Calcium Exchange and Contraction Strength of Guinea Pig Atrium in Normal and Hypertonic Media

A Krebs-Henseleit (KH) medium made hypertonic by adding nonpermeant molecules substantially increased the isometric peak tension at steady-state contractions below 3 per sec in guinea pig atrium at 27°C. Action potential durations were decreased. KH plus 100 mM raffinose or sucrose resulted in similar and nearly maximal changes which were essentially reversible upon return to normal KH. When one active contracting atrium was used to passively stretch a second atrium, the difference in Ca ion exchange (1 min exchange with the extracellular space) between active and stretched atria significantly increased at 1 per sec and at 2 per sec in going from normal to 100 mM hypertonic KH. The calculated mean Ca ion cellular exchange per beat per 100 g of cells (a) doubled in changing from normal to 100 mM hypertonic KH, and (b) decreased slightly in changing from contractions of 1 per sec to 2 per sec in normal KH. These data are consistent with the hypothesis (a) that Ca ion entry per beat from the extracellular space is proportional to membrane depolarized time with a constant medium and a steady-state condition, and the hypothesis (b) that 100 mM hypertonicity doubles the Ca ion entry rate during depolarization. These data enable rejection of the hypothesis that the peak tension is proportional to the Ca ion entry per beat from the extracellular space under steady-state conditions, and suggest that any additional Ca ion involved in the larger contractions at higher frequencies comes from an increase in Ca ion available from intracellular stores.

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Forsterite dissolution in superheated basaltic, andesitic and rhyolitic melts

Mineralogical Magazine ◽

10.1180/minmag.1990.054.374.06 ◽

1990 ◽

Vol 54 (374) ◽

pp. 67-74 ◽

Cited By ~ 20

Author(s):

C. H. Donaldson

Keyword(s):

Steady State ◽

Natural Convection ◽

Dissolution Rate ◽

Atmospheric Pressure ◽

Initial Value ◽

Steady State Condition ◽

Rate Of Dissolution ◽

Constant Rate ◽

The Difference ◽

Initial Dissolution Rate

AbstractDissolution rates of small forsterite spheres in superheated melts of basalt, andesite and rhyolite composition have been measured at 1300°C, atmospheric pressure. The rate is constant (83 µm hr−1) in the basalt, regardless of run duration. In the andesite the initial dissolution rate is 200µm hr−1, followed by a decrease to a constant value of 16µmhr−1 in 2–3 hours. Dissolution rate in the rhyolite decreases from an initial value of 1.7 to <0.1 µmhr−1 over 280 hours and never reaches a constant rate. Once the rate of dissolution has become constant, the film of contaminated melt that forms in melt about a crystal does not thicken with time, indicating attainment of a steady-state condition. Steady state is attributed to natural convection arising from the difference in density between the film of contaminated melt surrounding a crystal and that beyond. The density difference is approximately 2% of the density of the rock melt.

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CARDIAC MUSCLE

The Journal of Cell Biology ◽

10.1083/jcb.36.3.497 ◽

1968 ◽

Vol 36 (3) ◽

pp. 497-526 ◽

Cited By ~ 198

Author(s):

Joachim R. Sommer ◽

Edward A. Johnson

Keyword(s):

Electron Microscopy ◽

Skeletal Muscle ◽

Sarcoplasmic Reticulum ◽

Guinea Pig ◽

Cardiac Muscle ◽

Extracellular Space ◽

Light And Electron Microscopy ◽

Rabbit Heart ◽

Contraction Coupling ◽

The Difference

With light and electron microscopy a comparison has been made of the morphology of ventricular (V) and Purkinje (P) fibers of the hearts of guinea pig, rabbit, cat, dog, goat, and sheep. The criteria, previously established for the rabbit heart, that V fibers are distinguished from P fibers by the respective presence and absence of transverse tubules is shown to be true for all animals studied. No evidence was found of a permanent connection between the sarcoplasmic reticulum and the extracellular space. The sarcoplasmic reticulum (SR) of V fibers formed couplings with the sarcolemma of a transverse tubule (interior coupling) and with the peripheral sarcolemma (peripheral coupling), whereas in P fibers the SR formed only peripheral couplings. The forms of the couplings were identical. The significance, with respect to excitation-contraction coupling, of the difference in the form of the couplings in cardiac versus skeletal muscle is discussed together with the electrophysiological implications of the differing geometries of bundles of P fibers from different animals.

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Extracellular Space of Guinea-Pig Atrium Tissue During Metabolic Inhibition and During Contracture

Pharmacology ◽

10.1159/000136969 ◽

1967 ◽

Vol 16 (1) ◽

pp. 89-94

Author(s):

H. Lüllmann ◽

P.A. van Zwieten

Keyword(s):

Guinea Pig ◽

Extracellular Space ◽

Metabolic Inhibition ◽

Guinea Pig Atrium

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Simon's Steady State Assumption: A Critique of Okabe's Critique

Environment and Planning A Economy and Space ◽

10.1068/a141113 ◽

1982 ◽

Vol 14 (8) ◽

pp. 1113-1120 ◽

Cited By ~ 3

Author(s):

Y-S Kim

Keyword(s):

Steady State ◽

Total Population ◽

City Size ◽

State Condition ◽

Size Distributions ◽

Steady State Condition ◽

Steady State Assumption ◽

The Difference ◽

State Assumption

Simon's model of city-size distributions has been a classical way of explaining the rank-size rule. But the steady state condition he uses to solve his model was shown by Okabe to be mathematically inconsistent with the basic postulates of the model. Okabe is correct as long as the difference between individual city size and total population is small. But when t (total number of population units) is only moderately larger than i (individual city size), as it always would be in actual applications of this model, Simon's steady state assumption is found to be very reasonable. Thus, users of the Simon model need not concern themselves with the fine points and complexities of Okabe's exposition since Simon's steady state assumption holds for any value of t that might be empirically observed.

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Computational Performance of Disparate Lattice Boltzmann Scenarios under Unsteady Thermal Convection Flow and Heat Transfer Simulation

Computation ◽

10.3390/computation9060065 ◽

2021 ◽

Vol 9 (6) ◽

pp. 65

Author(s):

Aditya Dewanto Hartono ◽

Kyuro Sasaki ◽

Yuichi Sugai ◽

Ronald Nguele

Keyword(s):

Heat Transfer ◽

Steady State ◽

Natural Convection ◽

Lattice Boltzmann ◽

Numerical Results ◽

Convection And Heat Transfer ◽

Steady State Condition ◽

Physical Systems ◽

Flow And Heat Transfer ◽

Computational Performance

The present work highlights the capacity of disparate lattice Boltzmann strategies in simulating natural convection and heat transfer phenomena during the unsteady period of the flow. Within the framework of Bhatnagar-Gross-Krook collision operator, diverse lattice Boltzmann schemes emerged from two different embodiments of discrete Boltzmann expression and three distinct forcing models. Subsequently, computational performance of disparate lattice Boltzmann strategies was tested upon two different thermo-hydrodynamics configurations, namely the natural convection in a differentially-heated cavity and the Rayleigh-Bènard convection. For the purposes of exhibition and validation, the steady-state conditions of both physical systems were compared with the established numerical results from the classical computational techniques. Excellent agreements were observed for both thermo-hydrodynamics cases. Numerical results of both physical systems demonstrate the existence of considerable discrepancy in the computational characteristics of different lattice Boltzmann strategies during the unsteady period of the simulation. The corresponding disparity diminished gradually as the simulation proceeded towards a steady-state condition, where the computational profiles became almost equivalent. Variation in the discrete lattice Boltzmann expressions was identified as the primary factor that engenders the prevailed heterogeneity in the computational behaviour. Meanwhile, the contribution of distinct forcing models to the emergence of such diversity was found to be inconsequential. The findings of the present study contribute to the ventures to alleviate contemporary issues regarding proper selection of lattice Boltzmann schemes in modelling fluid flow and heat transfer phenomena.

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Effects of Genotypes and Treatment on Oxygenscan Parameters in Sickle Cell Disease

Cells ◽

10.3390/cells10040811 ◽

2021 ◽

Vol 10 (4) ◽

pp. 811

Author(s):

Camille Boisson ◽

Minke A. E. Rab ◽

Elie Nader ◽

Céline Renoux ◽

Celeste Kanne ◽

...

Keyword(s):

Steady State ◽

Sickle Cell Disease ◽

Blood Cell ◽

Sickle Cell ◽

Red Blood Cell ◽

Cell Disease ◽

Oxygen Gradient ◽

Acute Complication ◽

Adults And Children ◽

The Difference

(1) Background: The aim of the present study was to compare oxygen gradient ektacytometry parameters between sickle cell patients of different genotypes (SS, SC, and S/β+) or under different treatments (hydroxyurea or chronic red blood cell exchange). (2) Methods: Oxygen gradient ektacytometry was performed in 167 adults and children at steady state. In addition, five SS patients had oxygenscan measurements at steady state and during an acute complication requiring hospitalization. (3) Results: Red blood cell (RBC) deformability upon deoxygenation (EImin) and in normoxia (EImax) was increased, and the susceptibility of RBC to sickle upon deoxygenation was decreased in SC patients when compared to untreated SS patients older than 5 years old. SS patients under chronic red blood cell exchange had higher EImin and EImax and lower susceptibility of RBC to sickle upon deoxygenation compared to untreated SS patients, SS patients younger than 5 years old, and hydroxyurea-treated SS and SC patients. The susceptibility of RBC to sickle upon deoxygenation was increased in the five SS patients during acute complication compared to steady state, although the difference between steady state and acute complication was variable from one patient to another. (4) Conclusions: The present study demonstrates that oxygen gradient ektacytometry parameters are affected by sickle cell disease (SCD) genotype and treatment.

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Continuous determination of the volume of a space in a non steady state condition

Bulletin of Mathematical Biology ◽

10.1007/bf02461191 ◽

1974 ◽

Vol 36 (1) ◽

pp. 59-66

Author(s):

Oscar A. Gómez-Poviña ◽

Carmen Sainz de Calatroni ◽

Susana Orden de Puhl ◽

Mariano J. Guerrero

Keyword(s):

Steady State ◽

State Condition ◽

Steady State Condition ◽

Continuous Determination

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Comparison of changes evoked by GABA (γ-aminobutyric acid) and anoxia in [K+]o, [Cl-]o, and [Na+]o in stratum pyramidale and stratum radiatum of the guinea pig hippocampus

Canadian Journal of Physiology and Pharmacology ◽

10.1139/y00-001 ◽

2000 ◽

Vol 78 (5) ◽

pp. 378-391 ◽

Cited By ~ 2

Author(s):

G V Obrocea ◽

M E Morris

Keyword(s):

Guinea Pig ◽

Extracellular Space ◽

Hippocampal Slices ◽

Brain Slices ◽

Receptor Activation ◽

Ion Concentration ◽

Aminobutyric Acid ◽

Stratum Radiatum ◽

Bicuculline Methiodide ◽

Stratum Pyramidale

Ion-selective microelectrode recordings were made to assess a possible contribution of extracellular γ-aminobutyric acid (GABA) accumulation to early responses evoked in the brain by anoxia and ischemia. Changes evoked by GABA or N2 in [K+]o, [Cl-]o, [Na+]o, and [TMA+]o were recorded in the cell body and dendritic regions of the stratum pyramidale (SP) and stratum radiatum (SR), respectively, of pyramidal neurons in CA1 of guinea pig hippocampal slices. Bath application of GABA (1-10 mM) for approximately 5 min evoked changes in [K+]o and [Cl-]o with respective EC50 levels of 3.8 and 4.1 mM in SP, and 4.7 and 5.6 mM in SR. In SP 5 mM GABA reversibly increased [K+]o and [Cl-]o and decreased [Na+]o; replacement of 95% O2 -5% CO2 by 95% N2 -5% CO2 for a similar period of time evoked changes which were for each ion in the same direction as those with GABA. In SR both GABA and N2 caused increases in [K+]o and decreases in [Cl-]o and [Na+]o. The reduction of extracellular space, estimated from levels of [TMA+]o during exposures to GABA and N2, was 5-6% and insufficient to cause the observed changes in ion concentration. Ion changes induced by GABA and N2 were reversibly attenuated by the GABAA receptor antagonist bicuculline methiodide (BMI, 100 µM). GABA-evoked changes in [K+]o in SP and SR and [Cl-]o in SP were depressed by >=90%, and of [Cl-]o in SR by 50%; N2-evoked changes in [K+]o in SP and SR were decreased by 70% and those of [Cl-]o by 50%. BMI blocked Δ [Na+]o with both GABA and N2 by 20-30%. It is concluded that during early anoxia: (i) accumulation of GABA and activation of GABAA receptors may contribute to the ion changes and play a significant role, and (ii) responses in the dendritic (SR) regions are greater than and (or) differ from those in the somal (SP) layers. A large component of the [K+]o increase may involve a GABA-evoked Ca2+-activated gk, secondary to [Ca2+]i increase. A major part of [Cl-]o changes may arise from GABA-induced gCl and glial efflux, with strong stimulation of active outward transport and anion exchange at SP, and inward Na+/K+/2Cl- co-transport at SR. Na+ influx is attributable mainly to Na+-dependent transmitter uptake, with only a small amount related to GABAA receptor activation. Although the release and (or) accumulation of GABA during anoxia might be viewed as potentially protectant, the ultimate role may more likely be an important contribution to toxicity and delayed neuronal death. Key words: brain slices, ion-selective microelectrodes, stratum pyramidale, stratum radiatum, bicuculline methiodide, extracellular space shrinkage.

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