Vascular device interaction with the endothelium

Copyright @ 2008 Elsevier. This is the post-print version of the article.Cerebral stents and Intra Aortic Balloon Pumps (IABP) are examples of mechanical devices that are inserted into arteries to restore flows to clinically healthy states. The stent and the IABP ‘correct’ the arterial flow by static dilation and by cyclical occlusion respectively. As this presentation shows, these functions are effectively modelled by current engineering practice. As interventions however, by their very nature they involve physical contact between a non-biological structure and the sensitive endothelial surface. The possible damage to the endothelium is not currently well addressed and we also consider this issue. Cerebral stents generally have two primary clinical objectives: to mechanically dilate a stenosed artery and to have minimal detrimental impact upon local blood flow characteristics. These objectives are well served at the arterial scale as these devices are evidently effective in opening up diseased arteries and restoring vital flows. However, at the near-wall micro-scale the picture is less satisfactory, as thin stent wires apply stresses to the endothelium and glycocalyx and the local flow is disturbed rather than being ideally streamlined. This causes further interaction with this endothelium topography. Wall Shear Stress (WSS) is the measure commonly used to indicate the interaction between fluid and wall but it is a broad brush approach that loses fidelity close to the wall. We will present simulation results of blood flow through a stented cerebral saccular aneurysm under these limitations of WSS. The Intra Aortic Balloon Pump (IABP) is a widely used temporary cardiac assist device. The balloon is usually inserted from the iliac artery, advanced in the aorta until it reaches the desired position; with its base just above the renal bifurcation and the tip approximately 10cm away from the aortic valve. The balloon is inflated and deflated every- (1:1), every other- (1:2) or every second (1:3) cardiac cycle. Balloon inflation, which takes place during early diastole, causes an increase in the pressure of the aortic root which leads to an increase in coronary flow. Balloon deflation which takes place during late diastole achieves one of the main IABP therapeutic effects by reducing left ventricular afterload. Unavoidably, the balloon contacts the inner wall of the aorta with every inflation/deflation cycle. This repeated event and possible contact with atherosclerotic plaque have been reported to be responsible for balloon rupture. However, there has not been a methodical study to investigate the mechanical effects of balloon-wall interaction. For example, during inflation the balloon approaches the endothelium as it displaces a volume of blood proximally and distally. This squeezing process generates shear stresses, which hasn't yet been quantified. Similarly, when the balloon moves away from the endothelium during deflation, it generates micro pressure differences that may impose stretching (pulling) stresses on the endothelium cells. Both of the above cases indicate that a very high spatial resolution is required in order to fully understand the process of interaction between device and endothelium, and to interpret the effects at the cellular level

Micro and Nano Plastics: A Consumer Perception Study on the Environment, Food Safety Threat and Control Systems

The ubiquitous nature and regular occurrence of microplastics and nanoplastics in the food chain and environment have made them topical subject for investigations. The subject is widely researched but a small group study focusing on ethnic black British is sparse. Thus the paper aimed to assess the consumers’ perception of the control system, environmental and food safety threats of micro- nanoplastics through a critical review and an online survey restricted to the mentioned demography. The review and focus group survey with 72 respondents, demonstrated a general awareness of the environmental detriments of plastics, microplastics and nanoplastics but not the food safety threat. Reduction of the use of plastics, especially single use plastics was overwhelmingly supported, with over 80% being in favour, In all cases, the standard deviation was low and the coefficient of variation is less than one (CV >= 1). Awareness studies remain key driver to consumer’s perception

Microwave Radar-Based Breast Cancer Detection:Imaging in Inhomogeneous Breast Phantoms

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Is it time for integration of surgical skills simulation into the United Kingdom undergraduate medical curriculum? A perspective from King’s College London School of Medicine

PURPOSE: Changes in undergraduate medical curricula, combined with reforms in postgraduate education, have training implications for surgical skills acquisition in a climate of reduced clinical exposure. Confidence and prior experience influences the educational impact of learning. Currently there is no basic surgical skills (BSS) programme integrated into undergraduate curricula in the United Kingdom. We explored the role of a dedicated BSS programme for undergraduates in improving confidence and influencing careers in King's College London School of Medicine, and the programme was evaluated. METHODS: A programme was designed in-line with the established Royal College of Surgeons course. Undergraduates were taught four key skills over four weeks: knot-tying, basic-suturing, tying-at-depth and chest-drain insertion, using low-fidelity bench-top models. A Likert-style questionnaire was designed to determine educational value and influence on career choice. Qualitative data was collected. RESULTS: Only 29% and 42% of students had undertaken previous practice in knot-tying and basic suturing, respectively. 96% agreed that skills exposure prior to starting surgical rotations was essential and felt a dedicated course would augment undergraduate training. There was a significant increase in confidence in the practice and knowledge of all skills taught (p<0.01), with a greater motivation to be actively involved in the surgical firm and theatres. CONCLUSION: A simple, structured BSS programme can increase the confidence and motivation of students. Early surgical skills targeting is valuable for students entering surgical, related allied, and even traditionally non-surgical specialties such as general practice. Such experience can increase the confidence of future junior doctors and trainees. We advocate the introduction of a BSS programme into United Kingdom undergraduate curricula

Lymphoid/nonlymphoid compartmentalization of donor leukocyte chimerism in rat recipients of heart allografts, with or without adjunct bone marrow

Background. The role of leukocyte migration and chimerism in organ allograft acceptance has been obscured by the lack of information about the late localization of the donor cells. Methods. Male Lewis rat→female Brown Norway abdominal heart transplantation was performed under tacrolimus immunosuppression (days 0-13, 20, and 27) with or without donor bone marrow and (in bone marrow subgroups) a 1-week postoperative course of a possibly chimerism-enhancing drug. Using rat sex-determining region-Y-specific oligonucleotide primers, we determined the donor DNA concentration by polymerase chain reaction in serial venous blood sampies for 100 days and in tissue specimens when animals were killed. Results. Chimerism was detected out to 56 days in 89% of the blood samples but in none of the samples at 100 days. However, donor DNA was detected when animals were killed in 95% of the native hearts, 80% of the skin biopsy specimens, and 23% of the spleens. The presence and quantity of early and late chimerism were strongly correlated the administration of adjunct bone marrow and with a reduction in the vasculopathy and inflammation index in the cardiac allografts. Marginally significant further increases in chimerism and/or reductions in chronic heart rejection beyond those achieved with adjunct bone marrow alone were associated with additional treatment with the growth factors Flt-3 ligand, granulocyte colonystimulating factor, and a recombinant molecular variant of interleukin-6 (interleukin-6 mutein) but not with hepatocyte growth factor or lisofylline. Conclusions. The previously suspected shift of early chimerism in the blood and lymphoid organs to dominance in host nonlymphoid tissues is consistent with the dual mechanisms of clonal exhaustion and immune indifference, governed by antigen migration and localization, that have been postulated elsewhere to account for organ allograft acceptance

Candida carriage in the alimentary tract of liver transplant candidates

Thirty randomly selected patients with advanced chronic liver disease, which had been evaluated for possible liver transplantation, were sampled endoscopically at 7 alimentary tract locations to assess the frequency and amount of Candida carriage. Eightyone percent (127/156) of the samples obtained contained Candida and 53% (82/156) yielded high counts (> 300 CFU/ml). The most predominant Candida species isolated at each site was Candida albicana, which accounted for 103 (64%) of the 160 fungal isolates. The other Candida species isolated included C tropicalis 30 (19%), C krusei 16 (10%), and C glabrata 11 (7%), Although the number of sites at which yeast was present and the quantities of yeast at each site varied widely among the patients studied, 100% of the patients had Candida in at least one site of the gastrointestinal tract. Eighty-six percent (24/28) of the duodenal aspirates contained Candida and 50% (14/28) of the duodenal samples contained greater than 300 CFU/ml. A positive culture from the stomach was a reliable predictor of the presence of Candida in the duodenum (P=0.0001), but a positive culture at no other site readily predicted the presence of Candida at yet another site. Importantly, there was no correlation between the presence or absence of Candida in either oral or rectal swabs and colonization at other anatomic sites within the gastrointestinal tract, These findings are important in liver transplantation, particularly in those cases in which the bowel has been opened to create a choledochojejunostomy anastomosis. The operative attempts to reduce gastrointestinal fungal carriage using oral antifungal agents may be justified before liver transplantation in an effort to lower the risk of posttransplantation fungal infections, particularly in those patients expected to have a Roux-en-Y choledochojejunostomy biliary reconstruction. © 1994 by Williams and Wilkins

Introduction: Special Issue on Afro-Americanophilia in Germany.

From a ‘provincial’ and (hopefully) self-aware European perspective, it is clear that cultural forms or practices that originated among African Americans have, beyond their value to African Americans themselves and people elsewhere, contributed tremendously to life on the European continent. Those contributions include everything from the political imaginaries of the Civil Rights and Black Power movements, through philosophical thought, to literature, film, television, theatre, dance, sports, visual culture and everyday aesthetics. Most prominent, perhaps, have been forms of music—blues and jazz to r’n’b, rap, and hybrid electronic music forms—all of which have ‘furnished’ European listeners’ lives, whatever their so-called race. While deeply embedded racism can run through these processes of cultural flow, transfer, and appropriation, and numerous forms of exploitation are at work, in many cases there is also an ambiguous love for Black diasporic culture, at least according to the appropriating subjects’ view of themselves, which manifests itself in admiration, desire, a sense of affinity or connection, and sometimes in fantasies of ‘becoming blac