Development and Remodeling of Cerebral Blood Vessels and Their Flow in Postnatal Mice Observed with in vivo Videomicroscopy

Abstract

Summary:Changes of blood vessels in the mouse so matosensory (barrel) cortex were assessed from birth (PO) to adulthood. Surface vessel anatomy and flow were ob served directly with videomicroscopy through closed cra nial windows and with intravascular fluorescent tracers. Histology was used to determine the internal capillary density. At birth, arterioles had numerous anastomoses with each other, pial capillaries formed a dense surface plexus, and pial venules and veins were relatively small and irregular. Morphological changes over the next 2 weeks included (a) fewer arteriolar anastomoses, (b) for mation and growth of venules, (c) more uniform diame ters of all types of vascular segments, (d) increase in in traparenchymal capillary length density (Lv), and (e) de creases in superficial capillary density and diameters. A simple morphological test showed that wall shear rates at arteriolar branch points were matched on average in neo nates and adults. Flow characteristics in single vessels were evaluated. In arterioles of like diameters, (a) V ma x'The growth and development of the brain and its blood vessels are intimately linked. The somatosen sory cortex of mice and rats is an attractive model for following this development because its stereo typed neuronal organization (Woolsey, 1990) and its segregated vasculature (Woolsey and Rovainen, 199 1) are absent at birth. Bar (1980) surveyed the 935(b) peak wall shear rates, and (c) peak flows were similar at all ages; (d) velocity was very high in occasional arte riovenous (A V) shunts in newborns; and (e) flow in arte riolar anastomoses was slow and variable. Although flow was heterogeneous in all types of vessel, the marked sim ilarities in newborn and adult mice of average peak ve locities and calculated wall shear rates in arterioles of the same size suggest that blood flow regulates in part the remodeling of blood vessels during development (Rovainen et aI., 1992). The rodent barrel cortex under goes major neuronal and vascular development, func tional differentiation, and remodeling during the first weeks after birth. It provides special opportunities for testing how blood vessels grow and adapt to supply the local metabolic requirements of neural modules in the brain. Key Words: Arteriole-Anastomosis-Arteriove nous shunt-Diameter-Lv-Murray's rule-Neonate Capillary-Vascular remodeling-V elocity-Wall shear stress-Whisker barrels.angiogenesis and maturation of microvessels during the growth of the occipital cortex in rats with his tology and morphometry. Bar et al. (1986) illus trated corrosion casts of surface vessels in neonatal and adult rats in developing (parietal = somatosen sory) cortex. They showed that the surface of the cerebral cortex at birth to postnatal day 7 (PO-P7) is covered by a dense capillary plexus, which they likened to the embryonic cerebrovascular plexus. Immature surface vascular patterns included arteri olar circles and collaterals, venules crossing over arterioles, and direct connections between arteri oles and venules as candid...

Blood Flow in Single Surface Arterioles and Venules on the Mouse Somatosensory Cortex Measured with Videomicroscopy, Fluorescent Dextrans, Nonoccluding Fluorescent Beads, and Computer-Assisted Image Analysis

“…8) were previously re ported (Rovainen et aI., 1992;Wang et aI., 1992). The velocities we observed in mouse cerebral arte- Rovainen et al (1992); see also Wang et al (1992).…”

G-Protein–Coupled Receptor 91 and Succinate Are Key Contributors in Neonatal Postcerebral Hypoxia-Ischemia Recovery

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Modeling the large-scale geometry of human coronary arteries

“…Although Murray's Law has been confirmed for a large variety of arteries [see Sherman (1981) for a summary of research confirming Murray's Law prior to 1981, LaBarbera (1990 for data in the 1980s; a few more recent papers include Wang et al (1992), Rossitti and Löfgren (1993), and Rossitti and Frisén (1994)], it is well known that the assumptions behind Murray's Law stating that blood flow obeys Poiseuille's Law are questionable. In particular Murray's Law assumes that fluid flow is laminar and steady, neither of which can always be expected.…”