Chromosome fragility in 96 h, low-folate cultures was found to be associated with smoking status, coffee consumption, and blood folate level. The higher proportion of cells with chromosome aberrations in cigarette smokers was attributable to lower red cell folate levels in smokers compared with nonsmokers. There was a positive linear relationship between the average cups of coffee consumed per day and the proportion of cells with aberrations. This association was independent of the effects of smoking and red cell folate level. These data suggest that smoking history, coffee consumption, and red cell folate level are important considerations for the design and interpretation of fragile site studies in cancer cytogenetics.

A fourth ventricle lesion containing both areas of typical ependymoma and subependymoma has been studied with the electron microscope. Both foci show ependymal and astrocytic elements. In the subependymoma, a larger number of astrocytes, more frequent cytoplasmic degeneration, and increased glial filaments in the ependymal cells are found. These cellular changes in the subependymoma yield a distinctive light microscopic appearance. However, at the ultrastructural level, the similarity of cellular components, i.e. ependymal and astrocytic cells, makes us believe that subependymoma is a variant of ependymoma and not pure astrocytoma. Tissue culture study and further electron microscopic observation of these in vitro cells have also confirmed the presence of both ependymal and astrocytic cells. Like in vivo ependymal cells, these in vitro ependymal cells form not only glial filaments but also rosettes with specialized cell junctions, microvilli, and cilia. Perivascular pseudorosette formation is also described in detail.

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Sister chromatid exchange (SCE) is a very sensitive cytogenetic assay for detecting exposure to chemical mutagens and carcinogens. One application of SCE is the monitoring of populations believed to be exposed to such agents. We have, however, relatively little knowledge about common lifestyle factors that may influence SCE and therefore complicate any study designed to examine the effects of exposure to genotoxins. In this study, we assessed the effect of cigarette smoking and coffee consumption on SCE. Smoking was associated with an increase of approximately 2 SCEs per cell and a decrease in cell proliferation. A positive linear relationship between SCE and coffee consumption was also observed. This effect was similar for smokers and nonsmokers. Additiody, the folic acid content of cell culture medium seemed to a!Tect neither SCE nor cell proliferation.

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