Biomedical subjects

S Toya

Publications and source records attributed to S Toya.

At least 19 recordsLinked to original sources

PubMed1999

Successful survival of grafted transgenic neural plate cells in adult central nervous system environment.

1. Accumulating evidence indicates that damaged brain functions can be ameliorated in a variety of animal models by the grafting of fetal neuronal cell or tissue into damaged brain. Clinical trials are under way to determine whether human fetal mesencephalic tissue can ameliorate motor functions in patients with Parkinson's disease. 2. Autopsy findings of parkinsonian patient implanted with human fetal mesencephalic tissue clearly revealed that the fetal neuronal graft can survive for an extended period of time in the human brain and densely reinnervate the surrounding host striatal tissue. 3. It is, however, still important to obtain more practical, effective, and ethically justifiable donor material for the future clinical application of the procedures. Desirable properties for the donor cells include long-term survival in the brain, neuronal cell type for the reconstruction of damaged neural circuits, and susceptibility to genetic manipulation for the practical use. 4. With the development of molecular biology techniques, genetic modification and transplantation of the donor neuronal cells might be a feasible way to cure many kinds of central nervous system diseases toward a "graft-gene therapy."

Animals↗

PubMed1998

Plasma cell granuloma extending from the extracranial to the intracranial space associated with Epstein-Barr virus infection.

A 70-year-old male presented with a plasma cell granuloma extending from the extracranial to the intracranial space. Findings of preoperative magnetic resonance imaging and intraoperative observation indicated that the lesion extended from the temporal muscle to the subarachnoid space, penetrating the frontal bone. The subarachnoid lesion was composed of neutrophils indicating the presence of acute or subacute inflammation. The final diagnosis of the resected tumor was plasma cell granuloma. High levels of antibodies against Epstein-Barr (EB) virus in the cerebrospinal fluid and the immunohistochemical demonstration of EB nuclear antigens in the plasma cell granuloma suggested that EB virus infection was associated with the development of plasma cell granuloma in this patient.

Aged↗

PubMed1998

Quality of hearing preservation in acoustic neuroma surgery.

OBJECTIVE: This study aimed to investigate the factors affecting the quality of postoperative hearing in acoustic neuroma. STUDY DESIGN: The study was designed as a retrospective case review. SETTING: The study was performed at the Department of Otolaryngology, School of Medicine, Keio University, Tokyo, Japan. PATIENTS: The subjects were 94 patients with unilateral acoustic neuroma. INTERVENTION: Hearing preservation surgery was performed in the subjects via the extended cranial fossa approach or the middle cranial fossa approach. MAIN OUTCOME MEASURES: The outcome measures included patient's age and gender, hearing level, speech discrimination score, tumor size, and surgical approach. The relationship between the qualities of preoperative and postoperative hearing and the long-term prognosis of preserved hearing also was investigated. RESULTS: In 94 subjects, there were 47 patients whose hearing was preserved (HP group) and 47 patients whose hearing was not preserved (non-HP group). Overall, hearing preservation rate was 50%. There were no significant differences in age, gender, and tumor size between the two groups. The hearing preservation rate was significantly higher in patients with an intracanalicular tumor than that with a larger tumor. The better the preoperative quality of hearing was, the higher the postoperative one. Although the preserved hearing deteriorated after surgery in 4 patients, no significant hearing deterioration was observed in the other 43 patients. CONCLUSIONS: The results of this study indicated that the diagnosis for acoustic neuroma in the early stage with serviceable hearing is the most important to improve the quality of postoperative hearing.

Adolescent↗

PubMed1998

[Analysis of abnormal findings observed on brain MRI T 2 weighted image in a system for the detection of asymptomatic brain disease in 1,200 cases].

In this study we described the significance of asymptomatic cerebral infarction (ACI) and periventricular hyperintensity (PVH) observed on brain MRI in a system for detection of asymptomatic brain disease with 1,200 cases. The risk factors (RF), population in each age bracket of ACI and PVH, among groups with hypertension (HTG) and without RF (no-RFG), were investigated. The RF of ACI were hypertension (HT), diabetes mellitus (DM), and aging. Without DM, those are common RF of PVH. The population of PVH and ACI with PVH increased with aging in no -RFG. On the other hand, only the population of ACI with PVH increased with aging in HTG. The rate of these abnormal findings in HTG was significantly higher than that in no-RFG. In addition, HT accelerated the occurrence of these findings by 10-20 years. When patients were over 60 years old, ACI increased rapidly. Accordingly, we concluded that (1) PVH and ACI had a common background. (2) Long term follow up concerning the incidence of ACI in the group with only PVH was necessary. (3) It was desirable that treatment for RF should be effected before the age of sixty.

Adolescent↗

PubMed1997

Effects of spinal cord ischemia on the refractory period of descending spinal cord evoked potential.

The recovery cycle, following the conduction of action potentials along a nerve fiber, consists of the absolute refractory period (ARP), the relative refractory period (RRP) and the supernormal period (SNP). The recovery cycle of the descending conductive spinal cord evoked potential (SCEP) was shown during normal state, ischemia and after ischemia using paired stimuli in cats. During ischemia the refractory period revealed a trend towards increment. Five minutes after reperfusion the refractory period decreased transiently compared with the normal level and within 30 min the refractory period returned to the normal level. The recovery curve of the 2nd potential showed different pattern compared with that of the 1st potential. Moreover, during ischemia, firstly the 3rd potential and secondly the 2nd potential of the SCEP elicited by the 2nd stimulus were disturbed. These results demonstrated that there is increased excitability of the spinal cord to the second stimulus after a brief period of ischemia, and that the 2nd and 3rd potentials are evoked synaptically and easily disturbed during ischemia. Measuring the SCEP elicited by paired stimuli or constructing the recovery curve of the SCEP is useful for the electrophysiological assessment of spinal cord function.

Action Potentials↗

PubMed1997

Prediction of consistency of meningiomas with preoperative magnetic resonance imaging.

BACKGROUND: The consistency of a meningioma is one of the important factors in determining the surgical outcome. If the surgeon is aware of the consistency of a meningioma preoperatively, the surgical plans will be influenced. A few papers have described the correlation between consistency of meningiomas and their magnetic resonance imaging (MRI) findings. However, prediction of consistency with MRI is still difficult. We have tried to predict the consistency of meningiomas with MRI findings more precisely. METHODS AND RESULTS: Fifty patients diagnosed as having intracranial meningiomas were studied with 1.5 Tesla MRI. We compared the MRI findings with tumor consistency. The intensities of the tumors were categorized into three grades (low, iso, and high) compared to that of the gray matter. T1-weighted images had no specifics, but T2-weighted images and proton density images were useful for the prediction of tumor consistency. Hyperintensity on protein density (PD) and T2-weighted images was a sign of a soft tumor. CONCLUSION: We presume that T2 and PD are useful for predicting consistency of meningiomas, and their water content is one of the main factors in their consistency. Histology may be one of the factors helpful in defining the consistency of a tumor. In this series, we found no relationship between histology and MRI findings, nor between histology and consistency. If the meningioma is believed to be hard, preoperative endovascular embolization is beneficial, which will induce necrosis of the meningioma and make it soft enough to be removed more easily and safety.

Adult↗

PubMed1997

Bony foramina facilitate magnetic stimulation: an experimental cat sciatic nerve model.

We have established an experimental bony foramen model in vivo using a cat sciatic nerve, a section of skull bone and a column made from methylmethacrylate. In each model, a foramen-like slit or fissure was created. Motor responses of the cat right gastrocnemius were elicited with a figure-of-8-shaped magnetic coil. Very high intensities of magnetic stimulation were necessary to evoke motor responses with the coil placed on the thigh. However, when the bone section or methylmethacrylate column was placed under the thigh muscle layer with the sciatic nerve fitted into the foramen-like slit or fissure, motor responses could be elicited with a smaller intensity of magnetic stimulation. Despite changes in stimulation intensity or shifts in the magnetic coil, the latency of the motor responses remained constant. By comparing the latency with the electrical recording, the site of excitation was predicted to be at the exit of the foramen. Our studies have confirmed that bony structures, especially bony foramina, facilitate excitation of the nerve by magnetic stimulation and that the exit of the foramen could be the preferential site for magnetic stimulation.

Animals↗

PubMed1997

Neurotrophic activity in cytokine-activated astrocytes.

Accumulating evidence indicates that various neurotrophic factors (NTFs) exist and function in the brain. In the mature mammalian brain, NTF expression is exclusively restricted to neurons. However, astrocytes activated by various cytokines, including fibroblast growth factor and interleukin-1 beta, produce a significant amount of nerve growth factor (NGF) in vitro. Furthermore, non-NGF type NTF expression in astrocytes is also activated by the cytokines. The cytokines also enhance both release of ciliary neurotrophic factor from and expression of high-molecular weight basic fibroblast growth factor (FGF) in astrocytes. In the early phase following brain injury, cytokine-activated astrocytes rescue the damaged neurons via NTFs and other biologically active molecules.

Animals↗

PubMed1997

Electrophysiological investigation of hemifacial spasm after microvascular decompression: F waves of the facial muscles, blink reflexes, and abnormal muscle responses.

In patients with hemifacial spasm, it has been said that the spasm is due to cross compression of the facial nerve by a blood vessel and that microvascular decompression (MVD) of the facial nerve is an effective treatment. The F waves, which result from backfiring of antidromically activated motor neurons of the facial motor nucleus, are indices of the excitability of the facial motor nucleus and are enhanced in patients with hemifacial spasm. Measuring blink reflexes and abnormal muscle responses (lateral spread), a characteristic sign of hemifacial spasm, has been used to investigate the mechanism of hemifacial spasm pathophysiologically. Thus the authors measured F waves of the facial muscle, blink reflexes, and abnormal muscle responses before and after MVD in patients suffering from hemifacial spasm to investigate the excitability of the facial motor nucleus and the course of the cure of hemifacial spasm after MVD. The authors obtained facial nerve-evoked electromyograms in 20 patients with hemifacial spasm before and after the MVD procedure. On the spasm side, the F waves and blink reflexes were enhanced preoperatively compared to those on the normal side and abnormal muscle responses were recorded in all patients. In 12 patients whose hemifacial spasm had not disappeared completely for 5.1 +/- 1.7 (mean +/- standard error) months following the MVD procedure, F waves were still enhanced significantly and abnormal muscle responses were still recordable, albeit at lower amplitude. Within 1 month after the hemifacial spasm had disappeared completely. F waves were still significantly enhanced in 17 patients and abnormal muscle responses were recorded in seven of 15 patients. Subsequently, the enhanced F waves and abnormal muscle responses disappeared completely. The authors' study supports the hypothesis that the cause of hemifacial spasm is hyperexcitability of the facial motor nucleus and suggests that additional surgery should not be performed for at least 2 years after MVD, because that period is necessary for the disappearance of the hyperexcitability of the facial motor nucleus.

Adult↗

PubMed1997

[Practical localization of the central sulcus using a video display during surgery by cortical somatosensory evoked potentials and how to discern precentral P20 and central P25].

In patients with lesions around the central sulcus, cortical surface somatosensory evoked potentials (SEPs) have been applied for the purpose of localization of the central sulcus based on the polarity inversion of postcentral N20 to precentral P20 across the central sulcus. We have intraoperatively monitored SEPs to infer the location of the central sulcus in 16 cases since December 1988. Intraoperative localization of the central sulcus has been most useful in patients with frontal lobe gliomas in which the localization of the central sulcus enables the surgeon to extensively resect tumor without postoperative motor weakness. The localization of the central sulcus, however, might be misjudged by using the polarity inversion criterion alone, because central P25 following N20 and P20 complicates SEP waveforms. It is significant that P25, which is recorded also posterior to the central sulcus, is discerned from the precentral P20. In order to solve this matter, we regarded only the positivity in SEP waveforms having the identical peak latency to that of N20 as the precentral P20. Positive potentials having a later peak latency than that of N20 are the superposition of P20 and P25, and might also be recorded posterior to the central sulcus. For the observation of the polarity inversion of N20 to P20 across the central sulcus, a multi-channel SEP should be recorded using a sheet of silicone rubber embedded in a 16-electrode array consisting of a 4 by 4 grid. We projected the exposed cortical surface on the video display through the microscope apparatus and marked the locations of the recording electrodes on the video display. This enabled the location of the recording electrodes to correspond easily and precisely to the cortical surface. Our reliable and simple method of intraoperative localization of the central sulcus by cortical SEPs monitoring is presented in a practical case.

Adolescent↗

PubMed1997

[Cooperative multicentre study on posttraumatic epilepsy].

A multicentre cooperative prospective study have been conducted to investigate the factors influencing posttraumatic epilepsy (PTE) and to evaluate the prophylactic effect of anticonvulsants. Since April 1994, patients with head injury have been observed following our protocol as follows; anticonvulsants are administered only to the patients with brain parenchymal injury for one month just after head trauma and no anticonvulsants are administered after one month after trauma to any patients except those with posttraumatic epilepsy (PTE). Brain parenchymal injury included traumatic subarachnoid hemorrhage, acute subdural hematoma, contusion, intracerebral hematoma, and diffuse axonal injury. To April 1996, 635 patients with head injury have been registered and analyzed. During the follow-up period, 14 patients (2.2%) developed PTEs, which had only been observed in patients with brain parenchymal injury. Multiple regression analysis revealed that two factors, early epilepsy and brain parenchymal injury, could contribute to the prediction of PTE. The frequency of PTE in this study was compared with that in our previous retrospective study (Nakamura, 1995), in which anticonvulsants were administered to the patients with head injury. There was no significant difference in the percentage of patients having PTE between the group treated without anticonvulsants in this study and the untreated group in previous retrospective study. Anticonvulsants treatment after head injury was not likely to have a prophylactic effect against the development of PTE.

Adolescent↗

PubMed1996

Expression of CD44H in the cells of neural crest origin in peripheral nervous system.

We investigated the expression of the adhesion molecule CD44 in rat peripheral nervous system (PNS) at the protein and mRNA levels. Most migrating neural crest cells strongly expressed CD44, in contrast to the lack of expression in the neural tube. In dorsal root ganglion (DRG) and sciatic nerve, the distribution of CD44, neurofilament (NF) and S100 suggested the localization of CD44 on the membrane of Schwann cell and neurones and in extracellular matrix (ECM). The expression of CD44 was also confirmed on the membrane of cultured neurones and Schwann cells from DRG. mRNA coding for the haematopoietic form of CD44, CD44H, was detected in neural crest cells, DRG neurones and Schwann cells. These results show that CD44 may play some role in migration of neural crest cells and myelination in terms of adhesion between Schwann cells, axons and ECM.

Animals↗

PubMed1996

Stabilization of adhesion plaques by the expression of drebrin A in fibroblasts.

The expression of drebrin A was induced in mouse fibroblasts (L cells) after transformation of cells with a vector that carried cDNA for rat drebrin A (developmentally regulated brain protein A) under the control of the promoter of the gene for metallothionein-I. When drebrin was expressed in the transformed cells (MTI-5 cells), the organization of actin filaments changed such that stress fibers were converted to a mesh-like structure. After subsequent treatment with 5 micrograms/ml cytochalasin D (a reagent that depolymerizes actin filaments), MTI-5 cells maintained their shape, while cells of a drebrin-negative cell line, MTI-11, formed retraction processes. Simultaneously, actin filaments changed into patchy dot-like aggregates in the cytoplasm of both MTI-5 and MTI-11 cells. These aggregates are known as cytoplasmic pools. In MTI-5 cells, adhesion plaques that were resistant to treatment with cytochalasin D appeared upon expression of drebrin. These adhesion plaques were immunostained with vinculin-specific antibodies, while those in MTI-11 cells were hardly immunostained. The amount of vinculin in MTI-5 cells increased in parallel with increase in the level of drebrin. These results suggest that expression of drebrin A induces changes in the assembly of actin filaments and adhesion plaques, with resultant modulation of cellular adhesion to the substratum.

Blotting, Western↗

PubMed1996

The neural origin generating early cortical components of SEP: topographical analysis using temporal-second-order-differentiation of cortical SEPs.

In order to identify dipole generators of the N20/P20 and P25, we employed second-order-differentiation in the temporal dimension (temporal-second-order-differentiation; TSOD) with delta t = 2 msec. The rate of variation in the voltage of cortical SEPs calculated by TSOD identified responses of each dipole, reflecting the density of neuronal firing. On topographic analysis, the distributions of N20/P20 and P25 conformed to the shape of gyrus better in the TSOD maps than in the isovoltage maps. The TSOD maps indicated that N20 and P25 were post-central components and that P20 was a pre-central one. Therefore, we concluded that the two dipoles generating N20/P20 and P25 were located in the posterior wall of the central sulcus (area 3b) and the crown (areas 1 and 2) of the post-central gyrus, respectively.

Brain Mapping↗

PubMed1996

Electrophysiological investigation of hemifacial spasm: F-waves of the facial muscles.

In patients with hemifacial spasm (HFS), the spasm is due to cross-compression of the facial nerve by a blood vessel. There are currently two hypotheses for the mechanism of HFS: 1) the spasm is caused by ephaptic transmission and an increase in excitability at the site of compression; and 2) the spasm is caused by hyperexcitability in the facial nerve nucleus. In peripheral nerves, F-waves, which result from the backfiring of antidromically activated anterior horn cells, have been proposed as indices of proximal motoneuron conduction and anterior horn cell excitability. Enhancement of the F-waves indicates increased anterior horn cell excitability. We have therefore measured F-waves in the facial muscle of HFS patients in order to investigate the excitability of the facial nerve nucleus. The authors obtained facial nerve evoked responses from 20 HFS patients before microvascular decompression (MVD), 10 HFS patients after MVD and 10 healthy controls. The F-waves, obtained with surface electrodes from the mentalis muscle, were the second response after the M-wave. On the patient's spasm side, the F-wave duration, F/M amplitude ratio and frequency of F-wave appearance significantly increased compared with those of the normal side or healthy controls; minimum latency and chronodispersion did not significantly differ between these groups. In patients whose spasm disappeared completely following MVD, the abnormal muscle response (lateral spread), which is a characteristic sign of HFS, and the enhancement of the F-wave eventually also disappeared. Because of the correlation between HFS and F-waves, the authors' study supports the hypothesis that the cause of HFS is hyperexcitability of the facial motonucleus.

Adult↗

PubMed1996

Surgical approaches for vertebro-basilar trunk aneurysms located in the midline.

Fourteen cases of midline vertebro-basilar trunk aneurysms were operated on by four routes of surgical approach: middle fossa anterior transpetrosal approach (ATP), presigmoid transpetrosal approach (PTP), conventional lateral suboccipital approach (LSO) or suboccipital transcondylar approach (STC). There was no mortality, but the morbidity was different depending on the surgical approach. In basilar trunk aneurysms located higher than the internal auditory canal, excellent results were obtainable by ATP, especially in the case of posteriorly projecting aneurysms. For midline vertebral aneurysms located lower than the internal auditory canal, STC resulted in less surgical complications than LSO. Extradural resection of the jugular tubercle was necessary for aneurysms located on the distal vertebral artery at or close to the vertebro-basilar junction. For vertebro-basilar junction aneurysms located at the level of the internal auditory canal, hearing was preserved by STC, but not by ATP or PTP. However, choice of the surgical approach may depend on the direction of the aneurysm and the technical accessibility of the skull base. All these skull base approaches reduced surgical complications of retraction damage to the cranial nerves and the brain stem. This holds true for all aneurysms arising from the midline vertebro-basilar trunk.

Adult↗

PubMed1996

Primary spinal leptomeningeal gliomatosis presenting visual disturbance as the initial symptom: case report.

We report a case of diffuse leptomeningeal gliomatosis which spread from the cervical to the sacral spine. A 60-year-old man was admitted with visual disturbance due to papilledema. Magnetic resonance imaging revealed holocord leptomeningeal gliomatosis without a definite intraparenchymal lesion, and the patient's neurological examination was unremarkable except for papilledema. Intracranial hypertension secondary to spinal tumor is well known but unusual, and the mechanism is still unclear. In our case, an elevated protein concentration of cerebrospinal fluid is suggested as the cause of intracranial hypertension.

Brain↗

PubMed1996

Cytokine-induced selective increase of high-molecular-weight bFGF isoforms and their subcellular kinetics in cultured rat hippocampal astrocytes.

Cytokines such as interleukin-1 beta (IL-1 beta), tumor necrosis factor-alpha (TNF-alpha) and epidermal growth factor (EGF) are probable factors responsible for up-regulation of basic fibroblast growth factor (bFGF) expression in reactive astrocytes following brain damage, however the effect of these cytokines on the expression of each bFGF-isoform has not been elucidated. Western blot analysis revealed the expression of 18, 22 and 24-kD bFGF isoforms in cultured rat hippocampal astrocytes, and the expression of high molecular weight (HMW)-isoforms (22 and 24-kD isoforms) but not of 18-kD isoform was selectively increased by cytokines. Immunofluorescent analysis demonstrated that bFGF content in the cytoplasm of astrocytes is initially increased by cytokines followed by nuclear targeting and localization in agreement with the previous evidence that HMW-isoforms possess a nuclear targeting signal. The present results suggest the important role of HMW-bFGF isoforms in the response of nervous tissue to injury.

Animals↗