Vascular Remodeling in Hypertension

Cerebral arterioles in stroke-prone spontaneously hypertensive rats (SHRSP) paradoxically become more distensible, despite hypertrophy of the vessel wall. Cerebral arterioles in SHRSP also undergo remodeling with a reduction in external diameter. Based on these findings, we have proposed the concept that remodeling of cerebral arterioles may be an important mechanism, in addition to hypertrophy, for encroachment on the vascular lumen in SHRSP. The purpose of this review is threefold. First, consequences of vascular hypertrophy that have been proposed previously are reviewed with an emphasis on the hypothesis that encroachment on the vascular lumen by hypertrophy is an important mechanism of altered vascular responses in chronic hypertension. Second, the concept of vascular remodeling is considered with an emphasis on the possibility that remodeling with a reduction in external diameter may contribute importantly to altered cerebral vascular responses in SHRSP. Finally, possible mechanisms of vascular remodeling are considered with an emphasis on the hypothesis that a reduction in external diameter may be related to a decrease in the length of individual smooth muscle cells without an increase in cell number, or an increase in the number of times each smooth muscle cell wraps around the arteriole

Origin of the butterfly magnetoresistance in a Dirac nodal-line system

We report a study on the magnetotransport properties and on the Fermi surfaces (FS) of the ZrSi(Se,Te) semimetals. Density Functional Theory (DFT) calculations, in absence of spin orbit coupling (SOC), reveal that both the Se and the Te compounds display Dirac nodal lines (DNL) close to the Fermi level $\varepsilon_F$ at symmorphic and non-symmorphic positions, respectively. We find that the geometry of their FSs agrees well with DFT predictions. ZrSiSe displays low residual resistivities, pronounced magnetoresistivity, high carrier mobilities, and a butterfly-like angle-dependent magnetoresistivity (AMR), although its DNL is not protected against gap opening. As in Cd$_3$As$_2$, its transport lifetime is found to be 10$^2$ to 10$^3$ times larger than its quantum one. ZrSiTe, which possesses a protected DNL, displays conventional transport properties. Our evaluation indicates that both compounds most likely are topologically trivial. Nearly angle-independent effective masses with strong angle dependent quantum lifetimes lead to the butterfly AMR in ZrSiSe