FIXATION AND STAINING OF PLANARIA FOR HISTOLOGICAL STUDY

Fixation and staining of planaria can affect the interpretation of his topathological changes following their exposure to various agents. We assessed several fixation protocols with various stains in planaria to determine an optimal combination. Planaria were fixed in each of the following: 10% neutral buffered formalin, 2.5%, glutaraldehyde, Bouin' s, Zenker's, 70% ethanol, and relaxant. In addition, planaria were fix ed in relaxant and postfixed in each of the fixatives above. Paraffin embedded sections from each fixation protocol were stained with hemato xylin and eosin (H & E), toluidine blue, periodic acid-Schiff (PAS), o r phosphotungstic acid-hematoxylin (PTAH). Relaxant fixed planaria wer e also stained with Steiner's, Holmes, trichrome, Giemsa, Grocott's me thenamine silver (GMS) and antibodies for intermediate filaments (cyto keratin, vimentin and desmin). Relaxant and Zenker's gave the best fix ation with minimal artifacts. Formalin, glutaraldehyde, and ethanol we re unacceptable because they caused contortions of the body, crenation , and a darkly pigmented epidermis. Gastroderm could be differentiated from stroma best when stained with H & E, toluidine blue and PTAH. Ot her organ systems differentially stained included the epidermis, margi nal adhesion gland, nervous tissue, and muscle. PAS, Steiner's, Holmes , trichrome and the intermediate filament stains were not useful for p lanaria staining. The most morphological information was obtained with relaxant fixative and a combination of sections stained with H & E an d PTAH.