Iii. Decrease of Labeled Dna in Cells of the Adrenal Medulla After Intermittent Exposure to Cold

Abstract

Italico rats were injected with thymidine 3H 6 hr after the end of 300 hr of intermittent cold treatment . This plan of experiment ensured replacement in the adrenal medulla of lost DNA which is specifically sensitive to cold treatment and has a labeling index sufficiently high for statistical evaluation . The labeling index in the adrenal medulla decreases to one-half of the initial value within 10 days in animals subjected to further intermittent cold treatment and within 32 days in animals kept at room temperature . The very low mitotic index and the absence of doubling of the labeling index show that the observed labeling cannot be ascribed to pre-mitotic DNA synthesis . The concept of metabolic DNA adequately explains the findings .

Synthesis and turnover of DNA in hepatocytes of neonatal rats

“…A similar conclusion has been drawn for the adrenal medullary cells in which changes of DNA content per nucleus, accompanied by DNA synthesis not leading to mitotic division, take place following intermittent exposure to cold (Viola-Magni, 1965, 1966a. The turnover of DNA (Pelc & Viola-Magni, 1969) appears to be related to the functional activity of the adrenal cells, i.e. excretion and synthesis of cathecolamines (Bibbiani & Viola-Magni, 1971).…”

Sleep memory processing: the sequential hypothesis

“…These experiments were suggested by data demonstrating the high turnover of brain DNA in adult rats (Perrone Capano et al, 1982 ) and its modulation by a variety of activities (Pelc and Viola-Magni, 1969 ; Pelc, 1972 ) and learning protocols (Reinis and Lamble, 1972 ; Ashapkin et al, 1983 ; Giuditta et al, 1986 ). Brain metabolic DNA is distributed in brain cellular and subcellular fractions and is highly dispersed throughout the genome in a learning-dependent pattern (Giuditta et al, 1986 ).…”

DNA Turnover in Adrenal Medullary Cells of Long Evans Rats

“…'The great majority (5.76%) are weakly labelled (2-10 grains) and only 0.14% of the cells show a grain count between 10 and 100 (Fig. 7 It has been shown with histophotometric, microinterpherometric and biochemical techniques that nuclei of the adrenal medulla of Italico rats lose 45% of their DNA during intermittent exposure to cold for a total of 300 h.l,2 In Long Evans rats the loss of DNA per nucleus is less, amounting to 20% when evaluated with the microinterpherometric technique. 7 It has been shown with histophotometric, microinterpherometric and biochemical techniques that nuclei of the adrenal medulla of Italico rats lose 45% of their DNA during intermittent exposure to cold for a total of 300 h.l,2 In Long Evans rats the loss of DNA per nucleus is less, amounting to 20% when evaluated with the microinterpherometric technique.…”

“…1 majority of nuclei were also found weakly labelled. 7 It has been shown with histophotometric, microinterpherometric and biochemical techniques that nuclei of the adrenal medulla of Italico rats lose 45% of their DNA during intermittent exposure to cold for a total of 300 h.l,2 In Long Evans rats the loss of DNA per nucleus is less, amounting to 20% when evaluated with the microinterpherometric technique. Thus the rate of synthesis appears roughly proportional to the amount of cumulative loss.…”