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Development of a general Ag(I)-promoted reaction for the direct conversion of thioamides to amidines is disclosed. This reaction was employed to prepare a key series of vancomycin aglycon residue 4 substituted amidines that were used to clarify their interaction with model ligands of peptidoglycan precursors and explore their resulting impact on antimicrobial properties.

The glycopeptide antibiotics are the most important class of drugs used in the treatment of resistant bacterial infections including those caused by methicillin-resistant Staphylococcus aureus (MRSA). After more than 50 years of clinical use, the emergence of glycopeptide-resistant Gram-positive pathogens such as vancomycin-resistant enterococci (VRE) and vancomycin-resistant Staphylococcus aureus (VRSA) presents a serious global challenge to public health at a time few new antibiotics are being developed. This has led to renewed interest in the search for additional effective treatments including the development of new derivatives of the glycopeptide antibiotics. General approaches have been explored for modifying glycopeptide antibiotics, typically through the derivatization of the natural products themselves or more recently through chemical total synthesis. In this Perspective, we consider recent efforts to redesign glycopeptide antibiotics for the treatment of resistant microbial infections, including VRE and VRSA, and examine their future potential for providing an even more powerful class of antibiotics that are even less prone to bacterial resistance.

The total synthesis of [Ψ[C(═S)NH]Tpg(4)]vancomycin aglycon (8) and its unique AgOAc-promoted single-step conversion to [Ψ[C(═NH)NH]Tpg(4)]vancomycin aglycon (7), conducted on a fully deprotected substrate, are disclosed. The synthetic approach not only permits access to 7, but it also allows late-stage access to related residue 4 derivatives, alternative access to [Ψ[CH(2)NH]Tpg(4)]vancomycin aglycon (6) from a common late-stage intermediate, and provides authentic residue 4 thioamide and amidine derivatives of the vancomycin aglycon that will facilitate ongoing efforts on their semisynthetic preparation. In addition to early stage residue 4 thioamide introduction, allowing differentiation of one of seven amide bonds central to the vancomycin core structure, the approach relied on two aromatic nucleophilic substitution reactions for formation of the 16-membered diaryl ethers in the CD/DE ring systems, an effective macrolactamization for closure of the 12-membered biaryl AB ring system, and the defined order of CD, AB, and DE ring closures. This order of ring closures follows their increasing ease of thermal atropisomer equilibration, permitting the recycling of any newly generated unnatural atropisomer under progressively milder thermal conditions where the atropoisomer stereochemistry already set is not impacted. Full details of the evaluation of 7 and 8 along with several related key synthetic compounds containing the core residue 4 amidine and thioamide modifications are reported. The binding affinity of compounds containing the residue 4 amidine with the model D-Ala-D-Ala ligand 2 was found to be only 2-3 times less than the vancomycin aglycon (5), and this binding affinity is maintained with the model d-Ala-d-Lac ligand 4, representing a nearly 600-fold increase in affinity relative to the vancomycin aglycon. Importantly, the amidines display effective dual, balanced binding affinity for both ligands (K(a)2/4 = 0.9-1.05), and they exhibit potent antimicrobial activity against VanA resistant bacteria ( E. faecalis , VanA VRE) at a level accurately reflecting these binding characteristics (MIC = 0.3-0.6 μg/mL), charting a rational approach forward in the development of antibiotics for the treatment of vancomycin-resistant bacterial infections. In sharp contrast, 8 and related residue 4 thioamides failed to bind either 2 or 4 to any appreciable extent, do not exhibit antimicrobial activity, and serve to further underscore the remarkable behavior of the residue 4 amidines.

The emergence of bacteria resistant to vancomycin, often the antibiotic of last resort, poses a major health problem. Vancomycin-resistant bacteria sense a glycopeptide antibiotic challenge and remodel their cell wall precursor peptidoglycan terminus from d-Ala-d-Ala to d-Ala-d-Lac, reducing the binding of vancomycin to its target 1000-fold and accounting for the loss in antimicrobial activity. Here, we report [Ψ[C(═NH)NH]Tpg(4)]vancomycin aglycon designed to exhibit the dual binding to d-Ala-d-Ala and d-Ala-d-Lac needed to reinstate activity against vancomycin-resistant bacteria. Its binding to a model d-Ala-d-Ala ligand was found to be only 2-fold less than vancomycin aglycon and this affinity was maintained with a model d-Ala-d-Lac ligand, representing a 600-fold increase relative to vancomycin aglycon. Accurately reflecting these binding characteristics, it exhibits potent antimicrobial activity against vancomycin-resistant bacteria (MIC = 0.31 μg/mL, VanA VRE). Thus, a complementary single atom exchange in the vancomycin core structure (O → NH) to counter the single atom exchange in the cell wall precursors of resistant bacteria (NH → O) reinstates potent antimicrobial activity and charts a rational path forward for the development of antibiotics for the treatment of vancomycin-resistant bacterial infections.

BACKGROUND: There have been multiple reports concerning the predictors of fainting reactions in blood donors, but few attempts to reduce the rates of fainting reactions with concomitant rigorous attempts to monitor the success of the interventions. STUDY DESIGN AND METHODS: We used a retrospective observational cohort study design, comparing the likelihood of reaction from 213,031 allogeneic whole blood donations made by 17- to 22-year-old donors in two separate 12-month periods before and after the implementation of interventions to reduce reactions. The interventions were 1) a limit on the maximum percentage of estimated blood volume young donors could donate, 2) encouraging applied muscle tension during donation, and 3) providing approximately 500 mL of water before donation. Reactions were defined by severity and time in relation to the end of phlebotomy and documented according to standard procedures. Data analysis included comparison of stratified reaction rates and multivariable logistic regression analysis. RESULTS: The interventions decreased the aggregate reaction rates in male and female donors by 24% (p

BACKGROUND: Blood donation is safe, but a small proportion of donors have delayed and/or off-site reactions that have the potential to lead to serious injury. This retrospective study sought to identify risk factors for delayed reactions (DRs). STUDY DESIGN AND METHODS: The records of 793,293 allogeneic whole blood and apheresis donations in 2007 were assessed for vasovagal reactions. Donor demographic, biometric, and clinical measurements were captured. Incidents related to needle insertion and mild reactions were excluded. Based on the reaction onset time relative to the procedure end time, reactions were classified as delayed (>15 min) or immediate (≤15 min). Reactions were analyzed by multivariable logistic regression comparing donors with immediate reactions (IRs) or DRs to donors without reactions and comparing donors with DRs to IRs. The clinical consequences of off-site and on-site reactions are reported. RESULTS: The prevalence of reactions classified as moderate or severe was 41 in 10,000 donations; 24% of these reactions were delayed and 12% occurred off-site. DRs were associated with female sex (odds ratio [OR], 2.96; 95% confidence interval [CI], 2.21-3.96) and with low estimated blood volume (EBV; OR, 3.91; 96% CI, 2.84-5.51). Off-site reactions, particularly in female donors, were more likely to be associated with a fall, with head trauma, with other injury, and with the use of outside medical care. CONCLUSION: Low EBV, youth, and first-time donor status are major risk factors for IRs and DRs. Women are more likely than men to report DRs. Delayed and off-site reactions lead to potentially preventable morbidity. Understanding the physiologic basis of DRs may lead to the development of appropriate interventions to reduce their likelihood.

Objectives The aim was to construct and validate algorithms for osteoporosis case ascertainment from administrative databases and to estimate the population prevalence of osteoporosis for these algorithms. Study Design and Setting Artificial neural networks, classification trees, and logistic regression were applied to hospital, physician, and pharmacy data from Manitoba, Canada. Discriminative performance and calibration (i.e., error) were compared for algorithms defined from different sets of diagnosis, prescription drug, comorbidity, and demographic variables. Algorithms were validated against a regional bone mineral density testing program. Results Discriminative performance and calibration were poorer and sensitivity was generally lower for algorithms based on diagnosis codes alone than for algorithms based on an expanded set of data features that included osteoporosis prescriptions and age. Validation measures were similar for neural networks and classification trees, but prevalence estimates were lower for the former model. Conclusion Multiple features of administrative data generally resulted in improved sensitivity of osteoporosis case-detection algorithm without loss of specificity. However, prevalence estimates using an expanded set of features were still slightly lower than estimates from a population-based study with primary data collection. The classification methods developed in this study can be extended to other chronic diseases for which there may be multiple markers in administrative data.

© 2015 by The American Society for Biochemistry and Molecular Biology, Inc. The spliceosome is a dynamic complex of five structural RNAs and dozens of proteins, which assemble together to remove introns from nascent eukaryotic gene transcripts in a process called splicing. Small molecules that target different components of the spliceosome represent valuable research tools to investigate this complicated macromolecular machine. However, the current collection of spliceosome inhibitors is very limited. To expand the toolkit we used a high-throughput in vitro splicing assay to screen a collection of pre-fractions of natural compounds derived from marine bacteria for splicing inhibition. Further fractionation of initial hits generated individual peaks of splicing inhibitors that interfere with different stages of spliceosome assembly. With additional characterization of individual peaks, we identified N-palmitoyl-L-leucine as a new splicing inhibitor that blocks a late stage of spliceosome assembly. Structure-activity relationship analysis of the compound revealed that length of carbon chain is important for activity in splicing, as well as for effects on the cytological profile of cells in culture. Together these results demonstrate that our combination of in vitro splicing analysis with complex natural product libraries is a powerful strategy for identifying new small molecule tools with which to probe different aspects of spliceosome assembly and function.

Using the 1996--7 and 2002--3 nationally representative household surveys, we examine the extent to which growth in Mozambique has been pro-poor. Although all segments of the income distribution experienced a rapid increase in consumption between the sample periods, the rate of growth in consumption was slightly higher for richer households. This has led to a moderate increase in inequality at the national level, as demonstrated by the rise in the Gini coefficient from 0.40 to 0.42. However, this slight increase in inequality at the national level is not statistically significant, and its impact on poverty reduction efforts is small: the poverty headcount would have been 53.0% in 2002--3 if all sections of society had enjoyed the mean growth rate in consumption, compared with the 54.1% at which it actually stood. Interestingly, static decompositions of the generalised entropy class of inequality measures indicate that inequality in real consumption between provinces and regions has diminished over time, in contrast to popular claims. Maputo City continues to have the highest rates of inequality in the country and witnessed a significant increase in inequality between 1996--7 and 2002--3 (the Gini coefficient rose from 0.44 to 0.52). Copyright 2006, Oxford University Press.

The U.S. Environmental Protection Agency has classified 1,1-dichloroethylene (vinylidene chloride; VDC) as a "C" carcinogen and has developed an inhalation unit risk value and an oral cancer slope factor for this chemical. The development and use of these cancer potency estimates for risk assessment purposes are questionable. The inhalation unit risk value is based on increased kidney adenocarcinomas in Swiss mice from one study. This type of cancer was not increased in female mice or in rats or hamsters in the same study nor in male mice of a similar strain in another study with higher VDC exposures. The VDC oral cancer slope factor is based on a non-statistically significant increase in adrenal pheochromocytomas in male rats following oral exposure in a standard National Toxicology Program chronic bioassay. Both human and animal literature relevant to VDC carcinogenicity was reviewed according to the USEPA draft Guidelines for Carcinogen Risk Assessment with the objective of determining the weight-of-evidence for VDC carcinogenicity. We conclude that information currently available for VDC is most appropriately characterized in a weight-of-evidence narrative by the descriptor "inadequate for an assessment of human carcinogenic potential." For chemicals with this descriptor, dose-response assessment is not indicated. Under this guidance, quantitative estimates of cancer risks associated with VDC exposure are inappropriate until additional, more definitive evidence for human carcinogenicity becomes available.

Several soil ingestion studies have indicated that some children ingest substantial amounts of soil on given days. Although the EPA has assumed that 95% of children ingest 200 mg soil/day or less for exposure assessment purposes, some children have been observed to ingest up to 25-60 g soil during a single day. In light of the potential for children to ingest such large amounts of soil, an assessment was made of the possibility for soil pica episodes to result in acute intoxication from contaminant concentrations the EPA regards as representing conservative screening values (i.e., EPA soil screening levels and EPA Region III risk-based concentrations for residential soils). For a set of 13 chemicals included in the analysis, contaminant doses resulting from a one-time soil pica episode (5-50 g of soil ingested) were compared with acute dosages shown to produce toxicity in humans in clinical studies or case reports. For four of these chemicals, a soil pica episode was found to result in a contaminant dose approximating or exceeding the acute human lethal dose. For five of the remaining chemicals, the contaminant dose from a soil pica episode was well within the reported dose range in humans for toxicity other than lethality. Because both the exposure episodes and the toxicological response information are derived from observations in humans, these findings are regarded as particularly relevant for human health risk assessment. They suggest that, for some chemicals, ostensibly conservative soil criteria based on chronic exposure using current EPA methodology may not be protective of children during acute soil pica episodes.

The collection, aggregation and use of personal information are of increasing concern and importance to modern society. Yet data protection laws, designed to regulate trade in personal data, can pose important burdens on epidemiologic and social research. After a brief overview of epidemiology, the paper offers an analysis of surveillance and data protection, highlighting the concept of the ‘data image’, and the role of data protection in ensuring human rights in surveillance societies. The paper then delineates the potential conflict or tension between the goals of data protection and epidemiology. The paper concludes by observing that while the European Union recently has exempted public health datasets from strict conformity with the principles of data protection, there is considerable need to define ethical and technical standards for the management, use and disposition of personal health data used in research settings. As data protection standards are about to be introduced into Europe, a unique oportunity exists for epidemiologists and other social researchers to consult broadly to define standards for the management of personal data.

Reference doses (RfDs) and reference concentrations (RfCs) developed by the United States Environmental Protection Agency (USEPA) are typically used to assess the risk of potential adverse human health effects from exposure to environmental chemicals. For a large number of chemicals, however, USEPA RfDs or RfCs have not yet been determined. Thus, for risk assessments that involve a large number of chemicals, there may not be USEPA- or state-derived toxicity constants for all chemicals present at a particular site. A potential solution to this problem is to use estimated permissible concentrations (EPCs) to develop acceptable daily dosages from occupational exposure limits. The EPC is defined as the concentration of a chemical which, under continuous exposure conditions, is expected to be devoid of all acute and chronic toxicities. EPC values are based on allowable occupational exposure limits such as threshold limit values (TLVs), which are workplace exposure guidelines suggested by the American Conference of Governmental Industrial Hygienists. In the present analysis, the EPC method was used to develop interim toxicity constants for more than 30 chemicals which possess TLVs and which appear in the Appendix VIII Hazardous Constituents List, but for which the USEPA has not yet assigned a current RfD or RfC. Appendix VIII chemicals are commonly found at hazardous waste and other sites. Consequently, the development of toxicity constants for the more than 30 chemicals on this list would prove to be most useful for risk assessment purposes. These toxicity constants were then used, together with standard exposure assumptions, to develop acceptable human health-based soil and water concentrations for these chemicals. The use of these values as interim guidance would therefore allow individuals responsible for assessing human health effects posed by environmental contamination to address all site chemicals without performing extensive, chemical-specific toxicological analyses.

Recent studies have shown that methamphetamine is capable of potentiating the hepatotoxicity of carbon tetrachloride in mice. In the present study, it was found that this potentiation is sensitive to changes in the timing of the methamphetamine dose relative to the administration of carbon tetrachloride. Potentiation of hepatotoxicity, measured using serum alanine aminotransferase (ALT) activity, was observed only if the dose of methamphetamine (15 mg/kg, i.p.) was given with, or 3 h after, the carbon tetrachloride dose (0.005 ml/kg i.p.). No increase in carbon tetrachloride hepatotoxicity was evident when methamphetamine was administered 3 h before the carbon tetrachloride dose, or when given 6 or more hours after carbon tetrachloride. Increased covalent binding of carbon tetrachloride to proteins and lipids, shown previously to occur when methamphetamine and carbon tetrachloride are administered together, was not observed when methamphetamine was administered 3 h after the carbon tetrachloride dose and could not, therefore, account for the increased toxicity resulting from this treatment regimen. Pretreatment with the Kupffer cell inhibitor gadolinium chloride (10 mg/kg i.v.) significantly diminished the potentiation of carbon tetrachloride hepatotoxicity by methamphetamine, suggesting that potentiation by methamphetamine involves, at least in part, a stimulation of Kupffer cells. Mice administered a methamphetamine pretreatment regimen known to induce behavioral sensitization displayed an enhanced potentiation of carbon tetrachloride hepatotoxicity i.e. the extent of potentiation by methamphetamine was increased and the methamphetamine dose required for potentiation was diminished. Mice pretreated with a methamphetamine sensitization regimen were also found to be more responsive to the effects of morphine to enhance carbon tetrachloride hepatotoxicity. These observations suggest that there are important CNS, as well as hepatic, components in the potentiation of carbon tetrachloride-induced liver injury by methamphetamine and perhaps other drugs.

Cyclonite (RDX) is an explosive material that is commonly compounded with 2,4,6-trinitrotoluene. The current American Conference of Governmental Industrial Hygienists 8-hour, time-weighted average threshold limit value (TLV) for cyclonite is 1.5 mg/m3 and it contains a “skin” notation. The present study has reviewed the human and animal toxicity literature available for RDX for the purpose of assessing the relative safety of the current RDX standard. Although the only available health study of occupational exposure to RDX finds no evidence of chronic toxicity in areas where the current TLV level was achieved, the evidence for the reported effectiveness of this TLV is of a very limited nature. The animal data are more extensive, and several chronic studies have been completed. When no observed adverse effect levels identified from the chronic animal studies are used to derive a TLV for RDX, and these derivations adopt relatively standard safety factors for this type of animal-to-human dosage extra...

There have been multiple reports concerning the predictors of fainting reactions in blood donors, but few attempts to reduce the rates of fainting reactions with concomitant rigorous attempts to monitor the success of the interventions.We used a retrospective observational cohort study design, comparing the likelihood of reaction from 213,031 allogeneic whole blood donations made by 17- to 22-year-old donors in two separate 12-month periods before and after the implementation of interventions to reduce reactions. The interventions were 1) a limit on the maximum percentage of estimated blood volume young donors could donate, 2) encouraging applied muscle tension during donation, and 3) providing approximately 500 mL of water before donation. Reactions were defined by severity and time in relation to the end of phlebotomy and documented according to standard procedures. Data analysis included comparison of stratified reaction rates and multivariable logistic regression analysis.The interventions decreased the aggregate reaction rates in male and female donors by 24% (p0.0001). There was a 25% decrease in delayed reactions (p = 0.0006) and a 38% decrease in off-site reactions (p = 0.001) in female donors. The impact of the three interventions together on reaction rate was greater than the combined impact of exercises and water provision. Multivariable modeling showed that the interventions reduced reactions but did not prevent their occurrence in identified higher risk groups.The interventions to reduce vasovagal reactions in whole blood donors were effective. Future efforts to reduce reactions in blood donors can build on the strengths and avoid the weaknesses identified while conducting and analyzing the data from this study.

Cocaethylene is a novel metabolite of cocaine formed in the presence of ethanol. When administered to ICR male mice in dosages ranging from 10 to 50 mg/kg, i.p., cocaethylene was found to produce dose-dependent hepatic necrosis in the midlobular zone (zone 2). Severity of the lesion was maximal 12–24 hr after administration. A transient but significant decrease in hepatic glutathione content was observed 1 hr after cocaethylene administration. Pretreatment with the cytochrome P450 inhibitors cimetidine (200 mg/kg, i.p., in divided doses) or SKF 525A (50 mg/kg, i.p.) diminished toxicity. Pretreatment of mice with the esterase inhibitor diazinon (10 mg/kg, i.p.) increased cocaethylene hepatotoxicity, as did pretreatment with the cytochrome P450 inducing agents phenobarbital (80 mg/kg/day, i.p., for 3 days) or β-naphthoflavone (40 mg/kg/day, i.p., for 3 days). Phenobarbital pretreatment also caused a shift in the morphologic site of necrosis from midzonal to peripheral lobular (zone 1) regions. The type of hepatic lesion produced by cocaethylene, its morphologic distribution (including the shift with phenobarbital treatment), the potency of cocaethylene in producing this effect, and the apparent requirement of oxidative metabolism for hepatoxicity were all remarkably similar to observations with its parent compound, cocaine, in this and earlier studies. This suggests that these compounds produce liver toxicity through the same or similar mechanisms.

Soil cleanup guidelines were developed for diesel fuel No. 2 that are protective of human health. Guidelines were conservatively based on a residential land use scenario. This scenario estimates human health risks associated with long‐term exposure to site soil via the inhalation, dermal, and ingestion routes of exposure. Lifetime dermal cancer studies were selected as the basis for deriving a safe level of diesel fuel in soil. Soil cleanup guidelines for diesel fuel No. 2 ranged from 1166 to 11,287 mg/kg for adult or child residents and represent contaminant levels that pose acceptable health risks for both present and proposed future uses of a site.

Blood donation is safe, but a small proportion of donors have delayed and/or off-site reactions that have the potential to lead to serious injury. This retrospective study sought to identify risk factors for delayed reactions (DRs).The records of 793,293 allogeneic whole blood and apheresis donations in 2007 were assessed for vasovagal reactions. Donor demographic, biometric, and clinical measurements were captured. Incidents related to needle insertion and mild reactions were excluded. Based on the reaction onset time relative to the procedure end time, reactions were classified as delayed (15 min) or immediate (or=15 min). Reactions were analyzed by multivariable logistic regression comparing donors with immediate reactions (IRs) or DRs to donors without reactions and comparing donors with DRs to IRs. The clinical consequences of off-site and on-site reactions are reported.The prevalence of reactions classified as moderate or severe was 41 in 10,000 donations; 24% of these reactions were delayed and 12% occurred off-site. DRs were associated with female sex (odds ratio [OR], 2.96; 95% confidence interval [CI], 2.21-3.96) and with low estimated blood volume (EBV; OR, 3.91; 96% CI, 2.84-5.51). Off-site reactions, particularly in female donors, were more likely to be associated with a fall, with head trauma, with other injury, and with the use of outside medical care.Low EBV, youth, and first-time donor status are major risk factors for IRs and DRs. Women are more likely than men to report DRs. Delayed and off-site reactions lead to potentially preventable morbidity. Understanding the physiologic basis of DRs may lead to the development of appropriate interventions to reduce their likelihood.

Cold-restraint stress was found to produce a depression in hepatic glutathione content and to elevate circulating catecholamine levels in four mouse strains — ICR, NIH, B6C3F1, and ND/4. Serum norepinephrine concentrations were significantly elevated after cold-restraint (2–3 h) in all strains, and serum epinephrine levels were increased in the B6C3F1 and ND/4 strains. In time-course studies conducted using ND/4 mice, the decline in hepatic glutathione concentrations was found to slightly precede increases in serum epinephrine and norepinephrine concentrations. Also, pretreatment with phentolamine, and α-adrenoreceptor antagonist compound shown in previous studies to block epinephrine-induced hepatic glutathione suppression, had no effect on glutathione losses from cold-restraint. These observations are inconsistent with catecholamines as sole mediators of cold-restraint induced hepatic glutathione depression. Two other endogenous substances elevated during stress, corticosteroids and glucagon, were found to diminish glutathione concentrations in the liver in ND/4 mice when administered exogenously. The effects of catecholamines (epinephrine), corticosteroids (hydrocortisone) and glucagon were not additive, i.e. the depression in glutathione when these agents were administered in combination was generally no greater than that induced when the most effective agent was administered alone. It is postulated that during cold-restraint stress multiple endogenous agents are released which are independently capable of causing a depression in hepatic glutathione content.

Considers the need for major shifts in strategy resulting from various changes affecting the marketing environment. Examines a case study of NCR, the founding company of the business machine industry. Argues that marketing strategies alone cannot function effectively and must be developed together with other key strategies, which are outlined.

PCBs produce adverse effects in humans and animals by several modes of action. The first mode of action is binding of coplanar or mono-ortho-PCBs to the aryl hydrocarbon (Ah) receptor leading to effects associated with the activation of this receptor. The remaining PCB congeners do not activate this receptor and have different modes of action underlying their toxic effects. One mode of action that has been shown for di-ortho-substituted non-coplanar PCBs (PCB congeners with two or more chlorines in the ortho-positions) is the interference with intracellular signaling pathways dependent on Ca2+ homeostasis and the resulting cellular, organ-level and organismal effects. The ortho-substituted non-coplanar congeners produce other cellular or organ-level effects including changes in protein kinase C translocation, changes in cellular dopamine (DA) uptake, formation of reactive oxygen species, and thyroid effects. Here, we propose a scheme for developing relative potency estimates (REP) for the PCB congeners not considered in the TEF scheme used to assess the toxicity of coplanar and mono-ortho-PCBs and chlorinated dioxins and furans. Because a number of the modes of action listed here for the ortho-substituted non-coplanar PCB congeners have been implicated in the neurotoxic effects of these PCBs congeners, this relative potency scheme is referred to here as the Neurotoxic Equivalent (NEQ) scheme for estimating toxicity of PCB mixtures. The Neurotoxic Equivalent (NEQ) values are developed in a way similar in concept to the derivation of the well-known TEF congener values. Although this scheme is in its infancy and the set of NEQ values are limited by the current data, there are several compelling reasons for proposing such a scheme now. First, it should open discussions as to how different modes of action can be utilized to predict congener potency differences for the effects they produce. Second, consideration and evaluation of the ability of the proposed NEQ scheme to predict the toxicity of PCB mixtures will assist in the identification of the specific modes of action relevant to the effects produced by non-coplanar PCBs. If other modes of action are suggested and subsequently identified, then other schemes of relative potency could be developed specifically for those modes of action, distinct from either the TEF scheme or the NEQ scheme. Knowing these other modes of action and the relative toxicity of the various congeners would advance our understanding of PCB toxicology and thereby ultimately improve our ability to estimate the toxic potency of PCB mixtures for each identified mode of action. Third, a quantitative scheme for assessing the toxicity of the non-coplanar PCB congeners present in a mixture has the potential to improve significantly future risk assessments of PCB mixtures.

This paper identifies deficiencies in some current practices of causation and risk evaluation by toxicologists and formulates an evidence-based solution. The practice of toxicology focuses on adverse health events caused by physical or chemical agents. Some relations between agents and events are identified risks, meaning unwanted events known to occur at some frequency. However, other relations that are only possibilities – not known to occur (and may never be realized) – also are sometimes called risks and are even expressed quantitatively. The seemingly slight differences in connotation among various uses of the word ‘risk’ conceal deeply philosophic differences in the epistemology of harm. We label as ‘nomological possibilities’ (not as risks) all predictions of harm that are known not to be physically or logically impossible. Some of these nomological possibilities are known to be causal. We term them ‘epistemic’. Epistemic possibilities are risks. The remaining nomological possibilities are called ‘uncertainties’. Distinguishing risks (epistemic relationships) from among all nomological possibilities requires knowledge of causation. Causality becomes knowable when scientific experiments demonstrate, in a strong, consistent (repeatable), specific, dose-dependent, coherent, temporal and predictive manner that a change in a stimulus determines an asymmetric, directional change in the effect. Many believe that a similar set of characteristics, popularly called the ‘Hill Criteria’, make it possible, if knowledge is robust, to infer causation from only observational (nonexperimental) studies, where allocation of test subjects or items is not under the control of the investigator. Until the 1980s, medical decisions about diagnosis, prevention, treatment or harm were often made authoritatively. Rather than employing a rigorous evaluation of causal relationships and applying these criteria to the published knowledge, the field of medicine was dominated by authority-based opinions, expressed by experts (or consensus groups of experts) relying on their education, training, experience, wisdom, prestige, intuition, skill and improvisation. In response, evidence-based medicine (EBM) was developed, to make a conscientious, explicit and judicious use of current best evidence in deciding about the care of individual patients. Now globally embraced, EBM employs a structured, ‘transparent’ protocol for carrying out a deliberate, objective, unbiased and systematic review of the evidence about a formally framed question. Not only in medicine, but now in dentistry, engineering and other fields that have adapted the methods of EBM, it is the quality of the evidence and the rigor of the analysis through evidence-based logic (EBL), rather than the professional standing of the reviewer, that leads to evidence-based conclusions about what is known. Recent studies have disclosed that toxicologists (individually or in expert groups), not unlike their medical counterparts prior to EBM, show distressing variations in their biases with regard to data selection, data interpretation and data evaluation when performing reviews for causation analyses. Moreover, toxicologists often fail to acknowledge explicitly (particularly in regulatory and policymaking arenas) when shortcomings in the evidence necessitate reliance upon authority-based opinions, rather than evidence-based conclusions (Guzelian PS, Guzelian CP. Authority-based explanation. Science 2004; 303: 1468-69). Accordingly, for answering questions about general and specific causation, we have constructed a framework for evidence-based toxicology (EBT), derived from the accepted principles of EBM and expressed succinctly as three stages, comprising 12 total steps. These are: 1) collecting and evaluating the relevant data (Source, Exposure, Dose, Diagnosis); 2) collecting and evaluating the relevant knowledge (Frame the question, Assemble the relevant (delimited) literature, Assess and critique the literature); and 3) Joining data with knowledge to arrive at a conclusion (General causation – answer to the framed question, Dose-response, Timing, Alternative cause, Coherence). The second of these stages (which amounts to an analysis of general causation), is addressed by an EBM-styled approach (adapted for the infrequent availability of human experimental studies in environmental toxicology). This involves assembling literature (through documented algorithms for database queries), excluding irrelevancies by use of delimiters as filters, and ranking and rating the remaining articles for strength of study design and for quality of execution gauged by application of either a ready-made quality assessment instrument or a custom designed checklist or scale. The results of this systematic review (including a structured review of relevant animal and in vitro studies) are then themselves systematically used to determine which causation criteria are fulfilled. Toxicology is maturing from a derivative science largely devoted to routinized performance and interpretation of safety tests, to a discipline deeply enmeshed in the remarkable advances in biochemistry and molecular biology to better understanding the nature and mechanism of adverse effects caused by chemicals. It is time for toxicologists, like scientists in other fields, to formalize a method for differentiating settled toxicological knowledge of risk from mere nomological possibility, and for communicating their conclusions to other scientists and the public. It is time for EBT.

We present CoLe, a model for cooperative agents for mining knowledge from heterogeneous data. CoLe allows for the cooperation of different mining agents and the combination of the mined knowledge into knowledge structures that no individual mining agent can produce alone. CoLe organizes the work in rounds so that knowledge discovered by one mining agent can help others in the next round. We implemented a multi-agent system based on CoLe for mining diabetes data, including an agent using a genetic algorithm for mining event sequences, an agent with improvements to the PART algorithm for our problem and a combination agent with methods to produce hybrid rules containing conjunctive and sequence conditions. In our experiments, the CoLe-based system outperformed the individual mining algorithms, with better rules and more rules of a certain quality. From the medical perspective, our system confirmed hypertension has a tight relation to diabetes, and it also suggested connections new to medical doctors.

The Prairie Pilot Diabetes Surveillance Project was organized to design and test a prototype population-based surveillance system, using administrative data, for a chronic disease exemplar - diabetes mellitus. The Canadian model of a public health surveillance system for chronic conditions described here specifies a process by which administrative and claims data arising from provincial health insurance programs are merged into an annual person-level summary file (APLSF), yielding one summary record for each person insured within each province. The APLSF is the basis for a variety of estimates, including incidence, prevalence, mortality, complication rates and health services utilization. The model was used to produce comparable interprovincial estimates of several parameters with respect to diabetes for the entire population in the provinces of Alberta, Manitoba and Saskatchewan. All processing of identifiable health data occurred within the provinces where the data were generated. Combining results across provinces was based on further aggregation of the summary data from each province and not by pooling of identifiable person-level data. On the basis of preliminary outputs for diabetes mellitus, the model appears to provide coherent estimates of key diabetes parameters and reflects anticipated differences in health services and outcomes, by disease state. Three characteristics of the model recommend it as a resource for non-communicable disease surveillance in Canada: a) it maximizes the utility of existing data; b) it includes both those with and those without the disease in question; and c) it respects provincial legislation regarding personal health data, yet permits reporting of multi-provincial, population-based data.

Objective. We examined the location of commercial plasma donation centers in the United States over the period 1980 to 1995 relative to the geographic distribution of risk behaviors associated with transfusion-transmissible infections. Methods. The census tract locations of commercial source plasma clinics were described by measures of neighborhood social disadvantage and the prevalence of illicit drug use and active local drug economies. Results. Depending on the measure of social environment used, commercial plasma clinics were 5 to 8 times more likely to be located in census tracts designated high-risk than would be expected by chance. Conclusions. Commercial source plasma clinics were overrepresented in neighborhoods with very active local drug economies. These patterns persisted after the links between human immunodeficiency virus and hepatitis C virus infections and plasma products had been established and may present risks to blood system safety.

The diagnosis of cerebrovascular disease (CBVD) from administrative data has been critically examined by epidemiologists in recent years. Much of the existing literature suggests that hospital discharge diagnoses based on ICD-9-CM codes are an unreliable source of information for determining a diagnosis of stroke, particularly when four- and five-digit codes are used. We examined how diagnoses for CBVD in hospital inpatient and outpatient facilities vary between rural and urban areas and among the 16 administrative health regions. Our analysis revealed differences in diagnostic patterns between the two sources of data, differences between rural and urban areas, and variation across most of the regions. Geographic variation in health service utilization, diagnostic practices, specialty of the physician making the diagnosis, and disease burden may explain our findings. Our results suggest that the diagnosis of patients attending rural facilities are either coded differently (and less precisely) than those of urban residents or are coded more precisely only after the patients attend urban facilities. Regional differences in coding practices show that any CBVD surveillance system based on administrative data requires a large-scale (in this case, province-wide) and person-oriented approach.

Study Objective: This study examines the pattern of incidence and health service utilisation of cerebrovascular disease cases in urban and rural areas within a publicly funded health care system. Design: A population-based study covering a large geographic region, using population-wide administrative health data. Age- and sex-standardised incidence and mortality rates were calculated for rural and urban areas. Final status (discharge or death), place of service and place of residence were reported for all cases across several different subsets of cerebrovascular disease. Setting: The province of Alberta, located in western Canada. Participants: Incident cases of cerebrovascular disease (stroke and transient ischaemic attack) and 4 different definitions of incident stroke were identified from data on emergency department admissions in the 1999/2000 fiscal year. Main Results: The rate of cerebrovascular disease per 10,000 was similar between urban (13.24) and rural (13.82) areas. Rural residents frequently reported their incident episode to urban emergency departments. Although the mortality is similar between urban and rural residents, rural dwellers die more frequently in the emergency department setting than urban dwellers, who die more often as in-patients. Conclusions: Overall mortality is similar between urban and rural residents. A large proportion of rural residents receive diagnoses and treatment for cerebrovascular disease in urban areas. Location of service and location of death differs between rural and urban cases of cerebrovascular disease.

Rodent cancer bioassays indicate that substantial differences exist among PCB mixtures in terms of tumorigenic response, although no bioassay has been conducted with Aroclor 1268. The USEPA has used data from these studies to develop three sets of PCB cancer slope factors (CSFs) ranging from 0.07 to 2.0(mg/kg-day)(-1). Selection of the appropriate CSF for risk assessment purposes is largely a function of the exposure circumstances rather than the PCB mixture involved. Since the congener composition of Aroclor 1268 differs substantially from that of the predominant PCB mixture (Aroclor 1254) used to derive the CSFs, the validity of applying existing CSFs to Aroclor 1268 is questionable. We have therefore undertaken the task of developing cancer potency estimates specifically for Aroclor 1268. Potency estimation approaches for Aroclor 1268 were based in part on existing potency estimates for other PCB mixtures, coupled with the relative 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalents (TEQ) content and bioaccumulation potential of PCB mixtures. As such, both Ah-dependent and independent mechanisms of tumorigenesis were considered relevant. Both empirical evidence and mechanistic considerations indicate Aroclor 1268 is substantially less toxic and carcinogenic than the PCB mixtures that have been used by the USEPA to develop CSFs. The present analysis indicates that Aroclor 1268 is likely to be 1-2 orders of magnitude less potent than Aroclor 1254 in terms of potential tumorigenicity. Therefore, we suggest an upper-bound cancer potency factor of 0.27(mg/kg-day)(-1) for Aroclor 1268, a value that is 7- to 8-fold lower than the USEPA's current default, but nonetheless adequately conservative.

Summaries of the interactions caused by altering adrenoreceptor activity in conjunction with the administration of selected hepatotoxicants are provided in Table 2 and Fig. 1. These hepatotoxicants can be divided into two groups, one whose toxicity is increased by adrenergic agonist drugs (group I) and the other whose toxicity is decreased by adrenergic antagonists (group II). Group I includes carbon tetrachloride, acetaminophen, and methylphenidate. Perhaps the most remarkable aspect these chemicals have in common is the striking potentiation that occurs with cotreatment with certain adrenergic agonist drugs. For each of these, cotreatment with the appropriate adrenergic agent can result in massive hepatocellular necrosis from an otherwise nontoxic dose. In terms of the specific adrenoreceptors involved and mechanisms of potentiation, however, they have little in common. Potentiation of carbon tetrachloride hepatotoxicity appears to be mediated by alpha(2)-adrenoceptor stimulation, acetaminophen is potentiated by alpha(1)-adrenoreceptor agonists, and methylphenidate responds to beta(2)-adrenoreceptor stimulation. Studies of the potentiation of carbon tetrachloride and acetaminophen agree that the timing of adrenergic stimulation relative to the hepatotoxicant dose is critically important to the interaction but markedly different for these two toxicants. Acetaminophen was potentiated only when the adrenergic drug was administered as a 3-h pretreatment. This is apparently a consequence of a mechanism of potentiation that involves adrenergic depression of hepatic glutathione content and a requirement that peak effects on glutathione of both the adrenergic agent and acetaminophen be coincident. The mechanism of potentiation of carbon tetrachloride hepatotoxicity is uncertain but clearly does not involve hepatic glutathione content. In contrast to acetaminophen, adrenergic effects must occur within a time window a few hours after the carbon tetrachloride dose for potentiation to occur. The importance of dose timing has not been evaluated for adrenergic potentiation of methylphenidate hepatotoxicity, but it is clear that this interaction is based on yet a third mechanism. While only three hepatotoxicants of the group I type have been examined in detail, the diversity of receptor types and mechanisms involved suggest that this phenomenon may be relevant for a wide variety of hepatotoxic drugs and chemicals. This interaction is also of interest because factors or events that lead to increased adrenergic stimulation are common in everyday life. Most over-the-counter cold and allergy preparations contain sympathomimetic drugs, and many prescription drugs produce adrenergic effects as either an extension of the intended therapeutic effect or as a side effect. Stress and some disease states can also lead to significant increases in peripheral adrenergic activity, creating the potential for increased susceptibility to hepatic injury from exposure to certain drugs or chemicals. Cocaine and bromobenzene represent group II, chemicals whose hepatotoxicity is diminished by cotreatment with adrenergic antagonist drugs. In the case of cocaine, adrenergic antagonist cotreatment was capable of reducing serum alanine aminotransferase activities by approximately 50%. For bromobenzene, the protection afforded by adrenergic antagonist cotreatment was more profound, with minimal hepatic lesions resulting from doses of bromobenzene that otherwise produced lethal hepatic necrosis. For the chemicals in group II, experimental observations are consistent with a phenomenon in which adrenergic potentiation of toxicity is supplied by the hepatotoxicant itself. Both cocaine and bromobenzene, in hepatotoxic doses increase endogenous catecholamine levels. When the effects of the elevated catecholamines are removed with the appropriate adrenergic antagonist, much lower toxicity (presumably due only to the direct hepatotoxic effects of the drug or chemical) is obse

Risk estimates for contaminants in soil are currently calculated assuming that concentrations remain unchanged over time. In reality, biological and physicochemical processes can substantially diminish contaminant concentrations in soil. For exposure periods typically evaluated in USEPA risk assessments, failure to consider the decline in contaminant levels from environmental transport and degradation can result in a significant overestimation of the average daily dose of toxicant. This overestimation may be up to 2- to 3-fold for compounds with long half-lives (15-20 years) in soil and as much as 40-fold for compounds with short half-lives (0.5 years). Overestimation of dosages affects estimation of cancer risks because of the assumption that the probability of cancer increases directly with the cumulative dose of carcinogen. Thus, assuming static contaminant concentrations in soil adds unacknowledged conservatism to cancer risk estimates and target concentration limits. Furthermore, as significant time may elapse before future-use scenarios could possibly occur, soil half-life can affect the estimation of noncarcinogenic health hazards as well. Therefore, an increase in target concentration limits for some compounds could be allowed and corresponding remediation costs reduced by considering how soil half-life changes the dosage calculation. Specific examples of the influence of soil degradation rates on estimates of cancer risk are presented and the degree of added conservatism imparted to risk assessments through assumption of static site contaminant levels is discussed. Considering the potential importance of this parameter for risk assessment and risk management decisions, soil degradation of contaminants under site-specific conditions should be performed whenever possible and incorporated into the risk assessment exercise. When the soil degradation rate cannot be measured or reliably predicted, an estimate of the degree of conservatism should be made to provide risk managers with an appreciation of the degree of uncertainty in the calculation of risk.

The effect of methamphetamine cotreatment on carbon tetrachloride-induced liver toxicity was examined in male Sprague-Dawley rats. Concurrent administration of methamphetamine was found to greatly increase the extent of liver injury resulting from carbon tetrachloride treatment, as indicated both by measurement of serum alanine aminotransferase (ALT) activity and from direct histopathologic examination. Concurrent administration of methamphetamine doses less than 10 mg/kg (i.p.), or administration of methamphetamine either before (−3 h) or after (3–9 h) the carbon tetrachloride dose, did not significantly increase liver injury from carbon tetrachloride. These observations indicate that the potentiation by methamphetamine of carbon tetrachloride hepatoxicity previously observed in the mouse also occurs in the rat, and that the timing of the methamphetamine and carbon tetrachloride doses is critical for the interaction.

Reference doses (RfDs) and reference concentrations (RfCs) developed by the United States Environmental Protection Agency (USEPA) are typically used in the quantitation of risk of potential adverse human health effects from exposure to environmental chemicals. For a large number of chemicals, however, USEPA RfDs and RfCs have not yet been determined. Thus, for risk assessments that involve a large number of chemicals, there is insufficient toxicity information with which to evaluate potential adverse human health effects for all chemicals present at a particular site. Due to this insufficiency, the risk assessor must either (1) ignore potential exposures on the assumption that omitting these exposures does not significantly alter decisions concerning the remediation of the site or (2) undertake a lengthy and costly analysis to generate the necessary RfDs or RfCs. A potential solution to this problem is to develop estimated permissible concentrations (EPCs), values which represent permissible environmental concentrations or related acceptable daily dosages derived from occupational exposure limits. In the present analysis, acceptable daily dosages determined using the EPC method were compared to USEPA RfDs or RfCs which were converted to dosages based on standard exposure assumptions. Based on a comparative analysis of EPCs and USEPA reference values for 103 chemicals, it was found that EPC daily dosages represent a reasonably conservative surrogate value when USEPA or state reference values are unavailable. Given that there are hundreds of chemicals with occupational exposure limits but no state or USEPA reference values, acceptance of the EPC methodology would provide an interim solution for the problem of insufficient toxicity information for a substantial number of environmental chemical contaminants.

Methylphenidate hydrochloride, when administered as a single 75 to 100 mg/kg i.p. dose, was found to produce hepatic necrosis in male ICR mice. Peak hepatotoxicity, as measured by serum ALT elevations, occurred 16 hours post-treatment while maximal histopathological evidence of hepatotoxicity occurred 24-48 hours after the methylphenidate dose. Liver injury measured by either method was essentially nonexistent for dosages < or = 50 mg/kg in male mice, and was only minimally evident in female mice at the highest dosage testable. Co-treatment of mice with either alpha 1- or alpha 2-adrenergic agonist drugs had no meaningful effect on methylphenidate-induced hepatotoxicity. In contrast, the beta-adrenergic agonist drug isoproterenol produced a striking potentiation of the liver injury, and shifted the apparent threshold for toxicity approximately 5- to 10-fold. Co-administration of methylphenidate with the mixed alpha/beta-adrenergic agonist dobutamine or with the beta 2-selective agonists metaproterenol, ritodrine or terbutaline produced a similar potentiation of toxicity. Parallel tests with beta-adrenergic antagonists revealed that the potentiation by isoproterenol could be significantly diminished by a single dose of the non-selective beta-adrenoreceptor blocking drug nadolol or the beta 2-selective antagonist ICI-118,551, but not the beta 1-selective antagonist metoprolol. Collectively, these observations suggest that potentiation of methylphenidate hepatotoxicity occurs through stimulation of beta 2-adrenoreceptors. Mice co-treated with isoproterenol were found to have substantially higher serum and liver methylphenidate levels following the methylphenidate dose, and significant increases were also observed in the area-under-the-curve (AUC) for methylphenidate in both tissues of isoproterenol co-treated mice. The results of this study suggest that beta 2-adrenergic agonist drugs are capable of potentiating methylphenidate-induced hepatotoxicity in mice by increasing hepatic methylphenidate concentrations.

Pretreatment of male ICR mice with the adrenergic agonist phenylpropanolamine (200 mg/kg, ip) resulted in a marked potentiation of hepatotoxicity produced by acetaminophen (400 mg/kg, ip). Enhanced liver necrosis with phenylpropanolamine pretreatment was evident both by measurement of serum aminotransferase activity and by histopathologic examination. Several lines of experimental evidence suggest this interaction is a result of the hepatic glutathione depression produced by alpha-adrenergic compounds, which adds to the glutathione depression caused by toxic, or nearly toxic, doses of acetaminophen. First, the potentiation of acetaminophen hepatotoxicity was time-dependent, being observed only when phenylpropanolamine was administered as a 3-hr pretreatment and not when given 1 hr before, with, or 3 hr after acetaminophen. The 3-hr interval between phenylpropanolamine and acetaminophen doses corresponds to the characteristic lag period required for alpha-adrenergic agents (including phenylpropanolamine) to produce significant and maximal effects on hepatic glutathione content. Second, dose-response relationships for phenylpropanolamine and acetaminophen were such that increased toxicity was observed only when the interaction was sufficient to lower hepatic glutathione concentrations below a level regarded as critical in preventing acetaminophen-induced hepatotoxicity. Third, when animals were pretreated with two nonadrenergic depletors of hepatic glutathione, diethylmaleate (125 mg/kg, ip) or the glutathione synthesis inhibitor buthionine sulfoximine (222 mg/kg, ip), at doses producing glutathione depletion approximating that observed with the adrenergic agents, acetaminophen hepatotoxicity was potentiated to the same extent. From these observations it is postulated that a variety of adrenergic compounds known to deplete hepatic glutathione by a moderate 30-50% may potentiate the hepatotoxicity of acetaminophen and possibly other hepatotoxic compounds for which glutathione conjugation is an important detoxification pathway.