The American journal of physiology
-
To investigate the adaptation of melatonin secretion to an abrupt time shift and the effects of sleep facilitation with a hypnotic, eight subjects were submitted to an 8-h advance shift achieved by advancing bedtimes from 2300-0700 to 1500-2300. Each subject participated in two studies (i.e., placebo and zolpidem). Each study included a baseline period with dim light during waking hours and 2300-0700 bedtimes in total darkness. ⋯ There was no relationship between sleep parameters and the magnitude of the melatonin shifts. Thus the overall advance of melatonin profiles was primarily achieved during the initial exposure to an 8-h period of darkness. The present data suggest that exposure to dark affects human circadian phase.
-
Accumulating evidence demonstrates that genotoxic and oxidant stress can induce programmed cell death or apoptosis in cultured cells. However, little is known about whether oxidative stress resulting from the deleterious effects of hyperoxia can induce apoptosis in vivo and even less is known regarding the functional significance of apoptosis in vivo in response to hyperoxia. Using hyperoxia as a model of oxidant-induced lung injury in the rat, we show that hyperoxic stress results in marked apoptotic signals in the lung. ⋯ Furthermore, similar to the hyperoxia-tolerant LPS-pretreated young rats, the nontolerant LPS-pretreated aged rats also exhibited a significantly reduced apoptotic index compared with aged rats exposed to hyperoxia alone. Taken together, our data suggest that hyperoxia-induced apoptosis in vivo can be modulated by both aging and tolerance effects. We conclude that there is no overall relationship between apoptosis and tolerance.