Effects of cystic fibrosis serum ciliary inhibitor on oyster gill ultrastructure: analysis by scanning and transmission electron microscopy.

Ultrastructural analysis including scanning and transmission electron microscopic studies (SEM and TEM) were carried out on oyster gill tissue after exposure either to serum fractions from individuals homozygous or heterozygous for cystic fibrosis (CF), to comparable serum fractions from normal individuals, or to sea water. In 4 of the experiments examined topologically (SEM), the CF sera (either heterozygous or homozygous) stimulated the production of mucus that was found in close association with the cilia. The association of excessive mucus with the cell surface could be responsible, in part, for the well-known inhibition of ciliary activity by a factor in CF serum. In 3 additional SEM experiments involving shorter treatment times, very little difference could be observed between homozygous CF, heterozygous CF, and normal serum-fraction-treated oyster tissues. In parallel experiments, ultrathin sections of gill tissue were examined by means of TEM. Those samples that were responsive, as determined by TEM, displayed several characteristic features, including enlarged and partially exuded goblet cells, altered mucus structure along with twisted and matted cilia. An overall swelling of the gill filament was also observed in the responsive tissues. From TEM analysis no detectable alteration in fine structure was apparent in gill tissues that were treated with sera from heterozygous or normal individuals.