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The present study aimed at investigating the neuropsychological sequelae of transient ischaemic attacks. Transient ischaemic attacks are defined as those neurological disorders in which there is complete resolution of neurological symptoms within twenty·four hours. Transient ischaemic attacks may or may not reveal evidence of brain infarcts on imaging studies. In the present study, the neuropsychological sequelae of transient ischaemic attacks in the carotid circulation were investigated since, within the perspective of cognitive neuropsychology, it was assumed that localized changes in cognitive functions could be demonstrated.Since several psychological, medical and neurological factors are known to influence scores·on neuropsychological tests, regression analyses were performed to determine which factors contributed significantly to the variance of scores on neuropsychological tests in the transient ischaemic attack and control groups. Two transient ischaemic attack groups, each comprising forty left and forty right hemisphere involvement patients, were then compared with each other and with a control group of forty general medical patients. Stenosis of the carotid artery formed a significant predictor of test scores in the combined transient ischaemic attack group. When the groups were·analyzed independently, in the left transient ischaemic attack group stenosis predicted performance on the same tests reaching significance for the combined group, and for the Wisconsin Card Sorting Test (Perseverative Score). In the right transient ischaemic attack group, stenosis significantly predicted performance on Digits Forward, Backward and Total, the PASAT (2.4 seconds) and Trails B. On the other hand, education formed a significant predictor of performance on Digits Forward, Digits Backward and Digits Total and the PASAT (all levels) in the control group. Multivariate comparisons revealed that the left and right transient ischaemic attack groups performed worse than the controls on tests of attention, concentration and conceptual flexibi1ity. The left transient ischaemic attack group performed worse than the right transient ischaemic attack group on all tests of attention and concentration, but there was a significantly better performance of the former group on the Rey Auditory Verbal Learning Test (Trial 1), Block Designs and Verbal Fluency. The findings on the PASAT that left transient ischaemic attack patients performed significantly worse than the right hemisphere group ·were considered to be relatively unreported previously in the literature on transient ischaemic attacks. The findings obtained are discussed from a neurocognitive perspective of neuropsychological functioning in transient ischaemic attacks. / Psychology / Ph. D. (Psychology)

Distortion to hemodynamic, ischemic and metabolic stimuli during low load resistance exercise with blood flow restriction (BFR) may influence regional vascular adaptation. This thesis investigated the acute response and chronic adaptations of the peripheral vasculature to low load resistance exercise with BFR. The methodology utilised Doppler ultrasound, strain gauge plethysmography and muscle biopsy for insightful measures of the vasculature at different regions of the arterial tree. Short term (4-6 weeks) localised low load (30-40% 1RM) resistance exercise with BFR increased brachial (3.1%) and popliteal (3.3%) artery maximal diameter (in response to ischemic exercise), forearm (29%) and calf (24%) post-occlusive blood flow, and calf filtration capacity (14%). These findings indicate potential vascular remodelling at the conduit (chapters 3, 4) resistance (chapter 4) and capillary (chapter 4) level of the vascular tree. Regional, rather than systemic, factors are responsible for these adaptations as evidenced by an absent response in the contralateral control limb. Transient improvements in popliteal artery FMD% occurred at week 2 before increased maximal diameter at week 6, suggesting functional changes precede structural remodelling (chapter 4). Maximal brachial artery diameter and forearm post-occlusive blood flow returned to baseline values after a 2 week detraining period, signifying rapid structural normalisation after stimulus removal (chapter 3). Enhanced capillarity, despite low training loads, could be explained by augmentation of VEGF (~7 fold), PGC-1α (~6 fold) and eNOS (~5 fold) mRNA, and upregulation VEGFR-2 (~5 fold) and HIF-1α (~2.5 fold) mRNA with BFR (chapter 5). This indicates a targeted angiogenic response potentially mediated through enhanced metabolic, ischemic and shear stress stimuli. Large between subject variability in the level of BFR was observed during upper and lower limb cuff inflation protocols. Adipose tissue thickness and mean arterial pressure were the largest independent determinants of upper and lower limb BFR, respectively (Chapter 6). In conclusion, this thesis demonstrates that low load resistance exercise with BFR induces adaptation in the conduit, resistance and capillary vessels. The mediators of this response are likely to be the hemodynamic and chemical signals elicited by repeated bouts of BFR resistance exercise, although confirmation of these mechanisms is required. The functional significance of these adaptations is unknown and warrants further investigation.

Thesis (MScMed)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Protein kinases and phosphatases play important roles in the phosphorylation state of intracellular proteins under both physiologic and pathophysiologic conditions. Compared to the large number of studies investigating the significance of kinases, in particular the mitogen-activated protein kinases (MAPKs) in myocardial ischaemia/reperfusion and ischaemic preconditioning, relatively few studies have been done on the protein phosphatases in this scenario. Although several role players in the signal transduction cascade of ischaemia/reperfusion and ischaemic preconditioning have been identified thus far, the exact mechanism of cardioprotection still remains unclear. Previous studies from our laboratory have shown that the stress kinase, p38 MAPK, has a dual role in preconditioning: it acts as trigger of the process, while attenuation of its activation during sustained ischaemia and reperfusion is required for cardioprotection. Since the activation of p38 MAPK is dependent on both the upstream kinases for phosphorylation and phosphatases for dephosphorylation, we hypothesized that the balance between the activation state of the MAPKs and the induction of phosphatases may play a major role in determining the fate of cardiomyocytes exposed to ischaemic stress. The objectives of this study were: (i) to assess the activity of the myocardial protein phosphatases (PSPs and PP1) during sustained ischaemia and during reperfusion of non-preconditioned and ischaemic preconditioned hearts; (ii) to evaluate the significance of these phosphatases in ischaemia/reperfusion as well as in ischaemic preconditioning using available appropriate inhibitors; (iii) to give particular attention to the role of the phosphatase, mitogen-activated protein kinase phosphatase-1 (MKP-1), in ischaemia/reperfusion. MKP-1 is upregulated by stress conditions and selectively inactivates p38 MAPK by dephosphorylation of the regulatory Thr and Tyr residues. The glucocorticoid, dexamethasone which increases MKP-1 expression, was used as agonist to upregulate MKP-1 experimentally. The isolated perfused working rat heart was used as experimental model. After stabilization, hearts were subjected to either a one-cycle or multi-cycle ischaemic preconditioning protocol, followed by sustained global or regional ischaemia and reperfusion. Non-preconditioned hearts were subjected to ischaemia/reperfusion only. For Western blot analysis of MAPKs, PKB/Akt and MKP-1, hearts were freeze-clamped at different times during the perfusion protocol. Endpoints were infarct size, functional recovery and phosphorylation of the MAPKs (ERK and p38 MAPK) and PKB/Akt during reperfusion. Expression of MKP-1 was monitored. The results obtained showed that activation of PSPs and PP1 does not occur during sustained global ischaemia or reperfusion of non-preconditioned and preconditioned hearts. The role of the phosphatases was subsequently further investigated using two inhibitors namely cantharidin (5 μM, a concentration which inhibits both PP1 and PP2A) and okadaic acid (7.5 nM, a concentration which inhibits PP2A selectively). Administration of cantharidin or okadaic acid during the preconditioning phase, completely abolished preconditioning induced cardioprotection as indicated by mechanical failure during reperfusion and increased infarct size, associated with increased phosphorylation of p38 MAPK and PKB/Akt and dephosphorylation of ERK42/44. These results suggest a role for PP2A in the trigger phase of preconditioning. Administration of cantharidin or okadaic acid during early reperfusion of preconditioned hearts improved functional recovery. This was associated with increased phosphorylation of ERK42/44 and PKB, but not p38 MAPK. Dexamethasone, administered intraperitoneally to rats for 10 days (3mg/kg/day) or directly added to the perfusate (1 μM) resulted in significant cardioprotection of hearts subjected to 20 min sustained global ischaemia, followed by 30 min reperfusion. This is associated with a marked upregulation of MKP-1 and dephosphorylation of p38 MAPK during reperfusion. These studies suggest that the phosphatases are definitely involved in the phenomenon of ischaemia/reperfusion and ischaemic preconditioning. However, it also become clear that extensive further research is required to fully elucidate which phosphatases are involved and the mechanisms thereof. Due to the large size of the protein phosphatase family, this may prove to be a formidable task and far beyond the scope of this thesis. The results also suggested that pharmacological targetting of phosphatases involved in phosphorylation of the reperfusion injury salvage kinase (RISK) pathway (e.g. ERK42/44 and PKB/Akt) or dephosphorylation of pro-apoptotic kinases, such as p38 MAPK, may have significant clinical potential. / AFRIKAANSE OPSOMMING: Proteïenkinases en fosfatases speel 'n belangrike rol in die fosforileringstatus van intrasellulêre proteïene in beide fisiologiese en patofisiologiese toestande. In teenstelling met die groot aantal studies gedoen ten einde die rol van die kinases, veral die mitogeen-geaktiveerde proteïenkinases (MAPKs), in iskemie/herperfusie en iskemiese prekondisionering te ondersoek, is relatief min bekend aangaande die rol van die fosfatases in hierdie scenario. Hoewel verskeie rolspelers in die seintransduksieprosesse van iskemie/herperfusie en iskemiese prekondisionering reeds geïdentifiseer is, is die presiese meganisme van miokardiale beskerming steeds onbekend. Vroeëre studies vanuit ons laboratorium het getoon dat die streskinase, p38 MAPK, 'n tweeledige rol in prekondisionering speel: dit is 'n sneller ("trigger") van die proses, terwyl verlaagde aktivering tydens volgehoue iskemie en herperfusie, noodsaaklik vir beskerming is. Ons hipotese is dus dat die balans tussen die aktiveringstatus van die MAPKs en induksie van fosfatases die oorlewing van kardiomiosiete blootgestel aan iskemiese stres, bepaal. Die doelwitte van hierdie studie was: (1) bepaling van die aktiwiteit van miokardiale proteïen fosfatases (PSPs en PP1) tydens volgehoue iskemie en herperfusie van nie-geprekondisioneerde en iskemies-geprekondisioneerde harte; (ii) evaluering van die belang van fosfatases in iskemie/herperfusie beskadiging sowel as in iskemiese prekondisionering deur van geskikte inhibitore gebruik te maak; (iii) ondersoek na die rol van die fosfatase, mitogeen-geaktiveerde proteïen kinase fosfatase-1 (MPK-1) in iskemie/herperfusie beskadiging. Dit is bekend dat MKP-1 deur strestoestande opgereguleer word en p38 MAPK selektief deur defosforilasie van die regulatoriese Thr en Tyr residue inaktiveer word. Die glukokortikoïed, deksametasoon, wat MKP-1 uitdrukking stimuleer, is as agonis gebruik ten einde MKP-1 eksperimenteel op te reguleer. Die geïsoleerde, geperfuseerde werkende rothart is as eksperimentele model gebruik. Na stabilisasie, is die harte aan 'n enkel- of veelvuldige siklus iskemiese prekondisioneringsprotokol onderwerp, gevolg deur volgehoue globale of streeksiskemie. Nie-geprekondisioneerde harte is slegs aan iskemie/herperfusie onderwerp. Harte is op verskillende tye tydens die perfusieprotokol gevriesklamp vir Western blot analise van die MAPKs, PKB/Akt en MKP-1. Infarktgrootte en funksionele herstel tydens herperfusie is as indikators van iskemiese beskadiging gebruik. Fosforilasie van MAPKs en PKB/Akt sowel as uitdrukking van MKP-1 tydens vroeë herperfusie is gemonitor. Die resultate toon dat aktivering van PSP en PP1 tydens volgehoue iskemie en herperfusie nie plaasvind nie. Die rol van die fosfatases is verder ondersoek deur van twee inhibitore gebruik te maak, naamlik cantharidin (5 μM inhibeer beide PP1 en PP2A) en okadaic suur (7.5 nM inhibeer PP2A selektief). Toediening van of cantharidin of okadaic suur tydens die prekondisioneringsprotokol, hef prekondisionering-geïnduseerde beskerming totaal op, soos aangetoon deur hartversaking tydens herperfusie en 'n toename in infarktgrootte, tesame met 'n toename in die fosforilering van p38 MAPK en PKB/Akt en defosforilering van ERK42/44. Hierdie waarnemings dui op 'n rol vir PP2A as sneller in prekondisionering. Toediening van hierdie inhibitore tydens vroeë herperfusie het ook die miokardium beskerm, soos aangetoon deur 'n verbeterde meganiese herstel van geprekondisioneerde harte, tesame met ‘n verhoogde fosforilering van ERK42/44 en PKB (maar nie p38 MAPK nie). Deksametasoon, intraperitoneaal toegedien, vir 10 dae (3mg/kg/dag) of direk by die perfusaat gevoeg (1μM), het tot 'n hoogs beduidende beskerming teen iskemiese beskadiging gelei van harte blootgestel aan 20 min globale iskemie en 30 min herperfusie. Hierdie toename in funksionele herstel en afname in infarktgrootte het met 'n toename in MKP-1 uitdrukking en defosforilasie van p38 MAPK gepaard gegaan. Bogenoemde resultate dui op 'n definitiewe betrokkenheid van fosfatases in iskemie/herperfusie en iskemiese prekondisionering. Dit is egter ook duidelik dat intensiewe verdere navorsing benodig word om die presiese rol van die fosfatases te bepaal. Vanweë die grootte van die fosfatase familie, val dit egter buite die beskek van hierdie studie. Ten slotte, die resultate toon dat farmakologiese manipulasie van fosfatases betrokke by die fosforileringstatus van anti-apoptotiese kinases soos ERK42/44 en PKB/Akt en defosforilasie van pro-apoptotiese kinases, soos p38 MAPK, besondere kliniese toepassings mag hê.

Thesis (MScMedSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: It is well-established that transient activation of the β-adrenergic signalling pathway with ligands such as isoproterenol, formoterol and dobutamine, elicits cardioprotection against subsequent long periods of ischaemia. Initially the focus was on the β1- and β2-adrenergic receptors (β1-AR, β2-AR), but recently the β3-AR also emerged as a potential target in the treatment of heart disease. In heart failure, β1- and β2-AR are typically known to be down-regulated while β3-ARs, on the other hand, are up-regulated (Moniotte et al., 2001). Thus, it has become important to examine the significance of the β3-AR and its downstream signalling under similar states of stress. It has been shown that β3-AR stimulation is resistant to short term agonist-promoted desensitization in vitro and in vivo (Liggett et al., 1993) and after being activated, this receptor is able to convey continual intracellular signals (Lafontan et al., 1994). Thus, it could be an ideal target for therapeutic intervention, also in ischaemic heart disease. We hypothesized that selective β3-AR stimulation during ischaemia / reperfusion may be cardioprotective, whereas selective inhibition of this receptor may prove useful in the end stages of sustained ischaemia and early reperfusion. Methods: The isolated working rat heart, subjected to 35 min of regional ischaemia (RI) and 60 min reperfusion was used as model. The β3-AR agonist (BRL37344) (1 μM) or antagonist (SR59230A) (0.1 μM) were applied as follows: (i) before 35 min RI (PT), (ii) during the last 10 min of RI (PerT) and /or (iii) at the onset of reperfusion (PostT) and (iv) administration of BRL37344 during the last 10 min of RI BRL37344 (PerT) was followed by SR59230A during first 10 min of reperfusion SR59230A (Post). The contribution of nitric oxide synthase (NOS) in β3-AR was assessed, using the non-specific NOS inhibitor, L-NAME (50 μM). Endpoints were functional recovery and infarct size. In another set of experiments BRL37344 and SR59230A were applied according to the same protocols, but the left ventricle was dissected from the heart and freeze clamped at 10 min reperfusion for Western blot analysis of extracellular signal-regulated kinase (ERK p44/p42), protein kinase B (PKB/Akt), glycogen synthase kinase-3β (GSK-3β), and endothelial nitric oxide synthase (eNOS). Data were analyzed with one or two-way analysis of variance (ANOVA). Results: Administration of the selective β3-AR agonist (BRL37344) (1μM) before 35 min RI (BRL37344 (PT), significantly reduced infarct size when compared to the non-pretreatment group (NPT) (21.43±2.52 vs 43.17±1.20, p < 0.001). BRL37344 had similar effects on infarct size when applied during the last 10 min of regional ischaemia BRL37344 (PerT) (14.94±2.34, vs NPT, p < 0.001) or at the onset of reperfusion BRL37344 (PostT) (19.06±1.81, vs NPT, p < 0.001). When BRL37344 was applied as a (PerT+PostT) strategy, infarct size was once again significantly reduced (20.55±2.01 vs 43.17±1.20, p <0.001). In contrast, administration of the β3-antagonist SR59230A according to the same protocol did not reduce infarct size and values similar to those of untreated hearts (NPT) were obtained. Surprisingly, when BRL37344 was applied during the last 10 min of regional ischaemia followed by the administration of the β3-AR antagonist (SR59230A) at the onset of reperfusion, [BRL37344 (PerT) & SR59230A (PostT)], infarct size was significantly reduced to 20.78±3.02 (p <0.001 vs NPT and SR59230A (PerT + PostT). Involvement of nitric oxide (NO) was shown since the reduction in infarct size elicited by BRL37344 was totally abolished by, L-NAME, when administered in combination with BRL37344 for 10 minutes prior to RI or at the onset of reperfusion for 10 minutes (% infarct size: 41.48±3.18 and 35.75±3.54, p <0.001 vs BRL37344 (PT) and BRL37344 (PostT), respectively. Western blot results show that PKB/Akt is activated by BRL37344 regardless of the time of administration. The intervention BRL37344 (PerT+PostT), exhibited the most significant phosphorylation of PKB/Akt (fold increase: 14.2±3.71, p<0.01 vs NPT and p<0.05 vs BRL37344 (PostT). In addition, BRL37344 (PT), (PerT), (PostT) and [BRL37344 (PerT) +SR59230A (PostT)] showed significant activation of this kinase (2.92±0.22, 5.54±0.43, 4.73±0.47, and 6.60±0.78, respectively). ERKp44/p42 however, was not significantly activated by any of the treatments. Phosphorylation of eNOS and GSK-3β was significant only in the BRL37344 (PerT+PostT) and [BRL37344 (PerT) + SR59230A (PostT)] groups. The activation of eNOS-S-1177 in the BRL37344 (PerT+PostT) group was (2.82±0.46, p<0.01 and 0.05 vs NPT and BRL37344 (PostT), respectively) and in the [BRL37344 (PerT) + SR59230A (PostT)] group was (2.26±0.48, p<0.05 vs NPT). A very significant increased phosphorylation of GSK-3β was seen in the same two groups (68.8±7.73, p<0.001 vs NPT and 25.5±5.42 vs NPT, p<0.05, respectively). Conclusion: β3-AR has potent cardioprotective effects when administered either before, during and after ischaemia during early reperfusion as indicated by the reduction in infarct size as well as activation of PKB, GSK-3β and eNOS. These beneficial effects can be linked to NO production through activation of eNOS. / AFRIKAANSE OPSOMMING: Dit is bekend dat verbygaande aktivering van die β-adrenerge seinpad, met ligande soos isoproterenol, formoterol en dobutamien, die hart teen daaropvolgende lang periodes van iskemie beskerm. Aanvanklik was die fokus op die β1- en β2-adrenerge reseptore (β1-AR, β2-AR); maar onlangs is ook die β3-AR as 'n potensiële teiken in die behandeling van hartsiektes ge-eien. In hartversaking, is dit bekend dat β1- en β2-AR afreguleer word, terwyl β3-ARs, aan die ander kant, opreguleer word (Moniotte et al., 2001). Dit het dus belangrik geword om die belang van die β3-AR en sy stroomaf seinpad onder soortgelyke strestoestande te ondersoek. Dit is bewys dat β3-AR stimulasie teen korttermyn agonis geïnduseerde desensitisering in vitro en in vivo bestand is (Liggett et al., 1993) en wanneer geaktiveer, is hierdie reseptor in staat om intrasellulêre seine voortdurend oor te dra (Granneman, 1995). Dit kan dus ‘n ideale teiken vir terapeutiese intervensie wees, ook in iskemiese hartsiekte. Ons hipotetiseer dat selektiewe β3-AR stimulasie tydens iskemie / reperfusie kardiobeskermende mag wees, terwyl selektiewe inhibisie van hierdie reseptor effektief kan wees in die eindstadia van volgehoue iskemie en vroeë herperfusie. Metodes: Die geïsoleerde werkende rothart, onderwerp aan 35 min van streeksiskemie (SI) en 60 min herperfusie, is as model gebruik. Die β3-AR agonis (BRL37344) (1μM) of antagonis (SR59230A) (0.1 μM), is as volg toegedien: (i) voor 35 min SI (PT), (ii) gedurende die laaste 10 min van SI (PerT) en / of (iii) tydens die aanvang van herperfusie (PostT) en (iv) gedurende die laaste 10 min van SI is BRL toediening BRL37344 (PerT) gevolg deur SR59230A tydens die eerste 10 min van herperfusie SR59230A (Post). Die rol van stikstofoksiedsintase (NOS) in β3-AR is met behulp van die nie-spesifieke NOS inhibitor, L-NAME (50 μM) ondersoek. Eindpunte was funksionele herstel tydens herperfusie en infarktgrootte. In 'n ander reeks eksperimente is BRL37344 en SR59230A volgens dieselfde protokolle toegedien, maar die linker ventrikel is uit die hart gedissekteer na 10 min herperfusie en gevriesklamp vir Western klad analise van ekstrasellulêre-sein gereguleerde kinase (ERK p44/p42), proteïen kinase B (PKB/Akt), glikogeen sintase kinase-3β (GSK-3β), en endoteel stikstofoksied- sintase (eNOS). Data is met een of twee-rigting variansie analise (ANOVA) ontleed. Resultate: Administrasie van die selektiewe β3-AR agonis (BRL37344) (1μM) voor 35 min SI BRL37344 (PT), het die infarktgrootte beduidend verminder vergeleke met die nie-behandelde groep (NPT) (21.43±2.52 vs 43.17±1.20, p<0.001). BRL37344 het ‘n soortgelyke effek op infarktgrootte wanneer dit gedurende die laaste 10 min van streeksiskemie BRL37344 (PerT) (14.94±2.34, vs NPT, p<0.001) of by die aanvang van herperfusie (BRL37344 (PostT) (19.06±1.81, vs NPT, p<0.001) toegedien word. Wanneer BRL37344 as 'n (PerT+PostT) strategie toegedien is, was infarktgrootte weereens beduidend verlaag (20.55±2.01 vs 43.17±1.20, p<0.001). In teenstelling hiermee, het administrasie van die β3-antagonis SR59230A volgens dieselfde protokol, nie infarktgrootte verminder nie en waardes soortgelyk aan dié van onbehandelde harte (NPT) is verkry. Interessant, wanneer BRL37344 gedurende die laaste 10 min van streeksiskemie toegedien is, gevolg deur die administrasie van die β3-AR antagonis (SR59230A) by die aanvang van herperfusie, [BRL37344(PerT) & SR59230A(PostT)], was infarktgrootte aansienlik verminder tot 20.78±3.02 (p<0.001 vs NPT en SR59230A (PerT+PostT). Die betrokkenheid van stikstofoksied (NO) is waargeneem deurdat die vermindering in infarktgrootte ontlok deur BRL37344, heeltemal deur L-NAME opgehef is, wanneer dit in kombinasie met BRL37344 vir 10 minute voor SI of by die aanvang van herperfusie vir 10 minute toegedien is (% infarktgrootte: 41.48±3.18 en 35.75±3.54, p<0.001 vs BRL37344 (PT) en BRL37344 (PostT) onderskeidelik). Western kladresultate toon dat PKB/Akt deur BRL37344 geaktiveer word ongeag die tyd van die administrasie. Die intervensie BRL37344 (PerT+PostT), toon die mees beduidende fosforilering van PKB/Akt (voudige toename: 14.2±3.71, p<0.01 vs NPT en p<0.05 vs BRL37344 (PostT). Daarbenewens het BRL37344 (PT), (PerT), (PostT) en [BRL37344 (PerT) + SR59230A (PostT)] ook beduidende aktivering van hierdie kinase tot gevolg gehad (2.92±0.22, 5.54±0.43, 4.73±0.47 en 6.60±0.78, onderskeidelik). ERKp44/p42 is egter nie deur enige van die behandelings geaktiveer nie. Fosforilering van eNOS en GSK-3β was net beduidend in die BRL37344 (PerT+PostT) en [BRL37344 (PerT) + SR59230A (PostT)] groepe. Die aktivering van eNOS-S-1177 was beduidend in die BRL37344 (PerT+PostT) en [BRL37344 (PerT) + SR59230A (PostT)] groepe. 'n Baie beduidende toename in fosforilering van GSK-3β is in dieselfde twee groepe (68.8±7.73, p<0.001 en 25.5±5.42, p<0.05 vs NPT onderskeidelik) waargeneem. Gevolgtrekking: β3-AR het kragtige kardiobeskermende effekte wanneer dit, hetsy voor, tydens en na iskemie gedurende vroeë herperfusie toegedien word, soos deur die vermindering in infarktgrootte sowel as die aktivering van PKB, GSK-3β en eNOS aangedui is. Hierdie voordelige effekte kan aan NO produksie deur aktivering van eNOS gekoppel word.

Thesis (MSc)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Background: Athletes use androgenic anabolic steroids (AAS) to enhance their physical performance. The abuse of AAS is however associated with a host of side effects including sudden death due to cardiac arrest. The use of AAS leads to myocardial hypertrophy, which possibly makes the heart more prone to ischaemia/reperfusion injury, since it often develops in the absence of proper vasculature development. Chronic AAS use also disrupts myocardial p-adrenoreceptor function and possibly cAMP, signalling in the heart. Drugs increasing cAMP and decreasing cGMP levels in the ischaemic myocardium exacerbate myocardial ischaemia/reperfusion injury. We also know that AAS causes coronary artery disease secondary to the deleterious alteration of lipid profiles by increasing the LOL cholesterol and decreasing the HOLcholesterol levels. AAS treatment may increase systemic TNFa levels by stimulating lymphocyte TNFa secretion that has been implicated in the depression of myocardial function, myocardial hypertrophy and the worsening of ischaemia/reperfsuion injury. Aims: To determine whether chronic AAS treatment in trained and untrained rats influences: 1) heart function and susceptibility to ischaemia/reperfusion injury, 2) myocardial cyclic nucleotide levels (cAMP and cGMP) and 3) myocardial TNFa levels. Material and methods: Male Sprague-Dawley rats (n=100) were divided into 4 groups: sedentary vehicle (placebo) treated group, sedentary AAS treated group, exercise vehicle (placebo) treated group, and exercise AAS treated group. Steroid treated animals received an intramuscular injection of nandrolone laureate (0.375 mg/kg) once a week, for six weeks. Training consisted of swim sessions 6 days a week for 6 weeks. Swim time was incrementally increased up to a maximum of 50 minutes a day. For biometric parameters heart weight and body weight were documented. Hearts were mounted on a l.anqendorff perfusion apparatus and left ventricular developed pressure (LVDP), heart rate (HR) and coronary flow (CF) was monitored. The hearts were subjected to a period of 20 minutes of global ischaemia, followed by 30 minutes of reperfusion. Functional parameters was again monitored and documented. For biochemical analysis, blood was collected for the determination of serum lipid levels and myocardial tissue samples were collected before, during and after ischaemia for the determination of myocardial TNFa, cGMP and cAMP levels and p38 activity. Conclusions: Results obtained would suggest that AAS exacerbate exercise induced myocardial hypertrophy. It also prevents the exercise-induced improvement in cardiac function. AAS use reduces reperfusion function in treated hearts, which may suggest that AAS exacerbates ischaemie and reperfusion injury. Furthermore it was seen that AAS elevates basal (preischaemie) cyclic nucleotide levels and basal (pre-ischaemic) as well as reperfusion TNFa levels. This may also contribute to the exacerbation of ischaemic and reperfusion injury. / AFRIKAANSE OPSOMMING: Agtergrond: Androgeniese anaboliese steroïede (AAS) word dikwels deur atlete gebruik om sportprestasie te verbeter. Die misbruik van AAS het egter talle newe effekte, insluitende skielike dood wat gewoonlik toegeskryf word aan hartaanvalle. Die gebruik van AAS lei onder andere tot miokardiale hipertrofie wat opsigself, as gevolg van ontoereikende vaskulêre ontwikkeling tydens die ontwikkeling van hipertrofie, die hart nog meer vatbaar vir isgemie/herperfusie skade maak. Kroniese AAS toediening versteur miokardiale beta-adtenoresepter funksie en moontlik die tweede boodskapper, sAMP, seintransduksie in die hart. Ons weet ook dat AAS koronêre hartvatsiektes veroorsaak. Laasgenoemde is sekondêr tot die nadelige lipiedprofiel verandering, wat 'n verhoging in LDL-C en 'n verlaging in HDL-C insluit. Middels wat miokardiale sAMP vlakke verhoog en sGMP vlakke in die isgemiese miokardium verlaag, vererger miokardiale isgemie/herperfusie skade. AAS behandeling kan moontlik ook sistemiese TNFa vlakke verhoog deur limfosiet TNFa sekresie te stimuleer. Die verhoogde TNFa vlakke word verbind aan die onderdrukking van miokardiale funksie, miokardiale hipertrofie en die verergering van isgemie/herperfusie skade. Doelwitte: Die doelwitte van die studie was om te bepaal of kroniese AAS toediening in geoefende en ongeoefende rotte 1) hartfunksie en die hart se vatbaarheid vir isgemie/herperfusie skade beïnvloed, 2) miokardiale sikliese nukleotiedvlakke (sAMP en sGMP) beïnvloed en 3) miokardiale TNFa-vlakke beïnvloed. Materiale en metodes: Manlike Sprague-Dawley rotte (n=100) is gebruik en in 4 groepe verdeel: 'n ongeoefende placebo groep (kontrole); 'n ongeoefende steroïedbehandelde groep; 'n geoefende placebo groep (kontrole) en 'n geoefende steroïedbehandelde groep. Steroïed behandelde diere het 'n intramuskulêre nandroloon lauraat inspuiting (0.375 mg/kg) een keer per week vir ses weke ontvang. Die oefenprogram het bestaan uit ses swemsessies 'n week vir ses weke. Die swemtyd is geleidelik weekliks verhoog tot by 'n maksimum tyd 50 min. Die waterbadtemperatuur is tussen 30 - 32 oe gehandhaaf. Vir biometriese parameters is hartgewig en liggaamsgewig genoteer. Harte is op 'n Langendorff perfusie apparaat gemonteer en linker ventrikulêre ontwikkelde druk (LVOD), koronêre vloei (KV) en harttempo (HT) is genoteer. Die harte is vervolgens blootgestel aan 20 minute van globale isgemie gevolg deur 'n 30 minute herperfusieperiode. LVOD, KV en HT is weer eens noteer. Vir biochemiese doeleindes is bloed voor perfusie versamelom serum lipied vlakke te bepaal. Miokardiale weefsel is versamel voor, tydens en na isgemie vir die bepaling van TNFa, cGMP en AMP vlakke asook p38 aktiwiteit. Gevolgtrekkings: Na aanleiding van resultate verkry wil dit voorkom asof die gebruik van steroïde oefeningsgeïnduseerde miokardiale hipertrofie vererger. Dit verhoed ook oefeningsgeïnduseerde verbetering in miokardiale funksie. AAS lei tot 'n verlaagde herperfusiefunksie in behandelde harte, wat dalk mag dui op MS verergering van isgemie en herperfusie skade. Verder was daar ook waargeneem dat MS basale (pre-isgemiese) sikliese nukleotiedvlakke en basale TNFa-vlakke sowel as herperfusie TNFa vlakke verhoog. Die verhoging in TNF-a vlakke mag dus moontlik ook bydra tot die verergering van isgemie- en herperfusieskade.

Thessis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Although there is evidence for a protective role of long-chain polyunsaturated fatty acids (PUFAs) in cardiovascular disease, their mechanism of action as well as their participation in intracellular signalling processes remain to be elucidated. Therefore the aims of this study were twofold: (i) to characterize the roles of the mitogen-activated protein kinases (MAPKs) and protein kinase B (PKB/Akt) in ischaemia/reperfusion-induced apoptosis of neonatal cardiomyocytes and (ii) to establish whether long-chain PUFAs protect the heart via manipulation of these kinases. Rat neonatal ventricular myocytes exposed to simulated ischaemia and reperfusion (Sl/R) were used to characterize the role(s) of extracellular signalregulated kinase (ERK), p38 and c-Jun NH2-terminal protein kinase (JNK), as well as PKB/Akt in apoptosis. The effects of an omega-3 fatty acid (eicosapentaenoic acid - EPA) and an omega-6 fatty acid (arachidonic acid - ARA) on the response of neonatal rat cardiomyocytes to Sl/R with regard to the above parameters were determined. Exposure of the myocytes to SI (energy depletion induced by KCN and 2- deoxy-D-glucose) reduced cell viability, as measured by the 3-[4,5- dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and stimulated apoptosis (increased caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage). However, morphological evidence of increased apoptosis (Hoechst 33342 staining) occurred only after reperfusion. A rapid activation of p38 and PKB/Akt Ser473 occurred during SI, while significant activation of ERK and JNK was observed during reperfusion only. Myocytes pre-treated with SB203580, a p38-inhibitor, displayed a significant increase in cell viability and attenuation of apoptosis during Sl/R, while SP600125, a specific JNK inhibitor, significantly increased both caspase-3 activation and the apoptotic index. However, PD98059, an ERK inhibitor, was without effect. Wortmannin, a PI3-kinase inhibitor, reduced PKB/Akt Thr308 but not Ser473 phosphorylation during Sl/R and caused a significant increase in Although there is evidence for a protective role of long-chain polyunsaturated fatty acids (PUFAs) in cardiovascular disease, their mechanism of action as well as their participation in intracellular signalling processes remain to be elucidated. Therefore the aims of this study were twofold: (i) to characterize the roles of the mitogen-activated protein kinases (MAPKs) and protein kinase B (PKB/Akt) in ischaemia/reperfusion-induced apoptosis of neonatal cardiomyocytes and (ii) to establish whether long-chain PUFAs protect the heart via manipulation of these kinases. Rat neonatal ventricular myocytes exposed to simulated ischaemia and reperfusion (Sl/R) were used to characterize the role(s) of extracellular signalregulated kinase (ERK), p38 and c-Jun NH2-terminal protein kinase (JNK), as well as PKB/Akt in apoptosis. The effects of an omega-3 fatty acid (eicosapentaenoic acid - EPA) and an omega-6 fatty acid (arachidonic acid - ARA) on the response of neonatal rat cardiomyocytes to Sl/R with regard to the above parameters were determined. Exposure of the myocytes to SI (energy depletion induced by KCN and 2- deoxy-D-glucose) reduced cell viability, as measured by the 3-[4,5- dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and stimulated apoptosis (increased caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage). However, morphological evidence of increased apoptosis (Hoechst 33342 staining) occurred only after reperfusion. A rapid activation of p38 and PKB/Akt Ser473 occurred during SI, while significant activation of ERK and JNK was observed during reperfusion only. Myocytes pre-treated with SB203580, a p38-inhibitor, displayed a significant increase in cell viability and attenuation of apoptosis during Sl/R, while SP600125, a specific JNK inhibitor, significantly increased both caspase-3 activation and the apoptotic index. However, PD98059, an ERK inhibitor, was without effect. Wortmannin, a PI3-kinase inhibitor, reduced PKB/Akt Thr308 but not Ser473 phosphorylation during Sl/R and caused a significant increase in Although there is evidence for a protective role of long-chain polyunsaturated fatty acids (PUFAs) in cardiovascular disease, their mechanism of action as well as their participation in intracellular signalling processes remain to be elucidated. Therefore the aims of this study were twofold: (i) to characterize the roles of the mitogen-activated protein kinases (MAPKs) and protein kinase B (PKB/Akt) in ischaemia/reperfusion-induced apoptosis of neonatal cardiomyocytes and (ii) to establish whether long-chain PUFAs protect the heart via manipulation of these kinases. Rat neonatal ventricular myocytes exposed to simulated ischaemia and reperfusion (Sl/R) were used to characterize the role(s) of extracellular signalregulated kinase (ERK), p38 and c-Jun NH2-terminal protein kinase (JNK), as well as PKB/Akt in apoptosis. The effects of an omega-3 fatty acid (eicosapentaenoic acid - EPA) and an omega-6 fatty acid (arachidonic acid - ARA) on the response of neonatal rat cardiomyocytes to Sl/R with regard to the above parameters were determined. Exposure of the myocytes to SI (energy depletion induced by KCN and 2- deoxy-D-glucose) reduced cell viability, as measured by the 3-[4,5- dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay, and stimulated apoptosis (increased caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage). However, morphological evidence of increased apoptosis (Hoechst 33342 staining) occurred only after reperfusion. A rapid activation of p38 and PKB/Akt Ser473 occurred during SI, while significant activation of ERK and JNK was observed during reperfusion only. Myocytes pre-treated with SB203580, a p38-inhibitor, displayed a significant increase in cell viability and attenuation of apoptosis during Sl/R, while SP600125, a specific JNK inhibitor, significantly increased both caspase-3 activation and the apoptotic index. However, PD98059, an ERK inhibitor, was without effect. Wortmannin, a PI3-kinase inhibitor, reduced PKB/Akt Thr308 but not Ser473 phosphorylation during Sl/R and caused a significant increase in PARP cleavage during reperfusion, but had no effect on caspase-3 activation or the apoptotic index. EPA and ARA (20 jiM, present before and after SI) significantly reduced caspase-3 activation, PARP-cleavage and the apoptotic index during reperfusion. This was associated with increased ERK- and decreased p38 phosphorylation. Vanadate (a tyrosine phosphatase inhibitor), but not okadaic acid (a serine-threonine phosphatase inhibitor), significantly reduced ARAinduced inhibition of p38 phosphorylation, suggesting involvement of tyrosine phosphatases during Sl/R. MKP-1, a dual-specificity phosphatase, was targeted and a significant induction of MKP-1 by ARA and EPA was observed. An in vitro dephosphorylation assay confirmed that this phosphatase might be responsible for the inhibition of p38 activation. It was also demonstrated that the protective actions of ARA are PI3-K dependent. The results suggest that p38 has a pro-apoptotic role while JNK phosphorylation is protective and that these kinases act via caspase-3 to prevent or promote cell survival in response to SI/R-induced injury. It was demonstrated for the first time that EPA and ARA protect neonatal cardiac myocytes from ischaemia/reperfusion-induced apoptosis through induction of a dual-specific phosphatase, MKP-1, causing dephosphorylation of the proapoptotic kinase, p38. These beneficial effects of ARA and EPA were also reflected by improvement in functional recovery during ischaemia/reperfusion of the isolated perfused rat heart model. / AFRIKAANSE OPSOMMING: Dit word algemeen aanvaar dat lang-ketting poli-onversadigde vetsure teen kardiovaskulere siektes beskerm, maar hul meganisme van aksie sowel as hul invloed op intrasellulere seinoordragpaaie is egter onbekend. Die doelwitte van hierdie studie is dus tweevoudig: (i) om die belang van mitogeen-geaktiveerde proteien kinases (MAPKs) en protein kinase B (PKB/Akt) in isgemie/herperfusie-geinduseerde apoptose vas te stel en (ii) om te bepaal of lang-ketting poli-onversadigde vetsure die hart, deur manipulering van hierdie kinases, beskerm. Rot neonatale ventrikulere miosiete, blootgestel aan gesimuleerde isgemie en herperfusie (Sl/H), is gebruik om die aktivering van ekstrasellulere seingereguleerde kinase (ERK), p38, c-Jun NH2-terminale protein kinase (JNK) asook PKB/Akt tydens apoptose, te karakteriseer. Die effek van ‘n omega-3 vetsuur (eikosapentaenoSsuur - EPA) en ‘n omega-6 vetsuur (aragidoonsuur - ARA) op die respons van bogenoemde kinases in neonatale kardiomiosiete tydens Sl/H, is ondersoek. Blootstelling van miosiete aan SI (energie-uitputting gemduseer deur kaliumsianied en 2-deoksi-D-glukose) het ‘n afname in die vermoe van die sel om te oorleef, soos gemeet deur die MTT (3-[4,5-dimetieltiazol-2-yl]-2,5- difeniel tetrazolium bromied) bepaling, tot gevolg gehad. ‘n Toename in apoptose (kaspase-3 aktivering en poli(ADP-ribose) polimerase (PARP) kliewing) is ook waargeneem. Morfologiese bewyse van apoptose (Hoechst 33342 kleuring) was egter eers tydens herperfusie sigbaar. SI is gekenmerk deur vinnige aktivering van p38 en PKB/Akt Ser473, terwyl ERK en JNK fosforilering slegs tydens herperfusie waargeneem is. Vooraf-behandeling met SB203580, ‘n p38 inhibitor, het ‘n beduidende toename in sellewensvatbaarheid asook ‘n afname in die apoptotiese indeks tydens Sl/H teweeggebring, terwyl SP600125, ‘n spesifieke JNK inhibitor, apoptose bevorder het. PD98059, ‘n ERK inhibitor, het geen invloed op apoptose tydens Sl/H gehad nie. Wortmannin, ‘n PI3-kinase inhibitor, het Thr308 (nie Ser473) fosforilering onderdruk, gepaargaande met ‘n toename in PARP kliewing, maar dit het geen invloed op kaspase-3 aktivering of die apoptotiese indeks gehad nie. EPA en ARA (20 (iM, teenwoordig voor en na SI) het kaspase-3 aktivering en PARP kliewing asook die apoptotiese indeks tydens herperfusie beduidend verminder. Beide vetsure het ook ‘n beduidende toename in ERK en afname in p38 fosforilering veroorsaak. Vanadaat (‘n serien-threonien fosfatase inhibitor), maar nie “okadaic” suur (‘n tirosien fosfatase inhibitor), kon die ARA-gemduseerde inhibisie van p38 ophef nie. Induksie van MKP-1, ‘n tweeledige-spesifieke fosfatase, is beduidend deur ARA en EPA tydens herperfusie verhoog. 'n In vitro defosforileringbepaling het bevestig dat hierdie fosfatase wel betrokke by die inhibisie van p38 kan wees. Daarbenewens is gevind dat die beskermende aksie van ARA PI3-K afhanklik is. Hierdie resultate wys dat fosforilering van p38 pro-apoptoties is, terwyl JNK beskermend is en dat hierdie kinases via kaspase-3 seldood of oorlewing tydens SI/H-geinduseerde beskadiging bemiddel. In hierdie model is daar vir die eerste keer getoon dat EPA en ARA neonatale kardiale miosiete teen isgemie/herperfusie-geinduseerde apoptose beskerm deur induksie van MKP- 1, wat defosforilering van die pro-apoptotiese kinase, p38 teweegbring. Hierdie voordelige effekte van EPA en ARA is ook sigbaar in die funksionele herstel tydens isgemie/herperfusie van die geisoleerde rothart model.

Thesis (PhD (Physiological Sciences))--University of Stellenbosch, 2009 / ENGLISH ABSTRACT: Three main morphologies of cell death have been described in the diseased myocardium, type I, better known as apoptotic cell death, which is characterized by cell shrinkage and chromatin condensation, type II, or cell death with autophagy, presents a morphology with intracellular accumulation of autophagic vacuoles and type III, better known as necrosis, is characterized by cellular swelling and rapid loss in cellular membrane integrity. However, recent literature strongly argues against rigid classifications in the context of cell death mechanisms but rather suggests to adopt a view of cell death as a dynamic and integrative cellular response. Furthermore, the contribution of autophagy in cell death or cell survival is still poorly understood. Therefore the aims of this study were twofold: (i) to characterize the contribution of each cell death type in context of the severity and duration of an ischaemic insult and (ii) to determine whether manipulation of the autophagic pathway affects the contribution of cell death and translates into protection of the heart. Rodent derived cardiac myoblast cells were grown in Dulbecco’s Modified Eagle’s Medium (DMEM) supplemented with 10% fetal bovine serum (FBS), and incubated under 5% CO2 conditions. Cells were submitted to protocols of 2, 4 and 8 hrs of simulated ischaemia (SI) under hypoxic conditions in a humidified environment containing 0.1% O2, 5% CO2 and the balance N2, followed by 1 hr of reperfusion respectively. We employed a modified ischaemic buffer containing either 2-deoxy- D-glucose, sodium dithionate or both, with the aim to create an ischaemic insult of mild (mild SI), moderate (moderate SI) and severe (severe SI) character respectively. We evaluated the contribution of each cell death mode using a combination of viability- and ATP assays. Molecular markers for each cell death process such as LC3, PARP and HMGB1 were evaluated using 3-dimensional fluorescence techniques as well as western blot analysis and flow cytometry. Next, autophagy was induced or inhibited prior to the ischaemic insult, using rapamycin and 3MA respectively, and similar parameters were evaluated after 2 hours of mild or moderate SI. Propidium Iodide exclusion and Fluorescence Resonance Energy Transfer (FRET) in combination with mitochondrial inner membrane depolarization were employed to assess the onset of cell death dynamically. Flow cytometry was employed to evaluate the degree of protection. In addition, the ATP levels and reactive oxygen species (ROS) were evaluated. Our results strongly indicate a differential induction of cell death, which is dependent on the severity and duration of the ischaemic insult. Mild SI led to the induction of autophagy and apoptosis, whilst moderate or severe SI induced both apoptotic and necrotic cell death without an indication of autophagy. Only mild SI, but not moderate and severe SI, resulted in an ATP surge. Moreover, our data provide direct evidence that increased autophagy delays the loss of cellular membrane integrity and delays caspase-3 activation as well as mitochondrial depolarization in ischaemic cardiomyocytes. Our results show a profound effect of increased autophagy on the onset of apoptosis as well as necrosis under simulated ischaemic conditions, providing cellular protection. This ATP surge observed during mild SI was abolished with increased autophagy. Furthermore, our results indicate a profound effect of autophagy on ROS generation. Under normoxic conditions, increased autophagy induced a significant decrease in ROS while the inhibition of autophagy significantly increased ROS generation. However, when increasing or decreasing autophagy prior to the ischaemic insult, ROS increased significantly in both scenarios. The results suggest that the severity of ischaemia determines the mode of cell death differentially. An increase in autophagic responsiveness and flux, as induced through rapamycin treatment, provides a selective advantage for tissue against injury, possibly by maintaining intracellular ATP levels through the provision of metabolic substrates. Autophagy is described as an inherent cellular mechanism v which affects the onset of cell death and exhibits protective effects in the ischaemic myocardium when upregulated prior to the ischaemic insult. The protective effect of increased autophagy was mirrored in the isolated perfused rat heart model, reflected by improved functional recovery during ischaemia/reperfusion. / AFRIKAANSE OPSOMMING: Die drie belangrikste morfologiese beskrywings van seldood in die hart sluit die volgende in: tipe I, beter bekend as apoptose wat gekenmerk word deur selkrimping en chromatienkondensering, tipe II, of seldood deur middel van autofagie wat gekenmerk word deur die intrasellulêre versameling van autofagiese vakuole en tipe III, beter bekend as nekrose wat gekenmerk word deur sel swelling en ‘n vinnige verlies aan membraanintegriteit. Onlangse literatuur waarsku egter teen die onbuigsame klassifikasie van seldoodmeganismes en stel voor dat seldood as ‘n dinamiese proses met integrerende sellulêre meganismes beskou moet word. Die bydrae van autofagie in seldoodmeganismes word ook nog nie goed verstaan nie. Die doel van hierdie studie is dus tweevoudig: (i) om die bydrae van elke tipe seldood te bepaal in konteks van die felheid en tydperk van die iskemiese ingryping en (ii) om te bepaal of the manupilering van autofagie ‘n betekenisvolle bydrae lewer in seldoodmeganismes en sodoende tot beskerming van die hart kan lei. Kardiale mioblaste wat van rotweefsel afkomstig is, is in Dulbecco se gemodifiseerde Eagle medium (DMEM), waarby daar 10% fetale kalfserum gevoeg is en wat onderhewig was aan 5% CO2 toestande, onderhou. Selle was onderhewig aan protokolle van 2, 4 en 8 ure gesimuleerde iskemie (SI) onder hipoksiese toestande in ‘n humiditeitsomgewing wat 0.1% O2, 5% CO2 en die balans N2 bevat. Daarna was die selle onderhewig aan 1 uur reperfusie. ‘n Gemodifiseerde iskemiese buffer wat óf 2-deoksie-D-glukose óf natriumdithionaat, of beide bevat, is gebruik om lig, matig en strawwe iskemiese toestande na te boots. Die bydrae van elke tipe seldood is geëvalueer tydens bogenoemde toestande deur gebruik te maak van ‘n kombinasie van sellewensvatbaarheid- en ATP tegnieke. Molekulêre merkers, wat LC3, PARP en HMGB1 insluit, is gebruik om deur middel van 3-dimensionele fluoresensie tegnieke, westelike kladtegnieke en vii vloeisitometrie die verskillende vorme van seldood te ondersoek. Autofagie is ook geïnduseer en geïnhibeer voor die iskemiese ingryping, deur middel van rapamycin en 3MA, respektiewelik om die rol van autofagie tydens seldood te bepaal. Propidium iodite uitluiting en fluoresensie resonansie energie oordrag (FRET) in kombinasie met ‘n merker vir mitochondriale binneste membraan depolarisasie is gebruik om die aanvang van seldood dinamies te ondersoek. Vloeisitometrie is gebruik om die graad van beskerming aan te dui, terwyl intrasellulêre ATP vlakke en reaktiewe suurstof spesies (ROS) ook gemeet is. Ons resultate het getoon dat daar ‘n differensiële indusering van seldood plaasvind wat afhanklik is van die felheid en tydsduur van die iskemiese ingryping. ‘n Ligte graad van iskemie lei tot die indusering van autofagie en apoptose, terwyl matige en strawwe iskemie beide apoptose en nekrose induseer sonder autofagie. Verder het slegs ‘n ligte graad van iskemie ‘n skerp styging in ATP tweeggebring, terwyl dit nie die geval was tydens matige en strawwe iskemie nie. Ons data verskaf ook direkte bewyse dat ‘n toename in autofagie die verlies van sellulêre membraanintegriteit vertraag. Dit het ook ‘n vermindering in caspase-3 aktivering en mitochondriale depolarisasie in iskemiese kardiomiosiete teweegebring. Die data dui aan dat ‘n toename in autofagie ‘n beduidende effek op apoptose en nekrose tydens gesimuleerde iskemiese toestande het om sodoende selbeskerming te verskaf. Die skerp styging in ATP wat tydens die ligte graad van iskemie teweeggebring is, is opgehef met ‘n toename in autofagie. Ons resultate dui ook daarop dat autofagie ‘n beduidende rol in ROS generering speel. Onder normoksiese omstandighede veroorsaak ‘n toename in autofagie ‘n insiggewende afname in ROS generering, terwyl die inhibisie van autofagie ROS generering insiggewend laat toeneem. Wanneer autofagie egter voor die iskemiese ingryping verhoog of verlaag word, vermeerder ROS generering in beide gevalle. Hierdie resultate bewys dat die graad van iskemie ‘n invloed het op die tipe seldood wat geïnduseer word. ‘n Toename in autofagie reaksietyd en vloei, soos viii bewerkstellig deur rapamycin, verskaf ‘n selektiewe voordeel vir weefsel teen beskadiging, heel waarskynlik deur die handhawing van intrasellulêre ATP-vlakke deur die verskaffing van metaboliese substrate. Autofagie word beskryf as ‘n inherente sellulêre meganisme wat seldood beïnvloed en die iskemiese miokardium beskerm wanneer dit opgereguleer word voor die iskemiese ingryping. Hierdie beskermende rol van autofagie wat in die weefselkultuur waargeneem is, is ook in die geïsoleerde geperfuseerde rot hart model waargeneem, waar funksionele herstel verbeter is tydens iskemie/reperfusie.

published_or_final_version / abstract / Anaesthesiology / Master / Master of Philosophy