The stability of the yolk granules of Artemia. An improved method for their isolation and study

The yolk granules of Artemia behave as unstable structures during isolation, especially after hatching. A stringent dechorionization of the cysts is required for an easy homogenization and good extraction of the yolk granules. The use of Ficoll and the avoidance of high dilutions in the homogenization process allows the isolation in an intact state of a pure yolk granules fraction without nuclear contamination. Previously described methods for the isolation of yolk granules lead to low recoveries of these structures in preparations with nuclear contamination. Lipovitellin, the major yolk protein, can be used as a biochemical marker to monitor the recovery of yolk granules and the possible yolk contamination of other subcellular fractions. The isolation of nuclei is also improved, their double membrane preserved in an enriched fraction with less yolk contamination than usually obtained with previously described methods. The other major storage structure, the lipoid bodies, can be isolated intact in these conditions, whereas they are also disrupted in common homogenization media.