Teratogenic effects of acetaldehyde in the rat

Exploring the biological domain of the neural embryonic stem cell test (ESTn): Morphogenetic regulators, Hox genes and cell types, and their usefulness as biomarkers for embryotoxicity screening

Animal-free assessment of compound-induced developmental neurotoxicity will most likely be based on batteries of multiple in vitro tests. The optimal battery is built by combining tests with complementary biological domains that together ideally cover all relevant toxicity pathways. Thus, biological domain definition, i.e. which biological processes and cell types are represented, is an important assay characteristic for determining the place of assays in testing strategies. The murine neural embryonic stem cell test (ESTn) is employed to predict the developmental neurotoxicity of compounds. The aim of this study was to explore the biological domain of ESTn according to three groups of biomarker genes of early (neuro)development: morphogenetic regulators, Hox genes and cell type markers for the ectodermal and neural lineages. These biomarker groups were selected based on their crucial regulatory role in (neuro)development. Analysis of these genes in a series of previously generated whole transcriptome datasets of ESTn showed that at day 7 in culture cell differentiation resembled hindbrain/branchial/thoracic development between E6.5-E12.5 in vivo, with subsequent development into a mixed cell culture containing different neural subtypes, astrocytes and oligodendrocytes by day 13. In addition, the selected biomarkers showed common and distinct responses to compound exposure. Monitoring the biological domain of ESTn through gene expression patterns of morphogenetic regulators, Hox genes and cell type markers proved instrumental in providing mechanistic understanding of compound effects on neural differentiation in ESTn, and can aid in positioning of the test in a battery of complementary in vitro tests in integrated approaches to testing and assessment.

A critical assessment of the potential of pharmacological modulation of aldehyde dehydrogenases to treat the diseases of bone loss

Chronic alcoholism (CA) decreases bone mass and increases the risk of hip fracture. Alcohol and its main metabolite, acetaldehyde impairs osteoblastogenesis by increasing oxidative stress. Aldehyde dehydrogenase (ALDH) is the rate-limiting enzyme in clearing acetaldehyde from the body. The clinical relevance of ALDH in skeletal function has been established by the discovery of single nucleotide polymorphism, SNP (rs671) in the ALDH2 gene giving rise to an inactive form of the enzyme (ALDH2*2) that causes increased serum acetaldehyde and osteoporosis in the affected individuals. Subsequent mouse genetics studies have replicated human phenotype in mice and confirmed the non-redundant role of ALDH2 in bone homeostasis. The activity of ALDH2 is amenable to pharmacological modulation. ALDH2 inhibition by disulfiram (DSF) and activation by alda-1 cause reduction and induction of bone formation, respectively. DSF also inhibits peak bone mass accrual in growing rats. On the other hand, DSF showed an anti-osteoclastogenic effect and protected mice from alcohol-induced osteopenia by inhibiting ALDH1a1 in bone marrow monocytes. Besides DSF, there are several classes of ALDH inhibitors with disparate skeletal effects. Alda-1, the ALDH2 activator induced osteoblast differentiation by increasing bone morphogenic protein 2 (BMP2) expression via ALDH2 activation. Alda-1 also restored ovariectomy-induced bone loss. The scope of structure-activity based studies with ALDH2 and the alda-1-like molecule could lead to the discovery of novel osteoanabolic molecules. This review will critically discuss the molecular mechanism of the ethanol and its principal metabolite, acetaldehyde in the context of ALDH2 in bone cells, and skeletal homeostasis.

Prenatal Alcohol Exposure as a Case of Involuntary Early Onset of Alcohol Use: Consequences and Proposed Mechanisms From Animal Studies

Prenatal alcohol exposure has been found to be an important factor determining later consumption of this drug. In humans, despite the considerable diversity of variables that might influence alcohol consumption, longitudinal studies show that maternal alcohol intake during gestation is one of the best predictors of later alcohol use from adolescence to young adulthood. Experimental studies with animals also provide abundant evidence of the effects of prenatal alcohol exposure on later alcohol intake. In addition to increased consumption, other effects include enhanced palatability and attractiveness of alcohol flavor as well as sensitization to its sensory and reinforcing effects. Most of these outcomes have been obtained after exposing rats to binge-like administrations of moderate alcohol doses during the last gestational period when the fetus is already capable of detecting flavors in the amniotic fluid and learning associations with aversive or appetitive consequences. On this basis, it has been proposed that one of the mechanisms underlying the increased acceptance of alcohol after its prenatal exposure is the acquisition (by the fetus) of appetitive learning via an association between the sensory properties of alcohol and its reinforcing pharmacological effects. It also appears that this prenatal appetitive learning is mediated by the activation of the opioid system, with fetal brain acetaldehyde playing an important role, possibly as the main chemical responsible for its activation. Here, we review and analyze together the results of all animal studies testing these hypotheses through experimental manipulation of the behavioral and neurochemical elements of the assumed prenatal association. Understanding the mechanisms by which prenatal alcohol exposure favors the early initiation of alcohol consumption, along with its role in the causal pathway to alcohol disorders, may allow us to find strategies to mitigate the behavioral effects of this early experience with the drug. We propose that prenatal alcohol exposure is regarded as a case of involuntary early onset of alcohol use when designing prevention policies. This is particularly important, given the notion that the sooner alcohol intake begins, the greater the possibility of a continued history of alcohol consumption that may lead to the development of alcohol use disorders.

Detrimental effects of alcohol exposure around conception: putative mechanisms

In western countries, alcohol consumption is widespread in women of reproductive age, and in binge quantities. These countries also continue to have high incidences of unplanned pregnancies, with women often reported to cease drinking after discovering their pregnancy. This suggests the early embryo may be highly exposed to the detrimental effects of alcohol during the periconception period. The periconception and pre-implantation windows, which include maturation of the oocyte, fertilisation, and morphogenesis of the pre-implantation embryo, are particularly sensitive times of development. Within the oviduct and uterus, the embryo is exposed to a unique nutritional environment to facilitate its development and establish de-novo expression of the genome through epigenetic reprogramming. Alcohol has wide-ranging effects on cellular stress, as well as hormonal, and nutrient signalling pathways, which may affect the development and metabolism of the early embryo. In this review, we summarise the adverse developmental outcomes of early exposure to alcohol (prior to implantation in animal models) and discuss the potential mechanisms for these outcomes that may occur within the protected oviductal and uterine environment. One interesting candidate is reduced retinoic acid synthesis, as it is implicated in the control of epigenetic reprogramming and cell lineage commitment, processes that have adverse consequences for the formation of the placenta, and subsequently, fetal programming.

Alcohol Teratogenesis: Mechanisms of Damage and Strategies for Intervention

There are multiple mechanisms by which alcohol can damage the developing brain, but the type of damage induced will depend on the amount and developmental timing of exposure, along with other maternal and genetic factors. This article reviews current perspectives on how ethanol can produce neuroteratogenic effects by its interactions with molecular regulators of brain development. The current evidence suggests that alcohol produces many of its damaging effects by exerting specific actions on molecules that regulate key developmental processes (e.g., L1 cell adhesion molecule, alcohol dehydrogenase, catalase), interfering with the early development of midline serotonergic neurons and disrupting their regulatory-signaling function for other target brain structures, interfering with trophic factors that regulate neurogenesis and cell survival, or inducing excessive cell death via oxidative stress or activation of caspase-3 proteases. The current understanding of pathogenesis mechanisms suggests several strategic approaches to develop rational molecular prevention. However, the development of behavioral and biologic treatments for alcohol-affected children is crucial because it is unlikely that effective delivery of preventative interventions can realistically be achieved in ways to prevent prenatal damage in at-risk pregnancies. Toward that end, behavioral training that promotes experience-dependent neuroplasticity has been effective in a rat model of cerebellar damage induced by alcohol exposure during the period of brain development that is comparable to that of the human third trimester.

Differential vulnerability to motor deficits in second replicate HAS and LAS rats following neonatal alcohol exposure

Children exposed prenatally to alcohol suffer from a variety of behavioral alterations. However, variation exists in the pattern and severity of these alcohol-related neurodevelopmental disorders. We examined the influence of alcohol sensitivity in the etiology of fetal alcohol effects by studying rat lines selectively bred for extremes in alcohol-induced sleep time: high-alcohol-sensitive (HAS) and low-alcohol-sensitive (LAS) rats. Using subjects from the first replicate, we previously reported that HAS rats exposed to alcohol during development were more vulnerable to ethanol-induced hyperactivity and motor deficits compared to LAS rats. To determine if these effects were, in fact, related to the trait for which these subjects were selected, the present study examined the consequences of developmental alcohol exposure in second replicate HAS and LAS rats. Second replicate HAS and LAS rats, as well as Sprague-Dawley rats, were exposed to 6.0 g/kg/day ethanol on Postnatal Days (PD) 4-9, a period of brain development equivalent to the third trimester, via an artificial rearing procedure. Artificially and normally reared controls were included. Activity was measured on PD 18-21 and parallel bar motor coordination on PD 30-32. Ethanol exposure produced hyperactivity in all genetic groups, and there were no differences among HAS and LAS rats. In contrast, consistent with findings from the first replicate, ethanol-exposed HAS rats were more impaired on the motor coordination task compared with LAS rats. These data suggest that genetically mediated responses to alcohol may relate to behavioral vulnerability to motor deficits following developmental alcohol exposure. They also provide evidence that genetic factors play a role in fetal alcohol effects and suggest that phenotypic markers may indicate individuals at high risk for some fetal alcohol effects.

Limb-body wall complex: a case series

OBJECTIVE

Limb-body wall complex (LBWC) is a rare fetal polymalformation of uncertain etiology, but it has been regarded as sporadic in nature with a low recurrence risk. We review a case series in light of recent evidence about possible genetic and environmental associations.

METHODS

All abortions or births coded as limb-body wall defect or fetal acrania/exencephaly or with unclassified polymalformation between January 1996 and January 2001 were audited.

RESULTS

During the 5-year period there were 33,286 live births in our region. Eleven cases met the criteria of LBWC giving an incidence of 0.33/1000 live births. In 50%, 50% and 30% of women a history of cigarette, alcohol and marijuana use, respectively, was noted. Furthermore, 40% of the women had a history of a previous infant with a congenital anomaly. One patient delivered two consecutive male infants with LBWC.

CONCLUSIONS

Whilst the majority of cases of LBWC are sporadic, some women may have an underlying genetic predisposition. It may be prudent to advise against the use of alcohol, cigarettes and other drugs and to offer an ultrasound scan in a tertiary referral center in a subsequent pregnancy.

Impairment of pyruvate dehydrogenase activity by acetaldehyde

The facial features that are characteristic of fetal alcohol syndrome (FAS) are strikingly similar to those seen in pyruvate dehydrogenase (PDH) deficiency. Furthermore, alcohol-induced central nervous system insult results in midline anomalies such as agenesis of the corpus callosum, which has also been described in several metabolic diseases, including PDH deficiency. The purpose of this work was to examine the effect of acetaldehyde on PDH in vitro. The activity of PDH was measured in the presence of acetaldehyde (10 microM-1 mM) by measuring the formation of the reduced form of nicotinamide-adenine dinucleotide at 340 nm. Pyruvate dehydrogenase was separated by using the sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique after incubation with [1,2-(14)C]-acetaldehyde to detect the formation of covalent adducts autoradiographically. The effect of acetaldehyde on the phosphorylation of the complex was also determined autoradiographically after incubating of PDH with (32)P-adenosine triphosphate. The results of this study show that acetaldehyde impairs PDH activity by a mixed inhibition type mechanism (Kic=62.4+/-25.7 microM, Kiu=225+/-68 microM), which is not a result of the formation of covalent adducts with PDH, nor of a stimulation of phosphorylation or inactivation of the complex. Because PDH levels are low throughout development and that the competition between pyruvate and acetaldehyde may be enhanced due to ethanol-induced lowering of ambient pyruvate concentrations, we conclude that impairment of PDH may have a significant effect on the developing fetus.

The role of acetaldehyde in pregnancy outcome after prenatal alcohol exposure

It is not known why some heavy-drinking women give birth to children with alcohol-related birth defects (ARBD) whereas others do not. The objective of this study was to determine whether the frequency of elevated maternal blood acetaldehyde levels among alcoholics is in the range of ARBD among alcoholic women. MEDLINE was searched from 1980 to 2000 using the key words acetaldehyde, pharmacokinetics, and alcoholism for controlled trials reporting blood or breath acetaldehyde levels in alcoholics and nonalcoholics. Separately, using the key words fetal alcohol syndrome, epidemiology, prevalence, incidence, and frequency, articles were identified reporting ARBD incidences among the offspring of heavy drinkers. Of 23 articles reporting acetaldehyde levels in alcoholics, four met the inclusion criteria. Forty-three studies reported on the rate of ARBD in heavy drinkers, and 14 were accepted. Thirty-four percent of heavy drinkers had a child with ARBD, and 43% of chronic alcoholics had high acetaldehyde levels. The similar frequencies of high acetaldehyde levels among alcoholics and the rates of ARBD among alcoholic women provide epidemiologic support to the hypothesis that acetaldehyde may play a major role in the cause of ARBD.

In vitro comparison of the effects of ethanol and acetaldehyde on dorsal root ganglion neurons

Results of previous experiments designed to investigate the role of acetaldehyde, the primary metabolite of ethanol, have been contradictory. Experiments have provided evidence that supports and refutes the idea that acetaldehyde is responsible for the teratogenic effects observed in fetal alcohol syndrome. In the present study, cell culture techniques were used to examine the effects of acetaldehyde, both independently and in conjunction with ethanol. The purpose was to determine whether acetaldehyde had any effect on survival and process outgrowth of dorsal root ganglion (DRG) neurons cultured in vitro. This study revealed that acetaldehyde was as toxic to DRG survival as is ethanol, but had a lesser effect on neurite outgrowth than ethanol. Also, acetaldehyde and ethanol do not act synergistically to damage neurons in culture. The results indicate that, although acetaldehyde is probably not solely responsible for ethanol neurotoxicity, it does exhibit a secondary toxicity that could be the subject of future studies.

4-Methylpyrazole, an alcohol dehydrogenase inhibitor, exacerbates alcohol-induced microencephaly during the brain growth spurt

Whether alcohol-induced microencephaly occurs as a result of the effect of alcohol or acetaldehyde remains an unanswered, yet important, question. The present study addressed this issue by using an alcohol dehydrogenase (ADH) inhibitor, 4-methylpyrazole (4-MP), that works by blocking the metabolism of alcohol to its primary metabolite acetaldehyde, thereby prolonging the actions of alcohol while minimizing the generation of acetaldehyde. Four groups of artificially reared Sprague-Dawley rat pups were treated with alcohol treatment (3.3 g/kg EtOH or isocalorically matched control formula from postnatal days 4 through 9) and 4-MP administration (IP, 50 mg/kg or saline). A suckle control group was introduced to control the effects of the artificial rearing procedure. On postnatal day 10, all pups were perfused. Alcohol in combination with 4-MP treatment produced a marked microencephaly, as assessed by brain weights or brain to body weight ratios, compared with other artificially reared groups. The peak BACs in the pups that received both alcohol and 4-MP were increased at least twofold compared with those that received alcohol alone. These findings indicate that 4-MP is an effective nontoxic ADH inhibitor and that microencephaly is associated with BAC levels. Most importantly, these results support the hypothesis that alcohol is a causative agent for alcohol-induced microencephaly and implicates the importance of functional ADH activity in attenuating alcohol-induced neuroteratogenicity.

Fetal alcohol syndrome: the vulnerability of the developing brain and possible mechanisms of damage

Fetal alcohol exposure has multiple deleterious effects on brain development, and represents a leading known cause of mental retardation. This review of the effects of alcohol exposure on the developing brain evaluates results from human, animal and in vitro studies, but focuses on key research issues, including possible mechanisms of damage. Factors that affect the risk and severity of fetal alcohol damage also are considered.

Protective effect of Liv.52 on alcohol-induced fetotoxicity

The adverse effects of maternal alcohol consumption on the development of the fetus are well known. The adverse effects of ethanol on the liver are now believed to be due to acetaldehyde formed as an intermediate metabolite of ethanol. Liv.52 has been shown to bring about faster elimination of acetaldehyde from the body and thus prevent alcoholic liver damage. Other toxic effects of alcohol may also be due to acetaldehyde and may be prevented by Liv.52. In this study, rats were given 20% (v/v) ethanol in drinking water, during the gestation period, and the effect on maternal body weight and fetal outcome was noted. The protective effect of Liv.52 administration during the gestation period was studied. The results show that ethanol ingestion caused a decrease in gestational weight gain, total fetal weight, and number of live fetuses. There were increases in resorptions. Liv.52 administration reduced the deleterious effects of ethanol. The concentration of acetaldehyde in the amniotic fluid of ethanol-consuming animals was 0.727 microgram/ml. Liv.52 administration lowered it to 0.244 microgram/ml. The protective effect of Liv.52 could be due to the rapid elimination of acetaldehyde.

Effects of prenatal alcohol exposure in mice: influence of an ADH inhibitor and a chronic inhalation study

In order to examine the effects of an alcohol dehydrogenase inhibitor on the embryotoxic effects of ethanol, pregnant ICR mice were treated with 100 mg/kg pyrazole prior to ethanol injection. I.p. treatment with 2 or 4 g/kg ethanol on day 7 of gestation increased the prenatal mortality rate and produced external and skeletal malformations in the offspring, and the embryotoxic effects were potentiated by pyrazole pretreatment, suggesting that ethanol rather than its metabolites is mainly responsible for the embryotoxicity. In the second experiment, we housed pregnant mice in an ethanol-vapor box for 3 or 6 days in order to examine the effects of prolonged low level exposure to alcohol. The maternal blood alcohol concentration was maintained approximately 0.03 mg/mL during inhalation. The inhalation treatment with ethanol increased the prenatal mortality rate, although teratogenicity was not shown.

Embryonic development in the chick following exposure to ethanol, acetaldehyde and cyanamide

The influence of cyanamide, an inhibitor of aldehyde dehydrogenase, on the embryopathic effects of ethanol and acetaldehyde, was investigated in the chick embryo. Both ethanol and cyanamide significantly increased embryonic mortality, but did not affect embryonic growth, compared to treatment with either ethanol or cyanamide. Acetaldehyde combined with cyanamide increased embryonic mortality and retarded embryonic growth. Cyanamide influence on embryonic development was minimal. The extent of acetaldehyde involvement in ethanol teratogenicity remains unclear from the present findings.

Effects of ethanol and acetaldehyde on rat embryos developing in vitro

Rat embryos were explanted on Days 9.5 or 10 of gestation and cultured for 48 to 30h, respectively, in rat serum containing 0, 3, 6, 9 mg/ml of Ethanol (Eth); 0, 10, 20 micrograms/ml of Acetaldehyde (Ach); 3 mg/ml Eth + 10 micrograms/ml Ach. At the end of the culture period the embryos were evaluated for vitality, and scored. Some of them were also examined histologically. Embryos exposed to Eth from Day 9.5 showed a dose-related growth retardation associated with a high frequency of malformations (open neural tube, heart defects, branchial arch hypoplasia). The exposure of 9.5-day embryos to 20 micrograms/ml Ach resulted in 100% embryolethality, whereas 10 micrograms/ml induced growth retardation and teratogenic effects. When 10-day embryos were exposed to 3 mg/ml Eth or 10 microliters/ml Ach no effects were observed, but the highest levels of Eth produced a moderate growth retardation and morphologic defects. Exposure to 20 micrograms/ml Ach induced hypoplasia of the first arch, but did not alter the score value. The histologic examination of these embryos revealed severe lesions at the level of the neuroepithelium and of the branchial mesenchyma. Similar effects were observed in embryos exposed simultaneously to 3 mg/ml Eth and 10 micrograms/ml Ach. These results should make us reevaluate the role of Ach in the Eth-induced embryopathies.

Ethanol consumption inhibits fetal DNA methylation in mice: implications for the fetal alcohol syndrome

Acute ethanol administration (3 g/kg twice a day) to pregnant mice, from the 9th thru the 11th day of gestation, resulted in hypomethylation of fetal deoxyribonucleic acid (DNA). Nuclei isolated from the fetuses of the ethanol-treated mice had lower levels of methylase activity relative to controls even in the presence of excess S-adenosylmethionine, which serves as the methyl donor for the enzyme DNA methyltransferase. Acetaldehyde, at concentrations as low as 3 to 10 microM, inhibited DNA methyltransferase activity in vitro. Since DNA methylation is thought to play an important role in the regulation of gene expression during embryogenesis, ethanol-associated alterations in fetal DNA methylation may contribute to the developmental abnormalities seen in the fetal alcohol syndrome.

Reproductive hazards of fire fighting. II. Chemical hazards

Studies of the health of fire fighters have historically focused on non-malignant respiratory disease and cancer. More recently, concerns have surfaced about reproductive health effects in many areas of the workforce, including fire fighting. These concerns prompted this review of chemical exposures that may contribute to adverse reproductive health outcomes in male as well as female fire fighters. A review of the industrial hygiene literature was undertaken to identify agents commonly found in fire smoke. These agents were then examined for evidence of reproductive toxicity or mutagenicity/carcinogenicity. This profile of chemical agents and their reproductive toxicities permits a qualitative determination that fire fighters are exposed to potential reproductive toxicants as a part of their normal fire fighting duties. Considerations for mitigating these risks are also discussed.

Cardioteratogenic dose of ethanol in the chick embryo results in egg white concentrations comparable to human blood alcohol levels

Three-day-old chick embryos were exposed to a dose of ethyl alcohol (0.32 ml of 50% ethanol) that we previously demonstrated produces cardiac malformations in 96.6% of the animals. Ethanol was administered into the air sac at 72-80 h of incubation. Samples of egg white were drawn at 2, 6 and 24 h after treatment and analyzed by capillary gas-liquid chromatography. Ethanol concentrations were significantly higher at 6 and 24 h after exposure than at 2 h (P less than 0.01), but there were no differences in mean concentrations between 6 and 24 h (P greater than 0.2). Furthermore, concentrations (43-303 mg dl-1) were comparable to human blood alcohol levels during intoxication. These results suggest that the cardioteratogenic doses of ethanol administered to chick embryos in a previous study are not excessive in terms of potential human embryo exposure.

Effects of acute doses of ethanol administered at pre-implantation stages on fetal development in the mouse

The objective of the present study was to investigate the effects of maternal administration of acute doses of alcohol at preimplantation stages of pregnancy on the fetus and fetal membranes. Single doses of 0.02 ml and 0.03 ml/g body wt. of 25% v/v of absolute alcohol in saline were administered to groups of MF1 mice on one of days 1-6 of gestation. Controls were either pair-fed and pair-watered or saline-treated. Fetuses and placentae were collected on day 15. Resorption and fetal death were increased in most of the alcohol treatment groups. The reduction in fetal body weight was significant in the 0.03 ml group. Compared to the saline controls, most experimental groups exhibited a rise in placental weight. The reduction in cord length was significant in comparison to untreated controls. Craniofacial and systemic abnormalities appeared to correlate with retardation of fetal growth. Hence, following treatment of 0.03 ml/g body wt. of alcohol solution on days 2 and 6, fetuses were collected on days 14, 16 and 18. Most fetuses were found to recover gradually from anomalies associated with growth retardation but the 'catch up' growth was not adequate enough to compensate for the reduction in body weight. These observations indicate that the pre-implantation stage of mouse embryo development is susceptible to the deleterious effects (fetal death and intrauterine growth retardation) of acute doses of alcohol.

Mechanisms of fetal alcohol effects: role of acetaldehyde

Pregnant rats were treated from day 9 through 12 of gestation with 12.5% ethanol, 25% ethanol, 1% acetaldehyde, cyanamide (an inhibitor of the enzyme aldehyde dehydrogenase), or a combination of cyanamide and ethanol. Embryos were recovered on gestational day 12 and were quantitatively assessed on the basis of 16 recognizable developmental endpoints (morphological scores). The head and the crown-rump lengths of the embryos were also measured. Total resorption occurred in two animals treated with cyanamide and two treated with cyanamide and ethanol. Acetaldehyde and ethanol (at both concentrations) were found to reduce the head length of the embryos but had no significant effects on morphological scores and crown-rump length. The combination of ethanol with cyanamide caused a greater reduction in head length and also significantly reduced crown-rump length, as well as the morphological scores. The results suggest that the deleterious effects of ethanol could be attributed to acetaldehyde, its primary metabolite, although other underlying factors cannot be ruled out.

A mutagenicity assessment of acetaldehyde

Acetaldehyde has been shown in studies by several different laboratories to be a clastogen (chromosome-breaking) and inducer of sister-chromatid exchanges in cultured mammalian cells (Chinese hamster cells and human lymphocytes). Although there have been very few studies in intact mammals, the available evidence suggests that acetaldehyde produces similar cytogenetic effects in vivo. The production of cytogenetic abnormalities may be related to the ability of acetaldehyde to form DNA-DNA and/or DNA-protein cross-links. Acetaldehyde apparently has not been evaluated for its ability to cause gene mutations in cultured mammalian cells, but it has been shown to produce sex-linked recessive lethals in Drosophila. In general, bacteria tests have been negative. Although acetaldehyde is a genotoxic cross-linking agent, it does not appear to cause DNA strand breaks. There were no studies available regarding the potential of acetaldehyde to produce genetic damage in mammalian germ cells in vivo. Most mutagenicity testing on acetaldehyde has been motivated by attempts to define the proximate mutagen in ethanol metabolism.

Effects of administering caffeine to pregnant rats either as a single daily dose or as divided doses four times a day

From day 6 to day 20 of pregnancy, rats were treated with caffeine in a total daily dose of 10 or 100 mg/kg by gavage, either as a single bolus dose or as four divided doses given at 3-hr intervals throughout the day. Controls were given distilled water at the same times. Maternal body weight and food and water consumption were reduced in the two groups receiving a total of 100 mg caffeine/kg/day and in the group given 2.5 mg/kg four times daily. Dose-related decreases in foetal weight, placental weight and crown-rump length and dose-related retardation of skeletal ossification were observed. Major foetal abnormalities, mainly ectrodactyly, were seen only in the group given 100 mg caffeine/kg in a single daily dose.

Major limb malformations following intrauterine exposure to ethanol: two additional cases and literature review

Two children are reported in whom major limb malformations were identified and whose mothers had consumed large quantities of alcohol in the first trimester of pregnancy. In one there was complete amelia of the upper limbs, while the other had preaxial polydactyly of both hands. These cases, taken together with previously reported instances of major limb anomalies following intrauterine ethanol exposure, as well as animal investigations that have demonstrated virtually identical limb malformations following ethanol administration, suggest that maternal ethanol abuse may be casually related to these limb malformations. We suggest that interruption of blood supply to the developing limb may be caused by ethanol exposure and may result in all of the various limb malformations described.

Histological and histochemical changes of the placenta in fetal alcohol syndrome due to maternal administration of acute doses of ethanol in the mouse

In both clinical and experimental research on the fetal alcohol syndrome (FAS) the possible involvement of the placenta has not been considered. In an attempt to investigate the effects of alcohol on the placenta, single doses of 0.02 ml and 0.03 ml/g body weight of freshly prepared solutions (25%, v/v) of absolute alcohol in saline were administered to MF1 mice on day 8 of gestation. Controls were saline treated or/and pair fed and pair watered. Fetuses and placentas were collected on day 18, weighed individually, observed for malformations and fixed. Paraffin sections of placentas of control and of fetuses with FAS were stained with hematoxylin and eosin, Best's carmine and PAS with and without diastase (saliva). The experimental fetuses and placentas were lighter in weight than the controls. The decidua basalis of placentas of FAS cases were occasionally vacuolated and infiltrated by lymphocytes. The glycogen and mucopolysaccharide content in the basal zone was reduced. In most situations the glycogen cells had degenerated and were replaced by an acidophilic mass. The cytoarchitecture of the labyrinthine zone had been altered. Large cysts filled most parts of the placenta; besides fibrinoid accumulation, extensive vacuolisation was also clearly visible. The overall width of this zone and arborisation of fetal vasculature were also reduced. The consistent association of these placental abnormalities with FAS in this mouse model is suggestive of placental mechanisms in FAS.

Maternal toxicity: a possible etiological factor in embryo-fetal deaths and fetal malformations of rodent-rabbit species

Data from animal teratology studies were surveyed to determine whether embryo-fetal mortality and fetal malformations result from a primary action of the agent on the conceptus or if they are secondary to maternal toxicity--a consequence of administration with high dose levels of test chemicals. A fairly strong association between embryo-fetal mortality and maternal toxicity was revealed by analysis of data from hamsters, mice, rats, and rabbits in 234 studies of chemical and physical agents, of which 83 were conducted at both maternotoxic and nonmaternotoxic doses, 94 only at maternotoxic doses, and 49 at nonmaternotoxic doses. In the above studies, only nine chemicals (four each in hamsters and rabbits and one in rats) were reported to induce embryo-fetal deaths at apparently nonmaternotoxic doses. These findings tend to suggest a contributory role for maternal toxicity in the induction of embryo-fetal deaths. The previously reported hypothesis that certain fetal defects in mice may perhaps be caused by maternal toxicity was also found to be true in a review of data on hamsters, rats, and rabbits. Salient maternal toxicity-associated fetal malformations were exencephaly, encephalocele, micro- or anophalmia, and fused ribs in hamsters and defective (fused, missing, or extra) ribs, vertebrae, and sternebrae, ex-, an-, or microphthalmia, and cleft palate in rats and rabbits. These malformations occurred at low frequencies, generally with no readily apparent dose-response relationship. Presumptive evidence indicates that embryo-fetal deaths, and the above-mentioned fetal malformations in experimental animals, which in published literature are presently attributed to chemical induction for a large number of chemicals, may be a consequence of maternal toxicity per se.

Effect of acetaldehyde on skeletogenesis in rats

Acetaldehyde (ACH), the metabolite of ethanol was administered to pregnant CF rats intraperitoneally (50 mg/kg) from day 8 through 15 of gestation and fetuses from different mothers were collected from day 16 through 21 of gestation. Fetuses were processed for alizarin skeletal staining. There was significant delay in ossification besides certain skeletal malformations such as wavy ribs. The delay in ossification may be one of the reasons for reduced birth weight and increased postnatal mortality and growth.

Implication of the placenta in acetaldehyde-induced intrauterine growth retardation

Acetaldehyde (AcH) the proximal metabolite of ethanol was administered to pregnant CF rats intraperitoneally in single and triple doses (50, 75 and 100 mg/kg) on days 10, 11 and 12 of gestation and fetuses along with placentae were collected on day 21. Placentae were subjected to histological sectioning and the volume fractions of various zones of placenta were calculated using Weibels point counting techniques. There was no correlation between fetal weight and placental weight, but the fetal weight showed a positive correlationship with the percentage volume fraction of the labyrinthine zone suggesting that the reduction in the labyrinthine zone volume is probably responsible for intrauterine growth retardation following acetaldehyde maternal treatment.

Determination of the proximate teratogen of the mouse fetal alcohol syndrome. 1. Teratogenicity of ethanol and acetaldehyde

The proximate teratogen of the fetal alcohol syndrome is unknown. CD-1 mice were treated ip on Day 10 of gestation with 2, 4, 6, or 7 g/kg ethanol. The percentage of resorptions and malformed fetuses was increased and mean fetal weight was decreased in a dose-related manner. Treatment with 7 g/kg ethanol ip on one of gestational Days 7, 8, 9, 10, or 11 significantly increased the percentage of malformed fetuses and decreased fetal weight. In addition, treatment on Days 10 or 11 significantly increased the percentage of resorptions. Coadministration of 100 mg/kg of 4-methylpyrazole, an inhibitor of alcohol dehydrogenase, orally with 6 g/kg ethanol ip on Day 10 of gestation dramatically increased the embryotoxicity of ethanol. Five ip treatments of 200 mg/kg acetaldehyde at 2-hr intervals on Day 10 of gestation did not significantly increase the percentage of resorptions and malformed fetuses or decrease fetal weight. These data suggest that ethanol is the proximate teratogen of the fetal alcohol syndrome in CD-1 mice.