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M Kawamura

Publications and source records attributed to M Kawamura.

At least 217 records · Page 12Linked to original sources
PubMed1997

Self-sustained pH oscillations in a compartmentalized enzyme reactor system.

This work represents our continued effort toward fulfilling the need to discover a model system for experimental investigations of temporal oscillations in an enzyme-membrane system. In this paper, the regions in the parameter space where self-sustained pH oscillations can be induced for a compartmentalized enzyme reactor system, which consists of a well-stirred reactor, a reservoir and a membrane containing no enzyme, were determined via numerical simulation with two proteolytic enzymes: papain (EC 3.4.22.2) and alpha-chymotrypsin (EC 3.4.21.1). The sizes of the regions were qualitatively compared with those associated with enzymic membrane system. As a result, we found that the possibility of experimentally observing self-sustained oscillations in the compartmentalized papain reactor system, as well as in the papain-membrane system, is high. However, self-sustained pH oscillations are less likely in the compartmentalized alpha-chymotrypsin reactor system than in the alpha-chymotrypsin-membrane system.

Journal Article↗
PubMed1997

Tyrosine hydroxylase assay for detection of low levels of enzyme activity in peripheral tissues.

A nonisotopic assay for tyrosine hydroxylase, with optimized signal-to-noise ratios, enables determination of low levels of enzyme activity in peripheral tissues. DOPA produced by the enzyme is measured using HPLC with electrochemical detection. Increased signal-to-noise ratios are obtained by including in the reaction mixture glycerol for reduction of blank values and dihydropteridine reductase and NADPH for regeneration of the tetrahydropteridine cofactor. With this method, tyrosine hydroxylase activity can be detected in as few as 200 PC12 cells and in peripheral tissues at levels as low as 4.5 fmol/min/mg wet weight. The assay permits activity to be assessed in a variety of peripheral tissues.

Animals↗
PubMed1997

An ATP-dependent inwardly rectifying potassium channel, KAB-2 (Kir4. 1), in cochlear stria vascularis of inner ear: its specific subcellular localization and correlation with the formation of endocochlear potential.

Cochlear endolymph has a highly positive potential of approximately +80 mV. This so-called endocochlear potential (EP) is essential for hearing. Although pivotal roles of K+ channels in the formation of EP have been suggested, the types and distribution of K+ channels in cochlea have not been characterized. Because EP was depressed by vascular perfusion of Ba2+, an inhibitor of inwardly rectifying K+ (Kir) channels, but not by either 4-aminopyridine or tetraethylammonium, we examined the expression of Kir channel subunits in cochlear stria vascularis, the tissue that is supposed to play the central role in the generation of positive EP. Of 11 members of the Kir channel family examined with reverse transcription-PCR, we could detect only expression of KAB-2 (Kir4.1) mRNA in stria vascularis. KAB-2 immunoreactivity was specifically localized at the basolateral membrane of marginal cells but not in either basal or intermediate cells. Developmental expression of KAB-2 in marginal cells paralleled formation of EP. Furthermore, deaf mutant mice (viable dominant spotting; WV/WV) expressed no KAB-2 in their marginal cells. These results suggest that KAB-2 in marginal cells may be critically involved in the generation of positive EP.

4-Aminopyridine↗
PubMed1997

Effects of TAK-029, a novel GPIIb/IIIa antagonist, on arterial thrombosis in guinea pigs, dogs and monkeys.

The antithrombotic and bleeding time (BT) prolonging effects of TAK-029, a novel GPIIb/IIIa antagonist, were examined in three arterial thrombosis models. In guinea pigs, TAK-029 at 30 micrograms/kg (i.v.) inhibited ADP-induced ex vivo platelet aggregation completely and prolonged BT to 4.5 times the control value 5 min after administration, and it prevented thrombotic occlusion in 2 out of 5 animals in a photochemically-induced basilar thrombosis model. TAK-029 at 100 micrograms/kg (i.v.) prolonged BT more than 9 times 5 min after administration, and it prevented thrombus formation for over 60 min. In dogs, TAK-029 at 30 micrograms/kg (i.v.) inhibited ADP-induced ex vivo platelet aggregation by 87% 5 min after administration, and it prevented thrombotic occlusion in injured and stenosed coronary arteries for 22 min without prolonging the BT. TAK-029 at 100 micrograms/ kg (i.v.) inhibited platelet aggregation completely and prolonged BT 3.6 times 5 min after administration, and it prevented thrombus formation for over 45 min. In monkeys, TAK-029 at 10 micrograms/kg (i.v.) inhibited ADP-induced ex vivo platelet aggregation by 84% and prolonged BT 4.6 times 5 min after the administration, and it prevented thrombotic occlusion in injured and stenosed carotid arteries for 24 min. TAK-029 at 30 micrograms/kg (i.v.) completely inhibited platelet aggregation and thrombus formation for over 60 min, and it prolonged BT more than 7.3 times 60 min after administration. In conclusion, TAK-029 exerted potent antithrombotic effects with BT prolongation in three different arterial thrombosis models. TAK-029 may be effective for the treatment of various arterial thrombotic diseases.

Animals↗
PubMed1997

Suppression of neutral cholesterol ester hydrolase activity by antisense DNA of hormone-sensitive lipase.

In order to investigate the role of the hormone-sensitive lipase (HSL) gene in the activity of neutral cholesterol ester hydrolase (NCEH) from a molecular perspective, Chinese hamster ovary (CHO) cells were transfected with rat antisense hormone-sensitive lipase cDNA, and three different cell lines, designated as anti-HSL, were established. NCEH activity in anti-HSL cells was reduced to approximately 50% of that in control CHO cells. The concentration of cellular esterified cholesterol increased and the concentration of free cholesterol decreased in the anti-HSL cell lines. These results suggest that the HSL gene has a function of NCEH as well.

Animals↗
PubMed1997

Synthesis of methyl 6-O-beta-inulotriosyl-alpha-D-glucopyranoside by intermolecular transglycosylation reaction of cycloinulo-oligosaccharide fructanotransferase.

Incubation of cycloinulohexaose and methyl alpha-D-glucopyranoside in the presence of cycloinulo-oligosaccharide fructanotransferase gave some hetero-oligosaccharides. The main product was a tetrasaccharide whose sugar composition was methyl alpha-D-glucopyranoside-D-fructose in a ratio 1:3. This oligosaccharide was isolated from the reaction mixture by charcoal-column chromatography and was identified as methyl O-beta-D-fructofuranosyl-(2--> 1)-O-beta-D-fructofuranosyl-(2-->1)-O-beta-D-fructofuranosyl-(2-->6)- alpha-D-glucopyranoside (methyl 6-O-beta-inulotriosyl-alpha-D-glucopyranoside), by two-dimensional NMR spectroscopy.

Carbohydrate Conformation↗
PubMed1997

Enzyme immunoassay to detect antituberculous glycolipid antigen (anti-TBGL antigen) antibodies in serum for diagnosis of tuberculosis.

We report the development of an EIA specific for antituberculosis antibody in human serum for the clinical evaluation of tuberculosis. We developed a TLC immunostaining method to detect specific antigens for antibodies in the serum of patients with tuberculosis. The detected specific antigens, TDM and specific gylcolipid fraction, were individually purified from M. tuberculosis H37Rv by column chromatography. The two purified fractions were mixed and the mixture, termed TBGL antigen, was applied to an enzyme immunoassay suitable for the measurement of antituberculosis antibodies in serum. This EIA meets all the requirements of routine clinical assay in terms of sensitivity (detection limit: 0.125 U/ml), reproducibility (total CV : 3.3-6.0%), accuracy (recovery: 96-105%), simplicity and rapidity (< 2.5 h). Clinical validation of the assay was confirmed by the measurement of the anti-tuberculosis antibody in the serum of normal subjects and patients with pulmonary tuberculosis. The EIA tested in this study showed a high serodiagnostic discriminating power (90% sensitivity and 98% specificity).

Adult↗
PubMed1997

Distinct qualitative differences between normal and abnormal hemopoietic stem cells in vivo and in vitro.

The transplantation of partially purified hemopoietic stem cells (HSCs) plus the engraftment of bone from autoimmune-prone mice ((NZW x BXSB)F1 (W/BF1) mice) induces autoimmune diseases in major histocompatibility complex (MHC)-incompatible normal C3H/HeN mice. In contrast, W/BF1 mice die of infection or anemia within three weeks due to a failure in hemopoietic reconstitution when the mice receive partially purified HSCs plus bones from normal C3H/HeN mice, although they survive more than a year without showing any symptoms of autoimmune diseases when they receive T cell-depleted bone marrow cells (without bone grafts) from normal mice. This finding suggests that abnormal HSCs can proliferate even in MHC-incompatible microenvironments, while normal HSCs cannot. This is confirmed by spleen colony-forming assays (CFU-S) on day 12, using pluripotent HSCs (P-HSCs). The P-HSCs of old (> 4 mo) W/BF1 mice (after the development of autoimmune diseases) form high CFU-S counts on day 12 even in the allogeneic C3H environment, although the P-HSCs of normal mice form high CFU-S counts only in the MHC-compatible environments. In addition, abnormal P-HSCs of autoimmune-prone mice can proliferate in vitro in collaboration with MHC-incompatible stromal cells, although normal HSCs do so in collaboration with MHC-compatible stromal cells, but not MHC-incompatible stromal cells. These findings indicate that abnormal P-HSCs are more "resilient" than normal P-HSCs.

Animals↗
PubMed1997

Recurrent colonic cancer developing at the site of a stapled stump: report of a case.

We report herein the case of a 54-year-old woman who developed a recurrence of carcinoma in a stapled colon stump 2 years after undergoing an anterior resection for carcinoma of the rectosigmoid colon. At this time an end to end anastomosis (EEA) stapler had been used to perform a side-to-end anastomosis. The implantation of cancer cells was thought to have caused the recurrence.

Anastomosis, Surgical↗
PubMed1997

Lateral origin of the right internal thoracic artery: report of a case.

We report herein the unusual case of a patient in whom postoperative angiography following coronary artery bypass grafting (CABG) revealed a lateral origin of the right internal thoracic artery (ITA) and a normal origin of the left ITA, both of which were demonstrated to be patent and did not follow a tortuous course. The CABG had involved revascularization of the left anterior descending artery (LAD) with the right ITA, and the obtuse marginal artery with the left ITA. The patient had an uneventful postoperative course and developed no respiratory symptoms.

Coronary Angiography↗
PubMed1997

Blood concentrations of G-CSF and myelopoiesis in patients undergoing aortocoronary bypass surgery.

The pattern of changes in leukocyte counts and the blood concentration of G-CSF were observed in 15 patients undergoing aortocoronary bypass surgery. Myelopoietic function was assessed by examining the myelogram and performing flow cytometry to identify human leukocyte differentiation antigens on bone marrow aspirates obtained from the sternum when opening and closing the sternotomy. The blood concentration of G-CSF increased gradually after removal of the aortic cross clamp and peaked on the first postoperative day (232 +/- 98 ngml). The white blood cell count also increased during the operation and peaked on the second postoperative day, demonstrating a threefold increase (15,800 +/- 2700). Granulocytes represented most of the increase, while lymphocytes and monocytes showed no significant changes. The myelogram showed that the percentages of myeloblasts, promyelocytes, and metamyelocytes did not change; however, the percentage of myelocytes increased significantly during surgery (14.0 +/- 2.5% vs. 17.3 +/- 3.5%, p < 0.05). The number of mature myelocytes (LFA-1 beta and Leu-15 positive) decreased significantly (p < 0.01 and p < 0.05) during surgery. With the two-color method, the ratio of immature myelocytes (MCS-2 negative and Leu-15 negative) increased significantly (p < 0.01). The ratio of myeloblasts (Leu-11 and HLA-DR positive) and the ratio of stem cells (CD 34 and MY-9 positive) did not increase significantly during the operation. G-CSF concentrations increase substantially during aortocoronary bypass surgery and may be responsible for the rise in granulocyte and total leukocyte counts, as well as for the increase in immature myelocytes seen on bone marrow examination.

Aged↗
PubMed1997

Differences in factors associated with silent and symptomatic MRI T2 hyperintensity lesions.

The factors and symptomatology associated with different types of hyperintensity lesions on MRI were investigated. The study population consisted of 139 subjects who were recruited from 450 outpatients who had a neurological diagnosis in 1994. The subjects underwent brain magnetic resonance imaging between 1994 and 1995 and were divided into three groups (control, asymptomatic, and symptomatic) on the basis of T2 hyperintensity lesions, as well as a history of or neurological signs of stroke, or both. The demographic characteristics and risk factors were studied, and the T2 hyperintensity lesions were analysed semi-quantitatively. Results showed that: (1) the control and asymptomatic groups did not differ in terms of risk factors and demographic characteristics with the exception of age; (2) the symptomatic group was characterized by a significantly higher incidence of hypertension and electrocardiographic abnormalities, as well as significantly more numerous risk factors when compared with the other two groups; (3) the symptomatic patients also had higher proportion of men and higher levels of systolic blood pressure and blood glucose than the control patients, and more frequent hypertriglyceridaemia and higher triglyceride level than the asymptomatic patients; (4) the symptomatic group had a greater lesion distribution in the posterior basal ganglia-internal capsule and the infratentorial regions than did the asymptomatic group. We concluded that the asymptomatic and symptomatic groups should not be considered identical entities.

Aged↗
PubMed1997

Body temperature influences regional tissue blood flow during retrograde cerebral perfusion.

OBJECTIVE: This study compared the cerebral microcirculation during retrograde cerebral perfusion with that during antegrade cardiopulmonary bypass under normothermic and hypothermic conditions. METHODS: Brain tissue blood flow was measured with the hydrogen-clearance and colored microsphere (15 and 50 microns) methods during antegrade cardiopulmonary bypass and retrograde cerebral perfusion. Measurements were performed during normothermia (37 degrees C), moderate hypothermia (28 degrees C) and deep hypothermia (20 degrees C) in groups of mongrel dogs (n = 8). RESULTS: During antegrade cardiopulmonary bypass, the microsphere method showed a significant decrease in cerebral blood flow as body temperature decreased (40.1 +/- 20.8 ml/min/100 gm at 37 degrees C, 16.2 +/- 18.0 ml/min/100 gm at 20 degrees C with 50 microns microspheres) At 20 degrees C, the cerebral blood flow measured with the 15 microns microspheres was significantly lower than that assessed with the hydrogen-clearance method (11.3 +/- 7.0 vs 24.8 +/- 7.0 ml/min/100 gm). During retrograde cerebral perfusion, the microsphere method also showed a significant decrease in cerebral blood flow with cooling. At 37 degrees C, the cerebral blood flow measured with the 15 microns microspheres (0.8 +/- 0.7 ml/min/100 gm) was significantly lower than that assessed with the hydrogen-clearance method (10.1 +/- 3.5 ml/min/100 gm). At both 28 degrees and 20 degrees C, the hydrogen-clearance method showed significantly higher cerebral blood flow (10.1 +/- 5.8 and 8.2 +/- 3.7 ml/min/100 gm) than did the 50 microns microspheres (1.8 +/- 0.6 and 1.0 +/- 0.8 ml/min/100 gm) and 15 microns microspheres (0.23 +/- 0.14 and 0.18 +/- 0.15 ml/min/100 gm). CONCLUSION: (1) Cerebral blood flow that shunts to capillaries is increased during antegrade cardiopulmonary bypass under deep hypothermia. (2) During retrograde perfusion, the majority of the blood flow shunts away from brain capillaries, even under normothermic conditions, and blood flow through large venoarterial shunts increases as body temperature decreases. Although the cerebral microcirculation during retrograde perfusion is decreased, retrograde perfusion provides some degree of oxygenation to the body.

Animals↗
PubMed1997

Mutations of the RAS genes in childhood acute myeloid leukemia, myelodysplastic syndrome and juvenile chronic myelocytic leukemia.

Using the polymerase chain reaction-single strand conformation polymorphism method and direct sequencing, 12 acute myeloid leukemia (AML) cell lines and 108 fresh childhood myeloid tumor specimens, including 67 AML, 29 myelodysplastic syndrome (MDS), and 12 juvenile chronic myelocytic leukemia (JCML) were examined for mutation in H-, K-, and N-RAS genes. The mutation was found in eight of the 120 samples (6.7%), which consisted of four cell lines (33.3%) and four fresh myeloid tumors (3.7%). The frequency of the mutation in the cell lines was apparently higher than that in fresh myeloid tumors. K-RAS gene mutations were found in two of the 67 fresh AML specimens (3%). Interestingly, these two patients had 11q23 translocations. The N-RAS gene mutation was found in one of the 29 specimens (3.4%) of MDS and in one of the 12 specimens (8.3%) of JCML. All mutations were found in codon 12, 13 or 61 of the N-RAS and K-RAS genes. Frequency of mutation of RAS genes in fresh myeloid malignancies was very low. These findings suggest that mutation of RAS genes does not play an important role in the development of childhood myeloid malignancies.

Acute Disease↗
PubMed1997

Characterization of alpha, beta-methylene ATP binding sites in mouse crude synaptic membranes.

Since ATP has been reported to be a potent excitatory transmitter in the mammalian central nervous system (CNS), we studied the neurochemical characters of the binding sites of alpha,beta-methylene ATP, an agonist of P2x receptors, in mouse crude synaptic membranes. ATP and its related compounds inhibited [3H] alpha,beta-methylene ATP binding in a concentration-dependent manner. The potency order in the inhibition of the binding was as follows; alpha,beta-methylene ATP = ADP beta S > ATP gamma S > ATP > or = ADP > beta,gamma-methylene ATP >> UTP > 2-methylthio ATP. And adenosine did not affect the binding. The order was different from those reported in peripheral tissues. And Sr2+, Ca2+, Mg2+, and Cd2+ enhanced the binding. These results suggest that alpha,beta-methylene ATP binding sites in CNS have different characters from those in peripheral tissues.

Adenosine Triphosphate↗
PubMed1997

New serine protease inhibitors with leukotriene B4 (LTB4) receptor binding affinity.

A series of new trypsin-like serine protease inhibitors, 1, 2 and 7-23, containing amidinobenzene moiety was found to show potent LTB4-receptor affinity. Among them, compounds 1 and 2 were found to be LTB4 receptor antagonists based on an inhibition assay of human polymorphonuclear neutrophil (PMN) intracellular calcium mobilization induced by LTB4. Compounds 1 and 2, which satisfy the reported structural requirements for good oral activity, are expected to show a balanced dual mode of action, i.e., protease inhibitory activity and LTB4 receptor antagonist activity, in vivo.

Amidines↗
PubMed1997

Significance of the beta-subunit in the biogenesis of Na+/K(+)-ATPase.

This review summarizes our experiments on the significance of the beta-subunit in the functional expression of Na+/K(+)-ATPase. The beta-subunit acts like a receptor for the alpha-subunit in the biogenesis of Na+/K(+)-ATPase and facilitates the correct folding of the alpha-subunit in the membrane. The alpha-subunit synthesized in the absence of the beta-subunit is subjected to rapid degradation in the endoplasmic reticulum. Several assembly sites are assigned in the sequence of the beta-subunit from the cytoplasmic NH2-terminal domain to the extracellular COOH-terminus: the NH2-terminal region of the extracellular domain, the conservative proline in the third disulfide loop, the hydrophobic amino acid residues near the COOH-terminus and the cysteine residues forming the second and the third disulfide bridges. Upon assembly, the beta-subunit confers a resistance to trypsin on the alpha-subunit. The conformations induced in the alpha-subunit of Na+/K(+)-ATPase by Na+/K(+)- and H+/K(+)-ATPase beta-subunits are somehow different from each other and are named the NK-type and KH-type, respectively. The extracellular domain of the beta-subunit is involved in the folding of the alpha-subunit leading to trypsin-resistant conformations. The sequences from Cys150 to the COOH-terminus of the Na+/K(+)-ATPase beta-subunit and from Ile89 to the COOH-terminus of the H+/K(+)-ATPase beta-subunit are necessary to form trypsin-resistant conformations of the NK- and HK-type, respectively. The first disulfide loop of the extracellular domain of the beta-subunits is critical in the expression of functional Na+/K(+)-ATPase.

Amino Acid Sequence↗