RESUMO
The mutagenic activity in extracts of fried meat from 16 different animal species was studied in Salmonella typhimurium TA98. In each experiment, 1 meat sample together with a standard beef sample was fried, and the mutagenicity was expressed relative to the beef sample. All meat samples showed less mutagenic activity than beef. The contents of creatine, creatinine, water, protein, carbohydrate and fat in the meat samples were analyzed, but mutagenicity was not correlated with the concentration of any of these constituents. Beef meat treated with creatinase to remove creatine produced reduced mutagenic activity. Possibly a threshold concentration of creatine is necessary to give a high mutagenic response.
Assuntos
Creatina/análise , Temperatura Alta , Produtos da Carne/análise , Carne/análise , Mutagênicos/análise , Valor Nutritivo , Animais , Culinária , Testes de Mutagenicidade/veterinária , Especificidade da Espécie , Ureo-Hidrolases/farmacologiaRESUMO
Nitrovin, a nitrofuran feed additive, is shown to be directly mutagenic in Salmonella typhimurium TA 98 and TA 100 between 0.1 and 2.5 microgram per plate (0.09--2.3 micrometer). Addition of a rat-liver homogenate reduces the mutation rates. Nitrovin inhibits growth of the same bacteria in suspension cultures at concentrations above 0.09 micrometer.
Assuntos
Ração Animal , Mutagênicos , Mutação , Nitrofuranos/farmacologia , Nitrovin/farmacologia , Animais , Aditivos Alimentares/farmacologia , Fígado/enzimologia , Masculino , Ratos , Salmonella typhimurium/efeitos dos fármacosRESUMO
L-Asparaginase (L-asparagine amidohydrolase, EC 3.5.1.1) B from Acinetobacter calcoaceticus has been purified by precipitation with streptomycin, chromatography on DEAE-cellulose and CM-cellulose, gel filtration on Agarose and chromatography on phosphocellulose. The molecular weight of the enzyme was found to be 130 000. The enzyme was rather insensitive to pH changes between 7 and 9. The Michaelis constant was 3-10(-3) M. Hg2+, Cu2+, and Ni2+ as well as high ionic strength inhibited the activity of the enzyme, whereas citrate seemed to stimulate the activity. The enzyme catalyzed the deamination of L-glutamine to about the same extent as L-asparagine. The temperature stability of the enzyme is also reported. The enzyme had a weak tumor inhibitory power.
