ABSTRACT
Glucagon-like peptide-1 (GLP-1) secreted from enteroendocrine L-cells is a pleiotropic hormone with beneficial potential related to islet function, diet control, glucose homeostasis, inflammation relief, and cardiovascular protection. The present study aimed at investigating the effect of Polygonatum cyrtonema polysaccharide (PCP) after structural identification on GLP-1 secretion and the possible mechanism involved in the PCP-stimulated secretion of GLP-1. It was found that GLP-1 secretion was effectively promoted (p < 0.01) by PCP both in rats with oral administration for 5 weeks (13.9 ± 0.3-35.8 ± 0.3 pmol/L) and ileal administration within 2 h (13.6 ± 0.4-34.1 ± 1.1 pmol/L) and in enteroendocrine NCI-H716 cells with direct stimulation within 24 h (2.05 ± 0.3-20.7 ± 0.2 pmol/L). The sweet taste receptor T1R2/T1R3 was identified to be essential for NCI-H716 cells to directly recognize PCP. The intervention experiments showed that PCP-stimulated GLP-1 secretion was significantly depressed (p < 0.01) not only by antibodies, siRNA, and the inhibitor of T1R2/T1R3 but also by an adenylate cyclase inhibitor. These results suggest that PCP stimulates GLP-1 secretion from enteroendocrine cells possibly through activation of the T1R2/T1R3-mediated cAMP signaling pathway.
Subject(s)
Cyclic AMP/metabolism , Enteroendocrine Cells/metabolism , Glucagon-Like Peptide 1/metabolism , Plant Extracts/pharmacology , Polygonatum/chemistry , Polysaccharides/pharmacology , Receptors, G-Protein-Coupled/metabolism , Animals , Enteroendocrine Cells/drug effects , Male , Mice , Mice, Inbred C57BL , Rats , Rats, Sprague-Dawley , Receptors, G-Protein-Coupled/genetics , Signal Transduction/drug effectsABSTRACT
A field experiment using litterbags was conducted in an alpine forest of western Sichuan in order to understand the effects of snow patches on the dynamics of N and P during decomposition of six representative species foliar litter in different periods of winter. Net N immobilization during foliar litter decomposition was observed in the whole snow cover season regardless of species. In contrast, P mainly released from foliar litter in the snow cover season, with a rapid rate of P release in the snow melt stage. Thick and moderate snow patches showed higher P release rates, but lower N release rates of foliar litter. The rate of N release was negatively related to daily mean temperature regardless of species, but the rate of P release was positively related to daily mean temperature with the exception of fir needle-litter. The decrease of snow cover in the scenario of global warming could inhibit P release but promote N release from foliar litter decomposition in winter in the alpine forest.
Subject(s)
Nitrogen/chemistry , Phosphorus/chemistry , Plant Leaves/chemistry , Snow , Soil/chemistry , China , Forests , Global Warming , Seasons , TemperatureABSTRACT
This study investigated the dynamics of in situ root exudates and soil microbial composition among three Picea asperata plantations with different stand ages (9, 13 and 31 a) in Miyaluo, west Sichuan, China. The results showed that the secretion rates of root exudation per fine biomass, length, surface area and tip were significantly different among the three plantations with different stand ages. The secretion rate of root exudation was the highest in the 9-year-old plantation stand. The root activity of P. asperata was the weakest in the 13-year-old plantation stand. Besides, soil microbial biomass C (MBC) and N (MBN) between rhizosphere and non-rhizosphere soils were significantly different among the three plantation stands. MBC and MBN contents of rhizosphere soil gradually increased with stand ages, while those of non-rhizosphere soil were the largest in the 13-year-old plantation stand. The phospholipid fatty acids (PLFAs) of bacteria, fungi, actinomycetes and their summation in rhizosphere soil presented a trend of high-low-high with stand ages. The opposite pattern was found in the PLFAs of bacteria, fungi, the summation of PLFA, and the ratio of fungi number to bacteria in non-rhizosphere soil. It is suggested that root exudates might have a positive rhizosphere effect on soil microbial biomass C, N and PLFAs of functional groups.
Subject(s)
Picea/chemistry , Plant Exudates/chemistry , Soil Microbiology , Bacteria , Biomass , China , Forests , Fungi , Plant Roots/chemistry , Rhizosphere , Soil/chemistryABSTRACT
OBJECTIVE: To test the sensitivity and specificity of alpha-fetoprotein (AFP) colloidal gold diagnostic strip as compared with RIA-AFP diagnostic kit. METHODS: Double blind method was used to test sera from 426 healthy people and 1567 patients selected in two general hospitals and a cancer hospital. Each serum was measured by RIA-AFP and AFP colloidal gold diagnostic strip on the same day. RIA-AFP diagnostic results was identified as true positive or negative. RESULTS: Among 426 healthy people, all the RIA-AFP test showed negative result (serum AFP concentration less than 25 IU/ml), but the AFP colloidal gold diagnostic strip had 1.88% false positive. When comparing the result from 1567 patients measured by RIA-AFP, the sensitivity and specificity of AFP colloidal gold diagnostic strip were 99.3%, and 97.2%, respectively. The crude correspondence rate between the two diagnostic regents was 97.6%. CONCLUSION: AFP colloidal gold diagnostic strip showed very good result and could be used as a screening diagnostic kit in clinic and hospital settings.
