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Biomedical subjects

A Ohta

Publications and source records attributed to A Ohta.

At least 253 records · Page 14Linked to original sources
PubMed1988

A simple method for assessment of rat cytochrome P-448 isozymes responsible for the mutagenic activation of carcinogenic chemicals.

Cytochrome P-448H/L-enriched and cytochrome P-448L-enriched microsomes were prepared from the livers of Sprague-Dawley rats treated with 3-methylcholanthrene (MC) and with a combination of MC and carbon tetrachloride, respectively, and their activities for mediating mutagenic activation of 9 carcinogenic aromatic amines and benzo[a]pyrene, which are found to be different from cyt. P-450 isozymes as to mutagenic activation, were compared on the basis of microsomal cytochrome P-450 content using Salmonella typhimurium TA98 as a tester bacterium. With regard to the substrate-specificity of cytochrome P-448 isozymes, the present results reflected the reported results with use of a cytochrome P-450-reconstituted system. These findings indicate that the mutation test with cytochrome P-448H/L-enriched and cytochrome P-448L-enriched microsomes could be used as a simple method for the determination of the cytochrome P-448 isozymes responsible for the mutagenic activation of carcinogens and mutagens without the use of a cytochrome P-450-reconstituted system.

Amines↗
PubMed1988

Disruption of the CHO1 gene encoding phosphatidylserine synthase in Saccharomyces cerevisiae.

A Saccharomyces cerevisiae mutant that lacked phosphatidylserine synthase [EC 2.7.8.8] (CDP-1,2-diacyl-sn-glycerol: L-serine O-phosphatidyltransferase) completely was constructed by disrupting its structural gene, CHO1. Over two-thirds of its coding region, from the starting to the 200th codon, was replaced with a LEU2 DNA fragment. This new cho1 mutant showed no detectable synthesis of phosphatidylserine but grew slowly in a medium that contained either ethanolamine or choline. These results indicate that phosphatidylserine synthase and most probably phosphatidylserine are dispensable in S. cerevisiae but necessary for its optimal growth. Additional supplementation with myo-inositol raised the cellular content of phosphatidylinositol and improved the growth of the mutant, suggesting the importance of the negative charges of the membrane surface. The CHO1-disrupted mutant, when grown on choline, accumulated phosphatidylethanolamine to a significant level even after extensive dilution of the initial culture. It segregated prototrophic revertants that could synthesize phosphatidylethanolamine without recovery of phosphatidylserine synthesis. These results imply the presence of a route(s) for the formation of ethanolamine or its phosphorylated derivative in S. cerevisiae.

Blotting, Southern↗
PubMed1988

Disruption of the Escherichia coli cls gene responsible for cardiolipin synthesis.

The cls gene of Escherichia coli is responsible for the synthesis of a major membrane phospholipid, cardiolipin, and has been proposed to encode cardiolipin synthase. This gene cloned on a pBR322 derivative was disrupted by either insertion of or replacement with a kanamycin-resistant gene followed by exchange with the homologous chromosomal region. The proper genomic disruptions were confirmed by Southern blot hybridization and a transductional linkage analysis. Both types of disruptants had essentially the same properties; cardiolipin synthase activity was not detectable, but the strains grew well, although their growth rates and final culture densities were lower than those of the corresponding wild-type strains and strains with the classical cls-1 mutation. A disruptant harboring a plasmid that carried the intact cls gene grew normally. The results indicate that the cls gene and probably the cardiolipin synthase are dispensable for E. coli but may confer growth or survival advantages. Low but definite levels of cardiolipin were synthesized by all the disruptants. Cardiolipin content of the cls mutants depended on the dosage of the pss gene, and attempts to transfer a null allele of the cls gene into a pss-1 mutant were unsuccessful. We point out the possibilities of minor cardiolipin formation by phosphatidylserine synthase and of the essential nature of cardiolipin for the survival of E. coli cells.

Alleles↗
PubMed1988

Effect of antiarrhythmic drugs on the ventricular fibrillation induced by low intensity train pulses.

We evaluated the effects of antiarrhythmic drugs on ventricular fibrillation threshold (VFT) by analysing the electrophysiologic parameters obtained from strength-interval curves. The VFT determined by low intensity train pulses was significantly increased from the control value under the administration of clinical dosage of procainamide, lidocaine, propranolol, bepridil and prenylamine, although not verapamil. The elevation of VFT could be explained by changes in the strength-interval curve induced by the drugs, including disappearance of dip phenomenon, supernormal period, prolongation of effective refractory period (ERP) and elevation of end diastolic threshold (EDT).

Animals↗
PubMed1988

Effects of acylcarnitine-transferase inhibitors on adenine nucleotide metabolism and ischemic tissue injury in isolated perfused rat heart.

The ability of irreversible acylcarnitine-transferase inhibitors, sodium 2[5-(4-chlorophenyl)-pentyl]-oxirane-2-carboxylate (POCA) and 2-tetradecyl-glycidic acid (TDGA), to reduce myocardial ischemic injury was studied in Langendorff-perfused hearts exposed to ischemia (zero mmHg) followed by aerobic reperfusion (60 mmHg). Rat hearts were pretreated with either POCA (15 mg/kg) or TDGA (5 mg/kg) s.c. 120 min before the perfusion. Treated hearts showed a decreased release of creatine kinase and lactate on reperfusion after 30 min ischemia. POCA-treated hearts showed significantly higher ATP concentrations than control hearts on reperfusion. POCA also improved the maximum recovery of the pressure-rate product but with a significant delay. During the ischemic period, though, POCA decreased the ATP concentration at a rate three times that of controls during the first 10 min. No further reductions were observed for up to 30 min of ischemia. TDGA also showed a reduction of ATP. Thus, the observation that POCA stimulated ATP synthesis and reduced creatine kinase release on reperfusion after ischemia suggests that this agent provides some protection to the ischemic myocardium. However, during ischemia, it is likely that the depletion of ATP concentration induced by POCA resulted in delayed recovery of mechanical function on reperfusion.

Acyltransferases↗
PubMed1988

Conditioned reinforcement by conditional discriminative stimuli.

A concurrent-chains schedule was used to examine how a delay to conditional discriminative stimuli affects conditioned reinforcement strength. Pigeons' key-peck responses in the initial link produced either of two terminal links according to independent variable-interval 30-s schedules. Each terminal link involved an identical successive conditional discrimination and was segmented into three links: a delay interval (green), a color conditional discriminative stimulus (blue or red), and a line conditional discriminative stimulus (vertical or horizontal lines). Food delivery occurred 45 s after entering the terminal link with a probability of .5, but its conditional probability (1.0 or 0) depended on the combination of the color and the line stimuli. One of the color stimuli occurred independently of further responding, 5 s after entry into the right terminal link, but it occurred 35 s after entry into the left terminal link. One of the line stimuli occurred independently of responding 40 s after entry into either terminal link, synchronized with the offset of the color stimulus. The initial-link relative response rate for the right was consistently higher in comparison with a control condition in which the color stimuli occurred 20 s after entry into either terminal link. The preference for the short delay to the color conditional discriminative stimuli suggests the possibility of conditioned reinforcement by information about the relation between the line conditional discriminative stimuli and the outcomes.

Animals↗
PubMed1988

Genetic analysis of systemic lupus erythematosus: 1. Detection of disease-associated variant proteins by two-dimensional gel electrophoresis.

Various genetic studies indicate that development of systemic lupus erythematosus (SLE) is regulated by the mode of multifactorial inheritance, i.e., by the overall effect of polygenes and environmental factors. To elucidate some variant genes involved in the polygenic system responsible for onset of SLE, we resolved and measured the protein components of lymphocytes and sera from inactive-SLE patients, their relatives, and normal controls, using two-dimensional gel electrophoresis. Intercomparison of polypeptide patterns between patients and controls revealed three major variations, two detected in lymphocytes and one in sera. These variations were present in 66-82% of the patients, in 20-36% of the control group, and in 41-64% of the relatives. In addition, nearly half of SLE patients, but only one of 19 normal controls, possessed all three SLE-associated traits, suggesting that these variant proteins may reflect in part the genetic factors contributing to development of SLE.

Adolescent↗
PubMed1988

Still's disease associated with necrotizing lymphadenitis (Kikuchi's disease): report of 3 cases.

Necrotizing lymphadenitis (Kikuchi's disease) is recognized as one of the benign lymphadenopathies. Previously, this condition has not been described in Still's disease which is frequently associated with lymphadenopathy. We report 3 cases of Still's disease, 2 in adults and 1 in an older child, with the findings of necrotizing lymphadenitis on lymph node biopsy. Considering the common infectious and/or immunologic etiologies described in both disorders, coexistence of both conditions suggests the possibility that they share a common etiology.

Adolescent↗
PubMed1987

Ca2+-dependent ATP hydrolysis of the porcine intestinal brush-border membranes.

The brush-border membrane from the porcine small intestine possesses Ca2+-dependent ATPase activity. The Ca2+ stimulation of ATP hydrolysis by the membranes is biphasic with a high affinity (Km = 0.38 microM) and a low affinity (Km = 98.3 microM). Treatment of the membrane vesicles with n-heptylthioglucoside did not cause further increase of the Ca2+-ATPase activity. Mg2+ also stimulates the ATP hydrolysis in the absence of Ca2+ but decreases the Ca2+-ATPase activities at 0.59 and 200 microM free Ca2+. The Ca2+-ATPase activities are not inhibited by addition of vanadate, ouabain, sodium azide and alkaline phosphatase inhibitors (theophylline and L-phenylalanine), irrespective of the Ca2+ concentrations in medium. A specific calmodulin-inhibitor W-7 (up to 30 microM) also did not influence on the Ca2+-ATPase activities at 0.59 and 200 microM free Ca2+. The Ca2+-ATPase activities at 0.59 and 200 microM free Ca2+ show no specificity for ATP. ADP, GTP and CTP could also be used as substrates. From these results, it is suggested that the porcine intestinal brush-border membrane possesses Mg2+-independent Ca2+-ATPase activity and that the Ca2+-ATPase activities with biphasic responses for Ca2+ stimulation observed in the present study reside on the same protein. The physiological functions of the Ca2+-ATPase in the membranes, however, remain unknown at present.

Adenosine Triphosphate↗
PubMed1987

Procollagen gene expression by scleroderma fibroblasts in culture. Inhibition of collagen production and reduction of pro alpha 1(I) and pro alpha 1(III) collagen messenger RNA steady-state levels by retinoids.

Recent studies have demonstrated that retinoids (synthetic vitamin A analogs) can modulate connective tissue metabolism in human skin fibroblast cultures. In this study, we examined the effects of 3 retinoids, all-trans-retinoic acid (RA), 13-cis-RA, and an aromatic retinoid, RO-10-9359, on collagen gene expression in scleroderma fibroblast cultures and matched control fibroblast cultures. The results indicated that all-trans-RA and 13-cis-RA significantly reduced procollagen production both in control and scleroderma fibroblast cultures in a dose-dependent manner. The reduction in procollagen production was paralleled by a similar decrease in steady-state levels of type I and type III procollagen messenger RNAs, which suggests that there is coordinate inhibition on the transcriptional level. In contrast, RO-10-9359 elicited only limited effects on collagen production, and such effects were variable. The results suggest that further development of retinoids might provide an effective means to counteract tissue deposition of collagen in scleroderma and other fibrotic diseases.

Adult↗
PubMed1987

Laser modulation of human immune system: inhibition of lymphocyte proliferation by a gallium-arsenide laser at low energy.

Cultured human lymphocytes were subjected to irradiation with a gallium-arsenide laser at energy fluence varying from 2.17 to 651 mJ/cm2, and the cell proliferation was assessed by [3H]thymidine incorporation. Both mitogenic proliferation in response to phytohemagglutinin and spontaneous cell proliferation were markedly inhibited by the laser irradiation at energy fluence as low as 10.85 mJ/cm2. Similarly, the functional response of cells to antigen stimulation in a one-way mixed-lymphocyte reaction was also diminished as a result of laser irradiation. The results indicate that laser irradiation at low energy can interfere with immune system in vitro, and similar modulation could potentially occur in human subjects exposed to laser irradiation in vivo.

Dose-Response Relationship, Radiation↗
PubMed1987

Lipoid proteinosis: ultrastructural and biochemical studies.

Lipoid proteinosis, a rare autosomal recessive disease, is histologically characterized by deposition of hyalinlike material in the dermis. In this study the pathologic processes of lipoid proteinosis were evaluated by ultrastructural and biochemical analysis of skin and cultured fibroblasts from a patient with classic features of the disease. Transmission electron microscopy revealed the presence of hyalinlike material with a granular appearance interspersed between collagen fibers. Immediately surrounding the blood vessel walls, there was reduplication of basal laminae in an "onionskin" arrangement. The fibroblastic cells in the affected dermis contained peculiar cytoplasmic inclusions. Biochemical studies with the cultured fibroblasts showed that the total synthesis of extracellular matrix components, as detected by the synthesis of radioactive hydroxyproline or the incorporation of 35SO4(2-) and [3H]glucosamine into macromolecules, was not altered in lipoid proteinosis. However, the relative expression of type I and type III procollagen genes, as detected by molecular hybridizations with pro-alpha 1(I) and pro-alpha 1(III) procollagen complementary deoxyribonucleic acid probes, was markedly altered in cultured fibroblasts. Specifically, the type I procollagen messenger ribonucleic acid (mRNA) levels were significantly reduced, resulting in a decreased type I/III procollagen mRNA ratio. Furthermore, the replicative capacity of lipoid proteinosis fibroblasts, as detected by the incorporation of radioactive thymidine, was reduced. Thus the skin fibroblasts from lipoid proteinosis demonstrate ultrastructural changes, as well as alterations in their phenotypic characteristics, and these changes may have relevance to the pathologic processes of this systemic disease affecting the skin and other organs.

Adult↗
PubMed1987

Primary structure and product characterization of the Saccharomyces cerevisiae CHO1 gene that encodes phosphatidylserine synthase.

An open reading frame of 828 base pairs was found in the CHO1 gene region of Saccharomyces cerevisiae by nucleotide sequencing analysis. Its enhanced expression with the aid of the PHO5 regulatory sequence resulted in an overproduction of a protein with a molecular weight of approximately 30,000, which in turn was converted by proteolysis to active phosphatidylserine synthase, whose molecular weight was approximately 23,000. The larger protein was concluded to be the primary product of the CHO1 gene, since its amino-terminal sequence was identical to that deduced from the nucleotide sequence of the above open reading frame, except for the terminal methionine residue. A partial homology in primary structures was noticed between this yeast enzyme and phosphatidylglycerophosphate synthase of Escherichia coli which also uses CDP-diacylglycerol as a substrate. The overproduced phosphatidylserine synthase in both microsomal and extensively purified fractions displayed two different Km values for L-serine, i.e., 0.14 mM at low L-serine concentrations and 9.5 mM at high L-serine concentrations. This may indicate a negatively cooperative regulation of this enzyme activity or the presence of two active components with different affinities for L-serine.

Amino Acid Sequence↗