Giant cell tumor of bone in an aged Fischer 344 rat

A giant cell tumor (GCT) was detected on the distal end of the femur in a 98-wk-old male Fischer 344 rat. The yellowish white mass had expanded, compressing adjacent muscle tissues. The tumor had an osteolytic and relatively homogeneous appearance and was composed of multinuclear giant cells scattered in a mass of mononuclear stromal cells. No osteoid tissue formation was observed. The tumor cells were strongly immunoreactive for ED-1 and some were also positive for alpha-smooth muscle actin, suggesting that the tumor originated from the monocyte/macrophage lineage showing myofibroblastic differentiation. This is the first report concerning spontaneous GCT of bone in a rat.

Effects of vitamin K2 (menatetrenone) on atherosclerosis and blood coagulation in hypercholesterolemic rabbits

Gamma-Carboxyglutamic acid (Gla)-containing protein, synthesized in the presence of vitamin K, has been found in atherogenic plaques, but the pharmacological effect of vitamin K on atherosclerosis is unclear. We examined whether vitamin K2 (menatetrenone) could affect the progression of both atherosclerosis and hypercoagulability in hypercholesterolemic rabbits. Vitamin K2 in daily doses of 1, 10 and 100 mg/kg was given with a 0.5% cholesterol diet for 10 weeks to 8 rabbits each. The plasma levels of total-cholesterol in the vitamin K2-treated groups were clearly lower than that of the hypercholesterolemic control group. The excessive dose of vitamin K2, even at the high dose of 100 mg/kg/day for 10 weeks, did not accelerate the progression of atherosclerosis and did not promote the coagulative tendency in the rabbits. In contrast, the vitamin K2 treatment (1 to 10 mg/kg/day) suppressed the progression of atherosclerotic plaques, intima-thickening and pulmonary atherosclerosis, the increase of ester-cholesterol deposition in the aorta, and both the elevation in plasma factor X level and increase in Hepaplastin test value in the rabbits. These results indicate that the pharmacological dose of vitamin K2 prevents both the progression of atherosclerosis and the coagulative tendency by reducing the total-cholesterol, lipid peroxidation and factor X activity in plasma, and the ester-cholesterol deposition in the aorta in hypercholesterolemic rabbits.

Pituitary carcinoma of pars distalis as a common neoplasm in Fischer-344 rats

The incidence of invasive spontaneous pituitary carcinomas in Fischer-344 rats were studied. The pituitaries were examined histopathologically together with surrounding tissues including sphenoid bone. The incidence of carcinoma was higher than that previously reported in Fischer-344 rats. All the carcinomas observed in this study showed evidence of local invasion either ventrally into bone and bone marrow or laterally into peripheral nerves and blood vessels. No dorsal infiltration into the brain was recognized. Pituitary carcinoma with local invasion is a relatively common neoplasm when examined histopathologically together with the surrounding tissues.

Induction and immunohistochemical localization of cytochrome P-450 PCN by non-steroidal compound, in rat liver microsomes

Induction of cytochrome P-450 PCN (P-450 PCN) by non-steroidal compound, M79193 (cyclohexane spiro-2,6-chloro-1'-(3-dimethyl-aminopropyl) spiro(chroman-4,4'-imidazolidine)-2',5'-dione], was investigated in both sexes of rats. The immunohistochemical localization of P-450 PCN was also studied in liver lobules of untreated and M79193-treated male rats. Immunoblot analysis of rat liver microsomes with anti-P-450 PCN indicated that the amount of P-450 PCN increased 5- to 7-fold by the treatment with M79193, but no increase was observed in P-450 PB-1 (P450IIB1) or P-450 MC-1 (P-450IA1). P-450 PCN was uniformly distributed in liver lobule of untreated rats, and was significantly increased by the treatment with M79193 in both the periportal and pericentral regions of the lobules.

Modulation of diethylnitrosamine-initiated placental glutathione S-transferase positive preneoplastic and neoplastic lesions by clofibrate, a hepatic peroxisome proliferator

The effect of clofibrate (CF) on proliferation of diethylnitrosamine (DEN)-initiated glutathione S-transferase placental form (GST-P)-positive preneoplastic and neoplastic lesions as studied in male F344 rats. Animals were given a single i.p. injection of 200 mg/kg body weight of DEN, and then from 2 weeks later were given a diet containing 0.3% CF (group 1), or no supplement (group 2) until week 64. Group 3 received an injection of 0.9% NaCl instead of DEN and then a diet containing 0.3% CF, like group 1. Animals in all groups were subjected to partial hepatectomy at week 3 and killed at weeks 8, 20, 32, 49 or 64. The results showed that development of GST-P-positive lesions was significantly less in group 1 than in group 2 from week 8 (P less than 0.05). However, in group 1, morphologically distinguishable GST-P-negative preneoplastic lesions increased from week 20 (P less than 0.05), and the total number of GST-P-positive and -negative lesions was significantly greater than that in group 2 from week 32 (P less than 0.05). The induction of hepatocellular carcinoma (HCC) was greater in group 1 than in group 2 from week 49. All the HCCs induced in group 2 were GST-P-positive, whereas 38.9% (7/18) of those in group 1 were GST-P-negative. In group 3, only a few GST-P-positive and/or -negative preneoplastic lesions developed by week 64. These results suggest that CF has tumor-promoting activity, and that GST-P-positive cells induced by DEN changed to GST-P-negative cells on subsequent treatment with CF.

Strain differences in N-butyl-N-(4-hydroxybutyl)nitrosamine bladder carcinogenesis in rats

Differences in susceptibility of the urinary bladder epithelium to N-butyl-N-(4-hydroxybutyl)-nitrosamine (BBN) in various strains were examined. In experiment 1, 5 strains of male rats were given 0.025% BBN in the drinking water for 8 weeks followed by drinking water without BBN for 32 weeks. Analbuminemic rats (NAR) and ACI rats had high incidences of urinary bladder lesions (papillary or nodular hyperplasia, papilloma and carcinoma), F344 and Wistar rats had low incidences, and Sprague-Dawley (SD) rats showed an intermediate incidence. Carcinoma area was largest in NAR rats followed in decreasing order by SD, ACI and F344 rats. The extent of tumor invasion was higher in NAR and ACI rats than in SD rats. In experiment 2, the 5 strains of male rats were administered 0.025% BBN in the drinking water. Some rats from each group were killed after each of weeks 4 and 8. The urinary bladder of ACI and NAR rats given BBN had the most marked lesions observed by scanning electron microscopy, with less marked changes in SD rats. F344 and Wistar rats showed the weakest response. Cytochrome P-450 content of the liver in ACI rats treated with BBN for 4 weeks was significantly higher than those of controls. Cytochrome P-450 and cytochrome b5 contents of the control and BBN-treated rats were significantly higher in ACI and SD rats than in Wistar, F344 or NAR rats. These results indicate that there are strain differences in the urinary bladder response to BBN.

Different dose-response relationships in the induction of different types of colonic tumors in Wistar rats by 1,2-dimethylhydrazine

Four groups of 21 male Wistar rats were given weekly subcutaneous injections of 1,2-dimethylhydrazine at a dose of 20 mg/kg body weight for 2, 4, 6 and 8 weeks, respectively, and 7 animals of each group were killed in weeks 24, 32 and 40. This treatment induced a clear dose-related increase in the total number of colonic carcinomas. The number of tubular adenocarcinomas, which were mostly located in the descending colon, was clearly dose-related, whereas the number of signet ring cell carcinomas, which developed in the ascending colon, was apparently dose-independent.

Differences in susceptibility to sodium saccharin among various strains of rats and other animal species

Differences in the susceptibilities to sodium saccharin of the urinary bladder epithelium in various strains of rats and other animal species were examined. In Experiment 1, male ACI, Wistar, F344 and Sprague-Dawley rats were administered 5.0% sodium saccharin in the diet for 52 weeks. Rats were killed after weeks 12, 24, 36 and 52. In ACI rats, sodium saccharin induced not only preneoplastic lesions of the urinary bladder, but also tumors. However, in other strains it did not. The urinary bladder of ACI rats given sodium saccharin had the most marked lesions under scanning electron microscopy, with less marked changes in Wistar and F344 rats. Sprague-Dawley rats were resistant to sodium saccharin. In Experiment 2, male F344 rats, B6C3F1 mice, Syrian golden hamsters, and Hartley guinea pigs were given 5.0% sodium saccharin in the diet for 20 weeks. The animals were sacrificed sequentially. Rats developed urinary bladder lesions during the experiment, as detected by light microscopy and scanning electron microscopy. Increased DNA synthesis of the urinary bladder epithelium was detected in rats by autoradiography. However, mice, hamsters and guinea pigs were resistant to sodium saccharin. These results indicate that there are strain and species differences in the urinary bladder response to sodium saccharin.

Effect of partial cystectomy on the induction of pre-neoplastic lesions in rat bladder initiated with N-butyl-N-(4-hydroxybutyl)nitrosamine followed by bladder carcinogens and promoters

The effect of partial cystectomy on the occurrence of pre-neoplastic lesions, papillary or nodular hyperplasia (PN hyperplasia), of the bladder in male F344 rats was studied in an experiment in which bladder carcinogens and promoters were given to the rats after initiation with BBN. The bladder carcinogens tested were N-ethyl-N-(4-hydroxybutyl)nitrosamine (EHBN) and N-4[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) and the bladder promoters were sodium saccharin, sodium cyclamate, and DL-tryptophan. Partial cystectomy significantly decreased the occurrence of PN hyperplasia in rats treated with EHBN and tended to inhibit that in rats given saccharin or tryptophan. Thus partial cystectomy inhibited rather than enhanced the induction of PN hyperplasia.

Region-specific patterns of mucin reaction demonstrated by paradoxical concanavalin A-staining in normal colonic epithelium and in colorectal cancers induced in rats by 1,2-dimethylhydrazine

The histochemistry of mucin in normal large intestine and in experimental colorectal cancers induced in Wistar rats with 1,2-dimethylhydrazine was analyzed by modifications of the concanavalin A-horseradish peroxidase method (paradoxical concanavalin A-staining) and high-iron diamine-Alcian blue (pH 2.5) staining (HID-AB). Quantitative analysis of each mucin reaction was done by the use of an image analyzer. Regional variations in the percentage area of "labile class III mucin" were 1 to 50% in the distal colon and 50 to 90% in the proximal colon. Regional variations in the percentage area of sulfated sialomucin were 80 approximately 100% in the distal colon and under 20% in the proximal colon. The percentage area of "labile class III mucin" in primary colorectal cancers showed region-specific variation and that in metastatic colorectal cancers also showed similar region-specific variation of colorectal mucosa where primary tumors were located. In contrast, there were no region-specific mucin reactions for sulfated sialomucin in almost all primary and metastatic colorectal cancers.

A sequential quantitative study of the reversibility or irreversibility of liver hyperplastic nodules in rats exposed to hepatocarcinogens

The behavior of hyperplastic nodules following an in vivo short-term screening test for hepatocarcinogens was studied. Rats were injected ip with 200 mg/kg body weight of diethylnitrosamine (DEN), given basal diet containing 200 ppm of N-2-fluorenylacetamide (2-FAA) (group 1), 1000 ppm of the alpha-isomer of 1,2,3,4,5,6,-hexachlorocyclohexane (alpha-BHC) (group 2) or basal diet (group 3) from week 3 to week 8, and then given basal diet and tap water. They were subjected to partial hepatectomy at the end of week 3. Animals were killed at weeks 4, 6, 8, 10, 20, 30, 40, and 50. A significant disappearance of hyperplastic nodules following the cessation of carcinogen treatment was observed in group 1, but was not evident in groups 2 and 3. With gamma-glutamyltranspeptidase (GGTase) as a positive marker and adenosine triphosphatase (ATPase) as a negative marker, hyperplastic nodules were classified into 3 different phenotypic categories, i.e., (1) GGTase-positive and ATPase-negative, (2) GGTase-positive, and (3) ATPase-negative. The percentages of GGTase-positive and ATPase-negative hyperplastic nodules were almost 80 approximately 90% in group 1 and 70 approximately 80% in groups 2 and 3. Some of the hyperplastic nodules were necrotic from week 8 in groups 1 and 2, and from week 20 in group 3. Subsequently, the numbers of necrotic hyperplastic nodules increased with time. Hepatocellular carcinomas were found at weeks 30, 40, and 50 in group 1, and at weeks 40 and 50 in group 2. Significantly higher incidences of cancer were found in group 1 than in group 2. The hepatocellular carcinomas were also classified enzyme-histochemically into 3 different phenotypic categories as for hyperplastic nodules, but the percentage (20%) of GGTase-positive and ATPase-negative hepatocellular carcinomas was significantly lower than that (70 approximately 90%) of GGTase-positive and ATPase-negative hyperplastic nodules in each group.