Inter and intra-population phenotypic and genotypic structuring in the European whitefish Coregonus lavaretus, a rare freshwater fish in Scotland.

This study revealed between-lake genetic structuring between Coregonus lavaretus collected from the only two native populations of this species in Scotland, U.K. (Lochs Eck and Lomond) evidenced by the existence of private alleles (12 in Lomond and four in Eck) and significant genetic differentiation (FST = 0·056) across 10 microsatellite markers. Juvenile C. lavaretus originating from eggs collected from the two lakes and reared in a common-garden experiment showed clear phenotypic differences in trophic morphology (i.e. head and body shape) between these populations indicating that these characteristics were, at least partly, inherited. Microsatellite analysis of adults collected from different geographic regions within Loch Lomond revealed detectable and statistically significant but relatively weak genetic structuring (FST = 0·001-0·024) and evidence of private alleles related to the basin structure of the lake. Within-lake genetic divergence patterns suggest three possibilities for this observed pattern: (1) differential selection pressures causing divergence into separate gene pools, (2) a collapse of two formerly divergent gene pools and (3) a stable state maintained by balancing selection forces resulting from spatial variation in selection and lake heterogeneity. Small estimates of effective population sizes for the populations in both lakes suggest that the capacity of both populations to adapt to future environmental change may be limited.

Investigation of circadian rhythms in anaerobic power and capacity of the legs.

Previous work has demonstrated that exercise performance varies with time of day. The aim of this study was to investigate the influence of time of day on measures of anaerobic power and anaerobic capacity. Twelve male subjects, aged 18-22 years, performed a stair run test, a standing broad jump and the Wingate Anaerobic Test on twelve separate occasions. These were at 02:00, 06:00, 10:00, 14:00, 18:00 and 22:00 hours, duplicate measurements being obtained at each time point. Subjects' diet and activity prior to exercise and the laboratory temperature were controlled. Pre-exercise rectal temperature was measured on each occasion. The rectal temperature data conformed to a cosine function: its peak occurred at 18:11 hours and the peak to trough variation was 0.76 degrees C (p < 0.001). There was a rhythm in performance on the stair run and the broad jump tests, in phase with the curve in rectal temperature. Results for peak power and mean power production on the Wingate test did not display a significant circadian rhythm. The stair run and broad jump tests seem to be more sensitive to circadian rhythmicity than does the Wingate Anaerobic Test.

Effect of porcine relaxin and progesterone on rat, pig and human myometrial activity in vitro.

The in vitro effect of pure porcine relaxin on nonpregnant and pregnant myometrium before and after progesterone treatment was studied in the rat, pig and human. Myometrial strips from 45 rats, 30 pigs and 64 humans were studied. Porcine relaxin inhibited myometrial activity in the nonpregnant and pregnant rat until midpregnancy, when the sensitivity to it gradually decreased. By day 19 of rat pregnancy the myometrium was completely refractory to the inhibitory effect of porcine relaxin. Pretreatment of rat myometrial strips in vitro with progesterone increased their sensitivity to relaxin but did not overcome the refractory period in late pregnancy. In the pig, myometrial contractility was completely inhibited by porcine relaxin both in the nonpregnant state and throughout pregnancy (days 25-109). Progesterone was again synergistic, with relaxin in the pig inhibiting myometrial contractility. However, porcine relaxin had little or no effect on human myometrial contractility either in the nonpregnant state or during the pregnancies tested (28-42 weeks). Pretreatment of human myometrium with progesterone did not induce a response to porcine relaxin.