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Biomedical subjects

S Nishimura

Publications and source records attributed to S Nishimura.

At least 829 records · Page 46Linked to original sources
PubMed1983

Hydroxylation of the C-8 position of deoxyguanosine by reducing agents in the presence of oxygen.

The C-8 position of deoxyguanosine was hydroxylated by various reducing agents in the presence of oxygen in 0.1 M phosphate buffer (pH 6.8) at 37 degrees C. As reducing agents, ascorbic acid, hydroxylamine, hydrazine, sodium bisulfite and dihydroxymaleic acid were used. Metal powder (Fe, Ni) or metalethylenediaminetetraacetic acid (EDTA) complex (FeII-EDTA, TiIII-EDTA) was also effective for the hydroxylation reaction in the presence of oxygen. Guanine residues in calf thymus DNA were also modified by these reagents. The possible biological significance of the hydroxylation of guanine residue in DNA in relation to mutagenesis and carcinogenesis is discussed.

Ascorbic Acid↗
PubMed1983

Transforming activity of human melanoma DNA.

Cellular DNA transfection to mouse NIH3T3 cells revealed transforming activity of human malignant melanoma DNA. The corresponding human sequence was cloned from the transformed mouse cells. By hybridization to viral oncogenes, the transforming gene in human melanoma was identified as a homologue of viral Ha-ras gene.

Animals↗
PubMed1983

[ECG features of hypertrophy in hypertrophic cardiomyopathy, with special reference to asymmetric septal hypertrophy].

Thirty-eight cases of hypertrophic cardiomyopathy associated with asymmetric septal hypertrophy (ASH) were analyzed in order to correlate the electrocardiographic findings with the distribution of hypertrophic portions identified by two-dimensional echocardiograms. The electrocardiographic features which characterize the selected cases with ASH in this study were abnormal Q waves or regression of R waves in the left precordial leads (six obstructive type and six non-obstructive type) and a pattern of left ventricular hypertrophy (LVH) (31 cases including five cases with abnormal Q waves) (Table 1). There was no significant relation between the voltage of a R wave in V1 and the degree of septal thickness. From the electrocardiographic features mentioned above, the patients were divided into two groups, i.e., 1) the patients with abnormal Q waves (12 cases) and 2) those with LVH without abnormal Q waves (26 cases). The difference in the pattern of distribution of hypertrophy was evaluated based on the presence or absence of the abnormal Q waves. The results were as follows: Although there were no differences in the degree of septal thickness in both groups, the posterior wall in the group with LVH was significantly thicker. The group with LVH showed diffuse hypertrophy in the left ventricular free wall as well as the septum. Moreover, the short-axis view of two-dimensional echocardiograms revealed that hypertrophy in the septum was diffuse in both anterior and posterior portions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1982

DNA-binding of IQ, Me-IQ and Me-IQx, strong mutagens found in broiled foods.

Non-covalent DNA-binding has been studied of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), 2-amino-3,4-dimethylimidazo[4,5-f]quinoline (Me-IQ) and 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (Me-IQx), strong mutagens found in broiled foods. These mutagens are intercalated into DNA, as found by ultraviolet absorption and gel electrophoresis. The binding of IQ is stronger with GC pairs than AT pairs in DNA. The binding constants with calf thymus DNA are 1.6 X 10(6) (Me-IQ), 0.9 X 10(6) (IQ) and 0.7 X 10(6) M-1 (Me-IQx) at pH 6.0. This order of DNA affinity agrees with the order of mutagenicity towards Salmonella typhimurium TA98.

Animals↗
PubMed1982

Nucleotide sequence of Streptomyces griseus initiator tRNA.

The primary structure of initiator tRNA from Streptomyces griseus was determined by post-labeling procedures. The nucleotide sequence is pC-G-C-G-G-G-G-U-G-G-A-G-C-A-G-C-U-C-G-G-D-A-G-C-U-C-G-C-U-G-G-G-C-U-C-A-U-A-A-C-C- C-A-G-A-G-G-U-C-G-C-A-G-G-U-psi-C-A-m1A-A-U-C-C-U-G-U-C-C-C-C-G-C-U-A-C-C-A0H. The unique feature of the sequence of this tRNA is that residue 54 is occupied by unmodified U, while ribothymidine is located in that position in most initiator tRNAs from eubacteria.

Base Sequence↗
PubMed1982

A rat tRNA gene cluster containing the genes for tRNAPro and tRNALys. Analysis of nucleotide sequences of the genes and the surrounding regions.

A lambda clone carrying a rat DNA fragment of 11.9 kb was isolated from a rat gene library with total rat tRNA as a probe. Nucleotide sequence analysis revealed that the DNA fragment contained six tRNA genes, three for tRNAPro and three for tRNALys. Of the six genes all but one tRNAPro gene have the same polarity. Each tRNA gene is separated by a DNA region of 0.1 to 3.6 kb. The 5'-flanking regions of the six rat genes in the cluster do not have any significant sequence homology, but in the 3'-flanking region, each gene has a short T cluster, which is supposed to be a transcription termination signal.

Animals↗
PubMed1982

Changes of post-transcriptional modification of wye base in tumor-specific tRNAPhe.

Nucleotide sequences of normal mouse liver tRNAPhe and tumor-specific tRNAPhes isolated from Ehrlich ascites tumor and neuroblastoma cells were examined by post-labeling techniques. The results showed that their sequences are identical, except for changes in post-transcriptional modifications that are located in the anticodon region. Normal mouse liver tRNAPhe contained Cm32, Gm34 and YOH37. On the other hand, tumor-specific tRNAPhes were found in one of two possible configurations: 1) Cm32, Gm34 and Y*OH37 (under-modified YOH) or 2) C32, G34 and m1G37. The ratio of the two forms of tRNAPhes differed in different tumor cells; Ehrlich ascites tumor tRNAPhe had mainly Y*OH-containing tRNAPhe whereas neuroblastoma tRNAPhe has predominantly m1G-containing tRNAPhe. It was concluded that tumor-specific tRNAPhes are products of different extents of modification, rather than of new tRNA transcription.

Animals↗
PubMed1982

Characterization of a rat tRNA gene cluster containing the genes for tRNAAsp, tRNAGly and tRNAGlu, and pseudogenes.

The putative genes for tRNAGAUAsp(C), tRNAGGAGly(G) and tRNAGAGGlu are in a cluster on the rat chromosome and are present exclusively in a 3.3 kb region cleaved with a restriction endonuclease EcoRI. The cluster reiterates about 10 times on the haploid DNA. Four lambda clones each containing an independent repeating unit were isolated from a rat gene library. The studies on the cloned DNA revealed that the length of the repeating unit including the 3.3 kb EcoRI fragment was at least 13.5 kb. Nucleotide sequence analysis of the 3.3 kb DNA in the isolated clones showed sequence variations among the repeating units and incomplete genes for tRNAGly and tRNAGlu within the clusters.

Animals↗