Adenosine 3',5'-monophosphate: regional differences in chick embryos at the head process stage.

The concentrations of adenosine 3',5'-monophosphate and adenosine triphosphate and the activity of phosphodiesterase were determined in different regions of chick embryos at the head process stage. Adenosine 3',5'-monophosphate, adenosine triphosphate, and phosphodiesterase were estimated to be higher in the mesoderm-forming portions of the hypoblast than in portions that form neural structures from Hensen's node or the epiblast.

Effect of conotruncal constriction on aortic-mitral valve continuity in the stage 18, 21 and 24 chick embryo.

The effect of conotruncal constriction on the development of aortic-mitral valve continuity in stage 18, 21 and 24 chick embryos was studied. A 10-0 nylon suture was tied around the conotruncus, constricting the outflow tract of the heart. The loop was removed after 4 or 24 hours or left permanently in place in 3 subgroups of the 236 experimental embryos. The embryo hearts were harvested at stages after completion of cardiac morphogenesis, fixed in end-diastole and microdissected. The distance between the mitral and aortic anuli was measured from the base of the heart with a calibrated filar micrometer eyepiece. This measurement was compared with the mitral-aortic separation in 72 normal and 132 control embryos. The mitral-aortic separation was similar among normal, control and 4- and 24-hour experimental embryo hearts. However, the mitral-aortic separation increased from 0.34 +/- 0.02 mm in normal hearts to 0.82 +/- 0.25 mm in stage 18, 1.11 +/- 0.36 mm in stage 21 and 0.75 +/- 0.33 mm in stage 24 permanent loop experimental hearts (p less than 0.01). In embryo hearts with an increased mitral-aortic separation, both great vessels arose from the right ventricle, the semilunar valves were at the same level and the ventricular septal defect was present beneath the aortic anulus. We conclude that conotruncal constriction modifies the relation of the aortic and the mitral valve. We speculate that conotruncal constriction alters the migration of mesenchymal tissue into the heart.

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.

Truncus arteriosus communis: truncal valve anomalies associated with small conal or truncal septal defects.

Selected specimens of truncus arteriosus communis illustrate a spectrum of anomalous truncoconal septation in which the conal and truncal septal defects are so closely approximated to the truncal valve that portions of the valve tissue extend along the free margins of the adjacent ventricular or truncal septum.

Small left atrium and change in contour of the ventricular septum in total anomalous pulmonary venous connection: a morphometric analysis of 22 infant hearts.

Morphometric measurements of 22 hearts with total anomalous pulmonary venous connection (TAPVC) were compared with measurements of 8 matched control specimens without heart disease. Each of the TAPVC specimens had a shorter left atrium, smaller left atrial surface area and larger diameter of the fossa ovalis. In addition to increased length of the right ventricle and larger circumferences for tricuspid and pulmonary valve anuli, the left ventricular contour of the ventricular septum was flat or convex in 18 of the 22 hearts; the septum was significantly longer than normal in these specimens and wider at its midportion. Because mitral and aortic valve anuli were normal in circumference, the data suggest that left ventricular volume is not decreased despite change in ventricular shape.

Endoderm/mesoderm multiplication rates in stage 5-12 chick embryos.

Multiplication rates for the endoderm/mesoderm layer of the head-process to 17-somite-stage chick embryo were studied by implanting essentially identical transplants labeled with tritiated thymidine into paired recipient embryos. One recipient was fixed as soon as the transplant had healed (after 30 min) and the other was reincubated an additional 3.5 to 22.5 hr; the ratios of labeled cells in the paired embryos provided points on a graph that indicated that doubling of endoderm/mesoderm cells in head-process-stage chick embryos occurs at approximately 4.0 and 17.2 hr of reincubation.

The chorda center in Hensen's node of the chick embryo.

To learn the origin and early migration of notochordal cells in the chick embryo, tritiated thymidine-labeled grafts were implanted into homologous positions in Hensen's node of recipient embryos at homologous stages of development. The host embryos were reincubated to Hamburger-Hamilton stages 5-9, fixed, embedded in paraffin, and serially sectioned. Sections were coated with photographic emulsion and exposed for 7-30 days. Labeled cells were found in the notochord or chordamesoderm in 31 of the 35 embryos. Transplants to the dorsal portion of the node always formed notochord. Transplants to the ventral node formed notochord only when implanted during or after the definitive streak stage (H-H stage 4+), indicating that the chorda center is located in the dorsal layer. Moreover, the results suggest that the node depletes itself in producing the notochord: labeled cells migrated into notochord or chordamesoderm anterior to the primitive pit, rather than remaining in the node or primitive pit. Because transplants to the anterolateral portion of the node contributed only to trunk notochord and several transplants to the posteromedial portion contributed only to head notochord, Hensen's node may be equivalent to the median lip of a blastopore, over which prenotochordal material in the dorsal (epiblast) layer passes during gastrulation.

The normal anatomy of the atrial septum in the human heart.

The atrial septum is a blade-shaped structure with a concave anterior margin that reflects the curve of the ascending aorta, a convex posterior margin, and an inferior margin along the mitral annulus. The fossa ovalis comprises an average of 28 per cent of the total septal area, or 43 mm.2 in infants and 240 mm.2 in adults. The channel that persists between the fossa ovalis and the muscular atrial septum is patent except at the limbus, providing a useful explanation for the success of blunt transseptal atrial catheterization and right-to-left shunts in individuals with elevated right atrial pressure.

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.

Closed foramen ovale: a potential entrance to left atrium.

The anatomy of the limbus and its relationship to the fossa ovalis were studied in 90 normal human hearts in an attempt to explain the clinical success of blunt trans-septal catheterization. Previously reported rates of patent foramen ovale (25-35% of adult specimens) were confirmed, well below the reported rate of success for blunt trans-septal catheterization (67-87%). A possible reason for this success is the fragile attachment of the fossa ovalis to its limbus in nearly all hearts without persistent patency.

Assessing the blalock-hanlon atrioseptectomy at cardiac catheterization.

Blalock-Hanlon atrial septectomy (BH) is performed to increase systemic and pulmonary venous mixing at the atrial level. Failure of clinical improvement may be related to inadequate intraatrial communication. A simple catheterization technique employing a balloon catheter is used to assess the presence or absence of the limbus of the foramen ovale following BH, since persistence of the limbus of the fossa ovalis after BH is associated with significantly smaller percentage of communication (atrial communication area/total atrial area).

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 Down's 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.

Congenital mitral valve disease in transposition of the great arteries.

A spectrum of mitral valve disease was noted in 71 per cent of 163 specimens with transposition of the great arteries. At one end of the spectrum were hearts with normal mitral valve, except that the free margin of the anterior leaflet was shortened; at the other end were specimens with underdevelopment of the space between or behind the papillary muscles of the left ventricle. In additional specimens the anterior leaflet was indented and attached by chordae tendineae to the ventricular septum.

Plastic casts of embryonic respiratory and cardiovascular system: a technique.

This report describes a technique for producing plastic casts of the cardiovascular and respiratory systems of the chick embryo at Stage 36 or older. For casts of the cardiovascular system, polymerization compound is injected in the right ventricle filling the heart, venous, and arterial system. A two stage injection produced more detailed casts of the pulmonary vasculature. For respiratory system casts, the compound is injected in the trachea filling the bronchi and air sacs. Casts are prepared by tissue corrosion in 10% potassium hydroxide. This technique is an alternative to serial section reconstruction in the study of developing cardiovascular and respiratory system.

Increased mitral-aortic separation in discrete subaortic stenosis.

We recently speculated that mitral-aortic separation (MAS) might be increased in discrete subaortic stenosis (DSS). We have examined this hypothesis in 22 heart specimens in which the subaortic obstruction originated on the muscular ventricular septum below the right aortic sinus, either as a discrete band, an accumulation of several bands or a diffuse ridge, and extended posteriorly into the MAS or anterior leaflet of the mitral valve or both, with a variable relationship to the aortic cusps and sinuses. No specimen had ventricular septal defect, supravalvular aortic stenosis or other features of Shone syndrome. The mean MAS was nearly twice that of 80 normal specimens (4.9 vs 2.5 mm), the range of MAS was increased from normal (0.11 vs 0.7 mm) and the mean diameter of the aortic annulus was decreased compared with the normal specimens, data that will be of interest to echo- and angiocardiographers in the clinical description of DSS, and to the surgeon who must resect these lesions.

Atrial septal thickness and area in normal heart specimens and in those with ostium secundum atrial septal defects.

This anatomic study suggests that an understanding of the thickness of the atrial septum should allow better visualization of most portions of the blade-shaped atrial septum during cross-sectional echocardiography, both in normal subjects and in patients with ostium secundum atrial septal defects. The thickness measurements also demonstrate that difficulties in imaging the atrial septum are a function of resolution limits of existing echocardiographic equipment.