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The Body Electric
around, and then retract. The muscle will atrophy. If the nerves re-
establish the connections, new muscle cells will fill most of the original
volume, gradually build up strength, and then completely differentiate
into slow-twitch or fast-twitch fibers.
Attempts to enhance muscle regeneration in humans take two ap-
proaches. If available, a graft of a whole muscle from another source is
the more effective. This is actual single-tissue regeneration, because the
original muscle cells die and are replaced after new blood and nerve
connections are made. Since its first clinical use in 1971, this approach
has proven successful in replacing defective small muscles of the face and
also in restoring anal sphincter control. Large limb muscles haven't been
successfully transplanted yet.
Another method may soon be used in humans when grafts aren't pos-
sible. Muscle regeneration in birds and laboratory mammals has been
considerably enhanced by inserting muscle tissue minced with fine scis-
sors into pieces of no more than 1 cubic millimeter. Soviet biologist A.
N. Studitsky first devised this method in the 1950s, extending Pol-
ezhaev's work, but its development has been slow.
Abdominal Organs
Despite over two hundred years of descriptive work, new regenerative
capacities are still discovered in the animal kingdom from time to time.
We've recently learned, for example, that adult frogs can restore their
bile ducts, although for some reason females are better at it than males.
Doctors have long known that the liver can replace most of the mass lost
through injury by compensatory hypertrophy, in which its cells both
enlarge and increase their rate of division so that the organ's chemical-
processing duties can be maintained even though the ruined architecture
isn't restored. Similarly, damage in one kidney is made up by enlarge-
ment of the other without rebuilding the intricate mazes of microtubules
in the glomeruli. Recent studies of rat livers suggest that a combination
of insulin and an epidermal growth factor, modified by at least a dozen
other hormones, enzymes, and food metabolites, control the cell pro-
liferation.
Now it appears that the spleen can make the same kind of comeback,
at least in children.
Adults who must have their splens removed rarely
miss them, but children become more susceptible to meningitis. A few
years ago, medical researcgers noted that children whose excised spleens