Neurovascular coupling and the influence of luminal agonists via the endothelium

\u3cp\u3eA numerical model of neurovascular coupling (NVC) is presented based on neuronal activity coupled to vasodilation/contraction models via the astrocytic mediated perivascular K\u3csup\u3e+\u3c/sup\u3e and the smooth muscle cell Ca\u3csup\u3e2+\u3c/sup\u3e pathway. Luminal agonists acting on P2Y receptors on the endothelial cell surface provide a flux of IP\u3csub\u3e3\u3c/sub\u3e into the endothelial cytosol. This concentration of IP\u3csub\u3e3\u3c/sub\u3e is transported via gap junctions between endothelial and smooth muscle cells providing a source of sacroplasmic derived Ca\u3csup\u3e2+\u3c/sup\u3e in the smooth muscle cell. The model is able to relate a neuronal input signal to the corresponding vessel reaction. Results indicate that blood flow mediated IP\u3csub\u3e3\u3c/sub\u3e production via the agonist ATP has a substantial effect on the contraction/dilation dynamics of the SMC. The resulting variation in cytosolic Ca\u3csup\u3e2+\u3c/sup\u3e can enhance and inhibit the flow of blood to the cortical tissue. IP\u3csub\u3e3\u3c/sub\u3e coupling between endothelial and smooth muscle cells seems to be important in the dynamics of the smooth muscle cell. The VOCC channels are, due to the hyperpolarisation from K\u3csup\u3e+\u3c/sup\u3e SMC efflux, almost entirely closed and do not seem to play a significant role during neuronal activity. The current model shows that astrocytic Ca\u3csup\u3e2+\u3c/sup\u3e is not necessary for neurovascular coupling to occur in contrast to a number of experiments outlining the importance of astrocytic Ca\u3csup\u3e2+\u3c/sup\u3e in NVC, however this Ca\u3csup\u3e2+\u3c/sup\u3e pathway is not the only one mediating NVC. Importantly agonists in flowing blood have a significant influence on the endothelial and smooth muscle cell dynamics.\u3c/p\u3

Parametric optimization of the processing of all-cellulose composite laminae

Single-polymer composites based on cellulose I and/or II (aka all-cellulose composites) are emerging as a class of high-performance bio-based composite materials with mechanical properties suited to structural applications. There are various synthesis routes for the preparation of all-cellulose composites. However, little has been reported on the optimization of the processing variables affecting the properties of all-cellulose composites. In the present work, a range of all-cellulose composites were produced as single laminae via solvent infusion processing using a precursor of cellulose II fibers that were assembled as a woven 2D textile. The effects of dissolution time, dissolution temperature, and compaction pressure during hot pressing on the properties of the laminae were then systematically examined using a Taguchi design of experiment approach in order to identify the critical control factors. The tensile properties, fiber volume fraction, and crystallinity of the laminae were determined. Statistical analysis of variance and the signal-to-noise ratio were used to rank the importance of key control factors