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PubMed2003

Assessing food additive toxicity using a cell model.

Food additives are widely used for technological purposes and their presence is often substantial daily diet. They have also been accused forvarious toxic reactions in humans. The toxicity of the food color tartrazine, the preservatives sodium nitrate and sodium benzoate, and the antioxidant BHT, was studied using the protozoan Tetrahymenapyriformis as a toxicological model. The 4 food additives were added to Tetrahymena cultures and DNA content of the protozoan nuclei measured by an image analysis system. These food additives caused a statistically significant increase in DNA content suggesting stimulation of the mitotic process. This system may contribute to the investigation of the cellular action of food additives, since mitogenic stimuli substantially alter susceptibility to chemical carcinogenesis.

Animals↗
PubMed2006

Isolated lung perfusion with melphalan: pharmacokinetics and toxicity in a pig model.

BACKGROUND: In patients with unresectable lung cancer or pulmonary metastases, isolated lung perfusion (ILP) has been described as an alternative method to deliver high-dose chemotherapy to the lungs, thereby minimizing systemic toxicity. Pharmacokinetics of ILP have not been extensively investigated. Therefore, we studied the feasibility of ILP with melphalan in a pig model with emphasis on pharmacokinetics and acute lung damage. METHODS: Five pigs underwent ILP with melphalan. Blood and tissue samples were obtained for determination of melphalan levels. Tissue biopsies were taken for microscopic evaluation of lung damage. RESULTS: During ILP, no hemodynamic effects of importance were noted. No systemic leakage of melphalan was observed in any of the animals. Compared with normal lung tissue, microscopic examination of lung tissue after perfusion without melphalan showed pulmonary edema. Directly after melphalan perfusion additional hemorrhagic areas were seen; however, electron microscopy displayed no irreversible endothelial damage. CONCLUSION: This study on pigs proved to be a well reproducible model for ILP with melphalan. Pharmacokinetics show a safety profile with no systemic toxicity, which could justify further patient studies, necessary to determine its effect on pulmonary metastases in humans, especially in case of adjuvant therapy after surgical resection or in unresectable disease.

Animals↗
PubMed1997

Toxicity and carcinogenicity of Cr(VI) in animal models and humans.

The toxicity and carcinogenicity of hexavalent chromium (Cr) in animal and human models are reviewed. The focus of this review is not on the well-established fact that hexavalent Cr compounds of low and high water solubility can induce respiratory cancers, but rather this review addresses other types of cancers induced by exposure to hexavalent Cr compounds. Additionally, non-cancer endpoints are also discussed with documentation of human and animal studies showing non-cancer health effects of hexavalent Cr exposure on the respiratory system, GI system, immune system, liver, and kidney. There is an emerging understanding that because hexavalent chromate is isostructural with phosphate and sulfate, it is readily taken up by the G.I. tract and penetrates to many tissues and organs throughout the body. This is supported by animal studies and experiments using human volunteers. From the epidemiological studies, there is suggestive evidence that hexavalent Cr causes increased risk of bone, prostate, lymphomas, Hodgkins, leukemia, stomach, genital, renal, and bladder cancer, reflecting the ability of hexavalent chromate to penetrate all tissues in the body. A high accumulation of Cr(III) in all tissues and organs is a strong indication of the wide toxic potential of exposure to soluble hexavalent Cr in the drinking water and in the ambient environment.

Animals↗
PubMed1991

Comparison of the critical concentration and critical volume hypotheses to model non-specific toxicity of individual compounds.

The critical concentration and critical volume hypotheses for non-specific toxicity require the molar concentration (CC) and volume fraction (VF) of toxicant in target tissue to be constant. Thus these factors should be independent of the octanol-water partition coefficient (Kow) for individual compounds. CC and VF values were calculated based on acute sub-lethal, acute and chronic lethal toxicity data, Kow and pure component molar volume (MV) data. When these values were plotted against log Kow, the slopes of the regression equations were significantly different to zero but were not significantly different from each other. The observed slight increase in CC and VF with increasing log Kow was attributed predominantly, to the use of Kow values which overestimate the target tissue-water partition coefficient (Kow). An additional error associated with the volume fraction calculations was the use of the molar volume instead of partial molar volume. VF and CC values were calculated correcting for both these factors and regressed against log Kow. The resulting equation for VF had a gradient not significantly different from zero, while that for CC was, thus indicating the superiority of the critical volume hypothesis in modelling non-specific toxicity of individual compounds.

Animals↗
PubMed2006

Human liver slices as an in vitro model to study toxicity-induced hepatic stellate cell activation in a multicellular milieu.

INTRODUCTION: Hepatic stellate cell (HSC) activation is a key event in wound healing as well as in fibrosis development in the liver. Previously we developed a technique to induce HSC activation in slices from rat liver. Although this model provides a physiologic, multicellular milieu that is not present in current in vitro models it might still be of limited predictive value for the human situation due to species-differences. Therefore, we now aimed to evaluate the applicability of human liver slices for the study of HSC activation. METHOD: Liver slices (8 mm diameter, 250 microm thickness) were generated from human liver tissue and incubated for 3 or 16 h with 0-15 microl of carbon tetrachloride (CCl4) after which ATP-content and expression levels of HSC (activation) markers was determined. RESULTS: Human liver slices remained viable during incubation as shown by constant ATP levels. Incubation with CCl(4) caused a dose-dependent decrease in viability and an increase in mRNA expression of the early HSC activation markers HSP47 and alphaB-crystallin, but not the late markers for HSC activation, alphaSMA and pro-collagen 1a1. Synaptophysin mRNA expression remained constant during incubation with or without CCl4, indicating a constant number of HSC in the liver slices. CONCLUSION: We developed a technique to induce early toxicity-induced HSC activation in human liver slices. This in vitro model provides a multicellular, physiologic milieu to study mechanisms underlying toxicity-induced HSC activation in human liver tissue.

Carbon Tetrachloride↗
PubMed2000

Structure-toxicity relationships for aliphatic compounds encompassing a variety of mechanisms of toxic action to Vibrio fischeri.

QSARs based upon the logarithm of the octanol-water partition coefficient, log P, and energy of the lowest unoccupied molecular orbital, ELUMO were developed to model the toxicity of aliphatic compounds to the marine bacterium Vibrio fischeri. Statistically robust, hydrophobic-dependent QSARs were found for chloroalcohols and haloacetonitriles. Modelling of the toxicity of the haloesters and the diones required the use of terms to describe both hydrophobicity and electrophilicity. The differences in intercepts, slopes, and fit of these models suggest different electrophilic mechanisms occur between classes, as well as within the diones and haloesters. In order to model globally the toxicity of aliphatic compounds to V. fischeri, all the data determined in this study were combined with those determined previously for alkanones, alkanals, and alkenals. A highly predictive two-parameter QSAR [pT15 = 0.760(log P) - 0.625(ELUMO) - 0.466; n = 63, s = 0.462, r2 = 0.846, F = 171, Pr > F = 0.0001] was developed for the combined data that models across classes and is independent of mechanisms of action. The toxicity of these compounds to V. fischeri compares well to the toxicity (50% population growth inhibition) to the ciliate Tetrahymena pyriformis (r2 = 0.850).

Bacterial Toxins↗
PubMed2005

A shared response model for clustered binary data in developmental toxicity studies.

Existing distributions for modeling fetal response data in developmental toxicology such as the beta-binomial distribution have a tendency of inflating the probability of no malformed fetuses, and hence understating the risk of having at least one malformed fetus within a litter. As opposed to a shared probability extra-binomial model, we advocate a shared response model that allows a random number of fetuses within the same litter to share a common response. An explicit formula is given for the probability function and graphical plots suggest that it does not suffer from the problem of assigning too much probability to the event of no malformed fetuses. The EM algorithm can be used to estimate the model parameters. Results of a simulation study show that the EM estimates are nearly unbiased and the associated confidence intervals based on the usual standard error estimates have coverage close to the nominal level. Simulation results also suggest that the shared response model estimates of the marginal malformation probabilities are robust to misspecification of the distributional form, but not so for the estimates of intralitter correlation and the litter-level probability of having at least one malformed fetus. The proposed model is fitted to a set of data from the U.S. National Toxicology Program. For the same dose-response relationship, the fit based on the shared response distribution is superior to that based on the beta-binomial, and comparable to that based on the recently proposed q-power distribution (Kuk, 2004, Applied Statistics53, 369-386). An advantage of the shared response model over the q-power distribution is that it is more interpretable and can be extended more easily to the multivariate case. To illustrate this, a bivariate shared response model is fitted to fetal response data involving visceral and skeletal malformation.

2,4,5-Trichlorophenoxyacetic Acid↗
PubMed1995

Corticosteroid alteration of carboplatin-induced hematopoietic toxicity in a murine model.

Corticosteroids exhibit extensive hematopoietic effects both in vitro and in vivo. Some of the previously studied effects suggested that corticosteroids may alter hematopoietic toxicity of chemotherapeutic agents. In this study, we examined (1) the optimum dose and schedule of cortisone acetate (CA) to reduce hematopoietic toxicity of carboplatin (CB) and (2) possible mechanisms involved in this protective effect. CA given subcutaneously at 0.5 mg/d per mouse for 7 days before CB reduced CB-induced mortality due to neutropenia from 88% in controls to 14% in CA-treated mice (P < .05). Lower CA doses were not effective. Three days of pretreatment (but not 1 day) was as effective as 7 days. CA given after CB had no effect on mortality. Pharmacokinetic studies of CA at 0.5 mg per mouse demonstrated blood levels of cortisol achievable in patients (peak level, 82 micrograms/dL). CA treatment markedly reduced spleen cell number and colony-forming units-granulocyte/macrophage (CFU-GM) as well as bone marrow CFU-GM. Bone marrow CFU-GM removed from CA-treated mice demonstrated increased resistance to platinum and increased resistance to high specific activity 3H-thymidine. These findings suggest that treatment of mice with CA induces cellular resistance of hematopoietic precursors to platinum and, thus, reduces CB hematotoxicity. CA or other corticosteroids may be useful in reducing clinical toxicity of CB.

Animals↗
PubMed2006

Quantum chemistry based quantitative structure-activity relationships for modeling the (sub)acute toxicity of substituted mononitrobenzenes in aquatic systems.

Fifteen experimental literature data sets on the acute toxicity of substituted nitrobenzenes to algae (Scenedesmus obliquus, Chlorella pyrenoidosa, C. vulgaris), daphnids (Daphnia magna, D. carinata), fish (Cyprinus carpio, Poecilia reticulata), protozoa (Tetrahymena pyriformis), bacteria (Phosphobacterium phosphoreum), and yeast (Saccharomyces cerevisiae) were used to establish quantum chemistry based quantitative structure-activity relationships (QSARs). The logarithm of the octanol/water partition coefficient, log Kow, and the energy of the lowest unoccupied molecular orbital, Elumo, were used as descriptors. Suitable QSAR models (0.65 < r2 < 0.98) to predict acute toxicity of substituted mononitrobenzenes to protozoa, fish, daphnids, yeast, and algae have been derived. The log Kow was a sufficient descriptor for all cases, with the additional Elumo descriptor being required only for algae. The QSARs were found to be valid for neutral substituted mononitrobenzenes with no -OH, -COOH, or -CN substituents attached directly to the ring. From the 100,196 European Inventory of Existing Commercial Substances (EINECS), 497 chemicals were identified that fit the selection criteria for the established QSARs. Based on these results, an advisory tool has been developed that directs users to the appropriate QSAR model to apply for various types of organisms within specified log Kow ranges. Using this tool, it is possible to obtain a good indication of the toxicity of a large set of EINECS chemicals and newly developed substituted mononitrobenzenes to five different organisms without the need for additional experimental testing.

Animals↗
PubMed2006

QSAR models for Daphnia magna toxicity prediction of benzoxazinone allelochemicals and their transformation products.

The overall objective of this study is the ecotoxicological characterization of the benzoxazinone 2,4-dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), the benzoxazolinones benzoxazolin-2-one (BOA) and 6-methoxybenzoxazolin-2-one (MBOA), and their transformation products: phenoxazinones 2-acetylamino-7-methoxy-3H-phenoxazin-3-one (AAMPO), 2-acetylamino-3H-phenoxazin-3-one (AAPO), 2-amino-7-methoxy-3H-phenoxazin-3-one (AMPO), and 2-amino-3H-phenoxazin-3-one (APO); aminophenol 2-aminophenol AP); acetamide N-(2-hydroxyphenyl)acetamide (HPAA); and malonamic acid amide N-(2-hydroxyphenyl)malonamic acid (HPMA). A comparison between empirical results and theoretical ones using rules-based prediction of toxicity was done, and it can be concluded that only the degradation metabolites exhibited significant ecotoxic effect. Using synthetic pesticides knowledge, several QSAR models were trained with various approaches and descriptors. The models generated exhibited good internal predictive ability (R(cv)2 > 0.6) and were used to predict the toxicity of the natural compounds studied.

Animals↗
PubMed1989

Isolated, perfused bovine eye a model for acute retinal toxicity screening.

Excorporal bovine eye has been resuscitated and sustained with an aim of its development as an alternative to whole animal in evaluating acute retinal toxicity of xenobiotics. As indicated by the stable ERG response, such preparation is functionally reactive to photic stimuli over a span of 6-12 h. Moreover, after experienced a 20 min hypoxia the reperfused eyes recovered fully. This functionally responsive preparation was used to evaluate the influence of a highly purified bacterial collagenase (Nucleolysin) on the integrity of vitreoretinal junction. Nucleolysin at concentrations between 120-600 U/ml was injected into the posterior chamber for 15 min. Retinal surfaces were irrigated and eyes were perfusion fixed with glutaraldehyde. Ultrastructural analysis indicated that thinning of the internal limiting membrane occurred when enzyme exceeded 480 U. At 600 U concentration, the principle subcellular change involved the end-foot region of the Muller cells. These studies suggest that the isolated, perfused bovine eye is a suitable model for evaluating acute retinal toxicity of xenobiotics.

Animal Testing Alternatives↗
PubMed1983

Contents of free histidine and histamine in fish meals and in the model compounds and their toxicities to induce gizzard erosion.

Whole meal produced from fresh sardine had a high content of histidine, while that from rancid fish had a high content of histamine. The toxicity to induce gizzard erosion, which appeared after heating, was stronger in the former whole meal than in the latter. Thus, the content of histidine, not that of histamine, was well correlate to the degree of toxicity of the heated fish meal. Changes in the contents of histidine and histamine were also studied in model compounds during heating.

Animal Feed↗
PubMed1979

Current problems in the choice of animals for toxicity testing.

Animal models for the study of toxicity are chosen more for pragmatic reasons such as life-span, ease of handling, and economics than because of a comprehensive process of validation. There is also a tendency to seek the answers to nonspecific questions and then to use those answers in situations where they cannot lead to proper judgments. In some cases, such as in carcinogenicity testing, an uneasy compromise exists between the sensitivity of the model and the background noise. There is scope, by increased attention to both the control of environmental factors and the genetics of the animal models, to increase the sensitivity and validity of the systems that are used in toxicology.

Animals↗
PubMed1997

The importance of anatomical realism for validation of physiological models of disposition of inhaled toxicants.

The goodness of fit of three PBPK models to data for inhalation uptake of 1,3-butadiene by mice from closed chambers were compared. These models included a classical flow-limited model with blood consolidated into arterial and venous compartments, a flow-limited model with implicit blood and alveolar compartments, and a model with an actual alveolar compartment and blood distributed among compartments for arterial, venous, and capillary spaces. Using physiological and biochemical parameters from the literature, all three models reproduced observed steady-state blood butadiene concentrations. However, the first two models predicted more rapid uptake of butadiene than was observed. Assumptions such as ignoring extrahepatic metabolism or reducing the ventilation rate by 75% were required to enable these models to fit the butadiene uptake data. The behavior of the third model resembled that of the other two models when the single-pass extraction ratio of butadiene for all tissues was close to 1, but the model did reproduce observed butadiene uptake when an extraction ratio of 0.5 was used. The difference in predictions of the three models was traced to smaller computed blood:tissue gradients and tissue butadiene concentrations, hence reduced rates of metabolic clearance, when the blood is distributed. These results suggest that the common assumption of flow limitation in the disposition of an inhaled gas may not always be appropriate. Because structurally different models can reproduce the same uptake data and all these models cannot be correct, the assumptions on which these models were based must be investigated experimentally to ensure that they are physiologically realistic.

Animals↗