scholarly journals Evaluation of gravimetric techniques to estimate the microvascular filtration coefficient

2011 ◽  
Vol 300 (6) ◽  
pp. R1426-R1436 ◽  
Author(s):  
R. M. Dongaonkar ◽  
G. A. Laine ◽  
R. H. Stewart ◽  
C. M. Quick
Keyword(s):  
Steady State ◽  
Interstitial Fluid ◽  
Lymphatic Vessels ◽  
Analytical Framework ◽  
Filtration Coefficient ◽  
Balance Model ◽  
Rat Intestine ◽  
Transient Technique ◽  
Gravimetric Data ◽  
Reported Data

Microvascular permeability to water is characterized by the microvascular filtration coefficient ( K f). Conventional gravimetric techniques to estimate K f rely on data obtained from either transient or steady-state increases in organ weight in response to increases in microvascular pressure. Both techniques result in considerably different estimates and neither account for interstitial fluid storage and lymphatic return. We therefore developed a theoretical framework to evaluate K f estimation techniques by 1) comparing conventional techniques to a novel technique that includes effects of interstitial fluid storage and lymphatic return, 2) evaluating the ability of conventional techniques to reproduce K f from simulated gravimetric data generated by a realistic interstitial fluid balance model, 3) analyzing new data collected from rat intestine, and 4) analyzing previously reported data. These approaches revealed that the steady-state gravimetric technique yields estimates that are not directly related to K f and are in some cases directly proportional to interstitial compliance. However, the transient gravimetric technique yields accurate estimates in some organs, because the typical experimental duration minimizes the effects of interstitial fluid storage and lymphatic return. Furthermore, our analytical framework reveals that the supposed requirement of tying off all draining lymphatic vessels for the transient technique is unnecessary. Finally, our numerical simulations indicate that our comprehensive technique accurately reproduces the value of K f in all organs, is not confounded by interstitial storage and lymphatic return, and provides corroboration of the estimate from the transient technique.

scholarly journals FACTORS INFLUENCING THE INTERMITTENT PASSAGE OF LOCKE'S SOLUTION INTO LIVING SKIN

1941 ◽  
Vol 73 (1) ◽  
pp. 85-108 ◽  
Author(s):  
Philip D. McMaster
Keyword(s):  
Connective Tissue ◽  
Blood Vessels ◽  
Atmospheric Pressure ◽  
Interstitial Fluid ◽  
Lymphatic Vessels ◽  
Intermittent Flow ◽  
Venous Obstruction ◽  
Factors Influencing ◽  
Interstitial Connective Tissue ◽  
Living Mouse

Minute amounts of Locke's or Tyrode's solution have been brought into contact with the interstitial connective tissue of the skin of the living mouse, at atmospheric pressure, in such a manner that the blood or lymphatic vessels are not entered directly. Under such circumstances these absorbable fluids enter the tissue spontaneously. Entrance is strikingly intermittent, not continuous, and so too when very slight pressures are brought to bear on the fluids (1). Hyperemia of the tissues, with accompanying dilatation of the blood vessels, increases the entrance of fluids at atmospheric pressure but it is still intermittent. By contrast, venous obstruction leads to intermittent backflow into the apparatus, but reflex hyperemia, following release of the obstruction, is attended by an increase of flow into the tissues in spite of the great reactive dilatation of vessels. The inflow is also intermittent. If the skin is deprived of circulation, fluid does not enter it at all at atmospheric pressure, though it moves in regularly and continuously if slight pressure is put upon it. Edema-forming fluids, described in the text, also enter in a continuous manner when forced into the skin of either living or dead animals. So too do serum and sperm oil. The findings indicate that the passage of interstitial fluid into the blood vessels may be intermittent under normal circumstances and its escape from them as well. The observed occurrence of intermittent flow in the blood vessels of several tissues (9, 15–25) will go far to account for the intermittent entrance of fluid into the skin.

A transient technique for seismograph calibration

1962 ◽  
Vol 52 (4) ◽  
pp. 767-779
Author(s):  
A. F. Espinosa ◽  
G. H. Sutton ◽  
H. J. Miller
Keyword(s):  
Fourier Transform ◽  
Steady State ◽  
Input Pulse ◽  
Electrical Signal ◽  
Experimental Results ◽  
Response Curves ◽  
Amplitude Response ◽  
Transient Technique ◽  
Absolute Amplitude ◽  
The Fourier Transform

abstract A transient technique for seismograph calibration was developed and tested by a variety of methods. In the application of this technique a known transient in the form of an electrical signal is injected, through (a) a Willmore-type calibration bridge or (b) an independent coil, into the seismometer and the corresponding output transient of the system is recorded. The ratio of the Fourier transform of this transient to that of the input pulse yields phase and relative amplitude response of the seismograph as a function of period. Absolute amplitude response may be calculated if two easily determined constants of the seismometer are known. This technique makes practical the daily calibration of continuously-recording seismographs without disturbing the instruments more than a very few minutes. The transient technique was tested and proven satisfactory with results of more conventional steady-state methods, using both digital and analog analyses of the output transients. A variety of output transients corresponding to various theoretical response curves has been calculated for two standard input transients. By comparison of the calculated output transients with experimental results it is possible to obtain the response of the instrument with considerable precision quickly and without computation.

scholarly journals Climate, the Antarctic ice sheet and ground heat flux

1995 ◽  
Vol 21 ◽  
pp. 144-148
Author(s):  
Garth W. Paltridge ◽  
Christopher M. Zweck
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Climate Models ◽  
Global Climate ◽  
Ice Sheet ◽  
Global Climate Models ◽  
Balance Model ◽  
Antarctic Ice Sheet ◽  
Ground Heat Flux ◽  
The Antarctic

A simple steady-state energy and mass-balance model of the Antarctic ice sheet is developed. Basically it is a set of two equations with two unknowns of steady-state height h and potential basal temperature Tb. Tb determines whether, and to what extent, there is liquid water at the base of the ice which in turn affects the values of h and Tb. Simultaneous changes of sea-level temperature and precipitation (changes related to each other as might be expected from global climate models) indicate a maximum in the field of possible steady-state ice volumes which may not be far from the presently observed conditions. The possibility of cyclical variation in ground heat flux associated with convection of water and heat in the continental crust is discussed. The mechanism might be capable of generating cycles of ice-sheet volume with relatively short periods similar to those of Milankovitch forcing.

A model of unsteady-state transvascular fluid and protein transport in the lung

1984 ◽  
Vol 56 (5) ◽  
pp. 1389-1402 ◽  
Author(s):  
R. J. Roselli ◽  
R. E. Parker ◽  
T. R. Harris
Keyword(s):  
Steady State ◽  
Interstitial Fluid ◽  
Transport Theory ◽  
Fluid Pressure ◽  
Water Volume ◽  
Free Fluid ◽  
Base Line ◽  
Unsteady State ◽  
Total Change ◽  
Organ Systems

Models of steady-state fluid and solute transport in the microcirculation are used primarily to characterize filtration and permeability properties of the transport barrier. Important transient relationships, such as the rate of fluid accumulation in the tissue, cannot be predicted with steady-state models. In this paper we present three simple models of unsteady-state fluid and protein exchange between blood plasma and interstitial fluid. The first treats the interstitium as a homogeneous well-mixed compliant compartment, the second includes an interstitial gel, and the third allows for both gel and free fluid in the interstitium. Because we are primarily interested in lung transvascular exchange we used the multiple-pore model and pore sizes described by Harris and Roselli (J. Appl. Physiol.: Respirat . Environ. Exercise Physiol. 50: 1–14, 1981) to characterize the microvascular barrier. However, the unsteady-state transport theory presented here should apply to other organ systems and can be used with different conceptual models of the blood-lymph barrier. For a step increase in microvascular pressure we found good agreement between theoretical and experimental lymph flow and lymph concentrations in the sheep lung when the following parameter ranges were used: base-line interstitial volume, 150–190 ml; interstitial compliance, 7–10 ml/Torr; initial interstitial fluid pressure, -1 Torr; pressure in initial lymphatics, -5 to -6 Torr; and conductivity of the interstitium and lymphatic barrier, 4.25 X 10(-4) ml X s-1 X Torr-1. Based on these values the model predicts 50% of the total change in interstitial water volume occurs in the first 45 min after a step change in microvascular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Interstitial Fluid and Lymph Formation and Transport: Physiological Regulation and Roles in Inflammation and Cancer

2012 ◽  
Vol 92 (3) ◽  
pp. 1005-1060 ◽  
Author(s):  
Helge Wiig ◽  
Melody A. Swartz
Keyword(s):  
Interstitial Fluid ◽  
Cell Function ◽  
Biological Effects ◽  
Lymphatic Vessels ◽  
Peripheral Tolerance ◽  
Cellular Microenvironment ◽  
Physiological Regulation ◽  
Functional Implications ◽  
Biological Aspects ◽  
Lymph Fluid

The interstitium describes the fluid, proteins, solutes, and the extracellular matrix (ECM) that comprise the cellular microenvironment in tissues. Its alterations are fundamental to changes in cell function in inflammation, pathogenesis, and cancer. Interstitial fluid (IF) is created by transcapillary filtration and cleared by lymphatic vessels. Herein we discuss the biophysical, biomechanical, and functional implications of IF in normal and pathological tissue states from both fluid balance and cell function perspectives. We also discuss analysis methods to access IF, which enables quantification of the cellular microenvironment; such methods have demonstrated, for example, that there can be dramatic gradients from tissue to plasma during inflammation and that tumor IF is hypoxic and acidic compared with subcutaneous IF and plasma. Accumulated recent data show that IF and its convection through the interstitium and delivery to the lymph nodes have many and diverse biological effects, including in ECM reorganization, cell migration, and capillary morphogenesis as well as in immunity and peripheral tolerance. This review integrates the biophysical, biomechanical, and biological aspects of interstitial and lymph fluid and its transport in tissue physiology, pathophysiology, and immune regulation.

scholarly journals Lymph-migrating, tissue-derived dendritic cells are minor constituents within steady-state lymph nodes

2008 ◽  
Vol 205 (12) ◽  
pp. 2839-2850 ◽  
Author(s):  
Claudia Jakubzick ◽  
Milena Bogunovic ◽  
Anthony J. Bonito ◽  
Emma L. Kuan ◽  
Miriam Merad ◽  
...  
Keyword(s):  
Dendritic Cells ◽  
Lymph Node ◽  
Steady State ◽  
Lymph Nodes ◽  
Lymphatic Vessels ◽  
Inflammatory Stimulus ◽  
Major Fraction ◽  
Reporter Mouse ◽  
Relationship Of ◽  
The Relationship

Observations that dendritic cells (DCs) constitutively enter afferent lymphatic vessels in many organs and that DCs in some tissues, such as the lung, turnover rapidly in the steady state have led to the concept that a major fraction of lymph node DCs are derived from migratory DCs that enter the lymph node through upstream afferent lymphatic vessels. We used the lysozyme M–Cre reporter mouse strain to assess the relationship of lymph node and nonlymphoid organ DCs. Our findings challenge the idea that a substantial proportion of lymph node DCs derive from the upstream tissue during homeostasis. Instead, our analysis suggests that nonlymphoid organ DCs comprise a major population of DCs within lymph nodes only after introduction of an inflammatory stimulus.

Estimating submarine groundwater discharges of the Bohai Sea, China using radium, hydrogen and oxygen isotopes and salinity

2020 ◽  
Author(s):  
Hailong Li ◽  
Xiaolang Zhang ◽  
Xuejing Wang ◽  
Kai Xiao ◽  
Yan Zhang ◽  
...  
Keyword(s):  
Steady State ◽  
Mass Balance ◽  
River Water ◽  
Bohai Sea ◽  
Balance Model ◽  
Laizhou Bay ◽  
Bohai Bay ◽  
Fresh Groundwater ◽  
The Bohai Sea ◽  
Submarine Groundwater

<p>With an area of about 77,000 km<sup>2</sup>, the Bohai Sea includes three bays: Laizhou Bay, Bohai Bay and Liaodong Bay. In this study, <sup>228</sup>Ra, δD, δ<sup>18</sup>O and salinity data were collected from surface seawater in the entire Bohai Sea, river water, and groundwater along its coastline in August 2017. Based on the spatial distributions of δD, δ<sup>18</sup>O, and salinity in surface water in the entire Bohai Sea and δD-salinity relations, the marine hydrological processes were investigated and the members of river water and groundwater for δD and δ<sup>18</sup>O were determined. The steady-state mass-balance models of δD, δ<sup>18</sup>O and salinity are given and used to estimate submarine fresh groundwater discharges and the flushing times of the entire Bohai Sea and its three bays. Based on the results of the flushing times, the steady-state mass-balance model of <sup>228</sup>Ra is used to estimate submarine groundwater discharges of the entire Bohai Sea and its three bays.</p>

scholarly journals The Solid Mechanics of Cancer and Strategies for Improved Therapy

2017 ◽  
Vol 139 (2) ◽  
Author(s):  
Triantafyllos Stylianopoulos
Keyword(s):  
Tumor Progression ◽  
Interstitial Fluid ◽  
Solid Mechanics ◽  
Fluid Pressure ◽  
Lymphatic Vessels ◽  
Chemotherapeutic Agents ◽  
Interstitial Fluid Pressure ◽  
Mathematical Framework ◽  
Solid Stress ◽  
Stress Levels

Tumor progression and response to treatment is determined in large part by the generation of mechanical stresses that stem from both the solid and the fluid phase of the tumor. Furthermore, elevated solid stress levels can regulate fluid stresses by compressing intratumoral blood and lymphatic vessels. Blood vessel compression reduces tumor perfusion, while compression of lymphatic vessels hinders the ability of the tumor to drain excessive fluid from its interstitial space contributing to the uniform elevation of the interstitial fluid pressure. Hypoperfusion and interstitial hypertension pose major barriers to the systemic administration of chemotherapeutic agents and nanomedicines to tumors, reducing treatment efficacies. Hypoperfusion can also create a hypoxic and acidic tumor microenvironment that promotes tumor progression and metastasis. Hence, alleviation of intratumoral solid stress levels can decompress tumor vessels and restore perfusion and interstitial fluid pressure. In this review, three major types of tissue level solid stresses involved in tumor growth, namely stress exerted externally on the tumor by the host tissue, swelling stress, and residual stress, are discussed separately and details are provided regarding their causes, magnitudes, and remedies. Subsequently, evidence of how stress-alleviating drugs could be used in combination with chemotherapy to improve treatment efficacy is presented, highlighting the potential of stress-alleviation strategies to enhance cancer therapy. Finally, a continuum-level, mathematical framework to incorporate these types of solid stress is outlined.

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