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To investigate the effects of various types of farmland shelterbelts on soil quality and soil bacterial community diversity, this study focused on soil samples from four different shelterbelt types in the Alaer reclamation area, including Populus euphratica Oliv.- Populus tomentosa Carrière (PP), Elaeagnus angustifolia L.- Populus euphratica Oliv. (EP), Populus alba var. pyramidalis Bunge (P), and Salix babylonica L. (S). We analyzed their physical, chemical, biological properties as well as the differences in bacterial community structure, and explored the influencing factors on soil microbial community characteristics through microbial correlation network analysis. The results showed that: (1) There were significant differences in soil properties among the four types of farmland shelterbelts (p < 0.05), with P soils exhibiting the highest levels of organic matter, total nitrogen, and total phosphorus contents. (2) The Alpha diversity indices of soil bacteria showed significant differences among the four types of farmland shelterbelts (p < 0.05), with the P soils displayed the highest Chao1 and Shannon indices. (3) There were differences in the composition and abundance of dominant soil bacterial communities among different farmland shelterbelts, notably, the abundances of Verrucomicrobia, Acidobacteria, and Planctomycetes were significantly higher in P soils compared to the other three types. (4) The complexity of the correlation network between microbial species and environmental factors was highest in EP soils, soil microbial biomass nitrogen and available phosphorus were the main influencing factors. These findings indicated that different types of farmland shelterbelts had significant impacts on soil properties and soil bacterial communities. Soil bacterial communities were regulated by soil properties, their changes reflected a combined effect of soil characteristics and tree species.

Despite the importance of G-protein-coupled receptors in many cellular functions, their intracellular organisation is largely unknown. The authors identified periodically repeating clusters of cannabinoid receptor 1 hotspots within neuronal axons that are dynamically regulated by CB1 agonists.

The second messenger Ap4A contributes to mast cell activation by interacting with HINT1 but the molecular mechanism is not fully understood. Here, the authors show that Ap4A regulates downstream signaling by polymerizing HINT1 and provide insights into how specificity over other second messengers is achieved.

Summary: Data-independent acquisition mass spectrometry (DIA-MS) is a powerful technique that enables relatively deep proteomic profiling with superior quantification reproducibility. DIA data mining predominantly relies on a spectral library of sufficient proteome coverage that, in most cases, is built on data-dependent acquisition-based analysis of the same sample. To expand the proteome coverage for a pre-determined protein family, we report herein on the construction of a hybrid spectral library that supplements a DIA experiment-derived library with a protein family-targeted virtual library predicted by deep learning. Leveraging this DIA hybrid library substantially deepens the coverage of three transmembrane protein families (G protein-coupled receptors, ion channels, and transporters) in mouse brain tissues with increases in protein identification of 37%–87% and peptide identification of 58%–161%. Moreover, of the 412 novel GPCR peptides exclusively identified with the DIA hybrid library strategy, 53.6% were validated as present in mouse brain tissues based on orthogonal experimental measurement. : Analytical Chemistry; Biological Sciences; Classification of Proteins; Proteomics Subject Areas: Analytical Chemistry, Biological Sciences, Classification of Proteins, Proteomics

Summary: The axon initial segment (AIS) cytoskeleton undergoes rapid and irreversible disruption prior to cell death after injury, and loss of AIS integrity can produce profound neurological effects on the nervous system. Here we described a previously unrecognized mechanism for ischemia-induced alterations in AIS integrity. We show that in hippocampal CA1 pyramidal neurons Nav1.6 mostly preserves at the AIS after disruption of the cytoskeleton in a mouse model of middle cerebral artery occlusion. Genetic removal of neurofascin-186 leads to rapid disruption of Nav1.6 following injury, indicating that neurofascin is required for Nav1.6 maintenance at the AIS after cytoskeleton collapse. Importantly, calcineurin inhibition with FK506 fully protects AIS integrity and sufficiently prevents impairments of spatial learning and memory from injury. This study provides evidence that calcineurin activation is primarily involved in initiating disassembly of the AIS cytoskeleton and that maintaining AIS integrity is crucial for therapeutic strategies to facilitate recovery from injury. : Neuroscience; Molecular Neuroscience; Cellular Neuroscience Subject Areas: Neuroscience, Molecular Neuroscience, Cellular Neuroscience

Action potential (AP) generation in inhibitory interneurons is critical for cortical excitation-inhibition balance and information processing. However, it remains unclear what determines AP initiation in different interneurons. We focused on two predominant interneuron types in neocortex: parvalbumin (PV)- and somatostatin (SST)-expressing neurons. Patch-clamp recording from mouse prefrontal cortical slices showed that axonal but not somatic Na+ channels exhibit different voltage-dependent properties. The minimal activation voltage of axonal channels in SST was substantially higher (∼7 mV) than in PV cells, consistent with differences in AP thresholds. A more mixed distribution of high- and low-threshold channel subtypes at the axon initial segment (AIS) of SST cells may lead to these differences. Surprisingly, NaV1.2 was found accumulated at AIS of SST but not PV cells; reducing NaV1.2-mediated currents in interneurons promoted recurrent network activity. Together, our results reveal the molecular identity of axonal Na+ channels in interneurons and their contribution to AP generation and regulation of network activity.

Down-regulation of GABAergic inhibition may result in the generation of epileptiform activities. Besides spike-triggered synchronous GABA release, changes in asynchronous release (AR) following high-frequency discharges may further regulate epileptiform activities. In brain slices obtained from surgically removed human neocortical tissues of patients with intractable epilepsy and brain tumor, we found that AR occurred at GABAergic output synapses of fast-spiking (FS) neurons and its strength depended on the type of connections, with FS autapses showing the strongest AR. In addition, we found that AR depended on residual Ca²⁺ at presynaptic terminals but was independent of postsynaptic firing. Furthermore, AR at FS autapses was markedly elevated in human epileptic tissue as compared to non-epileptic tissue. In a rat model of epilepsy, we found similar elevation of AR at both FS autapses and synapses onto excitatory neurons. Further experiments and analysis showed that AR elevation in epileptic tissue may result from an increase in action potential amplitude in the FS neurons and elevation of residual Ca²⁺ concentration. Together, these results revealed that GABAergic AR occurred at both human and rat neocortex, and its elevation in epileptic tissue may contribute to the regulation of epileptiform activities.

We report on a low-loss fusion splice between a hollow-core photonic bandgap fiber (NKT's HC-1550-02) and a conventional single mode fiber (Corning's SMF28) using a high V-number intermediate fiber. Compared to the commonly used fiber postprocessing techniques, the intermediate fiber method offers a new adjusting degree of freedom of V-numbers, enabling the reduction of coupling loss to 0.35 dB. Experimentally, a low fusion splice loss of 0.63 dB has been achieved between Nufern's SM1950 (V =2.836) and HC-1550-02 fiber, resulting in an overall insertion loss of 0.73 dB from SMF28 to HC-1550-02 fiber. We believe this is the lowest splice loss value reported for HC-1550-02 fiber using an arc splicer, on the aspect of both using a step-index solid-core fiber (0.63 dB) and a SMF28 fiber (0.73 dB). [ABSTRACT FROM PUBLISHER]

Studies in rodents revealed that selective accumulation of Na+ channel subtypes at the axon initial segment (AIS) determines action potential (AP) initiation and back propagation in cortical pyramidal cells (PCs); however, in human cortex, the molecular identity of Na+ channels distributed at PC axons, including the AIS and the nodes of Ranvier, remains unclear. We performed immunostaining experiments in human cortical tissues removed surgically to cure brain diseases. We found strong immunosignals of Na+ channels and two channel subtypes, NaV1.2 and NaV1.6, at the AIS of human cortical PCs. Although both channel subtypes were expressed along the entire AIS, the peak immunosignals of NaV1.2 and NaV1.6 were found at proximal and distal AIS regions, respectively. Surprisingly, in addition to the presence of NaV1.6 at the nodes of Ranvier, NaV1.2 was also found in a subpopulation of nodes in the adult human cortex, different from the absence of NaV1.2 in myelinated axons in rodents. NaV1.1 immunosignals were not detected at either the AIS or the nodes of Ranvier of PCs; however, they were expressed at interneuron axons with different distribution patterns. Further experiments revealed that parvalbumin-positive GABAergic axon cartridges selectively innervated distal AIS regions with relatively high immunosignals of NaV1.6 but not the proximal NaV1.2-enriched compartments, suggesting an important role of axo-axonic cells in regulating AP initiation in human PCs.Together, our results show that both NaV1.2 and NaV1.6 (but not NaV1.1) channel subtypes are expressed at the AIS and the nodes of Ranvier in adult human cortical PCs, suggesting that these channel subtypes control neuronal excitability and signal conduction in PC axons. [ABSTRACT FROM AUTHOR]

The distal end of the axon initial segment (AIS) is the preferred site for action potential initiation in cortical pyramidal neurons because of its high Na+ channel density. However, it is not clear why action potentials are not initiated at the proximal AIS, which has a similarly high Na+ channel density. We found that low-threshold Nav1.6 and high-threshold Nav1.2 channels preferentially accumulate at the distal and proximal AIS, respectively, and have distinct functions in action potential initiation and backpropagation. Patch-clamp recording from the axon cut end of pyramidal neurons in the rat prefrontal cortex revealed a high density of Na+ current and a progressive reduction in the half-activation voltage (up to 14 mV) with increasing distance from the soma at the AIS. Further modeling studies and simultaneous somatic and axonal recordings showed that distal Nav1.6 promotes action potential initiation, whereas proximal Nav1.2 promotes its backpropagation to the soma. [ABSTRACT FROM AUTHOR]