[Control of bile duct and hepatic artery development by liver-specific transcription factors]. / Contrôle du développement des voies biliaires et de l'artère hépatique par des facteurs de transcription hépato-spécifiques.

During liver development, precursor cells called hepatoblasts differentiate into hepatocytes, which synthesize, degrade and store several molecules, or into cholangiocytes which form the bile ducts. The hepatic artery brings nutrients and oxygen to the hepatocytes and cholangiocytes. The aim of my work is to study the role of the transcription factor HNF-6 during liver development. In the course of this project, I made the first description of the development of the biliary tract and of the hepatic artery in the mouse. The analysis of transgenic mice in which the HNF-6 gene had been inactivated led me to the first identification of a genetic cascade that controls biliary development, a cascade wherein HNF-6 regulates the expression of the gene encoding the transcription factor HNF-1beta. Finally, I showed that biliary anomalies can cause perturbations in the development of the hepatic artery.

Fast algorithm for 3-D vascular tree modeling.

In this short paper, accelerated three-dimensional computer simulations of vascular trees development, preserving physiological and haemodynamic features, are reported. The new computation schemes deal: (i). with the geometrical optimization of each newly created bifurcation; and (ii). with the recalculation of blood pressures and radii of vessels in the whole tree. A significant decrease of the computation time is obtained by replacing the global optimization by the fast updating algorithm allowing more complex structure to be simulated. A comparison between the new algorithms and the previous one is illustrated through the hepatic arterial tree.

Comparative morphology of the hepatic and coronary artery walls. Part III. The insignificance of medial morphologic features in the determination of an autopsied unidentified subjects age.

Since hepatic arteries are free of atherosclerosis any possible wall structure change may be attributed to age. We determined the media of hepatic and coronary arteries in view of this assumption. We measured its thickness and myocytic density (per 1 mm2 of cross-section) from specimens collected from autopsied subjects, aged up to 90 years. The media gradually thickens with age, although values noted during particular decades remain statistically insignificant. The myocytic density (in 1 mm2) was almost constant throughout life. The latter observation is incompatible, in comparison with data reported by other authors (diminution was expected).

Modeling of the parenchymous vascularization and perfusion.

RATIONALE AND OBJECTIVES: The authors sought to create a realistic model of the parenchymous vascularization and perfusion. METHODS: A three-dimensional vascular model has been developed that reproduces the growth process of a vascular tree (angiogenesis). This model follows physical laws related to blood flow in vessels (Poiseuille's law), takes into account anatomic constraints, and optimizes a cost function related to the blood volume. RESULTS: Vascular trees, the ramifications of which go from main arteries to small arterioles, were simulated. Vascular structures corresponding to either a normal tissue perfusion or an abnormal perfusion (for example, a local hypervascularization) were presented in three dimensions (volume rendering). Geometric and hemodynamic characteristics computed on these trees were consistent with those of real data found in the literature. The vascular model is also a good tool for studying the propagation of the contrast product in normal and abnormal vessels. CONCLUSIONS: The three-dimensional vascular model presented in this article provides insight into the simulation and the understanding of anatomic or physiologic vascular modifications.