Human colonic myogenic dysfunction induced by mucosal lipopolysaccharide translocation and oxidative stress

Background

Impairment of gastrointestinal motility is frequently observed in patients with severe infection.

Aim

To assess whether exposure of human colonic mucosa to pathogenic lipopolysaccharide affects smooth muscle contractility.

Methods

Human colonic mucosa and submucosa were sealed between two chambers, with the luminal side facing upwards and covered with Krebs solution, with or without lipopolysaccharide from a pathogenic strain of Escherichia coli (O111:B4; 1000 ng/mL), and with the submucosal side facing downwards into Krebs. The solution on the submucosal side was collected following 30-min mucosal exposure to Krebs without (N-undernatant) or with lipopolysaccharide (lipopolysaccharide undernatant). Undernatants were tested for lipopolysaccharide and hydrogen peroxide levels and for their effects on smooth muscle cells in the presence of catalase, indomethacin or MG132.

Results

Smooth muscle cells incubated with N-undernatant had a maximal contraction of 32 ± 5% that was reduced by 62.9 ± 12% when exposed to lipopolysaccharide undernatant. Inhibition of contraction was reversed by catalase, indomethacin and MG132. Lipopolysaccharide levels were higher in the lipopolysaccharide undernatant (2.7 ± 0.7 ng/mL) than in N-undernatant (0.45 ± 0.06 ng/mL) as well as hydrogen peroxide levels (133.75 ± 15.9 vs 82 ± 7.5 nM respectively).

Conclusions

Acute exposure of colonic mucosa to pathogenic lipopolysaccharide impairs muscle cell contractility owing to both lipopolysaccharide mucosal translocation and production of free radicals.     

Low-level hypermutation in T cell-independent germinal centers compared with high mutation rates associated with T cell-dependent germinal centers

Exceptionally germinal center formation can be induced without T cell help by polysaccharide-based antigens, but these germinal centers involute by massive B cell apoptosis at the time centrocyte selection starts. This study investigates whether B cells in germinal centers induced by the T cell-independent antigen (4-hydroxy-3-nitrophenyl)acetyl (NP) conjugated to Ficoll undergo hypermutation in their immunoglobulin V region genes. Positive controls are provided by comparing germinal centers at the same stage of development in carrier-primed mice immunized with a T cell-dependent antigen: NP protein conjugate. False positive results from background germinal centers and false negatives from non-B cells in germinal centers were avoided by transferring B cells with a transgenic B cell receptor into congenic controls not carrying the transgene. By 4 d after immunization, hypermutation was well advanced in the T cell-dependent germinal centers. By contrast, the mutation rate for T cell-independent germinal centers was low, but significantly higher than in NP-specific B cells from nonimmunized transgenic mice. Interestingly, a similar rate of mutation was seen in extrafollicular plasma cells at this stage. It is concluded that efficient activation of hypermutation depends on interaction with T cells, but some hypermutation may be induced without such signals, even outside germinal centers.     

Striatal GABAergic and cortical glutamatergic neurons mediate contrasting effects of cannabinoids on cortical network synchrony

Activation of type 1 cannabinoid receptors (CB1R) decreases GABA and glutamate release in cortical and subcortical regions, with complex outcomes on cortical network activity. To date there have been few attempts to disentangle the region- and cell-specific mechanisms underlying the effects of cannabinoids on cortical network activity in vivo. Here we addressed this issue by combining in vivo electrophysiological recordings with local and systemic pharmacological manipulations in conditional mutant mice lacking CB1R expression in different neuronal populations. First we report that cannabinoids induce hypersynchronous thalamocortical oscillations while decreasing the amplitude of faster cortical oscillations. Then we demonstrate that CB1R at striatonigral synapses (basal ganglia direct pathway) mediate the thalamocortical hypersynchrony, whereas activation of CB1R expressed in cortical glutamatergic neurons decreases cortical synchrony. Finally we show that activation of CB1 expressed in cortical glutamatergic neurons limits the cannabinoid-induced thalamocortical hypersynchrony. By reporting that CB1R activations in cortical and subcortical regions have contrasting effects on cortical synchrony, our study bridges the gap between cellular and in vivo network effects of cannabinoids. Incidentally, the thalamocortical hypersynchrony we report suggests a potential mechanism to explain the sensory “high” experienced during recreational consumption of marijuana.     

Current findings on gastrointestinal stromal tumors: seven observations of malignant tumors

PURPOSE: Gastrointestinal stromal tumors (GIST) are rare neoplasms, 1-3% of malignant gastrointestinal tumors. They are immature proliferations of spindled and/or epithelioid cells, developed in the muscular layer of the digestive tract, showing uncompleted or partial muscular, nervous or mixed differentiation. Immunohistologic knowledge about these tumors has recently progressed because of the discovery of specific markers (coexpression vimentin-CD117, oncogenes): GIST can now be distinguished from the other mesenchymal tumors. METHODS: Retrospective study of seven patients with GIST who received the same treatment. RESULTS: For our seven patients the mean age was 49 years with a male predominance (sex-ratio 4/3). The tumoral localisations are principally the small bowel (four cases), the rectum (two cases) and the stomach (one case). The treatment consisted of a first surgery, adapted to the tumoral localisation and extension, associated to chemotherapy in case of metastasis or local recurrence. The study of the histological grading for the seven patients showed tumors with poor prognoses. Six patients developed recurrence in a 2-year period; for the survey we are too close for a proper view. CONCLUSIONS: A review of the literature on stromal tumors finds older patients (59 years) with an equal sex ratio. Against the results of our series, the most frequent location is the stomach (50%). But the main problem is the better understanding of the particular evolution of these tumors. The bad short-date prognosis imposes carrying out larger studies, in order to confirm the principal hypothesis of histogenesis and to improve the survey by an optimal treatment.     

The Outcome of Coxsackievirus B3-(CVB3-) Induced Myocarditis is Influenced by the Cellular Immune Status

Mice develop a marked age-related susceptibility to myocardial coxsackievirus B3 (CVB3) infections. The lesions observed in mice resemble closely those seen in the human disease. Experimental murine models of CVB3-induced myocarditis have shown that both, host and viral genetic factors, can influence susceptibility to the infection as well as the persistence and progression of the disease. Recently, we have shown that CD4 T cell-deficient MHC Class II knockout mice develop a strong fibrosis with virus persistence in the heart tissue and without production of neutralizing antibodies. To examine the role of CD4+ T cells and especially the role of the T helper 1 cell response for the outcome and pathogenesis of CVB3-induced myocarditis in more detail, 2 different mouse strains with identical genetic background (H-2b) were infected with CVB3-Mü/J (Nancy strain). Immunocompetent C57BL/6 mice and mice with targeted disruption of interleukin (IL-)4 gene (IL-4-/- mice) developed a severe acute myocarditis on day 7 post infection (p.i.). The CVB3-induced inflammation was cured until the 21st day p.i. in hearts of C57BL/6 mice. IL-4-/- mice with insufficient T helper-2 cell immune response developed a severe myocardial damage between day 7 and 21 p.i. with prolonged virus persistence in the heart tissue. Therefore, we suggest that despite an obvious normal T helper-1 cell cytokine pattern, IL-4-/- mice are more susceptible to long-term heart muscle injuries after infection with CVB3.     

First experience With the biostar‐device for various applications in pediatric patients With congenital heart disease

Background: Interventional closure of atrial septal defects (ASD) and surgical tunnel fenestrations in Fontan patients has become the procedure of choice for many years. Recently, the BioSTAR Occluder, a modification of the Starflex device with a resorbable matrix has become available. Patients: Ten Biostar devices were implanted in nine children with interatrial septal defects, one within a fontan baffle, eight with secundum atrial septal defects. The age of the patients ranged from 11 months to 17 years, the body weight ranged from 12.9–78 kg. Results: 10 BioSTAR devices were implanted in nine patients. In one patient, two BioSTAR devices were used to occlude multiple defects within the oval fossa. All defects were successfully and uneventfully occluded. Mean procedure time was 56 (range 28–125). Mean fluoroscopy time was 4.8 (range 1.1 to 13.0) min. None of the nine patients showed residual shunts after device implantation. After 30 days no shunt was seen in the control transthoracic echocardiography. No adverse effects like allergic reactions, tachyarrhythmia or thrombembolic events occurred in any of the patients. Conclusion: The BioSTAR closure device is a safe and effective device for the closure of a variety of interatrial shunts in children including multifenestrated interatrial defects and fontan fenestrations, however, possible long term consequences (e.g., fractures, recurrent shunts after scaffold degradation) remain to be studied. © 2009 Wiley‐Liss, Inc.     

Running enhances spatial pattern separation in mice

Increasing evidence suggests that regular exercise improves brain health and promotes synaptic plasticity and hippocampal neurogenesis. Exercise improves learning, but specific mechanisms of information processing influenced by physical activity are unknown. Here, we report that voluntary running enhanced the ability of adult (3 months old) male C57BL/6 mice to discriminate between the locations of two adjacent identical stimuli. Improved spatial pattern separation in adult runners was tightly correlated with increased neurogenesis. In contrast, very aged (22 months old) mice had impaired spatial discrimination and low basal cell genesis that was refractory to running. These findings suggest that the addition of newly born neurons may bolster dentate gyrus-mediated encoding of fine spatial distinctions.     

Ablation of Typical Atrial Flutter Using a Three-Dimensional Ultrasound Mapping System

Aims: The aim of the study was to test the feasibility of the new Realtime Position Management mapping system for ablation of typical atrial flutter. Methods and Results: The ultrasound multi-transducer catheters of the RPM Mapping System are placed in the coronary sinus and at the right ventricular apex. Position and movement of the ablation catheter can be depicted on the monitor at any time. Several guiding marks are set in the right atria and thus, define the subsequent lesion lines. A total of 15 patients were treated. In 13 patients complete bi-directional block was established after the ablation. In two patients only significant conduction delay was measured after the end of the procedure. A total of 10.2 ± 6.3 cooled RF-applications were needed to reach the end-point of the procedure. The total energy was 18.76 ± 13.23 J. The fluoroscopy time for ablation was 22.2 ± 8.34 min. During a mean follow-up of 8.4 ± 3.2 months no recurrence of atrial flutter occurred. One patient developed atypical flutter and another patient had atrial fibrillation. Both patients were treated with antiarrhythmic drugs. There was one ablation related complication, a pericardial effusion. Conclusion: The Realtime Position Management system is easy to manage and control. The precision of anatomical linear lesions is improved and fluoroscopic exposure time considerably reduced after learning curve.