[Management of multiresistant bacteria in urology]. / Management multiresistenter Erreger in der Urologie.

Contamination and infection with extensive drug resistant (XDR) bacteria are increasing in urology with the exception of methicillin resistant Staphylococcus aureus (MRSA) (stabilization). They often lead to logistic and therapeutical problems. Only 30-50% of XDR cases are of exogenous origin. To slow this trend, screening, hygiene programs, isolation, decontamination, targeted therapy of symptomatic infections, education programs, and success controls should be applied. Furthermore, all regulatory and legal instructions should be followed. Local hygiene networks help to find apt measures for XDR control. It is important to balance hygiene measures against hygiene hysteria. To prepare urological instruments, a local instrument preparation plan that takes into consideration all legal instructions should be followed. The efforts in health system general prophylactic measures should be supported. Only with consistent implementation in all areas of daily life (health care, local environment, animal husbandry, and soil contaminated within the framework of animal husbandry) can a substantial reduction of XDR bacteria be achieved in the long term.

Reduced expression of neural cell adhesion molecule induces metastatic dissemination of pancreatic beta tumor cells.

As in the development of many human cancers, in a transgenic mouse model of beta-cell carcinogenesis (Rip1Tag2), expression of neural cell adhesion molecule (NCAM) changes from the 120-kDa isoform in normal tissue to the 140/180-kDa isoforms in tumors. NCAM-deficient RiplTag2 mice, generated by crossing Rip1Tag2 mice with NCAM knockout mice, develop metastases, a tumor stage that is not seen in normal Rip1Tag2 mice. In contrast, overexpression of NCAM 120 in NCAM-deficient Rip1Tag2 mice prevents tumor metastasis. The results indicate that the loss of NCAM-mediated cell adhesion is one rate-limiting step in the actual metastatic dissemination of beta tumor cells.

A causal role for E-cadherin in the transition from adenoma to carcinoma.

Development of malignant tumours is in part characterized by the ability of a tumour cell to overcome cell-cell adhesion and to invade surrounding tissue. E-cadherin is the main adhesion molecule of epithelia, and it has been implicated in carcinogenesis because it is frequently lost in human epithelial cancers. Re-establishing the functional cadherin complex in tumour cell lines results in a reversion from an invasive to a benign epithelial phenotype. However, it remained unresolved whether the loss of E-cadherin-mediated cell adhesion was a cause or a consequence of tumour progression in vivo. Here we report that the loss of E-cadherin expression coincides with the transition from well differentiated adenoma to invasive carcinoma in a transgenic mouse model of pancreatic beta-cell carcinogenesis (Rip1Tag2). Intercrossing Rip1Tag2 mice with transgenic mice that maintain E-cadherin expression in beta-tumour cells results in arrest of tumour development at the adenoma stage, whereas expression of a dominant-negative form of E-cadherin induces early invasion and metastasis. The results demonstrate that loss of E-cadherin-mediated cell adhesion is one rate-limiting step in the progression from adenoma to carcinoma.

Cadherins regulate aggregation of pancreatic beta-cells in vivo.

It is thought that the cadherin protein family of cell adhesion molecules regulates morphogenetic events in multicellular organisms. In this study we have investigated the importance of beta-cell cadherins for cell-cell interactions mediating the organization of endocrine cells into pancreatic islets of Langerhans. To interfere with endogenous cadherin activity in beta-cells during pancreatic development, we overexpressed a dominant negative mutant of mouse E-cadherin, lacking nearly all extracellular amino acids, in pancreatic beta-cells in transgenic mice. Expression of the truncated E-cadherin receptor displaced both E- and N-cadherin from pancreatic beta-cells. As a result, the initial clustering of beta-cells, which normally begins at 13.5-14.5 days postcoitum, was perturbed. Consequently, the clustering of endocrine cells into islets, which normally begins at 17.5-18 days postcoitum, was abrogated. Instead, transgenic beta-cells were found dispersed in the tissue as individual cells, while alpha-cells selectively aggregated into islet-like clusters devoid of beta-cells. Furthermore, expression of truncated E-cadherin in beta-cells resulted in an accumulation of beta-catenin in the cytoplasm. Thus, we have for the first time shown in vivo that cadherins regulate adhesive properties of beta-cells which are essential for the aggregation of endocrine cells into islets.

Defective propagation of signals generated by sympathetic nerve stimulation in the liver of connexin32-deficient mice.

The gap junctional protein connexin32 is expressed in hepatocytes, exocrine pancreatic cells, Schwann cells, and other cell types. We have inactivated the connexin32 gene by homologous recombination in the mouse genome and have generated homozygous connexin32-deficient mice that were viable and fertile but weighed on the average approximately 17% less than wild-type controls. Electrical stimulation of sympathetic nerves in connexin32-deficient liver triggered a 78% lower amount of glucose mobilization from glycogen stores, when compared with wild-type liver. Thus, connexin32-containing gap junctions are essential in mouse liver for maximal intercellular propagation of the noradrenaline signal from the periportal (upstream) area, where it is received from sympathetic nerve endings, to perivenous (downstream) hepatocytes. In connexin32-defective liver, the amount of connexin26 protein expressed was found to be lower than in wild-type liver, and the total area of gap junction plaques was approximately 1000-fold smaller than in wild-type liver. In contrast to patients with connexin32 defects suffering from X chromosome-linked Charcot-Marie-Tooth disease (CMTX) due to demyelination in Schwann cells of peripheral nerves, connexin32-deficient mice did not show neurological abnormalities when analyzed at 3 months of age. It is possible, however, that they may develop neurodegenerative symptoms at older age.

Mouse R-cadherin: expression during the organogenesis of pancreas and gastrointestinal tract.

Members of the cadherin protein family of cell adhesion molecules are thought to regulate many morphogenetic events during the development of multicellular organisms. We are interested in which cell-cell interactions cadherins regulate during pancreas morphogenesis. Expression and function of E-cadherin in the pancreas have previously been characterized. Recently, R-cadherin cDNA was isolated and the expression patterns of R- and N-cadherin cDNA was isolated and the expression patterns of R- and N-cadherin mRNAs in the pancreas have been described. In the present study, we have investigated the expression of R-cadherin in the pancreas and gastrointestinal tract using specific anti-R-cadherin antibodies. During early stages of pancreas development (E10.5) R-cadherin is expressed in most hormone-producing cells in addition to in primitive duct-like cells. Later, at E18.5, when islets start to form, R-cadherin is not expressed in intraislet endocrine cells, but is instead found in intraductule endocrine and exocrine cells. In adult islets of Langerhans R-cadherin is absent from endocrine cells, but is present in ductule-like cells. Furthermore, the molecule is expressed in exocrine cells: apically and basolaterally on epithelial duct and ductule cells and apically on acinar cells. Interestingly, there appears to be a correlation between the downregulation of R-cadherin expression in intraductule endocrine cells and the migration out of the duct epithelium to form islets. In the gastrointestinal tract R-cadherin is expressed in the pit region of gastric glands and in absorptive cells of the small intestine. The subcellular localization in these tissues is on both the apical and basolateral surfaces. The potential function of R-cadherin, in particular its role in pancreas development, is discussed.

Non-diabetogenic insulitis in NOD<-->B10.GD allophenic mice in spite of permissive class I MHC antigens.

Allophenic mice (embryo aggregation mouse chimeras) enable us to dissect the process of spontaneous autoimmunity under physiological conditions. Our previous experiments showed that the autoimmune process in allophenic mice of the NOD<-->C57B1/6 strain combination does not progress from insulitis to diabetes. One possible explanation for this protection is that H-2 Kd-restricted CD8+ T cells kill only NOD beta cells (Kd,Db) in the chimeric islets, while the B6 beta cells (Kb,Db) are spared from destruction. To test this hypothesis we analysed 22 NOD<-->B10.GD chimeras in which the class I MHC are shared by both parental strains. Therefore all the beta cells in these chimeras express H-2 Kd molecules. Ten allophenic mice were killed at 7 weeks and studied for early pathology. No evidence for intra-islet infiltration was obtained at this age, suggesting that the autoimmune process in NOD<-->B10.GD chimeras is slower than in NOD mice. Twelve chimeras were followed up for 1 year for disease development and all failed to progress to full-blown diabetes, despite the occurrence of intra-insulitis in six out of 12 mice. The lack of disease in NOD<-->B10.GD chimeras demonstrates that class I MHC chimerism does not account for diabetes resistance in NOD-allophenic mice.

The phenotype of lymphoid cells and thymic epithelium correlates with development of autoimmune insulitis in NOD in equilibrium with C57BL/6 allophenic chimeras.

The mechanisms contributing to the development of autoimmune insulin-dependent diabetes mellitus have been analyzed in allophenic mouse chimeras of the NOD in equilibrium with C57BL/6 strain combination (where NOD is nonobese diabetic). Occurrence of lymphoid cell infiltration (insulitis) in pancreatic islets was observed in the majority of such chimeras. The development of insulitis was found to correlate with major histocompatibility complex chimerism in lymphoid cells and in thymus cortical regions. Chimeras with more than 50% of C57BL/6 lymphoid cells rarely developed insulitis. Our data suggest that the correlation with the thymic cortical region is absolute. Thus, all individuals displaying NOD or NOD/C57BL/6 thymic cortical regions developed insulitis, whereas we have not observed insulitis in chimeras with only C57BL/6 thymic cortical regions. Thus the positive selection of T cells appears to play a crucial role in the development of insulin-dependent diabetes mellitus.