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Biomedical subjects

L Skoog

Publications and source records attributed to L Skoog.

At least 163 records · Page 9Linked to original sources
PubMed1979

Viability of the cervical epithelium during carcinogenesis in mice.

Autoradiograms of histological specimens from the cervix of seventy-five mice were analysed after in vivo injection with an RNA precursor. All nucleated, non-pyknotic cells and some mitotic figures were labelled, which suggested that the tissue was metabolically active (i.e. viable). Only the uppermost epithelial pyknotic cells were devitalized, as deduced by the morphological appearance of the cells and by the absence of label. The viability of the whole epithelium suggests that the previously reported focal distribution of proliferating and non-proliferating areas in the cervical epithelium of mice is a genuine phenomenon.

Animals↗
PubMed1979

Age-related decrease of ultraviolet light-induced DNA repair synthesis in human peripheral leukocytes.

The capacity for ultraviolet light-induced DNA repair synthesis, studied in peripheral leukocytes from 58 healthy subjects 13 to 94 years old, was found to vary greatly between individuals. A negative, statistically significant correlation was obtained between age and this synthesis, indicating a decrease in repair capacity with age. An age-related decrease in DNA repair may increase the susceptibility of cells to agents causing DNA damage, i.e. carcinogens and certain cytostatic drugs.

Adolescent↗
PubMed1978

Proliferative activity of myocardial capillary wall cells in dipyridamole--treated rats.

The hearts of rats treated with dipyridamole were studied by light microscope autoradiography and measurement of tissue radioactivity after intravenous injection of 3H-thymidine. Total tissue radioactivity was significantly increased in the hearts of the dipyridamole-treated animals. Only capillary wall cells were labelled in the autoradiograms. The observations indicate a proliferation of capillary wall cells, suggesting a neoformation of myocardial capillaries during dipyridamole treatment.

Animals↗
PubMed1977

2'-Deoxy-2'-azidocytidine inhibits the initiation of polyoma DNA synthesis.

2'-Deoxy-2'-azidocytidine, a nucleoside analogue, inhibits polyoma DNA synthesis. The inhibition results in a 5.5-fold decrease in the amount of replicating intermediates, as detected by electron microscopy. The results indicate that replication is inhibited at an early step, possibly in the initiation of new rounds of replication. In contrast, the effect on the elongation of DNA chains appears to be less pronounced. As a result of the inhibition, polyoma DNA molecules at an early stage of replication accumulate in the nuclei. Upon incubation of such nuclei, DNA synthesis is induced in these molecules. The replication starts from the normal origin and elongation proceeds bidirectionally at a rate close to that observed during in vivo conditions. Analysis of polyoma DNA replication in nuclei isolated from control cells indicates that both initiation and termination of replication are impaired under in vitro conditions.

Azides↗
PubMed1977

2'-Deoxy-2'-azidocytidine, a new inhibitor of DNA replication in mammalian cells.

Cell growth is reversibly inhibited by the nucleoside analogue, 2'-deoxy-2'-azidocytidine and the inhibition is a result of interference with DNA replication. The 5'-diphosphate of the analogue was earlier shown to specifically inactivate the enzyme ribonucleotide reductase in vitro. However, measurements of the pools of deoxyribonucleoside triphosphates in cells incubated in azidocytidine showed only minor changes which appeared to result from and not to be the cause of the inhibition of DNA replication. The DNA synthesized in polyoma-infected cells after incubation in azidocytidine showed a sedimentation pattern quite different from that seen after inhibition of DNA synthesis with arabinosyl cytosine or hydroxyurea. Experiments with nuclei isolated from azidocytidine-inhibited, polyoma-infected cells indicated (a) that the number of replicating molecules is decreased during the inhibition and (b) that upon incubation of the nuclei there is a rapid synthesis of DNA occurring in a new class of DNA molecules which are at a very early state of replication. Neither the 5'-triphosphate of azidocytidine nor the nucleoside itself inhibit DNA synthesis in vitro in isolated nuclei from polyoma-infected cells and at present the nature of the DNA-synthesis-inhibiting compound acting in the cells after addition of azidocytidine is unknown. Taken together the results suggest that azidocytidine inhibits DNA synthesis at an early stage, possible by blocking the initiation of DNA synthesis at the origin or by interfering with the elongation of newly initiated DNA molecules.

Cell Line↗
PubMed1971

Structure and biological activity of deoxyribonucleic acid from Bacillus bacteriophage phi 105: effects of Escherichia coli exonucleases.

The effects of Escherichia coli exonuclease I, exonuclease III, and deoxyribonucleic acid (DNA) polymerase on the biological activity of mature DNA from temperate Bacillus bacteriophage phi105 were investigated. Intact DNA loses infectivity rapidly upon exposure to exonuclease III. Although there is an overall decrease in marker rescue from exonuclease III-digested DNA, digestion preferentially affects markers at the end of the genetic map. This is taken to indicate a nonpermuted gene sequence in mature DNA. Incubation of mature DNA in the presence of exonuclease I or DNA polymerase has no effect on its biological activity. The possible structure of the ends of mature phi105 DNA is discussed. The rate of digestion of mature phi105 DNA by exonuclease III is only about 1/20 the rate of lambda DNA. Results of digestion of various DNA substrates by exonuclease III indicate that the enzyme distinguishes between different DNA terminal structures.

Bacillus subtilis↗
PubMed1970

Deoxyribonucleotide pools and deoxyribonucleic acid synthesis in mouse embryo cells infected with three classes of polyoma virus particles.

Polyoma virus particles were purified by equilibrium centrifugation in CsCl. Particles from three regions of the density gradient were examined for infectivity, for their ability to induce expanded pools of deoxyribonucleic acid (DNA) precursors, and for their ability to stimulate the synthesis of DNA. The most infectious population of particles, the virions, having a buoyant density of 1.33 g/ml, gave the greatest stimulation of the DNA-synthesizing apparatus of mouse embryo cells. Empty particles at density 1.29 g/ml had no DNA stimulatory activity. A population of particles of intermediate density, referred to as pseudovirions, was also much less active than virions in stimulating DNA synthesis, and the limited stimulatory activity of the latter fraction may be accounted for by its measured contamination with infective particles.

Animals↗