The blood-brain barrier is an evolutionary ancient structure that provides direct support and protection of the nervous system. In all systems, it establishes a tight diffusion barrier that hinders uncontrolled paracellular diffusion into the nervous system. In invertebrates, the blood-brain barrier separates the nervous system from the hemolymph. Thus, the barrier-forming cells need to activel...

2 Macroscopic modeling 5 2.1 Concentration measures, mixture velocity and diffusion fluxes . . . . . . . . 5 2.2 Species transport equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Fick model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Limits of Fick model: osmotic diffusion, reverse diffusion and diffusion barrier 8 2.5 Maxwell-Stefan mo...

We consider diffusion on substrate with a frozen disorder. While in ordered state the moving particle meets always the same energy barrier in amorphous state there is a more or less broad distribution of the height of barriers. The effective activation energy Eeff that controls the diffusion process is not equal to the average activation energy barrier. Actually, Eeff is the highest barrier tha...

During mammalian embryogenesis the emerging epidermis is temporarily covered by an epithelial monolayer, the periderm. In chicken, a second epithelial layer, the subperiderm, located underneath the periderm develops in later embryogenesis. Together the periderm and the subperiderm are referred to as the PSP unit. The cells of the PSP unit are tightly connected by tight junctions (TJ), thereby p...

In animal cells, the primary cilium transduces extracellular signals through signaling receptors localized in the ciliary membrane, but how these ciliary membrane proteins are retained in the cilium is unknown. We found that ciliary membrane proteins were highly mobile, but their diffusion was impeded at the base of the cilium by a diffusion barrier. Septin 2 (SEPT2), a member of the septin fam...