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Dendritic dynamics

Victoria E B Hipolito, Erika Ospina-Escobar, Roberto J Botelho
Lysosomes are acidic and hydrolytic organelles responsible for receiving and digesting cargo acquired during endocytosis, phagocytosis, and autophagy. For macrophages and dendritic cells, the lysosome is kingpin, playing a direct role in microbe killing and antigen processing for presentation. Strikingly, the historic view that lysosomes are homogeneous and static organelles is being replaced with a more elegant paradigm, in which lysosomes are heterogeneous, dynamic and respond to cellular needs. For example, lysosomes are signaling platforms that integrate stress detection and molecular decision hubs like mTORC1 and AMPK to modulate cellular activity...
January 19, 2018: Cellular Microbiology
Masato Sawada, Nobuhiko Ohno, Mitsuyasu Kawaguchi, Shih-Hui Huang, Takao Hikita, Youmei Sakurai, Huy Bang Nguyen, Truc Quynh Thai, Yuri Ishido, Yutaka Yoshida, Hidehiko Nakagawa, Akiyoshi Uemura, Kazunobu Sawamoto
Newborn neurons maintain a very simple, bipolar shape, while they migrate from their birthplace toward their destinations in the brain, where they differentiate into mature neurons with complex dendritic morphologies. Here, we report a mechanism by which the termination of neuronal migration is maintained in the postnatal olfactory bulb (OB). During neuronal deceleration in the OB, newborn neurons transiently extend a protrusion from the proximal part of their leading process in the resting phase, which we refer to as a filopodium-like lateral protrusion (FLP)...
January 18, 2018: EMBO Journal
Giulia Pasqual, Aleksey Chudnovskiy, Jeroen M J Tas, Marianna Agudelo, Lawrence D Schweitzer, Ang Cui, Nir Hacohen, Gabriel D Victora
Interactions between different cell types are essential for multiple biological processes, including immunity, embryonic development and neuronal signalling. Although the dynamics of cell-cell interactions can be monitored in vivo by intravital microscopy, this approach does not provide any information on the receptors and ligands involved or enable the isolation of interacting cells for downstream analysis. Here we describe a complementary approach that uses bacterial sortase A-mediated cell labelling across synapses of immune cells to identify receptor-ligand interactions between cells in living mice, by generating a signal that can subsequently be detected ex vivo by flow cytometry...
January 17, 2018: Nature
Sonu Singh, Akanksha Mishra, Sachi Bharti, Virendra Tiwari, Jitendra Singh, Parul, Shubha Shukla
Neurogenesis involves generation of functional newborn neurons from neural stem cells (NSCs). Insufficient formation or accelerated degeneration of newborn neurons may contribute to the severity of motor/nonmotor symptoms of Parkinson's disease (PD). However, the functional role of adult neurogenesis in PD is yet not explored and whether glycogen synthase kinase-3β (GSK-3β) affects multiple steps of adult neurogenesis in PD is still unknown. We investigated the possible underlying molecular mechanism of impaired adult neurogenesis associated with PD...
January 11, 2018: Molecular Neurobiology
Michael P Hart, Oliver Hobert
During development and adulthood, brain plasticity is evident at several levels, from synaptic structure and function to the outgrowth of dendrites and axons. Whether and how sex impinges on neuronal plasticity is poorly understood. Here we show that the sex-shared GABA (γ-aminobutyric acid)-releasing DVB neuron in Caenorhabditis elegans displays experience-dependent and sexually dimorphic morphological plasticity, characterized by the stochastic and dynamic addition of multiple neurites in adult males. These added neurites enable synaptic rewiring of the DVB neuron and instruct a functional switch of the neuron that directly modifies a step of male mating behaviour...
January 10, 2018: Nature
Byung Hun Lee, Hye Yoon Park
Single particle tracking is a compelling technique for investigating the dynamics of nanoparticles and biological molecules in a broad range of research fields. In particular, recent advances in fluorescence microscopy have made single molecule tracking a prevalent method for studying biomolecules with a high spatial and temporal precision. Particle tracking algorithms have matured over the past three decades into more easily accessible platforms. However, there is an inherent difficulty in tracing particles that have a low signal-to-noise ratio and/or heterogeneous subpopulations...
January 9, 2018: Scientific Reports
Dmitri V Alexandrov, Alexander A Ivanov, Irina V Alexandrova
The processes of particle nucleation and their evolution in a moving metastable layer of phase transition (supercooled liquid or supersaturated solution) are studied analytically. The transient integro-differential model for the density distribution function and metastability level is solved for the kinetic and diffusionally controlled regimes of crystal growth. The Weber-Volmer-Frenkel-Zel'dovich and Meirs mechanisms for nucleation kinetics are used. We demonstrate that the phase transition boundary lying between the mushy and pure liquid layers evolves with time according to the following power dynamic law: [Formula: see text], where Z1(t)=βt7/2 and Z1(t)=βt2 in cases of kinetic and diffusionally controlled scenarios...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Dmitri V Alexandrov, Irina A Bashkirtseva, Lev B Ryashko
The time-dependent process of directional crystallization in the presence of a mushy layer is considered with allowance for arbitrary fluctuations in the atmospheric temperature and friction velocity. A nonlinear set of mushy layer equations and boundary conditions is solved analytically when the heat and mass fluxes at the boundary between the mushy layer and liquid phase are induced by turbulent motion in the liquid and, as a result, have the corresponding convective form. Namely, the 'solid phase-mushy layer' and 'mushy layer-liquid phase' phase transition boundaries as well as the solid fraction, temperature and concentration (salinity) distributions are found...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
P K Galenko, D V Alexandrov
Transport processes around phase interfaces, together with thermodynamic properties and kinetic phenomena, control the formation of dendritic patterns. Using the thermodynamic and kinetic data of phase interfaces obtained on the atomic scale, one can analyse the formation of a single dendrite and the growth of a dendritic ensemble. This is the result of recent progress in theoretical methods and computational algorithms calculated using powerful computer clusters. Great benefits can be attained from the development of micro-, meso- and macro-levels of analysis when investigating the dynamics of interfaces, interpreting experimental data and designing the macrostructure of samples...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
P K Galenko, I G Nizovtseva, K Reuther, M Rettenmayr
Phase-field analysis for the kinetic transition in an ordered crystal structure growing from an undercooled liquid is carried out. The results are interpreted on the basis of analytical and numerical solutions of equations describing the dynamics of the phase field, the long-range order parameter as well as the atomic diffusion within the crystal/liquid interface and in the bulk crystal. As an example, the growth of a binary A50B50 crystal is described, and critical undercoolings at characteristic changes of growth velocity and the long-range order parameter are defined...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
A Kao, J Gao, K Pericleous
In the undercooled solidification of pure metals, the dendrite tip velocity has been shown experimentally to have a strong dependence on the intensity of an external magnetic field, exhibiting several maxima and minima. In the experiments conducted in China, the undercooled solidification dynamics of pure Ni was studied using the glass fluxing method. Visual recordings of the progress of solidification are compared at different static fields up to 6 T. The introduction of microscopic convective transport through thermoelectric magnetohydrodynamics is a promising explanation for the observed changes of tip velocities...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Dieter M Herlach, Daniel Simons, Pierre-Yves Pichon
We report on measurements of crystal growth dynamics in semiconducting pure Ge and pure Si melts and in Ge100-x Si x (x = 25, 50, 75) alloy melts as a function of undercooling. Electromagnetic levitation techniques are applied to undercool the samples in a containerless way. The growth velocity is measured by the utilization of a high-speed camera technique over an extended range of undercooling. Solidified samples are examined with respect to their microstructure by scanning electron microscopic investigations...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
D Jou, P K Galenko
In standard descriptions, the master equation can be obtained by coarse-graining with the application of the hypothesis of full local thermalization that is equivalent to the local thermodynamic equilibrium. By contrast, fast transformations proceed in the absence of local equilibrium and the master equation must be obtained with the absence of thermalization. In the present work, a non-Markovian master equation leading, in specific cases of relaxation to local thermodynamic equilibrium, to hyperbolic evolution equations for a binary alloy, is derived for a system with two order parameters...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
I G Nizovtseva, P K Galenko
The dynamics of the diffuse interface between liquid and solid states is analysed. The diffuse interface is considered as an envelope of atomic density amplitudes as predicted by the phase-field crystal model (Elder et al. 2004 Phys. Rev. E70, 051605 (doi:10.1103/PhysRevE.70.051605); Elder et al. 2007 Phys. Rev. B75, 064107 (doi:10.1103/PhysRevB.75.064107)). The propagation of crystalline amplitudes into metastable liquid is described by the hyperbolic equation of an extended Allen-Cahn type (Galenko & Jou 2005 Phys...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
Cynthia K McClard, Mikhail Y Kochukov, Isabella Herman, Zhandong Liu, Aiden Eblimit, Yalda Moayedi, Joshua Ortiz-Guzman, Daniel Colchado, Brandon Pekarek, Sugi Paneerselvam, Graeme Mardon, Benjamin R Arenkiel
The mouse olfactory bulb (OB) features continued, activity-dependent integration of adult-born neurons, providing a robust model to examine mechanisms of plasticity in the adult brain. We previously reported that local OB interneurons secrete the neuropeptide corticotropin releasing hormone (CRH) in an activity-dependent manner onto adult-born granule neurons, and that local CRH signaling promotes expression of synaptic machinery in the bulb. This effect is mediated via activation of the CRH receptor 1 (CRHR1), which is developmentally regulated during adult-born neuron maturation...
January 5, 2018: Journal of Neuroscience: the Official Journal of the Society for Neuroscience
Shimrit Adutler-Lieber, Irina Zaretsky, Helena Sabany, Elena Kartvelishvily, Ofra Golani, Benjamin Geiger, Nir Friedman
Immune processes within the complex microenvironment of the lymph node involve multiple intercellular, cell-matrix, and paracrine interactions, resulting in the expansion of antigen-specific T cells. Inspired by the lymph node microenvironment, we aimed to develop an ex vivo "synthetic immune niche" (SIN), which could effectively stimulate the proliferation of antigen-activated CD4+ T cells. This engineered SIN consisted of surfaces coated with the chemokine C-C motif ligand 21 (CCL21) and with the intercellular adhesion molecule 1 (ICAM1), coupled with the soluble cytokine interleukin 6 (IL-6) added to the culture medium...
June 27, 2017: Blood Advances
Sorina Hirbod, Shohreh Nafisi, Howard I Maibach
Background: β-Cyclodextrin functionalized hyper-branched polyglycerol (HBCD: β-CD-g-PG), a biocompatible polymer, has recently been proposed for delivery of poorly water soluble compounds. Methods: The present study examines the interaction of HBCD with RNA, utilizing a constant concentration of RNA and different HBCD/RNA ratios of 1/16 to 1/1, at physiological condition in an aqueous solution. Circular Dichroism (CD), UV-visible, FTIR spectroscopic methods, zeta potential and Dynamic Light Scattering (DLS) were used to analyze the particle formation, particle charge, particle size, aggregation, RNA conformation, binding constant and mode, and the effect of polymer complexation on RNA stability...
January 2018: Avicenna Journal of Medical Biotechnology
Shaofang Wang, Jun Zhu, Tonghui Xu
The steroid hormone 17β-estradiol (E2) remodels neural circuits at the synaptic level in the mammalian hippocampus and cortex. However, the underlying mechanism of synapse dynamics remains unclear. To elucidate the mechanism, we traced individual dendritic spines on layer V pyramidal neurons of the primary sensory cortex in adult female mice under E2 intervention using two-photon in vivo imaging microscopy. We confirmed the increase of the spine density upon E2 treatment in the intact mouse cortex. Furthermore, we found that this increase is due to the promotion of spine formation and the stability of newly formed spines...
December 27, 2017: Brain Research Bulletin
Veerle Paternoster, Anto P Rajkumar, Jens Randel Nyengaard, Anders Dupont Børglum, Jakob Grove, Jane Hvarregaard Christensen
BACKGROUND: Dendritic spine morphology is heterogeneous and highly dynamic. To study the changing or aberrant morphology in test setups, often spines from several neurons from a few experimental units e.g. mice or primary neuronal cultures are measured. This strategy results in a multilevel data structure, which, when not properly addressed, has a high risk of producing false positive and false negative findings. METHODS: We used mixed-effects models to deal with data with a multilevel data structure and compared this method to analyses at each level...
December 26, 2017: Journal of Neuroscience Methods
Rianne D Stowell, Elissa L Wong, Hanna N Batchelor, Monique S Mendes, Cassandra E Lamantia, Brendan S Whitelaw, Ania K Majewska
Microglia are the innate immune cells of the central nervous system and are also important participants in normal development and synaptic plasticity. Here we demonstrate that the microglia of the mouse cerebellum represent a unique population compared to cortical microglia. Microglia are more sparsely distributed within the cerebellum and have a markedly less ramified morphology compared to their cortical counterparts. Using time-lapse in vivo imaging, we found that these differences in distribution and morphology ultimately lead to decreased parenchymal surveillance by cerebellar microglia...
December 29, 2017: Developmental Neurobiology
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