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Claes V.,University of Antwerp | Lecarpentier E.,University of Paris Descartes | Guerin C.,Center Hospitalier Regional Of Meaux | Hebert J.-L.,Institute Of Cardiologie | And 4 more authors.
PLoS ONE | Year: 2014

Human placental stem villi (PSV) present contractile properties. In vitro mechanics were investigated in 40 human PSV. Contraction of PSV was induced by both KCI exposure (n = 20) and electrical tetanic stimulation (n = 20). Isotonic contractions were registered at several load levels ranging from zero-load up to isometric load. The tension-velocity relationship was found to be hyperbolic. This made it possible to apply the A. Huxley formalism for determining the rate constants for myosin cross-bridge (CB) attachment and detachment, CB single force, catalytic constant, myosin content, and maximum myosin ATPase activity. These molecular characteristics of myosin CBs did not differ under either KCI exposure or tetanus. A comparative approach was established from studies previously published in the literature and driven by mean of a similar method. As compared to that described in mammalian striated muscles, we showed that in human PSV, myosin CB rate constants for attachment and detachment were about 103 times lower whereas myosin ATPase activity was 105 times lower. Up to now, CB kinetics of contractile cells arranged along the long axis of the placental sheath appeared to be the slowest ever observed in any mammalian contractile tissue. Copyright: © 2014 Lecarpentier et al. Source


Claes V.,University of Antwerp | Hebert J.-L.,Institute Of Cardiologie | Blanc F.-X.,University of Nantes | Michel F.,Center Hospitalier Regional Of Meaux | Timbely O.,Center Hospitalier Regional Of Meaux
PLoS ONE | Year: 2015

All near-equilibrium systems under linear regime evolve to stationary states in which there is constant entropy production rate. In an open chemical system that exchanges matter and energy with the exterior, we can identify both the energy and entropy flows associated with the exchange of matter and energy. This can be achieved by applying statistical mechanics (SM), which links the microscopic properties of a system to its bulk properties. In the case of contractile tissues such as human placenta, Huxley's equations offer a phenomenological formalism for applying SM. SM was investigated in human placental stem villi (PSV) (n = 40). PSV were stimulated by means of KCl exposure (n = 20) and tetanic electrical stimulation (n = 20). This made it possible to determine statistical entropy (S), internal energy (E), affinity (A), thermodynamic force (A /T) (T: temperature), thermodynamic flow (v) and entropy production rate (A /T x v). We found that PSV operated near equilibrium, i.e., A≺ ≺ 2500 J/mol and in a stationary linear regime, i.e., (A /T) varied linearly with v. As v was dramatically low, entropy production rate which quantified irreversibility of chemical processes appeared to be the lowest ever observed in any contractile system. © 2015 Lecarpentier et al.This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Source


Lecarpentier E.,University of Paris Descartes | Claes V.,University of Antwerp | Timbely O.,Center Hospitalier Regional Of Meaux | Hebert J.-L.,Institute Of Cardiologie | And 6 more authors.
Placenta | Year: 2013

Introduction Human placental stem villi (PSV) present contractile properties. We studied the role of actin-myosin cross bridges (CBs) and the effects of NO-cGMP pathway modulators in the PSV contraction and relaxation. Methods In vitro contractile properties were investigated in 71 PSV from term human placentas studied according to their long axis. Contraction was induced by both KCl and electrical tetanic stimulation. Relaxation was induced by inhibiting the CB cycle with either 2,3-butanedione monoxime (BDM) or blebbistatin (BLE) and by activating the NO-cGMP pathway with isosorbide dinitrate (ISDN), sildenafil (SIL) or ISDN + SIL. Results PSV tension slowly increased by 140% of the basal tone after KCl exposure and by 85% after tetanus. The addition of BDM, BLE, ISDN, SIL and ISDN + SIL induced a relaxation of PSV, the overall time course of relaxation (in s) was respectively (means ± SD) 3412 ± 1904, 14,250 ± 3095*, 3813 ± 1383, 2883 ± 1188 and 2440 ± 477; significantly longer in BLE compared with BDM, ISDN, SIL and ISDN + SIL:*p < 0.001). the overall time course of relaxation (in s) was respectively (means ± SD) 3412 ± 1904, 14,250 ± 3095*, 3813 ± 1383, 2883 ± 1188 and 2440 ± 477; significantly longer in BLE compared with BDM, ISDN, SIL and ISDN + SIL:*p < 0.001). These relaxation kinetics were particularly slow. Other relaxation parametres, i.e., maximum lengthening, -peak dT/dt, and resting tension, did not differ between these 5 subgroups. Discussion and conclusion Isolated human PSV were able to contract after both KCl exposure and tetanus. This increase in contractility was reversed by inhibiting the CB cycle with BDM or BLE and by stimulating the NO-cGMP pathway with ISDN or SIL. The association ISDN + SIL did not potentiate the relaxing processes © 2013 Elsevier Ltd. All rights reserved. Source

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