scholarly journals Myosin II and Arp2/3 crosstalk governs intracellular hydraulic pressure and lamellipodia formation

2021 ◽  
pp. mbc.E20-04-0227
Author(s):  
Shivani Patel ◽  
Donna McKeon ◽  
Kimheak Sao ◽  
Changsong Yang ◽  
Nicole M. Naranjo ◽  
...  
Keyword(s):  
High Pressure ◽  
Human Fibroblasts ◽  
Myosin Ii ◽  
Physical Structure ◽  
Hydraulic Pressure ◽  
Rhoa Activity ◽  
Water Influx ◽  
Actomyosin Contractility ◽  
Intracellular Pressure ◽  
Lamellipodia Formation

Human fibroblasts can switch between lamellipodia-dependent and -independent migration mechanisms on 2D surfaces and in 3D matrices. RhoA GTPase activity governs the switch from low-pressure lamellipodia to high-pressure lobopodia in response to the physical structure of the 3D matrix. Inhibiting actomyosin contractility in these cells reduces intracellular pressure and reverts lobopodia to lamellipodial protrusions via an unknown mechanism. To test the hypothesis that high pressure physically prevents lamellipodia formation, we manipulated pressure by activating RhoA or changing the osmolarity of the extracellular environment and imaged cell protrusions. We find RhoA activity inhibits Rac1-mediated lamellipodia formation through two distinct pathways. First, RhoA boosts intracellular pressure by increasing actomyosin contractility and water influx but acts upstream of Rac1 to inhibit lamellipodia formation. Increasing osmotic pressure revealed a second RhoA pathway which acts through non-muscle myosin II (NMII) to disrupt lamellipodia downstream of Rac1 and elevate pressure. Interestingly, Arp2/3 inhibition triggered a NMII-dependent increase in intracellular pressure, along with lamellipodia disruption. Together, these results suggest that actomyosin contractility and water influx are coordinated to increase intracellular pressure, and RhoA signaling can inhibit lamellipodia formation via two distinct pathways in high-pressure cells. [Media: see text] [Media: see text] [Media: see text]

Power Density Performance Improvements for High Pressure Ripple Energy Harvesting

2013 ◽  
Author(s):  
Nalin Verma ◽  
Kenneth A. Cunefare ◽  
Ellen Skow ◽  
Alper Erturk
Keyword(s):  
High Pressure ◽  
Root Mean Square ◽  
Power Output ◽  
Energy Harvester ◽  
Dynamic Pressure ◽  
Hydraulic Pressure ◽  
Pressure Amplitude ◽  
Mean Square ◽  
Pressure Ripple ◽  
Ripple Amplitude

A hydraulic pressure energy harvester (HPEH) device, which utilizes a housing to isolate a piezoelectric stack from the hydraulic fluid via a mechanical interface, generates power by converting the dynamic pressure within the system into electricity. Prior work developed an HPEH device capable of generating 2187 microWatts from an 85 kPa pressure ripple amplitude using a 1387 mm3 stack. A new generation of HPEH produced 157 microWatts at the test conditions of 18 MPa static pressure and 394 kPa root-mean-square pressure amplitude using a 50 mm3 stack, thus increasing the power produced per volume of piezoelectric stack principally due to the higher dynamic pressure input. The stack and housing design implemented on this new prototype device yield a compact, high-pressure hydraulic pressure energy harvester designed to withstand 35 MPa. The device, which is less than a 2.54 cm in length as compared to a 5.3 cm length of a previous HPEH, was statically tested up to 21.9 MPa and dynamically tested up to 19 MPa with 400 kPa root-mean-square dynamic pressure amplitude. An inductor was included in the load circuit in parallel with the stack and the load resistance to increase the power output of the device. A previously developed electromechanical power output model for this device that predicts the power output given the dynamic pressure ripple amplitude is compared to the power results. The power extracted from this device would be sufficient to meet the proposed applications of the device, which is to power sensor nodes in hydraulic systems.

scholarly journals Nonlinear Hydraulic Pressure Response of an Improved Fiber Tip Interferometric High-Pressure Sensor

Sensors ◽  
2020 ◽  
Vol 20 (9) ◽  
pp. 2548
Author(s):  
Wei Huang ◽  
Zhe Zhang ◽  
Jun He ◽  
Bin Du ◽  
Changrui Liao ◽  
...  
Keyword(s):  
High Pressure ◽  
Nonlinear Response ◽  
Arc Discharge ◽  
High Sensitivity ◽  
Measurement Range ◽  
Hydraulic Pressure ◽  
Discharge Process ◽  
Pressure Sensitivity ◽  
Diaphragm Thickness ◽  
Order Of Magnitude

We demonstrate a silica diaphragm-based fiber tip Fabry–Perot interferometer (FPI) for high-pressure (40 MPa) sensing. By using a fiber tip polishing technique, the thickness of the silica diaphragm could be precisely controlled and the pressure sensitivity of the fabricated FPI sensor was enhanced significantly by reducing the diaphragm thickness; however, the relationship between the pressure sensitivity and diaphragm thickness is not linear. A high sensitivity of −1.436 nm/MPa and a linearity of 0.99124 in hydraulic pressure range of 0 to 40 MPa were demonstrated for a sensor with a diaphragm thickness of 4.63 μm. The achieved sensitivity was about one order of magnitude higher than the previous results reported on similar fiber tip FPI sensors in the same pressure measurement range. Sensors with a thinner silica diaphragm (i.e., 4.01 and 2.09 μm) rendered further increased hydraulic pressure sensitivity, but yield a significant nonlinear response. Two geometric models and a finite element method (FEM) were carried out to explain the nonlinear response. The simulation results indicated the formation of cambered internal silica surface during the arc discharge process in the fiber tip FPI sensor fabrication.

Design and Modeling of Hydraulic Pressure Energy Harvesters for Low Dynamic Pressure Environments

2014 ◽  
Author(s):  
Ellen Skow ◽  
Kenneth Cunefare ◽  
Alper Erturk
Keyword(s):  
High Pressure ◽  
Piezoelectric Material ◽  
Load Transfer ◽  
Dynamic Pressure ◽  
Distribution Networks ◽  
Sensor Nodes ◽  
Hydraulic Pressure ◽  
Cross Sectional ◽  
Energy Harvesters ◽  
Pressure Ripple

Hydraulic Pressure Energy Harvesters (HPEHs) use the direct piezoelectric effect to extract electrical power from the dynamic pressure ripple present in hydraulic systems. As with other energy harvesters, an HPEH is intended to be an enabling technology for powering sensor nodes. To date, HPEH devices have been developed for high-pressure, high-dynamic pressure ripple systems. High-pressure applications are common in industrial hydraulics, where static pressures may be up to 35 MPa. Other fluid systems, such as cross-country pipelines as well as water distribution networks operate at much lower pressures, e.g., from around 1 to 4 MPa, with proportionally lower dynamic pressures. Single-crystal piezoelectric materials are incorporated into the HPEH design, along with means to increase the load transfer into the piezoelectric material as well as increased output harvester circuits, so as to increase the power output of these devices. The load transfer from the pressurized fluid into the piezoelectric material is through an interface, where the interface area may be designed such that the area exposed to the fluid is greater than the cross-sectional area of the piezoelectric, yielding higher stress in the material than the pressure in the fluid. Furthermore, given the relatively large capacitance of the piezoelectric elements used in HPEH devices, inductive-tuned resonant harvester circuits implemented with passive elements are feasible. HPEH devices integrating these features are shown to produce viable power outputs from low dynamic pressure systems.

High Pressure and Flow Rate Measurements on Peroxide Dosing Pumps Under Laboratory and Site Conditions

2006 ◽  
Author(s):  
Franz H. Trieb ◽  
Reinhard Karl ◽  
Rene Moderer
Keyword(s):  
High Pressure ◽  
Flow Rate ◽  
Research Work ◽  
Maximum Pressure ◽  
Hydraulic Pressure ◽  
Site Conditions ◽  
High Pressure Cylinder ◽  
Injection Pump ◽  
Pressure Cylinder ◽  
High Pressure Level

The performance and reliability of peroxide dosing pumps are essential for every LDPE plant. The paper presents the results of measurement at an initiator injection pump under laboratory and site conditions. The recording was done with a flow meter and a high pressure transducer, both suitable for a maximum pressure of 400 MPa. It compares the results of hydraulic pressure inside the actuating cylinder at the intensifier with high pressure level and flow rate on the discharge connection of the pump. Direct measurement inside the high pressure cylinder and the possibilities to influence the fluctuations with a servo valve system round out the research work.

scholarly journals Confinement hinders motility by inducing RhoA-mediated nuclear influx, volume expansion, and blebbing

2019 ◽  
Vol 218 (12) ◽  
pp. 4093-4111 ◽  
Author(s):  
Panagiotis Mistriotis ◽  
Emily O. Wisniewski ◽  
Kaustav Bera ◽  
Jeremy Keys ◽  
Yizeng Li ◽  
...  
Keyword(s):  
Nuclear Envelope ◽  
Cell Motility ◽  
Volume Expansion ◽  
Myosin Ii ◽  
Nuclear Volume ◽  
Linc Complex ◽  
Actomyosin Contractility ◽  
Dependent Pathway ◽  
Passive Influx

Cells migrate in vivo through complex confining microenvironments, which induce significant nuclear deformation that may lead to nuclear blebbing and nuclear envelope rupture. While actomyosin contractility has been implicated in regulating nuclear envelope integrity, the exact mechanism remains unknown. Here, we argue that confinement-induced activation of RhoA/myosin-II contractility, coupled with LINC complex-dependent nuclear anchoring at the cell posterior, locally increases cytoplasmic pressure and promotes passive influx of cytoplasmic constituents into the nucleus without altering nuclear efflux. Elevated nuclear influx is accompanied by nuclear volume expansion, blebbing, and rupture, ultimately resulting in reduced cell motility. Moreover, inhibition of nuclear efflux is sufficient to increase nuclear volume and blebbing on two-dimensional surfaces, and acts synergistically with RhoA/myosin-II contractility to further augment blebbing in confinement. Cumulatively, confinement regulates nuclear size, nuclear integrity, and cell motility by perturbing nuclear flux homeostasis via a RhoA-dependent pathway.

scholarly journals Disrupted filamin A/αIIbβ3 interaction induces macrothrombocytopenia by increasing RhoA activity

Blood ◽  
2019 ◽  
Vol 133 (16) ◽  
pp. 1778-1788 ◽  
Author(s):  
Alessandro Donada ◽  
Nathalie Balayn ◽  
Dominika Sliwa ◽  
Larissa Lordier ◽  
Valentina Ceglia ◽  
...  
Keyword(s):  
Cell Model ◽  
Filamin A ◽  
Rhoa Activity ◽  
Cellular Processes ◽  
Rhoa Activation ◽  
Actomyosin Contractility ◽  
Stem Cell Model ◽  
Proplatelet Formation ◽  
Von Willebrand ◽  
Willebrand Factor

Abstract Filamin A (FLNa) links the cell membrane with the cytoskeleton and is central in several cellular processes. Heterozygous mutations in the X-linked FLNA gene are associated with a large spectrum of conditions, including macrothrombocytopenia, called filaminopathies. Using an isogenic pluripotent stem cell model derived from patients, we show that the absence of the FLNa protein in megakaryocytes (MKs) leads to their incomplete maturation, particularly the inability to produce proplatelets. Reduction in proplatelet formation potential is associated with a defect in actomyosin contractility, which results from inappropriate RhoA activation. This dysregulated RhoA activation was observed when MKs were plated on fibrinogen but not on other matrices (fibronectin, vitronectin, collagen 1, and von Willebrand factor), strongly suggesting a role for FLNa/αIIbβ3 interaction in the downregulation of RhoA activity. This was confirmed by experiments based on the overexpression of FLNa mutants deleted in the αIIbβ3-binding domain and the RhoA-interacting domain, respectively. Finally, pharmacological inhibition of the RhoA-associated kinase ROCK1/2 restored a normal phenotype and proplatelet formation. Overall, this work suggests a new etiology for macrothrombocytopenia, in which increased RhoA activity is associated with disrupted FLNa/αIIbβ3 interaction.

scholarly journals Novel Functions of Ect2 in Polar Lamellipodia Formation and Polarity Maintenance during “Contractile Ring-Independent” Cytokinesis in Adherent Cells

2008 ◽  
Vol 19 (1) ◽  
pp. 8-16 ◽  
Author(s):  
Masamitsu Kanada ◽  
Akira Nagasaki ◽  
Taro Q.P. Uyeda
Keyword(s):  
Mammalian Cells ◽  
Polar Regions ◽  
Nucleotide Exchange ◽  
Contractile Ring ◽  
Rhoa Activity ◽  
Rhoa Activation ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Ht1080 Cells ◽  
Lamellipodia Formation

Some mammalian cells are able to divide via both the classic contractile ring-dependent method (cytokinesis A) and a contractile ring-independent, adhesion-dependent method (cytokinesis B). Cytokinesis A is triggered by RhoA, which, in HeLa cells, is activated by the guanine nucleotide-exchange factor Ect2 localized at the central spindle and equatorial cortex. Here, we show that in HT1080 cells undergoing cytokinesis A, Ect2 does not localize in the equatorial cortex, though RhoA accumulates there. Moreover, Ect2 depletion resulted in only modest multinucleation of HT1080 cells, enabling us to establish cell lines in which Ect2 was constitutively depleted. Thus, RhoA is activated via an Ect2-independent pathway during cytokinesis A in HT1080 cells. During cytokinesis B, Ect2-depleted cells showed narrower accumulation of RhoA at the equatorial cortex, accompanied by compromised pole-to-equator polarity, formation of ectopic lamellipodia in regions where RhoA normally would be distributed, and delayed formation of polar lamellipodia. Furthermore, C3 exoenzyme inhibited equatorial RhoA activation and polar lamellipodia formation. Conversely, expression of dominant active Ect2 in interphase HT1080 cells enhanced RhoA activity and suppressed lamellipodia formation. These results suggest that equatorial Ect2 locally suppresses lamellipodia formation via RhoA activation, which indirectly contributes to restricting lamellipodia formation to polar regions during cytokinesis B.

A Numerical Study of High Pressure Flow Through a Hydraulic Pressure Relief Valve Considering Pressure and Temperature Dependent Viscosity, Bulk Modulus and Density

2016 ◽  
Author(s):  
Sven Osterland ◽  
Jürgen Weber
Keyword(s):  
High Pressure ◽  
Bulk Modulus ◽  
Hydraulic Pressure ◽  
Temperature Dependent ◽  
Relief Valve ◽  
Temperature Dependent Viscosity ◽  
Pressure Region ◽  
Flow Through ◽  
The Mean ◽  
Dependent Viscosity

This paper investigates the flow through a hydraulic pressure relief valve at high levels of operating pressure up to 700 bar (10000 Psi). Following the flow path from the cold high pressure region before the metering edge to the warm low pressure region behind, the mean viscosity decreases by a factor of 16, the mean bulk modulus decreases by a factor of 2 and the mean density decreases by 6 %. Based on this preliminary considerations, a turbulent single phase flow considering pressure and temperature dependent viscosity, bulk modulus and density is modelled and steady state as well as transient calculations are performed. The results of this study show that a pressure and temperature dependent viscosity reduces the pressure drop and the spool force by 10 % compared to a simulation with constant fluid parameters. Moreover, it is shown that compressible flow modelling has negligible influence on pressure drop and spool force — nevertheless, it is required to describe the temperature correctly. Due to the effect of volumetric work an incompressible model approach predicts the mean temperature rise 20 % too high. Finally, it was found that the temperature on the spool exceeds 400 °C. Afterwards, this fact is experimentally validated obtaining tempering colors in high pressure tests.

scholarly journals PDZRhoGEF and myosin II localize RhoA activity to the back of polarizing neutrophil-like cells

2007 ◽  
Vol 179 (6) ◽  
pp. 1141-1148 ◽  
Author(s):  
Kit Wong ◽  
Alexandra Van Keymeulen ◽  
Henry R. Bourne
Keyword(s):  
Rho Gtpase ◽  
Myosin Ii ◽  
Nucleotide Exchange ◽  
Dependent Protein Kinase ◽  
Rhoa Activity ◽  
Guanine Nucleotide Exchange ◽  
Nucleotide Exchange Factor ◽  
Long Tails ◽  
Dependent Protein ◽  
Atpase Inhibition

Chemoattractants such as formyl-Met-Leu-Phe (fMLP) induce neutrophils to polarize by triggering divergent pathways that promote formation of a protrusive front and contracting back and sides. RhoA, a Rho GTPase, stimulates assembly of actomyosin contractile complexes at the sides and back. We show here, in differentiated HL60 cells, that PDZRhoGEF (PRG), a guanine nucleotide exchange factor (GEF) for RhoA, mediates RhoA-dependent responses and determines their spatial distribution. As with RNAi knock-down of PRG, a GEF-deleted PRG mutant blocks fMLP-dependent RhoA activation and causes neutrophils to exhibit multiple fronts and long tails. Similarly, inhibition of RhoA, a Rho-dependent protein kinase (ROCK), or myosin II produces the same morphologies. PRG inhibition reduces or mislocalizes monophosphorylated myosin light chains in fMLP-stimulated cells, and myosin II ATPase inhibition reciprocally disrupts normal localization of PRG. We propose a cooperative reinforcing mechanism at the back of cells, in which PRG, RhoA, ROCK, myosin II, and actomyosin spatially cooperate to consolidate attractant-induced contractility and ensure robust cell polarity.

Development of Test System for Subsea Tree Equipment

2013 ◽  
Vol 440 ◽  
pp. 222-227
Author(s):  
Bao Ping Cai ◽  
Yong Hong Liu ◽  
Yan Ting Zhang ◽  
Jiang Tao Ma ◽  
Yun Wei Zhang ◽  
...  
Keyword(s):  
High Pressure ◽  
Test System ◽  
Acceptance Testing ◽  
Hydraulic Pressure ◽  
Hydraulic Pump ◽  
Test Procedures ◽  
Hydraulic Power ◽  
Hydraulic Unit ◽  
Pressure Cycling ◽  
Function Testing

A test system for subsea tree equipment is developed for tree function testing after repair. The test system mainly consists of hydraulic unit and electric unit. The hydraulic unit is developed by revamping an old hydraulic power unit, which consist of six components, including reservoir, flush/fill pump circuit, high pressure hydraulic pump circuits, accumulator group, hydraulic supply circuits and fluid return circuit. The electric unit for subsea tree is developed by using NI Compact DAQ system, In order to control the hydraulic unit and acquire the pressure signals easily. The test procedures for flowloops, valve, and hydrostatic hydraulic pressure cycling are proposed based on the factory acceptance testing of subsea tree. A test for a repaired subsea tree is performed by using the developed test system. The results show that the repaired subsea tree is good enough after repair, and verify that the developed test system works well.

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