A new approach in the treatment of high flow native AV fistula: the open-pore external scaffolding prosthesis

Objective: The vascular access steal syndrome is a complication occurring in 1-6% after native arterio-venous (AV) fistulas, often due to huge diameter of the vein. This results in very high flow, which could also be responsible for cardiac overload. The aim of this study is to evaluate the efficiency of a new approach in the treatment of this pathology using open-pore external scaffolding prosthesis.Methods: This a retrospective review of all patients presenting symptomatic high flow after native AV fistula between January 2007 and December 2009 in 3 vascular centers. Pre-operative duplex exam confirmed the diagnosis of high flow. The operation consisted in preparation of the whole fistula, measurement of the flow and section on the venous side. The vein was wrapped with this 6 to 8 mm open-pore external scaffolding prosthesis (ProVena, BBraun, Germany) according to its diameter and to the flow and then sutured. Measurement of the flow was repeated. Patients were followed by duplex exam at 1 week and at 1, 3, 6 and 12 months. Procedural success was defined as complete implantation of the prosthesis and reduction of the flow. Primary outcomes were reduction of the flow and recovery of the symptoms and secondary endpoint was patency of the fistula.Results: During the study period, 14 patients, with a mean age of 65・8 years old, have been operated with this technique.There were 2 native forearmfistulas and 12 on the armwith a mean pre-operative flow of 2600 ml/min (1800-3800). The mode of presentation was pain in 6 patients, neurological disorders in 10 and necrosis in 4. Moreover, 3 patients had cardiac insufficiency due to high flow in the fistula. The procedure was technically successful in 100% of cases. Re-intervention was necessary in 2 patients due to hematoma. Recovery of the initial symptoms occurred in 13 patients (93%). The mean flow reduction was 1200 ml/min (600-2000). In 1 patient, a persistent steal syndrome despite flow reduction to 1400 ml/min resulted in fistula closure 2 months later. At a mean follow-up of 22 months (4-35), all remaining patients (13/14) presented a patent fistula without recurrence.Conclusion: This new approach seems to be safe and effective in the treatment of symptomatic high flow native AV fistulas by significantly reducing the flow and avoiding closure of the vascular access. Longer follow-up with more patients are necessary to evaluate the risk of recurrence.

Use of flow cytometric methods for single-cell analysis in environmental microbiology

Flow cytometry (FCM) is emerging as an important tool in environmental microbiology. Although flow cytometry applications have to date largely been restricted to certain specialized fields of microbiology, such as the bacterial cell cycle and marine phytoplankton communities, technical advances in instrumentation and methodology are leading to its increased popularity and extending its range of applications. Here we will focus on a number of recent flow cytometry developments important for addressing questions in environmental microbiology. These include (i) the study of microbial physiology under environmentally relevant conditions, (ii) new methods to identify active microbial populations and to isolate previously uncultured microorganisms, and (iii) the development of high-throughput autofluorescence bioreporter assays

The Vaccine Formulation Laboratory: a platform for access to adjuvants.

Adjuvants are increasingly used by the vaccine research and development community, particularly for their ability to enhance immune responses and for their dose-sparing properties. However, they are not readily available to the majority of public sector vaccine research groups, and even those with access to suitable adjuvants may still fail in the development of their vaccines because of lack of knowledge on how to correctly formulate the adjuvants. This shortcoming led the World Health Organization to advocate for the establishment of the Vaccine Formulation Laboratory at the University of Lausanne, Switzerland. The primary mission of the laboratory is to transfer adjuvants and formulation technology free of intellectual property rights to academic institutions, small biotechnology companies and developing countries vaccine manufacturers. In this context, the transfer of an oil-in-water emulsion to Bio Farma, an Indonesian vaccine manufacturer, was initiated to increase domestic pandemic influenza vaccine production capacity as part of the national pandemic influenza preparedness plan.

Remote control of pulmonary blood flow: a dream comes true.

The indication for pulmonary artery banding is currently limited by several factors. Previous attempts have failed to produce adjustable pulmonary artery banding with reliable external regulation. An implantable, telemetrically controlled, battery-free device (FloWatch) developed by EndoArt SA, a medical company established in Lausanne, Switzerland, for externally adjustable pulmonary artery banding was evaluated on minipigs and proved to be effective for up to 6 months. The first human implant was performed on a girl with complete atrioventricular septal defect with unbalanced ventricles, large patent ductus arteriosus and pulmonary hypertension. At one month of age she underwent closure of the patent ductus arteriosus and FloWatch implantation around the pulmonary artery through conventional left thoracotomy. The surgical procedure was rapid and uneventful. During the entire postoperative period bedside adjustments (narrowing or release of pulmonary artery banding with echocardiographic assessment) were repeatedly required to maintain an adequate pressure gradient. The early clinical results demonstrated the clinical benefits of unlimited external telemetric adjustments. The next step will be a multi-centre clinical trial to confirm the early results and adapt therapeutic strategies to this promising technology.

Reorganization of a deeply incised drainage: role of deformation, sedimentation and groundwater flow

Deeply incised drainage networks are thought to be robust and not easily modified, and are commonly used as passive markers of horizontal strain. Yet, reorganizations (rearrangements) appear in the geologic record. We provide field evidence of the reorganization of a Miocene drainage network in response to strike-slip and vertical displacements in Guatemala. The drainage was deeply incised into a 50-km-wide orogen located along the North America-Caribbean plate boundary. It rearranged twice, first during the Late Miocene in response to transpressional uplift along the Polochic fault, and again in the Quaternary in response to transtensional uplift along secondary faults. The pattern of reorganization resembles that produced by the tectonic defeat of rivers that cross growing tectonic structures. Compilation of remote sensing data, field mapping, sediment provenance study, grain-size analysis and Ar(40)/Ar(39) dating from paleovalleys and their fill reveals that the classic mechanisms of river diversion, such as river avulsion over bedrock, or capture driven by surface runoff, are not sufficient to produce the observed diversions. The sites of diversion coincide spatially with limestone belts and reactivated fault zones, suggesting that solution-triggered or deformation-triggered permeability have helped breaching of interfluves. The diversions are also related temporally and spatially to the accumulation of sediment fills in the valleys, upstream of the rising structures. We infer that the breaching of the interfluves was achieved by headward erosion along tributaries fed by groundwater flow tracking from the valleys soon to be captured. Fault zones and limestone belts provided the pathways, and the aquifers occupying the valley fills provided the head pressure that enhanced groundwater circulation. The defeat of rivers crossing the rising structures results essentially from the tectonically enhanced activation of groundwater flow between catchments.

Surgical approach for total hip arthroplasty: direct lateral or posterior?

OBJECTIVE: To determine the risks of prosthesis dislocation, postoperative Trendelenburg gait, and sciatic nerve palsy after a posterior approach compared to a direct lateral approach for adult patients undergoing total hip arthroplasty (THA) for primary osteoarthritis (OA). METHODS: Medline, Embase, CINHAL, and Cochrane databases were searched until August 2003. All published trials comparing posterior and direct lateral surgical approaches to THA in adults with a diagnosis of primary hip osteoarthritis were collected. Retrieved articles were assessed independently for their methodological quality. RESULTS: Four prospective cohort studies involving 241 participants met the inclusion criteria. Regarding dislocation rate, no significant difference between posterior and direct lateral surgical approach was found (relative risk 0.35). The presence of postoperative Trendelenburg gait was not significantly different between surgical approaches. The risk of nerve palsy or injury was significantly higher with the direct lateral approach (relative risk 0.16). However, there were no significant differences when comparing this risk nerve by nerve, in particular for the sciatic nerve. Of the other outcomes considered, only the average range of internal rotation in extension of the hip was significantly higher (weighted mean difference 16 degrees ) in the posterior approach group (mean 35 degrees, SD 13 degrees ) compared to the direct lateral approach (mean 19 degrees, SD 13 degrees ). CONCLUSION: The quality and quantity of information extracted from the trials performed to date are insufficient to make a firm conclusion on the optimum choice of surgical approach for adult patients undergoing primary THA for OA.

Phylogeographical structure, postglacial recolonization and barriers to gene flow in the distinctive Valais chromosome race of the common shrew (Sorex araneus).

Using one male-inherited and eight biparentally inherited microsatellite markers, we investigate the population genetic structure of the Valais chromosome race of the common shrew (Sorex araneus) in the Central Alps of Europe. Unexpectedly, the Y-chromosome microsatellite suggests nearly complete absence of male gene flow among populations from the St-Bernard and Simplon regions (Switzerland). Autosomal markers also show significant genetic structuring among these two geographical areas. Isolation by distance is significant and possible barriers to gene flow exist in the study area. Two different approaches are used to better understand the geographical patterns and the causes of this structuring. Using a principal component analysis for which testing procedure exists, and partial Mantel tests, we show that the St-Bernard pass does not represent a significant barrier to gene flow although it culminates at 2469 m, close to the highest altitudinal record for this species. Similar results are found for the Simplon pass, indicating that both passes represented potential postglacial recolonization routes into Switzerland from Italian refugia after the last Pleistocene glaciations. In contrast with the weak effect of these mountain passes, the Rhône valley lowlands significantly reduce gene flow in this species. Natural obstacles (the large Rhône river) and unsuitable habitats (dry slopes) are both present in the valley. Moreover, anthropogenic changes to landscape structures are likely to have strongly reduced available habitats for this shrew in the lowlands, thereby promoting genetic differentiation of populations found on opposite sides of the Rhône valley.

BIOMOD - a platform for ensemble forecasting of species distributions

BIOMOD is a computer platform for ensemble forecasting of species distributions, enabling the treatment of a range of methodological uncertainties in models and the examination of species-environment relationships. BIOMOD includes the ability to model species distributions with several techniques, test models with a wide range of approaches, project species distributions into different environmental conditions (e.g. climate or land use change scenarios) and dispersal functions. It allows assessing species temporal turnover, plot species response curves, and test the strength of species interactions with predictor variables. BIOMOD is implemented in R and is a freeware, open source, package

Beyond intracranial pressure: optimization of cerebral blood flow, oxygen, and substrate delivery after traumatic brain injury.

Monitoring and management of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is a standard of care after traumatic brain injury (TBI). However, the pathophysiology of so-called secondary brain injury, i.e., the cascade of potentially deleterious events that occur in the early phase following initial cerebral insult-after TBI, is complex, involving a subtle interplay between cerebral blood flow (CBF), oxygen delivery and utilization, and supply of main cerebral energy substrates (glucose) to the injured brain. Regulation of this interplay depends on the type of injury and may vary individually and over time. In this setting, patient management can be a challenging task, where standard ICP/CPP monitoring may become insufficient to prevent secondary brain injury. Growing clinical evidence demonstrates that so-called multimodal brain monitoring, including brain tissue oxygen (PbtO2), cerebral microdialysis and transcranial Doppler among others, might help to optimize CBF and the delivery of oxygen/energy substrate at the bedside, thereby improving the management of secondary brain injury. Looking beyond ICP and CPP, and applying a multimodal therapeutic approach for the optimization of CBF, oxygen delivery, and brain energy supply may eventually improve overall care of patients with head injury. This review summarizes some of the important pathophysiological determinants of secondary cerebral damage after TBI and discusses novel approaches to optimize CBF and provide adequate oxygen and energy supply to the injured brain using multimodal brain monitoring.

Reduced phototropism in pks mutants may be due to altered auxin-regulated gene expression or reduced lateral auxin transport.

Phototropism allows plants to orient their photosynthetic organs towards the light. In Arabidopsis, phototropins 1 and 2 sense directional blue light such that phot1 triggers phototropism in response to low fluence rates, while both phot1 and phot2 mediate this response under higher light conditions. Phototropism results from asymmetric growth in the hypocotyl elongation zone that depends on an auxin gradient across the embryonic stem. How phototropin activation leads to this growth response is still poorly understood. Members of the phytochrome kinase substrate (PKS) family may act early in this pathway, because PKS1, PKS2 and PKS4 are needed for a normal phototropic response and they associate with phot1 in vivo. Here we show that PKS proteins are needed both for phot1- and phot2-mediated phototropism. The phototropic response is conditioned by the developmental asymmetry of dicotyledonous seedlings, such that there is a faster growth reorientation when cotyledons face away from the light compared with seedlings whose cotyledons face the light. The molecular basis for this developmental effect on phototropism is unknown; here we show that PKS proteins play a role at the interface between development and phototropism. Moreover, we present evidence for a role of PKS genes in hypocotyl gravi-reorientation that is independent of photoreceptors. pks mutants have normal levels of auxin and normal polar auxin transport, however they show altered expression patterns of auxin marker genes. This situation suggests that PKS proteins are involved in auxin signaling and/or lateral auxin redistribution.

Are there vascular density gradients along myocardial laser channels?

BACKGROUND: Clinical studies suggest that transmyocardial laser revascularization may improve regional blood flow of the subendocardial layer. The vascular growth pattern of laser channels was analyzed. METHODS: Twenty pigs were randomized to undergo ligation of left marginal arteries (n = 5), to undergo transmyocardial laser revascularization of the left lateral wall (n = 5), to undergo both procedures (n = 5) or to a control group (n = 5). All the animals were sacrificed after 1 month. Computed morphometric analysis of vascular density of the involved area was expressed as number of vascular structures per square millimeter (+/-1 standard deviation). RESULTS: The vascular density of the scar tissue of the laser channel was significantly increased in comparison with myocardial infarction alone: 49.6+/-12.8/mm2 versus 25.5+/-8.6/mm2 (p < 0.0001). The vascular densities of subendocardial and subepicardial channel areas were similar: 52.9+/-16.8/mm2 versus 46.3+/-13.6/mm2 (p = 0.41). The area immediately adjacent to the channels showed a vascular density similar to that of normal tissue: 6.02+/-1.7/mm2 versus 5.2+/-1.9/mm2 (p = 0.08). In the infarction + transmyocardial laser revascularization group, the channels were indistinguishable from infarction scar. CONCLUSIONS: Scars of transmyocardial laser revascularization channels exhibit an increased vascular density in comparison with scar tissue of myocardial infarction, which does not extend into their immediate vicinity. There was no vascular density gradient along the longitudinal axis of the channels.

Effect of an I.V. bolus of phenylephrine or ephedrine on skin blood flow during spinal anesthesia

Effet d'un bolus intraveineux de phénylephrine ou d'éphedríne sur le flux sanguin cutané lors d'une anesthésie rachidienne Introduction : La phénylephrine et l'éphedrine sont des substances vaso-actives utilisées de routine pour corriger des épisodes d'hypotension artérielle induits par l'anesthésie intrarachidienne. L'influence de ces deux vasopresseurs sur le flux sanguin cutané (FSC) dans ce contexte n'a jusqu'à maintenant pas été décrite. Cette étude évalue l'effet d'une injection intraveineuse de 75 µg de phénylephrine ou de 7.5 mg d'éphedrine sur le FSC mesuré par Laser Doppler, dans les zones concernées parle bloc sympathiqué induit par l'anesthésie intrarachidienne (membres inférieurs) et dans les zones non concernées (membres supérieurs). Méthode :Après acceptation par le Comité d'Éthique, et obtention de leur accord écrit, 20 patients devant subir une intervention chirurgicale élective en décubitus dorsal sous anesthésie. intrarachidienne ont été inclus dans cette étude randomisée en double insu. Le FSC a été mesuré en continu par deux sondes fixées l'une à la cuisse (zone avec bloc sympathique) et l'autre sur l'avantbras (zone sans bloc sympathique). Les valeurs de FSC ont été enregistrées après l'anesthésie rachidienne (valeur contrôle), puis après l'injection i.v. dè phénylephrine (10 patients) ou d'éphedrine (10 patients) pour corriger une hypotension définie comme une chute de 20 mmHg de la pression artérielle systolique. Les variations de FSC exprimées en pourcentage de la valeur contrôle moyenne (+/- écart type) ont été analysées par le test t de Student. Résultats :Les données démographiques des patients et le niveau sensitif induit par l'anesthésie rachidienne sont similaires dans les deux groupes. Aux doses utilisées, seule l'éphedrine restaure la pression artérielle aux valeurs précédant l'anesthésie rachidienne. La phénylephrine augmente le FSC de l'avant-bras de 44% (+/- 79%) et de la cuisse de 34% (+/-24%), alors que l'éphedrine diminue le débit sanguin cutané de l'avant-bras de 16% (+/- 15%) et de la cuisse de 22% (+/-11%). Conclusion : L'injection intraveineuse de phénylephrine et d'éphedrine ont des effets opposés sur le flux sanguin cutané, et cette réponse n'est pas modifiée par le bloc sympathique.. Cette différence peut s'expliquer par la distribution des sous-types de récepteurs adrénergiques alpha et leur prédominance relative dans les veines et les artères de différents diamètres perfusant le tissu sous-cutané et la peau. L'éphedrine, èn raison de sa meilleure efficacité pour traiter les épisodes d'hypotension artérielle après anesthésie intrarachidienne devrait être préféré à la phénylephrine, leurs effets opposés sur le flux sanguin cutané n'étant pas pertinents en pratique clinique. SUMMARY Background: Phenylephrine or ephedrine is routinely used to correct hypotensive episodes fallowing spinal anaesthesia (SA). The influence of these two vasopressors on skin blood flow (SBF) has not yet been described. We have therefore evaluated the effects of an i.v. bolus of 75 µg phenylephrine or 7.5 mg of ephedrine on SBF measured by laser Doppler flowmetry during sympathetic blockade induced by SA. Methods: With Ethical Committee approval and written consent, 20 patients scheduled for elective procedures in supine position under SA were enrolled in this double-blind randomized study. SBF was measured continuously by two probes fixed at the thigh (area with sympathic blockade) and forearm level (area without sympathic blockade) respectively. SBF values were recorded after SA (control values) and then after a bolus administration of phenylephriné (n=10) or ephedrine (n=10) when systolic blood pressure decreased by 20 mmHg. Changes were expressed as percentage of control SBF values and analysed by Student's paired t-test. Results: Patient characteristics and dermatomal sensory levels were similar in both groups. Phenylephrine increases mean SBF at the forearm level by 44% (79%) [mean (SD)j and at the thigh by 34% (24%). Ephedrine decreases SBF at the forearm level by 16% (15%) and at the thigh by 22% (il%). Ephedrine bolus restores arterial blood pressure to pre-anaesthesia values, whereas phenylephrine does not. Conclusion: Administratión of phenylephrine and ephedrine has opposite effects on skin blood flow and sympathetic blockade does not modify this response. These findings could be explained by the distribution of the alpha-adrenoréceptor subtypes and their relative predominance among veins and arteries of different size perfusing the subcutaneous tissue and the skin. Ephedrine, due to its better efficacy to correct hypotensive episodes following SA, should be preferred, to phenylephrine, their opposite effects on SBF being not relevant for clinical practice.

An experimental study of discharge partitioning and flow structure at symmetrical bifurcations

Recent research has examined the factors controlling the geometrical configuration of bifurcations, determined the range of stability conditions for a number of bifurcation types and assessed the impact of perturbations on bifurcation evolution. However, the flow division process and the parameters that influence flow and sediment partitioning are still poorly characterized. To identify and isolate these parameters, three-dimensional velocities were measured at 11 cross-sections in a fixed-walled experimental bifurcation. Water surface gradients were controlled, and systematically varied, using a weir in each distributary. As may be expected, the steepest distributary conveyed the most discharge ( was dominant) while the mildest distributary conveyed the least discharge ( was subordinate). A zone of water surface super-elevation was co-located with the bifurcation in symmetric cases or displaced into the subordinate branch in asymmetric cases. Downstream of a relatively acute-angled bifurcation, primary velocity cores were near to the water surface and against the inner banks, with near-bed zones of lower primary velocity at the outer banks. Downstream of an obtuse-angled bifurcation, velocity cores were initially at the outer banks, with near-bed zones of lower velocities at the inner banks, but patterns soon reverted to match the acute-angled case. A single secondary flow cell was generated in each distributary, with water flowing inwards at the water surface and outwards at the bed. Circulation was relatively enhanced within the subordinate branch, which may help explain why subordinate distributaries remain open, may play a role in determining the size of commonly-observed topographic features, and may thus exert some control on the stability of asymmetric bifurcations. Further, because larger values of circulation result from larger gradient disadvantages, the length of confluence-diffluence units in braided rivers or between diffluences within delta distributary networks may vary depending upon flow structures inherited from upstream and whether, and how, they are fed by dominant or subordinate distributaries. Copyright (C) 2011 John Wiley & Sons, Ltd.