Germ cell division are frequently marked by the production of stable cytoplasmic bridges, which originate from incomplete cytokinesis. In testes and early stage ovaries, the connected cells exchange synchronizing cues and develop in step with each other. The ovaries of many insects depart from this pattern--each syncytium becomes polarized, with one cell forming an oocyte and the others forming nurse cells. During the growth of the oocyte in Hyalophora cecropia and Drosophila melanogaster the cell membranes of the syncytia hyperpolarize, with the nurse cells becoming more negative than the oocyte. Isoelectric focussing techniques are proposed here to establish whether this polarity provides a cytoplasmic environment richer in basic proteins in the nurse cells and in acidic proteins in the oocyte. Identification of the ions whose movements provide the electrogenic basis of polarity will be sought with conventional methods of electrophysiology. And an invarying relationship between the point of nurse cell attachment and the later polarity of the embryo will be investigated by relating the production and localization of the bicoid gene product of Drosophila and its presumed homologue in Hyalophora to the ontogeny of follicle polarity and yolk deposition.
|Singleton, K; Woodruff, R I (1994) The osmolarity of adult Drosophila hemolymph and its effect on oocyte-nurse cell electrical polarity. Dev Biol 161:154-67|
|Woodruff, R I; Telfer, W H (1994) Steady-state gradient in calcium ion activity across the intercellular bridges connecting oocytes and nurse cells in Hyalophora cecropia. Arch Insect Biochem Physiol 25:9-20|