International journal of microcirculation, clinical and experimental最新文献

In a placebo-controlled trial skeletal muscle biopsies were taken proximal and distal to the site of arterial stenosis, before cross-clamp and 20 min following reperfusion, in 8 well-matched critical limb ischaemia patients undergoing femorodistal bypass. Capillary endothelial swelling-a sign of reperfusion injury-was assessed following infusion with iloprost, a prostacyclin analogue, the prolonged beneficial effect of which on vascular graft flow rates has been demonstrated previously. Electron microscopy and image analysis of calf capillaries confirmed that critical limb ischemia patients had endothelial cell swelling before bypass, and that cross-clamp ischaemia caused further endothelial swelling in the placebo group. Samples from muscles proximal to the site of the bypass showed similar changes, indicating that systemic capillary damage occurs in muscle remote from the area of ischaemia. Iloprost treatment prevented endothelial swelling and increased the mean capillary lumen cross-sectional area. Iloprost, therefore, has a potentially beneficial effect on capillary function by limiting reperfusion injury during femorodistal bypass.

Stimulators of angiogenesis hold potential in promoting the development of collateral circulation in ischaemic tissue and accelerating would healing, but promote pathological vasoformation in angiogenesis-dependent diseases (solid tumours, atherosclerosis). The renin-angiotensin system is implicated in both beneficial angiogenesis and pathological vascular growth. We investigated the angiogenic activity of angiotensin II (AII) in a sponge implant model in mice; this peptide enhanced angiogenesis, as well as glycosaminoglycan (GAG, chondroitin sulfate proteoglycan) and protein synthesis in sponge matrix in mice in a dose-dependent fashion. Extensive angiogenesis was achieved with AII (1 microgram), which gave no significant increase in wet weight and protein and only a small effect on GAG. In the implants treated with AII (2 micrograms) no further increase in angiogenesis was observed, whereas a marked effect was shown in wet weight (326 +/- 15 vs. 424 +/- 27 mg), total protein (18 +/- 1 vs. 25 +/- 1 micrograms/ww) and GAG (98 +/- 10 vs. 160 +/- 13 ng/ww). The local blood flow has been determined by measuring the washout rate of 133Xe injected into the implants, correlated with histological evidence of vessel growth. This model of angiogenesis has allowed sequential studies of fibrovascular tissue infiltration simultaneously with histological and biochemical parameters of angiogenesis.

Fibroblasts growth factors (FGFs) exhibit well-known angiogenic actions, but there is some controversy about whether they have vasoactive effects on blood vessels which might contribute to angiogenesis per se. To clarify this, changes in arteriolar diameter were recorded during observation by videomicroscopy of 3rd- and 4th (terminal)-order arterioles (resting diameters 22.5 +/- 0.5 microns and 14.4 +/- 0.3 microns, respectively) in the hamster cheek pouch in response to FGF application. Recombinant human bFGF (basic) and aFGF (acidic) were applied from micropipettes positioned 5-10 microns from the adventitial surface of vessels. Maximum vasodilator effects of adenosine (10(-4) M) applied in a similar way were also observed. Adenosine increased the diameters of 4th-order arterioles by 37.2 +/- 3.8% and those of 3rd-order arterioles by 38.7 +/- 2.7. bFGF produced vasodilatation (threshold dose 0.1 ng ml-1) in both classes of arterioles, while aFGF produced dose-dependent constriction (threshold dose 0.01 ng ml-1). A maximal dilator effect in 4th-order arterioles was obtained with 100 ng ml-1 bFGF, when diameters reached 82.6 +/- 2.4% of those with adenosine. Maximal constrictor effect (-48.2 +/- 5.6% of resting diameter) occurred with a dose of 100 ng ml-1 aFGF. Vehicle alone (MOPS or bicarbonate buffer used as solvents for FGFs) had no effect. As vasoconstrictors are known to stimulate growth of smooth muscle cells while dilators stimulate growth of endothelial cells, it is possible that the opposing vasoactivities demonstrated for aFGF and bFGF are linked with their selective mitogenicity for smooth muscle and endothelial cells, respectively, and contribute to their angiogenic actions.

The aim of the present study was to investigate skin microcirculation in patients with diabetes to see if any differences in microvascular reactivity could be found between a skin area with low (fingers) or high risk (toes) of complications. Twelve male patients with type 1 diabetes were investigated, the age was 34.7 +/- 8.5 years, and diabetes duration 12.8 +/- 7.7 years (mean +/- SD). Twelve healthy male subjects served as controls. Capillary blood cell velocity (CBV) in the nailfolds of the great toe and left fourth finger was investigated with videophotometric capillaroscopy, and total skin microcirculation with laser Doppler fluxmetry (LDF). CBV and LDF were studied during rest, and following a 1-min arterial occlusion at the proximal phalanx of the digit. Skin temperature was similar in patients and controls. The diabetic patients showed normal CBV and LDF values in skin microcirculation of the fingers, while a reduced (p < 0.01) CBV was found during reactive hyperemia in the toes. The ratio between CBV and LDF was decreased (p < 0.01), indicating a maldistribution of blood between skin capillaries and subpapillary vessels in the toes of diabetic patients. These disturbances may be of importance for the development of foot complications in diabetic patients.

The ability of relaxin (RLX), which is a potent microcirculatory effector in many species including the rat, to induce de novo angiogenesis in vascularized mammalian tissue was tested using the rat mesenteric-window angiogenesis assay. RLX was administered intraperitoneally on days 1-5 at doses of 0.33, 3.3 and 33 nM. Controls received the vehicle by the same route. Groups of animals were sacrificed at the end of the 1st, 2nd and 3rd weeks. Using computer-aided microscopic morphometry including image analysis, the response was quantified by sensitive, technically independent, highly reproducible methods in terms of the vascularized area (VA), a measure of microvascular spatial extension, and the microvascular length (MVL), a measure of microvascular density. The total MVL was computed from VA x MVL. The results obtained show that RLX did not cause significant changes in any of the variables tested, regardless of dose and observation time. These findings indicate that RLX is apparently unable to mediate significant de novo angiogenesis in the system used in contrast to previously tested angiogens such as basic fibroblast growth factor, vascular endothelial growth factor, isoform 165, and tumor necrosis factor-alpha. In previous studies, RLX has been shown to exert antitumor activity on breast cancer cells in vitro. In the search for a possible role for RLX as an anticancer agent in vivo, it is important to know that this peptide is not angiogenic, since de novo angiogenesis is known to be a prerequisite for tumor growth and metastatic spread.

Voluntary hyperventilation (HV) provokes hemoconcentration due to a loss of fluid from the intravascular space. In 10 healthy male volunteers the hypothesis was tested whether HV increases transcapillary fluid shift into the interstitial compartment. For this purpose, fluorescent light intensity (FLI) alterations after intravenous injection of sodium fluorescein (Na fluorescein) before and during 3 min of HV were determined. Concomitantly, temperature and microvascular skin flux (laser Doppler fluxmetry, LDF) were recorded continuously. Hematocrit and serum proteins, as markers of hemoconcentration, increased significantly from 41.2 +/- 2.3 to 42.7 +/- 2.0% (p = 0.0023) and from 69.5 +/- 3.4 to 72.9 +/- 3.0 g/l (p = 0.0005, respectively). Skin temperature and LDF showed no changes during HV compared to baseline levels. Interstitial FLI indicating transcapillary diffusion of Na fluorescein was significantly higher (p < 0.001) during HV compared to the values recorded during the baseline period. The exact mechanism of enhanced transcapillary diffusion of Na fluorescein is not known. The distinct increase in FLI without a significant change in microvascular skin flux suggests an HV-induced increase in capillary pressure or an enhancement in capillary permeability for water and small solutes.

The aim of the study was to investigate the potential role of nitric oxide (NO) on the microcirculation in experimental acute pancreatitis in rats. Twenty-five rats were divided into the following groups: group A (5 rats) = control; group B (5 rats) = acute pancreatitis induced by retrograde taurocholate infusion into the pancreatobiliary duct without treatment; group C (5 rats) = acute pancreatitis treated with the NO donor L-arginine; group D (5 rats) = acute pancreatitis treated with the NO synthase inhibitor N-nitro-L-arginine (L-NNA); group E (5 rats) = without pancreatitis receiving L-NNA. The animals were observed throughout 4 h. The microcirculatory values of the pancreas, liver, colon, stomach and kidney were measured by means of laser Doppler flowmetry. Three animals of group D died after the third hour of the experiment. In rats with pancreatitis, a rapid decrease in microcirculatory values was observed. The most pronounced drop in capillary blood flow within all the organs was observed in rats treated with the NO synthase inhibitor L-NNA, L-arginine administration in rats with acute pancreatitis slightly improved the microcirculatory values, although the improvement was significant in colon perfusion only. We conclude that NO may have a beneficial influence on the capillary organ perfusion in acute pancreatitis. The administration of an NO synthase inhibitor seems to have a detrimental effect on acute pancreatitis.

Objective: This study was conducted to examine the effects of endothelin (ET)-1 and ET-3 on hepatic venules and sinusoids and to identify the subtypes of ET receptors.

Method: Hepatic venules and sinusoids of anesthetized mice were observed at the edge of the liver. ET-1, ET-3 and sarafotoxin (S6c, a selective ETB receptor agonist) were applied topically over the microvasculature.

Results: ET-1, ET-3 and S6c (1-100 microM, 30 microliters) induced dose-dependent vasoconstriction of the portal venules, the sinusoids and the central venules. The ETs and S6c were equipotent for these microvessels. BQ-123 (a selective ETA receptor antagonist) inhibited the constrictive effects of ET-3 (not of ET-1) on the portal venules and central venules, whereas it had no inhibitory effect on the sinusoids.

Conclusions: In mouse hepatic venules and sinusoids, the vasoconstriction induced by ET-1 and ET-3 was mediated mainly through the ETB receptor subtype and partly through an unknown BQ-123-sensitive ET receptor subtype in the portal and central venules, and only through the ETB receptor subtype in the sinusoids.