Identification of Wax Esters in Latent Print Residues by Gas Chromatography-Mass Spectromertry and Their Potential Use as Aging Parameters

Recent studies show that the composition of fingerprint residue varies significantly from the same donor as well as between donors. This variability is a major drawback in latent print dating issues. This study aimed, therefore, at the definition of a parameter that is less variable from print to print, using a ratio of peak area of a target compound degrading over time divided by the summed area of peaks of more stable compounds also found in latent print residues.Gas chromatography-mass spectrometry (GC/MS) analysis of the initial lipid composition of latent prints identifies four main classes of compounds that can be used in the definition of an aging parameter: fatty acids, sterols, sterol precursors, and wax esters (WEs). Although the entities composing the first three groups are quite well known, those composing WEs are poorly reported. Therefore, the first step of the present work was to identify WE compounds present in latent print residues deposited by different donors. Of 29 WEs recorded in the chromatograms, seven were observed in the majority of samples.The identified WE compounds were subsequently used in the definition of ratios in combination with squalene and cholesterol to reduce the variability of the initial composition between latent print residues from different persons and more particularly from the same person. Finally, the influence of a latent print enhancement process on the initial composition was studied by analyzing traces after treatment with magnetic powder, 1,2-indanedione, and cyanoacrylate.

CARDIAC AND MUSCLE CHANNELOPATHIES: ROLES AND REGULATION OF VOLTAGE-GATED SODIUM CHANNELS

Abstract :The contraction of the heart or skeletal muscles is mainly due to the propagation, through excitable cells, of an electrical influx called action potential (AP). The AP results from the sequential opening of ion channels that generate inward or outward currents through the cell membrane. Among all the channels involved, the voltage-gated sodium channel is responsible for the rising phase of the action potential. Ten genes encode the different isoforms of these channels (from Nav1.1 to Nav1.9 and an atypical channel named NavX). Nav1.4 and Nav1.5 are the main skeletal muscle and cardiac sodium channels respectively. Their importance for muscle and heart function has been highlighted by the description of mutations in their encoding genes SCN4A and SCNSA. They lead respectively to neuromuscular disorders such as myotonia or paralysis (for Nav1.4), and to cardiac arrhythmias that can deteriorate into sudden cardiac death (for Nav1.5).The general aim of my PhD work has been to study diseases linked with channels dysfunction, also called channelopathies. In that purpose, I investigated the function and the regulation of the muscle and cardiac voltage-gated sodium channels. During the two first studies, I characterized the effects of two mutations affecting Nav1.4 and Nav1.5 function. I used the HEK293 model cells to express wild-type or mutant channels and then studied their biophysical properties with the patch-clamp technique, in whole cell configuration. We found that the SCN4A mutation produced complex alterations of the muscle sodium channel function, that could explain the myotonic phenotype described in patients carrying the mutation. In the second study, the index case was an heterozygous carrier of a SCNSA mutation that leads to a "loss of function" of the channel. The decreased sodium current measured with mutated Nay 1.5 channels, at physiological temperature, was a one of the factors that could explain the observed Brugada syndrome. The last project aimed at identifying a new potential protein interacting with the cardiac sodium channel. We found that the protein SAP97 binds the three last amino-acids of the C-terminus of Na,, 1.5. Our results also indicated that silencing the expression of SAP97 in HEK293 cells decreased the sodium current. Sodium channels lacking their three last residues also produced a reduced INa. These preliminary results suggest that SAP97 is implicated in the regulation of sodium channel. Whether this effect is direct or imply the action of an adaptor protein remains to be investigated. Moreover, our group has previously shown that Nav1.5 channels are localized to lateral membranes of cardiomyocytes by the dystrophin multiprotein complex (DMC). This suggests that sodium channels are distributed in, at least, two different pools: one targeted at lateral membranes by DMC and the other at intercalated discs by another protein such as SAP97.These studies reveal that cardiac and muscle diseases may result from ion channel mutations but also from regulatory proteins affecting their regulation.Résumé :La contraction des muscles et du coeur est principalement due à la propagation, à travers les cellules excitables, d'un stimulus électrique appelé potentiel d'action (PA). C'est l'ouverture séquentielle de plusieurs canaux ioniques transmembranaires, permettant l'entrée ou la sortie d'ions dans la cellule, qui est à l'origine de ce PA. Parmi tous les canaux ioniques impliqués dans ce processus, les canaux sodiques dépendant du voltage sont responsables de la première phase du potentiel d'action. Les différentes isoformes de ces canaux (de Nav1.1 à Nav1.9 et NavX) sont codées par dix gènes distincts. Nav1.4 et Nav1.5 sont les principaux variants exprimés respectivement dans le muscle et le coeur. Plusieurs mutations ont été décrites dans les gènes qui codent pour ces deux canaux: SCN4A (pour Nav1.4) et SCNSA (pour Nav1.5). Elles sont impliquées dans des pathologies neuromusculaires telles que des paralysies ou myotonies (SCN4A) ou des arythmies cardiaques pouvant conduire à la mort subite cardiaque (SCNSA).Mon travail de thèse a consisté à étudier les maladies liées aux dysfonctionnements de ces canaux, aussi appelées canalopathies. J'ai ainsi analysé la fonction et la régulation des canaux sodiques dépendant du voltage dans le muscle squelettique et le coeur. A travers les deux premières études, j'ai ainsi pu examiner les conséquences de deux mutations affectant respectivement les canaux Nav1.4 et Nav1.5. Les canaux sauvages ou mutants ont été exprimés dans des cellules HEK293 afin de caractériser leurs propriétés biophysiques par la technique du patch clamp en configuration cellule entière. Nous avons pu déterminer que la mutation trouvée dans le gène SCN4A engendrait des modifications importantes de la fonction du canal musculaire. Ces altérations fournissent des indications nous permettant d'expliquer certains aspects de la myotonie observée chez les membres de la famille étudiée. Le patient présenté dans la deuxième étude était hétérozygote pour la mutation identifiée dans le gène SCNSA. La perte de fonction des canaux Nav1.5 ainsi engendrée, a été observée lors d'analyses à températures physiologiques. Elle représente l'un des éléments pouvant potentiellement expliquer le syndrome de Brugada du patient. La dernière étude a consisté à identifier une nouvelle protéine impliquée dans la régulation du canal sodique cardiaque. Nos expériences ont démontré que les trois derniers acides aminés de la partie C-terminale de Nav1.5 pouvaient interagir avec la protéine SAP97. Lorsque que l'expression de la SAP97 est réduite dans les cellules HEK293, cela induit une baisse importante du courant sodique. De même, les canaux tronqués de leurs trois derniers acides aminés génèrent un flux ionique réduit. Ces résultats préliminaires suggèrent que SAP97 est peut-être impliquée dans la régulation du canal Na,,1.5. Des expériences complémentaires permettront de déterminer si ces deux protéines interagissent directement ou si une protéine adaptatrice est nécessaire. De plus, nous avons préalablement montré que les canaux Nav1.5 étaient localisés au niveau de la membrane latérale des cardiomyocytes par le complexe multiprotéique de la dystrophine (DMC). Ceci suggère que les canaux sodiques peuvent être distribués dans un minimum de deux pools, l'un ciblé aux membranes latérales pax le DMC et l'autre dirigé vers les disques intercalaires par des protéines telles que SAP97.L'ensemble de ces études met en évidence que certaines maladies musculaires et cardiaques peuvent être la conséquence directe de mutations de canaux ioniques, mais que l'action de protéines auxiliaires peut aussi affecter leur fonction.

Low immunoglobulin levels in patients with cystic fibrosis: reduced inflammation or sign of common variable immunodeficiency syndrome?

Introduction: In children with cystic fibrosis (CF), low immunoglobulin (IgG) levels have been reported to be associated with significantly less severe lung disease. However, decreased IgG can be a sign for common variable immunodeficiency (CVID) and affect clinical outcome. The aim of this study was to analyze clinical and serological data of patients having low IgG levels in routine blood tests at annual assessment, particularly their antibody response to polysaccharide antigens. Method: Retrospective chart review of demographic data of CF patients followed at the pediatric CF clinic throughout 2009. Clinical parameters (genotype, pancreas sufficiency, FEV1), presence of Pseudomonas aeruginosa (PA) and number of exacerbations per year were correlated with immunoglobulin and vaccination antibodies levels (antibodies to pneumococcal serotypes 14, 19, 23, 1, 5 and 7F measured by enzyme-linked immune-sorbent assay). Results: 4 out of 60 patients (6.7%) had lower IgG-levels for age. Ages ranged from 1 year 8 months to 11 years, 2 boys, 2 girls. Three patients were delF508 homozygotes, one heterozygote composite delF508/G542X. All were pancreatic insufficient. FEV1 ranged from 74 to 108%. One patient never had colonization by PA, 2 had intermittent PA colonization and one was chronically infected. After conjugated vaccination all patients had protective antibodies against serotypes 14, 19, 23F. For serotypes not included in the vaccine, only one patient had protective titers for 1 out of 3 serotypes. None of the patients had received unconjugated pneumococcal vaccine. There was no significant clinical difference in FEV1, PA colonization or number of exacerbations according to IgG and vaccination antibody levels. Conclusion: Cystic Fibrosis patients with low immunoglobulin levels have normal antibody response to protein antigens. However, despite recurrent infections, there seems to be delayed or deficient antibody response to polysaccharide antigens. Prospective studies are needed to evaluate the development of polysaccharide antibody responses in CF-patients to monitor for CVID. With early detection of CF by newborn screening program, long term follow up could be started early in childhood.

Reduced left hemisphere dominance for multiple versus single anagram solutions and its modulation by individuals' schizotypy

Problem solving (including insight, divergent thinking) seems to rely on the right hemisphere (RH). These functions are difficult to assess behaviorally. We propose anagram resolution as a suitable paradigm. University students (n=32) performed three tachistoscopic lateralized visual half-field experiments (stimulus presentation 150ms). In Experiment 1, participants recalled four-letter strings. Subsequently, participants provided solutions for four-letter anagrams (one solution in Experiment 2; two solutions in Experiment 3). Additionally, participants completed a schizotypy questionnaire (O-LIFE). Results showed a right visual field advantage in Experiment 1 and 2, but no visual field advantage in Experiment 3. In Experiment 1, increasing positive schizotypy associated with a RH performance shift. Problem solving seems to require increasingly the RH when facing several rather than one solution. This result supports previous studies on the RH's role in remote associative, metaphor and discourse processing. The more complex language requirements, the less personality traits seem to matter.

PDZ domain-binding motif regulates cardiomyocyte compartment-specific NaV1.5 channel expression and function.

BACKGROUND: Sodium channel NaV1.5 underlies cardiac excitability and conduction. The last 3 residues of NaV1.5 (Ser-Ile-Val) constitute a PDZ domain-binding motif that interacts with PDZ proteins such as syntrophins and SAP97 at different locations within the cardiomyocyte, thus defining distinct pools of NaV1.5 multiprotein complexes. Here, we explored the in vivo and clinical impact of this motif through characterization of mutant mice and genetic screening of patients. METHODS AND RESULTS: To investigate in vivo the regulatory role of this motif, we generated knock-in mice lacking the SIV domain (ΔSIV). ΔSIV mice displayed reduced NaV1.5 expression and sodium current (INa), specifically at the lateral myocyte membrane, whereas NaV1.5 expression and INa at the intercalated disks were unaffected. Optical mapping of ΔSIV hearts revealed that ventricular conduction velocity was preferentially decreased in the transversal direction to myocardial fiber orientation, leading to increased anisotropy of ventricular conduction. Internalization of wild-type and ΔSIV channels was unchanged in HEK293 cells. However, the proteasome inhibitor MG132 rescued ΔSIV INa, suggesting that the SIV motif is important for regulation of NaV1.5 degradation. A missense mutation within the SIV motif (p.V2016M) was identified in a patient with Brugada syndrome. The mutation decreased NaV1.5 cell surface expression and INa when expressed in HEK293 cells. CONCLUSIONS: Our results demonstrate the in vivo significance of the PDZ domain-binding motif in the correct expression of NaV1.5 at the lateral cardiomyocyte membrane and underline the functional role of lateral NaV1.5 in ventricular conduction. Furthermore, we reveal a clinical relevance of the SIV motif in cardiac disease.

Reduced genetic diversity, increased isolation and multiple introductions of invasive giant hogweed in the western Swiss Alps.

Abstract The giant hogweed (Heracleum mantegazzianum) has successfully invaded 19 European countries as well as parts of North America. It has become a problematic species due to its ability to displace native flora and to cause public health hazards. Applying population genetics to species invasion can help reconstruct invasion history and may promote more efficient management practice. We thus analysed levels of genetic variation and population genetic structure of H. mantegazzianum in an invaded area of the western Swiss Alps as well as in its native range (the Caucasus), using eight nuclear microsatellite loci together with plastid DNA markers and sequences. On both nuclear and plastid genomes, native populations exhibited significantly higher levels of genetic diversity compared to invasive populations, confirming an important founder event during the invasion process. Invasive populations were also significantly more differentiated than native populations. Bayesian clustering analysis identified five clusters in the native range that corresponded to geographically and ecologically separated groups. In the invaded range, 10 clusters occurred. Unlike native populations, invasive clusters were characterized by a mosaic pattern in the landscape, possibly caused by anthropogenic dispersal of the species via roads and direct collection for ornamental purposes. Lastly, our analyses revealed four main divergent groups in the western Swiss Alps, likely as a consequence of multiple independent establishments of H. mantegazzianum.

Aminoterminal amphipathic α-helix AH1 of hepatitis C virus nonstructural protein 4B possesses a dual role in RNA replication and virus production.

Nonstructural protein 4B (NS4B) is a key organizer of hepatitis C virus (HCV) replication complex formation. In concert with other nonstructural proteins, it induces a specific membrane rearrangement, designated as membranous web, which serves as a scaffold for the HCV replicase. The N-terminal part of NS4B comprises a predicted and a structurally resolved amphipathic α-helix, designated as AH1 and AH2, respectively. Here, we report a detailed structure-function analysis of NS4B AH1. Circular dichroism and nuclear magnetic resonance structural analyses revealed that AH1 folds into an amphipathic α-helix extending from NS4B amino acid 4 to 32, with positively charged residues flanking the helix. These residues are conserved among hepaciviruses. Mutagenesis and selection of pseudorevertants revealed an important role of these residues in RNA replication by affecting the biogenesis of double-membrane vesicles making up the membranous web. Moreover, alanine substitution of conserved acidic residues on the hydrophilic side of the helix reduced infectivity without significantly affecting RNA replication, indicating that AH1 is also involved in virus production. Selective membrane permeabilization and immunofluorescence microscopy analyses of a functional replicon harboring an epitope tag between NS4B AH1 and AH2 revealed a dual membrane topology of the N-terminal part of NS4B during HCV RNA replication. Luminal translocation was unaffected by the mutations introduced into AH1, but was abrogated by mutations introduced into AH2. In conclusion, our study reports the three-dimensional structure of AH1 from HCV NS4B, and highlights the importance of positively charged amino acid residues flanking this amphipathic α-helix in membranous web formation and RNA replication. In addition, we demonstrate that AH1 possesses a dual role in RNA replication and virus production, potentially governed by different topologies of the N-terminal part of NS4B.

Reduced cardiorespiratory fitness, low physical activity and an urban environment are independently associated with increased cardiovascular risk in children.

AIMS/HYPOTHESIS: To assist in the development of preventive strategies, we studied whether the neighbourhood environment or modifiable behavioural parameters, including cardiorespiratory fitness (CRF) and physical activity (PA), are independently associated with obesity and metabolic risk markers in children. METHODS: We carried out a cross-sectional analysis of 502 randomly selected first and fifth grade urban and rural Swiss schoolchildren with regard to CRF, PA and the neighbourhood (rural vs urban) environment. Outcome measures included BMI, sum of four skinfold thicknesses, homeostasis model assessment of insulin resistance (HOMA-IR) and a standardised clustered metabolic risk score. RESULTS: CRF and PA (especially total PA, but also the time spent engaged in light and in moderate and vigorous intensity PA) were inversely associated with measures of obesity, HOMA-IR and the metabolic risk score, independently of each other, and of sociodemographic and nutritional parameters, media use, sleep duration, BMI and the neighbourhood environment (all p < 0.05). Children living in a rural environment were more physically active and had higher CRF values and reduced HOMA-IR and metabolic risk scores compared with children living in an urban environment (all p < 0.05). These differences in cardiovascular risk factors persisted after adjustment for CRF, total PA and BMI. CONCLUSIONS/INTERPRETATION: Reduced CRF, low PA and an urban environment are independently associated with an increase in metabolic risk markers in children.

Recombination is suppressed and variability reduced in a nascent Y chromosome.

Several hypotheses have been elaborated to account for the evolutionary decay commonly observed in full-fledged Y chromosomes. Enhanced drift, background selection and selective sweeps, which are expected to result from reduced recombination, may all share responsibilities in the initial decay of proto-Y chromosomes, but little empirical information has been gathered so far. Here we take advantage of three markers that amplify on both of the morphologically undifferentiated sex chromosomes of the European tree frog (Hyla arborea) to show that recombination is suppressed in males (the heterogametic sex) but not in females. Accordingly, genetic variability is reduced on the Y, but in a way that can be accounted for by merely the number of chromosome copies per breeding pair, without the need to invoke background selection or selective sweeps.

Identification of promising antigenic components in latent fingermark residues

An analysis of latent fingermark residues by Sodium-Dodecyl-Sulfate PolyAcrylamide Gel Electrophoresis (SDS-PAGE) followed by silver staining allowed the detection of different proteins, from which two major bands, corresponding to proteins of 56 and 64 kDa molecular weight, could be identified. Two other bands, corresponding to proteins of 52 and 48 kDa were also visualizable along with some other weaker bands of lower molecular weights. In order to identify these proteins, three antibodies directed against human proteins were tested on western blots of fingermarks residues: anti-keratin 1 and 10 (K1/10), anti-cathepsin-D (Cat.D) and anti-dermcidin (Derm.). The corresponding antigens are known to be present in the stratum corneum of desquamating stratified epithelium (K1/10, Cat.D) and/or in eccrine sweat (Cat.D, Derm.). The two major bands were identified as consistent with keratin 1 and 10. The pro-form and the active form of the cathepsin-D have also been identified from two other bands. Dermcidin could not be detected in the western blot. In addition, these antibodies have been tested on latent fingermarks left on polyvinylidene fluoride (PVDF) membrane, as well as on whitened and non-whitened paper. The detection of fingermarks was successful with all three antibodies.

Major mite allergen Der f 1 concentration is reduced in buildings with improved energy performance.

BACKGROUND: Environmental conditions play a crucial role in mite growth, and optimal environmental control is key in the prevention of airway inflammation in chronic allergic rhinoconjunctivitis or asthma. OBJECTIVE: To evaluate the relationship between building energy performance and indoor mite allergen concentration in a cross-sectional study. METHODS: Major allergen concentration (Der f 1, Der p 1, mite group 2, Fel d 1 and Bla g 2) was determined by quantitative dot blot analysis from mattress and carpet dust samples in five buildings designed for low energy use (LEB) and in six control buildings (CB). Inhabitants had received 4 weeks prior to mite measurement a personal validated questionnaire related to the perceived state of health and comfort of living. RESULTS: Cumulative mite allergen concentration (with Der f 1 as the major contributor) was significantly lower in LEB as compared with CB both in mattresses and in carpets. In contrast, the two categories of buildings did not differ in Bla g 2 and Fel d 1 concentration, in the amount of dust and airborne mould collected. Whereas temperature was higher in LEB, relative humidity was significantly lower than in CB. Perceived overall comfort was better in LEB. CONCLUSIONS: Major mite allergen Der f 1 preferentially accumulates in buildings not specifically designed for low energy use, reaching levels at risk for sensitization. We hypothesize that controlled mechanical ventilation present in all audited LEB may favour lower air humidity and hence lower mite growth and allergen concentration, while preserving optimal perceived comfort.

Energy deficit and length of hospital stay can be reduced by a two-step quality improvement of nutrition therapy: the intensive care unit dietitian can make the difference.

OBJECTIVE: Critically ill patients are at high risk of malnutrition. Insufficient nutritional support still remains a widespread problem despite guidelines. The aim of this study was to measure the clinical impact of a two-step interdisciplinary quality nutrition program. DESIGN: Prospective interventional study over three periods (A, baseline; B and C, intervention periods). SETTING: Mixed intensive care unit within a university hospital. PATIENTS: Five hundred seventy-two patients (age 59 ± 17 yrs) requiring >72 hrs of intensive care unit treatment. INTERVENTION: Two-step quality program: 1) bottom-up implementation of feeding guideline; and 2) additional presence of an intensive care unit dietitian. The nutrition protocol was based on the European guidelines. MEASUREMENTS AND MAIN RESULTS: Anthropometric data, intensive care unit severity scores, energy delivery, and cumulated energy balance (daily, day 7, and discharge), feeding route (enteral, parenteral, combined, none-oral), length of intensive care unit and hospital stay, and mortality were collected. Altogether 5800 intensive care unit days were analyzed. Patients in period A were healthier with lower Simplified Acute Physiologic Scale and proportion of "rapidly fatal" McCabe scores. Energy delivery and balance increased gradually: impact was particularly marked on cumulated energy deficit on day 7 which improved from -5870 kcal to -3950 kcal (p < .001). Feeding technique changed significantly with progressive increase of days with nutrition therapy (A: 59% days, B: 69%, C: 71%, p < .001), use of enteral nutrition increased from A to B (stable in C), and days on combined and parenteral nutrition increased progressively. Oral energy intakes were low (mean: 385 kcal*day, 6 kcal*kg*day ). Hospital mortality increased with severity of condition in periods B and C. CONCLUSION: A bottom-up protocol improved nutritional support. The presence of the intensive care unit dietitian provided significant additional progression, which were related to early introduction and route of feeding, and which achieved overall better early energy balance.

Characterization of Fas (Apo-1, CD95)-Fas ligand interaction.

The death-inducing receptor Fas is activated when cross-linked by the type II membrane protein Fas ligand (FasL). When human soluble FasL (sFasL, containing the extracellular portion) was expressed in human embryo kidney 293 cells, the three N-linked glycans of each FasL monomer were found to be essential for efficient secretion. Based on the structure of the closely related lymphotoxin alpha-tumor necrosis factor receptor I complex, a molecular model of the FasL homotrimer bound to three Fas molecules was generated using knowledge-based protein modeling methods. Point mutations of amino acid residues predicted to affect the receptor-ligand interaction were introduced at three sites. The F275L mutant, mimicking the loss of function murine gld mutation, exhibited a high propensity for aggregation and was unable to bind to Fas. Mutants P206R, P206D, and P206F displayed reduced cytotoxicity toward Fas-positive cells with a concomitant decrease in the binding affinity for the recombinant Fas-immunoglobulin Fc fusion proteins. Although the cytotoxic activity of mutant Y218D was unaltered, mutant Y218R was inactive, correlating with the prediction that Tyr-218 of FasL interacts with a cluster of three basic amino acid side chains of Fas. Interestingly, mutant Y218F could induce apoptosis in murine, but not human cells.

Contribution of isotope ratio mass spectrometry to the investigation of improvised explosives: isotopic study of black powders ans ammonium nitrates

The establishment of legislative rules about explosives in the eighties has reduced the illicit use of military and civilian explosives. However, bomb-makers have rapidly taken advantage of substances easily accessible and intended for licit uses to produce their own explosives. This change in strategy has given rise to an increase of improvised explosive charges, which is moreover assisted by the ease of implementation of the recipes, widely available through open sources. While the nature of the explosive charges has evolved, instrumental methods currently used in routine, although more sensitive than before, have a limited power of discrimination and allow mostly the determination of the chemical nature of the substance. Isotope ratio mass spectrometry (IRMS) has been applied to a wide range of forensic materials. Conclusions drawn from the majority of the studies stress its high power of discrimination. Preliminary studies conducted so far on the isotopic analysis of intact explosives (pre-blast) have shown that samples with the same chemical composition and coming from different sources could be differentiated. The measurement of stable isotope ratios appears therefore as a new and remarkable analytical tool for the discrimination or the identification of a substance with a definite source. However, much research is still needed to assess the validity of the results in order to use them either in an operational prospect or in court. Through the isotopic study of black powders and ammonium nitrates, this research aims at evaluating the contribution of isotope ratio mass spectrometry to the investigation of explosives, both from a pre-blast and from a post-blast approach. More specifically, the goal of the research is to provide additional elements necessary to a valid interpretation of the results, when used in explosives investigation. This work includes a fundamental study on the variability of the isotopic profile of black powder and ammonium nitrate in both space and time. On one hand, the inter-variability between manufacturers and, particularly, the intra-variability within a manufacturer has been studied. On the other hand, the stability of the isotopic profile over time has been evaluated through the aging of these substances exposed to different environmental conditions. The second part of this project considers the applicability of this high-precision technology to traces and residues of explosives, taking account of the characteristics specific to the field, including their sampling, a probable isotopic fractionation during the explosion, and the interferences with the matrix of the site.

Adaptive changes in a radial maze task: Efficient selection of baited arms with reduced foraging in senescent hooded rats

Qualitative differences in strategy selection during foraging in a partially baited maze were assessed in young and old rats. The baited and non-baited arms were at a fixed position in space and marked by a specific olfactory cue. The senescent rats did more re-entries during the first four-trial block but were more rapid than the young rats in selecting the reinforced arms during the first visits. Dissociation between the olfactory spatial cue reference by rotating the maze revealed that only few old subjects relied on olfactory cues to select the baited arms and the remainder relied mainly on the visuo-spatial cues.