Female Crj Research Articles

Characterization of mammary adenocarcinomas in male rats after N-methyl-N-nitrosourea exposure—Potential for human male breast cancer model

The frequency of breast cancer in men is extremely rare, reported to be less than 1% and there is currently no available animal model for male mammary tumors. We compared the characteristics of various immunohistochemical markers in N-methyl-N-nitrosourea (MNU)-induced mammary adenocarcinomas in male and female Crj:CD(SD)IGS rats including: estrogen receptor α (ER), progesterone receptor (PgR), androgen receptor (AR), receptor tyrosine-protein kinase erbB-2 (HER2), GATA binding protein 3 (GATA3), and proliferating cell nuclear antigen (PCNA). Female mammary adenocarcinomas were strongly positive in the nuclei of tumor cells for PCNA and ER (100%) with only 60% and 53% expressing PgR and GATA3, respectively. 100% of male adenocarcinomas also exhibited strongly positive expression in the nuclei of tumor cells for PCNA, with 25% expressing AR and only 8% showing positivity for ER. Male carcinomas did not express PgR or GATA3 and none of the tumors, male or female, were positive for HER2. Based on the observed ER and PgR positivity and HER2 negativity within these tumors, MNU-induced mammary adenocarcinomas in female rats appear to be hormonally dependent, similar to human luminal A type breast cancer. In contrast, MNU-induced mammary adenocarcinomas in male rats showed no reactivity for ER, PgR, HER2 or GATA3, suggesting no hormonal dependency. Both male and female adenocarcinomas showed high proliferating activity by PCNA immunohistochemistry. Based on our literature review, human male breast cancers are mainly dependent on ER and/or PgR, therefore the biological pathogenesis of MNU-induced male mammary cancer in rats may differ from that of male breast cancer in humans.

Effects of pyperonyl butoxide on the female reproductive tract in rats

This study was investigated the effects of piperonyl butoxide (PBO) on the female reproductive tract. Female Crj:Donryu rats were fed a basal diet containing 5,000, 10,000 or 20,000 ppm PBO for 28 days, and compared with food-restricted rats of comparable body weights to those in the PBO 10,000 or 20,000 ppm groups. Although treatment with 20,000 ppm PBO for 28 days depressed body weight gain, the abnormal estrous cyclicity, mainly prolonged diestrus, was also induced by the PBO treatment which was not correlated with body weight change. 20,000 ppm PBO treatment markedly decreased uterine weights and slightly decreased ovarian weights. 10,000 and 20,000 ppm PBO treatment increased liver weights. These cycle and organ weight changes were linked to atrophic uterus and increased atretic follicles in the ovary. In hormone assays, PBO at both doses reduced serum E2 levels, but did not affect corticosterone levels. An anti-uterotrophic assay showed a slight but significant decrease in absolute uterine weight and a reduction of endometrial epithelium height in the 20,000 ppm group. PBO was positive in an ER α antagonist reporter gene assay, although the activity was much weaker than that of 4-hydroxytamoxifen. These results indicate that high-dose PBO treatment directly induces atrophic changes in the female reproductive tract in rats, and these effects are likely the result of a hypoestrogenic state and the anti-estrogenic activity of PBO.

Evaluation of embryotoxic potential of olaquindox and vitamin a in micromass culture and in rats.

Limb bud (LB) and central nerve system (CNS) cells were prepared from 12.5 day old pregnant female Crj:CD (SD) rats and treated with olaquindox and vitamin A. Cytotoxicity and inhibition on differentiation were measured in each cell. Three doses of olaquindox (4, 21 and 100 mgkg) , and 0.2 and 75 mg/kg of vitamin A were administered to pregnant rat for 11 days from 6th to 16th of pregnancy. IC50 values of olaquindox for proliferation and differentiation in CNS cell were 22.74 and 28.32 μg/ml and 79.34 and 23.29 μg/ml in LB cell and those values of vitamin A were 8.13 and 5.94 μg/ml in CNS cell and 0.81 and 0.05 μg/ml in LB cell, respectively. Mean body weights of pregnant rats were decreased at high dose of olaquindox (110 mg/kg) but relative ovary weight, number of corpus lutea, and number of implantation were not changed. Resorption and dead fetus were increased at high dose of olaquindox, and relative ovary weight, the number of corpus lutea and implantation, and sex ratio of male to female were not significantly changed in all dose of olaquindox. Mean fetal and placenta weights were significantly (p < 0.01) decreased in rats of high group. Seven fetuses out of 103 showed external anomaly like bent tail, and 10 out of 114 fetuses showed visceral anomalies at high group. The ossification of sternebrae and metacarpals were significantly (p < 0.01) increased by low and middle dose of olaquindox but it was significantly (p < 0.01) prohibited by high dose of olaquindox. In rats treated with vitamin A, the resorption and dead fetus were increased by high dose. Mean fetal weights were significantly (p < 0.01) increased by low dose but significantly (p < 0.01) decreased by high dose. Thirty four fetuses out of 52 showed external anomaly; bent tail (1) , cranioarchschisis (14) , exencephaly (14) , dome shaped head (22) , anophthalmia (15) , brcahynathia (10) and others (19) . Forty five fetuses out of 52 showed soft tissue anomaly; cleft palate (42/52) and anophthalmia (22/52) by high dose of vitamin A. Sixty one fetuses out of 61 (85.2%) showed skull anomaly; defect of frontal, partial and occipital bone (21/61) , defect of palatine bone (52/61) and others (50/61) . In summary, we support that vitamin A is strong teratogen based on our micromass and in vivo data, and olaquindox has a weak teratogenic potential in LB cell but not in CNS cell. We provide the in vivo evidence that a high dose of olaquindox could have weak embryotoxic potential in rats.

Oral Toxicity of Indium in Rats: Single and 28‐Day Repeated Administration Studies

Indium is widely used in the electronics industry to make semiconductors, liquid-crystal panels, and plasma display panels, and its production is increasing. However, it is necessary to handle it more cautiously than before, because the pulmonary toxicity of inhaled indium has been identified. The present study aimed to characterize the potential toxic effects of indium through oral administration and observation for fourteen days following a single dose of 0 or 2,000 mg/kg (acute oral toxicity study), and repeated oral administration for 28 days at dose levels of 0, 40, 200, or 1,000 mg/kg daily (28-day repeated oral dose toxicity study) to male and female Crj:CD (SD) IGS rats (SPF). No deaths and no abnormalities in clinical signs, body weights, and necropsy findings were observed for any of the animals in the acute oral toxicity study. Furthermore, no changes related to indium were also observed in the dose groups up to 1,000 mg/kg of the 28-day repeated oral dose toxicity study. From the results described above, the lethal dose 50% (LD(50)) of indium is greater than 2,000 mg/kg under these study conditions, and the no-observed-adverse-effect-level (NOAEL) is considered to be 1,000 mg/kg for males and females under these conditions.

Malignant Amelanotic Melanoma Behind the Left Eye in a Female Crj:CD(SD)IGS Rat: A Case Report

A tumor behind the left eye in a female Crj:CD(SD)IGS rat was investigated histopathologically, immunohistopathologically, and electron microscopically. The tumor invaded and destroyed orbital tissues and bones. It consisted of various tumor cells; namely, spindle-shaped, epithelioid, anaplastic melanoma cells, and had prominent eosinophilic cytoplasm and nuclei with a greater variation in size. Immunohistochemically, almost all of the tumor cells were positive for antimelanoma, PNL2 antibody. Ultrastructurally, the tumor cells were rich in small vesicles containing fine granules and filamentous structures. This is the first report describing an amelanotic melanoma in the head of an albino rat.

Oral Toxicity of Bismuth in Rat: Single and 28‐Day Repeated Administration Studies

The consumption and production of bismuth are increasing, however there is very little information about the direct toxic effect of bismuth. The present study aimed to characterize the potential toxic effects of bismuth through oral administration and observation for fourteen days following single dose of 0 and 2,000 mg/kg (acute oral toxicity study), and repeated oral administration for twenty-eight days at dose levels of 0, 40, 200, and 1,000 mg/kg daily (28-d repeated oral dose toxicity study) to male and female Crj:CD (SD) IGS rats (SPF). We found no deaths and no abnormalities in clinical signs, body weights, and necropsy findings for any of the animals in the acute oral toxicity study and no changes attributable to bismuth in either males or females in the dose group up to 1,000 mg/kg of the 28-d repeated-dose toxicity study. Therefore, we determined that the lethal dose with a 50% mortality rate (LD50) is greater than 2,000 mg/kg and the no-observed-adverse-effect level (NOAEL) of bismuth is 1,000 mg/kg in both sexes. We conclude that the adverse toxic effects of bismuth as a simple metal substance are low compared to lead toxicity under the conditions tested in our studies.

Thirteen-week feeding study of thaumatin (a natural proteinaceous sweetener), sterilized by electron beam irradiation, in Sprague–Dawley rats

This study was designed to evaluate and characterize any subchronic toxicity of thaumatin sterilized by electron beam irradiation (5.0 kGy) when administered at dietary levels of 0% (control), 0.3%, 1.0% and 3.0% to groups of 10 male and 10 female Crj:CD (SD) IGS rats for 13 weeks. Separate groups of both sexes received 3.0% non-irradiated thaumatin. There were no treatment-related clinical signs or adverse effects on the survival rate, body weight, food consumption, water consumption and urinalysis, ophthalmology, haematology, or blood biochemistry data. No treatment-related alterations in gross pathology or organ weights were found in any group. On histopathological examination, sporadic spontaneous lesions known to occur in this strain of rats were the only findings, with no specific relation to the test substance. Thus, the no-observed-adverse-effect-level (NOAEL) was judged to be a dietary level of at least 3.0% (2502 mg/kg body weight/day for males, 2889 mg/kg body weight/day for females) for electron beam irradiated thaumatin under the present experimental conditions. It was concluded that electron beam-irradiation of thaumatin does not cause changes of any toxicological significance.

A GRAVIMETRIC SIMPLIFIED METHOD FOR NUCLEATED MARROW CELL COUNTING USING AN INJECTION NEEDLE

A simplified gravimetric marrow cell counting method for rats is proposed for a regular screening method. After fresh bone marrow was aspirated by an injection needle, the marrow cells were suspended in carbonate buffered saline. The nucleated marrow cell count (NMC) was measured by an automated multi-blood cell analyzer. When this gravimetric method was applied to rats, the NMC of the left and right femurs had essentially identical values due to careful handling. The NMC at 4 to 10 weeks of age in male and female Crj:CD(SD)IGS rats was 2.72 to 1.96 and 2.75 to 1.98 (x10(6) counts/mg), respectively. More useful information for evaluation could be obtained by using this gravimetric method in addition to myelogram examination. However, some difficulties with this method include low NMC due to blood contamination and variation of NMC due to handling. Therefore, the utility of this gravimetric method for screening will be clarified by the accumulation of the data on myelotoxicity studies with this method.

Carcinogenicity and chronic toxicity in mice and rats administered vinyl acetate monomer in drinking water.

Carcinogenicity and chronic toxicity of vinyl acetate monomer (VA) were examined in male and female Crj:BDF1 mice and F344/DuCrj Rats. Groups of 50 mice and 50 rats of each sex were orally administered VA in drinking water containing 0, 400, 2,000 or 10,000 ppm (g/g) VA for 104 wk. Squamous cell tumors were clearly evident in the upper digestive tract of treated mice and rats, and in the larynx of treated mice of both sexes. In mice, squamous cell carcinomas and papillomas were observed in the oral cavity, esophagus, forestomach and larynx of the 10,000 ppm group, together with basal cell hyperplasia, squamous cell hyperplasia and epithelial dysplasia. In rats, incidences of squamous cell carcinomas and papillomas were increased in the oral cavity of the 10,000 ppm group of both sexes, and an esophagus squamous cell carcinoma was observed in a 10,000 ppm female. Pre-neoplastic hyperplasias were also noted. Mapping of the neoplastic and pre-neoplastic lesions in the oral cavity of the 10,000 ppm group revealed that both the lesions occurred predominantly at Level V in mice and at Level VI in rats. A lower confidence limit of a benchmark dose (BMDL10) of 477 mg/kg/d was obtained from a dose-response relationship between combined incidence of squamous cell carcinomas and papillomas in the oral cavity of mice and rats and the estimated daily VA intakes per body weight, and compared with literature values.

Age-related changes of genital systems in the female Crj:CD (SD) IGS rats during sexual maturation.

The age-related changes of vaginal opening, body weight, the weights of the uterus and ovary, together with histological examination, serum 17beta-estradiol (E2) and progesterone levels were examined in intact female Crj:CD (SD) IGS rats between 21 and 36 days of age to understand the basic biological profile of changes of the female genital system during sexual maturation in the rat for female pubertal assays. With the beginning of the elevation of serum E2 level from 28 days of age, all parameters except body weight started to show drastic change until 31 days of age. The highest incidence of vaginal opening was recorded at 34 days of age. On macroscopic examinations, a number of rats showed uterine imbibition but vaginal opening. Immediately after the confirmation of the vaginal opening, the genital systems of three rats were observed microscopically. Both ovaries already had multiple corpora lutea, and degeneration of endometrial epithelial cells was observed. In conclusion, we obtained essential data on genital tract development of female Crj:CD (SD) IGS rats for in vivo screening assays that will contribute to detect potential endocrine active chemicals. In addition, it is assumed that the first ovulation precedes or occurs simultaneously with vaginal opening.

Determination of α2-macroglobulin concentrations in healthy rats of various ages and rats inoculated with turpentine oil by an enzyme-linked immunosorbent assay

Summary An enzyme-linked immunosorbent assay (ELISA) for rat α2-macroglobulin (α2M) was developed, and the concentrations of α2M in sera in normal Crj:CD and Crj:WI rats as well as in turpentine oil injected Crj:WI rats were determined. Anti-rat α2M serum was prepared by immunization of rabbits with the α2M fraction separated from rat acute phase serum using Sephacryl S-300. The specificity of the rabbit anti-rat α2M serum was confirmed by immunoelectrophoresis and Western blotting. The α2M concentrations in 180 normal Crj:CD (90 males and 90 females) and 180 Crj:WI (90 males and 90 females) rats were 14.5–94.9 μg/ml (mean 36.8 ± 13.3) and 13.6–65.8 μg/ml (mean 34.9 ± 12.4), respectively. There were no significant differences between male and female Crj:CD and Crj:WI rats, respectively (p

Rat two-generation reproductive toxicity study of bisphenol A

This study was conducted to determine the low-dose effects of bisphenol A (BPA) in a rat two-generation reproduction study. Groups of 25 male and 25 female Crj: CD (SD) IGS rats were given BPA at 0.2, 2, 20, or 200 μg/kg/day by gastric intubation throughout the study beginning at the onset of a 10- and 2-week premating period, in F0 males and females, respectively, and continuing through the mating, gestation, and lactation periods, for two generations. There were adult (F0, F1, F2) and postnatal day (PND) 22 (F1, F2) necropsies; the oldest F2 males and females being killed at postnatal weeks 7 and 14, respectively. No compound-related clinical signs or effects on body weight or food consumption were observed in any generation. There were no compound-related changes in surface righting reflex, negative geotaxis reflex, mid-air righting reflex, pinna detachment, incisor eruption, eye opening, testes descent, preputial separation, or vaginal opening in F1 and F2 generations, or behavior in the open field or water filled multiple T-maze in the F1 generation. No test compound-related changes in estrous cyclicity, copulation index, fertility index, number of implantations, gestation length, litter size, pup weight, pup sex ratio, pup viability, or other functional reproductive measures were noted in any generation. A few significant changes in the anogenital distance (AGD) per cube root of body weight ratio were found at 0.2 and 20 μg/kg in F1 males, at 2, 20, and 200 μg/kg in F1 females, and at 20 and 200 μg/kg in F2 females. However, the changes in the AGD were consistently small (within 5% of control values), and no continuous changes in the AGD or AGD/cube root of body weight ratio were detected. There were no compound-related changes in epididymal sperm counts or motility in F0 and F1 males. No compound-related necropsy findings or effects on organ weight including the reproductive organs were found in any generation. Histopathologic examinations revealed no evidence of compound-related changes in any organs including the reproductive organs of both sexes. The data indicate that oral doses of BPA of between 0.2 and 200 μg/kg over 2 generations did not cause significant compound-related changes in reproductive or developmental parameters in rats.

Rescue of mouse embryos from 2-cell blocks by microinjection of maturation promoting factor

Objective: To examine the rescue of mouse embryos from 2-cell blocks by the microinjection of maturation promoting factor (MPF) extracted from matured Xenopus eggs into one of the blastomeres of 2-cell stage mouse embryos. Design: Controlled laboratory study. Setting: First Department of Obstetrics and Gynecology, Toho University School of Medicine, Tokyo, Japan. Animal(s): Eight- to 10-week-old female Crj:CD-1(ICR) mice. Intervention(s): One of the blastomeres of the mouse 2-cell embryos was injected with MPF (MI group) or mHTF medium (MED group) at 28–32 hours after insemination. Main Outcome Measure(s): The developmental rate to blastocyst. Result(s): The developmental rate to blastocyst in the MI group (48.0%) was significantly higher than that in the MED group (0%). Conclusion(s): The 2-cell block was specifically rescued by the microinjection of MPF and not by the insertion of pipettes.

Reproductive effects of nonylphenol in rats after gavage administration: a two-generation study

The potential reproductive toxicity of nonylphenol (NP) was assessed in a two-generation reproductive toxicity study. Groups of 25 male and female Crj:CD (SD) IGS rats were given NP by gavage at levels of 2, 10, or 50 mg/kg, and 25 males and females were given corn oil as controls. No adverse changes in clinical signs were observed in any rats throughout the study. Significant increases in the liver, kidney and pituitary gland weights in males, and decreases in thymus weight in males and in ovary weight in females were observed in the 50 mg/kg group. NP did not affect sperm characteristics or the estrous cycle at any dose administered. A significant increase in the TSH level was observed in males in the 50 mg/kg group. No adverse effects of NP on reproduction were found. At necropsy, no treatment-related alterations were observed in any organs including the reproductive tissues in any group. Histopathologic changes were found in the liver of male and female rats and kidneys of males in the 50 mg/kg group. The viability of offspring from postnatal day 0 to 4 in the 50 mg/kg group was reduced as compared with that in the controls, although growth was not affected by NP administration. On postnatal day 22, an increase in the serum FSH level and decrease in T 3 level for males, and decreases in LH and TSH levels and an increase in T 3 levels for females were observed in the 50 mg/kg group. NP did not affect the timing of preputial separation, while vaginal opening was accelerated in the 50 mg/kg group. No adverse changes were found in behavior or learning in the offspring of NP-treated groups. There were no treatment-related changes in any reproductive parameter, including estrous cycle, mating, fertility, delivery, and lactation, except for significant decreases in the numbers of implantation sites and live pups, and a significant decrease in ovary weight in the 50 mg/kg group. Kidney and liver weight were increased in males in the 50 mg/kg group. Histopathologic examination revealed changes in the liver of males and females of the 50 mg/kg group. No treatment-related changes were observed in the sperm characteristics. Hormone data should be interpreted cautiously until the findings are repeated and confirmed by further studies. These results of NP suggested that the no observed adverse effect level (NOAEL) on reproductive capacity is 50 mg/kg/day or greater in parent animals, and 10 mg/kg/day in the next generation under the present experimental condition.

A three-month repeated oral administration study of a low viscosity grade of hydroxypropyl methylcellulose in rats.

The toxicity of the lowest viscosity grade of hydroxypropyl methylcellulose (HPMC) that is currently commercially available was investigated by means of a three-month repeated oral administration study in male and female Crj:CD (SD) IGS rats at doses of 505, 1,020 and 2,100 mg/kg/day. Body weights of males and females in the 2,100 mg/kg group were lower than those of the control group on and after day 28 of administration, but the differences were not statistically significant. The degree of suppression of body weight gain in males was higher than that in females. This tendency was similar to the results in other toxicity studies of HPMC that have been reported. Males in the 2,100 mg/kg group showed a tendency (not significant) for decreased food consumption and urine volume. Examinations of general signs, hematology, blood chemistry, ophthalmology, absolute and relative organ weights, autopsy and histopathology revealed only a few, apparently coincidental, statistically significant differences from the control, and no evidence of any dose-dependent changes was found. It was concluded that the lowest viscosity grade of HPMC showed extremely low toxicity under the conditions of this study, as has been found for higher viscosity grades.

Oral Teratogenicity Studies of Methyl Bromide in Rats and Rabbits

Teratogenicity studies of methyl bromide, a widely used fumigant, were conducted in rats and rabbits. Methyl bromide was dissolved in corn oil and administered orally to groups of 24 copulated female Crj:CD (SD) rats at dose levels of 0 (corn oil), 3, 10 or 30 mg/kg/day on days 6–15 of gestation and to groups of 18 artificially inseminated female Kbl:JW rabbits at 0, 1, 3 or 10 mg/kg/day on days 6–18 of gestation. Maternal rats and rabbits were euthanized on respective days 20 and 27 of gestation. Foetuses were examined for survival, growth and teratological alterations. Maternal toxicity was evident in the high-dose groups for both species. In these groups, maternal body weight gains and food consumption were significantly decreased during the dosing and post-dosing periods. Necropsy of maternal rats also revealed erosive lesions in the stomach and the surrounding organs. However, no treatment-related adverse effects were found in foetuses of the treated groups for both rat and rabbit studies. These results led to the conclusion that methyl bromide was not foetotoxic or teratogenic to rat and rabbit foetuses up to dose levels of 30 and 10 mg/kg/day, respectively, at which maternal toxicity was evident for both species.

Anomalies of Cartilaginous and Ossified Axial Skeleton in Rat Fetuses Treated with Cyclophosphamide: Type, Frequency, and Stage Specificity

AbstractThe purpose of the present study was to assess the type, frequency and stage specificity of axial skeletal anomalies induced by cyclophosphamide (CP). Female Crj: Wistar rats were mated with male rats (vaginal sperm = gestation day 0, GDO). They were then injected intravenously with 5 mg/kg of CP in a saline solution on GD7, 8, 9, 10, 11, 12, 13, or 14, or with saline on GD8 for controls. Dams were sacrificed on GD20. Fetuses were stained with alcian blue and alizarin red S. Eighteen types of axial skeletal anomaly were detected, e. g., shifted ventral lamina, cervical rib, cleft arch of the atlas, axis fused to atlas, sternebral misalignment, bipartite sternum, fused ribs, change in pre‐sacral vertebral number, supernumerary rib, misdirected transverse process, anteriorly‐shifted spinous process, short spinous process, fused vertebral bodies, cartilaginous short rib at Th.7, short or absent rib at Th.12 or 13, dumbbell‐shaped vertebral body, wavy rib, and rib cartilage not attached to the sternal cartilage. The present experimental study indicates that: 1) observations of cartilaginous skeletons can provide more information than observations of ossified skeletons; 2) the pattern of CP‐induced anomalies along the anterior–posterior axis may depend on the sequence of development progression among structures, spinous process, vertebral arch, vertebral body, rib/transverse process; and 3) in more cranial vertebrae, anteriorly‐shifted anomalies, such as anteriorly‐shifted ventral lamina and anteriorly‐shifted spinous processes, rather than posteriorly‐shifted anomalies, may be the primary indicators for detecting developmental toxicity, since CP injection increased the frequencies of these anomalies.

Symposium on estrogens in the environment, III.

Symposium on estrogens in the environment, III.

Effects of hydrochloric acid on the development of enterochromaffin-like (ECL) cell hyperplasia in the rat stomach induced by omeprazole.

In the present study, gastric pH was lowered by hydrochloric acid to investigate whether the cause of enterochromaffin-like (ECL) cell hyperplasia was due to the inhibition of acid secretion by omeprazole or due to the direct action of the drug. Omeprazole was given to female Crj:CD (SD) rats in a daily oral dose of 2 or 8 mg/kg for 13 weeks, and 20 ml/kg of 0.12 N HCl was further given orally to the animals 3 and 6 hours after each dosing. The animals were killed at the end of the dosing period, and the stomach was removed and weighed. The thickness of the gastric wall was measured and ECL cell count and area rate of the cells were calculated with an image analyzer. There were no effects of the treatment with HCl on stomach weight or thickness of the gastric wall, but ECL cell count and area rate of the cells decreased markedly by the treatment with HCl. Therefore, the cause of gastric ECL cell hyperplasia induced by omeprazole was suggested to be sustained high gastric pH levels.

Cystic Dilatation of the Vaginal Fornix in Aged Female Crj:F344/Du Rats

In the rodent, spontaneous vaginal lesions are rare. 1-3,6 No spontaneous lesions arising from the vaginal fornix in the rodent have been reported. Unexpectedly, a high incidence of cystic dilatation of the vaginal fornix was recognized in female Crj:F344/Du rats during a 2-year carcinogenicity study. To date, the cystic vaginal fornix has never been reported in the mammal, including the rodent.1-3.5,6,8 This report describes cystic dilatation of the vaginal fornix in Crj:F344/Du rats. Two hundred and fifty, 4-week-old, female Crj:F344/Du rats were purchased from Charles River Japan Inc. (Atsugi, Kanagawa, Japan). Two weeks after these rats had arrived, the animals were divided equally (50 in each group) into five groups: two control groups (untreated and vehicle [O. 1% lactose]) and three treated groups (0.01, 0.03, and 0.1% of testarticle). During a 2-year carcinogenicity study, the rats were fed powdered diet (CA1, CREA Japan Inc.) with and without the test-article and were given water ad libitum. The rats were housed five per cage, in a plastic cage with hardwood bedding and filter tops. The rats were kept at a constant room temperature of 21-25 C and a relative humidity of 50-60°/o, and the room was maintained on a 12-hour lightll2-hour dark cycle. Complete necropsies were performed both on rats dying spontaneously during the study and those euthanatized at the end of the study. More than 42 major organs including the ovary, uterus, cervix, and vagina were histologically examined on routinely hematoxylin and eosin-stained sections. During and at the end of the study, gross nodules were found in the cervix of the genital tract in 19.6% (491250) of the female F344 rats older than 667 days. As shown in Table 1, the incidence of nodules was 15.0% (1 5/100) and 22.7% (34/150) in two control and three treated groups, respectively. The occurrence of nodules in treated groups did not appear to be related to the test-article because the incidence did not increase in a dose-related fashion. In the rat, the uterus is a duplex consisting of two horns. The two uterine horns fuse at approximately the upper fourth of the cervix, but the cervical uterine canals are completely separated by the midsagittal septum shaped like the “tongue” (Fig. 1). In approximately the lower fourth of the cervix,the cervical uterus projects into the cavity of the vagina forming the “uterovaginal lips.” At this point, the vaginal fornix is between the lateral side of the projecting cervical uterus (the uterovaginal lips) and the vaginal wall (Fig. 1). The vaginal fornix is a bilateral fold forming a recess that is continuous with the cavity of the vagina. The apical portion of the midsagittal septum of the cervical uterus that projects into the cavity of the vagina through the two “lips” consists of four or five (lateral, dorsal, and ventral) lobes and may be termed as the portio vaginalis uteri (Fig. At the orifice of the vaginal fornix, the two uterine horns open into the vaginal cavity as a symmetrical, external orifice shaped in almost an “X” pattern, although a paired, separated canal is present in nearly the entire cervix. In the portio vaginalis uteri, the vaginal fornix becomes a ring-shaped fold, but its dorsocentral portion is symmetrically separated by the root of the dorsal lobe. Grossly, the nodules were usually located in the lower half of the cervix and were raised from the surface of the cervix (Fig. 2). Usually, the raised nodules were seen laterally. Of the 49 rats with nodules, 12 animals (24%) had bilateral nodules (Table 1). Thirty-seven animals (76%) had a unilateral nodule; twenty-four nodules were found on the left side and 13 on the right side in the cervix. The nodules were smooth and spherical to elongated in shape. They vaned in size, ranging from 2 x 2 x 2 to 14 x 15 x 30 mm. Nodules were green-yellow in color and in cut sections contained puslike or cheesy yellowish material. On microscopic examination, these cervical nodules proved to be the vaginal fornix, which was cystically dilated (Fig. 3). Small nodules consisted of partial, cystic dilatation of the