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R Mountford

Publications and source records attributed to R Mountford.

23 records · Page 2Linked to original sources
PubMed1988

Common organization of gene clusters for production of different capsular polysaccharides (K antigens) in Escherichia coli.

Southern blot analysis of cloned K5- and K7-antigen genes, using DNA fragments from cloned K1 genes as radiolabeled probes, demonstrated that each K-antigen gene cluster is organized in a manner similar to that shown for the K1 antigen. That is, a central DNA segment unique for a given antigen type is flanked by DNA sequences that encode common functions for the management of intracellular polymer. This has been confirmed by transposon and deletion mutagenesis of plasmids carrying the K5 and K7 genes. We also describe a series of complementation experiments in which transport or postpolymerizational modification functions for one K antigen are used to complement mutations in the corresponding regions of a different K-antigen gene cluster. Thus, postpolymerizational modification of polysaccharide and transport of mature polysaccharide from the periplasmic space are common mechanisms and are independent of polysaccharide structure.

Antigens, Bacterial↗
PubMed1986

Molecular cloning and analysis of genes for production of K5, K7, K12, and K92 capsular polysaccharides in Escherichia coli.

With a DNA fragment from within the region encoding the transport functions for K1 production as a hybridization probe in Southern blot experiments, homologous DNA sequences were detected in the DNA from Escherichia coli strains producing K5, K7, K92, and K100 capsular polysaccharides. No homology with the laboratory strain LE392 was detected. The same DNA probe was used to prescreen cosmid libraries in LE392 by colony hybridization, as a rapid method to isolate clones encoding the genes for K5, K7, K12, and K92 antigen production. Clones carrying sequences homologous to the probe that also produced capsular material were identified by using polyclonal and monoclonal antibodies raised against the K antigen in question and K antigen-specific phages. By restriction enzyme mapping of the appropriate cosmid clones it was possible to align the genes for the production of different K antigens in terms of common restriction endonuclease cleavage sites. A DNA fragment encoding the postulated transport functions for K7 antigen production could complement deletion mutations in the transport functions for K1 antigen production. Thus the transport to the cell surface of chemically distinct polysaccharides may be by a common process. Analysis in E. coli of the proteins produced by plasmids carrying the likely transport functions for K1, K5, and K7 antigen production revealed that each region coded for a similar polypeptide.

Antigens, Bacterial↗
PubMed1986

Increased superior mesenteric artery blood flow after glucose but not lactulose ingestion.

A transcutaneous Doppler ultrasound method was used to measure the superior mesenteric artery blood flow in nine healthy volunteers in the fasting state and serially for 1 h after the ingestion of 400 ml of an isotonic glucose solution. These measurements were repeated on a second occasion following the ingestion of 400 ml of an isotonic lactulose solution. Superior mesenteric artery blood flow increased by 53 per cent (p less than 0.05) 5 min after the end of ingestion of the glucose solution. The increase persisted at 10 min and declined to 47 per cent at 15 min and to 23 per cent at 30 min. No significant change in blood flow was found following the ingestion of the lactulose solution. Significant differences between the two responses were found at 5, 10 and 15 min (p less than 0.05). The increase in blood flow after a glucose solution and not after lactulose suggests therefore that the process of absorption is an important factor governing postprandial superior mesenteric artery blood flow.

Adult↗