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Biomedical subjects

D M Prescott

Publications and source records attributed to D M Prescott.

At least 109 records · Page 6Linked to original sources
PubMed1973

Initiation and continuation of DNA replication are not associated with the nuclear envelope in mammalian cells.

For determination of whether DNA replication is initiated at the nuclear envelope, synchronized Chinese hamster ovary cells labeled with [(3)H]thymidine were examined by electron microscope radioautography. The cells were synchronized initially by mitotic shake-off and held at the G(1)-S border by 5-fluorodeoxyuridine plus amethopterin. Cells were fixed at 1, 5, 10, and 30 min after the inhibitors were counteracted with [(3)H]thymidine. Radioautographic silver grains in each case were present over the more central parts of nuclei and were generally absent from the region of the nuclear envelope. We conclude that neither initiation nor continuation of DNA replication is associated with the nuclear envelope.

Animals↗
PubMed1972

Evidence of gene diminution during the formation of the macronucleus in the protozoan, Stylonychia (DNA density-melting curves-micronuclear DNA-polytene chromosomes).

The course of events by which a macronucleus is formed from a micronucleus after conjugation in the ciliated protozoan, Stylonychia, suggests that genetic diminution may occur. This idea is supported by determinations of the density profiles and melting curves for micro- and macronuclear DNAs. Macronuclear DNA consists of a single density component and melts as if it were a single component. Micronuclear DNA consists of four or more density components and melts as if it were a mixture of several DNAs of different base compositions. These data indicate that at least 60% of the micronuclear DNA components are absent from the macronuclear DNA.

Cell Nucleus↗
PubMed1972

Bidirectional replication of the chromosome in Escherichia coli.

E. coli cells initiating chromosome replication after release from amino-acid starvation were incubated in [(3)H]thymine of moderate specific activity, followed by incubation in [(3)H]thymine plus [(3)H]thymidine of very high specific activity. The grain tracks produced in autoradiographs of chromosomes were denser on both ends than in the middle. The autoradiographic patterns are, therefore, evidence that replication of the chromosome in E. coli is bidirectional.

Autoradiography↗