Characteristics of electrocardiographic repolarization in acute myocardial infarction complicated by ventricular fibrillation

Background and PurposeSome de- and re-polarization patterns can reflect an increased risk of ventricular tachyarrhythmias. We studied whether some electrocardiographic (ECG) patterns are able to predict the development of ventricular fibrillation (VF) during acute myocardial infarction (MI).MethodsWe compared the patterns of ST-T segment of 78 patients who developed VF during acute MI (patient with VF) vs 170 comparable patients with acute MI but with no VF complications.ResultsOf the VF group, 47 developed out-of-hospital VF and 31 developed VF after their admission to the hospital. A steep downsloping ST segment toward a negative T wave with or without a short, flat, or rising portion at the initial portion was observed in 69.2% of the 78 patients: 61.3% in patients with pre-VF and 74.5% in patients with post-VF, vs 9.4% of patients who did not develop VF (P < .0001). In 90.6% of the latter, a typical upward-concave or convex “ischemic” pattern of the ST segment was observed. Thus, the characteristic ST-T patterns were highly associated with VF with a specificity greater than 90%.ConclusionsA steep downsloping ST segment may characterize the ECGs of patients who develop VF during acute MI.     

Endoscopic and histopathological evaluation of collagenous colitis

Collagenous colitis (CC) is a well-known cause of chronic non-bloody diarrhea, especially in elderly women. CC is characterized histopathologically by an increase in the thickness of the subepithelial collagen layer to at least 10 μm, epithelial damage, and chronic inflammation of the lamina propria. Generally, the colonic mucosa in CC is macroscopically normal, although minor, non-specific abnormalities may be found. Due to the recent advancement of endoscopic and diagnostic technologies, however, microscopic mucosal abnormalities and specific longitudinal linear lacerations of the mucosa characteristic of CC have been identified. The association of CC with non-steroidal anti-inflammatory drugs and proton pump inhibitors has also been reported. Since definitive diagnosis of CC has to rely on pathologically documented collagen bands and mononuclear infiltration, the efficiency and precision of colonic biopsy need to be improved. Of the 29 CC patients that we have encountered at our institution, it was in 15 of 29 cases that the endoscopic finding that we performed a biopsy on was apparent. Our comparison of the endoscopic and histopathological findings of CC in the 15 patients showed that the mucosa frequently appeared coarse and nodular on the surface of the mucosa, which was also significantly thicker in collagen bands, demonstrating a strong correlation between collagen band formation and CC. Also, the coarse and nodular surface of the mucosa was most frequently seen affecting the proximal colon. The results suggest that endoscopic observation and biopsy of the proximal colon, where a coarse and nodular surface of the mucosa is often found, may be useful for confirmation of the diagnosis in patients with suspected CC.     

Mitochondrial ubiquitin ligase MITOL blocks S-nitrosylated MAP1B-light chain 1-mediated mitochondrial dysfunction and neuronal cell death

Nitric oxide (NO) is implicated in neuronal cell survival. However, excessive NO production mediates neuronal cell death, in part via mitochondrial dysfunction. Here, we report that the mitochondrial ubiquitin ligase, MITOL, protects neuronal cells from mitochondrial damage caused by accumulation of S-nitrosylated microtubule-associated protein 1B-light chain 1 (LC1). S-nitrosylation of LC1 induces a conformational change that serves both to activate LC1 and to promote its ubiquination by MITOL, indicating that microtubule stabilization by LC1 is regulated through its interaction with MITOL. Excessive NO production can inhibit MITOL, and MITOL inhibition resulted in accumulation of S-nitrosylated LC1 following stimulation of NO production by calcimycin and N-methyl-D-aspartate. LC1 accumulation under these conditions resulted in mitochondrial dysfunction and neuronal cell death. Thus, the balance between LC1 activation by S-nitrosylation and down-regulation by MITOL is critical for neuronal cell survival. Our findings may contribute significantly to an understanding of the mechanisms of neurological diseases caused by nitrosative stress-mediated mitochondrial dysfunction.     

Application of an optogenetic byway for perturbing neuronal activity via glial photostimulation

Dynamic activity of glia has repeatedly been demonstrated, but if such activity is independent from neuronal activity, glia would not have any role in the information processing in the brain or in the generation of animal behavior. Evidence for neurons communicating with glia is solid, but the signaling pathway leading back from glial-to-neuronal activity was often difficult to study. Here, we introduced a transgenic mouse line in which channelrhodopsin-2, a light-gated cation channel, was expressed in astrocytes. Selective photostimulation of these astrocytes in vivo triggered neuronal activation. Using slice preparations, we show that glial photostimulation leads to release of glutamate, which was sufficient to activate AMPA receptors on Purkinje cells and to induce long-term depression of parallel fiber-to-Purkinje cell synapses through activation of metabotropic glutamate receptors. In contrast to neuronal synaptic vesicular release, glial activation likely causes preferential activation of extrasynaptic receptors that appose glial membrane. Finally, we show that neuronal activation by glial stimulation can lead to perturbation of cerebellar modulated motor behavior. These findings demonstrate that glia can modulate the tone of neuronal activity and behavior. This animal model is expected to be a potentially powerful approach to study the role of glia in brain function.