Poss which of two types of myocyte were

Poss et al. (2002) examines how
heart muscle regenerates after damage in zebrafish. The hypothesis of the study
was that zebrafish, which can regenerate spinal cord, fin tissue, and retina,
would be able to regenerate damaged heart muscle as well. Researchers resected a
section of the ventricular wall of the hearts of adult zebrafish and sampled
the tissue at eight time points after the cut. These samples were variously
fixed and stained to reveal different cell types – some were stained for myosin
heavy chain in order to reveal cardiomyocytes, and some were measured for
levels of bromodeoxyuridine (a compound that marks cells undergoing DNA
synthesis). Researchers found that the injury site clotted with erythrocytes
(red blood cells) a few seconds after the injury had occurred. Until nine days
post-amputation, these erythrocytes were gradually replaced with fibrin;
beginning at nine days post-amputation, cardiomyocytes surrounded the injury
site and began to move into the injury itself, replacing the muscle. By sixty
days after the amputation, the hearts appeared to be functioning as normal per
visual inspection. In order to measure exactly how much of the zebrafish heart
muscle had been replaced, the researchers used computer models. To determine
which of two types of myocyte were present at the injury site, researchers used
an antibody to beta catenin (a protein that exists around adherin junctions)