Showing papers by "Monash University published in 2004"

Pollen limitation of plant reproduction: Ecological and evolutionary causes and consequences

Abstract: Determining whether seed production is pollen limited has been an area of intensive empirical study over the last two decades. Yet current evidence does not allow satisfactory assessment of the causes or consequences of pollen limitation. Here, we critically evaluate existing theory and issues concerning pollen limitation. Our main conclusion is that a change in approach is needed to determine whether pollen limitation reflects random fluctuations around a pollen–resource equilibrium, an adaptation to stochastic pollination environments, or a chronic syndrome caused by an environmental perturbation. We formalize and extend D. Haig and M. Westoby's conceptual model, and illustrate its use in guiding research on the evolutionary consequences of pollen limitation, i.e., whether plants evolve or have evolved to ameliorate pollen limitation. This synthesis also reveals that we are only beginning to understand when and how pollen limitation at the plant level translates into effects on plant population dynamics...

Glycogen synthase kinase-3β mediates convergence of protection signaling to inhibit the mitochondrial permeability transition pore

Abstract: Environmental stresses converge on the mitochondria that can trigger or inhibit cell death. Excitable, postmitotic cells, in response to sublethal noxious stress, engage mechanisms that afford protection from subsequent insults. We show that reoxygenation after prolonged hypoxia reduces the reactive oxygen species (ROS) threshold for the mitochondrial permeability transition (MPT) in cardiomyocytes and that cell survival is steeply negatively correlated with the fraction of depolarized mitochondria. Cell protection that exhibits a memory (preconditioning) results from triggered mitochondrial swelling that causes enhanced substrate oxidation and ROS production, leading to redox activation of PKC, which inhibits glycogen synthase kinase-3beta (GSK-3beta). Alternatively, receptor tyrosine kinase or certain G protein-coupled receptor activation elicits cell protection (without mitochondrial swelling or durable memory) by inhibiting GSK-3beta, via protein kinase B/Akt and mTOR/p70(s6k) pathways, PKC pathways, or protein kinase A pathways. The convergence of these pathways via inhibition of GSK-3beta on the end effector, the permeability transition pore complex, to limit MPT induction is the general mechanism of cardiomyocyte protection.

Leadership capacity in teams

Abstract: The present article examines the state of the field regarding leadership in teams. A perspective is advanced that considers leadership as an outcome of team processes (e.g., teamwork and team learning) that provides resources for better team adaptation and performance in subsequent performance cycles. This perspective complements but does not replace the perspective of leadership as an input to team processes and performance. Specific facets of the teaming cycle are reviewed, including the nature of teamwork and interventions designed to facilitate its development, the role of team learning as different from individual learning, and relatively recent advances in understanding shared and distributed leadership (DL). These components of team leadership are cast within an emerging IMOI (inputs, mediators, outcomes, inputs) framework proposed for understanding the cyclical and ongoing nature of teams in organizations.

In search of pedagogical content knowledge in science: Developing ways of articulating and documenting professional practice

Abstract: This study examines the development of ways of documenting and portraying science teachers' pedagogical content knowledge (PCK). As a result of a longitudinal study into science teachers' pedagogical content knowledge, a method is developed for capturing and portraying PCK that comprises two important elements. The first is linked to the particular science content, termed Content Representation (CoRe), and the second is linked to teaching practice, termed Professional and Pedagogical experience Repertoire (PaP-eR). Through this approach new understandings of PCK emerge that are of interest in terms of both academic (knowledge building about PCK) and teaching perspectives. This study includes a full CoRe and one PaP-eR and fully demonstrates how these two elements interact to begin to portray science teachers' pedagogical content knowledge. 2004 Wiley Periodicals, Inc. J Res Sci Teach 41: 370-391, 2004

Decision Support Systems Failure An Evolutionary Perspective.

Abstract: Most studies of DSS failure involve survey research, based on factor models. This paper takes an alternative approach and reports on the intensive investigation of a single DSS project in a manufacturing company. The theoretical model informing the research is Keen’s adaptive design approach that conceptualizes DSS development as a series of adaptive loops between the system, the client, and the analyst. The case study analysis identifies a series of factors or processes that can interfere with Keen’s adaptive loops; we call these factors evolutionary disruptors. Knowledge of these disruptors may alert DSS developers to the likelihood of project failure earlier than would otherwise be the case.

Identification of an antimalarial synthetic trioxolane drug development candidate.

Abstract: The discovery of artemisinin more than 30 years ago provided a completely new antimalarial structural prototype; that is, a molecule with a pharmacophoric peroxide bond in a unique 1,2,4-trioxane heterocycle. Available evidence suggests that artemisinin and related peroxidic antimalarial drugs exert their parasiticidal activity subsequent to reductive activation by haem, released as a result of haemoglobin digestion by the malaria-causing parasite. This irreversible redox reaction produces carbon-centred free radicals, leading to alkylation of haem and proteins (enzymes), one of which--the sarcoplasmic-endoplasmic reticulum ATPase PfATP6 (ref. 7)--may be critical to parasite survival. Notably, there is no evidence of drug resistance to any member of the artemisinin family of drugs. The chemotherapy of malaria has benefited greatly from the semi-synthetic artemisinins artemether and artesunate as they rapidly reduce parasite burden, have good therapeutic indices and provide for successful treatment outcomes. However, as a drug class, the artemisinins suffer from chemical (semi-synthetic availability, purity and cost), biopharmaceutical (poor bioavailability and limiting pharmacokinetics) and treatment (non-compliance with long treatment regimens and recrudescence) issues that limit their therapeutic potential. Here we describe how a synthetic peroxide antimalarial drug development candidate was identified in a collaborative drug discovery project.

Controlled Trial of Continuous Positive Airway Pressure in Obstructive Sleep Apnea and Heart Failure

Abstract: Obstructive sleep apnea (OSA) is highly prevalent among patients with congestive heart failure (CHF) and may contribute to progression of cardiac dysfunction via hypoxia, elevated sympathetic nervous system activity, and systemic hypertension. Our aim was to assess the long-term effect of OSA treatment with nocturnal continuous positive airway pressure (CPAP) on systolic heart function, sympathetic activity, blood pressure, and quality of life in patients with CHF. Fifty-five patients with CHF and OSA were randomized to 3 months of CPAP or control groups. End points were changes in left ventricular ejection fraction, overnight urinary norepinephrine excretion, blood pressure, and quality of life. Nineteen patients in the CPAP group and 21 control subjects completed the study. Compared with the control group, CPAP treatment was associated with significant improvements in left ventricular ejection fraction (Δ 1.5 ± 1.4% vs. 5.0 ± 1.0%, respectively, p = 0.04), reductions in overnight urinary norepinephrine ...

The influence of urban density and drainage infrastructure on the concentrations and loads of pollutants in small streams.

Abstract: Effective water quality management of streams in urbanized basins requires identification of the elements of urbanization that contribute most to pollutant concentrations and loads. Drainage connection (the proportion of impervious area directly connected to streams by pipes or lined drains) is proposed as a variable explaining variance in the generally weak relationships between pollutant concentrations and imperviousness. Fifteen small streams draining independent subbasins east of Melbourne, Australia, were sampled for a suite of water quality variables. Geometric mean concentrations of all variables were calculated separately for baseflow and storm events, and these, together with estimates of runoff derived from a rainfall-runoff model, were used to estimate mean annual loads. Patterns of concentrations among the streams were assessed against patterns of imperviousness, drainage connection, unsealed (unpaved) road density, elevation, longitude (all of which were intercorrelated), septic tank density, and basin area. Baseflow and storm event concentrations of dissolved organic carbon (DOC), filterable reactive phosphorus (FRP), total phosphorus (TP) and ammonium, along with electrical conductivity (EC), all increased with imperviousness and its correlates. Hierarchical partitioning showed that DOC, EC, FRP, and storm event TP were independently correlated with drainage connection more strongly than could be explained by chance. Neither pH nor total suspended solids concentrations were strongly correlated with any basin variable. Oxidized and total nitrogen concentrations were most strongly explained by septic tank density. Loads of all variables were strongly correlated with imperviousness and connection. Priority should be given to low-impact urban design, which primarily involves reducing drainage connection, to minimize urbanization-related pollutant impacts on streams.

A Neutral 3D Copper Coordination Polymer Showing 1D Open Channels and the First Interpenetrating NbO‐Type Network

Abstract: The construction of coordination networks with novel topologies and porous structures that provide new sizes, shapes, and chemical environments is of great interest in recent years, due to their intriguing structural diversity and potential for many applications. 2] In recent years many porous metal– organic frameworks with unique structures have been obtained and their adsorption properties were widely investigated, however, those with specially shaped channels such as 1D helices are rare. Metal–ligand coordination has been well used in the directed assembly of extended porous metal–organic networks, and one of the key points for such studies is the design or choice of components that organize themselves into desired patterns with useful functions. In this regard, considerable attention has been devoted to the networking ability of isonicotinic acid (1) and its derivatives, which are multifunctional ligands potentially able to act as bridging ligands to produce open lattice species with various structural topologies and large pores. In this study, we choose an analogy of 1, 9-acridinecarboxylic acid (HL), whose coordination chemistry has not been previously investigated, as a bridging ligand to construct new framework materials with novel structures and special properties based on combining its bridging coordination ability with its steric bulk. Although the coordination sites of HL and 1 are very similar, their coordination chemistry are found to be quite different due to the bulk of HL. We report herein a 3D twofold interpenetrating NbO-type network [Cu2(m2OMe)2(L)2·(H2O)0.69]n (2) with 1D channels.

Criminal offending in schizophrenia over a 25-year period marked by deinstitutionalization and increasing prevalence of comorbid substance use disorders

Abstract: OBJECTIVE: This study examined the pattern of criminal convictions in persons with schizophrenia over a 25-year period marked by both radical deinstitutionalization and increasing rates of substance abuse problems among persons with schizophrenia in the community. METHOD: The criminal records of 2,861 patients (1,689 of whom were male) who had a first admission for schizophrenia in the Australian state of Victoria in 1975, 1980, 1985, 1990, and 1995 were compared for the period from 1975 to 2000 with those of an equal number of community comparison subjects matched for age, gender, and neighborhood of residence. RESULTS: Relative to the comparison subjects, the patients with schizophrenia accumulated a greater total number of criminal convictions (8,791 versus 1,119) and were significantly more likely to have been convicted of a criminal offense (21.6% versus 7.8%) and of an offense involving violence (8.2% versus 1.8%). The proportion of patients who had a conviction increased from 14.8% of the 1975 coho...

Regulation of human embryonic stem cell differentiation by BMP-2 and its antagonist noggin

Abstract: Human embryonic stem cells differentiate spontaneously in vitro into a range of cell types, and they frequently give rise to cells with the properties of extra-embryonic endoderm. We show here that endogenous signaling by bone morphogenetic protein-2 controls the differentiation of embryonic stem cells into this lineage. Treatment of embryonic stem cell cultures with the bone morphogenetic protein antagonist noggin blocks this form of differentiation and induces the appearance of a novel cell type that can give rise to neural precursors. These findings indicate that bone morphogenetic protein-2 controls a key early commitment step in human embryonic stem cell differentiation, and show that the conservation of developmental mechanisms at the cellular level can be exploited in this system--in this case, to provide a facile route for the generation of neural precursors from pluripotent cells.

Treatment Outcomes for Serious Infections Caused by Methicillin-Resistant Staphylococcus aureus with Reduced Vancomycin Susceptibility

Abstract: Although infections caused by methicillin-resistant Staphylococcus aureus with reduced vancomycin susceptibility (SA-RVS) have been reported from a number of countries, including Australia, the optimal therapy is unknown. We reviewed the clinical features, therapy, and outcome of 25 patients with serious infections due to SA-RVS in Australia and New Zealand. Eight patients had endocarditis, 9 had bacteremia associated with deep-seated infection, 6 had osteomyelitis or septic arthritis, and 2 had empyema. All patients had received vancomycin before the isolation of SA-RVS, and glycopeptide treatment had failed for 19 patients (76%). Twenty-one patients subsequently received active treatment, which was effective for 16 patients (76%). Eighteen patients received linezolid, which was effective in 14 (78%), including 4 patients with endocarditis. Twelve patients received a combination of rifampicin and fusidic acid. Surgical intervention was required for 15 patients (60%). Antibiotic therapy, especially linezolid with or without rifampicin and fusidic acid, in conjunction with surgical debulking is effective therapy for the majority of patients with serious infections (including endocarditis) caused by SA-RVS.

Repelling class discrimination: ephrin-A5 binds to and activates EphB2 receptor signaling

Abstract: The interactions between Eph receptor tyrosine kinases and their ephrin ligands regulate cell migration and axon pathfinding. The EphA receptors are generally thought to become activated by ephrin-A ligands, whereas the EphB receptors interact with ephrin-B ligands. Here we show that two of the most widely studied of these molecules, EphB2 and ephrin-A5, which have never been described to interact with each other, do in fact bind one another with high affinity. Exposure of EphB2-expressing cells to ephrin-A5 leads to receptor clustering, autophosphorylation and initiation of downstream signaling. Ephrin-A5 induces EphB2-mediated growth cone collapse and neurite retraction in a model system. We further show, using X-ray crystallography, that the ephrin-A5-EphB2 complex is a heterodimer and is architecturally distinct from the tetrameric EphB2-ephrin-B2 structure. The structural data reveal the molecular basis for EphB2-ephrin-A5 signaling and provide a framework for understanding the complexities of functional interactions and crosstalk between A- and B-subclass Eph receptors and ephrins.

Impact of child sexual abuse on mental health: prospective study in males and females.

Abstract: Background The lack of prospective studies and data on male victims leaves major questions regarding associations between child sexual abuse and subsequent psychopathology. Aims To examine the association between child sexual abuse in both boys and girls and subsequent treatment for mental disorder using a prospective cohort design. Method Children ( n =1612; 1327 female) ascertained as sexually abused at the time had their histories of mental health treatment established by data linkage and compared with the general population of the same age over a specified period. Results Both male and female victims of abuse had significantly higher rates of psychiatric treatment during the study period than general population controls (12.4% v . 3.6%). Rates were higher for childhood mental disorders, personality disorders, anxiety disorders and major affective disorders, but not for schizophrenia. Male victims were significantly more likely to have had treatment than females (22.8% v .10.2%). Conclusions This prospective study demonstrates an association between child sexual abuse validated at the time and a subsequent increase in rates of childhood and adult mental disorders.

Control and testing of a dynamic voltage restorer (DVR) at medium voltage level

Abstract: The dynamic voltage restorer (DVR) has become popular as a cost effective solution for the protection of sensitive loads from voltage sags. Implementations of the DVR have been proposed at both a low voltage (LV) level, as well as a medium voltage (MV) level; and give an opportunity to protect high power sensitive loads from voltage sags. This paper reports practical test results obtained on a medium voltage (10 kV) level using a DVR at a distribution test facility in Kyndby, Denmark. The DVR was designed to protect a 400-kVA load from a 0.5-p.u. maximum voltage sag. The reported DVR verifies the use of a combined feed-forward and feed-back technique of the controller and it obtains both good transient and steady-state responses. The effect of the DVR on the system is experimentally investigated under both faulted and nonfaulted system states, for a variety of linear and nonlinear loads. Variable duration voltage sags were created using a controllable LV breaker fed by a 630 kVA distribution transformer placed upstream of the sensitive load. The fault currents in excess of 12 kA were designed and created to obtain the required voltage sags. It is concluded the DVR works well in all operating conditions.

Development and Validation of the Medication Regimen Complexity Index

Abstract: BACKGROUND:Medication regimen attributes, such as the number of drugs, dosage frequency, administration instructions, and the prescribed dosage forms, have been shown to influence patient outcomes. No single tool for quantifying the complexity of general medication regimens has been published in the medical literature.OBJECTIVE:To develop and validate a tool to quantify the complexity of prescribed medication regimens.METHODS:Literature findings and the expertise of the authors were used for developing the tool. Eight pharmacy researchers helped in establishing the tool's face and content validity. The new tool was tested on 134 medication regimens from patients with moderate to severe chronic obstructive pulmonary disease. Six regimens with a spread of scores on the tool were presented to a 5–member expert panel that subjectively ranked these regimens to confirm the tool's criterion-related validity. The relationships between scores on the tool and various independent variables were tested to judge the t...

Neogene and Quaternary rollback evolution of the Tyrrhenian Sea, the Apennines, and the Sicilian Maghrebides

Abstract: Reconstruction of the evolution of the Tyrrhenian Sea shows that the major stage of rifting associated with the opening of this basin began at similar to10 Ma. It involved two episodes of back arc extension, which were induced by the rollback of a west dipping subducting slab. The first period of extension (10-6 Ma) was prominent in the northern Tyrrhenian Sea and in the western part of the southern Tyrrhenian Sea. The second period of extension, mainly affected the southern Tyrrhenian Sea, began in the latest Messinian (6-5 Ma) and has been accompanied by subduction rollback at rates of 60-100 km Myr(-1). Slab reconstruction, combined with paleomagnetic and paleogeographic constraints, indicates that in the central Apennines, the latest Messinian (6-5 Ma) arrival of a carbonate platform at the subduction zone impeded subduction and initiated a slab tear and major strike-slip faults. These processes resulted in the formation of a narrow subducting slab beneath the Ionian Sea that has undergone faster subduction rollback and induced extreme rates of back arc extension.

CCR7 Signals Are Essential for Cortex–Medulla Migration of Developing Thymocytes

Abstract: Upon TCR-mediated positive selection, developing thymocytes relocate within the thymus from the cortex to the medulla for further differentiation and selection. However, it is unknown how this cortex-medulla migration of thymocytes is controlled and how it controls T cell development. Here we show that in mice deficient for CCR7 or its ligands mature single-positive thymocytes are arrested in the cortex and do not accumulate in the medulla. These mutant mice are defective in forming the medullary region of the thymus. Thymic export of T cells in these mice is compromised during the neonatal period but not in adulthood. Thymocytes in these mice show no defects in maturation, survival, and negative selection to ubiquitous antigens. TCR engagement of immature cortical thymocytes elevates the cell surface expression of CCR7. These results indicate that CCR7 signals are essential for the migration of positively selected thymocytes from the cortex to the medulla. CCR7-dependent cortex-medulla migration of thymocytes plays a crucial role in medulla formation and neonatal T cell export but is not essential for maturation, survival, negative selection, and adult export of thymocytes.

Explosive Yields of Massive Stars from Z = 0 to Z = Z?

Abstract: We present a new and homogeneous set of explosive yields for masses 13, 15, 20, 25, 30, and 35 M☉ and metallicities Z = 0, 10-6, 10-4, 10-3, 6 × 10-3, and 2 × 10-2. A wide network extending up to Mo has been used in all computations. We show that at low metallicities (Z ≤ 10-4), the final yields do not depend significantly on the initial chemical composition of the models, so a scaled solar distribution may be safely assumed at all metallicities. Moreover, no elements above Zn are produced by any mass in the grid up to a metallicity ~10-3. These yields are available for any choice of the mass cut on request.

Intense emotional responses to music: a test of the physiological arousal hypothesis

Abstract: A consistent theme across general theories of emotion is that intense emotions are accompanied by increased levels of physiological arousal. The aim in the current study was to determine whether mu...

Transplantation of human embryonic stem cell-derived neural progenitors improves behavioral deficit in Parkinsonian rats.

Abstract: Human embryonic stem cells (hESCs) may potentially serve as a renewable source of cells for transplantation. In Parkinson's disease, hESC-derived dopaminergic (DA) neurons may replace the degenerated neurons in the brain. Here, we generated highly enriched cultures of neural progenitors from hESCs and grafted the progenitors into the striatum of Parkinsonian rats. The grafts survived for at least 12 weeks, the transplanted cells stopped proliferating, and teratomas were not observed. The grafted cells differentiated in vivo into DA neurons, though at a low prevalence similar to that observed following spontaneous differentiation in vitro. Transplanted rats exhibited a significant partial correction of D-amphetamine and apomorphine-induced rotational behavior, along with a significant improvement in stepping and placing non-pharmacological behavioral tests. While transplantation of uncommitted hESC-derived neural progenitors induced partial behavioral recovery, our data indicate that the host-lesioned striatum could not direct the transplanted neural progenitors to acquire a dopaminergic fate. Hence, induction of their differentiation toward a midbrain fate prior to transplantation is probably required for complete correction of behavioral deficit. Our observations encourage further developments for the potential use of hESCs in the treatment of Parkinson's disease.