The peculiar changes previously observed in DNA content of rat adrenal medulla cell nuclei upon intermittent cold exposure (15 hr at +4°C followed by 9 hr at room temperature) have been further studied with the aid of Feulgen histophotometry and H3-thymidine radioautography. The amount of DNA decreases progressively with increasing length of cold exposure until 300 hr (-32%). Later a rapid change takes place, whereby DNA content per nucleus returns to values which are slightly, but consistently lower than normal. At termination of a period of cumulative exposure to cold, an analysis of a whole-day experimental cycle shows that the DNA decrease is due to loss of DNA during cold exposure and that DNA synthesis occurs upon return to room temperature. The balance between these two processes can be divided into three stages: (a) loss of DNA up to 300 hr of cumulative cold exposure; (b) marked increase in DNA by 350 hr; (c) oscillation around zero or slightly negative at 400 hr and beyond. These variations are due to: (1) the extension of DNA synthesis into the period of cold exposure as clearly demonstrated by radioautography (stage b), and (2) a later still greater DNA loss (stage c) which partly offsets the increased synthesis. A complex pattern of adaptation of the adrenal medulla cells, as regards DNA content, to the repetitive cold stimulus is thus demonstrated.
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1 August 1966
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August 01 1966
AN ANALYSIS OF DNA LOSS AND SYNTHESIS IN THE RAT ADRENAL MEDULLA NUCLEI UPON COLD STIMULATION
Maria Pia Viola-Magni
Maria Pia Viola-Magni
From the Istituto di Patologia Generale, University of Pisa, Italy
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Maria Pia Viola-Magni
From the Istituto di Patologia Generale, University of Pisa, Italy
Received:
December 30 1965
Online ISSN: 1540-8140
Print ISSN: 0021-9525
1966
J Cell Biol (1966) 30 (2): 213–225.
Article history
Received:
December 30 1965
Citation
Maria Pia Viola-Magni; AN ANALYSIS OF DNA LOSS AND SYNTHESIS IN THE RAT ADRENAL MEDULLA NUCLEI UPON COLD STIMULATION . J Cell Biol 1 August 1966; 30 (2): 213–225. doi: https://doi.org/10.1083/jcb.30.2.213
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