扩张莫尼茨绦虫(绦虫纲:圆叶目)卵黄细胞发育的超微结构

用透射电镜观察了扩张莫尼茨绦虫(Moniezia expansa)卵黄细胞发育的全过程。扩张莫尼茨绦虫卵黄细胞发育的规律为：(1)细胞体积不断增大;(2)质、核比不断增加而核体积几乎不发生改变,核表面从规则变为不规则,再由不规则变为规则,核内出现染色质浓缩成小块再分散的发育变化过程;(3)线粒体逐渐增多,发育不断完善;(4)粗面内质网及高尔基复合体出现由少到多,发育不断完善,再由多到少不断退化的变化;(5)由高尔基复合体组装的电子致密的小卵黄囊不断融合,至卵黄细胞成熟时仅有一卵黄囊,占据细胞大部分体积[动物学报49(2)：256—261,2003]。     

扩张莫尼茨绦虫(圆叶目:裸头科)精子的扫描结构

自Gresson 1962在Nature上报道了绦虫的精子发生及结构以来,至今已报道了近70种绦虫的精子结构。法国Justine（1991,1995,1998）对寄生动物的精子结构有较深人的研究,并对寄生扁虫的精子结构及其系统学意义有相关综述,对绦虫精子的系统学特征研究中,概述了11个目、43属、56种真绦虫精子结构的相关信息,不仅从精子的结构,而且从精子的发生过程来研究其系统意义,归结出真绦虫的一些共源性状如：绦虫的成熟精子中缺乏线粒体并且存在冠状体结构;     

扩张莫尼茨绦虫(圆叶目:裸头科)精细胞分化、精子形成及精子形态

本项研究应用光学显微镜、扫描和透射电子显微镜,观察了扩张莫尼茨绦虫的精细胞分化、精子形成全过程及精子的精细结构。扩张莫尼茨绦虫的精细胞分化过程为：1)初级精原细胞主要发生于幼节的睾丸滤泡中;2)次级精原细胞发生不完全分裂形成16个细胞一簇的初级精母细胞群,以共同的中央细胞质相连;3)初级精母细胞的特征为细胞核中出现联会复合体结构;4)紧接着的第二次成熟分裂,产生64个由中央细胞质相连的细胞核较小的精细胞。精子形成始于精细胞中分化区的形成,成熟精子缺乏线粒体,具有质膜和冠状体、1—4个领域排布的质膜下皮层微管,细胞质中存在电子致密的颗粒状物质,具一个不规则形态的细胞核,具有“9 1”类型的轴丝构造,缺乏轴丝周围鞘。从精子的纵切面上可将精子区分为5个区段(Ⅰ一Ⅴ区)。在精子形成过程中,中心粒基部出现螺旋形小根结构在寄生虫中为首次报导;成熟精子具有游离鞭毛,在绦虫中为首次发现[动物学报49(3)：370—379,2003]。     

扩张莫尼茨绦虫(圆叶目:裸头科)节间腺的超微结构及组织化学

用光学显微镜和透射电子显微镜观察了扩张莫尼茨绦虫节间腺形成过程的精细结构及一些组化变化。结果表明：节间腺是扩张莫尼茨绦虫皮层的特化部分,由节片后缘的皮层及其邻近细胞体向绦虫实质组织中陷入开始其形成过程,随着虫体发育的进行,新的陷入不断形成,原陷入的部分不断脱离皮层形成簇状腺体结构。节间腺的数目随着体节的发育不断增加,幼节中仅有少数几个(6～9个),而远端的孕节中多于100个。电镜下可见腺细胞体由细胞质管与腺皮层相联,簇状腺体结构为一合胞体形态,腺细胞体围绕并开口于椭球体或不规则形状的皮层腔中。离腺皮层远的腺细胞体电子密度高并含有与腺皮层相应的典型分泌颗粒,而靠近腺皮层的腺细胞体电子密度低,所含分泌颗粒较少。扩张莫尼茨绦虫节间腺的组化性质尚不完全清楚。糖与蛋白质等组化结果不稳定,随染液pH值及染色时间的变化等多种因素而改变。基于我们的研究及其他研究者的观察表明,节间腺可能参与外源基质形成虫卵的转运,同时他们可能在虫体节片脱落及虫卵溢出时起作用。     

中国绦虫三新种记述(绦虫纲:原头目,圆叶目)

报道绦虫纲3新种,即原头科的中华蛇带绦虫Ophiotaenia sinensis sp.nov、戴维科的林氏瑞列绦虫Raillietina(Paroniella)linisp.nov和囊宫科的苦恶鸟异带绦虫Anomotaenia amaurornisus sp.nov。     

囊宫科绦虫一新种(绦虫纲:圆叶目)

本文报道在湖北省鄂西地区鸟类绦虫标本中发现一新种,隶于囊宫科、侧孔属,定名为鄂西侧孔绦虫,新种Lateriporus exiensis,sp.nov.。本文对新种的形态作了详细描述,对新种与近似种的主要特征到表进行比较,并讨论了建新种的依据。     

膜壳绦虫属二新种(绦虫纲:圆叶目:膜壳科)

本文记述膜壳科膜壳属绦虫二新种,即卷尾膜壳绦虫Ｈｙｍｅｎｏｌｅｐｉｓ ｃｈｉｂｉａｅ ｓｐ．ｎｏｖ．和三宝鸟膜壳绦虫Ｈ．ａｂｕｎｄｕｓ ｓｐ．ｎｏｖ．卷尾膜壳绦虫标本采自福州的黑发冠卷属Ｃｈｉｂｉａ Ｈｏｔｔｅｎｔｏｔｔａ Ｂｒｅｖｉｒｏｓｔｒｉｓ;三宝鸟膜壳绦虫标本采自福州的三宝鸟Ｅｕｒｙｓｔ９ｏｍｕｓ ｏｒｉｅｎｔａｌｉｓ ａｂｕｎｄｕｓ均为肠道寄生虫。     

Reinvestigation of the ultrastructure of spermiogenesis and the spermatozoon of Hymenolepis nana (Cestoda, Cyclophyllidea), parasite of the small intestine of Rattus rattus.

Spermiogenesis in Hymenolepsis nana begins with the formation of a differentiation zone. This is limited at the front by arched membranes, is surrounded by cortical microtubules associated with 12 crested-like bodies, and contains a single centriole made up of doublets. The distal centriole gives rise to a flagellum that grows at the same pace as the cortical microtubules. Migration of the nucleus takes place after the formation of the flagellum. It is followed by the separation of the old spermatid from the residual cytoplasm. The mature H. nana spermatozoon is filiform and lacks mitochondria. The axoneme, of the 9 + "1" pattern of the Platyhelminthes, does not reach the extremities of the spermatozoon. The nucleus is electron dense and is in close contact with the axoneme around which it coils in a spiral making an angle of 10 degrees to 15 degrees with the spermatozoon axis. The cortical microtubules follow a 10 degrees to 15 degrees helicoidal path along almost their whole length, except at their posterior extremity, where they are parallel to the spermatozoon axis. H. nana is distinguished by the early development of 12 crested-like bodies of different lengths and by the existence of a single centriole in the differentiation zone. Such a high number of crested-like bodies had never previously been reported in a cestode.     

In vitro hatching of the tapeworm Moniezia expansa (Cestoda: Anoplocephalidae) and some properties of the egg membranes.

In vitro studies revealed that the hatching of oncospheres of Moniezia expansa requires the mechanical breakage of the eggshell and subshell membrane and enzymic digestion of the pyriform apparatus. Removal of the outer two egg membranes elicits the activation of most oncospheres. Between pH 5.0-7.8, there is no significant difference in numbers of oncospheres activated by eggshell removal and the addition of sodium bicarbonate has no effect. Solutions of more extreme pH values (2.0 and 10.0) are harmful and render oncospheres immobile. The subshell membrane forms a barrier to the passage of water in an osmotic gradient and to several molecular and ionic substances. Between the eggshell and subshell membrane is a layer of droplets which have a strong affinity for Sudan stains and which are partially removed by lipase. The eggshell is resistant to a variety of proteolytic enzymes, amylases and lipase. The pyriform apparatus is digested by chymotrypsin and pepsin, though not by trypsin. Both eggshell and pyriform apparatus are dissolved by solutions of sodium sulphide and sodium hypochlorite, indicating that their structures are stabilized by disulphide bonds and other covalent linkages.     

The complete mitochondrial DNA sequence of the cestode Echinococcus multilocularis (Cyclophyllidea: Taeniidae)

The 13,738 bp mitochondrial DNA from the cestode Echinococcus multilocularis has been sequenced. It contains two major noncoding regions and 36 genes (12 for proteins involved in oxidative phosphorylation, two for rRNAs and 22 for tRNAs) but a gene for ATPase subunit 8 is missing. All genes are transcribed in the same direction. Putative secondary structures of tRNAs indicate that most of them are conventional clover leaves but the dihydrouridine arm is unpaired in tRNA(Ser(AGN)), tRNA(Ser(UCN)), tRNA(Arg) and tRNA(Cys). The base composition at the wobble positions of fourfold degenerate codon families is highly biased toward U and against C.     

Development of the Embryonic Envelopes of Mesocestoides lineatus (Cestoda: Cyclophyllidea)

Summary

Transmission electron microscopy revealed that the eggs of Mesocestoides lineatus consisted of an oncosphere larva surrounded by various coverings. The outermost of these was the embryonic capsule, which appeared as a thin electron-dense membranous sac. The capsule enclosed inner and outer embryonic envelopes, each of which was syncytial and apparently formed from embryonic blastomeres. The envelopes became increasingly vesiculated during embryogenesis, and were attached to each other by desmosomes by the time the larva was fully formed. An electron-dense intracellular embryophore was produced by the inner envelope; it first appeared under the distal plasma membrane as a series of blocks, which grew and fused to form a thick unbroken layer. Early in development, the proximal plasma membrane of the inner envelope was connected to the larval epithelium by a multilaminate membrane complex that was ultrastructurally similar to a continuous junction. At the end of embryogenesis, this appeared to detach from its formative cells on both sides to form the distinctive oncospheral membrane. Several eggs were bound together in clusters by a cluster capsule that was ultrastructurally identical to the individual embryonic capsules. This type of egg packaging has not been described previously for any cestode. Both the cluster and individual capsules broke down by the end of embryogenesis.     

Studies of regulatory metabolism in Moniezia expansa: the role of phosphofructokinase (with a note on pyruvate kinase).

Some of the properties of a partially purified preparation of phosphofructokinase (PFK) from Moniezia expansa are described. PFK has a pH optimum between 7·4 and 8·0, and is activated by magnesium and divalent manganese ions. It exhibits sigmoid kinetics with fructose-6-phosphate, and ATP decreases the affinity of the enzyme for F6P. This inhibition is partially relieved by F6P, AMP and ammonium ions. GTP and ITP act as substrates for the PFK reaction but do not exert the same inhibitory effects. The effect of ATP on pyruvate kinase was also examined, and was found to inhibit both the activated and inactivated enzyme. Apparent K_m's for both enzymes are presented.Generally, PFK and pyruvate kinase from M. expansa show properties similar to the enzymes from mammalian sources. The presence of sigmoid kinetics for F6P and ATP at pH8 is, however, a significant departure from what is observed in PFK from mammalian sources. Possibilities exist in M. expansa for controls of metabolism similar to those found in mammalian tissues.