IMAGE-EELS FOR IN-SITU ESTIMATION OF THE PHOSPHORUS-CONTENT OF RNP GRANULES

Electron energy-loss spectroscopic imaging is performed on ultrathin s ections, in order to approach the in-situ distribution of individual e lements in the cellular constituents. In a previous ultrastructural st udy of salivary gland cells of Chironomus thummi and Ch. tentans by me ans of electron spectroscopic imaging and cytochemistry, we have descr ibed a new type of phosphorus-rich small granular ribonucleoprotein (R NP) component in the nucleoplasm of these cells; an attempt is made in the present work to estimate the phosphorus content of this component by the above mentioned method, using ribosomes as internal standard. Results show that these RNP granules contain, on average 3600 phosphor us atoms per granule. Another nuclear constituent also studied, the Ba lbiani ring granule, contains, on average, 43 000 phosphorus atoms per granule.