scholarly journals Ribonuclease-sensitivity of covalently closed rat liver mitochondrial deoxyribonucleic acid

1974 ◽  
Vol 141 (1) ◽  
pp. 155-158 ◽  
Author(s):  
David M. Lonsdale ◽  
I. Gwyn Jones
Keyword(s):  
Mitochondrial Dna ◽  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Reducing Agents

Preparations of covalently closed mitochondrial DNA of rat liver contain 10–30% of molecules that are converted into relaxed circular molecules after treatment with ribonuclease. Control experiments, with covalently closed bacteriophage PM2 DNA, indicate that ribonuclease-sensitivity cannot be induced either by depurination or by incubation with reducing agents.

scholarly journals Localization of the ribonucleotide sites in rat liver mitochondrial deoxyribonucleic acid

1978 ◽  
Vol 169 (1) ◽  
pp. 79-85 ◽  
Author(s):  
D M Lonsdale ◽  
I G Jones
Keyword(s):  
Mitochondrial Dna ◽  
Electron Microscope ◽  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Ribonuclease A ◽  
Single Strand ◽  
Ribonuclease H ◽  
Ribonuclease T1 ◽  
Dna Endonuclease ◽  
Calf Thymus

Supercoiled rat liver mitochondrial DNA is relaxed by treatment with ribonucleases A, T1 or H. All the supercoiled mitochondrial DNA is sensitive to ribonuclease H and ribonuclease A, but only 35% of the supercoiled population is sensitive to ribonuclease T1. Removal of the ribonucleotides with calf thymus ribonuclease H, followed by denaturation of the mitochondrial DNA and analysis of the single-strand fragment lengths in the electron microscope, showed that the ribonucleotides were randomly located on both strands of the DNA. Endonuclease-S1 digestion of mitochondrial DNA after removal of the ribonucleotides reveals that no unique fragments are produced and ribonucleotides are randomly distributed with respect to one another. The average number of ribonucleotide sites per molecule was estimated to be between 8 and 13. Two possible mechanisms for the origin of ribonucleotide sites are discussed.

DEOXYCYTIDYLATE DEAMINASE LEVELS IN REGENERATING RAT LIVER

1961 ◽  
Vol 39 (6) ◽  
pp. 1043-1054 ◽  
Author(s):  
D. K. Myers ◽  
C. Anne Hemphill ◽  
Constance M. Townsend
Keyword(s):  
Dna Synthesis ◽  
Liver Regeneration ◽  
Partial Hepatectomy ◽  
Rat Liver ◽  
Deoxyribonucleic Acid ◽  
Regenerating Liver ◽  
Regenerating Rat Liver ◽  
High Level ◽  
Early Regeneration

Deoxycytidylate deaminase activity and net synthesis of deoxyribonucleic acid (DNA) in vivo were found to increase at approximately the same time during the early stages of liver regeneration. However, deaminase activity in the regenerating liver remained at a high level for 1 day after DNA synthesis had slowed down again during the later stages of regeneration. The increase in deaminase activity was restricted as a result of exposure to 600 r X radiation during early regeneration, but this effect only became evident 11–16 hours after the irradiation. Irradiation on the second day after partial hepatectomy, when deaminase levels in control regenerating livers were relatively constant, failed to affect the deaminase activity immediately but did produce a 40–50% decrease in activity 11–16 hours later. Other antimitotic agents, e.g., colchicine, had little effect on deaminase activity.

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