Biomedical subjects

Geoffrey E Gerstner

Publications and source records attributed to Geoffrey E Gerstner.

3 recordsLinked to original sources

PubMed2005

Loading effects on rat craniomandibular morphology: a system for gravity studies.

Gravity effects on muscle and bone are a major impediment to long-term space travel. We introduce a model for studying these effects, the craniomandibular system. Some advantages of this system include: (1) craniomandibular morphology is determined by epigenetic factors including gravity, (2) relatively light forces can significantly alter its morphology, and (3) soft diet and tooth loss produce effects that are similar to those produced in lower limbs by weightlessness. In the study, implants made either of gold (experimental group) or lightweight acrylic (controls) were attached to adult rats' mandibles. After 13 weeks, the animals' skulls and mandibles were dissected. Pair-wise comparisons indicated that the experimental animals showed significantly shortened and narrowed cranial bases, and significant changes in the posterior zygomatic arch region. These results indicate that simulated macrogravity influences bone remodeling in the adult craniomandibular system.

Acrylic Resins↗

PubMed2005

Predicting masticatory jaw movements from chin movements using multivariate linear methods.

Previously, we have used bivariate correlations of maximum and minimum displacement, velocity and acceleration variables to compare masticatory chin and jaw movements (J. Prosthet. Dent. 81 (1999) 179). This previous study represented a first step in exploring the hypothesis that the chin contained useful information regarding jaw kinematics. The current study extends our understanding of the relationship between masticatory chin and jaw movements by: (1) reconstructing and evaluating a more continuous trajectory of chin and jaw movements, and (2) performing multivariate correlations comparing chin and jaw movements at discrete points along the trajectory in order to gain insight into the coupling of chin and jaw movements during a chewing cycle. Results indicated that chin and jaw movement trajectories were visually similar in the lateral, vertical, and anteroposterior axes. The adjusted R(2) results in the lateral, vertical, and anteroposterior dimensions averaged 0.74, 0.78, and 0.89, respectively. Within chewing cycles, the lowest correlations between chin and jaw movements in the lateral and vertical dimensions occurred when the jaw was relatively closed, whereas the lowest correlations between chin and jaw movements in the anteroposterior dimension occurred while the jaw was opening from a closed position. The results indicated that jaw and chin movements were qualitatively similar and that at least 74% of the variation in jaw movements could be accounted for by multivariate linear models of chin movement.

Adult↗

PubMed2003

A model of vertebrate resting metabolic rate: balancing energetics and O2 transport in system design.

In vertebrates, maximal rates of oxygen consumption (V(O(2),max)) exceed resting rates (V(O(2),rest)) by an average factor of ten. This pattern of factorial scope has led to the hypothesis that V(O(2),rest) and V(O(2),max) are causally linked in vertebrates (aerobic capacity model, Bennett and Ruben, Science 206, 649-654, 1979). We propose an alternate theory that vertebrate resting metabolic rates are regulated at levels to optimize metabolic performance during activity, by reducing cardiovascular response times for O(2) transport. First, we argue that circulatory convection has the potential to be rate-limiting to vertebrate aerobic adjustment. We then show mathematically that incremental changes in convection requirements exhibit a nonlinear dependence on initial values. From this, a cost-benefit model is constructed, using energetics and blood-convection requirements, to predict the optimal fractional allocation to V(O(2),rest) in vertebrates as 11% of V(O(2),max). The implications of our results to vertebrate metabolic design and the evolution of endothermy are discussed.

Adaptation, Physiological↗