| Abstrakt: |
When monkey cell sheet cultures were aged without further feeding, they markedly decreased in their capacity to be sensitized, and in their rate of sensitization, to transfection by picornavirus ribonucleic acid (RNA), when diethylaminoethyl (DEAE)-dextran was used as sensitizer (enhancer). Cell sensitizability, however, was nearly completely restored several hours after feeding the cell sheets with fresh complete cell growth medium. The active factors in the medium were found to be orthophosphate, threonine, tryptophan, arginine, histidine, and methionine, with possibly some low activity due to phenylalanine and tyrosine. Recently fed eta cell sheet cultures which had been treated with high concentrations of chymotrypsin, papain, or trypsin (to the point where some of the cells were sloughing), and then washed, showed unaltered sensitizability by DEAE-dextran. However, cells similarly treated with pancreatic ribonuclease, and then washed, showed a marked decrease in the subsequent transfection obtained using the method of pretreating the cells with DEAE-dextran. This ribonuclease effect was not due to remaining ribonuclease in the residual medium over the washed cell sheets. That one or more cellular ribonucleoproteins play important roles in the sensitization of the cells by DEAE-dextran, and thus presumably in the cellular uptake and/or processing of the DEAE-dextran, is suggested as an attractive hypothesis consistent with the observations and data so far obtained. [ABSTRACT FROM AUTHOR] |
