The spontaneous occurrence of aortic arch and cardiac malformations in the white Leghorn chick embryo (Gallus domesticus)

Teratogenic effects of implanting fibroblast growth factor-2-soaked beads in the cardiac region of the stage 24 chick embryo

The identification of fibroblast growth factor-2 (FGF-2), and other family members, in a variety of embryonic tissue extracts has implicated these growth factors as participants in many embryonic events, including cardiogenesis. The present study was conducted in an attempt to characterize the effects of exogenous FGF-2 on the development of the avian heart. Heparin acrylic beads, each soaked in 100 micrograms/ml FGF-2, were applied to the Hamburger and Hamilton [(1951) J. Morphol. 88:49-92] stage 24 (day 4 of incubation) chick heart, near the primitive ventricle. The embryos were allowed to develop until stage 41 (day 15), at which time they were observed for the presence of gross external and internal anomalies. Crown rump length (CRL), wet weight (WW), and various heart measurements were obtained and compared. The survival rate of the control group was significantly higher (P < 0.05) than that for the experimental group and the anomaly rate for the control group was significantly lower (P < 0.01) than that for the experimental group. The experimental group exhibited a wide range of anomalies, most of which were cardiac in nature; however, anomalies of the ventral thoracoabdominal wall were also noted. Our data suggest that application of exogenous FGF-2 has teratogenic effects on cardiac development as well as on the development of the ventral body wall of the avian embryo.

Unilateral vitelline vein ligation alters intracardiac blood flow patterns and morphogenesis in the chick embryo

To study the role of blood flow in normal and abnormal heart development, an embryonic chicken model was developed. The effect of altered venous inflow on normal intracardiac blood flow patterns was studied by visualization of blood flow with India ink. At stage 17, India ink was injected into a capillary or small venule within a specific yolk sac region. After determination of the normal intracardiac flow pattern, the right lateral vitelline vein was ligated, and the new intracardiac flow pattern was studied. Ligation resulted in disturbance of normal intracardiac flow patterns, which was most obvious in the conotruncus. The long-term effect of these abnormal intracardiac flow patterns on the development of the heart and pharyngeal arch arteries was investigated by permanent ligation in ovo with a microclip at stage 17 and subsequent evaluation at stages 34, 37, and 45. These experiments revealed anomalies of the vascular system in 58 of the 91 ligated embryos studied. We observed intracardiac malformations consisting of subaortic ventricular septal defects (n = 52), semilunar valve anomalies (n = 19), atrioventricular anomalies (n = 7), and pharyngeal arch artery malformations (n = 32). It is concluded that abnormal intracardiac blood flow, resulting from hampered venous inflow, may result in serious intracardiac and pharyngeal arch artery malformations comparable to defects observed in embryonic chicken models subjected to neural crest ablation, cervical flexure experiments, and excessive retinoic acid treatment.

Cardiovascular teratogenicity of terbutaline and ritodrine in the chick embryo

OBJECTIVE

We determined the teratogenic effects of terbutaline and ritodrine, both beta 2-sympathomimetic agonists, on the stage 24 (4-day) chick embryo.

STUDY DESIGN

We used a topical method of application of terbutaline or ritodrine to the stage 24 chick embryo in ovo. Doses of terbutaline ranged from 5.5 x 10(-10) to 6.5 x 10(-9) mol per embryo, and ritodrine doses ranged from 4.6 x 10(-11) to 4.6 x 10(-8) mol per embryo. To further determine the pharmacologic nature of the teratogenic potential of terbutaline or ritodrine, the experiments were repeated after pretreatment with butoxamine hydrochloride, a preferential beta 2-antagonist, or metoprolol tartrate, a preferential beta 1-antagonist, 4 hours before application of terbutaline or ritodrine.

RESULTS

Terbutaline treatment was associated with significantly higher rates of anomalies than in controls at all dosages used, whereas ritodrine induced significantly more anomalies at or above doses of 4.6 x 10(-9) mol per embryo. At an equimolar dose pretreatment with butoxamine hydrochloride significantly reduced the cardiovascular teratogenic effects of terbutaline and ritodrine. Pretreatment with metoprolol tartrate at any dose did not significantly reduce terbutaline's potential. Metoprolol, at doses tenfold or 100-fold higher than ritodrine, was able to significantly reduce the teratogenic effects of ritodrine.

CONCLUSIONS

Our data suggest that terbutaline and ritodrine are teratogenic in the chick and that these agents exert their teratogenic effects primarily through stimulation of the beta 2-adrenergic receptor.

Cardiovascular anomalies in chick embryos produced by bis-diamine in dimethylsulfoxide

N,N'-bis(dichloroacetyl)-1,8-octamethylenediamine(bis-diamin e) (100 micrograms) dissolved in dimethylsulfoxide (DMSO) was administered to early developing chick embryos (Hamburger-Hamilton stage 9-21) in order to clarify the teratogenic effects on the cardiovascular system and to determine whether bis-diamine interferes with the migration of neural crest cells. Of 346 cases, 154 (44.5%) survived. The incidence of cardiovascular anomalies was 149 out of 154 cases (96.8%). Infundibular ventricular septal defect, double outlet right ventricle, and persistent truncus arteriosus were the primary cardiac anomalies observed in this study. A high percentage of these anomalies were accompanied by hypoplasia of the right 6th aortic arch artery and persistent left 4th aortic arch artery. Particularly, administration of bis-diamine to chick embryos at stage 13 resulted in a high incidence of persistent truncus arteriosus (64.3%). Bis-diamine has been suspected to inhibiting the migration of neural crest cells. However, neural crest cells were observed in the tunica media of the great arteries and the truncal valves of persistent truncus arteriosus produced by bis-diamine in chimeric embryos at stage 13. Morphological changes such as cell death were not observed.