By contrast, loss of shear stress after flow cessation enhanced the blood-brain barrier permeability I looked up reference 3, the one about the shear forces here is a bit about that:found herehttp://www.ncbi.nlm.nih.gov/pubmed/15920760.....Brain ischemia is associated with an acute release of pro-inflammatory cytokines, notably TNF-alpha and IL-6 and failure of the blood-brain barrier.