Green tea extract attenuates MNU-induced photoreceptor cell apoptosis via suppression of heme oxygenase-1.

The effects of green tea extract (GTE) on N-methyl-N-nitrosourea (MNU)-induced photoreceptor cell apoptosis were examined, and the possible mechanisms of action of GTE were assessed. Alterations in the retinal morphological architecture were determined by hematoxylin-eosin staining, vimentin immunoreactivity, and photoreceptor cell apoptosis (TUNEL labeling). Expression of oxidant marker, heme oxygenase (HO)-1, mRNA levels in outer nuclear cells was assessed by laser capture microdissection (LCM). Sprague-Dawley rats were given 40 mg/kg MNU at 7 weeks of age in the absence and presence of 250 mg/kg GTE treatment (once daily from 3 days prior to MNU for a maximum 10 days). Although photoreceptor cell degeneration began 24 hr after MNU, the morphological effects of GTE at the time point were not definitive. However, GTE lowered TUNEL labeling and HO-1 mRNA expression. At 7 days after MNU, photoreceptor damage was attenuated by GTE treatment. Therefore, the ability of GTE to reduce MNU-induced photoreceptor cell apoptosis may be due to its antioxidant properties.

Susceptibility to N-methyl-N-nitrosourea-induced retinal degeneration in different rat strains.

To evaluate the potential role of genetic background in the susceptibility to retinal degeneration induced by N-methyl-N-nitrosourea (MNU), female rats of the Sprague-Dawley (SD), Long-Evans (LE) and Copenhagen (CH) strains were administered 50 mg/kg MNU or saline at 7 weeks of age. Retina morphology and morphometric analysis of all rats was performed 7 days after MNU administration. Atrophy of both the peripheral and central outer retina occurred in all rat strains exposed to MNU. Decreased photoreceptor cell ratio and increased retinal damage ratio were observed. The severities of the retinal atrophy were similar among all three rat strains. In conclusion, MNU-induced photoreceptor degeneration developed consistently in all three strains regardless of the absence (SD rats) or presence (LE and CH rats) of melanin in the retina, suggesting that genetic and melanin factors did not affect photoreceptor cell death after MNU.

A spontaneously occurring malignant ovarian Sertoli cell tumor in a young Sprague Dawley rat.

Primary ovarian tumors are generally uncommon in rats used in toxicologic studies. A malignant Sertoli cell tumor was present in the ovary of a 19-week-old female Sprague Dawley rat. Macroscopically, the mass was white and firm, 10 × 13 × 17 mm in size, and located in the right ovary. Histopathologically, the mass was composed of nests of pleomorphic cells, which formed seminiferous-like tubules separated by a thin fibrovascular stroma. The tubules were lined by tumor cells, which had basally located nuclei and abundant eosinophilic and vacuolated cytoplasm. In some areas, the tumor cells were arranged in a retiform growth pattern, mimicking a rete testis/ovarii. Disseminated metastases to the surfaces of the mesentery, spleen and liver were also present. Immunohistochemically, many tumor cells were strongly positive for vimentin, estrogen receptor α and Ki 67. Some tumor cells were positive for pancytokeratin and inhibin α. These findings closely resemble those of an ovarian-derived human malignant Sertoli cell tumor. From our review of the literature, we believe this is the first report of a spontaneous malignant Sertoli cell tumor in the ovary of a young laboratory rat. This case might provide useful historical control information for rat toxicity studies.

Mead acid supplementation does not rescue rats from cataract and retinal degeneration induced by N-methyl-N-nitrosourea.

Fatty acids and their derivatives play a role in the response to ocular disease. Our current study investigated the effects of dietary mead acid (MA, 5,8,11-eicosatrienoic acid) supplementation on N-methyl-N-nitrosourea (MNU)-induced cataract and retinal degeneration in Sprague-Dawley rats. Experiment 1 was designed to inhibit cataract formation, with the dams fed a 2.4% MA or basal (<0.01% MA) diet during lactational periods. On postnatal day 7, male pups received a single intraperitoneal (ip) injection of 50 mg/kg MNU or vehicle. Lens opacity and morphology were examined 7 and 14 days after the MNU injection. Experiment 2 was designed to inhibit retinal degeneration and was performed with female postweaning rats. In this experiment, dams were fed the 2.4% MA or basal diet during the lactational periods. Thereafter, the female pups were continuously fed the same diets during their postweaning periods. On postnatal day 21 (at weaning), pups received a single ip injection of 50 mg/kg MNU. Retinal morphology was examined 7 days after the MNU injection. In experiment 3, six-week-old female rats were fed the 2.4% MA or basal diet starting at one week before the MNU injection and were then continuously fed the same diets until sacrifice. Rats at 7 weeks of age were given a single ip injection of 40 mg/kg MNU, and the retina was then examined morphologically one week after the MNU injection. In experiment 1, mature cataract was found in all of the MNU-treated groups, with or without MA supplementation. In experiments 2 and 3, atrophy of both the peripheral and central outer retina occurred in all rats exposed to MNU, with or without MA supplementation, respectively. The severities of the cataracts and retinal atrophy in the rats were similar regardless of MA supplementation. Dietary mead acid, which is used as a substitute in essential fatty acid deficiency in the body, does not modify MNU-induced cataract and retinal degeneration in rat models.

Temporal and spatial dependence of inflammatory biomarkers and suppression by fluvastatin in dextran sodium sulfate-induced rat colitis model.

BACKGROUND: Dextran sodium sulfate (DSS)-induced colitis in rats is widely used as an experimental model for elucidating the etiology of ulcerative colitis (UC) and developing its novel remedy. We investigated the temporal and spatial changes in inflammatory mediators such as tumor necrosis factor (TNF)-α and inducible nitric oxide synthase (iNOS) in the regions of rectum and distal colon and examined whether statins, which were designed to lower plasma cholesterol levels, influenced those mediators. METHODS: Colitis was induced in rats by oral administration of 5 % DSS for 5 days, followed by 2 % DSS for 10 days. 5 % DSS rats were treated with fluvastatin (20 mg/kg) concomitantly for 5 days. The expression of inflammatory mediators of a sequence of four regions in rectum (R) and distal colon (D0, D1, and D2) was determined by quantitative RT-PCR. RESULTS: The peak of colitic damage, which was confirmed clinically and histopathologically, was found on days 4-6. The expression of TNF-α, iNOS, cytokine-induced neutrophil chemoattractant-1, interleukin (IL)-1ß, and IL-6 mRNA increased in R time dependently, showing the peak on days 4-6, and then decreased thereafter. The levels of mRNAs reduced from R to D0, D1, and D2 region dependently. Fluvastatin decreased the expression of these markers in addition to the prevention of DSS-induced damage. CONCLUSIONS: Results demonstrated that the expression of inflammatory biomarkers had time and region specificity and was markedly inhibited by fluvastatin. To obtain a precise drug effect for UC, it is important to elucidate the temporal and spatial dependence of inflammatory biomarkers in DSS colitis model.

Green tea extract suppresses N-methyl-N-nitrosourea-induced photoreceptor apoptosis in Sprague-Dawley rats.

BACKGROUND: Retinitis pigmentosa (RP) is a group of inherited neurodegenerative human diseases characterized by the loss of photoreceptor cells by apoptosis and eventual blindness. A single intraperitoneal (ip) injection of N-methyl-N-nitrosourea (MNU) causes photoreceptor cell apoptosis within 7 days in rats. Green tea extract (THEA-FLAN 90S; GTE) is a common herbal supplement with pluripotent properties including antioxidant activity. The purpose of the present study was to evaluate the efficacy of GTE against photoreceptor apoptosis in 7-week-old female Sprague-Dawley rats that received a single ip injection of 40 mg/kg MNU. METHODS: The oral administration of 250 mg/kg/day GTE was initiated 3 days prior to MNU injection and continued once daily throughout the experiment. Rats were sacrificed at 12, 24, and 72 h and 7 days after MNU injection, and the eyes were examined morphologically and morphometrically. The photoreceptor cell ratio, retinal damage ratio, and retinal preservation ratio were used to determine the structural and functional alterations. The number of apoptotic photoreceptor cells per mm(2) was determined in situ by TdT-mediated dUTP-digoxigenin nick end labeling (TUNEL). Our results indicated that oral administration of GTE significantly suppressed the loss of photoreceptor cells morphometrically 7 days after MNU injection. The number of TUNEL-positive cells per mm(2) in MNU-exposed rat central retina with or without GTE administration was 981 vs. 2056 at 24 h after MNU injection. CONCLUSIONS: GTE structurally and functionally suppressed MNU-induced photoreceptor cell apoptosis. These findings indicate that GTE may help to ameliorate the onset and progression of human RP.

Green Tea Extract-induced Acute Hepatotoxicity in Rats.

Although green tea is considered to be a healthy beverage, hepatotoxicity associated with the consumption of green tea extract has been reported. In the present study, we characterized the hepatotoxicity of green tea extract in rats and explored the responsible mechanism. Six-week-old IGS rats received a single intraperitoneal (ip) injection of 200 mg/kg green tea extract (THEA-FLAN 90S). At 8, 24, 48 and 72 hrs and 1 and 3 months after exposure, liver damage was assessed by using blood-chemistry, histopathology, and immunohistochemistry to detect cell death (TUNEL and caspase-3) and proliferative activity (PCNA). Analyses of malondialdehyde (MDA) in serum and the liver and of MDA and thymidine glycol (TG) by immunohistochemistry, as oxidative stress markers, were performed. Placental glutathione S-transferase (GST-P), which is a marker of hepatocarcinogenesis, was also immunohistochemically stained. To examine toxicity at older ages, 200 mg/kg green tea extract was administered to 18-wk-old female rats. In 6-wk-old rats, 12% of males and 50% of females died within 72 hrs. In 18-wk-old rats, 88% died within 72 hrs. The serum levels of aspartate aminotransferase, alanine aminotransferase and/or total bilirubin increased in both males and females. Single-cell necrosis with positive signs of TUNEL and caspase-3 was seen in perilobular hepatocytes from 8 hrs onward in all lobular areas. PCNA-positive hepatocytes increased at 48 hrs. MDA levels in the serum and liver tended to increase, and MDA- and TG-positive hepatocytes were seen immunohistochemically. GST-P-positive hepatocellular altered foci were detected in one female rat at the 3-month time point. In conclusion, a single injection of green tea extract induced acute and severe hepatotoxicity, which might be associated with lipid peroxidation and DNA oxidative stress in hepatocytes.

Similarity of GATA-3 Expression between Rat and Human Mammary Glands.

The GATA family members are zinc finger transcription factors involved in cell differentiation and proliferation. In particular, GATA-3 is necessary for mammary gland maturation and is a useful marker in the characterization of mammary carcinoma in humans. The expression of GATA-3 protein in normal mammary glands, fibroadenomas and carcinomas was immunohistochemically compared in female rats and humans. In normal mammary glands of rats and humans, scattered luminal cells in the acini and whole ductal epithelial cells were positive for GATA-3 in the nuclei. No positive cells were detected in rat or human fibroadenomas. In rat and human mammary carcinomas, the nuclei of proliferating luminal-derived cancer cells expressed GATA-3. Therefore, GATA-3 protein is a candidate marker for mammary carcinoma in rats as well as humans.

Two cases of malignant peritoneal mesothelioma without asbestos exposure: cytologic and immunohistochemical features.

Approximately half a century has passed since asbestos was first reported to be the main cause of malignant mesothelioma; yet the incidence of this disease continues to increase worldwide. Twenty percent of cases occur without prior asbestos exposure, and in these patients, malignant peritoneal mesothelioma is more common than malignant pleural mesothelioma. Here, we report the cytomorphologic and immunohistochemical features of 2 cases of malignant peritoneal mesothelioma where there was no history of asbestos exposure. Ascitic cytology showed that most cells were isolated and that clusters were rarely observed, but the findings were consistent with malignant mesothelioma in both cases. Immunohistochemical analysis for epithelial membrane antigen, calretinin, vimentin, ß-catenin, melan-A, glucose transporter-1, cytokeratin CAM5.2, Wilms tumor antigen-1, D2-40, CD146, progesterone receptor, estrogen receptor, and cytokeratin 5/6 was indicative of malignant mesothelioma. In malignant mesothelioma without prior asbestos exposure, the etiology and prognostic significance is still unclear. Further study is needed to clarify this point.

Histopathological and immunohistochemical characterization of spontaneously occurring uterine deciduomas in young adult rats.

Uterine deciduomas were found in two female virgin rats, a 15-week-old Lewis rat and a 7-week-old Sprague-Dawley rat. The firm white nodules were located at the base of unilateral uterine horns and were approximately 6 mm and 4 mm in diameter. Histopathologically, the nodules were composed of three areas, each with a distinct type of proliferating cells: large epithelioid decidual cells with round nuclei, prominent nucleoli and abundant eosinophilic cytoplasm (antimesometrial region); compact spindle-shaped cells with oval nuclei and vacuolar cytoplasm (transitional region); and pleomorphic and spiny cells with round to oval nuclei and compact eosinophilic cytoplasm (mesometrial region). These cells proliferated in sheet-like arrangements and transformed into the other types of cells located in surrounding regions. Immunohistochemically, proliferating cells in all regions were strongly positive for proliferating cell nuclear antigen. The proliferating cells were positive for vimentin, and large decidual cells were positive for common acute lymphoblastic leukemia antigen 10, a marker of uterine interstitial cells. Large decidual cells were positive for α-smooth muscle actin and desmin, suggesting differentiation into muscular cells. Progesterone receptor was expressed in all cell types; however, estrogen receptor α was not expressed in the antimesometrial region. These extremely rare tumor-like nodules represent nonneoplastic lesions referred as decidual reactions of endometrial interstitial cells, and their biological behavior is that of a space-occupying benign tumor in young rats. Our cases might provide information as a historical control in toxicity and pharmacological studies in rats.

N -Methyl- N -nitrosourea-induced Renal Tumors in Rats: Immunohistochemical Comparison to Human Wilms Tumors.

N-Methyl-N-nitrosourea (MNU)-induced renal tumors in rats and Wilms tumors in humans were compared. Renal mesenchymal tumors (RMTs) and nephroblastomas (blastemal and epithelial components) in female Lewis rats treated with a single intraperitoneal injection of 50 mg/kg MNU at birth and Wilms tumors (blastemal, epithelial and mesenchymal components) in humans were analyzed for the expression of pancytokeratin (CK), vimentin, p63, α-smooth muscle actin (SMA), desmin, S-100, CD57, CD117/c-kit, Wilms tumor 1 protein (WT1) and ß-catenin. The mesenchymal components of rat RMTs and human Wilms tumors expressed vimentin, SMA and ß-catenin. The blastemal components of rat nephroblastomas and human Wilms tumors expressed vimentin, CD117/c-kit and ß-catenin. The epithelial components of rat nephroblastomas and human Wilms tumors expressed vimentin and ß-catenin. WT1 was expressed in different cellular components of rat tumors as compared with human Wilms tumors; the expression was seen in mesenchymal tumors and blastemal components of nephroblastomas in rats and epithelial components in human Wilms tumors. CK, p63 and CD57 were not expressed in rat RMTs or nephroblastomas, while CK and WT1 were expressed in epithelial components and CD57 was expressed in blastemal and epithelial components of human Wilms tumors. Rat and human tumors were universally negative for the expression of desmin and S-100. The immunohistochemical characteristics of rat renal tumors and human Wilms tumors may provide valuable information on the differences in renal oncogenesis and biology between the two species.

Retinal degeneration induced in adult mice by a single intraperitoneal injection of N-ethyl-N-nitrosourea.

Seven-week-old female BALB/c mice received a single intraperitoneal injection of N-ethyl-N-nitrosourea (ENU) (50, 100, 200, 400, or 600 mg/kg), and retinal damage was evaluated after 7 days. Sequential morphological features of the retina and retinal apoptosis, as determined by the TUNEL assay, were analyzed 6, 12, 24, and 72 hr and 7 days after treatment with 600 mg/kg of ENU. Moreover, older mice (25 to 34 weeks of age) received an intraperitoneal injection of 600 mg/kg ENU and were sacrificed 7 days later. All animals were necropsied, and both eyes were examined histopathologically. Two of the 5 mice that received 600 mg/kg ENU died during the experimental period. Histopathologically, all mice that received 600 mg/kg of ENU experienced retinal degeneration characterized by the loss of photoreceptor cells (disappearance of the outer nuclear layer and photoreceptor layer) in both the central and peripheral retina within 7 days. One of 5 mice treated with 400 mg/kg ENU exhibited retinal damage that was restricted to the central retina. Older mice treated with 600 mg/kg ENU exhibited retinal damage that was similar to the retinal damage in younger mice. In the 600 mg/kg ENU-treated mice, TUNEL-positive photoreceptor cells peaked 72 hr after ENU treatment. Retinal thickness and the photoreceptor cell ratio in the central and peripheral retina were significantly decreased, and the retinal damage ratio was significantly increased 7 days after treatment. In conclusion, ENU induces retinal degeneration in adult mice that is characterized by photoreceptor cell apoptosis.

Effects of short-term estrogen treatment on the progression of N-methyl-N-nitrosourea-induced premalignant mammary lesions in female Lewis rats.

We studied the effects of short-term estrogen treatment (STET) on the progression of mammary lesions from ductal hyperplasia (DH) through ductal carcinoma in situ (DCIS) to invasive ductal carcinoma (IDC) in the N-methyl-N-nitrosourea (MNU)-induced rat mammary carcinogenesis model. Three-week-old female Lewis rats (n = 40) received an intraperitoneal injection of MNU (50 mg/kg). Three weeks later, a 3-week-release, 0.25-mg, 17ß-estradiol pellet was subcutaneously implanted for 2 weeks in 20 rats (STET); the remaining 20 rats did not receive the estradiol pellets (age-matched control). All rats were killed at 12 weeks of age, and their abdominal-inguinal mammary glands were histologically examined. The incidence and multiplicity of DHs were similar between groups (STET, 90% and 3.9 ± 0.6 vs. age-matched controls, 80% and 3.0 ± 0.5). However, DCIS and IDC did not develop in STET rats, whereas DCIS (25% and 1.4 ± 0.2) and IDC (35% and 1.4 ± 0.3) developed in the age-matched controls. Immunoscores of estrogen and progesterone receptors and positive rate of proliferative cell nuclear antigen (PCNA) in DH were similar in both groups, while the positive rate of cyclin D1 was significantly reduced in the STET group (P < 0.05). Thus, STET blocked the progression from DH to DCIS in MNU-induced mammary carcinogenesis, and decreased expression of cyclin D1 may play an important role in the blockade of cell transition from DH to DCIS.

Cerebromalacia with epilepsy and cortical blindness in a laboratory Japanese macaque (Macaca fuscata).

The authors performed a pathological examination of a 5-year-old female laboratory Japanese monkey who developed cortical blindness and epileptic seizures. Generalized, tonic-clonic seizures started to occur during behavioral training to get the animal to enter a carrying cage for future psychological experiments. Blindness was suspected because of a lack of approaching behavior toward foods such as fruits. Although the monkey was extensively treated with anticonvulsants, the clinical signs did not improve. An increased serum creatine phosphokinase (CPK) level and bilateral occipital brain atrophy were detected. Histopathologically, a severe degree of cerebromalacia was detected bilaterally in the occipital lobe, and necrosis and gliosis were seen mainly in the temporal lobe. Focal inflammation was found in the meninges. No other changes were observed in other nervous tissues or organs, and no signs of a parasitic or viral infection were found in the systemic organs. Spontaneously occurring lesions in the central nervous system have been rarely reported in laboratory monkeys. In the present case, the cause of cerebromalacia could not be confirmed, but the relationship between symptoms such as abnormal vision and the presence of brain lesions was distinct. The authors believe that this case is a valuable historical control case for the laboratory Japanese macaque.

Solitary fibrous tumor of soft tissue: a case report and immunohistochemical study.

A case of solitary fibrous tumor (SFT) arising in the soft tissue of the left inguinal region is reported. A 57-year-old Japanese woman presented with a nonadherent, well-defined, oval mass that was 2 x 3 cm in diameter and located in the inguinal soft tissue. Microscopic evaluation showed proliferation of spindle-shaped, fibroblast-like cells by the coexistence of hypo- and hypercellular areas with mast cell infiltration separated by hemangiopericytoma-like blood vessels. Immunohistochemistry revealed strong expression of CD34 and CD99 in the fibroblast-like cells, supporting the diagnosis of SFT. Although the patient was free of symptoms such as hypoglycemia, immunoreactive insulin-like growth factor (IGF)-II was localized in the socalled Golgi area of the spindle-shaped cells. In conclusion, immunoreactive IGF-II was detected in SFT that was not associated with hypoglycemia.

N-methyl-N-nitrosourea-induced retinal degeneration in mice is independent of the p53 gene.

PURPOSE: A single systemic administration of N-methyl-N-nitrosourea (MNU) causes retinal degeneration involving photoreceptor cell loss within 7 days. MNU-induced photoreceptor cell loss is due to apoptosis and is a reliable animal model for human retinitis pigmentosa. The purpose of this study was to determine if p53 contributes to the development of MNU-induced retinal degeneration in mice. METHODS: Eight-week-old p53(-/-), p53(+/-), and p53(+/+) mice received an intraperitoneal injection of 60 mg/kg bodyweight of MNU. Age-matched p53(+/+) mice received the vehicle only (physiologic saline containing 0.05% acetic acid). Mice were sacrificed and necropsied 7 days after the treatment. Both eyes were examined histologically and morphometrically to determine retinal thickness, photoreceptor cell ratio, and retinal damage ratio. RESULTS: No mice died during the experiment, but the p53 null mice treated with MNU had a statistically significant weight loss compared to the other groups. Histologically, all MNU-treated mice, regardless of p53 gene status, experienced retinal degeneration characterized by photoreceptor cell loss (the disappearance of the outer nuclear layer and photoreceptor layer) in both the central and peripheral retina. All MNU-treated mice had significantly decreased retinal thickness and photoreceptor cell ratios at the central and peripheral retina and an increased retinal damage ratio compared to the vehicle-treated control. The retinal changes caused by MNU in p53(+/+), p53(+/-), and p53(-/-) mice were not significantly different and hence were related to a p53-independent apoptotic mechanism. CONCLUSIONS: Because the absence of p53 did not prevent photoreceptor cell loss, we conclude that p53 is not essential for MNU-mediated photoreceptor cell degeneration.

Glomeruloid hemangioma.

A 64-year-old Japanese woman suffering from idiopathic thrombocytopenic purpura was treated with prednisolone. During the course of steroid withdrawal she developed parotid gland enlargement and cervical lymph node swelling with multiple dome-shaped red papules on her trunk and upper limbs. On admission the patient was found to have numbness of her lower limbs (polyneuropathy), lymph node swelling (organomegaly), high glucose level (endocrinopathy), Bence-Jones protein-kappa in the urine (M protein) and skin with hyperpigmentation, hypertrichosis and multiple glomeruloid hemangiomas (skin abnormalities), indicating polyneuropathy-organomegaly-endocrinopathy-M-protein-skin abnormality (POEMS) syndrome. The patient was also found to have peripheral edema, ascites, and pleural effusion. The glomeruloid hemangiomas had intravascular capillary growth, which was composed of conglomerates of capillaries resulting in structures resembling renal glomeruli. Cells within the capillary loops were lined by endothelial cells with scant cytoplasm (CD31(+)/CD34(+)/CD68(-)/CD105(+)/UEA-1(+)) while the outer surfaces of the loops were covered by either swollen endothelial cells containing PAS- and immunoglobulin-positive eosinophilic hyaline globules (CD31(+)/CD34(-)/CD68(-/+)/CD105(-)/UEA-1(-)) or cells without globules. These two phenotypically different endothelial cells were separated by alpha-smooth muscle actin-positive pericytes. Pericytes and endothelial cells covering the outer surface of the loops were bordered by basement membrane. Biopsy of parotid gland and lymph node indicated Sjögren's syndrome and Castleman's disease of a hyaline-vascular type, respectively. Resumed prednisolone therapy has been successful, and the patient was left with minimal residual symptoms. Glomeruloid hemangioma is a specific marker of POEMS syndrome and is related to Castleman's disease. Idiopathic thrombocytopenic purpura and Sjögren's syndrome may also be related.

Estrogen and progesterone treatment mimicking pregnancy for protection from breast cancer.

Early age at full-term pregnancy lowers the risk of breast cancer in women; lactation seems to be of marginal importance and aborted pregnancy is not associated with reduced risk. Although early full-term pregnancy provides protection against breast cancer, first full-term pregnancy in older women appears to increase the risk. The protective effect of pregnancy has also been observed in rats and mice; in these animals, lactation has an additive effect and interrupted pregnancy provides partial but significant protection. Pregnancy at a young age (< or = 3 months) is highly effective, but pregnancy in older animals (> or = 4 months) is less effective. Parity-induced protection against mammary cancer in rodents can be reproduced by short-term treatment (approximately equivalent to gestational period of rodent or shorter) with the pregnancy hormones, estrogen and progesterone. Administration of pregnancy hormones to nulliparous women may be a useful strategy for protection against breast cancer. However, estrogen and progesterone are thought to play major roles in promotion of the proliferation of breast epithelial cells. Thus, the duration of such treatment and the age at which it is administered are essential factors that require further study. Experimental data suggest that short-term treatment of older rats (aged 6 months) with estrogen and progesterone accelerates mammary carcinogenesis and that long-term (>20 weeks) treatment abolishes the cancer-suppressing effect or even accelerates mammary carcinogenesis. Thus, the available evidence suggests that age and duration of estrogen and progesterone treatment are particularly important factors for protection from breast cancer.

N-methyl-N-nitrosourea-induced mammary carcinogenesis is promoted by short-term treatment with estrogen and progesterone mimicking pregnancy in aged female Lewis rats.

We examined the effects of short-term estrogen and progesterone treatment mimicking pregnancy in aged female Lewis rats on the development of N-methyl-N-nitrosourea (MNU)-induced mammary carcinoma. Rats were administered a single intraperitoneal injection of 20 mg/kg MNU at 7 weeks of age and half of those rats were administered a subcutaneously implanted 21-day release pellet containing 0.5 mg 17beta-estradiol and 32.5 mg progesterone (E/P) at 24 weeks of age. The rats were then monitored for the occurrence of mammary tumors. Rats were sacrificed when the largest mammary tumor became > or = 1 cm in diameter, or when the rat reached 48 weeks of age. Development of MNU-induced mammary carcinomas was accelerated after short-term E/P treatment, compared with E/P-untreated rats: the incidence of > or = 1-cm mammary carcinomas tended to increase (60 vs. 44%); the latency tended to shorten (28.7 vs. 34.6 weeks); and cancer multiplicity (number of all-sized carcinomas per rat) significantly increased (1.8 vs. 0.8). In E/P-treated rats, comedo necrosis was frequently seen and the incidence of estrogen receptor and/or progesterone receptor-negative mammary carcinomas was significantly increased. Early age at full-term pregnancy or short-term hormone treatment mimicking pregnancy may suppress the risk of breast cancer, but the age of hormone exposure is a crucial factor, because hormone exposure mimicking pregnancy in aged individuals may exert effects opposite of those exerted in younger individuals.

PARP inhibitors accelerate N-methyl-N-nitrosourea-induced cataractogenesis in Sprague-Dawley rats.

BACKGROUND: There have been no previous studies of the effects of poly(ADP-ribose) polymerase (PARP) inhibitors on N-methyl-N-nitrosourea (MNU)-induced cataractogenesis in rats. MATERIALS AND METHODS: A single intraperitoneal injection of 70 mg/kg MNU was administered to 15-day-old male and female Sprague-Dawley rats. In Experiment 1, rats were then subcutaneously injected with 1000 mg/kg nicotinamide either once or 3 times at 1-week intervals. In Experiment 2, rats were subcutaneously injected once with 50 mg/kg 3-aminobenzamide. For comparison, the following age-matched controls were included: MNU-untreated nicotinamide-injected rats, MNU-untreated 3-aminobenzamide-injected rats, and MNU-untreated PARP-inhibitor-untreated rats. Rats were examined for lens opacity. At 28 days after MNU injection, 10 to 20 rats per group were sacrificed In Experiment 1, at 3 days after MNU injection, 10 rats per group were sacrificed for apoptosis and cell proliferation detection. RESULTS: MNU caused lens epithelial cell apoptosis in the germinative zone, as indicated by TUNEL staining. However, regardless of MNU treatment lens epithelial cell proliferation was consistently seen in the germinative zone and sporadically seen in the central zone. At 28 days after MNU, mature cataracts were observed Nicotinamide significantly accelerated lens opacity and cataractogenesis, as indicated by a cataract index 3-Aminobenzamide significantly accelerated the development of lens opacity and tended to accelerate cataractogenesis. CONCLUSION: The PARP inhibitors nicotinamide and 3-aminobenzamide accelerated MNU-induced cataractogenesis.