Search PubMed⌕ Search

Biomedical subjects

I Weber

Publications and source records attributed to I Weber.

At least 37 records · Page 2Linked to original sources
PubMed1999

Cytoskeletal protein mutations and cell motility in Dictyostelium.

Dictyostelium is a suitable experimental system in which to study the effects of mutations in actin-binding proteins on cell motility. Three cytoskeletal mutants that show distinct alterations in cell shape, chemotactic movement and cytokinesis serve to illustrate the diversity of phenotypes. Cells lacking talin, a protein which in many mammalian cell types is a constituent of focal complexes that link the actin cytoskeleton to the plasma membrane, are strongly impaired in adhesion to external surfaces. Coronin is an actin-associated protein that belongs to the WD-repeat family of proteins, which are engaged in protein-protein interactions involved in signalling pathways. Cells lacking coronin build large hyaline protrusions at their leading edge, diagnostic of an imbalance in the actin polymerization/depolymerization cycle. Cells devoid of a pair of cortexillins, which are novel members of the spectrin/alpha-actinin superfamily of actin-binding proteins, form an atypical cleavage furrow on a solid surface and fail to divide in suspension. Other mutants in which one or more actin-binding proteins have been knocked out have weaker phenotypes. With these mutants, cells need to be subjected to special conditions in order to reveal an effect on cell motility. For instance, only on weakly adhesive surfaces is a disturbance in the spatio-temporal co-ordination of protrusion and retraction of the cell body, and of the attachment to and detachment from a substratum, observed in a mutant that lacks three actin-binding proteins: alpha-actinin, 120 kDa F-actin gelation factor and severin.

Animals↗
PubMed1999

Computer-assisted morphometry of cell-substratum contacts.

AIM: Quantitative analysis of size and shape of the cell-substratum contacts in Dictyostelium and comparison of these parameters between wild-type cells and the cells bearing cytoskeletal protein mutations. METHODS: Reflection interference contrast microscopy (RICM) was used to image the areas of contact between aggregation-competent Dictyostelium cells and weakly adhesive mica surfaces. The cell-substratum contact areas were automatically identified in RICM micrographs by digital image processing. Information about the size and shape of the contact areas was obtained by using the shape descriptors based on two-dimensional geometrical moment invariants. RESULTS: Lack of either of the two actin-crosslinking proteins, a-actinin and 120 kDa gelation factor, similarly affects the cell-substratum interactions of Dictyostelium cells. The shape descriptors, elongation and dispersion, of the contact areas were reduced by 10% to 30% in mutant cells when compared to the wild type, but the size of the contacts was not affected. CONCLUSION: Video microscopy combined with digital image processing and quantitative image analysis is capable of revealing small phenotypic effects of cytoskeletal protein mutations on the level of single cells. Such automated microscopic methods are expected to gain importance and find a widespread use in biomedicine.

Actinin↗
PubMed1998

Normalization of fasting glycaemia by intravenous GLP-1 ([7-36 amide] or [7-37]) in type 2 diabetic patients.

Intravenous GLP-1 [7-36 amide] can normalize fasting hyperglycaemia in Type 2 diabetic patients. Whether GLP-1 [7-37] has similar effects and how quickly plasma glucose concentrations revert to hyperglycaemia after stopping GLP-1 is not known. Therefore, 8 patients with Type 2 diabetes (5 female, 3 male; 65+/-6 years; BMI 34.3+/-7.9 kg m(-2); HbA1c 9.6+/-1.2%; treatment with diet alone (n=2), sulphonylurea (n=5), metformin (n=1)) were examined twice in randomized order. GLP-1 [7-36 amide] or [7-37] (1 pmol kg(-1)min(-1) were infused intravenously over 4 h in fasted subjects. Plasma glucose (glucose-oxidase), insulin and C-peptide (ELISA) was measured during infusion and for 4 h thereafter. Indirect calorimetry was performed. Fasting hyperglycaemia was 11.7+/-0.9 [7-36 amide] and 11.3+/-0.9 mmol l(-1) [7-37]. GLP-1 infusions stimulated insulin secretion approximately 3-fold (insulin peak 168+/-32 and 156+/-47 pmol l(-1), p<0.0001 vs basal; C-peptide peak 2.32+/-0.28 and 2.34+/-0.43 nmol l(-1), p<0.0001, respectively, with GLP-1 [7-36 amide] and [7-37]). Four hours of GLP-1 infusion reduced plasma glucose (4.8+/-0.4 and 4.6+/-0.3 mmol l(-1), p<0.0001 vs basal values), and it remained in the non-diabetic fasting range after a further 4 h (5.1+/-0.4 and 5.3+/-0.4 mmol l(-1), for GLP [7-36 amide] and [7-37], respectively). There were no significant differences between GLP-1 [7-36 amide] and [7-37] (glucose, p=0.99; insulin, p=0.99; C-peptide, p=0.99). Neither glucose oxidation nor lipid oxidation (or any other parameters determined by indirect calorimetry) changed during or after the administration of exogenous GLP-1. In conclusion, GLP-1 [7-36 amide] and [7-37] normalize fasting hyperglycaemia in Type 2 diabetic patients. Diabetes therapy (diet, sulphonyl ureas or metformin) does not appear to influence this effect. In fasting and resting patients, the effect persists during administration of GLP-1 and for at least 4 h thereafter, without rebound. Significant changes in circulating substrate concentrations (e.g. glucose) are not accompanied by changes in intracellular substrate metabolism.

Age of Onset↗
PubMed1998

Immunohistochemical characterization of the pancreatic cellular infiltrate in normal pancreas, chronic pancreatitis and pancreatic carcinoma.

BACKGROUND/AIMS: Chronic pancreatitis is histologically characterized by an extended fibrosis and infiltration of leukocytes. We intended to differentiate the infiltration to evaluate the inflammatory process. METHODS: Samples of tissues of normal pancreas (NP, n = 12), of chronic pancreatitis (CP, n = 7), and pancreatic tissues surrounding pancreatic carcinoma (CA, n = 7) were investigated by immunohistochemical staining using the APAAP technique. RESULTS: In normal pancreas, mononuclear cells (47.1 +/- 26.0 cells/mm2) were observed with a predominance of macrophages (56.3%) and T lymphocytes (31.3%) which were differentiated in CD8+ lymphocytes (9.3 +/- 7.2 cells/ mm2) and CD4+ lymphocytes (6.7 +/- 3.2 cells/mm2). Rarely, plasma cells (5.3%) and B lymphocytes (7.1%) could be detected. In pancreatic tissue of patients with CP and in CA there was a significant increase of mononuclear cells to 264.4 +/- 120.3 cells/mm2 and 284.3 +/- 67.8 cells/mm2, respectively. In both diseases percentages of T lymphocytes (CP: 50.5%; CA: 48.1%) were higher than in normal controls. CD4+/CD8+ ratio of 0.77 in CP and 0.82 in CA demonstrated a predominance of CD8+ cells compared to the peripheral blood. In NP and CA, nearly all T lymphocytes expressed CD45R0 identifying memory cells, while only 58% of T lymphocytes were CD45R0 positive in CP. CONCLUSION: Our data suggest that the investigated cases of CP were of a common inflammatory type rather than due to an autoimmunological reaction. CD8+ T lymphocytes were the predominant T cell subset in the inflammatory infiltrates in both CP and CA.

Adenocarcinoma↗
PubMed1997

Three-dimensional patterns and redistribution of myosin II and actin in mitotic Dictyostelium cells.

Myosin II is not essential for cytokinesis in cells of Dictyostelium discoideum that are anchored on a substrate (Neujahr, R., C. Heizer, and G. Gerisch. 1997. J. Cell Sci. 110:123-137), in contrast to its importance for cell division in suspension (DeLozanne, A., and J.A. Spudich. 1987. Science. 236:1086-1091; Knecht, D.A., and W.F. Loomis. 1987. Science. 236: 1081-1085.). These differences have prompted us to investigate the three-dimensional distribution of myosin II in cells dividing under one of three conditions: (a) in shaken suspension, (b) in a fluid layer on a solid substrate surface, and (c) under mechanical stress applied by compressing the cells. Under the first and second conditions outlined above, myosin II does not form patterns that suggest a contractile ring is established in the furrow. Most of the myosin II is concentrated in the regions that flank the furrow on both sides towards the poles of the dividing cell. It is only when cells are compressed that myosin II extensively accumulates in the cleavage furrow, as has been previously described (Fukui, Y., T.J. Lynch, H. Brzeska, and E.D. Korn. 1989. Nature. 341:328-331), i.e., this massive accumulation is a response to the mechanical stress. Evidence is provided that the stress-associated translocation of myosin II to the cell cortex is a result of the dephosphorylation of its heavy chains. F-actin is localized in the dividing cells in a distinctly different pattern from that of myosin II. The F-actin is shown to accumulate primarily in protrusions at the two poles that ultimately form the leading edges of the daughter cells. This distribution changes dynamically as visualized in living cells with a green fluorescent protein-actin fusion.

Actins↗
PubMed1997

Talin-null cells of Dictyostelium are strongly defective in adhesion to particle and substrate surfaces and slightly impaired in cytokinesis.

Dictyostelium discoideum contains a full-length homologue of talin, a protein implicated in linkage of the actin system to sites of cell-to-substrate adhesion in fibroblasts and neuronal growth cones. Gene replacement eliminated the talin homologue in Dictyostelium and led to defects in phagocytosis and cell-to-substrate interaction of moving cells, two processes dependent on a continuous cross talk between the cell surface and underlying cytoskeleton. The uptake rate of yeast particles was reduced, and only bacteria devoid of the carbohydrate moiety of cell surface lipopolysaccharides were adhesive enough to be recruited by talin-null cells in suspension and phagocytosed. Cell-to-cell adhesion of undeveloped cells was strongly impaired in the absence of talin, in contrast with the cohesion of aggregating cells mediated by the phospholipid-anchored contact site A glycoprotein, which proved to be less talin dependent. The mutant cells were still capable of moving and responding to a chemoattractant, although they attached only loosely to a substrate via small areas of their surface. With their high proportion of binucleated cells, the talin-null mutants revealed interactions of the mitotic apparatus with the cell cortex that were not obvious in mononucleated cells.

Animals↗
PubMed1997

Cu/Zn-SOD in human pancreatic tissue and pancreatic juice.

CONCLUSION: Cu/Zn-SOD is present in pancreatic juice and tissue. Immunohistochemical studies reveal a localization of this enzyme in islet, duct, and centroacinar cells, but to a much lower extent in pancreatic acinar cells. BACKGROUND: It is generally accepted that oxygen radicals are involved in the pathogenesis of acute and chronic pancreatitis. An imbalance of radical-generating and radical-scavenging processes is thought to lead to the damage of pancreatic acinar cells that initiate the autodigestion of the whole organ. METHODS: We investigated the distribution pattern of the cytosolic radical-scavenging enzyme, copper/zinc-superoxide dismutase (Cu/Zn-SOD), in pancreatic juice and tissue. In patients with chronic pancreatitis or pancreatic malignancies, Cu-Zn-SOD was quantitated in different fractions of pancreatic juice by means of an enzyme immunoassay using two Cu/Zn-SOD-specific monoclonal antibodies. Cryostat or paraffin sections of pancreatic tissue were analyzed by immunohistochemical techniques. RESULTS: We found this enzyme to be present in the first secretin-triggered fraction of endoscopically obtained pancreatic juice in concentrations similar to serum. In contrast, after cholecystokinin stimulation, only low levels could be found in pancreatic juice, indicating that this enzyme is not actively secreted. Interestingly, pancreatic juice of patients with chronic pancreatitis or pancreas tumor contained higher levels (25-29 ng/mL) of Cu/Zn-SOD than juice of controls without pancreatic diseases (15 ng/mL). Immunohistochemical studies of Cu/Zn-SOD in pancreatic tissue revealed a more intense staining of duct cells, islet cells, and centroacinar cells, whereas acinar cells showed almost no staining for Cu/Zn-SOD.

Adult↗
PubMed1997

Image processing for combined bright-field and reflection interference contrast video microscopy.

Image processing algorithms for automatic extraction of cell body contours and cell-substratum contacts from video images, which were obtained by bright-field microscopy and reflection interference contrast microscopy, respectively, are described. Double-view imaging, which combines these two optical techniques, is used to investigate the relationship between cell-to-substratum adhesion and cell shape changes during locomotion of the amoeboid cells of Dictyostelium discoideum. Contact areas of cells are extracted from reflection interference contrast images via a routine which performs binarisation on the basis of threshold estimation, as it is calculated by a histogram minimum method. Boundaries of cells are extracted from bright-field images by utilising and algorithm that includes background subtraction and binarisation based on texture discrimination by means of a rank operator.

Animals↗
PubMed1996

Adhesion complexes formed by OVCAR-4 cells on laminin 1 differ from those observed on fibronectin.

Cell adhesion to laminin 1 or to fibronectin is mediated by distinct sets of integrins and is differentially regulated by protein kinase C (PKC). It suggests that upon integrin ligation to laminin 1 or to fibronectin different intracellular signaling pathways could be activated. we have therefore investigated the formation of signaling complexes induced during cell adhesion to laminin 1 or to fibronectin. Following cell adhesion to laminin 1 the re-arrangement of the cytoskeleton was slower than that observed on fibronectin and it was activated by treating the cells with H-7, an inhibitor of PKC. Conversely, treatment of laminin-adhering cells with a PKC activator resulted in a rapid disorganization of the actin cyto skeleton while a similar treatment had no effect on fibronectin-adhering cells. These results suggested that the structural organization of the adhesion complexes might be substrate-specific and might correspond to a different arrangement of cytoskeletal and/or cytoplasmic proteins. Reflection interference contrast microscopy (RICM) images revealed that cell-substratum contacts formed on laminin 1 were not well differentiated in contrast to those developed on fibronectin. However, immunofluorescence staining revealed a similar organisation of actin microfilaments, talin and phosphotyrosyl-containing proteins on both substrates. In contrast, differences were observed for vinculin distribution within cells spread on fibronectin or on laminin 1. Following cell adhesion to fibronectin most of the vinculin appeared as thick patches at the tips of the actin stress fibers while in laminin-adhering cells vinculin was recruited into thin streaks localized at the end of only some actin stress fibers.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1996

[Methadone substitution in public health management--results of a random day study sample].

Subject of this paper is methadone-maintenance given by the office-based physicians in Germany within the framework of the statutory health insurance (SHI). Results of a survey of the associations of SHI-accredited physicians are presented, comprising the number of substituted patients, the distribution of indications and the number of physicians engaged in this field. The increasing trend in the number of substituted patients continues, although less steeply. Strongholds of methadone maintenance are still the cities of Hamburg, Berlin, and Bremen, where the highest rates of substituted patients were found in relation to the resident population. The method of data-gathering used trends to overestimate the number of substituted patients. Comparing the determined numbers with different data sources, the actual number of addicts who are substituted in the longer term at the cost of the SHI is estimated to be 10 000 patients.

Costs and Cost Analysis↗
PubMed1995

Motility and substratum adhesion of Dictyostelium wild-type and cytoskeletal mutant cells: a study by RICM/bright-field double-view image analysis.

To investigate the dynamics of cell-substratum adhesion during locomotion, a double-view optical technique and computer-assisted image analysis has been developed which combines reflection interference contrast microscopy (RICM) with bright-field imaging. The simultaneous recording of cell-substratum contact and cell body contour has been applied to aggregation-competent cells of Dictyostelium discoideum. These cells are distinguished from cells at earlier stages of development by small areas of contact to a substratum. Three questions have been addressed in analysing the locomotion of aggregation-competent cells. (1) What is the relationship between changes in the shape of cells and their contact to a substratum during a chemotactic response? (2) What is the relationship between protrusion and retraction of the cell body, and between local attachment and detachment? (3) Are there differences between wild-type and mutant cells that lack certain cytoskeletal proteins? During a chemotactic response the front region of the amoeba can bend towards the gradient of attractant without being supported by its contact with a surface, which excludes the necessity for gradients of adhesion for the response. The finding that in locomoting cells protrusion of the leading edge often precedes retraction establishes a pioneer role for the front region. The finding that gain of contact area precedes loss provides evidence for the coordination of interactions between the cell surface and a substratum. For comparison with wild-type, aggregation-competent triple mutant cells have been used that lack two F-actin crosslinking proteins, alpha-actinin and 120 kDa gelation factor, and an actin filament fragmenting protein, severin. Disturbances in the spatial and temporal control of cytoskeletal activities have been unravelled in the mutant by RICM and quantified by cross-correlation analysis of attachment and detachment vectors. In order to detect these disturbances, it was essential to analyse cell locomotion on the weakly adhesive surface of freshly cleaved mica.

Animals↗
PubMed1995

[The Mannheim long-term study of schizophrenia. Initial results of follow-up of the illness over 14 years after initial inpatient treatment].

A 14-year follow-up was accomplished on 56 out of a total of 70 patients first admitted to hospital with Schneiderian first-rank symptoms. Data collected during 5 years after index admission were also at our disposal. Three quarters of the probands are living alone, and barely one third are in regular employment. At the time of the 14-year follow-up about one third showed delusions or hallucinations. Almost the same number had psychological impairments and 64% were socially disabled. Comparison with the data collected at 1 year and 5 years reveals no difference in the rates of impairments and symptomatology, but a significant increase of social disability.

Adult↗
PubMed1994

Fully-automated, nonradioactive solid-phase sequencing of genomic DNA obtained from PCR.

Nonradioactive sequencing in combination with solid-phase template purification is a powerful method for sequence analysis, especially of PCR-generated fragments. To perform DNA sequencing under optimal conditions, it is necessary to obtain a well-purified and single-stranded (ss) DNA template. The disadvantage of ssDNA sequencing is that additional steps are required to generate ssDNA templates before any sequencing reactions can be carried out and is thus more time-consuming. Here we describe an automated solid-phase system for direct sequencing of ssPCR products that incorporates magnetic beads coated with streptavidin as solid support and a computer-controlled device (PolySeq) with heating, magnetic and mixing functions, all of which are integrated into a robotic workstation (Biomek 1000). This solid-phase method is extremely useful for rapid template purification and strand separation of DNA obtained from PCR as well as for high-quality dideoxyribonucleotide chain termination sequencing with fluorescently labeled primers. The system allows the complete automation of the sequencing procedure starting with PCR amplicons. DNA sequencing results obtained with this system were reproducible and gave an excellent length of readable sequences with low background and an analysis capacity of 30,000-40,000 bp per week.

Base Sequence↗
PubMed1994

[Methadone substitution in national public health care in Germany--patients, indications, physicians. Results of a survey of public health service facilities].

Subject of this paper is methadone-maintenance given by office-based physicians in Germany in the framework of the statutory health insurance (SHI). Results of a survey of the associations of SHI-accredited physicians are presented, comprising the number of substituted patients, the distribution of indications and the number of the physicians engaged in this field. The results are presented under regional aspects and discussed. It was ascertained that in respect of the number of substituted patients, the increasing trend continues.

Ambulatory Care↗
PubMed1993

[Mortality of foreign and indigenous population in the German Federal Republic].

Comparative mortality studies with respect to nationality have not yet been published in a comprehensive way for the Federal Republic of Germany. A recent special analysis of causes of death for German mortality statistics of the year 1986 indicates a lower mortality risk among the migrant compared to the indigenous population. Apart from potential biases, such as underreporting of nationality of death cases or overestimation of the size of the non-indigenous population in Germany, from the perspective of socio-epidemiology the possibility arises that selection processes lastingly affect the mortality risk of migrants. The dependence of the length of stay from the quality of the state of health or rather a plausible increased likelihood of remigration in case of chronic disease may constitute important influences, which could explain the differences in mortality between indigenous and migrant population.

Adult↗
PubMed1992

Site-directed mutational analysis of human tumor necrosis factor-alpha receptor binding site and structure-functional relationship.

In order to define the receptor binding site and the structure-functional relationship of tumor necrosis factor (TNF), single amino acid substitutions were made by site-directed mutagenesis at selected residues of human tumor necrosis factor, using a phagemid mutagenesis/expression vector. The recombinant TNF mutants were compared to the wild type TNF in assays using crude bacterial lysates, for protein yield, solubility, subunit trimerization, receptor binding inhibition activity, and in vitro cytotoxic activity. All mutants which did not form cross-linkable trimer also showed little cytotoxic activity or receptor binding inhibition activity, indicating that trimer formation is obligatory for TNF-alpha activity. Most mutations of internal residues yielded no cross-linkable trimer, while most mutations of surface residues yielded cross-linkable trimer. Mutations at surface residues Leu29, Arg31, and Ala35 yielded cross-linkable trimers with good activities, except proline substitutions which may cause conformational changes in the polypeptide chain. This suggested that these residues are near the receptor binding site. Mutations at other strictly conserved internal residues such as Ser60, His78, and Tyr119 form cross-linkable trimer with little activity. These mutations may indirectly affect the receptor binding site by forming trimers with undetectable abnormalities. Mutants of surface residues Tyr87, Ser95, Ser133, and Ser147 affect receptor binding and cytotoxic activity but not trimer formation, suggesting that these residues are involved directly in receptor binding. The fact that residues Arg31, Ala35, Tyr87, Ser95, and Ser147, located on the opposite sides of a monomer, are clustered at the intersubunit grooves of TNF trimer supports the current notion that TNF receptor binding sites are trivalent and are located at the three intersubunit grooves. However, our finding that Ser133, which is outside the groove, can also be involved directly in receptor binding suggested that the receptor binding sites of TNF may not be confined to the intersubunit grooves, but extended to include additional surface residues.

Amino Acid Sequence↗