Pressure-induced depolymerization of spindle microtubules. III. Differential stability in HeLa cells.

Abstract

Evidence from light microscopy (principally polarization microscopy) demonstrated that hydrostatic pressure can reversibly inhibit mitosis by rapidly depolymerizing the spindle fiber microtubules. This finding was confirmed in ultrastructural studies of mitotic HeLa cells incubated at 37.degree. C and pressurized at 680 atm (10,000 psi). Although there are many spindle microtubules in the cells at atmospheric pressure, electron micrographs of cells pressurized for 10 min (and fixed while under pressure in a Landau-Thibodeau chamber) show few microtubules (MT). Pressure has a differential effect on the various types of spindle microtubules. Astral and interpolar MT appear to be completely depolymerized in pressurized cells, but occasional groups of kinetochore fiber microtubules are seen. The length and density of MT of the stem bodies and midbody of telophase cells appear unchanged by pressurization. In cells fixed 10 min after pressure was released, MT were again abundant, the density often appearing to be higher than in control cells. Reorganization seems incomplete since many of the MT are randomly oriented. Kinetochores appeared diffuse and were difficult to identify in sections of pressurized cells. Even after 10 min of recovery at atmospheric pressure, their structure was less distinct than in unpressurized cells.