadenomas within the follow-up period. CONCLUSION: Macroadenomas and hormone secreting adenomas are not uncommon in patients with pituitary incidentalomas. Macroadenomas should be closely monitored for tumour enlargement. All patients should undergo biochemical assessment and ophthalmological examination, since endocrine dysfunction or visual field defects may be present at the time a pituitary incidentaloma is detected.

Adenoma↗
PubMed1999

T cell reactivity to DR*0401- and DQ*0302-binding peptides of the putative autoantigen IA-2 in type 1 diabetes.

Type 1 diabetes is thought to be an autoimmune disease mediated by T lymphocytes recognizing critical islet cell antigens. Recently, the tyrosine phosphatase like protein IA-2 was suggested as a putative autoantigen in type 1 diabetes since autoantibodies are detected in sera of diabetic patients and prediabetic subjects. Similarly, T cell responses of peripheral blood lymphocytes of type 1 diabetic patients to this protein have been described. Only very few data is available about immunodominant epitopes of IA-2 recognized by T cells. We have studied T cell responses in type 1 diabetic patients and age and partly HLA matched controls to IA-2 peptides designed to bind HLA risk alleles of IDDM as DR*0401 and DQ*0302. Both diabetic patients and controls responded to IA-2ic and some of the peptides. Three peptides of the C-terminal region of IA-2 were recognised by T cells of a fraction of diabetic patients but at least two of these peptides triggered also T cell responses in DR*0401/DQ*0302-matched controls. Most peptides bound to different HLA alleles ("promiscous binders"). The identification of autoantigenic epitopes may offer clues to related sequences e.g. of viral origin what relates to models of diabetes pathogenesis ("molecular mimicry"). Secondly, the design of antigen- or even epitope-specific immune intervention strategies aiming at tolerization of disease specific T cells in type 1 diabetes may profit from the knowledge of immunodominant T cell epitopes of a putative autoantigen.

Adolescent↗
PubMed1999

Autoantibodies to adrenal cytochrome P450 antigens in isolated Addison's disease and autoimmune polyendocrine syndrome type II.

Adrenal P450 enzymes 21-hydroxylase (21OH), 17alpha-hydroxylase (17OH) and side chain cleavage enzyme (SCC) represent major target antigens in adrenal autoimmunity. To evaluate the diagnostic sensitivity of autoantibodies to recombinant adrenal antigens we established rapid and sensitive radioligand assays and compared the results with adrenocortical autoantibodies (ACA) as detected by the standard immunofluorescence test. A high prevalence of antibodies to 21OH (21OH-A) was observed in patients with isolated Addison's disease (IAD) and patients suffering from autoimmune polyendocrine syndrome type II (APS II). 21OH-A were found in 19 of 25 (76%) patients with IAD and in 34 of 40 (85%) patients with APS II. In contrast, antibodies to 17OH (17OH-A) as well as antibodies to SCC (SCC-A) were detected in 12 (30%) and 13 (33%) patients with APS II whereas only a few sera from patients with IAD had 17OH antibodies (n = 3) and SCC-A (n = 1), respectively (p < 0.0001). The majority of patients with 17OH-A (83.3%) or SCC-A (76.9%) were also found positive for 21OH-A and all three antibody specificities were positively correlated with the presence of ACA. Among 52 sera with ACA 49 (94.2%), 11 (21.2%), and 9 (17.3%) were positive for 21OH-A, 17OH-A and SCC-A, respectively. By combination of 21OH-A with 17OH-A all ACA positive individuals were identified. The availability of recombinant steroid P450 enzymes made it possible to develop radiobinding assays which allow simple, sensitive and quantitative detection of autoantibodies to defined adrenal autoantigens. We here demonstrate that autoantibodies to 21-hydroxylase are sensitive markers for autoimmune Addison's disease with and without polyglandular failure. The presence of 17OH-A or SCC-A may suggest the coexistence of or progression towards polyglandular autoimmunity.

Addison Disease↗
PubMed1999

Associations of fat and cholesterol intake with serum lipid levels and cardiovascular disease: the EURODIAB IDDM Complications Study.

The EURODIAB IDDM Complications Study, a cross-sectional, clinic-based study examined the fat and cholesterol intakes of European individuals with type 1 diabetes for possible relations to serum lipid levels (total cholesterol, HDL- and LDL-cholesterol, fasting triglycerides) and to the prevalence of cardiovascular disease (past history or electrocardiogram abnormalities). Fat intake (total fat, saturated fat, cholesterol) from 2,868 subjects with type 1 diabetes (mean age 32.9 +/- 10.2 years (range: 14-61 years), mean diabetes duration 14.7 +/- 9.4 years (range: 1-56 years)) was assessed by a standardized 3-day dietary record at the Nutrition Co-Ordinating Centre (Düsseldorf). Serum lipid levels were determined in the central laboratory (London) by standard enzymatic methods. Energy-adjusted total and LDL-cholesterol levels increased significantly with higher intakes of total fat, saturated fat and cholesterol. However, these relations were largely explained by concomitant decreases in dietary fibre intake. For levels of HDL-cholesterol and triglycerides no independent associations were observed with fat or cholesterol intake. Increased intakes of total fat, saturated fat and cholesterol were also related to higher prevalences of cardiovascular disease. These associations were, however, no longer significant after adjustment for dietary fibre intake for which we previously demonstrated independent associations with the serum cholesterol pattern and CVD. Since higher fat intakes are commonly accompanied by lower carbohydrate and fibre intakes we conclude that restricted intakes of cholesterol, saturated fat and total fat combined with higher fibre intakes beneficially affect both the levels of total and LDL-cholesterol and the risk for cardiovascular disease in European individuals with type 1 diabetes.

Adult↗
PubMed1999

Detection of Ob-receptor in human adrenal neoplasms and effect of leptin on adrenal cell proliferation.

Leptin, a hormone mainly secreted from adipose tissue, communicates a metabolic signal to the adrenal gland. Ob-Receptor (Ob-R) expression was reported in rat, mice and human adrenal glands. This study intended to investigate possible differences in the Ob-R expression and distribution of Ob-R protein in human adrenal tumors as compared to normal adrenal tissue. Proliferative effects of leptin were analyzed in the human adrenocortical carcinoma cell line (NCI-H295). The full length Ob-R mRNA and the isoforms B219.1 and B219.3 could be demonstrated by RT-PCR in all adrenal tumors (n=8), the tumor cell line (NCI-H295) and normal tissue. In contrast the Ob-R isoform B219.2 was absent in the carcinoma cell line and in most of the adrenal tumors (n=5), whereas it was present in normal adrenals. The Ob-R protein could be demonstrated in benign and malignant adrenocortical tumors. Pheochromocytomas showed only a weak immunostaining with the human Ob-R antibody. Human leptin did not affect the proliferation or variability of adrenal tumor cells as demonstrated by [3H]-thymidine assay and WST-1 test. In conclusion, although functional leptin receptors are expressed in human adrenal tumors, leptin does not regulate tumor cell proliferation.

Adenoma↗
PubMed1999

Fas-Mediated apoptosis is inhibited by TSH and iodine in moderate concentrations in primary human thyrocytes in vitro.

Programmed cell death (apoptosis) can be found in normal thyroid tissue and in various diseases affecting the thyroid gland. The Fas/Fas ligand (FasL) system is involved in the induction of apoptosis in human thyrocytes. Cross-linking the Fas receptor with its own ligand or with an antibody capable of oligomerizing with the receptor induces programmed cell death. We investigated the role of Fas-induced apoptosis in primary human thyrocytes in vitro. Cell cultures of normal human thyrocytes were prepared from specimens obtained during surgery for uninodular goiter. Apoptosis was induced by incubation of the cells with a monoclonal IgM anti-Fas antibody. The presence of apoptosis was determined by FACS analysis of FITC-labelled annexin V binding combined with dye exclusion of propidium iodide. We found a significant rate of Fas-induced apoptosis in normal thyrocytes after activation with a monoclonal anti-Fas antibody. TSH was able to inhibit Fas-mediated apoptosis in a dose-dependent manner. This effect was more pronounced when thyrocytes were incubated in the presence of interferon-gamma. Low concentrations of iodine were able to inhibit apoptosis, while high concentrations of iodine increased the rate of Fas-induced apoptosis. Our results show that Fas-mediated apoptosis is inducible in normal human thyrocytes in vitro and is influenced by TSH and iodine. The Fas/FasL system may play an important role in the regulation of cell number within the thyroid gland, and may be involved in the processes leading to goiter in iodine deficiency.

Apoptosis↗
PubMed1999

Antibodies to human recombinant tissue transglutaminase measured by radioligand assay: evidence for high diagnostic sensitivity for celiac disease.

Celiac disease is associated with endomysial antibodies (EmA), which have recently been reported to be directed to tissue transglutaminase (tTG). To demonstrate binding of antibodies to recombinant tTG, human tTG was cloned, expressed by in vitro transcription/translation and used to develop novel radioligand assays for combined and single detection of immunoglobulin A (IgA) and G (IgG)-specific antibodies. IgA and IgG-tTGA were found in 43 (95.6%) of 45 patients with newly-diagnosed celiac disease verified by biopsy. In addition, all 30 sera from patients with gastrointestinal symptoms and positive EmA were positive for IgA-tTGA, and all but one serum (96.7%) had antibodies of the IgG class. Receiver-operating characteristic analysis including 574 sera from healthy controls revealed a specificity of 99.5%. By means of these new assays, we identified all patients with endomysial antibodies and achieved, at equal specificity, an even improved sensitivity (95.6%) as compared to EmA (91.1%) detected by the standard immunofluorescence test. Here, we have provided direct evidence that recombinant tTG is a major target of antibodies in celiac disease. Our data suggest that tTGA measured by radioligand assay have the power to overcome the limitations of the EmA-test. This new strategy may considerably facilitate large-scale screening for silent and latent celiac disease.

Adolescent↗
PubMed1999

The combination of antibodies to GAD-65 and IA-2ic can replace the islet-cell antibody assay to identify subjects at risk of type 1 diabetes mellitus.

First-degree relatives of type 1 diabetic patients are at increased risk of developing diabetes and, until recently, islet cell antibodies (ICA) have represented the major risk marker used for identification of individuals at increased risk for subsequent progression to diabetes. In order to determine the value of antibodies to GAD-65 and IA-2ic to identify individuals at high risk for type 1 diabetes mellitus, we measured both autoantibodies and ICA in 1436 first-degree relatives of patients with type 1 diabetes. In addition, the sera were analyzed for thyroid, adrenal and gastric-parietal cell autoantibodies as markers for possible polyendocrine involvement. GAD-65 Abs were found in 135 out of 1436 (9.4%) first-degree relatives and in 57 of 98 (58.2%) ICA-positive subjects. IA-2ic were detected in 52 of 1436 (3.6%) first-degree relatives and in 44 of 98 (44.8%) ICA-positive relatives. IA-2ic and/or GAD-65 were detected in 73 of 98 (74.5%) ICA-positive relatives. Interestingly, antibodies to GAD-65 and/or IA-2ic were present in 91.2% of individuals with more than 20JDF-units. Anti-IA-2ic and GAD-65 were positively correlated with high levels of ICA. Anti-IA-2ic and GAD-65 were found in 19% and 48.5% of subjects with ICA levels of 5-20JDF-u but in 68.8% and 76.5% of individuals with ICA of 40JDF-u or more, respectively (p < 0.001), compared to subjects with ICA levels less than 5 JDF-u. When autoantibody frequencies among the relatives were analyzed according to relationship to the proband, the offspring and siblings had a higher frequency of ICA and IA-2ic (p<0.05) than the subgroup of parents. A significant association was observed between IA-2ic and thyroid antibodies. In addition, higher levels of IA-2ic were found in relatives with positive TPO antibodies (p < 0.001); this correlation was particularly strong in offspring and siblings (p < 0.01). Determination of GAD-65 and IA-2ic antibodies may be considered as an alternative to primary ICA-screening, enabling the screening of large populations.

Adolescent↗
PubMed1999

High frequency of diabetes-specific autoantibodies in parents of children with type 1 diabetes. DENIS study group.

Strategies to identify subjects at risk for type 1 diabetes are largely based on the detection of autoantibodies directed to various beta cell autoantigens. Most previous studies only comprise siblings and children of patients with type 1 diabetes; only scare data are available on the antibody profile in older relatives. In this study, we examined the prevalence of cytoplasmic islet cell antibodies (ICA), antibodies to glutamic acid decarboxylase (GADA), antibodies to the protein tyrosine phosphatase IA-2 (IA-2A) and IA-2beta (IA-2betaA) in 531 unaffected parents of patients with type 1 diabetes, and compared the results with antibody frequencies in 2425 siblings. The frequency of ICA, GADA and IA-2A was substantially higher among siblings as compared to parents of patients with type 1 diabetes (8.0% vs. 4.5%, 8.0% vs. 4.3%, and 4.5% vs. 1.9%, respectively; p<0.01). However, subdividing the probands according to age revealed a high prevalence of ICA (5.5 %), GADA (5.9 %), and IA-2A (3.1%) among parents aged 31 -40 years which was similar to that observed in siblings above 20 years of age (6.4%, 6.4%, and 3.1%). In both cohorts, GADA and IA-2A were significantly associated with the presence of ICA. The combined screening for GADA and IA-2A identified 100% of parents and 91.9% of siblings at high risk for type 1 diabetes (>10 JDF-U). Furthermore, the analysis of antibody combinations revealed that among antibody positive individuals the percentage of subjects with two or three antibodies was even higher in parents (69.0%) than in siblings (58.2%). The present study shows a high frequency of single and multiple autoantibodies in unaffected parents of patients with type 1 diabetes. Our data indicate that GAD and IA-2 not only represent the major target of autoantibodies in young siblings but also in adult relatives. These findings may be important for the design of future intervention studies.

Adolescent↗
PubMed1999

Dendritic cell immunotherapy induces antitumour response in parathyroid carcinoma and neuroendocrine pancreas carcinoma.

Parathyroid carcinomas and neuroendocrine carcinomas of the pancreas are rare malignancies in humans. Because of their low radio- and chemosensibility, they fail to respond to conventional therapy. We therefore tested a dendritic cell immunotherapy in an attempt to control the tumour growth in two patients. Studies on mice and humans have demonstrated the potent capacity of dendritic cells to induce specific antitumour immunity. Mature dendritic cells were generated from peripheral blood monocytes in the presence of granulocyte/macrophage colony-stimulating factor, interleukin 4 and tumour necrosis factor alpha. Dendritic cells were either loaded with parathyroid hormone (PTH) or with (pancreas) tumour-derived lysate (TL), respectively, and were delivered by subcutaneous injections. All immunizations were well tolerated with no side effects, and were administered on an outpatient basis. After repeated vaccinations, specific in vivo immune response was demonstrated by positive delayed-type hypersensitivity (DTH) toward PTH or TL, demonstrating the efficient generation of antigen-specific memory T-cells. DTH reactivity was accompanied by a significant decrease of tumour markers in both patients. This approach might be generally applicable to other advanced, radio- and chemotherapy-resistant endocrine malignancies.

Biomarkers, Tumor↗