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PubMed2005

A risk-based predictive tool to prevent accidental introductions of nonindigenous marine species.

Preventing the introduction of nonindigenous species (NIS) is the most efficient way to avoid the costs and impacts of biological invasions. The transport of fouling species on ship hulls is an important vector for the introduction of marine NIS. We use quantitative risk screening techniques to develop a predictive tool of the abundance and variety of organisms being transported by ocean-going yachts. We developed and calibrated an ordinal rank scale of the abundance of fouling assemblages on the hulls of international yacht hulls arriving in New Zealand. Fouling ranks were allocated to 783 international yachts that arrived in New Zealand between 2002 and 2004. Classification tree analysis was used to identify relationships between the fouling ranks and predictor variables that described the maintenance and travel history of the yachts. The fouling ranks provided reliable indications of the actual abundance and variety of fouling assemblages on the yachts and identified most (60%) yachts that had fouling on their hulls. However, classification tree models explained comparatively little of the variation in the distribution of fouling ranks (22.1%), had high misclassification rates (approximately 43%), and low predictive power. In agreement with other studies, the best model selected the age of the toxic antifouling paint on yacht hulls as the principal risk factor for hull fouling. Our study shows that the transport probability of fouling organisms is the result of a complex suite of interacting factors and that large sample sizes will be needed for calibration of robust risk models.

Animals↗
PubMed2000

Myocardial gene transfer by selective pressure-regulated retroinfusion of coronary veins.

Catheter-based percutaneous transluminal gene delivery (PTGD) into the coronary artery still falls behind the expectations of an efficient myocardial gene delivery system. In this study gene delivery was applied by selective pressure-regulated retroinfusion through the coronary veins to prolong adhesion of replication defective adenovirus within the targeted myocardium. Adenoviral vectors consisted either of luciferase (Ad.rsv-Luc) or beta-galactosidase (Ad.rsv-betaGal) reporter gene under control of an unspecific promotor derived from the Rous sarcoma virus (RSV). In this pig model, selective retrograde gene delivery into the anterior cardiac vein during a brief period of ischemia substantially increased reporter gene expression in the targeted myocardium (LAD region) compared with antegrade delivery as a control. Repeated retrograde delivery during two periods of brief ischemia resulted in a more homogeneous transmural expression predominantly observed in cardiomyocytes (X-gal-staining). In the nontargeted myocardium (CX region) there was no evidence for adenoviral transfection. From our data we infer that selective pressure-regulated retroinfusion is a promising approach for efficient percutaneous transluminal gene delivery to the myocardium. Gene Therapy (2000) 7, 232-240.

Adenoviridae↗
PubMed2006

More complete gene silencing by fewer siRNAs: transparent optimized design and biophysical signature.

Highly accurate knockdown functional analyses based on RNA interference (RNAi) require the possible most complete hydrolysis of the targeted mRNA while avoiding the degradation of untargeted genes (off-target effects). This in turn requires significant improvements to target selection for two reasons. First, the average silencing activity of randomly selected siRNAs is as low as 62%. Second, applying more than five different siRNAs may lead to saturation of the RNA-induced silencing complex (RISC) and to the degradation of untargeted genes. Therefore, selecting a small number of highly active siRNAs is critical for maximizing knockdown and minimizing off-target effects. To satisfy these needs, a publicly available and transparent machine learning tool is presented that ranks all possible siRNAs for each targeted gene. Support vector machines (SVMs) with polynomial kernels and constrained optimization models select and utilize the most predictive effective combinations from 572 sequence, thermodynamic, accessibility and self-hairpin features over 2200 published siRNAs. This tool reaches an accuracy of 92.3% in cross-validation experiments. We fully present the underlying biophysical signature that involves free energy, accessibility and dinucleotide characteristics. We show that while complete silencing is possible at certain structured target sites, accessibility information improves the prediction of the 90% active siRNA target sites. Fast siRNA activity predictions can be performed on our web server at http://optirna.unl.edu/.

Artificial Intelligence↗
PubMed2003

Summary of Group 8: Development and extension of linkage methods.

The diverse contributions to Group 8 focus on the development and extension of linkage methods, and share themes that are organized around approaches to analysis. The themes discussed include issues of the accuracy of estimates of marker identity-by-descent (IBD) information, the influence of such IBD information on linkage detection, and methods for dealing with genetic heterogeneity and multiple testing. In addition, challenges were identified and solutions were offered for coping with some of the common problems of complex trait analysis, including trait model selection and computational compromises. Analytic approaches based on Bayesian and Monte Carlo methods were prominent, and provided optimistic results.

Bayes Theorem↗
PubMed2002

[Visceral lesions in mammals and birds exposed to agents of human cercarial dermatitis].

Over the past few years, the cercarial dermatitis has become a new problem of public health, obviously linked to the prolonged stay of migrant birds on our territory. This is a skin affection characterized by pruriginous and papulous eruptions caused by penetration of avian bilharzian larvae under the skin. These larvae are emitted by molluscs, mostly limneids. In aquatic birds, especially in migrating Anatidae, these larvae reach the visceral vessels, become adults in a few weeks, lay eggs, then degenerate. Corresponding miracidia contaminate new limneids. Since 1993, the total number of annual cases of cercarial dermatitis has increased from only ten to thousands in France and the affection rages in pools where limneids, migrating water birds and swimmers gather together. Fever, respiratory and/or digestive allergic symptoms appear in some cases. This clinical pattern has encouraged to undertake research on the future of these bilharzian larvae in mammals organism. A preliminary investigation on a rodent model showed that, once the skin barrier had been crossed, the schistosomulae migrated into the lungs of the host; there they survived a week and induced lesions. The goal of this study is to carry on the research, over a longer period, after exposure to cercariae, simultaneously in mammals and birds, with two species of bilharziae present in France. The selected models are the gerbil Meriones unguiculatus for mammals, and the ducks Anas platyrhynchos and Cairina moschata, for birds. 5 M. unguiculatus and 2 A. platyrhynchos were exposed to cercariae emitted by Radix auricularia; 2 gerbils and 5 A. platyryhnchos to larvae of R. peregra, 3 C. moschata to larvae emitted by two species of molluscs: 70-230 from R. auricularia and 330-585 from R. peregra. 5 gerbils died between 2 and 5 weeks after exposure, 2 gerbils sacrificed early, served as control animals for skin manifestations. Eight ducks were sacrificed between 2 and 4 weeks after; the 2 last ones, exposed several times, were sacrificed respectively 7 and 13 weeks after the first exposure. Visceral and skin samples were submitted to histological study. The control gerbils developed skin dermatitis. In ducks, R. auricularia was the vector of Trichobilharzia franki, whose selective dwelling site was the mesentery; R. peregra was the vector of an indeterminate species found in the lungs and nose. This species is called Bilharzia sp. in this study. The ducks, exposed to two kinds of larvae, displayed worms in these two main locations. In gerbils, T. franki induced lesions in the mesenteric veins and the peritoneum. Bilharzia sp. gave rise to lesions in lung arteries, pleura and liver veins. Vascular changes encompassed endothelitis and lymphocytic vasculitis, while serosa displayed mesothelial hyperplasia. The types of lesions observed in gerbils were noticed in ducks, and, according to the species of bilharzia, in the homologous viscera. Additional foreign body granulomas centred on worm's debris or their eggs, and vascular thromboses were present, too. In addition, ducks displayed lesions involving several other viscera including the intestine, the kidneys and the peripheral nerves. These changes were multiple and diffuse in C. moschata exposed to two species of bilharziae. They were observed mainly in mesenteric and intestinal vessels, pulmonary arteries and hepatic veins. In gerbils, the lesions persisted 2 to 5 weeks after exposure, but worms were not identified in the neighbouring tissues near the damaged vessels. In ducks, lesions were important between 2 and 7 weeks after exposure; they co-existed with live or dead worms, sometimes paired, with or without eggs. The hepatic lesions regressed 13 weeks, after exposure. In mammals and birds, young worms could migrate into the same visceral vessels, and stimulating formation of persistent lesions. In individuals exposed to the same cercariae, development of similar lesions would be probable.

Animals↗
PubMed2005

What is the function of hippocampal theta rhythm?--Linking behavioral data to phasic properties of field potential and unit recording data.

The extensive physiological data on hippocampal theta rhythm provide an opportunity to evaluate hypotheses about the role of theta rhythm for hippocampal network function. Computational models based on these hypotheses help to link behavioral data with physiological measurements of different variables during theta rhythm. This paper reviews work on network models in which theta rhythm contributes to the following functions: (1) separating the dynamics of encoding and retrieval, (2) enhancing the context-dependent retrieval of sequences, (3) buffering of novel information in entorhinal cortex (EC) for episodic encoding, and (4) timing interactions between prefrontal cortex and hippocampus for memory-guided action selection. Modeling shows how these functional mechanisms are related to physiological data from the hippocampal formation, including (1) the phase relationships of synaptic currents during theta rhythm measured by current source density analysis of electroencephalographic data from region CA1 and dentate gyrus, (2) the timing of action potentials, including the theta phase precession of single place cells during running on a linear track, the context-dependent changes in theta phase precession across trials on each day, and the context-dependent firing properties of hippocampal neurons in spatial alternation (e.g., "splitter cells"), (3) the cholinergic regulation of sustained activity in entorhinal cortical neurons, and (4) the phasic timing of prefrontal cortical neurons relative to hippocampal theta rhythm.

Action Potentials↗
PubMed2002

Synthesis, biological activity and receptor-based 3-D QSAR study of 3'-N-substituted-3'-N-debenzoylpaclitaxel analogues.

3'-N-Substituted-3'-N-debenzoylpaclitaxel analogues were synthesized and investigated for their 3-D QSAR by using comparative molecular field analysis (CoMFA). The CoMFA model obtained from receptor(microtubule)-paclitaxel binding structure displays an excellent predictive power to forecast the biological activity of new 3'-N-substituted-3'-N-debenzoylpaclitaxel analogues as well as the ability to explain the activity of the known paclitaxel analogues. The cross-validated r(2)(cv) values of the selected models are 0.835 and 0.616 for A549 and SK-OV-3, respectively, and the non-cross-validated r(2)(ncv) values of them are 0.992 and 0.974.

Antineoplastic Agents↗
PubMed2003

Influence of implant length and bicortical anchorage on implant stress distribution.

BACKGROUND: Short implants present superior failure rates for everybody. PURPOSE: The aim of this theoretic study was to assess to what extent implant length and bicortical anchorage affect the way stress is transferred to implant components, the implant proper, and the surrounding bone. MATERIALS AND METHODS: Stress analysis was performed using finite element analysis. A three-dimensional linear elastic model was generated. All implants modeled were of the same diameter (3.75 mm) but varied in length, at 6, 7, 8, 9, 10, 11, and 12 mm (Brånemark System, Nobel Biocare AB, Gothenburg, Sweden). Each implant was modeled with a titanium abutment screw and abutment, a gold cylinder and prosthetic screw, and a ceramic crown. The implants were seated in a supporting bone structure consisting of cortical and cancellous bone. An occlusal load of 100 N was applied at a 30 degrees angle to the buccolingual plane. RESULTS: With the selected model and bone properties, the coronal cortical anchorage was dominating, and the bone stress concentrated to that area. CONCLUSIONS: The maximum bone stress was virtually constant, independent of implant length and bicortical anchorage. The maximum implant stress, however, increased somewhat with implant length and bicortical anchorage.

Bone and Bones↗
PubMed2001

Thrombospondin-1 and -2 in node-negative breast cancer: correlation with angiogenic factors, p53, cathepsin D, hormone receptors and prognosis.

OBJECTIVE: Thrombospondins (TSP(s)) are a multigene family of five secreted glycoproteins involved in the regulation of cell proliferation, adhesion and migration. Two members of the TSP family, namely TSP-1 and TSP-2, are also naturally occurring inhibitors of angiogenesis. The aim of the present study was to determine the prognostic significance of the determination of TSP-1 and -2 and their correlation with the angiogenic peptides vascular endothelial growth factor (VEGF) and thymidine phosphorylase (TP), as well as with other biological and clinicopathological features investigated. METHODS: We evaluated a series of 168 women with node-negative breast cancer with a median follow-up period of 66 months, not treated with adjuvant therapy. The cytosolic levels of TSP-1 and -2 were determined in the primary tumour by a commercially available immunometric assay. RESULTS: We found that 166 tested tumours had measurable levels of TSP-1 and -2 protein (median value 5.978, range 0.579-31.410 ng/mg of protein). On the basis of Spearman's rank correlation coefficient, a weak inverse association of TSP-1 and -2 with tumour size and cathepsin D was found. Moreover, principal component analysis on ranks evidenced a poor association between TSP-1 and -2, VEGF and TP. The results of the clinical outcome were analysed by both univariate and multivariate [for relapse-free survival (RFS) only]) Cox regression models. TSP-1 and -2 were not significant prognostic factors in univariate analysis for either RFS (p = 0.427) or overall survival (p = 0.069). To investigate the 'angiogenic balance hypothesis', bivariate analyses were performed to investigate the interactions of TSP-1 and -2 with VEGF, TP or p53, but none were included in the selected models. Finally, in multivariate analysis for RFS a baseline model, previously defined in a larger case series and inclusive of VEGF, TP and their interaction was adopted. It was highly significant (p = 0.002, Harrell c statistic value of 0.703); but when TSP-1 and -2 were added, their contribution was negligible (p = 0.731, Harrell c statistic value of 0.705). CONCLUSIONS: The results of this study suggest that TSP-1 and -2 do not provide additional prognostic contribution to the joint effects of VEGF and TP. In the series of node-negative breast cancer patients investigated, determination of the angiogenic peptides VEGF and TP gave significant prognostic information. On the contrary, TSP-1 and -2, potential naturally occurring negative regulators of angiogenesis, lacked prognostic value.

Biomarkers, Tumor↗
PubMed2003

On the formation of persistent states in neuronal network models of feature selectivity.

We study the existence and stability of localized activity states in neuronal network models of feature selectivity with either a ring or spherical topology. We find that the neural field has mono-stable, bi-stable, and tri-stable regimes depending on the parameters of the weighting function. In the case of homogeneous inputs, these localized activity states are marginally stable with respect to rotations. The response of a stable equilibrium to an inhomogeneous input is also determined.

Animals↗
PubMed1999

Release kinetics of a controlled-release multiparticulate dosage form prepared using a hot-melt fluid bed coating method.

Dissolution profiles of various multiparticulate controlled-release dosage forms prepared by applying lipophilic materials using a hot-melt coating technique were analyzed to determine release kinetics. The dosage forms were prepared using a novel solid dispersion hot-melt fluid bed coating method. Various lipophilic materials were investigated and those showing promise as potential controlled-release coating agents were analyzed further. Dissolution data were used as the primary basis of comparison. A dual equation combining first-order and square-root-of-time release kinetics was used to fit data. The statistical output from nonlinear regression software suggests that this equation describes the data better than the individual equations alone. Particular parameters used to compare the various models include R2, the model selection criteria, and the coefficient of determination. The high degree of fit offered by the dual equation implies that two distinct kinetic processes may be involved in the release of drug from the dosage forms. A possible release mechanism based on this information is offered. The dual equation was shown to be a superior model for the controlled-release system chosen for study. The equation also appears to be applicable to a variety of other controlled-release systems reported in the literature.

Chlorpheniramine↗
PubMedDate not supplied

Predicting the cost of illness: a comparison of alternative models applied to stroke.

Predictions of cost over well-defined time horizons are frequently required in the analysis of clinical trials and social experiments, for decision models investigating the cost-effectiveness of interventions, and for macro-level estimates of the resource impact of disease. With rare exceptions, cost predictions used in such applications continue to take the form of deterministic point estimates. However, the growing availability of large administrative and clinical data sets offers new opportunities for a more general approach to disease cost forecasting: the estimation of multivariable cost functions that yield predictions at the individual level, conditional on intervention(s), patient characteristics, and other factors. This raises the fundamental question of how to choose the "best" cost model for a given application. The central purpose of this paper is to demonstrate how to evaluate competing models on the basis of predictive validity. This concept is operationalized according to three alternative criteria: 1) root mean square error (RMSE), for evaluating predicted mean cost; 2) mean absolute error (MAE), for evaluating predicted median cost; and 3) a logarithmic scoring rule (log score), an information-theoretic index for evaluating the entire predictive distribution of cost. To illustrate these concepts, the authors conducted a split-sample analysis of data from a national sample of Medicare-covered patients hospitalized for ischemic stroke in 1991 and followed to the end of 1993. Using test and training samples of about 500,000 observations each, they investigated five models: single-equation linear models, with and without log transform of cost; two-part (mixture) models, with and without log transform, to directly address the problem of zero-cost observations; and a Cox proportional-hazards model stratified by time interval. For deriving the predictive distribution of cost, the log transformed two-part and proportional-hazards models are superior. For deriving the predicted mean or median cost, these two models and the commonly used log-transformed linear model all perform about the same. The untransformed models are dominated in every instance. The approaches to model selection illustrated here can be applied across a wide range of settings.

Cerebrovascular Disorders↗
PubMed2002

Effects of inspiratory oxygen concentration and ventilation method on a model of hemorrhagic shock in rats.

The effect of inspiratory oxygen concentration and the ventilation method on hemorrhagic shock was investigated. Twenty-eight rats were divided into four groups: mechanical ventilation with pure oxygen (M100); mechanical ventilation with air (M21); spontaneous respiration with pure oxygen (S100); and spontaneous respiration with air (S21). Under intravenous pentobarbital anesthesia, hemorrhagic shock (HS) was induced by withdrawal of blood from the femoral artery. Mean arterial blood pressure (MAP) was maintained at 40-50 mmHg for 2 h. After HS, the blood remaining in the reservoir was reinfused. Then survival rate and MAP were monitored for 2 h. Blood samples were withdrawn and vascular reactivity to norepinephrine (NE; 3.0 micrograms/kg) was tested before and after HS. Results were shown by changes in MAP in response to NE. During HS, the survival rate of the S21 group was lower than that of the M100 and S100 groups (p < .05). Before HS, MAPs of M100 and S100 groups were significantly higher than those of M21 and S21 groups (p < .05). In the M100 and M21 groups, MAPs at 2 h after reinfusion were significantly lower than the baseline value (p < .05). Before HS, reactivity to NE of the M21 group was significantly higher than that of the other groups (p < .05). In the M21 group, reactivity to NE after HS was significantly lower than it was before HS (p < .05). Inspiratory oxygen concentration and the ventilation method affect the survival rate and vascular reactivity of the rat hemorrhagic shock model. Selection of the inspiratory oxygen concentration and the ventilation method should be made according to the purpose of the individual experiment.

Animals↗
PubMed2006

The gene expression profile in refractory periodontitis patients.

BACKGROUND: There are no specific bacterial profiles or diagnostic tests capable of identifying refractory periodontitis patients before a treatment regimen is initiated. Therefore, in this high-risk cohort of patients who do not respond appropriately, host factors that might be partly under genetic control may play a crucial role in their susceptibility. Specifically, we tested the hypothesis that patients with refractory periodontitis have multiple upregulated and/or downregulated genes that might be important in influencing clinical risk. METHODS: Oral subepithelial connective tissues were harvested aseptically from seven refractory periodontitis and seven periodontally well-maintained patients. An RNA isolation kit was used to isolate total RNA from tissue samples that had been stabilized in the RNA stabilizing reagent. The isolated total RNA was then subjected to gene expression profiling using the microarray to measure gene expression levels. The retrieved data were analyzed with a computer program for the differential analysis of gene expression microarray experiments. In addition, real-time polymerase chain reaction (PCR) analysis was performed on selected samples to confirm the microarray data's gene expression patterns. RESULTS: A total of 68 upregulated and six downregulated genes were identified that were differentially expressed at least two-fold out of 22,283 genes we analyzed. The selected model provided a 93% intrinsic validation along with a 93% extrinsic validation. To validate the microarray data, five upregulated genes (lactotransferrin [LTF], matrix metalloproteinase-1 [MMP-1], MMP-3, interferon induced-15 [IFI-15], and Homo sapiens hypothetical protein MGC5566) and two downregulated genes (keratin 2A [KRT2A] and desmocollin-1 [DSC-1]) were randomly selected for further analysis by real-time PCR. The relative RNA expression level of these genes measured by real-time PCR was similar to those measured by microarrays. CONCLUSION: The combined use of microarray technology with the computer program for the differential analysis of gene expression microarray experiments provided a set of candidate genes that may serve as novel therapeutic intervention points and improved diagnostic and screening procedures for high-risk individuals.

Aged↗
PubMed2005

In silico microdissection of microarray data from heterogeneous cell populations.

BACKGROUND: Very few analytical approaches have been reported to resolve the variability in microarray measurements stemming from sample heterogeneity. For example, tissue samples used in cancer studies are usually contaminated with the surrounding or infiltrating cell types. This heterogeneity in the sample preparation hinders further statistical analysis, significantly so if different samples contain different proportions of these cell types. Thus, sample heterogeneity can result in the identification of differentially expressed genes that may be unrelated to the biological question being studied. Similarly, irrelevant gene combinations can be discovered in the case of gene expression based classification. RESULTS: We propose a computational framework for removing the effects of sample heterogeneity by "microdissecting" microarray data in silico. The computational method provides estimates of the expression values of the pure (non-heterogeneous) cell samples. The inversion of the sample heterogeneity can be facilitated by providing accurate estimates of the mixing percentages of different cell types in each measurement. For those cases where no such information is available, we develop an optimization-based method for joint estimation of the mixing percentages and the expression values of the pure cell samples. We also consider the problem of selecting the correct number of cell types. CONCLUSION: The efficiency of the proposed methods is illustrated by applying them to a carefully controlled cDNA microarray data obtained from heterogeneous samples. The results demonstrate that the methods are capable of reconstructing both the sample and cell type specific expression values from heterogeneous mixtures and that the mixing percentages of different cell types can also be estimated. Furthermore, a general purpose model selection method can be used to select the correct number of cell types.

Algorithms↗
PubMed2001

A semiparametric deconvolution model to establish in vivo-in vitro correlation applied to OROS oxybutynin.

In vitro-in vivo correlation (IVIVC) models may be used to predict in vivo drug concentration-time profiles given in vitro release characteristics of a drug. This prediction is accomplished by incorporating in vitro release characteristics as an input function (A(vitro)) to a pharmacokinetics model. This simple approach often results in biased predictions of observed in vivo drug concentrations, and it can result in rejecting IVIVC. To solve this problem we propose a population IVIVC model that incorporates the in vitro information and allows one to quantify possibly changed in vivo release characteristic. The model assumes linear kinetics and describes the in vivo release as a sum of A(vitro) and a nonparametric function (A(d), a spline) representing the difference in release due to in vivo conditions. The function A(vitro) and its variability enter the model as a prior distribution. The function A(d) is estimated together with its intersubject variability. The number of parameters associated with A(d) defines the model: no parameters indicates perfect IVIVC, a large number of parameters indicates poor IVIVC. The number of parameters is determined using statistical model selection criteria. We demonstrate the approach to solve the IVIVC problem of an oral extended release oxybutynin form (OROS), administered in three pharmacokinetic studies. These studies present a particular challenging case; that is, the relative bioavailability for the OROS administration is >100% compared with that of the immediate-release form. The result of our modeling shows that the apparent lack of IVIVC can be overcome: in vivo concentration can be predicted (within or across data sets) based on in vitro release rate together with a simple form of systematic deviation from the in vitro release.

Biological Availability↗
PubMed2006

Factors affecting patient-controlled analgesia requirements.

BACKGROUND/PURPOSE: Intravenous patient-controlled analgesia (IVPCA) is one of the most widely used postoperative analgesic methods. Many factors could affect the total analgesic consumption of IVPCA. This retrospective study investigated the relationship between patient characteristics and total morphine consumption during a 3-day course of postoperative IVPCA. METHODS: Patients receiving surgery under general anesthesia with postoperative IVPCA for 3 days during the period between January 2002 and December 2003 were included. Patient data including age, sex, weight, height, body mass index (BMI), operation type and site were collected. Total morphine consumption was recorded at the end of the 3-day IVPCA course. Stepwise regression analyses were conducted to select factors significantly associated with morphine consumption. Stratified analyses were also conducted among different surgical, BMI and age subgroups. RESULTS: A total of 1308 patients (646 men, 662 women) were included in the analysis. For all operations, weight, age, procedures involving malignant disease, and surgical sites were significantly associated with total morphine consumption. The R and adjusted R2 values of the selected model were 0.509 and 0.256, respectively. Weight was the only common factor among all stratified analyses (all p < 0.001). Age was negatively correlated with morphine consumption. Gender was not a significant factor except in lower abdominal operations. Height was not associated with total morphine consumption. BMI status was not significantly associated with components of the selected factors. CONCLUSION: This study demonstrated that weight and surgical sites significantly influence total IVPCA requirements. The effect of surgical sites should be considered when evaluating the influence of demographic characteristics on IVPCA demand.

Aged↗
PubMed2006

Utility of in vitro test methods to assess the activity of xenoestrogens in fish.

The results of the present study have demonstrated the utility of an estrogen receptor (ER) competitive ligand-binding assay, a hepatocyte vitellogenin (VTG) induction bioassay, and an ER reporter gene bioassay in characterizing the activity of model estrogen agonists (17beta-estradiol [E2], ethynylestradiol, and nonylphenol) and antagonists (tamoxifen and ZM 189154) in rainbow trout (Oncorhynchus mykiss). The in vitro results were validated against in vivo trout waterborne exposures to E2 and tamoxifen. The results showed that all three in vitro assays were capable of detecting the hormonal activities of the selected model compounds in a dose-dependent manner, with the exception of nonylphenol in the ER reporter gene bioassay. However, the relative potency rankings of the model compounds were not consistent between these assays, which suggests that the relative potencies obtained within assays may have limited predictive value between assays. Discrepancies in potencies most likely can be attributed to the different levels of cellular organization in each assay. In addition to model compounds, we also evaluated the responses of the ER-binding assay and the hepatocyte VTG induction bioassay to complex mixtures associated with endocrine effects in fish, specifically extracts of pulp mill effluent. Of the 14 pulp mill effluent extracts tested, only six showed activity in both assays, whereas the remaining eight samples showed activity in only one of the two assays. The hepatocyte VTG induction bioassay consistently showed that the pulp mill effluent extracts were antiestrogenic, which to our knowledge has not been reported in previous studies. Collectively, these results suggest that a combination of in vitro assays that depend on differing endpoints is required to identify potential xenoestrogens and to characterize their modes of action.

Animals↗