The relationship between succession and stability in plant community was discussed based on redundancy theory.We regarded that:① Successions are recombination of components (species,individuals,or patches) on paralle...The relationship between succession and stability in plant community was discussed based on redundancy theory.We regarded that:① Successions are recombination of components (species,individuals,or patches) on paralleled structures.In succession,simple paralleled redundancy structure in early stage changes into multiple one in later stage.② Community stability is redundancy structure stability.Every succession stage is stable,for replacement of species does not mean instability.③Resistance is related with redundancy structure and biological characters or longevity of species.In general,communities with complicated redundancy structure and long life span species are stronger in resistance than communities with simple redundancy structure and short life span species,especially in early stages.④Resilience is actually the rate of redundancy recruitments.Community redundancy structure will not be destroyed even in communities with simple redundancy structure and short life span species,if there are redundancy recruitments.⑤Resistance,resilience,persistence and variability are redundancy phenomenon at levels of individual,species and community.They should not be defined as 4 components of community stabilities.⑥ Succession speed or pattern,dominants,species diversity and so on have no innate relation with community stability.展开更多
AIM: To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms. METHODS: Expression of multidrug resistance-associated...AIM: To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms. METHODS: Expression of multidrug resistance-associated protein(MRP) was detected using reverse transcriptionpolymerase chain reaction(RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein(P-gp), Bcl-2,Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. Meanwhile, the protein levels of Bcl-2 and Bax were also detected by Western blotting analysis. The sensitivity of cells to the anticancer agent, vincrimycin(VCR), and the intracellular [^3H]VCR accumulation were determined by tetrazolium blue (MTT) assay and a liquid scintillation counter, respectively. RESULTS: Expression of MRP and P-gp in SGC7901/VCR cells was 6.04-and 8.37-fold higher as compared with its parental SGC7901 cells, respectively. After treatment with 1, 5, 10, and 20 umol/L mifepristone, SGC7901/VCR cells showed a 1.34-, 2.29-, 3.11-, and 3.71-fold increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901/VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901/VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17-fold after treatment with mifepristone at above-mentioned dose. After 96 h of incubation with mifepristone 10 umol/L, a concentration close to plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21+0.65)% from (25.32+1.44)%, whereas the expression of Bax protein was increased to (19.69+1.13)% from (1.24+0.78)% (P<0.01). Additionally, the effects of mifepristone on the expression of Bcl-2 and Bax proteins in SGC7901/VCR cells were further demonstrated by Western blotting analysis. CONCLUSION: Mifepristone has potent reversal effect展开更多
文摘The relationship between succession and stability in plant community was discussed based on redundancy theory.We regarded that:① Successions are recombination of components (species,individuals,or patches) on paralleled structures.In succession,simple paralleled redundancy structure in early stage changes into multiple one in later stage.② Community stability is redundancy structure stability.Every succession stage is stable,for replacement of species does not mean instability.③Resistance is related with redundancy structure and biological characters or longevity of species.In general,communities with complicated redundancy structure and long life span species are stronger in resistance than communities with simple redundancy structure and short life span species,especially in early stages.④Resilience is actually the rate of redundancy recruitments.Community redundancy structure will not be destroyed even in communities with simple redundancy structure and short life span species,if there are redundancy recruitments.⑤Resistance,resilience,persistence and variability are redundancy phenomenon at levels of individual,species and community.They should not be defined as 4 components of community stabilities.⑥ Succession speed or pattern,dominants,species diversity and so on have no innate relation with community stability.
基金Supported by the National Key Research Project Fundation of China,No.96-905-02-01,and the National Natural Science Fundation of China,No.39630340
文摘AIM: To explore the reversal effect of mifepristone on multidrug resistance (MDR) in drug-resistant human gastric cancer cell line SGC7901/VCR and its mechanisms. METHODS: Expression of multidrug resistance-associated protein(MRP) was detected using reverse transcriptionpolymerase chain reaction(RT-PCR). Flow cytometry was used to assay the expression of P-glycoprotein(P-gp), Bcl-2,Bax, and the mean fluorescent intensity of intracellular rhodamine 123 in the cells. Meanwhile, the protein levels of Bcl-2 and Bax were also detected by Western blotting analysis. The sensitivity of cells to the anticancer agent, vincrimycin(VCR), and the intracellular [^3H]VCR accumulation were determined by tetrazolium blue (MTT) assay and a liquid scintillation counter, respectively. RESULTS: Expression of MRP and P-gp in SGC7901/VCR cells was 6.04-and 8.37-fold higher as compared with its parental SGC7901 cells, respectively. After treatment with 1, 5, 10, and 20 umol/L mifepristone, SGC7901/VCR cells showed a 1.34-, 2.29-, 3.11-, and 3.71-fold increase in the accumulation of intracellular VCR, a known substrate of MRP, and a 1.03-, 2.04-, 3.08-, and 3.68-fold increase in the retention of rhodamine 123, an indicator of P-gp function, respectively. MTT assay revealed that the resistance of SGC7901/VCR cells to VCR was 11.96-fold higher than that of its parental cells. The chemosensitivity of SGC7901/VCR cells to VCR was enhanced by 1.02-, 7.19-, 12.84-, and 21.17-fold after treatment with mifepristone at above-mentioned dose. After 96 h of incubation with mifepristone 10 umol/L, a concentration close to plasma concentrations achievable in human, the expression of Bcl-2 protein was decreased to (9.21+0.65)% from (25.32+1.44)%, whereas the expression of Bax protein was increased to (19.69+1.13)% from (1.24+0.78)% (P<0.01). Additionally, the effects of mifepristone on the expression of Bcl-2 and Bax proteins in SGC7901/VCR cells were further demonstrated by Western blotting analysis. CONCLUSION: Mifepristone has potent reversal effect
