The Lazarus Heart
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brain, just as all our other amphibian blood donors had. We looked it
up just to make sure. The standard works on regeneration all agreed that
no animal's heart could repair major wounds. Unlike skeletal muscle,
the cardiac variety had no satellite cells to serve as precursors for mature
heart-muscle cells. In any case, the textbooks stated, the animal would
die long before such repair could occur.
Next week Sharon put our three intended sacrifices in a bowl of water
and with a straight face asked me if they looked healthy enough to use. I
told her they looked fine. "Good!" she exclaimed. "These are the same
three we used last week." Score one for the open mind!
Flabbergasted, I helped anesthetize and dissect this trio of miracles.
Their hearts were perfectly normal, with no evidence of ever having been
damaged in any way.
The Five-Alarm Blastema
Abruptly I changed my research plans. I asked Sharon to test a series of
newts by cutting away large sections of their hearts and sewing up their
chests, then killing some of the survivors every day and slicing, mount-
ing, and staining the hearts for study under the microscope. Over 90
percent lived through the first operation, and several weeks later we had
hundreds of slides ready for my examination and diagnosis. Unfor-
tunately they all looked the same! Even those from the day after that
horrendous mutilation showed only normal tissues with no sign of in-
jury.
By now we knew we had come upon a first-class mystery and had
better jettison our preconceptions. We reasoned that we could tell when
regeneration was finished by finding out when the blood began flowing
again. Under the microscope we could easily see blood cells streaming
through capillaries in the transparent tail fins of lightly anesthetized
newts. The motion stopped when we cut the heart, and restarted about
four hours later. We sectioned a new series of hearts, this time covering
the first six hours at intervals gradually increasing from fifteen minutes
to one hour.
While waiting for the specimens, we rummaged more thoroughly
through the literature for other reports on heart regeneration. There was
evidence for very limited repair—but no true regeneration—of small
heart wounds in a few animals. The process seemed limited to the very
young. Even then, the results were of poor quality, combining a lot of
scar tissue with only a little proliferation of nearby heart cells, but the