Recommendations on dose level selection for repeat dose toxicity studies

Prior to registering and marketing any new pharmaceutical, (agro)chemical or food ingredient product manufacturers must, by law, generate data to ensure human safety. Safety testing requirements vary depending on sector, but generally repeat-dose testing in animals form the basis for human health risk assessments. Dose level selection is an important consideration when designing such studies, to ensure that exposure levels that lead to relevant hazards are identified. Advice on dose level selection is provided in test guidelines and allied guidance documents, but it is not well harmonised, particularly for selection of the highest dose tested. This paper further builds on concepts developed in a technical report by the European Centre for Ecotoxicology and Toxicology of Chemicals (ECETOC) which recommends pragmatic approaches to dose selection considering regulatory requirements, animal welfare and state of the art scientific approaches. Industry sectors have differing degrees of freedom to operate regarding dose level selection, depending on the purpose of the studies and the regulatory requirements/legislation, and this is reflected in the overall recommended approaches. An understanding of systemic exposure should be utilised where possible (e.g., through toxicokinetic approaches) and used together with apical endpoints from existing toxicity studies to guide more appropriate dose level selection. The highest dose should be limited to a reasonable level, causing minimal but evident toxicity to the test animals without significantly compromising their well-being. As the science of predictive human exposure further develops and matures, this will provide exciting and novel opportunities for more human-relevant approaches to dose level selection.

Bioaccessibility of Difenoconazole in Rice Following Industry Standard Processing and Preparation Procedures

For pesticide registration a post application assessment is made on the safety of any residue remaining in the edible portion of the treated crop. This assessment does not typically consider the bioaccessibility of pesticide residues. The effects of this on potential exposure to incurred difenoconazole residues passing through the human gastrointestinal tract were studied, including the impact of commodity processing. It has previously been demonstrated that solvent extraction methods have the potential to overestimate the bioaccessible fraction, so in vitro simulated gut systems may offer a better approach to determine residue bioaccessibility to refine the risk assessment process. The bioaccessibility of difenoconazole residues associated with processed rice samples was assessed using in vitro intestinal extraction and colonic fermentation methods. The mean bioaccessibility following intestinal digestion was 33.3% with a range from 13% to 70.6%. Quantification of the colonic bioaccessible fraction was not possible due to compound metabolism. Mechanical processing methods generally increased the residue bioaccessibility, while chemical methods resulted in a decrease. Both mechanical and chemical processing methods reduced the total difenoconazole residue level by ca. 50%.

Development of a regulatory testing procedure to study the metabolism of pesticides in farmed fish

BACKGROUND

Diets used in commercial fish farming use significant proportions of crop-derived commodities, and it is important to understand the potential for transfer of any pesticide residues on the crop into edible tissues in fish. It is a current requirement in the EU that fish metabolism studies must be performed when a pesticide is used in crops where commodities or processed fractions are fed to farmed fish. Fish metabolism studies in both rainbow trout and common carp have been carried out, following the new working document on the nature of pesticide residues in fish using (14) C-labelled pesticide.

RESULTS

The ingestion of experimental diets by rainbow trout and common carp resulted in the uptake and metabolism of the test item, as shown by liquid scintillation counting combined with radio-thin-layer chromatography. The metabolite profiles for trout and carp were qualitatively similar regarding the main residue. However, species-specific differences were found regarding the remaining residue with rainbow trout showing additional metabolites in comparison to carp.

CONCLUSIONS

Metabolism studies for regulatory purposes can be carried out with both fish species under laboratory conditions. The experimental design reported is suitable for quantifying the transfer of residues to edible tissues and enables characterisation of the chemical nature of residues.

Investigation into feed preparation for regulatory fish metabolism studies

BACKGROUND

Test diets used in fish metabolism studies for regulatory purposes must be homogenously fortified with the radiolabelled test substance and stable with respect to leaching. Standard fish food, as used in commercial fish farming, should also be used in fish metabolism studies. Therefore, suitable spiking and coating procedures are required to ensure the correct dosing of the fish during the experiment.

RESULTS

Methods for the homogeneous, safe and efficient application of radiolabelled test items to the surface of commercial feeding pellets were developed. Leaching studies showed that test items of low lipophilicity applied to feeding pellets need to be stabilised, to reduce the risk of significant losses prior to ingestion by the fish. Coating of solvent-spiked pellets with calcium alginate was shown to reduce leaching losses of water-soluble test items significantly. Alternatively, commercial feeding pellets can be coated with alginate or vegetable oil fortified with a radiolabelled test item also leading to sufficiently stabilised test diets. Experimental conditions, such as the water temperature, may have a significant effect on the leaching behaviour of the test items.

CONCLUSIONS

A detailed description of different spiking and coating procedures for the preparation of experimental diets suitable for fish metabolism studies is provided.

Team approach to working through transference and countertransference in a pediatric/psychiatric milieu

The principles of transference and countertransference are essential to understanding and working through the intense pain and anger that often dominate the emotional field of the pediatric/psychiatric milieu. Using Winnicott's model of the maternal/infant relationship, this milieu can be seen as a holding environment where transferential phenomena can be expressed, interpreted, and worked through. Anger and pain are common elements of the transference/countertransference relationship matrix of the milieu. Staff often have a strong bias regarding anger and hostility. If they are willing to examine their bias, and are given the forums within which to do so, then patients' anger and hostility can be viewed and interpreted in an adaptive and facilitative manner. Working through in a milieu setting is accomplished by both verbal processing and the lived experience.

Individual rights vs institutional rights: nursing imperatives for the provision of aged care services

This paper offers nurses a legal perspective on some of the major issues arising from the Federal Government's proposal to establish a standard form contract and a charter of residents' rights and obligations for elderly residents in hostels and nursing homes. In emphasising the significance of these proposals it suggests that nurses, individually or collectively, have the potential to make a significant contribution to the continuing user rights debate. The proposed charter and contract and the objectives sought to be achieved by this package are considered. While there are strong and persuasive arguments favouring the concept, it is suggested that as proposed the charter and contract would be largely unworkable and impractical. Progress of the consultation process between Government and other interested bodies and the effect of subsequent drafting changes is discussed. Finally, the manner in which members of the nursing profession with experience and expertise in the provision of aged care services may contribute to the ongoing user rights debate is addressed.

In-hospital maternal mortality in the United States: time trends and relation to method of delivery

To study time trends in maternal mortality in the United States and to attempt to compare the risk of cesarean with vaginal delivery, information from the Professional Activities Study of the Commission on Professional and Hospital Activities for 3 years-1970, 1974, and 1978-was reviewed. For all deliveries, mortality per 100,000 deliveries declined from 25.7 in 1970 to 14.3 in 1978. For vaginal deliveries, mortality per 100,000 deliveries declined from 20.4 to 9.8. For cesarean deliveries, mortality per 100,000 births decreased more than for vaginal deliveries, from 113.8 to 40.9. Mortality for deliveries with no mention of complications, lacerations, or uterine rupture declined significantly from 1970 to 1978. Mortality for deliveries complicated by dystocia or malpresentation declined significantly from 1970 to 1974, but failed to decline thereafter. Mortality for deliveries complicated by a previous cesarean or by antepartum hemorrhage did not decline significantly from 1970 to 1978. For all complications with a sufficient number of vaginal and cesarean deliveries, except deliveries complicated by malpresentation or antepartum hemorrhage, mortality was at least twice as high in cesarean as in vaginal deliveries. Based on a comparison of mortality after a previous cesarean with mortality for all vaginal deliveries with no complication, the authors conclude that cesarean delivery is probably neither less than 2 nor more than 4 times more hazardous than vaginal delivery.

Mosaicism and lack of fluorescence of Y chromosome

A patient with a female phenotype with XO/XY and possibly XYY mosaicism is presented. In all cells studied, there was no fluorescence of the Y chromosome. It appears that a tendency exists for an association of a defective Y chromosome with chromosomal mosaicism.