Pre-cursors to physical employment standards for rural tanker-based bushfire suppression work

This thesis quantified the physical demands of Australian rural bushfire suppression and developed a controlled bushfire simulation suitable for ongoing bushfire research. The findings of this thesis will be used to develop physical employment standards and OH&S strategies to protect the 200,000 volunteer firefighters Australia wide.

Identification and characterization of Kava-derived compounds mediating TNF-alpha suppression

There is a substantial unmet need for new classes of drugs that block TNF-α-mediated inflammation, and particularly for small molecule agents that can be taken orally. We have screened a library of natural products against an assay measuring TNF-α secretion in lipopolysaccharide-stimulated THP-1 cells, seeking compounds capable of interfering with the TNF-α-inducing transcription factor lipopolysaccharide-induced TNF-α factor. Among the active compounds were several produced by the kava plant (Piper mysticum), extracts of which have previously been linked to a range of therapeutic effects. When tested in vivo, a representative of these compounds, kavain, was found to render mice immune to lethal doses of lipopolysaccharide. Kavain displays promising pharmaceutical properties, including good solubility and high cell permeability, but pharmacokinetic experiments in mice showed relatively rapid clearance. A small set of kavain analogs was synthesized, resulting in compounds of similar or greater potency in vitro compared with kavain. Interestingly, a ring-opened analog of kavain inhibited TNF-α secretion in the cell-based assay and suppressed lipopolysaccharide-induced TNF-α factor expression in the same cells, whereas the other compounds inhibited TNF-α secretion without affecting lipopolysaccharide-induced TNF-α factor levels, indicating a potential divergence in mechanism of action.

Frequency, intensity and duration of physical tasks performed by Australian rural firefighters during bushfire suppression

The current study combined, for the first time, video footage of individual firefighters wearing heart rate monitors and personal GPS units to quantify the frequency, duration and intensity of tasks performed by Australian rural fire crews when. suppressing bushfires. Across the four fireground 'shifts', the firefighters performed 34 distinct fireground tasks. Per shift, the task frequency ranged from once (raking fireline in teams, carrying a quick fill pump) to 103 times {lateral repositioning of a 38-mm charged firehose) .. The tasks lasted between 4 ± 2 s (bowling out 3-8-mm firehose) and 461 ± 387 s (raking fireline in teams). The task intensity~ as measured by average heart rate ranged between 97 ± 16 beats·min-1 (55.7 ± 8.7. %HRmax) and 157 ± 15 beats·min-1 (86.2 ± 10.8 %HRmax)· The tasks were performed a speeds that ranged from 0.12 ± 0.08 m·s-1 (manual hose retraction of 38-mm charged firehose) to 0.79 ± 0.40 m·s-1 (carrying a 38-mm coiled hose). Tasks found to be simultaneously frequent, long and intense (or two of these three) are likely to form the basis for job-specific testing of Australian rural firefighters suppressing bushfires.

Medial prefrontal cortex suppression of the hypothalamic–pituitary–adrenal axis response to a physical stressor, systemic delivery of interleukin-1β

Previous studies have shown that the medial prefrontal cortex can suppress the hypothalamic–pituitary–adrenal axis response to stress. However, this effect appears to vary with the type of stressor. Furthermore, the absence of direct projections between the medial prefrontal cortex and corticotropin-releasing factor cells at the apex of the hypothalamic–pituitary–adrenal axis suggest that other brain regions must act as a relay when this inhibitory mechanism is activated. In the present study, we first established that electrolytic lesions involving the prelimbic and infralimbic medial prefrontal cortex increased plasma adrenocorticotropic hormone levels seen in response to a physical stressor, the systemic delivery of interleukin-1β. However, medial prefrontal cortex lesions did not alter plasma adrenocorticotropic hormone levels seen in response to a psychological stressor, noise. To identify brain regions that might mediate the effect of medial prefrontal cortex lesions on hypothalamic–pituitary–adrenal axis responses to systemic interleukin-1β, we next mapped the effects of similar lesions on interleukin-1β-induced Fos expression in regions previously shown to regulate the hypothalamic–pituitary–adrenal axis response to this stressor. It was found that medial prefrontal cortex lesions reduced the number of Fos-positive cells in the ventral aspect of the bed nucleus of the stria terminalis. However, the final experiment, which involved combining retrograde tracing with Fos immunolabelling, revealed that bed nucleus of the stria terminalis-projecting medial prefrontal cortex neurons were largely separate from medial prefrontal cortex neurons recruited by systemic interleukin-1β, an outcome that is difficult to reconcile with a simple medial prefrontal cortex–bed nucleus of the stria terminalis–corticotropin-releasing factor cell control circuit.

Retroactive interference and mental practice effects on motor performance : a pilot study

This study examined the effect of similar versus dissimilar retroactive interference on the mental practice effects for performing a novel motor skill. Research has shown that mental practice of a motor task can interfere with learning and performance of the task; however, little is known about how different retroactive interference activities affect mental practice effects. 90 volunteers ages 18 to 51 years (M=26.8, SD=9.6) completed a pre-test and post-test of 10 sets of five trials of a throwing task with the non-preferred hand. In the practice phase, participants mentally practiced the throwing task and then mentally practiced a task that was similar, dissimilar, or completed an unrelated reading task. Performance for all groups improved from pre- to post-test; however, there were no differences in increases for the three groups. The findings suggest that mental practice of similar and dissimilar tasks produced no significant interference in performance.

RNA interference : more than a research tool in the vertebrates' adaptive immunity

In recent years, RNA silencing, usage of small double stranded RNAs of ~21 – 25 base pairs to regulate gene expression, has emerged as a powerful research tool to dissect the role of unknown host cell factors in this 'post-genomic' era. While the molecular mechanism of RNA silencing has not been precisely defined, the revelation that small RNA molecules are equipped with this regulatory function has transformed our thinking on the role of RNA in many facets of biology, illustrating the complexity and the dynamic interplay of cellular regulation. As plants and invertebrates lack the protein-based adaptive immunity that are found in jawed vertebrates, the ability of RNA silencing to shut down gene expression in a sequence-specific manner offers an explanation of how these organisms counteract pathogen invasions into host cells. It has been proposed that this type of RNA-mediated defence mechanism is an ancient form of immunity to offset the transgene-, transposon- and virus-mediated attack. However, whether 1) RNA silencing is a natural immune response in vertebrates to suppress pathogen invasion; or 2) vertebrate cells have evolved to counteract invasion in a 'RNA silencing' independent manner remains to be determined. A number of recent reports have provided tantalizing clues to support the view that RNA silencing functions as a physiological response to regulate viral infection in vertebrate cells. Amongst these, two manuscripts that are published in recent issues of Science and Immunity, respectively, have provided some of the first direct evidences that RNA silencing is an important component of antiviral defence in vertebrate cells. In addition to demonstrating RNA silencing to be critical to vertebrate innate immunity, these studies also highlight the potential of utilising virus-infection systems as models to refine our understanding on the molecular determinants of RNA silencing in vertebrate cells.

Salicylic acid suppression of clubroot in broccoli (Brassicae oleracea var. italica) caused by the obligate biotroph Plasmodiophora brassicae

The obligate soil-borne biotroph Plasmodiophora brassicae has a significant economic impact on Brassicaceae crops. The pathogen severely disrupts the roots by inducing the production of galls which leads to malformation and reduced growth of the roots and a reduced ability to take up water and nutrients. Control of P. brassicae is difficult because it has a number of survival and dissemination strategies that involve both motile and resting stages that need to be targeted by any control agent. We investigated, under controlled conditions and in glasshouse and field experiments, the potential of salicylic acid (SA), a key phytohormone, that is required for defence against certain biotic and abiotic stresses, to reduce infection by P. brassicae in broccoli (Brassicae oleracea var. italica). Under controlled conditions in a growth cabinet exogenous application of SA to roots resulted in its transport systemically to the leaves where it promoted the up-regulation of the pathogenesis related genes PR-1 and PR-2 in an SAR-like response as early as 24 h post-treatment. Concentrations of SA >20 mM reduced significantly both shoot and root weights when applied exogenously but lower concentrations had little measureable effect on plant growth. When SA was applied to plants above 5 mM there was a significant reduction (25-65 %) in gall formation 6 weeks post-inoculation with P. brassicae, indicating that the pathogen was being controlled by the addition of SA. A combination of SA and JA was also shown to reduce severity (25-35 %) of disease associated with P. brassicae. These findings indicate that there may be SA inducible mechanisms in B. oleracea that if fine-tuned could provide enhanced resistance to clubroot disease.

Salivary immunoglobulin A (sIgA) as a biomarker of immune suppression following the combat fitness assessment

SIgA is a potential biomarker for stress. The usual day-to-day and within day variation in sIgA amongst a group of healthy Army reservists was estimated and the acute response of sIgA to moderate intensity exercise (Combat Fitness Assessment) undertaken in both cool-dry and hot-humid conditions was determined. The results indicate that thermal and cardiovascular strain resulting from moderate intensity exercise in hot-humid conditions suppresses sIgA for at least 24 hours post-exercise. Salivary sIgA exhibits a wide biological variation which casts some doubt on its usefulness as a biomarker, however because sIgA has been shown to be sensitive to dietary restriction, alcohol consumption, loss of body mass, fatigue and negative emotions in previous studies and now heat-induced cardiovascular strain, further work is warranted to develop this biomarker.

Characterization of zebrafish polymerase iii promoters for the expression of short hairpin RNA interference molecules

RNA interference (RNAi) is a powerful, sequence specific, and long-lasting method of gene knockdown, and can be elicited by the expression of short-hairpin RNA (shRNA) molecules driven via polymerase III type 3 promoters from a DNA vector or transgene. To further develop RNAi as a tool in zebrafish, we have characterized the zebrafish U6 and H1 snRNA promoters and compared the efficiency of each of the promoters to express an shRNA and silence a reporter gene, relative to previously characterized U6 promoters from pufferfish, chicken, and mouse. Our results show that the zebrafish polymerase III promoters were capable of effective gene silencing in the zebrafish ZF4 cell line, but were ineffective in mammalian Vero cells. In contrast, mouse and chicken promoters were active in Vero but not ZF4 cells, highlighting the importance of homologous promoters to achieve effective silencing.

Trunk postures and upper-body muscle activation during physically demanding wildfire suppression tasks

This study examined the trunk postures and upper-body muscle activations during four physically demanding wildfire suppression tasks. Bilateral, wireless surface electromyography was recorded from the trapezius and erector spinae muscles of nine experienced, wildfire fighters. Synchronised video captured two retroreflective markers to allow for quantification of two-dimensional sagittal trunk flexion. In all tasks, significantly longer time was spent in the mild and severe trunk flexion (p ≤ 0.002) compared to the time spent in a neutral posture. Mean and peak muscle activation in all tasks exceeded previously established safe limits. These activation levels also significantly increased through the performance of each task (p < 0.001). The results suggest that the wildfire suppression tasks analysed impose significant musculoskeletal demand on firefighters. Fire agencies should consider developing interventions to reduce the exposure of their personnel to these potentially injurious musculoskeletal demands.