Studies on cathepsin B of Eimeria tenella and pyroglutamyl peptidase of Leishmania major

A sequence encoding a cathepsin B-like cysteine peptidase of the clan CA, family C1 was identified in the genome database of E. tenella. The sequence corresponded to a single copy gene, and did not carry any introns. The E. tenella enzyme, sharing 42% identity with the Toxoplasma gondii toxopain-1, which is reportedly involved in the invasion of host cells, was expressed as a soluble inactive zymogen in E. coli. Recombinant cathepsin B of E. tenella was functionally expressed as a mature enzyme in the Pichia pastoris inducible system as a glycosylation protein, but the glycosylations did not apparently affect the enzyme’s activity. The biochemical characteristics of the recombinant enzyme were consistent with what has been reported in the literature for cathepsin Bs. The cathepsin B of E. tenella was detected in oocyst and sporozoite extracts, and, more specifically, in microneme preparations. In the sexual stages, the enzyme localised to mature macrogametes in discrete granules, the size and location of which suggest that they are wall-forming bodies, organelles involved in the oocyst wall formation in Eimeria. These data suggest that the cathepsin B may play roles in both cell invasion by sporozoites and the formation of the protective wall of the oocyst. A single copy gene encoding a PPI was identified in the genome database of L. major. Active recombinant enzyme was successfully produced in E. coli and its biochemical properties coincided with those of mammalian PPIs. The active site catalytic triad E101, C210, and H234 (L. major PPI numbering) was confirmed by mutagenesis. The PPI activity was detected in L. major promastigotes, and the enzyme localised to the parasite cytoplasm. PPI knockout mutants were generated, and knock-out of the PPI activity did not seem to induce a phenotype in L. major. The parasites retained the properties in vivo and in vitro of L. major wild type cells. The over-expression of the active PPI in L. major promastigotes seemed to impair metacyclogenesis and in vivo infectivity, while the over-expression of the C210A mutant did not have any detrimental effect

Disease and De Soto: A Bioarchaeological Approach to the Introduction of Malaria to the Southeast US

It is well known through documentation in historical accounts that numerous diseases were introduced to the Americas during the time of Spanish and French exploration. Diseases such as smallpox, measles and yellow fever have been credited in playing a role in the Spanish conquest of the New World through drastic Native American population decline. Many researchers have studied the biological consequences of European contact, some using direct skeletal analyses to study changes in Native American health and disease. However, one major population disease that has not been part of these discussions is malaria. This is mostly due to the current paradigm in epidemiological history that malaria was first introduced by African slaves during the colonial period slave trades. In addition, the skeletal markers of this disease have not been known until recently. However, recent advances in bioarchaeology have developed a method to identify and diagnose malaria in skeletal remains. This study investigates the possible introduction of malaria to the Central Mississippi Valley (CMV) and Trans-Mississippi South (TMS) regions by the Hernando de Soto expedition. Numerous factors hint at the possibility that the members of the expedition were the first to introduce malaria to the region during their explorations in AD 1541-1542. These factors include endemic malaria in Spain during the age of exploration, the inclusion of numerous African slaves in the crew, the ability of the Plasmodium parasite to lay dormant within a hosts’ liver for an extended period of time, and various ecological characteristics of the protohistoric CMV/TMS environment. To investigate this possibility, the newly developed bioarchaeological method for identifying malaria in the skeletal record was employed on Native American skeletal data from 113 CMV/TMS sites spanning temporally from 8,000 BC to AD 1920. Results of this study confirm the presence and increase of malaria indicators in the region during the protohistoric period, which strongly suggests that members of the de Soto expedition could have been the first to introduce malaria to the region. These results will enhance our understanding of the spread of malaria to the New World, and contribute to studies on European contact with indigenous populations

Doctor of Philosophy in Physics

dissertationLithium is generally considered to be a simple metal, given its simple electronic structure with one valence electron. It is considered to follow a nearly free electron model and have a nearly spherical Fermi surface. However, away from ambient conditions, the behavior of lithium become much less simple. Under high pressures, lithium undergoes a series of symmetry-breaking phase transitions, even a metal to insulator transition; at low temperatures, lithium also undergoes a temperature-driven martensitic transformation. In this work, these deviations from simple models in lithium are investigated, both at ambient pressure and under high pressures, from the relative high temperature phenomenon of melting to low temperature measurements of superconductivity

On the reflection of Alfvén waves and its implication for Earth's core modelling

Alfvén waves propagate in electrically conducting fluids in the presence of a magnetic field. Their reflection properties depend on the ratio between the kinematic viscosity and the magnetic diffusivity of the fluid, also known as the magnetic Prandtl number Pm. In the special case, Pm = 1, there is no reflection on an insulating, no-slip boundary, and the incoming wave energy is entirely dissipated in the boundary layer. We investigate the consequences of this remarkable behaviour for the numerical modelling of torsional Alfvén waves (also known as torsional oscillations), which represent a special class of Alfvén waves, in rapidly rotating spherical shells. They consist of geostrophic motions and are thought to exist in the fluid cores of planets with internal magnetic field. In the geophysical limit Pm ≪ 1, these waves are reflected at the core equator, but they are entirely absorbed for Pm = 1. Our numerical calculations show that the reflection coefficient at the equator of these waves remains below 0.2 for Pm ≥ 0.3, which is the range of values for which geodynamo numerical models operate. As a result, geodynamo models with no-slip boundary conditions cannot exhibit torsional oscillation normal mode

Création artistique et relation esthétique : objets, cadres catégoriels et fonctions

Jean-Marie Schaeffer, directeur d’études Le fait esthétique I Le séminaire de cette année a été consacré en un premier moment à la mise en place du cadre méthodologique de l’analyse du fait esthétique. Le cadre méthodologique retenu est le cadre « naturaliste », le terme désignant ici une approche non-réductionniste (le naturalisme biologique), qu’on a essayé de distinguer du naturalisme réductionniste (cartésien et physicaliste). Après avoir distingué la problématique esthétique de la problé..

Quelles vérités pour quelles fictions?

RésuméLa fiction est en général considérée comme une notion univoque. Or, le terme renvoie selon les contextes à des faits très différents, voire incompatibles: illusion cognitive, leurre, postulat d’indétermination ontologique, expérience de pensée. La tendance actuelle qui consiste à interpréter les textes ethnographiques ou historiographiques comme relevant du régime fictionnel n’est pas faite pour clarifier la situation. L’hypothèse défendue ici est celle d’une spécificité irréductible de la fiction artistique fondée sur une détermination qui n’est pas d’ordre sémantique mais pragmatique: cristallisation culturelle d’une compétence mentale (la simulation) et interactionnelle (la feintise ludique) particulière, la fiction artistique se distingue à la fois des autres types de fiction (qui relèvent d’une définition sémantique) et des récits véridictionnels (pour lesquels la question de la référentialité est la pierre de touche).AbstractFiction is usually considered to be an unequivocal concept. However this term refers to quite different, even incompatible, facts depending on the context: illusions, artifices, the postulate of ontological indetermination, and thought experiments. The current tendency of interpreting anthropological or historical texts as fiction does not clarify the situation. The hypothesis is defended that «artistic fiction» has an irreducible specificity, which is determined pragmatically instead of semantically: the cultural crystallization of a mental (simulation) and an interactional (pretending to play) competence. This sort of fiction thus stands apart from other types (which answer to a semantic definition) and from veridical narratives (where the question of referentiality is the touchstone)

O corpo é imagem

A importância da imagem em nossa tradição cultural deve-se ao fato de ela ser lugar do pensamento do corpo. No entanto, essa suposta generalidade antropológica da relação entre imagem e corpo não é óbvia. Desenvolveremos aqui a hipótese de que a conjunção entre imagem e pensamento do corpo, longe de ser universal, é traço histórico da civilização cristã. O trabalho que está na base dessa hipótese originou-se de minha colaboração na exposição coletiva Qu’est-ce qu’un corps, inaugurada em junho de 2006 no Museu do Quai Branly em Paris

Création artistique et relation esthétique : objets, cadres catégoriels et fonctions

Jean-Marie Schaeffer, directeur d’études Le fait esthétique II Durant cette année, ce séminaire s’est intéressé à trois champs de problèmes. Au premier semestre, J.-M. Schaeffer a exploré la question de l’attention esthétique dans le domaine sonore en général et dans le domaine musical en particulier. Après avoir abordé la dichotomie « classique » mais hautement problématique entre son et bruit nous nous sommes intéressés aux travaux psychocognitifs étudiant la perception sonore, ainsi qu’aux..

Création artistique et relation esthétique : objets, cadres catégoriels et fonctions

Jean-Marie Schaeffer, directeur d’études La formation des préférences esthétiques et artistiques Après avoir étudié pendant les années précédentes la composante cognitive de l’expérience esthétique, nous avons travaillé cette année sur sa dimension appréciative. Après une analyse générale de la notion d’émotion telle qu’elle est étudiée actuellement dans le domaine de la psychologie des émotions, le séminaire s’est intéressé à la question plus spécifique du (dé-) plaisir – notion centrale dan..