Social competition in rats: cell proliferation and behavior.

Behavioral and physiological changes were studied following prolonged exposure to social competition in pairs of non-food-deprived rats competing daily for a limited supply of graham cracker crumbs. Stable dominant-subordinate relationships developed in most pairs, as measured by feeding time, which were maintained over a 5-6-week study period. In other behavioral tests, subordinates demonstrated a decreased latency to immobility in the forced swim test compared with dominants, but no difference in locomotor activity.

Changes in steroidogenic enzyme and steroidogenic acute regulatory protein messenger RNAs in ovarian follicles during ovarian development of rainbow trout (Oncorhynchus mykiss).

In salmonid fishes, estradiol-17beta (E2) and 17alpha,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P) are the major steroid hormones controlling oocyte growth (vitellogenesis) and final maturation (resumption of meiosis). The aim of this study was to determine changes in mRNAs encoding ovarian steroidogenic enzymes and steroidogenic acute regulatory protein (StAR) during ovarian development in female rainbow trout. We analyzed the levels of mRNAs encoding the enzymes P450 side-chain cleavage enzyme (P450scc), 3beta-hydroxysteroid dehydrogenase (3beta-HSD), 17alpha-hydroxylase/C17-C20 lyase (P450c17), aromatase (P450arom), and carbonyl reductase-like 20beta-hydroxysteroid dehydrogenase (20beta-HSD), and StAR in developing ovarian follicles of rainbow trout by Northern blot, in relation to the pattern of serum E2 and 17,20beta-P levels.