| Popis: |
Polyacrylamide gel electrophoresis of total RNA obtained from Strongylocentrotus purpuratus eggs and embryos have shown this material to contain a 12S and 9S RNA species, among others. These two species, found during early development of these cells, were not present in late prism or plutei stages. The RNA was extracted by cold phenol deproteinization in the presence of bentonite and precipitated by alcohol. RNAse, obtained from the 140 000 g egg-supernatant was tested against total RNA extracted from unfertilized eggs, blastulae, gastrulae and plutei embryos. The amount of nucleotides liberated was identical in all cases. Egg-RNAse, in the presence of plutei RNA, did not give rise to the 12S and 9S RNA species. The eggs and embryos were also separated by preparative ultracentrifugation into the nuclei, yolk, mitochondrial, microsomal and 140 000 g supernatant fractions. Electron microscopy revealed these fractions to be relatively pure, and the 12S and 9S RNA were found exclusively in, or associated with, the yolk granules. These granules, and the two RNA species, could not be observed in the pluteus stage. These results strongly suggest that these RNAs, present in early development, truly represent specific classes of RNA and not products of higher molecular weight degradation. |
