Clark P, Jones K J, LaVelle A
Department of Anatomy and Cell Biology, University of Illinois, Chicago 60680.
J Comp Neurol. 1990 Dec 22;302(4):749-60. doi: 10.1002/cne.903020407.
In this study, progressive developmental changes in the nucleus and associated organelles, including the nucleolus, coiled bodies, nuclear envelope, and nucleoplasm, of hamster facial motor neurons were characterized by two parallel analyses: ultrastructural and morphometric. Golden hamsters (Mesocricetus auratus) used for this series were the 14-day fetus, newborn (less than 6 hr), and 1, 2, 3, 4, 5, 7, 9, 11 and 13 days postnatal ages, with 3 animals per group. Following anesthesia and perfusion fixation, facial nuclear groups were dissected and processed for electron microscopy. Electron micrographs and camera lucida tracings of nuclear profiles were collected and analyzed. The ultrastructural analysis revealed progressive changes in the nucleolus from a compact, segregated type to a reticulated form characteristic of actively protein-secreting cells. Nucleolar microbodies and fibrillar centers were seen at all ages; the latter structures appeared to decrease in size and increase with age in the series. The nucleolus-associated chromatin became less condensed, suggesting an increase in the incorporation of rDNA into the nucleolus proper. Coiled bodies, both free and attached to nucleoli, were found in varying frequencies. The nucleoplasm of neurons at the earliest stages contained large numbers of heterochromatin clumps, which decreased concomitantly with an increase in interchromatin granules and fibrils during the later stages. Nuclear envelope invaginations, polarized along one side of the nucleus, increased throughout the developmental period examined. These changes occurred in concert with a 61% increase in nuclear size and a 47% increase in the length of nuclear envelope. The sequence of nuclear changes observed during this early period of normal facial neuronal growth completes the study of a series of distinctly defined cytomorphic events in this cell type, the lability of which can be experimentally tested for their functional roles in neuronal development.
在本研究中，通过超微结构和形态计量学这两种平行分析方法，对仓鼠面部运动神经元的细胞核及相关细胞器（包括核仁、卷曲小体、核膜和核质）的渐进性发育变化进行了表征。用于该系列研究的金黄仓鼠（Mesocricetus auratus）为14天龄胎儿、新生仓鼠（小于6小时）以及出生后1、2、3、4、5、7、9、11和13天龄的仓鼠，每组3只动物。麻醉和灌注固定后，解剖面部核群并进行电子显微镜处理。收集并分析核轮廓的电子显微照片和明场显微镜描图。超微结构分析显示，核仁从紧密、分离型逐渐转变为活跃分泌蛋白质细胞特有的网状形式。在所有年龄段均可见核仁微体和纤维中心；在该系列中，后一种结构的尺寸似乎减小且数量随年龄增加。与核仁相关的染色质凝聚程度降低，表明rDNA掺入核仁本体的量增加。发现游离的和附着于核仁的卷曲小体频率各异。最早阶段神经元的核质含有大量异染色质团块，在后期随着染色质间颗粒和纤维的增加而相应减少。沿核的一侧极化的核膜内陷在整个研究的发育期间均增加。这些变化与核大小增加61%和核膜长度增加47%同时发生。在正常面部神经元生长的这一早期阶段观察到的核变化序列，完成了对该细胞类型一系列明确界定的细胞形态事件的研究，其易变性可通过实验测试其在神经元发育中的功能作用。
