Exposure to As(III) and As(V) changes the Ca²⁺-activation properties of the two major fibre types from the chelae of the freshwater crustacean Cherax destructor

Arsenic is a known carcinogen found in the soil in gold mining regions at concentrations thousands of times greater than gold. Mining releases arsenic into the environment and surrounding water bodies. The main chemical forms of arsenic found in the environment are inorganic arsenite (As(III)) and arsenate (As(V)). Yabbies (Cherax destructor) accumulate arsenic at levels comparable to those in the sediment of their environment but the effect on their physiological function is not known. The effects of arsenic exposure (10 ppm sodium arsenite, AsNaO2 - 5.7 ppm As(III)) and 10 ppm arsenic acid, Na2HAsO4·7H2O - 2.6 ppm As(V)) for 40 days on the contractile function of the two major fibre types from the chelae were determined. After exposure, individual fibres were isolated from the chela, "skinned" (membrane removed) and attached to the force recording apparatus. Contraction was induced in solutions containing increasing [Ca(2+)] until a maximum Ca(2+)-activation was obtained. Submaximal force responses were plotted as a percentage of the maximum Ca(2+)-activated force. As(V) exposure resulted in lower levels of calcium required for activation than As(III) indicating an increased sensitivity to Ca(2+) after long term exposure to arsenate compared to arsenite. Myosin heavy chain and tropomyosin content in individual fibres was also decreased as a result of arsenic exposure. Single fibres exposed to As(V) produced significantly more force than muscle fibres from control animals. Long-term exposure of yabbies to arsenic alters the contractile function of the two major fibre types in the chelae.

The resource-based view of strategy: application to the agricultural industry

IP a The paper examines the application of the Resource-Based View of strategy (RBV) to the Australian floral industry. Despite the RBV's successful application to research in a number of discipline areas and the formalisation of its relationship with Competitive Advantage (CA) 15 years ago, the empirical support for the benefit of the RBV and development of research constructs has been inadequate. This has been partly due to the difficulty of identifying and separating the contribution of resources. The RBV literature is now consistent in the criteria required of a resource for CA and identifies a range of empirical research objectives (e.g. the need for contextual constructs), data evaluation focuses (e.g. measuring the impact of management, process, regional and scale affects) and results objectives (such as identifying the causal structure of resources). Research was conducted in the Australian floral industry to produce supporting generalisable data and constructs for the RBV. This industry is well bounded with several strongly differentiating resources and operates in a global market environment, which is necessary for these research objectives. Six hypotheses were examined; (1) the use of resources as the input of the CA, (2) the impact of the development process on resources, (3) the impact of management control on the development of resources (4) the impact on capability of management, process, region and scale, (5) the impact of resource development maturity on the approach to resource development and (6) the possibility of evaluating individual resources according to various criteria. The data was collected using selected participant interviews, with validation of conclusions by industry experts. It was analysed using content analysis, comparative analysis and cognitive mapping. The research determined that organisations in the Australian floral industry possessed important resources including geography, skills, technology, R&D, supply chains and production costs. These contributed to four CA creating production outputs; quality, capacity, reliability and customer convenience. The research findings supported hypotheses 1, 3, 4, 5 and 6. The lack of support for the two remaining hypotheses, relating to the process of resource development, may be explained by the low resource development maturity of the industry which masks the impact of the resource development process. The results also determined that one resource could contribute to a number of CAs and that resources not meeting all of the normal RBV CA criteria could still provide a CA in an industry where few resources met all criteria. It was postulated that these resources’ contribution to competitive was not durable.

Trace metal speciation in the Pieman River catchment, western Tasmania

The Pieman River catchment has seen continuous mining of economic deposits of gold, silver, lead, copper, zinc and tin since the 1870’s. Tributaries of this river which receive mining effluent, either directly or from acid mine drainage (AMID), have total metal concentrations considerably above background levels and are of regulatory concern. The lower Pieman River is however classified as a State Reserve in which recreational fishing and tourism are the major activities. It is therefore important that water entering the lower Pieman River from upstream hydroelectric impoundments is of high quality. Metals in natural waters exist in a variety of dissolved, colloidal and particulate forms. The bioavailability and hence toxicity of heavy metal pollutants is very dependant on their physico form. Knowledge of the speciation of a metal in natural aquatic environments is therefore necessary for understanding its geochemical behaviour and biological availability. Complexation of metal ions by natural ligands in aquatic systems is believed to play a significant role in controlling their chemical speciation. This study has investigated temporal and spatial variation in complexation of metal ions in the Pieman River. The influence of pH, temperature, organic matter, salinity, ionic strength and time has been investigated in a series of field studies and in laboratory-based experiments which simulated natural and anthropogenic disturbances. Labile metals were measured using two techniques in various freshwater and estuarine environments. Diffusive gradients in thin-films (DGT) allowed in situ measurement of solution speciation whilst differential pulse anodic stripping voltammetry (DPASV) was used to measure labile metal species in water samples collected from the catchment. Organic complexation was found to be a significant regulating mechanism for copper speciation and the copper-binding ligand concentration usually exceeded the total copper concentration in the river water. Complexation was highly dependent on pH and at the river-seawater interface was also regulated by salinity, probably as a result of competitive complexation by major ions in seawater (eg. Ca 2+ ions). Zinc complexation was also evident, however total zinc concentrations in the water column often far exceeded the potential binding capacity of available ligands. In addition to organic complexation, Zn speciation may also be associated with adsorption by flocculated or resuspended colloidal Mn and/or Fe oxyhydroxides. Metal ion complexation and hence speciation was found to be highly variable within the Pieman River catchment. This presents major difficulties for environmental managers, as it is therefore not possible to make catchment-wide assumptions about the bioavailability of these metals. These results emphasise the importance of site-specific sampling protocols and speciation testing, ideally incorporating continuous, in situ monitoring.

Stable isotopes reveal inter-annual and inter-individual variation in the diet of female Australian fur seals

Understanding the temporal and spatial variation of foraging habits of apex predators is central to understanding their role in marine ecosystems and how their populations may respond to environmental variability. In the present study, stable isotope analysis (C and N) of blood was used to investigate inter-individual and inter-annual differences in the diet of adult female Australian fur seals Arctocephalus pusillus doriferus. Positive correlations were observed between red cell and plasma values for δ¹³C and δ¹⁵N (r² = 0.47 and r² = 0.66, respectively, p < 0.001 in both cases), suggesting relatively consistent individual prey choices over 3 or 4 foraging trips. Mean δ¹⁵N values (12.8 to 17.5%) confirm the species occupies the highest marine trophic niche in the region. A significant decrease in plasma δ¹⁵N values, corresponding to two-thirds of a trophic level (ca. 2%), was observed between the 1998 to 2000 and 2003 to 2005 sampling periods. This was associated with a significant decrease in adult female body condition and is consistent with a decline, previously documented by faecal analysis, of the proportion of red cod Pseudophysis bachus, barracouta Thyrsites atun and Gould's squid Nototodarus gouldi in the diet and an increase in redbait Emmelichthys nitidus. While substantial variation in δ¹⁵N was observed within each age cohort, a significant decrease was observed with age, suggesting individual specialisation for particular prey types is evident early in adulthood, but that its composition changes as females age. In addition, generalized linear models indicated body mass had a negative influence on δ¹⁵N, which may reflect larger total body oxygen stores, facilitating individuals hunting cryptic prey of lower trophic level (e.g. octopus) on the sea floor.

Geochemical changes during recharge with tertiary-treated wastewater at a coastal sandfill

Results of experiments investigating geochemical changes during artificial recharge of treated wastewater at a coastal sandfill, reclaimed with sand dredged from the seabed, are reported in this paper. Laboratory batch experiments were conducted using secondary effluent (SE) and SE treated with an additional ultrafiltration process (UF), and wastewater treated by reverse osmosis (RO) process, mixed with surface sand obtained from the sandfill. Experiments with RO showed a net increase of 0.41 meq/L, 0.12 meq/L and 0.31 meq/L for Ca(2 + ), Mg(2 + ) and HCO(3) (-), respectively. UF and SE also exhibited net increase in Ca(2 + ), Mg(2 + ) and HCO(3) (-) indicating carbonate mineral dissolution. All three waters were found to be over-saturated with respect to calcite. Carbonate dissolution reactions were observed in the field experiments. However, the presence of imported clays from the borrow source gave rise to ion exchange reactions where Na(+) attached to the clay particles were exchanged for Ca(2 + ) and Mg(2 + ) inducing mineral dissolution, driven by sub-saturation conditions. This resulted in an increase in pH with maximum values in excess of 9.0. It was also found that the sodium adsorption ratio remained high (>10) even after the groundwater had been diluted sufficiently to freshwater levels (ionic strength, I <0.015) indicating a potential for the dispersion of clay particles. This could have a deleterious consequence on porosity and hydraulic conductivity.

Structure of the electrical double layer at aqueous gold and silver interfaces for saline solutions

We report the structure of the electrical double layer, determined from molecular dynamics simulations, for a range of saline solutions (NaCl, KCl, MgCl2 and CaCl2) at both 0.16 and 0.60molkg(-1) on different facets of the gold and silver aqueous interfaces. We consider the Au/Ag(111), native Au/Ag(100) and reconstructed Au(100)(5×1) facets. For a given combination of metallic surface and facet, some variations in density profile are apparent across the different cations in solution, with the corresponding chloride counterion profiles remaining broadly invariant. All density profiles at the higher concentration are predicted to be very similar to their low-concentration counterparts. We find that each electrolyte responds differently to the different metallic surface and facets, particularly those of the divalent metal ions. Our findings reveal marked differences in density profiles between facets for a given metallic interface for both Mg(2+) and Ca(2+), with Na(+) and K(+) showing much less distinction. Mg(2+) was the only ion for which we find evidence of materials-dependent differences in interfacial solution structuring between the Ag and Au.

Equilibrium conformational ensemble of the intrinsically disordered peptide n16N: linking subdomain structures and function in nacre

n16 is a framework protein family associated with biogenic mineral stabilization, thought to operate at three key interfaces in nacre: protein/β-chitin, protein/protein, and protein/CaCO3. The N-terminal half of this protein, n16N, is known to be active in conferring this mineral stabilization and organization. While some details relating to the stabilization and organization of the mineral are known, the molecular mechanisms that underpin these processes are not yet established. To provide these molecular-scale details, here we explore current hypotheses regarding the possible subdomain organization of n16N, as related to these three interfaces in nacre, by combining outcomes of Replica Exchange with Solute Tempering molecular dynamics simulations with NMR experiments, to investigate the conformational ensemble of n16N in solution. We verify that n16N lacks a well-defined secondary structure, both with and without the presence of Ca(2+) ions, as identified from previous experiments. Our data support the presence of three different, functional subdomains within n16N. Our results reveal that tyrosine, chiefly located in the center of the peptide, plays a multifunctional role in stabilizing conformations of n16N, for intrapeptide and possibly interpeptide interactions. Complementary NMR spectroscopy data confirm the participation of tyrosine in this stabilization. The C-terminal half of n16N, lacking in tyrosine and highly charged, shows substantive conformational diversity and is proposed as a likely site for nucleation of calcium carbonate. Finally, dominant structures from our predicted conformational ensemble suggest the presentation of key residues thought to be critical to the selective binding to β-chitin surfaces.

Augmented platelet calcium uptake in response to serotonin stimulation in patients with major depression measured using Mn2+ influx and 45Ca2+ uptake.

There is an augmented platelet intracellular calcium response to serotonin stimulation in major depression. The role that calcium influx has in this process is not known. The objective of this study was to determine platelet calcium influx in response to serotonin by two methods, Mn2+ influx and 45Ca2+ uptake, in order to observe if the uptake response to serotonin was augmented in major depression by comparing the response to normal controls. The use of the two methods of calcium influx showed that serotonin stimulates calcium uptake into platelets. Furthermore, patients with major depression have significantly augmented platelet calcium uptake in response to serotonin. The interesting finding was that calcium uptake into platelets is biphasic, occurring immediately and after five minutes. These results may support the two pool model for calcium oscillations within cells whereby extracellular calcium is needed for intracellular calcium release, and for replenishment of depleted stores once intracellular calcium is released.

Seasonal timing of the spring departure of waders from the Banc D'Arguin, Mauritania

The northward departure of 13 wader species was studied in the Baie d' Aouatif, Bane d'Arguin, Mauritania, in the springs of 1985, 1986 and 1988. Waders left the area in the late afternoon. Wind speed and direction were registered near ground level (all years) and at altitudes up to 5 km (in 1988). A total of 31 000 waders were observed heading northwards, with those species wintering locally in largest numbers being most common. The majority of wader species showed fairly short periods of departure and unimodal departure peaks. Redshank and Dunlin departed over extended periods. Average departure dates of species correlated positively with the estimated midpoints of ranges in breeding latitude (ca. 2 d per 0 latitude).  Since winds at ground level did not correlate with winds at higher altitudes, and since it is likely that the departing waders traveled at great heights, it was not surprising that there is no correlation between the average afternoon tail wind vector at ground level and the daily departure intensity. We suggest that the timing ofdeparture from the Bane d'Arguin is largely under internal, instead of under direct environmental, control.

Antidepressant actions of lateral habenula deep brain stimulation differentially correlate with CaMKII/GSK3/AMPK signaling locally and in the infralimbic cortex

High frequency deep brain stimulation (DBS) of the lateral habenula (LHb) reduces symptoms of depression in severely treatment-resistant individuals. Despite the observed therapeutic effects, the molecular underpinnings of DBS are poorly understood. This study investigated the efficacy of high frequency LHb DBS (130Hz; 200μA; 90μs) in an animal model of tricyclic antidepressant resistance. Further, we reported DBS mediated changes in Ca(2+)/calmodulin-dependent protein kinase (CaMKIIα/β), glycogen synthase kinase 3 (GSK3α/β) and AMP-activated protein kinase (AMPK) both locally and in the infralimbic cortex (IL). Protein expressions were then correlated to immobility time during the forced swim test (FST). Antidepressant actions were quantified via FST. Treatment groups comprised of animals treated with adrenocorticotropic hormone alone (ACTH; 100μg/day, 14days, n=7), ACTH with active DBS (n=7), sham DBS (n=8), surgery only (n=8) or control (n=8). Active DBS significantly reduced immobility in ACTH-treated animals (p<0.05). For this group, western blot results demonstrated phosphorylation status of LHb CaMKIIα/β and GSK3α/β significantly correlated to immobility time in the FST. Concurrently, we observed phosphorylation status of CaMKIIα/β, GSK3α/β, and AMPK in the IL to be negatively correlated with antidepressant actions of DBS. These findings suggest that activity dependent phosphorylation of CaMKIIα/β, and GSK3α/β in the LHb together with the downregulation of CaMKIIα/β, GSK3α/β, and AMPK in the IL, contribute to the antidepressant actions of DBS.

Effects of high salinity from desalination brine on growth, photosynthesis, water relations and osmolyte concentrations of seagrass Posidonia australis

Highly saline brines from desalination plants expose seagrass communities to salt stress. We examined effects of raised salinity (46 and 54psu) compared with seawater controls (37psu) over 6weeks on the seagrass, Posidonia australis, growing in tanks with the aim of separating effects of salinity from other potentially deleterious components of brine and determining appropriate bioindicators. Plants survived exposures of 2-4weeks at 54psu, the maximum salinity of brine released from a nearby desalination plant. Salinity significantly reduced maximum quantum yield of PSII (chlorophyll a fluorescence emissions). Leaf water potential (Ψw) and osmotic potential (Ψπ) were more negative at increased salinity, while turgor pressure (Ψp) was unaffected. Leaf concentrations of K(+) and Ca(2+) decreased, whereas concentrations of sugars (mainly sucrose) and amino acids increased. We recommend leaf osmolarity, ion, sugar and amino acid concentrations as bioindicators for salinity effects, associated with brine released in desalination plant outfalls.

Modulation of tumor necrosis factor receptors 1 and 2 in chronic hepatitis B and C: The differences and implications in pathogenesis

Tumor necrosis factor (TNF) plays a role in the pathogenesis of chronic hepatitis B (CHB) and chronic hepatitis C (CHC). The difference in the cytokine responses between hepatitis B virus (HBV) and hepatitis C virus (HCV) infections may have implications in the pathogenesis of these diseases. We performed a comparative study to examine the possible differences in the TNF-TNF receptor (TNFR) response between CHB and CHC. We studied the cytokine levels of 38 patients with CHB, 40 patients with CHC and 9 patients with dual hepatitis B and C, and compared them with the baseline levels of 12 healthy controls. The plasma levels of TNF-, interferon-, interleukin (IL)-2, IL-4, IL-10 and soluble TNFR-1 and 2 (sTNFR-1 and 2) were quantified by enzyme-linked immunosorbent assays. The expression of TNFR-1 and 2 in liver tissues was examined in 30 cases of CHB and 15 cases of CHC by semiquantitative reverse transcription polymerase chain reaction. The results showed that sTNFR-1 levels correlated with liver inflammation in all patients, whereas this correlation was not found with sTNFR-2 or other cytokines. Liver inflammation indicators were higher in HCV RNA+ than in HCV RNA– CHC. Most significantly, sTNFR-1 levels correlated with liver inflammation in CHB, but not in CHC. However, the expression of TNFR-1 and 2 in liver was similar between CHB and CHC. These findings suggest that the TNFR signal transduction pathway is modulated differently in HBV and HCV infection.