In order to obtain resistant mutants to nystatin, ultraviolet radiation and LiCl were used to mutagenize the protoplasts of taxol-producing fungi NCEU-1, and four positive mutants with high yield of taxol were screened out on nystatin flat. After further screening experiments on fermentation, a mutant strain--UL04-5 which was able to produce taxol with high yield and could be stably passed on in genetics was eventually found, it's ability to produce taxol was improved from 314.07 microg/L (strain NCEU-1) to 418.24 microg/L (strain U04-5).
Ascomycota ; drug effects ; genetics ; growth & development ; metabolism ; Fermentation ; Genetic Variation ; Mutagenesis ; Nystatin ; pharmacology ; Paclitaxel ; biosynthesis ; Protoplasts ; metabolism

Effects of intracellular Na+, K+ and Cl- on Ca(2+)-regulated exocytosis activated by 10 microM acetylcholine (ACh) were studied in guinea-pig antral mucous cells which are permeabilized by nystatin treatment. Ca(2+)-regulated exocytotic events were modulated by [Na+]i, [K+]i and [Cl-]i via mediation of PTX-sensitive G proteins. Increases in [Na+]i and PTX inhibit G protein (G(Na)), which suppressed the exocytosis. Increases in [K+]i caused the exchange of G proteins (from G(Na) to G(K)) to increase, and GK evoked activation of the exocytosis and was inhibited by PTX. Increases in [Cl-]i and PTX inhibit G protein (G(Cl)), which stimulates exocytotic events. Based on these observations, the exocytosis in antral mucous cells were modulated by intracellular ions, concentration of which were increased or decreased by cell volume changes caused by Ach.
Acetylcholine/pharmacology ; Animal ; Cell Membrane Permeability/drug effects ; Exocytosis/physiology* ; Exocytosis/drug effects ; Gastric Mucosa/metabolism ; Gastric Mucosa/cytology ; Guinea Pigs ; Hypertonic Solutions/pharmacology ; Ionophores/pharmacology ; Nystatin/pharmacology ; Pertussis Toxins/pharmacology ; Potassium/pharmacokinetics* ; Pyloric Antrum/metabolism* ; Pyloric Antrum/cytology ; Sodium Chloride/pharmacokinetics* ; Vasodilator Agents/pharmacology

OBJECTIVEGastric cancer cells are insensitive to tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). To sensitize gastric cancer cells to TRAIL, we treated gastric cancer MGC803 cells with TRAIL and cisplatin.

METHODSCell proliferation was measured using MTT assay. Cell apoptosis was determined by flow cytometry. Expression of proteins was analyzed by Western blot. The distribution of lipid rafts and death receptors was analyzed by immunofluorescence microscopy. MGC803 cells were pretreated with 50 mg/L nystatin for 1 h, and followed by the treatment of cisplatin and TRAIL.

RESULTS100 µg/L TRAIL resulted in (8.51 ± 3.45)% inhibition of cell proliferation and caused (3.26 ± 0.89)% cell apoptosis in MGC803 cells. Compared with the treatment with cisplatin alone, treatment with TRAIL (100 µg/L) and cisplatin (8.49 mg/L, IC(50) dose of 24 h) led to a dramatic increase in both inhibition of cell proliferation [(52.58 ± 4.57)% vs. (76.43 ± 5.35)%, P < 0.05] and cell apoptosis [(23.10 ± 3.41)% vs. (42.56 ± 4.11)%, P < 0.05]. Moreover, cleavage of caspase-8 and caspase-3 was detected. TRAIL (100 µg/L) did not induce obvious lipid rafts aggregation and death receptor 4 (DR4) clustering, while cisplatin (8.49 mg/L) significantly promoted the localization of DR4 in aggregated lipid rafts. Pretreatment with 50 mg/L nystatin, a cholesterol-sequestering agent, triggered (3.66 ± 0.52)% cell apoptosis after 24 h. Pretreatment with nystatin for 1 h before the addition of 8.49 mg/L cisplatin for 24 h caused a decreased tendency to cell apoptosis [(25.74 ± 3.28)% vs. (22.76 ± 2.97)%]. While, pretreatment with nystatin before the addition of cisplatin and TRAIL, the proportion of apoptotic cells decreased from (43.16 ± 4.26)% to (31.52 ± 3.99)% (P < 0.05).

CONCLUSIONCisplatin enhances TRAIL-induced apoptosis in gastric cancer MGC803 cells through clustering death receptors into lipid rafts.

Antineoplastic Agents ; administration & dosage ; pharmacology ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Caspase 8 ; metabolism ; Cell Line, Tumor ; Cell Proliferation ; drug effects ; Cisplatin ; administration & dosage ; pharmacology ; Dose-Response Relationship, Drug ; Humans ; Membrane Microdomains ; metabolism ; Nystatin ; pharmacology ; Receptors, TNF-Related Apoptosis-Inducing Ligand ; metabolism ; Stomach Neoplasms ; metabolism ; pathology ; TNF-Related Apoptosis-Inducing Ligand ; pharmacology