Evidence of a myoepithelial cell in tick salivary glands. 
Type III acini from feeding female Dermacentor variabilis varied in size during in vitro and in vivo fluid production.  As the type III acinus enlarged, its lumen enlarged and the adlumenal cell became thinner.  As the acinus contracted, its lumen became smaller while the adlumenal cell became wider.  Actin was demonstrated in salivary glands using an immunoblot technique.  Actin was localized in the adlumenal cells of type III acini with fluorescent microscopy using rhodamine-phalloidin and with electron microscopy using heavy meromyosin to decorate actin filaments.  Pre-treatment of salivary glands with cytochalasin D abolished fluorescence in adlumenal cells subsequently treated with rhodamine-phalloidin.  These results support the hypothesis that the adlumenal cell in type III acini functions as a myoepithelial cell.