Determination of chemical composition and its relationship with optical properties of Ti-N and Ti-V-N sputtered thin films

In the investigation of thin films of transition metal nitrides, an essential role is played by the accurate determination of their chemical composition. Actually the chemical composition depends on the deposition parameters and influences the optical properties. These relations are illustrated in thin films of TiNx and (Ti1-yVy)N-x deposited by reactive magnetron sputtering from composite targets of the elements. By variation of the nitrogen partial pressure and the target composition, different samples have been obtained. The chemical composition has been measured by electron probe microanalysis at low irradiation voltages. The optical properties are evaluated by ex-situ ellipsometry. Using the screened Drude model, they are correlated with the differences in composition. Adding vanadium or nitrogen in Ti-N is shown to have the same effect on the optical properties.

Evolution, maintenance and ecological consequences of genetic caste determination in " Pogonomyrmex " harvester ants

Summary Division of labor between reproducers (queens) and helpers (workers) is the main characteristic of social insect societies and at the root of their ecological success. Kin selection models predict that phenotypic differences between queens and workers should result from environmental rather than from genetic differences. However, genetic effects on queen and worker differentiation were found in two populations-of Pogonomyrmex harvester ants. Each of the two populations is composed of two genetically distinct lineages. Queens (which can be of either lineage) generally mate with males of their own and of the alternate lineage and produce two types of female offspring, those fertilized by males of the queens' lineage which develop into queens and those fertilized by males of the alternate lineage which develop into workers. All four lineages were further suggested to be themselves of hybrid origin between-the species P: barbatus and P. rugosus, in which queens and workers do not differ genetically. In a first set of experiments, we tested if female caste determination (the differentiation into queens and workers) in the lineages was genetically hardwired and if it was associated with costs in terms of the ability to optimally allocate resources to the production of queens and workers. To this end we first mated queens of-two lineages to a single male. Queens mated to a male of the alternate lineage successfully raised worker offspring whereas queens mated to a male of their own lineage almost always failed to produce workers. This reveals that pure-lineage individuals have lost the ability to develop into workers. Second, we analyzed offspring produced by naturally mated queens. During the stage of colony founding when only workers are produced, naturally mated queens laid a high proportion of pure-lineage eggs but the large majority of these eggs failed to develop. As a consequence, the number of offspring produced by incipient colonies decreased linearly with the proportion of pure-lineage eggs laid by queens. Moreover, queens of the lineage most commonly represented in a given population produced more pure-lineage eggs, in line with the view that they mate randomly with the two types of males and indiscriminately use their sperm. Altogether these results predict frequency-dependent founding success for pairs of lineages because queens of the more common lineage will produce more pure-lineage eggs and their colonies be less successful during the stage of colony founding. To describe the distribution of populations characterized with genetic caste determination relative to the populations with environmental caste determination we genotyped queens and workers collected during a large survey of -additional populations. Genetic caste determination associated with pairs of interbreeding lineages was frequent and widespread in the studied range and we identified four additional lineages displaying genetic caste determination. Overall, there were thus eight highly differentiated lineages with genetic caste determination. These lineages always co-occurred in the same complementary lineage pairs. Three of the four lineage pairs appeared to have a common origin, while their relationship with the forth could not be resolved. The genetic survey also revealed that, in addition to being genetically isolated from one another, all eight lineages were genetically distinct from P. rugosus and P. barbatus, even when colonies of interbreeding lineages co-occurred with colonies of either putative parent at the same site. This raised the question of the mechanisms involved in the reproductive isolation between the lineages and the parental species and between the two lineages of a lineage pair. At a site where one lineage pair co-occurred with P. rugosus, we identified two pre-zygotic mechanisms (differences in timing for mating flights between P. rugosus and the lineage pair and assortative mating) and one post-zygotic mechanism (high levels of hybrid unviablility) which in combination may largely account for the reproductive isolation between the lineages and their parental species. The mechanisms accounting for the reproductive isolation between the two lineages of a lineage pair varied across lineage pairs. In one lineage pair, inter-lineage individuals exclusively occurred in the sterile worker caste, raising the possibility that inter-lineage eggs have completely lost the ability to develop into queens in this lineage pair and that there is thus no opportunity for gene flow. In each of the three remaining lineage pairs, inter-lineage queens were produced by a minority of colonies. In these lineage pairs, colonies headed by inter-lineage queens failed to grow sufficiently to produce reproductive individuals which may account for the reproductive isolation between co-occurring lineages in three lineage pairs. In conclusion, the results of this thesis show that genetic caste determination is costly but widespread in Pogonomyrmex harvester ants. Reproductive isolation among the lineages and between the lineages and the parental species as well as frequency-dependent founding success for co-occurring lineages may contribute to the persistence of this extraordinary system. Résumé La division du travail entre individus reproducteurs (les reines) et individus non-reproducteurs (ouvrières) représente la caractéristique principale des sociétés d'insectes et est à la base de leur succès écologique. Des modèles de sélection de parentèle prédisent que les différences phénotypiques entre reines et ouvrières devraient provenir d'effets environnementaux plutôt que de différences génétiques. Malgré ce fait, des effets génétiques sur la différentiation entre reines et ouvrières ont été montrés dans deux populations de fourmis moissonneuses du genre Pogonomyrmex. Chacune des deux populations est composée de deux lignées génétiquement distinctes. Les reines de chaque lignée s'accouplent en général avec des mâles de leur propre lignée ainsi qu'avec des mâles de l'autre lignée et produisent deux types d'oeufs, ceux qui sont fécondés par les mâles de leur propre lignée qui se développent en nouvelles reines et ceux qui sont fécondés par les mâles de l'autre lignée qui se développent en ouvrières. Il a été suggéré que les lignées sont elles-mêmes des hybrides entre les deux espèces P. barbatus et P. rugosus. Dans ces deux espèces, les reines et ouvrières ne sont pas génétiquement distinctes. Dans une première série d'expériences, nous avons testé si la détermination de la caste femelle (le développement en reine ou en ouvrière) est génétiquement rigide et si elle est associée à des coûts en terme de capacité à allouer de façon optimale les ressources pour la production de reines et d'ouvrières. Pour cela nous avons accouplé des reines de deux lignées avec un seul mâle. Les reines accouplées avec un mâle de l'autre lignée ont élevé de nouvelles ouvrières avec succès alors que les reines accouplées avec un mâle de leur propre lignée ont presque toujours échoué à produire des ouvrières. Ceci montre que les individus de lignée pure ont perdu la capacité de se développer en ouvrière. Deuxièmement, nous avons analysé la descendance de reines qui se sont accouplées naturellement. Durant le stade de fondation de la colonie, où seules des ouvrières sont élevées, les reines accouplées naturellement ont pondu une grande proportion d'oeufs de lignée pure mais la majorité de ces derniers ne se sont pas développés. En conséquence, le nombre de descendants produits par des colonies fondatrices diminuait linéairement avec la proportion des oeufs de lignée pure pondus par la reine en accord avec l'hypothèse que les reines s'accouplent au hasard avec les deux types de mâles et utilisent leur sperme aléatoirement. Dans l'ensemble; ces résultats prédisent un succès de fondation fréquence-dépendant pour les deux lignées, car les reines de la lignée la plus fréquente produiront .plus d'oeufs de lignée pure et leurs colonies auront moins de succès lors de la fondation de colonies par rapport aux colonies de la lignée la moins fréquente. Pour décrire la distribution des-populations caractérisées par une détermination génétique des castes par rapport aux populations caractérisées par une détermination environnementale des castes, nous avons génotypé des reines et des ouvrières qui ont été collectées lors d'une analyse de populations supplémentaires. La détermination génétique des castes associée à des croisements entre lignées est fréquente et largement répartie dans l'aire étudiée. Nous avons identifié quatre lignées supplémentaires, ayant une détermination génétique des castes, pour un total de huit lignées. Ces huit lignées forment quatre paires de lignées et on ne trouve jamais deux lignées de paires différentes, dans une population. Trois des quatre paires de lignées s'avèrent avoir une origine commune alors que leur relation avec la quatrième paire de lignées n'a pas pu être résolue. L'analyse génétique de populations supplémentaires a également révélé qu'en plus d'être génétiquement isolées les unes des autres, les huit lignées sont génétiquement distinctes de P. rugosus et P. barbatus même si les colonies d'une paire de lignées se trouvent en sympatrie avec l'une ou l'autre des espèces parentales. Ceci relève la question des mécanismes impliqués dans l'isolation reproductive entre les lignées et les espèces parentales ainsi qu'entre les deux lignées d'une paire. En étudiant un site où une paire de lignées se trouve en sympatrie avec P. rugosus, nous avons identifié deux mécanismes pré-zygotiques (des différences dans le timing du vol nuptial entre P. rugosus et les lignées et des accouplements assortis) ainsi qu'un mécanisme post-zygotique (un niveau élevé de non-viabilité des hybrides). En combinaison, ces mécanismes peuvent largement expliquer l'isolement reproductif entre les lignées et leurs espèces parentales. Les mécanismes contribuant à l'isolement reproductif entre les deux lignées d'une paire variaient entre paires de lignées. Dans une paire, les individus de génotype inter-lignée se trouvent uniquement dans la caste stérile des ouvrières, suggérant qu'il n'y a pas d'opportunité pour avoir du flux de gènes entre les deux lignées ce cette paire. Dans chacune des trois autres paires de lignées des nouvelles reines de génotype inter-lignée sont produites par une minorité de colonies. Par contre, les colonies avec une reine mère de génotype inter-lignée ne se développent pas suffisamment pour produire des individus reproducteurs. Ceci peut donc expliquer pourquoi il n'y a pas de flux de gènes entre les deux lignées de trois paires. En conclusion, les résultats de cette thèse montrent que la détermination génétique de la caste est coûteuse mais très répandue chez les fourmis. moissonneuses du genre Pogonomyrmex. L'isolement reproductif des lignées entre elles et avec les espèces parentales, ainsi qu'un succès de fondation fréquence-dépendant contribuent à la persistance de ce système extraordinaire.

Cholesterol and sphingomyelin drive ligand-independent T-cell antigen receptor nanoclustering.

The T-cell antigen receptor (TCR) exists in monomeric and nanoclustered forms independently of antigen binding. Although the clustering is involved in the regulation of T-cell sensitivity, it is unknown how the TCR nanoclusters form. We show that cholesterol is required for TCR nanoclustering in T cells and that this clustering enhances the avidity but not the affinity of the TCR-antigen interaction. Investigating the mechanism of the nanoclustering, we found that radioactive photocholesterol specifically binds to the TCRβ chain in vivo. In order to reduce the complexity of cellular membranes, we used a synthetic biology approach and reconstituted the TCR in liposomes of defined lipid composition. Both cholesterol and sphingomyelin were required for the formation of TCR dimers in phosphatidylcholine-containing large unilamellar vesicles. Further, the TCR was localized in the liquid disordered phase in giant unilamellar vesicles. We propose a model in which cholesterol and sphingomyelin binding to the TCRβ chain causes TCR dimerization. The lipid-induced TCR nanoclustering enhances the avidity to antigen and thus might be involved in enhanced sensitivity of memory compared with naive T cells. Our work contributes to the understanding of the function of specific nonannular lipid-membrane protein interactions.

A single LC-tandem mass spectrometry method for the simultaneous determination of 14 antimalarial drugs and their metabolites in human plasma.

Among the various determinants of treatment response, the achievement of sufficient blood levels is essential for curing malaria. For helping us at improving our current understanding of antimalarial drugs pharmacokinetics, efficacy and toxicity, we have developed a liquid chromatography-tandem mass spectrometry method (LC-MS/MS) requiring 200mul of plasma for the simultaneous determination of 14 antimalarial drugs and their metabolites which are the components of the current first-line combination treatments for malaria (artemether, artesunate, dihydroartemisinin, amodiaquine, N-desethyl-amodiaquine, lumefantrine, desbutyl-lumefantrine, piperaquine, pyronaridine, mefloquine, chloroquine, quinine, pyrimethamine and sulfadoxine). Plasma is purified by a combination of protein precipitation, evaporation and reconstitution in methanol/ammonium formate 20mM (pH 4.0) 1:1. Reverse-phase chromatographic separation of antimalarial drugs is obtained using a gradient elution of 20mM ammonium formate and acetonitrile both containing 0.5% formic acid, followed by rinsing and re-equilibration to the initial solvent composition up to 21min. Analyte quantification, using matrix-matched calibration samples, is performed by electro-spray ionization-triple quadrupole mass spectrometry by selected reaction monitoring detection in the positive mode. The method was validated according to FDA recommendations, including assessment of extraction yield, matrix effect variability, overall process efficiency, standard addition experiments as well as antimalarials short- and long-term stability in plasma. The reactivity of endoperoxide-containing antimalarials in the presence of hemolysis was tested both in vitro and on malaria patients samples. With this method, signal intensity of artemisinin decreased by about 20% in the presence of 0.2% hemolysed red-blood cells in plasma, whereas its derivatives were essentially not affected. The method is precise (inter-day CV%: 3.1-12.6%) and sensitive (lower limits of quantification 0.15-3.0 and 0.75-5ng/ml for basic/neutral antimalarials and artemisinin derivatives, respectively). This is the first broad-range LC-MS/MS assay covering the currently in-use antimalarials. It is an improvement over previous methods in terms of convenience (a single extraction procedure for 14 major antimalarials and metabolites reducing significantly the analytical time), sensitivity, selectivity and throughput. While its main limitation is investment costs for the equipment, plasma samples can be collected in the field and kept at 4 degrees C for up to 48h before storage at -80 degrees C. It is suited to detecting the presence of drug in subjects for screening purposes and quantifying drug exposure after treatment. It may contribute to filling the current knowledge gaps in the pharmacokinetics/pharmacodynamics relationships of antimalarials and better define the therapeutic dose ranges in different patient populations.

Sex determination: why so many ways of doing it?

Sexual reproduction is an ancient feature of life on earth, and the familiar X and Y chromosomes in humans and other model species have led to the impression that sex determination mechanisms are old and conserved. In fact, males and females are determined by diverse mechanisms that evolve rapidly in many taxa. Yet this diversity in primary sex-determining signals is coupled with conserved molecular pathways that trigger male or female development. Conflicting selection on different parts of the genome and on the two sexes may drive many of these transitions, but few systems with rapid turnover of sex determination mechanisms have been rigorously studied. Here we survey our current understanding of how and why sex determination evolves in animals and plants and identify important gaps in our knowledge that present exciting research opportunities to characterize the evolutionary forces and molecular pathways underlying the evolution of sex determination.

Effect of changes in the deuterium content of drinking water on the hydrogen isotope ratio of urinary steroids in the context of sports drug testing.

The hydrogen isotope ratio (HIR) of body water and, therefore, of all endogenously synthesized compounds in humans, is mainly affected by the HIR of ingested drinking water. As a consequence, the entire organism and all of its synthesized substrates will reflect alterations in the isotope ratio of drinking water, which depends on the duration of exposure. To investigate the effect of this change on endogenous urinary steroids relevant to doping-control analysis the hydrogen isotope composition of potable water was suddenly enriched from -50 to 200 0/00 and maintained at this level for two weeks for two individuals. The steroids under investigation were 5β-pregnane-3α,20α-diol, 5α-androst-16-en-3α-ol, 3α-hydroxy-5α-androstan-17-one (ANDRO), 3α-hydroxy-5β-androstan-17-one (ETIO), 5α-androstane-3α,17β-diol, and 5β-androstane-3α,17β-diol (excreted as glucuronides) and ETIO, ANDRO and 3β-hydroxyandrost-5-en-17-one (excreted as sulfates). The HIR of body water was estimated by determination of the HIR of total native urine, to trace the induced changes. The hydrogen in steroids is partly derived from the total amount of body water and cholesterol-enrichment could be calculated by use of these data. Although the sum of changes in the isotopic composition of body water was 150 0/00, shifts of approximately 30 0/00 were observed for urinary steroids. Parallel enrichment in their HIR was observed for most of the steroids, and none of the differences between the HIR of individual steroids was elevated beyond recently established thresholds. This finding is important to sports drug testing because it supports the intended use of this novel and complementary methodology even in cases where athletes have drunk water of different HIR, a plausible and, presumably, inevitable scenario while traveling.

Determination of 13C/12C ratios of endogenous urinary 5-amino-imidazole-4-carboxamide 1-D-ribofuranoside (AICAR)

RATIONALE: AICAR (5-aminoimidazole-4-carboxamide 1β-D-ribofuranoside) is prohibited in sport according to rules established by the World Anti-Doping Agency. Doping control laboratories identify samples where AICAR abuse is suspected by measuring its urinary concentration and comparing the observed level with naturally occurring concentrations. As the inter-individual variance of urinary AICAR concentrations is large, this approach requires a complementary method to unambiguously prove the exogenous origin of AICAR. Therefore, a method for the determination of carbon isotope ratios (CIRs) of urinary AICAR has been developed and validated. METHODS: Concentrated urine samples were fractionated by means of liquid chromatography for analyte cleanup. Derivatization of AICAR yielding the trimethylsilylated analog was necessary to enable CIR determinations by gas chromatography/combustion/isotope ratio mass spectrometry. The method was tested for its repeatability and stability over time and a linear mixing model was applied to test for possible isotopic discrimination. A reference population of n = 63 males and females was investigated to calculate appropriate reference limits to differentiate endogenous from exogenous urinary AICAR. These limits were tested by an AICAR elimination study. RESULTS: The developed method fulfills all the requirements for adequate sports drug testing and was found to be fit for purpose. The investigated reference population showed a larger variability in the CIR of AICAR than of the endogenous steroids. Nevertheless, the calculated thresholds for differences between AICAR and endogenous steroids can be applied straightforwardly to evaluate suspicious doping control samples with the same statistical confidence as established e.g. for testosterone misuse. These thresholds enabled the detection of a single oral AICAR administration for more than 40 h. CONCLUSIONS: Determination of thee CIRs is the method of choice to distinguish between an endogenous and an exogenous source of urinary AICAR. The developed method will enable investigations into doping control samples with elevated urinary concentrations of AICAR and clearly differentiate between naturally produced/elevated and illicitly administered AICAR.

Strength of family history in predicting levels of blood pressure, plasma glucose and cholesterol.

Objective: Limited information is available on the quantitative relationship between family history and the corresponding underlying traits. We analyzed these associations for blood pressure, fasting blood glucose, and cholesterol levels. Methods: Data were obtained from 6,102 Caucasian participants (2,903 men and 3,199 women) aged 35-75 years using a population-based cross-sectional survey in Switzerland. Cardiovascular disease risk factors were measured, and the corresponding family history was self-reported using a structured questionnaire. Results: The prevalence of a positive family history (in first-degree relatives) was 39.6% for hypertension, 22.3% for diabetes, and 29.0% for hypercholesterolemia. Family history was not known for at least one family member in 41.8% of participants for hypertension, 14.4% for diabetes, and 50.2% for hypercholesterolemia. A positive family history was strongly associated with higher levels of the corresponding trait, but not with the other traits. Participants who reported not to know their family history of hypertension had a higher systolic blood pressure than participants with a negative history. Sibling histories had higher positive predictive values than parental histories. The ability to discriminate, calibrate, and reclassify was best for the family history of hypertension. Conclusions: Family history of hypertension, diabetes, and hypercholesterolemia was strongly associated with the corresponding dichotomized and continuous phenotypes.

Simultaneous B(0)- and B(1)+-map acquisition for fast localized shim, frequency, and RF power determination in the heart at 3 T.

High-field (>or=3 T) cardiac MRI is challenged by inhomogeneities of both the static magnetic field (B(0)) and the transmit radiofrequency field (B(1)+). The inhomogeneous B fields not only demand improved shimming methods but also impede the correct determination of the zero-order terms, i.e., the local resonance frequency f(0) and the radiofrequency power to generate the intended local B(1)+ field. In this work, dual echo time B(0)-map and dual flip angle B(1)+-map acquisition methods are combined to acquire multislice B(0)- and B(1)+-maps simultaneously covering the entire heart in a single breath hold of 18 heartbeats. A previously proposed excitation pulse shape dependent slice profile correction is tested and applied to reduce systematic errors of the multislice B(1)+-map. Localized higher-order shim correction values including the zero-order terms for frequency f(0) and radiofrequency power can be determined based on the acquired B(0)- and B(1)+-maps. This method has been tested in 7 healthy adult human subjects at 3 T and improved the B(0) field homogeneity (standard deviation) from 60 Hz to 35 Hz and the average B(1)+ field from 77% to 100% of the desired B(1)+ field when compared to more commonly used preparation methods.

Sex determination in dioecious Mercurialis annua and its close diploid and polyploid relatives.

Separate sexes have evolved on numerous independent occasions from hermaphroditic ancestors in flowering plants. The mechanisms of sex determination is known for only a handful of such species, but, in those that have been investigated, it usually involves alleles segregating at a single locus, sometimes on heteromorphic sex chromosomes. In the genus Mercurialis, transitions between combined (hermaphroditism) and separate sexes (dioecy or androdioecy, where males co-occur with hermaphrodites rather than females) have occurred more than once in association with hybridisation and shifts in ploidy. Previous work has pointed to an unusual 3-locus system of sex determination in dioecious populations. Here, we use crosses and genotyping for a sex-linked marker to reject this model: sex in diploid dioecious M. annua is determined at a single locus with a dominant male-determining allele (an XY system). We also crossed individuals among lineages of Mercurialis that differ in their ploidy and sexual system to ascertain the extent to which the same sex-determination system has been conserved following genome duplication, hybridisation and transitions between dioecy and hermaphroditism. Our results indicate that the male-determining element is fully capable of determining gender in the progeny of hybrids between different lineages. Specifically, males crossed with females or hermaphrodites always generate 1:1 male:female or male:hermaphrodite sex ratios, respectively, regardless of the ploidy levels involved (diploid, tetraploid or hexaploid). Our results throw further light on the genetics of the remarkable variation in sexual systems in the genus Mercurialis. They also illustrate the almost identical expression of sex-determining alleles in terms of sexual phenotypes across multiple divergent backgrounds, including those that have lost separate sexes altogether.

The evolution of sex determination

Sexual reproduction is a fundamental aspect of life. Sex-determination mechanisms are responsible for the sexual fate and development of sexual characteristics in an organism, be it a unicellular alga, a plant, or an animal. Surprisingly, sex-determination mechanisms are not evolutionarily conserved but are bewilderingly diverse and appear to have had rapid turnover rates during evolution. Evolutionary biologists continue to seek a solution to this conundrum. What drives the surprising dynamics of such a fundamental process that always leads to the same outcome: two sex types, male and female? The answer is complex but the ongoing genomic revolution has already greatly increased our knowledge of sex-determination systems and sex chromosomes in recent years. This novel book presents and synthesizes our current understanding, and clearly shows that sex-determination evolution will remain a dynamic field of future research. The Evolution of Sex Determination is an advanced, research level text suitable for graduate students and researchers in genetics, developmental biology, and evolution.

Determination of DNA persistence length by cryo-electron microscopy. Separation of the static and dynamic contributions to the apparent persistence length of DNA.

Axial deflection of DNA molecules in solution results from thermal motion and intrinsic curvature related to the DNA sequence. In order to measure directly the contribution of thermal motion we constructed intrinsically straight DNA molecules and measured their persistence length by cryo-electron microscopy. The persistence length of such intrinsically straight DNA molecules suspended in thin layers of cryo-vitrified solutions is about 80 nm. In order to test our experimental approach, we measured the apparent persistence length of DNA molecules with natural "random" sequences. The result of about 45 nm is consistent with the generally accepted value of the apparent persistence length of natural DNA sequences. By comparing the apparent persistence length to intrinsically straight DNA with that of natural DNA, it is possible to determine both the dynamic and the static contributions to the apparent persistence length.

A growth hormone-releasing peptide that binds scavenger receptor CD36 and ghrelin receptor up-regulates sterol transporters and cholesterol efflux in macrophages through a peroxisome proliferator-activated receptor gamma-dependent pathway.

Macrophages play a central role in the pathogenesis of atherosclerosis by accumulating cholesterol through increased uptake of oxidized low-density lipoproteins by scavenger receptor CD36, leading to foam cell formation. Here we demonstrate the ability of hexarelin, a GH-releasing peptide, to enhance the expression of ATP-binding cassette A1 and G1 transporters and cholesterol efflux in macrophages. These effects were associated with a transcriptional activation of nuclear receptor peroxisome proliferator-activated receptor (PPAR)gamma in response to binding of hexarelin to CD36 and GH secretagogue-receptor 1a, the receptor for ghrelin. The hormone binding domain was not required to mediate PPARgamma activation by hexarelin, and phosphorylation of PPARgamma was increased in THP-1 macrophages treated with hexarelin, suggesting that the response to hexarelin may involve PPARgamma activation function-1 activity. However, the activation of PPARgamma by hexarelin did not lead to an increase in CD36 expression, as opposed to liver X receptor (LXR)alpha, suggesting a differential regulation of PPARgamma-targeted genes in response to hexarelin. Chromatin immunoprecipitation assays showed that, in contrast to a PPARgamma agonist, the occupancy of the CD36 promoter by PPARgamma was not increased in THP-1 macrophages treated with hexarelin, whereas the LXRalpha promoter was strongly occupied by PPARgamma in the same conditions. Treatment of apolipoprotein E-null mice maintained on a lipid-rich diet with hexarelin resulted in a significant reduction in atherosclerotic lesions, concomitant with an enhanced expression of PPARgamma and LXRalpha target genes in peritoneal macrophages. The response was strongly impaired in PPARgamma(+/-) macrophages, indicating that PPARgamma was required to mediate the effect of hexarelin. These findings provide a novel mechanism by which the beneficial regulation of PPARgamma and cholesterol metabolism in macrophages could be regulated by CD36 and ghrelin receptor downstream effects.