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K Ohta

Publications and source records attributed to K Ohta.

At least 343 records · Page 19Linked to original sources
PubMed1996

Nucleotide sequence of a 28-kb mouse genomic region comprising the imprinted Igf2 gene.

The mouse insulin-like growth factor II gene (Igf2) is physically linked to the insulin II gene (Ins2) and both are subject to tissue-specific genomic imprinting. The paternal-specific expression of Igf2 has been associated with hypermethylation of some CpG sites in the 5' flanking region and in the body of the gene. As a first step in analyzing the structural features of this imprinted locus, we here report the complete nucleotide sequence of Igf2, including all introns and the intergenic region adjacent to Ins2. This 28-kb segment of mouse chromosome 7 exhibits 80% overall identity with the corresponding rat sequence and has a high GC content of 52%. In addition to the known CpG island within the second Igf2 promoter, another island was identified approximately 2 kb 5' to the first exon. Other features of this locus include a 35-fold tandem repeat of an 11-bp sequence that overlaps Igf2 pseudo-exon 2, and a B2 repeat element in the intergenic region between Ins2 and Igf2. The GC-richness and the presence of CpG islands associated with tandem repeats are common features of imprinted genes and thus may play a role in the imprinting mechanism.

Animals↗
PubMed1996

Contribution of local renin-angiotensin system to cardiac hypertrophy, phenotypic modulation, and remodeling in TGR (mRen2)27 transgenic rats.

BACKGROUND: The transgenic rat TGR(mRen2)27, carrying the mouse Ren-2 gene, is a new model to elucidate the role of the local renin-angiotensin system in vivo. However, the role of the local renin-angiotensin system in the heart remains to be determined in TGR(mRen2)27. METHODS AND RESULTS: TGR(mRen2)27 were treated with various antihypertensive drugs for 6 weeks to examine the effects on cardiac hypertrophy and gene expression. Cardiac mRNAs were examined by Northern blot analysis. In TGR(mRen2)27, left ventricular hypertrophy was associated with a decrease in alpha-myosin heavy chain expression of 31% and an increase in skeletal alpha-actin and atrial natriuretic polypeptide expression by 2.6- and 21-fold, respectively (P < .05), thereby showing the shift of myocardium to a fetal phenotype. Furthermore, cardiac collagen and laminin expressions were increased in TGR(mRen2)27 (P < .05), suggesting the occurrence of cardiac remodeling. Although treatment of TGR(mRen2)27 with a high dose of TCV-116 (angiotensin AT1 receptor antagonist) or manidipine (calcium antagonist) combined with atenolol (beta 1-adrenergic receptor blocker) completely normalized blood pressure, TCV-116 regressed cardiac hypertrophy and suppressed the changes in cardiac mRNA levels of TGR(mRen2)27 much more potently than manidipine with atenolol. Furthermore, the inhibitory effects of a low dose of TCV-116 on cardiac hypertrophy and altered gene expressions of TGR(mRen2)27 were greater than those of doxazosin (alpha 1-adrenergic receptor blocker) combined with atenolol, despite their similar hypotensive effects. CONCLUSIONS: Our present observations provide evidence that the cardiac renin-angiotensin system in TGR(mRen2)27 is responsible for cardiac hypertrophy, phenotypic modulation, and remodeling.

Actins↗
PubMed1996

Detection of molecular gas in the quasar BR1202 - 0725 at redshift z = 4.69.

Although great efforts have been made to locate molecular gas--the material out of which stars form--in the early Universe, there have been only two firm detections at high redshift. Both are gravitationally lensed objects at redshift z approximately = 2.5 (refs 9-14). Here we report the detection of CO emission from the radio-quiet quasar BR1202 - 0725, which is at redshift z = 4.69. From the observed CO luminosity, we estimate that almost 10(11) solar masses of molecular hydrogen are associated with the quasar; this is comparable to the stellar mass of a present-day luminous galaxy. Our results suggest that BR1202 - 0725 is a massive galaxy, in which the gas is largely concentrated in the central region, and that is currently undergoing a large burst of star formation.

Astronomical Phenomena↗
PubMed1996

Immunological characterization of antibodies against synthetic peptides of glutamic acid decarboxylase.

We characterized antibodies against synthetic N-terminal peptides (glutamic acid decarboxylase; GAD65N and GAD67N) and a C-terminal peptide (GAD67C) of human GAD isoforms. On Western blots, the GAD65N antibody specifically stained the 65 kDa isoform and the GAD67N antibody the 67 kDa one in various mammalian brain tissues, whereas the GAD67C antibody stained both. The immunotrapped GAD enzyme activity increased in a dose-dependent manner with increasing concentration of the N-terminal peptide antibodies, but the activity was completely inhibited by the C-terminal peptide antibody. By an enzyme-linked immunosorbent assay using rat brain GAD purified on a GAD67C antibody-affinity column, we detected GAD antibodies in 40% (24/60) of the patients with long-standing insulin-dependent diabetes mellitus (IDDM). These antipeptide antibodies are a useful tool not only for identifying the GAD isoforms, but also for purifying GAD.

Animals↗
PubMed1996

Endo.SK1: an inducible site-specific endonuclease from yeast mitochondria.

Site-specific endonucleases have been found in various eukaryotic organelles such as mitochondria, chloroplasts and nuclei. These endonucleases initiate site-specific or homologous gene conversion in mitochondrial and nuclear DNA. Here, we report a new site-specific endonuclease activity, Endo.SK1, identified in mitochondria of strain SK1, a homothallic diploid strain of Saccharomyces cerevisiae. Nucleotide sequences around the Endo.SK1-cleavage sites are different from those of known yeast site-specific endonucleases. The Endo.SK1 activity is, at least partly, specified by a gene in the SK1-derived mitochondria. A novel feature of the Endo.SK1 activity is its inducibility: the endonuclease activity was induced by ca. 40-fold by transfer of cells from a glucose medium into an acetate medium, and was then repressed. This transient induction was independent of the ploidy level of the cells, and coincided with induction of fumarase, a mitochondrial enzyme involved in the TCA cycle. Co-induction and co-repression of the mitochondrial site-specific endonuclease activity and a respiration-related enzyme indicate that the endonuclease activity in regulated in response to physiological conditions, and suggest a possible role for the endonuclease in mitochondrial DNA metabolism.

Bacillus Phages↗
PubMed1996

Nitric oxide regulates NMDA-induced dopamine release in rat striatum.

We investigated the effect of nitric oxide (NO) on N-methyl-D-aspartate (NMDA)-induced changes in levels of dopamine (DA) and its metabolite in the striatum using in vivo microdialysis. Local administration of 1mM NMDA into the striatum significantly augmented DA release in the striatum. Simultaneous administration of -5mM N(G)-nitro-L-arginine methyl ester (-NAME), a NO synthase inhibitor, into the striatum significantly potentiated NMDA-induced DA release. This effect of L-NAME was completely reversed in the presence of 50mM L-arginine (L-Arg). Administration of 1 mM NMDA significantly decreased the levels of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA). This effect of NMDA was not affected by concurrent administration of L-NAME. This study provides in vivo evidence for the involvement of NO in NMDA-induced DA release.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1996

Human ESP1/CRP2, a member of the LIM domain protein family: characterization of the cDNA and assignment of the gene locus to chromosome 14q32.3.

The LIM domain is present in a wide variety of proteins with diverse functions and exhibits characteristic arrangements of Cys and His residues with a novel zinc-binding motif. LIM domain proteins have been implicated in development, cell regulation, and cell structure. A LIM domain protein was identified by screening a human cDNA library with rat cysteine-rich intestinal protein (CRIP) as a probe, under conditions of low stringency. Comparison of the predicted amino acid sequence with several LIM domain proteins revealed 93% of the residues to be identical to rat LIM domain protein, termed ESP1 or CRP2. Thus, the protein is hereafter referred to as human ESP1/CRP2. The cDNA encompasses a 1171-base region, including 26, 624, and 521 bases in the 5'-noncoding region, coding region, and 3'-noncoding regions, respectively, and encodes the entire ESP1/CRP2 of 208 amino acids (M(r), 22,496). Human ESP1/CRP2 protein has two LIM domains, and each shares 35.1% and 77 or 79% identical residues with human cysteine-rich protein (CRP) and rat CRIP, respectively. Northern blot analysis of ESP1/CRP2 in various human tissues showed distinct tissue distributions compared with CRP and CRIP, suggesting that each might serve related but specific roles in tissue organization or function. Using a panel of human-rodent somatic cell hybrids, the ESP1/CRP2 locus was assigned to chromosome 14. Fluorescence in situ hybridization, using cDNA and a genome DNA fragment of the ESP1/CRP2 as probes, confirms this assignment and relegates regional localization to band 14q32.3.

Adaptor Proteins, Signal Transducing↗
PubMed1996

Right-sided ulcerative colitis.

This report describes a case of right-sided ulcerative colitis in which multiple shallow ulcers and erosion with symmetric luminal stenosis were distributed segmentally from the ascending colon to the cecum, with a skip lesion composed of superficial erosions in the right half of the transverse colon. Both the rectum and the left colon were spared at the time of onset. Biopsies taken from the lesions showed non-specific inflammation, while those from the rectum and sigmoid colon showed no abnormal findings. A 5-year follow-up study was made based on radiography and endoscopy. Other inflammatory bowel diseases, such as Crohn's disease, tuberculosis, Yersinosis, Behçet's disease, and ischemic colitis were all ruled out, based on the macroscopic and microscopic findings as well as the clinical course. To our knowledge, this is the first report of right-sided ulcerative colitis that has been followed for a long period.

Adult↗
PubMed1996

Correlation of in vivo nitric oxide and cGMP with glutamate/glutamine metabolism in the rat striatum.

We have examined how the suppression of endogenous production of nitric oxide (NO) in the striatal tissue affects release of glutamate (GLU) and glutamine (GLN) in pentobarbital-anesthetized male Sprague-Dawley rats. For the quantitative measurement of tissue NO production and amino acid release, an in vivo assay system for extracellular nitrite (NO2-) and amino acids was employed using an in vivo microdialysis technique. An NO synthase inhibitor (NG-nitro-L-arginine methyl ester, L-NAME) in concentrations ranging between 4-40 mM was perfused into the rat striatum using the assay system. Tissue NO production was found to be inversely proportional to the L-NAME concentration. L-NAME likewise decreased striatal levels of GLU and GLN. Furthermore, tissue NO production showed a positive correlation with GLU (R = 0.62, P < 0.02) and GLN (R = 0.86, P < 0.001) concentrations. Exogenous application of NO and cGMP by intrastriatal perfusion with 0.1-2.5 mM hydroxylamine and 0.4-10 mM 8-bromo-cGMP, respectively, increased striatal GLU release in a dose-related manner. Hydroxylamine reduced GLN release, and 8-bromo-cGMP showed a tendency to decrease GLN. In conclusion, striatal GLU/GLN metabolism is a function of the tissue concentration of NO. Normal endogenous concentration of NO causes GLU to be released at a consistent basal level, and enhanced tissue NO production facilitates GLU release via pathways including cGMP formation. We hypothesize that NO may suppress GLN formation by astrocytes.

Animals↗
PubMed1996

Developmental and denervation changes in c-ret proto-oncogene expression in chick motoneurons.

Receptor tyrosine kinases (RTKs) play important roles in cellular differentiation, survival, and proliferation. To search for genes involved in the survival of motoneurons, we isolated the RTKs specifically expressed on them. We used RT-PCR, by which RNA was obtained from purified embryonic day 5 (E5) chick motoneurons, and screened by in situ hybridization. Of 17 RTK cDNA clones, c-ret expression gradually increased in the motoneurons of the spinal cord during development. Compared with the expression of the neurotrophin receptor, TrkC, that of c-ret was very high in motoneurons from around E17 to adulthood. The level of c-ret expression on the motoneurons was unaffected by deafferentation at E2, but changed after denervation at post-hatching day 2. The in situ hybridization signal for c-ret mRNA increased slightly at day 1, then decreased progressively up to day 8, and increased again 2 weeks after sciatic nerve denervation in the motoneurons of the lumbar spinal cord. There were also changes in the signal of the lesioned sciatic nerve. In the most distal part from the lesioned site, the signal for c-ret mRNA significantly increased from day 3 on after denervation. These results suggested that the c-ret gene may encode the receptor for a factor involved in motoneuron differentiation and the promotion of regeneration of injured peripheral nerves.

Amino Acid Sequence↗
PubMed1996

The receptor tyrosine kinase, Cek8, is transiently expressed on subtypes of motoneurons in the spinal cord during development.

Receptor tyrosine kinases (RTKs) play important roles in cellular proliferation, differentiation, and survival. We performed reverse transcriptase-polymerase chain reactions (RT-PCR) from enriched embryonic day 5 (E5) chick motoneurons by panning to identify RTKs involved in the early development of motoneuron. In situ hybridization revealed that Cek8, a member of the eph family, was specifically expressed on motoneurons at the brachial and lumbar segments of the spinal cord which innervate limb muscles, and disappeared after the naturally occurring cell death period (E6-E11). Immunohistochemistry using an anti-Cek8 monoclonal antibody showed the localization of Cek8 protein at the cell bodies and axonal fibers of motoneurons and muscles. The unique expression of Cek8 suggests its involvement in cellular survival or cell-cell interactions for specific subpopulations of developing motoneurons.

Amino Acid Sequence↗
PubMed1996

Novel designed enediynes: molecular design, chemical synthesis, mode of cycloaromatization and guanine-specific DNA cleavage.

The molecular design and chemical synthesis of novel enediyne molecules related to the neocarzinostatin chromophore (1), and their chemical and DNA cleaving properties are described. The 10-membered enediyne triols 16-18 were effectively synthesized from xylitol (10) in a short step, and found to be quite stable when handled at room temperature. The representative and acylated enediyne 16 was cycloaromatized by 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) in cyclohexa-1,4-diene-benzene to give the benzenoid product 21 through a radical pathway. On the other hand, the enediyne 16 was cycloaromatized by diethylamine in dimethyl sulfoxide-Tris-HCl, pH 8.5 buffer to afford another benzenoid product 22 as a diethylamine adduct through a polar pathway. Furthermore, the enediynes 16-18 were found to exhibit guanine-specific DNA cleavage under weakly basic conditions with no additive.

Alkynes↗
PubMed1996

Nonreleasing basophils convert to releasing basophils by culturing with IL-3.

The extent of basophil histamine release initiated by IgE cross-linking stimuli has been known to vary greatly among donors. Studies on anti-IgE nonreleasing basophils are useful in understanding the IgE-specific control mechanism of mediator release. We attempted to determine (1) whether a mutation of Fc epsilon RI is present in nonreleasing basophils and (2) whether treatment with IL-3 converts anti-IgE nonreleasing basophils to releasing basophils. Basophils were purified from normal human blood and donors were divided into releasers (maximal histamine release > 5%) and nonreleasers (< 5%). The mutation of Fc epsilon RI alpha, beta, and gamma was evaluated by reverse transcriptase-polymerase chain reaction, and the DNA sequence was determined from amplified polymerase chain reaction products. Although antibodies against Fc epsilon RI failed to cause histamine release in anti-IgE nonreleasing basophils, no primary structural change of Fc epsilon RI was observed in nonreleaser basophils. After culturing with IL-3 for 7 days, nonreleasing basophils released histamine in response to anti-IgE, and dose-response curves of anti-IgE were equal in both releasers and nonreleasers. The conversion of nonreleasing basophils to releasing basophils was evident after 3 days of culture with IL-3. These findings indicate that nonreleasing basophils have recoverable defect(s) in the signal transduction pathway after IgE cross-linking.

Base Sequence↗
PubMed1996

Expression ratio of hepatocyte nuclear factor-1 to variant hepatocyte nuclear factor-1 in differentiation of hepatocellular carcinoma and hepatoblastoma.

BACKGROUND/AIMS: Liver-specific protein genes have multiple cis-/trans-acting elements, but those accountable for hepatocytic differentiation are unclear. An AT-rich core sequence (AT motif) is essential as a cis-acting element for the hepatic transcription. Homologous proteins hepatocyte nuclear factor-1 (HNF-1) and variant HNF-1 (vHNF-1) bind to this motif. The ratio of HNF-1 to vHNF-1 mRNA was examined in various liver tissues with respect to their differentiation. METHODS: The competitive reverse transcriptional polymerase chain reaction was employed to amplify HNF-1 and vHNF-1 mRNA simultaneously and to examine their expression ratio in total RNA extracted from frozen liver tissues of 37 patients with hepatocellular carcinoma, five patients with hepatoblastoma, and 15 non-neoplastic liver tissues. RESULTS: The ratio of HNF-1 to vHNF-1 mRNA was higher in well-differentiated cases than in poorly-differentiated and undifferentiated cases, except that one poorly-differentiated hepatoblastoma displayed a high ratio. Non-neoplastic liver tissues had low ratios similar to poorly-differentiated hepatocellular carcinoma, the reason for which remained unknown. However, chronic hepatitis and liver cirrhosis cases also demonstrated low ratios, and hence degenerative changes themselves displayed no obvious influence on such ratios. Thus, the gene expression of HNF-1 and vHNF-1 seemed to be differentially regulated in neoplastic and non-neoplastic hepatocytes. CONCLUSIONS: These results suggested that the ratio of HNF-1 to vHNF-1 mRNA correlated with histological differentiation of HCC and hepatoblastoma.

Adult↗
PubMed1996

Improvement of intestinal absorption of leucine enkephalin by sugar coupling and peptidase inhibitors.

Peptidase-degradable leucine enkephalin (LE) was coupled with cellobiose or gentiobiose. In the absorption experiments, cellobiose-coupled LE (CcpLE) was more stable than LE itself on the mucosal side, and CcpLE appeared on the serosal side. Destyrosyl LE coupled with cellobiose was not formed, indicating that sugar coupling provided LE with aminopeptidase resistance. In the presence of inhibitors of angiotensin-converting enzyme and enkephalinase, the stability of CcpLE on the mucosal side was increased, and as a result more was absorbed. Furthermore, the absorption clearance was much higher than the value expected from the mucosal concentration of CcpLE. Similar results were observed in the absorption of gentiobiose-coupled LE. In the LE absorption experiment, however, LE was not detected on the serosal side even in the presence of these peptidase inhibitors. Improvement of intestinal absorption by sugar coupling and peptidase inhibitors was evaluated kinetically, indicating the exclusive contribution of metabolic degradation of LE through intestinal tissues to the absorption process.

Animals↗
PubMed1996

Deletion mapping on chromosome 1p in well-differentiated gastric cancer.

To define the region on the short arm of chromosome 1 that is thought to include one or more tumour-suppressor genes for gastric cancers, we carried out loss of heterozygosity (LOH) studies in 26 gastric adenocarcinomas, using three restriction fragment length polymorphism (RFLP) markers and nine microsatellite markers. All tumours were informative with at least one locus; three revealed replication errors (RERs) at multiple microsatellite loci, and interstitial or telomeric allelic deletions were observed in 12 cases. Deletion mapping of these tumours defined a commonly deleted region between two loci, D1S201 and D1S197, that are 13 cM apart. As two loci within the commonly deleted region, D1S57 (pYNZ2) and D1S62 (pTHI54), were mapped respectively to 1p35 and 1p34.3 by fluorescence in situ hybridisation, we conclude that a locus likely to contain a tumour-suppressor gene for gastric cancer is located within a 13 cM region encompassing two chromosomal bands.

Chromosome Deletion↗
PubMed1996

Mutations in the TRKA/NGF receptor gene in patients with congenital insensitivity to pain with anhidrosis.

Congenital insensitivity to pain with anhidrosis (CIPA; MIM 256800) is an autosomal-recessive disorder characterized by recurrent episodes of unexplained fever, anhidrosis (absence of sweating) and absence of reaction to noxious stimuli, self-mutilating behaviour and mental retardation. The genetic basis for CIPA is unknown. Nerve growth factor (NGF) induces neurite outgrowth and promotes survival of embryonic sensory and sympathetic neurons. Mice lacking the gene for TrkA, a receptor tyrosine kinase for NGF, share dramatic phenotypic features of CIPA, including loss of responses to painful stimuli, although anhidrosis is not apparent in these animals. We therefore considered the human TRKA homologue as a candidate for the CIPA gene. The mRNA and genomic DNA encoding TRKA were analysed in three unrelated CIPA patients who had consanguineous parents. We detected a deletion-, splice- and missense-mutation in the tyrosine kinase domain in these three patients. Our findings strongly suggest that defects in TRKA cause CIPA and that the NGF-TRKA system has a crucial role in the development and function of the nociceptive reception as well as establishment of thermoregulation via sweating in humans. These results also implicate genes encoding other TRK and neurotrophin family members as candidates for developmental defect(s) of the nervous system.

Amino Acid Sequence↗