135 research outputs found
Dynamic regulation of histone H3 methylation at lysine 4 in mammalian spermatogenesis.
No full textSpermatogenesis is a highly complex cell differentiation process that is governed by unique transcriptional regulation and massive chromatin alterations, which are required for meiosis and postmeiotic maturation. The underlying mechanisms involve alterations to the epigenetic layer, including histone modifications and incorporation of testis-specific nuclear proteins, such as histone variants and protamines. Histones can undergo methylation, acetylation, and phosphorylation among other modifications at their N-terminus, and these modifications can signal changes in chromatin structure. We have identified the temporal and spatial distributions of histone H3 mono-, di-, and trimethylation at lysine 4 (K4), and the lysine-specific histone demethylase AOF2 (amine oxidase flavin-containing domain 2, previously known as LSD1) during mammalian spermatogenesis. Our results reveal tightly regulated distributions of H3-K4 methylation and AOF2, and that H3-K4 methylation is very similar between the mouse and the marmoset. The AOF2 protein levels were found to be higher in the testes than in the somatic tissues. The distribution of AOF2 matched the cell- and stage-specific patterns of H3-K4 methylation. Interaction studies revealed unique epigenetic regulatory complexes associated with H3-K4 methylation in the testis, including the association of AOF2 and methyl-CpG-binding domain protein 2 (MBD2a/b) in a complex with histone deacetylase 1 (HDAC1). These studies enhance our understanding of epigenetic modifications and their roles in chromatin organization during male germ cell differentiation in both normal and pathologic states
Geocharis antheroi Serrano & Aguiar, new species
No full textGeocharis antheroi Serrano & Aguiar, new species (Figs 4 a– 4 h, 5 c– 5 d, 6 b) Type material: Holotype, 3, Portugal, Carção (Vimioso) (U.T.M. coordinate: 29 TQG0010), 22.IV. 2010, (A. Serrano leg.). Paratypes, 8 3 and 12 Ƥ (23, 1Ƥ gold coated), same locality of holotype, 22.IV. 2010, (A. Serrano leg.), 1 Ƥ, Santulhão (Vimioso) (U.T.M. coordinate: 29 TPG 9806), 22.IV. 2010, (A. Serrano leg.). Diagnosis. Anophtalmous; body slightly depressed, brown with integument microreticulated. Sparse pubescence mainly on pronotum and elytra. Elytron with vestigial striae, humeral region strongly punctured, disk with one anterior and one posterior seta. Male forelegs with the first tarsomere dilated. Males and females without a median tooth on the internal margin of the metafemora. Mesotibiae with dense pubescence in both margins. Hind tibiae more or less straight. Aedeagus as in Figs 5 c– 5 d. Description. Length of holotype: 1.9 mm. Length of paratypes: 1.6–1.9 mm (males and females). Head (Fig. 4 a) more or less as long as wide [length: 0.31–0.37 mm (males), 0.27–0.37 mm (females); width: 0.32–0.38 (males), 0.33–0.38 mm (females)], microsculpture distinct. Cephalic chaetotaxy (fixed setae of right side): L 3 +C 1 +F 1 +SA 1 +SP 1 + V 1 +O 1 +P0+G 2. Frontal and clypeal setae inserted in two large and two small sulci, respectively. Antennae light brown, antennomeres 1–2 longer than the others, the latter subpyriform, the third and the fourth are the shortest ones and subpyriforms, antennomeres 5–10 gradually longer and oval-shaped, the last one acuminate. Mouth-parts (Fig. 4 b) show the general pattern of the genus. Pronotum cordiform (Fig. 4 c), transverse, about 1.2–1.3 times wider than long [length: 0.35–0.43 mm (males), 0.34–0.41 mm (females); width: 0.43–0.51 mm (males), 0.42–0.50 mm (females)]; anterior angles not produced, widely rounded off, lateral channel not recurved inside of anterior angles; disk slightly convex, depressed between the two basal pits, with a superficial central sulcus which does not reach the anterior margin; anterior margin slightly straight and posterior margin slightly arcuate outwards; lateral margins with two or three slight denticles just before the posterior angles, which are right and dentate. Vestiture (pubescence): surface covered with scattered erect pubescence; one seta on the lateral margin in the broadest part of the pronotum, another one near the posterior angle; two additional setae inserted near the anterior angles. Elytra (Figs. 4 d– 4 e) 1.7–1.8 times longer than wide [length: 0.96–1.12 mm (males), 0.94–1.08 mm (females), width: 0.54–0.63 mm (males and females)], slightly convex, parallel and oval posteriorly, with vestigial traces of striae. Tegument microsculptured, disk more punctured in the shoulders, punctures sparser and disappearing to apex (Figs. 4 d– 4 f); lateral margin narrow, finely serrate from the humeral angles, which are rounded, to the seventh seta of the umbilicate series. Vestiture: part of the pubescence of the disk is arranged in six irregular lines, these setae are erect and slightly directed anteriad (Fig. 4 e); umbilicate series follows the pattern of the genus. The longest setae of this series are the 2 nd, the 6 th and the 9 th with the 3 rd, 5 th, 7 th and 8 th, more slightly inserted within the elytral margin; besides these setae there are one parascutellar basad, two discal (one anterior and one posterior) and one apical seta (Figs 4 d– 4 f). Last abdominal ventrite with one pair of medium sub-marginal setae in males, two pairs of medium sub-marginal setae in females (Figs 4 g– 4 h). Male legs with the protarsomere 1 dilated; tarsomere 1 in all legs more pigmented (light brown) than the others; mesotibiae with a strong pubescence on both margins; hind femora (males and females) without any median tooth on the internal margin (Figs. 4 g– 4 h). Male genitalia (Figs 5 c– 5 d) with median lobe arcuate (lateral view), apex strongly sharp and bent down (lateral view), arcuate inwards in the right side and broadly rounded in the left side (dorsal view); basal lobe with apophysis prominent, basal edge arcuate; internal sac as in figures 5 c– 5 d; left and right parameres with 2 apical setae, left paramere with dorso-basal edge expanded (Fig. 5 c). The female genitalia follows the general pattern described for the other species of the genus (e.g., Zaballos & Jeanne 1987, Zaballos 1998, Zaballos, 2005). Female genitalia (Fig. 6 b) shows the gonocoxite IX sickle-shaped, and has a long ensiform seta in the middle region of the external margin, one ensiform seta in the middle dorsal region and a double nematiform seta in the internal margin near the beginning of the apical third. Gonosubcoxite IX without special features; laterotergite IX with a variable number of setae (8–10). Internal genitalia (not shown) with spermathecal duct long, parallel and enlarged very slightly near the bursa copulatrix (length: 0.16 mm), a spherical spermatheca (width: 0.019 mm), duct of spermathecal gland short and thin, gland fusiform (lenght: 0.096 mm), middle region membranous, apical portion sclerotized. Etymology. This new species is dedicated to the Portuguese naturalist Anthero Frederico Ferreira de Seabra, who greatly contributed to the knowledge of the Coleoptera of Portugal in the first half of the XX century. Morphological affinities. The two new species share with most species of Geocharis two setae on the elytral disk, one anterior and one posterior (Table 1). In Table 1 some other morphological characters like the presence or absence of elytral striae, a tooth on the internal margin of the hind femora and the number of setae of the left paramere are compared in all species of Geocharis. Taking into account the presence on the elytral disk of two setae, the absence of a tooth on the internal margin of the hind femora of males and females, as well as the fact that the adults present traces of elytral striae, the new species are close to G. b i v a r i Serrano & Aguiar, G. julianae Zaballos, G. k o r b i (Ganglbauer), G. massinissa (Dieck), G. montecristoi Zaballos and G. testatretafoveata Zaballos (all the adults of these species exhibit the above characters). Nevertheless, in G. b i v a r i and G. julianae the elytral striae are stronger than in the new species (see Zaballos 1989, Serrano & Aguiar 2004). Geocharis bivari, G. julianae and the remaining other four species are also easily segregated from the new ones by the shape of the median lobe of aedeagus plus the pattern of internal sac sclerites (Zaballos 1989, 2005, Serrano & Aguiar 2004 a). The new species are easily separated from one another by the aedeagus conformation (cf. Figs 5 a– 5 b and 5 c– 5 d) though they much resemble each other on external morphology. The growing knowledge of the genus Geocharis in terms of number of species and morphological peculiarities, corroborates former conclusions (e.g. Zaballos 2005) about the difficulty of identifying its species based only in the external morphology, with the exception of some taxa (see Table 1). Characters that are not mentioned in Table 1 like ovulate elytra and the presence of a vestigial sutural stria (G. coiffaiti and G. femoralis), left paramere features, the pronotum shape or even hind tibiae shape are useful for identifying particular Geocharis species. This happens with adults of G. leoni Zaballos which present the left paramere with lamellar and membranous scales in the apex instead of setae, the adults of G. portalegrensis which exhibit a pronotal disk strongly flattened, the adults of G. iborensis Zaballos which present the hind tibiae arcuate inwards instead of the general straight pattern, and the adults of G. julianae which present a fold in the internal margin of this structure (Zaballos 1989, 1990, 1998, Serrano & Aguiar 2000). Indeed, the best characters to identify and segregate the Geocharis species, besides the ones mentioned above, are found in the aedeagus, as are the general conformation of median lobe (lateral view), the apex of the same structure (dorsal view) and the armature pattern of the internal sac. Faunistic data on other Geocharis taxa and Hypotyphlus lusitanicus. Geocharis olisipensis Schatzmayr, 1937. Material examined: Bucelas (U.T.M. coordinates: 29 SMD 9305), 3.III.2011, 53, 4 Ƥ, 22.III.2011, 13, 2 Ƥ, 30.III.2011, 23, 1 Ƥ. Within the genus Geocharis this species was the first one described for Portugal based on two specimens collected near Lisbon (Schatzmayr 1937). Serrano & Aguiar (2004 a) after some efforts to locate this species found it in the outskirts of Lisbon (Valejas and Fanhões) and more recently in Serra de Montejunto (almost 50 km north of Lisbon) (Serrano & Aguiar 2008). The new locality near Bucelas is close to the former ones (Fig. 7). Geocharis quartaui Serrano & Aguiar, 2004. Material examined: Serra de Sicó (Pombal) (U.T.M. coordinates: 29 SNE 3319), 31.III.2008, 1Ƥ, 15.IV.2008, 13, 3 Ƥ; Serra do Sicó (Pombal) (U.T.M. coordinates: 29 SNE 3419), 15.IV.2008, 23 3, 10 Ƥ. This species was described on the basis of several specimens collected near Alcobaça (Carvalhal), a locality close to Serra de Aire e Candeeiros and recorded later in Serra de Montejunto (Serrano & Aguiar 2008). This new localization in Serra do Sicó (almost 40 km north of Serra de Montejunto), indicates for this species a wider distribution than the previously thought (Fig. 7). Interesting also is the fact that the Serra de Sicó male specimens exhibit a stronger median tooth on the internal margin of the hind femora than that observed in specimens of the other localities. Hypotyphlus lusitanicus Serrano & Aguiar, 2004. Material examined: Aldeia do Catarredor (Serra da Lousã) (U.T.M. coordinates: 29 TNE 6636), 2.IV.2008, 2 3; Fundeira (Pampilhosa da Serra) (U.T.M. coordinates: 29 TNE 8731), 3.IV.2008, 4 3, 3 Ƥ; Silvares (Fundão) (U.T.M. coordinates: 29 TPE 1141), 4.IV.2008, 1 Ƥ; Folgosa (Peso da Régua) (U.T.M. coordinates: 29 TPF 1357), 29.IV.2009, 1 Ƥ. One male and 1 female from Fundeira are deposited in the collection of Vicente Ortuño; all the remaining specimens are deposited in the collection of the first author, Departamento de Biologia Animal (Faculdade de Ciências da Universidade de Lisboa). This remarkable species was found in the centre of Portugal (Aldeia do Mato near Tomar) (Serrano & Aguiar, 2004 b). Lately it was found in a new locality (Barragem do Cabril, Pedrógão Grande) almost 60 km farther north (Serrano & Aguiar 2008). The new localities notably increase east- and northwards the distribution of this species (Fig. 7). Ecological and geographical considerations. The two new species of Geocharis inhabit the endogean environment in the same way than other congeneric taxa. This means that they live in the soil, usually at different depths of the B-horizon. They are found under sunken stones laying at different depths, from superficial (epigean) to well-buried (edaphic or endogean) environments. Individuals of endogean carabids are more easily found close to the superficial horizon layers after heavy rains because then the soil reaches higher percentage of humidity (saturation or close to saturation), pushing the beetles upwards. References to this behaviour are not abundant (e.g. Zaballos 2005; Zaballos & Pérez-González 2011), though we sampled several specimens of G. sacarraoi Serrano & Aguiar and Typhlocharis passosi Serrano & Aguiar, 2005 after rain in these conditions. However, the soil horizons do not always present the same depth and many times the bed rock is closer to the epigean environment. In this case endogean individuals may occur for instance between plates of sunken schistose rocks (e.g. Fig. 2). Though only one species of Geocharis occurs at a given locality, there are some recorded exceptions (e.g. Zaballos 2005; Serrano & Aguiar 2001, 2006, 2008). Sometimes Geocharis species can also be syntopic with species of the genus Typhlocharis (e.g. Dieck 1869, Serrano & Aguiar 2008). To date, all the Geocharis species located north of Tejo River in Portugal were recorded from localities ranging between the Lisbon region and Serra de Aire e Candeeiros. Interestingly, despite several field surveys to the north of Tejo River, only those conducted in the western region north of Lisbon led to the discovery of Geocharis species until now. Geocharis quartaui (also collected in this study) was found in Serra de Sicó, a mountain also located in the western region. The finding of the two new species here reported from surveys near the Douro River and Vimioso has increased the distribution of this genus 240 km farther north of Serra de Sicó. Yet, more remarkable was the discovery of Hypotyphlus lusitanicus in Folgosa in syntopy with G. barcorabelo n.sp. The presence of the former species north and south of Serra da Estrela (Fig. 7) corroborates the hypothesis that H. lusitanicus is a zoogeographical relict of a lineage that once must have extended westward from the Lionigurian massif to the Lusitanian massif (Serrano & Aguiar 2004 b). Finally we would like point out that G. barcorabelo n. sp. and G. antheroi n.sp. were not found within the limits of any Natural Park or protected area and as such are not currently under any conservation protection. From the 20 Geocharis species known in Portugal (including the new ones) (Table 1), only 7 (G. b i v a r i, G. boieiroi, G. monfortensis, G. m o s c a t e l u s, G. portalegrensis, G. quartaui and G. rodriguesi) were recorded inside the geographical limits of a protected area.Published as part of Serrano, Artur R. M. & Aguiar, Carlos A. S., 2011, Two new species of the genus Geocharis Ehlers, 1883 and new data on Anillina species from Portugal (Coleoptera: Carabidae), pp. 33-46 in Zootaxa 3116 on pages 38-45, DOI: 10.5281/zenodo.20716
Home Cooking, Food Consumption and Food Production among the Unemployed and Retired Households
No full textUtilizing the 1996 Canadian Food Expenditure survey matched with Canadian Nutrient File, we separate actual food consumption from observed expenditure and test the Permanent Income/Life Cycle Hypothesis on the true consumption data. We find that the lower food expenditure during periods of unemployment or retirement (previously reported in the literature), does not translate into poorer nutrition. Household calorie intake and major nutrient intake seem to be unaffected by changes in employment status. We find evidence that unemployed or retired households substitute food purchased from restaurants for food purchased for at home consumption. Further, with the 1998 Time Use Survey we find that individuals who are not employed devote more time for food preparation. Finally we present limited evidence that unemployed and retired households substitute precooked meals for meals made from primary ingredients.Food Production, Nutrition, Consumption Smoothing
«Pobreza» e «Caridade» no Portugal contemporâneo: O olhar (teológico) e a ação (social) de Padre Américo Monteiro de Aguiar
No full textO presente estudo, que retoma e aprofunda uma comunicação com o mesmo título apresentada no Seminário Permanente «Representações dos Pobres: espiritualidade, estética, sociologia», promovido pelo Grupo «Sociabilidades, Práticas e Formas de Sentimento Religioso» do CITCEM-UP, na Faculdade de Letras da Universidade do Porto, tem, na sua génese e estruturação, dois objetivos fundamentais e deste modo formuláveis: em primeiro lugar, concretizar uma tentativa de sistematização da reflexão em torno dos conceitos de «Pobreza» e «Caridade» protagonizada por Padre Américo Monteiro de Aguiar, sublinhando, desde logo, a íntima correlação existente entre tal exercício e aquele que se constitui, ainda hoje, como o legado e faceta mais conhecida do Autor em questão: a dimensão social do seu projeto, v. g. a «Obra da Rua – Casa do Gaiato». Em segundo lugar, e a partir de uma análise mais pormenorizada de tais conceitos e da formulação que sobre eles o Autor deixa transparecer, mostrar a «(não-)inscrição» (vd. José Gil) de tal conceptualização no quadro de outros universos de debate seus coetâneos. Deste modo, e em suma, tentar-se-á relevar não só a validade (e necessidade) de um permanente aprofundamento do estudo e análise contextualizada destas questões mas também e de modo particular da importância e o (des)enquadramento da proposta conceptual (e da ação social a ela correspondente) do Autor aqui eleito na contemporaneidade em que o seu pensar e agir se enxertamThis study, which resumes and deepens a communication with the same title presented at the Permanent Seminar «Representations of the Poor: spirituality, aesthetics, sociology», promoted by the Group Societies, Practices and Forms of Religious Sentiment of CITCEM – University of Porto, has, in its genesis and structure, two fundamental and thus formulable objectives: first, to concretize an attempt to systematize the reflection around the concepts of «Poverty» and «Charity» carried out by Father Américo Monteiro de Aguiar, emphasizing, first of all, the intimate correlation between this exercise and that which is still today the most famous legacy and facet of the Author in question: the social dimension of his project, the «Obra da Rua - Casa do Gaiato». Second, from a more detailed analysis of such concepts and the formulation that the author reveals about them, show the «(non)» inscription (see José Gil) of such a conceptualization in the context of other universes of their peers. In this way, it will be tried to highlight not only the validity (and necessity) of a permanent deepening of the study and contextualized analysis of these issues, but also in a particular way of the importance and the (dis) framing of the conceptual proposal and of the corresponding social action) of the Author elected here in the contemporaneity in which his thinking and acting are grafted.info:eu-repo/semantics/publishedVersio
Análise comportamental do direito: fundamentos para uma abordagem do direito como ciência comportamental aplicada
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Jurídicas. Programa de Pós-Graduação em Direito.Este trabalho expõe os fundamentos de uma nova abordagem do direito denominada análise comportamental do direito. Partindo da crítica ao dualismo entre ciência jurídica normativa e não-normativa, tal abordagem se fundamenta, primeiramente, na redefinição do direito como tecnologia de controle social do comportamento humano, por intermédio da imposição de contingências sociais normativas, destinadas a modelar, manter, modificar e, eventualmente, extinguir os padrões comportamentais humanos considerados, com base em pressupostos empiricamente válidos sobre os mesmos, necessários à obtenção de metas sociais politicamente definidas. O método de análise é o dos quase-experimentos em âmbito social, nos quais a hipótese a ser verificada é a relação causal entre a imposição da contingência social normativa e a obtenção da meta social. A análise comportamental do direito se funda ainda no paradigma comportamentalista nas Ciências Humanas, cujo ramo mais avançado é a Psicologia Comportamental. O trabalho sugere também algumas bases para uma síntese provisória da teoria do comportamento social humano, em que se destacam contribuições da teoria da troca social, da Economia Comportamental e da corrente neo-institucionalista. This work lays the grounds for a new approach to legal studies named behavioral analysis of law. To begin with, such an approach refuses to distinguish normative from non-normative legal science and redefines law as a form of technology which controls human behavior. This technology relies on imposing normative social contingencies which are meant to shape, maintain, change and, perhaps, extinguish behavioral patterns. Some of these patterns might be considered socially necessary to the achievement of politically chosen aims, a choice which requires empirically valid presuppositions. The author employs the method of quasi-experiments within the social realm, in which the hypothesis to be verified is the causal relation between imposing a normative social contingency and achieving a social aim. The theory that underlines behavioral analysis of law is the behaviorist paradigm in the Human sciences, the most developed branch of which is behavioral Psychology. This thesis suggests a few guidelines to provisionally summarize the theory of human social behavior, the main contributions to which being the theory of social exchange, behavioral Economics, and the neoinstitutionalist school
Scalable QoS-aware Mobility for Future Mobile Operators
No full textTelecom operators and Internet service providers
are heading for a new shift in communications
paradigms. The forthcoming convergence
of cellular and wireless data networks is often
manifested in an “all IP approach” in which all
communications are based on an end-to-end IP
protocol framework. The approach to network
design becomes user and service-centered, so
that continuous reachability of mobile users and
sustained communication capabilities are default
requirements for a prospective architecture. In
this article, we describe a network architecture
which is able to provide seamless communication
mobility, triggered either by the user or by the
network, across multiple technologies. The architecture
allows for media independent handovers
and supports optimized mobility and resource
management functions. The main focus of the
article is on major technical highlights of mobility
and quality-of-service (QoS) management subsystems
for converged networks.Publicad
Tradução comentada do texto dramático roabastiano La tierra sin mal
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Estudos da Tradução, Florianópolis, 2012Este trabalho tem como objeto principal a tradução, do castelhano para o português brasileiro, do texto dramático La tierra sin mal (1998) do autor paraguaio Augusto Roa Bastos. A partir de leituras críticas e considerações sobre o processo tradutório, este estudo vem reafirmar a importância do acesso aos textos do autor em língua portuguesa. O drama La tierra sin mal, apresenta aos leitores brasileiros, com esta tradução, um texto inédito em português. A tradução desta obra do gênero dramático também abre horizontes para uma integração entre as áreas das letras e das artes cênicas, ao criar uma oportunidade de encenação deste texto a um público brasileiro. Este trabalho traz ainda uma análise diretamente relacionada à cultura e aos temas que fundamentam a história da obra, pois em La tierra sin mal é possível observar aspectos relativos à realidade e cultura paraguaia, através de uma mescla entre história e mitologia guarani. Somada a esta análise, está um estudo sobre o processo de tradução desta obra dramática ao português e dos aspectos da poética do autor Augusto Roa Bastos. Compõem o trabalho observações de alguns fundamentos teóricos sobre cultura e tradução, especificamente na área da tradução teatral, a peça La tierra sin mal traduzida para o português seguida de uma análise do processo tradutório e por fim uma análise da poética do autor.Abstract : This paper has as main object translation, from Spanish to Brazilian Portuguese, the dramatic text La tierra sin mal (1998) of Paraguayan author Augusto Roa Bastos. From readings and critical considerations about the translation process, this study reaffirms the importance of access to the texts of the author in Portuguese. The drama La tierra sin mal, introduces for the readers to Brazil with this translation, an unpublished text in Portuguese. The translation of this work of dramatic genre also opens horizons for integration between the area of literature and arts, to create an opportunity of staging this text to a Brazilian public. This paper also carries an analysis directly related to culture and themes that underlie the history of the text, because in La tierra sin mal is possible to observe aspects of reality and Paraguayan culture through a blend of history and mythology Guarani. Added to this analysis is a study on the process of translating this dramatic text into Portuguese and poetic aspects of the author Augusto Roa Bastos. Compose the work of some theoretical observations on culture and translation, specifically in the area of theatrical translation, the piece theater La tierra sin mal translated into Portuguese followed by an analysis of the translation process and finally an analysis of the poetics of the author
The intraflagellar transport protein IFT27 promotes BBSome exit from cilia through the GTPase ARL6/BBS3
No full textThe sorting of signaling receptors into and out of cilia relies on the BBSome, a complex of Bardet-Biedl syndrome (BBS) proteins, and on the intraflagellar transport (IFT) machinery. GTP loading onto the Arf-like GTPase ARL6/BBS3 drives assembly of a membrane-apposed BBSome coat that promotes cargo entry into cilia, yet how and where ARL6 is activated remains elusive. Here, we show that the Rab-like GTPase IFT27/RABL4, a known component of IFT complex B, promotes the exit of BBSome and associated cargoes from cilia. Unbiased proteomics and biochemical reconstitution assays show that, upon disengagement from the rest of IFT-B, IFT27 directly interacts with the nucleotide-free form of ARL6. Furthermore, IFT27 prevents aggregation of nucleotide-free ARL6 in solution. Thus, we propose that IFT27 separates from IFT-B inside cilia to promote ARL6 activation, BBSome coat assembly, and subsequent ciliary exit, mirroring the process by which BBSome mediates cargo entry into cilia
Análisis de la producción científica en Biblioteconomía y Documentación en el periodo 1995-2004 : estudio en los principales programas españoles y brasileños
No full textA well-conserved Plasmodium falciparum var gene shows an unusual stage-specific transcript pattern
No full textThe var multicopy gene family encodes Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) variant antigens, which, through their ability to adhere to a variety of host receptors, are thought to be important virulence factors. The predominant expression of a single cytoadherent PfEMP1 type on an infected red blood cell, and the switching between different PfEMP1 types to evade host protective antibody responses, are processes thought to be controlled at the transcriptional level. Contradictory data have been published on the timing of var gene transcription. Reverse transcription-polymerase chain reaction (RT-PCR) data suggested that transcription of the predominant var gene occurs in the later (pigmented trophozoite) stages, whereas Northern blot data indicated such transcripts only in early (ring) stages. We investigated this discrepancy by Northern blot, with probes covering a diverse var gene repertoire. We confirm that almost all var transcript types were detected only in ring stages. However, one type, the well-conserved varCSA transcript, was present constitutively in different laboratory parasites and does not appear to undergo antigenic variation. Although varCSA has been shown to encode a chondroitin sulphate A (CSA)-binding PfEMP1, we find that the presence of full-length varCSA transcripts does not correlate with the CSA-binding phenotype
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