PubMed Health⌕ Search

Biomedical subjects

Brigitte Vollmar

Publications and source records attributed to Brigitte Vollmar.

At least 55 records · Page 3Linked to original sources
PubMed2004

Up-regulation of endothelial nitric oxide synthase inhibits pulmonary leukocyte migration following lung ischemia-reperfusion in mice.

Endogenous nitric oxide (NO) is known to modulate post-ischemic inflammatory response in various organs. However, the role of nitric oxide synthase isoforms (NOS) in mediating pulmonary post-ischemic inflammatory response is poorly understood. We therefore studied post-ischemic endothelial adhesion molecule expression and leukocyte migration in endothelial NOS knockout (eNOS-KO) mice subjected to pulmonary ischemia and reperfusion in vivo. Under anesthesia and mechanical ventilation, the left pulmonary hilum in wild-type (WT) and eNOS-KO mice was clamped for 1 hour, followed by reperfusion for up to 24 hours. In WT mice, we observed a selective up-regulation of both eNOS mRNA and protein in lung tissue, while inducible NOS (iNOS) and neuronal NOS (nNOS) remained unchanged. Survival in eNOS-KO mice was reduced due to severe pulmonary edema, underlining an increased susceptibility to ischemia-reperfusion (I/R) injury. Interstitial tissue infiltration by CD18- and CD11a-positive white blood cells as well as lung tissue water content peaked at 5 hours of reperfusion and were found significantly higher than in WT mice. Enhanced leukocyte-endothelial interaction was associated with pronounced up-regulation of vascular cell adhesion molecule (VCAM) in eNOS-KO mice during post-ischemic reperfusion. We conclude that eNOS attenuates post-ischemic inflammatory injury to the lung most probably via inhibition of endothelial adhesion molecule expression.

Animals↗
PubMed2004

Heme oxygenase does not contribute to control of basal vascular tone in isolated blood-perfused rat lung.

BACKGROUND: Vasoconstriction in pulmonary ischemia-reperfusion injury may involve dysfunction of the physiologic vasodilation of pulmonary arteries. Little is known of the relative importance of heme oxygenase (HO)/carbon monoxide (CO)-dependent vs nitric oxide synthase (NOS)/nitric oxide (NO)-dependent vasodilation of the pulmonary vasculature. We evaluated the significance of HO function on basal pulmonary vascular resistance (PVR) and compared it with the function of NOS. METHODS: Using an isolated blood-perfusion model, lungs of Lewis rats were assigned to 3 groups (n = 6/group). After stabilization, either an inhibitor of HO (tin-protoporphyrin-9 [SnPP-9]) or an inhibitor of NOS (NG-nitro-L-arginine methylester [L-NAME]) was added to the perfusate (50 micromol/liter and 1 mmol/liter as the final concentration, respectively). Lungs receiving saline served as controls. Gas exchange, hemodynamic and respiratory functions and the levels of cyclic 3',5'-guanosine monophosphate (cGMP) in the perfusate were measured. RESULTS: Inhibition of NOS by L-NAME resulted in a significant (p < 0.01) increase in PVR (DeltaPVR: 0.110 +/- 0.012 cm H(2)O/ml. min) within 5 minutes. In contrast, PVR was minimally affected by SnPP-9 (DeltaPVR: 0.005 +/- 0.005 cm H(2)O/ml. min), which was comparable to control lungs (DeltaPVR: 0.012 +/- 0.005 cm H(2)O/ml. min). The level of cGMP in the perfusate 5 minutes after drug application was markedly, but not significantly, lower in the L-NAME group (1.67 +/- 0.74 nmol/liter) when compared with controls (2.69 +/- 0.89 nmol/liter) and SnPP-9-treated lungs (2.65 +/- 0.66 nmol/liter). CONCLUSIONS: NOS but not HO contributes to the control of basal vascular tone in the rat lung.

Animals↗
PubMed2004

Microhemodynamic and cellular mechanisms of activated protein C action during endotoxemia.

OBJECTIVE: To characterize microcirculatory actions of activated protein C in an endotoxemia rodent model that allows in vivo studies of microvascular inflammation and perfusion dysfunction. DESIGN: Animal study using intravital microscopy. SETTING: Animal research facility. SUBJECTS: Male Syrian golden hamsters, 6-8 wks old with a body weight of 60-80 g. INTERVENTIONS: In skinfold preparations, endotoxemia was induced by intravenous administration of 2 mg/kg endotoxin (lipopolysaccharide, Escherichia coli). Intravital microscopy allowed quantitative analysis of arteriolar and venular leukocyte adhesion and functional capillary density (cm) that served as a measure of microvascular perfusion failure. Activated protein C (APC group, n = 8, 24 microg/kg intravenously) was substituted continuously during 8 hrs after lipopolysaccharide, whereas endotoxemic buffer-treated animals (control, n = 7) served as controls. MEASUREMENTS AND MAIN RESULTS: Lipopolysaccharide increased leukocyte adhesion and decreased functional capillary density to 50% of baseline values (p <.01 vs. baseline). Activated protein C treatment inhibited (p <.05) lipopolysaccharide-mediated leukocytic response and attenuated (p <.05) endotoxic perfusion failure in nutritive capillaries. CONCLUSIONS: Activated protein C-induced protection from lipopolysaccharide-mediated microcirculatory dysfunction was characterized in vivo for the first time. The impressive modification of leukocyte cross-talk indicates systemic anti-inflammatory activated protein C effects on leukocytes and the endothelium, subsequently improving capillary perfusion. These actions could represent the in vivo mechanism of activated protein C interactions observed in patients with severe sepsis.

Animals↗
PubMed2003

Efficiency of small-volume resuscitation in restoration of disturbed skeletal muscle microcirculation after soft-tissue trauma and haemorrhagic shock.

BACKGROUND AND AIMS: Despite advances in primary care, trauma in conjunction with shock remains the leading cause for morbidity and mortality of young adults in western countries. Herein, we report on the efficiency of small-volume resuscitation to improve compromised perfusion of traumatised skeletal muscle tissue in shock. METHODS: In pentobarbital anaesthetised, mechanically ventilated rats, closed soft-tissue trauma of the right hind limb was induced, followed by induction of haemorrhagic shock [mean arterial blood pressure (MAP) 40 mmHg for 1 h]. For resuscitation, animals received saline (four-times the shed blood volume/20 min), 10% hydroxyethyl starch (HES) 200/0.5 (equal to shed blood volume/5 min) or 7.2% sodium chloride/6% hydroxyethyl starch 200/0.5 (HyperHES; 10% of shed blood volume/2 min). At 2 h of resuscitation, traumatised skeletal muscle tissue was analysed by in vivo microscopy. Non-resuscitated animals served as shock controls. RESULTS: Despite incomplete restoration of systemic blood pressure, HyperHES was superior to saline, but not to HES, with respect to amelioration of nutritive perfusion. Inflammatory cell response within the traumatised skeletal muscle tissue escaped from the anti-adhesive properties of HyperHES when applied for resuscitation from hypovolaemic shock, and did not differ from values in HES-treated and saline-treated animals. CONCLUSION: Resuscitation with HyperHES is as effective as HES in improving capillary perfusion in traumatised skeletal muscle during haemorrhagic shock. However, because values of functional capillary density in the HyperHES-treated and HES-treated animals were still markedly below those reported in traumatised skeletal muscle of normovolaemic animals, further tools are needed to enhance efficiency in treatment of local skeletal muscle tissue injury during haemorrhagic shock.

Animals↗
PubMed2003

Experimental models to study microcirculatory dysfunction in muscle ischemia-reperfusion and osteomyocutaneous flap transfer.

BACKGROUND: During the past decade, experimental studies have provided convincing evidence that microcirculatory dysfunction plays a pivotal role in the manifestation of tissue injury in ischemia-reperfusion and osteomyocutaneous flap transfer. The study of the mechanisms of injury, however, requires sophisticated experimental in vivo models. With the use of microsurgical techniques, osteomyocutaneous flap transfer can successfully be performed in rat hind limbs, allowing in vivo fluorescent microscopic analysis of post-ischemic microcirculatory dysfunction in all tissues involved, including periosteum, striated muscle, subcutis and skin. The drawback of this "acute" model is that the period of analysis is restricted to a few hours only. METHOD: To overcome this limitation, the "chronic" dorsal skinfold chamber preparation, containing striated muscle and subcutis, can be used. This model allows one to study microcirculatory dysfunction after both tourniquet-induced and pressure-induced ischemia-reperfusion-induced tissue injury over a period of up to 3 weeks. RESULTS: With the use of these models, recent investigations have demonstrated that ischemia-reperfusion and osteomyocutaneous flap transfer are associated with capillary perfusion failure (no-reflow), mediated by intravascular hemoconcentration, endothelial swelling and endothelin (ET)-1-mediated microvascular constriction. In addition, post-ischemic reperfusion provokes an inflammatory response (reflow paradox) in post-capillary venules, which is characterized by beta2-integrin-mediated and intercellular adhesion molecule (ICAM)-1-mediated leukocyte adhesion and vascular hyperpermeability, which results in interstitial edema formation. Treatment studies have produced evidence that isovolemic hemodilution and heat shock protein induction are successful in ameliorating capillary no-reflow, while blockade of adhesion molecules, inactivation of oxygen radicals and, also, induction of heat shock proteins, are capable of reducing the post-ischemic inflammatory response. CONCLUSION: These experimental results not only demonstrate the importance of the use of advanced in vivo methods to delineate pathophysiological mechanisms in complex disease models, but may also provide a basis for potential prospective randomized trials to test the benefit for the patient in the daily clinical routine.

Animals↗
PubMed2003

Protective skeletal muscle arteriolar vasomotion during critical perfusion conditions of osteomyocutaneous flaps is not mediated by nitric oxide and endothelins.

BACKGROUND: After flap surgery, vasomotion, defined as oscillation of the arteriolar diameter, may protect tissue during critical perfusion conditions. The mechanisms that regulate vasomotion are still unclear; therefore, we studied the incidence of vasomotion in peripheral tissue and whether nitric oxide or endothelins are involved in regulation of vasomotion. MATERIALS AND METHODS: In Sprague-Dawley rats, an osteomyocutaneous flap was prepared. To induce critical perfusion conditions, we reduced arterial blood flow supplying the flap to 0.15 ml/min. Seven animals received NG-nitro-L-arginine methyl ester (L-NAME), a nitric oxide-synthase inhibitor, and six animals bosentan, an endothelin A/B receptor antagonist. Microcirculation of muscle, skin, subcutis and periosteum was assessed by intravital microscopy before and after drug application. RESULTS: In all animals, reduction of arterial blood supply induced arteriolar vasomotion in muscle (100%), but not in periosteum, subcutis and skin. Vasomotion was found to be affected by neither L-NAME (frequency 2.6+/-0.2 versus 2.4+/-0.2 cycles/min; amplitude 67+/-19 versus 55+/-20%; share of dilation period in vasomotion cycle 59+/-2 versus 58+/-3%) nor bosentan (1.8+/-0.1 versus 1.7+/-0.1 cycles/min; 60+/-10 versus 64+/-6%; 50+/-2 versus 53+/-1%). CONCLUSIONS: Our study indicates that during critical perfusion conditions, arteriolar vasomotion develops only in muscle, not in skin, subcutis and periosteum, and that nitric oxide and endothelins are not involved in the regulation of this protective vascular response.

Animals↗
PubMed2003

Noninvasive in vivo analysis of the human hepatic microcirculation using orthogonal polorization spectral imaging.

BACKGROUND: Analysis of hepatic microvascular perfusion in humans by direct imaging has been impossible so far. Orthogonal polarization spectral (OPS) imaging represents a new technology that combines simultaneous epi-illumination of the subject with linearly polarized light and noninvasive imaging of the microcirculation by reflectance spectrophotometry. The aim of this study was to evaluate the feasibility of studying the human hepatic microcirculation by OPS imaging in vivo and to define microcirculatory parameters for physiologic conditions. METHODS: The hepatic microcirculation was analyzed in four different regions of both liver lobes in 11 healthy individuals undergoing partial liver resection for living-donor liver transplantation. The optical probe was gently positioned on the liver surface and sequences of at least 20 sec per measurement were recorded by a charge-coupled device camera on videotape. Microhemodynamic parameters were quantified off-line by single-frame and frame-to-frame analysis using a computer-assisted image analysis system. RESULTS: OPS images of the hepatic microcirculation showed an acceptable quality with good resolution. Quantitative analysis revealed a sinusoidal red blood cell velocity of 0.97+/-0.43 mm/sec, a sinusoidal diameter of 8.8+/-0.9 microm, a sinusoidal volumetric blood flow of 58.2+/-9.6 pL/sec, an intersinusoidal distance of 22.6+/-2.5 microm, and a mean functional sinusoidal density of 391+/-30 cm-1. Apart from the sinusoidal red blood cell velocity, all data of the parameters studied matched the pattern of normal distribution. CONCLUSIONS: OPS imaging enabled for the first time direct in vivo visualization and quantification of the human hepatic microcirculation, providing significant insight into microvascular physiology of the human liver, to the extent that these data can be considered to represent physiologic values for human hepatic microcirculation.

Adult↗
PubMed2003

Improvement of microvascular graft equilibration and preservation in non-heart-beating donors by warm preflush with streptokinase.

Using in situ fluorescence microscopy with Sprague Dawley rats, we studied the hypothesis of compromised microvascular kidney perfusion on organ harvest in non-heart-beating donors (NHBDs), and we evaluated the potential benefit of an additional preflush with saline solution containing streptokinase. Aortal flush of NHBD kidneys solely with University of Wisconsin solution resulted in a significantly (P <0.05) reduced functional capillary density (FCD) with increased perfusion heterogeneity compared with kidneys of heart-beating controls. This was associated with an increased lactate dehydrogenase (LDH) release on 24 hr postpreservation rinse of the grafts (76.7+/-18.9 U/L). Warm preflush with low-viscosity Ringer's lactate (RL) solution alone did not influence the decreased renal FCD and the postpreservation LDH release (76.2+/-29.1 U/L). In contrast, the addition of streptokinase to the RL preflush solution resulted in a significant (P <0.05) improvement of FCD with values not statistically different from those of heart-beating controls. This was associated with an attenuation of perfusion heterogeneity and a significantly lowered postpreservation LDH release (17.0+/-2.5 U/L). Furthermore, in transplanted and reperfused NHBD kidney grafts, the use of streptokinase-supplemented RL for preflush during organ harvest significantly (P <0.05) reduced early manifestation of tubular necrosis (29%+/-8%) when compared with kidneys preflushed exclusively with University of Wisconsin solution (56%+/-4%). Thus, we conclude that kidney harvest from NHBDs is prone to severe microvascular perfusion deficits, which are likely to preclude successful preservation of organ integrity during cold storage. Temporary fibrinolytic preflush with streptokinase may represent a feasible tool to improve microvascular graft equilibration, which effectively protects the renal integrity during both cold storage and posttransplant reperfusion.

Adenosine↗
PubMed2003

Blockade of in vivo VEGF-KDR/flk-1 signaling does not affect revascularization of freely transplanted pancreatic islets.

BACKGROUND: The aim of this study was to analyze the role of vascular endothelial growth factor (VEGF) binding to its high-affinity receptor kinase insert domain (KDR)-containing receptor/fetal liver kinase (flk)-1 in mediating revascularization of freely transplanted pancreatic islets in vivo. METHODS: Isolated pancreatic islets were syngeneically transplanted into dorsal skinfold chambers of Syrian hamsters. Animals were treated daily with the VEGF-KDR/flk-1 antagonist SU5416 (25 mg/kg intraperitoneally) or received vehicle for control. Intravital fluorescence microscopy and computer-assisted off-line analysis were used to study islet graft angiogenesis and revascularization during days 6, 10, and 14 after transplantation. RESULTS: In controls, islets were revascularized within 10 to 14 days after transplantation. SU5416 treatment did not affect revascularization, inasmuch as both functional capillary density and size of revascularized endocrine tissue did not differ from that of vehicle-treated controls. CONCLUSION: Because blockade of VEGF-KDR/flk-1 function does not affect islet revascularization, we conclude that VEGF signaling through its high-affinity receptor KDR/flk-1 is not an essential prerequisite for the process of new-vessel formation in freely transplanted islets of Langerhans.

Animals↗
PubMed2003

Ischemic preconditioning protects from hepatic ischemia/reperfusion-injury by preservation of microcirculation and mitochondrial redox-state.

BACKGROUND/AIMS: Ischemic preconditioning (IP) is known to protect hepatic tissue from ischemia-reperfusion injury. However, the mechanisms involved are not fully understood yet. METHODS: Using intravital multifluorescence microscopy in the rat liver, we studied whether IP exerts its beneficial effect by modulating postischemic Kupffer cell activation, leukocyte-endothelial cell interaction, microvascular no-reflow, mitochondrial redox state, and, thus, tissue oxygenation. RESULTS: Portal triad cross-clamping (45 min) followed by reperfusion induced Kupffer cell activation, microvascular leukocyte adherence, sinusoidal perfusion failure (no-reflow) and alteration of mitochondrial redox state (tissue hypoxia) (P<0.05). This resulted in liver dysfunction and parenchymal injury, as indicated by decreased bile flow and increased serum glutamate dehydrogenase (GLDH) levels (P<0.05). IP (5 min ischemia and 30 min intermittent reperfusion) was capable to significantly reduce Kupffer cell activation (P<0.05), which was associated with a slight attenuation of leukocyte adherence. Further, IP markedly ameliorated sinusoidal perfusion failure (P<0.05), and, thereby, preserved adequate mitochondrial redox state (P<0.05). As a consequence, IP prevented the decrease of bile flow (P<0.05) and the increase in serum GLDH levels (P<0.05). CONCLUSIONS: IP may exert its beneficial effects on hepatic ischemia-reperfusion injury by preserving mitochondrial redox state, which is guaranteed by the prevention of reperfusion-associated Kupffer cell activation and sinusoidal perfusion failure.

Animals↗
PubMed2003

Iloprost ameliorates post-ischemic lung reperfusion injury and maintains an appropriate pulmonary ET-1 balance.

BACKGROUND: Ischemia-reperfusion (I/R) injury of the lung involves increased pulmonary vascular resistance. Prostaglandins are thought to have a beneficial effect in lung transplantation, but their mechanism in I/R injury is unknown. We investigated whether iloprost, a stable prostacyclin analogue, prevents I/R-associated pulmonary vascular dysfunction and whether it affects endothelin-1 (ET-1) balance. METHODS: In an isolated blood-perfusion model, we subjected lungs of Lewis rats to 45 minutes of ischemia at 37 degrees C and randomly allocated the lungs to 3 groups (n = 6 each): iloprost (33.3 nmol/liter) added to the perfusate before ischemia and reperfusion (ILO+IR), iloprost (33.3 nmol/liter) given only before reperfusion (ILO+R), and controls without iloprost treatment (ILO-). RESULTS: Reperfusion induced marked pulmonary edema in non-treated controls (ILO-), which was attenuated in ILO+R lungs and completely prevented in ILO+IR lungs. At 60 minutes reperfusion, arterial oxygen tension was significantly greater in both ILO+R and ILO+IR lungs compared with ILO- controls. Mean pulmonary artery pressure and pulmonary vascular resistance were slightly decreased in the ILO+R and significantly decreased in the ILO+IR group compared with the ILO- controls. Plasma levels of big ET-1, measured in both afferent and efferent blood, showed that I/R results in increased pulmonary venous levels of big ET-1. Interestingly, the increased venoarterial ET-1 gradient in ILO- lungs decreased significantly in the ILO+IR group. CONCLUSIONS: We demonstrated in an isolated lung perfusion model that iloprost ameliorates post-ischemic lung reperfusion injury and maintains an appropriate pulmonary ET-1 balance.

Animals↗
PubMed2003

Comparative analysis of platelet isolation techniques for the in vivo study of the microcirculation.

OBJECTIVE: In vitro and in vivo studies using isolated platelets require that the cells used for testing are not activated by the isolation procedure. This ensures that the effects measured by the test are the result of the environment or the applied stimulus, but is not an artifact resulting from activation by cell isolation. METHODS: Herein, we analyzed two different platelet isolation procedures (i.e., a Sepharose column versus density gradient centrifugation) with special emphasis on cell activation, including flow cytometric analysis of P-selectin expression, functional quantification of mechanical platelet retention, light microscopic assessment of platelet aggregation, and fluorescence microscopic determination of in vivo rat liver platelet-endothelium cell interaction. RESULTS: Under resting conditions, Sepharose column-isolated platelets showed a negligible fraction of only 2.7 +/- 3.3% cells (mean +/- SEM) with P-selectin expression, and an appropriate response (i.e., a 33-fold increase) upon activation with thrombin receptor-activating peptide (TRAP). In contrast, density gradient centrifugation resulted in P-selectin expression under resting conditions of approximately 50% of the isolated cells and only a 1.6-fold increase on further TRAP stimulation. In addition, density gradient-isolated platelets, but not Sepharose column-isolated platelets, showed increased mechanical retention and agglutination/aggregation in vitro, as well as pronounced adhesion to hepatic venular endothelium in vivo. Interestingly, density gradient-isolated platelets additionally induced in vivo an increase of colocalization of platelets with adherent leukocytes, indicating a generalized microvascular inflammatory response that is comparable to that observed after a 60-minute ischemia/30-minute reperfusion insult. CONCLUSION: Density gradient centrifugation-isolated platelets, but not Sepharose column-isolated platelets, are activated already under resting conditions and induce in vivo a platelet-leukocyte-endothelial cell-associated inflammatory response. Thus, we propose that the method of platelet isolation using the Sepharose column is superior to the density gradient centrifugation technique and might therefore be preferred for in vitro and in vivo assays to study platelet function.

Blood Platelets↗
PubMed2003

Heme oxygenase and nitric oxide synthase mediate cooling-associated protection against TNF-alpha-induced microcirculatory dysfunction and apoptotic cell death.

Local cooling protects against TNF-alpha-induced injury by attenuating inflammation-associated microcirculatory dysfunction and leukocytic response. Mechanisms of protection, however, are not fully understood. We studied whether the metabolites of the HO and NOS pathway, exerting potent vasodilatory, antioxidant, and anti-apoptotic properties, are involved in tissue cryoprotection. In animals pretreated with L-NAME or SnPP-IX, cooling-associated abrogation of TNF-alpha-induced microcirculatory dysfunction was abolished. Combined L-NAME/SnPP-IX pretreatment did not cause greater blunting than seen when each mediator system was inhibited separately. In SnPP-IX- but not L-NAME-pretreated animals, transient hypothermia failed to reduce TNF-alpha-mediated leukocyte adherence. Vice versa, treatment of TNF-alpha-exposed animals with either the NO donor l-arginine or the HO-1 inductor hemin mimicked cooling-associated tissue protection except for failure of l-arginine to abrogate the inflammatory leukocyte response. The efficiency of cooling to inhibit TNF-alpha-induced apoptotic cell death was blunted in SnPP-IX-, L-NAME-, and SnPP-IX/L-NAME-pretreated animals. Coadministration of Trolox in SnPP-IX-treated animals partly attenuated leukocyte adherence and cell apoptosis, implying that the HO pathway metabolite biliverdin contributes to the salutary effects of cooling. Thus, our study provides evidence that metabolites of the HO and the NOS pathway mediate the cooling-associated protection of inflamed tissue. Biliverdin rather than CO and NO mediates the anti-inflammatory action, whereas a coordinated function of the gaseous monoxides prevents microcirculatory dysfunction and apoptotic cell death.

Animals↗
PubMed2003

Anti-oxidant ebselen delays microvascular thrombus formation in the rat cremaster muscle by inhibiting platelet P-selectin expression.

Ebselen, a seleno-organic compound showing glutathione per-oxidase-like activity, has potent anti-inflammatory and anti-oxidant effects. Since selenium deficiency is thought to be associated with an increased incidence of vascular thrombosis, we studied the effect of ebselen on blood cell aggregate formation and vessel occlusion in vivo. In individual microvessels of rat cremaster muscle preparations, photochemically induced thrombus formation was analyzed in detail using intravital fluorescence microscopy. In ebselen-pretreated animals (30 mg/kg ip), venular thrombus formation was significantly delayed (50% vessel occlusion: 535+/-34 s; initial stasis: 872+/-82 s; complete occlusion: 908+/-87 s) as compared to vehicle-treated controls (416+/-42; 612+/-49; 647+/-51). Moreover, ebselen significantly prolonged the kinetics of arteriolar thrombus formation and even completely prevented blood cell aggregate and thrombus formation in 88.9% of all arterioles studied (p<0.05 vs controls: 37.5%). Anti-thrombotic properties of ebselen could also be observed in a model of ferric chloride-induced microvascular thrombosis, with a low dose (5 mg/kg ip) being as effective as a high dose pretreatment (30 mg/kg ip). As assessed by flow cytometry of platelet P-selectin immunfluorescence, whole blood isolated from ebselen-treated animals revealed a significantly lower fraction of P-selectin expressing platelets when compared with that of DMSO-treated controls. In addition, oxidant stress-induced upregulation of P-selectin on isolated platelets was found dose-dependently inhibited by increasing concentrations of ebselen (10-100 micro M). Moreover, ebselen dose-dependently inhibited H(2)O(2)-induced platelet-leukocyte aggregate formation in whole blood in vitro, suggesting that the anti-thrombotic effect of ebselen is achieved by attenuation of P-selectin dependent platelet-leukocyte aggregation. Thus, ebselen represents preventive and therapeutic value for disorders with increased risk for oxidant stress-associated thrombotic events.

Animals↗
PubMed2003

Long-term cell survival and hemodynamic improvements after neonatal cardiomyocyte and satellite cell transplantation into healed myocardial cryoinfarcted lesions in rats.

Cell engraftment is a new strategy for the repair of ischemic myocardial lesions. The hemodynamic effectiveness of this strategy, however, is not completely elucidated yet. In a rat model of cryothermia-induced myocardial dysfunction, we investigated whether syngeneic transplantation of neonatal cardiomyocytes or satellite cells is able to improve left ventricular performance. Myocardial infarction was induced in female Lewis rats by a standardized cryolesion to the obtuse margin of the left ventricle. After 4 weeks, 5 x 10(6) genetically male neonatal cardiomyocytes (n = 16) or satellite cells (n = 16) were engrafted into the myocardial scar. Sham-transplanted animals (n = 15) received injections with cell-free medium. Sham-operated animals (n = 15) served as controls. Left ventricular performance was analyzed 4 months after cell engraftment. Chimerism after this sex-mismatched transplantation was evaluated by detection of PCR-amplified DNA of the Y chromosome. The average heart weight of the infarcted animals significantly exceeded that of controls (p < 0.05). In sham-transplanted animals, mean aortic pressure, left ventricular systolic pressure, aortic flow (indicator of cardiac output), and left ventricular systolic reserve were significantly lower (p < 0.05) compared with sham-operated controls. This was associated with deterioration of ventricular diastolic function (maximal negative dP/dt, time constants of isovolumic relaxation; p < 0.05). Transplantation of satellite cells was found more effective than transplantation of neonatal cardiomyocytes, resulting in i) normalization of mean aortic pressure compared with sham-operated controls, and ii) significantly improved left ventricular systolic pressure and aortic flow (p < 0.05) compared with sham-transplanted animals. Left ventricular systolic reserve and diastolic function, however, were improved by neither satellite cell nor neonatal cardiomyocyte transplantation. Analysis of male genomic DNA revealed 3.98 +/- 2.70 ng in hearts after neonatal cardiomyocyte engraftment and 6.16 +/- 4.05 ng in hearts after satellite cell engraftment, representing approximately 10(3) viable engrafted cells per heart. Our study demonstrates i) long-term survival of both neonatal cardiomyocytes and satellite cells after transplantation into cryoinfarcted rat hearts, ii) slight superiority of satellite cells over neonatal cardiomyocytes in improving global left ventricular pump performance, and iii) no effect of both transplant procedures on diastolic dysfunction.

Animals↗
PubMed2002

Heat shock preconditioning impairs revascularization of freely transplanted pancreatic islets.

BACKGROUND: Revascularization of freely transplanted pancreatic islets is essential for appropriate graft function and survival. During the first days after transplantation, however, islet transplants are avascular, and successful engraftment is believed to be markedly hampered by hypoxia-induced tissue injury. Because heat shock has been shown to induce cell resistance against hypoxia, it seems reasonable to stress pancreatic islets by heat before transplantation. In contrast, hypoxia is a major stimulus for angiogenesis, and thus heat shock preconditioning-induced resistance against hypoxia may decrease stimulation of angiogenesis. The authors therefore studied in vivo whether heat shock preconditioning of isolated islets affects angiogenesis and revascularization after free transplantation. METHODS: After collagenase isolation, heat shock-preconditioned islets (42 degrees C for 30 min) were transplanted syngeneically into nontreated skinfold chambers of Syrian hamsters. In a second group of animals, nontreated islets were transplanted into heat shock-preconditioned chambers. Nontreated islets transplanted into nontreated chambers served as controls. Islet angiogenesis and revascularization were quantitatively analyzed during 14 days after transplantation using intravital fluorescence microscopy. Expression of heat shock proteins (HSP) was confirmed by immunohistochemistry and Western blotting. RESULTS: Immunohistochemistry revealed expression of HSP32 (heme oxygenase [HO]-1), HSP72, and also intracellular insulin in isolated and transplanted pancreatic islets. Western blot analysis showed enhanced HSP32 but slightly decreased HSP72 expression in heat shock-preconditioned islets when compared with controls. Intravital microscopy revealed appropriate vascularization of control islets within 14 days after transplantation. Heat shock preconditioning of the host tissue (i.e., the skinfold chambers) did not affect islet vascularization when compared with controls. In contrast, heat shock preconditioning of the isolated islets resulted in a significantly (P < 0.05) impaired take rate, a reduced (P < 0.05) size of the newly formed microvascular network, and thus a smaller area (P < 0.05) of microvascularly perfused endocrine tissue. CONCLUSION: These data suggest that heat shock preconditioning of isolated pancreatic islets before transplantation impairs the process of graft angiogenesis and revascularization. Therefore, transient exposure of isolated islets to heat may not be considered a promising tool to improve the outcome of islet transplantation.

Animals↗