A model for cellulase production from Trichoderma reesei in an airlift reactor.

A mathematical model for cellulase production by Trichoderma reesei RUT-C30 grown in a cellulose medium with lactose as fed batch in an airlift reactor is proposed. To describe adequately the mass transfer between the air bubbles and the broth, it uses computational fluid dynamics (CFD) including multiphase Eulerian-Eulerian formulation, with a detailed description of the bubble size distribution through the use of the population balance model (PBM) and the class method (CM). The kinetics of the biomass growth is further coupled to the fluid flow conditions using partial differential equations for all the species involved, providing detailed information of important reactor conditions such as the distribution of oxygen, cellulose, and the shear stress within the reactor over the entire period of fermentation. Predicted results agree well with the available overall measurements for a typical fed-batch operation and detailed profiles of the predicted concentration fields are discussed from an engineering viewpoint.

Diffusion of rhodamine B and bovine serum albumin in fibrin gels seeded with primary endothelial cells.

Scaffolds with adequate mass transport properties are needed in many tissue engineering applications. Fibrin is considered a good biological material to fabricate such scaffolds. However, very little is known about mass transport in fibrin. Therefore, a method based on the analysis of fluorescence intensity for measuring the apparent diffusion coefficient of rhodamine B and fluorescein-labelled bovine serum albumin (FITC-BSA) is described. The experiments are performed in fibrin gels with and without human umbilical vein endothelial cells (HUVEC). The apparent diffusion coefficients of rhodamine B and FITC-BSA in fibrin (fibrinogen concentration of 4 mg/mL) with different cell densities are reported. A LIVE/DEAD(®) assay is performed to confirm the viability of HUVEC seeded at high densities. Diffusion coefficients for rhodamine B remain more or less constant up to 5×10(5) cells/mL and correlate well with literature values measured by other methods in water systems. This indicates that the presence of HUVEC in the fibrin gels (up to 5×10(5) cells/mL) has almost no effect on the diffusion coefficients. Higher cell densities (>5×10(5) cells/mL) result in a decrease of the diffusion coefficients. Diffusion coefficients of rhodamine B and FITC-BSA obtained by this method agree with diffusion coefficients in water predicted by the Stokes-Einstein equation. The experimental design used in this study can be applied to measure diffusion coefficients in different types of gels seeded or not with living cells.

Bioreactor controlled by PI algorithm and operated with a perfusion chamber to support endothelial cell survival and proliferation.

This paper reports the optimization of a perfusion bioreactor system previously reported by us (Chouinard et al., 2009). The implementation of a proportional-integral (PI) controller algorithm to control oxygen concentration and pH is presented and discussed. P and I values used by the controller were first estimated using a First-Order-Plus-Dead-Time (FOPDT, Matlab Simulink) and then tuned manually. A new gas exchanger design compatible with the PI controller was introduced and validated to decrease interaction between the injected gases and overall inertia of the system. The gas exchanger was used to adjust both pH and dissolved oxygen (DO) concentration. This new bioreactor system allowed real-time PI control over pH and DO concentration at different flow rates (from 2 to 70 mL min(-1)). Cell viability and proliferation were investigated to validate the updated bioreactor design and performance.

Assessing a whiplash management model: a population-based non-randomized intervention study.

OBJECTIVE: To evaluate the effectiveness of a multidisciplinary clinical management approach for whiplash-associated disorders (WAD) following a motor vehicle injury in Quebec. METHODS: A clinical management model was implemented in 5 geographic regions of the Province of Quebec, Canada, in 7 hospitals and 19 clinics. A 2-group population-based parallel design was used to assess its effectiveness. All patients with a new whiplash injury seen in these 26 centers between March and September, 2001 were entered into the Whiplash Management Model (experimental group). A reference group included all subjects who had a whiplash injury during this same period but were not seen in these 26 intervention centers. All subjects were followed for up to a year. The outcome variables were time on compensation, time to file closure, and total direct costs. RESULTS: A total of 288 patients with WAD were identified in the experimental group and 1,875 patients in the reference group. The rate of ending of compensation was significantly higher in patients who received the experimental treatment model than those receiving the reference treatment approach (rate ratio, RR: 3.2; 95% confidence interval, CI: 2.8-3.6). The rate of file closure was also significantly higher with the experimental treatment (RR: 1.5; 95% CI: 1.2-1.8). The average cost per patient was significantly reduced with the experimental intervention. CONCLUSION: A coordinated whiplash management approach can lead to earlier return to work and lower costs for patients who have sustained a whiplash injury.

Functional recovery from paraplegia caused by syphilitic meningomyelitis.

BACKGROUND: Syphilitic involvement of the nervous system can present in many different ways. We report a patient who presented with rapidly evolving paraparesis secondary to syphilitic meningomyelitis. METHODS: Case report. FINDINGS: Cerebrospinal fluid (CSF) studies confirmed the diagnosis of neurosyphilis. Spinal magnetic resonance imaging (MRI) studies were indicative of leptomeningeal and thoracic spinal cord disease. Treatment with IV penicillin resulted in marked clinical, radiologic, and CSF improvement. MRI imaging provided documentation of spinal cord involvement and was useful in monitoring recovery. This patient's progressive neurologic improvement was monitored for 2 years and documented by periodic Functional Independence Measure scores. CONCLUSION: Recognition of this unusual complication of secondary neurosyphilis is important, because it is a treatable cause of paraparesis with potential for good recovery.