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Objective: The shortage of vascular surgeons can be attributed to multiple factors, including an aging population, the increasing demand for vascular surgeons, and an aging vascular surgery workforce. The distribution of vascular surgeons across the United States varies by locale; thus, the shortage affects regions of different sizes disproportionately. We collated the geographic data to characterize the current distribution of vascular surgeons with an emphasis on the practice location, population density, and population age., Methods: Vascular surgeons were identified using the Physician Compare National Downloadable file from the Centers for Medicare and Medical Services. The counties were matched with each surgeon's practice location. The locations were categorized into metropolitan, urban, or rural using the rural-urban continuum codes. Census Bureau data were used to match all counties with their population-level metrics. The distribution of vascular surgeons was analyzed by comparing the number of counties served, total patient population served, and patient population aged >50 and >65 years served. Finally, the density of vascular surgeons in the United States for the total population and for those aged >50 and >65 years was calculated., Results: In 2018, the U.S. population was 309.8 million, and there were 3145 counties. Of the 3145 counties, 533 (17%) had had a practicing vascular surgeon. The combined population of these counties was 213.8 million people (69% of the U.S. population). Stratified by age, the vascular surgeons in these 533 counties could treat 37.3 million people aged >50 years and 17.4 million people aged >65 years. However, 2612 counties (83%), with a total population of 96 million people (31% of the U.S. population), had had no practicing vascular surgeon. When stratified by age, 78.1 million people in the uncovered counties were aged >50 years and 35 million were aged >65 years. Of the 2612 uncovered counties, 48% were urban and 24% were rural., Conclusions: We found a nationwide shortage of vascular surgeons, with urban and rural areas disproportionately affected negatively. Although encouraging vascular surgeons to practice in underserved areas would be an ideal solution, it is not pragmatic. Therefore, developing alternatives such as using primary care providers, investing in telehealth and developing transfer systems could be viable methods of providing vascular care to geographically isolated populations. These findings have significant implications for hospitals, patients, and vascular surgeons, who would all stand to benefit from efforts to address these disparities., (Copyright © 2022 Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.)

Recent studies have shown that accounting for intraspecific trait variation (ITV) may better address major questions in community ecology. However, a general picture of the relative extent of ITV compared to interspecific trait variation in plant communities is still missing. Here, we conducted a meta-analysis of the relative extent of ITV within and among plant communities worldwide, using a data set encompassing 629 communities (plots) and 36 functional traits. Overall, ITV accounted for 25% of the total trait variation within communities and 32% of the total trait variation among communities on average. The relative extent of ITV tended to be greater for whole-plant (e.g. plant height) vs. organ-level traits and for leaf chemical (e.g. leaf N and P concentration) vs. leaf morphological (e.g. leaf area and thickness) traits. The relative amount of ITV decreased with increasing species richness and spatial extent, but did not vary with plant growth form or climate. These results highlight global patterns in the relative importance of ITV in plant communities, providing practical guidelines for when researchers should include ITV in trait-based community and ecosystem studies., (© 2015 John Wiley & Sons Ltd/CNRS.)

Plant communities and their ecosystem functions are expected to be more resilient to future habitat fragmentation and deterioration if the species comprising the communities have a wide range of dispersal and persistence strategies. However, the extent to which the diversity of dispersal and persistence traits in plant communities is determined by the current and historical characteristics of sites and their surrounding landscape has yet to be explored.Using quantitative information on long-distance seed dispersal potential by wind and animals (dispersal in space) and on species' persistence/longevity (dispersal in time), we (i) compared levels of dispersal and persistence trait diversity (functional richness, FRic, and functional divergence, FDiv) in seminatural grassland plant communities with those expected by chance, and (ii) quantified the extent to which trait diversity was explained by current and historical landscape structure and local management history - taking into account spatial and phylogenetic autocorrel.Null model analysis revealed that more grassland communities than expected had a level of trait diversity that was lower or higher than predicted, given the level of species richness. Both the range (FRic) and divergence (FDiv) of dispersal and persistence trait values increased with grassland age. FDiv was mainly explained by the interaction between current grazing intensity and the amount of grassland habitat in the surrounding landscape in 1938. Synthesis . The study suggests that the variability of dispersal and persistence traits in grassland plant communities is driven by deterministic assembly processes, with both history and current management (and their interactions), playing a major role as determinants of trait diversity. While a long continuity of grazing management is likely to have promoted the diversity of dispersal and persistence traits in present-day grasslands, communities in sites that are well grazed at the present day, and were also surrounded by large amounts of grassland in the past, showed the highest diversity of dispersal and persistence strategies. Our results indicate that the historical context of a site within a landscape will influence the extent to which current grazing management is able to maintain a diversity of dispersal and persistence strategies and buffer communities (and their associated functions) against continuing habitat fragmentation.

Whereas fossil evidence indicates extensive treeless vegetation and diverse grazing megafauna in Europe and northern Asia during the last glacial, experiments combining vegetation models and climate models have to-date simulated widespread persistence of trees. Resolving this conflict is key to understanding both last glacial ecosystems and extinction of most of the mega-herbivores. Using a dynamic vegetation model (DVM) we explored the implications of the differing climatic conditions generated by a general circulation model (GCM) in "normal" and "hosing" experiments. Whilst the former approximate interstadial conditions, the latter, designed to mimic Heinrich Events, approximate stadial conditions. The "hosing" experiments gave simulated European vegetation much closer in composition to that inferred from fossil evidence than did the "normal" experiments. Given the short duration of interstadials, and the rate at which forest cover expanded during the late-glacial and early Holocene, our results demonstrate the importance of millennial variability in determining the character of last glacial ecosystems.

Dispersal limitation and long-term persistence are known to delay plant species' responses to habitat fragmentation, but it is still unclear to what extent landscape history may explain the distribution of dispersal traits in present-day plant communities. We used quantitative data on long-distance seed dispersal potential by wind and grazing cattle (epi- and endozoochory), and on persistence (adult plant longevity and seed bank persistence) to quantify the linkages between dispersal and persistence traits in grassland plant communities and current and past landscape configurations. The long-distance dispersal potential of present-day communities was positively associated with the amounts of grassland in the historical (1835, 1938) landscape, and with a long continuity of grazing management-but was not associated with the properties of the current landscape. The study emphasises the role of history as a determinant of the dispersal potential of present-day grassland plant communities. The importance of long-distance dispersal processes has declined in the increasingly fragmented modern landscape, and long-term persistent species are expected to play a more dominant role in grassland communities in the future. However, even within highly fragmented landscapes, long-distance dispersed species may persist locally-delaying the repayment of the extinction debt.

Recent studies have shown that the complexities of the surface features in mountainous terrain require a re-assessment of climate impacts at the local level. We explored the importance of surface-air-temperature based on a recently published 50-m-gridded dataset, versus soil variables for explaining vegetation distribution in Swedish Lapland using generalised linear models (GLMs). The results demonstrated that the current distribution of the birch forest and snowbed community strongly relied on the surface-air-temperature. However, temperature alone is a poor predictor of many plant communities (wetland, meadow). Because of diminishing sample representation with increasing altitude, the snowbed community was under-sampled at higher altitudes. This results in underestimation of the current distribution of the snowbed community around the mountain summits. The analysis suggests that caution is warranted when applying GLMs at the local level.

The assembly of ribosomes from a discrete set of components is a key aspect of the highly coordinated process of ribosome biogenesis. In this review, we present a brief history of the early work on ribosome assembly in Escherichia coli, including a description of in vivo and in vitro intermediates. The assembly process is believed to progress through an alternating series of RNA conformational changes and protein-binding events; we explore the effects of ribosomal proteins in driving these events. Ribosome assembly in vivo proceeds much faster than in vitro, and we outline the contributions of several of the assembly cofactors involved, including Era, RbfA, RimJ, RimM, RimP, and RsgA, which associate with the 30S subunit, and CsdA, DbpA, Der, and SrmB, which associate with the 50S subunit.

Global change may substantially affect biodiversity and ecosystem functioning but little is known about its effects on essential biotic interactions. Since different environmental drivers rarely act in isolation it is important to consider interactive effects. Here, we focus on how two key drivers of anthropogenic environmental change, climate change and the introduction of alien species, affect plant-pollinator interactions. Based on a literature survey we identify climatically sensitive aspects of species interactions, assess potential effects of climate change on these mechanisms, and derive hypotheses that may form the basis of future research. We find that both climate change and alien species will ultimately lead to the creation of novel communities. In these communities certain interactions may no longer occur while there will also be potential for the emergence of new relationships. Alien species can both partly compensate for the often negative effects of climate change but also amplify them in some cases. Since potential positive effects are often restricted to generalist interactions among species, climate change and alien species in combination can result in significant threats to more specialist interactions involving native species., (© 2010 The Authors. Biological Reviews © 2010 Cambridge Philosophical Society.)

Although high-resolution structures of the ribosome have been solved in a series of functional states, relatively little is known about how the ribosome assembles, particularly in vivo. Here, a general method is presented for studying the dynamics of ribosome assembly and ribosomal assembly intermediates. Since significant quantities of assembly intermediates are not present under normal growth conditions, the antibiotic neomycin is used to perturb wild-type Escherichia coli. Treatment of E. coli with the antibiotic neomycin results in the accumulation of a continuum of assembly intermediates for both the 30S and 50S subunits. The protein composition and the protein stoichiometry of these intermediates were determined by quantitative mass spectrometry using purified unlabeled and (15)N-labeled wild-type ribosomes as external standards. The intermediates throughout the continuum are heterogeneous and are largely depleted of late-binding proteins. Pulse-labeling with (15)N-labeled medium time-stamps the ribosomal proteins based on their time of synthesis. The assembly intermediates contain both newly synthesized proteins and proteins that originated in previously synthesized intact subunits. This observation requires either a significant amount of ribosome degradation or the exchange or reuse of ribosomal proteins. These specific methods can be applied to any system where ribosomal assembly intermediates accumulate, including strains with deletions or mutations of assembly factors. This general approach can be applied to study the dynamics of assembly and turnover of other macromolecular complexes that can be isolated from cells., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

Relative levels of ribosomal proteins were quantified in crude cell lysates using mass spectrometry. A method for quantifying cellular protein levels using macromolecular standards is presented that does not require complex sample separation, identification of high-responding peptides, affinity purification, or postgrowth modifications. Perturbations in ribosomal protein levels by overexpression of individual proteins correlate to known autoregulatory mechanisms and extend the network of ribosomal protein regulation.

Climate change and biological invasions are key processes affecting global biodiversity, yet their effects have usually been considered separately. Here, we emphasise that global warming has enabled alien species to expand into regions in which they previously could not survive and reproduce. Based on a review of climate-mediated biological invasions of plants, invertebrates, fishes and birds, we discuss the ways in which climate change influences biological invasions. We emphasise the role of alien species in a more dynamic context of shifting species' ranges and changing communities. Under these circumstances, management practices regarding the occurrence of 'new' species could range from complete eradication to tolerance and even consideration of the 'new' species as an enrichment of local biodiversity and key elements to maintain ecosystem services.

Escherichia coli DbpA is an ATP-dependent RNA helicase with specificity for hairpin 92 of 23S ribosomal RNA, an important part of the peptidyl transferase center. The R331A active site mutant of DbpA confers a dominant slow growth and cold sensitive phenotype when overexpressed in E. coli containing endogenous DbpA. Ribosome profiles from cells overexpressing DbpA R331A display increased levels of 50S and 30S subunits and decreased levels 70S ribosomes. Profiles run at low Mg(2+) exhibit fewer 50S subunits and accumulate a 45S particle that contains incompletely processed and undermodified 23S rRNA in addition to reduced levels of several ribosomal proteins that bind late in the assembly pathway. Unlike mature 50S subunits, these 45S particles can stimulate the ATPase activity of DbpA, indicating that hairpin 92 has not yet been sequestered within the 50S subunit. Overexpression of the inactive DbpA R331A mutant appears to block assembly at a late stage when the peptidyl transferase center is formed, indicating a possible role for DbpA promoting this conformational change.

The ribosome is a complex macromolecular machine responsible for protein synthesis in the cell. It consists of two subunits, each of which contains both RNA and protein components. Ribosome assembly is subject to intricate regulatory control and is aided by a multitude of assembly factors in vivo, but can also be carried out in vitro. The details of the assembly process remain unknown even in the face of atomic structures of the entire ribosome and after more than three decades of research. Some of the earliest research on ribosome assembly produced the Nomura assembly map of the small subunit, revealing a hierarchy of protein binding dependencies for the 20 proteins involved and suggesting the possibility of a single intermediate. Recent work using a combination of RNA footprinting and pulse-chase quantitative mass spectrometry paints a picture of small subunit assembly as a dynamic and varied landscape, with sequential and hierarchical RNA folding and protein binding events finally converging on complete subunits. Proteins generally lock tightly into place in a 5' to 3' direction along the ribosomal RNA, stabilizing transient RNA conformations, while RNA folding and the early stages of protein binding are initiated from multiple locations along the length of the RNA.

The direct effects of CO2 level changes on plant water availability are usually ignored in plant habitat models. We compare traditional proxies for water availability with changes in soil water (fAWC) predicted by a process-based ecosystem model, which simulates changes in vegetation structure and functioning, including CO2 physiological effects. We modelled current and future habitats of 108 European tree species using ensemble forecasting, comprising six habitat models, two model evaluation methods and two climate change scenarios. The fAWC models' projections are generally more conservative. Potential habitats shrink significantly less for boreo-alpine and alpine species. Changes in vegetation functioning and CO2 on plant water availability should therefore be taken into account in plant habitat change projections.

Background: An important aspect of proteomic mass spectrometry involves quantifying and interpreting the isotope distributions arising from mixtures of macromolecules with different isotope labeling patterns. These patterns can be quite complex, in particular with in vivo metabolic labeling experiments producing fractional atomic labeling or fractional residue labeling of peptides or other macromolecules. In general, it can be difficult to distinguish the contributions of species with different labeling patterns to an experimental spectrum and difficult to calculate a theoretical isotope distribution to fit such data. There is a need for interactive and user-friendly software that can calculate and fit the entire isotope distribution of a complex mixture while comparing these calculations with experimental data and extracting the contributions from the differently labeled species., Results: Envelope has been developed to be user-friendly while still being as flexible and powerful as possible. Envelope can simultaneously calculate the isotope distributions for any number of different labeling patterns for a given peptide or oligonucleotide, while automatically summing these into a single overall isotope distribution. Envelope can handle fractional or complete atom or residue-based labeling, and the contribution from each different user-defined labeling pattern is clearly illustrated in the interactive display and is individually adjustable. At present, Envelope supports labeling with 2H, 13C, and 15N, and supports adjustments for baseline correction, an instrument accuracy offset in the m/z domain, and peak width. Furthermore, Envelope can display experimental data superimposed on calculated isotope distributions, and calculate a least-squares goodness of fit between the two. All of this information is displayed on the screen in a single graphical user interface. Envelope supports high-quality output of experimental and calculated distributions in PNG or PDF format. Beyond simply comparing calculated distributions to experimental data, Envelope is useful for planning or designing metabolic labeling experiments, by visualizing hypothetical isotope distributions in order to evaluate the feasibility of a labeling strategy. Envelope is also useful as a teaching tool, with its real-time display capabilities providing a straightforward way to illustrate the key variable factors that contribute to an observed isotope distribution., Conclusion: Envelope is a powerful tool for the interactive calculation and visualization of complex isotope distributions for comparison to experimental data. It is available under the GNU General Public License from http://williamson.scripps.edu/envelope/.

Quantitative proteomic mass spectrometry involves comparison of the amplitudes of peaks resulting from different isotope labeling patterns, including fractional atomic labeling and fractional residue labeling. We have developed a general and flexible analytical treatment of the complex isotope distributions that arise in these experiments, using Fourier transform convolution to calculate labeled isotope distributions and least-squares for quantitative comparison with experimental peaks. The degree of fractional atomic and fractional residue labeling can be determined from experimental peaks at the same time as the integrated intensity of all of the isotopomers in the isotope distribution. The approach is illustrated using data with fractional (15)N-labeling and fractional (13)C-isoleucine labeling. The least-squares Fourier transform convolution approach can be applied to many types of quantitative proteomic data, including data from stable isotope labeling by amino acids in cell culture and pulse labeling experiments.

We show that RNA base pairs have variable stability depending on their degree of solvation. This finding has far-reaching biological implications for nucleic acid structure in a partially solvated cellular environment such as inside RNA-protein complexes. Molecular dynamics simulations of partially solvated Watson-Crick RNA base pairs show that whereas water serves to destabilize a base pair by competing for and disrupting base-base hydrogen bonds, when sufficient water molecules are present, fewer hydrogen bonds are available to disrupt the base pairs and the destabilization effect is reduced. The result is that base pairs exist at a stability minimum when solvated in between 20 and 100 water molecules, the upper limit of which corresponds to the approximate number of water molecules contained in the first hydration shell.

Process-based models can be classified into: (a) terrestrial biogeochemical models (TBMs), which simulate fluxes of carbon, water and nitrogen coupled within terrestrial ecosystems, and (b) dynamic global vegetation models (DGVMs), which further couple these processes interactively with changes in slow ecosystem processes depending on resource competition, establishment, growth and mortality of different vegetation types. In this study, four models - RHESSys, GOTILWA+, LPJ-GUESS and ORCHIDEE - representing both modelling approaches were compared and evaluated against benchmarks provided by eddy-covariance measurements of carbon and water fluxes at 15 forest sites within the EUROFLUX project. Overall, model-measurement agreement varied greatly among sites. Both modelling approaches have somewhat different strengths, but there was no model among those tested that universally performed well on the two variables evaluated. Small biases and errors suggest that ORCHIDEE and GOTILWA+ performed better in simulating carbon fluxes while LPJ-GUESS and RHESSys did a better job in simulating water fluxes. In general, the models can be considered as useful tools for studies of climate change impacts on carbon and water cycling in forests. However, the various sources of variation among models simulations and between models simulations and observed data described in this study place some constraints on the results and to some extent reduce their reliability. For example, at most sites in the Mediterranean region all models generally performed poorly most likely because of problems in the representation of water stress effects on both carbon uptake by photosynthesis and carbon release by heterotrophic respiration (R h ). The use of flux data as a means of assessing key processes in models of this type is an important approach to improving model performance. Our results show that the models have value but that further model development is necessary with regard to the representation of the some of the key ecosystem processes.

Global change will alter the supply of ecosystem services that are vital for human well-being. To investigate ecosystem service supply during the 21st century, we used a range of ecosystem models and scenarios of climate and land-use change to conduct a Europe-wide assessment. Large changes in climate and land use typically resulted in large changes in ecosystem service supply. Some of these trends may be positive (for example, increases in forest area and productivity) or offer opportunities (for example, "surplus land" for agricultural extensification and bioenergy production). However, many changes increase vulnerability as a result of a decreasing supply of ecosystem services (for example, declining soil fertility, declining water availability, increasing risk of forest fires), especially in the Mediterranean and mountain regions.

Glutathione monolayer-protected gold clusters were reacted by place exchange with 19- or 20-residue thiolated oligonucleotides. The resulting DNA/nanoparticle conjugates could be separated on the basis of the number of bound oligonucleotides by gel electrophoresis and assembled with one another by DNA-DNA hybridization. This approach overcomes previous limitations of DNA/nanoparticle synthesis and yields conjugates that are precisely defined with respect to both gold and nucleic acid content.

The rapidly increasing wealth of structural information on RNA and knowledge of its varying roles in biology have facilitated the study of RNA structure using computational methods. Here, we present a new method to describe RNA structure based on nucleotide doublets, where a doublet is any two nucleotides in a structure. We restrict our search to doublets that are close together in space, but not necessarily in sequence, and obtain doublet libraries of various sizes by clustering a large set of doublets taken from a data set of high-resolution RNA structures. We demonstrate that these libraries are able to both capture structural features present in RNA and fit local RNA structure with a high level of accuracy. Libraries ranging in size from ten to 100 doublets are examined, and a detailed analysis shows that a library with as few as 30 doublets is sufficient to capture the most common structural features, while larger libraries would be more appropriate for accurate modeling. We anticipate many uses for these libraries, from annotation to structure refinement and prediction.

Recently, there has been increasing evidence of species' range shifts due to changes in climate. Whereas most of these shifts relate ground truth biogeographic data to a general warming trend in regional or global climate data, we here present a reanalysis of both biogeographic and bioclimatic data of equal spatio-temporal resolution, covering a time span of more than 50 years. Our results reveal a coherent and synchronous shift in both species' distribution and climate. They show not only a shift in the northern margin of a species, which is in concert with gradually increasing winter temperatures in the area, they also confirm the simulated species' distribution changes expected from a bioclimatic model under the recent, relatively moderate climate change.

Climate change has already triggered species distribution shifts in many parts of the world. Increasing impacts are expected for the future, yet few studies have aimed for a general understanding of the regional basis for species vulnerability. We projected late 21st century distributions for 1,350 European plants species under seven climate change scenarios. Application of the International Union for Conservation of Nature and Natural Resources Red List criteria to our projections shows that many European plant species could become severely threatened. More than half of the species we studied could be vulnerable or threatened by 2080. Expected species loss and turnover per pixel proved to be highly variable across scenarios (27-42% and 45-63% respectively, averaged over Europe) and across regions (2.5-86% and 17-86%, averaged over scenarios). Modeled species loss and turnover were found to depend strongly on the degree of change in just two climate variables describing temperature and moisture conditions. Despite the coarse scale of the analysis, species from mountains could be seen to be disproportionably sensitive to climate change (approximately 60% species loss). The boreal region was projected to lose few species, although gaining many others from immigration. The greatest changes are expected in the transition between the Mediterranean and Euro-Siberian regions. We found that risks of extinction for European plants may be large, even in moderate scenarios of climate change and despite inter-model variability.

Early postoperative changes in the hemodynamic parameters of infrainguinal bypass grafts in diabetics have not been well defined. We undertook this study to better define such changes in duplex-derived velocities and waveforms, and correlate any observed changes with intermediate-term outcomes. A prospective study of 68 primary vein bypasses for limb salvage was carried out, with scans obtained intraoperatively, daily until discharge, and at 8- to 12-weeks intervals. During follow-up (12 +/- 6 months), 20 grafts developed stenoses, 17 occluded, and 8 limbs were amputated. Most grafts show a variant of a biphasic waveform intraoperatively at the mid-graft (MG) and distal graft (DG) levels (54% and 57%); 65% of waveforms remain unchanged during the first week, and 54% remain unchanged at 3 months. No duplex-derived factors were predictive of the development of stenoses. A number of parameters were predictive of ultimate graft thrombosis. Intraoperative MG velocity was higher in grafts that eventually remained patent (83 +/- 36 vs. 60 +/- 29 cm/sec; p <0.025). Grafts that remained patent also had a much lower decline in DG and distal native (DN) velocities from immediately postoperative to 8-12 weeks later, than grafts that eventually thrombosed (-3 +/- 35 vs. -44 +/- 43 cm/sec for DG, p <0.001; and -17 +/- 66 vs. -76 +/- 53 cm/sec for DN, p <0.04 respectively). In terms of limb salvage, when the MG or DG waveform worsened (from postoperation to 12 weeks later), amputation was more likely than when it remained unchanged or improved (MG 67% vs. 9% limb loss, p <0.04; DG 43% vs. 8% limb loss, p <0.04). We conclude that intensive graft duplex surveillance does not identify grafts likely to develop stenoses. However, a number of features allow the prediction of ultimate graft failure or limb loss.

Feedbacks, or internal interactions, play a crucial role in the climate system. Negative feedback will reduce the impact of an external perturbation, a positive feedback will amplify the effect and could lead to an unstable system. Many of the feedbacks found in the climate system are positive; thus, for example, increasing CO2 levels will increase temperature, reduce the snow cover, increase the absorption of radiation and hence increase temperature further. The most obvious feedbacks, such as the snow example quoted above, are already included within our models of the climate and earth system. Others, such as the impact of increasing forest cover due to global warming, are only just being included. Others, such as, the impact of global warming on the northern peatlands and the impact of freshwater flows on the Arctic Ocean are not yet considered. The contrast in surface characteristics between low tundra vegetation to high taiga forest is considerable. The contrast is greatest in the winter, when the tundra is snow covered but the trees of the taiga protrude through the snow pack, and is probably the greatest contrast found on the land surface anywhere. This variation causes massive changes in the energy fluxes at the surface and hence the temperature conditions on the ground and within the atmosphere. There will be large resultant changes in the vegetation development, the carbon fluxes, the permafrost and the hydrology. The Arctic is already experiencing change and it is essential for us to understand the basic processes, and how these interact, to be confident of our predictions of environmental change in the future.

Our objective is to describe our current experience with major lower-extremity amputation secondary to vascular disease. We conducted a retrospective review of sequential amputations over a 3-year period at one Veterans Affairs institution. One hundred thirteen amputations were performed in 99 men (age 70 +/- 11 years). Seventy-five per cent were diabetic and 23 per cent were on dialysis. Fifty-six per cent were primary amputations. The final AKA/BKA (above-knee to below-knee amputation) ratio was 3:2 and was not related to prior bypass, ethnicity, or dialysis status (P > 0.5). Forty-three per cent of amputations were BKAs in diabetics versus 26 per cent in nondiabetics (P = 0.08). The in-hospital and 30-day mortality rates were 2.6 and 8 per cent and were not related to amputation level (P = 0.76). Forty per cent experienced postoperative complications that were most frequently wound related (22%). Wound complications were more frequent with BKA than AKA (P = 0.04). At an average follow-up of 10 +/- 8 months only 65 per cent were alive. Although 51 per cent were discharged to rehabilitation units only 26 per cent regularly wore a prosthesis with 23 per cent ambulating. BKA patients were more likely to ambulate than AKA (34% vs 9%; P = 0.001), and dialysis patients were less likely to ambulate than nondialysis patients (5% vs 25%; P < 0.02). During follow-up 17 per cent of patients discharged with an intact contralateral limb required amputation of that limb and 7 per cent had bypass surgery on that limb. Complication rates were higher in African Americans and Hispanics than in whites (59%, 45%, and 23%, respectively; P < 0.001), although mortality and ambulation rates were similar. Despite an acceptable perioperative mortality complication rates remain high especially in nonwhites. One-year mortality is high. Low rehabilitation rates especially in dialysis patients mandate further efforts in this regard. Vigilant follow-up of the contralateral limb is essential.

Patients with peripheral vascular disease are susceptible to neuropathy from chronic hypoxia. We wished to determine whether revascularization of chronically ischemic limbs results in any clinical changes in peripheral sensory thresholds. We prospectively measured quantitative vibration perception thresholds (VPT) using a Horwell neurothesiometer (in volts) in patients undergoing infrainguinal bypass, preoperatively and up to 6 month postoperatively. The bypassed limbs' preoperative VPT values were higher (lesser sensory perception) than the contralateral control limbs' preoperative values (mean score differences: 6 +/- 2 and 4 +/- 10 at toe and foot levels respectively; p ? 0.004). Preoperative VPT values were not different from the 6-month postoperative values for the revascularized legs at toe and foot levels for all 55 patients (mean score change of ?0.84 and ?1.32, p > 0.5). The contralateral limbs' VPT values did not change significantly over the 6-month period (mean change scores of 2.9, p > 0.15, and 2, p > 0.30, for toe and foot, respectively). A comparison of preoperative values between limbs that were eventually amputated and saved revealed no statistically significant differences. This study suggests that revascularization does not result in a clinically detectable improvement in sensory neuropathy. It may, however, prevent further degradation. The degree of preoperative neuropathy does not affect outcome in terms of limb salvage.

Hispanic patients suffer from a high rate of leg amputations, far beyond what would be expected from the high prevalence of diabetes in this population. This raises questions about the efficacy of bypass operations across ethnic lines. We focused this review on dorsalis pedis bypasses, as these are frequently performed in diabetic patients. We compared outcomes between Hispanics and non-Hispanics and sought to identify factors predictive of failure or complications. The authors conducted a retrospective review of 144 dorsalis pedis bypasses in 106 men and 29 women with a mean age of 62 years. Eighty-two percent were Hispanic; 96% of cases were done for tissue loss, and 4% for rest pain. Twenty-five percent of patients experienced perioperative complications; these were more frequent in non-Hispanics than Hispanics (40% vs 22%, p = 0.05). The most frequent complications were wound related (11%). The 30-day mortality was 1.5% and 30-day graft thrombosis was 5%. Follow-up ranged from 1 to 62 months and averaged 12 months. Eighty-one percent of the limbs at risk were saved, although 36% of cases required minor foot amputations. Estimated primary graft patency was 68% at 30 months. The 30-month Kaplan-Meier curves for primary patency, assisted patency, and limb salvage were not statistically different between Hispanics and non-Hispanics (p > 0.4). Grafts that remained patent had higher duplex-derived intraoperative flow velocities in the dorsalis pedis artery than grafts that eventually failed (121 +/-69 vs 74 +/-26 cm/sec, p = 0.02). In grafts that remained patent, dorsalis pedis velocity decreased from the perioperative period to the 8 to 12 weeks time point, whereas no change was seen in grafts that eventually failed (mean decline of 48 +/-76 vs 1 +/-58 cm/sec, p = 0.02). No other factors were predictive of graft failure. The results of dorsalis pedis bypass in Hispanic patients compare favorably to those seen in other ethnic groups. This suggests that other factors must account for the high amputation rates seen in Hispanics, such as a frequent occurrence of nonreconstructible disease or unaccounted for cardiovascular risk factors. The usefulness of duplex-derived flow velocities in the dorsalis pedis to predict long-term graft patency warrants further investigation.

Objective: We graded the severity of occlusive disease in foot vessels of patients with diabetes and correlated the scoring obtained with graft patency and limb salvage., Methods: In this retrospective review of 199 limbs studied by means of angiography in 117 patients with diabetes mellitus, 124 limbs underwent bypass grafting. Each dorsalis pedis (DP), lateral plantar (LP), and medial plantar (MP) artery was assigned a score according to the reporting standards of the Joint Vascular Societies Council (0, no stenosis > 20%; 1, 21%-49% stenosis; 2, 50%-99% stenosis; 2.5, < half the vessel length occluded; 3, > half the vessel length occluded.) A foot score (DP + MP + LP + 1) was calculated for each foot (1 to 10). The mean follow-up period was 14 months., Results: For all 199 limbs and for the 124 limbs that underwent bypass grafting, the mean scores were similar for the DP, MP, and LP (1.8 +/- 1.0, 1.9 +/- 1.0, 1.9 +/- 1.0, respectively; P >.4). Only the MP and LP correlated with each other (r = 0.57; P <.0001). There were no scoring differences between limbs with symptoms and limbs that did not undergo bypass grafting. Bypass graft patency correlated with both the foot score and the MP score for tibial and inframalleolar grafts (P <.04). Patency correlated with the LP score only for inframalleolar bypass grafting procedures. The DP score alone did not differ between bypass grafts that remained patent and bypass grafts that failed. Bypass grafts in limbs with a foot score less than 7 and an MP score less than 2 had only a 2% failure rate. A foot score greater or equal to 7 was associated with a 30% failure rate for all bypass grafts (41% for inframalleolar grafts). Bypass grafts with low foot scores that failed did so much later than bypass grafts with high foot scores that failed (17 +/- 11 months vs 6 +/- 8 months; P <.02), possibly reflecting different etiologies for the failure. The limb salvage rate correlated with foot score (P <.05). The limbs that were saved had an average foot score of 6.4 +/- 2.0, versus 7.2 +/- 1.4 for limbs that required amputation., Conclusion: In patients with diabetes mellitus, the foot score is a useful tool for predicting the likelihood of graft patency and limb salvage for infrapopliteal revascularization. However, the relatively high bypass success rate (70%) in the presence of a high foot score (>or= 7) does not allow its use in identifying the subgroup of patients who are unlikely to benefit from bypass grafting surgery. It cannot be used as a means of selecting patients for primary amputation.

Purpose: To report the endovascular exclusion of an abdominal aortic aneurysm (AAA) in a patient with a horseshoe kidney and an isthmus mass with preservation of accessory renal vessels., Case Report: A 70-year-old man with a 5-cm AAA and renal cell carcinoma involving a horseshoe kidney was treated with an AneuRx bifurcated graft. Two accessory renal arteries believed to feed the isthmus mass were sacrificed, but 2 other accessory renal arteries from the left common iliac artery (CIA) were preserved by using an extension cuff to cover the aneurysmal left CIA distal to their origins. The right renal isthmus mass decreased in size on follow-up imaging. At 9 months, there was no endoleak evident on computed tomographic scans, and the aneurysm measured 4.8 cm., Conclusions: The presence of accessory renal arteries in AAA patients with horseshoe kidneys should not automatically exclude them from consideration for endovascular repair. Creative stent-graft arrangements can be a treatment option.

Revision of lower extremity bypass graft stenoses identified by surveillance duplex scanning is frequently required in diabetic patients. The authors evaluated (1) the value of routine angiography before graft revision in diabetics, (2) factors that predict patients in whom angiography alters management, and (3) the incidence of recurrent stenosis and factors that might predict it. Forty-two infrainguinal primary vein bypasses undergoing primary revision were retrospectively studied. The initial graft stenosis was detected at a mean of 11.5 +/-3.6 months after the original bypass. Angiograms were obtained in 38 cases, revealing additional findings in 29 of 38 cases (76%), with a resultant alteration of the operative plan in 27 cases (71%). The most frequent additional angiographic finding was the identification or localization of a lesion in the inflow or outflow tracts (18 of 27 cases). Cases where the angiogram altered the management plan had a mean systolic velocity ratio across the stenosis (Vr) of 7.3 +/-6.1, versus a Vr of 4.8 +/-1.3 for cases where the angiogram did not alter the management plan (p<0.04). Duplex scanning identified 4 lesions that were not seen on angiography; 3 of 4 were confirmed as webs at surgery. Twenty of 42 grafts (48%) developed recurrent stenoses at a mean of 4.9 +/-3.8 months from initial revision. Restenosis occurred in 69% of female limbs as compared to 38% of male limbs (p=0.06). Recurrent stenosis was not a predictor of ultimate graft failure, unless left untreated. Four of 10 untreated grafts ultimately failed. A total of 9 of the 42 grafts eventually failed (21%), leading to 3 amputations (7%). The authors conclude that failing infrainguinal bypass grafts identified by duplex in diabetics should undergo a detailed angiographic evaluation. This frequently leads to an alteration in the management plan, especially in the presence of a high Vr across stenoses. High rates of limb salvage (93%) and assisted primary graft patency (79%) despite a high recurrent stenoses rate (48%) justify routine duplex surveillance, preoperative angiography, and aggressive graft revision in diabetic patients with infrainguinal grafts.

The authors report their experience with 15 cases of groin complications associated with the use of percutaneous closure devices following femoral arterial catheterization over a 2-year period. The complication rate was 1.7% for catheterizations in which a closure device was used. The 15 cases included 7 uncomplicated pseudoaneurysms (PSA), 3 infected pseudoaneurysms, 4 nonarterial groin infections (infected hematomas and/or abscesses), and 1 case of femoral artery occlusion. These complications presented at an average of 5 +/- 4 days postcatheterization. One patient with an infected PSA required a below-the-knee amputation. During the same time interval, there were no infectious complications in patients not receiving closure devices. We conclude that groin complications associated with such devices tend to present late and include a higher percentage of infections as opposed to complications occurring in patients not receiving closure devices. An aggressive surgical approach to these problems appears warranted.

The authors report a patient who presented with a ruptured mycotic aneurysm that destroyed the posterior segment of the suprarenal perimesenteric aorta. Initial in-line repair with a rifampin-soaked Dacron prosthetic patch failed 14 days postoperatively with recurrent hemorrhage. At reoperation, the aorta was repaired with a superficial femoral/popliteal vein interposition graft; a segment of superficial femoral/popliteal vein was also used in-line to revascularize the superior mesenteric and celiac arteries. The patient survived with no evidence of recurrence at 8 months postoperatively.

A retrospective review of 101 diabetics without aortoiliac disease was carried out to analyze the ability of various noninvasive tests to predict the level of significant (>50% stenosis) infrainguinal arterial disease. Patients were studied with anklebrachial indices (ABI), toebrachial indices (TBI), segmental pulse volume recordings (PVR), segmental pressures (SEGP), segmental Doppler waveforms (DWF), and arteriography. Results were classified as normal, disease at the femoropopliteal level, infrapopliteal level, or both levels (multilevel), or noninterpretable. Our findings for the entire study showed that, as a single test, DWF appears to have the best angiographic correlation, although the summed diagnosis of combined DWF and PVR data is superior in distinguishing multilevel disease from isolated tibial disease. SEGP are of very limited use in diabetics, even in multimodality testing, and we no longer include that test in our routine evaluation of diabetics.

The efficacy of infrainguinal bypass for limb salvage in young diabetic patients has not been well established. The purpose of this study is to determine the intermediate-term results (patency and limb salvage) of infrainguinal revascularization carried out for limb salvage (rest pain or ulceration) in young (<50 years old) diabetic atherosclerotic patients. Thirty-nine bypasses in 31 patients with a mean age of 44 years were retrospectively reviewed. There were no perioperative deaths. Minor or major complications occurred in 23% of cases. By life table analysis, the 18-month primary patency rate was 60+/-11%, assisted primary patency rate was 78+/-9%, and limb salvage rate was 71+/-9%. Most major amputations (five of nine) were required in patients with functional bypasses, either because of persistent infection or failure of wound healing. The presence of severe stenoses (>70%) in all three major named foot vessels (dorsalis pedis, medial and lateral plantar arteries) was associated with a high likelihood of limb loss despite a patent bypass (p<0.05). We could not identify any other factors statistically predictive of thrombosis, amputation, or the need for graft revision. Infrainguinal revascularization in this patient population can be carried out with acceptable limb salvage rates. However, patients should be made aware of the high incidence of amputation regardless of the success of the revascularization procedure, particularly in the presence of severe occlusive disease within the foot.

We report a rare case of primary aortoduodenal fistula (ADF) secondary to a Coxiella burnetii (Q fever) infection in a patient with an abdominal aortic aneurysm. A review of the available literature on the vascular complications of Q fever is presented. Q fever should be suspected in vascular patients with close animal contact when a standard infectious work-up is unrevealing. Diagnostic steps and management strategies for primary ADF are also briefly reviewed.

Scenarios of changes in biodiversity for the year 2100 can now be developed based on scenarios of changes in atmospheric carbon dioxide, climate, vegetation, and land use and the known sensitivity of biodiversity to these changes. This study identified a ranking of the importance of drivers of change, a ranking of the biomes with respect to expected changes, and the major sources of uncertainties. For terrestrial ecosystems, land-use change probably will have the largest effect, followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. For freshwater ecosystems, biotic exchange is much more important. Mediterranean climate and grassland ecosystems likely will experience the greatest proportional change in biodiversity because of the substantial influence of all drivers of biodiversity change. Northern temperate ecosystems are estimated to experience the least biodiversity change because major land-use change has already occurred. Plausible changes in biodiversity in other biomes depend on interactions among the causes of biodiversity change. These interactions represent one of the largest uncertainties in projections of future biodiversity change.

Ischemia plays a pivotal role in the management of the problem diabetic foot. Prompt revascularization offers the patient with diabetes with lower-extremity ischemia the best hope for limb salvage and normal ambulation. The true vascular status of the diabetic foot may be difficult to assess by clinical examination. Because of the dangers of missing correctable vascular disease, noninvasive vascular testing plays an important role in the evaluation of the problem diabetic foot. The laboratory should have documented reliability, and its results must be interpreted in the context of the patient's clinical progress. The most common laboratory error is overestimating the blood supply to the foot because of technical problems with mural calcification. Algorithms for the use of the vascular laboratory for common foot problems are presented. The vascular laboratory, although helpful, is no substitute for clinical judgement. When ischemia is suspected or when response to conservative care is poor, early vascular surgical consultation is prudent.

Demonstrating positive outcomes after surgical intervention is an important aspect for the patient and payor in today's health care setting. A lower extremity arterial reconstruction program was established and has shown a decrease in length of stay. Additional long-term outcome measures related to graft patency surveillance, readmission rate and related cause, and functional health status are being implemented.

Aneurysms constitute uncommon sequelae of injuries to the thoracic outlet. Most such aneurysms are secondary to blunt trauma and usually involve the great vessels at their take-off from the aortic arch. Penetrating injuries are more often identified in the more distal vessels and only very rarely present as pseudoaneurysms. Reported here is a single case of a chronic posttraumatic pseudoaneurysm arising from both the right common carotid artery and the right subclavian artery. The workup and surgical approach provide practical lessons, complemented with illustrations that aid in the understanding of the case. It is an unusual case because of the dual-inflow nature of the aneurysm.

Mires dominated by restionaceous rushes occur in valley and basin sites around New Zealand. The main restiad species is Empodisma minus which produces a surface mat of negative geotropic roots which eventually form a principal part of the underlying peat. Comparison of the peat chemistry of four such mires with a minerotrophic mire w*as consistent with their suspected ombrotrophic status. The base-exchange capacity achieved (704 + 23.3 mequiv m -2 of the surface) by the superficial roots of Empodisma is at least as great as that of the New Zealand Sphagnum cristatum which is not dominant in ombrotrophic conditions. The widespread development of a hummock and hollow microtopography may be associated with higher rainfall regimes and the propensity of Empodisma for directing most incoming rainfall (on which its nutrient economy depends) down its wiry stems.

Human ventral roots were examined in the light and electron microscopes. The noteworthy finding is that all roots contain large numbers of unmyelinated axons, and that they make up 27 per cent of the total population of ventral root axons. The function of these unmyelinated axons is not known, but for various reasons it is probable that a significant number are sensory. If so these axons might explain the failure of dorsal rhizotomy to relieve pain, and dorsal root gangionectomy, which would remove both dorsal and ventral root afferents, might be the procedure of choice for those patients where rhizotomy is contemplated.