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Biomedical subjects

I Jibiki

Publications and source records attributed to I Jibiki.

At least 73 records · Page 4Linked to original sources
PubMed1988

Acute kindling: interstimulation interval effects and spontaneous interictal or ictal epileptiform discharges.

With regard to "acute kindling" that signifies progressive changes in various epileptiform discharges produced with repeated electrical stimulations in a brief time span in acute experiments, the interstimulation interval effect was examined. Kindling developments produced respectively with 3 and 30-minute interval stimulations to the visual cortex of rabbits were compared with each other. Eventually, in kindling with a longer interstimulation interval, after-discharges induced in every trial of stimulation were often lengthened in duration more prominently than those with the shorter interstimulation interval and, furthermore, occasional slight relapses in the afterdischarge duration occurred more infrequently in the former than in the latter. These results suggest that the interstimulation interval plays an important role in the development of acute kindling, presumably in relation to postictal inhibition. In addition, spontaneous interictal or ictal epileptiform discharges occasionally arising during the 3-minute interstimulation intervals were reported. These spontaneous discharges may suggest a high epileptogenicity in acute kindling.

Animals↗
PubMed1988

Acute kindling: discrepancy between lengthening of after-discharge duration and increase of field EPSP evoked in kindled site during interstimulation interval.

For studies on acute kindling that signifies the progressive changes in various epileptiform discharges produced with repeated electrical stimulations within a brief time span in acute experiments, changes in field EPSP and IPSP evoked in the unilateral visual cortex of rabbits by single shocks to the adjacent visual region were serially observed during and after kindling produced with a 15-minute interval stimulation repeatedly applied to the same visual cortex. Eventually, both the field EPSP and IPSP in the primary kindled site were progressively potentiated at each postictal or interictal stage during the acute kindling, and these potentiations lasted for hours allowed for acute experiments. However, a clear discrepancy was observed between the increase in the field EPSP and the lengthening of the after-discharge duration reflecting a progressive development of epileptiform discharges in acute kindling. These results suggest that long-term potentiation (LTP) has no parallel correlation to kindling development, although there is no denying the fact that LTP may be at least partly responsible for kindling development.

Animals↗
PubMed1988

Visual cortical kindling in rabbit--consideration of difference between species.

Visual cortical kindling was studied in chronically prepared rabbits with regard to the electrographic progress of epileptiform discharge trains following the daily stimulation and corresponding ictal behaviors. The spread of epileptiform discharges from the stimulated visual cortex to the parietal and frontal cortices of the stimulated side was observed early with the development of independent discharges in these parietal and frontal regions, accompanied by ictal motor symptoms of the contralateral side. In view of the past studies on rats, cats and monkeys, it was considered that such a spread in the neocortex and corresponding ictal behaviors might be specific to the rabbit.

Animals↗
PubMed1986

Thalamocortical and intrathalamic interactions during slow repetitive stimulation of n. centralis lateralis.

Extracellular single unit activity was recorded simultaneously in cortex (anterior part of the middle suprasylvian gyrus, MSSG) and thalamus (n. ventralis anterior, VA; n. lateralis posterior, LP) during repetitive low frequency stimulation (RLFS) of n. centralis lateralis (CL) in lightly anesthetized cats. Such stimulation induced typical recruiting responses in the cortical EEG consisting of long-latency, surface-negative waves reversing in polarity at 0.1-2mm depth. These cortical EEG responses were associated with long-latency (8-20 ms) action potential (AP) discharges of cortical neurons appearing with the 2nd stimulus of the train. The number of AP discharges and response latency increased as the train of CL stimuli progressed. In 12 of these neurons there was a short-latency (up to 2-5 ms) response which, however, did not show incremental features during RLFS. Thalamic neurons in VA usually responded to the first stimulus within a train of RLFS of CL, while LP neurons responded only to the 2nd or 3rd stimulus. Peristimulus time histograms (PSTHs) of AP discharges in VA showed an increase in both number and latency of APs as the train of stimuli progressed. This was also observed in those thalamic neurons in LP which changed their firing during RLFS of CL. The peak of firing of 20 VA neurons preceded, and that of 7 followed that of the MSSG neurons, while 6 VA and MSSG neuronal pairs reached their peak firing simultaneous; peak firing of 29 LP neurons preceded, and that of 21 followed the firing peak of MSSG neurons. The thresholds of the incremental responses of MSSG, VA and LP neurons to progressively increased intensity of RLFS of CL were different: MSSG and VA neurons changed their firing pattern at an intensity incapable of modifying the activity of LP neurons. When stimulation intensity was increased to a level sufficient to change the responses of both neurons of a given pair (either MSSG-VA or MSSG-LP) the time sequence of involvement in the incremental process was in the following order: VA, MSSG, LP. Within a range of RLFS extending from 2-20 Hz, stimulation at 6.6 Hz (150 ms interstimulus intervals) induced the most prominent incremental responses both in the cortex and thalamus, i.e. response increases were largest when each subsequent stimulus occurred 50-130 ms before the expected rebound excitation following the preceding response.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1986

Lateral geniculate kindling and long-lasting photosensitivity in cats.

The kindling response of the lateral geniculate body (GL) was compared with that of the amygdala, using cats. Daily electrical stimulation in the GL group led to the generalized tonic-clonic convulsion in most subjects and the resulting state of seizure susceptibility was long-lasting, as in the amygdala group. The kindling response of the GL differed from that of the amygdala in some respects, i.e., rapid kindling, short latency for seizure generalization, a different pattern of behavioral seizure development, and seizure regression during the course of kindling. The effects of photic stimulation with pentylenetetrazol administration were also examined before and after kindling in both groups. This study revealed that the photically induced myoclonus, at times proceeding to the generalized tonic-clonic convulsion, was provoked repeatedly as a result of GL kindling, whereas none of the amygdala-kindled cats showed such marked photosensitivity. These photically induced seizures were invariably observed for at least 4 weeks after GL kindling. Our results suggest that a neural mechanism participating in GL kindling is different from that in amygdala kindling, and that there might be cross-sensitization between seizure susceptibility resulting from GL kindling and photosensitivity.

Amygdala↗
PubMed1983

"Convulsoid responses" suggesting development of autonomous epileptogenicity.

To test a convenient and reliable neuronal index that suggests the development of autonomous epileptogenicity, we conducted in acute experiments on rabbits a comparative study of the changes in direct cortical responses (DCRs) in primary and mirror sites during electrically induced primary (PRID) and projected seizure discharges (PROD). It has been assumed that the primary site shows autonomous epileptogenicity during the PRID, whereas the mirror site during the PROD does not. We observed that in the primary site, the dendritic potentials (field EPSPs) were remarkably suppressed in amplitude or disappeared during the PRID and that there was a loss of the after-positivity (field IPSPs); these DCRs recovered gradually after termination of the PRID. Instead of DCRs, "convulsoid responses" (a general term for responses similar to the individual spontaneous waves which occur in all types of seizures discharges) were usually elicited in the primary site during PRID. In the mirror site during PROD, the DCRs showed three different behaviors: they were either unaffected, increased, or suppressed. Convulsoid responses were never elicited. In a few cases, independent seizure discharges were induced in the mirror site. During the independent seizure discharges, the DCRs in the mirror site disappeared and convulsoid responses similar to the individual independent waves were usually elicited, as in the primary site during PRID. We conclude that the convulsoid response was the most reliable indicator of the development of autonomous epileptogenicity, and that suppression or disappearance of DCRs was the supplementary sign of that development. These neuronal indexes may be useful for identification of secondary epileptogenesis.

Animals↗
PubMedDate not supplied

The prevalence of Rett syndrome in Fukui prefecture.

The present study was performed to estimate the prevalence of Rett syndrome in Fukui prefecture by sending questionnaires to special classes (classes for handicapped children in schools for normal children) and schools for mentally/physically handicapped children, and observing children suspected of having this syndrome on the basis of answers to the questionnaire. The subjects were girls aged 6-14 years who were attending 11 special classes and 7 schools for handicapped children. The prevalence of Rett syndrome was estimated to be 0.22 per 10,000 girls aged 6-14 years in Fukui prefecture, as of April 1, 1993. The prevalence noted in this study was lower than those found in previous studies in Japan and Western countries.

Adolescent↗
PubMedDate not supplied

Effects of risperidone, an atypical antipsychotic drug, on excitatory synaptic responses in the perforant path-dentate gyrus pathway in chronically prepared rabbits.

The effects of an atypical antipsychotic drug, risperidone, were examined on excitatory synaptic responses in the dentate gyrus by single electrical stimulations to the perforant path and the induction of long-term potentiation (LTP) in this pathway in chronically prepared rabbits. Any of 0.5, 1.0 and 2.0 mg/kg doses of risperidone intraperitoneally injected had virtually no effect on the excitatory synaptic responses. However, these three doses of risperidone dose-dependently suppressed the LTP induction.

Animals↗
PubMedDate not supplied

Antiepileptic effects under steady state of phenytoin serum levels produced in acute experiments.

The antiepileptic effects of phenytoin (PHT) were examined during steady-state serum levels. Experiments were conducted on 69 adult male rabbits weighing 2.5-3.5 kg. A steady state of one or two different PHT serum levels per rabbit was produced with intravenous (i.v.) injections of loading and infusion doses. A train of focal and generalized seizure discharges (SDs) induced by electrical stimulation was compared before and after dosing with PHT. The results showed that PHT levels of 10-40 micrograms/ml induce inhibitory effects, shortening the duration of neocortical focal SDs. The inhibitory effects paralleled the PHT levels and were proportionally related to epileptogenicity in individual neocortical areas. At serum levels under approximately 5-10 micrograms/ml, the spread of secondarily generalized SDs originating from neocortical focal SDs was suppressed more than the shortening of the duration of the primary focus. On the other hand, PHT showed no effects or only slight inhibitory effects on hippocampal SDs, and the SDs spread from them even at levels of 15-40 micrograms/ml. Electroshock (ES)-induced generalized SDs were slightly suppressed in duration at levels of 20-30 micrograms/ml. Moreover, both the focal and the generalized SDs were greatly prolonged at high serum levels (greater than 40 micrograms/ml), although such facilitative effects were rare. The clinical contributions of these results to PHT treatment in human epilepsy are discussed.

Animals↗