title: Role of Cx36 gap junction modulation in general anaesthetic anticonvulsant action

authors: Voss, Logan J.

subjects: etomidate

abstract: Many GABAergic anaesthetics reduce gap junction coupling but it is currently unknown whether this effect contributes to anaesthetic anticonvulsant action. In this study we examined the possible role of connexin36 gap junctions in the anticonvulsant action of isoflurane and compared this to etomidate, an anaesthetic known for having proconvulsant effects. We compared the effect of anaesthetic concentrations of isoflurane (1 MAC) and etomidate (16 μM) on low-magnesium-induced interictal-like activity in isolated neocortical slices. The effect of connexin36 gap junction blockade was explored by comparing effects in slices from wild-type mice and from a transgenic mouse strain lacking the gene for connexin36. In slices from wild-type mice, both isoflurane (1 MAC) and etomidate (16 μM) reduced interictal-like event frequency; mean(S.D.) reduction of 44(13)% (P < 0.0001) and 25(24)% (P < 0.0001), respectively. The reduction in event frequency was greater for isoflurane (P < 0.005). Isoflurane had no effect on the amplitude of interictal-like events, but event amplitude was enhanced by etomidate (18(28)% increase, P < 0.005). The capacity for isoflurane to reduce event frequency was significantly reduced, but not eliminated in slices from connexin36 knock-out mice (33(15)% reduction, P < 0.05 for the difference with wild-type), while that of etomidate remained unchanged (23(39)% reduction). The etomidate-mediated increase in event amplitude was eliminated in connexin36 knock-out slices. The results from this study support the hypothesis that the anticonvulsant effect of isoflurane is in part mediated by gap junction blockade. The role of gap junction modulation by etomidate is more complicated and may be important in the mechanism of action of etomidate's proconvulsant effects.

text: Role of Cx36 gap junction modulation in general anaesthetic anticonvulsant action Many GABAergic anaesthetics reduce gap junction coupling but it is currently unknown whether this effect contributes to anaesthetic anticonvulsant action. In this study we examined the possible role of connexin36 gap junctions in the anticonvulsant action of isoflurane and compared this to etomidate, an anaesthetic known for having proconvulsant effects. We compared the effect of anaesthetic concentrations of isoflurane (1 MAC) and etomidate (16 μM) on low-magnesium-induced interictal-like activity in isolated neocortical slices. The effect of connexin36 gap junction blockade was explored by comparing effects in slices from wild-type mice and from a transgenic mouse strain lacking the gene for connexin36. In slices from wild-type mice, both isoflurane (1 MAC) and etomidate (16 μM) reduced interictal-like event frequency; mean(S.D.) reduction of 44(13)% (P < 0.0001) and 25(24)% (P < 0.0001), respectively. The reduction in event frequency was greater for isoflurane (P < 0.005). Isoflurane had no effect on the amplitude of interictal-like events, but event amplitude was enhanced by etomidate (18(28)% increase, P < 0.005). The capacity for isoflurane to reduce event frequency was significantly reduced, but not eliminated in slices from connexin36 knock-out mice (33(15)% reduction, P < 0.05 for the difference with wild-type), while that of etomidate remained unchanged (23(39)% reduction). The etomidate-mediated increase in event amplitude was eliminated in connexin36 knock-out slices. The results from this study support the hypothesis that the anticonvulsant effect of isoflurane is in part mediated by gap junction blockade. The role of gap junction modulation by etomidate is more complicated and may be important in the mechanism of action of etomidate's proconvulsant effects.

year: 2010

title: Impulse TDR and its application to measurement of antennas

authors: McCabe, Steven Owen

subjects: antenna measurements

abstract: The traditional stimulus signal used in a time-domain reflectometer (TDR) is a voltage step. We propose an alternative technique, whereby an impulse generator is employed in place of the step generator in a TDR. The advantage conferred by “impulse TDR” is that more energy is available at higher frequencies than with conventional step TDR, and so a higher bandwidth and signal-to-noise ratio (SNR) is achieved. The theoretical result is compared with measurement.

text: Impulse TDR and its application to measurement of antennas The traditional stimulus signal used in a time-domain reflectometer (TDR) is a voltage step. We propose an alternative technique, whereby an impulse generator is employed in place of the step generator in a TDR. The advantage conferred by “impulse TDR” is that more energy is available at higher frequencies than with conventional step TDR, and so a higher bandwidth and signal-to-noise ratio (SNR) is achieved. The theoretical result is compared with measurement.

year: 2011

title: Hau

authors: Lodge, Martin

subjects: music

abstract: The article presents reflections on some issues encountered when combining traditional Maori and Western concert music. These issues include tradition and repertoire versus innovation, control versus freedom, collaboration versus appropriation, and the overlapping roles of creator and performer. Focal to the article is "Hau," a Maori word meaning breath or wind. The author also presents a comparison of Western music with traditional Maori instrumental music.

text: Hau The article presents reflections on some issues encountered when combining traditional Maori and Western concert music. These issues include tradition and repertoire versus innovation, control versus freedom, collaboration versus appropriation, and the overlapping roles of creator and performer. Focal to the article is "Hau," a Maori word meaning breath or wind. The author also presents a comparison of Western music with traditional Maori instrumental music.

year: 2007