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Biomedical subjects

H Hirabayashi

Publications and source records attributed to H Hirabayashi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Usefulness of the dipole tracing method with a scalp-skull-brain head model: relationship between the epileptic focus and equivalent current dipole locations.

PURPOSE: We examined whether the dipole tracing (DT) method with a realistic three-shell head model and inhomogeneous electric conductivity is useful to estimate the epileptic focus from interictal spikes. METHOD: This study included 17 temporal lobe epilepsy (TLE) cases, classified into three types as type A (unilateral), type B (intermediate) and type C (bilateral) and 5 extratemporal epilepsy (XTLE) cases. The epileptic areas were determined by noninvasive and/or invasive examinations. Selected interictal spikes were analyzed and the calculated equivalent current dipoles (ECDs) of dipolarity greater than 0.98 were superimposed over the realistic head model in each patient. We evaluated the ECD concentration within and around the epileptic area. RESULTS: In TLE cases, types A showed better ECD concentration (87%) within the epileptic area than other types (type B: 68%; type C: 74%). XTLE exhibited variable ECD distribution within and around the epileptic area. CONCLUSION: The DT method with a realistic head model and inhomogeneous electric conductivity can be useful to estimate the epileptic area from interictal spikes, especially in unilateral TLE cases.

Action Potentials↗
PubMed1999

Intrameatal aneurysm successfully treated by meatal loop trapping--case report.

A 77-year-old female presented with a rare intrameatal aneurysm manifesting as sudden onset of headache, hearing loss, tinnitus, and vertigo associated with subarachnoid hemorrhage. Meatal loop trapping was performed. After surgery, the patient's functions recovered almost completely, probably because of the preservation of the 7th and 8th cranial nerves and the presence of effective collaterals in the area supplied by the anterior inferior cerebellar artery.

Aged↗
PubMed1999

[Reconstruction of great vessel for patients with advanced lung cancer or malignant mediastinal tumor].

Fifteen lung cancer (LC) and 11 malignant mediastinal tumor (MMT) patients who received surgical treatment in association with a reconstruction of great vessel from 1981 to 1997 were retrospectively reviewed. The aorta was resected in 7 (AO group) of 15 LC patients and the superior vena cava in the remaining 8 patients (SVC group). Pathological examination revealed actual tumor invasion in one (14%) of AO group and 6 (75%) of SVC group. In 7 p-T4 patients, 6 (85.7%) were p-N2 or N3 diseases. Five of the 6 patients belonged to SVC group and one to AO group. Five-year survival rate was 10% in all LC patients, 20% in p-T3 patients, 0% in p-T4 cancers, 50% in p-N0 patients and 0% in p-N2 or N3 patients. Eleven MMT patients included 5 thymomas, 2 thymic cancers and 4 germ cell tumors. SVC was resected and replaced with ringed PTFE graft in all patients. Invasion of vessel wall was diagnosed pathologically in 10 of 11 patients. Fifteen-year survival rate was 60% in 5 thymoma patients but 4 of whom had distant metastasis. Five-year survival rate was 50% in thymic cancers and 0% in germ cell tumors. Since the prognosis of LC and MMT patients who have tumor invasion of the great vessel is very poor, induction therapy based on preoperatively pathological diagnosis is recommended.

Adult↗
PubMed1999

[Peroxynitrite production in cerebral ischemia].

Peroxynitrite, generated by the reaction of nitric oxide and superoxide, has toxic effects including oxidation of sulfhydryls, lipid peroxidation and nitration of amino acid residues. So far peroxynitrite has not yet been detected in the ischemic brain because of its short half-life. Recently, we have succeeded in detecting 3-nitro-L-tyrosine, which is considered to be a footprint of peroxynitrite, in ischemic brain. Production of nitrotyrosine started during the ischemic period, increased after reperfusion, peaked at 48 hours, then declined up to 72 hours. Nitrotyrosine level was highest in the peri-infarct region, second highest in the core-of-infarct region, and lowest in the caudoputamen and the non-infarct region. Studies using pharmacological agents including MK-801, 7-nitroindazole and aminoguanidine suggest that peroxynitrite production originates from nNOS in the early phase of reperfusion, and from iNOS in the later phase of reperfusion. Further, the immunohistochemical study indicates that iNOS, located mainly in vascular cells, is predominantly responsible for nitrotyrosine production. Thus, peroxynitrite production depends on the stage of evolution of the ischemic process and on the cell type producing NO. These findings have important implications for the therapeutic time window and choice of NOS inhibitors in patients with cerebral infarction.

Animals↗
PubMed1998

Overview and initial results of the very long baseline interferometry space observatory programme

High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli-arc-second-scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.

Journal Article↗
PubMed1998

Effects of unilateral spatial neglect on spatial agraphia of kana and kanji letters.

Left unilateral spatial neglect (USN) and spatial agraphia are both caused by right hemisphere damage. However, effects of USN on spatial agraphia have not been fully investigated. This study examined performances of patients with or without neglect and normals on single letter writing, using Japanese unique writing systems, kana (phonogram) and kanji (ideogram). Our patients exhibited agraphia of kanji, but not of kana. However, accuracy of writing was not associated to neglect severity, and errors for writing to dictation occurred either on the left or right side of kanji. Right frontal damage seemed to be related to the genesis of duplication or omission errors of repeated elements. Effect of USN was limited to spatial arrangement of letters and copying performance.

Aged↗
PubMed1998

Disruption of the RB pathway and cell-proliferative activity in non-small-cell lung cancers.

The pathway consisting of retinoblastoma protein (pRB), cyclin D1 and p16 (RB pathway) which is involved in the phosphorylation of pRB plays an important role in G1/S progression. The disruption of this RB pathway has been reported in several types of human neoplasm. An immunohistochemical study of 101 non-small-cell lung cancers (NSCLCs) showed loss of p16 is in 47 tumors (46.5%) and loss of pRB in 42 tumors (41.6%). In 79 of 101 NSCLCs (78.2%), the expression of p16 and pRB was complementary (p < 0.0001). Methylation of the cdkn2 gene was detected in 50% of p16-negative tumors and in 11% of p16-positive tumors. Aberrant expression of cyclin D1 was found in 45 tumors (44.5%). The cyclin-D1-positive tumors had significantly higher Ki-67 indices than the cyclin-D1-negative tumors irrespective of the tumor p16 or pRB expression. Thus, 91 (90%) of 101 NSCLCs showed disturbed expression of at least 1 of the 3 components of the RB pathway. Our results suggest that the disruption of the RB pathway plays an important role in tumorigenesis in NSCLCs and that increased cyclin-D1 expression leads to strong proliferative activity which may over-ride the suppressive effect of p16 and pRB.

Adenocarcinoma↗
PubMed1998

Histomorphometric study of iliac bones in cervical myelopathy with ossification of the posterior longitudinal ligament.

To investigate whether there was any abnormal systemic bone metabolism in patients with ossification of the posterior longitudinal ligament (OPLL), we measured various histomorphometric indices of the iliac trabecular bones in 19 patients with OPLL (14 men, 5 women). For each index, the Z-score for each patient was calculated, using the SD and mean value for non-OPLL control group (n = 159) who underwent orthopaedic surgeries and had no systemic disease, age-matched for each decade. A Z-score of 1.0 meant that the observed data deviated 1 SD from the normal average, and a distribution from -2 to +2 was considered normal. All the averaged Z-scores were within +/-1.0 and there were no significant differences between the OPLL and the control groups. There was also no difference in Z-score among three types of OPLL (segmental, continuous, and mixed). From these results, we concluded that there was no common abnormal bone metabolism affecting the bone histomorphometry of the iliac bone in OPLL patients. However, in two patients, the Z-score for bone volume (BV/TV) was more than 2.0, with increased osteoid volume (OV/TV) and increased trabecular thickness, suggesting that there was some abnormal bone metabolism in these two patients with OPLL.

Adolescent↗
PubMed1998

Induction of heme oxygenase protein protects neurons in cortex and striatum, but not in hippocampus, against transient forebrain ischemia.

To clarify whether heme oxygenase-1 (HO-1) protein plays a protective role against cerebral ischemia, we investigated the effects of an HO inhibitor (tin mesoporphyrin IX [SnMP] three doses of 30 micromol/kg, intraperitoneally) and an HO inducer (hemin, three doses of 30 micromol/kg, intraperitoneally) on the pathologic outcome and on the immunohistochemical reaction for HO-1 after 20-minute transient forebrain ischemia followed by 3-day reperfusion in rats. Hemin significantly increased viable neurons in the cortex (compared to the SnMP-treated group, P < .05) and striatum (compared to the saline-treated group at P < .01 and SnMP-treated group at P < .05), and intense HO-1 immunoreactivity was observed in cortex and striatum, whereas the administration of SnMP tended to decrease viable neurons in the parietal cortex. In contrast, neither hemin nor SnMP affected the pathologic outcome in the CA1 and CA3 hippocampi, in which HO-1 immunoreactivity was weak. These results suggest that induction of HO-1 protein may contribute to cellular defense against ischemic damage in brain regions where potential ability to synthesize HO-1 is retained in ischemia.

Animals↗
PubMed1998

Spinal cord blood flow and pathophysiological changes after transient spinal cord ischemia in cats.

OBJECTIVE: The goal was to study the hemodynamics and regional pathophysiological changes in the spinal cord after transient vascular occlusion in cats. METHODS: We measured spinal cord blood flow (SCBF) continuously in the lumbar region with a laser-doppler flowmeter, before, during, and after spinal cord ischemia induced by balloon occlusion of the thoracic aorta, in 24 cats (divided into three groups) and simultaneously recorded the evoked spinal cord potentials (ESPs). In each group (n = 8), 10-, 20-, and 30-minute ischemic loading was performed. All animals were evaluated neurologically 36 hours later, and then their spinal cords were examined histologically. RESULTS: The amplitude of ESPs decreased 10 minutes and disappeared 20 minutes after occlusion. SCBF increased to as much as 2 times the control values after reperfusion and decreased gradually in all groups. Then, in all animals in the 10-minute group and six animals in the 20-minute group, SCBF returned to the control values, which were subsequently maintained throughout the experiment, and ESPs returned to normal patterns within 1 hour. For all animals in the 30-minute group and two in the 20-minute group, hypoperfusion after recirculation, irreversible amplitude changes in ESPs, postischemic paraparesis, and pathological ischemic changes in the lower thoracic and lumbar spinal segments were recognized. CONCLUSION: Our results showed that > 20-minute occlusion of the thoracic aorta in cats resulted in irreversible spinal perfusion disorders and that the monitoring of SCBF and ESPs could be useful for predicting potential neurological deficits. Furthermore, postischemic hypoperfusion may have an important role in the development of secondary spinal cord ischemia, resulting in severe neurological dysfunction. This observation suggested the possibility of therapeutic modification of the secondary processes inducing hypoperfusion after spinal ischemia.

Angiography↗
PubMed1998

Comparison between stereotactic CT and MRI coordinates of pallidal and thalamic targets using the Laitinen noninvasive stereoadapter.

The coordinates of one and the same target were compared between stereotactic CT and MRI studies, using the original Laitinen noninvasive Stereoadapter, and a slightly modified stereoadapter in 34 patients scheduled for pallidotomy or thalamotomy. The differences between CT and MRI coordinates were significant for the anteroposterior y (p < 0.001) and the vertical z (p < 0.01) coordinates. When the targets were analyzed separately for the coordinates in the right and left hemispheres, only those of the left-sided targets were significantly different between CT and MRI measurements. In patients where a vertex support was added to the Stereoadapter, there were no differences between CT and MRI target coordinates, regardless of the side of the target. However, in all patient groups, the three-dimensional vectorial difference between CT and MRI coordinates showed that the MRI-defined targets lay anterior and dorsal, that is, rostral, to the CT-defined targets, with a 95% confidence interval of the differences ranging from 1.8 to 2.4 mm. This rostral shift in target coordinates on MRI versus CT happens to coincide with the usual approach of the probe towards the target during surgery. It is concluded that the differences in target coordinates in our study are due partly to MRI distortion and partly to repositioning error of the Stereoadapter on the head. The relatively low magnitude of these differences does not preclude the use of the Stereoadapter for MRI-guided functional stereotactic surgery, provided careful impedance monitoring and macrostimulation of the target area prior to lesioning.

Adult↗
PubMed1998

[Complicated form of spastic paraplegia with congenital cataract: a case report].

We report a 33-year-old man who manifested spastic paraplegia with congenital cataract, dementia, deformity of the foot (pes cavus, high arch and hammer toes), ataxia, and peripheral neuropathy. Magnetic resonance imaging showed mild deformity of the trunk of the corpus callosum and atrophy of superior cerebellar vermis. Metabolic diseases were ruled out by the clinical course and special examinations. Other patients, including 2 of ours, with spastic paraplegia and thin corpus callosum have been reported, but the present case is different because of congenital cataract and the form of the corpus callosum. We consider that there may be a variety of complicated forms of spastic paraplegia. To assess the etiology of complicated forms of spastic paraplegia, further case accumulation is very important.

Adult↗
PubMed1997

p16INK4, pRB, p53 and cyclin D1 expression and hypermethylation of CDKN2 gene in thymoma and thymic carcinoma.

There have been few reports on genetic alterations in thymomas. To investigate the expression of p16INK4A, RB, p53 and cyclin D1 in thymomas, we first examined 36 thymomas (non-invasive type, 16 cases; invasive type, 20 cases) and 3 thymic carcinomas, using immunohistochemistry. Abnormal expression of p16INK4A, RB, p53 and cyclin D1 was observed in 18, 8, 10 and 7 cases, respectively. Only a subgroup of invasive thymomas and thymic carcinomas showed an inverse correlation between p16INK4A and RB expression. Subsequently, we examined the 36 thymomas and 4 thymic carcinomas for mutations in p53 and CDKN2 genes, using PCR-SSCP and direct-sequencing analyses. No mutation of these genes was detected in the thymomas and thymic carcinomas examined. A polymorphism in the 3' untranslated region of exon 3 of CDKN2 was detected in 5 cases of thymoma. We searched for hypermethylation in the promoter region of CDKN2, observing it in 4 thymomas and 1 thymic carcinoma. Our data suggest that, unlike other more common cancers, alteration of the p53 gene may not play a significant role in the tumorigenesis of thymoma. However, inactivation of p16INK4A and RB may play a role in the progression of thymoma and thymic carcinoma.

Blotting, Southern↗
PubMed1997

Is there a relationship between size and site of the stereotactic lesion and symptomatic results of pallidotomy and thalamotomy?

Forty-six patients who had 50 stereotactic procedures (36 pallidotomies and 14 thalamotomies) were assessed clinically with regard to akinesia, tremor, dyskinesias and dystonias, and underwent a stereotactic imaging study 6 months after surgery. The surgical results were rated as excellent, good/fair or no change, respectively, for each symptom, and were correlated to the volume and location of the stereotactic lesion. The effect of pallidotomy on akinesia was moderate and correlated with a larger lesion volume. The positive effect of pallidotomy on dyskinesias, dystonia and tremor was more pronounced and unrelated to the size of the lesion. The effect of thalamotomy on tremor was also unrelated to the lesion volume. The location of the pallidal lesions correlated only with the effect on akinesia: the more posterior the lesion in the pallidum, the better the effect on this symptom. For thalamotomy, there was no relationship between lesion location and effect on tremor. It is concluded that improvement in akinesia following pallidotomy is more difficult to obtain than improvement of the other parkinsonian symptoms, and this improvement requires a larger lesion which is located very posterior in the ventral pallidum.

Globus Pallidus↗
PubMed1997

[Pupillary abnormalities in a patient with clinically diagnosed corticobasal degeneration].

We report a 65-year-old woman, who suffered from clumsiness of the left hand for 6 years. Gait disturbance, body balance impairment and rigidity of the left arm appeared progressively. Anti-parkinsonian drugs such as 1-dopa, doroxidopa, amantadine and bromocriptine were ineffective. Magnetic resonance imaging showed brain atrophy, especially in the right fronto-parietal lobes. Positron emission tomography (18F-fluoro-2-deoxy-D-glucose) showed decreased glucose metabolism in the right cerebral cortex, putamen and thalamus. A diagnosis of corticobasal degeneration was made, based on the clinical manifestations, MRI and PET findings. She also showed anisocoria, vertical gaze palsy and abnormal pupillary reactions. Her left pupil showed an oval figure shifted from the center position. The pupils exhibited denervation supersensitivity in the 0.125% pilocarpine test. We consider that her pupillary abnormalities may be related to her midbrain lesion (midbrain corectopia) associated with corticobasal degeneration.

Aged↗
PubMed1997

Expansive laminoplasty for multilevel cervical OPLL.

Expansive laminoplasty is a new technique for the management of cervical ossification of the posterior longitudinal ligament (OPLL). Twenty patients were followed up for an average 3-year period. Follow-up examinations were performed every 3 months and at 1-year intervals. On lateral radiographs, the average increase in the anteroposterior (AP) diameter of the canal was 42%. Bone fusion was documented on computed tomography (CT) studies 3 months after surgery in 96% of patients. An average 83% of normal range of motion was preserved on long-term follow-up (3 years on average). Postoperative improvement over the same interval increased from an average preoperative Japanese Orthopaedic Association score of 7.9 to 14.1 Expansive laminoplasty as described is safe and has a high fusion rate, while better preserving the normal range of motion.

Constriction, Pathologic↗