The initiation of post-synaptic protrusions

cited By 0The post-synaptic spines of neuronal dendrites are highly elaborate membrane protrusions. Their anatomy, stability and density are intimately linked to cognitive performance. The morphological transitions of spines are powered by coordinated polymerization of actin filaments against the plasma membrane, but how the membrane-associated polymerization is spatially and temporally regulated has remained ill defined. Here, we discuss our recent findings showing that dendritic spines can be initiated by direct membrane bending by the I-BAR protein MIM/Mtss1. This lipid phosphatidylinositol (PI(4,5)P2) signaling-activated membrane bending coordinated spatial actin assembly and promoted spine formation. From recent advances, we formulate a general model to discuss how spatially concentrated protein-lipid microdomains formed by multivalent interactions between lipids and actin/membrane regulatory proteins might launch cell protrusions. © 2016 The Author(s). Published with license by Taylor & Francis Group, LLC, Pirta Hotulainen and Juha Saarikangas.Peer reviewe

Measured Attention in Prolonged Over-Learned Response Tasks and its Correlation to High Level Scientific Reasoning and School Achievement

The relationship between attention and academic performance has been of interest starting with early studies on academic success and failure. In this study we examine how attention measured in simple and prolonged over-learned response tasks correlates with and contributes to scientific reasoning and school achievement (GPA). To study attention the Attention Concentration Test (ACT) was used and to study scientific reasoning, a modified version of Science Reasoning Tasks, tapping control-of-variable schemata, was used. Of special interest were the highest performing attention group (+ 1 SD) formed from the ACT results. We gathered our data from Finnish ninth graders (n = 358; including 166 girls) from the city located eastern part of the Finland. Statistically analysed results showed that attention contributed scientific reasoning and which in turn explained the largest share of the GPA variance. The highest attention group differed from the lowest two attention groups in GPA and from all attention groups in scientific reasoning. For educational practitioners the ACT seems to be a useful tool in assessing exceptional academic learning potential in students.The relationship between attention and academic performance has been of interest starting with early studies on academic success and failure. In this study we examine how attention measured in simple and prolonged over-learned response tasks correlates with and contributes to scientific reasoning and school achievement (GPA). To study attention the Attention Concentration Test (ACT) was used and to study scientific reasoning, a modified version of Science Reasoning Tasks, tapping control-of-variable schemata, was used. Of special interest were the highest performing attention group (+ 1 SD) formed from the ACT results. We gathered our data from Finnish ninth graders (n = 358; including 166 girls) from the city located eastern part of the Finland. Statistically analysed results showed that attention contributed to scientific reasoning, which in turn explained the largest share of the GPA variance. The highest attention group differed from the lowest two attention groups in GPA and from all attention groups in scientific reasoning. For educational practitioners the ACT seems to be a useful tool in assessing exceptional academic learning potential in students.Peer reviewe

Changes and stability in daily cortisol values and their correlation to attention measured in a prolonged working task among Finnish six-year-old day-care children

Peer reviewe

The Probability Distribution of the Response Times in Self-paced Continuous Search Tasks

When psychologists began to use intelligence tests, they used simple, overlearned tasks to determine the pattern of individual reaction times (RT). Measures of RT variation were proposed as possible indicators of intelligence. However, a fundamental question has remained partly unanswered: Is there an existing theory that explains individual RT variation? In this paper, a theory is proposed for the response times obtained in the Attention Concentration Test. The test consists of two different conditions: a fixed condition and a random condition. For each of these conditions a different RT model was developed both based on the basic assumption, that the individual response times have an approximately shifted exponential distribution. Empirical data were obtained from two different samples (N = 362, N = 334) of Finnish students. The method used to check the validity of each model involved computing the intercept and slope of the linear regression of the standard deviation from the stationary response times on the mean corrected for shift. In this regression analysis, the standard deviation is the dependent variable and the mean corrected for the shift the independent variable. The shift parameter was estimated by using the smallest reaction time. The observed intercept and slope were compared with the predicted intercept and slope according to the proposed models. The model for the fixed condition of the test did not hold. The model for the random condition, however, did. The findings were interpreted according to the arrangement of the targets as they occurred in each bar.When psychologists began to use intelligence tests, they also used simple, overlearned tasks to determine the pattern of individual reaction times (RT). Measures of RT variation were proposed as possible indicators of intelligence. However, a fundamental question has remained partly unanswered: Is there an existing theory that explains individual RT variation? In this paper, a theory is proposed for the response times obtained in the Attention Concentration Test. The test consists of two different conditions: a fixed condition and a random condition. For each of these two conditions a different RT model was developed both based on the basic assumption that the individual response times have an approximately shifted exponential distribution. Empirical data was obtained from two different samples (N = 362, N = 334) of Finnish students. The method used to check the validity of each model involved computing the intercept and slope of the linear regression of the standard deviation from the stationary response times on the mean corrected for shift. In this regression analysis, the standard deviation is the dependent variable and the mean corrected for shift the independent variable. The shift parameter was estimated by using the smallest reaction time. The observed intercept and slope were compared with the predicted intercept and slope according to the proposed models. The model for the fixed condition of the test did not hold. The model for the random condition,however, did. The findings were interpreted according to the arrangement of the targets as they occurred in each bar.Peer reviewe

Work Demands and Resources, Stress Regulation and Quality of Pedagogical Work Among Professionals in Finnish Early Childhood Education Settings

This study examined early childhood professionals’ (ECPs) stress regulation and the demands and resources they encounter at work, and considered how these factors are associated with the quality of pedagogical work in daycare. The participants were 117 ECPs from 24 daycare centers in the Helsinki metropolitan area, Finland, with data collected using surveys, cortisol measurements, and observational assessments. The results indicated that the professionals generally found their work resources to be adequate and, on average, their stress regulation measured through cortisol activity showed a typical diurnal pattern. Highly important resources at work proved to be support from supervisors, which was associated with stress regulation and the quality of pedagogical work in teams. Although we found only minor associations between cortisol activity and job demands and resources, cortisol activity did relate to pedagogical work, particularly to teamwork; the higher the quality of the teamwork, the lower the ECPs morning cortisol values. Our multidisciplinary study highlights important findings regarding the resources and demands ECPs experience at work, and supports existing literature. In addition, the results demonstrate the importance of social support, especially the role of the supervisor, which proved to be one of the key factors positively enhancing well-being at work. These findings are applicable in planning interventions regarding workrelated well-being among ECPs.Peer reviewe

Purification of Tropomyosin Br-3 and 5NM1 and Characterization of Their Interactions with Actin

Tropomyosins were first identified in neuronal systems in 1973. Although numerous isoforms were found and described since then, many aspects of their function and interactions remained unknown. Tropomyosin isoforms show different sorting pattern in neurogenesis. As one example, TM5NM1/2 is present in developing axons, but it is replaced by TMBr-3 in mature neurons, suggesting that these tropomyosin isoforms contribute differently to the establishment of the functional features of the neuronal actin networks. We developed a method for the efficient purification of TMBr-3 and TM5NM1 as recombinant proteins using bacterial expression system and investigated their interactions with actin. We found that both isoforms bind actin filaments, however, the binding of TM5NM1 was much stronger than that of TMBr-3. TMBr-3 and TM5NM1 modestly affected actin assembly kinetics, in an opposite manner. Consistently with the higher affinity of TM5NM1 it inhibited actin filament disassembly more efficiently than TMBr-3. Similarly to other previously studied tropomyosins TM5NM1 inhibited the Arp2/3 complex-mediated actin assembly. Notably, TMBr-3 did not influence the Arp2/3 complex-mediated polymerization. This is a unique feature of TMBr-3, since so far it is the only known tropomyosin supporting the activity of the Arp2/3 complex, indicating that TMBr-3 may colocalize and work simultaneously with Arp2/3 complex in neuronal cells

Chemical LTD, but not LTP, induces transient accumulation of gelsolin in dendritic spines

Synaptic plasticity underlies central brain functions, such as learning. Ca2+ signaling is involved in both strengthening and weakening of synapses, but it is still unclear how one signal molecule can induce two opposite outcomes. By identifying molecules, which can distinguish between signaling leading to weakening or strengthening, we can improve our understanding of how synaptic plasticity is regulated. Here, we tested gelsolin's response to the induction of chemical long-term potentiation (cLTP) or long-term depression (cLTD) in cultured rat hippocampal neurons. We show that gelsolin relocates from the dendritic shaft to dendritic spines upon cLTD induction while it did not show any relocalization upon cLTP induction. Dendritic spines are small actin-rich protrusions on dendrites, where LTD/LTP-responsive excitatory synapses are located. We propose that the LTD-induced modest - but relatively long-lasting - elevation of Ca2+ concentration increases the affinity of gelsolin to F-actin. As F-actin is enriched in dendritic spines, it is probable that increased affinity to F-actin induces the relocalization of gelsolin.Peer reviewe

Coxiella burnetii Phagocytosis Is Regulated by GTPases of the Rho Family and the RhoA Effectors mDia1 and ROCK

The GTPases belonging to the Rho family control the actin cytoskeleton rearrangements needed for particle internalization during phagocytosis. ROCK and mDia1 are downstream effectors of RhoA, a GTPase involved in that process. Coxiella burnetii, the etiologic agent of Q fever, is internalized by the host´s cells in an actin-dependent manner. Nevertheless, the molecular mechanism involved in this process has been poorly characterized. This work analyzes the role of different GTPases of the Rho family and some downstream effectors in the internalization of C. burnetii by phagocytic and non-phagocytic cells. The internalization of C. burnetii into HeLa and RAW cells was significantly inhibited when the cells were treated with Clostridium difficile Toxin B which irreversibly inactivates members of the Rho family. In addition, the internalization was reduced in HeLa cells that overexpressed the dominant negative mutants of RhoA, Rac1 or Cdc42 or that were knocked down for the Rho GTPases. The pharmacological inhibition or the knocking down of ROCK diminished bacterium internalization. Moreover, C. burnetii was less efficiently internalized in HeLa cells overexpressing mDia1-N1, a dominant negative mutant of mDia1, while the overexpression of the constitutively active mutant mDia1-ΔN3 increased bacteria uptake. Interestingly, when HeLa and RAW cells were infected, RhoA, Rac1 and mDia1 were recruited to membrane cell fractions. Our results suggest that the GTPases of the Rho family play an important role in C. burnetii phagocytosis in both HeLa and RAW cells. Additionally, we present evidence that ROCK and mDia1, which are downstream effectors of RhoA, are involved in that processFil: Salinas Ojeda, Romina Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Ortiz Flores, Rodolfo Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Distel, Jesús Sebastián. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Aguilera, Milton Osmar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Colombo, Maria Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; ArgentinaFil: Beron, Walter. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos. Universidad Nacional de Cuyo. Facultad de Cienicas Médicas. Instituto de Histología y Embriología de Mendoza Dr. Mario H. Burgos; Argentin