Alternatives to Aerobic Exercise Prescription in Patients with Chronic Heart Failure

Background: Exercise is essential for patients with heart failure as it leads to a reduction in morbidity and mortality as well as improved functional capacity and oxygen uptake (v̇O2). However, the need for an experienced physiologist and the cost of the exam may render the cardiopulmonary exercise test (CPET) unfeasible. Thus, the six-minute walk test (6MWT) and step test (ST) may be alternatives for exercise prescription. Objective: The aim was to correlate heart rate (HR) during the 6MWT and ST with HR at the anaerobic threshold (HRAT) and peak HR (HRP) obtained on the CPET. Methods: Eighty-three patients (58 ± 11 years) with heart failure (NYHA class II) were included and all subjects had optimized medication for at least 3 months. Evaluations involved CPET (v̇O2, HRAT, HRP), 6MWT (HR6MWT) and ST (HRST). Results: The participants exhibited severe ventricular dysfunction (ejection fraction: 31 ± 7%) and low peak v̇O2 (15.2 ± 3.1 mL.kg-1.min-1). HRP (113 ± 19 bpm) was higher than HRAT (92 ± 14 bpm; p < 0.05) and HR6MWT (94 ± 13 bpm; p < 0.05). No significant difference was found between HRP and HRST. Moreover, a strong correlation was found between HRAT and HR6MWT (r = 0.81; p < 0.0001), and between HRP and HRST (r = 0.89; p < 0.0001). Conclusion: These findings suggest that, in the absence of CPET, exercise prescription can be performed by use of 6MWT and ST, based on HR6MWT and HRST

A vegetação do município de Ilhéus, Estado da Bahia: III - caracterização da vegetação pelo valôr dos índices das espécies

The indices found are analysed as a whole and general conclusions are drawn from them which may be of use in understanding many of the problems offered by the local flora (Ilhéus). The first column of the tables presented indicates the biological form of the species, showing the nature of the flora and the constitution of the climax. A total of 200 species of phanerophyta were found; 69 macrophanerophyta (trees), 54 are mesophanerophyta (treelets) and 77 are nanophanerophyta (shrubs). The macrophanerophyta are consequently considered as dominants and the meso-and nanophanerophyta as codominants (the biological forms: chamaephyta, hemicriptophyta, criptophyta, geophyta, therophyta, epiphyta and hydrophyta are subdominants), the more so as the first cover 80% and the others more or less 50%. This points to a climax of trees and a local vegetation mainly composed of trees also. The smaller forms are left out as they are beyond the present scope of this sort of wort in Brazil. The third column of ecological formulae indicates the reaction of the constituent species to light (C = sciophilous, F = photophilous and I = indifferents), the biological types of vegetation (H = hygrophytes, X = xerophytes and M = mesophytes) and the fidelity of the species to the climax. Of the species studied: 25 are pioneers (P. Table I), 63 are accidentals (A. Table II), 35 are companion species (O. Table III), 19 show preferences (E. Table with vitality Vn), 44 are selective (S. Table V) and 13 exclusive species (L. Table VI). This leads to the conclusion that the vegetation of the region is in full reconstitution. As to the ecological characteristics of the 200 species studied, 89 are either pioneers (a class separated by the author) or accidentals; this means that the devastated zones are being reconstituted in the subsere both with members of the prisere and alien species. Of the remaining species, 54 are companion, or accompanying species, which appear in most subclimax, serclímax and quasiclimax associations, and 57 are real constituents of the local climax. As all the species except the pioneers, selectives and exclusives (xerophytes and mesophytes) may be considered as hygrophytes this type evidently predominantes in the region and may constitute a hygrophilous serclimax and quasiclímax. In regard to light 101 are sciophilous, 32 indiferents and 67 photophilous. This leads to the conclusion that the vegetation comprises mainly tolerant species, showing the hygrophilous and mesophilous character of the region with a vegetation composed mostly of trees. The presence a large number of sciophilous species is easy to understand as the hygrophilous and mesophilous habitats and the dominance of trees favour the germination and growth of tolerant species. The last two columns analyse the percentage of individuals present and the occurrent classes to which they belong: 92 species vary between 1 and 9%; 50 between to 10 and 19%; 36 between 20 and 29%; 14 between 30 and 39%; and 8 between 40 and 49%. Only 8 species belong to occurrence class V; 14 to classe IV; 36 to class III; 50 to class II; and 92 to class I. This leads to the conclusion that the local formation is very unsociable and very complex, though the median coverture is 80% and the number of species is very large. The analysis of the data also shows that the climax is being reconstituted in the subsere with elements drawn from the prisere and alien species introduced either by man (following desvastation) or by other consequent factors (such as brusque changes of microclimates due to total or partial destruction). This modifies the subclimax appreciably and apparently also the climax of the local regional subsere. As a final conclusion it is suggested that as in the subsere the pioneer formation is xerophilous, the prisere also beging as a xerosere; but as there are and probably always were hydrophilous formation evolving in the same climate, the local climax is composed of species with medium exactions, that is of relative mesophites.

Cultured human fetal astrocytes can be induced by interferon-gamma to express HLA-DR.

Interferon-gamma (IFN-gamma) modulates the expression of Class II major histocompatibility antigens (MHC), thus providing a potential regulatory mechanism for local immune reactivity in the context of MHC-restricted antigen presentation. Within the central nervous system (CNS), the expression of MHC Class II antigens has been demonstrated on human reactive astrocytes and glioma cells. In order to investigate the modulation of HLA-DR on normal astrocytes, two cell lines were grown from a 20-week-old fetal brain. In situ none of the fetal brain cells expressed HLA-DR as determined by immunohistology on frozen tissue sections. The two cell lines, FB I and FB II, expressed GFAP indicating their astrocytic origin. FB I was HLA-DR negative at the first tissue culture passages, but could be induced to express HLA-DR when treated with 500 U/ml IFN-gamma. FB II was spontaneously HLA-DR positive in the early passages, lost the expression of this antigen after 11 passages and could also be induced to express HLA-DR by IFN-gamma. The induction of HLA-DR expression was demonstrated both by a binding RIA and by immunoprecipitation using a monoclonal antibody (MAB) directed against a monomorphic determinant of HLA-DR. The HLA-DR alloantigens were determined on FB II cells after IFN-gamma treatment, by immunofluorescence and by cytotoxicity assays, and were shown to be DR4, DR6, Drw52, DRw53 and DQwl. These results show that human fetal astrocytes can be induced to express HLA-DR by IFN-gamma in vitro and support the concept that astrocytes may function as antigen-presenting cells.

The nature of autoantigens

1. Autoimmunity in deisease is driven by autoantigen; 2. Cell surface molecules may stimulate autoreactive T-helpers if call II MHC is expressed; special factors may predispose to the ease of class II induction; 3. Soluble autoantigens may be focussed by primed B-cells and processed for presentation to T-cell; 4. autoantigenicity may be influenced by metabolic events: (a) Poorly iodinated thyroglobulin does not induce thyroiditis; (b) IgG rheumatoid arthritis has galactose deficient Fc oligosaccharides. Glycosylation defects may prove to have wide implications.

Correlation of wear in vivo and six laboratory wear methods.

OBJECTIVE: We examined the correlation between clinical wear rates of restorative materials and enamel (TRAC Research Foundation, Provo, USA) and the results of six laboratory test methods (ACTA, Alabama (generalized, localized), Ivoclar (vertical, volumetric), Munich, OHSU (abrasion, attrition), Zurich). METHODS: Individual clinical wear data were available from clinical trials that were conducted by TRAC Research Foundation (formerly CRA) together with general practitioners. For each of the n=28 materials (21 composite resins for intra-coronal restorations [20 direct and 1 indirect], 5 resin materials for crowns, 1 amalgam, enamel) a minimum of 30 restorations had been placed in posterior teeth, mainly molars. The recall intervals were up to 5 years with the majority of materials (n=27) being monitored, however, only for up to 2 years. For the laboratory data, the databases MEDLINE and IADR abstracts were searched for wear data on materials which were also clinically tested by TRAC Research Foundation. Only those data for which the same test parameters (e.g. number of cycles, loading force, type of antagonist) had been published were included in the study. A different quantity of data was available for each laboratory method: Ivoclar (n=22), Zurich (n=20), Alabama (n=17), OHSU and ACTA (n=12), Munich (n=7). The clinical results were summed up in an index and a linear mixed model was fitted to the log wear measurements including the following factors: material, time (0.5, 1, 2 and 3 years), tooth (premolar/molar) and gender (male/female) as fixed effects, and patient as random effect. Relative ranks were created for each material and method; the same was performed with the clinical results. RESULTS: The mean age of the subjects was 40 (±12) years. The materials had been mostly applied in molars (81%) and 95% of the intracoronal restorations were Class II restorations. The mean number of individual wear data per material was 25 (range 14-42). The mean coefficient of variation of clinical wear data was 53%. The only significant correlation was reached by OHSU (abrasion) with a Spearman r of 0.86 (p=0.001). Zurich, ACTA, Alabama generalized wear and Ivoclar (volume) had correlation coefficients between 0.3 and 0.4. For Zurich, Alabama generalized wear and Munich, the correlation coefficient improved if only composites for direct use were taken into consideration. The combination of different laboratory methods did not significantly improve the correlation. SIGNIFICANCE: The clinical wear of composite resins is mainly dependent on differences between patients and less on the differences between materials. Laboratory methods to test conventional resins for wear are therefore less important, especially since most of them do not reflect the clinical wear.

CD28/CTLA4-B7 interaction is dispensable for T cell stimulation by mouse mammary tumor virus superantigen but not for B cell differentiation and virus dissemination.

B cells are the primary targets of infection for mouse mammary tumor virus (MMTV). However, for productive retroviral infection, T cell stimulation through the virally-encoded superantigen (SAG) is necessary. It activates B cells and leads to cell division and differentiation. To characterize the role of B cell differentiation for the MMTV life cycle, we studied the course of infection in transgenic mice deficient for CD28/CTLA4-B7 interactions (mCTLA4-H gamma 1 transgenic mice). B cell infection occurred in CTLA4-H gamma 1 transgenic mice as integrated proviral DNA could be detected in draining lymph node cells early after infection by polymerase chain reaction analysis. In mice expressing I-E, B cells were able to present the viral SAG efficiently to V beta 6+ T cells. These cells expanded specifically and were triggered to express the activation marker CD69. Further stages of progression of infection appeared to be defective. Kinetics experiments indicated that T and B cell stimulation stopped more rapidly than in control mice. B cells acquired an activated CD69+ phenotype, were induced to produce IgM but only partially switched to IgG secretion. Finally, the dissemination of infected cells to other lymph nodes and spleen was reduced and the peripheral deletion of V beta 6+ T cells was minimal. In contrast, in mice lacking I-E, T cell stimulation was also impaired and B cell activation undetectable. These data implicate B7-dependent cellular interactions for superantigenic T cell stimulation by low-affinity TCR ligands and suggest a role of B cell differentiation in viral dissemination and peripheral T cell deletion.

Transcriptional regulation of CD4 gene expression by T cell factor-1/beta-catenin pathway.

By interacting with MHC class II molecules, CD4 facilitates lineage development as well as activation of Th cells. Expression of physiological levels of CD4 requires a proximal CD4 enhancer to stimulate basic CD4 promoter activity. T cell factor (TCF)-1/beta-catenin pathway has previously been shown to regulate thymocyte survival via up-regulating antiapoptotic molecule Bcl-xL. By both loss and gain of function studies, in this study we show additional function of TCF-1/beta-catenin pathway in the regulation of CD4 expression in vivo. Mice deficient in TCF-1 displayed significantly reduced protein and mRNA levels of CD4 in CD4+ CD8+ double-positive (DP) thymocytes. A transgene encoding Bcl-2 restored survival but not CD4 levels of TCF-1(-/-) DP cells. Thus, TCF-1-regulated survival and CD4 expression are two separate events. In contrast, CD4 levels were restored on DP TCF-1(-/-) cells by transgenic expression of a wild-type TCF-1, but not a truncated TCF-1 that lacks a domain required for interacting with beta-catenin. Furthermore, forced expression of a stabilized beta-catenin, a coactivator of TCF-1, resulted in up-regulation of CD4. TCF-1 or stabilized beta-catenin greatly stimulated activity of a CD4 reporter gene driven by a basic CD4 promoter and the CD4 enhancer. However, mutation of a potential TCF binding site located within the enhancer abrogated TCF-1 and beta-catenin-mediated activation of CD4 reporter. Finally, recruitment of TCF-1 to CD4 enhancer was detected in wild-type but not TCF-1 null mice by chromatin-immunoprecipitation analysis. Thus, our results demonstrated that TCF/beta-catenin pathway enhances CD4 expression in vivo by recruiting TCF-1 to stimulate CD4 enhancer activity.

The antibody response in mice to carrier-free synthetic polymers of Plasmodium falciparum circumsporozoite repetitive epitope is I-Ab-restricted: possible implications for malaria vaccines.

The immunogenicity of a novel synthetic peptide consisting of an average of 40 (Asn-Ala-Asn-Pro) repeats of the circumsporozoite protein of Plasmodium falciparum, (NANP)40, was studied in mice without using any carrier proteins. First, high titers of anti-(NANP)40 antibodies could be obtained after immunization of C57BL/6 mice. These antibodies also reacted with an extract of mosquitoes infected with P. falciparum sporozoites. C57BL/6 nu/nu mice did not produce antibodies against (NANP)40. Secondly, when 14 strains of mice with nine different H-2 haplotypes were immunized with (NANP)40 without carrier, only H-2b mice were found to produce anti-(NANP)40 antibodies, whereas all non-H-2b mice were consistently unresponsive. This response was demonstrated to be I-A-linked by using recombinant and mutant mice. I-Ab [B10.A(5R)] mice produced anti-(NANP)40 antibodies as well as H-2b inbred mice. B6CH-2bm12 I-Ab-mutant mice showed only a very low response. Third, the antibody response against (NANP)40 could be induced in nonresponder mice by immunization with the peptide coupled to a carrier protein. In view of the existence of such an exceptional H-2b restriction in the response to sporozoite synthetic peptides in mice, the triggering of peptide-specific T cell responses in humans receiving sporozoite malaria vaccines might be difficult to achieve.

A critical role for the T cell receptor alpha-chain connecting peptide domain in positive selection of CD1-independent NKT cells.

Natural killer T (NKT) cells are a subset of mature alpha beta TCR(+) cells that co-express NK lineage markers. Whereas most NKT cells express a canonical Valpha14/Vbeta8.2 TCR and are selected by CD1d, a minority of NKT cells express a diverse TCR repertoire and develop independently of CD1d. Little is known about the selection requirements of CD1d-independent NKT cells. We show here that NKT cells develop in RAG-deficient mice expressing an MHC class II-restricted transgenic TCR (Valpha2/Vbeta8.1) but only under conditions that lead to negative selection of conventional T cells. Moreover development of NKT cells in these mice is absolutely dependent upon an intact TCR alpha-chain connecting peptide domain, which is required for positive selection of conventional T cells via recruitment of the ERK signaling pathway. Collectively our data demonstrate that NKT cells can develop as a result of high avidity TCR/MHC class II interactions and suggest that common signaling pathways are involved in the positive selection of CD1d-independent NKT cells and conventional T cells.

The use of the murine model of infection with Leishmania major to reveal the antagonistic effects that IL-4 can exert on T helper cell development and demonstrate that these opposite effects depend upon the nature of the cells targeted for IL-4 signaling.

In contrast to mice from the majority of inbred strains, BALB mice develop aberrant Th2 responses and suffer progressive disease after infection with Leishmania major. These outcomes depend on the production of Interleukin 4, during the first 2 d of infection, by CD4+ T cells that express the Vbeta4-Valpha8 T cell receptors specific for a dominant I-A(d) restricted epitope of the LACK antigen from L. major. In contrast to this well established role of IL-4 in Th2 cell maturation, we have recently shown that, when limited to the initial period of activation of dendritic cells by L. major preceding T cell priming, IL-4 directs DCs to produce IL-12, promotes Th1 cell maturation and resistance to L. major in otherwise susceptible BALB/c mice. Thus, the antagonistic effects that IL-4 can have on Th cell development depend upon the nature of the cells (DCs or primed T cells) targeted for IL-4 signaling.

Cell populations in lesions of cutaneous leishmaniasis of leishmania (L.) amazonensis- infected rhesus macaques, Macaca mulatta

The cellular nature of the infiltrate in cutaneous lesion of rhesus monkeys experimentally infected with Leishmania (L.) amazonensis was characterized by immunohistochemistry. Skin biopsies from infected animals with active or healing lesions were compared to non-infected controls (three of each type) to quantitate inflammatory cell types. Inflammatory cells (composed of a mixture of T lymphocyte subpopulations, macrophages and a small number of natural killer cells and granulocytes) were more numerous in active lesions than in healing ones. T-cells accounted for 44.7 ± 13.1% of the infiltrate in active lesions (versus CD2+= 40.3 ± 5.7% in healing lesions) and T-cell ratios favor CD8+ cells in both lesion types. The percentage of cells expressing class II antigen (HLA-DR+) in active lesions (95 ± 7.1%) was significantly higher (P < 0.005) from the healing lesions (42.7 ± 12.7%). Moreover, the expression of the activation molecules CD25 (@ 16%), the receptor for interleukin-2, suggests that many T cells are primed and proliferating in active lesions. Distinct histopathological patterns were observed in lesions at biopsy, but healing lesions contained more organized epithelioid granulomas and activated macrophages, followed by fibrotic substitution. The progression and resolution of skin lesions appears to be very similar to that observed in humans, confirming the potential for this to be used as a viable model to study the immune response in human cutaneous leishmaniasis.

Influenza vaccination and humoral alloimmunity in solid organ transplant recipients.

Annual influenza vaccination is recommended in solid organ transplant (SOT) recipients. However, concerns have been raised about the impact of vaccination on antigraft alloimmunity. We evaluated the humoral alloimmune responses to influenza vaccination in a cohort of SOT recipients between October 2008 and December 2011. Anti-HLA antibodies were measured before and 4-8 weeks after influenza vaccination using a solid-phase assay. Overall, 169 SOT recipients were included (kidney = 136, lung = 26, liver = 3, and combined = 4). Five (2.9%) of 169 patients developed de novo anti-HLA antibodies after vaccination, including one patient who developed donor-specific antibodies (DSA) 8 months after vaccination. In patients with pre-existing anti-HLA antibodies, median MFI was not significantly different before and after vaccination (P = 0.73 for class I and P = 0.20 for class II anti-HLA antibodies) and no development of de novo DSA was observed. Five episodes of rejection (2.9%) were observed within 12 months after vaccination, and only one patient had de novo anti-HLA antibodies. The incidence of development of anti-HLA antibodies after influenza vaccination in our cohort of SOT recipients was very low. Our findings indicate that influenza vaccination is safe and does not trigger humoral alloimmune responses in SOT recipients.

Human invariant V alpha 24-J alpha Q TCR supports the development of CD1d-dependent NK1.1+ and NK1.1- T cells in transgenic mice.

A sizable fraction of T cells expressing the NK cell marker NK1.1 (NKT cells) bear a very conserved TCR, characterized by homologous invariant (inv.) TCR V alpha 24-J alpha Q and V alpha 14-J alpha 18 rearrangements in humans and mice, respectively, and are thus defined as inv. NKT cells. Because human inv. NKT cells recognize mouse CD1d in vitro, we wondered whether a human inv. V alpha 24 TCR could be selected in vivo by mouse ligands presented by CD1d, thereby supporting the development of inv. NKT cells in mice. Therefore, we generated transgenic (Tg) mice expressing the human inv. V alpha 24-J alpha Q TCR chain in all T cells. The expression of the human inv. V alpha 24 TCR in TCR C alpha(-/-) mice indeed rescues the development of inv. NKT cells, which home preferentially to the liver and respond to the CD1d-restricted ligand alpha-galactosylceramide (alpha-GalCer). However, unlike inv. NKT cells from non-Tg mice, the majority of NKT cells in V alpha 24 Tg mice display a double-negative phenotype, as well as a significant increase in TCR V beta 7 and a corresponding decrease in TCR V beta 8.2 use. Despite the forced expression of the human CD1d-restricted TCR in C alpha(-/-) mice, staining with mCD1d-alpha-GalCer tetramers reveals that the absolute numbers of peripheral CD1d-dependent T lymphocytes increase at most by 2-fold. This increase is accounted for mainly by an increased fraction of NK1.1(-) T cells that bind CD1d-alpha-GalCer tetramers. These findings indicate that human inv. V alpha 24 TCR supports the development of CD1d-dependent lymphocytes in mice, and argue for a tight homeostatic control on the total number of inv. NKT cells. Thus, human inv. V alpha 24 TCR-expressing mice are a valuable model to study different aspects of the inv. NKT cell subset.

New insights into the long-term evolutionary history of the avian MHC

SummaryGene duplication and neofunctidnalization are important processes in the evolution of phenotypic complexity. They account for important evolutionary novelties that confer ecological adaptation, such as the major histocompatibility complex (MHC), a multigene family with a central role in vertebrates' adaptive immune system. Multigene families, which evolved in large part through duplication, represent promising systems to study the still strongly depbated relative roles of neutral and adaptive processes in the evolution of phenotypic complexity. Detailed knowledge on ecological function and a well-characterized evolutionary history place the mammals' MHC amongst ideal study systems. However mammalian MHCs usually encompass several million base pairs and hold a large number of functional and non-functional duplicate genes, which makes their study complex. Avian MHCs on the other hand are usually way more compact, but the reconstruction of. their evolutionary history has proven notoriously difficult. However, no focused attempt has been undertaken so far to study the avian MHC evolutionary history in a broad phylogenetic context and using adequate gene regions.In the present PhD, we were able to make important contributions to the understanding of the long-term evolution of the avian MHC class II Β (MHCI1B). First, we isolated and characterized MHCIIB genes in barn owl (Tyto alba?, Strigiformes, Tytonidae), a species from an avian lineage in which MHC has not been studied so far. Our results revealed that with only two functional MHCIIB genes the MHC organization of barn owl may be similar to the 'minimal essential' MHC of chicken (Gallus gallus), indicating that simple MHC organization may be ancestral to birds. Taking advantage of the sequence information from barn owl, we studied the evolution of MHCIIB genes in 13 additional species of 'typical' owls (Strigiformes, Strigidae). Phylogenetic analyses revealed that according to their function, in owls the peptide-binding region (PBR) encoding exon 2 and the non-PBR encoding exon 3 evolve by different patterns. Exon 2 exhibited an evolutionary history of positive selection and recombination, while exon 3 traced duplication history and revealed two paralogs evolving divergently from each other in owls, and in a shorebird, the great snipe {Gallinago media). The results from exon 3 were the first ever from birds to demonstrate gene orthology in species that diverged tens of millions of years ago, and strongly questioned whether the taxa studied before provided an adequate picture of avian MHC evolution. In a follow-up study, we aimed at explaining a striking pattern revealed by phylogenetic trees analyzing the owl sequences along with MHCIIB sequences from other birds: One owl paralog (termed DAB1) grouped with sequences of passerines and falcons, while the other (DAB2) grouped with wildfowl, penguins and birds of prey. This could be explained by either a duplication event preceding the evolution of these bird orders, or by convergent evolution of similar sequences in a number of orders. With extensive phylogenetic analyses we were able to show, that indeed a duplication event preceeded the major avian radiation -100 my ago, and that following this duplication, the paralogs evolved under positive selection. Furthermore, we showed that the divergently evolving amino acid residues in the MHCIIB-encoded β-chain potentially interact with the MHCI I α-chain, and that molecular coevolution of the interacting residues may have been involved in the divergent evolution of the MHCIIB paralogs.The findings of this PhD are of particular interest to the understanding of the evolutionary history of the avian MHC and, by providing essential information on long-term gene history in the avian MHC, open promising perspectives for advances in the understanding of the evolution of multigene families in general, and for avian MHC organization in particular. Amongst others I discuss the importance of including protein structure in the phylogenetic study of multigene families, and the roles of ecological versus molecular selection pressures. I conclude by providing a population genomic perspective on avian MHC, which may serve as a basis for future research to investigate the relative roles of neutral processes involving effective population size effects and of adaptation in the evolution of avian MHC diversity and organization.RésuméLa duplication de gènes et leur néo-fonctionnalisation sont des processus importants dans l'évolution de la complexité phénotypique. Ils sont impliqués dans l'apparition d'importantes nouveautés évolutives favorisant l'adaptation écologique, comme c'est le cas pour le complexe majeur d'histocompatibilité classe II Β (CMH II Β). Nous avons isolé et caractérisé les gènes CMH I IB de la chouette effraie (Tyto alba; Strigiformes, Tytonidae), une espèce appartenant à une lignée aviaire dont le CMH n'avait pas été étudié jusqu'ici. Avec uniquement deux gènes CMHIIB fonctionnels, l'organisation CMH de la chouette effraie semble être comparable à celle "minimale" du poulet (Gallus gallus), ce qui suggère qu'une organisation simple du CMH pourrait être ancestrale chez les oiseaux. En se basant sur l'information obtenue pour cette espèce, nous avons ensuite étudié l'évolution des gènes CMHIIB chez 13 espèces de chouettes "typiques" (Strigiformes, Strigidae). Les analyses phylogénétiques ont révélé que chez les chouettes, selon leur fonction, l'exon 2 codant pour la 'peptide-binding region' (PBR) et l'exon 3 ne codant pas pour la région PBR évoluent de manière distincte. L'exon 2 montre une histoire évolutive de sélection positive et recombinaison, tandis que l'exon 3 retrace l'histoire de duplication et révèle deux paralogues évoluant de façon divergente chez les chouettes, ainsi que chez un limicole, la bécassine double (Gallinago media). Les résultats découlant de l'analyse de l'exon 3 ont montré pour la première fois chez les oiseaux une orthologie de gènes chez des espèces ayant divergé il y a des dizaines de millions d'années. Dans une deuxième étude, nous avons voulu expliquer le pattern surprenant révélé par les arbres phylogénétiques lorsque les séquences CMHIIB des chouettes sont analysées avec les séquences d'autres oiseaux: un paralogue de chouette (appelé DABI) forme un groupe avec les séquences de passereaux et faucons, tandis que l'autre (DAB2) se regroupe avec les gallo-ansériformes, les manchots et les rapaces diurnes. Ceci pourrait être expliqué soit par une duplication qui a précédé l'évolution de ces ordres aviaires soit par évolution convergente dans un certain nombre d'ordres. Grâce à des analyses phylogénétiques approfondies, nous avons pu montrer qu'un événement de duplication a effectivement précédé la radiation aviaire principale d'il y a environ 100 millions d'années, et qu'après cette duplication les paralogues ont évolué sous sélection positive. De plus, les résidus d'acides aminés évoluant de façon divergente dans la chaîne β codée par le CMHIIB interagissent potentiellement avec la chaîne α codée par le CMHII, et que la coévolution moléculaire de ces résidus pourrait être à la base de l'évolution divergente des paralogues CMHIIB.Dans cette thèse sont discutés entre autres l'importance d'inclure la structure des protéines dans l'étude phylogénétique des familles multigéniques, ainsi que les rôles respectifs des pressions sélectives écologique et moléculaire. La conclusion comporte une perspective sur la génomique des populations du CMH aviaire, qui pourrait servir de base pour de futures recherches sur les rôles relatifs joués par Îes processus neutres comprenant les effets de la taille efficace des populations et l'adaptation dans l'évolution de la diversité et l'organisation du MHC aviaire.

Biomphalaria tenagophila potencial vector of Schistosoma mansoni in the Paraná River basin (Argentina and Paraguay)

Susceptibility and compatibility experiments were carried out with 700 Biomphalaria tenagophila from the Paraná River basin exposed to infection with Schistosoma mansoni. Individual infection was performed with 10 miracidia of SJ2 strain from the Paraiba valley (Brazil) originally infective to B. tenagophila. These snails were laboratory-breed progeny of B. tenagophila collected from six localities of Argentina and one from Paraguay. From Argentina: Rincón de Vences (7%) and Posadas (11%) became infected with S. mansoni and the calculation of Frandsen's index (TCP/100) shows that they were Class II poorly compatible. Those snails from Goya (22%), Maloyas (5%), and Berón de Astrada (3%) were Class III compatible to the S. mansoni. None of the 100 snails exposed from Caá-Catí became infected (Class 0 incompatible). Tested samples from Paraguay (Encarnación) were infected (20%) and compatible (Class III). It was also studied the persistence of the infection in 244 snails of the first generation (F1) of those that were susceptible from three places. It was demonstrated an increment of the susceptibility in the F1 from Maloyas (chi2 = 27.22; p = 0.0001) and Posadas (chi2 = 4.24; p = 0.04). The results point out the possibility that schistosomiasis might be able to spread into the Paraná River basin where B. tenagophila exists.