Matrix-assisted ultraviolet laser desorption/ionization time-of-flight (UV-MALDI-TOF) mass spectra of N-acylated and N,O-acylated glycosylamines

Matrix-assisted ultraviolet laser desorption/ionization time-of-flight mass spectrometry (UV-MALDI-TOF-MS) has shown to be a very useful technique for the study of the non-volatile and thermally non-stable N-acylated glycopyranosyl- and glycofuranosyl-amines. Of the several matrices tested, 2,5-dihydroxybenzoic acid (DHB) was the most effective giving good spectra in the positive-ion mode. In the linear and reflectron modes, the [M+Na](+) ions appeared with high intensity. Their fragmentation patterns were investigated by post-source decay (PSD) UV-MALDI-TOF-MS showing mainly cross-ring cleavages. In addition, N,O-acylated glycopyranosyl- and glycofuranosyl-amines were also analyzed by this technique. PSD UV-MALDI-TOF-MS gave significant signals for several primary fragment ions, which were proposed but not detected, or observed with very low abundance, in electron ionization mass spectrometry (EI-MS) experiments.     

硒代蛋氨酸对Aβ1-42诱导N2a细胞损伤的保护作用

探索硒代蛋氨酸（Se-Met）的早期干预对Aβ1-42诱导的Neuro-2A（N2a）细胞损伤的保护作用。将N2a细胞分为对照组、Aβ1-42诱导损伤组、Se．Met组和Se—Met预处理的ADl-42组,CCK．8法检测显示不同浓度Se-Met对N2a细胞活力的影响不同,且Se．Met能减弱Aβ1-42诱导N2a细胞活力的降低（P〈0．01）：DCFH．DA标记检测可见Se-Met预处理明显抑制Aβ1-42引起的N2a细胞内总活性氧（reactive oxygen species,ROS）水平增高,Aβ1-42作用24h组效果更显著（P〈0．05）;Westernblot检测发现,Se-Met可显著回升Aβ1-42引起的N2a细胞synaptophysin和PSD95水平的降低（P〈0．05;P〈0．05）;同时,Se-Met可显著降低Aβ1-42引起的N2a细胞内LC3-II／LC3-I水平的升高（P〈0．05）。因此,Se-Met在一定作用时间和浓度下可以提高N2a细胞的活力,对Aβ1-42引起的N2a细胞ROS水平增高、自噬均有抑制作用,同时缓解Aβ1-42引起的突触损伤;Se-Met对Aβ1-42诱导N2a细胞损伤具有较好的保护作用。     

Determination of Matrix Pore Size Distribution in Fractured Clayey Till and Assessment of Matrix Migration of Dechlorinating Bacteria

The pore structure and pore size distribution (PSD) in the clayey till matrix from three Danish field sites were investigated by image analysis to assess the matrix migration of dechlorinating bacteria in clayey till. Clayey till samples had a wide range of pore sizes, with diameters of 0.1–100 μm, and two typical peaks of pore sizes were observed in all clayey till samples. A large area fraction of the individual pores centered around 2 μm in diameter, and another fraction centered around 20 μm. In general, the typical macropore sizes (1 μm < D < 30 μm) in clayey tills determined by image analysis account for approximately 30–60% of the total porosity (20–26%), which is within the range of those reported for clayey soils and other clayey deposits in the literature. The pore size, PSD, and interconnectivity of pores in clayey till matrix may play an important role in evaluation of the migration of dechlorinating bacteria between fractures and clayey till matrix. Dechlorinating bacteria are small (0.3–1 μm) and may have the ability to morphologically adapt to space constraints. The results in this paper in combination with recent field data indicate that the migration of dechlorinating bacteria in fractures and into the clayey till matrix is likely, which is of significance for natural and stimulated degradation of chlorinated solvents by reductive dechlorination in clayey tills.     

Effects of particle size distribution,compositional and color properties of ground corn on quality of distillers dried grains with solubles (DDGS)

Oftentimes, corn processors believe that ground corn (raw material) and distillers dried grains with solubles (DDGS) are interrelated in certain quality parameters. Yet, previous studies, although rather limited, have not established this relationship. In this study, six ground corn samples and their resulting DDGS were analyzed for particle size distribution (PSD), using a series of six selected US standard sieves: Nos. 8, 12, 18, 35, 60, and 100, and a pan. The original sample and sieve sized fractions were measured for contents of moisture, protein, oil, ash and starch, and surface color. Total carbohydrate (CHO) and total non-starch CHO were also calculated. Results show that the geometric mean diameter (d_gw) of particles varied with individual corn and DDGS samples, and that d_gw of DDGS was larger than that of corn (0.696 vs. 0.479 mm, average values), indicating that during conversion of corn to DDGS, certain particles became enlarged. For d_gw and mass frequency of individual particle size classes, the relationship between ground corn and DDGS varied, but PSD of the whole sample was well correlated between them (r = 0.807). Upon conversion from corn to DDGS, on an average, protein was concentrated 3.59 times; oil, 3.40 times; ash, 3.32 times; and total non-starch CHO, 2.89 times. There were some positive correlations in contents of protein and non-starch CHO and in L value between corn and DDGS. Yet, variations in nutrients and color attributes were larger in DDGS than in corn. For either corn or DDGS, these variations were larger in sieved fractions than in the whole fraction. Raw material, processing method and addition of yeasts are among major factors considered for causing larger variations in these attributes among DDGS. The study partially supports the common belief by processors that quality attributes of corn affect those of DDGS.     

Dually innervated dendritic spines develop in the absence of excitatory activity and resist plasticity through tonic inhibitory crosstalk

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右美托咪定对异丙酚麻醉所致新生大鼠脑损伤的保护作用及机制

高浓度的异丙酚可导致动物和人类发生脑损伤,而右美托咪定对多种脑损伤动物模型具有一定的神经保护作用。为了考察右美托咪定对异丙酚麻醉所致新生大鼠脑损伤的保护作用及机制,本研究对7日龄清洁级SD大鼠分别腹腔注射异丙酚(60 mg/kg)、右美托咪定(80μg/kg)和异丙酚(60 mg/kg)+右美托咪定(80μg/kg)。Morris水迷宫实验发现高剂量的异丙酚可显著增加大鼠的逃避潜伏期并减少穿越平台次数,然而右美托咪定预处理则可显著降低大鼠的逃避潜伏期并提高穿越平台次数(p<0.05)。异丙酚单独处理导致大鼠的海马神经元细胞凋亡程度显著增加,而右美托咪定预处理则可显著抑制神经元细胞的凋亡(p<0.05)。异丙酚单独处理可显著下调PSD95蛋白的表达,但右美托咪定预处理则可有效抑制PSD95蛋白的下调(p<0.05)。高剂量的异丙酚可明显下调大鼠海马组织P13K、Akt和GSK-3βmRNA的表达,而右美托咪定预处理则可抑制P13K、Akt和GSK-3βmRNA的下调。此外,右美托咪定预处理可显著提高p-Akt/Akt和p-GSK-3β/GSK-3β蛋白比值。本研究表明,右美托咪定可有效抑制异丙酚诱导的神经元细胞凋亡,改善大鼠的学习和记忆能力。右美托咪定的神经保护作用与其对PI3K/AKT/GSK-3β信号通路的激活有关。     

Ca2+/calmodulin binding to PSD‐95 mediates homeostatic synaptic scaling down

Postsynaptic density protein‐95 (PSD‐95) localizes AMPA‐type glutamate receptors (AMPARs) to postsynaptic sites of glutamatergic synapses. Its postsynaptic displacement is necessary for loss of AMPARs during homeostatic scaling down of synapses. Here, we demonstrate that upon Ca²⁺ influx, Ca²⁺/calmodulin (Ca²⁺/CaM) binding to the N‐terminus of PSD‐95 mediates postsynaptic loss of PSD‐95 and AMPARs during homeostatic scaling down. Our NMR structural analysis identified E17 within the PSD‐95 N‐terminus as important for binding to Ca²⁺/CaM by interacting with R126 on CaM. Mutating E17 to R prevented homeostatic scaling down in primary hippocampal neurons, which is rescued via charge inversion by ectopic expression of CaM^R126E, as determined by analysis of miniature excitatory postsynaptic currents. Accordingly, increased binding of Ca²⁺/CaM to PSD‐95 induced by a chronic increase in Ca²⁺ influx is a critical molecular event in homeostatic downscaling of glutamatergic synaptic transmission.     

Altered striatal actin dynamics drives behavioral inflexibility in a mouse model of fragile X syndrome

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Characterization of zebrafish PSD‐95 gene family members

The PSD‐95 family of membrane‐ associated guanylate kinases (MAGUKs) are thought to act as molecular scaffolds that regulate the assembly and function of the multiprotein signaling complex found at the postsynaptic density of excitatory synapses. Genetic analysis of PSD‐95 family members in the mammalian nervous system has so far been difficult, but the zebrafish is emerging as an ideal vertebrate system for studying the role of particular genes in the developing and mature nervous system. Here we describe the cloning of the zebrafish orthologs of PSD‐95, PSD‐93, and two isoforms of SAP‐97. Using in situ hybridization analysis we show that these zebrafish MAGUKs have overlapping but distinct patterns of expression in the developing nervous system and craniofacial skeleton. Using a pan‐MAGUK antibody we show that MAGUK proteins localize to neurons within the developing hindbrain, cerebellum, visual and olfactory systems, and to skin epithelial cells. In the olfactory and visual systems MAGUK proteins are expressed strongly in synaptic regions, and the onset of expression in these areas coincides with periods of synapse formation. These data are consistent with the idea that PSD‐95 family members are involved in synapse assembly and function, and provide a platform for future functional studies in vivo in a highly tractable model organism. © 2005 Wiley Periodicals, Inc. J Neurobiol, 2005     

EEG power spectral density in locked-in and completely locked-in state patients: a longitudinal study

Persons with their eye closed and without any means of communication is said to be in a completely locked-in state (CLIS) while when they could still open their eyes actively or passively and have some means of communication are said to be in locked-in state (LIS). Two patients in CLIS without any means of communication, and one patient in the transition from LIS to CLIS with means of communication, who have Amyotrophic Lateral Sclerosis were followed at a regular interval for more than 1 year. During each visit, resting-state EEG was recorded before the brain–computer interface (BCI) based communication sessions. The resting-state EEG of the patients was analyzed to elucidate the evolution of their EEG spectrum over time with the disease’s progression to provide future BCI-research with the relevant information to classify changes in EEG evolution. Comparison of power spectral density (PSD) of these patients revealed a significant difference in the PSD’s of patients in CLIS without any means of communication and the patient in the transition from LIS to CLIS with means of communication. The EEG of patients without any means of communication is devoid of alpha, beta, and higher frequencies than the patient in transition who still had means of communication. The results show that the change in the EEG frequency spectrum may serve as an indicator of the communication ability of such patients.Electronic supplementary materialThe online version of this article (10.1007/s11571-020-09639-w) contains supplementary material, which is available to authorized users.