Comparación de tensiones y desplazamientos entre mini-implantes de acero y titanio insertados con diferentes angulaciones: análisis de elementos finitos

Objective: The objective of this study was to quantify the tensions and displacements of steel and titanium mini-implants inserted at different angles and under a retraction force. Materials and Methods: A CAD model of the TD Orthodontics mini-implant was created. The material properties (steel or titanium alloy) were then assigned. SolidWorks software was used to mesh the mini-implant and bone models and perform the finite element analysis on the mini-implants inserted at angles of 30°, 60°, and 90° with a simulated orthodontic retraction force of 2 N applied to each of these finite element models. Results: With regards to the maximum von Mises stress, there appears to be no significant difference between the steel and titanium mini-implants at the evaluated angles. In terms of displacement, the titanium mini-implants generally experienced greater displacement at the three evaluated angles compared to the stainless steel mini-implants.Objectivo: El objetivo de este estudio fue evaluar cuantitativamente las tensiones y desplazamientos de los mini-implantes de acero y titanio insertados bajo diferentes ángulos y aplicando una fuerza de retractación. Materiales y métodos: Se creó un modelo CAD del mini-implante de la marca TD Orthodontics. Posteriormente, se asignaron las características de los materiales a evaluar (acero o aleación de titanio). Se utilizó el software SolidWorks para hacer la malla de los modelos de mini-implante y hueso, y así realizar el análisis de elementos finitos en los mini-implantes con ángulos de inserción de 30°, 60°, 90° y se aplicó una fuerza de retracción ortodóncica simulada de 2 N en cada uno de estos modelos de elementos finitos. Resultados: En cuanto al estrés máximo de von Mises, observamos que parece no haber una diferencia significativa entre los mini-implantes de acero y de titanio en las angulaciones evaluadas. En cuanto al desplazamiento, los mini-implantes de titanio en general sufrieron mayor desplazamiento en las tres angulaciones evaluadas en comparación con los mini implantes de acero inoxidable.&nbsp

Involvement of Hydrogen Peroxide and Nitric Oxide in Expression of the Ipomoelin Gene from Sweet Potato

The IPO (ipomoelin) gene was isolated from sweet potato (Ipomoea batatas cv Tainung 57) and used as a molecular probe to investigate its regulation by hydrogen peroxide (H(2)O(2)) and nitric oxide (NO) after sweet potato was wounded. The expression of the IPO gene was stimulated by H(2)O(2) whether or not the plant was wounded, but its expression after wounding was totally suppressed by the presence of diphenylene iodonium, an inhibitor of NADPH oxidase, both in the local and systemic leaves of sweet potato. These results imply that a signal transduction resulting from the mechanical wounding of sweet potato may involve NADPH oxidase, which produces endogenous H(2)O(2) to stimulate the expression of the IPO gene. The production of H(2)O(2) was also required for methyl jasmonate to stimulate the IPO gene expression. On the contrary, NO delayed the expression of the IPO gene, whereas N(G)-monomethyl-l-arginine monoacetate, an inhibitor of NO synthase, enhanced the expression of the IPO gene after the plant was wounded. This study also demonstrates that the production of H(2)O(2) stained with 3,3′-diaminobenzidine hydrochloride could be stimulated by wounding but was suppressed in the presence of NO. Meanwhile, the generation of NO was visualized by confocal scanning microscope in the presence of 4,5-diaminofluorescein diacetate after sweet potato was wounded. In conclusion, when sweet potato was wounded, both H(2)O(2) and NO were produced to modulate the plant's defense system. Together, H(2)O(2) and NO regulate the expression of the IPO gene, and their interaction might further stimulate plants to protect themselves from invasions by pathogens and herbivores

The Activity of the Chloroplastic Ndh Complex Is Regulated by Phosphorylation of the NDH-F Subunit

Hydrogen peroxide (H(2)O(2)) induces increases, to different degrees, in transcripts, protein levels, and activity of the Ndh complex (EC 1.6.5.3). In the present work, we have compared the effects of relatively excess light, H(2)O(2), dimethylthiourea (a scavenger of H(2)O(2)), and/or EGTA (a Ca(2+) chelator) on the activity and protein levels of the Ndh complex of barley (Hordeum vulgare cv Hassan) leaf segments. The results show the involvement of H(2)O(2) in the modulation of both the protein level and activity of the Ndh complex and the participation of Ca(2+) mainly in the activity regulation of pre-existing protein. Changes in Ndh complex activity could not be explained only by changes in Ndh protein levels, suggesting posttranslational modifications. Hence, we investigate the possible phosphorylation of the Ndh complex both in thylakoids and in the immunopurified Ndh complex using monoclonal phosphoamino acid antibodies. We demonstrate that the Ndh complex is phosphorylated in vivo at threonine residue(s) of the NDH-F polypeptide and that the level of phosphorylation is closely correlated with the Ndh complex activity. The emerging picture is that full activity of the Ndh complex is reached by phosphorylation of its NDH-F subunit in a H(2)O(2)- and Ca(2+)-mediated action

Reactive Oxygen Species in the Elongation Zone of Maize Leaves Are Necessary for Leaf Extension

The production and role of reactive oxygen species (ROS) in the expanding zone of maize (Zea mays) leaf blades were investigated. ROS release along the leaf blade was evaluated by embedding intact seedlings in 2′,7′-dichlorofluorescein-containing agar and examining the distribution of 2′,7′-dichlorofluorescein fluorescence along leaf 4, which was exposed by removing the outer leaves before embedding the seedling. Fluorescence was high in the expanding region, becoming practically non-detectable beyond 65 mm from the ligule, indicating high ROS production in the expansion zone. Segments obtained from the elongation zone of leaf 4 were used to assess the role of ROS in leaf elongation. The distribution of cerium perhydroxide deposits in electron micrographs indicated hydrogen peroxide (H(2)O(2)) presence in the apoplast. 2′,7′-Dichlorofluorescein fluorescence and apoplastic H(2)O(2) accumulation were inhibited with diphenyleneiodonium (DPI), which also inhibited O(⋅)(2)(−) generation, suggesting a flavin-containing enzyme activity such as NADPH oxidase was involved in ROS production. Segments from the elongation zone incubated in water grew 8% in 2 h. KI treatments, which scavenged H(2)O(2) but did not inhibit O(⋅)(2)(−) production, did not modify growth. DPI significantly inhibited segment elongation, and the addition of H(2)O(2) (50 or 500 μm) to the incubation medium partially reverted the inhibition caused by DPI. These results indicate that a certain concentration of H(2)O(2) is necessary for leaf elongation, but it could not be distinguished whether H(2)O(2), or other ROS, are the actual active agents