背景:tape虫Tigulaentreal(Diphyllobothriidea)是最迷人的cestode寄生虫之一,因为它可能导致其第二中间宿主的寄生性阉割,硬骨鱼淡水鱼,由于抑制了鱼类促性腺激素的产生。称为plerocercoids的大型(长度达1m)幼虫在淡水鱼的体腔中发育数月,并影响宿主行为以促进传播到最终宿主,吃鱼的鸟.卵黄发生,即卵黄细胞的形成,是雌配子形成和营养的关键过程,许多扁虫的卵母细胞,主要是寄生的新皮肤病。本研究提供了扁虫(Platyhelminthes)的第一个超微结构证据,该过程被解释为细胞质样细胞死亡,即肠乳球菌卵黄细胞中程序性细胞死亡(上凋亡)的特殊情况。
结果:由于目前尚不具备脱位的分子标记,它的鉴定是基于形态学标准。电子显微镜分析显示与进行性细胞质空泡相关的卵黄细胞明显的结构变化,颗粒内质网和线粒体肿胀。此外,本研究表明,肠乳球菌的卵黄细胞与其他最早进化的真核生物的成员具有许多共同特征。
结论:本研究表明,寄生扁虫(Neoderema)可能会发生凋亡样细胞死亡。成熟卵黄细胞中GER-体的存在表明二叶虫之间的密切关系,石竹和Spatebothriidea,被认为是Eucestoda最早进化的群体。除了一般的相似之处,然而,形态之间存在许多差异,这些内含物的化学成分和数量可能是由于胚胎发育的变化,生命周期策略和确定的主机组。
BACKGROUND: The tapeworm Ligula intestinalis (Diphyllobothriidea) is one of the most fascinating cestode parasites because it may cause parasitic castration of its second intermediate host, teleost freshwater fishes, due to inhibition of production of fish gonadotropic hormones. Large-sized (length up to 1 m) larvae called plerocercoids develop several months in the body cavity of freshwater fish and affect host behavior to facilitate transmission to the final host, a fish-eating bird. Vitellogenesis, i.e. formation of vitellocytes, is a key process in formation and nutrition of female gametes, oocytes in many flatworms, mainly parasitic Neodermata. The present
study provides the first ultrastructural evidence in flatworms (Platyhelminthes) of the process that is interpreted as cytoplasmic-like cell death, i.e. a special case of programmed cell death (paraptosis) in vitellocytes of L. intestinalis.
RESULTS: As molecular markers for paraptosis are not yet available, its identification was based on morphological criteria. Electron microscopy analyses revealed evident structural changes in vitellocytes associated with progressive cytoplasmatic vacuolation, swelling of the granular endoplasmic reticulum and mitochondria. In addition, the present
study has shown that vitellocytes of L. intestinalis share numerous features in common with the members of other earliest evolved eucestodes.
CONCLUSIONS: The present
study indicates that paraptotic-like cell death may occur in parasitic flatworms (Neodermata). The presence of GER-bodies in mature vitellocytes indicates close relationship between the Diphyllobothriidea, Caryophyllidea and Spathebothriidea, which are considered as the earliest evolved groups of the Eucestoda. Beyond the general similarities, however, a number of differences exist between the morphology, chemical composition and amount of these inclusions which could be due to the variations in their embryonic development, life cycle strategies and definitive host groups.