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T Ohta

Publications and source records attributed to T Ohta.

At least 433 records · Page 24Linked to original sources
PubMed1997

Food-derived heterocyclic amines potentiate the mutagenicity of a drinking water mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX).

We investigated the enhancing effect of heterocyclic amines on base-substitution mutations with 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole (Trp-P-1) and 2-amino-3,4-dimethyl-imidazo[4,5-f]quinoline (MeIQ). We compared the mutagenicity of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX) in the presence and absence of the heterocyclic amines in E. coli WP2 (trpE) and in excision repair-deficient strains WP2s (uvrA, trpE) and ZA500 (uvrA, rfa, trpE). Since the assay was performed without microsomal metabolic activation, Trp-P-1 and MeIQ alone were not mutagenic. In WP2, trp+ reversions induced by MX were greatly potentiated by Trp-P-1 and slightly potentiated by MeIQ. Mutation enhancement was not observed in strains WP2s and ZA500, suggesting that a functional DNA excision repair system is necessary for the combined action of MX and heterocyclic amines. Our finding implies that the combined effect of mutagens as well as the effect of individual mutagens, should be considered in risk evaluation.

Adenosine Triphosphatases↗
PubMed1997

Complete nucleotide sequence of the chloroplast genome from the green alga Chlorella vulgaris: the existence of genes possibly involved in chloroplast division.

The complete nucleotide sequence of the chloroplast genome (150,613 bp) from the unicellular green alga Chlorella vulgaris C-27 has been determined. The genome contains no large inverted repeat and has one copy of rRNA gene cluster consisting of 16S, 23S, and 5S rRNA genes. It contains 31 tRNA genes, of which the tRNALeu(GAG) gene has not been found in land plant chloroplast DNAs analyzed so far. Sixty-nine protein genes and eight ORFs conserved with those found in land plant chloroplasts have also been found. The most striking is the existence of two adjacent genes homologous to bacterial genes involved in cell division, minD and minE, which are arranged in the same order in Escherichia coli. This finding suggests that the mechanism of chloroplast division is similar to bacterial division. Other than minD and minE homologues, genes encoding ribosomal proteins L5, L12, L19, and S9 (rpl5, rpl12, rpl19, and rps9); a chlorophyll biosynthesis Mg chelating subunit (chlI); and elongation factor EF-Tu (tufA), which have not been reported from land plant chloroplast DNAs, are present in this genome. However, many of the new chloroplast genes recently found in red and brown algae have not been found in C. vulgaris. Furthermore, this algal species possesses two long ORFs related to ycf1 and ycf2 that are exclusively found in land plants. These observations suggest that C. vulgaris is closer to land plants than to red and brown algae.

Base Sequence↗
PubMed1997

Interleukin-18 activates NF-kappaB in murine T helper type 1 cells.

Interleukin-18 (IL-18) activated T helper type 1 (Th1) cells, OVA#4, and induced production of interleukin-2 (IL-2) in costimulation with anti-CD3 antibody. Upon stimulation with IL-18, IkappaB disappeared from cytoplasm and subsequently nuclear factor-kappaB (NF-kappaB) (p65) accumulated in the nucleus. Corresponding with that, DNA binding activity of NF-kappaB (p65 homodimer or p65/p50 heterodimer) was detected in the nucleus. In the transfection experiments, an IL-2 promoter-driven reporter construct showed the similar responsiveness against IL-18 to that of the intrinsic IL-2 gene, and a construct lacking kappaB site failed to respond to IL-18. These results suggest that IL-18 activates NF-kappaB and it is important for enhancement of IL-2 gene expression by Th1 cells stimulated with IL-18.

Animals↗
PubMed1997

Application of a beta-cyclodextrin sulfate-immobilized precolumn to selective on-line enrichment and separation of heparin-binding proteins by column-switching high-performance liquid chromatography.

A column-switching high-performance liquid chromatography (HPLC) system which consisted of a beta-cyclodextrin (beta-CD) sulfate-immobilized hydrophilic vinyl-polymer gel precolumn and a reversed-phase analytical column was developed for the selective on-line enrichment and separation of heparin-binding proteins. Of 15 proteins investigated, 10 proteins having heparin-binding activity were retained on the beta-CD sulfate precolumn almost quantitatively, in contrast 5 proteins having no heparin-binding activity were not retained. Calibration graphs for basic fibroblast growth factor constructed at various sample volumes were nearly identical, indicating that the protein could be enriched by this system. The system was successfully used for the selective separation of lysozyme in egg white. The beta-CD sulfate-immobilized precolumn showed no loss of analytical performance over 2 years during which about 400 samples were analysed.

Chromatography, High Pressure Liquid↗
PubMed1997

Species-specificity of pyrimethamine in the rodent bone marrow micronucleus test.

An antiprotozoal agent pyrimethamine is a potent clastogen that induces structural chromosome aberrations and micronuclei in cultured Chinese hamster (CHL) cells in vitro. Our previous study on the compound, however, demonstrated no significant induction of micronuclei in the mouse bone marrow micronucleus test, even with dosings on 4 consecutive days. In the present study, we investigated the clastogenicity of pyrimethamine in the rat bone marrow micronucleus test. An obvious dose-dependent increase in the frequency of micronucleated polychromatic erythrocytes (MNPCEs) was observed when the compound was given 3 times by oral gavage at 20-120 mg/kg/day. The MNPCE frequency at the highest dose was 80 times that of the control group. Single dose of pyrimethamine at 80 and 160 mg/kg also significantly induced MNPCEs. Thus, pyrimethamine showed species-specific effects in rodent bone marrow micronucleus assays. Our finding implies that micronucleus tests using not only mouse, but also rat, may be necessary for the evaluation of clastogens detected in in vitro cytogenetic studies.

Administration, Oral↗
PubMed1997

Cloning and analysis of a cDNA encoding a two-domain hemoglobin chain from the water flea Daphnia magna.

A cDNA encoding a two-domain hemoglobin (Hb) chain of Daphnia magna was cloned and its nucleotide (nt) sequence of 1261 bp was determined. The nt sequence contained 74 bp of the leader sequence, 1047 bp of an open reading frame (ORF), and 119 bp of the 3'-untranslated region (UTR), excluding the polyadenylation tail. A sequence, AATACA, located 24 bp upstream from the polyA sequence was considered to be a polyadenylation signal. cDNA-derived amino acid (aa) sequence revealed that D. magna Hb chain is synthesized as a secretory precursor with a signal peptide of 18 aa. Mature D. magna Hb chain consists of 330-aa residues with a calculated molecular weight of 36227, which is composed of two large repeated domains, domain 1 and 2. Several key aa that are invariant in all or most of other Hb and required for functional heme-binding are conserved in each of the two domains. The N-terminal extension (pre-A segment) of domain 1 was unusually long and contained an unusual threonine-rich sequence. The homology between the aa sequences of the two domains (24% identity) was much lower than that observed in other two-domain Hb chains from clams or nematode. Hb mRNA level in D. magna reared under low oxygen concentration was more than 12 times higher than that in D. magna reared with sufficient aeration, indicating that the expression of Hb gene is regulated by mRNA level.

Amino Acid Sequence↗
PubMed1997

Analysis of Cdc2 and Cyclin D1 Expression in Breast Cancer by Immunoblotting.

Cyclins and cyclin-dependent kinases may reflect the status of cell proliferation in cancer tissues. The authors sought to determine whether cdc2 and cyclin D1 are expressed in breast cancer and are useful as prognostic factors. Accumulation of cdc2 and cyclin D1 proteins was examined in 88 cases of breast cancer using immunoblotting techniques and correlations with clinicopathological factors and prognoses were investigated. Cdc2 and cyclin D1 proteins were observed in 27.3 % and 75.0 % of breast cancers studied, respectively. The incidence of lymph node metastasis was significantly high in cdc2/cyclin D1-double positive group and low in double negative group. On the other hand, the incidence of estrogen receptor (ER) negative cases was significantly higher in the cdc2-positive/cyclin D1-negative group. Relapse-free survival times of cdc2-positive cases were significantly shorter than those of Cdc2-negative cases. The relapse-free survival times of cyclin D1-positive cases also tended to be poorer than those of cyclin D1-negative cases. Multivariate analyses revealed cdc2 as the second most significant of the prognostic variables, following lymph node status. The three-year relapse-free survival rate of cdc2/cyclin D1-double positive cases was 58.9%, whereas that of cdc2/cyclin D1-doublue negative cases was 100%. Cdc2 and cyclin D1 represent the status of cell proliferation in breast cancer, and may be useful in breast cancer assessment.

Journal Article↗
PubMed1997

Evidence for the involvement of a muscarinic receptor in ascorbic acid secretion in the rat stomach.

It has been demonstrated that ascorbic acid is present in human gastric juice at a very high level even in the fasting state. In this study, we confirmed such a physiological event in pylorus-ligated rats and investigated the mechanism for gastric ascorbic acid secretion using the rat in vivo perfusion method. Gastric juice from fasting rats after a 4-hr ligation contained a 6-fold higher level of ascorbic acid than that in sera, indicating the presence of its active transport system across the gastric wall. To identify an endogenous mediator, four kinds of gastric stimulants were compared for their secretory abilities. Although all four secretagogues used stimulated acid secretion to comparable levels, ascorbic acid secretion was stimulated only by carbamylcholine chloride (carbachol). Carbachol-stimulated ascorbic acid secretion was abolished by atropine pretreatment, showing that it is mediated via a muscarinic cholinergic receptor. This cholinergic stimulation was also demonstrated in a rat mutant that genetically lacks the ability to synthesize ascorbic acid in the liver, similar to humans. In addition, a potent inhibitor of the gastric proton pump, which is a final regulatory component in the mechanism of acid secretion, caused no inhibition of ascorbic acid secretion in Osteogenic Disorder Shionogi (ODS) rats. These results are the first evidence indicating that ascorbic acid, the reduced form of vitamin C, is actively and independently secreted into the gastric juice under regulation of a cholinergic receptor system.

Animals↗
PubMed1997

Tacrine inhibits nicotinic secretory and current responses in adrenal chromaffin cells.

Tacrine enhanced acetylcholine-induced catecholamine secretion with a concentration of up to 10 microM, but inhibited it at over 10 microM in perfused adrenal glands. Qualitatively the same result was obtained with physostigmine. Both tacrine and physostigmine only inhibited the secretory responses to carbachol and/or nicotine in perfused glands and dispersed chromaffin cells. Acetylcholinesterase activity of adrenal homogenates was inhibited by tacrine and physostigmine in a concentration-dependent manner. In whole-cell patch-clamp experiments, tacrine and physostigmine caused reversible inhibition of nicotine-evoked inward currents with a dose range similar to that for the inhibitory action on the secretory response. These results suggest that the enhancing effect of tacrine and physostigmine on acetylcholine-induced catecholamine secretion results from the prevention of enzymatic hydrolysis of acetylcholine in adrenal glands and that the inhibitory effect is due to the inhibition of nicotinic receptor-mediated membrane currents in adrenal chromaffin cells.

Acetylcholine↗
PubMed1997

Enhanced generation of A:T-->T:A transversions in a recA730 lexA51(Def) mutant of Escherichia coli.

RecA730 belongs to a class of mutant RecA protein that is often referred to as RecA*, since it is constitutively activated for coprotease functions in the absence of exogenous DNA-damage. Escherichia coli strains carrying recA730 (or other recA* alleles) exhibit dramatic increases in SOS-dependent spontaneous mutator activity. We have analyzed the specificity of this mutator phenotype by employing F'-plasmids carrying a set of mutant lacZ genes that can individually detect two types of transitions, four types of transversions, and four kinds of specific frameshift events. Analysis revealed that most of the spontaneous mutagenesis in a recA730 lexA51(Def) strain (which expresses derepressed levels of all LexA-regulated proteins) can be attributed to a specific increase in A:T-->T:A, A:T-->C:G and G:C-->T:A transversions, with the A:T-->T:A transversions occurring most frequently. These transversion events were completely abolished in a delta umuDC strain, indicating that the functionally active UmuD'C proteins are normally required for their generation. The spectrum obtained was similar to that of strains with a defect in the epsilon (3'-->5' proofreading) subunit of DNA polymerase III. Such an observation raises the possibility that the wild-type epsilon protein is in activated in strains expressing the RecA730 and UmuD'C proteins.

Bacterial Proteins↗
PubMed1997

Neurotrophin-3 expression in human pancreatic cancers.

Some neurotrophic factors stimulate process outgrowth in peripheral and/or central nerve fibres. There is no published report that has focused on the expression of neurotrophic factors in human pancreatic cancer except basic fibroblast growth factor. This study was therefore designed to examine the mRNA and protein levels of neurotrophin-3 (NT-3), which is one of the representative neurotrophic factors. The mRNA level for NT-3 was first investigated in eight pancreatic cancers and two samples of normal pancreas, using reverse transcription-polymerase chain reaction (RT-PCR). NT-3 protein expression was then studied in 47 human pancreatic cancers, using a monoclonal antibody against human NT-3 protein. There was a notable difference in the level of NT-3 mRNA between normal and pancreatic carcinoma tissues, with no evident difference in the expression of the beta-actin gene. Immunohistochemically, 34 of 47 pancreatic cancers (72 per cent) were mildly to markedly immunoreactive for NT-3 in the cytoplasma. Immunoreactivity was usually more pronounced at the infiltrative margins of the tumours. These observations suggest that pancreatic carcinoma overexpresses NT-3.

Adult↗
PubMed1997

Mechanism of reduction of cortical blood flow in striatocapsular infarction: studies using [123I]iomazenil SPECT.

Single photon emission computed tomography (SPECT) using [123I]iomazenil (radioligand of central-type benzodiazepine receptors) was employed to examine two patients with striatocapsular infarction. Patient 1 was a 61-year-old female with motor aphasia and hemiplegia on the right side. Magnetic resonance imaging (MRI) showed a lesion in the anterior limb of internal capsule and putamen on the left side. SPECT using 99mTc-HMPAO revealed a reduction of cerebral blood flow (CBF) in the frontoparietal region on the left side, but the delayed images in SPECT using [123I]iomazenil showed only a mild decrease of accumulation in the frontal lobe. Patient 2 was a 55-year-old male with hemiplegia on the left side. MRI showed a lesion localized in the basal ganglia and posterior limb of the internal capsule on the right side. SPECT using 99mTc-HMPAO revealed a reduction of CBF in the frontoparietal region on the right side and in the cerebellar hemisphere on the left side, but the delayed images in SPECT using [123I]iomazenil showed little decrease of accumulation in parietal lobe. The discrepancy between CBF and receptor images suggested that cortical hypoperfusion on striatocapsular infarction might reflect hypometabolism due to disconnection of the neuronal network between subcortical structure and cortex.

Aphasia↗
PubMed1997

Endocrine cells in hepatobiliary cystadenomas and cystadenocarcinomas.

We investigated the distribution of endocrine cells in hepatobiliary cystadenoma (n = 5, two associated with mesenchymal stroma) and cystadenocarcinoma (n = 3) immunohistochemically. In normal livers (n = 20) and livers affected by hepatolithiasis (n = 15) used as controls, endocrine cells revealed by chromogranin immunostaining were located exclusively in normal or proliferating intrahepatic peribiliary glands. In the eight cases of hepatobiliary cystadenoma and cystadenocarcinoma, endocrine cells were present in four cases (50%) (1 cystadenoma, 1 cystadenoma with mesenchymal stroma, and 2 cystadenocarcinomas). Endocrine cells tended to be located beneath and among the columnar epithelial cells. Intrahepatic peribiliary glands were located in the vicinity of cystadenoma or cystadenocarcinoma in six (75%) of the eight cases, and they frequently showed cystic dilatation and contained endocrine cells. Intrahepatic peribiliary glands were located in the vicinity of the endocrine cells in all cystadenomas and cystadenocarcinomas that were positive for endocrine cells. These data show that about 50% of hepatobiliary cystadenomas and cystadenocarcinomas contain endocrine cells and suggest that hepatobiliary cystadenoma and cystadenocarcinoma may originate from intrahepatic peribiliary glands.

Aged↗
PubMed1997

Expression of the tumor necrosis factor alpha gene and early response genes by nodularin, a liver tumor promoter, in primary cultured rat hepatocytes.

Nodularin is a new liver carcinogen possessing a potent tumor-promoting activity in rat liver, mediated through inhibition of protein phosphatases 1 and 2A, and a weak initiating activity. Since we previously reported evidence that nodularin up-regulated expression of the tumor necrosis factor alpha gene (TNF alpha) and early-response genes in rat liver after its i.p. administration, and since TNF alpha had tumor-promoting activity in vitro, it is possible that TNF alpha itself is involved in liver tumor promotion. We investigated whether hepatocytes themselves induce expression of the TNF alpha gene and early-response genes in primary cultured rat hepatocytes treated with nodularin. Like nodularin, microcystin-LR, which is another liver tumor promoter belonging to the okadaic acid class, strongly induced TNF alpha gene expression in rat hepatocytes, as well as TNF alpha release from those cells into the medium. On the other hand, 12-O-tetradecanoylphorbol-13-acetate, which has been reported to induce no tumor promotion in rat liver, induced no apparent expression of the TNF alpha gene in primary cultured rat hepatocytes. As for the expression of early-response genes, 1 microM nodularin or microcystin-LR induced expression of the c-jun, jun B, jun D, c-fos, fos B and fra-1 genes in the hepatocytes, and the expression of these genes was prolonged up to 24 h, suggesting mRNA stabilization induced by inhibition of protein phosphatases 1 and 2A. This paper presents new evidence that the TNF alpha gene and early-response genes were expressed in hepatocytes treated with a liver tumor promoter.

Animals↗
PubMed1997

Usefulness of non-woven sheet (clip pad) on scalp incisions: technical note.

As an alternative to the gauze often used on scalp incisions, we prepared a pad made of non-woven sheets, coated with adhesive on one side. Unlike conventional gauze, the pad did not slip away from the incision line or become entangled with the scalp clips, thus demonstrating its high usefulness for this purpose.

Bandages↗
PubMed1997

Role of random genetic drift in the evolution of interactive systems.

Through comparative studies of DNA sequences it has become possible to test the neutral and the selection theories of molecular evolution. The separate estimation of the numbers of synonymous and non-synonymous substitutions is one of the most powerful tools for detecting selection. The patterns on the average and variance of these two types of substitutions of mammalian genes turned out to be in accord with the slightly deleterious or the nearly neutral mutation theory for non-synonymous changes. Interactive systems at the amino acid level were suggested to be responsible for such nearly neutral or very weak selection. An attractive model is the NK model of Kauffman, which assumes that each amino acid makes a fitness contribution that depends upon the amino acid and upon K other amino acids among the N that make the protein. It is known that the fitness landscape is very rugged for K > or = 2. Population genetic analysis of this model suggest that protein evolution obeys the nearly neutral theory and that random genetic drift is important. In other words, evolution becomes rapid in small populations because proportion of near-neutrality increases among new mutations, and proteins as interactive systems evolve by shifting through random genetic drift on the multipeaked fitness landscape.

Animals↗
PubMed1997

Topographic anatomy of paraclinoid carotid artery aneurysms: usefulness of MR angiographic source images.

We evaluated the usefulness of magnetic resonance angiography (MRA) for showing the topography of paraclinoid carotid artery aneurysms in 27 patients with 30 paraclinoid aneurysms undergoing conventional angiography, three-dimensional time-of-flight MRA and surgery. The anatomy shown on the axial MRA source images was consistent with that found at surgery. The neck of the aneurysm could always be identified on the source images, while it could not be analysed exactly on conventional angiography in 3 cases (10%). The optic nerves, including those displaced by the aneurysm, were recognised in all patients. The anterior clinoid process was shown as a low-intensity rim or area contiguous with the cortical bone. The source images were of great value in understanding the topography of paraclinoid carotid artery aneurysms.

Adult↗