bluuebunny/crossref_metadata_2025 huggingface dataset:
HMG‐CoA reductase mRNA in the post‐implantation rat embryo studied by in situ hybridization
Authors: Brewer Linda M. , Sheardown Steve A. , Brown Nigel A.
Published: June 2005

3‐Hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase (EC 1.1.1.34) is the rate limiting step in the mevalonate pathway that produces isoprenoids and cholesterol. Inhibitors of HMG‐CoA reductase are teratogenic in vivo and induce neural tube defects in rat embryo culture, effects which appear unrelated to cholesterol deficiency. This study is the first to localize HMG‐CoA reductase mRNA by in situ hybridization (ISH). Expression of reductase mRNA was examined in post‐implantation rat embryos, and for control purposes in rat liver and UT‐1 cells, using a digoxigenin‐11 (dig‐11) labelled cRNA probe. Eighteen‐day fetal liver showed heavy but patchy hybridization, and adult rat liver showed strong hybridization only on some periportal hepatocytes, which was absent in livers of fasted animals. UT‐1 cells stimulated to overexpress HMG‐CoA reductase mRNA were strongly positive with the same probe. Control hybridizations with sense strand RNA probe, or with cRNA probe on pre‐RNased tissue were negative. Strong hybridization signal for HMG‐CoA reductase mRNA was observed in all tissues of the post‐implantation rat embryo, from egg cylinder to 30 somite stages (7 to 12 days). Heavy signal was noted in primitive ectoderm and neural tube. The wide embryonic and extraembryonic distribution and abundance of HMG‐CoA reductase mRNA may reflect developmental requirements for products of the mevalonate pathway, e.g., isoprenoids for post‐translational farnesylation of p21ras. © 1993 Wiley‐Liss, Inc.
Skeletal development following heat exposure in the rat
Authors: Kimmel C. A. , Cuff J. M. , Kimmel G. L. , Heredia D. J. , Tudor N. , Silverman P. M. , Chen J.
Published: June 2005

The effects of gestation day (GD) 10 heat exposure in the rat were studied to determine the temperature‐response relationship for the induction of skeletal and other defects. Conscious pregnant rats (Experiment 1) were exposed to various temperatures in a warm air chamber. Body temperature was measured using a rectal probe, and these measurements were confirmed as representing core body temperature in separate animals using telemetric procedures. Those animals whose core body temperature was raised to 41–41.9°C had over 90% malformed pups (examined at postnatal day (PND) 3), and a 25% reduction in the percent of live pups per litter. Animals whose temperature was raised to 39.2–40.9°C had a low incidence of pups with similar types of malformations. The primary types of malformations were of the axial skeleton, consisting of fusions and other abnormalities of the ribs and vertebral elements, and a decrease in the total number of ribs and centra. The acute maternal effects of these temperature increases were signs of heat exhaustion during and 1–2 hr after exposure, but there were no permanent changes in weight gain or other signs. When temperatures were raised to ⩾42°C, all maternal animals died. In a second study (Experiment 2), pregnant rats (from a different supplier) were anesthetized to determine the effect of reducing maternal stress and were exposed to heat as in Experiment 1. Those animals whose core body temperature was raised to 42–42.5°C for 5 min had pups with similar responses to those in Experiment 1 at 41–41.9°C, although the reduction in litter size was not as great. Animals whose temperature was raised to 41°C had a much lower incidence of pups with similar defects, and animals whose temperature was raised to 43°C did not survive. A more detailed analysis of the skeletal defects in Experiment 2 showed rib and vertebral malformations that appear to be related to the stage of somite development at the time of exposure. © 1993 Wiley‐Liss, Inc.
Acardius acephalus after induced ovulation: A case report
Authors: Haring D. A. J. P. , Cornel M. C. , van der Linden J. C. , van Vugt J. M. G. , Kwee M. L.
Published: June 2005

An excess of structural defects occurs in monozygotic twins compared to dizygotic twins or singletons. Among these defects the acardius acephalus or chorangiopagus parasiticus is one of the most rare and severe and a possible cause of pathology to the other twin. Ovulation induction by clomiphene causes an increased frequency of multiple gestation and possibly of monozygotic multiple pregnancy. In the present report, we describe a prenatally diagnosed and autopsied case of acardius acephalus from a pregnancy established after ovulation induction by clomiphene. Approximately 1.4% of pregnancies are accomplished after use of ovulation inducing medication in the Netherlands. A possible etiological role of clomiphene justifies close monitoring of future cases. © 1993 Wiley‐Liss, Inc.
Effects of 5‐Fluorouracil on embryonic rat palate in vitro: Fusion in the absence of proliferation
Authors: Abbott B. D. , Lau C. , Buckalew A. R. , Logsdon T. R. , Setzer W. , Zucker R. M. , Elstein K. H. , Kavlock R. J.
Published: June 2005

5‐Fluorouracil (5‐FU) inhibits the enzyme thymidylate synthetase (TS) which results in inhibition of DNA synthesis. 5‐FU is teratogenic in many species, inducing cleft palate, limb, and tail defects. In the present study, gestation day (GD) 14 embryonic rat craniofacial explants were exposed to 5‐FU in organ culture with increasing concentrations and durations of exposure. Palates exposed to 5‐FU were morphologically abnormal and craniofacial shape, size, and palatal fusion pattern were affected with the severity of effects dependent on concentration and duration of exposure. Cleft palate was induced in vitro as opposing palates overlapped in a narrowed oral cavity. Palates exposed to higher levels of 5‐FU were growth inhibited, but fused even though proliferation ceased and few cells were available to participate in elevation and fusion. This was demonstrated as a biphasic concentration‐response profile for palatal fusion in which 0.05 to 0.15 μg 5‐FU/ml produced decreasing rates of palatal fusion, while exposure to 0.15 to 3.0 μg/ml resulted in progressively increasing rates of fusion. The effects of 5‐FU were detected biochemically as a reduction in TS activity which was concentration and time dependent during the first 12 hours, with a return to control levels by 24 hours. During the first day, 5‐FU did not alter protein levels, but DNA levels significantly decreased at the high concentration, 2.0 μg/ml. After 5 days in culture, both DNA and protein decreased with increasing 5‐FU concentration and duration of exposure. Also by the end of the culture period, 3H‐TdR incorporation had decreased in a concentration dependent manner. It is concluded that progressive inhibition of proliferation and growth in organ culture results in two different morphological outcomes: cleft palate resulting from a narrowed oral cavity and increased incidence of anterior palatal fusion under conditions of strong growth reduction. This study demonstrates that elevation and fusion can occur in the absence of growth and proliferation. Based on these observations, severe inhibition of growth or proliferation would not necessarily be sufficient to induce cleft palate. © 1993 Wiley‐Liss, Inc.

This article is a US government work and, as such, is in the public domain in the United States of America.
Risk factors for coarctation of the aorta
Authors: Tikkanen Jorma , Heinonen Olli P.
Published: June 2005

To test the hypothesis that environmental factors during early pregnancy may cause coarctation of the aorta (CoA), 50 cases of CoA and 756 controls were studied. The cases represented all verified CoAs in Finland during 1982–1983 and controls were randomly selected from all babies born during the same period. Both case and control mothers were interviewed by midwives approximately 3 months after delivery. In these data 18 patients had pure CoA only and the remaining 32 at least one other cardiac anomaly. Three CoA patients had a chromosomal anomaly. The relatives of CoA babies had more congenital anomalies than those of the control babies. Maternal overall exposure to chemicals at work was slightly more prevalent among the CoA group (32.0%) than the control group (26.2%). Maternal exposure to mineral oil products at work during early pregnancy was more common among CoA cases (8.0%) than controls (1.4%) [odds ratio (OR) = 5.9, 95% confidence interval (CI95) = 1.8–19.2]. The risk of CoA was also associated with previous miscarriages (OR = 2.3, CI95 = 1.2–4.4) and twin birth (OR = 16.3, CI95 = 4.0–67) of the child. The risk of CoA was not associated with seasonal variation, maternal smoking, alcohol consumption, or use of deodorants. It is concluded that genetic factors explain only a small fraction of the causes of CoA and that many common environmental exposures during early pregnancy are unlikely to be real risk factors for CoA. However, the power of this study was weak for testing the teratogenicity of specific chemicals. © 1993 Wiley‐Liss, Inc.
Penetrance and expressivity of acetazolamide‐ectrodactyly provide a method to define a right‐left teratogenic gradient that differs between the C57BL/6J and WB/ReJ mouse strains
Authors: Biddle Fred G. , Mulholland Lynda R. , Eales Brenda A.
Published: June 2005

Penetrance or the frequency of embryos with any degree of forelimb ectrodactyly is the usual method to describe the forelimb ectrodactyly response of mouse embryos to acetazolamide. A digit score for number of small or absent digits for the separate right and left forelimb response to acetazolamide provides a measure of expressivity or the severity of response. We examine the relationship between expressivity and penetrance using right and left forelimb data from a previously reported dose‐response analysis of the C57BL/6J and WB/ReJ strains to acetazolamide. The data show that expressivity and penetrance are highly correlated for the separate right and left forelimbs for both strains. In C57BL/6J, the dose‐response analyses of both expressivity and penetrance of the separate right and left forelimbs demonstrate a teratogenic gradient, decreasing from right to left, that depends on the symmetrical ectrodactyly response of the right and left forelimbs. In WB/ReJ, the right forelimb is also more sensitive than the left, but the dose‐response analyses of both penetrance and expressivity show the two forelimbs are asymmetrical in their ectrodactyly response and that there is not a simple teratogenic gradient in this strain. In WB/ReJ, the left forelimb is resistant at even the highest non‐lethal doses. The high correlation between expressivity and penetrance for the separate forelimbs of both C57BL/6J and WB/ReJ suggests that this right‐left difference between the two strains may not be a property of the limbs themselves but may be an intrinsic genetic difference between the two types of embryos perhaps in the amount of teratogen to which the embryos are exposed. The right and left forelimbs of the embryo may simply provide a biological assay of this intrinsic embryonic difference. © 1993 Wiley‐Liss, Inc.
Report of national institute of child health and human development workshop on chorionic villus sampling and limb and other defects, October 20, 1992
Authors: de la Cruz Felix
Published: June 2005

A Workshop on Chorionic Villus Sampling (CVS) was convened by the National Institute of Child Health and Human Development (NICHD) and the American College of Obstetricians and Gynecologists at the National Institutes of Health on April 17, 1992, to discuss recent reports of an increased occurrence of malformations of the upper and lower limbs and oral structures among CVS‐exposed infants. We summarize here the defects described in the CVS‐exposed infants, the retrospective reassessments of published studies of the safety of CVS, the prevalence of limb deficiencies in infants not exposed to CVS, the status of the 7–9 week (conception or fertilization age) embryo, and the relevant human and animal experimental models of how CVS might be harmful to the embryo or fetus. © 1993 Wiley‐Liss, Inc.
A case of a closed partial cloacal septation defect with a patent urachus
Authors: Stoler Joan M. , Doody Daniel P. , Holmes Lewis B.
Published: June 2005

A boy with a closed partial cloacal septation defect with a patent urachus is reported. He had an intact abdominal wall, a patent urachus, a colovesical fistula, intact genitalia and urethra, imperforate anus, and a lipomyelocystocoele. Patients with similar constellation of findings have been reported as cloacal exstrophy variants. What distinguishes this case from the other reported variants is the intact abdominal wall with the patent urachus, the small and normally formed phallus and urethra, and the presence of a lipomyelocystocoele.

We discuss the possible embryologic mechanism responsible for this boy's findings and possible relationship with the cloacal exstrophy spectrum. We also discuss new terminology for the epispadias‐exstrophy spectrum. Furthermore this case reminds us that there is considerable variability within the epispadiasexstrophy spectrum. © 1993 Wiley‐Liss, Inc.
Effects of sodium bicarbonate and ammonium chloride on the incidence of furosemide‐induced fetal skeletal anomaly, wavy rib, in rats
Authors: Nakatsuka Toshio , Fujikake Noboru , Hasebe Miki , Ikeda Hisataka
Published: June 2005

Furosemide produces fetal wavy ribs when administered to pregnant rats during late gestation. The compound is also known to produce metabolic alkalosis in laboratory animals and man. In order to evaluate the effect of furosemide on maternal blood pH, Crj:CD(SD) female rats received an oral administration of 150 or 200 mg/kg of furosemide by gavage on day 16 of gestation and were bled at 4 hr post‐dose. Compared to an average pH of 7.39 in control females, there was a significant elevation in blood pH in these furosemide‐treated females (average pH of 7.44 to 7.48). When 2% sodium bicarbonate was provided in the drinking water for females treated with 150 mg/kg of furosemide, there was a further rise in maternal blood pH (7.52) compared to females treated with furosemide alone. Associated with this elevation in maternal blood pH was a marked increase in the incidence of fetal wavy ribs (87.6% compared to 27.6%). When females treated with 200 mg/kg of furosemide were provided with 0.5% ammonium chloride, furosemide‐induced maternal alkalosis was corrected (pH decreased to 7.35) and there was a reduction in the incidence of fetal wavy ribs (7.0% compared to 37.2%). In addition, maternal blood pH among individual females was positively correlated with the incidence of fetal wavy ribs (r = 0.714). These results suggest that maternal metabolic alkalosis is involved in the pathogenesis of furosemide‐induced wavy ribs. © 1993 Wiley‐Liss, Inc.
Teratogenicity and developmental toxicity of carbon monoxide in protein‐deficient mice
Authors: Singh Jarnail , Aggison Lee , Moore‐Cheatum Linda
Published: June 2005

Experiments were carried out to determine the teratogenicity and developmental toxicity of carbon monoxide (CO) in mice fed protein‐deficient diets. Pregnant CD‐1 mice were fed 27 (control), 16, 8, or 4% protein diets throughout gestation and each group was exposed to 0 (control), 65, 125, 250, or 500 ppm of CO from gestation days 8–18. The CO exposure was continuous except for daily watering, feeding or cage changing. The animals were killed on gestation day 18. Pregnancy status of the dams was examined. Fetuses were examined for gross and skeletal malformations. The percentages of dead or resorbed fetuses and of grossly malformed fetuses per litter were related to the CO exposure levels and inversely related to the dietary protein levels. All levels of CO and 8 or 4% protein diets significantly decreased the fetal weight of normal fetuses. The most commonly seen gross malformations were brachygnathia accompanied by protruding tongue, microstomia, microcephaly, open mouth, or open eyes. Most of the grossly malformed fetuses also had dry, bleached and wrinkled skin. An increased incidence of skull (interparietal or supraoccipital), and jaw (mandible or premaxilla) malformation; wavy ribs and scoliosis of spine; and limb unossifications were observed in the litters of dams fed protein‐deficient diet and all levels of CO exposure. Malformed litters in each protein diet were related to CO exposure levels. The data suggest that CO is teratogenic under protein‐deficient conditions. Protein deficiency had additive effect on CO teratogenicity and synergistic effect on fetal mortality. Special groups at risk may include cigarette or marijuana smokers and malnourished or undernourished populations. © 1993 Wiley‐Liss, Inc.
Evidence that spontaneous situs inversus in cultured neural plate staged rat embryos is additive with and not mediated through adrenergic mechanisms
Authors: Flynn Thomas J. , Gibson Regina R. , Johannessen Jan N.
Published: June 2005

Approximately 50% of untreated presomite rat embryos in culture have demonstrated inversions of cardiac looping (laeval instead of dextral) or tail flexure (left‐sided instead of right‐sided), or both. This spontaneous situs inversus (SI) was not accompanied by growth inhibition or any other observable defects. The incidence of SI was directly related to the stage at dissection, and all heart defects and most flexure defects were eliminated by delaying explantation to the early somite stage. The incidence of SI was not lowered significantly either by removal of endogenous catecholamines from the culture serum by dialysis or by inclusion of α‐ or β‐adrenergic antagonists in the medium. However, the α‐adrenergic agonist L‐phenylephrine (50 μg/ml) increased the incidence of SI to 73%. These findings appear to rule out adrenergic mechanisms as a cause of spontaneous SI in cultured, neural plate‐staged rat embryos but suggest a mechanism, yet unknown, that is additive with SI induced by α‐adrenergic agonists. The low incidence of non‐SI‐related defects suggests that the high incidence of SI is not an artifact of suboptimal culture conditions. The virtual absence of SI in embryos cultured in bovine serum; a medium in which overall embryonic growth and development were retarded, provides further evidence against nonspecific artifacts. © 1993 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
Effects of cadmium on reproduction, an epizootologic study
Authors: Kreis I. A. , de Does M. , Hoekstra J. A. , de Lezenne Coulander C. , Peters P. W. J. , Wentink G. H.
Published: June 2005

The Dutch part of Kempenland has been exposed to cadmium pollution since the last century. Experimental data suggest effects by cadmium on reproduction such as diminished fertility, decreased foetal growth, and specific malformations. Use was made of a historical cohort of dairy cows, ascertained from a surveillance program conducted by the regional Veterinary Health Service between 1976 and 1986. Ten dairy farms in the cadmium region were matched by size with 40 dairy farms from a reference area. Logistic models were used to calculate Odds (OR) and Rate Ratios (RR) and their 95% confidence interval. In total 4,039 exposed and 15,552 reference gestations were compared. The reasons for the slaughter of 574 exposed and of 2,824 reference cows were ascertained. A lower twinning rate [OR = 0.63 (0.47–0.84)] was found and more birth complications, for both calves [OR = 1.50 (1.25–1.80)] and cows [OR = 1.49 (1.24–1.79)]. More inseminations [OR = 1.20 (1.01–1.43)] were needed for conception in the exposed area. Deaths among twins [OR = 1.66 (0.90–3.07)] were not significantly higher. Perinatal death, premature death, age at, or reasons for, slaughter were not consistently different. These results are consistent with those of other observational and experimental studies. Extrapolation from these large domestic animals to humans is problematic, as is the more frequent extrapolation from rodents to humans. It can be concluded that longterm exposure to low levels of cadmium is associated with impaired reproduction in dairy COWS. © 1993 Wiley‐Liss, Inc.
Chloroquine embryotoxicity in the postimplantation rat conceptus in vitro
Authors: Ambroso Jeffrey L. , Harris Craig
Published: June 2005

The embryotoxicity of the antimalarial drug chloroquine (CQ) was evaluated in vitro using the rat whole embryo culture system. CQ was found to be embryotoxic and dysmorphogenic when added directly to the culture media containing gestational day (GD) 10 rat conceptuses. Twenty‐six‐hr exposure to CQ elicited dose‐related decreases in embryonic crown‐rump length, protein and DNA contents and increases in the incidence of morphologically abnormal embryos. At 30 μM CQ, embryonic protein content was decreased to 67% and DNA content to 58% of control while the incidence of morphological abnormalities rose to 100%. Abnormal axial rotation, microophthalmia, and selective cephalic hypoplasia were the most common developmental abnormalities observed. Visceral yolk sac (VYS) vasculature and blood pigmentation were also decreased in a dose‐dependent manner, as was VYS DNA content (80% of control at 30 μM). VYS protein content, however, showed an alternate pattern of response, decreasing to 87% of control at 10 μM CQ but increasing to 125% of control at 30 μM. Histologic evaluation revealed that the cytoplasm of the VYS endoderm epithelium was distended due to vacuolization produced by CQ exposure. In the embryo proper, CQ inhibited cranial neural tube development and altered the morphology of cranial neural crest cells. These observations document the in vitro embryotoxicity of CQ and suggest altered VYS histiotrophic nutrition as well as direct embryonic effects as possible mechanisms of CQ embryotoxicity. © 1993 Wiley‐Liss, Inc.
Changes in dopamine, serotonin and their metabolites in discrete brain areas of rat offspring after in utero exposure to cocaine or related drugs
Authors: Henderson Mark G. , McMillen Brian A.
Published: June 2005

The concentrations of dopamine (DA), serotonin (5HT) and their metabolites were quantified in 5 brain areas of rats exposed to saline, cocaine (15 mg/kg b.i.d.), amitriptyline (10 mg/kg), or amfonelic acid (AFA, 1.5 mg/kg) throughout gestation. Male pups from 3 similarly treated dams were fostered to 2 surrogate dams. The process of breeding and rearing was repeated 4 times with new dams to build the groups to 4–12, since only one pup per litter was used for any one measurement. AFA was used to mimic the dopamine (DA) uptake blockade and stimulant properties of cocaine and amitriptyline was used to mimic the other pharmacological effects of cocaine. At postnatal days (PND)30, 60, and 180, one pup per litter was removed for HPLC analysis of monoamines. A second pup received 0.3 mg/kg haloperidol, catalepsy assessed after 1 hr, and the brain used for analysis. The cataleptic response to haloperidol was unaffected by any prenatal treatment. The striatum from PND 30 cocaine rats had decreased levels of DA without a decrease in DA metabolites. At PND 60 in cocaine exposed rats, DA and DOPAC concentrations were increased, and 5HT levels were decreased in the striatum. The amitriptyline‐exposed group exhibited decreased 5HT and 5‐HIAA levels in the striatum. The hypothalamus of the cocaine group had lower levels of 5‐HIAA, and other brain areas had a trend for lower levels of 5HT and 5‐HIAA. At PND 180, DOPAC was increased in the striatum and prefrontal cortex of the cocaine group. Haloperidol‐induced altered monoamine metabolism was unaffected by any prenatal treatment at any age. These data suggest that age‐related changes in the DA and 5HT neurotransmission systems occur in rats exposed prenatally to cocaine. However, the ability of the dopaminergic system to respond to a challenge by a DA receptor blocker is unaltered by these in utero treatments. © 1993 Wiley‐Liss, Inc.
Changes in the reproductive system following acute prenatal exposure to ethanol or methylazoxymethanol in the rat: I. Effects on immunoreactive LHRH cell number
Authors: Gavin Claire E. , Kates Barbara , Hoffman Gloria E. , Rodier Patricia M.
Published: June 2005

It has long been recognized that ethanol (EtOH) interferes with the hypo‐thalamo‐pituitary‐gonad axis in adults of many species, and recent studies have provided evidence for similar effects after prenatal EtOH exposure. Since EtOH is capable of injuring dividing cells, we investigated the possibility that a single acute in utero EtOH exposure during the period of LHRH neuron formation might change the number of immunoreactive LHRH cells in the hypothalamus. Final LHRH cell division in Long‐Evans rats was determined by [3H]thymidine autoradiography to take place over a short period between gestation days 12 and 13. Subsequently, pregnant rats were treated acutely with either EtOH or methyla‐zoxymethanol (MAM), a known neuroteratogen, and the numbers of immunoreactive LHRH cells were counted. On gestation day 22, LHRH‐positive cell numbers were significantly fewer than control numbers in both EtOH‐ and MAM‐exposed offspring. On postnatal day 60, cell numbers in EtOH‐exposed offspring did not differ from control numbers, whereas cells in MAM‐exposed offspring remained significantly reduced. In controls, there were 40% fewer LHRH‐positive cells on postnatal day 4 than in late gestation or at maturity. We conclude that 1) acute exposure to a high dose of EtOH at a critical time in early gestation can alter the expression of LHRH in late gestation; 2) exposure to MAM in the same period alters LHRH expression before birth and in the adult; and 3) in the early postnatal period, LHRH expression decreases profoundly. © 1994 Wiley‐Liss, Inc.
Interactions in developmental toxicology: A literature review and terminology proposal
Authors: Nelson B. K.
Published: June 2005

Developmental toxicologists have investigated the interactive effects from concurrent exposures to a variety of chemical and physical agents, including therapeutic drugs, industrial agents, and some biological organisms or their toxins. Of approximately 160 reports of concurrent exposures reviewed in this paper, about one third report no interactive effects (including additive effects‐‐usually referring to response‐‐as opposed to dose‐additivity); another one third report antagonistic effects, and the final third report potentiative or synergistic effects. The quality of the studies is highly variable. Frequently, only small numbers of animals were included, and very few dose levels were evaluated. Maternal toxicity was rarely discussed. Time‐effect relationships were examined infrequently. In addition, these studies are also inconsistent in the use of terms to describe interactive effects, and more than 90% of the terms were not in harmony with currently accepted definitions in toxicology. Because interaction studies will continue to be important in the future, this paper proposes uniform usage of terms for additivity and interactions in developmental toxicology: additivity (the combined effect of two or more developmental toxicants approximates the sum of the effects of the agents administered separately); antagonism (the combined effect of two or more agents, one or more of which are present at doses that would be developmentally toxic if given individually, is significantly less than the sum of the effects of the agents administered separately); potentiation (the increased effect of a developmental toxicant by concurrent action of another agent at a dose that is not developmentally toxic); synergism (the combined effect of two or more developmental toxicants is significantly greater than the sum of the effects of each agent administered alone); and, interaction if more precise terminology does not apply. © 1994 Wiley‐Liss, Inc.

This article is a US Government work and, as such, is in the public domain in the United States of America.
A physiologically based pharmacokinetic computer model for human pregnancy
Authors: Luecke Richard H. , Wosilait Walter D. , Pearce Bruce A. , Young John F.
Published: June 2005

A physiologically based pharmacokinetic (PBPK) model for human pregnancy must incorporate many factors that are not usually encountered in PBPK models of mature animals. Models for pregnancy must include the large changes that take place in the mother, the placenta and the embryo/fetus over the period of pregnancy. The embryo/fetal weight change was modeled using the Gompertz equation for growth which gave a good fit to extensive pooled weight data of the human embryo/fetus from 25 to 300 days of gestation. This equation is based on a growth rate that is proportional to the total weight of the organism with the proportionality factor decreasing exponentially with time. Allometric equations, which are widely used to relate organ weights, blood flow rates and other attributes of mature animals to total weight, were adapted to correlate fetal organ weights with total fetal weight. Allometric relationships were also developed for plasma flow rates and other organ‐related parameters. The computer model, written in FORTRAN 77, included 27 compartments for the mother and 16 for the fetus; it also accommodates two substances allowing representation of a parent compound and a metabolite (or a second drug or environmental substance). Although this model is large, the inherent sparsity in the equations allow it to be solved numerically in a reasonable time on currently available, reasonably priced desktop computers. A nonlinear regression routine is included to fit key model parameters to experimental data. Concentrations of chemicals administered and measured in the mother may be simulated in both maternal and fetal organs at any day(s) between 25 days and 300 days of gestation. Allometric relationships are also utilized to adopt this human model for use with data obtained from animal experiments. © 1994 Wiley‐Liss, Inc.

This article is US Government work and, as such, is in the public domain in the United States of America.
Ethyl alcohol reduces cardiac output, stroke volume, and end diastolic volume in the embryonic chick
Authors: Bruyere Harold J. , Stith Charles E.
Published: June 2005

It has been established that ethanol causes both human congenital cardiac malformations and structural intracardiac abnormalities in the embryonic chick. In view of a theory that reduced embryonic tissue hemodynamics are associated with the development of malformations, we attempted to determine whether or not a) ethanol altered cardiac blood flow and b) altered hemodynamics were a function of ethanol dose in the chick embryo. Cardiac function in Hamburger‐Hamilton stage 19 chick embryos was recorded on videotape before and up to 10 hours after exposure to graded doses of ethanol. Parameters of cardiac function, including cardiac output, were determined from videotaped images by means of computer assistance. Cardiac output decreased in a linear fashion with dose for up to 3 hours after exposure to ethanol. The maximum relative percent decrease in cardiac output was directly related to the dose of ethanol administered. Furthermore, the time required after ethanol treatment for mean cardiac output to return to pretreatment and control values was also dose‐dependent‐‐lower doses of ethanol required less time for mean cardiac output to return to pretreatment and control values. Although relatively high doses of ethanol depress cardiac rate, we attribute the significant decrease in cardiac output primarily to parallel dose‐dependent decreases in both stroke volume and end diastolic volume. Our data are consistent with the hypothesis that reduced embryonic cardiac blood flow during cardiogenesis is associated with the development of ethanol‐induced intracardiac defects in chick embryos. © 1994 Wiley‐Liss, Inc.
Effects of methanol on embryonic mouse palate in serum‐free organ culture
Authors: Abbott B. D. , Logsdon T. R. , Wilke T. S.
Published: June 2005

Methanol has widespread applications in industry and manufacturing and is under consideration as an alternative automotive fuel. Human exposure to methanol would be expected to increase if applications expand in coming years. Methanol has been shown to be a reproductive and developmental toxicant in the rodent, producing cleft palate in the CD‐1 mouse. Developmental toxicity has also been demonstrated in vitro for rat and mouse embryos in whole embryo culture. The present study examines the developmental toxicity of methanol in the palate using a serum‐free organ culture model. Gestation day 12 CD‐1 mouse embryos were dissected and mid‐craniofacial tissues were cultured in BGJ medium at 37°C for 4 days with medium changes at 24 hr intervals. Cultures were exposed to methanol from 0–20 mg/ml for 6 hr, 12 hr, 1 or 4 days. Some cultures were exposed to ethanol for 4 days at doses ranging from 0–15 mg/ml. All cultures were gassed with a 50% O2, 5% CO2, and 45% N2 upon addition of fresh medium and prior to the addition of alcohol. Following organ culture the craniofacial explants were examined for effects on morphology, fusion, proliferation, and growth. Incidence and completeness of palatal fusion decreased with increasing exposure. Depending on the concentration and duration of methanol exposure, the medial epithelium either degenerated completely or remained intact in unfused palates and either condition would interfere with fusion. Cellular proliferation appeared to be a specific and sensitive target for methanol as craniofacial tissues responded to methanol with reduction in total DNA content at an exposure that did not affect total protein. However, both DNA and protein decreased with increasing exposure to methanol. Incorporation of thymidine decreased significantly after 4 day exposure and autoradiography of 3H‐thymidine (TdR) demonstrated exposure‐dependent reduction in proliferation of palatal mesenchymal cells. Ethanol decreased fusion score, total protein, and DNA, but 3H‐TdR/DNA was not significantly changed. In general the ethanol was more potent than methanol for inhibition of protein and DNA synthesis and palatal fusion. This study demonstrated that methanol can selectively affect specific sensitive cell populations and has effects on proliferation and cell fate. © 1994 Wiley‐Liss, Inc.

This article is US Government work and, as such, is in the public domain in the United States of America.
Cocaine‐induced embryonic cardiovascular disruption in mice
Authors: Fisher J. Edward , Potturi Raju B. , Collins Michael , Resnick Elisabeth , Zimmerman Ernest F.
Published: June 2005

The purpose of this study was to determine whether vascular disruption is a feature of cocaine‐induced teratogenicity in early murine organogenesis. The embryotoxic effects of cocaine were assessed: (1) in vivo, (2) in embryos cultured in the presence of cocaine (in vitro), and (3) after cocaine was administered in vivo and the embryos subsequently cultured in the absence of cocaine (in vivo‐in vitro). When cocaine (78 mg/kg) was administered in vivo on day 8 and embryos were assessed on day 10, significant vascular perturbations, in the form of vasodilation and hemorrhage, as well as neural defects, were observed. In the in vitro system, day 8 embryos were cultured for 48 hr in the presence of 0, 10, 20, 33, and 66 μ/ml cocaine. At 10 and 20 μ/ml, vascular perturbation was not seen, while at higher cocaine concentrations, development of the yolk sac vasculature was inhibited. Hemorrhage was not a feature of in vitro cocaine embryotoxicity. However, significantly increased incidences of neural defects were seen at concentrations of 20 μ/ml or greater. Finally, in the in vivo‐in vitro system, 78 mg/kg cocaine was administered on day 8 in vivo and embryos were dissected after 15 min and cultured for 48 hr. Marked cardiovascular perturbation, as well as neural defects, were produced using this protocol. With cocaine treatment, only 26.6% of embryos had a functioning heartbeat and yolk sac circulation, compared to 85.6% of controls. This cardiovascular disruption was associated with pooling of blood in the embryo, with 59.9% of embryos exhibiting marked vasodilation and hemorrhage compared to 12.5% in controls. Additional manifestations of cardiovascular perturbation were edema and blisters observed in cocaine‐treated embryos. Neural tube defects, including open neural tube (8.3%) and microcephaly/hypoplastic prosencephalon (30.0%), were also significantly increased in cocaine‐treated embryos. The cardiovascular and neural effects produced by cocaine were dose‐dependent (40, 20 mg/kg). Thus, administration of cocaine in the in vivo or in vivo‐in vitro systems produced marked cardiovascular effects, while in vitro treatment did not. These results suggest that cocaine may elicit cardiovascular toxicity through a maternally mediated mechanism. © 1994 Wiley‐Liss, Inc.
Developmental phase alters dosimetry‐teratogenicity relationship for 2‐methoxyethanol in CD‐1 Mice
Authors: Terry Ketti K. , Elswick Barbara A. , Stedman Donald B. , Welsch Frank
Published: June 2005

The industrial solvent 2‐methoxyethanol (2‐ME) elicits phase‐specific terata in mice through its primary metabolite and proximate toxicant, 2‐methoxyacetic acid (2‐MAA). Recent pharmacokinetic studies indicate that the incidence and severity of digit malformations induced in CD‐1 mice by 2‐ME exposure on gestation day (gd) 11 (copulation plug = gd 0) correlate better with the total 2‐MAA exposure over time (= area under the curve; AUC) than with its peak concentrations (Cmax) in maternal plasma, embryo and extraembryonic fluid. In this study, the phase specificity of exencephaly induction by 2‐ME was investigated to ascertain whether the 2‐ME/2‐MAA dosimetry‐teratogenicity relationship remains consistent throughout organogenesis. Following a single intravenous (iv) bolus dose of 250 mg 2‐ME/kg given to pregnant mice, exposure on gd 8 was decidedly the gestation day that best balanced low embryo lethality and high malformation incidence as recorded in near‐term fetuses. Concentrations of 2‐MAA were measured during distribution and elimination in maternal plasma and conceptuses following iv bolus doses of 175, 250, and 325 mg 2‐ME/kg, as well as during and after termination of subcutaneous (sc) constant‐rate infusions (4, 6, and 8 hr; 8 μl/hr) of 277,392, and 606 mg 2‐ME/kg total doses. For all administration regimens, exencephaly incidence rates were determined in fetuses on gd 18. Similar plasma 2‐MAA Cmax values (∼5 mmol/l) and fetal malformation frequencies (∼12%) were induced by sc infusion of 392 mg 2‐ME/kg or a bolus dose of 250 mg 2‐ME/kg. However, the AUC produced by infusion was significantly larger than that following the iv bolus dose (38 vs. 26 mmol‐hr/l, respectively). In both maternal plasma and conceptuses, the correlation coefficients between Cmax and exencephaly rates, as well as developmental toxicity, were higher than they were for AUC and those end points. This outcome suggests that dosimetry‐teratogenicity determinants may be quite specific for a distinct developmental phase during which a particular organ differentiates and a specific chemical acts upon the embryo. © 1994 Wiley‐Liss, Inc.
On the use of affected controls to address recall bias in case‐control studies of birth defects
Authors: Khoury Muin J. , James Levy M. , Erickson J. David
Published: June 2005

Inferences regarding causes of birth defects in humans are often based on results of case‐control studies conducted after birth. To address bias in these studies caused by potential differential recall of past exposures between case and control mothers, many investigators have advocated the use of affected controls (babies with birth defects other than the one of interest). To evaluate whether the use of affected controls is warranted for a wide range of scenarios, we analyzed data from a population‐based case‐control study of birth defects in Atlanta, in which there were 4,918 babies with serious defects ascertained in the first year of life and 3,029 babies without defects. We compared the magnitude of the odds ratios for 10 specific defects–risk factor associations between normal and affected controls. These associations included demographic factors (e.g., advanced maternal age and Down syndrome), chronic maternal illnesses (e.g., diabetes and cardiac defects), chronic exposures (e.g., multivitamins and neural tube defects), and acute exposures (e.g., flu and neural tube defects). In all instances, the use of affected controls did not change etiologic inferences derived from using normal controls and there were only moderate changes in odds ratios. On the basis of theoretical considerations, we show that recall bias can lead to spurious inferences only under extreme conditions. We conclude that concerns about recall bias are overrated in birth defects studies and that the use of normal controls is acceptable unless evidence of substantial recall bias exists. © 1994 Wiley‐Liss, Inc.

The article is a US Government work and, as such, is in the public domain in the United States of America.
Trans‐2‐ene‐valproic acid is less behaviorally teratogenic than an equivalent dose of valproic acid in rats
Authors: Fisher J. Edward , Acuff‐Smith Karen D. , Schilling Mary A. , Nau Heinz , Vorhees Charles V.
Published: June 2005

Although animal experiments have shown the trans‐2‐ene metabolite (t‐2‐ene‐VPA) of valproic acid (VPA) to be pharmacologically equivalent to the parent compound in terms of anticonvulsant activity, it is considerably less teratogenic in studies which have examined prenatally exposed fetuses for morphological defects. This has made t‐2‐ene‐VPA an attractive potential antiepileptic agent. However, while neurobehavioral alterations have also been observed in rats prenatally exposed to VPA, even at doses below those which produce malformations, the developmental neurotoxicity of t‐2‐ene‐VPA had not previously been examined. The current study evaluated the long‐term behavioral effects of prenatal exposure to t‐2‐ene‐VPA. Pregnant CD rats were treated with 300 or 400 mg/kg t‐2‐ene‐VPA by gavage on days 7–18 of gestation, doses previously shown to produce no teratogenicity. A VPA group was administered 300 mg/kg for comparison. The pharmacokinetic profiles of the two compounds were similar. Behavioral findings in offspring prenatally exposed to VPA were consistent with previous findings, i.e., VPA offspring exhibited decreased locomotor activity, increased swimming maze errors, and reduced tactile startle responding compared to controls. In the 400 mg/kg t‐2‐ene‐VPA group, Cincinnati maze errors and auditory startle reactivity were increased, while no significant behavioral effects were detected in the 300 mg/kg t‐2‐ene group. These results indicate that the developmental neurotoxicity of t‐2‐ene‐VPA is lower than that of VPA but is still significant. © 1994 Wiley‐Liss, Inc.
Bendectin and birth defects: I. A meta‐analysis of the epidemiologic studies
Authors: McKeigue Paul M. , Lamm Steven H. , Linn Shai , Kutcher Jeffrey S.
Published: June 2005

“Bendectin”

Bendectin is the US trademark for a combination of doxylamine and dicyclomine used for the treatment of nausea and vomiting of pregnancy. Prior to 1977, it also contained pyridoxine. Analogous products were distributed in the United Kingdom under the trademark “Debendox” and in Germany under the trademark “Lenotan.”

(Doxylamine/Dicyclomine/Pyridoxine) was widely used for the treatment of nausea and vomiting of pregnancy until 1983, when production was discontinued in the face of lawsuits alleging that the drug caused congenital malformations. We have conducted a meta‐analysis of the 16 cohort and 11 case‐control studies that report birth defects from Bendectin‐exposed pregnancies. This meta‐analysis provides an estimate of the relative risk of malformation at birth in association with Bendectin exposure. The pooled estimate of the relative risk of any malformation at birth in association with exposure to Bendectin in the first trimester was 0. 95 (95% Cl 0. 88 to 1. 04). Separate analyses were undertaken for cardiac defects, central nervous system defects, neural tube defects, limb reductions, oral clefts, and genital tract malformations. In these categories, the pooled estimates of relative risk ranged from 0. 81 for oral clefts to 1. 11 for limb reductions, with all 95% confidence intervals enclosing unity. With the exception of studies for oral clefts and for pyloristenosis, tests for heterogeneity of association indicated for each table that all studies were estimating the same odds ratio. These studies, as a group, showed no difference in the risk of birth defects between those infants whose mothers had taken Bendectin during the first trimester of pregnancy and those infants whose mothers had not. It is unlikely that Bendectin exposure contributed to the prevalence of congenital malformations in the population.© 1994 Wiley‐Liss, Inc.
Paternal age and the risk of congenital heart defects
Authors: Olshan Andrew F. , Schnitzer Patricia G. , Baird Patricia A.
Published: June 2005

The effect of paternal age on the risk of birth defects among affspring is less well studied than the effect of maternal age, with few comprehensive epidemiologic studies having been conducted. Advanced paternal age has been shown to be associated with an increase in new dominant mutations that result in particular congenital anomalies. The relationship between paternal age more common birth defects, for example, cardiac defects, has not been as extensively evaluated. Therefore, a total of 4, 110 cases of congenital heart defects was identified from the British Columbia Health Surveillance Registry. Matched controls were obtained from the birth files of British Columbia for the years 1952–1973. Prevalence odds ratios for paternal age, adjusted for maternal age and other factors, were estimated for 8 cardiac defect groups.

A suggestive general pattern of increasing risk with increasing age among cases (excluding chromosomal anomalies) relative to controls was found for ventricular septal defects (VSD), atrial septal defects (ASD), and patent ductus arteriosus (PDA). In addition, an increased risk among men younger than 20 yr was found for VSD and ASD. These findings are consistent with the results of some previous epidemiologic studies. Based on the results of the study it is estimated that for cardiac defects such as VSD, approximately 5% of cases may be due to advanced paternal age (>35yr), Possibly through dominant mutations. © 1994 Wiley‐Liss, Inc.
Early sialylation on N‐CAM in splotch neural tube defect mouse embryos
Authors: Neale Sondra A. , Trasler Daphne G.
Published: June 2005

The splotch (Sp) mutant mouse is a model for neural tube defects and Waardenburg syndrome type I. The neural tube defects that arise in sp, which include spina bifida and exencephaly, are though to be caused by a change in the timing of the cellular events which are taking place during neurulation. Cell adhesion molecules are strongly implicated in a variety of cell‐cell interaction throughout development, thus the neural cell adhesion molecule (N‐CAM) may play a role in neural tube formation and closure. The N‐CAM in day 9Sp embryos is altered showing a heavy 200 kD species rather than the 180 and 140 kD isoforms which are normally present at that developmental stage [Moase and Trasler (1991) Development 113: 1049–1058]. These N‐CAM isoforms normally become modified post‐translationally by the addition of α‐2,8 linked polysialosyl (PSA) units beginning at gestational day 11. Sp/Sp, Sp/+, and +/+ embryos were examined by Western blot analysis with an antibody (mAb 5A5 ) which specifically recognizes PSA residues on N‐CAM. Mutant and heterozygote embryos display a sialylated N‐CAM form at 20, 14, and 12 somite‐stages which is absent in controls. Enzymatic removal of PSA on N‐CAM resulted in a reduction of the 200 kD species to the expected 180 and 140 kD PSA–free N‐CAM isoforms. These result demonstrate that PSA exits on N‐CAM at an abnormally early developmental stage which results in the observed 200 kD species, and suggest that the sp gene is involved in the regulation of expression or the post‐translational modification of N‐CAM. © Wiley‐Liss, Inc.