EcotoxicologyThe key aim of the Ecotoxicology group is to investigating the impacts of chemical pollutants on wildlife and organisms.
Brunel University has a long history of pioneering research in environmental toxicology with particular emphasis on the causes and effects of endocrine disruption in aquatic wildlife. The group has several important themes:
Chemical effects on the reproduction and sexual development of aquatic organisms, particularly fish and, more recently, molluscs
Thousands of chemicals enter rivers in effluent from sewage treatment works. Many of these chemicals are probably of no environmental concern, but a few are. We focus on those we consider most likely to be of concern and we study their effects on aquatic species, both in the laboratory and the environment.
Amphibian ecotoxicology and endocrine disruption
We have worked with the UK Government Department of Environment, Food and Rural Affairs on the potential for endocrine disruption in native British amphibians, and have contributed significantly to OECD initiatives to develop amphibian test methods for detecting thyroid active chemicals.
Our work is now considering the influence of the conditions of exposure on top of the exposure itself. For example, we are investigating factors such as temperature, oxygen levels and food availability.
Research in this area began with the unexpected finding that male fish living downstream of sewage treatment works synthesise the egg yolk protein, vitellogenin (1). Further studies, involving the exposure of caged fish to various concentrations of sewage effluent, revealed that this occured in a dose dependent manner (2)(Fig.1).
This phenomenon has been studies in greater depth using a combination of laboratory and field-based approaches. Extensive field studies have revealed further endocrine-mediated effects in fish such as intersexuality (4)(Fig.3). Recent research supervised by Dr Susan Jobling has associated this with reduced reproductive performance in terms of milt production, fertilisation rates and hatching success (5)(Fig.4), which has significant implications for populations of wild fish.
The groups interests expanded to address amphibians from 2003, when Dr. Dan Pickford joined Brunel from AstraZeneca. Dr Pickfords' research has addressed effects of endocrine disrupters on adult female reproductive function (doctoral research) and larval development (sexual differentiation and metamorphosis). His ongoing research in this area can be divided into two main themes:
- development of a laboratory amphibian model for assessing impacts of larval exposure to endocrine disrupters on adult reproductive function. To this end he has been supervising a doctoral research project focussed on impacts of larval estrogen exposure on adult male reproductive function in the emerging model Silurana (Xenopus) tropicalis, which may be a smaller more tractable model than the African clawed frog.
- assessing the impacts of endocrine disrupters in the aquatic environment on real populations of native amphibians species (in particular the Common toad, Bufo bufo). This work has been funded by the Department of Environment, Food and Rural Affairs (DEFRA), under their EDAQ programme, and has made use of Passive Accumulation Devices to asssess endocrine disrupting activity of surface waters at toad breeding sites
In Vitro Models
In vitro Models
The group has been instrumental in development and use of in vitro methods for investigating endocrine disrupting activity of chemicals, to complement in vivo research. For example, Dr. Edwin Routledge has helped to develop a recombinant yeast strain that is genetically modified to respond to oestrogenic activity (Fig. 2). This has aided in the identification of many endocrine disrupting chemicals, which include both natural and synthetic hormones, as well as a range of industrial chemicals that induce oestrogenic effects (3).
Recently an MSc student (MAK Hashmi) has used the Yeast Androgen Screen (YAS assay) to detect significant androgenic activity in extracts from black liquor (effluent) generated in a lab-scale model of wheat straw pulping for paper manufacturing (Dissertation project supervised by Dr Daniel Pickford
Dr Edwin Routledge has been closely involved with development of a transgenic fish model for detection of estrogenic chemicals, using Green-fluorescent protein to visualise estrogen receptor activiation.Zebrafish Transgensis: Application to Functional Genomics and Ecotoxicology Research
Ascidian metamorphosis assay
Urochordates offer great potential as invertebrate models for thyroid function which could be used as a simple whole-organismal screen for detection of thyroid active chemicals