Porous Allograft Bone Scaffolds: Doping with Strontium

Strontium (Sr) can promote the process of bone formation. To improve bioactivity, porous allograft bone scaffolds (ABS) were doped with Sr and the mechanical strength and bioactivity of the scaffolds were evaluated. Sr-doped ABS were prepared using the ion exchange method. The density and distribution of Sr in bone scaffolds were investigated by inductively coupled plasma optical emission spectrometry (ICP-OES), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectroscopy (EDS). Controlled release of strontium ions was measured and mechanical strength was evaluated by a compressive strength test. The bioactivity of Sr-doped ABS was investigated by a simulated body fluid (SBF) assay, cytotoxicity testing, and an in vivo implantation experiment. The Sr molar concentration [Sr/(Sr+Ca)] in ABS surpassed 5% and Sr was distributed nearly evenly. XPS analyses suggest that Sr combined with oxygen and carbonate radicals. Released Sr ions were detected in the immersion solution at higher concentration than calcium ions until day 30. The compressive strength of the Sr-doped ABS did not change significantly. The bioactivity of Sr-doped material, as measured by the in vitro SBF immersion method, was superior to that of the Sr-free freeze-dried bone and the Sr-doped material did not show cytotoxicity compared with Sr-free culture medium. The rate of bone mineral deposition for Sr-doped ABS was faster than that of the control at 4 weeks (3.28±0.23 µm/day vs. 2.60±0.20 µm/day; p<0.05). Sr can be evenly doped into porous ABS at relevant concentrations to create highly active bone substitutes.     

Effect of Tricalcium Aluminate on the Physicochemical Properties,Bioactivity, and Biocompatibility of Partially Stabilized Cements

Background/Purpose

Mineral Trioxide Aggregate (MTA) was widely used as a root-end filling material and for vital pulp therapy. A significant disadvantage to MTA is the prolonged setting time has limited the application in endodontic treatments. This study examined the physicochemical properties and biological performance of novel partially stabilized cements (PSCs) prepared to address some of the drawbacks of MTA, without causing any change in biological properties. PSC has a great potential as the vital pulp therapy material in dentistry.

Methods

This study examined three experimental groups consisting of samples that were fabricated using sol-gel processes in C3S/C3A molar ratios of 9/1, 7/3, and 5/5 (denoted as PSC-91, PSC-73, and PSC-55, respectively). The comparison group consisted of MTA samples. The setting times, pH variation, compressive strength, morphology, and phase composition of hydration products and ex vivo bioactivity were evaluated. Moreover, biocompatibility was assessed by using lactate dehydrogenase to determine the cytotoxicity and a cell proliferation (WST-1) assay kit to determine cell viability. Mineralization was evaluated using Alizarin Red S staining.

Results

Crystalline phases, which were determined using X-ray diffraction analysis, confirmed that the C3A contents of the material powder differed. The initial setting times of PSC-73 and PSC-55 ranged between 15 and 25 min; these values are significantly (p<0.05, ANOVA and post-hoc test) lower than those obtained for MTA (165 min) and PSC-91 (80.5 min). All of the PSCs exhibited ex vivo bioactivity when immersed in simulated body fluid. The biocompatibility results for all of the tested cements were as favorable as those of the negative control, except for PSC-55, which exhibited mild cytotoxicity.

Conclusion

PSC-91 is a favorable material for vital pulp therapy because it exhibits optimal compressive strength, a short setting time, and high biocompatibility and bioactivity.     

Exposing Diversity: A Methodological Approach to the Use of Video Narratives in Interdisciplinary Practices

This article explores the potential of ethnographic video narratives for collaborative learning in an interdisciplinary context. Previous research describes the area between tacit knowing and explicit knowledge as an area of “muddy water” that creates a space for constructing new understandings and knowledge. In this regard, video narratives can be seen as a pathway to feelings and other sensations, and therefore to tacit commonsense notions about the nature of practices. The question is how the methodical use of video narratives contributes to new understandings of practice. The article outlines a study in which two video narratives were presented in interdisciplinary focus groups in a nursing-home setting. The multilayered complexity of the video narratives, combined with different professional approaches to elderly care, opens up for diverse, opposing and detailed understandings of practice in the dialogue about the narratives. This diversity raises new questions about the nature of practice and seems to fuel a collaborative learning process. In conclusion, the article suggests that future interventions using video narratives would benefit from firmer facilitation and categorization of this diversity in order to enhance the potential for collaborative learning.     

Induction Cardiac Pacing: A New Approach

A new approach to induction cardiac pacing using a “skin tunnel” transformer has been developed and used in a patient. Initial results are encouraging. If the system proves reliable in the long term it may have important applications in the delivery of power to implanted artificial organs.     

The Mucolytic Activity of Amides: A New Approach to Mucus Dispersion

A method which will reduce significantly the viscosity of epithelial mucus is essential to the physiological mechanisms involved in the mobilization and removal of such secretions. The life expectancy of patients with chronic pulmonary conditions and cystic fibrosis has been considerably increased and consequently the problem of liquefying mucin acquires new importance. In view of these considerations, as well as to facilitate research into the structural relationship of the glycoprotein macromolecule, a systematic investigation of mucolysis was undertaken using gastric mucin. Three amides, carbamide, acetamide and formamide, were found to dissolve gastric gel mucin with minimal degradation, and rapidly disperse the viscous secretions produced in pathological conditions of the tracheobronchial tree. Their effect on secretions from patients with cystic fibrosis and bronchiectasis is dramatic, and within five minutes of adding the reagent the flow time was reduced by at least 95%. Clinical studies were carried out with carbamide (urea in anhydrous, lyophilized, sterile powder form) in 32 patients with a variety of bronchial conditions, including chronic bronchitis, cystic fibrosis, asthma, bronchiectasis and emphysema. With the concentrations used, no irritant, bronchospastic or other reactions were observed.It is concluded that amides of this type have at least two actions on the epithelial mucous secretion: (1) breakage of the three-dimensional gel structure and (2) a slower reduction in viscosity followed by solution of the solid material.     

The Sterility Testing of Aminoglycosides: A New Approach Using Enzymic Inactivation

The inactivation of various aminoglycosides prior to sterility testing has been studied. The preparation of the enzyme used in the inactivation, a 3-N-acetyl transferase of wide substrate specificity from Escherichia coli JR 225, is described. The enzyme is partially purified and some of its kinetic parameters described. The extent of the inactivation of the individual aminoglycosides can be related to the physiological efficiency of the enzyme. The lyophilization of the components of the inactivating system is successful when undertaken individually, but not together.     

The Ethnographic I: A Methodological Novel about Autoethnography

The Ethnographic I:. Methodological Novel about Autoethnography . Carolyn Ellis. Walnut Creek, CA: AltaMira Press, 2004. 448 pp.     

The Activity Approach : New Lines of Research

The emotional reactions of an actor that resemble those experienced by the character he is portraying serve as an index of the artist's penetration into the sphere of the needs (motives) of that dramatic character, an indicator of the naturalness, verisimilitude, and accuracy of the behavior ofthat character, which is the most important condition for fruitful creativity in the theater [6]. The ability to transform one's own artistic, creative need (a "meta-meta task," in the terminology of K. S. Stanislavskii) into the motives of the behavior of the portrayed person, into his "metatask," is an extremely important aspect of an actor's talent and also of his professionalism [2,8]. This ability is closely related to a personality trait that may, very provisionally, be designated by the term emotionality, by which is meant the ability to respond forcefully to emotion-producing stimuli. In an actor, emotional responses to the reproduction in the mind of corresponding emotionally colored situations assumes special importance [1,13]. The number of studies employing objective recording of the physiological changes accompanying an actor's emotional responses is still very limited [1,3,5,9,10,15].     

Worldwide Alien Invasion: A Methodological Approach to Forecast the Potential Spread of a Highly Invasive Pollinator

The ecological impacts of alien species invasion are a major threat to global biodiversity. The increasing number of invasion events by alien species and the high cost and difficulty of eradicating invasive species once established require the development of new methods and tools for predicting the most susceptible areas to invasion. Invasive pollinators pose serious threats to biodiversity and human activity due to their close relationship with many plants (including crop species) and high potential competitiveness for resources with native pollinators. Although at an early stage of expansion, the bumblebee species Bombus terrestris is becoming a representative case of pollinator invasion at a global scale, particularly given its high velocity of invasive spread and the increasing number of reports of its impacts on native bees and crops in many countries. We present here a methodological framework of habitat suitability modeling that integrates new approaches for detecting habitats that are susceptible to Bombus terrestris invasion at a global scale. Our approach did not include reported invaded locations in the modeling procedure; instead, those locations were used exclusively to evaluate the accuracy of the models in predicting suitability over regions already invaded. Moreover, a new and more intuitive approach was developed to select the models and evaluate different algorithms based on their performance and predictive convergence. Finally, we present a comprehensive global map of susceptibility to Bombus terrestris invasion that highlights priority areas for monitoring.     

A Porous Media Approach to Finite Deformation Behaviour in Soft Tissues

The present work presents a porous medium formulation for the biomechanical analysis of soft tissues. An updated Lagrangian approach is developed to study the coupled effects of low speed flows of fluid phases, in partially or fully saturated conditions, and the finite deformation occurring in the solid matrix. The procedure developed allows both for the evaluation of coupled geometric and material non-linearities. The main theoretical and computational aspects of this multiphase formulation are discussed. The finite element method is used for the numerical solution of the resulting coupled system of equations. A reference case is reported with regard to healthy and degenerative phases of intervertebral segment. Results reported allow for a detailed interpretation of the formulation reliability, also by comparison with existing experimental data. In particular, the role played by the fluid on the load carrying mechanism is pointed out, thus stressing the importance of a multiphase approach to the overall behaviour of the spinal motion segment in time.     

A New Computational Efficient Approach for Trabecular Bone Analysis using Beam Models Generated with Skeletonized Graph Technique

Micro-finite element (FE) analysis is a well established technique for the evaluation of the elastic properties of trabecular bone, but is limited in its application due to the large number of elements that it requires to represent the complex internal structure of the bone. In this paper, we present an alternative FE approach that makes use of a recently developed 3D-Line Skeleton Graph Analysis (LSGA) technique to represent the complex internal structure of trabecular bone as a network of simple straight beam elements in which the beams are assigned geometrical properties of the trabeculae that they represent. Since an enormous reduction of cputime can be obtained with this beam modeling approach, ranging from approximately 1,200 to 3,600 for the problems investigated here, we think that the FE modeling technique that we introduced could potentially constitute an interesting alternative for the evaluation of the elastic mechanical properties of trabecular bone.     

A Methodological Approach to Assess Cross-scale Relations and Interactions in Agricultural Ecosystems of Argentina

Agronomists, environmentalists, land managers, policy makers and development agents who make decisions at different levels (plot, farm, ecosystem, landscape, ecoregion, country) increasingly demand scientific information to understand cross-level links and interactions in systems that behave hierarchically. The purpose of this work is to study cross-scale relations and interactions in agricultural ecosystems of the Argentine Pampas. Based on public censuses and surveys from 1960 to 1996, data on crops cultivation, fossil energy (FE) consumption and energy productivity were used for the analysis. The whole region was divided into eight increasing geographic scales, and the impact of one scale on the broader ones was assessed through a simple analysis of energy productivity. Regression analysis was used to identify cross-scale linear slopes and to determine cross-scale interactions. We assume that non-parallel slopes in different years are attributable to cross-scale interactions. Given that the results show highly significant differences among inter-year slopes, we must accept that cross-scale interactions have occurred. Beyond any random behavior, it seems quite possible that decisions made at smaller scales may have a demonstrable effect on broader scales. Specific research is needed to elucidate key cause–effect relationships among scales. In principle, the possible interaction between intensification factors (for example, FE consumption) and spatial scales is a plausible hypothesis to be tested in the study area.     

多孔钛合金不同孔径大小对新骨长入的影响

目的:评价不同孔径多孔钛合金植入物在骨缺损区对新骨长入的影响。方法:采用电子束熔融(EBM)技术制备三种不同孔径(孔径分别为1.0 mm,2.0 mm,3.0 mm)的多孔钛合金材料,其孔隙率依次为73%,79%,86%。将18只家犬随机分为1.0 mm孔径材料组,2.0 mm孔径材料组,3.0 mm孔径材料组,每组6只。制备家犬双侧股骨外侧髁缺损模型,然后植入各孔径组材料,于术后4周,8周,12周分别行大体标本观察,X线片观察,组织形态学观察三组不同孔径材料与周围骨的整合情况及孔隙中的新骨长入情况。结果:通过大体标本观察和X线片观察显示,12周后三组材料均与周围紧密骨连接。其中1.0 mm孔径组材料中心明显成骨,2.0 mm孔径组和3.0 mm孔径组中心仍为较多白色组织填充。组织学观察显示,12周时2.0 mm孔径组和3.0 mm孔径组材料周围有骨质包绕,但中心空洞,基本无骨质形成。1.0 mm孔径组材料周围骨质包绕紧密,孔中新生骨形成较多,且有大量纤维母细胞和软骨细胞形成。各时间点1.0 mm孔径组新生骨面积百分比明显高于2.0 mm孔径组和3.0 mm孔径组,P<0.01,差异具有统计学意义。2.0 mm孔径组和3.0 mm孔径组相比,P>0.05,无显著差异。结论:孔径大小影响多孔钛合金材料的骨长入,适当孔径的设计将更有利于材料的传导成骨。     

A New Rapid Methodological Strategy to Assess BRCA Mutational Status

Hereditary cancers account for approximately 10 % of breast and ovarian cancers. Mutations of the BRCA1 and BRCA2 genes, encoding two proteins involved in DNA repair, underlie most cases of such hereditary cancers. Women with BRCA mutations develop breast cancer in 50–80 % of cases and ovarian cancer in 10–40 % of cases. Assessing BRCA mutational status is needed to direct the clinical management of women with predisposition to these hereditary cancers. However, BRCA screening constitutes a bottleneck in terms of costs and time to deliver results. We developed a PCR-based assay using 73 primer pairs covering the entire coding regions of BRCA1 and BRCA2. PCR primers, containing at the 5’ end the universal M13 primer sequences, were pre-spotted in 96-well plates. Following PCR, direct sequencing was performed using M13 primers, allowing to standardize the conditions. PCR amplification and sequencing were successful for each amplicon. We tested and validated the assay on 10 known gDNAs from patients with Hereditary breast and ovarian cancer (HBOC). Our strategy is a promising time and cost-effective method to detect BRCA mutations in the clinical setting, which is essential to formulate a personalized therapy for patients with HBOC.