Alterations of various genes during N-nitrosobis(2-hydroxypropyl)amine (BHP) -induced lung carcinogenesis in rats and N-nitrosobis(2-oxopropyl)amine (BOP) -induced pancreatic duct carinogenesis in hamsters were summarized. In both carinogenesis, Ki-ras mutation was the early event in lung alveolar and pancreatic duct hyperplasias. Although p53 mutation was not detected in lung adenocarcinomas, it was revealed as late events in transplantable pancreatic carcinoma and its cell lines. FHIT alterations were found in rat lung adenocarcinomas and in hamster pancreatic duct carcinomas. The induced lesions in both rat lung and hamster pancreas were histologically and genetically similar to those seen in humans. It was evident from this study that various gene alterations were accumulated from preneoplastic lesions to carcinomas induced by nitrosoamines in rat lung and hamster pancreas. Since cancer is a disease of gene alterations, the detection of genetic and environmental factors which induce organ specific gene alterations is important for the prevention and early detection and treatment of lung and pancreatic cancers.

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In order to assess the modifying effects of atrazine (ATR) on uterine endometrial carcinogenesis, female ICR mice received an intra-uterine injection via the vagina of 50 mg/kg body weight of N-ethyl-N-nitrosourea (ENU), followed by no further treatment, by a diet containing 5, 50 or 500 ppm ATR or by a diet containing 2.5 ppm ethinylestradiol (EE) for 26 weeks. In the ENU + EE (positive control) group, depression of body weight gain was seen throughout the treatment period, and the incidence of uterine endometrial proliferative lesions such as adenocarcinomas and atypical hyperplasias, and PCNA positive indices were significantly increased as compared to the ENU alone group. On the other hand, although only slight depression of body weight was seen throughout the study in the ENU + 500 ppm ATR group, but no significant differences in uterine weights, incidence of uterine proliferative lesions with their PCNA positive indices and the immunohistochemical expression of ERα were found in all of the ENU + ATR groups as compared with those of the ENU alone group. The results in the present study indicate that ATR up to 500 ppm in diet has no modifying effects on uterine carcinogenesis in ICR mice initiated with ENU.

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In the present study, we investigated epithelial cell proliferation in heterozygous p53 knockout (p53^+/-) mice after administration of two urinary bladder non-genotoxic carcinogens, in comparison with that in wild-type littermates (p53^+/+). Mice at 10-weeks of age were given 2% sodium ortho-phenylphenate (Na-OPP) or 2.5% uracil in the basal diet for 4 weeks. Uracil evoked a marked elevation of epithelial cell proliferation and development of papillary or diffuse epithelial hyperplasia associated with calculus formation in p53^+/- as well as p53^+/+ mice. Administration of Na-OPP caused alkalization of the urine in both. Neither Na-OPP nor uracil induced a higher epithelial cell proliferative response in p53^+/- mice as compared with p53^+/+ mice. While we previously reported p53^+/- mice to be highly sensitive to a genotoxic urinary bladder carcinogen, N-butyl-N-(4-hydroxybutyl)nitrosamine, the present results suggest that p53^+/- mice may not have a high susceptibility to induction of urinary bladder tumors by non-genotoxic carcinogens.

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The initial changes in rat liver after a single oral dose of 7,12-dimethylbenz[a]anthracene (DMBA) (100 mg/kg b.w.) were examined ultrastructually. Glycogen granules of centrilobular hepatocytes increased with time to peak on Day 1. After this, they sharply decreased on Day 2, and on Days 5-10 returned to levels similar to those of the vehicle group (corn oil). On Day 2, the size of the centrilobular hepatocytes was decreased significantly, and the nuclear to cytoplasmic ratio was increased significantly. While the activity of hepatic glycogen phosphorylase a was decreased at 6-12 hrs and on Day 1, on Days 2-10, it was elevated to a level similar to that of the vehicle group. Thus, the initial temporary storage of hepatic glycogen granules following DMBA administration involved the inhibition of glycogenolysis in centrilobular hepatocytes. Glycogen granules appeared in restricted regions near the smooth endoplasmic reticulum (sER). Following DMBA administration, proliferation of sER of the centrilobular hepatocytes also gradually increased with time to peak on Day 2, after which it decreased, and on Days 5-10 returned to a level similar to that of the vehicle group. Results from the present study indicate that exposure of rats to DMBA could induce a reversible initial change in the hepatic glycogen metabolism. Moreover, the glycogen depletion of hepatocytes might be related to the high proliferation of sER that occurred concurrently on Day 2.

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We previously indicated that coumaperine isolated from pepper can protect against the initiation of rat hepatocarcinogenesis. In the present study, potential modifying effects of coumaperine on post-initiation promotion stage were examined, using a medium term rat liver bioassay (Ito test). F344 rats were given a single intraperitoneal injection of diethylnitrosamine (200 mg/kg body wt.) and subjected to two-thirds partial hepatectomy at week 3. Commencing 2 weeks from the start, coumaperine at doses of 0, 2, 10, 50 mg/kg body wt. was given to the rats for 6 weeks. All surviving animals were killed at week 8, and their livers were immunohistochemically examined for expression of glutathione S-transferase placental form (GST-P) and transforming growth factor-α (TGF-α). The numbers and areas of GST-P positive foci in rats given 2, 10 or 50 mg/kg coumaperine were comparable to the control values. There were also no significant intergroup differences regarding numbers and areas of TGF-α positive foci. This study suggested that coumaperine does not inhibit liver carcinogenesis in the promotion stage.

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The study was designed to investigate whether testicular castration (TC) or sialoadenectomy (SE) can influence sodium L-ascorbate (Na-AsA)-promoting effects on urinary bladder carcinogenesis in male F344/DuCrj rats. The animals, 6 weeks old at the commencement of the treatment, were given 0.05% N-butyl-N- (4-hydroxybutyl)nitrosamine (BBN) in their drinking water for 4 weeks and then subjected to TC or SE. Thereafter they received basal diet with or without 5% Na-AsA supplement for 32 weeks. Na-AsA caused significant increase in urinary pH, the concentrations of sodium ion, and total ascorbic acid, whereas these urinary parameters were not influenced by TC and SE. TC significantly decreased the relative organ weights of the accessory sexual glands, kidneys, and livers whereas SE was without effect on these organs. TC and SE decreased very slightly BBN-induced carcinogenesis, but TC and SE did not influence the Na-AsA-promoting effects. The present results indicate that Na-AsA-promotion of two-stage urinary bladder carcinogenesis does not depend on the presence of testes or salivary glands.

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Two masses adjacent to the salivary glands of two Prairie dogs which were surgically removed and examined histopathologically as well as immunohistochemically, were diagnosed as pleomorphic adenomas. Histologically, each mass had a thin fibrous capsule, compressed surrounding tissue, and was lobulated by delicate connective tissue. The lobules mainly consisted of a solid growth of small ovoid-to spindle-shaped cells, and contained small duct or tubule lined with monolayered cuboidal epithelial cells. The amount of connective tissue stroma varied in different parts of the tumor mass, accompanied occasionally by a myxomatous stroma-rich area. Tumor cells in the solid growth area had indistinct cell borders, and usually showed spindle-like features resembling myoepithelial cells. Mitosis was prominent, whereas cellular pleomorphism was not seen. Tumor cells forming the tubular structure were positive for cytokeratin 19 and negative for smooth muscle actin (SMA), while the ovoid- to spindle-shaped tumor cells of the solid growth area were positive for SMA and negative for cytokeratin 19. Our results indicated that immunostaining was a useful and powerful method for the diagnosis of cell differentiation of salivary gland tumor cells.

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A gastric carcinoid was found in the glandular stomach of an untreated male B6C3F1 mouse of 109 weeks old. Neoplastic cells had a hyperchromatic nucleus and scant cytoplasm, and were grouped into lobules by fine connective tissue, a characteristic growth pattern of arrangement of the neuroendocrine organ. The cytoplasmic granules were argyrophilic when stained with Grimelius and Sevier-Munger stain. Immunohistochemically, the neoplastic cells were positive for neuron specific enolase and synaptophysin. In the electron microscopic examination, they contained numerous cytoplasmic granules consistent morphologically with neuroendocrine secretary granules. Metastases were present in the regional lymph nodes.

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A case of submucosal gland adenoma developed in the nasal cavity of a male BDF₁ mouse, 110 weeks of age, was presented. Histologically, a solitary nodule, 5 mm in diameter, showed an acinar structure resembling that of a serous gland. The present case was found in the posterior-most part of the nasal cavity, contrary to all previously reported, probably-induced, adenomas of the nasal cavity in mice, found in the anterior-most part of the nasal cavity.

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Craniopharyngeal duct cysts were examined in two beagles. Histologically, multiple cysts of various sizes were observed in the pars distalis. They were lined with flattened, cuboidal, or columnar shaped epithelial cells, with or without cilium, whereas the cysts in rats consisted of various shaped epithelial structures, such as tubular, mucous glandular, or fusiform. Immunohistochemically, the epithelial cells of the cysts were found to express epithelial markers. The morphological findings indicated that they originated from the stomatodeum, but not that the cystic epithelia obviously differentiated into the salivary gland.

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Previously we have shown that a modified Warthin-Starry (mWS) method, to which was added a minor change to prevent fading, is useful and convenient to detect chemically induced chromatin condensation during thymic apoptosis in rats treated with dexamethasone. In this study, we investigated the relationship between mWS-positive cells and programmed cell death in the interdigital spaces of the developing limb in fetal SD rats. The limbs were removed from fetuses at day 15 of gestation, and routinely processed for both hematoxylin and eosin (H&E) staining and the mWS method. The results clearly showed that the distribution pattern of mWS-positive cells coincided well with that for the programmed cell death observed by H&E staining in the mesenchyme of interdigital notches and at the areas corresponding to the interphalangeal joints. These results confirm that the mWS method might be useful and convenient to detect condensed chromatin during apoptosis in embryonic organogenesis as well as by chemical induction.

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DNA damages and changes in proliferating activity of keratinocytes in rat dorsal skin exposed to a high-dose ultraviolet B (UVB) irradiation were examined immunohistochemically. The number of cells that express cyclobutane pyrimidine dimer (CPD), which represents UVB-induced DNA damage, started to increase at 1 h after irradiation, peaked at 3 h and thereafter decreased rapidly. Bromodeoxyuridine (BrdU)-labeling index (LI) was lower than that in control group from 1 to 24 h after irradiation, and it returned to the control level at 36 h. Topoisomerase II α (TIIα)-LI was significantly lower than that in control group from 1 to 12 h and showed the lowest value at 9 h. Thereafter, it increased and showed higher values than that in control group at 24, 36 and 72 h. These results suggest that DNA damages in survival basal keratinocytes may be repaired during 12 to 24 h and cell growth of keratinocytes may be arrested at least at 24 h.

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