Modeling oscillatory Microtubule--Polymerization

Polymerization of microtubules is ubiquitous in biological cells and under certain conditions it becomes oscillatory in time. Here simple reaction models are analyzed that capture such oscillations as well as the length distribution of microtubules. We assume reaction conditions that are stationary over many oscillation periods, and it is a Hopf bifurcation that leads to a persistent oscillatory microtubule polymerization in these models. Analytical expressions are derived for the threshold of the bifurcation and the oscillation frequency in terms of reaction rates as well as typical trends of their parameter dependence are presented. Both, a catastrophe rate that depends on the density of {\it guanosine triphosphate} (GTP) liganded tubulin dimers and a delay reaction, such as the depolymerization of shrinking microtubules or the decay of oligomers, support oscillations. For a tubulin dimer concentration below the threshold oscillatory microtubule polymerization occurs transiently on the route to a stationary state, as shown by numerical solutions of the model equations. Close to threshold a so--called amplitude equation is derived and it is shown that the bifurcation to microtubule oscillations is supercritical.Comment: 21 pages and 12 figure

Human toxocariasis: contribution by Brazilian researchers

In the present paper the main aspects of the natural history of human infection by Toxocara larvae that occasionally result in the occurrence of visceral and/or ocular larva migrans syndrome were reviewed. The contribution by Brazilian researchers was emphasized, especially the staff of the Tropical Medicine Institute of São Paulo (IMT)

Diagn?stico y distribuci?n de Mycosphaerella spp. en mus?ceas de Rep?blica Dominicana

4 ilus. 3 tab. 5 ref.Las enfermedades de las manchas foliares causadas por Mycosphaerella spp. afectan los cultivos de mus?ceas, aumentando los costos de producci?n y disminuyendo la calidad de los frutos. El estudio consisti? en determinar la distribuci?n de las especies de este pat?geno en Rep?blica Dominicana y obtener cultivos monosp?ricos. Las muestras de hojas afectadas se recolectaron en las zonas productoras de pl?tano y banano. Estas se procesaron en el Laboratorio de Fitopatolog?a del CIRAD-AMIS, Montpellier, Francia. Se encontr? una amplia diseminaci?n de sigatoka, inclusive a regiones que se encontraban libres de la enfermedad. En cuanto a los aislamientos monosp?ricos Paracercospora fijiensis fue m?s com?n (60 por ciento) seguida de Pseudocercospora musae (37 por ciento). Los aislamientos obtenidos facilitar?an los estudios de la variabilidad de Myscosphaerella fijiensis en la regi?n

Characteristics of suicidal outpatients with mood, anxiety and somatoform disorders: The role of childhood abuse and neglect

Stress-related psychiatric disorders across the life spa

Effect of calcium and magnesium ions on the intestinal absorption of oleic acid in vitro

International audienc

A comparative analysis of personality pathology profiles among patients with pure depressive-, pure anxiety-, and pure somatoform disorders

Stress-related psychiatric disorders across the life spa

Eps8 controls actin-based motility by capping the barbed ends of actin filaments

Actin filament barbed-end capping proteins are essential for cell motility, as they regulate the growth of actin filaments to generate propulsive force. One family of capping proteins, whose prototype is gelsolin, shares modular architecture, mechanism of action, and regulation through signalling-dependent mechanisms, such as Ca(2+) or phosphatidylinositol-4,5-phosphate binding. Here we show that proteins of another family, the Eps8 family, also show barbed-end capping activity, which resides in their conserved carboxy-terminal effector domain. The isolated effector domain of Eps8 caps barbed ends with an affinity in the nanomolar range. Conversely, full-length Eps8 is auto-inhibited in vitro, and interaction with the Abi1 protein relieves this inhibition. In vivo, Eps8 is recruited to actin dynamic sites, and its removal impairs actin-based propulsion. Eps8-family proteins do not show any similarity to gelsolin-like proteins. Thus, our results identify a new family of actin cappers, and unveil novel modalities of regulation of capping through protein-protein interactions. One established function of the Eps8-Abi1 complex is to participate in the activation of the small GTPase Rac, suggesting a multifaceted role for this complex in actin dynamics, possibly through the participation in alternative larger complexes