Membrane aging experimental conditions

Significant interlaboratory differences in permeability measurements are observed with cell-based assays. It is important to standardize culture conditions and characterize a cell line within one s own laboratory. Permeability differences can be attributed to a number of factors, for example, heterogenecity of cell line, passage number, culture conditions, characteristics of the filter membrane, age of mono-layers and level of differentiation and experimental methodology used. Active... 

Another example may be checking of the blank response of an ammonia ion selective electrode under different experimental conditions, namely the age of the sensor membrane and the speed at which the measuring solution is stirred. 

Studies of Con A induced agglutination of live cells are susceptible to complications such as irreversibility of the agglutinated cells upon aging (17), endocytosis of bound lectin (18) and effects of experimental conditions such as temperature, pH and ionic strength on membrane properties (J). Alternatively, the use of aldehyde-fixed cells (19), heatkilled cells (20), enucleated cells (21) and glycoprotein-incorporated liposomes (22) may lead to less problems being encountered. 

It should be noted that the gas and vapor permeability of polymer membranes could be affected by pretreatment, ageing, plasticizatitm, crosslinking and/or crystallinity of the polymer and, in some cases, by the experimental conditions and measurement techniques employed. For example, the type of solvent(s) used in the casting of membranes may affect their permeability. 

In September 1993, the task group issued a preliminary report deseribing its activities and reporting aging conditions and experimental parameters for eaeh method and the interlaboratory results of unaged roofing membrane materials. Based on their study and results from previous research,P h[48][50][5i] Committee presented its final report in December... 

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