Intrapleural liquid flow down a gravity-dependent hydraulic pressure gradient

1988 ◽  
Vol 64 (2) ◽  
pp. 577-584 ◽  
Author(s):  
G. Miserocchi ◽  
D. Negrini ◽  
M. Pistolesi ◽  
C. R. Bellina ◽  
M. C. Gilardi ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Time Course ◽  
Sudden Change ◽  
Vertical Movement ◽  
Rate Of Change ◽  
Large Field ◽  
Liquid Volume ◽  
Hydraulic Pressure ◽  
Albumin Clearance ◽  
Turning Maneuver

We studied the vertical movement of 2 mg technetium-labeled albumin injected intrapleurally in 0.5 ml saline (15% of pleural liquid volume) in eight spontaneously breathing anesthetized dogs subject to a sudden change in posture (prone to supine or vice versa). The albumin movements were evaluated through a large field gamma camera placed laterally to the animal and detecting total (AT) and regional activities from two superimposed equal areas (At and Ab, top and bottom, respectively). The At/Ab ratio decreased from 2.1 to 1.3 in four animals up to 20 min from the change in posture and from 0.9 to 0.5 in four more animals studied from 50 to 90 min from turning maneuver. The rate of change in At and Ab was similar in the two groups of animals and unaffected by the acquisition posture. AT decreased by 7.7 and 3.5% for the two groups, respectively, reflecting albumin clearance from the pleural space. The opposite time course of regional activities and the independence of their rate of change of the At/Ab ratio and of the animal posture suggest a top-to-bottom albumin transfer occurring through a bulk flow of liquid estimated at 0.006 ml.kg-1.h-1. The data are consistent with a measured vertical pleural liquid pressure gradient that does not reflect a hydrostatic condition.

Fast-phase transvascular fluid flux and the Fahraeus effect

1987 ◽  
Vol 62 (4) ◽  
pp. 1513-1520 ◽  
Author(s):  
W. N. Richardson ◽  
D. Bilan ◽  
M. Hoppensack ◽  
L. Oppenheimer
Keyword(s):  
Mechanical Properties ◽  
Slow Rate ◽  
Time Course ◽  
Rate Of Change ◽  
Distributed Model ◽  
Slow Phase ◽  
Fluid Flux ◽  
Fast Phase ◽  
Constant Rate ◽  
Fahraeus Effect

Transvascular fluid flux was induced in six isolated blood-perfused canine lobes by increasing and decreasing hydrostatic inflow pressure (Pi). Fluid flux was followed against the change in concentration of an impermeable tracer (Blue Dextran) measured directly with a colorimetric device. The time course of fluid flux was biphasic with an initial fast transient followed by a slow phase. Hematocrit changes unrelated to fluid flux occurred due to the Fahraeus effect, and their contribution to the total color signal was subtracted to determine the rate of fast fluid flux (Qf). Qf was related to Pi to derive fast-phase conductance (Kf). Slow-phase Kf was calculated from the constant rate of change of lobe weight. For a mean change in Pi of 7 cmH2O, 40% of the color signal was due to fluid flux. Fast- and slow-phase Kf's were 0.86 +/- 0.15 and 0.27 +/- 0.05 ml X min-1. cmH2O–1 X 100 g dry wt-1. The fast-phase Kf is smaller than that reported for plasma-perfused lobes. Possible explanations discussed are the nature of the perfusate, the mechanical properties of the interstitium, and the slow rate of rise of the driving pressure at the filtration site on the basis of a distributed model of pulmonary vascular compliance.

scholarly journals Electromyography of the Respiratory Muscles and Gill Water Flow in the Dragonet

1968 ◽  
Vol 49 (3) ◽  
pp. 583-602
Author(s):  
G. M. HUGHES ◽  
C. M. BALLINTIJN
Keyword(s):  
Hydrostatic Pressure ◽  
Stroke Volume ◽  
Pressure Gradient ◽  
Time Course ◽  
Respiratory Muscles ◽  
Adverse Pressure Gradient ◽  
Pressure Head ◽  
Volume Flow ◽  
Frequency Change ◽  
Hydrostatic Pressure Gradient

1. An account is given of the main skeletal elements and muscles involved in the respiratory movements of the dragonet, Callionymus lyra. 2. Using electromyographic techniques it has been shown that the muscles chiefly involved in rapid ejection of water out of the opercular slit are the adductor mandibulae, protractor hyoideus, and hyohyoideus. During the expansion phase of the cycle, which is about six times the duration of the contraction phase, the levator hyomandibulae and sternohyoideus are active, though in some cases the latter only comes in at higher levels of pumping. 3. Changes in volume flow across the gills have been produced by either (a) altering the hydrostatic pressure gradient (Δp) across the system, or (b) altering the oxygen or carbon dioxide content of the water inspired by the fish. With (a), the volume flow decreases linearly at a rate of about 30 ml./min./cm. H2O static pressure head until an inflexion is reached in the curve at which rate of flow decreases and is normally when Δp is zero. That the relative increase in flow rate with negative Δp's is due to the activity of the fish pumping against the adverse pressure gradient has been confirmed by electromyogram recordings during such experiments. With (b), it was possible to demonstrate a clear relationship between stroke volume and the level of electrical activity as measured by the height of the integrated electromyogram. The integrated EMG increases more than linearly with increasing stroke volume during PO2 changes, but this relationship seems to be more nearly linear during changes in CO2 concentration. 4. The respiratory frequency is scarcely affected by changes in flow produced by altering the hydrostatic pressure gradient, but following a decrease in PO2 or an increase in CO2 there is a significant fall in frequency which accompanies the increased electromyogram. The time course of these changes during recovery from a decrease in PO2 or an increase in PCOCO2 suggests that the gas tensions of the inspired water are detected by receptors on the gills and thus influence the electromyogram activity, but the frequency change observed is due to a change in the blood affecting receptors in the brain.

Time course of changes in albumin synthesis and mRNA in diabetic and insulin-treated diabetic rats

1985 ◽  
Vol 248 (6) ◽  
pp. E656-E663 ◽  
Author(s):  
D. E. Peavy ◽  
J. M. Taylor ◽  
L. S. Jefferson
Keyword(s):  
Total Protein ◽  
Time Course ◽  
Insulin Treatment ◽  
Relative Rate ◽  
Cdna Probe ◽  
Diabetic Rats ◽  
Rate Of Change ◽  
Albumin Synthesis ◽  
Albumin Mrna

Albumin synthesis in rat liver in vivo decreased from 12.7 to 2.2% of total protein synthesis during the first 3 days after the induction of diabetes and then remained relatively constant at this depressed rate for another 3 days. Insulin treatment begun on the 3rd day after the induction of diabetes restored albumin synthesis to control values within 3 days. Hybridization of total polyadenylate-containing RNA with a specific albumin cDNA probe revealed a close correspondence between the relative abundance of albumin mRNA and the relative rate of albumin synthesis after induction of diabetes and in response to insulin treatment. The apparent half-life of albumin mRNA, based on the rate of change of the message from one steady-state level to another, was approximately 22 h in both diabetic and insulin-treated diabetic rats. Diabetes of 3-day duration had no effect on the average sizes of total and albumin-synthesizing polysomes or on the ribosomal half-transit time for total protein and albumin. However, the number of albumin-synthesizing polysomes decreased as a result of diabetes to approximately one-third the number found in control livers. Taken together the results indicate that albumin synthesis was regulated by the availability of albumin mRNA and not by alterations in degradation, sequestration, or translation of message.

Study on Liquid Volume Measurement Based on Wireless Transmission and Hydraulic Sensors

2012 ◽  
Vol 263-266 ◽  
pp. 392-397
Author(s):  
Jie Luo ◽  
Yun Hui Wang ◽  
Qian Wen Zhao ◽  
Hui Guo ◽  
Fei She
Keyword(s):  
Measurement System ◽  
Measurement Method ◽  
Pressure Sensors ◽  
Volume Measurement ◽  
Wireless Transmission ◽  
Liquid Volume ◽  
Hydraulic Pressure ◽  
General Packet Radio Service ◽  
Service Module ◽  
Wireless Measurement

Based on hydraulic sensors and wireless transmission, a new wireless measurement method of liquid volume in a tank is introduced. This measurement system includes hydraulic pressure sensors, A/D converter, GPRS (General Packet Radio Service) module and upper monitor in a computer, from which the users can get aware of the liquid volume in a tank at any time. The measurement system has been built，calibrated and tested. The experimental results show that this measurement system works well and the measurement error is less than 1%.

Gating currents in the node of Ranvier: voltage and time dependence

1975 ◽  
Vol 270 (908) ◽  
pp. 483-492 ◽  
Keyword(s):  
Membrane Potential ◽  
Time Constant ◽  
Time Course ◽  
Voltage Dependence ◽  
Sudden Change ◽  
Node Of Ranvier ◽  
Ionic Currents ◽  
Gating Currents ◽  
Myelinated Nerve ◽  
Sodium Conductance

Like the axolemma of the giant nerve fibre of the squid, the nodal membrane of frog myelinated nerve fibres after blocking transmembrane ionic currents exhibits asymmetrical displacement currents during and after hyperpolarizing and depolarizing voltage clamp pulses of equal size. The steady-state distribution of charges as a function of membrane potential is consistent with Boltzmann’s law (midpoint potential —33.7 mV; saturation value 17200 charges/(μm 2 ). The time course of the asymmetry current and the voltage dependence of its time constant are consistent with the notion that due to a sudden change in membrane potential the charges undergo a first order transition between two configurations. Size and voltage dependence of the time constant are similar to those of the activation of the sodium conductance assuming m 2 h kinetics, The results suggest the presence of ten times more sodium channels (5000/μm2) in the node of Ranvier than in the squid giant axon with similar sodium conductance per channel (2-3 pS),

[Ca2+]i and contraction of ear artery in response to rapid stimulation by NE: measurements with quin2 and fura-2

1989 ◽  
Vol 257 (2) ◽  
pp. H649-H657 ◽  
Author(s):  
M. Vonderlage ◽  
V. Schreiner
Keyword(s):  
Time Course ◽  
Rate Of Change ◽  
Maximal Response ◽  
Slow Increase ◽  
Fura 2 ◽  
Ear Artery ◽  
Rabbit Ear ◽  
Pressure Development ◽  
Rapid Stimulation ◽  
The Relationship

The relationship between the quin2 and fura-2 fluorescence and isovolumetric contraction of smooth muscle cells of everted segments of the rabbit ear artery in response to rapid stimulation by norepinephrine (NE) was investigated. The resting level measured with quin2 (91 +/- 10 nM, n = 4) and with fura-2 (87 +/- 9 nM, n = 5) did not significantly differ. After addition of NE, an initial slow increase (ISI) in emission could be measured with quin2; however, Ca2+ buffering by this indicator slowed the increase of intracellular Ca2+ concentration ([Ca2+]i) and of contraction. When using fura-2, no ISI could be measured, but this indicator did not significantly interfere with the normal time course of contraction. Maximal response in [Ca2+]i to 1 microM NE was 424 +/- 30 nM (with quin2) and 337 +/- 46 nM (with fura-2). Mechanical latency depended not only on the onset but also on the initial rate of the increase in [Ca2+]i. Contractile response was quickest around 0.1 s after the onset of the fura-2 signal. During its rising phase, the rate of pressure development was linearly correlated with the -log molar Ca2+ concentration (pCa) of the cytoplasm (pCai), whereas during slow relaxation, pressure was linearly related to the pCai. These results suggest that contraction may depend not only on [Ca2+]i but also depend on its rate of change.

Time Course of Pressure Gradient Response After First Alcohol Septal Ablation for Obstructive Hypertrophic Cardiomyopathy

2006 ◽  
Vol 97 (10) ◽  
pp. 1511-1514 ◽  
Author(s):  
Danita M. Yoerger ◽  
Michael H. Picard ◽  
Igor F. Palacios ◽  
Gus J. Vlahakes ◽  
Patricia A. Lowry ◽  
...  
Keyword(s):  
Hypertrophic Cardiomyopathy ◽  
Pressure Gradient ◽  
Time Course ◽  
Alcohol Septal Ablation ◽  
Obstructive Hypertrophic Cardiomyopathy

Evaluation of human diaphragm fatigue

1982 ◽  
Vol 53 (5) ◽  
pp. 1196-1206 ◽  
Author(s):  
F. Bellemare ◽  
A. Grassino
Keyword(s):  
Frequency Band ◽  
Time Course ◽  
Low Frequency ◽  
Normal Subjects ◽  
Rate Of Change ◽  
Center Frequency ◽  
Cycle Duration ◽  
Transdiaphragmatic Pressure ◽  
Inspiratory Resistance ◽  
Rate Of Decay

The time course of the frequency content of the electromyogram (EMG) was studied in the diaphragm of five normal subjects breathing through high inspiratory resistance. The ratio between the power content of a high-frequency band (150– Hz) (H) and a low-frequency band (20http://hwmaint.jap.physiology.org/cgi/content/abstract/53/4/99240 Hz) (L) was calculated for each breath and expressed as a fraction of the initial breath. The rate of decay (when existent) was exponential and was quantified by measuring the time constant of decay of H/L (TF). Runs were held sustaining the ratio of inspiratory time to total breath cycle duration (TI/Ttot) from 0.2 to 1 and transdiaphragmatic pressure (Pdi) of 0.1http://hwmaint.jap.physiology.org/cgi/content/abstract/53/4/992 0.8 of Pdimax. It was found that TF was monotonically related to Pdi X TI/Ttot, following a hyperbolic relationship. TF was compared with velocity of conduction of the myopotentials and with center frequency of the EMG power spectrum and found to follow similar trends showing, however, different absolute rate of change. The values of TF were found to be directly related to the time a given pattern could be sustained (Tlim). It is concluded that EMG changes and Tlim are related and are expressions of the metabolic changes induced by the contraction pattern.

scholarly journals The pentose phosphate pathway in rabbit liver. Studies on the metabolic sequence and quantitative role of the pentose phosphate cycle by using a system in situ

1971 ◽  
Vol 123 (5) ◽  
pp. 923-943 ◽  
Author(s):  
J. F. Williams ◽  
K. G. Rienits ◽  
P. J. Schofield ◽  
M. G. Clark
Keyword(s):  
Pentose Phosphate Pathway ◽  
Time Course ◽  
Specific Radioactivity ◽  
Glucose Production ◽  
Pentose Phosphate ◽  
Rate Of Change ◽  
Exchange Reactions ◽  
High Concentration ◽  
Pentose Phosphate Cycle ◽  
Definition Of

1. The reactions of the pentose phosphate cycle were investigated by the intraportal infusion of specifically labelled [14C]glucose or [14C]ribose into the liver of the anaesthetized rabbit. The sugars were confined in the liver by haemostasis and metabolism was allowed to proceed for periods up to 5min. Metabolism was assessed by measuring the rate of change of the specific radioactivity of CO2, the carbon atoms of glucose 6-phosphate, fructose 6-phosphate and tissue glucose. 2. The quotient oxidation of [1-14C]glucose/oxidation of [6-14C]glucose as measured by the incorporation into respiratory CO2 was greater than 1.0 during most of the time-course and increased to a maximum of 3.1 but was found to decrease markedly upon application of a glucose load. 3. The estimate of the pentose phosphate cycle from C-1/C-2 ratios generally increased during the time-course, whereas the estimate of the pentose phosphate cycle from C-3/C-2 ratios varied depending on whether the ratios were measured in glucose or hexose 6-phosphates. 4. The distribution of 14C in hexose 6-phosphate after the metabolism of [1-14C]ribose showed that 65–95% of the label was in C-1 and was concluded to have been the result of a rapidly acting transketolase exchange reaction. 5. Transaldolase exchange reactions catalysed extensive transfer of 14C from [2-14C]glucose into C-5 of the hexose 6-phosphates during the entire time-course. The high concentration of label in C-4, C-5 and C-6 of the hexose 6-phosphates was not seen in tissue glucose in spite of an unchanging rate of glucose production during the time-course. 6. It is concluded that the reaction sequences catalysed by the pentose phosphate pathway enzymes do not constitute a formal metabolic cycle in intact liver, neither do they allow the definition of a fixed stoicheiometry for the dissimilation of glucose.

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