Science Collected Works - Theses
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ItemThe sedimentary and tectonic structures of the Lower Devonian Liptrap formation, Victoria, Australia(University of Melbourne, 1978)The shore-platform and cliff exposures of the (Lower Devonian) Liptrap Formation were mapped around Cape Liptrap. In all, 3200 metres of interbedded sandstones and mudstones together with occasional slump beds were examined and the tectonic and sedimentary structures contained within them described in detail. In addition, the overall sedimentary and tectonic environments are discussed. The sediments were derived from two sources; a more distant provenance located on a granitic� metamorphic terrain in eastern Victoria and a local prevenance across the Waratah Fault located in Cambrian greenstones and Devonian sediments. The direction of overfolding of slumped beds indicates a palaeoslope from east to west, while current direction indicators show movement from the east. The sequence of sedimentary structures developed within sandstone-mudstone couples indicates emplacement of the sediments chiefly by bottom traction. Rapid deposition is suggested by structures indicating post-depositional instability with a variety of water-escape structures being developed. The overall sedimentary environment is interpreted as being that of a small-scale shallow water submarine fan deposit. Tectonic structures were developed under a low cover during a single phase of folding and regional cleavage formation - the Middle Devonian Tabberabberan deformation. Chevron folds plunge at low angles to the.north or south, while minor parasitic folds have a different but predictable orientation relative to major fold axes in that they diverge from the major anticlinal axes and converge on the synclines. This is caused by local reorientation of the overall stress field on the limbs of the major folds which have an initial plunge. Folds show evidence for generation at and migration from point sources with consequent rapid changes in plunge both between different folds and within individual folds. In the profile plane a cyclical change in fold form can be seen with single hinged chevron folds giving way to box folds which have two diverging hinges. These style changes are thought to reflect packing difficulties encountered during tightening of the folds. The regional cleavage is statistically axial planar to the folds and is developed as a penetrative differentiated layering best seen in the mudstones. Mica rich M foliae and quartz rich Q zones indicate pressure solution of the more soluble minerals (chiefly quartz) with concentration of less soluble minerals (chiefly mica) at the solution surfaces. Mechanical rotation and deformation of larger clastic flakes attended the shortening which accompanied this pressure solution process. The geometrical and spatial relationship between certain post-depositional soft sediment structures and certain hard rock tectonic structures is noted and a possible link between tectonic and sedimentary structures is suggested, in that they may have developed at the same time.
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ItemBonding and anharmonic vibration in some high symmetry crystals(University of Melbourne, 1977)
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ItemTrophic interactions among the macrofauna of an eelgrass community(University of Melbourne, 1978)This project investigated the dynamics of the trophic interactions between the macrobenthos and the predatory fish of an intertidal eelgrass community. The aim was to provide information on the ecology of many macrofaunal species inhabiting eelgrass flats in Westerport Bay; illustrate the dependence of fish species on these areas; and indicate the factors which are important in maintaining the structure of eelgrass communities. Investigations of the population dynamics of the 15 most abundant fish species showed that four species were permanent residents of intertidal flats, nine were tidal transients (i.e. move over the flats with incoming tides) and two were seasonal residents. Ten species breed over or near the eelgrass flats; while the remainder are represented only by juveniles. These areas are therefore important as nursery areas for immature fish of many species. The number and biomass of fish exhibited definite diel and seasonal changes. Of the 15 major species, nine were diurnal and five nocturnal inhabitants of eelgrass flats. Only one species was present in equal numbers during day and night. The total number and biomass of fish was lowest during the winter when most species moved away from the intertidal flats, presumably as a result of decreased food availability. Numbers and biomass increased during spring and summer (although at different rates) due to return of large fish and recruitment of 0+ aged fish from spring breeding periods. Maximum numbers and biomass were encountered during autumn, when there was the greatest density of large fish as well as 0+ aged recruits. Analysis of feeding relations showed that many fish depend on eelgrass flats for large proportions of their diets. Most, fish were carnivores and crustaceans were the major dietary group. Three species were omnivores consuming algae and detritus in addition to animal foods. Only one species, which was present in low numbers, consumed live eelgrass to a significant degree. Apart from permanent ontogenetic dietary shifts in the juveniles of some species, the diets of most fish exhibited seasonal changes which generally came about through fluctuations in the proportions of a few major prey types, rather than through prey switching. Most fish fed in distinct habitat patches within the eelgrass system, and exhibited marked patterns of food resource partitioning. The study of production by the major infaunal and epifaunal macrobenthic taxa indicated that the animals which are epifaunal on or among the eelgrass fronds are more productive than the infauna. Among the infauna, the active crustaceans are more productive than the sedentary infaunal polychaetes, and this was probably a result of the higher levels of predation on active crustaceans. Total secondary production in heavily-grassed areas of the eelgrass flats was found to be almost twice that in bare mud and lightly-grassed areas. Measurement of the rate of food consumption by the major fish species indicated that most of the food for the fish fauna came from bare mud and lightly-grassed areas of eelgrass flats, and predation pressure (defined as the amount of secondary production removed by predatory fish) was much higher in these areas than in heavily-grassed areas. It was concluded that although physical stresses and the differing above-ground biomass of eelgrass in regions of the intertidal flats set limits on the number and type of species that can inhabit different habitat patches within the eelgrass community, predation by fish was probably the major factor influencing the structure of the macroinvertebrate guild of bare mud and lightly-grassed areas of eelgrass flats. Competition for space and food has probably played a major role in structuring the invertebrate guild of heavily-grassed areas. The distinct pattern of resource allocation among the species of the fish guild, as well as the morphological specializations for feeding exhibited by most species were explained as responses to interspecific competition for food. The habits of only one fish species appeared to be controlled primarily by predation.
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ItemDevelopment and interactions of cultured sympathetic nerves and smooth and cardiac muscle cells(University of Melbourne, 1977)The patterns of autonomic innervation of cardiac and different smooth muscles in vertebrates vary. The reasons for this variation are not known. This thesis is an attempt to: (1) determine whether the innervation patterns could be duplicated in tissue culture ; (2) define the factors which control these innervation patterns ; and (3) determine their specificity by growing paravertebral autonomic ganglia together with smooth or cardiac muscles from mammalian and avian donors in a suitable environment. Tissue culture was chosen as the best technique because of the experimental control it affords. Its advantages and limitations are discussed in detail in Chapter 1, and a review of existing knowledge on the formation of relationships between nerves and their end organs is presented in Chapter 2. In order to justify the validity of culture techniques to the questions asked, the nerves and muscles were first grown and studied on their own to verify that they retained their functionally-differentiated properties over a suitable period, and to become familiar with their normal growth and development. The results showed that autonomic neurons regenerated their fibres ; synthesized noradrenaline, and ultrastructurally resembled adrenergic nerve fibres in vivo. They also responded to the catecholamine analogue 6-OHDA in the same way as do nerves in vivo. Quantitative studies on the response of rat neurons to the specific trophic protein nerve growth factor (NGF) showed that the concentration of this protein which stimulated optimal fibre outgrowth was lower than that which stimulated catecholamine synthesis. A variety of other cell types were identified within the ganglion cultures, including small intensely fluorescent cells. Their identity is discussed. A variety of smooth muscle tissues was studied, both as explants and as single trypsin-dispersed cell cultures. Three main morphological types could be identified. Their distribution depended on the donor tissue, the donor age, and the culture age. Ultrastructurally, the cultured cells resembled embryonic or regenerating smooth muscle. A study of cell contractility was made. In some cases this persisted for many months. Mitoses were found among - the contracting cells. The electrophysiological properties of cultured taenia coli smooth muscle were similar to those recorded from organ bath preparations of taenia coli from adult animals. The similarities and differences between fibroblasts and smooth muscle cells are discussed. Rat heart cells in culture increased in morphological differentiation and retained their beating characteristics over many weeks. A study was made of beating characteristics and of the synchronization of beating on cell contact. Mitoses occurred frequently among the contracting cells. Oxygen concentrations above 60% were found to be toxic to the heart muscle cells. Toxicity was related to the,time of exposure. Non-muscle cells were unaffected by hyperoxia. Hypoxia affected young and old cultures differently. Joint cultures of paravertebral ganglia and heart cells from rats showed no directional growth of nerve fibres towards heart explants across a 1 to 2 mm distance. Nerve fibre networks formed over and around trypsin-dispersed heart cells,but only after the fibres had made contact with the muscle cells. Control cultures with dorsal root ganglia did not show this growth pattern. Junctions between the paravertebral ganglia and heart cells were found to be functional, a high proportion being cholinergic. This is discussed. Joint cultures of chicken paravertebral ganglia with either amnion cells (non-innervated in vivo) or expansor secundariorum cells (densely innervated in vivo) revealed quite different nerve growth patterns. They mimicked those found in vivo in that the nerves formed no lasting contacts with contracting amnion cells. With differentiated expansor secundariorum cells they formed terminal endings within the muscle cell clumps, and ran from clump to clump in undeflected nerve bundles across the background fibroblasts. Control cultures of dorsal root ganglia did not show these specific growth patterns. Guinea-pig paravertebral ganglia in joint culture with taenia coli cells formed no networks or terminal endings in relation to the muscle cells. In vivo these cells are sparsely innervated by adrenergic nerves, with no close neuromuscular junctions. In all these joint cultures it appears, therefore, as though the target tissue controls its own innervation pattern, and that this duplicates the in vivo situation. There appeared to be no requirement for specificity within the autonomic paravertebral ganglia. However sensory nerve fibres did not form the specific growth patterns shown by the sympathetic nerves. This is discussed, with emphasis on the chemotrophic theory of specific nerve growth towards appropriate effector tissues, and the role of NGF. All nerves, both 'correct' and 'incorrect' formed closely adherent (sticky) contacts with muscle cells, but not with fibroblasts. These contacts were not related to final innervation patterns. The possible significance of this is discussed. These experiments have shown that the naturally-occurring innervation patterns can be duplicated in culture. Future work should be able to examine the differences between innervated and non-innervated cells in a more precise and quantitative way.
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ItemTaxonomy of Atriplex Vesicaria Heward ex Benth. (Chenopodiaceae) and related species(University of Melbourne, 1977)
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ItemCellular effects of chronic guanethidine administration(University of Melbourne, 1976)The effects of chronic guanethidine administration on the peripheral and central monoaminergic neurons of the rat and on the sympathetic nervous systems of mice and toads, have been examined at the cellular level using the techniques of fluorescence histochemistry, light and electron microscopy and organ bath physiology. High doses of guanethidine (over 20 mg/kg/day i.p.) caused selective degeneration, characterised by mitochondrial damage, of over 95% of peripheral noradrenergic neurons in male and female rats but did not cause degeneration of adrenergic neurons in mice or toads. Degeneration was apparently preceded by the retraction of noradrenergic axons from the musculature. Non-adrenergic neurons were not affected by this treatment. Over one year after cessation of high-dose guanethidine treatment fluorescence histochemistry showed the noradrenergic innervation of rats to be only 5-10% of control levels. However there was evidence suggesting that the vas deferens had been hyperinnervated by cholinergic fibres. Selective, long-lasting damage to the noradrenergic innervation of the male internal genitalia of rats (and to a lesser extent mice) was observed after treatment with low doses of guanethidine (1-10 mg/kg/day i.p.). This treatment did not affect the 'short' noradrenergic neurons of female rats (or the 'long' neurons of either sex) indicating a major difference between 'short' noradrenergic neurons of male and female rats. Damage to the male 'short' noradrenergic neurons included depletion of noradrenaline stores, blockade of the noradrenaline membrane uptake pump and a loss of nerve-mediated transmission which resulted in large spermatic granulomata associated with the cauda epididymis and Infertility. This damage could be prevented by simultaneous administration of imipramine and thus was attributed to an intraneuronal site of action. The relative inactivity of these neurons may be an important factor in their sensitivity to guanethidine since decentralisation was shown to increase the sensitivity of 'long' noradrenergic neurons to guanethidine - induced damage. Intracranially injected guanethidine caused widespread depletion of central noradrenergic nerve terminals but, even in extremely high doses, did not cause degeneration. Central dopaminergic neurons were comparatively resistant to depletion by guanethidine.
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ItemUltrastructural studies of the effects of chronic guanethidine treatment on sympathetic neurons(University of Melbourne, 1975)Guanethidine (Ismelin, CIBA) is one of a group of drugs (the "adrenergic neuron blockers") which prevent release of noradrenaline from adrenergic nerve terminals (Maxwell et al, 1959). Following the introduction of guanethidine into clinical practice (Page & Dustan, 1959) this drug became widely used in the treatment of hypertension even though disturbing side effects such as impairment of male reproductive function following chronic treatment were frequently reported in the literature (Schirger & Gifford, 1962; Turner, 1962; Sah et al., 1966; Nickerson, 1970; Klein, 1972). Previous studies have shown that acute treatment with high doses of guanethidine (Clementi, 1965; Devine & Simpson, 1966; Devine et al,, 1967) has little or no effect on the ultrastructure of adrenergic neurons apart from the depletion of the dense core of small amine storage vesicles. Dawborn et al (1969) reported that chronic treatment with the chemically related drug guanacline caused long-lasting postural hypotension in humans, Subsequent ultrastructural and fluorescence histochemical studies revealed massive deposition of "aging pigment" in the cell bodies and terminal processes of sympathetic neurons of rats treated with guanacline, suggesting a causal relationship between these cellular effects and the persistent hypotension (Burnstock et al,, 1970, 1971a; Gerkens et al., 1970). Chronic treatment of rats with low doses of guanethidine causes depletion of small granular vesicles but no other ultrastructural changes in sympathetic neurons (Burnstock et al,, 1970). However this treatment results in long-lasting depletion of noradrenaline in the internal genital organs, suggesting damage of adrenergic nerves (Gannon et at., 1971). In view of these reports of long-lasting clinical effects and persistent depletion of adrenergic nerves resulting from treatment with low doses of guanethidine, the effect of chronic treatment with high doses of this drug was examined. The dramatic effect observed on the peripheral sympathetic nervous system in this preliminary study (see Chapter III) have warranted a fuller investigation. This thesis is a study of the effects of chronic treatment with high doses of guanethidine on peripheral sympathetic neurons of the rat. Chapters III, IV and V deal with changes occurring during guanethidine treatment, while Chapters VI, VII and VIII concern extended periods following cessation of (similar periods of) treatment. Techniques of study include routine transmission electron microscopy and histology, light and electron microscopic histochemistry of acid phosphatase, organ bath pharmacology, fluorescence histochemistry of catecholamines and phase contrast microscopy. Those materials and methods which are common to more than one chapter are described in Chapter II. Additional description appears after the Introduction of each experimental chapter and includes details of techniques used only in that chapter, a list of other methods used, drug dose levels and periods of administration, numbers of animals used and times of sacrifice. In Chapter III, it is shown that chronic treatment of rats with high doses of guanethidine results in extensive "chemical sympathectomy" due to extensive degeneration of peripheral adrenergic neurons. Evidence that the degenerative action of guanethidine is selective for adrenergic neurons is presented and discussed. Chapter IV describes the fine structural changes in nerve cell bodies of adrenergic neurons during guanethidine-induced degeneration. Three sequential phases are identified, and these are related to the mechanism of action of the drug. Structural changes in neurons, similar to retrograde reactions observed after axotomy, are found. Particular attention is paid to the phagocytosis of neuronal debris, since the unusual process involved has been implicated in the mechanism of degeneration occurring after guanethidine treatment. The results of this Chapter are discussed in relation to those of Chapter V, which is a study of the changes in sympathetic axons during the period in which degeneration of their parent cell bodies occurs. Both the vas deferens from animals treated in vivo and cultured sympathetic ganglia are used as experimental models. It is demonstrated that retraction of axons occurs prior to complete degeneration of the nerve cell bodies. In Chapter VI the ultrastructure of nerve cell bodies in the superior cervical ganglion is examined at periods up to 63 weeks following cessation of guanethidine treatment. No structural differences in remaining nerve cell bodies are noted compared to those in ganglia of age- matched control rats. Although a small increase in the number of nerve cell bodies relative to the number remaining immediately after treatment may occur during this period, the total number in the ganglion is clearly still greatly reduced. However the evidence suggests that sprouting of axons occurs from nerve cell bodies remaining in the ganglion. The next chapter (VII) describes alterations in axon-sheath relationships of some small myelinated fibres in the superior cervical ganglion following cessation of guanethidine treatment. The persistence of structurally intact myelin sheaths entirely lacking contact with nerves is reported for the first time. A model for the development of these structures is suggested. Chapter VIII is a correlated structural and functional study of the re-innervation of the vas deferens following cessation of guanethidine treatment. An abnormal pattern of re-innervation is observed and related to the reduction in numbers of sympathetic nerve cell bodies demonstrated in Chapter VI. The major findings of the experimental chapters are summarized and correlated in the final chapter (IX). The relative merits of guanethidine, 6-hydroxydopamine, immunosympathectomy and surgery as methods of producing sympathectomy are considered. Questions arising from the experimental chapters are discussed.
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ItemMineralogy, geochemistry and petrogenesis of some Victorian palaeozoic rhyolites(University of Melbourne, 1975)During the Palaeozoic, the Victorian region, in the southeastern portion of the Lachlan Geosyncline, probably felt the effects of rhythmic interaction between continental and oceanic plates. Although no detailed interpretation of Victorian geology in terms of plate tectonics has yet been undertaken, the acid-intermediate volcanics occupying the Devonian cauldron subsidence complexes provide excellent evidence for a high level crustal origin for continental calc-alkaline magma of the Andean type. This study concentrated on the most voluminous rhyolitic rocks in the complexes - the Rubicon and Ryans Creek Rhyolites from the Cerberean - Acheron and Tolmie Highlands complexes respectively, and the Jemba Rhyolite in north eastern Victoria. Evidence for an ash-flow origin is present in all three rhyolites, in the form of remnant eutaxitic and vitroclastic textures in the basal regions. All three are quartz-rich, two feldspar rhyolites, potentially leucogranites. Quartz, the most abundant phenocryst, is frequently embayed, particularly in the Ryans Creek Rhyolite. An origin for the embayment process, arising from diffusion of ions through the quartz structure, is postulated. Variation in K feldspar and plagioclase composition with height above the base was investigated, as was the trace element content of co-existing K feldspar and groundmass pairs, in order to determine possible fractionation effects. The Rubicon and Ryans Creek Rhyolites contain a unique Fe - cordierite - almandine - biotite assemblage, not previously recorded. On the basis of zoning patterns, bulk compositions, petrographic features and relationships with other phases, garnets were subdivided into a number of types (1-6). Types 2, 4 5 and 6 were considered xenocrystic, but Types 1 and 3 igneous. The occurrence of Type 2 garnets (and Fe cordierite) in both the Rubicon and Ryans Creek Rhyolites suggests a common source, in part. Fe cordierite is probably xenocrystic, but biotite is a liquidus phase in all three rhyolites. The three rhyolites show broadly similar mineralogical variations with height above base. Quartz, K feldspar and biotite abundances increase with height, but plagioclase is more variable. Total phenocryst contents reach 60-65% at the top of the Rubicon Rhyolite, somewhat less in the other two rhyolites. P-T conditions in the Rubicon Rhyolite varied considerably, but were relatively uniform in the Jemba and Ryans Creek Rhyolites. The chemical variations with height are those typically associated with a fractionation series (e.g. increasing K/Rb, Ba/Rb, Sr, Ba and Zr and decreasing Rb with height). But most evidence, e.g. the nature of the ferromagnesian phases, the Sr isotope data and the trace element contents, strongly favours a crustal anatectic origin. The chemical variations are therefore attributed largely to the fusion process, rather than to crystal differentiation or volatile transfer models. Possible post-emplacement compositional modification was discussed. The rhyolites represent the lowest temperature liquids arising from partial melting of politic metasediments (quartzo-feldspathic cordierite gneisses, garnet-biotite schists and hypersthene-plagioclase granulites for the Cerberean and Tolmie Highlands Volcanics). P-T conditions of 4-4.5 Kb, 750�-780�C were estimated from compositions of co-existing ferromagnesian phases, and are supported by recent experimental data on granitic rock types. Melted fragments of a likely source rock for the Rubicon Rhyolite occur as Fe cordierite-bearing rhyolitic inclusions in the base of the overlying rhyodacite at one locality in the Cerberean Cauldron. The ferromagnesian phases which formed at the climax of granulite facies metamorphism (garnet, cordierite, hypersthene, spinel and possibly some biotite - together with calcic plagioclase) have relative distributions within the entire suite reflecting original vertical variation with depth of metamorphic grade. The parent material for the Cerberean and Tolmie Highlands Volcanics was probably a lower Palaeozoic (Cambro-Ordovician) sequence in Central Victoria, although recourse to a pre-Cambrian crustal layer (for which indirect evidence exists) as a source may be necessary if the Palaeozoic sediments are not sufficiently thick. An attempt was made to relate the composition of a hypothetical Cambro-Ordovician metapelite to the average composition of the acid volcanics. The mineralogical data suggest melting occurred at depths of the order of 15-18 Km. The geothermal gradients responsible (about 50�C/Km) may have been due to injection of basic magma into the crust during the Tabberabberan Deformation in the Upper Devonian (the last major event in the episodic Palaeozoic history of the Victorian region). The Jemba Rhyolite was probably derived by anatexis of either Ordovician metasediments or the Corryong Batholith during the late Silurian Bowning orogeny. Crystallization in the rhyolites was accompanied by a build up in water pressures. These were estimated by consideration of bulk rock and groundmass compositions in the Or-Ab-Q-H20 and An-Or-Ab-Q systems. This occurred to the greatest extent in the Rubicon Rhyolite, where a vapour phase was probably generated when PH2O>PLoad at some stage prior to eruption. Eventually, roof rock fracturing and large scale ash-flow eruptions emplaced magma rapidly into confined subsidence regions, and preserved the chemical and mineralogical variations present in the original magma bodies. All three rhyolites underwent dense welding and recrystallization following emplacement. The post emplacement ordering and exsolution history of K feldspar phenocrysts in the three rhyolites was investigated in detail. The degree of ordering and unmixing of original sanidines to orthoclase and microcline perthites was found to be dependent on position within an ash-flow cooling unit. The relationships between different structural state parameters and the nature of the ordering and exsolution processes are discussed.
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ItemInstrumentation for neutron detection in three body reactions(University of Melbourne, 1973)
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ItemA biochemical investigation of speciation in South Eastern Australian anuran amphibians(University of Melbourne, 1973)Electrophoretic variation in haemoglobins and plasma transferrins was studied in four recognised taxa, and one undescribed taxon of the Litoria ewingi complex (Anura: Hylidae) in south-eastern Australia* The taxa studied were L. ewingi, L. v. verreauxi, L. v. alpina, L. paraewingi, and 'neoewingi'. Phenotypic variation of haemoglobins of L. ewingi occurred only in a limited area to the north-east of Melbourne, Victoria. Electrophoretic patterns resembled those expected for segregation of two alleles at an autosomal locus. Populations contained deficits of heterozygotes compared to numbers expected from Hardy-Weinberg Equilibrium, indicating that the polymorphism is not maintained by heterozygote advantage of adults. Variation of haemoglobin phenotypes occurred throughout the range of L. v. verreauxi. Phenotypes could not be related to a mode of genetic control. L. v. alpina was monomorphic for the most common haemoglobin phenotype occurring in L. v. verreauxi; and L. paraewingi was monomorphic for the most common haemoglobin phenotype occurring in L. ewingi. Haemoglobin data supported relationships derived from morphological characteristics. Transferrins showed varying levels of polymorphism regionally, and in different taxa. Controlled breeding experiments and electrophoretic patterns for transferrins were generally consistent with inheritance by codominant alleles at a single autosomal locus. However, a small number of individuals of L. ewingi showed three-handed or four-banded transferrin electrophoretic patterns. These patterns may be due to gene duplication. Every individual of L. v. alpina analysed from samples from two peripheral populations was phenotypically heterozygous for transferrin. This may indicate intense selection against homozygotes rather than gene duplication. Transferrin polymorphism in other areas, and in other taxa of the L. ewingi complex appears to be maintained by some form of balancing selection other than heterozygote advantage of adults. Some samples showed significant deficits of heterozygotes compared to numbers expected from Hardy-Weinberg Equilibrium. However, in the majority of samples, numbers of phenotypes observed approximated numbers expected from Hardy-Weinberg Equilibrium. Selection is implicated as the major factor determining distribution of protein types across the ranges of taxa, and in hybrid zones between taxa. The width of a hybrid zone based on protein data, does not appear to be related to the level, or to the type, of reproductive isolation between the taxa, except where reproductive isolation involves ecological factors.