Cell Membrane Transport Properties Research Articles

Determination of activation energy of cross cell membrane transport properties under temperature dynamic: an integrated microfluidic method

Determination of activation energy of cross cell membrane transport properties under temperature dynamic: an integrated microfluidic method

Determination of cell membrane transport properties under temperature dynamic

Determination of cell membrane transport properties under temperature dynamic

129 Effect of different nanoparticles on the SF21 cell membrane transport properties to water and glycerol

Many researchers focus on the cell toxicity of nanoparticles and drug transportation with the nanoparticles. Recently cryobiologists found that the efficiency of cryopreservation of many cells and tissues is good when nanoparticles added to the cryoprotectant solution. However, the mechanism is not understood. Previous study demonstrated that the ice growth is accelerated and devitrification temperatures of cryoprotectant solutions are significantly lowered in these nanoparticles cryoprotectant solutions, and the nanoparticles could change the structure and property of cell membrane. To obtain the optimal protocols for freezing, thawing, and addition/removal of cryoprotectant agent (CPA), the membrane transport properties need to be determined. In our study, we applied the microperfusion system to the measurement of the SF21 cell membrane transport properties to water and glycerol with hydroxyapatite TiO 2 SiO 2 and AlO 3 at 20 °C. We found that the SF21 cell membrane transport properties to water and glycerol is significantly different with nanoparticles. The finding can be used to improve the efficiency of SF21 cell conventional and vitrified cryopreservation, also we should pay attention to the application of the nanoparticles in cryogenics. Source of funding: National Natural Science Foundation of China (No. 51076149). Conflict of interest: None declared. jywong@mail.ustc.edu.cn

MINERAL COMPOSITION OF SOME WALNUT CULTIVARS (JUGLANS REGIA L.) FOR EVALUATION OF IONOME AND IONOMICS UNDER SALT STRESS CONDITION

Walnut (J. regia L.) is a very sensitive plant to abiotic stresses and finding salt tolerant genetic resources is important in this species. Effects of salt stress on seed germination of seven walnut cultivars, 'Serr', 'Lara', 'Pedro', 'Chandler', 'Hartely', 'Vina' and 'Roun de Montignac', were studied. Stress treatments were applied using NaCl solutions ranging from 50 to 250 mM. With the increase in media salt stress, resistant cultivars accumulated K and Ca, especially in their shoots. However, in the semi-tolerant cultivars there was only accumulation of K in the root. It is proposed that different stress tolerant groups have different cell membrane transport properties. Salt stress increased K uptake from root to shoot, which is likely to be a regulation of osmotic adjustment. The differences in Mg accumulation in roots and shoots of all samples were significant at all stress levels and were not dependent on cultivars. Differences in Na accumulation were minimal compared to the other minerals at different stress levels. Na levels in roots were more than in shoots in most cultivars especially in the semi-sensitive and tolerant cultivars. It was proposed that the magnitude of K leakage from tissues after being exposed to osmotic stress might be used as a screen to identify salt tolerant walnut cultivars. There was a low correlation (P≤0.15) between walnut seed traits (seed weight and kernel weight) and growth indices in tolerance to salinity.

The guard cell as a single-cell model towards understanding drought tolerance and abscisic acid action

Stomatal guard cells are functionally specialized epidermal cells usually arranged in pairs surrounding a pore. Changes in ion fluxes, and more specifically osmolytes, within the guard cells drive opening/closing of the pore, allowing gas exchange while limiting water loss through evapo-transpiration. Adjustments of the pore aperture to optimize these conflicting needs are thus centrally important for land plants to survive, especially with the rise in CO(2) associated with global warming and increasing water scarcity this century. The basic biophysical events in modulating membrane transport have been gradually delineated over two decades. Genetics and molecular approaches in recent years have complemented and extended these earlier studies to identify major regulatory nodes. In Arabidopsis, the reference for guard cell genetics, stomatal opening driven by K(+) entry is mainly through KAT1 and KAT2, two voltage-gated K(+) inward-rectifying channels that are activated on hyperpolarization of the plasma membrane principally by the OST2 H(+)-ATPase (proton pump coupled to ATP hydrolysis). By contrast, stomatal closing is caused by K(+) efflux mainly through GORK, the outward-rectifying channel activated by membrane depolarization. The depolarization is most likely initiated by SLAC1, an anion channel distantly related to the dicarboxylate/malic acid transport protein found in fungi and bacteria. Beyond this established framework, there is also burgeoning evidence for the involvement of additional transporters, such as homologues to the multi-drug resistance proteins (or ABC transporters) as intimated by several pharmacological and reverse genetics studies. General inhibitors of protein kinases and protein phosphatases have been shown to profoundly affect guard cell membrane transport properties. Indeed, the first regulatory enzymes underpinning these transport processes revealed genetically were several protein phosphatases of the 2C class and the OST1 kinase, a member of the SnRK2 family. Taken together, these results are providing the first glimpses of an emerging signalling complex critical for modulating the stomatal aperture in response to environmental stimuli.

A microfluidic study of mouse dendritic cell membrane transport properties of water and cryoprotectants

Dendritic cells (DCs) are antigen presenting cells that have been increasingly used in immunotherapy treatment of various diseases and have a great potential for cancer vaccine preparation. Cryopreservation and banking of DCs is critical to facilitate flexible and effective immunotherapy treatment. Therefore, determination of water and cryoprotectant transport properties of DC membrane is indispensable for developing optimal conditions for DCs cryopreservation. Using mouse DCs (mDCs), membrane transport properties were investigated using a microfluidic perfusion system which has recently been developed and fabricated by soft lithography. Cells in the microfluidic system were perfused with various hyperosmotic solutions in the presence or absence of cryoprotectant. The kinetics of cell volume changes under various extracellular conditions were monitored by a video camera and analyzed using a biophysical model to determine water and cryoprotectant transport properties of the cell membrane as well as associated activation energies. It was also shown from this study that the microfluidic perfusion system readily allowed us to: (1) quickly change or manipulate extracellular environment of cells; (2) confine cells in a monolayer channel which prevents imaging ambiguity; and (3) study cell membrane transport kinetics and properties.

Development of a microfluidic device for determination of cell osmotic behavior and membrane transport properties

An understanding of cell osmotic behavior and membrane transport properties is indispensable for cryobiology research and development of cell-type-specific, optimal cryopreservation conditions. A microfluidic perfusion system is developed here to measure the kinetic changes of cell volume under various extracellular conditions, in order to determine cell osmotic behavior and membrane transport properties. The system is fabricated using soft lithography and is comprised of microfluidic channels and a perfusion chamber for trapping cells. During experiments, rat basophilic leukemia (RBL-1 line) cells were injected into the inlet of the device, allowed to flow downstream, and were trapped within a perfusion chamber. The fluid continues to flow to the outlet due to suction produced by a Hamilton Syringe. Two sets of experiments have been performed: the cells were perfused by (1) hypertonic solutions with different concentrations of non-permeating solutes and (2) solutions containing a permeating cryoprotective agent (CPA), dimethylsulfoxide (Me 2SO), plus non-permeating solute (sodium chloride (NaCl)), respectively. From experiment (1), cell osmotically inactive volume ( V b) and the permeability coefficient of water ( L p) for RBL cells are determined to be 41% [ n = 18, correlation coefficient ( r 2) of 0.903] of original/isotonic volume, and 0.32 ± 0.05 μm/min/atm ( n = 8, r 2 > 0.963), respectively, for room temperature (22 °C). From experiment (2), the permeability coefficient of water ( L p) and of Me 2SO ( P s) for RBL cells are 0.38 ± 0.09 μm/min/atm and (0.49 ± 0.13) × 10 −3 cm/min ( n = 5, r 2 > 0.86), respectively. We conclude that this device enables us to: (1) readily monitor the changes of extracellular conditions by perfusing single or a group of cells with prepared media; (2) confine cells (or a cell) within a monolayer chamber, which prevents imaging ambiguity, such as cells overlapping or moving out of the focus plane; (3) study individual cell osmotic response and determine cell membrane transport properties; and (4) reduce labor requirements for its disposability and ensure low manufacturing costs.

Endothelial and epithelial cells: general principles of selective vectorial transport.

Endothelial and epithelial cells are both barriers and bridges between different compartments. This contribution discusses the general principles of paracellular, transcellular, and transmembrane transport with special emphasis on the relation between asymmetry and net movement of small solutes. Asymmetry of cell membrane transport properties is found in both epithelial and endothelial cell layers and provides the basis for transcellular transport. Furthermore, the asymmetry of membrane transporters such as the blood-brain barrier GLUT1 and the renal sodium-glutamate cotransporter is discussed with regard to their different properties at the extra- and intracellular face. These molecular asymmetries play an important role in the efficiency, direction, and regulation of transport processes across the plasma membranes in endothelial and epithelial cells.

Development of a novel microperfusion chamber for determination of cell membrane transport properties

A novel microperfusion chamber was developed to measure kinetic cell volume changes under various extracellular conditions and to quantitatively determine cell membrane transport properties. This device eliminates modeling ambiguities and limitations inherent in the use of the microdiffusion chamber and the micropipette perfusion technique, both of which have been previously validated and are closely related optical technologies using light microscopy and image analysis. The resultant simplicity should prove to be especially valuable for study of the coupled transport of water and permeating solutes through cell membranes. Using the microperfusion chamber, water and dimethylsulfoxide (DMSO) permeability coefficients of mouse oocytes as well as the water permeability coefficient of golden hamster pancreatic islet cells were determined. In these experiments, the individual cells were held in the chamber and perfused at 22 degrees C with hyperosmotic media, with or without DMSO (1.5 M). The cell volume change was videotaped and quantified by image analysis. Based on the experimental data and irreversible thermodynamics theory for the coupled mass transfer across the cell membrane, the water permeability coefficient of the oocytes was determined to be 0.47 micron. min-1. atm-1 in the absence of DMSO and 0.65 microns. min-1. atm-1 in the presence of DMSO. The DMSO permeability coefficient of the oocyte membrane and associated membrane reflection coefficient to DMSO were determined to be 0.23 and 0.85 micron/s, respectively. These values are consistent with those determined using the micropipette perfusion and microdiffusion chamber techniques. The water permeability coefficient of the golden hamster pancreatic islet cells was determined to be 0.27 microns. min-1. atm-1, which agrees well with a value previously determined using an electronic sizing (Coulter counter) technique. The use of the microperfusion chamber has the following major advantages: 1) This method allows the extracellular condition(s) to be readily changed by perfusing a single cell or group of cells with a prepared medium (cells can be reperfused with a different medium to study the response of the same cell to different osmotic conditions). 2) The short mixing time of cells and perfusion medium allows for accurate control of the extracellular osmolality and ensures accuracy of the corresponding mathematical formulation (modeling). 3) This technique has wide applicability in studying the cell osmotic response and in determining cell membrane transport properties.

Ketoconazole activates chloride and fluid secretion by Necturus gallbladder at low pH.

Necturus gallbladder epithelium, normally a reabsorptive epithelium, was stimulated to secrete chloride and fluid by the combined effects of ketoconazole and a reduction in perfusate pH to 7.0. The reversal in the direction of net fluid transport was accompanied by inhibition of the conductance of the apical cell membrane to sodium, potassium, and a striking stimulation of the conductance to chloride. The results are consistent with a previously unidentified mechanism for regulation of the apical cell membrane transport properties of reabsorptive epithelia.

Electrical membrane potential and resistance in photoautotrophic suspension cells of Chenopodium rubrum L.

On photoautotrophically grown, suspension-cultured cells of Chenopodium rubrum L. the electrical potential difference V mand the electrical resistance across plasmalemma and tonoplast have been measured using one or two intracellular micro-electrodes. In a mineral test-medium of 5.8 mM ionic strength V mvalues between 100 and 250 mV, 40% thereof between 170 and 200 mV, and a mean value (±S.E.M.) of 180.6±3.4 mV have been recorded. The average membrane input resistance R mwas 269±36 MΩ, corresponding to an average membrane resistivity r mof 3.0 Ωm(2). V mand r mare sensitive to light, temperature, and addition of cyanide, suggesting the presence of an electrogenic hyperpolarizing ion pump, and are ascribed essentially to the plasmalemma. A hexose-specific saturable electrogenic membrane channel is identified through a decrease of V mand r mupon addition of hexoses. The hexoseconcentration-dependent depolarization ΔV msaturates at 92 mV and returns half-saturating concentrations (apparent k mvalues) of 0.16 mM galactose, 0.28 mM glucose, and 0.48 mM fructose. The magnitude of V mand r mwell agrees with pertinent data from mesophyll cells in situ (where only V mdata are available) and from photoautotrophic lower plant cells. However, V mis markedly higher than reported for heterotrophically grown suspension cells of different higher plants (with which r mdata have not been reported so far). It is concluded from the present study and a companion paper on water transport (Büchner et al., Planta, in press) that photoautotrophically grown Chenopodium suspension cells closely resemble mesophyll cells as to cell membrane transport properties.