Heterogeneous postnatal transitions in myosin heavy chain isoforms within the rabbit temporalis muscle

• Published in: The anatomical record. Part A, Discoveries in molecular, cellular, and evolutionary biology Vol. 288A; no. 10; pp. 1095 - 1104
• Main Authors: Korfage, Joannes A.M., Van Wessel, Tim, Langenbach, Geerling E.J., Van Eijden, Theo M.G.J.
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.10.2006
• Subjects: Animals; Animals, Newborn; fiber type; Immunohistochemistry; jaw muscle; Male; Muscle Development - physiology; Muscle Fibers, Skeletal - chemistry; Muscle Fibers, Skeletal - classification; Muscle Fibers, Skeletal - metabolism; Myosin Heavy Chains - analysis; Myosin Heavy Chains - metabolism; postnatal development; Protein Isoforms - analysis; Protein Isoforms - metabolism; rabbit; Rabbits; Temporal Muscle - chemistry; Temporal Muscle - cytology; Temporal Muscle - metabolism; temporalis
• ISSN: 1552-4884; 1552-4892
• DOI: 10.1002/ar.a.20375

Postnatal changes in the fiber type composition and fiber cross‐sectional area were investigated in the superficial (TEM1) and deep (TEM23) temporalis of male rabbits. It was hypothesized that, due to the transition from suckling to chewing during early postnatal development, the proportion of fast fiber types would decrease, while the proportion of fibers positive for myosin heavy chain (MyHC) cardiac α would increase, and that, due to the influence of testosterone during late postnatal development, the proportion of these α fibers would decrease again. Classification of the fibers types was performed by immunohistochemistry according to their MyHC content. The proportion of α fiber types significantly increased in both muscle portions from 2% and 8% for TEM1 and TEM23 at week 1 to 29% and 54% at week 8, respectively,. While in TEM1 the proportion of this fiber type did not change thereafter, it decreased again to 27% in TEM23 at week 20. The change for the fast fiber types was opposite to that of the α fiber types. Significantly more MyHC IIX fibers were found in TEM1 than in TEM23 in adult rabbits. In the first 8 weeks, the cross‐sectional areas of all fibers increased. After this period, only MyHC cardiac α + I fibers continued to increase significantly. It was concluded that there are developmental differences in the myosin heavy chain transitions of the two portions of the temporalis muscle. Anat Rec Part A, 288A:1095–1104, 2006. © 2006 Wiley‐Liss, Inc.