Glucagon-like peptide-1 facilitates cerebellar parallel fiber glutamate release through PKA signaling in mice in vitro.

Glucagon-like peptide-1 (GLP-1) is mainly secreted by preproglucagon neurons; it plays important roles in modulating neuronal activity and synaptic transmission through its receptors. In the present study, we investigated the effects of GLP-1 on parallel fiber-Purkinje cell (PF-PC) synaptic transmission in mouse cerebellar slices using whole-cell patch-clamp recording and pharmacology methods. In the presence of a γ-aminobutyric acid type A receptor antagonist, bath application of GLP-1 (100 nM) enhanced PF-PC synaptic transmission, with an increased amplitude of evoked excitatory postsynaptic synaptic currents (EPSCs) and a decreased paired-pulse ratio. The GLP-1-induced enhancement of evoked EPSCs was abolished by a selective GLP-1 receptor antagonist, exendin 9-39, as well as by the extracellular application of a specific protein kinase A (PKA) inhibitor, KT5720. In contrast, inhibiting postsynaptic PKA with a protein kinase inhibitor peptide-containing internal solution failed to block the GLP-1-induced enhancement of evoked EPSCs. In the presence of a mixture of gabazine (20 µM) and tetrodotoxin (1 µM), application GLP-1 significantly increased frequency, but not amplitude of miniature EPSCs via PKA signaling pathway. The GLP-1-induced increase in miniature EPSC frequency was blocked by both exendin 9-39 and KT5720. Together, our results indicate that GLP-1 receptor activation enhances glutamate release at PF-PC synapses via the PKA signaling pathway, resulting in enhanced PF-PC synaptic transmission in mice in vitro. These findings suggest that, in living animals, GLP-1 has a critical role in the modulation of cerebellar function by regulating excitatory synaptic transmission at PF-PC synapses.

GLP-1 enhances hyperpolarization-activated currents of mouse cerebellar Purkinje cell in vitro.

Glucagon-like peptide-1 (GLP-1) is mainly secreted by preglucagonergic neurons in the nucleus tractus solitarius, which plays critical roles in regulation of neuronal activity in the central nervous system through its receptor. In the cerebellar cortex, GLP-1 receptor is abundantly expressed in the molecular layer, Purkinje cell (PC) layer and granular layer, indicating that GLP-1 may modulate the cerebellar neuronal activity. In this study, we investigated the mechanism by which GLP1 modulates mouse cerebellar PC activity in vitro. After blockade of glutamatergic and GABAergic synaptic transmission in PCs, GLP1 increased the spike firing rate accompanied by depolarization of membrane potential and significantly depressed the after-hyperpolarizing potential and outward rectifying current of spike firing discharges via GLP1 receptors. In the presence of TTX and Ba2+, GLP1 significantly enhanced the hyperpolarized membrane potential-evoked instant current, steady current, tail current (I-tail) and hyperpolarization-activated (IH) current. Application of a selective IH channel antagonist, ZD7288, blocked IH and abolished the effect of GLP1 on PC membrane currents. The GLP1 induced enhancement of membrane currents was also abolished by a selective GLP1 receptor antagonist, exendin-9-39, as well as by protein kinase A (PKA) inhibitors, KT5720 and H89. In addition, immunofluorescence detected GLP1 receptor in the mouse cerebellar cortex, mostly in PCs. These results indicated that GLP1 receptor activation enhanced IH channel activity via PKA signaling, resulting in increased excitability of mouse cerebellar PCs in vitro. The present findings indicate that GLP1 plays a critical role in modulating cerebellar function by regulating the spike firing activity of mouse cerebellar PCs.

Nicotine Facilitates Facial Stimulation-Evoked Mossy Fiber-Granule Cell Long-Term Potentiation in vivo in Mice.

Nicotine is a psychoactive component of tobacco that plays critical roles in the regulation of neuronal circuit function and neuroplasticity and contributes to the improvement of working memory performance and motor learning function via nicotinic acetylcholine receptors (nAChRs). Under in vivo conditions, nicotine enhances facial stimulation-evoked mossy fiber-granule cell (MF-GrC) synaptic transmission, which suggests that nicotine regulates MF-GrC synaptic plasticity in the mouse cerebellar cortex. In this study, we investigated the effects of nicotine on facial stimulation-induced long-term potentiation (LTP) of MF-GrC synaptic transmission in urethane-anesthetized mice. Our results showed that facial stimulation at 20 Hz induced an MF-GrC LTP in the mouse cerebellar granular layer that was significantly enhanced by the application of nicotine (1 µM). Blockade of α4ß2 nAChRs, but not α7 nAChRs, during delivery of 20 Hz facial stimulation prevented the nicotine-induced facilitation of MF-GrC LTP. Notably, the facial stimulation-induced MF-GrC LTP was abolished by an N-methyl-D-aspartate (NMDA) receptor antagonist, but it was restored by additional application of nicotine during delivery of 20 Hz facial stimulation. Furthermore, antagonism of α4ß2 nAChRs, but not α7 nAChRs, during delivery of 20 Hz facial stimulation prevented nicotine-induced MF-GrC LTP. Moreover, inhibition of nitric oxide synthase (NOS) abolished the facial stimulation-induced MF-GrC LTP, as well as the effect of nicotine on it. Our results indicated that 20 Hz facial stimulation induced MF-GrC LTP via an NMDA receptor/nitric oxide (NO) cascade, but MF-GrC LTP was enhanced by nicotine through the α4ß2 AChR/NO signaling pathway. These results suggest that nicotine-induced facilitation of MF-GrC LTP may play a critical role in the improvement of working memory performance and motor learning function.

Temporal-spacial relationships between facial stimulation-evoked filed potential responses in mouse cerebellar granular layer and molecular layer.

The cerebellum receives sensory inputs from mossy fiber-granule cell or climbing fiber pathways, and generates motor-related outputs. However, the temporal and special mechanism of the sensory information processing in cerebellar cortex is still unclear. Therefore, we here investigated the temporal-spacial mechanism between the facial stimulation-evoked field potential responses in granular layer (GL) and molecular layer (ML), by duo-electrophysiological recording technique and pharmacological methods in urethane-anesthetized mice. Our results showed that air-puff stimulation of ipsilateral whisker pad evoked successively field potential responses in GL and ML. The field potential response in GL exhibited a strong excitatory component (N1) followed by an inhibitory component (P1), while the field potential response in ML exhibited a tiny excitatory component (N1) followed by strong inhibitory component (P1). The latency of N1 was decreased with the increase of recording depth in ML, and it was the shortest in GL. Notably, the latencies of P1 in GL and ML were similar regardless the relative recording sites. Furthermore, blocking α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor-mediated parallel fiber excitatory inputs by application of AMPA receptor antagonist, NBQX prevented P1 in both ML and GL. Moreover, application of GABAA receptors antagonist, gabazine simultaneously abolished P1 in both ML and GL. These results indicate that the facial stimulation evoked a simultaneous GABAergic inhibition in both ML and GL via mossy fiber-GC-parallel fiber pathway, suggesting that the sensory stimulation simultaneously evoked excitation of molecular layer interneurons (MLIs) and GL Golgi cells in cerebellar cortex.

Propofol Inhibits Cerebellar Parallel Fiber-Purkinje Cell Synaptic Transmission via Activation of Presynaptic GABAB Receptors in vitro in Mice.

Propofol is a widely used intravenous sedative-hypnotic agent, which causes rapid and reliable loss of consciousness via activation of γ -aminobutyric acid A (GABAA) receptors. We previously found that propofol inhibited cerebellar Purkinje cells (PC) activity via both GABAA and glycine receptors in vivo in mice. We here examined the effect of propofol on the cerebellar parallel fiber (PF)-PC synaptic transmission in mouse cerebellar slices by whole-cell recording technique and pharmacological methods. We found that following blockade of GABAA and glycine receptors activity, propofol reversely decreased the amplitude of PF-PC excitatory postsynaptic currents (PF-PC EPSCs), and significantly increased paired-pulse ratio (PPR). The propofol-induced decrease in amplitude of PF-PC EPSCs was concentration-dependent. The half-inhibitory concentration (IC50) of propofol for inhibiting PF-PC EPSCs was 4.7 µM. Notably, the propofol-induced changes in amplitude and PPR of PF-PC EPSCs were abolished by GABAB receptor antagonist, saclofen (10 µM), but not blocked by N-methyl-D-aspartate receptor (NMDA) receptor antagonist, D-APV (50 µM). Application of the GABAB receptor agonist baclofen induced a decrease in amplitude and an increase in PPR of PF-PC EPSCs, as well masked the propofol-induced changes in PF-PC EPSCs. Moreover, the propofol-induced changes in amplitude and PPR of PF-PC EPSCs were abolished by a specific protein kinase A (PKA) inhibitor, KT5720. These results indicate that application of propofol facilitates presynaptic GABAB receptors, resulting in a depression of PF-PC synaptic transmission via PKA signaling pathway in mouse cerebellar cortex. The results suggest that the interaction with GABAB receptors may contribute to the general anesthetic action of propofol.

Efficient purification of antiproliferative polysaccharides from Hypsizigus marmoreus with radial flow chromatography.

The increasing commercial significance of natural polysaccharides for use in medicinal products is stimulating the development of efficient and easy scale-up techniques for polysaccharide purification. In this research, the crude polysaccharides from submerged cultivation broth of Hypsizigus marmoreus were purified using radial flow chromatography (RFC), and the antiproliferative activity of the purified fractions was evaluated in vitro. DEAE Sepharose CL-6B was selected to be packed in the RFC column based on its good resolution, physical stability, and low cost. Compared with axial flow chromatography (AFC), an efficient chromatographic process with significantly less time and buffer consumption but yielding higher polysaccharide recovery and resolution was established in RFC, which could clearly purify the crude polysaccharides into different fractions. An acceptable linear scale-up effect of RFC from 100 to 500 mL was successfully achieved without loss of resolution and enhancement of time consumption. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assays in cell cultures indicated that the purified polysaccharide fractions possess moderate antiproliferative activities in three different human cancer cell lines, but have significantly lower cytotoxicity in normal human cell lines in vitro. Among the polysaccharide fractions, the main purified acidic fraction W-I could be considered as a novel potential antitumor agent candidate for several tumors, especially for human alveolar epithelial tumors. This research confirmed for the first time that RFC would be a new fast and efficient tool for purification of polysaccharides into different fractions, both at laboratory and commercial scales.

Chitinase from a novel strain of Serratia marcescens JPP1 for biocontrol of aflatoxin: molecular characterization and production optimization using response surface methodology.

Chitinase is one of the most important mycolytic enzymes with industrial significance, and produced by a number of organisms. A chitinase producing isolate Serratia marcescens JPP1 was obtained from peanut hulls in Jiangsu Province, China, and exhibited antagonistic activity against aflatoxins. In this study, we describe the optimization of medium composition with increased production of chitinase for the selected bacteria using statistical methods: Plackett-Burman design was applied to find the key ingredients, and central composite design of response surface methodology was used to optimize the levels of key ingredients for the best yield of chitinase. Maximum chitinase production was predicted to be 23.09 U/mL for a 2.1-fold increase in medium containing 12.70 g/L colloidal chitin, 7.34 g/L glucose, 5.00 g/L peptone, 1.32 g/L (NH4)2SO4, 0.7 g/L K2HPO4, and 0.5 g/L MgSO4 · 7H2O. Polymerase chain reaction (PCR) amplification of the JPP1 chitinase gene was performed and obtained a 1,789 bp nucleotide sequence; its open reading frame encoded a protein of 499 amino acids named as ChiBjp.

Potential of chitinolytic Serratia marcescens strain JPP1 for biological control of Aspergillus parasiticus and aflatoxin.

Serratia marcescens strain JPP1 was isolated from peanut hulls in Huai'an city, Jiangsu Province, China. Its potential to inhibit the mycelial growth of Aspergillus parasiticus and the subsequent aflatoxin production was evaluated. The strain JPP1 could produce chitinase to degrade fungal cell walls, which was the main mechanism of strain JPP1 for biocontrol. Scanning electron microscopy of fungi treated with the crude chitinase revealed abnormal morphological changes. While the strain was grown in the peanut hulls-based medium, the chitinase activity reached 7.39 units. RT-PCR analysis showed that the crude chitinase repressed the transcription of genes involved in the aflatoxin gene cluster, such as aflR, aflC (pksL1), and aflO (dmtA) genes. By visual agar plate assay and tip culture method, the strain JPP1 exhibited remarkable inhibitory effect on mycelia growth (antifungal ratio >95%) and subsequent aflatoxin production (antiaflatoxigenic ratio >98%). An in vitro assay with seed coating agent of bacterial suspension showed that strain JPP1 effectively reduced fungal growth and subsequent aflatoxin production on peanut seeds, and its antagonistic effect was superior to the common agricultural fungicide of carbendazim. These characteristics suggest that S. marcescens JPP1 strain could potentially be utilized for the biological control of phytopathogenic fungi and aflatoxin in Chinese peanut main producing areas.

Biodegradation of crude oil using an efficient microbial consortium in a simulated marine environment.

Ochrobactrum sp. N1, Brevibacillus parabrevis N2, B. parabrevis N3 and B. parabrevis N4 were selected when preparing a mixed bacterial consortium based on the efficiency of crude oil utilization. A crude oil degradation rate of the N-series microbial consortium reached upwards of 79% at a temperature of 25 °C in a 3.0% NaCl solution in the shake flask trial. In the mesocosm experiment, a specially designed device was used to simulate the marine environment. The internal tank size was 1.5 m (L)×0.8 m (W)×0.7 m (H). The microbial growth conditions, nutrient utilization and environmental factors were thoroughly investigated. Over 51.1% of the crude oil was effectively removed from the simulated water body. The escalation process (from flask trials to the mesocosm experiment), which sought to represent removal under conditions more similar to the field, proved the high efficiency of using N-series bacteria in crude oil degradation.

Acetylene hydrogenation on anatase TiO2(101) supported Pd4 cluster: oxygen deficiency effect.

Acetylene hydrogenation on both the perfect and oxygen defective anatase TiO(2)(101) surfaces supported Pd(4) cluster has been studied using density functional theory calculations with a Hubbard U correction (DFT + U). The adsorbed Pd(4) cluster on the perfect surface prefers to form a tetrahedral structure, while it likely moves to the oxygen defective site to form a distorted tetrahedral structure by removing a bridging oxygen atom. For the defective surface, it exhibits a stronger ability to capture Pd(4) cluster as charge transfer is significantly performed due to the oxygen deficiency. Moreover, it is found that the oxygen defective surface shows higher activity for acetylene hydrogenation, and the possible reason may lie in the weaker adsorption strength between the Pd cluster and the adsorbed molecules on the defective surface as compared to the case on the perfect surface.

A novel polyoxochromium borophosphate with new 6-membered ring crown-shaped clusters.

A novel chromium borophosphate with anionic clusters has been synthesized using boric acid as flux. X-ray diffraction analysis on a single crystal reveals that its structure comprises of crown-shaped 6-membered ring clusters [NaCr(8)B(4)P(12)O(60)H(8)](15-), which are built from [Cr(4)O(18)] groups, [BP(2)O(10)] anions and PO(4) tetrahedra with Na(+) cations encapsulated in the clusters. Magnetic investigation showed strong antiferromagnetic interactions between Cr(3+)-Cr(3+) dimers at low temperature.

[Synthesis and photoluminescent properties of core/shell structure ZnS : Mn/SiO2 nanocrystals].

Mn-doped ZnS nanopatricles synthesized by solvothermal method were successfully coated with SiO2 shells of various thicknesses by hydrolysis reaction of tetraethyl orthosilicate (TEOS). The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy images (TEM), X-ray photoelectron spectroscopy (XPS) and the room temperature photoluminescence (PL) spectra. When the ZnS : Mn nanoparticles were coated with SiO2 shells, an obvious increase in particle size and a clear shell of SiO2 can be observed. The XPS measurement also gave the evidence for the core/shell structure of ZnS : Mn/SiO2 nanoparticles. Because the surface modification effect and the decrease in luminescent centers effect are concurrent in the SiO2 shells, the Mn emission intensity first increased and then decreased with the thickening of the SiO2 shell. The intensity, which attained its maxium at 5 shell thickness, was as 7 times as that for the bare ZnS : Mn nanoparticles.

[Preparation and spectrum properties of ZnS : Ag nanocrystals].

In the present paper, ZnS : Ag nanoparticles were prepared with simple chemicals by hydrothermal method. XRD patterns indicated that the products have cubic zinc blende crystal structure. The particle diameters were calculated using the Scherer's formula, and the particle size showed a nonlinear increase with the rise of reaction temperature. TEM images demonstrated the approximate sphere shapes of products, and the crystal sizes approached the estimated ones respectively. The luminescence properties were investigated with PL and PLE spectra. Emission peaks were at about 450 nm. This emission was ascribed to the recombination between the sulfur vacancy-related electron trap donor having an energy level just below the conduction band and the Ag-related hole trap acceptor above the valence band. Excitation peaks were at about 333 nm, and the excitation was attributed to the near-band-edge absorption of ZnS matrix. The luminescence intensity was strongly influenced by the reaction temperatures and time. It increased, decreased, and then increased again with the rise of reaction temperature, and increased then decreased with the increase in reaction time. ZnS : Ag nanoparticles synthesized at 200 degrees C for 6 hours have a well luminescence intensity.

[Preparation and luminescence properties of core-shell ZnS : Cu/ZnS nano-particles].

Core-shell structured ZnS : Cu/ZnS nano-particles and Cu2+ -doped ZnS nano-particles without any shell were prepared, and the effect of ZnS shell on the luminescence properties of ZnS : Cu2+ nano-particles was studied. The observed emission peak at 450 nm was assigned to the recombination of an electron from the shallow delocalized donor levels at the t2 level of Cu2+. The ZnS shell did enhance the luminescence at 450 nm, which resulted from the reduction of nonradiative recombination sites.

[Optical properties of core-shell ZnS :Mn nanoparticles].

Mn(2+)-doped ZnS nanoparticles were prepared in reverse micelles and were coated by a shell of ZnS. The optical properties of the coated Mn(2+)-doped ZnS nanoparticles were studied and compared with those of the uncoated ones. The results indicate that Mn2+ ions emission at 580 nm in the coated nanoparticles was much stronger than that in the uncoated ones. The excitation spectra of the uncoated nanoparticles shifted to the red with the time after the initial preparation, while those of the coated ones changed little, which indicate that the coated nanoparticles had better stability than the uncoated ones.