New method for the resolution of the enantiomers of 5,6-Dihydroxy-2-Methyl-Aminotetralin by selective derivatization and HPLC analysis: Application to biological fluids

A new chiral derivatization procedure for the HPLC resolution of chiral catecholamines and structurally related compounds is described. The homochiral reagent, (+)-(R)-1-phenylethyl isocyanate (RPEIC), was added to separate and quantitate the enantiomers of rac-5,6-dihydroxy-2-methyl-aminotetralin, the main metabolite of rac-5,6-diisobutyryl-2-methyl-aminotetralin, a potent dopamine agonist, by reversed-phase HLPC analysis. To avoid catecholamine degradation in the basic reaction medium and to obtain the selective and quantitative derivatization of the amino group of the compound, the reversible complex formation between diphenylborinic acid (DPBA) and the catechol group, in alkaline medium, was performed before homochiral isocyanate addition. The RPEIC derivatization was completed in 30 min and then the DPBA complex was dissociated by adding dilute acid. The structure of intermediates and urea derivatives was confirmed by mass spectrometry. The use of an electrochemical detector, operating in redox mode, allowed HPLC quantitation of enantiomers at the nanogram level in plasma and urine. The derivatization procedure is also suitable for other catecholamine-related compounds. © 1996 Wiley-Liss, Inc.     

Metal‐Oxide‐Free Methylammonium Lead Iodide Perovskite‐Based Solar Cells: the Influence of Organic Charge Transport Layers

Metal‐oxide‐free methylammonium lead iodide perovskite‐based solar cells are prepared using a dual‐source thermal evaporation method. This method leads to high quality reproducible films with large crystal domain sizes allowing for an in depth study of the effect of perovskite film thickness and the nature of the electron and hole blocking layers on the device performance. The power conversion efficiency increases from 4.7% for a device with only an organic electron blocking layer to almost 15% when an organic hole blocking layer is also employed. In addition to the in depth study on small area cells, larger area cells (approx. 1 cm^?2) are prepared and exhibit efficiencies in excess of 10%.     

Chromatin Dynamics during DNA Repair Revealed by Pair Correlation Analysis of Molecular Flow in the Nucleus

Chromatin dynamics modulate DNA repair factor accessibility throughout the DNA damage response. The spatiotemporal scale upon which these dynamics occur render them invisible to live cell imaging. Here we present a believed novel assay to monitor the in vivo structural rearrangements of chromatin during DNA repair. By pair correlation analysis of EGFP molecular flow into chromatin before and after damage, this assay measures millisecond variations in chromatin compaction with submicron resolution. Combined with laser microirradiation we employ this assay to monitor the real-time accessibility of DNA at the damage site. We find from comparison of EGFP molecular flow with a molecule that has an affinity toward double-strand breaks (Ku-EGFP) that DNA damage induces a transient decrease in chromatin compaction at the damage site and an increase in compaction to adjacent regions, which together facilitate DNA repair factor recruitment to the lesion with high spatiotemporal control.     

Influence of soil texture and crop management on the productivity of miscanthus (Miscanthus × giganteus Greef et Deu.) in the Mediterranean

Biomass productivity is the main favorable trait of candidate bioenergy crops. Miscanthus × giganteus is a promising species, due to its high‐yield potential and positive traits including low nutrient requirements and potential for C sequestration in soils. However, miscanthus productivity appears to be mostly related to water availability in the soil. This is important, particularly in Mediterranean regions where the risk of summer droughts is high. To date, there have been no studies on miscanthus responses under different soil conditions, while only a few have investigated the role of different crop managements, such as irrigation and nitrogen fertilization, in the Mediterranean. Therefore, the effects of contrasting soil textures (i.e. silty‐clay‐loam vs. sandy‐loam) and alternative agricultural intensification regimes (i.e. rainfed vs. irrigated and 0, 50, 100 kg ha^?1 nitrogen fertilization), on miscanthus productivity were evaluated at three different harvest times for two consecutive years. Our results confirmed the importance of water availability in determining satisfactory yields in Mediterranean environments, and how soil and site characteristics strongly affect biomass production. We found that the aboveground dry yields varied between 5 Mg ha^?1 up to 29 Mg ha^?1. Conversely, nitrogen fertilization played only a minor role on crop productivity, and high fertilization levels were relatively inefficient. Finally, a marked decrease, of up to ?40%, in the aboveground yield occurred when the harvest time was delayed from autumn to winter. Overall, our results highlighted the importance of determining crop responses on a site‐by‐site basis, and that decisions on the optimal harvest time should be driven by the biomass end use and other long‐term considerations, such as yield stability and the maintenance of soil fertility.     

Removal of the cortical endplates has little effect on ultimate load and damage distribution in QCT-based voxel models of human lumbar vertebrae under axial compression

Every year, 500,000 osteoporotic vertebral compression fractures occur in Europe. Quantitative computed tomography (QCT)-based finite element (FE) voxel models predict ultimate force whether they simulate vertebral bodies embedded in polymethylmethacrylate (PMMA) or vertebral sections with both endplates removed. To assess the effect of endplate removal in those predictions, non-linear FE analyses of QCT-based voxel models of human vertebral bodies were performed. High resolution pQCT images of 11 human lumbar vertebrae without posterior elements were coarsened to clinical resolution and bone volume fraction was used to determine the elastic, plastic and damage behavior of bone tissue. Three model boundary conditions (BCs) were chosen: the endplates were cropped (BC1, BC2) or voxel layers were added on the intact vertebrae to mimic embedding (BC3). For BC1 and BC3, the bottom nodes were fully constrained and the top nodes were constrained transversely while both node sets were freed transversely for BC2. Axial displacement was prescribed to the top nodes. In each model, we compared ultimate force and damage distribution during post-yield loading. The results showed that ultimate forces obtained with BC3 correlated perfectly with those computed with BC1 (R(2)=0.9988) and BC2 (R(2)=0.9987), but were in average 3.4% lower and 6% higher respectively. Moreover, good correlation of damage distribution calculated for BC3 was found with those of BC1 (R(2)=0.92) and BC2 (R(2)=0.73). This study demonstrated that voxel models of vertebral sections provide the same ultimate forces and damage distributions as embedded vertebral bodies, but with less preprocessing and computing time required.     

Multimodal fMRI Resting-State Functional Connectivity in Granulin Mutations: The Case of Fronto-Parietal Dementia

Background

Monogenic dementias represent a great opportunity to trace disease progression from preclinical to symptomatic stages. Frontotemporal Dementia related to Granulin (GRN) mutations presents a specific framework of brain damage, involving fronto-temporal regions and long inter-hemispheric white matter bundles. Multimodal resting-state functional MRI (rs-fMRI) is a promising tool to carefully describe disease signature from the earliest disease phase.

Objective

To define local connectivity alterations in GRN related pathology moving from the presymptomatic (asymptomatic GRN mutation carriers) to the clinical phase of the disease (GRN- related Frontotemporal Dementia).

Methods

Thirty-one GRN Thr272fs mutation carriers (14 patients with Frontotemporal Dementia and 17 asymptomatic carriers) and 38 healthy controls were recruited. Local connectivity measures (Regional Homogeneity (ReHo), Fractional Amplitude of Low Frequency Fluctuation (fALFF) and Degree Centrality (DC)) were computed, considering age and gender as nuisance variables as well as the influence of voxel-level gray matter atrophy.

Results

Asymptomatic GRN carriers had selective reduced ReHo in the left parietal region and increased ReHo in frontal regions compared to healthy controls. Considering Frontotemporal Dementia patients, all measures (ReHo, fALFF and DC) were reduced in inferior parietal, frontal lobes and posterior cingulate cortex. Considering GRN mutation carriers, an inverse correlation with age in the posterior cingulate cortex, inferior parietal lobule and orbitofrontal cortex was found.

Conclusions

GRN pathology is characterized by functional brain network alterations even decades before the clinical onset; they involve the parietal region primarily and then spread to the anterior regions of the brain, supporting the concept of molecular nexopathies.     

High-Level Diversity of Tailed Phages,Eukaryote-Associated Viruses,and Virophage-Like Elements in the Metaviromes of Antarctic Soils

The metaviromes of two distinct Antarctic hyperarid desert soil communities have been characterized. Hypolithic communities, cyanobacterium-dominated assemblages situated on the ventral surfaces of quartz pebbles embedded in the desert pavement, showed higher virus diversity than surface soils, which correlated with previous bacterial community studies. Prokaryotic viruses (i.e., phages) represented the largest viral component (particularly Mycobacterium phages) in both habitats, with an identical hierarchical sequence abundance of families of tailed phages (Siphoviridae > Myoviridae > Podoviridae). No archaeal viruses were found. Unexpectedly, cyanophages were poorly represented in both metaviromes and were phylogenetically distant from currently characterized cyanophages. Putative phage genomes were assembled and showed a high level of unaffiliated genes, mostly from hypolithic viruses. Moreover, unusual gene arrangements in which eukaryotic and prokaryotic virus-derived genes were found within identical genome segments were observed. Phycodnaviridae and Mimiviridae viruses were the second-most-abundant taxa and more numerous within open soil. Novel virophage-like sequences (within the Sputnik clade) were identified. These findings highlight high-level virus diversity and novel species discovery potential within Antarctic hyperarid soils and may serve as a starting point for future studies targeting specific viral groups.     

The EF-Hand Ca2+ Binding Protein MICU Choreographs Mitochondrial Ca2+ Dynamics in Arabidopsis

Plant organelle function must constantly adjust to environmental conditions, which requires dynamic coordination. Ca²⁺ signaling may play a central role in this process. Free Ca²⁺ dynamics are tightly regulated and differ markedly between the cytosol, plastid stroma, and mitochondrial matrix. The mechanistic basis of compartment-specific Ca²⁺ dynamics is poorly understood. Here, we studied the function of At-MICU, an EF-hand protein of Arabidopsis thaliana with homology to constituents of the mitochondrial Ca²⁺ uniporter machinery in mammals. MICU binds Ca²⁺ and localizes to the mitochondria in Arabidopsis. In vivo imaging of roots expressing a genetically encoded Ca²⁺ sensor in the mitochondrial matrix revealed that lack of MICU increased resting concentrations of free Ca²⁺ in the matrix. Furthermore, Ca²⁺ elevations triggered by auxin and extracellular ATP occurred more rapidly and reached higher maximal concentrations in the mitochondria of micu mutants, whereas cytosolic Ca²⁺ signatures remained unchanged. These findings support the idea that a conserved uniporter system, with composition and regulation distinct from the mammalian machinery, mediates mitochondrial Ca²⁺ uptake in plants under in vivo conditions. They further suggest that MICU acts as a throttle that controls Ca²⁺ uptake by moderating influx, thereby shaping Ca²⁺ signatures in the matrix and preserving mitochondrial homeostasis. Our results open the door to genetic dissection of mitochondrial Ca²⁺ signaling in plants.