The surrounding microenvironment limits tumour expansion, imposing a compressive stress on the tumour, but little is known how pressure propagates inside the tumour. Here we present non-destructive ...cell-like microsensors to locally quantify mechanical stress distribution in three-dimensional tissue. Our sensors are polyacrylamide microbeads of well-defined elasticity, size and surface coating to enable internalization within the cellular environment. By isotropically compressing multicellular spheroids (MCS), which are spherical aggregates of cells mimicking a tumour, we show that the pressure is transmitted in a non-trivial manner inside the MCS, with a pressure rise towards the core. This observed pressure profile is explained by the anisotropic arrangement of cells and our results suggest that such anisotropy alone is sufficient to explain the pressure rise inside MCS composed of a single cell type. Furthermore, such pressure distribution suggests a direct link between increased mechanical stress and previously observed lack of proliferation within the spheroids core.
Introduction La glycation est une réaction organique non-enzymatique néfaste dans entre le glucose et différentes protéines. Elle est à l’origine de protéines non-fonctionnelles, elles-mêmes générant ...de nombreux effets indésirables (augmentation du stress oxydatif, dégradation des structures et fonctions des membranes cellulaires, accélération de la formation des rides, pathologies rénales ou oculaires, mort cellulaire accélérée des tissus cérébraux etc). Chez les diabétiques, la glycation est l’un des plus importants facteurs responsables de la sénescence des malades. Matériels et méthodes Sachant que les peroxydes de terpènes ont la capacité d’améliorer l’oxygénation tissulaire sans stress oxydatif , deux séries d’expériences ont été faites : – mesurer le taux d’hémoglobines glyquées dans le sang de trois séries de rats Wistar normoglycémiques exposés à des sessions respiratoires de 3, 6 ou 9 min d’extraits peroxydés d’huile essentielle de térébenthine, 1 à 3 fois par semaine versus rats témoins (vapeur d’eau), – mesurer le taux d’hémoglobines glyquées d’un même échantillon sanguin, traité ou pas. Résultats Les rats présentent des taux d’hémoglobines glyquées d’autant plus bas que leurs temps de sessions respiratoires est important. Le traitement oxygéné des échantillons permettent la réduction du taux de protéines glyquées, après un contact de trois heures, au contraire des témoins non traités. Conclusion S’il existe une relation connue entre le diabète et l’hypoxie, c’est, à notre connaissance, la première démonstration de l’action positive de l’oxygène sur le maintien d’un faible taux d’hémoglobines glyquées chez des Mammifères et surtout sur la diminution significative du taux de ces protéines, après trois heures d’incubation, sur un échantillon sanguin.
Active gel physics Prost, J.; Jülicher, F.; Joanny, J-F.
Nature physics,
02/2015, Letnik:
11, Številka:
2
Journal Article
Recenzirano
The continuity equation describing the balance of polymerized actin mass has both source and sink terms, whereas the total actin mass is conserved. All conservation equations for scalar densities ...have not only convection and diusion fluxes, but they have additional terms characteristic of activity. Indeed, both the bend and splay of a nematic director have the symmetry of a vector and, owing to the absence of time-reversal symmetry, they can enter the expression for the fluxes.
Hydrodynamics of soft active matter Marchetti, M. C.; Joanny, J. F.; Ramaswamy, S. ...
Reviews of modern physics,
07/2013, Letnik:
85, Številka:
3
Journal Article
Recenzirano
Active matter consists of self-driven particles (fish, birds, and many biological systems such as bacteria or cytoskeletal extracts) and exhibits intriguing non-equilibrium behavior such as flocking, ...swarming, bizarre fluctuations, and pattern formation. This article reviews continuum models for such systems, presenting the hydrodynamics of soft active matter. This review summarizes theoretical progress in the field of active matter, placing it in the context of recent experiments. This approach offers a unified framework for the mechanical and statistical properties of living matter: bio-filaments and molecular motors in vitro or in vivo, collections of motile microorganisms, animal flocks, and chemical or mechanical imitations. A major goal of this review is to integrate several approaches proposed in the literature, from semi-microscopic to phenomenological. Last, the outlook for a quantitative understanding of active matter, through the interplay of detailed theory with controlled experiments on simplified systems, with living or artificial constituents, is summarized.
We study theoretically the shapes of a dividing epithelial monolayer of cells lying on top of an elastic stroma. The negative tension created by cell division provokes a buckling instability at a ...finite wave vector leading to the formation of periodic arrays of villi and crypts. The instability is similar to the buckling of a metallic plate under compression. We use the results to rationalize the various structures of the intestinal lining observed in vivo. Taking into account the coupling between cell division and local curvature, we obtain different patterns of villi and crypts, which could explain the different morphologies of the small intestine and the colon.
In embryonic development or tumor evolution, cells often migrate collectively within confining tracks defined by their microenvironment 1,2. In some of these situations, the displacements within a ...cell strand are antiparallel 3, giving rise to shear flows. However, the mechanisms underlying these spontaneous flows remain poorly understood. Here, we show that an ensemble of spindle-shaped cells plated in a well-defined stripe spontaneously develop a shear flow whose characteristics depend on the width of the stripe. On wide stripes, the cells self-organize in a nematic phase with a director at a well-defined angle with the stripe's direction, and develop a shear flow close to the stripe's edges. However, on stripes narrower than a critical width, the cells perfectly align with the stripe's direction and the net flow vanishes. A hydrodynamic active gel theory provides an understanding of these observations and identifies the transition between the non-flowing phase oriented along the stripe and the tilted phase exhibiting shear flow as a Fréedericksz transition driven by the activity of the cells. This physical theory is grounded in the active nature of the cells and based on symmetries and conservation laws, providing a generic mechanism to interpret in vivo antiparallel cell displacements.
Aim
Transversus abdominis plane (TAP) block is a locoregional anaesthesia technique of growing interest in abdominal surgery. However, its efficacy following laparoscopic colorectal surgery is still ...debated. This meta‐analysis aimed to assess the efficacy of TAP block after laparoscopic colorectal surgery.
Method
All comparative studies focusing on TAP block after laparoscopic colorectal surgery have been systematically identified through the MEDLINE database, reviewed and included. Meta‐analysis was performed according to the Mantel–Haenszel method for random effects. End‐points included postoperative opioid consumption, morbidity, time to first bowel movement and length of hospital stay.
Results
A total of 13 studies, including 7 randomized controlled trials, were included, comprising a total of 600 patients who underwent laparoscopic colorectal surgery with TAP block, compared with 762 patients without TAP block. Meta‐analysis of these studies showed that TAP block was associated with a significantly reduced postoperative opioid consumption on the first day after surgery weighted mean difference (WMD) −14.54 (−25.14; −3.94); P = 0.007 and a significantly shorter time to first bowel movement WMD −0.53 (−0.61; −0.44); P < 0.001 but failed to show any impact on length of hospital stay WMD −0.32 (−0.83; 0.20); P = 0.23 although no study considered length of stay as its primary outcome. Finally, TAP block was not associated with a significant increase in the postoperative overall complication rate OR = 0.84 (0.62–1.14); P = 0.27.
Conclusion
Transversus abdominis plane (TAP) block in laparoscopic colorectal surgery improves postoperative opioid consumption and recovery of postoperative digestive function without any significant drawback.
Background
The effect of anastomotic leakage on oncological outcomes after total mesorectal excision (TME) is controversial. This study aimed to assess the influence of symptomatic and asymptomatic ...anastomotic leakage on oncological outcomes after laparoscopic TME.
Methods
All patients who underwent restorative laparoscopic TME for rectal adenocarcinoma with curative intent from 2005 to 2014 were identified from an institutional database. Asymptomatic anastomotic leakage was defined by CT performed systematically 4–8 weeks after rectal surgery, with no relevant clinical symptoms or laboratory examination findings during the postoperative course.
Results
Of a total of 428 patients, anastomotic leakage was observed in 120 (28·0 per cent) (50 asymptomatic, 70 symptomatic). After a mean follow‐up of 40 months, local recurrence was observed in 36 patients (8·4 per cent). Multivariable Cox regression identified three independent risk factors for reduced local recurrence‐free survival (LRFS): symptomatic anastomotic leakage (odds ratio (OR) 2·13, 95 per cent c.i. 1·29 to 3·50; P = 0·003), positive resection margin (R1) (OR 2·41, 1·40 to 4·16; P = 0·001) and pT3–4 category (OR 1·77, 1·08 to 2·90; P = 0·022). Patients with no risk factor for reduced LRFS had an estimated 5‐year LRFS rate of 87·7(s.d. 3·2) per cent, whereas the rate dropped to 75·3(4·3) per cent with one risk factor, 67(7) per cent with two risk factors, and 14(13) per cent with three risk factors (P < 0·001). Asymptomatic anastomotic leakage was not significantly associated with LRFS in multivariable analysis.
Conclusion
Symptomatic anastomotic leakage is a risk factor for disease recurrence in patients with rectal adenocarcinoma.
Not all leaks are equal
We propose a mechanism for the formation of contractile rings and the apparition of a flow in the cortical layer of cells undergoing cytokinesis at the end of cell division or during the healing of a ...wound in the cortex of Xenopus eggs. We generalize the hydrodynamic active gel theory along the lines of thin shell theory of continuum elasticity to describe the cell cortex. As in liquid crystal physics, the flow couples to the orientation of the actin filaments. The cortical flow is driven by an increased density of myosin motors in the cortex, and orients the filaments to form the ring.
Generic theory of colloidal transport Jülicher, F.; Prost, J.
The European physical journal. E, Soft matter and biological physics,
05/2009, Letnik:
29, Številka:
1
Journal Article
Recenzirano
Odprti dostop
We discuss the motion of colloidal particles relative to a two-component fluid consisting of solvent and solute. Particle motion can result from i) net body forces on the particle due to external ...fields such as gravity; ii) slip velocities on the particle surface due to surface dissipative phenomena. The perturbations of the hydrodynamic flow field exhibit characteristic differences in cases i) and ii) which reflect different patterns of momentum flux corresponding to the existence of net forces, force dipoles or force quadrupoles. In the absence of external fields, gradients of concentration or pressure do not generate net forces on a colloidal particle. Such gradients can nevertheless induce relative motion between particle and fluid. We present a generic description of surface dissipative phenomena based on the linear response of surface fluxes driven by conjugate surface forces. In this framework we discuss different transport scenarios including self-propulsion via surface slip that is induced by active processes on the particle surface. We clarify the nature of force balances in such situations.
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