Computed tomography to evaluate the association of fragmented heterolog cortical bone and methylmethacrylate to repare segmental bone defect produced in tibia of rabbits

A 6mm segmental defect was performed on the metaphyseal region of the tibia of 12 rabbits and the autoclaved fragmented heterolog cortical bone conserved in glycerin (98%) and methylmethacrylate was used as a bone graft for the reconstruction. The graft was placed in the receptor bed and its integration was evaluated by computed tomography after 30, 60 and 90 days. There was gradual bone graft incorporation in the receptor bed during the time in 100% of the cases. Fragmented cortical bone heterograft and methylmethacrylate was biologically compatible and promotes bone defect reparation without signs of infection, migration and or rejection, featuring a new option of osseous substitute to fill in bone defects.

Non-resorbable glass fibre-reinforced composite with porous surface as bone substitute material: Experimental studies in vitro and in vivo focused on bone-implant interface

The development of load-bearing osseous implant with desired mechanical and surface properties in order to promote incorporation with bone and to eliminate risk of bone resorption and implant failure is a very challenging task. Bone formation and resoption processes depend on the mechanical environment. Certain stress/strain conditions are required to promote new bone growth and to prevent bone mass loss. Conventional metallic implants with high stiffness carry most of the load and the surrounding bone becomes virtually unloaded and inactive. Fibre-reinforced composites offer an interesting alternative to metallic implants, because their mechanical properties can be tailored to be equal to those of bone, by the careful selection of matrix polymer, type of fibres, fibre volume fraction, orientation and length. Successful load transfer at bone-implant interface requires proper fixation between the bone and implant. One promising method to promote fixation is to prepare implants with porous surface. Bone ingrowth into porous surface structure stabilises the system and improves clinical success of the implant. The experimental part of this work was focused on polymethyl methacrylate (PMMA) -based composites with dense load-bearing core and porous surface. Three-dimensionally randomly orientated chopped glass fibres were used to reinforce the composite. A method to fabricate those composites was developed by a solvent treatment technique and some characterisations concerning the functionality of the surface structure were made in vitro and in vivo. Scanning electron microscope observations revealed that the pore size and interconnective porous architecture of the surface layer of the fibre-reinforced composite (FRC) could be optimal for bone ingrowth. Microhardness measurements showed that the solvent treatment did not have an effect on the mechanical properties of the load-bearing core. A push-out test, using dental stone as a bone model material, revealed that short glass fibre-reinforced porous surface layer is strong enough to carry load. Unreacted monomers can cause the chemical necrosis of the tissue, but the levels of leachable resisidual monomers were considerably lower than those found in chemically cured fibre-reinforced dentures and in modified acrylic bone cements. Animal experiments proved that surface porous FRC implant can enhance fixation between bone and FRC. New bone ingrowth into the pores was detected and strong interlocking between bone and the implant was achieved.

Effect of enamel matrix derivative and parathyroid hormone on bone formation in standardized osseous defects: an experimental study in minipigs

Previous experimental studies have indicated that locally administered enamel matrix derivative (EMD) and parathyroid hormone (PTH) may have a stimulatory effect on bone formation. However, it is not clear if the positive effect of EMD is related to its effect on the periodontium as a whole or directly on the bone-forming cells. In addition, it is not known if the presentation of PTH by adding the amino acid sequence Arg-Gly-Asp (RGD) is essential for its osteopromotive effect. Local delivery of a bioactive substance at the right time and in the right concentration often constitutes a major challenge. Polyethylene glycol-based hydrogel (PEG) is a degradable vehicle developed for delivery of bioactive proteins. To enhance the mechanical stability of the PEG-bioactive substance complex, an osteoconductive bone substitute material is often needed.

Viability of using enamel and dentin from bovine origin as a substitute for human counterparts in an intraoral erosion model

This study ascertained whether under dental erosion models that closely mimics the real-life situation enamel and root dentin from bovine origin would be reliable substitutes for human counterparts. Through a 2x2 crossover design, in a first trial, 14 volunteers wore a palatal device containing slabs of bovine and human enamel. Half of the participants ingested (4x daily, for 10 days) orange juice first, crossing over to mineral water, while the remainder received the reverse sequence. In a second trial, volunteers wore devices with slabs of bovine and human root dentin. Except for the duration of each intraoral phase, which lasted 2 rather 10 days, the experiment with root dentin run exactly as for enamel. Dental substrates were analyzed for surface microhardness. Two-way ANOVAs (α=0.05) indicated no difference between the microhardness values recorded for human and bovine enamel (p=0.1350), but bovine root dentin had lower microhardness compared to its human counterpart (p=0.0432). While bovine enamel can reliably substitute its human counterpart in in situ dental erosion models, bovine root dentin does not seem to be a viable alternative to the corresponding human tissue.

Alveolar osseous defect in rat for cell therapy: preliminary report

PURPOSE: To study were to reproduce an alveolar bone defect model in Wistar rats to be used for testing the efficacy of stem cell therapies. Additionally, we also aimed to determine the osteogenesis process of this osseous defect in the 1 month period post-surgery. METHODS: The animals were randomly divided into two groups of 7 animals each. A gingivobuccal incision was made, and a bone defect of 28 mm² of area was performed in the alveolar region. Animals were killed at 2 weeks after surgery (n=7) and 4 weeks after surgery (n=7). RESULTS: The average area of the alveolar defect at time point of 2 weeks was 22.27 ± 1.31 mm² and the average area of alveolar defect at time point of 4 weeks was 9.03 ± 1.17 mm². The average amount of bone formation at time point of 2 weeks was 5.73 ± 1.31 mm² and the average amount of bone formation at time point of 4 weeks was 19 ± 1.17 mm². Statistically significant differences between the amount of bone formation at 2 weeks and 4 weeks after surgery were seen (p=0.003). CONCLUSION: The highest rate of ossification occurred mostly from 2 to 4 weeks after surgery. This observation suggests that 4 weeks after the bone defect creation should be a satisfactory timing to assess the potential of bone inductive stem cells to accelerate bone regeneration in Wistar rats.

Removal from the Membrane Affects the Interaction of Rat Osseous Plate Ecto-Nucleosidetriphosphate Diphosphohydrolase-1 with Substrates and Ions

We have characterized the kinetic properties of ectonucleoside triphosphate diphosphohydrolase 1 (E-NTPDase1) from rat osseous plate membranes. A novel finding of the present study is that the solubilized enzyme shows high- and low-affinity sites for the substrate in contrast with a single substrate site for the membrane-bound enzyme. In addition, contrary to the Michaelian chraracteristics of the membrane-bound enzyme, the site-site interactions after solubilization with 0.5% digitonin plus 0.1% lysolecithin resulted in a less active ectonucleoside triphosphate diphosphohydrolase, showing activity of about 398.3 nmol Pi min(-1) mg(-1). The solubilized enzyme has M(r) of 66-72 kDa, and its catalytic efficiency was significantly increased by magnesium and calcium ions; but the ATP/ADP activity ratio was always < 2.0. Partial purification and kinetic characterization of the rat osseous plate E-NTPDase1 in a solubilized form may lead to a better understanding of a possible function of the enzyme as a modulator of nucleotidase activity or purinergic signaling in matrix vesicle membranes. The simple procedure to obtain the enzyme in a solubilized form may also be attractive for comparative studies of particular features of the active sites from this and other ATPases.

Rat osseous plate alkaline phosphatase as Langmuir monolayer - An infrared study at the air-water interface

A glycosylphosphatidylinositol (GPI)-anchored enzyme (rat osseous plate alkaline phosphatase-OAP) was studied as monolayer (pure and mixed with lipids) at the air-water interface. Surface pressure and surface potential-area isotherms showed that the enzyme forms a stable monolayer and exhibits a liquid-expanded state even at surface pressure as high as 30 mN m(-1). Isotherms for mixed dimyristoylphosphatidic acid (DMPA)-OAP monolayer showed the absence of a liquid-expanded/liquid-condensed phase transition as observed for pure DMPA monolayer. In both cases, pure or mixed monolayer, the enzyme preserves its native conformation under compression at the air-water interface as observed from in situ p-polarized light Fourier transform-infrared reflection-absorption spectroscopic (FT-IRRAS) measurements. Changes in orientation and conformation of the enzyme due to the presence or absence of DMPA, as well as due to the surface compression, are discussed. (C) 2008 Published by Elsevier Inc.

Biomechanical evaluation on tendon reinsertion by comparing trans-osseous suture and suture anchor at different stages of healing: Experimental study on rabbits

Background: Through an experimental biomechanical study on rabbits, tendon reinsertion by means of trans-osseous suture on a spongy bone bed and suture anchor were evaluated comparatively at different phases of healing. Methods: Twenty-four New Zealand White rabbits were used: 2 as pilots, 4 as the control group, and 18 as the experimental group. These 18 animals underwent sectioning and reinsertion of the Achilles tendon bilaterally, using the technique of trans-osseous suture on 1 side and suture anchor on the other. All the pelvic limbs that underwent the procedure were then immobilized for 3 weeks. The experimental group was divided into 3 groups that were sacrificed, respectively, 3, 6, and 12 weeks later. The tendon-bone complex was subjected to biomechanical tests to evaluate the parameters of maximum strength, stiffness, and yield strength. Results: There was no statistically significant difference between the suture anchor group and the trans-osseous suture group, in relation to yield strength (3 weeks, P = .222; 6 weeks, P = .465; and 12 weeks, P = .200) or maximum strength (3 weeks, P = .222; 6 weeks, P = .076; and 12 weeks, P = .078). In relation to stiffness, the suture anchor group showed a statistically significant difference only at 3 weeks of healing ( P = .032) over the trans-osseous suture group. Conclusion: The technique of suturing with an anchor was shown to be similar to the technique of trans-osseous suture for the studied parameters. Level of evidence: Basic Science Study, In-Vitro Biomechanics Study. (C) 2010 Journal of Shoulder and Elbow Surgery Board of Trustees.

Isolated osseous ovarian metaplasia: Case report

Background: Some ovarian metaplasias may contain bone or osteoid tissue. The most common tumors presenting these alterations are teratomas and mixed mesodermal tumors with heterologous elements. Case report: We report the case of a woman who, during gynecologic follow-up for chronic anovulation at the age of 31 years, presented a solid ovarian ultrasonographic image with calcifications. After laparoscopy and histological examination it was found to be an isolated ovarian osseous metaplasia. Conclusion: A rarely occurring condition, ovarian osseous metaplasia continues to be of uncertain clinical significance.

Aminoquinolone WR6026 as a feasible substitute for gentian violet in Chagas' disease prophylaxis in preserved blood for transfusional purposes

The search for a colorless, nontoxic and efficient drug to prevent transfusion-associated Chagas' disease (TACD) has been underway unsuccessfully since 1953 when gentian violet was preconized and to date is still being used as the only in vitro trypanocidal agent. The recent findings of aminoquinolone "WR6026" as a trypanocidal agent, led the authors to study the metabolism of red cells stored with this compound, the main objective of which was to define its applicability in TACD control. Ten units of human whole blood collected in CPDA-1 were divided into two equal satellite bags. One had "WR6026" (final concentration 62.5µg/mL) added and the other was used as a control, both were stored at 4ºC. At baseline, day 7, 14, 21 and 28, samples were taken for the following measurements: adenosine triphosphate (ATP), hemoglobin, electrolytes (sodium and potassium), gases (pO2 and pCO2) and osmotic fragility. The results of tests and control were analyzed through parametric t-student test. The results were similar in both groups throughout the experiment except for the level of ATP on day 14, which presented significantly higher values in the tests when compared with the controls (p = 0.012). It was concluded that WR6026 does not interfere in the preservation and probably the viability of the erythrocytes also until day 28 of storage. Consequently the authors suggest that WR6026 could emerge as a colorless substitute for gentian violet in the control of TACD in endemic areas.

Soft biomaterials as a substitute for the Nucleus Pulposus

One of the largest health problems faced worldwide, when evaluated by direct (clinical) as well indirect cost (absenteeism), is the degeneration of the intervertebral disc (IVD) that leads to back pain and, potentially disability and individual´s quality of life decreasing. The intervertebral disc is a mechanical and biological complex structure, formed by a tough outer layer of fibrocartilage called Annulus Fibrosus (AF),which surrounds a soft, elastic and gelatinous core called Nucleus Pulposus (NP). These two structures are completed by two upper and lower encasing layer called Vertebral Endplates (VEP). The degeneration of the IVD is marked by the dehydration of the Nucleus Pulposus, reducing the hydrostatic pressure inside the nucleus, resulting in a loss of capability to support compressive forces, during the active period, and to regain height during the resting period. This situation will compromise the role of shock absorber by the NP and transfers these forces to the AF. This transfer will result in cracks on the AF, deteriorating the IVD, allowing the ingrowth of vessels and nerves. This project was based on the developing a protocol to test suitable NP replacements, in hope to future assessment of discrete mechanical values and characteristics for an NP replacement. For this, Nucleus pulposus samples from goat, encapsulated Hydromed gel denominated “Raviolis” and Chitosan gels, produced via wet route using an ammonium environment, were confined compressed. Chitosan was rheologically tested and swelling capability of all the three type of materials was assessed. Results showed that the Nucleus Pulposus and “Raviolis” have similar mechanical behavior, being able to swell and “build up” hydrostatic pressure after a compression stage, while the Chitosan gel did not showed that ability. Therefore, “Raviolis” are a more suitable candidate to replace the NP than Chitosan gels. It was also observed that confined compression is the key test to perform on any possible candidate to replace the NP.

Los entornos virtuales como herramienta sustituta del laboratorio "real" y como complemento de la enseñanza de Química a alumnos de Ingeniería. Virtual environments as substitute tools for the "conventional" laboratories and as a complement for Chemistry teaching to Engineering students.

El presente proyecto se plantea el siguiente problema de investigación:¿Cuál es la eficacia de los entornos virtuales de enseñanza para optimizar los aprendizajes de Química? Se sostiene la hipótesis de que los entornos virtuales de enseñanza, empleados como mediación instrumental, son eficaces para optimizar los aprendizajes de química, particularmente facilitando la vinculación y reversibilidad entre "mundo micro y macroscópico"; capacidad que usualmente sólo se atribuye al trabajo experimental de laboratorio. Los objetivos propuestos son: Determinar la eficacia de entornos virtuales de enseñanza, como mediaciones instrumentales, para optimizar los aprendizajes de química en estudiantes de ingeniería. Implementar un entrono virtual de enseñanza de química, diseñado como mediación instrumental y destinado a estudiantes de dos carreras de ingeniería del IUA. Evaluar el desarrollo y los resultados de la innovación introducida. Comparar los resultados de la innovación con los resultados de la enseñanza usual. Derivar conclusiones acerca de la eficacia de la innovación propuesta. Socializar el conocimiento producido en ámbitos científico-tecnológicos reconocidos. Se generará un aula virtual en plataforma Educativa y utilidzando el laboratorio de computación de la institución se buscará desarrollar laboratorios virtuales donde se propondrán actividades de simulación de trabajo experimental. Los resultados esperados son: - Un Aula Virtual que cumpla funciones análogas a las de un laboratorio experimental. - Información válida y confiable acerca de la eficacia de la misma como medio para optimizar los aprendizajes de química. - Publicaciones en ámbitos científico-tecnológicos reconocidos que sometan a juicio público la innovación y la investigación efectuadas. La importancia del proyecto radica principalmente en poner a prueba la eficacia de los entornos virtuales para optimizar los aprendizajes de química, analogando tareas usualmente limitadas al trabajo experimental de laboratorio. Su pertinencia apunta a un replanteo del curriculo de los cursos de Química para estudiantes de Ingeniería.

Extra-osseous involvement of Langerhans' cell histiocytosis in children.

The predominant clinical and radiological features of Langerhans' cell histiocytosis (LCH) in children are due to osseous involvement. Extra-osseous disease is far less common, occurring in association with bone disease or in isolation; nearly all anatomical sites may be affected and in very various combinations. The following article is based on a multicentre review of 31 children with extra-osseous LCH. The objective is to summarise the diverse possibilities of organ involvement. The radiological manifestations using different imaging modalities are rarely pathognomonic on their own. Nevertheless, familiarity with the imaging findings, especially in children with systemic disease, may be essential for early diagnosis.

T1-weighted MRI as a substitute to CT for refocusing planning in MR-guided focused ultrasound.

Precise focusing is essential for transcranial MRI-guided focused ultrasound (TcMRgFUS) to minimize collateral damage to non-diseased tissues and to achieve temperatures capable of inducing coagulative necrosis at acceptable power deposition levels. CT is usually used for this refocusing but requires a separate study (CT) ahead of the TcMRgFUS procedure. The goal of this study was to determine whether MRI using an appropriate sequence would be a viable alternative to CT for planning ultrasound refocusing in TcMRgFUS. We tested three MRI pulse sequences (3D T1 weighted 3D volume interpolated breath hold examination (VIBE), proton density weighted 3D sampling perfection with applications optimized contrasts using different flip angle evolution and 3D true fast imaging with steady state precision T2-weighted imaging) on patients who have already had a CT scan performed. We made detailed measurements of the calvarial structure based on the MRI data and compared those so-called 'virtual CT' to detailed measurements of the calvarial structure based on the CT data, used as a reference standard. We then loaded both standard and virtual CT in a TcMRgFUS device and compared the calculated phase correction values, as well as the temperature elevation in a phantom. A series of Bland-Altman measurement agreement analyses showed T1 3D VIBE as the optimal MRI sequence, with respect to minimizing the measurement discrepancy between the MRI derived total skull thickness measurement and the CT derived total skull thickness measurement (mean measurement discrepancy: 0.025; 95% CL (-0.22-0.27); p = 0.825). The T1-weighted sequence was also optimal in estimating skull CT density and skull layer thickness. The mean difference between the phase shifts calculated with the standard CT and the virtual CT reconstructed from the T1 dataset was 0.08 ± 1.2 rad on patients and 0.1 ± 0.9 rad on phantom. Compared to the real CT, the MR-based correction showed a 1 °C drop on the maximum temperature elevation in the phantom (7% relative drop). Without any correction, the maximum temperature was down 6 °C (43% relative drop). We have developed an approach that allows for a reconstruction of a virtual CT dataset from MRI to perform phase correction in TcMRgFUS.