Twelve-month prostate volume reduction after MRI-guided transurethral ultrasound ablation of the prostate.

PURPOSE: To quantitatively assess 12-month prostate volume (PV) reduction based on T2-weighted MRI and immediate post-treatment contrast-enhanced MRI non-perfused volume (NPV), and to compare measurements with predictions of acute and delayed ablation volumes based on MR-thermometry (MR-t), in a central radiology review of the Phase I clinical trial of MRI-guided transurethral ultrasound ablation (TULSA) in patients with localized prostate cancer. MATERIALS AND METHODS: Treatment day MRI and 12-month follow-up MRI and biopsy were available for central radiology review in 29 of 30 patients from the published institutional review board-approved, prospective, multi-centre, single-arm Phase I clinical trial of TULSA. Viable PV at 12 months was measured as the remaining PV on T2-weighted MRI, less 12-month NPV, scaled by the fraction of fibrosis in 12-month biopsy cores. Reduction of viable PV was compared to predictions based on the fraction of the prostate covered by the MR-t derived acute thermal ablation volume (ATAV, 55°C isotherm), delayed thermal ablation volume (DTAV, 240 cumulative equivalent minutes at 43°C thermal dose isocontour) and treatment-day NPV. We also report linear and volumetric comparisons between metrics. RESULTS: After TULSA, the median 12-month reduction in viable PV was 88%. DTAV predicted a reduction of 90%. Treatment day NPV predicted only 53% volume reduction, and underestimated ATAV and DTAV by 36% and 51%. CONCLUSION: Quantitative volumetry of the TULSA phase I MR and biopsy data identifies DTAV (240 CEM43 thermal dose boundary) as a useful predictor of viable prostate tissue reduction at 12 months. Immediate post-treatment NPV underestimates tissue ablation. KEY POINTS: • MRI-guided transurethral ultrasound ablation (TULSA) achieved an 88% reduction of viable prostate tissue volume at 12 months, in excellent agreement with expectation from thermal dose calculations. • Non-perfused volume on immediate post-treatment contrast-enhanced MRI represents only 64% of the acute thermal ablation volume (ATAV), and reports only 60% (53% instead of 88% achieved) of the reduction in viable prostate tissue volume at 12 months. • MR-thermometry-based predictions of 12-month prostate volume reduction based on 240 cumulative equivalent minute thermal dose volume are in excellent agreement with reduction in viable prostate tissue volume measured on pre- and 12-month post-treatment T2w-MRI.

Further reduction of disqualification rates by additional MRI-targeted biopsy with transperineal saturation biopsy compared with standard 12-core systematic biopsies for the selection of prostate cancer patients for active surveillance.

BACKGROUND: Active surveillance (AS) is commonly based on standard 10-12-core prostate biopsies, which misclassify ~50% of cases compared with radical prostatectomy. We assessed the value of multiparametric magnetic resonance imaging (mpMRI)-targeted transperineal fusion-biopsies in men under AS. METHODS: In all, 149 low-risk prostate cancer (PC) patients were included in AS between 2010 and 2015. Forty-five patients were initially diagnosed by combined 24-core systematic transperineal saturation biopsy (SB) and MRI/transurethral ultrasound (TRUS)-fusion targeted lesion biopsy (TB). A total of 104 patients first underwent 12-core TRUS-biopsy. All patients were followed-up by combined SB and TB for restratification after 1 and 2 years. All mpMRI examinations were analyzed using PIRADS. AS was performed according to PRIAS-criteria and a NIH-nomogram for AS-disqualification was investigated. AS-disqualification rates for men initially diagnosed by standard or fusion biopsy were compared using Kaplan-Meier estimates and log-rank tests. Differences in detection rates of the SB and TB components were evaluated with a paired-sample analysis. Regression analyses were performed to predict AS-disqualification. RESULTS: A total of, 48.1% of patients diagnosed by 12-core TRUS-biopsy were disqualified from AS based on the MRI/TRUS-fusion biopsy results. In the initial fusion-biopsy cohort, upgrading occurred significantly less frequently during 2-year follow-up (20%, P<0.001). TBs alone were significantly superior compared with SBs alone to detect Gleason-score-upgrading. NPV for Gleason-upgrading was 93.5% for PIRADS⩽2. PSA level, PSA density, NIH-nomogram, initial PIRADS score (P<0.001 each) and PIRADS-progression on consecutive MRI (P=0.007) were significant predictors of AS-disqualification. CONCLUSIONS: Standard TRUS-biopsies lead to significant underestimation of PC under AS. MRI/TRUS-fusion biopsies, and especially the TB component allow more reliable risk classification, leading to a significantly decreased chance of subsequent AS-disqualification. Cancer detection with mpMRI alone is not yet sensitive enough to omit SB on follow-up after initial 12-core TRUS-biopsy. After MRI/TRUS-fusion biopsy confirmed AS, it may be appropriate to biopsy only those men with suspected progression on MRI.

Medical Liability and Patient Law in Germany: Main Features with Particular Focus on Treatments in the Field of Interventional Radiology.

UNLABELLED: On February 26th, 2013 the patient law became effective in Germany. Goal of the lawmakers was a most authoritative case law for liability of malpractice and to improve enforcement of the rights of the patients. The following article contains several examples detailing legal situation. By no means should these discourage those persons who treat patients. Rather should they be sensitized to to various aspects of this increasingly important field of law. To identify relevant sources according to judicial standard research was conducted including first- and second selection. Goal was the identification of jurisdiction, literature and other various analyses that all deal with liability of malpractice and patient law within the field of Interventional Radiology--with particular focus on transarterial chemoembolization of the liver and related procedures. In summary, 89 different sources were included and analyzed. The individual who treats a patient is liable for an error in treatment if it causes injury to life, the body or the patient's health. Independent of the error in treatment the individual providing medical care is liable for mistakes made in the context of obtaining informed consent. Prerequisite is the presence of an error made when obtaining informed consent and its causality for the patient's consent for the treatment. Without an effective consent the treatment is considered illegal whether it was free of treatment error or not. The new patient law does not cause material change of the German liablity of malpractice law. KEY POINTS: •On February 26th, 2013 the new patient law came into effect. Materially, there was no fundamental remodeling of the German liability for medical malpractice. •Regarding a physician's liability for medical malpractice two different elements of an offence come into consideration: for one the liability for malpractice and, in turn, liability for errors made during medical consultation in the process of obtaining informed consent. •Forensic practice shows that patients frequently enforce both offences concurrently.

Improved detection of anterior fibromuscular stroma and transition zone prostate cancer using biparametric and multiparametric MRI with MRI-targeted biopsy and MRI-US fusion guidance.

BACKGROUND: The objective of this study was to analyze the potential of prostate magnetic resonance imaging (MRI) and MRI/transrectal ultrasound-fusion biopsies to detect and to characterize significant prostate cancer (sPC) in the anterior fibromuscular stroma (AFMS) and in the transition zone (TZ) of the prostate and to assess the accuracy of multiparametric MRI (mpMRI) and biparametric MRI (bpMRI) (T2w and diffusion-weighted imaging (DWI)). METHODS: Seven hundred and fifty-five consecutive patients underwent prebiopsy 3 T mpMRI and transperineal biopsy between October 2012 and September 2014. MRI images were analyzed using PIRADS (Prostate Imaging-Reporting and Data System). All patients had systematic biopsies (SBs, median n=24) as reference test and targeted biopsies (TBs) with rigid software registration in case of MRI-suspicious lesions. Detection rates of SBs and TBs were assessed for all PC and sPC patients defined by Gleason score (GS)⩾3+4 and GS⩾4+3. For PC, which were not concordantly detected by TBs and SBs, prostatectomy specimens were assessed. We further compared bpMRI with mpMRI. RESULTS: One hundred and ninety-one patients harbored 194 lesions in AFMS and TZ on mpMRI. Patient-based analysis detected no difference in the detection of all PC for SBs vs TBs in the overall cohort, but in the repeat-biopsy population TBs performed significantly better compared with SBs (P=0.004 for GS⩾3+4 and P=0.022 for GS⩾4+3, respectively). Nine GS⩾4+3 sPCs were overlooked by SBs, whereas TBs missed two sPC in men undergoing primary biopsy. The combination of SBs and TBs provided optimal local staging. Non-inferiority analysis showed no relevant difference of bpMRI to mpMRI in sPC detection. CONCLUSIONS: MRI-targeted biopsies detected significantly more anteriorly located sPC compared with SBs in the repeat-biopsy setting. The more cost-efficient bpMRI was statistically not inferior to mpMRI in sPC detection in TZ/AFMS.

Bilateral test for potential subluxation of the DRUJ.

Untreated distal radioulnar joint (DRUJ) instability can lead to arthritis of the DRUJ. To date, however, the clinical determination of DRUJ instability still represents a challenge. We developed a new clinical test to determine its stability. This works by directly observing the ulnar head's dynamic behavior during active pro-supination or testing the DRUJ's static stability at different grades of rotation. With the test results, the examiner gains a better understanding of the ulna head's behavior during rotational movements and how that compares to that of the uninjured side.

[Dorsal capsular imbrication for dorsal instability of the distal radioulnar joint]. / Die dorsale Kapseldoppelung zur Therapie der dorsalen Instabilität des distalen Radioulnargelenks.

OBJECTIVE: To stabilize the distal radioulnar joint (DRUJ) by performing dorsal capsular imbrication in patients presenting with dorsal instability. The goal was to reduce pain and prevent the occurrence of posttraumatic arthrosis. INDICATIONS: Posttraumatic dorsal instability of the DRUJ with missing block while performing translational activities in the DRUJ or subluxation while actively rotating the forearm. Cases, in which other stabilizing techniques, such as, sutures of the triangular fibrocartilage complex failed. CONTRAINDICATIONS: DRUJ arthrosis, previous surgical interventions to the capsule area of the DRUJ, instabilities due to osseous reasons (malposition or pseudarthrosis) should already have been treated. SURGICAL TECHNIQUE: Dorsal approach and opening of the 5th extensor compartment to expose the dorsal joint capsule. A longitudinal division of the capsule was performed and sufficient tissue on the radial and ulnar border was retained to ensure a solid suture technique. Then 2 U-shaped sutures using FiberWire suture material were made. Correction of the malposition and repositioning the forearm into supination. Tightening of the prepared capsule sutures and closing of the retinaculum with a resorbable suture. POSTOPERATIVE MANAGEMENT: Patients wore a long-arm cast with the forearm being in supination for a period of 4 weeks. Following cast removal, patients wore a forearm splint for a period of 4 weeks to limit forearm pronation/supination at 45°. Full load on the wrist was allowed after 12 weeks. RESULTS: The subjective and functional outcomes of 20 patients having received capsular imbrication using this technique were good and entailed no significant complications. The postoperative DASH was 15.8 points. Of the 20 patients, 17 patients (85%) had a reduction of pain. Symptoms of DRUJ instability could be reduced in 18 patients (90%). Pronation/supination of the wrist was not restricted postoperatively.

Permanent muscular sodium overload and persistent muscle edema in Duchenne muscular dystrophy: a possible contributor of progressive muscle degeneration.

To assess the presence and persistence of muscular edema and increased myoplasmic sodium (Na(+)) concentration in Duchenne muscular dystrophy (DMD). We examined eight DMD patients (mean age 9.5 ± 5.4 years) and eight volunteers (mean age 9.5 ± 3.2 years) with 3-tesla proton ((1)H) and (23)Na density-adapted 3D-radial MR sequences. Seven DMD patients were re-examined about 7 months later without change of therapy. The eighth DMD patient was re-examined after 5 and 11 months under medication with eplerenone. We quantified muscle edema on STIR images with background noise as reference and fatty degeneration on T1-weighted images using subcutaneous fat as reference. Na(+) was quantified by a muscular tissue Na(+) concentration (TSC) sequence employing a reference containing 51.3 mM Na(+) with 5 % agarose. With an inversion-recovery (IR) sequence, we determined mainly the myoplasmic Na(+). The normalized muscular (23)Na IR signal intensity was higher in DMD than in volunteers (n = 8, 0.75 ± 0.07 vs. 0.50 ± 0.05, p < 0.001) and persisted at second measurement (n = 7, 1st 0.75 ± 0.07, 2nd 0.73 ± 0.06, p = 0.50). When compared to volunteers (25.6 ± 2.0 mmol/l), TSC was markedly increased in DMD (38.0 ± 5.9 mmol/l, p < 0.001) and remained constant (n = 7, 1st 37.9 ± 6.4 mmol/l, 2nd 37.0 ± 4.0 mmol/l, p = 0.49). Muscular edema (15.6 ± 3.5 vs. 6.9 ± 0.7, p < 0.001) and fat content (0.48 ± 0.08 vs. 0.38 ± 0.01, p = 0.003) were elevated in DMD when compared to volunteers. This could also be confirmed during follow-up (n = 7, p = 0.91, p = 0.12). Eplerenone slightly improved muscle strength and reduced muscular sodium and edema. The permanent muscular Na(+) overload in all DMD patients is likely osmotically relevant and responsible for the persisting, mainly intracellular muscle edema that may contribute to the progressive muscle degeneration.

Effect of advanced glycation end products on oxidative stress in endothelial cells in culture: a warning on the use of cells studied in serum-free media.

AIMS/HYPOTHESIS: Alterations in vascular permeability and oxidative stress are characteristics of endothelial dysfunction in diabetic vascular disease. Since AGE-proteins have been hypothesized to mediate these effects, we studied the effects of AGE-bovine serum albumin on endothelial monolayer permeability and intracellular glutathione. METHODS: AGE-BSA was prepared by incubating BSA for 30 days at 37 degrees C with 0.5 mol/l glucose and 0.2 mol/l phosphate buffer, pH 7.4. Permeability to fluorescently labelled BSA was assessed in a bovine pulmonary artery endothelial cell monolayer preparation. Glutathione was measured by an enzymatic assay. RESULTS: AGE-BSA concentrations greater than 3 to 4 micromol/l produced maximal increases in permeability (6-8 times basal) within 3 to 4 h of incubation with the cells. This effect persisted for at least 48 h. However, BSA incubated in the absence of glucose produced similar effects. Dialysis of the AGE-BSA showed that low molecular weight components contained the permeability-increasing activity. Phosphate buffer used to prepare the AGE-BSA, at concentrations equivalent to those present in phosphate-buffered saline and in the AGE preparation (approximately 5 mmol/l), produced similar permeability increases at equivalent incubation times. Metal chelators (0.5 mmol/l) or inclusion of fetal bovine serum (10-20 %) blocked these permeability increases. These increases in permeability were associated with a decrease in endothelial glutathione, both inhibited by 10 mmol/l N-acetylcysteine, and a loss of cell-to-cell and cell-to-matrix adhesion molecules. CONCLUSION/INTERPRETATION: Trace amounts of redox-active metal ions in biological buffers could induce oxidative stress and alterations in cellular functions attributed to AGE-proteins in vitro. It is important to use metal-free phosphate and bicarbonate buffers in studies on cell biology in vitro, especially in serum-free media.

Interaction of endothelin-1 and nitric oxide in endothelial barrier failure in the cat hindlimb.

OBJECTIVE: To determine the interactions of endothelin-1 (ET-1) and nitric oxide (NO) in the regulation of endothelial barrier function in skeletal muscle. METHODS: The protein sieving coefficient (1 - sigma f) was measured as an index of microvascular permeability in the isolated, perfused cat hindlimb preparation. The measurement was made to determine 1) the effects of ET-1 and NO on basal permeability by blocking the ETA receptor with BQ123 and NO production with the NO-synthase inhibitors L-NAME or L-NMMA; 2) if elevated NO (SNAP) affects permeability; and 3) the interaction of ET-1 and NO by ascertaining if NO-synthase inhibition or elevated NO can block the ET-1-induced permeability increases. Additionally, vascular resistance was determined under these conditions to see if increased microvascular pressures or increased shear stress might play a role in the permeability changes. RESULTS: Blocking either the ETA receptor or basal NO production did not affect basal permeability. Likewise, raising NO levels did not affect this permeability. Blocking the ETA receptor blocked the ability of ET-1 to cause a profound barrier failure. Increased NO also could block this ET-1-induced effect. Blocking the ETA receptor or elevating NO blocked the 2.5-fold increase in vascular resistance induced by ET-1. CONCLUSIONS: Since the ETA receptor does not reside on skeletal muscle endothelium, it is not likely that ET-1 acts directly on the endothelium to produce its effects. It could act through 1) increases in shear stress secondary to an ET-1-induced vasoconstriction; 2) ET-1-induced increases in microvascular pressure sufficient to cause an inflammatory reaction; or 3) stimulation of other cell types, such as leukocytes, to release inflammatory mediators that could damage the endothelium.

Endothelin-1 induces endothelial barrier failure in the cat hindlimb.

Our purpose was to see whether endothelin- (ET) 1 could produce a change in the endothelial membrane barrier to protein in skeletal muscle. Previous studies in other tissues have suggested that ET-1 affects this barrier, but the measurement methods used could not exclude vascular protein extravasation due to microvascular pressure changes or the effects of changes in perfused capillary surface area. We measured the protein sieving coefficient, a specific measure of the permeability of the membrane to protein, in the isolated, perfused cat hindlimb preparation. The integral-mass balance method determined this coefficient from the changes in hematocrit and plasma protein concentration induced by a period of transvascular fluid filtration. The data clearly indicate that ET-1 produces a dose (1-20 nM) dependent increase in permeability indicative of barrier dysfunction. Hence, elevated ET levels may contribute to the perivascular edema, hemoconcentration, and impaired tissue perfusion found in systemic inflammatory response syndromes and related diseases.

Prediction of permeability-surface area product data by continuous-distribution pore models.

OBJECTIVE: To investigate the ability of continuous-distribution pore models to accurately predict permeability-surface area product (PS) experimental data in skeletal muscle. METHODS: Models having a water-only (WO) pathway and continuous distributions of microvascular transport-pathway sizes were fit to solute reflection-coefficient (sigma) experimental data (approximately 0.5-16 nm Stokes radii) obtained from skeletal muscle to determine optimal parameter values. Without further modification, these models were used to predict experimental PS values obtained from the literature for small solutes ranging in size from NaCl to inulin and for three proteins, alpha-lactalbumin, ovalbumin, and albumin (approximately 0.23-3.7 nm radii). The protein PSs were determined from fluorescent tracer-diffusion curves and a nonlinear model of tracer diffusion in the cat hindlimb preparation. The model's PS predictions were compared to those of a discrete-pore model previously developed and a fiber-matrix (FM) model. RESULTS: A log-normal (LN) continuous pore-size distribution plus WO-pathway model (three free parameters) fit the sigma data to within the 95% confidence intervals of each of eight solutes spanning a 32-fold size range and was nearly as close to the data as was the two discrete-pore plus WO-pathway model (four free parameters). Both models closely described the PS data for nine solutes spanning a 14-fold size range. The fit of a fiber-matrix plus WO-pathway model (three free parameters) to the sigma data was much poorer than for the other models. CONCLUSIONS: The LN and two-discrete-pore models accurately describe sigma and PS experimental data in cat and human skeletal muscle. Therefore, experimental data resulting from complex microvascular transport processes are well characterized by simple pore models.

Voltage-gated sodium channels in cardiac microvascular endothelial cells.

The goal of this study was to determine whether inward Na+ or Ca2+ currents could be measured in cardiac microvascular endothelial cells (CMEC). CMEC were isolated from rat ventricular muscle and studied during days 1-4 in culture. Differential uptake of fluorescently labeled acetylated low-density lipoproteins (LDL) indicated that the primary culture contained > 90% CMEC. Membrane currents were measured with the use of the whole cell arrangement of the patch-clamp technique with a Cs+ internal solution to prevent contamination by outward K+ currents. Voltage steps positive to -30 mV resulted in the activation of a fast, inward Na+ current (INa). In 20 cells examined, the peak inward current measured at 0 mV was 2.1 pA/pF. The half-maximal voltage required for inactivation of INa was -45 mV, and the current recovered from inactivation with a time constant of 10 ms. Inward currents were eliminated by replacement of external sodium with N-methylglucamine and were blocked by both tetrodotoxin (TTX) (dissociation constant = 5 nM) and saxitoxin (50 nM). Stimulation of protein kinase C, through application of phorbol 12,13-dibutyrate, resulted in an increase in the amplitude of INa without any change in the voltage dependence of current activation. Thus the endothelium of cardiac microvessels may be unique in expressing voltage gated, TTX-sensitive Na+ channels.

Simulation of human thermoregulation during water immersion: application to an aircraft cabin water-spray system.

A model was developed of transient changes in metabolic heat production and core temperature for humans subjected to cold conditions. It was modified to predict thermal effects of the upper parts of the body being sprayed with water from a system designed to reduce the smoke effects of an airplane fire. Temperature changes were computed at 25 body segments in response to water immersion, cold-air exposure, and windy conditions. Inputs to the temperature controller were: (a) temperature change signals from skin segments and (b) an integrated signal of the product of skin and head-core (hypothalamic) temperature changes. The controller stimulated changes in blood flow to skin and muscle and heat production by shivering. Two controller parameters were adjusted to obtain good predictions of temperature and heat-production experimental data in head-out, water-immersion (0 degree-28 degrees C) studies in humans. A water layer on the skin whose thickness decreased transiently due to evaporation was added to describe the effects of the water-spray system. Because the layer evaporated rapidly in a very cold and windy environment, its additional cooling effect over a 60-min exposure period was minimal. The largest additional decrease in rectal temperature due to the water layer was < 1 degree C, which was in normal conditions where total decreases were small.

Determination of the magnitude of the water-exclusive pathway in cat skeletal muscle microvasculature.

OBJECTIVE: To measure the magnitude of the water-exclusive pathway in cat skeletal muscle. METHODS: The osmotic reflection coefficient (sigma d) was measured for sucrose, raffinose and cyancobalamine using osmotic transient techniques in the isolated, perfused cat hindlimb preparation at sufficiently high perfusate flows (60-80 ml/min-1 100 g-1) so that solute diffusion was not a factor. Microvascular filtration coefficient values required for the sigma d determination were measured using the capillary filtration coefficient (CFC) technique at these high flows. With these sigma d data and macromolecular reflection coefficient data from a previous study, discrete pore-modeling techniques were used to estimate the magnitude of the water movement through the water-exclusive pathway. RESULTS: CFC values increased significantly at very high flows ( > 80 ml/ min-1 100 g-1), but these values were unchanged from control at the lower flows used to measure sigma d. The sigma d values for sucrose and raffinose were 0.41 +/- 0.03 SE and 0.42 +/- 0.03 SE, respectively, in 12 limbs. In the same limbs, the sigma d for cyancobalamine was 0.52 +/- 0.03 SE, which was significantly (p < 0.05) larger, consistent with a larger Stokes-Einstein radius for this molecule. A 3-pathway model (small and large pores and a water-exclusive pathway) was fit to the data. The result was that 41 +/- 4% (95% confidence interval) of total water flow makes use of the water-exclusive pathway in this preparation. CONCLUSIONS: The very high fraction of water flow through the water-exclusive pathway in cat skeletal muscle suggests that this pathway is of major importance in microvascular water movement under normal conditions. Failure to take this finding into account can lead to inaccuracies in the estimation of parameters for pathways which carry solute.

Identification of microvascular transport pathways in skeletal muscle.

The solvent-drag reflection coefficient (sigma f) was measured from plasma disappearance (integral-mass balance method) for native albumin and four fluorescent solutes of radii from 2 to 16 nm in the isolated, plasma-perfused cat hindlimb preparation. The data for the smallest solutes were measured > 2 h after tracer addition and at high filtration rates to avoid underestimation of sigma f due to tracer diffusion. A two-pore model was fit (small-pore and large-pore radii, approximately 3.5 and 23 nm, respectively, 84% of hydraulic capacity in small pores) to these data using an objective computer-based estimation procedure. In the model, membrane sigma f was determined by flow weighting the sigma f values for the two pathways. Also, the phenomenon of volume circulation among the pathways was included. In different limbs, the permeability-surface area (PS) product was measured for the smallest solute, alpha-lactalbumin, from its perfusate-disappearance transient and a linear diffusion model. The PS value estimated was 0.11 +/- 0.026 (95% confidence limits) ml.min-1 times 100 g muscle-1. These PS values were found to be coincident with those predicted using parameter sets derived from the multiparameter 95% confidence space consistent with the two-pore model fits. The two-pore model also closely predicted PS data for small solutes from other studies in skeletal muscle; however, it failed to adequately describe small-molecule transport data from osmotic transient studies. It was necessary to add a water-exclusive pathway (40% of total hydraulic capacity) to account for these latter data; however, the predictions with this addition were still consistent with the data measured in the present study. We conclude that pore models can describe both macromolecular and small solute reflection coefficient and PS data in skeletal muscle.

Effect of cold on ischemia--reperfusion-induced microvascular permeability increase in cat skeletal muscle.

The effects of reduced temperature during ischemia (I) upon microvascular permeability and resistance increases during reperfusion (R) were assessed in skeletal muscle. Protein solvent-drag reflection coefficients (sigma f) and changes in vascular resistance were measured during 37 degrees C reperfusion of isolated, whole-blood perfused cat hindlimbs after the limbs had been subjected to 3.5 h of ischemia at several temperatures. sigma f was determined from the disappearance rates of water and protein from the circulating perfusate during a period of induced microvascular fluid filtration. The I/R procedure at 37 degrees C caused sigma f to fall from approximately 0.85 to approximately 0.5, indicating a large increase in microvascular permeability. Hypothermic ischemia at 30, 22, 17, or 12 degrees C totally abolished this drop in sigma f. However, when the ischemia was at approximately 5 degrees C, there was a significant fall in sigma f to approximately 0.7, which was similar to the value we found previously with 5 h of continuous perfusion at this low temperature. The normothermic I/R procedure led to an increase in vascular resistance of approximately 250% above the value measured prior to I/R. Hypothermic ischemia totally abolished this resistance increase, except for the lowest temperature, for which the increase was 150%. Therefore, hypothermia can prevent the microvascular dysfunction caused by 3.5 h of ischemia at 37 degrees C in this preparation. However, when the temperature was reduced too far (approximately 5 degrees C), a cold injury to the microvascular resulted in permeability and resistance increases.

Platelet activating factor-induced microvascular permeability increases in the cat hindlimb.

Changes in microvascular permeability induced by platelet activating factor (PAF) were measured in the isolated, perfused cat hindlimb preparation, and compared to the effect produced by another inflammatory mediator, histamine. Permeability was assessed from changes in the protein reflection coefficient, as measured from changes in hematocrit and protein concentration resulting from microvascular fluid filtration. The findings were 1) PAF produces transient increases in permeability similar to histamine, but PAF is approximately 30 times as potent; 2) the permeability changes induced by 76 nM PAF can be totally inhibited by the specific PAF receptor blocker WEB-2086, but the blocker can only partially inhibit 380 nM PAF, a dose that produces a maximal increase in permeability; 3) Diphenhydramine (2 microM), an H1-receptor blocker, totally inhibits the transient permeability increase produced by 2 microM histamine; 4) Cimetidine (2 or 20 microM), an H2 blocker, could not inhibit this latter increase; 5) Isoproterenol (1 microM), a beta-agonist, totally inhibited the permeability increase produced by 1 microM histamine, but 10 microM isoproterenol only partially inhibited the maximal permeability increase produced by 10 microM histamine; 6) Isoproterenol could not inhibit PAF's permeability effect; and 7) PAF's effects were unchanged by depletion of white blood cells in the perfusate. These results suggest that PAF and histamine work through different pathways to increase permeability, but the final step of endothelial contraction, which opens large inter-endothelial gaps, occurs in response to both mediators. In addition, when concentrations of these inflammatory agents are sufficient to produce maximal permeability increases, as can occur in shock situations, then the permeability increases are more sustained and resistant to receptor inhibition.

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.

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.

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)