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Biomedical subjects

M Sakakibara

Publications and source records attributed to M Sakakibara.

134 records · Page 8Linked to original sources
PubMed1983

Discrete nonlinear reduction model for horizontal cell response in the carp retina.

In this paper we present a new model for the spatial behavior of the external horizontal cells in the carp retina which elucidates more precisely the mechanisms of their intercellular connections. The area and intensity effects of a brief light stimulus on the L-type response were recorded and analysed. We discovered clear nonlinearities in the behavior of the response which could not be explained by the simple summative model presently accepted. Proposed here is a new model, the spatial reduction mechanism, which explains the experimental evidences including these nonlinearities. We also present the results of a computer simulation using our new model in parallel with the actual results obtained experimentally. The physiological implications of these findings are discussed.

Animals↗
PubMed1977

Spreading depression in isolated carp retina.

(1) Spreading depression (SD) could be elicited in isolated carp retina by KCI application, the concomitants of which were similar to those described in other vertebrates. (2) The threshold for generating SD was greatly reduced by brief immersion of the retina in low ci-ringer's solutions. The properties of SD waves were almost the same with treated and untreated retinas, except for intervals. (3) Extracellular negative potential shifts during SD, averaging 4.6 mV in amplitude and 27 sec in duration, were recorded in whole retinal layers with the maximum amplitude about at the inner plexiform layer. (4) The PIII potential of the local electroretinogram was virtually unaffected by SD. (5) Both L-and C-type S-potentials could be evoked with increase of 20-40% in amplitude around the peak of slow membrane depolarizations (mean value of maximal amplitude 5.8 mV) during SD in horizontal cells. (6) Increase in spike number was observed in both on-and off-center ganglion cells before and after the spike cessation during SD in the untreated retina. However, the off-discharges, which were a unique response to light in the immersed retina, only decreased during SD.

Animals↗
PubMedDate not supplied

Effect of slowed respiration on cardiac parasympathetic response to threat.

The present study was designed to examine the effect of voluntarily slowed respiration on the cardiac parasympathetic response to a threat: the anticipation of an electric shock. Thirty healthy college students were randomly assigned to the slow, fast, and nonpaced breathing groups (10 subjects each). Subjects in the slow and fast paced breathing groups regulated their breathing rate to 8 and 30 cpm, respectively, and those in the nonpaced breathing group breathed spontaneously. Immediately after the period of paced or nonpaced breathing for 5 minutes, the subjects were exposed for 2 minutes to the anticipation of an electric shock during breathing paced at 15 cpm. The amplitude of the high frequency (HF) component of the heart rate variability, an index of cardiac parasympathetic tone, significantly decreased during the threat in the fast and nonpaced breathing groups, whereas it was unchanged in the slow paced breathing group. No significant difference was observed among the three groups in the amplitude of respiration during the threat. Results suggest that a slowed respiration decreases the cardiac parasympathetic withdrawal response to the threat. This study provides a rationale for the therapeutic uses of the slowed respiration maneuver in attenuating the cardiac autonomic responses in patients with anxiety disorder.

Adult↗