Browsing by Author "Hiss, Donavon"

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    Open Access
    Combination of tunicamycin with anticancer drugs synergistically enhances their toxicity in multidrug-resistant human ovarian cystadenocarcinoma cells
    (BioMed Central Ltd, 2007) Hiss, Donavon; Gabriels, Gary; Folb, Peter
    BACKGROUND:The pharmacologic modulatory effects of the antibiotic, tunicamycin (TM), on multidrug-resistant human UWOV2 ovarian cancer cells are reported. The UWOV2 cell line was derived from a cystadenocarcinoma in a patient refractory to combination chemotherapy with actinomycin D, vincristine (VCR), cis-diaminedichloroplatinum (II) (CDDP) and doxorubicin (DXR). In an attempt to explain drug resistance in this cell line, we examined the effects of TM on their sensitivity to various anticancer drugs, the uptake, efflux and retention of [3H]VCR, and their ability to bind [14C]DXR and [3H]azidopine (AZD), a photoaffinity label of the multidrug transporter, P-glycoprotein (Pgp). RESULTS: TM effectively decreased the EC50 for DXR, EXR, VCR and CDDP, thus enhancing their cytotoxicity. The antibiotic also prolonged the intracellular retention time of [3H]VCR and increased the binding of both [14C]DXR and [3H]AZD to the cells. CONCLUSION: It is concluded that the pharmacomodulatory effects of TM in these cells are mediated by global inhibition of protein and glycoprotein synthesis and synergistic interaction with antineoplastic drugs. The ability of TM to enhance the sensitivity of drug resistant tumour cells may have impact on the design and optimization of novel resistance modifiers to improve the efficacy of combination treatment of intractable neoplasms.
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    Melamine contamination in nutritional supplements - Is it an alarm bell for the general consumer, athletes, and 'Weekend Warriors'?
    (BioMed Central Ltd, 2015) Gabriels, Gary; Lambert, Mike; Smith, Pete; Wiesner, Lubbe; Hiss, Donavon
    BACKGROUND: Nutritional supplements are used or experimented with by consumers, notably these are; competitive and recreational athletes of all ages, and 'weekend warriors'. As a consequence the supplement industry has grown to meet the increasing demand. A Global Industry Analysts Inc. report indicates that the herbal supplement market has not declined during the worldwide recession, but in fact exhibited steady growth over the period 2008 to 2009. It is anticipated that the market will reach US$93.15 billion by the year 2015. These supplements may contain adulterated substances that may potentially have harmful short - and long-term health consequences to the consumer. "Scrap Melamine" is such an example, which has been implicated in the kidney failure and death of several cats, dogs and pigs. In China in 2008, reports described very severe health effects in infants and young children. At the time over 294 000 infants were screened and diagnosed with urinary tract stones and sand-like calculi associated with melamine in milk products, of which 50 000 infants were hospitalised, and at least six associated deaths, recorded. The extent that melamine contamination occurs in nutritional supplements is not known. Therefore, the aim of this study was to determine whether commercially available nutritional and traditional supplement products contain melamine, even though they are not declared by the manufacturer on the product label. METHODS: A total of 138 nutritional supplements products were obtained from (i) direct purchases from shops, pharmacies and outlets, (ii) directly from consumers, and (iii) from suppliers, manufacturers and distributors. The products were laboratory analysed for melamine, using Tandem Liquid Chromatography Mass Spectrometry. RESULTS: Forty-seven % of all the products (n=138) tested positive for melamine. Eight-two % of the South African produced products (n=27) tested positive and 58 % of the products imported into South Africa (n=50) tested positive. The median concentration estimate for melamine in the products tested were, 6.0 mug/g for the 138 supplements tested, 8.9 mug/g for South African produced products, and 6.9 mug/g for products imported into South Africa. CONCLUSION: The melamine (undeclared on product label) levels detected in the nutritional supplements products investigated were within the Tolerable Daily intake (TDI) limit guidelines of 200 mug/g as set by WHO and others. Melamine over exposure within the context of the nutritional supplements consumption in the products investigated should not be of concern to the consumer provided the recommended guidelines of daily product use are adhered to. Further investigation is warranted to determine, (i) the link of melamine as (part) substitute for the perceived total declared protein content on the product label, (ii) cyanuric and uric acid presence in the supplement products that could form chemical-complex formation with melamine and/or analogues that could cause adverse health effects.
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    Will the new Consumer Protection Act prevent harm to nutritional supplement users?
    (2011) Gabriels, Gary; Lambert, Mike; Smith, Pete; Hiss, Donavon
    BACKGROUND: There is no clear distinction between the regulation of food, supplements and medicines in South Africa. Consequently, grey areas exist in implementing the legislation, particularly in the supplement industry. The increase in supplement sales in South Africa can be attributed to aggressive marketing by manufacturers whose claims are not always supported by published peer-reviewed evidence. Such claims often go unchecked, resulting in consumers being mislead about the role of supplements. As a result of poor regulation, contaminants or adulterants in supplements may also cause insidious effects unrelated to the listed ingredients. AIM: To assess the regulations, legislation, and claims associated with nutritional supplement products in South Africa. METHOD: Peer-reviewed literature and the relevant South African statutes were consulted. RESULTS: The National Health Act incorporates the Medicine Control Council, which is charged with ensuring the safety, quality and effectiveness of medicines, and related matters, including complementary/alternative medicines. The South African Institute for Drug-Free Sport and Amendment Act provides for testing athletes for using banned substances, but currently does not concern itself with monitoring nutritional supplements for contaminants or adulterants that may cause a positive drug test, which has implications for sports participants and also the health of the general population. The implementation of the Consumer Protection Act 68 of 2008 (CPA) could protect consumer rights if it is administered and resourced appropriately. CONCLUSION: The CPA should promote greater levels of policy development, regulatory enforcement, and consumer education of South Africa's supplement industry.