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Biomedical subjects

Y Yonemasu

Publications and source records attributed to Y Yonemasu.

At least 91 records · Page 5Linked to original sources
PubMed1990

GABA withdrawal syndrome: a model of the epilepsia partialis continua.

After the chronic infusion of GABA into the cortex of baboon Papio Papio, a sudden stop of the infusion provoked cortical epileptic discharges around the infused area. And the baboon exhibited partial epilepsy for about 3 days. The result suggested that GABA withdrawal syndrome should be a good model not only to understand the mechanism of epilepsia partialis continua but also partial epilepsy with a circumscribed cortical focus.

Animals↗
PubMed1990

[The effects of disturbance of cerebral venous drainage on focal cerebral blood flow and ischemic cerebral edema].

The effect of disturbance of cerebral venous drainage on acute ischemic cerebral edema and cerebral circulation were studied by measuring local cerebral blood flow (LCBF) and local changes in brain water content using a middle cerebral artery (MCA) occlusion model. Rats were anesthetized with halothane and the stem of the left MCA was occluded. Disturbance of cerebral venous drainage was induced by bilateral occlusion of the external jugular veins, i.e., the right external jugular vein was cannulated and the left one was occluded by a clip. LCBF was measured by the 14C-iodoantipyrine (14C-IAP) autoradiographic method at 2 hours after MCA occlusion. Local changes in brain water content were studied 2 hours after MCA occlusion by measuring the specific gravity of cerebral tissue in the gradient column with bromobenzene and kerosene. The control rats which underwent the same anesthesia and surgical procedure including the MCA occlusion and cannulation into the right external jugular veins, but which did not undergo occlusion of the left external jugular veins, were prepared and studied at the same time after MCA occlusion. In the rats with bilateral occlusion of the external jugular veins, the external jugular venous pressure was evaluated up to about 8 mmHg (100 mmH2O) (control: 1.3 mmHg). At 2 hours after MCA occlusion, LCBF in the ischemic core was decreased. The ischemic area was more extensive in the rats with bilateral occlusion of the external jugular veins compared with the controls. Furthermore, specific gravity of the brain was decreased in the entire left MCA territory in the rats with bilateral occlusion of the external jugular veins.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute Disease↗
PubMed1989

Ibotenic acid-induced nigral lesion and limbic seizure in cats.

The degenerative lesions of bilateral substantia nigra (SN) were made by means of microinjections of ibotenic acid (IBO) solutions and influences upon kainic acid (KA)-induced seizures were studied. IBO solutions were injected bilaterally into SN and circumscribed degenerative lesions were made within the bilateral SN. In a control group, phosphate buffer solutions were injected in the bilateral SN. More than one week after the procedures, 1 microgram KA was injected into unilateral amygdala via implanted cannula and limbic seizures were induced. The destruction of SN accelerated the secondary generalization of the limbic seizure within 3 days after the KA injection while no secondary generalization was observed within 3 days in the control group. The fact suggests that GABAergic systems of the substantia nigra and/or ascending norepinephrine pathway have a strong inhibitory influence on the secondary generalization of limbic seizures. The hypothesis of nigral mechanisms as a control system for secondary generalization is discussed.

Animals↗
PubMed1989

Regional calcium accumulation and kainic acid (KA)-induced limbic seizure status in rats.

The sites of calcium accumulation were studied by 45Ca autoradiography during kainic acid (KA)-induced limbic seizure in rats. Two hours after KA injection into unilateral amygdala, calcium accumulated in CA3 of the hippocampus, lateral septal nucleus and thalamic reticular nucleus on KA-injected side. Those sites coincided with the sites where neuronal cell damage appeared 4 h after KA injection. These results suggested that regional calcium accumulation might be responsible for neuronal cell loss induced by seizures.

Animals↗
PubMed1989

Surgical treatment of experimental limbic status epilepticus.

Limbic status epilepticus was induced by means of a KA microinjection into unilateral amygdala, and the focus extirpation (amygdalotomy) was made in order to examine whether the status was suppressed or not. The amygdalotomy was effective when the status was mild and the focus was circumscribed to the amygdala. However, the surgery was no more effective when a severe limbic status was induced and a secondary epileptogenic focus was established. Within 8 hours after induction of the limbic status, neuronal cell damage was observed in the pyramidal cell layer of the hippocampus.

Amygdala↗
PubMed1989

Intracranial malignant teratoma diagnosed in a fetus--case report.

The authors describe a case of intracranial malignant teratoma in a 28-week fetus, discovered on assessment of the mother's excessive abdominal enlargement. Alpha-fetoprotein levels in amniotic fluid and serum were high. Ultrasonography revealed a large, solid intracranial mass. The fetus was viable until completion of a cesarean delivery, at which time the heart stopped. At autopsy, the fetal brain was found to have been extensively replaced by a solid, cystic tumor, which proved to be a malignant teratoma comprising elements of all three germ cell layers. The authors' experience and review of the reported cases indicate that prenatal malignant intracranial teratoma can be safely and accurately diagnosed, and that immediate delivery or cranial decompression may be advisable when the diagnosis is established. The usefulness and limitations of ultrasonography are particularly emphasized.

Brain Neoplasms↗
PubMed1989

[Acute effect of penicillin G on feline models of focal epilepsy].

Penicillin is well known as a potent convulsive agent. A cortical topical, intracerebral or systemic administration of penicillin produces abnormal and paroxysmal activity which may lead to seizure, and has been used in the investigation of the mechanisms of epilepsy. This is a report on the studies of an acute effect of potassium penicillin G on two models of experimental focal epilepsy: a) amygdaloid kindling model, and b) kainic acid-induced limbic seizure model. Twelve adult cats for amygdaloid kindling model (kindling group), six for KA-induced limbic seizure model (KA group) and four for a control group were prepared for this study. In kindling group, after completion of kindling procedure, 40-60 X 10(4) unit/kg of potassium penicillin G (PC), dissolved in sterilized normal saline, was injected intraperitoneally during an interictal period. In KA group, 1 micrograms of KA was injected into the left amygdala. Limbic seizures occurred frequently during the initial 5 hours but subsided completely within 3 days. After a latent period, spontaneous secondarily generalized convulsion occurred from 30 to 60 days after KA injection. The cats were completely normal in their behavior during the interictal period. During the interictal stage after the first generalized convulsion has been observed, 15-20 X 10(4) unit/kg of PC was injected intraperitoneally. In the control group, 40-60 X 10(4) unit/kg was injected intraperitoneally. Electroclinical observations were continued until 5 hours after PC injection in three groups. In the control group, no cats developed generalized convulsion. In the kindling group, 4 of 12 cats developed focal amygdaloid seizures with secondary generalization by nearly the identical doses required in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗
PubMed1989

[Influence of destruction of bilateral hippocampus upon amygdaloid kindling in rats].

It is well known that hippocampus has an important role in the development of limbic seizures in the experimental model of epilepsy. Intrahippocampal microinjections of the ibotenic acid (IBO) resulted in various degree of hippocampal degenerations and influences of these lesion upon amygdaloid kindling rats. A stereotaxic operation was carried out and bipolar electrodes were placed unilaterally in amygdala and hippocampus. The IBO solutions were injected bilaterally into dorsal hippocampus (DH) in Group A, into ventral hippocampus (VH) in Group B and into DH and VH in Group C. Phosphate buffer solutions were injected in Group D as a control. All rats were subjected to amygdaloid kindling more than 8 days after the operation. Group A, Group B, Group C, and Group D (controls) required 10.3 +/- 2.6, 11.3 +/- 2.6, 17.4 +/- 4.4 and 8.7 +/- 2.3 stimulations for the Stage V seizures, respectively. The kindling rate in Group C increased compared with controls and this increase was statistically significant (P less than 0.01). A histopathological study revealed remarkable degenerative changes in DH of Group A, in VH of Group B and all over the hippocampus in Group C. The result suggested facilitatory interaction of the hippocampus upon amygdaloid kindling.

Amygdala↗
PubMed1989

[Experimental limbic seizure status epilepticus and focus resection in cats].

Status epilepticus is a neurological emergency and refractory one often resulted in neurological damage or death. Since the basic mechanisms of status epilepticus was not fully understood, a surgical treatment was not attempted until now. In the present study, a surgical resection of the epileptic focus was made in experimentally induced limbic status epilepticus and influences of the surgery upon status epilepticus was discussed. Limbic status epilepticus was induced by means of kainic acid (KA) microinjection into unilateral amygdala in cats and effects of focus resection upon limbic seizure status were studied. Ten adult cats were stereotaxically operated on under pentobarbital anesthesia. Bipolar electrodes were placed in bilateral amygdala and hippocampus. An injection cannula, designed for kainic acid injection, was placed in the left amygdala. The cats were then divided into two groups. Group A (5 cats) received 0.5 microgram of KA injection into the amygdala resulted in mild limbic status. Two of them were controls and 3 of them received amygdalotomy after induction of the limbic seizure status. Group B (5 cats) received 2.0 micrograms KA injection resulted in severe limbic status. Moreover, independent spontaneous seizure activities were observed in the ipsilateral hippocampus. Two of them were controls and 3 of them were operated on. After amygdalotomy, limbic seizure stopped in the operated cats of Group A. In the operated cats of Group B, repeated seizures in the epileptogenic focus (amygdala) was completely suppressed, however, spontaneous seizures of the ipsilateral hippocampus persisted even after the surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗
PubMed1989

[Brain death].

Explore the source record for details and available documents.

Brain Death↗
PubMed1989

[Clinical analysis of reoperation in cases of complex partial seizures].

Of a series of 526 cases of surgically treated refractory epilepsy, 387 cases were patients with complex partial seizures. Among 118 cases who had no improvement by the first operation, to prevent partial seizures, 20 patients underwent reoperation. Of the 20 patients, 12 (60%) were men. The mean age at the first operation was 21.7 years. A retrospective analysis of clinical findings, successive EEG findings, psychological studies, surgical findings and surgical treatment of these patients were made. Following the first operation, complex partial seizures reappeared within a mean period of 5.5 months. And the mean period from the first operation to the reoperation was 4.9 years. Following reoperations, 6 patients (30%) became seizure-free, 3 patients (15%) had a remarkable reduction of seizures and 7 patients (35%) had worthwhile improvement. But 4 patients (20%) had no improvement. Histopathological study of the resected hippocampus revealed gliosis in 16 patients (80%). The indication for and procedures of reoperation were discussed.

Adolescent↗
PubMed1989

[Limbic seizure and ibotenic acid-induced lesions of substantia innominata in cats].

The substantia innominata (SI) contains a lot of cholinergic neurons and mainly project their fibers to the cerebral cortex and to the amygdala. Degenerative lesions were made in the bilateral SI and influences of these lesions upon kainic acid-induced limbic seizure were studied. Eleven adult cats were stereotaxically implanted and 2.5 micrograms of ibotenic acid (IBO) was injected into the bilateral SI in 6 cats (IBO group) and 1 microliter of phosphate buffer (PB) in 5 cats (PB group). All animals were given freedom at least 8 days to recover from the operation. Kainic acid microinjection was made into the left amygdala and electroclinical observation was done. In PB group, the limbic status was elicited and these seizures persisted for about 3 days after the KA injection. Seizures were subsided but interictal discharges were observed at the injected site of the amygdala. Then, limbic seizures reappeared within 10 days and a slowly progressive development of limbic seizure was observed. These seizures developed further. Occasionally, these limbic seizures successively developed and secondarily generalized seizures occurred once or twice a week. Otherwise, their clinical behaviors were normal during the interictal periods. In IBO group, the limbic status were elicited and lasted for about 3 days after the KA injection. Although interictal discharges reappeared at the injected site of the amygdala, successive development of the limbic seizure was not observed. The secondarily generalized seizure never occurred in the IBO group. Histopathological studies revealed circumscribed degenerative changes in the bilateral SI. The KA microinjection into the amygdala resulted stereotyped amygdaloid degenerative lesions in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗
PubMed1988

Long-term observation of rats after unilateral intra-amygdaloid injection of kainic acid.

Electroencephalographic and clinical observations of the rats were done for 3 months after microinjection of kainic acid (KA, 0.2-1.2 micrograms) into the unilateral amygdala. With high doses of KA (0.6-1.2 micrograms) injection, 64% of rats developed spontaneous limbic seizures 14-25 days after KA injection. Among those which developed spontaneous limbic seizures, 33% of rats developed secondarily generalized seizures 26-71 days after KA injection. This is one of the best chronic models of spontaneous complex partial seizure secondarily generalized in rats, which is economical and easy to prepare.

Action Potentials↗
PubMed1988

Relationship between sleep-wakefulness cycle and regional cerebral blood flow in kainic acid-induced epileptic focus in hippocampus.

Concurrent monitorings of polygraph and continuous measurements of rCBF of the epileptic focus were made in the nonanesthetized chronic cats. The influences of the sleep-wakefulness cycle on IIDs and rCBF of the epileptic focus of the hippocampus were analyzed. 1) IIDs increased remarkably during LSW and DSW but not as much as during DSW-P. 2) The rCBF decreased gradually during LSW and DSW. But the rCBF during DSW-P increased slightly as compared to that of DSW. 3) The frequencies of IIDs increased in association with hypoperfusion of the epileptic focus. 4) The spiking rate of the hippocampal focus decreased with the appearance of PGO during the deep slow wave sleep stages.

Animals↗
PubMed1988

[Acute effect of flunarizine on amygdaloid kindling in cats].

Flunarizine (Flu), a difluoro derivative of cinnarizine, is well known as a calcium channel blocker. Recently, many authors have reported an antiepileptic effect of this drug in experimental models of epilepsy and in the clinical use. In the present study, acute effect of Flu was examined in the amygdaloid kindled cats, and add-on effects of Flu with valproic acid (VA) was also studied. Twenty three cats were used in this study. Amygdaloid kindling was established as previously reported. A strength of stimulations for kindling was at 300 microA. Same strength was used after completion of kindling. In this "high intensity" kindling, daily stimulation invariably induced initial amygdalo-hippocampal seizures followed by secondarily generalized seizures after completion of kindling. In addition, one amygdaloid stimulation was given daily for 5 days after completion of kindling in order to make it certain to induce secondarily generalized seizures. Drugs were injected on the 6th day intraperitoneally one or two hours before the stimulation daily given for 5 days after completion of kindling (GS 6) or after 4 days clearance period of previous administration of the drug. Pretreatment with Flu (high doses: 30 or 50 mg/kg, i.p.) abolished the secondary generalization after the GS 6. With this high doses of Flu animals died of side effect within 3 days after intraperitoneal administration. With lower doses of Flu less than 3 mg/kg, i.p. of Flu no side effect was encountered but antiepileptic effect was not obtained as well. Then add-on trials of Flu were performed with valproic acid (VA). The most effective combination was 100 mg/kg, i.p. of VA with 3 mg/kg, i.p. of Flu. With this combination, secondary generalization was suppressed at a ratio of 54.5% The results confirmed antiepileptic effect of Flu and add-on effect of Flu to VA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amygdala↗