Bedini C, Lanfranchi A, Nobili R, Miyake A
J Cell Sci. 1978 Aug;32:31-43. doi: 10.1242/jcs.32.1.31.
Cells of mating types I and II of Blepharisma japonicum interact with each other and unite in heterotypic (type I-type II) or homotypic (type I-type I, type II-type II) pairs. Heterotypic pairs undergo meiosis and other nuclear changes of conjugation, while homotypic pairs remain united for days without the nuclear changes taking place. We compared cell unions of these two kinds of pairs at the ultrastructural level. In the homotypic union, cell membranes are closely juxtaposed, separated by a distance of about 20 nm. This arrangement is interrupted in some places by vacuoles and small cytoplasmic bridges. Saccule-like structures tend to be more abundant near the united surfaces. Microtubules running at right or slightly obtuse angles with the cell surface (PACM microtubules) are characteristically present at the united region of cells. These structures are very similar to those observed in earlier stages of the heterotypic union. However, in homotypic pairs, cells unite only at the anterior half of the peristome, while in heterotypic pairs cells unite also at the posterior half of the peristome, where the cell membrane totally disappears in later stages. PACM microtubules persist for at least 18 h in homotypic unions, while they disappear within a few hours in heterotypic unions. These differences between the two kinds of cell union are discussed in relation to the initiation mechanism of meiosis and other nuclear changes of conjugation. Similarities between homotypic union and cell junctions in multicellular organisms are also discussed.
日本棘尾虫I型和II型交配型细胞相互作用，并以异型（I型-II型）或同型（I型-I型、II型-II型）配对的形式结合。异型配对会经历减数分裂和其他接合过程中的核变化，而同型配对则会在数天内保持结合状态，且不发生核变化。我们在超微结构水平上比较了这两种配对的细胞结合情况。在同型结合中，细胞膜紧密并列，相隔约20纳米的距离。这种排列在某些地方会被液泡和小的细胞质桥打断。囊状结构在结合表面附近往往更为丰富。与细胞表面呈直角或略钝角排列的微管（PACM微管）典型地存在于细胞的结合区域。这些结构与在异型结合早期观察到的结构非常相似。然而，在同型配对中，细胞仅在口围的前半部分结合，而异型配对中细胞在口围的后半部分也会结合，在后期细胞膜会完全消失。PACM微管在同型结合中至少持续18小时，而在异型结合中几小时内就会消失。本文讨论了这两种细胞结合之间的差异与减数分裂起始机制及其他接合过程中的核变化的关系。还讨论了同型结合与多细胞生物中细胞连接之间的相似性。
