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Biomedical subjects

M Ochiai

Publications and source records attributed to M Ochiai.

At least 181 records · Page 10Linked to original sources
PubMed1987

Activation of human c-raf-1 by replacing the N-terminal region with different sequences.

Two transformants of NIH 3T3 cells, obtained by the transfection of human colon cancer and normal colon DNAs, contained activated c-raf-1. In both the activated c-raf-1, the 5' half of the c-raf-1 sequence was replaced by sequences other than c-raf-1 as a result of recombinations which occurred at the intron between exons 7 and 8. It was suggested, however, that these recombinations, which conferred the transforming activity on the c-raf-1, occurred during the transfection. In one case analyzed, characteristic sequences were found near the breakpoint and these may be involved in the recombination. It was found, upon analysing the structure of the cDNA derived from one of the activated c-raf-1, that fused mRNA had been transcribed from the recombined gene comprising the non-raf gene and c-raf-1. The mRNA possibly encodes a fused protein. One cDNA clone was derived from alternatively spliced mRNA, although its physiological role is unclear. On comparing the structure of the two human activated c-raf-1 and the rat activated c-raf which we have reported previously, it was revealed that, in these three cases, the sequences joined to the truncated c-raf(-1)1 were different. It was suggested from data which we and others have previously reported that various sequences could be capable of activating c-raf(-1) by replacing its 5' half.

Amino Acid Sequence↗
PubMed1987

Devices external pulse generator: a reliable temporary pacemaker?

Two cases of malfunctioning APC (American Pacemaker Company) Devices pacemakers are reported. Two patients with sick sinus syndrome were temporarily paced using APC Devices pacemaker models EC 4542 and EV 4543 respectively, which showed transient increase (53% and 83% of the preset rate, respectively) in pacing rate. The sudden increase of the pacing rate might be the pacemaker's design to switch to fixed-rate pacing at nominally 25% higher than the selected rate in the presence of an excessive level of electrical interference. However, the increased rate was much faster than the interference rate. Great caution should be paid when APC Devices pacemaker is to be used.

Female↗
PubMed1987

Active H-ras and N-ras in rat fibrosarcomas induced by 1,6-dinitropyrene.

The activated oncogenes in rat fibrosarcomas induced by subcutaneous injection of 1,6-dinitropyrene (1,6-DNP), an environmental mutagen-carcinogen, were examined by NIH3T3 cell transfection assay and Southern blot analysis. DNAs from two of eleven fibrosarcomas, 1,6-DNP6 and 1,6-DNP9T, induced transformants which contained rat specific repetitive sequences. Three primary transformants, obtained with DNA from 1,6-DNP6, and two secondary transformants of one of these primary transformants tested, contained rat H-ras. DNA from 1,6-DNP9T; a fourth transplant of 1,6-DNP9, also induced transformants. All the primary transformants with DNA from 1,6-DNP9T, and three secondary transformants of one of them, contained rat N-ras. The DNA from the original tumor, 1,6-DNP9, however, did not give any transformants by several transfection assays. Activation of N-ras oncogene during serial transplantations is discussed.

Animals↗
PubMed1987

Activated N-ras oncogene in a transformant derived from a rat small intestinal adenocarcinoma induced by 2-aminodipyrido[1,2-a:3',2'-d]imidazole.

DNAs from five intestinal adenocarcinomas induced by 2-aminodipyrido[1,2-a:3',2'-d]imidazole, which is present in broiled fish, were subjected to transfection assay using NIH3T3 cells as recipients. The DNA from only one adenocarcinoma induced a morphologically transformed focus. Rat N-ras sequences were detected in the primary transformant and in three tested secondary transformants. In the activated N-ras oncogene, a G----T transversion at the first letter of codon 12 was detected. The original tumor DNA did not hybridize with the oligonucleotide representing the mutated allele, but did hybridize with the one representing the normal allele. From these data we concluded either that the activation of the N-ras oncogene had occurred during the transfection or that the activated N-ras oncogene had been present in a minor population of cells in the original tumor.

Adenocarcinoma↗
PubMed1987

Amino-acid substitution at codon 13 of the N-ras oncogene in rectal cancer in a Japanese patient.

The activation of proto-oncogenes in colorectal cancers in Japanese patients was studied using a mouse NIH3T3 cell transfection assay system. Of thirty-five colorectal cancers examined, one rectal cancer showed an unusually high transformation efficiency and, in this rectal cancer, the N-ras oncogene was found to be activated. Nucleotide sequence analysis of the activated N-ras showed a single G----C point mutation at the first letter of codon 13, resulting in the coding of arginine instead of glycine. This amino-acid substitution at codon 13 may be responsible for the efficient induction of transformants of NIH3T3 cells in vitro.

Animals↗
PubMed1987

Recently identified nitrite-reactive compounds in food: occurrence and biological properties of the nitrosated products.

Various Japanese foodstuffs are directly-acting mutagens in Salmonella typhimurium TA100 after nitrite treatment. Such mutagen precursors include tyramine and beta-carboline derivatives, isolated from soya sauce, and indole-3-acetonitrile, 4-methoxyindole-3-acetonitrile and 4-methoxyindole-3-aldehyde, isolated from fresh Chinese cabbage. A mutagen produced from tyramine with nitrite was found to be 4-(2-aminoethyl)-6-diazo-2,4-cyclohexadienone (3-diazotyramine), and one produced from indole-3-acetonitrile with nitrite to be 1-nitrosoindole-3-acetonitrile. These two mutagens were directly-acting mutagens not only in S. typhimurium TA100 and TA98 but also in Chinese hamster lung cells, using diphtheria toxin resistance as a selective marker. The carcinogenicity of 3-diazotyramine was demonstrated in male Fischer 344 rats. Tyramine, beta-carboline and indole compounds are present ubiquitously in our environment, especially in foods. Therefore, the role of these newly identified mutagen precursors in the development of human cancer should be taken into consideration.

Acetonitriles↗
PubMed1986

Beta-1,3-glucan receptor and peptidoglycan receptor are present as separate entities within insect prophenoloxidase activating system.

Silkworm plasma was passed over a peptidoglycan-Sepharose 4B column or a CPB column [CPB, curdlan type polysaccharide (beta-1,3-glucan) bead] in the absence of divalent cation and the effluents from the columns were named plasma-PG and plasma-CPB, respectively. Prophenoloxidase activating system in plasma-PG was triggered by beta-1,3-glucan but not by peptidoglycan and the system in plasma-CPB was triggered by peptidoglycan but not by beta-1,3-glucan, suggesting that the peptidoglycan-Sepharose 4B column and the CPB column remove peptidoglycan-receptor and beta-1,3-glucan-receptor, respectively, from plasma. This result indicates that both receptors exist as separate entities in silkworm plasma. It is suggested that plasma-PG and plasma-CPB may be used as specific reagents to detect minute amounts of beta-1,3-glucan and peptidoglycan.

Animals↗
PubMed1986

Mutagenicities of indole and 30 derivatives after nitrite treatment.

Indole and 7-derivatives, L- and D-tryptophan and 9 derivatives, and beta-carboline (norharman) and 11 derivatives were tested for mutagenicity to Salmonella typhimurium TA100 and TA98 after nitrite treatment. 1-Methylindole, which is present in cigarette smoke condensate (Grob and Voellmin, 1970; Hoffmann and Rathkamp, 1970), was the most mutagenic to TA100 without S9 mix after nitrite treatment, inducing 615,000 revertants/mg. 2-Methylindole, 1-methyl-DL-tryptophan, harmaline and (-)-(1S,3S)-1,2-dimethyl-1,2,3,4-tetrahydro-beta-carboline-3- carboxylic acid also showed strong mutagenicity after nitrite treatment, inducing 129,000, 184,000, 103,000 and 197,000 revertants/mg, respectively. These mutagenic potencies were comparable with those of benzo[alpha]pyrene, 3-methylcholanthrene and 2-amino-9H-pyrido[2,3-b]indole (A alpha C) (Sugimura, 1982). Of 31 compounds tested, 22 were mutagenic after nitrite treatment. Since various indole compounds are ubiquitous in our environment, especially in plants, the presence of their mutagenicities after nitrite treatment warrants further studies, including those on their in vivo carcinogenicities.

Alkaloids↗
PubMed1986

Mutagenicity of soy sauce treated with a physiologically feasible concentration of nitrite.

Soy sauce treated with nitrite was found to be more mutagenic to Escherichia coli WP2 uvrA/pKM101 than Salmonella typhimurium TA100 without S9 mix. The mutagenicity of soy sauce treated with nitrite was affected by the concentration of soy sauce in the nitrosation mixture, and a concentration of 5% resulted in the highest specific activity (revertants/ml soy sauce equivalent). By incubating soy sauce at a concentration of 5% in a solution of 1 mM nitrite at pH 3 for 1 h at 37 degrees C, the equivalent of 1 ml of soy sauce induced 2790 revertants of E. coli WP2 uvrA/pKM101 without S9 mix.

Biotransformation↗
PubMed1986

Structure of the c-Ki-ras gene in a rat fibrosarcoma induced by 1,8-dinitropyrene.

Restriction enzyme maps were made of the region around exons 1 and 2 of activated c-Ki-ras of a fibrosarcoma (1,8-DNP2) induced in a rat by 1,8-dinitropyrene. Nucleotide sequence analysis revealed that activated c-Ki-ras shows a G----T transversion in codon 12 and consequently encodes cysteine instead of glycine in normal rat c-Ki-ras.

Amino Acid Sequence↗
PubMed1986

Activation of rat and human c-raf(-1) by rearrangement.

Activated c-raf(-1) gene was found in three transformants obtained by transfecting DNAs from rat hepatocellular carcinoma, metastasis of human colon cancer in mesocolon and normal mucosa from a different colon cancer patient. Rat and human activated c-raf(-1) genes were cloned into cosmid vectors; restriction enzyme mapping revealed both activated c-raf(-1) genes to have rearrangement in the center of the normal form of the gene, and the upstream sequences were replaced by unrelated sequences. Using genomic DNA fragments located immediately downstream of the recombination points, the activations of all these c-raf(-1) were shown to have occurred during the transfection process. The recombination points in both the rat and human clones isolated were located in the intron between exons 7 and 8, and nucleotide sequencing around these recombination points showed there to be an inverted repeat which could be involved in inducing in vitro recombination. Nucleotide sequencing of rat and human c-raf(-1) cDNAs revealed the upstream sequences, recombined to the 3' half of c-raf(-1), to be expressed as fusion mRNAs; the production of fused proteins was predicted from a long open reading frame, which is in-frame with the kinase domain encoded from the 3' half of the c-raf(-1) gene. There is a cysteine clustering region in an N-terminal region of the c-raf(-1) product deduced from the nucleotide sequence, and this cysteine clustering region was found to be highly homologous to that present in an N-terminal region of protein kinase C, although, in the latter cysteine clusters are present in duplicate. From analogy with the activation mechanism of protein kinase C, the N-terminal region of serine/threonine kinase coded by the c-raf(-1) gene is suggested to be a regulatory part of the enzyme activity, and it proposed that the replacement or truncation of this regulatory part could be the mechanism whereby c-raf(-1) is activated.

Amino Acid Sequence↗
PubMed1985

Activated c-raf gene in a rat hepatocellular carcinoma induced by 2-amino-3-methylimidazo[4,5-f]quinoline.

A rat hepatocellular carcinoma, IQ7, induced by 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) gave two transformants of NIH 3T3 cells on DNA mediated gene transfer. One of these transformants was examined further and secondary and tertiary transformants were obtained. The secondary transformant was tumorigenic in nude mice. The activated oncogene in this primary transformant was identified as rat c-raf by Southern blot analysis.

Animals↗