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.

Pre-steady-state phosphorylation and dephosphorylation of detergent-purified plasma-membrane Ca2+-ATPase

2002 ◽  
Vol 361 (2) ◽  
pp. 355-361 ◽  
Author(s):  
Luis M. BREDESTON ◽  
Alcides F. REGA
Keyword(s):  
Plasma Membrane ◽  
Steady State ◽  
Time Course ◽  
Slow Phase ◽  
Fast Phase ◽  
Lauryl Ether ◽  
Phosphorylation Reaction ◽  
Steady Level ◽  
Biexponential Kinetics ◽  
Acidic Phospholipids

Pre-steady-state phosphorylation and dephosphorylation of purified and phospholipid-depleted plasma-membrane Ca2+-ATPase (PMCA) solubilized in the detergent polyoxyethylene 10 lauryl ether were studied at 25°C. The time course of phosphorylation with ATP of the enzyme associated with Ca2+, probably the true phosphorylation reaction, showed a fast phase (kapp near 400s−1) followed by a slow phase (kapp = 23s−1). With asolectin or acidic phosphatidylinositol, the concentration of phosphoenzyme (EP) increased at as high a rate as before, passed through a maximum at 4ms and stabilized at a steady level that was approx. half that without lipids. Calmodulin (CaM) did not change the rate of the fast phase, accelerated the slow phase (kapp = 93s−1) and increased [EP] with small changes in the shape of the time course. Dephosphorylation was slow (kapp = 30s−1) and insensitive to CaM. Asolectin accelerated dephosphorylation, which followed biexponential kinetics with fast (kapp = 220s−1) and slow (kapp = 20s−1) components. CaM stimulated the fast component by nearly 50%. The results show that the behaviour of the PMCA is complex, and suggest that acidic phospholipids and CaM activate PMCA through different mechanisms. Acceleration of dephosphorylation seems relevant during activation of the PMCA by acidic phospholipids.

scholarly journals Two Temporal Phases of Light Adaptation in Retinal Rods

2002 ◽  
Vol 119 (2) ◽  
pp. 129-146 ◽  
Author(s):  
Peter D. Calvert ◽  
Victor I. Govardovskii ◽  
Vadim Y. Arshavsky ◽  
Clint L. Makino
Keyword(s):  
Binding Sites ◽  
Time Course ◽  
Light Adaptation ◽  
Dynamic Range ◽  
Continuous Illumination ◽  
Slow Phase ◽  
Fast Phase ◽  
Slow Adaptation ◽  
Adaptation Phase

Vertebrate rod photoreceptors adjust their sensitivity as they adapt during exposure to steady light. Light adaptation prevents the rod from saturating and significantly extends its dynamic range. We examined the time course of the onset of light adaptation in bullfrog rods and compared it with the projected onset of feedback reactions thought to underlie light adaptation on the molecular level. We found that adaptation developed in two distinct temporal phases: (1) a fast phase that operated within seconds after the onset of illumination, which is consistent with most previous reports of a 1–2-s time constant for the onset of adaptation; and (2) a slow phase that engaged over tens of seconds of continuous illumination. The fast phase desensitized the rods as much as 80-fold, and was observed at every light intensity tested. The slow phase was observed only at light intensities that suppressed more than half of the dark current. It provided an additional sensitivity loss of up to 40-fold before the rod saturated. Thus, rods achieved a total degree of adaptation of ∼3,000-fold. Although the fast adaptation is likely to originate from the well characterized Ca2+-dependent feedback mechanisms regulating the activities of several phototransduction cascade components, the molecular mechanism underlying slow adaptation is unclear. We tested the hypothesis that the slow adaptation phase is mediated by cGMP dissociation from noncatalytic binding sites on the cGMP phosphodiesterase, which has been shown to reduce the lifetime of activated phosphodiesterase in vitro. Although cGMP dissociated from the noncatalytic binding sites in intact rods with kinetics approximating that for the slow adaptation phase, this hypothesis was ruled out because the intensity of light required for cGMP dissociation far exceeded that required to evoke the slow phase. Other possible mechanisms are discussed.

Time course of end-expired carbon monoxide concentration is important in studies of cigarette smoking

1987 ◽  
Vol 73 (5) ◽  
pp. 553-555 ◽  
Author(s):  
G. Woodman ◽  
D. M. Wintoniuk ◽  
R. G. Taylor ◽  
S. W. Clarke
Keyword(s):  
Carbon Monoxide ◽  
Cigarette Smoking ◽  
Time Course ◽  
Slow Phase ◽  
Fast Phase ◽  
Carbon Monoxide Concentration ◽  
The Mean

1. Fifteen asymptomatic habitual smokers each smoked one of their usual cigarettes, not having smoked for 2 h. End-expired carbon monoxide concentration (EECO) was measured with an Ecolyzer 2000 series analyser before smoking (pre-S value), 1 min after finishing smoking (post-S value) and then at intervals up to 1 h. 2. The mean EECO boost (increase) over all subjects declined biphasically after smoking, with an initial fast phase from 1 to 5 min, and then a slow phase from 5 to 60 min. EECO fell by as much in the first 5 min as in the next hour. 3. Post-S EECO was related to pre-S EECO (r = 0.89, P < 0.001), but EECO boost was not related to pre-S (r = 0.00). EECO boost was unaffected by the sampling manoeuvre. 4. EECO measurements in epidemiological and smoking studies should not be made for at least 5 min after a cigarette is finished

Slow phase of transvascular fluid flux reviewed

1990 ◽  
Vol 69 (2) ◽  
pp. 456-464 ◽  
Author(s):  
B. J. Hancock ◽  
K. P. Landolfo ◽  
M. Hoppensack ◽  
L. Oppenheimer
Keyword(s):  
Weight Gain ◽  
Time Course ◽  
Slow Phase ◽  
Base Line ◽  
Volume Changes ◽  
Fluid Flux ◽  
Significant Component ◽  
Rapid Weight Gain ◽  
Vascular Volume ◽  
Colorimetric Measurements

In six circuit experiments using a clinical hemofiltration device, we validated a colorimetric technique to measure transvascular volume exchange (VE). In 12 isolated excised canine left lower lobes, continuous colorimetric measurements of VE correlated well with calculations of VE from changes in microhematocrit obtained simultaneously. We introduced step increases in microvascular hydrostatic pressure (Pc) of 9 +/- 4.8 (SD) cmH2O and followed the time course of weight and continuous hematocrit changes measured colorimetrically for 40 min, after which Pc was returned to base line, while measurements were continuously obtained. This procedure was repeated for an additional 30 min. VE was calculated from the hematocrit signals and compared with the time course of the weight signal. After increases in Pc, followed by a rapid weight gain, weight signals followed a slow exponential time course, whereas the calculated VE changed linearly. VE reflected approximately 60% of the slow weight gain. When Pc was decreased, weight signals decreased exponentially, whereas VE continued to increase linearly at a slower rate. These results suggest that a significant component of the slow weight signal represents slow vascular volume changes. Contrary to what the weight signal suggested, edema was never reabsorbed over the range of Pc measured.

scholarly journals The reaction of fully reduced cytochrome c oxidase with oxygen studied by flow-flash spectrophotometry at room temperature. Evidence for new pathways of electron transfer

1984 ◽  
Vol 218 (3) ◽  
pp. 913-921 ◽  
Author(s):  
B C Hill ◽  
C Greenwood
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Time Course ◽  
Visible Region ◽  
Slow Phase ◽  
Second Phase ◽  
Difference Spectra ◽  
Fast Phase ◽  
O2 Concentration ◽  
Sensitive Phase

Absorption changes during the O2 reaction of reduced bovine cytochrome c oxidase were investigated by the rapid-reaction technique of flow-flash spectrophotometry in the Soret, visible and near-i.r. spectral regions. New features in the time courses of absorption change were observed relative to the earlier findings reported by Greenwood & Gibson [(1967) J. Biol. Chem. 242, 1782-1787]. These new features arise in the Soret and near-i.r. regions and allow the reaction to be described at all wavelengths as a composite of three exponential processes. There is a rapid O2-sensitive phase detectable in the Soret and visible region. The second phase has a rate that is somewhat less dependent on O2 concentration than is the fastest phase rate and is detectable in all three spectral regions. The rate of the third phase is almost independent of the O2 concentration and is also detectable in all spectral regions. Analysis of the three phases gives their rates and absorption amplitudes. The fast phase reaches a rate of 2.5 × 10(4) s-1 at the highest O2 concentration available at 20 degrees C, whereas the phase of intermediate rate is limited at a value of 7 × 10(3) s-1 and the slow phase rate is limited at 700 s-1. The ratios of the kinetic difference spectra for the fast phase and the slow phase do not correspond to the spectra of the individual haem centres. A branched mechanism is advanced that is able to reconcile the kinetic and static difference spectra. This mechanism suggests that some of the cytochrome a is oxidized along with cytochrome a3 in the initial O2-sensitive phase. In addition, the model requires that CuA is oxidized heterogeneously. This fits with the complex time course of oxidation observed at 830 nm while retaining CuA as virtually the sole contributor to absorbance at this wavelength.

Recovery from dynamic exercise

1995 ◽  
Vol 268 (6) ◽  
pp. H2311-H2320 ◽  
Author(s):  
R. E. Williams ◽  
S. M. Horvath
Keyword(s):  
Exercise Intensity ◽  
Time Course ◽  
Minute Ventilation ◽  
Dynamic Exercise ◽  
Slow Phase ◽  
Co2 Uptake ◽  
Exercise Tests ◽  
Fast Phase ◽  
Baseline Levels ◽  
Minimal Information

Minimal information is available on the basic interactions within the metabolic and cardiovascular systems during recovery from exercise. Nine men participated in three experiments: one control and two cost-equivalent (52 liters O2) exercise tests of 30 (EX30) and 45 (EX45) min. Exercise intensities were adjusted accordingly. During recovery, all parameters reestablished baseline levels within 10 min, except for heart rate (30 min). Correlations for each parameter for EX30 and EX45 were obtained by evaluating each subject's exercise cost and recovery "payback." A split, two-factor analysis of variance was run separately on the "fast" (minutes 1-7) and "slow" (minutes 10-60) phases of recovery to determine if the time course of recovery was related to exercise intensity. It was concluded that for a work cost of approximately 300 kcal, 1) the slow phase of recovery was unaffected by the exercise intensity, 2) the fast phase of cardiovascular recovery was unaffected by exercise intensity while minute ventilation and O2 and CO2 uptake were affected, and 3) cardiac output and the ventilatory equivalents for O2 and CO2 correlated well between work cost and recovery payback.

scholarly journals METABOLIC CONTROL OF LUMINESCENCE IN ISOLATED PHOTOPHORES OF PORICHTHYS: EFFECTS OF GLUCOSE ON OXYGEN CONSUMPTION AND LUMINESCENCE

1993 ◽  
Vol 181 (1) ◽  
pp. 279-293
Author(s):  
J. Mallefet ◽  
F. Baguet
Keyword(s):  
Oxygen Consumption ◽  
Time Course ◽  
Light Emission ◽  
Potassium Cyanide ◽  
Cellular Respiration ◽  
Slow Phase ◽  
Light Reaction ◽  
Fast Phase ◽  
Light Production ◽  
Rate Of Oxygen Consumption

1. Basal oxygen consumption of isolated photophores from Porichthys sp. at rest, i.e. without light emission, increased significantly from 0.101+/− 0.021 nmol min-1 to 0.173+/−0.016 nmol min-1 in response to the addition of 5.5 mmol l-1 glucose. 2. 5.5 mmol l-1 glucose pretreatment modified the time course of the two phases of adrenaline-induced luminescence; an increase in oxygen consumption was observed during the fast phase of light production but a decrease occurred during the slow phase of luminescence. 3. Pretreatment of isolated photophores with 5.5 mmol l-1 glucose totally inhibited the light emission induced by 1 mmol l-1 potassium cyanide. With this treatment, the respiration rate decreased progressively and after 40 min reached a value not significantly different from zero. 4. Even after blockage of cellular respiration by cyanide, an increase in the rate of oxygen consumption was observed during the fast adrenaline- induced luminescence. 5. Glucose utilisation by glycolysis or by oxidative metabolism may provide energy to an inhibitory mechanism that maintains the photophores in a non- luminescent state. 6. We suggest that the oxygen consumed during the fast phase of adrenaline luminescence could represent the activity of an extramitochondrial oxidative pathway involved in the light reaction.

Possible cues driving context-specific adaptation of optocollic reflex in pigeons (Columba livia)

2012 ◽  
Vol 107 (2) ◽  
pp. 704-717 ◽  
Author(s):  
Henri Gioanni ◽  
Pierre-Paul Vidal
Keyword(s):  
Columba Livia ◽  
Motor Command ◽  
Slow Phase ◽  
Gaze Stabilization ◽  
Specific Adaptation ◽  
Body Vibration ◽  
Fast Phase ◽  
Context Specific ◽  
Context Cues

Context-specific adaptation (Shelhamer M, Clendaniel R. Neurosci Lett 332: 200–204, 2002) explains that reflexive responses can be maintained with different “calibrations” for different situations (contexts). Which context cues are crucial and how they combine to evoke context-specific adaptation is not fully understood. Gaze stabilization in birds is a nice model with which to tackle that question. Previous data showed that when pigeons ( Columba livia) were hung in a harness and subjected to a frontal airstream provoking a flying posture (“flying condition”), the working range of the optokinetic head response [optocollic reflex (OCR)] extended toward higher velocities compared with the “resting condition.” The present study was aimed at identifying which context cues are instrumental in recalibrating the OCR. We investigated that question by using vibrating stimuli delivered during the OCR provoked by rotating the visual surroundings at different velocities. The OCR gain increase and the boost of the fast phase velocity observed during the “flying condition” were mimicked by body vibration. On the other hand, the newly emerged relationship between the fast-phase and slow-phase velocities in the “flying condition” was mimicked by head vibration. Spinal cord lesion at the lumbosacral level decreased the effects of body vibration, whereas lesions of the lumbosacral apparatus had no effect. Our data suggest a major role of muscular proprioception in the context-specific adaptation of the stabilizing behavior, while the vestibular system could contribute to the context-specific adaptation of the orienting behavior. Participation of an efferent copy of the motor command driving the flight cannot be excluded.

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.

scholarly journals Mechanism of retraction of the trailing edge during fibroblast movement.

1981 ◽  
Vol 90 (1) ◽  
pp. 187-200 ◽  
Author(s):  
W T Chen
Keyword(s):  
Slow Component ◽  
Fast Component ◽  
Slow Phase ◽  
Main Body ◽  
Elastic Recoil ◽  
Forward Movement ◽  
Trailing Edge ◽  
Fast Phase ◽  
Focal Contacts

Retraction of the taut, trailing portion of a moving chick heart fibroblast in vitro is an abrupt dynamic process. Upon retraction, the fibroblast tail always ruptures, leaving a small amount of itself attached to the substratum by focal contacts. Time-lapse cinemicrography shows that retraction produces a sudden, massive movement of both surface and cytoplasmic material toward a cluster of focal contacts near the main body of the cell. The appearance of folds on the upper cell surface at this time and the absence of endocytotic vesicles are consistent with this forward movement. Retraction of the trailing edge, either occurring naturally or produced artificially with a microneedle, consists of an initial fast component followed and overlapped by a slow component. Upon artificial detachment in the presence of iodoacetate, dinitrophenol, and sodium fluoride, and at 4 degrees C, the slow component is strongly inhibited and the fast one only slightly inhibited. Moreover of the bundles of microfilaments oriented parallel to the long axis of the tail seen in TEM. Most of the birefringence is lost during the fast phase and the rest during the slow phase of retraction. Concurrently, the bundles of microfilaments disappear during the fast phase of retraction and are replaced by a microfilament meshwork. All of these results are consistent with the hypothesis that the initial fast component of retraction is a passive elastic recoil, associated with the oriented bundles of microfilaments, and that the slow component of retraction is an active contraction, associated with a meshwork of microfilaments.

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