scholarly journals An Estimate of Reflection Coefficients for Rabbit Heart Capillaries

1964 ◽  
Vol 47 (4) ◽  
pp. 667-677 ◽  
Author(s):  
Fernando Vargas ◽  
John A. Johnson
Keyword(s):  
Weight Change ◽  
Rabbit Heart ◽  
Ringer Solution ◽  
Reflection Coefficients ◽  
Test Substance ◽  
Time Rate ◽  
Loss Of Weight ◽  
Test Molecule ◽  
Zero Time ◽  
Heart Capillaries

Isolated perfused rabbit hearts have been used to determine the reflection coefficients, σ, of the heart capillaries to certain lipoid-insoluble substances. This was done by initially perfusing the heart with a Ringer solution containing no test molecule and then suddenly switching to a solution which differed from the original only by containing a small amount of test substance. This produced a loss of weight of the heart which was continuously recorded as a function of time. Taking the "zero" time rate of weight change and using an equation given by Kedem and Katchalsky reflection coefficients for urea, sucrose, raffinose, and inulin were obtained. These turned out to be 0.1, 0.3, 0.38, and 0.69 respectively. Using the approach of Durbin and Solomon equivalent pore radii were estimated to be about 35 Angstroms.

Chemical and histological space determinations in rabbit heart

1962 ◽  
Vol 202 (3) ◽  
pp. 589-592 ◽  
Author(s):  
John A. Johnson ◽  
Mary A. Simonds
Keyword(s):  
Weight Change ◽  
Extracellular Space ◽  
Chemical Space ◽  
Freeze Substitution ◽  
Rabbit Heart ◽  
Quantitative Agreement ◽  
Tissue Water ◽  
Histological Techniques ◽  
Chemical Technique ◽  
Osmotic Activity

The extracellular space of perfused rabbit heart ventricles was estimated by chemical and histological techniques. Sucrose and thiocyanate were used for the chemical space estimations. The method proposed by Chalkley following fixation by freeze substitution was used for the histological extracellular space determination. The extracellular space fraction was altered by using perfusing solutions of different osmotic activity to shrink or swell the cells. The magnitude of the tissue water loss or gain was determined by weighing the heart. Using the assumption that the cells alone changed in volume during an osmotically induced weight change, an alteration in the fractional extracellular space was predicted from the original chemical or histological space determination and the magnitude of the weight change. This predicted change when compared to the observed change in the histological and chemical spaces always agreed in direction with the measured values of both the histological and chemical spaces but was in better quantitative agreement with the values from the chemical technique.

Liver uptake of amino acids and carbohydrates during a single circulatory passage

1975 ◽  
Vol 228 (4) ◽  
pp. 1155-1161 ◽  
Author(s):  
WM Pardridge ◽  
LS Jefferson
Keyword(s):  
Amino Acids ◽  
Glutamic Acid ◽  
Aspartic Acid ◽  
Amino Acid Uptake ◽  
Ringer Solution ◽  
Transport Systems ◽  
Test Substance ◽  
Acid Uptake ◽  
Liver Uptake ◽  
Rapid Injection

The uptake of 14C-labeled amino acids and carbohydrates by liver following rapid injection into the portal vein was measured relative to a simultaneously injected highly diffusible reference, tritium-labeled water, (3HOH). A 0.25-ml bolus of buffered Ringer solution containing 1-2 muCi of the 14C-labeled test substance and 3-6 muCi of 3HOH was administered by rabid portal injection in anesthetized rats. Circulation was terminated after a single passage of the bolus through the hepatic microvasculature and the tissue was immediately macerated, solubilized, and subjected to liquid scintillation counting. Liver uptake indices (LUI) were calculated from the ratio of 14C to 3H in liver tissue relative to the same ratio in the injection mixture. LUI's of five carbohydrates were measured: sucrose (24.3 percent), inulin (27.7 percent), D-mannitol (80.2 percent), D-glucose (96.8 percent) and L-glucose (26.7 percent). The LUI for cholic acid was 127.1 percent. Among 18 amino acids tested, the LUI's were the highest for the acidic ones (L-aspartic acid, 100.0 percent and L-glutamic acid, 86.4 percent) and lowest for the basic ones (L-arginine, 37.4 percent and L-lysine, 31.4 percent). Stereospecificity for glucose and alanine uptake, saturation kinetics for glutamic acid (Km equal to 4.8 mM) and aspartic acid (Km equal to 2.7 mM), and cross-inhibition among uptake of the acidic amino acids were observed. These findings confirmed the applicability of a technique which was originally developed for studies of amino acid uptake in brain to characterization of transport systems in liver.

Ammonia production in the isolated working rabbit heart

1961 ◽  
Vol 200 (2) ◽  
pp. 238-242 ◽  
Author(s):  
H. Feinberg ◽  
Sister Mary Alma
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Oxygen Consumption ◽  
Rabbit Heart ◽  
Ringer Solution ◽  
Heart Weight ◽  
Ammonia Production

Ammonia production, oxygen consumption, heart rate and blood pressure were observed in the isolated working rabbit heart perfused with Krebs-Ringer solution and with Krebs-Ringer solution containing dog hemoglobin. Oxygen consumption and an index to cardiac effort (heart rate x blood pressure) were shown to be correlated. There was a lesser correlation between ammonia production and cardiac effort. The ratio, ammonia production/oxygen consumption, when both are expressed as micromoles/minute/ gram of heart weight, averaged 0.064 ± .006. Perfusate pH was altered by alternately exposing the perfusate to 95%O2– 5%CO2 and 90%O2–10%CO2. No effect on the ratio ammonia production/oxygen consumption was noted. l-Epinephrine, 0.1–1.0 µg/ml, was continuously infused and resulted in an increase in cardiac effort, oxygen consumption, ammonia production and the ratio of ammonia production/ oxygen consumption.

Effect of hyperosmolarity on resting and developed tension in heart muscle

1977 ◽  
Vol 232 (3) ◽  
pp. C155-C162 ◽  
Author(s):  
F. F. Vargas ◽  
J. A. Johnson
Keyword(s):  
Weight Loss ◽  
Rabbit Heart ◽  
Ringer Solution ◽  
Base Line ◽  
Initial Value ◽  
Tension Level ◽  
Resting Tension ◽  
Tension Recovery ◽  
Initial Drop ◽  
Line Level

Simultaneous changes in weight, tension, and electrical activity were studied in the isolated perfused rabbit heart when the Ringer solution perfusion fluid was made hypertonic by the addition of sucrose, urea, glycerol, ethylene glycol, or formamide. The typical responses to each of the molecules was an initial drop in weight and tension followed by a return toward the base-line level. A 0.4 M concentration of sucrose, urea, or glycerol reduced the weight to 40 +/- 4.6, 48 +/- 3, and 52.2 +/- 3% of the initial value, respectively. The tension was simultaneously reduced to 23 +/- 3.5, 31 +/- 2, and 41 +/- 4% of its initial value. The tension drop produced by the solutes tested was linearly related to the amount of water lost by the heart. The falling phases of both tension and weight loss were closely correlated phases of both tension and weight loss were closely correlated in time a magnitude and were both related to the effectiveness of a particular molecule to move water out of the cells. In contrast, the subsequent rising phases of tension and weight were not as well correlated in time and magnitude. Whereas for most of the molecules used, the tension recovery was incomplete; urea, in contrast, caused an overshoot of the control tension level, thus pointing toward a unique inotropic effect of this compound. Resting tension rose for both urea and sucrose but not for the other compounds.

Transcapillary osmotic flows in the in vitro perfused heart

1981 ◽  
Vol 240 (4) ◽  
pp. H448-H456 ◽  
Author(s):  
F. F. Vargas ◽  
G. L. Blackshear
Keyword(s):  
Weight Change ◽  
Ringer Solution ◽  
The Other ◽  
Effect Of Temperature ◽  
Heart Weight ◽  
Volume Changes ◽  
Perfused Heart ◽  
Vascular Volume ◽  
Viscosity Changes

Hearts were removed from rabbits anesthetized with pentobarbitol sodium, heparinized, and then perfused through the aorta with Ringer solution. Addition of sucrose to the perfusate caused an osmotic transcapillary flow (Jv). Measurements of Jv with two independent methods, one using the rate of organ weight change and the other the variation of effluent concentration of an impermeant dye (Blue dextran), agreed very closely, giving an initial Jv per unit concentration and wet heart weight of 0.306 (microliters/s) (mmol/l).g (corrected for viscosity, 25 degrees C). Because dye dilution was free of vascular volume interference, its agreement with weight measurements suggests that vascular volume changes were relatively small. Measurements using 51Cr-labeled erythrocytes supported the above conclusion. The effect of temperature and concentration on Jv was ascribed to viscosity changes. Organ condition remained stable for several hours, based on maximum ventricular pressure (107 +/- 6.4 cmH2O) and dP/dt (1,145 +/- 98 cmH2O/s) values close to those in blood-perfused rabbit hearts. Repeat weight response to osmotic testing showed approximately 5% variation during an experiment.

Potassium efflux from isolated rabbit heart into a potassium-free solution

1961 ◽  
Vol 200 (1) ◽  
pp. 133-134
Author(s):  
E. W. Humphrey
Keyword(s):  
Potassium Concentration ◽  
Calcium Content ◽  
Rabbit Heart ◽  
Free Solution ◽  
Potassium Efflux ◽  
Isolated Rabbit Heart ◽  
Perfused Rabbit Heart ◽  
Zero Time

The efflux of potassium from the isolated perfused rabbit heart into a potassium-free solution has been calculated from the zero time slope of the washout curve and the initial potassium concentration. It was found that this efflux very closely approximated that calculated from the K42 equilibration curves. Increasing the calcium content of the perfusate twofold had no significant effect on the outflux of potassium.

Shot-profile true amplitude crosscorrelation imaging condition

Geophysics ◽  
2013 ◽  
Vol 78 (4) ◽  
pp. S221-S231 ◽  
Author(s):  
B. Arntsen ◽  
A. Kritski ◽  
B. Ursin ◽  
L. Amundsen
Keyword(s):  
Reflection Coefficient ◽  
Time Lag ◽  
Reflection Coefficients ◽  
Damping Factor ◽  
Simple Modification ◽  
Imaging Condition ◽  
Correct Angle ◽  
Zero Time ◽  
Amplitude Versus ◽  
Stable Result

The U/D imaging condition for shot profile migration can be used to estimate the angle dependent reflection coefficient, but is difficult to implement numerically because of the spectral division involved. Most techniques for stabilizing the division require a damping factor which might be difficult to estimate and which also introduces bias into the final result. A stable result can be achieved by approximating the imaging condition with a crosscorrelation of the up- and downgoing wavefields at zero time lag, but this will lead to incorrect amplitude-versus-angle (AVA) behavior of the estimated reflection coefficient. We use a simple model for wave propagation of primary reflections in the wavenumber frequency domain and invert the model with respect to the reflection coefficient. By using the properties of wavefield extrapolators it can then be shown that the reflection coefficients can be estimated by crosscorrelation of the upgoing wavefield and a downgoing wavefield where the initial wavefield is the inverse of the wavefield generated by a point source. The new imaging condition gives the correct AVA behavior for horizontal reflectors. For dipping reflectors it is shown that a postmigration correction factor can be used to recover the correct angle behavior of the reflection coefficient. The new imaging condition is numerically stable, does not involve damping factors, is simple to implement numerically, and is a simple modification of the classical crosscorrelation imaging condition. Numerical examples confirm the correct AVA behavior of the new imaging condition.

Alveolar epithelium transport of albumin and sucrose: concentration difference effect

1979 ◽  
Vol 47 (4) ◽  
pp. 846-850 ◽  
Author(s):  
D. Wangensteen ◽  
R. Yankovich
Keyword(s):  
Sucrose Concentration ◽  
Alveolar Epithelium ◽  
Compartment Model ◽  
Ringer Solution ◽  
Sucrose Transport ◽  
Gas Barrier ◽  
Concentration Difference ◽  
Two Compartment Model ◽  
Test Molecule ◽  
Difference Effect

Isolated Ringer-perfused rabbit lungs were used to study albumin and sucrose transport across the blood-gas barrier. Lungs were filled to about 20% total lung capacity (TLC) ith Ringer solution containing radioactive albumin and sucrose, and their rate of appearance in the recirculating perfusate was monitored. From this the product permeability x area (PA) was calculated. In the middle of the 180-min experiments, some alveolar fluid was removed. In control experiments, the same fluid was reinstilled, in other experiments new fluid with higher test molecule concentrations was infused. In all experiments the results for both molecules were similar: PA for the second half of the experiment was 80% of that in the first half. The reduction was probably due to a decrease in exchange area. We thus find the albumin and sucrose permeabilities to be proportional to their concentration difference. In addition, the PA for sucrose was roughly four times that of albumin. These results can possibly be explained by a two-compartment model with two parallel pathways across the alveolar epithelium. One pathway would be small pores, whereas the other would involve a bulk flow or pinocytosis process.

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