RNA synthesis was studied by autoradiographic analysis using tritiated uridine incorporation in the Chinese hamster cell line Dede after a one-minute pulse labeling period. RNA synthesis continues during all stages of interphase and mitosis except during metaphase and anaphase. Cytoplasmic RNA was a
The effect of actinomycin D on nucleolar formation in earlyXenopus laevis gastrulae
β Scribed by Sameshima, M. ;Shiokawa, K. ;Kawakami, I.
- Publisher
- John Wiley and Sons
- Year
- 1970
- Tongue
- English
- Weight
- 779 KB
- Volume
- 173
- Category
- Article
- ISSN
- 0022-104X
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β¦ Synopsis
Abstract
Electron microscopic examinations revealed drastic effects of actinomycin D on nucleolar formation in isolated cells of Xenopus laevis embryos. The nucleoli in newly isolated cells of early gastrulae were composed solely of a fibrous component. After culture for two to five hours in complete Stearns' solution without the antibiotic, a granular component appeared among the fibrous components in most of the nucleoli, which showed more elaborated structures. On the other hand, after being cultured for two hours in the presence of actinomycin D (l r/ml), by which inhibition of DNA synthesis was effected, all the nucleoli examined remained as spherical masses composed of fibrous component alone, lacking granular component. After five hours' treatment, inhibition of the synthesis of protein and DNA became biochemically detectable, and ultrastructural changes were observed in both the nucleoplasm and the cytoplasm: that is, fragmentation of nucleoli, condensation of chromatins and deformation of mitochondria. Relationships between the formation of nucleolar components and the RNA synthesis in amphibian embryogenesis are discussed.
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