Phosphorous Magnetic Resonance Spectroscopy to Detect Regional Differences of Energy and Membrane Metabolism in Naïve Glioblastoma Multiforme

Background: Glioblastoma multiforme (GBM) is a highly malignant primary brain tumor with infiltration of, on conventional imaging, normal-appearing brain parenchyma. Phosphorus magnetic resonance spectroscopy (31P-MRS) enables the investigation of different energy and membrane metabolites. The aim of this study is to investigate regional differences of 31P-metabolites in GBM brains. Methods: In this study, we investigated 32 patients (13 female and 19 male; mean age 63 years) with naïve GBM using 31P-MRS and conventional MRI. Contrast-enhancing (CE), T2-hyperintense, adjacent and distant ipsilateral areas of the contralateral brain and the brains of age- and gender-matched healthy volunteers were assessed. Moreover, the 31P-MRS results were correlated with quantitative diffusion parameters. Results: Several metabolite ratios between the energy-dependent metabolites and/or the membrane metabolites differed significantly between the CE areas, the T2-hyperintense areas, the more distant areas, and even the brains of healthy volunteers. pH values and Mg2+ concentrations were highest in visible tumor areas and decreased with distance from them. These results are in accordance with the literature and correlated with quantitative diffusion parameters. Conclusions: This pilot study shows that 31P-MRS is feasible to show regional differences of energy and membrane metabolism in brains with naïve GBM, particularly between the different “normal-appearing” regions and between the contralateral hemisphere and healthy controls. Differences between various genetic mutations or clinical applicability for follow-up monitoring have to be assessed in a larger cohort

A New Mass Conservation Approach to the Study of CO2 Advection in an Alpine Forest

A new method is proposed for the computation of CO2 Net Ecosystem Exchange (NEE) and its components in a forest ecosystem. Advective flux is estimated by taking into account the air mass conservation principle. For this purpose, wind and dry air density values on the surface of the control volume are first corrected and then the advective flux is estimated on the surface of the control volume. Turbulent flux is also computed along the surface of the control volume while storage flux is computed inside the volume. Additional characteristics of this method are that incompressibility of the mean flow is not assumed a priori, and that vertical and horizontal advective fluxes are not treated separately, but their sum is estimated directly. The methodology is applied to experimental data collected with a three-dimensional scheme at the alpine site of Renon during the ADVEX project (July 2005). The advection flux was found to be prevailing positive at night and negative during the day, as was found in previous studies on advection for the same site, but showed a lower scatter in half-hour calculated values. We tested the effect of its summation on turbulent and storage fluxes to produce half-hourly values of NEE. Nighttime NEE values were used in functional relations with soil temperature, daytime values with PPFD. The effect of addition of the advection component was an increase in the values of parameters indicating ecosystem respiration, quantum yield and photosynthetic capacity. The coefficient of correlation between NEE and environmental drivers increased.JRC.H.2-Air and Climat

A new mass conservation approach to the study of CO2 advection in an alpine forest

A new method is proposed for the computation of CO 2 Net Ecosystem Exchange(NEE) and its components in a forest ecosystem. Advective flux is estimated by takinginto account the air mass conservation principle. For this purpose, wind and dry airdensity values on the surface of the control volume are first corrected and then theadvective flux is estimated on the surface of the control volume. Turbulent flux is alsocomputed along the surface of the control volume while storage flux is computed insidethe volume. Additional characteristics of this method are that incompressibility of themean flow is not assumed a priori, and that vertical and horizontal advective fluxes are nottreated separately, but their sum is estimated directly. The methodology is applied toexperimental data collected with a three-dimensional scheme at the alpine site of Renonduring the Advex project (July 2005). The advection flux was found to be prevailingpositive at night and negative during the day, as was found in previous studies onadvection for the same site, but showed a lower scatter in half-hour calculated values. Wetested the effect of its summation on turbulent and storage fluxes to produce half-hourlyvalues of NEE. Nighttime NEE values were used in functional relations with soiltemperature, daytime values with PPFD. The effect of addition of the advectioncomponent was an increase in the values of parameters indicating ecosystem respiration,quantum yield, and photosynthetic capacity. The coefficient of correlation between NEEand environmental drivers increased