We compared the ultraviolet radiation-induced reversion of nonsense (lacZ53) and missense (leuB19) mutations in uvrB5, uvrB5 uvrD3, uvrB5 recB21, and uvrB5 uvrD3 recB21 strains of Escherichia coli K-12. Nonsense (trpE65) reversion was also compared in similar derivatives of E. coli B/r uvrA155. The uvrD mutation reduced mutagenesis in very case, but had its main effect in cells ultraviolet irra...

P ERIODIC REPORTS HAVE EMPHASIZED the lack of stability of repeated tuberCulin skin tests in children. Kunofsky and Katz1 reported on two large groups in two schools for mental defectives. Reversion rates of 4 to 19 per cent were found. Marks et al.2 reported reversion rates between 12 and 26 per cent, depending on Criteria used, during a one-year period of observation of 1,100 tuberculin posit...

Tumor reversion is defined as the process by which cancer cells lose their malignant phenotype. However, relatively little is known about the cellular proteome changes that occur during the reversion process. A biological model of multiple myeloma (MM) reversion was established by using the H-1 parvovirus as a tool to select for revertant cells from MM cells. Isolated revertant cells displayed ...

In a system described by Cairns and Foster, starvation of a particular leaky lac mutant (lacIZ33) in the presence of lactose appears to direct mutation in non-growing cells to sites that allow growth (adaptive mutation). This behaviour requires that the lac operon be located on an F' plasmid. This position effect was investigated by placing the mutant lac operon at many sites in the genome of S...

Ralstonia solanacearum is a plant pathogenic bacterium that undergoes a spontaneous phenotypic conversion (PC) from a wild-type pathogenic to a non-pathogenic form. PC is often associated with mutations in phcA, which is a key virulence regulatory gene. Until now, reversion to the wild-type pathogenic form has not been observed for PC variants and the biological significance of PC has been ques...

Breaking the strength-ductility paradox of very-low (≤0.05 wt.%)-C medium (3–12 wt.%)-Mn steels (MMnS) has been a hard-wired topic, since in these multi-step heat treatments are usually required to obtain austenite for improved ductility and precipitates higher strength. In this study, compact two-step treatment comprising short (2 min) annealing tempering was developed investigate synergetic e...

Grit blasting is a low cost surface modification treatment widely used to enhance mechanical fixation of implants through increasing their roughness. As a result of the severe surface plastic deformation, beneath the surface it produces additional effects such as grain size refinement, work hardening and compressive residual stresses, which are generally evaluated with destructive techniques. I...

The interest in using the pseudoelastic properties of NiTi wires in orthodontic practice arises chiefly from the expectation that they can afford low continuous forces at constant temperature. The reversion force developed by NiTi archwires depends, however, upon temperature since the superelastic force follows a Clausius-Clapeyron like equation. Actually the oral environment temperature is mod...