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MARI GOLUB |
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Adolescent Trends In Delayed Phase Shift In Rhesus Monkeys
MARI GOLUB  hesus monkeys provide a unique,
well-characterized model for human
adolescence. All species make a transition
from a juvenile to an adult stage
characterized by onset of fertility, but
primates are the only species that show "true"
adolescence„a growth spurt followed by
puberty, development of morphologic secondary
sex characteristics, onset of fertility and,
finally, epiphyseal closure and cessation of
linear growth. In humans, one of the most
dramatic changes in adolescence has to do with
sleep patterns. Recently we evaluated 10
female rhesus monkeys aged 18-33 months of age
(equivalent to 10-14 years of age in girls)
for changes in sleep patterns; 4 of these
monkeys continued to be studied through 45
months of age (equivalent to 17 years of age
for girls). Activity was measured using an
actimeter for a 48 h period every two weeks.
Diurnal rest/activity cycles were assessed by
measuring the duration of the active phase and
the time of onset of the rest phase. The time
of light offset was subtracted from the time
of onset of the rest phase to give a measure
of phase shift. The phase shift delay
increased by about 1.5 h in the adolescent
monkeys over the eighteen month period. The
developmental pattern for phase shift delay
was apparently superimposed on an annual cycle
with shortest delays occurring in November and
then increasing again through the next
September. The same experiment included a
group of monkeys fed a diet low in zinc, an
essential trace element that is particularly
important during periods of rapid growth. The
zinc deprived group showed slower growth,
retarded adolescent development, and in
addition, failed to demonstrate the change in
phase shift delay seen in the normal group.
This study indicates that later onset of sleep
is part of the biological program for
adolescent development in nonhuman primates,
and can be prevented by a nutritionally
inadequate diet that interferes with
adolescent growth and maturation.
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