Treatment with a Global Methyltransferase Inhibitor Induces the Intranuclear Aggregation of ALS-Linked FUS Mutant In Vitro.

FUS/TLS (fused in sarcoma/translocated in liposarcoma) encodes a multifunctional DNA/RNA binding protein with non-classical carboxy (C)-terminal nuclear localization signal (NLS). A variety of ALS-linked mutations are clustered in the C-terminal NLS, resulting in the cytoplasmic mislocalization and aggregation. Since the arginine methylations are implicated in the nuclear-cytoplasmic shuttling of FUS, a methylation inhibitor could be one of therapeutic targets for FUS-linked ALS. We here examined effects of methylation inhibitors on the cytoplasmic mislocalization and aggregates of ALS-linked C-terminal FUS mutant in a cell culture system. Treatment with adenosine dialdehyde (AdOx), a representative global methyltransferase inhibitor, remarkably mitigated the cytoplasmic mislocalization and aggregation of FUS mutant, which is consistent with previous reports. However, AdOx treatment of higher concentration and longer time period evoked the intranuclear aggregation of the ectopic expressed FUS protein. The pull down assay and the morphological analysis indicated the binding between FUS and Transportin could be potentiated by AdOx treatment through modulating methylation status in RGG domains of FUS. These findings indicated the treatment with a methylation inhibitor at the appropriate levels could alleviate the cytoplasmic mislocalization but in excess this could cause the intranuclear aggregation of FUS C-terminal mutant.

Repeated dose and reproductive/developmental toxicity of perfluorododecanoic acid in rats.

Perfluoroalkyl carboxylic acids (PFCAs) are a series of environmental contaminants that have received attention because of their possible adverse effects on wildlife and human health. Although many toxicological studies have been performed on perfluorooctanoic acid with carbon chain length C8, available toxicity data on PFCAs with longer chains are still insufficient to evaluate their hazard. A combined repeated dose and reproductive/developmental toxicity screening study for perfluorododecanoic acid (PFDoA; C12) was conducted in accordance with OECD guideline 422 to fill these toxicity data gaps. PFDoA was administered by gavage to male and female rats at 0.1, 0.5, or 2.5 mg/kg/day. The administration of PFDoA at 0.5 and 2.5 mg/kg/day for 42-47 days mainly affected the liver, in which hypertrophy, necrosis, and inflammatory cholestasis were noted. Body weight gain was markedly inhibited in the 2.5 mg/kg/day group, and a decrease in hematopoiesis in the bone marrow and atrophic changes in the spleen, thymus, and adrenal gland were also observed. Regarding reproductive/developmental toxicity, various histopathological changes, including decreased spermatid and spermatozoa counts, were observed in the male reproductive organs, while continuous diestrous was observed in the females of the 2.5 mg/kg/day group. Seven of twelve females receiving 2.5 mg/kg/day died during late pregnancy while four other females in this group did not deliver live pups. No reproductive or developmental parameters changed at 0.1 or 0.5 mg/kg/day. Based on these results, the NOAELs of PFDoA were concluded to be 0.1 mg/kg/day for repeated dose toxicity and 0.5 mg/kg/day for reproductive/developmental toxicity.

Vascular endothelial cells promote cortical neurite outgrowth via an integrin ß3-dependent mechanism.

The interaction of neurons with their non-neuronal milieu plays a crucial role in the formation of neural networks, and wide variety of cell-contact-dependent signals that promote neurite elongation have been identified. In this study, we found that vascular endothelial cells promote neurite elongation in an integrin ß3-dependent manner. Vascular endothelial cells from the cerebral cortex promoted neurite elongation of cortical neurons in a cell contact-dependent manner. This effect was mediated by arginine-glycine-aspartic acid (RGD), a major recognition sequence for integrins. Pharmacological blockade of integrin ß3 abolished the neurite elongation effect induced by the endothelial cells. Immunocytochemical analysis revealed that integrin ß3 was expressed on cultured cortical neurons. These results demonstrate that the neurite elongation promoted by vascular endothelial cells requires integrin ß3. Vascular endothelial cells may therefore play a role in the development and repair of neural networks in the central nervous system.

A novel mutation in the thyroglobulin gene that causes goiter and dwarfism in Wistar Hannover GALAS rats.

Outbred stocks of rats have been used extensively in biomedical, pharmaceutical and/or toxicological studies as a model of genetically heterogeneous human populations. One of such stocks is the Wistar Hannover GALAS rat. However, the colony of Wistar Hannover GALAS rat has been suspected of keeping a problematic mutation that manifests two distinct spontaneous abnormalities, goiter and dwarfism, which often confuses study results. We have successfully identified the responsible mutation, a guanine to thymine transversion at the acceptor site (3' end) of intron 6 in the thyroglobulin (Tg) gene (Tgc.749-1G>T), that induces a complete missing of exon 7 from the whole Tg transcript by mating experiments and subsequent molecular analyses. The following observations confirmed that Tgc.749-1G>T/Tgc.749-1G>T homozygotes manifested both dwarfism and goiter, while Tgc.749-1G>T/+ heterozygotes had only a goiter with normal appearance, suggesting that the mutant phenotypes inherit as an autosomal semi-dominant trait. The mutant phenotypes, goiter and dwarfism, mimicked those caused by typical endocrine disrupters attacking the thyroid. Hence a simple and reliable diagnostic methodology has been developed for genomic DNA-based genotyping of animals. The diagnostic methodology reported here would allow users of Wistar Hannover GALAS rats to evaluate their study results precisely by carefully interpreting the data obtained from Tgc.749-1G>T/+ heterozygotes having externally undetectable thyroidal lesions.

A functional analysis of GABARAP on 17p13.1 by knockdown zebrafish.

Array-based comparative genomic hybridization identified a 2.3-Mb microdeletion of 17p13.2p13.1 in a boy presenting with moderate mental retardation, intractable epilepsy and dysmorphic features. This deletion region was overlapped with the previously proposed shortest region overlapped for microdeletion of 17p13.1 in patients with mental retardation, microcephaly, microretrognathia and abnormal magnetic resonance imaging (MRI) findings of cerebral white matter, in which at least 17 known genes are included. Among them, DLG4/PSD95, GPS2, GABARAP and KCTD11 have a function in neuronal development. Because of the functional importance, we paid attention to DLG4/PSD95 and GABARAP, and analyzed zebrafish in which the zebrafish homolog of human DLG4/PSD95 and GABARAP was knocked down and found that gabarap knockdown resulted in small head and hypoplastic mandible. This finding would be similar to the common findings of the patients with 17p13.1 deletions. Although there were no pathogenic mutations in DLG4/PSD95 or GABARAP in a cohort study with 142 patients with idiopathic developmental delay with/without epilepsy, further studies would be required for genes included in this region.

Developmental toxicity of flucytosine following administration to pregnant rats at a specific time point of organogenesis.

To investigate the abnormalities that are specific to administration of flucytosine at one time point during embryonic organogenesis, flucytosine was administered orally to pregnant Sprague Dawley (SD) rats in a single dose on day 11 of pregnancy at 25 or 35 mg/kg. Fetuses on day 20 of pregnancy were externally, viscerally, and skeletally examined. Maternal body weight gain and food consumption were suppressed the day after administration of a 35 mg/kg. Fetal examinations revealed various alterations in both dose groups: externally preaxial polydactyly in the hind limb; skeletally fused lumbar centrum, absent sacral centrum, supernumerary sacral vertebra, and absent ribs. Our findings indicated that specific types of external and skeletal anomalies were induced following flucytosine administration on day 11 of pregnancy.

Two-generation reproductive toxicity study of the flame retardant hexabromocyclododecane in rats.

Male and female rats were fed a diet containing flame retardant hexabromocyclododecane (HBCD) at 0, 150, 1500 or 15,000 ppm throughout the study beginning at the onset of a 10-week pre-mating period and continuing through the mating, gestation and lactation periods for two generations. The mean daily intakes of HBCD during the whole period of administration were 10.2, 101 and 1008 mg/kg bw in F0 males, 14.0, 141 and 1363 mg/kg bw in F0 females, 11.4, 115 and 1142 mg/kg bw in F1 males, and 14.3, 138 and 1363 mg/kg bw in F1 females for 150, 1500 and 15,000 ppm, respectively. The incidence of rats with decreased thyroid follicles size was increased in F0 and F1 males and females at 1500 ppm and higher. Serum TSH levels were increased in F0 and F1 females at 1500 ppm and higher, and serum T4 levels were decreased in F0 males and females at 15,000 ppm. The number of the primordial follicles in the ovary of F1 females was reduced at 1500 ppm and higher. There were increases in the absolute and relative weights of the liver in male adults and male and female weanlings at 1500 ppm and higher, and in female adults at 15,000 ppm, and of the thyroid in male and female adults at 15,000 ppm. Decreased body weight and body weight gain associated with reduced food consumption were found in F1 males and females at 15,000 ppm. Decreases were found in the viability index of F2 pups and the body weight of male F1 and F2 pups and female F2 pups at 15,000 ppm. In F2 pups, there were low incidences of the completion of eye opening in males at 15,000 ppm and in females at 1500 ppm and higher, and of completed mid-air righting in females at 15,000 ppm. The data indicate that the NOAEL of HBCD in this study was 150 ppm (10.2mg/kg bw/day). The estimated human intake of HBCD is well below the NOAEL in the present study.

Two-generation reproductive toxicity study of the rubber accelerator N,N-dicyclohexyl-2-benzothiazolesulfenamide in rats.

Male and female Crl:CD(SD) rats were fed a diet containing rubber accelerator N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS) at 0, 80, 600 or 4500ppm throughout the study beginning at the onset of a 10-week pre-mating period and continuing through the mating, gestation, and lactation periods for two generations. At 4500ppm, decreases in the body weight, body weight gain, and food consumption were found in F0 males and females. No changes in the estrous cyclicity, copulation index, fertility index, gestation index, delivery index, number of implantations, precoital interval, or gestation length were observed in any generation at any dose of DCBS. Delayed preputial separation at 4500ppm as well as delayed vaginal opening and higher body weight at the age of vaginal opening at 600 and 4500ppm were found in the F1 generation. A transient change in performance in a water-filled multiple T-maze was found at 600 and 4500ppm in F1 females. There were no compound-related changes in number of pups delivered, sex ratio of pups, viability of pups, anogenital distance, surface righting reflex, negative geotaxis reflex, mid-air righting reflex, pinna unfolding, incisor eruption, or eye opening in the F1 and F2 generations. The body weight of F1 and F2 male and female pups was lowered at 4500ppm. Reduced uterine weight of the weanlings was noted in the F1 generation at 4500ppm and in the F2 generation at 600 and 4500ppm. The data indicate that the NOAEL of DCBS for two-generation reproductive toxicity is 80ppm (5.2mg/kgbw per day) in rats.

Characterization of human dental pulp cells grown in chemically defined serum-free medium.

Dental pulp cells (DPCs) are promising candidates for use as transplantable cells in regenerative medicine. However, ex vivo expansion of these cells typically requires culture media containing fetal bovine serum, which may cause infection and immunological reaction following transplantation. In addition, the proliferation and differentiation of DPCs markedly depend upon serum batches. Therefore, the present study examined whether DPCs could be expanded under serum-free conditions. DPCs obtained from four donors were identified to proliferate actively in the serum-free medium, STK2, when compared with those cells in control medium (Dulbecco's modified Eagle's medium containing 10% serum). The high proliferative potential with STK2 was maintained through multiple successive culture passages. DNA microarray analyses demonstrated that the gene expression profile of DPCs grown in STK2 was similar to that of cells grown in the control medium; however, a number of genes related to cell proliferation, including placental growth factor and inhibin-ßE, were upregulated in the STK2 cultures. Following induction of osteogenesis, DPCs grown in STK2 induced alkaline phosphatase activity and calcification at higher levels compared with the control medium cultures, indicating maintenance of differentiation potential in STK2. This serum-free culture system with DPCs may have applications in further experimental studies and as a clinical strategy in regenerative medicine.

Evaluation of reproductive and developmental toxicity of the rubber accelerator N,N-dicyclohexyl-2-benzothiazolesulfenamide in rats.

Male and female Crl:CD(SD) rats were fed a diet containing the rubber accelerator N,N-dicyclohexyl-2-benzothiazolesulfenamide (DCBS) at 0, 1500, 3000, 6000 or 10,000 p.p.m. (0, 83, 172, 343 or 551 mg/kg bw/day in males and 0, 126, 264, 476 or 707 mg/kg bw/day in females) for a total of 57 days beginning 16 days before mating in males, and a total of 61-65 days from 16 days before mating to day 21 of lactation in females. Body weight gains and food consumption were reduced in males at 6000 p.p.m. and higher and in females at 3000 p.p.m. and higher. The weights of the spleen at 6000 and 10,000 p.p.m. and of the thymus at 10,000 p.p.m. were decreased in females. No changes in estrous cyclicity, copulation index, fertility index, gestation index, delivery index, precoital interval or gestation length were observed at any dose of DCBS. Numbers of implantations at 6000 and 10,000 p.p.m. and pups delivered at 10,000 p.p.m. were reduced. There were no changes in the sex ratio or viability of pups. The body weights of male and female pups were lowered at 6000 p.p.m. and higher. Decreased weight of the spleen in weanlings was also observed in males at 1500 p.p.m. and higher and in females at 3000 p.p.m. and higher. The data indicate that DCBS possesses adverse effects on reproduction and development in rats.

Prenatal developmental toxicity study of the basic rubber accelerator, 1,3-di-o-tolylguanidine, in rats.

Pregnant rats were given 1,3-di-o-tolylguanidine (DTG) by gavage at 0, 10, 20 or 40 mg/kg bw/day on days 6-19 of pregnancy and the pregnancy outcome was determined on day 20 of pregnancy. At 40 mg/kg bw/day, deaths were observed in four out of 24 females. The incidences of females showing mydriasis at 20 and 40 mg/kg bw/day and showing decreased locomotor activity at 40 mg/kg bw/day were significantly increased. Alopecia, bradypnea, prone position and tremor were also observed at mg/kg bw/day. The maternal body weight gain at 20 and 40 mg/kg bw/day and food consumption at 40 mg/kg bw/day were significantly reduced. A significantly decreased weight of the gravid uterus, increased incidence of postimplantation loss, decreased number of live fetuses, and lowered weights of fetuses and placentae were found at 40 mg/kg bw/day. The incidences of the total number of fetuses with external malformations at 40 mg/kg bw/day and with skeletal malformations at 20 and 40 mg/kg bw/day were significantly increased. Significantly higher incidences of fetuses with brachydactyly and short tail and defects of caudal vertebrae, phalanges and metacarpals were observed at 40 mg/kg bw/day. Delayed ossification was also noted at 40 mg/kg bw/day. The data indicate that DTG is teratogenic at maternal toxic doses and the NOAELs of DTG for maternal and developmental toxicity are 10 mg/kg bw/day in rats.

Susceptibility of newborn rats to 3-ethylphenol and 4-ethylphenol compared with that of young rats.

Newborn rat studies were conducted with oral administration of 3-ethylphenol (3EP) and 4-ethylphenol (4EP) on postnatal days (PND) 4-21 to allow comparison of no observed adverse effect level (NOAEL) and unequivocally toxic level (UETL) with those from 28-day studies of young rats starting at 5-6 weeks of age. In the newborn rat studies, slightly lowered body weight was observed after 3EP treatment, and deaths, hypoactivity, Straub tail, deep respiration and delayed righting reflex were clearly observed after 4EP treatment. In the young rat studies, salivation, staggering gait, changes in the liver including high values of liver weight and alanine aminotransferase or total cholesterol and the lesions in the forestomach were clearly observed after 3EP and 4EP treatments. NOAELs of 3EP and 4EP in the newborn rat studies appeared to be almost 3 times lower than those in the young rat studies. As a clear toxicity of 3EP was not observed in newborn rats, UETLs were not established for 3EP. Regarding 4EP, UETL of young rats was 4-5 times higher than that of newborn rats. In conclusion, newborn rats were 3-5 times more susceptible to 3EP and 4EP than young rats.

Role of MSX1 in Osteogenic Differentiation of Human Dental Pulp Stem Cells.

Msh homeobox 1 (MSX1) encodes a transcription factor implicated in embryonic development of limbs and craniofacial tissues including bone and teeth. Although MSX1 regulates osteoblast differentiation in the cranial bone of young animal, little is known about the contribution of MSX1 to the osteogenic potential of human cells. In the present study, we investigate the role of MSX1 in osteogenic differentiation of human dental pulp stem cells isolated from deciduous teeth. When these cells were exposed to osteogenesis-induction medium, runt-related transcription factor-2 (RUNX2), bone morphogenetic protein-2 (BMP2), alkaline phosphatase (ALPL), and osteocalcin (OCN) mRNA levels, as well as alkaline phosphatase activity, increased on days 4-12, and thereafter the matrix was calcified on day 14. However, knockdown of MSX1 with small interfering RNA abolished the induction of the osteoblast-related gene expression, alkaline phosphatase activity, and calcification. Interestingly, DNA microarray and PCR analyses revealed that MSX1 knockdown induced the sterol regulatory element-binding protein 2 (SREBP2) transcriptional factor and its downstream target genes in the cholesterol synthesis pathway. Inhibition of cholesterol synthesis enhances osteoblast differentiation of various mesenchymal cells. Thus, MSX1 may downregulate the cholesterol synthesis-related genes to ensure osteoblast differentiation of human dental pulp stem cells.

A two-generation reproductive toxicity study of diethyl phthalate (DEP) in rats.

A two-generation reproductive toxicity study was performed to evaluate the effects of diethyl phthalate on parental reproductive performance, including features of the endocrine system and development and growth of offspring at dietary dose levels of 0, 600, 3000 and 15000 ppm. In F0 and F1 parents, no treatment-related adverse effects were observed in clinical findings, body weights, food consumption, reproductive parameters, and gross or histopathological findings in any treated group. Increased liver weights and enhanced activities of metabolic enzymes were observed in F0 males at 15000 ppm. F0 males also exhibited an increase in the content of CYP3A2, a cytochrome P450 isozyme, at 15000 ppm, and a decrease in the levels of serum testosterone at 3000 and 15000 ppm, suggesting sex steroid metabolism might be changed. However, these were not considered adverse effects because the degree of change was too slight to affect the reproductive capability to produce progeny. Body weight gains before weaning were inhibited in F1 and F2 pups and vaginal opening was slightly delayed in F1 females at 15000 ppm. No changes were observed in the reproductive performance. Therefore, the no-observed-adverse-effect level (NOAEL) from this study is considered to be 15000 ppm for parental animals, and 3000 ppm for development and growth of the pups.

Characteristic expression of MSX1, MSX2, TBX2 and ENTPD1 in dental pulp cells.

Dental pulp cells (DPCs) are a promising source of transplantable cells in regenerative medicine. However, DPCs have not been fully characterized at the molecular level. The aim of the present study was to distinguish DPCs from various source-derived mesenchymal stem cells (MSCs), fibroblasts (FBs) and other cells by the expression of several DPC-characteristic genes. DPCs were isolated from human pulp tissues by the explant method or the enzyme digestion method, and maintained with media containing 10% serum or 7.5% platelet-rich plasma. RNA was isolated from the cells and from dental pulp tissue specimens. The mRNA levels were determined by DNA microarray and quantitative polymerase chain reaction analyses. The msh homeobox 1, msh homeobox 2, T-box 2 and ectonucleoside triphosphate diphosphohydrolase 1 mRNA levels in DPCs were higher than that of the levels identified in the following cell types: MSCs derived from bone marrow, synovium and adipose tissue; and in cells such as FBs, osteoblasts, adipocytes and chondrocytes. The enhanced expression in DPCs was consistently observed irrespective of donor age, tooth type and culture medium. In addition, these genes were expressed at high levels in dental pulp tissue in vivo. In conclusion, this gene set may be useful in the identification and characterization of DPCs in basic studies and pulp cell-based regeneration therapy.

Curly vibrissae, a new mutation in the Wistar-derived rat.

A new mutation was identified in the PD (Preaxial Duplication) strain of rats, the main manifestations of which were curly and sparse vibrissae with retarded outer hair growth. As the main characteristic of this mutant rat is abnormally curled appearance of the vibrissae, "curly vibrissae" is proposed as the name of this mutant gene, and "cv" as its symbol. Genetic analyses reveal that the mutant characteristics are inherited as autosomal recessive traits and the cv gene is independent from the pd gene that carried by the original PD colony. The cv/cv homozygous rats have a small number of short and/or curly vibrissae around the nose. The vibrissae on the cheek and/or above the eyes are also short and curled; however, no vibrissa appears on the lower mandible. Although hair growth seems to be retarded, the outer hairs showed nearly normal length by 10 weeks of age. The outer hairs of matured cv/cv rats appear silky and translucent. The adult mutant rats often exhibit loss of hair on the head and/or back. Lactating females usually lose their abdominal hair. Both sexes of cv/cv homozygotes have normal reproductive ability. No internal malformations accompany vibrissa and hair abnormalities.

Higher susceptibility of newborn than young rats to 3-methylphenol.

To determine susceptibility of infants to 3-methylphenol, a repeated dose toxicity study was conducted with oral administration to newborn and young rats. In an 18-day newborn study from postnatal days 4 to 21 at doses of 30, 100 and 300 mg/kg/day, various clinical signs including deep respiration, hypersensitivity on handling and tremors under contact stimulus, and depressed body weight gain were observed at 300 mg/kg. At 100 mg/kg, hypersensitivity and tremors were also noted in a small number of males only on single days during the dosing period. No adverse effects were observed in the 30 mg/kg group. There were no abnormalities of physical development, sexual maturation and reflex ontogeny. The no observed adverse effect level (NOAEL) for newborn rats was considered to be 30 mg/kg/day and the unequivocally toxic level 300 mg/kg/day. In a 28-day study starting at 5 weeks of age, clinical signs and depression of body weight gain, as observed in the newborn rats, appeared in both sexes at 1000 mg/kg but not 300 mg/kg. The NOAEL and the unequivocally toxic level were 300 mg/kg/day and 1,000 mg/kg/day, respectively. From these results, newborn rats were concluded to be 3 to 10 times more susceptible to 3-methylphenol than young rats. However, the realistic no adverse effect dose for the newborn must be slightly lower than 100 mg/kg/day, at which the toxicity incidence was very low, rather than 30 mg/kg/day. Based on this speculation and the equal toxicity at unequivocally toxic levels, the differences in the susceptibility to 3-methylphenol could be concluded to be 3 to 4 times. This is consistent with the results of our previous comparative studies on 4-nitrophenol, 2,4-dinitrophenol and 3-aminophenol, which showed 2 to 4 times differences in the susceptibility between newborn and young rats.

Historical control data on developmental toxicity studies in rodents.

Historical control data on rodent developmental toxicity studies, performed between 1994 and 2010, were obtained from 19 laboratories in Japan, including 10 pharmaceutical and chemical companies and nine contract research organizations. Rats, mice, and hamsters were used for developmental toxicity studies. Data included maternal reproductive findings at terminal cesarean sections and fetal findings including the spontaneous incidences of external, visceral, and skeletal anomalies. No noticeable differences were observed in maternal reproductive data between laboratories. Inter-laboratory variations in the incidences of fetuses with anomalies appeared to be due to differences in the selection of observation parameters, observation criteria, classification of the findings, and terminology of fetal alterations. Historical control data are useful for the appropriate interpretation of experimental results and evaluation of the effects of chemical on reproductive and developmental toxicities.

Repeated dose and reproductive/developmental toxicity of perfluorooctadecanoic acid in rats.

Male and female rats were given perfluorooctadecanoic acid (PFOdA) by gavage at 40, 200 or 1,000 mg/kg/day, and each female was mated with a male in the same dose group after 14-day administration. Males were dosed for 42 days and females were dosed throughout the gestation period until day 5 of lactation. One female given 1,000 mg/kg/day was euthanized on day 18 of gestation due to a moribund condition; however, no other treatment-related clinical signs of toxicity were observed. Body weights fell at 1,000 mg/kg/day from day 28 through the administration period in males and throughout gestation and lactation in females. Red blood cell count, hemoglobin level and hematocrit were decreased at 200 and 1,000 mg/kg/day in males and activated partial thromboplastin time was prolonged at 1,000 mg/kg/ day in females. Histopathological examination revealed hepatic changes, such as centrilobular hypertrophy and necrosis, in males given 200 and 1,000 mg/kg/day and in females given 1,000 mg/kg/day. Pancreatic zymogen granule was decreased in both sexes at 1,000 mg/kg/day. As for reproductive and developmental toxicity, there were decreases in the number of corpora lutea, implantation, total number of pups born and the number of live pups on postnatal days 0 and 4 at 1,000 mg/kg/day. At this dose, birth weights of pups were decreased and postnatal body weight gain was inhibited. Based on these findings, the NOAEL of PFOdA was considered to be 40 mg/kg/day for repeated dose toxicity and 200 mg/kg/day for reproductive/developmental toxicity.

Historical control data on prenatal developmental toxicity studies in rabbits.

Historical control data on rabbit prenatal developmental toxicity studies, performed between 1994-2010, were obtained from 20 laboratories, including 11 pharmaceutical and chemical companies and nine contract laboratories, in Japan. In this paper, data were incorporated from a laboratory if the information was based on 10 studies or more. Japanese White rabbits and New Zealand White rabbits were used for prenatal developmental toxicity studies. The data included maternal reproductive findings at terminal cesarean sections and fetal findings including spontaneous incidences of morphological alterations. No noticeable differences between strains or laboratories were observed in the maternal reproductive and fetal developmental data. The inter-laboratory variations in the incidences of fetal external, visceral, and skeletal alterations seem to be due to differences in the selection of observation parameters, observation criteria, and classification of the findings, and terminology of fetal alterations.