A study by electron microscopy of the formation of new surface by Chaos chaos

Abstract

The cell surface of the ameba Chaos chaos was “coated” with Alcian Blue by exposure of the cells to dilute dye solutions at 5 °C. At this temperature the amebae are immobilized. Formation of new surface was studied after rinsing the specimens and removing them to a fresh drop of medium at room temperature. Direct observations of amebae indicated that complete turnover of surface occurred in about 35 min but that the resultant new surface was probably not as convoluted as the original. Rate of formation of surface when amebae were recycled through the dye treatment was much slower. As previously reported, electron micrographs of fixed specimens showed that in dye-treated cells the surface filaments seen in untreated cells were replaced by dense clumps occurring at irregular intervals. New surface possessed all the layers of surface found in untreated cells. In sections including recently formed surface, the plasmalemma was smooth and few vesicles were seen in the underlying cytoplasm. In some sections clumps of old surface were found with surface filaments passing through them. More typically, a series of transitional profiles between typical filaments and typical clumps could be seen. Frequency counts of the clumps on photomicrographs before and after new surface formation provided no evidence for the hypothesis that there may be slippage between surface coat and underlying plasmalemma. In the cytoplasm of the uroid of amebae 15 min after return to room temperature, extensive areas of convoluted membranes bearing typical dense clumps were found. It is concluded that under the present conditions there is rapid and extensive formation of new surface which possesses all the morphological layers of the original surface. A mechanism involving interpolation of ground cytoplasm into the new surface appears to account better for the findings than one involving fusions of vesicles with the surface.