Van Cleave S, Shall M S
Department of Physical Therapy, Virginia Commonwealth University, Richmond, VA 23298-0224, USA.
J Vestib Res. 2006;16(4-5):179-86.
Children with hearing deficits and hypofunctioning vestibular receptors frequently have delayed motor development. This study focuses on when the vestibular system needs to be active for normal motor behavior development and the maturation of the soleus muscle in the ferret. Both vestibular labyrinths were removed from ferrets at Postnatal day 10 (P10), P21, or P45 and the resulting data were compared with ferrets that had undergone a sham surgery at the same ages. The animals were sacrificed at P120 (young adult ferret). The resulting data from these ferrets revealed that standing and walking balance was significantly affected when the vestibular system was eliminated at or before P21. The soleus of P10 and P21 animals generally had smaller diameter muscle fibers and proportionally less type I Myosin Heavy Chain (MHC) and more type IIX MHC. The twitch contraction time of the soleus of the P21 group was significantly slower than the other groups. It appears that the vestibular system is important to motor and muscle fiber development in the ferret during the period before P21. The eyes are still closed at that age and all of the vestibular receptors are not fully mature. These findings imply a "critical period" for vestibular sensation and the development of a muscle that is important to standing balance.
听力有缺陷且前庭感受器功能减退的儿童通常运动发育迟缓。本研究聚焦于雪貂的前庭系统在正常运动行为发育和比目鱼肌成熟过程中何时需要保持活跃。在出生后第10天（P10）、第21天或第45天切除雪貂的双侧前庭迷路，并将所得数据与在相同年龄接受假手术的雪貂进行比较。这些动物在P120（幼年成年雪貂）时被处死。这些雪貂的所得数据显示，在前庭系统在P21或更早被消除时，站立和行走平衡会受到显著影响。P10和P21动物的比目鱼肌通常具有直径较小的肌纤维，且I型肌球蛋白重链（MHC）的比例较低，IIX型MHC的比例较高。P21组比目鱼肌的抽搐收缩时间明显慢于其他组。看来在前庭系统在P21之前的时期对雪貂的运动和肌纤维发育很重要。在那个年龄眼睛仍然闭合，所有前庭感受器也未完全成熟。这些发现意味着前庭感觉以及对站立平衡很重要的一块肌肉的发育存在一个“关键期”。
