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T Ohta

Publications and source records attributed to T Ohta.

At least 973 records · Page 54Linked to original sources
PubMed1991

Structure-function relationships of microcystins, liver tumor promoters, in interaction with protein phosphatase.

Microcystins, isolated from toxic blue-green algae, are potent inhibitors of protein phosphatases 1 and 2A. Recently, we have reported that microcystin LR has a potent tumor-promoting activity on rat liver initiated with diethylnitrosamine. The structure of microcystins is unique in having an unusual amino acid, 3-amino-9-methoxy-10-phenyl-2,6,8-trimethyl-deca-4(E),6(E)-dienoic acid (Adda), which is thought to be significant for the activity. Geometrical isomers at C-7 in the Adda portion of microcystins, 6(Z)-Adda microcystins LR and RR, have been isolated from cyanobacteria. To estimate their tumor-promoting activities and to understand the importance of the Adda portion for activity, the maternal microcystins LR and RR and their isomers were subjected to examination of their interaction with protein phosphatases 1 and 2A and the release of glutamic pyruvic transaminase from rat liver. 6(Z)-Adda microcystins LR and RR bound to protein phosphatases 1 and 2A, inhibited their activities and released glutamic pyruvic transaminase from rat liver into serum, ten to one hundred times more weakly than the maternal microcystins LR and RR. These results indicated that the conjugated diene with 4(E),6(E) geometry in the Adda portion is important in the interaction with protein phosphatases.

Alanine Transaminase↗
PubMed1991

Effects of vasoactive intestinal peptide (VIP) on contractile responses of smooth muscle in rat stomach.

1. The effects of vasoactive intestinal peptide (VIP) on contractile responses to carbachol (CCh), KCl and caffeine of the circular smooth muscle in rat stomach were examined by the isometric tension recording method and by measurement of the intracellular Ca level, [Ca]i, with fura 2. 2. Removal of extracellular Ca or nifedipine (0.1 microM) inhibited contractions induced by KCl (40 mM) and a low concentration (1 microM) of CCh but not that induced by caffeine (3 mM). After these treatments, the contraction induced by a high concentration of CCh (100 microM) changed to a phasic response. 3. VIP dose-dependently inhibited the contraction induced by 1 microM CCh, but not those caused by 40 mM KCl or 3 mM caffeine. 4. In Ca-free solution containing 2 mM EGTA, VIP inhibited the phasic contraction induced by 100 microM CCh, but not that induced by 30 mM caffeine. 5. CCh caused dose-dependent tension development concomitant with the increase in [Ca]i. VIP reduced both responses and thus did not affect the [Ca]i-force relation for CCh. In the chemically skinned muscle fibres, VIP had no effect on the pCa-tension relation. 6. It is suggested that the inhibitory effects of VIP on CCh-induced contractions are due to the inhibition of the processes of signal transduction from muscarinic receptors to voltage-dependent Ca channels and to intracellular Ca stores.

Animals↗
PubMed1991

Production and Extracellular Secretion of Aqualysin I (a Thermophilic Subtilisin-Type Protease) in a Host-Vector System for Thermus thermophilus.

Aqualysin I is synthesized as a large precursor, processed, and secreted into the culture medium by Thermus aquaticus YT-1. An expression plasmid for the aqualysin I gene in T. thermophilus HB27 was constructed. T. thermophilus cells harboring the recombinant plasmid produced correctly processed aqualysin I, and the mature enzyme was secreted into the culture medium.

Journal Article↗
PubMed1991

A novel, highly efficient gene-cloning system for Micromonospora strains.

A highly efficient gene-cloning system for Micromonospora olivasterospora, a producer of the antibiotic fortimicin A (astromicin), suited to shotgun cloning has been developed. The system is supported by two new advancements accomplished in this study. One is the construction of novel plasmid vectors pMO116, pMO126, pMO133, pMO136, and pMO217, all consisting of replicons from newly found Micromonospora plasmids and selectable markers cloned from a neomycin-producing Micromonospora strain. The other advancement is the establishment of a new protocol for bacterial protoplasting in which some kinds of sugar alcohols are added in precultures. Such sugar alcohols were found to sensitize a wide taxonomical range of bacteria to lysozyme. The system is reproducible and reliable and has a high efficiency of more than 10(6) CFU/micrograms of DNA.

Cloning, Molecular↗
PubMed1991

Development of a new perfusion system for pharmacological study on rabbit basilar arteries.

We developed a constant-flow perfusion system to measure vascular responses to vasoactive agents applied intraluminally or extraluminally. The intraluminal and extraluminal sides of a cylindrical section of rabbit basilar artery were isolated completely. By loading with 0.75 g of tension, the resting condition of each preparation was made constant. The intraluminal side was perfused at a constant flow of 8 ml/min and under an intraluminal pressure of 8 mm Hg. When 30 mM KCl was administered intraluminally the preparation showed marked contraction, whereas only slight contraction was observed with extraluminal administration. When 2 x 10(-7) M 5-hydroxytryptamine was administered, no significant differences in contraction could be detected between the intraluminal and extraluminal routes. Application of 10(-6) to 10(-4) M acetylcholine after precontraction with 30 mM KCl resulted in much stronger dilatation upon intraluminal application. Thus, it was demonstrated that under certain conditions significant differences exist in the responses of rabbit basilar arteries to vasoactive agents applied intraluminally or extraluminally. This system can detect the effects of vasoactive agents administered intraluminally and extraluminally at a high level of sensitivity and shows good reproducibility as a means of analyzing vascular functions and characteristics.

Acetylcholine↗
PubMed1991

Importance of polymerization initiator systems and interfacial initiation of polymerization in adhesive bonding of resin to dentin.

Although various adhesive resins for dentin have been developed and used clinically, most attention has been directed to adhesion-promoting monomers and pre-treatment agents. The role of polymerization initiator systems in bonding has been overlooked. The purpose of this work was to study the role of initiators from the viewpoint of interfacial initiation of polymerization in dentin bonding. The bond strength between dentin and methyl methacrylate resin was significantly improved by a possible interfacial initiation with (1) the combination of ferric chloride, adsorbed onto dentin, and oxidized tri-n-butylborane (TBBO) and (2) the addition of tertiary butyl peroxymaleic acid (containing a carboxylic acid group, which has an affinity with dentin) to chemically- or light-activated initiator systems.

Acid Etching, Dental↗
PubMed1991

Mechanism of decomposition of cyclic peroxides, 4-alkoxy-1,4-dihydro-2,3-benzodioxin-1-ols, to afford hydroxyl radical.

The decomposition of 4-alkoxy-1,4-dihydro-2,3-benzodioxin-1-ols (1, Bd) in aqueous media was examined. Increasing the water content of the medium accelerated the decomposition of 1 and increased the formation of the corresponding 2-formyl benzoic acid ester (2) as the decomposition product. Electron spin resonance (ESR) studies using dimethylpyrroline N-oxide (DMPO) as a spin trapping reagent had revealed that hydroxyl radicals are formed during the decomposition of 1 (Matsugo et al., FEBS Lett., 184, 25 (1985)). Thus, water-mediated decomposition of 1 was suggested to occur, affording the ester 2 and hydroxyl radical. Direct involvement of water was confirmed by an 18O isotopic tracer experiment which revealed that 18O was incorporated exclusively into the formyl position of the ester 2. It is plausible that a hydrated hydroperoxide (5) is formed by the addition of water at the formyl position of the ring-opened structure of 1 at the initial stage of the decomposition of 1. Preliminary studies on the antibacterial activities of 1 showed moderate cell-killing activity, especially to Pseudomonas strains, and the activity was found to be related to the decomposition of 1.

Alcohols↗
PubMed1991

Adenomatous hyperplasia of the bile duct epithelium of the canine liver, caused by bacterial infection.

Morphologic changes of the intrahepatic bile ducts after induction of bile stasis and bacterial infection of the biliary tract in two lobes of the liver in mongrel dogs were studied to examine the pathophysiology of hepatolithiasis. Three groups of dogs were prepared by cannulation of the bile duct branch draining the left lateral lobes of the liver and were treated as follows: in group 1 the cannula was clamped after injection of 10(7) Escherichia coli (aerobic bacteria) and 10(7) Bacteroides fragilis (anaerobic bacteria) organisms; in group 2 the cannula was clamped after injection of E. coli only; and in group 3 the cannula was clamped without injection of bacteria. Three months later the livers of killed dogs were examined. In group 1 epithelial adenomatous hyperplasia was noted in association with chronic cholangitis characterized by moderate to severe periductal fibrosis with a large number of inflammatory cells. In group 2 periductal fibrosis was severe, but epithelial hyperplasia was found to a much lesser degree than in group 1. In group 3 no periductal fibrosis or epithelial adenomatous hyperplasia was demonstrated. These findings suggest that adenomatous hyperplasia of the bile duct epithelium may be caused by bacterial infection of the biliary tract in combination with bile stasis.

Animals↗
PubMed1991

Signal peptide of the colicin E2 lysis protein causes host cell death.

Colicin E2 is encoded by the SOS-inducible colicin operon of plasmid ColE2-P9. Highly induced colicin E2 is excreted from the E. coli host cell, accompanied by quasi-lysis and cell death. These three events are all directed by the colicin lysis protein that comprises the signal peptide and a small mature lipoprotein. We constructed a mutant lysis gene encoding its complete signal peptide with addition of two external amino acids at the C-terminus. By using this mutant peptide as a reference, the wild type lysis signal peptide was identified and shown to remain quite stable after the cleavage. This mutant peptide also mimics the cleaved-off signal peptide avoiding the influence of the mature lysis lipoprotein, and suggested that cell death by the lysis protein, but neither colicin excretion nor quasi-lysis, is decided by the nature of its signal region.

Base Sequence↗
PubMed1991

Involvement of NH2-terminal pro-sequence in the production of active aqualysin I (a thermophilic serine protease) in Escherichia coli.

Aqualysin I is a heat-stable subtilisin-type protease produced by Thermus aquaticus YT-1. The precursor of aqualysin I consists of four domains: an NH2-terminal signal peptide, an NH2-terminal pro-sequence, a protease domain, and a COOH-terminal pro-sequence. In Escherichia coli cells harboring recombinant plasmid carrying the aqualysin I gene, proteolytic activity is obtained on treatment at 65 degrees C and mature enzyme is detected. In the case of mutant genes containing partial deletions in the NH2-terminal pro-sequence, no proteolytic activity was detected and the precursor protein was found to be unstable in E. coli. These results indicate that the NH2-terminal pro-sequence is required to produce the active enzyme by stabilizing the precursor structure. Amino acid substitutions in the conserved sequence of the NH2-terminal pro-sequence found among subtilisin-type proteases made the processing faster compared with the wild type.

Amino Acid Sequence↗
PubMed1991

Negative supercoiling of DNA by eukaryotic DNA topoisomerase II and dextran sulfate.

In the presence of a molar excess of eukaryotic DNA topoisomerase II and an appropriate concentration of dextran sulfate, relaxed closed circular DNA is converted to a negatively supercoiled form. The reaction is dependent on ATP. Neither adenosine 5'-[beta,gamma-imido]-triphosphate nor adenosine 5'-[gamma-thio]triphosphate can substitute for ATP. The negative supercoils formed are relaxed by subsequent addition of DNA topoisomerase I to the supercoiling reaction mixture. Covalent closure of a nicked circular DNA in the presence of DNA topoisomerase II and dextran sulfate but in the absence of ATP causes a small decrease in the linking number. These results suggest that when an appropriate concentration of dextran sulfate is present, the binding of a molar excess of eukaryotic DNA topoisomerase II constrains a small number of negative supercoils in DNA, which in turn generate unconstrained negative supercoils at the expense of ATP.

Adenosine Triphosphate↗
PubMed1991

Treatment of persistent sleep-wake schedule disorders in adolescents with methylcobalamin (vitamin B12).

Two adolescent patients suffering from persistent sleep-wake schedule disorders appear to have responded to treatment with vitamin B12 (methylcobalamin). A 15-year-old girl with delayed sleep phase syndrome (DSPS) and a 17-year-old boy with hypernychthemeral syndrome complained of not being able to attend school despite many trials of medication. The improvement of the sleep-wake rhythm disorders appeared immediately after the administration of high doses (3,000 micrograms/day) of methylcobalamin. Neither patient showed any laboratory or clinical evidence of vitamin B12 deficiency or hypothyroidism (which can cause B12 deficiency). Serum concentrations of vitamin B12 during treatment were in the high range of normal or above normal. The duration of the sleep period of the DSPS patient decreased gradually from 10 hours to 7 hours, and the time of sleep onset advanced from 2 a.m. to midnight. The period of the sleep-wake cycle of the hypernychthemeral patient was 24.6 hours before treatment and 24.0 hours after treatment. The relationship between the circadian basis of these disorders and vitamin B12 and its metabolites is discussed.

Achievement↗
PubMed1991

[An intradural arachnoid cyst of the craniovertebral junction; a case report].

An intradural arachnoid cyst of the craniovertebral junction possibly of traumatic origin is reported. A 59-year-old man was admitted to our hospital with a 10-month history of progressive gait disturbance. He had a history of head injury with a fracture of the occipital bone. Myelography revealed pooling of the contrast medium in the posterior fossa and on the dorsal sides of C1 and C2. Metrizamide-enhanced computed tomography also showed pooling at the same level. Magnetic resonance imaging indicated a large cystic lesion at the craniovertebral junction. Craniectomy of the posterior fossa and laminectomy of C1, C2 and C3 were performed, and an intradural cyst with thickened dura and arachnoid was found. The cyst wall was opened to communicate with the subarachnoid space. Histological findings of the specimen showed that the arachnoid was thickened. There are over 130 reports of intradural arachnoid cyst of the spine, but those of traumatic origin are rare, and cysts located in the intracranial to spinal region are extremely rare.

Arachnoid Cysts↗
PubMed1991

[Relation of baseline examination results to death from ischemic heart disease, cerebro-vascular disease and sudden death].

The relation of variables obtained from a baseline examination to death from ischemic heart disease (IHD), cerebro-vascular disease (CVD) and sudden death (SUD) was analyzed in a case-control study. From questionnaire survey of approximately 180,000 subjects who underwent baseline health examinations in 1971-1986 at Aichi prefectural center of health care, 148 deaths were selected for this study. The number of cases on IHD, CVD and SUD was 36, 60, and 52, respectively. Mean age of cases was 54.8 years old and the mean follow up interval between baseline examination and death was 3.7 years. Four controls matched according to year of baseline examination, age and sex were chosen arbitrarily for each case, and odds ratios for the three diseases were estimated. In some of the matched sets, odds ratios at a follow up examination were compared with that at the first examination. The results were as follows: 1) Variables showing positive relationships to death from each of the three diseases were hypertension, high fasting blood sugar, abnormality of cardio-thoracic ratio, ST-T abnormality in ECG, left ventricular hypertrophy in ECG. The odds ratio for ST-T abnormality in ECG was significant for all three causes of death. 2) High total cholesterol showed a significant positive relation only to death from IHD. As to death from CVD and SUD, albuminuria and sclerotic changes in fundus oculi were positively and significantly related. Risk factors differed for deaths from the three diseases. 3) In death from IHD and CVD, odds ratio at the second examination was apt to be higher than that at baseline examination. In death from SUD, however, odds ratios at the first and the second examination showed no significant difference.

Adult↗
PubMed1991

Reproductive and developmental toxicity studies on catena-(S)-[mu-[N alpha-(3-aminopropionyl) histidinato(2-)-N1,N2,O:N tau]-zinc].

To evaluate the effects of Z-103 (catena-(S)-[mu-[N alpha-(3-aminopropionyl) histidinato (2-)-N1,N2,O:N tau]-zinc], CAS 107667-60-7) on the reproductive performance of male and female rats, the general toxicity of dams, and the development, physical growth and reproductive performance of the next generation, Z-103 was administered to rats prior to, and in the early stages of pregnancy, during the period of fetal organogenesis, and during the perinatal and lactation periods, and to rabbits during the period of fetal organogenesis at the appropriate doses for each study. At the administration of Z-103 prior to and in the early stages of pregnancy in rats, no dose-related abnormalities were observed in the reproductive performance of either sex. Furthermore, there were no death or evidence of teratogenicity or repressive effect on growth in fetuses. Administration of Z-103 during the period of fetal organogenesis in rats affected the growth of embryos and fetuses at 1200 mg/kg. At 600 mg/kg or less, however, there were no death, teratogenicity or repressive effect on growth in fetuses, and furthermore, no dose-related abnormalities were observed in growth, physical development, behavior and reproductive performance in offspring. Administration of Z-103 during the period of fetal organogenesis in rabbits caused a decrease in the number of live fetuses at 300 mg/kg suggesting that 300 mg/kg of Z-103 may have a lethal effect on fetuses. There were, however, neither teratogenicity nor any repressive effect on the growth of fetuses.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Drug-Induced↗
PubMed1991

Mutagenicity studies on catena-(S)-[mu-[N alpha-(3-aminopropionyl)histidinato(2-)-N1,N2,O:N tau]-zinc].

Z-103 (catena-(S)-[mu-[N alpha-(3-aminopropionyl)histidinato (2-)-N1,N2,O:N tau]-zinc], CAS 107667-60-7) was examined in the bacterial mutation test, a chromosomal aberration test with mammalian cells in culture and the micronucleus test using male mice. 1. Z-103 did not increase the number of revertants in Escherichia coli WP2 uvrA when tested at up to 5000 micrograms/plate in the presence or absence of metabolic activation. And Z-103 did not increase mutants in Salmonella typhimurium SD 100 (streptomycin dependent strain) or in Salmonella typhimurium TM677 (8-azaguanine sensitive strain) when tested at up to 5000 micrograms/ml in the presence or absence of metabolic activation. 2. The chromosomal aberration test was carried out with cultured Chinese hamster lung cells (CHL). For the direct assay procedure, the cells were treated with 3.3 x 10(-4)-3.3 x 10(-6) mol/l Z-103 for 24 or 48 h, after which time chromosome preparations were made. For the metabolic activation assay procedure, the cells were treated with 1.0 x 10(-3)-3.3 x 10(-6) mol/l of Z-103 for 6 h in the presence or absence of metabolic activation, and the chromosome preparations were made after a further 18-h incubation in the absence of Z-103 and metabolic activation. Z-103 did not cause chromosome aberrations either in the presence or in the absence of metabolic activation. 3. The micronucleus test was performed in ddY male mice. Z-103 was administered orally to mice at a dose of 400, 200 or 100 mg/kg.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗