Alternative splicing, muscle calcium sensitivity, and the modulation of dragonfly flight performance

Calcium sensitivity of myosin cross-bridge activation in striated muscles commonly varies during ontogeny and in response to alterations in muscle usage, but the consequences for whole-organism physiology are not well known. Here we show that the relative abundances of alternatively spliced transcripts of the calcium regulatory protein troponin T (TnT) vary widely in flight muscle of Libellula pulchella dragonflies, and that the mixture of TnT splice variants explains significant portions of the variation in muscle calcium sensitivity, wing-beat frequency, and an index of aerodynamic power output during free flight. Two size-distinguishable morphs differ in their maturational pattern of TnT splicing, yet they show the same relationship between TnT transcript mixture and calcium sensitivity and between calcium sensitivity and aerodynamic power output. This consistency of effect in different developmental and physiological contexts strengthens the hypothesis that TnT isoform variation modulates muscle calcium sensitivity and whole-organism locomotor performance. Modulating muscle power output appears to provide the ecologically important ability to operate at different points along a tradeoff between performance and energetic cost.

Moral judgment in delinquents and nondelinquents: recognition versus production measures

Juvenile delinquents' (n = 60) and nondelinquents' (n = 73) stages of moral development were compared using both recognition and production measures. Juvenile delinquents were found to score significantly lower than nondelinquents on a production measure of moral judgment (the Sociomoral Reflection Measure). A recognition measure (the Sociomoral Reflection Objective Measure), however, did not discriminate between the two groups in an analysis controlled for significant covariates of age, socioeconomic status, and IQ. The possibility that delinquents are delayed in the production but not recognition of mature moral reasoning is considered. The possibility is also considered, however, that excessive error variance associated with recognition measures of moral reasoning when administered to juvenile delinquents is responsible for the inability of such measures to discriminate between delinquents and nondelinquents.