Search PubMed⌕ Search

Biomedical subjects

U Weiss

Publications and source records attributed to U Weiss.

At least 37 records · Page 2Linked to original sources
PubMed1998

Differential extraction of proteins from paraformaldehyde-fixed cells: lessons from synaptophysin and other membrane proteins.

While investigating the localization of synaptophysin in PC12 cells using immunofluorescence microscopy, we noticed a striking difference in its apparent subcellular distribution depending on whether digitonin or Triton X-100 was used as permeabilization agent of paraformaldehyde (PFA)-fixed cells. We found that this difference was due to epitope inaccessibility in the digitonin-treated cells combined with an almost quantitative extraction of the antigen on Triton X-100 permeabilization. Both phenomena were differential with respect to the various synaptophysin-containing compartments. The extraction of antigen from PFA-fixed cells was also seen with other membrane proteins but not with cytosolic proteins and proteins in the lumen of the secretory pathway. Significantly, some of the membrane proteins were extracted from the PFA-fixed cells in higher-molecular-weight forms which we believe represent their in vivo oligomeric states. The implications of our observations are discussed with respect to the method of immunofluorescence microscopy and also to the possible use of paraformaldehyde as an in vivo crosslinker for the study of membrane protein quaternary structure.

Animals↗
PubMed1998

Sustained hyperglycemia in vitro down-regulates the GLUT1 glucose transport system of cultured human term placental trophoblast: a mechanism to protect fetal development?

The trophoblast of human placenta is directly exposed to the maternal circulation. It forms the main barrier to maternal-fetal glucose transport. The present study investigated the effect of sustained hyperglycemia in vitro on the glucose transport system of these cells. Trophoblasts isolated from term placentas and immunopurified were cultured for 24, 48, and 96 h in DMEM containing either 5.5 (normoglycemia) or 25 mmol/l D-glucose (hyperglycemia), respectively. Initial uptake of glucose was measured using 3-O-[14C]methyl-D-glucose. Kinetic parameters were calculated as K(M) = 73 mmol/l and Vmax = 29 fmol s(-1) per trophoblast cell. Uptake rates of cells cultured under hyperglycemic conditions did not differ at exogenous D-glucose concentrations in the physiological range (1, 5.5, 10, and 15 mmol/l), but were significantly decreased by 25% (P<0.05) at diabetes-like concentrations (20 and 25 mmol/l) as compared to normoglycemic conditions. This effect was due to a decrease in Vmax (-50%), whereas K(M) remained virtually unaffected. GLUT1 mRNA levels were lower by 50% (P<0.05; Northern blotting) and GLUT1 protein was reduced by 16% (P<0.05; Western blotting) in trophoblast cells cultured under hyperglycemic vs. normoglycemic conditions. We conclude that prolonged hyperglycemia in vitro reduces trophoblast glucose uptake at substrate concentrations corresponding to blood levels of poorly controlled diabetic gravidas. This effect is due to diminished GLUT1 mRNA and protein expression in the trophoblast.

3-O-Methylglucose↗
PubMed1997

Functional MRI reveals left amygdala activation during emotion.

The potential of functional magnetic resonance imaging (fMRI) for experimental studies of the brain and behavior considerable given its superior time and spatial resolution, but few studies have attempted to validate them against established methods for measuring cerebral activation. In a previous study absolute regional cerebral blood flow was measured in 16 healthy individuals using quantitative H215O-PET during standardized happy and sad mood induction and during two non-emotional control conditions. During sad mood, blood flow increased in the left amygdala and these changes correlated with shifts towards a negative affect. In the present study blood oxygenation level dependent (BOLD) changes were measured with fMRI during the same experimentally controlled mood states and control tasks. Twelve right-handed normal subjects were examined with a T2*-weighted FLASH sequence. A significant increase in signal intensity was found during sad as well as happy mood induction in the left amygdala. This converging evidence supports the potential of fMRI for advancing the understanding of neural substrates for emotional experience in humans.

Adult↗
PubMed1997

Hepatic function in a family with a nonsense mutation (R154X) in the hepatocyte nuclear factor-4alpha/MODY1 gene.

Maturity-onset diabetes of the young (MODY) is a genetically heterogeneous monogenic disorder characterized by autosomal dominant inheritance, onset usually before 25 yr of age, and abnormal pancreatic beta-cell function. Mutations in the hepatocyte nuclear factor(HNF)-4alpha/MODY1, glucokinase/MODY2, and HNF-1alpha/MODY3 genes can cause this form of diabetes. In contrast to the glucokinase and HNF-1alpha genes, mutations in the HNF-4alpha gene are a relatively uncommon cause of MODY, and our understanding of the MODY1 form of diabetes is based on studies of only a single family, the R-W pedigree. Here we report the identification of a second family with MODY1 and the first in which there has been a detailed characterization of hepatic function. The affected members of this family, Dresden-11, have inherited a nonsense mutation, R154X, in the HNF-4alpha gene, and are predicted to have reduced levels of this transcription factor in the tissues in which it is expressed, including pancreatic islets, liver, kidney, and intestine. Subjects with the R154X mutation exhibited a diminished insulin secretory response to oral glucose. HNF-4alpha plays a central role in tissue-specific regulation of gene expression in the liver, including the control of synthesis of proteins involved in cholesterol and lipoprotein metabolism and the coagulation cascade. Subjects with the R154X mutation, however, showed no abnormalities in lipid metabolism or coagulation except for a paradoxical 3.3-fold increase in serum lipoprotein(a) levels, nor was there any evidence of renal dysfunction in these subjects. The results suggest that MODY1 is primarily a disorder of beta-cell function.

Adult↗
PubMed1997

Cholinergic control of catecholamine release in the eel.

The perifused posterior cardinal vein of the American eel (Anguilla rostrata) releases spontaneously dopamine (DA), norepinephrine (NE), and epinephrine (E). NE and E are secreted by innervated chromaffin cells, while DA is most likely released from a component of the vascular wall. Stimulation with acetylcholine strongly enhances the release of DA and E, and to a lesser degree the release of NE. Nicotine stimulates the release of all three catecholamines. Muscarine reduces the basal release of NE. Muscarine does not prevent nicotinic stimulation of NE and E release, but abolishes the nicotine effect on DA release. The muscarinic antagonist atropine stimulates the release of NE, but not of DA and E. The beta-adrenergic receptor antagonist propranolol suppresses the acetylcholine-stimulated release of NE and E, and reduces the DA response. From these findings, it appears that (1) nicotinic receptors regulate NE and E secretion from the chromaffin cells, (2) muscarinic receptors inhibit basal NE release, and (3) acetylcholine-stimulated release of NE and E requires the interaction with adrenergic receptors. On the other hand, DA release involves both nicotinic and adrenergic receptors, while the reduction of nicotine-stimulated (but not basal) DA release involves muscarinic receptors.

Acetylcholine↗
PubMed1997

Somatotosensory evoked potentials during baroreceptor stimulation in chronic low back pain patients and normal controls.

Nineteen chronic low back pain patients (aged 19-63) and 17 controls (aged 20-41) received electrical pain stimuli during manipulation of their carotid baroreceptors. The non-invasive mechanical manipulation of baroreceptors, using the PRES technique (Phase Related External Suction), simulates the end-effects of phasic blood pressure changes. This technique was developed to assess pain responses induced by changes in blood pressure without the typical shortcomings of pharmacological manipulation or lack of a control condition. During maximum baroreceptor activity, there was an unexpected increase in the amplitude of the somatosensory evoked potentials (SEPs) elicited by the electrical pain stimuli condition (N150-P260 peak-to-peak). In most other studies the opposite effect was found, with decreased pain responses during maximum baroreceptor activity. The chronic pain group reported greater pain during highest baroreceptor activation than did the controls. In addition, the chronic pain group showed lower diastolic blood pressure. To determine whether pain and baroreceptor responses observed in the chronic pain group depended on lower blood pressure levels, a second experiment with a non-clinical sample was performed. Results showed that lower tonic blood pressures are associated with greater baroreceptor activity amplifying pain, while higher blood pressure is associated with pain dampening during high baroreceptor activity. Data suggested that the differences in pain responses found in low back pain patients were associated with their lower tonic blood pressure levels. It is proposed that in general, lower blood pressures may be associated with greater pain during baroreceptor activation.

Adolescent↗
PubMed1996

HLA class II gene frequencies in Crohn's disease: a population based analysis in Germany.

BACKGROUND: Ulcerative colitis is the only known inflammatory bowel disease associated with particular HLA alleles. Whereas the association with the HLA-DRB1*15 allele has been described in several independent studies for ulcerative colitis, no contribution of HLA alleles to susceptibility in Crohn's disease has yet been shown. AIM: This study was designed to study the strength of association of HLA class II alleles as risk markers for Crohn's disease in a homogenous population in Germany. PATIENTS: A total of 4251 randomly selected control subjects, and 162 unrelated subjects with Crohn's disease were studied. Subjects were studied for their HLA-DRB1, HLA-DQA1, and HLA-DQB1 alleles. METHOD: HLA DNA typing was performed after locus specific amplification with the polymerase chain reaction and reverse dot blot hybridisation. RESULTS: The HLA-DRB1*07 was the only HLA class II allele found to be significantly associated with Crohn's disease (relative risk (RR) = 1.9, 95% CI: 1.66 to 2.14; p = 0.0001). This association remained significant after correction for the number of DRB1 alleles compared. In patients with disease onset before 35 years the RR for the disease in HLA-DRB1*07 positive subjects was found to be higher (RR = 3.1, 95% CI: 2.44 to 3.76). The HLA-DRB1*03 was significantly decreased in frequency in Crohn's disease (RR = 0.5, 95% CI: 0.39 to 0.61; p = 0.0028). CONCLUSION: The HLA-DRB1*07 allele provides risk for the disease especially in patients with younger ages of onset. These data also provide indirect evidence for an immunogenetically based heterogeneity of the disease.

Adolescent↗
PubMed1995

Computer-controlled flushing for long-term cannulation in freely moving rats.

An in vivo long-term perfusion system is presented, which is based on automated, computer-controlled high-frequency heparin (10 U/mL) flushing of the cannula inserted into the tail artery of freely moving rats. The short flushing intervals as achieved with this system guarantee stable conditions throughout an experiment of several days, and reduce blood clotting and the infiltration of fibroblasts. In addition, a specially developed software enables the periodical application of test substances into the blood stream under time-controlled conditions over long periods. The system can be used continuously to follow up blood parameters in single animals without significant elicitation of stress-sensitive plasma catecholamines for up to 12 days.

Animals↗
PubMed1995

In vitro stimulation with glutamic acid decarboxylase (GAD65) leads to an oligoclonal response of peripheral T-cells in an IDDM patient.

The enzyme glutamic acid decarboxylase (GAD65) is a major autoantigen in insulin-dependent diabetes mellitus (IDDM). To study T-cell reactivity towards GAD, peripheral blood leucocytes from seven patients with IDDM and five control subjects were stimulated in vitro with recombinant GAD. All diabetics studied were heterozygous for diabetes-associated HLA alleles, i.e. HLA-DRB1*03,*04-DQB1 *0302,*0201. A single IDDM subject (no. GAD65.05) revealed a strong response against GAD65. After stimulation, his T-cell receptor beta (TCRBV) usage was found to be oligoclonal. The sequence analysis of the putative peptide binding region of the T-cell receptor (CDR3 region) of 37 GAD-reactive T-cell clones revealed no common CDR3 motif. The stimulation of GAD-reactive T-cells could be inhibited with anti-class II monoclonal antibodies, indicating a class II restricted T-cell response. In addition, GAD65-responsive T-cells revealed a Th1 cytokine response pattern. The author's data suggest that GAD-reactive T-cells of Th1 phenotype can be obtained after in vitro stimulation of peripheral blood leucocytes from an HLA-DRB1*03/*04 heterozygous IDDM patient. The lack of a common CDR3 motif suggests the absence of an immunodominant T-cell epitope in that patient, or may indicate receptor repertoire spreading of peripheral T-lymphocytes.

Amino Acid Sequence↗
PubMed1994

The disulfide bond in chromogranin B, which is essential for its sorting to secretory granules, is not required for its aggregation in the trans-Golgi network.

Chromogranin B (secretogranin I), a protein sorted to secretory granules in many endocrine cells and neurons, undergoes selective aggregation during the sorting process in the trans-Golgi network. Reduction of the single, highly conserved intramolecular disulfide bond of chromogranin B by exposure of intact PC12 cells to the thiol reducing agent dithiothreitol has previously been shown to cause its missorting to the constitutive pathway of secretion. Using saponin perforation of membrane vesicles in aggregative buffer mimicking the milieu in the lumen of the trans-Golgi network (pH 6.4, 10 mM calcium), we show here that treatment with dithiothreitol does not prevent the aggregation of chromogranin B in this compartment. This implies that the loop in the chromogranin B polypeptide that is formed by the disulfide bond has a critical role in the membrane recognition of aggregated chromogranin B during secretory granule formation.

Animals↗
PubMed1994

[Movement, play and sports in the treatment of drug addicts].

In 1992 a campaign was initiated to bring to attention new ways for drug prevention in adolescents for health promotion in addicts and for therapy and follow-up of ex-addicts. By this broad base the Swiss Health Authority and the Federal Sports Institute at Magglingen together with partners from Swiss sport and addiction-care organizations try to contribute to a reduction of drug-related problems in Switzerland. The following article bases mainly on experiences with long-term therapy of the 'Drogenhilfe Aebihus' in Leubringen.

Adolescent↗