ISSN:0040-3709    

DOI:10.1002/tera.1420470602

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

年代:1993

数据来源: WILEY

ISSN:0040-3709    

DOI:10.1002/tera.1420470603

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

年代:1993

数据来源: WILEY

ISSN:0040-3709    

DOI:10.1002/tera.1420470604

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

年代:1993

数据来源: WILEY

ISSN:0040-3709    

DOI:10.1002/tera.1420470605

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

年代:1993

数据来源: WILEY

摘要:

Abstract5‐Fluorouracil (5‐FU) inhibits the enzyme thymidylate synthetase (TS) which results in inhibition of DNA synthesis. 5‐FU is teratogenic in many species, inducing cleft palate, limb, and tail defects. In the present study, gestation day (GD) 14 embryonic rat craniofacial explants were exposed to 5‐FU in organ culture with increasing concentrations and durations of exposure. Palates exposed to 5‐FU were morphologically abnormal and craniofacial shape, size, and palatal fusion pattern were affected with the severity of effects dependent on concentration and duration of exposure. Cleft palate was induced in vitro as opposing palates overlapped in a narrowed oral cavity. Palates exposed to higher levels of 5‐FU were growth inhibited, but fused even though proliferation ceased and few cells were available to participate in elevation and fusion. This was demonstrated as a biphasic concentration‐response profile for palatal fusion in which 0.05 to 0.15 μg 5‐FU/ml produced decreasing rates of palatal fusion, while exposure to 0.15 to 3.0 μg/ml resulted in progressively increasing rates of fusion. The effects of 5‐FU were detected biochemically as a reduction in TS activity which was concentration and time dependent during the first 12 hours, with a return to control levels by 24 hours. During the first day, 5‐FU did not alter protein levels, but DNA levels significantly decreased at the high concentration, 2.0 μg/ml. After 5 days in culture, both DNA and protein decreased with increasing 5‐FU concentration and duration of exposure. Also by the end of the culture period,3H‐TdR incorporation had decreased in a concentration dependent manner. It is concluded that progressive inhibition of proliferation and growth in organ culture results in two different morphological outcomes: cleft palate resulting from a narrowed oral cavity and increased incidence of anterior palatal fusion under conditions of strong growth reduction. This study demonstrates that elevation and fusion can occur in the absence of growth and proliferation. Based on these observations, severe inhibition of growth or proliferation would not necessarily be sufficient to induce cleft palate. © 1993 Wiley‐Liss, Inc.This article is a US government work and, as such, is in the public domain in

ISSN:0040-3709    

DOI:10.1002/tera.1420470606

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

年代:1993

数据来源: WILEY

摘要:

AbstractPreviously we have isolated the monopotential chondrogenic cell line RCJ 3.1 C5.18 from the multipotential mesenchymal cell line RCJ 3.1 [Grigoriadis et al.: Endocrinology,125:2103–2110, 1989]. When cultured for approximately 20 days under appropriate conditions, these cells form cartilage nodules. In the present investigation, we have used this cell line to study the effects of all‐trans retinoic acid (RA) on chondroblast differentiation, cartilage formation, and cartilage degradation. Continuous exposure of cultures to RA (0.01–100 nM) inhibited chondroblast differentiation and glycosaminoglycan (GAG) accumulation in a dose‐dependent manner, without comparable effects on cell growth. Pulse treatment with RA for various 4 day periods during a 17–24 day culture period established that RA inhibited differentiation of chondroprogenitors at all periods tested. These effects were reversible, except for part of the effect on early chondroprogenitors. Treatment with RA on days 13–17 in 17 day cultures not only resulted in cessation of cartilage formation, but also in disappearance of pre‐existing cartilage nodules. We demonstrated that this was associated with RA‐induced downregulation of GAG synthesis and increased degradation of cartilage proteoglycans. Hence, the inhibitory effects of RA on cartilage formation consist of inhibition of chondroblast differentiation, inhibition of GAG synthesis by differentiated chondroblasts, and stimulation of cartilage proteoglycan degradation by differentiated chondroblasts and/or chondrocytes. These results indicate that the clonal monopotential chondrogenic cell line RCJ 3.1 C5.18 forms a good model system to study the effects of retinoids on cartilage differentiation, formation, and degradation. © 1993

ISSN:0040-3709    

DOI:10.1002/tera.1420470607

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

年代:1993

数据来源: WILEY

摘要:

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

ISSN:0040-3709    

DOI:10.1002/tera.1420470608

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

年代:1993

数据来源: WILEY

摘要:

AbstractThe possible involvement of the neurotransmitter serotonin (5‐HT) and its binding protein (SBP) in cardiac morphogenesis was studied using mouse whole embryo culture (together with immunocytochemistry or3H‐thymidine autoradiography) and a cell migration assay. Embryos were cultured before and during the period of endocardial cushion formation, embryonic (E) days 9–12, in the presence of 5‐HT, the monoamine oxidase (MAO) inhibitor nialamide, or an uptake inhibitor (fluoxetine or sertraline). For the migration assay, cells from the outflow tracts of E12 embryos were dissociated and placed in a chemotaxis chamber together with different concentrations of 5‐HT. E9 embryos cultured in the presence of 10 μM 5‐HT and nialamide exhibited intense 5‐HT immunoreactivity (5‐HT IR) throughout the myocardium. This staining was greatly diminished by fluoxetine, sertraline, or the absence of nialamide. As morphogenesis proceeded, myocardial staining in embryos exposed to 5‐HT became restricted to developing endocardial cushion forming regions and was more completely blocked by uptake inhibitors. No evidence for 5‐HT synthesis by myocardium was found at any age studied using the precursor L‐tryptophan. SBP was present in endocardial cushions in cultured and uncultured embryos.3H‐thymidine autoradiography demonstrated that both fluoxetine and sertraline inhibited proliferation of cardiac mesenchyme, endocardium, and myocardium. These effects were most pronounced when exposure began at E9 (prior to cushion formation). Dose‐dependent effects of 5‐HT on migration of outflow tract cells were also observed. Taken together, these results suggest that 5‐HT may play a role in cardiac morphogenesis during endocardial cushion for

ISSN:0040-3709    

DOI:10.1002/tera.1420470609

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

年代:1993

数据来源: WILEY

摘要:

AbstractSidedness of left/right asymmetric body structures is strongly biased in most animals by mechanisms that are not well understood. In rat embryos, axial rotation starts at the 9–10 somite stage and is almost completed at the 17–18 somite stage. As a result, the ventrally flexed tail (caudal part of the body) and chorioallantoic placenta on the yolk sac take up their position normally on the right side of the embryo. Because the tail and chorion become connected via the allantois around the time when axial rotation takes place, we hypothesized that the allantois and possibly its connection to the chorion is important in determining sidedness of the tail. In the present study, we tested this hypothesis by surgically removing either the allantois or chorion before axial rotation started. Embryos were explanted at 8 am on Day 9 of gestation (presomite stage), and either the allantois or chorion was removed using microforceps. Embryos were then cultured in rotating bottles, and sidedness of the tail, chorioallantoic placenta, and bulboventricular loop (heart) was determined after 50 hours (∼25–26 somite stage). Removal of the allantois (n = 55) resulted in absence of the umbilical cord and a 49.1% incidence of inverted tail; a chorioallantoic placenta‐like structure developed on the yolk sac in the normal position. Removal of the chorion (n = 114) resulted in absence of the chorioallantoic placenta and a 20.2% incidence of inverted tail; the allantois either floated in the extraembryonic coelomic cavity or reached the yolk sac but did not form a chorioallantoic placenta‐like structure. Sidedness of the heart was not affected in either group. These results indicate that removal of the allantois results in complete loss of control of tail sidedness, whereas removal of the chorion results in only a partial loss of control. An incidental finding was that an avascular area developed on the yolk sac around the chorioallantoic placenta. This area became larger when the allantois was removed but disappeared when the chorion was removed. © 1993 Wil

ISSN:0040-3709    

DOI:10.1002/tera.1420470610

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

年代:1993

数据来源: WILEY

摘要:

AbstractApproximately 50% ofiv/ivmice havesitus inversus(mirror image reversal of viscera) and 40% have heterotaxia (anomalous arrangement of viscera). The occurrence of heterotaxia is independent ofsitus. Using the cross‐intercross breeding system to put the iv gene on the SWV background, an occasional presumediv/ + mouse was found that had an IV (situs inversusand/or heterotaxic) phenotype. Testcrosses of these reversed animals indicated aniv/ + genotype. Since iv is linked tightly toIgh‐Con chromosome 12, we inferred the genotype with a polymorphism ofIgh‐Cdemonstrated using the polymerase chain reaction (PCR). This confirmed them to beiv/ +. The expression of the IV phenotype in animals heterozygous for theivgene may be due to an interaction ofivwith an autosomal recessive gene found in SWV. We have not found the IV phenotype in heterozygousiv/+mice following placement of theivgene on six other inbred strains. Rarely, we also found that presumed SWV +/+ mice had the IV phenotype. Test matings of these phenodeviants, corroborated by PCR, have confirmed them to be +/+. Although the phenotypes of the affected SWV +/+ andiv/ + mice resembled those found iniv/ivmice, the occurrence ofsitus inversusand heterotaxia were not independent of each other, and most of the SWV mice with the IV phenotype had heterotaxia withsitus solitus.This infrequent dominant expression of the iv gene has so far only been seen whenivis on the SWV background. These findings are consistent with the idea that this phenomenon is due to the interaction of theivgene with another gene found so far only in the SWV strain. © 1993 Wiley‐L

ISSN:0040-3709    

DOI:10.1002/tera.1420470611

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

年代:1993

数据来源: WILEY