Thrombus aspiration in a series of patients with stable or unstable angina pectoris and lesion-site thrombus formation

Background. In acute myocardial infarction, thrombus aspiration prior to percutaneous coronary interventions (PCI) is often beneficial, but this approach has never been studied in patients without acute myocardial infarction. The aim of this retrospective study is to shed light on that topic based on our initial experience with manual thrombus aspiration in patients with stable or unstable angina pectoris and angiographic evidence of lesion-site thrombus. Methods. We assessed the feasibility (thrombus aspiration without predilatation) of this approach; in addition, we determined angiographic coronary flow and myocardial blush grade. Results. During 33 months in which a total of 4725 PCI were performed in our centre, manual thrombus aspiration was attempted in 14 patients with stable or unstable angina pectoris with angiographic evidence of thrombus. In nine of these 14 patients, the aspiration catheter could be advanced into the lesion without predilatation; in eight patients visible thrombus was obtained. The corrected TIMI frame count improved during the entire interventional procedure (21.1±11.2 vs. 12.8±5.9 frames; p=0.015). Myocardial blush grade, which overall improved during PCI (p<0.001), tended to show greater improvement in patients in whom thrombus aspiration could be achieved (1.6±0.9 vs. 0.7±0.5; p=0.06). Conclusions. Preliminary evidence suggests that manual thrombus aspiration may occasionally be considered in selected patients without acute myocardial infarction but with angiographic evidence of lesion-site thrombus. Nevertheless, prospective studies are required to clearly define the role of this approach in clinical practice. (Neth Heart J 2010;18:423-9.).

Glutathione depletion in rat hepatocytes: a mixture toxicity study with alpha, beta-unsaturated esters

1. Glutathione (GSH) depletion is often reported as an early cytotoxic effect, caused by many reactive organic chemicals. In the present study, GSH depletion in primary rat hepatocytes was used as an in vitro effect-equivalent to measure the toxic potency of alpha,beta-unsaturated esters (acrylates and methacrylates). 2. When these compounds were administered as a mixture, GSH depletion was dose additive. The result of the mixture study shows that GSH depletion may be a useful effect-equivalent for the risk assessment of mixtures of alpha,beta-unsaturated esters. 3. To get more insight in the underlying mechanisms of GSH depletion, the metabolism of two esters was investigated in greater detail. One of them, allyl methacrylate, was metabolized to acrolein. This metabolic pathway can explain the high potency of allyl methacrylate to deplete GSH despite its low intrinsic chemical reactivity.

Variation in the sensitivity of aquatic species in relation to the classification of environmental pollutants

Differences in species sensitivity to toxicants can be substantial. In this study this among-species variation in sensitivity was analyzed in relation to chemical's mode of action. Chemicals were classified as: non-polar narcotics, polar narcotics, reactive compounds and specifically acting compounds. Acute toxicity data of aquatic species were derived from the literature. Levels of enhanced toxicity, averaged over all species, and interspecies variation in sensitivity were analyzed for 35 chemicals, with data ranging from 12 to 62 aquatic species per compound. Non-polar and polar narcotic chemicals demonstrate the smallest variation in sensitivity and have levels of toxicity, which are highly predictable on the basis of their hydrophobicity. Reactive and specifically acting compounds can be much more toxic than predicted and variation in species sensitivity can be as large as 10(5) to 10(6). In general, the larger this interspecies variation the more asymmetric is the toxicity distribution due to extremely sensitive species. Reactive and specifically acting compounds pose a potentially larger risk for species in ecosystems than polar and non-polar narcotic compounds. They will need more testing to derive precisely equal estimates of safe environmental concentrations.

Pattern analysis of the variation in the sensitivity of aquatic species to toxicants

Our aim in this study was to identify groups of species showing a similar pattern in their sensitivity to toxicants and to relate the patterns to the mode of toxic action and biological species characteristics. A data matrix was composed of acute toxicity data for 26 aquatic species and 21 compounds. Most of the variation in the toxicological data was due to differences in toxicity of compounds and not intrinsic differences between species, so that practically every species can be used to order compounds with respect to average toxicity. Compounds with high overall toxicity also had large interspecies variation in sensitivity. The toxicity of non-polar narcotics correlated well with the log Kow. Compounds with a specific or reactive mode of action were more than a factor 10 toxic than predicted by their log Kow. Patterns in species sensitivity were more diffuse because only part of the variance in species sensitivity could be explained. Fishes and amphibians were more sensitive to dieldrin, lindane and pentachlorophenol than were invertebrates. Among the arthropods, the Phyllopoda (daphnids) were the most sensitive species. They were very sensitive to aniline, the heavy metals, malathion and parathion.

Assessment of QSARS for Predicting Fate and Effects of Chemicals in the Environment: An International European Project

Abstract In 1993, an international project on QSAR has been started with funding from the Commission of the European Union. The first part of the project is focused on preparing an overview of existing models for the prediction of environmental parameters such as bioconcentration, sorption, degradation and ecotoxicity. Emphasis will be given to defining the limitations of the models. Since all models, including QSARs, have their limitations, it is important that these limitations are known in case QSARs are actually used and applied within the risk assessment context. The second part of the project is directed towards experimental research on new developments with emphasis on the use of multivariate techniques and quantum chemical properties. In this short paper, a general outline of the project will be given, as well as some first results. Results of experimental work within this project will be published in the proceedings of the 6th International Workshop on QSAR in Environmental Sciences and will appear in this same journal.

Dietary uptake of superlipophilic compounds by earthworms (Eisenia andrei)

The uptake and elimination of three superlipophilic compounds (hexabromobenzene, PCB153, and octachloronaphthalene) after dietary uptake was studied in earthworms (Eisenia andrei). All three compounds were taken up from the food, although they did not significantly accumulate despite their hydrophobicity. Both uptake efficiencies (E) and biomagnification factors (BMF) were low. E varied between 0.70 and 7.5%, while BMF values were all below 0.17. The elimination of the compounds was slow, with elimination rate constants k2 varying between 0.04 and 0.09 day-1.

The toxicokinetic behavior of chlorobenzenes in earthworms (Eisenia andrei): experiments in water

The toxicokinetic behavior of five chlorobenzenes in earthworms (Eisenia andrei) was studied. Because exposure in soil is difficult to control, worms were kept in water. Bioconcentration factors (BCF) were studied in a static test system. The results show that a steady-state concentration in worms is reached within 5 days. BCF values increased with increasing octanol-water partition coefficient (Kow). To determine elimination rate constants (k2), worms were exposed to a mixture of chlorobenzenes for 6 days followed by a depuration period of 21 days. The data of the elimination process are described by one-compartment first order kinetics. Hexachlorobenzene was not eliminated within the observed period. Bioconcentration factors increase and elimination rate constants (k2 values) decrease with increasing log Kow. The resulting BCF and k2 values are comparable with those found in fish studies.

Qualitative and quantitative modelling of toxic effects of organophosphorous compounds to fish

In this paper a QSAR analysis is applied with the intention of analyzing toxicity data of 20 organophosphorous compounds in terms of possible rate-limiting steps. Several aspects will be discussed and related to the physico-chemical properties of the test compounds. These are: bioconcentration factors, inhibition of acetylcholinesterase (AChE) and biotransformation in oxidative and glutathione-mediated in vitro systems. As expected, relatively simple relationships between toxicity data and Kow, as obtained for narcotic chemicals, were not obtained. The results of this study show that large differences can occur in the toxicity of the chemicals to fish, despite the fact that in vitro parameters for AChE inhibition and biotransformation are approximately equal. From these observations it is concluded that the application of general QSAR models for the estimation of toxicity data of reactive compounds that can be metabolized in vivo is as yet restricted due to our lack of knowledge of specific enzyme activities and of the role of possible extrahepatic biotransformation processes.

Quantitative structure-activity relationships and mixture toxicity studies of chloro- and alkylanilines at an acute lethal toxicity level to the guppy (Poecilia reticulata)

Quantitative structure-activity relationships (QSARs) were calculated for the acute lethal toxicities (14-day LC50) to the guppy (Poecilia reticulata) of anilines, with several hydrophobicity characteristics and the Hammett sigma constant as parameters. Calculated and experimental Poct values and II constants were used as hydrophobicity characteristics. Introduction of Hammett constants improved the quality of the QSARs. Together with the QSAR studies the toxicities of mixtures of the anilines were determined. The toxicities of three mixtures did not deviate from concentration addition.