The mammalian urinary bladder: an accommodating organ

Probable in vivo induction of differentiation by retinoic acid of promyelocytes in acute promyelocytic leukaemia

A 30-year-old woman was diagnosed as having an acute promyelocytic leukaemia in September 1981. Chemotherapeutic courses of daunomycin, ara-C, thioguanine and prednisolone were administered, resulting in a complete remission. A relapse occurred in January 1982, and chemotherapy did not lead to a second complete remission; neutropenia persisted with a marked left shift of the marrow granulopoiesis. Courses of chemotherapy were given throughout the study. In September 1982, marrow promyelocytes markedly increased, making up 51% of the nucleated cells. One month later the situation was unchanged, and 13-cis-retinoic acid (1 mg/kg) was administered by mouth. Gradually the marrow proportion of promyelocytes decreased to normal levels. The peripheral blood and marrow were still normal after 20 weeks of treatment with retinoic acid. Thus, retinoic acid seemed to have been inducing differentiation in an abnormally increased, maturation-deficient population of promyelocytes in a patient with acute promyelocytic leukaemia.

Structure and function of the Ca antigen

The Ca antigen, which can be detected in a wide range of malignant human tumours by means of the Cal antibody, is a glycoprotein of the mucin type. At least 95% of the carbohydrate is 0-glycosidically linked to the polypeptide which contains high proportions of glycine, serine and glutamic acid. The carbohydrate has a very simple structure: it is composed almost entirely of tetra- tri- and disaccharides having the general formula (NeuNac)n leads to [Gal leads to GalNac] alpha leads to, where n = 0, 1 or 2. In many malignant cell lines, the antigen is produced constitutively in vitro; but in one that has been examined, its synthesis can be induced by high concentrations of lactate. Evidence is presented for the view that a primary function of this glycoprotein is to shield the cells that produce it from hydrogen ion concentrations outside of the physiological range. The presence of the Ca antigen in malignant tumours may thus be a reflection of metabolic conditions that are known to be characteristics of such tumours.

Saccharin: a toxicological and historical perspective

Saccharin, first synthesized in 1879, eventually became popular as an inexpensive substitute for sugar, particularly as a non-caloric sweetner. The dispute concerning the safety of saccharin for human consumption is almost as old as saccharin itself. In this article, the history concerning the uses of saccharin and the accompanying controversy are reviewed. In addition, the spectrum of toxicological and epidemiological studies to which saccharin has been subjected are also examined. While the toxicological data indicate that saccharin is probably the agent solely responsible for the bladder tumors observed in second generation male rats, the epidemiological studies provide, at best, an equivocal relationship between the consumption of saccharin and bladder cancer. A benefit-risk evaluation for saccharin showed few, if any documentable benefits from the use of saccharin and much genuine uncertainty concerning the potential risks for ingestion by man. This element of genuine uncertainty as to the extent of human risk posed to man is the crux of saccharin's past and its foreseeable future.

Epithelial-mesenchymal interactions in prostatic development. I. morphological observations of prostatic induction by urogenital sinus mesenchyme in epithelium of the adult rodent urinary bladder

Tissue recombinants of embryonic urogenital sinus mesenchyme (UGM) and epithelium of the urinary bladder (urothelium, BLE) of adult rats and mice were grown for 3-30 d in male syngeneic hosts. Short-term in vivo growth indicated that prostatic morphogenesis is initiated as focal outgrowths from the basal aspect of the adult urothelium. The solid epithelial buds elongate, branch, and subsequently canalize, forming prostatic acini. After 30 d of growth in the male hosts, prostatic acini exhibit secretory activity. The marked changes in urothelial morphology induced by the UGM are accompanied by the expression of fine-structural features indicative of secretory function (rough endoplasmic reticulum, Golgi apparatus, and secretory granules). During this process, urothelial cells express prostatic histochemical markers (alkaline phosphatase, nonspecific esterase, glycosaminoglycans) and prostate-specific antigens. The expression within BLE of prostatic characteristics is associated with the loss of urothelial characteristics. These data indicate that adult urothelial cells retain a responsiveness to embryonic mesenchymal inductors. Furthermore, mesenchyme-induced changes in urothelial cytodifferentiation appear to be coupled to changes in functional activity.

The distribution of cathepsin D in rat tissues determined by immunocytochemistry

The distribution of cathepsin D (CD) was surveyed in rat tissues by light microscopic immunocytochemistry. Although immunoreactive CD was detected in all tissues examined, there was a marked difference in the amount in the cytoplasm of different cell types of the same organ. In the retina large amounts of CD were present in the pigment epithelium, ganglion cells, and Müller cells. Moderate to large amounts of CD were also found in neuronal perikarya of the gastrointestinal tract and adrenal medulla; in macrophages in the lung, liver, and spleen; in some secretory cells of the submandibular and lacrimal glands; in parts of renal distal convoluted and collecting tubules; and in the surface transitional epithelium of the calyx, ureter, and urinary bladder. Other cells adjacent to cells containing large amounts of the enzyme had little or no detectable CD themselves. These included hepatocytes, the proximal tubular cells of the kidney, selected cells of the submandibular gland, cells of the zona glomerulosa of the adrenal cortex, and lymphocytes in lymphoid organs. The localization of CD indicates that its degradative effect is exerted preferentially in certain cell types and suggests that physiological influences on CD may have a variety of effects in different organs.

Cellular changes in rat urinary bladder carcinomas induced by FANFT: a quantitative electron microscopic analysis

Morphometric data of normal and neoplastic urinary bladder epithelia have been collected from the Fischer rat FANFT model. Sequential measurements of volumes, surface areas, and numerical densities of organelles, and where pertinent, cellular compartments have been made during FANFT carcinogenesis, utilizing standard point and intersection counting methods. The data show that neoplastic transformation of rat bladder epithelium, and progression of FANFT tumors are associated with increasing volume densities of cells, nuclei, microvilli, rough endoplasmic reticulum, and mitochondria, as well as with decreasing volume densities of the cytoplasmic matrix, fusiform vesicles, Golgi complex, and lysosomes. Surface densities of the plasma membrane (microvillar), nuclei, rough endoplasmic reticulum, as well as mitochondrial outer and inner membranes progressively increase while surface densities of non-microvillar plasma membrane, fusiform vesicles, and Golgi complex decrease with time. Smooth endoplasmic reticulum reaches its maximum volume and surface densities in tumors present 26 weeks after the initiation of FANFT feedings (26-F tumors). This may reflect the function of smooth endoplasmic reticulum as the site of detoxification of the carcinogen, noting that FANFT is metabolized by microsomal enzymes, and in this experiment is fed only for 26 weeks. The nuclear/cytoplasmic ratio is 1:4 in normal Fischer rat urothelium, 1:3 in 26-F and 43-F tumors, which are noninvasive, and 1:2 in 61-F, which are invasive tumors. The quantitative data correlate well with the changes in degree of differentiation of the tumors and with their biological behavior.

The induction of adenocarcinomatous differentiation in neoplastic bladder epithelium by an embryonic prostatic inductor

Epithelial cells of non-glandular, transitional cell carcinomas from rat urinary bladders were associated with embryonic rat urogenital sinus mesenchyme (a prostatic inductor) and transplanted into syngeneic adult male hosts. Neoplastic bladder epithelium formed glandular (adenocarcinomatous) acini in a substantial number of recombinants, suggesting that the mesenchyme (stroma) may influence the histotypic organization of carcinoma cells and induce the neoplastic epithelium to express a novel phenotype.

The induction of rat bladder cancer by 2-naphthylamine

The widely held belief that 2-naphthylamine is not carcinogenic for the rat has been re-examined. Twenty female Wistar rats were dosed by gastric intubation weekly for 57 weeks with 2-naphthylamine, 300 mg/kg body wt, in arachis oil and 20 controls were given arachis oil alone. Animals which became moribund were killed during the course of the experiment and the remainder after 100 weeks. A 2-naphthylamine-treated animal died at 21 weeks; all others survived 57 weeks or longer. The urinary tracts of all but two 2-naphthylamine-treated animals, which were found dead and cannibalized, were examined histologically.No neoplastic disease of the urinary tract was present in control animals. In 10 of the 2-naphthylamine-treated rats there was neither neoplasia nor hyperplasia of the urothelium, but 4 of the 18 examined histologically had large, macroscopically visible bladder cancers; one of these also had bilateral transitional cell tumours of the kidney calyces and multiple tumours in both ureters. Another animal had bilateral urothelial cancers in the ureters. The histology and ultrastructure of these urothelial cancers were comparable to those of rat transitional-cell carcinomas experimentally induced with other chemical carcinogens.These results, considered in the context both of early and more recently published biochemical studies of 2-naphthylamine metabolism in the rat, support the possibility that production of the active carcinogenic metabolite in this species may be influenced by a pH-dependent, non-enzymic mechanism in the urine, which could account for individual, strain- and diet-related variations in response in the rat.

Urothelium-specific antibody and lectin surface mapping of bladder urothelium

Coupled ligand-colloidal gold complexes were found to provide a convenient approach for the localization of scanning electron microscopy of cell surface membrane antigens and lectin-binding sites on bladder urothelium and for the immunocytochemical identification of urothelial cell populations at different stages of differentiation. The ligands used to prove the membrane were a urothelium-specific rabbit antibody raised to a urothelial membrane-associated antigen (UMA), and two lectins: Concanavalin A (Con A) and peanut agglutinin (PNA). A complex luminal surface distribution pattern was demonstrated by the UMA antigen related to the stage of urothelial cell maturation and differentiation. UMA could be detected on the surface of immature and early differentiating intermediate cells, but was absent from the late differentiation stage, becoming re-expressed as the cells matured and was found in greatest abundance on the terminally differentiated superficial cells. It was absent on cells in benign hyperplasia of the urothelium. Cellular and regional differences in lectin binding to the urothelial cell surface was suggested with Con A receptors localized uniformly over the superficial cells, and PNA receptors confined to linear arrays or occasional clusters over the apical surface but evenly dispersed over the lateral surface of these cells.

Early and late morphological changes (including carcinoma of the urothelium) induced by irradiation of the rat urinary bladder

Effects of X-irradiating the urinary bladder of female F344 rats with a single dose of 20 Gy were studied by light and electron microscopy. The animals were killed 1 week-20 months post-irradiation, and all tissues of the bladder wall were found to be affected by the irradiation. In the urothelium, damage was initially restricted to the basal cells but slowly extended to intermediate cells, and by 6 months post-irradiation the urothelium was focally hyperplastic. Twenty months post-irradiation, transitional-cell carcinomas were found in 10 of the surviving 17 animals (59%). The blood vessels in the bladder wall showed damage to both the endothelial cells and the smooth muscle. The fibroblasts in the connective tissue of the bladder wall appeared to show increased secretion after irradiation, and there was abundant collagen deposition, resulting in severe fibrosis of the bladder wall. After a latent period of a few months, focal degeneration and extensive necrosis of the smooth muscle cells were seen, leading to severe destruction and disorganization of the muscular coats of the bladder wall. Thus, a single dose of irradiation of 20 Gy was sufficient to produce severe fibrosis of the bladder wall with smooth muscle degeneration and to induce carcinoma of the urothelium in most of the treated animals within 20 months.

Membrane differentiation in the Golgi apparatus of mammalian urinary bladder epithelium

The endomembrane system in superficial and intermediate epithelial cells of mammalian urinary bladder was studied by cytochemistry, thin-section and freeze-fracture electron microscopy to determine the sites where special forms of membrane differentiation first appear. Glutaraldehyde-resistant NADH-ferricyanide reductase, distinctive 11-12 nm intramembrane particles (IMP), and asymmetry of membrane leaflets served as markers of membrane maturation. The three markers were specifically associated with the maturing face of Golgi apparatus and were absent from the remainder of the endomembrane system. Activity of this enzyme was associated with the lateral regions of the maturing face, fusiform vesicles, and the plasmalemma. Asymmetric unit membrane (AUM) plaques were not observed in the Golgi apparatus per se but were present in immature fusiform vesicles that had not detached from the maturing face. When freeze-fracture replicas and thin sections were compared, randomly arranged 11-12 nm IMP first appeared in maturing face membranes that were adjacent to clusters of "free" polyribosomes in the Golgi apparatus region. The proximity of these polyribosomes suggests that they may be related to the coincident appearance of the 11-12 nm IMP in the maturing face membrane. Our observations support the hypothesis that membranes undergo differentiation during "flow" through compartments of the endomembrane system. The lateral regions of the maturing face of the Golgi apparatus appear to be a critical location for the morphogenesis of plasma membranes in urinary bladder.

Localization of species cross-reactive epithelium and urothelium specific antigens in the urinary tract of the rat, mouse, hamster and guinea pig

Antiserum from a New Zealand white rabbit raised against the saline soluble fraction of calf bladder epithelium was absorbed to produce epithelial and urothelial specific stages. With indirect immunofluorescence antiepithelial antiserum reacted with all cell layers of the urothelium of a rat, mouse, hamster and guinea pig in all regions of the urinary tract, and in the epithelium of the renal pyramid and tubules. The most intense reaction in the urothelium was seen in the superficial cells of the rat and mouse but in the intermediate cells of the guinea pig. Urothelium specific antigens were demonstrated predominantly in the superficial cells of the urothelium as far as the fornix of the renal pelvis but not in the renal pyramids or tubules in all these rodents except for the guinea pig.

Neurosecretory granules in small cell invasive carcinoma of the urinary bladder

A 69-year-old man showed symptoms of urinary bladder irritability and hematuria. Cystoscopy and radiographic studies revealed a tumor within a bladder diverticulum. The tumor shared histologic and ultrastructural features with oat cell carcinoma of the lung, including the presence of small numbers of neurosecretory type granules. In spite of conservative surgical treatment, there has been no evidence of recurrent or metastatic tumor over 14 months of follow-up. Hypophosphatemia was present preoperatively, but resolved spontaneously after tumor resection. In regard to histogenesis, a metaplastic origin is favored. This appears to be the first reported case of a neoplasm of Kultschitzky-type cells arising in the urinary bladder.

Alteration of urinary levels of the carcinogen, N-hydroxy-2-naphthylamine, and its N-glucuronide in the rat by control of urinary pH, inhibition of metabolic sulfation, and changes in biliary excretion

The hepatic metabolism of arylamine bladder carcinogens to N-hydroxy arylamine N-glucuronides, their excretion in the urine, and their subsequent acidic hydrolysis to highly carcinogenic and reactive N-hydroxy arylamines have been proposed as essential steps in arylamine-induced urinary bladder carcinogenesis. In this study, alteration of urinary pH, inhibition of metabolic sulfation, and blockage of biliary disposition were shown to profoundly affect the urinary excretion of the probable ultimate bladder carcinogen, N-hydroxy-2-naphthylamine (N-HO-2-NA) and its N-glucuronide conjugate. The normal pH of rat urine (6.7) was altered to 5.7 or 7.7 by administration of NH4Cl or NaHCO3 in the drinking water. Subsequent treatment with either 2-naphthylamine (2-NA) or 2-nitronaphthalene (2-NN) resulted in increased urinary levels of free N-HO-2-NA (relative to its N-glucuronide) in acidic urines and decreased relative amounts of free N-HO-2-NA in alkaline urines. In addition, 2-NN yielded 5--10-fold greater levels of urinary N-HO-2-NA and its N-glucuronide than rats given 2-NA; and 2-NA was not detected as a urinary metabolite of 2-NN. Some 12 additional metabolites of 2-NA and 2-NN were also found. Of these, 2-amino-1-naphthol and its sulfate and glucuronide conjugates were quantitated. From these data, 2-NA and 2-NN appear to share common metabolic pathways which yield free N-HO-2-NA as a putative ultimate urinary bladder carcinogen. Pentachlorophenol, a known inhibitor of hepatic sulfotransferases, was shown to cause a 2--3-fold increase in the urinary levels of N-HO-2-NA N-glucuronide and N-HO-2-NA from 2-NA-treated rats. Similarly, inhibition of the biliary excretion of 2-NA by bile duct ligation resulted in a 6-fold increase in total urinary N-HO-2-NfA. Furthermore, analyses of bile revealed that substantial amounts of N-HO-2-NA N-glucuronide, but not free N-HO-2-NA, were present. The role of urinary versus biliary excretion of N-hydroxy arylamines in relation to bladder and colon carcinogenesis is discussed.

Effect of Schistosoma haematobium and N-butyl-N-(4-hydroxybutyl)nitrosamine on the development of urothelial neoplasia in the baboon

Experiments were conducted to determine whether bladder cancer would develop in primates (Papio sp.) infected with S. haematobium and concurrently exposed to low initiating doses of the bladder carcinogen N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN). To control for the systemic effects of schistosomiasis, 5 baboons were infected with S. mansoni, which does not lay its eggs in the bladder wall; to control for the effect of the carcinogen alone, 5 others were treated with BBN alone at the rate of 5 or 50 mg/kg per week for the duration of the experiment. Five animals were infected with S. haematobium and had no further treatment, and the main experimental group of 10 baboons was infected with S. haematobium and also treated weekly with 5 mg/kg BBN for up to 2½ years. Four of the 10 animals in the last group, but none in the three control groups developed neoplastic disease of the urothelium. Four animals with S. haematobium plus BBN treatment developed in situ carcinoma in the bladder (3 latent adenomatous lesions and 1 more advanced papillary tumour) and 2 of these animals plus 1 other had slightly dysplastic urothelial endophytic papillary growths of the ureter which penetrated the muscle layer. By contrast, none of the control animals developed urothelial carcinomas, though 4/5 of those with S. haematobium infection alone had inflamed bladders with polypoid lesions, and one individual had endophytic papillary hyperplasia of the ureter. The animals were killed after 2½ years while still relatively immature or adolescent, and it is possible that had they been allowed to survive longer some of the BBN-only group would have developed bladder cancer, and more of the latent lesions seen in the BBN + schistosomiasis group would have progressed to invasive carcinoma. It is postulated that, in this model for human bilharzial bladder cancer, schistosomiasis supplies the proliferative stimulus necessary to accelerate cancer growth from latent tumour foci produced by exposure to low doses of the bladder carcinogen. In areas of endemic schistosomiasis, carcinogenesis might be initiated, for example, by low doses of nitrosamines produced in the urinary tract during bouts of bacteriuria.

Intraepithelial asymmetric-unit-membrane plaques in mammalian urinary bladder

Asymmetric-unit-membrane (AUM) plaques are major components of the luminal surface of superficial cells in mammalian urinary bladder. We have now demonstrated ultrastructually identical AUM plaques in intraepithelial locations, at the lateral and basal surfaces of superficial cells and at the apical surfaces of intermediate epithelial cells in the urinary bladder. Typically, luminal apposing AUM plaques are present in clusters. Similar plaque clusters are present on apposing surfaces of cell pairs within the epithelium. These intraepithelial plaque clusters are in register, although often separated by a wide interspace. In areas where they come into closer apposition, they form membrane complexes resembling but distinctly different from certain types of cell-to-cell junctions. Both luminal and intraepithelial AUM plaques serve as membrane attachment sites for cytoplasmic microfilaments. Their intraepithelial location and association with microfilaments support the hypothesis that AUM plaques serve a mechanical function and modulate cell surface area during the urinary bladder distention-contraction cycle.

Bacterial colonization of human urethral mucosa. I. Scanning electron microscopy

A scanning electron microscopic investigation of the urethral mucosa of altogether ten men and women subjected to cystourethrectomy because of urothelial cancer of the urinary bladder was performed. The mucosal cells were found to be polygonal and characterized by the presence of microvilli and microridges. No sex difference could be demonstrated. Although a higher number of cells carrying microridges was found in the proximal part of the urethra, no statistical difference in the number of cells with various surface topography was found in different parts of the urethra. The micrographs revealed that the number of urethral cells to which bacteria were attached, was low, also in patients with proven preoperative infection. The bacteria, mainly cocci, seemed to exhibit a preferential adherence to a subpopulation of urethral cover cells, as indicated by the observation that the organisms were not attached randomly. The possibility that different cell surface properties may explain this distribution is considered.

The isolation and analysis of the luminal plasma membrane of calf urinary bladder epithelium

The luminal plasma membrane of calf urinary bladder epithelium (urothelium) has been isolated by a method designed to preserve enzymic activity as well as structural integrity. The yield was about 80 micrograms per calf bladder. Low levels of 5' nucleotidase, Mg2+-ATPase and (Na+ + K+)-ATPase activities were found in the luminal membrane fraction. Cerebroside was the major lipid present and dodecyl sulphate gel electrophoresis revealed a complex protein and glycoprotein composition in the whole membrane. A membrane fraction consisting of only the plaque areas was shown to have a simpler protein composition with major polypeptides of apparent Mr 12 000 and 22 000. These may associate to form a 30 000 apparent Mr complex which could represent the individual 'particles' of the dodecameric subunits seen by electron microscopy in the plaque regions.

Mitosis in milk secreting epithelial cells of mammary gland: an ultrastructural study

In all stages of lactation mitotic configurations were observed in mammary gland epithelial cells of rats. An electron microscopic study is presented which shows that ultrastructure of such mitotic stages is normal and that mitotic cells contain typical products of milk secreting cells such as casein micelle-containing vesicles and milk fat droplets. Such secretory products can even be observed in the immediate vicinity of the chromosomes and microtubules of the spindle apparatus. The endoplasmic reticulum of mitotic cells appeared altered in that it did not show typical cisternal stacks characteristic of interphase cells. While the numbers of such mitotic cells were very low, especially from the second week of lactation on (always less than 0.1% of the milk secreting epithelial cells encountered), the observations clearly demonstrate that differentiation for milk secretory activity and cells division are not mutually exclusive. We conclude that postpartum growth of mammary gland epithelium and replacement of epithelial cells lost during desquamation into the milk liquids can occur by division of existing differentiated milk secreting cells and does not require mitotic activity of non-lactating 'stem cells' which are not observed in lactating alveoli.

Identification and characterization of epithelial cells in mammalian tissues by immunofluorescence microscopy using antibodies to prekeratin

The occurrence of intermediate-sized filaments containing prekeratin-like proteins ('cytokeratins') has been examined in various organs of rat and cow by electron microscopy and by immunofluorescence microscopy on frozen sections using antibodies to defined constitutive proteins of various types of intermediate-sized filaments (prekeratin, vimentin, desmin). Positive cytokeratin reaction and tonofilament-like structures have been observed in the following epithelia: epidermis; ductal, secretory, and myoepithelial cells of sweat glands; mammary gland duct; myoepithelial cells of lactating mammary gland; milk secreting cells of cow; ductal, secretory, and myoepithelial cells of various salivary glands; tongue mucosa; bile duct; excretory duct of pancreas; intestinal mucosa; urothelium; trachea; bronchi; thymus reticulum, including Hassall corpuscles; mesothelium; uterus; and ciliated cells of oviduct. None of the epithelial cells mentioned has shown significant reaction with antibodies to vimentin, the major component of the type of intermediate-sized filaments predominant in mesenchymal cells. The widespread, if not general occurrence of cytokeratin filaments in epithelial cells is emphasized, and it is proposed to use this specific structure as a criterion for true epithelial character or origin.

Detection of neoplastic and preneoplastic urothelia by combined scanning and transmission electron microscopy of urinary surface of human and rat bladders

Scanning and transmission electron microscopy reveal distinct differences between the appearance of the luminal surface membrane of normal urothelium and those of transitional cell tumours of both human and rat bladder. The luminal surface membrane of the preneoplastic rat urothelium shows features similar to those seen in the fully developed tumour. In human tumour-bearing bladders the urothelium away from the transitional cell tumour is not recognizable as being preneoplastic by light microscopy. However, by scanning or transmission electron microscopy, the luminal membrane in some areas shows changes identical to those in the preneoplastic rat bladder. These observations are in accordance with the clinical behaviour of the urothelium in patients with vesical transitional cell tumours which tend to recur in disparate site. We suggest that scanning electron microscopy of the bladder urothelium away from the tumour may be of prognostic value for indicating the subsequent biological behaviour of the urothelium.

13-cis-retinoic acid: inhibition of bladder carcinogenesis in the rat

Transitional cell and squamous cell cancer of the bladder was induced in Wistar/Lewis female rats by direct instillation of N-methyl-N-nitrosourea into the bladder. Feeding of the synthetic retinoid, 13-cis-retinoid acid, inhibited the incidence and extent of bladder cancer in these rats, even when 13-cis-retinoic acid administration was begun after completion of the carcinogen treatment.

Development and characterization of cell lines of normal mouse bladder epithelial cells and 2-acetylaminofluorene-induced urothelial carcinoma cells grown in monolayer tissue culture

Normal urinary bladder epithelial cells and cells derived from 2-acetylaminofluorene-induced urothelial carcinomas from male Balb/c mice were grown in monolayer culture and were characterized. Cell lines of normal bladder epithelium were mononucleated, sheet-forming cells, with a modal chromosome number of 40. Bladder epithelial carcinoma cells induced by 2-acetylaminofluorene were polynucleate, relatively fast growing, grew in soft agar, demonstrated a higher cloning efficiency than normal cells and formed tumors when inoculated into syngeneic hosts. Differences in morphology were recorded by photomicrography using phase optics and scanning electron microscopy.