Capillary Blood Cell Velocity Research Articles

Microvascular dysfunction in rheumatoid arthritis assessed by laser Doppler anemometry: relationship to soluble adhesion molecules and extraarticular manifestations

In search of a noninvasive diagnostic test for rheumatoid vasculitis (RV), this study addressed the questions whether changes in capillary blood cell velocity (CBV) detected by laser Doppler anemometry in patients with rheumatoid arthritis (RA) were correlated with the levels of soluble adhesion molecules and whether cutaneous flow abnormalities may reflect extraarticular manifestations in RA. In 31 RA patients and 20 patients with osteoarthritis (OA), CBV was measured in the skin above the left ring finger at rest and after 3-min arterial occlusion. Serum levels of soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1), soluble E-selectin (sE-selectin), and soluble P-selectin (sP-selectin) were assessed by enzyme linked immunosorbent assay. Peak CBV was reduced in RA patients compared to OA patients (0.42 +/- 0.07 mm/s vs. 0.70 +/- 0.13 mm/s; P = 0.013). Both CBV during rest and reactive hyperemia were not correlated with the levels of soluble adhesion molecules. There were no significant differences in resting or peak CBV between RA patients with or without extraarticular manifestations. The lack of an inverse correlation between the levels of soluble adhesion molecules and CBV during rest and reactive hyperemia contradicts the assumption that inflammatory vascular damage indicated by increased levels of soluble adhesion molecules was the main reason for the impairment of microcirculation. The present results do not suggest that cutaneous flow abnormalities may reflect extraarticular manifestations in RA.

High Speed Digital Video Capillaroscopy: Nailfold Capillary Shape Analysis and Red Blood Cell Velocity Measurement

Nailfold capillaroscopy has been shown to reflect microvascular disturbances mainly in connective tissue diseases, and the development of video capillaroscopy made it possible to determine capillary red blood cell velocity by measuring the displacement of plasma gaps between red cells. We improved both temporal and spatial resolutions of video capillaroscopy by developing the high speed digital video capillaroscopy, integrating high speed digital video camera, deep-focus zoom lens, appropriate light source and light collecting adaptor. The first objective of this study is to present the novel method for quantitative capillary shape analysis by using the level-set method. The capillary radius distribution along the capillary center line is obtained and described by the level-set function. Based on this mathematical description of capillary shape, more rigorous definition of the capillary red blood cell velocity than the conventional method is discussed. The second objective of this study is to propose the innovative measurement method of red blood cell velocity in nailfold capillary, and then the possibility of tracking the individual red blood cell movement, not only in the axial direction but also lateral direction, in human nailfold capillary is discussed

Nailfold Videocapillaroscopy in Primary Sjögren’s Syndrome

Nailfold videocapillaroscopy was performed in 2 groups of subjects: 14 healthy volunteers (C) and 15 patients with primary Sjögren's syndrome (PSS). This was a controlled clinical trial, matched by age and sex. The aims of this study were to evaluate (1) functional capillary density (number of capillaries with flowing red blood cells per mm(2), FCD); (2) capillary red blood cell velocity at rest (RBV), maximum capillary red blood cell velocity (RBV(max)) after 1 minute ischemia, and the time to reach it (TRBV(max)), taking into account the presence or absence of Raynaud's phenomenon (RP) in the analysis; (3) nailfold capillary morphology; and (4) afferent (AFD), apical (APD), and efferent (EFD) capillary diameters. The mean values obtained for controls versus patients, respectively, were (mean +/- SD): FCD (per mm(2)) 8.0 +/-1.6 and 10.1 +/-3.6; RBV (mm/s) 0.9 +/-0.4 and 0.7 +/-0.2; RBV(max) (mm/s) 1.7 +/-0.9 and 1.3 +/-0.3; TRBV(max) (s) 4.5 +/-0.8 and 5.8 +/-1.6 (p=0.02); and TRBV(max) (s) in patients with RP=6.7 +/-1.6 and without RP=5.6 +/-1.6 (p=0.52). The correlation between RBV and RBV(max) for each group, using the Pearson's coefficient, was significant only for the control group (p=0.007), estimated correlation coefficient = 0.68. Controls and patients showed, in the majority of fields examined, normal morphologic patterns of capillaries. The capillary diameters were AFD (mum) 10.8 +/-1.5 and 11.3 +/-1.8; APD (mum) 16.3 +/-2.4 and 16.8 +/-2.9; and EFD (mum) 12.3 +/-1.4 and 13.7 +/-1.9. These results indicate that these patients have longer time to reach RBV(max), suggesting an impairment of the reactive hyperemia response, which could correlate with clinical features of the disease, ie, abnormal macrovascular and microvascular reactivity.

A cellular nonlinear network: real-time technology for the analysis of microfluidicphenomena in blood vessels

A new approach to the observation and analysis of dynamic structural and functionalparameters in the microcirculation is described. The new non-invasive optical system isbased on cellular nonlinear networks (CNNs), highly integrated analogue processor arrayswhose processing elements, the cells, interact directly within a finite local neighbourhood.CNNs, thanks to their parallel processing feature and spatially distributed structure, arewidely used to solve high-speed image processing and recognition problems and in thedescription and modelling of biological dynamics through the solution of timecontinuous partial differential equations (PDEs). They are therefore consideredextremely suitable for spatial–temporal dynamic characterization of fluidic phenomenaat micrometric to nanometric scales, such as blood flow in microvessels and itsinteraction with the cells of the vessel wall. A CNN universal machine (CNN-UM)structure was used to implement, via simulation and hardware (ACE16k), thealgorithms to determine the functional capillarity density (FCD) and red blood cellvelocity (RBCV) in capillaries obtained by intravital microscopy during in vivoexperiments on hamsters. The system exploits the moving particles to distinguishthe functional capillaries from the stationary background. This information isused to reconstruct a map and to calculate the velocity of the moving objects.

Gender differences in ischemia-reperfusion-induced microcirculatory and epithelial dysfunctions in the small intestine

Female sex hormones have been reported to preserve endothelial integrity and to reduce inflammation. However, gender-related differences in the intestinal mucosal barrier function during compromised perfusion after ischemia and transplantation have not been defined. Herein, we applied intravital microscopy to determine the mucosal epithelial and intestinal microcirculatory responses in ileal villus and longitudinal muscle layers in a murine model of 30-min intestinal ischemia and 90-min reperfusion. In male animals, the entire reperfusion period was characterized by a significantly increased epithelial permeability. This was associated with an early leukocytic inflammatory response and late alterations in functional capillary density, capillary red blood cell velocity and mitochondrial redox state. In contrast, the female intestine exhibited a delayed increase in epithelial permeability during postischemic reperfusion. This was associated with a late leukocytic inflammatory response which did not affect the microcirculatory function. Nonetheless, at the end of the 90-min reperfusion period, the neutrophilic infiltration and structural mucosal disintegration in the female intestine were found to be pronounced to a similar extent as in the male intestine. These results suggest that in small intestinal ischemia–reperfusion the leukocytic inflammatory response and microcirculatory dysfunction develop more rapidly and are initially more pronounced in males, but the hormonal status in females is not capable of preventing the final manifestations of reperfusion injury.

Time Course of Changes in Nail Fold Microcirculation Induced by Acupuncture Stimulation at the Waiguan Acupoints

Acupuncture has been used widely to treat disease; however, the time course for acupuncture to have an effect remains unclear. Therefore, the aim of the present study was to investigate the time course of changes in nail fold microcirculation (NFM) induced by acupuncture stimulation (AS) at the right and left Waiguan acupoints (WAs). A total of 38 healthy female volunteers, age range from 21 to 33, were studied. We recorded NFM of the right middle finger before, and 5 min, 10 min, 15 min and 20 min after initiating AS; NFM was also recorded 5 min and 10 min after secessions of AS. Nitric oxide (NO) and endothelin-1 levels were measured from the left cubital vein, before AS and 10 min after stopping AS. The results indicated that capillary density of NFM increased 5 min after AS at the right Waiguan acupoint (WA); however, similar changes were not noted at the left WA. The capillary density decreased beginning 15 min after AS at the right and left WA. Capillary red blood cell velocity increased 5 min and 10 min after AS at the right and left WAs, but decreased 5 min and 10 min after stopping AS at the left WA. NO and endothein-1 levels were similar before AS and 10 min after stopping AS. Therefore, we suggest that a segmental effect of the spinal nerve contributes to the increasing capillary density of NFM induced by AS. The effect of acupuncture on NFM lasts about 10-15 min. The changes of balance between the sympathetic nerve activities and parasympathetic nerve activities may be induced by AS.

Lack of a difference in increased capillary blood cell velocity in the skin over proximal interphalangeal joints between rheumatoid arthritis and osteoarthritis

Early detection of synovitis in rheumatoid arthritis (RA) and distinction from osteoarthritis (OA) are important to establish the most appropriate treatment. Increased perfusion over affected joints observed by laser Doppler perfusion imaging was supposed to arise from the underlying joint, because it was detected only by a near-infrared laser and not by a less penetrating red laser source. Using laser Doppler anemometry, this study addressed two questions: (1) whether capillary blood cell velocity (CBV) is increased in the skin over finger joints affected by RA or OA; (2) whether there is a difference between RA and OA in CBV above affected proximal interphalangeal (PIP) joints. Levels of soluble adhesion molecules were measured, because they indicate rheumatoid vasculitis raising flow resistance. Thirty-one patients with RA and 20 with OA were investigated. Compared to 18 controls, CBV (mean ± SEM) was elevated above PIP joints clinically affected by RA (0.35 ± 0.06 mm/s vs. 0.21 ± 0.02 mm/s; P < 0.05) and over PIP (0.27 ± 0.02 mm/s vs. 0.21 ± 0.02 mm/s; P < 0.05) and distal interphalangeal joints (0.27 ± 0.02 mm/s vs. 0.17 ± 0.01 mm/s; P < 0.001) affected by OA. Levels of soluble adhesion molecules were not correlated with CBV over PIP joints in RA. These observations demonstrated that elevated blood cell velocity is detectable by laser Doppler anemometry in skin capillaries over interphalangeal joints affected by RA or OA and contradict the previous assumption that there is hyperemia only in the affected joint. The lack of a significant difference in CBV over PIP joints between RA and OA patients might be due to some inflammation also occurring in OA rather than to vasculitic processes in RA associated with elevated levels of soluble adhesion molecules.

Nonlinear Regulation of Capillary Perfusion in Relation to Ambient pO2 Changes in Skeletal Muscle

To study the process of O(2) transport to tissue, we investigated how capillary perfusion is controlled in response to changes in tissue O(2) levels in skeletal muscle. Capillary red blood cell (RBC) velocity and perfused capillary recruitment were measured in rabbit tenuissimus muscle at various ambient oxygen tensions (pO(2)) by intravital microscopy. Both RBC velocity and capillary recruitment significantly decreased as the pO(2) level of the suffusate was increased, and the relationship between capillary perfusion, calculated from the velocity and recruitment data, and the pO(2) level of the suffusate clearly yielded a nonlinear correlation that fitted a sigmoidal curve. Capillary perfusion dramatically decreases or increases above or below a suffusate pO(2) level of around 40 Torr, where the O(2) dissociation curve of hemoglobin changes slope. These findings support the hypothesis that microvasculature possesses an intrinsic, effective flow-control mechanism by sensing the metabolic demands of tissue, intimately related to the O(2) saturation of hemoglobin.

Protective Effects of Insulin during Ischemia-Reperfusion Injury in Hamster Cheek Pouch Microcirculation

Objective: The effects of insulin (0.18 nM–0.18 µM) on reduced capillary perfusion, microvascular permeability increase and leukocyte adhesion induced by ischemia-reperfusion injury were investigated in the hamster cheek pouch microcirculation. To gain insight into the insulin’s mechanism of action, the effects of its higher concentration (0.18 µM) were investigated after inhibition of tyrosine kinase (TK), nitric oxide synthase (NOS), protein kinase C (PKC), phosphatidylinositol 3-kinase and K⁺_(ATP) channels, alone or in combination. Two concentrations for each inhibitor were used. Methods: Microcirculation was visualized by fluorescence microscopy. Perfused capillary length, microvascular permeability, leukocyte adhesion to venular walls, vessel diameter and capillary red blood cell velocity were assessed by computer-assisted methods. Measurements were made at baseline (B), after 30 min of ischemia (I), and after 30 min of reperfusion (R). Results: In control animals, perfused capillary length decreased by 63 ± 5% of baseline at R. Microvascular permeability increased at I and R, while leukocyte adhesion was most pronounced in V1 postcapillary venules at R. Insulin dose-dependently preserved capillary perfusion at R (–28 ± 6 and –15 ± 6% of baseline), but was unable to prevent the increase in permeability at I (0.25 ± 0.05 and 0.29 ± 0.06 Normalized Grey Levels, NGL) and R (0.49 ± 0.10 and 0.53 ± 0.09 NGL), according to the concentrations. Adhesion of leukocytes was observed mostly in V3 venules at R (9 ± 2 and 10 ± 2/100 µm venular length, with the lower and higher concentration, respectively). Nitric oxide synthase inhibition by N^G-nitro-L-arginine-methyl ester prior to insulin did not affect capillary perfusion at R (–18 ± 3% of baseline with higher concentration), but prevented permeability increase (0.20 ± 0.04 NGL, according to higher concentration) and reduced leukocyte adhesion in V3 venules at R (1.5 ± 1.0/100 µm of venular length, with higher concentration). Blockade of K⁺_(ATP) channels by glibenclamide prior to insulin decreased perfused capillary length at R (–58 ± 6% of baseline with higher concentration), attenuated leakage at R (0.30 ± 0.04 NGL, according to higher concentration) and caused leukocyte adhesion mainly in V1 venules at R (9.0 ± 1.5/100 µm of venular length, with higher concentration). Inhibition of either TK, PKC or phosphatidylinositol 3-kinase did not affect microvascular responses to insulin. Simultaneous inhibition of TK and NOS did not increase protection. Conclusions: Insulin prevents ischemia-reperfusion injury by promoting capillary perfusion through an apparent activation of K⁺_(ATP) channels and increase in nitric oxide release.

Microcirculatory heterogeneity in the rat small intestine during compromised flow conditions.

To characterize and compare microcirculatory changes in the rat small intestinal tissue layers when temporal or spatial microvascular perfusion heterogeneity is present. Intravital videomicroscopy with an orthogonal polarization spectral imaging technique was used to visualize the microcirculation of the intestinal mucosa and the longitudinal muscle during systemic (hemorrhagic shock, endotoxemia, and nitric oxide synthesis inhibition) and local (ischemia-reperfusion) circulatory disorders. The average capillary red blood cell velocity (A-RBCV) was calculated from the relative durations of the observed velocity or as a function of the perfused area, respectively. During hemorrhagic hypotension/resuscitation, timewise (flowmotion) and spatial heterogeneity were found to evolve in the mucosal villi and muscle layer. During resuscitation, the A-RBCV decreased by 40% in the villi and by 60% in the muscle. Reperfusion after a 30-min period of mesenteric ischemia caused a 20% reduction in A-RBCV in both layers, while endotoxin infusion caused a temporary 20% decrease in the mucosa, and a persistent, >25% decrease in the muscle. Nitric oxide synthesis inhibition resulted in spatial heterogeneity within the villi and in a 40% decrease in A-RBCV in both structures. Calculations of timewise variability and of heterogeneity within and between layers can be used for the comparison of distinct intramural microcirculatory changes.

Microvascular oxygen transport abnormalities in experimental sepsis interpreted using a computational model

Experimental studies using a peritonitis model of sepsis in rats have reported abnormalities in microvascular perfusion including increased stopped flow capillaries, increased fast flow capillaries and impaired regulation of blood flow. We have used a spectrophotometric functional microvascular imaging system to quantify capillary geometry, red blood cell flow and red blood cell hemoglobin oxygen saturation during sepsis. We found that while oxygen saturation at the entrance of the capillary bed was unaffected in sepsis, there was a significant drop in saturation at the venous end of capillaries with normal velocities. Although the fall in oxygen saturation correlated with the number of stopped flow capillaries, we could not determine from this data whether tissue oxygen consumption changed with sepsis, whether fast flow capillaries acted as functional oxygen shunts or whether any regions of the tissue were anoxic. To address these questions we constructed a computational model that simulated O2 transport in a three-dimensional volume of tissue supplied by heterogeneously spaced capillaries with fast, normal and stopped flow. The model was based on our experimental oxygen transport data (capillary density, number of stopped flow capillaries, capillary red blood cell velocity and supply rate, and entrance oxygen saturation levels) and the model predicted oxygen consumption, tissue oxygen levels and oxygen transport in fast flow capillaries; data that could not be measured experimentally with current technology. Tissue oxygen consumption in the model was adjusted to yield the same venous end oxygen saturation values as measured experimentally. Two cases were modeled; average sepsis (AS) with 33% stopped, 33% normal and 33% fast flow, and extreme sepsis (ES) with 50% stopped, 25% normal and 25% fast flow. Simulations found approximately twofold and fourfold increases in tissue oxygen consumption for AS and ES, respectively. Average (minimum) tissue PO2 decreased from 43(40) mmHg in control to 34 (27) and 26 (15) mmHg in AS and ES, respectively. Clustering fast flow capillaries to increase flow heterogeneity resulted in only a slight decrease in minimum tissue PO2, to 14.5 mmHg. Although fast flow capillaries did appear to be oxygen shunts with higher venous oxygen saturations, they were a significant factor in preventing tissue anoxia during sepsis. Despite the contribution of fast flow capillaries, simulated tissue PO2 values continued to fall as the degree of microvascular injury increased. The model predicts that microvascular oxygen transport abnormalities associated with sepsis expose the tissue to local regions of a hypoxic environment that may lead ultimately to significant changes in cellular function.

Effects of chronic heart failure on skeletal muscle capillary hemodynamics at rest and during contractions.

Chronic heart failure (CHF) reduces muscle blood flow at rest and during exercise and impairs muscle function. Using intravital microscopy techniques, we tested the hypothesis that the speed and amplitude of the capillary red blood cell (RBC) velocity (VRBC) and flux (FRBC) response to contractions would be reduced in CHF compared with control (C) spinotrapezius muscle. The proportion of capillaries supporting continuous RBC flow was less (P < 0.05) in CHF (0.66 +/- 0.04) compared with C (0.84 +/- 0.01) muscle at rest and was not significantly altered with contractions. At rest, VRBC (C, 270 +/- 62; CHF, 179 +/- 14 microm/s) and FRBC (C, 22.4 +/- 5.5 vs. CHF, 15.2 +/- 1.2 RBCs/s) were reduced (both P < 0.05) in CHF vs. C muscle. Contractions significantly (both P < 0.05) elevated VRBC (C, 428 +/- 47 vs. CHF, 222 +/- 15 microm/s) and FRBC (C, 44.3 +/- 5.5 vs. CHF, 24.0 +/- 1.2 RBCs/s) in C and CHF muscle; however, both remained significantly lower in CHF than C. The time to 50% of the final response was slowed (both P < 0.05) in CHF compared with C for both VRBC (C, 8 +/- 4; CHF, 56 +/- 11 s) and FRBC (C, 11 +/- 3; CHF, 65 +/- 11 s). Capillary hematocrit increased with contractions in C and CHF muscle but was not different (P > 0.05) between CHF and C. Thus CHF impairs diffusive and conductive O2 delivery across the rest-to-contractions transition in rat skeletal muscle, which may help explain the slowed O2 uptake on-kinetics manifested in CHF patients at exercise onset.

Microcirculatory changes in the canine oesophageal mucosa during experimental reflux oesophagitis: Comparison of the effects of acid and bile

Background: The response of the oesophageal microcirculation to luminal damaging agents may play an important role in reflux‐induced mucosal injury. We characterized the microcirculatory consequences of exposure to bile with or without hydrochloric acid, and determined the changes in the constitutive nitric oxide synthase and inducible nitric oxide synthase activities in a canine model of acute reflux oesophagitis. Methods: Group 1 served as a saline‐treated control, while groups 2–4 were exposed for 3 h to bile alone, to hydrochloric acid, or to bile + hydrochloric acid, respectively. The mucosal microcirculation was observed continuously by means of intravital videomicroscopy with an orthogonal polarization spectral imaging technique. Myeloperoxidase, constitutive and inducible nitric oxide synthase activities were measured via tissue biopsies, while the degree of mucosal damage was evaluated histologically. Results: Bile evoked deep tissue damage and leucocyte accumulation in the mucosa and muscle layer. The capillary red blood cell velocity and the relative vessel area increased significantly (P < 0.05). The constitutive NO synthase activity was decreased, and the inducible NO synthase activity was increased significantly. In the hydrochloric acid‐treated group the functional capillary density decreased, the mucosal damage was less severe, the constitutive NO synthase activity did not change, whereas the inducible NO synthase activity was increased significantly. The constitutive NO synthase activity did not change after the bile + hydrochloric acid treatment either. Conclusion: Reflux components induce characteristic microcirculatory alterations. The structural damage and leucocyte invasion are accompanied by bile‐induced constitutive NO synthase inhibition when hydrochloric acid production is suppressed.

L-arginine and antineutrophil serum enable venular control of capillary perfusion in hypercholesterolemic rats.

The purpose of this study was to investigate and counteract dysfunctional control of capillary flow in hypercholesterolemia. Capillary flow is controlled by arteriolar tone, which in turn is influenced by mediators released from closely paired venules in a mechanism that involves nitric oxide (NO). However, venular control of capillary flow is altered with hypercholesterolemia. Rats were given a normal or high-cholesterol diet before measurements of mesenteric capillary red blood cell velocity. The arteriolar pathway leading to the capillary was videotaped to measure the percent of the surrounding area (within 15 |gmm) that was occupied by a venule (% pairing). Venule-paired arterioles were significantly smaller in hypercholesterolemia compared with normocholesterolemia, corresponding to slower capillary flow. A positive correlation between capillary velocity and % pairing observed in normocholesterolemia was not observed during NO synthase inhibition or in hypercholesterolemic rats. However, positive correlations between the two parameters were found in hypercholesterolemia when the rats were given drinking water supplementation of L-arginine or an injection of antineutrophil serum, both of which tended to improve velocity in capillaries branching from venule-paired arteriolar pathways. Dysfunctional venular control of capillary perfusion in hypercholesterolemia may be a consequence of a neutrophil-mediated deficiency of NO.

The effect of polyneuropathy on foot microcirculation in Type II diabetes.

The aim of this study was to investigate the influence of peripheral polyneuropathy (PNP) on skin microcirculation and foot swelling rate in the feet of patients with Type II (non-insulin-dependent) diabetes mellitus. 38 Type II diabetic patients, 24 with PNP (PNP+), 14 without PNP (PNP-), and 16 healthy control subjects were studied, first supine and subsequently sitting with the foot dependent for 50 mn. In patients with PNP, foot skin temperature was higher, (p<0.04) and capillary blood cell velocity (CBV, nailfold capillary microscopy), was lower compared to patients without PNP (222 vs 313 micro m/s respectively, p<0.03). Compared to the control subjects, the percentage reduction in skin blood flux, (LDF, laser-Doppler fluxmetry), after 10 min was higher in the PNP- and PNP+ patients (3% vs 18% and 26% respectively, p<0.02). These disturbances were most pronounced in PNP+ patients with a history of a foot ulcer. Foot swelling rate (mercury strain gauge plethysmography) in the first 10 min of dependency, was lower in patients with PNP+ compared to the control subjects (0.00165 vs 0.00286 ml.100 ml(-1)s respectively, p<0.01). In addition, we found a negative correlation (r=-0.41; p<0.01) between Valk-score (severity of PNP) and FSR. Type II diabetes PNP is associated with multiple abnormalities in the (skin) microcirculation of the foot, characterised by reduced capillary blood flow, an enhanced reduction in skin blood flux and impaired fluid filtration after sitting up. The most severe abnormalities were observed in patients with a history of foot ulceration.

Endothelin-A Receptor in Rat Skeletal Muscle Microvasculature

Although the effect of endothelin-1 (ET-1) on vascular tone has been studied extensively at the arterial/arteriolar level, little is known about the direct effect of ET-1 at the level of the capillary. Using intravital microscopy, we determined capillary red blood cell velocity and arteriolar diameter responses to ET-1, ETA-receptor blocker BQ-123, and ETB-receptor blocker BQ-788 applied locally on capillaries in rat extensor digitorum longus (EDL) muscle. Using immunohistochemistry, we examined capillaries in this muscle and microvascular endothelial cells isolated from this muscle for immunoreactivity with ETA-receptor antibody. ET-1 (10−9 to 10−5 M in micropipette) caused quick reductions (i.e., within several seconds), whereas BQ-123 (10−8 to 10−4 M) and BQ-788 (10−6 and 10−4 M) caused quick increases, in both velocity and diameter. Capillaries and endothelial cells showed ETA-receptor immunoreactivity. We conclude that the microvasculature of the rat EDL muscle is sensitive to ET-1 and its receptor blockers and that the ETA receptor may be present in the capillary wall of this muscle, including the endothelium.

Protective effect of ketoprofen lysine salt on interleukin-1beta and bradykinin induced inflammatory changes in hamster cheek pouch microcirculation.

The purpose of this study was to assess the efficacy of topically applied ketoprofen lysine salt (KLS), a cyclooxygenase inhibitor, against the inflammatory changes induced by interleukin-1beta (IL-1beta) and bradykinin (BK) in hamster cheek pouch microcirculation. In addition, we characterised the pharmacological regulation of IL-1beta activity in this model. Male Syrian hamsters were used. Microcirculation was visualised by fluorescent microscopy. Leukocyte adhesion, permeability, perfused capillary length (PCL) and capillary red blood cell (RBC) velocity were evaluated. KLS (25 microg/ml/min to 1.6 mg/ml/min) was topically applied for 3 min before topically administered IL-1beta (1microg/ml) and BK (10(-4) M). Monoclonal anti-mouse IL-1beta receptor antagonist (200 ng/ml), BK-B2 receptor antagonist (10(-6) M), PAF inhibitor (10(-5) M) and cycloheximide (10 microg/ml) were added topically 15, 10, 15 and 60 min, respectively, before IL-1beta (1 microg/ml). IL-1beta caused a significant increase in microvascular permeability, a decrease in capillary RBC velocity followed by increased leukocyte adhesion in postcapillary venules. BK caused a marked increase in leukocyte adhesion and no decrease in PCL and RBC velocity. Treatment with KLS significantly inhibited both the leukocyte adhesion and microvascular leakage induced by the two mediators. The inflammatory effects induced by IL-1beta were reduced by blockade of IL-1beta receptors and by a BK-B2 receptor antagonist but were not affected by a PAF antagonist and protein synthesis inhibition. These results demonstrate that KLS is effective in preventing early inflammatory changes induced by both IL-1beta and BK in the capillary network. Prostaglandin release and BK are essential components for IL-beta mediated responses, whereas neither PAF nor new protein synthesis appear to be linked to the early inflammatory changes induced by IL-1beta.

Effect of Urate on Nitric Oxide Microcirculatory Response in the Rat Tail to Body Heating

Objective: The objective of this study was to determine if nitric oxide (NO)-mediated cutaneous vasodilation depends on urate concentrations. Methods: Capillary blood cell velocities (BCV) in the tail capillary vessels of anesthetized, heat-stressed Sprague-Dawley rats were measured by the videomicroscopy method, and the femoral mean arterial pressure (MAP) was recorded on a Grass polygraph. The effects of urate or urate and NO production on the above parameters were determined by using specific inhibitors of these compounds, for example, allopurinol (All) or All or N-nitro-L-arginine (NNA), respectively. Urate concentrations were determined by an enzymatic, colorimetric method, and total nitrite levels were measured fluorometrically. Results: During heat stress, All or All and NNA significantly decreased plasma urate or urate and total nitrite concentrations, respectively, and the response of vascular conductance (estimated as a ratio of BCV to MAP). Urate administration, after All and NNA pretreatment, restored plasma urate and total nitrite concentrations and increased BCV/MAP. Conclusions: Urate at physiological concentration helps to maintain vascular conductance of cutaneous capillaries in the rat tail during body heating. The effect of urate on vascular conductance may be mediated by NO.

L-Arginine and Antineutrophil Serum Enable Venular Control of Capillary Perfusion in Hypercholesterolemic Rats

Objective: The purpose of this study was to investigate and counteract dysfunctional control of capillary flow in hypercholesterolemia. Capillary flow is controlled by arteriolar tone, which in turn is influenced by mediators released from closely paired venules in a mechanism that involves nitric oxide (NO). However, venular control of capillary flow is altered with hypercholesterolemia. Methods: Rats were given a normal or high-cholesterol diet before measurements of mesenteric capillary red blood cell velocity. The arteriolar pathway leading to the capillary was videotaped to measure the percent of the surrounding area (within 15 µm) that was occupied by a venule (% pairing). Results: Venule-paired arterioles were significantly smaller in hypercholesterolemia compared with normocholesterolemia, corresponding to slower capillary flow. A positive correlation between capillary velocity and % pairing observed in normocholesterolemia was not observed during NO synthase inhibition or in hypercholesterolemic rats. However, positive correlations between the two parameters were found in hypercholesterolemia when the rats were given drinking water supplementation of L-arginine or an injection of antineutrophil serum, both of which tended to improve velocity in capillaries branching from venulepaired arteriolar pathways. Conclusions: Dysfunctional venular control of capillary perfusion in hypercholesterolemia may be a consequence of a neutrophil-mediated deficiency of NO.

Reproducibility of skin microcirculatory measurements in humans, with special emphasis on capillaroscopy.

The reproducibility of capillaroscopic measurements of capillary blood cell velocity (CBV) in human nailfolds was investigated by use of the computerized system CapiFlow. Therefore, CBV measurements of two capillaries of each of three fingers together with laser Doppler fluxmetry (LDF) and skin temperature measurements were performed three times in five healthy volunteers. Short-term (1.5 h) intra-individual coefficient of variation (CV) of CBV was 18.4%. Long-term (7 days) CV amounted to 55.8%. Inter-individual CV was 55.9%. Short- and long-term intra-individual CVs of LDF were 25.4% and 37.3%. Inter-individual variation was 36.0%. Skin temperature showed short- and long-term CVs of 3.7% and 5.5% and inter-individual CV of 5.8%. In conclusion, measurement of CBV using CapiFlow is a suitable method to assess acute effects, but has limited value in investigating long-term effects. Because of the wide interindividual variability in both CBV and LDF, power calculations will reveal large numbers to investigate. Skin temperature has a relatively small intra- and inter-individual variation and is more suitable for long-term studies.