Larson O R, Uglem G L, Lee K J
Department of Biology, University of North Dakota, Grand Forks 58202.
Parasitol Res. 1988;74(4):352-5. doi: 10.1007/BF00539457.
Encysted metacercariae of Clinostomum marginatum (Digenea) were obtained from tissues of yellow perch, Perca flavescens. The outermost wall (host response) as seen under electron microscopy consisted of a single, fibrous tissue layer, 10-25 micron thick. The tissue contained flattened fibrocytes, small fat deposits, and vacuoles embedded between layers of collagen fibers. The cyst cavity was filled with small vesicles, crystals, and debris. No layer corresponding to the primary (parasite-produced) cyst wall secreted by most species of metacercariae was noted. To determine the permeability of the cyst wall, encysted worms were incubated under initial rate conditions with [3H] glucose, with and without the glucose transport inhibitors phlorizin and phloretin. After incubation, the worms were mechanically excysted, washed, and processed to determine glucose uptake rates. Vmax and Kt were greater than those obtained for worms excysted prior to incubation with substrate. Moreover, the presence of phlorizin or phloretin in the incubation medium had no effect on glucose uptake by encysted worms. Thus, the selective permeability of the cyst wall permits free diffusion of glucose to the cutaneous transport systems of the worm, while restricting the movements of phlorizin and phloretin.
从黄斑鲈（Perca flavescens）组织中获取了边缘斜睾吸虫（复殖吸虫）的包囊后尾蚴。在电子显微镜下观察到，最外层壁（宿主反应）由一层单一的纤维组织层组成，厚度为10 - 25微米。该组织含有扁平的纤维细胞、小的脂肪沉积物以及嵌入胶原纤维层之间的液泡。囊腔内充满了小泡、晶体和碎片。未观察到与大多数后尾蚴种类分泌的初级（寄生虫产生的）囊壁相对应的层。为了确定囊壁的通透性，将包囊化的虫体在初始速率条件下与[3H]葡萄糖一起孵育，分别添加和不添加葡萄糖转运抑制剂根皮苷和根皮素。孵育后，将虫体机械脱囊、洗涤并进行处理以测定葡萄糖摄取率。最大反应速度（Vmax）和米氏常数（Kt）大于在与底物孵育前脱囊的虫体所获得的值。此外，孵育培养基中根皮苷或根皮素的存在对包囊化虫体的葡萄糖摄取没有影响。因此，囊壁的选择性通透性允许葡萄糖自由扩散到虫体的皮肤转运系统，同时限制根皮苷和根皮素的移动。
