Hammersmith R L
J Cell Sci. 1976 Dec;22(3):563-73. doi: 10.1242/jcs.22.3.563.
Heteropolar doublets of the hypotrichous ciliate Oxytricha fallax can encyst, as can monster cells containing multiple copies of at least part of the ciliature. The resulting cysts excyst as heteropolar doublets or monster cells, respectively. Transmission electron microscopy of resting cysts derived from monster cells and from singlets, however, indicates a complete loss of the ciliature - all kinetosomes, ciliary axonemes, and microtubules. Thus, the determination of each ciliature of a monster cell cannot be attributed to the persistence of any visible part of the ciliature. Transmission electron microscopy of monster and singlet cysts suggests that the information for a ciliature may be related to the system of cyst wall grooves and possibly to differentiations in the inner cell membrane which separates the cyst cytoplasm from the cyst wall. The redevelopment of heteropolar doublets upon excystment indicates that the anterior-posterior polarity is independently determined for each ciliature and is maintained through cystment. This polarity is not, however, reflected in a recognizable anterior-posterior polarity of any visible structure of the resting cyst. The number of adoral zones of membranelles (AZMs) may increase or decrease in some excysting monster cells compared with that observed in the encysting cells. Possible explanations for these changes are offered in the Discussion.
伪足纤毛虫类的异极双联体草履虫（Oxytricha fallax）能够形成包囊，含有至少部分纤毛器多个拷贝的巨型细胞也能形成包囊。所形成的包囊分别以异极双联体或巨型细胞的形式脱囊而出。然而，对源自巨型细胞和单细胞的静止包囊进行透射电子显微镜观察表明，纤毛器完全消失——所有动基体、纤毛轴丝和微管都不见了。因此，巨型细胞中每个纤毛器的确定不能归因于纤毛器任何可见部分的持续存在。对巨型细胞和单细胞包囊的透射电子显微镜观察表明，纤毛器的信息可能与包囊壁沟系统有关，也可能与将包囊细胞质与包囊壁分隔开的内膜分化有关。脱囊时异极双联体的重新发育表明，每个纤毛器的前后极性是独立确定的，并在包囊形成过程中得以维持。然而，这种极性在静止包囊的任何可见结构的可识别的前后极性中并未体现出来。与包囊形成细胞相比，一些脱囊的巨型细胞中口围膜带（AZM）的数量可能会增加或减少。讨论部分提供了对这些变化的可能解释。
