Nuclear mechanisms of protein synthesis

Waddington, Susan (1964) Nuclear mechanisms of protein synthesis. PhD thesis, University of Glasgow.

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A study has been made of ribonucleic acid (RNA) metabolism in the liver cell nuclei obtained from rats receiving various diets. Rats receiving a normal intake of protein and rats on a protein-free diet were used, and in the former group some animals were studied in the fasting state and some during active absorption after a meal of protein. A new technique for isolating pure liver nuclei in bulk was devised and the nuclei were then fractionated by successive extraction with phosphate buffer and molar sodium chloride, leaving a final "nucleolar" residue. The RNA content of the two amount in the nucleolar residue was increased, in agreement with histochemical examination. This was taken as evidence of storage of RNA in the nucleolus during protein depletion. Nucleolar RNA also increased during active absorption after a protein meal, but in this case the change may be due to stabilization by incoming amino acids of an unstable nuclear RNA species. Attempts to demonstrate a specially labile type of RNA were unsuccessful. The effect of diet on incorporation of labelled precursor in to nuclear RRA was also explored. Uptake of 14C-adehine into whole nuclear RMA was augmented by giving a protein-free diet. When the RNA of the nuclear subfractions was compared, the feeding of protein appeared to cause a preferential stimulus labelling in. the molar sodium' chloride fraction. Specimens of nuclear RNA and whole livor RITA were prepared by the phenol procedure, and examined for heterogeneity by various methods. Both nuclear and whole liver KNA separated in the analytical ultracentrifuge into four components (4-7S, 17-19S, 23-28S and 32S or heavier).When obtained from animals receiving the protein-free diet, the amount of the 4S component was reduced, whereas the heaviest component increased. These changes due to protein depletion were confirmed when whole liver RNA or cytoplasmic RNA was separated by centrifuging in a sucrose density gradient. The density gradients obtained with nuclear RNA were not satisfactory. Finally, the metabolism of nuclear and cytoplasmic inprttbronos was studied using incorporation of 14C-choline. The results show that nuclear membranes cannot be the precursor of the cytoplasmic membranes Moreover, feeding protein appeared m to stimulate 14C-choline uptake by the nuclear membrane, but not by cytoplasmic membranes.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: H N Munro
Keywords: Biochemistry
Date of Award: 1964
Depositing User: Enlighten Team
Unique ID: glathesis:1964-73308
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56

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