219 resultados para highlights


Relevância:

10.00% 10.00%

Publicador:

Resumo:

L'ectodysplasine Al (EDA1 ou EDA), un ligand de la famille du TNF, et son récepteur EDAR favorisent le développement des poils, des dents et de plusieurs types de glandes. Chez l'humain, une déficience en EDA cause une dysplasie ectodermique liée à l'X, caractérisée par la genèse défectueuse des phanères. Les souris Tabby, déficientes en Eda, présentent des symptômes similaires. Nous démontrons que les souris Tabby sont en moyenne 7% plus légères que les contrôles au moment du sevrage. Ce phénotype ne dépend pas du génotype des petits, mais exclusivement de celui de la mère, suggérant que l'absence d'EDA perturbe la fonction mammaire. La glande mammaire se développe en plusieurs étapes, principalement à la puberté et pendant la grossesse. Nous avons généré des anticorps pour activer ou inhiber la signalisation d'EDAR. Les anticorps agonistes corrigent le développement de souris ou de chiens déficients en EDA, alors que les antagonistes provoquent une dysplasie ectodermique chez les souris saines. L'exposition répétée de souris Tabby aux anticorps agonistes après le sevrage accroît la taille et la fonction des glandes sébacées, démonstration pharmacologique qu'EDA contrôle l'homéostasie de la glande sébacée adulte. Ces outils seront utiles pour étudier la fonction d'EDA aux diverses étapes du développement de la glande mammaire. Fc-EDAl, un stimulateur d'EDAR, est en phase d'évaluation clinique. Nous avons montré que les structures dépendantes d'EDA qui se forment à différentes étapes du développement répondent à l'action du Fc-EDAl dans des fenêtres temporelles étroites ou larges. De plus, certaines structures peuvent être induites plusieurs jours après le début naturel de leur formation. Alors que la plupart des structures se forment suite à un seul jour d'activation d'EDAR, d'autre demandent un temps de stimulation plus long. La formation des dents est régulée par des signaux activateurs et inhibiteurs. Une forte stimulation d'EDAR spécifiquement appliquée aux deux premières molaires induit des signaux négatifs qui avortent la formation de la troisième molaire, alors qu'une forte stimulation donnée à la troisième molaire la rend hypertrophique tout en induisant parfois une quatrième molaire jamais observée chez les souris de type sauvage ou Tabby. EDA est donc un activateur important de la formation dentaire. Pris dans leur ensemble, ces résultats ont des implications pour la thérapie des dysplasies ectodermiques. - The TNF family ligand Ectodysplasin Al (EDA1 or EDA) and its receptor ED AR regulate embryonic development of hair, teeth and several types of glands. In humans, EDA mutations cause X-linked hypohidrotic ectodermal dysplasia (XLHED), a condition characterized by defective development of skin appendages. £da-deficient (Tabby) mice suffer from similar defects. We observed that Tabby pups at weaning were on average 7% smaller than WT controls, a phenotype that was curiously not linked to the genotype of pups, but to that of mothers, suggesting decreased mammary gland function in the absence of EDA. Mammary glands develop in several steps, most of which are post-natal. We generated monoclonal antibodies to block or activate EDAR signaling. Agonist antibodies rescued developmental defects when administered timely in £cfo-deficient mice and dogs, whereas blocking antibodies induced ectodermal dysplasia in WT mice. Agonist antibodies administered after weaning in £da-deficient mice for several months markedly increased both size and function of sebaceous glands, providing the first demonstration that pharmacological activation of the EDAR pathway in adults can correct important aspects of the dry skin phenotype. This also highlights a role for EDA1 in the homeostasis of adult sebaceous glands. These tools will be useful to study the function of EDA 1 at different stages of mammary gland development. Another EDAR agonist, Fc-EDAl, is currently evaluated in clinical trials. We found that EDA 1-dependent structures forming at different time points during development can respond to Fc-EDAl during time response windows that are narrow or wide. Also, some structures can be triggered up to several days after their normal time of induction. While most structures could be rescued by a single day of EDAR signaling, others required longer exposure times to form. Tooth formation is regulated by activating and inhibitory signals that impact one on the other. When strong EDAR signals were specifically given to the first two molars, overwhelming inhibitory signals completely inhibited formation of the third molar. In contrast, strong signals specifically given to the third molar induced hypertrophy of the later with occasional appearance of a fourth molar never observed in WT or £da-deficient mice. This clearly positions EDA as an important activating signal in tooth formation. Taken together, these results have implications for the therapy of ectodermal dysplasias.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

HIV-1 sequence diversity is affected by selection pressures arising from host genomic factors. Using paired human and viral data from 1071 individuals, we ran >3000 genome-wide scans, testing for associations between host DNA polymorphisms, HIV-1 sequence variation and plasma viral load (VL), while considering human and viral population structure. We observed significant human SNP associations to a total of 48 HIV-1 amino acid variants (p<2.4 × 10(-12)). All associated SNPs mapped to the HLA class I region. Clinical relevance of host and pathogen variation was assessed using VL results. We identified two critical advantages to the use of viral variation for identifying host factors: (1) association signals are much stronger for HIV-1 sequence variants than VL, reflecting the 'intermediate phenotype' nature of viral variation; (2) association testing can be run without any clinical data. The proposed genome-to-genome approach highlights sites of genomic conflict and is a strategy generally applicable to studies of host-pathogen interaction. DOI:http://dx.doi.org/10.7554/eLife.01123.001.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Recognition and identification processes for deceased persons. Determining the identity of deceased persons is a routine task performed essentially by police departments and forensic experts. This thesis highlights the processes necessary for the proper and transparent determination of the civil identities of deceased persons. The identity of a person is defined as the establishment of a link between that person ("the source") and information pertaining to the same individual ("identifiers"). Various identity forms could emerge, depending on the nature of the identifiers. There are two distinct types of identity, namely civil identity and biological identity. The paper examines four processes: identification by witnesses (the recognition process) and comparisons of fingerprints, dental data and DNA profiles (the identification processes). During the recognition process, the memory function is examined and helps to clarify circumstances that may give rise to errors. To make the process more rigorous, a body presentation procedure is proposed to investigators. Before examining the other processes, three general concepts specific to forensic science are considered with regard to the identification of a deceased person, namely, matter divisibility (Inman and Rudin), transfer (Locard) and uniqueness (Kirk). These concepts can be applied to the task at hand, although some require a slightly broader scope of application. A cross comparison of common forensic fields and the identification of deceased persons reveals certain differences, including 1 - reverse positioning of the source (i.e. the source is not sought from traces, but rather the identifiers are obtained from the source); 2 - the need for civil identity determination in addition to the individualisation stage; and 3 - a more restricted population (closed set), rather than an open one. For fingerprints, dental and DNA data, intravariability and intervariability are examined, as well as changes in these post mortem (PM) identifiers. Ante-mortem identifiers (AM) are located and AM-PM comparisons made. For DNA, it has been shown that direct identifiers (taken from a person whose civil identity has been alleged) tend to lead to determining civil identity whereas indirect identifiers (obtained from a close relative) direct towards a determination of biological identity. For each process, a Bayesian model is presented which includes sources of uncertainty deemed to be relevant. The results of the different processes combine to structure and summarise an overall outcome and a methodology. The modelling of dental data presents a specific difficulty with respect to intravariability, which in itself is not quantifiable. The concept of "validity" is, therefore, suggested as a possible solution to the problem. Validity uses various parameters that have an acknowledged impact on teeth intravariability. In cases where identifying deceased persons proves to be extremely difficult due to the limited discrimination of certain procedures, the use of a Bayesian approach is of great value in bringing a transparent and synthetic value. RESUME : Titre: Processus de reconnaissance et d'identification de personnes décédées. L'individualisation de personnes décédées est une tâche courante partagée principalement par des services de police, des odontologues et des laboratoires de génétique. L'objectif de cette recherche est de présenter des processus pour déterminer valablement, avec une incertitude maîtrisée, les identités civiles de personnes décédées. La notion d'identité est examinée en premier lieu. L'identité d'une personne est définie comme l'établissement d'un lien entre cette personne et des informations la concernant. Les informations en question sont désignées par le terme d'identifiants. Deux formes distinctes d'identité sont retenues: l'identité civile et l'identité biologique. Quatre processus principaux sont examinés: celui du témoignage et ceux impliquant les comparaisons d'empreintes digitales, de données dentaires et de profils d'ADN. Concernant le processus de reconnaissance, le mode de fonctionnement de la mémoire est examiné, démarche qui permet de désigner les paramètres pouvant conduire à des erreurs. Dans le but d'apporter un cadre rigoureux à ce processus, une procédure de présentation d'un corps est proposée à l'intention des enquêteurs. Avant d'entreprendre l'examen des autres processus, les concepts généraux propres aux domaines forensiques sont examinés sous l'angle particulier de l'identification de personnes décédées: la divisibilité de la matière (Inman et Rudin), le transfert (Locard) et l'unicité (Kirk). Il est constaté que ces concepts peuvent être appliqués, certains nécessitant toutefois un léger élargissement de leurs principes. Une comparaison croisée entre les domaines forensiques habituels et l'identification de personnes décédées montre des différences telles qu'un positionnement inversé de la source (la source n'est plus à rechercher en partant de traces, mais ce sont des identifiants qui sont recherchés en partant de la source), la nécessité de devoir déterminer une identité civile en plus de procéder à une individualisation ou encore une population d'intérêt limitée plutôt qu'ouverte. Pour les empreintes digitales, les dents et l'ADN, l'intra puis l'inter-variabilité sont examinées, de même que leurs modifications post-mortem (PM), la localisation des identifiants ante-mortem (AM) et les comparaisons AM-PM. Pour l'ADN, il est démontré que les identifiants directs (provenant de la personne dont l'identité civile est supposée) tendent à déterminer une identité civile alors que les identifiants indirects (provenant d'un proche parent) tendent à déterminer une identité biologique. Puis une synthèse des résultats provenant des différents processus est réalisée grâce à des modélisations bayesiennes. Pour chaque processus, une modélisation est présentée, modélisation intégrant les paramètres reconnus comme pertinents. À ce stade, une difficulté apparaît: celle de quantifier l'intra-variabilité dentaire pour laquelle il n'existe pas de règle précise. La solution préconisée est celle d'intégrer un concept de validité qui intègre divers paramètres ayant un impact connu sur l'intra-variabilité. La possibilité de formuler une valeur de synthèse par l'approche bayesienne s'avère d'une aide précieuse dans des cas très difficiles pour lesquels chacun des processus est limité en termes de potentiel discriminant.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

BACKGROUND: Small RNAs (sRNAs) are widespread among bacteria and have diverse regulatory roles. Most of these sRNAs have been discovered by a combination of computational and experimental methods. In Pseudomonas aeruginosa, a ubiquitous Gram-negative bacterium and opportunistic human pathogen, the GacS/GacA two-component system positively controls the transcription of two sRNAs (RsmY, RsmZ), which are crucial for the expression of genes involved in virulence. In the biocontrol bacterium Pseudomonas fluorescens CHA0, three GacA-controlled sRNAs (RsmX, RsmY, RsmZ) regulate the response to oxidative stress and the expression of extracellular products including biocontrol factors. RsmX, RsmY and RsmZ contain multiple unpaired GGA motifs and control the expression of target mRNAs at the translational level, by sequestration of translational repressor proteins of the RsmA family. RESULTS: A combined computational and experimental approach enabled us to identify 14 intergenic regions encoding sRNAs in P. aeruginosa. Eight of these regions encode newly identified sRNAs. The intergenic region 1698 was found to specify a novel GacA-controlled sRNA termed RgsA. GacA regulation appeared to be indirect. In P. fluorescens CHA0, an RgsA homolog was also expressed under positive GacA control. This 120-nt sRNA contained a single GGA motif and, unlike RsmX, RsmY and RsmZ, was unable to derepress translation of the hcnA gene (involved in the biosynthesis of the biocontrol factor hydrogen cyanide), but contributed to the bacterium's resistance to hydrogen peroxide. In both P. aeruginosa and P. fluorescens the stress sigma factor RpoS was essential for RgsA expression. CONCLUSION: The discovery of an additional sRNA expressed under GacA control in two Pseudomonas species highlights the complexity of this global regulatory system and suggests that the mode of action of GacA control may be more elaborate than previously suspected. Our results also confirm that several GGA motifs are required in an sRNA for sequestration of the RsmA protein.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

Among all sports, football is the one that saw the largest diffusion during the 20th century. Professional leagues exist on all continents and professional footballers are constantly on the move, trying to reach the wealthiest European clubs. Using the football players' market as an example, this article highlights some key features of economic globalization: the new international division of labour, the ever increasing role played by intermediaries to bind the demand and supply of work on a transnational scale, and the setting up of spatially fragmented trade circuits. These processes form the basis for the creation of a global market of footballers in which clubs and championships play complementary roles and are more than ever functionally integrated beyond national borders.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

PURPOSE OF REVIEW: New insight in mitochondrial physiology has highlighted the importance of mitochondrial dysfunction in the metabolic and neuroendocrine changes observed in patients presenting with chronic critical illness. This review highlights specifically the importance of carnitine status in this particular patient population and its impact on beta-oxidation and mitochondrial function. RECENT FINDINGS: The main function of carnitine is long chain fatty acid esterification and transport through the mitochondrial membrane. Carnitine depletion should be suspected in critically ill patients with risk factors such as prolonged continuous renal replacement therapy or chronic parenteral nutrition, and evidence of beta-oxidation impairments such as inappropriate hypertriglyceridemia or hyperlactatemia. When fatty acid oxidation is impaired, acyl-CoAs accumulate and deplete the CoA intramitochondrial pool, hence causing a generalized mitochondrial dysfunction and multiorgan failure, with clinical consequences such as muscle weakness, rhabdomyolysis, cardiomyopathy, arrhythmia or sudden death. In such situations, carnitine plasma levels should be measured along with a complete assessment of plasma amino acid, plasma acylcarnitines and urinary organic acid analysis. Supplementation should be initiated if below normal levels (20 μmol/l) of carnitine are observed. In the absence of current guidelines, we recommend an initial supplementation of 0.5-1 g/day. SUMMARY: Metabolic modifications associated with chronic critical illness are just being explored. Carnitine deficiency in critically ill patients is one aspect of these profound and complex changes associated with prolonged stay in ICU. It is readily measurable in the plasma and can easily be substituted if needed, although guidelines are currently missing.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

There is a debate on whether an influence of biotic interactions on species distributions can be reflected at macro-scale levels. Whereas the influence of biotic interactions on spatial arrangements is beginning to be studied at local scales, similar studies at macro-scale levels are scarce. There is no example disentangling, from other similarities with related species, the influence of predator-prey interactions on species distributions at macro-scale levels. In this study we aimed to disentangle predator-prey interactions from species distribution data following an experimental approach including a factorial design. As a case of study we selected the short-toed eagle because of its known specialization on certain prey reptiles. We used presence-absence data at a 100 Km2 spatial resolution to extract the explanatory capacity of different environmental predictors (five abiotic and two biotic predictors) on the short-toed eagle species distribution in Peninsular Spain. Abiotic predictors were relevant climatic and topographic variables, and relevant biotic predictors were prey richness and forest density. In addition to the short-toed eagle, we also obtained the predictor's explanatory capacities for i) species of the same family Accipitridae (as a reference), ii) for other birds of different families (as controls) and iii) species with randomly selected presences (as null models). We run 650 models to test for similarities of the short-toed eagle, controls and null models with reference species, assessed by regressions of explanatory capacities. We found higher similarities between the short-toed eagle and other species of the family Accipitridae than for the other two groups. Once corrected by the family effect, our analyses revealed a signal of predator-prey interaction embedded in species distribution data. This result was corroborated with additional analyses testing for differences in the concordance between the distributions of different bird categories and the distributions of either prey or non-prey species of the short-toed eagle. Our analyses were useful to disentangle a signal of predator-prey interactions from species distribution data at a macro-scale. This study highlights the importance of disentangling specific features from the variation shared with a given taxonomic level.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

• Grasses rank among the world's most ecologically and economically important plants. Repeated evolution of the C(4) syndrome has made photosynthesis highly efficient in many grasses, inspiring intensive efforts to engineer the pathway into C(3) crops. However, comparative biology has been of limited use to this endeavor because of uncertainty in the number and phylogenetic placement of C(4) origins. • We built the most comprehensive and robust molecular phylogeny for grasses to date, expanding sampling efforts of a previous working group from 62 to 531 taxa, emphasizing the C(4)-rich PACMAD (Panicoideae, Arundinoideae, Chloridoideae, Micrairoideae, Aristidoideae and Danthonioideae) clade. Our final matrix comprises c. 5700 bp and is > 93% complete. • For the first time, we present strong support for relationships among all the major grass lineages. Several new C(4) lineages are identified, and previously inferred origins confirmed. C(3)/C(4) evolutionary transitions have been highly asymmetrical, with 22-24 inferred origins of the C(4) pathway and only one potential reversal. • Our backbone tree clarifies major outstanding systematic questions and highlights C(3) and C(4) sister taxa for comparative studies. Two lineages have emerged as hotbeds of C(4) evolution. Future work in these lineages will be instrumental in understanding the evolution of this complex trait.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

OBJECTIVES: This study aimed to identify the genetic defect in a family with idiopathic ventricular fibrillation (IVF) manifesting in childhood and adolescence. BACKGROUND: Although sudden cardiac death in the young is rare, it frequently presents as the first clinical manifestation of an underlying inherited arrhythmia syndrome. Gene discovery for IVF is important as it enables the identification of individuals at risk, because except for arrhythmia, IVF does not manifest with identifiable clinical abnormalities. METHODS: Exome sequencing was carried out on 2 family members who were both successfully resuscitated from a cardiac arrest. RESULTS: We characterized a family presenting with a history of ventricular fibrillation (VF) and sudden death without electrocardiographic or echocardiographic abnormalities at rest. Two siblings died suddenly at the ages of 9 and 10 years, and another 2 were resuscitated from out-of-hospital cardiac arrest with documented VF at ages 10 and 16 years, respectively. Exome sequencing identified a missense mutation affecting a highly conserved residue (p.F90L) in the CALM1 gene encoding calmodulin. This mutation was also carried by 1 of the siblings who died suddenly, from whom DNA was available. The mutation was present in the mother and in another sibling, both asymptomatic but displaying a marginally prolonged QT interval during exercise. CONCLUSIONS: We identified a mutation in CALM1 underlying IVF manifesting in childhood and adolescence. The causality of the mutation is supported by previous studies demonstrating that F90 mediates the direct interaction of CaM with target peptides. Our approach highlights the utility of exome sequencing in uncovering the genetic defect even in families with a small number of affected individuals.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

INTRODUCTION: Panarteritis nodosa (PAN) is a systemic vasculitis affecting small and medium-sized arteries. Neuro-ophthalmological complications of PAN are rare but numerous, and may affect the eye, the visual and the oculomotor pathways. Such complications occur mainly in patients previously diagnosed with PAN. OBSERVATION: A 51-year-old woman presented with an isolated right trochlear (IV) palsy, in the setting of headaches and fluctuating fever of unknown etiology. Erythrocyte sedimentation rate was 13 mm and full blood cell count was normal. Previous chest X-ray and blood studies were negative for an infection or inflammation. Orbital and cerebral CT scan was normal. Spontaneous recovery of diplopia ensued over four days. Two days later, paresthesia and sensory paresis of the dorsal portion of the left foot were present. Lumbar puncture revealed 14 leucocytes (76 percent lymphocytes) with elevated proteins, but blood studies and serologies were negative. A diagnosis of undetermined meningo-myelo-radiculoneuritis was made. Because of a possible tick bite six weeks previously the patient was empirically treated with 2 g intravenous ceftriaxone for 3 weeks. Fever rapidly dropped. Six weeks after the onset of diplopia, acute onset of blindness in her right eye, diffuse arthralgias and fever motivated a new hospitalization. There was a central retinal artery occlusion of the right eye. Blood studies now revealed signs of systemic inflammation (ESR 30 mm, CRP 12 mg/L, ANA 1/80, pANCA 1/40, leucocytosis 12.4 G/L, Hb 111 g/L, Ht 33 percent). Biopsy of the left sural nerve revealed arterial fibrinoid necrosis. A diagnosis of PAN was made. CONCLUSIONS: Transient diplopia can be the heralding symptom of a systemic vasculitis such as PAN, giant cell arteritis and Wegener granulomatosis. In this patient the presence of accompanying systemic symptoms raised a suspicion of systemic inflammation, but the absence of serologic and imaging abnormalities precluded a specific diagnosis initially. A few weeks later, the presence of a second ischemic event (retinal) and positive blood studies led to a further diagnostic procedure. Oculomotor and abducens palsies have rarely been reported in association with PAN. We report the first case of trochlear nerve paresis as the inaugural neurological sign of PAN. This case highlights the importance of considering inflammatory systemic disorders in patients with acute diplopia particularly when they are young, lack vascular risk factors or cause, and complain of associated systemic symptoms.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

INTRODUCTION: Triple-negative breast cancers (TNBCs) are characterised by lack of expression of hormone receptors and epidermal growth factor receptor 2 (HER-2). As they frequently express epidermal growth factor receptors (EGFRs), anti-EGFR therapies are currently assessed for this breast cancer subtype as an alternative to treatments that target HER-2 or hormone receptors. Recently, EGFR-activating mutations have been reported in TNBC specimens in an East Asian population. Because variations in the frequency of EGFR-activating mutations in East Asians and other patients with lung cancer have been described, we evaluated the EGFR mutational profile in tumour samples from European patients with TNBC. METHODS: We selected from a DNA tumour bank 229 DNA samples isolated from frozen, histologically proven and macrodissected invasive TNBC specimens from European patients. PCR and high-resolution melting (HRM) analyses were used to detect mutations in exons 19 and 21 of EGFR. The results were then confirmed by bidirectional sequencing of all samples. RESULTS: HRM analysis allowed the detection of three EGFR exon 21 mutations, but no exon 19 mutations. There was 100% concordance between the HRM and sequencing results. The three patients with EGFR exon 21 abnormal HRM profiles harboured the rare R836R SNP, but no EGFR-activating mutation was identified. CONCLUSIONS: This study highlights variations in the prevalence of EGFR mutations in TNBC. These variations have crucial implications for the design of clinical trials involving anti-EGFR treatments in TNBC and for identifying the potential target population.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

CONTEXT: The incidence of localised prostate cancer is increasing worldwide. In light of recent evidence, current, radical, whole-gland treatments for organ-confined disease have being questioned with respect to their side effects, cancer control, and cost. Focal therapy may be an effective alternative strategy. OBJECTIVE: To systematically review the existing literature on baseline characteristics of the target population; preoperative evaluation to localise disease; and perioperative, functional, and disease control outcomes following focal therapy. EVIDENCE ACQUISITION: Medline (through PubMed), Embase, Web of Science, and Cochrane Review databases were searched from inception to 31 October 2012. In addition, registered but not yet published trials were retrieved. Studies evaluating tissue-preserving therapies in men with biopsy-proven prostate cancer in the primary or salvage setting were included. EVIDENCE SYNTHESIS: A total of 2350 cases were treated to date across 30 studies. Most studies were retrospective with variable standards of reporting, although there was an increasing number of prospective registered trials. Focal therapy was mainly delivered to men with low and intermediate disease, although some high-risk cases were treated that had known, unilateral, significant cancer. In most of the cases, biopsy findings were correlated to specific preoperative imaging, such as multiparametric magnetic resonance imaging or Doppler ultrasound to determine eligibility. Follow-up varied between 0 and 11.1 yr. In treatment-naïve prostates, pad-free continence ranged from 95% to 100%, erectile function ranged from 54% to 100%, and absence of clinically significant cancer ranged from 83% to 100%. In focal salvage cases for radiotherapy failure, the same outcomes were achieved in 87.2-100%, 29-40%, and 92% of cases, respectively. Biochemical disease-free survival was reported using a number of definitions that were not validated in the focal-therapy setting. CONCLUSIONS: Our systematic review highlights that, when focal therapy is delivered with intention to treat, the perioperative, functional, and disease control outcomes are encouraging within a short- to medium-term follow-up. Focal therapy is a strategy by which the overtreatment burden of the current prostate cancer pathway could be reduced, but robust comparative effectiveness studies are now required.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

In line with educational issues involved in emergent literacy practices in preschool, in particular those concerning comprehension processes, this paper focuses on picture-based narrative comprehension during an interactive reading session of a wordless picture book, involving a group of children aged three and their teacher. Children are asked to make inferences about the meaning and outcome of the story, a procedure which gradually elicits their responses on how events link together, thus enhancing their capacity to use prior and implicit knowledge to build the story meaning. Moreover, this study highlights the importance of interaction for developing comprehension. Data collected was analysed following didactic microgenesis, an analytical approach showing that knowledge built during interaction depends on the joint construction of a zone of common meaning by which teacher and children try to adjust to each other. In order to help the process of merging different meanings of the story built online, a text written by researchers, following the narrative structure of the story, was read by the teacher after the picture-based reading. This led us to examine through interactional analysis which semiotic cues were used during recall on the following day, as an additional measure of knowledge construction.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

ABSTRACT : A firm's competitive advantage can arise from internal resources as well as from an interfirm network. -This dissertation investigates the competitive advantage of a firm involved in an innovation network by integrating strategic management theory and social network theory. It develops theory and provides empirical evidence that illustrates how a networked firm enables the network value and appropriates this value in an optimal way according to its strategic purpose. The four inter-related essays in this dissertation provide a framework that sheds light on the extraction of value from an innovation network by managing and designing the network in a proactive manner. The first essay reviews research in social network theory and knowledge transfer management, and identifies the crucial factors of innovation network configuration for a firm's learning performance or innovation output. The findings suggest that network structure, network relationship, and network position all impact on a firm's performance. Although the previous literature indicates that there are disagreements about the impact of dense or spare structure, as well as strong or weak ties, case evidence from Chinese software companies reveals that dense and strong connections with partners are positively associated with firms' performance. The second essay is a theoretical essay that illustrates the limitations of social network theory for explaining the source of network value and offers a new theoretical model that applies resource-based view to network environments. It suggests that network configurations, such as network structure, network relationship and network position, can be considered important network resources. In addition, this essay introduces the concept of network capability, and suggests that four types of network capabilities play an important role in unlocking the potential value of network resources and determining the distribution of network rents between partners. This essay also highlights the contingent effects of network capability on a firm's innovation output, and explains how the different impacts of network capability depend on a firm's strategic choices. This new theoretical model has been pre-tested with a case study of China software industry, which enhances the internal validity of this theory. The third essay addresses the questions of what impact network capability has on firm innovation performance and what are the antecedent factors of network capability. This essay employs a structural equation modelling methodology that uses a sample of 211 Chinese Hi-tech firms. It develops a measurement of network capability and reveals that networked firms deal with cooperation between, and coordination with partners on different levels according to their levels of network capability. The empirical results also suggests that IT maturity, the openness of culture, management system involved, and experience with network activities are antecedents of network capabilities. Furthermore, the two-group analysis of the role of international partner(s) shows that when there is a culture and norm gap between foreign partners, a firm must mobilize more resources and effort to improve its performance with respect to its innovation network. The fourth essay addresses the way in which network capabilities influence firm innovation performance. By using hierarchical multiple regression with data from Chinese Hi-tech firms, the findings suggest that there is a significant partial mediating effect of knowledge transfer on the relationships between network capabilities and innovation performance. The findings also reveal that the impacts of network capabilities divert with the environment and strategic decision the firm has made: exploration or exploitation. Network constructing capability provides a greater positive impact on and yields more contributions to innovation performance than does network operating capability in an exploration network. Network operating capability is more important than network constructing capability for innovative firms in an exploitation network. Therefore, these findings highlight that the firm can shape the innovation network proactively for better benefits, but when it does so, it should adjust its focus and change its efforts in accordance with its innovation purposes or strategic orientation.

Relevância:

10.00% 10.00%

Publicador:

Resumo:

PURPOSE OF REVIEW: HIV targets primary CD4(+) T cells. The virus depends on the physiological state of its target cells for efficient replication, and, in turn, viral infection perturbs the cellular state significantly. Identifying the virus-host interactions that drive these dynamic changes is important for a better understanding of viral pathogenesis and persistence. The present review focuses on experimental and computational approaches to study the dynamics of viral replication and latency. RECENT FINDINGS: It was recently shown that only a fraction of the inducible latently infected reservoirs are successfully induced upon stimulation in ex-vivo models while additional rounds of stimulation make allowance for reactivation of more latently infected cells. This highlights the potential role of treatment duration and timing as important factors for successful reactivation of latently infected cells. The dynamics of HIV productive infection and latency have been investigated using transcriptome and proteome data. The cellular activation state has shown to be a major determinant of viral reactivation success. Mathematical models of latency have been used to explore the dynamics of the latent viral reservoir decay. SUMMARY: Timing is an important component of biological interactions. Temporal analyses covering aspects of viral life cycle are essential for gathering a comprehensive picture of HIV interaction with the host cell and untangling the complexity of latency. Understanding the dynamic changes tipping the balance between success and failure of HIV particle production might be key to eradicate the viral reservoir.