https://www.um.edu.mt/library/oar/handle/123456789/24244 2026-04-15T17:57:57Z 2026-04-15T17:57:57Z https://www.um.edu.mt/library/oar/handle/123456789/50417 2020-11-06T10:27:02Z 2017-01-01T00:00:00Z

Title: Characterization of mouse model of focal ischemia and reperfusion to study the putative protective benefit of intraperitoneally administered lactate in gray and white matter regions of the brain. Abstract: Background: Stroke is a medical emergency requiring prompt intervention. In cerebral ischemia, early revascularisation is critical to salvage tissue at risk of infarction and minimize injury progression. Animal models have allowed for the characterization of several disease pathways that are amenable to therapeutic intervention. However, clinical translation remains elusive and the need for successful therapies is urgent. Future progress depends critically on animal models that allow ischemic stroke to be studied at various stages, from initial changes in blood flow, to the physiological reaction to ischemia, neuronal death, behavioural impairment and recovery. The intraluminal model of middle cerebral artery occlusion (MCAO) mimics the most common form of stroke in humans and is thus widely applicable to study putative neuroprotective strategies and test for promising compounds. Neuroprotection in cerebral ischemia, however, can only be successful if both gray and white matter components are protected through pharmacological or vascular interventions. L-lactate is a metabolite that is oxidised preferentially to glucose in conditions of high metabolic stress. lt has previously been found to be neuroprotective in vitro and in vivo when administered in a mouse model of stroke based on its sole use as an alternative energy substrate. However, in these studies, only neuronal protection in cortical gray matter regions in the brain had been assessed thus far. The aim of this study was to characterize in some histological detail a mouse model of focal ischemia to determine the structural components and the distinct cellular populations involved in this type of injury. We then tested whether L-lactate-mediated protection extends to deeper subcortical areas of white matter, apart from the already well documented gray matter protection. Recent work has suggested the involvement of lactate receptor HCA1 in mediating neuronal protection. A further extension of this study was to establish whether this receptor could be involved in L-lactate-mediated protection in white matter acting through unrecognized axon-glial interactions. Methods: The study was performed under tight control of animal physiology and important intraoperative control parameters including body temperature, intra-ischemic cerebral blood flow and vital signs. In initial studies, we selected two mouse strains (CD-1 and C57BL/6) to demonstrate a direct side-by-side comparison in histopathological and behavioural parameters between these strains that were exposed to varying degrees of ischemia to establish model reproducibility. CD-1 mice were eventually chosen to further most of these experiments because of their clear reproducibility in their depth of ischemia in correlation to the lesion size thus produced. Following in-depth histological and immunocytochemical analyses in response to 60-minute ischemia, putative protection afforded by Na L-lactate was assessed. In preliminary studies, Na L-lactate was administered intravenously (5mgkg-1). Administration was later changed to the more favourable intraperitoneal route (250mgkg-1). Single-dose administration occurred 5 minutes prior to ischemia induction or upon reperfusion onset. Putative protection was assessed via histological, immunocytochemical and functional outcome analyses. Results: In initial studies, infarct volumes and edema formation correlated well to the severity of the insult in both strains. We then demonstrated that Na L-lactate administered intraperitoneally significantly reduced infarct volumes in CD-1 and C57BL/6 strains Intraperitoneal administration of Na I –lactate resulted in the reducation of ischemia-induced neurological deficits and brain water content compared to vehicle treatment at an acute stage. Immunocytochemical characterization revealed attenuation of ischemia-induced oligodendrocyte loss and the appearance of less pyknotic nuclei in white matter at acute and subacute stages upon Na L-lactate administration before or after ischemia. Protection at both stages coincided with partially preserved phosphorylated neurofilament and axonal structure integrity. Myelin condition as observed histologically by Luxol Fast Blue (LFB) staining was ameliorated with Na L-lactate treatment in CD-1 mice. This observation extended to include the C57BL/6 strain, where improved LFB staining in WM was concomitant with partial preservation of yellow fluorescent protein {YFP) expression 24 hours following ischemia. We report for the first time the co-localization of the lactate receptor HCA1 in white matter oligodendrocytes. Increased receptor expression on oligodendrocytes was detected during ischemia, which was further elevated by Na L-lactate treatment at acute and subacute stages. Conclusion: HCA1 receptor expression on oligodendrocytes presents a role for lactate-mediated signalling in white matter. Protection in gray and white matter regions mediated by this natural and readily available substance could have important clinical implications and could provide impetus for future stroke research. Keywords: HCA1, ischemia, lactate, MCAO, white matter Description: PH.D.

2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/50206 2025-07-22T08:48:27Z 2017-01-01T00:00:00Z

Title: Endometrial cancer and its response to treatment and the quality of life after treatment. Abstract: The pituitary gland is integral in hormone secretion and regulation. Pituitary adenomas (PA) are the most frequent pituitary neoplasms, however molecular pathogenesis is largely unknown. The AHR is a ligand-activated transcription factor that regulates expression of various genes that mediate cellular response against xenobiotics, and is also involved in other physiological and pathological processes. Several AHR variants, particularly the Arg554Lys (rs2066853) and Val570Ile (rs4986826) have raised interest due to their location in ex on 10 of the AHR gene, which codes for the transactivation domain (TAD). The TAD domain plays a critical role in mediating transactivation activity of dioxin-responsive genes via recruitment of co-activators, hence suggesting that SNPs occurring within this region should interfere with AHR target gene expression. However, their exact functional role has not been established yet due to inconsistent results from different studies. Studies suggest that these mutations increase risk of developing P A, however functional analysis of these SNPs in a pituitary setting has never been carried out. In this research study, the two AHR variants were introduced in the wildtype AHR expression plasmid by site-directed mutagenesis (SDM). The wildtype and mutants AHR were introduced in GH3 cells by magnetofaction and were treated with 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD). Functional analysis of transfected GH3 cells treated with TCDD was carried out using luciferase assays and real-time PCR to detect and quantify AHR-transcriptional activity. Cell proliferation of transfected and TCDD treated GH3 cells was measured using the MTT assay. In the absence and presence of low TCDD concentration, over-expression of AHR and AHR mutants did not affect the proliferative capacity of GH3 cells. Gene expression analysis and quantification analysis of AHR-target genes suggested that these AHR mutants might interfere with AHR target gene expression. However further studies are required to elucidate the precise mechanisms. Genotyping of the Arg554Lys in patients with PA gave a MAF of 3% vs 0% in neonatal controls using allele specific PCR. Description: M.SC.REPRODUCTIVE HEALTH

2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/50087 2020-11-06T10:17:25Z 2017-01-01T00:00:00Z

Title: Functional analysis of rare polymorphisms within the Aryl Hydrocarbon receptor (AHR) gene in pituitary adenomas. Abstract: The pituitary gland is integral in hormone secretion and regulation. Pituitary adenomas (PA) are the most frequent pituitary neoplasms, however molecular pathogenesis is largely unknown. The AHR is a ligand-activated transcription factor that regulates expression of various genes that mediate cellular response against xenobiotics, and is also involved in other physiological and pathological processes. Several AHR variants, particularly the Arg554Lys (rs2066853) and Val570Ile (rs4986826) have raised interest due to their location in ex on 10 of the AHR gene, which codes for the transactivation domain (TAD). The TAD domain plays a critical role in mediating transactivation activity of dioxin-responsive genes via recruitment of co-activators, hence suggesting that SNPs occurring within this region should interfere with AHR target gene expression. However, their exact functional role has not been established yet due to inconsistent results from different studies. Studies suggest that these mutations increase risk of developing P A, however functional analysis of these SNPs in a pituitary setting has never been carried out. In this research study, the two AHR variants were introduced in the wildtype AHR expression plasmid by site-directed mutagenesis (SDM). The wildtype and mutants AHR were introduced in GH3 cells by magnetofaction and were treated with 2,3,7,8 tetrachlorodibenzo-p-dioxin (TCDD). Functional analysis of transfected GH3 cells treated with TCDD was carried out using luciferase assays and real-time PCR to detect and quantify AHR-transcriptional activity. Cell proliferation of transfected and TCDD treated GH3 cells was measured using the MTT assay. In the absence and presence of low TCDD concentration, over-expression of AHR and AHR mutants did not affect the proliferative capacity of GH3 cells. Gene expression analysis and quantification analysis of AHR-target genes suggested that these AHR mutants might interfere with AHR target gene expression. However further studies are required to elucidate the precise mechanisms. Genotyping of the Arg554Lys in patients with PA gave a MAF of 3% vs 0% in neonatal controls using allele specific PCR. Description: M.SC.PATHOLOGY

2017-01-01T00:00:00Z https://www.um.edu.mt/library/oar/handle/123456789/34107 2018-09-28T01:47:56Z 2017-01-01T00:00:00Z

Title: The effect of exercise on the gait biomechanics of the neuro-ischemic diabetic foot with peripheral neuropathy Abstract: The aim of the study was to investigate the effect of a six-week exercise program on the kinetics and kinematics during gait in people diagnosed with ischemia and diabetic peripheral neuropathy. The peak plantar pressures, pressure-time integral, lower limb joint angles in the sagittal plane and ground reaction forces were tested before and after the exercise program. Research in this area is lacking, providing only small scale studies with mixed results and decreased significance. The researcher aimed to add to the body of knowledge and provide further insight into the possible use of exercise to prevent and manage the complications of diabetic peripheral neuropathy such as the development of pressure ulcers. Methodology: Twelve participants were chosen for this pilot study, and were asked to carry out a specialised exercise program for six weeks, twice weekly. The kinematics and ground reaction forces were tested using 3D motion analysis (Vicon) and force plates (AMTI) and plantar pressures and pressure-time integral were tested via the TekScan HR mat. The patients acted as their own control, comparing pre- and post- intervention results. Results showed a statistically significant decrease in plantar pressures in all areas and in the pressuretime integral at the forefoot. Hip flexion at toe-off and knee extension at heel strike showed a statistically significant improvement. All other areas showed a slight improvement but were not statistically significant, thus failing to reject the null hypothesis. Conclusion: Although improvements were seen, this pilot study requires further research to support the findings in this study and possibly implement these findings in clinical practice in the future. Description: M.SC.CLINICAL BIOMECHANICS

2017-01-01T00:00:00Z