408 research outputs found
Intracytoplasmic Th1 and Th2 cytokines in rheumatoid arthritis blood and synovial tissue
No full textIn rheumatoid arthritis (RA), T cells have been proposed either as a main actor or as an epiphenomenon in such a primarily synoviocyte-driven disease. A major issue remains the remarkable paradox between the T cell infiltrate and the relative failure to detect definite markers of their activity. To determine the Th1/Th2 cytokine profile in RA synovium, we used a single cell flow cytometric assay for interleukin-2 (IL-2), interferon-γ (FN-γ), IL-4 and IL-10 in paired peripheral blood (PB) and synovial tissue (ST) lymphocytes from RA and osteoarthritis (OA) patients and PB lymphocytes from healthy controls. Cytokines were undetectable in unstimulated PB and ST lymphocytes. More stimulated PB arm ST CD4+ lymphocytes produced IFN-γ than IL-4, for all individuals tested. RA PB CD4+ lymphocytes showed the same Th1 cytokine pattern as normal controls. No increase of such a Th1 profile was observed for ST lymphocytes. A specific recruitment of T CD4+ lymphocytes in the rheumatoid inflamed synovium could not be concluded on the basis of these results
Tensile and Compressive Mechanical Behaviour of Human Blood Clot Analogues
No full textEndovascular thrombectomy procedures are significantly influenced by the mechanical response of thrombi to the multi-axial loading imposed during retrieval. Compression tests are commonly used to determine compressive ex vivo thrombus and clot analogue stiffness. However, there is a shortage of data in tension. This study compares the tensile and compressive response of clot analogues made from the blood of healthy human donors in a range of compositions. Citrated whole blood was collected from six healthy human donors. Contracted and non-contracted fibrin clots, whole blood clots and clots reconstructed with a range of red blood cell (RBC) volumetric concentrations (5–80%) were prepared under static conditions. Both uniaxial tension and unconfined compression tests were performed using custom-built setups. Approximately linear nominal stress–strain profiles were found under tension, while strong strain-stiffening profiles were observed under compression. Low- and high-strain stiffness values were acquired by applying a linear fit to the initial and final 10% of the nominal stress–strain curves. Tensile stiffness values were approximately 15 times higher than low-strain compressive stiffness and 40 times lower than high-strain compressive stiffness values. Tensile stiffness decreased with an increasing RBC volume in the blood mixture. In contrast, high-strain compressive stiffness values increased from 0 to 10%, followed by a decrease from 20 to 80% RBC volumes. Furthermore, inter-donor differences were observed with up to 50% variation in the stiffness of whole blood clot analogues prepared in the same manner between healthy human donors.Medical Instruments & Bio-Inspired Technolog
Le travail peut-il devenir supportable ? De Clot et Gollac
No full textLes deux auteurs de cet ouvrage ont une grande expérience acquise par des recherches souvent collectives en rapport avec des situations de travail diverses. L’un, Yves Clot, est psychologue du travail, l’autre, Michel Gollac, est sociologue et statisticien. Ces spécialités leur donnent une vue et des expériences variées des situations de travail. Ils considèrent comme une richesse les controverses résultant parfois de leurs échanges et ils souhaitent que leur livre aide les futurs lecteurs à ..
Contribution of Red Blood Cells and Platelets to Blood Clot Computed Tomography Imaging and Compressive Mechanical Characteristics
No full textThrombus computed tomography (CT) imaging characteristics may correspond with thrombus mechanical properties and thus predict thrombectomy success. The impact of red blood cell (RBC) content on these properties (imaging and mechanics) has been widely studied. However, the additional effect of platelets has not been considered. The objective of the current study was to examine the individual and combined effects of blood clot RBC and platelet content on resultant CT imaging and mechanical characteristics. Human blood clot analogues were prepared from a combination of preselected RBC volumes and platelet concentrations to decouple their contributions. The resulting clot RBC content (%) and platelet content (%) were determined using Martius Scarlet Blue and CD42b staining, respectively. Non-contrast and contrast-enhanced CT (NCCT and CECT) scans were performed to measure the clot densities. CECT density increase was taken as a proxy for clinical perviousness. Unconfined compressive mechanics were analysed by performing 10 cycles of 80% strain. RBC content is the major determinant of clot NCCT density. However, additional consideration of the platelet content improves the association. CECT density increase is influenced by clot platelet and not RBC content. Platelet content is the dominant component driving clot stiffness, especially at high strains. Both RBC and platelet content contribute to the clot’s viscoelastic and plastic compressive properties. The current in vitro results suggest that CT density is reflective of RBC content and subsequent clot viscoelasticity and plasticity, and that perviousness reflects the clot’s platelet content and subsequent stiffness. However, these indications should be confirmed in a clinical stroke cohort.Medical Instruments & Bio-Inspired Technolog
Travail, identités, métier : quelles métamorphoses ?
No full textColloque international organisé au Collège de France les 23, 24 et 25 juin 2009 par la chaire de Physiologie de la perception et de l’action (Pr Alain Berthoz) en collaboration avec la chaire de Psychologie du travail du Conservatoire national des arts et métiers (Pr Yves Clot
Premiers datages radiocarbone du Magdalénien des Hautes-Pyrénées
No full textRésumé — Les gisements magdaléniens, classiques ou inédits, des Hautes-Pyrénées sont inventoriés. Des travaux récents dans les grottes d'Espèche et des Espélugues ont fourni un matériel qui a pu être daté par C. 14. Des restes osseux des grottes d'Aurensan et de Labastide, fouillées anciennement, ont permis trois dates complémentaires. Ces datages mettent en évidence deux groupes, dont le plus ancien peut être rattaché au Magdalénien moyen.Clot André, Omnès Jacques. Premiers datages radiocarbone du Magdalénien des Hautes-Pyrénées. In: Bulletin de la Société préhistorique française, tome 76, n°10-12, 1979. Études et Travaux. pp. 324-339
Quantification of clot spatial heterogeneity and its impact on thrombectomy
No full textFull author list omitted for brevity. For the full list of authors, see article.BACKGROUND: Compositional and structural features of retrieved clots by thrombectomy can provide insight into improving the endovascular treatment of ischemic stroke. Currently, histological analysis is limited to quantification of compositions and qualitative description of the clot structure. We hypothesized that heterogeneous clots would be prone to poorer recanalization rates and performed a quantitative analysis to test this hypothesis. METHODS: We collected and did histology on clots retrieved by mechanical thrombectomy from 157 stroke cases (107 achieved first-pass effect (FPE) and 50 did not). Using an in-house algorithm, the scanned images were divided into grids (with sizes of 0.2, 0.3, 0.4, 0.5, and 0.6 mm) and the extent of non-uniformity of RBC distribution was computed using the proposed spatial heterogeneity index (SHI). Finally, we validated the clinical significance of clot heterogeneity using the Mann-Whitney test and an artificial neural network (ANN) model. RESULTS: For cases with FPE, SHI values were smaller (0.033 vs 0.039 for grid size of 0.4 mm, P=0.028) compared with those without. In comparison, the clot composition was not statistically different between those two groups. From the ANN model, clot heterogeneity was the most important factor, followed by fibrin content, thrombectomy techniques, red blood cell content, clot area, platelet content, etiology, and admission of intravenous tissue plasminogen activator (IV-tPA). No statistical difference of clot heterogeneity was found for different etiologies, thrombectomy techniques, and IV-tPA administration. CONCLUSIONS: Clot heterogeneity can affect the clot response to thrombectomy devices and is associated with lower FPE. SHI can be a useful metric to quantify clot heterogeneity
Correlation between acute ischaemic stroke clot length before mechanical thrombectomy and extracted clot area: Impact of thrombus size on number of passes for clot removal and final recanalization
No full textIntroduction We assessed the correlation between thrombus size before and after mechanical thrombectomy, measured as length by Computed Tomography Angiography/Non-Contrast Computed Tomography (CTA/NCCT) and Extracted Clot Area, ECA, respectively. We also assessed the influence of thrombus size on the number of passes required for clot removal and final recanalization outcome. Materials and methods Acute ischaemic stroke (AIS) thrombi retrieved by mechanical thrombectomy from 500 patients and data of clot length by CTA/NCCT were collected from three hospitals in Europe. ECA was obtained by measuring the area of the extracted clot. Non-parametric tests were used for data analysis. Results A strong positive correlation was found between clot length on CTA/NCCT and ECA (rho = 0.619,N = 500,P < 0.0001*). Vessel size influences clot length on CTA/NCCT (H2 = 98.6, P < 0.0001*) and ECA (H2 = 105.6,P < 0.0001*), but the significant correlation between CTA/NCCT length and ECA was evident in all vessels. Poorer revascularisation outcome was associated with more passes (H5 = 73.1, P < 0.0001*). More passes were required to remove longer clots (CTA/NCCT; H4 = 31.4, P < 0.0001*; ECA; H4 = 50.2, P < 0.0001*). There was no significant main association between recanalization outcome and length on CTA/NCCT or ECA, but medium sized clots (ECA 20–40 mm2) were associated with least passes and highest revascularisation outcome (N = 500, X2 = 16.2, P < 0.0001*). Conclusion Clot length on CTA/NCCT strongly correlates with ECA. Occlusion location influences clot size. More passes are associated with poorer revascularisation outcome and bigger clots. The relationship between size and revascularisation outcome is more complex. Clots of medium ECA take less passes to remove and are associated with better recanalization outcome than both smaller and larger clots.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This publication has emanated from research conducted with the financial support of Science Foundation Ireland (SFI) and is co-funded under the European Regional Development Fund under Grant Number 13/RC/2073_2. Furthermore, it was supported by the industrial partner Cerenovus.peer-reviewe
Quantitative structural mechanobiology of platelet-driven blood clot contraction
No full text© 2017 The Author(s). Blood clot contraction plays an important role in prevention of bleeding and in thrombotic disorders. Here, we unveil and quantify the structural mechanisms of clot contraction at the level of single platelets. A key elementary step of contraction is sequential extension-retraction of platelet filopodia attached to fibrin fibers. In contrast to other cell-matrix systems in wh ich cells migrate along fibers, the "hand-over-hand" longitudinal pulling causes shortening and bending of platelet-attached fibers, resulting in formation of fiber kinks. When attached to multiple fibers, platelets densify the fibrin network by pulling on fibers transversely to their longitudinal axes. Single platelets and aggregates use actomyosin contractile machinery and integrin-mediated adhesion to remodel the extracellular matrix, inducing compaction of fibrin into bundled agglomerates tightly associated with activated platelets. The revealed platelet-driven mechanisms of blood clot contraction demonstrate an important new biological application of cell motility principles
Quantitative structural mechanobiology of platelet-driven blood clot contraction
No full text© 2017 The Author(s). Blood clot contraction plays an important role in prevention of bleeding and in thrombotic disorders. Here, we unveil and quantify the structural mechanisms of clot contraction at the level of single platelets. A key elementary step of contraction is sequential extension-retraction of platelet filopodia attached to fibrin fibers. In contrast to other cell-matrix systems in wh ich cells migrate along fibers, the "hand-over-hand" longitudinal pulling causes shortening and bending of platelet-attached fibers, resulting in formation of fiber kinks. When attached to multiple fibers, platelets densify the fibrin network by pulling on fibers transversely to their longitudinal axes. Single platelets and aggregates use actomyosin contractile machinery and integrin-mediated adhesion to remodel the extracellular matrix, inducing compaction of fibrin into bundled agglomerates tightly associated with activated platelets. The revealed platelet-driven mechanisms of blood clot contraction demonstrate an important new biological application of cell motility principles
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