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Further ultrastructural studies on lymphocytic micronuclei
Folia Haematologica (Leipzig, Germany : 1928)
|January 1, 1981
Summary
Actinomycin D induces ultrastructural changes in human lymphocyte nucleoli, mirroring natural changes in mouse lymphocytes. These alterations involve component segregation, dense material formation, and fragmentation, with some unique changes observed in ring-shaped nucleoli.
Area of Science:
- Cell Biology
- Molecular Biology
- Toxicology
Background:
- Nucleoli are dynamic structures involved in ribosome biogenesis and are sensitive to various cellular insults.
- Ring-shaped nucleoli and micronucleoli represent specific morphological variations observed in lymphocytes.
- Actinomycin D is a known inhibitor of transcription, impacting cellular processes including nucleolar function.
Purpose of the Study:
- To compare the ultrastructural changes induced by actinomycin D in human blood lymphocyte nucleoli with naturally occurring modifications.
- To investigate the specific alterations in ring-shaped nucleoli and micronucleoli under experimental and natural conditions.
- To elucidate the impact of actinomycin D on nucleolar component segregation and morphology.
Main Methods:
- Transmission electron microscopy was used to examine the ultrastructure of human blood lymphocytes treated with actinomycin D.
- Comparison of these treated cells with naturally occurring ring-shaped nucleoli and micronucleoli in mouse thymic lymphocytes.
- Detailed morphological analysis focusing on nucleolar component segregation, density, and fragmentation.
Main Results:
- Actinomycin D treatment caused nucleolar changes in human lymphocytes, including component segregation, dense granular/fibrillar material appearance, plaque formation, and fragmentation.
- These induced changes were similar to naturally occurring modifications in mouse thymic lymphocytes' nucleoli.
- Specific changes observed in ring-shaped nucleoli included horseshoe-like and beaded formations, with ribonucleoprotein (RNP) segregation in the peripheral ring.
Conclusions:
- Actinomycin D induces significant ultrastructural alterations in lymphocyte nucleoli that share similarities with naturally occurring morphological variations.
- The study highlights the sensitivity of nucleolar components to transcriptional inhibition and provides insights into nucleolar dynamics.
- Observed changes in ring-shaped nucleoli offer specific ultrastructural markers for cellular stress or drug-induced effects.