Rozprawy doktorskie na temat „DNA damage”
Kliknij ten link, aby zobaczyć inne rodzaje publikacji na ten temat: DNA damage.
Utwórz poprawne odniesienie w stylach APA, MLA, Chicago, Harvard i wielu innych
Sprawdź 50 najlepszych rozpraw doktorskich naukowych na temat „DNA damage”.
Przycisk „Dodaj do bibliografii” jest dostępny obok każdej pracy w bibliografii. Użyj go – a my automatycznie utworzymy odniesienie bibliograficzne do wybranej pracy w stylu cytowania, którego potrzebujesz: APA, MLA, Harvard, Chicago, Vancouver itp.
Możesz również pobrać pełny tekst publikacji naukowej w formacie „.pdf” i przeczytać adnotację do pracy online, jeśli odpowiednie parametry są dostępne w metadanych.
Przeglądaj rozprawy doktorskie z różnych dziedzin i twórz odpowiednie bibliografie.
1
Sunter, Nicola. "DNA Damage Responses". Thesis, University of Newcastle Upon Tyne, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489314.
Pełny tekst źródłaStreszczenie:
The histone H2AX has been established as a reliable biomarker of DNA damage, becoming phosphorylated rapidly following damage in discrete foci which can be correlated with DNA DSB number. In the present study, the phosphorylation of H2AX was used as a marker of DNA DSB damage to compare and contrast the damage induced by ionizing radiation, the topo II poison, etoposide, and the topo II catalytic inhibitor, ICRF-193. To examine the DNA damage numbers at time-points in the 24 hours following exposure to these damaging agents. Topo lIP null cells were used to investigate the contribution of topo II a and Pthese damage responses and the Trapped in Agarose DNA Immunostaining assay was utilised to quantify the numbers of topo II_DNA complexes formed in response to these agents. This study aimed to examine the levels of DNA damage following exposure to these damaging agents and to investigate differences in the complement of proteins associated with DNA damage-induced foci. By using both the y-H2AX and TARDIS assays and protein colocalisation techniques, the studies detailed here presents novel findings on the differing damage responses induced following these three agents.
2
Fazendeiro, Marta Sofia Pereira Pingarilho. "DNA damage induced by acrylamide: roe of genetic polymorphisms in DNA damage levels". Doctoral thesis, Faculdade de Ciências Médicas. UNL, 2013. http://hdl.handle.net/10362/10000.
Pełny tekst źródłaStreszczenie:
RESUMO:Em 1994 a acrilamida (AA) foi classificada pela IARC como um provável cancerígeno para o homem. Para além da utilização de AA em numerosas aplicações industriais, a AA está também presente numa grande variedade de alimentos ricos em amido e processados a temperaturas elevadas. Esta exposição através da ingestão de produtos alimentares despoletou elevadas preocupações ao nível do risco para a saúde pública e poderá implicar um risco adicional para o aparecimento de cancro. A glicidamida (GA), o metabolito epóxido formado a partir da oxidação da AA provavelmente através do citocromo P450 2E1, é considerada por vários estudos, o principal responsável pela carcinogenicidade da AA.
Actualmente existe uma escassez de resultados relativamente aos mecanismos de genotoxicidade da AA e GA em células de mamífero. Por este motivo, o objectivo deste estudo centra-se na avaliação das consequências genéticas da exposição à AA e GA, recorrendo-se para tal ao uso de células de mamífero como modelo.
Tendo como base este objectivo avaliou-se a citotoxicidade da AA e GA, através do ensaio do MTT, e realizaram-se dois testes citogenéticos, o teste das aberrações cromossómicas (CAs) e o teste da troca de cromátides irmãs (SCEs), de modo a avaliar as lesões de DNA induzidas por estes compostos em células de hamster Chinês V79. Os resultados globalmente mostraram que a GA é mais citotóxica e clastogénica do que a AA.
No âmbito deste trabalho, foi também efectuada a quantificação de aductos específicos de DNA, nomeadamente N7-(2-carbamoil-2-hidroxietil)guanina (N7-GA-Gua) e N3-(2-carbamoil-2-hidroxietil)adenina (N3-GA-Ade). Os resultados obtidos permitem afirmar que os níveis de N7-GA-Gua e a concentração de GA apresentam uma relação linear dose-resposta. Foi também identificada uma óptima correlação entre os níveis de N7-GA-Gua e a frequência de troca de cromátides irmãs.
Adicionalmente, e de forma a compreender os mecanismos de toxicidade da AA, estudaram-se os mecanismos dependentes da modulação do glutationo reduzido (GSH), nomeadamente da butionina sulfoximina (BSO), um inibidor da síntese de GSH, do GSH-monoetil estér (GSH-EE), um composto permeável nas células e que é intra-celularmente hidrolisado a GSH e ainda do GSH adicionado exogenamente ao meio de cultura, em células V79. Os resultados obtidos reforçaram o papel da modulação do GSH nos efeitos de citotoxicidade e clastogenicidade da AA.
Para além dos estudos efetuados com células V79, procedeu-se também à determinação da frequência de SCEs, à quantificação de aductos específicos de DNA, bem como ao ensaio do cometa alcalino em amostras de dadores saudáveis expostos à AA e GA. Tanto os resultados obtidos através do ensaio das SCE, como pela quantificação de aductos específicos de DNA, ambos efectuados em linfócitos estimulados, originaram resultados comparáveis aos obtidos anteriormente para as células V79, reforçando a ideia de que a GA é bastante mais genotóxica do que a AA. Por outro lado, os resultados obtidos pelo ensaio do cometa para exposição à AA e GA mostraram que apenas esta última aumenta o nível das lesões de DNA.
Outro objectivo deste trabalho, foi a identificação de possíveis associações existentes entre as lesões de DNA, quantificadas através do ensaio das SCEs e do cometa, e biomarcadores de susceptibilidade, tendo em conta os polimorfismos genéticos individuais envolvidos na destoxificação e nas vias de reparação do DNA (BER, NER, HRR e NHEJ) em linfócitos expostos à GA. Tal permitiu identificar associações entre os níveis de lesão de DNA determinados através do ensaio das SCEs, e os polimorfismos genéticos estudados, apontando para uma possível associação entre o GSTP1 (Ile105Val) e GSTA2 (Glu210Ala) e a frequência de SCEs. Por outro lado, os resultados obtidos através do ensaio do cometa sugerem uma associação entre as lesões de DNA e polimorfismos da via BER (MUTYH Gln335His e XRCC1 Gln39Arg) e da via NER (XPC Ala499val e Lys939Gln), considerando os genes isoladamente ou combinados.
Estes estudos contribuem para um melhor entendimento da genotoxicidade e carcinogenicidade da AA e GA em células de mamífero, bem como da variabilidade da susceptibilidade individual na destoxificação e reparação de lesões de DNA provocadas pela exposição a estes xenobióticos alimentares. ----------- ABSTRACT:Acrylamide (AA) has been classified as a probable human carcinogen by IARC. Besides being used in numerous industrial applications, AA is also present in a variety of starchy cooked foods. This AA exposure scenario raised concerns about risk in human health and suggests that the oral consumption of AA is an additional risk factor for cancer. A considerable number of findings strongly suggest that the reactive metabolite glycidamide (GA), an epoxide generated presumably by cytochrome P450 2E1, plays a central role in AA carcinogenesis.
Until now there are a scarcity of results concerning the mechanisms of genotoxicity of AA and GA in mammalian cells. In view of that, the study described in this thesis aims to unveil the genetic consequences of AA and GA exposure using mammalian cells as a model system.
With this aim we evaluated the cytotoxicity of AA and GA using the MTT assay and subsequently performed two cytogenetic end-points: chromosomal aberrations (CAs) and sister chromatid exchanges (SCEs), in order to evaluate DNA damage induced by these compounds in V79 Chinese hamster cell line. The results showed that GA was more cytotoxic and clastogenic than AA.
Within the scope of this thesis the quantification of specific DNA adducts were also performed, namely N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) and N3-(2-carbamoyl-2-hydroxyethyl)adenine (N3-GA-Ade). Interestingly, the GA concentration and the levels of N7-GA-Gua presented a linear dose-response relationship. Further, a very good correlation between the levels of N7-GA-Gua and the extent of SCEs were observed.
In order to understand the mechanisms of AA-induced toxicity, the modulation of reduced glutathione (GSH)-dependent mechanisms were studied, namely the evaluation of the effect of buthionine sulfoximine (BSO), an effective inhibitor of GSH synthesis, of GSH-monoethyl ester (GSH-EE), a cell permeable compound that is intracellularly hydrolysed to GSH and also of GSH endogenously added to culture medium,z in V79 cell line. The overall results reinforced the role of GSH in the modulation of the cytotoxic and clastogenic effects induced by AA.Complementary to the studies performed in V79 cells, SCEs, specific DNA-adducts and alkaline comet assay in lymphocytes from healthy donors exposed to AA and GA were also evaluated. Both, the frequency of SCE and the quantification of specific GA DNA adducts, produced comparable results with those obtained in V79 cell line, reinforcing the idea that GA is far more genotoxic than AA. Further, the DNA damaging potential of AA and GA in whole blood leukocytes evaluated by the alkaline comet assay, showed that GA, but not AA, increases DNA damage.
Additionally, this study aimed to identify associations between DNA damage and biomarkers of susceptibility, concerning individual genetic polymorphisms involved in detoxification and DNA repair pathways (BER, NER, HRR and NHEJ) on the GA-induced genotoxicity assessed by the SCE assay and by the alkaline comet assay. The extent of DNA damage determined by the levels of SCEs induced by GA seems to be modulated by GSTP1 (Ile105Val) and GSTA2 (Glu210Ala) genotypes. Moreover, the results obtained from the comet assay suggested associations between DNA damage and polymorphisms of BER (MUTYH Gln335His and XRCC1 Gln399Arg) and NER (XPC Ala499Val and Lys939Gln) genes, either alone or in combination.
The overall results from this study contribute to a better understanding of the genotoxicity and carcinogenicity of AA and GA in mammalian cells, as well as the knowledge about the variability in individual susceptibility involved in detoxification and repair of DNA damage due to these dietary xenobiotics.
3
Håkansson, Pelle. "Ribonucleotide reductase and DNA damage". Doctoral thesis, Umeå universitet, Institutionen för medicinsk kemi och biofysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-706.
Pełny tekst źródłaStreszczenie:
A prerequisite for a multicellular organism to survive is the ability to correctly replicate and repair DNA while minimizing the number of heritable mutations. To achieve this, cells need a balanced supply of deoxyribonucleoside triphosphates (dNTPs), the precursors for DNA synthesis. The rate-limiting step in de novo biosynthesis of dNTPs is catalyzed by the enzyme ribonucleotide reductase (RNR). The classic eukaryotic RNR enzyme consists of a large and a small subunit. Together, these subunits form a heterotetrameric RNR complex. The larger subunit harbours active sites whereas the smaller subunit contains a stable tyrosyl free radical. Both subunits are required for RNR activity. Since failure to correctly regulate de novo dNTP biosynthesis can lead to misincorporation of nucleotides into DNA, genetic abnormalities and cell death, RNR activity is tightly regulated. The regulation of RNR activity involves cell cycle-specific expression and degradation of the RNR proteins, as well as binding of allosteric effectors to the large RNR subunit. In this thesis, in vitro assays based on purified recombinant RNR proteins, in combination with in vivo assays, have been used successfully to study the regulation of RNR activity in response to DNA damage. I present new findings regarding the function of an alternative mammalian RNR small subunit, and on the role of a small RNR inhibitor protein of fission yeast, during normal growth and after DNA damage. I also show conclusively that there are fundamental differences in the regulation of dNTP biosynthesis between the cells of higher and lower eukaryotes after DNA damage.
4
Håkansson, Pelle. "Ribonucleotide reductase and DNA damage /". Umeå : Medicinsk biokemi och biofysik, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-706.
Pełny tekst źródła
5
Johnstone, Elaine Claire. "Ifosfamide metabolism and DNA damage". Thesis, University of Newcastle Upon Tyne, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264417.
Pełny tekst źródła
6
Aldosari, Sahar. "Assessment of DNA damage and DNA damage response and repair in dormancy-enriched leukemia cells". Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/47257/.
Pełny tekst źródłaStreszczenie:
Acute myeloid leukaemia (AML) is a heterogeneous myeloid malignancy characterized by clonal expansion of abnormal/immature hematopoietic precursor cells in the bone marrow. A side compartment in the BM niche consists of abnormal, quiescent cells, which are called dormant leukemic initiating cells (DLICs). Patients with AML tend to respond well to remission induction chemotherapy, but relapse is common because current therapies cannot completely eradicate leukemic cells. It is widely accepted that CD34+CD38− DLICs are more resistant to chemotherapy and that they contribute to drug resistance and relapse of AML to a greater extent than progenitor CD34+CD38+ cells. DLICs have been extensively characterised, but they remain a critical area of investigation for clinical research because of the low prevalence of DLICs and similarity to normal HSCs. A model of dormancy in vitro that shows most of the features of DLICs had previously been established in the Nottingham Haematology Group. This study used this model and aimed to investigate whether the response to DNA damage was different in dormancy-enriched cells compared to cycling leukemic cells following chemotherapy. The amount of DNA damage was assessed up to 24 hours pre- and post- drug treatment using the neutral Comet assay. Lower levels of damage were observed in dormancy-enriched cells following etoposide (ETO) treatment at 4 hours (p = 0.04), although this switched at the 24 hour time point where accumulated DNA double-stranded breaks (DSBs), in dormancy-enriched KG1a cells were associated with a higher percentage of viable cells. DNA damage response cascade markers in both dormancy-enriched and cycling cells showed phosphorylation by flow cytometry (phospho-H2AX139, pATM-S1981, H2AX142, and pChk-Thr68) in response to conventional AML chemotherapy. Significantly lower levels of cleaved PARP-Asp214 and active caspase 3 were observed in dormancy-enriched cells treated with ara-c (p = 0.0001) or ETO (p = 0.0001) at 24 hours, strongly indicating that survival responses are activated in dormancy-enriched cells. Induction of 53BP1 foci, the hallmark of non-homologous end joining (NHEJ) was observed following treatment with ara-c (p = 0.038) and ETO (p = 0.049) in dormancy-enriched cells, indicating the NHEJ repair pathway is the preferred mechanism for DSB repair. At the molecular level, BTG2 expression was involved in the DNA damage response. Significant induction of BTG2 was detected in cycling treated cells with ETO for 24 hours. In conclusion, this study provides evidence that phosphorylation of H2AX139 and H2AX142 is a key response marker that may explain the mechanism underlying the drug resistance of DLICs and induction of repair. Therefore, results of this study may help in devising novel treatment strategies for AML that target H2AX142 of DLICs to permanently eradicate all leukemic cells and improve overall survival.
7
Yu, Emma Pei Kuen. "Mitochondrial DNA damage, dysfunction and atherosclerosis". Thesis, University of Cambridge, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.648537.
Pełny tekst źródła
8
Farooq, Sabya. "Free radical induced oxidative DNA damage". Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30749.
Pełny tekst źródłaStreszczenie:
Oxidative DNA damage has been implicated in processes such as carcinogenesis, mutagenesis, ageing and cell death. Reactive oxygen species (ROS) such as superoxide (O2), hydrogen peroxide (H2O 2) and hydroxyl radical (OH*) are produced in mammalian cells as a result of aerobic metabolism. However excess generation of these species by endogenous or exogenous sources can result in damage to DNA, producing a large number of sugar and base lesions. In order to understand the biological consequences of such free radical induced damage it is essential to characterise and quantitate this damage. This study describes the establishment of sensitive and specific techniques to chemically characterise and quantitate three markers of oxidative DNA damage, namely: cis-thymine glycol (Tg), 5-hydroxymethyluracil (5-OHMeU) and 8-hydroxyguanine (8-OHG). Techniques using gas chromatography/mass spectrometry (GC/MS) were established for Tg and 5-OHMeU, following their derivatisation with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide (MTBSTFA). Standards of Tg and 5-OHMeU were synthesised, and stable isotopically labelled analogues were prepared as internal standards. Analysis of the DNA was carried out at the base level and therefore required acidic hydrolysis of the DNA in order to release the modified and intact bases. For the quantitation of 8-OHG a novel procedure using high performance liquid chromatography (HPLC) - electrochemical detection (ECD) with guanase incubation of DNA hydrolysates was established. The established assays were used to quantitate DNA lesions in vitro and in vivo. In vitro dose response curves were established for the three markers upon gamma-irradiation of DNA. In vivo results of an animal inhalation study indicated there was not a significant increase in oxidative damage upon exposure to crocidolite. An antioxidant supplementation study in humans placental DNA also did not show a significant reduction in levels of the three markers upon supplementation. Comparable background levels of Tg and 5-OHMeU were observed in human and calf thymus DNA, while 8-OHG levels were found to be significantly higher.
9
Bykov, Vladimir J. "UV-induced DNA damage in humans /". Stockholm, 1999. http://diss.kib.ki.se/1999/91-628-3345-6/.
Pełny tekst źródła
10
Lampus, Daniele Jacopo. "Towards IR Probes of DNA Damage". Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.518828.
Pełny tekst źródła
11
Jansson, Martin D. "Regulation of the DNA damage response". Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504493.
Pełny tekst źródła
12
Kuimova, Marina K. "Designing infrared probes of DNA damage". Thesis, University of Nottingham, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416394.
Pełny tekst źródła
13
Alhebshi, H. "Molecular pathways controlling DNA damage response". Thesis, University of Salford, 2018. http://usir.salford.ac.uk/48475/.
Pełny tekst źródłaStreszczenie:
P53 is inactivated in around 50 % of human neoplasms and more than 26,000 somatic mutations of the p53 have reported in human cancers. P53 network is activated after cells are exposed to the DNA damage and depending on diverse conditions and type of DNA damage, p53 upregulation could lead to repression of the cell cycle progression and induction of apoptosis. Consequently, the p53 protein is considered vital to cancer progression and treatment and has been the focus of intense research. TTC5 (Tetratricopeptide repeat domain 5) or STRAP was identified as p53 cofactor and a key component of the p300/CBP (CREBB binding protein) complex. TTC5 enhances the interaction of JMY (Junction mediating and regulatory protein, p53 co- factor) and P300, leading to increase in HAT (Histone acetyltransferase) activity of P300, increase in p53 acetylation, stability and transcriptional activity. In this study, we investigated crosstalk between the total p53, p53 phosphorylated at serine 46 (S46), p53 acetylated at lysine 382 (K382) and the TTC5 protein expression in Etoposide treated lung and mesothelioma cancer cell lines (A549, Mero-14, and Mero-25). Our results suggest there is no impact of Etoposide treatment on the TTC5 protein levels in all treated cell lines. Upregulation of p53, K382 and S46 protein expression levels as a response to the DNA damage in A549 and Mero-14 but not in Mero-25 cell lines was observed. Co-immunoprecipitation results showed evidence of the interaction between p53 protein and its co-factor (TTC5). MiRNA-34 family members that are transcriptional p53 targets were also investigated in studied cancer cell lines. Decrease in the miR-34a expression was observed in treated A549, Mero-25, and Mero-14 cancer cells compared to untreated cells, whereas the expression of miR-34b was elevated in treated A549 and Mero-25 but not in Mero-14 mesothelioma cells. We also analysed expression of above mentioned proteins in 220 tissue microarrays (TMA) in human lung cancer tissues using immunohistochemistry (IHC) approach and correlated these data with clinicopathological features of patients. Significant correlation was detected between the p53 expression levels and the grade of lung cancer, which might support the theory that mutant p53 acts as an oncoprotein. In addition, significant correlation was observed between the TTC5 protein expression and age, grade, tumour size and the intensity of Ser-46 protein expression. Interestingly, some cases showed cytoplasmic staining of acetylated p53 at lysine 382 rather than nuclear staining. Immunofluorescence (IF) was used to demonstrate a nuclear staining of the K382 protein in A549 and U2OS cell lines, suggesting that cultured cancer cells might behave differently and/or that in patients tissues there is heterogeneity of K382 subcellular location. Overall, our results indicate that p53 isoforms analysis together with TTC5 expression might have future use as biomarkers, prognostic factors or drug targets in cancer. However, further research is needed to confirm these findings.
14
Parkes, Eileen. "The immune response to DNA damage". Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709693.
Pełny tekst źródłaStreszczenie:
Breast cancer is a highly heterogenous disease and current methods of treatment selection in the clinic do not take account of this heterogeneity. In order to improve outcomes in breast cancer, a personalised approach is required. Previously we identifed a DNA damage response deficient (DDRD) molecular subgroup within breast cancer. A 44-gene expression assay prospectively identifying this subgroup was validated as predicting benefit from DNA-damaging chemotherapy. This subgroup was defined by interferon signalling. In this study the biology identified by the subgroup is addressed, identifying activation of the cytosolic DNA-sensing innate immune pathway cGAS/STING/TBK1/IRF3 in DNA damage response deficient cancer cells. This study highlights the importance of this pathway in cancer cell chemokine production. Importantly, activation of this pathway is cell-cycle related and can be induced by exogenous S-phase DNA damage. We characterise the immune infiltrate in DNA damage response deficient breast tumours, identifying both anti-tumourigenic and pro-tumourigenic immune cell populations. Also, expression of the immune checkpoint protein PD-L1 is identified as upregulated in DDRD assay positive breast tumours. These data indicate that tumours with an endogenous DNA damage response deficiency employ expression of immune checkpoints as a means of immune escape. Therefore, immune checkpoints are important therapeutic targets in this subgroup of breast cancer. In addition, we present preliminary analysis of a clinical trial designed to assess the feasibility of using the 44-gene expression assay in predicting response to neoadjuvant chemotherapy in breast cancer. Given our findings, we identify potential targets in DNA damage response deficient tumours, combination strategies with anti-PD-1/PD-L1 targeted therapies and provide evidence for the prospective utility of the DDRD gene expression assay in predicting response to DNA damaging chemotherapy.
15
Ndlebe, Thabisile S. "Oxidative Damage in DNA: an Exploration of Various DNA Structures". Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-05112006-154326/.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2007.Donald F. Doyle, Committee Member ; Bridgette Anne Barry, Committee Member ; Dr. Gary B. Schuster, Committee Chair ; Nicholas V. Hud, Committee Member ; Roger M. Wartell, Committee Member.
16
Krusong, Kuakarun. "Recognition and repair of DNA damage by uracil DNA glycosylase". Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.417133.
Pełny tekst źródła
17
Cooley, Nicola. "Quantitative associations betweenn DNA damage, DNA repair and celluar outcomes". Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499845.
Pełny tekst źródła
18
Kaliyaperumal, Saravanan. "hMSH6 Protein Phosphorylation: DNA Mismatch Repair or DNA Damage Signaling?" Connect to full text in OhioLINK ETD Center, 2009. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=mco1242933021.
Pełny tekst źródłaStreszczenie:
Dissertation (Ph.D.)--University of Toledo, 2009."In partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomedical Sciences." Title from title page of PDF document. Bibliography: p. 174-180, p. 201-238.
19
Mikhed, Yuliya [Verfasser]. "The role of DNA damage in the pathogenesis of nitrate tolerance - nitrosative versus oxidative DNA damage / Yuliya Mikhed". Mainz : Universitätsbibliothek Mainz, 2015. http://d-nb.info/1080187529/34.
Pełny tekst źródła
20
Vonarx, Edward J., i mikewood@deakin edu au. "The repair and tolerance of DNA damage in higher plants". Deakin University. School of Biological and Chemical Sciences, 2000. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051110.135641.
Pełny tekst źródłaStreszczenie:
DNA repair mechanisms constitute an essential cellular response to DNA damage arising either from metabolic processes or from environmental sources such as ultraviolet radiation. Repair of these lesions may be via direct reversal, or by processes such as nucleotide excision repair (NER), a coordinated pathway in which lesions and the surrounding nucleotides are excised and replaced via DNA resynthesis. The importance of repair is illustrated by human disease states such as xeroderma pigmentosum and Cockayne's syndrome which result from defects in the NER system arising from mutations in XP- genes or XP- and CS- genes respectively
Little detail is known of DNA damage repair processes in plants, despite the economic and ecological importance of these organisms. This study aimed to expand our knowledge of the process of NER in plants, largely via a polymerase chain reaction (PCR)-based approach involving amplification, cloning and characterisation of plant genomic DNA and cDNA. Homologues of the NER components XPF/RAD1 and XPD/RAD3 were isolated as both genomic and complete cDNA sequences from the model dicotyledonous plant Arabidopsis thaliana. The sequence of the 3'-untranslated region of atXPD was also determined. Comparison of genomic and cDNA sequences allowed a detailed analysis of gene structures, including details of intron/exon processing. Variable transcript processing to produce three distinct transcripts was found in the case of atXPF. In an attempt to validate the proposed homologous function of these cDNAs, assays to test complementation of resistance to ultraviolet radiation in the relevant yeast mutants were performed. Despite extensive amino acid sequence conservation, neither plant cDNA was able to restore UV-resistance. As the yeast RAD3 gene product is also involved in vivo in transcription, and so is required for viability, the atXPD cDNA was tested in a complementation assay for this function in an appropriate yeast mutant. The plant cDNA was found to substantially increase the viability of the yeast mutant.
The structural and functional significance of these results is discussed comparatively with reference to yeast, human and other known homologues. Other putative NER homologues were identified in A. thaliana database sequences, including those of ERCC1/RAD10 and XPG/ERCC5/RAD2, and are now the subjects of ongoing investigations. This study also describes preliminary investigations of putative REVS and RAD30 translesion synthesis genes from A. thaliana.
21
Karakoula, Aikaterini. "Studies on UV-induced DNA damage and repair to human DNA". Thesis, University of Leicester, 2004. http://hdl.handle.net/2381/29692.
Pełny tekst źródłaStreszczenie:
The induction and repair of DNA damage has been shown to occur heterogeneously throughout the mammalian genome. As a consequence, analysis of these parameters at a global genome level may not reflect important gene-level events. Few techniques have been established to explore quantitatively gene-specific DNA damage and repair. Most of these are PCR-based assays and are relatively insensitive, relying on decreased PCR amplification arising from damage in template DNA. In this study, a quantitative assay that combines specific immunocapture of damaged DNA by an antiserum specific for thymine dimers (IgG479), with PCR amplification of a 149bp fragment of the human H-ras proto-oncogene was established. Quantification of DNA damage was based upon proportionality between the amount of the PCR product and the initial amount of damage. Detection of thymine dimers was possible with nanogram amounts of genomic DNA and increased in a linear, dose-responsive manner. Using this assay, gene-level induction of thymine dimers was shown to be directly proportional to levels induced in the global genome of UVC-and-UVB-irradiated genomic DNA, as measured by gas chromatography-mass spectrometry and enzyme-linked immunosorbent assay, respectively. This result suggests that global damage assessments do indeed reflect gene-level events. However, preferential repair of UVB-induced T < > T from the human H-ras proto-oncogene than the overall genome of human keratinocyte cells was detected. These findings demonstrate the suitability of this approach to the detection of UVR-induced DNA damage and repair at the level of individual genes.
22
Atwal, Mandeep. "Myeloperoxidase enhances DNA damage induced by drugs targeting DNA topoisomerase II". Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3956.
Pełny tekst źródłaStreszczenie:
Topoisomerase II (TOP2) poisons are effective anti-cancer agents used to treat a wide range of neoplasms. However, TOP2 poisons are subjected to enzymatic conversion which leads to metabolites with altered DNA damaging properties. Myeloperoxidase, present exclusively within developing myeloid progenitors and granulocytes, is capable of the biotransformation of TOP2 poisons to metabolites that are potentially more genotoxic in nature. Whilst TOP2 poisons are valuable chemotherapeutic agents, their use is associated with myelosuppression and with the risk of developing therapy related acute myeloid leukaemia. The reason that myeloid progenitor cells are particularly susceptible to TOP2 poison associated genotoxicity is unclear, however the presence of myeloperoxidase could potentially make myeloid progenitor cells more vulnerable to TOP2 poison mediated damage. This lead to the hypothesis that myeloperoxidase inhibition could protect developing hematopoietic cells from TOP2 poison associated genotoxic and/or cytotoxic damage. Data generated in this thesis supports the proposed hypothesis as expression of myeloperoxidase significantly enhanced the accumulation of TOP2 poison induced TOP2-DNA covalent complexes and the level of DNA breaks within myeloid cell lines. The use of two potential clinically relevant inhibitors of myeloperoxidase showed that reduction in myeloperoxidase activity reduced the abundance of TOP2 poison stabilised TOP2-DNA complexes and DNA breaks. Furthermore, depletion of glutathione to mimic conditions experienced during chemotherapy, resulted in a myeloperoxidase dependent increase in TOP2 poison mediated DNA damage. Taken together these results show inhibition of myeloperoxidase could protect developing hematopoietic cells from TOP2 poison mediated damage without compromising the effectiveness of these drugs as antineoplastic agents.
23
MENTEGARI, ELISA. "DNA damage tolerance by specialized DNA polymerases in humans and plants". Doctoral thesis, Università degli studi di Pavia, 2018. http://hdl.handle.net/11571/1243288.
Pełny tekst źródła
24
Jansson, Kristina. "Oxidative damage and the DNA glycosylase MutYH /". Göteborg : Department of Cell and Molecular Biology, University of Gothenburg, 2010. http://hdl.handle.net/2077/22092.
Pełny tekst źródła
25
Suwake, Natsuko. "D-type cyclins and DNA damage response". Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506678.
Pełny tekst źródła
26
Woollons, Arjida. "DNA damage induced by sunbeds and sunlight". Thesis, King's College London (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251706.
Pełny tekst źródła
27
Cooke, Marcus S. "Immunochemical investigation of UV-induced DNA damage". Thesis, University of Leicester, 1997. http://hdl.handle.net/2381/30738.
Pełny tekst źródłaStreszczenie:
In this thesis, immunochemical and chromatographic techniques were employed to assess the relative contribution of direct/indirect mechanisms to DNA damage in a number of model systems by measuring lesions associated with each mechanism. Efforts to produce polyclonal and monoclonal antibodies to oxidative DNA damage suggested that profiles of antigenicity and immunogenicity arise dependent on the method of reactive oxygen species (ROS) production. Furthermore, an antiserum, raised against DNA damaged by an established ROS-generating system, was shown to recognise direct UV damage and was characterised with a previously developed antiserum to UV-damaged DNA. ELISA demonstrated the main epitopes recognised to be dimerised adjacent thymines, suggested to be cyclobutadithymine, in conjunction with a flanking sequence, specific to each antiserum. Employing a dimer-containing DNA standard, calibrated by GC-MS, the limits of detection for each antiserum were found to be 0.9 and 1.9 fmol, compared with 20-50 fmol for GC-MS. Such results confirm these antisera to be a sensitive approach for determining levels of UV damage in DNA, supported by their successful demonstration of cyclobutadithymine formation in naked DNA following UVC-irradiation. No discernible binding was seen to UVA-irradiated DNA, which was confirmed immunohistochemically in fixed and embedded sections of human skin. The qualitative induction of dimers following UVB-, and ROS lesions, following UVA-irradiation of cultured human keratinocytes, was shown using an antiserum to cyclobutadithymine and a novel affinity technique for oxidised purines. Application of an antibody to 8-oxodG and a novel antiserum to ROS-modified DNA, allowed quantitative ELISA measurements of dimeric and oxidative DNA changes to be made, following irradiation of keratinocytes. It was concluded that oxidative DNA damage, along with cyclobutadithymine, represents an appreciable contribution to total damage following UVC irradiation and that oxidative processes, with little contribution by direct damage, represent the major mechanism responsible for UVA-induced DNA damage.
28
Kotturi, Gopaul. "Correlating and measuring DNA damage and mutations". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0009/NQ52763.pdf.
Pełny tekst źródła
29
Jiranusornkul, Supat. "Molecular modelling studies of DNA damage recognition". Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/11303/.
Pełny tekst źródłaStreszczenie:
How DNA repair proteins search and recognise the rare sites of damage from the massive numbers of normal DNA remains poorly understood. FapydG (2,6-diamino-4-hydroxy-5-formamidopyrimidine) is one of the most prevalent guanine derived lesions involving opening of the imidazole ring. It is typically repaired by formamidopyrimidine-DNA glycosylase (Fpg) as an initial step in base excision repair; if not repaired, the lesion generates a G: C -+ T: A transversion. Unfortunately, studies on the recognition of FapydG have been hindered by difficulties to synthesise and incorporate the FapydG residue into a DNA duplex. Crystal structures of Fpg-DNA complexes have demonstrated three common recognition events: the protein specifically binding to the extrahelical lesion, bending DNA centred on the damaged base, and flipping the damage into the pocket. Thus, molecular modelling and dynamics simulation have been used to gather dynamical information of those recognition events for damaged and undamaged DNA. The simulations were initially performed when FapydG or G occurs in several dodecamer B-DNA sequences in aqueous solution, then inside the lesion-recognition pocket of Fpg, and during the flipping pathway from the helical stack to an extrahelical position. The influence of the damage on DNA stability and flexibility was first investigated. Energetic analysis revealed that damage to DNA does appear to destabilise the duplex. DNA curvature analysis and a novel combined method of the principal component analysis (PCA) and the Mahalanobis distance (DM) indicated that damaged DNA can adopt the observed protein-bound conformation with lower energetic penalties than its normal counterpart. Results of these studies have provided the validation of DNA bending enhancement by the FapydG lesion. It also suggested that intrinsic DNA bending could be a principal element of how the repair protein locates the lesion from vast expanse of normal bases. Considering the specific recognition of FapydG by Fpg, the aF-/39 loop of the Fpg enzyme may function as a gatekeeping to accommodate the lesion while denying the normal base. Remarkably fluctuating movement of the flipped G residue and the aF-ß9 loop is due to the formation of the non-specific Fpg/G complex with a lower binding energy by 8.4 kcal/mol compared to the specific Fpg/FapydG complex. Free-energy profiles for both damaged and undamaged base flipping were generated from the umbrella sampling simulations and the Weight Histogram Analysis Method (WHAM). An energy barrier for flipping the damage out from the helix is 2.7 kcal/mol higher than its equivalent G and the lesion is highly stabilised inside the pocket. In contrast, G flipping seems to be rapidly rotated out and into the duplex without the formation of a specific complex. These studies could unravel a potentially comprehensive process of the repair protein to find and recognise the lesion through the slow kinetic pathway in which the more deformable damaged DNA is initially located by the protein; the protein subsequently compresses the duplex into an appropriate angle and direction to form a specific protein-DNA complex prior to being flipped and repaired.
30
Soman, Sony. "OXIDATIVE DAMAGE TO DNA IN ALZHEIMER'S DISEASE". UKnowledge, 2013. http://uknowledge.uky.edu/chemistry_etds/28.
Pełny tekst źródłaStreszczenie:
Previous studies from our laboratory and others show a significant increase in levels of both nuclear and mitochondrial DNA and RNA oxidation in vulnerable brain regions in the progression of Alzheimer’s disease (AD). Although total DNA oxidation is increased in AD it remains unclear whether oxidative damage is widespread throughout the genome or is concentrated to specific genes. To test the hypothesis that specific genes are more highly oxidized in the progression of AD, we propose to quantify the percent oxidative damage in genes coding for proteins shown to be altered in the progression of AD using quantitative/real-time polymerase chain reaction (qPCR/ RT-PCR). To further test the hypothesis that diminished DNA repair capacity in the progression of AD contributes to increased DNA oxidation we will use custom PCR arrays and qPCR, Western blot analysis and activity assays to quantify changes in enzymes involved in base excision repair (BER).
In order to carry out these studies tissue specimens from superior and middle temporal gyri (SMTG) and inferior parietal lobe (IP), as well as, a non-vulnerable region, the cerebellum (CER) will be analyzed from normal control (NC) subjects and subjects throughout the progression of AD including those with preclinical AD (PCAD), mild cognitive impairment (MCI), and late stage AD (LAD). We will also analyze specimens from diseased control subjects (DC; Frontotemporal dementia (FTD) and dementia with Lewy bodies (DLB)) to determine if the changes we observe in AD are specific.
31
Gordon, Anthony T. "Persistence of carcinogen damage in nuclear DNA". Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318312.
Pełny tekst źródła
32
Thomas, Nicola Alison. "RecA expression and DNA damage in mycobacteria". Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299376.
Pełny tekst źródła
33
Catterall, Helen. "Mechanisms of free radical damage to DNA". Thesis, University of York, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359256.
Pełny tekst źródła
34
Mittal, Sukant. "Micropatterned cell arrays for detecting DNA damage". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/44734.
Pełny tekst źródłaStreszczenie:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (leaves 66-72).
Numerous agents are capable of interacting with DNA and damaging it. Permanent changes in the DNA structure can be both mutagenic and cytotoxic; therefore, methods to measure the susceptibility of cells to mutations are important for risk assessment and identifying therapeutic interventions. One classical method for assessing DNA damage at a global level is the COMET assay, based on electrophoretic extension of the nuclear DNA in single cells embedded in agarose. In this assay, the size and shape of the extended 'comet tail' can be correlated to breaks in the DNA. This assay was first developed in the mid 1980s for non adherent cells such as lymphocytes; however, it has been plagued by technical difficulties, low throughput, and lab-to lab variation. These challenges have been exacerbated in adhesion-dependent cells as DNA damage accrues variably over time as they are enzymatically detached from their microenvironment. This thesis explores whether the COMET assay can be improved by micropatterning adherent cells prior to agarose embedding. Hepatocytes were chosen as a model cell type and x-ray radiation was chosen as a model DNA damaging agent. In order to establish the feasibility of measuring x-ray induced damage on hepatocyte DNA, standard curves were first generated for hepatocytes suspended in agarose. These experiments revealed a minimum detectable threshold of 1 Gy and displayed a monotonic increase in DNA damage in response to exposures up to 10 Gy. In comparison, adherent hepatocytes overlaid with agarose and irradiated in situ displayed similar levels of mean damage but lower levels of variability than suspended cells. We hypothesize that the decreased variability could be due to a reduction in programmed cell death incurred by detachment of adherent cells.
(cont.) Finally, we explored the feasibility of performing the comet assay by in situ irradiation of a micropatterned array of adherent cells. Single cell hepatocyte patterning was achieved by photolithographic patterning of collagen I on glass and optimization of seeding conditions. Gradiations of x-ray exposure were achieved by employing localized domains of lead shielding between the cells and the source. As a proof of principle, we obtained two domains of differential x-ray exposure and the resulting DNA damage was similar in the micropatterned format to the randomly-organized adherent format. Several challenges emerged from these experiments including potential interactions of DNA with the glass surface leading to 'streaking' artifacts. Nonetheless, with increased resolution of x-ray exposure, and further technical improvements, this assay has the potential to offer both reduced variability for adherent cells as well as assay multiplexing due to spatial encoding of x-ray dosage.
by Sukant Mittal.
S.M.
35
Haleux, Pauline. "DNA damage responses in plant stem cells". Thesis, University of East Anglia, 2014. https://ueaeprints.uea.ac.uk/52055/.
Pełny tekst źródłaStreszczenie:
Plants are sessile organisms that cannot escape environmental hazards, which induce DNA damage and cause mutations. Plants are also subject to DNA damage caused by endogenous processes such as transposon movement. Plant stem cell populations in particular must be protected from genotoxicity, as they are the origin of all organs, together with the germline. In accordance with this premise, plant stem cells were found to be hypersensitive to Double Strand Breaks (DSBs), leading to their specific killing via the ATAXIA TELANGIECTASIA MUTATED (ATM) and SUPPRESSOR OF GAMMA RESPONSE 1 (SOG1) genes. However, the components of the pathway leading to programmed cell death (PCD) in response to DSBs in plant stem cells are still unknown, and the in vivo DNA damaging agents relevant to this mechanism have not been characterised, providing the starting point of this thesis. Here, a candidate gene approach and a forward genetics screen in the root stem cells did not yield new factors of the pathway leading to PCD in root stem cells. However, a specific ecotype showed an absence of DSBs-induced PCD, revealing natural variation in stem cell responses to DSBs. In relation to responses to endogenous DNA damage in plant stem cells, I identified several chromatin‐silencing mutants showing spontaneous PCD in the root meristem, and studied the link between transposon silencing and the ATM/SOG1 pathway. Finally, by characterising responses to Cre‐catalysed recombination in the shoot meristem, I uncovered an unexpected link between the DNA damage response pathway and chromatin silencing, This silencing was dependent on ATM/SOG1, linked to the production of 24-nt siRNA, and required the RNA polymerase IV and ARGONAUTE 6. My work links DNA damage responses to chromatin silencing in Arabidopsis stem cells.
36
McAllister, Maeve. "Computational modelling of radiation damage to DNA". Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.707538.
Pełny tekst źródłaStreszczenie:
Ionising radiation is commonly used in radiation treatment of cancer to target cancerous cells. Upon entering a cell, ionising radiation can damage DNA directly or it can excite the cellular medium. The most abundant species produced following excitation of the medium is the low energy electron (LEE). LEE's can cause significant damage to DNA but the exact mechanism of this damage is unknown. This thesis investigates the indirect damage that LEEs do to DNA fragments, with particular emphasis on the influence of the surrounding water molecules. Using ab initio Molecular Dynamics, we investigated DNA-water systems, ranging from nucleobases to nucleotides. We found that water molecules in the environment are capable of forming hydrogen bonds with or transferring protons to the DNA fragment. In all these cases, when the DNA is H-bonded to or protonated by the water molecules, the energetic barriers to DNA damage reactions are affected. In the final parts of the thesis, we extended the research and investigated chemo-radiation therapy involving the chemotherapeutic agent cisplatin. We found once again that including the water environment around the DNA-cisplatin had an effect on the reactivity of this system with LEEs. Our results highlight the significant role that water molecules can play in DNA damage processes and demonstrate that it is therefore important to incorporate explicit water molecules in any simulation of the DNA damage process.
37
Little, Elizabeth J. "DNA damage sensors in the checkpoint response". Diss., The University of Arizona, 2003. http://hdl.handle.net/10150/289950.
Pełny tekst źródłaStreszczenie:
The DNA damage checkpoint response detects DNA damage and responds to the damage by promoting DNA repair, transcriptional regulation, and cell cycle arrest. Prior to the beginning of this dissertation the checkpoint sensor proteins in S. cerevisiae were identified as Ddc1, Mec3, Rad9, Rad17 and Rad24. However, none of the sensors had been shown to bind DNA directly, an anticipated function of checkpoint sensors. To characterize these proteins a biochemical approach was taken to test whether any of the checkpoint sensor proteins could detect DNA. The associated DNA binding properties of Rad24 and Rad9 were identified and characterized for the first time. Both of these checkpoint sensor proteins have an affinity for ssDNA, a common intermediate DNA structure of most DNA repair processes. In addition, the DNA damage checkpoint mutant protein Rad24-1 is defective for binding to ssDNA, suggesting that Rad24 DNA binding is required for its function in the checkpoint response. The potential exonuclease activity of Rad 17 tested using purified protein and various DNA substrates. This study was based on reports that the Rad 17 homolog Rec 1 from U. maydis is a 3'→5 ' DNA exonuclease, and genetic data that indicated that Rad 17 has a role in telomere degradation. Exonuclease assays with Rad17 protein preparations and ssDNA found an associated weak exonuclease that was not significantly above background levels. Conserved residues of Rad 17 thought to be required for exonuclease activity and checkpoint activity were mutated and studied for their affect on the DNA damage checkpoint. These studies imply that in addition to the region of Rad17 that is homologous to PCNA, the long carboxy-terminal region of Rad17 is also required for its checkpoint activity. Collectively, these studies suggest that the common DNA repair intermediate structure single-stranded DNA is recognized by multiple checkpoint sensor proteins to initiate the DNA damage checkpoint response. This suggests that the initiation of the checkpoint response is the recognition of a single DNA structure instead of the many different structures of primary DNA damage by free radicals, UV, γ-radiation, alklylation, double strand breaks, and base mismatches.
38
Zheng, Zhi-Ying 1957. "Bile acid-induced DNA damage in bacteria". Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/291421.
Pełny tekst źródłaStreszczenie:
Bile acids have been implicated by epidemiologic evidence as causative agents in colon cancer. Previous studies have indicated that the bile acids damage DNA. However, the conjugated forms of bile acids (eg. tauro conjugates) have not been tested for interaction with DNA. The present study compared the DNA-damaging ability of unconjugated and conjugated bile acids using the E. coli SOS test system. The E. coli tester strain was incubated with the bile acids and conjugated bile acids. Both cell survival and induction of the SOS response was measured. Among unconjugated bile acids, deoxycholate, chenodeoxycholate, and lithocholic acid were confirmed as DNA damaging agents by a decrease in surviving fraction and increase of the fraction of blue colonies undergoing SOS induction with increasing doses. Cholate, however, did not cause DNA damage by these criteria. Among the conjugated bile acids, taurochenodeoxycholate caused as much DNA damage as chenodeoxycholate. Taurodeoxycholate caused DNA damage, but had less of an effect than deoxycholate. Taurocholate and taurolithocholate failed to show a DNA damaging effect.
39
Miller, Olivia. "Reactive Intermediates in Hypoxia-Selective DNA Damage". Digital Commons @ East Tennessee State University, 2013. https://dc.etsu.edu/honors/73.
Pełny tekst źródłaStreszczenie:
A group of prospective drugs with the aromatic di-N-oxide (ANO) functionality as the common feature are currently undergoing testing for the ability to selectively target tumors surrounded by normal tissues. It has been long recognized that the mechanism of biological activity of these drugs involves DNA damage by free radical species generated through one-electron reduction, although the exact nature of the reactive intermediate responsible for DNA damage remains uncertain. It is believed, however, that one of the key factors defining, in particular, hypoxic selectivity of these drugs is the rate of N-O bond scission in the one-electron reduced intermediate. In this study we have made an attempt to verify whether the predictions made in the literature regarding the N-O bond dissociation rate in a related class of derivatives are applicable to the same process in ANO. For that purpose both theoretical (electronic structure calculations) and experimental (Electron Spin Resonance spectroscopy) have been employed. While our results are not conclusive, they have laid the groundwork for future studies.
40
Dogo, Federico. "MODELS OF DNA DAMAGE, REPAIR, AND MISREPAIR". Doctoral thesis, Università degli studi di Trieste, 2015. http://hdl.handle.net/10077/10889.
Pełny tekst źródłaStreszczenie:
2013/2014Within the range of the Virtual Biophysics Lab tumour growth numerical simulator, this work aims to develop a mathematical model able to describe the cell cycle desynchronization observed in the cell populations and the effects of DNA damage and repair due to ionizing radiation. Following a review of the already available models, some other original ones are proposed; one of these has been also tested on tumour cells by means of cytometry: the results of the related data analysis are not yet conclusive.
Nell'ambito del simulatore numerico di crescita tumorale Virtual Biophysics Lab, questo lavoro mira a sviluppare un modello matematico adatto a descrivere la desincronizzazione cellulare osservata nelle popolazioni cellulari e gli effetti del danno e riparazione del DNA indotti da radiazioni ionizzanti. A seguito di una recensione dei modelli già esistenti, ne vengono proposti alcuni altri originali; uno di questi è stato anche testato su cellule tumorali attraverso la citofluorimetria: i risultati della relativa analisi dati non sono ancora decisivi.
XXVII Ciclo
1983
41
Fisher, Mark. "Intra and extracellular responses to DNA damage". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/214106/1/Mark_Fisher_Thesis.pdf.
Pełny tekst źródła
42
Langerak, Petra. "@DNA damage tolerance from error free UV-damage bypass to mutagenesis of immunoglobulin genes /". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2007. http://dare.uva.nl/document/.
Pełny tekst źródła
43
Najeeb, Hishyar Azo. "Redox modulation of oxidatively induced DNA damage by ascorbate enhances melanoma cancer cell DNA damage formation & cell killing". Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/36021.
Pełny tekst źródłaStreszczenie:
Malignant melanoma (MM) is the 5th most common cancer in the UK and the most lethal form of skin malignancies. Its incidence has more than quadrupled and mortality more than doubled over the last three decades. With a five-year survival rate for patients with advanced melanoma of ≤ 20%, there is an obvious need for a better treatment approach. Heightened genome-instability in cancer-cells suggests a model-scenario for their selective killing via the therapeutic delivery of defined levels of further genomic damage. To interrogate/exploit this model-scenario, it was proposed to investigate intracellular ascorbate's redox-modulation of oxidatively-induced DNA damage in MM cancer-cells, to selectively enhance both DNA damage and cell-killing. Alkaline comet assay (ACA) data reveals MM-cells to have higher endogenous DNA damage levels than “normal” skin cells. This in turn correlates with MM-cells having higher intracellular ROS and lower catalase activity. ACA data also shows MM-cells to be more sensitive towards the induced-damaging effects of H2O2 than “normal” skin cells, and that ascorbate further enhances this effect in MM-cells. This effect was also noted in primary melanoma cancer cells exposed to H2O2 and other oxidants (e.g. Elesclomol). A proposed model for the enhancement of H2O2-induced oxidatively-damaged DNA by ascorbate suggests that an increased local production of hydroxyl radicals (●OH) at the DNA may lead to relatively greater increases in complex lesions (i.e. DSBs) relative to single/‘isolated’ lesions (i.e. SSBs). However, correlated measures of DSBs vs. SSBs reveal only a proportional increase in DSBs relative to SSBs with ascorbate. Further data shows that ascorbate enhances oxidative-induced cell death in MM-cells and that in HaCaT cells the effect was slightly protective. Together, these results suggest that ascorbate enhances DNA damage/cell-killing through modulation of oxidative stress in MM-cells. This could increase the possibility of using ascorbate plus novel oxidant therapies to treat metastatic melanomas.
44
Jumpathong, Watthanachai. "The dynamic interplay between DNA damage and metabolism : the metabolic fate and transport of DNA lesions and novel DNA damage derived from intermediary metabolism". Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/93772.
Pełny tekst źródłaStreszczenie:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biological Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references.
The work presented in this thesis explores two novel and complementary facets of endogenous DNA damage: the development of biomarkers of inflammation based on metabolites of DNA damage products and the formation of DNA adducts by electrophilic products of intermediary metabolism. From the first perspective, endogenous DNA damage generated by reactive oxygen and nitrogen species from inflammation and oxidative stress has shown strong mechanistic links to the pathophysiology of cancer and other human diseases, with the damage products reflecting all types of damage chemistries including oxidation, deamination, halogenation, nitration and alkylation. However, the use of DNA damage products as biomarkers has been limited by poor understanding of the damage actually arising in tissues and a lack of appreciation of the fate of DNA damage products from the moment of formation at the site of damage to release from cells to final excretion from the body. The goal of the work presented in the first part of this thesis was to investigate the metabolic fates of the base propenal products arising from 4'-oxidation of 2'-deoxyribose in DNA, one of the most common products of DNA oxidation, and to define base propenal metabolites as potential biomarkers of oxidative stress. This project was approached with systematic metabolite profiling, starting with prediction of potential base propenal metabolites based on a priori knowledge of its chemical reactivity as an [alpha],[beta]-unsaturated aldehyde toward glutathione (GSH) in non-enzymatic reactions and in rat liver cell extracts. Of 15 potential candidates predicted and identified from these in vitro studies, analysis of urine samples from rats given intravenous doses (IV) of thymine propenal revealed three major metabolites: thymine propenoic acid and two mercapturic acid derivatives, which accounted for ~6% of the injected dose. An additional four metabolites, including conjugates with GSH, cysteinylglycine and cysteine, were observed in bile and accounted for ~22% of the dose. One of the major metabolites detected in urine and bile, a bis-mercapturic acid adduct of reduced thymine propenal was detected as a background excretory product in saline-treated rats and was significantly elevated after oxidative stress caused by treatment with bleomycin and CCl₄. Our observations suggest that metabolism and disposition of damaged biomolecules should be considered as crucial factors in the development of biomarkers relevant to inflammation and oxidative stress. The second part of this thesis addresses the complementary hypothesis that electrophilic metabolites generated endogenously from intermediary metabolism can react with DNA to form adducts. This concept is illustrated here with glyoxylate from the glyoxylate metabolic cycle, whicvh plays a key role as an alternative to the TCA cycle in plants, bacteria, protists and fungi under changing conditions of environmental nutrients. The goal of this project was to characterize DNA adducts caused by glyoxylate in the mycobacterium M. smegmatis, with the studies motivated by the higher-than-expected mutation rate of mycobacteria during dormancy induced by nutrient deprivation and a shift to utilization of the glyoxylate cycle. Initially, in vitro reactions of 2'-deoxyguanosine (dG) with glyoxylate yielded N²-carboxyhydroxymethyl dG (N²-CHMdG) as the only adduct. However, the adduct proved to be unstable, so a reduction-based analytical method was developed to yield the stable amine derivative, N2-carboxymethyl dG (N²-CMdG). This stable adduct was used to develop an isotope-dilution chromatography-coupled tandem mass spectrometry method to quantify N²-CHMdG as N²-CMdG in calf thymus DNA treated with glyoxylate in vitro. This analytical method was then applied to quantify and compare the level N2-CMdG in (1) wild-type M. smegmatis grown in rich medium (7H9) or in minimal M9 medium supplemented with acetate, the latter inducing a switch from the TCA cycle to the glyoxylate cycle; and (2) the isocitrate dehydrogenase (ICD)-deficient mutant of M. smegmatis. Mycobacteria grown in the acetate medium experienced a 2-fold increase in the adduct compared to those grown in 7H9. Similarly, the adduct increased 2-fold in the ICD mutant compared to wild-type M. smegmatis grown in 7H9. The results support the idea that shifts in intermediary metabolism can lead to DNA damage that may cause mutations associated with nutrient deprivation in mycobacteria, with implications for the genetic toxicology of other metabolism-derived electrophiles.
by Watthanachai Jumpathong.
Ph. D.
45
Wiltshire, Timothy D. "DNA damage response activated by anti-cancer agent, irofulven". Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5390.
Pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--West Virginia University, 2007.Title from document title page. Document formatted into pages; contains ix, 227 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.
46
Xu, Meng. "Oxidative DNA Damage Modulates Trinucleotide Repeat Instability Via DNA Base Excision Repair". FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1576.
Pełny tekst źródłaStreszczenie:
Trinucleotide repeat (TNR) expansion is the cause of more than 40 types of human neurodegenerative diseases such as Huntington’s disease. Recent studies have linked TNR expansion with oxidative DNA damage and base excision repair (BER). In this research, we provided the first evidence that oxidative DNA damage can induce CAG repeat deletion/contraction via BER. We found that BER of an oxidized DNA base lesion, 8-oxoguanine in a CAG repeat tract, resulted in the formation of a CTG hairpin at the template strand. DNA polymerase β (pol b) then skipped over the hairpin creating a 5’-flap that was cleaved by flap endonuclease 1 (FEN1) leading to CAG repeat deletion. To further investigate whether BER may help to shorten an expanded TNR tract, we examined BER in a CAG repeat hairpin loop. We found that 8-oxoguanine DNA glycosylase removed the oxidized base located in the loop region of the hairpin leaving an abasic site. Apurinic/apyrimidinic (AP) endonuclease 1 then incised the 5’-end of the abasic site leaving a nick in the loop. This further converted the hairpin into an intermediate with a 3’-flap and a 5’-flap. As a 5’-3’ endonuclease, FEN1 cleaved the 5’-flap, whereas a 3’-5’ endonuclease, Mus81/Eme1, removed the 3’-flap. The coordination between FEN1 and Mus81/Eme1 ultimately resulted in removal of a CAG repeat hairpin attenuating or preventing TNR expansion. To further explore if pol β bypass of an oxidized base lesion, 5’,8-cyclodeoxyadenosine, may affect TNR instability, we examined pol β DNA synthesis in bypassing this base lesion and found that the lesion preferentially induced TNR deletion during BER and Okazaki fragment maturation. The repeat deletion was mediated by the formation of a loop in the template strand induced specifically by the damage. Pol β then skipped over the loop structure creating a 5’-flap that was efficiently removed by FEN1 leading to repeat deletion. Our study demonstrates that pol β-mediated BER plays an important role in mediating TNR deletion and removing a TNR hairpin to prevent TNR expansion. Our research provides a molecular basis for further developing BER as a target for prevention and treatment of neurodegenerative diseases caused by TNR expansion.
47
Phillips, Lara Gayle. "The role of DNA polymerase delta and WRN in DNA damage tolerance". Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608621.
Pełny tekst źródła
48
Roos, Wynand Paul. "The influence of DNA damage, DNA repair and chromatin structure on radiosensitivity". Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52540.
Pełny tekst źródłaStreszczenie:
Thesis (PhD)--Stellenbosch University, 2001.ENGLISH ABSTRACT: The factors which control radiosensitivity are of vital importance for the understanding of cell inactivation and for cancer therapy. Cell cycle blocks, total induced DNA damage, DNA repair, apoptosis and chromatin structure are likely to playa role in the responses leading to cell death. I have examined aspects of irradiation-induced G2/M blocks in DNA damage and repair. In HT29, L132 and ATs4 cells the total amount of induced DNA damage by isodoses of 4.5 Gy, 5 Gy and 2 Gy was found to be 14 %, 14 % and 12 % respectively. Most of the DNA repair was completed before the G2/M maximum and only 3 % of DNA damage remains to be restored in the G2/M block. The radiosensitivity in eleven cell lines was found to range from SF2 of 0.02 to 0.61. By FADU assay the undamaged DNA at 5 Gy was found to range from 56% to 93%. The initial DNA damage and radiosensitivity were highly correlated (r2=0. 81). After 5 Gy irradiation and 12 hours repair two groups of cell lines emerged. The group 1 cell lines restored undamaged DNA to a level ranging from 94 % to 98 %. The group 2 cell lines restored the undamaged DNA to a level ranging from 77 % to 82 %. No correlation was seen between residual DNA damage remaining after 12 hours repair and radiosensitivity. In CHO-K1 cells chromatin condensation induced by Nocodazole was found to marginally increase the radiosensitivity as shown by the change of the mean inactivation dose (D) from 4.446 to 4.376 Gy. Nocodazole also increased the initial DNA damage, induced by 5 Gy, from 7 % to 13 %. In xrs1 cells these conditions increased the radiosensitivity from D of 1.209 to 0.7836 Gy and the initial DNA damage from 43 % to 57 %. Disruption of chromatin structure with a hypertonic medium was found to increase radiosensitivity in CHO-K1 cells from D of 4.446 to 3.092 Gy and the initial DNA damage from 7 % to 15 %. In xrs1 cells these conditions caused radiosensitivity to decrease from D of 1.209 to 1.609 Gy and the initial DNA damage from 43 % to 36 %. Repair inhibition by Wortmannin increased the radiosensitivity in CHO-K1 from a D of 5.914 Gy in DMSO controls to a D 3.043 Gy. In xrs1 cells repair inhibition had no effect on radiosensitivity. Significant inhibition of repair was seen in CHO-K1 at 2 hours (p<0.0001) and at 20 hours (p=0.0095). No inhibition of repair was seen in xrs1 cells at 2 hours (p=0.6082) or 20 hours (p=0.6069). While DNA repair must be allocated to the post-irradiation period, the G2/M block seen in p53 mutants reaches a maximum only 12 hours post-irradiation when most of the repair is completed. As the G2/M block resolves and cells reenter cycle 28 hours after the G2 maximum it appears that repair processes cannot be the only reason for the G2IM cell cycle arrest. At low doses of irradiation initial DNA damage correlates with radiosensitivity. This suggests that the initial DNA damage is a determinant for radiosensitivity. Repair of DNA double-strand breaks by the non-homologous end joining (NHEJ) mechanism, identified by inhibition with Wortmannin, was shown to influence residual DNA damage and cell survival. Both the initial DNA damage and DNA repair were found to be influenced by chromatin structure. Chromatin structure was modulated by high salt and by Nocodazole, and has heen identified as a parameter which influences radiosensitivity.
AFRIKAANSE OPSOMMING: Die faktore wat betrokke is in die meganisme van stralings-sensitisering is van hoogs belang vir die begrip van sel inaktiveering en kanker terapie. Sel siklus blokke, totale geïnduseerde DNS skade, DNS herstel, apoptose en chromatien struktuur is moontlike rol vertolkers in die sellulêre response wat ly tot seldood. Ek het die aspekte van stralings-geïnduseerde G2/M blokke in DNS skade en DNS herstelondersoek. Die hoeveelheid geïnduseerde DNS skade, deur ooreenstemmende stralings-dosisse, in HT29, L132 en ATs4 selle is 14 %, 14 % en 12 %. Meeste van die DNS herstel is klaar voordat die G2/M maksimum beryk word en net 3 % DNS skade blyoor om herstel te word in die G2/M blok. Die stralings-sensitiwiteit in elf sel lyne varieer tussen 'n SF2 van 0.02 en 0.61. Deur die gebruik van die FADU metode is gevind dat die onbeskadigde DNS na 5 Gy bestraling varieer tussen 56 % en 93 %. Die totale geïnduseerde DNS skade en stralings-sensitiwiteit was hoogs gekorreleer (r2=0.81). Na 5 Gy bestraling en 12 ure herstel kan die sel lyne in twee groepe gegroepeer word. Die groep 1 sellyne herstel die onbeskadigde DNS terug na 'n vlak wat varieer tussen 94 % en 98 %. Die groep 2 sel lyne herstel die onbeskadigde DNS terug tot op 'n vlak wat varieer tussen 77 % en 82 %. Geen korrelasie is gesien tussen oorblywende DNS skade en stralings-sensitiwiteit na 12 ure herstel nie. In die CHO-K1 sel lyn, chromatien kompaksie geïnduseer deur Nocodazole, vererger die stralings- sensitiwiteit soos gesien deur die gemiddelde inaktiveerings dosis (D) wat verlaag het van 4.446 tot 4.376. Nocodazole het ook die totale DNS skade verhoog van 7 % tot 13 %. Onder dieselfde kondisies, in die xrs1 sel lyn, is 'n verergering van stralings-sensitiwiteit (D) gesien van 1.209 tot 0.7836 en verhoog ONS skade van 43 % tot 57 %. Die ontwrigting van die chromatien struktuur deur die gebruik van hipertoniese medium het die stralings-sensitiwiteit (D) vererger in CHO-K1 selle van 4.446 tot 3.092. Die totale ONS skade is verhoog van 7 % tot 15 %. Onder dieselfde kondisies, in die xrs1 sellyn, verbeter die stralings-sensitiwiteit (D) van 1.209 tot 1.609 en die totale ONS skade verminder van 43 % tot 36 %. ONS herstel inaktiveering in die teenwoordigheid van Wortmannin het die stralings-sensitiwiteit (D) in CHO-K1 selle vererger van 5.914 in DMSO verwysings kondisies tot 3.043. Die ONS herstel inaktiveering in xrs1 selle het geen uitwerking gehaat op stralingssensitiwiteit nie. Noemenswaardige inaktiveering van ONS herstel is gesien in CHO-K1 selle na 2 ure (p<0.0001) en na 20 ure (p=0.0095). Geen inaktiveering is gesien in xrs1 selle na 2 ure (p=0.6082) of na 20 ure (p=0.6069) nie. TerwylONS herstel moet plaasvind na die bestralings periode, beryk die G2/M blok in p53 gemuteerde selle sy maksimum 12 ure na bestraling terwyl meeste van die ONS herstel alreeds voltooi is. Aangesien die G2/M blok eers 28 ure later begin sirkuleer moet die G2/M blok nog 'n funksie vervul anders as ONS herstel. By lae dosisse van bestraling korreleer die totale geïnduseerde ONS skade met stralings-sensitiwiteit. Dit dui daarop dat die totale ONS skade 'n bepalende faktor moet wees in stralings-sensitiwiteit. Die herstel van ONS skade deur die nie-homoloë eindpunt samevoeging (NHES) meganisme, geïdentifiseer deur inaktiveering deur Wortmann in, het 'n invloed op oorblywende ONS skade en sellulêre oorlewing. Beide die totale ONS skade en ONS herstel was beïnvloed deur die chromatien struktuur. Chromatien struktuur was gemoduleer deur hoë sout konsentrasies en deur Nocodazole, en is geïdentifiseer as a belangrike parameter wat stralings-sensitiwiteit beïnvloed.
49
Brockmann, William G. Eick J. David. "An investigation of a rapid fluorescence microtiter plate methodology for measuring chemically-induced DNA damage, suitable for use in development of a primary DNA damage database". Diss., UMK access, 2004.
Znajdź pełny tekst źródłaStreszczenie:
Thesis (Ph. D.)--School of Dentistry and School of Pharmacy. University of Missouri--Kansas City, 2004."A dissertation in oral biology and pharmacology." Advisor: J. David Eick. Typescript. Vita. Title from "catalog record" of the print edition Description based on contents viewed Feb. 22, 2006. Includes bibliographical references (leaves 176-189). Online version of the print edition.
50
Bowden, Gemma M. "Assay of DNA photoproducts". Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318877.
Pełny tekst źródła