scholarly journals Contribution of Aquaporins to Cellular Water Transport Observed by a Microfluidic Cell Volume Sensor

2008 ◽  
Vol 80 (18) ◽  
pp. 6974-6980 ◽  
Author(s):  
Jinseok Heo ◽  
Fanjie Meng ◽  
Susan Z. Hua
Keyword(s):  
Cell Volume ◽  
Water Transport ◽  
Volume Sensor ◽  
Cellular Water ◽  
Cellular Water Transport

scholarly journals Role of intracellular poroelasticity on freezing-induced deformation of cells in engineered tissues

2016 ◽  
Vol 13 (123) ◽  
pp. 20160480
Author(s):  
Soham Ghosh ◽  
Altug Ozcelikkale ◽  
J. Craig Dutton ◽  
Bumsoo Han
Keyword(s):  
Water Transport ◽  
Biomedical Applications ◽  
Biological Tissues ◽  
Cell Dehydration ◽  
Spatio Temporal ◽  
Cellular Water ◽  
Induced Changes ◽  
Cellular Water Transport ◽  
Insight Into

Freezing of biomaterials is important in a wide variety of biomedical applications, including cryopreservation and cryosurgeries. For the success of these applications to various biomaterials, biophysical mechanisms, which determine freezing-induced changes in cells and tissues, need to be well understood. Specifically, the significance of the intracellular mechanics during freezing is not well understood. Thus, we hypothesize that cells interact during freezing with the surroundings such as suspension media and the extracellular matrix (ECM) via two distinct but related mechanisms—water transport and cytoskeletal mechanics. The underlying rationale is that the cytoplasm of the cells has poroelastic nature, which can regulate both cellular water transport and cytoskeletal mechanics. A poroelasticity-based cell dehydration model is developed and confirmed to provide insight into the effects of the hydraulic conductivity and stiffness of the cytoplasm on the dehydration of cells in suspension during freezing. We further investigated the effect of the cytoskeletal structures on the cryoresponse of cells embedded in the ECM by measuring the spatio-temporal intracellular deformation with dermal equivalent as a model tissue. The freezing-induced change in cell, nucleus and cytoplasm volume was quantified, and the possible mechanism of the volumetric change was proposed. The results are discussed considering the hierarchical poroelasticity of biological tissues.

scholarly journals Role of Cells in Freezing-Induced Cell-Fluid-Matrix Interactions Within Engineered Tissues

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Angela Seawright ◽  
Altug Ozcelikkale ◽  
Craig Dutton ◽  
Bumsoo Han
Keyword(s):  
Water Transport ◽  
Extracellular Space ◽  
Intracellular Water ◽  
Cell Matrix ◽  
Engineered Tissues ◽  
Matrix Interactions ◽  
Cell Concentrations ◽  
Cellular Water ◽  
Cell Matrix Interactions ◽  
Cellular Water Transport

During cryopreservation, ice forms in the extracellular space resulting in freezing-induced deformation of the tissue, which can be detrimental to the extracellular matrix (ECM) microstructure. Meanwhile, cells dehydrate through an osmotically driven process as the intracellular water is transported to the extracellular space, increasing the volume of fluid for freezing. Therefore, this study examines the effects of cellular presence on tissue deformation and investigates the significance of intracellular water transport and cell-ECM interactions in freezing-induced cell-fluid-matrix interactions. Freezing-induced deformation characteristics were examined through cell image deformetry (CID) measurements of collagenous engineered tissues embedded with different concentrations of MCF7 breast cancer cells versus microspheres as their osmotically inactive counterparts. Additionally, the development of a biophysical model relates the freezing-induced expansion of the tissue due to the cellular water transport and the extracellular freezing thermodynamics for further verification. The magnitude of the freezing-induced dilatation was found to be not affected by the cellular water transport for the cell concentrations considered; however, the deformation patterns for different cell concentrations were different suggesting that cell-matrix interactions may have an effect. It was, therefore, determined that intracellular water transport during freezing was insignificant at the current experimental cell concentrations; however, it may be significant at concentrations similar to native tissue. Finally, the cell-matrix interactions provided mechanical support on the ECM to minimize the expansion regions in the tissues during freezing.

Urea alters set point volume for K-Cl cotransport, Na-H exchange, and Ca-Na exchange in dog red blood cells

1993 ◽  
Vol 265 (2) ◽  
pp. C447-C452 ◽  
Author(s):  
J. C. Parker
Keyword(s):  
Red Blood Cells ◽  
Cell Volume ◽  
Okadaic Acid ◽  
Blood Cells ◽  
Regulatory System ◽  
Set Point ◽  
Volume Sensor

Urea equilibrates rapidly across the red blood cells of mammals. It was speculated that urea might affect the cell volume sensor by virtue of its properties as a protein perturbant. At concentrations of 0.1-0.6 M, urea caused a decrease in the set points for shrinkage-induced Na-H exchange, swelling-induced K-Cl cotransport, and swelling-induced Ca-Na exchange of dog red blood cells. Okadaic acid opposed the action of urea on all three pathways. The effects were reversible and not due to cyanate. Formamide and acetamide had actions similar to urea but not as potent. Equimolar concentrations of methanol had no effect. The coordinated influence of urea on three separate volume-activated transporters suggests that it acts on a mutual regulatory system that senses and transduces volume stimuli.

Comparative Freezing Response of Ejaculated and Epididymal Rhesus Monkey Sperm

2008 ◽  
Author(s):  
Raghava Alapati ◽  
Kelly Goff ◽  
Hans-Michael Kubisch ◽  
Ram V. Devireddy
Keyword(s):  
Rhesus Monkey ◽  
Membrane Permeability ◽  
Cell Volume ◽  
Water Transport ◽  
Sperm Cell ◽  
Transport Parameters ◽  
Cryoprotective Agents ◽  
Transport Response ◽  
Bovine Spermatozoa ◽  
Inactive Cell

In the present study, we report the effects of cooling ejaculated and epididymal rhesus monkey (Macaca mulatta) sperm in the presence of extracellular. Water transport data during freezing of ejaculated and epididymal sperm cell suspensions were obtained at a cooling rate of 20 °C/min in the absence of any cryoprotective agents. Additional water transport data was obtained from ejaculated sperm at a cooling of 5 °C/min without CPAs and at 20 °C/min in the presence of 0.7M of glycerol, as well. Using previously published values, the bovine sperm cell was modeled as a cylinder of length 73.83 μm and a radius of 0.32 μm with an osmotically inactive cell volume, Vb, of 0.772Vo, where Vo is the isotonic cell volume. The subzero water transport response is analyzed to determine the variables governing the rate of water loss during cooling of bovine spermatozoa, i.e. the membrane permeability parameters (reference membrane permeability, Lpg and activation energy, ELp). The predicted best-fit permeability parameters ranged from, Lpg = 0.0023 to 0.0029 μm/min-atm and ELp = 10.6 to 45.5 kcal/mol. The subzero water transport response and consequently the subzero water transport parameters are not significantly different between the ejaculated and epididymal macaque spermatozoa under corresponding cooling conditions.

Acetazolamide Reduces Retinal Inner Nuclear Layer Thickness in Microcystic Macular Edema Secondary to Optic Neuropathy

2018 ◽  
Vol 79 (3-4) ◽  
pp. 150-153
Author(s):  
François-Xavier Borruat ◽  
Muriel Dysli ◽  
Nathalie Voide ◽  
Mathias Abegg
Keyword(s):  
Macular Edema ◽  
Layer Thickness ◽  
Optic Neuropathy ◽  
Visual Function ◽  
Case Series ◽  
Inner Nuclear Layer ◽  
Retinal Layer ◽  
Segmentation Of Images ◽  
Cellular Water ◽  
Cellular Water Transport

Optic neuropathy (ON) is commonly complicated by microcystic macular edema (MME), that is, small vertical cystoid spaces in the inner nuclear layer (INL) of the macula. We performed a retrospective consecutive case series of 14 eyes from 11 patients with ON and MME that were treated with oral acetazolamide, acting on cellular water transport. Contralateral eyes without MME were used as controls. Segmentation of images obtained with OCT was used to determine changes of individual retinal layer thickness during treatment. Retinal INL thickness consistently decreased in all eyes after 2–3 weeks of treatment. Recurrence of MME was observed after treatment cessation. No significant change of retinal thickness was found in contralateral unaffected eyes. Visual function did not change with treatment. Acetazolamide significantly improved the MME in eyes with ON. However, visual function did not. Acetazolamide is a treatment option for MME associated with ON but without an impact on the visual function.

The nature of cell volume sensor in shrinkage‐induced apoptosis

2020 ◽  
Vol 34 (S1) ◽  
pp. 1-1
Author(s):  
Priyanka Rana ◽  
Manabu Kurokawa ◽  
Michael Model
Keyword(s):  
Cell Volume ◽  
Volume Sensor ◽  
Induced Apoptosis

Measurement and Simulation of Water Transport During Freezing in Mammalian Liver Tissue

1997 ◽  
Vol 119 (3) ◽  
pp. 269-277 ◽  
Author(s):  
P. V. Pazhayannur ◽  
J. C. Bischof
Keyword(s):  
Water Transport ◽  
Rat Liver ◽  
Liver Tissue ◽  
Subzero Temperature ◽  
Biophysical Parameters ◽  
Cylinder Model ◽  
Chi Squared ◽  
Controlled Freezing ◽  
Cellular Water ◽  
Krogh Cylinder

Optimization of cryosurgical procedures on deep tissues such as liver requires an increased understanding of the fundamental mechanisms of ice formation and water transport in tissues during freezing. In order to further investigate and quantify the amount of water transport that occurs during freezing in tissue, this study reports quantitative and dynamic experimental data and theoretical modeling of rat liver freezing under controlled conditions. The rat liver was frozen by one of four methods of cooling: Method 1—ultrarapid “slam cooling” (≥ 1000° C/min) for control samples; Method 2—equilibrium freezing achieved by equilibrating tissue at different subzero temperatures (−4, −6, −8, −10°C); Method 3°-two-step freezing, which involves cooling at 5°C/min. to −4, −6, −8, −10 or −20°C followed immediately by slam cooling; or Method 4—constant and controlled freezing at rates from 5–400°C/min. on a directional cooling stage. After freezing, the tissue was freeze substituted, embedded in resin, sectioned, stained, and imaged under a light microscope fitted with a digitizing system. Image analysis techniques were then used to determine the relative cellular to extracellular volumes of the tissue. The osmotically inactive cell volume was determined to be 0.35 by constructing a Boyle van’t Hoff plot using cellular volumes from Method 2. The dynamic volume of the rat liver cells during cooling was obtained using cellular volumes from Method 3 (two-step freezing at 5°C/min). A nonlinear regression fit of a Krogh cylinder model to the volumetric shrinkage data in Method 3 yielded the biophysical parameters of water transport in rat liver tissue of: Lpg = 3.1 X 10−13 m3/Ns (1.86 μ/min-atm) and ELP = 290 kJ/mole (69.3 kcal/mole), with chi-squared variance of 0.00124. These parameters were then incorporated into the Krogh cylinder model and used to simulate water transport in rat liver tissue during constant cooling at rates between 5–100°C/min. Reasonable agreement between these simulations and the constant cooling rate freezing experiments in Method 4 were obtained. The model predicts that the water transport ceases at a relatively high subzero temperature (−10°C), such that the amount of intracellular ice forming in the tissue cells rises from almost none (=extensive dehydration and vascular expansion) at ≤5°C/min to over 88 percent of the original cellular water at ≥50°C/min. The theoretical simulations based on these experimental methods may be of use in visualizing and predicting freezing response, and thus can assist in the planning and implementing of cryosurgical protocols.

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