Freeze-fractured membranes of digestive vacuoles of randomly feeding Paramecium caudatum exhibit dramatic differences in intramembrane particle (IMP) number and distribution on both E- and P-fracture faces. By pulse-feeding latex spheres to cells we have demonstrated that these differences are related to the age of the digestive vacuoles, and that the membranes of such vacuoles undergo a specif...

Cytochalasin B inhibits the formation of normal-sized food vacuoles in Tetrahymena but the cells do not starve. Treated cells differ from starved cells in that they retain a high rate of incorporation of tritiated uridine. Large numbers of smaller vacuoles, about 1 micrometer in diameter, are formed, presumably by pinocytic activity of the cytopharyngeal membrane. This effect may perhaps be due...

In the endosymbiotic unit of Paramecium bursaria (Ciliata) and Chlorella sp. (Chlorophyceae) algae are enclosed individually in perialgal vacuoles, which do not show acid phosphatase activity and thus differ from digestive vacuoles. Both types of vacuoles have been studied by freeze-fracture. Perialgal vacuoles are nearly spherical; their membrane always fits tightly to the algal surface. The v...

Previously it has been found that in tobacco callus cells nucleolar vacuoles repeatedly form and contract. In this study, nucleolar vacuoles were investigated by using radioautography, actinomycin D, and electron microscopy . It was found, from grain counts of nucleoli labeled with uridine 3H, that nucleoli containing vacuoles had more than three times as many grains/μ2 of nucleolar substance a...

Invasive Pseudomonas aeruginosa (PA) can enter epithelial cells wherein they mediate formation of plasma membrane bleb-niches for intracellular compartmentalization. This phenotype, and capacity for intracellular replication, requires the ADP-ribosyltransferase (ADPr) activity of ExoS, a PA type III secretion system (T3SS) effector protein. Thus, PA T3SS mutants lack these capacities and instea...