text: The origin of yolk-DNA in Xenopus laevis.
  Xenopus laevis serum and plasma was found to contain an average of 25 microgram DNA/ml. Isolated X. laevis oocytes incubated in medium containing 25 microgram DNA/ml labeled with either 125I, 32P or 14C and from three different sources (bovine, E. coli and X. laevis), incorporated the label at an average rate of 0.11 ng.mm-2.hr-1. Sucrose gradient fractionation of oocytes revealed that 40-75% of the acid-precipitable label incorporated was associated with the yolk platelets. Additional incubations of oocytes in unlabeled medium demonstrated that the DNA incorporated into the yolk platelets was undergoing turnover; only 20% of the yolk-associated DNA was still present after a one-week incubation. Our data suggest that yolk-DNA arises by the adventitious uptake of DNA present in the maternal serum by vitellogenic oocytes.
  
entities: ['serum']
entities: Organism_substance
entities: PMID-385804_T1
entities: ['plasma']
entities: Organism_substance
entities: PMID-385804_T2
entities: ['yolk']
entities: Developing_anatomical_structure
entities: PMID-385804_T3
entities: ['oocytes']
entities: Cell
entities: PMID-385804_T4
entities: ['oocytes']
entities: Cell
entities: PMID-385804_T5
entities: ['yolk platelets']
entities: Cell
entities: PMID-385804_T6
entities: ['oocytes']
entities: Cell
entities: PMID-385804_T7
entities: ['yolk platelets']
entities: Cell
entities: PMID-385804_T8
entities: ['yolk']
entities: Developing_anatomical_structure
entities: PMID-385804_T9
entities: ['yolk']
entities: Developing_anatomical_structure
entities: PMID-385804_T10
entities: ['serum']
entities: Organism_substance
entities: PMID-385804_T11
entities: ['oocytes']
entities: Cell
entities: PMID-385804_T12