Relationships between the actin cytoskeleton and cell volume regulation

Abstract

The actin cytoskeleton mediates a variety of essential biological functions in cells, including division, shape changes, and movement. A number of studies have suggested that the abundant submembranous actin cytoskeleton present in the cortex of many cell types is involved in the regulation of cell volume. This relationship is supported by numerous works which document the changes in the structural organization of the actin cytoskeleton which accompany cell volume changes and the F‐actin‐dependence of the regulatory volume responses. In addition, other studies demonstrate structural and functional relationships between the actin cytoskeleton and the membrane transporters known to be involved in cell volume homeostasis. This review provides a summary of the current level of knowledge in this area and discusses the mechanisms which may underlie the linkage between the actin cytoskeleton and cell volume regulation. Microsc. Res. Tech. 47:155–162, 1999. © 1999 Wiley‐Liss, Inc.

High-frequency ultrasound for monitoring changes in liver tissue during preservation

“…Previous studies have shown that high-frequency imaging and spectral analysis techniques may assess changes in cell structure following oncosis, apoptosis and cell mechanical structure manipulation like cell shrinking and swelling induced by osmotic stress in hypertonic/ hypotonic solutions (Czarnota et al 1997, 1999, Kolios et al 2002. This paper demonstrates that liver structural changes during preservation period are detectable using high-frequency ultrasound integrated backscatter.…”

“…Which anatomical components in liver tissue are responsible for ultrasonic scattering is an unresolved issue. Some investigators suggest that the cell nucleus is a strong source of ultrasonic scattering (Czarnota et al 1997, 1999, Kolios et al 2002 whereas others propose whole hepatic cells (Fei and Shung 1985).…”

“…If the same type of cells were left to die at room temperature by the withdrawal of nutrients for at least 5 h, an increase in HFU integrated backscatter by 6 dBr would be measured concomitantly with cell swelling and cytoplasmic vacuolization, features of oncotic cell death (commonly referred to as necrosis). With HFU from 20 to 60 MHz individual cells cannot be resolved, however, changes in the intensity of integrated backscatter from cell ensembles can be observed, as well as changes from tissue undergoing structural damage (Czarnota et al 1997, 1999, Kolios et al 2002. Therefore, HFU may constitute a potential technique to assess organ injury before the transplantation procedure, since tissue damage that cannot be easily assessed with conventional procedures may occur following preservation.…”

Regulation of Sodium Channel Activity by Capping of Actin Filaments

“…A large number of studies with localization and drugbased disruption methods have suggested a close relationship between structural organization of actin cytoskeleton and alterations in cell volume (Henson, 1999) mediated by activation of ion channels (Schwiebert et al, 1994;Levitan et al, 1995;Lang et al, 1998). In some cells, regulatory cell volume increase is accompanied by activation of sodium channels (Lang et al, 1998).…”

“…On the other hand, the linker proteins may play a capping role. The barbed end capping function is reported for radixin (Tsukita et al, 1989), whereas binding of ezrin at the sides of actin filament (Yao et al, 1996) might inhibit disassembly of actin monomers from the filament pointed ends as has been shown for tropomyosin (Broschat, 1990).A large number of studies with localization and drugbased disruption methods have suggested a close relationship between structural organization of actin cytoskeleton and alterations in cell volume (Henson, 1999) mediated by activation of ion channels (Schwiebert et al, 1994;Levitan et al, 1995;Lang et al, 1998). In some cells, regulatory cell volume increase is accompanied by activation of sodium channels (Lang et al, 1998).…”