Brief communication, P53 accumulation in N-methyl-N-nitrosourea-induced rat mammary tumors.

P53 aberrant protein expression and mutation is a component of many human tumors but less information is available regarding involvement in relevant animal models. We have examined invasive mammary epithelial neoplasms for p53 aberrant protein expression from Sprague-Dawley rats induced by two intrajugular injections of N-methyl-N-nitrosourea (NMU, 50 mg/kg), 7 days apart, beginning at 44-49 days of age. Positive nuclear staining was observed in 8/10 mammary tumor frozen sections using PAb 421, a mouse monoclonal antibody, compared to a mixed mouse IgG negative control antibody. Paraffin sections from two additional sets of similarly induced rat mammary tumors also showed positive nuclear staining (22/37 tumors) with CM-5, a rabbit polyclonal antibody. Our results indicate that elevated cellular content of p53 is a common event in invasive palpable mammary tumors induced by NMU in this dual-injection model system.

Effects in the rat of intranigral morphine and DAGO on eating and gnawing induced by stress.

Stress produced by pinching the tail is known to increase feeding behavior in rats, and endogenous opioids have been implicated in the mediation of this effect. We have reported previously that a nonspecific opioid antagonist and a mu-selective antagonist decrease this stress-induced eating (SIE) when they are microinjected into the substantia nigra (SN). The present study investigated the possibility that activation of opioid receptors in the SN might also alter SIE. Because oral stereotypy and nociception are affected by opioid mechanisms in the SN, measurements of gnawing and of tail flick and hot plate response latencies were also made. Bilateral injection of morphine (0.1-20 nmol) and the mu-selective agonist D-Ala2,N-Me-Phe4,Gly5-ol-enkephalin (DAGO; 0.03-1 nmol) increased response latency on the hot plate test and decreased gnawing produced by tail pinch. Tail flick latency and SIE were not affected. It is concluded that activation of opioid receptors in the SN does not produce an alteration in SIE as has been seen with opioid antagonists.

Bulimia nervosa symptomatology and body image disturbance associated with distance running and weight loss.

To investigate the hypothesis that problems characteristic of eating disorders may often be associated with distance running, 20 women who had lost weight through distance running were compared with a control group who did not exercise and had not lost weight and a comparison group of bulimia nervosa patients. Dependent variables were measures of depression, bulimia nervosa symptomatology, and body image disturbance. No differences were found between the runner group and the normal controls. Bulimics differed from runners and controls on most measures. Thus, the results did not support the proposition that weight loss through running leads to problems related to eating and body image. The failure to find disturbances in body image in runners suggests that body image disturbances are not a direct result of weight loss, as suggested by some theorists.

Mood-congruent memory in depression: emotional priming or elaboration?

We investigated whether mood-congruent memory (MCM) bias in depression is a function of implicit or explicit memory. Implicit memory is taken as a measure of ease of activation, whereas explicit memory also taps elaboration. As expected, MCM bias was found in the explicit memory task but not in the implicit memory task. We believe this finding supports the involvement of elaborative mechanisms in MCM. In addition, memory bias was found with words related to depression but not with words denoting physical threat. Thus, the MCM bias in explicit memory was found to be specific to information that was congruent with depression rather than to all negative information.