Biomedical subjects

T Nakahara

Publications and source records attributed to T Nakahara.

At least 19 recordsLinked to original sources

PubMed1992

Developmental changes in the incidence of chromosome anomalies of bovine embryos fertilized in vitro.

In total, 196 two- to 32-cell bovine embryo and 104 blastocysts were obtained by the in vitro fertilization of follicular oocytes matured in vitro, and 15 blastocysts fertilized in vivo were used. Chromosomal anomalies in these embryos and the inner cell mass (ICM) separated immunologically were investigated. Chromosomal anomalies were observed in 12.1% (5/41) of 2-cell embryos, 20.0-36.4% of 4- to 16-cell embryos, 7.1% (1/14) of 17- to 32-cell embryos, 44.2% (15/34) of blastocysts, and 18.6% (13/70) of ICM cells derived from in vitro fertilization. These anomalies were mainly 3N and 4N at 2-cell stage, 1N and 1N/2N at 4- to 32-cell stages, and 2N/4N in blastocysts and in their ICM cells. Chromosomal anomalies of blastocysts from in vivo fertilization and their ICM were observed in 20.0% (1/5) of blastocysts and 33.3% (3/9) of ICM cells and these compositions were mainly 2N/4N. These results indicate that the abnormalities at early and blastocyst stages of embryos derived from in vitro fertilization were caused by abnormal fertilization in vitro and abnormal cleavage, respectively. Furthermore, a definite location of the chromosomal anomalies was observed in the trophectoderm of blastocysts derived from in vitro fertilization.

Animals↗

PubMed1992

Effect of intracarotid infusion of etoposide with angiotensin II-induced hypertension on the blood-brain barrier and the brain tissue.

This study investigated the effects of the intracarotid infusion of etoposide in combination with angiotensin II (AT II)-induced hypertension on the blood-brain barrier (BBB) and brain tissue in rats. Eighty rats were divided into five groups: Group 1, intravenous infusion of AT II to increase arterial blood pressure; Group 2, intracarotid infusion of etoposide at 22.5 mg/m2 for 10 minutes; Group 3, intracarotid infusion of etoposide at 75.0 mg/m2 for 10 minutes; Group 4, intracarotid infusion of etoposide at 75.0 mg/m2 for 20 minutes; Group 5, intracarotid infusion of etoposide at 75.0 mg/m2 for 10 minutes with AT II-induced hypertension. Evans blue staining of the brain was used as a monitor of BBB disruption. Mean arterial blood pressure over the experimental period in Group 1 increased from 86.3 +/- 1.3 mmHg (mean +/- SEM) to 139.0 +/- 2.4 mmHg, and Group 5 from 85.9 +/- 1.8 mmHg to 137.3 +/- 2.4 mmHg. None of the animals in Group 1 and 2 showed any obvious neurological change, while all the animals in Group 3, 4 and 5 exhibited diminished activity as their sole neurological change throughout the course of the experiment. Slight evidence of BBB disruption was seen in only 25% of the animals in Group 1. Significant BBB disruption was found in the animals in Group 2, 3, 4 and 5. No histological change was observed in any animal in Group 1 and 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

PubMed1992

Cerebral myxopapillary ependymoma.

A rare case of myxopapillary ependymoma is reported. The tumor occurred in the cerebral hemisphere of an 8-year-old girl and had no relationship to the lateral ventricles. Microscopically, it showed abundant mucin production around papillary or reticular structures. Immunohistochemically, these tumor cells were weakly positive, with glial fibrillary acidic protein demonstrated in part of the tumor and vimentin strongly demonstrated throughout the tumor. The results may indicate the poorly differentiated nature of this tumor. This is the second reported case of intracranial myxopapillary ependymoma.

Brain Neoplasms↗

PubMed1992

Transcranial Doppler sonography in carotid-cavernous fistulas: analysis of five cases.

Transcranial doppler sonography was performed transorbitally in five patients clinically diagnosed as unilateral carotid-cavernous fistula. Dural arteriovenous malformation related-shunts were detected in all the patients. In the normal eyes, the only doppler signals observed at an insonation depth of 45 to 55 mm were those of the ophthalmic artery. In the affected eyes, abnormal doppler signals with relatively higher flow velocity and lower resistance were observed. In three of the cases, these abnormal signals showed a flow directed anteriorly or away from the cavernous sinus, consistent with changes in the ophthalmic veins caused by the presence of the shunts. In two cases, however, the observed flows were directed posteriorly, the normal direction of these veins. The possible explanations for this discrepancy are discussed in relation with angiographic findings. The use of transcranial doppler might provide a better understanding about hemodynamic changes in carotid cavernous fistulas.

Aged↗

PubMed1992

Inhibition of ischemia-induced dopamine release by omega-conotoxin, a calcium channel blocker, in the striatum of spontaneously hypertensive rats: in vivo brain dialysis study.

The effect of omega-conotoxin GVIA (CgTX), an N-and L-type voltage-sensitive calcium channel (VSCC) blocker, on the release of dopamine and 3,4-dihydroxyphenylacetic acid (DOPAC) in the striatum before and during transient cerebral ischemia in spontaneously hypertensive rats was studied using an in vivo brain dialysis technique. Continuous perfusion of CgTX in the striatum was started 20 min before ischemia and concentrations of dopamine and DOPAC in the dialysate were measured using HPLC with an electro-chemical detector. Before ischemia, both 10 and 100 microM CgTX significantly lowered the concentration of dopamine, to 49% of the basal values. DOPAC concentrations also decreased significantly, by 28 and 17%, respectively. Forebrain ischemia, produced by bilateral carotid artery occlusion, reduced striatal blood flow to less than 6% of the resting value in each group. During 20 min of ischemia, the vehicle group showed a marked increase in dopamine (175 times the basal concentration). In the 10 or 100 microM CgTX perfusion group, in contrast, dopamine release was significantly attenuated, to 38 or 29% of the vehicle group, respectively. DOPAC concentrations decreased during ischemia to 58% of the basal value in the vehicle group and 49% in both CgTX groups. These results indicate that the massive release of striatal dopamine during ischemia depends largely on the influx of extracellular calcium via CgTX-sensitive VSCCs.

3,4-Dihydroxyphenylacetic Acid↗

PubMed1992

Role of heterotrophic bacteria in complete mineralization of trichloroethylene by Methylocystis sp. strain M.

Biodegradation experiments with radioactively labeled trichloroethylene showed that 32% of the radioactive carbon was converted to glyoxylic acid, dichloroacetic acid and trichloroacetic acid and that the same percentage was converted to CO2 and CO after 140 h of incubation by a pure culture of a type II methane-utilizing bacterium, Methylocystis sp. strain M, isolated from a mixed culture, MU-81, in our laboratory. In contrast, these water-soluble (14C)trichloroethylene degradation products were completely or partially degraded further and converted to CO2 by the MU-81 mixed culture. This phenomenon was attributed to the presence of a heterotrophic bacterium (strain DA4), which was identified as Xanthobacter autotrophicus, in the MU-81 culture. The results indicate that the heterotrophic bacteria play an important role in complete trichloroethylene degradation by methanotrophs.

Biodegradation, Environmental↗

PubMed1992

Development of mouse enucleated oocytes receiving a nucleus from different stages of the second cell cycle.

The influence of the stage of the cell cycle of donor nuclei on the development of mouse oocytes enucleated at telophase I was examined. After nuclear transplantation and activation, a high proportion of the oocytes remodelled a nucleus, emitted a polar body and formed a pronuclear-like nucleus. Most of the reconstituted embryos that received an interphase nucleus 30-32 h or 34-36 h after treatment with human chorionic gonadotrophin (hCG) arrested at the 2-cell stage. The reconstituted embryos were able to develop to blastocysts when nuclei from late 2-cell embryos (44-46 and 48-50 h after hCG) were transferred to the oocytes. The resulting blastocysts were transferred to recipients and ten live young were obtained from the embryos that formed a pronuclear-like nucleus after extrusion of a polar body. Thus, the developmental ability of the reconstituted embryos was critically influenced by the stage of the cell cycle of the donor nuclei.

Animals↗

PubMed1992

Effect of radiation therapy against intracranial hemangiopericytoma.

Seven cases of intracranial hemangiopericytoma were studied retrospectively to investigate the efficacy of radiation therapy. Tumor response evaluated by computed tomography and magnetic resonance imaging was obvious after 20-30 Gy irradiation. The total reduction rate was 80-90% and continued as long as 5-7 months after treatment. In five patients receiving radiation therapy before radical removal, the tumors were easily removed without massive hemorrhage. Histological inspection of specimens after irradiation showed a significant disappearance of tumor cells. Pyknosis frequently occurred in endothelial cells, and proliferating vessels with hyalinoid degeneration were also seen. Reticulin fibers between tumor cells were fewer, split, or absent. Preoperative radiation therapy is useful in the treatment of hemangiopericytoma involving considerable surgical risk. Postoperative radiation therapy should be given even if removal is complete.

Adolescent↗

PubMed1992

Moyamoya disease associated with pituitary adenoma--report of two cases.

Moyamoya disease associated with prolactin (PRL)-producing pituitary adenomas occurred in two females with elevated blood PRL levels (285 and 120 ng/ml). Computed tomography revealed cystic tumors extending from the sella turcica to the suprasellar cistern. Carotid angiography demonstrated stenoses or obstructions of the bilateral internal carotid arteries at their end point and development of bilateral basal moyamoya vessels. Histological diagnosis in one case was PRL-producing chromophobe adenoma. No stigmata of neurofibromatosis or any history of irradiation was found. Compression of carotid arteries by the tumor was unlikely. These cases should therefore be classified as moyamoya disease accompanied by brain tumor, a very rare occurrence. The hypothalamic disturbance caused by moyamoya disease may have induced the hyperprolactinemia, resulting in secondary prolactinoma.

Adenoma, Chromophobe↗

PubMed1992

[Relationship between health services for maternal and child health and working hours of public health nurses].

Based on the "Maternal and Child Health Service Act", public health centers and municipalities offer health education, health counseling, health examination, and home visits for district children and for their mothers. The relationship between the number of the MCH services offered and the working hours of public health nurses at the public health centers and the municipalities was analyzed. Data were taken by a survey in 1989, which was used for evaluating services provided to the children and their mothers in 1988. Questionnaires were sent to 23 health centers and their districts and 100 responses from 8 wards, 20 cities, 47 towns, and 25 villages were analyzed. When total working hours of the public health nurse for MCH are allocated to the four parts-planning, implementation, evaluation and training-86.7% of working hours are for implementation itself. The correlation coefficient between the total working hours of the public health nurse for MCH and the population, and the number of births per year, were significantly positive. A total of 107 hours were supplied for the infant child health examination per 100 births per year, for which 64% was for implementation itself. In the case of the health examination for three-year-old children, total working hours were 143 hours, for with 79% was for implementation itself. The number of mother-child handbooks issued, the number of health education classes and health counselings conducted, various health examinations performed, and home visits made were correlated significantly with the working hours of the public health nurse.

Child↗

PubMed1991

Selective stimulation of human T cells with streptococcal erythrogenic toxins A and B.

Streptococcal exotoxins have been implicated in the pathogenesis of a toxic shock-like syndrome and scarlet fever. Previous studies have demonstrated that these toxins are potent stimulators of human T cells and have structural homology to staphylococcal enterotoxins. In the current study, we investigated the mechanism by which streptococcal erythrogenic toxins type A (SPEA) and B (SPEB) activate T cells and compared it with anti-CD3 and the known "superantigen" staphylococcal enterotoxin B. SPEA was found to selectively activate T cells bearing V beta 8, V beta 12, and V beta 14, whereas SPEB selectively activated T cells bearing V beta 2 and V beta 8. Furthermore, fibroblasts transfected with MHC class II molecules were capable of presenting SPEA and SPEB to purified T cells. The T cell response to these toxins, however, was not MHC-restricted. Although the streptococcal exotoxins stimulated both CD4+ and CD8+ T cells, SPEA but not SPEB stimulated the CD4+ T cell subset proportionately more than the CD8+ T cell subset. Our results indicate that SPEA and SPEB, like the staphylococcal enterotoxins, are superantigens and suggest a mechanism by which they may mediate particular systemic syndromes associated with streptococcal infections.

Animals↗

PubMed1991

Production of identical twin and triplet mice by nuclear transplantation.

Transplantation of a single nucleus from two- or four-cell embryos into one of the enucleated blastomeres of a two-cell embryo resulted in successful production of identical triplet and twin mice. The proportion of reconstituted embryos that developed in blastocysts was 71% (84/118) when four-cell embryos were used as donors of nuclei; 10 sets of quadruplet and nine sets each of triplet and twin blastocysts were obtained by this technique. After transfer to recipients, 30% (18/61) developed to term, and one set of identical triplet and four sets of identical twin mice were obtained. When two-cell embryos were used as donors of nuclei, 79 (95%) sets of twin embryos developed to blastocysts. Of 38 twin blastocysts transferred to recipients, 21 sets (55%) developed to term as identical twin mice. These results demonstrate that the enucleated two-cell embryo develops in vitro after transfer of a nucleus from a two- or four-cell embryo and the resultant blastocyst has high potential for development to term after transfer to a recipient.

Animals↗

PubMed1991

Pharmacokinetics of maprotiline and its demethylated metabolite in serum and specific brain regions of rats after acute and chronic administration of maprotiline.

The concentrations of maprotiline (MAP) and its demethylated metabolite desmethylmaprotiline (DMAP) in the serum and specific brain regions were determined periodically after acute or chronic administration of 20 mg/kg of MAP in rats. MAP was eliminated in a biexponential manner from the serum and monoexponentially from the brain. The DMAP declined monoexponentially from the serum and brain regions. No significant difference was observed in elimination among the eight brain regions examined. In the brain, MAP distributed unevenly after chronic administration, whereas DMAP showed an even distribution. In the acute administration, the AUCbrain: AUCserum ratio of MAP was similar to that of DMAP, and the AUCDMAP: AUCMAP ratio in the serum was almost equal to that in the brain, indicating equivalent ability of MAP and DMAP to penetrate into the brain. After chronic administration, the AUCDMAP value in the serum increased 4.1 times, whereas no marked change was observed for MAP. There was no evidence of enhanced N-demethylation activity from in vitro metabolism study, suggesting that the enhanced AUCDMAP value was not attributable to the enhancement of drug metabolizing activity. Although the AUCMAP value in the brain, as well as in the serum, increased slightly, the AUCDMAP in the brain increased 2.3 times, showing less increase than that in the serum. These findings suggest inhibited distribution of DMAP into tissue, including brain regions, after chronic administration. The pharmacokinetics of the demethylated metabolite DMAP is affected more than that of MAP by chronic administration of MAP.

Animals↗

PubMed1991

A new model of brainstem ischemia by embolization technique in cats.

An experimental model of brainstem ischemia was developed by embolization technique with cylindrical silicone rubber emboli in cats. The embolus reached the basilar artery in 55 cats (58.5%) and stopped in the upper basilar artery (UB) in 32, the middle basilar artery (MB) in 22 and the lower basilar artery (LB) in one animal. When the basilar artery distal to the embolus was not visualized (type 1) by postoperative vertebral angiogram, Evans blue extravasation was observed in the brainstem caudal to the embolus. When only a filling defect of the basilar artery at the site of the embolus was noted (type 2), dye extravasation was observed in the brainstem around the site of the embolus. In UB type 1, the regional cerebral blood flow of pons and medulla oblongata decreased immediately after embolization, and six hours after embolization it was 11.4 +/- 5.7 (pons) and 11.7 +/- 4.6 ml/100 g/min (medulla oblongata). In UB type 1 and MB type 1 animals, coma, apnea, tetraplegia, and disturbance of swallowing were noted. These animals died within 50 hours after embolization. Animals of UB type 2 and MB type 2 showed neurological deficits, but survived for three days. This paper discusses this method of producing experimental brainstem ischemia, the sites of ischemic lesions, and clinicopathological findings.

Animals↗

PubMed1991

Vasospasm after traumatic subarachnoid haemorrhage: transcranial Doppler evaluation. Case report.

A case of vasospasm after traumatic subarachnoid haemorrhage (SAH) is reported here. Transcranial Doppler Sonography (TCD) was used to evaluate mean flow velocity (MFV) changes of the basal cerebral arteries related to vasospasm. Acceleration of MFV of the right middle cerebral artery (MCA) indicating vasospasm was first noted on TCD evaluation, and then proved by carotid angiography (CAG). Evaluation of all TCD results revealed that the process of relaxation or normalization of the spastic artery started from the proximal side of the basal intracranial artery and gradually moving to the distal side. This interesting phenomenon could be a common process found in vasospasm cases.

Blood Flow Velocity↗

PubMed1991

Purification of endogenous inhibitors of [3H]flunitrazepam binding from bovine brain.

Endogenous substances which inhibited the binding of [3H]flunitrazepam ([3H]FNZ) to bovine synaptosomal membranes have been purified from the hot acetic acid extracts of the bovine brain. Three peaks of inhibitory activity were obtained by Sephadex G-10 gel chromatography. Two of the peaks (Peak 2, and Peak 3) which had lower molecular weights than that of peak 1 were identified as inosine and hypoxanthine by TLC methods. Another peak (Peak 1) was further purified to homogeneity using both cation and anion ion-exchange chromatography and the following two-step reversed-phase HPLC. The purified substance inhibited the [3H]FNZ binding dose-dependently and competitively but did not have an effect on the binding of the peripheral-type BZ ligand [3H]Ro 5-4864. It was also shown that the substance was heat-stable and resistant to proteolytic degradation (trypsin, alpha-chymotrypsin, pronase). However, a significant loss of inhibitory activity to [3H]FNZ binding was observed after acid hydrolysis. Molecular weight estimates based on gel filtration methods were less than 500 dalton, and the maximal ultraviolet absorption peak was at 314 nm. These results suggest that this substance is a new endogenous ligand for the central BZ receptor and may play an important role in regulating the GABAergic tone in the central nervous system.

Animals↗

PubMed1991

Development of vitrified mouse oocytes after in vitro fertilization.

Mouse oocytes were cryopreserved by the vitrification method using vitrification solution (VSI) and the effects of dilution methods were examined on the rate of in vitro and in vivo development. Eighty-three percent and 75% of vitrified oocytes exhibited normal morphology when diluted in glycerol + sucrose and sucrose alone, respectively. In contrast, only 35% of the oocytes diluted by a stepwise method exhibited a normal appearance. A high proportion of vitrified oocytes was fertilized in vitro (84-94%), 80 to 87% of which were normal. Of the later embryos, 69 to 78% developed to blastocysts after 4 days of culture. Thirty-six live young (51%) were obtained when vitrified oocytes were transferred to recipient females. The overall rate of development to live young was 25% when vitrified oocytes were diluted with glycerol + sucrose solution. These results indicate that the simple and rapid procedure of vitrification and glycerol + sucrose dilution is suitable for the cryopreservation of mouse oocytes.

Animals↗

PubMed1991

[3H]MK-801 binding to forebrain of E1 (epileptic) and non-epileptic strains of mice.

The El mouse is an animal model with genetically determined epilepsy. To elucidate the mechanism of convulsive seizures in El mice, the effects of L-glutamate and glycine on the binding of (+)[3H]MK-801 were studied in well-washed membranes from forebrains of ddY, BALB/c and El (stimulated and non-stimulated) mice. There were no significant differences in affinity (Kd) or density (Bmax) among the 4 groups of mice under basal conditions. Incubation in the presence of L-glutamate and/or glycine led to an increase in apparent density, but not in affinity. No significant change was observed in either Kd, Bmax, or the percentage increase in (+)[3H]MK-801 binding amount the 4 groups in the presence of L-glutamate and/or glycine. These results suggest that the seizure susceptibility of El mice cannot be explained by changes in affinity or density of the NMDA receptor/channel complex.

Animals↗