Seïte R, Pébusque M J
Laboratoire de Biologie Cellulaire et Tissulaire, Faculté de Médecine, Marseille, France.
Chronobiol Int. 1985;2(2):69-91. doi: 10.3109/07420528509055546.
Chronobiological studies on the nucleolus were performed, using stereological analysis at the electron microscopic level, on different cell types in permanent interphasic state, in rats submitted to various lighting regimen. During the dark span (12L/12D): (1) in sympathetic neurons of superior cervical ganglion circadian changes in nucleolar organization were characterized by an increase in volumes of the nucleolus and each of its components, namely, fibrillar centres, dense fibrillar, granular and vacuolar components; (2) concerning the fibrillar centres, regarded as the interphasic counterpart of nucleolar organizing regions (NORs), the most striking fact, only observed in sympathetic neurons, is the occurrence of a single large-type fibrillar centre, accompanied by small-type fibrillar centres which are present throughout the 24-hr period; (3) the overall increase in volume of fibrillar centres was shown to correspond to a marked drop in the number (up to 4 fold) of small-type fibrillar centres, the unit volume of which (0.01 mum3) remaining unchanged over the 24-hr period and to an increase in size of a large-type fibrillar centre, the volume of which is 100 fold greater than the latter and (4) cytochemical studies showed that the Ag-NOR proteins exhibit a marked increase in amount, suggesting a circadian rhythmicity of these nucleolar proteins. These results, discussed in the light of our current understanding of the nucleolus, briefly summarized in this paper, suggest that the circadian rhythm of the nucleolus and of its components is correlated with circadian rhythms in both transcriptional activity and processing of preribosomes. Analogies between sympathetic neurons and the two other cell types studied, namely, chromaffin cells of adrenal medulla and vagal sensory neurons of nodose ganglion, led to the conclusion that rhythmicity is a fundamental characteristic of the nuclear structure devoted to ribosome biogenesis. Attention is focused on the superior cervical ganglion in which amplitude of nucleolar rhythms are greater and in which fibrillar centres exhibit a particular pattern. These results are discussed with regard to the role played by this sympathetic paravertebral ganglion which is known to regulate circadian rhythmic activities of the rat pineal gland. The persistence of these nucleolar rhythms in continuous lighting, as demonstrated in sympathetic superior cervical ganglion neurons, provide evidence that they are endogenously generated. The intrinsic factors underlying these rhythms in morpho-functional organization of the nucleolus are yet unknown.(ABSTRACT TRUNCATED AT 400 WORDS)
利用电子显微镜水平的体视学分析，对处于永久间期状态的不同细胞类型进行了核仁的生物钟学研究，这些细胞来自接受各种光照方案的大鼠。在黑暗期（12小时光照/12小时黑暗）：（1）在颈上神经节的交感神经元中，核仁组织的昼夜变化表现为核仁及其各个组成部分（即纤维中心、致密纤维组分、颗粒组分和液泡组分）的体积增加；（2）关于被视为核仁组织区（NORs）间期对应物的纤维中心，最显著的事实（仅在交感神经元中观察到）是出现单个大型纤维中心，同时伴有在整个24小时期间都存在的小型纤维中心；（3）纤维中心总体积的增加显示与小型纤维中心数量的显著下降（高达4倍）相对应，其单位体积（0.01μm³）在24小时期间保持不变，并且与大型纤维中心大小的增加相对应，其体积比后者大100倍；（4）细胞化学研究表明，Ag-NOR蛋白的量显著增加，表明这些核仁蛋白存在昼夜节律。根据我们目前对核仁的理解对这些结果进行了讨论，本文简要总结如下，表明核仁及其组分的昼夜节律与转录活性和前核糖体加工中的昼夜节律相关。交感神经元与所研究的另外两种细胞类型（即肾上腺髓质嗜铬细胞和结状神经节的迷走感觉神经元）之间的相似性，得出节律性是致力于核糖体生物发生的核结构的基本特征这一结论。注意力集中在颈上神经节，其中核仁节律的幅度更大，并且纤维中心呈现出特定模式。就这个已知调节大鼠松果体昼夜节律活动的交感椎旁神经节所起的作用对这些结果进行了讨论。如在交感颈上神经节神经元中所证明的，这些核仁节律在持续光照下持续存在，这证明它们是内源性产生的。核仁形态功能组织中这些节律的内在因素尚不清楚。（摘要截短至400字）
