Biomedical subjects

A Ohta

Publications and source records attributed to A Ohta.

At least 73 records · Page 4Linked to original sources

PubMed1999

Role of the costimulatory molecule CD28 in the development of lupus in MRL/lpr mice.

MRL/Mpj-lpr/lpr (MRL/lpr) mice develop autoimmune disorders, including lymphoproliferation, glomerulonephritis, autoantibody production, and hypergammaglobulinemia. To investigate the role of the costimulatory molecule CD28 in the development of these disorders, MRL/lpr mice lacking CD28 were generated by gene targeting. Compared with CD28+/+ MRL/lpr mice, CD28-/- MRL/lpr mice showed decreased lymphadenopathy but increased splenomegaly associated with the expansion of abnormal B220+ TCRalphabeta+ T cells. Although levels of IgM Abs were unchanged in CD28-/- MRL/lpr mice, the production of anti-DNA IgG Abs and IgG rheumatoid factors were suppressed. IgG deposition in the glomeruli was markedly decreased, and the development of glomerulonephritis was significantly retarded. Furthermore, renal vasculitis and arthritis were absent in CD28-/- MRL/lpr mice. These results indicate that, although CD28 is not required for the generation of the abnormal T cell population in MRL/lpr mice, it does play an important role in the development of autoimmune disease in these animals.

Animals↗

PubMed1999

Distinct role of antigen-specific T helper type 1 (Th1) and Th2 cells in tumor eradication in vivo.

The role of T helper type 1 (Th1) and Th2 cells in tumor immunity was investigated using Th cells induced from ovalbumin (OVA)-specific T cell receptor transgenic mice. Although Th1 cells exhibited stronger cytotoxicity than Th2 cells, both cell types completely eradicated tumors when transferred into mice bearing A20 tumor cells transfected with the OVA gene (A20-OVA). Th1 cells eradicated the tumor mass by inducing cellular immunity, whereas Th2 cells destroyed the tumor by inducing tumor necrosis. Both Th1 and Th2 cells required CD8(+) T cells to eliminate tumors, and neither of these cells were able to completely eliminate A20-OVA tumors from T and B cell-deficient RAG2(-/-) mice. Mice cured from tumors by Th1 and Th2 cell therapy rejected A20-OVA upon rechallenge, but CD8(+) cytotoxic T lymphocytes were induced only from spleen cells prepared from cured mice by Th1 cell therapy. Moreover, we demonstrated that Th1 and Th2 cells used distinct adhesion mechanisms during tumor eradication: the leukocyte function-associated antigen (LFA)-1-dependent cell-cell adhesion step was essential for Th1 cell therapy, but not for Th2 cell therapy. These findings demonstrated for the first time the distinct role of antigen-specific Th1 and Th2 cells during eradication of established tumors in vivo.

Animals↗

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

B cells lacking RP105, a novel B cell antigen, in systemic lupus erythematosus.

OBJECTIVE: RP105 is a leucine-rich repeat (LRR) protein found on all mature mouse B cells. Its function is poorly defined, although it has been suggested that RP105 activates B cells to make them resistant to apoptosis. The human homolog of RP105 has been reported, but knowledge of its function is limited. We explored the expression and the function of the human homolog of murine RP105 on B cells in patients with systemic lupus erythematosus (SLE). METHODS: The expression of RP105 and various markers on B cells in patients with SLE was analyzed using monoclonal antibodies and flow cytometry. Susceptibility to corticosteroid-induced apoptosis was examined by annexin V binding, and the production of immunoglobulin by RP105-negative B cells was examined by intracellular staining of IgG. RESULTS: As in mice, virtually all B cells in the peripheral blood of normal humans expressed the RP105 molecule. However, a significant proportion of circulating B cells (15.9%) in SLE patients were RP105 negative. Serial analyses of B cells in 7 SLE patients revealed that RP105-negative B cells markedly decreased in parallel with a reduction in disease activity (from 35.2% to 3.3%; P = 0.000003). The SLE Disease Activity Index and serum levels of IgG also correlated with the percentage of RP105-negative B cells. The phenotype of RP105-negative B cells was defined as CD95-positive, CD86-positive, CD38-bright, IgD-negative, IgM-dull, indicating that the cells were highly activated, as further suggested by the detection of intracellular IgG. RP105-negative B cells were clearly distinct from CD5-positive B1 cells. In vitro experiments indicated that RP105-negative B cells were susceptible to corticosteroid-induced apoptosis. CONCLUSION: These findings suggest that loss of RP105 is associated with B cell activation and increased disease activity in SLE patients.

Adrenal Cortex Hormones↗

PubMed1999

Unfolded protein response-induced BiP/Kar2p production protects cell growth against accumulation of misfolded protein aggregates in the yeast endoplasmic reticulum.

Overproduction of delta(pro), a mutated secretory proteinase derived from a filamentous fungus Rhizopus niveus, results in formation of gross aggregates (delta(pro) aggregates) in the yeast endoplasmic reticulum (ER) lumen, activation of the unfolded protein response (UPR) and ER membrane proliferation. To investigate the roles of the UPR against the delta(pro) aggregates, we constructed an IRE1-deleted ((delta)ire1) strain. In contrast to wild-type cells, (delta)ire1 cells ceased to grow several hours after the overproduction of (delta)pro. Two lines of evidence argued against the possibility that the growth defect was due to the inability to make extra ER membrane which accommodates the (delta)pro aggregates. First, by electron microscopy, ER membrane proliferation was observed in (delta)ire1 cells overproducing (delta)pro. Second, disruption of the OPI1 gene in the (delta)ire1 mutant, which is considered to derepress the activities of phospholipid-synthesizing enzymes, did not restore the growth upon the overproduction of (delta)pro. Instead, the growth was restored when an extra copy of the KAR2 gene, which encodes yeast BiP, was introduced, indicating that an increase in the amount of BiP is essential for cell growth when the (delta)pro aggregates accumulate in the ER. Since BiP is included in the insoluble (delta)pro aggregates, it is likely that the amount of free BiP in the ER lumen is insufficient without the UPR to fully exert its functions. Consistently, overproduction of (delta)pro impaired protein translocation and folding in (delta)ire1 cells but not in wild-type cells. The tunicamycin sensitivity of (delta)ire1 cells was also suppressed by extra expression of KAR2, suggesting that BiP plays a principal role in protecting cell growth against misfolded proteins accumulated in the ER.

Base Sequence↗

PubMed1999

Measurement and prediction of hydrophobicity parameters for highly lipophilic compounds: application of the HPLC column-switching technique to measurement of log P of diarylpyrazines.

In the preparatory stage of structure-activity relationship (QSAR) studies of anti-platelet aggregant pyrazine derivatives, log P values (P: 1-octanol/water partition coefficient) of diarylpyrazines were measured by a newly developed HPLC column-switching technique. The system consists of two processes: (1) adsorption of the sample at the top end of a short precolumn, and then (2) quantifying the enriched analyte by a conventional analytical column. By using the log P values thus obtained, the correction factor for the steric hindrance caused by the vicinal diphenyl groups was estimated. The log k values (k; retention factor) were also measured with methanol-buffer (pH 7.4) eluents and related to log P. The eluent of 50% methanol content (M50) gave a good linear relationship over a wide range of log P (-0.3< log P < 5.2), indicating that log k(M50) parameter is useful for predicting the log P value.

Chemical Phenomena↗

PubMed1999

Dietary heme iron does not prevent postgastrectomy anemia but fructooligosaccharides improve bioavailability of heme iron in rats.

Gastrectomized rats exhibit iron deficiency anemia. We observed the effects of dietary heme-iron and short chain frucooligosaccharides (Sc-FOS) in relation to prevention of postgastrectomy anemia in rats. Twelve laparotomized (sham-operated) rats were fed iron-citrate (control) as iron source diet without or with Sc-FOS (75 g/kg of diet) and twenty four totally gastrectomized (Bilroth II) rats, were fed a iron-citrate (control) or heme-iron (heme) as iron source diet without or with Sc-FOS (75 g/kg of diet) for 4 weeks. All rats received an intramuscular injection of vitamin B-12 every two weeks. Tail blood was collected every other week for determination of hematocrit and hemoglobin concentration. At the end of the experiment, the rats were killed and whole blood was collected. The total gastrectomy induced the postgastrectomy anemia. Dietary Sc-FOS increase iron absorption and thereby prevented completely this anemia in gastrectomized rats fed the control diet but this effect of Sc-FOS in rats fed heme diet was not complete. Dietary heme iron could not prevent postgastrectomy anemia itself, but fructooligosaccharides improve bioavailability of not only non-heme iron such as iron-citrate, but also heme-iron in rats.

Anemia↗

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↗