1,438 research outputs found
Swine as an experimental model in dentistry: a proposal of surgical approach
Swine is widely used as an experimental model in several areas of medicine based on its anatomical and physiological similarities to humans. In this report, we describe an external surgical approach on the mandible of the swine as a suitable experimental model in dentistry. Several biomaterials were implanted by using this technique in order to evaluate the degree of bone regeneration as well as the suitable sites to accomplish perforation
Exclusion of PAX9 and MSX1 mutation in six families affected by tooth agenesis. A genetic study and literature review
Objectives: In the present study, it is described the phenotypical analysis and the mutational screening, for genes
PAX9 and MSX1, of six families affected by severe forms of tooth agenesis associated with other dental anomalies
and systemic entities.
Study Design: Six families affected by severe tooth agenesis associated with other dental anomalies and systemic
entities were included. Oral exploration, radiological examination, medical antecedents consideration and muta
-
tional screening for PAX9 and MSX1 were carried out.
Results: No mutations were discovered despite the fact that numerous teeth were missing. An important pheno
-
typical variability was observed within the probands, not being possible to establish a parallelism with the pat
-
terns associated to previously described PAX9 and MSX1 mutations.
Conclusions: These results bring us to conclude that probably other genes can determine phenotypical patterns
of dental agenesis in the families studied, different than the ones described in the mutations of PAX9 and MSX1.
Moreover, epigenetic factors can be involved, as those that can reduce gene dosage and other post-transcriptional
modulation agents, causing dental agenesis associated or not with systemic anomalies
Análisis semicuantitativo del calcio y fósforo en los tejidos calcificados de la mandíbula
El objetivo de nuestra investigación es realizar un estudio microanalítico semicuantitativo del
calcio y el fósforo en los tejidos calcificados de la mandíbula. Dentro de este estudio se pretende
calcular el valor de la ratio Ca/P por métodos semicuantitativos y compararlo con los valores
estequiométricos de la ratio Ca/P de la hidroxiapatita referidos en la literatura; conocer los valores
de la ratio Ca/P obtenidos para el tejido condroide, el hueso lamelar, el hueso fibrorreticular y el
cartílago calcificado en las muestras fetales, por una parte, y adultas, por otra; y si existen o no
diferencias significativas en la proporción Ca/P obtenidos para feto y adulto. El análisis morfológico
de los tejidos calcificados fue realizado por medio de Microrradiografía Electrónica de Barrido
(MEB) por electrones retrodispersados (Backscattering), y los resultados permiten afirmar que la
ratio obtenida por análisis semicuantitativo mediante dispersión de rayos X de los tejidos calcificados
(condroide, hueso lamelar y fibrorreticular) se encuentra más próxima a 1, y que no existen diferencias
significativas entre las muestras fetales y de adulto en los tejidos analizados
Análisis semicuantitativo del calcio y fósforo en el esmalte y la dentina
Existe una serie de características comunes asociadas al proceso biológico de formación de los
tejidos calcificados a pesar de que los productos finales sean estructuralmente distintos. La presente
investigación tiene como propósito determinar si la ratio Ca/P ratio es la misma para los tejidos
calcificados dentales tanto del feto como del adulto y si dicha ratio es diferente al valor de la ratio
Ca/P de la hidroxiapatita pura calculada por estequiometría. Se escogió como material de observación
el esmalte y la dentina, en muestras de fetos humanos y en un total de 30 ratas adultas de
raza Wistar y 20 dientes humanos sanos. Las observaciones se llevaron a cabo por medio de
Microscopia Electrónica de Barrido y Microanálisis por separación de energía de rayos X. Los
valores totales de la ratio Ca/P para el esmalte oscilaron en un intervalo de 0,9 y 1,2, con una media
que se encuentra entre 1,07 y 1,08. Los valores totales de la ratio Ca/P para la dentina oscilan entre
1,03 y 1,12 y la media entre 1,07 y 1,075. No se encontraron diferencias estadísticamente significativas
entre esmalte fetal y adulto ni entre la dentina fetal y adulta. Aún no pudiendo definir la
existencia de precursores específicos en los tejidos calcificados del diente (esmalte y dentina),
nuestros resultados sugieren que no toda la cristalización de estos tejidos corre a cargo de la
hidroxiapatita sino que deben haber otros compuestos que expliquen la disminución del valor de la
ratio Ca/P en las muestras estudiadas
Hypertension as a Risk Factor for Hip Fracture
Producción CientíficaArterial hypertension is a chronic disease in which prevalence
increases with age, as occurs in osteoporosis. It is
clinically silent and is only revealed in the form of complications,
an aspect that it also shares with osteoporosis.
Various alterations of calcium metabolism have been described
in association with hypertension; such alterations
can cause decreased bone mass, the principal determining
factor of fracture.1,2 Another important factor is the occurrence
of falls. Hypertensive patients may experience a
greater number of falls resulting from fainting associated
with diminished baroreflex sensitivity or hypotension secondary
to therapy.3,4 The purpose of this study was to
assess the effect of hypertension and its various therapeutic
alternatives on the risk of hip fracture.2015-09-0
Proceso de sacarificación y fermentación simultáneas para la conversión de la fracción celulósica del residuo de la extracción del aceite de oliva en etanol
In this work, the residue generated in the new two-step centrifugation process for olive oil extraction is assessed for the production of bioethanol. Both olive pulp and fragmented stones fractions comprised in such residue are analyzed and tested at laboratory scale for bioconversion to ethanol by a simultaneous saccharification and fermentation (SSF) process. Firstly, optima conditions for the enzymatic hydrolysis step of steam-exploded pretreated sustrates were determined. Then, simultaneous saccharification and fermentation process was assayed using the thermotolerant yeast Kluyveromyces marxianus in different assay conditions. For the selected conditions, 9 kg of unpretreated pulp or 6 kg of pretreated fragmented stones (both based on dry matter) would be necessary to obtain 1 liter of ethanol.En el presente trabajo se estudia la producción de etanol-combustible a partir de la celulosa contenida en las distintas fracciones (pulpa y fragmentos de huesos) que componen el residuo de la extracción de aceite de oliva mediante un proceso en dos fases. El trabajo ha consistido en una caracterización de las dos fracciones y en el estudio de la producción de etanol mediante un proceso de hidrólisis enzimática y fermentación simultáneas (SFS), a escala de laboratorio. Se ha estudiado el efecto que un pretratamiento termomecánico de explosión a vapor, previo a la etapa de hidrólisis enzimática y fermentación, tiene sobre la acción del complejo celulolítico. Por último, se han determinado las condiciones óptimas de ensayo para la sacarificación y fermentación simultáneas utilizando una cepa termotolerante de Kluyveromyces marxianus. En las condiciones de ensayo óptimas, serían necesarios 9 kg. de pulpa o 6 kg. de hueso pretratado (ambos sobre peso seco), para obtener 1 litro de etanol
Oval Domes: History, Geometry and Mechanics
An oval dome may be defined as a dome whose plan or profile (or both) has an oval form. The word Aoval@ comes from the latin Aovum@, egg. Then, an oval dome has an egg-shaped geometry. The first buildings with oval plans were built without a predetermined form, just trying to close an space in the most economical form. Eventually, the geometry was defined by using arcs of circle with common tangents in the points of change of curvature. Later the oval acquired a more regular form with two axis of symmetry. Therefore, an “oval” may be defined as an egg-shaped form, doubly symmetric, constructed with arcs of circle; an oval needs a minimum of four centres, but it is possible also to build polycentric ovals.
The above definition corresponds with the origin and the use of oval forms in building and may be applied without problem until, say, the XVIIIth century. Since then, the teaching of conics in the elementary courses of geometry made the cultivated people to define the oval as an approximation to the ellipse, an “imperfect ellipse”: an oval was, then, a curve formed with arcs of circles which tries to approximate to the ellipse of the same axes. As we shall see, the ellipse has very rarely been used in building.
Finally, in modern geometrical textbooks an oval is defined as a smooth closed convex curve, a more general definition which embraces the two previous, but which is of no particular use in the study of the employment of oval forms in building.
The present paper contains the following parts: 1) an outline the origin and application of the oval in historical architecture; 2) a discussion of the spatial geometry of oval domes, i. e., the different methods employed to trace them; 3) a brief exposition of the mechanics of oval arches and domes; and 4) a final discussion of the role of Geometry in oval arch and dome design
- …