Glenn C. Rosenquist

Location and movements of cardiogenic cells in the chick embryo: The heart-forming portion of the primitive streak

Abstract The precardiac portion of the primitive streak of the chick embryo was investigated by placing tritiated thymidine-labeled transplants within it. The movements and final positions of the transplanted cells in the incubated recipient embryos were documented by study of radioautographed serial sections. The precardiac portion of the primitive streak is located about halfway between the anterior and posterior ends of the streak from the early short streak to the head process stage; the anterior part of this portion contributes to dorsal myocardium, while the posterior part of this portion contributes to ventral myocardium. The initial migration of the grafts from the streak into the mesoderm layer is lateral, and is followed shortly by an anterior movement that places the grafts in the heart-forming region of the mesoderm layer at the head process stage. The sequence of migration of the precardiac cells from the heart-forming portion of the streak is orderly and logical, i.e., conus migrates into mesoderm before ventricle and ventricle migrates before atrium. The ventral half of each part of the heart, however, migrates from the streak before the dorsal half of each part. By the 10–22 somite stage transplants made to the heart-forming portion of the streak at the short streak stages had migrated into the ventral part of the conus and ventricle, transplants made at the medium streak stage contributed to the dorsal half of the conus and the ventral part of the ventricle and atrium, and transplants made at the definitive streak and head process stage contributed to dorsal ventricle and atrium, and to both dorsal and ventral parts of the sinus venosus.

The location of the pregut endoderm in the chick embryo at the primitive streak stage as determined by radioautographic mapping

Abstract Previously unmapped portions of the pregut endoderm were studied by tracing the movements of thymidine-3H-labeled grafts excised from explanted embryos at primitive streak stages, transplanted to similarly staged recipient embryos in ovo, and reincubated for 3–4 days. In addition to their contribution to endoderm, 11 of the transplants contributed to mesoderm and two to ectoderm; in the latter two layers, the labeled cells were found in regions that were expected from a study of transplants made previously in the explanted embryo. The transplants that contributed to the dorsal portion of the gut were more centrally positioned in the recipient embryos than were transplants that contributed to the ventral portions of the gut. Transplants that contributed to the posterior gut were more posteriorly positioned in the recipient embryos than were transplants that contributed to the anterior gut. The posterior intestinal portal (like the anterior intestinal portal) develops by inversion of a circumscribed area of endoderm, forming the posterior gut, suggesting that gastrulation in the chick is similar to that of other chordates except that the archenteron is not completely formed until the most peripheral pregut cells in the hypoblast layer are drawn together ventrally like pursestring at the umbilicus, enclosing the gut endoderm.

The normal spectrum of mitral and aortic valve discontinuity.

SUMMARY The relationship of the base of the left and noncoronary sinuses of the aortic valve and the adjacent aortic leaflet of the mitral valve was studied in 106 normal heart specimens and 184 specimens with isolated VSD. The results show a spectrum of per- sistence of the tissue along the inner curvature of the heart. This may help settle the recent controversy in the interpretation of echocardiograms of this area because the recorded mitral-aortic discontinuity may be due to this spectrum rather than to variations in technique.

Normal variations in tricuspid valve attachments to the membranous ventricular septum: a clue to the etiology of left ventricle-to-right atrial communication

In 39 out of 95 normal specimens, there was either no commissure between the anterior and medial leaflets of the tricuspid valve, which resulted in an interrupted valve margin at the center of the membranous ventricular septum, or an incompletely formed commissure. It is suggested that one end of this spectrum of normal anatomic variations could have a direct relationship to VSD associated with left ventricle-to-right atrial communication.

Acquired right ventricular outflow obstruction in a child with neurofibromatosis

Abstract A case of severe acquired localized right ventricular obstruction in an 8 1 2 - year-old child with von Recklinghausens syndrome is presented. The similarity of this case to vascular involvement in previously reported cases is pointed out. It is suggested that vascular lesions in neurofibromatosis may have varied manifestations and that this syndrome should be thought of in the future as a generalized disease which may affect any part of the cardiovascular system. For the lesion here reported, excision of the fibromuscular band has resulted in disappearance of her pressure difference, murmur, and right heart failure.

Enlargement of the membanous ventricular septum: An internal stigma of Down's syndrome

A study of heart specimens without ventricular septal defect from patients with Downs syndrome showed a significant enlargement of the membranous ventricular septum as compared to the normal heart. This increase in area of the ventricular septum occupied by membranous tissue from 2 to 9% may not only predispose patients with Downs syndrome to congenital heart disease, but may be one end of a spectrum of cardiac anomalies related to malalignment or maldevelopment of the ventricular septum in Downs syndrome.

Relationships of the tricuspid valve to the membranous ventricular septum in Down's syndrome without endocardial cushion defect: Study of 28 specimens, 14 with a ventricular septal defect☆☆☆

The commissure between the anterior and medial leaflets of the tricuspid valve is commonly absent in Downs syndrome without endocardial cushion defect (19 of 28 specimens). As a result, aneurysm of the membranous ventricular septum may develop (eight of 14 specimens with ventricular septal defect limited to the membranous ventricular septum) and the potential for left ventricle-to-right atrial communication is increased.

Overriding right atrioventricular valve in association with mitral atresia

Abstract Three cases of mitral atresia with overriding right atrioventricular valve, ventricular septal defect, and normally sized left ventricle are reported, two of them with transposition of the great vessels. Although the combination of anomalies is rare, the possibility that palliative and/or corrective surgery could be accomplished indicates that in suspected cases of mitral atresia, diagnostic efforts aimed at accurate delineation of the associated defects must be made.

Roentgenographic re-examination of the internal anatomy of the Taussig-Bing heart☆

Abstract A modification of the Wright double-contrast x-ray technique was used to clarify the internal anatomy of the original Taussig-Bing heart. The valves and ventricular outflow tracts were re-examined by marking internal structures with wires and radiopaque contrast material and then obtaining radiographs in standard and special views. These radiographs show valve positions and demonstrate that the pulmonary artery straddles the ventricular septal defect, and receives the outflow tracts of both left and right ventricles.

Atrial defect size after Blalock-Hanlon atrioseptectomy

In transposition of the great arteries, a Blalock-Hanlon closed atrial septectomy is performed to improve intracardiac mixing at the atrial level. Although the Blalock-Hanlon septectomy is a common surgical procedure in cyanotic congenital heart disease, it has not been adequately assessed pathologically. In 14 heart specimens from patients (aged 3 days to 19 years) with transposition of the great arteries and Blalock-Hanlon septectomy, the margins of the septectomy, fossa ovalis and atrial septum were identified. The total area of the septum and its defects was calculated using planimetry. The ratio of defect size to atrial septal area was expressed as percent communication, which ranged from 5 to 39 (mean 18) percent in eight specimens with intact limbus of the foramen ovale and 26 to 57 (mean 42) percent in six specimens in which the limbus had been excised. The finding that specimens in which the Blalock-Hanlon defect extended into the fossa ovalis had the largest total communication emphasizes that to obtain optimal bidirectional atrial mixing the surgeon should extend the Blalock-Hanlon procedure across the limbus into the foramen ovale.