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Biomedical subjects

T Kada

Publications and source records attributed to T Kada.

At least 73 records · Page 4Linked to original sources
PubMed1980

Rec assay and mutagenicity studies on metal compounds.

We carried out rec assays on 127 metal compounds with Bacillus subtilis to check their DNA-damaging capacity and mutagenicity. Certain compounds of beryllium, cobalt, cesium, iridium, osmium, platinum, rhodium, antimony, tellurium, thallium and vanadium were newly found to be positive in addition to those of known positive metals such as arsenic, cadmium, chromium, mercury, molybdenum and selenium. Reverse mutation assays with Escherichia coli and Salmonella strains showed that compounds of rhodium (RhCl3), tellurium (Na2H4TeO6, Na2TeO3) and platinum (PtCl4, (NH4)2PtCl6) are potent mutagens.

Bacillus subtilis↗
PubMed1978

Purification and properties of a Bacillus subtilis endonuclease specific for apurinic sites in DNA.

An endonuclease which hydrolyzes depurinated DNA has been purified from extracts of Bacillus subtilis cells. The endonuclease is a monomeric protein and has a molecular weight of around 56,000. The enzyme is specific for apurinic sites in double-stranded DNA, has a pH optimum at 8.0, and is slightly stimulated with 50 mM NaCl but completely inhibited with 500 mM NaCl. It requires no divalent cations and is insensitive to EDTA; it has no associated exonuclease. These properties are very similar to those of Escherichia coli endonuclease IV, which is also insensitive to EDTA and has no exonuclease activity, and very different from those of the main endonuclease for apurinic sites (endonuclease IV) of the same bacterium.

Apurinic Acid↗
PubMed1978

Mutagenicity of benzotrichloride and related compounds.

Benzotrichloride (BTC), benzal chloride (BDC), benzyl chloride (BC) and benzoyl chloride (BOC) were surveyed for their mutagenicity in microbial systems such as rec-assay using Bacillus subtilis and reversion assays using E. coli WP2 and Ames Salmonella TA strains with or without metabolic activation in vitro. BTC and BDC required metabolic activation for their mutagenic activities in several strains of E. coli and Salmonella. The mutagenic metabolites of these compounds may not have been produced by hydrolysis. BC was weakly mutagenic without metabolic activation. Only BOC exhibited no mutagenic activity in the detection procedures used. The mutagenic metabolite of BTC might be very unstable under our experimental conditions. The strain E. coli WP2 try hcr was more sensitive than E. coli B/r WP2 try (hcr+) with regard to the mutagenicity of BTC.

Bacillus subtilis↗
PubMed1977

DNA repair enzymes in ataxia telangiectasia and Bloom's syndrome fibroblasts.

Ataxia telangiectasia, Bloom's syndrome and normal fibroblasts were compared as to the capacity of their cellular extracts to enhance the priming activity of gamma-irradiated colicin E1 DNA for purified DNA polymerase. It was found that an ataxia strain had substantially lower, and a Bloom's syndrome strain had slightly lower capacity than a normal strain; while the activities of apurinic site specific endonuclease in these extracts were comparable.

Ataxia Telangiectasia↗
PubMed1977

Studies on DNA repair in Bacillus subtilis. III. Identification of an exonuclease which enhances the priming activity of gamma-irradiated dna by "cleaning' damaged ends.

An enzyme which enhances the priming activity of gamma-irradiated DNA for type I DNA polymerase (EC 2.7.7.7) was identified and partially purified from extracts of Bacillus subtilis cells. The enzyme preferentially degraded gamma-irradiated DNA into acid-soluble materials. DNA preparations treated with heat, ultraviolet light, pancreatic DNAase (EC 3.1.4.5) or micrococcal DNAase (EC 3.1.4.7) were not susceptible to the enzyme. However, sonication rendered DNA susceptible to the enzyme to some extent. From these results, it is supposed that this enzyme may function by 'cleaning' damaged terminals produced by gamma-irradiation to serve as effective priming sites for repair synthesis by the type I DNA polymerase.

Bacillus subtilis↗
PubMed1976

Mutagenicity screening of pesticides in the microbial system.

A survey on the mutation induction capacity was made in the microbial system on 166 pesticides including 57 fungicides, 63 herbicides and 46 insecticides. The screening methods consisted of the rec-assay procedure, a sensitivity test utilizing H17 Rec+ and M45 Rec- strains of Bacillus subtilis, as well as the reversion assays on plates utilizing auxotrophic strains of Escherichia coli (WP2) and Salmonella typhimurium (Ames series). Chemicals inducing reversions were detected only among those showing positive effects in the rec-assay but not among negative samples. In addition to Captafol, Captan, Dexon and NBT of which mutagenicities have been previously reported, Dichlorvos, Folpet, 2-hydrazinoethanol (HEH), 5-nitro-1-naphthonitrile (NNN) and Vamidothion were found to be mutagens in our systems.

Bacillus subtilis↗
PubMed1976

Recombination-deficient mutants of Bacillus subtilis.

Two mutant strains of Bacillus subtilis Marburg, NIG43 and NIG45, were isolated. They showed high sensitivities to gamma rays, ultraviolet light (UV), and chemicals. Deficiencies in genetic recombination of these two mutants were shown by the experiments on their capacity in transformation. SPO2 transfection, and PBS1 phage transduction, as well as on their radiation and drug sensitivities and their Hcr+ capacity for UV-exposed phage M2. Some of these characteristics were compared with those of the known strains possessing the recA1 or recB2 alleles. Mapping studies revealed that the mutation rec-43 of strain NIG43 lies in the region of chromosome replication origin. The order was purA dna-8132 rec-43. Another mutation, rec-45, of strain NIG45 was found to be tightly linked to recA1. The mutation rec-43 reduced mainly the frequency of PBS1 transduction. On the other hand, the mutation rec-45 reduced the frequency of recombination involved both in transformation and PBS1 transduction. The mutation rec-43 of strain NIG43 is conditional, but rec-45 of strain NIG45 is not. The UV impairment in cellular survival of strain NIG43 was gradually reverted at higher salt or sucrose concentrations, suggesting cellular possession of a mutated gene produce whose function is conditional. In contrast to several other recombination-deficient strains, SPO2 lysogens of strain NIG43 and NIG45 were not inducible, indicating involvement of rec-43+ or rec-45+ gene product in the development of SPO2 prophage to a vegetative form. The UV-induced deoxyribonucleic acid degradation in vegetative cells was higher in rec-43 and rec-45 strains.

Bacillus subtilis↗
PubMed1975

Studies on DNA repair in Bacillus subtilis. I. A cellular factor acting on gamma-irradiated DNA and promoting its priming activity for DNA polymerase I.

Initiation of new DNA synthesis was observed in B. subtilis cells upon gamma-ray irradiation followed by toluene treatment and incubation in the presence of the four deoxynucleotide triphosphates and Mg2+. This DNA synthesis took place in the absence of ATP and was refractory to 6-(p-hydroxyphenylazo)-uracil which is a specific inhibitor for the type III polymerase of Bacillus subtilis. This repair-type DNA synthesis was greatly reduced in mutant cells deficient in DNA polymerase I. Restoration of transforming activity of cellular DNA was found to occur in parellel with the above repair type DNA synthesis. A protein factor which enhances the priming activity of gamma-irradiated DNA for DNA polymerase I was detected in DNA-free extracts prepared from B. subtilis cells by means of lysis with a buffer containing lysozyme, Brij-58 and EDTA.

Bacillus subtilis↗
PubMed1975

Studies on DNA repair in Bacillus subtilis. II. Partial purification and mode of action of an enzyme enhancing the priming activity of gamma-irradiated DNA.

A cellular factor which makes T7 DNA irradiated with gamma-rays a better primer for Micrococcus DNA polymerase was partially purified by DEAE and phosphocellulose column chromatography and named "primer activating enzyme". Sucrose density gradient sedimentation analysis was carried out to examine actions of one major active fraction that appeared by phosphocellulose chromatography. It was shown that this factor introduced new nicks in T7 DNA in addition to those introduced directly by gamma-ray irradiation. This enzyme fraction also had an endonucleolytic activity towards DNA containing apurinic sites induced by heat treatment and had capacity to enhance the priming activity of heat- or methyl methansulfonate-treated DNA but affected very little that of ultraviolet-irradiated DNA. This enzyme had no effect on T7 DNA when it was not treated with the DNA-damaging agents. From these results we concluded that this enzyme may be analogous to the endonuclease II or apurinic site-specific enconuclease of Escherichia coli.

Bacillus subtilis↗