STUDIES ON THE PERMEABILITY OF CALF THYMUS NUCLEI ISOLATED IN SUCROSE

A study of the permeability of calf thymus nuclei isolated in sucrose was carried out with sucrose-(14)C, glycerol-(14)C, and carboxydextran-(14)C (molecular weight, 60,000–90,000). The results indicate that the nuclei are very permeable to both sucrose and glycerol but they exclude the carboxydextran. Results obtained with other low molecular weight non-electrolytes (malonamide-(14)C, erythritol-(14)C, D-arabinose-(14)C, and D-mannitol-(14)C) are in agreement with the view that the nuclei are freely permeable to these molecular species. A sucrose-impermeable space is also present in these preparations and it has been attributed to the presence of intact cells. The high permeability of nuclei to sucrose was confirmed with Ficoll-separated preparations. The possibility of the presence of a substantial particulate space that allows the penetration of dextran cannot be excluded by these experiments, and this space may correspond to damaged nuclei.