Preliminary research on the receptor-ligand recognition mechanism of umami by an hT1R1 biosensor.

The aim of this study was to determine the interaction between the human umami receptor hT1R1 and a ligand while avoiding the cross-talk among various signal pathways in cells. The hT1R1 was modified and mounted onto a signal amplification system on a glassy carbon electrode surface, and the response current towards four umami ligands (sodium glutamate (MSG), disodium inosinate (IMP), disodium guanylate (GMP), and disodium succinate (SUC)) was measured. The allosteric constants of the receptor-ligand interaction were calculated by the method of sensing kinetics, and the results indicated that the sensing ability of hT1R1 towards the abovementioned four ligands was as follows: GMP > MSG > IMP > SUC. After the analysis of the molecular structure and simulation through the molecular docking model, we have found that hT1R1 is essentially a recognition receptor for the nitrogen signal in the body, and it may recognize the umami substance through its amino group. The new research method developed in this study shows promising application in the mechanism study of signal transduction and drug screening.

Quantification of Neoagaro-Oligosaccharide Production through Enzymatic Hydrolysis and Its Anti-Oxidant Activities.

Neoagaro-oligosaccharides (NAOS) have health benefits that are related to their amount and degree of polymerization (DP). However, the current methods that are used to quantify enzymatically released NAOS are un-specific and time-consuming. Agar has been extracted from Gelidium amansii and has been degraded by AgaXa (a recombinant ß-agarase). Polysaccharide analysis using carbohydrate gel electrophoresis (PACE) has been adapted in order to quantify NAOS. In addition, the anti-oxidant activity of the degraded samples has been assessed. We have found that the PACE method provided sensitive, precise, and accurate quantification for each of the six NAOS samples. PACE has revealed that the DP of the enzymatic products from the AgaXa digestion were mainly neoagaro-octaose and neoagaro-decaose. The degraded samples exhibited increased radical-scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl and 2,2-azino-bis(3-ethylbenzothiazoline sulfonic acid) radicals. While the anti-oxidant activity may have been from NAOS activity and contributions from neoagaro-octaose and neoagaro-decaose. The adapted PACE method that has been presented here is promising for large sample analysis during quality control and for characterizing novel ß-agarase degradation mechanisms.

Influence of JuA in evoking communication changes between the small intestines and brain tissues of rats and the GABAA and GABAB receptor transcription levels of hippocampal neurons.

ETHNOPHARMACOLOGICAL RELEVANCE: Jujuboside A (JuA) is a main active ingredient of semen ziziphi spinosae, which can significantly reduce spontaneous activity in mammals, increase the speed of falling asleep, prolong the sleeping time as well as improve the sleeping efficiency. In this study, the mechanism and the pathway of the sedative and hypnotic effect of JuA were investigated. MATERIALS AND METHODS: After being treated with JuA (in vitro), the rat׳s small intestine tissues cultures were used to stimulate the brain tissues. Then 27 cytokine levels were detected in the two kinds of tissue culture via liquid protein chip technology; In addition, the cultured hippocampal neurons of rat were treated with JuA, and γ-aminobutyric acid (GABA) receptor subunits (GABAAα1, GABAAα5, GABAAß1 and GABABR1) mRNAs were evaluated by Real-time PCR. RESULTS: The levels of IL-1α, MIP-1α, IL-1ß and IL-2 were reduced significantly after 3h of treating the small intestine tissues with JuA (200µl/ml), and the concentration change rates, in order, were -59.3%, -3.59%, -50.1% and -49.4%; these cytokines were transmitted to brain tissues 2h later, which could lead to significant levels of reduction of IL-1α, IFN-γ, IP-10 and TNF-α; the concentration change rates were -62.4%, -25.7%, -55.2% and -38.5%, respectively. Further, the intercellular communication network diagram was mapped out, which could suggest the mechanism and the pathway of the sedative and hypnotic effect of JuA. The results also indicated that JuA (50µl/ml) increased significantly GABAAα1 receptor mRNAs and reduced GABABR1, mRNAs in hippocampal neurons after 24h of stimulation; however, all the mRNA transcription levels of GABAAα1,GABAAα5, GABAAß1 and GABABR1 receptors increased significantly after 48h. CONCLUSION: JuA performed its specific sedative and hypnotic effect through not only adjusting GABA receptors subunit mRNAs expression, but also down-regulating the secretion of relevant inflammation cytokines on the intestinal mucosal system to affect the intercellular cytokine network between nerve cells in the brain. This mechanism is similar to that of melatonin.

[Effects of mitomycin C on the expression and transport of ice-nuclei proteins of Erwinia herbicola].

Abstract: In this paper, Mitomycin C (MMC) was added to different kinds of medium to study the effects of different cultural conditions on the Erwinia herbicola 10025A. For the first time it was confirmed that the expressed activity of the ice-nuclei active protein was different from its transportable manner from the ice nucleation active bacteria (Erwinia herbicola 10025A). The findings indicated that MMC could stimulate the SOS response,and induce the synthesis of some enzymes and proteins, which take part in repairing the damaged DNA. The effects of the MMC on the E. herbicola under different media were different. It could increase the ice nucleation activity of the E. herbicola, forming new small vesicles, which are secreted to the outside of membrane. The importance of this research for study the living mechanism of cells ander poor condition was discussed.