Characterization of Xylella fastidiosa Virulence Factors and Host Physiological Responses That Contribute to Pierce's Disease in Grapevine

Xylella fastidiosa is a xylem-limited bacterium that causes Pierce’s Disease (PD) in grapevine. PD symptom progression is correlated with systemic colonization by X. fastidiosa, which occurs via pit membrane degradation. Previous studies determined that a polygalacturonase, one of several cell wall degrading enzymes (CWDEs) secreted by X. fastidiosa, is necessary for pit membrane degradation. Here, it is demonstrated that the loss of two X. fastidiosa β-1,4-endoglucanases (EGases) in tandem causes significantly slower PD symptom development and progression, and reduces X. fastidiosa virulence and population size. Furthermore, differences in the PD symptom progression rate between two cultivars appear to be caused by variations in pit membrane carbohydrate composition, which influence the rate of enzymatic degradation, and subsequently, the rate of systemic colonization. How these CWDEs and other virulence factors are secreted has not been fully elucidated. However, several are predicted to be secreted via the Type II secretion system (T2SS). T2SS-deficient X. fastidiosa mutants did not induce PD symptoms, and the mutant bacteria were not recovered from infected vines, indicating that the T2SS and its secreted substrates are necessary for virulence and survival. Analysis of wild type X. fastidiosa and T2SS-deficient mutant secretomes found six potential Type II secreted proteins for further characterization, including three lipases, a β-1,4-cellobiohydrolase, a protease, and a hypothetical protein. However, none of the CWDEs were present in the secretomes, but their high transcript abundance indicates that these enzymes could be post-transcriptionally regulated. Several PD symptoms appear similar to drought stress symptoms. Under drought conditions, decreased photosynthesis, cessation of plant growth, and carbon starvation occur. Tylose formation in response to X. fastidiosa infection occludes vessels to prevent the spread of pathogens and air embolisms. Interestingly, genes involved in photosynthesis and plant growth are down-regulated during PD symptom development, and tylose formation increases significantly. This increased vessel occlusion in the absence of new vessel formation over time could cause prolonged water stress. Furthermore, starch in the ray parenchyma depletes as PD symptoms progress, indicating that carbon starvation occurs. These results indicate that, along with X. fastidiosa-mediated virulence factors, host responses also contribute to PD

Tensile Testing Environmental Chamber – Structural

Environmental chambers for tensile testing machines are used to study how a multitude of materials behave in extreme temperatures. These chambers provide the necessary information to innovate cutting edge technology for materials in fields such as aerospace. These chambers are often heavy and expensive requiring a significant amount of time and money just in the installation process alone. This report will serve to outline and define the design and fabrication of an environmental chamber, conducted by a team of four senior mechanical engineering students at California Polytechnic State University, San Luis Obispo. The goals of the project include a low-weight product, accurate and precise temperature changes within the chamber, visibility of the testing area, and ease of installation of the product on the tensile testing machine. This document provides an in-depth definition of the problem and a description of the background research conducted and presents the team’s initial design ideas as well as the concep

Characterization of Xylella fastidiosa Virulence Factors and Host Physiological Responses That Contribute to Pierce's Disease in Grapevine

Xylella fastidiosa is a xylem-limited bacterium that causes Pierce’s Disease (PD) in grapevine. PD symptom progression is correlated with systemic colonization by X. fastidiosa, which occurs via pit membrane degradation. Previous studies determined that a polygalacturonase, one of several cell wall degrading enzymes (CWDEs) secreted by X. fastidiosa, is necessary for pit membrane degradation. Here, it is demonstrated that the loss of two X. fastidiosa β-1,4-endoglucanases (EGases) in tandem causes significantly slower PD symptom development and progression, and reduces X. fastidiosa virulence and population size. Furthermore, differences in the PD symptom progression rate between two cultivars appear to be caused by variations in pit membrane carbohydrate composition, which influence the rate of enzymatic degradation, and subsequently, the rate of systemic colonization. How these CWDEs and other virulence factors are secreted has not been fully elucidated. However, several are predicted to be secreted via the Type II secretion system (T2SS). T2SS-deficient X. fastidiosa mutants did not induce PD symptoms, and the mutant bacteria were not recovered from infected vines, indicating that the T2SS and its secreted substrates are necessary for virulence and survival. Analysis of wild type X. fastidiosa and T2SS-deficient mutant secretomes found six potential Type II secreted proteins for further characterization, including three lipases, a β-1,4-cellobiohydrolase, a protease, and a hypothetical protein. However, none of the CWDEs were present in the secretomes, but their high transcript abundance indicates that these enzymes could be post-transcriptionally regulated. Several PD symptoms appear similar to drought stress symptoms. Under drought conditions, decreased photosynthesis, cessation of plant growth, and carbon starvation occur. Tylose formation in response to X. fastidiosa infection occludes vessels to prevent the spread of pathogens and air embolisms. Interestingly, genes involved in photosynthesis and plant growth are down-regulated during PD symptom development, and tylose formation increases significantly. This increased vessel occlusion in the absence of new vessel formation over time could cause prolonged water stress. Furthermore, starch in the ray parenchyma depletes as PD symptoms progress, indicating that carbon starvation occurs. These results indicate that, along with X. fastidiosa-mediated virulence factors, host responses also contribute to PD

Flapped or Flapless Surgery for Narrow-Diameter Implant Placement for Overdentures: Advantages, Disadvantages, Indications, and Clinical Rationale

Narrow-diameter implants for overdenture applications have gained in popularity due to their ability to be placed with simplified and less traumatic surgical protocols in limited-width alveolar ridges. The decision of whether to use a flapped or flapless procedure must be guided by a thorough evaluation and evidence-based diagnosis. This article reviews current principles relating to the use of narrow-diameter implants, along with the advantages and disadvantages of current surgical protocols. The indications for the use of each surgical procedure are demonstrated by case reports that highlight diagnosis, surgical planning, and final treatment outcomes

Overall Survival with Osimertinib in Untreated, EGFR-Mutated Advanced NSCLC

BACKGROUND: Osimertinib is a third-generation, irreversible tyrosine kinase inhibitor of the epidermal growth factor receptor (EGFR-TKI) that selectively inhibits both EGFR-TKI-sensitizing and EGFR T790M resistance mutations. A phase 3 trial compared first-line osimertinib with other EGFR-TKIs in patients with EGFR mutation-positive advanced non-small-cell lung cancer (NSCLC). The trial showed longer progression-free survival with osimertinib than with the comparator EGFR-TKIs (hazard ratio for disease progression or death, 0.46). Data from the final analysis of overall survival have not been reported. METHODS: In this trial, we randomly assigned 556 patients with previously untreated advanced NSCLC with an EGFR mutation (exon 19 deletion or L858R allele) in a 1:1 ratio to receive either osimertinib (80 mg once daily) or one of two other EGFR-TKIs (gefitinib at a dose of 250 mg once daily or erlotinib at a dose of 150 mg once daily, with patients receiving these drugs combined in a single comparator group). Overall survival was a secondary end point. RESULTS: The median overall survival was 38.6 months (95% confidence interval [CI], 34.5 to 41.8) in the osimertinib group and 31.8 months (95% CI, 26.6 to 36.0) in the comparator group (hazard ratio for death, 0.80; 95.05% CI, 0.64 to 1.00; P = 0.046). At 3 years, 79 of 279 patients (28%) in the osimertinib group and 26 of 277 (9%) in the comparator group were continuing to receive a trial regimen; the median exposure was 20.7 months and 11.5 months, respectively. Adverse events of grade 3 or higher were reported in 42% of the patients in the osimertinib group and in 47% of those in the comparator group. CONCLUSIONS: Among patients with previously untreated advanced NSCLC with an EGFR mutation, those who received osimertinib had longer overall survival than those who received a comparator EGFR-TKI. The safety profile for osimertinib was similar to that of the comparator EGFR-TKIs, despite a longer duration of exposure in the osimertinib group. (Funded by AstraZeneca; FLAURA ClinicalTrials.gov number, NCT02296125.).status: publishe

Perioperative Pembrolizumab for Early-Stage Non-Small-Cell Lung Cancer

BACKGROUND Among patients with resectable early-stage non-small-cell lung cancer (NSCLC), a perioperative approach that includes both neoadjuvant and adjuvant immune checkpoint inhibition may provide benefit beyond either approach alone.METHODS We conducted a randomized, double-blind, phase 3 trial to evaluate perioperative pembrolizumab in patients with early-stage NSCLC. Participants with resectable stage II, IIIA, or IIIB (N2 stage) NSCLC were assigned in a 1:1 ratio to receive neoadjuvant pembrolizumab (200 mg) or placebo once every 3 weeks, each of which was given with cisplatin-based chemotherapy for 4 cycles, followed by surgery and adjuvant pembrolizumab (200 mg) or placebo once every 3 weeks for up to 13 cycles. The dual primary end points were event-free survival (the time from randomization to the first occurrence of local progression that precluded the planned surgery, unresectable tumor, progression or recurrence, or death) and overall survival. Secondary end points included major pathological response, pathological complete response, and safety.RESULTS A total of 397 participants were assigned to the pembrolizumab group, and 400 to the placebo group. At the prespecified first interim analysis, the median follow-up was 25.2 months. Event-free survival at 24 months was 62.4% in the pembrolizumab group and 40.6% in the placebo group (hazard ratio for progression, recurrence, or death, 0.58; 95% confidence interval [CI], 0.46 to 0.72; P<0.001). The estimated 24-month overall survival was 80.9% in the pembrolizumab group and 77.6% in the placebo group (P = 0.02, which did not meet the significance criterion). A major pathological response occurred in 30.2% of the participants in the pembrolizumab group and in 11.0% of those in the placebo group (difference, 19.2 percentage points; 95% CI, 13.9 to 24.7; P<0.0001; threshold, P = 0.0001), and a pathological complete response occurred in 18.1% and 4.0%, respectively (difference, 14.2 percentage points; 95% CI, 10.1 to 18.7; P<0.0001; threshold, P = 0.0001). Across all treatment phases, 44.9% of the participants in the pembrolizumab group and 37.3% of those in the placebo group had treatment-related adverse events of grade 3 or higher, including 1.0% and 0.8%, respectively, who had grade 5 events.CONCLUSIONS Among patients with resectable, early-stage NSCLC, neoadjuvant pembrolizumab plus chemotherapy followed by resection and adjuvant pembrolizumab significantly improved event-free survival, major pathological response, and pathological complete response as compared with neoadjuvant chemotherapy alone followed by surgery. Overall survival did not differ significantly between the groups in this analysis