Browsing by Subject "San (African people)"

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    Diamphotoxin : the arrow poison of the !Kung Bushmen
    (1980) De la Harpe, Jonathan H; Dowdle, Eugene B
    In this thesis I describe a toxic protein, diamphotoxin, that is present in the pupae of the beetle Diamphidia nigro-ornata. This insect is used as an arrow poison by the !Kung Bushmen inhabiting the savannah of eastern Namibia and western Botswana. Preliminary investigations showed that the pupae contained a 3,7 S cationic protein which caused haemolysis and, after intramuscular injection, local paralysis followed by death. By intravenous lethality assay, one 200 mg pupa contained 20 000 mouse lethal doses. Assays for the toxin were developed based upon haemolysis in vitro and lethality in vivo. These assays were used to monitor purification of the toxin. Diamphotoxin was purified by acid extraction in 0,1M glycine-HCl pH 3,0 followed by ammonium sulphate fractionation, chromatography on hydroxyl apatite, phosphocellulose and, finally, on DEAE cellulose. A consistent increase in activity after the hydroxyl apatite chromatography pointed to the removal of an inhibitor during this step. A subsequent severe loss of activity after chromatography on phosphocellulose could neither be explained nor overcome. The phosphocellulose chromatography step yielded three peaks of toxic activity. Immunological studies revealed cross-reactivity but not identity between these three toxin species. The toxin in the first peak to elute from the phosphocellulose column was purified to electrophoretic homogeneity by chromatography on DEAE cellulose. Attempts to purify the toxin in the other two phosphocellulose peaks were not successful. The isolated molecule was confirmed to be the toxin by haemolysis in a blood-agarose underlay after SDS-gel electrophoresis. The molecular weight estimate for the toxin by SDS-gel electrophoresis was 60 700 daltons and by analytical ultracentrifugation 62 100 daltons. The molecule appeared to exist as a single polypeptide chain. The amino acid composition showed a high proportion of hydrophobic amino acids. Isoelectric focussing showed an isoelectric point of pH 9,45. Toxin mediated haemolysis was studied in detail. The haemolytic event could be broken down into two stages. In the first stage toxin bound irreversibly to the cell but, provided no divalent cations were present, no damage to the cell could be detected. The second stage required the presence of free calcium (or certain other divalent cations), with an optimum concentration at 1 mM. The interaction of calcium with the cell-bound toxin resulted in the cell membrane becoming highly permeable to Na⁺ and K⁺ ions. Experiments designed to detect phospholipase or protease activity in toxin solutions gave negative results. Erythrocytes incubated with ¹²⁵I-labelled pure toxin in calcium-free medium retained a quantity of bound toxin which could not be removed by repeated washing. Incubation of erythrocytes with calcium-free toxin resulted in depletion of the activity of the toxin solution. The kinetics of the haemolytic action of the toxin were shown to be stoichiometric rather than catalytic. It was estimated that haemolysis by the toxin required a minimum of approximately 100 molecules per cell. Studies using circular dichroism measurements and the fluorescent probe 8-anilino-1-naphthalene sulphonic acid (ANS) indicated that a conformational change occurred in the toxin upon exposure to calcium. The ANS studies indicated that upon the addition of calcium the toxin molecule became more hydrophobic. It was concluded that the toxin functions as a calcium regulated Na⁺ and K⁺ ionophore in that it binds to the cell membrane and, in the presence of calcium or certain other divalent cations, assumes a conformation which mediates the free passage of Na⁺ and K⁺ ions. The resultant disruption of normal transmembranous ionic concentration gradients leads to cell lysis by loss of osmoregulation and, in the case of excitable membranes, disruption of electrophysiological activity.
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    The social and gender identity of gatherer-hunters and herders in the Southwestern Cape
    (1996) Anderson, Gavin Craig; Hall, Martin; Du Preez, Peter; Parkington, John
    Southern African archaeology has experienced several changes in theoretical perspectives over the past few decades. More recently there have been renewed calls for a more social and theoretical approach to the analysis of the prehistoric past, especially the Late Stone Age. This thesis is an account of the last 4000 years in the southwestern Cape, where material culture is analysed in terms of contextual meaning. Contextual meaning is used in conjunction with social identity theory to analyse the interaction between Khoi herders and San gatherer-hunters. I use the active processes of identity formation and maintenance to argue that both the isolationist and revisionist arguments have simplified the concepts of identity, where identity is seen to have a passive role in interaction. I argue that identity is dynamic and changeable, and that individuals have several social identities which are made salient according to the context of interaction. I use specific fine line images in the rock art to argue that these images, in conjunction with scraper styles, were used as strategies by San males to increase their self-esteem. I further argue that interaction would result in unequal gender relations and San females used specific adzes to reassert their gender identity within San society. I further argue that finger paintings and handprints may have been painted by Khoi females as part of their menstruation and/or menarche rituals. I use both the gender and social identities from the Khoi and the San to argue that these are interrelated and cannot be separated. I argue that interaction would result in unequal gender and social practices and these practices would be expressed in the material culture of that group.