A Kinematic And Electromyographic Study Of The Mechanisms Contributing To Cerebellar Intention Tremor And Dysmetria

The kinematic and electromyographic (EMG) characteristics of cerebellar tremor and dysmetria were investigated in six Cebus monkeys. Cerebellar dysfunction was produced by reversible cooling lesions of the dentate and interposed nuclei. The aims of the study were (1) to compare the characteristics of the cerebellar intention tremor that occurs after the end of a voluntary movement (static or terminal tremor) with the tremor that occurs after the limb has been perturbed, (2) to determine the role played by stretch-evoked activity in generating this tremor, (3) to investigate the nature of the tremor that occurs during a voluntary movement (kinetic tremor) and (4) to describe the characteristics of dysmetric movements.;It was found that the static intention tremor after an elbow movement had the same characteristics as the tremor that occurs after a perturbation of the same limb. The frequency of the tremor in both situations was affected in a similar way by different mechanical loads and neither was dependent on visual feedback of limb position. Stretch-evoked proprioceptive activity was essential to produce the classic 3-4Hz cerebellar intention tremor.;The kinetic tremor was associated with an early burst of EMG activity in the antagonist muscle. This burst was no longer accurately programmed and appeared to be produced from stretch of the antagonist muscle. This antagonist burst was followed by a second burst of activity in the agonist muscle. This burst had the properties of a motor-servo as it was independent of vision, of short latency (50-80 ms) from the time of the deflection in trajectory produced by the early antagonist and its size was directly proportional to the size of the deflection.;Dysmetric (hypermetric) movements made during cerebellar cooling were asymmetric; that is, they had accelerations of long duration and small magnitude and decelerations of short duration and large magnitude. Control movements of all amplitudes, on the other hand, are nearly symmetric. Thus dysmetric movements were not simply inappropriately triggered normal movements. Hypermetric movements were associated with prolonged and less phasic bursts of agonist activity and a delayed burst of antagonist activity.;It is concluded that cerebellar disorders result from inappropriate stretch-evoked activity and from disordered descending central commands

The glycine-rich motif of Pyrococcus abyssi DNA polymerase D is critical for protein stability.

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/00002/11293/7879.pdfInternational audienceA glycine-rich motif described as being involved in human polymerase delta proliferating cell nuclear antigen (PCNA) binding has also been identified in all euryarchaeal DNA polymerase D (Pol D) family members. We redefined the motif as the (G)-PYF box. In the present study, Pol D (G)-PYF box motif mutants from Pyrococcus abyssi were generated to investigate its role in functional interactions with the cognate PCNA. We demonstrated that this motif is not essential for interactions between PabPol D (P. abyssi Pol D) and PCNA, using surface plasmon resonance and primer extension studies. Interestingly, the (G)-PYF box is located in a hydrophobic region close to the active site. The (G)-PYF box mutants exhibited altered DNA binding properties. In addition, the thermal stability of all mutants was reduced compared to that of wild type, and this effect could be attributed to increased exposure of the hydrophobic region. These studies suggest that the (G)-PYF box motif mediates intersubunit interactions and that it may be crucial for the thermostability of PabPol D

Uncooled bolometer response of a low noise La2/3Sr1/3MnO3 thin film

We report measurements of the optical responses of a La2/3Sr1/3MnO3 (LSMO) sample at a wavelength of 533 nm in the 300-400 K range. The 200 nm thick film was grown by pulsed laser deposition on (100) SrTiO3 substrate and showed remarkably low noise. At 335 K the temperature coefficient of the resistance of a 100 micrometers wide 300 micrometers long LSMO line was 0.017 K-1 and the normalized Hooge parameter was 9 e-30 m3, which is among the lowest reported values. We then measured an optical sensitivity at I = 5 mA of 10.4 V.W-1 and corresponding noise equivalent power (NEP) values of 8.1 e-10 W.Hz-1/2 and 3.3 e-10 W. Hz-1/2 at 30 Hz and above 1kHz, respectively. Simple considerations on bias current conditions and thermal conductance G are finally given for further sensitivity improvements using LSMO films. The performances were indeed demonstrated on bulk substrates with G of 10-3 W.K-1. One could expect a NEP reduction by three orders of magnitude if a membrane-type geometry was used, which makes this LSMO device competitive against commercially available uncooled bolometers.Comment: 15 pages. Accepted for publication in Appl. Phys. Let

Binding to PCNA in Euryarchaeal DNA Replication requires two PIP motifs for DNA polymerase D and one PIP motif for DNA polymerase B

En libre-accès sur Archimer : http://archimer.ifremer.fr/doc/2009/publication-7317.pdfInternational audienceReplicative DNA polymerases possess a canonical C-terminal proliferating cell nuclear antigen (PCNA)-binding motif termed the PCNA-interacting protein (PIP) box. We investigated the role of the PIP box on the functional interactions of the two DNA polymerases, PabPol B (family B) and PabPol D (family D), from the hyperthermophilic euryarchaeon Pyrococcus abyssi, with its cognate PCNA. The PIP box was essential for interactions of PabPol B with PCNA, as shown by surface plasmon resonance and primer extension studies. In contrast, binding of PabPol D to PCNA was affected only partially by removing the PIP motif. We identified a second palindromic PIP box motif at the N-terminus of the large subunit of PabPol D that was required for the interactions of PabPol D with PCNA. Thus, two PIP motifs were needed for PabPol D for binding to PabPCNA. Moreover, the C-terminus of PabPCNA was essential for stimulation of PabPol D activity but not for stimulation of PabPol B activity. Neither DNA polymerase interacted with the PabPCNA interdomain connecting loop. Our data suggest that distinct processes are involved in PabPol D and PabPol B binding to PCNA, raising the possibility that Archaea require two mechanisms for recruiting replicative DNA polymerases at the replication fork

Characterization of a small tRNA-binding protein that interacts with the archaeal proteasome complex

Authors acknowledge financial support from the French Agence Nationale de la Recherche (grant [ANR-18-CE11-0018-01] to B.F. and [ANR-16-CE12-0016-01] to B.C.O). This work used the platforms of the Grenoble Instruct-ERIC Centre (ISBG: UMS3518 CNRS-CEA-UGA-EMBL) with support from FRISBI (ANR-10-INBS-05-02) and GRAL, a project of the University Grenoble Alpes graduate school (Ecoles Universitaires de Recherche) CBH-EUR-GS (ANR-17-EURE-0003) within the Grenoble Partnership for Structural Biology. The IBS Electron Microscope facility is supported by the Auvergne Rhône-Alpes Region, the Fonds Feder, the Fondation pour la Recherche Médicale and GIS-IBiSA.The proteasome system allows the elimination of functional or structurally impaired proteins. This includes the degradation of nascent peptides. In Archaea, how the proteasome complex interacts with the translational machinery remains to be described. Here, we characterised a small orphan protein, Q9UZY3 (Uniprot ID) conserved in Thermococcales. The protein was identified in native pull-down experiments using the proteasome regulatory complex (PAN) as bait. X-ray crystallography and SAXS experiments revealed that the protein is monomeric and adopts a β-barrel core structure with an Oligonucleotide/oligosaccharide-Binding (OB) fold, typically found in translation elongation factors. Mobility shift experiment showed that Q9UZY3 displays tRNA binding properties. Pull-downs, co-immunoprecipitation and ITC studies revealed that Q9UZY3 interacts in vitro with PAN. Native pull-downs and proteomic analysis using different versions of Q9UZY3 showed that the protein interacts with the assembled PAN-20S proteasome machinery in Pyrococcus abyssi cellular extracts. The protein was therefore named Pbp11, for Proteasome Binding Protein of 11 kDa. Interestingly, the interaction network of Pbp11 also includes ribosomal proteins, tRNA processing enzymes and exosome subunits dependent on Pbp11's N-terminal domain that was found to be essential for tRNA binding. Together these data suggest that Pbp11 participates in an interface between the proteasome and the translational machinery.Publisher PDFPeer reviewe

La résistance à la pourriture des cabosses due à Phytophthora spp., recherche des composantes de la résistance

La pourriture des cabosses du cacaoyer, due à des #Phytophthora#, sévit dans toutes les zones de production. Avec plus de 50 % de pertes de cabosses, l'Afrique centrale est la région la plus affectée par cette maladie. Le contrôle de cette maladie représente donc un enjeu majeur pour l'avenir de la cacaoculture mondiale et la sélection de matériel résistant constitue l'un des thèmes de recherche prioritaire pour de nombreux pays producteurs. Un projet international sur ce sujet, recevant un support financier de Caobisco, a débuté en juillet 1995. Ce projet, d'une durée de 5 ans, a pour objectifs : d'identifier les facteurs intervenants dans la résistance à cette maladie, de mettre au point et de valider des tests précoces de résistance, de détecter d'éventuels QTLs associés à la résistance et d'effectuer une première sélection de matériel résistant.Cet article présente les principaux résultats obtenus après 3 ans de fonctionnement. (Résumé d'auteur

MARINE-EXPRESS: taking advantage of high throughput cloning and expression strategies for the post-genomic analysis of marine organisms

Background: The production of stable and soluble proteins is one of the most important steps prior to structural and functional studies of biological importance. We investigated the parallel production in a medium throughput strategy of genes coding for proteins from various marine organisms, using protocols that involved recombinatorial cloning, protein expression screening and batch purification. This strategy was applied in order to respond to the need for post-genomic validation of the recent success of a large number of marine genomic projects. Indeed, the upcoming challenge is to go beyond the bioinformatic data, since the bias introduced through the genomes of the so called model organisms leads to numerous proteins of unknown function in the still unexplored world of the oceanic organisms. Results: We present here the results of expression tests for 192 targets using a 96-well plate format. Genes were PCR amplified and cloned in parallel into expression vectors pFO4 and pGEX-4T-1, in order to express proteins N-terminally fused to a six-histidine-tag and to a GST-tag, respectively. Small-scale expression and purification permitted isolation of 84 soluble proteins and 34 insoluble proteins, which could also be used in refolding assays. Selected examples of proteins expressed and purified to a larger scale are presented. Conclusions: The objective of this program was to get around the bottlenecks of soluble, active protein expression and crystallization for post-genomic validation of a number of proteins that come from various marine organisms. Multiplying the constructions, vectors and targets treated in parallel is important for the success of a medium throughput strategy and considerably increases the chances to get rapid access to pure and soluble protein samples, needed for the subsequent biochemical characterizations. Our set up of a medium throughput strategy applied to genes from marine organisms had a mean success rate of 44% soluble protein expression from marine bacteria, archaea as well as eukaryotic organisms. This success rate compares favorably with other protein screening projects, particularly for eukaryotic proteins. Several purified targets have already formed the base for experiments aimed at post-genomic validation