A biomechanical study of the effects of simulated ulnar deviation on silicone finger joint implant failure.

Silicone finger arthroplasties are used widely, especially for metacarpophalangeal joint replacement in patients with inflammatory arthritis. Implant failure is well recognized. The rates of failure in vivo differ substantially from experience in vivo. One cause of failure is felt to be post-operative ulnar deviation. The aim of our study was to test the effect of ulnar deviation testing on silicone finger implants. We tested 12 implants in three groups of four implants. The implants were submerged in a bath of Ringer's solution at 370 °C throughout the experiment and tested in a rig held in 0°, 10° and 20° deviation. The rig was cycled at 1.5 Hz from 0°-90°. The implants were inspected every 500,000 cycles until a total of 4 million cycles. There was consistently increased wear and supination plastic deformity in going from 0°-20° deviation. This study confirms the adverse effects of ulnar deviation on silicone finger implant wear. It is likely that this combines with lateral pinch forces and sharp bone edges to cause catastrophic silicone implant failure. LEVEL OF EVIDENCE: III.

Reef-coral proteins as visual, non-destructive reporters for plant transformation.

Recently, five novel fluorescent proteins have been isolated from non-bioluminescent species of reef-coral organisms and have been made available through ClonTech. They are AmCyan, AsRed, DsRed, ZsGreen and ZsYellow. These proteins are valuable as reporters for transformation because they do not require a substrate or external co-factor to emit fluorescence and can be tested in vivo without destruction of the tissue under study. We have evaluated them in a large range of plants, both monocots and dicots, and our results indicate that they are valuable reporting tools for transformation in a wide variety of crops. We report here their successful expression in wheat, maize, barley, rice, banana, onion, soybean, cotton, tobacco, potato and tomato. Transient expression could be observed as early as 24 h after DNA delivery in some cases, allowing for very clear visualization of individually transformed cells. Stable transgenic events were generated, using mannose, kanamycin or hygromycin selection. Transgenic plants were phenotypically normal, showing a wide range of fluorescence levels, and were fertile. Expression of AmCyan, ZsGreen and AsRed was visible in maize T1 seeds, allowing visual segregation to more than 99% accuracy. The excitation and emission wavelengths of some of these proteins are significantly different; the difference is enough for the simultaneous visualization of cells transformed with more than one of the fluorescent proteins. These proteins will become useful tools for transformation optimization and other studies. The wide variety of plants successfully tested demonstrates that these proteins will potentially find broad use in plant biology.

Creation of ecdysone receptor chimeras in plants for controlled regulation of gene expression.

Transformation with a chimeric receptor containing the glucocorticoid transactivation and DNA-binding domains fused to an ecdysteroid receptor ligand-binding domain permits ecdysone agonist-inducible gene expression in monocotyledonous plant cells. The inducible system is based on the specific activation of a chimeric receptor containing the ligand-binding domain of the Heliothis virescens ecdysteroid receptor and the inducer RH5992 (a 20-hydroxyecdysone agonist). RH5992 is an non-steroidal agrochemical with a high specificity for lepidopteran ecdysone receptors. Addition of RH5992 to transformed cells results in high levels of inducible expression in a ligand-specific manner, particularly when the effector receptor is coupled to the strong transactivator VP16. A chimeric construct containing the Drosophila ecdysone ligand-binding domain failed to activate reporter gene activity with RH5992, while activation was observed in the presence of muristeroneA. The system described provides the basis for an inducible gene expression system that is compatible with agricultural use.