E. A. Cook

Bio: E. A. Cook is an academic researcher. The author has contributed to research in topics: Chloride & Sodium. The author has an hindex of 1, co-authored 1 publications receiving 180 citations.

Isolation of deoxyribonucleic acid from mammalian tissues

Abstract: 1. DNA has been isolated from different mammalian tissues. The DNA preparations were free from RNA, protein and polysaccharides and have a similar range of sedimentation coefficients (approx. 24s). 2. Protein was removed by a two-stage extraction with a phenol-cresol mixture by using a detergent with 4-aminosalicylate in the first stage and sodium chloride in the second. 3. Polysaccharides remained in solution when DNA was precipitated with 2-butoxyethanol in the presence of 0.5m-sodium chloride and 1.5m-sodium benzoate. 4. Ribosomal RNA was removed by precipitation in the presence of 3m-sodium chloride at 0 degrees , when DNA remained soluble.

Liver microsomal metabolism of aflatoxin B 1 to a reactive derivative toxic to Salmonella typhimurium TA 1530.

Abstract: Summary A reduction in the survival of Salmonella tryphimurium TA 1530 was observed when the bacteria were incubated with aflatoxin B 1 , rat liver microsomes, and a reduced nicotinamide adenine dinucleotide phosphate-generating system. The lethality appeared to depend on the formation of a metabolite of aflatoxin B 1 by a mixed-function oxygenase system. The killing was very rapid; only 1% of the bacteria were able to form colonies after 2 min of incubation with large amounts of microsomes and aflatoxin B 1 . Attempts to separate the toxic metabolite from the microsomal system have not been successful. Toxic metabolites for S. typhimurium TA 1530 were also formed if aflatoxin B 1 was replaced by either aflatoxin G 1 or sterigmatocystin in the microsome-mediated toxicity assay. Except for aflatoxicol, the derivatives that were tested either had much less activity or were inactive. The livers from a number of other species of rodents and a single autopsy sample of human liver also were active in the microsome-mediated aflatoxin B 1 toxicity assay. The addition of RNA or DNA to the incubation mixture inhibited the killing of the bacteria. The RNA (which was reisolated after its incubation with aflatoxin B 1 ), liver microsomes, and a reduced nicotinamide adenine dinucleotide phosphate-generating system showed a low, broad absorption, with a maximum at 366 to 370 nm. This high wavelength absorption was not removed by Sephadex G-10 chromatography of the RNA or by extraction procedures and appeared to be attributable to covalently bound aflatoxin B 1 toxicity assay. The formation of the conjugated RNA was dependent on reduced nicotinamide adenine dinucleotide phosphate and was inhibited by the addition of aniline; the amount formed was a function of the activity of the mixed-function oxygenases in the incubation mixture. On the basis of the data presented, it is tentatively suggested that the derivative that is toxic to S. typhimurium TA 1530 and the one that reacts with nucleic acids are identical. The possible relationship of this derivative to the hepatocarcinogenicity of aflatoxin B 1 is discussed.

Cross-linking of complementary strands of DNA in mammalian cells by antitumour platinum compounds.

Abstract: Cis platinum (II) diammino-dichloride, cis Pt(II)(NH3)2Cl2 (A), is very effective against sarcoma 180 and leukaemia L 1210 in mice1,2 as well as Dunning ascites leukaemia and Walker 256 carcinosarcoma tumours in rats3. This and related compounds also reversibly inhibit cell division and induce cell elongation in E. coli B4,5. At a concentration below 5 µ, cis Pt(II)(NH3)2Cl2 selectively inhibits DNA synthesis in human amnion AV3 cells6, and there is a correlation between the relative effectiveness of a series of compounds and their capacity to inhibit DNA synthesis6. Support for the suggestion that in this cell line the effective platinum compounds acted by binding directly to DNA was obtained by Howie and Gale7. They found that DNA synthesis was selectively and persistently inhibited in Ehrlich ascites tumour cells removed from rats up to 4 days after treatment with a single injection of 10 mg/kg of A.