Social amoebae mating types do not invest unequally in sexual offspring

Unequal investment by different sexes in their progeny is common and includes differential investment in the zygote and differential care of the young. The social amoeba Dictyostelium discoideum has a sexual stage in which isogamous cells of any two of the three mating types fuse to form a zygote which then attracts hundreds of other cells to the macrocyst. The latter cells are cannibalized and so make no genetic contribution to reproduction. Previous literature suggests that this sacrifice may be induced in cells of one mating type by cells of another, resulting in a higher than expected production of macrocysts when the inducing type is rare and giving a reproductive advantage to this social cheat. We tested this hypothesis in eight trios of field-collected clones of each of the three D. discoideum mating types by measuring macrocyst production at different pairwise frequencies. We found evidence that supported differential contribution in only two of the 24 clone pairs, so this pattern is rare and clone-specific. In general, we did not reject the hypothesis that the mating types contribute cells relative to their proportion in the population. We also found a significant quadratic relationship between partner frequency and macrocyst production, suggesting that when one clone is rare, macrocyst production is limited by partner availability. We were also unable to replicate previous findings that macrocyst production could be induced in the absence of a compatible mating partner. Overall, mating type-specific differential investment during sex is unlikely in microbial eukaryotes like D. discoideum

La reorientación de la comunicación popular alternativa ante las demandas de los actores sociales. El caso del Centro de Educación Popular, CEDEP

Esta tesis representa el intento de definir la nueva concepción y práctica de la comunicación popular alternativa en las instituciones del Ecuador, a partir del estudio y comprensión de las transformaciones que ésta ha experimentado en las últimas décadas, obedeciendo a nuevas demandas y comportamientos de los actores sociales que llevan a redefinir la comunicación popular. Para ello, se indaga sobre los determinantes tanto teóricos como históricos que propiciaron dicho cambio y, con el propósito de ilustrar mejor el estudio, se aborda con especial énfasis el caso del Centro de Educación Popular, CEDEP. El trabajo trata de reflejar de qué manera la comunicación popular fue recorriendo tres esquemas, cuya configuración obedece a fines de investigación, sin ser rígida y mucho menos la única; estos esquemas son: el del cambio social y modernización de los pueblos, el de dominación - subordinación, y el de las mediaciones sociales y culturales. Este recorrido obliga a preguntarnos qué es actualmente la comunicación popular y cómo se desarrollan las prácticas comunicativas en un contexto distinto a aquel en el cual nació, es decir en un nuevo contexto caracterizado por las crecientes urbanizaciones, la globalización de la cultura, la reorientación del modelo económico, irrupción de nuevas tecnologías, y sus consecuencias como la conformación de comunidades "desterritorializadas", la revitalización de los particularismos y la fragilidad de las monoidentidades

Comunicación popular: del paradigma de la dominación al de las mediaciones sociales y culturales

Este trabajo tiene como objetivo definir la nueva concepción y práctica de la comunicación popular alternativa, particularmente en las instituciones del Ecuador, a partir del estudio y comprensión de las transformaciones experimentadas en las últimas décadas. De una comunicación lineal y manipuladora, que otorga absoluto poder a los medios, de una comunicación politizada e inscrita en la lucha de clases, se advierte el cambio a una comunicación plural y ciudadana que recupera al sujeto y que reconoce en él las múltiples mediaciones sociales y culturales. La investigación sobre los determinantes teóricos e históricos que propiciaron dicho cambio es lo que sustenta este trabajo. La autora indaga sobre la manera en que la comunicación popular fue recorriendo tres paradigmas -cuya configuración, sin ser rígida y mucho menos la única, obedece a fines de esta investigación-: el del cambio social y modernización de los pueblos, el de dominación-subordinación, y el de las mediaciones sociales y culturales. Este recorrido obliga a preguntarnos qué es actualmente la comunicación popular y cómo se desarrollan las prácticas comunicativas en un nuevo contexto caracterizado por las crecientes urbanizaciones, la globalización de la cultura, la reorientación del modelo económico, la irrupción de nuevas tecnologías, y sus consecuencias expresadas en la conformación de comunidades "desterritorializadas", la revitalización de los particularismos y la fragilidad de las monoidentidades

Patient Satisfaction after Revision Hip Arthroplasty or Resection Hip Arthroplasty due to Periprosthetic Infection

In this retrospective study we have analysed 10-year period results of all type periprosthetic hip joint infection treatments at our Department. Data for 73 patients were analysed and functional status for 41 patients evaluated. A smaller proportion of patients (45%) with resection arthroplasty as the definitive solution were satisfied. These were mostly females with numerous comorbidities and lower functional demands. Much better results were achieved in 2-stage revision arthroplasty group. In conclusion whenever possible revision arthroplasty should be done because probability of re-infection is much lower than was previously believed, and the functional status of patients and their general life satisfaction is much higher

Acute promyelocytic leukemia after whole brain irradiation of primary brain lymphomainan HIV-infected patient

The occurrence of acute promyelocytic leukemia (APL) in HIV-infected patients has been reported in only five cases. Due to a very small number of reported HIV/APL patients who have been treated with different therapies with the variable outcome, the prognosis of APL in the setting of the HIV-infection is unclear. Here, we report a case of an HIV-patient who developed APL and upon treatment entered a complete remission. A 25-years old male patient was diagnosed with HIV-infection in 1996, but remained untreated. In 2004, the patient was diagnosed with primary central nervous system lymphoma. We treated the patient with antiretroviral therapy and whole-brain irradiation, resulting in complete remission of the lymphoma. In 2006, prompted by a sudden neutropenia, we carried out a set of diagnostic procedures, revealing APL. Induction therapy consisted of standard treatment with all-trans-retinoic-acid (ATRA) and idarubicin. Subsequent cytological and molecular analysis of bone marrow demonstrated complete hematological and molecular remission. Due to the poor general condition, consolidation treatment with ATRA was given in March and April 2007. The last follow-up 14 months later, showed sustained molecular APL remission. In conclusion, we demonstrated that a complete molecular APL remission in an HIV-patient was achieved by using reduced-intensity treatment

Concurrent enrollment in lecture and laboratory enhances student performance and retention

Laboratories have been a cornerstone in teaching and learning across multiple scientific disciplines for more than 100 years. At the collegiate level, science laboratories and their corresponding lectures are often offered as separate courses, and students may not be required to concurrently enroll in both. In this study, we provide evidence that enrolling in an introductory laboratory concurrently with the corresponding lecture course enhances learning gains and retention in comparison to students who enroll in the lecture alone. We examined the impact of concurrent versus nonconcurrent enrollment on 9,438 students' withdrawal rates from and final grades in the general chemistry lecture at the University of Michigan at Ann Arbor using multiple linear and binary logistic regression analyses, respectively, at a significance level of 0.05. We found that concurrent enrollment in the lecture and laboratory positively impacts (1) the odds of retention in the lecture by 2.2 times on average and (2) final lecture grades by up to 0.19 grade points on a 4.0 scale for the lowest‐scoring students according to university‐level mathematics and chemistry placement exam scores. These data provide important results for consideration by curriculum advisors and course planners at universities that do not require concurrent enrollment in general chemistry as well as other science courses. In the face of current budget cuts that threaten to shorten or eliminate laboratory experiences altogether at multiple educational levels, this study demonstrates the value of laboratories in promoting science learning and retention. © 2012 Wiley Periodicals, Inc. J Res Sci Teach 49: 659–682, 2012Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/91231/1/21016_ftp.pd

The Effect of a Paired Lab on Course Completion and Grades in Nonmajors Introductory Biology

This paper explores the effect of a paired lab course on students’ course outcomes in nonmajors introductory biology at the University of Alaska Anchorage. We compare course completion and final grades for 10,793 students (3736 who simultaneously enrolled in the lab and 7057 who did not). Unconditionally, students who self-select into the lab are more likely to complete the course and to earn a higher grade than students who do not. However, when we condition on observable course, academic, and demographic characteristics, we find much of this difference in student performance outcomes is attributable to selection bias, rather than an effect of the lab itself. The data and discussion challenge the misconception that labs serve as recitations for lecture content, noting that the learning objectives of science labs should be more clearly articulated and assessed independent of lecture course outcomes. This paper explores the effect of a paired lab course on students’ course outcomes in introductory biology for nonmajors at the University of Alaska Anchorage (UAA), a large, open-enrollment, 4-year university. We compare outcomes for 10,793 students, 3736 who simultaneously enrolled in the lab and 7057 who did not, and analyze the degree to which they select into the lab on observable characteristics to explore the following research questions: 1. Are students who take a paired lab more likely to complete the lecture component (i.e., receive a final grade as opposed to withdrawing or receiving an Incomplete)? 2. Are students who take a paired lab more likely to receive a higher grade in the lecture component? 3. Does the laboratory experience differently affect course outcomes for students in specific demographic subgroups (e.g., gender, race, high school urbanicity, age, prior academic performance, and socioeconomic status)

Analyse quantitative de l'évolution du cycle de vie des amibes sociales

Social amoebae are eukaryotic organisms that inhabit soil of almost every climate zone. They are remarkable for their switch from unicellularity to multicellularity as an adaptation to starvation. When starved, millions of single cells aggregate and form a multicellular fruiting body, which contains reproductive spore cells and dead stalk cells, which help in spore dispersion. This costly behavior made social amoebae a model system for addressing major questions of the evolution of cooperation and multicellularity. In this study we look at three different aspects of social amoebae behavior; aggregation, non-aggregation and competition, and ask how they contribute to our understanding of cooperation in social amoebae and microbial systems in general.We explored the known but neglected observation that, upon starvation, not all cells aggregate and engage in multicellular development. We describe phenotypically and genetically non-aggregating cell proportion in D. discoideum species. Both aggregating and non-aggregating strategy are costly or beneficial depending on duration of starvation. With our computational model we propose that partitioning the population into unicellular and multicellular states is adaptive in fluctuating environments with unpredicted duration of starvation periods. Social amoebae may therefore lie at the intersection of cooperation and bet-hedging. In the second part, we provide a new framework for addressing the contrasting observations of high genetic diversity in natural populations of social amoebae and experimentally suggested low diversity-high relatedness required for cooperation. We propose that complex life cycle of social amoebae provides multiple competition points that can possibly play an important role in maintaining diversity and cooperation. We explore this experimentally and computationally by looking at competition over the whole life cycle between 6 natural isolates of D. discoideum. Our simulation model indicates that competition at different stages of the life cycle can lead to exclusion of “social winners”. Though we failed to explain strain coexistence. Although preliminary, our results emphasize the importance of integrating species ecology in cooperative studies.Finally, we focus on a new aggregation dynamics in P. pallidum species observed in our lab. Aggregation is a population level process during which population gets divided into numerous subpopulations/aggregates that face selection independently. Such population partitioning can have strong evolutionary consequences on cooperation that have not yet been explored experimentally. We describe the population dynamics qualitatively and propose several quantitative measurements of population partitioning into aggregates. Our preliminary results suggest that there is a preference for aggregates of certain size, but there is no spatial organization of aggregates.Les amibes sociales sont des organismes eucaryotes présents dans le sol de presque toutes les zones climatiques. Ils sont remarquables pour leur passage d'un état unicellulaire à un état multicellulaire en réponse à la carence en nutriments. En période de carence, des millions de cellules forment des agrégats qui constituent chacun un nouvel organisme multicellulaire, contenant des spores, cellules reproductives, et des cellules de tige, cellules mortes qui favorisent la dispersion des spores. Ce comportement, de par le coût payé par les cellules de tige, a permis d'utiliser les amibes sociales en tant que système-modèle pour aborder des questions majeures de l'évolution de la coopération et de la multicellularité. Dans cette étude, nous examinons trois aspects différents du comportement des amibes sociales; agrégation, non-agrégation et compétition, et nous analysons comment ces aspects contribuent à notre compréhension de la coopération chez les amibes et systèmes microbiens en général.Nous avons exploré le fait bien connu mais négligé qu'en phase de carence nutritive, une fraction des cellules ne participent pas à la formation des agrégats pas et ne sont pas engagées dans le développement multicellulaire. Nous décrivons les facteurs phénotypiques et génétiques qui déterminent la fraction de cellules hors-agrégats chez D. discoideum. Les deux stratégies, d'agrégation et de non-agrégation, sont coûteuses ou bénéfiques d'un point de vue évolutif selon la durée de la phase de carence. Nous avons développé un modèle pour simuler ce processus. Nous proposons que le partitionnement de la population dans des états unicellulaire et multicellulaire est adaptative dans des environnements fluctuants avec une durée imprévisible des périodes de carence nutritive. Les amibes sociales sont donc situées à l'intersection de deux thèmes émergents en évolution microbienne, la coopération et le "placement des paris".Dans la deuxième partie, nous proposons un nouveau cadre pour aborder les observations a priori contradictoires de la diversité génétique dans les populations naturelles d'amibes sociales et une faible diversité nécessaire pour la coopération. Nous proposons que le cycle de vie complexe des amibes sociales fournit plusieurs points de compétition qui peut servir à la fois comme stabilisateur de la diversité et de la coopération. Nous explorons cette hypothèse expérimentalement avec un modèle en analysant la compétition entre 6 isolats naturels de D. discoideum. Notre simulation-modèle indique que la compétition à différents stades du cycle de vie peut conduire à l'exclusion des "gagnants sociaux". Toutefois nous n'avons pas réussi à expliquer la coexistence à long terme de souches génétiquement distinctes. Bien que préliminaires, nos résultats soulignent l'importance d'intégrer l'écologie des espèces dans les études de coopération microbienne.Enfin, nous nous concentrons sur une nouvelle dynamique d'agrégation chez P. pallidum observée dans notre laboratoire. L'agrégation est un processus au niveau de la population au cours duquel la population se divise en nombreuses sous-populations (agrégats) qui font face à la sélection de manière indépendante. Un tel fractionnement de la population peut avoir de fortes conséquences évolutives du point de vue de la coopération qui n'ont pas encore été explorées expérimentalement. Nous décrivons la dynamique des populations qualitativement et proposons plusieurs mesures quantitatives de partitionnement de la population en agrégats. Nos résultats préliminaires suggèrent qu'il existe une préférence pour les agrégats d'une certaine taille, mais qu'il n'existe aucune organisation spatiale des agrégats