Narrow Results

Simple one-dimensional models of blood flow are widely used in simulating the transport of blood around the human vasculature. However, the effects of gravity have only been previously examined briefly and the effects of changes in wall properties and their interaction with gravitational forces have not been investigated. Here the effects of both gravitational forces and local changes in wall stiffness on the one-dimensional flow through axisymmetric vessels are studied. The governing fluid dynamic equations are derived from the Navier-Stokes equations for an incompressible fluid and linked to a simple model of the vessel wall, derived here from an exponential stress-strain relationship. A closed form of the hyperbolic partial differential equations is found. The flow behavior is examined in both the steady state and for wave reflection at a junction between two sections of different wall stiffness. A significant change in wave reflection coefficient is found under the influence of gravity, particularly at low values of baseline non-dimensional wall stiffness.

Microgravity in space has been reported to enhance bone resorption in vitro and in vivo, however, the gravity effect on bone remodeling is not well understood. In particular, there are only a few reports about gravity effect on osteoclasts. In the present study, we examined the hypergravity effect on mRNA expressions of osteoclast marker enzymes such as TRAP (tartrate-resistant acid phosphatase) and cathepsin K. Osteoclasts were exposed to 30 xg for 2 hr or 18 hr. Results suggested that hypergravity enhanced the mRNA expression of both enzymes with different manner; the expression of the TRAP showed a slight increase, that of the cathepsin K showed a non-monotonous time course with maximum hypergravity effect for short time (2 hr) incubation.