Developmental toxicity of orally administered 2',3'-dideoxycytidine in mice

2',3'-Dideoxycytidine (DDC), a potent inhibitor of human immunodeficiency virus (HIV), is presently undergoing clinical trials as a promising anti-AIDS drug. Since there are very limited published animal toxicity data available, and nucleoside analogues are being considered for treatment of HIV-infected pregnant women, a study was conducted in mice to investigate the potential adverse developmental effects of this drug. DDC, suspended in 0.5% methyl cellulose, was administered via gavage twice per day during gestation days (gd) 6 through 15 to C57Bl/6N mice in a total dose of 0, 200, 400, 1,000, or 2,000 mg/kg/day. Maternal weight gain during the gestation and treatment period, as well as gravid uterine weight, decreased significantly in the 2,000 mg group, but weight gain, corrected for gravid uterine weight, was not affected by DDC. The percent resorptions per litter increased significantly in the highest dose group, and there were fewer live litters because of complete litter resorption in six dams. Among litters with live fetuses, the mean litter size was significantly reduced in the 2,000 mg group. Average fetal body weight per litter decreased significantly in the 1,000 and 2,000 mg groups. The number of fetuses with any malformation, the number of litters with one or more malformed fetuses and the percent of malformed fetuses per litter increased significantly in the 1,000 and 2,000 mg groups. There was an increase in malformations at 400 mg/kg/day; however, it was not statistically significant. In conclusion, DDC produced developmental toxicity (malformations, reduced fetal body weight, and resorptions) in the absence of overt maternal toxicity except for body weight changes due to resorptions and reduced fetal weights.     

Interactions of radiofrequency radiation-induced hyperthermia and 2-methoxyethanol teratogenicity in rats

Radiofrequency (RF) radiation is used in a variety of workplaces. In addition to RF radiation, many workers are concurrently exposed to numerous chemicals; exposed workers include those involved with the microelectronics industry, plastic sealers, and electrosurgical units. The developmental toxicity of RF radiation is associated with the degree and duration of hyperthermia induced by the exposure. Previous animal research indicates that hyperthermia induced by an elevation in ambient temperature can potentiate the toxicity and teratogenicity of some chemical agents. We previously demonstrated that combined exposure to RF radiation (10 MHz) and the industrial solvent, 2-methoxyethanol (2ME), produces enhanced teratogenicity in rats. The purpose of the present research is to determine the effects of varying the degree and duration of hyperthermia induced by RF radiation (sufficient to maintain colonic temperatures at control [38.5], 39.0, 40.0, or 41.0 °C for up to 6 h) and 2ME (100 mg/kg) administered on gestation day 13 of rats. Focusing on characterizing the dose-response pattern of interactions, this research seeks to determine the lowest interactive effect level. Day 20 fetuses were examined for external and skeletal malformations. The results are consistent with previous observations. Significant interactions were observed between 2ME and RF radiation sufficient to maintain colonic temperatures at 41 °C for 1 h, but no consistent interactions were seen at lower temperatures even with longer durations. These data indicate that combined exposure effects should be considered when developing both RF radiation and chemical exposure guidelines and intervention strategies. Bioelectromagnetics 18:349–359, 1997. © 1997 Wiley-Liss, Inc.     

Acetazolamide: maternal toxicity, pattern of malformations, and litter effect

Thirty litters of C57BL 6J mice were administered intraperitoneally one of four doses (0, 500, 750, and 1,000 mg/kg maternal weight) of acetazolamide on day 9 of gestation. The fetuses were removed on day 18 and fixed, stained, cleared, and examined for the pattern of malformations. The forelimb postaxial limb deficiency was the most common abnormality, but forelimb postaxial polydactyly and a postaxial deficiency in the hindlimb were also observed. Males were significantly more likely to be malformed than females at all doses, in contrast to the predominance of females observed in rat fetuses exposed to acetazolamide (Scott et al.: Teratology 6:239-240, '73). The occurrence of limb malformations did not correlate with maternal weight loss, the birth weight of the fetus, or the position of the fetus in the uterus. A "litter effect" was demonstrated in that there was a nonuniform distribution of litters with different proportions of malformed fetuses.     

Embryotoxic and teratogenic effects of aluminum nitrate in rats upon oral administration

In order to determine the embryotoxic and teratogenic potential of aluminum, pregnant Sprague-Dawley rats were treated by gavage with a daily dose of 180, 360, or 720 mg/kg of aluminum nitrate from the sixth through to the fourteenth day of gestation. Fetal examinations were performed on day 20. The number of corpora lutea, total implants, and resorptions as well as the number of live and dead fetuses in the treated animals were not significantly different from the control group. Therefore, embryolethality of aluminum cannot be induced (as a measure of percent dead and resorbed fetuses). However, exposure of rats to aluminum nitrate resulted in decreased fetal body weight and increased the incidence and types of external, visceral, and skeletal malformations and variations in all the treated groups. Consequently, teratogenic effects of aluminum-nitrate administration may result in rats given high oral doses that induce concomitant maternal toxicity.     

Reproduction and development in rats chronologically exposed to 60-Hz electric fields

Previous studies have raised the possibility of reproductive and developmental changes in miniature swine chronically exposed to a strong 60-Hz electric field. Two replicate experiments on rats were performed to determine if similar changes could be detected in animals exposed under a comparable regime, which was based on average, induced-current densities and on the chronology of reproductive development, as dosimetrically and biologically scaled. Beginning at three months of age, female rats of the F0 generation and their subsequent offspring were chronically exposed to a 60-Hz electric field (100 kV/m unperturbed) for 19 h/day for the duration of experimentation. After four weeks of exposure, F0 female rats were mated to unexposed male rats during the field-off period. No significant developmental effects were detected in their litters, confirming our previous results with swine and rats. The F0 females were mated for a second time at 7.2 months of age, and the fetuses were evaluated shortly before term. In the first experiments, the incidence of intrauterine mortality was significantly less in exposed than in sham-exposed litters, and there was a tendency (P = .12) for an increased incidence of malformed fetuses in exposed litters. Neither end point was significantly affected in the second experiment. Copulatory behavior of the female F1 offspring, which were bred at three months of age, was not affected in either experiment. There was a statistically significant decrease in the fertility of F1 exposed females and a significant increase in the fraction of exposed litters with malformed fetuses in the first experiment; both end points were essentially the same in the sham and exposed groups of the second experiment. That the significant effects detected in the first experiment were not seen in the second may be attributed to random or biological variation. Alternatively, the finding may indicate that the response threshold for induction of malformations lies near 100 kV/m.     

Electrocardiographic study of rat fetuses exposed to ethylene glycol monomethyl ether (EGME)

The widely used industrial solvent ethylene glycol monomethyl ether (EGME) is teratogenic to rats and mice, inducing a variety of heart and major vessel abnormalities. In the present study, electrocardiography was used to evaluate heart function in day 20 rat (Sprague-Dawley) fetuses from mothers treated on gestation days 7-13 (sperm = day 1) with 0, 25, or 50 mg/kg EGME by gavage in 10 ml/kg water. The increased incidence of fetuses with cardiovascular malformations (primarily right ductus arteriosus and ventricular septal defect) and abnormal electrocardiograms (EKG) was dose dependent. The most prevalent EKG abnormality was a prolonged QRS wave. Mean QRS intervals were not significantly increased by EGME exposure, but there were significantly more litters in the 50-mg/kg EGME group that had one or more fetuses with QRS complexes of 40 msec or longer. The enhanced duration and the appearance of the aberrant QRS's suggested the presence of an intraventricular conduction delay in these fetuses. Heart rate and other EKG characteristics such as the P wave or P-R and Q-T intervals were not significantly affected by exposure to EGME. There did not appear to be an association between abnormal EKG's and fetal heart dysmorphology.     

Cocaine as a cause of congenital malformations of vascular origin: experimental evidence in the rat

Cocaine hydrochloride was administered to pregnant Sprague-Dawley rats as a single intraperitoneal dose or as two doses 1-4 hours apart. A single dose administered on day 16 of gestation was teratogenic in a dose-dependent manner, with 40 mg/kg being a no-effect dose and 50 mg/kg the lowest teratogenic dose; 80 mg/kg was lethal to the dam. Forty-eight hours after exposure to a teratogenic dose on day 16 of pregnancy, the fetuses showed severe hemorrhage and edema in the their extremities, particularly the footplates, tail, genital tubercle, and upper lip/nose. When the fetuses were examined on day 21 of gestation, the main externally visible malformations were reduction deformities of the limbs and tail. When two doses of cocaine were administered 1-4 hours apart, the incidence of affected fetuses increased as the time interval between the two doses decreased. Two doses of cocaine administered 2 hours apart were not teratogenic on day 9, 10, 11, 12, 13, or 14 of gestation but did induce reduction deformities on days 15, 16, 17, 18, or 19. The same dose administered 1 hour apart was teratogenic on days 14-19. In general, cocaine administration on gestational days 14, 15, or 16 induced more severe and more widespread hemorrhage and edema than administration on days 17, 18, or 19. In the latter cases, damage was restricted to the distal parts of the hindlimb digits and the tail. The results show that in the rat cocaine is only teratogenic during the late organogenic or postorganogenic period.(ABSTRACT TRUNCATED AT 250 WORDS)     

Increased postimplantation loss and malformations among the F2 progeny of male rats chronically treated with cyclophosphamide.

Cyclophosphamide, administered to the male rat, produces increased pre- and postimplantation loss in the progeny as well as an increase in the numbers of malformed and growth retarded fetuses. The purpose of this study was to determine whether the adverse effects of chronic paternal cyclophosphamide exposure are transmissible to the next generation, the F2 progeny. Adult male rats were treated by gavage daily with saline or with cyclophosphamide (3.4 or 5.1 mg/kg) for 4 or 18 weeks and mated. The male and female offspring in each treatment group (F1 generation) were randomly mated. The resulting pregnant females were killed on day 20 of gestation to evaluate progeny outcome in the F2 generation. There was a significant increase in postimplantation loss among the offspring of the group whose fathers had been treated with cyclophosphamide at a dose of 5.1 mg/kg/day. Exposure to a dose of 5.1 mg/kg/day of cyclophosphamide also resulted in an F2 generation with a significantly decreased mean fetal weight per litter and a significant increase in the number of malformed fetuses. The malformations observed among the F2 progeny included open eyes, omphalocele, generalized edema, syndactyly, gigantism, and dwarfism. Thus, exposure of the father to cyclophosphamide does result in a specific and heritable alteration in the fertility of the surviving "apparently normal" F1 progeny. Interestingly, the adverse consequences of exposure of male rats to cyclophosphamide are similar in the F2 generation to those previously reported for the F1 progeny.     

Effects of protein deficiency on the teratogenicity of cytochalasins in mice

The developmental toxicity of cytochalasins B (CB) and D (CD) was evaluated in protein-deprived mice. Pregnant CD-1 mice were assigned to control (26%), 16%, 8%, or 4% dietary protein groups on gestation day 1 and dosed by gavage with 0 or 1.5 mg/kg CB or CD on gestation day 8 (plug = day 1). They were killed and subjected to teratological examination on day 18. CD, but not CB, increased prenatal mortality but failed to interact significantly with dietary protein level. Fetal weights were decreased in the 4% and 8% dietary protein groups, but cytochalasin treatment did not exacerbate this effect. Cytochalasin treatment was associated with gross fetal malformations, primarily neural tube defects. Although CB and CD did not significantly increase the percentage of grossly malformed fetuses per litter, the data was suggestive of such an effect, and the incidence of affected litters was increased by cytochalasin treatment in all but the 4% protein group. Skeletal defects, such as jaw malformations, rib or sternebrae variations, and unossified skull bones appeared to be increased by both cytochalasin treatment and dietary protein deficiency. The differences from control values were nonsignificant, however, except for some cases of cytochalasin effects on skull ossification. These results show a general lack of effect of protein deprivation on the developmental toxicity of cytochalasins.     

Developmental toxicity evaluation of Bendectin in CD rats

Bendectin, composed of doxylamine succinate and pyridoxine HCl (1:1), is an antinauseant previously prescribed for nausea and vomiting during pregnancy. The present study examined the maternal and developmental effects of Bendectin (0, 200, 500, or 800 mg/kg/day, po) administered to timed-pregnant CD rats (36-41/group) during organogenesis (gestational days [gd] 6-15). At death (gd 20), all live fetuses were examined for external, visceral, and skeletal abnormalities. At 500 and 800 mg/kg/day, maternal toxicity included reduced food consumption during treatment and for the gestation period, increased water consumption in the posttreatment period, reduced weight gain during treatment, and sedation; water consumption was reduced during treatment and for the gestation period, and maternal mortality (17.1%) was observed only at the high dose. Developmental toxicity included reduced prenatal viability (800 mg/kg/day) and reduced fetal body weight/litter (500 and 800 mg/kg/day). In addition, reduced ossification of metacarpals (800 mg/kg/day), phalanges of the forelimbs (500 and 800 mg/kg/day), and of caudal vertebral centra (all doses) was observed. No increase in percent malformed live fetuses/litter was observed. The proportion of litters with one or more malformed fetuses was higher than vehicle controls only at 800 mg/kg/day, with short 13th rib (to which the test species is predisposed) as the predominant observation. By contrast, a positive control agent (nitrofen, 50 mg/kg/day, po, 14 dams) produced 85% malformed fetuses/litter with the predominant malformation being diaphragmatic hernia. In conclusion, the incidence of litters with one or more malformed fetuses was increased only at a dose of Bendectin which produced maternal mortality (17.1%) and other indices of maternal and developmental toxicity (see Discussion).     

Evaluation of heart malformations in B6C3F1 mouse fetuses induced by in utero exposure to methyl chloride

C57BL/6 female mice impregnated by C3H males mice to produce B6C3F1 fetuses were exposed daily for six hr to atmospheres containing 0, 250, 500, or 750 ppm methyl chloride, from gestation day 6 to gestation day 18. There were 74 to 77 females with copulation plugs per exposure concentration. Females exposed to 750 ppm ethyl chloride exhibited ataxia commencing on the seventh day of exposure (gestation day 12). They also showed hypersensitivity to touch or sound, tremors and convulsions. Six females in the 750 ppm group died and one was euthanized in extremis prior to scheduled sacrifice. On gestation day 18, all other females were euthanized for evaluation. Only dams exposed to 750 ppm exhibited significant decrease in body weight by gestation day 18, weight gain during the gestation period, and absolute weight gain (weight gain minus gravid uterine weight) versus controls. There were no treatment related-effects on these parameters in the other exposure groups. None of the groups exhibited exposure-related differences in pregnancy rate, gravid uterine weight, or maternal liver weight. There were no differences in the numbers of implantations, resorption, dead fetuses, nonlive (dead plus resorbed) fetuses, live fetuses, sex-ratio, or mean fetal body weight per litter. There was a significant exposure-related increase in the number and percentage of affected (nonlive plus malformed) fetuses per litter with the incidence of affected fetuses in the 750 ppm group significantly higher than controls. There was a statistically significant increase in the incidence of heart defects in the 500 and 750 ppm group relative to controls. Of the 37 fetuses in the study with heart defects, 23 were females, 14 were males. The heart defects observed included: absent or abnormal tricuspid valve, reduced number of papillary muscles and/or chordae tendineae on the right side, small right ventricle, globular heart, and white spots in the left ventricular wall. Multiple malformations were observed in one fetus from the 500 ppm group and in three fetuses in the 750 ppm group. It is concluded that methyl chloride inhalation exposure to pregnant C57BL/6 mice from gestation day 6 through gestation day 17 resulted in maternal toxicity only at the 750 ppm exposure concentration and was teratogenic to B6C3F1 conceptuses at exposure concentrations of 750 and 500 ppm, leading to fetal heart malformations. No evidence of embryo or fetotoxicity other than teratogenicity was seen at any of the exposure concentrations employed. No maternal, embryo or fetotoxicity or teratogenicity was associated with exposure of mice, during critical periods of embryo and fetal development, to 250 ppm of methyl chloride.     

Potentiating effects of methylxanthines on teratogenicity of mitomycin C in mice

A previous study demonstrated that caffeine strongly potentiated the teratogenic action of mitomycin C in mice. In the present study the effect of methylxanthines including caffeine, theophylline, theobromine (theobromine sodium salicylate), paraxanthine, and 1-methylxanthine was compared in order to analyze the structure-activity relationship. Jcl:ICR mice were injected IP with 3 mg/kg of mitomycin C, immediately followed by SC injection of each methylxanthine on day 11 of gestation. The doses of methylxanthines were calculated so that the mice received 50 mg/kg of caffeine or the equimolecular amount of the other methylxanthines. Fetuses were examined for external malformations on day 18 of gestation. Mitomycin C at 3 mg/kg and the methylxanthines at the doses used were not teratogenic. Combined administration of caffeine or theophylline with mitomycin C produced more than 80% of malformed fetuses. Although less effective than caffeine or theophylline, paraxanthine also significantly increased the incidence of malformed fetuses. Theobromine and 1-methylxanthine were virtually ineffective. From these findings, it is suggested that the methyl group at N-1 position of the xanthines is important for the enhancement but the N-1 methylation alone is ineffective unless accompanied with the substitution of the methyl moiety at the other position(s).     

Interactions of salicylate, dietary zinc, and genetic strain in teratogenesis in rats

The influence of dietary zinc concentration on salicylate teratogenesis was studied in Wistar and Sprague-Dawley rats. Females were fed purified diets containing 0.4, 4.5, 9, 100, or 1,000 micrograms zinc/gm diet, or a stock diet (Purina Rat Chow) from day zero to day 21 of gestation, when they were killed and the fetuses were examined. On day 9, rats were given saline or 250, 500, or 750 mg sodium salicylate/kg body weight by gavage. Increasing drug dose caused increased frequency of malformed or resorbed fetuses, while increasing dietary zinc reduced the teratogenic effects of salicylate, but in different patterns in the two strains. The teratogenic effect of zinc deficiency also varied by strain. Statistical analysis showed that the frequency of malformed fetuses was significantly affected by levels of dietary zinc or salicylate dose, and interactions of zinc X salicylate and genetic strain X zinc. Frequency of resorption was affected by strain, zinc, salicylate, and interactions of strain X salicylate, zinc X salicylate, and strain X zinc X salicylate. Frequency of abnormal sites (malformed or resorbed) was affected by strain, zinc, salicylate, and interactions of strain X salicylate, zinc X salicylate, and strain X zinc X salicylate. The results suggest that marginal zinc deficiency in certain pregnant women might increase the possibility of salicylate teratogenicity.     

Malformations in offspring of diabetic rats: morphometric analysis of neural crest-derived organs and effects of maternal vitamin E treatment

BACKGROUND: We have previously reported on a malformation-prone Sprague-Dawley rat substrain (U), which presents a high frequency of micrognathia in the offspring of diabetic mothers. This malformation is related to impaired development of the cranial neural crest cells (NCC); the defect may be prevented by antioxidative treatment of the mother. METHODS: We have therefore investigated whether fetuses of diabetic rats display other malformations associated with altered cranial NCC development and whether maternal vitamin E supplementation may affect such malformations. RESULTS: Fetuses of diabetic rats showed low-set external ears, severely malformed Meckel's cartilage, small thyroid and thymus, and absence of parathyroid glands. Cardiac anomalies were frequently observed, including rightward displacement of the aorta, double outlet right ventricle (DORV), persistent truncus arteriosus (PTA) combined with ventricular septal defects due to a malaligned outlet septum. The malformations in the outflow tract included abnormalities of the great arteries; right-sided aortic arch/descending aorta, and double aortic arches. These defects tended to occur together within individual fetuses. Maternal dietary treatment with 2% vitamin E markedly reduced the severity of the malformations. CONCLUSIONS: The phenotypic appearance of these defects is strikingly similar to the DiGeorge anomaly in humans, which has been found in children of diabetic mothers together with an overrepresentation of PTA and DORV. The malformations associated with defective NCC development in the offspring of diabetic U rats show several morphological similarities to those in humans; hence the teratogenic mechanisms may be similar and accessible for study.     

Evaluation of the protective activity of deferiprone, an aluminum chelator, on aluminum-induced developmental toxicity in mice

BACKGROUND: Since deferiprone can be an effective chelating agent for the treatment of aluminum (Al) overload, in the present study we investigated whether this chelator could protect against Al-induced maternal and developmental toxicity in mice. METHODS: A single oral dose of Al nitrate nonahydrate (1,327 mg/kg) was given on gestation day 12, the most sensitive time for Al-induced maternal and developmental toxic effects in mice. At 2, 24, 48, and 72 hr thereafter, deferiprone was given by gavage at 0 and 24 mg/kg. Cesarean sections were performed on day 18 of gestation and fetuses were examined for malformations and variations. RESULTS: Aluminum-induced maternal toxicity was evidenced by significant reductions in body weight gain, corrected body weight change, and food consumption. Developmental toxicity was evidenced by a significant decrease in fetal weight per litter and an increase in the total number of fetuses and litters showing bone retardation. No beneficial effects of deferiprone on these adverse effects could be observed. By contrast, a more pronounced decrease in maternal weight gain and corrected body weight change, as well as a higher number of litters with fetuses showing skeletal variations was noted in the group exposed to Al nitrate and treated with deferiprone at 24 mg/kg. CONCLUSIONS: According to the current results, deferiprone would not be effective to prevent Al-induced maternal and embryo/fetal toxicity in mice.     

A genetic characterization of differences in the sensitivity to radiation-induced malformation frequencies in the mouse strains Heiligenberger,C57Bl,and Heiligenberger × C57Bl

We studied the frequency of malformations induced in two mouse strains (Heiligenberger, C57Bl/6J) by exposure to x-rays 3 h after conception. Whereas there was a high number of malformed fetuses in Heiligenberger mice (mostly gastroschises) on day 19 of pregnancy, C57Bl did not respond to radiation exposure shortly after conception with an increased frequency of malformed fetuses. Cross-breeding of both strains revealed that no statistically significant increase in radiation-induced malformations was obtained in the F₁ fetuses when the father was Heiligenberger and the mother C57Bl. In the opposite case (Heiligenberger mother, C57Bl father a small but statistically significant increase was observed.     

Effects of low-frequency magnetic fields on fetal development in rats

We studied effects of alternating magnetic fields on the embryonic and fetal development of rats. Mated females of the Han:Wistar-strain were sham exposed or exposed continuously to a 50-Hz field or to a 20,000 pulse-per-second (pps) sawtooth magnetic field from day 0 to day 20 of pregnancy for 24 h/day until necropsied on day 20. The respective peak-to-peak intensities of the fields were 35.6 μT (sinewave) and 15.0 μT (sawtooth). Each treatment group contained 72 bred females. Control animals were kept under the same conditions without the magnetic field. No adverse effects were seen in the dams. The mean numbers of implantations and living fetuses per litter were statistically significantly increased in the 50-Hz group. There were, however, three total resorptions of litters in dams of the control group, which contributed to the difference in the number of living fetuses. The corrected body-mass gains (gains without uterine content) of dams were similar in all groups. Pregnancy rates, incidences of resorptions. late fetal deaths, and fetal body masses were similar in all groups. The incidence of fetuses with minor skeletal anomalies was statistically significantly increased in both exposed groups. Only one serious malformation (anophthalmia, sawtooth-exposed group) and a few minor visceral malformations were found. In conclusion, the magnetic fields used in this study did not increase the incidence of major malformations or resorptions in Wistar rats. The increased number of skeletal anomalies and implantations we observed indicates, however, that some developmental effects in rats may attend exposure to time-varying magnetic fields. © 1993 Wiley-Liss. Inc.     

Potentiating effect of caffeine on the teratogenicity of acetazolamide in C57BL/6J mice

Pregnant C57BL/6J mice were treated with 0 or 50 mg of caffeine (CAFF) per kg, and 0, 200 mg/kg (L) or 1,000 mg/kg (H) of acetazolamide (ACZM) during day 9 of gestation (9DPC). Individual fetuses were examined for gross morphological abnormalities and skeletal variations. The increase in fetal malformations seen, especially right forelimb electrodactyly, was augmented at both dose levels of acetazolamide by concomitant exposure to caffeine. Both frequency and severity of ectrodactyly were potentiated by caffeine. Skeletal examination revealed a reduction of the number of ossified cervical and caudal vertebral centra among litters exposed to ACZM at either dose. In either case (ACZM-H, ACZM-L) that effect was augmented by co-administration of CAFF. The first cervical vertebra (C1) appeared to provide the most sensitive index of teratogenic exposure. This study provides evidence that a subteratogenic dose of caffeine can potentiate the teratogenic effect of acetazolamide in C57BL/6J mice when dams are treated on day 9 of gestation. In addition, skeletal examination provided evidence that simultaneous treatment with both agents delayed fetal development. Many litters exposed to ACZM or both agents displayed a reduction in skeletal ossification even in the absence of gross morphological abnormalities, suggesting that ossification can be used as an indicator of prenatal exposure to potentially harmful substances in the C57BL/6 mouse strain.     

Prevention of caffeine-induced limb malformations by maternal adrenalectomy

Caffeine at high doses is a known rodent teratogen and induces limb malformations along with cleft palate in various strains of rats and mice. Fujii and Nishimura ('74) postulated that caffeine was teratogenic by virtue of catecholamine release from maternal or embryonic tissue. We tested this hypothesis by surgically removing the maternal adrenal gland on day 6 of pregnancy and then administering 175 mg/kg of caffeine intraperitoneally at 1600 h day 11 and 900 h day 12. The teratogenic effects of caffeine in adrenalectomized versus nonadrenalectomized AKR mice were assessed in day 18 fetuses. Thirty percent of the surviving offspring were malformed in caffeine-treated, nonadrenalectomized dams compared to 7% of the offspring from adrenalectomized dams. Therefore we believe caffeine teratogenesis is initiated by release of catecholamines from the maternal adrenal gland.     

Vitrification of mouse oocytes results in aneuploid zygotes and malformed fetuses

Vitrification of mouse oocytes adversely affected the subsequent developmental potential of embryos and fetuses derived from the fertilization of such oocytes after thawing. Only 5% of oocytes vitrified formed viable fetuses on the 15th day of gestation as compared to 47% in the controls. The incidence of chromosomally aneuploid zygotes, derived from cryopreserved oocytes, was approximately threefold higher than the controls irrespective of whether the oocytes were cryopreserved by vitrification or DMSO slow-freezing. Malformed fetuses were obtained from oocytes that had been vitrified as well as those that had been exposed to vitrification solutions only, whereas no malformed fetuses were obtained in oocytes slow-frozen by DMSO or fresh controls--thus demonstrating that the exposure of oocytes to the vitrification chemicals was responsible for the fetal malformations. The data in this study suggest that the vitrification technique should be cautiously applied to human oocyte cryopreservation. Furthermore, the data also demonstrate that the exposure of female gametes to carcinogenic and/or teratogenic chemicals may result in malformed embryos when such oocytes are subsequently fertilized.