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Biomedical subjects

A A Watson

Publications and source records attributed to A A Watson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Fimbrial biogenesis genes of Pseudomonas aeruginosa: pilW and pilX increase the similarity of type 4 fimbriae to the GSP protein-secretion systems and pilY1 encodes a gonococcal PilC homologue.

Type 4 fimbriae of Pseudomonas aeruginosa are surface filaments involved in host colonization. They mediate both attachment to host epithelial cells and flagelia-independent twitching motility. Four additional genes, pilW, pilX, pilY1 and pilY2, are located on Spel fragment E in the 5 kb intergenic region between the previously characterized genes pilV and pilE, which encode prepilin-like proteins involved in type 4 fimbrial biogenesis. The phenotypes of a transposon insertion and other mutations constructed by allelic exchange show that these genes are involved in the assembly of type 4 fimbriae. The PilW and PilX proteins are membrane located, possess the hydrophobic N-terminus characteristic of prepilin-like proteins, and appear to belong to the GspJ and GspK group of proteins that are required for protein secretion in a wide range of Gram-negative bacteria. These findings increase the similarities between the fimbrial biogenesis and the Gsp-based protein-secretion supersystems. PilY1 is a large protein with C-terminal homology to the PilC2 protein of Neisseria gonorrhoeae, thought to be a fimbrial tip-associated adhesin, and which, like PilY1, is involved in fimbrial assembly. PilY1 appears to be located in both the membrane and the external fimbrial fractions. PilY2 is a small protein that appears to play a subtle role in fimbrial biogenesis and represents a new class of protein.

Alleles↗
PubMed1995

Characterization of a five-gene cluster required for the biogenesis of type 4 fimbriae in Pseudomonas aeruginosa.

The opportunistic pathogen Pseudomonas aeruginosa produces type 4 fimbriae which promote adhesion to epithelial cells and are associated with a form of surface translocation called twitching motility. Transposon mutagenesis was used to identify loci required for fimbrial assembly or function by screening for mutants that lack the spreading colony morphology characteristic of twitching motility. Six mutants were isolated that contain transposon insertions upstream of the previously characterized gene pilQ. This region contains four genes: pilM-P, which encode proteins with predicted sizes of 37.9, 22.2, 22.8 and 19.0 kDa, respectively. pilM-P appear to form an operon and to be expressed from a promoter in the intergenic region between pilM and the divergently transcribed upstream gene ponA. PilM-P were found to be required for fimbrial biogenesis by complementation studies using twitching motility and sensitivity to fimbrial-specific phage as indicators of the presence of functional fimbriae. This was confirmed by electron microscopy. PilO and PilP did not have homologues in the sequence databases, but the predicted PilN amino acid sequence displayed similarity to XpsL from Xanthamonas campestris, a protein required for protein secretion. PilP contained a hydrophobic leader sequence characteristic of lipoproteins, while PilN and PilO have long internal hydrophobic domains which may serve to localize them to the cytoplasmic membrane. PilM has shared sequence motifs with the cell division protein FtsA from Bacillus subtilis and Escherichia coli, as well as the rod-shape-determining protein MreB from E. coli. These motifs are also conserved in eukaryotic actin, in which they are involved in forming an ATPase domain. Deletion mutants of pilM and pilQ displayed a dominant negative phenotype when transformed into wild-type cells, suggesting that these genes encode proteins involved in multimeric structures.

Amino Acid Sequence↗
PubMed1985

The histopathology and electron microscopy of a human monkeypox lesion.

The histological and electron microscopic findings from a solitary cutaneous monkeypox lesion taken post mortem from a child who died after a five-day illness are reported. This child is 44th in the WHO register of monkeypox cases. The lesion was at the papulonecrotic stage, with early evidence of vesiculation and minimal evidence of pustulation. Necrosis affected the stratum basale, the related basement membrane and adjacent areas of the dermal papillae at the centre of the lesion. Cell necrosis affected the next two or three layers of stratum spinosum above the destroyed stratum basale. Lateral to this zone, marked hyperplasia and intracellular oedema of the stratum spinosum constituted the papule and produced spindle-cell features. In the middle layer of the stratum spinosum, above the necrotic focus, there were minute vesicles and between these were occasional multinuclear giant cells. Bodies similar to Guarnieri bodies (GB) were present in the cytoplasm of sweat duct-lining cells in the epidermis and upper corium. Very scanty similar bodies were evident elsewhere in the papular epidermis but were difficult to distinguish from debris. Granules in the lesion with the same size as mature virions (elementary bodies) have been assessed not to be these because similar granules are present in the normal epidermis. Changes in the dermis apart from those mentioned above were minimal oedema, very mild perivascular infiltration by round cells and an occasional eosinophil. Electron microscopy showed abundant immature and mature orthopoxvirus particles in the cytoplasms of infected epidermal cells. A limited range of histochemical tests is detailed. In general, the features are indistinguishable from the papulonecrotic stage of smallpox (variola) and from tanapox as recorded in man.

Child, Preschool↗
PubMed1985

Magnesium, potassium, sodium and calcium in post-mortem vitreous humour from humans.

Levels of magnesium, potassium, sodium and calcium in post-mortem vitreous humour from human controls, fire fatalities and drowning victims have been determined. The effects of time-related internal changes, external environmental parameters and different causes of death are evaluated. Despite the positive correlation and marked increase of potassium and, to a lesser extent, of magnesium and calcium with the length of the post-mortem interval, individual biological variability severely limits the usefulness of predictions of post-mortem interval based on electrolyte metal data. At best, there is only a 2/3 chance of a prediction being within 12 h of the true value. Vitreous humour metal concentrations are affected by external influences, such as the elevated temperatures of fires which increase the rate of release of intracellular magnesium and potassium. In cases where drowning is suspected, establishment or exclusion of this cause of death is not possible on the basis of vitreous humour electrolyte metal data because of possible post-immersion diffusion across the permeable membrane of the eyeball. It appears, however, that magnesium in salt-water cases and sodium in fresh-water cases are related, albeit erratically, to the length of the immersion period.

Adult↗
PubMed1985

A study of stab wounds.

A study was made of patients with stab wounds who attended the Accident and Emergency Department of Glasgow Royal Infirmary during 1978 and 1983. There were 318 patients. The majority, 304 (96%), were males. A total of 87 (27%) were teenagers. The most common sites of the wounds were the chest (143 patients) and the abdomen (113 patients). The features of the patients and their wounds are compared with those of a previous study carried out at the same hospital in the early 1960s (Batey & MacBain, 1967). The post-mortem reports of 25 fatal stab injury cases occurring in Glasgow between 1971 and 1978 are also reviewed. Some aspects of diagnosis, management and prevention of stab wounds are discussed.

Abdominal Injuries↗
PubMed1983

Subarachnoid haemorrhage due to upper cervical trauma.

Seventeen cases are reported in which fatal subarachnoid haemorrhage was associated with injury to the upper cervical region. Most of these cases were alcohol-intoxicated, most had sustained their injuries in an altercation, and death was usually but not invariably rapid. It is proposed that trauma to the upper cervical region can cause subarachnoid haemorrhage, by a mechanism involving tracking of blood into the subarachnoid space from a damaged vertebral artery or one of its branches.

Adult↗