Salmonella/S-9 system

TABLE 2. Mutagenicity in Salmonella/S-9 System of Six Mrak Commission Carcinogenic Pesticides ... 

The testing results in the Salmonella/S-9 system as reported by McCann et Sugimura et Heddle and Bruce,and Odashima with the identifier assigned... 

The considerable variation among laboratories in the reversion frequencies found with the /Salmonella test system has been ascribed largely to the variable source and method of preparation of the S-9 fraction, and experimental conditions used. ° ° Similar variation is to be expected in the results of the SCE test with S-9. For example, CP is metabolized to an SCE-inducing metabolite far more effectively by S-9 prepared from liver of rats induced with Aroclor 1254 or phenobarbital than with 3-methylcholanthrene. ° An additional factor to be considered is the inactivation of compounds by either serum or S-9 components e.g., the SCE-inducing ability of AAAF and N-hydroxyacetylaminofluorene is reduced in the presence of S-9 Mix. Thus, any compound under investigation must be tested both with and without S-9 Mix and serum. 

The metabolism of Monuron in the rat consists of oxidative A -demethyla-tions, ring hydroxylation, and, to a limited extent, degradation of the urea residue to yield an aromatic amine. Using four microbial systems, Simmon et tested 20 pesticides, including Monuron, Simazine 120), and PCNB 224) no positive results were reported for these pesticides with or without S-9 in Salmonella or the other systems. 

Oxidative A -demethylation produces formaldehyde, a classic mutagen (reviewed in Auerbach et al. ). Butterworth has suggested that the lack of mutagenicity in Salmonella with hexamethylphosphoramide (HMPA), an inhalation carcinogen in the rat, is related to the bacterium s insensitivity to formaldehyde. HMPA, the hydroxymethylpentamethyl analogue of HMPA, and formaldehyde are all active in the mouse lymphoma system, the former only in the presence of S-9 (see also Ashby et Aldehyde formation may... 

Weigel, N. Kukuruzinska, M.A. Nakazawa, A. Waygood, E.B. Roseman, S. Sugar transport by the bacterial phosphotransferase system. Phosphoryl transfer reactions catalyzed by enzyme I of Salmonella typhimurium. J. Biol. Chem., 257, 14477-14491 (1982)... 

A second advantage of the LC-ESI-MS approach is the increased mass accn-racy of the measurement, making possible the detection of small mass differences between proteins. These mass differences can be eqirivalent to single-nucleotide polymorphisms (SNP) mutations or post-translational modifications. Recent work by McFarland and coworkers (2014) best illustrates the implementation of LC-(ESI)-MS (intact protein mass) and MS/MS top-down analyses to bacteria differentiation at the strain level. Proteins extracted from bacterial samples of Salmonella typhimurium (strain LT2) and S. heidelberg (strain A3 9) were first separated by reversed-phase (RP) LC and the eluent analyzed directly by ESI-MS using Q-TOF MS system (operated in the full-scan mode or MS). Following the data processing... 

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