Early effect of Botox-A injection into the masseter muscle of rats: functional and histological evaluation / 대한악안면성형재건외과학회지

BACKGROUND: The purpose of this study was to evaluate the change of food intake after different dosages of botulinum toxin A (BTX) injection in the animal model. Additionally, the dimensional and histological change at 14 days after BTX injection was also evaluated. METHODS: The comparative study was performed using the BTX injection model in rats (n = 5 for each group). Group 1 was the saline-injected group. Group 2 was the 5-unit BTX-injection group to each masseter muscle. Group 3 was the 10-unit BTX-injection group to each masseter muscle. Food intake rates and body weight were checked daily before and after BTX injection until 10 days. All animals were sacrificed at 14 days after BTX injection, and the specimens underwent hematoxylin and eosin stain and immunohistochemical staining for myosin type II (MYH2). RESULTS: The recovery of food intake in groups 2 and 3 decreased significantly compared with group 1 from day 2 to day 7 and day 9 after injection (p < 0.05). The BTX-treated masseter muscles were significantly smaller than those in group 1 (p = 0.015). The immunohistochemical findings demonstrated that the expression of MYH2 was significantly higher in group 3 compared to groups 1 and 2 (p < 0.001). CONCLUSIONS: BTX injection to the masseter muscle in rats demonstrated short food-intake-rate reduction with recovery until 10 days after injection. The thickness of the masseter muscle and MYH2 expression were significantly changed according to the injected dose of BTX.

Immunohistochemical fiber type profile in the human vocal muscle / Perfil inmunohistoquímico de los tipos de fibras en el músculo vocal humano

The vocal muscle is a striated muscle with important functions in the emission of laryngeal sound and physiology of the voice. Therefore the knowledge of its constitution is the basis for the prevention and management of voice disorders. We used 10 samples from the middle third of vocal muscles obtained from autopsies of 6 male and 4 female subjects aged between 36 and 71 years. The samples were analyzed with BA-F8 monoclonal antibody to slow type I fibers, and antimyosin HC monoclonal antibody and antimyosin fast clone MY-32 antibody for types IIA, IIB, IIX, and neonatal fibers. We determined the distribution of the muscle fiber types and morphometric characteristics, evaluating the differences by sex and age group. The human vocal muscle presented a heterogeneous formation with a predominance of type II fibers at 51.99 percent, while type I fibers reached 48.01 percent; this difference was significant (p <0.05). Comparing fiber subtypes IIA and IIX, there is a slight predominance of type IIX fibers, although this is not statistically significant (p>0.05). In conclusion, the human vocal muscle the fibers were predominantly type II fast.

El músculo vocal es un músculo estriado con importantes funciones en la emisión del sonido laringeo y fisiología de la voz. Por ello el conocimiento de su constitución sirve de base para la prevención y manejo de los trastornos vocales. Se realizó un estudio morfométrico e inmunohistoquímico de músculo vocal humano. Se utilizaron 10 muestras del tercio medio del músculo vocal obtenidas de necropsias, 6 de individuos de sexo masculino y 4 femenino, con edades de entre 36 y 71 años. Las muestras fueron analizadas con anticuerpos monoclonales antimyosin skeletal slow BA-F8 para fibras tipo I y antimyosin skeletal fast HC y MY-32 para fibras tipo IIA, IIB, IIX y neonatal. Se determinó la distribución de los distintos tipos de fibras musculares y sus características morfométricas, evaluándose las diferencias por sexo y grupo etáreo. El músculo vocal humano presentó una constitución heterogénea con predominio de fibras tipo II con un 51,99 por ciento, mientras que las tipo I alcanzaron el 48,01 por ciento, estas diferencias resultaron significativas (p<0,05). Al comparar los subtipos de fibras IIA y IIX, se observa un leve predominio de las fibras IIX, aunque no significativo estadísticamente (p>0,05). No se encontraron diferencias en cuanto a los diámetros mayor y menor de las fibras ni en la constitución del músculo por sexo o grupo etáreo. Se concluye que en el músculo vocal humano predominan las fibras musculares rápidas tipo II.

Implication of phosphorylation of the myosin II regulatory light chain in insulin-stimulated GLUT4 translocation in 3T3-F442A adipocytes

In adipocytes, insulin stimulates glucose transport primarily by promoting the translocation of GLUT4 to the plasma membrane. Requirements for Ca2+/ calmodulin during insulin-stimulated GLUT4 translocation have been demonstrated; however, the mechanism of action of Ca2+ in this process is unknown. Recently, myosin II, whose function in non-muscle cells is primarily regulated by phosphorylation of its regulatory light chain by the Ca2+/calmodulin-dependent myosin light chain kinase (MLCK), was implicated in insulin-stimulated GLUT4 translocation. The present studies in 3T3- F442A adipocytes demonstrate the novel finding that insulin significantly increases phosphorylation of the myosin II RLC in a Ca2+-dependent manner. In addition, ML-7, a selective inhibitor of MLCK, as well as inhibitors of myosin II, such as blebbistatin and 2,3-butanedione monoxime, block insulin- stimulated GLUT4 translocation and subsequent glucose transport. Our studies suggest that MLCK may be a regulatory target of Ca2+/calmodulin and may play an important role in insulin-stimulated glucose transport in adipocytes.