Respective roles of organic and mineral components of human cortical bone matrix in micromechanical behavior: An instrumented indentation study

International audienceBone is a multiscale composite material made of both a type I collagen matrix and a poorly crystalline apatite mineral phase. Due to remodeling activity, cortical bone is made of Bone Structural Units (BSUs) called osteons. Since osteon represents a fundamental level of structural hierarchy, it is important to investigate the relationship between mechanical behavior and tissue composition at this scale for a better understanding of the mechanisms of bone fragility. The aim of this study is to analyze the links between ultrastructural properties and the mechanical behavior of bone tissue at the scale of osteon. Iliac bone biopsies were taken from untreated postmenopausal osteoporotic women, embedded, sectioned and microradiographed to assess the degree of mineralization of bone (DMB). On each section, BSUs of known DMB were indented with relatively high load (∼500 mN) to determine local elastic modulus (E), contact hardness (Hc) and true hardness(H) of several bone lamellae. Crystallinity and collagen maturity were measured by Fourier Transform InfraRed Microspectroscopy (FTIRM) on the same BSUs. Inter-relationships between mechanical properties and ultrastructural components were analyzed using multiple regression analysis. This study showed that elastic deformation was only explained by DMB whereas plastic deformation was more correlated with collagen maturity. Contact hardness, reflecting both elastic and plastic behaviors, was correlated with both DMB and collagen maturity. Norelationship was found between crystallinity and mechanical properties at the osteon level

Multicenter evaluation of the new Etest gradient diffusion method for piperacillin-tazobactam susceptibility testing of Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex

Piperacillin-tazobactam (P/T) is a β-lactam-β-lactamase inhibitor combination frequently used in the hospital setting. Etest is a gradient diffusion method that represents an alternative to broth microdilution (BMD) for performing antimicrobial susceptibility testing. We conducted a multicenter evaluation of the performance of the new P/T Etest compared to that of BMD following U.S. Food and Drug Administration (FDA) and International Standards Organization (ISO) standard ISO 20776-2 criteria using Clinical and Laboratory Standards Institute (CLSI)-FDA and European Committee on Antimicrobial Susceptibility Testing (EUCAST) interpretive breakpoints, respectively. A total of 977 isolates (77

Severe early onset preeclampsia: short and long term clinical, psychosocial and biochemical aspects

Preeclampsia is a pregnancy specific disorder commonly defined as de novo hypertension and proteinuria after 20 weeks gestational age. It occurs in approximately 3-5% of pregnancies and it is still a major cause of both foetal and maternal morbidity and mortality worldwide1. As extensive research has not yet elucidated the aetiology of preeclampsia, there are no rational preventive or therapeutic interventions available. The only rational treatment is delivery, which benefits the mother but is not in the interest of the foetus, if remote from term. Early onset preeclampsia (<32 weeks’ gestational age) occurs in less than 1% of pregnancies. It is, however often associated with maternal morbidity as the risk of progression to severe maternal disease is inversely related with gestational age at onset2. Resulting prematurity is therefore the main cause of neonatal mortality and morbidity in patients with severe preeclampsia3. Although the discussion is ongoing, perinatal survival is suggested to be increased in patients with preterm preeclampsia by expectant, non-interventional management. This temporising treatment option to lengthen pregnancy includes the use of antihypertensive medication to control hypertension, magnesium sulphate to prevent eclampsia and corticosteroids to enhance foetal lung maturity4. With optimal maternal haemodynamic status and reassuring foetal condition this results on average in an extension of 2 weeks. Prolongation of these pregnancies is a great challenge for clinicians to balance between potential maternal risks on one the eve hand and possible foetal benefits on the other. Clinical controversies regarding prolongation of preterm preeclamptic pregnancies still exist – also taking into account that preeclampsia is the leading cause of maternal mortality in the Netherlands5 - a debate which is even more pronounced in very preterm pregnancies with questionable foetal viability6-9. Do maternal risks of prolongation of these very early pregnancies outweigh the chances of neonatal survival? Counselling of women with very early onset preeclampsia not only comprises of knowledge of the outcome of those particular pregnancies, but also knowledge of outcomes of future pregnancies of these women is of major clinical importance. This thesis opens with a review of the literature on identifiable risk factors of preeclampsia

Discutindo a educação ambiental no cotidiano escolar: desenvolvimento de projetos na escola formação inicial e continuada de professores

A presente pesquisa buscou discutir como a Educação Ambiental (EA) vem sendo trabalhada, no Ensino Fundamental e como os docentes desta escola compreendem e vem inserindo a EA no cotidiano escolar., em uma escola estadual do município de Tangará da Serra/MT, Brasil. Para tanto, realizou-se entrevistas com os professores que fazem parte de um projeto interdisciplinar de EA na escola pesquisada. Verificou-se que o projeto da escola não vem conseguindo alcançar os objetivos propostos por: desconhecimento do mesmo, pelos professores; formação deficiente dos professores, não entendimento da EA como processo de ensino-aprendizagem, falta de recursos didáticos, planejamento inadequado das atividades. A partir dessa constatação, procurou-se debater a impossibilidade de tratar do tema fora do trabalho interdisciplinar, bem como, e principalmente, a importância de um estudo mais aprofundado de EA, vinculando teoria e prática, tanto na formação docente, como em projetos escolares, a fim de fugir do tradicional vínculo “EA e ecologia, lixo e horta”.Facultad de Humanidades y Ciencias de la Educació

Multiscale study of the effects of bisphosphonates on bone quality in postmenopausal osteoporotic women

L’ostéoporose ménopausique par une accélération du remodelage osseux, conduit à une masse osseuse basse et à des altérations de la microarchitecture, augmentant ainsi le risque de fracture. Les bisphosphonates diminuent l’activité du remodelage osseux en inhibant la résorption osseuse qui conduit à un maintien de la densité minérale osseuse et à une diminution du risque fracturaire. Ce traitement étant la plupart du temps chronique, l’étude de ses effets sur les différents niveaux d’organisation de l’os, du cristal à sa macrostructure, est primordiale. A travers deux études portant sur l’ibandronate et l’alendronate, nous avons montré que leur utilisation préservait la minéralisation osseuse tissulaire. Cependant, une utilisation prolongée (6,4 ans) de l’alendronate, nous a permis de mettre en évidence un mécanisme d’action impliquant des modifications de la structure des cristaux avec un effet sur les propriétés mécaniques locales. Si l’efficacité anti fracturaire de l’alendronate est démontrée après dix ans de traitement, nos résultats suggèrent des altérations de la qualité osseuse à une échelle plus localePostmenopausal osteoporosis is characterized by an increase in remodelling activity leading to a low bone mass and alterations in microarchitecture, increasing the risk of fracture. Bisphosphonates slowdown remodeling inhibiting bone resorption, thus bone mineral density is preserved with a decrease in the risk of fracture. Such a treatment is often chronic, making the study of their long-term effects on multiscale bone quality (from the crystal to the macrostructure) of clinical relevance. Thank to two different studies on ibandronate and alendronate, we showed that these treatments preserved the mineralization of bone tissue. However, we firstly described that a long-term treatment with alendronate alter the structure of bone mineral crystals with a direct effect on micromechanical properties. Even if, the reduction in the risk of fracture under alendronate has been established after a ten year treatment, our results suggest alterations in bone quality at tissular and sub-tissular levels of organizatio

Étude multi-échelles des effets osseux des bisphosphonates au cours du traitement de l’ostéoporose ménopausique

Postmenopausal osteoporosis is characterized by an increase in remodelling activity leading to a low bone mass and alterations in microarchitecture, increasing the risk of fracture. Bisphosphonates slowdown remodeling inhibiting bone resorption, thus bone mineral density is preserved with a decrease in the risk of fracture. Such a treatment is often chronic, making the study of their long-term effects on multiscale bone quality (from the crystal to the macrostructure) of clinical relevance. Thank to two different studies on ibandronate and alendronate, we showed that these treatments preserved the mineralization of bone tissue. However, we firstly described that a long-term treatment with alendronate alter the structure of bone mineral crystals with a direct effect on micromechanical properties. Even if, the reduction in the risk of fracture under alendronate has been established after a ten year treatment, our results suggest alterations in bone quality at tissular and sub-tissular levels of organizationL’ostéoporose ménopausique par une accélération du remodelage osseux, conduit à une masse osseuse basse et à des altérations de la microarchitecture, augmentant ainsi le risque de fracture. Les bisphosphonates diminuent l’activité du remodelage osseux en inhibant la résorption osseuse qui conduit à un maintien de la densité minérale osseuse et à une diminution du risque fracturaire. Ce traitement étant la plupart du temps chronique, l’étude de ses effets sur les différents niveaux d’organisation de l’os, du cristal à sa macrostructure, est primordiale. A travers deux études portant sur l’ibandronate et l’alendronate, nous avons montré que leur utilisation préservait la minéralisation osseuse tissulaire. Cependant, une utilisation prolongée (6,4 ans) de l’alendronate, nous a permis de mettre en évidence un mécanisme d’action impliquant des modifications de la structure des cristaux avec un effet sur les propriétés mécaniques locales. Si l’efficacité anti fracturaire de l’alendronate est démontrée après dix ans de traitement, nos résultats suggèrent des altérations de la qualité osseuse à une échelle plus local

Cortical thickness and porosity in human raddi and tibias: an ex-vivo- study

22d congress of the European Society of Biomechanics (ESB), LYON, FRANCE, 10-/07/2016 - 13/07/2016Cortical microstructure (porosity and thickness) is a major determinant of fragility fracture risk across life in human. Age-related alterations in bone remodeling result in a thinner and more porous cortex, traits that are both associated with higher risk for non-vertebral fracture. However, whether these age-related alterations impact similarly loaded and non-loaded bones is not known. We hypothesized that the cortical thickness and porosity are age-dependent and could match between loaded (Tibia) and non-loaded bones (Radius)

Influence of remodeling on the mineralization of bone tissue.

International audienceThe degree of mineralization of bone is a determinant of its mechanical strength and hardness. It is influenced by the level of activity of bone remodeling. Quantitative studies of bone mass, trabecular microarchitecture, bone organic matrix, and the degree of mineralization of bone are required to explain the anti-fracture effect of therapies at the tissue level and associated increases in lumbar bone density

Regional heterogeneity in the configuration of the intracortical canals of the femoral shaft

Three-dimensional (3D) characterization of cortical porosity, most of which is under 100 µm in diameter, is usually confined to measurements made in 3–4 mm diameter cylinders of bone. We used micro-computed tomography (micro-CT) scanning of entire transaxial cross sections of human proximal femoral shafts (30–35 mm diameter) to quantify regional variation in porosity within the same scan. Complete, up to 10-mm-thick, transaxial slices of femoral upper shafts from 8 female cadavers were studied (n = 3 aged 29–37 years, n = 5 aged 72–90 years). Scanning was performed using high-resolution micro-CT (8.65 µm/voxel). Micro-CT volumes (10 × 10 × 5 mm) were selected via software in the anterior, medial and lateral regions. Images were segmented with voids appearing as 3D-interconnected canals. The percent void-to-tissue volume (Vo.V/TV) and the corresponding void surface area/TV were 86–309 % higher in older than younger subjects in anterior (p = 0.034), medial (p = 0.077), and lateral aspects (p = 0.034). Although not significant, void separation was reciprocally lower by 19–39 %, and void diameter was 65 % larger in older than younger subjects; void number tended to be 24–25 % higher medially and laterally but not anteriorly. For all specimens combined, medially there was higher Vo.V/TV and void surface area/TV than anteriorly (+48 %, p = 0.018; +33 %, p = 0.018) and laterally (+56 %, p = 0.062; +36 %, p = 0.043). There is regional heterogeneity in the 3D microarchitecture of the intracortical canals of the femoral shaft. The higher void volume in advanced age appears to be due to larger, rather than more, pores. However, creation of new canals from existing canals may contribute, depending on the location. High-resolution micro-computed tomography scanning of entire bone segments enables quantification of the 3D microanatomy of the intracortical void network at multiple locations