| Abstract |
The surface properties of neoplastic cells receive increasing attention
because surface alteration accompanies and may even cause altered growth
properties and tumorogenicity. The Mahlavu line of human hepatoma cells
was studied by scanning electron microscopy and compared with human
diploid fibroblasts and HeLa cells. Cultures were grown on glass
coverslips in medium 50:50 containing 10% fetal calt serum. Coverslips
were drained, then washed in phosphatebuffered saline, placed in 1%
osmium tetroxide for 10 min and taken step-wise through decreasing ethanol
and increasing amyl acetate mixtures, ending in pure amyl acetate.
Specimens were then dried from liquid CO2, in a Sorvall critical-point
drying apparatus. Preparations were coated with carbon followed by gold
and examined in a modified JSM-U3 scanning electron microscope of the
National Physics Research Laboratory, CSIR. Specimens were tilted at 30
degree to 45 degree and observed at 30 kV. Photographs were taken with a
Polaroid camera and stereo images could be obtained by taking successive
photographs at different angles of tilt. Treatment with osmium tetroxide
was found to be obligatory for satisfactory specimens. The surface of the
Mahlavu cell shows a very large flat cytoplasmic area, ending in an
undulating membrane with large numbers of microvilli. The flat cytoplasmic
'skirt' has some ruffles at the edges and is fringed by long slender
filopodia which reach across intercellular gaps. A prominent feature,
especially of cells at confluency, is the presence of large numbers of
cytoplasmic blebs. These blebs have constrictions at their bases and are
often shed. The blebs may serve an excretory or secretory function.
Microvilli sometimes originate from blebs. Mahlavu cells could be readily
distinguished from fibroblasts and HeLa cells and their surface morphology
resembles that of papovavirus transformed cells described by Porter and co-
workers. Different methods of drying and fixing of cells caused gross
variability in morphology and standard methods should be employed.
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