Comparative teratogenicity of triamcinolone acetonide, triamcinolone, and cortisol in the rat

Pregnant rats were injected im with 0.5 mg/kg triamcinolone acetonide (TAC) on day 12, 13, or 14 of gestation and the fetuses were examined for cleft palate on day 20. All three TAC-treated groups showed an increased proportion of fetuses with cleft palate compared to an untreated control group. Only the group treated on day 13 showed a significant increase in the proportion of litters affected. This indicates that day 13 of gestation is the most sensitive day for cleft palate induction by TAC in the rat. Pregnant rats were then treated on day 13 of gestation with either TAC, triamcinolone (TA), or cortisol. TAC was 59 times as potent as TA in inducing cleft palate, with ED50 values of 1.1 mg/kg and 65 mg/kg respectively. Cortisol induced a significant increase in cleft palates at 500 mg/kg, but the efficacy of this compound was too low to calculate an ED50 and relative teratogenic potency value. Other developmental abnormalities including umbilical hernias, resorption, and fetal death resulted from TAC treatment. Fetal growth retardation was produced by all three compounds. The rank order of teratogenic potency was determined to be TAC greater than TA greater than cortisol.     

Craniofacial abnormalities induced by retinoic acid: a preliminary histological and scanning electron microscopic (SEM) study.

Exogenous retinoic acid has been found to be teratogenic in animals and man. Craniofacial defects induced by retinoic acid have stimulated considerable research interest. The present report deals with scanning electron microscopical observations of the craniofacial region concurrent with histological examination of craniofacial dysmorphism induced in rat embryos following maternal treatment treated with varying dosages of all-trans-retinoic acid (tretinoin). Two groups of pregnant rats were treated with rat embryos exposed to retinoic acid suspended in corn oil (100 mg/kg b.w. on gestational day 11.5 and 50 mg/kg b.w. on gestational day 10, 11 and 12 respectively). A third group was treated with corn oil (vehicle) while a fourth group remained untreated. A wide spectrum of congenital abnormalities, including exophthalmos, microphthalmia and anophthalmia, maxillo-mandibular dysostosis, micrognathia of both maxilla and mandible, cleft palate, subdevelopment of ear lobe, preauricular tags and macroglossia, were observed in the offspring of retinoic acid treated animals. The abnormalities were both time and dosage dependent, and characteristic of Treacher Collins syndrome when retinoic-acid was administered on gestational day 11.5. In contrast, when retinoic acid was administered were on gestational days 10-12, the defects were similar to those seen in the first and second pharyngeal arch syndrome, as well as in the oculo-auriculo-vertebral spectrum. Whereas our data support the hypothesis that all-trans retinoic-acid disturbs growth and differentiation of several embryonic cell types essential for normal craniofacial development, its mechanism of action remains unclear.     

Simultaneous quantification of retinol, retinal, and retinoic acid isomers by high-performance liquid chromatography with a simple gradiation.

A new method of high-performance liquid chromatography (HPLC) analysis to quantify isomers of retinol, retinal and retinoic acid simultaneously was established. The HPLC system consisted of a silica gel absorption column and a linear gradient with two kinds of solvents containing n-Hexane, 2-propanol, and glacial acetic acid in different ratios. It separated six retinoic acid isomers (13-cis, 9-cis, all-trans, all-trans-4-oxo, 9-cis-4-oxo, 13-cis-4-oxo), three retinal isomers (13-cis-, 9-cis-, and all-trans) and two retinol isomers (13-cis- and all-trans). Human serum samples were subjected to this HPLC analysis and at least, all-trans retinol, 13-cis retinol, and all-trans retinoic acid were detectable. This HPLC system is useful for evaluating retinoic acid formation from retinol via a two-step oxidation pathway. Moreover, it could be applied to monitoring the concentrations of various retinoids, including all-trans retinoic acid in human sera.     

Effects of retinoids on in vitro and in vivo IgE production

BACKGROUND: Retinoids modulate the growth and number of different cell types, including B cells. We could previously show that retinoic acid (RA) strongly inhibits CD40 + IL-4-mediated IgE production in vitro. The aim of the present study was to extend these findings regarding the potential use of retinoids for the treatment of allergic diseases. METHODS: In vitro IgE production was studied in anti-CD40 + IL-4-stimulated peripheral blood mononuclear cells (PBMC) from allergic donors in the presence of 10(-15)-10(-5) M all-trans and 13-cis RA and in ovalbumin (OVA)-sensitized BALB/c mice treated with RA (20 mg/kg) before and during sensitization. IgE and IgG1 levels were determined in the sera of the mice at day 21 after 2 injections (days 1 and 8) of aluminum hydroxide-absorbed OVA. RESULTS: All-trans and 13-cis RA inhibited in vitro IgE production from PBMC in a dose-dependent manner, but were more efficient in atopic dermatitis patients with low total serum IgE levels (< 400 kU/ml), maximal inhibition for all-trans RA at 10(-7) M (87%) and for 13-cis RA at 10(-5) M (96%) compared to patients with high serum IgE levels (>2,000 kU/ml), maximal inhibition for both all-trans and 13-cis RA at 10(-5) M (53 and 39%, respectively). In contrast, the in vivo data from OVA-sensitized mice revealed comparable total IgE and IgG1 levels in control versus all-trans RA or CD336-treated groups, specific IgE was even higher in the CD336-treated group (n = 10, 2,814 ng/ml), and was comparable in mice treated with OVA alone or with additional all-trans RA (n = 10, 1,447 and 1,354 ng/ml, respectively). CONCLUSIONS: These results indicate that the efficacy of retinoids to inhibit IgE production in vitro depends on the frequency of switched cells in the peripheral blood and that in an in vivo model using OVA-sensitized mice, retinoids fail to inhibit IgE production.     

Suppression by cyclohexanetriones of retinoic acid-induced cartilage degradation in vitro and teratogenicity in vivo

In cultured fetal rat bones, cyclohexanetriones that stimulate prostaglandin synthesis inhibited retinoic acid-induced cartilage degradation in a dose-dependent manner. The inhibition by the cyclohexanetrione Ro 31-0521 was reversible, indicating that the effect was not due to cytotoxicity. Excess retinoic acid is teratogenic in rats and adversely affects the normal differentiation of various morphogenetic systems, depending on the time of administration. The following retinoic acid-induced malformations were suppressed by Ro 31-0521: malformations of long bones and of apical phalanges induced on days 13 and 15 of gestation, respectively; spina bifida and tail malformations induced on day 11 of gestation and cleft palate induced on day 15 of gestation. However, cleft palate and other head malformations including exencephaly induced by retinoic acid on day 11 of gestation were not suppressed but even increased by Ro 31-0521. At a high dose, Ro 31-0521 given alone on day 11 of gestation was embryolethal and teratogenic but was not on the tested other days, indicating that the cyclohexanetrione at specific stages and doses also interfered with normal morphogenesis like retinoic acid. Assuming that stimulation of prostaglandin synthesis is the main biological effect of the cyclohexanetriones, our findings suggest that prostaglandins may be involved in mediating retinoid action.     

Production of congenital limb defects with retinoic acid: Phenomenological evidence of progressive differentiation during limb morphogenesis

Summary Maternal administration of a single dose of retinoic acid (vitamin A acid, 100 mg/kg) on either the 11 th, 11 1/2, 12th, 12 1/2, 13th or 13 1/2 day of gestation produced phocomelia or partial phocomelia in ICR/DUB fetuses. The results depended upon the time of treatment and two gradients of effect were produced: 1) cranio-caudal gradient, since forelimb defects resulted from treatment between days 11 and 13, while similar hindlimb abnormalities were produced by administration of retinoic acid 12 to 24 hours later: 2) proximo-distal gradient, due to the heterogenous sensitivity among individual bones of the limb. In the forelimb, early treatment (11th day) produced humero-ulnar defects and later treatment (12th day) ulnoradial defects. A similar proximo-distal gradient was observed in the hindlimb. The use of teratological studies as a tool to assist morphogenetic investigation is discussed.This work was supported by NIH-Grant No. HD-06550 awarded to Dr. Kochhar while at the University of Virginia, Charlottesville, Va.     

Estimation of creatine phosphokinase and hydroxyproline in the developing limb: its use in evaluating the effect of teratogens on myogenesis and chondrogenesis

Forelimbs of mouse fetuses were examined for tissue-specific, drug-induced alterations in their biochemical composition. The activity of the enzyme creatine phospholinase (CPK; to estimate myogenesis) and the content of hydroxyproline (HP; to estimate chondrogenesis) were compared in homogenates of control and treated mouse-fetus forelimbs on day 14 of gestation. In addition, the content of DNA, RNA, and protein was also measured. Injection of 6-aminonicotinamide (6-AN) (15 mg/kg) on day 10 resulted in an overall growth retardation in day 14 fetuses and all biochemical parameters tested were reduced. The ratio of PH:CPK was unaffected by 6-AN treatment. Retinoic acid (vitamin A acid; 100 mg/kg), administered to pregnant female mice on day 10, produced severe forelimb defects and resulted in a signific 10 resulted in an overall growth retardation in day 14 fetuses and all biochemical parameters tested were reduced. The ratio of PH:CPK was unaffected by 6-AN treatment. Retinoic acid (vitamin A acid; 100 mg/kg), administered to pregnant female mice on day 10, produced severe forelimb defects and resulted in a signific 10 resulted in an overall growth retardation in day 14 fetuses and all biochemical parameters tested were reduced. The ratio of PH:CPK was unaffected by 6-AN treatment. Retinoic acid (vitamin A acid; 100 mg/kg), administered to pregnant female mice on day 10, produced severe forelimb defects and resulted in a significant reduction in day 14 forelimb HP and RNA content, without altering CPK, DNA, or protein; thus, the HP:CPK ratio was decreased. These results indicated that 1) 6-AN nonspecifically retards growth and cyto-differentiation in limbs; 2) retinoic acid inhibits synthesis of collagen and RNA; 3) retinoic acid has a differential effect upon chondrogenic and myogenic tissues of the limb, and 4) the comparison of HP content and CPK activity in tissue homogenates is an acceptable method of evaluating teratogenic compounds for selective effects.     

Visceral heterotaxy syndrome induced by retinoids in mouse embryo.

Visceral heterotaxy syndrome causes abnormal arrangement of thoracoabdominal organs and severe complex cardiac anomalies by abnormal laterality. The purpose of the present study is to analyze the incidence and pattern of heterotaxy syndrome in etretinate and all-tran retinoic acid treated pregnant DDY mice. Pregnant DDY mice were intragastrically given a single dose of 15 mg/kg of etretinate at day 6, 7 of gestation, 30 mg/kg of etretinate at day 7 of gestation and 20 mg/kg of all-trans retinoic acid at day 7 of gestation. The incidence of visceral heterotaxy was highest in the etretinate 15 mg/kg treated group on day 7 of gestation (38.5%). The major cardiovascular anomalies in heterotaxy syndrome were common atrium, common atrioventricular valve, atrioventricular septal defect, transposition of great arteries, pulmonary atresia, pulmonary artery hypoplasia and aortic arch anomalies. Atrial situs of heterotaxy syndrome were right isomerism, solitus-like, inversus-like and left atrial aplasia, but right isomerism was observed most frequently. The results suggest that retinoic acid exerts a significant effect on the determination of atrial situs during the development of mouse embryo.     

Histological observations of palatal malformations in rat embryos induced by retinoic acid treatment.

Malformations of the palate were induced in white rat embryos following maternal exposure to retinoic acid (tretinoin). Five experimental groups and the controls were treated by the following protocol: Group 1: pregnant rats received 100 mg retinoic acid (RA)/kg b.w. suspended in corn oil on gestational day (GD) 11.5; Group 2: 20 mg RA/kg b.w. from GD 8-12; Group 3: 20 mg RA/kg b.w. from GD 7.5-11.5; Group 4: 100 mg RA/kg b.w. on GD 10-11; Group 5: 100 mg RA/kg b.w. on GD 10 and 12; Group 6 received corn oil vehicle from GD 7-14.5; and Group 6: served as non-injected controls. In all retinoic acid treated groups, varying degrees of clefts with occasional attempts of fusion were noted. The severity and frequency of the malformations were dependent on dosage or gestational day of drug treatment. Our results indicate that RA, even at the lowest dose tested (20 mg/kg b.w.) severely affects the various tissues constituting the embryonic palatal shelves by altering cell interaction and possibly programmed cell death. These events would then result in lack of or inadequate differentiation with subsequent formation of aberrant craniofacial architecture.     

Enhancement of the expression of activation markers on human peripheral blood mononuclear cells by in vitro culture with retinoids and carotenoids

Retinoids (retinol, retinal, retinoic acid, retinyl beta-glucuronide, and 13-cis retinoic acid) and carotenoids (beta-carotene and canthaxanthin) were evaluated for their immunomodulatory effects on human peripheral blood T-lymphocyte subpopulations and natural killer (NK) cells. Peripheral blood mononuclear cells (PBMC) from healthy young volunteers were isolated and incubated for 72 hours at various levels of retinoids and carotenoids including a physiological concentration (10(-8) M). Expression of surface antigens for total T cells, T-helper and T-suppressor cells, and activation markers (transferrin receptor, HLA-Dr antigen, and interleukin 2 receptor) were analyzed with an EPICS V flow cytometer. Retinoic acid and 13-cis retinoic acid (13-cRA) produced significant increases in the percentage of cells with markers for total T-helper cells, with a minimal effect on percentage of lymphocytes with markers for NK cells. However, beta-carotene (BC), canthaxanthin (CTX), and retinyl beta-glucuronide (RBG) dramatically increased the percentage of PBMC with markers for NK cells and produced a smaller increase in lymphocytes with surface antigens identifying them as T-helper cells. Furthermore, retinol and retinal did not show significant change either in the percentage of lymphocytes with markers for T-helper cells or in the helper/suppressor ratio. An increase in the expression of HLA-Dr antigen and transferrin receptors was greater when cells were incubated with 13-cRA than with either BC, CTX, or RBG, while carotenoids produced a greater increase in the expression of IL-2 receptors than 13-cRA. Our study indicates that both retinoids and carotenoids might be activating different subpopulations of immune cells.     

腭裂小鼠牙胚发育中β-连环蛋白的表达

背景：牙齿发育生物学中信号传导是热点问题,β-连环蛋白是Wnt信号传导通路中的关键效应因子,其在发育的牙胚中有普遍表达,并且在内釉上皮、釉结、星网状层、中间层的表达有时空变化。 目的：通过苏木精-伊红染色和免疫组化技术,观察牙胚在维甲酸诱导腭裂发生中的形态学变化及β-连环蛋白的表达变化。 方法：选取C57BL/6J近交系小鼠,按雌雄比2∶1于晚8时合笼,次日8时检查雌鼠,发现阴栓视为妊娠,定为E0 d。18只孕鼠随机分为3组：在E10 d,实验组以维甲酸100 mg/kg对孕鼠行一次性灌胃,制备腭裂动物模型;植物油对照组给予10 mL/kg橄榄油灌胃;空白对照组不做任何处理。 结果与结论：β-连环蛋白在空白对照组E13 d牙胚蕾状期、E14 d帽状期、E16 d钟状期上皮内均有表达,且空白对照组的表达随着牙胚发育的成熟而逐渐增加,实验组的变化趋势与空白对照组相同。3个时期的实验组β-连环蛋白在牙胚中的表达水平均高于空白对照组,植物油对照组和空白对照组表达无明显差异。提示维甲酸在诱导腭裂发生过程中,可能通过干扰上皮-间充质间的相互作用,上调β-连环蛋白在牙胚中的表达,使牙胚发育受阻。     

Mandibulofacial dysostosis (Treacher Collins syndrome): a new proposal for its pathogenesis

Acute exposure to 400 mg/kg 13-cis retinoic acid (13-cis RA, isotretinoin, Accutane) on the ninth day postfertilization in mice (a time that corresponds to the fourth week postfertilization in humans) results in malformations that characterize mandibulofacial dysostosis (MFD, Treacher Collins syndrome). Deficiencies in the infraorbital region and in the mandibular ramus and condyle, abnormalities of the secondary palate, and external ear malformations were observed. Light and scanning electron microscopic analyses of affected embryos illustrate that within 12 hours of maternal 13-cis RA treatment, markedly excessive (possibly premature) cell death occurs in regions where some of the cells are normally destined to undergo programmed cell death. Previous studies with retinoids have shown that they labilize lysosomal membranes and expand and strengthen regions of programmed cell death. Of particular interest for this study was cell death occurring in the dorsal (proximal) aspects of the maxillary and mandibular prominences of the first visceral arch, the second visceral arch, and the first visceral cleft, areas that correspond to the locations of the first and second arch ectodermal ("ganglionic") placodes and first closing membrane, respectively. The derivatives of this region are those that are severely affected in MFD. As described in previous reports from this laboratory, 13-cis RA is known to interfere with neural crest cells, resulting in major craniofacial malformations. However, the exposure times involved were earlier than those described herein. It is hypothesized that effects on the first and second arch ectodermal placodal cells at a time following the release from the neural folds of neural crest cells into the developing cranial region are of great significance in the pathogenesis of MFD. This is in contrast to the prevailing hypothesis that these malformations are the direct result of a primary interference with neural crest cells.     

Teratogenic profile of retinylidene methyl nitrone and retinol in Swiss-Webster mice

A single oral dose of 75 mg/kg of all-trans-retinol or all-trans-retinylidene methyl nitrone, retinoids with potential cancer chemopreventive properties, on one of five successive days of embryogenesis resulted in a shift in the pattern of developmental anomalies in fetal mice. Treatment on days 7, 8, or 9 with retinal primarily induced malformations of the head whereas treatment on day 11 induced bilateral forelimb reduction defects. Treatment on day 8 with either retinoid produced the highest in utero death rate. Intubation of either retinoid on day 10 failed to induce a significant increase in the number of litters containing offspring with malformations, and the embryonic death rate declined to control values. The malformations induced by administration of either retinoid were similar, but retinol was always associated with a higher total percentage of malformed offspring. The similar teratogenic profile of these two retinoids may be related to their in vivo biotransformation to all-trans-retinoic acid.     

Cardiac laterality and ventricular looping in retinoic acid-treated rat embryos.

To determine the ventricular looping pattern in relation to cardiac laterality, we studied rat embryos treated with retinoic acid (RA). A total of 243 Wistar rat embryos from an in vivo treated group (a single dose of 20-40 mg/kg all-trans RA administered to pregnant rats on day 6.5 to 9.5) and 29 control embryos were examined on day 13 of gestation. Twenty-nine embryos from the in-vitro treated group (treated by all-trans RA at 2 x 10(-7) M for 6 hr on day 9.0 or 9.5 during the entire embryo culture for 72 hr) and seven control embryos were examined on day 12 of gestation. Abnormalities in cardiac laterality and ventricular looping were found in the in-vivo groups treated on day 8.5 and 8.75 and in the in-vitro group on day 9.0. Among 25 animals with abnormal laterality, right isomerism was the most common feature (22 cases), while the type of ventricular looping varied. Cases with normal laterality had a low incidence of abnormal looping (1.4%). In rat embryos treated with all-trans RA, normal cardiac looping was expected when cardiac laterality was normal. But in cases with abnormal laterality, the type of abnormal ventricular looping was unexpected.     

All trans retinoic acid interfering with palatal development. Scanning electron microscopical and light microscopical observations on embryonic rat palate

Diverse studies on retinoic acid teratogenesis, during the recent years, indicate that the drug's analogues target on diverse cell population during differentiation in mammals. During an extended teratological protocol concerning retinoic acid influence in diverse embryonic tissue differentiation in experimental animals we studied all-trans-retinoic acid's influence on palatal development in the white rat embryo. For this purpose, six groups of white rat embryos were studied: Group 1 was treated with 100 mg/kilogram of body weight (k.b.w.) on gestational days (g.d.) 10th and 11th, Group 2 was treated with 100 mg all-trans-retinoic acid/k.b.w. on g.d. 11.5, Group 3 was treated with 50 mg all-trans retinoic acid/k.b.w. on g.d. 10th, 11th and 12th, Group 4 was treated with 50 mg all-trans-retinoic acid/k.b.w. on g.d. 11th and 12th, Group 5 was treated with 20 mg all-trans-retinoic acid/k.b.w. on g.d. 7.5, 8.5, 9.5, 10.5 and 11.5, Group 6 remained untreated. Embryonic heads aged 20 days were observed by light microscopy and scanning electron microscopy. In all treated groups clefts and malformations concerning the differentiation of palatal cell populations were observed. All our findings were compared with normal palatal morphology of untreated "control" embryos. Among the malformations, median clefts were observed, extended along only a part of the primary and all the secondary palate for group 2, the primary and secondary palate for groups 1, 3 and 5 while on group 4, an irregularity of the median palatal raphe and rugae were combined with a median incomplete cleft extended between the primary and secondary palate. Our results are discussed in relation with the international literature results.     

桉叶油对维甲酸干扰大鼠胚胎植入及生长发育的影响

目的探讨桉叶油对维甲酸干扰大鼠胚胎植入及生长发育的影响。方法 SD孕鼠42只,随机分为6组,FA组正常对照组、溶剂组(花生油+RA)、3个实验组(桉叶油高、中、低剂量+RA)及RA组。溶剂组用花生油2ml/只于孕第7~14天灌胃,每天1次,孕第10天维甲酸40mg/kg灌胃1次。桉叶油3个剂量组分别用300mg/kg、200mg/kg、100mg/kg的桉叶油于孕第7~14天灌胃,每天1次,孕第10天维甲酸40mg/kg灌胃1次。RA组用40mg/kg的维甲酸于孕第10天灌胃1次。正常对照组给予自由摄食饮水。各组于孕21d早上处死孕鼠,取胚胎,记录孕鼠体重,子宫重,胎盘重。计胚胎植入总数,吸收胎数、活胎数、死胎数。观察胚胎外形,并测量胎鼠体重、身长、尾长。结果正常对照组、桉叶油+RA和溶剂+RA组孕鼠增重、子宫重、胎盘重与RA组比较均无差异;溶剂+RA组的孕鼠的胎盘重较其他各组低,与RA和桉叶油+RA各组比较差异无显著性,与正常对照组比较有差异(P0.05)。正常对照组的活胎率[(97.3±4.6)%]较灌胃维甲酸各组的活胎率高(P0.05),吸收胎率[(2.6±4.6)%]和畸形率(0)较灌胃维甲酸各组低(P0.05),死胎率为0;在灌胃维甲酸各组中,桉叶油高[(79.6±14.5)%]、中[(67.6±30.8)%]剂量组的活胎率较RA[(58.6±26.6)%]组高,但比较无差异;畸胎率[(44.5±41.6)%;(57.5±35.1)%]较RA[(68.1±43.6)%]组低,但差异无统计学意义。灌胃维甲酸各组的吸收胎率比较无差异。正常对照组的胎鼠体重、身长、尾长均值明显高于灌胃维甲酸各组胎鼠的体重、身长、尾长均值(P0.05);在灌胃维甲酸各组中,桉叶油各组胎鼠体重、身长的均值明显高于RA组和溶剂对照组(P0.05);溶剂对照组胎鼠体重、身长、尾长与RA组比较无差异;桉叶油各组胎鼠尾长的均值均高于RA组,但比较无差异。结论维甲酸干扰了大鼠胚胎的植入和发育,桉叶油对RA干扰大鼠胚胎植入有一定的拮抗作用,对RA引起的胎鼠生长发育迟缓有一定的抑制作用。     

The effects of cyclophosphamide, melatonin and carvedilol on neural tube and skeletal system of mice fetuses in prenatal period

Cyclophosphamide (CP) as an alkylating agent is used for treatment of cancer and to prevent rejection of tissue transplantation. There are many reports that the teratogenic effects of cyclophosphamide can be prevented by application of antioxidant drugs and stimulation of the maternal immune system. Also, there is some evidence that melatonin and carvedilol are antioxidant.Therefore, in this study, the prophylactic effects of melatonin and carvedilol on teratogenic effects of CP was compared. This study was performed on 31 pregnant mice that were divided into six groups. The control group received normal saline and test groups received CP (20 mg/kg), carvedilol (5 mg/kg), melatonin (10 mg/kg), CP (20 mg/kg) pluscarvedilol (5 mg/kg) and CP (20 mg/kg) plus melatonin (10 mg/kg) intraperitoneally on the 10th day of gestation, respectively. Fetuses were collected on the 19th day of gestation and after determination of weight and length; they were stained by Alizarin red-Alcian blue method. Cleft palate, spina bifida and exencephalyincidence were 62.79%, 62.79% and 30.23% in fetuses of mice that received only CP. Cleft palate,spina bifida, exencephaly, and incidence were 45.45%, 9.09% and 0% in group which received CP plus carvedilol (5 mg/kg), respectively.However, cleft palate, spina bifida and exencephalyincidence were 62.5%, 45.83% and 4.16% range in the group which received CP plus melatonin (10 mg/kg), respectively. In addition, theincidence of skeletal anomalies including limb, vertebral, and sternaldefects were decreased by melatonin and carvedilol. The mean weight and length of animal fetuses that had received melatonin and carvedilol were significantly greater than those receiving only CP. It is concluded; carvedilol has a significant effect in preventing CP-induced malformations and in cases like CP-induced exencephaly, cleft palate and spina bifidahas better prophylactic effect than melatonin, but this improvement is not significant.     

Characterization of three RXR genes that mediate the action of 9-cis retinoic acid.

An understanding of the differences and similarities of the retinoid X receptor (RXR) and retinoic acid receptor (RAR) systems requires knowledge of the diversity of their family members, their patterns of expression, and their pharmacological response to ligands. In this paper we report the isolation of a family of mouse RXR genes encoding three distinct receptors (RXR alpha, beta, and gamma). They are closely related to each other in their DNA- and ligand-binding domains but are quite divergent from the RAR subfamily in both structure and ligand specificity. Recently, we demonstrated that all-trans retinoic acid (RA) serves as a "pro-hormone" to the isomer 9-cis RA, which is a high-affinity ligand for the human RXR alpha. We extend those findings to show that 9-cis RA is also "retinoid X" for mouse RXR alpha, beta, and gamma. Trans-activation analyses show that although all three RXRs respond to a variety of endogenous retinoids, 9-cis RA is their most potent ligand and is up to 40-fold more active than all-trans RA. Northern blot and in situ hybridization analyses define a broad spectrum of expression for the RXRs, which display unique patterns and only partially overlap themselves and the RARs. This study suggests that the RXR family plays critical roles in diverse aspects of development, from embryo implantation to organogenesis and central nervous system differentiation, as well as in adult physiology.