bluuebunny/crossref_metadata_2025 huggingface dataset:
Neural tube defects caused by local anesthetics in early chick embryos
Authors: Lee H. , Nagele R. G.
Published: June 2005

The effects of local anesthetics (ketamine HCl, lidocaine HCl, procaine HCl, and tetracaine HCl) on stage 8 (four‐somite) chick embryos were investigated. In general embryos responded to drug treatment in a dose related manner during the first 6 hr of incubation. Concentrations of 500 μg/ml (ca. 2 mM) or higher were embryolethal, whereas 100–200 μg/ml (0.1–0.8 mM) preferentially inhibited elevation of neural folds. The latter effect was detectable within 3 hr of treatment and was readily reversible. Tetracaine was the most potent among the four local anesthetics tested at any given dose. Compared to controls, cells in the defective neuroepithelium were less elongated and exhibited smoother apical (luminal) surfaces, thinner microfilament bundles, and less intense actin‐specific fluorescence. Furthermore, the effects of local anesthetics (100–200 μg/ml) on stage 8 chick embryos were not identical to those of cytochalasin D (0.05 μg/ml), colchicine (1 μg/ml), or ionophore A23187 (25 μg/ml), although all treatments produced neural tube defects. Overall results suggest that local anesthetics inhibit closure of the neural tube through their disruptive action on the organization and function of microfilaments in developing neuroepithelial cells.
Thyroxine‐induced differential mortality of cleft lip mouse embryos: Dose‐ and time‐response studies of the A/WySn strain
Authors: Juriloff D. M. , Harris M. J.
Published: June 2005

Pregnant A/WySn mice, 20 to 30% of whose offspring have spontaneous cleft lip, were treated with thyroxine. Following treatment, cleft lip and normal embryos died, but cleft lip embryos died at a higher rate. The increased liability of cleft lip embryos to thyroxine‐induced death was considered as a possible experimental route to identify the basic genetic defect that causes cleft lip. A time‐response study indicated that cleft lip embryos responded more than normals following treatment on any of days 7 to 12 of gestation, that there is no sharply defined critical period, and that normal and cleft lip embryos do not differ in time of maximum sensitivity. A dose‐response study showed linear responses of normal and cleft lip embryos on a probit‐log dose scale, with a common slope and LD50's of 1.9 and 1.3 mg respectively. These dose‐response properties indicate that normal and cleft lip embryos are probably killed by the same mechanism, but differ in dosage tolerance. That is, they differ quantitatively, not qualitatively. Thyroxine did not significantly change the cleft lip frequency, and the difference between normal and cleft lip embryos that leads to cleft lip itself is therefore not in the same pathway as that which leads to thyroxine‐induced death. A hypothetical example of the defect basic to both pathways is presented.
Phenytoin teratogenicity and effects on embryonic and maternal folate metabolism
Authors: Hansen Deborah K. , Billings Ruth E.
Published: June 2005

It has been postulated that the mechanism of teratogenicity of the anticonvulsant drug phenytoin (PHT), is via a deficiency of folic acid. To test this hypothesis, Swiss Webster mice were administered PHT in the diet prior to and throughout gestation. Animals received a daily dose of approximately 75 mg/kg body weight. The maternal plasma PHT levels were within the therapeutic range for this drug. This dose increased the incidence of malformations, primarily cleft palate, in the absence of embryolethality. There was a decrease in maternal plasma folate levels on day 12 of gestation but no effect on days 10 and 18. Even in the presence of a maternal folate deficiency on day 12, PHT had no effect on total embryonic folate levels on days 10, 12, and 14. Previous experiments have demonstrated that PHT decreases activity of the enzyme 5, 10‐methylenetetrahydrofolate reductase in the liver of non‐pregnant Swiss Webster mice. Data from the current study indicate that this enzyme activity is also decreased in hepatic tissue of pregnant mice, but it is not altered in embryos on the days examined. These data show that a teratogenic dose of PHT affects maternal folate metabolism. However embryonic folate metabolism, when measured in total embryos, was not affected.
Studies on the mechanism of trypan blue teratogenicity in the rat developing in vivo and in vitro
Authors: Rogers John M. , Daston George P. , Ebron Marian T. , Carver Brenda , Stefanadis James G. , Grabowski Casimer T.
Published: June 2005

Trypan blue is a potent teratogen in vivo and in vitro in the rat. Many of the abnormalities produced by trypan blue–including swollen neural tube and pericardium, subectodermal blisters, hematomas, and generalized edema–may result from altered fluid balance in and around the embryo. The present study demonstrates relationships between changes in the fluid environment around the embryo and appearance of anomalies. Rat embryos were exposed in utero or in vitro to trypan blue during the early period of organogenesis. Both exposures resulted in defects that are typical of trypan blue treatment. Osmolality of exocoelomic fluid (ECF) was measured on gestation day 10 in vivo and day 12 in vitro, both after 48 hr of exposure to trypan blue. In both cases ECF osmolality was significantly lower than controls. This was correlated with the presence of edema‐related anomalies in the embryo. On gestation day 11 in vivo, three days after maternal injection of trypan blue, ECF osmolalities were significantly higher than controls; however, there was tremendous variability in this parameter in day 11 treated embryos, and some had ECF osmolalities below the control range. Increased frequency of abnormalities was correlated with abnormal ECF osmolality, below and above the control range. Trypan blue probably exerts its teratogenic effects by disturbing the function of the visceral yolk sac. The movements of an amino acid and a monosaccharide across the visceral yolk sac were measured on gestation day 12 embryos in vitro. This aspect of yolk sac function was not altered by trypan blue exposure. Ultrastructure of the visceral yolk sac was observed after trypan blue exposure in vivo and in vitro. Endodermal cells in trypan blue‐treated yolk sacs contained fewer large, electron dense lysosomes than controls. These were replaced by numerous small vacuoles, which may contain trypan blue. Trypan blue causes osmotic changes in the rat embryo in vivo and in vitro. These changes are correlated with embryonic malformations. Alterations in yolk sac ultrastructure indicate that trypan blue affects the function of this membrane.
A postulated mechanism of β‐sympathomimetic induction of rib and limb anomalies in rat fetuses
Authors: Sterz H. , Sponer G. , Neubert P. , Hebold G.
Published: June 2005

Treatment of gravid rats (days 6–15 of gestation) with the β‐sympathomimetic doxaminol resulted in wavy ribs and bent limbs in the offspring. The fetuses also exhibited defective mineralization. These anomalies were produced by pharmacologically effective doses of the drug. Prior treatment with the β‐receptor blocker carazolol prevented their formation, so that the β‐sympathomimetic action of doxaminol is evidently a causative factor. Various hypotensive agents whose activity is not mediated by β‐receptors failed to produce abnormalities. This eliminates the possibility of a non‐specific etiology such as diminished placental perfusion. The cyclooxygenase inhibitor indomethacin lowered the incidence of wavy ribs. Furosemide, a loop diuretic that stimulates renal prostaglandin synthesis, increased the incidence of abnormalities when combined with doxaminol. The nature of the anomalies found suggests that 1) fetal compression by the myometrium and 2) defective mineralization are prerequisites for their development. The first condition could be produced via the complex mechanism of β‐sympathomimetic‐induced stimulation of prostaglandin synthesis. Defective mineralization can result directly from cAMP‐mediated activation of osteoclasts and possibly be further promoted by β‐sympathomimetic‐mediated prostaglandin action on the osteoclast. The pathological findings in the fetal rat skeleton cannot be correlated with corresponding findings in human neonates whose mothers were subjected to prolonged therapeutic uterine relaxation with β2‐sympathomimetics, for example. Since the anomalies in the rat disappear spontaneously in the postnatal period, their clinical relevance appears to be slight.
External examination of limb positions in near‐term mouse fetuses: An experimental study and review of the literature published in Teratology
Authors: Pinto‐Machado J.
Published: June 2005

The accidental finding of near‐term mouse fetuses exhibiting limb positions that could have been interpreted as malformations but that were, in fact, spurious, led us to study the posture of the limbs in the offspring of 100 CD‐1 mouse dams. A total of 1,015 fetuses (18 days‐old, vaginal plug: day 0), was examined. Fifteen of these fetuses presented positions that deviated markedly from the norm and were therefore considered to be “unusua,” although the usual position was recovered in 6 of the 15 by placing the affected limb in a standard position and eventually eliciting locomotion. A broad review of the literature was made in order to evaluate our results fully. This review included 43 reports published in Teratology that recorded abnormal limb positions in near‐term mouse and rat fetuses, and another 9 reports where these were not referred to but that included photographs showing such abnormalities. The data obtained from our experimental study and review led us to conclude that for a correct record of abnormal positions in near‐term mouse and rat fetuses, authors must (1) follow appropriate, clearly described technical procedures, including manoeuvers to rule out spurious displacements; (2) give adequate information in the legends of the photographs; (3) use unequivocal terminology; and (4) carry out further research to determine accurately the range in variation of normal limb positions.
Sex difference in susceptibility to teratogenic effect of maternal biotin deficiency in mouse embryos
Authors: Goto Tadashi , Watanabe Toshiaki , Endo Akira
Published: June 2005

When pregnant mice were fed biotin‐deficient diets, cleft palate occurred more frequently in male fetuses than in female fetuses. Possible underlying mechanisms are speculated on, and some methodological problems in the analysis of sex‐related differences in multiparous animals are discussed.
Electrocardiographic study of rat fetuses exposed to ethylene glycol monomethyl ether (EGME)
Authors: Toraason Mark , Stringer Barbara , Stober Paul , Hardin Bryan D.
Published: June 2005

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.
Induction of chick embryo feather malformations by an influenza C virus
Authors: Spence Hilda Adele , O'Callaghan Richard J.
Published: June 2005

The effect of influenza C virus, strain JJ/50, on the development of chicken embryos infected at 10 or 12 days was documented by microscopic techniques, as well as by gross observations of embryos or chicks at hatching. The infected, newly hatched chicks displayed marked abnormalities in their feathering. Such abnormalities were observed neither in mock‐infected embryos nor in embryos injected with virus which had been previously treated with specific influenza C virus antibody. At a microscopic level, the abnormalities apparently are a result of hypertrophy and/or hyperplasia of the developing barb and barbule cells. Further, the additional development of integumental necrotic foci was correlated with the development of relatively high viral titers (>256) as measured by hemagglutination (HA). Embryos infected after 12 instead of 10 days incubation showed normal feathering at hatching. Infection at 12 days, however, was correlated with the development of relatively low viral titers (HA = 4) and limited degeneration of the respiratory epithelium. The relationship of teratogenic effects to the site of viral replication in rapidly differentiating tissue is discussed.
Effect of ethinyl estradiol on the differentiation of mouse fetal testis
Authors: Yasuda Yoshiko , Kihara Takahide , Tanimura Takashi
Published: June 2005

In an evaluation of the effect of ethinyl estradiol (EE) on the differentiation of fetal mouse testes, the ratio of the seminiferous tubular region to the testicular tissue region, the ratio of Sertoli cells to gonocytes in tubule cross sections, and the size of Leydig cells were determined by the Texture Analyse System (T.A.S., Leitz) in histological preparations of the testes. The testes were those of fetuses taken from dams given orally 0, 0.02, 0.2 or 2.0 mg/kg of body weight of EE in olive oil from day 11 through day 17 of gestation and killed at term. From experimental and the control testes, five sections were taken at 40‐μm intervals. The areas of the seminiferous tubular region and the testicular region were determined and the Sertoli cells and gonocytes in tubule cross section were counted in each of the five sections. The diameters of 100 Leydig cells selected at random were averaged. These data were analyzed by Student's t test. The seminiferous tubular region was significantly increased in the testes treated with 0.02 mg/kg of EE and significantly decreased in those treated with 0.2 mg/kg of EE. The number of gonocytes per tubule cross section was significantly increased in the testes treated with 0.02 or 2.0 mg/kg of EE. The number of Sertoli cells per tubule cross section and the number of Sertoli cells per gonocyte were significantly decreased in the experimental testes. The size of the Leydig cells was significantly decreased in the testes treated with 0.2 mg/kg of EE. These findings suggest that prenatal exposure to EE before testicular differentiation affects tubular formation, the proliferation of fetal Sertoli cells, and Leydig cell differentiation, resulting in disturbances of spermatogenesis.
Teratogen update: Clinical aspects of thalidomide embryopathy—A continuing preoccupation
Authors: Newman C. G. H.
Published: June 2005

There is much misinformation in the medical community regarding the thalidomide syndrome. Some physicians and scientists are unaware of the fact that organs other than the limbs were frequently affected. Some believe that thalidomide could produce any type of limb reduction defect. Most were aware of the very narrow period of early organogenesis during which the thalidomide‐type malformations could be produced. Important features include the fact that limb reduction defects were primarily preaxial, included concomitant girdle hypoplasia when limb reductions were severe, were almost universally bilateral and did not include distal transverse‐type defects often called “hemimelia”. While it can be said that some spontaneous (non‐thalidomide) malformations can mimic the thalidomide syndrome, it can also be said that many limb reduction defects can be determined not to have been produced by thalidomide. The risks of the various defects can be estimated following exposure, with most certainty for limb defects, with less certainty for other defects. Many defects were not associated with exposure to thalidomide such as cleft lip and severe mental retardation.
Evaluation of Bendectin embryotoxicity in nonhuman primates: I. Ventricular septal defects in prenatal macaques and baboon
Authors: Hendrickx A. G. , Cukierski M. , Prahalada S. , Janos G. , Rowland J.
Published: June 2005

Cynomolgus monkeys, rhesus monkeys and baboons were administered 10 to 40 times the human dose equivalent of Bendectin throughout the major period of organogenesis (22(±3)–50 days of gestation). In animals examined prenatally (100 ± 2 days gestation) the total incidence of ventricular septal defects (VSD) was 40% in cynomolgus monkeys, 18% in rhesus monkeys, and 23% in baboons. The majority of VSD involved the muscular portion of the septum. No dose response was evident and there were no other cardiac or extracardiac defects found except for one baboon fetus with multiple defects. No defects were observed in cynomolgus monkeys administered Bendectin for 4‐day periods between 22 and 41 days of gestation. There was no association of Bendectin treatment with any noncardiac defect. In cynomolgus and rhesus monkeys examined at term there was one mitral valve defect and no incidence of VSD. The increased incidence of VSD observed prenatally in all three species and the absence of defects in macaques at term suggests a delay in closure of the ventricular septum in treated animals. The Bendectin‐treated monkey may be a suitable model for the study of the pathogenesis of VSD and the mechanism of spontaneous closure of the defect.
Morphological and biochemical aspects of monofunctional phosphoramide mustard teratogenicity in rat embryos cultured in vitro
Authors: Mirkes P. E. , Greenaway J. C. , Hilton John , Brundrett Robert
Published: June 2005

Day 10 rat embryos were exposed in vitro to a monofunctional analog of phosphoramide mustard (MPM) at concentrations of 25 to 200 μg/ml (144 to 1,156 × 10−6 M). After a 24‐hour exposure, embryos exhibited a dosedependent decrease in growth parameters (crown‐rump length, number of somites, and protein content) as well as incidence of malformations. Abnormal embryos were characterized by hypoplasia of the prosencephalon as well as hypoplalsia of the mandibula arches, tail, and limb buds. Histological analysis revealed abnormal levels of necrotic cells, particularly in the neuroepithelium and surrounding mesenchyme. In all respects embryos exposed to MPM could not be distinguished from embryos exposed to phosphoramide mustard. We also determined using mouse L1210 cells that at the maximum nonlethal concentration used in our embryo exposure experiments, MPM did not cause DNA cross‐linking but did cause single‐strand DNA breaks. Phosphoramide mustard, at concentrations teratogenic to embryos in vitro, did produce DNA cross‐linking. Taken together, our results indicate that although cyclophosphamide (CP)‐induced DNA cross‐linking may play a role in CP teratogenesis, DNA cross‐linking is not an absolute requirement.
Fetal development in mice exposed to isoflurane
Authors: Mazze Richard I. , Wilson Anne I. , Rice Susan A. , Baden Jeffrey M.
Published: June 2005

The developmental toxicity of trace (0.006%), subanesthetic (0.06%), and light anesthetic (0.6%) exposure to isoflurane was examined in Swiss/Webster mice. No adverse effects were demonstrated following exposure of dams to 0.006% (n = 26) and 0.06% (n = 27) isoflurane for 4 hr daily on days 6–15 of pregnancy. Exposure to 0.6% isoflurane (n = 23) for the same period resulted in significantly decreased fetal weight, decreased skeletal ossification, minor hydronephrosis, and increased renal pelvic cavitation. The incidence of cleft palate also was significantly increased, abnormalities occurring in 12.1% of fetuses and affecting 11 of 23 litters. This incidence was considerably higher than that of the combined treatment and colony control groups (0.75%) and those that we have found in previous experiments with this mouse strain following exposure to halothane (1.2%) or enflurane (1.9%).
Lead‐induced early lesions in the brain of the chick embryo
Authors: Narbaitz Roberto , Marino Irma , Sarkar Kiriti
Published: June 2005

A single dose consisting of a solution of lead nitrate containing 1 mg lead in 0.1 ml distilled water was injected into the air chamber of chicken eggs on the tenth day of incubation. The injected embryos were killed 24, 48, or 72 hours after the injection. Control embryos were injected with a similar volume of distilled water or of an equimolar calcium nitrate solution on the tenth day and killed 72 hours after. Portions of the optic lobes were processed for their electron microscopic study. Multiple hemorrhagic foci appeared 24 hours after the administration of lead. Red blood cells were found to exit the blood vessels through the spaces between otherwise normal‐looking endothelial cells; tight junctions were always found blocking the interendothelial spaces except during the migration of red blood cells through them. Vacuolization of the cytoplasm and mitochondrial swelling and disorganization were observed in the endothelial cells only during the third day after the injection. Similarly, histological and ultrastructural alterations of nerve cells were only found on the third day after the treatment. Hemorrhagic foci were never found in control embryos. Our observations are consistent with the idea that the hemorrhages constitute the primary lesion produced by lead. They also suggest that the hemorrhages are not the result of rupture of previously altered endothelial walls but occur by diapedesis through the interendothelial clefts.
Embryotoxicity of a single dose of medroxyprogesterone acetate (MPA) and maternal serum MPA concentrations in cynomolgus monkey (Macaca fascicularis)
Authors: Prahalada S. , Carroad E. , Cukierski M. , Hendrickx A. G.
Published: June 2005

A single dose of MPA (Depo‐Provera; Upjohn Co., Kalamazoo, Michigan) was administered intramuscularly to 12 time‐mated pregnant cynomolgus monkeys on day 27 (±2) of gestation at 25 mg/kg or at 100 mg/kg. Maternal blood samples were collected immediately prior to MPA injection and then at regular intervals until cesarean section at term (day 152 ± 3). Infants in both dose groups had external genital abnormalities. Female infants in the low–dose groups had partial or complete labial fusion, prominent median raphe, and clitoral hypertrophy; at high doses (100 mg/kg), the female infants had complete labial fusion and a distinct penile urethra. MPA had an opposite effect on external genitalia of male infants. The penis was short and the scrotal swelling was absent or less conspicuous, and two males had hypospadias. The adrenal glands were significantly smaller (P < 0.05) in infants of both sexes treated with 100 mg/kg. One of the infants treated with 25 mg/kg of MPA had a muscular ventricular septal defect. Serum concentrations of MPA were determined by radioimmunoassay in eight pregnant monkeys. In the 25 mg/kg group the patterns of MPA profiles in the serum were similar in all four animals. An initial peak occurred at 24–48 hr postinjection (2.7–9.6 ng/ml), followed by a slight decrease at 3 days postinjection (gestational day 30), and then a steady increase to maximum levels of 10–14 ng/ml occurring between gestational days 37 and 50. Serum levels gradually declined to concentrations below 5 ng/ml by midgestation in three of four monkeys. By comparison, both the patterns and magnitude of MPA concentration showed great interanimal variation in the 100mg/kg group. MPA was present in cord blood at measurable concentrations in infants at both dose groups; the levels ranged from 0.6 to 8.3 ng/ml, corresponding to 40–72% of the maternal concentrations. These results demonstrate that a single injection of MPA during early pregnancy causes selective embryotoxicity in both male and female fetuses. Presence of high levels of MPA in maternal sera during the critical period of genital development can cause specific genital defects; however, the exact mechanism by which MPA causes these paradoxical genital abnormalities is unknown.
Histological changes induced in developing limb buds of C57BL mouse embryos submitted in utero to the combined influence of acetazolamide and cadmium sulphate
Authors: Milaire J.
Published: June 2005

Microscopic defects in limb buds of C57BL mouse embryos after the combined teratogenic action of acetazolamide plus cadmium sulphate administered on day 9 of gestation were studied in serial sections. Postaxial deficiencies observed in 12–15‐day embryos and affecting preferentially the right forelimbs were classified in nine morphological types according to increasing amounts of missing parts. Type X defect consists of a nearly complete amelia in which all four limbs are represented only by the girdle and proximal end of the stylopod. Type XI abnormality appears as an intermediate reduction affecting the area of digit IV. In addition to modifications of the forelimb bud shape detected from the 10‐day stage onwards, observations made 24 and 48 hr after treatment confirmed that the postaxial defects result from an absolute lack of postaxial mesoderm occurring without cell necrosis as a consequence of a postaxial shortening of the apical ectodermal ridge (aer). In 10‐day embryos, the latter appears shortened and hypertrophied; it is later fragmented into alternate thick and thin portions in 11‐day affected limb buds. These ectodermal changes might account for the genesis of all types of defects observed. Untreated 9‐day embryos with 12–25 pairs of somites display a number of asymmetries between their right and left forelimb territories: Until the 19‐somite stage, the vascular supply to that area is provided exclusively by the umbilical vein, which is larger on the right side; the initial amount of somatopleural limb mesoderm is greater in the right rudiment and the genesis of its aer is slightly protracted as compared to the left one. These asymmetries might contribute to the right side predominance of the forelimb defects induced by acetazolamide and cadmium.
Studies of human achondroplasia: Oxidative metabolism in tissue culture cells
Authors: Mackler Bruce , Grace Richard , Davis Kenneth A. , Shepard Thomas H. , Hall Judith G.
Published: June 2005

Mitochondria prepared from the first growth of cells (fibroblasts) from skin biopsies from homozygous (but not heterozygous) achondroplastic human subjects were unable to carry out oxidative phosphorylation. However, successive crops of cells gained the ability to phosphorylate with normal P:O ratios with pyruvate‐malate and succinate as substrates. Concentrations of cytochromes a + a3 were markedly and significantly lower in homogenates of homozygous achondroplastic tissue culture cells than in homogenates of normal cells. Levels of cytochromes a + a3 in the heterozygous achondroplastic cells were intermediate between the levels in normal cells and the homozygous achondroplastic cells. Activities of the mitochondrial oxidative systems (NADH, succinic and cytochrome oxidases) were not significantly lower in the achondroplastic cell preparations than in normal cell preparations under standard assay conditions (saturation levels of oxygen).
Comparative anatomical analysis of human trisomies 13, 18, and 21: I. The forelimb
Authors: Dunlap S. S. , Aziz M. A. , Rosenbaum K. N.
Published: June 2005

Human trisomies 13, 18 and 21 exhibit specific neuromuscular phenotypes (Pettersen and Bersu, '82) which include a high proportion of neuromuscular forelimb variations, many of which are atavistic in nature (de Beer, '58; Barash et al., '79; Aziz, '81a). In order to test the neuromuscular phenotype, examine the atavistic nature, and analyze the developmental delay of the trisomy forearm musculature, we dissected the forelimbs of five trisomy 13, ten trisomy 18, and two trisomy 21 cases. Our dissections compare favorably with the existing published trisomy cases (Opitz et al., '79; Pettersen and Bersu, '82). Additionally, we found significant differences in the stage at which developmental arrest occurred in trisomies 13 and 18 for the pectoral complex, extensor digitorum profundus, and intrinsic hand musculature. Some of these muscles, which occur normally in nonhuman primates (Cihak, '67, '69; Dunlap et al., '85), also appear briefly in normal human ontogeny (Cihak, '72), constituting further evidence for developmental delay in aneuploids. The disproportionately effected limb tissues also lend support to the evidence for some degree of autonomy in their development in normal individuals. Our observations are consistent with Shapiro's amplified developmental instability model ('83). Aneuploids may be viewed as genetic variants from which much may be learned about normal limb development, how aneuploidy affects dysmorphogenesis, and the kind of information which exists on the duplicated (or monosomic) chromosome.
Risk factors in the prevalence of anencephalus and spina bifida in New Zealand
Authors: Barry Borman G. , Smith Allan H. , Keir Howard J.
Published: June 2005

This paper presents results from an epidemiological study on the 51 anencephalus and 53 spina bifida cases in the 1978 New Zealand birth cohort. Multiple sources were used in the ascertainment, and the prevalence rates were 0.98 and 1.02 per 1,000 total births, respectively. No association was found with the traditional indicators of the effect of environmental factors: maternal age, social class, nuptiality, month of birth, or estimated month of conception. Males comprised 41% of anencephalus and 36% of spina bifida cases; the prevalence was higher in the non‐Maori than in the Maori population. New Zealand‐born mothers appear to have a much lower risk of spina bifida, but not anencephaly, than those born in England/Scotland. The rate for the latter population was within the range of a number of UK‐based studies. As the bloodstock of New Zealand whites has been predominantly derived from the UK population, and as New Zealand is a low prevalence area, this suggests that the higher risk for these women is likely to be attributable to factors present in their birthplace but absent in New Zealand. These findings provide further evidence that the epidemiologic patterns of anencephalus and spina bifida in low‐prevalence areas are at variance with those in high‐prevalence areas, such as the United Kingdom. They also support the hypothesis that the contrast in rates between high‐ and low‐prevalence areas is a reflection of the impact of environmental factors in high‐prevalence areas on the “background” or baseline frequency of anencephalus and spina bifida found in low‐prevalence areas.
Maternal metabolism and teratogenesis in zinc‐deficient rats
Authors: Record I. R. , Dreosti I. E. , Tulsi R. S. , Manuel S. J.
Published: June 2005

Embyos removed at 11.5 days gestation from pregnant rats allowed a zinc‐deficient diet from the time of mating showed a high frequency of malformations of all organ systems. There were, however, large differences between litters of individual dams. Comparison of the daily food intake of zinc‐deficient dams with the appearance of the embryos suggested that fluctuations in the maternal serum zinc levels induced by feeding or fasting influenced the availability of zinc to the embryos. By cyclically feeding zinc‐deficient dams to a predetermined schedule, low maternal serum zinc levels were induced at selected stages of development. This was accompanied by specific malformations of the organs developing at that time.
Caffeine effects on cyclic AMP levels in the mouse embryonic limb and palate in vitro
Authors: Schreiner Claire M. , Zimmerman Ernest F. , Wee Elizabeth L. , Scott William J.
Published: June 2005

Caffeine is a teratogen that causes limb and palate malformations in rodents. Since the ability to raise cyclic nucleotide levels is a known biological action of caffeine, cyclic AMP levels were measured in CD‐1 mouse embryonic forelimb from whole embryo culture and embryonic limb and palate cells grown in primary culture following treatment with various concentrations of caffeine (0, 1, 3, or 10 mM). In forelimb buds from whole embryo culture, a dose‐dependent response was observed. Caffeine at 1 mM concentration stimulated cyclic AMP levels to 151% of control value at 60 min. Even greater stimulation of cyclic AMP occurred at higher caffeine concentrations. A dose‐dependent response was seen in both limb and palate cell culture. In limb cell culture, all caffeine concentrations significantly stimulated cyclic AMP after 10 min compared to control. In palate cell culture, there was a twofold increase in cyclic AMP at the 1‐mM caffeine concentration. At higher caffeine concentrations, cyclic AMP was significantly increased after 60 min. In addition, stimulation of cyclic AMP in cultured limb and palate cells by isoproterenol, a beta‐adrenergic agonist, was used as a positive control. Isoproterenol stimulated a 2.5‐fold greater response in the palate cells than in the limb bud cells at isoproterenol levels of 10−5 or 10−4 M. The increase of cyclic AMP may be influential in the process of abnormal limb or palate development.
The position effect in mice on day 14
Authors: Domarus Helmut V. , Louton Tom , Lange‐Wühlisch Frank
Published: June 2005

Previous publications have produced conflicting results concerning the effect and nature of uterine horn position on embryonic weight and development in the uterus bicornis. For this investigation we used 503 embryos from 41 litters of NMRI ‐ mice on gestational day 14. The relative position of each embryo was determined by measuring the distance from the center of each placenta to the cervix in relation to the total length of the uterine horn. After cessation of shrinkage due to fixation the umbilical cord and remaining membranes were removed under the dissecting microscope and the embryos were weighed to the nearest 0.1 mg. Analysis of potential embryonic positions along the uterine horns indicated that 10% at the extreme ovarian and cervical ends were almost devoid of implantations. A mixed nested analysis of variance was used as the appropriate model to test a position on weight effect. Not only was a position effect found but, in contrast to other studies, it is also quantitatively represented. Embryos were lighter both at the ovarian and cervical ends, the mean weight difference being in the range of less than 10% of the average embryo weight.
Methods for testing hypotheses across studies: Applications for teratologists and toxicologists
Authors: Barron Susan , Jaccard James , Riley Edward P.
Published: June 2005

Methods are presented for analyzing research results across independent studies. These techniques allow researchers to test hypotheses across studies using multiple investigations as data points. The procedures and rationale are developed for purposes of research synthesis and interpretation in teratology and toxicology.
Acetazolamide teratogenesis in Wistar rats: Potentiation and antagonism by adrenergic agents
Authors: Ugen Kenneth E. , Scott William J.
Published: June 2005

Acetazolamide, a carbonic anhydrase inhibitor, induced right forelimb ectrodactyly in rat fetuses when the mothers were treated on late day 10 and early day 11 of gestation. Coadministration of the selective alpha‐1‐adrenergic agonist phenylephrine significantly increased the incidence of acetazolamide‐induced right forelimb ectrodactyly while failing to induce the lesion when administered alone. Pretreatement with the alpha‐adrenergic antagonists phenoxybenzamine and prazosin prevented the phenylephrine‐induced increase in right forelimb ectrodactyly. In addition, treatment with either phenoxybenzamine or prazosin in the absence of stimulation with phenylephrine significantly decreased the incidence of acetazolamide‐induced ectrodactyly. The results suggest an adrenergic component in acetazolamide teratogenesis. Alterations in uterine blood flow are discussed as a plausible mechanism for the modification of the incidence of ectrodactyly by these adrenergic agents.
Effect of inorganic lead on the primordial germ cells in the mouse embryo
Authors: Wide Mariann , D'argy Roland
Published: June 2005

Embryos from mice exposed to lead chloride (20 μg/gm body weight) by a single intravenous injection on day 8 of gestation were examined regarding the number and distribution of their primordial germ cells on 4 consecutive days of development. The cells, visulized by histochemical staining for alkaline phosphatase, showed a normal body distribution but were significantly fewer at all four stages compared with those of control embryos of corresponding age. Furthermore, the staining of the primordial germ cells was much weaker in the embryos from the lead‐treated dams than in those from control dams, suggesting that the lead had interfered with the production or activity of alkaline phosphatease. It is assumed that these effects could have contributed to the fertility reduction previously observed in female offspring of mice exposed to lead at an early stage of pregnancy.
Operant behavior in transition reflects neonatal exposure to cadmium
Authors: Newland M. Christopher , Ng Wendy W. , Baggs Raymond B. , Gentry G. David , Weiss Bernard , Miller Richard K.
Published: June 2005

Male Long‐Evans rats were injected with 0, 1, 3, or 6 mg/kg of cadmium chloride on the first day of life. Animals free of morphological stigmata at weaning were selected for study. Tissue concentrations of cadium and operant behavior under various fixed‐ratio (FR) schedules of reinforcement were evaluated when these rats were adults. Dose‐related increases in cadmium were present in the brains, livers, and kidneys. Dose‐related differences in behavior were most evident during the transition from fixed ratio 25 (FR 25 or 25 responses/reinforcer) to FR 75. An inverted U describes the relationship between response output during the transition to FR 75 and cadmium chloride dose:response output increased at 3 mg/kg and decreased at 6 mg/kg. The rate decreases were not correlated with weight loss that appeared after some of the animals exposed to 6 mg/kg reached 60 days of age. Challenge doses of damphetamine revealed no interaction between neonatal exposure to cadmium and d‐amphetamine. The occurrence of alterations in operatnt behavior in animals that appeared normal on a number of preweaning evaluations suggests that operant behavior in transition was sensitive to subtle effects not observed with other commonly used tests. The data provide evidence for delayed effects in the adult that are due to neonatal exposure to cadmium.
Differential effects of 4‐hydroperoxycyclophosphamide on limb development in vitro
Authors: Hales Barbara F. , Jain Ranjana
Published: June 2005

Cyclophosphamide must be metabolically activated to produce malformations in limbs developing in culture; 4‐hydroperoxycyclophosphamide is an analog of the active metabolite of cyclophosphamide, that breaks down spontaneously in solution to form 4‐hydroxycyclophosphamide. To study the mechanism by which metabolites of cyclophosphamide produce limb malformations in vitro we determined the effects of exposure of cultured limb buds to 4‐hydroperoxycyclophosphamide. Fore‐ and hindlimbs were excised from ICR mice on day 12 of gestation and cultured in roller bottles for 6 days. Limbs were exposed to 4‐hydroperoxycyclophosphamide for the first 20 hours of the culture period. Addition of 10 μg/ml of 4‐hydroperoxycyclophosphamide to forelimb or to hindlimb buds in culture produced limb reduction malformations. A dramatic decrease in total limb bone area in fore‐ and hindlimbs was observed with 10 μg/ml of 4‐hydroperoxycyclophosphamide. In forelimbs, the long bone area decreased and the paw area remained constant so that the relative contribution of the long bone area to total limb bone area was decreased. In hindlimbs treated with 10 μg/ml of 4‐hydroperoxycyclophosphamide, no paw skeleton was observed. The DNA, RNA, and protein contents of the limbs were not affected by exposure to 1 μg/ml of 4‐hydroperoxycyclophosphamide, but were decreased by exposure to 10 μg/ml of this compound. Exposure to the higher concentration of 4‐hydroperoxycyclophosphamide also decreased alkaline phosphatase activity, a marker for osteogenesis, in both fore‐ and hindlimbs; in contrast, neither concentration of 4‐hydroperoxycyclophosphamide had an effect on creatine phosphokinase activity, a marker for myogenesis. Thus, the higher concentration of 4‐hydroperoxycyclophosphamide had differential effects on enzyme markers for osteogenesis and myogenesis and, in the forelimbs, on the long bones relative to the paw skeleton. The limb reduction malformations produced by exposure in vivo to cyclophosphamide may be a consequence of selective inhibition of osteogenesis.
Effects of cadmium on lactate dehydrogenase activities in mouse pre‐embryos at various stages
Authors: Yu H. S. , Chan S. T. H.
Published: June 2005

A decline in LDH activity from four‐cell to late blastocyst was demonstrated in pre‐embryos from F1 (C57 female × A2G male) female mice. An exposure to 0.5 or 1 μg/ml cadmium did not affect the in vitro development of the four‐cell pre‐embryos and morulae or their LDH activities. At 5 or 10 μg/ml cadmium, the in vitro development of the treated pre‐embryos was affected. Although most of the treated four‐cell pre‐embryos had proceeded to compaction, they became degenerated 24 h after treatment. The LDH activity of these degenerated pre‐embryos was higher than that in the control blastocysts. We propose that cadmium may interfere with the general energy metabolism of the cells. This causes a reduced rate of LDH degradation, leading to a slower decline in LDH activity in cadmium‐treated pre‐embryos. Failure of some critical biochemical processes after cadmium treatment may ultimately lead to the subsequent degeneration of the treated pre‐embryos.
Identification of Dh/ + and Dh/Dh embryos through close linkage of Dh and peptidase‐3
Authors: Holmes Lewis B.
Published: June 2005

The close linkage between the genes Dominant hemimelia (Dh) and peptidase‐3 (Pep‐3) has been determined in 65 informative matings with the recombination freqency of 3.8%. Progeny testing showed that non‐penetrance does occur in Dh/+ adults. The presence of the “slow” and “fast” variants of Pep‐3 can be determined in homogenates of kidney tissue as well as in a portion of the day 10 and 11 embryos. In a litter of embryos born to an informative mating, those which are Dh/Dh, Dh/+, and +/+ can be distinguished by the presence of the Pep‐3 allele known to be in coupling with the Dh gene. This technique makes it possible to identify and to study the limb malformations and other phenotypic effects of Dh during their development and before the limb deformity is visible.
Teratogenicity of di(2‐ethylhexyl) phthalate, 2‐ethylhexanol, 2‐ethylhexanoic acid, and valproic acid, and potentiation by caffeine
Authors: Ritter E. J. , Scott W. J. , Randall J. L. , Ritter J. M.
Published: June 2005

It is hypothesized that the teratogen di(2‐ethylhexyl) phthalate (DEHP) acts by in vivo hydrolysis to 2‐ethylhexanol (2‐EHXO), which in turn is metabolized to 2‐ethylhexanoic acid (2‐EHXA), the proximate teratogen. Teratological studies were conducted with Wistar rats, with administration of these agents on day 12 of gestation. On an equimolar basis DEHP was least potent, 2‐EHXO was intermediate, and 2‐EXHA was the most potent of the three agents, which is consistent with the hypothesis. Similarity in the types of defects found with these agents also suggests a common mechanism, with 2‐EHXA as the proximate teratogen. All three agents were potentiated by caffeine. Valproic acid, which is an isomer of 2‐EXHA, also produced similar defects, and was approximately twice as potent as 2‐EHXA.
Search for teratogenic risks with the aid of malformation registries
Authors: Källén Bengt
Published: June 2005

A summary is given of experiences in the use of the Swedish registries of birth defects for causal epidemiological studies. Case‐control studies and cohort studies are described and exemplified. The application of case‐control techniques to cohorts of women selected for probable or possible exposure is also described. The importance of using large‐scale registry studies in the search for common but low‐risk teratogens is stressed.
Ethyl alcohol‐induced cardiovascular malformations in the chick embryo
Authors: Fang Tzann‐Tarn , Bruyere Harold J. , Kargas Steve A. , Nishikawa Toshio , Takagi Yasuo , Gilbert Enid F.
Published: June 2005

Chick embryos incubated for 72–80 hours were exposed to various volumes (0.20–0.40 m1/egg) of 50% ethyl alcohol. Examination of embryos at day 14 of incubation showed that higher doses of ethanol decreased the survival rate of embryos compared with control embryos. Three major categories of cardiovascular malformations were observed in this study: intracardiac anomalies characterized primarily by isolated ventricular septal defect, ventricular septal defect with overriding aorta, double outlet right ventricle or common aorticopulmonary trunk; aortic arch anomalies; and subclavian artery anomalies. Frequencies of embryos with intracardiac anomalies were equal to or greater than 64.8% in the six groups exposed to ethanol. Administration of ethanol also induced high frequencies of embryos with subclavian artery anomalies (11.2–89.1%). Absence or hypoplasia of the right and/or left secondary subclavian artery was commonly associated with persistence of the corresponding primary subclavian artery. Bilateral absence and/or hypoplasia of the secondary subclavian arteries was more common than unilateral anomalies, whereas absence of the left secondary subclavian artery was more commonly observed than an absent right secondary subclavian artery. No embryos in the two control groups combined (n = 94) demonstrated aortic arch or subclavian artery anomalies.
Strain differences in phenobarbital‐induced teratogenesis in mice
Authors: Finnell Richard H. , Shields Heidi E. , Taylor Stephen M. , Chernoff Gerald F.
Published: June 2005

Anticonvulsant drugs are widely prescribed medications known to complicate more than 11,500 pregnancies each year in the United States. Although there is no clear consensus as to the teratogenicity of all of the clinically available compounds, it appears that most anticonvulsant drugs can induce congenital abnormalities in susceptible individuals. In a study designed to examine the role of the genotype on sensitivity to phenobarbitalinduced malformations, three highly inbred mouse strains (SWV, C57BL/6J, and LM/Bc) received the drug via chronic oral administration. Phenobarbital was found to have a significant teratogenic potential in mice, resulting in skeletal, cardiac, renal, neural, and urogenital defects in a dose‐related fashion. The LM/Bc strain was most sensitive to phenobarbital, with 46.7% of the fetuses exposed to the highest maternal plasma concentrations having malformations. C57BL/6J fetuses were the most resistant strain, with only 28.6% abnormalities.