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Biomedical subjects

K Morimoto

Publications and source records attributed to K Morimoto.

At least 505 records · Page 28Linked to original sources
PubMed1989

Nodding attacks (infantile spasms) associated with temporal lobe astrocytoma--case report.

A 2-year-old boy suffered nodding attacks (infantile spasms) that were refractory to anticonvulsants. Computed tomography showed a mass with cystic components in the right temporal lobe, and electroencephalography (EEG) disclosed polyspike and wave discharges in the bilateral temporoparietal regions. At surgery, a firm, gray, well circumscribed tumor was radically removed. The nodding attacks disappeared immediately after surgery and EEG improved gradually. The pathological diagnosis was grade 1 astrocytoma with abundant capillaries and calcospherites. He remained free of seizures during the following 6 years.

Astrocytoma↗
PubMed1989

[Dynamic study of titanium-hydroxyapatite implant by finite element method].

In order to evaluate the strength of titanium-hydroxyapatite implant, adhesive tests and loading tests were performed. The results of the loading tests were compared with the computed results by finite element method. Axisymmetric 8-node quadrilateral element for arbitrary loading was used for the analysis. Implants of 3.2 mm diameter were loaded at 45 degrees of the implant axis by using an Instron testing machine at crosshead speed of 0.5 mm/min. The results were obtained as follows: 1. The mean value of the adhesive test of titanium-resin (Panavia)-hydroxyapatite was 2.3 kgf/mm2. The fracture was caused at Panavia layer. 2. The mean value of the fracture loads of implants was 10.9 kgf. The fracture was caused at Panavia layer, similarly to the result described in 1. 3. The principal stress caused at Panavia layer of the implant was approximately 2.3 kgf/mm2, which was calculated under the load of 10.9 kgf by the finite element method. This result corresponds to that of the loading test described in 1 and 2. It was ascertained by these findings that finite element method is effective for the evaluation of the strength of this implant.

Dental Implants↗
PubMed1989

Lymphocyte transformation with cobalt in hard metal asthma.

Lymphocyte transformation tests with cobalt were done in 9 hard metal asthma patients diagnosed on the basis of a positive bronchial provocation test with cobalt. Positive lymphocyte proliferation in response to the metal was defined statistically from the results of 18 controls comprising 12 hard metal-exposed and 6 non-exposed controls. Out of the 4 patients who had been reported to have IgE antibody specific to cobalt, the lymphocytes of 2 proliferated with metal: one showed positive lymphocyte transformation to free cobalt, the other to both free cobalt and cobalt-conjugated human serum albumin. These results suggest that cobalt-sensitized lymphocytes play a role in some hard metal asthmatics. However, the mechanism underlying the hard metal asthma in the other 5 asthmatics who had neither cobalt-specific IgE antibody nor cobalt-sensitized lymphocytes remain to be elucidated.

Adult↗
PubMed1989

Seizure-triggering mechanisms in the kindling model of epilepsy: collapse of GABA-mediated inhibition and activation of NMDA receptors.

Our recent studies on seizure-triggering mechanisms in the kindling model of epilepsy are reviewed. Electroencephalographic (EEG) events during kindling-inducing tetanic stimulation from the site of stimulation were recorded, with an emphasis on EEG suppression and rhythmic synchronous discharge. From electrophysiological and pharmacological analyses of these events, it is hypothesized that activation and subsequent collapse of GABA-A-mediated inhibition is an essential precondition in the initiation of kindled seizures. The excitatory role of NMDA receptors in kindling were also investigated by examining the effects of a noncompetitive antagonist of NMDA receptors (MK-801) on amygdala kindling and hippocampal long-term potentiation (LTP). The results indicate that activation of NMDA receptor complex combined with the collapse of GABA-A-mediated inhibition may be critical for kindling development.

Brain↗
PubMed1989

[Measurement of DNA damage in forestomach squamous epithelium by alkaline elution assay].

The alkaline elution assay were applied for assessing DNA damage of forestomach squamous epithelium in the male F344 rat. The animals were starved for 18 hr and then given a single oral dose of the sample in saline or corn oil. After 3 hr the stomach was removed, opened along the greater curvature and washed with cold 0.024M EDTA-0.075M NaCl (pH 7.5). The mucosa of the forestomach was scraped off gently with the edge of a cover glass, and the stratified squamous epithelium was collected by scraping off firmly with the edge of a cover glass. Since the collected epithelium cells adhere to the pipettes, these cells were transferred onto a polycarbonate filter by using a micro spatula. The dose-dependent DNA damages (5 approximately 150 mg/kg) were observed after administration of 1-methyl-3-nitro-1-nitrosoguanidine (MNNG), a forestomach carcinogen.

Animals↗
PubMed1989

Quantitative study on the interface between bone tissue and Blade-vent implants using the image processing system.

Undecalcified histopathologic sections of two titanium blade-vent implants (which had survived for five years in a dog) were made, and image analyses of the bone-implant interface were determined. One implant was inserted conventionally in the right mandible, and the other was inserted shallower than usual in the left mandible, so that the shoulder was located at the same level as the residual bone ridge. Using an image analysis technique, we observed, on the deeper implant, a 0-56% rate of bony contact around the implant and a 71-84% rate of bone-vent occupancy in the vents. With the shallower implant, a 0-46% rate of bony contact and a 26-60% rate of bone-vent occupancy were observed. When the two implants were compared, the deeper implant showed relatively higher bony contact and bone-vent occupancy than its less-submerged control in the five-year study.

Animals↗
PubMed1989

[Antenatal detection of developing nervous system abnormalities and perinatal surgical management].

As the use of prenatal ultrasound sonographic study becomes more popular, it is likely that several fetal anomalies of the central nervous system will be diagnosed in utero more frequently and accurately. Obstetric sonogram correlates well with the results of postnatal CT scanning. Now, with improved diagnosis and support facilities for the newborn, neurosurgical intervention is being requested, as more concern is expressed for such fetus. We have experienced seven cases of fetal disorders of the central nervous system-meningocele, meningoencephalocele, myeloschisis, arachnoid cyst and maximal hydrocephalus. When diagnosed late in gestation (after the 2nd trimester), it may be reasonable to consider early delivery at the time of pulmonary maturity, and extrauterine management to decrease secondary damage to the developing central nervous system. The method of delivering a fetus must be tailored to suit each case. We present our program for the management of fetal hydrocephalus-placement of a subcutaneous low profile Ommaya's reservoir for neonate immediately after birth, and then subsequently conversion to a ventriculoperitoneal shunt three or four weeks later. As advances are made in antenatal diagnostic techniques and appropriate therapy, prognostic data on congenital abnormalities of the central nervous system will increase and become more pertinent.

Arachnoid↗
PubMed1989

Improved method using a bubble-free adhesion technique for the preparation of semi-serial undecalcified histologic sections containing dental implants.

The preparation technique, with the minimum of artifacts for the semi-serial undecalcified histologic sections containing dental implants, is presented in this study. The sections enabled finer light-microscopic observations to be made. A formalin-fixed tissue block containing a dental implant was dehydrated in ethanol and acetone, and then embedded in polyester resin under 76 cm Hg reduced pressure. The embedded block was trimmed by a cutter and ground by abrasive paper. In a 1.5 Kg f/cm2 pressurized chamber, its polished surface was bonded to a methacrylate slide by means of ethylcyanoacrylate used in an adhesion loading device. This meant that no bubbles could arise in the interface between the slide and the block. The slide-block was then attached to an adsorptive specimen-holder of a hard-tissue cutting machine and cut to a thickness of approximately 50 microns, with use of a diamond blade. The slide-section was ground to 15-40 microns with wet-type abrasive paper and film on a polishing table. Etching with weak acid and surface staining with toluidine blue and methylene blue/basic fuchsin/light green were performed on the section.

Acrylic Resins↗
PubMed1989

[Application of preoperative chemotherapy to postoperative chemotherapy in malignant bone and soft tissue tumors].

We analyzed the effectiveness of preoperative chemotherapy mainly with radiographic images in 9 patients with osteosarcoma, 5 patients with other malignant bone tumor and 14 patients with malignant soft tissue tumor. Judging from the application of preoperative to postoperative chemotherapy and outcome, its evaluation was useful in osteosarcoma and malignant soft tissue tumors. Changes in radiographic images by preoperative chemotherapy were the same in malignant bone and soft tissue tumors, but the reactivity of the latter was more evident. In malignant bone and soft tissue tumors, the effects of preoperative chemotherapy should be evaluated for the cases with resection of primary tumor. Malignant bone tumors excepting osteosarcoma also should be assessed through further accumulation of many more cases.

Adolescent↗
PubMed1989

[Anticonvulsant effects of bifemelane hydrochloride on kindled seizures from the amygdala and hippocampus in rats].

The anticonvulsant affects of bifemelane hydrochloride, a novel therapeutic drug for cerebrovascular dementia, were investigated in the kindling model of epilepsy in rats. The results obtained were as follows. (i) Both the seizure stage and afterdischarge duration of kindled seizures from the amygdala and hippocampus were significantly suppressed following systemic injection of bifemelane hydrochloride (5-30 mg/kg) in a dose-dependent manner. (ii) The efficacy of anticonvulsant action on kindled seizures from the hippocampus was more potent than from the amygdala. (iii) The maximum anticonvulsant effects were observed between 1 and 4 h after injection, and this time course was very similar to that of the previously reported increasing effects of bifemelane hydrochloride on noradrenaline levels in the rat brain. Thus, it is suggested that these anticonvulsant effects in kindling may be mediated by central noradrenergic systems. These results indicate that bifemelane hydrochloride has a potent anticonvulsant action on kindled seizures and may be useful for dementia patients with epilepsy or other seizure disorders.

Amygdala↗
PubMed1989

[Extracellular purine catabolites and tissue nucleotides and purine catabolites during progression and recovery of ischemia].

During progression and recovery of ischemia, extracellular purine catabolites were measured and compared with purine catabolites and adenine nucleotide levels in the tissue. Ischemia was induced by bilateral occlusion of the common carotid arteries in gerbil. Extracellular purine catabolites were sampled by in vivo brain microdialysis technique, and tissue adenine nucleotides and purine catabolites were extracted from in situ frozen and lypholized brain tissue. These metabolites were measured with simple method of isoclatic condition by HPLC system. Ischemia depleted tissue ATP and ADP, whereas AMP and purine catabolites accumulated strikingly. In parallel, extracellular purine catabolites increased as consecutive degradation on the biochemical metabolic pathway in the same animal. Levels of tissue ATP and adenosine normalized in the recovery phase of ischemia immediately. However, extracellular purine catabolites during the recovery are much higher than those during the progression of ischemia. These data indicated extracellular high levels of purine catabolites during the ischemic insult, and especially adenosine as neuromodulator which may turn off spontaneous neuronal activity and exert antiepileptic effects during the recovery rather than the progression of ischemia.

Adenine Nucleotides↗
PubMed1988

Anticonvulsant action of a non-competitive antagonist of NMDA receptors (MK-801) in the kindling model of epilepsy.

Anticonvulsant action of MK-801, a novel non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors, was investigated in the kindling model of epilepsy in rats. The results obtained were as follows. (1) Both the seizure stage and afterdischarge duration of previously kindled seizures from the amygdala were significantly suppressed following systemic injection of MK-801 (0.25-4 mg/kg) in a dose-dependent manner. The maximum effects were observed between 2 and 4 after the injection. (2) The MK-801 also showed significant anticonvulsant effects on kindled seizures from the frontal cortex and the ventral and dorsal hippocampus. The efficacy, however, significantly differed between these kindled sites. (3) Daily treatment of MK-801 (0.25 and 1 mg/kg) prior to each electrical stimulation of the amygdala significantly retarded kindling seizure development and increased the total amount of afterdischarge (accumulated AD) required to reach the first stage 5 seizure. During drug sessions of 1 mg/kg MK-801 for 19 days, all rats showed only partial seizures and the growth of afterdischarge was strongly prevented. (4) Pretreatment with reserpine did not antagonize the anticonvulsant effects of MK-801 on previously kindled seizures from the amygdala, suggesting that the effects may not be mediated by catecholaminergic systems. These results indicate that MK-801 has potent anticonvulsant actions on kindled seizures from both limbic and cortical foci, the NMDA system may play a critical role in the seizure-triggering mechanism of kindling. The possible application of NMDA antagonists in clinical epilepsy is suggested.

Animals↗
PubMed1988

Investigation of the specificity of O6-alkylguanine-DNA-alkyltransferase.

Comparison of the abilities of alkylated RNA and DNA to serve as substrates for the O6-alkylguanine-DNA-alkyltransferase have been carried out. It was found that the O6-methylguanine in tRNA was much less active as a substrate for the protein than O6-methylguanine in double stranded DNA. The difference in rates of repair was such that it is unlikely that the alkyltransferase would act on RNA in vivo and, therefore, the reaction with RNA should not contribute towards the exhaustion of its repair capacity.

Chromatography, High Pressure Liquid↗
PubMed1988

Alkylation of DNA in F344 rat thymus following administration of 1-n-propyl-1-nitrosourea in vivo and comparison of O6-alkylguanine DNA alkyltransferase activity in thymus from F344 and Long-Evans rats in vitro.

The tissue distribution of radioactivity 1 h after i.p. injection of [n-propyl-2,3-3H]1-n-propyl-1-nitrosourea (PNU) (100 mg/kg) was studied in male F344 rats. This treatment results in a high incidence of thymic lymphomas. The 3H concentration in the thymus, testis and brain was significantly higher than that in blood. 7-n-propylguanine and O6-n-propylguanine were detected in thymus DNA of F344 rats treated with PNU; the ratio of O6-n-propylguanine/7-n-propylguanine was 0.35, lower than following DNA alkylation in vitro. This suggests the presence of O6-alkylguanine DNA alkyltransferase (AGT) in thymus. AGT activity in F344 and Long-Evans rats was compared by using a 3H-propylated DNA as a substrate. AGT activity in the thymus of F344 rats was lower than that in the liver. The AGT activity in the thymus of Long-Evans strain, which had a low incidence of PNU-induced thymic lymphomas, was higher than that of F344 strain. The high level of DNA alkylation by PNU and the low activity of AGT in the thymus may contribute to the high incidence of thymic lymphoma in F344 rat.

Alkylation↗