Ultrastructural aspects of a glycerinated model ofAmoeba proteus

Abstract

Two types of filamentous structures were observed by electron microscopy in both non-glycerinated cell and glycerinated model ofAmoeba proteus. One was a thin filament 6–8 nm in diameter and the other was a thick rod-shaped filament 30 nm in diameter and 0.6 μm long. Upon addition of Mg-ATP at all Ca2+ concentration examined, these filaments in the glycerinated model aggregated around the nucleus, forming thick filament clusters from which thin filaments radiated. After that, at 10−8 M Ca2+, the filament layer containing thick and thin filaments separated from the plasma membrane, surrounded the granular cytoplasm and contracted centripetally. At 10−6 M Ca2+, a thin filament meshwork containing thick filaments was seen in the area where streaming occurred. At 10−4 M Ca2+, the filament aggregates formed by the initial contraction around the nucleus disappeared, and few thin filaments were observed in the cytoplasm 10 minutes after the reactivation.