A Major Role for the Plasmodium falciparum ApiAP2 Protein PfSIP2 in Chromosome End Biology

The heterochromatic environment and physical clustering of chromosome ends at the nuclear periphery provide a functional and structural framework for antigenic variation and evolution of subtelomeric virulence gene families in the malaria parasite Plasmodium falciparum. While recent studies assigned important roles for reversible histone modifications, silent information regulator 2 and heterochromatin protein 1 (PfHP1) in epigenetic control of variegated expression, factors involved in the recruitment and organization of subtelomeric heterochromatin remain unknown. Here, we describe the purification and characterization of PfSIP2, a member of the ApiAP2 family of putative transcription factors, as the unknown nuclear factor interacting specifically with cis-acting SPE2 motif arrays in subtelomeric domains. Interestingly, SPE2 is not bound by the full-length protein but rather by a 60kDa N-terminal domain, PfSIP2-N, which is released during schizogony. Our experimental re-definition of the SPE2/PfSIP2-N interaction highlights the strict requirement of both adjacent AP2 domains and a conserved bipartite SPE2 consensus motif for high-affinity binding. Genome-wide in silico mapping identified 777 putative binding sites, 94% of which cluster in heterochromatic domains upstream of subtelomeric var genes and in telomere-associated repeat elements. Immunofluorescence and chromatin immunoprecipitation (ChIP) assays revealed co-localization of PfSIP2-N with PfHP1 at chromosome ends. Genome-wide ChIP demonstrated the exclusive binding of PfSIP2-N to subtelomeric SPE2 landmarks in vivo but not to single chromosome-internal sites. Consistent with this specialized distribution pattern, PfSIP2-N over-expression has no effect on global gene transcription. Hence, contrary to the previously proposed role for this factor in gene activation, our results provide strong evidence for the first time for the involvement of an ApiAP2 factor in heterochromatin formation and genome integrity. These findings are highly relevant for our understanding of chromosome end biology and variegated expression in P. falciparum and other eukaryotes, and for the future analysis of the role of ApiAP2-DNA interactions in parasite biology

Triterpenos pentacíclicos e esteróides da casca do uchi (Sacoglottis uchi, Humiriaceae)

The ethanol extract from stem bark of Sacoglottis uchi Huber (popularly known as \x93uchi\x94 in the Amazon Region) was submitted to chromatographic fractionation. The dichloromethane fractions provided the pentacyclic triterpene 3-oxo-friedelin (1). The dichloromethane:methanol fractions provided the pentacyclic triterpenes pseudotaraxasterol (2), lupeol (3), a-amyrin (4), betulin (5), and methyl 2ß,3ß-dihydroxy-urs-12-en-28-oate (6) and a mixture of the steroids sitosterol (7) and stigmasterol (8). Their chemical structures were determined by NMR spectroscopy and comparison with spectroscopic data from the literature. All compounds are described for the first time in this species.O extrato etanólico da casca do caule de Sacoglottis uchi Huber (conhecida popularmente como \x93uchi\x94 na Amazônia) foi submetido a fracionamento cromatográfico. As frações eluídas com diclorometano forneceram o triterpeno pentacíclico 3-oxo-friedelina (1). As frações em diclorometano:metanol forneceram os triterpenos pentacíclicos pseudotaraxasterol (2), lupeol (3), a-amirina (4), betulina (5) e 2ß,3ß-di-hidroxi-urs-12-en-28-oato de metila (6), além de uma mistura dos esteróides sitosterol (7) e estigmasterol (8). Suas estruturas químicas foram determinadas por espectroscopia de RMN e comparação com os dados espectroscópicos descritos na literatura. Todas as substâncias isoladas são descritas pela primeira vez nesta espécie

Low-field and high-field characterization of THUNDER actuators

Abstract. THUNDER (THin UNimorph DrivER) actuators are pre-stressed piezoelectric devices developed at NASA Langley Research Center (LaRC) that exhibit enhanced strain capabilities. As a result, they are of interest in a variety of aerospace applications. Characterization of their performance as a function of electric field, temperature and frequency is needed in order to optimize their operation. Towards that end, a number of THUNDER devices were obtained from FACE International Co. with a stainless steel substrate varying in thickness from 1 mil to 20 mils. The various devices were evaluated to determine low-field and high-field displacement as well as the polarization hysteresis loops. The thermal stability of these drivers was evaluated by two different methods. First, the samples were thermally cycled under electric field by systematically increasing the maximum temperature from 25°C to 200°C while the displacement was being measured. Second, the samples were isothermally aged at 0°C, 50°C, 100°C, and 150°C in air, and the isothermal decay of the displacement was measured at room temperature as a function of time. Key words. piezoelectric, pre-stressed ceramic, hysteresis, temperature effect, isothermal aging Subject classification. Materials 1. Introduction. This work describes the results of a characterization study of THin UNimorph-like DrivER (THUNDER) actuators to determine the effects of metal thickness on free displacement at both sub-switching an

Concours d’internat des Hôpitaux de Lomé de 1974 à 2006 : etat des lieux

Objectif: Faire l’état des lieux du concours d’internat des hôpitaux de LoméMéthodologie: Etude transversale descriptive réalisée à la faculté des sciences de la santé de l'université de Lomé et dans les centres hospitaliers universitaires de Lomé. Elle a consisté au dépouillement des documents et des archives du concours d’internat des hôpitaux de Lomé et en des entretiens semi-directs avec un échantillon d’individus ayant un rapport avec l’internat des hôpitaux de LoméRésultats: Vingt-quatre sessions ont été organisées en 33 ans. Le concours était ouvert aux étudiants ayant validé la 5è année d’études médicales. 425 candidatures ont été enregistrées : 0,08% de filles, 51,29% d’étudiants de 6ème année et 15,33% d’étudiants militaires. Au total 135 internes ont été nommés au cours des 24 sessions organisées (87,41% de sexe masculin). Les étudiants de sixième année (54,81%) et les civils (77,78%) étaient les plus représentés. La spécialisation des internes s’est faite au Togo dans la majorité des cas mais aussi dans certains pays africains (Sénégal, Côte d’Ivoire, Bénin). Les internes se spécialisaient plus en chirurgie (33,6%) et en gynéco-obstétrique (19,2%). Vingt-six anciens internes des hôpitaux ont opté pour la carrière universitaire. Une forte émigration des anciens internes a été notée : 80% se trouvaient en France.Conclusion: L’internat des hôpitaux de Lomé mérite des réformes prenant en compte les progrès de la Médecine, les besoins réels de l’exercice sur le terrain, et l’avenir à réserver aux lauréatsMots clés: Internat des hôpitaux- LoméEnglish Title: Lome Hospital internship competition from 1974 to 2006: the situation todayEnglish AbstractObjective: To review the state of the hospital internship competition in LoméMethodology: Descriptive cross-sectional study conducted at the Faculty of Health Sciences of the University of Lome and in the teaching hospitals of Lome. It consisted of counting the documents and archives of the hospital internship competition of Lomé and also semi-direct interviews with a sample of individuals related to the Lome hospital internship.Results: Twenty-four sessions were organized in 33 years. The competition was open to students who have validated the 5th year of medical studies. 425 applications were registered: 0.08% of girls, 51.29% of 6th year students and 15.33% of military students.  A total of 135 interns were appointed during the 24 sessions organized (87.41% boys). Sixth year students (54.81%) and civilians (77.78%) were the most represented. The specialization of interns was done in Togo in the majority of cases but also in some African countries (Senegal, Ivory Coast, Benin). The interns specialized more in surgery (33.6%) and obstetrics and gynecology (19.2%). Twenty-six former hospital interns opted for the university career. A strong emigration of former interns was noted: 80% were in France.Conclusion: Lome hospital internship deserves reforms taking into account the progress of Medicine, the actual needs of the field exercise, and the future to be reserved for the laureatesKeywords: Hospitals internship, Lom