Friday, March 18, 2005

Heinrich - Guest-blogging: What Is Sleep For?

I am really excited to introduce to you my first guest blogger here on Circadiana, Heinrich, not Hindrocket whose blog, She Flies With Her Own Wings (http://coeruleus.blogspot.com/) is a worthy daily read. Heinrich does research on mammalian clocks and sleep, and his first contribution is this post about exciting new research on adaptive function of sleep. Here it is - enjoy:


One intriguing question in sleep research has been what, exactly, is bad about not sleeping? What's going on in neurons during sleep deprivation that might eventually lead to certain cognitive deficits we experience while we're sleep deprived? A growing body of research suggests that proteins - possibly those responsible for cell-to-cell communication that is important in learning and cognition - are not made properly within neurons during sleep deprivation.

A recent paper in Journal of Neurochemistry examines the temporal expression of "BiP/GRP78, a molecular chaperone,[that] is a classical marker of the ER stress response/unfolded protein response (UPR) activation in yeast and mammalian cells" in various time points during sleep deprivation. In other words, the more you have of BiP/GRP78, the less likely your cells are of producing properly folded proteins.

The authors show that "all of the components of the UPR occur" in mouse cortical areas, and hence possibly other areas of the brain. Hence, in the words of the authors: "In humans, it has recently been shown that there is the beginning of impairment in performance when continued wakefulness exceeds 16 h" (Van Dongen and Dinges 2003). Beyond this time, wakefulness is much more difficult to sustain and is unstable (Van Dongen and Dinges 2003). There are increasingly frequent performance lapses when wakefulness exceeds this limit (Van Dongen and Dinges 2003). This is important clinically because performance of activities such as driving a vehicle will be impaired. Epidemiological studies show that being awake for more than 20 h is a major risk factor for crashes that result from the driver falling asleep at the wheel (Stutts et al. 2003). Although we do not know whether in humans UPR occurs when wakefulness is prolonged, our data raise this as a hypothesis."

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