Electron microscopy and microchemical analysis of cystic fibrosis diploid fibroblasts in vitro.

Fibroblasts derived from cystic fibrosis homozygotes and heterozygotes were compared to normal 
fibroblasts topologically, ultrastructurally, and microchemically. Topological examinations, by means of scanning 
electron microscopy (SEM) revealed no significant differences between the 3 genotypes 
surveyed. The cells were generally flattened and/or fusiform structures that were 
more or less devoid of surface details. However, the dividing cells, 
in all of the populations surveyed, were found to have a 
more or less spherical configuration involving a highly complicated surface. The 
surface manifestations included blebs, ridges, and microvilli. Representative samples of the 
cells in all stages of growth, lag phase, exponential phase, and 
plateau phase, were surveyed in this study. Ultrastructurally, the fibroblasts of 
the 3 genotypes were found to have similar cytological detail. Highly 
infolded nuclei, distinct organelle components, and surface details, also seen in 
the SEM study, were observed. Numerous bundles of microfilaments were noted 
within the cytoplasm. Metachromatic granules were observed in cells from all 
3 genotypes. Microchemical analysis, by means of energy dispersive X-ray analysis, 
demonstrated slight but recognizable differences in the elemental composition of the 
3 genotypes. Of notable interest were the peak intensities of calcium 
and sulfur. The CF homozygous cells presented higher values for both 
of the elements when compared to the values observed in the 
CF heterozygous and normal cell populations. Although consistent differences could be 
observed in the CF genotypes when compared to the non-CF cells, 
no attempt was made to quantitate the concentrations of each of 
the elements within the cells. 