Showing papers in "Teratology in 1979"

Prenatal ethanol exposure in mice: teratogenic effects.

Abstract: C57BL/6J mice were fed a liquid diet in which 17, 25, or 30% of the calories were derived from ethanol from the fifth through the tenth day of gestation. Control mice were fed lab chow or pair-fed identical diets, except that sucrose substituted isocalorically for ethanol. At term the fetuses were removed and. following fixation, examined by microdissection. The incidence of fetal resorptions and congenital malformations increased in a dose-related manner. Anomalies included skeletal, neurological, urogenital, and cardiovascular systems. These data indicate that in mice, an alcohol diet which is adequate in vitamins and protein results in increased fetal wastage and birth defects.

Smoking during pregnancy.

Abstract: Smoking during pregnancy can lead to a higher risk of miscarriage, complications during labour, low birth weight and sudden infant death. Smoking during pregnancy increases the risk of infant mortality by an estimated 40%. Children born to mothers who smoke are more likely to suffer from respiratory problems such as asthma, problems of the ear, nose and throat and may have a physical or learning disability. (Public Health England).

The extent of fetal ossification as an index of delayed development in teratogenic studies on the rat.

Abstract: In teratogenic studies toxic effects may manifest themselves in retarded fetal development, such as a reduction in fetal weight. In searching for an additional index, the number of centers of ossification in seven skeletal districts (sternum, metacarpus, metatarsus, cervical and caudal vertebrae, anterior and posterior proximal phalanges) of rat fetuses delivered on days 19, 20 and 21 of gestation were counted and compared. Results showed uneven ossification in day-19 and -20 fetuses, but sufficiently advanced, homogeneous and uniform ossification in day-21 fetuses to provide a reliable quantitative index for evaluating retarded fetal development. It is therefore proposed that the stage of skeletal ossification in day-21 fetuses be used in teratogenic studies in the rat to evaluate retarded fetal development.

The Murine Ah locus: In utero toxicity and teratogenesis associated with genetic differences in benzo[a]pyrene metabolism

Abstract: Benzo[a]pyrene, at doses between 50 and 300 mg per kg body weight given at Day 7 or 10 of gestation, causes in utero toxicity and teratogenicity more so in genetically “responsive” C57BL/6 than in “nonresponsive” AKR inbred mice. With the use of AKR × (C57BL/6)(AKR)F1, and (C57BL/6) (AKR)F1 × AKR backcrosses, it was shown that allelic differences at the Ah locus in the fetus can be correlated with dysmorphogenesis. If the mother is nonresponsive (Ahd/Ahd), the Ahb/Ahd genotype in the fetus is associated with more stillborns and resorptions, decreased fetal weight, increased congenital anomalies, and enhanced P1,-450-mediated covalent binding of BP metabolites to fetal protein and DNA, when compared with the Ahd/Ahd genotype in the fetus from the same uterus. If the mother is responsive (Ahb/Ahd), however, none of these parameters can be distinguished between Ahb/Ahd and Ahd/Ahd individuals in the same uterus, presumably because enhanced BP metabolism in maternal tissues and placenta cancels out these differences between individual fetuses. Of particular interest in our study is the fact that the mother and the father both must be of a particular genotype before differences in teratogenesis among fetuses (due to their genotype) will be expressed. These data might provide an example in attempting to explain clinically why only one child is affected with an apparent “drug-induced syndrome” although the mother has taken the same dose of the particular drug during each of numerous pregnancies.

Cadmium induced limb defects in mice: strain associated differences in sensitivity.

Abstract: Cadmium (CdSO4) was given ip on day 9 at 12 or 24 mumol/kg to pregnant CD-1 (non-inbred) mice. Fetuses showed malformations of the limbs, face, trunk, and tail. There was a statistically significant relationship between the dose of cadmium and the malformation rate. Cadmium (12 mumol/kg ip on day 9) was then given to mice of six inbred strains three of which (A/J, BALB/cJ, and C57BL6J) carry a gene cdm for resistance to cadmium-induced testicular damage, and three strains (AKR/J, CBA/J, and DBA/2J) which do not. Paradoxically, the three strains resistant to cadmium induced testicular damage were significantly more sensitive to its teratogenic effects than were the other three strains. In all inbred strains most malformations involved the limbs. All forelimb defects found in inbred or non-inbred cadmium treated mice were postaxial and indistinguishable from those produced by acetazolamide in mice. The remarkable similarity of the cadmium- and acetazolamide-induced forelimb malformations may be a reflection of the limited number of ways that a rodent forelimb can react to a teratogenic insult. The hindlimb defects were all preaxial.

Teratogenic action and embryo lethality of AY 9944R. Prevention by a hypercholesterolemia-provoking diet.

Abstract: Embryomortality and teratogenesis provoked by inhibitors of cholesterol synthesis are well demonstrated. Teratogenic action is particularly reflected by holoprosencephalies, but also by uro-genital abnormalities. A hypercholesterolemia-provoking diet has been shown to be completely effective for preventing holoprosencephaly, but only partially so for preventing the uro-genital malformations and fetal mortality. It is thus possible that the two types of abnormalities are governed by different mechanisms. In addition, the diet itself, whose hypercholesterolemic effect is considerable, has certain disadvantages. It seems to have a certain effect on fetal mortality and could be responsible for several uro-genital malformations. This deserves further study.

Selective proliferation and accumulation of chondroprogenitor cells as the mode of action of biomechanical factors during secondary chondrogenesis

Abstract: Secondary cartilage fails to differentiate on membrane bones of embryonic chicks which have been paralyzed by the in ovo injection of D-tubocurarine chloride at ten days of incubation. A planimetric analysis of serial sections of a membrane bone (the quadratojugal) from control (mobile), and from paralyzed embryos, indicated that osteogenesis was not slowed in paralyzed embryos. However the rate of accumulation of periosteal progenitor cells was significantly lower in paralyzed than in mobile embryos. Quantitative analysis of 3H-thymidine-labelled progenitor cells indicated that the slowed accumulation of progenitor cells was the result of fewer progenitor cells initiating DNA synthesis and mitosis. Between 10 and 11 days of incubation, 60 to 75 more 3H-thymidine-labelled progenitor cells accumulated in mobile embryos than accumulated on each quadratojugal in paralyzed embryos. This subpopulation of cells could represent the chondroprogenitor cells which produce secondary cartilage in mobile embryos. If this is so, then biomechanical factors control the ability of the embryo to produce secondary cartilage by allowing the selective accumulation of chondrogenic progenitor cells.

Teratogenic effects of external egg applications of methyl mercury in the mallard, Anas platyrhynchos.

Abstract: The embryotoxic potential of external applications of methyl mercury on mallard eggs was investigated to assess the possible impact of mercury transferred from the plumage of effluent-contaminated aquatic birds to their eggs Eggs were treated on day 3 of development with microliter applications of methyl mercury that was dissolved with ethyl acetate into an aliphatic hydrocarbon vehicle Mercury analysis by atomic absorption indicated that almost half of the mercury applied entered the eggs past the shell membranes within several days of treatment Most mortality occurred within this period at doses of 9 microgram of mercury per egg or higher Decreased embryonic growth resulted with similar doses A significant incidence of malformations occurred at a dose of 1 microgram per egg These malformations were mainly minor skeletal aberrations and incomplete ossification With higher doses of mercury, defects included gross external ones such as micromella, gastroschisis, and eye and brain defects Application of the aliphatic hydrocarbon vehicle did not result in any of these defects

Comparative distribution and embryotoxicity of methotrexate in pregnant rats and rhesus monkeys.

Abstract: Dosages of methotrexate of roughly comparable embryotoxicity were determined to be 0.3 mg/kg on gestation day 10 in rats and 3.0 mg/kg/d on days 29 through 32 of gestation in rhesus monkeys. These times represented similar periods in development. This regimen in rats was moderately embryolethal, slightly teratogenic, and caused some intrauterine growth retardation; in monkeys it was mildly embryolethal, not teratogenic, and caused only transitory growth retardation. Methotrexate was largely cleared from maternal plasma of both species within 8 hours, and in spite of a higher administered dose and initial concentration in monkey, the rate of fall was faster than in rat. The fraction of total drug concentration remaining unbound in plasma was approximately 30-40% during the first 4 hours after treatment in both species. Embryo concentrations, however, were strikingly different during the first 8 hours, ranging between 108 and 209 ng/g in monkey but between 3.4 and 7.7 ng/g in rat. A slow rate of fall in embryo concentrations in both species was estimated to be inversely proportioned to the rate of growth of embryos, which was in accord with the fact that the absolute amount per embryo was little changed in 24 hours. Thus, the degree and type of embryotoxicity was not closely correlated with the level or duration of concentration in the embryos: a small maternal dosage in rat produced moderate embryotoxicity and very low embryo concentrations; a large maternal dosage in monkey produced slight embryotoxicity despite high embryo concentrations.

Teratogenic effects of hyperthermia in the bonnet monkey (Macaca radiata).

Abstract: Seventeen timed-mated bonnet monkeys (Macaca radiata) were exposed to hyperthermia in a forced-draft incubator for a duration of one, three, four or eight days between 21 and 46 days of gestation. On each day of exposure the core temperature of the pregnant animal was elevated 2.4 to 5.4°C above the reference temperature recorded before heat exposure. Malformations occurred following a one-hour daily elevation of the core temperature above the reference temperature under the following exposure conditions: 3.8°C, days 23 to 26; 3.9°C, days 24 to 27; 2.4°C, days 27, 28 and 30; and 4.1°C, day 26 of gestation. Five resorptions occurred following exposure for one, three or four days between days 24 and 29 of gestation after core temperature elevation of 3.7 to 4.4°C and three abortions occurred following exposure for four days between days 24 and 35 of gestation after core temperature elevation of 2.6 to 3.9°C. The results clearly indicate that the teratogenic sensitive period is from 23 to 30 days gestation following elevations of the core temperature from 2.4 to 4.1°C. No distinct pattern of malformations was observed although skeletal and umbilical cord malformations were the most common. Pathological changes in placental structure, expecially maternal surface infarctions and intervillous thrombi, were associated with three of the four abnormal fetuses, suggesting a relationship between pathological placental characteristics and fetal malformations in this study. The degree of core temperature elevation which resulted in malformations in the present study are similar to those applied to other mammalian species, and the specific anomalies observed in the bonnet monkey resemble those observed in other mammalian species, including man.

Aspirin: teratogenic evaluation in the dog.

Abstract: Beagle bitches were administered aspirin at either 100 or 400 mg/kg/day between Days 15 and 22 or Days 23 and 30 postmating, and corresponding control groups were dosed with vehicle during one of these same time periods. Maternotoxicity was evident in all dogs dosed with 400 mg/kg/day of aspirin, but no signs of toxicity were observed when 400 mg/kg/day of aspirin was administered from Days 15 to 22 postmating. Teratogenicity, as evidenced by 50% malformation rate, was seen in fetuses from dams treated with 400 mg/kg/day on Days 23 to30 postmating. Observed malformations included, but were not limited to cleft palate,micrognathia, anasarca, cardiovascular malformations, and tial anomalies. No evidence of embryotoxic or teratogenic effects was seen in fetuses from either 100 mg/kg/day dosage level group. Examination of fetuses from 12 untreated litters and 4 vehicle-control litters revealed a very low spontaneous malformation rate confined almost entirely to minor tail abnormalities. These data support use of the dog as an acceptable alternative species in teratogenic screening.

The history of the A family of inbred mice and the biology of its congenital malformations.

Abstract: The A family of inbred mice which originated in 1921, came during its early development to have incorporated into its genome the tendency to several congenital malformations, among them cleft lip and palate. These sporadic abnormalities are of interest because they closely resemble their human counterparts in morphology and development, and because they share with them a multifactorial basis. The origins and development of the A family are traced, and the abnormalities are described and the forces affecting them detailed.

Fetal and placental responses to artificially induced hyperthermia in rats

Abstract: Pregnant rats were utilized to study the effect of maternal hyperthermia on fetal development. Eight groups of six to eight rats were ex- posed to ambient temperatures of 43-44"C at various stages of pregnancy. All rats were killed on day 20 of gestation. Edema, microencephaly and microph- thalmia followed heat treatment on day 4, 6, or 8 and skeletal defects occurred on day 10 of gestation. Apparently heat stress of dams after day 14 of gestation had little or no effect on embryos. Most placentas from day 6-10 treatment groups were significantly heavier than control and exhibited extensive thicken- ing and necrosis of decidua basalis. Our results suggest that the rat is a useful model for investigating maternal hyperthermia as a possible cause of human placentophathies and fetal retardation A variety of factors contribute to the inci- dence of congenital malformations in animals and in man. Genetic mutation, irradiation, infections, drugs and nutritional deficiencies are among the well established inciting causes. Evidence implicating hyperthermia as a teratogenic agent is now overwhelming. Studies with rodents have shown that both the duration and level of hyperthermia affect- ed maternal survival as well as the incidence of fetal malformations; the disturbances of central nervous system were by far the most common defects (Edwards, '69; Kilham and Ferm, '76). Earlier, Skreb and Frank ('63) re- ported various types of defects in fetal rats fol- lowing the immersion of exteriorized pregnant uterine horns in warm saline. However, the mechanism by which heat stress produces em- bryopathies when associated with elevated maternal temperature is less well understood. Edwards et al. ('74) revealed that subjecting of pregnant animals to high incubation tem- peratures caused clumping of chromosomes, inhibition of mitotic activity and later death of neuro-ectoderm cells in the fetus. Presuma- bly, similar cellular changes in response to heat stress would be expected to cause devel- opmental anomalies in other embryonic struc- tures as well. In human subjects, fever is a possible, but unproven cause of spontaneous fetal abor- tions, retardations and abnormalities. The dif- TERATOmY (1979) 19: 251-260. ficulty in obtaining clinical or experimental evidence on the fetal or placental effect of maternal hyperthermia resulting from infec- tions or exposure to higher than normal environmental temperatures in human sub- jects is obvious. The significant problems involved can best be examined in animal models. Experiments on the influence of maternal hyperthermia on fetal rat develop- ment in utero are the subject of this report. This study also includes observations on hyperthermia-induced alterations in decidua basalis of placentas. AND METHODS Animals

Abnormal circulatory development in medaka caused by the insecticides carbaryl, malathion and parathion.

Abstract: Three insecticides, carbaryl, malathion and parathion were tested for teratogenic effects in developing medaka eggs. The concentrations of insecticides ranged from 0.5 to 40.0 parts per million (ppm). The insecticides, dissolved in acetone, were added to dishes containing 10 newly fertilized eggs and 10 ml of embryo rearing solution. Circulatory anomalies which resulted in-cluded defects in heart morphology, pericardial edema, irregular heart beat, blood clots and oscillating blood in the heart. The ED50 (effective dose) for cabaryl was 2.5 ppm; malathion, 10.0 ppm and parathion, 2.0 ppm. Limited exposure experiments were undertaken to determine possible sensitivity periods during development. These experiments, using 10 ppm carbaryl were initiated on days 0–7. Exposure lasted 24 to 96 hours. No periods of sensitivity were observed in these experiments. In a slightly varied experiment, eggs developed normally for 0–5 days, but were not removed from the insecticide once exposed. These results showed that carbaryl could cause circulatory abnormalities in 92% of the embryos which had completed cardiac morphogenesis before exposure. Combinations of malathion and carbaryl were administered to determine possible interactions. Twenty-five different combinations ranging from 0.0 to 25.0 ppm were employed. At low concentrations, combinations had slightly greater than additive effects. At higher concentrations additive and antagonistic effects were observed. The above experiments show that (a) these insecticides are teratogenic, (b) carbaryl at 10 ppm does not disrupt developmental events but rather affects-cell physiology and (c) combinations of some insecticides have an additive effect.

Behavioral consequences of interference with CNS development in the early fetal period.

Abstract: As a part of a series of investigations into the structural and functional consequences of interference with cell proliferation, mice were treated with 5-azacytidine during two stages of early fetal life. Treatment on either the twelfth or fourteenth day of gestation led to permanent significant reductions in body weight and brain weight. Behaviorally, the earlier treatment was associated with a delay in development of the righting reflex, permanent deficits in locomotor coordination, and hypoactivity. Treatment on the fourteenth day of gestation led to decreased passive avoidance, increased active avoidance, and hyperactivity — the same syndrome observed after treatment on the eighteenth day. Both treatments led to abnormal behavior on a spatial maze task. The developmental outcome of injuries induced in the early fetal period appears similar to the outcome of injuries at later stages of development.

Development and standardization of screening methods for behavioral teratology

Abstract: Behavioral alterations have been reported following perinatal exposures to a variety of agents. If subtle effects of this type are to be detected and prevented, sensitive and appropriate measures are needed for prospective screening of new compounds. However, studies reported in the literature have used differing exposure regimens, postnatal environmental conditions and behavioral testing procedures thus making it difficult to determine which existing techniques have particular relevance to screening new drugs and chemicals. It is imperative that such techniques be identified or new ones be developed for screening purposes, as the incorporation of behavioral evaluation into regulatory guidelines and protocols is being considered seriously. Before behavioral assessment can become a meaningful aspect of a routine screening system, considerable research and development must occur. The objectives of such a behavioral screen must be defined. Procedural standardization must be included in efforts to identify those methods which: (1) yield reproducible results within and across laboratories; (2) are sensitive to alterations produced by a range of agents; (3) are predictive of effects in man; (4) are cost-efficient. Identification of positive control agents, critical periods for testing and early indicators of behavioral dysfunction is urgently needed. The utility of pharmacologic/environmental challenges in unmasking functional abnormalities, and the possibility of multitesting interactions should be investigated. As the resources necessary to accomplish such a task are enormous, it is imperative that behavioral teratologists from academia, industry and government work together during all phases of such development. Interlaboratory cooperation in standardization, validation and interpretation of test methods and results is especially encouraged.

Selective inhibition of mandibular growth and induction of cleft palate by diazo-oxo-norleucine (DON) in the rat

Abstract: A high percentage of cleft palates can be induced in rat fetuses by a single injection of the glutamine analog diazo-oxo-norleucine (DON) on day 15 of gestation. The purpose of this study was to evaluate the effects of DON in vivo on craniofacial growth and spatial relations in order to identify factors that may contribute to the palatal defects. Sprague-Dawley rats in the experimental groups were given a single IP injection of 2.0 mg DON (6 mg/kg maternal body weight) on day 15 and were killed on day 16 or 17. Control fetuses were collected on days 15, 16 and 17. Fetal heads were fixed in Bouin's solution, embedded in Paraplast and serially-sectioned. Midsagittal and coronal sections were projected at 30 × and a series of linear and angular measurements were made. DON had limited effect on growth of the cranial base, nasomaxillary complex, and palatine processes, but dramatically reduced the length of Meckel's cartilage. Treatment with DON delayed shelf elevation approximately 24 hours, and tongue position remained high in the oronasal cavity. Growth retardation in Meckel's cartilage therefore may contribute to delayed shelf movement by retarding downward and forward positioning of the tongue-mandibular complex.

In vitro metabolism of cyclophosphamide in limb bud culture

Abstract: The presence of a drug-metabolizing system in any in vitro bioassay for teratogenicity is necessary because many chemical agents require metabolism before their activity can be expressed, and limb bud cells lack the enzymes necessary to activate these chemicals. We have taken three approaches to add a drug-metabolizing system to limb bud culture; addition of a 9,000 × g supernatant (S9) or a purified microsomal fraction, both from mouse liver, and co-incubation of limb buds with hamster embryo cells (HEC). The liver preparations were able to convert the teratogen cyclophosphamide to five separate metabolites with alkylating activity in limb bud culture but the cytotoxicity of these preparations limited their usefulness as metabolizing systems in limb bud culture. HEC did not exert a toxic effect on limb buds and they were able to continue metabolism of cyclophosphamide for three days. Analysis of the metabolites indicated that HEC did not convert cyclophosphamide to the same products as the liver preparations. The metabolic products were capable of inducing abnormal limb development in vitro. Addition of 14C-cyclophosphamide in the presence of an HEC activating system led to uptake of radioactivity into limb buds. In the absence of HEC, little radioactivity was detected in the target tissue. These results suggest that culturing intact cells capable of drug metabolism with limb buds may be the most likely method to follow in achieving in vitro activation of chemicals.

Correlation between the growth inhibitory effects, partition coefficients and teratogenic effects of lipophilic acids.

Abstract: The inhibition of cell duplication by many lipophilic acids was measured in Bacillus subtilis and in the following mammalian cell lines, the hunran epithelial-type cell lines HeLa, strain R and strain L-132, the human fibroblast cell line VA-13, and the rat glial cell line C. The results were correlated to the partition coefficient and the distribution coefficient (= apparent partition coefficient at pH 7.2) of the compounds, using octanol/water partition coefficients and pKa values either from the literature or measured for this work. For B. subtilis, the logarithm of the inhibitory potency of most compounds increases linearly with the logarithm of the partition coefficient. Exceptional high potencies were observed for compounds that can efficiently delocalize the charge of the negative ion over the whole molecule. Most compounds inhibit tissue cultures at least as potently as they inhibit B. subtilis. But some compounds are significantly more potent in tissue cultures than would have been expected from the B. subtilis data; such compounds (analgesics/antipyretics, anti-inflammatory compounds, but rate, norepinephrine) presumably inhibit mammalian cells by specific reactions with certain cell components. However, most compounds inhibit the different cell lines to a similar degree, indicating no cellular specificity; exceptions to this rule are chlorambucil, chlortetracycline and dexamethasone. Many of the lipophilic acids that are potent inhibitors of mammalian cell replication are also teratogenic. Exceptional compounds may not reach the embryo. We propose that a number of other lipophilic acids that are potent inhibitors and to which humans are frequently exposed should be tested for their teratogenic effect.

Teratogenic effects of nickel chloride on embryonic mice and its transfer to embryonic mice.

Abstract: Administration of nickel chloride to the pregnant mice on the seventh to eleventh day of their gestational period, resulted in significant embryotoxic effects in terms of an increased resorption rate, a decreased fetal weight, delay in skeletal ossification and high incidence of malformation. Among the cases of fetal malformation, the following malformations were observed to occur at a higher rate of incidence: acephalia, exencephaly, cerebral hernia, open eyelid, cleft palate, micromelia, ankylosis of the extremity, club foot and skeletal anomalies. Most skeletal anomalies were in the form of vertebral and/or rib fusions and were found mostly at thoracic and lumbar levels. The concentration of nickel retained in embryonic tissues was 800 times higher in the exposed compared to control groups and indicated that increased tissue levels of nickel chloride had a toxic influence on the developing embryo.

Equivalent ages in rat, mouse and chick embryos

Abstract: Data for estimating equivalent ages of rat, mouse and chick embryos are presented, using several sources from the literature. When the time of development of various embryonic structures is matched for the three species, the differences in time for the stages are primarily due to delays in development of the preimplantation blastulas of the rat and mouse in comparison with the incubated chick egg. Development from the blastula stage to completion of major organogenesis proceeds at approximately the same rate for all three species.

Retrospective study of the relationship between agricultural use of 2,4,5‐T and cleft palate occurrence in Arkansas

Abstract: The relationship between use of the herbicide 2,4,5-T in Arkansas and the concurrent incidence of facial clefts in children was studied retrospectively. Pertinent animal studies of the toxicity of 2,4,5-T, and related compounds were reviewed; embryotoxic and teratogenic effects, including cleft palate, have been noted in several mammalian species. Although newspaper articles appeared linking defoliant use with increased birth anomalies in South Vietnam in 1969, human epidemiology studies have not established a causal relationship between use of 2,4,5-T and birth defects. We felt that additional information concerning the human problem was needed to complement the experimental animal data, so we analyzed facial cleft rates and concurrent estimated use of 2,4,5-T in Arkansas during 1948-1974. Estimated level of exposure to 2,4,5-T was determined by categorizing the 75 Arkansas counties into high-, medium-, or low-exposure groups on the basis of their rice acreage during 6- or 7-year intervals beginning in 1943. A total of 1,201 cases of cleft lip and/or cleft palate for these 32 years was detected by screening birth certificates and checking the records of the Crippled Children's Services. Facial cleft rates, presented by sex, race, time period, and exposure group, generally rose over time. No significant differences were found for any race or sex combination. We believe that the general increase seen in facial cleft incidence in the high and low-exposure groups is attributable to better case finding rather than maternal exposure to 2,4,5-T.

Is there a fetal gasoline syndrome

Abstract: Two children from a small Amerindian community presented with profound retardation, initial hypotonia progressing to hypertonia, scaphocephaly, a prominent occiput, poor postnatal head growth, and additional minor anomalies. Abuse of gasoline by inhalation was a widespread problem in the community, and gasoline inhalation during the pregnancy could be documented in both of the pregnancies. We are raising the question as to whether inhalation of gasoline during pregnancy may be teratogenic in humans.

Teratogenic effects of the plant hormone indole-3-acetic acid in mice and rats.

Abstract: These studies evaluated the teratogenic potential of indole-3-acetic acid (IAA), a naturally occurring plant hormone, in CF-1 mice and Sprague-Dawley rats. Mice were given 5, 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. Rats were given 50, 200, or 500 mg IAA/kg/day by gavage on days 7 through 15 of gestation. IAA was teratogenic in mice and rats at 500 mg/kg/day; cleft palate was induced in both species at this dose level. In mice, other malformations including exencephaly, ablepharia, dilated cerebral ventricles, and crooked tail were also observed. Mice given 500 mg/kg of IAA gained less than control mice during gestation; no evidence of maternal toxicity was observed in rats. IAA did not cause fetal resorptions in either species and was not teratogenic at dose levels below 500 mg/kg.

Cytogenetics of extragonadal tumors.

Abstract: Tissue from six human extragonadal teratomas was obtained for cytogenetic study. These included two gluteal lesions in infant females, and one each of thyroid, mediastinal, sacral and gastric teratomas in males. Tissue culture characteristics indicated tumor growth. All tumors, except the mediastinal lesion showed the presumed karyotype of its host, XX or XY. The mediastinal mass was tetraploid XXYY and contained an X chromatin body and double Y bodies. Our data support the concept that extragonadal teratomas in males and females arise mitotically from diploid cells and are more similar to identical twins. No heterosexual (XX) tumors were seen in males which would be expected in parthenogenetic tumors. The sex chromatin positive tumors seen in earlier studies may have resulted from polvploidy. Thus, male and female extragonadal teratomas have a different origin from the postmeiotic ovarian teratomas.

The evolution of teratological testing

Abstract: The beginnings of mammalian experimental teratology in this century are briefly reviewed and it is noted that prior to 1960 a degree of sophistication in concept and technology had already been achieved. Thus, contrary to claims that teratology had its beginning with the thalidomide catastrophe, a modest but expanding activity and body of knowledge already existed before this unfortunate event. This activity and this knowledge, however, were largely confined to academic and research institute laboratories and made little impact on the agencies in medicine, government and industry which oversaw public health and safety and set policies intended to preserve them. No individual, group, or agency can rightly be blamed for not having sooner brought together the concepts and methodology needed for meaningful animal testing and the regulatory insignt and experience needed intelligently to apply test data to human safety evaluation and experience needed intelligently to apply test data to human safety evaluation. To accomplish this liaison seems to have required the largest toxicological catastrophe yet recorded in human history. The major events leading to formulation of the first standardized guidelines are reviewed, but it is emphasized that even today the best animal testing can only provide a limited statement of probability regarding human risk vis-a-vis safety.

Folate antagonism following teratogenic exposure to diphenylhydantoin

Abstract: Previous studies have reported indirect evidence for the mediation of folate antagonism in the induction of malformations by diphenylhydantion. We have demonstrated that a teratogenic regimen of folate-deficiency and antagonism using 9-methyl PGA in the rat produces significantly decreased rates of oxygen consumption in the maldeveloping embryos. The present study reports similar reductions in oxygen uptake by mouse embryos from mothers treated with teratogenic doses of diphenylhydantoin, and documents a significant depression of the actual folate levels in such embryos. The differences are less significant with lower doses of diphenylhydantoin, and do not occur with a nonteratogenic dose.

Neural tube closure defects caused by papaverine in explanted early chick embryos.

Abstract: Papaverine (50 micrograms/ml) preferentially inhibited uplifting of neural folds in explanted stage 8 chick embryos. Affected neuroepithelial cells often lost their wedge-shaped and elongated appearance. Also, luminal surfaces of most affected cells were smoother than usual as evidenced by the marked decrease in the number of cytoplasmic extensions, but the integrity of other structures (including cytoskeletal components) was not noticeably affected. The observed changes in cell surface topography were due, at least in part, to the imparied ability of apical microfilaments to contract and their eventual relaxation. The "relaxing" effect of papaverine on neural folds could be reversed by subsequent treatment with ionophore A23187. Since papaverine and ionophore A23187 are known to alter the normal distribution of intracellular Ca2+ and changes in cell surface topography are correlated with contractile activities of apical microfilaments, papaverine elicits neural tube closure defects by lowering intracellular free Ca2+ levels, thereby relaxing contracted apical microfilaments in neuroepithelial cells.

Correlation between mandibular retrognathia and induction of cleft palate with 6-aminonicotinamide in the rat

Abstract: A single injection of the niacin antimetabolite 6-aminonicotinamide (6-AN) late in gestation produces cleft palate in the rat. In order to achieve an understanding of the mechanism of induction of cleft palate, craniofacial growth and palate development were studied in Sprague-Dawley rats after treatment with 6-AN on day 15 of gestation. The rats were maintained on a high niacin diet (95 ppm) and subjected to three different teratogenic levels of 6-AN. The first group was injected with 8 mg/kg, the second was fasted and injected with 8 mg/kg and the third was treated with 16 mg/kg. The lowest teratogenic dose, 8 mg/kg, produced mild mandibular retrognathia on day 16, delayed shelf elevation a few hours and resulted in small rostral and small caudal clefts of the secondary palate. The moderate dose, 8 mg/kg with fasting, produced more severe mandibular retrognathia, delayed shelf elevation about 24 hours and resulted in 37% full clefts and 63% partial clefts of the palate. The highest teratogenic dose, 16 mg/kg, produced severe mandibular retrognathia, delayed shelf elevation by more than 24 hours and resulted in 100% full clefts of the palate. In each 6-AN group, the most severe mandibular retrognathia was present between days 16 and 17, the critical time for palate closure in the rat. Treatment with 6-AN also produced abnormality of the epithelial cells of the palate, the toothbuds and the nasal septum. Molar and incisor toothbuds were small and malformed, and the epithelial surfaces of the palate and the soft tissue nasal septum did not fuse.

A teratogenicity study on hydroxyurea and diphenylhydantoin in cats.

Abstract: Hydroxyurea, an antitumor drug and known teratogen in rat, miniature swine and dog, and diphenylhydantoin, a teratogen in mouse and rat, were assessed for teratogenic effects in cat. Pregnancies were induced, by synchronizing gonadotropin-stimulated estrus and ovulation with natural copulations. Hydroxyurea at 50 or 100 mg/kg, and sodium diphenylhydantoin at 1 or 2 mg/kg dosages, were administered orally in single daily doses from gestation days 10-22. Appropriate controls given empty capsules, were included for each drug. Cats were necropsied on gestation day 43. Fetuses were examined for external, visceral and skeletal malformations. Hydroxyurea at 50 mg/kg dose produced a low teratogenic activity and at 100 mg/kg a high incidence of non-pregnancy and resorptions with, consequently, fewer live fetuses. Diphenylhydantoin gave no clear evidence of teratogenicity at any test dose but was embryolethal at the maternally toxic dose of 2 mg/kg. So far, studies conducted suggest that the cat is a useful species for screening drugs and chemicals for their teratogenic potential.