Several herbal plants such as Chinese herb Rhizoma Coptidis have been reported to possess antidiabetic activity. Berberine is its major active constituent and functions as an insulin sensitizer and insulin secretagogue. It has been reported to modulate several signaling pathways and targets. The objective of the current study is to investigate if berberine can function as a ligand of fatty acid receptor GPR40, which stimulates glucose dependent insulin secretion. Towards this objective, a mammalian cell line with stable overexpression of GPR40 was generated and characterized. Berberine stimulated calcium mobilization with an EC(50) of 0.76 microM in this GPR40 overexpressing cell line. Further, berberine stimulated glucose dependent insulin secretion from rat pancreatic beta cell line. This suggests that berberine functions as an agonist of fatty acid receptor GPR40 and might be a novel antidiabetic mechanism of action for berberine.
In modern drug discovery, numerous assay formats are available to screen and quantitate receptor-ligand interactions. Radioactive assays are "gold standard" because they are fast, easy, and reproducible; however, they are hazardous, produce radioactive waste, require special lab conditions, and are expensive on a large scale. Thus, it provides a lot of importance to the "mix & measure" assays that have an optical readout. Fluorescence techniques are likely to be among the most important detection approaches used for high throughput screening due to their high sensitivity and amenability to automation. The aim of the present study was to determine the functional antagonistic affinities of standard muscarinic antagonists in CHO cells over expressing m1, m3, and m5 receptors and to compare them with the respective binding affinities. This study was further extended to elucidate that Ca+2 measurement assays can serve as a functional screening tool for GPCRs. For this purpose, standard muscarinic receptor antagonists, namely, tolterodine, oxybutynin, and atropine were used. We determined and compared the IC50 values of these three standard inhibitors in fura 2 AM loaded m1, m3, and m5 overexpressing CHO cells and in radioligand binding assay. Both the assays exhibited comparable rank order potencies of the standard inhibitors. This study suggests that Ca+2 mobilization assays can be an alternate to radioligand binding assays.
Methods for the preparation of antigens from clinically isolated cultures of Aspergillus were standardized. Sera from 25 suspected cases of pulmonary aspergillosis were tested against antigens prepared by us, from 4 strains of A. fumigatus and one strain of A. flavus, using the Ouchterlony double diffusion and immunoelectrophoretic techniques. Of the 25 sera, 18 reacted positively with antigens of A. fumigatus, one with A. flavus and 2 with both these species. Antigens of two non-pathogenic Aspergilli included in the study failed to react with any of the sera. Our antigen preparations gave more numerous as well as sharper precipitin lines than the commercial Bencard antigens which were used for comparison. Moreover, mycelial antigens from 48 to 96 h old cultures revealed precipitin lines comparable to that of the routine, 4 week old culture filtrate antigens, thus suggesting that the incubation period for obtaining antigens could be cut down considerably.
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