Biomechanical forces exert anabolic effects on osteoblasts by activation of SMAD 1/5/8 through type 1 BMP receptor

Osteoblasts are mechanosensitive cells, which respond to biomechanical stimuli to regulate the bone structure through anabolic and catabolic gene regulation. To examine the effects of mechanical forces on the osteogenic responses through the SMAD signaling in osteoblasts, the cells were cultured in well-characterized mechanoresponsive 3-D scaffolds and exposed to 10% dynamic compressive strain (Cmp) at 1 Hz. Subsequently, SMAD phosphorylation and osteogenic gene induction was examined. Osteoblasts cultured in 3-D scaffolds exhibited increased constitutive SMAD 1/5/8 phosphorylation, as compared to monolayers cultures. This SMAD 1/5/8 phosphorylation was further upregulated after 10, 30 and 60 min in response to Cmp, exhibiting a peak activation at 30 min. No significant changes in SMAD2 phosphorylation were observed, suggesting signals generated by Cmp may not activate the Transforming Growth Factor-β signaling cascade. Subsequently, biomechanical stimulation-induced SMAD 1/5/8 phosphorylation upregulated the expression of osteogenic genes such as Osteoprotegrin, Msx2 and Runx2. Dorsomorphin, a selective inhibitor of the bone morphogenetic protein (BMP) receptor type 1 (BMPR1), blocked Cmp-induced SMAD 1/5/8 phosphorylation, as well as Osteoprotegrin, Msx2 and Runx2 gene expression. Collectively, the present findings demonstrate that biomechanical stimulation of osteoblasts activates SMAD 1/5/8 in the BMP signaling pathway through BMPR1 and may enhance osteogenesis by upregulating SMAD-dependent osteogenic genes.

Space-time least-squares finite element method for convection-reaction system with transformed variables

We present a method to solve a convection-reaction system based on a least-squares finite element method (LSFEM). For steady-state computations, issues related to recirculation flow are stated and demonstrated with a simple example. The method can compute concentration profiles in open flow even when the generation term is small. This is the case for estimating hemolysis in blood. Time-dependent flows are computed with the space-time LSFEM discretization. We observe that the computed hemoglobin concentration can become negative in certain regions of the flow; it is a physically unacceptable result. To prevent this, we propose a quadratic transformation of variables. The transformed governing equation can be solved in a straightforward way by LSFEM with no sign of unphysical behavior. The effect of localized high shear on blood damage is shown in a circular Couette-flow-with-blade configuration, and a physiological condition is tested in an arterial graft flow.

Observation of ultrahigh-energy cosmic rays with the ANITA balloon-borne radio interferometer

We report the observation of 16 cosmic ray events with a mean energy of 1.5 × 10¹⁹ eV via radio pulses originating from the interaction of the cosmic ray air shower with the Antarctic geomagnetic field, a process known as geosynchrotron emission. We present measurements in the 300-900 MHz range, which are the first self-triggered, first ultrawide band, first far-field, and the highest energy sample of cosmic ray events collected with the radio technique. Their properties are inconsistent with current ground-based geosynchrotron models. The emission is 100% polarized in the plane perpendicular to the projected geomagnetic field. Fourteen events are seen to have a phase inversion due to reflection of the radio beam off the ice surface, and two additional events are seen directly from above the horizon. Based on a likelihood analysis, we estimate angular pointing precision of order 2° for the event arrival directions.

Pharmacoeconomics of Volatile Inhalational Anaesthetic Agents: An 11-Year Retrospective Analysis

With continuously increasing expenditure on health care resources, various cost containment strategies have been suggested in regard to controlling the cost of inhalational anaesthetic agents. We performed a cost identification analysis assessing inhalational anaesthetic agent expenditure at a tertiary level hospital, along with an evaluation of strategies to contain the cost of these agents.

The number of bottles of isoflurane, sevoflurane and desflurane used during the financial years 1997 to 2007 was retrospectively determined and the acquisition costs and cumulative drug expenditure calculated. Pharmacoeconomic modelling using low fresh gas flow anaesthesia was performed to evaluate practical methods of cost reduction.

The use of isoflurane decreased from 384 bottles during 1997 to 204 in 2007. In contrast, use of sevoflurane increased from 226 bottles during 1998 to 875 during 2007. Desflurane use increased from 34 bottles per year during 2002 (its year of introduction) to 163 bottles per year in 2007. While the inflation-adjusted cumulative expenditure for these inhalational agents (Australian dollars) increased from $132,000 in 1997 to over $326,000 in 2007, an increase of 168%, patient workload over the same period increased by only 11%. Pharmacoeconomic modelling demonstrated that sevoflurane at 2 l/minute costs 19 times more than isoflurane at 0.5 l/minute.

For the financial years 1997 to 2007, we found a progressive shift from the cheaper isoflurane to the more expensive agents, sevoflurane and desflurane, a shift associated with marked increases in costs. Low flow anaesthesia with isoflurane is one strategy to reduce costs.