05-2005 Newsletter

Minnesota State University, Mankato, Library Services Newsletter for May 2005

GRANULOCYTE-COLONY STIMULATING FACTOR ENHANCES BONE FRACTURE HEALING

International audienceBackgroundCirculating mesenchymal stem cells contribute to bone repair. Their incorporation in fracture callus is correlated to their bioavailability. In addition, Granulocyte-colony stimulating factor induces the release of vascular and mesenchymal progenitors. We hypothesized that this glycoprotein stimulates fracture healing, and analyzed the effects of its administration at low doses on bone healing. Methods27 adult male Sprague-Dawley rats underwent mid-femur osteotomy stabilized by centromedullar pinning. In a post (pre) operative group, rats were subcutaneously injected with 5µg/kg per day of Granulocyte-colony stimulating factor for 5 days after (before) surgery. In a control group, rats were injected with saline solution for 5 days immediately after surgery. A radiographic consolidation score was calculated. At day 35, femurs were studied histologically and underwent biomechanical tests. Findings5 weeks after surgery, mean radiographic scores were significantly higher in the Preop group 7.75 (SD 0.42) and in the Postop group 7.67 (SD 0.52) than in the control group 6.75 (SD 0.69). Biomechanical tests showed femur stiffness to be more than three times higher in both the Preop 109.24N/mm (SD 51.86) and Postop groups 100.05N/mm (SD 60.24) than in control 32.01N/mm (SD 15.78). Mean maximal failure force was twice as high in the Preop group 68.66 N (SD 27.78) as in the control group 34.21N (SD 11.79). Histological results indicated a later consolidation process in control than in treated groups. InterpretationGranulocyte-colony stimulating factor injections strongly stimulated early femur fracture healing, indicating its potential utility in human clinical situations such as programmed osteotomy and fracture

Mechanical Characterization at the Microscale of Mineralized Bone Callus after Bone Lengthening

International audienceDistraction osteogenesis (DO) involves several processes to form an organized distracted callus. While bone regeneration during DO has been widely described, no study has yet focused on the evolution profile of mechanical properties of mineralized tissues in the distracted callus. The aim of this study was therefore to measure the elastic modulus and hardness of calcified cartilage and trabecular and cortical bone within the distracted callus during the consolidation phase. We used a microindentation assay to measure the mechanical properties of periosteal and endosteal calluses; each was subdivided into two regions. Histological sections were used to localize the tissues. The results revealed that the mechanical properties of calcified cartilage did not evolve over time. However, trabecular bone showed temporal variation. For elastic modulus, in three out of four regions, a similar evolution profile was observed with an increase and decrease over time. Concerning hardness, this evolves differently depending on the location in the distracted callus. We also observed spatial changes in between regions. A first duality was apparent between regions close to the native cortices and the central area, while latter differences were seen between periosteal and endosteal calluses. Data showed a heterogeneity of mechanical properties in the distracted callus with a specific mineralization profile

Estimating the change in cellular size variance during cell death using the polydisperse structure factor model

International audienceQuantitative UltraSound (QUS) techniques for determining the tissue microstructure are promising tools to detect and quantify cell death, and thus monitor the tumor response to therapy. Previous in vitro experimental studies suggested that the changes in the backscatter coefficient (BSC) during cell death were linked to the increase of the cellular size variance. The aim of this work was to estimate the change in cellular size variance from the polydisperse structure factor model (SFM) by using experimental ultrasonic measurement before and after therapy. The polydisperse SFM was recently demonstrated to be efficient for explaining the measured BSCs on cell pellet biophantoms. Cell pellet biophantoms consist in centrifugated densely packed cells and serve as simplified in vitro versions of real tumors. Ultrasonic backscatter measurements were performed at frequencies ranging from 10 to 42 MHz on colon adenocarcinoma cell pellet biophantoms treated with staurosporine, a drug which induces mainly cell apoptosis. Blind estimates of QUS parameters were performed by fitting one measured BSC with a standard ultrasonic scattering model, namely the fluid sphere model (FSM). A novel approach was also proposed to estimate QUS parameters from the polydisperse SFM by using two measured BSCs before and after therapy. Finally, the relationship between the actual cellular structures and QUS parameters was investigated

Estimating the change in cellular size variance during cell death using the polydisperse structure factor model

IEEE International Ultrasonics Symposium (IUS), Kobe, JAPAN, OCT 22-25, 2018International audienceQuantitative UltraSound (QUS) techniques for determining the tissue microstructure are promising tools to detect and quantify cell death, and thus monitor the tumor response to therapy. Previous in vitro experimental studies suggested that the changes in the backscatter coefficient (BSC) during cell death were linked to the increase of the cellular size variance. The aim of this work was to estimate the change in cellular size variance from the polydisperse structure factor model (SFM) by using experimental ultrasonic measurement before and after therapy. The polydisperse SFM was recently demonstrated to be efficient for explaining the measured BSCs on cell pellet biophantoms. Cell pellet biophantoms consist in centrifugated densely packed cells and serve as simplified in vitro versions of real tumors. Ultrasonic backscatter measurements were performed at frequencies ranging from 10 to 42 MHz on colon adenocarcinoma cell pellet biophantoms treated with staurosporine, a drug which induces mainly cell apoptosis. Blind estimates of QUS parameters were performed by fitting one measured BSC with a standard ultrasonic scattering model, namely the fluid sphere model (FSM). A novel approach was also proposed to estimate QUS parameters from the polydisperse SFM by using two measured BSCs before and after therapy. Finally, the relationship between the actual cellular structures and QUS parameters was investigated

Probing the cellular size distribution in cell samples undergoing cell death

International audienceA polydisperse scattering model adapted for concentrated medium, namely the polydisperse structure factor model, was examined in order to explain the backscatter coefficients (BSCs) measured from packed cell samples undergoing cell death. Cell samples were scanned using high-frequency ultrasound in the 10-42 MHz bandwidth. A parameter estimation procedure was proposed in order to estimate the volume fraction and the relative impedance contrast that could explain the changes in BSC pattern by considering the actual change in cellular size distribution. Quantitative ultrasound parameters were estimated and related to the percentage of dead cells determined by flow cytometry. The standard deviation of scatterer size distribution extracted from the polydisperse structure factor model and the spectral intercept were found to be strongly correlated to the percentage of dead cells (r^2 =0.79 and r^2 =0.72, respectively). The current study contributes to the understanding of ultrasonic scatteringfrom cells undergoing cell death toward the monitoring of cancer therapy

Estimating the change in cellular size variance during cell death using the polydisperse structure factor model

International audienceQuantitative UltraSound (QUS) techniques for determining the tissue microstructure are promising tools to detect and quantify cell death, and thus monitor the tumor response to therapy. Previous in vitro experimental studies suggested that the changes in the backscatter coefficient (BSC) during cell death were linked to the increase of the cellular size variance. The aim of this work was to estimate the change in cellular size variance from the polydisperse structure factor model (SFM) by using experimental ultrasonic measurement before and after therapy. The polydisperse SFM was recently demonstrated to be efficient for explaining the measured BSCs on cell pellet biophantoms. Cell pellet biophantoms consist in centrifugated densely packed cells and serve as simplified in vitro versions of real tumors. Ultrasonic backscatter measurements were performed at frequencies ranging from 10 to 42 MHz on colon adenocarcinoma cell pellet biophantoms treated with staurosporine, a drug which induces mainly cell apoptosis. Blind estimates of QUS parameters were performed by fitting one measured BSC with a standard ultrasonic scattering model, namely the fluid sphere model (FSM). A novel approach was also proposed to estimate QUS parameters from the polydisperse SFM by using two measured BSCs before and after therapy. Finally, the relationship between the actual cellular structures and QUS parameters was investigated

New method for distraction callus material properties measurement with the use of nanoindentation

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Method for measurement of distracted callus tissues properties with the use of Nanoindentation

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