Functional analysis and structural modeling of human APOBEC3G reveal the role of evolutionarily conserved elements in the inhibition of human immunodeficiency virus type 1 infection and Alu transposition.

Retroelements are important evolutionary forces but can be deleterious if left uncontrolled. Members of the human APOBEC3 family of cytidine deaminases can inhibit a wide range of endogenous, as well as exogenous, retroelements. These enzymes are structurally organized in one or two domains comprising a zinc-coordinating motif. APOBEC3G contains two such domains, only the C terminal of which is endowed with editing activity, while its N-terminal counterpart binds RNA, promotes homo-oligomerization, and is necessary for packaging into human immunodeficiency virus type 1 (HIV-1) virions. Here, we performed a large-scale mutagenesis-based analysis of the APOBEC3G N terminus, testing mutants for (i) inhibition of vif-defective HIV-1 infection and Alu retrotransposition, (ii) RNA binding, and (iii) oligomerization. Furthermore, in the absence of structural information on this domain, we used homology modeling to examine the positions of functionally important residues and of residues found to be under positive selection by phylogenetic analyses of primate APOBEC3G genes. Our results reveal the importance of a predicted RNA binding dimerization interface both for packaging into HIV-1 virions and inhibition of both HIV-1 infection and Alu transposition. We further found that the HIV-1-blocking activity of APOBEC3G N-terminal mutants defective for packaging can be almost entirely rescued if their virion incorporation is forced by fusion with Vpr, indicating that the corresponding region of APOBEC3G plays little role in other aspects of its action against this pathogen. Interestingly, residues forming the APOBEC3G dimer interface are highly conserved, contrasting with the rapid evolution of two neighboring surface-exposed amino acid patches, one targeted by the Vif protein of primate lentiviruses and the other of yet-undefined function.

Role of BRCA2 in control of the RAD51 recombination and DNA repair protein.

Individuals carrying BRCA2 mutations are predisposed to breast and ovarian cancers. Here, we show that BRCA2 plays a dual role in regulating the actions of RAD51, a protein essential for homologous recombination and DNA repair. First, interactions between RAD51 and the BRC3 or BRC4 regions of BRCA2 block nucleoprotein filament formation by RAD51. Alterations to the BRC3 region that mimic cancer-associated BRCA2 mutations fail to exhibit this effect. Second, transport of RAD51 to the nucleus is defective in cells carrying a cancer-associated BRCA2 truncation. Thus, BRCA2 regulates both the intracellular localization and DNA binding ability of RAD51. Loss of these controls following BRCA2 inactivation may be a key event leading to genomic instability and tumorigenesis.

Essential diagnostics - the role of the Department of Biomedical Research of the Royal Tropical Institute in the 21st century

In the light of emerging and overlooked infectious diseases and widespread drug resistance, diagnostics have become increasingly important in supporting surveillance, disease control and outbreak management programs. In many low-income countries the diagnostic service has been a neglected part of health care, often lacking quantity and quality or even non-existing at all. High-income countries have exploited few of their advanced technical abilities for the much-needed development of low-cost, rapid diagnostic tests to improve the accuracy of diagnosis and accelerate the start of appropriate treatment. As is now also recognized by World Healt Organization, investment in the development of affordable diagnostic tools is urgently needed to further our ability to control a variety of diseases that form a major threat to humanity. The Royal Tropical Institute's Department of Biomedical Research aims to contribute to the health of people living in the tropics. To this end, its multidisciplinary group of experts focuses on the diagnosis of diseases that are major health problems in low-income countries. In partnership we develop, improve and evaluate simple and cheap diagnostic tests, and perform epidemiological studies. Moreover, we advice and support others - especially those in developing countries - in their efforts to diagnose infectious diseases.

Role of the immune response induced by superantigens in the pathogenesis of microbial infections.

Superantigens (SAgs) are microbial proteins which have potent effects on the immune system. They are presented by major histocompatibility complex (MHC) class II molecules and interact with a large number of T cells expressing specific T cell receptor V beta domains. Encounter of a SAg leads initially to the stimulation and subsequently to the clonal deletion of reactive T cells. SAgs are expressed by a wide variety of microorganisms which use them to exploit the immune system to their own advantage. Bacterial SAgs are exotoxins which are linked to several diseases in humans and animals. A classical example is the toxic shock syndrome in which the massive release of cytokines by SAg-reactive cells is thought to play a major pathogenic role. The best characterized viral SAg is encoded by mouse mammary tumour virus (MMTV) and has proved to have a major influence on the viral life cycle by dramatically increasing the efficiency of viral infection. In this paper, we review the general properties of SAgs and discuss the different types of microorganisms which produce these molecules, with a particular emphasis on the role played by the SAg-induced immune response in the course of microbial infections.

R&D cooperation between Spanish firms and scientific partners: what is the role of tertiary education?

This paper explores the factors that determine firm’s R&D cooperation with different partners, paying special attention on the role of tertiary education (degree and PhDs level) in facilitating the connection between the firms and the to scientific bodies (technology centres, public research centres and universities). Here, we attempt to answer two questions. First, are innovative firms that carry out internal and external R&D activities more likely to cooperate on R&D projects with other partners? Second, do Spanish innovative firms with a high participation of researchers with degrees or PhDs tend to cooperate more with scientific partners? To answer both questions we apply a three-dimensional approach on a firm level Panel Data with a sample of 4.998 manufacturing and services Spanish firms. First, we run a complementary test between external R&D acquisition and skilled research workers and find that firms which carry out external R&D activities obtain a greater return on R&D cooperation when they have skilled workers in R&D, especially in high-tech manufactures and KIS services. Second, we carry out a 2-step tobit model to estimate, in the first stage, the determinants that explain whether Spanish innovative firms cooperate or not; and in the second stage the factors that affect the choice of partners. And third, we apply an ordered probit model to test the marginal effects of explanatory variables on the different partners. Here we contrast some of the most interesting empirical hypotheses of previous studies, and which emphasize the role of employees with degrees and PhDs in facilitating cooperative R&D between firms and scientific partners. JEL classification: O31, O33, O38. Key words: Determinants R&D cooperation, industry-university flows, PhD research workers.

Innovation and absorptive capacity: What is the role of technological frontier?

This paper explores how absorptive capacity affects the innovative performance and productivity dynamics of Spanish firms. A firm’s efficiency levels are measured using two variables: the labour productivity and the Total Factor Productivity (TFP). The theoretical framework is based on the seminal contributions of Cohen and Levinthal (1989, 1990) regarding absorptive capacity; and the applied framework is based on the four-stage structural model proposed by Crépon, Duguet and Mairesse (1998) for setting the determinants of R&D, the effects of R&D activities on innovation outputs, and the impacts of innovation on firm productivity. The present study uses a twostage structural model. In the first stage, a probit estimation is used to investigate how the sources of R&D, the absorptive capacity and a vector of the firm’s individual features influence the firm’s likelihood of developing innovations in products or processes. In the second phase, a quantile regression is used to analyze the effect of R&D sources, absorptive capacity and firm characteristics on productivity. This method shows the elasticity of each exogenous variable on productivity according to the firms’ levels of efficiency, and thus allows us to distinguish between firms that are close to the technological frontier and those that are further away from it. We used extensive firm-level panel data from 5,575 firms for the 2004-2009 period. The results show that the internal absorptive capacity has a strong impact on the productivity of firms, whereas the role of external absorptive capacity differs according to nature of the each industry and according the distance of firms from the technological frontier. Key words: R&D sources, innovation strategies, absorptive capacity, technological distance, quantile regression.

Role of two Triatoma (Hemiptera: Reduviidae: Triatominae) species in the transmission of Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) to man in the West Coast of Mexico

From August 1997 to August 1998, 334 specimens of Triatoma longipennis and 62 of T. picturata were collected in four groups of localities placed in the zone from Guadalajara, Jalisco to Tepic, Nayarit, in the West Coast of Mexico. Most T. longipennis were collected outdoors (69.2%) while most T. picturata (58.1%) were collected indoors. All collected specimens were examined for Trypanosoma cruzi infection, which was detected on 98 (29.3%) T. longipennis and 17 (27.4%) T. picturata. This study confirms the role of T. longipennis and T. picturata as some of the main T. cruzi vectors to humans in Mexico. Habitation Infestation Rate with T. longipennis was of 0.09 and with T. picturata was of 0.03 and the predominating ecotopes were pile of blocks, chicken coops, pigsties, wall crawls and beds.

Rôle de l'inactivité physique dans l'étiologie de l'obésité [The role of physical inactivity in the etiology of obesity].

The activity-related energy expenditure mainly depends upon body weight, the type, intensity and duration of the exercise as well as the mechanical efficiency with which the subjects perform the work. Controversy still exist about the role of hypoactivity in the aetiology of obesity both in adolescence and adulthood. A number of experimental studies based on indirect assessment of physical activity (such as pedometers, accelerometers, cinematography and heart rate) have demonstrated a significant reduction in spontaneous physical activity in certain obese groups as compared to lean matched controls. On the other hand, direct measurements of energy expenditure (by indirect calorimetry) have shown a linear relationship between body weight and 24-hour (or activity-related) energy expenditure. It therefore appears that despite the greater placidity characterising some grossly obese subjects, the absolute rate of energy expenditure - particularly in weight bearing activities - is not lower than in lean subjects, since the hypoactivity does not fully compensate for the greater gross energy cost of a given activity.

Role of glutathione in macrophage activation: effect of cellular glutathione depletion on nitrite production and leishmanicidal activity.

We have examined the effects of two agents depleting the intracellular pool of glutathione (GSH) on macrophage activation induced by IFN-gamma + LPS, as measured by nitrite production and leishmanicidal activity. Diethylmaleate (DEM), which depletes intracellular GSH by conjugation via a reaction catalyzed by the GSH-S-transferase, strongly inhibited nitrite secretion and leishmanicidal activity when added before or at the time of addition of IFN-gamma + LPS; this inhibition was progressively lost when addition of DEM was delayed up to 10 hr. A close correlation was observed between levels of intracellular soluble GSH during activation and nitrite secretion. Inhibition was partially reversed by the addition of glutathione ethyl ester (GSH-Et). Buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamylcysteine synthetase, also inhibited macrophage activation, although to a lesser extent than DEM despite a more pronounced soluble GSH depletion. This inhibition was completely reversed by the addition of GSH-Et. DEM and BSO did not alter cell viability or PMA-triggered O2- production by activated macrophages, suggesting that the inhibitory effects observed on nitrite secretion and leishmanicidal activity were not related to a general impairment of macrophage function. DEM and BSO treatment reduced iNOS specific activity and iNOS protein in cytosolic extracts. DEM also decreased iNOS mRNA expression while BSO had no effect. Although commonly used as a GSH-depleting agent, DEM may have additional effects because it can also act as a sulhydryl reagent; BSO, on the other hand, which depletes GSH by enzymatic inhibition, has no effect on protein-bound GSH. Our results suggest that both soluble and protein-bound GSH may be important for the induction of NO synthase in IFN-gamma + LPS-activated macrophages.

Role of MIF and glutathione, in association with fetal ovine globin chain (Hbgamma) and LPS, in induction of TNFalpha from cells of young and aged mice, and PBL from healthy human populations.

Previous reports from our group have established that the fetal ovine gamma globin chain (Hbgamma) and LPS can synergize in the induction of pro-inflammatory cytokines, especially TNFalpha, from mouse and human leukocytes. A fetal sheep liver extract (FSLE) which was observed to have marked immunoregulatory properties in vivo and in vitro had independently been observed to contain significant amounts of each of these molecules. However, the biological activity of this extract (hereafter FSLE) was not explained solely by its content of Hbgamma and LPS, and independent analysis confirmed also the presence of migration inhibitory factor, MIF, and glutathione in FSLE. We have investigated whether MIF and the cellular anti-oxidant glutathione can further synergize with Hbgamma and LPS in TNFalpha induction from human cells in vitro, and mouse cells activated in vivo/in vitro. Our data show that indeed there is evidence for such a synergy. Treatment or mouse cells with FSLE produced an enhanced TNFalpha production which could be inhibited independently both by anti-Hbgamma and by anti-MIF, and optimally by a combination of these reagents.

Decomposing the Tourist’s Satisfaction Gap: The Role of Expectations and Cognitions

In this paper we present an empirical methodology that allows the tourist’s satisfaction gap between two destinations to be decomposed into two components. One explains the role of differences in observed characteristics of the tourists and the stay (endowments). The other captures the share of the gap due to differences in the utility that tourists derive from those characteristics (cognitive). To illustrate the use of this method, we employ data coming from a sample of tourists visiting two touristic enclaves in Tarragona (Spain). Our results indicate that the cognitive component explains most of the satisfaction gap. Keywords: Satisfaction, expectations, cognition, touristic destination