Biomedical subjects

N Firth

Publications and source records attributed to N Firth.

27 records · Page 2Linked to original sources

PubMed1994

Possible role of insertion sequence IS257 in dissemination and expression of high- and low-level trimethoprim resistance in staphylococci.

The transposon-like structure Tn4003 and related elements were found to encode high- and low-level trimethoprim resistance (Tpr) in Staphylococcus aureus and coagulase-negative staphylococci. By using transcriptional fusions in Escherichia coli, the variation in resistance levels was found to correlate with the transcriptional activity of the region presumed to carry the promoter for the operon containing the Tpr dihydrofolate reductase gene, dfrA, encoded by these elements. The reduced transcriptional activities exhibited by elements encoding low-level Tpr appear to be a consequence of deletions adjacent to the copy of IS257 which normally encodes the -35 sequences of these promoters. The data obtained not only support the involvement of IS257 in the transcription of the proposed thyE-dfrA-orf-140 operon of Tn4003 but may also implicate this insertion sequence in the mechanisms resulting in the variation in Tpr levels observed in staphylococci.

Base Sequence↗

PubMed1994

Molecular analysis of the F plasmid traVR region: traV encodes a lipoprotein.

The nucleotide sequences of the conjugative F plasmid transfer region genes, traV and traR, have been determined. The deduced amino acid sequence of TraV indicated that it may be a lipoprotein; this was confirmed by examining the effect of globomycin on traV-encoded polypeptides synthesized in minicells. An open reading frame that may represent a previously undetected transfer gene, now designated trbG, was identified immediately upstream of traV. The deduced product of traR was found to share amino acid similarity with proteins from the bacteriophages 186 and P2 and with the dosage-dependent dnaK suppressor DksA.

Amino Acid Sequence↗

PubMed1994

A lipoprotein signal peptide encoded by the staphylococcal conjugative plasmid pSK41 exhibits an activity resembling that of Enterococcus faecalis pheromone cAD1.

The traH gene of the staphylococcal conjugative plasmid pSK41 has recently been shown to encode a lipoprotein (N. Firth, K. P. Ridgway, M. E. Byrne, P. D. Fink, L. Johnson, I. T. Paulsen, and R. A. Skurray, Gene 136:13-25, 1993). Here we report that traH encodes a product recognized as a pheromone by Enterococcus faecalis cells harboring the conjugative plasmid pAD1. The mature traH product is not essential for this phenomenon, as expression of pheromone-like activity was found to require sequences encoding only the pro-TraH signal peptide.

Amino Acid Sequence↗

PubMed1993

Analysis of a transfer region from the staphylococcal conjugative plasmid pSK41.

The nucleotide sequence of a 14.4-kb region (tra) associated with DNA transfer of the staphylococcal conjugative plasmid, pSK41, has been determined. Analysis of the sequence revealed the presence of 15 genes potentially involved in the conjugative process. Polypeptide products likely to correspond to ten of these genes have been identified, of which one was found to be a lipoprotein. Comparison of the deduced tra products to the protein databases revealed several interesting similarities, one of which suggests an evolutionary link between this Gram+ bacterial conjugation system and DNA transfer systems of Gram- bacteria, such as Escherichia coli and Agrobacterium tumefaciens. The nt sequence also provided an insight into the transcriptional organisation and regulation of the region.

Amino Acid Sequence↗

PubMed1992

Characterization of the F plasmid bifunctional conjugation gene, traG.

The Escherichia coli F plasmid gene, traG, is required for two stages of the conjugation process: pilus biosynthesis and mating aggregate stabilization. The nucleotide sequence of traG has been determined and the topology of its product in the cytoplasmic membrane analysed using protease accessibility experiments. Complementation analysis employing plasmid deletions revealed a correlation between an N-terminal periplasmic segment of the protein product (TraGp) and its pilus assembly activity. Production of an anti-TraGp antiserum has facilitated the detection of TraGp*, a possible internal cleavage product of TraGp. Although its function is unknown. TraGp* is located in the periplasm and has been shown to possess sequences required for aggregate stabilization. The detection of TraGp* raises the possibility that the two functions of traG are carried out by separate products.

Amino Acid Sequence↗

PubMed1992

Oral ulceration.

Oral ulceration is a common problem. The presentation is often very similar, irrespective of the underlying cause. This paper illustrates some of the more commonly encountered forms of oral ulceration.

Diagnosis, Differential↗

PubMed1991

Oral pemphigus vulgaris in young adults.

Three patients, aged 31, 26, and 22 years, had pemphigus vulgaris. A delay in diagnosis and appropriate treatment occurred because the initial presentation was confined to the oral mucosa.

Adult↗

PubMed1989

Nucleotide sequence of the F plasmid transfer gene, traH: identification of a new gene and a promoter within the transfer operon.

The nucleotide sequence of the F plasmid transfer gene traH, which is involved in F-pilus assembly in Escherichia coli K-12, has been determined. From the sequence data, it would appear that traH encodes a 38,897-dalton precursor polypeptide which is processed to give a periplasmic protein. Furthermore, a new gene, trbF, has been located immediately upstream of traH and shown to be expressed by means of a translational fusion to lacZ. Using galK fusion and S1 nuclease protection studies, a weak traJ-dependent promoter, P trbF, has been mapped upstream and adjacent to trbF. Transcription of trbF and traH from P trbF may well serve to complement transcription from the major tra operon promoter PY located some 16 kb upstream of these genes.

Amino Acid Sequence↗

PubMed1989

Fatal acute left ventricular outflow obstruction due to interventricular septal haematoma--diagnosis by transoesophageal echocardiography.

We describe a case of fatal left ventricular outflow obstruction detected by intraoperative transoesophageal echocardiography. This resulted from acute haematoma formation within the interventricular septum following internal mammary artery grafting to the left anterior descending coronary artery. This unusual case highlights the emerging role of transoesophageal echocardiography in the diagnosis and management of the complications of cardiac surgery.

Echocardiography, Doppler↗