Staining Neural End Feet and Mitochondria After Postchroming and Carbowax Embedding

Abstract

Spinal cord of cat and rabbit was fixed by perfusion with 10% formalin in physiological salt solution followed by a 2-day immersion in 10% aqueous formalin. Further treatment (postchroming) consisted of a 5-day immersion in: K₂Cr₂O₇, 5 gm; CrFl₃-4H₂O, 2 gm; distilled water, 100 ml; followed by 5% aqueous K₂Cr₂O₇ at 38–40°C for 2–4 wks. After thorough washing, blocks were embedded by infiltration first with polyethylene glycol 1000 M. E. and then with Nonex 63B (Gemec Chemicals Co., London, E. C. 2), and casting in the Nonex. Sections were stained, either mounted or unmounted, by modifications of the Bielschowsky-Gros method, and mounted sections by Weigert-Pal's hematoxylin or by Silver's Protargol method. All 3 methods gave apparently complete staining of pericellular end feet and showed also an abundance of mitochondria. Cytologic preservation was much better than that seen after the usual procedures for this type of staining. Retention of lipoid material in the sections is considered to be the cause of efficient staining of end feet and mitochondria.