Ultrastructural characterization of isolated rat Kupffer cells by transmission X-ray microscopy

The ultrastructure of primary cultured rat Kupffer cells was studied using transmission X-ray microscopy as well as transmission electron microscopy. X-ray microscopical images of intact, hydrated Kupffer cells demonstrated s tructures such as cell nucleus separated by a nuclear membrane and filament s concentrated in the perinuclear area. Within the cytoplasm, a number of v acuoles were visible: some of these were crescent-shaped vacuoles that were half X-ray lucent, half X-ray dense; others were uniformly dense. The numb er of crescent-shaped vacuoles was predominant. After phagocytosis of haema tite particles. enlarged vacuoles containing the ingested material were vis ible within the cytoplasm of Kupffer cells while crescent-shaped vacuoles w ere no longer detectable. Densitometric analysis of the two types of vacuol e revealed that the X-ray absorption of the uniform vacuole was approximate ly half that of the dense part of the crescent-shaped vacuoles, This observ ation led to speculation on the existence of only one type of vacuole in th e cytoplasm of Kupffer cells, The different morphological aspects - crescen t-shaped versus uniform vacuoles - might be due to different three-dimensio nal orientation with respect to the image plane. Using transmission electro n microscopy, the morphology of vacuoles differed more widely in diameter, density and shape. Two main types of vacuole were identified: electronlucen t and electron-dense. Based on the observation of only one type of vacuole by transmission X-ray microscopy, the different morphological aspects of va cuoles obtained by transmission electron microscopy could be explained by i maging several different sections of a crescent-shaped vacuole. From the pr esent data it can be concluded that transmission X-ray microscopy is a vers atile technique that reveals the ultrastructure of intact, unsectioned biol ogical specimens in their aqueous environment, thereby allowing a more comp rehensive interpretation of data obtained by transmission electron microsco py.