Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Progressive familial heart block type I (PFHBI) is a cardiac ventricular conduction disorder of unknown cause associated with risk of sudden death, which has been described in several South African families. Clinically, PFHBI is characterised by right bundle branch block on ECG, which may progress to complete heart block, necessitating pacemaker implantation. The disease shows an autosomal dominant pattern of inheritance with evidence of genetic anticipation. Using genetic linkage analysis, the PFHBI-causative gene was mapped to a 10 eentimorgan (cM) gene-rich area of chromosome (C) 19q13.3, which has, subsequently, been reduced to 7cM by fine mapping with polymorphic dinucleotide (CA)n short tandem repeat (STR) markers. Several attractive candidate genes, including muscle glycogen synthase (GSY 1) and histidine-rich calcium binding protein (HRC), lie within this region. The aim of the present study was two-fold: 1) to identify and characterise tetranucleotide (AAAT)n STRs within the PFHBI critical region that could be developed as polymorphic markers for use in genetic fine mapping and 2) to screen selected regions of GSY 1and HRC, positional candidate genes, for the presence ofPFHBI-causing mutation(s). Cosmids harbouring CI9q13.3 insert DNA were screened for the presence of (AAAT)n STRs by dot blot and Southern blot hybridisation using a radiolabelled (AAAT)lO oligonucleotide probe. To characterise the harboured (AAAT)n STRs, the positively hybridising fragments identified by Southern blot were sub-cloned, sequenced and primers designed from the unique repeat-flanking sequences. These primers were used to genotype the (AAAT)n repeat locus to assess its polymorphic nature in a panel of unrelated individuals. Alternatively, vectorette PCR, a rapid method of identifying repeat sequences and obtaining the flanking sequences in large inserts, was employed to develop polymorphic markers from the positively hybridising clones. Selected exons of GSY1 and HRC were screened for the presence of potentially disease-causing mutations by PCR-SSCP analysis and direct sequencing, respectively, in PFHBI-affected and unaffected family members. Of the available cosmid clones that gave strong signals on dot blot and Southern blot hybridisation, three, 29395, 24493 and 20381, were located within the critical PFHBI area and were used for marker development. An interrupted (AAAT)n repeat motif (n less than 5) was identified in cosmid 29395, however, the repeat locus was not polymorphic in the tested population. No (AAAT)n motif, single or repeated was observed in the partial sequence of the sub-cloned fragment of cosmid 24493. Using vectorette peR, no repeated (AAAT)n motif was identified on sequencing the generated products in either cosmid 24493 or 2038l. However, diffuse single AAAT motifs were detected in both cosmids. Exons 4, 5, 11, 12 and 16 of GSY 1, containing domains that are conserved across species, and the conserved eterminus- encoding exons 2-6 of HRC were selected for screening for potential PFHBI-causing mutation(s). However, no sequence variations were detected. The interrupted (AAAT)n repeat identified in cosmid 29395 was not polymorphic, which confirmed reports that complex repeats, especially those containing AAAT motifs of less than 6 repeats, are not polymorphic. One possible explanation for the absence of a repeated AAAT motif in cosmids 24493 and 20381, which both gave positive hybridisation signals, is that the low annealing temperature of the AfT -rich repeat-anchored primers used in vectorette peR may have resulted in transient annealing to the diffuse single AAAT motifs detected on sequencing. The screened regions of candidate genes GSYI and HRC were excluded from carrying the disease-causing mutation(s). The availability of new sequence data generated by the Human Genome Project will influence future strategies to identify the PFHBI gene. Electronic searches will allow identification of STR sequences for development of polymorphic markers and gene annotation will allow selection of new candidate genes for mutation screening. / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Heart disease including ischemic heart disease is the highest contributor to death and morbidity in the western world. The studies presented were conducted to determine possible pathways of protection of the heart against ischemia/reperfusion. We employed adenovirus mediated over-expression of Methionine sulfoxide reductase A (MsrA) in primary neonatal rat cardiac myocytes to determine the effect of this enzyme in protecting against hypoxia/reoxygenation. Cells transfected with MsrA encoding adenovirus and subjected to hypoxia/reoxygenation exhibited a 45% decrease in apoptosis as compared to controls. Likewise total cell death as determined by levels of Lactate Dehydrogenase (LDH) release was dramatically decreased by MsrA overexpression. The initial hypothesis that led to our testing sulindac was based on the fact that the S epimer of sulindac was a substrate for MsrA and that this compound might function as a catalytic anti-oxidant based on a reaction cycle that involved reductio n to sulindac sulfide followed by oxidation back to sulindac. To test this we examined the protective effect of sulindac in hypoxia re-oxygenation in both cardiac myocytes in culture and using a Langendorff model of myocardial ischemia. Using this model of myocardial ischemia we showed that pre-incubation of hearts with sulindac, or the S and R epimers of sulindac resulted in protection against cell death. We present several lines of evidence that the protective effect of sulindac is not dependent on the Msr enzyme system nor does it involve the well established role of sulindac as a Cyclooxygenase (COX) inhibitor. Numerous signaling pathways have been implicated in myocardial protective mechanisms, many of which require fluctuations in ROS levels as initiators or mediators. / Sulindac shows very good potential as a preconditioning agent that could induce tissue protection against oxidative damage.Blocking of preconditioning pathways by administration of the PKC blocker chelerythine abrogated the ischemic protection afforded by sulindac. Secondly, an end-effector of preconditioning, inducible nitric oxide synthase (iNOS),was found to be induced by greater than 5 fold after 48 h prior feeding sulindac. / by Ian Moench. / Thesis (Ph.D.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.