Pensando la educación en medios desde los discursos: psicológico-biomédico, hermenéutico-construccionista post-estructural y crítico. Cuatro miradas al sujeto joven que educamos

El texto que sigue resulta de una re-construcción de cuatro aproximaciones -biomédica-evolutiva, crítica, hermenéutico-construccionista y post-estructural- a la educación en medios con jóvenes en contextos educativos formales, entendida ésta en un sentido amplio como la enseñanza y aprendizaje de los medios de comunicación analógicos y digitales. Uno de los propósitos de la re-construcción tiene que ver, en primer lugar con la visibilización de la diversidad de opciones y epistemologías disponibles a la hora de plantear un escenario formativo en educación con medios, y con las posibilidades formativas que dicha multiplicidad nos ofrece...

Influence of pre partum and post partum plane of nutrition on the performance of crossbred suckler cows and their progeny

Selostus: Sisäruokintakauden energiamäärien vaikutus risteytysemolehmien tuotantoon

Cuando Frankenstein encontró a Dorian Gray: dandysmo, post-identidad y sujetos virtuales

The appearance and popularization of the internet has created new forms of writing, which compel us to think anew about identity and subjectivity. Webjournals or blogs are specially interesting because they are a massive phenomenon that use autobiographical writing in a peculiar way. These forms of writing stress a particular paradox of the genre: the coexistence between a purpose of private, confessional and spontaneous writing and a public image, carefully built, as a result of its writing. The technology is new, but, in fact, the paradox is old. This paper tries to explore this old paradox, our eternal condition of cyborgs, our use of technologies in order to construct a public, unique and recognizably identity. In oder to do so, I will try to show the virtual condition of any written individual ¿this issue has already been dealt with by autobiographical studies¿, focusing on blogs, and especially on concrete example (Lord Whimsy¿s Journal). I will pay attention to gender as a technology that constructs identity and, at the same time, is deconstructed by the autobiographical narratives analyzed. In short, I attempt to show that virtual and autobiographical discourse do not bring forth a new kind of subject but the permanence of an old phenomenon "clearly developed by dandyism, for instance¿: the use of tehnologies to re-invent, re-formulate and re-construct us as multiple, hybrid and mixed subjects."

Altered expression and posttranslational modification of neurofilaments in methylmalonic aciduria

Neurofilaments (NF), the main components of axonal cytoskeleton, are known to be involved in several neurodegenerative diseases. It has been reported that methylmalonate and propionate affect phosphorylation of NFs. In an in vitro model for methylmalonic aciduria our group has recently shown that 2- methylcitrate (2-MCA) is the most toxic metabolite for developing brain cells. Here, we studied the effects of repetitive administration of 1mM 2- MCA every 12 hours over 3 days on the development of NFs in 3D organotypic rat brain cell cultures. By immunohistochemistry with antibodies specific for the different NF subunits (light NFL, medium NFM, heavy NFH) as well as for phosphorylated (p) and glycosylated (g) forms of NFs, we observed a decrease of axonal labeling and a disorganized axonal pattern. Interestingly, signal retention of p-NFM and g-NFM was observed in neuronal soma. Western blotting showed the decrease of NFL and NFH subunits. Taken together, our data show that 2-MCA alters expression of the different NF subunits as well as their post-translational modifications. This likely results in disturbed NF assembly, abnormal accumulation of NF in neuronal cell bodies and impairment of axonal development.We conclude thatNF are involved in 2-MCA-induced neurodegeneration in methylmalonic aciduria.

Analyse des modifications de la chromatine impliquées dans l'effet barrière de CTF1 aux télomères humains

Eukaryotic genomes are compartmentalized in different structural domains that can affect positively or negatively gene expression. These regions of euchromatin and heterochromatin are characterized by distinct histones marks which can facilitate or repress gene transcription. The chromatin environment represents thus one of the main problems to control gene expression in biotechnological applications or gene therapy, since its expression is affected by the chromatin neighboring its locus of insertion. Some chromatin regions like telomeres are composed of constitutive heterochromatin which leads to the telomeric position effect (TPE) that silences genes adjacent to the telomere. TPE is known to spread by the selfrecruitment of the SIR histone deacetylase complex from the telomere in S.cerevisiae, but the histone marks that are associated to telomeric chromatin in mammalian cells remain mostly unknown. The transcription factor CTF1 has shown antisilencing properties in mammalian cells and also a boundary activity against TPE in yeast cells when fused to the yeast Gal4 DNA binding domain. In the work presented here, we describe a dual-reporter system to assess the boundary activity of proteins such as CTF1 at human telomeres. When located between the two reporter genes, CTF1 shields the telomere distal gene from TPE, while the telomereproximal gene remains silenced by telomeric heterochromatin. The boundary activity of CTF1 is shown to act regardless its function of transcriptional activator, by opposition to the transcriptional activator VP16 which activates indifferently both transgenes. Moreover, this study shows that CTF1 boundary activity is linked to its H3 binding function, as expected from a chromatin remodeler. ChIP experiments showed that histone deacetylation is the main histone modification involved in gene silencing at mammalian cell telomeres. Distinctly to yeast cells, the histone deacetylation signal in human cells extented over a short range along the chromosome. CTF1 may help to block this propagation and therefore to restore histones acetylation level on telomere protected locus. Surprisingly, other histone marks such as trimethyl-H3K9 or trimethyl-H4K20 were found on telomere protected locus, while in another clone, unsilencing of telomere distal transgene was associated with recruitment of the histone variant H2A.Z. Thus, I conclude that CTF1 displays a chromatin boundary function which is independent of its transcriptional activity and therefore exhibit features required for use as chromatin insulator in biotechnological applications. RESUME Les génomes eucaryotes sont compartementalisés en domaines structurels qui peuvent affecter positivement ou négativement l'expression des gènes avoisinants. Ces régions dites d'euchromatine ou d'hétérochromatine sont caractérisées par des modifications posttraductionnelles des histones qui peuvent faciliter ou au contraire inhiber la transcription des gènes qui s'y trouvent. Ainsi, isoler un gène de son environnement chromatinien est problème fréquent lorsqu'il s'agit de contrôler son expression dans le cadre d'applications en biotechnologie ou encore en thérapie génique. Certaines régions de chromatine telles que les télomères sont composées d'hétérochromatine constitutive qui mène au silençage des gènes avoisinants. Cet effet de position télomérique (TPE) est connu dans la levure S.cerevisiae comme se propageant par auto-recrutement du complexe de déacétylation d'histone SIR, alors que peu de modifications de chromatine ont pu être associées à ce phénomène dans les cellules de mammifères. Le facteur de transcription CTF1 a montré des propriétés d'anti-silençage dans les cellules de mammifères, ainsi qu'une activité barrière contre le silençage télomérique dans les cellules de levures lorsqu'il est fusionné au domaine de liaison à l'ADN de la protéine de levure Gal4. Dans le travail présenté ci-après est décrit un système à deux gènes rapporteurs permettant de mesurer l'activité barrière de protéines telles que CTF1 aux télomères humains, et les modifications de chromatine qui y sont associées. Lorsque CTF1 est placé entre les deux gènes rapporteurs, le gène distant du télomère est protégé du silençage qui lui est associé, alors que le gène proche du télomère reste soumis à ce silençage induit par l'hétérochromatine télomérique. L'activité barrière de CTF1 est montrée ici comme agissant indépendamment de son activité transcriptionnelle, par opposition à l'activateur transcriptionnel VP16 qui active indifféremment les deux transgènes. En outre, cette étude appuie l'hypothèse stipulant que CTF1 agisse comme remodeleur chromatinien puisqu'elle démontre que son activité barrière est directement dépendante de son activité de liaison avec l'histone H3. De plus, des expériences d'immuno-précipitation de la chromatine démontrent que la déacétylation des histones est le majeur phénomène intervenant dans le silençage télomérique. Par opposition à la levure, ce signal de déacétylation ne se propage dans les cellules humaines que sur une courte distance le long du chromosome. CTF1 agit ainsi en bloquant cette propagation et en restaurant le niveau d'acétylation des histones sur le locus protégé du télomère. De manière surprenante et inattendue, d'autres modifications d'histones telles que 4 les H3K9 et H4K20 triméthylées sont aussi observées à ce locus, tandis le recrutement du variant H2A.Z peut aussi être suffisant à restaurer l'expression du gène distant du télomère. En terme de cette analyse, CTF1 exhibe ainsi une fonction de barrière chromatinienne qui exclue une activité transcriptionnelle non désirée - propriété qui est requise dans l'établissement des isolateurs visant à permettre le contrôle d'un transgène dans le cadre d'applications en biotechnologies.

Characterization of the effect of mammary gland irridiation on experimental brest cancer progression and analysis of the implicated mechanisms

SUMMARY Radiotherapy is commonly and efficiently used to treat solid cancer in the clinic. Experimental evidence however suggests that radiation can promote tumor progression by inducing chronic modifications of the tumor microenvironment. Clinically, these observations are highly relevant to aggressive tumoral lesions relapsing after radiation therapy, a leading cause of patients' death. The investigation and understanding of the biological mechanisms implicated in the malignant progression of post-radiation relapses are therefore of major importance. Here we used a syngeneic (immunocompetent) breast cancer orthotopic xenograft model, to show that local irradiation of the mammary gland promotes the appearance of an invasive and metastatic tumor phenotype. Previous studies in our laboratory revealed that inhibition of tumor-induced angiogenesis and consequent increase in tumor hypoxia promotes metastasis formation through the activation of pro-invasive programs in the tumor cells. Our results extend these observations suggesting that mammary gland irradiation induces the recruitment of CD11b+ cells to both the primary tumor and the lungs at pre-metastatic stages through the hypoxia-dependent induction of Kit-ligand (KITL) expression in primary tumors. Abrogation of KITL expression in tumor cells prevented CD11 b+ cells accumulation in both the primary tumor and lungs and significantly reduced metastases of tumors growing in irradiated mammary gland. Importantly, irradiated mammary gland enhanced tumor-induced mobilization of circulating CD11b+cKit+ myelomonocytic cells through a HIF1- and KITL-dependent process. By cell transfer experiments, mobilized circulating CD11b+cKit+ cells were shown to supply both tumor- and lungs infiltrating CD11b+ cells. Using a blocking antibody against cKit (the KITL receptor), the mobilization of CD11b+cKit+ ceils was prevented as well as lung metastases derived from tumors growing in irradiated mammary gland. Taken together, these results indicate that tumors growing in a pre-irradiated mammary gland partially promote their malignant progression through the distant mobilization of circulating myelomonocytic precursor cells. They identify KITL inhibition and/or cKit receptor neutralization as potentially promising therapeutic approaches for post-radiation relapses. RESUME La radiothérapie est largement utilisée comme traitement de choix de nombreux types de cancers. L'agressivité des récidives tumorales observée en clinique après radiothérapie suggère cependant que le recours à l'irradiation pourrait dans certains cas accélérer la progression tumorale. De récents travaux expérimentaux ont en effet permis d'appuyer cette hypothèse, en montrant notamment l'effet néfaste des modifications chroniques de l'environnement induites par l'irradiation sur la progression tumorale. A l'aide d'un modèle murin syngénique orthotopique de cancer de sein, nous avons pu montrer que l'irradiation locale de la glande mammaire facilite l'invasion et la dissémination métastatique des cellules tumorales en favorisant le recrutement de cellules myéloïdes CD11 b+ vers la tumeur primaire et les poumons à un stade pré-métastatique. Comme mécanisme impliqué dans le recrutement des cellules CD11b+, nous avons pu observer après irradiation locale de la glande mammaire une expression augmentée de Kit-ligand (KITL) dans la tumeur (induite par l'hypoxie) ainsi que la mobilisation de cellules myéloïdes circulantes exprimant le récepteur cKit et précurseurs des cellules CD11b+ infiltrant la tumeur et les poumons. En empêchant la mobilisation par la tumeur de cellules circulantes cKit+ par des approches à la fois génétique et pharmacologique nous avons pu prévenir l'accumulation de cellules myéloïdes CD11 b+ dans la tumeur primaire et les poumons ainsi que la dissémination métastatique induites par' l'irradiation de la glande mammaire. De façon générale, ces résultats montrent que la progression agressive des tumeurs qui se développent dans un environnement irradié repose à la fois sur l'expression tumorale de KITL et la mobilisation de cellules myéloïdes précurseurs cKit*. Ils auront permis d'identifier KITL et/ou cKit comme des cibles thérapeutiques potentielles intéressantes pour le traitement des récidives tumorales après radiothérapie.

Post-exercise parasympathetic reactivation and sensibility to hypoxia

Introduction Exposure to hypoxia leads to several reactions of the organism, which try to compensate the reduced oxygen level in the blood. Acute response is characterized by an increase in pulmonary ventilation (Hypoxia Ventilatory Response, HVR) and in cardiac output (cardiac response to hypoxia). Heart rate (HR) at rest and during exercise is higher at high altitude than at sea level, whereas HRmax is lower. These cardiac adaptations are partially explained by an increased sympathetic stimulation associated with a reduced parasympathetic tone (12). The precise mechanisms of HRmax decline in acute hypoxia are however still to be identified, although several hypothesis have been suggested, such as a direct effect of hypoxia on the electrophysiological properties, an influence of skeletal maximal VO2 or a modulation of the autonomic nervous system (8). Some authors have reported that endurance trained athletes present an increased sensitivity to hypoxia shown by a large reduction in VO2max and an important decrease in arterial saturation. (9,11, 13) A hypoxia test can assess the sensibility of chemoreceptors to the reduction of oxygen by calculating hypoxic ventilatory and cardiac responses, knowing that low sensibility is correlated with poor acclimatization. Two parameters results from the differences in ventilation (and heart rate) divided by the difference in the arterial oxygen saturation between normoxia and hypoxia (18). Objective The hypothesis tested by this study is that parasympathetic reactivation after moderate effort in hypoxic condition can be used as a marker of individual sensibility to hypoxia. Parasympathetic reactivation is a marker of vagal tone that predict endurance capacity and aerobic fitness (2,7). Methods Subjects This study uses data obtained from two groups of athletes participating into two larger studies about adaptation to hypoxia. One group is composed of elite athletes (Swiss ski mountaineering team), the other one of mid-level athletes (ski mountaineering amateurs). The particularity of this target population is that they often train at high altitude, and therefore could show a better response to hypoxia than athleltes of other disciplines. Protocol The athletes performed a submaximal exercise (6min run at 9 km/h, flat) followed by 10 min of seated rest either in an hypoxic chamber (simulated altitude of 3000m) or in normoxic conditions. During the resting phase parasympathetic reactivation was assessed by beat-to-beat HR measurements.A test of tolerance to altitude was also performed. Analysis Parasympathetic reactivation, assessed by the calculation of the root mean square of successive differences in the R-R intervals (RMSSD)(4), is compared to individual responses at altitude, in order to appreciate the correlation between the two phenomena.

Effects of gastric bypass and gastric banding on glucose kinetics and gut hormone release

Rapport de Synthèse : Introduction : outre son effet bénéfique sur le poids, la chirurgie bariatrique améliore de façon considérable l'homéostasie glucide chez les patients diabétiques. Cette amélioration survient très tôt dans la période post-opératoire, avant que le poids ne soit réduit de manière importante. De plus, les interventions chirurgicales qui "court-circuitent" une partie de l'intestin grêle, telle que le by-pass gastrique, apparaissent être plus efficaces que les interventions purement restrictives, telles que le cerclage gastrique. Objectifs : cette étude a pour but d'étudier la cinétique du glucose et la sécrétion d'hormones gastro-intestinales, consécutive à l'ingestion d'une dose charge de glucose, chez des patients opérés d'un by-pass ou d'un cerclage gastrique. Méthodes : nous avons comparé des groupes de femmes non diabétiques ayant bénéficié d'un by-pass gastrique (BPG, n=8) ou d'un cerclage gastrique (CG, n=6) à un groupe de femmes contrôles d'âge et de poids appariées n'ayant subi aucune intervention bariatrique (C, n=8). L'étude a été réalisée alors que le poids des volontaires était stable, soit entre 9 et 48 mois après le BPG, et 25 à 85 mois après le CG. Nous avons étudié, pendant les 4 heures qui ont suivies l'ingestion d'une dose charge de glucose; la cinétique du glucose ingéré et du glucose total à l'aide d'un glucose radio-activement marqué, ainsi que la cinétique de l'insuline et de différentes hormones gastro-intestinales. Résultats : l'apparition du glucose exogène dans la circulation systémique est plus rapide chez les patients opérés d'un BPG et s'accompagne d'une hyperglycémie postprandiale plus brève. La réponse insulinique est également plus précoce et plus importante que dans les deux autres groupes. S'agissant des hormones gastro-intestinales, on observe dans la période postprandiale une augmentation de PYY et de GLP-1 et une suppression de la grehline significativement plus importante après BPG. Discussion : ces différentes observations suggèrent que le BPG est associé à de profonds changements de la cinétique du glucose et des altérations de la régulation d'hormones gastro-intestinales. Les modifications susmentionnées apparaissant être secondaires aux modifications anatomiques consécutives au BPG, i.e. la mise "hors-circuit" de l'estomac distal et de l'intestin grêle proximal, compte tenu du fait qu'elles ne sont pas observées après CG. Finalement, la stimulation de PYY et de GLP-1 ainsi que la suppression postprandiale plus importante de ghréline est compatible avec la diminution spontanée de la prise alimentaire observée chez les patients opérés d'un BPG.

IgG subclass switch capacity is low in switched and in IgM-only, but high in IgD+IgM+, post-germinal center (CD27+) human B cells.

Recent studies have shown that in humans the germinal center reactions produce three types of V(D)J mutated B cells in similar proportions, i.e. Ig-switched, IgD-IgM+ (IgM-only) and IgD+IgM+ cells, and that together they form the CD27+ compartment of recirculating B cells. We investigated the Ig isotype switch capacity of these cells. Peripheral blood B subsets were sorted and IgG subclass secretion in presence or absence of IL-4 was compared in B cell assays which lead to Ig secretion in all (coculture with EL-4 thymoma cells) or only in CD27+ (CD40L stimulation) B cells. Already switched IgG+ B cells showed no significant sequential switch and IgM-only cells also had a low switch capacity, but IgD+CD27+ switched as much as IgD+CD27- B cells to all IgG subclasses. Thus, in switched B cells some alterations compromising further switch options occur frequently; IgM-only cells may result from aborted switch. However, IgD+CD27+ human B cells, extensively V(D)J mutated and "naive" regarding switch, build up a repertoire of B cells combining (1) novel cross-reactive specificities, (2) increased differentiation capacity (including after T-independent stimulation by Staphylococcus aureus Cowan I) and (3) the capacity to produce appropriate isotypes when they respond to novel pathogens.

Performance and hormonal profile in broiler chickens fed with different energy levels during post restriction period

The aim of this work was to investigate the influence of diet energy level on performance and hormonal profiles of broilers during post restriction period. It was a split-plot experiment, and the main treatments were in a 2x2 factorial scheme. Birds were fed restricted to 30% of the ad libitum intake, from 7 to 14 days of age. After the restriction period, birds were fed ad libitum with diets containing low (2,900 kcal ME/kg) or high (3,200 kcal ME/kg) energy until 49 days of age. Broilers fed with high energy ration showed lower feed intake and better feed conversion and decreased carcass protein; however, abdominal fat pad, and total carcass fat were not affected by ration energy levels or feeding program. Neither diet energy level nor feed restriction program changed body weight at 49 days. The profile of insulin-like growth factor-1 (IGF-1) was reduced during the feed restriction period, but increased at refeeding period. Feeding program and ration energy level did not affect T3, T4 and growth hormone serum concentrations. Feed restriction at 30% of ad libitum intake is not enough to promote changes on carcass quality, related to fat deposition, and on metabolic hormone levels, except IGF-1 seric level that has rapid increase after feed restriction.

Sensitive gene expression profiling of human T cell subsets reveals parallel post-thymic differentiation for CD4+ and CD8+ lineages.

The differentiation of CD4(+) or CD8(+) T cells following priming of naive cells is central in the establishment of the immune response against pathogens or tumors. However, our understanding of this complex process and the significance of the multiple subsets of differentiation remains controversial. Gene expression profiling has opened new directions of investigation in immunobiology. Nonetheless, the need for substantial amount of biological material often limits its application range. In this study, we have developed procedures to perform microarray analysis on amplified cDNA from low numbers of cells, including primary T lymphocytes, and applied this technology to the study of CD4 and CD8 lineage differentiation. Gene expression profiling was performed on samples of 1000 cells from 10 different subpopulations, defining the major stages of post-thymic CD4(+) or CD8(+) T cell differentiation. Surprisingly, our data revealed that while CD4(+) and CD8(+) T cell gene expression programs diverge at early stages of differentiation, they become increasingly similar as cells reach a late differentiation stage. This suggests that functional heterogeneity between Ag experienced CD4(+) and CD8(+) T cells is more likely to be located early during post-thymic differentiation, and that late stages of differentiation may represent a common end in the development of T-lymphocytes.

Changes in Aortic Pulse Wave Velocity in Hypertension Post-Menopausal Women: Comparison Between Calcium Channel Blocker (CCB) Vs Angiotensin Receptor Blocker (ARB) Regimen

Objective: To compare effects of a non-renin-angiotensin system (RAS) blocker, using a CCB, or a RAS blocker, using an ARB regimen on the arterial stiffness reduction in postmenopausal hypertensive women. Methods: In this prospective study, a total of 125 hypertensive women (age: 61.4_6 yrs; 98% Caucasian; BW: 71.9_14 kg; BMI: 27.3_5 kg/m2; SBP/ DBP: 158_11/92_9 mmHg) were randomized between ARB (valsartan 320mg_HCTZ) and CCB (amlodipine 10mg _ HCTZ). The primary outcome was carotid-femoral pulse wave velocity (PWV) changes after 38 weeks of treatment. Results: There were no significant differences in baseline demographic data between the two groups. Both treatments effectively lowered BP at the end of the study with similar (p>0.05) reductions in the valsartan (_22.9/_10.9 mmHg) and amlodipine based (_25.2/_11.7 mmHg) treatment groups. Despite a lower (p<0.05 for DBP) central SBP/DBP in the CCB group (_19.2/_10.3 mmHg) compared to the valsartan group (_15.7/_7.6 mmHg) at week 38, a similar reduction in carotid-femoral PWV (_1.7 vs _1.9 m/sec; p>0.05) was observed between both groups. The numerically larger BP reduction observed in the CCB group was associated with a much higher incidence of peripheral edema (77% vs 14%) than the valsartan group. Conclusion: In summary, BP lowering in postmenopausal women led to a reduction in arterial stiffness assessed by PWV measurement. Both regimens reduced PWV at 38 weeks of treatment to a similar degree, despite differences in BP lowering suggesting that the effect of RAS blockade to influence PWV may partly be independent of BP.

Active packaging containing nisin and high pressure processing as post-processing listericidal treatments for convenience fermented sausages

Listeria monocytogenes was inoculated on the surface of sliced fermented sausages with no added sodium salt. The pathogen was progressively inactivated during the product shelf life (90 days). Antimicrobial packaging of fermented sausages with PVOH films containing nisin induced a more pronounced reduction of L. monocytogenes counts during refrigerated storage. HPP alone (600 MPa, 5 min, 12 °C) had no antimicrobial effect against L. monocytogenes at the studied conditions. Combination of HPP with antimicrobial packaging did not produce any extra protection against L. monocytogenes compared to antimicrobial packaging alone. The lack of effect of HPP on L. monocytogenes was attributed to a protective effect exerted by the low water activity of the product and its lactate content. These results reflect that antimicrobial packaging with the inclusion of nisin as a natural antimicrobial could be considered as an effective method to reduce the levels of L. monocytogenes in sliced fermented sausages with no added sodium salt