bluuebunny/crossref_metadata_2025 huggingface dataset:
Synergism between temperature and estradiol: A common pathway in turtle sex determination?
Authors: Wibbels Thane , Bull J. J. , Crews David
Published: June 2005

In many reptiles, the temperature at which the eggs are incubated determines the sex of the hatchlings. Administration of estradiol will counteract the masculinizing effects of a male‐producing temperature, resulting in female hatchlings. To address whether temperature and estrogen are biologically equivalent, two experiments were conducted with the red‐eared slider turtle, Trachemys scripta. In the first experiment, varying dosages of estrogen were administered at Stage 17 (the middle of the temperature‐sensitive window) to eggs maintained at two temperatures, 26°C (which normally produces all males) and 28.2°C (which produces mostly males but lies at the threshold of the transition from male‐ to female‐producing temperatures). Results indicate that estrogen and temperature exert a synergistic effect on sex determination. In the second experiment, estrogen was administered at different stages of embryonic development. The results indicate an estrogen‐sensitive period ranging from Stage 14 through Stage 21, a period similar to the temperature‐sensitive period for this species. The results of these experiments are consistent with the hypothesis that temperature and estradiol act in a common pathway in temperature‐dependent sex determination.
Insulin but not progesterone promotes the biosynthesis of glycogen in Xenopus laevis oocytes: Implications on the control of glycogen synthase by phosphorylation, dephosphorylation
Authors: Debauche Pascal , Baras Benoǐt , Devos Pierre
Published: June 2005

Insulin, the well‐known hypoglycemic hormone, mimics progesterone in promoting the resumption of meiosis within the oocyte of Xenopus laevis. Both hormones exert their action through the inhibition of protein kinases and the activation of protein phosphatases. Because glycogen synthase is an enzyme regulated by a kinases/phosphatases cascade, we investigated the effect of insulin and progesterone on the regulation of glycogen synthesis and glycogen synthase throughout the oogenesis of Xenopus laevis oocytes. In this framework the maximal activity of synthase “a” is concomitant with the vitellogenic period characterized by a drastic increase in the amount of glycogen. Oocyte glycogen synthase is inhibited by cAMP‐dependent phosphorylation and stimulated by 20 mM Mg2+. The magnesium effect is inhibited by μmolar concentrations of okadaic acid and suggests that oocyte glycogen synthase is activated by dephosphorylation achieved by protein phosphatase‐1. The okadaic acid effect is itself thwarted by the specific inhibitor of protein kinase A, confirming the role of this kinase in the regulation of glycogen synthase. Finally, working on intact ripe oocytes, we showed that insulin but not progesterone increases glycogen synthesis and glycogen synthase “a” activity and lowers the rates of phosphorylation, especially in the glycogen‐bound proteins. © Wiley‐Liss, Inc.
Ovarian follicles of rainbow trout (Oncorhynchus mykiss) cultured within lamellae survive well, and sequester and process vitellogenin
Authors: Nagler J. J. , Tyler C. R. , Sumpter J. P.
Published: June 2005

The culture of ovarian follicles of fish has proved difficult and this has hindered research on factors controlling oocyte growth. Here we describe a system for the in vitro culture of vitellogenic ovarian follicles from rainbow trout (Oncorhynchus mykiss) contained within their lamellae, and compare it to results obtained with individual follicles. Gross morphological appearance, volume change, rate of vitellogenin (VTG) uptake, and subsequent processing of VTG were used as indicators of viability and physiological status. In culture, follicles maintained within ovarian lamellae had significantly higher survival rates compared to individual follicles divested of connective tissue and surface epithelia (90% vs. 45% survival, respectively) after 6 d. Although surrounded by follicle cell layers and surface epithelia, oocytes within lamellae still sequestered VTG, albeit at a lower rate than individual follicles devoid of their surface epithelia. Further, VTG sequestered by follicles within lamellae was processed into lower molecular weight proteins within the oocyte. The superior survival rate of ovarian follicles within lamellae (compared to those divested of their surface epithelia), together with their ability to incorporate VTG and process it suggest that this method provides an excellent system for studying factors controlling oocyte growth. © Wiley‐Liss, Inc.
Role of glutamate and GABA in the pathophysiology of epilepsy
Authors: Holmes Gregory L.
Published: June 2005

Epilepsy, a paroxysmal disorder characterized by abnormal neuronal discharges, is common in children. While the causes of epilepsy are many, the fundamental disorder is secondary to abnormal synchronous discharges of a network of neurons. Whether or not a seizure occurs in a child depends upon the balance between excitability and inhibition. Central nervous system neurotransmitters have significant effects on neuronal excitability and play a pivotal role in brain excitability. The most common excitatory neurotransmitter in the brain, glutamate, has been implicated in both the initiation and propagation of seizures as well as brain damage that can occur following prolonged or repeated seizures. Gammaaminobutyric acid, the most common inhibitory neurotransmitter, usually suppresses seizure activity, although in absence seizure drugs that enhance GABA may exacerbate seizures. Experience with GABA indicates that certain neurotransmitters may have either anticonvulsant or proconvulsant effects depending on the neuronal networks involved. While other neurotransmitters also have effects on neuronal excitability, their function in epilepsy remains to be defined. © 1995 Wiley‐Liss, Inc.
Empiric recurrence risks in common and uncommon congenital heart lesions
Authors: Nora James J. , McGill Charles W. , McNamara Dan G.
Published: June 2005

Empiric recurrence risks in sibs for the eight most common and four uncommon congenital heart lesions have been obtained from a study of 1405 patients with congenital cardiovascular malformations. Risks to offspring of parents with any of four common congenital heart diseases were determined in a study of 210 adults who had congenital heart defects and who had reproduced. The recurrence risks are presented and are found to approximate the prediction of the multifactorial inheritance hypothesis.
Influence of 2‐deoxy‐D‐glucose and sodium fluoroacetate on respiratory metabolism of rat embryos during organogenesis
Authors: Spielmann Horst , Meyer‐Wendecker Rainer , Spielmann Frauke
Published: June 2005

The effect of various concentrations of 2‐deoxy‐D‐glucose (2DG) and sodium fluoroacetate (SFA) on the Q of day‐11 and 12 rat embryos was studied in vitro. The dose‐response curves—% inhibition versus log concentration—were linear for 2DG between 500 μM and 50 mM; day‐11 rat embryos showed a higher rate of inhibition than day‐12 embryos and adult kidney tissue. The inhibitory effect of SFA on the embryonic Q in vitro was significantly lower than on adult kidney tissue slices. These in vitro effects are in agreement with recent investigations on the energy metabolism of rat embryos that revealed a change from glycolysis to an oxidative, respiratory metabolism during organogenesis. The administration of a single dose of 2DG and SFA to pregnant rats at day 9 or 10 of pregnancy significantly reduced the Q and dry weight of the embryos at day 11, whereas both parameters were unchanged at day 12. The same treatment was nonteratogenic, which is in contrast to the findings of other investigators.
Glucocorticoid inhibition of RNA synthesis and the critical period for cleft palate induction in inbred mice
Authors: Andrew Floyd D. , Bowen Donna , Zimmerman Ernest F.
Published: June 2005

A comparison was made of the teratogenic effects of triamcinolone (induction of cleft palate) and its ability to inhibit RNA synthesis in the C3H and A/J strains of mice. The “critical period” for induction of cleft palate in C3H mice was at day 11.5 of gestation, 3 days before palate shelf elevation. The extent of inhibition of RNA synthesis decreased when the drug was administered at later times of development and was correlated with a lower concentration of drug in fetuses. However when a higher dose (15 mg/kg) was administered at a later time (day 13.5), although the fetal drug concentration and inhibition of RNA synthesis were approximately equal to that produced by 10 mg/kg triamcinolone administered at day 11.5 (which produces 80% cleft palate), the frequency of cleft palate was much lower (33%). Thus the critical period for teratogenesis is not related to maximal absorption of drug. In A/J mice the critical period was at day 12.5. When one‐fifth as much triamcinolone (2 mg/kg) was administered to A/J mice the inhibition of RNA synthesis in palate and total fetus was similar to that seen after 10 mg/kg in the C3H strain. The concentration of drug in fetuses of each strain was approximately proportional to the dose administered. Thus A/J may be more sensitive to the effect of triamcinolone on RNA synthesis than C3H. The mechanism of action of the glucocorticoid with respect to the “critical period,” inhibition of RNA synthesis, and strain differences is discussed.
Evaluation of the teratogenic potential of a spray adhesive in hamsters
Authors: Murphy James C. , Collins Thomas F. X. , Black Thomas N. , Osterberg Robert E.
Published: June 2005

Pregnant Syrian hamsters were placed in a 100‐1 static inhalation chamber for 30 min twice daily on days 5‐10 of gestation and exposed to 8.0 ± 0.13, 11.6 ± 0.11, or 13.23 ± 0.49 g of “Foil Art Adhesive” and killed on day 14. Controls were placed in adjacent identical chambers but received no spray. The spray adhesive was toxic but not teratogenic at the doses administered. Maternal alopecia occurred upon exposure to the 2 highest dose levels, and 1 female died during exposure to the highest dose level. Fetal survival was not affected. Mean fetal weight was significantly decreased after exposure to all 3 dose levels, and delayed skeletal development occurred but was not dose related.
Prenatal ossification in rabbits as indicative of fetal maturity
Authors: Fritz Hans
Published: June 2005

During the prenatal period of development of the rabbit skeleton (days 21–30) the successive phases of fetal maturity can be distinguished by reference to the progress of ossification, particularly in the distal limbs and sternum. In the present study absent or incomplete ossification of sternebra 5 occurred in 8% of term fetuses. The incidence of anomalies of prenatal ossification of the axial skeleton was 1.9%. The relevance of delayed and disturbed ossification with regard to teratological tests is discussed.
Teratogenic effects of excess glucose on head‐fold rat embryos in culture
Authors: Cockroft D. L. , Coppola P. T.
Published: June 2005

Rat embryos explanted at nine and one‐half days of gestation (early head‐fold stages) were cultured for 48 hours in rotating bottles containing rat serum and a gas phase. Addition of 12‐15 mg/ml of D‐glucose to the culture medium resulted in severe abnormalities and retarded development in a high proportion of embryos, whether or not the osmolarity increase brought about by the addition of glucose was corrected. The raised osmolarity, however, increased the frequency and severity of malformations observed. L‐glucose produced no abnormalities, though embryonic development was retarded.
A comparison of the distribution, metabolism and excretion of ethylenethiourea in the pregnant mouse and rat
Authors: Ruddick Joseph A. , Newsome W. H. , Iverson F.
Published: June 2005

Pregnant mice and rats were treated by stomach intubation on day 15 of gestation with 240 mg/kg of ethylenethiourea (ETU) made up in part with radiolabeled ETU. Animals were sacrificed at specific times post‐treatment, and maternal tissues, fetus, urine and feces were collected for determination of radioactivity. Maternal and fetal tissue levels of ETU were similar at three hours post treatment; thereafter, the mouse (maternal and fetus) showed much less ETU than the rat. The t½ of ETU elimination from the maternal blood was 9.4 and 5.5 hours for the rat and mouse, respectively. Analysis of urine by thinlayer chromatography and radiochromatography revealed that the mouse and rat metabolized ETU by different pathways. Furthermore, the mouse is able to metabolize ETU to a greater extent than the rat.
Translocation heterozygosity in a malformed piglet and its normal littermates
Authors: Miyake Yoh‐Ichi , Kawata Keiichiro , Ishikawa Tsune , Umezu Masatoshi
Published: June 2005

A translocation with centric fusion between the Nos. 13 and 17 acrocentric chromosomes was described in a malformed female piglet and three phenotypically normal littermates by the G‐banding staining technique. Since the translocation was heterozygous, the chromosome number was 37. The differences between the translocation of the present cases and those previously reported in the domestic swine species, as well as in some wild pigs, are mentioned.
Teratogenic effects of combined administration of ethylenethiourea and nitrite in mice
Authors: Teramoto S. , Saito R. , Shirasu Y.
Published: June 2005

Teratogenic potential of ethylenethiourea (ETU) was investigated in SLC‐ICR mice after its reaction with sodium nitrite. ETU was given orally in dose of 400 mg/kg on various days of pregnancy in combination with 200 mg/kg NaNO2 at varied intervals. When NaNO2 was given to females immediately after their treatment with ETU on day 6 or 8 of pregnancy, fetal survival was significantly decreased. Various types of malformations were observed in the living fetuses from mothers treated on day 6, 8, or 10 of pregnancy, but not on day 12. The teratogenicity disappeared when NaNO2 was given 2 h after the treatment with ETU.
Maternal fever and neural tube defects
Authors: Layde Peter M. , Edmonds Larry D. , Erickson J. David
Published: June 2005

It has been proposed that hyperthermia in the pregnant woman is associated with neural tube defects in her offspring. We analyzed retrospective interview data for a maternal history of probable febrile illness during the first trimester of pregnancy among mothers of infants with anencephaly or spina bifida. There were two control groups—mothers of infants with Down syndrome and mothers of infants with cleft lip or palate. With the Down syndrome group serving as controls, the incidence of febrile illness among mothers of all infants with neural tube defects was significantly elevated. With the cleft group as controls, the fever incidence was not significantly increased in the neural tube defect groups. When the combined cleft and Down syndrome controls were used, only mothers of the spina bifida group had an elevated fever incidence. Epidemiologic data suggest an association of maternal fever during pregnancy with neural tube defects in the offspring.
Effect of phenytoin on maternal heart rate in A/J mice: Possible role in teratogenesis
Authors: Watkinson William P. , Millicovsky Guillermo
Published: June 2005

Phenytoin (diphenylhydantion, Dilantin®, PHT), an anticonvulsant and antiarrhythmic drug, is teratogenic to A/J mice, producing an increased incidence of cleft lip with or without cleft palate [CL(P)] and cardiac defects. Although its mechanism of teratogenic action remains unclear, one possibility may involve uterine ischemia resulting from an exaggerated depressant effect on maternal cardiovascular function. To test this hypothesis, the heart rate response of susceptible A/J and resistant C57B1/6J mice was monitored following intraperitoneal injection of doses of PHT of known teratogenic potential.

Heart rate (HR) was obtained electrocardiographically from unanesthetized, pregnant mice on day 10 of gestation via previously implanted subcutaneous electrodes. The HR of A/J mice was significantly depressed relative to vehicle‐injected controls following doses of 40, 60, and 75 mg/kg, with the greatest effect occurring in the high‐dose group. In C57B1/6J mice, the HR response of the group treated with 75 mg/kg was not different from that of the vehicle‐treated controls. At the same dose level, the depression of HR of A/J mice was significantly greater in magnitude and duration than that of C57B1/6J mice.

A proposed maternally mediated mechanism of CL(P) in A/J mice involving low placental/embryonic oxygen delivery is discussed. The results of the present study indicate the potential significance that changes in maternal physiology may have on embryonic development.
Monozygotic twin aborted fetuses discordant for holoprosencephaly/synotia
Authors: Machin G. A. , Sperber G. H. , Wootliffe J.
Published: June 2005

A pair of monozygotic twin fetuses aborted at 15 weeks were found to be discordant for holoprosencephaly and synotia. They were studied grossly, radiologically, and histologically. Features of first brancial arch dysplasia (synotia, agnathia, and astomia) and holoprosencephaly (absent ethmoid bone and Rathke's pouch) observed in one twin were contrasted with minimal dysmorphology in the co‐twin. Some evidence of the twin transfusion syndrome was also apparent, perhaps contributing to the twins' spontaneous abortion.
Developmental toxicity of the cyanogenic glycoside linamarin in the golden hamster
Authors: Frakes Robert A. , Sharma Raghubir P. , Willhite Calvin C.
Published: June 2005

Cassava, a staple food in many tropical countries, has been suspected as a cause of human congenital defects. Ingestion of the material during pregnancy has been reported to induce limb defects, microcephaly, open eye, and growth retardation in rats. Linamarin is a natural cyanogenic glycoside that occurs in high concentrations in cassava. In the present study, pregnant hamsters received an oral dose of 70, 100, 120 or 140 mg/kg linamarin or an equivalent volume of isotonic saline during the early primitive streak stage of gestation. A dose of 120 or 140 mg/kg of the glycoside was associated with an increased incidence of vertebral and rib anomalies as well as the production of encephaloceles in the offspring. These larger doses of linamarin also resulted in obvious maternal toxicity. Linamarin treatment had no effect on fetal body weight, ossification of fetal skeletons, embryonic mortality, or litter size. Although ingestion of the cyanogenic glycoside was associated with a significant teratogenic response, the effects occurred only at doses that elicited signs of maternal intoxication.
Pathogenesis of the mouse forelimb deformity induced by acetazolamide: An electron microscopic study
Authors: Datu Abdul Razak , Nakamura Harukazu , Yasuda Mineo
Published: June 2005

Scanning electron microscopic observations after removal of the epidermis from developing limb buds reveal a fine mesenchymal cell process meshwork (CPM). The relationship between apical ectodermal ridge (AER) development and CPM density was investigated and related to the postaxial reduction deformities induced by acetazolamide (AA). AA was given orally to pregnant mice at 9 A.M. and 4 P.M. of day 9 and 9 A.M. of day 10 (VP = 0) in a dose of 1,000 mg/kg. Forelimb ectrodactyly, especially on the right, was the most common deformity observed. Scanning electron microscopic observations showed that the AER in AA‐treated right forelimb buds did not extend postaxially as far as that in controls. The postaxial region with the hypoplastic AER became defective. Scanning and transmission electron microscopic observations revealed that in control and treated right forelimb buds, the CPM underneath the typical AER was sparser than that underneath the dorsal or ventral non‐ridge epidermis. However, in treated right forelimb buds, the CPM underneath a hypoplastic AER was denser than that underneath the normal AER. These findings suggest that AA‐induced deformity results from a disturbance of the AER‐mesenchymal interactions.
Developmental toxicity of aflatoxin B1 in the rodent embryo in vitro: Contribution of exogenous biotransformation systems to toxicity
Authors: Geissler Francis , Faustman Elaine M.
Published: June 2005

Aflatoxin B1 (AFB1) is a known carcinogen and developmental toxin in various species of mammals, birds, amphibians, and fish. AFB1 requires metabolic activation (biotransformation) to the 2,3‐epoxide metabolite for carcinogenicity; however, it is unknown if biotransformation is a prerequisite for AFB1 embryotoxicity. Cultured day 10 rat embryos were exposed to AFB1 alone and AFB1 in the presence of cofactors and hepatic S9 fractions from adult male rats induced with either phenobarbital or 3‐methylcholanthrene. Under these different culture conditions qualitatively similar patterns of malformation were seen in all embryos exposed to AFB1. At culture concentrations of 15 μM or greater, AFB1 produced abnormalities in neural tube development in a concentration‐dependent manner. The presence of hepatic S9 fractions had no effect on the ability of AFB1 to produce dysmorphogenesis in vitro or on the spectrum of malformations elicited. However, the addition of hepatic S9 fractions did greatly enhance the embryolethality of AFB1. This enhancement was greater with phenobarbital‐ than 3‐methylcholanthrene‐preinduced hepatic S9 fractions. Our results suggest that separate chemical mediators may be responsible for the embryolethal and dysmorphogenic effects of AFB1 observed in day 10 rat embryos in vitro. We found that the embryolethality of AFB1, but not the dysmorphogenicity, could be greatly modulated by exogenous biotransformation.
Brain changes in rats induced by prenatal injection of methylazoxymethanol
Authors: Tamaru Masao , Hirata Yukari , Nagayoshi Michiko , Matsutani Tenhoshimaru
Published: June 2005

Various doses (0, 1, 5, 10, 15, 20, or 25 mg/kg) of methylazoxymethanol acetate (MAM), a potent alkylating agent, were injected singly into pregnant rats intraperitoneally on day 15 of gestation. Relationships between brain weights and neurochemical changes in the cerebral hemispheres (CHs; cerebral cortex and subjacent white matter, hippocampus, amygdala) and remainder of the brain (BGDM; basal ganglia, diencephalon, and mesencephalon) were examined at 60 days of age in offspring; varying degrees of microencephaly were observed. Dose‐dependent reductions in the weights of CH and BGDM were observed. Reductions in total DNA content positively correlated with decreases in brain weights also observed. Dose‐dependent elevations of noradrenaline (NA) and dopamine (DA) were observed in CH at MAM levels 10 mg/kg and above; dose‐dependent elevations of 5‐hydroxytryptamine (5‐HT) were observed at 15 mg/kg and above; and in BGDM at 20 mg/kg and above dose‐dependent elevations for NA and 5‐HT were observed; dose‐dependent elevations at 15 mg/kg and above were observed for DA. Monoamine concentrations were negatively correlated with brain weights or total DNA contents. NA and DA concentrations increased to the extent of approximately 1.3 times of control at a time when an 18% loss of CH weight was noted in animals treated with 10 mg/kg MAM. It is suggested that the above variables might be appropriately sensitive neurochemical markers for detecting minor developmental anomalies in the brain.
Valproic acid developmental toxicity and pharmacokinetics in the rhesus monkey: An interspecies comparison
Authors: Hendrickx A. G. , Nau H. , Binkerd P. , Rowland J. M. , Rowland J. R. , Cukierski M. J. , Cukierski M. A.
Published: June 2005

This study was undertaken to assess the developmental toxicity and drug distributional and metabolic characteristics of prenatal valproic acid (VPA) exposure in rhesus monkeys. Oral administration of 20–600 mg/kg/ day VPA (approximately 1–15 × human therapeutic dose) to 33 animals on variable gestational days (GD) during organogenesis resulted in dose‐dependent developmental toxicity manifested as increased embryo/fetal mortality, intrauterine growth retardation, and craniofacial and skeletal defects. Biphasic plasma elimination curves were observed for total and free VPA on the first (GD 21) and last (GD 50) days of treatment in the 100‐ and 200‐mg/kg/day dose groups. VPA exhibited dose‐independent elimination kinetics at the plasma concentrations observed in this study. There was no significant change in pharmacokinetic parameters (maternal plasma elimination rate, area under the curve, peak plasma concentration) between the first and last days of treatment at either dose level. Placental transfer studies indicated that embryos were exposed to half the free VPA concentrations present in maternal plasma on GD 37. Comparisons of interspecies sensitivity to VPA‐induced developmental toxicity in the mouse, rat, monkey, and man are made.
Incidence of anencephalus and spina bifida in Greece
Authors: Lekea Vasso , Tzoumaka‐Bakoula Chryssa , Golding Jean
Published: June 2005

A cross‐sectional national survey of 11,048 births in the whole of Greece in April 1984 identified 7 cases of anencephalus and 9 of spina bifida. There was thus an incidence of 1.45 neural tube defects per 1,000 total births. This is the first geographically defined population study from southern Europe. In comparison with hospital‐based data from the 2 countries on its borders, the Greek rates are rather similar to those of Yugoslavia but much lower than reports from Turkey.
Retroperitoneal teratoma with fetuses
Authors: Nadimpalli V. R. , Reyes H. , Manaligod J. R.
Published: June 2005

Teratomas occur infrequently in retroperitoneal areas and are usually benign. They may contain highly organized structures like digits and limbs. The presence of a well‐formed fetus in teratomas is extremely rare. This report further documents an instance in which two fetuses were embedded within the retroperitoneal teratoma.
Effects of paternal subacute exposure to tordon 202c on fetal growth and development in CD‐1 mice
Authors: Blakley Patricia M. , Kim Jin Suk , Firneisz Gay D.
Published: June 2005

Male CD‐1 mice were exposed to Tordon 202c (a picloram and 2,4‐D combination herbicide) in the drinking water at concentrations of 0.21, 0.42, and 0.84% solutions for 60 days prior to mating with untreated females. Subsequently there was no exposure to Tordon 202c during gestation. Fetal weight and crown‐rump length were reduced in the highest dosage group. The incidence of malformed fetuses (e.g., ablepharon, cleft palate, and unilateral agenesis of the testes) was increased in the middle dosage group while the incidence of fetuses with variants was increased in the lowest (e.g., an extra pair of ribs) and the highest dosage groups (e.g., incomplete ossification of the skeleton). The frequency of pregnancy failure was increased in the middle dosage group. Indices of paternal toxicity included increased lethality and decreased water consumption in the highest dosage group and increased relative spleen weights in the lowest and middle dosage groups. The results suggest paternally mediated reproductive toxicity.
Direct effects of retinoic acid on the development of the tail bud in chick embryos
Authors: Griffith C. M. , Wiley M. J.
Published: June 2005

Retinoic acid (RA) has been reported to induce vascular lesions and haematoma formation in the vicinity of the tail bud during the critical period for inducing abnormalities of tail bud development in hamsters (Wiley, '83; Tibbles and Wiley, '88), mice (Tibbles and Wiley, '88) and chicken embryos (Jelinek and Kistler, '81). Experiments were conducted to determine whether or not these vascular lesions were the primary cause of the malformations which they accompanied. Chick embryos were exposed for varying lengths of time to several dosages of RA. Primitive streaks or tail buds from treated embryos were then excised prior to vascularization and transplanted to the coelomic walls of untreated host embryos. The grafts were harvested at 3 or 6 days after grafting and processed for histological examination. Observations of serial sections of controls showed that the primitive streak and early (stage 13–14) tail bud were able to form neural tubes and a variety of other structures including ganglia, nerve fibres, and kidney tubules. Treatment of donor embryos with RA prior to grafting, however, affected the frequency and characteristics of the neural tubes and other tissues developing in the grafts. The effects of RA on development were correlated with both the dosage and length of exposure to the teratogen prior to grafting. Since the grafts were made before the appearance of blood vessels in the tail buds, we have concluded that the effects of RA on the development of tail bud tissues, and especially the secondary neural tube, are direct and are not mediated solely through the disruptive effects of vascular lesions seen in intact embryos.
In vitro differential developmental toxicity of vitamin a congeners
Authors: Johnson E. Marshall , Chun Y. H.
Published: June 2005

Several forms of vitamin A were tested in the in vitro hydra assay for their developmental toxicity hazard potential and site of action on progressive ontogenesis. Retinol, retinyl acetate, retinaldehyde, all trans retinoic acid, and 13 cis retinoic acid were tested fully, and each was established clearly as being able to perturb development of artificial hydra ‘embryos’ at, or near, adult toxic treatment levels. All forms of vitamin A tested interfered with differentiation, but, although the alcohol, acetate, and aldehyde forms (group I) prevented the initial stages of differentiation from occurring, the acid forms (group II) allowed the initial stages of differentiation to occur but not the final differentiation of tentacle buds. Group I compounds produced the developmental toxicity endpoint after as little as 24 h of transient exposure on the first day of development, but had no permanent effect on development at their minimal affective developmental concentration (D‐MAC) when exposure began after the first day of development. In contrast, transient 24‐h exposure to group II forms did not interfere with development. At, or even above, a concentration greater than the D‐MAC, more continuous exposure to them was required to interfere with differentiation. Consistent with tests of other chemicals, the concentrations needed to produce effects in hydra bore no relation to those needed to produce effects in mammals.
Prenatal exposure to a low‐frequency electromagnetic field demasculinizes adult scent marking behavior and increases accessory sex organ weights in rats
Authors: McGivern Robert F. , Sokol Rebecca Z. , Adey W. Ross
Published: June 2005

Pregnant Sprague‐Dawley dams were exposed to a low‐level, low‐frequency pulsed electromagnetic (EM) field (15 Hz, 0.3 msec duration, peak intensity 8 gauss) for 15 min twice a day from day 15 through day 20 of gestation, a period in development that is critical for sexual differentiation of the male rat brain. No differences in litter size, number of stillborns, or body weight were observed in offspring from field‐exposed dams. At 120 days of age, field‐exposed male offspring exhibited significantly less scent marking behavior than controls. Accessory sex organ weights, including epididymis, seminal vesicles, and prostate, were significantly higher in field‐exposed subjects at this age. However, circulating levels of testosterone, luteinizing hormone, and follicle‐stimulating hormone, as well as epididymal sperm counts, were normal. These data indicate that brief, intermittent exposure to low‐frequency EM fields during the critical prenatal period for neurobehavioral sex differentiation can demasculinize male scent marking behavior and increase accessory sex organ weights in adulthood.
Embryotoxic effects of sodium arsenite and sodium arsenate on mouse embryos in culture
Authors: Chaineau Eric , Binet Stéphane , Pol Didier , Chatellier Gilles , Meininger Vincent
Published: June 2005

Embryotoxic effects of two inorganic arsenic compounds, sodium arsenite (Asi) and sodium arsenate (Asa), on the development of mouse embryos during early organogenesis were studied using the whole embryo culture technique. Embryos with three to five somites exposed to 1–40 μM Asi or to 10–400 μM Asa were cultured for 48 hours and their development was compared with that of control embryos. Asi proved to be teratogenic between 3 and 4 μM and embryolethal at higher concentrations; Asa had similar activity but at concentrations ten times higher than for Asi. Both compounds produced a growth retardation and a similar pattern of defects. Growth retardation was indicated by a statistically significant reduction in crown‐rump length, head length, and yolk sac diameter. Abnormal embryos were characterized by hypoplasia of the prosencephalon with open neural tube, hydropericardium, somite abnormalities, and failure of development of limb buds and sensory placodes. These results confirm that both Asa and Asi are embryotoxic compounds and that the Asi activity occurs at concentrations ten times lower than for Asa. Our results suggest that in humans both of these compounds may be involved in part of “unaccountable” early abortions and malformations claimed to be due to the toxicity of heavy metals.
Nitrous oxide alters body laterality in rats
Authors: Fujinaga Masahiko , Baden Jeffrey M. , Shepard Thomas H. , Mazze Richard I.
Published: June 2005

Seventy timed‐pregnant Sprague‐Dawley rats were exposed to either air (control) or 75% nitrous oxide (N2O) for 24 hours on day 8 of gestation. Four rats from each group were killed on days 11–16, 18, and 20, and laparotomy was performed. The viability of the embryos/fetuses was determined, as was the side of tail flexion on days 11 and 12, the direction from which the umbilical artery emerged from the body on days 13 and 14, the side of the body facing the placenta on days 15 and 16, and the side to which the aortic arch curved on days 18 and 20. Mean mortality rate in the control group was 8.9 ± 6.1% (± S.D.), and there were no control embryos/fetuses with altered laterality except the 9% that faced left on day 16. In contrast, N2O treatment on day 8 of gestation resulted in significantly increased mortality (40.8 ± 3.3%) beginning on day 14 of gestation and increased incidence of altered laterality overall (31.3%) and at all stages of development. The mechanisms underlying these events remain to be defined, as do the implications of our findings for pregnant surgical patients and occupationally exposed workers.
Timely monthly surveillance of birth prevalence rates of congenital malformations and genetic disorders ascertained by registries or other systematic data bases
Authors: Hook Ernest B.
Published: June 2005

In many jurisdictions large data sets on malformations are now collected routinely in order to define prevalence rates of malformations in infants and children, to detect long‐term secular trends, and to ascertain cases, for ad hoc case‐control studies. With slight modifications, these data sets may be used for prompt surveillance of changes in the birth prevalence of malformations, changes that conceivably could be possibly due to the introduction of a teratogen into the environment. A specific logistic approach is suggested, modeled on the New York State Malformation Registry, for prompt detection of changes in rates.
Histological and in vitro studies supporting decreased uteroplacental blood flow as explanation for digital defects after administration of vasodilators
Authors: Danielsson Bengt R. G. , Danielson Margareta , Reiland Sven , Rundqvist Eva , Dencker Lennart , Regård Carl‐Gunnar
Published: June 2005

In a recent study, the vasodilating drugs nifedipine, nitrendipine, felodipine, and hydralazine induced phalangeal defects in rabbits, when given on day 16 of pregnancy. Histologically, the changes were characterized by disturbed chondrogenesis. In order to elucidate mechanisms behind the defects, the fetal concentration of felodipine was measured, and the fetal limb plates were examined histologically, at 0, 2, 4, 8, 12, and 24 hours after single oral administration of felodipine (12 μmol/kg) on day 16 in pregnant rabbits. The effects of nifedipine, nitrendipine, and felodipine were also investigated in an in vitro system, in which chick embryonic mesenchymal limb bud cells differentiated into chondrocytes. In this system, no inhibition of chondrogenesis was observed below concentrations 3 × 105 M. At this concentration, unspecific cytotoxicity was found. The highest fetal concentrations of felodipine were more than 500 times lower than what was required for in vitro toxicity. Histologically, the digital areas of the limb plates showed extensive edema and dilatation of marginal sinus within 2 hours. After 8 hours, rupture of the thin‐walled vessels occurred with hemorrhages. Finally, small necroses and blisters were observed. Similar early changes have been reported in experiments where digital defects were induced by clamping uterine vessels. This study thus indicates that the phalangeal defects after administration of high doses of vasodilators are secondary to pharmacological action (associated with a significant reduction in the uteroplacental blood flow), and not a direct effect on fetal chondrogenesis.
Binding of (chloroethyl 3H) cyclophosphamide to rat embryo proteins: Two‐dimensional gel analysis
Authors: Mirkes Philip E. , Little Sally A.
Published: June 2005

Cells of the heart of the day 10 rat embryo are resistant to the cytotoxic effects of cyclophosphamide (CP) while cells of neuroepithelium (head) are sensitive. Using radiolabeled CP we have investigated the hypothesis that this difference in sensitivity is related to the binding (alkylation) of drug to specific proteins in heart and head cells. Two‐dimensional gel analysis reveals that CP alkylates a variety of proteins in both heart and head cells. Although minor differences in the profiles of alkylated proteins exist between heart and head cells, the major proteins alkylated by CP in the two populations are identical. These data, therefore, do not support the hypothesis that sensitivity to the cytotoxic effects of CP is related to drug binding to specific proteins.
Teratogenic effects on the neuroepithelium of the CD‐1 mouse embryo exposed in utero to sodium valproate
Authors: Turner Susan , Sucheston Martha E. , De Philip Robert M. , Paulson Ruth B.
Published: June 2005

A causal association has now been recognized between the use of the anticonvulsant drug sodium valproate during pregnancy and the increased incidence of spina bifida in the human population. The objective of this study was to investigate the teratogenic effects of sodium valproate on the cephalic 1) neuroepithelium, 2) extracellular matrix, and 3) embryonic protein content in the CD‐1 mouse embryo. Nulliparous female CD‐1 mice were dosed intraperitoneally on day 8 of gestation with 340 mg/kg of sodium valproate. On day 10 of gestation, females were killed by cervical dislocation, and all live embryos were assigned to one of the following groups and processed accordingly for: 1) head measurements, 2) scanning electron microscopy, 3) total protein determination, 4) two‐dimensional polyacrylamide gel electrophoresis, 5) immunohistochemistry, and 6) light microscopy. Exposure to sodium valproate at the selected dosage resulted in a 30% incidence of neural tube defects in the cranial region of these embryos. Treated embryos showed a significant reduction in head size, indicating a drug‐induced microcephaly. No major differences were seen in the total embryonic protein patterns between control and treated embryos. Immunoreactivity to laminin and fibronectin showed a similar distribution in control and treated embryos except in the vasculature pattern of the hindbrain neuroepithelium. The neuroepithelium of the treated embryos showed marked disorganization when it was examined histologically, particularly in the forebrain region. Cells were disoriented, and there was a noticeable loss of intercellular adhesion in the juxtaluminal region. Increased cellular blebbing was apparent at the ependymal surface, and large protrusions of cells were seen invading the neural tube lumen. The lumen was distorted in shape and frequently contained blood cells. Irregularities and gaps were observed in the underlying basal lamina. These results suggest that treatment with sodium valproate during a critical time in neurogenesis in the CD‐1 mouse embryo alters the normal architecture of the neuroepithelium, with a loss of integrity at both the basal and apical surfaces. The alterations seen in the neuroepithelium at any of these sites in this animal model could help explain the increased incidence of spina bifida seen in children of epileptic mothers receiving sodium valproate.
Ethanol‐induced limb defects in mice: Effect of strain and Ro 15‐4513
Authors: Zimmerman Ernest F. , Scott William J. , Collins Michael D.
Published: June 2005

It is now thought that ethanol exerts many of its behavioral effects in the CNS by interaction with the γ‐aminobutyric acid (GABA) receptor, and it has been shown that the benzodiazepine reverse agonist Ro15–4513 reverses some of the CNS effects produced by ethanol. The hypothesis was tested that ethanol exerts its teratogenic effects through interaction with a putative embryonic GABA receptor by determining whether Ro15‐4513 reverses ethanol‐induced forelimb ectrodactyly in C57BL/6 mice. First, pregnant C57BL/6 dams were injected twice i.p. with ethanol (2.9 g/kg body weight, 4 hr apart) on day 10 of gestation: 49% of the fetuses were resorbed or dead and 46% of the survivors showed forelimb ectrodactyly. In contrast, when SWV mice were treated with ethanol, embryolethality was only 11.9% and no forelimb ectrodactyly was observed. In a second experiment, when ethanol (2.6 g/kg × 2) was administered to C57BL/6 mice, 34% resorptions and 31% forelimb ectrodactyly were observed. Ectrodactyly induced by ethanol was primarily of the forelimb and exclusively postaxial. Ethanol produced an unusual forelimb defect in a small number of instances where there was a postaxial autopod reduction defect coupled with a preaxial zeugopod reduction defect. Ro15‐4513 administered alone (50 mg/kg × 2) was neither embryolethal nor teratogenic in C57BL/6 mice. To attempt to reverse the teratogenic effect of ethanol, dams that were injected 5 min before each ethanol administration with Ro15‐4513 (0.5, 1, 2.5, 5, 10 mg/kg twice) showed no significant change in frequency of forelimb ectrodactyly compared to embryos treated with ethanol alone. However, resorptions increased significantly to 77% and 62% with the 5 and 10 mg/kg doses of Ro15‐4513. Thus there appears to be an embryolethal interaction of Ro15‐4513 with ethanol. Nevertheless, since Ro15‐4513 did not reverse the teratogenic effect induced by ethanol, these results do not support the hypothesis that the teratogenic mechanism of ethanol is mediated through a putative embryonic GABA receptor.
Fetal laser surgery in genetic Polydactyly mice
Authors: Naruse Ichiro , Kameyama Yoshiro
Published: June 2005

The first digital ray of the hindlimb plate in Slc:ICR mouse fetus was irradiated with 2 watts argon laser beam for 0.3 sec after releasing from the abdominal cavity and envelop of uterine myometrium on day 13 of gestation, and then the fetuses were allowed to develop in the abdominal cavity contacting with the uterus via the placenta exo utero until term. ICR mouse fetuses which received fetal laser surgery lost their first digits completely, resulting in 4‐digit hindfoot on day 18 of gestation. The homozygous Polydactyly Nagoya (Pdn/Pdn) mice exhibit 1–3 extra digits both in the fore‐ and hindlimbs preaxially. The extra digital rays in the left hindlimbs of Pdn/Pdn fetuses were irradiated with 2 watts argon laser beam for 0.3 sec on day 13 of gestation exo utero. The left hindlimbs of the Pdn/Pdn fetuses which received fetal laser surgery lost their preaxial extra digits on day 18 of gestation, resulting in 5 digits, though their 1st digit was triphalangia. The combination of a laser instrument with the fetoscope and/or ultrasound scanner may promote the fetal surgery of congenital anomalies in humans.
Central nervous system lesions in the wistar rat fetus following direct fetal injections of cadmium
Authors: White Tacey E. K. , Baggs Raymond B. , Miller Richard K.
Published: June 2005

During embryogenesis, maternal administration of cadmium (Cd) produces teratogenic effects, including hydrocephalus (HC), whereas later in gestation (during the fetal period), such effects have not been reported. Since there is little placental transfer of Cd late in gestation, such differences in response could be due to a lower Cd concentration in the fetus compared with the embryo after maternal Cd exposure, or could be due to a decreased sensitivity of the fetal central nervous system (CNS) to Cd. To test the susceptibility of the late gestational CNS to Cd, day 19 (sperm plug = day 0) rat fetuses were directly injected i.p. with CdCl2 (165, 100, 50 nmoles/fetus in 5 μl saline). All fetuses in one horn were treated with Cd, while fetuses in the other horn were treated with saline. Fetuses were collected on day 21, grossly examined, weighed, fixed in Bouin's fixative, and later razor sectioned. Cd did not affect fetal viability or body weight. However, Cd caused a dose‐dependent increase in hydrocephalus, with the total number of fetuses showing moderate to severe HC being 0/45, 0/11, 6/10, and 18/20 for controls, low, medium, and high doses, respectively. Mild HC was noted in one control and two low Cd fetuses. Brain necrosis was correlated with hydrocephalus, being observed in 0/45, 0/11, 5/10, and 16/20 fetuses, respectively. In medium‐dose fetuses without HC or brain necrosis, extravasation of erythrocytes was noted histologically within the cortical parenchyma, suggesting that hemorrhaging may lead to brain necrosis and hydrocephalus in Cd‐exposed fetuses. Thus, the fetal CNS is susceptible to the toxic effects of Cd.
Teratogenicity of etretinate during early pregnancy in the rat and its correlation with maternal plasma concentrations of the drug
Authors: Agnish Narsingh D. , Vane Floie M. , Rusin Gregory , DiNardo Barbara , Dashman Thedore
Published: June 2005

Sprague‐Dawley female rats were treated with a single oral dose of 0 (vehicle), 10, or 25 mg/kg of etretinate (ET), an aromatic retinoid, on gestation day 6, 7, or 8. While treatment on day 8 with both dosages of ET was highly teratogenic, no evidence of embryotoxicity, considered to be treatment related, was observed when the same doses were administered on day 6 or 7. We concluded that the rat embryo is not susceptible to teratogenic effects of ET on gestation day 6 or 7 and that day 8 is the earliest susceptible period for ET teratogenesis. This may well be true of retinoids as a class since we have observed similar results for all‐trans‐ and 13‐cis‐retinoic acids (unpublished findings). In another study, mated rats were treated with a single oral dose of ET on day 8. No evidence of embryotoxicity was observed at dosages of 1, 3, and 6 mg/kg; in contrast, treatment with 10, 15, or 25 mg/kg of ET resulted in an increasingly greater number of malformed fetuses and resorptions.

Plasma concentrations of ET and three metabolites [acitretin (AC), 13‐cis‐etretinate (13‐cis‐ET), and 13‐cis‐acitretin (13‐cis‐AC)] were determined in mated rats given a single oral non‐teratogenic (3 or 6 mg/kg) or teratogenic (10 or 25 mg/kg) dose of ET on gestation day 8. The AUC0→24hr values of ET and AC, the major metabolite and suspected proximal teratogen, were roughly proportional to the administered dose. The data suggest that a teratogenic response would not be expected in rats after a single dose on gestation day 8 unless the plasma concentrations of ET or AC exceeded 400 and 600 ng/ml, respectively. Plasma concentrations of ET and metabolites were also determined after 3 weeks of multiple dosing of 5 or 10 mg/kg of ET to nonpregnant rats. The AUC value of ET was twofold higher after the high‐dose regimen than after the low‐dose regimen, while the AUC values of the three metabolites were only 1.2 to 1.5 times higher. Multiple dosing resulted in accumulation (2–3–fold) of ET, 13‐cis‐ET, and 13‐cis‐AC, while no accumulation of AC was observed.