Giant Polysome Formation in Chironomus Salivary Gland Cells as Studied by Microdissection Techniques

Abstract

Microdissection procedures can be used to study nucleocytoplasmic transport and to follow the fate of RNA molecules in the cytoplasm after their release from the nucleus (1, 2). After administration of an RNA precursor cells are fixed and microdissected. The distribution of RNA molecules in different parts of the cell is followed as a function of time after precursor administration. The advantage of the procedure over cell fractionation is that results reflect in vivo conditions. Redistributions and losses that can follow upon cell fractionation of fresh material are avoided and results can be related to a defined cytoplasmic region. The techniques have been applied to salivary gland cells of Chironomus larvae. Two different dissection schedules have been used. In one procedure (Fig. 1) the appearance in the cytoplasm of newly labelled RNAs is followed as a function of the distance from the nucleus (1). In another approach (2) cytoplasm with different amounts of endoplasmic reticulum (Fig. 2) is isolated (Fig. 3). The information obtained by these techniques can be used to draw conclusions regarding the mode of formation and function of the giant, GO ribosome-polysomes dominating the polysome population of these cells.