Effectiveness of light-curing units in vocational training practices. A project administered by the Research Committee of the Faculty of General Dental Practitioners (UK).

A project has been organised by the Research Committee of the Faculty of General Dental Practitioners (UK) in conjunction with vocational training advisers in which vocational dental practitioners (VDPs) tested the effectiveness of the light-curing units in their surgeries using Heliotests (Ivoclar-Vivadent) and Z100 Composite (3M). The VDPs also completed a questionnaire giving details of their light-curing units. The mean incremental depth stated as being used by the respondents was 2.6 mm; 43.5% of the participants' light-curing units (n = 63) were found to produce a depth of cure less than this figure. However, no correlation was found between reported post-operative clinical problems and cure depth lower than 2.6 mm. A negative correlation between depth of cure and age of light-curing unit was noted, with older units tending to cure the composite samples to less depth than newer units (p = 0.002). One-fifth of the participating VDPs' practices had some means of checking curing-light effectiveness. Greater awareness of the need to monitor practice light-curing units is therefore required.

Using clinical audit in practice: a pilot peer review project.

A well-established study group undertook a pilot peer review project testing the use of clinical audit in members' practices. Two peer review groups were formed involving a total of 16 practices. Practice visits were undertaken and a series of meetings were held to prepare and discuss the various projects. The progress of the groups was monitored by questionnaires. All practitioners reported benefits from the project (specifically, from the practice visits) and made changes in areas of their practice other than those specifically chosen for their project. The benefits of carrying out audit projects in a peer review setting are stressed as are the benefits of reciprocal practice visits. The importance of prior establishment of mutual trust and confidence in the peer review group is emphasised.

The construction of Bacillus thuringiensis strains expressing novel entomocidal delta-endotoxin combinations.

Using our recently reported method of electroporation to transform Bacillus thuringiensis [Bone & Ellar (1989) FEMS Microbiol. Lett. 58, 171-178], cloned B. thuringiensis entomocidal delta-endotoxin genes have been introduced into several native B. thuringiensis strains. In many cases the resulting transformants expressed both their native toxins and the cloned toxin, producing strains with broader toxicity spectra. The introduction of the var. tenebrionis toxin gene into B. thuringiensis var. israelensis resulted in a strain with activity against Pieris brassicae (cabbage white butterfly), an activity which neither parent strain possesses. We discuss further the possibility of synergism and also the problems associated with introducing cloned DNA by this method.

Amplification of genomic sequences flanking transposable elements in host and heterologous plants: a tool for transposon tagging and genome characterization.

The isolation of sequences flanking integrated transposable elements is an important step in gene tagging strategies. We have demonstrated that sequences flanking transposons integrated into complex genomes can be simply and rapidly obtained using the polymerase chain reaction. Amplification of such sequences was established in a model system, a transgenic tobacco plant carrying a single Ac element, and successfully applied to the cloning of a specific Spm element from a maize line carrying multiple Spm hybridizing sequences. The described utilization of methylation sensitive restriction enzymes (including those with degenerate recognition sequences) in the generation of templates for amplification will simplify the cloning and mapping of genomic sequences adjacent to transposable elements.

Hydrocarbons and aromatic hydrocarbons in groundwater surrounding an earthen waste disposal pit for produced water in the Duncan oil field of New Mexico.

Samples of groundwater and soil were collected from test pits placed 25 m intervals on five axes extending from an earthen waste disposal pit for produced water near the San Juan River of northwest New Mexico. Samples were obtained at depths of 1.2 to 1.5 m and were analyzed using GC and GC/MS techniques for purgable hydrocarbons, including benzenes, and for solvent extractable organic compounds. Water samples from test pits down-gradient from the disposal pit contained purgable and extractable hydrocarbons that were similar to contents of the waste disposal pit. In contrast, water samples obtained from test pits up-gradient from the waste pit were free of detectable organic components. Major purgable components in the waste pit and in surrounding groundwater included saturated/unsaturated hydrocarbons and aromatic/alkylated aromatic hydrocarbons. Samples collected 25 m from the waste pit contained concentrations of all compounds greater than in samples taken at 50 m in distance on the same exis. Total concentration of purgable aromatic hydrocarbons in groundwater from test plots ranged from a high of 200 ppb at 25 m, to a low of 12 ppb at 50 m on an axis through the plume center.