Developmental Toxicity of Aspirin Prenatally Given to Rats: Assessment in Sic: Wistar-KY Rats

Abstract Slc:Wistar-KY rats were administered orally with 62.5, 125, 187.5 or 250 mg/kg aspirin suspended with 0.5 % CMC-Na on days 9–11 of gestation (plug += day 0). Suppression of maternal weight gain and food consumption during treatment was observed at and over 187.5 mg/kg. At term, the fetal mortality increased at and over 187.5 mg/kg and the fetal weight was lowered at and over 125 mg/kg. Among 15 live fetuses at 250 mg/kg, 4 had external malformations. In the skeletal examination (double staining), skeletal anomalies increased at and over 187.5 mg/kg. The skeletal variations such as vertebral anomalies, fused costal cartilages and increased presacral vertebrae were often encountered and delayed ossification was also found at and over 125 mg/kg. The internal anomalies tended to increase at and over 187.5 mg/kg. The live birth rate was significantly lower at 187.5 mg/kg than that in controls, and all pups, except for 3 from a dam, died before weaning. At 125 mg/kg, the pivoting locomotion on day 7 post partum was poorer as compared with controls. The physical and functional development at 62.5 mg/kg was not changed. There were no significant effects on male offspring in the open-field, rotarod, under-water T-maze and avoidance learning tests. However, in the Biel T-maze test (9–10 weeks of age), the aspirin-treated groups showed more errors and the increased elapsed time on the 1st trial day than controls. These results indicate that aspirin may induce a slight learning defect on rat offspring even at the non-teratogenic dose and the Biel T-maze test is more sensitive than any other learning tests given in this study.     

Developmental Toxicity of Aspirin Prenatally Given to Rats: Assessment in Sic: Wistar-KY Rats

Abstract Slc:Wistar-KY rats were administered orally with 62.5, 125, 187.5 or 250 mg/kg aspirin suspended with 0.5 % CMC-Na on days 9–11 of gestation (plug += day 0). Suppression of maternal weight gain and food consumption during treatment was observed at and over 187.5 mg/kg. At term, the fetal mortality increased at and over 187.5 mg/kg and the fetal weight was lowered at and over 125 mg/kg. Among 15 live fetuses at 250 mg/kg, 4 had external malformations. In the skeletal examination (double staining), skeletal anomalies increased at and over 187.5 mg/kg. The skeletal variations such as vertebral anomalies, fused costal cartilages and increased presacral vertebrae were often encountered and delayed ossification was also found at and over 125 mg/kg. The internal anomalies tended to increase at and over 187.5 mg/kg. The live birth rate was significantly lower at 187.5 mg/kg than that in controls, and all pups, except for 3 from a dam, died before weaning. At 125 mg/kg, the pivoting locomotion on day 7 post partum was poorer as compared with controls. The physical and functional development at 62.5 mg/kg was not changed. There were no significant effects on male offspring in the open-field, rotarod, under-water T-maze and avoidance learning tests. However, in the Biel T-maze test (9–10 weeks of age), the aspirin-treated groups showed more errors and the increased elapsed time on the 1st trial day than controls. These results indicate that aspirin may induce a slight learning defect on rat offspring even at the non-teratogenic dose and the Biel T-maze test is more sensitive than any other learning tests given in this study.     

Male-Mediated Developmental Toxicity: Enhanced Susceptibility to Induced Teratogenesis in the Offspring of Male Mice Treated with Ethylnitrosourea

Male ICR strain mice were injected intraperitoneally with ENU at 50 mg/kg daily for 5 days and mated to untreated virgin females of the same strain on days 64–80 after the last dose. Copulations during this period involved spermatogonial stem cells at the time of the last treatment. Subsequently, copulated females were injected intraperitoneally with ENU at 25–100 mg/kg on day 8 of gestation, at 50–200 mg/kg on day 12 of gestation or injected subcutaneously with triamcinolone acetonide at 1.25–10 mg/kg on day 12 of gestation. The uterine contents were examined on day 18 of gestation. Fetuses of dams treated on day 8 of gestation were inspected for external and skeletal abnormalities, and those of dams treated on day 12 were inspected for external abnormalities including cleft palate. Frequencies of microphthalmia and cleft palate in the group in which females mated with ENU-treated males were treated with ENU at 50 mg/kg on day 8 of gestation or with ENU at 50 mg/kg on day 12 of gestation, respectively, were significantly higher than those in the group in which females mated with phosphate buffer-treated males were treated with ENU at 50 mg/kg on day 8 or at 50 mg/kg on day 12. No significant increases in the frequency of cleft palate were observed in the groups in which females mated with ENU-treated males were treated with triamcinolone acetonide on day 12 of gestation as compared with groups in which females mated with phosphate buffer-treated males were treated with triamcinolone acetonide on day 12 of gestation. These results suggested the increased susceptibility to induced teratogenesis (congenital malformations induced by exposure of embryo/fetus during gestation) in the offspring derived from paternal germ cells treated with the potent mutagen ENU, but not the non-mutagen triamcinolone acetonide.     

Teratogenicity of Azosemide, a Loop Diuretic, in Rats, Mice and Rabbits

Teratogenic effects of azosemide, a loop diuretic, were investigated in rats, mice and rabbits. Azosemide was given orally to pregnant rats, mice and rabbits during organogenesis. The pregnant animals were killed at term and their fetuses were examined for external, visceral and skeletal abnormalities. In rats, azosemide at 10–30 mg/kg/day did not affect intrauterine growth, resorptions and rates of external and visceral malformations. Treatment with 90 mg/kg/day resulted in a significant increase in skeletal abnormalities such as wavy ribs, bent scapula and bent humerus. However, the skeletal abnormalities observed in term fetuses could not be found in adult offspring, indicating that they were temporary. In mice, 1250 mg/kg/day of azosemide caused maternal death, abortion, and retarded maternal and fetal weight. Treatment with 200–500 mg/kg/day did not induce fetal mortalities, external and visceral malformations. Skeletal abnormalities increased in dose-dependent fashion. The type of abnormalities was identical to that encountered in rat fetuses. Furosemide as a positive control also produced similar types of skeletal abnormalities in mouse fetuses. In rabbits, azosemide did not have embryolethal or teratogenic effects even at the highest dose (6 mg/kg/ day), which caused maternal death. Treatment for a different 3-day period and then a different day during organogenesis in rats and mice showed that the sensitive period was days 15–17 of gestation with a peak on day 16 in rats, and days 12–15 with a peak on day 13 in mice.     

Induction of Congenital Malformations in Mice by Paternal Methylnitrosourea Treatment

ABSTRACT A single dose of methylnitrosourea (MNU, 25–100 mg/kg) was injected intraperitoneally into ICR strain male mice. The males were mated to untreated females of the same strain on days 1–21 and 64–80 after the treatment. On day 18 of pregnancy, the fetuses were examined for external and skeletal abnormalities. MNU treatment of paternal germ cells caused significant increases in the incidence of abnormal fetuses over the control level. The induction rate per live fetus per unit dose in mg/kg by treating spermatogonial stem cells was estimated to be 3.0 × 10⁻⁴, which is quite similar to the rate previously estimated for the same endpoint at the same germ cell stage with the fractionated doses of MNU (daily doses at 5–25 mg/kg for 5 days). Cleft palate and dwarfism were the most frequent external abnormalities in the MNU-treated and the control series. Malformed ribs was the most frequent skeletal abnormality in the treated series. It was concluded that congenital malformations induced after treating male mice with a single dose of MNU were quantitatively and qualitatively similar to those induced after treating male mice with the fractionated doses of MNU.     

Evaluation of a core battery of tests for detecting behavioral dysfunction of rat offspring induced by retinoic acid: Collaborative work II of the Japanese behavioral teratology committee

ABSTRACT  The Japanese Behavioral Teratology Meeting, a satellite meeting of the Japanese Teratology Society, proposed a core battery of tests to detect behavioral teratogens in animals in 1992. The core battery consists of examining maternal body weight, offspring weight, external anomalies, viability, preweaning landmarks of physical development (pinna, incisor and eyelids), preweaning reflex tests (surface righting, negative geotaxis and mid-air righting), an open-field test at 5 weeks of age, a water-filled multiple T-maze (Biel-type water maze) test at 6 weeks, a shuttlebox test at 7 weeks and brain weight at termination on postnatal day 56. In order to evaluate the detectability of behavioral dysfunction in rat offspring by this core battery, the first collaborative study was carried out in 1993 using phenytoin. The present, second collaborative study using retinoic acid (RA) was performed in twenty-eight laboratories to further evaluate the proposed core test battery. Pregnant SD rats received 5 mg/kg RA orally from days 14 to 16 of gestation, and postnatal development of their offspring was evaluated. The effects of RA on offspring were detected as lower viability, increased incidence of minor anomalies in the paw and nail, delayed pinna detachment, negative geotaxis and air righting, and less frequent rearing and grooming behaviors in the open-field test. However, no effects were observed in the Biel-type maze and shuttlebox tests. These results suggest that our proposed core battery of tests is useful as a screening method to detect postnatal development disorders, including behavioral dysfunction, in SD rat offspring exposed to RA in utero.     

Modifying Effect of Folinic Acid on Methotrexate-induced Embryotoxicity in Rats

Abstract Embryotoxicity of methotrexate (MTX) and modification of its effect by folinic acid (FA) were evaluated in rats. MTX was administered intraperitoneally to pregnant rats on day 9 of gestation (vaginal plug = day 0), and was followed by an intraperitoneal injection of FA after various time intervals (0-8 hours). Two dose combinations were used; 0.3 mg/kg of MTX and 1.0 mg/kg of FA, and 3.0 mg/kg of MTX and 10.0 mg/kg of FA. The dams were sacrificed on day 20 of gestation, and the fetuses were examined for visceral and skeletal development. The results are as follows: 1) A single dose of 0.3 mg/kg of MTX resulted in high embryolethality and growth retardation in all live fetuses and a single dose of 3.0 mg/kg of MTX showed 100% embryolethality. 2) A single dose of 1.0 or 10.0 mg/kg of FA showed no embryotoxicity. 3) The mitigating effect of FA on MTX-induced embryotoxicity was observed when FA was administered simultaneously with MTX, but was rapidly decreased as the time interval between MTX and FA dosings became longer. 4) Some live fetuses which escaped from MTX embryolethality showed growth retardation and dilation of the cerebral ventricles. The dilation of the cerebral ventricles was found even in the simultaneously treated groups, though the incidences were much lower than the belatedly treated groups.     

Teratogenic effect of semicarbazide in Wistar rats

Five groups of pregnant Wistar rats were injected intraperitoneally with a single dose of semicarbazide (SC) on day 5, 7, 10, 13, or 15 of gestation. The lots in each group received either 50, 75, 100 or 150 mg/kg SC. A sixth group received 17 mg/kg of the drug during the entire course of pregnancy. SC produced a significantly smaller number of live fetuses with respect to controls. This toxic effect after injection at days 7 and 10 of gestation was highest for all single doses. The mean of fetal weight decreased with respect to controls with almost all of the SC treatment studied. The number of implantations and live fetuses was significantly decreased in the rats receiving the continuous treatment. Most abnormalities in the 21-day-old fetuses were found in the brain, kidney, intestines and liver; skeletal anomalies were seen in the skull, sternum and ribs. SC also produced high postnatal mortality rates during the first month of life with the single doses as well as with the continuous treatment. Thus, SC produced signs of toxicity and/or teratogenic effects in rats with all doses administered.     

Effect of Prenatal Methylazoxymethanol Acetate Exposure on the Motor Behavior of the Rat Offspring

Abstract Crj:CD (Sprague-Dawley) rats were treated intraperitoneally with methylazoxymethanol acetate (MAM) at 0 and 30 mg/kg on day 13 of gestation and were allowed to deliver. On day 4 postpartum, the litter size was adjusted to 8 with an equal sex distribution. Two males and females from each litter were tested between 3 and 5 weeks of age for open field activity and rotorod performance. At week 7 postpartum, all offspring were sacrificed and examined for brain anomalies.
The open field activity of MAM treated offspring tended to increase; number of ambulations and rearings were significantly increased at 3 weeks of age in male offspring treated with MAM when compared to those of male controls. At 3 weeks of age, the male offspring in the MAM treated group showed significantly reduced rotorod performance when compared to that in the control. Severe reductions of the cerebral hemispheres were observed at 7 weeks of age in the male and female offspring treated with MAM.
These results indicate that the motor behavior of offspring is significantly impaired at weaning when they were exposed to MAM prenatally. The effects were more severe for males than females.     

Prenatal developmental toxicity studies of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (p, p'-DDT) in rats and rabbits

ABSTRACT  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.     

Antiandrogenic effects of dibutyl phthalate and its metabolite,monobutyl phthalate,in rats

ABSTRACT  Developmental toxicity following administration of dibutyl phthalate (DBF) and its major metabolite, monobutyl phthalate (MBuP), by gavage was determined in Wistar rats. DBF on days 0–8 of pregnancy induced an increase in the incidence of preimplantation loss at 1250 mg/kg and higher and postimplantation loss at 750 mg/kg and higher. MBuP on days 0–8 of pregnancy produced an increase in the incidence of pre-and postimplantation loss at 1000 mg/kg. DBF on days 7–15 of pregnancy caused an increase in the incidence of fetuses with malformations at 750 mg/kg. MBuP on days 7–15 of pregnancy produced an increased incidence of fetuses with malformations at 500 mg/kg and higher. DBF on days 15–17 of pregnancy resulted in a decrease in the anogenital distance (AGD) of male fetuses and increase in the incidence of fetuses with undescended testes at 500 mg/kg and higher. MBuP on days 15–17 of pregnancy caused a decreased male AGD and increased incidence of fetuses with undescended testes at 250 mg/kg and higher. No effect of DBF and MBuP on the AGD was found in female offspring. The spectrum of fetal malformations, dependence of gestational days of treatment on the manifestation of teratogenicity, and alterations in development of the male reproductive system observed after administration of DBF were in good agreement with those observed after administration of MBuP. These findings suggest that MBuP may be responsible for the induction of developmental toxic effects of DBP. The doses that produced a decrease in the AGD and undescended testes in male offspring were lower than those producing maternal toxicity, fetal malformations after administration during major organogenesis, and embryonic loss. The male reproductive system may be more susceptible than other organ systems to DBP and MBuP toxicity after maternal exposure.     

Collaborative Behavioral Teratology Study of Phenytoin: A Test Battery for Neurobehavioral Developmental Toxicity in Rats.

Abstract: At the Behavioral Teratology Meeting (BTM) of the Japanese Teratology Society in 1992, a core test battery was proposed from a practical and simple point of view as an estimation of developmental neurobehavioral toxicity for use in pharmaceutical drug screening. The validity of the core test battery is being examined in a new series of collaborative studies. The present study is the first such study; phenytoin, a well-known behavioral teratogen, was selected as the test compound, and 32 laboratories took part in a behavioral teratology study of phenytoin using the new test battery. Sprague-Dawley strain rats from four breeds were used. Phenytoin (200 mg/kg) was administered orally to pregnant rats from days 10 to 14 of gestation (sperm detection = day 0), and in the male offspring, the survival rate, development of physical landmarks, functional developments, open field test scores, and Biel water maze test results were assessed and the brain weights were measured. The shuttle box conditioned avoidance test was also performed in some laboratories. In the present collaborative study, by taking an aggregate of the relative values converted from the measured values of each breed (providing a much larger sample size than that recommended by reproduction toxicity study guidelines), a high detectability level for phenytoin's effects was established. Under these conditions, the effects of phenytoin on eye opening, incisor eruption, the surface righting reflex, the negative geotaxis reflex, and performance of the open field test, Biel water maze test and shuttle box conditioned avoidance test were observed. It was found that present collaborative study made it possible to evaluate the detectable capacity of each of these test battery items. In addition, the critical period of abnormalities demonstrated in many test items was identified, and the results of several previous reports were confirmed. Furthermore, a breed difference in the effect of phenytoin for several test items was found. The present results established that the core test battery accurately detected the effects of phenytoin.     

Low-dose cyclosporin A microemulsion in children with severe atopic dermatitis: Clinical and immunological effects

Cyclosporin A (CsA) is an effective and well-tolerated treatment for severe childhood atopic dermatitis (AD). By starting at a low dose, the therapeutic safety should be further increased. The aim of this study was to evaluate low-dose CsA in childhood AD with respect to clinical outcome and modulation of T-cell dysregulation. In an open prospective study, 10 children (age: 22–106 months) with severe AD (mean objective SCORAD score > 40 on two baseline measurements at a minimum interval of 2 weeks) were treated with CsA solution for 8 weeks. All patients received a starting dose of 2.5 mg/kg/day, which was increased stepwise in non-responders to a maximum of dose of 5 mg/kg/day. Disease activity was monitored using the SCORAD index. The frequency of cytokine-producing peripheral blood T lymphocytes was analyzed by intracellular cytokine staining, and T-cell numbers were measured by fluorescence-activated cell sorter (FACS) analysis. Twenty healthy age-matched children were included as controls for the immunological data. Nine of the 10 patients had a SCORAD reduction of at least 35%. In seven patients this was achieved with low-dose CsA at 2.5 mg/kg/day (n = 4) and 3.5 mg kg/day (n = 3). Seven of the nine responders experienced no relapse within the 4-week follow-up period. At baseline the percentage of interleukin-4 (IL-4), IL-13, and human leucocyte antigen (HLA)-DR-positive CD3⁺ cells was higher in the patient group than in the controls. After CsA treatment there was a significant reduction in interferon-γ (IFN-γ), IL-2, IL-4, IL-13, and HLA-DR-positive CD3⁺ cells. Hence, in severe pediatric AD, CsA microemulsion, when started at a low dose (2.5 mg/kg/day), improves clinical measures of disease, reduces T-lymphocyte cytokine production, and regulates T-cell activation.     

Behavioral Effects of Hydroxyurea Exposure during Organogenetic Period of the Sprague-Dawley Rats

Abstract As an attempt to establish the methodology of behavioral teratology, this study was carried out to investigate whether the effects of HU would be different between Wistar and Sprague-Dawley (SD) rats. Hydroxyurea (HU) was intraperitoneally injected to pregnant SD rats at does of 50 or 100 mg/kg/day during the organogenetic period (days 9 to 12 of gestation). Male offspring from these dams were observed for their morphological and behavioral developments. Microphthalmia was found in only 2 pups at the 21st day of the 100 mg/kgyday group. No adverse effect of postnatal growth was observed in all treated groups. The number of ambulation in the open field test at 3 and 4 weeks of age in the 50 mg/kg/day group and at 5 weeks of age in the 100 mg/kg/day group was decreased. No inhibition of reflex development, traction response and rotorod performance was observed in all treated groups. These findings suggested that the morphological and behavioral effects of HU in SD male rats are less severe than those in Wistar male rats as was in our previous study. The strain differences in the exploratory behavior seemed to be more severe, because the specific behavioral type in both strains might be potentiated by HU treatment.     

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.     

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

The 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.     

Studies on the Effect of Long-Term Use of Low Dose Aspirin in Kawasaki Disease

The inhibitory action of long-term low dose aspirin (1–2 mg/kg/day for over 10 months) on the cyclooxygenase pathway in platelets and vascular endothe-lium was evaluated in 10 patients with Kawasaki disease. The results were compared with those obtained after taking aspirin at 5–10 mg/kg/day during the acute phase of the illness. Platelet aggregations induced by adenosinedi-phosphate (ADP), epinephrine and collagen were inhibited by aspirin doses of 1–2 and 5–10 mg/kg/day, when compared with those of controls (p < 0.05). Platelet synthesis of thromboxane B₂ (TXB₂) under doses of 1–2 and 5–10 mg/kg/day was 0.57 ± 0.07 and 0.72 ± 0.09 ng/ml platelet-rich plasma (PRP) /10⁵ platelets, respectively (p > 0.1). These values were significantly lower than those of the control group (22.88± 3.42 ng/ml PRP/10⁵ platelets) (p < 0.05). No differences were found in platelet aggregation and TXB₂ productivity between the two aspirin doses. Levels of 6 keto-prostaglandin F₁α (6k-PGF₁α) in platelet-poor plasma (PPP) did not differ significantly in these 3 sets of data. The results indicate that long-term administration of low dose aspirin (1–2 mg/kg/day) inhibits platelet aggregation by inhibiting synthesis of thromboxane A₂ (TXA₂), without interfering with prostacyclin production probably in the endothelium of blood vessels.     

Disruption of brain development in male rats exposed prenatally to 5-bromo-2'-deoxyuridine

ABSTRACT  Sprague-Dawley rats were treated intraperitoneally with 5-bromo-2'-deoxyuridine (BrdU) at 0,12.5 or 50 mg/kg/day on days 9 through 15 of gestation to evaluate the effects on development of the brain of offspring. Prenatal exposure to BrdU induced abnormal development of the brain; dilatation of the lateral ventricles in male offspring in the postnatal period. The ratio of the length of the longitudinal fissure to that of the cerebral cortex decreased in a dose-dependent manner in the embryonic period and thereafter. In 14-week-old male offspring exposed prenatally to BrdU at 50 mg/kg, the cortex layer of the cerebrum was thinner than that of the controls. Masculine sexual behavior was markedly impaired and the volume of the sexually dimorphic nucleus of the preoptic area (SDN-POA) was decreased in the 50 mg/kg group as compared with the controls. These results demonstrate that prenatal exposure to BrdU affected the development of the brain hi the prenatal and postnatal stages and reduced the volume of SDN-POA after puberty, resulting in a disruption of reproductive ability in male rats.     

Prenatal developmental toxicity studies of 1,1,1-trichloro-2,2-bis(4-methoxyphenyl)ethane (methoxychlor) in rats and rabbits

ABSTRACT  The studies were conducted in rats and rabbits to elucidate the potential developmental toxicity of methoxychlor in general accordance with the improved Japanese MAFF guidelines (12-Nousan-No. 8147, 2–1–18, 2000). Methoxychlor dissolved in corn oil was administered orally to pregnant Jcl:SD rats on gestational days (GD) 6–19 at a dose of 0,1,50, or 150 mg/kg/day and to pregnant Kbl:JW rabbits on GD 6–27 at a dose of 0,1, 15, or 45 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 at 2 higher doses in both species; i.e. vaginal red discharge (rat only), abortion or premature delivery (rabbit only), and significantly decreased body weight gains and food consumption. While the numbers of corpora lutea and implants were comparable between the control and treated groups in both species, slight increase in the percent resorptions and fetal deaths in rats and a reduction of fetal weights in both species were observed at the highest dose. Anogenital distance and testicular histology were not affected in rats. Although fetal examination revealed significant increase in the incidences of 27 presacral vertebrae at 2 higher doses in rabbits, there was no treatment-related increase in the incidence of malformations in rats and rabbits.
Based on these results, it is concluded that methoxychlor causes no malformations, including male reproductive organ abnormalities, in either rats or rabbits, although it results in decreased fetal weights and an increased incidence of fetal resorptions or skeletal variations at maternally toxic doses.     

Effect of nicotine on the development of fetal and suckling rats.

Nicotine, administered at a dose of 100 micrograms/kg/day from day 14 of gestation, did not affect maternal food intake, weight gain, length of gestation, litter size or fetal development; however, a daily dose of 1 mg/kg led to smaller litter size and higher incidence of stillbirth. Continued maternal administration of nicotine (100 micrograms/kg/day) until 12 days post partum did not affect newborn growth (body weight and length and size of heart and lung) during the first week after birth; during the second week, however, the nicotine-treated group lagged behind the controls. The stomachs of pups of nicotine-treated rats contained less food than those of controls; this difference increased with age, becoming more than 40% at 12 days. We suggest that lower milk production of nicotine-treated rats interferes with the normal development of the offspring during periods of rapid growth.