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Dynamic organization of Physarum plasmodium
N Kamiya1, R D Allen, Y Yoshimoto
1National Institute for Basic Biology, Okazaki, Japan.
Cell Motility and the Cytoskeleton
|January 1, 1988
Summary
Birefringent fibrils (BRFs) composed of F-actin exhibit distinct behaviors in Physarum plasmodium. Their dynamic presence at the front contrasts with stable fibrils in posterior channels, indicating localized contraction rhythms.
Area of Science:
- Cell Biology
- Biophysics
- Cytoskeletal Dynamics
Background:
- Physarum plasmodium exhibits complex internal dynamics and movement.
- Actin-based structures play a crucial role in cellular mechanics.
- Understanding cytoplasmic streaming and fibril organization is key to plasmodial locomotion.
Purpose of the Study:
- To investigate the distribution and behavior of birefringent fibrils (BRFs) in Physarum plasmodium.
- To differentiate the roles of BRFs in different regions of the plasmodium.
- To elucidate the relationship between BRF dynamics and cytoplasmic streaming patterns.
Main Methods:
- Microscopic observation of birefringent fibrils (BRFs) in Physarum plasmodium.
- Analysis of BRF behavior correlated with cytoplasmic sol-gel phases and streaming direction.
- Distinguishing fibril stability in frontal versus posterior regions.
Main Results:
- BRFs, composed of F-actin, showed dynamic appearance and disappearance in the frontal zone, linked to cytoplasmic flow cycles.
- Stable BRFs were observed in posterior streaming channels, oriented parallel or helically.
- BRF cyclic dynamics ceased in the frontal zone when forward movement stopped, with fibrils persisting.
Conclusions:
- Active contraction-relaxation rhythms are localized to the frontal zone of advancing Physarum plasmodium.
- Posterior regions maintain a state of "tonus," providing continuous hydrostatic pressure.
- Hypotheses on tonus and tensile force production are proposed based on contraction wave phase relationships.