PMC:6194691 / 17707-20663
Annnotations
MyTest
{"project":"MyTest","denotations":[{"id":"30340614-7356021-30705876","span":{"begin":375,"end":377},"obj":"7356021"},{"id":"30340614-29704892-30705877","span":{"begin":553,"end":555},"obj":"29704892"},{"id":"30340614-29023798-30705878","span":{"begin":954,"end":956},"obj":"29023798"},{"id":"30340614-4366438-30705879","span":{"begin":958,"end":960},"obj":"4366438"},{"id":"30340614-2396537-30705879","span":{"begin":958,"end":960},"obj":"2396537"},{"id":"30340614-18208483-30705879","span":{"begin":958,"end":960},"obj":"18208483"},{"id":"30340614-27306753-30705879","span":{"begin":958,"end":960},"obj":"27306753"},{"id":"30340614-29283289-30705879","span":{"begin":958,"end":960},"obj":"29283289"},{"id":"30340614-26463008-30705880","span":{"begin":1007,"end":1009},"obj":"26463008"},{"id":"30340614-29283289-30705881","span":{"begin":1716,"end":1718},"obj":"29283289"},{"id":"30340614-29023798-30705882","span":{"begin":1826,"end":1828},"obj":"29023798"},{"id":"30340614-18923183-30705883","span":{"begin":1830,"end":1832},"obj":"18923183"},{"id":"30340614-29283289-30705884","span":{"begin":1834,"end":1836},"obj":"29283289"},{"id":"30340614-9610885-30705885","span":{"begin":1838,"end":1840},"obj":"9610885"},{"id":"30340614-23298378-30705885","span":{"begin":1838,"end":1840},"obj":"23298378"},{"id":"30340614-27836940-30705885","span":{"begin":1838,"end":1840},"obj":"27836940"},{"id":"30340614-27929105-30705885","span":{"begin":1838,"end":1840},"obj":"27929105"},{"id":"30340614-28826498-30705885","span":{"begin":1838,"end":1840},"obj":"28826498"},{"id":"30340614-28847942-30705885","span":{"begin":1838,"end":1840},"obj":"28847942"}],"namespaces":[{"prefix":"_base","uri":"https://www.uniprot.org/uniprot/testbase"},{"prefix":"UniProtKB","uri":"https://www.uniprot.org/uniprot/"},{"prefix":"uniprot","uri":"https://www.uniprot.org/uniprotkb/"}],"text":"Some of the possible routes for perivascular movements of solutes are indicated in Fig. 5. Whether or not actual fluid filled spaces exist around the blood vessels, it is believed that substances can move along preferential routes parallel to the blood vessels. (The description that follows is primarily for grey matter. As suggested originally by Rosenberg et al. in 1980 [65] there are likely to be preferential routes for fluid movement parallel to axons in white matter. It should also be noted that there may be regional variations, see e.g. [66, 67]). The idea that the basement membranes of microvessels can provide a preferential route stems from observations that when horseradish peroxidase is introduced into CSF with consequential influx along arteries the peroxidase is found to be localized in the basement membranes around microvessels. The idea has subsequently been supported by similar observations for other macromolecules (see e.g. [16, 68–72]). However, calculations by Asgari et al. [73] imply that unless the matrix of the microvascular basement membranes has a resistance substantially less than a sleeve of ®Matrigel with the same dimensions, they will not provide a preferential route for fluid flow parallel to the microvessels. A preferential route for movement along the vessels does not conflict with the movements of solutes outward by diffusion into the surrounding interstitial fluid. Regardless of whether or not the microvessel basement membranes provide a route with relatively low resistance, the distance from anywhere in the parenchyma to the nearest larger vessel is still likely to be relatively small, e.g. 100–200 µm. (Striking images of the vascular tree can be seen in [72]). For distances this short, diffusion is expected to be the dominant mechanism of extracellular movement [16, 24, 72, 74–81].\nFig. 5 Diagram indicating putative perivascular routes for substances to move into, out of and through the brain parenchyma. The lumens of arteries, arterioles, venules and veins are surrounded by a layer of endothelial cells with a basement membrane, then a layer of vessel wall including smooth muscle, and outside that there may be a further perivascular space with fluid and connective tissue bounded by basement membranes of the smooth muscle, pial and glial cells. Close to the surfaces of the brain these further spaces are often called Virchow-Robin spaces. Movements parallel to the large vessels may be intramural, through the extracellular space of the vessel wall, or extramural either in the outermost basement membranes or, in the opinion of some workers, in a fluid filled space. In this review both intramural and extramural pathways are called perivascular routes. Parallel to microvessels movement may be preferentially within the basement membrane separating the endothelial cells from the glial endfeet or it may be more diffuse through the interstitial spaces between the parenchymal cells"}
2_test
{"project":"2_test","denotations":[{"id":"30340614-7356021-30705876","span":{"begin":375,"end":377},"obj":"7356021"},{"id":"30340614-29704892-30705877","span":{"begin":553,"end":555},"obj":"29704892"},{"id":"30340614-29023798-30705878","span":{"begin":954,"end":956},"obj":"29023798"},{"id":"30340614-4366438-30705879","span":{"begin":958,"end":960},"obj":"4366438"},{"id":"30340614-2396537-30705879","span":{"begin":958,"end":960},"obj":"2396537"},{"id":"30340614-18208483-30705879","span":{"begin":958,"end":960},"obj":"18208483"},{"id":"30340614-27306753-30705879","span":{"begin":958,"end":960},"obj":"27306753"},{"id":"30340614-29283289-30705879","span":{"begin":958,"end":960},"obj":"29283289"},{"id":"30340614-26463008-30705880","span":{"begin":1007,"end":1009},"obj":"26463008"},{"id":"30340614-29283289-30705881","span":{"begin":1716,"end":1718},"obj":"29283289"},{"id":"30340614-29023798-30705882","span":{"begin":1826,"end":1828},"obj":"29023798"},{"id":"30340614-18923183-30705883","span":{"begin":1830,"end":1832},"obj":"18923183"},{"id":"30340614-29283289-30705884","span":{"begin":1834,"end":1836},"obj":"29283289"},{"id":"30340614-9610885-30705885","span":{"begin":1838,"end":1840},"obj":"9610885"},{"id":"30340614-23298378-30705885","span":{"begin":1838,"end":1840},"obj":"23298378"},{"id":"30340614-27836940-30705885","span":{"begin":1838,"end":1840},"obj":"27836940"},{"id":"30340614-27929105-30705885","span":{"begin":1838,"end":1840},"obj":"27929105"},{"id":"30340614-28826498-30705885","span":{"begin":1838,"end":1840},"obj":"28826498"},{"id":"30340614-28847942-30705885","span":{"begin":1838,"end":1840},"obj":"28847942"}],"text":"Some of the possible routes for perivascular movements of solutes are indicated in Fig. 5. Whether or not actual fluid filled spaces exist around the blood vessels, it is believed that substances can move along preferential routes parallel to the blood vessels. (The description that follows is primarily for grey matter. As suggested originally by Rosenberg et al. in 1980 [65] there are likely to be preferential routes for fluid movement parallel to axons in white matter. It should also be noted that there may be regional variations, see e.g. [66, 67]). The idea that the basement membranes of microvessels can provide a preferential route stems from observations that when horseradish peroxidase is introduced into CSF with consequential influx along arteries the peroxidase is found to be localized in the basement membranes around microvessels. The idea has subsequently been supported by similar observations for other macromolecules (see e.g. [16, 68–72]). However, calculations by Asgari et al. [73] imply that unless the matrix of the microvascular basement membranes has a resistance substantially less than a sleeve of ®Matrigel with the same dimensions, they will not provide a preferential route for fluid flow parallel to the microvessels. A preferential route for movement along the vessels does not conflict with the movements of solutes outward by diffusion into the surrounding interstitial fluid. Regardless of whether or not the microvessel basement membranes provide a route with relatively low resistance, the distance from anywhere in the parenchyma to the nearest larger vessel is still likely to be relatively small, e.g. 100–200 µm. (Striking images of the vascular tree can be seen in [72]). For distances this short, diffusion is expected to be the dominant mechanism of extracellular movement [16, 24, 72, 74–81].\nFig. 5 Diagram indicating putative perivascular routes for substances to move into, out of and through the brain parenchyma. The lumens of arteries, arterioles, venules and veins are surrounded by a layer of endothelial cells with a basement membrane, then a layer of vessel wall including smooth muscle, and outside that there may be a further perivascular space with fluid and connective tissue bounded by basement membranes of the smooth muscle, pial and glial cells. Close to the surfaces of the brain these further spaces are often called Virchow-Robin spaces. Movements parallel to the large vessels may be intramural, through the extracellular space of the vessel wall, or extramural either in the outermost basement membranes or, in the opinion of some workers, in a fluid filled space. In this review both intramural and extramural pathways are called perivascular routes. Parallel to microvessels movement may be preferentially within the basement membrane separating the endothelial cells from the glial endfeet or it may be more diffuse through the interstitial spaces between the parenchymal cells"}