Modelling chase-and-run migration in heterogeneous populations.

Cell migration is crucial for many physiological and pathological processes. During embryogenesis, neural crest cells undergo coordinated epithelial to mesenchymal transformations and migrate towards various forming organs. Here we develop a computational model to understand how mutual interactions between migrating neural crest cells (NCs) and the surrounding population of placode cells (PCs) generate coordinated migration. According to experimental findings, we implement a minimal set of hypotheses, based on a coupling between chemotactic movement of NCs in response to a placode-secreted chemoattractant (Sdf1) and repulsion induced from contact inhibition of locomotion (CIL), triggered by heterotypic NC-PC contacts. This basic set of assumptions is able to semi-quantitatively recapitulate experimental observations of the characteristic multispecies phenomenon of "chase-and-run", where the colony of NCs chases an evasive PC aggregate. The model further reproduces a number of in vitro manipulations, including full or partial disruption of NC chemotactic migration and selected mechanisms coordinating the CIL phenomenon. Finally, we provide various predictions based on altering other key components of the model mechanisms.

Modelling human perception processes in pedestrian dynamics: a hybrid approach.

In this paper, we present a hybrid mathematical model describing crowd dynamics. More specifically, our approach is based on the well-established Helbing-like discrete model, where each pedestrian is individually represented as a dimensionless point and set to move in order to reach a target destination, with deviations deriving from both physical and social forces. In particular, physical forces account for interpersonal collisions, whereas social components include the individual desire to remain sufficiently far from other walkers (the so-called territorial effect). In this respect, the repulsive behaviour of pedestrians is here set to be different from traditional Helbing-like methods, as it is assumed to be largely determined by how they perceive the presence and the position of neighbouring individuals, i.e. either objectively as pointwise/localized entities or subjectively as spatially distributed masses. The resulting modelling environment is then applied to specific scenarios, that first reproduce a real-world experiment, specifically designed to derive our model hypothesis. Sets of numerical realizations are also run to analyse in more details the pedestrian paths resulting from different types of perception of small groups of static individuals. Finally, analytical investigations formalize and validate from a mathematical point of view selected simulation outcomes.

Coherent modelling switch between pointwise and distributed representations of cell aggregates.

Biological systems are typically formed by different cell phenotypes, characterized by specific biophysical properties and behaviors. Moreover, cells are able to undergo differentiation or phenotypic transitions upon internal or external stimuli. In order to take these phenomena into account, we here propose a modelling framework in which cells can be described either as pointwise/concentrated particles or as distributed masses, according to their biological determinants. A set of suitable rules then defines a coherent procedure to switch between the two mathematical representations. The theoretical environment describing cell transition is then enriched by including cell migratory dynamics and duplication/apoptotic processes, as well as the kinetics of selected diffusing chemicals influencing the system evolution. Finally, biologically relevant numerical realizations are presented: in particular, they deal with the growth of a tumor spheroid and with the initial differentiation stages of the formation of the zebrafish posterior lateral line. Both phenomena mainly rely on cell phenotypic transition and differentiated behaviour, thereby constituting biological systems particularly suitable to assess the advantages of the proposed model.

[Biological risk prevention in agriculture and animal breeding: immunization strategies]. / Strategie vaccinali per la prevenzione del rischio biologico in agricoltura e zootecnia.

Vaccine preventable diseases are, so far, a main focus of Public Health programmes all over the world since people still die in consequence of Dyphteria or Tetanus. Biological risk is widely represented in agriculture and animal breeding, due to environmental characteristics and to injury typology. Moreover, aged people and migrants represent a significant part of the workforce. These two groups are, for instance, more exposed to Clostridium tetani infection because not fully immunized. Among infectious diseases that can affect agricultural workers, just tetanus can be well controlled by immunization programmes. Teaching and training activities are the most important tools to get protection against Leptospira interrogans, Salmonella spp and hepatitis E Virus infection. As for every training activity, linguistic and cultural barriers have to be taken into account.

[The occupational health physician and the health surveillance in agriculture]. / Il medico del Lavoro Competente e la Sorveglianza Sanitaria in Agricoltura.

Despite the underreporting of occupational diseases in agriculture, available data clearly show a significant health risk, and therefore the need of health surveillance at the workplace. The implementation of health surveillance programs for agricultural workers relies on the possibility of creating a system able to reach the workers at their workplaces, with the collaboration of employers' associations, able to support enterprises in several issues, including risk assessment and management. The health surveillance program can be organized in a component common for all workers, based on physical examination, chemistry, electrocardiography, hearing and lung functions examinations, and on tests addressing specific risks, if present: vibration, physical overload, chemicals, biological agents, allergens. The frequency of examinations must be decided based on risk assessment and health surveillance outcomes.

Neurobehavioural effects of pesticides with special focus on organophosphorus compounds: which is the real size of the problem?

The risk of neurobehavioural impairment as a consequence of a prolonged, low dose exposure to neurotoxic pesticides is not clearly demonstrated despite numerous publications addressing the topic. We reviewed the 24 papers published on human neurobehavioural effects of organophosphorus and/or carbamates pesticides up to May 1st 2008. Variables evaluated were compound/s addressed, number of subjects, approach to measure or estimate exposure, characteristics of control groups and presence of confounders, methodological approach, and type of alteration, taking into account cognitive, sensory-motor, psychological, and psychomotor measures. A total of 6 papers considered the whole spectrum of functions, the studies yielding positive or uncertain results were 13 (68%) for cognitive function, 11 (69%) for psychomotor function, 11 (65%) for sensory-motor function, and 11 (65%) for psychological function impairment. In 46% of the positive studies a previous severe acute poisoning was reported. Exposure levels were measured only in 5 studies, and very often there were problems in the selection of controls, and firm conclusions on the risk of neurobehavioural effects cannot be reached yet. The main limits of the available data are: limited number of studies and compounds addressed, significant differences in the approach among studies, poor concordance of the results of different studies, and difficulties in controlling confounding factors. Nevertheless, there are sufficient data to conclude that neurobehavioural impairment might be the consequence of an acute poisoning, and possibly the consequence of relatively high and prolonged exposures.

An integrated approach to biomonitoring exposure to styrene and styrene-(7,8)-oxide using a repeated measurements sampling design.

The aim of this work was to investigate urinary analytes and haemoglobin and albumin adducts as biomarkers of exposure to airborne styrene (Sty) and styrene-(7,8)-oxide (StyOX) and to evaluate the influence of smoking habit and genetic polymorphism of metabolic enzymes GSTM1 and GSTT1 on these biomarkers. We obtained three or four air and urine samples from each exposed worker (eight reinforced plastics workers and 13 varnish workers), one air and urine samples from 22 control workers (automobile mechanics) and one blood sample from all subjects. Median levels of exposure to Sty and StyOX, respectively, were 18.2 mg m(-3) and 133 microg m(-3) for reinforced plastics workers, 3.4 mg m(-3) and 12 microg m(-3) for varnish workers, and <0.3 mg m(-3) and <5 microg m(-3) for controls. Urinary levels of styrene, mandelic acid, phenylglyoxylic acid, phenylglycine (PHG), 4-vinylphenol (VP) and mercapturic acids (M1+M2), as well as cysteinyl adducts of serum albumin (but not those of haemoglobin) were significantly associated with exposure status (controls

[Workers with alcohol and drug addiction problems. Consensus Document of the Study Group on Hazardous Workers]. / Lavoratori con problemi di alcol e dipendenze. Documento di Consenso del gruppo La.R.A. (Lavoratori Rischiosi per gli Altri).

BACKGROUND: Italian Law 81/08 (so-called "Unified Text of Laws on Health and Safety at Work"), came into force on 15 May 2008 and incorporates provisions related to medical surveillance of drug and alcohol dependency at the workplace. OBJECTIVES: Occupational health traditionally addresses the issue of protection of worker from occupational hazards. The issue of protection of third parties from behaviour of workers resulting from drug and alcohol dependency implies an original methodological approach, involving full cooperation of employer, employees, and health and safety consultants. METHODS: A consensus development meeting was organized under the leadership of the Italian Study Group on Hazardous Workers (La.R.A. group). The meeting brought together physicians of different specialties, legal experts and bioethicists, labour and management policy-makers, to discuss the issue and define the research data available, the standards that were appropriate, and which policies were fair. RESULTS: The efficacy of medical surveillance, including workplace drug-testing, relies on a comprehensive policy, including written and verbal information on the use of alcohol and drugs on the job, training for supervisors and management, employee education, and employee assistance structures. Sample collection and testing should be carried out in accordance with standardized and tested procedures. Small businesses will need assistance, including development of model policies, setting up consortia for testing services and if necessary request for National Insurance benefits to reduce costs. CONCLUSIONS: The recently introduced Italian legislation on occupational safety and health closely resembles Finnish law since it consists of a "double channel" for workplace drug testing. At recruitment, the employer is entitled to ask a job applicant for a certificate of "Job fitness", including drug tests, that can be issued only by a public health institution, where the job applicant works on a well-defined set of tasks which require accuracy, trustworthiness, independent judgement or a very good reaction capacity. The employer may also refer the employee to the public health institution to obtain a certificate in the course of an employment contract when there is a legitimate suspicion that the employee is working while under the effects of drugs or alcohol or that the employee is a drug addict. After recruitment, the physician responsible for medical surveillance of workers (the so-called "Competent Physician") is entitled to perform drug tests on employees. The need for a test is decided by the health care professional, not by the employer, and only a general report on the health of the employee ("fit", fit with restrictions" or "unfit") may be given to the employer. Workers positive for drug tests will be referred to a public health institution for re-testing and treatment.

[Occupational and environmental exposure to anilide and dicarboximide pesticides]. / Esposizione ambientale e professionale a pesticidi propionanilidici e dicarbossimidici.

Dicarboximide fungicides (DF) such as vinclozolin, iprodione, procymidone are widely used on vines, fruit and vegetables, and anilide herbicides (AH) such as diuron, linuron, propanil are used to control weeds on hard surfaces, such as, roads, railway tracks, paths, and in crops, forestry. Italian reports on food safety found many samples contaminated by pesticides belonging to these categories, even though only few exceeding L.M.R. Since adverse effects on human health, such as endocrine disruption, have been reported, biological monitoring is essential for exposure assessment both of occupationally exposed subjects and of the general population. Common metabolites of DF and AH are dichloroanilinines such as 3,4-DCA and 3,5-DCA, urine samples from 153 subjects living in Novafeltria, central Italy, were collected for analysis of 3,4- and 3,5-DCAs, each participant was invited to complete a very detailed questionnaire. A total of 151 out of 153 samples were found to be positive for 3,5-DCA, and 81.7% were positive for 3,4-DCA. Also 33 workers, engaged in application of propanil on rice in northern Italy, were involved in the study and 3,4-DCA was determined as marker of exposure. 3,4 and 3,5 dichloroaniline are useful and promising biological indicators for monitoring occupational and environmental exposure to these classes of pesticides.

[The impact of personal protective equipment in reducing risk for operators exposed to pesticides: from theory to practice]. / La stima dell'impatto dei dispositivi di protezione nella riduzione del rischio in ambito di regolamentazione dei prodotti fitosanitari: dalla teoria alla pratica.

In Europe, the use of plant protection products is authorized provided the operator risk assessment carried out does not show exposure levels above the health-based triggers. Two models are currently available (German and UK models) to estimate exposure levels of agricultural operators. They consider, among different variables, the use of Personal Protective Equipment (PPE), based on their capacity to reduce exposure through the application of specific "reduction factors", derived from laboratory or field studies. Such factors, which date back to '90s, could be obsolete, as indicated by recent literature, posing problems on the reliability of current estimates. Therefore, the exposure estimates produced in Europe from 2005 to 2007, for 52 active ingredients in 395 scenarios, have been collected and analysed to check whether the application of recent exposure reduction factors might have an impact on the final outcomes. In some case the exposure levels resulted underestimated, highlighting the problem of operator safety with regard to the use of specific PPE and to an adequate training programme.

[Occupational risk and prevention in the biotechnology industry: a review]. / Rischio professionale e prevenzione nell'industria biotecnologica: revisione della letteratura.

BACKGROUND: The biotechnology industry has expanded greatly in the last 20-30 years and has led to a number of applications in different sectors of work, i.e., medical and pharmaceutical, agricultural, chemical, energetic and others. Nowadays hundreds of thousands of workers worldwide are employed in biotechnology plants. Health and safety issues related to such working activities are considered as relevant to workers as well as to the general public. In particular, when compared to traditional biotechnology, modern methods of processing microrganisms have given rise to public concern that they might generate hazards to human beings and to the environment. OBJECTIVES AND METHODS: After summarizing the most important products and fields of application, the paper sets out to detail potential adverse effects for the health of biotechnology workers; in addition, an analysis of the literature highlights the various concepts of primary and secondary prevention. RESULTS AND CONCLUSION: Along with occupational risk factors common to other working activities (i.e. the well-known physical and chemical hazards), the peculiarity of handling microrganisms and/or different biologic systems may induce infections, immunological alterations or non-infective and non-immunologic toxic reactions in the workers involved The need is emphasized for an accurate risk assessment, careful control by means of the current monitoring strategies and implementation of the confinement measures, taking into account the criteria set by Italian legislation for occupational biological risk. Lastly, attention is focussed on examinations for the medical surveillance of workers at risk.

Aluminum determination in biological fluids and dialysis concentrates via chelation with 8-hydroxyquinoline and solvent extraction/fluorimetry.

We describe a simple, rapid, and sensitive fluorescence method for measurement of aluminum (Al) in human biological fluids, in dialysis solutions, and in tap water, which uses 8-hydroxyquinoline for ion chelation. The fluorescence intensity of the toluene-extracted metal chelate (excitation wavelength, 380 nm; emission wavelength, 504 nm) remains unchanged for over 48 h at room temperature. Fluorescence intensity is a linear function of the concentration of Al in the 2-1000 microg/L range with detection limits of 0.7-2 microg/L. A large excess of other ions normally found in biological fluids does not interfere in Al determination. The method developed was successfully used in assaying Al in serum and urine of reference subjects, in serum samples from patients undergoing long-term dialysis, and in dialysis solutions. Al concentrations, measured by this fluorimetric procedure, were compared with those obtained by Zeeman graphite-furnace atomic absorption spectrometry. A correlation coefficient of 0.98 was obtained. The proposed method could be used for routine analysis in clinical laboratories for accurate determination of aluminum in aqueous or biological fluids.

[New biomarkers of exposure]. / Nuovi indicatori di esposizione.

In this paper we have defined the new biomarkers of exposure (NBE) as those biomarkers discovered in the last five years and, among previously validated biomarkers, also those applied in different ranges of doses or those determined in biological matrices which differ from matrices originally considered. We examined the results from the surveys carried out by the main Italian research units involved in biological monitoring, i.e. those from the Universities of Brescia, Milan, Naples, Padua, Parma, Pavia, Turin and Verona. The data were collected using a standardized model and included the following: type of element or organic compound, type of biomarker, analytical technique and method, their relationship with environmental monitoring data, their relationship with effect indicators or effects in general, improvement with respect to old biomarkers, reference values. Twenty two NBEs were identified: 14 elements and chemical compounds as such or as metabolites, 4 examples of mixtures, 3 of new matrices, one of speciation. Among the others, aspects such as interest in requiring NBE, quality assurance, availability, cost-benefit ratio were discussed. We conclude that development of this specific field of research appears to be a crucial point for future improvement in risk assessment and health surveillance procedures.

[European multicenter cross-sectional study on exposure to low doses of benzene]. / Studio trasversale multicentrico europeo su esposizione a basse dosi di benzene.

A cross-sectional multicenter european study has been carried out to evacuate the relations between exposure to low level of benzene and biological markers of internal dose (t,t-MA, S-PMA) and early biological effect (DNA-SSB). The research has shown significantly increased levels (adjusted for smoking habits) of the urinary excretion of t,t-MA, S-PMA and DNA-SSB in petrochemical workers (mean benzene level = 5,694 micrograms/m3) but not in filling station attendants, traffic police officers, and bus drivers compared to referent workers. Dose-response relations were detected between benzene air levels, t,t-MA, S-PMA and DNA-SSB in petrochemical workers, with significantly increased levels of DNA-SSB detected for benzene exposure levels in the range 391-1,800 micrograms/m3 (0.12-0.58 ppm).

[Evolution of industrial toxicology toward vanishing doses and the human genome]. / Evoluzione della tossicologia industriale tra dosi effimere e genoma umano.

BACKGROUND: This article aims to discuss the influence that the application of the recent discoveries in genomics will have on the theory and practice of industrial toxicology in developed post-industrial countries. It is stressed that the recent advances in toxicogenomics can be integrated into the existing wealth of knowledge on the toxic properties of industrial chemicals to improve the efficacy of prevention of toxicological risk. METHODS AND RESULTS: The understanding of the biochemical and physiological mechanisms underlying susceptibility or resistance to the toxic effects of industrial xenobiotics, and in particular to carcinogens, allows us to split the epidemiologically derived relationship linking the frequency of disease in the exposed population to the level of workplace contamination into a set of sequential sub-relationships linking: a) the exposure level to that of workplace contamination; b) the internal dose to the exposure level; c) the biological effect (e.g., measured through biochemical markers of early effect) to the internal dose; d) the frequency of disease to that of observation of early biochemical effects. Each of the cited relationships is affected by a degree of uncertainty due to the variability of biological response among the examined individuals, which in turn requires a definition of the statistical limits for the association functions between the variables. As a consequence, the possibility of investigating the individual biochemical and physiological steps in the causal mechanism that links toxic exposure to disease does not necessarily lead to an increase in the information potential of biological monitoring, since the uncertainty due to inter-individual variability is amplified through the sequence of causal relationships to the point that the data from biological monitoring become valueless with regard to the prediction of the frequency or probability of disease. This is particularly true when exposure to 'low doses' is investigated, as is now increasingly frequent in post-industrial developed countries, where workplace contamination is now greatly reduced to levels which may be borderline with those in the general environment. Thus at the low-dose end of the range of contamination and exposure values there is an area where, for statistical reasons consequent to the heterogeneity of examined populations, a quantitative prediction of internal exposure due to environmental contamination, of biological adverse effects due to exposure levels and of frequency of disease due to the extent or frequency of biological effects is no longer reliably possible. This in turn impairs the preventive efficacy of biological monitoring. CONCLUSIONS: A closer integration between industrial toxicology and state-of-the-art molecular genetics derived from the recent sequencing of the human genome is the way to overcome the limitations described. In particular, the individual subjects in the examined populations can be classified with regard to some genetically controlled characters relevant to the biotransformation of xenobiotics and to DNA repair and the statistical analysis of data can be performed on more homogeneous subpopulations, in order to decrease inter-individual variability of biochemical and physiological response. This in turn increases the predictive power of the biological markers, both of dose and effect, and improves the efficacy of prevention, e.g., by highlighting oversensitive subpopulations or lifestyles which can increase the risk of occupational and environmental disease.

[Evaluation of the dose of mercury in exposed and control subjects]. / Valutazione delle dosi di mercurio negli esposti e nei controlli.

OBJECTIVES: The aim of this paper was to analyse the concentrations of HgU and HgB in three different groups: 122 workers exposed, 18 workers formerly exposed and 196 subjects not occupationally or environmentally exposed to mercury. METHODS: All the subjects filled out a questionnaire concerning personal data, lifestyle, occupational or non-occupational exposure to Hg and medical history. The amalgam fillings area was measured by a standardised method. RESULTS: Urinary mercury excretion was significantly greater in the group of the exposed workers respect to the group of subjects not occupationally exposed (Median value of 8.3 micrograms/g creatinine and the 5 degrees and 95 degrees percentile respectively of 2.66 e 23.50 micrograms/g creatinine against Median value of 1.2 micrograms/g creatinine and the 5 degrees and 95 degrees percentile respectively of 0.18 and 5.42 micrograms/g creatinine). U-Hg in formerly exposed workers were comparable to U-Hg in non-occupationally exposed subjects, with a median value of 1.6 micrograms/g creatinine. B-Hg values were similar in the three groups: the median value was 3.1 micrograms/l in the non-occupationally exposed, 4.0 micrograms/l in the exposed workers and 3.9 micrograms/l in the past exposed. These value were not significantly different. Among the considered variables (amalgam fillings, fish consumption, age, sex, alcohol intake, chewing-gum and smoking) dental amalgam and fish consumption were significantly related with the Hg urinary excretion and the B-Hg levels. This is particularly true considering the subjects altogether: for the exposed workers, indeed, the occupational exposure was the most relevant variable. CONCLUSIONS: The results of the present research confirmed that the U-Hg excretion in non-occupationally exposed subjects is influenced by amalgam dental fillings. Furthermore, in our study Hg urinary excretion was significantly related with fish consumption. This fact can be explained, according to several recent experimental human and animal trials, considering that methylmercury contained in fish is partially converted, through breakage of the carbon-Hg bond, into Hg inorganic forms, which accumulate in the kidney and have a urinary excretion pathway.

[Renal effects of low doses of mercury]. / Effetti renali di basse dosi di mercurio.

OBJECTIVES: The present study was aimed at investigating early markers of renal damage and dysfunction in subjects exposed to low doses of mercury from different sources. Different groups of subjects were examined with urinary Hg excretion (HgU) ranging from 0.1 to 35.0 micrograms/g creatinine: 122 occupationally exposed workers, 22 subjects living in a non-polluted area, but consuming large amounts of tuna and sword fish, and 197 controls. METHODS: Several markers of renal changes were measured in urine (albumin, fibronectin, beta 2-microglobulin, retinol-binding protein, tubular antigens, N-acetyl-beta-D-glucosaminidase activity) and serum (beta 2-microglobulin and cystatin C). Serum autoantibodies towards collagen, laminin and tubular antigens were assessed in subjects with abnormal renal markers. The role of glutathione-S-tranferases GSTT1 and GSTM1 polymorphisms in the inter-individual variability of biological response to Hg was also investigated. RESULTS: Renal markers were not correlated with HgU. None of such markers differed significantly between exposed workers and controls, except for urinary beta 2-microglobulin, which was decreased in Hg-exposed workers (GM = 55.8 vs 86.6 micrograms/g creatinine), in the absence of any changes in serum concentration. Subjects usually eating tuna and sword fish showed an increased urinary excretion of beta 2-microglobulin, albumin and fibronectin. Serum titres of auto-antibodies did not differ between the groups. Neither in controls nor in exposed workers were the observed differences modified by the GSTM1 and GSTT1 genotypes. CONCLUSION: The present study did not provide evidence of any changes in kidney integrity and function in subjects exposed to very low levels of inorganic Hg resulting in urinary Hg lower than 35 micrograms/g creatinine. Nor did we obtain evidence of Hg-induced autoimmunity towards kidney components. The potential modifying role of GST polymorphisms could not be clarified in the absence of effects associated with exposure to the risk factor, i.e., to inorganic Hg. Preliminary data suggesting nephrotoxic effects of organic Hg from a diet rich in large fish resulting in increased levels of both blood and urinary Hg--which however did not exceed 20 micrograms/g creatinine--deserves further investigation.

[Immunologic effects of exposure to low levels of inorganic mercury]. / Effetti immunitari da esposizione a basse dosi di mercurio inorganico.

OBJECTIVE: The immune system is a target for the toxic effects of inorganic mercury, both in humans and animals. In humans it has been observed that occupational and environmental exposure to inorganic mercury may cause both clinical (autoimmunity, hypersensitivity) and subclinical effects (cellular and humoral immunologic variable modifications). To obtain a better definition of these effects with respect to the exposure levels, a multicentre study was performed on 117 workers exposed to very low doses of inorganic mercury and 172 subjects from the general population of the same geographical area with environmental exposure to mercury from dental amalgams and dietary fish intake. RESULTS: The white blood cell count was included in the normality range for all subjects and there was no difference between exposed and non exposed subjects. The immunologic variables studied showed an increase of the CD4+ and CD8+ number in exposed workers compared to non-exposed subjects, with a statistically significance only for CD4+, while no difference was observed regarding CD4+, CD8+, NK+ percentage and CD4+/CD8+ ratio. A significative decrease of serum IL-8 and an inverse correlation between serum levels of this cytokine and HgU were observed in exposed workers compared to non exposed subjects. No association between immunologic variables and both dental amalgams and dietary fish intake was found in subjects not occupationally exposed to inorganic mercury. DISCUSSION: The decrease in IL-8 serum levels observed in exposed workers might suggest an immunosuppressive effect of occupational exposure to very low doses of inorganic mercury. This result suggests the need to revise of current HgU BEI after further definition of its prognostic significance.