Adamstone F B, Taylor A B
J Morphol. 1977 Dec;154(3):459-77. doi: 10.1002/jmor.1051540306.
A process of nucleolar reorganization apparently identical to that encountered in intestinal epithelial cells (Adamstone and Taylor, '72) develops in kidney cells of aging rats. The polymorphic nucleoli of young tubule cells soon change to amphinucloeli and, while terminal nucleolar reorganization is delayed in cells of collecting tubules, in the nephrons nucleoli soon begin to undergo terminal reorganization becoming bipartite structures with separate plasmosomes and karyosomes. This suggests disruption of the DNA-dependent RNA protein transcription system and failure to maintain the flow of messenger RNA into the cytoplasm. Old cells are not discarded immediately from the kidney tubules and they retain much rough endoplasmic reticulum, numerous ribosomes and polysomes and large plasmosomes. Thus a high RNA concentration is known to develop in old kidney tissue while protein synthesis is also known to be low (Kanungo et al., '70; Buetow and Ghandi, '73). Nucleolar counts show gradual increase in bipartite nucleoli at the expense of amphinucleoli and in the senescent kidney bipartite nucleoli predominate. It is suggested that nucleolar reorganization, with final separation of plasmosomes and karyosomes, includes the process of nucleolar segregation and is triggered by some innate nucleolar mechanism in response to encoded genetic information stored in the nucleolus during nucleogenesis. At this time both DNA and RNA are incorporated into the developing nucleolus. It is also to be noted that two shifts in nucleolar dominance occur with advancing age. These may be fundamental to the process of aging and to the onset of senescence. Furthermore, the changes in dominant nucleolar types are the direct result of the process of nucleolar reorganization.
在衰老大鼠的肾细胞中，出现了一个核仁重组过程，该过程显然与在肠上皮细胞中观察到的过程相同（Adamstone和Taylor，1972年）。年轻肾小管细胞的多形核仁很快转变为双泡核仁，虽然集合管细胞中的终末核仁重组延迟，但在肾单位中，核仁很快开始进行终末重组，成为具有独立染色质体和核小体的二分结构。这表明依赖DNA的RNA蛋白质转录系统受到破坏，且无法维持信使RNA向细胞质的流动。衰老细胞不会立即从肾小管中被清除，它们保留了大量粗面内质网、众多核糖体和多核糖体以及大的染色质体。因此，已知衰老肾组织中RNA浓度较高，而蛋白质合成也较低（Kanungo等人，1970年；Buetow和Ghandi，1973年）。核仁计数显示，二分核仁逐渐增加，以双泡核仁为代价，在衰老肾脏中，二分核仁占主导。有人认为，核仁重组，最终染色质体和核小体分离，包括核仁分离过程，是由某种先天的核仁机制触发的，以响应核仁形成过程中存储在核仁中的编码遗传信息。此时，DNA和RNA都被整合到发育中的核仁中。还应注意的是，随着年龄的增长，核仁优势发生了两次转变。这些可能是衰老过程和衰老开始的基础。此外，占主导地位的核仁类型的变化是核仁重组过程的直接结果。
