Gas distribution in a two-compartment model during volume or pressure ventilation: Role of elastic elements

Approximately four decades ago, the countercurrent theory became influential in studies on the concentrating process in the mammalian kidney. The theory successfully represented the concentrating process in the outer medulla, but the problem of the concentrating mechanism in the inner medulla, as defined by Homer Smith has remained essentially intractable. In a recent comprehensive review by Knepper and coworkers of various theories and models, attention was refocused on the possible role of hyaluronate (HA) in the inner medullary concentrating process. The authors proposed a hypothesis that HA can convert hydrostatic pressure to concentrating work. Here, we briefly survey the earlier ideas on the role imputed to HA and present a new hypothesis which is different from that of Knepper and coworkers. We estimate that the hydrostatic pressures available in the inner medulla can account only for a very small fraction of the concentrating work. We hypothesize that the role of HA is tied up with extravasated plasma albumin and suggest that owing to the property of HA solutions to exclude other macromolecules, extravasated plasma albumin and HA constitute two fluid compartments in the interstitium in the inner medulla. In this proposed two-compartment model, the Gibbs-Donnan distribution influences the movement of ions and water between the HA and the extravasated albumin compartment. To relate the hypothetical role of HA to the concentrating process, we briefly describe new results obtained by other investigators on the accumulation of urea in the inner medulla. This subject has been critically reviewed recently by Yang & Bankir. Many processes have been identified as contributing to the concentrating process in the mammalian inner medulla. We speculate that among these many processes, the primary responsibility for the final concentration of the excreted urine may be portioned out differently in different mammalian species.

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On Firing Rate Estimation for Dependent Interspike Intervals

Neural Computation ◽

10.1162/neco_a_00709 ◽

2015 ◽

Vol 27 (3) ◽

pp. 699-724 ◽

Cited By ~ 2

Author(s):

Elisa Benedetto ◽

Federico Polito ◽

Laura Sacerdote

Keyword(s):

Firing Rate ◽

Conditional Distribution ◽

Compartment Model ◽

Nonparametric Estimator ◽

Interspike Intervals ◽

Instantaneous Rate ◽

Two Compartment Model ◽

Consistency Properties

If interspike intervals are dependent, the instantaneous firing rate does not catch important features of spike trains. In this case, the conditional instantaneous rate plays the role of the instantaneous firing rate for the case of samples of independent interspike intervals. If the conditional distribution of the interspikes intervals (ISIs) is unknown, it becomes difficult to evaluate the conditional firing rate. We propose a nonparametric estimator for the conditional instantaneous firing rate for Markov, stationary, and ergodic ISIs. An algorithm to check the reliability of the proposed estimator is introduced, and its consistency properties are proved. The method is applied to data obtained from a stochastic two-compartment model and to in vitro experimental data.

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The role of relative membrane capacitance and time delay in cerebellar Purkinje cells

Biomedical Engineering / Biomedizinische Technik ◽

10.1515/bmt-2015-0212 ◽

2017 ◽

Vol 62 (5) ◽

Author(s):

Jing Wang ◽

Shenquan Liu ◽

Bo Lu ◽

Yanjun Zeng

Keyword(s):

Time Delay ◽

Purkinje Cells ◽

Compartment Model ◽

Signal Propagation ◽

Electrical Signal ◽

Membrane Capacitance ◽

Neuronal Firing ◽

Two Compartment Model ◽

Cerebellar Purkinje Cells

AbstractThe membrane capacitance of a neuron can influence the synaptic efficacy and the speed of electrical signal propagation. Exploring the role of membrane capacitance will help facilitate a deeper understanding of the electrical properties of neurons. Thus, in this paper, we investigated the neuronal firing behaviors of a two-compartment model in Purkinje cells. We evaluated the influence of membrane capacitance under two different circumstances: in the absence of time delay and in the presence of time delay. Firstly, we separately studied the influence of somatic membrane capacitance

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Role of ligandin in transfer of bilirubin from plasma into liver.

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1979.236.6.e638 ◽

1979 ◽

Vol 236 (6) ◽

pp. E638

Author(s):

A W Wolkoff ◽

C A Goresky ◽

J Sellin ◽

Z Gatmaitan ◽

I M Arias

Keyword(s):

Compartment Model ◽

Volume Of Distribution ◽

Multiple Indicator Dilution ◽

Two Compartment Model ◽

Net Uptake ◽

Group A ◽

Multiple Indicator ◽

Intracellular Binding ◽

Rat Livers

Multiple-indicator dilution studies of labeled bilirubin uptake were carried out on isolated perfused rat livers with variable ligandin concentrations (from normal and thyroidectomized animals with and without phenobarbital pretreatment). Ligandin concentrations, measured immunologically, increased 25% after thyroidectomy and approximately doubled after phenobarbital pretreatment but decreased to normal during perfusion in the thyroidectomized nonpretreated group. A distributed two-compartment model was fitted to the dilution data and estimates of influx, efflux, and sequestration coefficients were obtained. Influx and sequestration coefficients did not vary significantly between the groups. Efflux coefficients were significantly smaller (P less than 0.001), and hepatic ligandin concentrations were significantly larger (p less than 0.001) in phenobarbital-treated rats than in other groups. The efflux coefficient varied inversely with ligandin concentration and the volume of distribution in tissue, as perceived from the plasma space, increased in proportion to the concentration of ligandin. The increased net uptake of tracer bilirubin by the liver of phenobarbital-pretreated animals is due to decreased tracer efflux secondary to the increase in intracellular binding of bilirubin by ligandin.

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Two-Compartment Model of Cholesterol Kinetics for Establishment of Treatment Strategy of LDL Apheresis in Nephrotic Hypercholesterolemia

Blood Purification ◽

10.1159/000170180 ◽

1994 ◽

Vol 12 (6) ◽

pp. 317-326 ◽

Cited By ~ 4

Author(s):

Masatomo Yashiro ◽

Eri Muso ◽

Munehiro Matsushima ◽

Ryoichi Nagura ◽

Kenji Sawanishi ◽

...

Keyword(s):

Treatment Strategy ◽

Compartment Model ◽

Ldl Apheresis ◽

Two Compartment Model

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Clearance and Non-Invasive Determination of the Hepatic Extraction of Indocyanine Green in Baboons and Man

Clinical Science ◽

10.1042/cs0640207 ◽

1983 ◽

Vol 64 (2) ◽

pp. 207-212 ◽

Cited By ~ 64

Author(s):

S. L. Grainger ◽

P. W. N. Keeling ◽

I. M. H. Brown ◽

J. H. Marigold ◽

R. P. H. Thompson

Keyword(s):

Indocyanine Green ◽

Accurate Determination ◽

Liver Blood Flow ◽

Compartment Model ◽

Hepatic Extraction ◽

Non Invasive ◽

Two Compartment Model ◽

Hepatic Extraction Ratio ◽

Plasma Disappearance Curve

1. The disposition of an intravenous bolus of indocyanine green (ICG) has been studied in healthy man and baboons using a novel analysis of a two compartment pharmacokinetic model. 2. This analysis enabled the hepatic extraction ratio (ER) of dye to be determined solely from the plasma disappearance curve, and the ER determined did not differ from that measured by hepatic vein catheterization. 3. When compared with clearance measured at steady state, the two compartment model gave a significantly more accurate determination of plasma clearance than did the conventional one compartment model. 4. It is concluded that, in health, liver blood flow may be calculated accurately and noninvasively after a single intravenous injection of ICG.

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