Browsing by Author "Swart, P."

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    Degradation of synthetic xylan effluent using a membrane bioreactor
    (Academy of Science for South Africa, 2003) Edward, V. A.; Pillay, V. L.; Swart, P.; Jacobs, E.; Singh, S.
    We have built a novel membrane bioreactor for the degradation of synthetic xylan effluent. The reactor contains 30 internally skinned polysulphone membranes as an immobilization matrix for xylanase, the degrading agent, and was constructed with stainless steel to withstand high temperatures, as Thermomyces lanuginosus SSBP xylanase has an optimum temperature of 50°C. Overall, 85.1% of the xylanase was immobilized onto the polysulphone membranes by adsorption. Preliminary results showed that the immobilized enzyme was capable of degrading the xylan effluent. Prior to contact with xylanase, there was 0.0 μg ml-1 xylose, 14.2 μg ml-1 xylobiose and 7.2 μg ml-1 xylotriose present in the xylan effluent. After 180 min, the xylose, xylobiose and xylotriose concentrations were 246, 103 and 91 μg ml-1, respectively. Substantial increase in degradation products is promising for the development of a larger-scale bioreactor for effluent treatment.
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    Evaluation of production and reproduction of three South African Angora goat CYP17 genotypes
    (South African Society for Animal Science, 2017-06-05) Snyman, M. A.; Storbeck, K-H.; Swart, P.
    Two CYP17 genes, located on different loci and expressing enzymes with significantly different activities, have been identified in the South African Angora goat population. Three unique genotypes (named He, Hu, and Ho), which differed not only in the genes encoding CYP17, but also in copy number were subsequently identified in the Angora goat. The aim of this study was to evaluate the production and reproduction performance of these three genotypes. Bodyweight, fleece and reproduction data, and blood samples from 466 Angora ewes from three flocks were obtained from the GADI-Biobank. Data had been collected on Flock 1 from 2000 to 2015, Flock 2 from 2000 to 2014 and Flock 3 from 2000 to 2010. Bodyweight data included birth weight, weaning weight, 8-, 12-, and 16-month bodyweight, as well as bodyweight recorded annually for the ewe flock before mating. Fleece data included fleece weight and fibre diameter recorded at the second and third shearings at 12 and 18 months old, respectively. Fleece weight, fibre diameter, style and character were also recorded annually for the ewe flocks during the winter shearing. Individual reproduction records included information on whether the ewe had kidded, whether the ewe had aborted, number of kids born, stillborn kids, kids that died soon after birth, kids reared by a foster mother, kids reared as orphans, number of kids weaned and total weight of kids weaned. Total lifetime reproductive performance of genotyped ewes was calculated for number of kids born, number of kids weaned, and total weight of kids weaned. Blood samples were also collected from 100 sexually active Angora rams from four sources. CYP17 genotyping was carried out using an ARMS-qPCR (amplification refractory mutation system qPCR) assay. Serum testosterone was quantified using high performance liquid chromatography mass spectrometry. The distribution of the ewes across the three CYP17 genotypes was 36.7% He, 51.5% Hu, and 11.8% Ho, and was in accordance with the distribution of the Angora veld rams (38.0% He, 46.4% Hu, and 15.6% Ho). In this study, animals of the Hu genotype were heavier from weaning age onwards, although this difference in bodyweight was significant only at 8 months old and in the adult ewes. No differences were observed between the He and Ho animals. Adult ewes of the He genotype (1.35 kg) produced heavier (P <0.05) fleeces than the Hu (1.27 kg) and Ho (1.24 kg) genotypes. Fibre diameter of the fleeces of the Ho ewes (33.0 μm) was higher than that of the fleeces of the He ewes (32.2 μm; P <0.05) and the Hu ewes (32.7 μm; P >0.05). No significant differences were recorded in reproductive performance among the genotypes, although the Ho ewes had the lowest (1.03 and 0.89) and the He ewes the highest (1.07 and 0.93) number of kids born and weaned per year respectively. Results on the rams indicated that the CYP17 genotype had no effect on testosterone production by Angora rams. From the results of this study no evidence could be found that selection for any of the three genotypes would adversely affect any growth, mohair production or reproduction function of Angora ewes. A breeding strategy incorporating selection for productive traits and the CYP17 genotype, aimed at increasing the frequency of the ACS+ gene and thus the He genotype in the population, could be followed without having a negative effect on the genetic progress of productive traits.
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    Inhibition of cytochrome P450c11 by biogenic amines and an aziridine precursor, 2-(4-acetoxyphenyl_-2-chloro-n-methyl-ethylammonium chloride
    (Informa Healthcare, 2000) Louw, Ann; Allie, F.; Swart, A. C.; Swart, P.
    The interaction of several biogenic amines and Compound A (2-(4-acetoxyphenyl)-2-chloro- N-methyl-ethylammonium chloride), an analogue of the active substance in a HPLC fraction isolated from the shrub, Salsola tuberculatiformis Botsch., with cytochrome P450c11 was investigated. Noradrenaline, octopamine and Compound A inhibited the type I DOC induced difference spectrum of P450c11 and elicited a type II difference spectrum when added alone. The Ks-values for noradrenaline, octopamine, and Compound A were 0.8 mM, 0.16 mM and 0.36 mM, respectively. Dopamine, adrenaline and synephrine did not interact with, or inhibit, P450c11. Further investigation of Compound A indicated that it is a mixed inhibitor of sheep P450c11 with a stronger competitive (Kic = 106-110 µM) than uncompetitive (Kiu = 667-737 µM) element.
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    Modulation of Hepatic Drug Metabolizing Enzymes and Oxidative Status by Rooibos (Aspalathus linearis) and Honeybush (Cyclopia intermedia), Green and Black (Camellia sinensis) Teas in Rats
    (2003) Marnewick, J. L.; Joubert, E.; Swart, P.; Der Westhuizen, F. V.; Gelderblom, W. C.
    Rooibos and honeybush teas significantly (P < 0.05) enhanced the activity of cytosolic glutathione S-transferase alpha. A significant (P < 0.05) to marginal (P < 0.1) increase in the activity of the microsomal UDP-glucuronosyl transferase was obtained with unprocessed rooibos and honeybush teas, respectively. Oxidized glutathione (GSSG) levels were significantly (P < 0.05) reduced in the liver of all tea treated rats while reduced glutathione (GSH) was markedly increased in the liver of the herbal tea treated rats. These changes resulted in a significant (P < 0.05) increase in the GSH/GSSG ratio by the unprocessed, processed rooibos and unprocessed honeybush teas. Green and black teas markedly to significantly decreased the oxygen radical absorbance capacity in liver homogenates, respectively. Modulation of phase II drug metabolizing enzymes and oxidative status in the liver may be important events in the protection against adverse effects related to mutagenesis and oxidative damage.
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    Salsola tuberculatiformis botschantzev and an aziridine precursor analog mediate the in vivo increase in free corticosterone and decrease in corticosteroid-binding globulin in female wistar rats
    (The Endocrine Society, 1999-05) Louw, Ann; Swart, P.
    Salsola tuberculatiformis Botschantzev causes prolonged gestation in sheep and contraception in rats. An active fraction isolated from the shrub, containing a highly labile hydoxyphenyl aziridine or precursor, and a more stable analog, compound A, inhibits sheep adrenal cytochrome P450c11. In addition, compound A has been shown to bind to and be stabilized by corticosteroid-binding globulin (CBG). Binding may result in concomitant displacement of endogenous steroids, which could contribute to the biological effects of these compounds. The present study was undertaken to establish which mechanism would predominate in female rats. Compound A significantly (P,0.01) displaced glucocorticoids, but not progesterone, from corticosterone in both S. tuberculatiformis (P , 0.05)- and compound A (P , 0.01)-treated rats was also significantly higher due to displacement from CBG. In addition, both ACTH and CBG concentrations were significantly (P , 0.05) lower than control values. The levels of the gonadotropins were also reduced during treatment, but only LH values significantly (P , 0.05) so. These results suggest that binding of the test substances to CBG in female rat plasma and concomitant displacement of endogenous corticosterone could be part of the contraceptive mechanism of S. tuberculatiformis and the aziridine precursor, compound A.