@article {11617,
	title = {Increase in the degree of coexpression of myosin heavy chain isoforms in skeletal muscle fibers of the very old.},
	journal = {Muscle Nerve},
	volume = {22},
	year = {1999},
	month = {1999 Apr},
	pages = {449-54},
	abstract = {Myosin heavy chain (MHC) isoform composition was determined in 2264 single skeletal muscle fibers from vastus lateralis muscle of a group (n = 12) of very old subjects (average age, 88 years). The number of fibers containing only MHC I, IIA, or IIX was 19.9\%, 27.2\%, and 0.3\%, respectively. Surprisingly, 28.5\% of the fibers displayed coexpression of both MHC I and IIA, a phenotype that is present in younger adults in very small percentages. Among these fibers coexpressing MHC I and IIA, the majority had a dominant expression of MHC I. Additionally, a small number of fibers coexpressing MHC I and IIX without any MHC IIA, and fibers co-expressing all three isoforms were observed. Altogether, 52.6\% of all fibers examined in these very old subjects coexpressed two or three MHC isoforms. The present study provides evidence that advanced age leads to a significant elevation of skeletal muscle fibers displaying coexpression of two MHC isoforms and that a separation into slow and fast fibers in very old individuals may therefore be somewhat misleading. The clinical significance of the elevated number of fibers coexpressing MHC I and IIA is uncertain.},
	keywords = {Aged, Aged, 80 and over, Aging, Female, Humans, Male, Muscle Fibers, Skeletal, Muscle, Skeletal, Myosin Heavy Chains, Myosins},
	issn = {0148-639X},
	author = {Andersen, J L and Terzis, G. and Kryger, A}
}
