SUMMARYFrom a large number of cultures of cellulolytic bacteria isolated from rumen contents of sheep conditioned to low-protein teff hay through the use of both a selective medium containing finely ground cellulose as energy source and a less selective medium containing cellobiose, xylan and starch, thirty isolates, representing three morphological types, were selected for detailed characterization. Nineteen isolates of Gram-negative curved rods belonged to the genus Butyrivibrio. Of these one was identical with and ten closely related to B. Jibrisolvens. The remaining eight Butyrivi brio cultures differed in several respects from the only other defined species within this genus, B. alactacidigens. Four coccal isolates were identified as Rminococcus albus and five as R.j ¶avefaciens. Two strains of sporeformers belonged to the genus Clostridium but could not be identified with any of the cellulolytic species of this genus listed by Bergey's Manual.

No abstract

The mutation spectrum of the lacI gene from the liver of C57Bl6 Big Blue transgenic mice treated with benzo[a]pyrene (B[a]P) has been compared with the spectrum of spontaneous mutations observed in the liver of untreated Big Blue mice. Mice were treated with B[a]P for 3 days followed by a partial hepatectomy one day after the last injection. Liver tissue was removed for analysis at hepatectomy and, again, 3 days later at the time of sacrifice. Earlier, we reported that the lacI mutant frequency in these B[a]P-treated mice was elevated in the liver both at the time of hepatectomy and at sacrifice; however, a statistically significant increase in the mutant frequency was observed only at sacrifice. In this study, the DNA sequence spectra of lacI mutations observed in the liver of B[a]P-treated Big Blue mice at hepatectomy and at time of sacrifice were compared with each other and with the spectrum of spontaneous liver mutations. No differences were observed between the two B[a]P-treatment spectra. However, mutation frequencies of both GC-->TA and GC-->CG at the time of hepatectomy and at sacrifice were significantly elevated compared with the spontaneous frequency of these same transversions. Also, the frequency of AT-->TA transversions was significantly higher than the spontaneous frequency at the time of hepatectomy but not at sacrifice. The frequency of all other classes of mutations scored was not significantly different from the frequency of these same events in the spontaneous spectra. These data support the view that B[a]P treatment results in the induction of GC-->TA and GC-->CG transversions within 1 day of the last injection and they provide insights regarding the relative roles of benzo[a]pyrene-7,8-diol-9, 10-epoxide and radical cations of B[a]P in B[a]P-induced mutagenesis in vivo. Finally, these data provide evidence for B[a]P-induced mutagenesis under conditions where no statistical increase in mutant frequency could be shown.

No abstract

ABSTRACT. Fish from Silver Stream reservoir in Newburgh, New York (USA) were examined in 1985 and 1986 following reports by fishermen who had found a high prevalence of skin lesions in brown bullheads Ictalurus nebulosus caught in the reservoir Oral and skin papillomas were found in 43.2 % and 60.0 O/o of the brown bullheads from these respective samplings, whereas no papillomas were found in yellow bullheads I. natalis. No viral particles could be idenuied by electron microscopy in the lesions nor were cytopathic effects observed in primary cell cultures of tumor cells or from coculti\ration of these cells with an established brown bullhead cell line. Extracts of the sediment from the reservoir contained known promutagens but the concentrations of these compounds were low and similar to those found at reference sites considered to be non-contaminated. Nevertheless a positive response in the Ames assay of the extracts of the sediment was recorded. Elevated levels of chromium, copper, manganese, lead and vanadium were found in the sediments and copper, manganese, nickel, strontium and lead were elevated in the water. The pH of the interstitial water was 4.5. It is unlikely that any of these parameters was the sole causative factor in the etiology of the papillomas.