RNA TRANSPORT FROM NUCLEUS TO CYTOPLASM IN CHIRONOMUS SALIVARY GLANDS
RNA TRANSPORT FROM NUCLEUS TO CYTOPLASM IN CHIRONOMUS SALIVARY GLANDS
复制标题
摇蚊唾液腺中从细胞核到细胞质的 RNA 转运
作者：
B. Stevens;H. Swift
本文研究了土蠓幼虫唾液腺核中巨大的RNA泡（Balbiani环）的精细结构和细胞化学。巴尔比亚尼环由电子不透明的400 - 500 a颗粒、直径约180 - 220 a的短线和相关的细染色质原纤维组成。这些成分似乎被组织成刷子状的元素，形成了环。电镜细胞化学表明，颗粒和短线含有RNA。核糖核酸酶酶切后，Balbiani环中仅可见50 ~ 100个A染色质原纤维，颗粒不再明显。脱氧核糖核酸酶酶切对这些结构无明显影响。观察表明，颗粒由短线形成并释放到核质中，颗粒在核质中均匀分布。在核膜处，可以观察到许多颗粒部分或完全位于核孔内。这些颗粒变得细长，并以棒状形式穿透孔的中心，直径约200a。巴尔比亚尼环颗粒在靠近核膜的细胞质内通常不可见，但在该区域很少发现。这表明，颗粒代表巴尔比亚尼环的产物，可能是一种与蛋白质结合的信使RNA，它们通过核膜孔中的狭窄中央通道有规律地进入细胞质。
The fine structure and cytochemistry of the extremely large RNA puffs, or Balbiani rings, in salivary gland nuclei of midge, Chironomus thummi, larvae have been investigated. The Balbiani rings are composed of a diffuse mass of electron-opaque 400 to 500 A granules, short threads about 180 to 220 A in diameter and associated fine chromatin fibrils. These components appear to be organized into brushlike elements which form the ring. Electron microscope cytochemistry has shown that the granules and short threads contain RNA. After ribonuclease digestion, only 50 to 100 A chromatin fibrils were apparent in the Balbiani ring, and the granules were no longer demonstrable. Deoxyribonuclease digestion had no apparent effect on these structures. Observations indicate that the granules are formed from the short threads and released into the nucleoplasm in which they are evenly distributed. At the nuclear envelope, many granules have been observed partially or completely within the nuclear pores. These granules become elongated and are shown to penetrate the center of the pore in a rodlike form, about 200 A in diameter. The Balbiani ring granules are not normally visible within the cytoplasm adjacent to the nuclear envelope, but have been rarely found in this region. It is suggested that the granules represent the product of the Balbiani ring, possibly a messenger RNA bound to protein, and that they regularly pass into the cytoplasm through a narrow central channel in the pores of the nuclear envelope.