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Vivo Methods (vivo + methods)
Selected AbstractsEcdysteroid synthesis and imaginal disc development in the midge Chironomus riparius as biomarkers for endocrine effects of tributyltinENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2002Torsten Hahn Abstract Acute effects of the endocrine disruptor bis (tri- n -butyltin) oxide (TBTO) on molting-hormone biosynthesis and imaginaldisc development were investigated in larvae of the midge Chironomus riparius (Meigen). Ecdysteroid synthesis was measured by 24-h incubation of molting-hormone-synthesizing tissues (prothoracic glands) in vitro with or without the addition of TBTO. The amount of ecdysteroids produced was analyzed by radioimmunoassay. Developmental effects in vivo were investigated by determining the developmental phase of the genital imaginal discs before and after a 48-h exposure to TBTO in water. Sex-specific effects were found with both endpoints. Ecdysteroid synthesis was significantly reduced (analysis of variance [ANOVA], p , 0.005) in female larvae at all concentrations (TBTO-Sn at 50, 500, and 5,000 ng/L), whereas a significant elevation of the biosynthesis rate occurred in male larvae in the 500-ng/L treatment (ANOVA, p , 0.05). In vivo experiments with development of the genital imaginal disc within a 48-h exposure period revealed a significantly slower development in female larvae and a significantly faster development in male larvae (contingency tables, p , 0.001) at all concentrations tested (TBTO-Sn at 10, 50, 200, and 1,000 ng/L). These results partly coincided with the in vitro effects on molting-hormone synthesis. The 48-h median lethal concentration (LC50) was 25 ,g/L (20,30 ,g/L 95% confidence intervals). The combination of in vitro and in vivo methods has proven to be a useful approach for the detection of endocrine effects of TBTO in C. riparius at levels 2,000-fold below the LC50 value. High sensitivity and short test duration suggest that chironomids may have potential as freshwater sentinel organisms for endocrine-disrupting chemicals. [source] In vitro evaluation of sun protection factors of sunscreen agents using a novel UV spectrophotometric techniqueINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 4 2008M. D. Bleasel Synopsis A method for the in vitro determination of low- and high-value sun protection factors (SPF) of sunscreens using artificial substrates and a novel pseudo double beam (PDB) mode of operation of a standard double beam UV spectrophotometer is described. The method allows transmittance to be calculated from detector responses of reference and sample beams measured at different gain levels and facilitates the accurate quantification of low levels of electromagnetic radiation transmitted through highly absorbing samples. The spectrophotometer was modified to hold quartz diffusing plates on which a substrate [TransporeÔ adhesive tape or human stratum corneum obtained from a skin surface biopsy (SSB)] and the sunscreens to be tested were applied. The PDB mode of operation increased the effective linear range of the detector response of the spectrophotometer by a factor of approximately 20000-fold, enabling the in vitro SPF determination technique to be applied to both high and low SPF value sunscreens. Eight commercial sunscreens with known SPF values ranging from 4 to 77, previously determined by in vivo methods, were tested in vitro using both test substrates and correlations between the in vivo and in vitro values were determined. SPF values determined using the in vitro method correlated well with the known in vivo results (TransporeÔ tape, R2 = 0.611; SSB, R2 = 0.7928). The in vitro SPF obtained for one of the tested products differed substantially from the cited in vivo SPF value. Independent in vitro and in vivo re-evaluation of the SPF of this product matched the value predicted by the present method much more closely than the originally cited in vivo value. All determined SPFs were ordered correctly in comparison to in vivo ranking and the technique appeared to correctly identify a sunscreen that had a labelled SPF value that was significantly higher than its true SPF. Résumé Une méthode destinée à déterminer in vitro les facteurs de protection solaire (SPF) d'écrans solaires de faible et haut indice est décrite. Elle met en ,uvre des substrats artificiels et un nouveau mode opératoire reposant sur l'utilisation du pseudo double faisceau (PDB) d'un spectrophotomètre UV double faisceau standard. La méthode permet le calcul de la transmittence à partir des réponses du détecteur de référence et la mesure en simple faisceau à différents niveaux de gain facilitant ainsi la quantification précise des faibles niveaux de radiation électromagnétique (EMR) transmis à travers des échantillons hautement absorbants. Le spectrophotomètre a été modifié de façon à fixer des plaques diffusantes en quartz sur lesquelles un substrat (ruban adhésif Transport TM ou du stratum corneum humain obtenu à partir de biopsie de surface de peau (SSB) et les écrans solaires testés ont été appliqués. Le mode opératoire PTB augmente la gamme linéaire effective de la réponse du détecteur du spectrophotomètre d'un facteur approximatif 20.000 permettant, à cette technique de détermination des SPF in vitro, d'être appliquée à la fois sur les écrans solaires de haut et bas SPF. Huit écrans solaires commerciaux de SPF connus allant de 4 à 77, préalablement déterminés par des méthodes in vivo, ont été testés in vitro en utilisant les deux substrats, et les corrélations entre les valeurs in vivo et in vitro ont été déterminées. Les valeurs SPF déterminées en utilisant la méthode in vitro est bien corrélée avec les résultats in vivo connus (ruban transport, R2 = 0.611; SSB, R2 = .7928). Le SPF in vitro pour l'un des produits testés diffère fortement des valeurs SPF citées in vivo. Une réévaluation indépendante des SPF in vitro et in vivo de ce produit ajuste la valeur prédite par la présente méthode de façon beaucoup plus proche que la valeur originale citée in vivo. Tous les SPF ainsi déterminés sont ordonnés correctement en comparaison au classement in vivo et la technique semble identifier correctement un écran solaire qui possède un SPF libellé significativement plus haut que son vrai SPF. [source] A pilot study into the chemical and sensorial effect of thyme and pennyroyal essential oil on hens eggsINTERNATIONAL JOURNAL OF FOOD SCIENCE & TECHNOLOGY, Issue 9 2009Tegan J. Smith Summary Previously, it has been shown that thyme and pennyroyal essential oils have potential as acaricides against the poultry red mite Dermanyssus gallinae. The effect of these oils on the occurrence of taint in hens' eggs was investigated using in vitro immersion tests and in vivo methods where poultry huts containing laying hens were sprayed weekly with oil. Analysis of extracts from eggs by gas chromatography mass spectrometry (GCMS) showed that no detectable taint was present in hens' eggs. However, consumer sniff tests, although restricted and only preliminary in nature, showed a significant negative response to the smell of both unbroken and cracked open eggs between those taken from poultry huts treated with pennyroyal essential oil and all other eggs tested. Some essential oils, such as thyme, may be more suitable as an acaracidal product than others, such as pennyroyal, for the use within a commercial poultry system for laying hens. [source] Approaches in the safety evaluations of veterinary antimicrobial agents in food to determine the effects on the human intestinal microfloraJOURNAL OF VETERINARY PHARMACOLOGY & THERAPEUTICS, Issue 1 2005C. E. CERNIGLIA The administration of antimicrobial agents to livestock creates potential for antibiotic residues to enter the food supply and be consumed by humans. Therefore, as a process of food animal drug registration, national regulatory agencies and international committees evaluate data regarding the chemical, microbiologic, pharmacokinetic, pharmacodynamic, pharmacologic, toxicologic, and antimicrobial properties of veterinary drugs to assess the safety of ingested antimicrobial residues to consumers. Currently, European, Australian and United States guidelines for veterinary drug registration require a safety assessment of microbiologic hazards from consumption of antimicrobial residues taking into account the potentially adverse effects on human intestinal microflora. The main concerns addressed are selection of resistant bacteria in the gastrointestinal tract and disruption of the colonization barrier of the resident intestinal microflora. Current requirements differ among national agencies. Efforts are ongoing internationally to review and harmonize approaches and test methods and protocols for application to these microbiologic safety evaluations of antimicrobial drug residues in food. This review describes the background to current regulatory approaches used in applying in vitro and in vivo methods to set a microbiologic acceptable daily intake for residues in food derived from animals treated with an antimicrobial agent. This paper also examines the current research needs to support these evaluations. [source] 004 Validation of in vivo and in vitro methods to measure UVA protectiveness of sunscreenPHOTODERMATOLOGY, PHOTOIMMUNOLOGY & PHOTOMEDICINE, Issue 2 2002C. Cole Standard methods for measuring the sunburning protection of sunscreens (SPF) are globally established. In vivo methods of determining UVA protectiveness of sunscreens have been reduced to either a Persistent Pigment Darkening (PPD) or Protection Factor A (PFA-either persistent pigment darkening or erythema endpoints) test protocols. Both of these techniques require human exposure to UVA radiation that can be time consuming and do not benefit the human subject. Validated methodologies that would minimize the UVA exposure, or could be performed in vitro would simplify the determination of UVA protectiveness and assist product optimization. Diffuse reflectance spectroscopy of sunscreens on human skin was utilized to evaluate a series of seven model sunscreen systems that were previously evaluated in vivo by both PPD and PFA testing. Correlation of the values found with this technique correlated highly with the in vivo test results, with 1:1 correspondence of protection values. Separately, an in vitro test model was assessed on these same model sunscreens. Sunscreen was applied to roughened surface quartz plates, and the absorbance of the sunscreens was measured before and after UV exposure. The absorbance was mathematically forced to fit the in vivo SPF value and the UVA protectiveness was calculated using both erythema and pigment darkening action spectra. The in vitro predictions of UVA was highly correlated with the in vivo PPD and PFA values. It was determined that preirradiation of the sunscreen samples is needed to accurately predict the protection provided by sunscreens that are not photostable. Both of these techniques provide new ways to accurately predict sunscreen UVA protectiveness. [source] A method to determine protein digestibility of microdiets for larval and early juvenile fishAQUACULTURE NUTRITION, Issue 6 2009J.M. HANSEN Abstract A method to evaluate protein quality using in vivo methods was developed for larval fish. FluoSpheres® fluorescent microspheres (10 ,m) were incorporated into two test diets, our standard zein microdiet (ZMD) and a microdiet with identical ingredients except for the replacement of high quality fish meal with the same product cooked for 24 h at 80 °C (ZMD-CF). Several trials were performed to design a reliable method to test digestibility using FluoSpheres® as a marker. The developed in vivo technique was tested on 35 days posthatch (dph) larval Atlantic cod (Gadus morhua L.) and two tropical fish species in the early juvenile stage. The method took into account loss of total protein to the faecal pellet and water column. Apparent digestibility of protein in larval cod fed ZMD was significantly higher than that of larvae fed ZMD-CF (P < 0.05). A growth study to validate differences between the two diets showed significant differences in growth and survival of larvae fed ZMD versus ZMD-CF (P < 0.05). Further validation of our results was indicated through the use of a pH-stat method using enzymes extracted from 35 dph larval cod guts. This novel technique will be advantageous for researchers to evaluate feed ingredients for larval marine fish and is adaptable to many different areas of larval fish nutrition. [source] | ||||||||||