Can mechanism help explain insect host choice?

Evolutionary theory predicts that herbivorous insects should lay eggs on plants in a way that reflects the suitability of each plant species for larval development. Empirical studies, however, often fail to find any relationship between an adult insect’s choice of host–plant and offspring fitness, and in such cases, it is generally assumed that other ‘missing’ factors (e.g. predation, host–plant abundance, learning and adult feeding sites) must be contributing to overall host suitability. Here, I consider an alternative theory – that a fitness cost inherent in the olfactory mechanism could constrain the evolution of insect host selection. I begin by reviewing current knowledge of odour processing in the insect antennal lobe with the aid of a simple schematic: the aim being to explain the workings of this mechanism to scientists who do not have prior knowledge in this field. I then use the schematic to explore how an insect’s perception of host and non-host odours is governed by a set of processing rules, or algorithm. Under the assumptions of this mechanistic view, the perception of every plant odour is interrelated, and seemingly bad host choices can still arise as part of an overall adaptive behavioural strategy. I discuss how an understanding of mechanism can improve the interpretation of theoretical and empirical studies in insect behaviour and evolution.

Mathematical modelling of tumour growth and interaction with host tissue and the immune system

In this thesis, three mathematical models describing the growth of solid tumour incorporating the host tissue and the immune system response are developed and investigated. The initial model describes the dynamics of the growing tumour and immune response before being extended in the second model by introducing a time-varying dendritic cell-based treatment strategy. Finally, in the third model, we present a mathematical model of a growing tumour using a hybrid cellular automata. These models can provide information to pre-experimental work to assist in designing more effective and efficient laboratory experiments related to tumour growth and interactions with the immune system and immunotherapy.

Citrus host utilisation by the Queensland fruit fly, Bactrocera tryoni (Frogatt) (Diptera:Tephritidae) : from individuals to populations

Fruit flies are the insects which cause maggots in your backyard fruit and vegetables. They are not just a nuisance to gardeners, but the single greatest insect threat to commercial and subsistence fruit growers throughout Asia, Australia and the Pacific. Queensland fruit fly, the focus of this PhD, costs Australia an estimated $100million per year. I focused specifically on how Queensland fruit fly uses different commercial citrus varieties. I identified specific plant related mechanisms which increase a fruit’s resistance to fruit fly attack. This information can be used by plant breeders to make fruit less prone to fruit fly damage.

TLR2, but Not TLR4, is required for effective host defence against Chlamydia respiratory tract infection in early life

Chlamydia pneumoniae commonly causes respiratory tract infections in children, and epidemiological investigations strongly link infection to the pathogenesis of asthma. The immune system in early life is immature and may not respond appropriately to pathogens. Toll-like receptor (TLR)2 and 4 are regarded as the primary pattern recognition receptors that sense bacteria, however their contribution to innate and adaptive immunity in early life remains poorly defined. We investigated the role of TLR2 and 4 in the induction of immune responses to Chlamydia muridarum respiratory infection, in neonatal wild-type (Wt) or TLR2-deficient (−/−), 4−/− or 2/4−/− BALB/c mice. Wt mice had moderate disease and infection. TLR2−/− mice had more severe disease and more intense and prolonged infection compared to other groups. TLR4−/− mice were asymptomatic. TLR2/4−/− mice had severe early disease and persistent infection, which resolved thereafter consistent with the absence of symptoms in TLR4−/− mice. Wt mice mounted robust innate and adaptive responses with an influx of natural killer (NK) cells, neutrophils, myeloid (mDCs) and plasmacytoid (pDCs) dendritic cells, and activated CD4+ and CD8+ T-cells into the lungs. Wt mice also had effective production of interferon (IFN)γ in the lymph nodes and lung, and proliferation of lymph node T-cells. TLR2−/− mice had more intense and persistent innate (particularly neutrophil) and adaptive cell responses and IL-17 expression in the lung, however IFNγ responses and T-cell proliferation were reduced. TLR2/4−/− mice had reduced innate and adaptive responses. Most importantly, neutrophil phagocytosis was impaired in the absence of TLR2. Thus, TLR2 expression, particularly on neutrophils, is required for effective control of Chlamydia respiratory infection in early life. Loss of control of infection leads to enhanced but ineffective TLR4-mediated inflammatory responses that prolong disease symptoms. This indicates that TLR2 agonists may be beneficial in the treatment of early life Chlamydia infections and associated diseases.

Response variation of optically stimulated luminescence dosimeters

This study investigates the variability in response of optically stimulated luminescence dosimeters (OSLDs). Examining the source of sensitivity variations in these dosimeters allows for a more comprehensive understanding of the Landauer nanoDots and their potential for current and future applications. In this work, OSLDs were scanned with a MicroCT scanner to determine potential sources for the variation in relative sensitivity across a selection of Landauer nanoDot dosimeters. Specifically, the correlation between a dosimeters relative sensitivity and the loading density of Al2O3:C powder was determined. When extrapolating the sensitive volume's radiodensity from the CT data, it was shown that there is a non-uniform distribution in crystal growth. It was calculated that a 0.05% change in the nominal volume of the chip produces a 1% change in the overall response. Additionally, the ‘true’ volume of an OSLD's sensitive material is, on average, 18% less than that which has been reported in literature, mainly due to the presence of air cavities in the material's structure. This work demonstrated that the amount of sensitive material is approximately linked to the total correction factor.

ZnO nanocones with high-index {101̅1} facets for enhanced energy conversion efficiency of dye-sensitized solar cells

ZnO is a promising photoanode material for dye-sensitized solar cells (DSCs) due to its high bulk electron mobility and because different geometrical structures can easily be tailored. Although various strategies have been taken to improve ZnO-based DSC efficiencies, their performances are still far lower than TiO2 counterparts, mainly because low conductivity Zn2+–dye complexes form on the ZnO surfaces. Here, cone-shaped ZnO nanocrystals with exposed reactive O-terminated {101̅1} facets were synthesized and applied in DSC devices. The devices were compared with DSCs made from more commonly used rod-shaped ZnO nanocrystals where {101̅0} facets are predominantly exposed. When cone-shaped ZnO nanocrystals were used, DSCs sensitized with C218, N719, and D205 dyes universally displayed better power conversion efficiency, with the highest photoconversion efficiency of 4.36% observed with the C218 dye. First-principles calculations indicated that the enhanced DSCs performance with ZnO nanocone photoanodes could be attributed to the strength of binding between the dye molecules and reactive O-terminated {101̅1} ZnO facets and that more effective use of dye molecules occurred due to a significantly less dye aggregation on these ZnO surfaces compared to other ZnO facets.

Enterovirus71 (EV71) utilise host microRNAs to mediate host immune system enhancing survival during infection

Hand, Foot and Mouth Disease (HFMD) is a self-limiting viral disease that mainly affects infants and children. In contrast with other HFMD causing enteroviruses, Enterovirus71 (EV71) has commonly been associated with severe clinical manifestation leading to death. Currently, due to a lack in understanding of EV71 pathogenesis, there is no antiviral therapeutics for the treatment of HFMD patients. Therefore the need to better understand the mechanism of EV71 pathogenesis is warranted. We have previously reported a human colorectal adenocarcinoma cell line (HT29) based model to study the pathogenesis of EV71. Using this system, we showed that knockdown of DGCR8, an essential cofactor for microRNAs biogenesis resulted in a reduction of EV71 replication. We also demonstrated that there are miRNAs changes during EV71 pathogenesis and EV71 utilise host miRNAs to attenuate antiviral pathways during infection. Together, data from this study provide critical information on the role of miRNAs during EV71 infection.

One-step synthesis of titanium oxide with trilayer structure for dye-sensitized solar cells

Titanium oxide films with trilayer structure grown on fluorine doped tin oxide substrate were prepared from one-step hydrothermal process. The trilayer structure consists of microflowers, nanorod array and compact nanoparticulates, which is expected to possess the merits of good light harvesting, a high electron transport rate, while avoiding the issues of electron shunting. The photovoltaic performance was comprehensively studied and a 60% enhancement in short circuit photocurrent density was found from microflowers contribution as a light scattering layer. This unique trilayer structure exhibits great potential application in future dye-sensitized solar cells.

Response variation of optically stimulated luminescence dosimeters

Introduction This study investigates uncertainties pertaining to the use of optically stimulated luminescence dosimeters (OSLDs) in radiotherapy dosimetry. The sensitivity of the luminescent material is related to the density of recombination centres [1], which is in the range of 1015–1016 cm-3. Because of this non-uniform distribution of traps in crystal growth the sensitivity varies substantially within a batch of dosimeters. However, a quantitative understanding of the relationship between the response of an OSLD and its sensitive volume has not yet been investigated or reported in literature. Methods In this work, OSLDs are scanned with a MicroCT scanner to determine potential sources for the variation in relative sensitivity across a selection of Landauer nanoDot dosimeters. Specifically, the correlation between a dosimeters relative sensitivity and the loading density of Al2O3:C powder was determined. Results When extrapolating the sensitive volume’s radiodensity from the CT data, it was shown that there is a non-uniform distribution incrystal growth as illustrated in Fig. 1. A plot of voxel count versus the element-specific correction factor is shown in Fig. 2 where each point represents a single OSLD. A line was fitted which has an R2-value of 0.69 and a P-value of 8.21 9 10-19. This data shows that the response of a dosimeter decreases proportionally with sensitive volume. Extrapolating from this data, a quantitative relationship between response and sensitive volume was roughly determined for this batch of dosimeters. A change in volume of 1.176 9 10-5 cm3 corresponds to a 1 % change in response. In other words, a 0.05 % change in the nominal volume of the chip would result in a 1 % change in response. Discussion and conclusions This work demonstrated that the amount of sensitive material is approximately linked to the total correction factor. Furthermore, the ‘true’ volume of an OSLD’s sensitive material is, on average, 17.90 % less than that which has been reported in literature, mainly due to the presence of air cavities in the material’s structure. Finally, the potential effects of the inaccuracy of Al2O3:C deposition increases with decreasing chip size. If a luminescent dosimeter were manufactured with a smaller volume than currently employed using the same manufacturing protocol, the variation in response from chip to chip would more than likely exceed the current 5 % range.

Host rather than graft origin of Matrigel-induced adipose tissue in the murine tissue-engineering chamber

We have recently shown that Matrigel-filled chambers containing fibroblast growth factor-2 (FGF2) and placed around an epigastric pedicle in the mouse were highly adipogenic. Contact of this construct with pre-existing tissue or a free adipose graft was required. To further investigate the mechanisms underpinning formation of new adipose tissue, we seeded these chambers with human adipose biopsies and human adipose-derived cell populations in severe combined immunodeficient mice and assessed the origin of the resultant adipose tissue after 6 weeks using species-specific probes. The tissues were negative for human-specific vimentin labeling, suggesting that the fat originates from the murine host rather than the human graft. This was supported by the strong presence of mouse-specific Cot-1 deoxyribonucleic acid labeling, and the absence of human Cot-1 labeling in the new fat. Even chambers seeded with FGF2/Matrigel containing cultured human stromal-vascular fraction (SVF) labeled strongly only for human vimentin in cells that did not have a mature adipocyte phenotype; the newly formed fat tissue was negative for human vimentin. These findings indicate that grafts placed in the chamber have an inductive function for neo-adipogenesis, rather than supplying adipocyte-precursor cells to generate the new fat tissue, and preliminary observations implicate the SVF in producing inductive factors. This surprising finding opens the door for refinement of current adipose tissue-engineering approaches.

Graft versus host disease in oncology nursing practice

INTRODUCTION: Gastrointestinal graft-versus-host disease (GI-GvHD) is extremely debilitating and is multifactorial in its causative factors, management and treatment. It is an exaggeration of normal physiological mechanisms wherein the donor immune system attempts to rid itself of the host. The inflammatory process that follows has the benefit of providing an anti-tumour effect for many diseases, but unfortunately in patients undergoing human stem-cell transplantation, the nature of the inflammation can result in disability, wasting and death. AIM: The aim of this article is to discuss the pathophysiology of this often misunderstood or misdiagnosed condition, as well as its signs and symptoms, management and considerations for nursing care. Considerations for nursing practice: While the medical management is aimed at minimising GvHD through the reduction of T-cell production and proliferation and gastrointestinal decolonisation, the nursing care is often focused on the signs and symptoms that can have the most prominent impact on patients. CONCLUSION: GI-GvHD has serious life-threatening complications, namely wasting syndrome, diarrhoea and dehydration. The basis of signs and symptomology is easily recognisable owing to the stages of progression through the human stem-cell transplantation process. Oncology nurses are in a prime position to identify these serious risks, initiate treatment immediately and collaborate effectively within the multidisciplinary team to minimise GvHD onset and provide expert support to patients, family and caregivers.

Room-temperature, atmospheric plasma needle reduces adenovirus gene expression in HEK 293A host cells

Room-temperature, atmospheric-pressure plasma needle treatment is used to effectively minimize the adenovirus (AdV) infectivity as quantified by the dramatic reduction of its gene expression in HEK 293A primary human embryonic kidney cells studied by green fluorescent protein imaging. The AdV titer is reduced by two orders of magnitude within only 8 min of the plasma exposure. This effect is due to longer lifetimes and higher interaction efficacy of the plasma-generated reactive species in confined space exposed to the plasma rather than thermal effects commonly utilized in pathogen inactivation. This generic approach is promising for the next-generation anti-viral treatments and imunotherapies.

Understanding Heliothine (Lepidoptera: Heliothinae) pests: What is a host plant?

Heliothine moths (Lepidoptera: Heliothinae) include some of the world's most devastating pest species. Whereas the majority of nonpest heliothinae specialize on a single plant family, genus, or species, pest species are highly polyphagous, with populations often escalating in size as they move from one crop species to another. Here, we examine the current literature on heliothine host-selection behavior with the aim of providing a knowledge base for research scientists and pest managers. We review the host relations of pest heliothines, with a particular focus on Helicoverpa armigera (Hubner), the most economically damaging of all heliothine species. We then consider the important question of what constitutes a host plant in these moths, and some of the problems that arise when trying to determine host plant status from empirical studies on host use. The top six host plant families in the two main Australian pest species (H. armigera and Helicoverpa punctigera Wallengren) are the same and the top three (Asteraceae, Fabaceae, and Malvaceae) are ranked the same (in terms of the number of host species on which eggs or larvae have been identified), suggesting that these species may use similar cues to identify their hosts. In contrast, for the two key pest heliothines in the Americas, the Fabaceae contains approximate to 1/3 of hosts for both. For Helicoverpa zea (Boddie), the remaining hosts are more evenly distributed, with Solanaceae next, followed by Poaceae, Asteraceae, Malvaceae, and Rosaceae. For Heliothis virescens (F.), the next highest five families are Malvaceae, Asteraceae, Solanaceae, Convolvulaceae, and Scrophulariaceae. Again there is considerable overlap in host use at generic and even species level. H. armigera is the most widely distributed and recorded from 68 plant families worldwide, but only 14 families are recorded as a containing a host in all geographic areas. A few crop hosts are used throughout the range as expected, but in some cases there are anomalies, perhaps because host plant relation studies are not comparable. Studies on the attraction of heliothines to plant odors are examined in the context of our current understanding of insect olfaction, with the aim of better understanding the connection between odor perception and host choice. Finally, we discuss research into sustainable management of pest heliothines using knowledge of heliothine behavior and ecology. A coordinated international research effort is needed to advance our knowledge on host relations in widely distributed polyphagous species instead of the localized, piecemeal approaches to understanding these insects that has been the norm to date.

The functional significance of fruit exocarp on host selection and oviposition by Queensland fruit fly, Bactrocera tryoni (Froggatt) (Tephritidae: Diptera)

Queensland fruit fly is Australia's most serious insect pest of horticulture. The fly lays its eggs into fruit, where they hatch into maggots which destroy the fruit. Understanding egg laying behaviour, known as oviposition, is a critical but under-researched aspect of fruit fly biology. This thesis focused on three aspects of oviposition: the role of fruit peel as a physical barrier to oviposition; the quality of fruit for maggot development; and the structure and wear of the egg laying organ – the ovipositor. Results showed that flies selected fruit based on their suitability for offspring survival, not because of the softness or hardness of fruit peel. Previously reported use of holes or wounds in fruit peel by ovipositing females was determined to be a mechanism which saved the female time, not a mechanism to reduce ovipositor wear. The results offer insights into the evolution of host use by fruit flies and their sustainable management.

The infectivity and host range of Orgyia anartoides nucleopolyhedrovirus

The painted apple moth (PAM), Teia anartoides (Walker) (Lepidoptera: Lymantriidae) made a recent incursion into New Zealand. A nucleopolyhedrovirus (NPV), Orgyia anartoides NPV (OranNPV), originally isolated from PAM in Australia, was tested for its pathogenicity to PAM and a range of non-target insect species found in New Zealand, to evaluate its suitability as a microbial control for this insect invader. Dosage-mortality tests showed that OranNPV was highly pathogenic to PAM larvae; mean LT50 values for third instars ranged from 17.9 to 8.1 days for doses from 102 to 105 polyhedral inclusion bodies/larva, respectively. The cause of death in infected insects was confirmed as OranNPV. Molecular analysis established that OranNPV can be identified by PCR and restriction digestion, and this process complemented microscopic examination of infected larvae. No lymantriid species occur in New Zealand; however, the virus had no significant effects on species from five other lepidopteran families (Noctuidae, Tortricidae, Geometridae, Nymphalidae and Plutellidae) or on adult honeybees. Thus, all indications from this initial investigation are that OranNPV would be an important tool in the control of PAM in a future incursion of this species into New Zealand.