Masahito Yamamoto1, Takashi Shinomiya2, Asuka Kishi3, Shigeki Yamane4, Takashi Umezawa3, Yoshinobu Ide3, Shinichi Abe4. 1. Department of Anatomy, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba City, Chiba 261-8502, Japan. Electronic address: yamamotomasahito@tdc.ac.jp. 2. Department of Pharmacology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba City, Chiba 261-8502, Japan. 3. Department of Anatomy, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba City, Chiba 261-8502, Japan. 4. Department of Anatomy, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba City, Chiba 261-8502, Japan; Oral Health Science Center hrc8, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba City, Chiba 261-8502, Japan.
Abstract
OBJECTIVE: In adults, the lateral pterygoid muscle (LPM) is usually divided into the upper and lower head, between which the buccal nerve passes. Recent investigations have demonstrated foetal developmental changes in the topographical relationship between the human LPM and buccal nerve. However, as few studies have investigated this issue, we clarified the expression of desmin and nerve terminal distribution during embryonic development of the LPM in mice. METHODS: We utilized immunohistochemical staining and reverse transcription chain reaction (RT-PCR) to clarify the expression of desmin and nerve terminal distribution. RESULTS: We observed weak expression of desmin in the LPM at embryonic day (ED) 11, followed by an increase in expression from embryonic days 12-15. In addition, starting at ED 12, we observed preferential accumulation of desmin in the vicinity of the myotendinous junction, a trend that did not change up to ED 15. Nerve terminal first appeared at ED 13 and formed regularly spaced linear arrays at the centre of the muscle fibre by ED 15. The results of immunohistochemical staining agreed with those of RT-PCR analysis. CONCLUSION: We found that desmin accumulated in the vicinity of the myotendinous junction starting at ED 12, prior to the onset of jaw movement. We speculate that the accumulation of desmin is due to factors other than mechanical stress experienced during early muscle contraction. Meanwhile, the time point at which nerve terminals first appeared roughly coincided with the onset of jaw movement.
OBJECTIVE: In adults, the lateral pterygoid muscle (LPM) is usually divided into the upper and lower head, between which the buccal nerve passes. Recent investigations have demonstrated foetal developmental changes in the topographical relationship between the human LPM and buccal nerve. However, as few studies have investigated this issue, we clarified the expression of desmin and nerve terminal distribution during embryonic development of the LPM in mice. METHODS: We utilized immunohistochemical staining and reverse transcription chain reaction (RT-PCR) to clarify the expression of desmin and nerve terminal distribution. RESULTS: We observed weak expression of desmin in the LPM at embryonic day (ED) 11, followed by an increase in expression from embryonic days 12-15. In addition, starting at ED 12, we observed preferential accumulation of desmin in the vicinity of the myotendinous junction, a trend that did not change up to ED 15. Nerve terminal first appeared at ED 13 and formed regularly spaced linear arrays at the centre of the muscle fibre by ED 15. The results of immunohistochemical staining agreed with those of RT-PCR analysis. CONCLUSION: We found that desmin accumulated in the vicinity of the myotendinous junction starting at ED 12, prior to the onset of jaw movement. We speculate that the accumulation of desmin is due to factors other than mechanical stress experienced during early muscle contraction. Meanwhile, the time point at which nerve terminals first appeared roughly coincided with the onset of jaw movement.