Gyroscopic Centrioles Bornens

French molecular biologist Michel Bornens (1979) has investigated cellular mechanisms of organization and argues for a dynamic stability based on organizational properties of centrioles and the cytoskeleton. Specifically, Bornens proposes that centrioles are animated by rapid oscillatory rotation about their longitudinal axis which results in a dynamic stability and inertia analogous to a spinning top or gyroscope. Peripheral movements throughout the cell are interconnected by the cytoskeleton, with the gyroscopic centrioles an inert point of reference which provides cellular gravity. Centrioles and microtubule organizing centers (MTOC) are the origin for the cell's spatial coordinates and cytoplasmic movement appears to occur relative to the MTOC. Bornens likens movement in each cylinder to a stepwise electric motor in which the central "cartwheel" (or "pinwheel") is equivalent to an ATP-dynein "stator," and the centriolar wall the moving "rotor." Continuous torque rotation of centrioles could serve to propel them through cytoplasm, like an "Archimedes screw" (Record, 1986). Bornens also considers the possibility of "back and forth" oscillation with utility for scanning the cell environment.

Reviewing Bornens' gyroscopic centriole model, Albrecht-Buehler (1981) questioned the high rate of rotation required for significant inertia. Albrecht-Buehler calculated that centrioles would have to rotate at frequencies of 2.3 million revolutions per minute before their kinetic energy matches one kT (the thermal energy of one molecular degree of freedom). Consequently, "much greater rotational frequencies would be required before the centriole could withstand the impact of thermally moving molecules around them and maintain stable axial orientation" (Albrecht-Buelhler, 1981). Bornens responded by suggesting a submicroscopic mechanism "allowing more independence of the centriole with respect to surrounding material." Factors which could support his contention include ordered water coupled to centriolar oscillation, some unknown property of the "pericentriolar material," ionic charge layer, or even superconductivity as suggested by Fröhlich and Del Giudice's group (Chapter 6).

Rotatory oscillations in the range of 107 per second would be consistent with the findings of several researchers (Chapter 9) who found collective energy absorption in the range of 107 per second by protein assemblies such as virus coats.

Bornens views centrioles as the center of a dynamic cytoskeleton which communicates and integrates cellular information. In Bornens' view of cytoskeletal organization, microtubules are conductors of spatial centrifugal information, rigid organizers of cell space in which physical or electrical signals propagate as conformational modifications of MT subunits. Intermediate filaments and the microtrabecular lattice also participate in Bornens' vision of a dynamic network of pulsating polymers. He also suggests that ATP generated centriolar rotation triggers propagating impulses along microtubules by transitory contact/stimulus of the nine rotating MT doublet/triplets in the centriole wall with their surrounding satellite bodies. This would lead to rhythmic signals through the cytoskeleton with a frequency nine times greater than that of the centriole's rotation. Rhythmic, propagating signals are compatible with coherency, solitons, and other models. Their occurrence throughout the cytoskeleton would be mechanisms close to the nature of life itself.

0 0

Post a comment