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Biomedical subjects

Y Kano

Publications and source records attributed to Y Kano.

At least 289 records · Page 16Linked to original sources
PubMed1983

Defective thymine dimer excision from xeroderma pigmentosum chromatin and its characteristic catalysis by cell-free extracts.

Specific excision of thymine dimers from isolated normal human and xeroderma pigmentosum (XP complementation groups A, C, D and G) chromatin was investigated under cell-free conditions. Crude extracts derived from unirradiated XP groups A, C and G cells were unable to excise dimers from their own nuclear sonicates, native chromatin and whole-cell sonicates prepared after exposure to 100 J/m2 of u.v. radiation at 254 nm, while normal-cell extracts were able to do so from all substrates including purified DNA. However, the extracts of XP groups A, C and G cells became capable of excising thymine dimers from chromatin preparations depleted of loosely bound nonhistone proteins with 0.35 M NaCl and from purified DNA. Extracts of XP group D cells catalyzed normal levels of excision from nuclear sonicates, native chromatin and 0.35 M NaCl-treated chromatin. These results suggest that none of the XP groups examined is deficient in a dimer-specific u.v. endonuclease. XP groups A, C and G cells are apparently defective in 'XP factors' present in the non-histone protein fraction, which are required for the excision of thymine dimers from chromatin. The XP group D factor appears to be different from the others. Extracts from XP groups A, C and G cells were able to complement each other with respect to dimer excision from chromatin. Novobiocin (200 micrograms/ml) completely inhibited dimer excision effected by extracts of normal cells or by complementing extracts of XP cells.

Cell Line↗
PubMed1983

Change in free amino acids and phospholipids in the head of adult Sarcophaga peregrina with age.

The amino acid and phospholipid contents in the head of adult Sarcophaga peregrina (flesh-fly) were measured with age. Only aspartic acid was found to increase significantly with aging. A significant difference was also detected in the fatty acid composition of the phospholipids. Phospholipids isolated from old flies contained more unsaturated fatty acid than young flies, suggesting that the properties of the membrane of head cells change with age. These changes were observed irrespective of sex or rearing conditions. Thus, it is possible that certain metabolic pathways in post-mitotic cells are selectively affected by aging.

Aging↗
PubMed1983

Developmental changes in fetal adrenal hypertrophy following maternal bilateral and fetal unilateral adrenalectomy at different stages of gestation in the rat.

Maternal adrenalectomy on days 14 and 15 of gestation did not alter the fetal adrenal weight 2 days later. The same operation on day 16 caused a significant increase in the adrenal weight with a hypertrophy of the cortical cells. Nevertheless, the operation on days 17 and 18 induced no change in the fetal adrenals. Subsequently on days 19 and 20, the operation resulted in a significant hypertrophy of the fetal adrenals. Fetal unilateral adrenalectomy on day 18 caused, 2 days later, significant hypertrophy of the contralateral adrenal, in contrast with no significant change after maternal adrenalectomy. This is perhaps due to the difference in the amount of fetal plasma corticoids, as evidenced by the previous reports of high concentrations of fetal plasma corticosterone on days 19 and 20. The overall results suggest that the fetal pituitary-adrenal feedback mechanism begins to appear between days 16 and 18 of gestation.

Adrenal Glands↗
PubMed1983

Effects of nitrous oxide on human cell lines.

Hematopoietic and nonhematopoietic cell lines cultured in media containing either 5-methyltetrahydrofolate or 5-formyltetrahydrofolate grow well to the same extent. However, when these same cell lines are grown in the presence of nitrous oxide, selective growth inhibition can be shown for hematopoietic cells cultured in 5-methyltetrahydrofolate-containing media. These cells also demonstrated a decreased ability to suppress [3H]-thymidine incorporation into DNA in deoxyuridine suppression tests.

B-Lymphocytes↗
PubMed1982

Higher inductions of twin and single sister chromatid exchanges by cross-linking agents in Fanconi's anemia cells.

Twin and single sister chromatid exchanges (SCEs) induced by short treatments with mitomycin C (MC) and 4,5',8-trimethylpsoralen (TMP)-plus-near ultraviolet light (NUV) were analyzed in colcemid-induced endoreduplicated normal human and typical Fanconi's anemia (FA) fibroblasts with diplochromosomes. The induction rate of twin SCEs that had occurred in the first cycle (S1) after the treatment was 1.7--2.4 times higher in FA cells than in normal cells. The induction rate of single SCEs that had arisen during the second cycle (S2) long after the treatment was also much higher, though less than the twin SCE rate, in FA cells than the almost negligible rate after repair of cross-links and monoadducts in normal cells. These results in FA cells, which specifically lack the first half-excision step of the two-step cross-link repair but retain the normal monoadduct repair, indicate that MC or TMP cross-links remaining unrepaired are indeed responsible for higher inductions of twin (S1 exchange) and single SCEs (S2 exchange). Thus, these findings indicate that Shafer's model of replication bypass for cross-link-induced SCE, which predicts greatly reduced twin SCE formation in FA cells due to half cancellation, is apparently inadequate as such. We present three plausible models, incorporating the ordinary replication model, random unilateral cross-link transfer, and chromatid breakage/reunion, that can account for the probabilistic inductions of single and twin SCEs and even for no SCE formation.

Anemia, Aplastic↗
PubMed1982

Involvement of the nusB gene products in transcription of Escherichia coli tryptophan operon in vitro.

Synthesis of trp mRNA in vitro directed by plasmid DNA carrying the entire trp operon was studied using crude protein extracts (S-100) from Escherichia coli strains carrying the nusA or nusB mutation or both. It was found that the levels of trp mRNA transcribed from the promoter-distal genes (trpCBA) relative to that from the promoter-proximal genes (trpED) was markedly lower with extracts from the nus- mutants than that from the nus+ strain. Kinetic experiments suggest that termination of RNA transcripts at intragenic transcriptional barriers is prevented by the nus gene products from allowing efficient expression of the operon.

Bacterial Proteins↗
PubMed1982

Amplification and abnormal chromosomal distribution of ribosomal genes (rDNA) in rat erythroleukemia cells.

The ribosomal cistrons (rDNA)/genome ratio was measured in five cell lines derived from three chemically induced erythroblastic leukemias (D-1, D-2, and NE26) in the Long-Evans (LE) rat and compared with values in the normal liver, bone marrow, and fetus. The ratio was 20-42% higher in the leukemias than in normal tissues. The number of autoradiographic silver grains of 125I-labeled rRNA hybridized in situ over three nucleolus organizer regions (NORs) of leukemia cells was determined and compared with that of the normal cells. Although the distribution of silver grains of normal cells averaged 44.6%, 25.9%, and 29.5% in NORs of chromosomes #3, #11, and #12, respectively, their distribution was abnormal in two of the leukemias examined; rDNA was amplified in chromosomes #12 of two sublines (K1DA and K1DB) of one leukemias (D-1), and in one chromosome #3 of two sublines (K2D and K3D) of another leukemia (D-2). We consider the possibility that these abnormal patterns of rDNA distribution are related to the increase in rDNA in leukemia cells.

Animals↗
PubMed1982

Comparative studies of the effect of DNA superhelicity on in vitro transcription catalyzed by Escherichia coli S100 proteins and purified RNA polymerase.

The effect of DNA superhelicity on in vitro transcription catalyzed by purified Escherichia coli RNA polymerase or S100 crude extract proteins was examined at various KCl concentrations. DNA from a recombinant plasmid pMT48 harboring the pL promotor-controlled fused N-trp genes and the pR promotor-controlled tof (cro) gene was employed as a template. Stimulation of transcription by superhelicity is generally more pronounced with the S100 crude extract proteins than with pure RNA polymerase. At KCl concentrations lower than 100 mM with pure RNA polymerase, there is no significant difference in the template activity between the supercoiled and relaxed forms of pMT48 DNA. In contrast, the dependence of efficient template activity on superhelicity is great over a whole range of KCl concentrations from 1.7 to 400 mM in the system using the S100 crude extract. The relative insensitivity of the pR promotor to superhelicity can be observed in either transcription assay system. Analysis of the kinetics of pL-promoted synthesis of trp mRNA indicates that diminished transcription in vitro on a relaxed template results mainly from less frequent RNA chain initiations, but at least in part from premature arrest of the chain elongation.

Bacterial Proteins↗
PubMed1982

In vivo evidence for nusA and nusB gene function in general transcription of the Escherichia coli genome.

The requirements for nusA and nusB gene products for the effective transcription of E. coli genes, including the trp operon, were demonstrated by analysis of RNA transcripts produced in nusA, nusB and nusAnusB mutants. In the nusA1 mutant, the levels of overall synthesis of both bulk RNA and trp mRNA were reduced more at 37 C than at 30 C, consistent with the idea of temperature-sensitive nus protein function (Friedman et al., 1973). In the nusB27 and nusA1nusB27 mutants (Friedman et al., 1976), decrease in the overall rates of these RNA synthesis was notable even at 30 C. In nus mutants harboring trp delta LD1412, in which the trp operon attenuator site is deleted, the reduction in the trp mRNA level was less severe. Thus, the effect of nus mutations seems to result in part from more frequent transcription termination at the attenuator site. Also in nusA1nusB27 mutants, in which the distal portion of the trp operon is deleted, the trp mRNA level was not reduced much. Thus, transcription in the nus- mutants seems to be frequently and prematurely arrested at sites along the trp operon.

Escherichia coli↗
PubMed1982

Methionine dependency of cell growth in normal and malignant hematopoietic cells.

Normal and malignant hematopoietic cell lines, with the exception of MOLT-3, were unable to grow in the methionine-depleted medium which was supplemented with homocysteine. Normal lymphocytes were less stimulated by mitogens in the medium containing homocysteine. Colony-forming units in culture from normal bone marrow cells were not formed in the medium in which homocysteine was substituted for methionine. These data suggest that there are no differences in the methionine requirement for cell growth between normal and malignant hematopoietic cells.

B-Lymphocytes↗