Faculty of Veterinary Science
Department of Paraclinical Sciences (Veterinary)
Selected Highlights from Research Findings
Aquatic animals respond with great sensitivity to chemical changes in their environment and are considered to be important bio-indicators of pollution. They are, therefore, widely used to monitor pollution. One of the biggest challenges in aquatic toxicology is to develop in vitro tissue culture systems to replace or reduce the number of aquatic animals used for research or routine monitoring.
Primary hepatocyte cultures are powerful in vitro tools, as liver-specific functions and responses to toxic insults are maintained for about ten days in culture. In comparison, commercial cell lines are not as biologically active as the primary hepatocytes and are not very useful to investigate biotransformation, enzyme induction (e.g. CYP) and protein production (e.g. vitellogenin) by hepatocytes. Researchers were successful to harvest and maintain primary hepatocytes from both the Sharptooth catfish and Nile crocodile.
Hepatocytes are collected from the Nile crocodile and Sharp tooth catfish by a sterile perfusion method developed and optimised for the two species. As far as we could ascertain, hepatocytes from the Nile crocodile have never been cultured before. The hepatocyte research is conducted in collaboration with the Onderstepoort Veterinary Institute (Sharp tooth catfish) and the Bio-artificial Liver Unit (Nile crocodile).
Catfish primary hepatocytes responded positively when exposed to the pollutant, benzo-a-pyrene (BaP), by showing significant CYP1A induction. Crocodile CYP1A induction and gene expression are evaluated at the moment. Vitellogenin (Vtg) is currently investigated as another biomarker for our in vitro system. Vitellogenin is a phospholipoglycoprotein precursor of egg yolk protein, which is normally produced by the liver in sexually active females of all oviparous species.
The production of Vtg is controlled by the interaction of endogenous oestrogens with the oestrogen receptor. Since males maintain the capacity to produce Vtg in response to stimulation by oestrogens (pollutants), the production of Vtg by males, immature females and hepatocytes has been successfully used as a biomarker of exposure to oestrogenic pollutants.
Primary hepatocytes from the Sharp tooth catfish and Nile crocodile can now be used to assess and monitor aquatic pollution in southern and East Africa, especially where pollutants such as polychlorinated dibenzodioxins, dibenzofurans, biphenyls and polycyclic aromatic hydrocarbons are involved.
Funding was received from NUFU (Norwegian Council for Higher Education’s Program for Development, Research and Education) for a research project on environmental toxicology, entitled: The use of biomarkers as an indication of pollution in selected aquatic ecosystems in eastern and southern Africa.
Dr JG Myburgh
Paraclinical Sciences
+27 (0) 12 529 8350
jan.myburgh@up.ac.za
The activities of the phytomedicine group consist mainly of the preparation and testing of plant extracts for possible medicinal use. The focus is on plants identified by indigenous knowledge systems.
The fourth product derived from research generated by this group is currently being licensed to private companies for commercial exploitation. In three cases provisional patents have been submitted and in one case a provisional patent is now expanded.
In addition the group is coordinating attempts to standardize herbal medicines exported by various African countries to Europe.
Highlights of these activities during the past year included the following:
· Preliminary results obtained from research on the development of plant extracts that can be used to replace antibiotic feed additives, are positive and this product may have substantial commercial value; and
· A contract was obtained from the European Union Centre for the Development of Enterprise to produce a set off African medicinal plant standards [AMPS] for 21 Pan-African Herbal Medicines exported to Europe. The project was coordinated with subcontracts to colleagues in the rest of Africa. All the quality control aspects were carried out at the Onderstepoort laboratory. The second phase of this project is to develop at least another 29 profiles during 2006. Prof JN Eloff
Paraclinical Sciences
+27 (0) 12 529 8244
kobus.eloff@up.ac.za
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