Denervation effects on myonuclear domain size of rat diaphragm fibers
Denervation effects on myonuclear domain size of rat diaphragm fibers
复制标题
DOI：
10.1152/japplphysiol.01277.2005
复制
发表时间：
2006-05-01
影响因子：
3.3
通讯作者：
Sieck, GC
中科院分区：
文献类型：
--
作者：
Aravamudan, B;Mantilla, CB;Sieck, GC
去神经支配（DNV）大鼠膈肌（DIAm）导致IIx型和IIb型纤维选择性萎缩，而I型和IIa型纤维的横截面积保持不变或轻度肥大。DIAm DNV还增加卫星细胞有丝分裂活性和肌细胞凋亡。与其他骨骼肌类似，DIAm纤维是多核的，每个肌核在有限的纤维体积中调节基因产物，即，myc结构域（MND）。MND大小按等级顺序在DIAm纤维类型之间变化，I < IIa < IIx < IIb [基于肌球蛋白重链同种型表达的纤维类型]。我们假设，在DNV后，每根纤维的肌核总数没有变化，因此，无论纤维类型如何，MND的变化与纤维大小的变化成正比。成年大鼠进行单侧（右侧）DIAm DNV，2周后解剖单纤维。通过共聚焦显微镜测量纤维横截面积、肌纤维数目和MND，并将DNV DIAm中的这些值与对照组中获得的值进行比较。与对照组相比，DNV后I型纤维肥大，IIa型纤维大小不变，IIx和IIb型纤维萎缩。每根肌纤维的肌核总数不受DNV的影响。因此，DNV后，I型纤维MND增加了25%，而IIx和IIb型纤维MND分别下降了50%和70%。这些结果表明，在DNV诱导的DIAm纤维肥大或萎缩后，MND不能维持。这些结果被解释为DNV对myocytes转录活性和蛋白质周转的影响。
Denervation (DNV) of rat diaphragm muscle (DIAm) leads to selective atrophy of type IIx and IIb fibers, whereas the cross-sectional area of type I and IIa fibers remains unchanged or slightly hypertrophied. DIAm DNV also increases satellite cell mitotic activity and myonuclear apoptosis. Similar to other skeletal muscles, DIAm fibers are multinucleated, and each myonucleus regulates the gene products in a finite fiber volume, i.e., myonuclear domain (MND). MND size varies across DIAm fiber types in rank order, I < IIa < IIx < IIb [ fiber type based on myosin heavy chain isoform expression]. We hypothesized that, after DNV, the total number of myonuclei per fiber does not change and, accordingly, that MND changes proportionately to the change in fiber size regardless of fiber type. Adult rats underwent unilateral ( right side) DIAm DNV, and after 2 wk single fibers were dissected. Fiber cross-sectional area, myonuclear number, and MND were measured by confocal microscopy, and these values in DNV DIAm were compared with those obtained in controls. After DNV, type I fibers hypertrophied, type IIa fiber size was unchanged, and type IIx and IIb fibers atrophied compared with control. The total number of myonuclei per fiber was not affected by DNV. Accordingly, after DNV, type I fiber MND increased by 25%, whereas it decreased in type IIx and IIb fibers by 50 and 70%, respectively. These results suggest that MND is not maintained after DNV-induced DIAm fiber hypertrophy or atrophy. These results are interpreted with respect to consequent effects of DNV on myonuclear transcriptional activity and protein turnover.