Actomyosin structure in contracting muscle detected by rapid freezing

It is now widely accepted that the ATP-induced active sliding of adjacent thin and thick filaments mediated by myosin heads (cross-bridges) is responsible for muscle contraction. Despite intensive studies, the behaviour of the myosin heads during muscle contraction is still unclear. Recent progress in the rapid freezing electron microscope technique has greatly improved the temporal resolution of the images that can be obtained. Here, we report a new type of actomyosin structure captured by rapid freezing. We have analysed images from thin sections of freeze-substituted rabbit skeletal muscle rapidly frozen during isometric contraction. For comparison, we also studied relaxed and rigor muscles. Our results show that, during isometric contraction, most myosin heads are regularly arrayed along the helix of the actin filaments and that this actomyosin structure appears to be distinct from that observed in rigor muscle.     

肥大细胞在人正常子宫的分布规律

目的：探讨肥大细胞(mast cell,MC)在人正常子宫内膜和肌层中的变化规律。方法：采用免疫组织化学和图象分析系统,对11例增生期、10例分泌期、9例绝经期子宫组织切片的MC进行测定。结果：人子宫内膜的MC数在增生期和分泌中晚期中明显增多,在分泌早期减少,在绝经期中显著减少。在肌层则未见MC数有周期性改变。结论：MC在子宫内膜呈周期性变化,分泌早期MC数量减少,将有利于胚泡的着床,绝经期MC数量的显著减少,提示其可能与绝经期妇女易患妇科恶性肿瘤相关。     

川金丝猴输卵管和子宫的组织学研究

对２只川金丝猴的输卵管和子宫作了组织学观察,结果显示：①川金丝猴输卵管粘膜向内突出形成许多纵行而分支的皱襞,其中外侧部皱襞最发达,至子宫部皱襞渐趋减少,且低矮,粘膜上皮为单层柱状上皮,由纤毛柱状细胞和分泌细胞构成;②子宫内膜由上皮和固有膜组成,上皮常限入固有膜形成管状的子宫腺,腺上皮主要由分泌细胞和少量纤细胞构成;③川金丝猴子宫壁肌层发达,由许多平滑肌束和结缔组织构成,平滑肌束分层不明显,大致可区     

内容中心网络碎片化内容访问的统计机制研究

内容中心网络(content centric networking,CCN)通过在路由器中引入缓存,能够显著地提高用户访问内容的速度并减少网络中的流量.但CCN的缓存机制导致了内容以碎片化形式在网络中,只有一部分内容访问请求能够直接到达内容提供商,导致内容提供商无法真实准确地获得内容的访问统计数据,从而增加其制定恰当的内容收费策略的难度.针对这一问题,提出了一种可以保证内容提供商准确获得内容的访问信息的统计机制.在该机制中,中间网络设备中通过新增内容计数器来统计用户请求的内容信息,在满足阈值条件、缓存内容替换或过期时将内容统计信息反馈给内容提供商,提供商据此可以制定合适的内容收费策略和付费缓存策略.实验结果表明,通过本机制网络设备能够准确地统计用户的内容访问统计信息并及时反馈给内容提供商,内容提供商从而可以准确感知其内容的访问统计数据.