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Biomedical subjects

A Hirai

Publications and source records attributed to A Hirai.

At least 19 recordsLinked to original sources
PubMed1996

Mitochondrial DNA 3394 mutation in the NADH dehydrogenase subunit 1 associated with non-insulin-dependent diabetes mellitus.

Mitochondrial DNA (mtDNA) mutation is associated with a subtype of non-insulin-dependent diabetes mellitus (NIDDM). We identified two homoplasmic mtDNA mutations at the positions of 3394 (T-C) and 3423 (G-T) in a NIDDM patient with clinical features of mitochondrial encephalopathy. The mtDNA 3394T-C mutation changed a conserved tyrosine to a histidine in NADH dehydrogenase subunit 1. The frequency of mtDNA 3994 T-C mutation was determined with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) in general NIDDM patients and nondiabetic control subjects. The mutation was seen in 4.9% of NIDDM patients and 1.3% of nondiabetic controls. It is indicated that the mtDNA 3394 T-C mutation is associated with NIDDM in Japan.

Base Sequence↗
PubMed1996

Loss of H19 imprinting in esophageal cancer.

Recent articles have reported that loss of imprinting (LOI) of the endogenous gene H19 was frequently found in lung cancer and chorio-carcinoma, common adulthood cancers. Consequently, we examined the status of genomic imprinting of H19 in 29 esophageal and 48 colorectal cancer specimens, and studied its relation to the expression of H19. Of 12 esophageal cancer specimens heterozygous for the RsaI polymorphism, 6 (50%) exhibited LOI of H19, but none of the 18 colorectal cancer specimens heterozygous for the RsaI polymorphism exhibited LOI of H19. The present study suggests that LOI of H19 may play an important role in the pathogenesis of esophageal cancer. Moreover, H19 expression was frequently abundant in both cancers, and all six esophageal cancers carried LOI with overexpressed H19. Therefore, this overexpression of H19 seems to be an important phenomenon for the development of esophageal and colorectal cancer cells.

Base Sequence↗
PubMed1996

The gene for a subunit of an ABC-type heme transporter is transcribed together with the gene for subunit 6 of NADH dehydrogenase in rice mitochondria.

We previously identified a chloroplast-derived (ct-derived) sequence of 32 base pairs (bp) in rice mitochondrial DNA that includes a part (30 bp; psitrnI) of a gene for isoleucine tRNA (CAU) of the chloroplast. Analyzing the ct-derived psitrnI, we found that an open reading frame (orf240), which was homologous to the gene for a subunit of an ATP-binding cassette-type (ABC-type) heme transporter, namely helC, of Rhodobacter capsulatus, and a gene for subunit 6 of NADH dehydrogenase (nad6) were located upstream of and downstream from the ct-derived psitrnI, respectively. Northern-blot hybridization and analysis by reverse transcription-polymerase chain reaction (RT-PCR) revealed that both orf240 and nad6 were co-transcribed in rice mitochondria. An analysis of PCR-amplified fragments of the region of orf240/nad6 from the DNA of some Gramineae suggests that the arrangement of orf240/nad6 was generated in the mitochondrial genome of the genus Oryza during evolution after its divergence from the other Gramineae. Most of the transcripts of orf240 are edited, with a change from cytidine to uridine, at 35 positions. Editing of the RNA changes 33 amino-acid residues among the 240 encoded amino-acid residues, suggesting that the orf240 gene is functional in rice mitochondria.

ATP-Binding Cassette Transporters↗
PubMed1996

Multiple initiation sites for transcription of a gene for subunit 1 of F1-ATPase (atp1) in rice mitochondria.

We identified the sites for the initiation of transcription of a gene for subunit 1 of F1-ATPase (atp1) in rice mitochondrial DNA. Capping and ribonuclease protection experiments in vitro, together with primer extension analysis, demonstrated that there were at least eight transcription initiation sites upstream of atp1. One initiation site, expressed most actively, was flanked by a sequence identical to the consensus promotor motif of rice mitochondrial genes. However, the sequences surrounding the other seven initiation sites exhibited no similarity to the consensus sequence.

Base Sequence↗
PubMed1996

Thyrotropin induces G1 cyclin expression and accelerates G1 phase after insulin-like growth factor I stimulation in FRTL-5 cells.

We have investigated the mechanism by which TSH pretreatment potentiates insulin-like growth factor I (IGF-I)-induced DNA synthesis in FRTL-5 cells. As previously described, pretreatment with TSH increased IGF-I-induced DNA synthesis, suggesting that the effect of TSH is mediated through the cAMP pathway. TSH and A kinase activators required at least 12 h to precondition cells to respond to IGF-I stimulation. The presence of cycloheximide abolished the effect of TSH to increase IGF-I-induced DNA synthesis. When the time course of thymidine uptake after IGF-I addition was studied, TSH pretreatment increased the maximum DNA incorporation and shortened the G1 phase interval. These results indicated that some proteins induced by TSH are required for the effect of TSH on IGF-I activity, and the proteins are important for cell cycle progression. Cyclins are key regulators of the cell cycle; therefore, we investigated the expression of cyclins D1 and E after TSH stimulation. TSH- and A kinase-activating agents increased the expression of cyclins D1 and E after 24 h. The same amounts of cyclins D1 and E induced by IGF-I were increased after TSH pretreatment. TSH pretreatment induced the expression of G1 cyclin in FRTL-5 cells, and IGF-I caused the accumulation of enough G1 cyclins to drive the cell cycle from G1 to S phase in a short time, which accounts for the effect of TSH on IGF-I induced DNA synthesis.

Animals↗
PubMed1995

c-Myc and cyclin D3 (CcnD3) genes are independent targets for glucocorticoid inhibition of lymphoid cell proliferation.

Glucocorticoids inhibit the expression of critical cell cycle-regulatory genes. The G1 cyclin gene CcnD3, which encodes cyclin D3, is inhibited by dexamethasone in P1798 murine T lymphoma cells. Glucocorticoids also inhibit expression of the catalytic partner of cyclin D3, Cdk4. Inhibition of these two genes results in a decrease in the ability to phosphorylate the Rb-1 tumor suppressor gene product. Stable transformation with SV40 T antigen expression vectors prevents glucocorticoid-mediated cell cycle arrest, which is consistent with the conclusion that glucocorticoids inhibit Rb-1 phosphorylation. Overexpression of cyclin D3 suffices to restore Rb-kinase activity in glucocorticoid-treated cells. Nevertheless, overexpression of cyclin D3 does not prevent glucocorticoid inhibition of cell proliferation. Cells transformed with Cdk4 expression vectors, with or without cyclin D3 expression vectors, also undergo G0 arrest in the presence of dexamethasone. Glucocorticoids inhibit c-Myc expression in lymphoid cells, and transient expression of c-Myc protein attenuates the lytic response in glucocorticoid-treated human leukemia cells (R. Thulasi, D. V. Harbour, and E. B. Thompson, J. Biol. Chem., 268: 18306-16312, 1993). However, P1798 cells stably transfected with c-Myc expression vectors are sensitive to glucocorticoid-mediated G0 arrest. Such transformants withdraw from the cell cycle when treated with dexamethasone. P1798 cells were transformed so as to express both c-Myc protein and cyclin D3 in the presence of glucocorticoids. These Myc/D3 cells continue to proliferate in the presence of dexamethasone, and virtually all of these cells are capable of entering S phase in the presence of the steroid. Rapid apoptotic cell death occurs when wild-type P1798 cells are treated with dexamethasone in serum-free medium. Myc-transformed and cyclin D3-transformed cells also die rapidly when treated with glucocorticoids in the absence of serum. T antigen transformants are resistant to glucocorticoid-mediated apoptosis in serum-free medium. Double transformants that express both cyclin D3 and c-Myc are also resistant to apoptosis in the presence of dexamethasone. We conclude that inhibition of both CcnD3 and c-Myc genes is critical to glucocorticoid-mediated G0 arrest. Furthermore, those genes that convey resistance to growth arrest also convey resistance to cell death.

Animals↗
PubMed1995

A small repeated sequence contains the transcription initiation sites for both trnfM and rrn26 in rice mitochondria.

The 76 bp sequence found in the upstream region of a gene for 26S rRNA (rrn26) is duplicated in the upstream region of a gene for initiator methionine tRNA (trnfM) in the mitochondrial genome of rice. An in vitro capping/ribonuclease protection assay and primer extension analysis demonstrated that the transcription of trnfM and of rrn26, which are at least 190 kb from one another in the rice mitochondrial genome, starts from these same sequences in the upstream regions of the respective genes. This result indicates that the short sequence that is duplicated in the upstream regions of trnfM and rrn26 in rice mtDNA is recognized as the promoter of each respective gene.

Base Sequence↗
PubMed1995

Neurofibroma of the stomach: report of a case.

We report herein the case of a 71-year-old-Japanese woman who was admitted to hospital for surgical treatment of a lower abdominal tumor. At laparotomy the tumor was found to be pedunculated and growing extramurally from the greater curvature of the stomach. Thus, a wedge resection of the stomach, including the mass, was performed. The tumor measured about 9 x 8 x 7 cm and histological examination of the resected specimen showed that the main elements consisted of wavy, long-spindled cells, which crossed irregularly, indicating that it was palisading negative. Immunohistochemically, the specimen was positive for both S-100 protein and Alcian blue. From these findings, the tumor was histologically diagnosed as a neurofibroma. The patient had an uneventful postoperative course and no signs of recurrence have been recognized in the 3 years since her operation.

Aged↗
PubMed1995

The rps3-rpl16-nad3-rps12 gene cluster in rice mitochondrial DNA is transcribed from alternative promoters.

The two gene clusters rps3-rpl16 and nad3-rps12 are separated from each other in the mitochondrial genome and are expressed as the individual transcription units in many plants. In rice mitochondrial DNA (mtDNA), the four genes rps3, rpl16, nad3 and rps12 are located within a region of 6 kbp. Northern-blot analysis revealed that a large transcript (6.6 kb) hybridized to both the rps3-rpl16 and the nad3-rps12 gene clusters. Using RT-PCR, we amplified a fragment of anticipated size (790 bp) from two primers that corresponded to sequences in the coding regions of rpl16 and nad3, demonstrating that at least two of the four genes, namely rpl16 and nad3, were co-transcribed. These results together indicated that all four genes, namely, rps3, rpl16, nad3 and rps12, were co-transcribed in rice mitochondria. Transcription initiation sites were determined by an in vitro capping/ribonuclease protection assay and primer extension analysis. Two initiation sites were identified in the rps3-rpl16-nad3-rps12 gene cluster: one was located upstream of rps3 and the other was located between rpl16 and nad3. This evidence indicates that the rps3-rpl16-nad3-rps12 gene cluster is transcribed from two alternative promoters.

Base Sequence↗
PubMed1995

Reduced rejoining ability of DNA strand breaks with differentiation in barley root cells.

To investigate the relationship between differentiation and the rejoining ability of DNA strand breaks, DNA strand breaks induced by gamma-rays were analyzed in barley roots using the alkaline unwinding assay. The extent of unwinding in an alkaline solution containing 0.5 M NaCl was found to be significantly inhibited at the root tip consisting of meristematic cells but not in the remainder of the root consisting of differentiated cells immediately after 100 Gy of gamma-irradiation. The difference in the extent of unwinding was diminished when the alkaline solution contained 2 M NaCl, suggesting a difference of chromosome structure and/or cell skeleton between the two regions. The rejoining kinetics of DNA strand breaks consisted of a fast and a slow component in both regions. DNA strand breaks were rejoined to the level of unirradiated control at the root tip but remained partly unrejoined in the remainder of the root during 6 h post-irradiation incubation. The difference of rejoining ability observed between the two regions originated from the different efficiency of rejoining at the slow component. The rejoining at the slow component in the root tip was found to be inhibited in the presence of the protein synthesis inhibitor cycloheximide, suggesting that de novo synthesized proteins are involved in the rejoining of DNA strand breaks. In contrast, the slow component in the remainder of the root was not inhibited by cycloheximide. These results suggest that the reduced rejoining ability of DNA strand breaks of differentiated cells may result from a deficiency of rejoining DNA strand breaks by inducible repair at the slow component. In addition, the lack of an apparent correlation between rejoining ability and growth inhibition of the root is discussed.

Cell Differentiation↗
PubMed1995

The Thrombostat system. A useful method to test antiplatelet drugs and diets.

UNLABELLED: The use of platelet inhibitory drugs, like aspirin, has resulted in a significant reduction of thrombotic complications in primary and secondary prevention of heart attacks. To find more effective substances or better drug combinations, inhibition of primary hemostasis in vitro (Thrombostat system) was investigated, with different drugs and fish diet, using small samples (1 ml) of anticoagulated (Na- citrate 3.8%, 1/9) human blood. RESULTS: 1. In the presence of 1 mM aspirin, which had no effect on bleeding volume, only 0.6 nM iloprost were necessary to show a 50% inhibition, in contrast to 2.5 nM without aspirin. 2. At aspirin concentrations of 1 mM, 50% inhibition of primary hemostasis could be achieved with 20 microM SIN-1, or with 7 microM SIN-1 together with iloprost (500 pM). The same effect was seen only with very high doses of SIN-1 (1000 microM) alone. 3. For 50% inhibition of primary hemostasis in vitro, RGDS concentrations were reduced from 250 microM to 160 microM when blood was pretreated with 1 mM aspirin and to 75 microM when 500 pM iloprost were added additionally. 4. Japanese fishermen (eating 270 g fish/day) demonstrated significantly longer in-vivo bleeding times and in-vitro bleeding volumes (6.49 min/224 microliters), respectively, as compared to Japanese farmers (90 g fish/day, 4.85 min/137 microliters). 5. In Japanese subjects in-vivo bleeding times correlated with in-vitro bleeding volumes (0.69). The Thrombostat system proved to be a sensitive method to detect synergistic effects of various antiplatelet drugs in vitro and of a platelet inhibitory diet ex vivo.

Bleeding Time↗
PubMed1995

Polymorphic distribution and molecular diversification of mitochondrial plasmid-like DNAs in the genus Oryza.

Four kinds of circular plasmid-like DNA, designated B1, B2, B3 and B4, have been found in the mitochondria of rice (Oryza sativa L.). We analyzed the distribution of families of plasmid-like DNAs homologous to those of O. sativa in 40 strains of the genus Oryza with AA, BB, BBCC, CC, CCDD and EE genomes. Plasmid-like DNAs were observed only strains having AA, CC and CCDD genomes. The distribution patterns of strains with AA genome were highly polymorphic. We amplified the plasmid-like DNAs from strains with the AA genome by PCR and examined restriction fragments length polymorphisms (RFLPs). RFLPs were detected among families of plasmid-like DNA amplified from different strains. This result indicated that some mutations, such as base substitutions and the insertion or deletion of a small fragment of DNA, had occurred and had accumulated during the differentiation of strains with an AA genome.

Base Sequence↗
PubMed1994

Palindromic repeated sequences (PRSs) in the mitochondrial genome of rice: evidence for their insertion after divergence of the genus Oryza from the other Gramineae.

We have identified a family of small repeated sequences (from 60 to 66 bp in length) in the mitochondrial genome of rice (Oryza sativa cv. Nipponbare). There are at least ten copies of these sequences and they are distributed throughout the mitochondrial genome. Each is potentially capable of forming a stem-and-loop structure and we have designated them PRSs (palindromic repeated sequences). Their features are reminiscent of the small dispersed repeats in the mitochondrial DNA (mtDNA) of some lower eukaryotes, such as Saccharomyces cerevisiae, Neurospora crassa and Chlamydomonas reinhardtii. Some of the PRSs of rice mtDNA are located in the intron of the gene for ribosomal protein S3 (rps3) and in the flanking sequence of the gene for chloroplast-like tRNA(Asn) (trnN). analysis of PCR-amplified fragments of these regions from the DNA of some Gramineae suggests that the PRSs were inserted into these regions of the Oryza mtDNA after the divergence of Oryza from the other Gramineae.

Base Sequence↗