Hershey John D, Robbins Charles T, Nelson O Lynne, Lin David C
Department of Veterinary Comparative Anatomy, Pharmacology and Physiology, Washington State University, Pullman, Washington 99164, USA.
Physiol Biochem Zool. 2008 Mar-Apr;81(2):138-47. doi: 10.1086/524391.
Abstract Previous studies on wild black bears (Ursus americanus) have shown that skeletal muscle morphology, composition, and overall force-generating capacity do not differ drastically between seasons despite prolonged inactivity during hibernation. However, the amount and characteristics of the seasonal variations were not consistent in these studies. The goals of this study were to compare the amount of muscle atrophy in captive brown bears (Ursus arctos) with that observed in wild black bears and measure seasonal differences in twitch characteristics. Samples from the biceps femoris muscle were collected during the summer and winter. Protein concentration, fiber-type composition, and fiber cross-sectional area were measured along with twitch characteristics. The protein concentration of the winter samples was 8.2% lower than that of the summer samples; fiber cross-sectional area and the relative proportion of fast and slow fibers remained unchanged between seasons. Myosin heavy chain isoforms I, IIa, and IIx were identified by immunoblotting and electrophoresis, and the proportions did not change between seasons. The half-rise time in the twitch contractions increased in winter relative to summer samples, which is unexpected under disuse conditions. These results agreed with a study that showed minimal skeletal muscle atrophy between seasons in wild black bears.
摘要 以往对野生黑熊（美洲黑熊）的研究表明，尽管在冬眠期间长时间不活动，但骨骼肌的形态、组成和整体力量产生能力在不同季节之间并没有显著差异。然而，这些研究中季节性变化的程度和特征并不一致。本研究的目的是比较圈养棕熊（棕熊）的肌肉萎缩程度与野生黑熊的情况，并测量抽搐特征的季节性差异。在夏季和冬季采集股二头肌样本。测量蛋白质浓度、纤维类型组成、纤维横截面积以及抽搐特征。冬季样本的蛋白质浓度比夏季样本低8.2%；纤维横截面积以及快肌纤维和慢肌纤维的相对比例在不同季节之间保持不变。通过免疫印迹和电泳鉴定了肌球蛋白重链同工型I、IIa和IIx，其比例在不同季节之间没有变化。与夏季样本相比，冬季抽搐收缩的半上升时间增加，这在废用条件下是出乎意料的。这些结果与一项表明野生黑熊不同季节之间骨骼肌萎缩最小的研究一致。
