Effect of defensive pressure on movement behaviour during an under-18 basketball game.

The aim of this study was to examine the effect of defensive pressure on movement behaviour during an under-18 basketball game. 20 international male players (age: M=16.05, SD=2.09 years old; weekly practice: M=10.9, SD=1.94 h; playing experience: M=7.1, SD=1.1 years) played two 10-min basketball quarters, using man-to-man »-court for the first 4 min (F»), man-to-man full court defence for the next 3 min (FULL), and man-to-man »-court defence for the last 3 min (S»). The positional data were captured by the Ubisense Real Time Location System and analysed with non-linear signal processing methods (approximate entropy) and repeated measures ANOVA. There were differences in the regularity values between F» and FULL in distance to the basket and to the opponents' basket. A stronger in-phase attraction in both lateral and longitudinal directions was identified; however, the centroids (i. e., the mean position from all team players) were closer and revealed higher values of irregularity in lateral displacements for all defensive systems. The individual speed displacements became more coordinated with teammates, particularly in the offensive court. Overall, this study provided evidence on how changing the level of defensive pressure promotes different collective behaviours.

Epinephrine, but not dexamethasone, induces apoptosis in retinal pigment epithelium cells in vitro: possible implications on the pathogenesis of central serous chorioretinopathy.

BACKGROUND: The pathogenesis of central serous chorioretinopathy is poorly understood. It is believed to be due to dysfunction of the retinal pigment epithelium and/or choroid and has been associated with elevated levels of epinephrine and administration of corticosteroids. Epinephrine and corticosteroids have previously been shown to induce apoptosis (programmed cell death) in various types of cells. The objective of this study was to investigate whether these agents can induce apoptosis in cultured retinal pigment epithelium cells. This may help elucidate the pathogenesis of central serous chorioretinopathy. METHODS: Third-passage porcine retinal pigment epithelium cells were grown to confluence and incubated for 1-7 days in culture medium containing epinephrine (10(2)-10(9) pg/ml) or a corticosteroid, dexamethasone (4-4x10(4) ng/ml). The cultures were evaluated for apoptosis by phase-contrast microscopy and in situ terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling. RESULTS: Epinephrine (7x10(7)-10(9) pg/ml) induced apoptosis in a dose- and time-dependent manner. Exposure to lower concentrations of epinephrine (10(2)-6x10(7) pg/ml) and all tested levels of dexamethasone did not result in apoptosis. CONCLUSION: Retinal pigment epithelium cells may undergo apoptosis following exposure to elevated levels of epinephrine. These findings suggest a possible pathophysiologic mechanism for the development of central serous chorioretinopathy.