Computational Modeling of the Vacuolar pH-Homeostasis in Arabidopsis thaliana

The aim of this work is the analysis of the vacuolar pH homeostasis in Arabidopsis thaliana root cells by means of computational modeling. The pH is an important parameter for a range of cellular processes such as the control of enzyme activity and the maintenance of osmotic pressure acting through the establishment of a proton motive force across the vacuolar membrane that in turn is used in the homeostasis of other ions on both sides of the membrane. Although many processes are known to be important for the establishment and maintenance of an acidic vacuolar lumen, recent experimental results have shown that our current understanding of those processes is not complete. To study the vacuolar pH homeostasis in an integrative manner, this work focuses on three different aspects. In the first part, an overview over computational systems biology approaches in Arabidopsis thaliana is given to demonstrate the state of the art and put the rest of the work in a broader context. The second part then focuses on transmembrane transport reactions and the importance of the correct scaling of the kinetic rate laws of those reactions in mathematical models employing sets of ordinary differential equations, which is of importance for any multi-compartment model such as the one presented in part three of this thesis. In the third part, a mathematical modeling approach is subsequently used to explain experimental data concerning the vacuolar pH homeostasis. To do so, three hypotheses of the mechanisms contributing to vacuolar acidification are developed: An as of yet unknown direct proton import, protons released by protein degradation and the reversal of a proton-calcium antiporter. Each of those hypotheses is implemented in an ordinary differential equations model and tested for feasibility against the experimental data

Evaluation of a Point-of-Care Test for Pre-Vaccination Testing to Detect Antibodies against Canine Adenoviruses in Dogs

(1) Background: Antibody testing is commonly used to assess a dog’s immune status. For detection of antibodies against canine adenoviruses (CAVs), one point-of-care (POC) test is available. This study assessed the POC test´s performance. (2) Methods: Sera of 198 privately owned dogs and 40 specific pathogen-free (SPF) dogs were included. The reference standard for detection of anti-CAV antibodies was virus neutralization (VN) using CAV-1 and CAV-2 antigens. Specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy (OA) of the POC test were assessed. Specificity was considered most important. (3) Results: Prevalence of CAV-1 neutralizing antibodies (≥10) was 76% (182/238) in all dogs, 92% (182/198) in the subgroup of privately owned dogs, and 0% (0/40) in SPF dogs. Prevalence of CAV-2 neutralizing antibodies (≥10) was 76% (181/238) in all dogs, 91% (181/198) in privately owned dogs, and 0% (0/40) in SPF dogs. Specificity for detection of CAV-1 antibodies was lower (overall dogs, 88%; privately owned dogs, 56%; SPF dogs, 100%) compared with specificity for detection of CAV-2 antibodies (overall dogs, 90%; privately owned dogs, 65%; SPF dogs, 100%). (4) Conclusions: Since false positive results will lead to potentially unprotected dogs not being vaccinated, specificity should be improved to reliably detect anti-CAV antibodies that prevent infectious canine hepatitis in dogs

Health Risk Appraisals for Health Insurance

La evaluación de riesgos individuales en salud (ERIS) provee una oportunidad para enfatizar la promoción y prevención de enfermedades en individuos, lo cual se traduce a poblaciones. Un componente importante de la evaluación de riesgos en salud es la recolección de datos detallados en la historia clínica, y los antecedentes médicos familiares. Esta información es determinante y de importante ayuda en los riesgos individuales en condiciones crónicas y enfermedades hereditarias. A pesar de que el concepto de evaluación de riesgos en salud se ha utilizado desde 1940, y las evaluaciones son comúnmente realizadas en espacios laborales, han tenido un pobre acoplamiento en la práctica clínica y del aseguramiento en salud, a pesar de la importancia que confiere la prevención primaria de enfermedades. En este trabajo describimos y fomentamos el uso de evaluación de riesgos individuales como una herramienta fundamental en la práctica clínica a todo nivel, así como en los modelos de aseguramiento y sistemas de salud.Health Risk Assessment Studies allows opportunities to emphasize on health promotion and disease prevention on single individuals, which generalizes to populations. Well written medical records and family history are key components of health risk assessments. This information is determinant to figure out individual health risks in chronic conditions and hereditary diseases. Despite health risk assessments have been around since 1940, and their use is commonly used in work environments, it has not been in widespread use in clinical practice and in health insurance. This dissertation describes and foments the use of health risk assessments in single individuals as a fundamental tool for all level clinical practice, as well in health insurance and health systems

Comparison of Four Commercially Available Point-of-Care Tests to Detect Antibodies against Canine Parvovirus in Dogs

Measuring antibodies to evaluate dogs’ immunity against canine parvovirus (CPV) is useful to avoid unnecessary re-vaccinations. The study aimed to evaluate the quality and practicability of four point-of-care (POC) tests for detection of anti-CPV antibodies. The sera of 198 client-owned and 43 specific pathogen-free (SPF) dogs were included; virus neutralization was the reference method. Specificity, sensitivity, positive and negative predictive value (PPV and NPV), and overall accuracy (OA) were calculated. Specificity was considered to be the most important indicator for POC test performance. Differences between specificity and sensitivity of POC tests in the sera of all dogs were determined by McNemar, agreement by Cohen’s kappa. Prevalence of anti-CPV antibodies in all dogs was 80% (192/241); in the subgroup of client-owned dogs, it was 97% (192/198); and in the subgroup of SPF dogs, it was 0% (0/43). FASTest® and CanTiCheck® were easiest to perform. Specificity was highest in the CanTiCheck® (overall dogs, 98%; client-owned dogs, 83%; SPF dogs, 100%) and the TiterCHEK® (overall dogs, 96%; client-owned dogs, 67%; SPF dogs, 100%); no significant differences in specificity were observed between the ImmunoComb®, the TiterCHEK®, and the CanTiCheck®. Sensitivity was highest in the FASTest® (overall dogs, 95%; client-owned dogs, 95%) and the CanTiCheck® (overall dogs, 80%; client-owned dogs, 80%); sensitivity of the FASTest® was significantly higher compared to the one of the other three tests (McNemars p-value in each comparison: <0.001). CanTiCheck® would be the POC test of choice when considering specificity and practicability. However, differences in the number of false positive results between CanTiCheck®, TiterCHEK®, and ImmunoComb® were minimal

Solid-state structure and anti­microbial and cytotoxicity studies of a cucurbit[6]uril-like Cu6L4 constructed from 3,5-bis­[(1H-tetra­zol-5-yl)meth­yl]-4H-1,2,4-triazol-4-amine

3,5-Bis[(1H-tetra­zol-5-yl)meth­yl]-4H-1,2,4-triazol-4-amine (H2L) associates under deprotonation with CuSO4 in aqueous medium to form a new waisted barrel-shaped M6L4 cluster, namely hexa­aqua­tetra­kis­{μ4-3,5-bis­[(1H-tetra­zol-5-yl)meth­yl]-4H-1,2,4- triazol-4-amine}-μ4-sulfato-hexa­copper(II) sulfate hydrate, [Cu6(SO4) (C6H6N12)4(H2O)6]SO4·nH2O (n = ∼23) (1). Cluster 1 resembles concave cucurbit[6]uril and has one disordered sulfate anion trapped inside the cage, which additionally stabilizes the Cu6 unit. The CuII ions have either a square-pyramidal or a distorted octa­hedral geometry. The equatorial positions are filled by N atoms from the L2− ligand, while the axial positions are occupied by coordinated water mol­ecules and O atoms of the sulfate counter-ion. In the solid state, the Cu6 clusters are connected through a large number of hydrogen bonds formed by uncoordinated water mol­ecules and an additional sulfate anion. The compound shows good anti­microbial activity against E. coli tested with the Kirby Bauer approach. In addition, the cell viability towards HeLa and L-929 cells was studied

Electric Birefringence Spectroscopy of Montmorillonite Particles

Full version available at http://pubs.rsc.org/en/Content/ArticleLanding/2016/SM/C6SM00512H#!divAbstractElectric birefringence (EB) of suspensions of anisotropic particles can be considered an electrokinetic phenomenon in a wide sense, as both liquid motions and polarization of the electrical double layer (EDL) of the particles participate in the process of particle orientation under the applied field. The EB spectrum can be exploited for obtaining information on the dimensions, average value and anisotropy of the surface conductivity of the particles, and concentration and Maxwell-Wagner polarization of the EDLs. It is thus a highly informative technique, applicable to non-spherical particles. In this paper, we investigate the birefringent response of plate-like montmorillonite particles as a function of the frequency and amplitude of the applied AC electric field, for different compositions (pH, ionic strength, particle concentration) of the suspensions. The transient electric birefringence (i.e., the decay of the refractive index anisotropy with time when the field is switched off) is used for estimating the average dimensions of the particle axes, by modeling it as an oblate spheroid. The obtained values are very similar to those deduced from electron microscopy determinations. The frequency spectra show a very distinct behaviour at low (on the order of a few Hz) and high (up to several MHz) frequencies: the $\alpha$ and Maxwell-Wagner-O'Konski relaxations, characteristic of EDLs, are detected at frequencies above 10 kHz, and they can be well explained using electrokinetic models for the polarization of EDLs. At low frequencies, in contrast, the birefringence changes to negative, an anomalous response meaning that the particles tend to orient with their symmetry axis parallel to the field. This anomaly is weaker at basic pHs, high ionic strengths and low concentrations. The results can be explained by considering the polydispersity of real samples: the fastest particles redistribute around the slowest ones, inducing a hydrodynamic torque opposite to that of the field, in close similarity with results previously described for mixtures of anisometric particles with small amounts of spherical nanoparticles.Junta de Andalucía, Spain (PE2012-FQM0694)MINECO, Spain (project No. FIS2013-47666-C3-1-R)Ramón y Cajal Programme (RYC-2014-16901)[EMBARGADO hasta mayo 2017

Determination of the size distribution of non-spherical nanoparticles by electric birefringence-based methods

The in situ determination of the size distribution of dispersed non-spherical nanoparticles is an essential characterization tool for the investigation and use of colloidal suspensions. In this work, we test a size characterization method based on the measurement of the transient behaviour of the birefringence induced in the dispersions by pulsed electric fields. The specific shape of such relaxations depends on the distribution of the rotational diffusion coefficient of the suspended particles. We analyse the measured transient birefringence with three approaches: the stretched-exponential, Watson-Jennings, and multiexponential methods. These are applied to six different types of rod-like and planar particles: PTFE rods, goethite needles, single- and double-walled carbon nanotubes, sodium montmorillonite particles and gibbsite platelets. The results are compared to electron microscopy and dynamic light scattering measurements. The methods here considered provide good or excellent results in all cases, proving that the analysis of the transient birefringence is a powerful tool to obtain complete size distributions of non-spherical particles in suspension.Financial support of this investigation by Junta de Andalucía, Spain (grant No. PE2012-FQM0694) and University of Granada (Program “Proyectos de investigación precompetitivos”) is gratefully acknowledged

Temperature controls diel oscillation of the CO2 concentration in a desert soil

The diel dynamic of the CO2 concentration in soils in relation to temperature is not yet fully understood. Air temperature might control the soil CO2 concentration due to thermal convective venting at sites experiencing large temperature differences between the atmosphere and the soil. Therefore, the objective of this study was to determine the soil CO2 concentration and its temporal dynamic in a deep desert soil in relationship to soil and air temperature based on high frequency measurements. For this purpose, CO2 concentration and temperature were measured in six soil depths (ranging from 15 to 185 cm) in a coarse-textured desert soil in the North of Chile every 60 min together with precipitation and air temperature for one year. The mean CO2 concentration calculated across the whole measuring period increased linearly with soil depth from 463 ppm in 15 cm to 1542 ppm in 185 cm depth. We observed a strong diel oscillation of the CO2 concentration that decreased with soil depth and a hysteretic relationship between the topsoil CO2 concentration and both air and soil temperature. The Rayleigh-Darcy number calculated for different times indicates that thermal convective venting of the soil occurred during the night and in the early morning. A small precipitation event (4 mm) increased the CO2 concentrations in 15, 30, and 50 cm depths for several days but did not alter the amplitude of the diel oscillation of the CO2 concentration. The diel oscillation of the CO2 concentration and the hysteretic relationship between soil CO2 concentration and air temperature were likely caused by thermal convection, leading to transport of CO2-rich air from the soil to the atmosphere at night. In conclusion, our results indicate that the soil CO2 concentration can be largely controlled by convection caused by temperature differences, and not only by diffusion. The results have important implications as they provide further evidence that thermal convective venting contributes to gas exchange at sites experiencing large temperature differences between the atmosphere and the soil, which is relevant for soil chemical reactions