Microdomains bounded by endoplasmic reticulum segregate cell cycle calcium transients in syncytial Drosophila embryos

Cell cycle calcium signals are generated by the inositol trisphosphate (InsP3)–mediated release of calcium from internal stores (Ciapa, B., D. Pesando, M. Wilding, and M. Whitaker. 1994. Nature. 368:875–878; Groigno, L., and M. Whitaker. 1998. Cell. 92:193–204). The major internal calcium store is the endoplasmic reticulum (ER); thus, the spatial organization of the ER during mitosis may be important in shaping and defining calcium signals. In early Drosophila melanogaster embryos, ER surrounds the nucleus and mitotic spindle during mitosis, offering an opportunity to determine whether perinuclear localization of ER conditions calcium signaling during mitosis. We establish that the nuclear divisions in syncytial Drosophila embryos are accompanied by both cortical and nuclear localized calcium transients. Constructs that chelate InsP3 also prevent nuclear division. An analysis of nuclear calcium concentrations demonstrates that they are differentially regulated. These observations demonstrate that mitotic calcium signals in Drosophila embryos are confined to mitotic microdomains and offer an explanation for the apparent absence of detectable global calcium signals during mitosis in some cell types

Critical media literacy after the media

En este trabajo se reflexiona sobre las relaciones entre alfabetización, alfabetización mediática y educación para los medios, relacionándolas con los hallazgos de diferentes investigaciones etnográficas, a fin de proponer nuevas formas de práctica para la alfabetización crítica en los medios. Vivimos en la postmodernidad, en la era «después de los medios» –y no es que ya no existan los medios–, sino que, por el contrario, surge una forma de pensar –y enseñar– que se resiste a la idea de considerar los medios como algo ajeno a la ciudadanía en la vida cotidiana. Para el autor, la permanencia de preceptos y prácticas anquilosadas sobre educación en los medios dificulta la puesta en marcha de proyectos de alfabetización mediática, al igual que una visión tradicionalista de la literatura genera prácticas viciadas de lectura en el aula. La enseñanza formal de la lengua ha obstaculizado el desarrollo de lectores críticos y competentes, imponiendo un modelo de lector unidimensional. Igualmente, los estudios mediáticos han ensombrecido la alfabetización en los medios, subestimando la legitimidad del estudio de la cultura popular en sí misma desde un punto de partida erróneo. La educación en medios es aun una asignatura pendiente y requiere un cambio de perspectiva. En este artículo, fruto de investigaciones, se propone una «pedagogía del inexperto» como estrategia para la alfabetización crítica en los medios.This article questions the relationships between literacy, media literacy and media education. In the process, we connect the findings from a range of our ethnographic research and use these to propose new forms of practice for critical media literacy. By ‘after the media’, we do not posit a temporal shift (that ‘the media’ has ceased to be). Instead, we conceive of this as akin to the postmodern – a way of thinking (and teaching) that resists recourse to the idea of ‘the media’ as external to media literate agents in social practice. The preservation of an unhelpful set of precepts for media education hinder the project of media literacy in the same way as the idea of ‘literature’ imposes alienating reading practices in school. Just as the formal teaching of English has obstructed the development of critical, powerful readers by imposing an alienating and exclusive model of what it means to be a reader, so has Media Studies obscured media literacy. Despite ourselves, we have undermined the legitimation of studying popular culture as an area by starting out from the wrong place. This incomplete project requires the removal of ‘the media’ from its gaze. The outcomes of our research thus lead us to propose a ‘pedagogy of the inexpert’ as a strategy for critical media literacy

Combined effect of cell geometry and polarity domains determines the orientation of unequal division

Cell division orientation is thought to result from a competition between cell geometry and polarity domains controlling the position of the mitotic spindle during mitosis. Depending on the level of cell shape anisotropy or the strength of the polarity domain, one dominates the other and determines the orientation of the spindle. Whether and how such competition is also at work to determine unequal cell division (UCD), producing daughter cells of different size, remains unclear. Here, we show that cell geometry and polarity domains cooperate, rather than compete, in positioning the cleavage plane during UCDs in early ascidian embryos. We found that the UCDs and their orientation at the ascidian third cleavage rely on the spindle tilting in an anisotropic cell shape, and cortical polarity domains exerting different effects on spindle astral microtubules. By systematically varying mitotic cell shape, we could modulate the effect of attractive and repulsive polarity domains and consequently generate predicted daughter cell size asymmetries and position. We therefore propose that the spindle position during UCD is set by the combined activities of cell geometry and polarity domains, where cell geometry modulates the effect of cortical polarity domain(s)

Quantifying debris-flow hazard and risk based on fan sector

We show how a quantitative estimate of debris-flow hazard and risk can be derived simply from the position of infrastructure on the fan relative to the fan apex and the most likely flow path (e.g., active channel). Fan sectors and the spatial probability of impact in each sector are based on a fan-normalized heat map of debris-flow impacts derived from 146 mapped impact areas across 30 fans in southwestern British Columbia, Canada. As a proof-of-concept, we provide an example for annual life loss risk to an individual who occupies a home in various sectors of a debris-flow fan. The results are comparable to broad findings from quantitative risk assessments completed at 10 fans in British Columbia and Alberta, Canada with similar characteristics. The method presented here is a way to obtain a high-level quantitative risk estimate prior to a detailed site-specific assessment

Étude qualitative sur l’expérience des résidents canadiens du modèle d’éducation médicale fondée sur les compétences

Background: Competency-based medical education (CBME) is an outcomes-based curricular paradigm focused on ensuring that graduates are competent to meet the needs of patients. Although resident engagement is key to CBME’s success, few studies have explored how trainees have experienced CBME implementation. We explored the experiences of residents in Canadian training programs that had implemented CBME. Methods: We conducted semi-structured interviews with 16 residents in seven Canadian postgraduate training programs, exploring their experiences with CBME. Participants were equally divided between family medicine and specialty programs. Themes were identified using principles of constructivist grounded theory. Results: Residents were receptive to the goals of CBME, but in practice, described several drawbacks primarily related to assessment and feedback. For many residents, the significant administrative burden and focus on assessment led to performance anxiety. At times, residents felt that assessments lacked meaning as supervisors focused on “checking-boxes” or provided overly broad, non-specific comments. Furthermore, they commonly expressed frustration with the perceived subjectivity and inconsistency of judgments on assessments, especially if assessments were used to delay progression to greater independence, contributing to attempts to "game the system". Faculty engagement and support improved resident experiences with CBME. Conclusion: Although residents value the potential for CBME to improve the quality of education, assessment and feedback, the current operationalization of CBME may not be consistently achieving these objectives. The authors suggest several initiatives to improve how residents experience assessment and feedback processes in CBME.Contexte : L’éducation médicale fondée sur les compétences (EMFC) est un paradigme dans lequel le programme de formation est axé sur les résultats et vise à garantir que les diplômés aient les compétences nécessaires pour répondre aux besoins des patients. Bien que l’engagement des résidents soit la clé du succès de l’EMFC, peu d’études ont exploré comment ils vivent son introduction. Nous nous sommes penchés sur l’expérience des résidents dans les programmes de formation canadiens qui ont mis en œuvre l’EMFC. Méthodes : Nous avons mené des entrevues semi-structurées avec 16 résidents de sept programmes de formation postdoctorale canadiens, afin de sonder leur expérience de l’EMFC. Les participants étaient répartis de façon égale entre la médecine familiale et les programmes de spécialité. Les thèmes ont été dégagés en appliquant les principes de la théorie enracinée constructiviste. Résultats : Bien que réceptifs aux objectifs de l’EMFC, les résidents décrivent des inconvénients de sa mise en pratique, notamment sur le plan de l’évaluation et de la rétroaction. Pour beaucoup d’entre eux, la focalisation sur l’évaluation et le fardeau administratif qui y est lié ont été une source d’anxiété de performance. Les résidents ont l’impression que les évaluations manquent parfois de pertinence, car les superviseurs, se sentant contraints de « cocher des cases », font des commentaires trop généraux et peu ciblés. De plus, un sentiment de frustration a été fréquemment exprimé face à la subjectivité et l’incohérence perçues des jugements dans les évaluations, surtout lorsque ces dernières sont utilisées pour retarder le cheminement vers une plus grande indépendance, constituant ainsi une tentative de « déjouer le système ». L’implication et le soutien du corps professoral ont aidé à bonifier l’expérience des résidents. Conclusion : Bien que les résidents apprécient le potentiel de l’EMFC pour rehausser la qualité de l’éducation, de l’évaluation et de la rétroaction, son opérationnalisation actuelle ne permet pas d’atteindre ces objectifs de façon systématique. Les auteurs proposent quelques initiatives pour améliorer la façon dont les résidents vivent les processus d’évaluation et de rétroaction dans le cadre de l’EMFC

The production of Necator americanus larvae for use in experimental human infection

Background: Although there is unprecedented interest in experimental human hookworm infection, details of hookworm manufacture and characterisation have been sparsely reported. In this report, we detail the production and characterisation of Necator americanus larvae for use in a recently published clinical trial. Methods: Faeces was obtained from an experimentally infected donor. Faecal hookworm DNA was determined by quantitative PCR. Paired samples were incubated in either sterile water or sterile water mixed with antimicrobials (amphotericin and gentamicin). Coproculture was performed by modified Harada-Mori method. The harvested larvae were then processed in either sterile water or antiseptic solution. Larval yield was then calculated (larvae per gram), larval viability was determined by thermally induced motility assay and microbial burden was determined at the day of harvest, at 48 h and at 7 days. Results: Twenty-eight faecal cultures were performed over 16 months. The faecal hookworm DNA content was variable over this time. There was no association of larval yield with faecal hookworm DNA content. Pre-treatment of faeces with antimicrobials did not influence larval yield. Larval motility was 85.3% (95% CI 79.3–91.3%). Incubation of larvae in antiseptics did not reduce viability at 14 days with a marginal mean of 68.6% (95% CI 59.1–78.1%) washed in water vs. 63.3% (95% CI 53.8 – 72.9%) when incubated in betadine (p = 0.38). Larvae washed in sterile water did not meet microbial bioburden criteria. Incubation in antiseptic resulted in acceptable microbial bioburden at 48 h but not at 7 days. Although the addition of gentamicin did reduce the microbial bio-burden acceptable levels, it was found to significantly lower larval motility at 7 days compared to incubation in sterile water and motility at 7 days 37.8% (95% CI 4.7–70.9%) vs. 67.3% (95% CI 35.2–99.3%, p < 0.001), respectively. Conclusions: Despite standardised culture methodologies and the use of a single donor, larval yield varied considerably between batches and had no association with faecal hookworm DNA. Larval viability decreases over time and the age of larvae at time of use are likely to be important. Microbial bioburden maybe temporarily reduced by incubation in antiseptics and has little effect on viability. Incubation of larvae in gentamicin is effective at reducing microbial bioburden but is deleterious to larval viability

RESULTS

Cells are arranged into species-specific patterns during early embryogenesis. Such cell division patterns are important since they often reflect the distribution of localized cortical factors from eggs/fertilized eggs to specific cells as well as the emergence of organismal form. However, it has proven difficult to reveal the mechanisms that underlie the emergence of cell positioning patterns that underlie embryonic shape, likely because a systems-level approach is required that integrates cell biological, genetic, developmental, and mechanical parameters. The choice of organism to address such questions is also important. Because ascidians display the most extreme form of invariant cleavage pattern among the metazoans, we have been analyzing the cell biological mechanisms that underpin three aspects of cell division (unequal cell division (UCD), oriented cell division (OCD), and asynchronous cell cycles) which affect the overall shape of the blastula-stage ascidian embryo composed of 64 cells. In ascidians, UCD creates two small cells at the 16-cell stage that in turn undergo two further successive rounds of UCD. Starting at the 16-cell stage, the cell cycle becomes asynchronous, whereby the vegetal half divides before the animal half, thus creating 24-, 32-, 44-, and then 64-cell stages. Perturbing either UCD or the alternate cell division rhythm perturbs cell position. We propose that dynamic cell shape changes propagate throughout the embryo via cell-cell contacts to create the ascidian-specific invariant cleavage pattern

The PP2A inhibitor I2PP2A is essential for sister chromatid segregation in oocyte meiosis II.

Haploid gametes are generated through two consecutive meiotic divisions, with the segregation of chromosome pairs in meiosis I and sister chromatids in meiosis II. Separase-mediated stepwise removal of cohesion, first from chromosome arms and later from the centromere region, is a prerequisite for maintaining sister chromatids together until their separation in meiosis II [1]. In all model organisms, centromeric cohesin is protected from separase-dependent removal in meiosis I through the activity of PP2A-B56 phosphatase, which is recruited to centromeres by shugoshin/MEI-S332 (Sgo) [2-5]. How this protection of centromeric cohesin is removed in meiosis II is not entirely clear; we find that all the PP2A subunits remain colocalized with the cohesin subunit Rec8 at the centromere of metaphase II chromosomes. Here, we show that sister chromatid separation in oocytes depends on a PP2A inhibitor, namely I2PP2A. I2PP2A colocalizes with the PP2A enzyme at centromeres at metaphase II, independently of bipolar attachment. When I2PP2A is depleted, sister chromatids fail to segregate during meiosis II. Our findings demonstrate that in oocytes I2PP2A is essential for faithful sister chromatid segregation by mediating deprotection of centromeric cohesin in meiosis II

Genetic diversity and host alternation of the egg parasitoid Oencyrtus pityocampae between the pine processionary moth and caper bug

Research ArticleThe increased use of molecular tools for species identification in recent decades revealed that each of many apparently generalist parasitoids are actually a complex of morphologically similar congeners, most of which have a rather narrow host range. Ooencyrtus pityocampae (OP), an important egg parasitoid of the pine processionary moth (PPM), is considered a generalist parasitoid. OP emerges from PPM eggs after winter hibernation, mainly in spring and early summer, long before the eggs of the next PPM generation occurs. The occurrence of OP in eggs of the variegated caper bug (CB) Stenozygum coloratum in spring and summer suggests that OP populations alternate seasonally between PPM and CB. However, the identity of OP population on CB eggs seemed uncertain; unlike OP-PPM populations, the former displayed apparently high male/female ratios and lack of attraction to the PPM sex pheromone. We studied the molecular identities of the two populations since the morphological identification of the genus Ooencyrtus, and OP in particular, is difficult. Sequencing of COI and ITS2 DNA fragments and AFLP analysis of individuals from both hosts revealed no apparent differences between the OP-PPM and the OP-CB populations for both the Israeli and the Turkish OPs, which therefore supported the possibility of host alternation. Sequencing data extended our knowledge of the genetic structure of OP populations in the Mediterranean area, and revealed clear separation between East and West Mediterranean populations. The overall level of genetic diversity was rather small, with the Israeli population much less diverse than all others; possible explanations for this finding are discussed. The findings support the possibility of utilizing the CB and other hosts for enhancing biological control of the PPMinfo:eu-repo/semantics/publishedVersio