Transient loss of venous integrity during developmental vascular remodeling leads to red blood cell extravasation and clearance by lymphatic vessels.

Maintenance of blood vessel integrity is crucial for vascular homeostasis and is mainly controlled at the level of endothelial cell (EC) junctions. Regulation of endothelial integrity has largely been investigated in the mature quiescent vasculature. Less is known about how integrity is maintained during vascular growth and remodeling involving extensive junctional reorganization. Here, we show that embryonic mesenteric blood vascular remodeling is associated with a transient loss of venous integrity and concomitant extravasation of red blood cells (RBCs), followed by their clearance by the developing lymphatic vessels. In wild-type mouse embryos, we observed activated platelets extending filopodia at sites of inter-EC gaps. In contrast, embryos lacking the activatory C-type lectin domain family 1, member b (CLEC1B) showed extravascular platelets and an excessive number of RBCs associated with and engulfed by the first lymphatic EC clusters that subsequently form lumenized blood-filled vessels connecting to the lymphatic system. These results uncover novel functions of platelets in maintaining venous integrity and lymphatic vessels in clearing extravascular RBCs during developmental remodeling of the mesenteric vasculature. They further provide insight into how vascular abnormalities characterized by blood-filled lymphatic vessels arise.

Regressing vitelline vein and the initial development of the superior mesenteric vein in human embryos.

The superior mesenteric vein was considered to develop in situ in the midgut mesentery secondary to regression of the left vitelline vein. We revisited the morphology using serial sections of 20 embryos at 5-6 weeks (CRL 9-15 mm). The regressing vitelline vein provided a long peritoneal fold in the immediately superior side of the midgut mesentery containing the thick superior mesenteric artery. Notably, in a half of specimens, there were tissue clefts along the superior mesenteric artery in the mesentery and they were communicated with the left vitelline vein at the superior end of the peritoneal fold. The tissue clefts appeared not to carry the endothelial lining. We considered the cleft as the initial superior mesenteric vein. Conversely, the initial vein seemed not to develop from budding or venous plexus.

Optical coherence tomography as a tool for measuring morphogenetic deformation of the looping heart.

Optical coherence tomography (OCT) was used to investigate morphogenesis of the embryonic chick heart during the first phase of looping (c-looping), as the heart bends and twists into a c-shaped tube. The present study focuses on the morphomechanical effects of the splanchnopleure (SPL), a membrane that has been shown to play a major role in cardiac torsion by pressing against the ventral surface of the heart. Without the SPL, rightward torsion (rotation) is delayed. The images show that compressive forces exerted by the SPL alter the shapes of the heart tube and primitive atria, as well as their spatial relationships. The SPL normally holds the heart in the plane of the embryo and forces cardiac jelly (CJ) out of adjacent regions in the atria. When the SPL is removed, cross-sections become more circular, CJ is more uniformly distributed, and the heart displaces ventrally. In addition, OCT-based morphogenetic strain maps were measured during looping by tracking the three-dimensional motions of microspheres placed on the myocardium. The spatial-temporal patterns of the strains correlated well with the observed behavior of the heart, including delayed torsion that occurs in SPL-lacking embryos. These results illustrate the potential of OCT as a tool in studies of morphogenesis, as well as provide a better understanding of the mechanical forces that drive cardiac looping.

[The prepancreatic course of superior mesenteric vein--a case report]. / Prepankreatický prubeh v. mesenterica superior--kazuistika.

A case of a prepancreatic course of the superior mesenteric vein found at post-mortem is described and a possible hypothesis of its development is offered. The prepancreatic course of the superior mesenteric or portal vein is not frequent, but in abdominal surgery it is necessary to take these anomalies into the consideration because of possible severe sequelae in the case of an inadvertent ligature of important vessels.

The role of mechanical forces in dextral rotation during cardiac looping in the chick embryo.

Cardiac looping is a vital morphogenetic process that transforms the initially straight heart tube into a curved tube normally directed toward the right side of the embryo. While recent work has brought major advances in our understanding of the genetic and molecular pathways involved in looping, the biophysical mechanisms that drive this process have remained poorly understood. This paper examines the role of biomechanical forces in cardiac rotation during the initial stages of looping, when the heart bends and rotates into a c-shaped tube (c-looping). Embryonic chick hearts were subjected to mechanical and chemical perturbations, and tissue stress and strain were studied using dissection and fluorescent labeling, respectively. The results suggest that (1) the heart contains little or no intrinsic ability to rotate, as external forces exerted by the splanchnopleure (SPL) and the omphalomesenteric veins (OVs) drive rotation; (2) unbalanced forces in the omphalomesenteric veins play a role in left-right looping directionality; and (3) in addition to ventral bending and rightward rotation, the heart tube also bends slightly toward the right. The results of this study may help investigators searching for the link between gene expression and the mechanical processes that drive looping.

[Mesenteric-portal confluence aneurysm]. / Anévrysme du confluent mésentérico-portal.

The authors take interest in the portal aneurysm about the observation of a 52 year-old woman with an echographic lesion in the head of the pancreas. Radiological examination was done with abdominal CT and MRI. Because of no accurate diagnosis, an explorative laparotomy was done and showed an aneurysm at the junction of the portal and superior mesenteric veins. These lesions are rare: they can be acquired particularly with underlying hepatocellular diseases and portal hypertension; they can be congenital due to an incomplete obliteration of the right vitelline vein. If asymptomatic, only a close surveillance must be proposed.

[The structural reorganization of the wall of the inferior mesenteric vein and of its vascular-neural components in fetuses and children]. / Strukturnaia perestroika stenki nizhnei bryzheechnoi veny i ee sosudisto-nervnykh komponentov u plodov i detei.

Structural changes of the inferior mesenteric vein wall and it vascular-nervous apparatus were studied in 93 inferior mesenteric veins of human foetuses and children, aged to 3 years using the complex of histological and neuromorphological methods. While changing the structure of the wall became more complicated in myocyte and fibres number.