Biomedical subjects
Publications and source records attributed to B Krijgsman.
The conventional technique of carotid endarterectomy involves approaching the carotid sheath, anterior and medial to the internal jugular vein with division of the facial vein. Mobilisation of the ansa cervicalis and identification of the hypoglossal nerve is usually required. We describe our results of retrojugular approach in a consecutive nonrandomised cohort of 50 carotid endarterectomy patients.
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Small bowel intussusception, presenting acutely in adults is an extremely rare event. We present an exceptional case, previously unreported in the English language, of a lipoma within a Meckel's diverticulum giving rise to this clinical scenario.
BACKGROUND: Bilirubin and albumin may act as antioxidants. Their circulating levels are lower in those patients with ischemic heart disease (IHD) and could be further reduced by more extensive atherosclerosis, i.e. peripheral vascular disease (PVD). METHODS: Serum bilirubin and albumin were measured in 456 patients classified into 3 groups: 1) no clinically evident cardiovascular disease (CVD), 2) IHD present and 3) PVD present. Smoking status and gender (which affect bilirubin and albumin levels in healthy individuals) were considered separately. RESULTS: Bilirubin was lower in smoking men without CVD or with PVD than in non-smokers (p=0.02 and p=0.04, respectively) in the same groups. Non-smoking women without CVD had significantly (p=0.004) lower bilirubin levels than the corresponding group of men. Frequency analysis of male non-smokers revealed significantly (p=0.04) more patients with a lower bilirubin (<6.5 mmol/l) in the PVD compared with the no CVD group. Albumin levels showed the same trends. CONCLUSIONS: Prospective studies should consider smoking and gender when assessing the relevance of bilirubin and/or albumin levels in patients with vascular disease. Our findings support those of other studies that show that low serum bilirubin and albumin levels are associated with the presence of vascular disease.
For the improvement of vascular graft patency, an endothelial cell (EC) lining is desirable. It is essential that the EC remains viable after being seeded onto the prosthetic graft. The aim of this study was to adapt an Alamar redox assay (ABRA) as a technique to monitor the viability of ECs seeded on prosthetic grafts. To test the graft types, we seeded human umbilical vein ECs on compliant polyurethane (CPU), expanded polytetrafluoroethylene, and Dacron at a density of 2 x 10(5) cell/cm(2). After 24 h of incubation, ABRA was added, and the absorbance was measured at 4, 8, and 24 h. To assess seeded cell concentrations on grafts, we seeded CPU at densities ranging from 1 x 10(5) to 8 x 10(5) cell/cm(2). The validity of the test was assessed with sodium azide and mitomycin C, known physiological perturbators. ABRA reduction demonstrated that ECs were viable and functional postseeding on the prosthetic grafts. A significant correlation was observed with ABRA reduction and cell concentrations (p < 0.001). The acid phosphatase assay demonstrated enzyme activity in the cells, but they were not maintained under normal physiological conditions. The ABRA bioreduced product was soluble, stable, and noncytotoxic over 24 h. The assay is independent of the geometry or physiochemistry of the graft type. The technique allows the continuous assessment of the metabolism and viability of seeded cells, is simple to perform, and does not destroy the cells or graft materials.
We report the development of a hybrid vascular graft using an innovative compliant poly(carbonate-urea)urethane unlike any previous polyurethane MyoLink as a permanent scaffold. The engineered graft has a hierarchical arterial structure: a monolayer of oriented microvascular endothelial cells (MVECs) and 3-D matrix (human collagen Type 4/dermatan sulfate) bonded onto MyoLink. The grafts' clinical feasibility was evaluated by determining optimal MVEC seeding density, incubation time, viability, and adhesion of these cells when exposed to arterial shear stress. MVECs from human omentum were isolated by a new centrifugation protocol, radiolabeled and seeded onto hybrid graft 2 to 18 x 105 cells/cm(2) for 24 h at 37 degrees C and for 1 to 5 h at 6 x 105 cells/cm(2), washed 3 times, and gamma counted. Qualitative assessment of seeding density/incubation was also undertaken with scanning electron microscopy (SEM) and viability tested with a modified Alamar Blue assay. A pulsatile flow phantom was used to subject the hybrid graft (200 mm length, 5 mm internal diameter) seeded with radiolabeled MVECs (6 x 105 cells/cm(2) at 2 h) to arterial shear and dynamic scintigraphy images acquired in real time using a nuclear medicine gamma camera system during 14 h of perfusion (n = 6). The optimal seeding density was 6 x 105 cells/cm(2), and qualitative SEM confirmed this. Incubating cells for 2 h produced significantly greater cell attachment than was seen for 1 h incubation (p < 0.05), and there was no significant difference in adhesion between cells incubated over the 2 h. Exposure of grafts to acute shear stress resulted in significantly higher proportions of initial cells attached to hybrid grafts compared to native MyoLink grafts (67 +/- 3% versus 55 +/- 2%, p < 0.001). As shown here, tissue engineering of native Myolink grafts significantly reduces the seeding density and incubation time to produce a monolayer onto which cells adhere to better.
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OBJECTIVES: Compliance mismatch between graft and native artery, and failure of the graft to develop an endothelial lining are the two main factors in graft failure. The objective of this study was to assess a new compliant graft for effective cell attachment and cell retention at physiological levels of pulsatile shear stress over a 6-hour period of physiological pulsatile flow. DESIGN: Laboratory haemodynamic study. MATERIALS AND METHODS: Human umbilical vein endothelial cells labelled with 111In-oxine were seeded on compliant polyurethane (CPU) and polytetrafluoroethylene (PTFE) vascular grafts. These were then exposed to varying shear stresses of up to 13.8 +/- 0.6 dyn/cm2 using a pulsatile flow model. Dynamic scintigraphy images were acquired using a gamma camera linked to an on-line computer during 6 h of perfusion and data presented as mean +/- standard error of mean. RESULTS: Mean seeding efficiencies were significantly different at 4,316 +/- 505 and 825 +/- 504 CPM/cm2 on the CPU and PTFE grafts, respectively (p = 0.018). The flow experiment showed a higher percentage of cells retained on the CPU graft after exposure to shear stress caused by pulsatile flow compared to PTFE with respect to time. After 6 h pulsatile perfusion there was a significantly higher proportion of initial cells attached to CPU graft compared to PTFE graft (73 +/- 8% vs 42 +/- 8%, p = 0.018). The areas under the time activity curves over the 6-hour period were 280 +/- 26.4 for CPU and 176.0 +/- 30.0 for PTFE, confirming a significant greater total cell loss from PTFE compared with CPU grafts (51 +/- 7.0% vs 23 +/- 8.3%, p = 0.018, Wilcoxon matched-pairs signed-ranks test). CONCLUSIONS: This flow model provides an effective method of assessing cell retention on graft materials under physiological conditions over a 6-hour period; CPU combines both excellent compliance and endothelial cell attachment rates after 6 h exposure to shear stress.
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BACKGROUND: Central to the pathophysiology of stenosis following balloon angioplasty and arterial bypass surgery is proliferation of vascular smooth muscle cells (VSMCs). To investigate the role of calcium (Ca2+) in VSMC proliferation, the effect of thapsigargin, Ca2+ ionophore A23187, ionomycin, cyclopiazonic acid and di-tert-butylhydroquinone (all of which raise intracellular Ca2+ levels) on the proliferation of cultured human VSMCs was observed. METHODS: Cultured VSMCs from human saphenous vein were treated with calcium-modulating drugs and proliferation was assessed by determining [3H]thymidine and 5-bromo-2'-deoxyuridine incorporation and cell number. RESULTS: Over a 48-h exposure, thapsigargin inhibited VSMC replication (median 50 per cent maximal inhibitory concentration 2 nmol/l) whereas the other drugs were much less effective. Short-term exposure (5, 10, 30 and 60 min) to thapsigargin elicited a significant dose-dependent inhibition of VSMC replication whereas, again, the other drugs were without significant effect. CONCLUSION: Thapsigargin-sensitive intracellular Ca2+ pools play a key role in controlling VSMC proliferation and specialized means of administering thapsigargin may constitute a possible approach to preventing stenosis.
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