Internal luminal pressure during early chick embryonic brain growth: Descriptive and empirical observations

Abstract

If the intraluminal pressure of the brain is decreased for 24 hr, the brain and neuroepithelium volumes are both reduced in half. The current study measured the intraluminal pressure throughout the period of rapid brain growth using a servo-null micropressure monitoring system. From 613 measurements made on 55 embryos, we show that the intraluminal pressure over this time period is appropriately described by a linear model with correlation coefficient of 0.752. To assess whether sustained hyperpressure would increase mitosis, elevated intraluminal pressure was induced in 10 embryos for 1-hr duration via a gravity-fed drip. The mitotic density and index of the mesencephalon were measured for the 10 embryos. Those embryos, in which the colchicine solution was added to the intraluminal cerebrospinal fluid creating a sustained hyperpressure, exhibited at least a 2.5-fold increase in both the mitotic density and index compared with control embryos. Based on the small sample size, we cautiously conclude that sustained hyper-intraluminal pressure does stimulate mitosis.

Expansion, folding, and abnormal lamination of the chick optic tectum after intraventricular injections of FGF2

“…This second hypothesis implies that intraventricular pressure is relatively high and that the pia mater, rather than the ventricular surface (i.e., the ependymal layer), provides the major resistance to cerebrospinal fluid efflux. Evidence thus far exists only for the former assumption (39). The vimentin-positive radial glia fibers running up the center of individual volcanoes (Fig.…”

Focal adhesion kinase as a mechanotransducer during rapid brain growth of the chick embryo

“…Discovering FAK within the neuroepithelium is an extremely important finding because it has been known for years that growth of the vertebrate embryonic brain requires a delicate balance between increases of cavity size via fluid acquisition to maintain intraluminal pressure and increases in tissue volume via cellular proliferation (Desmond & Jacobson 1977;Pacheco et al, 1986;Alonso et al, 1998Alonso et al, , 1999Desmond et al, 2005;Gato & Desmond, 2009;Levitan & Desmond, 2010). Perhaps this is better understood in light of the fact that the early vertebrate embryonic brain is mostly cavity (70%) surrounded by a relatively thin neuroepithelium (30%).…”

“…In fact, the intraluminal pressure within the aorta is at least 23 times more than that within the embryonic brain based on the measurements of static pressure within the aorta and the embryonic brain. The internal static pressure in the aorta is 80 mm Hg (Lehoux, et al, 2005) compared with the average static pressure of 3.5 mm Hg of the CSF within the embryonic brain vesicles (Desmond, et al, 2005). This great difference in magnitude of internal pressure, may mean that the mechano-receptors on the surface of the aorta are more primed to respond to changes in pressure than they are in the embryonic brain.…”

Cerebrospinal fluid control of neurogenesis induced by retinoic acid during early brain development

“…It has previously been reported, in chick and rat embryos at early stages of development, that E-CSF exerts positive pressure against the neuroepithelial walls to generate an expansive force that drives morphogenesis Desmond and Jacobson, 1977;Alonso et al, 1998Alonso et al, , 1999Desmond et al, 2005). However, in recent years new roles for E-CSF have been demonstrated in the behaviour of neuroepithelial cell precursors, as it contributes to the regulation of the survival, proliferation, and neural differentiation of the neuroepithelial progenitor cells during early (Gato et al, 2005) and late development (Mashayekhi et al, 2002;OwenLynch et al, 2003;Miyan et al, 2003), as well as collaborating with the isthmic organiser in regulating mesencephalic gene expression (Parada et al, 2005a).…”