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S Tas

Publications and source records attributed to S Tas.

23 records · Page 2Linked to original sources
PubMed1982

Influence of disulfide-reducing agents on fractionation of the chromatin complex by endogenous nucleases and deoxyribonuclease I in aging mice.

Age-related alterations in chromatin were evaluated by a fractionation procedure involving limited digestion of liver cell nuclei from young adult and old mice with endogenous nucleases and deoxyribonuclease I. The results suggest that in the chromatin the bulk of the nuclear deoxyribonucleic acid (DNA) may be folded or compacted into domains or loops and associated at a few points with a nuclear protein skeleton structure represented by the final pellet fraction which is resistant to deoxyribonuclease I. Disulfide bonds appear to play a role in the linkage of regions of DNA with this nuclear protein skeleton structure. The amount of DNA that could be released from the pellet fraction by disulfide-reducing agents was significantly greater with old than with young adult mice. In addition, the amount of chromatin material released into the first soluble fraction decreased and that in the second soluble fraction increased with age. Treatment of the nuclei with disulfide-reducing agents did not correct this particular age-related change. Previous results had shown a similar alteration with age of chromatin subjected to digestion by micrococcal nuclease. The combined results suggest the existence of a supranucleosomal alteration in chromatin structure during aging.

Aging↗
PubMed1980

Disulfide bonds and the structure of the chromatin complex in relation to aging.

Triton X-100 washed nuclei from livers of young-adult and old mice were digested with micrococcal nuclease and pelleted. Supernatants (1SF) were saved and the pellets lysed in a hypotonic EDTA buffer. A second supernatant (2SF) and a final pellet (P) were obtained by recentrifugation (7000 g, 7 minutes). The 1SF/2SF ratio, which has been shown to be an index of the transcriptionally active to inactive chromatin ratio, was lower in older mice. The fraction relatively resistant to solubilization by the nuclease (P) was found by isopycnic sucrose gradient centrifugation to be in a more compatc, condensed state when prepared from older mice. Higher amounts of heavy density chromatin were obtained from nuclei of old than young mice by hypotonic lysis plus minimal mechanical shearing. 2-Mercaptoethanol (2ME) treatment brought the density of the material of P from old mice back to the levels of young mice. In both age groups 2ME decreased the densities of mechanically sheared chromatin as well as of the whole Triton X-100 washed nuclei. In nuclease digestion experiments treatment of the nuclei from both age groups with S-S reducing agents increased the release of DNA from P into the supernatants. The results are consistent with S-S bonds being involved in the condensed structure of chromatin in young and old mice and in the shift of the chromatin complex towards a more compact, condensed state in old age.

Aging↗
PubMedDate not supplied

Ulcerated dystrophic calcinosis cutis secondary to localised linear scleroderma.

Dystrophic calcinosis is a more common form of calcinosis cutis; calcium salts are deposited secondary to local inflammation, tissue damage and degeneration. Various conditions can cause dystrophic calcinosis, including connective tissue disease, infection, inflammatory processes, chronic venous stasis, cutaneous neoplasm and trauma. We report a case of ulcerated cutaneous calcinosis associated with a localised linear scleroderma or morphea. Healing of the ulcerations took place after four months of treatment with colchicine 1 mg per day.

Aged↗