[Constructions of the scale of difficulty in the extraction of impacted mandibular third molars by using Delphi method].

OBJECTIVE: To evaluate the relevant indicators affecting difficulty in the extraction of impacted mandibular third molars and score difficulty of different operation and risk indicators, so as to build an intuitive and accurate scale to help operators make more accurate analysis and prediction of difficulty before the operation. METHODS: Based on literature and the clinical review, the difficulty indicators of tooth extraction were summarized. Firstly, 10 doctors from Peking University School and Hospital of Stomatology who had been engaged in alveolar surgery for a long time established an expert nominal group, and then rated whether the summarized indicators needed to be retained in the form of face-to-face questionnaires. A level 1 and 2 item frame for evaluating difficulty in the tooth extraction was formed after discussion; Then Delphi method was used to send a questionnaire to 30 experts by e-mail. After two rounds of scoring and modification, the scale of difficulty in the extraction of impacted mandibular third molars was formed. RESULTS: The recycling rate of two rounds of questionnaires was 100.0%, which showed that the experts were very enthusiastic about the study; The authority coefficients (Cr) of the two rounds of Delphi expert consultation were both 0.92, which showed that the results were representative and authoritative. After two rounds of grading and revision, the variable coefficient (CV) decreased and the Kendall's concordance coefficient (W) increased, which were statistically significant: In the first round, the CV was 0.24 and W was 0.56 (P < 0.001), and in the second, the CV was 0.19 and W was 0.72 (P < 0.001), which indicated that there was a good convergence among the expert opinions. Finally, a scale of difficulty in the tooth extraction containing 12 items at level A and 37 items at level B was formed, including operation difficulty indicators, risk difficulty indicators and common difficulty indicators. CONCLUSION: Based on comprehensive literature retrieval, the study has put forward the concept that difficulty in the extraction of impacted mandibular third molars is composed of operation difficulty and risk difficulty. Using Delphi method, the long-term clinical experience and professional knowledge of experts are transformed into quantitative indicators as a scoring scale. The scale has certain representativeness and authority.

A HU-like protein binds to specific sites within nod promoters of Rhizobium leguminosarum.

Nodulation genes (nod) of rhizobia are essential for establishment of its symbiosis with specific legume hosts and are usually located on the Sym(biosis) megaplasmid. In this work we identified a new Sym plasmid independent protein in Rhizobium leguminosarum, Px, by its ability to bind to nod promoters and induce DNA bending. Depending upon its concentrations relative to DNA templates, Px could either stimulate or inhibit in vitro transcription of the major regulatory nodulation gene nodD. This may result from its property to bind to specific sites within nod promoters at lower concentration or in the presence of competitor calf thymus DNA but nonspecifically associate with DNA at higher levels or in the absence of competitors. Its binding sites within nodD and nodF promoters were determined by DNase I footprinting but showed no sequence consensus. N-terminal sequencing and Western blot revealed that Px belongs to the HU class of prokaryotic histone-like proteins. Its binding feature and functioning mechanism were discussed in the light of this discovery.

Rapid method for identifying subclones bridging gaps between contiguous DNA sequences.

Randomly sequencing of a limited number of unidirectional deletion subclones efficiently generated contiguous DNA sequences with some gaps between them. Gap-bridging subclones were identified by agarose gel electrophoresis. Those located at either end of each individual contiguous sequence were used as standard marker molecules; the subclones between them proved to be correctly identified in most cases. A 4064 bp DNA fragment containing the psr gene was sequenced with the strategy described in this paper.