Brainstem structures involved in rapid eye movement sleep behavior disorder

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by the loss of muscle atonia during paradoxical (REM) sleep (PS). The neuronal dysfunctions responsible for RBD are not known. In the present review, we propose an updated integrated model of the mechanisms responsible for PS and explore different hypotheses explaining RBD. We propose that RBD appears based on a specific degeneration of PS-on glutamatergic neurons localized in the caudal pontine sublaterodorsal tegmental nucleus or the glycinergic/GABAergic premotoneurons localized in the medullary ventral gigantocellular reticular nucleus.

     

Strain-Independent Increases of Crystallin Proteins in the Retina of Type 1 Diabetic Rats

Diabetic retinopathy is the leading cause of vision loss in working-age individuals in the United States and is expected to continue growing with the increased prevalence of diabetes. Streptozotocin-induced hyperglycemia in rats is the most commonly used model for diabetic retinopathy. Previous studies have shown that this model can lead to different inflammatory changes in the retina depending on the strain of rat. Our previous work has shown that crystallin proteins, including members of the alpha- and beta/gamma-crystallin subfamilies, are upregulated in the STZ rat retina. Crystallin proteins have been implicated in a number of cellular processes, such as neuroprotection, non-native protein folding and vascular remodeling. In this current study, we have demonstrated that unlike other strain-dependent changes, such as inflammatory cytokines and growth factor levels, in the STZ rat, the protein upregulation of crystallins is consistent across the Brown Norway, Long-Evans and Sprague-Dawley rat strains in the context of diabetes. Taken together, these data illustrate the potential critical role played by crystallins, and especially alpha-crystallins, in the retina in the context of diabetes.     

1H nuclear magnetic resonance determination of the membrane-bound conformation of senktide,a highly selective neurokinin B agonist

Summary Senktide is a highly specific and potent analog of neurokinin B, the natural ligand of the tachykinin receptor NK-3. The membrane-bound conformation of senktide, interacting with negatively charged membrane vesicles composed of perdeuterated phosphatidylcholine and phosphatidylglycerol (70:30), has been investigated using two-dimensional transferred nuclear Overhauser effect spectroscopy (TRNOESY). The occurrence of an N-methylated phenylalanine in the peptide's sequence induces a cis-trans-isomerisation of the corresponding peptide bond which is slow on the chemical-shift scale. NMR data indicate a much stronger membrane affinity of the trans isomer, allowing the determination of a highly resolved membrane-bound conformation using distance geometry and energy minimization. The membrane-bound backbone conformation of several residues is found to be close to a left-handed helix, certainly due to the presence of nonnatural residues (succinylated N-terminal, N-methyl-phenylalanine) as well as a glycine. The results are discussed in the context of a possible biological relevance of the membrane-bound conformation, in terms of the affinity and specificity of this neuropeptide.     

Crop responses to applications of both chlorsulfuron and monoammonium phosphate

Field studies were conducted at two locations of different soil pH in Saskatchewan using preemergence chlorsulfuron and granular monoammonium phosphate. In year one, barley was not adversely affected by chlorsulfuron applied in the spring at 11.25 and 22.5 g a.i. ha^–1 (Kernen location, soil pH 7.5) or 22.5 and 45.0 g a.i. ha^–1 (Scott location, soil pH 5.5). In year two, the residual chlorsulfuron did not affect flax seed yield on the acid soil, but caused substantial crop damage to flax and lentil on the neutral soil. In general, flax and lentil were more injured by chlorsulfuron residues where lower rates of MAP had been applied the previous year, suggesting that the presence of a MAP band in the soil at the time of herbicide application may have slowed the rate of chlorsulfuron degradation. A corn-root bioassay procedure was adapted to estimate residue levels in soil samples taken from the field trials.     

Incorporating dipolar solvents with variable density in Poisson-Boltzmann electrostatics

We describe a new way to calculate the electrostatic properties of macromolecules that goes beyond the classical Poisson-Boltzmann treatment with only a small extra CPU cost. The solvent region is no longer modeled as a homogeneous dielectric media but rather as an assembly of self-orienting interacting dipoles of variable density. The method effectively unifies both the Poisson-centric view and the Langevin Dipole model. The model results in a variable dielectric constant in the solvent region and also in a variable solvent density that depends on the nature of the closest exposed solute atoms. The model was calibrated using small molecules and ions solvation data with only two adjustable parameters, namely the size and dipolar moment of the solvent. Hydrophobicity scales derived from the solvent density profiles agree very well with independently derived hydrophobicity scales, both at the atomic or residue level. Dimerization interfaces in homodimeric proteins or lipid-binding regions in membrane proteins clearly appear as poorly solvated patches on the solute accessible surface. Comparison of the thermally averaged solvent density of this model with the one derived from molecular dynamics simulations shows qualitative agreement on a coarse-grained level. Because this calculation is much more rapid than that from molecular dynamics, applications of a density-profile-based solvation energy to the identification of the true structure among a set of decoys become computationally feasible. Various possible improvements of the model are discussed, as well as extensions of the formalism to treat mixtures of dipolar solvents of different sizes.     

Anion channel activity is necessary to induce ethylene synthesis and programmed cell death in response to oxalic acid

Oxalic acid is thought to be a key factor of the early pathogenicity stage in a wide range of necrotrophic fungi. Studies were conducted to determine whether oxalate could induce programmed cell death (PCD) in Arabidopsis thaliana suspension cells and to detail the transduction of the signalling pathway induced by oxalate. Arabidopsis thaliana cells were treated with millimolar concentrations of oxalate. Cell death was quantified and ion flux variations were analysed from electrophysiological measurements. Involvement of the anion channel and ethylene in the signal transduction leading to PCD was determined by using specific inhibitors. Oxalic acid induced a PCD displaying cell shrinkage and fragmentation of DNA into internucleosomal fragments with a requirement for active gene expression and de novo protein synthesis, characteristic hallmarks of PCD. Other responses generally associated with plant cell death, such as anion effluxes leading to plasma membrane depolarization, mitochondrial depolarization, and ethylene synthesis, were also observed following addition of oxalate. The results show that oxalic acid activates an early anionic efflux which is a necessary prerequisite for the synthesis of ethylene and for the PCD in A. thaliana cells.     

Functional characterization of FTDP-17 tau gene mutations through their effects on Xenopus oocyte maturation.

tau gene mutations cause frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17). Here we have used Xenopus oocyte maturation as an indicator of microtubule function. We show that wild-type four-repeat Tau protein inhibits maturation in a concentration-dependent manner, whereas three-repeat Tau has no effect. Of the seven four-repeat Tau proteins with FTDP-17 mutations tested, five (G272V, DeltaK280, P301L, P301S, and V337M) failed to interfere significantly with oocyte maturation, demonstrating a greatly reduced ability to interact with microtubules. One mutant protein (R406W) almost behaved like wild-type Tau, and one (S305N) inhibited maturation more strongly than wild-type Tau. With the exception of R406W, wild-type Tau and all the mutants studied were similarly phosphorylated during the Xenopus oocyte maturation, and this was independent of their effects on this process. Data obtained with R406W and S305N may be related to charge changes (phosphorylation and basic amino acids). Our results demonstrate variable effects of FTDP-17 mutations on microtubules in an intact cell situation. Those findings establish Xenopus oocyte maturation as a system allowing the study of the functional effects of tau gene mutations in a quantitative manner.     

Intracellular Localization of the Peanut Clump Virus Replication Complex in Tobacco BY-2 Protoplasts Containing Green Fluorescent Protein-Labeled Endoplasmic Reticulum or Golgi Apparatus

RNA-1 of Peanut clump virus (PCV) encodes the proteins P131 and P191, containing the signature motifs of replication proteins, and P15, which regulates viral RNA accumulation. In PCV-infected protoplasts both P131 and P191 were immunodetected in the perinuclear region. Laser scanning confocal microscopy (LSCM) showed that P131 and P191 colocalized with neosynthesized 5-bromouridine 5'-triphosphate-labeled RNA and double-stranded RNA, demonstrating that they belong to the replication complex. On the contrary, the P15 fused to the enhanced green fluorescent protein (EGFP) never colocalized with the two proteins. In endoplasmic reticulum (ER)-GFP transgenic BY-2 protoplasts, the distribution of the green fluorescent-labeled ER was strongly modified by PCV infection. LSCM showed that both P131 and P191 colocalized with ER green fluorescent bodies accumulating around the nucleus during infection. The replication process was not inhibited by cerulenin and brefeldin A, suggesting that PCV replication does not depend on de novo-synthesized membrane and does not require transport through the Golgi apparatus. Electron microscopy of ultrathin sections of infected protoplasts showed aggregates of broken ER but also visualized vesicles, some of which resembled modified peroxisomes. The results suggest that accumulation of PCV during infection is accompanied by specific association of PCV RNA-1-encoded proteins with membranes of the ER and other organelles. The concomitant extensive rearrangement of these membranous structures leads to the formation of intracellular compartments in which synthesis and accumulation of the viral RNA occur in defined areas.