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Tumor escape is linked to multiple mechanisms, notably the liberation, by tumor cells, of soluble factors that inhibit the function of dendritic cells (DC). We have shown that melanoma gangliosides impair DC differentiation and induce their apoptosis. The present study was aimed to give insight into the mechanisms involved. DC apoptosis was independent of the catabolism of gangliosides since lactosylceramide did not induce cell death. Apoptosis induced by GM3 and GD3 gangliosides was not blocked by inhibitors of de novo ceramide biosynthesis, whereas the acid sphingomyelinase inhibitor desipramine only prevented apoptosis induced by GM3. Furthermore, our results suggest that DC apoptosis was triggered via caspase activation, and it was ROS dependent with GD3 ganglioside, suggesting that GM3 and GD3 induced apoptosis through different mechanisms.

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The reflexion electron microscope has been used in a direct study of the shape and surface structure of small fibres of orlon, viscose rayon, cellulose acetate, glass wool, and undrawn and drawn nylon. The images obtained are superior in resolution and depth of field to those obtained by conventional optical methods and have the particular advantage of presenting a focused image of a large part of the curved surface. It is thus possible to evaluate the shape and surface structure of a fibre much more readily than with the optical microscope. The friction and wear of single fibres of drawn nylon when a flat platinum slider is rubbed once along the fibre has been investigated, using the reflexion technique. It has been found that under high sliding pressures the fibre undergoes considerable permanent deformation and severe tearing occurs at the centre of the track.

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