Some Chemical Properties of Isolated Pea Nucleoli

Abstract

Isolated nuclei and nucleoli of ungerminated pea embryos have been analyzed chemically for their content of DNA, RNA, zinc, iron, phosphorus, and protein sulfhydryl groups. The values obtained cannot be considered to represent the whole of the riving nucleolar body as an undetermined amount of material is extracted from nucleoli in the course of their isolation. Only negligible amounts of DNA have been found in the isolated nucleofi; most of the DNA released on disruption of nuclei appears in a fraction showing very few structures under the light microscope. RNA is more concentrated in the nucleolus than in the nucleus or cytoplasm, but since nucleolar protein is 6 per cent of nuclear and less than 1 per cent of cytoplasmic protein, the total amount of nucleolar RNA is comparatively small. None of the other components listed occurs in high concentration in either nucleus or nucleolus.

The Distribution of the Water-Soluble Inorganic Orthophosphate Ions Within the Cell: Accumulation in the Nucleus

“…X 3,800 . FIGURE 6 The image for the KaI-emission wave length of phosphorus of a "control" section fixed in glutaraldehyde alone . It represents the phosphorus distribution due to the organic material only, and there is no difference in concentration over nucleoli and cytoplasm .…”

“…In the nucleolus, the phosphate due to a water-soluble inorganic orthophosphate pool is three to five times greater than the phosphate due to the macromolecular organic phosphate . Some calculations can be made, assuming that practically all the organic phosphate in the nucleolus is due to RNA (6) Phosphorus concentration along a 39-µ traverse line on the same area as Figs . 3 and 5 .…”

Studies on Isolated Nuclei

“…The salt insoluble R N A of whole nuclear fractions isolated from liver and other tissues (28) has a high G M P / U M P ratio, which might reflect the high G M P content of the NaCl-insoluble nucleolar RNA. 4. PSEUDOURIDYLIC ACID CONTENT RESULTS: Only 0.020 #moles of ~/uridine were found in 4.46 mg total R N A extracted from our nuclear fraction.…”

“…The first, proposed by Litt et al (1) and by Monty et al (2), relied on sonic vibrations to disrupt liver cell nuclei and disperse their nucleoplasm; it yielded a nucleolar fraction with a high content of DNA. In the second approach (3,4), the "solubilization" of the nucleoplasm was obtained through Ca 2+ removal effected by suspending the nuclei in a citrate-containing medium; the nuclear envelope was subsequently ruptured and the nucleoplasm dispersed by stirring the suspension in a mixer. In a third approach (5), isolated nuclei were homogenized in a high density medium and the liberated nucleoli separated by differential centrifugation upon dilution of this homogenate.…”

Nucleolus and Chromosomes in <i>Euglena gracilis</i>

“…Feulgen positive structures have been described inside the nucleolus of a variety of cell types (7,15,16,17,18,36,43,84,87,88,105,108,109,110,139,141); and a "nu cleolar" DNA fraction has been reported in chemical analysis of isolated nucleoli (19,29,30,44,104,106,130,136,149). This chemically identified nucleolar DNA has been regarded as contamination by chromatin; however, nucleolar incorporation of DNA precursors has been shown to occur (65, 68, 69, 121) and a nucleolar constituent has been demonstrated to be hydrolyzable by DNAse (15,108,109,110,139,141).…”