BACKGROUND:To decrease operation amount of finite element analysis and increase its clinical practice,previous studies explored the material properties and 10 kinds of material attributes were assigned,which met the requirements of finite element analysis.Moreover,it can be used to calculate bone density.OBJECTIVE:To explore a method for measurement of bone density based on three-dimensional reconstruction and finite element analysis.METHODS:A total of 11 specimens of femoral superior segment were selected.The mass of control group was firstly measured.The experimental groups were treated with thin-slice high resolution CT scan and three-dimensional reconstruction in Mimics 10.0,volume meshing in Ansys,assigned with 10,100 and 400 kinds of material attributes Mimics,exported to Ansys to calculat the volumes of the block elements of every types of material attributes.The mass and the density of the specimens was harvested according to the empirical formula concerning the gray value and the bone density.All results were treated with one-way ANOVA.RESULTS AND CONCLUSION:One-way ANOVA showed that there were no significant differences between control group and experimental groups assigned with 10,100 and 400 kinds of material attributes (P＞0.28),and there were no significantly among the experimental groups (P＞0.8).Results show that the method was able to measure the mass and the density of bone quantitatively,as well as the proportion between compact bone and cancellous bone;to assign 10 kinds of material attributes to three-dimensional model of femur could match the needs for measurements.The results can be used as an initial preparation for the unification of bone density and finite element analysis for osteoporosis.

Development of controllable hypermutable cells can greatly benefit understanding and harnessing microbial evolution. However, there have not been any similar systems developed for Clostridium, an important bacterial genus. Here we report a novel two-step strategy for developing controllable hypermutable cells of Clostridium acetobutylicum, an important and representative industrial strain. Firstly, the mutS/L operon essential for methyldirected mismatch repair (MMR) activity was inactivated from the genome of C. acetobutylicum to generate hypermutable cells with over 250-fold increased mutation rates. Secondly, a proofreading control system carrying an inducibly expressed mutS/L operon was constructed. The hypermutable cells and the proofreading control system were integrated to form a controllable hypermutable system SMBMutC, of which the mutation rates can be regulated by the concentration of anhydrotetracycline (aTc). Duplication of the miniPthl-tetR module of the proofreading control system further significantly expanded the regulatory space of the mutation rates, demonstrating hypermutable Clostridium cells with controllable mutation rates are generated. The developed C. acetobutylicum strain SMBMutC2 showed higher survival capacities than the control strain facing butanol-stress, indicating greatly increased evolvability and adaptability of the controllable hypermutable cells under environmental challenges.
Butanols ; pharmacology ; Cell Engineering ; methods ; Clostridium acetobutylicum ; cytology ; drug effects ; genetics ; physiology ; DNA Methylation ; genetics ; DNA Mismatch Repair ; genetics ; Evolution, Molecular ; Genome, Bacterial ; genetics ; MutS DNA Mismatch-Binding Protein ; genetics ; Mutation ; Operon ; genetics ; Stress, Physiological ; drug effects ; genetics

Cyanobacteria are important photosynthetic autotrophic microorganisms and are considered as one of the most promising microbial chassises for photosynthetic cell factories. Glycogen is the most important natural carbon sink of cyanobacteria, playing important roles in regulating its intracellular carbon distributions. In order to optimize the performances of cyanobacterial photosynthetic cell factories and drive more photosynthetic carbon flow toward the synthesis of desired metabolites, many strategies and approaches have been developed to manipulate the glycogen metabolism in cyanobacteria. However, the disturbances on glycogen metabolism usually cause complex effects on the physiology and metabolism of cyanobacterial cells. Moreover, the effects on synthesis efficiencies of different photosynthetic cell factories usually differ. In this manuscript, we summarized the recent progress on engineering cyanobacterial glycogen metabolism, analyzed and compared the physiological and metabolism effects caused by engineering glycogen metabolism in different cyanobacteria species, and prospected the future trends of this strategy on optimizing cyanobacterial photosynthetic cell factories.
Carbon/metabolism* ; Carbon Dioxide/metabolism* ; Cyanobacteria/metabolism* ; Glycogen/metabolism* ; Metabolic Engineering ; Photosynthesis/physiology*

Bioethanol is one of the most promising and representative biofuel products. Photosynthetic production of ethanol using CO₂ and solar energy based on cyanobacteria is of great significance for research and application, due to the potential to reduce CO₂ emission and to provide renewable energy simultaneously. Here we review the history and updated development of cyanobacteria cell factories for ethanol photosynthetic production, the progress and problems in pathway optimization, chassis selection, and metabolic engineering strategies, and finally indicate the future development in this area.

Biorefinery technologies provide promising solutions to achieve sustainable development facing energy and environment crisis, while abundant sugar feedstock is an essential basis for biorefinery industries. Photosynthetic production of sucrose with cyanobacteria is an alternative sugar feedstock supply route with great potentials. Driven by solar energy, cyanobacteria photosynthetic cell factory could directly convert carbon dioxide and water into sucrose, and such a process could simultaneously reduce carbon emissions and supply sugar feedstocks. Here we introduced the history and updated the state-of-the-art on development of cyanobacteria cell factories for photosynthetic production of sucrose, summarized the progress and problems on mechanisms of sucrose synthesis, metabolic engineering strategies and technology expansions, and finally forecasted the future development direction in this area.
Carbon Dioxide ; Cyanobacteria ; Metabolic Engineering ; Photosynthesis ; Sucrose