Susceptibility to @entity8708 -induced XXXX and epithelial cell proliferation characteristics of F1, F2, and reciprocal backcrosses derived from SWR/J and AKR/J parental mouse strains.

@entity894 @entity5 @entity18399 @entity8708 @entity694
Hybrid crosses were performed between SWR/J, a strain highly sensitive to @entity8708 ( @entity18399 ), and AKR/J, a strain highly resistant to the carcinogen. F1 and F2 and reciprocal backcrosses were tested to determine if proliferative characteristics such as high activity, wide compartment (PC), and a large S-phase population in the middle third of crypts were linked to susceptibility and inherited as a dominant autosomal trait as was reported for @entity18399 @entity5 response. A blend of resistant and sensitive @entity5 and proliferative characteristics was observed in the F1 and F2 crosses. A @entity5 incidence of 43.7% in the F1 and 52% in the F2 was obtained rather than the respective 100% and 75% expected frequencies. One week after the sixth injection of @entity18399 , the incidence of focal areas of atypism (FAA) in the backcross to resistance (BCR) and the backcross to sensitivity (BCS) was the same (4.1 per FAA-bearing animal). This suggested that the response to the carcinogen was similar in both groups up to this point. Yet 20 weeks later, the BCR had a 7.3% @entity5 incidence, far lower than the 50% incidence expected. The BCS had an incidence of 98.6%, not unlike SWR frequencies and close to the expected 100% @entity5 incidence. Proliferative characteristics in the backcrosses, however, did not revert to parental levels. Instead, the @entity894 ( @entity894 ) or percentage of S-phase cells to total cells scored was significantly higher in the BCR than in the BCS (10.2% +/- 3.2% versus 8.1% +/- 2.2%, P less than 0.02). This study has shown that in crosses between these two strains (SWR/J and AKR/J), susceptibility to @entity18399 -induced @entity5 is not inherited as a dominant trait. Neither are the proliferative characteristics of the colonic mucosa inherited in a simple Mendelian manner nor are the kinetic properties of the epithelial cells linked to @entity18399 @entity5 susceptibility. It is suggested that the parental AKR/J strain may contribute a protective or resistant factor, that is, a repressor gene, which impedes the progression of carcinogen-induced foci of @entity694 .
