Intercellular Junctions In Fanft‐Induced Carcinomas Of Rat Urinary Bladder In Tissue Culture: In Situ Thin‐Section, Freeze‐Fracture, And Scanning Electron Microscopy Studies

Abstract

This paper describes a set of simple methods for comparative light and electron microscopy studies on tissue cultured tumour cells derived from both noninvasive and invasive carcinogen-induced rat urinary bladder carcinomas. Cells are grown on Thermanox plastic coverslips and fixed in situ. Each plastic coverslip is then divided with scissors into four parts: the first is processed for light microscopy, the second for thin-section electron microscopy, the third for freeze-fracture electron microscopy, and the fourth for scanning electron microscopy. In some experiments, portions of the culture which have first been examined by light microscopy are subsequently prepared for electron microscopy. In this way, the culture conditions are kept constant and comparison of structural features (i.e. intercellular junctions) by several preparative techniques is possible. Noninvasive and invasive rat bladder tumour cells, characterized by numerous pleomorphic microvilli, have normal zonulae occludentes at the apices of lateral surfaces of tumour cells in all cultures. In some areas of invasive tumour cells, occludens junctions are focally attenuated, consisting of only one or two strands, and occasionally the strands are discontinuous. Gap junctions, type PF-1, as well as numerous demosomes are present in all cell lines. Thus, intercellular junctions in noninvasive and invasive rate bladder epithelial cell lines bear a striking resemblance to those previously described in the comparable solid primary tumours. These culture systems may be useful for studying factors which influence the formation of intercellular junctions during malignant transformation.

Tumor invasion and host extracellular matrix

“…The significance of this isolated finding remains to be established. The ultrastructure and numerical densities of cell junctions in experimental urinary bladder carcinomas in Fischer rats do not correlate with invasiveness (12), nor are consistent differences in cell junctions observed in tissue culture lines derived from noninvasive and invasive rat bladder tumors (154). This may not be incompatible with the findings in human bladder carcinomas, since tumor morphology in humans and in rats is significantly different.…”

Surface Topography of Deeper Cells Exposed by Ultrasonic Wave Forces in Neoplastic and Non-Neoplastic Epithelium of Human Urinary Bladder

“…Cohen et al [9] and Pauli et al [7] revealed that cultured tumor cells of the rat bladder showed filopodia, pleomorphic microvilli and blebs. As mentioned above, deeper cells were reported to have slender strands, filopodia or microvilli on the sur faces of bladder tumors or non-neoplastic bladder mu cosa in vivo.…”

“…Since Arai et al [2], Jacobs et al [3] and Hicks and Wakefield [4] reported that these surface features of luminal cells changed in the neoplastic condition in duced by chemical carcinogens, the luminal surface to pography of these cells has been the focus of early mor phological changes of carcinogenesis in the urinary blad der. Namely, pleomorphic microvilli are recognized on the luminal surface of the superficial cells in irreversible hyperplasia and transitional cell carcinoma of the mam malian urinary bladder instead of the reticular micro ridges or short uniform microvilli on the luminal surface of superficial cells in the non-neoplastic epithelium [2][3][4], However, TEM observations showed that the superfi cial cells and the deeper cells in the mammalian transi tional cell epithelium and in bladder tumors had micro villous cellular processes and that some of these micro villous cellular processes were interwoven with others of neighboring cells in vivo as interdigitations in the inter cellular spaces [7,8]. Despite these descriptions of the topography of the luminal surfaces of these tissues, there have not been many reports describing the surface fea tures of the deeper cells in mammalian bladder tumors or bladder mucosa.…”

In situ liquid propane jet‐freezing and freeze‐etching of monolayer cell cultures

“…In the case of some specimens, the copper hats were covered with a thin film of specimen mounting medium made according to Pauli et al (1979) before mounting the inverted plastic square on to the hat. The frozen specimens were fractured, etched for 1 min at 173 K and replicated using a freeze-etch unit manufactured according to Elgsaeter (1978).…”