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Biomedical subjects

Y Yonemasu

Publications and source records attributed to Y Yonemasu.

At least 19 recordsLinked to original sources
PubMed1995

Zonisamide: electrophysiological and metabolic changes in kainic acid-induced limbic seizures in rats.

We studied the pharmacological mechanism of zonisamide (ZNS) using an electrophysiological and autoradiographical method in a limbic seizure model in rats. Limbic seizure status epilepticus was induced by a unilateral microinjection of kainic acid (KA) into the amygdala. Initially, observed seizures were limited to the side of the injected amygdala and then propagated to bilateral sensorimotor cortex. Eighty minutes after injection, secondarily generalized seizure status epilepticus was induced, with each seizure lasting approximately 30 s and recurring every 5 min. ZNS 100 mg/kg was administered intravenously (i.v.) during the generalized seizure. Forty minutes after ZNS administration, epileptic activity was observed only at the KA-injected amygdalar site and spikes were not observed in the bilateral sensorimotor cortex. We studied local cerebral glucose utilization (LCGU) after ZNS or saline administration using an autoradiographical method in the same limbic seizure preparation. In the ZNS group, LCGU decreased in the ipsilateral sensorimotor cortex and hippocampus, whereas in the controls LCGU increased in these structures. On the other hand, ZNS did not suppress the epileptic activity of the primary focus and no decrease in LCGU was observed in the KA-injected amygdala. ZNS inhibited seizure propagation from the epileptogenic focus but did not suppress the epileptic activity of the focus. Our results suggest that ZNS is effective for the treatment of secondarily generalized seizure.

Animals↗
PubMed1995

Cavernous sinus invasion by pituitary adenomas--relationship between magnetic resonance imaging findings and histologically verified dural invasion.

The relationship between magnetic resonance (MR) imaging findings and histologically verified invasion of the cavernous sinus by tumor cells was studied in 26 patients treated surgically for pituitary adenoma. Dural invasion of the sellar floor by tumor cells was found in 10 cases (38%). All patients were classified according to MR imaging findings into three types. Type I showed a gadolinium-enhanced stripe medial to the carotid artery (5 patients), none of which showed dural invasion. Type II showed no enhanced stripe (17 patients), six of which showed dural invasion. Within this type, tumor size and dural invasion showed no correlation. Type III showed displacement or encasement of the carotid artery by the tumor with or without extracranial extension (4 patients), all of which showed massive infiltration of the tumor cells into the dura mater. This study shows that preoperative MR imaging can provide information for assessment of invasion into the cavernous sinus in patients with pituitary adenoma.

Adenoma↗
PubMed1995

[De novo aneurysm associated with a persistent primitive trigeminal artery: case report].

This paper presents a case of a de novo unruptured anterior communicating aneurysm associated with a persistent primitive trigeminal artery. The patient was a 65-year-old female with tinitis, for whom computed tomography with contrast medium indicated right dural enhancement. Dural arteriovernous malformation was suspected and angiography was thus conducted. A right persistent primitive trigeminal artery was demonstrated but no aneurysm could be found. Six years later, magnetic resonance angiography indicated an aneurysm on the anterior communicating artery. It was subsequently removed by surgery. A persistent primitive artery is frequently found to accompany aneurysm but de novo aneurysm associated with such an artery does not appear in the literature to date. The authors emphasize the importance of follow-up angiography in cases of persistent primitive artery not accompanied by an aneurysm.

Aged↗
PubMed1995

[Posttraumatic pseudoaneurysm of the middle meningeal artery: a case report].

An epidural hematoma associated with posttraumatic pseudoaneurysm of the middle meningeal artery is a very rare clinical entity. Only 31 such cases have been reported in the literature. A 54-year-old man was admitted with lethargy and right hemiparesis. A skull X-ray film revealed a linear fracture in the left parietal and temporal bone, extending to the base of the skull. A brain CT scan disclosed an acute epidural hematoma over the left cerebral hemisphere, contusional hematoma in the right frontal lobe and thalamus, and subarachnoid hemorrhage in the left Sylvian fissure. During an emergency craniotomy a large epidural hematoma was evacuated and external decompression was performed. Angiography, which was performed about one month after the head injury, revealed an aneurysm of the middle meningeal artery. The aneurysm was removed to avoid delayed rupture at the time of cranioplasty. Histological diagnosis was pseudoaneurysm. We discussed the pathogenesis of a pseudoaneurysm of the meningeal artery and the necessity to pay attention to the presence of a pseudoaneurysm when an active bleeding point is not observed during surgery of the epidural hematoma.

Aneurysm, False↗
PubMed1995

[Jacksonian seizure model induced by a kainic acid microinjection into unilateral sensori-motor cortex].

Kainic acid microinjection into unilateral sensori-motor cortex induced focal seizure status and secondarily generalized seizure status for about 4 hours. After these seizure status, focal myoclonic jerkings were induced for about 2 days. EEG demonstrated generalized synchronous periodic spikes with these myoclonic jerkings. This phenomenon was very similar to those symptoms of epilepsia partialis continua in man. During focal seizure status, autoradiographic study with 14C-deoxyglucose demonstrated increased local cerebral glucose utilizations in the injected site of the sensori-motor cortex, ipsilateral caudate nucleus, globus pallidus, substantia nigra and thalamic nuclei. The result suggested that subcortical pathways played an important roles in the seizure propagation from the cortical epileptogenic focus.

Animals↗
PubMed1994

Accumulation of exogenous 45Ca after middle cerebral artery occlusion in rats.

The distribution of exogenous 45Ca in the focal ischemia rat model (middle cerebral artery occlusion) was studied using 45Ca autoradiography. High 45Ca accumulations were observed in the frontal cortex and caudate-putamen corresponding with morphological damage shown by HE staining. Regional 45Ca concentrations were calculated from the optical density on the 45Ca autoradiograms. Rapid uptake of 45Ca in the ischemic brain occurred during the first 5 hours, and continued more slowly between 5 and 24 hours after ischemia. The area of 45Ca accumulation was also expanded between 5 and 24 hours. An area of low 45Ca concentration around the area of high accumulation developed 5 hours after ischemia, which presumably accumulated 45Ca between 5 and 24 hours after ischemia. The lower concentration of 45Ca in the periphery of ischemia may result from: 1) a decrease in the total amount of calcium due to narrowing of extracellular space accompanied by cytotoxic edema, and 2) delayed accumulation of exogenous 45Ca due to reduced clearance of extracellular fluid.

Animals↗
PubMed1994

[Basic and clinical approaches for surgical treatment of intractable epilepsies].

Recent reports demonstrated that patients with medically intractable epilepsy were benefited with surgical treatments. Even in pediatric patients, early surgery is effective not only in seizure control but also in verbal, intelligent and social outcomes. In the present study, basic and clinical approaches in the treatment of intractable epilepsies were studied. In chronic cat model of intractable temporal lobe epilepsy induced by a microinjection of kainic acid, temporal cortical excision with amygdala focus resection or focus and hippocampal resections were examined by means of microsurgical technics. The cats with amygdala focus resection demonstrated spontaneous hippocampal seizures while cats with focus and hippocampal resection did not show seizures in the long time course after the surgery. In a cat model of cortical focal seizures, multiple subpial transection(MST) was examined. The cortical seizures, induced by a microinjection of kainic acid into unilateral sensori-motor cortex, were suppressed immediately after the MST. Postoperative course was uneventful and seizure was not recurred. However, pathological study demonstrated subpial scar formation at the site of MST in the sensori-motor cortex. In 38 patients with medically intractable epilepsies, surgical treatments were performed in the Department of Neurosurgery. Asahikawa Medical College. The site of the epileptogenic lesion was studied with Video-EEG longterm monitorings, Neuro-imagings with CT, MRI, interictal SPECT and/or ictal SPECT. At the surgery, intraoperative electrocorticograms(ECoGs) were monitored under light neuroleptanalgesia in order to localize epileptic focus. Seizure free rate with or without postoperative medication was 72%. Remarkable improvement was observed in 7 patients (18%), but, 4 patients (10%) did not show any improvement.

Adolescent↗
PubMed1994

[Electrophysiological and behavioral features of septal seizures in cats--experimental sham-rage seizures induced by injection of kainic acid].

The septal nucleus has close connections with the hippocampus and amygdala and is known to be involved in emotional behavior. We analyzed the electrophysiological and behavioral features of seizures induced by an injection of kainic acid into the lateral septal nucleus of the cat. Stereotactic surgery was performed to implant a cannula into the lateral septal nucleus to make the injection, and deep electrodes were implanted into the hippocampus and amygdala bilaterally. Seven days post operatively kainic acid, 0.5 microgram/0.5 microliter, was injected via the cannula, and three to five minutes later the cats began to exhibit head turning to the contralateral side. The seizures subsequently progressed limbic seizure status. The electroencephalogram revealed that the spike discharges started in the lateral septal nucleus, extended to the ipsilateral hippocampus and amygdala, then propagated to the contralateral side. Spontaneous sham-rage seizures occurred more than seven days after the injection. These seizure were characterized by sudden onset of aggressive and violent behavior which included hissing, biting and scratching. The electroencephalogram showed synchronization of rhythmic spikes in the ipsilateral septal nucleus, hippocampus and amygdala during such seizures. Further study of this model is important not only to understand the relationship between the septal nucleus and the hippocampus and amygdala but to understand the mechanism of sham-rage seizures. In addition, this model may be useful in understanding the emotional features of intractable complex partial seizures in man.

Animals↗
PubMed1993

Magnetic resonance imaging in kainic acid-induced limbic seizure status in cats.

Magnetic resonance imaging before, during, and after kainic acid (KA)-induced limbic seizure status in cats demonstrated the bilateral hippocampi as slightly high-intensity areas on the T2-weighted images during the limbic seizure status, and isointensity areas 1-2 weeks after KA injection when the limbic seizure status subsided. However, the hippocampi again became high-intense 1-3 months after KA injection. Histological study suggested that the high-intensity area during the limbic seizure status resulted from regional edema, and in the chronic period from marked gliosis and/or atrophic change as a consequence of tissue damage in the hippocampus.

Amygdala↗
PubMed1993

Pathology of infantile brain tumor.

Five brain tumors in infancy were studied histopathologically. Though four of them could be included in primitive neuroectodermal tumor, histopathological findings were diverse. The diagnoses were medulloblastoma, cerebellar neuroblastoma, pineoblastoma, ependymoblastoma and ependymoma. While conventional stain for microscopy exhibited their specific findings, immunohistochemical and electron microscopical studies revealed morphological findings related functional structures of the tumor cells. These methodology is mandatory in order to elucidate cytogenesis and differentiation of infantile brain tumors.

Brain Neoplasms↗
PubMed1992

Effects of intracarotid infusion of neuropeptide Y on cerebral blood flow in rats.

Neuropeptide Y (NPY) was continuously administered to Wistar rats intracarotidly via the external carotid artery and local cerebral blood flow (LCBF) was measured by a quantitative autoradiography using [14C]iodoantipyrine. A remarkable reduction in LCBF was observed in the NPY infused hemisphere. This depression was irregular and was particularly evident in the hippocampus, selective thalamic nuclei and the cerebral cortex.

Animals↗
PubMed1992

Cerebral blood flow and histopathological changes following permanent bilateral carotid artery ligation in Wistar rats.

Cerebral blood flow and histopathological changes after bilateral carotid artery ligation (BCAL) in Wistar rats were studied. Eight of the 38 rats (21%) died within one week. In the 30 survivors, the incidence of histopathological change was 90% in the caudate nucleus, 23% in the cortex, 30% in the hippocampus, and 0% in the other structures. Local cerebral blood flow (LCBF) was measured using the quantitative autoradiographic 14C-iodoantipyrine technique in 24 anatomically discrete regions of the brain. BCAL induced ischemia in the entire forebrain. The percent reduction of LCBF was between 25-94% of the control at 2.5 h after BCAL. LCBF tended to recover 1 week after BCAL except for the regions of neuronal damage. These results suggest that neuronal damage does not correlate with the flow rate. In the present study, selective neuronal damage was also observed in rats with chronic cerebral ischemia.

Animals↗
PubMed1992

Kainic acid-induced thalamic seizure in cats--a possible model of petit mal seizure.

Bipolar depth electrodes were implanted stereotaxically in the thalamus, hippocampus and midbrain reticular formation of cats. Cortical screw electrodes were placed over the bilateral sensorimotor cortex. A guide cannula with an inner injection cannula was inserted unilaterally into the posterolateral ventral nuclei (VPL) of the thalamus. Eight days after the procedures, kainic acid (2.0 micrograms) was injected unilaterally into the VPL via the injection cannula in freely moving animals and electro-clinical observations were made. About 1 h after the kainic acid injection, multiple spikes were observed in the VPL (injection site), which propagated to the subcortical structures. These seizures finally propagated bilaterally to the cortex about 2 h after the injection. About 3-4 h after the injection, small spike and wave complexes repeatedly appeared for a short period of time in cortical leads and cats exhibited behavioral arrest with unresponsiveness during the seizures. About 24 h after the injection, generalized small spike and wave complexes were observed intermittently in cortical and subcortical structures. They persisted for 4-5 s and were associated with behavioral arrest and staring. The results demonstrate that a unilateral microinjection of kainic acid into VPL induced petit mal-like seizure, and suggest that VPL plays an important role in the generation or transfer of spike and wave complexes.

Animals↗
PubMed1992

The effects of oxiracetam (CT-848) on local cerebral glucose utilization after focal cerebral ischemia in rats.

The effects of oxiracetam on the reduction of brain metabolism induced by focal cerebral ischemia were investigated by measuring local cerebral glucose utilization (LCGU) in rats 24 hr after left middle cerebral artery occlusion. Focal cerebral ischemia reduced LCGU in the entire ipsilateral cortex, the greatest reduction being in the lateral parts of the frontoparietal cortex. LCGU was slightly reduced in the contralateral cortex; this reduction was considered to be caused by diaschisis. Oxiracetam was administered intraperitoneally for 3 days prior to middle cerebral artery occlusion. In the ipsilateral cortex, LCGU reduction was minimized in the ischemic center areas by oxiracetam at a dose of 400 mg/kg and in more extensive areas, by a dose of 800 mg/kg. Moreover, oxiracetam at a dose of 800 mg/kg enhanced metabolism impaired by diaschisis in the caudal areas of the contralateral cortex. These findings suggest that oxiracetam minimizes the reduction of brain function induced by ischemia and may therefore be useful in the treatment of cerebrovascular disease.

Animals↗
PubMed1992

Lipoma involving the skull. Case report.

The case of an intraosseous lipoma involving the left frontal bone is reported. Lipomas of the bone are rare; only three cases of lipomas involving the skull have previously been reported. The differential diagnosis includes a healing bone infarction or fracture, meningioma, hemangioma, and fibrous dysplasia. Diagnosis prior to surgery is difficult.

Adult↗