Anatomy and Neuroscience - Masters by Research Theses
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Item Long term potential of a saturated sodium chloride solution for the anatomical preservation of human cadavers(University College Cork, 2022-03-23) O'Flynn, Carrie; Toulouse, AndréThe anatomical world has relied heavily on formaldehyde as an embalming agent since its use began in the 1890s. Efforts to move away from formaldehyde have intensified in recent years, largely in response to health concerns. Another important motivation is to seek out ways to an improved anatomical cadaver. Several new techniques have been investigated for their abilities to provide cadavers with both life-like features and longevity of preservation. A simple saturated salt solution (saturated NaCl solution) was used to embalm 4 cadavers in two phases of study, without the addition of formalin. As “soft-fix” methods are generally viewed as short-term preservatives, the long-term preservative action of the saturated NaCl solution method was assessed. The suitability of this cadaver type for teaching and training was considered; specifically, its utility as a training model for ultrasound-guided regional anaesthesia (USGRA). The saturated NaCl solution method conferred long-lasting preservation of structures with retention of tissue colour and pliability; however, the rapid onset of deterioration occurred when gross dissection began. The cadavers proved to have some utility as simulation models for USGRA training, but lack of vascular circulation limited this suitability.Item The role of retinoic acid in glioma growth control(University College Cork, 2021-07-22) Flynn, Patricia Margaret; Toulouse, André; Hand, Collette; Bermingham, Niamh; Jansen, MichaelTumours of the central nervous system are known as gliomas, arising from the astrocytes, oligodendrocytes, ependymal cells or from glial progenitor cells. Although a relatively rare diagnosis, there is disproportionate morbidity associated with a glioma diagnosis, owing to its diffuse and infiltrative nature and partly, in the restricted accessibility of the tumour to treatment. Several obstacles prevent effective treatment, namely, the blood brain barrier, peripheral inactivation of systemic treatment, outward tumoural convection pressures, and cancer stem cell resistance. Despite therapeutic advances, the relapse rate and the mortality linked to glioma remains high, with most patients surviving less than 2 years following diagnosis. The terminal differentiation of malignant cells using a differentiation agent such as retinoic acid (RA) could be a promising scientific advance in the treatment of this disease. Endogenous retinoic acid is the primary active metabolite of vitamin A. It is a small, lipophilic differentiation agent that acts as a ligand for a family of nuclear receptors (RARs) to regulate the expression of target genes. The main family of nuclear receptors comprises three genes, RARα, RARβ and RARγ, each coding for multiple isoforms. The selective stimulation of these isoforms with RA has been shown to mainly inhibit cellular proliferation but is also known in some cases to promote such proliferation. The use of all-trans retinoic acid as an agent of differentiation has also been highly successful in the treatment of acute promyelocytic leukaemia. The canonical retinoic acid pathway involves proteins that are responsible for the conversion of precursors of RA, their transport and the transcription of genes downstream of the RARs. In this thesis, gene expression of components of the canonical RA signalling pathway was analysed from existing microarray data for a panel of 1100 gliomas of various histological grades. The analysis was performed on the R2 Genomics Analysis and Visualization Platform. Expression of individual genes was extracted from the datasets and analysed according to WHO grade. The results showed that the expression of key components of the pathway was altered in high grade gliomas compared to the lower grades. The expression levels of RBP1, RBP2, and RBP3 (involved in the transport of retinol) were significantly altered in high grade glioma, with an increase in the expression levels of RBP1 and RPB2 and the decrease in expression level of RBP3. The genes involved in the oxidation of retinol to retinal, ADH1A, ADH1B, ADH1C, ADH4, ADH7, RDH5 RDH10, RDH11 and RDH16 were all significantly lower in high grade glioma. The expression levels of the genes involved in the oxidation of retinal to retinoic acid, ALDH8A1, and ALDH1A1 (RALDH1) are also significantly reduced in high grade glioma. The genes involved in the intranuclear transcription of the RA pathway are affected by high grade glioma. Retinoic acid receptor genes RARA, RARB, RARG, retinoid X receptor genes RXRA, RXRB, RXRG, transcriptional co-activator genes EP300, NCOA1, NCOA2, transcriptional co-repressor genes HDAC2, NCOR1, and NRPI1 are all significantly lower in high grade glioma with an increase in the expression of transcriptional repressor HDAC1. There is also significantly reduced expression of CYP26B1, involved in the metabolism of RA. Together, lower expression of the enzymes responsible for the intracellular formation of RA from its precursors and its intranuclear transcriptional machinery could potentially lead to a reduction in RA signalling. This suggests that the targeted activation of the RA pathways in gliomas with reduced signalling capacity could be used to regulate cancerous growth. Using two established glioblastoma cell lines, the growth altering properties of retinoic acid, some of its synthetic derivatives and specific retinoic acid receptor isoforms was assessed. Results show that manipulation of the retinoic acid signalling pathway by selectively stimulating different isoforms of the RARs can lead to changes in growth patterns that differ depending on the cellular context. Opposing growth patterns were produced in the two glioblastoma cell lines, A172 and U87-MG in response to ATRA, with growth suppression of the A172 cell line and proliferation of the U87-MG cell line. More detailed insight into the growth responses mediated by isoform specific retinoids and overexpression of isoforms highlighted the potential for suppressing the growth of the cell lines by targeting individual receptor isoforms. While further research is needed, these results show that targeting specific receptors in cell lines can lead to growth reduction and may pave the way to the use of isoform selective retinoids in the treatment of glioma.Item Preclinical evaluation of a novel AAV-GDF5 vector in a 6-OHDA model of Parkinson’s disease and evaluation of the effect of 6-OHDA on the expression of HDACs(University College Cork, 2020-08-17) Shanahan, Sarah Elizabeth; Sullivan, Aideen M.; O'Keeffe, Gerard W.Neurotrophic factors have shown promising results as potential disease-altering treatment methods for Parkinson’s disease (PD). However, there are many risks associated with surgically accessing such deeply located regions of the brain as the striatum or substantia nigra. Directly administered proteins will be broken down, meaning that such an intervention would have short-lived benefits. For this reason, the use of viral vectors to deliver neurotrophic factor genes has become a popular alternative, as this would allow for prolonged expression of the neurotrophic factor. In this study, we used an AAV2/5 vector to deliver GDF5 to the substantia nigra of rats, both at the same time as striatal administration of 6-OHDA and two weeks prior to 6-OHDA administration. We found that those animals which received AAV2/5-GDF5 had similar levels of TH immunopositive cell body loss in the substantia nigra and similar decreases in TH immunstaining in the striatum as those animals which had just received 6-OHDA. The 6-OHDA rodent model is commonly used in PD research. As such, it is important to understand the characteristics of this model in order to best interpret observations made when using this model. In this study we examined how 6-OHDA administration affects HDAC3, 5 and 9 expression in the rat brain. HDAC5 and HDAC9 are of particular interest to our group as our group has shown that their expression correlates with three markers of dopaminergic neurons in both the mouse and human substantia nigra. HDAC3 was also selected as an example of a different HDAC class. We found that striatal administration of 6-OHDA resulted in bilaterally increased expression of HDAC3 and 9 in the striatum, no changes were seen in HDAC3 in the midbrain, while HDAC9 was unilaterally upregulated in the midbrain. HDAC5 is known to shuttle between the nucleus and the cytoplasm of the cell. For this reason, we examined nuclear and cytop-lasmic levels of HDAC5. HDAC5 was also found to be upregulated bilaterally in the midbrain and it was observed that this increase was restricted to the nucleus.