Showing papers on "Nucleolar chromatin published in 1980"

Fine structure of degenerating nuclei in intergeneric fusion products fromZygnemataceae protoplasts

Abstract: Structural alterations visible early in degeneratingZygnema nuclei in intergeneric fusion products fromZygnema extenue andSpirogyra gracilis protoplasts were nuclear swelling and nucleolar segregation of the granular and fibrillar regions. This segregation was followed by fragmentation of the fibrillar region, which resulted in the formation of globular bodies and their migration into the nucleoplasm. Part of the granular region seemed to be converted into a new area that contained densely stainable nodules or spherules as well as heterogenous granules. Enzymatic digestion studies suggested that the nucleoli in the degenerating nuclei maintained RNA as granular and fibrillar components and an area with amorphous debris after pepsin digestion. Also, the nucleolar chromatin seemed to develop poorly and retract into the nucleolar periphery. These morphological characteristics probably indicate a reduction in various aspects of the nuclear and nucleolar functions. Between 12 and 20 hours after fusion, the degenerating nuclei underwent drastic alterations which began with the rupture of the nuclear envelope and the condensation of the chromatin. Then the chromatin aggregates converged into one clump, which was again enclosed by membranes derived from fragments of the nuclear envelope and possibly from some vesicles. By this process, remnants of the nucleoli were excluded from the chromatin clump. Reaction of acid phosphates was not detected. The membrane-bound clump of condensed chromatin and the granular remnants of the nucleoli persisted; they were the terminal features of the degenerate nuclei.