THE USE OF DIFFERENT FIXATIVES AND HYDROPHILIC EMBEDDING MEDIA (HISTORESIN(TM) AND UNICRYL(TM)) FOR THE STUDY OF EMBRYONIC-TISSUES

The effects of different fixatives, dehydration procedures, and embedd ing media on the structural, and ultrastructural preservation of young chick embryos (Hamburger and Hamilton stages 18-24) have been studied by means of light and electron microscopy techniques. Under the light microscope, the results obtained with the use of Bouin, glutaraldehyd e, or glutaraldehyde-paraformaldehyde mixtures, followed by partial, d ehydration of the samples and the embedding with two different polar r esins (Historesin(TM) and Unicryl(TM)), were compared with the results obtained using conventional paraffin-embedding methods. Cell and tiss ue shrinkage was determined by comparing blood cells from those embryo s embedded in either of resins with those embedded in paraffin. Sample s were also compared with blood smears, either methanol-fixed or unfix ed, obtained from embryos at the same Hamburger and Hamilton stages. T he results obtained when Unicryl(TM) and Araldite were used for electr on microscopy have also been compared. When ultrastructural images fro m glutaraldehyde-tannic acid/osmium tetroxide fixed, Unicryl(TM) embed ded samples were compared with those from araldite embedded samples, t he same good results were observed with either of the resins. Araldite embedding requires a complete dehydration of the samples, while Unicr yl(TM) allows the embedding of partially dehydrated embryos with optim al ultrastructural results. We suggest that these polar resins can be considered as complementary tools for embedding delicate embryonic tis sues, allowing partial dehydration of the specimens with an excellent cell and tissue preservation. (C) 1997 Wiley-Liss, Inc.