Pressure-induced depolymerization of spindle microtubules. I. Changes in birefringence and spindle length

Area of Science:

• Cell Biology
• Biophysics
• Cytoskeleton Dynamics

Background:

• Mitotic spindle structure and function are crucial for cell division.
• Microtubules form the primary component of the mitotic spindle.
• External factors like pressure can influence microtubule stability and cell division.

Purpose of the Study:

• To investigate the effects of increased hydrostatic pressure on meiotic spindle birefringence retardation (BR) and length.
• To analyze the kinetics of spindle depolymerization and repolymerization under varying pressure conditions.
• To propose a hypothesis explaining the observed phenomena based on microtubule stability.

Main Methods:

• Utilized polarized-light microscopy with a novel optical pressure chamber.
• Observed changes in birefringence retardation (BR) and spindle length of Chaetopterus meiotic metaphase-arrested spindles.
• Applied increased hydrostatic pressures ranging up to 6,000 psi at 22 degrees C.

Main Results:

• Increased hydrostatic pressure caused rapid, reversible decreases in spindle BR and length.
• Pressures of 3,500 psi or higher led to complete disappearance of spindle BR within 3 minutes.
• Spindle shortening and BR decay rates increased with pressure up to 6,000 psi; above this, BR decreased without significant shortening.

Conclusions:

• The observed pressure-induced changes in spindle BR and length are consistent with microtubule depolymerization.
• A two-phase kinetic model explains spindle depolymerization and repolymerization, suggesting differential microtubule stabilities.
• Microtubule end attachment status may influence their stability, impacting spindle dynamics under hydrostatic pressure.