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Introduction: Preventable medication errors have been proven to cause significant public health burden, and ePrescription is a key part of the process where medication errors and adverse effects could be prevented. Information systems and "intelligent" computational approaches could provide a valuable tool to prevent such errors with profound impact in clinical practice., Objectives: The PrescIT platform is a Clinical Decision Support System (CDSS) that aims to facilitate the prevention of adverse drug reactions (ADRs) and drug-drug interactions (DDIs) in the phase of ePrescription in Greece. The proposed platform could be relatively easily localized for use in other contexts too., Methods: The PrescIT platform is based on the use of Knowledge Engineering (ΚΕ) approaches, i.e., the use of Ontologies and Knowledge Graphs (KGs) developed upon openly available data sources. Open standards (i.e., RDF, OWL, SPARQL) are used for the development of the platform enabling the integration with already existing IT systems or for standalone use. The main KG is based on the use of DrugBank, MedDRA, SemMedDB and OpenPVSignal. In addition, the Business Process Management Notation (BPMN) has been used to model long-term therapeutic protocols used during the ePrescription process. Finally, the produced software has been pilot tested in three hospitals by 18 clinical professionals via in-person think-aloud sessions., Results: The PrescIT platform has been successfully integrated in a transparent fashion in a proprietary Hospital Information System (HIS), and it has also been used as a standalone application. Furthermore, it has been successfully integrated with the Greek National ePrescription system. During the pilot phase, one psychiatric therapeutic protocol was used as a testbed to collect end-users' feedback. Summarizing the feedback from the end-users, they have generally acknowledged the usefulness of such a system while also identifying some challenges in terms of usability and the overall user experience., Conclusions: The PrescIT platform has been successfully deployed and piloted in real-world environments to evaluate its ability to support safer medication prescriptions., (© 2024. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Adverse Drug Reactions (ADRs) are a crucial public health issue due to the significant health and monetary burden that they can impose. Real-World Data (RWD), e.g., Electronic Health Records, claims data, etc., can support the identification of potentially unknown ADRs and thus, they could provide raw data to mine ADR prevention rules. The PrescIT project aims to create a Clinical Decision Support System (CDSS) for ADR prevention during ePrescription and uses OMOP-CDM as the main data model to mine ADR prevention rules, based on the software stack provided by the OHDSI initiative. This paper presents the deployment of OMOP-CDM infrastructure using the MIMIC-III as a testbed.

Adverse Drug Reactions (ADRs) are an important public health issue as they can impose significant health and monetary burdens. This paper presents the engineering and use case of a Knowledge Graph, supporting the prevention of ADRs as part of a Clinical Decision Support System (CDSS) developed in the context of the PrescIT project. The presented PrescIT Knowledge Graph is built upon Semantic Web technologies namely the Resource Description Framework (RDF), and integrates widely relevant data sources and ontologies, i.e., DrugBank, SemMedDB, OpenPVSignal Knowledge Graph and DINTO, resulting in a lightweight and self-contained data source for evidence-based ADRs identification.

Malignant pleural effusion (MPE) may be diagnosed by cytologic evaluation of pleural fluid, though false negative results can occur. Pleural effusions may provide a source of tumour material for genotyping in lung cancer patients. Detection of MPE may be improved through use of highly sensitive molecular techniques. We identified five patients with non-small cell lung cancer (NSCLC) with initial pleural fluid samples that were non-malignant on cytology, but were subsequently clinically confirmed to have MPE. Tumour mutation status was confirmed via routine testing of diagnostic clinical specimens. Cytologically negative pleural fluid cell-block specimens were analysed by amplicon-based parallel sequencing (APS) for somatic mutations commonly detected in NSCLC, and selected cases by improved and complete enrichment CO-amplification at lower denaturation temperature PCR (ICECOLD PCR) for known mutations. Mutations were detected in three out of three (sensitivity 100%) cytologically non-malignant pleural fluids from patients with a known mutation: two patients with known Kirsten rat sarcoma ( KRAS ) mutation demonstrated the same KRAS mutation in their pleural fluids by APS, both at approximately 2% mutant allele frequency. In one patient with a known KRAS mutation, ICECOLD PCR detected the same KRAS variant at 0.7% frequency. No mutations were detected in patients with wild-type findings from reference samples (specificity 100%). Sensitive DNA sequencing methods can detect cancer-driver mutations in cytologically non-malignant pleural fluid specimens from NSCLC patients with MPE. Our findings demonstrate the feasibility of sensitive molecular diagnostic techniques for improvement of diagnostic assessment of pleural effusions in patients with lung cancer., Competing Interests: Conflicts of Interest: The authors have no conflicts of interest to declare.

Background: Use of a widely accepted quality assurance tool is an essential procedure of effective and result-oriented quality management in the rehabilitation sector, and generally in health care and social services, but is still lacking in Greece., Objective: This study aims to explore to what extent a Quality Assurance System in Rehabilitation (QASR) in the Greek setting could respond to the needs for quality evaluation of the facilities for people with a disability and to discuss possibilities of its use in rehabilitation organizations, sites and hospitals., Methods: The European Quality in Social Services (EQUASS) Assurance self-assessment questionnaire was officially translated and used as the basis for the new tool, which consisted of 110 questions in 11 sections on development and 6 questions on its evaluation. This tool was tested in 15 specialized centers., Results: The study received a high (93.75%) response rate. Overall score ranged from 11% to one perfect 100%; 53.3% of the facilities fell short of the preset qualification standards, while 4 (26.7%) were qualified for level-1 accreditation. Evaluation of the QASR questionnaire for the function of the rehabilitation facilities for the disabled was extremely positive., Conclusions: The EQUASS assurance-based Greek QASR has received proper attention in its first implementation and it was shown promising to assess the needs of sites that would like to improve their services. The next steps are to establish its validity and reliability so that it can significantly emerge as the standard system for guiding policy in the rehabilitation sector in Greece., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Values of five biomarkers related to cell stress or pollution were evaluated in tissues of the land snail Eobania vermiculata under starvation or hibernation conditions. The biomarkers applied were lysosomal membrane stability in digestive gland cells (LMS) or in haemocytes (neutral red retention assay (NRR)), acetylcholinesterase activity (AchE; EC 3.1.1.7), metallothionein content (MTs), and cyclic AMP content (cAMP). Three groups of snails were studied that were kept under starvation, hibernation and normal conditions, respectively. The results indicated statistically lower values of LMS and NRR in snails kept under starvation or hibernation compared to control ones. Higher values of AChE activity were measured in snails under hibernation compared to controls. MT contents were statistically higher in snails under starvation compared to controls. Measurement of cAMP contents showed no significant differences among the tested groups. The values of the first four biomarkers may be affected by factors other than pollution, such as starvation or hibernation. Therefore, these factors should be taken into consideration when biomonitoring studies are performed in time intervals of hibernation or starvation., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Background: Despite international interest on quality assessment systems (QAS) and their importance in health care accreditation, implementation of a Rehabilitation Services Quality Measurement System still remains a neglected subject in Greece., Objective: To identify appropriate tools for researchers and policy makers to assess the quality of rehabilitation services in Greece, within the current active debate on national health care reform., Methods: A critical review methodology was undertaken, using a systematic approach, aiming to identify the most appropriate tools in the field. Multi-step strategy was followed to gather relevant data, including bibliographical database, internet and hand searches., Results: Twenty-two studies, articles and documents were identified as meeting all inclusion criteria, representing four QAS, compared according to appropriateness, efficiency, and feasibility for general use. The European Quality in Social Services (EQUASS) was evaluated as meeting all of the desired features, such as proper certification, objective measuring, equality, education and training, established guidelines and person-centered approach., Conclusions: EQUASS initiative, developed according to European standards and implemented in resource-limited settings, was recognized as the most adaptive and appropriate system for Greek rehabilitation settings. Health policy makers are urged to take findings into consideration in establishing an integrated, quality-assured rehabilitation system throughout the country., (Copyright © 2013 Elsevier Inc. All rights reserved.)

The present study examines the influence of environmentally relevant concentrations of two pesticides, chlorpyrifos and penoxsulam on mussel physiological status. For this reason, lysosomal membrane stability (LMS), reactive oxygen species (ROS), DNA damage, protein carbonylation (PCC) and antioxidant capacity (TAC) in hemaolymph and hemocytes of the mussels was measured. Mussels were exposed to a range of concentrations of the pesticides chlorpyrifos and penoxsulam and the response of animals to the destabilization of lysosomal membrane in hemocytes (LMS) was studied. Subsequently, the half maximal effective concentration (EC50) for both pesticides was calculated. The animals were subsequently exposed for 0, 1, 3, 5, 7, 15 and 30 days to 10 times less concentration than EC50 of each pesticide (0.05 μg/l) and changes in LMS, ROS, DNA damage, protein carbonylation and antioxidant capacity of mussels was evaluated. Our results showed a significant change in the response of mussels for all parameters tested after 30 days exposure, in relation to the controls. The pesticides at the environmental concentrations used induced changes to the animal physiology through causing oxidative stress and lysosomal abnormalities and their usage in the agriculture demands great care. In addition, the results show that ROS, DNA damage, protein carbonylation and antioxidant capacity could constitute, after further investigation, reliable biomarkers for the evaluation of pollution or other environmental stressors., (Copyright © 2012 Elsevier B.V. All rights reserved.)

In the present study a package of biomarkers was applied on land snails E. vermiculata collected from polluted areas, as well as from an unpolluted reference one. Snail collection was performed during two different sampling periods characterized by reduced and augmented organism activity, October and May, respectively. The biomarkers applied were lysosomal membrane stability on digestive cells (LMS), neutral red lysosomal retention assay on haemocytes (NRR), morphometric changes of the lysosomal system (VDL, NDL), morphometric alterations of the neutral lipids (VDLP, NDLP), acetylcholinesterase activity on digestive gland and hemolymph (AChE), metallothionein content on digestive gland (MTs) and cyclic AMP content on digestive gland (cAMP). The results revealed significant differences in biomarker values between the two sampling periods. Significant differences were also detected among the sampling groups. The fluctuation of the parameters applied indicated that spring is a more suitable period for sampling conduction compared to autumn and that biomonitoring studies should be performed with special attention during the last mentioned period., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The present study investigates the histochemical localization of N-acetyl-β-hexozaminidase (Hex), acid phosphatase (AcP) and β-glucuronidase (β-Gus) in the digestive gland of mussels Mytilus galloprovincialis, as well as the clarification of suitable enzyme for biomarkers' application dealing with lysosomes. The results show more intense and homogenous localization of Hex, in relation to AcP and β-Gus and, thus, Hex histochemistry is supported as more suitable procedure for the evaluation of "lysosomal membrane stability" and "morphometrical alterations of lysosomes". The affection of lipofuscin granules on lysosomal enzymes' activity is also discussed. Additionally, the present study examines the response of small- and large-sized mussels M. galloprovincialis by assessing the "lysosomal membrane stability", "morphometrical alterations of lysosomes", "lysosomal response index (LRI)" and "structural epithelial changes in digestive tubules". The results indicate appreciable alterations of the above parameters in large-sized mussels, supporting their greater influence by the environmental factors, in relation to small-sized ones., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The present study focused on early responses of land snails Eobania vermiculata to organic environmental contaminants, by investigating the use of a newly-established method for the measurement of protein carbonylation as a new biomarker of terrestrial pollution, as well as by measuring the ROS production and the DNA damage. Land snails were exposed to different concentrations of chlorpyrifos, parathion-methyl or PAHs in vivo or in vitro in the laboratory. The susceptibility of exposed snails was increased in relation to oxidative stress induced by contaminants tested. A statistically significant increase in ROS production, protein carbonylation and DNA damage was revealed in the snails treated with pollutants, compared to the untreated ones. The results indicated the effectiveness of measuring ROS production and DNA damage and reinforce the application of the present ELISA method in organic terrestrial pollution biomonitoring studies., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The aim of the present study is the comparative examination of accumulation and detoxification of Cu and Hg in digestive gland and gills of mussels Mytilus galloprovincialis, using atomic absorption spectrophotometry and autometallography. Mussels were exposed to 0.08 mg L(-1) Cu, 0.08 mg L(-1) Hg, as well as to a mixture of 0.08 mg L(-1) Hg and 0.08 mg L(-1) Cu for 11 d. After the experimental exposure, animals were kept under laboratory conditions for a detoxification period of 7d. An antagonistic effect of Cu against to Hg accumulation was noted in the digestive gland of mussels after the experimental exposure, as well as after the detoxification period, supporting the protective role of Cu against to Hg toxicity in this tissue. Digestive gland was suggested as a main organ for Hg accumulation and gills as a target position for Cu accumulation. Additionally, lower time was evaluated for Hg detoxification in the digestive gland and gills of mussels, in relation to those addressed for Cu detoxification in the same tissues. The evaluation of black silver deposits (BSD) extent performed in digestive gland and gills was suggested as a less sensitive approach, in relation to atomic absorption spectrophotometry (AAS), to identify the concentration of heavy metals in tissues of mussels. The toxic effects of Hg, Cu and a mixture of them on lysosomal system of the digestive cells are also discussed., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

The present study aimed to enrich the group of sentinel organisms of terrestrial pollution biomonitoring, by investigating the efficacy of the land snail Eobania vermiculata. For this reason, a package of biomarkers was performed on land snails E. vermiculata collected from polluted areas in the field or treated with heavy metals in the laboratory. The biomarkers used were neutral red lysosomal retention assay of the haemocytes, acetylcholinesterase activity in the digestive gland and the haemolymph, and metallothionein content of the digestive gland. Moreover, the morphometric changes in the lysosomal system and the morphometric alterations of the neutral lipids were also investigated. In addition, the content of cadmium, lead and copper was evaluated in the digestive gland of the snails. The results revealed appreciable alterations in the biomarker values both in field- and laboratory-conditions, accompanied by significant correlations among the biomarkers. Therefore, this exploratory study suggests the utility of E. vermiculata as a sentinel organism for biomonitoring the biologic impact of terrestrial pollution, and supports the package's efficacy of the selected biomarkers., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Pollution biomarkers were assessed in the digestive gland of mussels Mytilus galloprovincialis collected from Greek coasts (Thermaikos and Strymonikos Gulf, Northern Greece) on July 2004. The values of biomarkers were integrated using three ecosystem health indices: health status index (HIS) calculated by the expert system, lysosomal response index (LRI) and integrated biomarker response (IBR). The HIS is based on the integration of the biomarker values, classifying the health status of mussels according to pollution degree. The LRI combines two lysosomal responses (lysosomal membrane stability and lysosomal structural changes) in a single index, which is associated with the ecosystem contamination. The IBR is a useful tool for the visualization of biological responses in marine environments. The results support the use of HIS and LRI as powerful tools for the qualitative and quantitative evaluation of environmental stress, while enhance the use of IBR as a constructive method for the qualitative discrimination of contaminated sites. HIS and LRI revealed high stress conditions in all sampling stations of Thermaikos gulf, whereas unstressed conditions were detected in Olympiada (reference station) by the use of HIS and low stress conditions were shown by the use of LRI. The IBR illustrated higher levels of stress in mussels collected from Thermaikos Gulf, compared to mussels gathered from the reference station. The advantages and disadvantages of the HIS, LRI and IBR are also discussed., (Copyright © 2010 Elsevier Inc. All rights reserved.)

The present study investigates the role of the signal transduction molecule cAMP, and the lysosomal membrane stability (LMS), as biomarkers of terrestrial environmental pollution using the land snail Eobania vermiculata. Snails were exposed to different concentrations of heavy metals (Cd, Pb and Cu) and organic pollutants (chlorpyrifos, parathion-methyl and PAHs) in laboratory conditions for 25 days. In addition, snails were collected from various sites located at different distances away from two polluted areas in northern Greece (the road Agiou Dimitriou in Thessaloniki city and a lignite power station in the district of Kozani). The results of the current investigation showed significantly increased levels of cAMP in the digestive gland of snails, as well as decreased LMS values in all experimental groups compared to control animals. In support of our data, cAMP levels were significantly negatively correlated with the conventional biomarker LMS, thus encouraging the use of cAMP as a new potential stress index in terrestrial pollution biomonitoring studies.

We applied a newly-established method in haemolymph of mussels, Mytilus galloprovincialis, exposed to different concentrations of heavy metals, such as zinc and cadmium and organic pollutants, such as PAHs and lindane, for the detection of total antioxidant capacity (TAC). The susceptibility of exposed mussels was increased in relation to oxidative stress induced by contaminants tested. Oxidative modifications of proteins were estimated by measuring protein carbonyl content (PCC) and malondialdehyde levels (MDA). For PCC measurement, a highly sensitive and accurate ELISA method, which requires only 5 microg of protein, was used. The significant increase of PCC and MDA in haemolymph of exposed mussels reinforces its role as biomarkers of oxidative stress. Significant correlation of TAC assay, PCC and MDA was conducted in order to evaluate the utility of PCC and TAC assay, used in the present study, as tools for determining oxidative effects of pollutants in mussels. The results reinforce the application of PCC method as useful tool for the determination of PCC alterations in haemolymph of mussels exposed to different levels of contaminants. In addition, the TAC method gives encouraging results, concerning its ability to predict antioxidant efficiency in haemolymph of mussels exposed to inorganic and organic contaminants.

By using cellular biomarkers, such as the formation of the micronucleus, the morphometric alterations of lipids and the morphometric changes in the lysosomal system, we investigated effects of experimental exposure to phenanthrene, Cu, Cd, and Hg for 15 days in mussels. Concerning micronuclei, the evaluation of the total nuclear abnormalities, instead of the micronucleus only, as a biomarker of marine pollution, indicated more statistically significant differences between the control and the pollutant treated groups. Contrary to the existing knowledge showing that there is an increase in lipid content after pollutant exposure, our results showed that there was a decrease in the amount of lipid, as well as an increase in the number of neutral lipids. Furthermore, although prior studies found that fewer lysosomes formed after pollutant exposure, this was not confirmed by our work, as pollutant treated animals exhibited a decrease in the volume and an increase in the numerical density of lysosomes, compared to control groups.

The results of the present study suggest that the signaling molecule cAMP could constitute a reliable biomarker of pollution monitoring. Increased levels of cAMP were observed in tissues of mussels Mytilus galloprovincialis exposed to PAHs, 2,4-dichlorophenoxyacetic acid and lindane for 15 days. cAMP levels were higher in mantle/gonad complex, in relation to other tissues studied (digestive gland and gills). In support of our suggestion, cAMP was significantly correlated with established biomarkers, such as lysosomal membrane stability, AChE activity and metallothionein content. In addition, our results support the establishment of morphometrical alterations of neutral lipids as biomarker of organic pollution, since high accumulation of neutral lipids in the digestive gland of mussels exposed to organic pollutants in relation to non-exposed mussels was noted. In addition, correlation analysis between cellular and biochemical biomarkers showed that the volume density of neutral lipids negatively correlated with both lysosomal membrane stability and AChE activity. Regarding micronucleus test, our results do not support its use as a biomarker of organic pollution, since no statistical differences were found between control and exposed mussels. On the other hand, significant correlations were observed among the battery of biomarkers, such as lysosomal membrane stability, AChE activity and metallothionein content after the mussels' exposure to the specific organic compounds, thus supporting the important role of these biomarkers as reliable indicators of organic pollution. In conclusion, our results support cAMP and morphometrical alterations of neutral lipids as biomarkers of environmental pollution.

The histological and ultrastructural localization of heavy metals in the digestive gland of the mussel, Mytilus galloprovincialis, was evaluated using autometallography and X-ray microanalysis on epoxy resin sections. Mussels were collected from two populations along Thermaikos gulf (port of Thessaloniki and Halastra) and one population in Strymonikos Gulf (Olympiada). With the use of autometallography, the light and electron microscopic observations indicated that in the digestive gland, the metals are localized in lysosomal structures, such as heterolysosomes and the residual bodies of digestive cells. Through both techniques, mussels collected from the port of Thessaloniki displayed concentrations of metals higher than those recorded in mussels from Halastra and Olympiada. This fact is consistent with other reports indicating a similar distribution of metals in Thermaikos Gulf and Strymonikos Gulf. The results of the study support the use of both techniques, autometallography and X-ray microanalysis, as a suite of stress indices for pollution biomonitoring studies., (Copyright 2003 Elsevier Inc.)

The simultaneous study of two biomarkers, the lysosomal membrane stability (LMS) of the digestive gland and the metallothionein (MT) content of the digestive gland, the gills and the mantle/gonad complex of the mussel Mytilus galloprovincialis was examined in an enclosed estuarine system in June and October 2001. Mussels were collected along the Gulf of Thermaikos (northern Greece) from stations displaying a pollution gradient, while Olympiada in the Gulf of Strymonikos was used as a reference station. In addition, the heavy metal (Cd, Pb, Cu and Zn) content, using atomic absorption spectrophotometry (AAS), were evaluated in the digestive gland, the gills and the mantle/gonad complex of mussels collected from the same sites and seasons. LMS values were significantly greater, and the MT content of the studied tissues were significantly less in mussels collected from the reference station compared to mussels from more polluted stations located in the Gulf of Thermaikos. Significant correlation was observed between the MT content of the gills and the mantle/gonad complex with the LMS values.

The neutral red lysosomal retention assay (NRR) of the haemocytes, and the acetylcholinesterase activity (AChE) in the haemolymph, the digestive gland, the gills and the mantle/gonad complex have been evaluated on mussels Mytilus galloprovincialis collected from Thermaikos and Strymonikos gulfs (northern Greece) in June and October 2001. The validity of performing the above core biomarkers is supported, firstly by their ability to respond to different pollution levels and, secondly, by the significant linear correlation among them. The evaluation of the micronuclei frequency (MN) has been performed in gill tissue and haemocytes of the same mussels and, according to the results, it needs more research in order its use as stress indices to be validated. In addition, the first results on cAMP levels in the gills, the mantle/gonad complex and the digestive gland, whose concentrations correlated to both, NRR and AChE introduce this signal transduction molecule as a new, promising biomarker.

The intracellular localization of heavy metals using autometallography (AMG) and X-ray microanalysis was studied in the palps, the digestive gland and the gills of mussels Mytilus galloprovincialis, after an experimental exposure to 0.1 mg l(-1) of Hg and 0.1 mg l(-1) of Pb, for 30 and 60 days. In the examined tissues, autometallographical black silver deposits (BSD) were localized mainly in the residual bodies and heterolysosomes of the digestive cells, as well as in the dense bodies of the epithelial cells. Metal deposition after Hg exposure was much more abundant compared to Pb exposure. Using X-ray microanalysis, Hg was traced on the BSD in all examined tissues, while Pb was not traced in these deposits. The results are discussed in comparison to previous results on long-term exposure to the same metals; in addition, the palps are introduced as a new metal storing organ and, finally, the use of X-ray microanalysis under a scanning electron microscope in order to enhance the specificity of AMG is suggested.

In the present study, autometallography (AMG) has been performed on resin-embedded tissue sections, cryosections, as well as on isolated cells from the digestive gland, the gills and the haemolymph of mussels (Mytilus galloprovincialis) collected from the field. The AMG reaction was more intense in cryosections and isolated cells compared to resin sections. This intense AMG reaction found in cryosections and in isolated cells and the time effectiveness of the procedures enhances their use in a variety of studies, such as biomonitoring, even if small amount of metals are to be detected. In addition, the preparation of isolated cells does not require specific instruments or qualified personnel and, thus, the use of isolated cells is encouraging for AMG applications, although further laboratory investigation is required. On the other hand, the use of resin-embedded tissue sections for AMG applications, even though it is complicated and time consuming, leads to a high preservation of structural morphology and allows the exact localization of metals in discrete cellular compartments.

Lysosomal and lipid alterations in the digestive gland cells of the common mussel Mytilus galloprovincialis collected from six stations along Thermaikos Gulf (Northern Greece) were monitored through a 1-year period. The ultrastructural observations of the digestive cells of sampled mussels indicated a higher incidence of "granular" or "dark" residual bodies in the relatively more polluted stations compared to less polluted ones. Alterations in the lysosomal system of digestive cells were assessed: (1) using the lysosomal membrane stability test (2) quantifying lysosomal structural alterations of the residual bodies and the heterolysosomes of the digestive cells at the ultrastructural level, and (3) determining the elemental composition of lysosomes by means of X-ray microanalysis on epoxy resin sections. Evaluation of neutral lipids was realized using image analysis on histochemical resin sections. Mussels from the most heavily polluted stations exhibited reduced lysosomal membrane stability, higher volume density and diameter of heterolysosomes and residual bodies, and, in some cases, relatively higher lysosomal heavy metal content compared to mussels from less polluted stations. The results showed that the lysosomal membrane stability and the volume density of the residual bodies are more sensitive to general stress compared to the other biomarkers used, and could be used successfully as early warning tools in biomonitoring programs.