Assessment of hydroxylated metabolites of polychlorinated biphenyls as potential xenoestrogens: a QSAR comparative analysis∗.

Alternative methods, including quantitative structure-activity relationships (QSAR), are being used increasingly when appropriate data for toxicity evaluation of chemicals are not available. Approximately 40 mono-hydroxylated polychlorinated biphenyls (OH-PCBs) have been identified in humans. They represent a health and environmental concern because some of them have been shown to have agonist or antagonist interactions with human hormone receptors. This could lead to modulation of steroid hormone receptor pathways and endocrine system disruption. We performed QSAR analyses using available estrogenic activity (human estrogen receptor ER alpha) data for 71 OH-PCBs. The modelling was performed using multiple molecular descriptors including electronic, molecular, constitutional, topological, and geometrical endpoints. Multiple linear regressions and recursive partitioning were used to best fit descriptors. The results show that the position of the hydroxyl substitution, polarizability, and meta adjacent un-substituted carbon pairs at the phenolic ring contribute towards greater estrogenic activity for these chemicals. These comparative QSAR models may be used for predictive toxicity, and identification of health consequences of PCB metabolites that lack empirical data. Such information will help prioritize such molecules for additional testing, guide future basic laboratory research studies, and help the health/risk assessment community understand the complex nature of chemical mixtures.

Functional analysis of multiple genomic signatures demonstrates that classification algorithms choose phenotype-related genes.

Gene expression signatures of toxicity and clinical response benefit both safety assessment and clinical practice; however, difficulties in connecting signature genes with the predicted end points have limited their application. The Microarray Quality Control Consortium II (MAQCII) project generated 262 signatures for ten clinical and three toxicological end points from six gene expression data sets, an unprecedented collection of diverse signatures that has permitted a wide-ranging analysis on the nature of such predictive models. A comprehensive analysis of the genes of these signatures and their nonredundant unions using ontology enrichment, biological network building and interactome connectivity analyses demonstrated the link between gene signatures and the biological basis of their predictive power. Different signatures for a given end point were more similar at the level of biological properties and transcriptional control than at the gene level. Signatures tended to be enriched in function and pathway in an end point and model-specific manner, and showed a topological bias for incoming interactions. Importantly, the level of biological similarity between different signatures for a given end point correlated positively with the accuracy of the signature predictions. These findings will aid the understanding, and application of predictive genomic signatures, and support their broader application in predictive medicine.

The gene expression sequence of radiated mucosa in an animal mucositis model.

Oral mucositis is a common, dose-limiting, acute toxicity of radiation therapy administered for the treatment of cancers of the head and neck. Accumulating data would suggest that the pathogenesis of mucositis is complex and involves the sequential interaction of all cell types of the oral mucosa, as well as a number of cytokines and elements of the oral environment. While a number of studies have reported on gene expression of particular cell types in response to radiation, the overall response of irradiated mucosa has only been evaluated in a limited way. The present study was undertaken to evaluate the expression of a target group of genes using RNA quantification assays and, more broadly, to assess patterns of mucosal gene expression using DNA microarray hybridization. Our results demonstrate the sequential upregulation of a series of genes that, when taken collectively, suggest an intricate functional interaction.

Complex humanitarian emergencies: a major global health challenge.

Complex humanitarian emergencies have been a major political, security and public health feature of the post-Cold War world. These man-made disasters account for more morbidity and mortality than all natural and technological disasters combined. In order to deliver effective aid during complex humanitarian emergencies, international relief agencies must have a solid understanding of the political and social climates in which they are operating. In addition, they should base their health interventions on objective epidemiological data, especially standardized rates of morbidity and mortality. Most deaths during complex humanitarian emergencies are due to preventable causes, especially increased rates of infectious diseases malnutrition and violent trauma. The most appropriate health interventions are therefore based on the models of public health and primary health care, emphasizing disease prevention and health promotion. The field of humanitarian assistance has become increasingly professionalized in recent years, with its own professional standards, literature, research agenda and training opportunities. It is an unfortunate reflection on the current state of international affairs that the number of complex humanitarian emergencies and the enormous levels of suffering associated with them are unlikely to decline in the foreseeable future.

Persistent genomic instability in the yeast Saccharomyces cerevisiae induced by ionizing radiation and DNA-damaging agents.

A "hypermutable" genome is a common characteristic of cancer cells, and it may contribute to the progressive accumulation of mutations required for the development of cancer. It has been reported that mammalian cells surviving exposure to gamma radiation display several highly persistent genomic instability phenotypes which may reflect a hypermutability similar to that seen in cancer. These phenotypes include an increased mutation frequency and a decreased plating efficiency, and they continue to be observed many generations after the radiation exposure. The underlying causes of this genomic instability have not been fully determined. We show here that exposure to gamma radiation and other DNA-damaging treatments induces a similar genomic instability in the yeast Saccharomyces cerevisiae. A dose-dependent increase in intrachromosomal recombination was observed in cultures derived from cells surviving gamma irradiation as many as 50 generations after the exposure. Increased forward mutation frequencies and low colony-forming efficiencies were also observed. Persistently elevated recombination frequencies in haploid cells were dominant after these cells were mated to nonirradiated partners, and the elevated recombination phenotype was also observed after treatment with the DNA-damaging agents ultraviolet light, hydrogen peroxide, and ethyl methanesulfonate. Radiation-induced genomic instability in yeast may represent a convenient model for the hypermutability observed in cancer cells.

Rehabilitating public health infrastructure in the post-conflict setting: epidemic prevention and preparedness in Kosovo.

The war in Kosovo in 1999 resulted in the displacement of up to 1.5 million persons from their homes. On the subsequent return of the refugees and internally displaced persons, one of the major challenges facing the local population and the international community, was the rehabilitation of Kosovo's public health infrastructure, which had sustained enormous damage as a result of the fighting. Of particular importance was the need to develop a system of epidemic prevention and preparedness. But no single agency had the resources or capacity to implement such a program. Therefore, a unique six-point model was developed as a collaboration between the Kosovo Institute of Public Health, the World Health Organization, and an international, non-governmental organization. Important components of the program included a major Kosovo-wide baseline health survey, the development of a province-wide public health surveillance system, rehabilitation of microbiology laboratories, and the development of a local capacity for epidemic response. While all program objectives were met, important lessons were learned concerning the planning, design, and implementation of such a project. This program represents a model that potentially could be replicated in other post-conflict or development settings.

The aromatic amine carcinogens o-toluidine and o-anisidine induce free radicals and intrachromosomal recombination in Saccharomyces cerevisiae.

Aniline-based aromatic amine carcinogens are poorly detected in short-term mutagenicity assays such as the Salmonella reverse mutation (Ames) assay. More information on the mechanism of toxicity of such Salmonella-negative carcinogens is needed. Aniline and o-toluidine are negative in the Ames assay, but induce deletions (DEL) due to intrachromosomal recombination in Saccharomyces cerevisiae with an apparent threshold. We show here that the DEL assay also detects the genotoxic activity of another aromatic amine carcinogen, o-anisidine, which is also negative in the Salmonella assay. We also show that the DEL assay distinguishes between o-anisidine and its non-carcinogenic structural analog 2, 4-dimethoxyaniline. We have investigated whether the ability of the DEL assay to detect the carcinogens and to distinguish between the carcinogen/non-carcinogen pair is linked to rises in intracellular free radical species following exposure to the carcinogens. Toxicity induced by all three compounds was reduced in the presence of the free radical scavenger and antioxidant N-acetyl cysteine, recombination induced by o-anisidine and o-toluidine was also reduced by N-acetyl cysteine. All three compounds induced oxidation of the free radical-sensitive reporter compound dichlorofluorescin diacetate. Superoxide dismutase-deficient strains, however, were hypersensitive to cytotoxicity induced by o-toluidine and o-anisidine but not by the non-carcinogen 2,4-dimethoxyaniline, indicating a different potential for generating superoxide radical between the carcinogens and the non-carcinogen analog. The results indicate that the yeast DEL assay is a useful tool for investigating the genotoxic activity of aromatic amine carcinogens.

Chemical warfare agents: emergency medical and emergency public health issues.

The threat of exposure to chemical warfare agents has traditionally been considered a military issue. Several recent events have demonstrated that civilians may also be exposed to these agents. The intentional or unintentional release of a chemical warfare agent in a civilian community has the potential to create thousands of casualties, thereby overwhelming local health and medical resources. The resources of US communities to respond to chemical incidents have been designed primarily for industrial agents, but must be expanded and developed regarding incident management, agent detection, protection of emergency personnel, and clinical care. We present an overview of the risk that chemical warfare agents presently pose to civilian populations and a discussion of the emergency medical and emergency public health issues related to preparedness and response.

Free radicals generated in yeast by the Salmonella test-negative carcinogens benzene, urethane, thiourea and auramine O.

A large fraction of carcinogens score negative in short-term genotoxicity assays such as the Salmonella reverse mutation (Ames) assay. More information is needed about the mechanism of action of such Salmonella-negative carcinogens. Many Salmonella-negative carcinogens induce deletions due to intrachromosomal recombination in Saccharomyces cerevisiae with an apparent threshold. We have previously shown that the Salmonella-negative carcinogens cadmium, aniline, chloroform and carbon tetrachloride generate free radical species in S. cerevisiae. We have further investigated the possible generation of intracellular free radical species by the diverse Salmonella-negative carcinogens benzene, urethane, thiourea and auramine O. The toxicity and recombinagenicity of thiourea and auramine O was reduced in the presence of the free radical scavenger N-acetyl cysteine. N-acetyl cysteine did not protect against toxicity or recombination induced by the Salmonella-positive carcinogens ethyl methane sulfonate, methyl methane sulfonate or nitroquinoline-N-oxide. A strain deficient in the enzyme superoxide dismutase, which catalyses the dismutation of superoxide anion radical, was hypersensitive to killing by benzene, urethane and thiourea. The sod- strain was only slightly more sensitive to the Salmonella-positive carcinogens. Intracellular oxidation of the free radical-sensitive reporter compound dichlorofluorescin diacetate was increased in yeast cultures exposed to benzene, urethane and auramine O; again, the Salmonella mutagens had no effect on oxidation of the dye. These data show that free radical species are produced in Saccharomyces cerevisiae following exposure to benzene, urethane, thiourea and auramine O, and suggest a possible role for oxidative stress is recombination induced by these carcinogens.

Medical preparedness for a terrorist incident involving chemical or biological agents during the 1996 Atlanta Olympic Games.

During the 1996 Centennial Olympic Games in Atlanta, Georgia, unprecedented preparations were undertaken to cope with the health consequences of a terrorist incident involving chemical or biological agents. Local, state, federal, and military resources joined to establish a specialized incident assessment team and science and technology center. Critical antimicrobials and antidotes were strategically stockpiled. First-responders received specialized training, and local acute care capabilities were supplemented. Surveillance systems were augmented and strengthened. However, this extensive undertaking revealed a number of critical issues that must be resolved if our nation is to successfully cope with an attack of this nature. Emergency preparedness in this complex arena must be based on carefully conceived priorities. Improved capabilities must be developed to rapidly recognize an incident and characterize the agents involved, as well as to provide emergency decontamination and medical care. Finally, capabilities must be developed to rapidly implement emergency public health interventions and adequately protect emergency responders.

Chloroform and carbon tetrachloride induce intrachromosomal recombination and oxidative free radicals in Saccharomyces cerevisiae.

Chlorination of drinking water results in the generation of low levels of numerous chlorinated hydrocarbons due to the reaction of chlorine with naturally occurring organic compounds in the water. Concern has been raised about the safety of these chlorinated contaminants as several of them, most notably chloroform (trichloromethane), have been shown to be carcinogenic in long-term rodent bioassays and weak correlations between trihalomethane levels in drinking water and an increased risk of bladder and colorectal cancer in humans have been found. Chloroform and carbon tetrachloride induce liver cancer in rats and mice only at doses where significant hepatotoxicity is observed and have been classed as non-genotoxic carcinogens. We have investigated the ability of chloroform, carbon tetrachloride and 1,1,1-trichloroethane to induce deletions via intrachromosomal recombination in the yeast Saccharomyces cerevisiae. Chloroform and carbon tetrachloride induced this genotoxic recombination event at similar doses, 1,1,1-Trichloroethane gave only a weak response in the DEL recombination assay and only at the highest dose. We further show that chloroform and carbon tetrachloride, but not trichloroethane, induced oxidative free radical species in our yeast strain. The free radical scavenger N-acetylcysteine reduced chloroform-induced toxicity and recombination, and both chloroform and carbon tetrachloride were able to oxidize the free radical-sensitive reporter compound dichlorofluorescein diacetate in vivo. The implications of these findings to the carcinogenic activities of the three compounds are discussed.

Nitrate therapy is an alternative to furosemide/morphine therapy in the management of acute cardiogenic pulmonary edema.

BACKGROUND: Nitrates are superior to furosemide in the management of acute pulmonary edema associated with myocardial infarction; however, their role in the absence of infarction is unclear. METHODS AND RESULTS: A randomized comparison was undertaken of the relative effectiveness of primary therapy with either intravenous morphine/furosemide (men/women; n = 32) or nitroglycerin/N-acetylcysteine (NTG/NAC; n = 37) in consecutive patients with acute pulmonary edema. The primary end point was change in PaO2/FIO2 over the first 60 minutes of therapy. Secondary end points were needed for mechanical respiratory assistance (ie, continuous positive airway pressure via mask or intubation and ventilation) and changes in other gas exchange parameters. Both treatment groups showed improvement in oxygenation after 60 minutes of therapy; however, this reached statistical significance only with NTG/NAC therapy. There was no significant difference between groups in the assessed parameters (95% CI for differences in Pao2/FIO2: furosemide/morphine -12 to 23 and NTG/NAC 4 to 44), a finding also confirmed in 32 patients presenting with respiratory failure. Only 11% of the study group required mechanical ventilatory assistance (continuous positive airway pressure in 4 patients and intubation and ventilation in 3 patients). CONCLUSIONS: NTG/NAC therapy is as effective as furosemide/morphine in the initial management of acute pulmonary edema, regardless of the presence or absence of respiratory failure. The necessity for mechanical ventilatory assistance is infrequent in these patients, regardless of the initial medical treatment regimen.

Aniline and its metabolites generate free radicals in yeast.

The carcinogen aniline is negative in the Ames Salmonella mutagenicity assay. Aniline does, however, induce intrachromosomal recombination between repeated sequences in Saccharomyces cerevisiae, resulting in deletion (DEL) of intervening sequences. We have investigated whether the generation of oxidative free radical species by aniline and/ or its metabolites may be responsible for its recombinagenic activity in yeast. The toxicity and recombinagenicity of aniline in yeast were greatly reduced in the presence of the free radical scavenger N-acetyl cysteine. Aniline cytotoxicity was many-fold increased in strains of S.cerevisiae lacking the antioxidant enzyme superoxide dismutase. Aniline also induced oxidation of the intracellular free radical-sensitive reporter compound 2,4-dichlorofluorescin diacetate to its fluorescent derivative 2,4-dichlorofluorescein in vivo in S.cerevisiae. The aniline metabolites 4-aminophenol and 2-aminophenol were significantly more potent inducers of DEL recombination in yeast than aniline. In contrast, the secondary metabolite 4-acetamidophenol (acetaminophen) was non-toxic and non-recombinagenic in yeast. 4-Aminophenol and 2-aminophenol were also significantly more toxic than aniline in a superoxide dismutase deficient yeast strain. 4-aminophenol was a significantly more potent oxidizer of 2,4-dichlorofluorescin diacetate than aniline. The Escherichia coli soxS promoter, which is induced in the presence of redox cycling agents like paraquat, was induced weakly by aniline at toxic doses. The soxS promoter was strongly induced by 4-aminophenol and 2-aminophenol. The results indicate a role for oxidative stress, mediated by generation of superoxide radical, in the toxicity and recombinagenicity of aniline. The increased activity of 4-aminophenol and 2-aminophenol suggests that ring hydroxylation may be an important activating step in this process.

Medical and public health services at the 1996 Atlanta Olympic Games: an overview.

Planning for the 2000 Sydney Olympic Games may benefit from the experience of the 1996 Atlanta Olympics. Excellent health promotion and prevention activities before and during the Games resulted in fewer medical and public health problems than anticipated. Despite this, there was room for improvement in the level of communication and cooperation between the many service providers to ensure the most appropriate and efficient responses.

Diaminotoluenes induce intrachromosomal recombination and free radicals in Saccharomyces cerevisiae.

The carcinogenicity of aniline-based aromatic amines is poorly reflected by their activity in short-term mutagenicity assays such as the Salmonella typhimurium reverse mutation (Ames) assay. More information about the mechanism of action of such carcinogens is needed. Here we report the effects on DEL recombination in Saccharomyces cerevisiae of the carcinogen 2,4-diaminotoluene and its structural isomer 2,6-diaminotoluene, which is reported to be non-carcinogenic. Both compounds are detected as equally mutagenic in the Salmonella assay. In the absence of any external metabolizing system both compounds were recombinagenic in the DEL assay with the carcinogen being a more potent inducer of deletions than the non-carcinogen. In the presence of Aroclor-induced rat liver S9, however, the carcinogen 2,4-diaminotoluene became a 2-fold more potent inducer of deletions, and the non-carcinogen 2,6-diaminotoluene was rendered less toxic and no induced recombination was observed. 2,4-Diaminotoluene is distinguished from its non-carcinogen analog in the DEL assay, therefore, on the basis of a preferential activation of the carcinogen in the presence of a rat liver microsomal metabolizing system. Free radical species are produced by several carcinogens and have been implicated in carcinogenesis. We further investigated whether exposure of yeast to either 2,4-diaminotoluene or 2,6-diaminotoluene resulted in a rise in intracellular free radical species. The effects of the free radical scavenger N-acetylcysteine on toxicity and recombination induced by the two compounds and intracellular oxidation of the free radical-sensitive reporter compound dichlorofluorescin diacetate were studied. Both 2,4- and 2,6-diaminotoluene produced tree radical species in yeast, indicating that the reason for the differential activity of the compounds for induced deletions is not reflected in any difference in the production of free radical species.

Cadmium is an inducer of oxidative stress in yeast.

The heavy metal cadmium is a carcinogen in long-term rodent studies and is a suspect human carcinogen. Cadmium scores negative in the Ames Salmonella mutagenicity assay and in most other short-term genotoxicity assays, but induces deletions in the yeast Saccharomyces cerevisiae. We have investigated whether cadmium induces an oxidative stress in S. cerevisiae which may be responsible for its recombinagenic activity. The free radical scavenger N-acetylcysteine blocked toxicity and recombination induced in S. cerevisiae by cadmium. Yeast strains deficient in the antioxidant defense enzymes superoxide dismutase or gamma-glutamylcysteine synthetase were hypersensitive to cadmium toxicity. Cells grown in the absence of oxygen were more resistant to cadmium. An intracellular free radical-sensitive reporter compound was activated in S. cerevisiae exposed to cadmium. Toxicity or recombination induced by the mutagenic carcinogen methyl methanesulfonate were unaffected in any of the above experiments. These results suggest that the toxicity and recombinagenic activity of cadmium in S. cerevisiae is caused by oxidative stress.

Saturated and monofluoro analogs of the oriental fruit fly attractant methyl eugenol show reduced genotoxic activities in yeast.

Methyl eugenol, is a commercially used fruit fly attractant and a suspected carcinogen. Several phenylpropenes, including methyl eugenol and the known carcinogen safrole, score negative in the Salmonella assay but score positive in the yeast DEL assay that selects for intrachromosomal recombination events in the yeast Saccharomyces cerevisiae. In an attempt to dissociate the beneficial properties of methyl eugenol from its genotoxic properties, saturated or fluorinated analogs were evaluated for their ability to induce intrachromosomal (DEL) recombination in yeast. Field tests have previously shown that all of the analogs used have appreciable properties as fruit fly attractants. The analogs 1,2-dimethoxy-4-ethylbenzene, 1,2-dimethoxy-4-(2-fluoro-2-propenyl)benzene, 1,2-dimethoxy-4-(2-fluoroethyl)benzene and 1,2-dimethoxy-4-(3-fluoro-2-propenyl)benzene all showed reduced toxicity and reduced recombinagenicity in yeast compared to methyl eugenol. These results confirm the validity of fluorination and/or removal of the 2-propenyl moiety in reducing the toxicity and recombinagenicity of methyl eugenol derivatives.