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Article ; Online: On kinetics and extreme values in systems with random interactions.

Girard, Martin

2022 Volume 20, Issue 1

Abstract: Biological environments such as the cytoplasm are comprised of many different molecules, which makes explicit modeling intractable. In the spirit of Wigner, one may be tempted to assume interactions to derive from a random distribution. Via this ... ...

Abstract	Biological environments such as the cytoplasm are comprised of many different molecules, which makes explicit modeling intractable. In the spirit of Wigner, one may be tempted to assume interactions to derive from a random distribution. Via this approximation, the system can be efficiently treated in the mean-field, and general statements about expected behavior of such systems can be made. Here, I study systems of particles interacting via random potentials, outside of mean-field approximations. These systems exhibit a phase transition temperature, under which part of the components precipitate. The nature of this transition appears to be non-universal, and to depend intimately on the underlying distribution of interactions. Above the phase transition temperature, the system can be efficiently treated using a Bethe approximation, which shows a dependence on extreme value statistics. Relaxation timescales of this system tend to be slow, but can be made arbitrarily fast by increasing the number of neighbors of each particle.
MeSH term(s)	Kinetics ; Temperature ; Physics ; Phase Transition
Language	English
Publishing date	2022-12-20
Publishing country	England
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	2133216-2
ISSN	1478-3975 ; 1478-3967
ISSN (online)	1478-3975
ISSN	1478-3967
DOI	10.1088/1478-3975/aca9b2
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Article ; Online: Induced asymmetries in membranes.

Girard, Martin / Bereau, Tristan

Biophysical journal

2022 Volume 122, Issue 11, Page(s) 2092–2098

Abstract: Lipid asymmetry in plasma membrane of eukaryotes is ubiquitous. The first measurements reported compositional asymmetry: phosphatidylethanolamine and phosphatidylserine are mostly on the cytoplasmic leafet, while phosphatidylcholine and sphingomyelin are ...

Abstract	Lipid asymmetry in plasma membrane of eukaryotes is ubiquitous. The first measurements reported compositional asymmetry: phosphatidylethanolamine and phosphatidylserine are mostly on the cytoplasmic leafet, while phosphatidylcholine and sphingomyelin are mostly on the exoplasmic leaflet. More recent experiments using lipidomics have evidenced the presence of saturation asymmetry between the two leaflets. A question that naturally arises is why such an asymmetry? To complicate matters, it is still largely unknown in which leaflet cholesterol lies. Here, we use chemical potentials to mimic flippase proteins responsible for maintenance of compositional asymmetry in silico. We show that saturation asymmetry naturally arises as a byproduct of phospholipid number asymmetry and sphingomyelin contents, thereby showing that some reported asymmetries may naturally result from others and do not necessarily require being externally driven. We also show that plasmalogen lipids' tendency to be highly unsaturated is also natural. Additionally, we tackle the problem of cholesterol and show that, while it is influenced by all asymmetries, the resulting cholesterol asymmetry tends to be fairly mild.
MeSH term(s)	Sphingomyelins/metabolism ; Cell Membrane/metabolism ; Phospholipids/chemistry ; Membranes/metabolism ; Cholesterol/metabolism
Chemical Substances	Sphingomyelins ; Phospholipids ; Cholesterol (97C5T2UQ7J)
Language	English
Publishing date	2022-12-06
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	218078-9
ISSN	1542-0086 ; 0006-3495
ISSN (online)	1542-0086
ISSN	0006-3495
DOI	10.1016/j.bpj.2022.12.004
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Zs.A 235: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (1.OG) ab Jg. 2022: Lesesaal (EG)
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Article ; Online: Finite-size transitions in complex membranes.

Girard, Martin / Bereau, Tristan

Biophysical journal

2021 Volume 120, Issue 12, Page(s) 2436–2443

Abstract: The lipid-raft hypothesis postulates that cell membranes possess some degree of lateral organization. The hypothesis has attracted much attention while remaining controversial, with an underlying mechanism that remains elusive. One idea that supports ... ...

Abstract	The lipid-raft hypothesis postulates that cell membranes possess some degree of lateral organization. The hypothesis has attracted much attention while remaining controversial, with an underlying mechanism that remains elusive. One idea that supports rafts relies on the membrane lying near a critical point. Although supported by experimental evidence, holding a many-component membrane at criticality requires a delicate tuning of all components-a daunting task. Here, we propose a coherent framework to reconcile critical behavior and lipid regulation. Using a lattice model, we show that lipid regulation of a complex membrane, i.e., allowing composition to fluctuate based on relative chemical potentials, can lead to critical behavior. The results are robust against specific values of the chemical potentials. Instead of a conventional transition point, criticality is observed over a large temperature range. This surprising behavior arises from finite-size effects, causing nonequivalent time and space averages. The instantaneous lipid distribution effectively develops a translational symmetry, which we relate to long-wavelength Goldstone modes. The framework is robust and reproduces important experimental trends; membrane-demixing temperature closely follows cell-growth temperature. It also ensures criticality of fixed-composition extracts, such as giant plasma membrane vesicles. Our clear picture provides a strong argument in favor of the critical-membrane hypothesis, without the need for specific sensing mechanisms.
MeSH term(s)	Cell Membrane ; Lipids ; Membrane Microdomains ; Membranes ; Temperature
Chemical Substances	Lipids
Language	English
Publishing date	2021-05-04
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	218078-9
ISSN	1542-0086 ; 0006-3495
ISSN (online)	1542-0086
ISSN	0006-3495
DOI	10.1016/j.bpj.2021.03.043
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Zs.A 235: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (1.OG) ab Jg. 2022: Lesesaal (EG)
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Article ; Online: Computer simulations of lipid regulation by molecular semigrand canonical ensembles.

Girard, Martin / Bereau, Tristan

Biophysical journal

2021 Volume 120, Issue 12, Page(s) 2370–2373

Abstract: The plasma membrane is the interface between cells and exterior media. Although its existence has been known for a long time, organization of its constituent lipids remain a challenge. Recently, we have proposed that lipid populations may be controlled ... ...

Abstract	The plasma membrane is the interface between cells and exterior media. Although its existence has been known for a long time, organization of its constituent lipids remain a challenge. Recently, we have proposed that lipid populations may be controlled by chemical potentials of different lipid species, resulting in semigrand canonical thermodynamic ensembles. However, the currently available molecular dynamics software packages do not facilitate the control of chemical potentials at the molecular level. Here, we propose a variation of existing algorithms that efficiently characterizes and controls the chemical nature of each lipid. Additionally, we allow coupling with collective variables and show that it can be used to dynamically create asymmetric membranes. This algorithm is openly available as a plugin for the HOOMD-Blue molecular dynamics engine.
MeSH term(s)	Algorithms ; Cell Membrane ; Computer Simulation ; Lipid Bilayers ; Molecular Dynamics Simulation ; Thermodynamics
Chemical Substances	Lipid Bilayers
Language	English
Publishing date	2021-05-01
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	218078-9
ISSN	1542-0086 ; 0006-3495
ISSN (online)	1542-0086
ISSN	0006-3495
DOI	10.1016/j.bpj.2021.04.025
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Zs.A 235: Show issues			Location: Je nach Verfügbarkeit (siehe Angabe bei Bestand) bis Jg. 1994: Bestellungen von Artikeln über das Online-Bestellformular Jg. 1995 - 2021: Lesesall (1.OG) ab Jg. 2022: Lesesaal (EG)
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Article ; Online: The Crucial Role of Solvation Forces in the Steric Stabilization of Nanoplatelets.

Petersen, Nanning / Girard, Martin / Riedinger, Andreas / Valsson, Omar

Nano letters

2022

Abstract: The steric stability of inorganic colloidal particles in an apolar solvent is usually described in terms of the balance between three contributions: the van der Waals attraction, the free energy of mixing, and the ligand compression. However, in the case ...

Abstract	The steric stability of inorganic colloidal particles in an apolar solvent is usually described in terms of the balance between three contributions: the van der Waals attraction, the free energy of mixing, and the ligand compression. However, in the case of nanoparticles, the discrete nature of the ligand shell and the solvent has to be taken into account. Cadmium selenide nanoplatelets are a special case. They combine a weak van der Waals attraction and a large facet to particle size ratio. We use coarse grained molecular dynamics simulations of nanoplatelets in octane to demonstrate that solvation forces are strong enough to induce the formation of nanoplatelet stacks and by that have a crucial impact on the steric stability. In particular, we demonstrate that for sufficiently large nanoplatelets, solvation forces are proportional to the interacting facet area, and their strength is intrinsically tied to the softness of the ligand shell.
Language	English
Publishing date	2022-12-09
Publishing country	United States
Document type	Journal Article
ISSN	1530-6992
ISSN (online)	1530-6992
DOI	10.1021/acs.nanolett.2c02848
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Article ; Online: Regulating Lipid Composition Rationalizes Acyl Tail Saturation Homeostasis in Ectotherms.

Girard, Martin / Bereau, Tristan

Biophysical journal

2020 Volume 119, Issue 5, Page(s) 892–899

Abstract: Cell membranes mainly consist of lipid bilayers with an actively regulated composition. The underlying processes are still poorly understood, in particular, how the hundreds of components are controlled. Cholesterol has been found to correlate with ... ...

Abstract	Cell membranes mainly consist of lipid bilayers with an actively regulated composition. The underlying processes are still poorly understood, in particular, how the hundreds of components are controlled. Cholesterol has been found to correlate with phospholipid saturation for reasons that remain unclear. To better understand the link between cell membrane regulation and chemical composition, we establish a computational framework based on chemical reaction networks, resulting in multiple semigrand canonical ensembles. By running computer simulations, we show that regulating the chemical potential of lipid species is sufficient to reproduce the experimentally observed increase in acyl tail saturation with added cholesterol. Our model proposes a different picture of lipid regulation in which components can be regulated passively instead of actively. In this picture, phospholipid acyl tail composition naturally adapts to added molecules such as cholesterol or proteins. A comparison between regulated membranes with commonly studied ternary model membranes shows stark differences: for instance, correlation lengths and viscosities observed are independent of lipid chemical affinity.
MeSH term(s)	Cell Membrane ; Cholesterol ; Homeostasis ; Lipid Bilayers ; Phospholipids
Chemical Substances	Lipid Bilayers ; Phospholipids ; Cholesterol (97C5T2UQ7J)
Language	English
Publishing date	2020-08-06
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	218078-9
ISSN	1542-0086 ; 0006-3495
ISSN (online)	1542-0086
ISSN	0006-3495
DOI	10.1016/j.bpj.2020.07.024
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Article ; Online: Individualizing Intraoperative Ventilation: Comment.

Girard, Martin / Carrier, François Martin

Anesthesiology

2019 Volume 131, Issue 2, Page(s) 447–448

MeSH term(s)	Lung ; Positive-Pressure Respiration ; Respiration
Language	English
Publishing date	2019-08-26
Publishing country	United States
Document type	Journal Article
ZDB-ID	269-0
ISSN	1528-1175 ; 0003-3022
ISSN (online)	1528-1175
ISSN	0003-3022
DOI	10.1097/ALN.0000000000002834
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Article ; Online: Intraoperative Vasoactive Medications and Perioperative Outcomes in Liver Transplantation: A Systematic Review and Network Meta-analyses.

Carrier, François Martin / Girard, Martin / Zuo, Rui Min / Ziegler, Daniela / Trottier, Helen / Chassé, Michaël

Transplantation

2023 Volume 108, Issue 4, Page(s) 854–873

Abstract: We conducted a systematic review and network meta-analyses evaluating the effects of different intraoperative vasoactive drugs on acute kidney injury (AKI) and other perioperative outcomes in adult liver transplant recipients. We searched multiple ... ...

Abstract	We conducted a systematic review and network meta-analyses evaluating the effects of different intraoperative vasoactive drugs on acute kidney injury (AKI) and other perioperative outcomes in adult liver transplant recipients. We searched multiple electronic databases using words from the "liver transplantation" and "vasoactive drug" domains. We included all randomized controlled trials conducted in adult liver transplant recipients comparing 2 different intravenous vasoactive drugs or 1 against a standard of care that reported AKI, intraoperative blood loss, or any other postoperative outcome. We conducted 4 frequentist network meta-analyses using random effect models, based on the interventions' mechanism of action, and evaluated the quality of evidence (QoE) using Grading of Recommendations, Assessment, Development, and Evaluations recommendations. We included 9 randomized controlled trials comparing different vasopressor drugs (vasoconstrictor or inotrope), 3 comparing a somatostatin infusion (or its analogues) to a standard of care, 11 comparing different vasodilator infusions together or against a standard of care, and 2 comparing vasoconstrictor boluses at graft reperfusion. Intravenous clonidine was associated with shorter duration of mechanical ventilation, intensive care unit, and hospital length of stay (very low QoE), and some vasodilators were associated with lower creatinine level 24 h after surgery (low to very low QoE). Phenylephrine and terlipressin were associated with less intraoperative blood loss when compared with norepinephrine (low and moderate QoE). None of the vasoactive drugs improve any other postoperative outcomes, including AKI. There is still important equipoise regarding the best vasoactive drug to use in liver transplantation for most outcomes. Further studies are required to better inform clinical practice.
MeSH term(s)	Adult ; Humans ; Liver Transplantation/adverse effects ; Blood Loss, Surgical ; Network Meta-Analysis ; Vasoconstrictor Agents/adverse effects ; Vasodilator Agents ; Acute Kidney Injury/etiology ; Acute Kidney Injury/drug therapy
Chemical Substances	Vasoconstrictor Agents ; Vasodilator Agents
Language	English
Publishing date	2023-08-01
Publishing country	United States
Document type	Meta-Analysis ; Systematic Review ; Journal Article
ZDB-ID	208424-7
ISSN	1534-6080 ; 0041-1337
ISSN (online)	1534-6080
ISSN	0041-1337
DOI	10.1097/TP.0000000000004744
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Article ; Online: Effects of an open lung extubation strategy compared with a conventional extubation strategy on postoperative pulmonary complications after general anesthesia: a single-centre pilot randomized controlled trial.

Girard, Julie / Zaouter, Cédrick / Moore, Alex / Carrier, François M / Girard, Martin

Canadian journal of anaesthesia = Journal canadien d'anesthesie

2023 Volume 70, Issue 10, Page(s) 1648–1659

Abstract: Purpose: Postoperative pulmonary complications (PPCs) are a common cause of morbidity. Postoperative atelectasis is thought to be a significant risk factor in their development. Recent imaging studies suggest that patients' extubation may result in ... ...

Title translation	Effets d’une stratégie d’extubation à poumon ouvert par rapport à une stratégie d’extubation conventionnelle sur les complications pulmonaires postopératoires après une anesthésie générale : une étude randomisée contrôlée pilote monocentrique.
Abstract	Purpose: Postoperative pulmonary complications (PPCs) are a common cause of morbidity. Postoperative atelectasis is thought to be a significant risk factor in their development. Recent imaging studies suggest that patients' extubation may result in similar postoperative atelectasis regardless of the intraoperative mechanical ventilation strategy used. In this pilot trial, we hypothesized that a study investigating the effects of an open lung extubation strategy compared with a conventional one on PPCs would be feasible. Methods: We conducted a pilot, single-centre, double-blinded randomized controlled trial. Adult patients at moderate to high risk of PPCs and scheduled for elective surgery were eligible. Patients were randomized to an open lung extubation strategy (semirecumbent position, fraction of inspired oxygen [F Results: We randomized 35 patients to the conventional extubation group and 34 to the open lung extubation group. We observed a global protocol adherence of 96% (95% confidence interval, 88 to 99), which was not different between groups. Eight PPCs occurred (two in the conventional extubation group vs six in the open lung extubation group). Less postoperative supplemental oxygen and better lung aeration were observed in the open lung extubation group. Conclusions: In this single-centre pilot trial, we observed excellent feasibility. A multicentre pilot trial comparing the effect of an open lung extubation strategy with that of a conventional extubation strategy on the occurrence of PPCs is feasible. Study registration date: ClinicalTrials.gov (NCT04993001); registered 6 August 2021.
MeSH term(s)	Adult ; Humans ; Pilot Projects ; Airway Extubation/adverse effects ; Lung ; Pulmonary Atelectasis/epidemiology ; Pulmonary Atelectasis/etiology ; Pulmonary Atelectasis/prevention & control ; Postoperative Complications/epidemiology ; Postoperative Complications/prevention & control ; Postoperative Complications/etiology ; Anesthesia, General/adverse effects ; Oxygen
Chemical Substances	Oxygen (S88TT14065)
Language	English
Publishing date	2023-07-27
Publishing country	United States
Document type	Randomized Controlled Trial ; Journal Article
ZDB-ID	91002-8
ISSN	1496-8975 ; 0832-610X
ISSN (online)	1496-8975
ISSN	0832-610X
DOI	10.1007/s12630-023-02533-z
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Article ; Online: Response to Assessing Association Between Intraoperative Fluid Balance and the Risk of Acute Kidney Injury After Liver Transplantation: Methodological Issues.

Carrier, François Martin / Girard, Martin / Chassé, Michaël

Transplantation

2020 Volume 104, Issue 10, Page(s) e304–e305

MeSH term(s)	Acute Kidney Injury/diagnosis ; Acute Kidney Injury/epidemiology ; Acute Kidney Injury/etiology ; Cohort Studies ; Humans ; Liver Transplantation/adverse effects ; Water-Electrolyte Balance
Language	English
Publishing date	2020-09-23
Publishing country	United States
Document type	Journal Article ; Comment
ZDB-ID	208424-7
ISSN	1534-6080 ; 0041-1337
ISSN (online)	1534-6080
ISSN	0041-1337
DOI	10.1097/TP.0000000000003313
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