The initiation effects of the novel heterocyclic amine, 9-(4’-aminophenyl)-9 H-pyrido[3,4-b]indole (aminophenylnorharman, APNH) on carcinogenesis were investigated in an in vivo five-week assay system. A total of 65 F344 male rats, 7 weeks old, were subjected to two-thirds partial hepatectomy (PH) and administered APNH intragastrically at doses of 10, 3, 1, and 0 mg/kg body weight (b.w.) (groups 1, 2, 3, and 5, respectively) twice, at 12 and 30 h after PH. Then the rats were fed diet containing 0.015% 2-acetylaminofluorene and given a single dose of CCl₄ at week 3. Group 4 received 10 mg/kg b.w. APNH without 2-AAF and CCl₄ treatment. Analysis of glutathione S-transferase placental form (GST-P) positive foci in liver sections revealed areas in groups 1, 2, and 3 to be increased in a dose dependent manner to 3.43 ± 1.38, 2.18 ± 1.41, and 0.94 ± 0.51 mm ²/cm², respectively, compared with the control value (0.22 ± 0.20 in group 5) (groups 1-3 vs. group 5, P<0.001; groups 1 vs. 2, P<0.05; groups 2 vs. 3, P<0.01). The numbers of GST-P positive foci in groups 1, 2, and 3 were, 19.34 ± 7.20, 22.75 ± 8.16 and 13.61 ± 4.92 foci/cm² and were significantly higher than in the controls (2.67 ± 1.27 in group 5). These data suggested initiation activity of APNH. Furthermore, the area of GST-P positive foci in group 4 was increased to 0.59 ± 0.31 mm²/cm² (P<0.05 vs. group 5) indicating promoting activity of APNH for hepatotumorigenesis. In conclusion, the above results provide evidence of initiating carcinogenic potential for APNH.

View full abstract

N-Ethyl-N-nitrosourea (ENU) is known to induce a wide spectrum of tumors in various organs in adult experimental animals. The renal and neuroectdermal tumors are known as representative lesions by transplacental exposure to ENU in the offspring animals. However, little information is available about tumorigenicity in other organs and tissues in offspring when their mother animals are treated with ENU during gestation. Thus, the purpose of this study was to evaluate the effects of transplacentally treated-ENU on the various organ tumorigenicity in offspring rats. ENU was injected intraperitoneally to female Sprague-Dawley (SD) rats with a single dose at 50 mg/kg on the 18th day of gestation. After spontaneous delivery, 44 male and 64 female offspring, including moribund and dead after birth, were subjected to the evaluation of carcinogenicity. At the 54th to 55th week of birth, all surviving offspring were euthanized under ether anesthesia for histopathology. ENU showed a wide spectrum of transplacental tumorgenesis in the kidney, central nervous system, peripheral nervous system, thyroid gland, and teeth. The tumors of the thyroid and teeth were characteristic in particular in this study. The thyroid tumors included various histopathological types (follicular cell adenoma and adenocarcinoma, C-cell adenoma and carcinoma, squamous cell carcinoma, and fibroma). As a characteristic tumor of the teeth, ameloblastic odontoma was detected in 3 (one male and 2 females) of 108 offspring. In conclusion, the results indicate that the transplacental exposure of a single ENU dose induces various types of thyroid gland tumors and odontogenic tumors as well as the renal or neuroectodermal tumors in rat offspring.

View full abstract

The carcinogenic potential of long term exposure to 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) was investigated in severe combined immunodeficiency (SCID) mice. A total of 130 female SCID mice, 7 weeks old, were administered 0 (45 mice) or 300 ppm IQ (85 mice) in the diet for 78 weeks. IQ-treatment and control groups were sacrificed at weeks 32, 52, and 78, and examined for tumorigenicity in the colon and other organs. The survival rate was 46% (control group) and 50% (IQ-treatment group) at the termination of the experiment 78 weeks. Tumors in the liver were significantly increased in the 300 ppm-IQ treated mice. Concerning colon cancer development, aberrant crypt foci (ACF), putative pre-cancerous lesions of the colon, were found in all IQ-treated mice at 32, 52, and 78 weeks. The number of ACF was increased in relation to the duration of exposure. The major induction site of ACF was the proximal colon, however, no colon tumors were observed except for an inflammatory polyp. One of the intestinal microflora, Lactobacillus, which was reported to detoxify IQ, was detected in IQ-treated and non-treated mice. Thus IQ showed hepatocarcinogenicity in SCID mice of the present study, but not colon carcinogenicity.

View full abstract

Hypocatalasemic mice (C^b_s) were examined for their life span and compared to C3H mice with reference to oxidase enzyme activity and spontaneous tumor development. N¹-methylnicotinamice oxidase, xanthine oxidase (XO), xanthine dehydrogenase (XDH), and XO+XDH activities in 8 week-old male C^b_s mice were decreased as compared to the C3H counterparts. On the other hand, benzaldehyde oxidase in both sexes and xanthine dehydrogenase activity in females were significantly elevated as compared to the C3H. The total tumor incidence, number of tumors per mouse, liver tumors, and other tumor induction were significantly greater in as compared with until 499 days group in both sexes (P<0.01). The total incidence of tumors and incidence of liver tumors were not significantly different between the two strains in both sexes. The number of tumors per animal in C3H females and incidence of sarcoma in both sexes were significantly decreased as compared with the C^b_s case but the numbers of liver tumor per animal and ovarian tumors were significantly greater.

View full abstract

The purpose of this study was to make a new experimental colon ulcer model that is independent on chemicals and to assess the ulcerations and subsequent changes at various time points. Histological and mucin histochemical assessment of colon ulcers and associated regeneration induced in Wistar rats using a rapid freezing method was performed. Male rats were fasted 48 hours prior to surgery. A lower midline incision of the abdominal wall was made and a stainless steel rod, kept in dry ice-acetone, was applied to the serosal surface of the colon for 4 seconds, twice, with a 5 seconds interval. The rats were sacrificed at various time points thereafter. Histological examination showed the ulcers to be accompanied by acute inflammation, and healing was complete in almost all cases at day 24. In the ascending colon, sulfomucin was found in goblet cells in the upper half of the normal crypts, and sialomucin was found in the lower half. In the descending colon, sulfomucin was apparent almost throughout normal crypts remote from ulcers. Sialomucin dominant regenerative crypts were found near areas of ulceration in both the ascending and descending colon. Thus, the simple freezing method can produce colon ulcers, and the sialomucin that was predominant in regenerative crypts may have an important role for regeneration.

View full abstract

1,3-dichoro-1,2-propanediol (1,3-DCP) is a contaminant of acid-hydrolyzed vegetable protein and a chlorinated compound used in the fabrication of industrial products such as hard resins, celluloid or paints. Several reports have suggested that chronic exposure to 1,3-DCP could produce neurotoxicity in vitro or in neurobehavioral aspects of experimental animals. The present study further explored the in vitro neurotoxic effects of 0.1-100 μM 1,3-DCP on PC12 and N18D3 cell lines. In addition, to investigate the effects of repeated ingestions of 1,3-DCP on neurobehavioral impairments parameters in rats, locomotor activity and landing foot splay tests were preformed, following the treatment of 1,3-DCP at doses of 10, 20, and 30 mg/kg/day for 11 weeks. We demonstrated that no significant neurotoxic effects in vitro and in neurobehavior were observed in the 1,3-DCP-treated rats compared to saline-treated control rats, whereas, acrylamide, used as a positive control, induced significant increases of all neurobehavioral deficit parameters in both male and female rats. On the other hand, body weight gain was significantly decreased in high dose 1,3-DCP-treated male rats as well as in acrylamide-treated rats. Taken together, these results suggest that 1,3-DCP does not produce in vitro neurotoxicity and the neuromotor deficits, at the dose levels of this study.

View full abstract

Hepatocytes with 2 or more nuclei are seen at a certain percentage in the normal rat liver and show changes according to mitogenic stimuli including regeneration from injury. In the present study, analysis of nuclearity and cell kinetics of hepatocytes was conducted by combining cytocentrifuge preparations of isolated hepatocytes and bromodeoxyuridine (BrdU) cumulative labeling in 6-week-old female Sprague-Dawely rats at periods of 7, 14, and 28 days, respectively. In cytocentrifuge preparations, hepatocytes with intact cytoplasms were obtained, from which nuclearity was clearly and readily defined. The majority of hepatocytes were mononuclear or binuclear. The percentage of cells with 3 or more nuclei was very low. The percentages of each nuclearity class were similar throughout all labeling periods. The ratio of mononuclear to binuclear cells was approximately 6:4. The BrdU labeling index per total nuclei increased according to the labeling period. For the labeling index of each cell type, the number of BrdU positive mononuclear cells and binuclear cells with 2 positive nuclei (WP) increased according to the labeling period at a ratio of approximately 3:1. In the binuclear cells, WP cells and cells with 2 negative nuclei were dominant, whereas, cells with 1 positive and 1 negative nuclei were very rare. From these observations, the present method was thought to be well suited for analysis of nuclearity and cell kinetics in hepatocytes and may be useful for analysis of changes in the liver induced by various compounds.

View full abstract

We encountered a case of nonsuppurative meningoencephalitis with neurologic signs of depression, tremor, and ataxic gait in a 15-month-old vaccinated male beagle dog. Hematologic and biochemical parameters indicated no significant changes except for some findings suggesting dehydration and anorexia. Microscopically, the main features consisted of nonsuppurative meningoencephalitis with disseminated foci of perivascular cuffing of mononuclear cell in the leptomeninges and gray matter of the cerebrum and cerebellum. Some glial nodules, which were characterized by accumulation of microglia, were seen in the molecular layer of the cerebellum. Demyelination and neuronal necrosis were not observed in the central nervous system. Although the dog had a slightly elevated serum antibody titer to canine distemper virus (CDV), neither viral inclusion bodies, nor CDV antigens were detected in the brain tissue. The cause of disease in this case remained unclear.

View full abstract

A 20-month-old female beagle showed a pancreatic nesidioblastosis with a curious proliferation of islet hormone-positive cells. These cells were characterized by a tubular or columnar pattern, occasionally with a rosette-like structure. Immunohistochemistry revealed that they were positive to insulin and chromogranin A and weakly-positive to glucagon and somatostatin in the cytoplasm, but negative for cytokeratin. PCNA- positive cells were also scattered among these proliferating cells. The present case appears to be a specific type of nesidioblastosis accompanied by a proliferation of previously unidentified islet-cells in a beagle.

View full abstract

Nitrofurazone (NF), a well-known testicular toxicant, was given to rats at 500 mg/kg to characterize its effects on the liver and adrenal gland. Marked degenerative or necrotic changes were seen in the adrenal gland, and, to a lesser extent, in the liver. The adrenal gland displayed coagulative necrosis involving the cortex, especially the zonae fasciculata and reticularis, which was apparent as early as at 1.5 h postdose and had spread to the whole area by 3 h. Hepatic changes became clear at 3 h, but the degree and the extent of the lesion were far less than in the adrenal gland. The lesions consisted of foci of hepatocyte degeneration and necrosis, which were exacerbated by diethyl maleate (DEM), a hepatic glutathione-depleting agent. The results suggest that NF induces changes possibly by a mechanism which involves free radical production.

View full abstract

Exposure to radiation during brain development stage cause microcephaly or mental retardation. Although X- and gamma-rays induced cerebral hypoplasia in rodents has been well characterized, little is known about such effects of neutrons. To examine the effects of prenatal exposure to neutrons on the development of brain and other organs, both male and female B6C3F1 mice were irradiated with fast neutrons (0.1, 0.2, 0.5, 1 Gy) or gamma-rays (0.8, 1.5 Gy) at embryonic day 13.5, and the animals were examined histopathologically 56 days after birth. Both types of radiation mainly caused hypoplasia of the cerebral cortex and lowered brain absolute weight. No sex differences were seen. These changes were remarkable in each highest dose group. The weight loss of the brain was noted at the lowest dose group of neutrons. In addition, the weight loss of the thymus, atrophy of the seminiferous tubules, and a decrease in follicles of the ovary were also noted in the higher dose groups of neutrons and gamma-rays. The degrees of these changes were larger for neutrons.

View full abstract