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T Oshima

Publications and source records attributed to T Oshima.

At least 361 records · Page 20Linked to original sources
PubMed1992

An extremely stable inorganic pyrophosphatase purified from the cytosol of a thermoacidophilic archaebacterium, Sulfolobus acidocaldarius strain 7.

A highly active inorganic pyrophosphatase was purified to electrophoretical homogeneity from the cytosol of Sulfolobus acidocaldarius strain 7, an extremely thermoacidophilic archaebacterium. The enzyme has an apparent molecular mass of 80 kDa as estimated by gel permeation chromatography, and showed a 21-kDa polypeptide on SDS-PAGE, suggesting that the archaebacterial enzyme is similar to most of the eubacterial pyrophosphatases rather than eukaryotic ones. The pI = 5.1. The enzyme showed relatively high content of Pro and low content of Ser plus Thr. The optimal pH was 6.5 (at 56 degrees C). From the Arrhenius plot an activation energy of 11.2 kcal/mol was obtained between 37-95 degrees C. The specific activity was 617 mumol Pi release min-1 mg-1 at 56 degrees C. The S. acidocaldarius pyrophosphatase was extremely stable. Complete activity remained after incubation at 100 degrees C for 10 min. No dissociation into subunit or unfolding of polypeptide chain occurred in the presence of 8 M urea. Experiments using guanidine-HCl suggested that the transition between a native tetrameric state and an unfolded state is completely reversible, and essentially independent of any additional factors such as divalent metal cation or dithiothreitol.

Amino Acids↗
PubMed1992

Prospective study on maternal, intrauterine, and perinatal infections with cytomegalovirus in Japan during 1976-1990.

Since 1976, sera obtained serially from 10,218 pregnant women during the first, second, and third trimesters of gestation and cord sera were tested for CMV complement-fixing (CF) and immunofluorescent (IF) antibodies. CMV IgG-IF antibody was positive in 9,735/10,218 (95%) in the first trimester, and a significant rise of CF antibodies during pregnancy was found in 70/9,206 (0.76%) of the seropositive group and in 5/438 (1.14%) of the seronegative group. IgM antibody was found in 6/9,206 (0.06%) of seropositive women during the first trimester and in 7/70 (10.0%) of seropositive mothers with CF antibody rise and in 4/5 of seroconverted mothers of the seronegative group, suggesting that the incidence of primary infection with CMV during pregnancy was approximately 1% of susceptible women. All the mothers with immune response had infants with neither viruria nor IgM antibody in the cord blood, whereas seropositive mothers without an immune response had infants with viruria (7/1,826; 0.4%) or with IgM antibody in the cord blood (6/9,136; 0.06%). None of these 13 babies, shedding CMV or with IgM IF antibody, had physical or mental retardation. CMV IgG-IF antibody was present in almost 80% of infants between 7 and 12 months of age in 1988, suggesting that perinatal or postnatal CMV infection may occur in infants born to seropositive mothers in 70-80% of pregnancies.

Antibodies, Viral↗
PubMed1992

Survival rates of some terrestrial microorganisms under simulated space conditions.

In connection with planetary quarantine, we have been studying the survival rates of nine species of terrestrial microorganisms (viruses, bacteria, yeasts, fungi, etc.) under simulated interstellar conditions. If common terrestrial microorganisms cannot survive in space even for short periods, we can greatly reduce expenditure for sterilizing space probes. The interstellar environment in the solar system has been simulated by low temperature, high vacuum (77 k, 4 x 10(-6) torr), and protons irradiation from a Van de Graaff generator. After exposure to a barrage of protons corresponding to about 250 years of irradiation in solar space, Tobacco mosaic virus, Bacillus subtilis spores, Aspergillus niger spores and Clostridiun mangenoti spores showed survival rates of 82%, 45%, 28%, and 25%, respectively. Furthermore. pathogenic Candida albicans showed 7% survival after irradiation corresponding to about 60 years in space.

Bacteria↗
PubMed1992

Lack of effect of parathyroid hormone on calcium homeostasis in rat platelets.

The in vitro effects of parathyroid hormone on Ca2+ handling by fura-2 loaded rat platelets were studied. The incubation of these platelets with rat parathyroid hormone (1-34) for 10 min had no effect on intracellular fura-2 metabolism or [Ca2+]i in the resting state. The [Ca2+]i response to 0.1 U/mL thrombin was unaffected by preincubation with parathyroid hormone in the presence or absence of extracellular Ca2+. Furthermore, the recovery rate of [Ca2+]i after the thrombin-induced peak in Ca(2+)-depleted media was not altered with parathyroid hormone. These data indicate that parathyroid hormone may not have a significant effect on Ca2+ homeostasis in rat platelets in unstimulated and stimulated conditions.

Animals↗
PubMed1992

Sternocleidomastoid muscle contractility at different levels of isoflurane anaesthesia in humans.

We have measured force-frequency curves of the sternocleidomastoid muscle in six patients at three different levels of isoflurane anaesthesia (1.0, 1.4 and 1.8 MAC). Spontaneous ventilation was suppressed by mild hypocapnia induced by mechanical ventilation. An anterior force vector of the sternocleidomastoid muscle was measured during isometric contraction induced by supramaximal electrical stimulation at 20, 50 and 100 Hz to the i.m. accessory nerves of the muscle. The force response at 20 Hz and 50 Hz did not change with an increase in isoflurane concentration, but it decreased at 100 Hz as isoflurane concentration increased. The reduction in the force at 100 Hz may be caused mainly by impaired neuromuscular transmission.

Adolescent↗
PubMed1992

Crystallization and preliminary X-ray studies of a Bacillus subtilis and Thermus thermophilus HB8 chimeric 3-isopropylmalate dehydrogenase and thermostable mutants of it.

A new type of chimeric 3-isopropylmalate dehydrogenase (2T2M6T) was produced by expressing the fused gene of Bacillus subtilis and Thermus thermophilus. The enzyme shows heat stability intermediate between those of the parents. The crystal of the enzyme belongs to the space group of P3(2)21, with cell dimensions of a = b = 78.9 A and c = 158.9 A. Two thermostable mutants of the chimeric enzyme were prepared by site-directed mutagenesis and then crystallized.

3-Isopropylmalate Dehydrogenase↗
PubMed1992

Percutaneous angioplasty of chronic obstruction of peripheral arteries by a temperature-controlled Nd:YAG laser system.

The feasibility of an Nd:YAG laser system with automatic control of hot-tip probe temperature was examined in 15 segments (14.7 +/- 6 cm in length) of iliofemoral arteries from 13 patients. The hot-tip temperature to be attained and the upper limit temperature at which lasing was to be stopped were preset. A catheter with a 1.8-mm hot-tip probe was introduced into the obstructed segment and angioplasty (lasing time 5-10 sec) was performed under angioscopic guidance. Recanalization was observed in all segments without obvious complications. No thermal effects below 50 degrees C, coagulation at 100 degrees C, carbonization at 200 degrees C, or sticking of the hot-tip to the luminal surface at 300 degrees C or over, were observed by angioscopy. Rapid recanalization was obtained between 200 degrees C and 300 degrees C. The results indicate that this novel laser system is feasible and hot-tip temperature between 200 degrees C and 300 degrees C is ideal for treatment of chronic arterial obstruction in Japanese patients.

Aged↗
PubMed1992

Molecular cloning of the isocitrate dehydrogenase gene of an extreme thermophile, Thermus thermophilus HB8.

The gene coding for isocitrate dehydrogenase of an extreme thermophile, Thermus thermophilus HB8, was cloned and sequenced. This gene consists of a single open reading frame of 1,485 bp preceded by a Shine-Dalgarno ribosome binding site. Promoter- and terminatorlike sequences were detected upstream and downstream of the open reading frame, respectively. The G + C content of the coding region was 65.6%, and that of the third nucleotide of the codons was 90.3%. On the basis of the deduced amino acid sequence, the Mr of the monomeric enzyme was calculated as 54,189, an Mr which is similar to that of the purified protein determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A comparison of the amino acid sequence of the T. thermophilus enzyme with that of the Escherichia coli enzyme showed (i) a 37% overall similarity; (ii) the conservation of the Ser residue, which is known to be phosphorylated in the E. coli enzyme, and of the surrounding sequence; and (iii) the presence of 141 extra residues at the C terminus of the T. thermophilus enzyme. T. thermophilus isocitrate dehydrogenase showed a high sequence homology (33% of the amino acid sequence is identical) to isopropylmalate dehydrogenase from the same organism and was suggested to have evolved from a common ancestral enzyme.

3-Isopropylmalate Dehydrogenase↗
PubMed1992

Cloning and characterization of the CYS3 (CYI1) gene of Saccharomyces cerevisiae.

A DNA fragment containing the Saccharomyces cerevisiae CYS3 (CYI1) gene was cloned. The clone had a single open reading frame of 1,182 bp (394 amino acid residues). By comparison of the deduced amino acid sequence with the N-terminal amino acid sequence of cystathionine gamma-lyase, CYS3 (CYI1) was concluded to be the structural gene for this enzyme. In addition, the deduced sequence showed homology with the following enzymes: rat cystathionine gamma-lyase (41%), Escherichia coli cystathionine gamma-synthase (36%), and cystathionine beta-lyase (25%). The N-terminal half of it was homologous (39%) with the N-terminal half of S. cerevisiae O-acetylserine and O-acetylhomoserine sulfhydrylase. The cloned CYS3 (CYI1) gene marginally complemented the E. coli metB mutation (cystathionine gamma-synthase deficiency) and conferred cystathionine gamma-synthase activity as well as cystathionine gamma-lyase activity to E. coli; cystathionine gamma-synthase activity was detected when O-succinylhomoserine but not O-acetylhomoserine was used as substrate. We therefore conclude that S. cerevisiae cystathionine gamma-lyase and E. coli cystathionine gamma-synthase are homologous in both structure and in vitro function and propose that their different in vivo functions are due to the unavailability of O-succinylhomoserine in S. cerevisiae and the scarceness of cystathionine in E. coli.

Amino Acid Sequence↗
PubMed1992

Can high blood pressure alone increase erythrocytic intracellular sodium concentration?

In order to clarify the direct effects of high blood pressure on erythrocytic intracellular sodium concentration ([Na+]i) and sodium transport systems, a static pressure of 2.5 atm was applied to whole blood in plastic syringes at room temperature for 5 and 24 h. In the control samples, 5 h incubation under atmospheric pressure produced a significant decrease in ouabain-sensitive Na(+)-K+ pump activity and plasma pH, but no change in other parameters. After 24 h incubation, [Na+]i and mean corpuscular volume were significantly increased and intracellular potassium concentration, ouabain-sensitive Na(+)-K+ pump activity, and plasma pH were decreased. The change in [Na+]i during incubation under atmospheric pressure may be due to the increased permeability of the cell membrane and the decrease in ouabain-sensitive Na(+)-K+ pump activity. The pressure load did not increase erythrocytic [Na+]i but did decrease it relative to the control. The pressure load had no apparent effects on sodium transport systems, mean corpuscular volume and pH of plasma relative to the control. Although the mechanisms of the effect of pressure load on [Na+]i were not determined, we did find that high blood pressure alone was unable to increase erythrocytic [Na+]i.

Adult↗
PubMed1992

Immunoreactivity of recombinant carcinoembryonic antigen proteins expressed in Escherichia coli.

Immunoreactivities of recombinant carcinoembryonic antigen (CEA) proteins expressed in Escherichia coli (E. coli) were analyzed in relation to the CEA domain structure [domains N, I (A1-B1), II (A2-B2), III (A3-B3) and M]. We reconstructed in a prokaryotic expression vector, pUCPL-cI, the cDNAs fro CEA-N, CEA-I, CEA-II, and CEA-III-M. The latter three were expressed as fusion products with bacterial beta-galactosidase. The recombinant proteins were solubilized by sonication in 1% sodium dodecyl sulfate (SDS) and purified by preparative SDS-polyacrylamide gel electrophoresis followed by electroelution. Their molecular weights judged from Western blotting coincided with those calculated from their cDNA sequences, respectively. By solid-phase enzyme immunoassays, the immunoreactivities of the purified recombinant proteins were tested with 21 distinct anti-CEA monoclonal antibodies (MAbs) which had been found to recognize the peptide epitopes of the CEA molecule and to be reactive with the recombinant CEA proteins expressed in Chinese hamster ovary (CHO) cells. Fourteen of the 21 MAbs reacted with the recombinant CEA proteins expressed in E. coli and confirmed the localization of the epitopes identified by using the recombinant CEA proteins expressed in CHO cells. The reactivities of 5 MAbs with the recombinant proteins expressed in E. coli were remarkably low when compared with those of the proteins expressed in CHO cells but also confirmed the localization of the epitopes identified with the recombinant CEA proteins expressed in CHO cells. The remaining 2 MAbs did not react with any recombinant protein expressed in E. coli. These results indicate that the fusion CEA-proteins expressed in E. coli are useful in the localization of the epitopes on the polypeptide chains when they reacted with the MAbs tested. However, one third of the epitopes of CEA peptides may be profoundly affected by the presence of disulfide bonds and/or sugar chains which do not seem to be formed well in E. coli.

Base Sequence↗
PubMed1992

Familial influence upon NaCl sensitivity in patients with essential hypertension.

OBJECTIVE: The role of genetic factors in the pathogenesis of essential hypertension has not been fully clarified. In order to characterize the relation between NaCl sensitivity and genetic features of hypertension, the responses to dietary Na manipulations were examined in essential hypertensive patients with and without a family history of hypertension. METHODS: Fifteen essential hypertensive patients, both of whose parents were hypertensive, were compared with 25 hypertensive patients in whom a family history of hypertension was known to be absent in first- and second-degree relatives. There were no differences in gender distribution, age, blood pressure or duration of hypertension between the two groups. Subjects were studied as inpatients on a daily diet of 170 mmol NaCl for 1 week, followed by 1 week on a low-NaCl diet (50 mmol/day) and then by 1 week on a high-NaCl diet (340 mmol/day). RESULTS: Plasma renin activity on a low-NaCl diet was lower, and the erythrocyte Na+ concentration on both diets higher, in hypertensive patients with than in those without a family history. The elevations in mean blood pressure and in erythrocyte Na+ concentration with a high-NaCl diet were greater in patients with a family history. A significant correlation between the change in mean blood pressure and the change in erythrocyte Na+ concentration was found in patients with a positive family history, but not in those with a negative family history. CONCLUSIONS: Essential hypertensive patients with an apparent hereditary component of hypertension can be characterized as the low-renin and Na-sensitive subgroup with intracellular Na+ accumulation. Genetic features may underlie, at least in part, the heterogeneity of essential hypertension.

Blood Pressure↗
PubMed1992

Electrocortical arousal and spindles on physiological cortico-subcortical interactions.

The neuronal mechanisms of electrocortical arousal and sleep spindles were reviewed on the basis of intracellular analyses on the motor cortex in atraumatically maintained encéphale isolé cat preparations. When arousal is initiated by subcortical afferents from the brainstem, the cortical neurons respond with either excitation (E), inhibition (I), disfacilitation (DF), or disinhibition (DI), in a cascade pattern proceeding from the superficial to deep layers. These neuronal activities on arousal involve DF of the output neurons that may set the subcortical sensorimotor functions in a readiness state for a possible adaptive behavior of animals. This initial transient arousal termed phasic develops soon to the next, more sustained phase termed tonic by the action of other subcortical afferents. The cascade transmissions then occur again, producing E, I, DF, and DI in the cortical neurons but with a reverse laminar pattern proceeding from the deep to superficial layers. These neuronal activities on tonic and arousal deliver the cortical outputs to the subcortical systems that may trigger an orienting or searching behavior of animals in their environment. Sleep spindles also accompany the cascade transmissions that are partly common to those in arousal. Various modes of the cascade transmissions were further examined by applying electric shock stimuli to the cortical surface, the ventrolateral nucleus of the thalamus, and the cerebral peduncle to activate the subcortical afferents converging onto different cortical layers. The combined results from these experiments may imply that the cortico-subcortical interactions in which all the cortical neurons participate with dynamic harmony are instrumental to set a physiological sequence of animal behavior. If these interactions be impaired on the way of normal growth of the brain, as in the case of disorders with the Rett syndrome, many forms of ill adaptation may be brought about by dedifferentiation of sensorimotor functions.

Action Potentials↗
PubMed1992

Modification of platelet and lymphocyte calcium handling and blood pressure by dietary sodium and calcium in genetically hypertensive rats.

Abnormal cellular calcium handling has been postulated to be involved in the pathogenesis of hypertension. To determine whether the blood pressure response to dietary manipulation of sodium level (as the chloride salt) and calcium level is associated with changes in cellular cation metabolism, the interactive effects of both dietary components on blood pressure and intracellular free calcium concentration [( Ca2+]i) in blood platelets and thymic lymphocytes, erythrocyte sodium content, and blood ionized calcium were examined in stroke-prone spontaneously hypertensive rats. Rats were fed low (0.3%) or high (3.1%) sodium and low (0.2%) or high (2.0%) calcium diet for 6 weeks. With the rats receiving the high sodium-low calcium diet, systolic blood pressure was higher than with other diets, among which no difference was detected. Both basal [Ca2+]i and ionomycin (50 and 150 nmol/L) stimulated [Ca2+]i in platelets, and in lymphocytes, were higher with the high sodium-low calcium diet than with the others. Thus the high sodium diet elevated blood pressure and increased [Ca2+]i in the resting and stimulated state in both cell lines with the low-calcium but not the high-calcium diet. The high-sodium diet was associated with increased sodium content of erythrocytes, whereas manipulations of dietary calcium level had no effect on erythrocyte sodium content. Dietary calcium level had more of an effect on blood ionized calcium than did dietary sodium level. In combined diet groups, blood pressure was positively, significantly correlated with basal and ionomycin-induced [Ca2+]i in platelets (r = 0.64 and 0.67, respectively) and in lymphocytes (r = 0.53 and 0.60, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Three-dimensional structure of a highly thermostable enzyme, 3-isopropylmalate dehydrogenase of Thermus thermophilus at 2.2 A resolution.

The three-dimensional structure of the highly thermostable 3-isopropylmalate dehydrogenase (IPMDH) from Thermus thermophilus has been determined by the multiple isomorphous replacement method and refined to 2.2 A resolution. The final R-factor is 0.185 for 20,307 reflections. The crystal asymmetric unit has one subunit consisting of 345 amino acid residues. The polypeptide chain of this subunit is folded into two domains (first and second domains) with parallel alpha/beta motifs. The domains are similar in their conformations and folding topologies, but differ from those of the NAD-binding domains of such well-known enzymes as the alcohol and lactate dehydrogenases. A beta-strand that is a part of the long arm-like polypeptide protruding from the second domain comes into contact with another subunit and contributes to the formation of an isologous dimer with a crystallographic 2-fold symmetry. Close subunit contacts are also present at two alpha-helices in the second domain. These helices strongly interact hydrophobically with the corresponding helices of the other subunit to form a hydrophobic core at the center of the dimer. Two large pockets that exist between the first domain of one subunit and the second domain of the other include the amino acid residues responsible for substrate binding. These results indicate that the dimeric form is essential for the IPMDH to express enzymatic activity and that the close subunit contact at the hydrophobic core is important for the thermal stability of the enzyme.

3-Isopropylmalate Dehydrogenase↗