Three pairs of structurally similar carcinogenic/non-carcinogenic chemicals were tested for in vivo genotoxic activity in B6C3F1 mice. The carcinogenic/non-carcinogenic pairs, respectively, were o-toluidine hydrochloride/o-anthranilic acid, 4-chloro-o-phenylenediamine/4-nitro-o-phenylenediamine, and 3-(chloromethyl)pyridine hydrochloride/2-(chloromethyl)pyridine hydrochloride. Bone marrow cells from mice given intraperitoneal injections of up to the maximum tolerated dose were evaluated for chromosomal aberration, sister chromatid exchange, and micronucleus induction, o-anthranilic acid and o-toluidine hydrochloride did not increase the frequency of chromosomal aberrations or micronuclei. o-Toluidine hydrochloride increased the frequency of sister chromatid exchanges in two successive trials, while o-anthranilic acid had a positive effect on sister chromatid exchanges in two of three trials. Both 2-(chloromethyl) and 3-(chloromethyl)pyridine hydrochloride were negative for all three endpoints. Assays for chromosomal aberrations and micronuclei each distinguished between 4-chloro-o-phenylenediamine and its non-carcinogenic companion, 4-nitro-o-phenylenediamine. In the aberration test, 4-chloro-o-phenylenediamine produced a few cells with very large numbers of aberrations rather than an even distribution of damage among cells.

The direct detection of gonococcal DNA in rectal and pharyngeal specimens was evaluated by using a DNA probe-based assay (Gen-Probe, Inc., San Diego, Calif.). Rectal (234) and pharyngeal (608) swab specimens were obtained from 249 men and 372 women attending sexually transmitted disease clinics in Las Vegas and Reno, Nevada. The prevalence of gonococcal infection by culture at the pharyngeal and rectal sites was 2.91% (16 of 548 specimens) in women and 2.7% (8 of 294 specimens) in men. No false-positive reactions were observed among the 234 rectal specimens tested. Two probe-positive, culture-negative specimens were detected among the 361 pharyngeal specimens obtained from women. Both of these samples were confirmed as Neisseria gonorrhoeae by a probe competition assay. The overall correlation of the DNA probe test with pharyngeal and rectal cultures was 99.4% (837 of 842 cultures), with a sensitivity of 87.5% (21 of 24 cultures) and specificity of 99.7% (816 of 818 cultures). The positive and negative predictive values of the DNA assay were 91.3 and 99.8%, respectively. The direct DNA probe assay provides an alternative to culture screening for rectal and/or pharyngeal gonococcal infections.

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