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Biomedical subjects

T Obata

Publications and source records attributed to T Obata.

At least 91 records · Page 5Linked to original sources
PubMed1998

GC/MS analysis of urinary excretion of 9alpha,11beta-PGF2 in acute and exercise-induced asthma in children.

BACKGROUND: 9Alpha,11beta-prostaglandin (PG) F2 is an initial metabolite of PGD2 which has a potent bronchoconstrictive activity. OBJECTIVES: We measured the urinary levels of 9alpha,11beta-PGF2 in asthmatic children to investigate its role in not only acute asthmatic attack in a time course study but also in exercise-induced asthma (EIA). METHODS: In the acute asthma study, 30 asthmatic children were examined. Urine samples were collected on the first, third, and sixth days. Urinary levels of 9alpha,11beta-PGF2 were measured with gas chromatography mass spectrometry using the electron impact method. In the exercise challenge study, 14 children with EIA and 14 children without EIA were studied. Urine samples were collected before exercise challenge, and at 1 h, and 5 h after exercise challenge. Urinary levels of 9alpha,11beta-PGF2 were measured. RESULTS: Elevated urinary levels of 9alpha,11beta-PGF2, which were observed on the first day when treatment was started in the hospital, were gradually decreased on the third day (P < 0.05), and on the sixth day (P < 0.01). A significant correlation between urinary levels of 9alpha,11beta-PGF2 and symptom scores (P < 0.005) was observed on the first day. In EIA, there was a significant increase in urinary levels of 9alpha,11beta-PGF2 at 1 h (P < 0.01) and at 5 h (P < 0.01) after exercise challenge, but not in the children without EIA. CONCLUSION: 9Alpha,11beta-PGF2 may be involved in the pathogenesis of acute and exercise-induced asthma in children.

Acute Disease↗
PubMed1998

Dialysate pressure isobars in a hollow-fiber dialyzer determined from magnetic resonance imaging and numerical simulation of dialysate flow.

A procedure to determine dialysate pressure isobars by comparing the results of magnetic resonance imaging (MRI) and numerical simulation of the dialysate flow was established. The assumption used in the filtration analyses, that the dialysate pressure varies only in the central-axial direction, is supported by the finding that the determined isobars have no steep radial gradient. MRI of the contrast solution permeating the hollow fibers verifies the uniformity of the hollow fiber density in the dialyzer.

Algorithms↗
PubMed1998

High glucose-induced abnormal epidermal growth factor signaling.

We have reported that high glucose conditions (27 mM for 4 days) induces activation of protein tyrosine phosphatases (PTPases) which are associated with impaired insulin signaling in Rat 1 fibroblasts expressing human insulin receptors [Maegawa, H. et al. (1995) J. Biol. Chem. 270, 7724-7730]. In this study, we found increased mRNA-levels of a non-receptor type PTPase, protein tyrosine phosphatase 1B (PTP1B), and receptor type PTPases, leukocyte common antigen-related phosphatase (LAR), and LAR-related phosphatase (LRP), under high glucose conditions. In accordance with these results, LAR content was significantly increased, whereas LRP content was not increased. Cytosolic PTP1B content was increased, but membrane-associated PTP1B content showed no detectable change. Pioglitazone, a thiazolidinedione, normalized increased cytosolic PTPase activity through reduction of cytosolic PTP1B content, but it had no effect on mRNA levels of these PTPases. Under the high glucose condition, we also found that epidermal growth factor (EGF)-stimulated signaling, including tyrosine-phosphorylation of EGF receptor and phosphatidylinositol 3'-kinase activities, was attenuated. Nevertheless, pioglitazone failed to restore the attenuated EGF-signaling. These results indicate that the high glucose conditions cause dysfunction of EGF receptor. However, the increased cytosolic PTP1B content is not involved in the abnormal regulation of EGF-signaling, in contrast to insulin-signaling.

Animals↗
PubMed1998

Cytotoxic principles of a Bangladeshi crude drug, akond mul (roots of Calotropis gigantea L.).

Three cardenolide glycosides, calotropin (1), frugoside (2), and 4'-O-beta-D-glucopyranosylfrugoside (3), were obtained as the cytotoxic principles of "akond mul" (roots of Calotropis gigantea L.). The cytotoxicity of these compounds against various cell lines of human and mouse origin was tested. They showed similar cell line selectivity to those of cardiac glycosides such as digoxin and ouabain: they are toxic to cell lines of human origin, but not to those from mouse at 2 micrograms/ml.

Animals↗
PubMed1998

[A case of systemic lupus erythematosus overlapping with progressive systemic sclerosis accompanied by deposition of AA amyloid in the stomach].

A 52-year-old woman was admitted to our department because of fever and dysphasia in November 1994. She had noticed Raynaud's phenomenon, arthralgia, and stiffness in the skin for the past 20 years without receiving specific treatment. A diagnosis of progressive systemic sclerosis (PSS) was made based on the presence of sclerosis of the skin, sclerodactyly, pulmonary fibrosis, and the dilatation of the lower esophagus. It was also confirmed that systemic lupus erythematosus (SLE) overlapped based on the presence of an oral ulcer, polyarthralgia, leukocytopenia, renal dysfunction, positive tests for antinuclear antibodies and anti-DNA antibodies. A gastric biopsy specimen revealed amyloid deposits which showed green birefrigence by Congo red staining under polarized light microscopy. The disappearance of the green birefrigence after potassium permanganate treatment indicated that the deposits consisted of AA amyloid. No amyloid deposits were detected in the rectum or the kidney. The average of the SAA level in active SLE patients is 174 micrograms/ml in our department and the SAA level in the present case was 280 micrograms/ml. Although AA amyloidosis is rarely associated with SLE and PSS, a long-term elevation of SAA level could cause the development of amyloidosis even in the cases of SLE and PSS.

Amyloidosis↗
PubMed1998

Simultaneous quantitative analysis of prostaglandins and thromboxane after low-dose X irradiation.

The appearance of prostaglandins and thromboxane in mouse serum after X irradiation was observed by simultaneous quantitative analysis using gas chromatography/mass spectrometry/selected ion monitoring with stable isotope dilution methods. Mice of two strains (C57BL/CN Jcl and BALB/c) showed similar responses to X irradiation. In C57BL/6N Jcl mice, 0.2 Gy irradiation elicited a significant increase in generation of prostanoids: Immediately after irradiation, the 6-keto PGF1 alpha:TXB2 ratio and the level of PGE2 increased, after 20 min 6-keto PGF1 alpha and PGE2 increased, and after 4 h PGE1 and PGE2 increased. In BALB/c mice, generation of prostanoids was increased significantly immediately after irradiation (6-keto PGF1 alpha, 6-keto PGF1 alpha:TXB2 ratio, PGE2), and the increase was maintained from 20 min to 4 h (PGE1, PGE2) after 0.2 Gy irradiation. In C57BL/6N Jcl mice, a significant increase in production of 9alpha,11beta-PGF2 was observed at 20 min after irradiation. In BALB/c mice, a significant increase in 9alpha,11beta-PGF2 was seen immediately after irradiation and was maintained for 20 min. In C57BL/6N Jcl mice, the level of 8-epi PGF2 alpha was clearly increased 4 h after 4 Gy irradiation. A slight and slow increase was also seen after 0.2 Gy irradiation. In BALB/c mice, 8-epi PGF2 alpha was increased significantly at 20 min and 4 h after 4 Gy irradiation. These results show that 0.2 Gy irradiation stimulates production of prostanoids related to the inflammatory response in mice.

Animals↗
PubMed1998

High density culture of immortalized liver endothelial cells in the radial-flow bioreactor in the development of an artificial liver.

Liver endothelial cells are important components of the tissue along the hepatic sinusoid. They are responsible for microcirculation in the liver and scavenger functions. It would therefore be important to include these cells in any hybrid type of artificial liver in addition to hepatocytes. However, it is difficult to culture these cells in vitro. The development of a liver endothelial cell line, which maintains the characteristics of the primary culture, would thus be of great benefit in the development of an artificial liver. In the present study we established immortalized liver endothelial cells from the liver of an H-2Kb-tsA58 transgenic mouse, which harbors the SV40 TAg gene. Hepatic sinusoidal cells isolated from H-2Kb-tsA58 mouse proliferated in the presence of gamma-interferon at 33 degrees C. Four clones were established, out of which clone M1 had the highest amounts of PGI2 production, as well as plasminogen activator activity and internalized acetylated low density lipoprotein. On culture dishes the M1 cells grew individually and spread. Sieve plates on the cell surface were not readily visible, but small pores were detected under electron microscopic observation. These results suggest that M1 clone cells originated from liver endothelial cells. Moreover it was possible to culture the immortalized liver endothelial cells in a radial-flow bioreactor for 5 days, with a maximum 6-keto prostaglandin F1alpha production of 25 microg per day. This suggests that immortalized liver endothelial cells and a radial-flow bioreactor can prove useful tools in the development an artificial liver.

Animals↗
PubMed1997

Stimulation of alpha 1-adrenoceptors and protein kinase C-mediated activation of ecto-5'-nucleotidase in rat hearts in vivo.

1. To determine whether protein kinase C (PKC)-mediated activation of ecto-5'-nucleotidase would increase interstitial adenosine concentrations in the rat heart in vivo, we made use of the microdialysis technique and a flexibly mounted probe, which was implanted in the left ventricular myocardium and perfused with Tyrode solution. 2. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM (n = 16). Perfusion of adenosine 5'-monophosphate (AMP, 100 microM) through the probe increased the dialysate adenosine concentration markedly to 9.25 +/- 0.46 microM (n = 15). alpha, beta-Methyleneadenosine 5'-diphosphate (AOPCP, 100 microM), an inhibitor of ecto-5'-nucleotidase, abolished the AMP-induced increase in dialysate adenosine, but did not affect the baseline level of adenosine. These observations suggest that the dialysate adenosine obtained during the perfusion with AMP, but not the baseline levels of adenosine, originated from the dephosphorylation of AMP by ecto-5'-nucleotidase. Thus, the level of adenosine measured during AMP perfusion gives an index of the activity of ecto-5'-nucleotidase in the tissue. 3. Noradrenaline (10 microM) increased the adenosine concentration measured in the presence of 100 microM AMP (i.e. the activity of ecto-5'-nucleotidase) by 38.7 +/- 9.6% (n = 5, P < 0.05), an increase which was inhibited by an antagonist of the alpha 1-adrenoceptor (prazosin, 50 microM) or of PKC (chelerythrine, 10 microM). Further application of either the alpha 1-adrenoceptor agonist methoxamine (100 microM) or the diacylglycerol analogue 1,2-dioctanoyl-sn-glycerol (DOG, 100 microM) also increased the adenosine concentration by 35.1 +/- 10.0% (n = 6, P < 0.05) or 40.6 +/- 8.3% (n = 5, P < 0.05), respectively. 4. The presence of okadaic acid (50 microM), an inhibitor of protein phosphatase, enhanced the noradrenaline-induced increase in adenosine concentration by 112.4 +/- 35.9% (n = 4, P < 0.05), to a level significantly (P < 0.05) greater than the increase caused by noradrenaline alone (38.7 +/- 9.6%). 5. These data provide the first evidence that alpha 1-adrenoceptor stimulation and the subsequent activation of PKC can increase adenosine concentrations in interstitial spaces of ventricular muscle in vivo, through activation of endogenous ecto-5'-nucleotidase.

5'-Nucleotidase↗
PubMed1997

Anti-tumor mechanisms of 3'-ethynyluridine and 3'-ethynylcytidine as RNA synthesis inhibitors: development and characterization of 3'-ethynyluridine-resistant cells.

To discover the mechanisms of anti-tumor action of 3'-ethynyluridine (EUrd) and 3'-ethynylcytidine (ECyd), we established an EUrd-resistant variant from human fibrosarcoma HT-1080 cells. The cells were cross-resistant to ECyd. Uridine/cytidine kinase activity diminished in the resistant cells. The incorporation of EUrd and ECyd into the RNA fraction in the resistant cells was less than that of the parental cells. EUrd-triphosphate inhibited RNA synthesis by human RNA polymerase II. The results led us to conclude that EUrd and ECyd are phosphorylated by uridine/cytidine kinase to 5'-triphosphates, and that their triphosphates might inhibit RNA polymerase.

Antimetabolites, Antineoplastic↗
PubMed1997

Cardiac microdialysis of salicylic acid .OH generation on nonenzymatic oxidation by norepinephrine in rat heart.

The effect of pargyline, a monoamine oxidase inhibitor, on the generation of hydroxyl free radicals (.OH) was investigated using cardiac microdialysis. Salicylic acid in Ringer's solution (0.5 nmol x microL(-1) x min(-1)) was infused directly through a microdialysis probe to detect the generation of .OH as reflected by the formation of dihydroxybenzoic acid (DHBA) in the myocardium of anesthetized rats. When pargyline (100 nmol x microL(-1) x min(-1)) was infused in rat heart, the level of norepinephrine (NE) gradually increased in a time-dependent manner and an increase of DHBA was also observed. When NE was administered to the pargyline pretreated animals, a marked elevation in the levels of 2,3- and 2,5-DHBA formation was obtained, as compared to the group treated with NE only, showing a positive linear correlation between NE and .OH formation trapped as 2,3-DHBA (R2 = 0.981) or 2,5-DHBA (R2 = 0.984) in the dialysate. NE clearly produced an increase in .OH formation. These results indicate that accumulation of NE in the extracellular fluid elicited by pargyline can be auto-oxidized, which in turn, leads (possibly by an indirect mechanism) to the formation of cytotoxic .OH free radicals.

Animals↗
PubMed1997

The measurement of blood flow parameters with deuterium stable isotope MR imaging.

METHODS: Because there are no radioactive hydrogen isotopes which can be used for clinical examinations, deuterium as a non-radioactive, freely diffusible tracer has some advantages compared with the radioactive tracers in the measurement of blood flow parameters. A non-invasive technique to estimate the mean tissue blood flow parameter in vivo was developed by using deuterium nuclear magnetic resonance (NMR) imaging in rat. We obtained the NMR signal changes from deuterium NMR images in nine male Wister rats after intravenous injection of D2O and applied exponential curve fitting analyses to calculate blood flow parameters of the brain, heart and skeletal muscle. RESULTS: While fitting the reducing of the monoexponential function yielded a blood flow parameter of 27.9 +/- 1.6 ml/min/100 g tissue weight for the brain and 46.7 +/- 3.7 ml/min/100 g tissue weight for the heart, fitting the early reducing of the signal intensity of the biexponential function yielded a blood flow parameter of 95.6 +/- 10.9 ml/min/100 g tissue weight for the brain and 108.0 +/- 13.1 ml/min/100 g tissue weight for the heart. The mean muscle blood flow parameter determined by the monoexponential uptake function was 43.8 +/- 7.3 ml/min/100 g tissue weight. CONCLUSIONS: The blood flow parameter measurement by means of an imaging coil for deuterium is less invasive and reflects the mean tissue blood flow parameter for the entire tissue sample more homogeneously than spectroscopic monitoring.

Animals↗
PubMed1997

Protective effect of diltiazem on myocardial ischemic injury associated with .OH generation.

We examined the protective effect of diltiazem, a calcium antagonist, on myocardial ischemic injury associated with generation of hydroxyl free radicals (.OH). Salicylic acid in Ringer's solution (0.5 nmol.microliter-1.min-1) was infused directly through a microdialysis probe to detect the generation of .OH as reflected by the formation of 2,3-dihydroxybenzoic acid (DHBA) in the myocardium. Cardiac dialysate was assayed for 2,3-DHBA by a high-performance liquid chromatographic-electrochemical (HPLC-EC) procedure. The heart was subjected to myocardial ischemia for 15 min by occlusion of left anterior descending artery (LAD). The presence of .OH was indicated in the ischemic reperfused rat heart. However, when heart was reperfused, the elevation of 2,3-DHBA by 15-min ischemia was not observed in the ischemic zone following systemic administration of diltiazem (100 micrograms.min-1.kg-1), a calcium antagonist. When corresponding experiments were performed with allopurinol (10 mg.kg-1) administration of i.v. injection, the elevation of 2,3-DHBA was not observed. These results suggest that diltiazem may suppress the .OH generation from xanthine-xanthine oxidase system by ischemia-reperfusion.

Allopurinol↗
PubMed1997

The effect of glibenclamide on the production of interstitial adenosine by inhibiting ecto-5'-nucleotidase in rat hearts.

1. Adenosine exerts cardioprotective effects on the ischaemic myocardium. The production of adenosine in the ischaemic myocardium is attributed primarily to the enzymatic dephosphorylation of adenosine 5'-monophosphate (AMP) by 5'-nucleotidase. We determined the activity of 5'-nucleotidase in rat hearts. The objective of the study was to determine the effects of ATP-sensitive K+ (K[ATP]) channel antagonists (glibenclamide and 5-hydroxydecanoate) on the production of adenosine, by use of a flexibly mounted microdialysis technique. 2. Rats were anaesthetized and the microdialysis probe was implanted in the left ventricular myocardium, followed by perfusion with Tyrode solution. The baseline level of dialysate adenosine was 0.51 +/- 0.09 microM (n = 16). Introduction of AMP (100 microM) through the probe increased the dialysate adenosine markedly to 9.79 +/- 0.43 microM (n = 12, P < 0.001 vs baseline), and this increase was inhibited by the ecto-5'-nucleotidase inhibitor, alpha,beta-methyleneadenosine 5'-diphosphate (100 microM), to 0.76 +/- 0.12 microM (n = 8). Thus, the dialysate adenosine noted during the perfusion of AMP originated from dephosphorylation of AMP by ecto-5'-nucleotidase, and the dialysate level of adenosine attained reflects the ecto-5'-nucleotidase activity in the tissue in situ. 3. Glibenclamide (0.1-100 microM) decreased the adenosine concentration measured during the perfusion of AMP (100 microM) in a concentration-dependent manner (IC50 = 10.5 microM). In contrast, 5-hydroxydecanoate (10-100 microM) did not affect the concentrations of dialysate adenosine, measured in the presence of AMP (100 microM). These results suggest that glibenclamide inhibits the activity of endogenous ecto-5'-nucleotidase and decreases the concentration of adenosine in the interstitial space of rat ventricular muscles in situ.

5'-Nucleotidase↗
PubMed1997

Human hepatic carbohydrate metabolism. Dynamic observation using 13C MRS without proton decoupling.

PURPOSE: Dynamic natural-abundance 13C MR spectroscopy (MRS) studies without proton decoupling were performed in the human liver using commercial 1.5 T MR equipment. MATERIAL AND METHODS: A single tuned custom-made circular surface coil with an OD of 20 cm operating at 16.04 MHz was used for the 13C study. Seventy-five grams of glucose dissolved in water was administered for the natural-abundance 13C-MRS dynamic study which lasted for approximately 40 to 60 min. Data acquisition was broken into 20-min and 1.7-min blocks. Localized proton shimming with a whole-body coil was performed with sufficient volume to include the observing area of the surface coil; the line width of the water signal was less than 20 Hz. RESULTS AND CONCLUSION: The glucose and glycogen spectra were clearly visible at 80 to 120 ppm after oral administration of the glucose solution. These data demonstrate that dynamic hepatic carbohydrate metabolism can be observed with commercially available MR equipment. Given that the human hepatic glycogen pool reaches maximum level within less than 10 min, this technique should provide a direct diagnosis of hepatic carbohydrate metabolic disorders.

Administration, Oral↗
PubMed1997

Use of microdialysis for in-vivo monitoring of hydroxyl free-radical generation in the rat.

Free-radicals are reported to cause the tissue-damage associated with some toxins and diseases, yet there is no suitable method for routine in-vivo monitoring of these species. This paper introduces an in-vivo microdialysis technique in which the hydroxyl radical reacts with salicylate to generate dihydroxybenzoic acids (DHBA) which are measured by HPLC with electrochemical detection. When pargyline, a monoamine oxidase inhibitor, was infused into rat brain, the levels of DHBA increased markedly. When noradrenaline was administered to animals pre-treated with pargyline, DHBA levels increased markedly compared with the group treated with noradrenaline only. When the heart was subjected to 15-min regional ischaemia by occlusion of the left anterior descending coronary artery, levels of DHBA in heart dialysate were unchanged. Electrical stimulation of the stellate ganglion resulted in marked elevation of levels of DHBA the myocardial dialysate. Infusion of Fe2+ into rat liver resulted in increased formation of DHBA. When the intestine was rendered ischaemic for 10, 20 and 30 min, the highest DHBA level was obtained after 10-min ischaemia and the lowest after 30 min. These results confirm that free-radical production might make a major contribution at certain stages in the progression of the injury.

Animals↗
PubMed1997

Evidence of hydroxyl free radical generation by calcium overload in rat myocardium.

Although calcium (Ca2+) is important in cardiac dysfunction and has also been reported as a source of oxidative toxicity, the connection between Ca2+ overload and oxygen free radicals in the myocardium is not clear. We have investigated whether Ca2+ overload generates hydroxyl free radicals in rat ventricle. HPLC with electrochemical detection was used to measure the levels of 2,3- and 2,5-dihydroxybenzoic acid (DHBA) formed when the hydroxyl free radical reacts with salicylate. Ringer's solution containing salicylic acid (0.5 nmol microL-1 min-1) was infused through a microdialysis probe in the region of the left anterior descending coronary artery of the rat ventricle. A positive linear correlation was obtained between Ca2+ and hydroxyl free radical formation trapped as 2,3-DHBA (r2 = 0.976) and 2,5-DHBA (r2 = 0.982) in the myocardial dialysate. The administration of ouabain (1 mg kg-1, i.v.), a Ca2+ elevator, into the femoral vein significantly increased the level of 2,3- and 2,5-DHBA. These results indicate that Ca2+ overload generates hydroxyl free radicals in rat heart.

Animals↗
PubMed1997

Acacia concinna saponins. I. Structures of prosapogenols, concinnosides A-F, isolated from the alkaline hydrolysate of the highly polar saponin fraction.

A highly polar saponin mixture from pods of Acacia concinna (Leguminosae) was hydrolyzed with alkali to yield five new triterpenoidal prosapogenols named concinnosides A (6), B (3), C (7), D (4), and E (8), together with four known glycosides, acaciaside, (2), julibroside A1 (10) julibroside A3 (9), albiziasaponin C (5), and their aglycone, acacic acid lactone (1). The structures of these new prosapogenols were elucidated based on spectroscopic means. A less polar saponin fraction from the pods gave spinasteryl glucoside and its dihydro derivative.

Acacia↗