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M B Wolf

Publications and source records attributed to M B Wolf.

13 recordsLinked to original sources
PubMed1992

Transport parameter estimation from lymph measurements and the Patlak equation.

Two methods of estimating protein transport parameters for plasma-to-lymph transport data are presented. Both use IBM-compatible computers to obtain least-squares parameters for the solvent drag reflection coefficient and the permeability-surface area product using the Patlak equation. A matrix search approach is described, and the speed and convenience of this are compared with a commercially available gradient method. The results from both of these methods were different from those of a method reported by Reed, Townsley, and Taylor [Am. J. Physiol. 257 (Heart Circ. Physiol. 26): H1037-H1041, 1989]. It is shown that the Reed et al. method contains a systematic error. It is also shown that diffusion always plays an important role for transmembrane transport at the exit end of a membrane channel under all conditions of lymph flow rate and that the statement that diffusion becomes zero at high lymph flow rate depends on a mathematical definition of diffusion.

Animals↗
PubMed1992

Effects of cold on vascular permeability and edema formation in the isolated cat limb.

We investigated the effects of cold temperatures on microvascular protein permeability in the isolated constant-flow perfused cat hindlimb. The perfusates were 20% cat plasma-80% albumin-electrolyte solution (low-viscosity perfusate, approximately 1 cP) or whole blood (high-viscosity perfusate, approximately 4 cP). The time at low temperature (less than 10 degrees C) was less than 3 h (short term) or greater than 5 h (long term). Decreases in the solvent drag reflection coefficient (sigma f) indicated increases in permeability. The sigma f's were determined with the integral-mass balance method from measurement of changes in protein concentration and hematocrit induced by fluid filtration into the tissues. Short-term cold exposure did not increase permeability with either a low- or a high-viscosity perfusate, whereas long-term exposure with limb temperatures of approximately 5 degrees C significantly increased permeability when the perfusate was whole blood. In addition, we verified our previous prediction that flow had to be reduced to 6-8 ml.min-1.100 g-1 to avoid the hydrostatic edema caused by short-term perfusion with whole blood at approximately 5 degrees C. Also, we found that at approximately 3 degrees C histamine's permeability-increasing effect was totally abolished, whereas at approximately 20 degrees C this effect was partially inhibited. Hence, constant-flow perfusion at low temperature with whole blood can cause edema by a pressure-dependent mechanism, whereas long-term perfusion with this perfusate at low temperatures can cause a permeability increase that further compounds edema formation. Histamine is not responsible for this permeability increase.

Animals↗
PubMed1991

Microvascular permeability transients due to histamine in cat limb.

We measured the protein solvent drag reflection coefficient (sigma f) and the capillary filtration coefficient (CFC) before and after adding 1 or 10 microM histamine to the recirculating fluid (20% plasma, remainder albumin and electrolytes, hematocrit of 1-2%) perfusing the isolated cat hindlimb preparation. Transient sigma f measurements were made at 3- to 15-min intervals after histamine using a modification of the steady-state integral-mass balance method. CFC measurements were made at approximately 10-min intervals after histamine in separate experiments. A 1 microM dose of histamine caused sigma f to fall from approximately 0.8 to approximately 0.3 in 2-3 min; sigma f then returned to control in approximately 20 min. CFC response to the 1 microM histamine was a peak increase approximately 2 times control and a return to control in approximately 40 min. A 10 microM dose caused sigma f to fall rapidly to near zero. In general, recovery was much slower than for the 1 microM dose, most of the limbs not returning to control by 40 min after histamine. CFC measurements after 10 microM histamine increased only approximately 5 times control even though sigma f was near zero at the same time. CFC remained above control for approximately 60 min. The combined sigma f and CFC data could be described quantitatively if histamine simultaneously opened both short-lived large gaps (approximately 1,000 A) and a longer-lived pathway that sieved protein like the normal pathway and if the numbers of channels of each pathway closed exponentially with 4- and 15-min time constants, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effects of cold on microvascular fluid movement in the cat limb.

We investigated the effects of low temperatures down to approximately 5 degrees C on postcapillary resistance (Rv) and isogravimetric capillary pressure (Pci) in the isolated constant-flow-perfused cat hindlimb to see if a low-temperature-induced increase in Rv and decrease in Pci could lead to an increase in filtration pressure and edema formation. A low-viscosity perfusate (20% cat plasma, 80% albumin-electrolyte solution; viscosity approximately 1 cP) was used. Isoproterenol (10(-7) M) was added to vasodilate the limb and achieve normal microvascular permeability. Rv and Pci were estimated from the slope and zero-flow intercept, respectively, of the straight-line fit to the isogravimetric venous pressure vs. flow data. Rv and Pci were determined in each experiment at an initial 37 degrees C control, at a lowered temperature (30, 23, 15, or 5-10 degrees C), and then at 37 degrees C again. The ratio of Rv at the low temperatures relative to the initial 37 degrees C control increased almost linearly as temperature was reduced. The increase was 3.4 times control at the lowest temperature. Pci decreased significantly from control only in the lowest temperature group where the change was -5.4 mmHg. Analysis of our data with the low-viscosity perfusate shows that the limb can become edematous if temperature is lowered to approximately 5 degrees C unless venous pressure (Pv) is lowered to venous collapse and flow reduced to less than approximately 20 ml.min-1.100g-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Filtration coefficient in cat hindlimb using protein concentration changes.

The maximum value of capillary filtration coefficient (CFC) in maximally vasodilated cat skeletal muscle is disputed. It was hypothesized that the wide range of reported values was caused by the inability of gravimetric and volumetric measurements of tissue volume to separate transcapillary filtration from vascular volume changes. Consequently, we developed a method of measuring filtration rates from changes in venous protein concentration using Evan's blue-labeled albumin in the isolated hindlimb (pentobarbital sodium anesthesia). The filtration coefficient (PFFC) calculated from these filtration rates after a step in venous pressure should not be influenced by vascular volume changes. When the perfusate flow rate through the hindlimb was greater than 15 ml.min-1.100 g muscle-1, PFFC was 0.0085 +/- 0.0015 (SD, n = 8) ml.min-1.mmHg-1.100 g muscle-1. PFFC was observed to be unvarying from 1 to 12 min after the venous pressure elevation, in contrast to CFC values, which fall during the same period. It is argued that the difference between CFC and PFFC values is caused by vascular volume changes.

Algorithms↗
PubMed1989

Measurement of osmotic reflection coefficient for small molecules in cat hindlimbs.

Capillary osmotic reflection coefficients (sigma) for NaCl, urea, sucrose, and raffinose were measured in the isolated, perfused cat hindlimb using the osmotic transient technique. sigma were determined from the ratio of the maximum rate of transcapillary absorption [delta Jv(max)] to the increase in the osmotic pressure (25-35 mosmol/kg H2O) in the arterial inflow (delta pi a) produced by adding one of the molecules to an albumin-electrolyte perfusate containing isoproterenol (greater than 10(-7) M). delta Jv (max) was determined from organ weight and delta pi a from perfusate osmolalities. For each molecule, the delta Jv(max)/delta pi a ratio increased monotonically with perfusate flow rates (Q) to Q greater than 100 ml.min-1.100 g-1. This ratio was independent of the size of the delta pi a. Apparent sigma values were calculated by dividing these ratios by the capillary hydraulic capacity determined in other studies. At low Q, apparent sigma was comparable to the approximately 0.1 values found by others in skeletal muscle. At the highest Q, apparent sigma for these molecules were at least 0.5. These data are consistent with at least 50% of transcapillary water flow moving through a water-exclusive pathway.

Algorithms↗
PubMed1989

Effects of elevated venous pressure on capillary permeability in cat hindlimbs.

We investigated the effects of elevated venous pressure, Pv, (up to 140 mmHg) on the solvent drag reflection coefficient, sigma f, for protein and on the capillary filtration coefficient, CFC, in the isolated cat hindlimb perfused at constant flow. The perfusate contained 30% cat plasma and the remainder was a dialyzed albumin-electrolyte mixture. Cat red cells were added to a hematocrit of approximately 2%. sigma f was measured from the changes in hematocrit and plasma protein concentration (Integral-Mass Balance method) resulting from the fluid filtration caused by the Pv elevation. CFC was measured from the slope of the limb weight recording 2-4 min after the Pv elevation. sigma f decreased linearly from 0.807 (Pv less than 50 mmHg) to approximately 0.2 at 140 mmHg. CFC increased linearly from 0.0086 ml.min-1.mmHg-1.100 g-1 to about 0.04 over the same pressure range. A weight-independent filtration coefficient calculated from the change in hematocrit and a measurement of the initial perfusate volume gave comparable results, except at the very highest of pressures, where this coefficient was sometimes 20-40% less than CFC. Successive sigma f determinations at Pv at about 40 mmHg did not return to control after an initial measurement in which Pv was approximately 110 mmHg. Pore-theory analysis of the data suggests that the elevated Pv causes large pores to open as opposed to the stretching of small pores. Also, these large pores may remain open for a period of hours.

Animals↗
PubMed1987

Integral-mass balance method for determination of solvent drag reflection coefficient.

We have developed the integral-mass balance (IMB) method to measure the solvent drag reflection coefficient (sigma f) for transcapillary macromolecular transport in skeletal muscle and other organs. Of course, sigma f is calculated from the cumulative amounts of water and macromolecule that move convectively across the microvascular membrane as determined from changes in hematocrit and plasma macromolecule concentration over a period of fluid filtration. We have investigated the effects of both theoretical and experimental factors that affect the validity and accuracy of the method. The effect of the following factors on sigma f determination by the IMB method were explored: low Peclet number; random-measurement errors; and systematic errors due to vascular leakage, hemolysis of red blood cells, evaporation, and osmolality changes. We found that all of these factors produced overestimations of sigma f, but their effects could be corrected. Also, appropriate experimental design could minimize these effects. Experiments using the IMB method in the isolated, perfused cat hindlimb preparation to determine sigma f for albumin and plasma proteins resulted in mean values of 0.82 +/- 0.08 (SD) (n = 7) and 0.83 +/- 0.02 (n = 4), respectively.

Animals↗
PubMed1985

Dextran and capillary filtration coefficient in cat hindlimb.

To investigate the possible mechanisms through which dextran modifies capillary filtration coefficient (CFC), the effects of perfusion with a protein-free dextran solution were compared with those of perfusion with a Ringerlike solution. With the use of the isolated cat hindlimb, CFC was measured during perfusion at constant flow with three solutions, a control blood-albumin mixture, a Ringerlike solution called dialysate, and 3.7 g/dl dextran dissolved in dialysate. The solutions were warmed to 37-38 degrees C, bubbled with 95% O2-5% CO2, and contained 0.015 g/dl or more papaverine. CFC was calculated from the rate of limb weight gain following a step increase in venous pressure. Dextran perfusion increased CFC to 2.0 +/- 0.2 (SD, n = 8) times control, which was significantly less (P less than 0.001) than 3.1 +/- 0.6 (n = 8) times control previously reported for dialysate perfusion. The difference between the measured viscosity of dextran (1.35 cP) and dialysate (0.72) could account for this reduction. However, when a dialysate perfusion followed a dextran perfusion, CFC only increased to 2.3 +/- 0.4 (n = 8) times control. This value is also significantly less (P less than 0.01) than 3.1. This observation suggests 1) that dextran is retained within the transcapillary channel and 2) that dextran reduces CFC mainly by partially blocking the transcapillary channel rather than by increasing viscosity.

Animals↗
PubMed1975

Dynamic palatometry.

A computer-based instrumental system is described for continuous palatometry. Thin pseudopalatal plates (approximately 0.2 mm) with embedded electrodes are used to detect linguapalatal contact during speech articulation. Geometric configurations of such contacts are then derived and displayed to reveal articulatory characteristics.

Computers↗