El quad-hélix, un aparato versátil / The quad-hélix, a versatile appliance

El quad-hélix (QH) es un aparato de expansión maxilar, fabricado con alambre de acero inoxidable soldado a bandas en molares, que dispone de espirales o hélices que aumentan la longitud de alambre del aparato, lo que lo hace muy elástico y aligera la magnitud de la fuerza sobre los dientes, es ampliamente usado tanto en dentición mixta como en permanente temprana, fácil de fabricar, higiénico y bien tolerado por los pacientes. Su principal acción es mover hacia vestibular los procesos dentoalveolares de la arcada maxilar, influyendo secundariamente en la expansión de la sutura palatina media en pacientes con dentición mixta o permanente temprana. El QH es muy práctico y tiene muchos usos y adaptaciones y se puede utilizar como auxiliar en el tratamiento de problemas de hábito de dedo o lengua, para abrir mordida, rotar y dar torque a molares permanentes o para mover sólo un diente en particular. En este artículo describimos una nueva aplicación del QH que consiste en la tracción, de dientes anteriores superiores permanentes retenidos, después del abordaje quirúrgico para localizarlos. También revisaremos las indicaciones, contraindicaciones, ventajas y desventajas del aparato QH soldado a bandas en molares así como su elaboración, variantes y forma de activación (AU)

The quad-helix (QH) is a maxillary expansion appliance, manufactured with stainless steel wire welded to bands in molars, which has spirals or helix to increase the length of wire of the device, which makes it very elastic and lightens the magnitude of the force on the teeth, is widely used both in mixed and in early permanent dentition, is easy to manufacture, hygienic and well tolerated by patients. Its major action is to move towards the dentoalveolar process of the maxillary arcade, secondarily influencing the expansion of the middle palatal suture in young patients with mixed or permanent early dentition. The QH is very practical and has many uses and adaptations as an aid in the treatment of problem of thumb sucking or tongue habit, to open bite, to rotate and torque permanent molars or to move only one particular tooth. In this article we describe a new application of the QH that consist of the traction or retained permanent upper teeth, after surgical approach to locate them. We will also review the indications, contraindications, advantages and disadvantages of the QH welded to molar bands, as well as its construction, variants and activation form (AU)

Cloning,Expressing and Sequence Analysis of a Novel vip3Aa Gene / 微生物学通报

The vip3A gene of Bt9816C was cloned and the sequencing result was submitted to GenBank (accession no.AY945939). The gene was identified as a novel vip3Aa gene, which was assigned name vip3Aa18 by the Bacillus thuringiensis delta-endotoxin nomenclature committee. Subsequently, vip3Aa18 was expressed in Escherichia coli BL21 and bioassay demonstrated that the purified recombinant Vip3Aa18 had high toxicity against Helicoverpa armigera and Spodoptera exigua. The results of sequence analysis revealed that a carbohydrate binding domain exists on the C-termini 536 to 667 residues of Vip3Aa18,which maybe participate in binding to midgut receptors in susceptible insects. Moreover, a transmembrane helices located on N-termini 272 to 292 residues was proposed responding for pore formation. Furthermore, a putative disulfide bond was found in the Vip3Aa18 sequence. The specific structures and sites of Vip3Aa18 sequence imply potential function.

Chain flexibility and configurational dimensions of left handed Z- DNA and right handed B-DNA helices.

The configurational behaviour of flexible helices of right handed B- and left handed Z-types have been analysed using statistical mechanical procedures. The configurationependent parameter, most importantly, the persistence length has been computed, using the heminucleotide scheme of treating polynucleotide chains under the approximation that perturbations in the backbone torsions produce sufficient flexibility in these helices. The values of persistence lengths obtained for Z-helices are very much higher than that of B-helices indicating that former is less flexible compared to the latter. These are in accordance with the results obtained recently on B- and Z-forms of poly(dG-dC) · (dG-dC) using light scattering studies. Also the persistence lengths of BII-DNA helices characterised by a skew 3'-hemiucleotide ( ε ~ 270°), and also when they coexist with B-DNA have been computed and the values lie within the range of experimentally reported values on B-helices. It is argued that the decrease in the persistence length values of B-DNA at higher salt concentration is due to additional small fluctuations in sugar residue torsions induced due to neutralisation of electrostatic repulsions between adjacent phosphates of the nucleotide. Noteworthy is that these are correlated to winding angle variations and the consequent bending of the helix.