Cellular autophagocytosis in mouse seminal vesicle cells in vitro.

Cellular autophagocytosis was observed in mouse seminal vesicle cells incubated in vitro up to 8 h in medium 199 or Krebs-Ringer bicarbonate buffer. During the first 2 h of incubation, early forms of autophagic vacuoles were seen in the cells, advanced forms containing degraded material began to cumulate later. After 6--8 h, early vacuoles occurred sparsely, while advanced forms were detected in a great number. During the first 2 h of incubation, we often observed smooth surfaced membrane pairs between the cisternae of rough surfaced endoplasmic reticulum resembling isolating membranes of autophagic vacuoles. They varied in size and shape from short, straight cisternae to long, curved ones, almost completely encircling areas of the cytoplasm. Based on these observations, we propose a tentative scheme of the formation of autophagic vacuoles, viz., the short, straight cisternae would represent the first stage in the development of an autophagic vacuole, while the curved sack-like forms are interpreted as successive steps leading to the complete sequestration of an area of the cytoplasm.