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Biomedical subjects

K Kuroki

Publications and source records attributed to K Kuroki.

At least 91 records · Page 5Linked to original sources
PubMed1986

[Effect of glutaraldehyde on cultured cells--restraining effect on multiplication of L cells].

Glutaraldehyde (GA) was tested for its cytotoxic effect on L cell tissue culture system in comparison with formaldehyde (FA). In the first study, the replanted cells were grown to monolayers on the flattened bases of the culture tubes, and then exposed to the drug. In the second study, the drug was added to the cell suspension just put in the culture tubes. In either case, the cells were kept in contact with the drug at 37 degrees C for 24, 48 or 72 hr, after which time the monolayers were removed and the viable cells in each of the tubes were counted up. The change in the number of viable cells was examined in the various concentrations of the drugs and time intervals of cell-drug contact. Both GA and FA showed relatively slight toxic effect when each concentration was 1 microgram/ml. The cells exposed to 1, 10 micrograms/ml of GA or 1 microgram/ml of FA were able to increase in number, though markedly restrained from their multiplication if compared with the control. GA and FA seriously diminished the viable cells at a concentration of 100 micrograms/ml and 10 micrograms/ml, respectively, and they were so toxic that complete cell death was immediately caused even when the concentration of each drug was at 1000 micrograms/ml. Just replanted cells showed less tolerance to the drug effects than the cells of established monolayers; suppression of cell growth was noted with the concentration of 0.8 microgram/ml and above of either GA or FA, and complete cell death was caused by 58 micrograms/ml of GA and 7.0 micrograms/ml of FA.(ABSTRACT TRUNCATED AT 250 WORDS)

Aldehydes↗
PubMed1985

Topical immunology of nasal allergy and mucosal IgE antibodies.

In the present study, the in vitro tissue-radioallergosorbent test (t-RAST) was performed in two groups of patients: one with perennial attacks of sneezing, serous hypersecretion and nasal congestion, the other with nasal congestion only. The results obtained were compared with those obtained by a series of conventional allergy tests. We then found that t-RAST provided objective data comparable to those obtained with serum-RAST and that the t-RAST is a reliable means of quantitatively detecting specific IgE antibodies in the nasal mucosa. t-RAST is of special value to diagnosticians because it is able to discern unequivocally and easily those patients with localized nasal allergy.

Humans↗
PubMed1985

Lectin histochemistry in a case of ulcerative colitis complicating rectal carcinoma.

The large bowel from a patient with ulcerative colitis complicating a rectal carcinoma was histochemically investigated by using two lectins; Ulex europaeus agglutinin-I (UEA-I) and peanut lectin (PNA). Much UEA-I binding glycoantigen and PNA binding glycoantigen appeared in the carcinoma and dysplastic lesion whereas only a small amount of both antigens was found in the non-dysplastic regenerating epithelium. Consequently, a very sharp contrast between the dysplastic lesion and non-dysplastic regenerating epithelium was demonstrated by the lectin staining.

Adenocarcinoma↗
PubMed1984

tRNAMetf2 gene in the leader region of the nusA operon in Escherichia coli.

The promoter-proximal portion of the operon containing the Escherichia coli nusA gene has been cloned. Its nucleotide sequence shows that genes for tRNAMetf2 and a 15-kilodalton protein of unknown function precede the nusA protein gene. The sequence suggests that the three genes form a single transcription unit. Consistent with this hypothesis, purified RNA polymerase formed full-length transcripts on the cloned DNA in vitro, although transcription was frequently arrested at the intercistronic site(s) between the gene for tRNAMetf2 and the 15-kilodalton protein.

Bacterial Proteins↗
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

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↗
PubMed1981

In vivo correlation between DNA supercoiling and transcription.

The superhelical density of pMT plasmid DNA in Escherichia coli cells was measured as a function of the transcriptional activity, which was reduced by treatment with coumermycin or oxolinic acid. Superhelicity was assayed by agarose gel electrophoresis of DNA extracted from cells gently lysed by sarkosyl. Coumermycin treatment reduced the proportion of supercoiled plasmid DNA in concert with a decrease in the rate of plasmid-coded synthesis of trp mRNA, implying a correlation between supercoiling of DNA and its suitability for transcription. On the other hand, the oxolinic acid-induced loss of supercoiled plasmid DNA was relatively small, while concomitant inhibition of trp mRNA synthesis was very severe. Treatment of the cells with these two drugs never removed all of supertwists from the pMT plasmids carried.

Aminocoumarins↗
PubMed1980

Purification and characterization of the N gene product of bacteriophage lambda.

The N protein (pN) specified by bacteriophage lambda is an antitermination factor and is required for phage development. pN can be assayed by making use of the observation that the in vitro synthesis of trp mRNA in a reaction programmed with DNA template from lambda trp transducing phage bearing N- and fed- mutations is pN dependent (Ishii et al., 1980). The assay has been used to purify pN. We have observed that pN forms a complex with E. coli protein(s) and is dissociated in the presence of urea. The complex is not formed in host bacteria bearing the nusA-nusB- mutations. pN is a basic protein and heat-stable. Using these characteristics, we have purified pN to virtual homogeneity as judged by polyacrylamide gel electrophoresis in the presence of SDS. pN is a monomeric protein and its mol. wt. is approx. 14 000. The antiterminating activity of pN appears to be enhanced by complex formation with host-encoded protein(s) depending on the nusA and/or nusB gene function.

Bacteriophage lambda↗