Occurrence, Histopathological Findings, and Molecular Identification of Pathogenic Eimeria Infections in Rabbits (Mammalia: Lagomorpha) in Japan.

PURPOSE: Eimeria spp. are commonly found among rabbits (Mammalia: Lagomorpha) worldwide. Among the 11 Eimeria species, several are highly virulent, including E. intestinalis and E. flavescens, which cause intestinal coccidiosis, and E. stiedae, which causes hepatic coccidiosis. Unlike other countries, the occurrence of Eimeria infections in rabbits in Japan remains unknown, except for one reported case of natural infection. METHODS: We surveyed Eimeria infections in clinically affected rabbits over the past approximately 10 years at Livestock Hygiene Centers in 42 prefectures. A total of 16 tissue samples (14 liver, 1 ileum, and 1 cecum) were collected from 15 rabbits in 6 prefectures. RESULTS: Characteristic histopathologic findings were observed, especially around the bile ducts, depending on the developmental stages of the parasites. Eimeria stiedae and E. flavescens were successfully identified by PCR and sequencing analyses in 5 liver samples and 1 cecum sample, respectively. CONCLUSION: Our results could enhance understanding of infection with Eimeria spp. in rabbits in Japan and contribute to pathological or molecular diagnoses.

Molecular identification of Eimeria species in liver and feces of naturally infected rabbits in Japan.

Among the 11 species of Eimeria in rabbits, some of which are known to be pathogenic and cause enteritis, E. stiedae induces severe liver lesions resulting in elevated mortality. Unlike in other countries, the incidence and prevalence of the parasites in rabbits have not been reported in Japan. In the present study, we histopathologically analyzed hepatic coccidiosis in a rabbit and attempted several primers to genetically identify the parasites and investigated the prevalence of Eimeria species at the same farm. In the liver of the affected rabbit, we observed fibrosis and edema around multiple bile ducts and epithelial cell hyperplasia of the bile ducts. Large numbers of developing parasites of Eimeria spp., mainly oocysts, were present in the bile ducts. PCR and sequencing analyses with the published primers for Cyclospora and Eimeria spp. were used to successfully identify the parasites in the liver as E. stiedae. The oocysts of Eimeria spp. were detected in 13 out of 20 fecal samples collected from other rabbits at the farm, and five Eimeria spp. (E. perforans, E. flavescens, E. exigua, E. magna, and E. vejdovskyi) were genetically confirmed. Our results provide the first indication that Eimeria spp., including highly pathogenic species, are present in Japan and the primer set used herein can be a useful tool for the identification of rabbit Eimeria spp.

Horseradish extract promotes urinary bladder carcinogenesis when administered to F344 rats in drinking water.

Horseradish extract (HRE), consisting mainly of a mixture of allyl isothiocyanate and other isothiocyanates, has been used as a food additive. To evaluate the potential hazards of HRE, a 104-week chronic study, a 2-week analysis of cell proliferation in the urinary bladder and a medium-term promotion bioassay of HRE were conducted with administration at concentrations of up to 0.04% HRE in the drinking water to male F344 rats. In the 104-week chronic study with 32 male rats per group, no treatment-related increases in the incidences of neoplastic lesions in any organ, including urinary bladder, were observed, except for simple hyperplasia in the urinary bladder in rats treated with HRE at concentrations of more than 0.01% (5.0 mg kg-1 body weight day-1 ). In the promotion study, HRE treatment after N-butyl-N-(4-hydroxybutyl)nitrosamine initiation caused a clear increase in papillary or nodular hyperplasia, papilloma, and urothelial carcinoma of the urinary bladder in the groups given HRE for 13 weeks at doses higher than 0.005%, 0.01%, and 0.04% (2.7, 5.4 and 20.5 mg kg-1 body weight day-1 ), respectively. In the 2-week cell proliferation analysis, treatment with HRE at concentrations greater than 0.005% (3.9 mg kg-1 body weight day-1 ) caused transient increases in 5-bromo-2'-deoxyuridine labeling indices in the urothelium. Although clear tumor induction was not observed, administration of relatively low-dose HRE increased cell proliferation in the urothelium and exerted obvious promoting effects on rat urinary bladder carcinogenesis. Further studies are needed to elucidate the mode of action of HRE in the rat urinary bladder to facilitate data extrapolation from the present study and provide insights into risk assessment. Copyright © 2017 John Wiley & Sons, Ltd.

Repeated-dose liver and gastrointestinal tract micronucleus assays for quinoline in rats.

Repeated-dose liver, bone marrow, and gastrointestinal tract micronucleus assays that use young adult rats were evaluated in a collaborative study that was organized by the Japanese Environmental Mutagen Society-Mammalian Mutagenicity Study Group. A genotoxic hepatocarcinogen quinoline was orally administered to independent groups of five Crl:CD (SD) male rats at doses of 30, 60 and 120mg/kg for 14 days and at doses of 15, 30 and 60mg/kg for 28 days. After treatment, the livers were harvested and hepatocytes were isolated by collagenase treatment. The frequency of micronucleated hepatocytes (MNHEPs) increased significantly in both the 14- and 28-day repeated dose studies. However, the frequency of micronucleated cells did not increase in the bone marrow, stomach or colon cells, which were not quinoline-induced carcinogenic target organs in the rats. These results indicate that a repeated-dose liver micronucleus (RDLMN) assay using young adult rats is capable of detecting the genotoxicity of quinoline at the target organ of carcinogenicity. The protocol may also permit the integration of the genotoxic endpoint into general repeated-dose toxicity studies. Furthermore, we elucidated that conducting the micronucleus assay in multiple organs could potentially assess organ specificity.

High susceptibility of heterozygous (+/fa) lean Zucker rats to 7,12-dimethylbenz(a)anthracene-induced mammary carcinogenesis.

Susceptibility to 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary carcinogenesis was investigated in lean Zucker (+/fa) rats carrying one mutated leptin receptor gene and wild-type controls (+/+). Rats with both genotypes were given a single DMBA administration and divided into two groups, one group was fed on basal diet mixed with 10% corn oil and the other was fed on basal diet alone. The minimum latency period of palpable carcinomas in +/fa rats of both groups was 8 weeks following DMBA treatment, in contrast to the 11-12 weeks in +/+. The incidence and multiplicity of carcinomas increased or showed a tendency for increase in the early stages in +/fa rats of both groups as compared to the +/+ counterparts. The volumes of carcinomas showed a tendency to increase in the corn oil diet groups of both genotypes. The major histopathological phenotype of carcinomas in all groups was well-differentiated without distinct atypia (multiplicity, 0.69-1.09/rat), but moderately/poorly differentiated carcinomas with atypia were also found, predominantly in +/fa rats (0.09-0.21). These latter tumors were characterized by elevated ERK activity but not estrogen receptor expression. Serum leptin concentrations in +/fa rats at 7 weeks of age were higher than those in +/+ and were elevated by the corn oil diet; however, no obvious change was detected in other serum parameters examined. In conclusion, +/fa rats proved more susceptible to DMBA-induced mammary carcinogenesis than +/+ controls, and hyperleptinemia was suggested to contribute to tumor growth as well as to susceptibility to tumorigenesis and more aggressive phenotypes in Zucker lean rats.

Female heterozygous (+/fa) Zucker rats as a novel leptin-related mammary carcinogenesis model.

The homozygous mutant fatty Zucker rat (fa/fa) is the prominent model for the research of obesity, one of the most well-known risk factor of postmenopausal mammary cancer. But the usage as a mammary gland carcinogenesis model is considered to be restricted due to the hypoplasia of mammary gland. In the present study, to find the validity of heterozygous mutant (+/fa) lean Zucker rats as a new leptin-related mammary carcinogenesis model, we examined whether the number of terminal end buds of mammary gland, the serum biochemistry, leptin concentration in serum and adipose tissue are changed in 7-week-old female +/+, +/fa and fa/fa rats, and whether these changes and leptin, TNF-α and VEGF mRNA expression in adipose tissue of +/+ and +/fa rats are influenced by 10% corn oil diet for 5 weeks. We confirmed that mild hyperleptinemia was more pronounced in 7-week-old +/fa as compared with wild type (+/+) and hypoplasia of mammary glands characterized by fewer numbers of terminal end buds in fa/fa was not observed in +/fa. With 10% corn oil diet, leptin mRNA expression in adipose tissue showed increasing tendency both in +/fa and +/+. Comparing with +/+, adipose tissue in +/fa treated with 10% corn oil diet was found to be significantly increased in the concentration of leptin protein and tended to be elevated expression of TNF-α mRNA. These results suggest that +/fa with 10% corn oil diet may be a useful model for investigation of the participation of leptin and TNF-α in mammary gland carcinogenesis.

Prostaglandin synthases influence thyroid follicular cell proliferation but not carcinogenesis in rats initiated with N-bis(2-hydroxypropyl)nitrosamine.

To clarify roles of prostaglandin synthases in rat thyroid follicular carcinogenesis, effects of an antithyroid agent, sulfadimethoxine (SDM), and two prostaglandin H synthase (COX) inhibitors, indomethacin and nimesulide, on prostaglandin synthase expression, follicular cell proliferation, and tumor induction in thyroids of rats with or without N-bis(2-hydroxypropyl)nitrosamine (DHPN) initiation were examined. In experiment 1, F344 male rats were allowed free access to drinking water containing SDM (0.1%), SDM + indomethacin (0.0025% in diet), or SDM + nimesulide (0.04% in diet) for 4 weeks. Both COX inhibitors suppressed goitrogenic activity of SDM, but they did not significantly affect microsomal prostaglandin E synthase-2 (mPGES-2) expression levels enhanced by SDM. In experiment 2, all rats received an injection of DHPN (2800 mg/kg body weight), and starting 1 week later, they were treated as in experiment 1 for 4 or 10 weeks. Cell proliferation was suppressed or showed a tendency for suppression by the COX inhibitors in the follicular preneoplastic/neoplastic lesions and surrounding parenchyma, and this was obviously thyroid stimulating hormone independent at least at week 4. However, neither of the COX inhibitors altered the incidence or multiplicity of preneoplastic/neoplastic lesions. Immunohistochemistry revealed significant reduction and elevation of COX-2 and mPGES-2 expression, respectively, in the lesions, but these were also not changed by the COX inhibitors. These results suggest that COX-2 and PGES, and in turn PGE(2), might play important roles in follicular cell proliferation but do not affect tumor induction in this rat thyroid carcinogenesis model. Further studies are needed to clarify the significance of the reduction of COX-2 expression in preneoplastic/neoplastic lesions.

Juvenile rats do not exhibit elevated sensitivity to acrylamide toxicity after oral administration for 12 weeks.

Acrylamide (AA), a neurotoxic, testicular toxic, genotoxic and carcinogenic chemical, has been reported to be formed in processed food, and sensitivity to AA intoxication in childhood is a concern. In the present study, to clarify the general toxicological profile of AA in juvenile rats, subchronic toxicity was evaluated in F344 rats administered AA in the drinking water at 0 (control), 10, 20 and 40 ppm, presented to the dams (three per group) immediately after the birth of their litters, through lactation (3 weeks), and directly to the offspring in their drinking water after weaning for a further 9 weeks (12 weeks total). Treatment with AA caused a decrease in body weights in 20 and 40 ppm F(1) females, compared with the controls. Average AA intake throughout the treatment period for the 10, 20 and 40 ppm groups after weaning was equivalent to 1.0, 2.1 and 4.4 mg kg(-1) body weight per day, respectively, in males and 1.2, 2.5 and 4.9 mg kg(-1) body weight per day, respectively, in females. No toxicologically significant organ weight changes were observed. AA-induced histopathological changes were limited to focal degeneration and necrosis of the seminiferous epithelium in the testes and desquamated epithelium in the ducts of epididymides, noted only in 40 ppm males. Taken together with previous reports, juvenile rats are not necessarily more susceptible to AA-induced toxicity as compared with young adults.

In vivo genotoxicity study of titanium dioxide nanoparticles using comet assay following intratracheal instillation in rats.

Titanium dioxide (TiO2) is widely used as a white pigment in paints, plastics, inks, paper, creams, cosmetics, drugs and foods. In the present study, the genotoxicity of anatase TiO2 nanoparticles was evaluated in vivo using the comet assay after a single or repeated intratracheal instillation in rats. The nanoparticles were instilled intratracheally at a dosage of 1.0 or 5.0 mg/kg body weight (single instillation group) and 0.2 or 1.0 mg/kg body weight once a week for 5 weeks (repeated instillation group) into male Sprague-Dawley rats. A positive control, ethyl methanesulfonate (EMS) at 500 mg/kg, was administered orally 3 h prior to dissection. Histopathologically, macrophages and neutrophils were detected in the alveolus of the lung in the 1.0 and 5.0 mg/kg TiO2 groups. In the comet assay, there was no increase in % tail DNA in any of the TiO2 groups. In the EMS group, there was a significant increase in % tail DNA compared with the negative control group. TiO2 nanoparticles in the anatase crystal phase are not genotoxic following intratracheal instillation in rats.

Acrylamide genotoxicity in young versus adult gpt delta male rats.

The recent discovery that the potent carcinogen acrylamide (AA) is present in a variety of fried and baked foods raises health concerns, particularly for children, because AA is relatively high in child-favoured foods such as potato chips and French fries. To compare the susceptibility to AA-induced genotoxicity of young versus adult animals, we treated 3- and 11-week-old male gpt delta transgenic F344 rats with 0, 20, 40 or 80 p.p.m. AA via drinking water for 4 weeks and then examined genotoxicity in the bone marrow, liver and testis. We also analysed the level of N7-(2-carbamoyl-2-hydroxyethyl)-guanine (N7-GA-Gua), the major DNA adduct induced by AA, in the liver, testis and mammary gland. At 40 and 80 p.p.m., both age groups yield similar results in the comet assay in liver; but at 80 p.p.m., the bone marrow micronucleus frequency and the gpt-mutant frequency in testis increased significantly only in the young rats, and N7-GA-Gua adducts in the testis was significantly higher in the young rats. These results imply that young rats are more susceptible than adult rats to AA-induced testicular genotoxicity.

Uterine Carcinosarcoma in a 2-year-old Female Wistar Hannover GALAS Rat.

Carcinosarcomas are rare tumors in humans as well as rats and most commonly occur in the uterus. Recently, we observed a case of incidental carcinosarcoma of the uterus in a female Wistar Hannover GALAS [BrlHan:WIST@ Jcl (GALAS)] rat at 2 years of age. Histopathologically, the tumor was characterized by an admixture of malignant epithelial and nonepithelial elements. The carcinomatous components represented a type of endometrial carcinoma, consisting of glandular and solid proliferation of large-sized tumor cells. Prominent mitoses and tumor cell invasion were observed. The sarcomatous components were characterized by multifocal proliferation of severe atypical cells with cartilage matrix and were diagnosed as chondrosarcoma. Transitions between carcinomatous and sarcomatous components were observed, and many tumor cells in the solid lesion showed immunohistochemical reactivity with both cytokeratin and vimentin. Based on these findings, this tumor was diagnosed as a uterine carcinosarcoma. This is the first report of uterine carcinosarcoma in Wistar Hannover GALAS [BrlHan:WIST@Jcl (GALAS)] rats.

Lack of modifying effects of prepubertal exposure to acrylamide (AA) on N-methyl-N-nitrosourea (MNU)-induced multi-organ carcinogenesis in F344 rats.

Acrylamide (AA) has been reported to be formed in fried and baked foods with various concentrations, and exposure levels to AA from cooked foods in children are estimated to be higher than those in adults. In order to evaluate the carcinogenicity of AA exposure during childhood, we conducted a medium-term carcinogenicity study with prepubertal administration of AA followed by treatments of a multi-organ-targeted genotoxic carcinogen and a promoting agent for thyroid carcinogenesis in rats. A total of 36 postpartum F344 rats were given drinking water containing AA at 0, 20, 40 or 80 ppm for 3 weeks during the lactation period, and their weaned offspring received the same AA-containing water for 3 more weeks. Offspring were then injected with N-methyl-N-nitrosourea (MNU; 40 mg/kg body weight, i.p.) once at week 7 after birth. Half the animals of the 0 and 40 ppm groups were additionally treated with the anti-thyroid agent sulfadimethoxine (SDM; 125 ppm) in the drinking water thereafter. Offspring were subjected to complete necropsy at week 50. All the major organs and macroscopic abnormalities were excised and examined histopathologically. There was no significant difference in the incidences of hyperplastic and neoplastic lesions in the target organs of AA and/or MNU, such as the brain, spinal cord, pituitary gland, thyroid, adrenal glands, uterus, mammary glands, clitoral gland and tunica vaginalis. In conclusion, no significant modifying actions of AA on MNU-induced multi-organ carcinogenesis were exhibited in any organs of rats when exposed prepubertally under the present experimental conditions.

Inhibitory effects of aminoguanidine on thyroid follicular carcinoma development in inflamed capsular regions of rats treated with sulfadimethoxine after N-bis(2-hydroxypropyl)nitrosamine-initiation.

We have reported that thyroid capsular thickening with inflammation induced by an antithyroidal agent, sulfadimethoxine (SDM), might play a role in the development of invasive follicular carcinomas in rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). Inducible nitric oxide synthase (iNOS) expressed in the inflamed capsular regions further appeared to be implicated in the tumor progression. In the present study, the effects of an iNOS inhibitor, aminoguanidine (AG), on thyroid carcinogenesis were examined. F344 male rats were treated with SDM in drinking water (0.1%) with or without concomitant dietary administration of AG (0.2%) for 4 and 10 weeks after subcutaneous injection of DHPN at 2800 mg/kg bodyweight. At week 4, thyroid capsular thickening with inflammation was observed and iNOS-positive foci were found in the inflamed regions. In addition, single-strand DNA-positive inflammatory cells were scattered among neighboring follicular cells, indicating some cellular damage, at least partly in association with iNOS induction. Concurrent dietary administration of AG with SDM treatment slightly decreased the number of single-strand DNA-positive cells but did not alter the incidence and multiplicity of iNOS-positive foci in the inflamed capsular regions at week 4. At week 10, however, invasive follicular carcinomas predominantly arose in the thickened capsule in the DHPN-SDM-treated rats, and AG administration decreased (P < 0.05) their multiplicity. The carcinoma cells were partly positive for iNOS. These results thus suggested that iNOS induction in both inflammatory and tumor cells might play pivotal roles in tumor progression in this DHPN-SDM rat model.

A 55-week chronic toxicity study of dietary administered kojic acid (KA) in male F344 rats.

A chronic toxicity study of kojic acid (KA) was performed using male F344 rats by dietary administration at concentrations of 0 (control), 0.5 and 2.0% for 55 weeks. Body weight gain was suppressed in the 2.0% group. The major hematological findings were decreased red blood cell (RBC) count and hematocrit (Ht) values at both 0.5 and 2.0%. In serum biochemistry, increased aspartate transaminase (AsT), alanine transaminase (AlT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (gamma-GTP) levels were detected in the 0.5 and 2.0% groups. Histopathologically, single cell necrosis of hepatocytes and proliferation of bile ductules in both treatment groups, and hypertrophy of hepatocytes, granulomas and proliferation of bile ducts in the 2.0% group were increased in incidence, and numbers and areas of glutathione-S-transferase placental-form (GST-P) positive foci were increased in the liver of the 2.0% group. In the thyroids, diffuse follicular cell hyperplasia at 0.5 and 2.0% and focal follicular cell hyperplasia and follicular adenoma at 2.0% were increased. A thyroid follicular carcinoma was also observed at 2.0%. Additionally, increased incidences of hyaline casts and basophilic tubules in the kidneys at 2.0% and microgranulomas containing crystals in the lung in both treatment groups were noted. At 2.0%, hypertrophy of cortical cells in zona fasciculata was also increased in the adrenals. In conclusion, no observed adverse effect level of KA was below 0.5%, which is equivalent to 227 mg/kg body weight/day in male rats.

Modifying effects of prepubertal exposure to potassium perchlorate and tetrabromobisphenol A on susceptibility to N-bis(2-hydroxypropyl)nitrosamine- and 7,12-dimethylbenz(a)anthracene-induced carcinogenesis in rats.

Early life exposure to certain kinds of chemicals is of concern because of a possible increase in cancer risk, but relevant data are limited. In the present experiment, modifying effects of prepubertal administration of potassium perchlorate (KClO(4)) and tetrabromobisphenol A (TBBPA) on susceptibility to multi-organ carcinogenesis were evaluated. F344 dam rats were administered 0% (control), 0.01%, 0.1% or 1% TBBPA in diet or 0.01% KClO(4) in drinking water after parturition. Their weaned offspring in each group were treated for 2 weeks in the same manner. From 6 weeks of age, all offspring were treated with N-bis(2-hydroxypropyl)nitrosamine in drinking water for 4 weeks. In addition the females at 7 weeks of age were gavaged once with 7,12-dimethylbenz(a)anthracene. At weeks 39 and 47 of age, the males and females, respectively, were euthanized and the liver, kidney, lung, esophagus, thyroid, urinary bladder, testis, epididymis, ovary and mammary gland were histopathologically examined. The incidences of thyroid follicular adenomas in 1% TBBPA females (p<0.05) and of transitional cell papillomas in the urinary bladder of 0.01%, 0.1% and 1% TBBPA females were increased (p<0.05) as compared to the controls. These results indicate that prepubertal exposure to TBBPA raises susceptibility to thyroid and urinary bladder tumorigenesis in rats. Although causes of the effect on thyroid carcinogenesis might be direct and/or indirect hormonal actions, further studies are needed for confirmation.

Rhabdomyosarcoma in the abdominal cavity of a 12-month-old female donryu rat.

Neoplasms of skeletal muscle origin are very rare in the rat. Recently, we experienced a case of rhabdomyosarcoma as a white mass involving the junction of the esophagus and stomach in the abdominal cavity of a 12-month-old female Donryu rat. Histopathologically, the neoplastic cells composing the mass invasively spreaded from the lamina propia to the tunica serosa in the stomach as well as the esophagus. Although the neoplastic cells varied in appearance, pleomorphic atypical cells with abundant eosinophilic cytoplasm were prominent. Some tumor cells were stained blue with phosphotungstic acid hematoxylin. The nuclei of spindle-shaped neoplastic cells were arranged longitudinally like beads. Multinucleate giant cells and mitotic figures were also frequently observed. Immunohistochemically, these neoplastic cells were positive for desmin and myoglobin, whereas they were negative for alpha-smooth muscle actin. Taken together these findings, this tumor was diagnosed as a pleomorphic rhabdomyosarcoma, probably derived from the muscle layer of the lower part of the esophagus. This is the first report of rhabdomyosarcoma in a Donryu rat.

A new medium-term rat colorectal bioassay applying neoplastic lesions as end points for detection of carcinogenesis modifiers effects with weak or controversial modifiers.

We have established a two-stage, medium-term rat colorectal carcinogenesis model featuring induction of neoplastic lesions within ten weeks. In the present study, we examined the ability of this model to detect weak modifiers. F344 male rats were given three subcutaneous (sc) injections of 1,2-dimethyl-hydrazine (DMH, 40 mg/kg b.w.) in one week followed by drinking water containing 1% dextran sodium sulfate (DSS) for a second week. One week after this regimen, basal diet alone, or diets containing 10% perilla oil, 10% corn oil, 10% dextrin, or 0.1% indole-3-carbinol (I3C) were supplied. The perilla oil and corn oil groups did not show significant differences in the numbers of aberrant crypt foci (ACF) and incidences or multiplicity of proliferative lesions as compared to the controls at either time point. In the dextrin group, the total number of ACF at week ten was significantly increased. With I3C, the total number of ACF and incidence and multiplicities of adenocarcinomas at week ten and the incidence of invasive tumors at week twenty were significantly increased. These data essentially correspond with earlier reported results, except in the vegetable oil cases. Thus, the system is suitable for detection of colorectal carcinogenesis modifiers with advantages over previous models using ACF alone as end points.

Significance of inflammation-associated regenerative mucosa characterized by Paneth cell metaplasia and beta-catenin accumulation for the onset of colorectal carcinogenesis in rats initiated with 1,2-dimethylhydrazine.

Short-term dextran sodium sulfate (DSS) treatment has been shown to notably accelerate colorectal tumor development in rats initiated with 1,2-dimethylhydrazine (DMH). In the present study, to clarify mechanisms underlying the DSS influence, time-course studies of histopathological and immunohistochemical characteristics and beta-catenin gene mutations in colorectal mucosa in early stages of this model were conducted. F344 males were given three subcutaneous injections of DMH (40 mg/kg body wt) within a week, followed by free access to drinking water containing 1% DSS for a week. At weeks 1, 4, 6 and 8 after the DSS treatment, rats were euthanized and colorectal samples were collected. At week 1, the colorectal mucosa demonstrated extensive erosion along with significant inflammatory cell infiltration and neighboring reactive hyperplasia. By week 4, the mucosal damage was repaired and regenerative mucosa, partly characterized by Paneth cell metaplasia and altered subcellular localization of beta-catenin, was apparent. Areas with Paneth cells/beta-catenin accumulation were significantly more likely to be accompanied by interstitial inflammation and 17 of 24 dysplastic foci were found in regenerative mucosa with Paneth cells. Furthermore, adenomas/carcinomas frequently featured various degrees of Paneth cell differentiation. Point mutations mainly in codons 34 and 41 of beta-catenin gene were detected in 6 of 27 samples of regenerative mucosa with Paneth cells and four of nine dysplastic foci/adenomas/carcinomas. These findings indicate that inflammation-associated regenerative mucosa with Paneth cell metaplasia and alteration in the APC/beta-catenin/Tcf signal transduction pathway are possibly involved in the acceleration of colorectal carcinogenesis in this DMH-DSS rat model.

Systemic spindle-cell proliferative disease in broiler chickens.

The major organs and tissues of 24 broiler chickens (70 or 71 days old) suspected of spindle-cell proliferative disease (SPD) because of showing the tumorous lesions distributed throughout the body at meat inspection were collected for histopathological and immunohistochemical examination. Macroscopically, liver, spleen and cecal tonsil showed severe enlargement and white nodules or plaques were observed in the liver, spleen, kidney, intestine and bone marrow of the femur. All chickens were diagnosed with SPD based on the histopathological examination. The lesions of SPD were observed in the liver, spleen, kidney, heart, lung, pancreas, proventriculus, gizzard, duodenum, jejunum, ileum, rectum, cecal tonsil, bursa of Fabricius, bone marrow of the femur and skin. Hemangioma was observed in the lung of 1 bird. Eight 1-day-old specific pathogen-free chicks were inoculated intraperitoneally with 0.25 ml of a 20% homogenate of the affected spleens of three naturally occurring cases. One inoculated bird, necropsied at 10 weeks of age, macroscopically had a white nodule in the kidney and histopathologically had spindle-cell proliferative lesions, a pattern similar to that seen in the naturally occurring cases, in the liver, spleen, kidney, heart, lung, pancreas, proventriculus, duodenum, cecal tonsil and bone marrow of the femur, and was diagnosed with SPD. Immunohistochemically, significant positive reactions with a rabbit antiserum against avian leukosis virus antigens were detected in all spindle cells in the proliferative lesions of all examined SPD cases and in tumor cells of the hemangioma of a field case.

Bovine leukemia virus high tax molecular clone experimentally induces leukemia/lymphoma in sheep.

Sheep were inoculated with high tax coded pBLV-IF (H group, Nos.1-5) of bovine leukemia virus (BLV), wild tax coded pBLV-IF (W group, Nos. 6-11), or control plasmid (C group, Nos. 12-14). During the observation period (4 to 46 months), 5 of 5 cases in H group and 3 of 6 cases (Nos. 6, 7, 9) in W group became positive for gp 51. Only 1 case in H group became leukemic, and one case each of H and W groups developed lymphoma. In No. 3, lesions were found in multiple organs including the lymph nodes, gastrointestinal tract following abomasum, and heart. In No. 6, lesions of lymphoma were found only in the jejunum and heart. Morphologically, small to middle-sized lymphocytic neoplastic (NP) cells were found in both cases, but lymphoblastic NP cells were found only in No. 3. By immunohistochemical examination, the phenotypes of NP cells were determined as CD1-, CD4-, CD5- -, CD8alpha-, sIgM+, lambda light chain+, B-B4+, MHC class II+ in both case. The results of this study indicate that inoculation of pBLV-IF can induce lymphocytic and lymphoblastic leukemia/lymphoma in sheep. Additionally, it is suggested that the expression rate of tax gene is not associated with the development of leukemia/lymphoma in sheep experimentally inoculated with pBLV-IF.