Potential factors underlying the tumorigenic activity of ethylbenzene (EB) were examined in F344 rats and B6C3F1 mice inhaling 750 ppm EB vapor 6 h/day, 5 days/week, for one or four weeks. Target tissues (kidneys of rats and livers and lungs of mice) were evaluated for changes in organ weights, mixed function oxygenases (MFO), glucuronosyl transferase activities, S-phase DNA synthesis, apoptosis, alpha2u-globulin deposition, and histopathology. In male rats, kidney weight increases were accompanied by focal increases in hyaline droplets, alpha2u-globulin, degeneration, and S-phase synthesis in proximal tubules. In female rats, only decreased S-phase synthesis and MFO activities occurred. In mice, increased liver weights were accompanied by hepatocellular hypertrophy, mitotic figures, S-phase synthesis, and enzyme activities. S-phase synthesis rates in terminal bronchiolar epithelium were elevated and accompanied by loss of MFO activity. Exposure to a nontumorigenic level of 75 ppm for one week caused few changes. These data, considered with the general lack of EB genotoxicity, suggest a mode of tumorigenesis dependent upon increased cell proliferation and altered population dynamics in male rat kidney and mouse liver and lungs. A similar response in the kidneys of female rats appears to require a longer exposure period than was employed.

No abstract

The potential of 1,3‐dichloropropene (1,3‐DCP) to induce dominant lethal mutations in the germ cells of male CD® rats following inhalation exposure was investigated. Groups of 11‐week‐old males (30 animals/group) were exposed to 1,3‐DCP vapors by inhalation at targeted concentrations of 0 (negative control), 10, 60, and 150 ppm for 10 weeks (6 hr/day, 7 days/week). An additional group of 30 males (designated the pairfed group) was kept on dietary restriction for 10 weeks. This group served as a control for any effects of decreased feed consumption and the associated body weight loss on the dominant lethal indices in the males exposed to 1,3‐DCP. At the termination of the exposures, each male was cohoused with naive adult virgin CD females for two consecutive mating trials (1 week/trial, 2 females/male). Females were necropsied 13 days after the conclusion of each weekly mating trial and the number of corpora lutea, live implantations, and resorptions were determined. There were no statistically significant increases in either the pre‐ or postimplantation embryonic/fetal loss in females mated with 1,3‐DCP‐exposed males relative to controls at any weekly mating period. Based on these results, it can be concluded that 1,3‐DCP is not mutagenic to the male germ cells of CD® rats at exposure levels ≤ 150 ppm, the highest concentration tested. Environ. Mol. Mutagen. 32:351–359, 1998 © 1998 Wiley‐Liss, Inc.

A monoclonal antibody (18B/A5) has been generated against human first trimester trophoblast membranes which, unlike others so far reported in the literature, reacted only with cytotrophoblast and not with syncytiotrophoblast. Although the identity of the target antigen has not yet been established, the antibody could be a valuable tool for the identification and eventual separation and purification of human cytotrophoblast cells.

No abstract