Evaluating urban surface water quality in Luton.

Using a single numerical value to indicate the quality of water, a so-called Water Quality Index (WQI) is a well-established way of rating the overall water quality status of a given water body. During the last few years, researchers in the water sector have developed different such indices to address their specific needs. In this study, we attempt to obtain a WQI formula suited for evaluating the water quality of the River Lea.

The use of fetal bovine serum for cryopreservation of stage III zebrafish (Danio rerio) ovarian follicles.

Although several studies on fish ovarian follicles cryopreservation have been carried out, their cryopreservation still remains unsuccessful. In this study, for the first time the effect of Fetal Bovine Serum (FBS) in combination with several concentrations of methanol (1, 2 or 4M) as cryoprotectant on stage III ovarian follicles viability was investigated and cryopreservation using controlled slow cooling was undertaken. Membrane integrity assessed by trypan blue (TB) staining and ATP level of stage III ovarian follicles were evaluated following cryoprotectant treatment and cryopreservation.

Impact of cryoprotectants and cryopreservation on metabolic activity and cytoskeleton proteins of zebrafish (Danio rerio) ovarian fragments.

Cryopreservation of reproductive cells and tissues of aquatic species offers many benefits to the field of conservation, aquaculture and biomedicine. Although cryopreservation of fish sperm has been successfully achieved, cryopreservation of embryos and oocytes remains unsuccessful. Several studies have been undertaken on cryopreservation of isolated fish ovarian follicles at different stages, although the protocols used lead to a compromised viability.

Studies on cryoprotectant toxicity to zebrafish (Danio rerio) ovarian tissue fragments.

Cryopreservation of ovarian tissue is a viable alternative to cryopreservation of oocytes and embryos in many species but it has not been studied in fish. Selection of cryoprotectant is an important step in designing cryopreservation protocols. In order to identify the optimum cryoprotectant (CPA) in a suitable concentration for zebrafish ovarian tissue cryopreservation, studies on toxicities of five commonly used cryoprotectants methanol, ethanol, dimethyl sulfoxide (DMSO), ethylene glycol (EG) and propylene glycol (PG) were carried out.

Cryopreservation of zebrafish (Danio rerio) oocytes by vitrification.

Cryopreservation of fish oocytes is challenging because these oocytes have low membrane permeability to water and cryoprotectant and are highly chilling sensitive. Vitrification is considered to be a promising approach for their cryopreservation as it involves rapid freezing and thawing of the oocytes and therefore minimising the chilling injury. In the present study, vitrification properties and the toxicity of a range of vitrification solutions containing different concentrations of Me2SO, methanol, propylene glycol and ethylene glycol were investigated.

Development of in vitro culture method for early stage zebrafish (Danio rerio) ovarian follicles for use in cryopreservation studies.

There have been no reported methods for in vitro growth of early stage ovarian follicles for fish and their cryopreservation is still under investigation. If cryopreservation of early stage ovarian follicles can be achieved, in vitro procedures for ovarian follicle culture, development, ovulation and fertilisation after cryopreservation would be needed. The aim of the present study was to develop an in vitro culture method for early stage zebrafish ovarian follicles for use after their cryopreservation.

Effect of methanol and Me2SO exposure on mitochondrial activity and distribution in stage III ovarian follicles of zebrafish (Danio rerio).

In this study the effect of cryoprotectants that have been shown to be the least toxic to zebrafish ovarian follicles (methanol and Me(2)SO), on mitochondria of stage III ovarian follicles was evaluated. The mitochondrial distributional arrangement, mitochondrial membrane potential, mtDNA copy number, ATP levels and ADP/ATP ratios were assessed following exposure to cryoprotectants for 30 min at room temperature. Results obtained by confocal microscopy showed that 30 min exposure to 2M methanol induced a loss of membrane potential, although viability tests showed no decrease in survival even after 5h post-exposure incubation.

Cryopreservation of zebrafish (Danio rerio) blastomeres by controlled slow cooling.

Cryopreservation is now a common practice in the fields of aquaculture, conservation and biomedicine. One approach for maintaining the genetic diversity of both nuclear genome and mitochondrial DNA is cryopreservation of the blastomere. This study sets out to determine an optimum cryopreservation protocol for blastomeres isolated from 50% epiboly zebrafish embryos.

Effect of chilling and cryopreservation on expression of Pax genes in zebrafish (Danio rerio) embryos and blastomeres.

Cryopreservation is now common practice in the fields of aquaculture, conservation and biomedicine. However, there is a lack of information on the effect of chilling and cryopreservation at the molecular level. In the present study, we used real-time RT-PCR analysis to determine the effect of chilling and cryopreservation on expression of Pax2a, Pax2b, Pax5 and Pax8 which constitute one subgroup of the Pax gene family.

Distributional arrangement of mitochondria in the granulosa cells surrounding stage III zebrafish (Danio rerio) oocytes.

Mitochondria play a vital role during oocyte maturation, fertilization, and embryo development. In this study, confocal microscopy with the mitochondrial membrane potential-sensitive dye JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide) was used to investigate mitochondria distribution and activity of stage III zebrafish ovarian follicles. To support the mitochondrial origin of the fluorescence obtained by JC-1, a second mitochondrial probe, MitoTracker Green FM, was used.

Studies on cryoprotectant toxicity to early stage zebrafish (Danio rerio) ovarian follicles.

Cryoprotectants are substances characterised by their ability to reduce cryoinjury of biological materials during the course of freezing. Unfortunately cryoprotectants can be toxic for cells. The aim of this study is to investigate the toxicity of cryoprotectants to early stage ovarian follicles of zebrafish (Danion rerio) before designing protocols for their cryopreservation.

Evaluation of zebrafish (Danio rerio) ovarian follicle viability by simultaneous staining with fluorescein diacetate and propidium iodide.

Reliable fish oocyte quality assessment methods are essential in developing protocols for cryopreservation as well as their in vitro maturation and fertilisation. Current ovarian follicle viability assessment methods either lack sensitivity (e.g.

Development of cryopreservation protocols for early stage zebrafish (Danio rerio) ovarian follicles using controlled slow cooling.

Cryopreservation of germplasm of aquatic species offers many benefits to the fields of aquaculture, conservation and biomedicine. Although successful fish sperm cryopreservation has been achieved with many species, there has been no report of successful cryopreservation of fish embryos and late stage oocytes which are large, chilling sensitive and have low membrane permeability. In the present study, cryopreservation of early stage zebrafish ovarian follicles was studied for the first time using controlled slow freezing.

Studies on chilling sensitivity of early stage zebrafish (Danio rerio) ovarian follicles.

Cryopreservation of fish gametes is of great importance in aquaculture, conservation and human genomic research. The creation of gamete cryobanks allows the storage of genetic material of targeted species for almost unlimited time periods. Cryopreservation has been successfully applied to fish sperm of many species, but there has been no success with fish embryos and oocytes.

Cryopreservation of zebrafish (Danio rerio) oocytes using improved controlled slow cooling protocols.

Cryopreservation of gametes provides a promising method to preserve fish genetic material. Previously we reported some preliminary results on cryopreservation of zebrafish (Danio rerio) oocytes using controlled slow cooling and determined the optimum cryoprotective medium and cooling rate for stage III zebrafish oocytes. In the present study, the effects of two different cryopreservation media, cryoprotectant removal method, final sample freezing temperature before LN(2) plunge, warming rate, and the post-thaw incubation time on oocyte viability were investigated.

Cathepsin activities and membrane integrity of zebrafish (Danio rerio) oocytes after freezing to -196 degrees C using controlled slow cooling.

This study investigated enzymatic activity of cathepsins and the membrane integrity of zebrafish (Danio rerio) oocytes after freezing to -196 degrees C using controlled slow cooling. Stage III oocytes (>0.5mm), obtained through dissection of anaesthetised female fish and desegregation of ovarian cumulus, were exposed to 2M methanol or 2M DMSO (both prepared in Hank's medium) for 30min at 22 degrees C before being loaded into 0.

Ultrasound enhanced methanol penetration of zebrafish (Danio rerio) embryos measured by permittivity changes using impedance spectroscopy.

Studies on permittivity changes in fish embryos measured by impedance spectroscopy after ultrasound treatment during exposure to cryoprotectant is reported here for the first time. The permittivity changes of zebrafish embryos in cryoprotectant solutions before and after ultrasound treatment were measured using impedance spectroscopy. Zebrafish (Danio rerio) embryos at 50% epiboly stage were exposed to 2 M methanol for 25 min before ultrasound treatment for 5 min at 22 degrees C.

Development of a new method for isolating zebrafish oocytes (Danio rerio) from ovary tissue masses.

In order to study cryopreservation of zebrafish (Danio rerio) oocytes, large numbers of oocytes need to be isolated from the ovaries for experimental use. Zebrafish oocytes have been previously separated from ovaries mechanically and the method is laborious and time consuming. The aim of the present study was to develop a simple and rapid method for obtaining large number of morphologically and functionally intact zebrafish oocytes at different stages of development.

Development of a new rapid measurement technique for fish embryo membrane permeability studies using impedance spectroscopy.

Information on fish embryo membrane permeability is vital in their cryopreservation. Whilst conventional volumetric measurement based assessment methods have been widely used in fish embryo membrane permeability studies, they are lengthy and reduce the capacity for multi-embryo measurement during an experimental run. A new rapid 'real-time' measurement technique is required to determine membrane permeability during cryoprotectant treatment.

Study on fish embryo responses to the treatment of cryoprotective chemicals using impedance spectroscopy.

Investigations using electrical impedance spectroscopy to measure the responses of fish embryos to the cryoprotective chemicals, methanol and dimethyl sulphoxide (DMSO), were carried out. Zebrafish (Danio rerio) embryos were used as a model to study the newly proposed technique. The normalised permittivity and conductivity changes of the embryos were measured continuously over a 20-min period in a customised embryo-holding chamber.

The effect of external medium composition on membrane water permeability of zebrafish (Danio rerio) embryos.

The effect of external medium composition on chorion and plasma membrane permeability of zebrafish (Danio rerio) embryos was investigated in this study. Initially, survival of embryos spawned into varying strengths (10-40%) of Hank's solution (HBSS) was assessed. Development and hatching rates for embryos spawned into 30% and 40% HBSS were significantly lower than those obtained with embryos spawned into system water.

Studies on membrane permeability of zebrafish (Danio rerio) oocytes in the presence of different cryoprotectants.

Investigation into fish oocyte membrane permeability is essential for developing successful protocols for their cryopreservation. The aim of the present work was to study the permeability of the zebrafish (Danio rerio) oocyte membrane to water and cryoprotectants before cryopreservation protocol design. The study was conducted on stage III and stage V zebrafish oocytes.

Rapid ecotoxicological testing using transformed BF-2 cells incorporating a luminescent reporter gene.

Since there is an ethical need to minimise the experimental use of higher organisms such as fish, especially those used in acute toxicity testing, fish cells are considered to be useful surrogates for fish in toxicity screening. The use of fish cell lines in conventional bioassays such as neutral red retention assays is however labour intensive, lengthy and costly. The use of luminescent reporter genes has been explored in our laboratory.

Effect of cryopreservation on mitochondrial DNA of zebrafish (Danio rerio) blastomere cells.

Cryopreservation has been extensively used in human reproductive medicine, aquaculture and conservation programmes for endangered species. However, despite the growing successes of cryopreservation, post-thaw recovery of reproductive and embryonic cells very often remains poor. Many studies have been devoted to the mechanisms of cryodamage.

Studies on cryoprotectant toxicity to zebrafish (Danio rerio) oocytes.

Cryopreservation of fish germ cells is an important measure in conservation of fish genetic material. Although investigations on cryopreservation of fish sperm and embryos have been carried out extensively, cryopreservation of fish oocytes has not been studied systematically. In the present study the toxicity of cryoprotectants to zebrafish (Danio rerio) oocytes was investigated.