A cardiac sudden death is caused by ventricular fibrillation (VF) of 70% of the time and bradyarrhythmia (cardiac arrest) of 30% of the time. Due to recent advances in electrophysiological and clinical research, the relation of the characteristics of cardiac ion channel and electrophysiological response in patients with lethal arrhythmia became clear. A lethal arrhythmic event such as VF is caused by an acute myocardial infarction, non-uniform delayed conduction due to myocardial scar, drug-induced QT prolongation and microvolt T-wave alternance, and idiopathic VF in Brugada symptom. In this report, we will introduce the development of 187-ch vector-projected high-resolution electrocardiography (DREAM-ECG) and the clinical application. DREAM-ECG can analyze 12-leads ECG, ventricular late potential (LP) by signal-averaged X,Y,Z-leads ECG, and synthesized 187-ch body surface ECGs using the Mason-Likar lead system. In addition, a functional map generated by an integration of LP might evaluate a space distribution of ventricular fractionated activity and high risk patients for implanted cardiac defibrillation. Furthermore, a functional map of RTc (corrected recovery time) dispersion as a repolarization might evaluate a risk stratification of drug-induced QT prolongation and myocardial injury by anti-cancer drugs.
Mycoplasmas depend on the host cells for various nutrients such as nucleic acid precursors and steroids. It has been mentioned that the acquisition of the nucleotides from the host cells is probably mediated through their own nucleases. However, in Mycoplasma salivarium, the existence of nuclease has not yet been known.
In this study, we examined the nuclease activity in M. salivarium, and analyzed the properties of the enzyme. The Triton X-114 solubilized supernatant (Tx) obtained from lysate of M. salivarium was used for the enzymatic analysis. The nuclease activity was detected as a specific band of 25kDa by SDS-PAGE and the following in-gel digestion (SDS-PAGE nuclease assay). The nuclease activity of Tx was strictly dependent on Ca2+.The nuclease was heat-stable, and the optimum pH was in the range of 7-9. The nuclease showed a low substrate specificity. From these findings, it was revealed that M. salivarium has a novel type of 25 kDa and Ca2+ dependent nuclease.
Moreover, we examined whether Tx could cleave the chromatin DNA in the nuclei originated from eukaryote cells. Consequently, Tx cleaved the DNA of HS-72 B cell nuclei .in vitro.
From these results, it has been suggested that M. salivarium in the host cells, obtains nucleotides by the digestion of DNA and RNA from the host cells with their own nuclease, and these cleavage results in injury in host cells and the following various pathogenesis of the oral region.
We have reported that conditioning electrical stimulation of the amygdala has an inhibitory effect on responses of nociceptive neurons of the rat medullary dorsal horn to electrical stimulation of the receptive field. However, it is not clear if amygdala stimulation has influences on the non-noxious response. The purpose of the present study is to determine using natural stimulation whether amygdala stimulation induces inhibition of noxious and non-noxious responses of wide-dynamic range (WDR) neurons. Rats were anesthetized with N2O-O2 and 0.5% halothane and immobilized with pancuronium bromide. Peripheral natural stimulus was applied continuously to the facial area, and ipsilateral amygdala stimulations (trains of 33 pulses, 0.5msec in duration, 300μA) to the recording site were delivered at a stimulus interval of 5-6sec. In 7 WDR neurons, noxious responses were inhibited by amygdala (central, cortical basomedial or basolateral nuclei) stimulation. Effects of amygdala stimulation on the responses to 3 kinds of stimuli (brushing, pressure and pinching) was tested in 4 neurons. In 3 of those neurons, both noxious and non-noxious responses were inhibited and the mean inhibitory effect were nearly equivalent (58.7-38.7%) for those responses. Amygdala stimulation inhibited noxious responses without affecting non-noxious responses in the remaining neuron. These inhibitory effects lasted for 200-300msec. In addition, responses of low-threshold mechanoreceptive (LTM) neurons were not affected by amygdala stimulation of the same site at which stimulation inhibited responses of nociceptive neurons. These findings suggest that excitation of neurons in the amygdala induce postsynaptic inhibition on the most of nociceptive neurons but not on non-nociceptive neurons in the medullary dorsal horn.
Porphyromonas endodontalis, a black-pigmented anaerobe, is a predominant pathogen of human periapical periodontitis. In contrast to P. gingivalis, a major pathogen of chronic periodontitis, the pathogenic factor(s) of P. endodontalis has been poorly characterized. In this study, the protease activities in the P. endodontalis extracellular fraction were examined using various MCA polypeptides. The results indicated that the extracellular fraction had a spectrum of proteolytic activities distinct from that of P. gingivalis, and that Ala- and Asp-specific proteolytic activities were substantially present in the extracellular fraction. Then, the extracellular fraction was subjected to ion-exchange chromatography. The Asp-specific proteolytic activity was eluted from a DEAE-Sephacel column separately from the Ala-specific one, and the fraction was designated as the DEAE-purified fraction. The further experiments on the effects of protease inhibitors also suggested that the DEAE-purified fraction contains a novel Asp-specific dipeptidylpeptidase. It was confirmed by the MALDI-TOF MS analyses on the substrate preference using neuromedin B and a series of synthetic neuromedin B analogues. Taken together, P. endodontalis possesses a novel Asp-specific dipeptidylpeptidase in the extracellular fraction, which could be involved in an important etiologic process in the specific pathological potential of this organisms in human periapical periodontitis.