Mechanism of Lithium Metal Penetration through Inorganic Solid Electrolytes

Li deposition is observed and measured on a solid electrolyte in the vicinity of a metallic current collector. Four types of ion‐conducting, inorganic solid electrolytes are tested: Amorphous 70/30 mol% Li₂S‐P₂S₅, polycrystalline β‐Li₃PS₄, and polycrystalline and single‐crystalline Li₆La₃ZrTaO₁₂ garnet. The nature of lithium plating depends on the proximity of the current collector to defects such as surface cracks and on the current density. Lithium plating penetrates/infiltrates at defects, but only above a critical current density. Eventually, infiltration results in a short circuit between the current collector and the Li‐source (anode). These results do not depend on the electrolytes shear modulus and are thus not consistent with the Monroe–Newman model for “dendrites.” The observations suggest that Li‐plating in pre‐existing flaws produces crack‐tip stresses which drive crack propagation, and an electrochemomechanical model of plating‐induced Li infiltration is proposed. Lithium short‐circuits through solid electrolytes occurs through a fundamentally different process than through liquid electrolytes. The onset of Li infiltration depends on solid‐state electrolyte surface morphology, in particular the defect size and density.     

Tactile stimulation during artificial rearing influences adult function and morphology in a sexually dimorphic neuromuscular system

Maternal licking of rat pups affects the development of the spinal nucleus of the bulbocavernosus (SNB), a sexually dimorphic motor nucleus that controls penile reflexes involved with copulation. Maternal licking influences SNB motoneurons, with reductions in licking producing decreased SNB number, size, and dendritic length in adulthood. Reduced maternal licking also produces deficits in adult male copulatory behavior. In this experiment, we used an artificial rearing paradigm to assess the potential role of tactile stimulation in mediating the effects of maternal licking on the SNB neuromuscular system. During artificial rearing, pups were stroked with a paintbrush to mimic maternal licking, receiving low, medium, or high levels of daily stimulation. In adulthood, ex copula penile reflex behavior was tested and the morphology of SNB motoneurons assessed. SNB motoneurons were retrogradely labeled with cholera toxin-conjugated HRP and dendritic arbor was reconstructed in three dimensions. Animals that received low levels of stimulation showed deficits in penile reflexes relative to maternally reared controls, including a longer latency to erection, fewer cup erections, and fewer erection clusters. SNB dendritic morphology was also shaped by stimulation condition, with animals that received low or medium levels of stimulation showing an average 27% reduction in dendritic length. In addition, several reflex behaviors were significantly correlated with dendritic length, including latency to first erection, percent of cup erections, and number of erection clusters. These results suggest that tactile stimulation provided by maternal licking mediates some of the effects of maternal care on the development of male copulatory behavior.     

Genetic manipulation of single neurons in vivo reveals specific roles of flamingo in neuronal morphogenesis

To study the roles of intracellular factors in neuronal morphogenesis, we used the mosaic analysis with a repressible cell marker (MARCM) technique to visualize identifiable single multiple dendritic (MD) neurons in living Drosophila larvae. We found that individual neurons in the peripheral nervous system (PNS) developed clear morphological polarity and diverse dendritic branching patterns in larval stages. Each MD neuron in the same dorsal cluster developed a unique dendritic field, suggesting that they have specific physiological functions. Single-neuron analysis revealed that Flamingo did not affect the general dendritic branching patterns in postmitotic neurons. Instead, Flamingo limited the extension of one or more dorsal dendrites without grossly affecting lateral branches. The dendritic overextension phenotype was partially conferred by the precocious initiation of dorsal dendrites in flamingo mutant embryos. In addition, Flamingo is required cell autonomously to promote axonal growth and to prevent premature axonal branching of PNS neurons. Our molecular analysis also indicated that the amino acid sequence near the first EGF motif is important for the proper localization and function of Flamingo. These results demonstrate that Flamingo plays a role in early neuronal differentiation and exerts specific effects on dendrites and axons.     

Superoxide generation via the NR2B-NMDAR/RasGRF1/NOX2 pathway promotes dendritogenesis

N-methyl-D-aspartate receptors (NMDARs) that contain the NR2A and NR2B subunits play a critical role in neuronal plasticity and dendritogenesis. Gain-and-loss-of function studies indicate that NR2B, but not NR2A, promotes dendritic branching. Accumulating evidence indicates that stimulation of NMDARs activates NADPH oxidase (NOX2), thereby generating superoxide. However, the molecular underpinnings of this process are not understood. RasGRF1, a guanine nucleotide exchange factor, is key for several forms of neuronal plasticity and interacts directly with the tail of NR2B. We investigated whether the NR2B-NMDAR/RasGRF1 pathway regulates the activity of NOX2 and whether superoxide production is required for dendritogenesis. We measured superoxide production in developing primary cultures of hippocampal neurons from 3 to 25 days in vitro (DIV) with the probe dihydroethidium (dHE). We found the highest dHE levels at early and intermediate developmental stages (3–15 DIV), when the NR2B-NMDAR expression is abundant. During these early/intermediate developmental stages, but not in mature neurons (>15 DIV), NMDAR activity is required for superoxide production. We also found that disrupting the NR2B-RasGRF1 interaction led to reduced dHE fluorescence intensity and moreover inhibited dendritic branching in hippocampal neurons. Together, our data indicate that superoxide production is induced by the NR2B-NMDARs/RasGRF1/NOX2 pathway and promotes dendritogenesis.     

Vertically Aligned Lithiophilic CuO Nanosheets on a Cu Collector to Stabilize Lithium Deposition for Lithium Metal Batteries

Uncontrollable dendrite growth hinders the direct use of a lithium metal anode in batteries, even though it has the highest energy density of all anode materials. Achieving uniform lithium deposition is the key to solving this problem, but it is hard to be realized on a planar electrode surface. In this study, a thin lithiophilic layer consisting of vertically aligned CuO nanosheets directly grown on a planar Cu current collector is prepared by a simple wet chemical reaction. The lithiophilic nature of the CuO nanosheets reduces the polarization of the electrode, ensuring uniform Li nucleation and continuous smooth Li plating, which is difficult to realize on the normally used lithiophobic Cu current collector surface. The integration of the grown CuO arrays and the Cu current collector guarantees good electron transfer, and moreover, the vertically aligned channels between the CuO nanosheets guarantee fast ion diffusion and reduce the local current density. As a result, a high Columbic efficiency of 94% for 180 cycles at a current density of 1 mA cm^?2 and a prolonged lifespan of a symmetrical cell (700 h at 0.5 mA cm^?2) can be easily achieved, showing a simple but effective way to realize Li metal‐based anode stabilization.     

Zipper‐Inspired SEI Film for Remarkably Enhancing the Stability of Li Metal Anode via Nucleation Barriers Controlled Weaving of Lithium Pits

The lithium dendrite, inducing short circuit and breaking solid electrolyte interphase (SEI) films, is deleterious to the stability of Li metal batteries due to the uncontrollable occurrence of miscellaneous stresses. In contrast to conventional suppression routes, herein a strategy is proposed via controlling SEI film broken regions to minimize releasing stress in terms of weaving lithium pits. Inspired by the principle of zippers, zipper‐like SEI films enable offering ordered pattern on the surface of Li anode via mechanical rolling. For the available cells, net‐like sewing/breaking patterns alternatively occur in Li plating/stripping. In the same electrolyte, a stable and dendrite‐free Li homogeneous growth is achieved.     

GPI‐anchored human placental alkaline phosphatase has a nonpolarized distribution on the cell surface of mouse cerebellar granule neurons in vitro

The glycosyl phosphatidylinositol (GPI) lipid anchor, which directs GPI‐anchored proteins to the apical cell surface in certain polarized epithelial cell types, has been proposed to act as an axonal protein targeting signal in neurons. However, as several GPI‐anchored proteins have been found on both the axonal and somatodendritic cell‐surface domains of a variety of neuronal cell types, the role of the GPI anchor in protein localization to the axon remains unclear. To begin to address the role of the GPI anchor in neuronal protein localization, we used a replication‐incompetent retroviral vector to express a model GPI‐anchored protein, human placental alkaline phosphatase (hPLAP), in early postnatal mouse cerebellar granule neurons developing in vitro. Purified granule neurons were cultured in large mitotically active cellular reaggregates to allow retroviral infection of undifferentiated, proliferating granule neuron precursors. To more easily visualize hPLAP localization during the sequence of differentiation of single postmitotic granule neurons, reaggregates were dissociated following infection, plated as high‐density monolayers, and maintained for 1–9 days under serum‐free culture conditions. As we previously demonstrated for uninfected granule neurons developing in monolayer culture, hPLAP‐expressing granule neurons likewise developed in vitro through a series of discrete temporal stages highly similar to those observed in situ. hPLAP‐expressing granule neurons first extended either a single neurite or two axonal processes, and subsequently attained a mature, well‐polarized morphology consisting of multiple short dendrites and one or two axons that extended up to 3 mm across the culture substratum. hPLAP was expressed uniformly on the entire cell surface at each stage of granule neuron differentiation. Thus, it appears that the GPI anchor is not sufficient to confer axonal localization to an exogenous GPI‐anchored protein expressed in a well‐polarized primary neuronal cell type in vitro; other signals, such asthose present in the extracellular domain of these proteins, may be necessary for the polarized targeting or retention of axon‐specific GPI‐anchored proteins. © 1999 John Wiley & Sons, Inc. J Neurobiol 39: 119–141, 1999     

Glycinergic transmission regulates dendrite size in organotypic culture

We previously demonstrated that inhibitory synaptic transmission influences dendrite development in vivo. We now report an analogous finding in an organotypic culture of a glycinergic projection nucleus, the medial nucleus of the trapezoid body (MNTB), and its postsynaptic target, the lateral superior olive (LSO) of gerbils. Cultures were generated at 6–7 days postnatal and grown in serum containing medium with or without the glycine receptor antagonist, strychnine (SN), at 2 μM. LSO neurons were then labeled with biocytin, and the dendritic arbors were analyzed morphometrically. Compared to neurons from age-matched in vivo tissue, the neurons cultured in control media were somewhat atrophic, including decreases in dendritic branching and length. Incubation in strychnine led to a dramatic increase in dendritic branching and total dendritic length. Control neurons averaged 6.3 branches, compared to 18 branches/neuron in SN-treated cultures. There was a similar increase in primary dendrites and total dendritic length. The physical elimination of MNTB cells did not mimic SN treatment, presumably because glycinergic LSO neurons generated intrinsic connections. In fact, the LSO soma area was significantly greater following MNTB removal, suggesting that these afferents provide a second signal to postsynaptic neurons. These results suggest that spontaneous glycinergic transmission regulates the growth of postsynaptic processes. © 1996 John Wiley & Sons, Inc.     

Modeling organelle transport in branching dendrites with a variable cross-sectional area

The purpose of this paper is to develop a method for calculating organelle transport in dendrites with a non-uniform cross-sectional area that depends on the distance from the neuron soma. The model is based on modified Smith–Simmons equations governing molecular motor-assisted organelle transport. The developed method is then applied to simulating organelle transport in branching dendrites with two particular microtubule (MT) orientations reported from experiments. It is found that the rate of organelle transport toward a dendrite’s growth cone heavily depends on the MT orientation, and since there is experimental evidence that the MT orientation in a particular region of a dendrite may depend on the dendrite’s developmental stage, the obtained results suggest that a rearrangement of the MT structure may depend on the amount of organelles needed at the growth cone.