Resumo de Rhythms Of Life - RUSSELL FOSTER, LEON KREITZMAN

In Rhythms of Life Foster, a neuroscientist specializing
in circadian rhythms, and Kreitzman, a science populariser with a background in
biochemistry, provide an introduction to the new science of chronobiology. It
is popular science written for a general audience, but it is solidly referenced
to the scientific literature and may be useful for biologists as a survey of
the area.

They begin with an introduction to daily (circadian) rhythms in the natural
world, a look at the abilities of animals such as bees to tell time, and some
general background on clocks and oscillators. Organisms can better meet the
challenge posed by daily changes if they can predict them.

The search for a clock led, through experimental work on rats, hamsters and
other mammals, to the suprachiasmatic nuclei. Circadian clocks are kept in time
by entrainment to the daily cycle, with a similar phase response cycle in
different species; investigation of the details uncovered additional mammalian
light sensors in addition to the well-known rods and cones.

Work on Drosophila has revealed the molecular workings of one
clock, where per and tim genes produce proteins which provide
negative feedback on their expression. Much remains poorly understood, however,
and other species have different systems ? there is considerable variation just
among birds, involving different parts of the brain and different genes and
proteins.

Seasonal or circannual rhythms are especially important in reproduction and
migration; they are often controlled by critical day lengths, and are thus
connected to circadian rhythms. Turning to evolution, attempts have been made
to show experimentally that circadian rhythms are adaptive, while research into
cyanobacteria, mammals, insects, and plants has revealed something of their
phylogenetics.

The last third of Rhythms of Life turns to humans. Performance and
physiology vary during the day, and sleeping patterns also interact with
circadian rhythms. Modern phenomena such as shift-work and jet-lag can have
drastic negative impacts on circadian rhythms and well-being. (A brief appendix
provides some practical tips on alleviating jet lag.) Clinically, measurement
of physiological variables depends on the time of day, and the timing of
therapies can improve their effectiveness or reduce side effects. A final
chapter places both chronobiology and chronobiological research into their
broader philosophical, historical, and social contexts.

Though no background is assumed and basic science is explained ? there''s
even an explanation of the structure of DNA ? Rhythms of Life may have
too much detail for those primarily attracted by the practical aspects which
are played up in the back-cover blurb. For anyone curious about the actual
science behind the daily rhythms of life, however, it''s an excellent book.

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