Wistar Hannover rats, which have recently been introduced into Japan, are expected to be used in reproductive and developmental toxicity studies, yet the accumulation of background data is insufficient. This paper describes our historical data on the reproductive ability of this strain of rat. Three lots of sexually matured females (40 each) were received from CLEA JAPAN, Inc. with males of the same strain (30 or 36 each) and mated. A total of 47 dams were killed on gestation day 20 to examine their fetuses. The remaining 71 pregnant females were allowed to deliver spontaneously and observed for common reproductive parameters. The mating and fertility indices of females were both 99.2%. Overall mean numbers of implants and live fetuses at cesarean sectioning were 12.5 and 11.5, respectively. Fetal resorptions and deaths occurred at an incidence of 8.6%. Morphological examinations of fetuses revealed low incidences of spontaneous malformations (each one case of double aortic arch and absent cervical vertebral arch) and a variety of common variations. The followings are overall means of major reproductive parameters obtained from females with live birth: no. of implants, 12.5; no. of pups delivered, 11.8; viability index of pups at birth, 99.8%; and days of age at sexual maturation (vaginal opening and preputial separation), 30.3 and 42.8, respectively. Our present observations confirmed a minimal deviation among 3 lots of animals in terms of reproductive abilities. These results suggest that this strain of rat can be used in reproductive and developmental toxicity studies, although the sensitivity to toxicants remains to be elucidated.

The studies were conducted in rats and rabbits to elucidate the potential developmental toxicity of p, p'‐DDT in general accordance with the improved Japanese MAFF guidelines (12‐Nousan‐No. 8147,2–1–18, 2000). p, p'‐DDT suspended in 1% aqueous solution of CMC was administered orally to pregnant Jcl:SD rats on gestational days (GD) 6–19 at a dose of 0,5, 25, or 100 mg/kg/day and to pregnant KbI: JW rabbits on GD 6–27 at a dose of 0,5,20, or 80 mg/kg/day. Maternal animals were killed on the day after the last day of administration for morphological examination of their fetuses with special attention to the reproductive organs. Adverse effects on maternal animals were found only at the highest dose in both species; i.e., clonic convulsion (2/24 in rats, 5/22 in rabbits), mortality (1/24 in rats), abortion or premature delivery (4/22 in rabbits), and reduced body weight gains and food consumption. However, the control and treated groups showed comparable values for the numbers of corpora lutea and implants, percent preimplantation losses, number of live fetuses, percent resorptions and fetal deaths, sex ratio, fetal body weights, and placental weights in both species, and anogenital distance and testicular histology in rats. Although fetal examination revealed slightly increased incidence of 27 presacral vertebrae in the highest dose group in rats, there was no treatment‐related increase in the incidence of malformations in any of the species. Based on these results, it is concluded that p, p'‐DDT causes no malformations, including male reproductive organ abnormalities, in either rats or rabbits, although it results in an increased incidence of skeletal variations in rats at a maternally toxic dose.

This report describes the photochemical behavior of single-walled carbon nanotubes (SWNTs) in the presence of propylamine. The SWNTs are characterized by absorption and Raman spectroscopy. The spectral changes due to photoirradiation indicate that reactions occur predominantly with the metallic SWNTs and small-diameter SWNTs. The detection of amine radicalcation species by ESR spectroscopy reveals photoinduced electron transfer from the amine to the excited SWNTs. After exposure of the photoirradiated SWNTs to air, the characteristic spectra were recovered, except for that of the small-diameter SWNTs. The results suggest that, after photoreduction of the SWNTs, subsequent selective sidewall functionalization of the small-diameter SWNTs occurs.

3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a by-product of wood pulp manufacture and a contaminant of chlorinated drinking water, was investigated for potential teratogenicity using the micromass in vitro test system. Twelve-day rat embryo midbrain (central nervous system, CNS) and limb bud (LB) cells were exposed to MX at concentrations of 1, 2, 5, or 10 microg/ml in the culture medium with or without S9 mix. Under the experimental conditions, the amount of MX rapidly declined in the culture medium with a half-life of 56 min. Nevertheless, differentiation of CNS and LB cells was significantly inhibited at concentrations of 2 microg/ml or more, when the cells were exposed to MX in the absence of S9 mix. The estimated IC50 was approximately 3 microg/ml for both CNS and LB cell cultures. On the other hand, exposure of CNS and LB cells to MX along with S9 mix did not reduce the number of differentiated foci at any concentrations tested. These results suggest that MX may be a potential direct-acting in vitro teratogen.

3‐Chloro‐4‐(dichloromethyl)‐5‐hydroxy‐2(5H)‐furanone (MX) causes complete inhibition of rat embryonic midbrain (CNS) cell differentiation in the micromass in vitro test when applied at a concentration of 5 μg/ml under conditions where MX is rapidly degraded in culture medium with a half‐life of 56 min. This study investigated whether or not degradation products of MX have inhibitory effects on CNS cell differentiation following pre‐incubation of MX in culture medium for 0.5, 1 or 2 hr. When MX was pre‐incubated for 0.5 hr, the mean number of differentiated foci was 0.2 against 62.5 for the control. However, the number increased to 44.7 when pre‐incubation time was extended to 2 hr. These results suggest that MX, but not its degradation products, is a teratogen in vitro. MX manifested almost complete inhibitory effects on CNS cell differentiation by 0.5 hr of exposure.