Vichy Thermal Spring Water (VTSW), a cosmetic ingredient of potential interest in the frame of skin ageing exposome: an in vitro study.

OBJECTIVE: To study the effects of the very high minerality Vichy Thermal Spring Water (VTSW) on human keratinocytes grown in vitro. METHODS: The effect of VTSW was monitored by full genome transcriptomic technology and immunofluorescence microscopy. RESULTS: In the presence of 50% VTSW, the expression of a number of skin homoeostasis-related genes is increased, specifically with respect to dermal-epidermal junction, epidermal cohesion and communication, keratinocyte proliferation-differentiation balance, antioxidant mechanisms and DNA repair. CONCLUSION: This work suggests that VTSW could be considered as an ingredient of potential interest to address some of the deleterious effects of skin ageing exposome.

Morphological and molecular characterization of actinic lentigos reveals alterations of the dermal extracellular matrix.

BACKGROUND: Actinic lentigos (AL) are benign hyperpigmented skin lesions associated with photoageing. Despite their high prevalence, biological mechanisms driving their formation remain unclear. OBJECTIVES: To provide new insights about the physiopathology of AL through a comprehensive description of their histological and molecular features. METHODS: Quantitative analysis of dermoscopic images was used to select AL containing elongated patterns, predicted to display a highly deformed dermal-epidermal junction (DEJ), on the back of the hands of 15 Caucasian women. Biopsies from lesional and adjacent nonlesional (NL) areas were processed for histological analysis or gene expression profiling. RESULTS: Histological staining confirmed a drastic deformation of the DEJ in AL, with deep epidermal invaginations into the dermis. Although the melanin content was significantly higher in AL compared with NL epidermis, the distribution of melanocytes along the DEJ was unchanged. Transcriptomic analysis revealed a signature of 529 genes differently expressed in AL vs. NL skin. Alteration of epidermal homeostasis was confirmed by the dysregulation of keratinocyte proliferation and differentiation markers. Surprisingly, canonical genes involved in melanogenesis were not significantly modulated in AL. A striking finding was the overexpression of a large group of genes involved in dermal extracellular matrix organization and remodelling. Dermal alterations were confirmed by immunolabellings on AL and NL sections. CONCLUSIONS: Drastic disorganization of the cutaneous structure in AL is accompanied by a specific molecular signature revealing alterations in both epidermal and dermal compartments. In particular, our results suggest that local modifications of the dermal extracellular matrix might contribute to hyperpigmentation in AL.

2-Mercaptonicotinoyl glycine prevents UV-induced skin darkening and delayed tanning in healthy subjects: A randomized controlled clinical study.

BACKGROUND: Chronic nonextreme sun exposure induces two mechanisms of skin pigmentation, causing immediate darkening and delayed tanning. A new molecule, 2-mercaptonicotinoyl glycine (2-MNG), has been shown in vitro to inhibit both immediate darkening and new melanin synthesis via covalent conjugation of the thiol group of 2-MNG to melanin precursors. OBJECTIVE: To evaluate 2-MNG in preventing both mechanisms in vivo. METHODS: In a randomized, intra-individual and controlled study, 33 subjects with melanin-rich skin were exposed to UV daylight on designated areas on the back and treated with a cosmetic formula containing 0.5% or 1% 2-MNG alone or 0.5% 2-MNG in association with lipohydroxy acid (LHA, 0.3%) plus Mexoryl-SX (MSX, 1.5%). The respective vehicles were used as controls and 4-n-butyl-resorcinol (4-n-BR, 2.5%) as a positive reference. RESULTS: 2-MNG alone significantly reduced immediate darkening and inhibited new melanin production when compared with vehicle, with higher performance at 1% than at 0.5%. 2-MNG at 0.5% in association with LHA and MSX showed significantly higher performance than 2-MNG 0.5% alone. 2-MNG at 0.5% and 1% showed significantly better performance than 4-n-BR. CONCLUSIONS: 2-MNG inhibited both UV-induced skin pigmentation mechanisms in vivo. The association of 2-MNG with LHA plus MSX showed the highest efficacy on melanin-rich skin with pigmentation induced by UV exposure.

Surveillance of leishmaniases in France, 1999 to 2012.

Leishmaniasis is endemic in the south of France, where autochthonous disease is caused by Leishmania infantum, and affects both humans and dogs. The prevalence of canine leishmaniasis is between 3 and 66% depending on the region and the methods used. Human leishmaniases are also imported into France, mainly from French Guiana and North Africa. The surveillance of autochthonous and imported human leishmaniases is based on passive notification to the National Reference Centre for Leishmaniases (NRCL) created in 1998. Between 1999 and 2012, 317 autochthonous and 1,154 imported cases were notified to the NRCL. The average number of autochthonous cases notified per year was 22.6, mainly cases of visceral leishmaniasis (84.5%). All cases were infected in the south of France. Leishmaniasis incidence is 0.22 per 100,000 inhabitants in the endemic area. Imported cases were more frequent (annual mean of 82.4 cases) and consisted predominantly in cutaneous leishmaniasis (CL) cases (91%), essentially L. major CL imported from Maghreb and Sub-Saharan Africa, and L. guyanensis CL from French Guiana. This national notification system allowed a better understanding of the incidence and distribution of the disease; it is also useful to assess the temporal-spatial evolution of the disease in France, which appears relatively stable.

Crystal-Phase Control of Ternary Metal Oxides by Solid-State Synthesis with Nanocrystals.

Ternary metal oxides are materials of interest for many applications, from batteries to catalysis. Their crystalline structure and composition determine their properties, and thus it is important to achieve control over these features. Here, we demonstrate that solid-state chemistry among nanocrystalline precursors is a promising approach for their synthesis. We show that the crystalline phase of nanocrystal precursors direct that of the ternary reaction product. The combination of X-ray and electron microscopy techniques reveals that the spinel and rhombohedral phases of copper iron oxide are obtained by reacting copper nanocrystals with spinel γ-Fe2O3 and corundum α-Fe2O3 nanocrystals, respectively. Considering the available library of nanocrystals with tunable crystal phases, this discovery opens up an alternative pathway toward the synthesis of a wide variety of ternary and quaternary materials, including those with metastable phases.

'Active chronic visceral leishmaniasis' in HIV-1-infected patients demonstrated by biological and clinical long-term follow-up of 10 patients.

OBJECTIVES: The aim of the study was to describe a new evolutionary form of visceral leishmaniasis observed in immunocompromised patients. METHODS: We carried out long-term clinical and biological follow-up of 10 HIV-1/Leishmania-coinfected patients presenting numerous secondary visceral leishmaniasis episodes despite treatment, with the follow-up time ranging from 0.5 to 10 years. RESULTS: Analysis of polymerase chain reaction (PCR) and blood culture results demonstrated continuous multiplication and circulation of parasites despite treatment, both during asymptomatic periods and during secondary visceral leishmaniasis episodes. This condition may be termed 'chronic' because of the presence of relapses over a period of several years and 'active' because of the continuous blood circulation of the parasite. CONCLUSION: We wish to define 'active chronic visceral leishmaniasis' as a novel nosological entity observed in HIV-1/Leishmania-coinfected patients.

(Not so) Great Expectations: Listening to Foreign-Accented Speech Reduces the Brain's Anticipatory Processes.

This study examines the effect of foreign-accented speech on the predictive ability of our brain. Listeners actively anticipate upcoming linguistic information in the speech signal so as to facilitate and reduce processing load. However, it is unclear whether or not listeners also do this when they are exposed to speech from non-native speakers. In the present study, we exposed native Dutch listeners to sentences produced by native and non-native speakers while measuring their brain activity using electroencephalography. We found that listeners' brain activity differed depending on whether they listened to native or non-native speech. However, participants' overall performance as measured by word recall rate was unaffected. We discussed the results in relation to previous findings as well as the automaticity of anticipation.

Multicenter comparative evaluation of five commercial methods for toxoplasma DNA extraction from amniotic fluid.

Over the past few years, a number of new nucleic acid extraction methods and extraction platforms using chemistry combined with magnetic or silica particles have been developed, in combination with instruments to facilitate the extraction procedure. The objective of the present study was to investigate the suitability of these automated methods for the isolation of Toxoplasma gondii DNA from amniotic fluid (AF). Therefore, three automated procedures were compared to two commercialized manual extraction methods. The MagNA Pure Compact (Roche), BioRobot EZ1 (Qiagen), and easyMAG (bioMérieux) automated procedures were compared to two manual DNA extraction kits, the QIAamp DNA minikit (Qiagen) and the High Pure PCR template preparation kit (Roche). Evaluation was carried out with two specific Toxoplasma PCRs (targeting the 529-bp repeat element), inhibitor search PCRs, and human beta-globin PCRs. The samples each consisted of 4 ml of AF with or without a calibrated Toxoplasma gondii RH strain suspension (0, 1, 2.5, 5, and 25 tachyzoites/ml). All PCR assays were laboratory-developed real-time PCR assays, using either TaqMan or fluorescent resonance energy transfer probes. A total of 1,178 PCRs were performed, including 978 Toxoplasma PCRs. The automated and manual methods were similar in sensitivity for DNA extraction from T. gondii at the highest concentration (25 Toxoplasma gondii cells/ml). However, our results showed that the DNA extraction procedures led to variable efficacy in isolating low concentrations of tachyzoites in AF samples (<5 Toxoplasma gondii cells/ml), a difference that might have repercussions since low parasite concentrations in AF exist and can lead to congenital toxoplasmosis.

Effects of nonpathogenic gram-negative bacterium Vitreoscilla filiformis lysate on atopic dermatitis: a prospective, randomized, double-blind, placebo-controlled clinical study.

BACKGROUND: Atopic dermatitis (AD) is associated with elevated IgE levels and Th2 responses. The oral administration of nonpathogenic bacteria such as probiotics may improve the course of atopic diseases. It is believed that nonpathogenic bacteria prevent the development of allergic diseases by modulating intestinal immune responses. However, the effects of oral probiotics on AD could not be reproduced in all studies and the direct immunomodulation of the skin-associated immune response by nonpathogenic bacteria has not yet been investigated. OBJECTIVES: We performed a prospective, double-blind, placebo-controlled clinical study with a cream containing a 5% lysate of the nonpathogenic bacteria Vitreoscilla filiformis. PATIENTS AND METHODS: Seventy-five volunteers with AD (6-70 years of age) were randomized to receive either V. filiformis cream 5% or vehicle cream daily for 30 days. Efficacy was evaluated by the SCORe of Atopic Dermatitis (SCORAD), transepidermal water loss (TEWL), assessment of microflora, and the patient's assessment of itch and loss of sleep. RESULTS: Compared with placebo, V. filiformis lysate significantly decreased SCORAD levels (P=0.0044) and pruritus (P=0.0171). Active cream significantly decreased loss of sleep from day 0 to day 29 (P=0.0074). Qualitative and quantitative assessment of cutaneous microbial colonization revealed that V. filiformis lysate reduced Staphylococcus aureus colonization of the skin. The skin barrier as determined by TEWL also improved significantly with the cream alone. CONCLUSIONS: V. filiformis lysate significantly improved AD. This may be in part due to reduction of S. aureus, but seems to relate in most parts to a direct immunomodulatory effect on skin-associated immune responses.

Pediatric angiostrongyliasis.

Angiostrongyliasis, the leading cause worldwide of eosinophilic meningitis, is an emergent disease due to Angiostrongylus cantonensis larvae, transmitted accidentally to humans. Contamination of children usually occurs by direct contact with an infected mollusk. Eosinophilic meningoencephalitis is the major clinical feature of this parasitic infection in humans. It is usually benign for adults, but more severe for children. Clinical symptoms usually combine fever, meningitis, and neurological signs (somnolence, moaning, hypotonia, convulsions, and increased intracranial pressure). Presumptive diagnosis of human angiostrongyliasis is based on epidemiologic characteristics, clinical symptoms, medical history, and laboratory findings, in particular, hypereosinophilia in blood and cerebrospinal fluid. Treatment is based on corticosteroids associated with anthelmintics. This work reviews the diagnosis and treatment of this life-threatening (especially in children) parasitic disease and the need for preventive action.

Evaluation of five automated and one manual method for Toxoplasma and human DNA extraction from artificially spiked amniotic fluid.

OBJECTIVES: Molecular detection of Toxoplasma gondii plays a crucial role in the prenatal and neonatal diagnosis of congenital toxoplasmosis (CT). Sensitivity of this diagnosis is partly related to the efficiency of parasite DNA extraction and amplification. DNA extraction methods with automated platforms have been developed. Therefore, it is essential to evaluate them in combination with adequate PCR amplification assays. METHODS: In this multisite study, we investigated the suitability of two recent automated procedures for the isolation of Toxoplasma DNA from amniotic fluid (AF) (Magtration system 12GC, PSS and Freedom EVO VacS, Tecan), compared with three other automated procedures (MagNAPure Compact, Roche, BioRobot EZ1, Qiagen and modified NucliSens easyMAG, bioMérieux) and with the manual DNA extraction QIAamp DNA Mini kit (Qiagen). Two Toxoplasma PCR assays targeting the '529-bp' repeat DNA element were used, based upon dual hybridization (FRET) or hydrolysis (TaqMan) probes. A total of 1296 PCRs were performed including 972 Toxoplasma PCRs. RESULTS: We showed variable efficacy (4.2%-100% positive results) among the DNA extraction procedures in isolating up to five T. gondii cells/mL in AF samples. Moreover, for a given DNA extraction method, variable results were obtained among the two Toxoplasma PCR assays for detecting up to five T. gondii cells/mL: when using TaqMan PCR, all the automated systems yielded more than 60% positive results. Nevertheless, when testing the DNA extracts in triplicate, four out of six extraction methods allowed a satisfactory detection of low amounts of T. gondii DNA (≥33% of positive results) independently of the PCR assay used. CONCLUSIONS: Despite the influence of the subsequent PCR method used, this study should help microbiologists in the choice of DNA extraction methods for the detection of T. gondii in amniotic fluid. The extraction method should be checked as adequate for the PCR assay used.

Three years of multi-laboratory external quality control for the molecular detection of Toxoplasma gondii in amniotic fluid in France.

Between 2002 and 2004, panels of amniotic fluid containing varying concentrations of Toxoplasma gondii were sent to up to 23 laboratories in France for molecular (PCR-based) detection as part of a national quality assurance initiative in the molecular prenatal diagnosis of toxoplasmosis. Participants were free to enroll and no fees were required. The general level of sensitivity was high, and the rate of false-positive reactions was relatively low. Considerable diversity among PCR methods and primers was revealed. This external quality assurance scheme provided the opportunity to improve laboratory practice and performance, and to increase communication among laboratories involved in making this diagnosis.

The positive benefit of Lactobacillus paracasei NCC2461 ST11 in healthy volunteers with moderate to severe dandruff.

Dandruff is a common persistent, relapsing inflammatory condition affecting the scalp. An imbalanced proportion of the major bacterial and fungal populations colonising the scalp, a skin barrier dysfunction, and hyperseborrhoea are three main etiological factors of dandruff. The efficacy of Lactobacillus paracasei NCC 2461 ST11 (ST11) to manage dandruff and to restore a balanced scalp microbiome was assessed. Sixty healthy male volunteers aged 18 to 60 years with moderate to severe dandruff consumed on a daily basis a sachet containing ST11 (1×109 cfu) or a placebo for 56 days. Clinical efficacy (free and adherent dandruff, erythema, scalp seborrhoea, global clinical score), subject self-assessments, safety reporting as well as scalp microbiota assessments were performed every two weeks (day 1, 15, 29, 43, 57 and 64/follow-up). Free and adherent dandruff, erythema and the global clinical score improved significantly (all P<0.05) over time in the ST11 group and as compared to the placebo when day 57 was compared to day 1. Self-assessments paralleled these findings. ST11 enhanced restoring the scalp microbiota after 56 days of supplementation when compared to the placebo. No adverse events were reported. Regular intake of ST11 over 56 days is safe and reduces significantly the severity of signs and symptoms of moderate to severe dandruff. Its efficacy is potentially due to its positive impact on the skin barrier and skin immune system.

Effect of large targeted deletions on the mitotic stability of an extra chromosome mediating drug resistance in Leishmania.

A mitotically stable linear extra chromosome obtained in a Leishmania donovani strain rendered mycophenolic acid-resistant has been physically mapped. This 290-kb chromosome has an inverted duplicated structure around a central inversion region, and is derived from a conservative amplification event of a approximately 140-kb subtelomeric end of chromosome 19. Large-sized targeted deletions of the central region were performed through homologous recombination using three specific transfection vectors. The size of the extra chromosome was thus successfully reduced from 290 to 260, 200 and 120 kb respectively. The mitotic stability of these chromosomes was then analysed in drug-free cultures over >140 days. Results differed according to the deletion created. By contrast with the smallest deletion the two largest deletions altered mitotic stability, leading to progressive loss of the size-reduced chromosomes with similar kinetics in both mutants. The 30-kb region common to both deletions may therefore be considered as involved in mitotic stability. A 44-kb contig covering this region could be assembled and sequenced. The analysis of this sequence did not reveal any sequence elements typical of centromeric DNA. By contrast, its enrichment in homopolymer tracts suggests that this region might contain an origin of replication.

Induction of the skin endogenous protective mitochondrial MnSOD by Vitreoscilla filiformis extract.

Vitreoscilla filiformis (Vf), a filamentous bacteria living in fresh water is thought to contribute to the observed beneficial effects of Spa water on skin. An active fraction obtained from a Vf biomass was evaluated for its ability to modulate mRNA expression in cultured skin cells. cDNA array analysis was conducted first using a customized membrane including 1176 selected and fully identified genes involved in skin physiology and homeostasis then the newly developed full genome U133 plus 2.0 GeneChip from Affymetrix. The mitochondrial protective manganese superoxide dismutase (MnSOD/SOD-2) was identified as a preferentially induced mRNA target in both normal human dermal fibroblasts and keratinocytes. Induction at the transcriptional level in both cell types was confirmed using quantitative real time/polymerase chain reaction and a kinetic analysis revealed a maximal increase in mRNA expression 20 h after stimulation with Vf extract (Vfe). Using immunofluorescent (fluorescent cell sorter) analysis, an induction of MnSOD protein in both normal human dermal skin fibroblasts (x1.6; P < 0.01) and epidermal keratinocytes (x1.4; P < 0.01) was confirmed. As MnSOD is a major inducible free-radical scavenger in skin, these results suggest that the Vfe could induce skin cells to produce their own endogenous protective defences in vivo against both exogenous environmental stressors such as UV irradiation or microflora as well as to combat endogenous sources of deleterious free radicals involved in skin ageing. Finally, in order to confirm the in vivo potential of this original extract in human, we evaluated its protective activity vs. placebo on the generation of sunburn cells in epidermis under UVB stress. As expected from in vitro profiling, Vfe was indeed found to significantly inhibit the appearance of sunburn cells in UVB-exposed areas, a signature of skin alteration which has been suggested to be linked to a defect in MnSOD protective activity. Altogether, those data suggest that the combination of a suitable protective UV filter together with this bioactive Vfe might improve skin protection through complementary pathways.

Protective effects of taurine on human hair follicle grown in vitro.

Taurine is a naturally occurring beta-amino acid produced by methionine and cysteine metabolism. It is involved in a variety of physiological functions, including immunomodulatory and antifibrotic. Taking advantage of the ability of human hair follicle grown in vitro to recapitulate most of the characteristic features of normal hair follicle in vivo, we studied (i) taurine uptake by isolated human hair follicles; (ii) its effects on hair growth and survival rate; and (iii) its protective potential against transforming growth factor (TGF)-beta1, an inhibitor of in vitro hair growth and a master switch of fibrotic program. We showed that taurine was taken up by the connective tissue sheath, proximal outer root sheath and hair bulb, promoted hair survival in vitro and prevented TGF-beta1-induced deleterious effects on hair follicle.

Skin ageing: a comparison between Chinese and European populations. A pilot study.

BACKGROUND: Although limited data are available, it is commonly considered that Europeans and Asians have different skin ageing features. OBJECTIVES: The present studies have been carried out to evaluate the influence of age and sun-exposure on the main clinical signs of Asian skin ageing. METHODS: One hundred and sixty Chinese and 160 French age-matched women (age range: 20-60 years old) were clinically examined and scored by the same dermatologist. Facial wrinkles (crow's-feet, glabella and perioral wrinkles) and pigmented spots (on face and hands) were assessed in situ and standardized photographs of the face were taken. Lifelong sun-exposure was estimated from answers to a questionnaire. Comparisons were made between 10-year age groups. RESULTS: Results show that, for each facial skin area, wrinkle onset is delayed by about 10 years in Chinese women as compared to French women. Facial wrinkling rate over the years is linear in French women and not linear in Chinese women who appear to experience a fast ageing process between age 40 and 50. Pigmented spot intensity is a much more important ageing sign in Chinese women (severe for 30% of women over 40) than in French women (severe for less than 8% of women, irrespective of age). CONCLUSION: These first results underline that main skin ageing features (wrinkles, spots) progress differently in the Chinese and French women we have studied. They require to be confirmed on broad multicentre studies involving larger cohorts.

Usefulness of PCR in the diagnosis of cutaneous leishmaniasis in Tunisia.

We assessed the efficiency of a PCR method in establishing the diagnosis of cutaneous leishmaniasis (CL) in Tunisian patients. Four hundred and thirty specimens collected passively from patients with cutaneous ulcers suggestive of leishmaniasis attending health centres for diagnosis were included in the study. Dermal scrapings were analysed both by parasitological (examination of Giemsa-stained smears and in vitro cultivation) methods and by a genus-specific PCR detecting a fragment of the 18S rRNA gene. Microscopy revealed amastigotes in 245 samples (57.0%) and in vitro cultivation gave positive results in 88 cases (20.5%), whereas PCR detected Leishmania in 301 samples (70%). The sensitivities inferred from our results were 99.3%, 80.8% and 29% for PCR, microscopic examination and in vitro cultivation, respectively. The different forms of CL in this country are caused by three species of Leishmania and are treated with the same protocol. Of 303 well-documented cases in our study, 99% were probably caused by Leishmania major and 1% by Leishmania infantum. The lack of species-specific diagnosis is not known to affect treatment or prognosis in Tunisia. These data support the incorporation of PCR into diagnostic strategies for CL, particularly in Tunisia.

Molecular karyotype analysis in Leishmania.

The advent of pulsed field electrophoresis has allowed a direct approach to the karyotype of Leishmania. The molecular karyotype thus obtained is a stable characteristic of a given strain, although minor modifications may occur during in vitro maintenance. Between 20 and 28 chromosomal bands can be resolved depending on the strain, ranging in size from approximately 250 to 2600 kb. The technique has revealed a striking degree of polymorphism in the size and number of the chromosomal bands between different strains, and this seems independent of the category (species, zymodeme, population) to which the strains belong. It appears that only certain strains originating from the same geographic area may share extensive similarities. This polymorphism can largely be accounted for by chromosome size variations, which can involve up to 25% of the chromosome length. As a result, homologous chromosomes can exist in versions of markedly different size within the same strain. When this occurs with several different chromosomes, the interpretation of PFE patterns appears difficult without prior identification of the size-variable chromosomes and of the chromosome homologies. DNA deletions and amplifications have been shown to account for some of these size modifications, but other mechanisms are probably involved; nevertheless, interchromosomal exchange does not seem to play a major role in these polymorphisms. These chromosomal rearrangements, yet in an early stage of characterization, exhibit two relevant features: they seem (1) to affect essentially the subtelomeric regions and (2) to occur in a recurrent nonrandom manner. Chromosomal rearrangements sharing the same characteristics have been identified in yeast and other protozoa such as Trypanosoma and Plasmodium. The significance of this hypervariability for the biology of the parasite remains unknown, but it can be expected that such mechanisms have been maintained for some purpose; genes specifically located near chromosome ends might benefit from rapid sequence change, alternating activation, or polymorphism of expression. The chromosomal plasticity could represent a general mode of mutation in these parasites, in parallel with genetic exchange which may be uncommon in nature. The molecular characterization of these rearrangements, the identification of each chromosome with the help of physical restriction maps and linkage maps, and the collation of such data on a number of strains and species should allow a significant progress in the understanding of the genetics of Leishmania, in particular as regards ploidy, generation of phenotypic diversity, and genome evolution. Finally, like other models, this is susceptible to improve our knowledge of DNA-DNA interactions and of the chromosome functional structure and dynamics.

Conserved linkage groups associated with large-scale chromosomal rearrangements between Old World and New World Leishmania genomes.

The genus Leishmania can be taxonomically separated into three main groups: the Old World subgenus L. (Leishmania), the New World subgenus L. (Leishmania) and the New World subgenus L. (Viannia). The haploid genome of Old World Leishmania species has been shown to contain 36 chromosomes defined as physical linkage groups; the latter were found entirely conserved across species. In the present study, we tried to verify whether this conservation of the genome structure extends to the New World species of Leishmania. 300 loci were explored by hybridization on optimized pulsed field gel electrophoresis separations of the chromosomes of polymorphic strains of the six main pathogenic Leishmania species of the New World. When comparing these New World karyotypes with their Old World counterparts, 32 out of 36 linkage groups were found conserved among all species. Four chromosomal rearrangements were found. All species belonging to the L. (Viannia) subgenus were characterized by the presence (i) of a short sequence exchange between chromosomes 26 and 35, and (ii) more importantly, of a fused version of chromosomes 20 and 34 which are separated in all Old World species. 69 additional markers were isolated from a plasmid library specifically constructed from the rearranged chromosomes 20+34 in an attempt to detect mechanisms other than a fusion or breakage: only two markers out of 40 did not belong to the linkage groups 20 and 34. On the other hand, all strains belonging to the New World subgenus L. (Leishmania) were characterized by two different chromosomal rearrangements of the same type (fusion/breakage) as above as compared with Old World species: chromosomes 8+29 and 20+36. Consequently, these two groups of species have 35 and 34 heterologous chromosomes, respectively. Overall, these results show that large-scale chromosomal rearrangements occurred during the evolution of the genus Leishmania, and that the three main groups of pathogenic species are characterized by different chromosome numbers. Nevertheless, translocations seem particularly rare, and the conservation of the major linkage groups should be an essential feature for the compared genetics between species of this parasite.