Fracture rates of IPS Empress all-ceramic crowns: a systematic review.

Purpose: The aim of this study was to evaluate the clinical fracture rate of crowns fabricated with the pressable, leucite-reinforced ceramic IPS Empress, and relate the results to the type of tooth restored. Materials and Methods: The database SCOPUS was searched for clinical studies involving full-coverage crowns made of IPS Empress. To assess the fracture rate of the crowns in relation to the type of restored tooth and study, Poisson regression analysis was used. Results: Seven clinical studies were identified involving 1,487 adhesively luted crowns (mean observation time: 4.5 +/- 1.7 years) and 81 crowns cemented with zinc-phosphate cement (mean observation time: 1.6 +/- 0.8 years). Fifty-seven of the adhesively luted crowns fractured (3.8%). The majority of fractures (62%) occurred between the third and sixth year after placement. There was no significant influence regarding the test center on fracture rate, but the restored tooth type played a significant role. The hazard rate (per year) for crowns was estimated to be 5 in every 1,000 crowns for incisors, 7 in every 1,000 crowns for premolars, 12 in every 1,000 crowns for canines, and 16 in every 1,000 crowns for molars. One molar crown in the zinc-phosphate group fractured after 1.2 years. Conclusion: Adhesively luted IPS Empress crowns showed a low fracture rate for incisors and premolars and a somewhat higher rate for molars and canines. The sample size of the conventionally luted crowns was too small and the observation period too short to draw meaningful conclusions. Int J Prosthodont 2010;23:129-133.

A 3 years retrospective study of survival for zirconia-based single crowns fabricated from intraoral digital impressions.

OBJECTIVE: To evaluate the clinical performance of glass-ceramic/zirconia crowns fabricated using intraoral digital impressions - a retrospective study with a three-year follow-up. METHODS: 70 consecutive patients with a total of 86 glass-ceramic/zirconia crowns were treated by a single clinician using standardized clinical and laboratory protocols. A complete digital workflow was adopted for the purpose except for the veneering procedure for the glass-ceramic crowns. Occlusal adjustments were made before the ceramic glazing procedure. Before cementation, all abutments where carefully cleaned with a 70% alcoholic solution and air dried. Cementation was performed using dual-curing, self-adhesive resin cement. Patients were re-examined after 12, 24 and 36 months, to assess crown chipping/fractures. RESULTS: After the three-year follow-up, none of the zirconia-based restoration was lost ("apparent" survival rate 100%) otherwise, the chipping rate of the veneering material increased from 9.3% after 12 months, to 14% after 24 months to 30.2% after 36 months. As a consequence, the "real" success rate after 3 years was 69.8%. CONCLUSIONS: After 3 years the success rate of zirconia-based crowns was 69.8%, while the incidence of the chipping was 30.2%. Assuming an exponential increase in chipping rate between 12 and 36 months it can be argued that, among others, the fatigue-mechanism could be advocated as the main factor for the failure of glass-ceramic veneered zirconia especially after 24 months.

Salicylic Acid Biosynthetic Genes Expressed in Pseudomonas fluorescens Strain P3 Improve the Induction of Systemic Resistance in Tobacco Against Tobacco Necrosis Virus.

ABSTRACT Application of salicylic acid induces systemic acquired resistance in tobacco. pchA and pchB, which encode for the biosynthesis of salicylic acid in Pseudomonas aeruginosa, were cloned into two expression vectors, and these constructs were introduced into two root-colonizing strains of P. fluorescens. Introduction of pchBA into strain P3, which does not produce salicylic acid, rendered this strain capable of salicylic acid production in vitro and significantly improved its ability to induce systemic resistance in tobacco against tobacco necrosis virus. Strain CHA0 is a well-described biocontrol agent that naturally produces salicylic acid under conditions of iron limitation. Introduction of pchBA into CHA0 increased the production of salicylic acid in vitro and in the rhizosphere of tobacco, but did not improve the ability of CHA0 to induce systemic resistance in tobacco. In addition, these genes did not improve significantly the capacity of strains P3 and CHA0 to suppress black root rot of tobacco in a gnotobiotic system.

Defining molecular components of symbiotic phosphate uptake in rice

Phosphate (Pi) acquisition of crops via arbuscular mycorrhizal (AM) symbiosis acquires increasing importance due to the limited rock Pi reserves and the demand for environmentally sustainable agriculture. However, the symbiotic Pi uptake machinery has not been characterized in any monocotyledonous plant species. Among these, rice is the primary staple food for more than half of the human population and thus central for future food security. However, the relevance of the AM symbiosis for rice Pi nutrition is presently unclear. Here, we show that 70% of the overall Pi acquired by rice is delivered via the symbiotic route. To better understand this pathway we combined genetic, molecular and physiological approaches to determine the specific functions of the two rice Pi transporters, PT11 and PT13, which are expressed only during AM symbiosis. The PT11 lineage of proteins is present in mono- and dicotyledons whereas PT13, while found across the Poaceae, is absent from dicotyledons. Surprisingly, mutations in either PT11 or PT13 affected fungal colonization and arbuscule formation demonstrating that both genes are essential for AM symbiosis between rice and Glomus intra.rad.ices. Importantly, for symbiotic Pi uptake, only PT11 is necessary and sufficient. We found that mycorrhizal rice, remarkably, received almost all Pi via the symbiotic route. Such dominating mycorrhizal Pi uptake was found in plants grown under controlled conditions as well as in field soils, suggesting that the AM symbiosis is relevant for the Pi nutrition of field grown rice. Development of smaller arbuscules in PT11 mutants suggested that symbiotic Pi signaling is required for fungal nourishment by the plant. However, co-culture of mutant with wild type nurse plants did not restore normal arbuscule size in mutant roots, indicating that other factors than malnutrition accounted for the altered arbuscule phenotype. Surprisingly, the loss of PT13 did not affect symbiotic Pi uptake although it impacted arbuscule morphology, suggesting that PT13 is involved in signaling during arbuscule development. However, induction of PT13 was not only monitored in arbusculated cells but also in inner cortex cells of non-inoculated roots of plants grown under high Pi fertilization conditions. According to preliminary observations, PT13 localized at the tonoplast in arbusculated and non-arbusculated cells, suggesting that it might be involved in transporting Pi into the vacuole, possibly for maintaining cellular Pi homeostasis. The further investigation showed that fungal colonization level was significantly affected in the crown roots of two ptlS mutant alleles, but not in large lateral roots, implying the possible role of PT13 for maintaining Pi homeostasis in the crown roots. - L'acquisition de phosphate (Pi) par les plantes cultivées s'effectue grâce à une symbiose mycorhizienne arbasculaire (AM). L'étude de cette symbiose devient fondamentale puisque d'une part, les réserves en phosphate minéral sont limitées, et, d'autre part, la demande pour une agriculture écologiquement soutenable se renforce. La machinerie d'absorption symbiotique du phosphate n'est cependant pas encore élucidée chez les plantes monocotylédones. Parmi celles-ci, le riz occupe une place primordiale. Aliment de base pour plus de la moitié de la population mondiale, il revêt de ce fait une dimension essentielle en termes de sécurité alimentaire. Pourtant, l'importance de la symbiose AM chez le riz dans le processus d'acquisition du phosphate n'est, encore de nos jours, que peu comprise. Dans cette étude, nous montrons que 70% du phosphate acquis par le riz est mis à disposition de la plante grâce à la symbiose AM. Afin de mieux comprendre ce mécanisme, nous avons employé des approches physiologiques et génétiques nous permettant de déterminer les fonctions spécifiques de deux transporteurs de Pi, PT11 et PT13, présents chez le riz et exprimés uniquement durant la symbiose AM. La famille de gènes à laquelle appartient PT11 est présente chez les monocotylédones ainsi que chez les dicotylédones tandis que PT13, bien que retrouvé au sein des Poaceae, est absent chez les dicotylédones. Etonnamment, des versions mutées de PT11 ou de PT13 affectent la colonisation par le champignon endo-mycorhizien ainsi que la formation d'arbuscules, démontrant l'importance de ces deux gènes dans la symbiose AM entre le riz et Glomus intraradices. Il est à noter que seul PT11 se révèle nécessaire et suffisant pour l'apport de Pi grâce à la symbiose. Nous avons observé que la presque totalité du phosphate dont dispose le riz lors d'une symbiose AM provient du champignon. De telles proportions ont été observées tant chez des plantes cultivées en conditions contrôlées que chez des plantes cultivées dans les champs. Cela suggère l'importance de la symbiose AM dans le processus d'acquisition du Pi chez le riz cultivé à l'extérieur. Le développement d'arbuscules plus petits chez le mutant PT11 tend à montrer qu'une voie signalétique impliquant le Pi symbiotique est nécessaire pour l'entretien du champignon par la plante. Toutefois, une co-culture du mutant avec des plantes sauvages ne permet pas de restaurer des arbuscules de taille normale dans les racines du mutant. Ce résultat indique le rôle de facteurs autres que la malnutrition aboutissant à la formation d'arbuscules altérés. Si la perte de PT13 n'affecte pas l'acquisition de phosphate symbiotique, la morphologie de l'arbuscule est, quant à elle, modifiée. Ceci suggère un rôle de PT13 durant le développement de l'arbuscule. Or, l'induction de PT13 est non seulement détectée dans des cellules contenant des arbuscules mais également dans des cellules du cortex, ceci chez des plantes cultivées sans champignon mais dans des conditions de fortes concentrations en engrais phosphaté. En accord avec des observations précédentes, PT13 est localisé au niveau du tonoplaste des cellules contenant ou non des arbuscules. Ceci suggère que PT13 pourrait être impliqué dans le transport du Pi vers la vacuole, éventuellement pour maintenir une certaine homéostasie du phosphate. Dans cette étude, nous démontrons également que le niveau de colonisation par le champignon est affecté de manière significative dans les racines principales des deux allèles du mutants ptl3, mais pas dans les grosses racines latérales. Cela impliquerait un rôle possible de PT13 dans le maintien de l'homéostasie du phosphate dans les racines principales. RESUME POUR UN LARGE PUBLIC Le phosphate (Pi), l'un des éléments minéraux essentiel au développement des plantes, se trouve généralement en faible quantité dans le sol, limitant ainsi la croissance des plantes. Le rendement de la production agricole dépend dès lors de l'addition d'engrais contenant du phosphate inorganique (Pi), obtenu à partir de ressources minières riches en phosphate. Or, ces ressources devraient être épuisées d'ici la fin du siècle. Les racines des plantes possèdent des transporteurs de phosphate efficaces leur permettant d'acquérir rapidement le Pi présent dans le sol. Comme le Pi s'avère immobile dans le sol, l'absorption rapide par les racines crée des zones pauvres en Pi autour des systèmes racinaires. Pour surmonter cet obstacle, les plantes ont développé une symbiose avec des champignons endomycorhiziens, la symbiose mycorhizienne arbusculaire (AM). Cette association leur donne accès à d'autres ressources en phosphate puisque le mycélium de ces champignons se développe sur une surface 100 fois supérieure à celle des racines. Cela augmente considérablement la surface de nutrition, dépassant ainsi la zone appauvrie en Pi. Le phosphate, transporté grâce au champignon jusqu'à l'intérieur des racines, est fourni à la plante par le biais de structures établies à l'intérieur des cellules végétales, appelées arbuscules. De leur côté, les plantes possèdent des transporteurs spécifiques afin de recevoir le Pi fourni par les champignons. A l'heure actuelle, la machinerie nécessaire à cette absorption a été uniquement décrite chez des plantes dicotylédones. Or, comprendre l'apport de phosphate par les champignons mycorhiziens s'avère particulièrement pertinent dans le cas des espèces monocotylédones cultivées telles que les céréales. Ces dernières constituent en effet la majeure partie de l'alimentation humaine. Parmi les céréales, le riz demeure l'aliment de base de la population mondiale, d'où son importance en terme de sécurité alimentaire. Durant mon travail de thèse, j'ai identifié et caractérisé le transporteur du riz impliqué dans l'apport de phosphate par ce type de symbiose AM. J'ai également démontré que le riz, lorsqu'il vit en symbiose, bénéficie de la presque totalité du Pi transporté par le champignon. Environ 40% de la production globale de riz est cultivée dans des conditions permettant la symbiose avec des mycorhizes arbusculaires. Les variétés de riz adaptées à ces conditions aérobiques deviennent des alternatives favorables aux cultivars actuels nécessitant une forte irrigation. Elles se révèlent en effet plus tolérantes aux pénuries d'eau et permettent l'utilisation de pratiques agricoles moins intensives. Les données présentées dans cette étude enrichissent nos connaissances concernant l'absorption du phosphate chez le riz grâce à la symbiose AM. Ces connaissances peuvent s'avérer décisives pour le développement de cultivars du riz plus adaptés à une agriculture écologiquement soutenable.

RpoN (sigma54) controls production of antifungal compounds and biocontrol activity in Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens CHA0 is an effective biocontrol agent of root diseases caused by fungal pathogens. The strain produces the antibiotics 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) that make essential contributions to pathogen suppression. This study focused on the role of the sigma factor RpoN (sigma54) in regulation of antibiotic production and biocontrol activity in P. fluorescens. An rpoN in-frame-deletion mutant of CHAO had a delayed growth, was impaired in the utilization of several carbon and nitrogen sources, and was more sensitive to salt stress. The rpoN mutant was defective for flagella and displayed drastically reduced swimming and swarming motilities. Interestingly, the rpoN mutant showed a severalfold enhanced production of DAPG and expression of the biosynthetic gene phlA compared with the wild type and the mutant complemented with monocopy rpoN+. By contrast, loss of RpoN function resulted in markedly lowered PLT production and plt gene expression, suggesting that RpoN controls the balance of the two antibiotics in strain CHA0. In natural soil microcosms, the rpoN mutant was less effective in protecting cucumber from a root rot caused by Pythium ultimum. Remarkably, the mutant was not significantly impaired in its root colonization capacity, even at early stages of root infection by Pythium spp. Taken together, our results establish RpoN for the first time as a major regulator of biocontrol activity in Pseudomonas fluorescens.

Two novel MvaT-like global regulators control exoproduct formation and biocontrol activity in root-associated Pseudomonas fluorescens CHA0.

Pseudomonas fluorescens CHA0 protects various crop plants against root diseases caused by pathogenic fungi. Among a range of exoproducts excreted by strain CHA0, the antifungal compounds 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin (PLT) are particularly relevant to the strain's biocontrol potential. Here, we report on the characterization of MvaT and MvaV as novel regulators of biocontrol activity in strain CHA0. We establish the two proteins as further members of an emerging family of MvaT-like regulators in pseudomonads that are structurally and functionally related to the DNA-binding protein H-NS. In mvaT and mvaV in frame-deletion mutants of strain CHA0, PLT production was enhanced about four- and 1.5-fold, respectively, whereas DAPG production remained at wild-type levels. Remarkably, PLT production was increased up to 20-fold in an mvaT mvaV double mutant. DAPG biosynthesis was almost completely repressed in this mutant. The effects on antibiotic production could be confirmed by following expression of gfp-based reporter fusions to the corresponding biosynthetic genes. MvaT and MvaV also influenced levels of other exoproducts, motility, and physicochemical cell-surface properties to various extents. Compared with the wild type, mvaT and mvaV mutants had an about 20% reduced capacity (in terms of plant fresh weight) to protect cucumber from a root rot caused by Pythium ultimum. Biocontrol activity was nearly completely abolished in the double mutant Our findings indicate that MvaT and MvaV act together as further global regulatory elements in the complex network controlling expression of biocontrol traits in plant-beneficial pseudomonads.

Prevalence of cerebral amyloid pathology in persons without dementia: a meta-analysis.

IMPORTANCE: Cerebral amyloid-β aggregation is an early pathological event in Alzheimer disease (AD), starting decades before dementia onset. Estimates of the prevalence of amyloid pathology in persons without dementia are needed to understand the development of AD and to design prevention studies. OBJECTIVE: To use individual participant data meta-analysis to estimate the prevalence of amyloid pathology as measured with biomarkers in participants with normal cognition, subjective cognitive impairment (SCI), or mild cognitive impairment (MCI). DATA SOURCES: Relevant biomarker studies identified by searching studies published before April 2015 using the MEDLINE and Web of Science databases and through personal communication with investigators. STUDY SELECTION: Studies were included if they provided individual participant data for participants without dementia and used an a priori defined cutoff for amyloid positivity. DATA EXTRACTION AND SYNTHESIS: Individual records were provided for 2914 participants with normal cognition, 697 with SCI, and 3972 with MCI aged 18 to 100 years from 55 studies. MAIN OUTCOMES AND MEASURES: Prevalence of amyloid pathology on positron emission tomography or in cerebrospinal fluid according to AD risk factors (age, apolipoprotein E [APOE] genotype, sex, and education) estimated by generalized estimating equations. RESULTS: The prevalence of amyloid pathology increased from age 50 to 90 years from 10% (95% CI, 8%-13%) to 44% (95% CI, 37%-51%) among participants with normal cognition; from 12% (95% CI, 8%-18%) to 43% (95% CI, 32%-55%) among patients with SCI; and from 27% (95% CI, 23%-32%) to 71% (95% CI, 66%-76%) among patients with MCI. APOE-ε4 carriers had 2 to 3 times higher prevalence estimates than noncarriers. The age at which 15% of the participants with normal cognition were amyloid positive was approximately 40 years for APOE ε4ε4 carriers, 50 years for ε2ε4 carriers, 55 years for ε3ε4 carriers, 65 years for ε3ε3 carriers, and 95 years for ε2ε3 carriers. Amyloid positivity was more common in highly educated participants but not associated with sex or biomarker modality. CONCLUSIONS AND RELEVANCE: Among persons without dementia, the prevalence of cerebral amyloid pathology as determined by positron emission tomography or cerebrospinal fluid findings was associated with age, APOE genotype, and presence of cognitive impairment. These findings suggest a 20- to 30-year interval between first development of amyloid positivity and onset of dementia.

Transcriptome diversity among rice root types during asymbiosis and interaction with arbuscular mycorrhizal fungi.

Root systems consist of different root types (RTs) with distinct developmental and functional characteristics. RTs may be individually reprogrammed in response to their microenvironment to maximize adaptive plasticity. Molecular understanding of such specific remodeling-although crucial for crop improvement-is limited. Here, RT-specific transcriptomes of adult rice crown, large and fine lateral roots were assessed, revealing molecular evidence for functional diversity among individual RTs. Of the three rice RTs, crown roots displayed a significant enrichment of transcripts associated with phytohormones and secondary cell wall (SCW) metabolism, whereas lateral RTs showed a greater accumulation of transcripts related to mineral transport. In nature, arbuscular mycorrhizal (AM) symbiosis represents the default state of most root systems and is known to modify root system architecture. Rice RTs become heterogeneously colonized by AM fungi, with large laterals preferentially entering into the association. However, RT-specific transcriptional responses to AM symbiosis were quantitatively most pronounced for crown roots despite their modest physical engagement in the interaction. Furthermore, colonized crown roots adopted an expression profile more related to mycorrhizal large lateral than to noncolonized crown roots, suggesting a fundamental reprogramming of crown root character. Among these changes, a significant reduction in SCW transcripts was observed that was correlated with an alteration of SCW composition as determined by mass spectrometry. The combined change in SCW, hormone- and transport-related transcript profiles across the RTs indicates a previously overlooked switch of functional relationships among RTs during AM symbiosis, with a potential impact on root system architecture and functioning.