82,723 research outputs found
Patronin-mediated minus end growth is required for dendritic microtubule polarity.
Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra Patronin made terminal dendrites almost completely minus-end-out, indicating low Patronin normally limits minus-end-out microtubules. To determine whether minus end growth populated new dendrites with microtubules, we analyzed dendrite development and regeneration. Minus ends extended into growing dendrites in the presence of Patronin. In sum, our data suggest that Patronin facilitates sustained microtubule minus end growth, which is critical for populating dendrites with minus-end-out microtubules
Suppression of zinc dendrites in zinc electrode power cells
Addition of various tetraalkyl quarternary ammonium salts, to alkaline zincate electrolyte of cell, prevents formation of zinc dendrites during charging of zinc electrode. Electrode capacity is not impaired and elimination of dendrites prolongs cell life
Flux Dendrites of Opposite Polarity in Superconducting MgB rings observed with magneto-optical imaging
Magneto-optical imaging was used to observe flux dendrites with opposite
polarities simultaneously penetrate superconducting, ring-shaped MgB films.
By applying a perpendicular magnetic field, branching dendritic structures
nucleate at the outer edge and abruptly propagate deep into the rings. When
these structures reach close to the inner edge, where flux with opposite
polarity has penetrated the superconductor, they occasionally trigger anti-flux
dendrites. These anti-dendrites do not branch, but instead trace the triggering
dendrite in the backward direction. Two trigger mechanisms, a non-local
magnetic and a local thermal, are considered as possible explanations for this
unexpected behaviour. Increasing the applied field further, the rings are
perforated by dendrites which carry flux to the center hole. Repeated
perforations lead to a reversed field profile and new features of dendrite
activity when the applied field is subsequently reduced.Comment: 6 pages, 6 figures, accepted to Phys. Rev.
Mechanisms of Dendrites Occurrence during Crystallization: Features of the Ice Crystals Formation
Dendrites formation in the course of crystallization presents very general
phenomenon, which is analyzed in details via the example of ice crystals growth
in deionized water. Neutral molecules of water on the surface are combined into
the double electric layer (DEL) of oriented dipoles; its field reorients
approaching dipoles with observable radio-emission in the range of 150 kHz. The
predominant attraction of oriented dipoles to points of gradients of this field
induces dendrites growth from them, e.g. formation of characteristic form of
snowflakes at free movement of clusters through saturated vapor in atmosphere.
The constant electric field strengthens DELs' field and the growth of
dendrites. Described phenomena should appear at crystallization of various
substances with dipole molecules, features of radio-emission can allow the
monitoring of certain processes in atmosphere and in technological processes.
Crystallization of particles without constant moments can be stimulated by DELs
of another nature with attraction of virtual moments of particles to gradients
of fields and corresponding dendrites formation.Comment: 6 page
Dendrites and conformal symmetry
Progress toward characterization of structural and biophysical properties of
neural dendrites together with recent findings emphasizing their role in neural
computation, has propelled growing interest in refining existing theoretical
models of electrical propagation in dendrites while advocating novel analytic
tools. In this paper we focus on the cable equation describing electric
propagation in dendrites with different geometry. When the geometry is
cylindrical we show that the cable equation is invariant under the
Schr\"odinger group and by using the dendrite parameters, a representation of
the Schr\"odinger algebra is provided. Furthermore, when the geometry profile
is parabolic we show that the cable equation is equivalent to the Schr\"odinger
equation for the 1-dimensional free particle, which is invariant under the
Schr\"odinger group. Moreover, we show that there is a family of dendrite
geometries for which the cable equation is equivalent to the Schr\"odinger
equation for the 1-dimensional conformal quantum mechanics.Comment: 19 page
Understanding the formation of twinned dendrites (‘feather’ grains)
The phenomenon of feather grain growth is interesting from both a theoretical and commercial point of view. Here we report the results of phase-field simulations aimed at understanding the formation of twinned dendrites. We show that, while a competition between oppositely directed capillary and kinetic anisotropies with a simple four-fold symmetry can produce low anisotropy structures such as dendritic seaweed, there is no indication that this can give rise to twinned dendrites. In contrast, adding small components of an anisotropy, with higher order harmonics, can produce features reminiscent of twinned dendrites and may also be able to stabilise the grooved tip morphology
Tetanic Stimulation Leads to Increased Accumulation of Ca^(2+)/Calmodulin-Dependent Protein Kinase II via Dendritic Protein Synthesis in Hippocampal Neurons
mRNA for the ɑ-subunit of CaMKII is abundant in dendrites of neurons in the forebrain (Steward, 1997). Here we show that tetanic stimulation of the Schaffer collateral pathway causes an increase in the concentration of ɑ-CaMKII in the dendrites of postsynaptic neurons. The increase is blocked by anisomycin and is detected by both quantitative immunoblot and semiquantitative immunocytochemistry. The increase in dendritic ɑ-CaMKII can be measured 100-200 µm away from the neuronal cell bodies as early as 5 min after a tetanus. Transport mechanisms for macromolecules from neuronal cell bodies are not fast enough to account for this rapid increase in distal portions of the dendrites. Therefore, we conclude that dendritic protein synthesis must produce a portion of the newly accumulated CaMKII. The increase in concentration of dendritic CaMKII after tetanus, together with the previously demonstrated increase in autophosphorylated CaMKII (Ouyang et al., 1997), will produce a prolonged increase in steady-state kinase activity in the dendrites, potentially influencing mechanisms of synaptic plasticity that are controlled through phosphorylation by CaMKII
Effects of Effective Dendrite Size on Dynamic Tensile Properties of Ti-Based Amorphous Matrix Composites
In this study, dynamic tensile properties of dendrite-containing Ti-based amorphous matrix composites were examined, and effects of dendrite size on dynamic deformation were investigated. The composites contained 73 to 76 vol pct of dendrites whose effective sizes were varied from 63 to 103 mu m. The dynamic tensile test results indicated that the ultimate tensile strength increased up to 1.25 GPa, whereas the elongation decreased to 1 pct, although the overall strength and elongation trends followed those of the quasi-static tensile test. According to the observation of dynamic tensile deformation behavior, very few deformation bands were observed beneath the fracture surface in the composite containing large dendrites. In the composite containing small dendrites, deformation bands initiated inside small dendrites propagated into adjacent dendrites through the amorphous matrix, and were crossly intersect perpendicularly in widely deformed areas, which beneficially worked for elongation as well as strength.open1131sciescopu
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