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Biomedical subjects

A Ohta

Publications and source records attributed to A Ohta.

At least 19 recordsLinked to original sources
PubMed1999

The Excess Thermodynamic Quantities of Adsorption of a Binary Nonionic Surfactant Mixture.

The thermodynamic relations were developed for examining the miscibility of surfactants in the adsorbed film from the viewpoints of the thermodynamic quantities of adsorption such as Gibbs free energy, entropy, volume, enthalpy, and energy. The deviation from the additivity relation, the straight line connecting the thermodynamic quantities of the respective pure surfactants as a function of the composition of the adsorbed film, was proved to yield the corresponding excess quantities of adsorption. The criterion of the ideal mixing was offered and summarized with respect to the composition of adsorbed film, the mean area occupied by surfactants, and the thermodynamic quantities of adsorption. The resulting equations were applied to the simple nonionic surfactants mixture of decyl methyl sulfoxide (DeMS) and octyl methyl sulfoxide (OMS). The surface tension of the aqueous solution was measured as a function of not only the total molality and mole fraction of surfactants but also temperature under atmospheric pressure. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Structure Effect on Nonideal Mixing of Alkyl Methyl Sulfoxide and Alkyldimethylphosphine Oxide in Adsorbed Film and Micelle.

The surface tension of aqueous solutions of the octylmethylsulfoxide (OMS)-decyldimethylphosphine oxide (DePO) and decylmethylsulfoxide (DeMS)-octyldimethylphosphine oxide (OPO) mixtures was measured as a function of the total molality of the surfactants and the composition in the surfactants. Compositions in the adsorbed film and micelle were thermodynamically evaluated from the total molality vs composition and the critical micelle concentration (CMC) vs compositon curves, respectively. The phase diagrams of adsorption and micelle formation were drawn and compared with those of the DeMS-DePO mixture previously studied. A large gap in composition was observed between the adsorbed film and the micelle coexisting at the CMC and ascribed to the differences in geometric structure between them and the constituent molecules. Negative deviation from ideal mixings in adsorbed film and micelle was observed for the OMS-DePO mixture, whereas a positive one was observed for the DeMS-OPO. The structure effect on the nonideal mixings was clarified by using the excess thermodynamic functions of adsorption and micelle formation calculated from the activity coefficients in the adsorbed film and micelle. Copyright 1999 Academic Press.

Journal Article↗
PubMed1999

Neuronal expression of a Caenorhabditis elegans elav-like gene and the effect of its ectopic expression.

We examined the expression of a Caenorhabditis elegans (C. elegans) elav-like gene, which we designated elr-1. The elr-1 gene encodes a predicted 456-amino-acid protein containing three putative RNA-binding domains and belongs to the ELAV family, which is functionally involved in neuronal differentiation. Northern blot analysis suggested that the levels of elr-1 mRNA are regulated developmentally. A elr-1::gfp reporter gene under the control of the elr-1 promoter was expressed specifically in the ring ganglia near the nerve ring, the ventral nerve cord (VNC), and the pre-anal and lumbar ganglia. In the VNC, GFP-positive cells were shown to be acetylcholine-producing motor neurons which increased in number as development proceeded, suggesting that elr-1 is expressed in mature neurons. Ectopic expression of ELR-1 protein at the L4 larval and adult stages, but not earlier stages, caused irreversible death, accompanied by uncoordinated movement (Unc), clear (Clr), and egg-laying defective (Egl) phenotypes, which are often observed in mutants with neuronal defects. These results suggest that ELR-1 may have important functions in specific mature neurons in C. elegans.

Amino Acid Sequence↗
PubMed1999

A critical role for antigen-specific Th1 cells in acute liver injury in mice.

A novel liver injury model was established in mice by targeting of OVA-containing liposomes into the liver, followed by adoptive transfer of OVA-specific Th1 cells. Combined treatment of mice with OVA-containing liposomes and Th1 cell transfer caused an increase in serum transaminase activity that was paralleled with an elevation of serum IFN-gamma levels. In sharp contrast, OVA-specific Th2 cell transfer resulted in an increase of serum IL-4 levels, but did not induce liver injury. Neither NK, NK T, nor CD8+ T cells were required for the Th1-induced liver injury. The liver injury was blocked by anti-IFN-gamma mAb and anti-TNF-alpha mAb, but not by anti-Fas ligand mAb. The Fas/Fas ligand independency was also demonstrated using Fas-deficient lpr mice. These findings indicate that Th1 cells are the major effector cells in acute liver injury.

Acute Disease↗
PubMed1999

A gene coding for a ribosomal protein L41 in cycloheximide-resistant ribosomes has a promoter which is upregulated under the growth-inhibitory conditions in yeast, Candida maltosa.

We previously found by using yeast, Candida maltosa, that cycloheximide (CYH) sensitivity of ribosomes is dependent on the 56th amino acid residues of a ribosomal protein, L413 (proline in sensitive and glutamine in resistant ribosomes). We also revealed that in this yeast, which has both L41-P type and L41-Q type genes, the expression of the latter type genes is induced by the addition of CYH in the medium to make the cells inducibly resistant to CYH. In this paper, we analyzed the promoter region of L41-Q2a, one of the CYH-inducible L41-Q type genes and found two elements required for the induction of expression: one was a GCRE (Gcn4p-responsive element of Saccharomyces cerevisiae)-like element and the other was a GT-rich element. This promoter region was also required for its expression under some other growth inhibitory conditions. Furthermore, it was suggested that Q-type ribosomes synthesized under these conditions are more resistant to these inhibitory conditions.

Base Sequence↗
PubMed1999

The natural killer T (NKT) cell ligand alpha-galactosylceramide demonstrates its immunopotentiating effect by inducing interleukin (IL)-12 production by dendritic cells and IL-12 receptor expression on NKT cells.

The natural killer T (NKT) cell ligand alpha-galactosylceramide (alpha-GalCer) exhibits profound antitumor activities in vivo that resemble interleukin (IL)-12-mediated antitumor activities. Because of these similarities between the activities of alpha-GalCer and IL-12, we investigated the involvement of IL-12 in the activation of NKT cells by alpha-GalCer. We first established, using purified subsets of various lymphocyte populations, that alpha-GalCer selectively activates NKT cells for production of interferon (IFN)-gamma. Production of IFN-gamma by NKT cells in response to alpha-GalCer required IL-12 produced by dendritic cells (DCs) and direct contact between NKT cells and DCs through CD40/CD40 ligand interactions. Moreover, alpha-GalCer strongly induced the expression of IL-12 receptor on NKT cells from wild-type but not CD1(-/-) or Valpha14(-/-) mice. This effect of alpha-GalCer required the production of IFN-gamma by NKT cells and production of IL-12 by DCs. Finally, we showed that treatment of mice with suboptimal doses of alpha-GalCer together with suboptimal doses of IL-12 resulted in strongly enhanced natural killing activity and IFN-gamma production. Collectively, these findings indicate an important role for DC-produced IL-12 in the activation of NKT cells by alpha-GalCer and suggest that NKT cells may be able to condition DCs for subsequent immune responses. Our results also suggest a novel approach for immunotherapy of cancer.

Adjuvants, Immunologic↗
PubMed1999

Isolation of csm1 encoding a class V chitin synthase with a myosin motor-like domain from the rice blast fungus, Pyricularia oryzae.

A gene encoding a chitin synthase with a myosin motor-like domain (csm1) was isolated from Pyricularia oryzae using a PCR fragment amplified from a fungal chitin synthase conserved region. The deduced amino acid sequence of csm1 is homologous to that of CsmA of Aspergillus nidulans (65% identity). The putative gene product of csm1 is consisted of the myosin motor-like domain and a chitin synthase domain as in A. nidulans csmA. The chitin synthase domain of its C-terminus was also homologous to Aspergillus fumigatus ChsE (61.4% identity) and Ustilago maydis Chs6 (48.6% identity) that encode class V chitin synthases. Northern analysis demonstrated that the csm1 was expressed throughout the mycelial growth of P. oryzae. This is the first report on the isolation of the gene encoding a class V chitin synthase with the myosin motor-like domain from P. oryzae.

Amino Acid Sequence↗
PubMed1999

The essential role of phorbol ester-sensitive protein kinase C isoforms in activation-induced cell death of Th1 cells.

Th1 and Th2 cells, which were induced from naive T cells of TCR-transgenic mice, showed differential sensitivity to activation-induced cell death (AICD) triggered by stimulation with anti-CD3 monoclonal antibody. The Th1 cells showed more rapid AICD than Th2 cells. This accelerated AICD of Th1 cells was strongly blocked by protein kinase C (PKC) inhibitors (H-7 or GF 109203X). Moreover, long-term treatment of Th1 cells with phorbol 12-myristate 13-acetate (PMA) caused the abrogation of anti-CD3-induced AICD in parallel with the disappearance of PMA-sensitive PKC isoforms such as PKC alpha, gamma, epsilon and theta. Therefore, it was clearly demonstrated that PMA-sensitive PKC isoforms are essential for AICD of Th1 cells. The different susceptibility to AICD between Th1 and Th2 cells was not due to their differential expression levels of PMA-sensitive PKC isoforms but appeared to be due to their differential requirement for PMA-sensitive isoforms in the up-regulation of Fas ligand which is involved in suicide killing of activated Th1 cells.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1999

The quantitative and qualitative defect of CD4+ CD45RO+ memory-type T cells are involved in the abnormality of TH1 immunity in atopic dermatitis patients.

Peripheral blood mononuclear cells (PBMCs) obtained from atopic dermatitis (AD) patients produced low levels of IFN-gamma in response to Dermatophagoides farinae antigen (Der f Ag) plus IL-2 or OKT3 MoAb in contrast with PBMCs obtained from healthy donors. The reduced IFN-gamma production in AD patients' T cells appeared to be derived from the defect of CD4+ T cells but not CD8+ T cells. Indeed, from the cytoplasmic staining analysis of cytokines, it was demonstrated that the frequency of IFN-gamma producing CD4+ T cells (TH1 cells) in AD patients was markedly lower than that of healthy donors. From the phenotypic analysis using flow cytometry, it was also found that the number of CD4+ CD45RO+ memory type T cells was significantly reduced in AD patients compared with that of healthy donors. In addition to quantitative defect of memory type CD4+ T cells, functional defect of CD4+ CD45RO+ memory type T cells was also demonstrated in AD patients. Enriched CD4+ CD45RO+ T cells obtained from AD patients, who exhibited greatly reduced delayed-type hypersensitivity (DTH) response in tuberculin test, showed no significant TH1 immunity in terms of IFN-gamma production by stimulation with OKT3 MoAb or purified protein derivative (PPD). Thus, the immunological abnormality of TH1 immunity in AD patients appeared to be induced in concomitant with both the quantitative and qualitative defect of memory type CD4+ T cells.

Antibodies, Monoclonal↗
PubMed1999

Ingestion of guar gum hydrolysate, a soluble fiber, increases calcium absorption in totally gastrectomized rats.

Gastrectomy induces osteopenia. We examined the effects of feeding a diet containing soluble dietary fiber, guar gum hydrolysate (GGH, 50 g/kg diet), on intestinal calcium absorption and bone mineralization in totally gastrectomized (Roux-en-Y esophagojejunostomy) rats by comparing them with those in two control groups (laparotomized and bypassed rats). In the bypassed rats, chyme bypassed the duodenum and upper jejunum without gastrectomy. In a second separate experiment, we compared calcium absorption and bone mineralization in the gastrectomized rats fed diets containing soluble and insoluble calcium salts and in bypassed rats fed insoluble calcium. In Experiment 1, apparent absorption of calcium supplied as a water-insoluble salt was more than 50% lower in gastrectomized rats than in the intact (laparotomized) or bypassed rats 3 wk after the start of feeding the test diets (P < 0.05). Calcium absorption was higher (P < 0.05) in gastrectomized rats fed the GGH diet than in those rats fed the GGH-free diet. In Experiment 2, absorption of soluble calcium in the gastrectomized rats did not differ from the absorption of calcium from calcium carbonate by bypassed rats. The soluble calcium pool in the cecal contents was significantly lower in gastrectomized rats (Experiment 1) than in intact or bypassed control rats, and was higher (P < 0.05) in the GGH-fed gastrectomized rats than in those fed the GGH-free diet. However, calcium absorption correlated most closely (r = 0.787, P < 0.01) with cecal propionic acid concentration. The femur calcium content was significantly lower in gastrectomized rats fed insoluble calcium than in bypassed rats fed the same diet, but was partially restored in the rats fed soluble calcium (Experiment 2). Bone calcium was not increased by feeding GGH in gastrectomized rats (Experiment 1). We conclude that the severely diminished calcium absorption following total gastrectomy is totally due to a decrease in calcium solubilization, and feeding GGH partially restores calcium absorption. The decrease in bone calcium that occurs as a result of gastrectomy is mainly due to diminished intestinal calcium absorption.

Administration, Oral↗
PubMed1999

High-linoleate and high-alpha-linolenate diets affect learning ability and natural behavior in SAMR1 mice.

Semipurified diets incorporating either perilla oil [high in alpha-linolenate, 18:3(n-3)] or safflower oil [high in linoleate, 18:2(n-6)] were fed to senescence-resistant SAMR1 mouse dams and their pups. Male offspring at 15 mo were examined using behavioral tests. In the open field test, locomotor activity during a 5-min period was significantly higher in the safflower oil group than in the perilla oil group. Observations of the circadian rhythm (48 h) of spontaneous motor activity indicated that the safflower oil group was more active than the perilla oil group during the first and second dark periods. The total number of responses to positive and negative stimuli was higher in the safflower oil group than in the perilla oil group in the light and dark discrimination learning test, but the correct response ratio was lower in the safflower oil group. The difference in the (n-6)/(n-3) ratios of the diets reflected the proportions of (n-6) polyunsaturated fatty acids, rather than those of (n-3) polyunsaturated fatty acids in the brain total fatty acids, and in the proportions of (n-6) and (n-3) polyunsaturated fatty acids in the total polyunsaturated fatty acids of the brain phospholipids. These results suggest that in SAMR1 mice, the dietary alpha-linolenate/linoleate balance affects the (n-6)/(n-3) ratio of brain phospholipids, and this may modify emotional reactivity and learning ability.

Aging↗
PubMed1999

Null mutation in IRE1 gene inhibits overproduction of microsomal cytochrome P450Alk1 (CYP 52A3) and proliferation of the endoplasmic reticulum in Saccharomyces cerevisiae.

Overproduction of microsomal cytochrome P450Alk1 (P450Alk1) of Candida maltosa in Saccharomyces cerevisiae resulted in an extensive proliferation of endoplasmic reticulum (ER) and induction of Kar2p and Pdi1p. The ire1 null mutation severely suppressed ER proliferation, reduced the level of functional P450Alk1, and showed no induction of these ER chaperones, suggesting that the function of Ire1p is required for ER proliferation upon the overproduction of P450Alk1. Cerulenin, a potent inhibitor of lipid biosynthesis, also induced these chaperones in an Ire1p-dependent manner and limited the production of functional P450Alk1. These results imply that Ire1p may function to restore the balance between membrane proteins and lipids of the ER when the ER is relatively overcrowded by membrane proteins.

Cytochrome P-450 Enzyme System↗
PubMed1999

[An analysis of fever of unknown origin defined by newly proposed practical criteria. A prospective study of 56 cases].

The criteria proposed by Petersdorf has been in use internationally to define the fever of unknown origin (FUO) since 1961 and the research of FUO has progressed with this criteria. Mean-while, new diagnostic methods have been developed and illness behavior of febrile patients has changed considerablly. Accordingly, the definition by Petersdorf is becoming less matched to current clinical situation. Therefore, we have developed a new practical criteria of FUO; i.e., out-patients who are febrile more than 2 weeks, documented temperature higher than 37.5 degrees C at least on one occasion and undetermined diagnosis and in-patients who are febrile more than 1 week with documented temperature higher than 37.5 degrees C, and undetermined diagnosis. Between October 1, 1993, and October 31, 1996, we prospectively collected a series of febrile patients who fulfilled our new criteria. We identified 56 patients by our criteria (23 male and 33 female, age: 49.7 +/- 20.6. range 15 to 88). Of this 56 patients, 19 (32%) were found to have infections, 18 (31%) had collagen disorders, 5 (9%) had malignancy and 6 (10%) had died. Of 56 patients, 38 (68%) were in the newly added group. Of these 38 patients, 4 patients had subacute necrotizing lymphoadenitis, 4 cytomegalovirus infection, 3 polymyalgia rheumatica, 3 tuberculosis. Four patients (10%) died. With our criteria, febrile patients who previously had not been included were found to have as poor a prognosis as with the Petersdorf group.

Adolescent↗
PubMed1999

Proliferation of intrahyphal hyphae caused by disruption of csmA, which encodes a class V chitin synthase with a myosin motor-like domain in Aspergillus nidulans.

We have found that the Aspergillus nidulans csmA gene encodes a novel protein which consists of an N-terminal myosin motor-like domain and a C-terminal chitin synthase domain (M. Fujiwara, H. Horiuchi, A. Ohta, and M. Takagi, Biochem. Biophys. Res. Commun. 236:75-78, 1997). To clarify the roles of csmA in fungal morphogenesis, we constructed csmA null mutants. The growth rate of the mutant colonies was almost the same as that of the wild-type strain, but hyphal growth was severely inhibited when a chitin-binding reagent, Calcofluor white or Congo red, was added to the medium. Moreover, morphological abnormalities in tip growth and septum formation were identified microscopically. Proliferation of intracellular new hyphae, called intrahyphal hyphae, which behaved as intrinsic hyphae, was the most striking phenotypic feature among them. These phenotypes were not suppressed when the only chitin synthase domain of csmA was expressed under the control of the alcA promoter, whereas they were suppressed when the intact form of csmA was expressed. Therefore, it was concluded that the product of csmA (CsmA) has important roles in polarized cell wall synthesis and maintenance of cell wall integrity and that the myosin motor-like domain is indispensable for these functions.

Aspergillus niger↗
PubMed1998

Studies on cycloheximide-sensitive and cycloheximide-resistant ribosomes in the yeast Candida maltosa.

Cycloheximide sensitivity or resistance in yeast is under the control of genes encoding different forms of ribosomal protein L41. In our previous studies, we have shown by isolating L41-Q1a, L41-P1a and their respective allelic genes, L41-Q1b and L41-P1b, from the partial diploid genome of C. maltosa, that this species, which is inducibly resistant to CYH, has both types of the L41 genes and that the expression of at least one of the L41-Q genes is induced by CYH, whereas L41-P genes are constitutively expressed. Here, we have identified another L41 (L41-Q2a), its allelic gene (L41-Q2b) and a third gene (L41-Q3) from the genome of C. maltosa. By gene disruption experiments, we now show that L41-Q1a and L41-Q1b are not responsible for the resistance to CYH and that the DeltaL41-Ps strain, which has only functional L41-Q genes, shows constitutive resistance to CYH, but grows more slowly than the DeltaL41-Qs strain, which has only functional L41-P genes, in the absence of CYH. Our results also show that in vitro, ribosomes containing L41-Q-type are less active in translation than those containing L41-P-type, although only the former ribosomes are active in the presence of CYH. These data suggest that ribosomes containing L41-Q-type are less active under normal growth conditions, but that this activity is not affected in the presence of CYH. We discuss the possible multi-step evolutionary event(s) by which C. maltosa has acquired the property of inducible resistance to CYH.

Amino Acid Sequence↗
PubMed1998

Isolation of a class IV chitin synthase gene from a zygomycete fungus, Rhizopus oligosporus.

We found the presence of DNA sequence which shows sequence similarity to the class IV chitin synthase gene (CHS3) of Saccharomyces cerevisiae in the genome of 14 Rhizopus species which belong to zygomycetes. We cloned a gene (chs3), which might correspond to one of these homologous sequences, from Rhizopus oligosporus by low stringency plaque hybridization probed with CHS3. The deduced amino acid sequence of this gene showed highest similarity to the class IV chitin synthase of Neurospora crassa (46.7% identity over 1087 amino acids), showing that this gene encodes a class IV chitin synthase. Northern analysis revealed the differential expression pattern of this gene in the asexual life cycle with highest expression in the early stage of asexual spore formation. This is the first report of the isolation and analysis of a class IV chitin synthase gene from zygomycete fungi.

Amino Acid Sequence↗
PubMed1998

Relation between evolutionary distance and enzymatic properties among the members of the CYP52A subfamily of Candida maltosa.

The CYP52A subfamily of the alkane-assimilating yeast Candida maltosa consists of six structurally related isoforms. Four of them (CYP52A3, 4, 5, and 9) are strongly induced by alkanes and play an important role for the conversion of various alkanes and fatty acids. Taking advantage of a homologous overexpression system, we found in the present study that both of the two other CYP52A forms, CYP52A10 and CYP52A11, represent specialists for the hydroxylation of lauric acid suggesting their preference for short-chain fatty acids. At the same time, they hydroxylated palmitic acid only moderately and failed to convert hexadecane. Based on the now completed knowledge about the principal substrate specificities of all members of the CYP52A subfamily of C. maltosa, it became apparent that evolutionarily more distantly related P450 forms developed either to alkane or to fatty acid hydroxylases, whereas P450 forms which retained the ability to convert both types of substrates were also found to be evolutionarily related to both alkane and fatty acid hydroxylases.

Candida↗