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“Study Design. An in vitro biomechanical study investigating interbody device subsidence measures

in synthetic vertebrae, polyurethane foam blocks, and human cadaveric vertebrae.

Objective. To compare subsidence measures of bone surrogates with human vertebrae for interbody devices varying in size/placement.

Summary of Background Data. Bone surrogates are alternatives click here when human cadaveric vertebrae are unavailable. Synthetic vertebrae modeling cortices, endplates, and cancellous bone have been developed as an alternative to polyurethane foam blocks for testing interbody device subsidence.

Methods. Indentors placed on the endplates of synthetic vertebrae, foam blocks, and human vertebrae were subjected to uniaxial compression. Subsidence, measured with custom-made extensometers, was evaluated for an indentor seated either centrally or peripherally on the endplate. Failure force and indentation stiffness were determined

from force-displacement curves.

Results. Subsidence measures in human vertebrae varied with indentor placement: failure forces were higher and indentors subsided less with peripheral placement. Subsidence measures in foam blocks were insensitive to indentor size/placement; they were similar to human vertebrae for centrally placed but not for peripherally placed indentors. Although subsidence measures in synthetic vertebrae were sensitive SB273005 mouse to indentor size/placement, failure force and indentation stiffness were overestimated, and subsidence underestimated, for both centrally placed and peripherally placed indentors.

Conclusion. The synthetic endplate correctly represented the human endplate geometry, and thus, failure force, stiffness, and subsidence in synthetic vertebrae were sensitive to indentor size/ placement. U0126 However, the endplate was overly strong and thus synthetic vertebrae did not accurately model indentor subsidence in human cadaveric vertebrae. Foam blocks captured subsidence measures more accurately than synthetic vertebrae for centrally placed indentors, but because

of their uniform density were not sufficiently robust to capture changes generated from different indentor sizes/placements. The current bone surrogates are not accurate enough in terms of material property distribution to completely model subsidence in human cadaveric vertebrae.”
“Acetic acid widely spreads in atmosphere, aquatic ecosystems containing residues and anoxic soil. It can inhibit aquatic plant germination and growth, and even cause programmed cell death (PCD) of yeast. In the present study, biochemical and physiological responses of the model unicellular green algae Chlamydomonas reinhardtii were examined after acetic acid stress. H2O2 burst was found in C. reinhardtii after acetic acid stress at pH 5.0 for 10 min. The photosynthetic pigments were degraded, gross photosynthesis and respiration were disappeared gradually, and DNA fragmentation was also detected.