Bone remodeling continuously changes the architecture, mass and strength of the adult skeleton. The process is under hormonal control but also responds to changes in the local tissue load. Each remodeling cycle leads to a net loss of bone mass, and during aging this causes a significant reduction in strength, a process that appears to be accelerated during menopause. We have developed a simulation model of vertebral trabecular bone that can evaluate the long term effects of various treatments in terms of available histomorphometric information. Applying the techniques of cell mapping, we have also developed a computer program for automatic alignment and adjustment of consecutive bone sections and for direct determination of 3D-connectivity data.
E. Mosekilde, (Li. Mosekilde) and J.S. Thomsen
Bifurcations in Nephron Pressure and Flow Regulation
We have developed a new and physiologically more satisfactory model of how the individual nephron of the kidney regulates the incoming blood flow and hence protects itself against variations in arterial blood pressure. The model includes a relatively detailed account of the myogenic response of the incoming arteriole. With physiologically based relations between the various variables, and with realistic parameter values, the model reproduces many of the findings from experiments with rat kidneys. In particular, the model can perform self-sustained oscillations of the correct amplitude and period, and the model can also reproduce the period-doubling and chaotic dynamics observed under certain circumstances. Using one- and two-dimensional continuation methods we have performed a more detailed analysis of the bifurcation structure.
M. Barfred, (N.-H. Holstein-Rathlou) and E. Mosekilde
The Dynamics of Folding of Globular Proteins
Using a new micro-mechanical apparatus developed here over the past two years, I have observed, for the first time, that the dynamics of protein folding is characterized by discrete steps in time.
Taking advantage of the large conformational changes exhibited by globular proteins upon unfolding, I have prepared a "protein brush", analogous to the well-known polymer brushes. I attach the molecules to a solid surface at high densities while they are in the compact (folded) state, and let them swell subsequently in a denaturant, thus obtaining the brush.
The Spring Constant of Single Polymer Molecules
We obtain a measurement of the mechanical properties of a single polymer molecule of size approx. 30 nm. Using a micro-mechanical technique we show directly that the polymer chain behaves like a spring, and we measure the spring constant.
H. Jensenius and G. Zocchi