摘要:

AbstractRetinoic acid (RA) has been shown to be teratogenic in many species, and 13‐cis‐RA is teratogenic in humans. Exposure to RA during embryonic morphogenesis produced a variety of malformations including limb defects and cleft palate. The type and severity of malformation depended on the stage of development exposed. The purpose of this study was to compare the effects of RA exposure in vivo on different stages of palate development. These results were compared to effects observed after exposure in organ culture. The vehicle used in RA dosing was also shown to be a major factor in the incidence of RA‐induced cleft palate. For the in vivo studies, RA (100 mg/kg) in 10 ml corn oil/kg was given p.o. on gestation day (GD) 10 or 12, and the embryos were examined on GD 14 and 16. Exposure to RA in an oil:DMSO vehicle resulted in much higher incidences of cleft palate than were observed after dosing with RA in oil only. After exposure on GD 10, to RA, small palatal shelves formed which did not make contact and fuse on GD 14. The medial cells did not undergo programmed cell death. Instead, the medial cells differentiated into a stratified, squamous, oral‐like epithelium. The RA‐exposed medial cells did not incorporate3H‐TdR on GD 14 or 16, but the cells expressed EGF receptors and bound125I‐EGF. In contrast, RA‐induced clefting after exposure on GD 12 did not involve growth inhibition. Shelves of normal size formed and made contact, but because of altered medial cell differentiation did not fuse. Medial cells differentiated into a pseudostratified, ciliated, nasal‐like epithelium. This response was produced in vivo at exposure levels which produced cleft palate, and after exposure of palatal shelves to RA in vitro from GD 12–15. The medial cells exposed on GD 12 incorporated3H‐TdR on GD 14, expressed EGF receptors, and bound125I‐EGF. The responses to RA which lead to cleft palate differed after exposure on GD 10 or 12, and the pathways of differentiation which the medial cells followed depended on the deve

ISSN:0040-3709    

DOI:10.1002/tera.1420400602

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEthylenethiourea (ETU) is a potent teratogen in the rat but. not in the mouse or any other species tested. Embryotoxic and teratogenic effects are produced in mice only after exposure to 10‐40 times the teratogenic dose of ETU in rats. This study was undertaken to determine whether the difference in sensitivity between rats and mice is due to differences within the embryo, to maternal metabolic differences, or both. Comparably staged rat and mouse embryos (gestation day 10.5 and 8.5, respectively) with intact extra‐embryonic membranes were maintained under identical conditions in whole embryo culture and exposed to static concentrations of ETU for 48 hours. The teratogenic effects of ETU were qualitatively similar in both species, characterized by excessive fluid accumulations in embryonic structures., The most common abnormalities were distended neural tube, especially in the hindbrain, and clear blisters on the caudal region. At least two times as much ETU was required to produce a similar incidence of abnormalities in mice as in rats. Thus, there is some intrinsic difference in the quantitative response of rat and mouse embryos to ETU, but it is insufficient to account for the in vivo discrepancy. The role of maternal metabolism in modifying the teratogenicity of ETU was assessed by adding hepatic S‐9 fractions from Aroclor 1254‐induced rats and mice to whole embryo culture. Rat S‐9 had no effect on ETU teratogenicity. Mouse S‐9 virtually eliminated the formation of abnormalities typical of ETU in both rat and mouse embryos. Decreased exocoelomic fluid osmolality, a physiological effect produced by ETU, also was not observed in embryos exposed to ETU and mouse S‐9. ETU‐typical defects were observed in embryos exposed to ETU and mouse S‐9 which had been treated with carbon monoxide to inactivate its monooxygenase system, indicating that the mouse S‐9 was metabolizing ETU. A surprising result was that adding mouse S‐9 to embryo cultures containing ETU resulted in the formation of abnormalities (principally open neural tube) that were not observed in in vitro rat or mouse embryos exposed to ETU alone, or in mouse embryos in vivo. We believe that the most likely cause of these abnormalities is a putative ETU metabolite, which is rapidly excreted by the dam in vivo, but accumulates to teratogenic co

ISSN:0040-3709    

DOI:10.1002/tera.1420400603

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe red nucleus of Swiss Webster mouse fetuses was examined for morphological changes following maternal ethanol exposure. Pregnant females were given a liquid diet containing 30% or 0% ethanol‐derived calories. Changes in numerical density of neurons and in neuronal nuclear volume were found in the rostral red (RR) nucleus of ethanol‐exposed pups but not in the caudal red (CR) nucleus. Because of the integrative nature of the RR, changes in neuronal morphology that might relate to synaptic connections could affect the behavioral response mechanisms of these off spr

ISSN:0040-3709    

DOI:10.1002/tera.1420400604

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractA summary is presented of previous studies by other investigators of human achondroplasia and dyschondroplastic animal models. In addition, studies previously reported from our laboratories are discussed, and they demonstrate that defective oxidative energy metabolism is present in mitochondrial preparations from achondroplastic human subjects and rabbits (ac/ac) with chondrodystrophy. The results of the studies support the hypothesis discussed fully in the manuscript that a partial defect in mitochondrial oxidative metabolism in achondroplastic subjects is expressed specifically in the growth plates of the long bones because this tissue has the lowest oxygen tension of any bodily organ undergoing active proliferation, thus leading to the achondroplastic phenotype in humans and the ac/ac rabbit. In the ac/ac rabbit phosphorylation at the cytochrome c oxidase region (site III) of the terminal respiratory system was shown to be absent in mitochondrial preparations from the livers of newborn ac/ac rabbits. Normal‐appearing littermates did not exhibit the defect. Studies of mitochondrial preparations from human skin fibroblasts (grown in tissue culture) from normal human subjects and subjects with homozygous achondroplasia demonstrated that concentrations of cytochrome a3were decreased approximately 80% in preparations from homozygous achondroplastic cells. Levels of cytochrome a3in heterozygous achondroplastic cells were intermediate between the levels in normal cells and homozygous achondroplastic cells demonstrating the effects of gene dosage. Determination of total heme a (as the pyridine hemochromogen) in the normal and achondroplastic preparations from human subjects showed that the observed decrease in concentration of cytochrome a3in the achondroplastic preparations was due to an absence of cytochrome a3and not to a change in its absorbancy (extinction coefficient

ISSN:0040-3709    

DOI:10.1002/tera.1420400605

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractThe effects of heat shock on cell cycling in the mammalian neuroectoderm were determined by applying heat shocks to cultured rat embryos at the neural plate stage, as part of a study on the teratogenic effects of heat shock on neural development. The heat shocks had been characterized previously (Walsh et al.:Teratology36:181‐191, 1987) with respect to their effects on the gross morphological development of the rat embryos. The effects on cell cycling were observed in DNA histograms of neural plate cells recorded in a flow cytometer after staining with DAPI. The mild heat shock (42°C for 10 min) arrested cells at entry to S phase. The teratogenic heat shock (43°C for 7.5 min) arrested cells at entry to S phase also but for a longer time and inhibited cycling through S phase. After each arrest, a synchronized peak of cells later entered S phase and progressed through the cycle. The induced‐thermotolerance heat shock, which was the mild heat shock followed after an interval by the teratogenic heat shock, showed that pre‐treatment with the mild heat shock reduced the magnitude of the response to the teratogenic heat shock. The cell‐cycle inhibitor ICRF 159 showed the effects on cycling rates of the heat‐shock treatments. The arrest of cells at entry to S phase by heat‐ shock may function to prevent cells entering DNA synthesis under non‐optimal conditions. We report estimates of proportions of nonproliferative cells in the neural plate of

ISSN:0040-3709    

DOI:10.1002/tera.1420400606

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractEthanol and GABA (γ‐aminobutyric acid) and their interaction on36Ci−influx were analyzed in cultured embryonic palate and limb mesenchymal cells in order to determine whether ethanol exerts its teratogenic action through a GABA receptor involved in embryogenesis. Cl−transport in secondary cultures of C57BL/6 palate mesenchymal cells was shown to consist of three systems including the electroneutral Cl−HCO3−exchange (50%) and Na+/K+/Cl−cotransport (30%) pathways and the voltage‐dependent Cl−channel (20%). Treatment with DIDS (4,4′‐diisothiocyanostilbene 2,2′‐disulfonic acid) or SITS (4‐acetamido‐4′‐isocyano‐stilbene‐2,2′ disulfonic acid) in SWV palate cells inhibited the Cl−HCO3−exchange pathway, while treatment with DIDS and bumetanide inhibited both the exchange and cation cotransport pathways, the residual Cl−influx inferred to be the electrogenic pathway. Inhibition of Cl−transport by anthracene‐9‐carboxylic acid confirmed the presence of the electrogenic Cl−pathway. It was observed that the rate of Cl−transport was significantly greater in palate cells of C57BL/6 mice than those of SWV mice. Also the rate of Cl−transport was significantly greater in secondary cultures of palate cells from C57BL/6 mice than from primary cultures of limb cells from the same strain. No evidence could be obtained that ethanol (10 to 100 mM) or GABA (3 × 10−5M) or their combination stimulated total Cl−influx in either C57BL/6 or SWV palate mesenchymal cells, putative voltage‐dependent Cl−influx in C57BL/6 palate cells, or tota

ISSN:0040-3709    

DOI:10.1002/tera.1420400607

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractCells from 4‐day chicken embryo limb buds plated as micromass cultures differntiate and form cartilage nodules after a 5‐ to 6‐day growth period. The innate ability of these cells to biotransform compounds, such as cyclophosphamide (CP), into reactive metabolites is apparently inadequate. Protocols used rat liver S9 from Aroclor 1254 pretreated (PCB) rats or hepatocytes from control rats or polychlorinated biphenyls (PCB)‐pretreated rats and were added to micromass cultures with CP causing concentration‐related toxicity in the cell cultures. Coculturing chicken limb bud cells with PCB‐hepatocytes was the most efficient method, yielding an IC50of 2 μg CP per ml. Toxic CP metabolites accumulated in the medium of PCB‐hepatocyte cultures and were quite stable. The toxicity of bioactivated CP was nearly identical for both proliferation and cartilage proteoglyca

ISSN:0040-3709    

DOI:10.1002/tera.1420400608

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractAdenosine deaminase (ADA) catalyzes the hydrolytic deamination of adenosine (or 2′‐deoxyadenosine) to inosine (or 2′‐deoxyinosine). Previously, we have shown that ADA activity is subject to strong cell‐specific developmental regulation in placental tissues of mice between days 6 and 11 of gestation (Knudsen et al.:Biology of Reproduction39:937–951, 1988). In the present study, we examined the effects of intrauterine exposure to 2′‐deoxycoformycin (dCF; pentostatin), a potent irreversible inhibitor of ADA, on early postimplantation development. Deoxycoformycin was administered to pregnant ICR mice as a single intraperitoneal injection at a dose of 5 mg/kg on one of days 6 through 11 of gestation (plug day 0). A marked increase in the incidence of implantation site resorptions was observed following treatment specifically on days 7 (61% resorbed) or 8 (78% resorbed). No effect was observed following treatment on days 6, 9, 10, or 11. ADA‐immunoreactive protein was shown, by ABC‐immunoperoxidase staining on days 7 or 8 of gestation, to be present at high levels in decidual cells of the antimesometrial region but at below‐detectable levels in the embryo. Treatment of pregnant dams with dCF on day 7 produced a complete (>99%) inhibition of ADA activity in the antimesometrial decidua by 30 min, induced excessive cell death in the prospective neural plate and primary mesenchyme of the trilaminar disc by 6 h, and arrested embryonic development at an early somite stage. These results suggest that the antimesometrial decidua plays a protective role in preventing an inappropriate accumulation of endogenous ADA substrates in

ISSN:0040-3709    

DOI:10.1002/tera.1420400609

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractSkeletal anomalies present in trisomy 16 in the mouse—an animal model of human trisomy 21—are described. Altogether 27 fetuses with trisomy 16 and 118 chromosomally balanced siblings were examined radiographically and by alizarin staining on day 20 of gestation; the radiographs were analyzed by computer‐aided densitometry and structural differentiation. Extensive asymmetry or abnormal fusion of the vertebral centers and alterations of the vertebral arches were observed along with rib malformations (rib‐vertebra syndrome). The skull primarily exhibited anomalies of the occipital bone. Ossification of the humerus, femur, and tibia was characterized by reduced mineralization. Typical, fracture‐like alterations affecting only the tibia were also observed. Measurement of the lengths of the humeri of fetuses of comparable weight revealed a growth retardation not correlatable with the degree of mineralization. The significance of these skeletal abnomalies with regard to the trisomy 21 syndrome is

ISSN:0040-3709    

DOI:10.1002/tera.1420400610

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY

摘要:

AbstractTrisomy 1 embryos consistently show eye defects (e.g., aphakia, microphakia, retention of lens stalk). To determine if the plane of division of mitotic figures is abnormal in the eyes of these animals, trisomic embryos (9.5 through 12 gestational days) were produced from mice doubly heterzygous for Robertsonian translocation chromosomes [Rb(1.3)/Rb(1.10)]. To accommodate for the known delay in trisomic embryo development, animals were grouped according to stages of eye development rather than to gestational age. Serial sections were evaluated without knowledge of karyotype for orientation of mitotic figures (parallel, perpendicular, oblique) in lens, optic cup, and diencephalon. Location of mitotic figures was scored as apical (nearest the lumen), middle, and basal. Numerous anomalies were noted in trisomic eye development. No difference was found between orientation of mitotic figures in the lens and optic cup of trisomy 1 and normal embyros. Location of mitotic figures in trisomy 1 lens was significantly different from that of normal littermates. The data confirm earlier studies that trisomy 1 affects the eye, and they tend to corroborate evidence that this trisomy affects the lens more than it affects the optic cup.

ISSN:0040-3709    

DOI:10.1002/tera.1420400611

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1989

数据来源: WILEY