Influences of AT1 receptor blockade on tissue metabolism in obese men

ANG II applied to the interstitial space influences carbohydrate and lipid metabolism in a tissue-specific fashion. Thus endogenous ANG II may have a tonic effect on tissue metabolism that could be reversed with ANG II type 1 (AT1) receptor blockade, particularly during adrenergic stimulation. We studied 14 obese men. They were treated for 10 days with the AT1 receptor blocker irbesartan or with placebo in a double-blind and crossover fashion. At the end of each treatment period, we assessed skeletal muscle and adipose tissue metabolism using the microdialysis technique. The ethanol dilution technique was applied to follow changes in tissue blood flow. Measurements were obtained at baseline and during application of incremental isoproterenol concentrations through the microdialysis catheter. Blood pressure decreased from 133 +/- 3/84 +/- 3 to 128 +/- 3/79 +/- 2 mmHg for systolic and diastolic blood, respectively (P = 0.02 and 0.006, respectively) with AT1 receptor blockade. Isoproterenol perfusion caused a dose-dependent increase in dialysate glycerol in adipose tissue and in skeletal muscle. Irbesartan slightly reduced the isoproterenol-induced glycerol response in adipose tissue (P < 0.05 by ANOVA). Ethanol ratio, interstitial glucose supply, and lactate production in adipose tissue and skeletal muscle were similar with placebo and irbesartan. We conclude that AT1 receptor blockade in obese men does not reveal a major tonic ANG II effect on interstitial glucose supply, lipolysis, or glycolysis in skeletal muscle, either at rest or during beta-adrenergic stimulation. Endogeneous ANG II may slightly increase adipose tissue lipolysis. The mechanism may promote the redistribution of triglycerides from adipose tissue toward other organs.     

Function-Triggering Antibodies to the Adhesion Molecule L1 Enhance Recovery after Injury of the Adult Mouse Femoral Nerve

L1 is among the few adhesion molecules that favors repair after trauma in the adult central nervous system of vertebrates by promoting neuritogenesis and neuronal survival, among other beneficial features. In the peripheral nervous system, L1 is up-regulated in Schwann cells and regrowing axons after nerve damage, but the functional consequences of this expression remain unclear. Our previous study of L1-deficient mice in a femoral nerve injury model showed an unexpected improved functional recovery, attenuated motoneuronal cell death, and enhanced Schwann cell proliferation, being attributed to the persistent synthesis of neurotrophic factors. On the other hand, transgenic mice over-expressing L1 in neurons led to improved remyelination, but not improved functional recovery. The present study was undertaken to investigate whether the monoclonal L1 antibody 557 that triggers beneficial L1 functions in vitro would trigger these also in femoral nerve repair. We analyzed femoral nerve regeneration in C57BL/6J mice that received this antibody in a hydrogel filled conduit connecting the cut and sutured nerve before its bifurcation, leading to short-term release of antibody by diffusion. Video-based quantitative analysis of motor functions showed improved recovery when compared to mice treated with conduits containing PBS in the hydrogel scaffold, as a vehicle control. This improved recovery was associated with attenuated motoneuron loss, remyelination and improved precision of preferential motor reinnervation. We suggest that function-triggering L1 antibodies applied to the lesion site at the time of injury over a limited time period will not only be beneficial in peripheral, but also central nervous system regeneration.     

Exoribonuclease R interacts with endoribonuclease E and an RNA helicase in the psychrotrophic bacterium Pseudomonas syringae Lz4W

Endoribonuclease E, a key enzyme involved in RNA decay and processing in bacteria, organizes a protein complex called degradosome. In Escherichia coli, Rhodobacter capsulatus, and Streptomyces coelicolor, RNase E interacts with the phosphate-dependent exoribonuclease polynucleotide phosphorylase, DEAD-box helicase(s), and additional factors in an RNA-degrading complex. To characterize the degradosome of the psychrotrophic bacterium Pseudomonas syringae Lz4W, RNase E was enriched by cation exchange chromatography and fractionation in a glycerol density gradient. Most surprisingly, the hydrolytic exoribonuclease RNase R was found to co-purify with RNase E. Co-immunoprecipitation and Ni(2+)-affinity pull-down experiments confirmed the specific interaction between RNase R and RNase E. Additionally, the DEAD-box helicase RhlE was identified as part of this protein complex. Fractions comprising the three proteins showed RNase E and RNase R activity and efficiently degraded a synthetic stem-loop containing RNA in the presence of ATP. The unexpected association of RNase R with RNase E and RhlE in an RNA-degrading complex indicates that the cold-adapted P. syringae has a degradosome of novel structure. The identification of RNase R instead of polynucleotide phosphorylase in this complex underlines the importance of the interaction between endo- and exoribonucleases for the bacterial RNA metabolism. The physical association of RNase E with an exoribonuclease and an RNA helicase apparently is a common theme in the composition of bacterial RNA-degrading complexes.     

Electrostatic recognition in substrate binding to serine proteases

Serine proteases of the Chymotrypsin family are structurally very similar but have very different substrate preferences. This study investigates a set of 9 different proteases of this family comprising proteases that prefer substrates containing positively charged amino acids, negatively charged amino acids, and uncharged amino acids with varying degree of specificity. Here, we show that differences in electrostatic substrate preferences can be predicted reliably by electrostatic molecular interaction fields employing customized GRID probes. Thus, we are able to directly link protease structures to their electrostatic substrate preferences. Additionally, we present a new metric that measures similarities in substrate preferences focusing only on electrostatics. It efficiently compares these electrostatic substrate preferences between different proteases. This new metric can be interpreted as the electrostatic part of our previously developed substrate similarity metric. Consequently, we suggest, that substrate recognition in terms of electrostatics and shape complementarity are rather orthogonal aspects of substrate recognition. This is in line with a 2‐step mechanism of protein‐protein recognition suggested in the literature.     

Population Structure and Evidence for Both Clonality and Recombination among Brazilian Strains of the Subgenus Leishmania (Viannia)

Background/Objectives: Parasites of the subgenus Leishmania (Viannia) cause varying clinical symptoms ranging from cutaneous leishmaniases (CL) with single or few lesions, disseminated CL (DL) with multiple lesions to disfiguring forms of mucocutaneous leishmaniasis (MCL). In this population genetics study, 37 strains of L. (V.) guyanensis, 63 of L. (V.) braziliensis, four of L. (V.) shawi, six of L. (V.) lainsoni, seven of L. (V.) naiffi, one each of L. (V.) utingensis and L. (V.) lindenbergi, and one L. (V.) lainsoni/L. naiffi hybrid from different endemic foci in Brazil were examined for variation at 15 hyper-variable microsatellite markers. Methodology/Principal findings: The multilocus microsatellite profiles obtained for the 120 strains were analysed using both model- and distance-based methods. Significant genetic diversity was observed for all L. (Viannia) strains studied. The two cluster analysis approaches identified two principal genetic groups or populations, one consisting of strains of L. (V.) guyanensis from the Amazon region and the other of strains of L. (V.) braziliensis isolated along the Atlantic coast of Brazil. A third group comprised a heterogeneous assembly of species, including other strains of L. braziliensis isolated from the north of Brazil, which were extremely polymorphic. The latter strains seemed to be more closely related to those of L. (V.) shawi, L. (V.) naiffi, and L. (V.) lainsoni, also isolated in northern Brazilian foci. The MLMT approach identified an epidemic clone consisting of 13 strains of L. braziliensis from Minas Gerais, but evidence for recombination was obtained for the populations of L. (V.) braziliensis from the Atlantic coast and for L. (V.) guyanensis. Conclusions/Significance: Different levels of recombination versus clonality seem to occur within the subgenus L. (Viannia). Though clearly departing from panmixia, sporadic, but long-term sustained recombination might explain the tremendous genetic diversity and limited population structure found for such L. (Viannia) strains.     

Mapping Cortical Degeneration in ALS with Magnetization Transfer Ratio and Voxel-Based Morphometry

Pathological and imaging data indicate that amyotrophic lateral sclerosis (ALS) is a multisystem disease involving several cerebral cortical areas. Advanced quantitative magnetic resonance imaging (MRI) techniques enable to explore in vivo the volume and microstructure of the cerebral cortex in ALS. We studied with a combined voxel-based morphometry (VBM) and magnetization transfer (MT) imaging approach the capability of MRI to identify the cortical areas affected by neurodegeneration in ALS patients. Eighteen ALS patients and 18 age-matched healthy controls were examined on a 1.5T scanner using a high-resolution 3D T1 weighted spoiled gradient recalled sequence with and without MT saturation pulse. A voxel-based analysis (VBA) was adopted in order to automatically compute the regional atrophy and MT ratio (MTr) changes of the entire cerebral cortex. By using a multimodal image analysis MTr was adjusted for local gray matter (GM) atrophy to investigate if MTr changes can be independent of atrophy of the cerebral cortex. VBA revealed several clusters of combined GM atrophy and MTr decrease in motor-related areas and extra-motor frontotemporal cortex. The multimodal image analysis identified areas of isolated MTr decrease in premotor and extra-motor frontotemporal areas. VBM and MTr are capable to detect the distribution of neurodegenerative alterations in the cortical GM of ALS patients, supporting the hypothesis of a multi-systemic involvement in ALS. MT imaging changes exist beyond volume loss in frontotemporal cortices.