Theoretical analysis of adenosine release from cardiac tissue as influenced by transport inhibitors

1983 ◽  
Vol 61 (8) ◽  
pp. 946-949 ◽  
Author(s):  
H. Wiener ◽  
W. G. Schützenberger ◽  
E. Tuisl ◽  
N. Kolassa
Keyword(s):  
Theoretical Analysis ◽  
Model Equation ◽  
Cardiac Tissue ◽  
Diffusion Mechanism ◽  
Facilitated Diffusion ◽  
Adenosine Release ◽  
Proposed Model ◽  
Transport Inhibitors ◽  
Transfer Term

The release of adenosine from cardiac tissue was simulated by use of a model equation which consists of a saturable transfer term for both unidirectional influx and efflux, representing a symmetrical facilitated diffusion mechanism. This proposed model can account for positive and negative changes in adenosine release from cardiac tissue brought about by competitive transport inhibitors.

scholarly journals Influence of Chemical Osmosis on Solute Transport and Fluid Velocity in Clay Soils

2020 ◽  
Vol 18 (1) ◽  
pp. 232-238
Author(s):  
Zhihong Zhang ◽  
Gailei Tian ◽  
Lin Han
Keyword(s):  
Solute Transport ◽  
Transport Model ◽  
Fluid Velocity ◽  
Diffusion Mechanism ◽  
Clay Material ◽  
Chemical Osmosis ◽  
Advection Diffusion Equation ◽  
Test Study ◽  
Proposed Model ◽  
Membrane Effect

AbstractSolute transport through the clay liner is a significant process in many waste landfills or unmanaged landfills. At present, researchers mainly focus on the test study about semi-membrane property of clay material, however, the influence of chemical osmosis caused by membrane effect on solute transport and fluid velocity is insufficient. In this investigation, based on the classical advection-diffusion equation, a one-dimensional solute transport model for low-permeable clay material has been proposed, in which the coupled fluid velocity related with hydraulic gradient and concentration gradient is introduced, and the semi-membrane effect is embodied in the diffusion mechanism. The influence of chemical osmosis on fluid velocity and solute transport has been analyzed using COMSOL Multiphysics software. The simulated results show that chemical osmosis has a significant retarded action on fluid velocity and pollutant transport. The proposed model can effectively reveal the change in process of coupled fluid velocity under dual gradient and solute transport, which can provide a theoretical guidance for similar fluid movement in engineering.

scholarly journals PnuT uses a facilitated diffusion mechanism for thiamine uptake

2017 ◽  
Vol 150 (1) ◽  
pp. 41-50 ◽  
Author(s):  
Michael Jaehme ◽  
Rajkumar Singh ◽  
Alisa A. Garaeva ◽  
Ria H. Duurkens ◽  
Dirk-Jan Slotboom
Keyword(s):  
Substrate Binding ◽  
Diffusion Mechanism ◽  
Vitamin B1 ◽  
Pyridine Nucleotide ◽  
Thiamine Pyrophosphate ◽  
Facilitated Diffusion ◽  
Nicotinamide Riboside ◽  
Thiamine Transport ◽  
Shewanella Woodyi ◽  
Thiamine Analogues

Membrane transporters of the bacterial pyridine nucleotide uptake (Pnu) family mediate the uptake of various B-type vitamins. For example, the PnuT transporters have specificity for vitamin B1 (thiamine). It has been hypothesized that Pnu transporters are facilitators that allow passive transport of the vitamin substrate across the membrane. Metabolic trapping by phosphorylation would then lead to accumulation of the transported substrates in the cytoplasm. However, experimental evidence for such a transport mechanism is lacking. Here, to determine the mechanism of thiamine transport, we purify PnuTSw from Shewanella woodyi and reconstitute it in liposomes to determine substrate binding and transport properties. We show that the electrochemical gradient of thiamine solely determines the direction of transport, consistent with a facilitated diffusion mechanism. Further, PnuTSw can bind and transport thiamine as well as the thiamine analogues pyrithiamine and oxythiamine, but does not recognize the phosphorylated derivatives thiamine monophosphate and thiamine pyrophosphate as substrates, consistent with a metabolic trapping mechanism. Guided by the crystal structure of the homologous nicotinamide riboside transporter PnuC, we perform mutagenesis experiments, which reveal residues involved in substrate binding and gating. The facilitated diffusion mechanism of transport used by PnuTSw contrasts sharply with the active transport mechanisms used by other bacterial thiamine transporters.

scholarly journals Real sequence effects on the search dynamics of transcription factors on DNA

2015 ◽  
Vol 5 (1) ◽  
Author(s):  
Maximilian Bauer ◽  
Emil S. Rasmussen ◽  
Michael A. Lomholt ◽  
Ralf Metzler
Keyword(s):  
Transcription Factors ◽  
Target Detection ◽  
Diffusion Mechanism ◽  
Coli Strain ◽  
Dna Looping ◽  
Real Sequence ◽  
Facilitated Diffusion ◽  
E Coli ◽  
Sliding Motion ◽  
Sequence Effects

Abstract Recent experiments show that transcription factors (TFs) indeed use the facilitated diffusion mechanism to locate their target sequences on DNA in living bacteria cells: TFs alternate between sliding motion along DNA and relocation events through the cytoplasm. From simulations and theoretical analysis we study the TF-sliding motion for a large section of the DNA-sequence of a common E. coli strain, based on the two-state TF-model with a fast-sliding search state and a recognition state enabling target detection. For the probability to detect the target before dissociating from DNA the TF-search times self-consistently depend heavily on whether or not an auxiliary operator (an accessible sequence similar to the main operator) is present in the genome section. Importantly, within our model the extent to which the interconversion rates between search and recognition states depend on the underlying nucleotide sequence is varied. A moderate dependence maximises the capability to distinguish between the main operator and similar sequences. Moreover, these auxiliary operators serve as starting points for DNA looping with the main operator, yielding a spectrum of target detection times spanning several orders of magnitude. Auxiliary operators are shown to act as funnels facilitating target detection by TFs.

scholarly journals The Mechanical Bidomain Model: A Review

2013 ◽  
Vol 2013 ◽  
pp. 1-8 ◽  
Author(s):  
Bradley J. Roth
Keyword(s):  
Cell Membrane ◽  
Theoretical Analysis ◽  
Cardiac Tissue ◽  
Elastic Behavior ◽  
Bidomain Model ◽  
Future Directions ◽  
Open Questions ◽  
Model Predictions ◽  
Tissue Surface ◽  
Primary Advantage

The mechanical bidomain model is a new mathematical description of the elastic behavior of cardiac tissue. Its primary advantage over previous models is that it accounts for forces acting across the cell membrane arising from differences in the displacement of the intracellular and extracellular spaces. In this paper, I describe the development of the mechanical bidomain model. I emphasize new predictions of the model, such as the existence of boundary layers at the tissue surface where the membrane forces are large, and pressure differences between the intracellular and extracellular spaces. Although the theoretical analysis is quite mathematical, I highlight the types of experiments that could be used to test the model predictions. Finally, I present open questions about the mechanical bidomain model that may be productive future directions for research.

Diatomic gas—thermal radiation interaction A model equation for the internal fluid

1972 ◽  
Vol 7 (2) ◽  
pp. 235-246 ◽  
Author(s):  
Warren F. Phillips ◽  
Vedat S. Arpaci
Keyword(s):  
Kinetic Equation ◽  
Thermal Radiation ◽  
Model Equation ◽  
Diatomic Molecules ◽  
Collision Term ◽  
Model Kinetic Equation ◽  
Photon Interaction ◽  
Internal Fluid ◽  
Proposed Model ◽  
Alternative Approach

A model kinetic equation for the internal fluid of diatomic molecules which interacts with thermal radiation is proposed. The cross-collision term developed for the molecule-photon interaction has the property that molecules and the sum of internal and photon energies are conserved. An alternative approach to this term based on the product of two BGKW collision operators yields the same result. It is also shown that the proposed model leads to an H-theorem.

Experimental and Theoretical Analysis of Phase Singularity Dynamics in Cardiac Tissue

2001 ◽  
Vol 12 (6) ◽  
pp. 716-722 ◽  
Author(s):  
MARK-ANTHONY BRAY ◽  
SHIEN-FONG LIN ◽  
RUBIN R. ALIEV ◽  
BRADLEY J. ROTH ◽  
JOHN P. WIKSWO
Keyword(s):  
Theoretical Analysis ◽  
Cardiac Tissue ◽  
Phase Singularity

scholarly journals Research on Pressure Drop in the Accelerate Zone of Horizontal Conveying of Concrete Spraying

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Guanguo Ma ◽  
Zhaoxia Liu ◽  
Xiaobing Gong ◽  
Lianjun Chen ◽  
Guoming Liu ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Model Equation ◽  
Approximate Model ◽  
Momentum Equation ◽  
Experimental Results ◽  
Model Research ◽  
Proposed Model ◽  
Specific Position ◽  
Pressure Transmitter ◽  
Working Parameters

A pressure transmitter was installed at a specific position in a concrete conveying line to disclose the pressure drop when compressed air was conveyed during concrete spraying. A statistical analysis of the pressure at different positions was undertaken. Experimental results demonstrated that in the accelerate zone of horizontal conveying of concrete in the line, the pressure drop mainly occurred during the acceleration, collision, and friction processes. The momentum equation was introduced during the experiment, which interpreted the pressure drop caused by the accelerated conveying of concrete. The theoretical equation was corrected based on the results of theoretical experiments by introducing the value of α, and the experimental results were then optimized, thus obtaining an approximate model of pressure drop during the conveying of concrete. In addition, experimental results were compared with a model equation that showed the reliability of the proposed model. Research conclusions are of great significance to regulate the pressure drop in the conveying line of concretes, to design working parameters of concrete spraying devices, and to predict the ultimate distance for the conveying of concrete.

The membrane permeability of nonelectrolytes and carbohydrate metabolism of Amazon fish red cells

1978 ◽  
Vol 56 (4) ◽  
pp. 863-869 ◽  
Author(s):  
Hyun Dju Kim ◽  
R. E. Isaacks
Keyword(s):  
Membrane Permeability ◽  
Carbohydrate Metabolism ◽  
Diffusion Mechanism ◽  
Red Cells ◽  
Facilitated Diffusion ◽  
Metabolic Substrates ◽  
Urea Permeability ◽  
Arapaima Gigas ◽  
Electric Eel ◽  
Order Of Magnitude

The membrane permeability to nonelectrolytes and carbohydrate metabolism were examined in red cells obtained from the Amazon fishes including the electric eel (Electrophorus electrocus), the arawana (Osteoglossum bicirrhosum), the pirarucu (Arapaima gigas), the lungfish (Lepidosireti paradoxa), and the armored catfish (Pterygoplichthys). Glucose permeability was fastest in the electric eel, followed by the lungfish. The red cells of the arawana were only slightly permeable to glucose. Both the armored catfish and the pirarucu red cells were found to be totally impermeable to glucose. There was no evidence for the presence of the facilitated diffusion mechanism for glucose transport in any of these fish red cells. In sharp contrast with glucose, red cells of all five species were quite permeable to ribose and urea. Urea permeability of red cells decreased in order of magnitude with the lungfish > the electric eel > the arawana > the armored catfish [Formula: see text] the pirarucu. The urea permeability of the lungfish was inhibited in the presence of phloretin.Of the two metabolic substrates, glucose but not ribose was metabolized to lactate with a concomitant contribution to ATP maintenance by the lungfish red cells. Even though the glucose-impervious pirarucu cells could not utilize glucose, ribose was readily metabolized by the pirarucu cells.

The Radar Signal Feature-Separability Model Analysis

2011 ◽  
Vol 268-270 ◽  
pp. 1484-1487
Author(s):  
Zhi Bin Yu ◽  
Chun Xia Chen
Keyword(s):  
Probability Theory ◽  
Statistical Theory ◽  
Theoretical Analysis ◽  
Feature Space ◽  
Radar Signal ◽  
One Dimensional ◽  
Proposed Model ◽  
The One ◽  
Recognition Capability ◽  
Original Feature

The one-dimensional feature-separability model concerning the feature-separability issue of radar emitter signals is proposed based on the probability theory and statistical theory, to evaluate the deinterleaving and recognition capability of extracted features. The proposed method is applied to analyze convention features of radar emitter signals. The theoretical analysis and experimental results show that the proposed model offers a new way to analyze the validity of extracted features, and is valid in both the original feature space and linear-transformed feature space.

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