RESUMEN
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.
Asunto(s)
Músculo Masetero/embriología , Microftalmía/embriología , Microftalmía/patología , Fibras Musculares Esqueléticas/patología , Envejecimiento , Animales , Músculo Masetero/citología , Músculo Masetero/crecimiento & desarrollo , Músculo Masetero/patología , Ratones , Ratones Mutantes , Microscopía Confocal , Valores de ReferenciaRESUMEN
To clarify functions of the mouse-tongue muscles, proteins such as myocin heavy chain (MHC) 2a and MHC-2b, which are isoforms of the fast-twitch fiber type myosin heavy chain, in the lateral margin of the tongue were observed by reverse transcription polymerase chain reaction and immunohistochemical analyses. The main MHC isoform in the superior longitudinal muscle of the tongue was MHC-2b, with the fastest function and the main MHC isoform in the transverse muscle of the tongue was MHC-2a. These findings suggested that the fastest function is necessary for the superior longitudinal muscle of the tongue, which is useful for moving the tongue in and out of the mouth in the sagittal direction, showing different cellular biological properties of the myofibers from those of the transverse muscle of the tongue.