Biomedical subjects
Publications and source records attributed to M Kok.
Extraction of R1162 plasmid DNA with the alkaline lysis method yields considerable amounts of single-stranded circular plasmid DNA. Destabilization of plasmid DNA is stimulated by the R1162 mob region in cis. The formation of single-stranded circular DNA is initiated at a specific site on the plasmid, presumably the origin of transfer (oriT).
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We cloned sequences of the alk (alkane utilization) operon of Pseudomonas and characterized them physically and genetically. These sequences were used to construct a DNA restriction map of the alkBAC region. We physically mapped alk::Tn7 insertions and delta alkBA deletions, and we were able to show complementation or marker rescue of alk point mutations by cloned DNA sequences. Our results confirmed the existence of an operon containing structural loci encoding activities for membrane alkane hydroxylase component (alkB), soluble alkane hydroxylase component (alkA) and membrane alcohol dehydrogenase (alkC). Physical mapping of alkC::Tn7 insertions and complementation of alkC point mutations by cloned sequences from the alkBA region showed that we were previously mistaken in inferring the existence of a separate unlinked alkC cluster. Studies with an alkB-lacZ transcription fusion construct established that the operon is transcribed in the order alkBAC and is under positive regulation by alkR regulatory functions.
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Two methylation methods are compared in relation to the determination of low levels (less than microgram/ml) of the acidic metabolite of bezitramide in human urine. It was necessary to use alkali flame ionisation detector, which specifically detects nitrogen-containing compounds. Several difficulties associated with the use of this detector are described.
The prevalence of bacterial diseases and bacterial resistance is currently increasing, emphasizing the need for alternative vaccines. The body of knowledge on molecular determinants of bacterial virulence has tremendously increased during the recent years, and new molecular targets are available for immunization. Intramuscular injection of plasmid DNA containing bacterial genes with a suitable appropriate promotor is followed by transfection of host cells which will produce bacterial proteins, and elicit humoral and cytotoxic lymphocyte-mediated responses. Mucosal vaccines induce local immune response, both by type 1 and type 2 dependent pathways. Living bacterial vectors can provide conditional delivery of foreign antigens in selected host sites. A series of new substances allows us to steer the immune response in a way that optimizes immune protection. All this impressive progress will undoubtedly lead to the development of novel vaccines enabling us to ensure improved protection against bacterial diseases.