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

ABSTRACT  Slc:Wistar-KY rats were administered orally with 62.5, 125, 187.5 or 250mg/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.     

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.     

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.     

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.     

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.     

Gamma-linoleic acid and ascorbate improves skeletal ossification in offspring of diabetic rats

Maternal diabetes causes a range of complications in offspring, including reduced skeletal ossification. This study examined whether feeding gamma-linoleic acid (GLA) and ascorbate, alone or in combination, to diabetic pregnant rats improves skeletal development in their offspring. In addition, Ca(2+) concentration was monitored in maternal plasma and fetal tissue, as well as placental mRNA expression of calbindin-D(9k). Female rats rendered diabetic with streptozotocin were fed GLA (500 mg/kg/d), ascorbate (290 mg/kg/d), ascorbyl-GLA (790 mg/kg/d), or GLA and ascorbate (500 and 290 mg/kg/d, respectively) throughout pregnancy. Fetal skeletons were studied after alizarin red staining. Fewer ossification centers were observed in offspring of diabetic rats compared with offspring of control rats (68 +/- 4% of control, p = 0.01). An almost complete restoration of ossification occurred with all the treatments (92-95 +/- 3% of control). The effects of treatment on fetal ossification could not be explained by altered maternal plasma Ca(2+) concentrations or by mRNA expression of the placental Ca(2+)-transporting protein calbindin-D(9K). We conclude that GLA and/or ascorbate treatment was effective against diabetes-induced fetal ossification defects by a mechanism not related to placental Ca(2+) supply.     

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.     

Delayed developmental sequences in rodent diabetic embryopathy

Diabetes induced by alloxan at day 6 of gestation in Wistar rats produced decreased fetal growth, delayed skeletal ossification, decreased fetal kidney beta-glucuronidase, and an increased frequency of fetal birth defects which correlated with the degree of diabetic control. Offspring of severely diabetic mothers (mean blood glucose greater than 501 mg/dl) sacrificed at 20 days had a mean weight of 2.12 +/- 0.16 g, a mean of 1.8 +/- 0.46 caudal ossification centers, and a 28% incidence of birth defects as compared to 3.70 +/- 0.22 g, 5.9 +/- 0.42 caudal centers, and 1.1% defects for controls. Offspring of severely diabetic mothers sacrificed at 21 days had mean numbers of caudal and sternal ossification centers which did not significantly differ from controls, indicating that decreased ossification observed at 20 days of gestation is a delayed developmental sequence which is mostly corrected by 21 days. Offspring of moderately diabetic (mean blood glucose 300-500 mg/dl) and insulin-treated dams (mean blood glucose 152-168 mg/dl) had intermediate degrees of growth or ossification delay and birth defect frequency at both the 20- and 21-day sacrifices. Maternal diabetes also retards the developmental increase in fetal kidney beta-glucuronidase such than 20-day offspring of severely diabetic mothers had a mean specific activity of 1.1 nmol/min/mg compared to 3.0 nmol/min/mg for controls. The results support prior studies in rodents suggesting a progression of early growth delay, altered developmental sequences, and birth defects in diabetic pregnancy. This progression is suggested as a common teratogenic mechanism which has implications for evaluating analogous pregnancies in man.     

Protective Effects of Glutathione on the Teratogenicity of 5-Fluorouracil in Mice and Rats

Abstract The influence of endogenous or exogenous glutathione (GSH) on the teratogenicity of 5-fluorouracil (5-FU) was studied after a single intraperitoneal injection of 5-FU at a teratogenic dose (20 or 30 mg/kg) to ICR mice on day 11 of gestation. Pretreatment with intravenous GSH at 300 mg/kg, 5 minutes before 5-FU administration, decreased the incidence of oligodactyly induced with 5-FU and lowered the fetal mortality, but it did not prevent the decrease in body weight of fetuses. Pretreatment with intraperitoneal diethylmaleate, which decreases the level of endogenous GSH, at 350 mg/kg 6 hours before 5-FU administration increased the incidence of oligodactyly. Pretreatment orally with GSH at a dose of 300 mg/kg 30 minutes before intraperitoneal injection of 5-FU at 30 mg/kg to Wistar rats on day 13 of gestation decreased the frequency of limb malformations, but it did not prevent the decrease in body weight of fetuses.     

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.     

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.     

Developmental Abnormalities Due to Exposure of Mouse Paternal Germ Cells, Preimplantation Embryos, and Organogenic Embryos to Acrylamide

ABSTRACT The developmental toxicity of acrylamide was investigated after paternal germ cells and preimplantation and organogenic embryos were exposed to the agent. In the first experiment, ICR male mice were injected intraperitoneally with single doses of 62.5 or 125 mg/kg acrylamide or daily doses of 50 mg/kg for 5 days. They were mated with untreated virgin ICR female mice on days 1–21 and 64–80 after the last injection. The sperms involved in fertilization during these two periods were postmeiotic germ cells and spermatogonial stem cells, respectively, at the time of acrylamide treatment. The uterine contents were examined on day 18 of gestation for dominant lethal effects, and the fetuses were examined for external malformation. Acrylamide exposure during the postmeiotic cell or spermatogonial stem cell stage caused no significant increases in the incidence of abnormal fetuses. Dominant lethals, however, were clearly induced when the germ cells had been postmeiotic at the time of acrylamide exposure. In the second experiment, ICR mice were injected intraperitoneally with a single dose of 125 mg/kg acrylamide on day 0, 1, 2, or 3 of gestation. The uterine contents were examined on day 18 of gestation. Acrylamide treatment on day 0 of gestation caused a significant increase in the incidence of malformed fetuses, while treatment on day 1, 2, or 3 of gestation failed to cause an increase in malformation. Polydactyly was the most common type of abnormality. In the third experiment, pregnant mice were treated with three daily doses of 50 or 100 mg/kg acrylamide on days 6–8 or 9–11 of gestation, respectively. There was no significant difference between the incidence of malformed fetuses in the control and acrylamide-treated groups. These experiments demonstrate the vulnerability of preimplantation embryos to the toxic effects of acrylamide, while paternal germ cells and the organogenic embryos are resistant to the induction of fetal malformations.     

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.     

Effect of chronic caffeine intake on myocardial function during early growth

The purpose of these studies was to evaluate the effects of chronic caffeine ingestion on the myocardium during fetal and neonatal growth and development. The isolated perfused working heart preparation was used to evaluate cardiac function. During gestation and lactation, one group of dams consumed a caffeine supplemented diet (10 mg/kg/day). Their offspring were sacrificed and the hearts analyzed 50 days after birth. We found that the intake of caffeine by the dams resulted in significant increases in the offspring's coronary flow, peak systolic pressure, and myocardial work. A second group of dams ingested a diet containing caffeine (10 mg/kg/day) during lactation only. Their pups continued to consume the caffeine diet until 50 days. Pup hearts exhibited significant reductions in cardiac output, stroke volume, pressure development, myocardial work, and external efficiency when compared to controls. Caffeine did not affect body or heart weight or adipose size or number in these experiments. Thus, continued caffeine consumption following birth may alter cardiac performance of the offspring.     

Congenital malformations in offspring of diabetic rats: experimental study on the influence of the diet composition and magnesium intake

In spite of improvements in the treatment of diabetes, the risk of congenital malformations in diabetic pregnancy is three to four times higher than in normal pregnancy. This might be due to the metabolic abnormalities of diabetic pregnancy that also affect mineral metabolism. Since diabetes can lower both maternal and fetal blood Mg levels, and Mg deficiency has been shown to be teratogenic in laboratory animals, we decided to investigate which effects Mg deficiency would have in inducing embryopathy in diabetic animals. Female CD rats were divided into six groups. Groups 1 and 2 were fed a standard diet (Mg content 4,200 ppm), groups 3-6 a purified diet (Mg contents 4,200, 500, 250, or 125 ppm). Groups 2-6 had been made diabetic by an intravenous injection of 50 mg/kg streptozocin 1 week before mating. The rats were killed on day 21 of pregnancy, and the live fetuses were examined for external, skeletal, and visceral malformations. The maternal and fetal blood glucose levels were the same in all diabetic groups. The maternal Mg levels in groups 2 and 3 were the same as in controls, but definitely lower in groups 4-6. Embryotoxicity (embryonic deaths, delayed development, congenital malformations) was higher in the groups fed the purified diet than in group 2, but without a clear relation to the dietary Mg levels. We cannot draw any conclusions about the effects of Mg deficiency in diabetic pregnancy from our results, but they show that the quality of the diet is of major importance in the manifestation of embryotoxicity in diabetes.     

Exposure to Ethylnitrosourea Before Implantation Induces Congenital Malformations in Mouse Fetuses

Abstract The effects of ethylnitrosourea (ENU) on the development of preimplantation mouse embryos were investigated. ICR mice were treated intraperitoneally with single doses of 25, 50 or 100 mg ENU/kg body weight on day 0, 1, 2 or 3 of gestation, or with single doses of 25, 50 or 75 mg ENU/kg on day 8 of gestation. The uterine contents were examined on day 18 of gestation, and viable fetuses were inspected for external and skeletal malformations. No significant differences were observed in the number of implants between the ENU-treated groups on day 1, 2 or 3 of gestation and controls, while the number of implants in all of the groups treated with ENU on day 0 of gestation was significantly decreased compared to that in the control group. The frequencies of early postimplantation deaths were significantly increased in all of the groups treated with ENU on each gestational day before implantation, compared to the control frequencies. ENU treatment before implantation caused dose-dependent increases in the incidence of externally or skeletally malformed fetuses. Cleft palate, exencephaly and umbilical hernia were the most common types of external malformations in the groups treated with ENU before implantation and in the control group. The skeletal malformations seen in the ENU-treated groups were malformed vertebrae, malformed ribs, and bending of appendicular skeleton. Fused ribs was the most common skeletal malformation seen in the control fetuses. The type distributions of external and skeletal malformations induced by the treatment with ENU before implantation is quite different from those of fetal malformations induced by the treatment with ENU at the organogenesis stage. The results in the present study demonstrate that embryos before implantation in the uterus are susceptible with regard to the induction of congenital malformations by chemicals, and I propose that a large portion of the external malformations in fetuses treated at the preimplantation stages is the result of increased yields of spontaneously-occurring malformations.     

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.     

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.