Massey Documents by Type

Permanent URI for this communityhttps://mro.massey.ac.nz/handle/10179/294

Browse

Filters

Settings

Subject: search.filters.subject.Pathophysiology

Search Results

Now showing 1 - 5 of 5
  • Thumbnail Image
    Item
    Non-inflammatory mechanisms in asthma : a thesis with publications presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Public Health, Massey University, Wellington, New Zealand
    (Massey University, 2023-07-31) Ali, Hajar
    Until relatively recently asthma was considered to be an allergic disease characterised by airway inflammation. However, emerging evidence suggests that approximately 50% of asthmatics have no overt signs of inflammation. The pathophysiological mechanisms underlying disease in this group - non-eosinophilic asthma (NEA) - remain poorly understood. In 130 young-adults with generally well-controlled asthma and 79 non-asthmatics (aged 14-21 years), various non-invasive approaches were used to assess both inflammatory and non-inflammatory mechanisms in eosinophilic asthma (EA) and NEA. Studies focussed on: (i) neural mechanisms (including autonomic nervous system (ANS) activity, sensory nerve activity, and levels of neural mediators in induced sputum); and (ii) airway remodelling (measuring induced sputum levels of airway remodelling mediators), in different asthma phenotypes, whilst also taking into account clinical and inflammatory characteristics. In addition, the response to short acting β-agonist (SABA) and short acting muscarinic-antagonist (SAMA) treatment was compared between asthma phenotypes. Differences in some aspects of neural regulation were observed between EA, NEA, and non-asthmatics. In particular, airway sensory nerve reactivity was enhanced in NEA compared with non-asthmatics (p<0.05). Sensory nerve reactivity was also higher in NEA compared to EA, but this did not reach statistical significance (p=0.07). There was no evidence of an imbalance in ANS activity when comparing asthmatics and non-asthmatics, or EA and NEA. Increased levels of nociceptin were found in asthmatics and EA compared with non-asthmatics (P<0.05); nociceptin was positively associated with sputum eosinophils. Several inflammatory and remodelling mediators (including IL-1β, ECP, periostin, and VEGF-A) were elevated in EA but not NEA. There was no evidence of a differential response to SAMA between EA and NEA; however, a small subgroup of asthmatics responded better to SAMA. In conclusion, the studies described in this thesis suggest that sensory nerve reactivity may play an important role in the pathophysiology of NEA, but not EA, and may potentially represent a novel phenotype-specific treatable trait. Autonomic dysregulation does not appear to play a role in well-controlled asthma or specific asthma phenotypes. Findings suggest a potential involvement of nociceptin in asthma pathology, particularly in relation to airway eosinophilia. Finally, the identification of a small group of asthmatics who responded better to SAMA than SABA challenges current asthma treatment guidelines and suggests a need for a more personalised treatment approach. Further investigation of non-inflammatory mechanisms is warranted to improve understanding of other mechanisms underlying different asthma phenotypes, which will contribute to the identification of more specific treatable traits.
  • Thumbnail Image
    Item
    Loss of HP1α alters nuclear integrity to promote cellular invasion : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Biochemistry at Massey University, Manawatū, New Zealand
    (Massey University, 2019) Solomon, Raoul
    The onset of invasion is a key step towards the development of metastatic cancer. For a cell to invade through interstitial spaces in the tissue requires a reduction in nuclear rigidity as the cell needs to deform to squeeze through small spaces. Heterochromatin Protein 1α (HP1α) is a protein that defines domains of heterochromatin, the highly compact regions of the genome, and is essential for maintaining the appropriate patterns of gene expression and genome stability. Loss or reduction of HP1α has been correlated with an increase in invasive potential in human tumours. Using an established model of Drosophila melanogaster epithelial cell invasion, the causative role HP1α plays in suppressing cellular invasive is confirmed within an epithelial tissue microenvironment. This model also demonstrates that loss of the Drosophila melanogaster HP1 homologue synergistically promotes cellular invasion in conjunction with an activated malignant signalling pathway. Importantly, human HP1α is shown to rescue this highly invasive Drosophila phenotype and demonstrates the relevance of this model to human disease, and its use for exploring protein interactions in a cellular microenvironment. As loss of nuclear integrity has been linked to a reduction in peripheral heterochromatin, the biophysical mechanisms by which HP1α acts as a suppressor of invasive potential were explored in the poorly invasive MCF7 breast cancer cell line with constitutive HP1α knock-down. These cells with reduced HP1α expression had a significant loss of nuclear membrane integrity and stiffness. The underlying nuclear lamina meshwork and associated peripheral heterochromatin was disrupted. This was associated with an increased solubility of lamina proteins, particularly lamin A, as well as the altered localisation of a number of peripheral nuclear proteins. In summary, this work established the important contribution of HP1α to the mechanical integrity of the nucleoskeleton and the role HP1α plays in suppressing malignant signalling pathways that promote cell invasion.
  • Thumbnail Image
    Item
    Airway hypersensitivity and remodelling induced by repeated exposure to ascaris suum antigen : an ovine model of human asthma : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Physiology at Massey University
    (Massey University, 2001) Lamahewa, H Nalaka
    This study was an attempt to develop a model of asthma which shows all the structural changes of airways that occur in human disease by repeatedly exposing sheep to an aerosol of Ascaris suum antigen. Twenty two sheep were tested for cutaneous reactivity to a commercial preparation of the antigen. For each of three experiments three sheep were selected, two skin reactive and one non-reactive. One week prior to the experiment a tracheostomy was performed according to the method described by Dueck et al., (1985). In each group, the respiratory response of the two reactive sheep to the Ascaris antigen was augmented using 2-3 fortnightly respiratory exposures to the antigen (82,000 protein nitrogen units/ml) for twenty minutes delivered via an endotracheal tube passed through the tracheostomy. One of the reactive sheep (experimental) was then further exposed to antigen for twenty minutes daily for two weeks. The other reactive sheep (sensitized control) and the non-reactive sheep (non-sensitized control) were exposed to the saline vehicle alone daily for two weeks. Airway resistance (Raw) and dynamic lung compliance (Cdyn) were measured before the antigen/saline exposures and at five minutes intervals during the exposure. On the last day the experiment was carried out under general anesthesia. In addition to respiratory measurements, cardiac output, pulmonary arterial pressure, pulmonary wedge pressure, systemic arterial pressure and central venous pressure were obtained to calculate cardiac power output. At the end of the last exposure sheep were killed, necropsied and samples of lung and airway fixed for morphological studies. Sixty four percent of the sheep tested showed an immediate skin reaction to the antigen. The antigen exposure caused significant changes in respiratory parameters and increased the cardiac work load of the right side of the heart in the experimental sheep. Morphological studies revealed that antigen exposure caused an increase in number of eosinophils and goblet cells in the airways and an increase in the thickness of the 'pseudo-basement membrane' at some levels of the respiratory tract. Antigen exposure also caused an increase in the percentage smooth muscle area in the airway wall cross-sectional area in the membranous bronchioles. Based on these observations it can be concluded that repeated daily exposure of sheep airway to Ascaris suum antigen can be used to reproduced morphological changes observed in human asthmatic airways.
  • Thumbnail Image
    Item
    A comparison of univariate and multivariate statistical and data mining approaches to the behavioural and biochemical effects of vestibular loss related to the hippocampus : a thesis submitted in partial fulfilment of the requirements of the MApplStat in Applied Statistics, Massey University, Manawatu
    (Massey University, 2013) Smith, Paul F
    Vestibular dysfunction is associated with a complex syndrome of cognitive and anxiety disorders. However, most studies have used simple univariate analyses of the effects of vestibular loss on behaviour and brain function. In this thesis, univariate statistical, and multivariate statistical and data mining approaches, to the behavioural and neurochemical effects of bilateral vestibular deafferentation (BVD), were compared. Using linear mixed model analyses, including repeated measures analyses of variance and analyses with the covariance structure of the repeated measures specified, rats with BVD were found to exhibit increased locomotor activity, reduced rearing and reduced thigmotaxis. By contrast, there were no significant differences between BVD and sham control animals in the elevated plus maze and the BVD animals exhibited a longer escape latency in the elevated T maze, with no change in avoidance latency. In the spatial T maze, the BVD animals demonstrated a significant decrease in accuracy compared to the sham control animals. Using linear discriminant analysis, cluster analysis, random forest classification and support vector machines, BVD animals could be distinguished from sham controls by their behavioural syndrome. Using multiple linear regression and random forest regression, the best predictors of performance in the spatial T maze were whether the animals had received a BVD or sham lesion, and the duration of rearing. In the neurochemical data set, the expression of 5-7 glutamate receptor subunits was measured in 3 different subregions of the rat hippocampus, at various times following BVD, using western blotting. In the 6 month group, half of the animals underwent training in a T-maze. Using multivariate analyses of variance, there was no significant effect of surgery for any hippocampal subregion. Linear discriminant analysis could not determine a linear discriminant function that could separate BVD from sham control animals. A random forest classification analysis was also unsuccessful in this respect. However, for the 6 month data set, T maze training had a significant effect independently of surgery. The results of these experiments suggest that BVD results in profound spatial memory deficits that are not associated with large changes in the expression of glutamate receptors in the hippocampus. The results of the multivariate statistical and data mining analyses, applied to both the behavioural and neurochemical data sets, suggested that research in this field of neuroscience would benefit from analysing multiple variables in relation to one another, rather than simply conducting univariate analyses. Since the different behavioural and neurochemical variables do interact with one another, it is important to determine the nature of these interactions in the analyses conducted. However, this will require researchers to design experiments in which multiple variables can be measured under the one set of conditions.
  • Thumbnail Image
    Item
    Nitric oxide production in the mammary gland : a thesis submitted in partial fulfilment for the degree of Doctor of Philosophy at Massey University, New Zealand
    (Massey University, 2001) Turner, Sally-Anne
    Although the effects of nitric oxide (NO) have been widely studied in many different cell and tissue types, very little is known of the role it plays in the mammary gland. Thus, the production of NO by mammary gland was investigated in a series of experiments. NO is a free radical gas which is produced by a wide variety of cells by the action of the enzyme nitric oxide synthase (NOS) on arginine. This results in the formation of citrulline and NO. The study first examined several methods for their suitability for the detection of NO or NOS. Evaluation of the methods revealed that the indirect measurement of NO production by the detection of nitrate and nitrite (NOx), the spontaneously produced metabolites of NO, was the most valid and reliable. The measurement of NOx was carried out in culture medium using a fluorescent-based assay, which was developed by the modification of published methods, during the course of this study. Comma-D cells (murine mammary epithelial cell line) were used to investigate the production of NOx by the inducible form of NOS (iNOS) following treatment with cytokines and cytotoxins. The cell's response was characterised and showed that mammary epithelial cells produce NOx in a dose dependent manner in response to interferon-γ (IFN-γ). Lipopolysaccharide (LPS), a component of bacterial cell walls, was employed to examine the response of the mammary epithelial cells to cytotoxins and it was found that the treated cells produced more NOx than the untreated ones, however, no dose response was apparent. The specific iNOS inhibitor, aminoguanidine (AG) and general NOS inhibitor Nω-nitro-L-arginine (L-NNA) were both used to confirm that the NOx measured in the medium was produced by NOS. The production of NOx by the mammary gland was also examined in cultured explants of mammary tissue taken from pregnant (D 12-14 of pregnancy) and lactating (D 12-14 postpartum or D 17-18 postpartum) rats. A significant difference was found in the basal production of NOx between the different developmental stages. The method of euthanasia of the rats also affected the amount of NOx produced. The inclusion of prolactin (PRL) also increased the production of NOx from both Comma-D cells and explants of mammary tissue. Xanthine oxidase (XO), an enzyme responsible for the conversion of NOx to NO under anaerobic conditions, does not interfere with the determination of NO production using the NOx assay. The measurement of NOx was carried out in the milk of cows following the intramammary infusion of Streptococcus uberis or interleukin-1β (IL-1β). By comparing the milk NOx concentration with the somatic cell count (SCC) and electrical conductivity (EC) of the milk, it was concluded that the source of the NOx in the milk could not be attributed entirely to the epithelium or the somatic cells. The experiments in this Thesis clearly show that the mammary gland is capable of the production of NO in response to a variety of situations and that the regulation of the production is very complex. The work also identifies some new areas of research, which if completed would further enhance the understanding of the role NO plays in the mammary gland.