Evidence supporting the interaction of CYP2B4 and CYP1A2 in microsomal preparations.

Recent studies have demonstrated that the catalytic behavior of one cytochrome P450 (P450) enzyme can be influenced by the presence of a second P450. This effect has been observed using reconstituted systems containing reductase, CYP2B4, and CYP1A2, primarily at subsaturating reductase. Addition of 1A2 caused a 75% inhibition of CYP2B4-dependent 7-pentoxyresorufin-O-dealkylation (PROD). Conversely, CYP2B4-dependent benzphetamine (bzp) demethylation did not exhibit this response after CYP1A2 addition. Addition of CYP2B4 to a reconstituted system containing reductase and CYP1A2 caused synergism of CYP1A2-dependent 7-ethoxyresorufin-O-dealkylation (EROD). This behavior was consistent with the formation of heteromeric CYP1A2-CYP2B4 complexes with altered catalytic properties. Although such responses have been documented in reconstituted systems, they have not been demonstrated in microsomal preparations. The goal of the present study was to determine whether such interactions were observed in rabbit liver microsomes. In an effort to detect such changes, we took advantage of the differential effect of CYP1A2 on CYP2B4-selective PROD and bzp metabolism. Rabbits were treated with phenobarbital (PB), beta-naphthoflavone (betaNF), and both PB + betaNF-conditions that enrich microsomes with CYP2B4, CYP1A2, or both enzymes, respectively. Benzphetamine demethylation activity was equivalently elevated in both the PB and the PB + betaNF groups, consistent with the induction of CYP2B4 in both groups. In contrast, PROD activity in the PB + betaNF group was less than 25% of that found in the PB-treated rabbits. These results demonstrate that the interactions observed in reconstituted systems are not an artifact of reconstitution but are observed under the more natural conditions of the microsomal membrane.

Comparison of media for isolation of poultry intestinal bacteria.

The effects of medium composition, incubation temperature, and length of incubation were determined for recovery of the predominant intestinal bacteria from turkey poults. Incubation of recovery media at 41 degrees C resulted in significantly higher counts than at 37 degrees C. In 2- and 3-week-old turkey poults. RGCAP-30, RGCAP-10, and RGCA-30 gave the highest recoveries of cecal bacteria. M98-5 was less effective and brain heart infusion agar was definitely inadequate. However, there was no significant difference between RGCAP-30 and brain heart infusion agar for recovery of duodenal bacteria. In older birds (6 weeks of age), M98-5 was equal or superior to the RGCA-based media. The choice of a primary isolation medium is thus dependent on the site to be sampled and the age of the bird.

Computer-assisted identification of anaerobic bacteria.

A computer program was developed to identify anaerobic bacteria by using simultaneous pattern recognition via a Bayesian probabilistic model. The system is intended for use as a rapid, precise, and reproducible aid in the identification of unknown isolates. The program operates on a data base of 28 genera comprising 238 species of anaerobic bacteria that can be separated by the program. Input to the program consists of biochemical and gas chromatographic test results in binary format. The system is flexible and yields outputs of: (i) most probable species, (ii) significant test results conflicting with established data, and (iii) differential tests of significance for missing test results.