Doppler OCT imaging of cytoplasm shuttle flow in <i>Physarum polycephalum</i>

Bykov, Alexander; Priezzhev, Alexander V.; Lauri, Janne; Myllylä, Risto

doi:10.1002/jbio.200910057

Cited by 23 publications

(21 citation statements)

References 23 publications

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“…Micro-PIV measurements along a line placed perpendicularly to a straight and unbranched vein (of 330 μm internal diameter) demonstrate that the flow profile developed in the strand is indeed parabolic (figure 2), indicating a laminar Poiseuille flow. Such a flow profile has also been reported in earlier studies [22,23]. From the measured data, the Womersley and the Reynolds numbers may be calculated.…”

Section: Laminar Flowsupporting

confidence: 80%

“…External cues may lead to the spreading of phase waves of vein contractions, for instance, as the cell makes judgments about a cue-induced attraction or repulsion [20,21].As the typical diameter of the veins of P. polycephalum is around 10-300 μm, the vein system forms a microfluidic system. In the plasmodia, the flow profile of the protoplasm in the veins of P. polycephalum is always parabolic, indicating laminar flow [22,23]. However, particles suspended in the protoplasm are known to be effectively and rapidly distributed within the cell [24], as demonstrated in studies where radioactive traces were introduced in the plasmodium [25], or either mRNA [26], pigments [27], or fluorescent particles [28,29] were locally injected into a vein of a P. polycephalum network.…”

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confidence: 99%

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Effective mixing due to oscillatory laminar flow in tubular networks of plasmodial slime moulds

Haupt

Hauser

2020

New J. Phys.

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The plasmodium of the unicellular slime mould Physarum polycephalum forms an extended vascular network in which protoplasm is transported through the giant cell due to peristaltic pumping. The flow in the veins is always parabolic and it performs shuttle streaming, i.e., the flow reverses its direction periodically. However, particles suspended in the protoplasm are effectively and rapidly distributed within the cell. To elucidate how an effective mixing can be achieved in such a microfluidic system with Poiseuille flow, we performed micro-particle imaging velocimetry experiments and advected virtual tracers in the determined time-dependent flow fields. Two factors were found to be crucial for effective mixing: (i) flow splitting and flow reversals occurring at junctions of veins and (ii) small delays in the reversals of flows in the veins at a junction. These factors enhance the distribution of fluid volumes and hence promote mixing due to chaotic advection. From the residence time distributions of particles at a junction, it is estimated that about 10% of the volume is effectively redistributed at a junction during one period of the shuttle streaming. We presume that the principles of mixing unravelled in P. polycephalum represent a promising approach to achieve efficient mixing in man-made microfluidic devices. Figure 1. Network of tubular veins in the plasmodium of P. polycephalum strand HU195 × HU200. The cell extends and propagates to the right. The dense apical front (at the right) gives way to a vast network of tubular stands, where protoplasm is transported by peristalsis. Dimensions: 6.14 × 4.60 cm 2 .can be adapted to the situation in P. polycephalum. By contrast to linear veins, in branched hemo-dynamic flow networks, there are feedbacks between the local pressures generated by the contraction of the veins, the flow velocity of protoplasm, and the compliance of the veins (i.e., the increase in their diameter) [11]. This leads to phase shifts between the flows that emanate from (and lead to) a junction of veins.Several models have been put forward to describe the interplay between the cellular mechanics of the vein and the peristaltic flow [8,12,13]. These models all rely on a coupling between the underlying biochemical (driving) system, that is coupled to cell and fluid mechanics. These models have sparked a novel interest in studying the mechanical properties of P. polycephalum [14].The vein network of P. polycephalum forms regular graphs, i.e., graphs with a unique node degree k = 3 [1, 2]. The vein segments have different thicknesses and lengths [1,2] in order to provide for an optimized transport of protoplasm through the cell [15,16]. With respect to transport efficiency, the architecture of these networks is hierarchic and self-similar [16]. Furthermore, the networks are highly adaptive [1,2,15], and an originally dense network may coarsen with time [1,2,[15][16][17][18]. In the absence of any external cue, the contraction of the thicker veins is almost synchronous over the entire network [19], ...

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Section: Laminar Flowsupporting

confidence: 80%

mentioning

confidence: 99%

Effective mixing due to oscillatory laminar flow in tubular networks of plasmodial slime moulds

Haupt

Hauser

2020

New J. Phys.

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“…Alternatively, one can calculate the sol viscosity from velocity profiles measured in Physarum [50]. With this method we obtain a dynamic sol viscosity of around .…”

Section: Methodsmentioning

confidence: 99%

An Active Poroelastic Model for Mechanochemical Patterns in Protoplasmic Droplets of Physarum polycephalum

2014

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Motivated by recent experimental studies, we derive and analyze a two-dimensional model for the contraction patterns observed in protoplasmic droplets of Physarum polycephalum. The model couples a description of an active poroelastic two-phase medium with equations describing the spatiotemporal dynamics of the intracellular free calcium concentration. The poroelastic medium is assumed to consist of an active viscoelastic solid representing the cytoskeleton and a viscous fluid describing the cytosol. The equations for the poroelastic medium are obtained from continuum force balance and include the relevant mechanical fields and an incompressibility condition for the two-phase medium. The reaction-diffusion equations for the calcium dynamics in the protoplasm of Physarum are extended by advective transport due to the flow of the cytosol generated by mechanical stress. Moreover, we assume that the active tension in the solid cytoskeleton is regulated by the calcium concentration in the fluid phase at the same location, which introduces a mechanochemical coupling. A linear stability analysis of the homogeneous state without deformation and cytosolic flows exhibits an oscillatory Turing instability for a large enough mechanochemical coupling strength. Numerical simulations of the model equations reproduce a large variety of wave patterns, including traveling and standing waves, turbulent patterns, rotating spirals and antiphase oscillations in line with experimental observations of contraction patterns in the protoplasmic droplets.

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“…Potential applications in blood monitoring also include measuring hemoglobin 7 and glucose 8 concentrations. The microflows have been extensively studied in complex vessels by Doppler OCT. [9][10][11][12][13] The spatial distribution of RBCs in microchannels has been previously evaluated with OCT. 14,15 Due to an insufficient axial resolution of the used OCT systems, the thickness of a CFL has not been measured previously.…”

Section: Introductionmentioning

confidence: 99%

Quantification of cell-free layer thickness and cell distribution of blood by optical coherence tomography

2016

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Abstract. A high-speed optical coherence tomography (OCT) with 1-μm axial resolution was applied to assess the thickness of a cell-free layer (CFL) and a spatial distribution of red blood cells (RBC) next to the microchannel wall. The experiments were performed in vitro in a plain glass microchannel with a width of 2 mm and height of 0.2 mm. RBCs were suspended in phosphate buffered saline solution at the hematocrit level of 45%. Flow rates of 0.1 to 0.5 ml∕h were used to compensate gravity induced CFL. The results indicate that OCT can be efficiently used for the quantification of CFL thickness and spatial distribution of RBCs in microcirculatory blood flow.

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Doppler OCT imaging of cytoplasm shuttle flow in Physarum polycephalum

Cited by 23 publications

References 23 publications

Effective mixing due to oscillatory laminar flow in tubular networks of plasmodial slime moulds

Effective mixing due to oscillatory laminar flow in tubular networks of plasmodial slime moulds

An Active Poroelastic Model for Mechanochemical Patterns in Protoplasmic Droplets of Physarum polycephalum

Quantification of cell-free layer thickness and cell distribution of blood by optical coherence tomography

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