scholarly journals Limiting lumens: a new role for Cdc42

2008 ◽  
Vol 183 (4) ◽  
pp. 575-577 ◽  
Author(s):  
Terry Lechler
Keyword(s):  
Fluid Transport ◽  
Three Dimensional ◽  
Intestinal Lumen ◽  
Dimensional System ◽  
In Vitro System ◽  
Lumen Formation ◽  
Tissue Organization ◽  
Single Lumen ◽  
Three Dimensional System

The formation of a single lumen is a necessary step in the formation of biological tubes. Different tissues have developed diverse ways to form their lumens. In this issue, Jaffe et al. (Jaffe, A.B., N. Kaji, J. Durgan, and A. Hall. 2008. J. Cell Biol. 183:625–633) report the development of an in vitro system for studying lumen formation that is driven by fluid transport, recapitulating intestinal lumen formation. Effective ion and fluid transport requires both cell polarity and proper tissue organization. Surprisingly, polarization of cells in this three-dimensional system does not require Cdc42. Instead, Cdc42 prevents formation of multiple lumens by orienting cell divisions and directing apical membrane biogenesis.

Fluid transport across cultured rat alveolar epithelial cells: a novel in vitro system

2004 ◽  
Vol 287 (1) ◽  
pp. L104-L110 ◽  
Author(s):  
Xiaohui Fang ◽  
Yuanlin Song ◽  
Rachel Zemans ◽  
Jan Hirsch ◽  
Michael A. Matthay
Keyword(s):  
Epithelial Cells ◽  
Fluid Transport ◽  
Alveolar Epithelial Cells ◽  
Lung Epithelial Cells ◽  
Morphological Evidence ◽  
Alveolar Type ◽  
Type Ii ◽  
In Vitro System ◽  
Alveolar Epithelial

Previous studies have used fluid-instilled lungs to measure net alveolar fluid transport in intact animal and human lungs. However, intact lung studies have two limitations: the contribution of different distal lung epithelial cells cannot be studied separately, and the surface area for fluid absorption can only be approximated. Therefore, we developed a method to measure net vectorial fluid transport in cultured rat alveolar type II cells using an air-liquid interface. The cells were seeded on 0.4-μm microporous inserts in a Transwell system. At 96 h, the transmembrane electrical resistance reached a peak level (1,530 ± 115 Ω·cm2) with morphological evidence of tight junctions. We measured net fluid transport by placing 150 μl of culture medium containing 0.5 μCi of 131I-albumin on the apical side of the polarized cells. Protein permeability across the cell monolayer, as measured by labeled albumin, was 1.17 ± 0.34% over 24 h. The change in concentration of 131I-albumin in the apical fluid was used to determine the net fluid transported across the monolayer over 12 and 24 h. The net basal fluid transport was 0.84 μl·cm−2·h−1. cAMP stimulation with forskolin and IBMX increased fluid transport by 96%. Amiloride inhibited both the basal and stimulated fluid transport. Ouabain inhibited basal fluid transport by 93%. The cultured cells retained alveolar type II-like features based on morphologic studies, including ultrastructural imaging. In conclusion, this novel in vitro system can be used to measure net vectorial fluid transport across cultured, polarized alveolar epithelial cells.

Scaffold topography alters intracellular calcium dynamics in cultured cardiomyocyte networks

2004 ◽  
Vol 287 (3) ◽  
pp. H1276-H1285 ◽  
Author(s):  
Lihong Yin ◽  
Harold Bien ◽  
Emilia Entcheva
Keyword(s):  
Ventricular Myocytes ◽  
Three Dimensional ◽  
Triggered Release ◽  
In Vitro System ◽  
Functional Changes ◽  
Cardiac Electromechanics ◽  
Intracellular Ca ◽  
Intracellular Calcium Dynamics ◽  
Cell Networks

Structural and functional changes ensue in cardiac cell networks when cells are guided by three-dimensional scaffold topography. We report enhanced synchronous pacemaking activity in association with slow diastolic rise in intracellular Ca2+ concentration ([Ca2+]i) in cell networks grown on microgrooved scaffolds. Topography-driven changes in cardiac electromechanics were characterized by the frequency dependence of [Ca2+]i in syncytial structures formed of ventricular myocytes cultured on microgrooved elastic scaffolds (G). Cells were electrically paced at 0.5–5 Hz, and [Ca2+]i was determined using microscale ratiometric (fura 2) fluorescence. Compared with flat (F) controls, the G networks exhibited elevated diastolic [Ca2+]i at higher frequencies, increased systolic [Ca2+]i across the entire frequency range, and steeper restitution of Ca2+ transient half-width ( n = 15 and 7 for G and F, respectively, P < 0.02). Significant differences in the frequency response of force-related parameters were also found, e.g., overall larger total area under the Ca2+ transients and faster adaptation of relaxation time to pacing rate ( P < 0.02). Altered [Ca2+]i dynamics were paralleled by higher occurrence of spontaneous Ca2+ release and increased sarcoplasmic reticulum load ( P < 0.02), indirectly assessed by caffeine-triggered release. Electromechanical instabilities, i.e., Ca2+ and voltage alternans, were more often observed in G samples. Taken together, these findings 1) represent some of the first functional electromechanical data for this in vitro system and 2) demonstrate direct influence of the microstructure on cardiac function and susceptibility to arrhythmias via Ca2+-dependent mechanisms. Overall, our results substantiate the idea of guiding cellular phenotype by cellular microenvironment, e.g., scaffold design in the context of tissue engineering.

Inner-product theory calculations for some rational potentials in a three-dimensional system

1996 ◽  
Vol 74 (1-2) ◽  
pp. 4-9
Author(s):  
M. R. M. Witwit
Keyword(s):  
Energy Levels ◽  
Three Dimensional ◽  
Inner Product ◽  
Dimensional System ◽  
Product Technique ◽  
Special Cases ◽  
Wide Range ◽  
Perturbation Parameters ◽  
Three Dimensional System ◽  
Range Of Values

The energy levels of a three-dimensional system are calculated for the rational potentials,[Formula: see text]using the inner-product technique over a wide range of values of the perturbation parameters (λ, g) and for various eigenstates. The numerical results for some special cases agree with those of previous workers where available.

The influence of mean shear on Alfvén-internal wave propagation

1976 ◽  
Vol 15 (2) ◽  
pp. 197-222
Author(s):  
R. J. Hartman
Keyword(s):  
Three Dimensional ◽  
Dimensional System ◽  
Linear Wave ◽  
Mean Flow ◽  
Wave Processes ◽  
Initial Value ◽  
Initial Wave ◽  
Wave Phenomena ◽  
Three Dimensional System

This paper uses the general solution of the linearized initial-value problem for an unbounded, exponentially-stratified, perfectly-conducting Couette flow in the presence of a uniform magnetic field to study the development of localized wave-type perturbations to the basic flow. The two-dimensional problem is shown to be stable for all hydrodynamic Richardson numbers JH, positive and negative, and wave packets in this flow are shown to approach, asymptotically, a level in the fluid (the ‘isolation level’) which is a smooth, continuous, function of JH that is well defined for JH < 0 as well as JH > 0. This system exhibits a rich complement of wave phenomena and a variety of mechanisms for the transport of mean flow kinetic and potential energy, via linear wave processes, between widely-separated regions of fluid; this in addition to the usual mechanisms for the absorption of the initial wave energy itself. The appropriate three-dimensional system is discussed, and the role of nonlinearities on the development of localized disturbances is considered.

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