Bloodstreams and the formation of the interatrial septum in the anuran heart

Abstract

Patterns of blood flow have been observed at several critical stages in the development of the frog heart. Shortly after the onset of circulation (Shumway stage 20) two inflowing streams were noted to cross in the sinus venoms and then continue through the atrium, parallel to each other. With the development of the hepatic return (stage 24) the right stream becomes much larger and its course diverted into the area that will become the definitive right atrium. The smaller left stream is then noted to flow around the right stream with the development of a spiralling of the streams. The left stream now leads into the area which will become the left atrium. This is the hemodynamic situation as the interatrial septum forms; the septum forms between the streams. ExperimentaI and histological evidence indicate that the interatrial septum is formed by a molding action of the bloodstreams on the tissues of the atrial wall.Experimental modifications of the vascular morphology of the anuran embryo have been found to influence the form of the developing heart (Jaffee, '62a). In order to evaluate hemodynamic factors involved in cardiogenesis more precisely a mapping of the bloodstreams within the developing heart itself is in progress. The observations to be described have been made of the venous inflow into the developing anuran heart with special reference to the formation of the interatrial septum. Histological aspects of septa1 development are included. METHODS AND MATERIALSEmbryos of the Leopard frog (Rana pipiens) were obtained by induced breeding, For observing the heart, specimens were anesthetized with tricaine methanesulfonate, placed in depression slides filled with amphibian Ringer solution and the ventral body wall opened exposing the heart. Observations of the sinus venosus and atrium were facilitated by displacing the ventricle cephalad with a glass needle held by a micromanipulator, and by displacing the intestine caudad.Observations were made on the stage of a compound microscope with transmitted light for the most part. Embryos of Shumway stages 20 to 22 could not be transilluminated and observations of blood flow in the atria of these specimens was made by placing a quartz rod dorsal to the heart using the technique developed by Knisely ('36). Motion pictures of blood flow were taken with a Bolex Rex 16mm camera at 16 frames per sec.Techniques for producing cardiac anomalies in this form as well as the histological methods utilized have been described (Jaffee, '62a). RESULTSTwo streams of blood cells flowing parallel to each other were observed in the atria at stages 20 to 22. This was of special interest since Bremer ('32) has described a crossing of the streams in the atria of the embryonic chick. The pattern of blood flow through the atrium noted at stages 20 to 22 was again seen at stage 23 when transillumination of the embryo was possible. Crossing of the bloodstreams was noted in the sinus venosus at this time.The sinus venosus at stage 23 is a symmetrical structure with a broad base which re...

Intracardiac flow patterns in early embryonic life. A reexamination.

“…Bremer and Jaffee based their conclusions from visual analysis of the forward movements of the blood cells (Bremer, 1932;Jaffee, 1962Jaffee, , 1963Jaffee, , 1965Jaffee, , 1966Jaffee, , 1967. In our experience, it is extremely difficult-in fact, virtually impossible-to delineate the entire course of the two streams by this method.…”

“…According to the flow-molding theory, there are two spiral streams in the primary heart rube which mold the primitive cardiac chambers and play a major role in the septation process (Spitzer, 1923;Bremer, 1932;Goerttler, 1955;Barthel, 1960;De Vries et al, 1962;Jaffee, 1962Jaffee, , 1963Jaffee, , 1965Jaffee, , 1966Jaffee, , 1967. One stream is the so-called right heart stream which flows selectively through the future right atrium, the right part of the atrioventricular canal, right part of the primitive ventricle, and then spirally through the ventral and left portion of the conotruncus to reach the more caudal branchial arches.…”

“…IT IS a traditional view that spiral streams of blood mold the primary heart tube during its development, and play a major role in the formation of the ventricular, bulbar, and aortico-pulmonary septa (Spitzer, 1923;Bremer, 1932;Goerttler, 1955;Barthel, 1960;De Vries et al, 1962;Jaffee, 1962Jaffee, , 1963Jaffee, , 1965Jaffee, , 1966Jaffee, , 1967. Experiments have been carried out to test this hypothesis.…”

“…Two spiral streams have been described, based on observations of the moving blood cells within the primitive heart (Bremer, 1932;Jaffee, 1962Jaffee, , 1963Jaffee, , 1965Jaffee, , 1966Jaffee, , 1967. This method of evaluation, however, is inadequate for tracing the entire course of the streams in the heart tube, and is subject to error.…”

The Paradox Of Portal Metastases In HCC Patients

“…The heart, for example, shows a transition from three consecutive chambers in cyclostomata (Augustinsson et al, 1956), to four consecutive chambers of chondrichthyans and bony fishes (Kardong, 2012), and to a double circulation in lungfishes (Icardo et al, 2015). Then it transitions from amphibians' left and right atrial chambers (Jaffee, 1963;Kardong, 2012) to reptiles' three-chambered hearts with two atria and one common ventricle (with the exception of crocodiles' four chamber heart) (Kardong, 2012;O'Malley, 2005), and then to mammals' hearts with four chambers and parallel double circulation circuits (Jensen et al, 2013;Kardong, 2012).…”