Perinuclear organization in the heterotrich ciliateStentor coeruleus

Summary Different fixation techniques were employed to obtain satisfactory fixation of the endoplasm ofStentor coeruleus for ultrastructural investigations. The nuclei ofS. coeruleus are surrounded by a flattened fenestrated cisterna. The space between the nuclear envelope and the cisterna (= perinuclear space) is continuous with the cytoplasm via channels. The envelopes of both, micronucleus and macronucleus, are connected to the fenestrated cisterna by filamentous material. This organization accounts for the close association between micronucleus and macronucleus inStentor coeruleus. The fenestrated cisterna is compared to similar structures occurring in other organisms, and its possible function is discussed.Abbreviations fC fenestrated cisterna - FV food vacuole - km km fibers - MaNu macronucleus - MiNu micronucleus - My myonome - NE nuclear envelope - PC perinuclear cisterna - PfC pore of fenestrated cisterna - PS perinuclear cytoplasmic space - EGTA ethyleneglycol-bis-(-aminoethylether)-N,N,N,N-tetraacetic acid) - GA glutaraldehyde - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - PEG polyethylene glycol - PIPES piperazine-N,N-bis2-ethanesulfonic acid] - PTA phosphotungstic acid