Transmission electron microscopy of thin sections of Drosophila: Preparation of embryos using n-heptane and glutaraldehyde

This protocol describes the simultaneous permeabilization of Drosophila embryos with n-heptane and initial fixation with glutaraldehyde. Even though the vitelline membrane around the embryo is chemically permeabilized, it must be manually removed to achieve infiltration with embedding resins. Once the embryo is embedded, it can be sectioned for transmission electron microscopy (TEM). This procedure can produce excellent preservation for ultrastructural analysis, and is useful for situations where optimal preservation (e.g., by high-pressure freezing) is not required or is not feasible.