International journal of microcirculation, clinical and experimental最新文献

Although microvasculitis is one of the more common manifestations of systemic lupus erythematosus, there is no data on the hemodynamics of the skin microcirculation in such patients. The combination of dynamic capillaroscopy measuring capillary blood cell velocity (CBV) and laser Doppler fluxmetry (LDF) was used to simultaneously evaluate the nutritional and the total skin microcirculation in the fingers of 24 consecutive patients with SLE, using normal matched subjects as controls. The nutritional skin flow, as assessed by the CBV, was significantly impaired in patients, as compared with controls, both at rest (p = 0.001) and during postocclusive reactive hyperemia (p = 0.006). By contrast, no differences were observed in total skin microcirculation, as assessed by LDF (n.s.). There was no significant correlation between hemodynamic parameters and the presence of Raynaud's phenomenon, morphological capillary changes or anticardiolipine antibodies. There was no correlation between the magnitude of the alteration of the capillary blood flow and capillary morphological abnormalities, suggesting that the microvascular damage might be caused by different pathophysiological mechanisms.

The objective of this study was to determine the role of hypotension and hypoperfusion in the induction of regular slow-wave flowmotion (SWFM) in skeletal muscle in vivo. SWFM and microcirculatory muscle blood flow (MBF) were assessed by laser Doppler flowmetry in anesthetized rats exposed to: (1) graded hemorrhage (n = 15); (2) partial occlusion of the feeding artery (n = 6); (3) partial occlusion of the vein (n = 6), and (4) the vasodilator hydralazine (n = 10). Mean arterial pressure (MAP) was significantly reduced to 65 +/- 2.1% after hemorrhage and hydralazine before (64 +/- 2.4%) and after (42 +/- 1.8%) additional blood loss, but remained unchanged after venous occlusion. The pressure of the feeding artery fell to 38 +/- 1.2% after partial occlusion. MBF dropped significantly to 74 +/- 4.2% after hemorrhage, 54 +/- 5.6% after arterial and 53 +/- 3.0% after venous occlusion. Hydralazine caused MBF to rise to 192 +/- 21.8% before additional blood withdrawal and returned to normal values after it. SWFM was observed in all animals after hemorrhage and arterial occlusion, but in none after venous occlusion. In the hydralazine group, SWFM occurred only after blood loss. The hemoglobin concentration was reduced to 82 +/- 2.1% after hemorrhage. It remained normal after hydralazine administration, but decreased to 79 +/- 1.2% after the subsequent blood withdrawal. We conclude that arterial hypotension, but not hypoperfusion, induces SWFM, and hyperperfusion prevents it. Our results support the hypothesis that SWFM is generated by a reduction of vascular wall tension.

There are no reports on the autologous transplantation and patency of microvessels in living tissue. We autotransplanted microvessel fragments (Mvf) labeled with DiI-Ac-LDL into the peritoneum and then observed the peritoneum for 7 days postoperatively with a conventional fluorescence or laser scanning confocal microscope. We illustrated a neomicrovascular network of transplanted Mvf labeled with DiI-Ac-LDL in the peritoneum with both a fluorescence and a laser scanning confocal microscope. Furthermore, we demonstrated not only the existence of erythrocytes in the lumina of transplanted DiI-Ac-LDL-labeled Mvf, but also the presence of India ink perfused through the superior mesenteric artery in the lumina of the labeled Mvf. This evidence directly suggests that transplanted Mvf can survive and proliferate to connect adjacent microvascular branches of the superior mesenteric artery in the very early phase of wound healing. Moreover, these findings imply that implantation of Mvf in the microvascular ischemic circulatory tissue might accelerate angiogenesis to reconstitute a new microvascular network connecting to the nearby host microvascular system, which ultimately improves microcirculation.

A modified technique of vital capillary microscopy with intraarterial application of Na-fluorescein has been introduced in the study of nutritional skin microcirculation to assess skin microcirculation of different diabetic patients, comprising one group without neurocutaneous complications (group 2; n = 9), one suffering only from neuropathy (group 3; n = 9) and one with trophic skin lesions in the contralateral foot (group 4; n = 8), all without macroangiopathy, compared to healthy controls (group 1; n = 9). Femoroarterial injection of small boli (10 mg) of Na-fluorescein allowed repeated investigation of the dye appearance times (AT) and capillary-filling times of forefoot skin capillaries within small periods of time before, during and after reactive hyperemia. At rest, AT was significantly shorter in patients of group 4 (16.8 +/- 4.4 s; p < 0.05) compared with groups 1-3 (34.3 +/- 12.8; 31.7 +/- 11.7 and 35.9 +/- 15.3 s). Fifteen seconds after the end of arterial occlusion, dye propagation to the skin was markedly accelerated in groups 1-3 (19.8 +/- 14.0; 14.4 +/- 7.6 and 18.7 +/- 10.6 s, respectively; p < 0.001), but prolonged in group 4 (18.4 +/- 7.4 s). After 10 min, the values at rest were reestablished. No differences between the four groups were found concerning capillary density and morphology. It is concluded that the development of skin lesions in diabetic patients without significant macroangiopathy may be favored by hyperperfusion and impaired vasoregulation. Intraarterial dye injection presents a valuable tool to assess dynamic alterations of the microcirculation at the level of skin capillaries.

As regional diaphragmatic microvascular blood flow varies widely, the aim in this study was to estimate the number of repeated measurements, obtained by Laser-Doppler flowmetry (LDF), required to achieve a standard level of precision. In 40 urethane-anesthetized Sprague-Dawley rats, computer-aided LDF scanning coupled with a microscope generated diaphragmatic blood flow (Qdi) ranging between 94 and 944 mV with the frequency histogram displaying non-Gaussian distributions. A sampling technique was used to assess the number of measuring sites required for valid estimates of the regional diaphragmatic microvascular flow. From a total of 1,000 Qdi values, random samples of sizes between 5 and 100 were repeatedly drawn to estimate the variability of median flow. Our data shows that the 95th percentile decreased gradually, from a +30% error at n = 5 down to +20% at n = 15-20, remained between +20 and +15% up to n = 35, and reached +10% at n = 50. Moreover, by expressing the precision level of measurements as the length of a 95% confidence interval (beta), a linear relationship between beta values obtained either by the sampling method or repeated measures analysis of variance can be shown (r = 0.902, p < 0.001); beta values by either method were within +/-20% error of the mean values at sample sizes above n = 15. It is therefore recommended that for microscope-guided LDF scanning in the assessment of the distribution of diaphragmatic microvascular blood flow, at least 15 repeated measurements should be done to reach an acceptable standard level of precision. However, facing with clinical situations where 'blind' LDF scanning inevitably includes measurements over large vessels, the minimal sample sizes required to represent tissue perfusion demand further exploration.

Intravital microscopy was used for 1 h in the cremaster skeletal muscles of normotensive 4- to 5-week-old rats. The total duration for experimentation was 5 h in order to mimic the controls used previously for a 4-hour ischemia and 1-hour reperfusion model which was equilibrated with room air. Responsiveness of third-order (3A) arterioles with resting vasomotor tone (VT) was assessed to topically applied 10(-2) to 10(-6) M acetylcholine (ACh) or sodium nitroprusside (NP) using a suffusate PO2 of 25-30 mm Hg. ACh (10(-4) M) or NP (10(-6) M) were retested at this Po2 in 3A arterioles with norepinephrine (NE) (10(-6) M)-enhanced VT. Results were compared against those using room air to increase VT. No dose-response relationships were demonstrated for ACh or NP in resting conditions. Moreover, our current and former responses were maximal and of a lesser magnitude than those reported by others using room air. All doses except 10(-4) or 10(-6) M ACh, or 10(-6) M NP, also severely depressed systemic arterial blood pressure. Enhancement of VT by 29% resulted in a 3-fold greater dilation to 10(-4) M ACh or 10(-6) M NP. The relative increase in volumetric blood flow (Q) to ACh or NP was 5.3-5.7 times greater than with resting VT. However, there were no differences in the absolute maximal values attained for internal diameter (D) or Q between drugs. The times to peak response and recovery were accelerated for Q but not D in NE-preconstricted arterioles, and the relative increases in D were less than reported by others after equilibration with room air. At both levels of tone, topical administration of NE at the end of each experiment caused similar decreases in D and Q, while mean centerline cellular velocity, wall shear rate (WSR), and VT were found to increase. These results suggested that the relative increases in D and Q were due to NE-induced decreases in absolute predrug baselines, while both the depressed VT and peak responses in D were caused by a fall in vasoreactivity. Po2 did not appear to be a factor attenuating endothelium-dependent responses, since ACh was equipotent to NP in resting or NE-preconstricted arterioles at physiological suffusate Po2 or in cremaster flaps equilibrated with room air. Therefore, either NE at physiological suffusate Po2 or room air appears acceptable for elevating initial VT/WSR when examining the endothelium-dependent and endothelium-independent mechanisms regulating physiological (dilator) tone and perfusion in 3A arterioles.

For the first time measurements of lymph flow velocities in cutaneous microlymphatics of patients with lymphedema were performed and compared with healthy subjects. Flow velocity in single lymphatic skin capillaries was measured using fluorescence video microscopy after subepidermal microinjection of FITC-dextran 150,000 in 15 healthy volunteers and 16 patients with primary lymphedema. Initial filling of the lymphatic capillary network was fast with significantly higher mean velocities in patients with primary lymphedema than in healthy controls (890 +/- 43 vs. 550 +/- 390 microns/s, p < 0.05). The resting velocities were not significantly different between controls and patients (10.3 +/- 4.1 vs. 16.6 +/- 13.9 microns). In 12 out of the 16 lymphedema patients cutaneous backflow of the fluorescent contrast medium from deeper invisible lymphatics was observed. In 4 of these patients rhythmic reflux with a mean frequency of 1.4 +/- 0.5 cycles/min was measured by video densitometry in microlymphatics with a significantly (p < 0.01) enhanced diameter. Mean flow velocity (Vp) in these precollectors was significantly increased compared to the resting velocities (p < 0.01). On the basis of these results the hypothesis is advanced that rhythmic cutaneous backflow originates from intrinsic contractions of deeper lymph collector segments and is transmitted to the superficial microlymphatics through incompetent connecting channels. This newly recognized mechanism appears to be an important factor for the pathophysiology of lymphedema.

A new laser Doppler perfusion imaging (LDI) system was evaluated by comparing it with the well-established radiolabelled microsphere technique for measuring blood flow in the rabbit knee joint capsule. In this study two laser sources (635 and 835 nm) were compared at three scan speeds (50, 10 and 4 ms/pixel). With blood flow to the rabbit hindlimb controlled via a peristaltic pump, the comparison of LDI and microsphere measurement techniques yielded highly significant correlations for both laser sources (r = 0.9; p = 0.0001; 14 measurements in 7 animals). Comparison of the three scan speeds demonstrated acceptable agreement without significant bias between measurements, suggesting that the inevitable narrowing of the bandwidth at the fastest scan speed does not cause significant deterioration of the signal. The flux values obtained with 635 and 835 nm laser sources were linearly related (r = 0.93, p = 0.0001; 66 measurements in 12 animals), although there was a small but significant bias for higher values with the 635-nm laser (mean ratio of flux values 1.06, 95% confidence interval 1.01-1.12). These results validate the use of LDI with either wavelength laser for the assessment of joint capsule perfusion.

Background: Human malignant tumors grown as xenografts in immunocompromised animals have been used extensively to study tumor growth and tumor response to therapy. The endothelium functions as an effective barrier between the intravascular space and the tumor cells. In a previous study we used species-specific monoclonal antibodies against endothelial cell adhesion molecules to demonstrate the host origin of the endothelium in xenotransplanted pancreatic islet grafts [Am J Pathol 1995;146:1397-1405]. We now investigated in this study whether the vascular endothelium of different xenografted human malignant tumors expresses mouse (= host)- or human (= graft)-specific CD31 (platelet endothelial cell adhesion molecule, PECAM-1) adhesion molecules.

Methods and results: Cultured human prostate, kidney, and colon cancer cells (passages 15-17) were transplanted subcutaneously into 8-week-old athymic nude mice and removed after another 8 weeks. The avidin biotin peroxidase method was utilized on frozen sections to demonstrate that the endothelium of the vasculature of all three human xenografts expressed mouse (= host)-specific CD31, but not human (= graft)-specific CD31.

Conclusion: The presence between the intravascular space and the human tumor cells of a mouse-derived endothelium, expressing mouse-specific antigens, needs to be taken into careful consideration when evaluating results of antitumor therapies in these animal models. This caveat pertains particularly to the study of novel cell- or tissue-specific treatment modalities, such as antibody-targeted drugs, toxins or radionuclides, 'immuno'-liposomes, or tumor vaccines.

The transcapillary and interstitial diffusion of intravenously administered sodium fluorescein is used as a marker for capillary permeability. Fluorescein diffusion has been expressed by different parameters with reported coefficients of variation of 14-20%. Aim of the present study is to select a parameter which combines excellent reproducibility with the potential for discriminating insulin-dependent diabetic patients from healthy subjects. We performed three experiments to assess day-to-day reproducibility: 5 healthy subjects were measured twice, 1 healthy subject was measured 6 times and 1 subject with insulin-dependent diabetes mellitus was measured 5 times. We averaged the relative fluorescence light intensity (IREL(t)] from dye arrival until a certain time point [IAV(t)], instead of using the relative intensity at one time point. IAV (7 min) showed markedly improved reproducibility, expressed as geometric mean of the coefficients of variation of the three separate experiments: 10%. In addition, a group of 12 insulin-dependent diabetic subjects was compared with 12 healthy control subjects. Median IAV (7 min) was 69.5% (95% CI: 65.3-78.1%) in the diabetic subjects and 54.9% (95% CI: 52.1-60.0%) in the control subjects (p < 0.001). Since IAV (7 min) combines excellent reproducibility with a good discriminating power, we advise its use in further studies.