Mechanistic studies on myrosinase

Myrosinase is the beta-thioglucosidase enzyme which catalyses the hydrolysis of glucosinolates, a group of naturally occurring plant metabolites. Glucosinolates are S-glucosides which occur predominantly in the family Cruciferae, and are abundant in the Brassica vegetables. The hydrolysis reaction, specifically activated by L-ascorbic acid, gives beta-D-glucose and an aglucone fragment, which then rearranges to give sulfate and an isothiocyanate. The aim of this study was the investigation of the chemical mechanism of myrosinase, in order for it to be compared with those of the much more widely studied (3-glycosidases. Myrosinase catalysed transglycosylation reactions were examined as a potential synthetic method. However, no transglycosylation was detected, even though a wide range of glycosyl acceptors was examined, including simple alcohols and thiols and examples with charged side chains to mimic the glucosinolate. Such reactions are commonly observed with beta-glycosidases. However, the stability and activity of myrosinase was not substantially affected by the presence of the acceptors. A small amount of transglycosylation was observed using azide, a charged glycosyl acceptor. This is consistent with the other transglycosylation reactions failing due to the lack of a suitable basic residue at the active site to deprotonate the acceptor. A range of potential substrates was synthesised, although only the nitrophenyl-p-D-glucosides showed any substrate activity. All S-glucosides were inactive. Myrosinase therefore appears to be very specific. Inhibition studies revealed that D-glucono-y-lactone, a potent competitive inhibitor and transition state mimic of p-glucosidases, was a poor noncompetitive inhibitor of myrosinase. It was proposed that this inhibitor binds at the L-ascorbic acid activator site. The inhibitory properties of a number of other compounds were examined, including reaction products and potential substrates (S-glucosides). [1-2H]-Sinigrin, p-nitrophenyl- and 2,4-dinitrophenyl-beta-D-[1-2H]-glucoside were prepared to measure the secondary deuterium isotope effects. The isotope effect obtained for 2,4-dinitrophenyl-p-D-[1-2H]-glucoside (DV= 1.26 +/- 0.11) indicated an sp2 hybridised intermediate via an SN1-Iike mechanism. The solvent kinetic isotope effect for sinigrin hydrolysis was determined (DV = 1.54 +/- 0.07, DV/K = 1.24 +/- 0.15) implying that a proton transfer was partially rate limiting

The SISO CSPI PDG standard for commercial off-the-shelf simulation package interoperability reference models

For many years discrete-event simulation has been used to analyze production and logistics problems in manufactur-ing and defense. Commercial-off-the-shelf Simulation Packages (CSPs), visual interactive modelling environ-ments such as Arena, Anylogic, Flexsim, Simul8, Witness, etc., support the development, experimentation and visua-lization of simulation models. There have been various attempts to create distributed simulations with these CSPs and their tools, some with the High Level Architecture (HLA). These are complex and it is quite difficult to assess how a set of models/CSP are actually interoperating. As the first in a series of standards aimed at standardizing how the HLA is used to support CSP distributed simula-tions, the Simulation Interoperability Standards Organiza-tion’s (SISO) CSP Interoperability Product Development Group (CSPI PDG) has developed and standardized a set of Interoperability Reference Models (IRM) that are in-tended to clearly identify the interoperability capabilities of CSP distributed simulations

Additive opportunistic capture explains group hunting benefits in African wild dogs

African wild dogs (Lycaon pictus) are described as highly collaborative endurance pursuit hunters based on observations derived primarily from the grass plains of East Africa. However, the remaining population of this endangered species mainly occupies mixed woodland savannah where hunting strategies appear to differ from those previously described. We used high-resolution GPS and inertial technology to record fine-scale movement of all members of a single pack of six adult African wild dogs in northern Botswana. The dogs used multiple short-distance hunting attempts with a low individual kill rate (15.5%), but high group feeding rate due to the sharing of prey. Use of high-level cooperative chase strategies (coordination and collaboration) was not recorded. In the mixed woodland habitats typical of their current range, simultaneous, opportunistic, short-distance chasing by dogs pursuing multiple prey (rather than long collaborative pursuits of single prey by multiple individuals) could be the key to their relative success in these habitats

Further evidence supporting a role for gs signal transduction in severe malaria pathogenesis.

With the functional demonstration of a role in erythrocyte invasion by Plasmodium falciparum parasites, implications in the aetiology of common conditions that prevail in individuals of African origin, and a wealth of pharmacological knowledge, the stimulatory G protein (Gs) signal transduction pathway presents an exciting target for anti-malarial drug intervention. Having previously demonstrated a role for the G-alpha-s gene, GNAS, in severe malaria disease, we sought to identify other important components of the Gs pathway. Using meta-analysis across case-control and family trio (affected child and parental controls) studies of severe malaria from The Gambia and Malawi, we sought evidence of association in six Gs pathway candidate genes: adenosine receptor 2A (ADORA2A) and 2B (ADORA2B), beta-adrenergic receptor kinase 1 (ADRBK1), adenylyl cyclase 9 (ADCY9), G protein beta subunit 3 (GNB3), and regulator of G protein signalling 2 (RGS2). Our study amassed a total of 2278 cases and 2364 controls. Allele-based models of association were investigated in all genes, and genotype and haplotype-based models were investigated where significant allelic associations were identified. Although no significant associations were observed in the other genes, several were identified in ADORA2A. The most significant association was observed at the rs9624472 locus, where the G allele (approximately 20% frequency) appeared to confer enhanced risk to severe malaria [OR = 1.22 (1.09-1.37); P = 0.001]. Further investigation of the ADORA2A gene region is required to validate the associations identified here, and to identify and functionally characterize the responsible causal variant(s). Our results provide further evidence supporting a role of the Gs signal transduction pathway in the regulation of severe malaria, and request further exploration of this pathway in future studies

Tissue distribution of migration inhibitory factor and inducible nitric oxide synthase in falciparum malaria and sepsis in African children

BACKGROUND: The inflammatory nature of falciparum malaria has been acknowledged since increased circulating levels of tumour necrosis factor (TNF) were first measured, but precisely where the mediators downstream from this prototype inflammatory mediator are generated has not been investigated. Here we report on the cellular distribution, by immunohistochemistry, of migration inhibitory factor (MIF) and inducible nitric oxide synthase (iNOS) in this disease, and in sepsis. METHODS: We stained for MIF and iNOS in tissues collected during 44 paediatric autopsies in Blantyre, Malawi. These comprised 42 acutely ill comatose patients, 32 of whom were diagnosed clinically as cerebral malaria and the other 10 as non-malarial diseases. Another 2 were non-malarial, non-comatose deaths. Other control tissues were from Australian adults. RESULTS: Of the 32 clinically diagnosed cerebral malaria cases, 11 had negligible histological change in the brain, and no or scanty intravascular sequestration of parasitised erythrocytes, another 7 had no histological changes in the brain, but sequestered parasitised erythrocytes were present (usually dense), and the remaining 14 brains showed micro-haemorrhages and intravascular mononuclear cell accumulations, plus sequestered parasitised erythrocytes. The vascular walls of the latter group stained most strongly for iNOS. Vascular wall iNOS staining was usually of low intensity in the second group (7 brains) and was virtually absent from the cerebral vascular walls of 8 of the 10 comatose patients without malaria, and also from control brains. The chest wall was chosen as a typical non-cerebral site encompassing a range of tissues of interest. Here pronounced iNOS staining in vascular wall and skeletal muscle was present in some 50% of the children in all groups, including septic meningitis, irrespective of the degree of staining in cerebral vascular walls. Parasites or malarial pigment were rare to absent in all chest wall sections. While MIF was common in chest wall vessels, usually in association with iNOS, it was absent in brain vessels. CONCLUSIONS: These results agree with the view that clinically diagnosed cerebral malaria in African children is a collection of overlapping syndromes acting through different organ systems, with several mechanisms, not necessarily associated with cerebral vascular inflammation and damage, combining to cause death

A cross-sectional study of Victorian mobile intensive care ambulance paramedics knowledge of the Valsalva manoeuvre

<p>Abstract</p> <p>Background</p> <p>The Valsalva Manoeuvre (VM) is a primary measure for terminating haemodynamically stable supraventricular tachycardia (SVT) in the emergency care setting. The clinical use and termination success of the VM in the prehospital setting has not been investigated to date. The objective of this study was to determine Melbourne Mobile Intensive Care Ambulance (MICA) Paramedic knowledge of the VM, and to compare this understanding with an evidence-based model of VM performance.</p> <p>Methods</p> <p>A cross-sectional study in the form of a face-to-face interview was used to determine Melbourne MICA Paramedic understanding of VM instruction between January and February, 2008. The results were then compared with an evidence-based model of VM performance to ascertain compliance with the three criteria of position, pressure and duration. Ethics approval was granted.</p> <p>Results</p> <p>There were 28 participants (60.9%) who elected a form of supine posturing, some 23 participants (50%) selected the syringe method of pressure generation, with 16 participants (34.8%) selecting the "as long as you can" option for duration. On comparison, one out of 46 MICA Paramedics correctly identified the three evidence-based criteria.</p> <p>Conclusions</p> <p>The formal education of Melbourne's MICA Paramedics would benefit from the introduction of an evidence based model of VM performance, which would impact positively on patient care and may improve reversion success in the prehospital setting. The results of this study also demonstrate that an opportunity exists to promote the evidence-based VM criteria across the primary emergency care field.</p

Crystallization of Ranasmurfin, a blue-coloured protein from Polypedates leucomystax

A novel blue protein from frog nests has been crystallized

Authenticity, Culture and Language Learning

In philosophy, authenticity has been used with two meanings: one entails the notion of correspondence; the other entails the notion of genesis (Cooper, 1983: 15). As in certain branches of philosophy, language teaching has perhaps clung too long to the first of these notions of authenticity at the expense of the other. This paper reviews four key conceptualisations of authenticity which have emerged in the field of applied linguistics: text authenticity, authenticity of language competence, learner authenticity and classroom authenticity. If any of these types of authenticity is couched exclusively in terms of one usage or the other, it can lead to an impoverishment and objectification of the experience of language learning. Text authenticity can lead to a poverty of language; authenticity of competence can lead to a poverty of performance; learner authenticity can lead to a poverty of interpretation; classroom authenticity can lead to a poverty of communication. This paper proposes that a pedagogy of intercultural communication be informed by a more hybrid view of authenticity as a process of subjectification, derived from the Heideggerian concept of self-concern