Zebrafish: bridging the gap between development and disease

The zebrafish has been the model of choice amongst developmental biologists for many years. This small freshwater species offers many advantages to the study of organ and tissue development that are not provided by other model systems. Against this background, modern molecular genetic approaches are being applied to expand the physical and genetic mapping of the zebrafish genome. These approaches complement the large-scale mutagenic screens that have led to the isolation of mutant phenotypes. Some of the phenotypes have been found to resemble human disease states, while mapping and sequencing data have revealed zebrafish genes with significant homology to human disease-causing genes. It is the realization that the zebrafish offers an amenable system for understanding disease, as opposed to development, that underpins this review. The adventitious identification of disease phenotypes amongst zebrafish mutants and the important area of deliberate disease modelling using transgenesis and gene targeting should lead to a better application of the zebrafish as a vertebrate model of human diseases.

Instrumentation for automated determination of protein stability

A new instrument system has been developed that automatically carries out solvent and thermal denaturations of proteins using fluorescence as a probe of structure. This instrument also automatically performs pH titrations and can make kinetic measurements on the time scale of seconds. The design philosophy and implementation are described. The prototype instrument was subjected to extensive testing. The instrument can very reproducibly and accurately collect data that allow the calculation of the thermodynamics of protein denaturation. This data collection can proceed without human intervention after acquisition start until the data are saved.

Effects of gamma radiation on the in vitro wear of composite restorative materials

The effects of gamma radiation at therapeutic dosage levels on the wear of three anterior (two light-cured and one autocured) composites and a light-cured posterior composite were studied in vitro. Specimens were subjected to successive sets of 100 abrades to a maximum of 500 abrades on a reciprocating arm abrader, with the dimensional change being recorded between the sets of abrades. The data showed that there were no significant effects on the wear rates of any of the materials tested. The rate of height loss was similar for the two hybrid composites tested (P less than 0.05), as was that for the microfilled and conventional material (P less than 0.05). There was, however, a significant difference (P greater than 0.001) in the wear behaviour between the two groups.

The radiographic density of composite restorative resins

The radiodensities of enamel, dentin, aluminum, and 14 modern composite resins at thicknesses of 1 to 4 mm were compared. Nine of the 14 composites were radiopaque with respect to that of aluminum. Radiolucent lesions or voids were simulated by cutting grooves 0.5, 1.0, and 2.0 mm deep in aluminum stepwedge blocks, superimposing stepwedges of the radiopaque composites over the blocks, and radiographing the combination. It was found that only five of the nine radiopaque composite materials possessed radiodensities that permitted clear radiographic detection of the smaller defects.