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A method is described for the determination of cellular F-actin content using fluorometry of TRITC-phalloidin at very high dilution. In this case no saturation of all binding sites available is reached, however the staining is highly specific and the specificity is not affected by the preparative procedure as may be the case at high concentrations of TRITC-phalloidin. The method is based on calculation of fluorescence intensity at equilibrium conditions from measurements at two different numbers of exchange of the staining solution by using Lineweaver-Burk plotting.

The scanning of fluorescence of a cell culture along a path several milimeters long, gives a series of signals, which allow calculation of the fluorescence emitted per cell. The emission at 450±10 nm, excited at 360 nm, provides a measure of NADH (and NADPH) per cell. Combination of this method with modifications in energy metabolism, allows determination in the same sample of total NAD content, of NAD redox state, content of NAD in the mitochondria and content of NAD plus NADP in the cytoplasm. The method can be extended to measure other cellular constituents by labelling with fluorescent markers, e.g. antibodies.

A population of endothelial cells growth from Xenopus laevis tadpole hearts was investigated by microinterferometry. The resulting interferograms were evaluated by an automatic image analyzer. The mean values of dry mass were 778±340 pg (10-15 g) for whole cells, 648±309 pg for cytoplasm, 116±45 pg for nuclei, and 19±10 pg for nucleoli. Two subpopulations of cells were identified, an actively growing one and a less active one. The density (dry mass per µm2) of the nuclei and nucleoli of less active cells was greater than that of the nuclei and nucleoli of actively growing cells. In addition, the inactive cells were always large and possessed a considerable amount of cytoplasm. The entrance of cells into S-phase could not be detected by microinterferometry; and no differences were apparent between cells possessing one nucleolus and those containing two nucleoli. The values obtained in these amphibian cells were compared with those derived from mammalian cells.

FITC-Con A-fluorescence and electron microscopy have been used in parallel for the visualization of rough endoplasmic reticulum inXenopus laevis tadpole heart primary tissue culture cells. rER distribution pattern as revealed by both methods is compared by superimposition of images of the same cell. Coincidence of rER distribution is established.

A method for evaluation of microtubule content in cultured cells has been developed. The method is based on scanning microfluorometric measurement of immunofluorescently labelled microtubules. The method has been applied to the comparison of microtubule content in epithelial XTH-2 cells grown in culture at various cell densities. The results have shown that the microtubule content in the cells is not dependent on their proliferative state rather than it depends on cellular contacts.