Regulation der Zellfunktion durch den Hydratationszustand

Liver cell hydration and integrin signaling

Liver cell hydration (cell volume) is dynamic and can change within minutes under the influence of hormones, nutrients, and oxidative stress. Such volume changes were identified as a novel and important modulator of cell function. It provides an early example for the interaction between a physical parameter (cell volume) on the one hand and metabolism, transport, and gene expression on the other. Such events involve mechanotransduction (osmosensing) which triggers signaling cascades towards liver function (osmosignaling). This article reviews our own work on this topic with emphasis on the role of β1 integrins as (osmo-)mechanosensors in the liver, but also on their role in bile acid signaling.

Age-dependent effect of static magnetic field on brain tissue hydration

Age-dependent effect of Static Magnetic Field (SMF) on rats in a condition of active and inactive Na(+)/K(+) pump was studied for comparison of brain tissues hydration state changes and magnetic sensitivity. Influence of 15 min 0, 2 Tesla (T) SMF on brain tissue hydration of three aged groups of male albino rats was studied. Tyrode's physiological solution and 10(-4) M ouabain was used for intraperitoneal injections. For animal immobilization, the liquid nitrogen was used and the definition of tissue water content was performed by tissue drying method. Initial water content in brain tissues of young animals is significantly higher than in those of adult and aged ones. SMF exposure leads to decrease of water content in brain tissues of young animals and increase in brain tissues of adult and aged ones. In case of ouabain-poisoned animals, SMF gives reversal effects on brain tissue's hydration both in young and aged animals, while no significant effect on adults is observed. It is suggested that initial state of tissue hydration could play a crucial role in animal age-dependent magnetic sensitivity and the main reason for this could be age-dependent dysfunction of Na(+)/K(+) pump.

Changes of hydration of rats' tissues after in vivo exposure to 0.2 Tesla steady magnetic field

Hydration and [3H]ouabain uptake by different tissues of adult male rats were measured immediately after exposure to homogenous 0.2 T steady magnetic field. A time-dependent decrease of hydration and adaptation, followed by disadaptation, was detected in brain and liver tissues in most of the rats after 3.5-5 h of exposure. The number of functional active ouabain binding receptors, which correlates with cell volume, was also decreased in brain, liver, and spleen and increased in kidney tissue after half an hour of exposure. It is suggested that cell hydration is a second messenger through which the SMF exerts its influence.

Fourier transform infrared spectroscopy as a probe for the study of the hydration of lipid self-assemblies. I. Methodology and general phenomena

An algorithm for the study of the gradual hydration of phospholipid assemblies by means of Fourier transform infrared (FTIR) spectroscopy is presented. A complete series of diacyl phosphatidylcholines (PCs) including all possible analogues with palmitoyl and oleoyl residues, namely DPPC, DOPC, POPC, and OPPC, was investigated at room temperature. The lipid samples were prepared as cast films probably consisting of aligned multilamellar bilayers. The range of water activities studied in these films was regulated by adsorption via the gas phase corresponding to relative humidities of between 0 and 100%. Analyses of the IR-spectroscopic data have concentrated mainly on determining the amounts of water incorporated by each lipid as well as the hydration-induced response observed for some absorption bands of the different lipids. The water uptake at high relative humidity (RH) increases with the portion of unsaturated acyl chains in the molecular structure of the PCs. Isothermal phase transitions triggered lyotropically have been detected in demonstrating the occurrence of the main transition in POPC and OPPC films at room temperature. Moreover, it appears that both lamellar phases, the gel as well as the liquid-crystalline phase, are not uniform. They seem to comprise an amazingly large span of order/disorder states of the lipid chains generally depending on the degree of hydration. As exemplified by the significant variation in the onset of wavenumber shifts for the PO2- and C=O stretching-vibration modes, obtained as a function of hydration, a sequence of attachment to polar lipid binding sites by water molecules was established for DPPC.