Infectious diseases that spread from person-to-person and continent-to-continent are a cause for concern for any health entity. One such disease is malaria, a mosquito-borne infection instigated by the protozoan parasite, Plasmodium falciparum. Hundreds of millions of people are affected annually and it is responsible for nearly 1 million deaths. It is the most fatal species causing malaria and proliferates in human red blood cells with a life cycle occurring every 48 hours. At this time, the parasite’s late stage form or schizont bursts from the erythrocyte releasing immune-inducing particles and infective forms (merozoites) into the bloodstream. The merozoites go on to infect other red blood cells as human immunity leads to fever. Fever is a hallmark symptom of malaria and effectively inhibits the growth of late stage parasites. Plasmodium still manages to complete its life cycle as early stages or rings are not affected by febrile temperatures. It is this facet of parasite biology that prompts our research into identifying genetic factors associated with fever. The parasite’s response under elevated body temperature may offer further insight into its adaptive mechanism. A heat shock assay was developed in order to simulate fever in vitro. Mutant parasite cultures were subjected to 41°C for 8 hours and returned to normal body temperature or 37°C for the remainder of the life cycle. The piggyBac mutagenesis system allows for the evaluation of phenotypes associated with a particular genotype as the transposon inserts randomly into the gene. This often leads to changes in function that may cause delays in invasion or attenuation of growth. Determining the genes responsible for these phenotypes would be a great advantage to the field of drug discovery. Collaborative efforts to develop vaccines and new antimalarial drugs are underway as resistance to current methods of treatment is on the rise. Such circumstances require new technologies for detecting novel drug targets or pathways in the parasite that can be significantly affected by these therapeutics. QISeq is a next generation sequencing tool that identifies genes with a particular phenotype that may alter intraerythrocytic development of P. falciparum. This technique was utilized in our study to confirm the heat shock phenotype with a high-throughput approach. The genomic DNA of pooled parasite cultures was sequenced to reveal those mutants sensitive and/or resistant to febrile temperature exposure. Through bioinformatics analyses, functional associations between genes can be made that lead to biological pathways of interest for therapeutic research.

Malaria is a threat to United States military personnel operating in endemic areas, from which there have been hundreds of cases reported over the past decade. Each of these cases might have been avoided with proper adherence to malaria chemoprophylaxis medications. Military operations may detract from the strict 100% adherence required of these preventive medications. However, the reasons for non-adherence in military populations are not well understood. This behavior was investigated using a cross sectional study design on a convenience sample of U.S. Army Ranger volunteers (n=150) located at three military instillations. Theoretical support was based on components of the Health Belief Model, the Theory of Reasoned Action/Theory of Planned Behavior, and the Social Cognitive Theory. Data on knowledge, attitudes, and practices, as well as multiple environmental domains was collected using an original yet unvalidated questionnaire. The data was analyzed using bivariate Pearson correlations, binary logistic regression, and moderated logistic regressions employing a 0.05 criterion of statistical significance. Power analyses predicted 96-98% power for this analysis. Multiple significant medium strength Pearson correlation coefficients were identified relative to the two dependent variables Take medications as directed and Intend to take the medications as directed the next time. Binary logistic regression analyses identified multiple variables that may predict behavioral intentions to adhere to these preventive medications, as a proxy for behavioral change. Moderated logistic regression analyses identified Command Support for adherence to these medications as a potential significant moderator that interacts with independent variables within three domains of the survey questionnaire. The findings indicate that there may be potential significant beneficial effects, which may improve this behavior in this population of Rangers through 1) promoting affirmative interpersonal communications that emphasize adherence to these medications, 2) including malaria chemoprophylaxis medications in the mission planning process, and 3) military command support, in the form of including the importance of proper adherence to these medications in the unit safety briefings.

A malária acompanha os seres humanos há cerca de 50 mil anos. Diferentes fatores genéticos do hospedeiro humano já foram relacionados à suscetibilidade ou resistência a malária: hemoglobinas S, C e E; Duffy; G6PD; TNF; TLRs; entre outros. Poucos estudos genético-epidemiológicos foram, até agora, conduzidos em populações misturadas, como a população brasileira e, em regiões com predominância da infecção por P. vivax. Estudos anteriores mostraram a presença de um fator genético principal, possivelmente localizado no cromossomo 4, relacionado ao número de episódios de malária no município de Monte Negro (RO). O presente trabalho buscou fatores genéticos relacionados à característica em questão em Monte Negro (RO). A análise do polimorfismo I602S do gene TLR1 (4p) pela técnica de RFLP mostrou ausência de associação. O GWAS encontrou sugestões de marcadores, que devem ser replicados em futuros estudos para verificar possíveis associações verdadeiras, sendo os mais relevantes os rs3796504, rs17518475, rs17527389, rs17660753, rs221188, rs7918405, rs7068695. / Malaria is present in humans since 50,000 years ago. Different Human host genetic factors are known to be related to susceptibility or resistance to malaria: S, C and E hemoglobins, Duffy, G6PD, TNF, TLRs, among others. Otherwise, few studies have been conducted in admixed populations, such as Brazilian populations and, in P. vivax predominance regions. Previous studies have shown the presence of a major genetic factor related to the number of malaria episodes of in the municipality of Monte Negro (RO) and, it was also suggested that this genetic factor may be located on chromosome 4. Thus, this study aimed to search genetic factors related to the number of individual malaria episodes in Monte Negro TLR1 candidate gene (4p) using RFLP and by GWAS. The first approach did not show any association with the studied phenotype, whereas GWAS data was able to suggest candidate markers that can be replicated in further studies in order to identify truly associations. The more relevant ones were rs3796504, rs17518475, rs17527389, rs17660753, rs221188, rs7918405, rs7068695.

Abnormal carbohydrate metabolism is a commonly encountered feature of malaria in people, and similar derangements have been detected in veterinary patients with canine babesiosis. Glucose, the major metabolic fuel source, is a key resource in critically ill patients as they mount an immunological response to infection and inflammation. The ability of the individual to effectively mobilise, distribute and utilise glucose is a major determinant of morbidity and mortality. Hypoglycaemia has been identified as a life threatening metabolic complication in almost 20% of severely ill dogs suffering from babesiosis due to Babesia rossi infection. Insulin and glucagon are the primary hormones involved in glucose homeostasis. Insulin lowers blood glucose concentration by facilitating cellular uptake and utilisation of glucose. Hyperinsulinaemia as a result of inappropriate insulin secretion may precipitate hypoglycaemia, and has been identif ed as a cause of hypoglycaemia in human and murine malaria. A similar phenomenon may exist in canine babesiosis. This prospective, cross-sectional, observational study, including 94 dogs with naturally acquired virulent babesiosis, sought to investigate and characterise the relationship between blood glucose concentrations and insulin concentrations in cases of canine babesiosis. Pre-treatment jugular blood samples were collected for simultaneous determination of plasma glucose and insulin concentrations. Animals were retrospectively divided into three groups: hypoglycaemic (plasma glucose concentration < 3.3 mmol/L; n=16), normoglycaemic (3.3-5.5 mmol/L; n=62), and hyperglycaemic (> 5.5 mmol/L; n=16). The median plasma insulin concentrations (IQR in parentheses) for the hypoglycaemic, normoglycaemic and hyperglycaemic groups were 10.7 pmol/L (10.7-18.8 pmol/L), 10.7 pmol/L (10.7-29.53 pmol/L; i.e below the detection limit of the assay), and 21.7 pmol/L (10.7-45.74 pmol/L), respectively. Statistical analysis revealed no significant difference in insulin concentration between the three groups. These results suggest that insulin secretion was appropriately suppressed in these dogs. Only two dogs had elevated insulin concentrations, one of which was hypoglycaemic. The median time since last meal (available for 87 dogs) was 24 hours (IQR 2-4 days), constituting a significant period of illness-induced starvation. We conclude that hyperinsulinaemia is not a cause of hypoglycaemia in virulent canine babesiosis. It is speculated that prolonged fasting due to disease-induced anorexia, in addition to increased glucose consumption, depletion of hepatic glycogen stores, and hepatic dysfunction with impaired gluconeogenesis, may play important roles in the pathophysiology of hypoglycaemia in canine babesiosis. / Dissertation (MMedVet)--University of Pretoria, 2010. / Companion Animal Clinical Studies / unrestricted

Malaria parasites are responsible for an increase in the morbidity and mortality in several tropical regions in Southern Africa. In this thesis, research was undertaken on Plasmodium, which is responsible for more than 95% of these cases. Although pharmacological prophylaxis is available, a worldwide resistance against existing drugs have been encountered. A study on chloroquineresistance in North-Eastern Transvaal in 1988, indicated that 11% of the strains in this area were resistant against chloroquine. Only 78% of these parasites were sensitive to the new drug, Mefloquine, which could serve as a substitute in chloroquine-resistant infections. Furthermore, no strain was found to be resistant or insensitive to both anti-malarial drugs. Malaria parasites can be obtained for research purposes from long term in vitro cultures. The initiation of cultures of some wild isolates of P.falciparum appears to be problematic at certain levels above sea-level. The gas composition of the medium was identified as a probable cause due to its dependence on the partial pressures of gasses at different heights above sealevel. The toxic effect of a too high oxygen concentration on the parasite, caused by the lower atmospheric pressure of the Highveld area, was prevented after the concentration of dissolved carbon dioxide in the medium was increased through equilibration with the special gas mixture. Possible shortcomings in the long-term culture method for malaria parasites that could retard optimum growth, were also investigated. Local parasite isolates could be supported on medium enriched with bovine serum although the growth rate was lower than when human serum was used. By increasing the frequency of medium replacement with progressing parasitemia, less stress were placed on the system since parasites was exposed for shorter periods and to lower concentrations of byproducts such as lactic acid. In addition, the ATP-concentration in infected cultures decreased by nearly 50 % over a growth period of 4 days. The stress in the host cell was reflected by the decrease in the total adenyl-nucleotide pool and the increase in AMP-concentration. An increase in the intracellular IMP-concentration indicated that the purine salvage pathway was inhibited which may explain the decrease in the ATP-concentration. It therefore appears that the regular replacement of medium and replenishment of erythrocytes only partially contribute to the successful establishment of malaria cultures. More research is necessary to identify the factors that are responsible for the inhibition of the purine salvage pathway. The stress placed on the human body by the parasite is complicated by the thrombocytopenia observed in some infections. Increases in the concentrations of thrombocyte-associated immunoglobulin G and M which are a characteristic for this condition, can be determined by a modified microo-method developed in our laboratory. By monitoring the parasite-infected patient over a period of time with the micro-method, the increase in thrombocytes and decrease in thrombocyte-associated antibodies were correlated with the recuperation of the patient. This method does not destroy the thrombocytes, thereby allowing displacement studies to be undertaken with purified parasite antigens of synthetic peptides. An investigation of parasite-infected erythrocytes by means of light microscopy, transmission and scanning electronmicroscopy, indicated that the local isolate could be composed of a mixture of strains, of which some have the ability to induce knobs on the erythrocyte. Furthermore, the investigation illustrated that fast fixation with gluteraldehyde is superior to slow fixation when transmission electronmicroscopy is performed. However, no difference could be observed when scanning electron microscopy was performed on infected erythrocytes that had been fixed by either of these methods. AFRIKAANS : Malaria parasiete is verantwoordelik vir 'n toenemende morbiditeit sowel as mortaliteit in verskeie tropiese streke in Suider-Afrika waarvan meer as 95 % van die gevalle deur Plasmodium falciparum veroorsaak word. Navorsing in die tesis is gevolglik op hierdie parasiet toegespits. Ten spyte daarvan dat far'makologiese profilakse toegepas word, kan malaria nog steeds opgedoen word as gevolg van n wereldwye weerstandigheid teen bestaande geneesmiddels. 'n Ondersoek van die klorokien-weerstandigheidstatus in die Noord-Oostelike Transvaal het in 1988 getoon dat 11 % van die stamme in die area weerstandig is teenoor klorokien. Slegs 78% van die parasiete was sensitief vir die nuwe middel, Meflokien, wat as moontlike plaasvervanger in klorokien-weerstandige parasietinfeksies gebruik kan word. Geen parasietstam was egter weerstandig of onsensitief teen beide middels nie. Langtermyn kultuurkweking van malaria parasiete is essensieël vir die verkryging van uitgangsmateriaal vir navorsing op die parasiet. Dit blyk egter dat inisiasie van kulture van wilde stamme van P. falciparum problematies by sekere hoogtes bo seespieël is. Die gassamestelling van die medium is as 'n moontlike oorsaak gëidentifiseer aangesien dit afhanklik is van die parsiële drukke van gasse by verskillende hoogtes bo seespieël. Die toksiese effek van te hoë suurstofkonsentrasies op die parasiet a.g.v. die laer atmosferiese druk op die Hoëveldstreek, is oorkom deur die konsentrasie van opgeloste koolsuurgas in die medium te verhoog deur vooraf 'n spesiale gasmengsel daardeur te borrel. Moontlike tekortkominge in die langtermyn kultuur metode vir malaria parasiete wat optimale groei kan belemmer, is ook ondersoek. Plaaslike parasietstamme kon op medium wat verryk is met beesserum onderhou word, alhoewel die groeitempo laer is as wanneer mensserum gebruik word. 'n Toenemende tempo van mediumvervanging soos die parasitemia in kulture toeneem, het getoon dat minder stres op die sisteem geplaas word deurdat die parasiete vir 'n korter periode en aan laer konsentrasies van byprodukte soos melksuur blootgestel word. Die ATP-konsentrasies in gëinfekteerde kulture daal egter met ongeveer die helfte oor 'n groeiperiode van 4 dae. Tesame hiermee, is daar ook 'n daling in die totale adeniel-nukleotied poel van die gëinfekteerde rooibloedsel en 'n styging in die AMP-konsentrasie wat die stres in die gasheersel weerspieël. 'n Verhoging in die intrasellulêre IMP-konsentrasie dui op 'n moontlike inhibisie van die purienherwinningspadweg wat die verlaagde ATP-konsentrasie mag verklaar. Uit die studie blyk dit dus of meer gereelde vervanging van medium en toevoeging van rooibloedselle slegs 'n gedeeltelike bydrae maak tot die suksesvolle vestiging van malariakulture. Die identifikasie van die faktore wat lei tot die inhibisie van die purienherwinningspadweg, verg nog verdere ondersoeke. Die stres wat die parasiet in die menslike liggaam veroorsaak, word ook weerspieël deur onderandere die trombositopenie wat in sommige infeksies waargeneem word. Verhogings in die konsentrasie van trombosiet-geassosieërde immunoglobuliene G en M wat kenmerkend is van die toestand, kan gemeet word deur 'n gemodifiseerde mikrometode wat in ons laboratoriums ontwikkel is. Deur die parasiet-gëinfekteerde pasiët oor 'n paar dae met die mikrometode te monitor, kon die verhoging in trombosiete en afname in trombosiet-geassosieërde antiliggame met herstel van die pasiënt gekorreleer word. Die metode veroorsaak geen skade aan die trombosiete nie sodat antigeenverplasingstudies ook na die tyd gedoen kan word. In 'n ondersoek van die parasiet met behulp van ligmikroskopie, deurstraal- sowel as skandeer-elektronmikroskopie, is gevind dat die plaaslike isolaat moontlik uit 'n mengsel van stamme bestaan, waarvan sommige die vermoë het om knoppe op die rooibloedsel te induseer. Verder het die ondersoek getoon dat indien deurstraal-elektronmikroskopie gebruik word, 'n vinnige fikseringsmetode met gluteraldehied beter is as 'n stadige fikseringsmetode. In vergelyking hiermee kon geen verskil waargeneem word met skandeer-elektronmikroskopie van geparasiteerde rooibloedselle wat met enige van hierdie metodes gefikseer is nie. Copyright / Dissertation (MSc)--University of Pretoria, 1992. / Biochemistry / unrestricted

Mefloquine hydrochloride is an antimalarial agent that has been used for the past 40 years. Numerous reports of neurological side effects have recently led the FDA to issue a strong warning regarding long-term neurological effects. This warning lead to the U.S. Army’s Special Forces and other components to discontinue its use in July of 2013. Despite reported adverse side effects, mefloquine remains in circulation and is recommended to travelers going to specific Asian countries. Mefloquine has been used as a treatment for those already infected with the malaria parasite (blood concentrations ranging from 2.1 to 23 µM), and as prophylaxis (blood concentrations averaging 3.8 µM) (Dow 2003). The purpose of this study was to quantify Mefloquine’s toxicity using spontaneously active nerve cell networks growing on microelectrode arrays in vitro and to identify compounds that alleviate or reduce toxic effects. The current literature on mefloquine toxicity is lacking electrophysiological data. These data will contribute to research on the mechanism of adverse side effects associated with mefloquine use. Sequential titration experiments were performed by adding increasing concentrations of mefloquine solution to cultured neurons. Network responses were quantified and reversibility was examined. In each network, activity decreases were normalized as a percent of reference activity yielding a mean IC50 value of 5.97 ± 0.44 (SD) µM (n=6). After total activity loss, no activity was recovered with two successive medium changes. To test for network response desensitization resulting from sequential applications over 5-6 hr periods, one-point titrations at varying concentrations were conducted with fresh networks. These experiments yielded a single concentration response curve with an IC50 value of 2.97 µM. This represents a statistically significant shift (p < 0.0001) to lower concentrations of mefloquine, demonstrating that sequential applications result in network desensitization. After mefloquine exposures, cells were evaluated for irreversible cytotoxic damage. Over a 12-hour period under 6 µM mefloquine, process beading and granulation of somal cytoplasm were observed. At 8 µM mefloquine cell stress was apparent after only 10 minutes with major glial damage and process beading at 120 minutes. In this study, quinolinic acid served as a neuroprotectant at 20 µM. There have been multiple studies on the endogenous concentrations of quinolinic acid and current literature is quite variable. Immunocompromised individuals have some of the highest blood levels of quinolinic acid (up to 20 µM). With 30 min pre-applications of quinolinic acid, the mefloquine IC50 value shifted from 5.97 ± 0.44 µM (n=6), to 9.28 ± 0.55 µM (n=3). This represents a statistically significant change to higher mefloquine concentrations and demonstrates neuroprotection.

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology and Toxicology Student: Ondrej Tomáš Supervisor: PharmDr. Marie Vopršalová, CSc. Consultant supervisor: mjr. PharmDr. Vendula Hepnarová, Ph.D. Title of diploma thesis: Evaluation of newly prepared insecticides in vitro Malaria is a widespread infection and one of the most dangerous diseases transmitted by insects. It threatens lives of millions of people all around the world, thus its regulation is necessary. Most common malaria vectors are mosquitoes of genus Anopheles. Novel structures of insecticides with selective inhibition of mosquito acetylcholinesterase are subjects of research, with an intention to deal with this problem. The aim of this work was to test six newly prepared succinimide derivatives with insecticidal potential. The ability of these compounds to inhibit Anopheles gambiae mosquito (AgAChE) and human acetylcholinesterase (hAChE) was evaluated. Leading structures of these compounds were also tested to find relations between chemical structure and biological activity. The modified Ellman's method was used to obtain the half maximal inhibitory concentration (IC50) values for both enzymes. Tested substances were able to inhibit only hAChE and none of them displayed activity against AgAChE. Compound...

Charles University Faculty of Pharmacy in Hradec Králové Department of Pharmacology and Toxicology Student: Ondrej Tomáš Supervisor: PharmDr. Marie Vopršalová, CSc. Consultant supervisor: mjr. PharmDr. Vendula Hepnarová, Ph.D. Title of diploma thesis: Evaluation of newly prepared insecticides in vitro Malaria is a widespread infection and one of the most dangerous diseases transmitted by insects. It threatens lives of millions of people all around the world, thus its regulation is necessary. Most common malaria vectors are mosquitoes of genus Anopheles. Novel structures of insecticides with selective inhibition of mosquito acetylcholinesterase are subjects of research, with an intention to deal with this problem. The aim of this work was to test six newly prepared succinimide derivatives with insecticidal potential. The ability of these compounds to inhibit Anopheles gambiae mosquito (AgAChE) and human acetylcholinesterase (hAChE) was evaluated. Leading structures of these compounds were also tested to find relations between chemical structure and biological activity. The modified Ellman's method was used to obtain the half maximal inhibitory concentration (IC50) values for both enzymes. Tested substances were able to inhibit only hAChE and none of them displayed activity against AgAChE. Compound...

The multistage life cycle of malaria-causing P. falciparum is complex, making prevention and treatment difficult. As a result of resistance to many antimalarial drugs, novel compounds with unexplored targets are constantly sought after for the purpose of treating the symptoms of malaria. Here, novel compounds were screened for antiplasmodial activity against the symptom-causing asexual intraerythrocytic malaria-causing parasites. Unfortunately, many novel compounds in the drug discovery pipeline and drugs in clinical use possess underlying pharmacological issues that makes administration challenging. These include low aqueous solubility and short half-life which negatively impact bioavailability resulting in toxicity. This, in turn, increases patient non-compliance and the emergence of drug-resistant strains. Nanoparticles (NP) have the ability to mask drugs from the external environment while increasing circulation time and often alleviate many issues at once. Furthermore, the selected drugs do not need to be modified. Drug conjugation NPs with a targeting ligand and stimuli-responsive linkers have been extensively researched in many diseases, however, none have been reported for malaria clinically. Here, the first acid-labile targeted NP (tNP) that exploits the biology of infected erythrocytes and the specialised food vacuole (FV) of P. falciparum is interrogated for ability to decrease toxicity while retaining antimalarial activity. This dissertation describes the effect of tNPs on the efficacy and toxicity of selected compounds. In vitro haemolysis and cytotoxicity assays revealed that the tNPs are biocompatible to erythrocytes and HepG2 cells. The data also shows that tNPs decrease the toxicity of drugs and the chosen novel compound against human cells. A decrease in antiplasmodial activity was observed in vitro for the tNPs when compared to the novel compound and drugs on their own. However, this was due to the biogenesis of the FV and a shortened window of release. Nonetheless, the NP backbone was not active against P. falciparum intraerythrocytic parasites whereas tNPs were, showing activity due to released drug. The targeting ligand was also not specific for antiplasmodial activity. Although a significant loss in activity is observed, the results presented here suggests that these novel acid-labile tNPs serve as an attractive starting point for targeted treatment of malaria with an improved patient tolerance. Furthermore, novel compounds with issues can be selected without having to be modified or completely discarded. Therefore, increasing the chances of finding a variety of compounds that can be used to treat malaria while keeping patients safe. / Dissertation (MSc (Biochemistry))--University of Pretoria, 2020. / NRF / Biochemistry / MSc (Biochemistry) / Unrestricted

Malaria remains one of the most serious tropical infectious diseases affecting mankind. The prevention of the disease is hampered by the increasing resistance of the parasite to existing chemotherapies. The need for novel therapeutic targets and drugs is therefore of the utmost importance and detailed knowledge of the biochemistry of the parasite is imperative. This study was directed at the biochemical characterisation of the polyamine metabolic pathway of P. falciparum in order to elucidate differences between the parasite and its human host that can be exploited in the design of novel antimalarials. The thesis focussed on the two rate-limiting enzymes in polyamine biosynthesis, S¬adenosylmethionine decarboxylase (AdoMetDC) and ornithine decarboxylase (ODC), which occur as a unique bifunctional complex in P. falciparum. The genomic structure of the bifunctional gene indicated a single, monocistronic transcript with large untranslated regions that were predicted to be involved in unique translational regulatory mechanisms. This gives rise to a bifunctional protein containing both decarboxylase activities on a single polypeptide forming a heterotetrameric complex. Activity of the decarboxylases decreases dramatically if these proteins are expressed in their monofunctional forms as homodimeric ODC and heterotetrameric AdoMetDC. The deduced amino acid sequence indicated that all the essential residues for catalysis are conserved and highlighted the presence of three parasite-specific insertions. The parasite-specific inserts were shown to be essential for the catalytic activity of the respective domains and also to influence the activity of the neighbouring domain, indicating that intramolecular communication exists in the heterotetrameric complex. The most structured and smallest insert was also shown to mediate protein-protein interactions between the two domains and to stabilise the complex. Further structure- functional characterisations of specifically the ODC domain were deduced from a comparative homology model. The model predicted an overall structure corresponding to those of other homologous proteins. The validity of the model is supported by mutagenesis results. However, certain parasite-specific properties were identified in the active site pocket and dimerisation interface. The former was exploited in the rational design of novel putative ODC inhibitors directed only against the P. falciparumprotein by in silico screening of chemical structure libraries. This study therefore describes the identification of certain parasite-specific properties in a unique bifunctional protein involved in regulation of polyamine metabolism of P. falciparum. Such discoveries are invaluable in strategies aimed at elucidating biochemical and metabolic differences between the parasite and its human host that could be exploited in the design of alternative, parasite-specific chemotherapies. Moreover, the thesis also contributed new knowledge on certain less well-understood biological phenomena characteristic of P. falciparum, the nature and origin of bifunctional proteins and the functional properties of parasite-specific inserts found in some proteins of the parasite. / Thesis (PhD (Biochemistry))--University of Pretoria, 2002. / Biochemistry / unrestricted