bluuebunny/crossref_metadata_2025 huggingface dataset:
Coadministration of methylxanthines and inhibitor compounds potentiates teratogenicity in Xenopus embryos
Authors: Dawson Douglas A. , Bantle John A.
Published: June 2005

Inhibitors of DNA synthesis (hydroxyurea and cytosine arabinoside), protein synthesis (cycloheximide and emetine), and nucleic acid synthesis (5‐fluorouracil) were administered with each of three methylxanthines (caffeine, theophylline, and theobromine) to determine if teratogenic effects could be potentiated in Xenopus laevis embryos. The animals were exposed for 96 hours to methylxanthine and inhibitor concentrations that, alone, produced low percentages of malformations.

Coadministration of caffeine or theophylline with each inhibitor greatly increased the incidence of malformed embryos. Similar potentiation was induced when theobromine and the protein synthesis inhibitors were tested. A lesser potentiative response was produced when theobromine and the nucleic acid synthesis inhibitor were administered together. Teratogenic potentiation did not occur when theobromine was administerd in conjunction with the DNA synthesis inhibitors. Growth reduction in the treatments proved to be the most sensitive indicator of the potentiative effects.

This study had two significant findings: the teratogenicity of the protein synthesis inhibitors was greatly increased upon coadministration with each methylxanthine, even though they are typically not very teratogenic by themselves, and coadministration of the DNA synthesis inhibitors with theobromine did not result in teratogenic potentiation. Additionally, this study serves as one method of validating the frog embryo teratogenesis assay‐Xenopus (FETAX), since the results obtained concur with results from similar mammalian studies.
Enhanced susceptibility of mouse embryos heterozygous for oligosyndactyly (Os/+) to mitomycin C‐induced skeletal abnormalities
Authors: Moreno Patricia A. , Epstein Charles J.
Published: June 2005

The mouse mutation, oligosyndactyly (Os), results in syndactyly, muscle anomalies, and deficiency of nephrons in heterozygous animals and early embryonic lethality in homozygotes. Since the homozygous lethality results from mitotic arrest with intact spindles at the time of implantation, we have hypothesized that the heterozygous manifestations may result from impairment of cell proliferation in regions with high proliferative rates. To test this hypothesis, Os/+ and +/+ mouse embryos at 6.5 days of gestation were exposed to mitomycin C (MMC), an agent that causes a high degree of embryonic cell death which is “compensated” for by a period of rapid cell proliferation. 17.9% of MMC‐treated +/+ fetuses had fused vertebrae, a significant increase over untreated fetuses, and this frequency was further increased to 33.6% in MMC‐treated Os/+ fetuses. Saline treated Os/+ and +/+ fetuses showed the same low rate (0.3%) of vertebral fusion. These results indicate that Os/+ embryos have an increased sensitivity to the vertebral fusioninducing effect of MMC at 6.5 days of gestation, a finding compatible with the hypothesis that rapid cell proliferation may be impaired in Os/+ embryos and fetuses.
Microscopic‐anatomical changes in the chick embryo after administration of 9‐(RS)‐(2,3‐dihydroxypropyl) adenine
Authors: Jelínek R. , Doskočil M. , Holý A.
Published: June 2005

Microscopic‐anatomical changes were followed in embryos of white leghorn fowl 1–5 days after administration of 9‐(RS)‐2,3‐dihydroxypropyl) adenine on day 2 of incubation. The main changes involved the spinal cord, eyes, and extremities, manifesting gross structural abnormalities. Development of the limb buds appeared to be arrested at stages corresponding to the third day of incubation, with their apical ectodermal ridges frequently absent. A conspicuous feature of all the experimental embryos was a seriously damaged spinal cord. The disturbance of spinal cord development was reflected in defective formation of vertebral anlagen. Development of eye anlagen was arrested at the optic cup stage. The lens, however, developed normally. No causal relationship between the CNS abnormalities and limb damage was determined.
Diazepam‐induced cleft palate in the mouse and lack of correlation with the H‐2 locus
Authors: Tocco Donald R. , Renskers Kevin , Zimmerman Ernest F.
Published: June 2005

Cleft palate frequencies were studied in AJ and SW mice following either 1‐ or 2‐day dosing schedules with the anxiolytic drug diazepam (DAZ). In all cases, mice were food and water deprived for 24 and 48 hours in the 1‐ and 2‐day dosing schedules, respectively. High cleft palate frequencies in control mice of both strains resulting from 48‐hour food and water deprivation (on days 13.5 and 14.5 of gestation) were reduced in mice deprived for 24 hours, indicating a stress related effect. Two‐day dosing with DAZ (400 mg/kg) produced a net increase in cleft palate frequency in SW (33%) and AJ (18%) mice. Mice treated only on day 13.5 had reduced control and DAZ cleft palate frequencies, neither of which were significant. Clefting was significant but reduced following 1‐day dosing on day 13/20 of gestation (13 days 20 hours) in SW mice (18%), whereas no clefting was seen in the AJ strain. This strain difference was shown not to be related to differences in developmental timing. Production of cleft palate seen in AJ mice after 2 days of dosing may be indicative of an interaction of DAZ with the stresses resulting from food and water deprivation. Genes of the major histocompatibility locus, H‐2, have been shown to regulate cleft palate formation following glucocorticoid and phenytoin administration to mice. Despite pharmacological similarities between DAZ and phenytoin, comparison of cleft palate frequencies following administration of DAZ to various strains of mice of different H‐2 haplotypes indicated that genes associated with the H‐2 locus do not regulate DAZ‐induced cleft palate in these strains.
Influence of β‐D‐xyloside on growth and histological aspect of long bones in chicken embryos
Authors: Groot C. G. , Thesingh C. W. , te Pas M. , Moskalewski S.
Published: June 2005

It is known that β‐D‐xylosides interfere with the proteoglycan synthesis in several tissues. A possible influence of this disturbed synthesis on the matrix formation of bone and cartilage has not been described light microscopically. In the present study we used 10‐day‐old chicken embryos which were exposed in ovo to a final concentration of 0.5 β‐D‐xyloside. After 3, 6, 9, 20, 25, 31, 35 and 40 days, lengths of several skeletal elements were determined and the middle metatarsal bones were processed for light microscopical demonstration of acidic groups.

The results demonstrate that β‐D‐xyloside inhibits growth of long bones and induces synthesis of a cartilage matrix with a very low concentration of chondroitin sulphate. It has no noticeable influence on the amount of acidic groups in the organic bone matrix. Despite the absence of chondroitin sulphate, the cartilage matrix becomes mineralized normally.
6.5‐mm human embryo with a single nasal placode: Cyclopia or hypotelorism?
Authors: Vermeij‐Keers Christl , Poelmann Rob E. , Smits‐Van Prooije Annette E.
Published: June 2005

A macroscopic study on the missing elements in cyclopia (a single eye or closely approximated eyes with all intergrades in a single orbit) with or without proboscis and hypotelorism was performed on 12 human fetuses and 2 human fetal skulls. In addition, microscopic investigations were carried out on the orbital contents of the cyclops with a single eye without proboscis, crown–heel length (C–HL) 37 cm, and on the 6.5‐mm‐crown–rump length (C–RL) human embryo with a single nasal placode localized in front of two eye cups. In the embryo and in all 14 fetal cases the midfacial region was more‐or‐less deficient. In the two cyclopia cases without proboscis the nasal placode(s) had not developed at all during the embryonic period. In cases with proboscis, consisting of a single tube localized above both eyes, and in the hypotelorismic specimens, there could only have been a single nasal placode during development: a situation evident in the 6.5‐mm‐C–RL human embryo. In this holoprosencephalic embryo the single nasal placode was undulated, as if formed from two fused nasal placodes, and flanked by the prospective areas for the lateral nasal processes. Caudally, it was bordered by the maxillary processes. In view of the position of the single placode in this embryonic face, as described above, it is most likely that this is a preliminary stage of hypotelorism. Moreover, both medial nasal processes with the internasal groove in between, i.e., the interplacodal area, were missing. In the fetal cyclopic skulls this missing area is indicated by the agenesis of, for example, the ethmoid, nasal, and lacrimal bones; the nasal septum; and two premaxillae. All specimens under study, including the microscopically investigated cyclops with a single eye, showed elements of two eye primordia. It can be concluded, therefore, that cyclopses with or without proboscis and hypotelorismic specimens have the same abnormal stages of development of the prosencephalon in relation to the eye primordia. In cyclopia cases with proboscis, the single nasal placode develops out of the range of the maxillary processes.
Developmental effects of isotretinoin and 4‐oxo‐isotretinoin: The role of metabolism in teratogenicity
Authors: Kochhar D. M. , Penner John D.
Published: June 2005

Previous observations have indicated that isotretinoin (IT), a drug in common use for therapy of cystic acne, is teratogenic in humans but possesses low embryotoxicity in pregnant mice, probably because of its shorter half‐life and limited placental transfer in rodents. In human volunteers and patients, one major blood metabolite of IT is 4‐oxo‐isotretinoin (4‐oxo‐IT) which undergoes slower elimination than IT and may itself be a participant in teratogenesis. To investigate the problem of species differences displayed by IT and the role of its metabolism, embryotoxic effects of 4‐oxo‐IT were examined after its single or repeated intubations into pregnant ICR mice and compared with the effects of a similar regimen of IT. The two compounds were also tested for their relative ability to suppress chrondrogenesis in the in vitro cell and organ culture assays. We found that a single dose of 4‐oxo‐IT, 100 mg/kg, given on day 11 of gestation (plug day = day 0 of gestation) produced a moderate incidence of limb reduction defects and cleft palate (39% and 27% of surviving fetuses, respectively), while a dose of 150 mg/kg affected virtually every fetus. IT, on the other hand, produced no defects in fetuses exposed to similar dose levels. Repeated intubations with IT, however, resulted in increasing the frequencies of limb reduction defects and cleft palate to levels obtained after 4‐oxo‐IT administration. We found that a 3‐hour interval between IT intubations was more effective in this regard than an 8‐hour interval. Repeated IT intubations also uncovered sharper stage‐dependency of limb and palatal defects than obtained otherwise. IT and 4‐oxo‐IT were equally effective in suppressing chondrogenesis in vitro. We conclude that 4‐oxo‐IT is a potent teratogen in the mouse and that the extent or rate of IT metabolism by the mother may determine the apparent embryotoxic activity of IT in a given species.
Evaluation of the embryotoxic potential of ten chemicals in the whole mouse embryo culture
Authors: Van Maele‐Fabry G. , Picard J. J.
Published: June 2005

Ten widely different chemicals, actinomycin D, mithramycin, podophyllotoxin, vincristine sulfate, triaziquone, chlorambucil, mercaptopurine riboside, methyl‐mercaptopurine riboside, dimethylsulfoxide, and L‐lysine were tested in the whole mouse embryo culture system. The highest concentration was always the concentration that induced 100% lethality (ELC100). The lowest concentration varied from 1/2 to 1/10 of the ELC100.

The chemicals that had the most noxious effect on embryonic growth and differentiation were actinomycin D, triaziquone, and mercaptopurine riboside. Podophyllotoxin, methyl‐mercaptopurine riboside, and L‐lysine were the less embryotoxic. As a whole, no significant discrepancies were observed between the results and the teratological data obtained from the literature. These observations support the assumption that the whole murine embryo culture system can give valuable information on the teratogenicity of chemicals.
Soft tissue anomalies in a patient with congenital tibial aplasia and talo‐calcaneal synchrondrosis
Authors: Hootnick David R. , Packard David S. , Levinsohn E. Mark , Cady Robert B.
Published: June 2005

We have carried out the third in a series of anatomical dissections of amputated congenitally deformed human limbs in an attempt to determine the etiological relationship between the bony and soft tissue anomalies. This specimen consisted of a limb with congenital tibial aplasia and an adducted foot with five toes. The arterial and nerve patterns were reminiscent of those seen previously by us. The arteries were characterized by absence of the anterior tibial artery and an incomplete plantar arch. The superficial peroneal nerve terminated at the ankle. Extra branches from the sural, deep peroneal, and medial plantar nerves supplied branches to the dorsum of the foot. There were two extra muscles in the leg. The remaining muscles were normal, with the exception that most muscles normally inserting on the plantar surface of the foot inserted instead into a common tendon sheet. The tibia was replaced by a tendinous band, and the talus and calcaneus were united by a complete synchondrosis. The contralateral limb clinically appeared to have a clubfoot. The combination of an absent anterior tibial artery and an incomplete plantar arch is consistent with our theory that a reduced number of vessels puts the embryonic limb at increased risk of congenital defects due to the reduction in the number of collateral blood routes. Some event, such as extravasation of blood or embolization, may concurrently or subsequently compromise blood flow in the remaining vessels. We have previously observed abnormal arterial patterns similar to that described above in limbs having absence of the tibia and in other patients having clubfeet. The presence of abnormal arterial patterns in a limb with absence of the tibia and a contralateral limb with clubfoot suggests that absent tibia and clubfoot may be etiologically related.
D‐(–)‐beta‐hydroxybutyrate‐induced effects on mouse embryos in vitro
Authors: Hunter E. S. , Sadler T. W.
Published: June 2005

The effects of the “physiologically occurring” D‐isomer of betahydroxybutyrate (D‐BOHB) were evaluated in neurulating mouse embryos by using the technique of whole embryo culture. Following a 24‐hour culture period D‐BOHB induced malformations and growth retardation in a concentration‐dependent manner. At a 48 mM concentration essentially all embryos exhibited neural tube defects, and decreased rates of glucose metabolism by the pentose phosphate pathway (PPP) and Krebs cycle were observed when compared to controls. The relationship between an inhibition of the PPP and induction of malformations by DL‐BOHB has been reported, and thereby suggests a similar mechanism may be operating for the D‐isomer. In contrast, the effect of the D‐isomer on the Krebs cycle may result from a replacement of glucose intermediates by those generated from metabolism of D‐BOHB. Concentrations as high as 20 mM D‐BOHB have been reported in the serum of uncontrolled diabetic patients, and since ketones rapidly equilibrate across extraembryonic membranes, embryos in vivo may be exposed to concentrations equivalent to those which induced malformations in vitro. However, the incidence of malformations induced by D‐BOHB was less than that reported for the DL‐racemic mixture at equivalent concentrations, thereby suggesting that the L‐isomer is also teratogenic. Therefore, until the presence and concentration of L‐BOHB in the serum of diabetics are documented, the assessment of the impact of maternal ketosis on the embryo remains incomplete.
Whole embryo morphometry in teratogen screening
Authors: Lanning John C.
Published: June 2005

Current methodology in embryo evaluation involves qualitative assessment of razor blade and paraffin serial sections. Presently, no one has applied existing computerized morphometric techniques to examine embryos. A technique has been developed that enables investigators to section embryos at 150μ, thereby greatly reducing the number of sections and making morphometric analysis possible. This type of analysis permits the precise volumetric determination of several developing organ systems. The aim of this study was to evaluate the feasibility and sensitivity of whole embryo morphometry in teratogen screening. Cadmium chloride, a well‐established teratogen, was chosen because of its ability to induce exencephaly in approximately one‐half of offspring while having no observable effects on the remaining exposed embryos. It was found that both exencephalic and normal‐appearing cadmium‐exposed embryos had significantly smaller total cellular, neuroepithelial, otic vesicle, optic assembly, limb bud, and cardiac mesenchyme volumes when compared to controls. Also, the neuroepithelial volume of the exencephalic embryos was significantly smaller than the normal‐appearing cadmium‐exposed embryos. These results suggest that in addition to inducing exencephaly, cadmium chloride has an overall inhibitory effect on embryonic growth. We have shown that whole embryo morphometry is a sensitive means of evaluating embryonic growth that permitted determination of cadmium‐induced aberrations not discernable by currently employed techniques. In light of these results, we feel this technique shows promise for future investigations of known and suspected teratogens.
Predictive value of minor anomalies: II. Use in cohort studies to identify teratogens
Authors: Holmes Lewis B. , Kleiner Beth C. , Leppig Kathleen A. , Cann Cristina I. , Muñoz Alvaro , Polk B. Frank
Published: June 2005

Cohort studies of putative human teratogens can identify the full spectrum of phenotypic effects, including both major malformations and minor anomalies. Cohort studies which include the much more common minor anomalies make it possible to use a relatively small number of exposed and unexposed infants to identify an increase in the frequency of malformations. We evaluated this use of minor anomalies in a cohort study of newborn infants who had been exposed in utero to three putative teratogens: insulin‐dependent diabetes mellitus in the mother and the use of the anticonvulsant phenytoin and exogenous sex hormones by the mother. In addition, the reproducibility of identifying minor anomalies was tested by comparing the results of examinations by two independent observers of 444 unexposed infants. The frequency of minor anomalies was increased among infants of diabetic mothers. However, the reproducibility of identifying minor anomalies was poor. We conclude that the examination of teratogen‐exposed infants for minor anomalies cannot be used in epidemiologic studies of putative teratogens unless special efforts are made to maximize consistency in the identification of these features.
Retinoic acid‐induced selective mortality of splotch‐delayed mouse neural tube defect mutants
Authors: Moase Connie E. , Trasler Daphne G.
Published: June 2005

The allelic loci splotch (Sp) and splotch‐delayed (Spd) cause neural tube defects (NTDs) in mice homozygous for either of these genes. The polymorphic enzyme isocitrate dehydrogenase (Idh‐1) in conjunction with a recombination suppressor was used as a genetic marker to identify embryos homozygous for these alleles. A split dose of all‐trans retinoic acid (RA) totalling 5.0 mg/kg administered on gestation day 9/15 and 9/18 (days/h) significantly reduced the frequencies of NTD and of mutant genotypes in marked Spd embryos examined on day 16 without significantly increasing the resorption frequency. There was a nonsignificant decrease in the frequencies of NTD and mutant genotypes in embryos examined on day 11 of gestation. Thus, retinoic acid treatment was associated with selective mortality of the homozygous Spd mutants. No evidence of selective mortality was observed in RA‐treated Sp embryos.
Monitoring for multiple malformations in the detection of epidemics of birth defects
Authors: Khoury Muin J. , Adams Melissa M. , Rhodes Phil , Erickson J. David
Published: June 2005

Although most known human teratogens often produce a combination of birth defects in an affected infant, surveillance programs aimed at detecting epidemics of birth defects usually only monitor rates of individual defects. A drawback to this approach is that an increase in the rate of infants affected with a specific combination of defects may lead to little or no increase in the rates of component defects. Using the Poisson distribution, we show that, compared with monitoring for individual defects, monitoring for combinations of two and three defects may require fewer numbers of births to detect an epidemic. In general, an increase can be detected more rapidly by monitoring the rates of defect combinations than by monitoring the rates of individual defects if most affected infants have combinations of defects rather than isolated defects. For example, in the case of Congenital rubella syndrome (CRS), monitoring for the combination of cataracts with deafness and/or patent ductus arteriosus could have led to earlier detection of an epidemic than could monitoring for cataracts alone. In contrast, in the case of thalidomide embryopathy, monitoring for reduction defects of upper limbs in combination with reduction defects of lower limbs and/or microtia/anotia would not have led to earlier detection of an epidemic than would monitoring for reduction defects of upper limbs alone. This is due mainly to the low frequency of defect combinations among affected cases. When used with regular monitoring for individual defects, surveillance of defect combinations can enhance the ability of monitoring programs to detect epidemics of birth defects.
The in vitro embryotoxicity of 5‐fluorouracil in rat embryos
Authors: Grafton Thomas F. , Bazare Johnny J. , Hansen Deborah K. , Sheehan Daniel M.
Published: June 2005

The fluorinated pyrimidine 5‐fluorouracil (5‐FU) is an effective chemotherapeutic agent that is teratogenic in a number of species. The mechanism for the embryopathic effect of the drug is unknown. We examined the effects of this compound on gestation day 10.5 rat embryos cultured for 48 hours in a rodent whole embryo culture system. Embryos were exposed for 1–4 hours to various doses of 5‐FU. Embryolethality was minimal in all treatment groups. The malformation frequency increased with higher doses; within a dose, the malformation frequency increased with longer exposure to the drug. The tail and hindlimb bud were the most commonly affected structures in vitro; tail and leg defects are produced in several species by exposure to the, drug in vivo. The embryopathic drug concentration in the culture media (2–8 μg/ml) is similar to the plasma level of 2–17 μg/ml, which is associated with embryopathy in vivo. Results from this study suggest that the whole embryo culture system is an appropriate model for developmental toxicity studies of 5‐FU.
The effect of cadmium on the development of the facial prominences: Surface area measurements of day 10‐8 A.M. hamster embryos
Authors: Gale Thomas F. , Horner Jack A.
Published: June 2005

The environmental contaminant cadmium (Cd) is a proven teratogenic agent in rodents. In hamsters, it causes craniofacial dysmorphogenesis. The underlying mechanism for this damage is unknown. Early facial development in hamsters occurs during gestation days 9–11 and involves the formation and appropriate fusion of several prominences surrounding the stomodeum. The hypothesis for this study is that the occurrence of Cd‐induced facial defects involves a disruption of the normal formation and/or fusion of one or more of the facial prominences. Pregnant hamsters were treated with Cd (2 mg/kg) or water intravenously on gestation day 8 (8 A.M.). On gestation day 10 (8 A.M.) surviving embryos were processed to obtain scanning electron micrographs of the frontal view of the face. Measurements of the surface areas of 15 different portions of the face were obtained using a microcomputer equipped with a digitizer. Both qualitative and quantitative differences in the faces were detected upon comparing the Cd‐exposed and control embryos. The surface areas of the prominences measured were significantly smaller in the Cd‐exposed embryos. However the sizes of the other regions of the Cd‐exposed faces were either little affected (nasal pit areas) or markedly increased (the interval of the face between the medial nasal prominences). Two possible explanations for these data are discussed.
Anesthetic agents
Authors: Friedman J. M.
Published: June 2005

Although many pregnant women undergo anesthesia and many others are occupationally exposed to anesthetics every year, assessment of the teratogenic risk of anesthetic agents in humans must currently be made on the basis of very limited data. Available studies suggest that administration of an anesthetic to a pregnant woman will usually not have a deleterious effect on embryonic or fetal development. The risk of congenital anomalies does not appear to be substantially increased among children of women who have chronic occupational exposure to anesthetic gases during pregnancy, either, but miscarriages may occur more frequently than expected among such women. There is an urgent need for publication of good human epidemiologic and experimental animal studies on the teratogenicity of anesthetics.
Potential role of somatomedin inhibitors in the production of diabetic embryopathies
Authors: Balkan Wayne , Phillips L. S. , Goldstein Steve , Sadler T. W.
Published: June 2005

Mouse conceptuses at the 18–21‐somite stage were grown for 2–24 h in vitro in the presence of a serum fraction (Mr = 800–1,080 daltons) possessing somatomedin‐inhibitory activity (SI) isolated from diabetic rats. Following an 8‐h exposure to the SI, DNA and incorporation of 3H‐thymidine were reduced in the embryos while 12 h was required to observe a reduction in total protein and RNA. At the 24‐h time point, the neurectoderm was thinner than in controls, and autoradiograms of this region showed a substantial decrease in grain density with 3H‐thymidine, but not 3H‐leucine or ‐uridine. Effects on the visceral yolk sac (VYS) preceded those on the embryo. The cytoplasm of the VYS endoderm cells from conceptuses exposed to the SI contained many vacuoles by 4 h, which were larger by 24 h. Total protein was greater than in controls from 4 h onward, although 3H‐leucine incorporation, which had increased after 2 h of SI exposure, returned to control levels by 8 h. As seen by SDS‐polyacrylamide gel electrophoresis, VYSs from conceptuses exposed to the SI for 4 or 24 h were enriched (compared to control VYSs) in four protein bands also present in the culture medium (primarily rat serum), suggesting that protein degradation and/or transfer of amino acids and peptides to the embryo was inhibited in these VYSs. Such a conclusion was supported by a quantitative decrease in proteins and amino acids in the exocoelomic fluid of conceptuses exposed to the SI for 24 h. The altered processing of proteins may therefore represent a primary cause of the SI‐induced embryonic abnormalities.
Cryptorchidism, an epidemiologic study with emphasis on the relationship to central nervous system dysfunction
Authors: Depue Robert H.
Published: June 2005

This case‐control study examines the relation of cryptorchidism to central nervous system dysfunction. Elevated odd ratios were found for cerebral palsy (RR = 34), low IQ (RR = 2.7), and low motor function measured by the Bayley test (RR = 3.6). Low IQ and cerebral palsy were independent risk factors for cryptorchidism. Breech labor (RR = 2.6), a gestation < 34 weeks (RR = 2.0), and being a twin (RR = 4.1) were also independent risks. Other risk factors were estrogen use by the mother (RR = 3.3) and a maternal Quetelet index < 24 (RR = 1.6). All of these risks were statistically significant. These factors suggest that cryptorchidism may be caused either by sex steroid action directly on the testes or by CNS damage, which in turn causes suppression of pituitary gonadotropins. The increased occurrence of cryptorchidism in twins and small babies indicates that retarded general fetal development can be another mechanism for maldescent of the testes.
Acetazolamide: Maternal toxicity, pattern of malformations, and litter effect
Authors: Holmes Lewis B. , Kawanishi Hiroaki , Munoz Alvaro
Published: June 2005

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.
Secalonic acid D‐induced changes in palatal cyclic AMP and cyclic GMP in developing mice
Authors: Eldeib Mohamad M. R. , Reddy C. S.
Published: June 2005

Secalonic acid D (SAD) induces cleft palate in the developing mouse by an unknown mechanism. To investigate possible roles of cyclic nucleotides (cAMP and cGMP) in the teratogenesis of SAD, cAMP and cGMP levels were measured in the extracts of fetal palates of gestational age 130 through 1612 (dayshours). Fetuses were obtained from pregnant CD‐1 mice treated on day 110 of gestation, with either 5% (wt./vol.) sodium bicarbonate (NaHCO3, control) or 30 mg/kg of SAD in 5% NaHCO3, intraperitoneally (i.p.). Radioimmunoassay was used to quantitate cyclic nucleotide levels. Cyclic AMP levels peaked on day 1412 of gestation in controls. In the SAD group there was a significant decrease in cAMP levels on days 1312 and 140 of gestation and a decrease of 30% in total cAMP on days 130 through 140 of gestation, with little or no change at the peak on day 1412. On day 1512, however, the SAD group had a 68% increase in palatal cAMP level over the control. Control levels of cGMP appeared to follow a diurnal pattern reaching maximal levels at the end of the dark cycle. In contrast, SAD decreased the cGMP level by 31% on day 1312 (P < 0.05) and increased it 100% above that of the control level on day 150 (P < 0.01). Total cGMP during days 150 through 1612 of gestation was 33% higher than control (P < 0.01). The number of clefts in the SAD group was significantly higher at all points following palate closure in the control fetuses (140 through 1612) with values ranging from 20% to 34% versus 0% in the control (P < 0.01–0.005). Morphological changes on days 130 through 150 indicated a failure of shelf elevation in middle and posterior palatal regions of SAD‐treated fetuses. These results suggest that the induction of cleft palate by SAD is associated with dynamic changes (initial decrease followed by later increase), in vivo, in established cyclic nucleotide patterns and support a mechanistic role for cyclic nucleotide‐mediated cellular processes in normal as well as abnormal palate development.
Postnatal uterine development in the rat: Estrogen and antiestrogen effects on luminal epithelium
Authors: Branham William S. , Zehr David R. , Chen James J. , Sheehan Daniel M.
Published: June 2005

We examined the effects of the synthetic estrogens, diethylstilbestrol (DES) and ethynylestradiol (EE), and the triphenylethylene antiestrogen, clomiphene citrate (CC), on uterine growth and development in the rat. These compounds, unlike estradiol, do not bind significantly to rat serum alphafetoprotein (AFP). Administration of DES or EE during the period of normal uterine gland genesis (postnatal days 10–14) induced luminal epithelium hypertrophy and increased uterine wet weight. The durations of these responses were dose‐related. By day 26, luminal epithelium cell numbers were significantly depressed, compared to controls. Uterine gland development was delayed 6 to 9 days, depending upon estrogen dose, and the numbers of uterine glands ultimately achieved were generally less than in untreated control animals. While a daily dose of 0.1 μg CC/rat did not alter uterine development, 10 μg CC/rat caused prolonged luminal epithelium hypertrophy and inhibited uterine gland genesis without inducing the large increases in uterine weight or the decreases in luminal epithelium cell number seen after estrogen exposure. The number of stromal cells was significantly increased on day 26 after CC exposure. Together with previous studies, these data demonstrate the greater potency and developmental stage specificity of non‐AFP‐bound estrogens with respect to altering uterine gland development. In addition, these data suggest that the disruptive influence of antiestrogens on gland genesis may be mediated through an indirect influence on the uterine stroma.
Halothane prevents nitrous oxide teratogenicity in Sprague‐Dawley rats; folinic acid does not
Authors: Mazze Richard I. , Fujinaga Masahiko , Baden Jeffrey M.
Published: June 2005

The teratogenic effects of nitrous oxide (N2O) administered with halothane or folinic acid (FA) were studied in two separate experiments using a total of 206 timed‐pregnant Sprague‐Dawley rats. In each experiment, rats were exposed to either 1) air (n = 30–40); 2) N2O (50–75% for 24 h on day 8 of pregnancy, n = 20–30); 3) test agent (i.e., 0.27% halothane for 24 h on day 8 of pregnancy; or 5 mg/kg/day of FA on day 5–13 of pregnancy, subcutaneously by osmotic pump, n = 20–30); or 4) N2O + test agent (n = 20–30). Cesarean sections were performed on day 20, and fetuses were examined for visceral and skeletal abnormalities. There were no differences in pregnancy rate, number of implantations and live fetuses per rat, and fetal weight among any of the groups. Treatment with N2O resulted in significantly higher incidences of resorptions and of major visceral and minor skeletal abnormalities. Halothane administered with N2O protected against these effects; folinic acid did not. Using an additional 65 nonpregnant rats, hepatic methionine synthase activity was measured after treatment with 50% N2O, 50% N2O plus 0.27% halothane, or 50% N2O plus 5 mg/kg/day of folinic acid. Methionine synthase activity was equally depressed in all groups. These findings do not support the commonly held theory that inactivation of methionine synthase is the sole cause of N2O teratogenicity; rather, they suggest a multifactorial etiology, which may include changes in uterine blood flow.
Distribution of mercury 203 in pregnant rats and their fetuses following systemic infusions with thiol‐containing amino acids and glutathione during late gestation
Authors: Aschner Michael , Clarkson Thomas W.
Published: June 2005

To investigate the effect of amino acids and the tripeptide glutathione (GSH) on tissue uptake of methylmercury (MeHg) in the developing rat fetus in utero, pregnant rats were continuously infused into the external jugular vein with 0.1 mM L‐cysteine, 0.1 mM L‐leucine, 0.1 mM GSH or saline commencing on day 17 of gestation. This was followed at 24, 48, and 72 hours by external jugular infusion of 50 μM [203Hg]‐MeHgCl administered in 1 ml over 1 hour. Pups were surgically removed from the uterus on gestational day 21. Whole body, brain, kidney, liver, and placental 203Hg radioactivity was measured by means of gamma‐spectrometry. Brain 203Hg concentration in pups exposed in utero to L‐cysteine was significantly higher compared with pups exposed to saline (P <0.05). Brain 203Hg concentration in pups exposed in utero to L‐leucine and GSH was significantly depressed compared with pups exposed to saline (P <0.05). Kidney 203Hg concentration was not significantly changed in all treatment groups compared with controls. Liver 203Hg concentration was significantly depressed in L‐leucine‐ and GSH‐treated pups compared with controls (P <0.05). Placental 203Hg concentration was not affected by any treatment compared with controls. These effects occurred despite no difference in total 203Hg body burden among pups, irrespective of the treatment. In addition, infusion with L‐cysteine resulted in a significant increase in 203Hg brain concentration in dams compared with controls, and 203Hg brain concentration in L‐leucine‐ and GSH‐treated dams was significantly depressed compared with controls. Thus 203Hg distribution in both adult and developing animals is altered by chronic amino acid or GSH infusions and suggests that MeHg uptake may be mediated through the formation of a cysteine‐MeHg complex which is transported across the blood‐brain barrier by the neutral amino acid carrier transport system.
Embryotoxic and teratogenic effects of aluminum nitrate in rats upon oral administration
Authors: Paternain Jose L. , Domingo Jose L. , Llobet Juan M. , Corbella Jacinto
Published: June 2005

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.
Central nervous system malformations induced by triamcinolone acetonide in nonhuman primates: Pathogenesis
Authors: Tarara R. P. , Wheeldon E. B. , Hendrickx A. G.
Published: June 2005

The pathogenetic sequence for TAC‐induced encephalocele is in agreement with hypotheses proposing that neural tube closure is followed by protrusion of the mesencephalon, with subsequent growth and development resulting in herniation of the cerebrum and cerebellum. This model could serve to clarify the pathogenesis of encephalocele and to stimulate further study in comparing this defect to other dysraphic states. Triamcinolone acetonide (TAC) was administered intramuscularly (10 mg/kg) to 16 pregnant rhesus monkeys (Macaca mulatta) for 5 alternate days of pregnancy, beginning on gestational day (GD) 23. Conceptuses were removed by hysterotomy at GD 35, 42, 50, or 70 and examined grossly and histologically. Length, area, and perimeter of the tectum and aqueduct area and perimeter were measured with an image analyzer. Changes in treated specimens were suggestive of forces within or ventral to the tectum resulting in dorsal protrusion, rostral‐posterior stretching, and attenuation. The angle of the cephalic, pontine, and cervical flexures was also measured. The more acute angle of the cephalic flexure and less acute cervical flexure of treated specimens could represent altered orientation secondary to a mesenchymal deficiency. However, the less acute angle of the pontine flexure in treated specimens suggests an intrinsic alteration in the neural tube. This suggests that encephalocele may result from a combination of mesenchymal and neural tube abnormalities.
Changes with gestational age in the nutritional requirements of postimplantation rat embryos in culture
Authors: Cockroft D. L.
Published: June 2005

Rat embryos explanted at 9.0, 9.5, and 10.5 days of gestation were cultured for periods of 61, 49, or 45 h, respectively, in extensively dialysed rat serum supplemented with various combinations of glucose, amino acids, and vitamins. Glucose was found to be a necessary and sufficient energy source for embryos of all three ages, and virtually no development took place in its absence. Only the youngest embryos required free amino acids for good development in dialysed serum, whereas at all three ages, vitamin supplementation was necessary. However, lack of vitamins had a much more marked deleterious effect on the younger embryos than on those explanted at 10.5 d. Experiments with media deficient in individual vitamins showed that for normal development, 9.0‐d embryos required a number of vitamins—principally pantothenic acid, riboflavin, inositol, folic acid and niacinamide, whereas 10.5‐d embryos needed only riboflavin. For embryos explanted at 9.5 d, the position was intermediate, with riboflavin and inositol the most significant vitamins. Inositol deficiency in embryos explanted at 9.5 d produced a characteristic neural tube defect—failure of closure at the level of the hindbrain. Thus it appears that both the range of micromolecular nutrients and the severity of developmental impairment in their absence decrease with advancing gestational age.
Teratological assessment of exposure to time‐varying magnetic field
Authors: Stuchly M. A. , Ruddick J. , Villeneuve D. , Robinson K. , Reed B. , Lecuyer D. W. , Tan K. , Wong J.
Published: June 2005

A teratological assessment was performed using rats that were exposed to an alternating magnetic field. The magnetic field had a sawtooth waveform similar to that produced by video display terminals (VDTs). Female rats were exposed 2 weeks prior to and throughout pregnancy at a rate of 7 h/day. Three intensities of magnetic field (5.7, 23 or 66 μT) were used. All of these field intensities were much greater than those to which VDT users are exposed. A slight but statistically significant decrease in maternal lymphocyte count for the highest intensity field was found as compared with the control group. However, the lymphocyte count was within the normal range, and the observed changes in hematological parameters were considered mild. No other maternal or fetal parameters that were examined showed a significant difference for any of the three field intensities. Where minor variations in skeleton, development were observed they were known to be the common “noise” that appears in every teratological evaluation.
Alterations in cell surface galactosyltransferase activity during limb chondrogenesis in brachypod mutant mouse embryos
Authors: Elmer William A. , Pennybacker Mark F. , Knudsen Thomas B. , Kwasigroch Thomas E.
Published: June 2005

The autosomal mutation brachypod (bpH/bpH) in the mouse affects the development of precartilage mesenchymal condensation in the limb‐bud. We have previously shown that this defect is localized to the expression of terminal N‐acetylglucosamine (GlcNAc) glycoproteins in the plasma membrane (Elmer and Wright, '83). The present study is focused on cell surface galactosyltransferase (GalTase), an ectoenzyme that transfers galactose to its GlcNAc substrate. Purified plasma membrane preparations derived from wild‐type ( +/+ ), heterozygote (+ /bpH) and brachypod (bpH/bpH) embryonic mouse limb cells were assayed for GalTase activity during in vitro and in utero chondrogenesis using High‐Performance Liquid Chromatography (HPLC). On embryonic day E12, prior to overt expression of the mutant gene, no significant difference in GalTase activity was observed. By the third day in culture, all major chondrogenic elements of the autopod were present in +/+ and +/bpH embryos, whereas the mutant autopods were markedly deficient in staining and appeared consistently shorter. The accumulation of alcianophilic cartilage matrix in the wild‐type was accompanied by a 29% increase in GalTase activity, which reflected the net change (29%) observed during development from days E12 to E13 in utero. The GalTase activity for the in utero E13 mutant (13%) was significantly different from control. In culture, day E12 mutant autopods actually decreased in their GalTase level by 3 days so that the activity was reduced to only 57% of the wild‐type. Though GalTase activity in the heterozygote showed an intermediate expression, optical image analysis did not reveal consistent differences in cartilage development when compared to +/+, arguing against a gene‐dosage effect at the gross anatomical level. These data indicate that an increase in plasma membrane GalTase activity is a natural developmental event that occurs during limb‐bud chondrogenesis and a decrease in GalTase activity contributes to the dysmorphogenesis in brachypod limb‐buds.
Chondrodystrophic mice with coincidental agnathia: Evidence for the tongue obstruction hypothesis in cleft palate
Authors: Clarke Laura , Hepworth W. Bradford , Carey John C. , Seegmiller Robert E.
Published: June 2005

Mice homozygous for either of two mutations, chondrodysplasia (cho) or cartilage matrix deficiency (emd), have short‐limbed chondrodystrophy. This phenotype includes retroganthia, relative macroglossia, and cleft palate. It has been postulated that the cleft palate in these mice is the result of tongue obstruction during palatogenesis. Agnathia associated with microglossia is an independent spontaneously occurring defect in the strains bearing these mutations. The coincidental occurrence of agnathiamicroglossia with chondrodystrophy lends itself to the study of the mechanism of cleft palate formation. We examined approximate midsagittal histological sections of normal and chondrodystrophic newborn mice, both with and without agnathia. Mandibular measurements and examinations of palate closure and tongue structure were made from photographic prints. Typical chondrodystrophic mutants with cleft palates had a mean mandibular length that was 66% of normal and a tongue that appeared large relative to the shortened mandible. Chondrodystrophic mutants with agnathia and microglossia had a mean mandibular length that was further reduced to 30% of normal, yet had a closed palate. We also observed two nonagnathic chondrodystrophic mutants that had slightly decreased mandibular lengths, microglossia, and closed palates. These observations suggest that tongue obstruction during palatogenesis is the pathogenetic mechanism of cleft palate in chondrodystrophic mice. A similar tongue obstruction hypothesis has been proposed as the mechanism of cleft palate formation in the human Pierre Robin sequence, which consists of retrognathia, glossoptosis, and cleft palate. This mechanistic hypothesis has been challenged, but our findings support the tongue obstruction hypothesis in the Robin cleft.
Intrauterine herpes simplex virus infection
Authors: Baldwin Steven , Whitley Richard J.
Published: June 2005

Neonatal herpes simplex virus (HSV) infection usually is the consequence of intrapartum infection, with disease onset between 5 and 15 days of life. More recently, intrauterine HSV infection has been identified. Intrauterine infection is apparent within the first 24–48 hr of life and is associated with skin vesicles/scarring, chorioretinits, and/or hydraencephaly. The recognition that babies with these findings can have disease caused by HSV should prompt enhanced physician awareness in the evaluation of newborns with suspected intrauterine infection. The frequency of intrauterine infection appears to be about 5% of all babies with neonatal HSV infection.