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Biomedical subjects

G Canning

Publications and source records attributed to G Canning.

8 recordsLinked to original sources
PubMed1998

In vitro activity of hepatitis B virus polymerase: requirement for distinct metal ions and the viral epsilon stem-loop.

Hepadnaviruses have a complex replication cycle which includes reverse transcription of the pregenomic RNA. The initial step in this process in hepatitis B virus (HBV) requires the viral polymerase to engage a highly stable region of secondary structure within the pregenomic RNA termed the epsilon stem-loop. While reverse transcriptases belonging to the retrovirus family use a specific cellular tRNA as primer, HBV polymerase utilizes a tyrosine residue located within its own N terminus. Therefore, the first deoxyribonucleotide is covalently coupled to HBV polymerase prior to extension of the DNA strand by conventional reverse transcription. We have expressed HBV polymerase in a baculovirus and following purification have found it to be active with respect to protein-priming and reverse transcription of copurified RNA. Importantly, we found both of these processes to be critically dependent on the presence of the epsilon stem-loop. The metal ion preferences of HBV polymerase were also investigated for both the protein-priming and reverse transcription activities of this enzyme. Reverse transcription was dependent on magnesium, with an optimal concentration of 5 mM. However, protein-priming was strongly favoured by manganese ions and was optimal at a concentration of 1 mM. Thus, using manganese as sole source of metal ions our activity assay is restricted to the protein-priming event and will allow the search for novel antivirals specifically blocking this unique mechanism.

Animals↗
PubMed1997

Protein interactions in the herpes simplex virus type 1 VP16-induced complex: VP16 peptide inhibition and mutational analysis of host cell factor requirements.

The herpes simplex virus VP16 protein functions as a potent transcriptional activator and targets DNA sites with the consensus TAATGARAT present in all the viral immediate-early gene promoters. To do so, VP16 directs assembly of a multiprotein complex involving two cellular proteins, host cell factor (HCF) and the Oct-1 DNA-binding transcription factor. To investigate the importance of specific protein-protein interactions to formation of this VP16-induced complex (VIC), we used oligopeptides to prevent VIC assembly. Linear and cyclic peptides corresponding to a region of VP16 previously implicated in complex formation were potent inhibitors of VIC assembly. To further characterize the protein interactions involved, we cloned a human cDNA encoding the minimal VP16 interaction domain of HCF, containing amino acids 1 to 380 [HCF (1-380)]. The REHAYS-based peptides active in preventing VIC assembly were found to specifically block binding of VP16 to HCF (1-380), without affecting VP16-Oct-1 binding. The inhibitory activity of these VP16 peptides was strictly sequence specific for the EHAY residues. Site-directed mutagenesis of the HCF (1-380) domain revealed residues E102 and K105 to be critical determinants in support of VIC formation. Alteration of a single residue in HCF, K105, was shown to virtually abolish complex assembly. Interestingly however, none of the HCF mutants that were impaired in their ability to support complex formation exhibited defects in direct VP16 binding, supporting loss of function at a higher order in complex assembly.

Amino Acid Sequence↗
PubMed1993

Comparative study of abdominal incision techniques.

The characteristics of surgical incisions made with an electrosurgical technique were compared with those made using conventional methods in a prospective randomized trial. In particular, the claim that the method of incision may influence postoperative pain was investigated. A total of 101 consecutive patients receiving full-length midline laparotomy incisions for gastrointestinal resection were studied. A record was kept of the time required to make the incision and blood loss as well as postoperative pain (using a linear analogue scale), ventilatory function and requirement for analgesia. There were 50 patients in group 1 (scalpel; 15 men, 35 women) and 51 in group 2 (electrocautery; 26 men, 25 women). The groups were similar in age, body-weight, diagnosis and the type of surgical procedures being performed. Incision time was similar in the two groups but median blood loss during incision was significantly less in group 2 patients than in group 1 (10 versus 25 ml, P < 0.0001). Linear analogue pain scores were not significantly different between the groups at any stage after operation. The same was true of postoperative ventilatory function and requirement for analgesia. A total value for morphine use during the entire postoperative period was derived for each group and the median was 1.55 mg/kg for group 1 compared with 1.49 mg/kg for group 2. The electrosurgical method is associated with less blood loss during incision, although this study has failed to confirm any reduction in postoperative pain or requirement for analgesia in these patients.

Abdominal Muscles↗
PubMed1987

Failure to diagnose the milk-alkali syndrome.

A case of recurrent hypercalcaemia due to chronic continuous ingestion of a calcium-containing antacid is described in whom the diagnosis was delayed because of an insufficiently detailed drug history. Specific named enquiry must be made of all the various calcium-containing drugs when seeking a history of excessive calcium intake if the diagnosis of the milk-alkali syndrome is not to be missed.

Antacids↗