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Biomedical subjects

S Doughty

Publications and source records attributed to S Doughty.

9 recordsLinked to original sources
PubMed1999

Candidate vaccine antigens and genes in Pasteurella multocida.

Pasteurella multocida is the causative agent of fowl cholera and other diseases of production animals. Isolates are classified into five groups based on capsular antigens and into 16 serotypes based on LPS antigens. Strains causing fowl cholera are most frequently designated A:1, A:3 or A:4. Whole cell bacterins can provide some degree of protection, but only against the homologous LPS serotype. There is good evidence that cross-protective antigens are expressed only under in vivo conditions. Empirically derived, live, attenuated vaccines can protect against heterologous serotypes, but because the basis for attenuation is undefined, reversion to virulence is not uncommon. Work in our laboratory is aimed at using a variety of approaches to identify potential protective antigens or virulence genes to be used as candidates for attenuating mutations or as the basis for vaccine antigen delivery systems. The gene encoding an outer membrane protein, Oma87, which is a homologue of the D15 protective antigen of Haemophilus influenzae, was cloned and sequenced. Rabbit antiserum prepared against recombinant Oma87 could passively protect mice against infection. Type 4 fimbriae form the basis of vaccines against ovine footrot and bovine keratoconjunctivitis. We have identified type 4 fimbriae on the surface of P. multocida, purified the fimbrial subunit protein, PtfA, and determined its N-terminal amino acid sequence. Subsequent cloning of the ptfA gene and its inactivation will now be used to assess the importance of type 4 fimbriae in virulence. There has long been anecdotal evidence for the importance of capsule in virulence, but unequivocal genetic evidence for such a role is lacking. We have cloned and characterised the capsule biosynthetic locus in P. multocida A:1 and identified four bex genes involved in capsule transport and genes encoding enzymes involved in the biosynthesis and transfer of the N-acetyl glucosamine and glucuronic acid components of the capsule. It has been suggested that the low concentration of available iron in vivo acts as an environmental cue for expression of cross-protective antigens. Accordingly, we have cloned and characterised the gene encoding transferrin binding protein, Tbpl, so that its role in immunity and virulence can be investigated. Although P. multocida is not normally considered haemolytic, we have observed haemolysis under anaerobic conditions. Standard library construction and screening resulted in the identification of the mesA gene which encodes an esterase enzyme resulting in a haemolytic phenotype under anaerobic conditions. Virulence studies with mesA- mutants were performed to assess its role in pathogenesis. Using a promoterless phoA gene vector system, the cloning of proteins homologous to known surface proteins of other species as well as proteins unique to P. multocida, allowing their potential as vaccine components to be assessed.

Amino Acid Sequence↗
PubMed1997

Training, skills and approach to high-risk obstetrics in rural GP obstetricians.

One hundred and sixty seven (82%) of the 204 practising South Australian rural GP obstetricians responded to a questionnaire on training, skills and approach to high-risk obstetrics. The mean length of training was 8.5 months; 78% of GP obstetricians held a diploma. There was a mean of 13 years experience and 22 deliveries per year. However, 26.3% of practitioners had stopped obstetrics in the previous 12 months and cited indemnity insurance and lifestyle factors as the main reason for stopping. The GPs practised a wide range of skills; forceps (96%), Caesarean section (42%) and had good access to epidural services (83.6%), blood transfusions (91%) and specialist advice. High-risk obstetrics such as twin pregnancy, fetal growth retardation, insulin-dependent diabetes and preterm labour, are avoided by most rural GP obstetricians. The mean visual analogue comfort score for providing obstetric care was 7.46 (2.16) and correlated with length of training (p = 0.008) and number of deliveries per year (p = 0.02). Health authorities must continue to support and encourage country GP obstetricians to provide this essential service to rural women.

Attitude of Health Personnel↗
PubMed1996

Restricted B-cell responses to microbial challenge of the respiratory tract.

The local B-cell response in the respiratory tract to infectious challenge has been analyzed in pigs and calves using two techniques: flow cytometry and antibody secreting cell (ASC) probes. Pneumonia in pigs caused by experimental infection with Mycoplasma hyopneumoniae resulted in a 25-fold increase in the B-cell population in BAL and lung parenchyma 28 days post infection. ASC probes revealed that the B-cell response of immune pigs to a large challenge infection was localized to lung parenchyma and tracheobronchal lymph nodes. Naive calves infected with Pasteurella multocida had a 5-fold increase in the B-cell blast population in lung parenchyma and BAL, and a greater than 60-fold increase in the draining lymph node at 9 days post infection. The ASC probes prepared post challenge from immune calves showed the response to be localized to the draining lymph nodes, with little response in lung parenchyma. A major finding was that ASC probes prepared from lung parenchyma and from pulmonary lymph nodes of both calves and pigs recognized a restricted range of bacterial antigens, particularly compared to the range of antigens recognized by concurrently circulating sera. The use of ASC probes demonstrates that there is a restricted B-cell repertoire in the respiratory tract.

Animals↗
PubMed1992

Intracellular regulation of cell adhesion to extracellular matrix components in murine B16 melanoma cells.

The involvement of signal transduction systems in the initial attachment of two murine B16 melanoma clones of differing metastatic potential to extracellular matrix components was examined to learn more of the early events in cell-matrix interaction. Clones of high and low metastatic capacity attached similarly in the absence of any stimulators, exhibiting a two phase time course of attachment with 100% attachment by 60 min. A slight difference in attachment characteristics between the clones was seen in response to phorbol ester stimulation, which significantly inhibited attachment of the low metastatic clone but which had no effect on the highly metastatic clone. Total protein kinase C activity and distribution was similar for both clones. Attachment of both clones was severely reduced, however, if intracellular calcium was elevated or intracellular calmodulin inhibited. This study suggests that signal transduction mechanisms are involved in melanoma cell attachment to matrix proteins and offers an approach to pharmacological manipulation of these cell-matrix interactions which may be relevant to reducing metastatic spread.

Animals↗
PubMed1978

Nutrition, sex, gestational age, and hair growth in babies.

Hair growth measurements are a sensitive indicator of nutrition and we have assessed their value in the perinatal period. The proportion of growing roots and their diameter were studied at birth in 114 babies and repeated 3 weeks later in 29 low birthweight babies. Intrauterine malnutrition resulted in thinner roots but the changes after birth were not related to nutrition and these measurements will not be useful in feeding studies in this period. At birth, gestational age and sex affected the hair root, and it may be important to recognise these differences if the hair root is used in biochemical screening tests. We have used a new simple technique for measuring the root diameter using an image-splitting eye-piece.

Female↗