PERMEABILIZATION, STAINING AND CULTURE OF LIVING DROSOPHILA EMBRYOS

The organic solvent octane has been used routinely to permeabilize the hydrophobic vitelline membrane surrounding the Drosophila embryo, the reby allowing the movement of small molecules into the egg. We present evidence that hexane is a more effective permeabilizing agent than oc tane and compare the effects of these solvents on uniformity of permea bilization and embryonic viability. The ability of each solvent to mak e the embryo accessible to a range of biological stains was compared. The effect of octane versus hexane permeabilization on subsequent embr yonic viability was measured at seven different stages during early em bryogenesis. We found that although hexane is a superior solvent for p ermeabilizing the vitelline membrane, it decreases the viability of em bryos exposed between 0 and 3 hr of age. Older embryos treated with ei ther hexane or octane are usually viable. We also showed that molecule s with a molecular mass of 984 Daltons or more did not diffuse into th e embryo following treatment with either hexane or octane. Results pre sented here challenge a phase-partition model that has been proposed p reviously to explain the molecular basis of permeabilization of the Dr osophila egg. An alternative model is described as well as an optimize d protocol for permeabilizing and staining Drosophila embryos at any s tage during early embryogenesis while maintaining viability for subseq uent culture.