ABSTRACT
The purpose of this work was to investigate the influence of acid treatment on the surface properties and in vivo performance of titanium grade 5 (Ti6Al4V) alloy. Mini-implants with surface treatment were inserted into New Zealand rabbit tibia for 1, 4 and 8 weeks. SEM analysis showed intercommunicated micropores in acid treated samples. AFM showed micron and sub-micron roughness. The thickness of the titanium oxide layer increased with surface treatment, with a significant reduction of Al and V concentration. Acid treated implant removal torque was larger than without treatment. The implants/bone interface of acid treated implants showed dense adhered Ca/P particles with spreading osteoblasts after 4 weeks and newly formed bone trabeculae after 8 weeks. Analysis of rabbit blood that received treated implant showed lower Al and V contents at all times. Acid treatment improved surface morphology and mechanical stability, which allowed initial events of osseointegration, while Al-V ion release was reduced. GRAPHICAL ABTSRACT.
Subject(s)
Biomedical and Dental Materials , Coated Materials, Biocompatible/chemistry , Hydrochloric Acid/pharmacology , Implants, Experimental , Titanium/chemistry , Alloys , Animals , Biomedical and Dental Materials/chemical synthesis , Biomedical and Dental Materials/chemistry , Bone Screws , Bone-Implant Interface , Coated Materials, Biocompatible/chemical synthesis , Dental Implantation, Endosseous/instrumentation , Dental Implants , Female , Osseointegration , Porosity/drug effects , Rabbits , Surface Properties/drug effectsABSTRACT
Avian eggshells may break easily when impacted at a localized point; however, they exhibit impressive resistance when subjected to a well-distributed compressive load. For example, a common demonstration of material strength is firmly squeezing a chicken egg along its major axis between one's hands without breaking it. This research provides insight into the underlying mechanics by evaluating both macroscopic and microstructural features. Eggs of different size, varying from quail (30 mm) to ostrich (150 mm), are investigated. Compression experiments were conducted along the major axis of the egg using force-distributing rubber cushions between steel plates and the egg. The force at failure increases with egg size, reaching loads upwards of 5000 N for ostrich eggs. The corresponding strength, however, decreases with increasing shell thickness (intimately related to egg size); this is rationalized by a micro-defects model. Failure occurs by axial splitting parallel to the loading direction-the result of hoop tensile stresses due to the applied compressive load. Finite-element analysis is successfully employed to correlate the applied compressive force to tensile breaking strength for the eggs, and the influence of geometric ratio and microstructural heterogeneities on the shell's strength and fracture toughness is established.
Subject(s)
Ceramics/chemistry , Compressive Strength , Egg Shell/chemistry , Ovum/chemistry , Stress, Mechanical , Animals , ChickensABSTRACT
OBJECTIVES: To compare the sliding resistance forces produced by polycarbonate self-ligating brackets with esthetic archwires. MATERIALS AND METHODS: Samples of Opal, Oyster and conventional Blonde brackets were tested each one with 30 segments of .018x.025-in wires. The archwires were slipped at 8mm/min for 40 seconds with an universal testing machine. Two way ANOVA with Bonferroni correction were used. RESULTS: Blonde brackets presented the highest sliding resistance, followed in decreasing order by Oyster and Opal. The TP Shiny Bright Wire produced the highest surface friction, while the lowest was observed for Imagination archwires (except for Opal brackets where the TP Pearltone Wire achieved the best performance). CONCLUSIONS: Self-ligating system is more effective to reduce the sliding force resistance than conventional brackets. Esthetic stainless steel archwires produce less friction resistance than those without surface treatment. Polycarbonate self-ligating brackets are more effective to reduce the frictional forces than esthetic archwires with surface treatment.
Subject(s)
Dental Alloys/chemistry , Dental Materials/chemistry , Orthodontic Appliance Design , Orthodontic Brackets , Orthodontic Wires , Polymers/chemistry , Stainless Steel/chemistry , Dental Stress Analysis/instrumentation , Friction , Glass/chemistry , Humans , Materials Testing , Models, Anatomic , Stress, Mechanical , Surface Properties , Tensile Strength , Time FactorsABSTRACT
OBJECTIVE: The aim of this study was to assess resistance to sliding of stainless steel passive self-ligating brackets with 0° and 2.5° angulations and to compare them to active self-ligating brackets at zero angulation. The hypothesis to be tested was that passive self-ligating brackets produce lower frictional forces than active self-ligating brackets. METHODS: Twenty five 0.022 x 0.028-in slot maxillary canine brackets were divided into 5 groups of 5 brackets: Damon SL II (Ormco, CA, USA) self-ligating bracket and Gemini (3M/Unitek, CA, USA) conventional bracket with angulation of 0 and 2.5° and a group of Speed 2 (American Orthodontics, WI, USA) active clip self-ligating system with zero angulation. Twenty five segments of stainless steel 0.020-in archwire (TP Orthodontics, IN, USA) were tested and each bracket/wire interface was evaluated at 4 successive points during sliding. Overall, 100 frictional values were analyzed by parametric analysis of variance and Bonferroni tests. RESULTS AND CONCLUSION: Frictional tests were performed with an Emic DL 10000 testing machine (Emic, Brazil) with a load cell of one kilogram. Passive self-ligating brackets produced lower frictional forces than active self-ligating brackets (p < 0.01). Under angulation, brackets with a slide mechanism produced higher friction than the same brackets under zero angulation (p < 0.01). Nevertheless, the slide system under angulation produced smaller friction values than conventional brackets tied with elastomeric ligatures in 0° tests.
OBJETIVO: avaliar a fricção apresentada por braquetes autoligáveis de aço inoxidável com sistema passivo de tampa deslizante sob angulação de 0 grau e 2,5 graus, e comparar o comportamento desse grupo sob angulação nula com o de um grupo de braquetes autoligáveis com sistema ativo de tampa resiliente. MÉTODOS: foram utilizados 25 braquetes de caninos superiores, divididos em 5 grupos - braquetes autoligáveis passivos Damon SL II sob angulação de 0 grau e de 2,5 graus; braquetes convencionais Gemini amarrados com ligaduras elásticas sob as mesmas angulações; e um grupo formado pelo sistema ativo Time 2, sob angulação nula. A hipótese a ser testada é se artefatos autoligáveis com sistema de tampa passiva são mais efetivos no controle da fricção do que dispositivos contendo coberturas ativas. O tracionamento foi realizado segundo emprego de 25 segmentos de fio de aço inoxidável 0,020" na máquina de ensaios EMIC DL 10000 com célula de carga de 2,0kg. Cada conjunto braquete/fio foi responsável pela geração de quatro corpos de prova, totalizando-se 100 leituras. As comparações entre médias dos valores foram realizadas através da Análise de Variância (one-way ANOVA) com correções pelo coeficiente de Bonferroni. RESULTADOS E CONCLUSÃO: as médias de fricção encontradas confirmaram a hipótese em teste, de que o sistema de braquetes Damon SL II é mais eficiente no controle do atrito do que o sistema de tampa ativa sob angulação de 0 grau (p<0,01). Quando submetidos a angulações de 2,5 graus, a fricção aumentou significativamente (p<0,01), porém mantendo-se ainda muito inferior aos patamares evidenciados no grupo de braquetes convencionais amarrados com ligaduras elásticas.
ABSTRACT
Nickel-titanium (NiTi) shape-memory alloys (SMAs) have been used in the manufacture of orthodontic wires due to their shape memory properties, super-elasticity, high ductility, and resistance to corrosion. SMAs have greater strength and lower modulus of elasticity when compared with stainless steel alloys. The pseudoelastic behavior of NiTi wires means that on unloading they return to their original shape by delivering light continuous forces over a wider range of deformation which is claimed to allow dental displacements. The aim of this paper is to discuss the physical, metallurgical, and mechanical properties of NiTi used in Orthodontics in order to analyze the shape memory properties, super-elasticity, and thermomechanical characteristics of SMA.
ABSTRACT
To evaluate force extension relaxation of different brands and diameters of latex elastics subjected to static tensile testing under an apparatus designed to simulate oral environments, sample sizes of 5 elastics from American Orthodontics (AO), Tp, and Morelli Orthodontics (Mo) of equivalent medium force, (3/16, 1/4, and 5/16 inch size) were tested. The forces were read after 1-, 3-, 6-, 12- and 24-hour periods in Emic testing machine with 30 mm/min cross-head speed and load cell of 20 N. Two-way ANOVA and Bonferroni tests were used to identify statistical significance. There were statistically differences among different manufacturers at all observation intervals (P < 0.0001). The relationships among loads at 24-hour time period were as follows: Morelli>AO>Tp for 3/16, 1/4, and 5/16 elastics. The force decay pattern showed a notable drop-off of forces until 3 hours, a slight increase in some groups from 3-6 hours and a more homogeneous force pattern over 6-24 hours.
ABSTRACT
OBJETIVO: o objetivo do presente trabalho foi determinar a força de atrito estático entre braquetes de aço inoxidável autoligados com sistema de fechamento resiliente e fios ortodônticos redondos e retangulares do mesmo material. MÉTODOS: empregaram-se 30 braquetes referentes aos caninos superiores divididos em 6 grupos formados por braquetes autoligados Smartclip, In-Ovation R e convencionais Gemini amarrados com ligaduras elásticas. A hipótese testada neste trabalho foi quanto à possibilidade dos braquetes autoligados ativos serem suscetíveis à elevação da força de atrito com o aumento e alteração da secção transversal dos fios ortodônticos. Os ensaios foram realizados com tração de 30s em fios de aço inoxidável 0,020" e 0,019"X0,025" na máquina de ensaios Emic DL 10000, com uma célula de carga de 20 newtons. Cada conjunto braquete/fio foi responsável pela geração de quatro corpos de prova, totalizando 120 leituras. As comparações entre as médias foram realizadas através da Análise de Variância (one way ANOVA) com correções pelo coeficiente de Bonferroni. RESULTADOS E CONCLUSÃO: os braquetes autoligados apresentaram maior força de atrito do que os braquetes convencionais amarrados com ligaduras elásticas. O grupo Smartclip foi o mais efetivo no controle do atrito (p<0,01). A hipótese em teste, influência da forma da seção transversal do fio na força de atrito, foi confirmada, uma vez que os fios de secção retangular 0,019"X0,025" apresentaram maior força de atrito ao serem tracionados do que os fios redondos 0,020" (p<0,01). O sistema Smartclip foi mais efetivo mesmo quando o tracionamento de fios retangulares foi comparado com o ensaio de braquetes In-Ovation R conjugados a fios redondos (p<0,01).
OBJECTIVES: The purpose of this study was to assess the surface friction produced by self-ligating stainless steel brackets equipped with a resilient closure system and compare the friction generated during traction of round and rectangular orthodontic wires made from the same material. METHODS: Thirty maxillary canine brackets were divided into six groups comprising SmartClip and In-Ovation R self-ligating brackets, and conventional Gemini brackets tied with elastomeric ligatures. This investigation tested the hypothesis that self-ligating brackets are susceptible to increases in friction that are commensurate with increases and changes in the cross-section of orthodontic wires. Traction was performed with the aid of thirty segments of 0.020" and 0.019" x 0.025" stainless steel wires in an EMIC DL 10000 testing machine with a 2N load cell. Each set of bracket/wire generated four samples, totaling 120 readings. Comparisons between means were performed using analysis of variance (one way ANOVA) corrected with the Bonferroni coefficient. RESULTS AND CONCLUSION: The self-ligating brackets exhibited lower friction than conventional brackets tied with elastomeric ligatures. The SmartClip group was the most effective in controlling friction (p <0.01). The hypothesis under test was confirmed to the extent that the traction performed with rectangular 0.019" x 0.025" cross-section wires resulted in higher friction forces than those observed in the 0.020" round wire groups (p<0.01). The SmartClip system was more effective even when the traction produced by rectangular wires was compared with the In-Ovation R brackets combined with round wires (p<0.01).
Subject(s)
Orthodontic Brackets , Friction , Orthodontic Wires , Stainless Steel , OrthodonticsABSTRACT
OBJECTIVE: To evaluate the force extension relaxation of different manufacturers and diameters of latex elastics subjected to static tensile testing under dry and wet conditions. MATERIALS AND METHODS: Sample sizes of 15 elastics from American Orthodontics (AO) (Sheboygan, Wis), TP (La Porte, Ind), and Morelli Orthodontics (Sorocaba SP, Brazil) were used. Equivalent medium force products were tested--3/16, 1/4, and 5/16 inch lumen size from each manufacturer--making a total of 1080 specimens. An apparatus was designed to simulate oral environments during elastics stretching. Forces were read after 1, 3, 6, 12, and 24 hour periods using the Emic Testing Machine (Emic Co., Sao Paulo, Brazil) with 30 mm/min cross-head speed and load cell of 20 N (Emic Co). Kruskal-Wallis and Dunn's tests were used to identify statistical significance. RESULTS: Statistical differences between AO and the other brands were noted for all testing times. Significant variation in mechanical properties was observed in latex elastics from Morelli. Relationships among loads at the 0 hour time period were as follows: Morelli>AO>TP for 3/16 elastics (P = .0016), 1/4 elastics (P = .0016), and 5/16 elastics (P = .0087). CONCLUSION: Significant differences in force extension relaxation were noted for elastics from these manufacturers. Force relaxation over the 24 hour time period was AO>Morelli>TP for 3/16 elastics, AO>TP>Morelli for 1/4 elastics, and TP>AO>Morelli for 5/16 elastics. The force decay pattern showed a notable drop-off of forces during 0 to 3 hours, a slight increase in force values from 3 to 6 hours, and a progressive force reduction over 6 to 24 hours.
Subject(s)
Latex/chemistry , Orthodontic Appliances , Rubber/chemistry , Dental Stress Analysis/instrumentation , Desiccation , Elastic Modulus , Humans , Humidity , Materials Testing , Orthodontic Appliance Design , Stress, Mechanical , Surface Properties , Temperature , Tensile Strength , Time Factors , Water/chemistryABSTRACT
AIM: To evaluate the frictional forces generated by ceramic- (Opal, Ultradent) and glass-fiber-reinforced polycarbonate self-ligating brackets (Oyster, Gestenco) and compare the effectiveness of these ligatureless systems with glass-fiber-reinforced polycarbonate conventional brackets (Blonde, Gestenco). The hypothesis is that there is no difference between frictional forces generated by ceramic- and glass-fiber-reinforced polycarbonate self-ligating and glass-fiber-reinforced polycarbonate conventional brackets. METHODS: Twelve preadjusted 0.022 3 0.028-inch maxillary canine brackets were tested, divided into three groups: Opal, Oyster, and Blonde. Frictional tests were conducted with the Emic DL 10000 testing machine with a 20 N loadcell for 40 seconds at a 0.5 cm/min speed. Each bracket-wire combination was tested five times. The data generated were analyzed by parametric analysis of variance (one-way ANOVA) and Bonferroni tests. RESULTS: Analysis of variance indicated significant differences for the three groups (P<.01). The frictional forces of the Oyster glass-fiber-reinforced polycarbonate self-ligating brackets were significantly lower (37.0 ± 8.9 cN) than those of the Opal ceramic-reinforced polycarbonate self-ligating brackets (49.5 ± 10.1 cN), while the Blonde glass-fiber-reinforced conventional bracket frictional forces were 105.8 ± 6.4 cN. CONCLUSION: Oyster glass-fiber-reinforced polycarbonate brackets produced less friction than Opal ceramic-reinforced polycarbonate brackets. The polycarbonate ligatureless system showed significantly lower frictional forces compared to Blonde conventional polycarbonate brackets tied with elastomeric ligatures. The study rejected the initial hypothesis because there are significant differences of frictional forces among the tested systems.
Subject(s)
Orthodontic Appliance Design , Orthodontic Brackets , Polycarboxylate Cement/chemistry , Ceramics/chemistry , Dental Alloys/chemistry , Dental Stress Analysis/instrumentation , Elastomers/chemistry , Friction , Glass/chemistry , Humans , Materials Testing , Orthodontic Wires , Stainless Steel/chemistry , Stress, Mechanical , Surface PropertiesABSTRACT
ß(2)-adrenergic receptors (ß(2)-AR) are low abundance, integral membrane proteins that mediate the effects of catecholamines at the cell surface. Whereas the processes governing desensitization of activated ß(2)-ARs and their subsequent removal from the cell surface have been characterized in considerable detail, little is known about the mechanisms controlling trafficking of neo-synthesized receptors to the cell surface. Since the discovery of the signal peptide, the targeting of the integral membrane proteins to plasma membrane has been thought to be determined by structural features of the amino acid sequence alone. Here we report that localization of translationally silenced ß(2)-AR mRNA to the peripheral cytoplasmic regions is critical for receptor localization to the plasma membrane. ß(2)-AR mRNA is recognized by the nucleocytoplasmic shuttling RNA-binding protein HuR, which silences translational initiation while chaperoning the mRNA-protein complex to the cell periphery. When HuR expression is down-regulated, ß(2)-AR mRNA translation is initiated prematurely in perinuclear polyribosomes, leading to overproduction of receptors but defective trafficking to the plasma membrane. Our results underscore the importance of the spatiotemporal relationship between ß(2)-AR mRNA localization, translation, and trafficking to the plasma membrane, and establish a novel mechanism whereby G protein-coupled receptor (GPCR) responsiveness is regulated by RNA-based signals.
Subject(s)
Cell Membrane/metabolism , Receptors, G-Protein-Coupled/metabolism , Animals , Antigens, Surface/metabolism , Biological Transport , CHO Cells , Cell Line, Tumor , Cricetinae , Cricetulus , ELAV Proteins , ELAV-Like Protein 1 , Humans , Models, Biological , Polyribosomes/metabolism , Protein Binding , Protein Sorting Signals , RNA-Binding Proteins/metabolism , Receptors, Adrenergic, beta-2/metabolismABSTRACT
The antiapoptotic Bcl-2 protein is overexpressed in a variety of cancers, particularly leukemias. In some cell types this is the result of enhanced stability of bcl-2 mRNA, which is controlled by elements in its 3'-untranslated region. Nucleolin is one of the proteins that binds to bcl-2 mRNA, thereby increasing its half-life. Here, we examined the site on the bcl-2 3'-untranslated region that is bound by nucleolin as well as the protein binding domains important for bcl-2 mRNA recognition. RNase footprinting and RNA fragment binding assays demonstrated that nucleolin binds to a 40-nucleotide region at the 5' end of the 136-nucleotide bcl-2 AU-rich element (ARE(bcl-2)). The first two RNA binding domains of nucleolin were sufficient for high affinity binding to ARE(bcl-2). In RNA decay assays, ARE(bcl-2) transcripts were protected from exosomal decay by the addition of nucleolin. AUF1 has been shown to recruit the exosome to mRNAs. When MV-4-11 cell extracts were immunodepleted of AUF1, the rate of decay of ARE(bcl-2) transcripts was reduced, indicating that nucleolin and AUF1 have opposing roles in bcl-2 mRNA turnover. When the function of nucleolin in MV-4-11 cells was impaired by treatment with the nucleolin-targeting aptamer AS1411, association of AUF1 with bcl-2 mRNA was increased. This suggests that the degradation of bcl-2 mRNA induced by AS1411 results from both interference with nucleolin protection of bcl-2 mRNA and recruitment of the exosome by AUF1. Based on our findings, we propose a model that illustrates the opposing roles of nucleolin and AUF1 in regulating bcl-2 mRNA stability.
Subject(s)
3' Untranslated Regions , Heterogeneous-Nuclear Ribonucleoprotein D/metabolism , Models, Biological , Phosphoproteins/metabolism , Proto-Oncogene Proteins c-bcl-2/biosynthesis , RNA Stability/physiology , RNA-Binding Proteins/metabolism , Aptamers, Nucleotide , HeLa Cells , Heterogeneous Nuclear Ribonucleoprotein D0 , Heterogeneous-Nuclear Ribonucleoprotein D/genetics , Humans , Leukemia/genetics , Leukemia/mortality , Oligodeoxyribonucleotides/pharmacology , Phosphoproteins/antagonists & inhibitors , Phosphoproteins/genetics , Protein Binding/drug effects , Protein Binding/physiology , Protein Structure, Tertiary , Proto-Oncogene Proteins c-bcl-2/genetics , RNA Stability/drug effects , RNA, Neoplasm/genetics , RNA, Neoplasm/metabolism , RNA-Binding Proteins/antagonists & inhibitors , RNA-Binding Proteins/genetics , NucleolinABSTRACT
Overexpression of the proto-oncogene bcl-2 promotes abnormal cell survival by inhibiting apoptosis. Expression of bcl-2 is determined, in part, by regulatory mechanisms that control the stability of bcl-2 mRNA. Elements in the 3'-untranslated region of bcl-2 mRNA have been shown to play a role in regulating the stability of the message. Previously, it was found that the RNA binding proteins nucleolin and Ebp1 have a role in stabilizing bcl-2 mRNA in HL60 cells. Here, we have identified HuR as a component of bcl-2 messenger ribonucleoprotein (mRNP) complexes. RNA coimmunoprecipitation assays showed that HuR binds to bcl-2 mRNA in vivo. We also observed an RNA-dependent coprecipitation of HuR and nucleolin, suggesting that the two proteins are present in common mRNP complexes. Moreover, nucleolin and HuR bind concurrently to bcl-2 AU-rich element (ARE) RNA in vitro, suggesting separate binding sites for these proteins on bcl-2 mRNA. Knockdown of HuR in A431 cells leads to down-regulation of bcl-2 mRNA and protein levels. Observation of a decreased ratio of bcl-2 mRNA to heterogeneous nuclear RNA in HuR knockdown cells confirmed a positive role for HuR in regulating bcl-2 stability. Recombinant HuR retards exosome-mediated decay of bcl-2 ARE RNA in extracts of HL60 cells. This supports a role for HuR in the regulation of bcl-2 mRNA stability in HL60 cells, as well as in A431 cells. Addition of nucleolin and HuR to HL60 cell extracts produced a synergistic protective effect on decay of bcl-2 ARE RNA. HuR knockdown also leads to redistribution of bcl-2 mRNA from polysomes to monosomes. Thus, HuR seems to play a positive role in both regulation of bcl-2 mRNA translation and mRNA stability.
Subject(s)
Antigens, Surface/metabolism , Carcinoma, Squamous Cell/pathology , Leukemia/pathology , Proto-Oncogene Proteins c-bcl-2/genetics , Proto-Oncogene Proteins c-bcl-2/metabolism , RNA-Binding Proteins/metabolism , Carcinoma, Squamous Cell/genetics , Centrifugation, Density Gradient , ELAV Proteins , ELAV-Like Protein 1 , Gene Expression Regulation, Neoplastic , Gene Knockdown Techniques , HL-60 Cells , Humans , Immunoprecipitation , Leukemia/genetics , Phosphoproteins/metabolism , Polyribosomes/metabolism , Protein Binding , Proto-Oncogene Mas , RNA Stability , RNA, Messenger/genetics , RNA, Messenger/metabolism , RNA, Neoplasm/metabolism , RNA, Small Interfering/metabolism , Recombinant Proteins/metabolism , Regulatory Sequences, Ribonucleic Acid/genetics , NucleolinABSTRACT
AS1411 is a DNA aptamer that is in phase II clinical trials for relapsed or refractory acute myeloid leukemia and for renal cell carcinoma. AS1411 binds to nucleolin, a protein that is overexpressed in the cytoplasm and on the plasma membrane of some tumor cells compared with normal cells. Studies were performed to determine whether cell surface nucleolin is a receptor for AS1411 in the acute myeloid leukemia cell line MV4-11. Biotinylation of MV4-11 cell surface proteins followed by immunoblotting of the biotinylated proteins showed that full-length (106 kDa) and truncated forms of nucleolin were present on the cell surface. In contrast, K-562 cells, which are 4-fold less sensitive than MV4-11 cells to AS1411, showed no full-length nucleolin and lesser amounts of the truncated forms of nucleolin on the cell surface. Incubation of MV4-11 cells with [(32)P]AS1411 and immunoprecipitation of the plasma membrane fraction with anti-nucleolin antibody demonstrated the presence of [(32)P]AS1411-nucleolin complexes. Anti-nucleolin antibody inhibited binding of fluorescein isothiocyanate (FITC)-AS1411 to plasma membrane nucleolin 56 +/- 10% SE (P < 0.01) compared with cells incubated with FITC-AS1411 only. Cellular uptake of [(32)P]AS1411 into MV4-11 cells was blocked by a 20-fold excess of unlabeled AS1411 but not by a 20-fold excess of the biologically inactive oligonucleotide CRO-26. Uptake was approximately 3-fold faster into MV4-11 cells than into K-562 cells. Partial knockdown of plasma membrane and cytosolic nucleolin in MCF-7 cells resulted in a 3-fold decrease in AS1411 uptake. These results provide evidence that plasma membrane nucleolin is a functional receptor for AS1411 in MV4-11 cells.
Subject(s)
Antineoplastic Agents/metabolism , Aptamers, Nucleotide/metabolism , Leukemia, Myeloid, Acute/metabolism , Membrane Proteins/metabolism , Oligodeoxyribonucleotides/metabolism , Phosphoproteins/metabolism , RNA-Binding Proteins/metabolism , Animals , Antineoplastic Agents/pharmacology , Antineoplastic Agents/therapeutic use , Aptamers, Nucleotide/pharmacology , Aptamers, Nucleotide/therapeutic use , Cell Line, Tumor , Humans , K562 Cells , Leukemia, Myeloid, Acute/drug therapy , Mice , Oligodeoxyribonucleotides/pharmacology , Oligodeoxyribonucleotides/therapeutic use , Protein Binding/drug effects , Protein Binding/physiology , Receptors, Cell Surface/metabolism , NucleolinSubject(s)
Gene Expression Regulation, Leukemic , Leukemia, Myeloid, Acute/metabolism , Phosphoproteins/biosynthesis , RNA-Binding Proteins/biosynthesis , Animals , Female , Humans , Leukemia, Myeloid, Acute/pathology , Male , Mice , Mice, Inbred NOD , Mice, SCID , Neoplasm Transplantation , Proto-Oncogene Proteins c-bcl-2/metabolism , NucleolinSubject(s)
Composite Resins , Molar/pathology , Orthodontic Appliance Design , Orthodontic Appliances , Orthodontic Wires , Tooth Movement Techniques/methods , Tooth, Impacted/therapy , Child , Female , Humans , Orthodontic Appliances, Removable , Stainless Steel , Tooth Movement Techniques/instrumentationABSTRACT
INTRODUÇÃO: os braquetes autoligáveis foram, inicialmente, idealizados com objetivo de otimização do tempo de atendimento clínico. Por dispensar qualquer tipo de amarração, inúmeras vantagens foram atribuidas a este sistema, com a redução da fricção superficial na interface braquete/fio ortodôntico. Com esta redução, são necessárias forças de menor intensidade para o estabelecimento da movimentação dentária, realizada, assim, de uma forma mais rápida e eficiente. Em decorrência da maior demanda estética por parte dos pacientes, os braquetes autoligáveis começaram a ser confeccionados em policarbonato, promovendo ganhos estéticos únicos, quando em comparação a seus anólogos metálicos. OBJETIVO: realizar uma revisão de literatura sobre o sistema de braquetes autoligáveis estéticos.
INTRODUCTION: The self-ligating system was introduced aiming the reduction of chair time. Once this system does not need any ligation form, several advantages were observed, such as the reduction on superficial friction in couple bracket/ orthodontic wire, and the reduction on the force level that is necessary to establish the orthodontic tooth movement. The growing demands of aesthetic patients induced the self-ligating system to be made of polycarbonate material, resulting in unique aesthetic advantages when compared with the metallic form of this system. AIM: The objective of this paper was to proceed with a literature review about aesthetic self-ligating brackets.
Subject(s)
Orthodontic Brackets/trends , Esthetics, Dental , Dental Materials , FrictionABSTRACT
We sought to determine whether nucleolin, a bcl-2 mRNA-binding protein, has a role in the regulation of bcl-2 mRNA stability in MCF-7 and MDA-MB-231 breast cancer cells. Furthermore, we examined the efficacy of the aptamer AS1411 in targeting nucleolin and inducing bcl-2 mRNA instability and cytotoxicity in these cells. AS1411 at 5 micromol/L inhibited the growth of MCF-7 and MDA-MB-231 cells, whereas 20 micromol/L AS1411 had no effect on the growth rate or viability of normal MCF-10A mammary epithelial cells. This selectivity of AS1411 was related to a greater uptake of AS1411 into the cytoplasm of MCF-7 cells compared with MCF-10A cells and to a 4-fold higher level of cytoplasmic nucleolin in MCF-7 cells. Stable siRNA knockdown of nucleolin in MCF-7 cells reduced nucleolin and bcl-2 protein levels and decreased the half-life of bcl-2 mRNA from 11 to 5 hours. Similarly, AS1411 (10 micromol/L) decreased the half-life of bcl-2 mRNA in MCF-7 and MDA-MB-231 cells to 1.0 and 1.2 hours, respectively. In contrast, AS1411 had no effect on the stability of bcl-2 mRNA in normal MCF-10A cells. AS1411 also inhibited the binding of nucleolin to the instability element AU-rich element 1 of bcl-2 mRNA in a cell-free system and in MCF-7 cells. Together, the results suggest that AS1411 acts as a molecular decoy by competing with bcl-2 mRNA for binding to cytoplasmic nucleolin in these breast cancer cell lines. This interferes with the stabilization of bcl-2 mRNA by nucleolin and may be one mechanism by which AS1411 induces tumor cell death.
Subject(s)
Breast Neoplasms/therapy , Genes, bcl-2 , Oligodeoxyribonucleotides/pharmacology , Phosphoproteins/antagonists & inhibitors , Phosphoproteins/genetics , RNA, Messenger/metabolism , RNA-Binding Proteins/antagonists & inhibitors , RNA-Binding Proteins/genetics , Apoptosis/drug effects , Apoptosis/genetics , Aptamers, Nucleotide , Breast Neoplasms/genetics , Breast Neoplasms/metabolism , Cell Line, Tumor , Humans , Oligodeoxyribonucleotides/genetics , Phosphoproteins/biosynthesis , Phosphoproteins/metabolism , Proto-Oncogene Proteins c-bcl-2/biosynthesis , Proto-Oncogene Proteins c-bcl-2/genetics , RNA, Messenger/genetics , RNA-Binding Proteins/biosynthesis , RNA-Binding Proteins/metabolism , NucleolinABSTRACT
O objetivo deste artigo foi realizar uma revisão de literatura sobre o processo de soldagem autógena em Ortodontia. A soldagem autógena, muito presente no cotidiano clínico, viabiliza a união de dispositivos, principalmente de aço inoxidável, necessários à realização da mecânica ortodôntica. A técnica foi descrita juntamente com as modificações apresentadas pelos componentes envolvidos no processo. Comparou-se, também, tal procedimento com a soldagem heterógena, evidenciando-se uma menor ocorrência de alterações estruturais nos elementos envolvidos, bem como uma menor subordinação da técnica à destreza do operador.
Subject(s)
Stainless Steel , Metallurgy , Dental Soldering/methodsABSTRACT
Objetivou-se neste trabalho realizar uma revisão de literatura sobre o processo de soldagem em Ortodontia, pelo fato do mesmo só ser conhecido sob um enfoque empírico. A técnica de soldagem é universalmente aceita e de resultados clinicamente eficazes. Descreveu-se não somente a técnica em si, mas também o comportamento de todos os componentes qua a interagem durante o procedimento de soldagem, incluindo alterações atômicas, mecânicas e físicas. Abordou-se o processo de soldagem a ouro por ter sido o percursor em Ortodontia de todas as outras técnicas envolvendo solda, além de demandar grande habilidade manual, por ser um procedimento de extrema complexidade de execução. Comparou-se também tais procedimentos com a soldagem autógena, avaliando-se vantagens e desvantagens clínicas de seu emprego. Não foram observadas alterações significativas nas características físico-estruturais dos elementos a serem soldados heteroginamente, não havendo assim, nenhuma desvantagem relevante em relação à soldagem autógena
Subject(s)
Gold , Metallurgy , Silver , Dental Soldering/methodsABSTRACT
B-cell chronic lymphocytic leukemia (CLL) is characterized by the accumulation of clonal B cells that are resistant to apoptosis as a result of bcl2 oncogene overexpression. Studies were done to determine the mechanism for the up-regulation of bcl-2 protein observed in CD19+ CLL cells compared with CD19+ B cells from healthy volunteers. The 11-fold higher level of bcl-2 protein in CLL cells was positively correlated with a 26-fold elevation in the cytosolic level of nucleolin, a bcl2 mRNA-stabilizing protein. Measurements of the bcl2 heterogeneous nuclear/bcl2 mRNA (hnRNA)/mRNA ratios and the rates of bcl2 mRNA decay in cell extracts indicated that the 3-fold higher steady-state level of bcl2 mRNA in CLL cells was the result of increased bcl2 mRNA stability. Nucleolin was present throughout the nucleus and cytoplasm of CLL cells, whereas in normal B cells nucleolin was only detected in the nucleus. The addition of recombinant human nucleolin to extracts of normal B cells markedly slowed the rate of bcl2 mRNA decay. SiRNA knockdown of nucleolin in MCF-7 cells resulted in decreased levels of bcl2mRNA and protein but no change in beta-actin. These results indicate that bcl-2 overexpression in CLL cells is related to stabilization of bcl2 mRNA by nucleolin.
