Toxoplasma encephalitis of immunocompetent and nude mice: immunohistochemical characterisation of Toxoplasma antigen, infiltrates and major histocompatibility complex gene products

The experimental infection of immunocompetent and immunodeficient athymic mice with an avirulent encephalitogenic Toxoplasma strain (DX strain) was employed to study the ensuing encephalitic process by use of histological and immunocytochemical methods. In the acute phase of the infection Toxoplasma cysts and tachyzoites were accompanied by an infiltrate composed of macrophages, CD4+ and CD8+ T cells. In the chronic stage a granulomatous encephalitis developed. In contrast to immunocompetent NMRI mice, athymic nude NMRI mice died 3 weeks post-infection because of a generalized toxoplasmosis with predominant involvement of the brain. A salient feature of murine Toxoplasma encephalitis was up-regulation of class I and II major histocompatibility complex (MHC) gene products. Class I antigen was widely expressed on microglial cells and astrocytes. Class II antigen was only expressed on microglial cells despite a considerable astrogliosis. Our results indicate a differential expression of MHC-determined antigens on brain cells in acute and chronic murine Toxoplasma encephalitis.     

Basophil releasability in severely burned patients.

Thermal injury is known to induce dysregulation of the immune system; however, the precise mechanisms have to be clarified. We investigated the histamine release of basophil granulocytes from severely burned patients (n = 12) after stimulation with anti-IgE or the Ca-ionophore A 23187, respectively. The anti-IgE-induced basophil histamine release of all patients was reduced in comparison to healthy donors beginning at day one postburn (p.b.) (5.0 +/- 2.3% vs. 30.5 +/-3.4%), while the Ca-ionophore-induced release was not decreased before day two p.b. Basophils of patients who finally succumbed to their injuries showed poor responsiveness (to zero levels) over the total time. In contrast, the basophil releasability of surviving patients returned to nearly normal levels (fifth to seventh week p.b.). Already in the second week p.b. there was a significant difference in histamine release between survivors and nonsurvivors [e.g., days 6-9 p.b.: 23.7 +/- 4.0 vs. 6.9 +/- 2.7 (p less than 0.005) after Ca-ionophore stimulation]. The altered basophil histamine release was neither due to a diminished dose- or a delayed time-response to the stimuli nor due to differences in the basophil counts or the cellular histamine content. Our data indicate that the decrease of the basophil releasability, which may be secondary to altered signal transduction pathways in severely burned patients correlates with the clinical outcome.     

Präimplantationsdiagnostik, Pränataldiagnostik und Schwangerschaftsabbruch

Preimplantation genetic diagnosis (PGD) has been vigorously debated in Germany ever since the Bundesärztekammer (BÄK) published a draft of guidelines for PGD in March 2000. Many stakeholders such as churches, medical societies, and diverse associations have participated in the discussion. However, little is known about the attitudes of experts, directly affected patient groups, and the public in Germany. In several studies that are part of the German research program on ethical implications of the Human Genome Project, representative surveys were undertaken to assess the attitudes of the general population (n=1017), five relevant expert groups (n=879), and couples at high risk for genetic disorders(n=324) towards PGD and prenatal diagnosis (PD). All groups favor legislation for PGD. Differences exist in regard to the extent of their approval. For 17% of the high-risk couples with a persisting desire for a child, PGD performed in a neighboring country is the most probable reproductive option. These results should be carefully considered in the ongoing legislation process on human reproduction in our country.     

Comparative analysis of mRNA and protein expression of Popdc1 (Bves) during early development in the chick embryo.

The isolation of the Popeye gene family was based on its preferential expression in striated muscle tissue. Recently, a monoclonal antibody against chick Popdc1 (also known as Bves) became available and was used in this study to comparatively analyze the expression pattern of Popdc1 at both the protein and mRNA level during early chick embryogenesis. Using whole-mount immunohistochemistry, expression in the heart was first observed at Hamburger and Hamilton (HH) stage 10 in the presumptive left ventricular segment. Cardiac expression was confined to differentiated cardiac myocytes, and undifferentiated myocytes at the anterior and posterior pole showed little expression. After looping, the outer curvature myocardium showed prominent Popdc1 staining, whereas the inner curvature was unlabeled. Despite previous reports, Popdc1 protein was not detectable at any time point in the proepicardium, epicardium, or the smooth muscle layer of the coronary vessels. Whole-mount in situ hybridization using a full-length Popdc1 probe detected novel expression domains, which have not been described previously. Popdc1 mRNA was found in Hensen's node at HH stage 4, and by HH stage 5+, expression became asymmetric. In addition, Popdc1 mRNA was found in pharyngeal endoderm and in the notochordal plate. Subsequently, beginning at HH stage 9, Popdc1 mRNA expression was found in the cardiac mesoderm and expression was maintained in the heart in a pattern very similar to the one observed by antibody staining.     

Unilateral Meesmann‘s dystrophy

We report the first case of a unilateral microcysticMeesmann‘s epithelial dystrophy, observed in the left cornea of a 43-year-old patient. The diagnosis was verified histologically by the unilateral occurrence of a ’peculiar substance‘ within epithelial cysts and within the cytoplasm of the corneal epithelial cells. In an attempt to resolve thepatient‘s frequent corneal erosions, we performed an autologous stem cell transplantation from the non-involved right eye. The results are, so far, satisfactory. This revised version was published online in August 2006 with corrections to the Cover Date.     

Sklerosierende Läsion des Os sphenoidale

Ohne Zusammenfassung     

The ubiquitin ligase Rnf6 regulates local LIM kinase 1 levels in axonal growth cones

LIM kinase 1 (LIMK1) controls important cellular functions such as morphogenesis, cell motility, tumor cell metastasis, development of neuronal projections, and growth cone actin dynamics. We have investigated the role of the RING finger protein Rnf6 during neuronal development and detected high Rnf6 protein levels in developing axonal projections of motor and DRG neurons during mouse embryogenesis as well as cultured hippocampal neurons. RNAi-mediated knock-down experiments in primary hippocampal neurons identified Rnf6 as a regulator of axon outgrowth. Consistent with a role in axonal growth, we found that Rnf6 binds to, polyubiquitinates, and targets LIMK1 for proteasomal degradation in growth cones of primary hippocampal neurons. Rnf6 is functionally linked to LIMK1 during the development of axons, as the changes in axon outgrowth induced by up- or down-regulation of Rnf6 levels can be restored by modulation of LIMK1 expression. Thus, these results assign a specific role for Rnf6 in the control of cellular LIMK1 concentrations and indicate a new function for the ubiquitin/proteasome system in regulating local growth cone actin dynamics.     

Mice with neonatally induced inactivation of the vascular cell adhesion molecule-1 fail to control the parasite in Toxoplasma encephalitis

Under various inflammatory conditions, cell adhesion molecules are up-regulated in the central nervous system (CNS) and may contribute to the recruitment of leukocytes to the brain. In the present study, the functional role of vascular cell adhesion molecule (VCAM)-1 in Toxoplasma encephalitis (TE) was addressed using VCAM(flox/flox MxCre) mice. Neonatal inactivation of the VCAM-1 gene resulted in a lack of induction of VCAM-1 on cerebral blood vessel endothelial cells, whereas the constitutive expression of VCAM-1 on choroid plexus epithelial cells and the ependyma was unaffected; in these animals, resistance to T. gondii was abolished, and VCAM(flox/flox MxCre) mice died of chronic TE caused by a failure to control parasites in the CNS. Although leukocyte recruitment to the CNS was unimpaired, the B cell response was significantly reduced as evidenced by reduced serum levels of anti-T. gondii-specific IgM and IgG antibodies. Furthermore, the frequency and activation state of intracerebral T. gondii-specific T cells were decreased, and microglial activation was markedly reduced. Taken together, these data demonstrate the crucial requirement of VCAM-1-mediated immune reactions for the control of an intracerebral infectious pathogen, whereas other cell adhesion molecules can efficiently compensate for VCAM-1-mediated homing across cerebral blood vessels.