Biomedical subjects

B Nebe

Publications and source records attributed to B Nebe.

29 records · Page 2Linked to original sources

PubMed1996

Stimulation of integrin receptors using a magnetic drag force device induces an intracellular free calcium response.

Mechanical loading of cells is of fundamental relevance in physiological processes and induces several functional responses in cells. Integrins, a family of adhesion receptors, which are responsible for the interaction with the extracellular matrix, may play a role in transmission of mechanical signals into cells. The osteogenic cell line U-2 OS expresses different integrin subunits which are uniformly distributed over the cell surface. We applied defined physical forces on individual integrin receptor subunits using paramagnetic microbeads coated with anti-integrin antibodies. Application of an inhomogeneous magnetic field consequently leads to a mechanical stress on the receptor. Intracellular Ca2+ increased when the alpha 2 or the beta 1 integrin subunits were stressed, whereas mechanical loading of the transferrin receptor had a significantly lower effect. This result indicates that forces specifically exerted to individual integrin receptors induce signal transduction pathways.

Calcium↗

PubMed1995

Mechanical induction of beta 1-integrin-mediated calcium signaling in a hepatocyte cell line.

Mechanical stress influences growth, differentiation, and gene expression in a variety of cell types. It is believed that via extracellular matrix the mechanical stimulus is transmitted to integrin receptors which thus play a key role in transducing signals into the cell interior. Here we demonstrate that incubation of suspended hepatocytes with specific antibodies to beta 1-integrin subunits followed by a short-term mechanical stimulation is sufficient to induce a rise in intracellular Ca2+. The results indicate that mechanical loading of individual integrin subunits activates Ca(2+)-specific signal pathways.

Animals↗

PubMed1995

Flow cytometric measurements of intracellular Ca2+ mobilization in isolated rat pancreatic acinar cells after hormone stimulation and action of lectins.

Isolated rat pancreatic acinar cells were loaded with the Ca(2+)-sensitive fluorescence dye Fluo 3 in vitro and the intracellular Ca2+ changes were analysed by flow cytometry. Morphology, viability, and loading with the dye were studied by light microscopy. Stimulation with cholecystokinin/pancreozymin (CCK) and its agonist caerulein as well as with carbamylcholine (Jestryl) led to an increase of intracellular calcium ions and a fluorescence peak. The slope and height of the Ca2+ signals were found to be influenced by preincubation of cells with some plant lectins (WGA, UEA, PHA, Con A, LCA, PNA). These effects are discussed with respect to the interaction of lectins with the carbohydrate chains of cell membrane receptors.

Aniline Compounds↗

PubMed1995

Mineral fibers induce apoptosis in Syrian hamster embryo fibroblasts.

It is known that asbestos and other mineral fibers induce lung cancer and mesothelioma. However, the primary mechanisms of fiber-induced carcinogenesis still remain to be elucidated. Previous studies, including our own, have shown that asbestos causes specific mitotic disturbances, micronucleus formation and typical changes in chromatin structure resembling those of apoptosis. This effect has been considered as programmed cell death removing damaged or pre-cancerous cells. We investigated the induction of apoptosis by asbestos (amosite, crocidolite, chrysotile) and ceramic fibers. The typical ladder pattern of DNA fragments was identified by means of gel electrophoresis, the intracellular calcium concentration was measured and flow cytometry analyses were carried out to determine the percentage of apoptotic cells. The different fibers showed different potencies for the induction of apoptosis in Syrian hamster embryo (SHE) cells. Depending on the type of fiber applied 3-33% of cells underwent apoptosis. Chrysotile proved to be the most potent inducer of apoptosis compared to the other fibers. In addition, an increase intracellular calcium level was observed in apoptotic SHE cells. Chrysotile induced apoptosis after a considerably longer exposure time (66-72 h) than cisplatin (24 h). In view of these findings we hypothesize that chrysotile induces apoptosis resulting from long-term changes in intracellular regulation pathways.

Animals↗

PubMed1995

Effects of selenium supplementation on immune parameters in chronic uraemic patients on haemodialysis.

BACKGROUND: The involvement of selenium (Se) in immune response has been increasingly recognized, cell-mediated immunity being principally affected by Se deficiency. Blood Se levels in chronic uraemic patients are frequently lower than in controls, and in these patients cellular immunity in generally impaired. METHODS: The present study was designed to assess the effects of Se supplementation over 6 consecutive months on immune parameters in haemodialysis (HD) patients from Rostock (Germany) and Chieti (Italy). In both cities, five patients were supplemented with Se (500 micrograms thrice weekly for 3 months, then 200 micrograms thrice weekly for the next 3 months), whereas another five patients received placebo. All Se determinations were performed in a single laboratory. RESULTS: In both cities, basic plasma Se levels were significantly lower in patients than in their corresponding normal controls. After beginning Se supplementation, plasma Se concentration promptly normalized and levelled off in the normal range throughout the study. Se administration was well tolerated by all patients, and no side-effects attributable to Se toxicity were observed. Although no major change in immunocompetent cells (white blood count, total lymphocyte count, lymphocyte subpopulations) was observed during Se therapy, an improvement in T-cell response to phytohaemoagglutinin (as evaluated in Rostock patients) and a significant progressive increase in delayed-type hypersensitivity (as evaluated in Chieti patients) was observed in supplemented patients. After 6 months of Se therapy, the increase in delayed-type hypersensitivity of supplemented patients proved to be significantly higher when compared to both presupplementation values and to the results found in non-supplemented patients. Three months after suspension of Se supplementation, plasma Se levels and delayed hypersensitivity significantly decreased in Chieti patients, with both parameters returning similar to presupplementation values. CONCLUSIONS: In accordance with previous studies done in non-uraemic subjects, our investigation demonstrates for the first time the immunostimulatory properties of Se in HD patients. Though several problems on Se metabolism in uraemia remain unresolved, in our opinion moderate and safe Se supplementation can be beneficial in chronic uraemic patients.

Adjuvants, Immunologic↗

PubMed1994

Local increase of beta 1-integrin expression in cocultures of immortalized hepatocytes and sinusoidal endothelial cells.

The expression and spatial arrangement of beta 1-integrins was determined on two immortalized liver cell lines held in coculture, namely the epithelial cell line mHepR1 and a sinusoidal endothelial cell line. On mHepR1 cells the distribution of beta 1-integrins was restricted to the basolateral plasma membrane domains, a staining pattern that is typical of polarized epithelial cells. On the endothelial cell line the beta 1-integrins were distributed all over the cell surface. In coculture the endothelial cells tended to cover over the epithelial cells. Epithelial cells located in their vicinity exhibited an increased staining of beta 1-integrins at basolateral plasma membrane domains, which was most prominent with regard to the alpha 2-subunit. When mHepR1 cells were cultivated on various types of extracellular matrix also synthesized by the endothelial cells only collagen IV was found to increase the intensity of beta 1-integrin expression at the cell surface. The results indicate that beta 1-integrin expression in epithelial cell colonies can locally be modulated by interactions with non-parenchymal cells. In addition, the data suggest that mHepR1 cells may be a favorable system for analyzing basic functions of beta 1-integrins in polarized epithelial cells.

Aldehydes↗

PubMed1993

Bromodeoxyuridine distribution patterns in L 929 fibroblasts and influence of tumor necrosis factor.

Incorporation of bromodeoxyuridine during the S phase of the cell cycle provides an appropriate method to study the replication of DNA in proliferating cells. We analyzed the distribution patterns of incorporated bromodeoxyuridine in L 929 cells and studied the influence of tumor necrosis factor-alpha in vitro by indirect immunofluorescence. Using conventional epifluorescent and confocal laser scanning microscopy, we defined three types of bromodeoxyuridine distribution patterns in synchronized L 929 cells which showed typical differences in their percentages during the time course of the S phase. Type I with small spots and unstained areas was typical for the early S phase. Type II was characterized by a texture of homogeneously distributed fluorescence and increased during middle and late S phase. Type III with a small number of larger clusters revealed its highest proportion in the late S phase. Incubation with tumor necrosis factor reduced the number of bromodeoxyuridine-positive cells. We found that the cytokine, when present in late S phase, provoked an increase in the percentage of type III distribution pattern. The results show that bromodeoxyuridine distribution pattern analysis can be used to detect influences on cell cycle kinetics induced by therapeutics.

Animals↗

PubMed1988

[Extracorporeal blood circulation in the unanesthetized free-moving rabbit--an animal model for biocompatibility studies].

The rabbit is suitable as a basis model for the extracorporal circuit (ECC) in long-term test (20 days). A decrease of the leucocytes and platelets is established already in the blank test qualified by catheter material and pumping influence. This effect can be compensated by the rabbit in long-term test. The typical decrease of the leucocytes and platelets does not show any significant alteration during many test days independent of the number of tests which were carried out in one rabbit (blank test and hemoperfusion). A hemoperfusion across activated carbon--independent of the albumin coating--leads to a significant decrease of the leucocytes in comparison to the blank test. This rabbit model is well-suitable for biocompatibility investigations respectively also for effective investigations of detoxication techniques taken as a basis of our results.

Animals↗

PubMed1986

Experiments with continuous hemofiltration and hemofiltrate regeneration in the rat.

Experimental studies were made with continuous hemofiltration treatment for bilaterally nephrectomized rats and initial observations regarding the effects of such treatment on leukocyte and thrombocyte counts are reported. Hemofiltration of unanesthetized rats able to move freely within their cage could be continued for up to 30 h using a pump-driven ECC system. Blood parameters recorded during this treatment indicate that the detoxification was effective. In another series of experiments the water and electrolyte reabsorption capacity of the colon ascendens of healthy rats was tested by continuously supplying NaCl solution into the colon via a fistula. A large proportion, if not all, of the hemofiltrate can be discharged into the colon without diarrhoea. A final series of experiments showed that the three-stage operation (implantation of permanent catheters, connection of a permanent intestinal fistula and bilateral nephrectomy) is possible with the rat.

Animals↗

PubMed1984

[Animal experiments using the left-ventricular-assist system].

The left ventricular assist device (LVAD) was tested in 27 sternotomied dogs using hemodynamic parameters. The left ventricular failure was attained by the starvation of the coronary vessels. The use of cannulae and ventriculi fitting for the size of the animals, and a diastolic vacuum were an essential premise for an effective support of the left heart. By variation of the latent period, the systole duration, and the operating pressures were selected for optimal pumping conditions. The effectiveness of the LVAD was shown by the detected pressure and flow parameters.

Animals↗

PubMed1983

[Possibilities for using extracorporeal circulation in the rat].

An extracorporal system of freely mobile, unanaesthetized rats is presented. This model was used in experiments on the biocompatibility of silicone rubber and new types of hollow membranes. The results confirm a sensitive reaction of haematological parameters to various test substances, thus indicating that the model is very suitable. Carrying out a membrane plasma separation in rats makes it possible also to use rats for studies on detoxification and thus to use the advantages offered by this experimental animal to the full.

Animals↗