R. H. Dunstan

Blood parameters indicative of oxidative stress are associated with symptom expression in chronic fatigue syndrome

Abstract Full blood counts, ESR, CRP, haematinics and markers for oxidative stress were measured for 33 patients diagnosed with chronic fatigue syndrome (CFS) and 27 age and sex matched controls. All participants also completed symptom questionnaires. CFS patients had increases in malondialdehyde (P <0.006), methaemoglobin (P <0.02), mean erythrocyte volume (P <0.02) and 2,3-diphosphoglycerate (P <0.04) compared with controls. Multiple regression analysis found methaemoglobin to be the principal component that differentiated between CFS patients and control subjects. Methaemoglobin was found to be the major component associated with variation in symptom expression in CFS patients (R2 = 0.99, P <0.00001), which included fatigue, musculoskeletal symptoms, pain and sleep disturbance. Variation in levels of malondialdehyde and 2,3-diphosphoglycerate were associated with variations in cognitive symptoms and sleep disturbance (R2 = 0.99, P <0.00001). These data suggest that oxidative stress due to excess free radical formation is a contributor to the pathology of CFS and was associated with symptom presentation.

Effects of 4-nonylphenol and 17α-ethynylestradiol exposure in the Sydney rock oyster, Saccostrea glomerata: vitellogenin induction and gonadal development

Adult Saccostrea glomerata were exposed to environmentally relevant concentrations of 4-nonylphenol (1microg/L and 100microg/L) and 17alpha-ethynylestradiol (5ng/L and 50ng/L) in seawater over 8 weeks. Exposures were performed to assess effects on vitellogenin induction and gonadal development during reproductive conditioning. Chronic direct estrogenicity within gonadal tissue was assessed via an estrogen receptor-mediated, chemical-activated luciferase reporter gene-expression assay (ER-CALUX). Estradiol equivalents (EEQ) were greatest in the 100microg/L 4-nonylphenol exposure (28.7+/-2.3ng/g tissue EEQ) while 17alpha-ethynylestradiol at concentrations of 50ng/L were 2.2+/-1.5ng/g tissue EEQ. Results suggest 4-nonylphenol may be accumulated in tissue and is partly resistant to biotransformation; maintaining its potential for chronic estrogenic action, while 17alpha-ethynylestradiol, although exhibiting greater estrogenic potency on biological endpoints possibly exerts its estrogenic action before being rapidly metabolised and/or excreted. A novel methodology was developed to assess vitellogenin using high-performance liquid chromatography (HPLC). Exposure to both 17alpha-ethynylestradiol (50ng/L) and 4-nonylphenol (100microg/L) produced increases in vitellogenin for females, whereas males exhibited increases in vitellogenin when exposed to 50ng/L 17alpha-ethynylestradiol only. Females exhibited greater vitellogenin responses than males at 50ng/L 17alpha-ethynylestradiol only. Histological examination of gonads revealed a number of individuals exhibiting intersex (ovotestis) in 50ng/L 17alpha-ethynylestradiol exposures. Male individuals in 1microg/L and 100microg/L 4-nonylphenol exposures and 5ng/L 17alpha-ethynylestradiol were at earlier stages of spermatogenic development than corresponding controls.

Differential bioaccumulation of heavy metals and organopollutants in the soft tissue and shell of the marine Gastropod, Austrocochlea constricta

Austrocochlea constricta (Gastropodia) has the potential to act as a useful biomonitoring system of pollutants in the marine environment. The organism was used in the present study to investigate the distribution of both heavy metals and organopollutants in the soft tissue and shell of individuals sampled from various sites in the Newcastle region of New South Wales (Australia). The heavy metals and organopollutants were extracted from the mollusc and determined by atomic absorption spectroscopy (AAS) and gas chromatography-mass spectrometry (GC-MS), respectively. The heavy metals zinc, cadmium, copper, and lead were detected both within the soft tissue and the shell extract, but the proportions of these metals partitioned into the extracts were different for each location. It was concluded that the accurate evaluation of heavy metal exposure in Austrocochlea should include analyses of both soft tissue and shell fractions. The accumulation of aliphatic hydrocarbons was more rigorously partitioned between the two tissue types than the heavy metals. Short chain aliphatic hydrocarbons were limited to the soft tissue while the longer chain aliphatic hydrocarbons were primarily confined to the shell. The data suggest that the shell may act as a safe storage matrix for toxic contaminants resistant to soft tissue detoxification mechanisms. The organic contaminants measured in the shell can be utilized as a valuable indicator of refuse dumping or release of pulp mill effluent as well as petrochemical contamination from industrial and recreational activity.

Pearl aquaculture—profitable environmental remediation?

Bivalve molluscs are filter feeders, with pearl oysters able to filter water at rates up to 25 lh(-1)g(-1) of dry wt. tissue. Since this process leads to rapid bioaccumulation of recalcitrant pollutants such as heavy metals, organochlorine pesticides and hydrocarbons from impacted sites, it has prompted the widespread use of molluscs as biomonitors to quantify levels of marine pollution. This paper proposes pearl oyster deployment as a novel bioremediation technology for impacted sites to remove toxic contaminants, reduce nutrient loads and lower concentrations of microbial pathogens. Estimates extrapolated from the literature suggest that a modest pearl oyster farm of 100 t oyster material per year could remove 300 kg heavy metals plus 24 kg of organic contaminants via deposition into the tissue and shell. Furthermore, it was estimated that up to 19 kg of nitrogen may be removed from the coastal ecosystem per tonne of pearl oyster harvested. Pearl oysters are also likely to filter substantial amounts of sewage associated microbial pathogens from the water column. Method of cultivation and site selection are the key to minimising negative environmental impacts of bivalve cultivation. Deployment of oysters at sites with high nutrient and contaminant loadings would be advantageous, as these compounds would be removed from the ecosystem whilst generating a value-added product. Future potential may exist for harvesting bio-concentrated elements for commercial production.

The mechanism of phosphonic (phosphorous) acid action in Phytophthora

Phosphonates exhibit a complex mode of action in their control of fungi. Using Phytophthora palmivora as a model, we have shown that phosphonate anion can act directly on the fungus, reducing growth, and that growth reduction is associated with a rapid reduction in the total pool of adenylate. At lower concentrations, phosphonate alters fungal metabolism without reduction in growth rate. Under these conditions there is a reduction in the amount of macromolecular materials which can be washed from the surface of the mycelia grown on an agar plate. We suggest that these materials contain suppressors, which normally act to delay the expression of the host defence systems. Therefore, a reduction in their synthesis induced by phosphonate could alter the host response and change the host reaction from compatible to incompatible. Superimposed on these effects is that of orthophosphate, which competes for the same carrier as phosphonate and determines the rate at which phosphonate is absorbed into the fungus.

The role of erythrocytes in the inactivation of free radicals

We propose that, in addition to its function of gas exchange, the erythron provides a mechanism for the inactivation of reactive oxygen and oxide radicals in vivo. In carrying out this function, individual erythrocytes undergo changes in biochemical and structural properties, which are reflected by shape and functional alterations. The changes indicate damage to the labile components of the red cell and demonstrate the expendable nature of the individual red cell. We propose that a superoxide anion channel allows the transport of superoxide and other free radicals into the red cell, where they are deactivated by the erythrocyte antioxidant system which effectively prevents extensive oxidative damage to tissues.

Bioaccumulation of pollutants and changes in population parameters in the gastropod mollusc Austrocochlea constricta

The gastropod mollusc Austrocochlea constricta was collected from four marine locations within the Newcastle region of New South Wales, Australia to assess the range and distribution of major bioaccumulated organic and heavy metal pollutants. The metals and organopollutants were extracted from the soft tissue and the shell of the mollusc for analysis using atomic absorption spectroscopy (AAS) and gas chromatography-mass spectroscopy (GC-MS). The organisms accumulated heavy metals from the sea water and concentrated them to levels substantially higher than those in the surrounding environment. A wide range of organopollutants was also detected in varying levels in Austrochochlea from each location. Abietic and dehydroabietic acids were detected only in the shell and not in the soft tissue suggesting that the shell may act as a “toxic waste sink” to facilitate the removal of potentially harmful compounds from the more metabolically active soft tissue. Aliphatic hydrocarbon contaminants were detected in Austrocochlea derived from the three sites associated with either heavy industry or recreational boating, but no hydrocarbons were detected in organisms from the control site. It was concluded that Austrocochlea may serve as a useful biomonitoring system of pollutants bioaccumulated from marine environments.

The detection of pollutant impact in marine environments: Condition index, oxidative DNA damage, and their associations with metal bioaccumulation in the Sydney rock oyster Saccostrea commercialis

Specimens of the Sydney rock oyster Saccostrea commercialis were deployed for a 3-month period at control and sewage disturbed marine locations in the Hunter Region, New South Wales, Australia. The DNA damage product, 8-hydroxyguanine, was measured by GC/MS-SIM from chromatin extracts of the gill tissues of oysters to assess oxidative damage. The levels ranged from 11.5 to 18.8 modified bases per 107 guanine bases. Although the condition indices were significantly different between the Redhead control site (178.3±3.6) and the Burwood sewage disturbed location (140.4±4.4), no significant differences in 8-hydroxyguanine concentrations were detected between the sites, and the concentration of 8-hydroxyguanine was not correlated to condition index. However, levels of the DNA base modification were correlated with the concentrations of bioaccumulated lead (r=0.84, P=0.036). This association provides in vivo evidence that the bioaccumulation of lead results in oxidative damage to DNA. An additional control and sewage disturbed site were included to investigate the relationship between heavy metal bioaccumulation and the condition index of deployed oysters. After the 3-month deployment period, the condition index was negatively correlated to concentrations of bioaccumulated mercury (r=−0.80, P<0.001), cobalt (r=−0.65, P<0.01), and nickel (r=−0.69, P<0.01), suggesting a strong negative influence of these metals at relatively low concentrations on the physiological condition of the oysters.

The effects of sub-toxic levels of phosphonate on the metabolism and potential virulence factors of Phytophthora palmivora

Abstract Potassium phosphonate (phosphite) altered the metabolism of P. palmivora in liquid cultures even under conditions where growth of the fungus was not restricted. However, under these conditions, the composition of the lipid and cell wall material was altered, as were the standing concentrations of intermediary metabolites (e.g. amino acids). The compound dehydroabietic acid, a diterpenoid, was detected as part of a neutral/cationic macromolecule in young Phytophthora mycelium. In the presence of phosphonate, this compound was absent. These changes in fungal metabolism and in the composition of the cell wall complex suggest a mechanism by which phosphonate may reduce the virulence of the pathogen in the host plant and consequently expose it to the natural host defences at an earlier stage of the invasion processes. Under the experimental conditions used, the fungus was able to reduce intracellular levels of phosphonate to levels below detection during the exponential growth stage. As phosphonate concentrations within the fungus fell, the number of metabolic changes observed in the fungus were also reduced.

Elemental composition at different points of the rainwater harvesting system.

Entry of contaminants, such as metals and non-metals, into rainwater harvesting systems can occur directly from rainfall with contributions from collection surfaces, accumulated debris and leachate from storage systems, pipes and taps. Ten rainwater harvesting systems on the east coast of Australia were selected for sampling of roof runoff, storage systems and tap outlets to investigate the variations in rainwater composition as it moved throughout the system, and to identify potential points of contribution to elemental loads. A total of 26 elements were screened at each site. Iron was the only element which was present in significantly higher concentrations in roof runoff samples compared with tank tap samples (P<0.05). At one case study site, results suggested that piping and tap material can contribute to contaminant loads of harvested rainwater. Increased loads of copper were observed in hot tap samples supplied by the rainwater harvesting system via copper piping and a storage hot water system (P<0.05). Similarly, zinc, lead, arsenic, strontium and molybdenum were significantly elevated in samples collected from a polyvinyl chloride pipe sampling point that does not supply household uses, compared with corresponding roof runoff samples (P<0.05). Elemental composition was also found to vary significantly between the tank tap and an internal cold tap at one of the sites investigated, with several elements fluctuating significantly between the two outlets of interest at this site, including potassium, zinc, manganese, barium, copper, vanadium, chromium and arsenic. These results highlighted the variability in the elemental composition of collected rainwater between different study sites and between different sampling points. Atmospheric deposition was not a major contributor to the rainwater contaminant load at the sites tested. Piping materials, however, were shown to contribute significantly to the total elemental load at some locations.