Ontogeny of putative GABAergic neurons and their receptors in the nervous system of the crayfish Cherax destructor

Inhibitory neurons exert control the expression of many aspects of behaviour by regulating the effectiveness of excitatory neural function. By comparison with excitatory neural systems, relatively little is known about the development of inhibitory neurons and the influence which these neurons exert on the development of other neural systems. Two issues which relate to the development of inhibitory neurons are of particular interest. First, a paradox arises when inhibitory neurons are considered in terms of modern models of synaptic development which involve activity-dependent mechanisms of synaptic plasticity. Second, there is some evidence that inhibitory neurotransmitters may act in a special trophic manner during the early development of nervous systems. Investigations of these issues would be greatly facilitated in a neural system in which it was possible to experimentally control aspects of the development of individual pre- and postsynaptic cells. The aim of the results presented in this thesis was to characterise the normal development of one such system: the GABAergic inhibitory system of the Australian freshwater crayfish, Cherax destructor. The ontogeny of the inhibitory neurotransmitter GABA across the embryonic period of 30% to 100% development was investigated using immunohistochemical techniques. GABA-like immunoreactive cells and fibres were first detected in the embryonic brain region. The expression of GABA-like immunoreactivity progressed along a rostro-caudal gradient, with GABA-like immunoreactive cells being detected in the most anterior thoracic ganglia at 45% development and in all ganglia by 65% development. GABA-like immunoreactive fibres were evident in peripheral nerves as early as 55% development and ramified extensively throughout the neuropil of the nervous system by 65% development. By contrast, immunoreactivity to the primary excitatory neurotransmitter, glutamate, was not detected until 60-65% development. Glutamate-like immunoreactivity at 60-65% development was evident only in the form of punctate staining in the midline of the ventral nerve cord. Cell body staining was observed only at 90% development and was restricted to only a few cells on the periphery of the ventral nerve cord. Radio-labelled ligand binding methods and autoradiography were used to study the expression of putative GABA receptors in the Cherax embryos from 30% to 100% development. Specific binding was evident in the earliest embryos studies at 30% development. There was an initial increase in binding from 30% to 40% development, followed by a dramatic drop to almost zero binding at 50-55% development. This was followed by a gradual increase in binding levels with age, reaching a plateau at 85% development. Preliminary pharmacological evaluation of binding indicated that at least three GABA receptor types were expressed during embryonic development. Methods for culturing, dissociated neural tissues explanted form Cherax embryos at 85% development were established. The success of cultures was demonstrated by neurite extension, and neuronal networks in which neurons appeared to form connections with other neurons and with explanted muscle cells after two days in culture. Immunohistochemical studies demonstrated that some explanted neurons expressed GABA-like immunoreactivity within two days of explanting. These studies have provided a comprehensive description of the development of GABAergic neurons and their receptors in Cherax destructor embryos. The very early expression of GABA-like immunoreactivity, coupled with the early onset of specific GABA binding, strongly indicates that the GABAergic neurons are functional and able to exert an effect on other cells during much of the period of nervous system development in crayfish embryos. These results support the hypothesis that inhibitory neurons may play an important role as regulators of the overall process of assembly and maturation of the nervous system and provide a substantial basis for future experimental studies in which the specific action of inhibitory neurons on the development of discrete components of the crayfish nervous system may be investigated.

Policy, practice and purpose in the field of education : a critical review

This paper provides a critical review of papers in this special issue on Bourdieu and practice. What is different about this collection is that, in analysing policy and practice through a Bourdieusian lens, the thinking tools of field, disposition (collective and individual), logics of practice and doxa have been mobilised with regard to the social practices of educational policy - its production, circulation and reception. First, these papers illustrate how, as a field, education has its own language, boundaries and power relations informed by particular modes of distinction and legitimation around different forms of capital formation, thus providing explanations for both social mobility and social stratification. Second, this collection foregrounds 'policy as practice' in terms of the social practices involved in the production of policy, the practices involved with the articulation and vernacularisation of policy through the processes of its reception, as well as the intent and effects of policy changing practice. Third, in focusing on specific policy problematics in higher education and schools, teacher professional development, leadership and educational reform, these contributions illustrate multiple methodological approaches as to how Bourdieu's thinking tools can be used to theorise educational policy, change, practice and effects. The value of Bourdieu's work lies on getting past the impasses between divisions between material and cultural analyses, between the materialist and linguistic focus, by talking about social practices, what people are doing, how they are thinking and how they are acting.

An evaluation of the Victorian Certificate of Education common study of English

This paper traces the development of the Victorian Certificate of Education and in particular the common English Field of Study demonstrating that the VCE is the culmination of many forces acting both within and from outside education. Changes in education are traced and the stimuli for these changes are shown to be economic, social, political and educational.

Effects of education on the therapeutic use of oxygen by emergency nurses

Nurses' factual knowledge increased and oxygen administration decisions improved following education. Variability in nurses' knowledge and decisions, both before and after education, suggests that factual knowledge is only one component of clinical decisions. If nursing education is to improve clinical practice, then we need to better understand the relationship between factual knowledge and clinical decisions.

Hope of education : Somali families and social connection

This thesis examines Somali parents' experience of their children's education after settling in Melbourne following the outbreak of civil war in Somalia in 1991. The research found that Somali parents instigate connections with teachers to generate social capital to enhance their children's education.

The natriuretic peptide system of the heart and central blood vessels of the toad, Bufo marinus

This research has established the presence of a natriuretic peptide system in the cardiovascular system of the toad, Bufo marinus. The presence of atrial natriuretic peptide mRNA and the peptide itself were shown in the heart which does not contain natriuretic peptide receptors in contrast to the large arteries and veins. In arteries these receptors mediated vasodilation. Atrial natriuretic peptide released from the heart may act on large arteries to regulate blood flow, but the action does not target the heart.

Interpreting and modeling baggage handling systems as a system of systems

The topic of systems of systems has been one of the most challenging areas in science and engineering due to its multidisciplinary scope and inherent complexity. Despite all attempts carried out so far in both academia and industry, real world applications are far remote. The purpose of this paper is to modify and adopt a recently developed modeling paradigm for system of systems and then employ it to model a generic baggage handling system of an airport complex. In a top-down design approach, we start modeling process by definition of some modeling goals that guide us in selection of some high level attributes. Then functional attributes are defined which act as ties between high level attributes (the first level of abstraction) and low level metrics/measurements. Since the most challenging issues in developing models for system of systems are identification and representation of dependencies amongst constituent entities, a machine learning technique is adopted for addressing these issues.

The Australian journal of education in chemistry

The article traces the history of the "Australian Journal of Education in Chemistry". The journal, which was founded in 1978, is the only refereed periodical that is wholly owned by the Royal Australian Chemical Institute (RACI). It is designed to improve the quality of chemistry teaching and learning in Australia. It was initially called "Chemeda: The Newsletter of the Chemical Education Division RACI". Overview of some article published in the journal is presented.