Computational fluid dynamics (CFD) and magnetic resonance (MR) gas velocimetry were concurrently performed to study airflow in the same model of human proximal airways. Realistic in vivo-based human airway geometry was segmented from thoracic computed tomography. The three-dimensional numerical description of the airways was used for both generation of a physical airway model using rapid prototyping and mesh generation for CFD simulations. Steady laminar inspiratory experiments (Reynolds number Re = 770) were performed and velocity maps down to the fourth airway generation were extracted from a new velocity mapping technique based on MR velocimetry using hyperpolarized (3)He gas. Full two-dimensional maps of the velocity vector were measured within a few seconds. Numerical simulations were carried out with the experimental flow conditions, and the two sets of data were compared between the two modalities. Flow distributions agreed within 3%. Main and secondary flow velocity intensities were similar, as were velocity convective patterns. This work demonstrates that experimental and numerical gas velocity data can be obtained and compared in the same complex airway geometry. Experiments validated the simulation platform that integrates patient-specific airway reconstruction process from in vivo thoracic scans and velocity field calculation with CFD, hence allowing the results of this numerical tool to be used with confidence in potential clinical applications for lung characterization. Finally, this combined numerical and experimental approach of flow assessment in realistic in vivo-based human airway geometries confirmed the strong dependence of airway flow patterns on local and global geometrical factors, which could contribute to gas mixing.

-Molecular detection of pathogenic microorganisms in ticks is based on DNA amplification of the target pathogen; therefore, extraction of DNA from the tick is a major step. In this study, we compared three different tick DNA extraction protocols based on an enzymatic digestion by proteinase K followed by DNA extraction by a commercial kit (method 1), or on mortar crushing, proteinase K digestion and phenol/chloroform DNA extraction (method 2) and fine crushing with a beads beater, proteinase K digestion and DNA extraction using a commercial kit (method 3). The absence of PCR inhibitors and the DNA quality were evaluated by PCR amplification of the tick mitochondrial 16S rRNA gene using tick-specific primers. With method 1, 23/30 (77%) of the samples were extracted; with method 2, 30/31 (97%) of the samples were extracted and with method 3, 30/30 (100%) of the samples were extracted. DNA extraction efficiency using method 3 is significantly higher than DNA extraction efficiency using method 1 (100% versus 77%, P < 0.05). There was no significant difference between methods 2 and 3. Method 3 was however more adapted to cohort studies than method 2. This technique was validated for cohort tick DNA extraction and applicable to the treatment of small samples such as nymphs and soft ticks with 100% efficiency. tick / DNA extraction / PCR / nymphal stage

Heterozygosity‐fitness correlations (HFCs) are increasingly reported but the underlying mechanisms causing HFCs are generally poorly understood. Here, we test for HFCs in roe deer (Capreolus capreolus) using 22 neutral microsatellites widely distributed in the genome and four microsatellites in genes that are potentially under selection. Juvenile survival was used as a proxy for individual fitness in a population that has been intensively studied for 30 years in northeastern France. For 222 juveniles, we computed two measures of genetic diversity: individual heterozygosity (H), and mean d2 (relatedness of parental genomes). We found a relationship between genetic diversity and fitness both for the 22 neutral markers and two candidate genes: IGF1 (Insulin‐like Growth Factor I) and NRAMP (natural resistance‐associated macrophage protein). Statistical evidence and the size of genetic effects on juvenile survival were comparable to those reported for early development and cohort variation, suggesting a substantial influence of genetic components on fitness in this roe deer population. For the 22 neutral microsatellites, a correlation with fitness was revealed for mean d2, but not for H, suggesting a possible outbreeding advantage. This heterosis effect could have been favored by introduction of genetically distant (Hungarian) roe deer to the population in recent times and, possibly, by the structuring of the population into distinct clans. The locus‐specific correlations with fitness may be driven by growth rate advantages and resistance to diseases known to exist in the studied population. Our analyses of neutral and candidate gene markers both suggest that the observed HFCs are likely mainly due to linkage with dominant or overdominant loci that affect fitness ("local" effect) rather than to a genome‐wide relationship with homozygosity due to inbreeding ("general" effect).

This paper describes a technique that combines radial MRI and phase contrast (PC) to map the velocities of hyperpolarized gases ( 3 He) in respiratory airways. The method was evaluated on well known geometries (straight and U-shaped pipes) before it was applied in vivo. Dynamic 2D maps of the three velocity components were obtained from a 10-mm slice with an in-plane spatial resolution of 1.6 mm within 1 s. Integration of the in vitro throughplane velocity over the slice matched the input flow within a relative precision of 6.4%. As expected for the given Reynolds number, a parabolic velocity profile was obtained in the straight pipe. In the U-shaped pipe the three velocity components were measured and compared to a fluid-dynamics simulation so the precision was evaluated as fine as 0.025 m s ؊1. Ventilation and particle-deposition studies are important parts of functional and physiological explorations of the lungs. Normal or altered geometries of the bronchial tree directly affect airflow distributions in the lungs (1). Particle deposition is involved in inhalation toxicology, and its study is motivated to achieve a better understanding of its effects and devise new therapies based on drug inhalation (2,3). Knowledge of flow patterns in large tracheobronchial airways is required to understand flow distribution, gas mixing, and inhaled particle deposition.Several experimental and numerical studies have focused on the velocity patterns in large airways. Experimentally, velocity fields in various airway models were obtained with the available techniques for measuring gas velocity, including hot-wire anemometry, laser Doppler anemometry, and particle-image velocimetry (4 -6). Numerical simulations were also performed with computational fluid dynamics (CFD) (2,6 -8). Both approaches independently yielded basic results that led to a better understanding of gas-flow dynamics in the bronchi. However, in vivo, functional respiratory tests provide only global information on the airflow, and some invasive techniques introduce sensors to probe flow properties locally but only at a few specific points (9). Nevertheless, noninvasive direct measurements of gas velocities have never been obtained in living subjects, since none of the abovecited measurement techniques are able to do so.Recently it was shown that ventilation dynamics in the lungs of small animals and humans can be monitored by hyperpolarized (HP) gas MRI (10) using EPI (11), fast gradient-echo (12), spiral (13,14), or radial sequences (15,16). However, quantifying the gas-flow rate from signal dynamics is not straightforward because it is difficult to separate flip angle and inflow effects (12,(17)(18)(19). Moreover, additional signal losses result from oxygen-dependent longitudinal relaxation times that become relevant over long acquisition times (20), and from short effective transverse relaxation times, while the gas diffuses through the magnetic field gradients within the airways (21,22).In proton MRI, phase contrast (PC) has been widely used to map blood v...