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Biomedical subjects

M Ohta

Publications and source records attributed to M Ohta.

At least 235 records · Page 13Linked to original sources
PubMed1999

Structure of bioactive glass and its application to glass ionomer cement.

We prepared a new glass ionomer cement using bioactive CaO-P2O5-SiO2(-MgO) glass and investigated its setting process using FT-IR and MAS NMR analyses. The compressive strengths of the cements depended on the glass composition and a maximum strength of 33.3 +/- 4.7 MPa was obtained using cement with the glass composition of MgO:4.6, CaO:44.9, SiO2:34.2 and P2O5:16.3% in weight. FT-IR analysis showed that the COOH group in the polyacrylic acid decreased and carboxylate ion (COO-Ca2+) increased after the setting reaction. A broad signal appeared around -82 ppm in 29Si MAS-NMR spectra of the glass and a new signal corresponding to hydrated silica gel formation appeared around -102 and -111 ppm after setting. This suggests that Ca2+ was released from the glass powder to form carboxylate salt and that a degree of polymerization in the silicate network increased. The setting mechanism of the cement was found to be essentially the same as in conventional glass ionomer cement.

Biocompatible Materials↗
PubMed1999

[Hyponatremia and inflammation].

We experienced four cases with hyponatremia due to SIADH, which seems to be related to inflammation. The plasma Na concentration decreased when the patients had fever and increased plasma CRP level. In such conditions, plasma vasopressin concentration (PAVP) and the plasma interleukin-6 (IL-6) concentration were increased. There was significant correlation between them. The animal experiments were carried out to investigate the role of interleukin in the development of SIADH. Intravenous administrations of IL-1 beta increased AVP, atrial natriuretic hormone (ANH) and ACTH. The changes in AVP and ACTH were abolished by the pretreatment with an intravenous administration of indomatacin. Moreover, the intracerebroventricular administration (ICV) of IL-1 beta also increased AVP, atrial natriuretic hormone (ANH) and ACTH. The pretreatment of indomatacin attenuated the changes in AVP and ACTH. The intravenous administration of IL-1 beta increased the urinary sodium excretion. The pretreatement of HS142-1, an ANH antagonist, abolished the increase in urinary sodium excretion induced by IL-1 beta. These results suggested that the interleukin play an important role in the development of SIADH associated with inflammation.

Adrenocorticotropic Hormone↗
PubMed1999

[Subacute motor neuronopathy associated with myasthenia gravis and thymoma].

We reported a 63-year-old woman, suffered from myasthenia gravis with thymoma who later developed subacute motor neuronopathy after thymectomy. She noticed distally dominant muscle weakness and atrophy of bilateral upper extremities without sensory loss 4 month after thymomectomy. Her muscle weakness did not improve by intravenous administration of anti-cholinesterase (Tensilon test). Electrophysiological examinations showed no decremental response of examined muscles during repetitive nerve stimulation, nor motor nerve conduction block nor demyelination of affected peripheral nerves. Laboratory study demonstrated positive anti-acetylcholine receptor, anti-nuclear and SS-A antibodies. On immunohistochemistry, the patient's sera positively stained human and rat anterior horn cell cytoplasm as well as axoplasm of spinal white matter and root nerve axon, suggesting the presence of anti-axon antibody, possibly against neurofilament or tubulin components. The biopsied muscle specimen showed neurogenic muscle changes, but with no evidence of vasculitis nor cellular infiltration. Therapeutic trial of plasmapheresis was effective for her muscle weakness. Further recovery of weakness and muscle atrophy of hand muscles was obtained by combined therapy of intravenous and oral corticosteroid administration and plasmapheresis. These clinical, electrophysiological and histological findings suggested that antibodies against neuronal component might be responsible for her motor neuronopathy associated with myasthenia gravis. The findings of our case study may support the idea that some cases of motor neuron disease are caused by auto-immune mechanism.

Autoantibodies↗
PubMed1999

[A patient with intractable myasthenia gravis successfully treated with total lymphoid irradiation].

We report a 20-year-old man with intractable myasthenia gravis successfully treated with total lymphoid irradiation (TLI). An encapsulated thymoma in the anterior mediastinum was resected as extended thymectomy by video-assisted thoracoscopic surgery at 2 months after the onset of ptosis and muscle weakness. Following treatments, such as ambenonium hydrochloride, an immunosuppression therapy (prednisolone and azatioprine), 5 courses of immunoadsorption therapy, and a high dose of cyclophosphamide and methylprednisolone, did not make persistent improvement of myasthenic symptoms. Ageusia occurred twice prior to myasthenic crises and subsided with other myasthenic symptoms after treatments. Steroid psychosis and secondary Cushing's syndrome made us to reduce the dose of prednisolone. Post-operative residual, recurrent, or metastatic thymus was not unveiled, then we added the low dose fractionated irradiation (1.5 Gy x 12 = 18 Gy) to the mediastinum. Three months after the irradiation, however, a crisis occurred and the titer of anti-acetylcholine receptor antibody increased up to 100 nmol/l. Therefore, we performed TLI (Mantle; 1.5 Gy x 9 = 13.5 Gy, paraaortic and inverted-Y; 1.5 Gy x 14 = 21 Gy), which brought about persistent improvement of myasthenic symptoms with decrease in the titer of anti-acetylcholine receptor antibody.

Adult↗
PubMed1999

Activity of the rat pontomedullary reticular neurons related to rhythmical jaw movements.

Electrical stimulation of the cerebral peduncle or oral mechanical or chemical stimulation induced rhythmical jaw movements (RJM) in the anesthetized rat. Extracellular recording was made from the pontomedullary reticular neurons in relation to RJM. The RJM-related activity was classified to a tonic, a transient and a phase-dependent rhythmical activities (116, 92 and 45 neurons, respectively). We found that the neurons showing the phase-dependent activities discharged exclusively or almost exclusively during RJM without responding to at least one of three kinds of RJM-inducing stimulation. Fourteen neurons were activated by all kinds of RJM-inducing stimulation and majority of them showed weak or no change in activity during RJM, although some showed the transient or the rhythmical activity during RJM. We propose that the phase-dependent rhythmical activity is necessary to generate RJM since any stimulation-induced RJM was reversibly blocked by microinjection of lidocaine or glutamate receptor blocking agents into the brainstem site concentrated by this type of neurons. No other type of activity was observed exclusively during RJM.

Animals↗
PubMed1999

Glutamate activates neuronal discharges and rhythmical jaw movements in the rat.

Rhythmical jaw movements (RJM) were induced by stimulation of the cerebral peduncle or the oral cavity in the anesthetized rat and iontophoretic application of glutamate was examined on each reticular neuron with phase-dependent rhythmical activity during RJM (RJM-phasic neuron). Glutamate activated six neurons rhythmically with simultaneous rhythmical jaw movements in five rats. However, glutamate activated fifty of the other 52 RJM-phasic neurons tonically without RJM. Therefore, a small number of RJM-phasic neurons (10.3%) was involved in the generation of RJM. The rhythmical activities of most RJM-phasic neurons should have been synaptically induced by activities of those RJM-generator neurons. Glutamate receptor blocking agents, cyano-nitroquinoxaline-dione and D-amino-phosphono-valerate were examined and the former was more effective on 17 neurons although the latter was more effective on three and both were equally effective on 13. Inhibitory synaptic mechanism is not necessary for RJM-generation since bicuculline or strychnine did not significantly alter the rhythmical pattern of activity in any neuron.

Animals↗
PubMed1999

Palpability of breast tumors--correlation with ultrasonic findings.

With the recent development of high-resolution real-time ultrasonic devices and their application to clinical examination and breast screening, small non-palpable breast lesions have frequently been detected and controversy has arisen concerning their diagnosis and treatment. In order to evaluate the relationship between ultrasonic B-mode images and palpability of breast tumors, 71 breast tumors including 21 cancers were analyzed. Five basic measurements on tumor size and location were performed followed by calculation of secondary parameters of palpability. Larger size (D and W), less distance from the skin surface (S-T), less embeddedness within or more protrusion from the mammary gland (G-T) and greater relative size of tumor with respect to whole breast thickness (D/(S-P)) were found to be significantly related to greater palpability of breast tumors. Among the qualitative diagnostic criteria for breast tumors, an irregular shape, rough border, thick boundary echoes, heterogeneous internal echoes and indirect signs were statistically more frequent in palpable than non-palpable tumors, and in malignant than in benign tumors. In cases of cancer, palpability was related significantly only to size and to heterogeneous internal echoes. For early detection of breast cancer, identification of breast cancer among small non-palpable breast lesions less than 1 cm in size in ultrasonic B-mode images is considered to be essential.

Breast Neoplasms↗
PubMed1999

Autografting with peripheral blood CD34-positive cells following high-dose chemotherapy against breast cancer.

We report autologous CD34+ cell transplantation performed in 3 cases of recurrent breast cancer. The hematological recovery in these cases was assessed by comparing with that in the previous cases of autologous hematopoietic stem cell transplantation performed with the same high-dose chemotherapy regimen. Patient 1 was a 32-year-old woman with pulmonary and skeletal metastases; patient 2, a 55-year-old woman with pulmonary metastases; and patient 3, a 48-year-old woman with hepatic metastases. On day 1, cyclophosphamide 1000 mg/m2 and epirubicin 130 mg/m2 were administered concurrently with granulocyte colony-stimulating factor, and peripheral blood stem cells were harvested on days 14-16. These stem cells were processed using anti-CD34 monoclonal antibody and an immunomagnetic bead device, Isolex 300i. The high-dose chemotherapy regimen consisted of cyclophosphamide 2000 mg/m2/day, div, and thiotepa 200 mg/m2/day, div on day -5, -4, and -3. The harvested CD34+ cells numbered 3.9 +/- 2.8 x 10(6)/kg (range: 0.73-7.8/10(6)/kg), and the CFU-GM, 8.3 +/- 5.6 x 10(5)/kg (range: 1.2-15.1/10(5)/kg). After the separation, the percent of CD34+ cells was 81.9 +/- 11.6% (range: 65.8-96.4%), the CD34+ cell yield, 71.8 +/- 30.2% (range: 46.0-129.6%), and the CFU-GM yield, 48.9 +/- 9.1% (range: 35.3-62.0%). At the time of transplantation, the number of nucleated cells was 0.55 +/- 0.31 x 10(5)/kg, and that of CFU-GM, 31.2 +/- 17.8 x 10(5)/kg. Comparison of the hematological recovery in these three cases with that in patients receiving an identical high-dose chemotherapy regimen revealed recovery rates significantly faster than in patients having bone marrow transplants, and approximately identical with that in peripheral blood stem cell transplantation cases.

Adult↗
PubMed1998

HLA-DRB1 and tumor necrosis factor gene polymorphisms in Japanese patients with multiple sclerosis.

We studied genetic polymorphisms in the tumor necrosis factor (TNF) region as well as HLA-DRB1 of 42 patients with Western-type multiple sclerosis (MS) and 38 with Asian-type MS in Japan. The sex ratio (Female:Male) was significantly higher in Asian than in Western type MS (3.8 vs. 1.3, P = 0.038). The frequency of HLA-DRB1 * 1501 allele in the Western-type MS group increased significantly compared with the control group, while Asian-type MS and control groups showed similar distribution in the frequencies of HLA-DRB1 alleles. No significant differences existed in the TNF region, however, including TNF-a microsatellite alleles. The results suggest that MS in Asians may present two different clinical and immunogenetic manifestations.

Adult↗
PubMed1998

Expression cloning and functional characterization of human cDNA for ganglioside GM3 synthase.

Ganglioside GM3 is a major glycosphingolipid in the plasma membrane and is widely distributed in vertebrates. We describe here the isolation of a human cDNA whose protein product is responsible for the synthesis of GM3. The cloned cDNA spanned 2,359 base pairs, with an open reading frame encoding a protein of 362 amino acids with a predicted molecular mass of 41.7 kDa. The deduced primary structure shows features characteristic of the sialyltransferase family, including a type II transmembrane topology and the sialylmotifs L at the center and S at the C-terminal region. An amino acid substitution from aspartic acid to histidine was demonstrated at a position invariant in sialylmotif L of all the other sialyltransferases so far cloned. The best acceptor substrate for the gene product was lactosylceramide, and cells transfected with the cloned cDNA clearly exhibited de novo synthesis of GM3, with a measurable decrease in the precursor lactosylceramide. Despite the ubiquitous distribution of ganglioside GM3 in human tissues, a major 2.4-kilobase transcript of the gene was found in a tissue-specific manner, with predominant expression in brain, skeletal muscle, and testis, and very low expression in liver.

Amino Acid Sequence↗
PubMed1998

Crystallization and preliminary X-ray diffraction study of lactonohydrolase from Fusarium oxysporum.

The lactonohydrolase from the fungus Fusarium oxysporum AKU 3702 was crystallized by the vapour-diffusion procedure in the presence of polyethylene glycol 4000 as a precipitant. The crystals belong to the monoclinic space group P21 with unit-cell parameters a = 156, b = 100, c = 94.1 A, beta = 91.7 degrees. Assuming that there are two lactonohydrolase-dimer molecules in the asymmetric unit, the crystal volume per unit molecular mass, Vm, is calculated to be 2.94 A3 Da-1.

Carboxylic Ester Hydrolases↗
PubMed1998

Variation in CD4+ T and CD8+ T lymphocyte subpopulations in bovine mammary gland secretions during lactating and non-lactating periods.

Mammary gland secretions (MGS) of dairy cows at different stages of lactation were studied by immunofluorescence cytometry for T lymphocyte subpopulations using monoclonal antibodies. During early and late lactation, the mean ratio of CD4+/CD8+ T lymphocytes in the MGS was 0.5 and 0.8, respectively. A large proportion of the CD8+ cells coexpressed the activation molecule, ACT2. These results indicate that CD8+ ACT2+ cells constituted the major phenotype in the T lymphocytes throughout lactation. In the mammary gland of cows in which drying off was induced, however, the proportion of CD8+ ACT2+ cells decreased, resulting in the increase of the CD4+/ CD8+ ratio in the MGS. At the late non-lactation stage, the ratio reached a maximal level of 2.5-4.0, which was similar to or higher than that found in the peripheral blood. This selective increase of CD4+/CD8+ cell ratio correlated with an increase in the concentrations of total cells in the MGS. This high CD4+/CD8+ cell ratio during the drying off stage rapidly decreased just before parturition, correlating with the decrease in concentrations of total cells in the MGS, reaching the lowest level at early lactation. The cells isolated at the non-lactation stage produced the cytokines IL-2 and IL-4 at a level much higher than those of cells isolated at lactation stages, and the increases were correlated with the CD4+ T lymphocyte proportions.

Animals↗
PubMed1998

Cloning and characterization of a new subtype of thyrotropin-releasing hormone receptors.

A new subfamily member of thyrotropin releasing hormone (TRH) receptor gene, TRHR2, was isolated from rat brain cDNAs. The deduced amino acid sequence of TRHR2 is 51 % identical to that of rat TRH receptor gene which was reported previously. Northern blot analysis with TRHR2 probe revealed brain-specific expression of a 9.5 kb mRNA. In a binding experiment using the TRHR2-expressing COS cells, specific binding of TRH to TRHR2 was observed with Kd value of 9 nM which was equivalent to the Kd value (= 13 nM) of TRH binding to the TRH receptor previously reported. The active metabolite of TRH, histidyl-proline diketopiperazine, or cyclo(His-Pro), showed no specific binding activity. These results suggest that TRHR2 is a novel subtype of TRH receptor.

Amino Acid Sequence↗