Guided tissue regeneration using bioresorbable membranes: what is the limit in the treatment of combined periapical and marginal lesions?

The maintenance of single teeth may often be of crucial importance for the prognosis of the total dentition. In such cases, as when a single tooth supports a fixed partial denture, a special effort should be made to maintain that tooth. This study reports the treatment of six such terminal cases. The results of a combination of local and systemic antibiotics and the use of guided tissue regeneration with resorbable membranes and grafting material is demonstrated. After defect debridement and root planing, the defects were filled with Biostite (Coletica), and Paroguide (Coletica) membranes were placed. The results at reentry demonstrated the efficacy of these treatments, and all six treatments were considered successful. The influence of the individual components used in treatment is discussed.     

A general strategy for the expression of recombinant human cytochrome P450s in Escherichia coli using bacterial signal peptides: expression of CYP3A4, CYP2A6, and CYP2E1

Heterologous expression of unmodified recombinant human cytochrome P450 enzymes (P450s) in Escherichia coli has proved to be extremely difficult. To date, high-level expression has only been achieved after altering the 5'-end of the native cDNA, resulting in amino acid changes within the P450 protein chain. We have devised a strategy whereby unmodified P450s can be expressed to high levels in E. coli, by making NH2-terminal translational fusions to bacterial leader sequences. Using this approach, we initially tested two leader sequences, pelB and ompA, fused to CYP3A4. These were compared with an expression construct producing a conventional NH2-terminally modified CYP3A4 (17alpha-3A4). Both leader constructs produced spectrally active, functional protein. Furthermore, the ompA-3A4 fusion gave higher levels of expression, and a marked improvement in the recovery of active P450 in bacterial membrane fractions, when compared with 17alpha-3A4. We then tested the ompA leader with CYP2A6 and CYP2E1, again comparing with the conventional (17alpha-) approach. As before, the leader construct produced active enzyme, and, for CYP2E1 at least, gave a higher level of expression than the 17alpha-construct. The ompA fusion strategy thus appears to represent a significant advance for the expression of P450s in E. coli, circumventing the previous need for individual optimization of P450 sequences for expression.