Continuing education: agent of change; proceedings.

Sponsored by National Institute of Mental Health, Continuing Education Branch, and University of Chicago, Center for Continuing Education.

The station agent : official publication of the Order of Railroad Station Agents.

Mode of access: Internet.

Plasma concentrations of tafenoquine, a new long-acting antimalarial agent, in Thai soldiers receiving monthly prophylaxis

We measured plasma tafenoquine concentrations in Thai soldiers given a monthly regimen of tafenoquine to determine whether these concentrations adequately suppressed malarial infections on the Thai- Cambodian border. After receiving a treatment course of artesunate and doxycycline, 104 male soldiers were administered a loading dose of tafenoquine ( 400 mg daily for 3 days), followed by tafenoquine monthly ( 400 mg every 4 weeks) for 5 months. Consecutive monthly mean ( +/- standard deviation) trough plasma tafenoquine concentrations were 223 +/- 41, 127 +/- 29, 157 +/- 51. 120 +/- 24, and 88 +/- ng/ mL. Only 1 soldier developed malaria during the study. At the time of malaria diagnosis, his plasma tafenoquine concentration was 40 ng/ mL, which was similar to 3- fold lower than the trough concentrations of the other soldiers. Although low tafenoquine concentrations appear to be uncommon, additional investigations are needed to determine the relationship between plasma tafenoquine concentrations and suppression of malaria.

Why is Coccidoxenoides perminutus, a mealybug parasitoid, ineffective as a biocontrol agent - Inaccurate measures of parasitism or low adult survival?

Coccidoxenoides perminutus achieves only low levels of parasitism of its host Planococcus citri in southeast Queensland citrus. Two possible causes were investigated. Adult survival under natural conditions was assessed to determine whether providing adult food sources could enhance survival. Behavioural changes of hosts, induced by C perminutus parasitism, was also investigated to establish if parasitised P. citri move from their feeding site to seek protected shelters some distance away and are thus not accounted for in field assessments of parasitism rates. Unparasitised mealybugs placed in the field for two periods were retrieved before the effects of parasitism were manifested and parasitism rates were still low (0.3% at 5 days and 1.2% at 10 days). Levels of locomotion of P. citri exposed to C perminutus were compared with those of unexposed ones. Parasitised mealybugs, regardless of instar, undergo behavioural changes. In comparison to unparasitised controls, the mealybugs become highly active 7-14 days after exposure to wasps. All parasitised mealybugs undergo physical changes, their body becomes cylindrical, their legs go so rigid that the mealybugs become immobile, and this signifies the typical mummy appearance. All mealybugs that became mummies eventually fell from the host lemon fruit because of impaired locomotion and were caught on sticky traps that had been placed beneath the lemons. Consequently, their final site of mummification was not established. C perminutus adults provided with nectar or honey survived longer (about 5 days) in the field than those without food (about a day). Nectar from two plant species, Alpinia zerumbet and Datura candida, proved to be good sources of food for the adult wasps, and were comparable in quality to honey. The low level of parasitism achieved by C perminutus in southeast Queensland citrus thus appears to be a consequence of the short adult life and the negative effects of a harsh environment. Provision of a suitable food source (e.g., nectar) may well enhance levels of parasitism in the field. (c) 2005 Elsevier Inc. All rights reserved.

Inconclusiveness of chytridiomycosis as the agent in widespread frog declines

Although there is considerable evidence to support the hypothesis that the chytrid fungus Batrachochytrium dendrobatidis is the primary agent responsible for widespread declines in amphibian populations, particularly rainforest frog populations in Australia and Central America, I argue the case has not yet been made conclusively. Few specimens were collected at the time of population declines, so it may never be possible to conclusively determine their cause. It remains unclear whether the pathogen is novel where declines have occurred. Although it is not necessary that the infection be novel for it to be implicated in declines, if a preexisting pathogen has only recently caused extinctions, cofactors must be important. Whether the pattern of outbreaks represents a wave of extinctions is unclear, but if it does, the rate of spread in Australia is implausibly high for a waterborne pathogen, given the most likely estimates of epidemiological parameters. Although B. dendrobatidis is an amphibian pathogen according to Koch's postulates, the postulates are neither necessary nor sufficient criteria to identify a pathogen. The following key pieces of information are necessary to better understand the impact of this fungus on frog communities: better knowledge of the means and rate of transmission under field conditions, prevalence of infection among frog populations, as distinct from morbid individuals, and the effect of the fungus on frogs in the wild. It is crucial to determine whether there are strains of the fungus with differing pathogenicity to particular frog species and whether host-pathogen coevolution has occurred or is occurring. Recently developed diagnostic tools bring into reach the possibility of addressing these questions and thus developing appropriate strategies to manage frog communities that may be affected by this fungus.

TRAP220 is modulated by the antineoplastic agent 6-Mercaptopurine, and mediates the activation of the NR4A subgroup of nuclear receptors

The NR4A1-3 (Nur77, NURR1 and NOR-1) subfamily of nuclear hormone receptors (NRs) has been implicated in Parkinson's disease, schizophrenia, manic depression, atherogenesis, Alzheimer's disease, rheumatoid arthritis, cancer and apoptosis. This has driven investigations into the mechanism of action, and the identification of small molecule regulators, that may provide the platform for pharmaceutical and therapeutic exploitation. Recently, we found that the purine antimetabolite 6-Mercaptopurine (6-MP), which is widely used as an anti-neoplastic and anti-inflammatory drug, modulated the NR4A1-3 subfamily. Interestingly, the agonist-mediated activation did not involve modulation of primary coactivators' (e.g. p300 and SRC-2/GRIP-1) activity and/or recruitment. However, the role of the subsequently recruited coactivators, for example CARM-1 and TRAP220, in 6-MP-mediated activation of the NR4A1-3 subfamily remains obscure. In this study we demonstrate that 6-MP modulates the activity of the coactivator TRAP220 in a dose-dependent manner. Moreover, we demonstrate that TRAP220 potentiates NOR-1-mediated transactivation, and interacts with the NR4A1-3 subgroup in an AF-1-dependent manner in a cellular context. The region of TRAP220 that mediated 6-MP activation and NR4A interaction was delimited to amino acids 1-800, and operates independently of the critical PKC and PKA phosphorylation sites. Interestingly, TRAP220 expression does not increase the relative induction by 6-MP, however the absolute level of NOR-1-mediated trans-activation is increased. This study demonstrates that 6-MP modulates the activity of the NR4A subgroup, and the coactivator TRAP220.

Identification of the causal agent of pistachio dieback in Australia

Symptoms associated with pistachio dieback in Australia include decline (little or no current season growth), xylem staining in shoots two or more years old, trunk mu and limb lesions (often covered by black, superficial fungal growth), excessive exudation of resin, dieback and death of the tree. Bacteria belonging to the genus Xanthomonas have been suggested as the causal agent. To confirm the constant association between these bacteria and the disease syndrome, the absence of other pathogens and the identity of the pathogen, we performed a series of isolations and pathogenicity tests. The only microorganism consistently isolated from diseased tissue was a bacterium that produced yellow, mucoid colonies and displayed morphological and cultural characteristics typical of the genus Xanthomonas. Database comparisons of the fatty acid and whole-cell protein profiles of five representative pistachio isolates indicated that they all belonged to X. translucens, but it was not possible to allocate the isolates to pathovar. Pathogenicity tests on cereals and grasses supported this identification. However, Koch's postulates have been only partially fulfilled because not all symptoms associated with pistachio dieback were reproduced on inoculated two-year-old pistachio trees. While discolouration was observed, dieback, excessive resinous exudate and trunk and limb lesions were not produced; expression of these symptoms may be delayed, and long-term monitoring of a small number of inoculated trees is in progress.

Depolymerisation and biodegradation of a synthetic tanning agent by activated sludges, the bacteria Arthrobacter globiformis and Comamonas testosteroni, and the fungus Cunninghamella polymorpha

Degradation of a synthetic tanning agent CNSF (a condensation product of 2-naphthatenesulfonic acid (2-NSA) and formaldehyde) by four activated sludges, two previously characterised bacterial strains, Arthrobacter sp. 2AC and Comamonas sp. 4BC, and the fungus Cunninghamella polymorpha, was studied in batch culture at 25 degrees C by determining the changes in the concentrations of CNSF and its component monomers and oligomers (n2-n11). The loss of individual oligomers was correlated with the length of the NSA-CH2 chain. Approximately 25% of the total CNSF was degraded (i.e. mineralised) by the microbes contained in the four activated sludges and by the two bacterial isolates but with different lag phases and at different overall rates. The decline in CNSF concentration was due almost entirely to the biodegradation of the monomers (34.3% of CNSF) and, in particular, 2-NSA (27% of CNSF). There was no change in the n2-n 11 components. The growth of C. polymorpha, on the other hand, arose from extracellular depolymerisation of CNSF oligomers and the biodegradation of the lower molecular mass products. Between 38% and 42% of total CNSF was degraded by C. polymorpha at 25 degrees C. The order of oligomer degradation was inversely related to degree of polymerisation. Eighty percent and 90% of the n4 and n5 and 100% oligomers n6-n11 were degraded after 120 h. At a higher temperature (37 degrees C) oligomers n4-n11 were degraded completely after 120 h. A combination of biodegradation (75%) and sorption to fungal biomass (25%) accounted for the measured loss of all oligomers from the solution phase. The CNSF degradation rates and the volume of fungal biomass produced (and therefore the extent of biosorption) were dependent on the presence of a second carbon source (both optimum at glucose 5 g/l). This is the first report that identifies and distinguishes between depolymerisation, sorption and biodegradation processes in the removal of CNSF and its component oligomers. The use of combinations of the depolymerising fungus C. polymorpha, and the monomer-degrading bacteria, Arthrobacter sp. 2AC and Comamonas sp. 4BC, have potential for wastewater treatment.

Intelligent agent supported personalization for virtual learning environments

Virtual learning environments (VLEs) are computer-based online learning environments, which provide opportunities for online learners to learn at the time and location of their choosing, whilst allowing interactions and encounters with other online learners, as well as affording access to a wide range of resources. They have the capability of reaching learners in remote areas around the country or across country boundaries at very low cost. Personalized VLEs are those VLEs that provide a set of personalization functionalities, such as personalizing learning plans, learning materials, tests, and are capable of initializing the interaction with learners by providing advice, necessary instant messages, etc., to online learners. One of the major challenges involved in developing personalized VLEs is to achieve effective personalization functionalities, such as personalized content management, learner model, learner plan and adaptive instant interaction. Autonomous intelligent agents provide an important technology for accomplishing personalization in VLEs. A number of agents work collaboratively to enable personalization by recognizing an individual's eLeaming pace and reacting correspondingly. In this research, a personalization model has been developed that demonstrates dynamic eLearning processes; secondly, this study proposes an architecture for PVLE by using intelligent decision-making agents' autonomous, pre-active and proactive behaviors. A prototype system has been developed to demonstrate the implementation of this architecture. Furthemore, a field experiment has been conducted to investigate the performance of the prototype by comparing PVLE eLearning effectiveness with a non-personalized VLE. Data regarding participants' final exam scores were collected and analyzed. The results indicate that intelligent agent technology can be employed to achieve personalization in VLEs, and as a consequence to improve eLeaming effectiveness dramatically.