A method for the determination of the DNA content of isolated nuclei of different ploidy has been developed. It is based on measurement of the nuclear dry mass, with an integrating microinterferometer, before and after DNase treatment . The values found are slightly low, because, as indicated by biochemical determinations, consistently 5 % to 8 % of DNA is not extracted by DNase under these conditions . The average DNA values thus obtained for diploid and tetraploid nuclei of adult rat liver are 7 .7 and 15 .6 pg (10 -12 g), respectively .
SUMMARYPrevious findings have shown a turnover of nuclear DNA, a condition related to the functional activity of these cells, in the adrenal medullae of rats intermittently exposed to cold. Striking differences have been observed between various strains of rats, particularly Italico and Wistar rats.In order to evaluate the function of the adrenal medullary cells, the content of catecholamines in the organ and their urinary excretion have been evaluated, with the fluorimetric method, in rats of Italico and Wistar strains kept at room temperature and exposed intermittently to cold. The results show that (i) at room temperature the levels of excretion are lower in Italico than in Wistar rats in spite of the equal amine contents of the adrenal medullae, (ii) the first exposure to cold causes a large increase in the urinary excretion and a decrease of adrenaline and noradrenaline content of the adrenal glands in both strains, (iii) after 3 days the catecholamine content in the organ was higher than normal in Wistar rats, whereas in the Italico strain it continued to decrease, and (iv) a new steady state at higher levels is reached after 20 days of exposure, when not only the catecholamine content but also the urinary excretion is equal in both strains.These differences between the two strains of rats during intermittent cold exposure are discussed in relation to the behaviour of DNA.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.