Long-term effect of 2-hydroxyethyl retinamide on urinary bladder carcinogenesis and tumor transplantation in Fischer 344 rats.

The effects of HER upon early and late stages of BBN-induced bladder cancer in rats were examined. Female Fischer 344 rats were administered HER in the diet either before and during or continuously after BBN administration and were monitored periodically for up to 2 years. The total dose of BBN was 600 mg administered over a 6-week period. In a separate experiment, the effects of HER administration to syngeneic recipients of a transplanted primary bladder cancer were examined. No effects on neoplastic development were observed as the result of HER treatment before and during carcinogen administration. However, at the 1-year sacrifice, there was a significant increase in bladder tumor incidence in the animals receiving BBN followed by continuous retinoid treatment versus animals receiving BBN only. At the 2-year sacrifice, there was a significant increase in tumor progression in the continuous retinoid group versus the animals receiving BBN alone, based upon grading and staging of tumors, although tumor incidences were not significantly different. In the transplantation experiment, more recipients (9/20 versus 2/20) receiving continuous HER had large, anaplastic tumors following 9 months of observation than did control animals. This study supports the view that retinoids should not be considered as only inhibitors of carcinogenesis, but rather as modifiers which vary in their effects depending upon factors yet to be understood.

Haematology and pathology of captive southern grasshopper mice (Onychomys torridus).

A colony of Onychomys torridus was evaluated for the prevalence of infectious, parasitic and congenital diseases. Multiple limb defects including brachydactyly, syndactyly, and hemimelia were observed in offspring from the colony. The colony was parasitized by Ornithonyssus bacoti (tropical rat mites) on 2 occasions. No infectious diseases were detected. Normal haematologic values were determined in healthy adult animals.

Toxicity of cecal filtrates from guinea pigs with penicillin-associated colitis.

Lethal enterocolitis was induced in guinea pigs by intramuscular injection of penicillin. The presence of filterable toxic substance in the cecal contents of penicillin-treated guinea pigs was demonstrated. The toxin was heat-labile and produced enterosorption activity in rabbit intestinal loops and morphologic changes in Y-1 adrenal cell cultures. The cecal filtrates were lethal for mice when injected intraperitoneally and lethal for guinea pigs when injected intraperitoneally or intracecally. Cecal filtrates from saline-treated guinea pigs were not lethal to experimental animals. Filtrates prepared from broth cultures of cecal contents from penicillin or saline-treated guinea pigs also showed the presence of a lethal toxic substance. The study demonstrated that bacteremia is minimal, nonspecific and probably a terminal event in penicillin-associated deaths in guinea pigs.