Interaction between Didelphis albiventris and Triatoma infestans in relation to Trypanosoma cruzi transmission

This paper attempts to prove if a high Trypanosoma cruzi prevalence of opossums might be reached with few potential infective contacts. One non-infected Didelphis albiventris to T. cruzi and 10 infected nymphs of Triatoma infestans were left together during 23 hr in a device that simulated a natural opossum burrow. Twenty-six replicates were perfomed using marsupials and triatomines only once. Potentially infective contacts occurred in all the trials. From the 26 opossums used in trials, 54% did not eat any bug. Of the 260 bugs used, 21% were predated. In the 25 trials involving 205 surving bugs, 36 % of them did not feed. In 15/25 cases, maior ou igual a 60% of the triatomines were able to feed. The parasitological follow-up of 24 opossums showed that among 10 that had eaten bugs, 4 turned out infected and among the 14 that had not predate, 3 (21%) became positive. In sum, 7/24 (29%) of the marsupials acquired the infection after the experiment. This infection rate was similar to the prevalences found for the opossum population of Santiago del Estero, Argentina, suggesting that the prevalences observed in the field might be reached if each marsupial would encounter infected bugs just once in its lifetime.

Revisiting the size-R&D productivity relation: introducing the mediating role of decision-making style on the scale and quality of innovative output

We develop a mediation model in which firm size is proposed to affect the scale and quality of innovative output through the adoption of different decision styles during the R&D process. The aim of this study is to understand how the internal changes that firms undergo as they evolve from small to larger organizations affect R&D productivity. In so doing, we illuminate the underlying theoretical mechanism affecting two different dimensions of R&D productivity, namely the scale and quality of innovative output which have not received much attention in previous literature. Using longitudinal data of Spanish manufacturing firms we explore the validity of this mediation model. Our results show that as firms evolve in size, they increasingly emphasize analytical decision making, and consequently, large-sized firms aim for higher-quality innovations while small firms aim for a larger scale of innovative output.

The Potential for Dispersal of Onchocerciasis in Ecuador in Relation to the Distribution of the Vector Simulium exiguum (Diptera:Simuliidae)

The future dispersal of onchocerciasis in Ecuador is dependent on the distribution of cytotypes of the vector species complex Simulium exiguum. Over the last 14 years, collections of larvae have been made from over 25 rivers, between 80-1600 m altitude, from various sites on both sides of the Andes. Analysis of larval polytene chromosomes was used to determine the distributions of each cytotype. On the western side of the Andes, the Cayapa cytotype (the only cytotype directly incriminated as a vector) has a distribution from Santo Domingo de los Colorados northwards. The Quevedo and Bucay cytotypes occur from Santo Domingo de los Colorados southwards. On the eastern side of the Andes, the Aguarico cytotype occurs in the Rio Aguarico and a new cytotype is present in the tributaries of the Rio Napo. Whether the disease will spread south of Santo Domingo and on the eastern side of the Andes depends on vector capacity of the cytotypes and the dispersal patterns of individuals infected with onchocerciasis. At present the Aguarico, Bucay and Quevedo cytotypes are known to be efficient hosts, but their biting preferences and biting densities have not yet been evaluated

Improvement in coronary circulatory function in morbidly obese individuals after gastric bypass-induced weight loss: relation to alterations in endocannabinoids and adipocytokines.

AIMS: To investigate the effect of surgical gastric bypass-induced weight loss and related alterations in endocannabinoids (ECs) and adipocytokine plasma levels on coronary circulatory dysfunction in morbidly obese (MOB) individuals. METHODS AND RESULTS: Myocardial blood flow (MBF) responses to cold pressor test (CPT) from rest (ΔMBF) and during pharmacologically induced hyperaemia were measured with &supl;³N-ammonia PET/CT in 18 MOB individuals with a body mass index (BMI) > 40 kg/m² at baseline and after a median follow-up period of 22 months. Gastric bypass intervention decreased BMI from a median of 44.8 (inter-quartile range: 43.3, 48.2) to 30.8 (27.3, 34.7) kg/m² (P < 0.0001). This decrease in BMI was accompanied by a marked improvement in endothelium-related ΔMBF to CPT and hyperaemic MBFs, respectively [0.34 (0.18, 0.41) from 0.03 (-0.08, 0.15) mL/g/min, P = 0.002; and 2.51 (2.17, 2.64) from 1.53 (1.39, 2.18) mL/g/min, P < 0.001]. There was an inverse correlation between decreases in plasma concentrations of the EC anandamide and improvement in ΔMBF to CPT (r = -0.59, P = 0.009), while increases in adiponectin plasma levels correlated positively with hyperaemic MBFs (r = 0.60, P = 0.050). Conversely, decreases in leptin plasma concentrations were not observed to correlate with the improvement in coronary circulatory function (r = 0.22, P = 0.400, and r = -0.31, P = 0.250). CONCLUSIONS: Gastric bypass-related reduction of BMI in MOB individuals beneficially affects coronary circulatory dysfunction. The dysbalance between ECs and adipocytokines appears to be an important determinant of coronary circulatory function in obesity.

Mycoplasma hominis in mid-trimester amniotic fluid : relation to pregnangy outcome

RESUME Introduction : Les naissances prématurées compliquent 6-10 % des grossesses dans les pays industrialisés et contribuent de façon notable aux taux de mortalité périnatale et de morbidité néonatale. Il a été démontré que la colonisation bactérienne du liquide amniotique joue un rôle dans l'étiologie des accouchements prématurés spontanés et des ruptures prématurées des membranes. Le but de ce travail était d'évaluer la présence de Mycoplasma hominis dans le liquide amniotique prélevé au 2eme trimestre de grossesse chez des patientes asymptomatiques et de déterminer son association avec une issue défavorable de la grossesse. Matériels et méthodes : Les échantillons de liquide amniotique de 456 patientes ayant subi une amniocentèse trans-abdominale entre les 15eme et I7eme semaines de grossesse pour diverses indications ont été testés par PCR (Polymerase Chain Reaction) afin d'identifier Mycoplasma hominis. Les produits ainsi amplifiés étaient ensuite détectés par ELISA (Enzyme-Linked Immunosorbent Assay). Les données cliniques étaient obtenues après l'accouchement. Résultats : Mycoplasma hominis a été identifié dans 29 (6,4%) des échantillons de liquide amniotique. Le taux de menace d'accouchement prématuré chez les patientes positives pour Mycoplasma hominis (14,3%) était plus élevé que chez les patientes négatives (3,3 %) (p=0,01). De même, les naissances prématurées spontanées avec membranes intactes étaient plus fréquentes chez les patientes positives (10,7%) que chez les patientes négatives (1,9 %) (p=0,02). Le taux de menace d'accouchement prématuré lors d'une grossesse antérieure était plus de trois fois plus élevé chez les patientes positives, cependant ce résultat n'était pas statistiquement significatif. Finalement, la présence du mycoplasme n'était pas corrélée à la gestose, au retard de croissance intra-utérin ou aux anomalies chromosomiques foetales. Conclusions : Les résultats montrent que la présence de Mycoplasma hominis dans le liquide amniotique prélevé entre les 15eme et I7eme semaines d' aménorrhée chez des patientes asymptomatiques est associée à un taux plus élevé de menace d'accouchement prématuré et de naissances prématurées spontanées. La détection de ce microorganisme au 2eme trimestre de la grossesse peut donc identifier les patientes à risque de menace d'accouchement et de naissance prématurées. Abstract Objective: The relationship between detection of Mycoplasma hominis in mid-trimester amniotic fluid and subsequent pregnancy outcome was investigated. Study design: Amniotic fluids from 456 women of European background who underwent a transabdominal amniocentesis at weeks 15-17 of pregnancy were tested for M. hominis by polymerase chain reaction (PCR). The amplicons were hybridized to an internal probe and detected by ELISA. Pregnancy outcomes and clinical data were subsequently obtained. Results: M. hominis were identified in 29 (6.4%) of the amniotic fluids. The rate of preterm labor in women positive for M. hominis (14.3%) was higher than in the negative women (3.3%) (p = 0.01). Similarly, a spontaneous preterm birth with intact membranes occurred in 10.7% of the M. hominis-posltive women as opposed to only 1.9% of the negative women (p = 0.02). The presence of this mycoplasma was not correlated with fetal chromosomal aberrations, intrauterine growth restriction or preeclampsia. Conclusions: Detection of M. hominis in second-trimester amniotic fluids can identify women at increased risk for subsequent preterm labor and delivery.

Mothers' and Fathers' Early Relationship With Their Infant: Similar Yet Temporally Discordant Themes [La relation initiale des parents avec leur nourrisson: Thèmes similaires quoique temporellement discordants]

Objective: To examine first-time mothers' and fathers' themes in their relationship with their infant, how these themes change during the first four months postpartum, and similarities and differences in mothers' and fathers' themes. Participants: Eighteen first-time mother-father couples were separately interviewed at one; six and 16 weeks postpartum. Data Analysis: Audio-taped, transcribed interviews were analysed using a Grounded Theory approach. Results: Our findings reveal a common set of themes for mothers and fathers in relation to the infant : 1: Discovery, 2: Physical Proximity, 3: Emotional Closeness, 4: Initiation of Complementary Interactions and 5: Commitment to Love and Care. However, there was a striking lack of concordance between mothers and fathers for these themes at each point in time. Conclusions: Mothers' and fathers' experience of the early relationship with their infant is unique. Focussing on maternal as well as paternal ways of experiencing the early relationship with their infant sets the way to understanding early developing relationships in the family context.

Pale and dark reddish melanic tawny owls differentially regulate the level of blood circulating POMC prohormone in relation to environmental conditions.

Knowledge of the hormonal pathway controlling genotype-specific norms of reaction would shed light on the ecological factors to which each genotype is adapted. Environmentally mediated changes in the sign and magnitude of covariations between heritable melanin-based colouration and fitness components are frequent, revealing that extreme melanin-based phenotypes can display different physiological states depending on the environment. Yet, the hormonal mechanism underlying this phenomenon is poorly understood. One novel hypothesis proposes that these covariations stem from pleiotropic effects of the melanocortin system. Melanocortins are post-translationally modified bioactive peptides derived from the POMC prohormone that are involved in melanogenesis, anti-inflammation, energy homeostasis and stress responses. Thus, differential regulation of fitness components in relation to environmental factors by pale and dark melanic individuals may be due to colour-specific regulation of the POMC prohormone. Accordingly, we found that the degree of reddish melanic colouration was negatively correlated with blood circulating levels of the POMC prohormone in female tawny owls (Strix aluco) rearing a brood for which the size was experimentally reduced, but not when enlarged, and in females located in rich but not in poor territories. Our findings support the hypothesis that the widespread links between melanin-based colouration and fitness components may be mediated, at least in part, by the melanocortin system.

Interactions between learning and immunity in Drosophila melanogaster

Learning and immunity are two adaptive traits with roles in central aspects of an organism's life: learning allows adjusting behaviours in changing environments, while immunity protects the body integrity against parasites and pathogens. While we know a lot about how these two traits interact in vertebrates, the interactions between learning and immunity remain poorly explored in insects. During my PhD, I studied three possible ways in which these two traits interact in the model system Drosophila melanogaster, a model organism in the study of learning and in the study of immunity. Learning can affect the behavioural defences against parasites and pathogens through the acquisition of new aversions for contaminated food for instance. This type of learning relies on the ability to associate a food-related cue with the visceral sickness following ingestion of contaminated food. Despite its potential implication in infection prevention, the existence of pathogen avoidance learning has been rarely explored in invertebrates. In a first part of my PhD, I tested whether D. melanogaster, which feed on food enriched in microorganisms, innately avoid the orally-acquired 'novel' virulent pathogen Pseudomonas entomophila, and whether it can learn to avoid it. Although flies did not innately avoid this pathogen, they decreased their preference for contaminated food over time, suggesting the existence of a form of learning based likely on infection-induced sickness. I further found that flies may be able to learn to avoid an odorant which was previously associated with the pathogen, but this requires confirmation with additional data. If this is confirmed, this would be the first time, to my knowledge, that pathogen avoidance learning is reported in an insect. The detrimental effect of infection on cognition and more specifically on learning ability is well documented in vertebrates and in social insects. While the underlying mechanisms are described in detail in vertebrates, experimental investigations are lacking in invertebrates. In a second part of my PhD, I tested the effect of an oral infection with natural pathogens on associative learning of D. melanogaster. By contrast with previous studies in insects, I found that flies orally infected with the virulent P. entomophila learned better the association of an odorant with mechanical shock than uninfected flies. The effect seems to be specific to a gut infection, and so far I have not been able to draw conclusions on the respective contributions of the pathogen's virulence and of the flies' immune activity in this effect. Interestingly, infected flies may display an increased sensitivity to physical pain. If the learning improvement observed in infected flies was due partially to the activity of the immune system, my results would suggest the existence of physiological connections between the immune system and the nervous system. The basis of these connections would then need to be addressed. Learning and immunity are linked at the physiological level in social insects. Physiological links between traits often result from the expression of genetic links between these traits. However, in social insects, there is no evidence that learning and immunity may be involved in an evolutionary trade-off. I previously reported a positive effect of infection on learning in D. melanogaster. This might suggest that a positive genetic link could exist between learning and immunity. We tested this hypothesis with two approaches: the diallel cross design with inbred lines, and the isofemale lines design. The two approaches provided consistent results: we found no additive genetic correlation between learning and resistance to infection with the diallel cross, and no genetic correlation in flies which are not yet adapted to laboratory conditions in isofemale lines. Consistently with the literature, the two studies suggested that the positive effect of infection on learning I observed might not be reflected by a positive evolutionary link between learning and immunity. Nevertheless, the existence of complex genetic relationships between the two traits cannot be excluded. - L'apprentissage et l'immunité sont deux caractères à valeur adaptative impliqués dans des aspects centraux de la vie d'un organisme : l'apprentissage permet d'ajuster les comportements pour faire face aux changements de l'environnement, tandis que l'immunité protège l'intégrité corporelle contre les attaques des parasites et des pathogènes. Alors que les interactions entre l'apprentissage et l'immunité sont bien documentées chez les vertébrés, ces interactions ont été très peu étudiées chez les insectes. Pendant ma thèse, je me suis intéressée à trois aspects des interactions possibles entre l'apprentissage et l'immunité chez la mouche du vinaigre Drosophila melanogaster, qui est un organisme modèle dans l'étude à la fois de l'apprentissage et de l'immunité. L'apprentissage peut affecter les défenses comportementales contre les parasites et les pathogènes par l'acquisition de nouvelles aversions pour la nourriture contaminée par exemple. Ce type d'apprentissage repose sur la capacité à associer une caractéristique de la nourriture avec la maladie qui suit l'ingestion de cette nourriture. Malgré les implications potentielles pour la prévention des infections, l'évitement appris des pathogènes a été rarement étudié chez les invertébrés. Dans une première partie de ma thèse, j'ai testé si les mouches, qui se nourrissent sur des milieux enrichis en micro-organismes, évitent de façon innée un 'nouveau' pathogène virulent Pseudomonas entomophila, et si elles ont la capacité d'apprendre à l'éviter. Bien que les mouches ne montrent pas d'évitement inné pour ce pathogène, elles diminuent leur préférence pour de la nourriture contaminée dans le temps, suggérant l'existence d'une forme d'apprentissage basée vraisemblablement sur la maladie générée par l'infection. J'ai ensuite observé que les mouches semblent être capables d'apprendre à éviter une odeur qui était au préalable associée avec ce pathogène, mais cela reste à confirmer par la collecte de données supplémentaires. Si cette observation est confirmée, cela sera la première fois, à ma connaissance, que l'évitement appris des pathogènes est décrit chez un insecte. L'effet détrimental des infections sur la cognition et plus particulièrement sur les capacités d'apprentissage est bien documenté chez les vertébrés et les insectes sociaux. Alors que les mécanismes sous-jacents sont détaillés chez les vertébrés, des études expérimentales font défaut chez les insectes. Dans une seconde partie de ma thèse, j'ai mesuré les effets d'une infection orale par des pathogènes naturels sur les capacités d'apprentissage associatif de la drosophile. Contrairement aux études précédentes chez les insectes, j'ai trouvé que les mouches infectées par le pathogène virulent P. entomophila apprennent mieux à associer une odeur avec des chocs mécaniques que des mouches non infectées. Cet effet semble spécifique à l'infection orale, et jusqu'à présent je n'ai pas pu conclure sur les contributions respectives de la virulence du pathogène et de l'activité immunitaire des mouches dans cet effet. De façon intéressante, les mouches infectées pourraient montrer une plus grande réactivité à la douleur physique. Si l'amélioration de l'apprentissage observée chez les mouches infectées était due en partie à l'activité du système immunitaire, mes résultats suggéreraient l'existence de connections physiologiques entre le système immunitaire et le système nerveux. Les mécanismes de ces connections seraient à explorer. L'apprentissage et l'immunité sont liés sur un plan physiologique chez les insectes sociaux. Les liens physiologiques entre les caractères résultent souvent de l'expression de liens entre ces caractères au niveau génétique. Cependant, chez les insectes sociaux, il n'y a pas de preuve que l'apprentissage et l'immunité soient liés par un compromis évolutif. J'ai précédemment rapporté un effet positif de l'infection sur l'apprentissage chez la drosophile. Cela pourrait suggérer qu'une relation génétique positive existerait entre l'apprentissage et l'immunité. Nous avons testé cette hypothèse par deux approches : le croisement diallèle avec des lignées consanguines, et les lignées isofemelles. Les deux approches ont fournies des résultats similaires : nous n'avons pas détecté de corrélation génétique additive entre l'apprentissage et la résistance à l'infection avec le croisement diallèle, et pas de corrélation génétique chez des mouches non adaptées aux conditions de laboratoire avec les lignées isofemelles. En ligne avec la littérature, ces deux études suggèrent que l'effet positif de l'infection sur l'apprentissage que j'ai précédemment observé ne refléterait pas un lien évolutif positif entre l'apprentissage et l'immunité. Néanmoins, l'existence de relations génétiques complexes n'est pas exclue.

Age-dependent gain of alternative splice forms and biased duplication explain the relation between splicing and duplication.

We analyze here the relation between alternative splicing and gene duplication in light of recent genomic data, with a focus on the human genome. We show that the previously reported negative correlation between level of alternative splicing and family size no longer holds true. We clarify this pattern and show that it is sufficiently explained by two factors. First, genes progressively gain new splice variants with time. The gain is consistent with a selectively relaxed regime, until purifying selection slows it down as aging genes accumulate a large number of variants. Second, we show that duplication does not lead to a loss of splice forms, but rather that genes with low levels of alternative splicing tend to duplicate more frequently. This leads us to reconsider the role of alternative splicing in duplicate retention.

Relation between intraoperative EMG values and final pedicle screw position as seen on CT images

Introduction: Intraoperative EMG based neurophysiological monitoring is increasingly used to assist pedicle screw insertion. We carried out a study comparing the final screw position in the pedicle measured on CT images in relation to its corresponding intraoperative muscle compound action potential (CMAP) values. Material and methods: A total of 189 screws were inserted in thoracolumbar spines of 31 patients during instrumented fusion under EMG control. An observer, blinded to the CMAP value, assessed the horizontal and vertical 'screw edge to pedicle edge' distance perpendicular to the longitudinal axis of the screw on reformatted CT reconstructions using OsiriX software. These distances were analysed with their corresponding CMAP values. Data from 62 thoracic and 127 lumbar screws were processed separately. Interobserver reliability of distance measurements was assessed. Results: No patient suffered neurological injury secondary to screw insertion. Distance measurements were reliable (paired t-test, P = 0.13/0.98 horizontal/vertical). Two screws had their position altered due to low CMAP values suggesting close proximity of nerve tissue. Seventy five percent of screws had CMAP results above 10mA and had an average distance of 0.35cm (SD 0.23) horizontally and 0.46cm (SD 0.26) vertically from the pedicle edge. Additional 12% had a distance from the edge of the pedicle less than 0mm indicating cortical breach but had CMAP values above 10mA. A poor correlation between CMAP values and screw position was found. Discussion: In this study CMAP values above 10mA indicated correct screw position in the majority of cases. The zone of 10-20mA CMAP carries highest risk of a misplaced screw despite high CMAP value (17% of screws this CMAP range). In order to improve accuracy of EMG predictive value further research is warranted including improvement of probing techniques.