In an attempt to achieve accurate quantification of DNA levels in cell nuclei, we studied the influence of salt concentration on the fluorescence of cell nuclei complexed with Hoechst-33258 (Hoe) fluorochrome. The fluorescence of cell nuclei was compared with that of extracted DNA as well as that of nucleosome core. Conformational changes in these complexes were examined by measuring both fluorescence anisotropy and fluorescence lifetime in the nanosecond region. The results showed that the fluorescence of DNA-Hoe was quenched by the nucleosomal structure, there being an associated increase in anisotropy and a decrease in the fluorescence lifetime; however, the fluorescence was restored to the original level by the addition of a high concentration of NaCl, CsCl, or LiCl. The reduction in fluorescence may have been due to loss of fluorescence energy caused by collision of the fluorophore with histones in the nucleosome. The addition of 1 M NaCl to the medium used for staining with Hoe greatly stabilized the fluorescence of DNA in cell nuclei. The DNA content of individual cell nuclei was determined by comparing the fluorescence of these nuclei with that of a standard DNA solution. For lymphocytes and liver ploidy cells, reasonably accurate values were obtained by applying the present method.

To elucidate accumulations of minerals in the human aorta and internal thoracic artery, their relative contents (RCs) of minerals were analyzed by inductively coupled plasma atomic emission spectrometry. Aortas from 47 men and 24 women subjects were examined. The ages of these subjects ranged from newborn to 99 yr. After the age of 40 yr, RCs of calcium and phosphorus began to increase, and thereafter increased stepwise in the 50s and 70s. In the 70s, their accumulations were markedly increased. Internal thoracic arteries from 16 men and 7 women subjects were examined. These subjects ranged in age from 65-93 yr. It was found that all the RCs of calcium were low, <5.0 mg/g dry wt, and there was no age-dependent increase of calcium contents in internal thoracic arteries.

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To elucidate compositional changes of the articular disk (AD) of the temporomandibular joint (TMJ) by aging, elements of the ADs resected from 18 cadavers were determined by inductively coupled plasma atomic-emission spectrometry. It was found that calcium contents of ADs in TMJs increased progressively with aging, whereas the sulfur contents of the ADs decreased slightly with aging. Regarding the content of phosphorus, the contents increased progressively with aging. The study revealed that age-related changes of calcium contents in the ADs of TMJs were similar to those in women's pubic symphyses, but not those in intervertebral disks and menisci.

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