Internalization of microparticles by endothelial cells promotes platelet/endothelial cell interaction under flow.

BACKGROUND: Microparticles (MPs) released by activated or apoptotic cells increase in number in the blood of subjects with vascular or metabolic diseases and may contribute to thrombotic complications. OBJECTIVES: In this study, we investigated whether MPs promoted platelet recruitment to endothelial cells in flow conditions, and by which mechanism. METHODS: Human umbilical vein endothelial cells (HUVECs) grown in microslide perfusion chambers were exposed to MPs prepared in vitro from HUVECs, monocytes or platelets. RESULTS: Videomicroscopy of DIOC-labelled blood perfused at arterial rate on human umbilical vein ECs demonstrated that, irrespective of their cell origin, MPs promoted the formation of platelet strings at the surface of HUVECs. This platelet/endothelial cell interaction was dependent on von Willebrand factor (VWF) expression at the HUVEC surface and involved Glycoprotein Ib and P-selectin. Interestingly, HUVECs internalized MPs within a few hours through a process involving anionic phospholipids, lactadherin and αvß3 integrin. This uptake generated the production of reactive oxygen species via the xanthine/xanthine oxidase system (inhibited by allopurinol and the ROCK inhibitor Y-27632) and the NADPH oxidase (inhibited by SOD). Reactive oxygen species appeared essential for VWF expression at the endothelial cell surface and subsequent platelet/endothelial cell interaction under flow. The pathophysiological relevance of this process is underlined by the fact that circulating MPs from Type I diabetic patients induced platelet/endothelial cell interaction under flow, with an intensity correlated with the severity of the vasculopathy.

Structure and rheological properties of model microemulsion networks filled with nanoparticles.

Model microemulsion networks of oil droplets stabilized by non-ionic surfactant and telechelic polymer C18 -PEO(10k)- C18 have been studied for two droplet-to-polymer size ratios. The rheological properties of the networks have been measured as a function of network connectivity and can be described in terms of simple percolation laws. The network structure has been characterised by Small Angle Neutron Scattering (SANS). A Reverse Monte Carlo (RMC) approach is used to demonstrate the interplay of attraction and repulsion induced by the copolymer. These model networks are then used as matrix for the incorporation of silica nanoparticles (R = 10 nm), individual dispersion being checked by scattering. A strong impact on the rheological properties is found for silica volume fractions up to 9%. q(A-1).

[Laryngeal schwannomas]. / Schwannomes du larynx.

Laryngeal schwannoma is a rare benign tumour of the larynx. Schwannomas derive from the Schwann cells. The majority occurs in supraglottic area and may arise at any age. Magnetic resonance imaging (MRI) is the best imaging tool for suggesting the diagnosis in the appropriate clinical context. Conservative surgery is the treatment of choice. These tumors have to be distinguished from neurofibromas. We report 2 cases of laryngeal schwannoma. The first one concerned an 8-month-old baby with a laryngeal stridor history which seemed to be related to laryngomalacia. The second case was a 22-year-old man with a 5-year history of dysphonia. On nasofibroscopic examination, a sub mucosal mass enlarged the posterior part of the right false vocal cord in both cases. Both CT scan and MRI sequences showed a well margined lesion in the same place. Histological biopsies identified a schwannoma. External surgeries were subsequently and successfully performed. Diagnosis (imaging), specific treatment (endoscopic or external surgery), and possible association of laryngeal schwannomas are discussed.

[Treatment of thoracolumbar junction burst fractures (Magerl A3) by balloon kyphoplasty: anatomic study]. / Traitement des burst fractures (Magerl A3) de la charnière thoracolombaire par cyphoplastie à ballonnets: étude anatomique.

PURPOSE OF THE STUDY: Balloon kyphoplasty is a not widely used method for the treatment of vertebral burst fractures with displacement of the posterior wall. The purpose of this study was to measure the posterior height of the vertebral body and the posttraumatic canal surface area before and after balloon kyphoplasty for the treatment of burst fractures (Magerl A3). MATERIAL AND METHODS: This anatomic study was conducted on ten experimental burst fractures of the thoracolumar junction prepared on cadaver specimens. The surface area of the canal and the height of the posterior wall were measured by computed tomography before and after balloon kyphoplasty. These two variables were then compared with search for correlation. RESULTS: The posttraumatic canal surface area increased significantly after kyphoplasty (p=0.02). Gain in posterior height was not significant and there was no correlation between the two variables. Cement leakage into the canal was not observed. DISCUSSION: It is known that balloon kyphoplasty can re-establish anterior height and correct for the posttraumatic kyphosis in patients with compression fractures of osteoporotic vertebrae. The present cadaver study shows that when the posterior wall is displaced posteriorly, balloon expansion does not exaggerate the wall displacement. On the contrary, the posttraumatic canal surface area is increased due to the ligamentotaxis effect. CONCLUSION: Balloon kyphoplasty could be an alternative to posterior instrumentation for burst fractures without associated neurological deficit, even if the posterior wall is damaged. This technique can be used to reduce and stabilize the fracture while sparing the adjacent levels and limiting the risk inherent with an extensive surgical approach.

[Sporadic cerebral amyloidotic angiopathy]. / Angiopathie amyloïde cérébrale sporadique.

INTRODUCTION: Sporadic cerebral amyloid angiopathy (CAA) is a microangiopathy identified by neuropathological examination in more than 30 percent of patients over 85 years of age. STATE OF ART: Boston criteria for diagnosis of CAA--related hemorrhage are as follows: "definite CAA", "Probable CAA with supporting pathology", "Probable CAA" and "Possible CAA". Clinical manifestations of CAA are either lobar, cortical, corticosubcortical or cerebellar hemorrhages associated with progressive dementia. Dementia, corresponding either to Alzheimer disease, vascular or mixed dementia, precedes hemorrhages in 25 to 40 percent of cases. Brain MRI can demonstrate microbleeding. PERSPECTIVES: This review compares data regarding CAA prevalence, intracranial hemorrhages, and their risk factors in old patients. Diagnosis and preventive strategies are discussed. It would be useful to identify those affected by CAA among elderly demented patients with atrial fibrillation requiring anticoagulation therapy. CONCLUSIONS: CAA is suspected in the presence of recurrent lobar or cerebellar hemorrhages, and moreover if associated with pre-existing dementia. In elderly demented patients, MRI criteria to detect CAA should be considered in order to prevent hemorrhage risk, particularly after anticoagulation therapy.