Randomized comparison of ePTFE/nitinol self-expanding stent graft vs prosthetic femoral-popliteal bypass in the treatment of superficial femoral artery occlusive disease

BackgroundA randomized prospective study comparing the treatment of superficial femoral artery occlusive disease percutaneously with an expanded polytetrafluoroethylene (ePTFE)/nitinol self-expanding stent graft (stent-graft) vs surgical femoral to above knee popliteal artery bypass with synthetic graft material.MethodsOne hundred limbs in 86 patients with superficial femoral artery occlusive disease were evaluated from March 2004 to May 2005. Patient symptoms included both claudication and limb threatening ischemia with or without tissue loss. The TransAtlantic InterSociety Consensus (TASC) II A (N = 18), B (N = 56), C (N = 11), and D (N = 15) lesions were included. Patients were randomized prospectively into one of two treatment groups; a percutaneous treatment group (group A; N = 50) with angioplasty and placement of one or more stent-grafts or a surgical treatment group (group B; N = 50) with a femoral to above knee popliteal artery bypass using synthetic conduit (Dacron graft or ePTFE). Patients were followed for a total of 24 months. Follow-up evaluation included clinical assessment and physical examination, ankle-brachial indices (ABI), and color flow duplex sonography at 3, 6, 9, 12, 18, and 24 months.ResultsThe mean total lesion length of the treated arterial segment in the stent-graft group was 25.6 cm (SD ± 15 cm). The stent-graft group demonstrated a primary patency of 81%, 72%, and 63% with a secondary patency of 86%, 83%, and 74% at 6, 12, and 24 months, respectively. The surgical femoral-popliteal group demonstrated a primary patency of 84%, 77%, and 64% with a secondary patency of 89%, 86%, and 76% at 6, 12, and 24 months, respectively. No statistical difference was found between the two groups with respect to primary (P = .716) or secondary patency (P = .695). Grouping of less severe (TASC II A/B) vs more severe (TASC II C/D) lesions demonstrated patency at 24 months for the femoral-popliteal arm of 63% and 67%, respectively while that of the stent-graft arm was 64% and 47%, respectively. Secondary patency was 76% in both TASC classifications for the femoral-popliteal arm with 78% and 47% patency found respectively in the stent-graft group. These resulted in no significant difference for primary (P = .978) or secondary (P = .653) patency overall, although there is a trend for decreased patency with higher TASC II lesions.ConclusionManagement of superficial femoral artery occlusive disease with percutaneous stent-grafts exhibits similar primary patency at 24-month follow-up when compared with conventional femoral-popliteal artery bypass grafting with synthetic conduit. This treatment method may offer an alternative to treatment of the superficial femoral artery segment for revascularization when prosthetic bypass is being considered or when autologous conduit is unavailable

Estimating species trees using multiple-allele DNA sequence data

Several techniques, such as concatenation and consensus methods, are available for combining data from multiple loci to produce a single statement of phylogenetic relationships. However, when multiple alleles are sampled from individual species, it becomes more challenging to estimate relationships at the level of species, either because concatenation becomes inappropriate due to conflicts among individual gene trees, or because the species from which multiple alleles have been sampled may not form monophyletic groups in the estimated tree. We propose a Bayesian hierarchical model to reconstruct species trees from multiple-allele, multilocus sequence data, building on a recently proposed method for estimating species trees from single allele multilocus data. A two-step Markov Chain Monte Carlo (MCMC) algorithm is adopted to estimate the posterior distribution of the species tree. The model is applied to estimate the posterior distribution of species trees for two multiple-allele datasets - yeast (Saccharomyces) and birds (Manacus - manakins). The estimates of the species trees using our method are consistent with those inferred from other methods and genetic markers, but in contrast to other species tree methods, it provides credible regions for the species tree. The Bayesian approach described here provides a powerful framework for statistical testing and integration of population genetics and phylogenetics. © 2008 The Author(s)

Mentoring Undergraduate Research in Statistics: Reaping the Benefits and Overcoming the Barriers

Undergraduate research experiences (UREs), whether within the context of a mentor-mentee experience or a classroom framework, represent an excellent opportunity to expose students to the independent scholarship model. The high impact of undergraduate research has received recent attention in the context of STEM disciplines. Reflecting a 2017 survey of statistics faculty, this article examines the perceived benefits of UREs, as well as barriers to the incorporation of UREs, specifically within the field of statistics. Viewpoints of students, faculty mentors, and institutions are investigated. Further, the article offers several strategies for leveraging characteristics unique to the field of statistics to overcome barriers and thereby provide greater opportunity for undergraduate statistics students to gain research experience

The Major Histocompatibility Complex–related Fc Receptor for IgG (FcRn) Binds Albumin and Prolongs Its Lifespan

The inverse relationship between serum albumin concentration and its half-life suggested to early workers that albumin would be protected from a catabolic fate by a receptor-mediated mechanism much like that proposed for IgG. We show here that albumin binds FcRn in a pH dependent fashion, that the lifespan of albumin is shortened in FcRn-deficient mice, and that the plasma albumin concentration of FcRn-deficient mice is less than half that of wild-type mice. These results affirm the hypothesis that the major histocompatibility complex–related Fc receptor protects albumin from degradation just as it does IgG, prolonging the half-lives of both

Distinct conformational behaviors of four mammalian dual‐flavin reductases (cytochrome P450 reductase, methionine synthase reductase, neuronal nitric oxide synthase, endothelial nitric oxide synthase) determine their unique catalytic profiles

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109651/1/febs13073.pd

Distinct Conformational Behaviors of Four Mammalian Dual-Flavin Reductases (Cytochrome P450 Reductase, Methionine Synthase Reductase, Neuronal Nitric Oxide Synthase, Endothelial Nitric Oxide Synthase) Determine Their Unique Catalytic Profiles

Multidomain enzymes often rely on large conformational motions to function. However, the conformational setpoints, rates of domain motions and relationships between these parameters and catalytic activity are not well understood. To address this, we determined and compared the conformational setpoints and the rates of conformational switching between closed unreactive and open reactive states in four mammalian diflavin NADPH oxidoreductases that catalyze important biological electron transfer reactions: cytochrome P450 reductase, methionine synthase reductase and endothelial and neuronal nitric oxide synthase. We used stopped-flow spectroscopy, single turnover methods and a kinetic model that relates electron flux through each enzyme to its conformational setpoint and its rates of conformational switching. The results show that the four flavoproteins, when fully-reduced, have a broad range of conformational setpoints (from 12% to 72% open state) and also vary 100-fold with respect to their rates of conformational switching between unreactive closed and reactive open states (cytochrome P450 reductase \u3e neuronal nitric oxide synthase \u3e methionine synthase reductase \u3e endothelial nitric oxide synthase). Furthermore, simulations of the kinetic model could explain how each flavoprotein can support its given rate of electron flux (cytochrome c reductase activity) based on its unique conformational setpoint and switching rates. The present study is the first to quantify these conformational parameters among the diflavin enzymes and suggests how the parameters might be manipulated to speed or slow biological electron flux