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.     

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.     

Developmental toxicity of pentostatin (2'-deoxycoformycin) in rats and rabbits

The developmental toxicity of the potent adenosine deaminase (ADA) inhibitor, pentostatin (2'-deoxycoformycin), was investigated in pregnant rats and rabbits administered daily iv doses during organogenesis. Rats received 0, 0.01, 0.10, or 0.75 mg/kg on gestation days 6-15 and rabbits received 0, 0.005, 0.01, or 0.02 mg/kg on gestation days 6-18 and maternal and fetal parameters were evaluated on gestation day 21 (rats) or 30 (rabbits). Live fetuses were examined for external, visceral, and skeletal malformations and variations. In rats, maternal body weight gain and food consumption were significantly suppressed at doses of 0.10 and 0.75 mg/kg during the treatment period but returned to control levels during posttreatment. Increased postimplantation loss and decreased numbers of live fetuses, litter size, and fetal body weight were observed at 0.75 mg/kg. A statistically significant increase in the incidence of vertebral malformations occurred at 0.75 mg/kg. The incidence of certain skeletal variations (extra presacral vertebrae, extra ribs, hypoplastic vertebrae) was also increased at 0.75 mg/kg. Ossification of cervical centra was reduced at 0.75 mg/kg compared with controls. In rabbits, marked maternal toxicity (death, body weight loss, and decreased food consumption) and reproductive toxicity (abortion and premature delivery) occurred in all pentostatin-treated groups. However, there were no significant effects on number of live fetuses, pre- or postimplantation loss, litter size, or fetal body weights in the animals with live litters. There was also no apparent increase in the incidence of malformations or variations in the live fetuses of pentostatin-treated rabbits. Thus, these studies demonstrate developmental toxicity of pentostatin in rats and rabbits, and teratogenicity in rats, at maternally toxic doses.     

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.     

Teratogenicity and developmental toxicity of valproic acid in rats

The teratogenicity and developmental toxicity of valproic acid (VPA) was investigated in Sprague-Dawley CD rats at doses of 0, 150, 200, 300, 400, and 600 mg/kg administered by gavage on days 7-18 of gestation. The VPA-600 dose was maternally toxic, causing death in two of four dams. This dose produced 100% embryonic resorption. The VPA-400 dose was maternally toxic in as much as maternal weight gain was reduced, but no deaths occurred. At this dose five of fifteen litters were completely resorbed, and 52% of all embryos were resorbed. Among survivors, 49% were malformed (68% having skeletal defects and 41% visceral defects). Fetal weight was reduced by 43% in this group. Most of the defects were ectrodactyly, hydronephrosis, cardiovascular defects, hypoplastic bladder, rib and vertebral defects, and other defects of the limbs and tail. The VPA-300 dose (nine litters) produced fewer defects, larger fetuses, and no increase in resorptions. The defects at this dose were primarily cariovascular, rib, and vertebral. The VPA-200 dose (12 litters) produced no reduction in fetal weight, no increase in resorptions, and few defects. The defects noted were hydronephrosis, cardiovascular abnormalities, and rib defects, primarily wavy ribs. Additional litters were prepared using doses of 150 and 200 mg/kg and were allowed to deliver and grow until 70 days. These doses produced no reduction in maternal weight gain, no reduction in litter size, birth weight, or sex ratio of the offspring. These doses produced no reduction in offspring weight to day 70, no increase in mortality, and only rare cases (two offspring of each dose) of tail defects.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

Structural teratogenicity evaluation of methyl chloride in rats and mice after inhalation exposure

One hundred bred Fischer-344 female rats were exposed daily for 6 hours to atmospheres containing 0, 100, 500, or 1,500 ppm methyl chloride, 25 females per exposure concentration, from gestation day (gd) 7 through gd 19. On gd 20, the females were sacrificed for evaluation of maternal reproductive and fetal parameters. Maternal and fetal toxicity was apparent at the highest exposure concentration. There were no methyl chloride-induced external, skeletal, or visceral abnormalities seen in the fetuses. One hundred thirty-two C57BL/6 female mice bred to C3H males to produce B6C3F1 offspring were exposed daily for 6 hours to atmospheres containing 0, 100, 500, or 1,500 ppm methyl chloride, 33 females per exposure concentration, from gd 6 through gd 17. Exposure to the entire 1,500-ppm group was terminated on gd 10-14, with the animals killed in extremis. Selective necrosis of neurons in the internal granular layer of the cerebellum, ranging from individual cell involvement to focal areas comprising large numbers of neurons, was found in all females. On gd 18, the females from the other treatment groups, all of which survived, were killed for evaluation of maternal reproductive and fetal parameters. No evidence was seen of maternal or fetal toxicity in these exposure groups. There were no significant alterations in external appearance in fetuses from any of the exposure groups. Visceral examination of mouse fetuses revealed a small, but statistically significant, incidence of heart defects in litters of the 500-ppm group. The anomaly, a reduction or absence of the atrioventricular valve, chordae tendineae, and papillary muscle, was observed on the left side (bicuspid valve) in three fetuses and the right side (tricuspid valve) in six fetuses: three males and six females. It is concluded that methyl chloride inhalation exposure in pregnant rats, during critical periods of embryo and fetal development, is not teratogenic at concentrations which elicit maternal and fetal toxicity. In pregnant mice, methyl chloride was severely toxic to dams following 4 days or more of exposure to 1,500 ppm in air. Methyl chloride, at 500, but not 100 ppm, was teratogenic in mice, leading to a malformation in the heart. No embryo-fetal toxicity or teratogenicity was associated with exposure of mice, during critical periods of embryo and fetal development, to 100 ppm of ethyl chloride.     

Teratologic evaluation of synthetic delta 9-tetrahydrocannabinol in rabbits.

Synthetic delta 9-tetrahydrocannabinol (THC) was dissolved in undiluted propylene glycol and administered in daily subcutaneous doses of 15.0, 30.0 or 60.0 mg/kg to pregnant New Zealand white rabbits on days 7--19 of gestation. Maternal food consumption and weight gain were markedly reduced at all dose levels. Embryotoxicity and embryocidal effects were observed in the form of reduced litter weight and number of viable fetuses, respectively, in offspring from pregnant mothers treated with THC. However, on the basis of extensive external, visceral and skeletal examination of all fetuses it may be concluded that THC is not teratogenic in the New Zealand white strain rabbit following subcutaneous administration of doses as high as 60.0 mg/kg/day during the critical period of organogenesis (days 7--19 of gestation). On the other hand, an oral dose of thalidomide (200.0 mg/kg/day), the positive control used in this study, was both embryocidal and teratogenic.     

Evaluation of developmental toxicity in rats exposed to the environmental estrogen bisphenol A during pregnancy.

Bisphenol A (BPA) is an essential component of epoxy resins used in the lacquer lining of metal food cans, as a component of polycarbonates, and in dental sealants. The present study was conducted in an attempt to evaluate the adverse effects of the environmental estrogen BPA on initiation and maintenance of pregnancy and embryofetal development after maternal exposure during the entire period of pregnancy in Sprague-Dawley rats. The test chemical was administered by gavage to mated females from days 1 to 20 of gestation (sperm in varginal lavage = day 0) at dose levels of 0, 100, 300, and 1000 mg/kg. All females were subjected to caesarean section on day 21 of gestation and their fetuses were examined for external, visceral and skeletal abnormalities. In the 1000 mg/kg group, significant toxic effects including abnormal clinical signs, decreased maternal body weight and body weight gain, and reduced food consumption were observed in pregnant rats. An increase in pregnancy failure was also found in the successfully mated females. In addition, increased number of embryonal deaths, increased postimplantation loss, reduced litter size and fetal body weight, and decreased number of fetal ossification centers of several skeletal districts were seen. On the contrary, no significant changes induced by BPA were detected in the number of corpora lutea and implantation sites and by fetal morphological examinations. In the 300 mg/kg group, suppressed maternal body weight and body weight gain, decreased food intake and reduced body weight of male fetuses were seen. There were no adverse signs of either maternal toxicity or developmental toxicity in the 100 mg/kg group. It was concluded that BPA administration during the entire period of pregnancy in rats produced pregnancy failure, pre- and postimplantation loss, fetal developmental delay and severe maternal toxicity, but no embryo-fetal dysmorphogenesis at an oral exposure level of 1000 mg/kg.     

Marked increase in the teratogenicity of the combined administration of the industrial solvent 2-methoxyethanol and radiofrequency radiation in rats

Limited published animal research reports synergistic teratogenic effects following combined hyperthermia (induced by elevated ambient temperature) and administration of chemical teratogens. Radiofrequency (RF) radiation is widely used in occupational environments. Since RF radiation also elevates the body temperature of, and is teratogenic to, exposed animals, concurrent RF radiation and chemical agent administration may enhance teratogenicity. The present exploratory study, consisting of preliminary dose-finding studies and the primary study, was designed to investigate whether concurrent exposure of rats to RF radiation and the industrial solvent 2-methoxyethanol (2ME) can enhance the developmental toxicity of either agent acting alone. Preliminary dose-finding studies using small numbers of rats investigated the ability of various RF radiation conditions and doses of 2ME to produce external malformations (primarily of the paws) when administered on gestation day 13. Based on these preliminary studies, RF radiation exposure [sufficient to elevate rectal temperature to 42.0 degrees C (4 degrees C above normal for rats) for 30 min] and 2ME administration (150 mg/kg) were selected for the primary study. In the primary study, groups of 18 to 27 pregnant rats were administered RF radiation exposure and distilled water gavage, 2ME gavage and sham RF exposure, RF radiation exposure and 2ME gavage concurrently, or sham RF exposure and distilled water gavage. Pregnant rats were sacrificed on gestation day 20, and the offspring were examined for external malformations. Combined exposures enhanced the adverse effects produced by either experimental agent alone (no malformations were detected in the double sham group). Mean fetal malformations/litter increased from 14% after 2ME and sham RF (15/26 litters affected, with an average of 2 fetuses/litter malformed) and 30% after RF radiation and water gavage (10/18 litters affected, with an average of 4 fetuses/litter malformed), to 76% after the combined treatment (18/18 litters affected, with an average of 12 fetuses/litter malformed). In addition to a significant increase in the frequency of malformations, the severity of malformations also was enhanced by the combination treatment (on a relative severity ranking scale, the 2ME severity score was less than 1, the RF score was 3, and the combination score was 6). This study provided evidence of synergism between RF radiation and 2ME administration, but additional research will be required to characterize the extent of synergism between these two agents. Potential interactive effects between chemical and physical agents need to be investigated to determine the extent to which such interactions should impact occupational exposure standards.     

Conduct and interpretation of a dermal developmental toxicity study with KBR 3023 (a prospective insect repellent) in the Sprague-Dawley rat and Himalayan rabbit

KBR 3023, 1-(1-methyl-propoxycarbonyl)-2-(2-hydroxyethyl)piperidine, a prospective insect repellent being developed by Bayer Corporation, was evaluated for developmental toxicity in the Sprague-Dawley rat and Himalayan rabbit. As the intended human usage of the test compound is topical, the test systems were exposed to the compound via the dermal route. Specifically, the animals were fitted with Elizabethan collars, to reduce the likelihood of oral ingestion, and dermally administered either 0, 50, 200, or 400 mg KBR 3023/kg (rat), and 0, 50, 100, or 200 mg KBR 3023/kg (rabbit) on gestation days 0-19 (rat) and 0-28 (rabbit). Maternal toxicity, as demonstrated by clinical signs and changes in body weight gain and food consumption during gestation, was characterized. Animals were sacrificed on gestation day 20 (rat) and 29 (rabbit), at which time fetuses were removed by cesarean section and a gross maternal necropsy was performed. All fetuses were evaluated for external anomalies. With rats, approximately half of each litter was examined for visceral effects; the other half underwent a skeletal examination. With rabbits, all fetuses underwent both visceral and skeletal examinations. No effects were observed on maternal body weight gain or food consumption in either the rat or rabbit. In the rat, dermal effects (scaling/sloughing), were observed at the dose site of all test substance-treated groups from approximately gestation day 7 until termination of the study. Also noted were an increase in both absolute and relative liver weights in rats in the 400-mg/kg dose group. In the rabbit, dermal effects (slight erythema, squamous and cracked skin) were noted at the dose site of virtually all does administered the test compound, from approximately gestation day 7 until termination. Also observed in the rabbits was a potentially compound-related increase in soft stool, particularly at the highest dose level. In both species, there were no statistically significant effects on any reproductive parameters, or any embryonic endpoints, including pre/post-implantation loss and resorptions. There were no statistically significant effects on litter size or fetal or placental weights. No test compound-related external, visceral, or skeletal findings were observed. No effect on the individual fetal or litter incidence of total malformations or variations was observed and there was no difference in the incidence of malformations between males and females. KBR 3023 Technical, administered as described in these studies, produced maternal effects in the rat (liver weight) at a dose of 400 mg/kg, and in the rabbit (soft stool) in the 200-mg/kg dose group. No developmental toxicity was observed at any dose level.     

Developmental anomalies induced by all-trans retinoic acid in fetal mice: I. Macroscopic findings

The administration of a single dose of all-trans retinoic acid on day 8 of gestation to pregnant mice, ICR strain, led to malformed fetuses in all of the litters. All-trans retinoic acid (RA) was dissolved in olive oil and given in doses of 60 or 40 mg/kg of body weight. The control mice were given vehicle alone. Examination on day 18 of gestation of the fetuses exposed to 60 mg/kg showed various malformations, such as exencephaly, exophthalmus, micrognathia, agnathia, cleft palate, cleft lower lip, spina bifida, atresia ani, tail anomalies, agenesis of the kidneys, or hydronephrosis. In the fetuses exposed to 40 mg/kg, isolated cleft palate was much more common than in those exposed to 60 mg/kg. Double-stained preparations of bone and cartilage showed cranio-facial anomalies and axial skeletal anomalies: a- or hypogenesis of palatine or maxillary bones, tympanic ring, squamosal temporal bone or otic ossicles in cartilage, and fusion of basioccipital to basisphenoid and maxilla, zygomatic and mandibular bones; a- or hypogenesis of caudal vertebrae and supernumerary thoracic and lumbar vertebrae. These results indicate that anomalies comparable to those seen in the infants of mothers treated with isotretinoin, 13-cis retinoic acid, during pregnancy can also be induced in mice and suggest that the site affected by RA may be neural crest cells, including those in the cephalic and caudal regions, and cells committed to somitic mesoderm in the trunk region.     

Teratogenic action of platinum thymine blue

The teratogenic activity of the antitumor agent cisplatinum-2-thymine (platinum thymine blue) was investigated in rats. Pregnant Wistar-derived albino rats were given single ip injections of an aqueous solution of platinum thymine blue (PTB) at one day of pregnancy from day 5 through day 14 (sperm day=day 0). The dosages used ranged from 20 to 80 mg/kg maternal body weight. At autopsy (day 20) fetuses were recovered and subsequently examined for skeletal and soft-tissue abnormalities. PTB was embryolethal and teratogenic at several stages during rat gestation. Embryonic deat occured following all doses, and was dose dependent, except at day 5. The majority of malformed fetuses, however, were observed only after treatment at day 6 or 7 following injection with 50, 60, or 80 mg/kg. Eye defects were the predominant abnormality followed by hydrocephalus, gastroschisis, and ectopia cordis. The skeleton was only slightly affected. PTB is a potent inhibitor of DNA synthesis, but its mechanism of teratogenic action is unknown.     

Valproic acid-induced placental and teratogenic effects in rats.

Studies on teratogenicity and pathology of the cenceptus were conducted in Sprague-Dawley rats treated with 600, 800, and 1,000 mg/kg valproic acid po on day 13 of pregnancy. Each of the three doses was maternotoxic and caused (1) resorptions and/or abortions, reduction in the number of live fetuses per litter and mean fetal weight, and defects of the tail, rib and phalanx; and (2) degenerative changes in the labyrinth (thrombosis, angiectasis in the maternal lacunar network, necrosis of cytotrophoblasts and suppressed proliferation of fetal capillaries), reduced diameter nearing obliteration of umbilical vessels, with or without karyorrhexis of embryonic tissues. The lesions in the placental labyrinth were specific but, in the embryonic tissues, they were generalized. It was postulated that the vascular lesions in the labyrinth and umbilicus may have influenced embryonic development by reducing maternoembryonic gaseous and nutritional exchange.     

Benzofuranyl ureas with potent cardiovascular teratogenicity in rats

Studies of embryo-fetal development in rats were conducted with two 5-lipoxygenase inhibitors. SB-202235 (1,000 mg/kg/day) or SB-210661 (50, 100, or 500 mg/kg/day) was administered orally by gavage to female rats on days 6-17 postcoitus (pc) or days 7-16 pc. SB-202235 (1,000 mg/kg/day) and SB-210661 (100 mg/kg/day) reduced maternal body weight gain for the treatment period by 16% and 21%, respectively, relative to controls. SB-202235 (1,000 mg/kg/day) or SB-210661 (50 or 100 mg/kg/day), did not affect numbers of resorptions, dead or live fetuses/litter, but 500 mg/kg/day of SB-210661 caused 100% embryo lethality. SB-202235 (1,000 mg/kg/day) and SB-210661 (50 and 100 mg/kg/day) reduced fetal body weight by 15-30% and produced extensive cardiovascular malformations, as well as diaphragmatic hernias. SB-210661 also caused thymic abnormalities and cryptorchidism. Cardiovascular defects included abnormalities in aorticopulmonary septation, the aortic arch, pulmonary trunk, and ventricular septal defects are discussed relative to comparable human syndromes of cardiovascular malformation.     

The mouse teratogen dinocap has lower A/D ratios and is not teratogenic in the rat and hamster

The fungicide dinocap is currently used in the control of powdery mildew. We have reported that dinocap is teratogenic in the CD-1 mouse, causing cleft palate, otolith defects, and fetal weight deficits well below maternotoxic dose levels. In this study the maternal and fetal toxicity of dinocap was determined in the Sprague-Dawley rat and Syrian golden hamster, and adult-to-developmental (A/D) toxicity ratios were calculated and compared with the previously established A/D ratio of dinocap in the mouse. Dinocap in corn oil was administered by gavage to pregnant rats on gestation days 7-20 (0, 100, 150, 200 mg/kg/day) and to hamsters on gestation days 7-14 (0, 12.5, 25, 50, 75, 100, 200 mg/kg/day). Dams were killed on day 21 (rat) or day 15 (hamster), and litters were removed, counted, and weighed; half of each litter was necropsied for soft tissue defects, and the remaining half was processed for skeletal examination. In the rat, maternal extrauterine weight gain was significantly affected at 150 and 200 mg/kg/day, relative liver weight was elevated at 100 mg/kg/day and above, and fetal weight was lower at 150 and 200 mg/kg/day. In the hamster, maternal extrauterine weight was lower at 12.5 mg/kg/day and above; fetal weight was reduced, and the incidence of dilated renal pelvis was higher, at 25 mg/kg/day and above. Thus the A/D ratios for dinocap in the rat and hamster are similar, approximately 1.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of thalidomide on reproductive function and early embryonic development in male and female New Zealand white rabbits

BACKGROUND : The present work was performed to determine the effect of thalidomide exposure on reproductive function and early embryonic development. METHODS : Twenty‐five female New Zealand White rabbits were orally gavaged with 0, 10, 50, or 100 mg/kg/day thalidomide 14 days prior to mating through to gestation day 7 for a total of 22 days. Treated females were Caesarean‐sectioned approximately 29 days after the date of attempted mating. Following mating with treated females, male rabbits (25/dose) were gavaged with 0, 30, 150, or 500 mg/kg/day beginning 14 days prior to mating with a group of untreated females (25/dose). Doses were administered through mating until the day before sacrifice for a minimum of 56 days. Untreated females were Caesarean‐sectioned 29 days after the last attempted mating. Comprehensive necropsy and histopathology of the reproductive system were performed. RESULTS : Treated females had reduction in body weight gain during gestation. Mating and pregnancy parameters were unaffected by thalidomide. At 100 m/kg, litter averages for corpora lutea, implantations, litter sizes, does with viable fetuses and live fetuses decreased and the number of early resorptions, does with any resorptions, does with all conceptuses resorbed, and the percent resorbed conceptuses per litter increased. The number of early resorptions, the average number of early resorptions per litter, and the percent resorbed conceptuses per litter increased at 10 and 50 mg/kg. There were no thalidomide‐related external fetal malformations. Mating and fertility in male rabbits were unaffected by thalidomide. There was an increased incidence of flaccid testes at 150 and 500 mg/kg and of bilateral small testes in all treated groups. At 500 mg/kg, there was degeneration of the germinal epithelium of the testicles with an increase in multinucleated giant cells in seminiferous tubule and a loss of round and elongating spermatids. CONCLUSIONS : Thalidomide had no adverse effects on mating and fertility in male and female rabbits dosed up to 500 and 100 mg/kg/day, respectively, for 14 days prior to mating. After 56 day of dosing, histopathologic changes with no associated sperm abnormalities were observed in the testicles. Embryonic development NOAEL for treated females mated to untreated males was <10 mg/kg. Corresponding fertility NOAEL for treated males mated to untreated females was 500 mg/kg. Birth Defects Res B 71:1–16, 2004. © 2004 Wiley‐Liss, Inc.     

Methanol exposure during gastrulation causes holoprosencephaly, facial dysgenesis, and cervical vertebral malformations in C57BL/6J mice

BACKGROUND: Exposure of pregnant outbred CD-1 mice to methanol during the period of gastrulation results in exencephaly, cleft palate, and cervical vertebra malformations [Rogers and Mole, Teratology 55: 364, 1997], while inbred C57BL/6J mice are sensitive to the teratogenicity of ethanol. C57BL/6J fetuses exhibit the holoprosencephaly spectrum of malformations after maternal exposure to ethanol during gastrulation, but the sensitivity of C57BL/6J mice to methanol-induced teratogenesis has not been previously described. METHODS: Pregnant C57BL/6J mice were administered two i.p. injections totaling 3.4 or 4.9 g/kg methanol or distilled water four hrs apart on gestation day 'GD' 7. On GD 17, litters were examined for numbers of live, dead and resorbed conceptuses, fetuses were weighed as a litter and examined externally, and all fetuses were double stained for skeletal analysis. RESULTS: No maternal intoxication was apparent, but the high dosage level caused a transient deficit in maternal weight gain. The number of live fetuses per litter was reduced at both dosages of methanol, and fetal weight was lower in the high dosage group. Craniofacial defects were observed in 55.8% of fetuses in the low dosage group and 91.0% of fetuses in the high dosage group, including micro/anophthalmia, holoprosencephaly, facial clefts and gross facial angenesis. Skeletal malformations, particularly of the cervical vertebrae, were observed at both dosages of methanol, and were similar to those previously reported in the CD-1 mouse following methanol exposure. CONCLUSIONS: The types of craniofacial malformations induced in the C57BL/6J mouse by methanol indicate that methanol and ethanol have common targets and may have common modes of action.     

Developmental stages of the CD (Sprague-Dawley) rat skeleton after maternal exposure to ethylene glycol.

Ethylene glycol (EG), a chemical which causes skeletal malformations in rats, was administered by gavage to sperm positive CD rats on gestational days (gd) 6 through 15 at doses of 0 or 2,500 mg/kg/day to assess its effects on the pre- and postnatal skeletal development. Dams and fetuses/pups were killed on gd 18, 20, postnatal day (pnd) 1, 4, 14, 21, or 63, and offspring were double-stained for examination of skeletal malformations and degree of ossification of rapidly developing skeletal districts. No difference in gestational day of delivery between controls and the EG-treated dams was seen. Fetal weights per litter were significantly decreased with EG treatment in both the gd 18 and 20 groups. Pup body weight on pnd 1 was significantly below controls; however, EG had no effect on pup body weight on pnd 4-63. The percentage of fetuses/pups with skeletal malformations per litter was significantly increased after EG exposure for all time points except at pnd 63, with a predominance of axial skeletal defects. The percentages of total ossification, of sternabrae ossified, and of vertebral centra ossified were significantly reduced in the EG groups on gd 20 and on pnd 1-21, but not on gd 18 or on pnd 63. When the ossification data were subjected to statistical analysis with fetal/pup weights as a covariate, the values for EG-exposed pups on gd 20 were not statistically significantly different from the control values. The reduced ossification values for EG-exposed pups on pnd 1-21 retained statistical significance even after covariate analysis. There was no effect of dose or body weight on ossification of fore- or hindlimb digits. In conclusion, the differences in incidence of skeletal alterations observed prenatally and through pnd 21 were not evident by pnd 63, suggesting that perinatal skeletal abnormalities may not always be permanent.