The Effects of Thromboxane Antagonism on the Transit Time of Platelets Through the Spleen

1985 ◽  
Vol 54 (02) ◽  
pp. 495-497 ◽  
Author(s):  
A M Peters ◽  
I F Lane ◽  
M Sinclair ◽  
J T C Irwin ◽  
C N McCollum
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Thromboxane A2 ◽  
Time Measurement ◽  
Thromboxane A2 Receptor ◽  
Group Research ◽  
The Mean ◽  
A Site ◽  
Kinetics Of ◽  
Transit Time Measurement

SummaryThe spleen is well-known as a site for platelet pooling, although the mechanisms controlling intrasplenic platelet transit are essentially unknown. We tested the possibility that thromboxane A2 might be involved in this control by measuring intrasplenic platelet transit time in 10 subjects receiving a specific thromboxane A2 receptor antagonist (AH23848B; 70 mg; Glaxo Group Research Ltd), in 10 receiving aspirin (300 mg) plus dipyridamole (75 mg), and in 9 receiving placebo. All doses were administered 3 times daily commencing 4 days prior to transit time measurement.Mean intrasplenic platelet transit time was measured by monitoring the kinetics of equilibration of 111In radiolabelled platelets between blood and spleen following intravenous injection. There was no difference between the mean transit time in the 3 groups of subjects, lending no support to the hypothesis that thromboxane A2 is involved in the control of platelet traffic through the spleen.

Kinetics of Na+ uptake and transcellular transit by the pancreas

1975 ◽  
Vol 228 (4) ◽  
pp. 1199-1205 ◽  
Author(s):  
M Rossier ◽  
SS Rothman
Keyword(s):  
Steady State ◽  
Transit Time ◽  
Mean Transit Time ◽  
Uptake Curve ◽  
Rabbit Pancreas ◽  
In Series ◽  
The Mean ◽  
22Na Uptake ◽  
Kinetics Of

22Na uptake into strips of rabbit pancreas was measured for up to 10 min. The uptake curve was characterized by the presence of two plateaus separated by an inflexion point; a first "plateau" or an approximation of steady-state uptake was observed between 1 and 3 min; betwen 3 and 4 min the slope of the uptake curve increased again, finally decreasing to a new and higher steady-state uptake between 4 and 6 min. The data suggest that the first part of the uptake curve (from 0 to 3 min) represents uptake into most if not all cells, and the second part (from 3 to 10 min) represents the sum of "quasi" steady-state cellular uptake and of the equilibration of the ductal compartment in series with the cells. In this model a substantial delay (2.5-3.25 min) elapses between the filling of cellular and ductal compartments which is apparently of intracellular origin, implying restricted Na+ diffusion within the cytoplasm and an intracellular Na+ gradient. If this model is correct, then the mean transit time for Na+ across the whole organ should be approximately 3-4 min and be primarily the result of transcellular transit. The mean transit time for Na+ across the whole organ in vitro was measured and found to be 3.5 min on the average. The step that accounts for most of this time appears to be the transepithelial transit of Na+.

Reabsorption kinetics of albumin from pleural space of dogs

1988 ◽  
Vol 255 (2) ◽  
pp. H375-H385 ◽  
Author(s):  
M. Miniati ◽  
J. C. Parker ◽  
M. Pistolesi ◽  
J. T. Cartledge ◽  
D. J. Martin ◽  
...  
Keyword(s):  
Control Mechanism ◽  
Mean Transit Time ◽  
Input Function ◽  
Pleural Space ◽  
Frequency Function ◽  
Liquid Pressure ◽  
Physiological Conditions ◽  
Transit Times ◽  
The Mean ◽  
Kinetics Of

The reabsorption of albumin from the pleural space was measured in eight dogs receiving 0.5 ml intrapleural injection of 131I-labeled albumin and a simultaneous intravenous injection of 125I-labeled albumin. Plasma curves for both tracers were obtained over 24 h. The 125I-albumin curve served as input function of albumin for interstitial spaces, including pleura, whereas the 131I-albumin curve represented the output function from pleural space. The frequency function of albumin transit times from pleural space to plasma was obtained by deconvolution of input-output plasma curves. Plasma recovery of 131I-albumin was complete by 24 h, and the mean transit time from pleura to plasma averaged 7.95 +/- 1.57 (SD) h. Albumin reabsorption occurred mainly via lymphatics as indicated by experiments in 16 additional dogs in which their right lymph ducts or thoracic ducts were ligated before intrapleural injection. A pleural lymph flow of 0.020 +/- 0.003 (SD) ml.kg-1.h-1 was estimated, which is balanced by a comparable filtration of fluid into the pleural space. This suggests that, under physiological conditions, the subpleural lymphatics represent an important control mechanism of pleural liquid pressure.

scholarly journals Use of the mean transit time of an intravascular contrast agent as an exchange-insensitive index of myocardial perfusion

1999 ◽  
Vol 9 (3) ◽  
pp. 402-408 ◽  
Author(s):  
Massimo Lombardi ◽  
Richard A. Jones ◽  
J�rgen Westby ◽  
Geir Torheim ◽  
Timothy E. Southon ◽  
...  
Keyword(s):  
Myocardial Perfusion ◽  
Contrast Agent ◽  
Transit Time ◽  
Mean Transit Time ◽  
Intravascular Contrast Agent ◽  
The Mean

Lung water measurements with the mean transit time approach

1985 ◽  
Vol 59 (3) ◽  
pp. 673-683 ◽  
Author(s):  
R. M. Effros
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Tissue Perfusion ◽  
Time Data ◽  
Lung Water ◽  
Thermal Signal ◽  
The Mean ◽  
Points Of View ◽  
Vascular Obstruction ◽  
Pulmonary Vascular Obstruction

The potential usefulness and limitations of the double-indicator mean transit time approach for measuring lung water are evaluated from both theoretical and empirical points of view. It is concluded that poor tissue perfusion is the most serious factor that can compromise the reliability of this approach. Replacement of the conventional water isotopes with a thermal signal enhances indicator delivery to ischemic areas but the diffusion of heat is not sufficiently rapid to permit measurements of water in macroscopic collections of fluid which remain unperfused. The frequency of pulmonary vascular obstruction in patients with pulmonary edema related to lung injury suggests that interpretation of transit time data will be complicated by uncertainties concerning perfusion. Thermal-dye measurements of lung water may prove more helpful in situations where pulmonary blood flow remains relatively uniform.

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