[Determination of residual humidity in lyophilized vaccines by gas chromatography].
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Chromatography, Gas↗
Biomedical subjects
J Dayan
Publications and source records attributed to J Dayan.
Purification and kinetics of tyrosine-sensitive 3-deoxy-D-arabino-heptulosonic acid 7-phosphate synthetase from Salmonella.
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Aldehyde-Lyases↗
Enzyme alterations in tyrosine and phenylalanine auxotrophs of Salmonella typhimurium.
The enzyme activities specified by the tyrA and pheA genes were studied in wildtype strain Salmonella typhimurium and in phenylalanine and tyrosine auxotrophs. As in Aerobacter aerogenes and Escherichia coli, the wild-type enzymes of Salmonella catalyze two consecutive reactions: chorismate --> prephenate --> 4-hydroxy-phenylpyruvate (tyrA), and chorismate --> prephenate --> phenylpyruvate (pheA). A group of tyrA mutants capable of interallelic complementation had altered enzymes which retained chorismate mutase T activity but lacked prephenate dehydrogenase. Similarly, pheA mutants (in which interallelic complementation does not occur) had one group with altered enzymes which retained chorismate mutase P but lacked prephenate dehydratase. Tyrosine and phenylalanine auxotrophs outside of these categories showed loss of both activities of their respective bifunctional enzyme. TyrA mutants which had mutase T were considerably derepressed in this activity by tyrosine starvation and consequently excreted prephenate. A new and specific procedure was developed for assaying prephenate dehydrogenase activity.
Cell-Free System↗
Mutagenic activity of 4 active-principle forms of pharmaceutical drugs. Comparative study in the Salmonella typhimurium microsome test, and the HGPRT and Na+/K+ ATPase systems in cultured mammalian cells.
The nitroimidazole derivatives used in human therapy have shown a strong mutagenic activity in bacterial tests using Ames strains of Salmonella typhimurium. Our study compared the response of 4 products of this family on bacterial target cells as well as on mammalian target cells (Chinese hamster V79 cells). The strong positive response on TA100 was greatly reduced on the nitroreductase-deficient strain TA100 Frl. Furthermore, no mutagenic activity was found in V79 mammalian cells that we examined for ouabain and 6-thioguanine resistance.
Animals↗