Biomechanics of a posture-controlling cervical artificial disc: mechanical, in vitro, and finite-element analysis

Different methods have been described by numerous investigators for experimentally assessing the kinematics of cervical artificial discs. However, in addition to understanding how artificial discs affect range of motion, it is also clinically relevant to understand how artificial discs affect segmental posture. The purpose of this paper is to describe novel considerations and methods for experimentally assessing cervical spine postural control in the laboratory. These methods, which include mechanical testing, cadaveric testing, and computer modeling studies, are applied in comparing postural biomechanics of a novel postural control arthroplasty (PCA) device versus standard ball-and-socket (BS) and ball-in-trough (BT) arthroplasty devices. The overall body of evidence from this group of tests supports the conclusion that the PCA device does control posture to a particular lordotic position, whereas BS and BT devices move freely through their ranges of motion.

Fungal beta-tubulin, expressed as a fusion protein, binds benzimidazole and phenylcarbamate fungicides

Benzimidazoles are important antitubulin agents used in veterinary medicine and plant disease control. Resistance is a practical problem correlated with single amino acid changes in beta-tubulin and is often linked to greater sensitivity to phenylcarbamates. This negative cross-resistance creates opportunities for durable antiresistance strategies. Attempts to understand the molecular basis of benzimidazole resistance have been hampered by the inability to purify tubulin from filamentous fungi. We have overcome some of these problems by expressing beta-tubulin as a fusion with a maltose binding protein. This fusion protein is soluble, and we confirm for the first time using a gel filtration assay that benzimidazoles indeed bind to beta-tubulin. This binding is reduced by the mutation Glu198-->Gly198, which also confers resistance. Binding of phenylcarbamates is the complete opposite, reflecting their biological activity and the negative cross-resistance. This suggests that the fungicide binding sites fold correctly in the fusion protein.