scholarly journals Mechanical state, material properties and continuous description of an epithelial tissue

2012 ◽  
Vol 9 (75) ◽  
pp. 2614-2623 ◽  
Author(s):  
Isabelle Bonnet ◽  
Philippe Marcq ◽  
Floris Bosveld ◽  
Luc Fetler ◽  
Yohanns Bellaïche ◽  
...  
Keyword(s):  
Continuous Model ◽  
Epithelial Tissue ◽  
Mechanical State ◽  
Continuous Description ◽  
Time Continuum ◽  
Shaped Domain ◽  
Internal Viscosity ◽  
Shape Changes ◽  
Good Agreement

During development, epithelial tissues undergo extensive morphogenesis based on coordinated changes of cell shape and position over time. Continuum mechanics describes tissue mechanical state and shape changes in terms of strain and stress. It accounts for individual cell properties using only a few spatially averaged material parameters. To determine the mechanical state and parameters in the Drosophila pupa dorsal thorax epithelium, we severed in vivo the adherens junctions around a disc-shaped domain comprising typically a hundred cells. This enabled a direct measurement of the strain along different orientations at once. The amplitude and the anisotropy of the strain increased during development. We also measured the stress-to-viscosity ratio and similarly found an increase in amplitude and anisotropy. The relaxation time was of the order of 10 s. We propose a space–time, continuous model of the relaxation. Good agreement with experimental data validates the description of the epithelial domain as a continuous, linear, visco-elastic material. We discuss the relevant time and length scales. Another material parameter, the ratio of external friction to internal viscosity, is estimated by fitting the initial velocity profile. Together, our results contribute to quantify forces and displacements, and their time evolution, during morphogenesis.

In vitro and in vivo pathologic effects of Vibrio parahaemolyticus on human epithelial cells

1984 ◽  
Vol 30 (3) ◽  
pp. 381-388 ◽  
Author(s):  
B. R. Merrell ◽  
R. I. Walker ◽  
S. W. Joseph
Keyword(s):  
Epithelial Cells ◽  
Epithelial Tissue ◽  
Ileal Mucosa ◽  
Cytotoxic Factor ◽  
Culture Cells ◽  
Vibrio Parahemolyticus ◽  
Buccal Epithelial Cells ◽  
Culture Supernate

The initial interaction and adherence of Vibrio parahemolyticus to epithelial tissue culture cells, human buccal epithelial cells, and the ileal mucosa of mice were studied. Using scanning electron microscopy, adherent bacteria were observed only on degenerating human embryonic intestinal, HeLa, and buccal cells; healthy normal cells were devoid of bacteria. Sheared V. parahaemolyticus, i.e., lacking flagella, did not adhere to either normal or degenerating tissue cells. Neither ultraviolet-inactivated organisms nor cell-free culture supernate affected the epithelial cells. Similar findings were observed on the mucosa of the ileum in mice inoculated with V. parahaemolyticus. It appears that V. parahaemolyticus possesses a cytotoxic factor which alters epithelial cells. This factor appears to be closely associated with viable organisms and may be a functional element in the adherence process of flagellated V. parahaemolyticus to mammalian epithelial cells.

Compartmental modeling of the hepatic transport of taurocholate in the rat in vivo

1989 ◽  
Vol 257 (2) ◽  
pp. G210-G220 ◽  
Author(s):  
X. Deroubaix ◽  
T. Coche ◽  
E. Depiereux ◽  
E. Feytmans
Keyword(s):  
Excretion Rate ◽  
Compartmental Analysis ◽  
Hepatic Transport ◽  
Lumped Model ◽  
Perfusion Model ◽  
Direct Measurements ◽  
Distribution In Blood ◽  
Variability Model ◽  
Good Agreement

Compartmental analysis was used to study the hepatobiliary transport of taurocholate (TC) in the rat in vivo. The available data are the following: [14C]TC kinetics in blood and bile, weighting factors associated with these data and computed from a theoretical variability model, and TC excretion rate in bile. The lumped model that best fits the data contains five compartments: three compartments for TC distribution in blood and two compartments for the liver. It includes a compartmental representation of the laminar flow of bile in the collecting catheter. This model overestimates TC concentration in blood. A perfusion model that includes a compartment representing explicitly the sinusoidal TC concentration gradient was developed. TC concentration in blood estimated by this model is in good agreement with direct measurements, showing that the perfused model has a better descriptive capacity than the lumped model. The amounts of TC estimated in the two hepatic compartments are similar to values previously published.

Comparison of Experimental and Numerical Simulations of Flow Within an Arterio-Venous Graft

2000 ◽  
Author(s):  
Paul F. Fischer ◽  
Seung Lee ◽  
Francis Loth ◽  
Hisham S. Bassiouny ◽  
Nurullah Arslan
Keyword(s):  
Flow Field ◽  
Steady Flow ◽  
Laser Doppler Anemometry ◽  
Transition To Turbulence ◽  
Flow Conditions ◽  
Venous Graft ◽  
Venous Anastomosis ◽  
Av Graft ◽  
Good Agreement

Abstract This was a study to compare computational and experimental results of flow field inside the venous anastomosis of an arteriovenous (AV) graft. Laser Doppler anemometry (LDA) measurements were conducted inside an upscaled end-to-side graft model under steady flow conditions at Reynolds number 1820 which is representative of the in vivo flow conditions inside a human AV graft. The distribution of the velocity and turbulence intensity was measured at several locations in the plane of the bifurcation. This flow field was simulated using computation fluid dynamics (CFD) and shown to be in good agreement. Under steady flow conditions, the flow field demonstrated an unsteady character (transition to turbulence).

scholarly journals Group I PAKs function downstream of Rac to promote podosome invasion during myoblast fusion in vivo

2012 ◽  
Vol 199 (1) ◽  
pp. 169-185 ◽  
Author(s):  
Rui Duan ◽  
Peng Jin ◽  
Fengbao Luo ◽  
Guofeng Zhang ◽  
Nathan Anderson ◽  
...  
Keyword(s):  
Cell Shape ◽  
Myoblast Fusion ◽  
Small Gtpase ◽  
Fusion Pore ◽  
Cellular Processes ◽  
Filament Assembly ◽  
Group I ◽  
Redundant Functions ◽  
Shape Changes

The p21-activated kinases (PAKs) play essential roles in diverse cellular processes and are required for cell proliferation, apoptosis, polarity establishment, migration, and cell shape changes. Here, we have identified a novel function for the group I PAKs in cell–cell fusion. We show that the two Drosophila group I PAKs, DPak3 and DPak1, have partially redundant functions in myoblast fusion in vivo, with DPak3 playing a major role. DPak3 is enriched at the site of fusion colocalizing with the F-actin focus within a podosome-like structure (PLS), and promotes actin filament assembly during PLS invasion. Although the small GTPase Rac is involved in DPak3 activation and recruitment to the PLS, the kinase activity of DPak3 is required for effective PLS invasion. We propose a model whereby group I PAKs act downstream of Rac to organize the actin filaments within the PLS into a dense focus, which in turn promotes PLS invasion and fusion pore initiation during myoblast fusion.

scholarly journals Myosin-dependent remodeling of adherens junctions protects junctions from Snail-dependent disassembly

2016 ◽  
Vol 212 (2) ◽  
pp. 219-229 ◽  
Author(s):  
Mo Weng ◽  
Eric Wieschaus
Keyword(s):  
Cell Shape ◽  
Adherens Junctions ◽  
Myosin Ii ◽  
Cell Junctions ◽  
Snail Expression ◽  
Quantitative Image ◽  
Early Expression ◽  
Temporally Correlated ◽  
Shape Changes

Although Snail is essential for disassembly of adherens junctions during epithelial–mesenchymal transitions (EMTs), loss of adherens junctions in Drosophila melanogaster gastrula is delayed until mesoderm is internalized, despite the early expression of Snail in that primordium. By combining live imaging and quantitative image analysis, we track the behavior of E-cadherin–rich junction clusters, demonstrating that in the early stages of gastrulation most subapical clusters in mesoderm not only persist, but move apically and enhance in density and total intensity. All three phenomena depend on myosin II and are temporally correlated with the pulses of actomyosin accumulation that drive initial cell shape changes during gastrulation. When contractile myosin is absent, the normal Snail expression in mesoderm, or ectopic Snail expression in ectoderm, is sufficient to drive early disassembly of junctions. In both cases, junctional disassembly can be blocked by simultaneous induction of myosin contractility. Our findings provide in vivo evidence for mechanosensitivity of cell–cell junctions and imply that myosin-mediated tension can prevent Snail-driven EMT.

In vivo reprogramming of wound-resident cells generates skin epithelial tissue

Nature ◽  
2018 ◽  
Vol 561 (7722) ◽  
pp. 243-247 ◽  
Author(s):  
Masakazu Kurita ◽  
Toshikazu Araoka ◽  
Tomoaki Hishida ◽  
David D. O’Keefe ◽  
Yuta Takahashi ◽  
...  
Keyword(s):  
Epithelial Tissue

scholarly journals In Vitro Pharmacodynamic Parameters of Sordarin Derivatives in Comparison with Those of Marketed Compounds against Pneumocystis carinii Isolated from Rats

2000 ◽  
Vol 44 (5) ◽  
pp. 1284-1290 ◽  
Author(s):  
Pablo Aviles ◽  
El-Moukhtar Aliouat ◽  
Antonio Martinez ◽  
Eduardo Dei-Cas ◽  
Esperanza Herreros ◽  
...  
Keyword(s):  
Pneumocystis Carinii ◽  
Maximum Effect ◽  
Drug Concentrations ◽  
Number Of Microorganisms ◽  
Immunosuppressed Patients ◽  
The Hill ◽  
Drug Free ◽  
Good Agreement

ABSTRACT Pneumocystis carinii pneumonia remains one of the most serious complications of immunosuppressed patients. In this study, the in vitro pharmacodynamic parameters of four sordarin derivatives (GM 191519, GM 237354, GM 193663, and GM 219771) have been evaluated by a new quantitative approach and compared with the commercially available drugs pentamidine, atovaquone, and trimethoprim-sulfamethoxazole (TMP-SMX). In vitro activities and in vivo therapeutic efficacies of sordarin derivatives against P. carinii were also evaluated. In vitro activity was determined by the broth microdilution technique, comparing the total number of microorganisms in treated and drug-free cultures by using Giemsa staining. The in vitro maximum effect (E max), the drug concentrations to reach 50% of E max(EC50), and the slope of the dose-response curve were then estimated by the Hill equation (E max sigmoid model). Sordarin derivatives were the most potent agents againstP. carinii, with EC50s of 0.00025, 0.0007, 0.0043, and 0.025 μg/ml for GM 191519, GM 237354, GM 193663, and GM 219771, respectively. The EC50s of pentamidine, atovaquone, and TMP-SMX were 0.025, 0.16, and 26.7/133.5 μg/ml, respectively. The results obtained with this approach showed GM 237354 and GM 191519 to be approximately 35- and 100-fold more active in vitro than pentamidine, the most active marketed compound. All sordarin derivatives tested were at least 5,000-fold more active in vitro than TMP-SMX. The three sordarin derivatives tested in vivo—GM 191519, GM 237354, and GM 219771—showed a marked therapeutic efficacy, defined as reduction of cyst forms per gram of lung. GM 191519 was the most potent (daily dose reducing 50% of the P. carinii burden in the lungs [ED50], 0.05 mg/kg/day) followed by GM 237354 and GM 219771 (ED50s, 0.30 and 0.49 mg/kg/day, respectively). Good agreement between in vitro parameters and in vivo outcome was obtained when P. carinii pneumonia in rats was treated with sordarin derivatives.

The role of laminin-5 and its receptors in mammary epithelial cell branching morphogenesis

1997 ◽  
Vol 110 (1) ◽  
pp. 55-63 ◽  
Author(s):  
S. Stahl ◽  
S. Weitzman ◽  
J.C. Jones
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Mammary Epithelial Cells ◽  
Branching Morphogenesis ◽  
Mammary Epithelial ◽  
Breast Epithelial Cell ◽  
Epithelial Tissue ◽  
Laminin 5 ◽  
Normal Mammary Epithelial

In vivo, normal mammary epithelial cells utilize hemidesmosome attachment devices to adhere to stroma. However, analyses of a potential role for hemidesmosomes and their components in mammary epithelial tissue morphogenesis have never been attempted. MCF-10A cells are a spontaneously immortalized line derived from mammary epithelium and possess a number of characteristics of normal mammary epithelial cells including expression of hemidesmosomal associated proteins such as the two bullous pemphigoid antigens, alpha 6 beta 4 integrin and its ligand laminin-5. More importantly, MCF-10A cells readily assemble mature hemidesmosomes when plated onto uncoated substrates. When maintained on matrigel, like their normal breast epithelial cell counterparts, MCF-10A cells undergo a branching morphogenesis and assemble hemidesmosomes at sites of cell-matrigel interaction. Function blocking antibodies specific for human laminin-5 and the alpha subunits of its two known receptors (alpha 3 beta 1 and alpha 6 beta 4 integrin) not only inhibit hemidesmosome assembly by MCF-10A cells but also impede branching morphogenesis induced by matrigel. Our results imply that the hemidesmosome, in particular those subunits comprising its laminin-5/integrin ‘backbone’, play an important role in morphogenetic events. We discuss these results in light of recent evidence that hemidesmosomes are sites involved in signal transduction.

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