Karnovsky fixative

Abstract: Prolonged storage of Karnovsky's fixative, at both 4 and -20 degrees C, is possible in the diagnostic electron microscopy setting. Ultrastructural detail was not compromised in specimens processed in fixative that had been stored for 6 months. Evidence of smooth muscle and neuroendocrine differentiation was present in the form of actin filaments/dense bodies and neurosecretory granules, respectively. No difference in preservation was detected between specimens fixed in freshly prepared Karnovsky's fixative and fixative that had been stored at either 4 or -20 degrees C for up to 6 months. Thus, community hospitals can be provided with Karnovsky's fixative on a semiannual basis for surgical pathology specimens that may require electron microscopy for diagnosis.

Abstract: The epithelium lining the tympanic cavity of the chicken possesses distinct morphological characteristics. Its ultrastructure was studied using 2 preparative techniques. (1) After fixation in Karnovsky's solution, postfixation in osmium tetroxide and embedding in Epon, the epithelium was observed to contain 2 kinds of cell: secretory and basal. The secretory cells (which we refer to as mixed granulated cells) showed numerous secretory vesicles that varied in appearance, some containing paracrystalline formations. The basal cells, located close to the basement membrane, showed no evidence of secretory activity. (2) Other specimens were immersed in Karnovsky fixative and subsequently in a mixture of glutaraldehyde and tannic acid. They were then osmicated and embedded in polar Epon mix. With this method, the epithelium was seen to be covered by electron-dense material made up of thin intertwined tubules. In addition, the secretory cells contained vesicles with concentrically arranged lamellae; such vesicles resembled the multilamellar bodies of mammalian type II pneumocytes. The hypothesis is advanced that tubules and lamellar vesicles are related to the presence of surfactant substances.