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Biomedical subjects

A Levine

Publications and source records attributed to A Levine.

At least 145 records · Page 8Linked to original sources

Isolation of purified insoluble aortic collagen.

The chemistry of collagen from major blood vessels, such as the aorta, is poorly defined because of problems encountered in solubilization techniques. Normal extraction of calf aorta with acetic acid and/or pepsin does not yield significant quantities of collagen. However, treatment of the aorta with purified pancreatic elastase results in a residue containing a significant portion of the collagen. The amino acid analysis, the acrylamide gel electrophoretic patterns and the electron micrographs of this residue display characteristics consistent with relatively pure collagen. Using this purified collagen preparation approximately 90% of the collagenous material present can be solubilized by pepsin treatment.

Amino Acids↗

Expression of a bacterial gene turned on by a potent carcinogen.

Contrary to mutagenesis, lysogenic induction produced by chemical carcinogens occurs in the majority of a population of lysogenic cells. Such a mass effect can therefore be measured at the biochemical level using an E. coli tester strain in which the galactose operon has been put under the negative control of the lambda repressor. In this publication we show that galactokinase synthesis is turned on by aflatoxin B1 metabolites within an hour after treatment of the tester bacteria. Such a biochemical assay provides a useful means for identifying potential chemical carcinogens.

Aflatoxins↗

Lack of lysogenic induction in "diaminopimelic acid spheroplasts".

As part of an attempt to develop a semi-in vitro system of lysogenic induction, using spheroplasts of Escherichia coli K-12 lysogenic for prophage lambda, we prepared spheroplasts by depriving E. coli dap of diaminopimelic acid (DAP-spheroplasts). DAP-spheroplasts made from E. coli (lambda cI857) were thermally inducible. However, DAP-spheroplasts of E. coli (lambda) were not inducible by UV light. Thus, it appears that a functional cell wall is required for UV induction of prophage lambda.

Coliphages↗