Biomedical subjects

Y Oyama

Publications and source records attributed to Y Oyama.

At least 19 recordsLinked to original sources

PubMed1997

5,6-Cis-penems: broad-spectrum anti-methicillin-resistant Staphylococcus aureus beta-lactam antibiotics.

5,6-cis-Penem derivatives have been synthesized and evaluated as anti-MRSA antibiotics. The cis-penems 5 and 6 showed potent activities against not only MRSA but also a wide variety of bacteria including beta-lactamase-producing microorganisms. These compounds were designed to have high affinity to the penicillin-binding protein 2a of MRSA and to form stable acyl intermediates with beta-lactamases by blocking the deacylating water molecule.

Anti-Bacterial Agents↗

PubMed1997

Conversion of inactive glycosylation inhibiting factor to bioactive derivatives by modification of a SH group.

Escherichia coli-derived recombinant human glycosylation inhibiting factor (rhGIF) contains three cysteine residues (Cys-57, -60, and -81). All SH groups in the cysteine residues are free, and the GIF molecule had no biologic activity. Carboxymethylation of the SH group of Cys-60 in the molecule resulted in the generation of bioactivity, although the activity of the carboxymethylated GIF was 10- to 20-fold less than that of suppressor T cell (Ts)-derived GIF. However, treatment of the inactive rhGIF with ethylmercurithiosalicylate or 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) resulted in the generation of derivatives whose bioactivity was comparable to that of the Ts-derived bioactive GIF. The activity of these derivatives was lost by treatment with DTT. Isolation and chemical analysis of the DTNB-treated GIF derivative revealed that binding the 5-thio-2-nitrobenzoic acid group with Cys-60 was responsible for the generation of the highly bioactive derivative. Inactive cytosolic GIF from mammalian cells could also be converted to bioactive derivative by treatment with the SH reagent, while Ts-derived bioactive GIF was inactivated by DTT. These results, together with an x-ray crystal structure of GIF molecules, strongly suggest that the generation of bioactivity of GIF in Ts cells is due to posttranslational modifications that result in conformational changes in the molecule.

Amino Acid Sequence↗

PubMed1997

[Energy spectral analysis in a photopeak region of 201Hg X-rays for 201Tl imaging].

For thallium-201 (201Tl) imaging, a photopeak of X-ray region of mercury-201 (201Hg) around 70 keV is usually employed. In such a low energy region, scatter and attenuation in the body become serious problems for quantitative scintigraphic imaging. We measured energy spectra around 201Hg X-ray region by a 201Tl line source with scattering materials and a gamma camera, and analyzed them to investigate the amount of scattered photons in 201Tl imaging window. Furthermore, Monte Carlo calculations were performed to distinguish primary photons from scattered photons. The results of analysis of energy spectra showed that the 201Hg X-ray photopeak consists of four different X-rays and do not have a perfect Gaussian shape. It was also found that not only forward scatter but also much backward scatter are included in this region. These scattered photons were reduced by using an off-peak window moved toward the higher energy region. We conclude that the data obtained from the analysis of scattered photons in 201Tl imaging window are very useful to develop a new scatter correction method and evaluate the scatter rejection methods proposed.

Gamma Cameras↗

PubMed1996

Presence of Ca(2+)-sensitive and -insensitive SM22 alpha isoproteins in bovine aorta.

Two proteins (25- and 22-kDa) that cross-react with anti-gizzard SM22 alpha antibody were isolated from bovine aorta. The former, identical to a SM22 alpha homolog reported previously (Kobayashi, R., Kubota, T., and Hidaka, H. (1994) Biochem. Biophys. Res. Commun. 198, 1275-1280), associates with the membrane fraction in the presence of Ca2+ and dissociates in the presence of EGTA, while the latter is insensitive to Ca2+. Peptide mapping and partial sequence analysis revealed that the 22-kDa protein is an isoform of the 25-kDa protein, without 22 amino acid residues from the C-terminus. Immunological analysis of the tissue distribution of these proteins showed that the 25-kDa protein exists in lung and spleen besides aorta, while the 22-kDa protein occurs specifically in the aorta and spleen.

Amino Acid Sequence↗

PubMed1996

Flow-cytometric estimation on glutamate- and kainate-induced increases in intracellular Ca2+ of brain neurons: a technical aspect.

Effects of glutamate and kainate on the intracellular Ca2+ concentration ([Ca2+]i) in a large population (several thousand) of dissociated cerebellar granule cell neurons were evaluated using a flow-cytometer and a combination of two fluorescent dyes, fluo-3-AM for estimating [Ca2+]i and ethidium bromide for removing neurons that had compromised membranes from the cell population examined. The number of neurons responding to glutamate or kainate in augmenting the fluo-3 fluorescence increased in a dose-dependent manner. The number of neurons responding to kainate was much greater than that to glutamate. CNQX, a blocker of non-NMDA receptors, completely blocked the response elicited by kainate while the complete blockade of this glutamate-induced response was made by a combination of MK-801, a NMDA receptor blocker, and CNQX. Nicardipine, a calcium antagonist, decreased the number of neurons responding to glutamate and kainate, suggesting involvement of voltage-dependent calcium channels. These results indicate that the flow-cytometric measurement of glutamate and kainate responses has the potential to provide answers to such questions as what percentage of the population of neurons respond to these amino acids and what is the resulting distribution of [Ca2+]i.

Aniline Compounds↗

PubMed1996

Ginkgo biloba extract protects brain neurons against oxidative stress induced by hydrogen peroxide.

Effect of Ginkgo biloba extract was examined on dissociated rat cerebellar neurons suffering from oxidative stress induced by hydrogen peroxide using a flow cytometer and ethidium bromide. Hydrogen peroxide at a concentration of 3 mM increased the number of neurons stained with ethidium (presumably dead neurons) in a time-dependent manner. Pretreatment of neurons with G. biloba extract (10 micrograms/ml) greatly delayed a time-dependent increase in number of dead neurons during exposure to hydrogen peroxide. It was true, but less effective, in the case of treatment with G. biloba extract immediately or 60 min after start of oxidative stress. Results implicate G. biloba extract as a potential agent in protecting the neurons suffering from oxidative stress induced by hydrogen peroxide.

Animals↗

PubMed1996

Postcolumn co-immobilized leucine dehydrogenase-NADH oxidase reactor for the determination of branched-chain amino acids by high-performance liquid chromatography with chemiluminescence detection.

A liquid chromatographic system with a co-immobilized leucine dehydrogenase-NADH oxidase reactor is described for the determination of branched-chain amino acids such as I-leucine, I-isoleucine and I-valine. The enzymes were simultaneously immobilized on tresylate-containing poly(vinyl alcohol) beads. The separation was achieved by means of an ODS column with elution with phosphate buffer (pH 7.5). The hydrogen peroxide produced was detected chemiluminometrically via a luminol-hexacyanoferrate(III) reaction. The system gave a linear response from 0.3 to 300 mu M for each amino acid and the detection limit was 0.1 mu M.

Amino Acid Oxidoreductases↗

PubMed1996

Cytotoxic action of tri-n-butyltin on dissociated rat cerebellar neurones: a flow-cytometric study.

The effects of tri-n-butyltin on cell viability and intracellular Ca2+ concentration ([CA2+]i) were examined by a flow cytometer in rat cerebellar neurones to reveal the contribution of tri-n-butyltin-induced increased in the [Ca2+]i to its cytotoxicity. Tri-n-Butyltin decreased the cell viability in association with increased [Ca2+]i at concentrations of 0.3 microM or more. Decrease or increase of the extracellular Ca2+ concentration ([Ca2+]o) respectively decreased or increased the cell viability. However, cell viability in the presence of ionomycin which increased [Ca2+]i more significantly than tri-n-butyltin was higher than that in the presence of tri-n-butyltin. Tri-n-butyltin also decreased cell viability under nominally [Ca2+]o-free conditions although the [Ca2+]i increase by tri-n-butyltin was still lower than the control [Ca2+]i under normal [Ca2+]o (2 mM). Therefore, it is unlikely that neuronal death induced by tri-n-butyltin is entirely dependent on the tri-n-butyltin-induced increase in [Ca2+]i.

Aniline Compounds↗

PubMed1996

Flow cytometric analysis of the H2O2-induced increase in intracellular Ca2+ concentration of rat thymocytes.

The effect of hydrogen peroxide (H2O2) on the intracellular Ca2+ concentration ([Ca2+]i) of rat thymocytes was examined by a flow cytometer and two fluorescent dyes, fluo-3-AM and ethidium bromide, a dye impermeant to intact membranes, to characterize the H2O2-induced increase in [Ca2+]i. H2O2 at concentrations greater than 30 microM dose-dependently increased the [Ca2+]i of thymocytes which were not stained with ethidium. Removal of external Ca2+ greatly reduced the degree of H2O2-induced increase in [Ca2+]i. However, H2O2 still increased the [Ca2+]i under the external Ca(2+)-free condition. Diethylmaleate, which is known to produce a chemical depletion of cellular nonprotein thiol, significantly increased the [Ca2+]i. Dithiothreitol, which is used to protect cellular nonprotein thiol, slightly decreased the [Ca2+]i, but greatly reduced the H2O2-induced increase in [Ca2+]i. Therefore, it is considered that H2O2 may increase the [Ca2+]i through a mechanism related to the effects of H2O2 on the cellular nonprotein thiol.

Aniline Compounds↗

PubMed1996

Fluorescent estimation of H2O2-induced changes in cell viability and cellular nonprotein thiol level of dissociated rat thymocytes.

We have developed a procedure to simultaneously estimate cell viability and the cellular level of nonprotein thiol (presumably glutathione) using two fluorescent dyes, 5-chloromethylfluorescein (5CMF) and ethidium, and rat thymocytes. Diethylmaleate and N-ethylmaleimide reduced, respectively, the intensity of 5CMF fluorescence to 0.23 and 0.1, relative to the control. Incubation with buthionine sulfoximine, an inhibitor of glutathione synthesis, decreased the intensity of 5CMF fluorescence to 0.61. Results indicate that 5CMF fluorescence can be attenuated by agents that decrease the level of cellular nonprotein thiols, suggesting that 5CMF fluorescence is utilized for estimating the level of cellular glutathione. Hydrogen peroxide (10 microM to 3 mM) reduced the intensity of 5CMF fluorescence in a dose-dependent manner and increased the number of thymocytes stained with ethidium (presumably dead cells or cells with compromised membranes) at concentrations of 300 microM or greater. Reduction of cellular glutathione level seems to precede cell death in which oxidative stress is involved.

Animals↗

PubMed1996

Oxidative stress-induced increase in intracellular Ca2+ and Ca(2+)-induced increase in oxidative stress: an experimental model using dissociated rat brain neurons.

In order to study the oxidative stress-induced change in intracellular concentration of Ca2+ ([Ca2+]i) and Ca(2+)-induced oxidative stress, effects of hydrogen peroxide and ionomycin, a calcium ionophore, on rat cerebellar neurons were examined using a flow cytometer and fluorescent dyes: fluo-3 for monitoring [Ca2+]i; 2',7'-dichlorofluorescin, for reactive oxygen species; and 5-chloromethylfluorescein, for cellular nonprotein thiols. Oxidative stress induced by hydrogen peroxide dose-dependently increased [Ca2+]i and decreased the content of nonprotein thiols. Ionomycin increased oxidative metabolism and decreased the content of nonprotein thiols. Results suggest that oxidative stress induces an increase in [Ca2+]i while an increase in [Ca2+]i increases oxidative stress in neurons.

Aniline Compounds↗

PubMed1996

Late onset bone marrow transplant nephropathy.

We report a patient who exhibited proteinuria and renal failure 93 months after receiving an allogeneic bone marrow transplantation (BMT) from his HLA-identical brother. A renal biopsy specimen revealed segmental sclerosis, mesangiolysis, subendothelial lucency in the glomeruli, fibrosis and small round cell infiltration in the interstitium, and hyaline droplets in the intimal spaces of arterioles and small arteries. These histological findings were consistent with late onset BMT nephropathy. This nephropathy may represent a more serious problem in the near future in Japan, since the number of BMT performed has been increasing with the establishment of a bone marrow bank.

Adult↗

PubMed1996

Clinicopathological analysis and therapy in hepatitis C virus-associated nephropathy.

We analyzed the clinicopathological features and therapy in 19 patients with kidney disease accompanied by hepatitis C viral infection, including 12 patients with mesangial proliferative glomerulonephritis (including eight with IgA nephropathy), six with membranoproliferative glomerulonephritis (MPGN), and one with membranous nephropathy. Persistent hematuria and/ or proteinuria (10 patients) was the most common finding, followed by nephrotic syndrome (8 patients). Cryoglobulinemia was detected in six of 19 patients examined (four of six patients with MPGN). Analysis of hepatitis C virus (HCV)-RNA genotype in 13 patients revealed that nine of them had type II genotype. All four patients with MPGN, who had serum positive for HCV-RNA, had type II genotype. Five patients were treated with interferon-alpha (IFN-alpha) without a demonstrable effect on renal impairment, whereas five of 11 patients treated with steroids showed improvement of the renal impairment. During the course of steroid therapy, the serum titer of HCV-RNA decreased in 5 of 7 patients. These observations suggest that HCV infection may be associated with several forms of glomerulonephritis. Type II HCV-RNA may have a strong association with MPGN in Japan. Steroid therapy is not contraindicated in patients with HCV-associated nephropathy if they are resistant to IFN-alpha treatment.

Adolescent↗

PubMed1996

[Isolated angiitis of the central nervous system presenting as subcortical hemorrhage--a case report of benign type].

A 47-year-old woman had an episode of severe headache for a few days. She suddenly experienced right leg weakness and sensory loss. A CT scan revealed subcortical hematoma at the left parietal lobe on admission. Cerebral angiography showed multiple vascular irregularities such as segmentally narrow or sausage-like dialatated areas. Her laboratory studies were entirely normal including antinuclear antibody and coagulation tests. The diagnosis of isolated angiitis of the CNS was made and she responded well to the low dose corticosteroid therapy. Repeated cerebral angiography two months after the onset demonstrated most of the areas of segmental irregularity had improved with a few unchanged areas. Some cerebral angiitis do exist that respond well to corticosteroid therapy, therefore, early diagnosis and treatment are suggested in cases of angiitis.

Cerebral Arterial Diseases↗

PubMed1996

[Evaluation of simultaneous acquisition of transmission and emission data on thallium-201 myocardial SPECT].

This study evaluates the usefulness of attenuation correction on regional myocardial tracer distributions defined by Thallium-201 myocardial SPECT images obtained from cardiac phantoms and patients with or without coronary heart disease. A three-detector SPECT system equipped with a Technetium-99m line source and a fan-beam collimator was used for simultaneous transmission and emission data acquisition. All three detectors were equipped with fan-beam collimators. Thallium-201 myocardial scintigraphy was performed on phantom study and 19 patients. Transmission images, uncorrected and corrected emission images were iteratively reconstructed with a EM-ML algorithm. Attenuation map computed from the transmission data was utilized for the attenuation correction. For the phantom study, circumferential profile analysis was applied to both datasets of horizontal long-axis slices through the center of the phantom. The maximum profile value in the circumferential profile set to 100% in the normalized uncorrected and corrected profiles. The uncorrected circumferential profiles from cardiac insert model 7070 and RH-2 cardiophantom showed decrease in activity in basal regions which appeared improvement in the attenuation corrected profiles. In clinical study, the inferior-to-anterior activity ratio, changed from 0.78 +/- 0.10 to 0.97 +/- 0.11 on stress images in patients with inferior ischemia and from 0.96 +/- 0.12 to 1.15 +/- 0.13 on 4 hour delayed or rest images in normal cases. The anteroapical wall of the attenuation corrected images, however, showed a decrease in activity relative to the inferior wall in normal cases. The increase in activity in inferior wall on attenuation corrected images was observed frequently in clinical study but not in phantom study. A presence of scatter from the liver or bowels may cause the increase in activity in the inferior wall in clinical study. In conclusion, transmission scan is one of the useful methods for the attenuation correction. Scatter correction, however, is also necessary to make an accurate attenuation corrected images.

Heart↗

PubMed1995

Methylmercury induces Ca(2+)-dependent hyperpolarization of mouse thymocytes: a flow cytometric study using fluorescent dyes.

The effect of methylmercury on mouse thymocytes was examined using fluorescent dyes for membrane potential and intracellular Ca2+. Methylmercury at concentrations of 1 microM or higher (up to 30 microM) produced hyperpolarization in a dose-dependent fashion. Charybdotoxin and quinine, but not 4-aminopyridine and tetraethylammonium, greatly suppressed methylmercury-induced hyperpolarization. Removal of external Ca2+ reduced the degree of hyperpolarization. Pretreatment of thymocytes with A23187 under Ca(2+)-free conditions abolished the hyperpolarization induced by methylmercury. Under both normal and Ca(2+)-free conditions methylmercury increased the intracellular concentration of Ca2+. The results suggest that the increase in intracellular Ca2+ is mediated through a Ca2+ release from intracellular stores as well as through influx of external Ca2+. Therefore, it is likely that methylmercury increases the intracellular concentration of Ca2+, resulting in activation of Ca(2+)-dependent K+ conductance of mouse thymocytes.

Animals↗

PubMed1995

Correlation of Tc-99m GSA hepatic studies with biopsies in patients with chronic active hepatitis.

To determine whether scintigraphic findings of Tc-99m DTPA-galactosyl-HSA (GSA) correspond to histopathologic findings, Tc-99m GSA hepatic scintigraphy and biopsy were compared in 65 patients with chronic active hepatitis. After injecting 185 MBq of Tc-99m GSA, anterior images were obtained at 5 minutes and 15 minutes. Scintigrams were classified into three grades according to the extent of visualization of the cardiac blood pool on 5 minute and 15 minute images. Biopsies were subjectively graded for findings of necrosis and fibrosis. Scintigraphic grades on 5 minute images were correlated with hepatic necrosis and fibrosis and those on 15-minute images with hepatic fibrosis. Scintigraphic abnormalities of Tc-99m GSA correlated well with histopathologic abnormalities, especially with hepatic fibrosis and necrosis in patients with chronic active hepatitis.

Adult↗

PubMed1995

Change in membrane permeability induced by amyloid beta-protein fragment 25-35 in brain neurons dissociated from rats.

Effects of amyloid beta-protein fragment 25-35, A beta P(25-35), on the membrane permeability of organic molecules were examined in the brain neurons dissociated from rats by using an argon laser (equipped in flow cytometer and laser microscope) and a combination of two fluorescent dyes, fluo-3-AM and ethidium bromide. A beta P(25-35) at concentrations of 1 microM or greater induced both leakage of fluo-3 from the neurons and permeation of ethidium across the membrane in a dose-dependent manner, although both dyes are highly impermeant to the intact plasma membrane. Thus, A beta P(25-35) seems to increase not only membrane permeability of inorganic ions such as Ca2+, Na+ and K+, as previously suggested, but also that of organic molecules. Therefore, the brain neuron membrane is suggested to lose its integrity in the presence of A beta P(25-35) that leads to neuronal death.

Amyloid beta-Peptides↗