Search PubMed⌕ Search

Biomedical subjects

N Tsuchida

Publications and source records attributed to N Tsuchida.

At least 73 records · Page 4Linked to original sources
PubMed1990

Gene cloning of an Actinobacillus actinomycetemcomitans Y4 antigen which reacts with peripheral blood sera in patients with advanced destructive periodontitis.

Actinobacillus actinomycetemcomitans has been implicated in the aetiology of juvenile periodontitis and advanced destructive periodontitis. Levels of IgG antibody against A. actinomycetemcomitans in peripheral blood sera of patients with advanced destructive periodontitis are high, as are those against Bacteroides gingivalis. To clone the genes of antigens reactive with sera of such patients, a library of the A. actinomycetemcomitans strain Y4 DNA in lambda L47 was constructed and then screened, using an immunochemical detection method, with serum from a patient with the advanced disease. Six clones from among nearly 1000 reacted with the serum and also with that of another patient. They were designated 3, 4, 6, 7, 8 and 9. Restriction enzyme and Southern blot analyses indicated that clones 8 and 9 were identical and that all the clones were overlapping because they shared in common the 4 and 5 kbp HincII DNA fragments of A. actinomycetemcomitans. The cloned DNA fragment hybridized to the DNA of two other strains of A. actinomycetemcomitans but not to those of six periodontopathic bacteria examined. These findings suggest that a DNA sequence encoding an A. actinomycetemcomitans strain Y4 antigen strongly reactive with sera of patients with advanced destructive periodontitis was cloned. This sequence is present specifically in A. actinomycetemcomitans but not in other bacteria isolated from patients with periodontal diseases. Thus, the cloned DNA could serve as a probe for the diagnosis of periodontitis.

Actinobacillus↗
PubMed1990

Nonlethal G0-ts mutant tsJT60 becomes lethal at the nonpermissive temperature after transformation: a hint for new cancer chemotherapeutics.

tsJT60 is a nonlethal temperature-sensitive (ts) mutant of a Fischer rat cell line (3Y1) classified as a G0 mutant; i.e., the ts defect is not expressed within the cell growth cycle but is expressed only between the G0 and S phase. tsJT60 clones transformed with oncogenes such as adenovirus E1A, polyoma large T, polyoma middle T, v-Ki-ras, and LTR activated c-myc, or with a chemical carcinogen N-methyl-N'-nitro-N-nitrosoguanidine, grew well at 34 degrees C. However, most of these clones grew slowly at 40 degrees C, producing many floating dead cells, and some clones were killed at 40 degrees C. When they were cultured under conditions inadequate for growth of untransformed cells, such as high cell density or serum restriction, they were killed at 40 degrees C. These and previous results from SV40- and adenovirus-transformed tsJT60 clones favour the idea that transformed tsJT60 cells occasionally enter the G0 phase and are metabolically imbalanced at 40 degrees C during self-stimulation from the G0 to S phase. We propose that a drug which exclusively block, G0-G1 transition would be cytocidal to transformed cells but cytostatic to normal cells.

Adenovirus Early Proteins↗
PubMed1989

Altered ganglioside expression in ras-oncogene-transformed cells.

Alteration of ganglioside composition in mouse BALB/3T3 cells transformed either by DNA transfection with viral K-, H-, or cellular H-ras oncogene, or by infection with the K-ras oncogene-carrying murine sarcoma virus (Ki-KSV) was studied using a highly sensitive thin-layer chromatography/enzyme immunostaining method. Marked common decreases in the content of GD3 ganglioside and the increase of its metabolic precursor GM3 were bound in BALB/3T3 cell lines transformed by either K- or H-ras oncogenes. Moreover, a common decrease or loss in the contents of "A" series ganglio-tetraose gangliosides such as GM1a and GD1a was also found in all transformed cell lines, indicating that the alteration of cellular glycosphingolipids by ras oncogenes apparently does not depend on the type of ras-concogenes (K- and H-ras).

Animals↗
PubMed1989

Activation of oncogenes in human oral cancer cells: a novel codon 13 mutation of c-H-ras-1 and concurrent amplifications of c-erbB-1 and c-myc.

By NIH3T3 transfection assay in conjunction with in vitro transient neomycin selection, activated c-H-ras-1 oncogenes were detected in two squamous cell carcinoma cell lines, ZA and HOC-313, newly established from human oral cancer patients. ZA had a point mutational activation at the 13th codon, this activation of c-H-ras-1 being novel in human cancer cells, while HOC-313 appeared to have an activation at the 12th codon. In ZA, 16- to 32-fold amplification of the EGF receptor gene, c-erbB-1 and a few-fold amplification of c-myc were detected. The significance of these findings is discussed in relation to multistep carcinogenesis in human cells.

Aged↗
PubMed1989

Inactivation of the N-myc gene product by single amino acid substitution of leucine residues located in the leucine-zipper region.

To verify the importance of the hypothetical leucine-zipper structure in the N-myc protein, a series of mutants of the mouse N-myc gene were constructed, in which codons for the first and second leucine residues within this structure were systematically replaced by other amino acids. The expression plasmids which contained the mutated and wild type N-myc genes were cotransfected into rat embryo cells with activated c-Ha-ras gene and their transforming abilities were compared. It was shown that single amino acid substitutions in the leucine-zipper region inactivate the transforming ability of the N-myc gene product. In particular, proline, which is known to disrupt an alpha-helical structure, completely inactivated the transforming activity even when it was substituted for another amino acid located between these two leucine residues. Among several amino acid species used for substitution of the leucine residues, only methionine was able to retain the transforming activities in both the first and second leucine positions, although the activity was reduced as compared with wild-type N-myc gene product. It also appeared that the integrity of the first leucine is more important than the second leucine. Our results provide experimental evidence for the physiological importance of the hypothetical leucine-zipper structure.

Animals↗
PubMed1988

Increased formation of unintegrated viral DNA in skin fibroblasts from patients with familial polyposis coli shortly after infection with Kirsten murine sarcoma virus.

Skin fibroblasts from patients with familial polyposis coli (FPC) exhibit increased frequency of morphological transformation, anchorage-independent growth, and enhanced production of viral RNA and viral particles after infection with murine sarcoma virus(murine leukemia virus), MSV(MLV). These FPC fibroblasts form greater amounts of unintegrated viral DNA as compared to normal fibroblasts during the first 4 to 24 hr after infection with Kirsten MSV(KiMLV), suggesting that increased susceptibility of FPC cells to MSV is determined at an early stage of viral transformation. Several MSV-transformed clones of both FPC and normal fibroblasts, isolated from agarose gel, were non-producers having integrated viral genome which was expressed into viral RNA and rescued by infection with MLV.

Adenomatous Polyposis Coli↗
PubMed1987

Myc genes linked to viral promoters can collaborate with a transformation-deficient simian virus 40 early gene mutant to transform established rat cells.

Cotransfection of a transformation-deficient and immortalization-positive SV40 early gene mutant with various constructs of viral promoter-linked myc genes induced dense foci in 3Y1 cells, an established cell line derived from rat embryo fibroblasts, whereas transfections with either species alone did not. Four cell clones were isolated from colonies grown in soft agar medium, and found to contain at least a single copy of both DNA species and to express both sequences at relatively high levels. These results indicate that the two immortalizing genes used in the present study collaborate to transform 3Y1 cells.

Animals↗
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

Nucleotide sequence of exon I of the rat c-K-ras gene.

We have isolated a DNA fragment containing exon I of rat cellular proto-oncogene of K-ras and sequenced the exon I. The obtained sequence was compared with that of the corresponding region in viral oncogene of Kirsten strain of murine sarcoma virus (Ki-MSV). The results showed that the exon I sequences of cellular K-ras genes in rat and human cells could encode the same amino acid sequence, while the viral K-ras gene could code for two different amino acids corresponding to the 12th and 37th positions from the N-terminus of K-ras gene product. The amino acid substitutions found between viral and cellular K-ras genes are discussed in relation to the transforming ability of Ki-MSV.

Animals↗
PubMed1985

Amplification of c-Ki-ras gene and aberrant expression of c-myc in WI-38 cells transformed in vitro by gamma-irradiation.

The expression of c-oncogenes was examined with normal human fibroblasts (WI-38) and the cells transformed in vitro by gamma-irradiation (CT-1). The amount of Ki-ras-specific mRNA in CT-1 cells was found to be approximately twice that in WI-38 cells. By Southern blot hybridization, the c-Ki-ras 2 gene of CT-1 cells was found to be amplified about two-fold. CT-1 cells have higher levels of c-myc mRNA than normal cells, although the gene dosage and the restriction nuclease pattern of the c-myc gene was the same. The content of c-myc mRNA in CT-1 cells was found to be constitutively high, whereas that in normal cells was increased by serum addition.

Cell Line↗
PubMed1985

ISL1: a new transposable element in Lactobacillus casei.

The genome structures of a temperate Lactobacillus phage, phi FSW, and its virulent mutants, phi FSVs, were examined by restriction, heteroduplex and nucleotide-sequence analyses. The results showed that two out of three phi FSVs had the same 1.3 kbp insertion (designated as ISL1) at different positions in the phi FSW sequence. ISL1 was 1,256 bp long and contained at least two long open reading frames of 279 and 822 bases on one strand. Inverted repeats were found at the termini of the ISL1 which was bracketed by 3 bp direct repeats of the phi FSW sequence. From this evidence, we concluded that ISL1 was a transposable element in Lactobacillus casei.

Bacteriophages↗
PubMed1985

Activation of K-ras and oncogenes other than ras family in rat fibrosarcomas induced by 1,8-dinitropyrene.

Oncogenes of fibrosarcomas of rats, induced by subcutaneous injection of 1,8-dinitropyrene (1,8-DNP), were examined by NIH 3T3 cell transfection assay and Southern blot analysis. Transformants containing rat specific repetitive sequences were obtained with DNAs of 4 fibrosarcomas, 1,8-DNP1, 1,8-DNP2, 1,8-DNP3 and 1,8-DNP7. A transformant, 1,8-DNP2-2, induced by DNA of a fibrosarcoma, 1,8-DNP2, and 7 secondary transformants derived from it contained rat K-ras sequences. Another transformant, 1,8-DNP2-1, induced by the same sarcoma did not have a ras family oncogene. This indicates that the sarcoma, 1,8-DNP2, has at least 2 transforming genes. The transforming genes of 6 other transformants derived from 3 sarcomas did not contain ras family or neu transforming genes.

Animals↗
PubMed1985

[Oncogenes].

Explore the source record for details and available documents.

Amino Acid Sequence↗
PubMed1985

Amplification and enhanced expression of cellular oncogene c-Ki-ras-2 in a human epidermoid carcinoma of the lung.

The level of c-Ki-ras-2-specific mRNA was found to be markedly enhanced (10- to 20-fold) in a human epidermoid lung carcinoma transplanted into nude mice, compared with that in other lung carcinomas. Analysis of DNA revealed that c-Ki-ras-2 gene was amplified approximately 10-fold in this carcinoma, while c-Ha-ras, c-myc and c-sis were not amplified. Chromosome abnormalities were also observed in this carcinoma.

Aged↗
PubMed1984

A novel combination of K-ras and myc amplification accompanied by point mutational activation of K-ras in a human lung cancer.

Amplifications of two oncogenes, c-K-ras-2 and c-myc, were found in a human lung giant cell carcinoma (LGCC) Lu-65, which is maintained in nude mice. The extent of c-K-ras-2 and myc amplifications were estimated to be 10- and 8-fold, respectively, by means of the Southern hybridization procedure. In addition, NIH3T3 cells were transformed by transfection of Lu-65 DNA and the transforming gene was identified as c-K-ras-2. c-K-ras-2 genes were cloned from a gene library of Lu-65 and a single point mutation causing a substitution of cysteine for glycine in codon 12 was found by DNA sequencing. It was concluded that the amplification of the c-myc and c-K-ras-2 genes are accompanied by point mutational activation of c-K-ras-2 in the human LGCC Lu-65. This is the first report of multiple gene amplification accompanied by a point mutation of oncogenes in human cancer cells, providing further support for the idea that co-operation of at least two activated cellular oncogenes is required for carcinogenesis.

Amino Acid Sequence↗