Safety of Shunting Strategies During Carotid Endarterectomy: A Vascular Quality Initiative Data Analysis.

OBJECTIVE: This study aimed to evaluate in hospital outcomes after carotid endarterectomy (CEA) according to shunt usage, particularly in patients with contralateral carotid occlusion (CCO) or recent stroke. Data from CEAs registered in the Vascular Quality Initiative database between 2012 and 2020 were analysed, excluding surgeons with < 10 CEAs registered in the database, concomitant procedures, re-interventions, and incomplete data. METHODS: Based on their rate of shunt use, participating surgeons were divided in three groups: non-shunters (< 5%), selective shunters (5 - 95%), and routine shunters (> 95%). Primary outcomes of in hospital stroke, death, and stroke and death rate (SDR) were analysed in symptomatic and asymptomatic patients. RESULTS: A total of 113 202 patients met the study criteria, of whom 31 147 were symptomatic and 82 055 were asymptomatic. Of the 1 645 surgeons included, 12.1% were non-shunters, 63.6% were selective shunters, and 24.3% were routine shunters, with 10 557, 71 160, and 31 579 procedures in each group, respectively. In the univariable analysis, in hospital stroke (2.0% vs. 1.9% vs. 1.6%; p = .17), death (0.5% vs. 0.4% vs. 0.4%; p = .71), and SDR (2.2% vs. 2.1% vs. 1.8%; p = .23) were not statistically significantly different among the three groups in the symptomatic cohort. The asymptomatic cohort also did not show a statistically significant difference for in hospital stroke (0.9% vs. 1.0% vs. 0.9%; p = .55), death (0.2% vs. 0.2% vs. 0.2%; p = .64), and SDR (1.0% vs. 1.1% vs. 1.0%; p = .43). The multivariate model did not show a statistically significant difference for the primary outcomes between the three shunting cohorts. On subgroup analysis, the SDRs were not statistically significantly different for patients with CCO (3.3% vs. 2.5% vs. 2.4%; p = .64) and those presenting with a recent stroke (2.9% vs. 3.4% vs. 3.1%; p = .60). CONCLUSION: No statistically significant differences were found between three shunting strategies for in hospital SDR, including in patients with CCO or recent stroke.

Endovascular treatment of an iatrogenic right subclavian artery pseudoaneurysm associated with an arteriovenous fistula.

This report describes the case of a frail 36-year-old patient who underwent an endovascular treatment of a right subclavian artery pseudoaneurysm (SAP) associated with an arteriovenous fistula secondary to a traumatic central venous catheter insertion. The deployment of a covered stent from the innominate to the right common carotid artery combined with coiling of the SAP and the internal mammary artery was performed. Two additional covered stents were deployed from the vertebral artery to the distal subclavian artery to preserve right upper extremity circulation. This case highlights the feasibility of an endovascular treatment of a complex SAP in a candidate unsuitable for open surgery.

Treating a Large Thoracoabdominal Aneurysm With Aberrant Right Subclavian Artery With a Physician-Modified Graft.

CLINICAL IMPACT: Large thoracoabdominal aortic aneurysms due to chronic aortic dissection in patients with connective tissue disorders such as Loeys-Dietz syndrome present a challenging scenario, particularly in cases of variant anatomy and when patients are not candidates for conventional open repair. We demonstrate how by combining and modifying off-the-shelf devices during a hybrid procedure, one can create an endovascular solution tailored to the patient's complex anatomy, making use of an aberrant right subclavian artery, and allow for good clinical outcomes.

The Streptomyces scabiei Pathogenicity Factor Thaxtomin A Induces the Production of Phenolic Compounds in Potato Tubers.

The phytotoxin thaxtomin A (TA) is the key pathogenicity factor synthesized by the bacteria Streptomyces scabiei, the main causal agent of common scab of potato (Solanum tuberosum L.). TA treatment of potato tuber flesh produces a brown color that was attributed to necrosis. The intensity of TA-induced browning was generally thought to correlate with potato sensitivity to the disease. In this study, we found that TA-induced browning was much more intense in the potato tuber flesh of the common scab moderately resistant variety Russet Burbank (RB) than that observed in tubers of the disease-susceptible variety Yukon Gold (YG). However, there was no significant difference in the level of TA-induced cell death detected in both varieties, suggesting that tubers response to TA does not correlate with the level of sensitivity to common scab. TA-treated potato tuber tissues accumulated significantly higher levels of phenolic compounds than untreated controls, with a higher phenol content detected in RB TA-treated tissues than in those of YG. Browning was associated with a significant induction of the expression of genes of the phenylpropanoid pathway in RB tubers, indicating that TA activated this metabolic pathway. These results suggest that tuber flesh browning induced by TA is due to the accumulation of phenolic compounds. These phenolics may play a role in the protection of potato tubers against S. scabiei.

Habituation to thaxtomin A increases resistance to common scab in 'Russet Burbank' potato.

Common scab is a potato disease characterized by the formation of scab-like lesions on the surface of potato tubers. The actinobacterium Streptomyces scabiei is the main causal agent of common scab. During infection, this bacterium synthesizes the phytotoxin thaxtomin A which is essential for the production of disease symptoms. While thaxtomin A can activate an atypical programmed cell death in plant cell suspensions, it is possible to gradually habituate plant cells to thaxtomin A to provide resistance to lethal phytotoxin concentrations. Potato 'Russet Burbank' calli were habituated to thaxtomin A to regenerate the somaclone RB9 that produced tubers more resistant to common scab than those obtained from the original cultivar. Compared to the Russet Burbank cultivar, somaclone RB9 generated up to 22% more marketable tubers with an infected tuber area below the 5% threshold. Enhanced resistance was maintained over at least two years of cultivation in the field. However, average size of tubers was significantly reduced in somaclone RB9 compared to the parent cultivar. Small RB9 tubers had a thicker phellem than Russet Burbank tubers, which may contribute to improving resistance to common scab. These results show that thaxtomin A-habituation in potato is efficient to produce somaclones with increased and durable resistance to common scab.

Safety of transition from a routine to a selective intensive care admission pathway after elective open aneurysm repair.

Background: There is a growing trend to implement intermediate care units to avoid unnecessary costs associated with intensive care unit (ICU) admission and associated resources. We sought to evaluate the safety of transitioning from a routine to a selective policy of postoperative transfer to the ICU for elective open abdominal aortic aneurysm (AAA) repair. Methods: This retrospective study included consecutive open elective AAA repair procedures performed at a single centre from Aug. 8, 2010, to Dec. 1, 2014. Patients were identified through a prospectively maintained database, and electronic charts were reviewed. Patients with interventions before Mar. 13, 2012, were routinely sent to the ICU after operation (group A). Patients treated after this date were sent directly to an intermediate care unit (group B) unless preoperative or intraoperative factors deemed them suitable for ICU admission. The primary outcome was in-hospital death; secondary outcomes were perioperative complications and length of stay. We used logistic and linear regression to determine the association between the use of an intermediate care unit and the primary and secondary outcomes after adjusting for confounders and clinically relevant covariates. Results: The cohort comprised 310 patients (266 men, 44 women) with a mean age of 69.7 (standard deviation 10.1) years and a mean AAA diameter of 61.2 mm (SD 9.6 mm). Groups A and B included 118 and 192 patients, respectively. Admission to the ICU was spared in 149 patients (77.6%) in group B. Only 2 patients (1.3%) in group B were subsequently admitted to the ICU. There was no statistically significant difference in in-hospital mortality or perioperative complications between the 2 groups on multivariable logistic regression. There was a nonsignificant trend toward slightly shorter length of stay in group B. Conclusion: In this single-centre experience with the majority of patients sent directly to an intermediate care unit, there was no statistically significant difference in mortality or morbidity between routine and selective ICU admission. Our results confirm the safety of a selective ICU admission pathway.

Contexte: La tendance est à la création d'unités de soins intermédiaires pour éviter les coûts inutiles entraînés par les séjours aux unités de soins intensifs (USI) et les ressources associées. La présente étude visait à évaluer la sécurité d'un transfert aux USI sélectif, plutôt que systématique, après la réparation ouverte élective d'un anévrisme aortique abdominal (AAA). Méthodes: Cette étude rétrospective portait sur des réparations ouvertes électives d'AAA consécutivement réalisées à un même centre pour la période du 8 août 2010 au 1er décembre 2014. Nous avons recensé les cas dans une base de données maintenue de manière prospective, puis avons étudié les dossiers électroniques. Les patients opérés avant le 13 mars 2012 ont été envoyés d'emblée à l'USI après l'intervention (groupe A). Ceux traités après cette date ont été transférés directement en soins intermédiaires (groupe B), sauf s'ils se qualifiaient pour l'admission à l'USI en raison de facteurs préopératoires ou intraopératoires. Le principal résultat à l'étude était les décès à l'hôpital; les résultats secondaires étaient les complications périopératoires et la durée du séjour. Un modèle de régression logistique a servi à déterminer les associations entre le transfert direct en soins intermédiaires et les résultats primaire et secondaires en tenant compte des facteurs de confusion et des covariables pertinentes sur le plan clinique. Résultats: La cohorte regroupait 310 patients (266 hommes et 44 femmes) dont l'âge moyen était de 69,7 ans (écart-type 10,1) et le diamètre moyen de l'AAA était de 61,2 mm (ET 9,6 mm). Les groupes A et B comptaient 118 et 192 patients, respectivement. L'admission aux soins intensifs a été évitée chez 149 patients (77,6 %) du groupe B. Seuls 2 (1,3 %) d'entre eux ont dû être admis à l'USI après coup. La régression logistique multivariable n'a montré aucune différence statistiquement significative entre les groupes à l'égard de la mortalité à l'hôpital et des complications périopératoires. Nous avons noté une réduction non significative de la durée de séjour pour le groupe B. Conclusion: Cette étude monocentrique où la majorité des patients ont été transférés directement en soins intermédiaires n'a pas révélé de différence statistiquement significative à l'égard de la mortalité et de la morbidité entre les admissions systématiques et sélectives aux USI. Nos résultats confirment que l'admission sélective en soins intensifs est une option sécuritaire.

Carotid endarterectomy after systemic thrombolysis in a stroke population.

OBJECTIVE: Vascular specialists are increasingly being requested to perform carotid endarterectomy (CEA) after intravenous thrombolysis (IVT) for stroke patients, raising concerns about hemorrhagic complications. Few case series and registry reports have assessed the question, and even fewer studies have included a control group. The aim of this study was to evaluate the overall outcome of patients undergoing CEA after IVT and to compare them with contemporary patients with CEA after simple stroke (non-IVT group). It also aimed to evaluate the differences in outcomes of stroke patients requiring CEA between nonvascular and vascular centers. METHODS: The data of 169 consecutive patients who have undergone CEA after stroke in a single center was analyzed from January 2011 to December 2016, 27 of them (16%) having undergone previous IVT. A comparative analysis between the non-IVT and the IVT groups was performed. The time between stroke diagnosis and referral to a vascular specialist was also studied. RESULTS: Age, sex, and cardiovascular comorbidities were similar in both groups. Median time between stroke and CEA was 13 days (Q1-Q3, 8-23 days), with 16 of the 27 patients (59%) in the IVT group undergoing CEA less than 14 days after the initial event. There were three intracranial hemorrhages (2.1%) in the non-IVT group versus one (3.7%) in the IVT group (P = NS). The overall 30-day combined stroke and death rate was 7.1% (6.3% in the non-IVT group vs 11.1% in the IVT group; P = .70). The incidence of postoperative cervical hematoma requiring reoperation was similar in both groups (2.1% vs 3.7%; P = NS). The median time between diagnosis of stroke and referral to a vascular specialist was higher for patients in nonvascular centers compared with vascular centers (3.5 days vs 1.0 day; P < .001), which translated to fewer patients referred from nonvascular centers undergoing surgery in the 14-day window period (38% vs 67%; P < .001). CONCLUSIONS: In this retrospective analysis, CEA after IVT showed similar outcomes when compared with the overall CEA after stroke population. Stroke patients diagnosed in nonvascular centers were referred later than those in vascular centers and, although postoperative outcomes were similar, that was correlated with fewer patients undergoing surgery in a timely fashion.

The Plant Pathogenic Bacterium Streptomyces scabies Degrades the Aromatic Components of Potato Periderm via the ß-Ketoadipate Pathway.

The outer potato periderm layer consists of dead suberized cells. Suberin, a protective biopolymer, is made of a polyaliphatic portion covalently linked to polyaromatic moieties. Evidence accumulates that Streptomyces scabies, the main causal agent of potato common scab, can degrade the suberin aliphatic part but its ability to degrade the aromatic portion has not been documented. This polyaromatic portion is mainly composed of cinnamic acids. In this study, two cinnamates (trans-ferulic or p-coumaric acids) were added to the culture medium of S. scabies strains EF-35 and 87.22. HPLC quantification revealed that both strains efficiently utilized these compounds. A proteomic study coupled with gene expression analysis led to the identification of putative catabolic pathways for cinnamates. Catabolism of both compounds appeared to occur via the ß-ketoadipate pathway. Gene SCAB_15301, encoding for a putative vanillate monooxygenase, was partly deleted from S. scabies strain 87.22 genome. The mutant retained its ability to catabolize trans-ferulic acid into vanillate but lost its ability to further degrade the latter compound. When the wild-type mutant and complemented strains were grown in the presence of suberin-enriched potato periderm, accumulation of vanillic acid was observed only in the mutant culture medium. This work presents evidence that S. scabies can degrade not only the aliphatic part of suberin but also the constituents of suberin aromatic portion. This may provide ecological and pathological advantages to S. scabies as a saprophyte and pathogen.

Auxin protects Arabidopsis thaliana cell suspension cultures from programmed cell death induced by the cellulose biosynthesis inhibitors thaxtomin A and isoxaben.

BACKGROUND: Thaxtomin A (TA) is a natural cellulose biosynthesis inhibitor (CBI) synthesized by the potato common scab-causing pathogen Streptomyces scabies. Inhibition of cellulose synthesis by TA compromises cell wall organization and integrity, leading to the induction of an atypical program of cell death (PCD). These processes may facilitate S. scabies entry into plant tissues. To study the mechanisms that regulate the induction of cell death in response to inhibition of cellulose synthesis, we used Arabidopsis thaliana cell suspension cultures treated with two structurally different CBIs, TA and the herbicide isoxaben (IXB). RESULTS: The induction of cell death by TA and IXB was abrogated following pretreatment with the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D) and the natural auxin indole-3-acetic acid (IAA). The addition of auxin efflux inhibitors also inhibited the CBI-mediated induction of PCD. This effect may be due to intracellular accumulation of auxin. Auxin has a wide range of effects in plant cells, including a role in the control of cell wall composition and rigidity to facilitate cell elongation. Using Atomic Force Microscopy (AFM)-based force spectroscopy, we found that inhibition of cellulose synthesis by TA and IXB in suspension-cultured cells decreased cell wall stiffness to a level slightly different than that caused by auxin. However, the cell wall stiffness in cells pretreated with auxin prior to CBI treatment was equivalent to that of cells treated with auxin only. CONCLUSIONS: Addition of auxin to Arabidopsis cell suspension cultures prevented the TA- and IXB-mediated induction of cell death. Cell survival was also stimulated by inhibition of polar auxin transport during CBI-treatment. Inhibition of cellulose synthesis perturbed cell wall mechanical properties of Arabidopsis cells. Auxin treatment alone or with CBI also decreased cell wall stiffness, showing that the mechanical properties of the cell wall perturbed by CBIs were not restored by auxin. However, since auxin's effects on the cell wall stiffness apparently overrode those induced by CBIs, we suggest that auxin may limit the impact of CBIs by restoring its own transport and/or by stabilizing the plasma membrane - cell wall - cytoskeleton continuum.

Reactive Oxygen Species Alleviate Cell Death Induced by Thaxtomin A in Arabidopsis thaliana Cell Cultures.

Thaxtomin A (TA) is a cellulose biosynthesis inhibitor synthesized by the soil actinobacterium Streptomyces scabies, which is the main causal agent of potato common scab. TA is essential for the induction of scab lesions on potato tubers. When added to Arabidopsis thaliana cell cultures, TA induces an atypical programmed cell death (PCD). Although production of reactive oxygen species (ROS) often correlates with the induction of PCD, we observed a decrease in ROS levels following TA treatment. We show that this decrease in ROS accumulation in TA-treated cells is not due to the activation of antioxidant enzymes. Moreover, Arabidopsis cell cultures treated with hydrogen peroxide (H2O2) prior to TA treatment had significantly fewer dead cells than cultures treated with TA alone. This suggests that H2O2 induces biochemical or molecular changes in cell cultures that alleviate the activation of PCD by TA. Investigation of the cell wall mechanics using atomic force microscopy showed that H2O2 treatment can prevent the decrease in cell wall rigidity observed after TA exposure. While we cannot exclude the possibility that H2O2 may promote cell survival by altering the cellular redox environment or signaling pathways, our results suggest that H2O2 may inhibit cell death, at least partially, by reinforcing the cell wall to prevent or compensate for damages induced by TA.

An institutional study of time delays for symptomatic carotid endarterectomy.

OBJECTIVE: The aim of this study was to assess time delays between first cerebrovascular symptoms and carotid endarterectomy (CEA) at a single center and to systematically evaluate causes of these delays. METHODS: Consecutive adult patients who underwent CEAs between January 2010 and September 2011 at a single university-affiliated center (Centre Hospitalier de l'Université Montréal-Hôtel-Dieu Hospital, Montreal) were identified from a clinical database and operative records. Covariates of interest were extracted from electronic medical records. Timing and nature of the first cerebrovascular symptoms were also documented. The first medical contact and pathway of referral were also assessed. When possible, the ABCD2 score (age, blood pressure, clinical features, duration of symptoms, and diabetes) was calculated to calculate further risk of stroke. The nonparametric Wilcoxon test was used to assess differences in time intervals between two variables. The Kruskal-Wallis test was used to assess differences in time intervals in comparing more than two variables. A multivariate linear regression analysis was performed using covariates that were determined to be statistically significant in our sensitivity analyses. RESULTS: The cohort consisted of 111 patients with documented symptomatic carotid stenosis undergoing surgical intervention. Thirty-nine percent of all patients were operated on within 2 weeks from the first cerebrovascular symptoms. The median time between the occurrence of the first neurologic symptom and the CEA procedure was 25 (interquartile range [IQR], 11-85) days. The patient-dependent delay, defined as the median delay between the first neurologic symptom and the first medical contact, was 1 (IQR, 0-14) day. The medical-dependent delay was defined as the time interval between the first medical contact and CEA. This included the delay between the first medical contact and the request for surgery consultation (median, 3 [IQR, 1-10] days). The multivariate regression model demonstrated that the emergency physician as referral source (P = .0002) was statistically significant for reducing CEA delay. Patients who were investigated as an outpatient (P = .02), first medical contact with a general practitioner (P = .0002), and hospital center I as referral center (P = .045) were also found to be statistically significant to extend CEA delay when the model was adjusted over all covariates. In this center, there was no correlation between ABCD2 risk score and waiting time for surgery. CONCLUSIONS: The majority of our cohort falls short of the recommended 2-week interval to perform CEA. Factors contributing to reduced CEA delay were presentation to an emergency department, in-patient investigations, and a stroke center where a vascular surgeon is available.

Source of errors and accuracy of a two-dimensional/three-dimensional fusion road map for endovascular aneurysm repair of abdominal aortic aneurysm.

PURPOSE: To evaluate the accuracy and source of errors using a two-dimensional (2D)/three-dimensional (3D) fusion road map for endovascular aneurysm repair (EVAR) of abdominal aortic aneurysm. MATERIALS AND METHODS: A rigid 2D/3D road map was tested in 16 patients undergoing EVAR. After 3D/3D manual registration of preoperative multidetector computed tomography (CT) and cone beam CT, abdominal aortic aneurysm outlines were overlaid on live fluoroscopy/digital subtraction angiography (DSA). Patient motion was evaluated using bone landmarks. The misregistration of renal and internal iliac arteries were estimated by 3 readers along head-feet and right-left coordinates (z-axis and x-axis, respectively) before and after bone and DSA corrections centered on the lowest renal artery. Iliac deformation was evaluated by comparing centerlines before and during intervention. A score of clinical added value was estimated as high (z-axis < 3 mm), good (3 mm ≤ z-axis ≤ 5 mm), and low (z-axis > 5 mm). Interobserver reproducibility was calculated by the intraclass correlation coefficient. RESULTS: The lowest renal artery misregistration was estimated at x-axis = 10.6 mm ± 11.1 and z-axis = 7.4 mm ± 5.3 before correction and at x-axis = 3.5 mm ± 2.5 and z-axis = 4.6 mm ± 3.7 after bone correction (P = .08), and at 0 after DSA correction (P < .001). After DSA correction, residual misregistration on the contralateral renal artery was estimated at x-axis = 2.4 mm ± 2.0 and z-axis = 2.2 mm ± 2.0. Score of clinical added value was low (n = 11), good (n= 0), and high (n= 5) before correction and low (n = 5), good (n = 4), and high (n = 7) after bone correction. Interobserver intraclass correlation coefficient for misregistration measurements was estimated at 0.99. Patient motion before stent graft delivery was estimated at x-axis = 8 mm ± 5.8 and z-axis = 3.0 mm ± 2.7. The internal iliac artery misregistration measurements were estimated at x-axis = 6.1 mm ± 3.5 and z-axis = 5.6 mm ± 4.0, and iliac centerline deformation was estimated at 38.3 mm ± 15.6. CONCLUSIONS: Rigid registration is feasible and fairly accurate. Only a partial reduction of vascular misregistration was observed after bone correction; minimal DSA acquisition is still required.

Reduction in allogeneic blood products with routine use of autotransfusion in open elective infrarenal abdominal aortic aneurysm repair.

BACKGROUND AND OBJECTIVES: Concern about allogeneic blood product cost and complications has prompted interest in blood conservation techniques. Intraoperative autotransfusion (IAT) is currently not used routinely by vascular surgeons in open elective infrareanl abdominal aortic aneurysm (AAA) repair. The objective of this study is to review our experience with IAT and its impact on blood transfusion. METHODS: We retrospectively reviewed the medical records of consecutive patients treated electively over a 4-year period and compared 2 strategy related to IAT, routine use IAT (rIAT) versus on-demand IAT (oIAT). Outcomes measured were number of units of allogeneic red blood cells and autologous red blood cells transfused intraoperatively and postoperatively, preoperative, postoperative, and discharge hemoglobin levels; postoperative infections; length of postoperative intensive care stay; and length of hospital stay. T-independent and Fisher exact test were used. RESULTS: A total of 212 patients were included, 38 (18%) in the rIAT and 174 (82%) in the oIAT. Groups were similar except for an inferior creatinine and a superior mean aneurysm diameter for the rIAT group. Patients in the rIAT group had a lower rate of transfusion (26% vs 54%, P = .002) and a lower mean number of blood unit transfused (0.8 vs 1.8, P = .048). These findings were still more significant for AAA larger than 60 mm (18% rIAT vs 62% oIAT, P = .0001). Postoperative hemoglobin was superior in the rIAT group (107 vs 101 g/L, P = .01). Mean postoperative intensive care length of stay was shorter for the rIAT group (1.1 vs 1.8 days, P = .01). No difference was noted for infection, mortality, or hospital length of stay. CONCLUSION: The rIAT reduced the exposure to allogeneic blood products by more than 50%, in particular for patients with AAA larger than 60 mm. These results support the use of rIAT for open elective infrarenal AAA repair.

Stress-responsive mitogen-activated protein kinases interact with the EAR motif of a poplar zinc finger protein and mediate its degradation through the 26S proteasome.

Mitogen-activated protein kinases (MAPKs) contribute to the establishment of plant disease resistance by regulating downstream signaling components, including transcription factors. In this study, we identified MAPK-interacting proteins, and among the newly discovered candidates was a Cys-2/His-2-type zinc finger protein named PtiZFP1. This putative transcription factor belongs to a family of transcriptional repressors that rely on an ERF-associated amphiphilic repression (EAR) motif for their repression activity. Amino acids located within this repression motif were also found to be essential for MAPK binding. Close examination of the primary protein sequence revealed a functional bipartite MAPK docking site that partially overlaps with the EAR motif. Transient expression assays in Arabidopsis (Arabidopsis thaliana) protoplasts suggest that MAPKs promote PtiZFP1 degradation through the 26S proteasome. Since features of the MAPK docking site are conserved among other EAR repressors, our study suggests a novel mode of defense mechanism regulation involving stress-responsive MAPKs and EAR repressors.

Habituation to thaxtomin A in hybrid poplar cell suspensions provides enhanced and durable resistance to inhibitors of cellulose synthesis.

BACKGROUND: Thaxtomin A (TA), a phytotoxin produced by the phytopathogen Streptomyces scabies, is essential for the development of potato common scab disease. TA inhibits cellulose synthesis but its actual mode of action is unknown. Addition of TA to hybrid poplar (Populus trichocarpa x Populus deltoides) cell suspensions can activate a cellular program leading to cell death. In contrast, it is possible to habituate hybrid poplar cell cultures to grow in the presence of TA levels that would normally induce cell death. The purpose of this study is to characterize TA-habituated cells and the mechanisms that may be involved in enhancing resistance to TA. RESULTS: Habituation to TA was performed by adding increasing levels of TA to cell cultures at the time of subculture over a period of 12 months. TA-habituated cells were then cultured in the absence of TA for more than three years. These cells displayed a reduced size and growth compared to control cells and had fragmented vacuoles filled with electron-dense material. Habituation to TA was associated with changes in the cell wall composition, with a reduction in cellulose and an increase in pectin levels. Remarkably, high level of resistance to TA was maintained in TA-habituated cells even after being cultured in the absence of TA. Moreover, these cells exhibited enhanced resistance to two other inhibitors of cellulose biosynthesis, dichlobenil and isoxaben. Analysis of gene expression in TA-habituated cells using an Affymetrix GeneChip Poplar Genome Array revealed that durable resistance to TA is associated with a major and complex reprogramming of gene expression implicating processes such as cell wall synthesis and modification, lignin and flavonoid synthesis, as well as DNA and chromatin modifications. CONCLUSIONS: We have shown that habituation to TA induced durable resistance to the bacterial toxin in poplar cells. TA-habituation also enhanced resistance to two other structurally different inhibitors of cellulose synthesis that were found to target different proteins. Enhanced resistance was associated with major changes in the expression of numerous genes, including some genes that are involved in DNA and chromatin modifications, suggesting that epigenetic changes might be involved in this process.

Chitooligosaccharide sensing and downstream signaling: contrasted outcomes in pathogenic and beneficial plant-microbe interactions.

In plants, short chitin oligosaccharides and chitosan fragments (collectively referred to as chitooligosaccharides) are well-known elicitors that trigger defense gene expression, synthesis of antimicrobial compounds, and cell wall strengthening. Recent findings have shed new light on chitin-sensing mechanisms and downstream activation of intracellular signaling networks that mediate plant defense responses. Interestingly, chitin receptors possess several lysin motif domains that are also found in several legume Nod factor receptors. Nod factors are chitin-related molecules produced by nitrogen-fixing rhizobia to induce root nodulation. The fact that chitin and Nod factor receptors share structural similarity suggests an evolutionary conserved relationship between mechanisms enabling recognition of both deleterious and beneficial microorganisms. Here, we will present an update on molecular events involved in chitooligosaccharide sensing and downstream signaling pathways in plants and will discuss how structurally related signals may lead to such contrasted outcomes during plant-microbe interactions.

Involvement of the plant polymer Suberin and the disaccharide cellobiose in triggering thaxtomin A biosynthesis, a phytotoxin produced by the pathogenic agent streptomyces scabies.

Streptomyces scabies is a gram-positive soil bacterium recognized as the main causal agent of common scab. Pathogenicity in Streptomyces spp. depends on their capacity to synthesize phytotoxins called thaxtomins. Genes involved in biosynthesis of these secondary metabolites are known to be induced by cellobiose, a plant disaccharide. However, growth of S. scabies in a minimal medium containing cellobiose as a carbon source is very poor and only generates traces of thaxtomins. The effect of suberin, a lipid plant polymer, on thaxtomin A biosynthesis and the expression of genes involved in its biosynthetic pathway was analyzed. S. scabies was grown in a starch-containing minimal medium supplemented with cellobiose (0.5%), suberin (0.1%), or both. The presence of both cellobiose and suberin doubled bacterial growth and triggered thaxtomin A production, which correlated with the upregulation (up to 342-fold) of genes involved in thaxtomins synthesis. The addition of either suberin or cellobiose alone did not affect these parameters. Suberin appeared to stimulate the onset of secondary metabolism, which is a prerequisite to the production of molecules such as thaxtomin A, while cellobiose induced the biosynthesis of this secondary metabolite.

Streptomyces scabiei and its toxin thaxtomin A induce scopoletin biosynthesis in tobacco and Arabidopsis thaliana.

Streptomyces scabiei is the predominant causal agent of common scab of potato in North America. The virulence of common scab-causing streptomycetes relies on their capacity to synthesize thaxtomins. In this study, the effects of S. scabiei infection and of thaxtomin A, the main toxin produced by S. scabiei, were tested for the elicitation of plant defense molecules in the model plants tobacco (Nicotiana tabacum) and Arabidopsis thaliana. Tobacco leaves infected with spores of S. scabiei strain EF-35 or infiltrated with purified thaxtomin A produced a blue fluorescent compound that was not detected in leaves infiltrated with spores of a S. scabiei mutant deficient in thaxtomin A biosynthesis. Thin layer chromatography and high performance liquid chromatography identified this fluorescent compound as scopoletin, a plant defense phytoalexin. Arabidopsis seedlings grown in liquid medium also excreted scopoletin as a reaction to S. scabiei and thaxtomin A. The effects of the presence of scopoletin on S. scabiei were also investigated. The phytoalexin scopoletin caused a slight reduction of bacterial growth and a severe decrease of thaxtomin A production. Scopoletin was shown to inhibit thaxtomin A production by repression of a gene involved in the toxin biosynthesis.

Transcriptional profiling in response to inhibition of cellulose synthesis by thaxtomin A and isoxaben in Arabidopsis thaliana suspension cells.

The plant cell wall determines cell shape and is the main barrier against environmental challenges. Perturbations in the cellulose content of the wall lead to global modifications in cellular homeostasis, as seen in cellulose synthase mutants or after inhibiting cellulose synthesis. In particular, application of inhibitors of cellulose synthesis such as thaxtomin A (TA) and isoxaben (IXB) initiates a programmed cell death (PCD) in Arabidopsis thaliana suspension cells that is dependent on de novo gene transcription. To further understand how TA and IXB activate PCD, a whole genome microarray analysis was performed on mRNA isolated from Arabidopsis suspension cells exposed to TA and IXB. More than 75% of the genes upregulated by TA were also upregulated by IXB, including genes encoding cell wall-related and calcium-binding proteins, defence/stress-related transcription factors, signalling components and cell death-related proteins. Comparisons with published transcriptional analyses revealed that half of these genes were also induced by ozone, wounding, bacterial elicitor, Yariv reagent, chitin and H(2)O(2). These data indicate that both IXB and TA activate a similar gene expression profile, which includes an important subset of genes generally induced in response to various biotic and abiotic stress. However, genes typically activated during the defence response mediated by classical salicylic acid, jasmonate or ethylene signalling pathways were not upregulated in response to TA and IXB. These results suggest that inhibition of cellulose synthesis induces PCD by the activation of common stress-related pathways that would somehow bypass the classical hormone-dependent defence pathways.

Regional anesthesia for carotid surgery: less intraoperative hypotension and vasopressor requirement.

Regional anesthesia (RA) is the gold standard of neuromonitoring during carotid endarterectomy (CEA). Recent data show that RA for CEA is associated with fewer postoperative complications. The aim of the present study was to assess hemodynamic stability and vasoactive drug use for CEA performed under RA versus general anesthesia (GA). All patients undergoing CEA from January 2005 to January 2006 were identified from our prospective database. Electronic and paper charts were reviewed. Intraoperative monitoring data were reviewed retrospectively. Hypotension was defined as systolic blood pressure (SBP) <100 mm Hg and deemed prolonged if it lasted more than 10 min. Hypertension was defined as SBP >160 mm Hg. BP variation was defined as the difference between the highest and lowest SBP, and bradycardia as heart rate (HR) below 60. The data were expressed as means +/- standard deviation. Seventy-two consecutive patients underwent CEA: 25 under RA and 47 under GA. There was no difference in preoperative HR and BP. Most patients had symptomatic severe carotid stenosis (80% in RA vs. 85% in GA, nonsignificant). Intraoperatively, RA was associated with less BP variation (60 +/- 27 vs. 78 +/- 22 mm Hg, p = 0.005), bradycardia (5% vs. 63%, p < 0.001), hypotension (20% vs. 70%, p < 0.01), and prolonged hypotension (0% vs. 23%, p = 0.009) and more hypertension (80% vs. 47%, p = 0.007). Vasopressor requirements were less frequent under RA (20% vs. 77%, p < 0.001). There was no significant difference between groups in hypotension or hypertension episodes seen in the postoperative recovery room. RA was associated with less hypotension and less vasopressor used during CEA compared to GA. The improved hemodynamic stability may account for the lower incidence of complications after CEA.