Microtubule reorganization during mitotic cell division in the dinoflagellate Ostreospis cf. ovata.

Dinoflagellates are marine organisms that undergo seasonal proliferation events known as algal blooms. Vegetative cell proliferation is a main contributing factor in these events. However, mechanistical understanding of mitosis and cytokinesis in dinoflagellates remains rudimentary. Using an optimized immunofluorescence protocol, we analysed changes in microtubule organization occurring during the mitotic cycle of the toxic dinoflagellate Ostreopsis cf. ovata. We find that the flagella and the cortical microtubule array persist throughout the mitotic cycle. Two cytoplasmic microtubule bundles originate from the ventral area, where the basal bodies are located - a cortical bundle and a cytoplasmic bundle. The latter associates with the nucleus in the cell centre before mitosis and with the acentrosomal extranuclear spindle during mitosis. Analysis of tubulin post-translational modifications identifies two populations of spindle microtubules - polar acetylated microtubules, whose length is constant, and central tyrosinated microtubules, which elongate during chromosome segregation. During cell division a microtubule-rich structure forms along the dorsal-ventral axis, associated with the site of cytokinesis, consistent with a cytokinetic mechanism that is independent of the actomyosin ring typical of animal and yeast cells.

Hacia una epistemología evolutiva extendida: la retroalimentación entre variación y selección / Toward an Extended Evolutionary Epistemology: Feedback Between Variation and Selection

Este artículo se sitúa en la perspectiva de la naturalización del conocimiento científico, toda vez que es un intento por caracterizar y describir la evolución del conocimiento a partir de nociones de la biología. El objetivo principal es responder si es posible sostener la analogía que propone la epistemología evolutiva (EE): que la evolución del conocimiento científico (ECC) es similar a la evolución orgánica (EO). La pregunta surge tras las críticas que han atacado el núcleo de la analogía. La respuesta es que la analogía sí se sostiene si se tienen en cuenta las relaciones de retroalimentación, y que es posible proponer a la luz de la síntesis extendida (SE), una teoría posterior que complementa la síntesis moderna (SM). Así, este trabajo comienza con una descripción del estado de la "epistemología evolutiva", prosigue señalando por qué la síntesis moderna, que sirvió de base para su formulación, no es suficiente para fundamentar la epistemología evolutiva y finaliza proponiendo que es pertinente una modificación que puede describirse como "epistemología evolutiva extendida".

This paper is situated from naturalized epistemology perspective. It is an attempt to describe the evolution of knowledge using the theoretical structure of the evolution of species. The main objective of this work is to address whether is it possible to maintain the analogy in evolutionary epistemology and which aspects of the evolution of knowledge are similar to organic evolution? This question arises after some critics against the nucleus of its formulation. The analysis presented in this work suggests that the evolution of the knowledge can be understand through an framework analogous to that of the theory of organic evolution. For this, is necessary to take into account novel feedbacks relations between variation and selection, which are part of the Extended Synthesis theory. In such way, this paper begins with an introduction to evolutionary epistemology. After that, it shows why modern synthesis theory is not enough to maintain this kind of epistemology. It ended with the idea of an extended evolutionary epistemology.

Atorvastatin requires geranylgeranyl transferase-I and Rac1 activation to exert neuronal protection and induce plasticity.

Statins are widely used cholesterol-lowering drugs that may reduce the incidence of stroke and the progression of Alzheimer's disease (AD). However, how statins exert these beneficial effects remains poorly understood. Thus, this study evaluated the roles of Rac1 geranylgeranylation and the relationship between Rac1 and αN-catenin in the protective activity of atorvastatin (ATV) in a cortical neuronal culture model of glutamate (GLU) excitotoxicity. We found that ATV-induced neuroprotection and plasticity were blocked by isoprenoids, such as farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), inhibition of farnesylation (FTI-277) and geranylgeranylation (GGTI-286), down-regulation of GGTase-Iß and Rac activity and promotion of active RhoA. Additionally, ATV rescued the distribution of dendritic αN-catenin and increased the number and length of dendritic branches; these effects were reversed by GGTI-286, GGTase-Iß shRNA, Rac1 shRNA and a dominant-negative version of Rac1 (T17N). In summary, our findings suggest that ATV requires GGTase-Iß, prenylation and active Rac1 to induce protection and plasticity. In this regard, αN-catenin is a marker for stable interactions between adhesion proteins and the actin cytoskeleton and is necessary for the neuroprotective action of ATV.