3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item An approach to the evaluation of iron status and the prevention of iron deficiency(1981) Macphail, Andrew, PatrickThis thesis took advantage of the very wide spectrum of iron status encountered amongst the people of Southern Africa. Established methods of measuring iron status were used to illustrate features of dietary iron overload, iron deficiency and the relationship between maternal and infant iron status. Attention was also paid to the prevention of iron deficiency in the heterogeneous South African population. In a comparative autopsy study measurement of hepatic iron showed a significant reduction in the prevalence and severity of dietary iron overload in urban black males over the past 17 years. Although hepatic iron concentration rose with age, there had been no iron accum ulation during this period. Liberalisation of the Liquor Laws has resulted in a decrease in the consumption of traditionally brewed, iron-rich, maize-sorghum beer. The resulting increase in spirit consumption has increased the prevalence of portal fibrosis and cirrhosis. Iron overload was significantly greater in subjects dying from carcinoma of the oesophagus and idiopathic heart failure suggesting excessive exposure of these subjects to traditionally-brewed iron-rich beverages. Serum ferritin concentration, an established measure of iron stores, was used to illustrate an age-related rise in iron stores in a sample of rural black male South trations greater than 200 ^g/l and comparison with the urban autopsy study indicated that iron overload is currently more severe in rural than in urban black males. Geographical differences in serum ferritin concentration showed that iron overload was less common in the northern regions of Southern Africa. Measurements of iron stores, iron deficient erythropoiesis and haemoglobin concentration were necessary to give a comprehensive evaluation of the iron status of a sample of women taken from the South African Indian population. Nearly half the women had evidence of depleted iron stores while the prevalence of iron deficiency anaemia was 14 per cent. Improvement in iron status was related to age and reduced duration of menstruation. A profile of iron status based on the cumulative distribution of calculated iron stores showed that the sample had median iron stores of 150 mg with lower and upper 10 percentiles of -355 mg and 655 mg. Serum ferritin, iron, haemoglobin and placental non-haem iron concentrations were used to study the relationship between maternal and infant iron status at birth. Correlations, similar to those seen in adults, showed that cord serum ferritin concentrations reflect neonatal iron stores. However, its indirect correlation with cord haemoglobin concentration (r = -0.35) suggests that the amount of iron in foetal stores is influenced by that required for haemoglobin and that low serum ferritin concentrations' * do not necessarily indicate reduced iron transfer. Placental non-haem iron was related to maternal serum ferritin concentration (r = 0.^1) but not to measurements of foetal iron status suggesting that stored placental iron is not available to the foetus. Finally the possibility of preventing iron deficiency in the Indian population through the fortification of food with Fe(lll) EDTA was studied. In comparative studies with ferrous sulphate, iron absorption from Fe(lll) EDTA was shown to be significantly less influenced by inhibitors in maize porridge and by bran. Ascorbic acid did enhance absorption but, paradoxically, increased the inhibitory effect of maize porridge. Although curry powder (masala), which is used in large quantities by the Indian population, enhanced iron absorption from both ferrous sulphate and Fe(lll) EDTA, absorption from Fe(lll) EDTA was significantly higher. Evidence that the mechanism whereby Fe(lII) EDTA forms a common pool with intrinsic iron differs from that occurring with simple iron salts, was provided by both the marginally higher absorption from Fe(lll) EDTA than from intrinsic food iron and by studying the exchange of iron between ^Fe(lIl) EDTA and ^FeSO^. This was shown to occur in vitro and the appearance of small amounts of radio-labelled Fe(lll) EDTA in the urine served to demonstrate that the exchange also took place during absorption. p It is concluded that Fe(lll) EDTA may be a useful compound for food fortification of cereals because the iron is well absorbed and utilized for haemoglobin synthesis. The substances in cereals which inhibit absorption of simple iron salts do not appear to inhibit absorption of iron from Fe(lll) EDTA. In addition, the combination of Fe(lll) EDTA and masala as a fortification vehicle is seen to be particularly suitable for a fortification programme in South Africa where such a wide range of iron status is f ound.Item Iron and Malaria(1997-02-07) Van Zyl, Robyn L.Malaria is one of the most devastating infections found in man and the resurgence of drug resistance has prompted the search for novel chemotherapeutic strategies. Clinical observations have exposed the susceptibility of malaria parasites to iron deficiency, thus the metabolism of iron in parasitized erythrocytes could be a potential antimalarial target. In in vitro experiments, the parasites accumulated approximately four times more non-transferrin-bound iron than diferric transferrin. Both forms were accumulated in a concentration- and time-dependent manner, with more iron being associated with the trophozoite stage than the ring stage. The ferric iron chelating agent, desferrioxamine inhibited the uptake of transferrin and non-transferrin-bound iron in a concentration dependent manner. 2,2’-Bipyridyl, a ferrous iron chelating agent also inhibited the uptake of non-transferrin-bound iron, but did not affect the uptake of diferric transferrin. This indicated that the parasite does not accumulate diferric transferrin by transferrin-receptor mediated endocytosis, but rather by a non-specific endocytotic pathway. A large quantity of the accumulated iron was associated with the parasite haemozoin. Desferrioxamine effectively reduced the amount of iron associated with the haemozoin, whilst 2,2’-bipyridyl did not, which indicates that the haemozoin-associated iron is in the ferric state. The parasitized erythrocytes were more susceptible to haemolysis by the haemozoin subunits than the uninfected erythrocytes. The presence of chloroquine and 2,2’-bipyridyl potentiated the haemolysis induced by the subunits, whilst desferrioxamine protected the parasitized erythrocytes. The plasma chelating agents and aminocarboxylate compounds were not as effective in inhibiting parasite growth, as desferrithiocin, bathophenanthroline, desferrioxamine and 2,2’-bipyridyl which avidly chelate iron. The additive interaction between the latter two agents and chloroquine, quinine and pyrimethamine, completely eliminated the malaria infection. As did the combination of two lipophilic ferrous or two hydrophilic ferric iron chelating agents, as well as the combination of a hydrophilic ferric and lipophilic ferrous iron chelating agent. Whilst the combination of hydrophilic ferric and hydrophilic ferrous iron chelating agents antagonised each others antimalarial actions. Variables such as inoculum size, extracellular pH, cation supplementation and stage dependency, all affected the antimalarial activity of the iron chelating agents. Thus, the unique pathways involved in the iron metabolism of P. falciparum-infected erythrocytes, could be potential targets for new antimalarial drugs, which are membrane permeable and avidly chelate iron.Item The increasing role of direct reduced iron (DRI) in global steelmaking(1997) Grobler, FrancoisThis report gives an overview of the role and use of directly reduced iron (DRI/HBI) used in the electric arc furnace (EAF) steelrnaking route as a substitute to the traditionally favoured ferrous scrap. A comparison of the main steelmaking technologies showed that the electric arc furnace (EAF) has emerged as the preferred route for producing steel since the early 1900's. Due to its lower costs, scale and flexibility, it is expected to outgrow the conventional steelmaking method based on the blast furnace and basic oxygen converter in the next century. A look at historical steelmaking patterns showed that electric arc steelmaking has relied almost entirely on ferrous scrap as Its primary feedstock up to the present time. This traditionally low-priced commodity has in tha past fulfilled the steelmakers' criteria in terms of quantity and quality. Investigation of the current situation, however, showed the mounting pressure on high quality scrap more recently, with the subsequent rise in the price as well. The most important factors contributing to the tightness in scrap availability proved to be the increasing popularity of the EAF, and especially the "mini-mills", accompanied by improvements in technology such as continuous casting (CO) and near net shape casting (NNSC). This has forced EAF steelmakers to consider other Substitutes such as direct reduced iron (DR!) and pig iron, not just as an alternative to scrap. but as an effective blending material to reduce residual elements in the scrap melt. A comparison of different metal charges in the EAF showed that the blending of DRI with scrap enabled the steelrnaker to utilise the move abundant, less expensive, lower quality scrap grades, whilst maintaining quality requirements. A study of the trends in DRI technologies indicated that the gas-based technologies, such as Midrex and HyL, still dominate the market for DRI, as they have in the past, enjoying economies of scale and other favourable cost advantages. It appears as if coal-based processes have traditionally encountered constant economical problems, which disabled them in competing with those based on gas. Another trend of the past was the high proportion of captive DRI production, compared to the very limited amo...merchant product available on the market. That was the status quo in past years. The present situation seems to be different. It appears as if that current problems with scrap availability and quality is actually paving the way for the use of DRI. Prices asked for good quality scrap are on the way upwards as steelmakers frantically search for low-residual, reasonably priced iron units. This has lead to a multitude of new DRI projects, either being built, planned, or considered, aimed at fulfilling this demand. Some of the new projects are based on older, tested technologies, but the amount of new projects based on newer, customised technologies that utilise low-cost fines, non-coking coal and other incentives to minimise costs seems to be increasing as well. Another change in the past trend lies in the large proportion of the new non-captive capacity that will come on stream, specifically aimed at the merchant market. The most critical determinant for such a merchant DRI project is its location. The strategic positioning of it in terms of its raw materials i.e. iron ore, natural gas, coal etc., as well as its location with regard to the potential market, will determine whether it will be competitive or not. Operating costs are considered and compared to determine the competitive advantages with regard to different location- and technology options. Additionally, it seems as if the successful DRI producer of the future will be the one who, apart from optimising its position, will minimise cost by utilising low-cost iron ore fines, cheap low-grade coal, nas recycling and many other cost cutting incentives vigorously explored by all DR technology producers in recent years. In summary, there proves to be an increasing need for DRI and other scrap substitutes in the steelmaking industry and such projects will definitively have a market in the future, but care must be exercised in the decision on the location, and other cost-contributing determinants of such facilities. Another potentially dangerous situation stems from the fact that this "hungry" market, although currently undernourished, is ultimately not insatiable, and care must be taken to prevent the development of a massive oversupply, which could cause imbalances in the market again. In any event, with all the new merchant product coming into the market, it seems evident that DRI will develop its own spot market, and competition between different DRI technologies, as well dS with scrap will become fierce in the future.Item Iron storage in the neonatal period of the human infant(1950) Van Dongen, L. G. R.Iron is one of the vital elements of the human body. Without it respiration would be quite impossible. Haemoglobin, the transporter of oxygen throughout the body, has iron as an essential constituent, and it is in this protein complex that the greatest bulk of the metal is found. Iron also plays a very essential part in the respiration of the tissues, as it is a vital element in intracellular respiratory enzymes such as catalase, cytochrome, cytochrome oxidase, etc. Further it is found in the chromatin material of nuclei in the cells of all the tissues.Item The role of ferritin in iron absorption(1967-01) Torrance, J. D.Although reports of the medicinal use of iron date back to ancient times it was not until the present century that the many functions of iron in the body were studied. Once started, the investigation received impetus from the seriousness of iron deficiency anaemia, a major cause of ill health throughout the world. The introduction of radio-isotope tracer techniques in 1939 greatly facilitated investigation of absorption, excretion and the metabolic pathways of iron. The tremendous amount of work already carried out has led to a fairly comprehensive knowledge of the various aspects of iron metabolism. Nevertheless, there remain wide gaps in the overall picture. InItem Reticuloendothelial ferritin messenger RNA in inflammatory states(1989) Lapinsky, Stephen. E.Ferritin is an iron storage protein, made up of heavy (H) and light (L) subunits. Ferritin synthesis is regulated at a post transcriptional level by iron, which induces a redistribution of ferritin mRNA from a free cytoplasmic pool to polyribosomes. Inflammatory states influence iron metabolism, causing a decrease in serum iron levels associated with an increase in reticuloendothelial ferritin synthesis and iron storage.Item Factors involved in the handling of iron by the reticulo-endothelial system(1972) Lipschitz, D. A.For centuries iron was regarded as a source of health and vigour, and it has been known for at least 200 years that it is a component of blood and effective in the treatment of chlorosis. However, its metabolism remained largely a mystery until the advent of radioactive iron isotopes in 1938. Since then most of the major pathways of this metal into, through and out of the body have been elucidated. In addition the functions which it subserves have been partially characterized.Item An in vivo and in vitro study of some luminal and cellular factors influencing iron absorption(1966-03) Jacobs, PeterAlthough the various factors which influence the absorption of iron from the gastrointestinal tract have been extensively investigated, there still remains uncertainty concerning several basic aspects of this processItem Body iron excretion(1975-05-19) Green, RalphAn attempt was made to document iron losses from the body as a whole, as well as from individual excretory routes using a combination of radioisotopic and chemical techniques. The purpose of this work was to gain a better understanding of external body exchange, and to resolve some of the existing controversies regarding the magnitude of daily iron losses. The basis for this controversy is extensively reviewed in the thesisItem The relationship between iron nutrition and the factors present in vegetable and cereal foods that affect iron absorption(1986) Gillooly, Mary . A.The iron nutrition of populations is largely determined by the quality of the diet consumed. As this is frequently cereal or vegetable based, the interplay of the different enhancers and inhibitors that influence iron absorption from the "common pool" of non-haem iron assumes a profound significance in iron nutrition. This thesis took advantage of the widespread occurrence of iron deficiency among Indian women in Natal to establish more clearly the factors in frequently consumed foods which affect iron absorption.