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Components of the activated complement cascade are considered to play a pivotal role in ischemia-reperfusion-induced organ injury. With the use of intravital epifluorescence microscopy, we investigated the effect of complement inhibition by the recombinant soluble complement receptor 1 (sCR1; TP10) on the effect of macromolecular microvascular permeability, functional capillary perfusion, and leukocyte endothelium interaction in postischemic pancreatitis. Anaesthetized Sprague-Dawley rats were subjected to 60 min of normothermic pancreatic ischemia induced by micro-clipping of the blood-supplying arteries of the organ. Rats who received sCR1 (15 mg/kg body wt iv; n = 7) during reperfusion showed a significant reduction of permeability (1.77 [+ or -] 1.34 x [10.sup.-8] cm/s; n = 7) of tetramethylrhodamine isothiocyanate-labeled albumin injected 90 min after the onset of reperfusion compared with vehicle-treated animals (6.95 [+ or -] 1.56 x [10.sup.-8] cm/s; n = 7). At 120 min after the onset of reperfusion, the length of red blood cell-perfused capillaries (functional capillary density) was significantly improved (from 279 [+ or -] 15.7 to 330 [+ or -] 3.7 [cm.sup.-1]; n = 7) and the number of leukocytes adherent to postcapillary venules was significantly reduced (from 314 [+ or -] 87 to 163 [+ or -] 71 [mm.sup.-2]; n = 7) by sCR1 compared with vehicle treatment. Complement inhibition by sCR1 effectively ameliorates pancreatic ischemia-reperfusion-induced microcirculatory disturbances and might be considered for treatment of postischemic pancreatitis. permeability; ischemia; reperfusion; acute pancreatitis; transplantation

Orthogonal polarization spectral (OPS) imaging is a new technique that can be used to visualize the microcirculation with reflected light. It uses hemoglobin absorption to visualize the red blood cells (RBCs). Thus the method could fail at low hematocrit (Hct). The aim of this study was to validate OPS imaging for quantitative measurements of diameter and functional capillary density (FCD) under conditions of hemodilution of varying degrees to achieve a wide range of Hcts. The validation was performed in the dorsal skinfold chamber of nine awake Syrian golden hamsters. Measurements of vessel diameter and FCD were performed off-line using Cap-Image on video sequences captured using OPS imaging and standard intravital fluorescence microscopy at baseline, 85, 70, 55, and 40% of the initial Hct. For hemodilution, isovolumic exchange of blood for 6% Dextran 60 was performed. Bland-Altman plots for the vessel diameter and FCD show good agreement between the two methods for both parameters at all studied Hcts. As expected, there was a systematic bias of ~4 [micro]m in the diameter measurements since the RBC column was measured and not the intravascular diameter. In conclusion, OPS imaging can be used to measure diameter and FCD at a wide range of Hcts. Cytoscan; orthogonal polarization spectral imaging

A substantial loss of fluorescent-labeled microspheres (FM) is often a problem in the utilization of FM for measuring regional blood flow. A filtration device was designed that permits the tissue sample to remain in a single container throughout the process to make it easier and to prevent the loss of FM. The main part of the sample-processing unit is a single-tube filtration device with a polyamide wire mesh.

The role of leukocyte plugging and edema in skeletal muscle ischemia-reperfusion injury was examined to observe the effects of interstitial edema and leukocyte-capillary plugging. Results of the experiment revealed that phalloidin treatment preserved the endothelial barrier, improved functional capillary density and reduced the amount of PI measured. Furthermore, macromolecular leakage plays an essential role in tissue injury.

Intravital microscopy was utilized to determine the effects of dextran in rabbit striated muscles during ischemia-reperfusion injury. Administration of dextran reduced postischemic leukocyte rolling and leukocyte adherence by preventing the reduction in functional capillary density in rabbit striated muscles during ischemia-reperfusion. Furthermore, the effects of dextran were mediated by steric interference of large polysaccharide molecules with the different binding sites involved in leukocyte rolling and adherence.

The effects of varying duration of ischemia in hamster striated skeletal muscles were analyzed to determine the various stages of ischemia-reperfusion injury. One to two hours of ischemia produced negligible damage in microvascular function and increased venule diameter and rolling fraction. Furthermore, ischemia stimulated leukocyte activity by increasing the number of adherent leukocytes and reductions in capillary perfusion.

We used venous congestion strain gauge plethysmography (VCP) to measure the changes in fluid filtration capacity (K(f)), isovolumetric venous pressure (Pv(i)), and blood flow in six volunteers before, on the 118th day (D118) of head-down tilt (HDT), and 2 days after remobilization (Post). We hypothesized that 120 days of HDT cause significant micro- and macrovascular changes. We observed a significant increase in K(f) from 3.6 +/- 0.4 x 10(-3) to 5.7 +/- 0.9 x 10(-3) ml. min(-1). 100 ml(-1). mmHg(-1) (+51.4%; P < 0.003), which returned to pretilt values (4.0 + 0.4 x 10(-3) ml. min(-1). 100 ml(-1). mmHg(-1)) after remobilization. Similarly, Pv(i) increased from 13.4 +/- 2.1 mmHg to 28.9 +/- 2.8 mmHg (+105.8%; P < 0.001) at D118 and was not significantly different at Post (12.4 +/- 2.6 mmHg). Blood flow decreased significantly from 2.3 +/- 0.3 to 1.3 +/- 0.2 ml. min(-1). 100 ml tissue(-1) at D118 and was found elevated to 3.4 +/- 0.7 ml. min(-1). 100 ml tissue(-1) at Post. We believe that the increased K(f) is caused by a higher microvascular water permeability. Because this may result in edema formation, it could contribute to the alterations in fluid homeostasis after exposure to microgravity.

Because 6 degrees head-down tilt (HDT) is an established method to mimic low gravity on earth, the aim of the present study was to determine the effects of 120-day HDT on psychic stress and peripheral blood immune cells in six healthy male volunteers. Psychological state was assessed by a current stress test, and cortisol was measured in saliva. During HDT, all volunteers developed psychic stress, and the diurnal rhythm of cortisol secretion was significantly altered. In addition, urine excretion of dopamine and norepinephrine increased. The innate part of the immune response was activated, as evidenced by the increase in the expression of beta(2)-integrins on polymorphonuclear leukocytes and a rise in the number of circulating natural killer (NK) cell lymphocytes. The ratio of T-helper to T-cytotoxic and T-suppressor cells decreased, whereas no changes in T and B lymphocytes were observed. Plasma levels of interleukin-6 increased significantly and returned to basal levels after the end of the HDT period. Thus 6 degrees HDT appears to be a valid model to induce psychic stress and neuroendocrine-related changes in the immune system, changes that might also be encountered by astronauts and cosmonauts during long-duration spaceflights.

Hemorrhagic shock alters heterogeneity of regional myocardial perfusion (RMP) in the presence of critical coronary stenosis in pigs. Conventional resuscitation has failed to reverse these effects. We hypothesized that improvement of the resuscitation regime would lead to restoration of RMP heterogeneity. Diaspirin-cross-linked hemoglobin (10 g/dl; DCLHb) and human serum albumin (8.0 g/dl; HSA) were used. After baseline, a branch of the left coronary artery was stenosed; thereafter, hemorrhagic shock was induced. Resuscitation was performed with either DCLHb or HSA. At baseline, the fractcal dimension (D) of subendocardial myocardium was 1.31 +/- 0.083 (HSA) and 1.35 +/- 0.106 (DCLHb) (mean +/- SD). Coronary stenosis increased subendocardial D slightly but consistently only in the DCLHb group (1.39 +/- 0.104; P < 0.05). Shock reduced subendocardial D: 1.21 +/- 0.093 (HSA; P = 0.10), 1.25 +/- 0.092 (DCLHb; P < 0.05). Administration of DCLHb increased subendocardial D in 7 of 10 animals (1.31 +/- 0.097; P = 0.066). HSA was ineffective in this respect. DCLHb infusion restored arterial pressure and increased cardiac index (CI) to 80% of baseline values. Administration of HSA left animals hypotensive (69 mmHg) and increased CI to 122% of the average baseline value. Shock-induced disturbances of the distribution of RMP were improved by administration of DCLHb but not by HSA.

Microcirculatory alterations with reduced nutritive supply to the pancreas could be the cause of hyperamylasemia, which occurs in some patients receiving the vasoactive oxygen carrier diaspirin cross-linked hemoglobin (DCLHb) in clinical studies. Therefore, the effects of DCLHb on rat pancreas microcirculation were evaluated. Anesthetized Sprague-Dawley rats received one of the following treatments during baseline conditions (n = 7 rats/group): 10% hydroxyethyl starch (HAES) (0.4 ml/kg), DCLHb (400 mg/kg), or DCLHb (1,400 mg/kg). After 1 h of complete, reversible pancreatic ischemia, other animals received 10% HAES (0.4 ml/kg) or DCLHb (400 mg/kg) during the onset of reperfusion. The number of red blood cell-perfused capillaries (functional capillary density, FCD) and the level of leukocyte adherence in postcapillary venules in the pancreas were assessed by means of intravital microscopy during 2 h after treatment. In the nonischemic groups, FCD was 18% greater after DCLHb (1,400 mg/kg) than after 10% HAES treatment without any increase in leukocyte adherence. In the inschemia-reperfusion (I/R) 10% HAES group, FCD was significantly (P < 0.05) lowered, leukocyte adherence enhanced, and mean arterial pressure (MAP) reduced by 31% compared with nonischemic animals. DCLHb treatment in the I/R group resulted in a slight increase in FCD, a significant (P < 0.05) reduction of leukocyte adherence, and a complete restoration of MAP compared with the animals of the I/R control group. Thus our data provide no evidence for a detrimental effect on the pancreatic microcirculation or an enhanced risk of postischemic pancreatitis by DCLHb.

Acute normovolemic hemodilution (ANH) is efficient in reducing allogenic blood transfusion needs during elective surgery. Tissue oxygenation is maintained by increased cardiac output and oxygen extraction and, presumably, a more homogeneous tissue perfusion. The aim of this study was to investigate blood flow distribution and oxygenation of skeletal muscle. ANH from hematocrit of 36 +/- 3 to 20 +/- 1% was performed in 22 splenectomized, anesthetized beagles (17 analyzed) ventilated with room air. Normovolemia was confirmed by measurement of blood volume. Distribution of perfusion within skeletal muscle was determined by using radioactive microspheres. Tissue oxygen partial pressure was assessed with a polarographic platinum surface electrode. Cardiac index (3.69 +/- 0.79 vs. 4.79 +/- 0.73 l. min-1. m-2) and muscle perfusion (4.07 +/- 0.44 vs. 5.18 +/- 0.36 ml. 100 g-1. min-1) were increased at hematocrit of 20%. Oxygen delivery to skeletal muscle was reduced to 74% of baseline values (0.64 +/- 0.06 vs. 0.48 +/- 0.03 ml O2. 100 g-1. min-1). Nevertheless, tissue PO2 was preserved (27.4 +/- 1.3 vs. 29.9 +/- 1. 4 Torr). Heterogeneity of muscle perfusion (relative dispersion) was reduced after ANH (20.0 +/- 2.2 vs. 13.9 +/- 1.5%). We conclude that a more homogeneous distribution of perfusion is one mechanism for the preservation of tissue oxygenation after moderate ANH, despite reduced oxygen delivery.

Hemoglobin-based oxygen carriers have been suggested to enhance the formation of oxygen free radicals, especially under conditions of ischemia-reperfusion (I/R), in which activation and adhesion of leukocytes play a pivotal role for propagation of reperfusion injury. This study investigates the effects of the hemoglobin-based oxygen carrier diaspirin-cross-linked hemoglobin (DCLHb) in an I/R model of hamster striated skin muscle. The dorsal skinfold chamber model in the awake Syrian golden hamster was used for analysis of the microcirculation and local tissue PO2 in striated skin muscle utilizing the technique of intravital fluorescence microscopy and a multiwire platinum surface (Clark type) electrode. Measurements were made before 4 h of pressure-induced ischemia and at 0.5, 2, and 24 h of reperfusion. Animals were treated with 5 ml/kg body wt of either 10% DCLHb (n = 8), 6% Dextran 60 (Dx-60; 60 kDa, n = 8), or 0.9% NaCl (n = 7), which was given intravenously 15 min before reperfusion. In animals treated with DCLHb or Dx-60, a significant decrease of leukocytes rolling along and sticking in postcapillary venules, associated with a recovery of functional capillary density and red blood cell velocity, was observed compared with saline-treated controls. In the early reperfusion period (0.5 h), DCLHb and Dx-60 efficiently restored local tissue PO2, whereas tissue PO2 decreased from 18.3 +/- 1.9 to 15.3 +/- 5.3 mmHg in 0.9% NaCl-treated animals. Electron microscopic analysis of the postischemic tissue at 24 h of reperfusion revealed markedly reduced tissue damage in animals treated with DCLHb compared with Dx-60 or isotonic saline. These results indicate that DCLHb attenuates postischemic reperfusion injury of striated skin muscle, presumably through alterations of leukocyte-endothelial cell interactions.

In seven anesthetized dogs, the effects of acute normovolemic hemodilution (ANH) to a hematocrit of 20 and 8% and the effects of hyperoxic ventilation (100% oxygen) on distribution of regional pulmonary blood flow (rPBF; radioactive microspheres) were investigated. Normovolemia was monitored with blood volume measurements (indocyanine green dilution kinetics). Before ANH, fractal dimension (D) of rPBF in the whole lung was 1.19 +/- 0.09 (mean +/- SD). Spatial correlation (rho) of rPBF in the whole lung was 0.6 +/- 0.08. D is a resolution-independent measure for global rPBF distribution, and rho is the averaged flow relationship of directly neighboring lung samples. With regard to the entire lung, neither ANH nor hyperoxia changed D or rho. With regard to horizontal, isogravitational planes, ANH induced opposite changes of rPBF heterogeneity depending on the vertical location of the plane and the parameter used. In ventral planes, a change in relative dispersion (SD/mean) indicated decreased homogeneity. However, rho suggested more homogeneous perfusion. Hyperoxia restored baseline rPBF distribution. Our data suggest that ANH causes different alterations of heterogeneity of rPBF depending on location within the lung.

Myocardial blood flow heterogeneity in shock and small-volume resuscitation in pigs with coronary stenosis. J. Appl. Physiol. 83(6): 1832-1841, 1997.-We analyzed the effects of shock and small-volume resuscitation in the presence of coronary stenosis on fractal dimension (D) and spatial correlation (SC) of regional myocardial perfusion. Hemorrhagic shock was induced and maintained for 1 h. Pigs were resuscitated with hypertonic saline-dextran 60 [HSDex, 10% of shed blood volume (SBV)] or normal saline (NS; 80% of SBV). Therapy was continued after 30 min with dextran (10% SBV). At baseline, D was 1.39 +/- 0.06 (mean +/- SE; HSDex group) and 1.34 +/- 0.04 (NS group). SC was 0.26 +/- 0.07 (HSDex) and 0.26 +/- 0.04 (NS). Left anterior descending coronary artery stenosis changed neither D nor SC. Shock significantly reduced D (i.e., homogenized perfusion): 1.26 +/- 0.06 (HSDex) and 1.23 +/- 0.05 (NS). SC was increased: 0.41 +/- 0.1 (HSDex) and 0.48 +/- 0.07 (NS). Fluid therapy with HSDex further decreased D to 1.22 +/- 0.05, whereas NS did not change D. SC was increased by both HSDex (0.56 +/- 0.1) and NS (0.53 +/- 0.06). At 1 h after resuscitation, SC was constant in both groups, and D was reduced only in the NS group (1.18 +/- 0.02). We conclude that hemorrhagic shock homogenized regional myocardial perfusion in coronary stenosis and that fluid therapy failed to restore this.