Locke M, Leung H
Cell Science Laboratories, Department of Zoology, University of Western Ontario, Ontario, Canada.
Tissue Cell. 1985;17(4):589-603. doi: 10.1016/0040-8166(85)90034-5.
Previous work on the last (fifth) larval stadium of Calpodes showed two phases of elaboration of epidermal nucleoli correlated with RNA synthesis, the first after ecdysis at the beginning of the intermolt and the second near the end of the stadium prior to molting. Both phases followed periods of elevated hemolymph ecdysteroid. The demonstration of four hemolymph ecdysteroid peaks and an improvement in the bismuth-staining procedure for nucleoli has prompted further study of nucleolar changes in relation to hemolymph edcysteroids. We have found that three of the four ecdysteroid peaks (I, II and IV) are followed by nucleolar changes. The exception is the commitment peak (III) for which there is no corresponding nucleolar change. The three nucleolar cycles are similar in their essential features. An intercycle nucleolus consists of one or a few irregularly shaped particles that become more densely stained and condense into a knot at the beginning of each cycle. The knot unfolds into a necklace which becomes beaded as it elongates to a length of about 23 microm. Cells have one or two, rarely more, necklaces presumably depending on their ploidy. At the end of the cycle the necklaces contract, becoming coarser and fragmented before they condense to the intercycle condition of central irregular cores. Whereas nucleolar necklaces are a general response to hemolymph ecdysteroids, mitoses are locally determined and are imposed over other nuclear activities at any time in the third nucleolar cycle.
先前对角纹夜蛾最后（第五）龄幼虫期的研究表明，表皮核仁的发育有两个阶段与RNA合成相关，第一个阶段在蜕皮后刚进入蜕皮间期时，第二个阶段在龄期末蜕皮前。这两个阶段都出现在血淋巴蜕皮甾类升高的时期之后。四个血淋巴蜕皮甾类峰值的证实以及核仁铋染色程序的改进促使人们进一步研究核仁变化与血淋巴蜕皮甾类的关系。我们发现，四个蜕皮甾类峰值中的三个（I、II和IV）之后会出现核仁变化。例外的是承诺峰值（III），其之后没有相应的核仁变化。这三个核仁周期在基本特征上相似。周期间核仁由一个或几个形状不规则的颗粒组成，在每个周期开始时，这些颗粒染色变深并凝聚成一个小结。小结展开形成一条项链，随着项链伸长到约23微米长时会形成串珠状。细胞有一条或两条项链，很少有更多的，这可能取决于它们的倍性。在周期结束时，项链收缩，在凝聚成中央不规则核的周期间状态之前变得更粗并破碎。虽然核仁项链是对血淋巴蜕皮甾类的一般反应，但有丝分裂是局部决定的，并且在第三个核仁周期的任何时候都会叠加在其他核活动之上。
