Hybridization and speciation.

Hybridization has many and varied impacts on the process of speciation. Hybridization may slow or reverse differentiation by allowing gene flow and recombination. It may accelerate speciation via adaptive introgression or cause near-instantaneous speciation by allopolyploidization. It may have multiple effects at different stages and in different spatial contexts within a single speciation event. We offer a perspective on the context and evolutionary significance of hybridization during speciation, highlighting issues of current interest and debate. In secondary contact zones, it is uncertain if barriers to gene flow will be strengthened or broken down due to recombination and gene flow. Theory and empirical evidence suggest the latter is more likely, except within and around strongly selected genomic regions. Hybridization may contribute to speciation through the formation of new hybrid taxa, whereas introgression of a few loci may promote adaptive divergence and so facilitate speciation. Gene regulatory networks, epigenetic effects and the evolution of selfish genetic material in the genome suggest that the Dobzhansky-Muller model of hybrid incompatibilities requires a broader interpretation. Finally, although the incidence of reinforcement remains uncertain, this and other interactions in areas of sympatry may have knock-on effects on speciation both within and outside regions of hybridization.

Developing a Simple and Rapid Test for Monitoring the Heat Evolution of Concrete Mixtures for Both Laboratory and Field Applications, January 2006

Various test methods exist for measuring heat of cement hydration; however, most current methods require expensive equipment, complex testing procedures, and/or extensive time, thus not being suitable for field application. The objectives of this research are to identify, develop, and evaluate a standard test procedure for characterization and quality control of pavement concrete mixtures using a calorimetry technique. This research project has three phases. Phase I was designed to identify the user needs, including performance requirements and precision and bias limits, and to synthesize existing test methods for monitoring the heat of hydration, including device types, configurations, test procedures, measurements, advantages, disadvantages, applications, and accuracy. Phase II was designed to conduct experimental work to evaluate the calorimetry equipment recommended from the Phase I study and to develop a standard test procedure for using the equipment and interpreting the test results. Phase II also includes the development of models and computer programs for prediction of concrete pavement performance based on the characteristics of heat evolution curves. Phase III was designed to study for further development of a much simpler, inexpensive calorimeter for field concrete. In this report, the results from the Phase I study are presented, the plan for the Phase II study is described, and the recommendations for Phase III study are outlined. Phase I has been completed through three major activities: (1) collecting input and advice from the members of the project Technical Working Group (TWG), (2) conducting a literature survey, and (3) performing trials at the CP Tech Center’s research lab. The research results indicate that in addition to predicting maturity/strength, concrete heat evolution test results can also be used for (1) forecasting concrete setting time, (2) specifying curing period, (3) estimating risk of thermal cracking, (4) assessing pavement sawing/finishing time, (5) characterizing cement features, (6) identifying incompatibility of cementitious materials, (7) verifying concrete mix proportions, and (8) selecting materials and/or mix designs for given environmental conditions. Besides concrete materials and mix proportions, the configuration of the calorimeter device, sample size, mixing procedure, and testing environment (temperature) also have significant influences on features of concrete heat evolution process. The research team has found that although various calorimeter tests have been conducted for assorted purposes and the potential uses of calorimeter tests are clear, there is no consensus on how to utilize the heat evolution curves to characterize concrete materials and how to effectively relate the characteristics of heat evolution curves to concrete pavement performance. The goal of the Phase II study is to close these gaps.

A novel bioinformatics pipeline to discover genes related to arbuscular mycorrhizal symbiosis based on their evolutionary conservation pattern among higher plants.

BACKGROUND: Genes involved in arbuscular mycorrhizal (AM) symbiosis have been identified primarily by mutant screens, followed by identification of the mutated genes (forward genetics). In addition, a number of AM-related genes has been identified by their AM-related expression patterns, and their function has subsequently been elucidated by knock-down or knock-out approaches (reverse genetics). However, genes that are members of functionally redundant gene families, or genes that have a vital function and therefore result in lethal mutant phenotypes, are difficult to identify. If such genes are constitutively expressed and therefore escape differential expression analyses, they remain elusive. The goal of this study was to systematically search for AM-related genes with a bioinformatics strategy that is insensitive to these problems. The central element of our approach is based on the fact that many AM-related genes are conserved only among AM-competent species. RESULTS: Our approach involves genome-wide comparisons at the proteome level of AM-competent host species with non-mycorrhizal species. Using a clustering method we first established orthologous/paralogous relationships and subsequently identified protein clusters that contain members only of the AM-competent species. Proteins of these clusters were then analyzed in an extended set of 16 plant species and ranked based on their relatedness among AM-competent monocot and dicot species, relative to non-mycorrhizal species. In addition, we combined the information on the protein-coding sequence with gene expression data and with promoter analysis. As a result we present a list of yet uncharacterized proteins that show a strongly AM-related pattern of sequence conservation, indicating that the respective genes may have been under selection for a function in AM. Among the top candidates are three genes that encode a small family of similar receptor-like kinases that are related to the S-locus receptor kinases involved in sporophytic self-incompatibility. CONCLUSIONS: We present a new systematic strategy of gene discovery based on conservation of the protein-coding sequence that complements classical forward and reverse genetics. This strategy can be applied to diverse other biological phenomena if species with established genome sequences fall into distinguished groups that differ in a defined functional trait of interest.

Evolution at Two Levels in Fire Ants: The Relationship between Patterns of Gene Expression and Protein Sequence Evolution.

Variation in protein sequence and gene expression each contribute to phenotypic diversity, and may be subject to similar selective pressures. Eusocial insects are particularly useful for investigating the evolutionary link between protein sequence and condition-dependent patterns of gene expression because gene expression plays a central role in determining differences between eusocial insect sexes and castes. We investigated the relationship between protein coding sequence evolution and gene expression patterns in the fire ants Solenopsis invicta, S. richteri, and their hybrids to gain greater insight into how selection jointly operates on gene expression and coding sequence. We found that genes with high expression variability within castes and sexes were frequently differentially expressed between castes and sexes, as well as between species and hybrids. These results indicate that genes showing high variation in expression in one context also tend to show high variation in expression in other contexts. Our analyses further revealed that variation in both intra- and interspecific gene expression was positively associated with rate of protein sequence evolution in Solenopsis. This suggests that selective constraints on a gene operate both at the level of protein sequence and at the level of gene expression regulation. Overall, our study provides one of the strongest demonstrations that selective constraints mediate both protein sequence evolution and gene expression variability across different biological contexts and timescales.

Pollinator guild organization and its consequences for reproduction in three synchronopatric species of Tibouchina (Melastomataceae)

Pollinator guild organization and its consequences for reproduction in three synchronopatric species of Tibouchina (Melastomataceae). In co-flowering plant species, pollinator sharing can result in interspecific pollen transfer and fecundity reduction. Competition will be relaxed whenever there is a large amount of initial pollen supply or if each plant species occupies different habitat patches. Reproduction in Tibouchina cerastifolia (Naudin) Cogn., T. clinopodifolia (DC.) Cogn. and T. gracilis (Bonpl.) Cogn. was studied in an area of Atlantic rainforest to examine whether synchronopatry induces time partitioning among pollinator species. Eleven bee species comprised the pollinator guild. Among pollinators, there were overlaps in bee species composition and in flower visitation time. Direct competition for pollen in Tibouchina Aubl. at the study site seems to lead to different activity periods among the bee species, in which Bombus pauloensis Friese,1913 was most active earlier, while the other species were active later in the day. Bombus pauloensis, the largest bee species recorded on Tibouchina flowers, was the most important and efficient pollinator. This species harvested pollen before the other species and had the shortest handling time. The plants reproduced sexually by selfing or outcrossing, and hybridization was not avoided by incompatibility reactions at the style. The avoidance of direct competition for pollen and no pollinator partitioning among the synchronopatric species of Tibouchina may reflect a facilitative interaction among these pioneer plants.

The growth and diffusion of knowlegde and the theory of the firm

We analyze the implications of a market imperfection related to the inability to establish intellectual property rights, that we label {\it unverifiable communication}. Employees are able to collude with external parties selling ``knowledge capital'' of the firm. The firm organizer engages in strategic interaction simultaneously with employees and competitors, as she introduces endogenous transaction costs in the market for information between those agents. Incentive schemes and communication costs are the key strategic variables used by the firm to induce frictions in collusive markets. Unverifiable communication introduces severe allocative distortions, both at internal product development and at intended sale of information (technology transfer). We derive implications of the model for observable decisions like characteristics of the employment relationship (full employment, incompatibility with other jobs), firms' preferences over cluster characteristics for location decisions, optimal size at entry, in--house development vs sale strategies for innovations and industry evolution.

Molecular characterization of HLA-C incompatibilities in HLA-ABDR-matched unrelated bone marrow donor-recipient pairs. Sequence of two new Cw alleles (Cw*02023 and Cw*0707) and recognition by cytotoxic T lymphocytes.

While the influence of HLA-AB and -DRB1 matching on the outcome of bone marrow transplantation (BMT) with unrelated donors is clear, the evaluation of HLA-C has been hampered by its poor serological definition. Because the low resolution of standard HLA-C typing could explain the significant number of positive cytotoxic T lymphocyte precursor frequency (CTLpf) tests found among HLA-AB-subtype, DRB1/B3/B5-subtype matched patient/donor pairs, we have identified by sequencing the incompatibilities recognized by CD8+ CTL clones obtained from such positive CTLpf tests. In most cases the target molecules were HLA-C antigens that had escaped detection by serology (e.g. Cw*1601, 1502 or 0702). Direct recognition of HLA-C by a CTL clone was demonstrated by lysis of the HLA class I-negative 721.221 cell line transfected with Cw*1601 cDNA. Because of the functional importance of Cw polymorphism, a PCR-SSO oligotyping procedure was set up allowing the resolution of 29 Cw alleles. Oligotyping of a panel of 382 individuals (including 101 patients and their 272 potential unrelated donors, 5 related donors and 4 platelet donors) allowed to determine HLA-C and HLA A-B-Cw-DRB1 allelic frequencies, as well as a number of A-Cw, B-Cw, and DRB1-Cw associations. Two new HLA-Cw alleles (Cw*02023 and Cw*0707) were identified by DNA sequencing of PCR-amplified exon 2-intron 2-exon 3 amplicons. Furthermore, we determined the degree of HLA-C compatibility in 287 matched pairs that could be formed from 73 patients and their 184 potential unrelated donors compatible for HLA-AB by serology and for HLA-DRB1/ B3/B5 by oligotyping. Cw mismatches were identified in 42.1% of these pairs, and AB-subtype oligotyping showed that 30% of these Cw-incompatible pairs were also mismatched for A or B-locus subtype. The degree of HLA-C incompatibility was strongly influenced by the linkage with B alleles and by the ABDR haplotypes. Cw alleles linked with B*4403, B*5101, B18, and B62 haplotypes were frequently mismatched. Apparently high resolution DNA typing for HLA-AB does not result in full matching at locus C. Since HLA-C polymorphism is recognized by alloreactive CTLs, such incompatibilities might be as relevant as AB-subtype mismatches in clinical transplantation.

Religious beliefs in schizophrenia: Their relevance for adherence to treatment

The study examined how religious beliefs and practices impact upon medication and illness representations in chronic schizophrenia. One hundred three stabilized patients were included in Geneva's outpatient public psychiatric facility in Switzerland. Interviews were conducted to investigate spiritual and religious beliefs and religious practices and religious coping. Medication adherence was assessed through questions to patients and to their psychiatrists and by a systematic blood drug monitoring. Thirty-two percent of patients were partially or totally nonadherent to oral medication. Fifty-eight percent of patients were Christians, 2% Jewish, 3% Muslim, 4% Buddhist, 14% belonged to various minority or syncretic religious movements, and 19% had no religious affiliation. Two thirds of the total sample considered spirituality as very important or even essential in everyday life. Fifty-seven percent of patients had a representation of their illness directly influenced by their spiritual beliefs (positively in 31% and negatively in 26%). Religious representations of illness were prominent in nonadherent patients. Thirty-one percent of nonadherent patients and 27% of partially adherent patients underlined an incompatibility or contradiction between their religion and taking medication, versus 8% of adherent patients. Religion and spirituality contribute to shaping representations of disease and attitudes toward medical treatment in patients with schizophrenia. This dimension should be on the agenda of psychiatrists working with patients with schizophrenia.

In-furrow inoculation of soybean as alternative to fungicide and micronutrient seed treatment

Soybean is a major grain crop in Brazil, and yields can be considerably improved by inoculation with selected Bradyrhizobium strains. However, the incompatibility between inoculation and seed treatments with fungicides and micronutrients represents a major barrier to the achievement of high rates of biological N2 fixation. Inoculation practices that can alleviate the negative effects of agrochemicals must therefore be found and in-furrow inoculation seems to be an attractive alternative. This study reports the results of seven field experiments conducted in three growing seasons in Brazil; three in soils previously cropped with inoculated soybean (> 10(4) cells g-1 of soil of Bradyrhizobium), and four in areas where the crop was sown for the first time (< 10² cells g-1 of soil of Bradyrhizobium). The compatibility with fungicides and micronutrients was compared in seeds inoculated with peat or liquid inoculants, or treated with different doses of liquid inoculant in-furrow. In areas with established Bradyrhizobium populations, seed-applied agrochemicals did generally not affect nodulation, but also did not increase yields, while inoculation always increased N grain accumulation or yield, and N fertilizer decreased both nodulation and yield. Where soybean was sown for the first time, the seed treatment with agrochemicals affected nodulation when applied together with peat or liquid inoculant. In-furrow inoculation alleviated the effects of seed treatment with agrochemicals; the best performance was achieved with high Bradyrhizobium cell concentrations, with up to 2.5 million cells seed-1.

Rapid disease emergence through horizontal gene transfer between eukaryotes.

Among different species of eukaryotes, the extent and evolutionary significance of horizontal gene transfer remains poorly understood. A newly published study by Friesen and colleagues indicates that a recent gene transfer between two species of fungi has enabled the recipient to rapidly acquire high virulence on wheat. The study highlights a mechanism by which diseases can suddenly emerge, but also brings up the controversial issues of how horizontal gene transfer occurs and whether fungal incompatibility barriers to gene flow are more 'leaky' than was previously thought.

Mechanisms involved in the maintenance of inbreeding depression in gynodioecious "Silene vulgaris" (Caryophyllaceae): an experimental investigation

Summary Gynodioecy, the joint occurrence of females and hermaphrodites within natural populations, is a widely studied mating system ever since Darwin (1877). It is an exceptional mating system because continuous selection is necessary to maintain it. Since females only reproduce through ovules whereas hermaphrodites transmit genes through ovules and pollen, larger female fitness, in terms of seed output, is required to allow their maintenance. Two non-exclusive mechanisms can account for the maintenance of females. First, as females do not produce pollen they can reallocate their resources towards a higher ovule production. Second, hermaphrodites can self- and cross-fertilize whereas females are obligate outcrossers. Thus hermaphrodites should partly suffer from inbreeding depression (i.e.: the fitness decline of inbred relative to outbred individuals) and thereby produce less fit progeny than females. This thesis investigated the effects of self- and cross-fertilization of heimaphrodites over two consecutive generations. Inbreeding depression increased across the successive stages of the life- cycle (i.e.: from "seed traits" to "reproductive traits") displaying large inbreeding depression estimates (up to 0.76). This investigation not only detected large inbreeding depression estimates but also detected mechanisms involved in the maintenance of inbreeding depression. For instance cryptic self-incompatibility which is here a larger in vivo pollen performance of distant pollen compared to self-pollen; the expression of inbreeding depression especially in late life-cycle stages, and the appearance of females in the progeny of selfed hermaphrodites. The female biased sex ratio in the progeny of selfed hermaphrodites was a surprising result and could either come from the sex determining mechanisms (complex nucleo-cytoplasmic interaction(s)) and/or from inbreeding depression. Indeed, we not only got females and hermaphrodites but also partial male-sterile (PMS) individuals (i.e.: individuals with differing number of viable stamens). We detected that inbred pollen bearing plants (excluding females) have less viable stamens per flower than outbred plants. A positive correlation was detected between inbreeding depression for the number of viable stamens per flower and the difference in sex ratio between inbred and outbred individuals. A positive relationship was also detected between inbreeding depression for pollen viability and inbreeding depression for number of viable stamens per flower. Each correlation can either account for pleiotropic effects (a major gene acting on the two considered traits) or linkage disequilibrium between genes controlling each of the two related traits. If we hypothesize that these correlations are due to a major gene with pleiotropic effects, the positive relationship between inbreeding depression for number of viable stamens per flower and inbreeding depression for pollen viability showed that deleterious alleles present on a major gene coding for pollen production and viability depressed male fitness within inbred plants. The positive relationship between sex ratio difference between inbred and outbred individuals and inbreeding depression for number of viable stamens per flower indicates that (1) either number of viable stamens per flower is, in addition to inbreeding, also affected by the loci coding for sex determinism or, (2) the presence of females within the progeny of selfed hermaphrodites is a consequence of large inbreeding depression inhibiting pollen production, or (3) sex is here determined by a combination of loci coding for sex expression and inbreeding depression for male reproductive traits. In conclusion, Silene vulgaris has been shown to be a good model for understanding the evolution of mating systems that promote outbreeding. Résumé La gynodïoécie est définie comme étant la présence simultanée d'hermaphrodites et de femelles au sein de populations naturelles d'une même espèce. Ce système de reproduction a toujours fasciné le monde scientifique depuis Darwin, comme en témoigne ses écrits (1876, 1877) sur les systèmes de reproduction chez les plantes. Les femelles ne transmettent leurs gènes qu'à travers leurs ovules alors que les hermaphrodites transmettent leurs gènes à la fois par la voie mâle (le pollen) et la voie femelle (les ovules). La condition pour que la gynodïoécie se maintienne nécessite donc une fitness de la fonction femelle plus élevée chez les femelles que chez les hermaphrodites. Deux mécanismes mutuellement non exclusifs peuvent expliquer le maintien des femelles au sein de ces populations gynodioïques. D'une part, les femelles peuvent réallouer les ressources non utilisées pour la production de pollen et peuvent par conséquent produire plus d'ovules. D'autre part, la reproduction des femelles ne peut se faire que par allo-fécondation alors que les hermaphrodites, peuvent se reproduire à la fois par auto- et allo-fécondation. L'autofécondation s'accompagne en général d'une diminution de fitness de la descendance relativement à la progéniture issue d'allo-fécondation ; ce phénomène est connu sous le nom de dépression de consanguinité. Cette thèse avait pour but de mettre en évidence une éventuelle dépression de consanguinité chez Silene vulgaris, une espèce gynodioïque. Des hermaphrodites, issus de trois vallées alpines, ont été auto- et allo¬fécondés sur deux générations successives. La dépression de consanguinité pouvant s'exprimer à tous les stades de vie d'un individu, plusieurs traits de fitness, allant du nombre de graines par fruit à la production de gamètes ont été mesurés sur différents stades de vie successifs. L'estimation de la dépression de consanguinité totale atteignait des valeurs allant de 0.52 à 0.76 selon la vallée considérée, ce qui indiquerait que les hermaphrodites ont tout intérêt à limiter l'autofécondation et que les femelles ne devraient pas avoir de peine à subsister dans les vallées étudiées. Par la même occasion des mécanismes diminuant la purge potentielle du fardeau génétique, et permettant ainsi le maintien du « niveau » de dépression de consanguinité et par conséquence le maintien de la gynodïoécie ont été mis en évidence. En effet, nos résultats montrent que la dépression de consanguinité s'exprimait tard dans le cycle de vie permettant ainsi à un certain nombre individus consanguins de transmettre leurs allèles délétères à la génération suivante. D'autre part, la croissance in vivo des tubes polliniques d'auto-pollen était plus lente que celle de l'allo-pollen et donc en situation de compétition directe, les ovules devraient plutôt être issus d'allo-fécondation, diminuant ainsi les chances de purges d'allèles délétères. Enfin, l'apparition de femelles dans la progéniture d'hermaphrodites autofécondés diminue aussi les chances de purge d'allèles délétères. Il nous a été impossible de déterminer si l'apparition de femelles dans la descendance d'hermaphrodites autofécondés était due au déterminisme génétique du sexe ou si la différence de sexe ratio entre la descendance auto- et allo-fécondée était due à une éventuelle dépression de consanguinité inhibant la production de pollen. Nous avons observé que S. vulgaris ne présentaient pas uniquement des hermaphrodites et des femelles mais aussi toute sorte d'individus intermédiaires avec un nombre variable d'étamines viables. Nous avons pu mettre' en évidence des corrélations positives entre (1) la différence de sexe ratio (la proportion d'individus produisant du pollen) entre individus consanguins et non consanguins et une estimation de la dépression de consanguinité pour le nombre d'étamines viables d'individus produisant du pollen, ainsi qu'entre (2) la dépression de consanguinité pour le nombre d'étamines viables et celle estimée pour la viabilité du pollen. Chaque corrélation indique soit l'effet d'un (ou plusieurs) gène(s) pléiotropique(s), soit un déséquilibre de liaison entre les gènes. En considérant que ces corrélations sont le résultat d'effet pléiotropiques, la relation entre le nombre d'étamines viables par fleur et la viabilité du pollen, indiquerait un effet négatif de la consanguinité sur la production et la viabilité du pollen due partiellement à un gène majeur. La seconde corrélation indiquerait soit que les gènes responsables de la détermination du sexe agissent aussi sur l'expression de la fonction mâle soit que l'expression du sexe est sujette à la dépression de consanguinité, ou encore un mélange des deux. Aux regards de ces résultats, Silene vulgaris s'est avéré être un bon modèle de compréhension de l'évolution des systèmes de reproduction vers la séparation des sexes.

Anti-60-kDa heat shock protein antibodies in fetal serum: a biomarker for unexplained small for gestational age fetuses.

Introduction: Small for gestational age (SGA) is an important problem affecting 10% of pregnancies and is associated with significant perinatal morbidity. In about 80% of cases, a probable etiology or a major risk factor can be identified. But almost 20% of SGA cases are considered unexplained. The 60-kDa heat shock protein (HSP60) is a highly immunogenic protein whose synthesis is greatly upregulated under nonphysiological conditions. Bacterial and human HSP60 share a high degree of sequence homology, and immunity to conserved epitopes may result in development of autoimmunity following a bacterial infection. We hypothesized that unexplained SGA could be the consequence of immune sensitization to human HSP60. Methods: Unexplained SGA fetuses were identified by ultrasound biometry with normal Doppler velocimetry and with no detectable maternal or fetal abnormalities. Fetal sera were obtained by cordocentesis performed for a karyotype analysis in cases of unexplained SGA (study group) or for screening of Rhesus incompatibility (control group). Fetal sera were tested for HSP60 antigen and for IgG and IgM anti-HSP60 by ELISA as well as for other immune and hematological parameters. Results: Maternal parameters were similar between the 12 study cases and the 23 control cases. The mean gestational age at cordocentesis was 29 weeks. IgM anti-HSP60 was detected in 12 cases (100%) and in no controls (p < 0.00017), while IgG anti-HSP60 was detected in 7 cases (58%) and only 1 control (p < 0.001). Three of the 4 cases with the highest IgM antibody levels died. There were no differences in fetal serum levels of HSP60 antigen or other immune and hematological markers between the two groups. Conclusion: Fetuses with unexplained SGA are positive for IgM and IgG antibody to human HSP60 and the specific IgM antibody level is predictive of fetal mortality. Detection of these antibodies indicates that a placental perturbation and a fetal autoimmune reaction to HSP60 are associated with this developmental delay.

Evolution of uni- and bifactorial sexual compatibility systems in fungi.

Mating systems, that is, whether organisms give rise to progeny by selfing, inbreeding or outcrossing, strongly affect important ecological and evolutionary processes. Large variations in mating systems exist in fungi, allowing the study of their origin and consequences. In fungi, sexual incompatibility is determined by molecular recognition mechanisms, controlled by a single mating-type locus in most unifactorial fungi. In Basidiomycete fungi, however, which include rusts, smuts and mushrooms, a system has evolved in which incompatibility is controlled by two unlinked loci. This bifactorial system probably evolved from a unifactorial system. Multiple independent transitions back to a unifactorial system occurred. It is still unclear what force drove evolution and maintenance of these contrasting inheritance patterns that determine mating compatibility. Here, we give an overview of the evolutionary factors that might have driven the evolution of bifactoriality from a unifactorial system and the transitions back to unifactoriality. Bifactoriality most likely evolved for selfing avoidance. Subsequently, multiallelism at mating-type loci evolved through negative frequency-dependent selection by increasing the chance to find a compatible mate. Unifactoriality then evolved back in some species, possibly because either selfing was favoured or for increasing the chance to find a compatible mate in species with few alleles. Owing to the existence of closely related unifactorial and bifactorial species and the increasing knowledge of the genetic systems of the different mechanisms, Basidiomycetes provide an excellent model for studying the different forces that shape breeding systems.

L'intégration de l'étranger dans la tragédie athénienne : remarques sur la Médée d'Euripide

Both the civic discourse and the religious ritual present in the festival of Great Dionysia make the question of foreigners and their integration a central issue for the Athenian tragedy. The self-image that Athens builds through the tragedy uses this theme to differentiate itself from barbarians and from other Greek cities. Nevertheless there are situations where the integration of the foreigner becomes problematic even in the tragic Athens. Such is in particular the case when the integration involves the marriage. This paper focuses on a case of incompatibility, by confronting the image of Athens in the third stasimon of Euripides' Medea and that of the infanticidal heroine.

Recognition of major histoincompatibilities after transplantation with marrow from HLA closely matched donors.

BACKGROUND: To determine the extent to which major histoincompatibilities are recognized after bone marrow transplantation, we characterized the specificity of the cytotoxic T lymphocytes isolated during graft-versus-host disease. We studied three patients transplanted with marrow from donors who were histoincompatible for different types of HLA antigens. METHODS: Patient 1 was mismatched for one "ABDR-antigen" (HLA-A2 versus A3). Two patients were mismatched for antigens that would usually not be taken into account by standard selection procedures: patient 2 was mismatched for an "HLA-A subtype" (A*0213 versus A*0201), whereas patient 3 was mismatched for HLA-C (HLA-C*0501 versus HLA-C*0701). All three HLA class I mismatches were detected by a pretransplant cytotoxic precursor test. RESULTS: Analysis of the specificity of the cytotoxic T lymphocyte clones isolated after transplantation showed that the incompatibilities detected by the pretransplant cytotoxic precursor assay were the targets recognized during graft-versus-host disease. CONCLUSIONS: Independent of whether the incompatibility consisted of a "full" mismatch, a "subtype" mismatch, or an HLA-C mismatch, all clones recognized the incompatible HLA molecule. In addition, some of these clones had undergone antigen selection and were clearly of higher specificity than the ones established before transplantation, indicating that they had been participating directly in the antihost immune response.