scholarly journals Osmotic Loading of Spherical Gels: A Biomimetic Study of Hindered Transport in the Cell Protoplasm

2006 ◽  
Vol 129 (4) ◽  
pp. 503-510 ◽  
Author(s):  
Michael B. Albro ◽  
Nadeen O. Chahine ◽  
Matteo Caligaris ◽  
Victoria I. Wei ◽  
Morakot Likhitpanichkul ◽  
...  
Keyword(s):  
Mixture Theory ◽  
Transport Mechanisms ◽  
Permeable Membrane ◽  
Partial Volume ◽  
Equilibrium Volume ◽  
Equilibrium Response ◽  
Osmotic Loading ◽  
Volume Recovery ◽  
Volume Response

Osmotic loading of cells has been used to investigate their physicochemical properties as well as their biosynthetic activities. The classical Kedem–Katchalsky framework for analyzing cell response to osmotic loading, which models the cell as a fluid-filled membrane, does not generally account for the possibility of partial volume recovery in response to loading with a permeating osmolyte, as observed in some experiments. The cell may be more accurately represented as a hydrated gel surrounded by a semi-permeable membrane, with the gel and membrane potentially exhibiting different properties. To help assess whether this more elaborate model of the cell is justified, this study investigates the response of spherical gels to osmotic loading, both from experiments and theory. The spherical gel is described using the framework of mixture theory. In the experimental component of the study alginate is used as the model gel, and is osmotically loaded with dextran solutions of various concentrations and molecular weight, to verify the predictions from the theoretical analysis. Results show that the mixture framework can accurately predict the transient and equilibrium response of alginate gels to osmotic loading with dextran solutions. It is found that the partition coefficient of dextran in alginate regulates the equilibrium volume response and can explain partial volume recovery based on passive transport mechanisms. The validation of this theoretical framework facilitates future investigations of the role of the protoplasm in the response of cells to osmotic loading.

The Role of Microtubule Organization in Chondrocyte Response to Osmotic Loading

2007 ◽  
Author(s):  
Elizabeth S. Oswald ◽  
Pen-hsiu Grace Chao ◽  
J. Chloe Bulinski ◽  
Gerard A. Ateshian ◽  
Clark T. Hung
Keyword(s):  
Intracellular Transport ◽  
Morphological Changes ◽  
Cellular Responses ◽  
Microtubule Organization ◽  
Osmotic Loading ◽  
Volume Response ◽  
Cytoplasmic Organization

The cytoskeleton, including actin filaments and microtubules, provides chondrocytes with structure, cytoplasmic organization, and intracellular transport. The cytoskeleton is known to be involved in cellular responses to physiologic mechanical and osmotic loading signals, including morphological changes and mechanostransduction [1, 2]. Here, we examine microtubule (MT) involvement in volume response of chondrocytes to osmotic loading, as well as organization of stable MT with hypoosmotic loading. We also explore the hypothesis that chondrocytes from different zones of cartilage possess cytoskeletons with different properties, which help explain variations in their volume response to osmotic loading in situ and in vitro [3].

Quantitative accuracy of serotonergic neurotrans-mission imaging with high-resolution 123I SPECT

2004 ◽  
Vol 43 (06) ◽  
pp. 185-189 ◽  
Author(s):  
J. T. Kuikka
Keyword(s):  
High Resolution ◽  
Scatter Correction ◽  
Region Of Interest ◽  
Binding Potential ◽  
Partial Volume ◽  
Therapeutic Drugs ◽  
Quantitative Accuracy ◽  
Critical Error ◽  
Statistical Noise

Summary Aim: Serotonin transporter (SERT) imaging can be used to study the role of regional abnormalities of neurotransmitter release in various mental disorders and to study the mechanism of action of therapeutic drugs or drugs’ abuse. We examine the quantitative accuracy and reproducibility that can be achieved with high-resolution SPECT of serotonergic neurotransmission. Method: Binding potential (BP) of 123I labeled tracer specific for midbrain SERT was assessed in 20 healthy persons. The effects of scatter, attenuation, partial volume, mis-registration and statistical noise were estimated using phantom and human studies. Results: Without any correction, BP was underestimated by 73%. The partial volume error was the major component in this underestimation whereas the most critical error for the reproducibility was misplacement of region of interest (ROI). Conclusion: The proper ROI registration, the use of the multiple head gamma camera with transmission based scatter correction introduce more relevant results. However, due to the small dimensions of the midbrain SERT structures and poor spatial resolution of SPECT, the improvement without the partial volume correction is not great enough to restore the estimate of BP to that of the true one.

scholarly journals The Bioavailability of Astaxanthin Is Dependent on Both the Source and the Isomeric Variants of the Molecule

2016 ◽  
Vol 73 (2) ◽  
pp. 61 ◽  
Author(s):  
Myriam MIMOUN-BENARROCH ◽  
Cindy HOGOT ◽  
Larbi RHAZI ◽  
Claude Narcisse NIAMBA ◽  
Flore DEPEINT
Keyword(s):  
Cultured Cells ◽  
Haematococcus Pluvialis ◽  
Animal Experiments ◽  
Intestinal Barrier ◽  
Potential Health ◽  
Permeable Membrane ◽  
Natural Sources ◽  
Uptake Studies ◽  
Colonic Cells

Astaxanthin is a marine carotenoid that has a number of potential health benefits, including a very strong antioxidant potential. Present in the flesh of salmonids and shellfish, its natural sources currently on the market for food supplements come from the algae Haematococcus pluvialis and krill. However other natural sources can be found and may be of interest. Cellular uptake studies were performed on Caco-2/TC7 colonic cells. The cells were cultured on a semi-permeable membrane to create a polarized and functional epithelium, representative of the intestinal barrier. Four sources of astaxanthin were selected and compared; synthetic, natural extracts from bacteria, algae or yeast. Astaxanthin was incorporated at a concentration of 5µM into mixed micelles and applied to cultured cells and concentration of astaxanthin measured by HPLC in both apical and basolateral compartments. Small variations in bioavailability were observed at 3 hours. After 6 hours, only the algae source of astaxanthin was still present in the apical compartment as the esterified form. Structure-activity relationships are further discussed. Animal experiments using yeast and algae sources in different types of matrices confirm the role of source and formulation in the bioavailability potential of astaxanthin.

Modelling sarcoplasmic reticulum calcium ATPase and its regulation in cardiac myocytes

2009 ◽  
Vol 367 (1896) ◽  
pp. 2181-2202 ◽  
Author(s):  
Jussi T. Koivumäki ◽  
Jouni Takalo ◽  
Topi Korhonen ◽  
Pasi Tavi ◽  
Matti Weckström
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Large Scale ◽  
Cardiac Myocyte ◽  
Model Complexity ◽  
Transport Mechanisms ◽  
Physiological Properties ◽  
Theoretical Considerations ◽  
Sarcoplasmic Reticulum Calcium ◽  
Modelling Approach

When developing large-scale mathematical models of physiology, some reduction in complexity is necessarily required to maintain computational efficiency. A prime example of such an intricate cell is the cardiac myocyte. For the predictive power of the cardiomyocyte models, it is vital to accurately describe the calcium transport mechanisms, since they essentially link the electrical activation to contractility. The removal of calcium from the cytoplasm takes place mainly by the Na + /Ca 2+ exchanger, and the sarcoplasmic reticulum Ca 2+ ATPase (SERCA). In the present study, we review the properties of SERCA, its frequency-dependent and β -adrenergic regulation, and the approaches of mathematical modelling that have been used to investigate its function. Furthermore, we present novel theoretical considerations that might prove useful for the elucidation of the role of SERCA in cardiac function, achieving a reduction in model complexity, but at the same time retaining the central aspects of its function. Our results indicate that to faithfully predict the physiological properties of SERCA, we should take into account the calcium-buffering effect and reversible function of the pump. This ‘uncomplicated’ modelling approach could be useful to other similar transport mechanisms as well.

scholarly journals The Role of Data Providers as Information Intermediaries

2018 ◽  
Vol 53 (4) ◽  
pp. 1805-1838 ◽  
Author(s):  
Nic Schaub
Keyword(s):  
Capital Markets ◽  
Earnings Announcements ◽  
Financial Data ◽  
Significant Part ◽  
Earnings Information ◽  
Post Earnings Announcement Drift ◽  
Information Intermediaries ◽  
Thomson Reuters ◽  
Volume Response

This study investigates whether financial data providers serve as information intermediaries in capital markets. To this end, I examine whether the timeliness of earnings information disseminated by First Call (Thomson Reuters) affects the market’s reaction to earnings announcements. I document that the immediate price and volume response is weaker and the post-earnings-announcement drift stronger for earnings news disseminated with a delay by First Call. To mitigate endogeneity concerns, I study the market reaction on the day of the delayed dissemination and show that a significant part of the stronger drift is clustered around this day.

scholarly journals The role of heterointerfaces and subgap energy states on transport mechanisms in silicon heterojunction solar cells

2020 ◽  
Vol 28 (9) ◽  
pp. 935-945 ◽  
Author(s):  
Paul Procel ◽  
Haiyuan Xu ◽  
Aurora Saez ◽  
Carlos Ruiz‐Tobon ◽  
Luana Mazzarella ◽  
...  
Keyword(s):  
Solar Cells ◽  
Transport Mechanisms ◽  
Heterojunction Solar Cells ◽  
Energy States ◽  
Silicon Heterojunction Solar Cells

The role of moisture transport mechanisms on the performance of lightweight aggregates in internal curing

2021 ◽  
Vol 268 ◽  
pp. 121191
Author(s):  
Alvaro Paul ◽  
Sofía Murgadas ◽  
José Delpiano ◽  
Patricio A. Moreno-Casas ◽  
Magdalena Walczak ◽  
...  
Keyword(s):  
Moisture Transport ◽  
Internal Curing ◽  
Lightweight Aggregates ◽  
Transport Mechanisms

Basolateral membrane H-OH-HCO3 transport in the proximal tubule

1989 ◽  
Vol 256 (5) ◽  
pp. F751-F765
Author(s):  
P. A. Preisig ◽  
R. J. Alpern
Keyword(s):  
Metabolic Acidosis ◽  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Respiratory Acidosis ◽  
Cell Voltage ◽  
Transport Mechanisms ◽  
Transport Capacity ◽  
Chronic Metabolic Acidosis

This review focuses on the basolateral membrane mechanisms of H-OH-HCO3 transport in the proximal tubule. The mechanism that has the greatest transport capacity and mediates most of transepithelial H-HCO3 transport is the electrogenic, Na-3HCO3 cotransporter. This transporter has been extensively characterized in the salamander, rat, and rabbit proximal tubule, and has now been found in a number of other epithelia that effect transepithelial NaHCO3 transport. Transporter rate is sensitive to intra- and extracellular [Na], intra- and extracellular [HCO3]/pH, and cell voltage. Adaptations in transporter activity have been demonstrated in chronic metabolic acidosis and alkalosis, chronic respiratory acidosis and alkalosis, and chronic hyperfiltration. In addition to the Na-3HCO3 cotransporter, the basolateral membrane possesses both Na-dependent and -independent Cl-HCO3 exchangers, a H leak, and in the S3 proximal tubule an Na-H antiporter. The role of these H-OH-HCO3 transport mechanisms in transcellular HCO3 and Cl absorption and pHi defense is discussed.

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