Biomedical subjects

A Ohta

Publications and source records attributed to A Ohta.

At least 145 records · Page 8Linked to original sources

PubMed1996

The Aspergillus nidulans genes chsA and chsD encode chitin synthases which have redundant functions in conidia formation.

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↗

PubMed1996

Degradation of Rhizopus niveus aspartic proteinase-I with mutated prosequences occurs in the endoplasmic reticulum of Saccharomyces cerevisiae.

Rhizopus niveus aspartic proteinase-I (RNAP-I) is secreted by Saccharomyces cerevisiae extracellularly (Horiuchi, H., Ashikari, T., Amachi, T., Yoshizumi, H., Takagi, M., and Yano, K. (1990) Agric. Biol. Chem. 54, 1771-1779). The prosequence of RNAP-I has the function to promote correct folding of its mature part. Deletion (Deltapro) and amino acid substitutions (M1) in the prosequence block secretion of RNAP-I (Fukuda, R., Horiuchi, H., Ohta, A., and Takagi, M. (1994) J. Biol. Chem. 269, 9556-9561). In this study, little accumulation of Deltapro was observed in Western blot analysis of the cell extracts of the transformants producing Deltapro using anti-RNAP-I antisera. In contrast, M1 was accumulated in the yeast cells. Pulse-chase analysis revealed that they were synthesized at almost the same rates and that Deltapro was degraded in the cells more rapidly than M1. In subcellular fractionation analysis, Deltapro was found in the fraction that contained most of the activity of an endoplasmic reticulum (ER) marker enzyme, NADPH-cytochrome c reductase. In indirect immunofluorescence microscopy, Deltapro was observed in the ER. Similar result was also observed in a mutant which is deficient of the two vacuolar proteases, proteinase A and proteinase B. So, the vacuolar proteases are not involved in degradation of Deltapro. From these results, we concluded that RNAP-Is with the mutated prosequences, which probably could not be folded correctly, were retained and degraded in the ER.

Alanine↗

PubMed1996

Peroxisome proliferators activate cytochrome P450 genes in an alkane-assimilating yeast, Candida maltosa.

Candida maltosa can assimilate n-alkane as a sole carbon source and cytochromes P450ALK (P450ALK) are critical for the first oxidation step. Four major P450ALKs that are encoded by genes ALK1, ALK2, ALK3 and ALK5 are induced by n-alkane and repressed by glucose at the transcriptional level. In the present work, we found that all these four genes but ALK5 are transcriptionally activated in response to a peroxisome proliferator, clofibrate. This is the first report on the peroxisome proliferator responsive gene expression in lower eucaryotes.

Alkanes↗

PubMed1996

A lea-class gene of tomato confers salt and freezing tolerance when expressed in Saccharomyces cerevisiae.

During periods of water deficit, plants accumulate late embryogenesis-abundant (LEA) proteins which are thought to protect cells from stresses associated with dehydration. One of these genes, le25, is expressed in tomato leaves and roots in response to water deficit and abscisic acid accumulation. To study the function of this protein and to test the effect of overproduction of the LE25 protein in Saccharomyces cerevisiae (Sc), a recombinant plasmid in which le25 is expressed under the control of the GAL1 promoter was constructed. The content of LE25 was high in Sc cells transformed with the recombinant plasmid. The transformant exhibited several stress-tolerant phenotypes. Growth of the transformant in a medium with 1.2 M NaCl was improved, as compared to a control strain. While the control strain showed a long lag phase of 40 h, le25-expressing cells showed a shortened lag phase of 10 h. However, no growth improvement was observed in a medium with 2 M sorbitol. In addition, the transformant had an increased survival rate after freezing stress, but not after high-temperature stress. These results, together with its predicted secondary structure, may indicate that LE25 functions as an ion scavenger.

Culture Media↗

PubMed1996

Relationship of plasma CCK to acinar cell regeneration in acute pancreatitis as studied by proliferating cell nuclear antigen.

In order to elucidate the relationship of cholecystokinin to acinar cell regeneration, the current study examined the changes in plasma cholecystokinin and immunostaining of proliferating cell nuclear antigen in the pancreas of rats with acute necrotizing pancreatitis. Proliferating cell nuclear antigen immunohistochemistry has been used to examine the proliferation of cells in several types of tissues. We compared the usefulness of proliferating cell nuclear antigen immunostaining and the incorporation of 5-bromodeoxyuridine to demonstrate acinar cell proliferation in the pancreas of rats with acute necrotizing pancreatitis. We also examined the relationship between these labeling indices and plasma cholecystokinin concentrations. The labeling index of paraformaldehyde-fixed specimens stained with proliferating cell nuclear antigen showed biphasic peaks at 12 hr and day 7. On the other hand, the methanol-fixed specimens stained with proliferating cell nuclear antigen and specimens stained with bromodeoxyuridine showed monophasic peaks in their labeling indices on day 5. There was a linear correlation (r = 0.808, P < 0.001) between the labeling index of bromodeoxyuridine and that of methanol-fixed proliferating cell nuclear antigen during the entire experimental period. During the regenerating phase, plasma cholecystokinin bioactivity showed positive correlations with the labeling index of bromodeoxyuridine and that of methanol-fixed proliferating cell nuclear antigen, r = 0.555 and 0.566, respectively (P < 0.001). Immunostaining of methanol-fixed proliferating cell nuclear antigen may be a useful tool for analyzing proliferating acinar cells. Acinar cell proliferation correlates with the bioactivity of plasma cholecystokinin during the regenerating phase of acute pancreatitis.

Acute Disease↗

PubMed1996

Increases in calcium absorption with ingestion of soluble dietary fibre, guar-gum hydrolysate, depend on the caecum in partially nephrectomized and normal rats.

Effects of feeding soluble dietary fibre on apparent Ca absorption and the contribution of the caecum to Ca absorption were examined in five-sixths nephrectomized (NPX) and normal rats with or without caecectomy in four experiments. It is known that Ca absorption is lowered by renal failure. In the first experiment the amounts of femur Ca increased linearly with increasing dietary Ca up to 3.0 g Ca/kg diet in intact rats. Partial nephrectomy decreased apparent Ca absorption in rats fed on diets containing 3-0 and 4.5 g Ca/kg diet. In the NPX groups, Ca absorption in rats fed on the diet containing guar-gum hydrolysate (GGH; 50 g/kg diet; 3.0 g Ca/kg diet) was significantly higher than that in rats fed on a fibre-free diet, and the increase in Ca absorption with GGH feeding was completely abolished by caecectomy. Also, ingestion of GGH increased Ca absorption in normal rats, but not in normal, caecectomized rats. Mg absorption was also increased with GGH feeding and was decreased with caecectomy in NPX and normal rats. In experiments which used caecectomized rats, coprophagy was prevented with an anal cup to avoid re-ingestion of faecal Ca. We conclude that ingestion of the soluble dietary fibre, GGH, increased apparent Ca absorption in NPX and non-NPX rats, and the caecum was responsible for these increases in Ca absorption.

Animals↗

PubMed1996

Prevention of coprophagy modifies magnesium absorption in rats fed with fructo-oligosaccharides.

We developed a new type of anal cup for prevention of coprophagy and determined whether the absorption of Ca and Mg and the stimulatory effects of feeding fructo-oligosaccharides (FO) on the absorption of Ca and Mg were altered by prevention of coprophagy in rats. Rats were fed on a FO-free diet or a diet containing 50 g FO/kg for 2 weeks with or without prevention of coprophagy. FO-feeding increased the apparent absorptive ratio of Ca and Mg in rats with or without prevention of coprophagy. However, in the FO-fed groups the absorptive ratio of Mg in rats with prevention of coprophagy was higher than in rats without prevention of coprophagy. The Ca content of the femur was higher in rats fed on the FO-diet than in rats fed on the FO-free diet both with and without coprophagy. In conclusion, FO-feeding increased the absorption of Ca and Mg in rats both with and without coprophagy. Moreover, prevention of coprophagy enhanced the absorption of Mg in rats fed with FO. Coprophagy has to be considered when the effects of luminal fermentation or mineral absorption are examined in rats.

Animals↗

PubMed1996

Isolation and characterization of ECT1 gene encoding CTP: phosphoethanolamine cytidylyltransferase of Saccharomyces cerevisiae.

Saccharomyces cerevisiae mutants that were unable to utilize extracellular ethanolamine for phosphatidylethanolamine synthesis were isolated. Two of them carried recessive chromosomal mutations in a same gene and were defective in CTP:phosphoethanolamine cytidylyltransferase (ECT) activity in vitro (Ect-). In an Ect- mutant that also carried the cho1 mutation, phosphatidylethanolamine accounted for less than 2% of total phospholipids, suggesting the importance of ECT in phosphatidylethanolamine synthesis. By screening a genomic library on a low copy number vector, three complementary clones of different size were isolated. A 2.8-kb common DNA region carried an open reading frame (ORF) of 969 bp in length, of which a truncated from failed to complement the Ect- mutation. This ORF was identical to the previously isolated MUQ1 gene of unknown function. Its deduced amino acid sequence had significant similarity to CTP: phosphocholine cytidylyl-transferases of yeast and rat. The entire ORF, when combined with the glutathione S-transferase gene and expressed in Escherichia coli, exhibited ECT activity. These results indicate that the cloned gene encodes a catalytic subunit of ECT of S. cerevisiae.

Amino Acid Sequence↗

PubMed1996

Effects of 3,6-dimethylpyrazine-2-thiol on reproductive and accessory reproductive organs in male rats.

The weights of prostate and seminal vesicle were decreased by treatment with 3,6-dimethylpyrazine-2-thiol(3,6-DMP-SH) but the weights of testes and the plasma testosterone levels were not changed. The recovery of the weight of prostate and seminal vesicles of testosterone-treated orchidectomized rats were inhibited by treatment with 3,6-DMP-SH. Direct injection of 3,6-DMP-SH into accessory reproductive organs also induced the decrease in the weight of relevant organs. Administration of oxendrone or chlormazinone along with 3,6-DMP-SH decreased the weights of accessory reproductive organs more than administration of only one substance. In vitro uptake of testosterone into prostate and seminal vesicle were blocked by the presence of 3,6-DMP-SH. These results suggest that 3,6-DMP-SH directly inhibited testosterone uptake into the accessory reproductive organs.

Androgen Antagonists↗

PubMed1996

Cloning and characterization of the Rhizopus niveus leu1 gene and its use for homologous transformation.

The Rhizopus niveus leul gene was cloned using a 2-kb HindIII fragment of the leuA gene of Mucor circinelloides as a hybridization probe. The coding region of this gene comprises 1890 bp that encode a putative protein of 630 amino acids. The predicted amino acid sequence is similar to those of other alpha-isopropylmalate isomerases (alpha-IPMIs), showing 79.4%, 71.7%, and 60.6% identity with the Mucor circinelloides LeuA, Phycomyces blaskesleeanus Leu1, and Ustilago maydis Leu1, respectively. The vector pRN1, which contains a 3.7-kb BamHI-SacI fragment of the R. niveus leul gene, could complement leucine auxotrophy of R. niveus M-37 (leu1-), suggesting that the gene codes for alpha-IPMI of R. niveus. Both the transformation frequency and mitotic stability with pRN1 were higher than those with leuA gene-containing vectors. It was found by using the leul gene that the autonomously replicating sequence (ARS) of P. blakesleeanus partially functions as an ARS in R. niveus.

Amino Acid Sequence↗

PubMed1996

[A case of Takayasu arteritis diagnosed by magnetic resonance imaging].

We report a case of Takayasu arteritis. A woman, 24 years old, was admitted because of fever of unknown etiology. Infection was ruled out. Bruit and asymmetrical pulsation were not found. Ga-scintigram showed abnormal uptake in her upper abdomen. Abdominal echogram revealed neither evidence of abscess nor lymphadenopathy. On abdominal computed tomography, a wall thickening of the abdominal aorta was revealed. In addition, abdominal magnetic resonance imaging(MRI) showed a wall thickening and an enhanced image by gadrinium enhancement. Although we could not carry out conventional aortography because of an allergy to lidocaine, she was diagnosed as having Takayasu arteritis. In response to steroid therapy, the fever promptly dropped and the data indicating inflammation were improved. On the MRI examination after 40 days of steroid therapy, the wall thickening of the abdominal aorta was found to be less prominent. We conclude magnetic resonance imaging is useful for diagnosis and follow-up of early and acute stage of Takayasu arteritis.

Adult↗

PubMed1996

[The effect of beraprost sodium on the Raynaud's phenomenon].

We investigated the effect of beraprost sodium (BPS) on the Raynaud's phenomenon on 15 patients with systemic sclerosis, 3 with mixed connective tissue disease and 1 with Raynaud's disease, respectively. After 12 weeks of administration of 60 micrograms/d BPS, the duration and the incidence of the Raynaud's symptom were significantly reduced and the dermal temperature on the fingers was found to be elevated. Of the parameters which are known to reflect vascular endothelial damages such as tissue plasminogen activator (t-PA), von Willebrand's factor (vWF) and endothelin, the plasma level of t-PA was significantly reduced by BPS. Furthermore, the capillary loop in the nail bed of the fingers seemed to increase in one patient by the treatment with BPS. These results suggest that BPS has a capacity to repair peripheral vascular damages resulting in the improvement of Raynaud's phenomenon.

Adult↗

PubMed1996

[A case of POEMS syndrome with various complications].

A 65-year old man presented with complaints of sclerosis of skin and numbness in the extremities. During last 10 year, he had developed monoclonal gammopathy, Raynaud's phenomenon, ischemic heart disease, sigmoid colon cancer, hyperkalemia, polyneuropathy and scleroderma-like skin changes. Laboratory examinations revealed a monoclonal protein (IgA-lambda) and an elevated serum level of IL-6. Subsequently a diagnosis of POEMS syndrome was made based on the clinical features and laboratory findings which were characteristic of this syndrome. Further examinations showed the presence of glomerulonephritis and brain tumor. These various complications are of great interest in understanding the pathogenesis of POEMS syndrome.

Aged↗

PubMed1996

[Neutron activation analysis of biological samples].

Multi-element analysis by neutron activation analysis (NAA) in respect to medical applications is discussed. Examples of trace element determinations in pathological human liver tissues, human serum, and rat liver are given. A very sensitive method for determining fluorinated drug in very small samples of human serum by neutron activation is also described. Each biological samples (ca. 100-200 mg, lyophilized matter) was irradiated for short time (10 s or 5 min.) and for long time (24 hrs) in Rikkyo University Research Reactor or Musashi Institute of Technology Research Reactor. Concentration of 12 elements (127I, 55Mn, 26Mn, 65Cu, 23Na, 41K, 37Cl, 27Al, 48Ca, 36S, 58Fe, 64Zn) in human pathological liver, Futraful (19F) (anti-cancer fluorinated drug) clearance of human serum, and calcium uptake (48Ca) in liver of rats were determined by NAA.

Animals↗

PubMed1996

TCR gamma delta + T cells in peripheral blood of patients with adult Still's disease.

OBJECTIVE: Adult Still's disease, a systemic inflammatory disorder of unknown etiology, shows few specific laboratory markers and histological features. We investigated T cell subsets in peripheral blood lymphocytes (PBL) of patients with adult Still's disease to elucidate immunological features of the disease. METHODS: We studied T cell subsets in PBL of 12 patients with adult Still's disease by flow cytometric analysis. T cell subsets were also investigated for more than 6 months in PBL of 3 patients with adult Still's disease. RESULTS: Both the percentage and absolute number of T cell receptor gamma delta positive (TCR gamma delta +) T cells in active adult Still's disease (n = 6) were significantly (p < 0.05) higher than those in inactive adult Still's disease (n = 6), inactive rheumatoid arthritis (n = 8), or healthy controls (n = 20). An increase of TCR gamma delta + T cells was observed in 5 of 6 patients with adult Still's disease at the active phase. TCR gamma delta + T cells also increased for a considerable period in all the patients tested. In contrast, there were no significant differences in the other T cell subsets (CD3, CD4, CD8, TCR alpha beta) between all the patients and healthy donors. Levels of TCR gamma delta + T cells in PBL correlated well with those of serum ferritin and C-reactive protein in one of the 3 patients whose PBL could be serially investigated. These increased TCR gamma delta + T cells mostly consisted of a V gamma 9/V delta 2 subset. CONCLUSION: TCR gamma delta + T cells in PBL are significantly increased in the active phase in patients with adult Still's disease.

Adult↗

PubMed1996

Morphological studies on Mn-SOD, NOS and calcium binding proteins in the rat hippocampus.

The immunohistochemical localization of manganese superoxide dismutase (Mn-SOD), nitric oxide synthase (NOS) and calcium (Ca) binding proteins; calbindin-D28K (Calb) and parvalbumin (Parv), was investigated in the rat hippocampus by using a double immunostaining method and an enzyme histochemical staining method. These substances showed considerable regional immunoreactivities in the hippocampus. (1) Although Mn-SOD- and NOS-immunoreactive neurons showed a similar distribution, virtually all of the latter neurons had no or weak Mn-SOD immunoreactivity in all subfields. This finding suggests that NO-producing neurons are not directly associated with Mn-SOD scavenger system in the hippocampus. (2) The co-localization of NOS and Parv or Calb was rarely found throught the hippocampus. (3) Neurons which were intensely immunostained for Mn-SOD were frequently found to be Parv-immunoreactive non-pyramidal cells, or Calb-immunoreactive pyramidal and non-pyramidal cells. From the latter two findings, it is speculated that Ca buffering effects of Parv and Calb are required in Mn-SOD neurons, but not in NO-producing neurons. Since Parv- or Calb-containing non-pyramidal cells are known to be GABAergic, most if not all, Mn-SOD-containing non-pyramidal cells may be GABAergic inhibitory neurons in the rat hippocampus. On the other hand, NOS neurons are also known to belong to GABAergic non-pyramidal cells. Therefore, Mn-SOD and NOS neurons constitute two distinct subclasses of non-pyramidal inhibitory neurons in the hippocampus.

Animals↗

PubMed1995

Cloning and characterization of the POX2 gene in Candida maltosa.

To study the function of acyl-CoA oxidase in an n-alkane-assimilating yeast, Candida maltosa, we isolated the POX2 gene which is a member of the acyl-CoA oxidase gene family. POX2 had a 2172-bp open reading frame (ORF) encoding an approx. 84-kDa polypeptide (724 amino acids (aa)) and was contiguous to POX4, another member of the acyl-CoA oxidase gene family on the same chromosomal DNA in a convergent arrangement. Northern blot analysis revealed that the expression of POX2 was induced in cells grown on oleic acid, n-tetradecanol and n-tetradecane. By using a gene-disruption technique, we constructed strains (termed P2DD and P4DD) in which both alleles of POX2 and POX4 were disrupted. The P2DD strain was normal in assimilation of various hydrophobic carbon sources, such as n-tetradecane, n-tetradecanol and oleic acid. In contrast, the P4DD strain was defective in its ability to grow on such hydrophobic carbon sources.

Acyl-CoA Oxidase↗

PubMed1995

Identification of a centromeric activity in the autonomously replicating TRA region allows improvement of the host-vector system for Candida maltosa.

A centromeric activity was identified in the previously isolated 3.8 kb DNA fragment that carries an autonomously replicating sequence (ARS) from the yeast Candida maltosa. Plasmids bearing duplicated copies of the centromeric DNA (dicentric plasmids) were physically unstable and structural rearrangements of the dicentric plasmids occurred frequently in the transformed cells. The centromeric DNA activity was dissociated from the ARS, which is 0.2 kb in size, and was delimited to a fragment at least 325 bp in length. The centromeric DNA region included the consensus sequences of CDEI (centromeric DNA element I) and an AT-rich CDEII-like region of Saccharomyces cerevisiae but had no homology to the functionally critical CDEIII consensus. A plasmid bearing the whole 3.8 kb fragment was present in 1-2 copies per cell and was maintained stably even under non-selective culture conditions, while a plasmid having only the 0.2 kb ARS was unstable and accumulated to high copy numbers. The high-copy-number plasmid allowed us to overexpress a gene to a high level, which had never been attained before, under the control of both constitutive and inducible promoters in C. maltosa.

Base Sequence↗