The fine structure of "dividers" and "non-dividers" in phase II human glial cell cultures.

A method is described which allows a comparison in the transmission electron microscope (TEM) of cells with different remaining proliferative capacity from one and the same culture. The method takes advantage of a mini-cloning technique employing hapatotactic palladium islands in combination with micro-dissection and preparation for TEM of islands carrying various numbers of cells after 10 days in culture, when all miniclones have become density dependent growth inhibited. By means of this technique non-dividers were compared with miniclones of dividers composed of five to eight cells originating from single cells. Moreover, large, immotile cells without peripheral ruffling activity, known to be non-dividers, were compared with small, ruffling cells, known to be dividers, in the reflection-interference mode in sparse cultures of living cells, and in the TEM mode as whole cell preparations after critical point drying of cells cultured on formvar-coated, gold EM-grids. Non-dividers proved to contain a moderate number of residual bodies, well developed Golgi areas, and often branched or circular mitochondria; they were thinly spread over the substratum with many focal points of contact, and large areas of close apposition between cell and substratum.