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Biomedical subjects

M Shigemori

Publications and source records attributed to M Shigemori.

At least 55 records · Page 3Linked to original sources
PubMed1998

Mild hypothermia protects rat hippocampal CA1 neurons from irreversible membrane dysfunction induced by experimental ischemia.

In order to examine the effects of hypothermia on the changes in membrane potential induced by experimental ischemia (deprivation of oxygen and glucose), intracellular recordings were made from single CA1 pyramidal neurons in slice preparations of rat hippocampus. Application of ischemic medium caused irreversible changes in membrane potential consisting of an initial hyperpolarization, then a slow depolarization and a rapid depolarization. At temperatures of 35 degrees C and 37 degrees C, once the rapid depolarization occurred, readministration of oxygen and glucose failed to restore the membrane potential, a state referred to as irreversible membrane dysfunction. When the temperature was lowered to between 27 degrees C and 33 degrees C, the membrane potential returned to the control resting membrane potential in 75% of the neurons. The temperature coefficients (Q10) of the latency, the amplitude, and the maximal slope of the rapid depolarization were 2.5, 1.4 and 2.9, respectively. It is concluded that the critical neuroprotective temperature in ischemia-induced membrane dysfunction is found to be 33 degrees C in single CA1 neurons in vitro.

Animals↗
PubMed1998

Nitric oxide contributes to irreversible membrane dysfunction caused by experimental ischemia in rat hippocampal CA1 neurons.

The effects of agents which affect the action of nitric oxide (NO) were studied intracellularly on the ischemia-induced changes in membrane potential of single CA1 pyramidal neurons of the rat hippocampal slice preparations. The N-methyl-D-aspartate (NMDA) receptor antagonists, (+/-)-2-amino-5-phosphonopentanoic acid (AP5, 250 microM) or Co2 (2 mM) restored the membrane potential in more than 80% of the neurons. In about 60% of the neurons, the membrane potential was partially recovered as a result of exposure to the NO synthase inhibitor, NG-nitro-L-arginine (100 microM). The NO scavengers, carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (carboxy-PTIO, 300 microM) and hemoglobin (10 microM) restored the membrane potential in all neurons examined. Superoxide dismutase (50 U/ml) protected about 75% of the neurons from irreversible membrane dysfunction. It is concluded that the release of NO induced by experimental ischemia may result in the irreversible membrane dysfunction, and that a NO scavenger, carboxy-PTIO, prevents the ischemic changes in membrane potential. With respect to ischemic brain damage, the neuroprotection provided by carboxy-PTIO may have clinical relevance in the management of a variety of neurological conditions.

2-Amino-5-phosphonovalerate↗
PubMed1998

Cranioplasty with split lateral skull plate segments for reconstruction of skull defects.

This paper reports the use of cranioplasty using segments of split lateral skull plate to correct large skull defects (larger than 8 x 8 cm). The subjects consisted of 10 patients with head trauma who had undergone decompression surgery, and two patients who had undergone tumour resection. Bone grafts were obtained by cutting approximately 2 cm wide strips from the lateral skull plate using a bone saw that was inserted from a free margin of the bone defects. By cutting strips laterally from the bone defect, the necessary amount of split lateral skull plate can be obtained without performing craniotomy. The pieces of split lateral skull plate are then fixed to the defect using wire or titanium mini-plates. At this point, the selection of bone grafts that match the curvature of the dura mater is important, so that no dead spaces are created between the dura mater and the bone grafts. Infection was not detected in any of the 12 patients, and all bone grafts took completely. One of the 12 patients suffered from a pathological fracture and bone resorption 6 months after surgery. The fracture occurred because the use of basket-shaped reconstruction plates resulted in large spaces between the plate segments, and in addition the intracranial pressure was kept low by a V-P shunt, thus rendering the patient more vulnerable to atmospheric pressure.

Adolescent↗
PubMed1998

Ultrastructure of obstructive tissue in malfunctioning ventricular catheters without infection.

The obstructive tissue in eight malfunctioning ventricular catheters without infection was studied using scanning and transmission electron microscopy. Shunt obstruction was due to debris from ventricular structures such as the choroid plexus and ependymal tissue. There was a preponderance of collagen fibers, and many fibroblasts were present within these tissues. The cytoplasm of the fibroblasts contained extended endoplasmic reticulum. The tissues filled the lumen of the catheters in radially arranged layers. Peeling the silicone was seen on the surface of the ventricular catheters but was not present in normal silicone catheters. Finger-like microvilli were observed on the free surface of the tissue. Many vessels were seen in the transverse section of the tissue. Activated fibroblasts and vascularization may be important in tissue growth in ventricular catheters.

Adolescent↗
PubMed1998

Clinicopathological features of intraorbital neurinoma--report of two cases.

Clinicopathological features of intraorbital neurinomas were investigated in two patients. Magnetic resonance imaging (MRI) findings in Case 1 were similar to those in Case 2. The central region of the neurinomas showed a slightly high intensity area with a marginal low intensity on T1-weighted images (T1WI), whereas on T2-weighted images (T2WI), the central area of the tumor was very low intensity with a marginal high intensity area. After gadolinium-DTPA (Gd-DTPA) injection, these areas were homogeneously enhanced in both cases. The deference in enhancement after Gd-DTPA injection reflected the distribution of cellularity and vessels in the tumor.

Humans↗
PubMed1998

Microsurgical management of craniopharyngiomas--outcomes in 56 patients.

Fifty-six patients with craniopharyngiomas were operated by microsurgical techniques during a 20-year period. Of the 56 patients, 28 were males and 28 were females, with a mean age of 33 years (range 1 to 78 years). Twenty patients (35.7%) were less than 15 years of age. Remission was defined as clinical improvement with stable ophthalmological and neurological status, CT and/or MRI evidence of a decrease in tumor size or tumor disappearance when a patient was discharged from hospital. Ineffectiveness was defined as lack of change in the preoperative clinical status. The mean follow-up period in this study was 6.9 years, with 11 patients monitored. The most common presentation was visual dysfunction (69.6%). 33.9% of the patients presented with headache. The most frequent preoperative finding was a visual field defect, with 55.4% of the patients so affected; 39.5% of patients had preoperative hypothyroidism and 40% had hypoadrenalism. Diabetes insipidus was found preoperatively in 7.1%. Three female patients had amenorrhea. Hydrocephalus was uncommon, being present in only 10.7%. Unruptured aneurysms were found incidentally in 2 cases. A pterional approach was used in 29 patients (52%), a transcallosal approach in 13 (23%), a transcortical approach and a transsphenoidal approaches in 3 (5%), and a lamina terminalis approach in 1 patient. Multiple procedures were required in 8 patients in order to provide significant relief of compressive symptomatology. Overall, 12.5% of the tumors were completely resected. 92.9% of our patients were in remission, 2 had ineffectiveness result, and 2 died of postoperative complications. Except for the completely resected cases, all the other patients underwent radiotherapy postoperatively. The results of this series show that microsurgical management of craniopharyngiomas yields good operative results.

Adolescent↗
PubMed1998

Fibroblast growth factor-2 and -9 regulate proliferation and production of matrix metalloproteinases in human gliomas.

Fibroblast growth factor (FGF) signaling has been recognized in human gliomas. We tested the effect of FGF-2 and FGF-9 on the proliferation and the expression of matrix metalloproteinases (MMPs) and their inhibitor (TIMP-1) in vitro. Both FGFs showed mitogenic activity on U251MG and NMC-G1 cells. MMP-1 expression and collagenolytic activity of NMC-G1 but not of U251MG, and TIMP-1 expression of both cells were stimulated by FGFs. MMP-2 expression, gelatinolytic activity, and chemoinvasion on the matrigel were not altered. FGFs may regulate proliferation and microenvironmental factors independently in each glioma type.

Brain Neoplasms↗
PubMed1998

[A case of crushing head injury with bilateral abducens and facial nerve palsies].

A 20-year-old male was admitted to our hospital suffering from a crushing head injury. At accident, his head had been compressed by the printing machine on both temporal regions. He remained at dull conscious. On admission one hour after the injury, he showed bilateral sixth-nerve and seventh nerve palsies and bleeding from the nose. CT scan showed marked pneumocephalus, traumatic subarachnoid hemorrhage, fluid collections in the bilateral sphenoid sinuses and right mastoid air cells. Bone CT disclosed bilateral temporal bone fractures. MRI did not show cerebral parenchymal damage. He recovered fully conscious at four hours after the injury, but cranial nerve palsies sustained over 30 days after the injury. Bilateral decompression of the facial canal were performed at day 31. At one year after the injury, bilateral abducens nerve palsies and facial nerve palsies recovered incompletely (grade III). The case report and the mechanism of such cranial nerve injuries by low-velocity crushing head injury is described.

Abducens Nerve↗
PubMed1997

Posttraumatic edema in the corpus callosum shown by MRI.

MRI was performed on 120 patients who sustained closed head injury of varying severity. Patients ranged in age from 4 to 87 years (average, 32 years). All patients had an initial MRI within 28 days (median 12 days) of injury. MRI disclosed areas of abnormal signals in the corpus callosum of 21 (18%) of the 120 patients; 1 (2%) of the 44 patients who sustained mild injuries (GCS > or = 13), 3 (10%) of the 31 moderate injuries (GCS 9-12), and 17 (38%) of the 45 severe injuries (GCS < or = 8) (p < 0.0001). All but 2 of the 21 patients with corpus callosum lesions had other parenchymal lesions that were visualized by MRI. Of these 21 patients, MRI was repeated in 19. In 13 of the 19 patients, repeat MRI scans at 25 to 42 days after injury showed the disappearance of lesions that had on the first MRI shown a high signal on T2-weighted and FLAIR images and a normal signal on T1-weighted images. The MRI findings and time source of the disappearance of the corpus callosum lesions mirrored those of paracontusional edema in the subcortical white matter. Patients in whom the corpus callosum lesion disappeared had a better outcome than those in whom the lesion remained (good recovery/moderate disability; 92% vs 63%). The present MRI results suggest that some lesions in the corpus callosum following closed head injury are reversible, thus resembling edema that may be produced by a relatively mild shear strain force to the corpus callosum.

Adolescent↗
PubMed1997

Clinical features of Japanese children and adolescents with systemic lupus erythematosus: results of 1980-1994 survey.

Marked advances have been made in the past decade in the management of adults with systemic lupus erythematosus (SLE). Therefore, a nationwide retrospective survey was conducted between 1980 and 1994 to investigate the clinical manifestations of SLE in Japanese children and adolescents. Questionnaires were sent to 340 hospitals. Of 405 patients reported by 176 hospitals, 373 patients, diagnosed by the criteria established by the Pediatric Study Group of the Japanese Ministry of Health and Welfare in 1985, were enrolled in the study. Forty-nine of the 354 patients (13.8%) had relatives with a connective tissue disease within the third degree of consanguinity. The frequent manifestations in 373 patients were the presence of antinuclear antibody (98.9%), immunologic disorders (93.0%), hypocomplementemia (87.1%), malar rash (79.6%) and fever (74.0%). Lupus nephritis was present in 148 of the 309 patients (47.9%) at their first visit to a clinic, and 261 of the 373 patients (70.0%) developed renal involvement during the observation period. Of 370 patients, 92 patients (24.9%) exhibited central nervous system lupus. Of 368 patients, 192 patients (52.2%) were treated by methylprednisolone pulse therapy and 148 patients (40.2%) received immunosuppressants in combination with steroid therapy at some stage during the observation period, Survival rate at 5 years from onset was 95.9%. Management of infection, coagulopathies, and central nervous system involvement is essential to improve the prognosis of SLE in Japanese children and adolescents.

Adolescent↗
PubMed1997

Contribution of ATP-sensitive potassium channels to hypoxic hyperpolarization in rat hippocampal CA1 neurons in vitro.

To investigate the mechanism of generation of the hypoxia-induced hyperpolarization (hypoxic hyperpolarization) in hippocampal CA1 neurons in rat tissue slices, recordings were made in current-clamp mode and single-electrode voltage-clamp mode. Superfusion with hypoxic medium produced a hyperpolarization and corresponding outward current, which were associated with an increase in membrane conductance. Reoxygenation produced a further hyperpolarization, with corresponding outward current, followed by a recovery to the preexposure level. The amplitude of the posthypoxic hyperpolarization was always greater than that of the hypoxic hyperpolarization. In single-electrode voltage-clamp mode, it was difficult to record reproducible outward currents in response to repeated hypoxic exposure with the use of electrodes with a high tip resistance. The current-clamp technique was therefore chosen to study the pharmacological characteristics of the hypoxic hyperpolarization. In 60-80% of hippocampal CA1 neurons, glibenclamide or tolbutamide (3-100 microM) reduced the amplitude of the hypoxic hyperpolarization in a concentration-dependent manner by up to approximately 70%. The glibenclamide or tolbutamide concentrations producing half-maximal inhibition of the hypoxic hyperpolarization were 6 and 12 microM, respectively. The chord conductance of the membrane potential between -80 and -90 mV in the absence of glibenclamide (30 microM) or tolbutamide (100 microM) was 2-3 times greater than that in the presence of glibenclamide or tolbutamide. In contrast, the reversal potential of the hypoxic hyperpolarization was approximately -83 mV in both the absence and presence of tolbutamide or glibenclamide. In approximately 40% of CA1 neurons, diazoxide (100 microM) or nicorandil (1 mM) mimicked the hypoxic hyperpolarization and pretreatment of these drugs occluded the hypoxic hyperpolarization. When ATP was injected into the impaled neuron, hypoxic exposure could not produce a hyperpolarization. The intracellular injection of the nonhydrolyzable ATP analogue 5'-adenylylimidodiphosphate lithium salt reduced the amplitude of the hypoxic hyperpolarization. Furthermore, application of dinitrophenol (10 microM) mimicked the hypoxic hyperpolarization, and the dinitrophenol-induced hyperpolarization was inhibited by either pretreatment of tolbutamide or intracellular injection of ATP, indicating that the hypoxic hyperpolarization is highly dependent on intracellular ATP. It is therefore concluded that in the majority of hippocampal CA1 neurons, exposure to hypoxic conditions resulting in a reduction in the intracellular level of ATP leads to activation of ATP-sensitive potassium channels with concomitant hyperpolarization.

Adenosine Triphosphate↗
PubMed1997

Orbital hemangiopericytoma--case report.

A 43-year-old male presented with swelling involving the right eye. T1-weighted magnetic resonance imaging demonstrated a round tumor in the lateral region of the right orbit, which was isointense relative to the cerebral gray matter and homogeneously enhanced by gadolinium-diethylenetriaminepenta-acetic acid with a flow-void signal area in the mass. The tumor was totally resected through the transcranial and fronto-orbitotemporal approach after embolization of feeding arteries arising from the external carotid artery. The histological findings were characteristic of hemangiopericytoma. No radiation therapy was administered. The transcranial and fronto-orbitotemporal approach provides a wide operative field with excellent exposure of the highly vascular orbital tumor.

Cerebral Angiography↗
PubMed1997

[Postoperative complications of anterior and middle skull base surgery].

The authors present the postoperative complications of skull base surgery based on a 10-year experience with 26 patients operated on via the supraorbital trans-basal or orbitozygomatic approach. The lesions included 19 malignant tumors and seven benign tumors. Postoperative cerebrospinal (CSF) leak occurred in one of the two patients in whom the dural defects were repaired with a fascia lata graft. None of the remaining 24 patients who were repaired with a musculopericranial flap suffered postoperative CSF leak. Three patients developed epidural abscess, but no infection was seen in the patients who had been reconstructed with a vascularized musculo-cutaneous flap to occlude the dead space. Preoperative radiation therapy correlated with a high incidence of postoperative infection. Cranial nerve deterioration or palsy occurred in four patients. Intraoperative injury of the internal carotid artery occurred in one patient who developed severe neurological deterioration. After an average follow-up period of 40 months (range 12 to 109 months), 68% of patients with malignant tumors and 100% of patients with benign tumors were alive with no evidence of recurrence.

Abscess↗
PubMed1997

[Two cases with SLE and MCTD developed after a long period of chronic arthritis that was initially diagnosed as JRA].

In order to discuss the diversity of clinical features and the difficulty in diagnosis of children with juvenile rheumatoid arthritis (JRA), we present two cases who have documented the development of systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD) after a long period of disease characterized only by arthritis that was initially diagnosed as JRA. The first case was a girl diagnosed for her arthritic joints as polyarticular JRA at 15 years of age. At onset, she had Raynaud phenomenon but autoantibodies such as anti-nuclear antibody (ANA), anti-DNA antibody, and rheumatoid factor were negative. Five years after onset, she became ANA positive and 3 years later she became pregnant. During her pregnancy, she became positive for anti-DNA antibody without any signs of nephritis. One month after the delivery, however, she developed butterfly rash, carditis, nephritis, and was diagnosed as SLE. No destructive changes were observed in her joints though arthritis continued for 8 years form onset to pregnancy. The second case was a 3 years old girl who was diagnosed as polyarticular JRA. Treatment by aspirin induced complate remission after one year from the onset. However, 10 years after that remission, she developed Raynaud phenomenon and arthralgia in her knees and hip joints. Her laboratory findings showed hypergammaglobulinemia, positive ANA, positive anti-DNA antibody, positive anti-RNP antibody. She was eventually diagnosed as MCTD when she was found to have polymyositis by EMG and serum CK. In the present paper, two cases imply the difficulty in diagnosing JRA and diversity of rheumatic diseases such as JRA, SLE and MCTD. Closer and longer period of observation is essential for the JRA patients with nondestructive arthritis.

Adolescent↗
PubMed1996

New surgical treatment of middle fossa arachnoid cyst.

BACKGROUND: A new surgical treatment of middle fossa arachnoid cyst is reported. The benefit of our surgical procedure is to maintain the physiologic pathway of the cerebrospinal fluid (CSF) without a shunting procedure. METHODS: Following a small frontotemporal craniotomy, a linear incision in the outer wall of the cyst is made. The basal subarachnoid cisterns and distal sylvian cisterns are widely opened microsurgically. The outer wall of the cyst is then closed to prevent CSF leakage (arachnoidplasty). RESULTS: We have experienced six patients who underwent this new surgical treatment. All their cysts showed nor or delayed influx of the contrast medium on preoperative computed tomography cisternogram. A favorable outcome was attained in the long-term follow-up without any complications. CONCLUSIONS: The present technique was designed to secure physiologic CSF circulation and to avoid the use of a shunting system. A total of six patients treated with our new technique have been followed-up 6 years, and a good clinical outcome has been observed in all of them without complications.

Adult↗
PubMed1996

Ultrastructure of collagen fibers in the outer membrane of recurrent chronic subdural hematoma.

The three-dimensional structure of the collagen fibers in the outer membrane of recurrent chronic subdural hematoma was studied by scanning electron microscopy (SEM). Specimens obtained at surgery were treated with NaOH at room temperature to digest away all cellular components and expose the collagen fibers. SEM observation of the dural side of the outer membrane showed the collagen fibers were woven into a compact feltwork with a dense arrangement. The fiber bundles had a honeycomb structure framed by the collagen fibers. Observation of the hematoma side found the collagen bundles had a sparse wavy appearance. The arrangement of the collagen fibers on the dural side is different from that on the hematoma side. The thick outer membrane may be formed by granulation resulting from inflammatory reaction. Collagen fibrillar networks are not fragile, and may reinforce the outer membrane of the recurrent hematoma.

Chronic Disease↗
PubMed1996

Correlation of histology and dynamic MR imaging (MRI) of intracranial meningiomas with a 0.5 tesla MR system.

In 33 histologically verified intracranial meningiomas, the correlation between the pattern of the time-signal intensity curve (TIC) from dynamic MR imaging and the histological subtypes were studied. The patterns of TIC for meningiomas were classified into two types: type A with a steep rise to a peak within a short time; type B with a slow rise to a peak followed by a plateau. Of the 16 meningiomas of the meningothelial types, 14 (87%) were type A on the TIC. On the contrary, all of the fibroblastic meningiomas were type B. The others had an almost equal distribution between the two types. These results indicate that dynamic MRI does not always have a predictive value for the histological subtype of an intracranial meningioma or for the histological architecture of the meningothelial or fibroblastic components.

Brain Neoplasms↗