Der schweizerische Bienenvater : praktische Anleitung zur Bienenzucht

von Jeker ; Kramer ; Theile

Maintenance of a normal thymic microenvironment and T-cell homeostasis require Smad4-mediated signaling in thymic epithelial cells

Signals mediated by the transforming growth factor-β superfamily of growth factors have been implicated in thymic epithelial cell (TEC) differentiation, homeostasis, and function, but a direct reliance on these signals has not been established. Here we demonstrate that a block in canonical transforming growth factor-β signaling by the loss of Smad4 expression in TECs leads to qualitative changes in TEC function and a progressively disorganized thymic microenvironment. Moreover, the number of thymus resident early T-lineage progenitors is severely reduced in the absence of Smad4 expression in TECs and directly correlates with extensive thymic and peripheral lymphopenia. Our observations hence place Smad4 within the signaling events in TECs that determine total thymus cellularity by controlling the number of early T-lineage progenitors

Changes in spatio-temporal gait parameters and vertical speed during an extreme mountain ultra-marathon

The aim of the present study was to investigate the effects of altitude and distance on uphill vertical speed (VS) and the main spatio-temporal gait parameters during an extreme mountain ultra-marathon. The VS, stride height (SH) and stride frequency (SF) of 27 runners were measured with an inertial sensor at the shank for two different altitude ranges (low 1300-2000\u2005m vs high 2400-3200 m) of 10 mountains passes distributed over a 220\u2005km course. There was a significant interaction (F(4,52)\u2009=\u20094.04, p\u2009<\u20090.01) for the effect of altitude and distance on VS. During the first passes, the mean VS was faster at lower altitudes, but this difference disappeared at a quarter of the race length, suggesting that neuromuscular fatigue influenced the uphill velocity to a larger extent than the oxygen delivery. The average VS, SH and SF were 547\u2009\ub1\u2009135 m/h, 0.23\u2009\ub1\u20090.05 m and 0.66\u2009\ub1\u20090.09 Hz. The individual VS change for each uphill portions was more strongly correlated with the changes in SH (r\u2009=\u20090.80, P\u2009<\u20090.001, n\u2009=\u2009321) than SF (r\u2009=\u20090.43, P\u2009<\u20090.001, n\u2009=\u2009321). This suggests a large effect of the knee extensors strength loss on the diminution of VS