Showing papers by "University of Western Australia published in 1994"

A large-conductance mechanosensitive channel in E. coli encoded by mscL alone

Abstract: All cellular organisms respond to vibration, touch, gravity or changes in osmolarity, although the molecules on which such mechanosensations depend are unknown. Candidates include certain channels that gate in response to membrane stretch. Patch-clamp experiments with Escherichia coli envelope have revealed a mechanosensitive channel with very large conductance (MscL) and one with a smaller conductance (MscS) which may be important in osmoregulation. Here we have solubilized and fractionated the envelope, reconstituted the MscL activity in vitro, and traced it to a small protein, whose gene, mscL, we then cloned. Insertional disruption of mscL removes the channel activity, whereas re-expression of mscL borne on an expression plasmid restores it. MscL-channel activities were observed in material from a cell-free expression system with mscL as the only template. The mscL nucleotide sequence predicts a unique protein of only 136 amino acids, with a highly hydrophobic core and very different from porins or other known proteins.

Selective suppression of the magnocellular visual pathway during saccadic eye movements

Abstract: VISUAL scientists have long sought to explain why the world remains stable during saccades, the ballistic eye-movements that continually displace the retinal image at fast but resolvable1 velocities. An early suggestion was that vision may be actively suppressed during saccades2, but experimental support has been variable3–5. Here we present evidence that saccadic suppression does occur, but that it is selective for patterns modulated in luminance at low spatial frequencies. Patterns of higher spatial frequency, and equiluminant patterns (modulated only in colour) at all spatial frequencies were not suppressed during saccades, but actually enhanced. The selectivity of the suppression suggests that it is confined to the colour-blind magnocellular stream (which provides the dominant input to motion centres and areas involved with attention), where it could dull the otherwise disturbing sense of fast low-spatial-frequency image motion. Masking studies suggest that the suppression precedes the site of contrast masking and may therefore occur early in visual processing, possibly as early as the lateral geniculate nucleus.

Collision between the North and South China Blocks: a crustal detachment model for suturing in the region east of the Tanlu fault

Abstract: A crustal-detachment model, based on the interpretation of linear aeromagnetic anomalies, surface geological observations, and deep seismic profiles, is proposed for the continent-continent collision between the North and South China blocks east of the Tanlu fault. The model suggests that during the mid-Mesozoic collision between the two continental blocks, the upper crust of the South China block in the Subei-Yellow Sea region was detached from the lower crust and thrust over the North China block for >400 km, whereas the lower part of the lithosphere was subducted under the North China block along a subsurface suture running east from Nanjing. The sinistral offset of the Qinling suture by the Tanlu fault is only 110-120 km in the deep crust—much less than previously suggested.

Sun exposure and non-melanocytic skin cancer

Abstract: Non-melanocytic skin cancer has long been regarded as one of the harmful effects of solar ultraviolet (UV) radiation on human health. In this review, we examine epidemiologic evidence linking sun exposure and skin cancer coming from both descriptive studies in populations and analytical studies involving estimates of exposure in individuals. Particular attention is given to the quality of the published data. The epidemiologic evidence that sun exposure causes skin cancer is mainly indirect. Incidence or mortality is inversely related to latitude in populations of mainly European origin (e.g., the United States, Australia), and is higher in people born in Australia (high ambient solar radiation) than in migrants to Australia from the United Kingdom (lower ambient radiation). Skin cancer occurs mainly at sun-exposed body sites and in people who are sensitive to the sun; a reduced capacity to repair UV-induced DNA damage appears to increase the risk. The direct evidence linking sun exposure and skin cancer is weaker with few well-conducted studies of sun exposure in individuals. Mostly, studies of total sun exposure have not found statistically significant positive associations; those that did, had not adjusted for potential confounding by age and gender and thus their interpretation is limited. Studies of occupational sun exposure had relative risks not greater than 2.0; recreational exposure has been little studied. Other measurements, less direct but potentially less prone to measurement error, are sunburn (not evidently associated with skin cancer risk) and indicators of benign cutaneous sun-damage (strongly associated but lacking empirical evidence that sun exposure is their main cause). Many questions remain about the relationship between sun exposure and skin cancer.Cancer Causes and Control 1994, 5, 367–392

Wave-induced soil response in an unsaturated anisotropic seabed of finite thickness

Abstract: An analytical solution for the wave-induced soil response is developed for a seabed of finite thickness subject to a three-dimensional (3-D) wave system produced by two intersecting waves of equal properties. These 3-D exact solutions for the pore pressure and effective stresses, proposed for a non-cohesive soil matrix of finite depth in a homogeneously unsaturated and anisotropic condition, are readily reducible to the limiting two-dimensional cases of progressive and standing waves, for which no explicit solutions are available for finite thickness. The effects of soil isotropy, degree of saturation, seabed thickness and grain size on the wave-induced pore pressure are discussed in detail. The explicit solutions presented in this study for the wave-induced pore pressure and effective stresses should benefit the laboratory experiments and field monitoring programs carried out in soil of finite depth.

Arboviruses causing human disease in the Australasian zoogeographic region.

Abstract: Over 65 arboviruses have been reported from countries in the Australasian zoogeographic region, but only a few have been implicated in human disease. These include the flaviviruses Murray Valley encephalitis (MVE), Kunjin (KUN), Kokobera (KOK), and dengue, particularly types 1 and 2; the alphaviruses Ross River (RR), Barmah Forest (BF), and Sindbis (SIN); and the bunyaviruses, Gan Gan and Trubanaman. In this paper recent epidemiological and clinical results pertaining to these viruses are reviewed, with major emphasis on MVE and RR viruses. The extensive early studies of Australian arboviruses have been reviewed by Doherty [49, 50], and their ecology and vectors more recently by Kay and Standfast [87]. In addition, the biology of MVE and KUN [113] and RR [87, 114] viruses have been the subjects of more detailed reviews.

Tumour induction by activated abl involves tyrosine phosphorylation of the product of the cbl oncogene.

Abstract: v-cbl is the transforming gene of a murine retrovirus which induces pre-B cell lymphomas and myelogenous leukaemias. It encodes 40 kDa of a gag fusion protein which is localized in the cytoplasm and nucleus of infected cells. The c-cbl oncogene encodes a 120 kDa cytoplasmic protein and its overexpression is not associated with tumorigenesis. The c-cbl sequence has shown that v-cbl was generated by a truncation that removed 60% of the C-terminus. In this study, we carried out experiments to identify the position within cbl where the transition occurs between non-tumorigenic and tumorigenic forms. These experiments focused attention on a region of 17 amino acids which is deleted from cbl in the 70Z/3 pre-B lymphoma due to a splice acceptor site mutation. This mutation activates cbl's tumorigenic potential and induces its tyrosine phosphorylation. We also show that the expression of the v-abl and bcr-abl oncogenes results in the induction of cbl tyrosine phosphorylation, and that abl and cbl associate in vivo. These findings demonstrate that tyrosine-phosphorylated cbl promotes tumorigenesis and that cbl is a downstream target of the bcr-abl and v-abl kinases.

Two inhibitors of pro-inflammatory cytokine release, interleukin-10 and interleukin-4, have contrasting effects on release of soluble p75 tumor necrosis factor receptor by cultured monocytes

Abstract: The biological activity of the pro-inflammatory cytokine, tumor necrosis factor (TNF)-alpha depends on the level of TNF-alpha itself, the expression of the p55 and p75 cell surface receptors for TNF on target cells and the concentrations of the natural inhibitors of TNF-alpha, the soluble p55 and p75 TNF receptors (TNF-R). Interleukin (IL)-10 and IL-4 are known to inhibit TNF-alpha production by monocytes. We, therefore, investigated the effects of IL-10 and IL-4 on the cell surface expression and release of TNF-R by human monocytes to determine whether these cytokines also indirectly modulated the biological activity of TNF-alpha. Exposure to IL-10 (1-10 U/ml) for 24 or 48 h increased soluble p75 TNF-R expression and concomitantly reduced surface expression of p75 TNF-R. Further, IL-1 alpha-stimulated production of TNF-alpha was diminished by IL-10 and only a small proportion of this TNF-alpha was bioactive, consistent with increased production of inhibitory soluble TNF-R. IL-10 also induced down-regulation of surface p55 TNF-R on monocytes, and increased release of soluble p55 TNF-R. However, the expression of soluble p55 TNF-R was much lower than soluble p75 TNF-R, indicating that it contributed less importantly to neutralization of TNF-alpha under these conditions. Like IL-10, IL-4 supressed the release of TNF-alpha by monocytes. In contrast to IL-10, however, IL-4 (0.1-10 ng/ml) supressed the release of soluble p75 TNF-R from monocytes in a dose-dependent manner. Release of soluble p55 TNF-R was also supressed by IL-4. IL-10, therefore, reduces the pro-inflammatory potential of TNF in three ways: by down-regulating surface TNF-R expression whilst increasing production of soluble TNF-R and inhibiting the release of TNF-alpha itself. This suggests that IL-10 may be useful in the treatment of diseases where overexpression of TNF-alpha occurs.

The role of lifestyle factors in the etiology of stroke. A population-based case-control study in Perth, Western Australia.

Abstract: We sought to examine risk factors for all strokes and for ischemic stroke and primary intracerebral hemorrhage separately.This was a population-based case-control study. Each case subject meeting World Health Organization criteria for stroke (n = 536) from a population-based register of acute cerebrovascular events compiled in Perth, Western Australia, in 1989 to 1990 was matched for age and sex with up to five control subjects drawn from the same geographical area. Objective confirmation of the type of stroke was available from computed tomography, magnetic resonance imaging, or necropsy for 86% of the case subjects. Data on medical history and lifestyle factors were collected from case and control subjects by interview of the subject or a proxy informant.Current smoking, consumption of meat more than four times weekly, and a history of hypertension or intermittent claudication were each associated with increased risk in multivariate models for all strokes and for all first-ever strokes. Consumption of 1...

Mechanisms of brittle fracture of rock with pre-existing cracks in compression

Abstract: Fracture of rocks containing a multitude of pre-existing cracks is considered from both theoretical and experimental points of view, paying attention mainly to the underlying mechanisms The competition between a number of mechanisms in producing tear or shear type fractures is discussed in relation to the properties of the rock and the system of pre-existing cracks on the one hand and the type of loading on the other hand First, 2-D theoretical models and experimental results aimed at the explanation and description of brittle fracture under compression are considered Their insufficiency and the necessity to address the 3-D peculiarities of crack growth in rock are shown on the basis of new experimental results on 3-D crack propagation in transparent rock-like brittle materials under uniaxial compression The results show that in contrast to the 2-D case, a single 3-D crack cannot propagate any appreciable distance and the loading results in dynamic, burst-like failure of the sample Possible mechanisms of the routinely observed extensive fracture propagation in rock samples (splitting), as well as the possibility of shear (oblique) fracture in uniaxial compression, are discussed in connection with these experiments

Modification of forearm resistance vessels by exercise training in young men

Abstract: The aim of this study was to determine whether a 4-wk handgrip training program would elicit changes in endothelium-dependent and endothelium-independent vasodilatation in resistance vessels of the human forearm. Minimum vascular resistance after a 10-min ischemic stimulus, an index of peak vasodilator capacity, was also determined. Forearm blood flow response to the endothelium-dependent vasodilator methacholine chloride did not change over the 4-wk-intervention period either in the group undertaking training (n = 11) or in control subjects (n = 6). Similarly, the response to sodium nitroprusside was not influenced by the handgrip training program. Peak vasodilator capacity of the trained forearms significantly increased, whereas no change was evident in the untrained limbs. These results suggest that 4 wk of forearm exercise training enhances peak vasodilator capacity of the vasculature without influencing stimulated activity of the nitric oxide dilator system.

Thermodynamic analysis of the martensitic transformation in NiTi—II. Effect of transformation cycling

Abstract: The effect of transformation cycling, with and without applied stress, on the martensitic transformation in NiTi has been studied. Changes in transformation temperatures resulting from cycling are interpreted in terms of changes to the elastic strain energy and the irreversible energy associated with the transformation. It is found that the main effect of thermal cycling under zero stress is to increase the elastic strain energy. With pseudoelastic cycling and extensive thermal cycling under stress the elastic strain energy decreases with increasing cycling due to the development of a directional internal stress field associated with the formation of aligned variants.

65Zn uptake in subterranean clover (Trifolium subterraneum L.) by three vesicular-arbuscular mycorrhizal fungi in a root-free sandy soil

Abstract: The uptake of Zn by the hyphae of three vesicular-arbuscular (VA) mycorrhizal fungi, Acaulospora laevis Gerdemann & Trappe, Glomus sp. resembling Glomus fasciculatum (Thaxter) Gerdemann & Trappe emend. Walker & Koske and Scutellospora calospora (Nicol. & Gerd.) Walker & Sanders, in association with subterranean clover Trifolium subterraneum L. (cv. Seaton Park) was examined. The plants were grown in PVC tubes for 5 weeks before transfer to an experimental system, where a root compartment was separated from a root-free hyphal compartment by a 37μm nylon mesh. 65Zn was placed in the hyphal compartment at distances of 0, 10, 20 or 40mm from the roots. For the non-mycorrhizal control, 65Zn was placed at 0 or 10 mm from the roots. At 14 and 28 days after transfer (DAT) the youngest opened leaves (YOL) were harvested, and at 21 and 35 DAT whole plants were harvested. Dry weights, P and Zn concentrations, root length and mycorrhizal colonization, length of external hyphae and specific 65Zn activity were recorded. At all harvests 65Zn activity in shoots of plants colonized by A. laevis was greater than for non-mycorrhizal plants and plants colonized by either Glomus sp. or S. calospora. Plants inoculated with A. laevis absorbed 65Zn placed 40 mm from the roots, whereas no 65Zn uptake from this distance occurred with other treatments. The ability of plants colonized by A. laevis to access 65Zn 40mm from the roots was associated with a much greater hyphal length at this distance from the roots than for the two other mycorrhizal fungi. However, immediately adjacent to the roots there was a greater length of external hyphae for Glomus sp. than for A. laevis. Hyphal length was much lower for S. calospora at all distances from the roots than for the other mycorrhizal fungi. The results show great differences in the abilities of the hyphae of VA mycorrhizal fungi to grow in root-free soil and to absorb and transport labelled Zn to the host plants in a soil with a luxury supply of Zn.

The Treatment of Anxiety Disorders: Clinician's Guide and Patient Manuals

Abstract: In this completely revised 2002 second edition of their well-received book, Gavin Andrews and his team continue to draw upon materials and methods that they have used successfully in clinical practice for 15 years. Over half the material in the second edition is new, and there is an entirely new section covering post-traumatic stress disorder. This is a unique and authoritative overview of the recognition and treatment of anxiety disorders, giving Clinician Guides and Patient Treatment Manuals for each. The Clinician Guides describe how to create a treatment program, and by working through the Patient Treatment Manual together with the clinician enables each patient to understand and put into effect the strategies of cognitive behaviour therapy. The Treatment of Anxiety Disorders offers both a theoretical overview and a framework to help psychiatrists and clinical psychologists build successful treatment programs.

A new polymorphic and multicopy MHC gene family related to nonmammalian class I

Abstract: We have used genomic analysis to characterize a region of the central major histocompatibility complex (MHC) spanning ∼ 300 kilobases (kb) betweenTNF andHLA-B. This region has been suggested to carry genetic factors relevant to the development of autoimmune diseases such as myasthenia gravis (MG) and insulin dependent diabetes mellitus (IDDM). Genomic sequence was analyzed for coding potential, using two neural network programs, GRAIL and GeneParser. A genomic probe, JAB, containing putative coding sequences (PERB11) located 60 kb centromeric ofHLA-B, was used for northern analysis of human tissues. Multiple transcripts were detected. Southern analysis of genomic DNA and overlapping YAC clones, covering the region fromBAT1 toHLA-F, indicated that there are at least five copies of PERB11, four of which are located within this region of the MHC. The partial cDNA sequence ofPERB11 was obtained from poly-A RNA derived from skeletal muscle. The putative amino acid sequence ofPERB11 shares ∼ 30%o identity to MHC class I molecules from various species, including reptiles, chickens, and frogs, as well as to other MHC class I-like molecules, such as the IgG FeR of the mouse and rat and the human Zn-α2-glycoprotein. From direct comparison of amino acid sequences, it is concluded thatPERB11 is a distinct molecule more closely related to nonmammalian than known mammalian MHC class I molecules. Genomic sequence analysis ofPERB11 from five MHC ancestral haplotypes (AH) indicated that the gene is polymorphic at both DNA and protein level. The results suggest thet we have identified a novel polymorphic gene family with multiple copies within the MHC.

Psychological and immunological correlates of acute overtraining.

Abstract: Five men undertook two intensive interval training sessions per day for 10 days, followed by 5 days of active recovery. Subjects supplied a venous blood sample and completed a mood-state questionnaire on days 1, 6, 11 and 16 of the study. Performance capabilities were assessed on days 1, 11 and 16 using a timed treadmill test to exhaustion at 18 kmh-1 and 1% grade. These individuals became acutely overtrained as indicated by significant reductions in running performance from day 1 to day 11. The overtrained state was accompanied by severe fatigue, immune system deficits, mood disturbance, physical complaints, sleep difficulties, and reduced appetite. Mood states moved toward baseline during recovery, but feelings of fatigue and immune system deficits persisted throughout the study.

An Exponential Lower Bound to the Size of Bounded Depth Frege Proofs of the Pigeonhole Principle

Abstract: We prove lower bounds of the form exp(ne d), ed > 0, on the length of proofs of an explicit sequence of tautologies, based on the Pigeonhole Principle, in proof systems using formulas of depth d, for any constant d. This is the largest lower bound for the strongest proof system, for which any superpolynomial lower bounds are known.

An Empirical Investigation of the Audit Expectation Gap: Australian Evidence

Abstract: This paper examines the existence and nature of the expectation gap in Australia and whether recent changes to the wording of audit reports have affected that gap. A mail questionnaire was completed by auditors, accountants, directors, creditors, shareholders and undergraduate students. There was a gap between auditors and the various user groups under the old report wording prior to the issuance of the revised AUP 3. The modified wording in the revised AUP 3 had a significant impact on beliefs about the nature of an audit and the relative responsibilities of auditors and management. The modified wording eliminated some of the differences, but also created some new differences in beliefs about the messages communicated through audit reports. The auditing profession's fears about an expectation gap appear to be justified.

Distribution, abundance and breeding cycle of the Australian sea lion Neophoca cinerea (Mammalia: Pinnipedia)

Abstract: Surveys of the Australian sea lion Neophoca cinerea were conducted throughout its range in Western and South Australia between December 1987 and February 1992. Almost every island was visited between Houtman Abrolhos and The Pages (n = 255), many of them more than once. Sea lions breed on at least 50 islands, 27 in Western Australia and 23 in South Australia. Of the 50 breeding sites, 31 have not been reported previously. A further 19 islands may also support breeding colonies. A total of 1,941 pups was counted and pup production was estimated at 2,432. Only five colonies produced more than 100 pups each and they accounted for almost half of the pup production. Most of these colonies are near Kangaroo Island, South Australia. A breeding cycle of 17–18 months has been reported for N. cinerea at Kangaroo Island and on the west coast of Western Australia; this was also noted at another 11 islands where repeated visits coincided with breeding. No evidence was found for breeding seasons shorter or longer than 17–18 months. The breeding season was not synchronized between islands, as it is in other pinnipeds. A predictive model is developed to estimate the population size from pup production figures. It indicates that pup numbers should be multiplied by between 3.81 and 4.81 to estimate the total population size just before the pupping season begins. This leads to estimates of 9,300–11,700 for the total population, considerably greater than earlier estimates. Causes of the unique reproductive cycle of N. cinerea are unknown, but we hypothesize that it results from living in a temperate climate in some of the most biologically depauperate waters of the world. It is also clear that day length and water temperature cannot act as exogenous cues for implantation of the blastocyst; the physiological events of gestation must, rather, be cued endogenously.