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Biomedical subjects

M Oshima

Publications and source records attributed to M Oshima.

At least 19 recordsLinked to original sources
PubMed1992

Substrate specificity and distribution of UDP-GalNAc:sialylparagloboside N-acetylgalactosaminyltransferase in the human stomach.

The detailed substrate specificity of the UDP-GalNAc:sialylparagloboside N-acetylgalactosaminyltransferase to form the Sd(a+) blood group active carbohydrate determinant GalNAc beta 1-4(NeuAc alpha 2-3)Gal was studied using a membrane fraction prepared from human gastric fundic mucosa. Various sialosylated oligosaccharides and gangliosides were examined as acceptor substrates. Oligosaccharide substrates were fluorescence-labelled with 2-aminopyridine, and the transferase activity was quantified by h.p.l.c. using a reversed-phase column. The structures of the products were determined by glycosidase degradation and proton n.m.r. 3'-Sialyl-lactose (II3NeuAcLac), 3'-sialyl-lactotetraose (IV3NeuAcLc4), and 3'-sialyl-lactoneotetraose (IV3NeuAcnLc4) were good substrates for the beta 1-4GalNAc transferase in gastric fundic mucosa, but 6'-sialyl-lactoneotetraose (IV6NeuAcnLc4) or 6'-sialyl-lactose (II6NeuAcLac) were not. Gangliosides with a terminal NeuAc alpha 2-3Gal residue such as GM3, sialylparagloboside, GM1b and GD1a were also studied. The activity of beta 1-4GalNAc transfer to sialylparagloboside was much higher than that to GM2, GM1b or GD1a in spite of them having the same terminal residue. Measurement of the activity of the beta 1-4GalNAc transferase in biopsy specimens demonstrated that the activity was localized in gastric fundic mucosa and was absent in pyloric mucosa, intestinal metaplasia and gastric cancer tissue. Thus the beta 1-4GalNAc transferase present specifically in fundic mucosa required a NeuAc alpha 2-3Gal residue connected to either type-1-chain or type-2-chain oligosaccharides. In glycolipids, the acceptor specificity was restricted to NeuAc alpha 2-3Gal beta 1-4GlcNAc because the NeuAc alpha 2-3Gal beta 1-3GalNAc structure in ganglio-series glycolipids was not a good acceptor substrate.

Aminopyridines↗
PubMed1992

Epitope-specific suppression of antibody response in experimental autoimmune myasthenia gravis by a monomethoxypolyethylene glycol conjugate of a myasthenogenic synthetic peptide.

A synthetic peptide corresponding to a myasthenogenic region of Torpedo californica acetylcholine (AcCho) receptor (AcChoR) alpha subunit, AcChoR alpha-(125-148), was conjugated to monomethoxypolyethylene glycol (mPEG). Injection of mice with the mPEG-AcChoR alpha-(125-148) conjugate and subsequent immunization with whole Torpedo AcChoR suppressed the development of experimental autoimmune myasthenia gravis (EAMG) by electrophysiological criteria. In anti-AcChoR sera from these animals, the antibody response against unconjugated AcChoR alpha-(125-148) was decreased, while the antibody responses against whole AcChoR and other epitopes were not altered. There were no detectable changes in T-cell proliferation responses to AcChoR alpha-(125-148) or to whole AcChoR in these animals. Prior injections with a "nonsense" peptide-mPEG conjugate had no effect on responses to the subsequent immunization with whole Torpedo AcChoR. The results indicate that the mPEG-AcChoR alpha-(125-148) conjugate has epitope-specific tolerogenicity for antibody responses in EAMG and that the AcChoR alpha-subunit region comprising residues 125-148 plays an important pathophysiological role in EAMG. The epitope-directed tolerogenic conjugates may be useful for future immunotherapies of human myasthenia gravis. The strategy of specific suppression of the antibody response to a predetermined epitope by using a synthetic mPEG-peptide conjugate may prove useful in manipulation and suppression of unwanted immune responses such as autoimmunity and allergy.

Amino Acid Sequence↗
PubMed1992

Comparison of thallium-201 and technetium-99m teboroxime myocardial single photon emission tomography with coronary arteriography.

Myocardial single photon emission tomography (SPET) using technetium-99m teboroxime (teboroxime) was studied and the results compared with those of thallium-201(thallium) SPET and coronary arteriography in 19 patients. Resting teboroxime SPET was performed initially. Two hours later, exercise teboroxime SPET was performed. Exercise ergometer tests for both teboroxime and thallium were carried out in a supine position. The levels of exercise achieved for both tests were similar. Agreement for the identification of myocardial segments between thallium SPET and teboroxime SPET was 147/171(86%) (NS). When a significant stenosis was defined as greater than or equal to 75% or greater than or equal to 50%, agreement between two radiopharmaceuticals for the detection of diseased vessels was 89% (NS, k = 0.601) or 88% (NS, k = 0.713), respectively. In only 2/19 cases were inferior and posterior segments (3/171) difficult to interpret in teboroxime SPET due to hepatic activity. Thus, teboroxime SPET with a short data acquisition time resulted in a rapid completion for each study and had a good correlation with thallium SPET.

Adult↗
PubMed1992

Initial stage of Legg-Calve-Perthes disease: comparison of three-phase bone scintigraphy and SPECT with MR imaging.

Twenty-one patients with initial stage Legg-Calve-Perthes (LCP) disease were examined by three-phase bone scintigraphy, single photon emission scintigraphy (SPECT), and magnetic resonance (MR) imaging. On dynamic study, increased activity was present in the epiphysis or the growth plate in 39%; the corresponding figure for blood-pool images was 94%. Pinhole images demonstrated the lateral stripe of revascularization in 57% of patients. Decreased signal intensity in the epiphysis on T1-weighted images proved to be the most sensitive indicator of epiphyseal necrosis on MR imaging and was absent in only 10% of the cases. The subchondral fracture occurred in 62% (including the above 10% of cases), identified by T1-weighted image. Cartilaginous hypertrophy, detected by T1-weighted image, had a high incidence (81%). Joint effusion was identified on T2-weighted images in 90% of patients. The cross-sectional views provided by SPECT and MR imaging permits a better appreciation of the extent of epiphyseal necrosis in LCP disease.

Bone and Bones↗
PubMed1992

Comparison of Tc-99m HMPAO fast SPECT with Tc-99m HMPAO conventional SPECT in patients with acute stroke.

Tc-99m HMPAO SPECT is more likely to detect a stroke in early stages than CT. However, a conventional HMPAO SPECT study takes at least 30 minutes to complete. This paper compares fast Tc-99m HMPAO SPECT scans and conventional Tc-99m HMPAO SPECT scans with respect to spatial resolution and diagnostic efficacy in vitro and in a small series of patients, respectively. The spatial resolution of fast Tc-99m HMPAO SPECT did not match that of images obtained from conventional SPECT, though the difference proved to be of no clinical significance. Since fast SPECT requires only one-fourth to one-fifth the time necessary for conventional SPECT, it may be more suitable for investigating cases of acute stroke in critical clinical situations.

Acute Disease↗
PubMed1992

Recurrent rectal cancer and scar: differentiation with PET and MR imaging.

The value of positron emission tomography (PET) and magnetic resonance (MR) imaging in differentiating recurrent rectal cancer and scar was investigated. PET with fluorine-18 2-fluoro-2-deoxy-D-glucose (FDG) and MR imaging were performed in 15 patients with suspected recurrence. FDG accumulation in the mass was measured by means of the differential absorption ratio (DAR). All 11 patients with confirmed recurrent rectal cancer had increased accumulation of FDG in the mass (DAR = 4.73 +/- 2.28). Low FDG accumulation in the mass (DAR = 0.97 +/- 0.15) was noted in the remaining four patients, in whom the presence of a scar was proved by means of follow-up observation with or without biopsy. On the MR images, the recurrent tumor could be differentiated from scar in all but one case. The lesion-muscle signal intensity ratios on the T2-weighted images for the recurrent tumor and scar were 2.18 +/- 0.55 and 0.89 +/- 0.30, respectively. PET and MR imaging complement each other in the differential diagnosis between recurrent rectal cancer and scar. PET may also permit the evaluation of the effect of therapy.

Adult↗
PubMed1992

Microcirculatory characteristics in patients with Buerger's disease.

The most characteristic pathophysiologic change in Buerger's disease or thromboangiitis obliterans (TAO) is considered the breakdown of microcirculation in the extremity, but this has not yet been proven. The purpose of this study is to examine the damage of microcirculation in TAO objectively, by means of intra-arterial injection of two kinds of radioisotope. In 7 TAO and 4 infrainguinal arteriosclerosis obliterans (ASO) patients, thallium 201 chloride (201Tl) and 99mTc macroaggregated human serum albumin (99mTc-MAA) were administered through bilateral common femoral artery injections. In the planar image of the foot, rectangular regions of interest (ROIs) were placed on the foot muscles and toes. Normalized counts of 99mTc-MAA in each ROI were divided by that of 201Tl, and the result was defined as the microcirculation damage index, based on their different kinetics. The damage index of the foot muscle was not different between ASO and TAO, but that of the toe was lower in TAO than ASO patients. Lumbar sympathectomy was performed in 5 TAO patients, but it did not improve the damage index. It is concluded that there is breakdown of the microvascular defense system from the beginning of the disease, and critical ischemia make the regional cell function deteriorate as if a precursor to a trophic lesion. Lumbar sympathectomy did not immediately improve microcirculation.

Adult↗
PubMed1992

Ganglioside composition and its relation to clinical data in brain tumors.

The ganglioside composition of 15 cases of meningioma, 15 cases of astrocytoma, 5 cases of neurinoma, 4 cases of ependymoma, 3 cases of metastatic brain tumor and 1 case each of mixed glioma, oligodendroglioma, medulloblastoma, embryonal carcinoma, and cultured glioma cell line were analyzed by thin-layer chromatography. The GM2, GD3, and GD2 content of the tumors was determined using specific monoclonal antibodies (MAb). Cases were grouped according to the difference in ganglioside pattern and various clinical features. In meningiomas and astrocytomas, GM3 and GD3 were the major gangliosides. The tumor content of the rather simple gangliosides (GM3, GM2, GD3, GD2) increased or was almost equal to that of normal tissue (leptomeninges tissue in the case of meningiomas, and brain tissue in the case of astrocytomas), while the tumor content of complex gangliosides (GM1, GD1a, GT1a, GT1b) decreased as compared with normal tissue. The GM3 content of meningiomas increased in middle-aged patients, who comprised the majority of the patients with these tumors. The GD2 content decreased in middle-aged patients with initial symptoms of meningioma within a year. The GM3 content of astrocytomas decreased in patients who underwent radiotherapy. The amount of GM3 and GD3 increased in small tumors. GM3 may be related to the early proliferative stage. The ganglioside patterns of brain tumors are shown in this study to differ according to clinical features and also to be changeable in their clinical courses.

Aging↗
PubMed1992

High prevalence of coronary artery spasm in survivors of cardiac arrest with no apparent heart disease.

The pathogenesis of cardiac arrest in the absence of any apparent heart disease remains unclear. Based on the hypothesis that coronary spasm may be a cause of cardiac arrest in the absence of apparent heart disease, ergonovine testing and/or electrophysiologic studies (EPS) were performed to evaluate the cause of cardiac arrest. Fourteen patients resuscitated from cardiac arrest had no apparent heart disease. A spontaneous episode of angina with ST-segment elevation occurred in 4 patients while under observation. Ergonovine testing was performed in 9 patients, and coronary spasm was induced in 5. EPS were performed in 8 patients, including 3 patients with coronary spasm. No electrophysiologic abnormalities were found in the 3 patients with coronary spasm. Ventricular fibrillation was induced by programmed ventricular stimulation in 2 patients with documented ventricular fibrillation at the time of resuscitation. All but one of the patients with coronary spasm had chest pain preceding cardiac arrest or at least a history of chest pain at rest, while 4 of 5 patients without coronary spasm had no prodromal symptoms. Patients with coronary spasm had a good prognosis when treated with a Ca-antagonist and/or long-acting nitrate. In conclusion, coronary spasm is the most frequent cause of cardiac arrest in cardiac arrest survivors with no apparent heart disease. Ergonovine testing should be performed to evaluate the cause of cardiac arrest when patients have no apparent heart disease.

Cardiac Pacing, Artificial↗
PubMed1992

Tumor-specific binding of radiolabeled G-22 monoclonal antibody in glioma patients.

Iodine-131-labeled G-22 monoclonal antibody F(ab')2 fragment reaching specifically with a glioma-associated surface glycoprotein was administered to 12 glioma patients to investigate its use in radioimaging of intracranial gliomas. No immediate or delayed side effects were attributable to antibody injection. Nine patients received the radiolabeled complex intravenously. The images of low-grade gliomas were generally poor and disappeared within 4 days. High-contrast images were obtained beyond the 7th day in high-grade gliomas except one case in the pineal region. Three patients received intraventricular or intratumoral administration. Clear images of all tumors were demonstrated from the 2nd until later than the 7th day. One patient with cerebrospinal fluid (CSF) dissemination of brainstem glioma demonstrated negative CSF cytology after intraventricular administration.

Antibodies, Monoclonal↗
PubMed1991

The phosphorylation and activation of B-raf in PC12 cells stimulated by nerve growth factor.

Treatment of PC12 cells with nerve growth factor does not alter the levels of B-raf mRNA, but does induce rapid phosphorylation of B-raf proteins. Phosphorylation was observed after 1.5 min and reached a maximum by 10-15 min. B-raf protein was phosphorylated almost exclusively on serine residues; no tyrosine phosphorylation was detected. Nerve growth factor-induced phosphorylation was not affected by depletion of protein kinase C or by removal of extracellular calcium but was inhibited by K-252a. Concomitant with the increase in serine phosphorylation, nerve growth factor treatment also increased the serine/threonine kinase activity of B-raf protein within 1-2 min.

Amino Acid Sequence↗
PubMed1991

Localization of UDP-GalNAc:NeuAc alpha 2,3Gal-R beta 1,4(GalNAc to Gal)N-acetylgalactosaminyltransferase in human stomach. Enzymatic synthesis of a fundic gland-specific ganglioside and GM2.

A glycolipid detected in human gastric mucosa with anti-GM2 monoclonal antibody was characterized to be GalNAc beta 1-4[NeuAc alpha 2-3]Gal beta 1-4GlcNAc beta 1-3Gal 1-4Glc-Cer (NGM-1), which was lost in gastric cancer tissue with complementary increase of GM2 sharing the same terminal carbohydrate structure as NGM-1 (Dohi, T., Ohta, S., Hanai, N., Yamaguchi, K., and Oshima, M. (1990) J. Biol. Chem. 265, 7880-7885). The study on differential expression of NGM-1 in gastric fundic mucosa, pyloric mucosa, gastric cancer, and various other tissues indicated that NGM-1 existed specifically in fundic mucosa. The content of GM3 and sialylparagloboside (SPG), which are the substrates for the synthesis of GM2 and NGM-1, respectively, were not significantly different in these tissues. Therefore, the presence of two kinds of beta 1,4GalNAc transferases having different substrate specificity was considered to be critical for the expression of NGM-1 and GM2. The activity of beta 1,4GalNAc transferase which synthesizes GM2 or NGM-1 was determined by detecting the products with specific monoclonal antibodies. The activity of beta 1,4GalNAc transfer to SPG was high in fundic mucosa, while it was absent in pyloric mucosa or cancer. On the other hand, the increased activity of beta 1,4GalNAc transfer to GM3 was observed in cancer tissues and cancer cell lines which were rich in GM2. Our conclusion is that the limited expression of NGM-1 in fundic mucosa and the increase of GM2 in cancer are attributed to two types of beta 1,4GalNAc transferases localized in each region with different substrate specificity; the one in fundic mucosa transfers GalNAc to SPG but not to GM3, and the other one enhanced in cancer transfers GalNAc to GM3 but not to SPG.

Antibodies, Monoclonal↗
PubMed1991

Differentiation of PC12 cells with K-ras: comparison with nerve growth factor.

The cell line PC12, derived from a rat pheochromocytoma, has served as a model for studies on the mechanism of action of nerve growth factor, as well as for the exploration of neuronal differentiation in general. When treated with nanomolar concentrations of nerve growth factor, these neoplastic chromaffin-like cells stop dividing and acquire, for all intents and purposes, the phenotype of mature sympathetic neurons. This phenotype is characterized by the extensive outgrowth of electrically excitable neurites, the ability to form functional synapses, and the acquisition of a number of biochemical markers. Treatment of PC12 cells with retroviral vectors encoding the K-ras, the N-ras, or the v-src oncogenes also produces a marked morphological differentiation very similar to that seen upon treatment with nerve growth factor. Treated cells stop dividing and develop an extensive network of neurites. It has recently been shown that PC12 cells differentiated with v-src, while resembling, morphologically, those treated with nerve growth factor, differ substantially in the biochemical characteristics normally associated with nerve growth factor-induced differentiation. Cells infected with K-ras also develop a neurite network similar to that seen after treatment with nerve growth factor. In addition, such cells develop tetanus toxin-binding sites and saxitoxin-binding sites, as do cells treated with nerve growth factor. Decreases in the binding of epidermal growth factor and in the activity of calpain also occur and these, as well, are characteristic of nerve growth factor-treated cells. But the adhesive properties of cells infected with K-ras are different than those of nerve growth factor-treated cells, and the former do not show an increase in the NILE glycoprotein. Finally, K-252a, an inhibitor of the actions of nerve growth factor on PC12 cells, has no effect on the neurite outgrowth produced by infection with K-ras. Thus, many of the key markers of nerve growth factor-induced differentiation of PC12 cells also appear upon differentiation with K-ras, but there are, nevertheless, some crucial differences in the properties of these two sets of cells.

Amphibian Proteins↗
PubMed1991

Acidic glycosphingolipids of human amnion.

Six major acidic glycosphingolipids were isolated from human amnion using DEAE Sephadex A-25 and silica beads column chromatography. The structures of these glycosphingolipids were determined by methylation analysis, TLC immunostaining and/or negative ion FAB-MS, and were concluded to be II3 alpha NeuAcLacCer(GM3), IV3 alpha NeuAcnLc4-Cer (sialyl[alpha 2-3]paragloboside), IV6 alpha NeuAcnLc4Cer (sialyl[alpha 2-6]paragloboside), IV3 alpha NeuAcIII4 alpha FucLc4Cer (sialyl Lea), VI3 alpha NeuAcnLc6Cer (i-ganglioside) and II3 alpha (NeuAc alpha 2----8NeuAc)LacCer (GD3). In addition, several minor glycosphingolipids were detected with specific monoclonal antibodies, including glycolipids with NeuAc alpha 2-3Gal beta 1-4GlcNAc-beta 1- or NeuAc alpha 2-6Gal beta 1-4GlcNAc beta 1- determinant. Our results show that the glycosphingolipids of human amnion are characterized by having mainly type II chain analogues and onco-fetal antigens.

Amnion↗