This study highlights the usefulness of laser scanning confocal microscopy in the examination of subcellular disposition of anthracyclines in tumour cell lines. The distribution of anthracycline compounds has been studied in two pairs of parental and multidrug resistant (MDR) cell lines. For the parental EMT6 mouse mammary tumour cell line EMT6/P treated with doxorubicin (DOX) the anthracycline fluorescence was shown to be predominantly nuclear but with some particulate cytoplasmic fluorescence and very low levels of plasma membrane staining. In the same experiments much fainter fluorescence was seen for the EMT6/AR1.0 MDR subline which hyperexpresses P-glycoprotein. The loss of nuclear fluorescence was comparatively greater than loss of cytoplasmic fluorescence. For the human large cell lung cancer line COR-L23/P cellular DOX disposition was markedly nuclear with nuclear membrane staining and diffuse cytoplasmic fluorescence. For the MDR line COR-L23/R, which lacks P-glycoprotein expression, DOX fluorescence was reduced in the nucleus compared with the parental line, but an intense area of perinuclear staining was seen consistent with localisation to the Golgi apparatus. The morpholinyl-substituted analogue MR-DOX achieved very similar subcellular distribution in both parental and MDR lines, consistent with its retention of activity in the latter. The presence of verapamil during anthracycline exposure increased the intensity of fluorescence in the MDR lines, particularly in the nucleus. Relatively little effect was seen in the parental lines. Confocal microscopy provides high resolution images of the subcellular distribution of anthracyclines in parent and MDR cell lines. Differences in drug disposition in various cell lines may provide insights into the mechanism of multidrug resistance and suggest strategies for its therapeutic circumvention.

The costa is a rod-shaped intracellular organelle lying in the cytoplasm immediately below the undulating membrane. In certain large species of Trichomonas (T. gigantea, T. termopsidis and an undescribed species from the termite Porotermes adamsoni) this organelle is motile. Bending waves are transmitted along the length of the costa, in either direction. It is shown that the bending is actively produced by the costa itself. The form of the movements is described in detail. The costa is birefringent. At the point at which bending occurs there is a sharply localized reduction in birefringence. Electron microscopy shows that the costa is composed of longitudinally running lamellae, 2--3 nm thick and spaced 12 nm apart. These are connected to transversely running elements spaced at intervals of about 37 nm. The lamellae occur in two alternative configurations: straight and zig-zag. Bending probably results from a local, transient change from the straight to the zig-zag configuration. This would account for the local change in birefringence which accompanies bending. Polyacrylamide gel electrophoresis of isolated costas shows them to contain a number of protein components, of which the principal one has a molecular weight of about 90,000. Preliminary cytochemical evidence is presented for ATPase activity in the costa. The costa is a type of motile system distinct from any hitherto described.