A comparison of biologically variable ventilation to recruitment manoeuvres in a porcine model of acute lung injury

BackgroundBiologically variable ventilation (return of physiological variability in rate and tidal volume using a computer-controller) was compared to control mode ventilation with and without a recruitment manoeuvre – 40 cm H₂O for 40 sec performed hourly; in a porcine oleic acid acute lung injury model.MethodsWe compared gas exchange, respiratory mechanics, and measured bronchoalveolar fluid for inflammatory cytokines, cell counts and surfactant function. Lung injury was scored by light microscopy. Pigs received mechanical ventilation (F_IO₂ = 0.3; PEEP 5 cm H₂O) in control mode until PaO₂ decreased to 60 mm Hg with oleic acid infusion (PaO₂/F_IO₂ <200 mm Hg). Additional PEEP to 10 cm H₂O was added after injury. Animals were randomized to one of the 3 modes of ventilation and followed for 5 hr after injury.ResultsPaO₂ and respiratory system compliance was significantly greater with biologically variable ventilation compared to the other 2 groups. Mean and mean peak airway pressures were also lower. There were no differences in cell counts in bronchoalveolar fluid by flow cytometry, or interleukin-8 and -10 levels between groups. Lung injury scoring revealed no difference between groups in the regions examined. No differences in surfactant function were seen between groups by capillary surfactometry.ConclusionsIn this porcine model of acute lung injury, various indices to measure injury or inflammation did not differ between the 3 approaches to ventilation. However, when using a low tidal volume strategy with moderate levels of PEEP, sustained improvements in arterial oxygen tension and respiratory system compliance were only seen with BVV when compared to CMV or CMV with a recruitment manoeuvre.     

Charaterization and hydrodynamic behaviour of modified gelatin: II. Characterization by high performance size exclusion chromatography — comparison with dextrans and proteins

Gelatin samples obtained by chemical modification (succinylation) are studied by SEC on silica based chromatographic supports. The influence of the pH of eluent mixtures (potassium phosphate added to NaCl) in the range 7-3.3 shows that the void volume peak (VVP) is lowered or even vanishes at pH 3.3 with the 3000 SW (TSK) gel. A process using an ultrasound treatment before injection is reported in order to determine accurately the molecular parameters of gelatin onto TSK gel with a minimal VV P. This peak is attributed to molecular aggregation of a part of the modified gelatin. After disaggregation by ultrasound or heat treatment the results are in good accordance with those obtained by other methods. It is demonstrated that with proteins and dextrans the TSK 3000 SW gel does not agree with the universal calibration curve (log[ν] · versus K_d as reported previously. A single calibration curve is obtained when the Stokes radius is plotted versus K_d. Gelatin fractions are eluted at pH 7 close to this calibration curve. This plot shows that gelatin fractions at pH 3.3 are not eluted by a pure size exclusion mechanism on 3000 SW gel. It is concluded that hydrophobic interactions between fractions of gelatin and the gel explain the high retention of these samples.     

Production of penicillin by immobilized films ofPenicillium chrysogenum

Summary Various materials were tested and polycarbonate was chosen as the support material for attachment and film growth ofP. chrysogenum in rotating disc fermenters. During batch runs using a penicillin production medium attached biomass increased at a linear rate and penicillin G was produced by the immobilized mycelium over a six day period.     

3D immuno-confocal image reconstruction of fibroblast cytoskeleton and nucleus architecture

Computational models of cellular structures generally rely on simplifying approximations and assumptions that limit biological accuracy. This study presents a comprehensive image processing pipeline for creating unified three-dimensional (3D) reconstructions of the cell cytoskeletal networks and nuclei. Confocal image stacks of these cellular structures were reconstructed to 3D isosurfaces (Imaris), then tessellations were simplified to reduce the number of elements in initial meshes by applying quadric edge collapse decimation with preserved topology boundaries (MeshLab). Geometries were remeshed to ensure uniformity (Instant Meshes) and the resulting 3D meshes exported (ABAQUS) for downstream application. The protocol has been applied successfully to fibroblast cytoskeletal reorganisation in the scleral connective tissue of the eye, under mechanical load that mimics internal eye pressure. While the method herein is specifically employed to reconstruct immunofluorescent confocal imaging data, it is also more widely applicable to other biological imaging modalities where accurate 3D cell structures are required.