Key result
Postnatal pig muscle contains small developmental myosin fibers, suggesting hyperplastic growth continues after birth.
Why the study?
The postnatal development and persistence of tertiary myotubes containing developmental myosin isoforms in growing pig skeletal muscle were not fully characterized.
The detection of tertiary myotubes containing developmental myosin isoforms in postnatal growing pigs suggests that hyperplastic muscle growth may not cease at birth.
Answers are grounded in this paper and cite their sources.
May support persistent hyperplasia in growing pigs; leaves open relevance to human myogenesis or clinical translation.
The postnatal development of skeletal muscles was studied in growing pigs from 8 to 210 d of age. Indirect immunoperoxidase staining of frozen sections of porcine semimembranosus muscle and longissimus muscle revealed a distinct population of small fibers (tertiary myotubes) that were stained specifically by an antibody (anti-NE) selective for the developmental (embryonic and neonatal) isoforms of muscle myosin. At 8 d of age the other larger fibers were already anti-NE negative and differentiated into Types I and II. A gradual decrease in the number of anti-NE positive fibers together with a gradual increase in area of the remaining positive fibers was observed throughout the pigs' growth. These results may indicate that hyperplastic growth does not cease at birth. Possible mechanisms to explain the origin of these tertiary myotubes containing developmental isoforms of myosin are suggested.
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Mascarello et al. (1992) studied postnatal development of skeletal muscles. Postnatal growing pig muscle contains a distinct population of small fibers expressing developmental myosin isoforms, suggesting hyperplastic growth does not cease at birth.
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