Clinically and industrially relevant incurred reference materials to improve analysis of food allergens, milk, egg, almond, hazelnut and walnut.

Measurement of food allergen protein concentrations against thresholds can improve allergen risk management and precautionary allergen labelling. Such measurement suffers well known problems which could be ameliorated by well characterised reference materials (RMs) providing meaningful information for risk assessors. We investigated the preparation and characterisation of the first consensus informed industrially and clinically relevant multi-allergen matrix RM kit for five priority allergens.

Trenbolone causes mortality and altered sexual differentiation in Xenopus tropicalis during larval development.

Trenbolone is an androgen agonist used in cattle production and has been measured in aquatic systems associated with concentrated animal-feeding operations. In this study, the authors characterized the effects of aqueous exposure to 17β-trenbolone during larval Xenopus tropicalis development. Trenbolone exposure resulted in increased mortality of post-Nieuwkoop-Faber stage 58 tadpoles at concentrations ≥100 ng/L.

Effects of 4-tert-octylphenol on Xenopus tropicalis in a long term exposure.

Endocrine disrupting chemicals that activate the estrogen receptor are routinely detected in the environment and are a concern for the health of both exposed humans and indigenous wildlife. We exposed the western clawed frog (Xenopus tropicalis) to the weak estrogen octylphenol from Nieuwkoop-Faber (NF) stage 46 tadpoles through adulthood in order to document the effects of a weak estrogen on the life history of an amphibian species. Frogs were exposed to 1, 3.

In vivo assessment and potential diagnosis of xenobiotics that perturb the thyroid pathway: Proteomic analysis of Xenopus laevis brain tissue following exposure to model T4 inhibitors.

As part of a multi-endpoint systems approach to develop comprehensive methods for assessing endocrine stressors in vertebrates, differential protein profiling was used to investigate expression patterns in the brain of the amphibian model (Xenopus laevis) following in vivo exposure to a suite of T4 synthesis inhibitors. We specifically address the application of Two Dimensional Polyacrylamide Gel Electrophoresis (2D PAGE), Isobaric Tags for Relative and Absolute Quantitation (iTRAQ) and LC-MS/MS to assess changes in relative protein expression levels. 2D PAGE and iTRAQ proved to be effective complementary techniques for distinguishing protein changes in the developing amphibian brain in response to T4 synthesis inhibition.

Early temporal effects of three thyroid hormone synthesis inhibitors in Xenopus laevis.

Thyroid axis disruption is an important consideration when evaluating risks associated with chemicals. Bioassay methods that include thyroid-related endpoints have been developed in a variety of species, including amphibians, whose metamorphic development is thyroid hormone (TH)-dependent. Inhibition of TH synthesis in these species leads to developmental delay, and assays designed to capture these effects take several weeks to complete.

Sex reversal of the amphibian, Xenopus tropicalis, following larval exposure to an aromatase inhibitor.

Aromatase is a steroidogenic enzyme that catalyzes the conversion of androgens to estrogens in vertebrates. Modulation of this enzyme's activity by xenobiotic exposure has been shown to adversely affect gonad differentiation in a number of diverse species. We hypothesized that exposure to the aromatase inhibitor, fadrozole, during the larval development of the tropical clawed frog, Xenopus tropicalis, would result in masculinization of the developing female gonad.

Production and certification of four frozen human serum certified reference materials containing creatinine and electrolytes.

Background: This paper describes the preparation, analysis and certification of four frozen human serum certified reference materials (CRMs) containing creatinine and the electrolytes calcium, lithium, magnesium, potassium and sodium. These materials have been prepared to give concentrations of these analytes that cover the currently accepted analytical range.

Methods: The analysis of the materials for certification purposes has been carried out using methodology traceable to primary standards, and which is acceptable as a reference method.

Identification of gene expression indicators for thyroid axis disruption in a Xenopus laevis metamorphosis screening assay. Part 1. Effects on the brain.

Thyroid hormones (TH), thyroxine (T(4)) and 3,5,3'-triiodothyronine (T(3)), play crucial roles in regulation of growth, development and metabolism in vertebrates and their actions are targets for endocrine disruptive agents. Perturbations in TH action can contribute to the development of disease states and the US Environmental Protection Agency is developing a high throughput screen using TH-dependent amphibian metamorphosis as an assay platform. Currently this methodology relies on external morphological endpoints and changes in central thyroid axis parameters.

Identification of gene expression indicators for thyroid axis disruption in a Xenopus laevis metamorphosis screening assay. Part 2. Effects on the tail and hindlimb.

Thyroid hormones (TH), thyroxine (T(4)) and 3,5,3'-triiodothyronine (T(3)), play crucial roles in regulation of growth, development and metabolism in vertebrates and are targets for endocrine disruptive agents. Perturbations in TH action can contribute to the development of disease states and the US Environmental Protection Agency is developing a high throughput screen using TH-dependent metamorphosis of the Xenopus laevis tadpole as an assay platform. Currently this methodology relies on external morphological endpoints and changes in central thyroid axis parameters.

The analysis and interpretation of cognitive interviews for instrument development.

Cognitive interviews assess respondents' understanding of questionnaire items and are increasingly used to improve instrument design. Although investigators have described the contributions of cognitive interviews for instrument development, few guidelines are available for analyzing data from cognitive interviews when they are used for that purpose. In this article we address the development and application of analytic strategies for summarizing, interpreting, and using data from cognitive interviews that were conducted during the process of creating a measure of parental management of childhood chronic conditions.

Factors related to depressive symptoms among long-term survivors of cervical cancer.

In this article we describe depressive symptoms among survivors of cervical cancer. Study participants were previously diagnosed and treated with cervical cancer 5 to 25 years prior to the completion of a telephone survey. Through a population-based survey of women identified via a state tumor registry in southern New England, the investigators learned that depressive symptoms are prevalent among a subgroup of long-term survivors long after diagnosis and treatment.

Evaluation of gene expression endpoints in the context of a Xenopus laevis metamorphosis-based bioassay to detect thyroid hormone disruptors.

Thyroid hormones (TH) are important in growth, development and the maintenance of proper cellular metabolism in vertebrates. Amphibian metamorphosis is completely dependent on TH and forms the basis of a screen for thyroid axis disrupting chemicals that currently relies on external morphological endpoints and changes in thyroid gland histology. The requirement for TH-dependent gene expression makes it possible to augment this screen through the addition of molecular endpoints.

Progress towards development of an amphibian-based thyroid screening assay using Xenopus laevis. Organismal and thyroidal responses to the model compounds 6-propylthiouracil, methimazole, and thyroxine.

In response to the initial Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC) recommendations, research was conducted on the development of a Xenopus laevis based tail resorption assay for evaluating thyroid axis disruption. This research highlighted key limitations associated with relying on tail resorption as a measure of anti/thyroid activity. The most critical limitation being that tail tissues of tadpoles at metamorphic climax are insensitive to perturbation by thyroid axis agonists/antagonists.

Metamorphic inhibition of Xenopus laevis by sodium perchlorate: effects on development and thyroid histology.

The perchlorate anion inhibits thyroid hormone (TH) synthesis via inhibition of the sodium-iodide symporter. It is, therefore, a good model chemical to aid in the development of a bioassay to screen chemicals for affects on thyroid function. Xenopus laevis larvae were exposed to sodium perchlorate during metamorphosis, a period of TH-dependent development, in two experiments.

Comparing the effects of stage and duration of retinoic Acid exposure on amphibian limb development: chronic exposure results in mortality, not limb malformations.

Recently, high frequencies of malformations have been reported in amphibians across the United States. It has been suggested that the malformations may be the result of xenobiotic disruption of retinoid signaling pathways during embryogenesis and tadpole development. Therefore, a series of experiments were undertaken to examine life-stage specific effects of continuous retinoid exposure on Xenopus laevis.

Developmental toxicity of methoprene and several degradation products in Xenopus laevis.

Methoprene is an insect juvenile growth hormone mimic, which inhibits pupation and is used for the control of emergent insect pests such as mosquitoes. Researchers have hypothesized that methoprene use in US may be a contributing factor to the recent increase in malformed amphibians. However, little is known concerning the developmental toxicity of methoprene and its degradation products in amphibians.

Assessment of the risk of solar ultraviolet radiation to amphibians. I. Dose-dependent induction of hindlimb malformations in the northern leopard frog (Rana pipiens).

A number of environmental stressors have been hypothesized as responsible for recent increases in limb malformations in several species of North American amphibians. The purpose of this study was to generate dose-response data suitable for assessing the potential role of solar ultraviolet (UV) radiation in causing limb malformations in a species in which this phenomenon seemingly is particularly prevalent, the northern leopard frog (Rana pipiens). Frogs were exposed from early embryonic stages through complete metamorphosis to varying natural sunlight regimes, including unaltered (100%) sunlight, sunlight subjected to neutral density filtration to achieve relative intensities of 85%, 75%, 65%, 50%, and 25% of unaltered sunlight, and sunlight filtered with glass or acrylamide to attenuate, respectively, the UVB (290-320 nm) and UVB plus UVA (290-380 nm) portions of the spectrum.

Ambient solar UV radiation causes mortality in larvae of three species of Rana under controlled exposure conditions.

Recent reports concerning the lethal effects of solar ultraviolet-B (UV-B) (290-320 nm) radiation on amphibians suggest that this stressor has the potential to impact some amphibian populations. In this study embryos and larvae of three anuran species, Rana pipiens, Rana clamitans and Rana septentrionalis, were exposed to full-spectrum solar radiation and solar radiation filtered to attenuate UV-B radiation or UV-B and ultraviolet-A (UV-A) (290-380 nm) radiation to determine the effects of each wavelength range on embryo and larval survival. Ambient levels of solar radiation were found to be lethal to all three species under exposure conditions that eliminated shade and refuge.

Acute and long-term effects of nine chemicals on the Japanese medaka (Oryzias latipes).

Ninety-six-hour acute and 28-day larval survival and growth tests were conducted with nine organic chemicals, using the Japanese medaka (Oryzias latipes) as the test organism. The nine tested chemicals were allyl isothiocyanate, aniline, benzyl acetate, 4-chloroaniline, 2-chloroethanol, 2,4-diaminotoluene, 1,2-dibromoethane, 2,4-dichlorophenoxyacetic acid (2,4-D), and phenol. The derived 96-h LC50 values for medaka for all chemicals ranged from 0.

Iodine in British foods and diets.

Levels of I were determined in selected foods and dietary supplements, and in samples of the British 'Total Diet'. The average concentration of I in British milk collected in thirteen areas on four occasions during 1990 and 1991 was 150 micrograms/kg (range 40-310 micrograms/kg), compared with 230 micrograms/kg in 1977-79. No difference was found between skimmed and whole milk.

Relationships of quantitative structure-activity to comparative toxicity of selected phenols in the Pimephales promelas and Tetrahymena pyriformis test systems.

The relative toxic response of 27 selected phenols in the 96-hr acute flowthrough Pimephales promelas (fathead minnow) and the 48- to 60-hr chronic static Tetrahymena pyriformis (ciliate protozoan) test systems was evaluated. Log Kow-dependent linear regression analyses revealed that the data from each test system consisted of two linear equations. The less toxic chemicals form a relationship which models polar narcosis; these chemicals are slightly more active than the baseline toxicity of nonionic narcotic chemicals.