A. Pudmenzky

Metal-binding particles alleviate lead and zinc toxicity during seed germination of metallophyte grass Astrebla lappacea.

Combining metal-binding particles and metal-tolerant plants (metallophytes) offers a promising new approach for rehabilitation of heavy metal contaminated sites. Three types of hydrogel metal-binding polymer particles were synthesized and their effects on metal concentrations tested in vitro using metal ion solutions. The most effective of the tested polymers was a micron-sized thiol functional cross-linked acrylamide polymer which reduced the available solution concentrations of Pb(2+) (9.65 mM), Cu(2+) (4mM) and Zn(2+) (10mM) by 86.5%, 75.5% and 63.8%, respectively, and was able to store water up to 608% of its dry mass. This polymer was not toxic to seed germination. In deionised water, it enhanced seed germination, and at otherwise phytotoxic Pb(2+) (9.65 mM) and Zn(2+) (10mM) concentrations, it allowed normal germination and root elongation of the metallophyte grass Astrebla lappacea. We conclude that the polymer has the potential to facilitate restoration of heavy metal contaminated lands by reducing the concentration of metal cations in the soil solution and improving germination rates through reduced toxicity and enhanced plant water relations.

Micron-size metal-binding hydrogel particles improve germination and radicle elongation of Australian metallophyte grasses in mine waste rock and tailings.

Metal contamination of landscapes as a result of mining and other industrial activities is a pervasive problem worldwide. Metal contaminated soils often lack effective vegetation cover and are prone to contaminant leaching and dispersion through erosion, leading to contamination of the environment. Metal-binding hydrogel particle amendments could ameliorate mine wastes prior to planting and enhance seedling emergence. In this study, micron-size thiol functional cross-linked acrylamide polymer hydrogel particles (X3) were synthesised and tested in laboratory-scale experiments on phytotoxic mine wastes to determine their capacity to: (i) increase substrate water holding capacity (WHC); (ii) reduce metal availability to plants to below the phytotoxicity threshold; and (iii) enhance germination characteristics and early radicle development of two Australian metallophyte grasses under limiting and non-limiting water conditions. Addition of X3 to mine wastes significantly increased their WHC and lowered toxic soluble metal concentrations in mine waste leachates. Germination percentages and radicle elongation of both grasses in wastes were significantly increased. Highest germination percentages and greater radicle development recorded in X3 amended wastes under water limited conditions suggests that X3 was able to ameliorate metal toxicity to radicles, and provide moisture, which improved the imbibition and consequent germination of the seeds.

Metal-binding hydrogel particles alleviate soil toxicity and facilitate healthy plant establishment of the native metallophyte grass Astrebla lappacea in mine waste rock and tailings

Soil contaminants are potentially a major threat to human and ecosystem health and sustainable production of food and energy where mineral processing wastes are discharged into the environment. In extreme conditions, metal concentrations in wastes often exceed even the metal tolerance thresholds of metallophytes (metal-tolerant plants) and sites remain barren with high risks of contaminant leaching and dispersion into the environment via erosion. A novel soil amendment based on micron-size thiol functional cross-linked acrylamide polymer hydrogel particles (X3) binds toxic soluble metals irreversibly and significantly reduces their concentrations in the soil solution to below the phytotoxicity thresholds. X3 mixed into the top 50mm of phytotoxic mine waste materials in pots in glasshouse conditions reduced total soluble concentrations of toxic contaminants by 90.3-98.7% in waste rock, and 88.6-96.4% in tailings immediately after application. After 61 days, quality of unamended bottom layer of X3-treated pots was also significantly improved in both wastes. Combination of X3 and metallophytes was more efficient at improving soil solution quality than X3 alone. Addition of X3 to substrates increased substrate water retention and water availability to plants by up to 108% and 98% for waste rock and tailings respectively. Soil quality improvement by X3 allowed successful early establishment of the native metallophyte grass Astrebla lappacea on both wastes where plants failed to establish otherwise.

On the advantages of non-cooperative behavior in agent populations

We investigate the amount of cooperation between agents in a population during reward collection that is required to minimize the overall collection time. In our computer simulation agents have the option to broadcast the position of a reward to neighboring agents with a normally distributed certainty. We modify the standard deviation of this certainty to investigate its optimum setting for a varying number of agents and rewards. Results reveal that an optimum exists and that (a) the collection time and the number of agents and (b) the collection time and the number of rewards, follow a power law relationship under optimum conditions. We suggest that the standard deviation can be self-tuned via a feedback loop and list some examples from nature were we believe this self-tuning to take place.

‘Repeat’ prescriptions and antibiotic resistance: findings from Australian community pharmacy

Australians are among the highest users of antibiotics in the developed world. The primary aim was to determine the ‘age’ of antibiotic prescriptions at the time of dispensing as a possible contributor to antibiotic misuse and ultimately, resistance. The secondary aim was to test customised software to permit extraction and de‐identification of dispensing records for analysis.

Assessing germination characteristics of Australian native plant species in metal/metalloid solution

This study investigated tolerance of Australian native grass species Astrebla lappacea, Themeda australis, and Austrostipa scabra and a tree species Acacia harpophylla to different concentrations of arsenic As(V) (13.34-667.36 μM), Cu2+ (0.5-200 μM), Zn2+ (9-500 μM), Mn2+ (8-10240 μM) and Pb2+ (240-9600 μM) in single solutions in germination experiments. Metal/loid tolerance indicators used were maximum germination percentage (Gmax), mean germination time (MGT), radicle and shoot tolerance indexes (RTI & STI). Radicle tolerance index was the most sensitive indicator of metal tolerance in germinating seeds. All native species were highly tolerant to the metal/loids tested, however, they showed different metal toxicity thresholds and levels of tolerance based on RTI as a metal tolerance indicator during germination. Overall, all four species could be classified as metallophytes, confirming their current suitability for and established use in mine site rehabilitation. This work may also serve as a basis for future studies on metal/loid tolerance of other plant species during germination.

A new conceptual framework for plant responses to soil metals based on metal transporter kinetic parameters

Based on a review of the literature, we have developed a functional conceptual framework of plant metal uptake in relation to plant available metal concentration in the soil. This framework applies to all plant parts and plant available metal levels in soils, and was validated using independent datasets from field surveys and the literature. This is the first framework based on metal transporter kinetic parameters and combining Michaelis-Menten (hyperbolic) kinetics facilitated by the High Affinity Transport System (HATS) for soil concentrations below the transition concentration between transport systems, and linear metal uptake facilitated by the Low Affinity Transport System (LATS) for higher soil available metal concentrations. We propose a new terminology for metal tolerant plants, i.e. metal tolerators, based on this framework. Depending on the plant available metal levels in the soil, tolerator responses to metals can be described best by either Vmax and Km for soil concentrations below the transition concentration between metal transport systems (HATS), or by the slope for greater soil concentrations (LATS). This conceptual framework may be a useful tool for selecting suitable metal tolerators for specific phytoremediation purposes, and may be also applied to non-metal elements or ions.

Dispensing patterns of anxiolytics and sedative-hypnotics: a feasibility study comparing datasets from a developed and a developing country (Australia and South Africa)

BACKGROUND Dispensing patterns reflect drug usage trends. Benzodiazepines are known as drugs with potential for misuse, and frequent dispensing may be a surrogate marker of misuse. OBJECTIVE The primary aim of this study was to obtain a comparative snapshot of anxiolytic and sedative-hypnotic dispensing in a developing country and a developed country, to determine whether further research about benzodiazepines is warranted. METHOD A cross-national, cross-sectional retrospective drug utilisation study was conducted on benzodiazepines and z-drugs. The South African database was obtained from a national medical insurance administrator and the Australian data were de-identified and extracted from pharmacies in the city of Brisbane in Queensland. RESULTS Diazepam was the most frequently dispensed anxiolytic in the Australian dataset (26.4%; n=1057/4010) while in the South African data, diazepam dispensing (17.2%; n=11597/67354) was superseded by alprazolam (17.8%; n=12009/67354) and followed by bromazepam (13.6%; n=9146/67354). The most frequently dispensed hypnotic in the South African data was zolpidem which accounted for 18.7% of records (n=12603/67354), while in the Australian data it was temazepam (24.9%; n=998/4010). Zolpidem was dispensed more frequently than zopiclone in both datasets. CONCLUSION In South Africa there was relatively frequent use of alprazolam, bromazepam and zolpidem while in the Australian data diazepam, oxazepam and temazepam were most frequently dispensed. The use of alprazolam, identified as a drug of abuse in Australia, warrants further research in South Africa. The indicator described in this paper permitted a (qualitative) cross-sectional comparison of anxiolytics and sedative-hypnotics between a developed and a developing country (Australia and South Africa).