SITE-SPECIFIC SEED DORMANCY IN SPARTINA ALTERNIFLORA (POACEAE)

Seed dormancy in Spartina alterniflora was studied with regard to: 1) the specific site of the dormancy mechanism, and 2) the influence of three growth-regulating substances: gibberellic acid, fusicoccin, and abscisic acid. The site of the mechanism was determined by assessing the germinability of surgically altered dormant seeds. Effects of the growth substances were determined by assessing the germinability of seeds incubated in their presence. Results revealed that dormancy could be broken surgically by altering the scutellum or chemically by applying fusicoccin. Dormancy could be restored by abscisic acid in the former case but not the latter. It is concluded that the dormancy mechanism is located in the scutellum, that it consists of at least two sequential steps, and that it involves a leachable chemical inhibitor.     

Evaluation of an enzyme immunoassay test for the diagnosis of Chlamydia psittaci infection in free-ranging koalas (Phascolarctos cinereus) in southeastern Queensland, Australia

The IDEIA Chlamydia Test, a commercially available antigen-capture enzyme-linked immunosorbent assay (ELISA) test, based on a monoclonal antibody for the detection of chlamydia in clinical specimens, was evaluated in a population of 65 free-ranging koalas in southeastern Queensland determined to be infected with Chlamydia psittaci. Compared to isolation of the organism in tissue culture, the sensitivity of the IDEIA test ranged from 3 to 11%, and the specificity from 90 to 97%. The results indicated that the IDEIA test is unsuitable for use as a diagnostic screening test for C. psittaci in free-ranging koalas.     

Design and receptor interactions of obligate dimeric mutant of chemokine monocyte chemoattractant protein-1 (MCP-1)

Chemokine-receptor interactions regulate leukocyte trafficking during inflammation. CC chemokines exist in equilibrium between monomeric and dimeric forms. Although the monomers can activate chemokine receptors, dimerization is required for leukocyte recruitment in vivo, and it remains controversial whether dimeric CC chemokines can bind and activate their receptors. We have developed an obligate dimeric mutant of the chemokine monocyte chemoattractant protein-1 (MCP-1) by substituting Thr(10) at the dimer interface with Cys. Biophysical analysis showed that MCP-1(T10C) forms a covalent dimer with similar structure to the wild type MCP-1 dimer. Initial cell-based assays indicated that MCP-1(T10C) could activate chemokine receptor CCR2 with potency reduced 1 to 2 orders of magnitude relative to wild type MCP-1. However, analysis of size exclusion chromatography fractions demonstrated that the observed activity was due to a small proportion of MCP-1(T10C) being monomeric and highly potent, whereas the majority dimeric form could neither bind nor activate CCR2 at concentrations up to 1 μM. These observations help to reconcile previous conflicting results and indicate that dimeric CC chemokines do not bind to their receptors with affinities approaching those of the corresponding monomeric chemokines.     

Comparing ecological restoration in South Africa and Western Australia: the benefits of a ‘travelling workshop’

Researchers and practitioners of ecological restoration from South Africa and Western Australia recently undertook a travelling workshop across several South African biomes to discuss and evaluate the various approaches currently being utilised in the field. Key findings from the workshop highlighted the contrasting nature of ecological restoration undertaken in these two ecologically similar, but socially and politically different regions.     

Distribution of complement protein C4 concentrations in bovine plasma

Complement component C4 concentrations were measured in 40 pure bred Hereford cattle and 40 cattle from a mixed breed herd. Significant differences were not observed between the two groups studied nor between bulls and cows. However, the distribution of C4 concentrations was relatively disperse and appeared polymodal suggesting the presence of two isotypes of C4. Polyacrylamide gel electrophoresis of immunoprecipitated bovine C4 showed many samples to have two C4 alpha chains differing in relative molecular mass by about 1800. Isoelectric focusing of bovine plasma in agarose gels followed by immunofixation with specific anti-C4 antisera revealed two populations of native C4 differing in pI by about 0.3 pH unit. An association between the type of C4 alpha chain present and the pI of the native C4 molecule was observed. Collectively these findings indicate the presence of two structural C4 genetic loci in cattle.