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At least 73 records · Page 4Linked to original sources
PubMed2002

Plasmin generation plays different roles in the formation and removal of arterial and venous thrombus in mice.

The role of plasminogen (Plg) and alpha2-antiplasmin (alpha2-AP) in vascular thrombolysis in vivo was investigated in mice deficient in plasminogen (Plg-/-) or a2-AP (alpha2-AP-/-) or their wild type (PAI-1+/+, alpha2-AP+/+). A thrombus was induced in the murine carotid artery or the internal jugular vein by endothelial injury. Blood flow was continuously monitored for 90 min and for 6 h 30 min after the initiation of endothelial injury. The times to occlusion by the developing thrombus in the carotid artery and the jugular vein of wild type mice were 12+/-1.8 and 7.2+/-1.9 min, respectively. The arterial thrombus formation in alpha2-AP-/- mice was indistinguishable from the one in wild type mice, whereas the time to occlusion in Plg-/- was significantly shortened to 5.9+/-1.7 min. Vascular patency after spontaneous reperfusion was markedly improved in alpha2-AP-/- mice. On the contrary, arteriarpatency in Plg-/- mice was aggravated. In venous thrombus formation, the time to occlusion in alpha2-AP-/- mice was significantly prolonged (27.1+/-5.2 min), whereas in Plg-/- it was slightly shortened to 6.5+/-2.5 min. Vascular patency after spontaneous reperfusion was also improved in alpha2-AP-/- mice, but not in Plg-/- mice. Histological observations using SEM indicated that fibrin nets were firmly fixed on the injured area in Plg-/- mice, but not in alpha2-AP-/- mice. The tail bleeding time was not different in any type of mice. However, re-bleeding time using a template bleeding device was significantly prolonged in alpha2-AP-/- as compared with that of wild type mice. In conclusion, lack of plasminogen markedly reduces the antithrombotic activities in vivo, whereas alpha2-AP plays a more important role in the formation and removal of venous thrombus in mice. Consequently, the inhibition of alpha2-AP could be a useful tool for the therapy of venous thrombosis and the prevention of re-thrombus formation.

Animals↗
PubMed1991

Successful treatment of diabetes with the biohybrid artificial pancreas in dogs.

We have investigated a new hybrid artificial pancreas device to transplant islet allografts without immunosuppression. The device consists of a chamber through which passes a copolymer membrane connected to standard vascular grafts. Islets are placed inside the chamber but are outside of the blood stream. Nominal molecular porosity of 80,000 daltons permits free diffusion of nutrients and insulin across the membrane but inhibits the entry of immunoglobulins and immunocytes from the blood stream into the chamber. Initial studies focused on the technical feasibility of implanting the unseeded (no islets) devices. In 12 normal mongrel dogs, the arterial limb of the device was anastomosed end-to-end to the common iliac artery and the venous limb end-to-side to the common iliac vein. Vascular patency was monitored by an audible bruit over the device. Two devices currently remain patent at 388 and 421 days. The remaining experiments failed due to thrombosis and membrane rupture, with 2 failing as late as 170 and 279 days. In a second series, both arterial and venous anastomoses were done end-to-side and dogs were placed on low-dose aspirin therapy. All 8 dogs are currently maintaining patent unseeded devices (96-226 days postimplantation). Subsequent studies determined the function of devices seeded with isolated canine pancreatic islet allografts in totally pancreatectomized, severely diabetic dogs. Diabetes was controlled by once-a-day insulin injection. After 2-3 weeks of diabetic control, a seeded device was implanted. Diabetic control was monitored by fasting blood levels and postprandial and intravenous glucose tolerance tests, and vascular patency by the loudness of the bruit. In the first series of 6 dogs given seeded devices without aspirin, no significant function was discernible, with failure attributable to thrombosis, poor islet viability, and surgical complications. In the second series of 13 dogs given aspirin, 8 dogs have required an appreciably lower dose of injected insulin to maintain fasting blood glucose at acceptable levels. Of note are 4 dogs that required virtually no exogenous insulin for at least 3 weeks. One dog lost function on day 74 and another still requires no insulin at 267 days postimplantation. However, despite normal fasting glucose levels, the glucose tolerance tests showed delayed return to normal levels. Weight lost following pancreatectomy was rapidly regained in the presence of a functioning seeded device. Histologic examination of the removed devices revealed no signs of rejection.

Animals↗
PubMed1994

MR imaging of middle cerebral artery stenosis and occlusion: value of MR angiography.

PURPOSE: To investigate the effectiveness of MR angiography in conjunction with spin-echo imaging for evaluating vascular patency in patients with middle cerebral artery (MCA) stenosis or occlusion. METHODS: Seven patients with MCA stenosis or occlusion, verified with contrast angiography in five and correlated with transcranial Doppler sonography in two, were examined using two-dimensional and/or three-dimensional time-of-flight MR angiographic techniques as well as conventional spin-echo imaging. RESULTS: Of the seven patients, six demonstrated basal ganglionic and/or cortical infarct in the MCA territory. Except one case with minimal stenosis immediately distal to the MCA origin, all six cases with either severe stenosis or occlusion of the main trunk of the MCA showed the absence of normal flow voids using spin-echo imaging in the sylvian fissure on the affected side. However, it was not possible to discriminate between stenosis and occlusion. Although different mechanisms (ie, flow-induced spin dephasing for the 2-D technique and progressive spin saturation for the 3-D technique) were predominantly responsible for the loss of signal through the area of stenosis, both the 2-D and 3-D MR angiograms clearly depicted the compromised flow of the MCA: a focal discontinuity with decreased vessel caliber corresponded to stenosis, and nonvisualization of distal MCA branches represented occlusion. CONCLUSION: Either 2-D or 3-D time-of-flight MR angiography is a useful adjunct to conventional parenchymal spin-echo imaging for evaluating vascular patency in patients with MCA stenosis or occlusion, although it is important to recognize that each technique has a different basis for the loss of signal through the area of stenosis.

Adult↗
PubMed1998

Visualizing blood flow patterns using streamlines, arrows, and particle paths.

A customized computer program (MRIView) is described for visualizing and quantifying complex blood flow patterns in major vessels, using nongated and cardiac-gated three-dimensional (3D) velocity data obtained with MR velocity-encoded phase pulse sequences. Streamlines, arrows, and particle paths (collectively referred to as "paths") can be computed interactively, using both forward and backward time integration of the velocity field. The program provides interactive cross-sectional and 3D perspective visualization of the paths, with quantification and statistical analysis of average speed, through-plane velocity, cross-sectional area, and flow. Normal flow patterns in the carotid artery, basilar artery tip, ascending aorta, coronary arteries, descending aorta, and renal arteries, as well as abnormal flow patterns in basilar tip aneurysms, have been investigated. The program revealed flow patterns in these regions with features that are well known from Doppler ultrasound and other features that have not been reported previously. The association between specific abnormal flow patterns and development of atherosclerosis suggests that particle paths can be used to assess risk of plaque formation and progression, as well as to evaluate flow dynamics and vascular patency before and after vascular interventions.

Adult↗
PubMed1992

Elucidating the vascular response to burns with a new rat model.

Burn injury causes acute thrombosis and occlusion of vessels in the dermis directly killed by thermal energy. A vascular response also occurs in the uninjured dermis bordering the site of injury. Diminished blood flow leads to progressive ischemia and necrosis in the dermis beneath and surrounding the burn. If blood flow is maintained or restored in this area, the tissue survives. A noninvasive technique for studying dynamic changes in blood flow in this transitional dermis in rats is presented. A rectangular brass bar 19 mm wide with 5-mm transverse notches was heated in boiling water and applied to the skin surface for 20 seconds, making a "comb" burn composed of a row of four rectangular 10 x 19-mm full-thickness burns. Between the burns were 5 x 19-mm bands of uninjured skin, called "interspaces." After burning, blood flow near the surface of both the burn sites and the interspaces was monitored with a laser Doppler perfusion monitor for 24 hours. The vascular patency of blood vessels was directly visualized by latex vascular casts made 24 hours after burn. The possible prevention of progressive ischemia by injecting systemic ibuprofen was examined in this new model. Normal skin has a surface blood flow reading of 80 +/- 16 mV, burn sites have a reading of 11 +/- 4 mV, and interspaces have a reading of 21 +/- 4 mV at 24 hours postburn in untreated rats. Systemic ibuprofen given IM immediately postburn at 12.5 mg/kg increased blood flow to 80 +/- 28 mV within the interspaces, to 17 +/- 12 mV in the burn site, and to 80 +/- 9 mV in normal skin. The vascular casts showed an absence of patent vessels within both the burn sites and interspaces in untreated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

The influence of radiofrequency ablation on hepatic vessels in porcine liver.

BACKGROUND/AIMS: The objective of this study was to clarify the influence of radiofrequency ablation on the portal and hepatic vein. METHODOLOGY: Hepatic radiofrequency ablation was performed on 18 swine (mean weight, 22 kg). The livers were removed immediately, 1 week or 3 weeks following ablation. Vessel patency and diameter were determined by computed tomography, and the severity of endothelial injuries was determined histopathologically. RESULTS: The patency rate for portal and hepatic veins with diameters less than 3.0 mm decreased sequentially. At three weeks following ablation, the patency rate for vessels with diameters more than 3.0 mm was significantly higher (P<0.05) compared to those with diameters less than 2.0 mm. In portal and hepatic veins contiguous to ablated hepatic parenchyma, the endothelium with intimal thickening was found at 1 to 3 weeks following ablation, although its detection rate was decreased until 3 weeks. CONCLUSIONS: The portal and hepatic vein with diameters more than 3.0 mm in radiofrequency lesions maintained high patency. The endothelium seems to play an important role for maintaining vessels patency and the distal hepatic tissue following ablation. We believe that this maintained vascular patency may be the advantage of radiofrequency ablation over the PEIT.

Animals↗
PubMed2003

Reactive thrombocytosis without endothelial damage does not affect the microvascular anastomotic patency.

There is still controversy about the correlation of thrombocytosis and thrombosis complication. Using a rodent splenectomy-induced thrombocytosis model and a thrombogenic endothelial damage model (inverted suture resulting in an intraluminal thrombogenic adventitia of divided femoral artery), the authors investigated whether reactive thrombocytosis with or without endothelial damage contributes to the patency of microvascular anastomosis. Four experimental groups were evaluated in this study: 1) sham operation without thrombogenic anastomosis after femoral artery division; 2) sham operation with thrombogenic anastomosis; 3) thrombocytosis alone without thrombogenic anastomosis; 4) thrombocytosis with thrombogenic anastomosis (each subgroup n = 10, total N = 40). Vascular patency was assessed after immediate operation and on the seventh day postoperatively. Platelet counts and platelet activation (CD62P) were studied in correlation to microvascular patency. In rats without thrombogenic anastomosis groups, there were no significant differences in CD62P expression on platelets (p = 0.09), the patency rates (p = 0.561), or perfusion units (p = 0.746) before and after arterial reanastomosis between rats with and without thrombocytosis, respectively. However, the thrombogenic anastomosis of femoral artery in thrombocytosis and control groups showed significantly increased CD62P expression (p < 0.05), decreased the perfusion unit (p < 0.05), and patency rate (p < 0.001), compared with rats without thrombogenic anastomosis of femoral artery in both groups. In summary, this study demonstrates that microvascular anastomosis can be performed safely with reactive thrombocytosis alone without thrombogenic anastomosis. Meticulous microvascular anastomosis without triggering platelet activation is the most important factor to prevent thrombosed vessels in microsurgical anastomosis.

Anastomosis, Surgical↗
PubMed2000

[Vascular endothelial dysfunctions, possible detection and treatment].

The basic physiological functions of the endothelium are functions of a semipermeable membrane, control of optimal vascular patency and safeguarding of the vascular integrity. Endothelial dysfunction may be considered the first functionally important stage of atherosclerosis. The most frequent evoking factors include hyperlipoproteinaemia, arterial hypertension, smoking and diabetes mellitus. The clinically most important manifestations of impaired endothelial function are disorders in the coronary circulation and transient cerebral ischaemias. Ways of detection of endothelial dysfunctions include invasive methods and at present non-invasive ultrasonic methods. Treatment of endothelial dysfunction is based on elimination of the basic risk factors of atherosclerosis, i.e. elimination of active and passive smoking, in indicated cases strict dietetetic and pharmacological hypolipidaemic treatment, effective antihypertensive treatment and compensation of DM.

Arteriosclerosis↗
PubMed1997

Endothelial dysfunction and atherothrombotic occlusive disease.

The endothelium plays a crucial role in the regulation of vascular function through the release of locally important molecular effectors such as endothelium-derived relaxing factor (EDRF) and prostacyclin. Endothelial cells also regulate vascular patency and tissue perfusion by inhibiting platelet aggregation and thrombosis, suppressing intimal proliferation, and maintaining vascular tone. Disturbances of the regulatory functions of the endothelium contribute to the pathophysiology of various disease states, including cardiovascular disease and stroke. Most studies focused on endothelial control of vasomotion and, in particular, on the action of EDRF; many studies have also emphasised that altered endothelial control of fibrinolysis and intimal growth influence the clinical expression of atherothrombotic disease. Importantly, understanding the pathophysiological role of endothelial dysfunction may lead to new therapeutic approaches for disease states caused by vascular disease.

Animals↗
PubMed2005

Biological vascularized matrix for bladder tissue engineering: matrix preparation, reseeding technique and short-term implantation in a porcine model.

PURPOSE: We generated a vascularized, autologous, reseeded bladder substitute and evaluated immediate vascularization and perfusion of the graft after implantation to the recipient organism in a porcine model. MATERIAL AND METHODS: Acellular matrix was processed from porcine small bowel segments by subsequent mechanical, chemical and enzymatic decellularization, preserving the jejunal arteriovenous pedicles. In 2 separate steps the matrix was reseeded with primary bladder smooth muscle cells (SMCs) and urothelial cells (UCs), and its vascular structures were resurfaced with endothelial progenitor cells (EPCs). To evaluate graft perfusion short-term implantation was performed. RESULTS: The acellular scaffold was successfully repopulated with multilayers of ingrowing SMCs and superficial UCs. After reseeding the jejunal arteriovenous pedicles with EPCs and cultivation for 3 weeks the larger vessels as well as the intramural scaffold capillary network were repopulated with cell monolayers expressing endothelial specific proteins. Perfusion stagnation and implant thrombosis occurred within 30 minutes after the implantation of acellular scaffolds not reseeded with EPCs. In the EPC reseeded group the vascular system revealed intact perfusion and no relevant thrombus formation was observed after 1 or 3 hours. CONCLUSIONS: The current study of successful SMC and UC reseeding, vessel resurfacing with EPCs and short-term vascular patency represents the promising in vitro and in vivo basis for further evaluation of this biological vascularized matrix in chronic long-term large animal implantation experiments.

Animals↗
PubMed1995

Vascular complications of pancreatic transplantation: MR evaluation.

PURPOSE: To determine the value of magnetic resonance (MR) angiography and MR imaging with dynamic gadopentetate dimeglumine-enhanced gradient-echo (Gd-GRE) sequences in detection of vascular complications of pancreatic transplantation. MATERIALS AND METHODS: Three radiologists evaluated findings of 32 MR examinations in 20 adult patients who underwent pancreatic transplantation. The images were obtained with a surface coil and T1-weighted and T2-weighted fast spin-echo sequences, Gd-GRE sequences, and MR angiography. Vascular abnormality was confirmed at surgery or biopsy, and vascular patency with clinical correlation. RESULTS: Absence of flow was found in six of 32 studies (19%): acute vascular thrombosis of the vascular pedicle and/or branch vessels in four studies (three patients) and chronic pancreatic rejection in two studies (one patient). Gd-GRE images helped identify infarction in two patients. The sensitivity of MR angiography for detection of acute vascular compromise was 100%, and the specificity was 93%. CONCLUSION: MR angiography and MR imaging with Gd-GRE sequences allow detection of vascular complications of pancreatic transplantation.

Adult↗
PubMedDate not supplied

Gadolinium enhanced MR imaging of vascular stents.

The feasibility of obtaining in-plane magnetic resonance (MR) vascular images in the presence of a vascular stent and the value of infusing an MR contrast agent during imaging was assessed. Coronal and sagittal MR imaging at 1.5 T was performed on six dogs with tantalum aortic stents using single-section gradient echo (GRE) imaging and MR angiography techniques before and during intravenous infusion of gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA). In-plane gradient echo (GRE) imaging and MR angiography clearly showed flow within the stented vessel as increased signal, with a minimum amount of stent-related artifact. Infusion of Gd-DTPA significantly increased the signal of flowing blood and allowed for better delineation of the stented aortic lumina. Our results demonstrate that in-plane GRE imaging and MR angiography can potentially be used as noninvasive methods for evaluating vascular patency in the presence of MR-compatible endovascular devices. In addition, Gd-DTPA infusion during MR vascular imaging clearly enhances the definition of flowing blood in the lumina of stented vessels.

Animals↗