3. Electronic Theses and Dissertations (ETDs) - All submissions

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Start date: 1970End date: 1979

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    The Morphology and Transport of Mucus in Mammalian Airways.
    (1975) Andre William Wessels van As
    The mucociliary clearance mechanisms in mammalian pulmonary airways have been re-examined. In this investigation Wistar rats, housed both under specific pathogen free (SPF) and normal animal house conditions, were examined. An intact airway . system from the trachea down to the level of the terminal bronchioles was used. The airway preparation was rapidly isolated and examined under carefully controlled in vitro conditions. Specimens remained viable for at least 10 h. Mucociliary activity was observed through the intact bronchial wall with the aid of incident light. This function could be examined at all levels of the pulmonary tree in the same specimen. In contrast to the previously described presence of a continuous mucous bl~ket, the morphology of mucus in the airways of the rat has been shown to be discontinuous. Mucus is present as discrete particles of varying size. Under the light microscope these particles appeared to fall into three categories: droplets less than 4 μm in diameter; flakes 10-70 μm in diameter; and plaques which are conglomerations of droplets and flakes. Scanning electron microscopy reveals that droplets (i.e. single particles) may be as small as 0,5 μm and that composite particles made up of numerous aggregated droplets may be as small as 5 μm in diameter. Plaques are conglomerations of these particles. In the normal intrapulmonary airways only smaller particles are seen and are transported over the individual metachronal fields. In the larger extralobar airways these particles move together to be transported in well defined streams which may be up to 500 μm wide. These streams may follow a winding course up the trachea and more than one may be in operation at a time. Under conditions of hypersecretion such as occurs with chronic respiratory disease in rats (CRD) the number of particles increase peripherally and plaques may be found in small airways. The transport of mucus is however still intermittent and it never becomes confluent. Acute bronchitis results in wide-spread abnormalities of ciliary activity and mucus transport, which leads to total disorganisation of pulmonary clearance. "Chronic bronchitis" associated with CRD results in more organised abnormalities of mucociliary activity. Cilia may become inactive, reverse the .direction of their effective stroke, beat retrogradely, and exhibit abnormal beat patterns which result in impaired mucus clearance. Squamous metaplastic areas further impede mucus transport. In general mucus transport rates were found to be faster in rats with "chronic bronchitis" than SPF rats, provided that the extent of the damage to the mucous membrane was ( not too great in the "bronchitic" animal. This finding was confirmed by the examination of airway preparations approximately 19 h after the exposure to a charcoal aerosol. While significant amounts of charcoal were retained at the bifurcations of bronchi in SPF rats, most of the charcoal was cleared in "bronchitic rats'.'. The only areas where particles were seen were on bronchitic patches or on whirlpools. The findings of this study indicated that mucus was present in a discontinuous form, and that in both SPF and non-SPF animals no evidence for a mucous blanket was found.
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    The Morphology and Transport of Mucus in Mammalian Airways.
    (1975) Andre William Wessels van As
    The mucociliary clearance mechanisms in mammalian pulmonary airways have been re-examined. In this investigation Wistar rats, housed both under specific pathogen system frfroeme (tShPeFt)raacnhdeanodrmowanl taonimthael lheovuelseofcotnhdeititoenrms, inwael rbe roexnacmhiionleeds . wAans uinsetadc. t airway The airway preparation was rapidly isolated and examined under carefully controlled in vitro conditions. Specimens remained viable for at least 10 h. Mucociliary activity was observed through the intact bronchial wall with the aid of incident light. This function could be examined at all levels of the pulmonary tree in the same specimen. In contrast to the previously described presence of a continuous mucous bl�ket, the morphology of mucus in the airways of the rat has been shown to be discontinuous. Mucus is present as discrete particles of varying size. Under the light microscope these particles appeared to fall into three categories: droplets less than 4 µm in diameter; flakes 10-70 µm in diameter; and plaques which are conglomerations of droplets and flakes. Scanning electron microscopy reveals that droplets (i.e. single particles) may be as small as 0,5 µm and that composite particles made up of numerous aggregated droplets may be as small as 5 µm in diameter. Plaques are conglomerations of these particles. In the normal intrapulmonary airways only smaller particles are seen and are transported over the individual metachronal fields. In the larger extralobar airways these particles move together to be transported in well defined streams which may be up to 500 µm wide. These streams may follow a winding course up the trachea and more than one may be in operation at a time. Under conditions of hypersecretion such as occurs with chronic respiratory disease in rats (CRD) the number of particles increase peripherally and plaques may be found in small airways. The transport of mucus is however still intermittent and it never be­ comes confluent. Acute bronchitis results in wide-spread abnormalities of ciliary activity and mucus transport, which leads to total disorganisation of pulmonary clearance. "Chronic bronchitis" associated with CRD results in more organised abnormalities of mucociliary activity. Cilia may become inactive, reverse the .direction of their effective stroke, beat retrogradely, and exhibit abnormal beat patterns which result in impaired mucus clearance. Squamous metaplastic areas further impede mucus transport. In general mucus transport rates were found to be faster in rats with "chronic bronchitis" than SPF rats, provided that the extent of the damage to the mucous membrane was not too great in the "bronchitic" animal. This finding was confirmed by the examination of airway preparations approximately 19 h after the exposure to a charcoal aerosol. While significant amounts of charcoal were retained at the bifurca­ tions of bronchi in SPF rats, most of the charcoal was cleared in "bronchitic rats .The only areas where particles were seen were on bronchitic patches or on whirlpools. The findings of this study indicated that mucus was present in a discontinuous form, and that in both SPF and non-SPF animals no evidence for a mucous blanket was found.
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    Sedimentological control of gold and uraninite mineralisation in the White Reef of the West Rand
    (1975) Steyn, L S
    The primary objective of the study was to determine the controls of mineralization in the White Reef, which occurs at the base of the Bird Reef Stage of the Upper Witwatersrand System on the West Rand. It is a quartzite with scattered pebbles and occasional 'banket' conglomerates. The average gold content at 317 gm-cm per tonne is low, but uranium grade is amongst the highest on the Witwatersrand. In 1963 the author demonstrated some sedimentological properties of the Livingstone Reef are qualitatively related to gold content. More intensive studies have since confirmed the sedimentological control of gold mineralization. For instance, Pretorius (1974 a, 1975) recognizes a general fluvial fan geometry for the Witwatersrand reefs. However other factors, such as variations in environments, mechanisms of deposition, and behavior of the heavy minerals require further clarification; these form the main subject matter of this study. A pilot study established interrelationships between sedimentary features and ore grade. Follow-up work revealed systematic downslope changes. The reef was sampled on a systematic grid over the four West Rand mines. All pebbles were measured over complete reef sections. Measurements include 526 of reef thickness, 1 312 of crossbedding, 45 ripple marks, 2 of sand waves, 63 801 of pebble size and sorting, 63 761 for packing, 1 200 of fabric, 33 987 of composition, and 1 162 of shape and sphericity. Very large numbers of gold and uranium values, reef elevations, and thicknesses were compiled from records. The area investigated formed a subsiding part of a basin edge between granitic buttresses. Primary structures include the north-south Randfontein trough in the west, which controlled sedimentation from the Main Reef Stage onwards and the smaller north-east trending Witpoortjie trough. Additional control was exercised later by northeast and northwest-trending depressions. The major West Rand syncline running north-west, and the basin north of the Witpoortjie fault, are post-depositional features. The White Reef is comparable in geometry and sedimentological features to the Basal Reef (Sims, 1969) and generally conforms to the model of Pretorius (197 5). The subsiding Randfontein trough controlled the direction of major pay shoots, whilst smaller paystreaks formed along braided channels. The paleo-environment for the White Reef was that of a braided fluvial fan conforming to the model of Eynon and Walker (1974) for braided rivers. The distribution of depositional facies is related to fan geometry. (Abbreviations abstract)
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    Comparison of activities, electrophoretic patterns and kinetic properties of some enzymes in normal and cancerous liver
    (1976-11) Hammond, Kathryn D.
    Glucose present in tissues is metabolised either by means of glycolysis, gluconeogenesis, glycogenesis or glycogenolysis, as shown in Figs. 1 and 2. Glycolysis occurs in almost all tissues, whereas gluconeogenesis is restricted mainly to liver and kidney cortex; the synthesis and degradation of glycogen takes place mainly in liver, skeletal muscle and heart. The patterns of carbohydrate metabolism characteristic of normal tissue are often altered in various diseased states; this is particularly evident in cancer. Tumour tissues, such as hepatoma, appear to lose the functional properties of adult differentiated tissue and their metabolism often seems to resemble that of rapidly-dividing, undifferentiated foetal tissue.
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    A study of some cultural characteristics and blood serum antibody titres of enterococci isolated from the mouth and faeces
    (1975-06) Slabbert, J.C.G.
    Crevicular epithelium presents no effective barrier to the biologically active constituents of plaque. Moreover, it seems that the production of circulating antibodies, the development of a state of delayed hypersensitivity and the development of immunological tolerance all play a part in the pathogenesis of periodontal disease. An investigation was undertaken to study the cultural characteristics of enterococci isolated from the mouth and gut of a group of students, and to determinethe serum antibody titres to these organisms. Enterococci were isolated from faeces and the gingival crevice of 9 male dental students. Blood was obtained from each subject and allowed to clot. The serum was removed and stored at -20°C until required. Blood serum antibody titres to the bacteria were obtained by the indirect fluorescent antibody technique.
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    Physico-chemical properties of titaniferous iron-making slags under neutral and under reducing conditions
    (1974) Van Der Colf, Jacobus Cornelius Gideon Kotze.
    Available data on particularly viscosities of titaniferous melts under oxidizing conditions are reviewed, and an attempt is made to explain the high fluidity of such melts. (Abbreviation abstract)
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    A taxonomic and ecological study of the living and fossil hystricidae with particular reference to Southern Africa.
    (1976) Maguire, J. M.
    The taxonomy of modern and fossil Hystricidae and the evolutionary history of the family has been reviewed, with particular reference to 203 undescribed South African specimens from the Transvaal australopithecine deposits and Cave of Hearths. After comparison with all contemporaneous fossil forms (only 10 of the 28 described fossil species seem valid) it was concluded that Xenohystrix crassidens Greenwood 1955, Hystrix makapanensis (Greenwood 1958) and H. africaeaustralis Peters 1852 are present at Hakapansgat Limeworks, whereas only the latter species is present at the remaining australopithecine sites, with the possible exception of a few tentatively referred specimens of H. makapanensis. There are insufficient grounds for erecting a distinct species for the fossil form of H. africaeaustralis present in the australopithecine deposits and the Cave of Hearths material is likewise referred to the modern species. The distribution and minimum numbers of individuals of porcupine species present in the different breccias of the five sites is detailed and a reconstruction of the skull and mandible of X. crassidens attempted. The environment, stratigraphy and potential ages of the source deposits is discussed; it is concluded that with the exception of Taung, the dates suggested by Partridge and Vrba agree with the limited evidence provided by the fossil Hystricidae. Numerous skull characters used in the diagnoses of new Hystrix were examined for variability within a single modern species (only 3 of the 77 extant species proved to be valid) and then tested for diagnostic significance by comparison with the remaining valid species. Special attention was paid to mandibular and dental characters, particularly the crown enamel pattern, but the only reliable diagnostic characters were found to be associated with the anterior part of the cranium, which is seldom preserved in fossil form. The sequence of tooth replacement, a method for identifying isolated teeth, methods for segregating specimens into growth stages, and a standard terminology have been outlined. A taphonomic study, attempting to determine the extent to which fossil porcupines may have been responsible for the accumulation of the Makapansgat Limeworks bone assemblage and for the manufacture of the bone tools described by Dart, was undertaken. Unlike the fossil assemblage porcupine bone accumulations are characterized by a high percentage of much-gnawed bones, a large average fragment size, a high proportion of intact shafts with the concomitant near-absence of bone flakes anci a low survival potential for the articular ends of all limb bones. Comparison showed that the damage done by porcupines differs from that evident on the corresponding skeletal elements from Makapansgat. It is concluded that fossil porcupines had very little to do with either the accumulation or fracture of the Makapansgat Limeworks bones.
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    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.
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    Body iron excretion
    (1975-05-19) Green, Ralph
    An 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 thesis
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    Some physiological aspects of iron transport - studies on the fortification of sugar with iron
    (1976) Disler, Peter, Barry
    An attempt was made to fortify sugar with iron in order to prevent the development of iron deficiency. It was possible to add various iron salts and ascorbic acid to sugar without discolouring the vehicle even after storage for many months under hot humid conditions. The absorption of iron from fortified sugar and cereal meals was then measured in human volunteers using either an "extrinsic tag" to label the iron compound or intrinsically labelled food iron.
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