Search

Using muon spin rotation, well-defined bulk approximately 100% magnetic phases in NaxCoO2 are revealed. A novel magnetic phase is detected for x=0.85 with the highest transition temperature ever observed for x>or=0.75. This stresses the diversity of x>or=0.75 magnetic phases and the link between magnetic and structural degrees of freedom. For the charge-ordered x=0.50 compound, a cascade of transitions is observed below 85 K. From a detailed analysis of our data, we conclude that the ordered moment varies continuously with temperature and suggest that the two secondary transitions at 48 and 29 K correspond to a moderate reorientation of antiferromagnetically coupled moments.

Intra spinal primary melanoma is a rare entity. We report a new case, atypical in relation to its primary radicular location, and to its early metastatic intradural and extra-medullary location, six months later. MRI is the more valuable examination, showing a spontaneously hyper-intense lesion on T1-weighted MR images, intense enhancement after gadolinium administration, and decreased signal on T2-weighted MR images, thus suggesting a diagnosis of melanocytic or hemorrhagic lesion. Signal abnormalities are not specific and definitive diagnosis is established after histological analysis.

Human endothelial lipase (EL), a member of the triglyceride lipase gene family, has five potential N-linked glycosylation sites, two of which are conserved in both lipoprotein lipase and hepatic lipase. Reduction in molecular mass of EL after treatment with glycosidases and after treatment of EL-expressing cells with the glycosylation inhibitor tunicamycin demonstrated that EL is a glycosylated protein. Each putative glycosylation site was examined by site-directed mutagenesis of the asparagine (Asn). Mutation of Asn-60 markedly reduced secretion and slightly increased specific activity. Mutation of Asn-116 did not influence secretion but increased specific activity. In both cases, this resulted from decreased apparent K(m) and increased apparent V(max). Mutation of Asn-373 did not influence secretion but significantly reduced specific activity, as a result of a decrease in apparent V(max). Mutation of Asn-471 resulted in no reduction in secretion or specific activity. Mutation of Asn-449 resulted in no change in secretion, activity, or molecular mass, indicating that the site is not utilized. The ability of mutants secreted at normal levels to mediate bridging between LDL and cell surfaces was examined. The Asn-373 mutant demonstrated a 3-fold decrease in bridging compared with wild-type EL, whereas Asn-116 and Asn-471 were similar to wild-type EL.

We present muSR experiments in the S=3/2 kagomé bilayer compound Ba(2)Sn(2)ZnGa(10-7p)Cr(7p)O22 [BSZCGO(p)] and compare it to the isostructural SrCr(9p)Ga(12-9p)O19 [SCGO(p)], including for the latter new results for p > or =0.89. Quantum-dynamical low energy magnetic excitations are evidenced in this novel compound. We study the evolution of the muon relaxation rate with p, T, and field. A phenomenological model for the muon relaxation based on sporadic dynamics due to spin excitations in a singlet sea proposed by Uemura et al. is extended to all fields and T range. Its connection to the RVB picture is discussed, and we argue that such coherent states might mediate the interactions between "impurities" which induce the spin glass freezing.

Oriented powder samples of NaxCoO2 are studied by 23Na NMR and SQUID magnetometry. In nominal 0.50

The objective of the present study was to compare two configurations of the hepatocyte model namely suspensions (SH) and conventional primary cultures (CPC) for their ability to predict the hepatic clearance in vivo in the rat and, to investigate the impact of serum on the prediction accuracy. The metabolic competences of several cytochrome P450 isoenzymes were investigated both in CPC and SH in the presence or absence of serum. Under the same conditions, the in vitro intrinsic clearance of six test compounds metabolised by a variety of phase I and phase II enzymes (antipyrine, RO-X, mibefradil, midazolam, naloxone and oxazepam) were derived from Vmax/Km scaled up to the corresponding in vivo hepatic metabolic clearance. CYP activities were shown to be stable in both CPC and SH for up to 6 h of incubation, except for the CYP 3A1 activity that decreased in CPC even in the presence of serum. Moreover, the clearances predicted from SH in the presence of serum were closer to the in vivo values than those obtained from CPC. SH represent a convenient model to assess the hepatic metabolism of xenobiotics, the presence of serum in the incubation medium significantly improved in several instances the quality of the predictions.

The exact function of TCR clustering and organized macromolecular patterns at the immune synapse between APCs and T lymphocytes is unclear. Using human immature or mature dendritic cells (DCs) and autologous CD4(+) effector T cells, we demonstrate that, within a given conjugate, mature DCs induce strong and long-lasting TCR clustering and protein kinase C-theta translocation in a superantigen dose-dependent manner. Moreover, mature DCs promote CD43 exclusion in a dose-independent manner. In contrast, immature DCs are less potent at inducing these molecular rearrangements. Using these models to correlate T cell functions with the frequency, the intensity, and the duration of TCR clustering, we show, in Jurkat T cells, that weak and transient TCR clustering is sufficient to promote TCR down-modulation, protein kinase C-theta translocation at the synapse, and substantial NFAT transcriptional activation. Moreover, we show, in CD4(+) T cell blasts, that strong TCR clustering is required for neither TCR down-modulation nor optimal IFN-gamma production. Together, our results demonstrate that some CD4(+) functional responses, such as cytokine production, are independent of central supramolecular activation cluster formation.

The enantioselective total synthesis of the cytotoxic plecomacrolide natural product formamicin (1) is described. Key aspects of this synthesis include the efficient transacetalation reactions of MOM ethers 28 and 38 to form the seven-membered formyl acetals 29 and 39, a late-stage Suzuki cross-coupling reaction of the highly functionalized vinyl boronic acid 6 and vinyl iodide 7, a highly beta-selective glycosidation reaction of beta-hydroxy ketone 4 with 2,6-dideoxy-2-iodoglucopyranosyl fluoride 3, and the global desilylation of penultimate intermediate 77 mediated by in situ generated Et(3)N.2HF.

A total synthesis of the naturally occurring ionophore zincophorin has been realized. The route features an intramolecular oxymercuration of a cyclopropanemethanol and a Carroll-Claisen rearrangement for the respective elaboration of the C1-C12 and C13-C25 subunits, which have been assembled by using a highly diastereoselective titanium-mediated aldol condensation.

[reaction: see text] alpha-Acetoxynitroso compound 3 has been prepared as a new stable, isolable, and reactive dienophile in nitroso Diels-Alder reactions. The yield of the [4 + 2] cycloaddition of alpha-acetoxynitroso dienophile with 1,3-dienes could be enhanced in the presence of 20 mol % Lewis acid. An unexpected retro hetero-Michael reaction from 26 was observed, leading to the cleavage of the N-O bond of the cycloadduct. This tandem nitroso Diels-Alder/retro hetero-Michael sequence has been used with cyclic and acyclic 1,3-dienes.

The integral membrane adaptor protein linker for activation of T cells (LAT) couples the T-cell receptor (TCR) with downstream signalling and is essential for T-cell development and activation. Here, we investigate the dynamic distribution of LAT-GFP fusion proteins by time-lapse video imaging of live T lymphocytes interacting with antigen-presenting cells. We show that LAT forms two distinct cellular pools, one at the plasma membrane and one that co-distributes with transferrin-labelled intracellular compartments also containing the TCR/CD3-associated zeta chain. The distribution of LAT between these two pools is dependent on LAT intracytoplasmic residues. Whereas plasma membrane-associated LAT is recruited to immune synapses after a few seconds of cell conjugate formation, the intracellular pool is first polarized and then recruited after a few minutes. We further show that LAT intracytoplasmic amino acid residues, particularly the Tyr136, 175, 195 and 235 residues, are required for its own recruitment to the immune synapse and that a herein-identified juxtamembrane LAT region (amino acids 32-104) is involved in the localization of LAT in intracellular pools and in T-cell signalling. Altogether, our results demonstrate that LAT controls its own recruitment at the immune synapse, where it is required as a scaffold protein for the signalling machinery. The results also suggest that the intracellular pool of LAT might be required for T-cell activation.

Endothelial lipase (EL) is a new member of the triglyceride lipase gene family, which includes lipoprotein lipase (LpL) and hepatic lipase (HL). Enzymatic activity of EL has been studied before. Here we characterized the ability of EL to bridge lipoproteins to the cell surface. Expression of EL in wild-type Chinese hamster ovary (CHO)-K1 but not in heparan sulfate proteoglycan (HSPG)-deficient CHO-677 cells resulted in 3-4.4-fold increases of 125I-low density lipoprotein (LDL) and 125I-high density lipoprotein 3 binding (HDL3). Inhibition of proteoglycan sulfation by sodium chlorate or incubation of cells with labeled lipoproteins in the presence of heparin (100 microg/ml) abolished bridging effects of EL. An enzymatically inactive EL, EL-S149A, was equally effective in facilitating lipoprotein bridging as native EL. Processing of LDL and HDL differed notably after initial binding via EL to the cell surface. More than 90% of the surface-bound 125I-LDL was destined for internalization and degradation, whereas about 70% of the surface-bound 125I-HDL3 was released back into the medium. These differences were significantly attenuated after HDL clustering was promoted using antibody against apolipoprotein A-I. At equal protein concentration of added lipoproteins the ratio of HDL3 to VLDL bridging via EL was 0.092 compared with 0.174 via HL and 0.002 via LpL. In summary, EL mediates binding and uptake of plasma lipoproteins via a process that is independent of its enzymatic activity, requires cellular heparan sulfate proteoglycans, and is regulated by ligand clustering.

2-Deoxy-2-iodo-beta-glucopyranosyl fluoride 14 is a highly stereoselective glucopyranosyl donor that may be activated under mild conditions. Application of this new glycosyl donor to the glycosidation reactions of a variety of acceptors including beta-hydroxy ketones affords beta-glycosides with high efficiency and stereoselectivity. [reaction--see text]

Recognition by T cells of their ligands at the surface of antigen-presenting cells (APCs) leads to T cell activation, polarization of the T cell toward the APC, and formation of an immune synapse. Using ZAP-70-deficient T cells expressing zeta-GFP, we show that ZAP-70 signaling drives the TCR-dependent reorientation of the microtubule-organizing center thus leading to relocation of a zeta-GFP(+) intracellular compartment close to the APC. ZAP-70 is also necessary to supply the synapse with the signaling molecules PKC-theta and LAT. In contrast, ZAP-70 is not required for clustering of zeta-GFP and CD2 or exclusion of CD45 and CD43 from the synapse. These data show that ZAP-70-dependent signaling is required for formation of a functional immune synapse.

Before T cells of the immune system can recognize pathogens, antigen presenting cells (APCs) must process pathogen-derived peptides and present them together with major histocompatibility complex molecules (MHC) to T lymphocytes. T lymphocytes then scan the surface of APCs and antigen-specific activation of the T cell will happen after interaction of T cell antigen receptor (TCR) with MHC-peptide complexes expressed at the membrane of APCs. This interaction takes place in a nanometer scale gap between the two cells, referred to as an immunological synapse. Recent three-dimensional fluorescence analysis of this synapse revealed a dynamic spatial organization of membrane receptors, cytoskeleton and intracellular signaling complexes on the T cell side showing specific patterns, which depend on the nature of the T cell:APC pair. Although it is obvious that establishment of an intimate contact between T cells and APCs will facilitate cell:cell communication it is not clear what is the role, if any, of this receptors patterning. This molecular reorganization has long been thought to enhance and/or sustain TCR signaling and thus T cell activation, but this is now a matter of controversy. Moreover, mechanisms controlling immunological synapse formation are still unraveled. Segregation of proteins may occur spontaneously as proposed by mathematical modeling taking into account membrane fluidity, protein size and receptor/ligand affinity. Alternatively patterning of the molecules at the cell:cell interface could be driven by active processes involving T cell signaling and/or specific features of the APC. These different questions will be discussed herein.

TCR down-modulation following binding to MHC/peptide complexes is considered to be instrumental for T cell activation because it allows serial triggering of receptors and the desensitization of stimulated cells. We studied CD3/TCR down-modulation and zeta degradation in T cells from two ZAP-70-immunodeficient patients. We show that, at high occupancy of the TCR, down-modulation of the CD3/TCR is comparable whether T cells express or do not express ZAP-70. However, if TCR occupancy was low, we found that CD3/TCR was down-regulated to a lesser extent in ZAP-70-negative than in ZAP-70-positive T cells. We studied CD3/TCR down-modulation in P116 (a ZAP-70-negative Jurkat cell-derived clone) and in P116 transfected with genes encoding the wild-type or a kinase-dead form of ZAP-70. Down-modulation of the TCR at high occupancy did not require ZAP-70, whereas at low TCR occupancy down-modulation was markedly reduced in the absence of ZAP-70 and in cells expressing a dead kinase mutant of ZAP-70. Thus, the presence of ZAP-70 alone is not sufficient for down-modulation; the kinase activity of this molecule is also required. The degradation of zeta induced by TCR triggering is also severely impaired in T cells from ZAP-70-deficient patients, P116 cells, and P116 cells expressing a kinase-dead form of ZAP-70. This defect in TCR-induced zeta degradation is observed at low and high levels of TCR occupancy. Our results identify ZAP-70, a tyrosine kinase known to be crucial for T cell activation, as a key player in TCR down-modulation and zeta degradation.

We show in this study that human T cells purified from peripheral blood, T cell clones, and Jurkat T cells release microvesicles in the culture medium. These microvesicles have a diameter of 50-100 nm, are delimited by a lipidic bilayer membrane, and bear TCR beta, CD3epsilon, and zeta. This microvesicle production is regulated because it is highly increased upon TCR activation, whereas another mitogenic signal, such as PMA and ionomycin, does not induce any release. T cell-derived microvesicles also contain the tetraspan protein CD63, suggesting that they originate from endocytic compartments. They contain adhesion molecules such as CD2 and LFA-1, MHC class I and class II, and the chemokine receptor CXCR4. These transmembrane proteins are selectively sorted in microvesicles because CD28 and CD45, which are highly expressed at the plasma membrane, are not found. The presence of phosphorylated zeta in these microvesicles suggests that the CD3/TCR found in the microvesicles come from the pool of complexes that have been activated. Proteins of the transduction machinery, tyrosine kinases of the Src family, and c-Cbl are also observed in the T cell-derived microvesicles. Our data demonstrate that T lymphocytes produce, upon TCR triggering, vesicles whose morphology and phenotype are reminiscent of vesicles of endocytic origin produced by many cell types and called exosomes. Although the exact content of T cell-derived exosomes remains to be determined, we suggest that the presence of TCR/CD3 at their surface makes them powerful vehicles to specifically deliver signals to cells bearing the right combination of peptide/MHC complexes.

Objective: To evaluate the effects of hemofiltration performed during rewarming before emergence from cardiopulmonary bypass on hemodynamic and echocardiographic parameters., Design: Prospective randomized study; blind analysis of echocardiographic parameters and hemodynamic parameters., Setting: Single-center study performed in a university hospital., Participants: Two groups of 13 adult patients undergoing coronary artery bypass graft surgery., Intervention: Patients were randomized to conventional procedure or hemofiltration performed with a polysulfone hemofilter. Hemofiltration, started at the time of rewarming on cardiopulmonary bypass, was performed with a flow rate adjusted to achieve an ultrafiltrate volume of 15 mL/kg on completion of rewarming., Measurements and Main Results: Hemodynamic (systemic mean arterial pressure, right atrial pressure, heart rate) and echocardiographic parameters (shortening fraction, segmental kinetic score, cardiac output, systemic vascular resistance) were measured before and after hemofiltration and on arrival in the intensive care unit. Heart rate and cardiac index were increased significantly in both groups during the postoperative period. In the control group, systemic vascular resistance was decreased significantly, and cardiac index was increased during the postoperative period, together with significant alterations of segmental kinetic score and shortening fraction. In the hemofiltration group, systemic vascular resistance remained unchanged, associated with a significantly improved segmental kinetic score compared with the control group., Conclusions: Hemofiltration performed during rewarming before emergence from cardiopulmonary bypass is associated with stability of hemodynamic parameters and improved segmental myocardial kinetics.

This article deals with the interpretations of coordination among actors solicited to participate in an experimental programme in the gerontological area of Lunel of the Hérault department of France. The article presents the conclusions of an evaluation report which includes two survey phases: a pre-test and a post-test survey implemented at the end of the programme with a parallel survey implemented in a control site, the Pézenas area of the Hérault department. The analysis of the initial perceptions of coordination and their evolution relies on the theory of the plurality of worlds (L. Boltanski and L. Thevenot). It aims to show that making a move toward coordination is a complex phenomenon that requires the elaboration of a common language. The material collected during this evaluation allows us to suggest that coordination questions the actors on their professional situation. It questions institutions and their internal functioning. Finally, this type of intervention brings to light the stakes in the examined field.

Chest trauma in children is rare but shows that trauma is severe and the mortality rate is high (30%). Multidisciplinary management of children includes an initial evaluation of respiratory distress, freeing the airways, placing an intercostal tube, stabilizing the chest wall, and analgesia. When vital signs are stable, secondary evaluation includes an etiologic, radiologic and biologic check-up, ending with the therapeutic strategy. Thoracotomy is rarely required, and for most children, only monitoring will be necessary, though this is important because of the risk of secondary decompensation and late diagnosis of potentially fatal lesions.

The class A beta-lactamase PER-1, which displays 26% identity with the TEM-type extended-spectrum beta-lactamases (ESBLs), catalyses the hydrolysis of oxyimino-beta-lactams such as cefotaxime (CTX), ceftazidime (CAZ) and aztreonam (AZT). Molecular modelling was used to identify in PER-1 the amino acid residues corresponding to those found at positions 104, 164, 238 and 240 in the TEM-type ESBLs, which are critical for hydrolysis of oxyimino-beta-lactams. The function of these residues in PER-1 was assessed by site-directed mutagenesis. In this enzyme, residue 104 could be either a glutamine, an asparagine or a threonine. The Gln-->Gly mutation did not significantly affect the catalytic efficiency, while Asn-->Gly and Thr-->Glu resulted in a marked decrease in catalytic activity, probably due to the alteration of a hydrogen bond network connecting the putative Asn-104 residue to Asn-132 and Glu-166. Replacement of Ala-164 by Arg in PER-1 resulted in a mutant with no detectable activity, thus suggesting that Ala-164 is important for catalysis and stability of PER-1. Conversely, Ser-238-->Gly and Gly-240-->Glu had little effect on kcat and Km values. Finally, the replacement of the catalytic residue Glu-166 by an alanine resulted in a complete loss of activity for CTX and a marked decrease of kcat for CAZ and AZT. These results suggest that Glu-166 is an important residue in PER-1. However, residues other than Glu-166 could contribute in maintaining residual activity towards oxyimino-beta-lactams in the Ala-166 mutant.

Case report of a 26-year-old patient, admitted for severe craniofacial trauma, with facial injuries and intracranial haemorrhage. Preoperative tests showed an aPTT = 64 s (control = 29 s), rapidly recognized as being caused by a major constitutional factor XI deficiency (0.06 Ul.mL-1). Considering the neurological risk and the indication for surgery, concentrates of factor XI were administered at a dosage of 25 Ul.kg-1. This treatment was associated with a biological normalization and uneventful surgery. In patients experiencing a factor XI deficiency, the use of fresh frozen plasma will probably decrease and only administered in emergency cases when factor XI concentrates are not available.

Objective: To compare the effects of the laryngeal mask airway (LMA), and the tracheal tube (TT) insertion on intra-ocular pressure (IOP) in eye surgery., Study Design: Prospective non-randomized study., Patients: Eighty patients scheduled for eye surgery under general anaesthesia were allocated into either a LMA group (n = 37) or a TT group (n = 43)., Methods: After induction of anaesthesia with propofol, vecuronium and phenoperidine, either a TT or a LMA were inserted. IOP, heart rate (HP) and mean arterial pressure (MAP) were measured before (TO) and after induction (T1), after TT or LMA insertion (20 s:T2, 6 min:T3), and before extubation (T4)., Results: The HR, MAP and IOP increased significantly at T2 (compared to T1 but not to T0) in the TT group, for a short time, whereas no significant changes occurred in the LMA group., Conclusion: LMA insertion does not elicit significant haemodynamic or IOP changes. Conversely, the TT increases HR, MAP and IOP. These changes can be deleterious in case of emergency surgery for perforating eye injuries. The LMA can be recommended as an alternative to TT in eye surgery, provided security rules are followed, because of the risk of displacement of LMA during surgery.

Recent studies have helped to define the mechanisms by which thrombin activates platelets and other cells. Those studies show that the human thrombin receptor has a structure similar to other G protein-coupled receptors, but is activated by a novel mechanism in which thrombin cleaves its receptor, creating a new N-terminus that can serve as a tethered ligand. Shortly after activation, thrombin receptors become temporarily resistant to re-activation. Present evidence suggests that this loss of function is due to a combination of receptor desensitization, phosphorylation and internalization, and that recovery may involve dephosphorylation, as well as receptor recycling and the expression of newly-synthesized receptors. Together these processes provide a potent mechanism for limiting the duration of thrombin-initiated events in platelets and other thrombin-responsive vascular cells.

In vivo half-life of a 125I-labeled human anti-D monoclonal antibody (mAb) and that of 131I-labeled Rho-GAM was assessed in a rhesus monkey injected simultaneously with both reagents. The half-life of the mAb was 7.9 days, compared to 17 days of Rho-GAM. Survival of the second dose of mAb, given 34 days after the first injection, was identical to that of the first dose, thus showing that the human mAb did not elicit an immune response. The in vitro produced human mAbs appear to be an alternative, unlimited source of anti-D antibodies for possible use in prevention of feto-maternal Rh immunization.

Injections of Copolymer 1 (Cop-1), a synthetic cathodic polymer, have been reported to prevent and treat successfully acute and recurrent EAE and has been employed in patients with multiple sclerosis (MS). It has been suggested that the therapeutic effect is due to cell-mediated immune (CMI) cross-reactivity between Cop-1 and myelin basic protein (MBP), the antigen that induces EAE. We found that Cop-1 treatment of guinea pigs (GP) sensitized with MBP in adjuvant (20 micrograms/animal): (a) lowers the incidence of clinical disease (8/20 vs 14/15); (b) decreases severity of disease in affected GP; (c) has little effect on pathologic lesions (mean pathology index +/- SEM: 1.2 +/- 0.2 vs 1.6 +/- 0.3; P greater than 0.1). Lymphocytes of MBP-sensitized GP treated with Cop-1 exhibited in vitro proliferative responses to MBP equivalent to lymphocytes of untreated EAE-GP (14,134 +/- 6,532 vs 11,821 +/- 3,874; mean cpm +/- SEM). GP sensitized to MBP or Cop-1 (100 micrograms/animal) showed reactivity to the sensitizing antigen but little in vitro reactivity to the other antigen. There was no correlation between the in vitro lymphocytes response to MBP and Cop-1 in individual GP. Treatment of MBP sensitized GP with calf-thymus histone (CTH) also resulted in a lower incidence of clinical EAE with less severe disease in affected GP. There was little effect on the pathologic index and no evidence of either inhibition of MBP-induced lymphocyte proliferative responses or cross-reactivity between MBP and CTH. Thus, treatment with Cop-1 or CTH inhibits clinical manifestations of acute EAE without suppressing inflammatory cell infiltrates or sensitization to MBP.

The cerebrospinal fluid (CSF) of guniea pigs with experimental allergic encephalomyelitis was examined for the presence of oligoclonal IgG using polyacrylamide gel electrophoresis. Oligoclonal IgG (greater than or equal to 2 bands) was seen in the CSF obtained from 3/4 animals with experimental allergic encephalomyelitis induced by myelin basic protein and 2/3 with spinal cord-induced disease. It was not seen in CSF of 3 non-sensitized, 4 adjuvant-sensitized and 7 liver-sensitized guinea pigs. Scanning of stained gels confirmed the oligoclonal pattern. The bands were found in the region of gels which bound [125I]Staphylococcal Protein A. The data demonstrate that a non-infectious inflammatory reaction within the central nervous system can result in an oligoclonal IgG pattern in the CSF.