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Biomedical subjects

A Ohta

Publications and source records attributed to A Ohta.

At least 127 records · Page 7Linked to original sources
PubMed1997

Involvement of IL-4-producing Vbeta8.2+ CD4+ CD62L- CD45RB- T cells in non-MHC gene-controlled predisposition toward skewing into T helper type-2 immunity in BALB/c mice.

It was found that freshly isolated BALB/c CD4+ T cells produced high levels of IL-4 and IL-10 in response to immobilized anti-CD3 mAb, while C57BL/6 CD4+ T cells produced low amounts of IL-4 and IL-10. The high IL-4-producing ability of BALB/c mice was demonstrated to be genetically dominant and it was controlled by non-MHC gene (or genes). The cells responsible for IL-4 production in BALB/c mice were defined as TCRVbeta8.2+ CD4+ CD62L- CD45RB- memory-type T cells, which were distinct from NK1.1+ CD4+ NKT cells. Although these memory-type T cells were also detected in C57BL/6 mouse spleen at the same frequency, they showed a functionally different property from BALB/c CD4+ CD62L- CD45RB- T cells in terms of IL-4 production. The fact that germfree BALB/c mouse spleen cells also produced high levels of IL-4 suggested that the IL-4 producer in BALB/c mice might be developed under the influence of unknown factors other than environmental Ags. The CD4+ CD62L- CD45RB- T cells obtained from BALB/c mice accelerated the development of IL-4-producing memory-type CD4+ T cells from CD4+ CD62L+ CD45RB+ naive T cells prepared from OVA-specific TCR-transgenic mice. Therefore, IL-4-producing CD4+ CD62L- CD45RB- T cells might play an important role in the preferential induction of Th2-dominant immunity in BALB/c mouse strain.

Animals↗
PubMed1997

The Aspergillus nidulans genes chsA and chsD encode chitin synthases which have redundant functions in conidia formation [corrected and republished article originally appeared in Mol Gen Genet 1996 Jun; 251(4):442-50].

We previously isolated three chitin synthase genes (chsA, chsB, and chsC) from Aspergillus nidulans. In the present work, we describe the isolation and characterization of another chitin synthase gene, named chsD, from A. nidulans. Its deduced amino acid sequence shows 56.7% and 55.9% amino acid identity, respectively, with Cal1 of Saccharomyces cerevisiae and Chs3 of Candida albicans. Disruption of chsD caused no defect in cell growth or morphology during the asexual cycle and caused no decrease in chitin content in hyphae. However, double disruption of chsA and chsD caused a remarkable decrease in the efficiency of conidia formation, while double disruption of chsC and chsD caused no defect. Thus it appears that chsA and chsD serve redundant functions in conidia formation.

Amino Acid Sequence↗
PubMed1997

Galactose-inducible expression systems in Candida maltosa using promoters of newly-isolated GAL1 and GAL10 genes.

The GAL1 and GAL10 gene cluster encoding the enzymes of galactose utilization was isolated from an asporogenic yeast, Candida maltosa. The structure of the gene cluster in which both genes were divergently transcribed from the central promoter region resembled those of some other yeasts. The expression of both genes was strongly induced by galactose and repressed by glucose in the medium. Galactose-inducible expression vectors in C. maltosa were constructed on low- and high-copy number plasmids using the promoter regions of both genes. With these vectors and the beta-galactosidase gene from Kluyveromyces lactis as a reporter, galactose-inducible expression was confirmed. Homologous overexpression of members of the cytochrome P-450 gene family in C. maltosa was also successful by using a high-copy-number vector under the control of these promoters.

Amino Acid Sequence↗
PubMed1997

Protein quality--a determinant of the intracellular fate of membrane-bound cytochromes P450 in yeast.

To elucidate mechanisms determining the intracellular localization of cytochromes P450, authentic and mutant cytochromes P450 52A4 (P450Cm2) and P450 52A5 (P450Alk2A) were heterologously expressed in Saccharomyces cerevisiae and the ultrastructure of the respective transformants was investigated by means of immunoelectron microscopy. As a result, overproduction of both wild-type P450 forms resulted in a massive proliferation of tubular membrane structures distributed over the whole cytoplasm. In contrast, all mutant P450Cm2 and Alk2A forms tested were mainly localized within stacks of paired membranes which often occurred in close vicinity to the nucleus. As found by serial sectioning of a single cell, these stacked membranes bearing the mutant P450 actually represented plates of consecutive membranes arranged one upon the other. A tubular network of endoplasmic reticulum membranes as observed after expression of the wild-type proteins could not be detected. Generally, the kind of mutation introduced into the P450 forms did not influence the morphology of the induced membranes. Even single amino acid exchanges in the cytosolic domain caused the formation of membrane stacks. The common feature of all mutant P450 forms causing the formation of stacked membranes was, however, their lower protein stability after heterologous expression in the S. cerevisiae host cells, compared to the stability of the authentic cytochromes P450. Furthermore, the proliferated membranes containing the different P450 forms were characterized by means of subcellular fractionation experiments. Using this approach, clear differences in the distribution of spectrally active and inactive P450 molecules were found. The results obtained suggest the presence of an intracellular sorting mechanism based on the protein quality, which finally leads to the differences in the intracellular distribution of wild-type and mutant cytochromes P450.

Candida↗
PubMed1997

Polycistronic expression and RNA-binding specificity of the C. elegans homologue of the spliceosome-associated protein SAP49.

Splicing of mRNA precursors (pre-mRNAs) occurs in a multimolecular complex, termed spliceosome, which is comprised of pre-mRNA, small nuclear ribonucleoprotein particles (snRNPs), and other protein factors including spliceosome-associated proteins (SAPs). SAP49 is thought to be a subunit of the essential splicing factor SF3b and is involved in U2 snRNP function in mammalian cells. We have isolated a Caenorhabditis elegans cDNA encoding an RNA-binding protein with two RNA recognition motifs (RRMs) which shows extensive similarity to the human SAP49. The primary transcript for this C. elegans SAP49 homologue (cSAP49) seems to contain at least two additional cistrons and can be processed into three different mature mRNAs by trans-splicing. The cSAP49 mRNA, like other mRNAs in the same polycistronic unit, is expressed in most of the developmental stages, consistent with its putative essential function for mRNA splicing. By means of an in vitro RNA selection system, we demonstrate that cSAP49 possesses specific RNA-binding activity which resides in its second RRM.

Amino Acid Sequence↗
PubMed1997

Different female reproductive phenotypes determined by human growth hormone (hGH) levels in hGH-transgenic rats.

The effect of continuous human GH (hGH) secretion on female reproduction was studied in adult female transgenic rats expressing the hGH gene with a mouse whey acidic protein (mWAP) promoter. Two lines of transgenic female rats carrying the mWAP/hGH gene were established and used in the study. One was characterized by relatively high levels of serum hGH (high line), and the other had relatively low levels (low line). High-line female rats had recurring, pseudopregnancy-like estrous cycles accompanied by increased serum progesterone levels for 2 wk after ovulation, and they were fertile. In these rats, luteinization occurred spontaneously without cervical stimulation, probably due to high levels of serum hGH, which has prolactin (PRL)-like activity in the rat. Although low-line female rats had recurring, regular 4-day estrous cycles, they were sterile. In these rats, pseudopregnancy could not be induced by mating or by mechanical cervical stimulation. PRL surges following cervical stimulation were not detected, and PRL secretion was not induced by a dopamine antagonist, metoclopramide. The ovarian tissue in this line had a much higher number of corpora lutea and grew much heavier than in normal littermates, suggesting impairment of PRL-induced structural luteolysis. Suppression of PRL secretion in low-line rats was, at least in part, due to a marked decrease in the number of lactotrophs in the pituitary. The present study shows that the serum hGH level plays a crucial role in regulating luteal function in female transgenic rats expressing the hGH gene.

Animals↗
PubMed1997

Evidence that part of a centromeric DNA region induces pseudohyphal growth in a dimorphic yeast, Candida maltosa.

We observed that a YCp-type vector having the centromeric DNA (CEN) sequence previously isolated from the genome, but not a YRp-type vector lacking the CEN sequence, induced pseudohyphal growth in a dimorphic fungi, Candida maltosa, which had been shown to be closely related to Candida albicans by phylogenetic analysis. Deletion analysis of the CEN sequence revealed that the intact CEN sequence was not required for the induction, but part of it, having partial centromeric activity, was enough for the induction. By screening the gene library of this yeast for the sequences which induced pseudohyphal growth, we isolated three different DNA fragments which also had part of the centromere-like sequence. Partial centromeric activity of these fragments was confirmed by three criteria: low copy number and high stability of the plasmids carrying these fragments and rearrangement at high frequency of the plasmid DNA with one of these fragments plus the CEN sequence. Furthermore, when the GGTAGCG sequence commonly found in one copy in each of these four sequences was mutated in the CEN sequence by site-directed mutagenesis, both partial centromeric activity and pseudohyphal growth-inducing activity of the CEN sequence were lost. These results indicated that part of CEN region with partial centromeric activity induces pseudohyphal growth in C. maltosa. It is suggested that some cellular components which interact with the sequence containing GGTAGCG required for centromeric activity are involved in the regulation of the transition between yeast forms and pseudohyphal forms of the cells.

Base Sequence↗
PubMed1997

Anti-platelet aggregation activity of some pyrazines.

This report describes the anti-platelet aggregation activity of 48 pyrazines. Among alkyl- and arylpyrazines tested, 2,3-diphenylpyrazines showed the strongest anti-platelet aggregation activity. Then, various substituents were introduced into the phenyl groups, and the 2,3-bis(p-methoxyphenyl)pyrazine derivatives were consequently found to possess considerably strong inhibitory activity.

Animals↗
PubMed1997

[Reactions and syntheses of pyrazines].

This review deals with syntheses and reactions of pyrazines, especially, of 2,5-disubstituted pyrazines. The description was made in due to order of 1) synthesis and properties of 2,5-disubstituted pyrazines, 2) synthesis of 2,5-disubstituted pyrazine N-oxides, 3) synthesis of pyrazinols, 4) synthesis and utilization of pyrazinethiols; preparation of aldehydes, utilization as an acyl carrier, and preparation of olefins via the elimination of pyrazinylsulfinyl group, 5) synthesis of aminopyrazines, 6) synthesis of azidopyrazines and their transformation to imidazoles, 7) palladium-catalyzed reactions of chloropyrazines; dechlorination, introduction of cyano, alkenyl, alkynyl, alkyl, and aryl groups to the pyrazine ring. The cross-coupling of chloropyrazines with aromatic heterocycles such as furan, thiophene, pyrroles, indoles, benzo[b]furan, benzo[b]thiophene, oxazole, thiazole, benz[b]oxazole, and benzo[b]thiazole is also described.

Pyrazines↗
PubMed1997

[Physiological and pharmacological activities of simple alkyl- and arylpyrazines].

This review describes the physiological and pharmacological effect of simple alkyl- and arylpyrazines. The description is made in the following order 1) the presence of 2,5-dimethylpyrazine in the urine samples of human being and rodents 2) the effects of tetramethyl- and tetraethylpyrazines on the vascular smooth muscles 3) the activity of alkyl- and arylpyrazines on the aggregation of arachidonic acid- and collagen-induced platelets 4) the effects of 2,5-dimethylpyrazine on the reproductive and the accessory reproductive organs of female and male rats 5) the effects of 2,5-dimethylpyrazine on the plasma and on the contents of polyamines and fructose in the accessory reproductive organs of rats.

Animals↗
PubMed1997

[A case of Wegener's granulomatosis associated with refractory bowel granulomatous ulcers].

We describe a 58-year-old woman who developed Wegener's granulomatosis (WG) complicated by a perforation of the transverse colon caused by necrotizing granulomatous vasculitis. In addition, her colon lesion continued in spite of high dose corticosteroid and cyclophosphamide therapy. She was admitted to our hospital because of her severe tonsillitis in Dec., 1994. She was diagnosed as having WG because she had oral ulcer, antibiotics-resistant lung infiltration, renal dysfunction and positive C-ANCA. Just after we started high dose steroid therapy, the transverse colon was perforated because of vasculitis, and she underwent emergency operation. Many vasculitic lesions were found in the small intestine, colon, and mesenterium. The disease was improved by corticosteroid and cyclophosphamide therapy except for a sustained ulcer with necrotizing vasculitis in the sigmoid colon region even 1 year after the operation. Although WG rarely complicates digestive tract lesions as initial manifestations, they reach 12% of the causes of death of WG in Japan. Therefore, we should take care of digestive tract lesions when we follow-up patients with WG.

Antibodies, Antineutrophil Cytoplasmic↗
PubMed1997

Estimated prevalence and incidence of adult Still's disease: findings by a nationwide epidemiological survey in Japan.

To estimate prevalence and incidence of adult Still's disease in Japan, and to describe the epidemiological features of the patients, a nationwide epidemiological survey was conducted in 1994. The study consisted of two questionnaires which were distributed to the heads of the relevant departments, randomly sampled, in hospitals throughout Japan. Following major epidemiological findings emerged from the study: (a) The total annual number of patients treated for adult Still's disease was estimated as 1,100 in 1993 in Japan. The estimated crude prevalence among those aged 16 years or older were calculated as 0.73 and 1.47 per 100,000 population for males and females, respectively, with the corresponding crude incidence rate of 0.22 and 0.34. (b) The sex ratio (female to male) of the reported patients was 2.1. This female predominance might be specific to Japan, though additional surveys in other countries will be warranted. The mean age of the patients was 38.1 years, and female patients tended to be older than male ones; 50% of the female patients aged 40 years or older, while so did only 28% of the male patients.

Adolescent↗
PubMed1997

In vivo absorption of calcium carbonate and magnesium oxide from the large intestine in rats.

This study was conducted to evaluate the ability of the large intestine to absorb calcium (Ca) and magnesium (Mg) from their sparingly water-soluble salts, and also to determine whether fructooligosaccharides (FOS) stimulate the absorption of these minerals in rat large intestine in vivo. Rats were fed Ca- and Mg-free diets with and without 5% FOS. An aqueous suspension of CaCO3 and MgO was infused into the stomach via a gastric tube or into the cecum via an implanted catheter. Coprophagy was prevented by using wire-mesh anal cups throughout the experiment so as to exclude the re-ingestion of feces as an oral mineral source. In rats fed an FOS-free diet, the absorption degrees of Ca and Mg infused into the cecum were the same as those infused into the stomach. The absorption degree of phosphorus (P) was slightly but significantly higher in rats with the infusion of Ca and Mg into the cecum than in rats with the infusion of Ca and Mg into the stomach. FOS-feeding increased the absorption of Mg to a similar extent in either case of infusion via cecal and oral routes, while FOS-feeding did not increase the absorption of Ca in rats with infusion of Ca and Mg into the cecum. We concluded that both CaCO3 and MgO are absorbed in the large intestine, and we ascertained that the increasing effect of FOS on the absorption of Mg took place mainly in the large intestine.

Analysis of Variance↗
PubMed1997

The alginate reduce the postprandial glycaemic response by forming a gel with dietary calcium in the stomach of the rat.

Soluble dietary fibers include an alginate which reduces the postprandial glycaemic response. We speculated that the cause of the reduction of alginate on the glycaemic response is the gel formation of alginate with dietary calcium in the stomach. The aim of the present study was to confirm our hypothesis and to examine the effect of the sugar composition of alginates on the glycaemic response and the effect of continuous feeding of alginate-containing diet to rats. Diabetic rats were made by injecting streptozotocin (STZ) intravenously. These rats were fed 5 g of the experimental diet with or without sodium alginate and with or without calcium after overnight fasting. In the rats fed the diet containing both alginate and calcium, the postprandial glycaemic response was lower than in the rats fed other diets and gastric contents were retained as gel form. Three beta-d-mannuronic acid (M) to alpha-l-guluronic acid (G) (ratios (M/G 0.5, 1.3, 2.1) of alginates were not associated with the acute glycaemic response in STZ rats. Then, we fed normal rats with an alginate-free or one of three respective alginate-containing diets for 4 weeks. During the first 2 weeks of the feeding period, the total amount of food intake of rats fed the G-rich alginate diet was smaller than that of rats in the other dietary groups. Moreover, the weight of the dorsal abdominal adipose tissue of rats given the G-rich alginate diet was the lowest among the dietary groups. We conclude that the reductive effect of alginate feeding on the postprandial glycaemic response was not caused only by their inherent viscosity, but also by gel formation with dietary calcium in the stomach. Moreover, it is necessary to pay attention to the M/G ratio of alginates for estimating their physiological effect.

Adipose Tissue↗
PubMed1997

[Severe aortic regurgitation with marked thickening of the aortic annulus: a case report].

A 74-year-old woman with severe aortic regurgitation and marked thickening of the aortic annulus received aortic valve replacement. Transesophageal echocardiography demonstrated marked thickening of the aortic annulus. The maximum thickness of the aortic annulus was about 11 mm at the side of the right coronary cusp. Histological examination revealed non-specific inflammation of the aortic annulus and aortic valve chiefly composed of lymphocytes and plasma cells. Thickening of the aortic annulus associated with inflammatory aortitis was the cause of aortic regurgitation in this patient.

Aged↗
PubMed1996

Functional characterization of NK1.1 + Ly-6C+ cells.

It was found that NK1.1+ cells were subdivided by their different expression pattern of Ly-6C antigen. To characterize their functional significance in immunoregulation, we separated NK1.1 + Ly6C+ cells and NK1.1 + Ly-6C- cells from C57BL/6 mouse nylon-passed spleen cells by FACStar. Both NK1.1 + Ly-6C+ and NK1.1 + Ly-6C- cells responded to the stimulation with IL-2 plus IL-12 and showed strong cytotoxicity against YAC-1 cells. However, these cells revealed different ability in terms of IFN-gamma production. Only NK1.1 + Ly-6C+ cells, but not NK1.1 + Ly-6C- cells, cultured with IL-12 alone or IL-2 plus IL-12, produced high levels of IFN-gamma. Flow cytometric analysis demonstrated that NK1.1 + Ly-6C+ cells consisted of NK1.1 + CD3-Ly-6C+ NK cells and NK1.1 + CD3 + Ly-6C+ NKT cells. Therefore, we further separated these two populations from NK1.1 + Ly-6C+ cells to define their functions. Although, both NK1.1 + CD3-Ly-6C+ NK cells and NK1.1 + CD3+ NKT cells showed the same level of cytotoxicity. It was clearly demonstrated that NK1.1 + CD3+Ly-6C+ NKT cells were major immunoregulatory cells to produce IFN-gamma in respond to IL-12 alone or IL-2 plus IL-12.

Animals↗
PubMed1996

The CYP52 multigene family of Candida maltosa encodes functionally diverse n-alkane-inducible cytochromes P450.

The n-alkane-assimilating yeast Candida maltosa contains several structurally related cytochromes P450 (P450) encoded by the CYP52 multigene family, which are inducible by various long-chain hydrocarbons and fatty acids and which are responsible for the initial hydroxylation steps in the metabolism of these substrates. In the present work, the four major n-alkane-inducible C. maltosa P450 forms; CYP52A3, CYP52A4, CYP52A5, and CYP52A9, were enzymatically characterized, taking advantage of heterologous P450/reductase coexpression in Saccharomyces cerevisiae. Testing various alkanes and fatty acids, distinct preferences of the individual P450 forms concerning substrate class and chain length were detected, thus providing new insight into the functional diversity of the C. maltosa CYP52 family. Moreover, the results obtained emphasize these structurally related enzymes as a powerful tool for future studies on P450 structure-function relationships.

Alkanes↗