Perception of the relationship between TMD and orthodontic treatment among orthodontists

INTRODUCTION: The consensus about the relationship between TMD and orthodontic treatment has gone from a cause and effect association between TMD and orthodontic treatment to the idea that there is no reliable evidence supporting this statement. OBJECTIVE: To assess the beliefs, despite scientific evidence, of Brazilian orthodontists about the relationship between TMD and orthodontic treatment with regards to treatment, prevention and etiology of TMD. METHODS: A survey about the relationship between TMD and orthodontic treatment was prepared and sent to Brazilian orthodontists by e-mail and social networks. Answers were treated by means of descriptive statistics and strong associations between variables were assessed by qui-square test. RESULTS: The majority of orthodontists believe that orthodontic treatment not only is not the best treatment option for TMD, but also is not able to prevent TMD. Nevertheless, the majority of orthodontists believe that orthodontic treatment can cause TMD symptoms. CONCLUSION: This study suggests that orthodontists' beliefs about the relationship between orthodontic treatment and TMD are in accordance with scientific evidence only when referring to treatment and prevention of TMD. The majority of orthodontists believe that, despite scientific evidence, orthodontic treatment can cause TMD. .

INTRODUÇÃO: o consenso sobre a relação entre DTM e tratamento ortodôntico foi de uma associação de causa e efeito à ideia de que não há evidências confiáveis que suportem essa afirmação. OBJETIVO: avaliar as crenças, sem considerar as evidências, de ortodontistas brasileiros sobre a relação entre DTM e tratamento ortodôntico com relação ao tratamento, prevenção e etiologia da DTM. MÉTODOS: um questionário sobre a relação entre DTM e tratamento ortodôntico foi preparado e enviado a ortodontistas brasileiros por meio de e-mail e mídias sociais. As respostas foram analisadas por estatística descritiva, e fortes associações entre as variáveis foram verificadas pelo teste χ2. RESULTADOS: a maioria dos ortodontistas acredita que o tratamento ortodôntico não é o melhor tratamento para DTM. Além disso, acreditam que não é a melhor forma para sua prevenção. Também, a maioria dos ortodontistas acredita que o tratamento ortodôntico pode causar sintomas de DTM. CONCLUSÃO: este estudo sugere que as crenças dos ortodontistas sobre a relação entre tratamento ortodôntico e DTM estão de acordo com as evidências científicas apenas quando se trata do tratamento e da prevenção de DTM. A maioria dos ortodontistas acredita que, apesar das evidências científicas, o tratamento ortodôntico pode causar DTM. .

Intrinsic bent DNA sites in the chromosomal replication origin of Xylella fastidiosa 9a5c

The features of the nucleotide sequences in both replication and promoter regions have been investigated in many organisms. Intrinsically bent DNA sites associated with transcription have been described in several prokaryotic organisms. The aim of the present study was to investigate intrinsic bent DNA sites in the segment that holds the chromosomal replication origin, oriC, of Xylella fastidiosa 9a5c. Electrophoretic behavior analyses, as well as in silico analyses of both the 2-D projection and helical parameters, were performed. The chromosomal segment analyzed contains the initial sequence of the rpmH gene, an intergenic region, the dnaA gene, the oriC sequence, and the 5' partial sequence of the dnaN gene. The analysis revealed fragments with reduced electrophoretic mobility, which indicates the presence of curved DNA segments. The analysis of the helical parameter ENDS ratio revealed three bent DNA sites (b1, b2, and b3) located in the rpmH-dnaA intergenic region, the dnaA gene, and the oriC 5' end, respectively. The chromosomal segment of X. fastidiosa analyzed here is rich in phased AT tracts and in CAnT motifs. The 2-D projection indicated a segment whose structure was determined by the cumulative effect of all bent DNA sites. Further, the in silico analysis of the three different bacterial oriC sequences indicated similar negative roll and twist >34.00° values. The DnaA box sequences, and other motifs in them, may be associated with the intrinsic DNA curvature.

Mapping autonomously replicating sequence elements in a 73-kb region of chromosome II of the fission yeast, Schizosaccharomyces pombe.

Autonomously replicating sequence (ARS) elements are the genetic determinants of replication origin function in yeasts. They can be easily identified as the plasmids containing them transform yeast cells at a high frequency. As the first step towards identifying all potential replication origins in a 73-kb region of the long arm of fission yeast chromosome II, we have mapped five new ARS elements using systematic subcloning and transformation assay. 2D analysis of one of the ARS plasmids that showed highest transformation frequency localized the replication origin activity within the cloned genomic DNA. All the new ARS elements are localized in two clusters in centromere proximal 40 kb of the region. The presence of at least six ARS elements, including the previously reported ars727, is suggestive of a higher origin density in this region than that predicted earlier using a computer based search.

The chromatin structure of the lysozyme GAS41 origin of DNA replication changes during the cell cycle

We used a rapid and simple protocol using lysolecithin for mapping HS sites in vivo. The protocol is based on partial digestion with DNase I of exponentially growing cells following permeabilization by short treatment with lysolecithin. Using this protocol, we analyzed the chromatin structure of the region surrounding two overlapping elements, an origin of bidirectional DNA replication and the GAS41 promoter, in chicken myelomonocytic HD11 cells arrested in G0, G0 and S phases as well as at the G0/S border. The results show that the chromatin of this region became more nuclease sensitive when cells were arrested in G0 phase and that this change in chromatin structure was reversible after the cells began to enter S phase.

Cell cycle, DNA replication, repair, and recombination in the dimorphic human pathogenic fungus Paracoccidioides brasiliensis

DNA replication, together with repair mechanisms and cell cycle control, are the most important cellular processes necessary to maintain correct transfer of genetic information to the progeny. These processes are well conserved throughout the Eukarya, and the genes that are involved provide essential information for understanding the life cycle of an organism. We used computational tools for data mining of genes involved in these processes in the pathogenic fungus Paracoccidiodes brasiliensis. Data derived from transcriptome analysis revealed that the cell cycle of this fungus, as well as DNA replication and repair, and the recombination machineries, are highly similar to those of the yeast Saccharomyces cerevisiae. Among orthologs detected in both species, there are genes related to cytoskeleton structure and assembly, chromosome segregation, and cell cycle control genes. We identified at least one representative gene from each step of the initiation of DNA replication. Major players in the process of DNA damage and repair were also identified.

Cell cycle control and cancer.

This review consists of two parts. In the first part normal mechanisms regulating the progression of cells through the cell cycle are briefly reviewed. Besides mitogenic stimulation, cyclin kinase inhibition, the G1 restriction point and the prb pathway, accuracy of DNA replication and DNA repair, the G2 to M transition, apoptosis and the p 53 pathway, proteolytic, in particular ubiquitin-dependent mechanisms involved in the initiation of DNA synthesis in the separation of sister chromatids and in the telophase to GO/G1 transition, are discussed. In the second part oncogene and tumor suppressor gene products are briefly characterized. Aberrations of cell cycle control mechanisms associated with cancer are grouped as follows: deregulation of protooncogenes by translocations juxtaposing protooncogenes to immunoglobulin--or T cell receptor genes; translocations producing chimeric proteins unique to cancer cells; inversions and amplifications resulting in over expression of regulator genes; and deletions and mutations of tumor suppressor genes. It is emphasized that cancer is the result of a multistep process and that uncontrolled cell production and other alterations are, as a rule, late phenomena.

Regulation of DNA replication initiation in mammalian lymphocyte systems.

The control of DNA replication is central to the control of cell proliferation, and defects in S phase regulation have been implicated in senescence and neoplasia. To examine the regulation of DNA replication in lymphocytes, an in vitro system was developed in which lymphocyte derived proteins could regulate the initiation of DNA replication in isolated quiescent nuclei. Cytosolic extracts from mitogen or IL-2 activated lymphocytes as well as lymphoblastoid cell lines produce a factor (Activator of DNA replication; ADR) that can induce DNA synthesis in isolated quiescent nuclei, and DNA synthesis in this system is consistent with DNA replication and not repair. ADR activity is tightly associated with a protease activity and is not detectable in resting cells, but can be induced by a mechanism dependent on serine/threonine and tyrosine phosphorylation. Quiescent cells contain an ADR inhibitor which blocks DNA synthesis in isolated normal nuclei but not in nuclei from transformed cells, a potential factor in the uncontrolled proliferation of neoplastic cells. The control of cellular DNA replication is dependent on the interaction of origin sequences with specific replicative and regulatory proteins. However, mammalian origins of DNA replication are not well defined. Plasmids containing a replication origin within the human rRNA gene can act as replicative templates in our cell-free replication system, thus allowing a detailed molecular dissection of replication initiation in a completely human experimental system.

DNA sequence amplification in sciarid flies: results and perspectives

The discovery of Dna sequence amplification in sciarid flies and investigations into its control and biological significance are reviewed. Results thus far show that amplification of specific salivary gland polytene chromosome bands is a general phenomenon in sciarids. It brought about as part of a final endoreplication cycle by the rising titer of ecdysterone that occurs as the Larvae approach the prepupal period. Amplification and transcription of these bands is a late, multistep effect of this hormone.The Dna puffs which form in amplified region produce mRNAs which are translated into polypeptides that appear to be involved in coccon formation. Application of molecular cloning techniques to the study of Dna amplification has allowed precise quantitation of amplification for several Dna puffs and is yielding maps of their transcription units.These techniques will ultimately help to define the origins of Dna puff replication and contribute to an understanding of the mechanism and control of the amplification phenomenon in sciaridae. Projections for future experimental approaches are presented