Expression of GCaMP6s in the dentate gyrus induces tonic-clonic seizures.

GCaMP is a genetically encoded calcium indicator (GECI) widely used in neuroscience research. It measures intracellular Ca2+ level by fluorescence changes as it directly binds to Ca2+. In this process, the effect of this calcium buffer on the intracellular calcium signaling and cell physiology is often not taken into consideration. However, growing evidence from calcium imaging studies shows GCaMP expression under certain conditions can generate aberrant activity, such as seizures. In this study, we examined the effect of GCaMP6 expression in the dentate gyrus (DG) on epileptogenesis. We found that viral expression of GCaMP6s but not GCaMP6f in the DG induces tonic-clonic seizures several weeks after viral injection. Cell-type specific expression of GCaMP6s revealed the granule cells (GCs) as the key player in GCaMP6s-induced epilepsy. Finally, by using slice electrophysiology, we demonstrated that GCaMP6s expression increases neuronal excitability in the GCs. Together, this study highlights the ability of GCaMP6s in DG-associated epileptogenesis.

[Characteristics and Sources of DOM in Lake Sediments Under Different Inundation Environments].

The characteristics and sources of DOM in sediments are significantly affected by fluctuations in lake water levels. However, the impact of spatial differences on water levels remain unclear. Here, 36 sediment samples were collected from the flood passage and coastal beach of East Dongting Lake. The differences in the composition and source of DOM in sediments under perennial inundation and seasonal inundation were studied using UV-visible absorbance (UV-Vis) and fluorescent excitation-emission matrix (EEM)-parallel factor analysis (PARAFAC). Three fluorescent components of DOM in the sediment were identified. The relative abundance of protein-like components was as high as (72.95±8.94)%, including tryptophan (C2) and tyrosine (C3). However, the humic-like component (C1) abundance was (27.05±8.94)%. Compared with that in perennial inundation, DOM in seasonal inundation had a higher and lower relative abundance of protein-like components and humic-like components, respectively. Further, the aromatic and hydrophobic components were higher in perennial inundation, showing a spatial pattern of the middle>entrance>outlet of the lake, which was more conducive to the migration of pollutants. The high FI (1.93) and BIX (0.91) and low HIX (1.57) indicated that the DOM in sediments had the mixed characteristics of being mainly endogenic and relatively weakly terrigenous. This was mainly influenced by human input and sediment characteristics. The direct effect of sewage discharge was intensified by sediment exposure in the seasonal inundation zone. Additionally, the contents of clay and total nitrogen (TN) were significantly positively correlated with FI, indicating that high nutrients and clay in sediments enhanced the endogenous input of DOM (FI>1.9). The perennial inundation zone was influenced by external runoff input. At the same time, the pH and C/N were significantly positively correlated with HIX and C1, indicating that DOM in the sediments had higher terrigenic characteristics (HIX=1.38±0.57) than those in the seasonal inundation zone owing to the alkaline environment (pH>7.5) and runoff input. The results above revealed the relevant theories of the response of DOM in sediment to water quality and pollution in the process of hydrology and human activities and provide a scientific basis for the prevention and control of sediment pollution in lakes.

[Promotion and Mechanisms of DOM on Copper Adsorption by Suspended Sediment Particles].

The adsorption of heavy metals by suspended sediment particles is a key process in the migration of heavy metals in lakes and is affected by various environmental conditions. To reveal the effects and mechanisms of dissolved organic matter (DOM) on the adsorption of copper ions by suspended sediment particles, a Cu(Ⅱ) adsorption test was conducted through a laboratory simulation test. The results showed that DOM promoted the adsorption of Cu(Ⅱ) onto the suspended particles. Under the respective influences of fulvic acid and DOM extracted from the sediment of the Xiangjiang River, the adsorption percentage of Cu(Ⅱ) increased from 71.51% to 75.31% and 85.69%. Scanning electron microscope-energy spectroscopy results showed that under the influence of DOM, Cu(Ⅱ) existed inside the sediment particles after being adsorbed. The results of UV-visible (UV-Vis) spectroscopy showed that Cu(Ⅱ) and DOM were first complexed and then dissociated during the adsorption reaction. The results of fluorescent excitation-emission matrix spectroscopy combined with parallel factor analysis and synchronous fluorescence spectroscopy combined with two-dimensional correlation analysis indicate that protein-like components promoted the adsorption of Cu(Ⅱ) onto the sediment suspended particles. In particular, tyrosine-like components played a critical role in promoting adsorption. However, humic-like components hardly promote this adsorption. This study has improved the theory of heavy metal migration in lakes and can be used as a basis for the prevention and control of heavy metal pollution in sediments.

Development of a Copper-Based Metal Organic Electrode for Nitrite Sensing.

BACKGROUND: Nitrite is naturally present in vegetables and added to processed meats to enhance their color and prolong their shelf life. It is of concern because it reacts to form nitrosamines, which have been linked to cancer. OBJECTIVE: To develop a quick, reliable, and inexpensive method for quantifying nitrite in foods. METHOD: A copper-based metal organic framework (Cu-MOF)/gold-platinum alloy nanoparticle(Au@Pt)-modified glassy carbon electrode (GCE) was developed via a simple wet chemical synthesis followed by electrochemical deposition of gold-platinum alloy nanoparticles onto the surface of a GCE. Morphological characterization and component analysis of the prepared nanomaterials were carried out by Fourier transform infrared spectroscopy and scanning electron microscopy. Cyclic voltammetry and electrochemical impedance spectroscopy were used to study the electrochemical behavior of the fabricated electrodes. RESULTS: The quantitative and specific detection of nitrite was obtained by the amperometric i-t method. At a pH of 7, temperature of 25°C, and ionic strength of 0.4 M, the electrode exhibited a linear range of 0.001-12.2 mM nitrite with a low detection limit of 72 nM (S/N = 3). CONCLUSIONS: The Cu-MOF/Au@Pt/GCE exhibited good repeatability, reproducibility, stability, and selectivity to provide a capable analysis method for food samples. HIGHLIGHTS: A Cu-MOF with a large surface area and high porosity was developed to provide an electrode with many active sites. The Au@Pt alloy nanoparticle improved the electrocatalytic activity toward nitrite. The synergistic action between the Cu-MOF and Au@Pt alloy nanoparticle enhanced the electrochemical performance of the sensor.