A simple cytological technique to analyze nuclear divisions during preblastodermic development in Drosophila

We have developed a very simple and fast method that allows the dividing nuclei of Drosophila embryos to be obtained spread as a monolayer on a microscope slide. This new methodology makes the fine cytological analysis of embryonic nuclei possible since the structural morphologies of chromosomes and spindles through cell division stages are particularly well preserved. The method is especially indicated for analyzing embryos at early developmental stages whenever a three-dimensional analysis of the embryo is not required. This method involves, firstly, the mechanical cracking of the embryos placed in a neutral buffer between a coverslip and a microscope slide and, secondly, the spreading and subsequent squashing of the embryo content on the microscope slide. For this reason, we propose that the technique should be called the `CSS technique', short for `cracking±spreading±squashing embryo technique'.We acknowledge the support of DGICYT (grant PB96-0810)