International journal of microcirculation, clinical and experimental最新文献

The wick technique and the blister suction technique are the most common methods for sampling of subcutaneous interstitial tissue fluid in man. The blister suction technique has the advantage of being less invasive than the wick technique, but the reliability of this method is still controversial. The aim of this study was to evaluate whether the simpler blister suction technique using large (8 mm) blisters could replace the wick technique in the investigation of patients with postreconstructive leg edema. Fifteen patients with ipsilateral leg edema following infrainguinal bypass surgery for lower limb atherosclerosis were investigated. The two different fluid sampling techniques were applied simultaneously on both legs. The concentration of total protein and albumin as well as colloid osmotic pressure of the subcutaneous interstitial tissue fluid in the leg were measured in all fluid samples. Agreement analysis was applied to compare the two methods, while the correspondence between the methods was estimated with linear regression analysis. The agreement index was found to be positive for all variables from the operated as well as from the contralateral control limb. Furthermore, all values were within the agreement limit. The best agreement between the two methods was found for colloid osmotic pressure on the operated side. According to the equation of linear regression, there was a slight overestimation of the wick values compared to the observed blister values. In conclusion, there was a good methodological agreement between the blister suction technique and the wick technique. The less invasive blister suction technique should be regarded as the method of choice for the investigation of subcutaneous interstitial tissue fluid in patients with postreconstructive leg edema.

Hyperoxemia is known to alter tissue oxygenation, which in the brain results in a scattered and an uneven distribution of cerebrocortical tissue oxygen pressures (PtO2). This study examined the effect of ritanserin (a highly specific serotonin receptor antagonist, 5-HT2) on the PtO2 distribution during hyperoxemia. The measurements of brain oxygenation were performed on the motor cortex in anesthetized pigs with a multiwire Clark-type microelectrode. Ritanserin was administered (0.035 mg/kg i.v.) during hyperoxemia (inspired oxygen fraction = 0.70). In 4 of 5 animals, the disturbed oxygenation that was registered during hyperoxemia was normalized after the ritanserin injection. These results indicate that serotonin may be involved in the regulation of brain oxygenation during hyperoxemia, and they also suggest that serotonin may be a link in the coupling between the oxygen metabolism and the regulation of blood flow in the brain.

Most studies of neutrophil-endothelial interactions in vivo necessarily require the use of general anesthetic agents which are well known to be immunosuppressive. By using whole-mount preparations of the rat mesoappendix, we were able to study tumor necrosis factor alpha (TNF-alpha) induced neutrophil adhesion to the mesenteric venular endothelium in vivo without necessarily using general anesthesia. TNF-alpha significantly increased venular-neutrophil accumulation in a dose-dependent manner, accumulation was markedly increased at 1, 2, and 4 h, but returned to baseline after 24 h. After these preliminary dose-response and time-course studies, we evaluated the influence of standard clinically effective doses of several commonly used anesthetic agents (thiopental, pentobarbital, ketamine, alpha-chloralose, methoxyflurane, and halothane) on the extent of neutrophil-venular accumulation induced 2 h after intraperitoneal injection of 0.4 mg/kg TNF-alpha, compared to unanesthetized rats. All general anesthetics tested, with the exception of methoxyflurane, significantly suppressed this response. In most cases this suppression was striking (from 60 to 85%) such that a statistically significant proinflammatory response was obscured. Although methoxyflurane also tended to suppress this response to TNF-alpha, it was the only agent that allowed the response to be clearly seen. Because anesthesia markedly suppresses cytokine-induced neutrophil-venular adhesion, this model should provide an important complementary technique to the classical in vivo microcirculatory approaches which do necessarily require general anesthesia.

The introduction of the servonulling technique by Wiederhielm in 1963 allowed for the first time continuous and dynamic recording of capillary blood pressure (CP). In 1979 Mahler used this technique for the first measurements in humans. Data analysis was limited to manual analysis of chart recordings. Nowadays fast analog-digital converters with ay high sampling frequency are used for data recordings, and consequently there is a need for an easy-to-use software for data analysis of CP data. The presented newly developed computer software allows analysis of mean CP, taking into account the zero pressure measured before and after capillary cannulation. The simultaneously recorded electrocardiogram R wave is used as a marker for the calculation of the mean capillary pulse pressure waves and of their characteristic data. This may help determine the significance of the capillary pulse waveform for microvascular function. Changes in the pulse waveform may be the only detectable difference between patients and healthy controls. Analysis of simultaneously recorded temperature, the display of markers for valid readings, and the possibility of excluding nonvalid data or artefacts from analysis are additional features.

Disturbances in sympathetic cutaneous vasomotor reflexes may be of pathogenetic importance in several microvascular problems. Laser Doppler fluxmetry (LDF) enables one to study the influence of sympathetic reflexes on skin blood flow. A matter of concern is the high variability of skin blood flow and its reactivity to sympathetic reflex test resulting in a poor reproducibility. In this study we evaluated two sympathetic stimulation tests, distant cooling and inspiratory gasp, and their influence on LDF-measured skin blood flow of the pulp of the big toe in 63 healthy volunteers. No age or sex dependency of the LDF test results was found. Absolute and relative LDF decrease during distant cooling was highly variable between the subjects (LDF decrease, mean +/-SD: 0.7 +/- 5.3%) compared to an LDF decrease of 46.5 +/- 3.1% during an inspiratory gasp test. The reproducibility, however, was better for the distant cooling test [coefficient of variation (CV): distant cooling: 5.8%, inspiratory gasp test: 35.4%]. With the use of a thermostatically controlled LDF probe holder fixed at a temperature of 36 degrees C, the short-term reproducibility of the two sympathetic vasomotor tests did not improve, probably because of a steady increase in baseline skin blood flow during the test. Surprisingly long-term variability of the percentage LDF decrease during the inspiratory gasp test, performed with the heated LDF probe, was lower compared to the short-term variability (CV 19.2 vs. 39.0%, p < 0.05). In conclusion to study sympathetic skin vasomotor reflexes with LDF, vasoconstriction during the inspiratory gasp test was more uniform compared to the distant cooling test, although the latter was more reproducible. Measuring skin blood flow reactivity with a heated LDF probe (36 degrees C) did not improve reproducibility.

The aim of the present study was to examine the nailfold capillary morphology and dynamics in treated chronic heart failure (CHF) in relation to parameters of left ventricular structure and function. Twenty patients with CHF class II according to the New York Heart Association underwent a capillaroscopic examination at the finger nailfold using a computerized videophotometric system (Capiflow) at rest and after 1 min arterial occlusion. Study parameters ere number, length and diameter of the capillaries as well as capillary blood velocity (CBV). Further experiments included echocardiography and determination of left ventricular ejection fraction by Tc scintigraphy. Nailfold capillaries in established CHF are enlarged and the CBV is dramatically decreased. The reactive hyperemic response to 1 min arterial occlusion is attenuated. CBV correlates positively with left ventricular ejection fraction (r = 0.61, p = 0.01) and inversely with left ventricular end-diastolic (r = -0.56, p = 0.04) and end-systolic (r = -0.69, p = 0.01) diameters. The time-to-peak flow after 1 min arterial occlusion is positively related (r = 0.68, p < 0.05) to the duration of CHF. Our data indicate that finger microcirculation in CHF deteriorates as a function of the severity and duration of heart failure.

The aim of this study was to examine whether the hyperpermeable structure of the liver endothelium in vivo is related to the interactions of hepatocytes in a culture system. The permeation of macromolecular FITC-labeled dextran (molecular weight 70,000) through a monolayer of bovine aortic endothelial cells (BAEC), cocultured with rat parenchymal hepatocytes (P-hep), was increased. When the BAEC were cocultured with nonparenchymal hepatocytes (N-hep), the permeability of the BAEC monolayer was not increased. However, when the BAEC were cocultured with a mixture of P-hep and N-hep (PN-hep), the BAEC monolayer was more permeable than when BAEC were cocultured with P-hep alone. The conditioned medium of P-hep did not alter the BAEC monolayer permeability, nor did the extracellular matrix of P-hep alter BAEC permeability. When the BAEC were cocultured with PN-hep, the F-actin content was not altered. These findings suggest that the interaction between hepatocytes and endothelial cells exerts an important effect on the hyperpermeable structure of the liver vessels in vivo.

In order to investigate laser Doppler (LD) flux motion in healthy subjects and patients with peripheral arterial occlusive disease (PAOD), spectrum analysis of LD signals is needed. Autoregressive analysis (AR) is presented as an alternative method of power spectrum estimation. This procedure is compared to the commonly used fast Fourier transform algorithm (FFT) by describing the analytical power of both spectra in the analysis of flux motion waves. LD signals were recorded from the forefoot of 8 healthy volunteers and 11 patients with different degrees of PAOD. The flux, concentration of moving blood cells and velocity signal was digitized and stored for off-line analysis. Special software was designed to calculate AR and FFT spectra of the LD signals and to compare the suitability of both methods for the spectral analysis of LD recordings. Additionally, three-dimensional spectrum diagrams were calculated to demonstrate time-dependent flux changes during standardized provocation maneuvers. AR facilitates the determination of frequency and amplitude of flux motion waves as compared to the FFT. Low frequency-large amplitude waves (LF waves) were detected in both groups. High frequency-small amplitude waves (HF waves), which predominantly appear in severe ischemia, were observed in 7 of the 11 patients and in 2 of the 8 controls. The spectra revealed pulsatile waves in all healthy controls, but only in 1 of the 11 patients. AR modelling allows a reliable description of important flux motion components and has considerable advantages in spectral estimation of LD signals as compared to the FFT.

The observed positive correlation between cessation of red blood cell flow in capillaries at low perfusion pressures and the oxygen tension (PO2) in the superfusion solution may be due to oxygen-dependent arteriolar constriction. To test this hypothesis, we investigated capillary flow cessation during aortic occlusion and concomitant changes in diameters of terminal arterioles and capillaries in normal and vasodilated vascular beds of rabbit tenuissimus muscle (n = 15) by means of video intravital microscopy. In the vasodilated bed, arteriolar tone was eliminated by local application of 10(-4) M adenosine (ADO). The PO2 in the superfusate was varied locally, i.e., in the solution between objective lens and muscle surface. At a local PO2 of 40 mm Hg without ADO, flow ceased in about 50% of the capillaries during aortic occlusion while the arterioles dilated to 118% of control (median; p < 0.001). Addition of ADO led to an increase in arteriolar and capillary diameter to 220% (median; p < 0.001) and 121% (median; p < 0.05), respectively. Under ADO, the incidence of capillary flow cessation was reduced (p < 0.05) to about 20%. Elevation of the local PO2 from 40 to 100 mm Hg in the presence of ADO did not lead to a significant change in the incidence of flow cessation, nor to changes in arteriolar or capillary diameter. In the presence of ADO, median arteriolar and capillary diameters during aortic occlusion were 96% (p < 0.001) and 7% (p < 0.05) larger than their control diameters without ADO, respectively. In summary, it is suggested that the incidence of flow cessation may depend on both the arteriolar and the capillary diameter. Of these two factors, capillary diameter may be the most important one, because its changes affect the interaction between red blood cells and the vessel wall in the narrow capillaries, and, hence, the resistance to flow. In the presence of ADO, at elevated local PO2 levels flow cessation still occurs in about 20-30% of the capillaries, suggesting that arteriolar contraction is only in part responsible for the incidence of flow cessation.

The effects of an extract of Ginkgo biloba (EGb 761) on arteriolar spasm were confirmed using a preparation of rat cremaster muscle. When vasospasm was induced by rat serum, arteriolar constriction reached 25-30% of the initial diameter after 10 min. Intravenous injection of EGb 761 (30 mg/kg) 5 min after inducing spasm inhibited about 80% of this serum-induced vasoconstriction. As previous studies have shown that EGb 761 has an antiaggregatory effect on platelets, thrombin, serotonin (platelet-derived compounds that are present in the serum) and a thromboxane analogue (U46619) were also used to induce vasospasm. Administration of EGb 761 (30 mg/kg) 5 min after exposure of the preparation to serotonin (10(-3) M) or 10 min after exposure to thrombin (20 units) did not affect vasospasm induced by these agents. In contrast, treatment with this same dose of EGb 761 5 min after exposure of the preparation to U46619 (10(-4) M) abolished the arteriolar constriction induced by this agent in 15 min. The thromboxane/prostaglandin H2 receptor antagonist SQ29548 antagonized serum-induced vasospasm, indicating an involvement of thromboxane. Other experiments indicated that the effects of EGb 761 of counteracting vasospasm may be mediated in part by ginkgolide B, a triterpene constituent of the extract that is an antagonist of platelet-activating factor and in part by an 'NO-like' action of its proanthocyanidin constituents. Taken together, these results have revealed that EGb 761 treatment can antagonize the vasoconstrictor effect of thromboxane on arterioles. As thromboxane is implicated in many cardiovascular disorders, this property of EGb 761 may explain some of its beneficial clinical effects in such pathologies.