Cellular Traction Forces and Locations of Adhesion Site Regulate Cell Functions

The plasma membranes of most animal cells contain transport proteins which function to provide passageways for the transported species across essentially impermeable lipid bilayers. The channel is a passive transport system which allows the movement of ions and low molecular weight molecules along their concentration gradients. The pump is an active transport system and can translocate cations against their natural concentration gradients. The actions and interplay of these two kinds of transport proteins control crucial cell functions such as active transport, excitability and cell communication. In this paper, we will describe and compare several features of the molecular organization of pumps and channels. As an example of an active transport system, we will discuss the structure of the sodium and potassium ion-activated triphosphatase [(Na+ +K+)-ATPase] and as an example of a passive transport system, the communicating channel of gap junctions and lens junctions.

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Multimode light microscopy and fluorescence-based reagents as tools for the study of chemical and molecular dynamics of living cells and tissues

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122496 ◽

1992 ◽

Vol 50 (1) ◽

pp. 418-419

Author(s):

D. L. Taylor

Keyword(s):

Living Cells ◽

Cellular Level ◽

Molecular Techniques ◽

Cellular Functions ◽

Macromolecular Assemblies ◽

Cell Functions ◽

Molecular Events ◽

Yield Information ◽

Full Knowledge ◽

Structural Methods

Cells function through the complex temporal and spatial interplay of ions, metabolites, macromolecules and macromolecular assemblies. Biochemical approaches allow the investigator to define the components and the solution chemical reactions that might be involved in cellular functions. Static structural methods can yield information concerning the 2- and 3-D organization of known and unknown cellular constituents. Genetic and molecular techniques are powerful approaches that can alter specific functions through the manipulation of gene products and thus identify necessary components and sequences of molecular events. However, full knowledge of the mechanism of particular cell functions will require direct measurement of the interplay of cellular constituents. Therefore, there has been a need to develop methods that can yield chemical and molecular information in time and space in living cells, while allowing the integration of information from biochemical, molecular and genetic approaches at the cellular level.

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The photoreceptor cytoskeleton visualized

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122800 ◽

1992 ◽

Vol 50 (1) ◽

pp. 480-481

Author(s):

Beth Burnside

Keyword(s):

Outer Segment ◽

Pigment Epithelium ◽

Retinal Pigment ◽

Cell Polarization ◽

Synaptic Proteins ◽

Cell Functions ◽

Vertebrate Photoreceptor ◽

Numerous Cell ◽

Turn Over

The vertebrate photoreceptor provides a drammatic example of cell polarization. Specialized to carry out phototransduction at its distal end and to synapse with retinal interneurons at its proximal end, this long slender cell has a uniquely polarized morphology which is reflected in a similarly polarized cytoskeleton. Membranes bearing photopigment are localized in the outer segment, a modified sensory cilium. Sodium pumps which maintain the dark current critical to photosensory transduction are anchored along the inner segment plasma membrane between the outer segment and the nucleus.Proximal to the nucleus is a slender axon terminating in specialized invaginating synapses with other neurons of the retina. Though photoreceptor diameter is only 3-8u, its length from the tip of the outer segment to the synapse may be as great as 200μ. This peculiar linear cell morphology poses special logistical problems and has evoked interesting solutions for numerous cell functions. For example, the outer segment membranes turn over by means of a unique mechanism in which new disks are continuously added at the proximal base of the outer segment, while effete disks are discarded at the tip and phagocytosed by the retinal pigment epithelium. Outer segment proteins are synthesized in the Golgi near the nucleus and must be transported north through the inner segment to their sites of assembly into the outer segment, while synaptic proteins must be transported south through the axon to the synapse.The role of the cytoskeleton in photoreceptor motile processes is being intensely investigated in several laboratories.

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Video-microscopic measurement of cell-substratum traction forces generated by locomoting keratocytes

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100146783 ◽

1993 ◽

Vol 51 ◽

pp. 188-189

Author(s):

Tim Oliver ◽

Michelle Leonard ◽

Juliet Lee ◽

Akira Ishihara ◽

Ken Jacobson

Keyword(s):

Silicone Rubber ◽

Molecular Motors ◽

Video Frame ◽

Traction Forces ◽

Cell Traction Forces ◽

Latex Beads ◽

Cell Traction ◽

Local Cell ◽

Microscopic Measurement ◽

Kinetics Of

We are using video-enhanced light microscopy to investigate the pattern and magnitude of forces that fish keratocytes exert on flexible silicone rubber substrata. Our goal is a clearer understanding of the way molecular motors acting through the cytoskeleton co-ordinate their efforts into locomotion at cell velocities up to 1 μm/sec. Cell traction forces were previously observed as wrinkles(Fig.l) in strong silicone rubber films by Harris.(l) These forces are now measureable by two independant means.In the first of these assays, weakly crosslinked films are made, into which latex beads have been embedded.(Fig.2) These films report local cell-mediated traction forces as bead displacements in the plane of the film(Fig.3), which recover when the applied force is released. Calibrated flexible glass microneedles are then used to reproduce the translation of individual beads. We estimate the force required to distort these films to be 0.5 mdyne/μm of bead movement. Video-frame analysis of bead trajectories is providing data on the relative localisation, dissipation and kinetics of traction forces.

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The hepatic acute phase response controls inflammation during sepsis by promoting myeloid suppressor cell functions

Zeitschrift für Gastroenterologie ◽

10.1055/s-0029-1191949 ◽

2009 ◽

Vol 47 (01) ◽

Author(s):

LE Sander ◽

S Dutton-Sackett ◽

C Trautwein

Keyword(s):

Acute Phase ◽

Acute Phase Response ◽

Suppressor Cell ◽

Phase Response ◽

Myeloid Suppressor Cell ◽

Cell Functions

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Defibrotide Inhibits Platelet Activation by Cathepsin G Released From Stimulated Polymorphonuclear Leukocytes

Thrombosis and Haemostasis ◽

10.1055/s-0038-1648519 ◽

1992 ◽

Vol 67 (06) ◽

pp. 660-664 ◽

Cited By ~ 17

Author(s):

Virgilio Evangelista ◽

Paola Piccardoni ◽

Giovanni de Gaetano ◽

Chiara Cerletti

Keyword(s):

Platelet Activation ◽

Polymorphonuclear Leukocytes ◽

Direct Interaction ◽

Cathepsin G ◽

In Vivo Test ◽

Cell Functions ◽

Test Models ◽

Antithrombotic Effects

SummaryDefibrotide is a polydeoxyribonucleotide with antithrombotic effects in experimental animal models. Most of the actions of this drug have been observed in in vivo test models but no effects have been reported in in vitro systems. In this paper we demonstrate that defibrotide interferes with polymorphonuclear leukocyte-induced human platelet activation in vitro. This effect was not related to any direct interaction with polymorphonuclear leukocytes or platelets, but was due to the inhibition of cathepsin G, the main biochemical mediator of this cell-cell cooperation. Since cathepsin G not only induces platelet activation but also affects some endothelial cell functions, the anticathepsin G activity of defibrotide could help to explain the antithrombotic effect of this drug.

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