Masticatory function and properties of masseter muscle fibers in microphthalmic (mi/mi) mice during postnatal development.
It is well known that teeth do not erupt in microphthalmic (mi/mi) mice, a type of osteopetrotic mice, due to bone resorption failure. Therefore, we surmise that the masticatory function of these mice is different from that of normal mice. In this study, the differences to the properties of masseter muscle fibers were clarified morphologically and immunohistochemically in the mi/mi and normal mice. Morphological observations revealed that the muscle fibers in the mi/mi mice were smaller than those in normal mice at 9 weeks of age. However, no marked differences between mi/mi and normal mice at 2 and 4 weeks of age. Immunohistochemical observations showed myosin heavy chain (MHC) slow type fibers, which were usually seen at only early stages of development, in 4-week old mi/mi mice. There were also differences in isoform compositions between the mi/mi and normal mice. These results suggest that differences in masticatory function affect the properties of its muscle fibers.
Tokyo Dental College Department of Anatomy, 1-2-2 Masago, Mihama-ku, Chiba-shi, Chiba, 261-8502 Japan. doi@tdc.ac.jp
Tomoyoshi
T
Doi
Shinichi
S
Abe
Yoshinobu
Y
Ide
D000375:Aging; D000818:Animals; D008406:Masseter Muscle / Q000166:cytology / Q000196:embryology* / Q000254:growth & development / Q000473:pathology; D051379:Mice; D008817:Mice, Mutant Strains; D008850:Microphthalmos / Q000196:embryology* / Q000473:pathology*; D018613:Microscopy, Confocal; D018485:Muscle Fibers, Skeletal / Q000473:pathology*; D012016:Reference Values