Extracellular GABA assisting in organizing dynamic cell assemblies to shorten reaction time to sensory stimulation.

Until recently, glia, which exceeds the number of neurons, was considered to only have supportive roles in the central nervous system, providing homeostatic controls and metabolic supports. However, recent studies suggest that glia interacts with neurons and plays active roles in information processing within neuronal circuits. To elucidate how glia contributes to neuronal information processing, we simulated a sensory neuron-glia (neuron-astrocyte) network model. It was investigated in association with ambient (extracellular) GABA level, because the astrocyte has a major role in removing extracellular GABA molecules. In the network model, transporters, embedded in plasma membranes of astrocytes, modulated local ambient GABA levels by actively removing extracellular GABA molecules which persistently acted on receptors in membranes outside synapses and provided pyramidal cells with inhibitory currents. Gap-junction coupling between astrocytes mediated a concordant decrease in local ambient GABA levels, which solicited a prompt population response of pyramidal cells (i.e., activation of an ensemble of pyramidal cells) to a sensory stimulus. As a consequence, the reaction time of a motor network, to which axons of pyramidal cells of the sensory network project, to the sensory stimulus was shortened. We suggest that the astrocytic gap-junction coupling may assist in organizing dynamic cell assemblies by coordinating a reduction in local ambient GABA levels, thereby shortening reaction time to sensory stimulation.

Detection of Cholera Toxin by an Immunochromatographic Test Strip.

As cholera toxin (CT) is responsible for most of the symptoms induced by Vibrio cholerae O1 or O139 infection, detection of CT is an important biomarker for diagnosis of the disease. The procedure for pathogenicity analysis of V. cholerae isolates must be carefully developed for the reason that the amount of CT produced by V. cholerae varies according to the medium used and culture conditions (i.e. temperature and aeration status) applied. Here we describe a reproducible rapid method for analysis of CT production by toxigenic V. cholerae with an immunochromatographic test strip that can detect as low as 10 ng/mL of purified recombinant CT.

Development of an immunochromatographic test strip for detection of cholera toxin.

Because cholera toxin (CT) is responsible for most of the symptoms induced by Vibrio cholerae infection, detection of CT is critical for diagnosis of the disease. In this study, we constructed an immunochromatographic test strip for detection of CT (CT-IC) with polyclonal antibodies developed against purified recombinant whole CT protein. The detection limit of the CT-IC was 10 ng/mL of purified recombinant CT, and it could detect the CT in culture supernatant of all 15 toxigenic V. cholerae isolates examined, whereas no false-positive signal was detected in all 5 nontoxigenic V. cholerae isolates examined. The specificity of the CT-IC was examined with recombinant heat-labile toxin (LT), which shares high homology with CT, and it was revealed that the minimum detection limit for LT was 100 times higher than that for CT. In addition, lt gene-positive enterotoxigenic Escherichia coli (ETEC) was examined by CT-IC. The false-positive signals were observed in 3 out of 12 ETEC isolates, but these signals were considerably faint. The CT-IC did not develop false-positive signals with all 7 V. parahaemolyticus isolates. These results showed the high specificity of CT-IC and the feasible use of it for the detection and surveillance of toxigenic V. cholerae.