Biomedical subjects

G J Tangelder

Publications and source records attributed to G J Tangelder.

At least 19 recordsLinked to original sources

PubMed2003

Direct coronary stent implantation does not reduce the incidence of in-stent restenosis or major adverse cardiac events: six month results of a randomized trial.

STUDY OBJECTIVE: To compare the long-term angiographic, clinical and economic outcome of direct stenting vs stenting after balloon predilatation. PATIENT POPULATION AND METHODS: Four hundred patients with coronary stenoses in a single native vessel were randomized to direct stenting vs stenting after predilatation. A major adverse cardiac and cerebral event (MACCE) was defined as death, myocardial infarction, stent thrombosis, target restenosis, repeat target- and non-target vessel-related percutaneous coronary intervention, target lesion revascularization, coronary artery bypass surgery and stroke. RESULTS: Stents were successfully implanted in 98.3% of patients randomized to direct stenting vs 97.8% randomized to stenting preceded by predilatation. The primary success rate of direct stenting was 88.3%, vs 97.8% for stenting preceded by balloon dilatation (P=0.01). The angiographic follow-up at 6 months included 333 of the 400 patients (83%). The binary in-stent restenosis rate was 23.1% of 163 patients randomized to direct stenting vs 18.8% of 166 patients randomized to balloon predilatation (P=0.32). By 185+/-25 days, MACCE had occurred in 31 of 200 (15.5%) patients randomized to direct stenting, vs 33 of 200 (16.5%) randomized to predilatation (P=0.89). At 6 months, costs associated with the direct stenting strategy (Euros 3222/patient) were similar to those associated with predilatation (Euros 3428/patient, P=0.43). However, procedural costs were significantly lower. It is noteworthy that, on multivariate analysis, a baseline C-reactive protein level >10 mg l(-1)was a predictor of restenosis (odds ratio: 2.10, P=0.025) as well as of MACCE (odds ratio: 1.94, P=0.045). CONCLUSIONS: Compared to stenting preceded by balloon predilatation, direct stenting was associated with similar 6-month restenosis and MACCE rates. Procedural, but not overall 6-month costs, were reduced by direct stenting. An increased baseline CRP level was an independent predictor of adverse long-term outcome after coronary stent implantation.

Angina Pectoris↗

PubMed2003

Direct coronary stenting compared with stenting after predilatation is feasible, safe, and more cost-effective in selected patients: evidence to date indicating similar late outcomes.

OBJECTIVES: To review the currently available data from studies assessing feasibility, safety, clinical outcome and cost-effectiveness of direct stenting. BACKGROUND: With technical advances of stent designs and their delivery systems a new strategy has become increasingly popular: direct stent implantation without prior balloon dilatation. METHODS: The Medline database was searched from January 1996 to March 2001 for clinical trials investigating direct stenting using the index terms direct stenting, coronary intervention, percutaneous transluminal coronary angioplasty (PTCA), PCI, angioplasty and ischemic heart disease. Studies were chosen based on the number of patients involved and endpoints mentioned. Data not yet published but presented at recent international meetings were also included. A comparison between direct stenting and stenting with predilatation was performed using for the latter results of the randomized trials supplemented with Benestent II data. RESULTS: At least 26 studies have investigated direct stenting, showing high primary and final success rates with few complications. Direct stenting provides a way to reduce costs, shorten procedural and fluoroscopy times and lower material consumption. Immediate and long-term clinical outcomes appear to be similar to stenting with predilatation. Preliminary results of large randomized trials with angiographic follow-up indicate that restenosis rates are similar to those of conventional stenting strategies. CONCLUSIONS: Direct stenting compared with stenting with predilatation is feasible, safe, faster and more cost-effective. The evidence to date shows similar late outcomes.

Angioplasty, Balloon, Coronary↗

PubMed2002

Angiotensin converting enzyme inhibiting therapy is associated with lower vitreous vascular endothelial growth factor concentrations in patients with proliferative diabetic retinopathy.

AIMS/HYPOTHESIS: Vascular endothelial growth factor (VEGF) is thought to be instrumental in the progression of diabetic retinopathy. Indications exist that the renin-angiotensin system is involved in VEGF overexpression. We assessed the vitreous VEGF concentrations in patients and related them to anti-hypertensive treatment, with special interest in the use of ACE-inhibitors. METHODS: Samples of vitreous fluid (10-80 microl) were obtained from 39 patients both with Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes mellitus and 11 non-diabetic patients undergoing intra-ocular surgery. The VEGF-A concentrations were assessed by immunoassay. RESULTS: Control patients and patients without proliferative diabetic retinopathy ( n = 8) had low and comparable VEGF concentrations (medians < 50 pg/ml). In contrast, patients with proliferative diabetic retinopathy ( n = 31) had high vitreous VEGF concentrations (median 1134 pg/ml), which showed a negative correlation with the use of ACE inhibiting medication (Spearman rank-R = - 0.54; p = 0.002, n = 13). Diastolic and systolic blood pressure did not differ significantly between the two subgroups with proliferative diabetic retinopathy, i. e. those patients receiving ACE-inhibition (medians 88/160 mm Hg, respectively) and the others (90/160). For the mostly used ACE-inhibitor in the proliferative diabetic retinopathy group, i. e. enalapril ( n = 8), a linear dose-effect relation was observed (-20 +/- 4 pg x ml(-1) x mg(-1) x day(-1); p = 0.024; coefficient +/- SEM). CONCLUSION/INTERPRETATION: Treatment with ACE-inhibitors attenuates retinal overexpression of VEGF-A in patients with proliferative diabetic retinopathy, probably by interference with a local effect of angiotensin II.

Adult↗

PubMed2001

The human internal thoracic artery releases more nitric oxide in response to vascular endothelial growth factor than the human saphenous vein.

OBJECTIVE: Endothelial nitric oxide inhibits smooth muscle cell proliferation, reducing the chance of vascular intimal thickening. In this study we investigated whether the superior long-term patency of the internal thoracic artery in human coronary bypass grafting compared with that of the saphenous vein could be explained by different levels of nitric oxide production. METHODS: The baseline endogenous nitric oxide production appeared to be 50% higher in the internal thoracic artery than in the saphenous vein. Previously, it was shown that vascular endothelial growth factor and the vascular endothelial growth factor receptors KDR (Flk-1) and Flt-1 are expressed in both internal thoracic arteries and saphenous veins and that vascular endothelial growth factor receptor density was higher in internal thoracic arteries than in saphenous veins. Therefore, we also investigated the influence of vascular endothelial growth factor on nitric oxide release in both the internal thoracic artery and the saphenous vein. RESULTS: Vascular endothelial growth factor augmented nitric oxide production by approximately 50% in the saphenous vein and 100% in the internal thoracic artery. As shown by means of immunohistochemistry, expression of endothelial constitutive nitric oxide synthase was similar in the internal thoracic artery and the saphenous vein, and no inducible nitric oxide synthase was expressed in any of the vascular segments. CONCLUSION: Vascular endothelial growth factor augments endothelial constitutive nitric oxide synthase-dependent nitric oxide release to a greater extent in the internal thoracic artery than in the saphenous vein. These findings may help to explain the long-term superiority of the internal thoracic artery versus the saphenous vein as a conduit for coronary artery bypass.

Analysis of Variance↗

PubMed2001

Endogenous nitric oxide and prostaglandins synergistically counteract thromboembolism in arterioles but not in venules.

It has been shown that NO and prostacyclin (prostaglandin I(2)) from cultured endothelium synergistically inhibit blood platelet aggregation in vitro. However, it is unknown whether this synergism is also effective in the inhibition of thromboembolism in vivo and, if it is, whether it differs between vessel types. Therefore, the effect of endogenous NO and prostacyclin, in combination or alone, on thromboembolism was studied in an in vivo model. Thromboembolism was induced by micropipette puncture of rabbit mesenteric arterioles and venules (diameter 18 to 40 micrometer). In addition, the influence of wall shear rate was analyzed. In arterioles, the combined inhibition of NO synthase (N(G)-nitro-L-arginine [L-NA] 0.1 mmol/L; local superfusion) and of cyclooxygenase (aspirin [ASA] 100 mg/kg IV) resulted in a pronounced, significant prolongation of embolization duration (median >600 seconds) compared with control (median 153 seconds) or treatment with either L-NA (234 seconds) or ASA (314 seconds). This combined effect of L-NA+ASA was greater than the sum of the individual effects of L-NA and ASA. In contrast, in venules L-NA+ASA had no additional effect on embolization duration (209 seconds) compared with the effect of L-NA alone (230 seconds); ASA alone had no effect (122 seconds; control 72 seconds). Interestingly, only in the L-NA+ASA arterioles did embolization correlate positively with wall shear rate (r(s)=0.687; P=0.028). In conclusion, this study indicates that in arterioles, but not in venules, endogenous NO and prostaglandins synergistically counteract ongoing thromboembolism after vessel wall injury and that the combination of endogenous NO and prostaglandins appears to protect against enhancement of arteriolar thromboembolism by wall shear rate.

Animals↗

PubMed2001

Impaired skin capillary recruitment in essential hypertension is caused by both functional and structural capillary rarefaction.

Capillary rarefaction occurs in many tissues in patients with essential hypertension and may contribute to an increased vascular resistance and impaired muscle metabolism. Rarefaction may be caused by a structural (anatomic) absence of capillaries, functional nonperfusion, or both. The aim of this study was to assess the extent of structural versus functional capillary rarefaction in the skin of subjects with essential hypertension. We examined skin capillary density with video microscopy before and during maximization of the number of perfused capillaries by venous congestion (structural capillary number) and before and during postocclusive reactive hyperemia (capillary recruitment, which may have a structural and/or functional basis). The study group was composed of 26 patients with never-treated essential hypertension and 26 normotensive control subjects. In both groups, intermittently perfused capillaries in the resting state were an important functional reserve for recruitment during postocclusive hyperemia. Recruitment of perfused capillaries during postocclusive reactive hyperemia was decreased in the hypertensive subjects compared with normotensive control subjects (47.9+/-6.8 versus 55.3+/-8.2 capillaries/mm(2), respectively; P<0.01). During venous occlusion, maximal capillary density was significantly lower in the hypertensive subjects than in the control subjects (52.5+/-6.6 versus 57.2+/-8.6 capillaries/mm(2), respectively; P<0.05), suggesting structural rarefaction. However, in the hypertensive subjects compared with the normotensive subjects, a smaller proportion of the maximal number of capillaries was perfused during postocclusive hyperemia (91.6+/-7.5% versus 97.2+/-2.7%, respectively; P<0.05), suggesting an additional functional impairment of capillary recruitment. If the difference in capillary numbers during venous congestion ( approximately 4.6 capillaries/mm(2)) truly reflects the structural difference between the normotensive and hypertensive subjects, then, at most, 62% (4.6/7.4x100%) of the difference in capillary numbers during postocclusive hyperemia ( approximately 7.4 capillaries/mm(2)) can be explained by structural defects, and at least 38% can be explained by functional defects. In conclusion, in patients with essential hypertension, recruitment of perfused capillaries is impaired, which can be explained by both functional and structural rarefaction.

Capillaries↗

PubMed2000

The influence of prostaglandins on leukocyte-endothelium interactions in rabbit mesenteric venules.

Contradictory results have been reported concerning the effects of prostaglandins (PGs) on leukocyte-endothelium interactions. Therefore, we investigated the in vivo effects of PGE1, PGE2, Iloprost (a stable PGI2-analogue), and also of a combination of these PGs on leukocyte rolling and FMLP-induced leukocyte adhesion in venules of rabbit mesentery. This preparation was used because of its low level of vasoactivity, eliminating hemodynamic effects on leukocyte-endothelium interactions. The mesentery was superfused with PGs or vehicle. After 30 min FMLP was added to the PG-solution for 15 min, whereupon the tissue was superfused with the PG-solution alone for another 30 min. Neither the PGs nor the cocktail influenced leukocyte rolling. During FMLP administration leukocyte adhesion increased and leukocyte rolling decreased; adhesion was highest in the presence of PGE2. The FMLP-induced decrease in leukocyte rolling was similar in all groups. After FMLP administration had been stopped the number of adherent cells almost returned to baseline and the level of leukocyte rolling increased, the baseline level being reached only in the presence of PGE2. In conclusion, these findings indicate that the effects of PGs on leukocyte-endothelium interactions are limited.

Animals↗

PubMed2000

In vivo visualization of hemodialysis-induced alterations in leukocyte-endothelial interactions.

BACKGROUND: The aim of this study was to develop a model for hemodialysis (HD) in small animals using conventional dialysis equipment that would allow the intravital microscopic observation of leukocyte-endothelial interactions in vivo. METHODS: Cuprophan dialyzers were adapted to obtain a similar ratio of membrane area to blood volume as in clinical HD. A silicone ring was inserted into the dialyzer's inlet to limit the number of blood-perfused capillaries. Rabbits were dialyzed for one hour without a dialysate flow. RESULTS: Extracorporeal circulation with the cuprophan dialyzer resulted in a transient leukopenia and complement activation. At the nadir of leukopenia, leukocytes that rolled along the venular wall were scarcely observed, whereas rolling was abundant (54 +/- 9 per min) prior to extracorporeal circulation. The adhesion of leukocytes to the vascular endothelium was not induced. After 60 minutes, rolling of leukocytes was still reduced by 73 +/- 5.5%, despite the full recovery of circulating leukocyte counts. Extracorporeal circulation without a dialyzer also tended to reduce leukocyte rolling, although systemic leukocyte counts were not affected. CONCLUSIONS: The use of adapted conventional cuprophan hemodialyzers in rabbits yielded a transient leukopenia similar to that in clinical HD. Using intravital microscopy, we demonstrated impairment of leukocyte-endothelial interactions. In addition, our data indicate that tissues, in which leukocytes can roll and adhere, are not automatically sites of leukocyte sequestration during HD-induced leukopenia.

Animals↗

PubMed2000

Extracorporeal circulation can induce hypotension by both blood-material contact and pump-induced platelet aggregation.

OBJECTIVE: Use of extracorporeal systems in cardiopulmonary bypass and dialysis induces vascular reactions, which can lead to hypotension and lung edema. METHODS: To study the contribution of blood-material contact and use of a roller pump, as well as prevention of their adverse effects, we perfused a rat hind leg with a tube connecting a carotid and a femoral artery. RESULTS: Autoperfusion of an uncoated tube caused a fall of aortic pressure and femoral resistance to 66% +/- 16% and 76% +/- 15%, respectively, of their initial values within 2 hours, whereas in control animals without a shunt, these variables hardly changed (to 94% +/- 2.8% and 99% +/- 2.8%, respectively). Lung water content became significantly higher than that found in control animals (79.4% +/- 1.50% versus 77. 0% +/- 1.67%). If we coated the tube with albumin, these changes were largely prevented. When the coated tube was placed in a roller pump, aortic pressure and femoral resistance immediately fell to 79% +/- 17.2% and 63% +/- 13.5%, respectively, whereas lung water content did not increase. The vasodilation was caused by platelet aggregation and could be prevented with aurintricarboxylic acid, which inhibits shear-induced platelet aggregation by blocking the binding of von Willebrand factor to platelet glycoprotein Ib receptors. CONCLUSIONS: Extracorporeal circulation may induce hypotension and lung edema by means of blood-material contact. Hypotension can be prevented by coating the system with albumin but can still result from pump-induced platelet aggregation.

Animals↗

PubMed2000

Tumor angiogenesis factors reduce leukocyte adhesion in vivo.

Leukocyte-endothelium interactions are diminished in tumors. It is reported here that, in a tumor-free in vivo model, angiogenic factors can down-regulate leukocyte adhesion to endothelium. Slow releasing pellets were loaded with either basic fibroblast growth factor (bFGF), vascular endothelial cell growth factor (VEGF) or vehicle alone and were placed in the scrotum of mice. After 3 days, a single intrascrotal injection of 1 microg/kg IL-1beta was given 4 h before vessels of the cremaster muscle were investigated for leukocyte rolling and adhesion by means of intravital microscopy. Exposure of normal tissue to either bFGF or VEGF resulted in markedly decreased levels of cytokine-induced leukocyte adhesion. Suppression of leukocyte rolling was not observed. Instead a moderate enhancement of rolling by VEGF was found. The observed differences could not be explained by differences in fluid dynamic parameters or systemic leukocyte counts. In conclusion, evidence is presented that, in vivo, angiogenic factors significantly reduce leukocyte adhesion, the final step preceding leukocyte infiltration. This observation may explain why tumors escape from immune surveillance.

Angiogenesis Inducing Agents↗

PubMed2000

Total warm ischemia and reperfusion impairs flow in all rat gut layers but increases leukocyte-vessel wall interactions in the submucosa only.

OBJECTIVE: To study the effect of warm ischemia and reperfusion (I/R) on local perfusion and leukocyte-vessel wall interactions in vivo in all small bowel layers, and to quantify small bowel tissue injury histologically and by measuring intestinal fatty acid binding protein (I-FABP) release from the enterocytes. SUMMARY BACKGROUND DATA: Gut injury as a result of I/R plays a pivotal role in a variety of clinical conditions, such as small bowel transplantation, heart or aortic surgery, and (septic) shock. The precise mechanism behind I/R injury and the role of microvascular changes remain unclear. The influence of warm I/R of the gut on microvascular parameters in the different gut layers has not been studied before. METHODS: Anesthetized Lewis rats were either subjected to 30 minutes of ischemia and 1 hour of reperfusion or sham-treated as controls. After ligating the inferior mesenteric artery, total warm ischemia was induced by clamping the superior mesenteric artery. Intravital video microscopic measurements were obtained at intervals. Tissue injury of the small bowel and other organs was histologically evaluated afterward. In addition, plasma levels of I-FABP were determined to measure enterocyte damage. RESULTS: After ischemia, mean red blood cell velocity decreased significantly in all layers of the small bowel, but no diameter changes were observed. Leukocyte-vessel wall interactions increased in the submucosa but not in the muscle layers. Plasma levels of I-FABP significantly increased from 30 minutes of reperfusion onward. The intestinal mucosa was severely injured; no histologic damage was detected in other tissues. CONCLUSIONS: This is the first in vivo study showing that total warm ischemia of the rat gut impairs perfusion in the whole small bowel, whereas leukocyte-vessel wall interactions increase in the submucosal layer only. Therefore, the early inflammatory response to I/R seems to be limited to the submucosa. Both microvascular effects may have contributed to the severe morphologic and functional mucosal injury observed after I/R.

Animals↗

PubMed2000

Alterations in nitric oxide activity and sensitivity in early streptozotocin-induced diabetes depend on arteriolar size.

Changes in NO activity may play an important role in the early increase in microvascular flow that has been implicated in the pathogenesis of diabetic microangiopathy. We assessed, in the in situ spinotrapezius muscle preparation of 6 weeks' streptozotocin-diabetic rats (n = 6) and of age-matched controls (n = 8), basal inside diameters of A2-A4 arterioles and the reactivity to topically applied acetylcholine and nitroprusside, before and after N(G)-nitro-L-arginine. In diabetic rats, cholinergic vasodilatation in A2-A4 arterioles was intact. Basal diameter in A3 and A4 arterioles was significantly higher in streptozotocin-diabetic rats. The increased basal diameter in A3 arterioles was partially due to an increased contribution of NO to basal diameter. The response to nitroprusside was impaired in streptozotocin-diabetic rats in A2, but not in A3 and A4 arterioles. Thus, this study shows that NO activity and sensitivity are altered after 6 weeks of streptozotocin-induced diabetes. These streptozotocin-induced changes are anatomically specific and, for arterioles, depend on their position within the vascular tree.

Acetylcholine↗

PubMed1999

Pump-induced platelet aggregation in albumin-coated extracorporeal systems.

OBJECTIVE: Coating of extracorporeal systems with heparin does not prevent platelet activation and subsequent bleeding disorders. We investigated whether this could be due to elevated shear stress caused by a roller pump. METHODS: Human or rat blood was made to flow through an uncoated or an albumin-coated medical polyvinyl chloride tube with or without a roller pump. Aggregation of platelets in the tubing was recorded continuously with a photometric device. RESULTS: Although in vitro gravitational flow in uncoated tubes caused immediate platelet aggregation and platelet loss, this remained absent in coated tubes. When the pump was started in experiments with a coated tube strong platelet aggregation was observed and platelet count fell within 5 minutes to 78% +/- 2% and 71% +/- 3% of control values in human and rat blood, respectively. In vivo, no aggregation was observed during spontaneous flow in rats with an albumin-coated tube running from the carotid artery to the femoral artery, but aggregation started as soon as the blood was pumped. Pump-induced platelet aggregation, both in vitro and in vivo, could be prevented with aurintricarboxylic acid, which specifically inhibits shear-induced platelet aggregation as has recently been shown. Pump perfusion of blood in an uncoated tube did not elicit platelet aggregation. CONCLUSIONS: Pump perfusion of blood in coated systems elicits shear-induced platelet aggregation, which may be prevented by administration of substances that block the binding of von Willebrand factor to glycoprotein Ib receptors on the platelets. The effects of pumping on platelets are masked in uncoated circuits because of the dominant influence of blood-material contact.

Albumins↗

PubMed1999

The visceral perfusion system and distal bypass during thoracoabdominal aneurysm surgery: an alternative for physiological blood flow?

There are potential benefits to addition of visceral organ perfusion, by means of a 9-Fr. catheter system (octopus), to distal aortic perfusion during thoracoabdominal aneurysm surgery. However, in the literature there are reports of adverse effects. The authors therefore compared two groups of patients who underwent thoracoabdominal aneurysm surgery with and without visceral organ perfusion. In the group in which the visceral perfusion was applied, the use of platelets (26 versus 11 units; P < 0.05), fresh frozen plasma (3.4 versus 1.5 units; P < 0.05) and packed cells (20 versus 8 units, P < 0.05) was significantly increased. An equal number of patients in both groups developed renal failure postoperatively. An explanation for this adverse effect can be found in the high shear rates in the catheters used, mainly as a result of the small diameter. High shear rates cause haemolysis. Also, the flow through the catheters is insufficient to maintain adequate perfusion of the visceral organs. A higher flow in these catheters would result in an even higher shear rate. It is therefore concluded that coagulopathy and insufficient bloodflow is caused by the small internal diameter of the catheters, which renders the device insufficient.

Acute Kidney Injury↗

PubMed1998

The role of mast cells and histamine in leukocyte-endothelium interactions in four rat strains.

The objective of the present study was to determine the role of mast cells and histamine in leukocyte-endothelium interactions in mesenteric venules of four rat strains: Brown Norway, Lewis, Sprague-Dawley and Wistar. Intravital microscopy showed that the mast cell stabilizer cromoglycate (5 mg/kg i.v. just before exteriorization of the mesentery) did not affect the baseline level and velocity of leukocyte rolling in any of the four strains. This finding is in agreement with the observation that cromoglycate pretreatment only slightly influenced mast cell degranulation in all strains except the Brown Norway. After mast cell stabilization, only in Sprague-Dawley did topical administration of histamine (10(-4) M) result in a significant increase in the level of leukocyte rolling and a decrease in the rolling velocity compared with the time control. Histamine induced leukocyte adhesion only in the Brown Norway strain. In conclusion, the hypothesis presented in other studies, that degranulation of mast cells, and more specifically the release of histamine, is of major importance for the induction of leukocyte-endothelium interactions in rat mesenteric venules is not generally applicable; the present study shows a clear strain dependency.

Animals↗

PubMed1998

Endogenous nitric oxide protects against thromboembolism in venules but not in arterioles.

Because nitric oxide (NO) inhibits aggregation and adhesion of blood platelets, NO may play a role in platelet-vessel wall interactions. Therefore, the purpose of this study was to investigate the involvement of endogenous NO in thromboembolic processes, as induced by wall puncture, in rabbit mesenteric arterioles and venules (diameters 20 to 43 microm). In venules, inhibition of NO synthase by superfusion of the mesentery with N omega-nitro-L-arginine (L-NA; 0.1 mmol/L) significantly increased the duration of embolization (from 50 seconds to 511 seconds) and the number of emboli produced (from 2 to 11 emboli per vessel), while the median period of time needed to produce an embolus was not influenced. On the contrary, in arterioles, L-NA had no significant effect on embolization (duration of embolization: 426 seconds in the control and 382 seconds in the L-NA group, with 20 and 12 emboli per vessel, respectively). Addition to the L-NA superfusate of L-arginine (L-ARG; 1 mmol/L), the active precursor for endogenous NO synthesis, resulted in a complete reversal of the L-NA effects in venules, while addition of the inactive D-arginine (D-ARG; 1 mmol/L) had no effect. Addition of L-ARG and D-ARG had no significant effect in arterioles. Addition to the L-NA superfusate of the exogenous NO donor sodium nitroprusside (0.1 micromol/L) also resulted in reversal of the L-NA effects in venules, while in arterioles, it slightly but significantly decreased embolization duration. The differences in effect of L-NA on embolization between arterioles and venules were not caused by differences in fluid dynamic conditions. It is concluded that the role of endogenous NO in inhibiting thromboembolic processes is more important in venules than in arterioles.

Animals↗

PubMed1997

Skin blood flow abnormalities in a rat model of neuropathic pain: result of decreased sympathetic vasoconstrictor outflow?

Loose ligation of a sciatic nerve in rats provokes signs and symptoms like those observed in human conditions of neuropathic pain. Some of these have been associated with sympathetic dysfunction. Since the skin microcirculation in the rat is strongly influenced by sympathetic tone, abnormalities in skin blood flow may be used as an indirect measure of sympathetic dysfunction. We measured, by means of laser Doppler flowmetry, skin blood flow at the plantar surface of the rat hind paw before and after ipsilateral loose sciatic nerve ligation. We assessed basal skin blood flow as well as the vasoconstrictor response which follows cooling of the rat abdomen. The effectiveness of this response may be used as a measure of sympathetic vasoconstrictor outflow. As compared to the values obtained before ligation (= 100%): (1) the vasoconstrictor response was impaired (65%, P < 0.01) from day 1 onwards, whereas (2) basal skin blood flow was increased (171%; P < 0.01) from day 3 until day 5, and decreased (51%, P < 0.0001) from day 7 until day 28. At day 28, blockade of impulse propagation in the loosely ligated sciatic nerve (by means of lidocaine) did not increase the lowered level of skin blood flow. These findings suggest that in the chronic construction injury model loose ligation of a sciatic nerve reduces sympathetic vasoconstrictor outflow, which, in turn may induce supersensitivity of skin microvessels to catecholamines.

Animals↗

PubMed1997

Effects of different durations of total warm ischemia of the gut on rat mesenteric microcirculation.

BACKGROUND: Gut injury due to ischemia and reperfusion (I/R) plays a pivotal role in many clinical conditions, such as small bowel transplantation, heart or aortic surgery in adults, and necrotizing enterocolitis in neonates. The influence of ischemic events on microcirculatory mechanisms is not well understood. Therefore, we studied, in vivo, local perfusion and leukocyte-vessel wall interactions before and after different periods of total warm ischemia of the whole gut and subsequent reperfusion in mesenteric microvessels. MATERIALS AND METHODS: Groups of pentobarbital-anaesthetized Lewis rats were subjected to 15 (n = 9), 30 (n = 12), or 60 min (n = 5) of total warm gut ischemia and 2 h reperfusion. As control a sham group (n = 10) was included. After ligating the inferior mesenteric artery, total warm ischemia was induced by clamping the superior mesenteric artery. Before and at different time periods after start of reperfusion intravital video microscopic measurements were performed. RESULTS: Rats subjected to 60 min ischemia died during the early reperfusion phase. Fifteen, 30, and 60 min ischemia induced in venules a significant decrease in blood flow, while diameter changes were not observed. This flow decrease was severe in the 15- and 30-min ischemia groups, dropping to 40 and 25% of control, respectively. Following 60 min ischemia blood flow did not exceed 10% of control. The total number of interacting leukocytes, a parameter which includes both leukocyte rolling and adhesion in venules, increased up to 5 or 10 times its control value following 15 or 30 min ischemia, respectively. Leukocyte-vessel wall interactions could not be studied in the 60-min ischemia group, due to the low blood flow. CONCLUSIONS: Even short periods of total warm ischemia of the whole gut induce severe attenuation of venular blood flow with an increase in leukocyte-vessel wall interactions. These changes increase with prolongation of the ischemic period. A 60-min period of total warm ischemia is fatal during the early reperfusion phase.

Animals↗