For anyone who has doubts about the genome running a variety of
"programs" (which *are* imperfect), they should take a look at
a paper this week in Science:
Resetting Central and Peripheral Circadian Oscillators in Transgenic Rats
Shin Yamazaki, et al, Science 288:682-685 (2000).
In multicellular organisms, circadian oscillators are organized into
multitissue systems which function as biological clocks that regulate
the activities of the organism in relation to environmental cycles and
provide an internal temporal framework. To investigate the organization
of a mammalian circadian system, we constructed a transgenic rat
line in which luciferase is rhythmically expressed under the control of
the mouse Per1 promoter. Light emission from cultured suprachiasmatic nuclei
(SCN) of these rats was invariably and robustly rhythmic and persisted for
up to 32 days in vitro. Liver, lung, and skeletal muscle also expressed
circadian rhythms, which damped after two to seven cycles in vitro. In
response to advances and delays of the environmental light cycle, the
circadian rhythm of light emission from the SCN shifted more rapidly than
did the rhythm of locomotor behavior or the rhythms in peripheral tissues.
We hypothesize that a self-sustained circadian pacemaker in the SCN entrains
circadian oscillators in the periphery to maintain adaptive phase control,
which is temporarily lost following large, abrupt shifts in the environmental
Gives new meaning to the concept of our clocks "unwinding".
Also makes me wonder about the self-experimentation I'm doing
with periodic 12-hour time zone shifts...
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