Absence of PhIP adducts,p53 and Apc mutations,in rats fed a cooked beef diet containing a high level of heterocyclic amines

Meat cooked at high temperatures contains mutagens and carcinogens known as heterocyclic amines (HCA). Cooking temperature and time determine the amount of HCA produced. The present study examined the DNA of liver, colon, and stomach from rats fed a high level of HCA for 27 weeks. Male Sprague‐Dawley rats were fed a high‐fat AIN‐76A‐based diet containing 60% by weight cooked beef containing a high level of HCA, especially 2‐amino‐l‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP, 72 ng/g cooked beef), the most abundant HCA in cooked meat products. At the end of 27 weeks the rats were terminated, and small portions of liver, colon, and stomach were quick‐frozen in liquid nitrogen. The DNA was isolated from the thawed tissue by phenol‐chloroform extraction, and the genomic DNA was analyzed for the presence of PhIP adducts by ³²P‐postla‐beling analysis. The DNA was also used in polymerase chain reactions to amplify the rat p53 and Apc genes, then direct dye‐terminator DNA sequencing was carried out. Results showed no PhIP adducts in any tissue. In addition, no signature p53 or Apc gene mutations were seen in colon or stomach DNA. These results indicate that the high level of HCA present in a diet of well‐cooked meat does not cause 1) persistent PhIP adducts similar to those produced by feeding pure PhIP at high doses or 2) p53 and Ape gene mutations in nontumor tissue.     

Peer influence on students’ estimates of performance: social comparison in clinical rotations

Context During clinical rotations, students move from one clinical situation to another. Questions exist about students’ strategies for coping with these transitions. These strategies may include a process of social comparison because in this context it offers the student an opportunity to estimate his or her abilities to master a novel rotation. These estimates are relevant for learning and performance because they are related to self‐efficacy. We investigated whether student estimates of their own future performance are influenced by the performance level and gender of the peer with whom the student compares him‐ or herself. Methods We designed an experimental study in which participating students (n = 321) were divided into groups assigned to 12 different conditions. Each condition entailed a written comparison situation in which a peer student had completed the rotation the participant was required to undertake next. Differences between conditions were determined by the performance level (worse, similar or better) and gender of the comparison peer. The overall grade achieved by the comparison peer remained the same in all conditions. We asked participants to estimate their own future performance in that novel rotation. Differences between their estimates were analysed using analysis of variance (anova) . Results Students’ estimates of their future performance were highest when the comparison peer was presented as performing less well and lowest when the comparison peer was presented as performing better (p < 0.001). Estimates of male and female students in same‐gender comparison conditions did not differ. In two of three opposite‐gender conditions, male students’ estimates were higher than those of females (p < 0.001 and p < 0.05, respectively). Conclusions Social comparison influences students’ estimates of their future performance in a novel rotation. The effect depends on the performance level and gender of the comparison peer. This indicates that comparisons against particular peers may strengthen or diminish a student’s self‐efficacy, which, in turn, may ease or hamper the student’s learning during clinical rotations. The study is limited by its experimental design. Future research should focus on students’ comparison behaviour in real transitions.