Elements in the co-evolution of relaxases and their origins of transfer.

The central elements in the conjugative mobilization of most plasmids are the relaxase and its cognate origin of transfer (oriT). The relaxase of the plasmid R1162, together with its oriT, belong to a large and widely distributed family of related relaxase/oriT pairs. Several of the properties of these elements are considered for R1162 and for other members of this family with a view to understanding how systems for mobilization might have evolved.

Conjugative DNA synthesis: R1162 and the question of rolling-circle replication.

Strand-replacement synthesis during conjugative mating has been characterized by introducing into donor cells R1162 plasmid DNA containing a base-pair mismatch. Conjugative synthesis in donors occurs in the absence of vegetative plasmid replication, but with a lag between rounds of transfer, and with most strands being initiated at the normal site within the replicative origin. These characteristics argue against the idea that multiple plasmid copies are generated for successive rounds of transfer by rolling-circle replication.

Selection of plasmid molecules for conjugative transfer and replacement strand synthesis in the donor.

Plasmid selection and strand replacement synthesis in donor cells during conjugative transfer was examined by a procedure involving electroporation of test plasmid DNA, containing a base pair mismatch, into donor cells prior to mating. Multiple copies of the plasmid were transferred from a donor cell that allowed vegetative replication of the plasmid. Under conditions non-permissive for vegetative replication, there were further rounds of transfer after a lag period.

A dose-volume histogram analysis of the seminal vesicles in men treated with conformal radiotherapy to 'prostate alone'.

Background And Purpose: There is no consensus on whether the seminal vesicles should be included in the clinical target volume (CTV) for radiotherapy of localized prostate cancer. To inform the debate, we have undertaken a dose-volume histogram (DVH) analysis of the seminal vesicles in patients treated with escalated dose conformal radiation to 'prostate alone'.

Material And Methods: Twenty-five consecutive patients receiving conformal radiation to the prostate, to a dose of 75.