Fipronil and fipronil sulfone in chicken: From in vitro experiments to in vivo PBK model predictions.

In 2017 a large-scale fipronil contamination in eggs occurred in several European countries. Fipronil and its metabolites have the potential to be transferred into the eggs of laying hens, thereby entering the human food chain. Here, first the metabolism of fipronil was measured in vitro using chicken liver S9. The results show that fipronil is mainly metabolised into fipronil sulfone and the clearance obtained in vitro was extrapolated to in vivo liver clearance. In a second step a physiologically based kinetic model was developed with a focus on fipronil and its major sulfone metabolite and the model outcome was compared to available in vivo data in eggs from the literature. The experimentally obtained clearance was used as model input to evaluate whether such an in vitro-based model can be used in an early phase of a contamination incident to predict the time-concentration curves. Overall, all model predictions were within a 10-fold difference and the estimated elimination half-life for fipronil equivalents was 14 days. In vitro experiments are definitely recommended compared to in vivo studies, since they provide a fast first insight into the behaviour of a chemical in an organism.

A broad tuneable birdcage coil for mouse 1H/19F MR applications.

In this paper, we present the design and implementation of a 1H/19F volume coil for mouse body magnetic resonance (MR) imaging and spectroscopy using a high magnetic field (4.7 T). By changing the geometry of the coil rungs to include both nuclei for MR experiments, this innovative coil can be tuned over an extremely wide range of frequency. The coil, 45 mm in diameter and 55 mm in length, consists of a 12-rung birdcage-like structure. Using two types of tuning, the coil can generate a sufficiently homogeneous B1+ electromagnetic field within a working volume optimized for laboratory mouse. The first tuning involves changing the resonance frequency over a large frequency range. The electrical capacitance between the wires can be adjusted to reflect changes in the length of the coil. The second tuning comprises a habitual tuning transformer for precise detection in a narrow band. In contrast to widely used multinuclear coils, the coil presented here features only one resonance peak and can be manipulated according to the Larmor frequencies given for 1H and 19F. The coil was successfully tested using full-wave simulations of magnetic and electric field distributions under in vivo MR conditions.

Influenza-binding sialylated polymer coated gold nanoparticles prepared via RAFT polymerization and reductive amination.

We report on a straightforward strategy to fabricate bioactive glycosylated gold nanoparticles via a combination of RAFT polymerization, carbohydrate ligation through reductive amination and thiol-gold self-assembly. This approach is used for the design of gold nanoparticles decorated with the complex sialylated glycan Neu5Ac-α-2-6-Gal, and we demonstrate multivalent and specific recognition between the nanoparticles, lectins and hemagglutinin on the surface of the influenza virus.

Transiently responsive protein-polymer conjugates via a 'grafting-from' RAFT approach for intracellular co-delivery of proteins and immune-modulators.

We report on transiently responsive protein-polymer conjugates that temporarily change their protein conformation from the soluble to the particle-like state. 'Grafting-from' RAFT polymerization of a dioxolane-containing acrylamide with a protein macroCTA is used to design polymer-protein conjugates that self-assemble into nanoparticles at physiological temperature and pH. Acid triggered hydrolysis of the dioxolane units into diol moeities rendered the conjugates fully water soluble irrespective of temperature.

Application of an untargeted metabolomics approach for the identification of compounds that may be responsible for observed differential effects in chickens fed an organic and a conventional diet.

The aim of this study was to apply an untargeted NMR and LC-MS-based metabolomics approach to detect potential differences between an organically and a conventionally produced feed, which caused statistically significant differences in growth, in the response to an immunological challenge and in the gene expression profiles in the small intestine of laying hens. A fractionation procedure was set up to create multiple fractions of the feed, which were subsequently analysed by NMR and UPLC-TOF/MS operating in positive mode. Comparison of the profiles revealed that the most apparent differences came from the isoflavones in the soy as well as a compound with a molecular mass of 441.202 (M + 1)⁺, which was identified as N,N'-diferuloylputrescine (DFP) and came from the corn. Whether the observed differences in effects are due to the higher levels of isoflavones and DFP is unclear, as is the fact whether the observed differences are typical for organic or conventional produced corn and soy. However, this study shows that this metabolomics approach is suitable for detecting potential differences between products, even in levels of compounds that would have been overlooked with a more targeted approach. As such, the method is suitable for a more systematic study on differences between conventionally and organically produced food.

Tracing and analytical results of the dioxin contamination incident in 2008 originating from the Republic of Ireland.

High levels of dioxins (PCDD/Fs) in pork were discovered in France and the Netherlands at the end of 2008. The contamination was rapidly traced back to a feed stock in the Republic of Ireland (RoI). Burning oil, used for the drying of bakery waste, appeared to be contaminated with PCBs. Consequently, very high levels up to 500 pg TEQ g⁻¹ fat were found in pork. The congener pattern clearly pointed to PCB-oil as a source, but the ratio between the non-dioxin-like indicator PCBs (PCBs 28, 52, 101, 138, 152 and 180) and PCDD/Fs was much lower than observed during the Belgian incident, thereby limiting the suitability of indicator PCBs as a marker for the presence of dioxins and dioxin-like PCBs. This paper describes the tracking and tracing of the incident, the public-private cooperation, the surveillance activities and its results. A major lesson to be learned from this incident is the importance of good private food safety systems. In this incident, it was the private surveillance systems that identified the origin of contamination within 10 days after the first signal of increased dioxin levels in a product. On the other hand, retrospective analyses showed that signals were missed that could have led to an earlier detection of the incident and the source. Above all, the incident would not have occurred when food safety assurance systems had been effectively implemented in the involved feed chain. It is discussed that besides primary responsibility for effective private food safety systems, the competent authorities have to supervise whether the food safety procedures are capable of coping with these kinds of complex food safety issues, while private food companies need to implement the law, and public authorities should supervise and enforce them. Finally, it is discussed whether the health risks derived from consumption of the contaminated batches of meat may have been underestimated during the incident due to the unusually high intake of dioxins.

Gynaecomastia linked to the intake of a herbal supplement fortified with diethylstilbestrol.

This study reports the findings of a supplement marketed on the Internet for prostate problems. The supplement was orally taken by a 60-year-old man with divergent hormonal levels and who was surgically treated for gynaecomastia: development of abnormally large mammary glands in males. The supplement showed a strong effect in a yeast oestrogen bioassay, expressing a yeast-enhanced green fluorescent protein (yEGFP) upon exposure to oestrogens. Using both nuclear magnetic resonance (NMR) and a gradient liquid chromatographic time-of-flight mass spectrometric (LC/TOF-MS) method, the response was shown to be caused by very high levels of diethylstilbestrol, known for causing gynaecomastia. The gynaecomastia was most probably caused by this orally taken 'natural' herbal supplement, as the patient's hormonal levels also returned to normal again when stopping the use of it. This case demonstrates that physicians need to be aware of the use of supplements with illegal components that may be responsible for unwanted side-effects.

The versatility of progress testing assessed in an international context: a start for benchmarking global standardization?

Sharing and collaboration relating to progress testing already takes place on a national level and allows for quality control and comparisons of the participating institutions. This study explores the possibilities of international sharing of the progress test after correction for cultural bias and translation problems. Three progress tests were reviewed and administered to 3043 Pretoria and 3001 Maastricht medical students. In total, 16% of the items were potentially biased and removed from the test items administered to the Pretoria students (9% due to translation problems; 7% due to cultural differences). Of the three clusters (basic, clinical and social sciences) the social sciences contained most bias (32%), basic sciences least (11%). The differences that were found, comparing the student results of both schools, seem a reflection of the deliberate accentuations that both curricula pursue. The results suggest that the progress test methodology provides a versatile instrument that can be used to assess medical schools across the world. Sharing of test material is a viable strategy and test outcomes are interesting and can be used in international quality control.

Global clinical performance rating, reliability and validity in an undergraduate clerkship.

BACKGROUND: Global performance rating is frequently used in clinical training despite its known psychometric drawbacks. Inter-rater reliability is low in undergraduate training but better in residency training, possibly because residency offers more opportunities for supervision. The low or moderate predictive validity of global performance ratings in undergraduate and residency training may be due to low or unknown reliability of both global performance ratings and criterion measures. In an undergraduate clerkship, we investigated whether reliability improves when raters are more familiar with students' work and whether validity improves with increased reliability of the predictor and criterion instrument. METHODS: Inter-rater reliability was determined in a clerkship with more student-rater contacts than usual. The in-training assessment programme of the clerkship that immediately followed was used as the criterion measure to determine predictive validity. RESULTS: With four ratings, inter-rater reliability was 0.41 and predictive validity was 0.32. Reliability was lower and validity slightly higher than similar results published for residency training. CONCLUSION: Even with increased student-rater interaction, the reliability and validity of global performance ratings were too low to warrant the usage of global performance ratings as individual assessment format. However, combined with other assessment measures, global performance ratings may lead to improved integral assessment.

Effects of an in-training assessment programme on supervision of and feedback on competencies in an undergraduate Internal Medicine clerkship.

Assessment drives the educational behaviour of students and supervisors. Therefore, an assessment programme targeted at specific competencies may be expected to motivate supervisors and students to pay more attention to those competencies. In-training assessment (ITA) is regarded as a feasible method for assessing a broad range of competencies. Before and after the implementation of an ITA programme in an undergraduate Internal Medicine clerkship we surveyed students on the frequency of unobserved and observed supervision, and the quality of feedback as inferred from the seniority of the person providing it. After the implementation of the ITA programme supervision increased, but the difference was not statistically significant. The quality of feedback showed no significant change either. Inter-student variation in supervision and feedback remained invariably high after the implementation of the ITA programme. Whether these results are attributable to the way the programme was implemented or to the way the results were assessed remains to be clarified.

Feasibility and reliability of an in-training assessment programme in an undergraduate clerkship.

INTRODUCTION: Structured assessment, embedded in a training programme, with systematic observation, feedback and appropriate documentation may improve the reliability of clinical assessment. This type of assessment format is referred to as in-training assessment (ITA). The feasibility and reliability of an ITA programme in an internal medicine clerkship were evaluated. The programme comprised 4 ward-based test formats and 1 outpatient clinic-based test format. Of the 4 ward-based test formats, 3 were single-sample tests, consisting of 1 student-patient encounter, 1 critical appraisal session and 1 case presentation. The other ward-based test and the outpatient-based test were multiple sample tests, consisting of 12 ward-based case write-ups and 4 long cases in the outpatient clinic. In all the ITA programme consisted of 19 assessments. METHODS: During 41 months, data were collected from 119 clerks. Feasibility was defined as over two thirds of the students obtaining 19 assessments. Reliability was estimated by performing generalisability analyses with 19 assessments as items and 5 test formats as items. RESULTS: A total of 73 students (69%) completed 19 assessments. Reliability expressed by the generalisability coefficients was 0.81 for 19 assessments and 0.55 for 5 test formats. CONCLUSIONS: The ITA programme proved to be feasible. Feasibility may be improved by scheduling protected time for assessment for both students and staff. Reliability may be improved by more frequent use of some of the test formats.

Effectiveness of clinical rotations as a learning environment for achieving competences.

Competences are becoming more and more prominent in undergraduate medical education. Workplace learning is regarded as crucial in competence learning. Assuming that effective learning depends on adequate supervision, feedback and assessment, the authors studied the occurrence of these three variables in relation to a set of clinical competences. They surveyed students at the end of their rotation in surgery, internal medicine or paediatrics asking them to indicate for each competence how often they had received observed and unobserved supervision, the seniority of the person who provided most of their feedback, and whether the competence was addressed in formal assessments. Supervision was found to be scarce and mostly unobserved. Senior staff did not provide much feedback, and assessment mostly targeted patient-related competences. For all variables, the variation between students exceeded that between disciplines. We conclude that conditions for adequate workplace learning are poorly met and that clerkship experiences show huge inter-student variation.

Effectiveness of basic clinical skills training programmes: a cross-sectional comparison of four medical schools.

OBJECTIVE: Training in physical diagnostic skills is an important part of undergraduate medical education. The objective of this study was to study the outcome of skills training at four medical schools. CONTEXT: At the time of the study, three schools had a traditional lecture-based curriculum and one school had a problem-based learning curriculum with a longitudinal skills training programme. All schools offer extended exposure to clerkships. METHOD: A cross-sectional study in four medical schools was performed, using a written test of skills that has good correlation with actual student performance. The scores attained from four student groups were compared within and between the four medical schools. A total of 859 volunteer students from the later four years at each medical school participated in the study. RESULTS: The mean scores in the traditional medical schools increased with the start of skill training and the hands-on experience offered during the clerkships. Students from the school with the longitudinal skills training programme and the problem-based learning approach had significantly higher mean scores at the start of the clerkships, and maintained their lead in the subsequent clinical years. CONCLUSIONS: Longitudinal skills training seems to offer the students a superior preparation for clerkships as well as influencing the students' learning abilities during the clerkships. The effect of the problem-based learning approach, also related to the innovative philosophy of the curriculum, could not be accounted for.

The effect on reliability of adding a separate written assessment component to an objective structured clinical examination.

PURPOSE: To determine the effect on test reliability when a separate written assessment component is added to an objective structured clinical examination (OSCE). METHOD: Volunteers (n=38) from Maastricht Medical School were recruited to take a skills-related knowledge test in addition to their regular end-of-year OSCE. The OSCE scores of these volunteers did not differ from those of the other students of their class. Multivariate generalizability theory was used to investigate the combined reliability of the two test formats as well as their respective contributions to overall reliability. RESULTS: Combining the two formats has an added value. The loss of reliability due to the use of fewer stations in the OSCE can be fully compensated by lengthening the written test component. CONCLUSION: From the perspective of test reliability, it is possible to economize on the resources needed for performance-based assessment by adding a separate written test component.

The effect of a 'don't know' option on test scores: number-right and formula scoring compared.

OBJECTIVES: In multiple-choice tests using a 'don't-know' option the number of correct minus incorrect answers was used as the test score (formula scoring) in order to reduce the measurement error resulting from random guessing. In the literature diverging results are reported when comparing formula scoring and number-right scoring, the scoring method without the don't-know option. DESIGN: To investigate which method was most appropriate, both scoring methods were used in true-false tests (block tests) taken at the end of a second- and third-year educational module (block). The students were asked to answer each item initially by choosing from the response options true, false or don't know, and secondly to replace all don't-know answers by a true-false answer. SETTING: Maastricht University, The Netherlands. SUBJECTS: Medical students. RESULTS: The correct scores for the don't-know answered items were found to be 4.5% and 5.9%, respectively, higher than expected with pure random guesswork. This represents a source of bias with formula scoring, because students who were less willing to guess obtained lower scores. The average difference in the correct minus incorrect score for the two scoring methods (2.5%, P < 0.001, and 3.4%, P < 0. 001, respectively) indicates the size of the bias (compare: the standard deviation of the score equals 11%). Test reliability was higher with formula scoring (0.72 vs. 0.66 and 0.74 vs. 0.66), but the difference decreased when the test was restricted to items which were close to the core content of the block (0.81 vs. 0.77, resp. 0. 75 vs. 0.70). CONCLUSIONS: In deciding what scoring method to use, less bias (number-right scoring) has to be weighed against higher reliability (formula scoring). Apart from these psychometric reasons educational factors must be considered.

Aflatoxin and liver cancer in Sudan.

This study investigated whether aflatoxin contamination of peanut products may contribute to the incidence of hepatocellular carcinoma (HCC) in Sudan. Thirty-seven peanut butter and peanut samples were collected from local markets. Aflatoxin concentrations were significantly higher in West Sudan [87.4 +/- 197.3 (SD) micrograms/kg], a high-risk area, than in Central Sudan (8.5 +/- 6.8 micrograms/kg), a low-risk area. In West Sudan, humid local storage conditions of peanut products were related to high aflatoxin concentrations. In a small case-control study of HCC patients (n = 24) and controls (n = 34), an odds ratio of 7.5 (95% confidence interval = 1.4-40.2) was observed for humid vs. dry local storage conditions. Development of an index of individual HCC exposure was less successful, probably because of year-to-year variability in aflatoxins in food. These preliminary findings justify further research into the role of aflatoxins and hepatitis in HCC incidence in Sudan.

Relative or Absolute Standards in Assessing Medical Knowledge Using Progress Tests.

Norm-referenced pass/fail decisions are quite common in achievement testing in health sciences education. The use of relative standards has the advantage of correcting for variations in test-difficulty. However, relative standards also show some serious drawbacks, and the use of an absolute and fixed standard is regularly preferred. The current study investigates the consequences of the use of an absolute instead of a relative standard. The performance of the developed standard setting procedure was investigated by using actual progress test scores obtained at the Maastricht medical school in an episode of eight years. When the absolute instead of the relative standard was used 6% of the decisions changed: 2.6% of the outcomes changed from fail to pass, and 3.4% from pass to fail. The failure rate, which was approximately constant when using the relative standard, varied from 2% to 47% for different tests when an absolute standard was used. It is concluded that an absolute standard is precarious because of the variations in difficulty of tests.

Identification of metabolites of the anabolic steroid methandienone formed by bovine hepatocytes in vitro.

Monolayer cultures of bovine hepatocytes were used to investigate the biotransformation of methandienone in vitro. After incubation of bovine hepatocytes with methandienone, samples were taken at different times. The samples were treated with deconjugation enzymes and extracted with diethyl ether. The metabolites formed were converted to their trimethylsilylether derivatives. By using gas chromatography-mass spectrometry with electron impact and chemical ionisation, several metabolites were identified. After 24 h of incubation with bovine hepatocytes, 83% of the parent compound was converted to its metabolites. The major metabolite found was 6-beta-hydroxymethandienone with a yield of 24%. This compound was identified after comparison with an authentic sample of 6 beta-hydroxymethandienone, which was synthesized chemically.

An international comparison of knowledge levels of medical students: the Maastricht Progress Test.

The increasing international mobility of medical students has inspired the search for an international assessment format. As one step along this line, kinetics of knowledge acquisition and final cognitive levels of students were compared among one Dutch, one German and four Italian medical faculties. For this comparison, the Maastricht Progress Test (MPT) was used. For four out of the six participating faculties, it was possible to compare the level of knowledge of sixth-year students. These data showed no significant differences on the test as a whole. On the other hand, as judged from cross-sectional data on students from all study years, the kinetics of knowledge acquisition showed different trends. In one school applying problem-based learning, acquisition of knowledge by students occurred almost linearly. In another school, over the first 2 years, acquisition of knowledge occurred only in the basic sciences but not in clinical or public health/behavioural sciences. In two other schools over that same period, students seemed to gain no knowledge at all. In some faculties, a marked boost in knowledge was noted with third- or fourth-year students. These findings may be explained by peculiarities of the respective curricula, selection of students during their studies, and national or local assessment procedures. It is preliminarily concluded that the different educational approaches and assessment systems in medical education in Europe seem to have only limited influence on the final level of knowledge of the graduates. On the other hand, these differences may influence the kinetics of knowledge acquisition, especially in distinct domains like basic or clinical sciences. Therefore, the MPT may not be suitabe to solve the problem of assessment of individual international exchange students, but it may be helpful in identifying corresponding cognitive levels on, for example, basic sciences for students in different curricula.

Digestibility of casein, formaldehyde-treated casein and soya-bean protein in relation to their effects on serum cholesterol in rabbits.

Adult male rabbits were fed on semi-purified diets containing soya-bean protein isolate, casein or formaldehyde-treated casein as the protein source and 1 g cholesterol and 5 g of the non-absorbable marker chronic oxide/kg diet. The concentration of cholesterol in serum and in liver was increased on both the casein and formaldehyde-treated-casein diets. Excretion of bile acids and their concentration in faeces were lower in rabbits fed on casein or formaldehyde-treated casein when compared with rabbits fed on soya-bean protein. Apparent digestibility of nitrogen was lowest when formaldehyde-treated casein was fed, and highest on the casein diet. In rabbits fed on casein treated with formaldehyde, higher proportions of N were found in the water-soluble and trichloroacetic acid-insoluble protein fractions of the gastrointestinal tract contents compared with rabbits on the other two diets. Absorption of phosphate from the gastrointestinal tract was higher in rabbits fed on casein than in rabbits fed on soya-bean protein or formaldehyde-treated casein. The results indicate that, in rabbits, protein digestibility may not be an important determinant of serum cholesterol.