Differential reflex activity determines claw and closer muscle asymmetry in developing lobsters

The paired claws and closer muscles of the lobster, Homarus americanus, are identical in the early juvenile stages, but subsequently differentiate into a stout crusher claw with only slow fibers and a slender cutter with largely fast fibers. Rearing with different substrates or exercise of the claws revealed that claw laterality is determined in the central nervous system by differential reflex activity in the paired claws; the side with greater activity becomes the crusher, while the contralateral side becomes the cutter.     

Calcium-sensitive cross-bridge transitions in mammalian fast and slow skeletal muscle fibers

The fundamental mechanism underlying the differing rates of tension development in fast and slow mammalian skeletal muscle is still unknown. Now, in skinned (membrane-permeabilized) single fibers it has been shown that the rate of formation of the strongly bound, force-producing cross-bridge between actin and myosin is calcium-sensitive in both fast and slow fibers and that the rate is markedly greater in fast fibers. The transition rates obtained at high calcium concentrations correlated with myosin isoform content, whereas at low calcium concentrations the thin filament regulatory proteins appeared to modulate the rate of tension development, especially in fast fibers. Fiber type-dependent differences in rates of cross-bridge transitions may account for the characteristic rates of tension development in mammalian fast and slow skeletal muscles.     

鳜骨骼肌快肌和慢肌的组成特征比较

骨骼肌组成特征是鱼类肉质性状评价的重要基础。为全面了解鳜（Siniperca chuatsi）肉质性状的组成特征,通过制作骨骼肌石蜡切片,比较了鳜快肌和慢肌两种类型骨骼肌的组织学特征,快肌和慢肌在肌纤维细胞直径、形态上存在差异。利用SDS聚丙烯酰胺凝胶电泳（SDS-PAGE）分析了鳜快肌和慢肌的蛋白质组成特征,它们在50～60 ku和10～15 ku大小的条带中存在差异。克隆了鳜快肌和慢肌肌球蛋白重链（MHC）S1结构域的序列,快肌和慢肌S1结构域cDNA序列长度分别为2 523 bp、2 520 bp,编码841、840个氨基酸,氨基酸序列的相似度为87.6%,以两个loop区的差异最大。研究结果表明,鳜快肌、慢肌在肌纤维细胞形态、蛋白质组成以及肌球蛋白重链分子结构上均存在较明显的差异,这些差异与其担负不同的运动功能相关。     

骨骼肌肌纤维形成机制的研究进展

骨骼肌是动物躯体最重要的组成部分,占到产肉动物躯体的40%,肌纤维作为骨骼肌组织的主要成分,其类型的差异是影响产肉动物肌肉品质的重要因素之一。因此,骨骼肌的生长发育与产肉动物肉的产量有着密切的联系,而其生理生化特性的差异也将会直接影响到产肉动物屠宰之后肉品的质量。一般而言,动物骨骼肌肌纤维数目在胚胎发育期间基本上就已固定,出生之后,由于肌纤维的肥大,动物躯体肌肉块才表现出增大增粗。另外,动物肌肉块在生长发育过程中,其肌纤维组成类型并不是完全固定的,它们会随着骨骼肌对代谢与功能需求的改变而发生转变。骨骼肌的生长发育,以及骨骼肌肌纤维类型的发生与发展是一个非常复杂的生物学过程,受到许多信号通路与因子的调控。随着分子生物学技术的飞速发展,各种先进技术相继被应用于生物学现象的研究中,利用这些分子生物学技术很好的阐明了许多复杂生物学现象形成的分子机制。目前,骨骼肌生长发育的分子遗传调控机制取得了长足的进展,许多与骨骼肌形成发育相关的关键因子已被鉴定出来。然而,在早期研究中,人们对于骨骼肌肌纤维的研究主要集中在类型的鉴定,以及不同肌纤维类型生理生化特性的分析,对于骨骼肌肌纤维形成的具体分子遗传调控机制的研究相对较少。近年来,随着研究的不断深入,骨骼肌肌纤维形成的分子遗传调控机制也取得了突破性的进展。因此,有必要进一步对骨骼肌肌纤维类型的特性,骨骼肌肌纤维类型形成的分子机制,以及肌纤维类型与肌肉品质的关系进行全面的综述。本文首先对肌纤维的类型、特性进行了综述;进一步分别对慢型肌纤维与快型肌纤维形成的分子调控机制的研究进展进行了回顾;最后对肌纤维类型与肉品质的关系进行了讨论。总之,本综述的撰写将有助于对骨骼肌肌纤维类型形成的遗传机制的进一步了解,为将来进一步的深入研究肌纤维形成的分子机制提供参考;同时也将有助于揭示肌肉品质形成的分子遗传调控机制,为利用分子生物学技术培育高品质新品种或新品系产肉动物提供分子理论依据。     

斑马鱼下颌再生中神经与肌肉的关系

本研究旨在揭示斑马鱼下颌再生中神经和肌肉的关系。通过HE染色技术、免疫荧光组织化学等实验技术分别观察斑马鱼下颌神经和肌肉的再生过程,考察神经和肌肉的关系。研究结果显示,截面附近的神经纤维在剪切后5 h降解,剪切后2 d时完全消失。剪切后3 d,整个芽基所在位置已出现新生的神经纤维。剪切5 d时,芽基上布满大量的神经纤维。肌纤维在剪切后12 h已发生断裂,剪切后5 d形成芽基细胞并分化成各种前体细胞如肌肉前体细胞,剪切后9 d出现新生的肌细胞,剪切后14 d新生的肌细胞与新生的神经纤维建立神经肌肉接头联系,30 d后成为成熟的肌肉组织。结果表明:如果斑马鱼1/3的下颌被人为切除,下颌肌肉可以实现功能性再生,同时神经极可能在肌肉再生中发挥作用。但是如果切除部分超过1/3,则下颌无法再生复原,其原因有待进一步研究。     

Peptide and steroid regulation of muscle degeneration in an insect

Two types of cell death occur in the intersegmental muscles of the giant silkmoth Antheraea polyphemus. The first results from a slow atrophy of the fibers, and the second is a rapid, programmed dissolution of the muscle. Both types appear to be mediated by endocrine factors. The slow atrophy is brought about by the decline in the steroid molting hormone 20-hydroxyecdysone and can be prevented with exogenous steroid. The rapid degeneration is triggered by the peptide eclosion hormone, but the sensitivity of the muscle to the peptide depends on the history of exposure of the muscle to 20-hydroxyecdysone.     

Snapping Behavior of the Shrimp Alpheus californiensis

A pair of very smooth disks, located on the claw of the snapping shrimp Alpheus californiensis, are temporarily held together by cohesive forces of water. This allows the closer muscle of the claw to generate a large amount of tension before these cohesive forces are overcome, and results in a rapid closing movement.     

Effects of manipulated diet on size and performance of brachyuran crab claws

Crabs grown experimentally on fully shelled prey developed larger and stronger claws than those raised on nutritionally equivalent unshelled prey. When one claw was immobilized, claws also became asymmetrical. These use-induced changes differ from skeletal remodelling in vertebrates and many invertebrates because changes in the rigid exoskeleton can occur only after molting, and claw muscle mass must be reduced substantially before the molt. Such short-term adaptive responses to environmental stimuli, if heritable, could yield long-term evolutionary changes in claw size and, if combined with behavioral biases toward one side (handedness), could also promote the evolution of claw dimorphism.     

Stimulation-dependent alterations in peroxidase uptake at lobster neuromuscular junctions

The uptake of cytochemically demonstrable horseradish peroxidase into small vesicles within nerve endings in lobster stretcher muscles can be enhanced by electrical stimulation of transmitter release by the endings. This is observed particularly if stimulation is interrupted periodically and the nerves     

家兔骨骼肌肌球蛋白重链构成的电泳

[目的]探究家兔骨骼肌肌球蛋白重链构成的电泳的作用机制。[方法]应用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)检测成年家兔后肢肌胫前肌、腓肠肌和比目鱼肌的肌球蛋白重链异构体(MyHCs),采用大体解剖法依次取出家兔的每块骨骼肌,分别与样品缓冲液一起研磨成肌细胞匀浆,经高速冷冻离心后取出上清液,按照不连续SDS-聚丙烯酰胺小孔梯度凝胶电泳操作程序依次试验。[结论]该研究进一步证实3种快纤维型在成年啮齿动物肢体肌肉中的作用,但同源结构是否有这些肌纤维值得继续深入探索。     

褐菖鲉发声肌中小清蛋白的特性及肌肉纤维的超微结构特性

通过对褐菖鲉发声系统的研究,尤其是发声肌形态、小清蛋白含量和肌纤维超微结构等特征,发现褐菖鲉发声肌和白色肌肉中小清蛋白分子量均为10~14 ku。在白色肌肉肌纤维显微结构中,三联体(一个T小管+两个肌质网终池)仅处于Z膜,而在发声肌纤维中,三联体不仅在Z膜处,也在A带与I带交联处。与白色肌相比,发声肌超微结构中的肌质网更宽,肌膜更发达。在发声肌细胞中,线粒体多且聚集;而白肌细胞中,线粒体相对少且分散。结果显示:在褐菖鲉发声肌的快速收缩中,小清蛋白可能没有起重要作用,而是发达的肌膜、三联体和肌质网结构确保了该特殊肌肉快速收缩和放松的发声功能与行为,同时,大量聚集的线粒体保证其发声肌的持续工作能力。     

MUSCLE: VOLUME CHANGES IN ISOLATED SINGLE FIBERS

Volumetric experiments on single fibers isolated from semiten-dinosus muscles of frogs, some performed in correlation with measurements of membrane potential, confirm the data obtained on whole muscles, but only for the specific range of conditions in which most of the latter experiments have been done. These conditions are restricted to media in which the anion ( Cl usually) is permanent and the K is 10 to 12.5 meqlliter, or four to five times above the normal level in Ringer's solution. When other ionic conditions are employed, phenomena are disclosed which have not previously been described. The findings throw doubt upon the validity of some generally accepted views regarding the permeability properties of the membrane of frog muscle fibers and regarding the nature of the mechanisms which regulate their volume.     

新西兰白兔中Myh6基因的表达及与肌纤维性状的相关性

【目的】分析Myh6基因在新西兰白兔Oryctolagus cuniculus肌肉中的表达规律及与肌纤维特性的相关性,探究Myh6基因在肌纤维发育过程中的作用。【方法】利用冰冻切片技术测量了2、4、6、8、10、12周龄新西兰白兔背腿肌中不同类型肌纤维的密度、面积、长径和短径等性状,采用qRT-PCR测量了Myh6基因在不同周龄新西兰白兔背腿肌中的表达量,分析了上述性状与Myh6基因表达的相关性。【结果】2~8周龄新西兰白兔各类型肌纤维的密度逐渐变小,面积、长径和短径则逐渐变大(白肌纤维短径除外,仅在2~6周龄有变大趋势)。Myh6基因在4周龄表达量最高。Myh6基因表达量与公兔背部红肌纤维的面积呈极显著负相关(P0.01),与公兔腿部红肌纤维的密度呈极显著正相关(P0.01)。【结论】Myh6基因表达与肌纤维类型和肌纤维的生长发育密切相关。     

Junctional physiology and motor nerve distribution in the fast adductor muscle of the scallop

Electrical recordings from single muscle cells in the fast portion of the scallop adductor have revealed a multiterminal distribution of motor nerves. All motor junctions appear to be of the fast designation, and several nerve fibers supply each muscle cell. The muscle fibers, by virtue of common innervation, are grouped into functional motor units. The pattern of innervation in scallops thus shares functional similarities with the motor distribution to skeletal muscle fibers of both vertebrates and arthopods.     

鸭发育早期骨骼肌TNNI1基因mRNA表达 及与肌纤维生长的相关性分析

为探讨慢收缩骨骼肌型Tnl(slow skeletal muscle troponin I,TNNI1)基因在鸭早期肌肉发育中的m RNA表达规律及与肌纤维发育的相关性,以地方品种高邮鸭为素材,采用实时荧光定量PCR方法,检测胚胎期21、25、27胚龄及出雏后5日龄时腿肌腓肠肌外侧头中TNNI1基因m RNA表达量,结果发现,25胚龄是TNNI1基因的表达高峰期,之后显著下调,并持续至5日龄。肌纤维类型变化则是随时间的推移,慢肌纤维比例逐渐升高,快白肌纤维比例逐渐下调;25胚龄时,慢肌纤维直径和横切面积均出现显著增高(P0.05),快白肌纤维横切面积则出现下调;之后,3种类型肌纤维直径和横切面积在各个时间点之间无显著差异(P0.05);相关性分析结果显示,TNNI1基因m RNA表达量与快红肌纤维比例呈显著负相关(P0.05),与肌纤维直径、横切面积均无显著相关性(P0.05)。提示TNNI1可能在鸭发育早期骨骼肌肌纤维类型转换中具有重要的作用。     

Hypothalamic reward mechanism: two first-stage fiber populations with a cholinergic component

Refractory periods were estimated for fibers of the hypothalamic substrate of brain stimulation reward. Two nonoverlapping populations were evident: a homogeneous fast population and a more heterogeneous slow population. Cholinergic blockade eliminated the contribution of the fast but not the slow fibers, while dopaminergic blockade reduced responding without significantly influencing either directly activated fiber population. These data indicate that the hypothalamic reward substrate is more complex than has been widely appreciated; it contains two or more parallel subsystems, and one of these subsystems has a cholinergic link.     

狮头鹅和乌鬃鹅不同生长阶段肌纤维发育规律的研究

为研究狮头鹅和乌鬃鹅在不同生长阶段肌纤维的发育规律,分别选取健康的１、４０和１２０日龄乌鬃鹅和狮头鹅,屠宰并取其胸肌和腿肌做石蜡切片,观察并测定两种鹅不同部位不同时期肌纤维的直径和横截面积．结果表明两种鹅１日龄胸肌肌纤维差异不明显,腿肌肌纤维横截面积和直径差异显著（Ｐ＜０.０５）;４０日龄两种鹅胸肌肌纤维横截面积差异显著（Ｐ＜０.０５）,但胸肌直径和腿肌的直径和横截面积差异不显著（Ｐ＞０.０５）;１２０日龄两种鹅胸肌肌纤维和腿肌肌纤维的横截面积和直径差异极显著（Ｐ＜０.０１）．研究结果表明乌鬃鹅肌肉纤维在１至４０日龄期间生长发育迅速,但４０日龄后肌纤维生长潜力不如狮头鹅．     

高效液相色谱法测定大鼠比目鱼肌和内侧腓肠肌内ATP·ADP及AMP含量的研究

[目的]比较成年大鼠比目鱼肌和内侧腓肠肌内ATP、ADP及AMP的含量。[方法]采用大体解剖法取出大鼠的比目鱼肌和内侧腓肠肌,置于液氮内研磨成粉末,再分别加入EDTA和HClO4、NaHCO3,经高速冷冻离心取出上清液,用高效液相色谱仪测定。[结果]慢肌(比目鱼肌)ADP的含量多于快肌(内侧腓肠肌),慢肌(比目鱼肌)ATP、AMP的含量少于快肌(内侧腓肠肌)。[结论]使用高效液相色谱仪可以检测出快慢肌的差异。     

Giant Muscle Fibers in a Barnacle, Balanus nubilus Darwin

Cross-striated muscle fibers of very large size have been found in the scutal-tergal adductor and depressor muscles of the large barnacle B. nubilus. Adductor muscle fibers are up to 2 mm thick. They are innervated by separate nerves, each supplying one end, but not the central region, with terminals; each fiber receives two or three excitor axons. Depressor muscle fibers are up to 1.4 mm thick and receive multiterminal innervation along their entire length; they are innervated by two excitor axons. Postsynaptic potentials are of small or large size and lead to small or large twitches; they do not show facilitation. The muscle fibers shorten to as little as one-sixth resting length.     

Mechanism of Supercontraction in a Striated Muscle Fiber

Cross-striated muscle fibers may contract reversibly to less than 30 percent of their rest length and it is not easy to reconcile this fact with the sliding filament model of muscular contraction. The mechanism of supercontraction has been studied in fibrils obtained from the giant muscle fibers of the barnacle Balanus nubilus. They were examined by phase-contrast light microscopy and electron microscopy. Contraction beyond the 50-percent stage was found to be achieved largely by the passage of thick filaments through the Z-disks, which are perforated. The overlap of thick filaments from adjacent sarcomeres causes the appearance of the contraction bands about the Z-disks. Subsequent contraction is associated with a folding and loose coiling, but not a shortening, of the thick filaments.