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Subject: Growing Up Fitfully; Study Finds Babies' Spurts, Lulls Alternate<By David
Date: Fri, 30 Oct 92 04:28:31 EST
Message-ID: <3.1992Oct30.042831@AmeriCast.com>

Growing Up Fitfully; Study Finds Babies' Spurts, Lulls
Alternate<By David Brown=Washington Post Staff Writer=

Score one for the old wives.

The observation that a growing child "shot up overnight" - long
assumed by scientists to be nothing more than one of folklore's
overstatements - may actually be true.

Traditionally, biologists have believed that growth occurs con-
tinuously during childhood, though at varying rates that include
the "spurts" with which every parent is familiar.

A new study, however, suggests that normal growth in infants may
occur in brief - possibly even 24-hour - bursts that punctuate
long periods during which no measurable growth takes place.
Furthermore, growth follows no regular cycle and can occur after
"quiet" periods that last as long as four weeks.

The research, reported in today's issue of the journal Science,
is part of a small but increasing body of evidence that growth
operates in an off-or-on fashion, much like a light switch.

"The difference is that we are not saying there is a change in
Lampl, a physician and anthropologist at the University of
Pennsylvania who conducted the study.

In children measured daily, growth was always noted in a single
24-hour period bounded by at least two days of no growth. The
biggest overnight spurt was about 5/8 inch, recorded in a 6-
month-old boy.

"All of a month's growth in 24 hours? I would raise a questioning
eyebrow - but not more than that," said James M. Tanner, emeritus
professor at the University of London and one of the world's
leading authorities on human growth. "It is biologically plausi-
ble and there is nothing inherently ridiculous about this theory.
But it needs to be replicated in other labs."

Lampl measured 31 white children between the ages of 3 days and
21 months. Three were measured daily for four months; <18 were
measured twice a week <for up to 18 months; and 10 were measured
weekly for up to 12 months.

The measurements were conducted with the infants lying <on their
backs and up against a <headboard.  The researchers stretched
them gently to reduce as much as possible the effects of posture
and activity. The measuring error was less than 1/16 inch, Lampl
said.

The children measured daily had growth spurts measuring about
3/16 inch to 5/8 inch, separated by  lulls ranging from 2 to 28
days. The semiweekly children had spurts of up to one inch and
lulls of 3 to 60 days.  The weekly children also had spurts of up
to one inch, and exhibited periods of no measurable growth last-
ing up to 63 days.

That kind of stuttering pattern is called "saltatory" growth. The
term is borrowed from physiology, and was originally used to
describe the conduction of current in quick jumps down a nerve
suspended in a salt solution.

Proof of the theory that growth occurs in saltatory fashion may
have to await much more precise methods of measurement, noted
Michael A. Preece, a professor at the Institute of Child Health
at the University of London, and a colleague of Tanner's.

"The uncertainty is: Is what you are seeing truly biological, or
is it a function of the methodology? If the changes are very,
very small and smooth, it may be that in one day you cannot
detect anything. But after a couple of days, you can <because it
has come over your threshold (of measuring error)," he said.
Lampl believes that recent <insights from cell biology, how-
<ever, provide a theoretical basis <for her observation of salta-
tory growth.

Cells have a well-described cycle that includes a resting phase,
in which activity appears to be inhibited by still unknown
mechanisms. Division occurs, however, when the inhibitory forces
are lifted, allowing a complicated cascade of biochemical events
to begin.

"It is possible that in the normal conditions of a growing organ-
ism, growth itself occurs as the result of the release of inhibi-
tory mechanisms," she said.

The great variation in the length of quiet periods raises the is-
sue that human growth may be an example of "chaos" - the ap-
parently random behavior of systems that are governed by ap-
parently deterministic physical laws.

"If I had a gut feeling, I would say it might be - but there is
no way to prove it with this number of data points. In order to
demonstrate that something has chaotic behavior, you literally
need to have thousands of events," said Michael L. Johnson, a
biophysicist at the University of Virginia who, along with J.D.
Veldhuis, also of Virginia, was a co-author of the study.

Lampl said that she asked the three mothers of the children who
were measured daily to keep diaries of what their infants ate,
when they slept, and how they behaved. On the day or two before a
growth spurt, children were usually fussy and voraciously hungry.

"Frequently (the mothers) weren't surprised at all" when they
discovered the child immediately thereafter had a spurt of
growth, she said.<02:05 10-30C9999-----

Copyright 1992, The Washington Post.  This story is from the
Washington Post's Capitol Edition On-Line and is not to be ar-
chived or redistributed.

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poration (usa@AmeriCast.COM)