Contribution of D-Dimer determination in the exclusion of deep venous thrombosis in spinal cord injury patients.

Deep vein thrombosis (DVT) is a common complication of paraplegia despite prophylactic anticoagulant therapy. The diagnosis relies primarily on ultrasonography or phlebography; these investigations are difficult, expensive and can be time-consuming in paraplegic patients. STUDY DESIGN: To evaluate the usefulness of coagulation activation markers in excluding a diagnosis of DVT, D-Dimers, thrombin-antithrombin complexes, prothrombin fragments (F1+2) and activated factor VIIa. OBJECTIVES: To improve the diagnosis of deep venous thrombosis in paraplegic patients. SETTING: This collaborative work was done at Raymond Poincaré Hospital, Garches, France. METHODS: To evaluate the usefulness of coagulation activation markers in excluding a diagnosis of DVT, D-Dimers (D-Di), thrombin-antithrombin (TAT) complexes, prothrombin fragments (F1+2) and activated factor VIIa (FVIIa), were determined in a prospective study of 67 consecutive patients with paraplegia or tetraplegia. Doppler ultrasonography and/or phlebography of the lower limbs and D-Di, TAT, F1+2 level determination were systematically done in each patient at admission to our rehabilitation unit. RESULTS: Despite prophylactic low molecular weight heparin therapy, six of the 67 patients developed DVT diagnosed by radiologic explorations. D-Di levels measured by a reference ELISA (Asserachrom D-Di, Diagnostica Stago) or a new rapid automated turbidimetric test (STA-Liatest D-Di) were greater than 500 ng/ml in all DVT patients and in 40 non-DVT patients, of whom most had urinary tract infections, osteomas, or pressure sores. D-Di values were normal in only 21/67 patients (31%). The negative predictive value of D-Di in our study was 100% since all DVT patients had D-Di values greater than 500 ng/ml. TAT and F1+2 levels were not correlated with D-Di levels but also had a negative predictive value of 100%. Comparison of D-Di levels obtained using the two tests showed that results of the reference ELISA were closely correlated to those of the new rapid automated turbidimetric. TAT, F1+2, and factor VIIa are not useful for measuring hypercoagulability in paraplegic or tetraplegic patients since no rapid tests for determining these parameters are available. CONCLUSION: D-Di levels determined using an ELISA or a new rapid automated turbidimetric test have a good negative predictive value for DVT in paraplegic or tetraplegic patients and may reduce the need for Doppler ultrasonography and/or phlebography by 31%.     

Hydration water mobility is enhanced around tau amyloid fibers

The paired helical filaments (PHF) formed by the intrinsically disordered human protein tau are one of the pathological hallmarks of Alzheimer disease. PHF are fibers of amyloid nature that are composed of a rigid core and an unstructured fuzzy coat. The mechanisms of fiber formation, in particular the role that hydration water might play, remain poorly understood. We combined protein deuteration, neutron scattering, and all-atom molecular dynamics simulations to study the dynamics of hydration water at the surface of fibers formed by the full-length human protein htau40. In comparison with monomeric tau, hydration water on the surface of tau fibers is more mobile, as evidenced by an increased fraction of translationally diffusing water molecules, a higher diffusion coefficient, and increased mean-squared displacements in neutron scattering experiments. Fibers formed by the hexapeptide ³⁰⁶VQIVYK³¹¹ were taken as a model for the tau fiber core and studied by molecular dynamics simulations, revealing that hydration water dynamics around the core domain is significantly reduced after fiber formation. Thus, an increase in water dynamics around the fuzzy coat is proposed to be at the origin of the experimentally observed increase in hydration water dynamics around the entire tau fiber. The observed increase in hydration water dynamics is suggested to promote fiber formation through entropic effects. Detection of the enhanced hydration water mobility around tau fibers is conjectured to potentially contribute to the early diagnosis of Alzheimer patients by diffusion MRI.Amyloid fibers are the most stable forms of ordered protein aggregates. They have attracted much attention because of their implication in so-called conformational diseases, which include a variety of neurodegenerative disorders (1). Consequently, means of hindering or reversing fiber formation are actively researched (2). Pathological fibers are often formed by intrinsically disordered proteins (IDPs) that lack a well-defined 3D structure in their native state and are best described by an ensemble of different conformations (3). The human protein tau is an IDP that normally regulates microtubule stability in neurons. When tau aggregates, it forms paired helical filaments (PHF) that are one of the two histological hallmarks of Alzheimer disease (AD) (4, 5). As yet, and despite considerable effort over the past 30 y, the understanding of tau fibrillation in AD and other taupathies remains largely incomplete (6). The longest human tau isoform, htau40, is composed of 441 amino acid residues and is organized into several domains (see Fig. 1), including the repeat domains R1−R4 (residues 244–369) that constitute, together with the P1 and P2 domains, the microtubule binding regions (7). Essential for the nucleation of tau fibers is the presence of hexapeptides (²⁷⁵VQIINK²⁸⁰ and ³⁰⁶VQIVYK³¹¹) in R2 and R3 (8) that have a high propensity to form β-structures. Although precise structures of tau PHF remain unknown (6), they can be divided into two structurally different regions (see Fig. 1): (i) a rigid β-rich core (denoted as the fiber core domain), which is essentially composed of the four repeat domains, and (ii) the remainder, the so-called fuzzy coat, which is highly flexible (9–11).Open in a separate windowFig. 1.Schematic representation of the tau isoform htau40 in its monomeric (Top) and fibrillated (Bottom) forms. The microtubule binding domain is roughly composed of the four repeat domains R1−R4 (residues 244–369) and the proline-rich domains P1 and P2. R1−R4 constitute the core domain, which forms cross-β structures as well as steric zippers in the fiber, whereas the rest of the protein is referred to as the fuzzy coat domain, which remains disordered in the fiber form. The amyloidogenic hexapeptide ³⁰⁶VQIVYK³¹¹ can be used as a model for the fiber core.Water is known to play key roles in protein folding, stability, and activity (12). It mediates protein−protein and protein−DNA recognition, is involved in allostery, partakes in enzymatic reactions and proton and electron transfer, and more generally plasticizes biological macromolecules by providing their surface with an extensive and highly dynamic network of hydrogen bonds. Compared with folded proteins, tau has been shown to have a stronger coupling with its hydration water (13). However, very little is known about the role water plays in protein aggregation in general and in tau fibrillation in particular. A recent study on two different amyloid systems concluded that water plays a key role in fiber growth and polymorphism, inter alia through entropic effects (14). A study by Chong and Ham (15) highlighted the role of water in protein aggregation propensity by revealing a tight relation between the hydration free energy of a protein and its propensity to aggregate.Among the experimental methodologies available to study protein hydration water, neutron scattering (NS) stands out owing to its pronounced sensitivity to motions of hydrogen atoms. Indeed, hydrogen atoms incoherently scatter neutrons about two orders of magnitude more strongly than all other atoms present in a biological sample, including deuterium atoms. Consequently, NS has been widely used to study bulk and confined water at room temperature (16), hydration water of peptides (17), proteins (18–21), and water inside cells (22). More specifically, NS probes atomic motions on the nanosecond to picosecond timescales and on the angstrom length scales (23), thus ensuring the time and space resolution necessary for investigating water dynamics with atomistic detail. Elastic incoherent NS (EINS) reflects the global dynamics averaged over all atoms but does not provide any information on the nature of the observed motions. Quasi-elastic NS (QENS), however, allows the quantification of energy exchanges between the sample and the neutron beam and provides quantitative information about the nature of motions observed. Because of a pronounced isotope effect, the replacement of hydrogen by deuterium atoms effectively masks the labeled part of a sample in incoherent NS experiments. Perdeuteration of proteins (i.e., deuteration of the entire protein) hydrated in H₂O thus puts the focus on hydration water dynamics by minimizing the protein contribution to the NS signal. All-atom molecular dynamics (MD) simulation is a useful complement to NS because both methods probe atomic motions on the same time and length scales. Whereas incoherent NS provides an accurate measure of the average dynamics of hydrogen atoms throughout the sample, MD simulations provide atomic-scale insight into motions occurring within particular space and time windows of interest (24).Here we experimentally and computationally address the effect of tau fiber formation on the dynamics of its surrounding hydration water. We produced perdeuterated htau40 as well as a perdeuterated heparin analog, and measured by NS the dynamical properties of hydration water on the surface of tau monomers and of tau fibers whose formation was triggered by the heparin analog. Both elastic and quasi-elastic NS indicate an increased mobility of hydration water on tau fibers compared with tau monomers. MD simulations provide circumstantial evidence suggesting that it is the increase in water dynamics around the disordered fuzzy coat and not around the fiber core that is at the origin of the experimentally observed increase in tau hydration water dynamics after fibrillation. We conjecture that the observed gain in water dynamics reflects an increase in water entropy that is favorable to the fiber formation.     

Aseptic avascular necrosis of the femoral condyles in renal transplant patients: clinical and radiological aspects on 69 knees

The purpose of this study was to analyze clinical and radiological aspects of aseptic avascular necrosis (AVN) of the femoral condyles in renal transplant patients. Forty-five renal transplant patients were followed between 1971 and 1993, and 69 knees have been studied. The immunosuppressive protocol comprised in all cases corticosteroïds, with aziathioprine and since 1983 cyclosporin in 80% of patients. Episodes of rejection were treated with bolus doses of methylprednisolone. In 53.3% of patients, both knees were involved. The necrosis was bicondylar in 60.8% of knees. In the case of an unicondylar lesion, the lateral condyle was involved in 24.7% of knees vs 14.5% for the medial condyle. Symptoms occurred on average 4.9 years after transplantation (range 3 months–10.5 years). This period appeared significantly shorter for patients who had suffered an episode of rejection. In only 24.4% of patients was the knee involvement isolated. Pain was the initial symptom for 83% of patients. Other symptoms included locked knee (20.7%), effusion (49.2%), instability (14.5%), and loss of motion (15.9%). The diagnosis was established by standard radiographs, and in 8 patients by magnetic resonance imaging. Aseptic AVN of the femoral condyles in renal transplant patients is not rare even if it is less frequent than femoral head necrosis. Medication with corticosteroïds is the main risk factor.     

Traumatic hemipelvectomy in children: report on 2 survivors with urological involvement

Traumatic hemipelvectomy through the sacroiliac joint is a devastating injury, mainly because of motor vehicle accidents. Recent improvements in prehospital trauma care have increased the chances of survival for victims. Besides amputation of the lower limb, associated complications usually involve digestive and urological systems.We report on 2 pediatric patients from 2 different European countries.

Patient 1

A 9-year-old boy suffered uprooting of his left lower limb, laceration of the rectum and anal sphincter, as well as an injury to distal urethra with partial loss of cavernous bodies. Initial management included a colostomy and an essay of contention by means of a polypropylene prosthesis that had to be removed in the following months. After several attempts at urethral reconstruction, he underwent a Mitrofanoff derivation.

Patient 2

An 18-month-old girl lost her left lower limb and suffered severe lacerations of bladder and rectum. Among other measures, management included a colostomy, a skin graft, and 2 attempts at reconstruction of her bladder neck, including a modified Casale procedure (cecum and ileocecal appendix were in a high position that made a Mitrofanoff derivation impossible) and a Malone procedure. To the authors' knowledge, she would be the youngest reported survivor of this kind of injury.     

Anesthésie et insuffisance cardiaque droite

Objective

The purpose of this review was to present an update of the anaesthesic management in patients with right ventricular failure (RVF).

Data sources

All references obtained from the medical database Medline^® related to the area and more specifically during the last five years were reviewed.

Data synthesis

The preanaesthesic visit leads to identify the etiology of RVF, to evaluate the functional reserve of the patient, to plan complementary exams and to inform the patients about the risks associated with the perioperative period. During the peroperative period, the monitoring depends of the severity of the illness; however the invasive monitoring of the systemic blood pressure seems always necessary. Any hemodynamic instability should be avoided during the peri-operative period. Since the risk of death is maximal in the first days after the anaesthesia, the patient is ideally managed in intensive care during this period.

Conclusion

Right ventricular failure is often misestimates. However, the perioperative morbidity and mortality of patients with RVF are important. In the perioperative period, the anaesthesiologist should identify patients at risk of right ventricular failure in order to adapt their management.     

Polymorphism of the cell wall-anchoring domain of the autolysin-adhesin AtlE and its relationship to sequence type, as revealed by multilocus sequence typing of invasive and commensal Staphylococcus epidermidis strains

We sequenced the adhesin-cell wall-anchoring domain of the atlE gene of 49 invasive and commensal Staphylococcus epidermidis strains. We identified 22 alleles, which could be separated into two main groups: group 1 (alleles 1 and 6 to 16, 32/49 strains) and group 2 (alleles 2 to 5 and 17 to 22, 17/49 strains). Allele 1 (the type strain sequence) was by far the most prevalent (21 of 49 strains). Multilocus sequence typing showed a clear relationship between the atlE allele and the sequence type (ST), with the "nosocomial" ST27 clone and closely related STs expressing group 1 alleles.     

Prosthetic hip infection caused by Tropheryma whipplei

We report a case of prosthetic hip infection due to Tropheryma whipplei in a 74-year-old man not previously known to have Whipple's disease. Diagnosis was based on systematic 16S rRNA gene amplification and sequencing of samples obtained during revision hip arthroplasty.     

Purification and characterization of endocan (endothelial cell-specific molecule-1), a circulating proteoglycan involved in tumour progression and inflammatory diseases

Introduction   By virtue of the multiplicity of their protein-binding partners (e.g. growth factors, cytokines/chemokines), proteoglycans have been shown to be involved in the regulation of a large number of pathophysiological processes including cancer and inflammatory diseases. We have studied and characterized endocan, also called endothelial cell-specific molecule-1 (ESM-1), which represents a new group of circulating proteoglycans. Endocan is mainly expressed by endothelial cells but also by epithelial cells from lung, gut and kidney. Structurally, endocan is constituted of a mature polypeptide of 165 amino acids with a single glycosaminoglycan chain covalently linked to the serine at position 137 ( Béchard et al . 2001 ).
Methods and results   We showed that human umbilical vein endothelial cells expressed endocan specifically with a single chain of dermatan sulfate (DS) as glycosaminoglycan moiety. As shown by surface plasmon resonance, the DS chain directly interacts with cytokines and growth factors including hepatocyte growth factor/scatter factor and could be responsible for endocan's biological activities. Human embryonic kidney 293 cells, which have been genetically engineered to overexpress endocan, induce tumour growth when injected subcutaneously in SCID mice. Moreover, inflammatory cytokines such as TNF-a and IL-1 have been shown to increase the synthesis and the secretion of endocan from human umbilical vein endothelial cells.
Conclusion   These results suggest that circulating levels of endocan may represent a novel marker for cancer and inflammatory diseases. Further studies on its GAG structure could help us to better understand the biological activities of endocan and to design future glycomic-based therapies.     

High-affinity binding of interferon-gamma to a basement membrane complex (matrigel).

Recently it was demonstrated that growth factors are bound to the extracellular matrix, and can regulate cell behavior. Using three different types of binding assays, we have examined the interaction of interferon-gamma with a basement membrane produced by the Engelbreth-Holm-Swarm tumor. Basement membrane was found to bind interferon-gamma in both a time- and concentration-dependent manner. Equilibrium binding analysis revealed a high-affinity site with a dissociation constant of 1.5 10(-9) M and a maximum binding capacity of 1.6 10(9) sites/mm2 of basement membrane. Competition studies show that the binding is inhibited by heparan sulfate, suggesting that basement membrane-heparan sulfate proteoglycan could be the binding site. This interaction was clearly confirmed by native polyacrylamide gel electrophoresis and dot-blot analysis with purified basement membrane molecules. Furthermore, the carboxy-terminal part of the interferon-gamma molecule contains an amino acid cluster, very closely related to a consensus sequence, present in more than 20 proteins known to bind sulfated glycosaminoglycans such as heparin. These data demonstrate a possible role of extracellular matrix components in storing cytokines and in modulating the cellular response to such factors.