Addition Of Competitors Research Articles

Filling ephemeral ponds affects development and phenotypic expression in Ambystoma talpoideum

Abstract Populations and communities are often greatly affected by disturbances and variation in abiotic habitat conditions. Many of these effects are contingent on relatively predictable, yet still variable, environmental conditions that drive the life history strategies and development pathways of organisms in those habitats. However, much focus has been placed on aspects of such changes that cause mortality or movement from patches, whereas a multitude of outcomes can occur in natural systems. In lentic freshwater habitats, hydroperiod is a defining environmental characteristic, with temporary ponds supporting distinct communities of organisms with complex life cycles and plastic developmental trajectories. Little consideration has been given to the effects of refilling of ponds with variable hydroperiods, as lengthening the hydroperiod can extend the time organisms spend in their aquatic stages, allowing for the acquisition of more resources. We hypothesised that increasing the volume of small ponds and adding competitors (Ambystoma maculatum) at the time of filling would interactively affect the development and phenotypic expression of Ambystoma talpoideum. We introduced larval A. talpoideum to experimental mesocosms and manipulated water level (small, low volume mesocosms; filled, full mesocosms) and the addition of competitors (A. maculatum) at the time of filling in a 2 × 2 factorial design. We found that low volume mesocosms were dominated by metamorphs, while filling resulted in a more even mix of metamorphs, larvae and paedomorphs in full mesocosms. Filling resulted in larger metamorphs and paedomorphs, but did not affect larvae, whereas addition of A. maculatum shortened the larval period of metamorphs. We provide evidence that changes in abiotic habitat conditions, such as variation in the volume of ponds, can shift the development and phenotype of organisms. This plasticity may allow species to ensure the success of populations under both improvement and deterioration of environmental conditions. Hence, phenotypes like paedomorphic A. talpoideum can breed sooner than metamorphs, theoretically maximising the fitness of both individuals and populations.

Selective Downregulation of the MDR1 Gene Product in Caco-2 Cells by Stable Transfection To Prove Its Relevance in Secretory Drug Transport

Considerable interest is focused on overcoming multidrug resistance (MDR) in cancer chemotherapy. The in vitro experiments to characterize P-glycoprotein's (P-gp) function and to decrease its effects have led to a variety of strategies such as addition of competitors or supplementation of the medium with oligonucleotides complementary to the 5'-end of the MDR1-mRNA. For the Caco-2 cell line, an in vitro model for absorption screening, expressing multiple transporters including P-gp, which pumps substances back into the apical solution, P-gp activity might mask other relevant transport proteins' activity. The objective of the present study was to construct a Caco-2 subline with reduced P-gp expression level. Caco-2 cells were transfected by electroporation with two different mammalian expression vectors, and the obtained subclones were investigated at RNA (Northern blotting, RT-PCR), protein (FACS analysis), and functional (transport studies) levels for reduction in P-gp expression. Northern blotting showed that the levels of transcription of the inserted gene were different among the several clones, but those results did not completely correlate with the FACS analysis for P-gp expression. The clones with the strongest reduction in P-gp expression detected by the FACS analysis also showed the lowest secretory fluxes of the P-gp substrate talinolol in transport studies. Repetition of FACS analysis after 7 and 24 months on 20 to 30 passage older subclones still showed reduction in P-gp expression and indicated that they are stably transfected. The new cell lines constructed in the present study provide the possibility to perform in vitro absorption studies in a cell system composed of differentiated enterocytes growing as a monolayer like the normal Caco-2 cell line but with a lower down to almost lacking expression of P-gp.

Analysis of the phase solubility diagram of a phenacetin/competitor/beta-cyclodextrin ternary system, involving competitive inclusion complexation.

The competitive inclusion complexations in the ternary phenacetin/competitors/beta-cyclodextrin (beta-CyD) systems were investigated by the solubility method, where m-bromobenzoic acid (m-BBA) and o-toluic acid (o-TA) were used as competitors. The solubility changes of the drug and competitors as a function of beta-CyD concentration in the ternary systems were formulated using their stability constants and intrinsic solubilities. The decrease in solubility of phenacetin by the addition of competitors could be quantitatively simulated by the formulation, when both drug and competitor give A(L) type solubility diagrams. On the other hand, when one of the guests gives a B(S) type solubility diagram, its solubility change was clearly reflected in that of the another guest, i.e., phenacetin gave an A(L) type solubility diagram in the binary phenacetin/beta-CyD system and o-TA gave a B(S) type diagram in the binary o-TA/beta-CyD system, but in the ternary phenacetin/o-TA/beta-CyD system, a new plateau region appeared in the original A(L) type diagram of phenacetin. This was explained by the solubilization theory of Higuchi and Connors. The solubility analysis of the ternary drug/competitor/CyD systems may be particularly useful for determination of the stability constant of a drug whose physicochemical and spectroscopic analyses are difficult, because they can be calculated by monitoring the solubility change of a competitor, without monitoring that of a drug. Furthermore, the present results suggest that attention should be paid to the type of the phase solubility diagram, as well as the magnitude of the stability constant and the solubility of the complex, for a rational formulation design of CyD complexes.