Other
Scientific paper
Jul 1953
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1953natur.172..119d&link_type=abstract
Nature, Volume 172, Issue 4368, pp. 119 (1953).
Other
Scientific paper
THE amount of deoxyribonucleic acid recovered from ultra-violet light irradiated intact rat thymocytes has been found to be significantly less than the amount recovered from non-irradiated controls. The thymus glands of twenty normal 150-gm. Wistar-strain male rats were removed immediately after decapitation of the animals, placed in 140 ml. of Ringer's solution and homogenized for 30 sec. in a Waring blendor. The resultant suspension of thymocytes was removed to a dark-room and divided into two equal portions, one of which served as a control. The other was placed in an 80-ml. quartz-bottom van Tieghem cell. While being constantly agitated by a slowly rotating stirrer, in order to ensure uniform exposure of all the cells, the suspension was irradiated from below for 30 min. with ultra-violet light (3.4 × 108 ergs). The ultra-violet source, used without filters, was an air-cooled, quartz-spiral mercury resonance lamp (Hanovia), which, according to a Hanovia ultra-violet meter, Model AV971, emits about 25 per cent of the total output in the ultra-violet below λ = 2800 A. The irradiated and control suspensions were left in the dark-room to avoid possible side effects due to photo-reactivation. A period of 5½ hr. was allowed to elapse before extraction of deoxyribonucleic acid, in order to provide sufficient time for possible depolymerization of the acid induced by the radiation. Thymocyte viability for a period of 5½ hr. after homogenization and irradiation was verified by means of tissue culture. Deoxyribonucleic acid was extracted according to the Limperos modification1 of the Mirsky-Pollister method2, dissolved in distilled water and then lyophilized. The weight of deoxyribonucleic acid obtained from irradiated tissue homogenates (seven replicate experiments) was only 52.9 per cent (S.E.mean 4.6) of the weight of that obtained from the non-irradiated controls. Nitrogen and phosphorus content were determined on aliquot portions made up on the basis of percentage weight of deoxyribonucleic acid. Adjustment to equal concentrations of the acid was based on phosphorus content. No appreciable differences between irradiated and control samples were found in relative viscosities, structural viscosities, or sedimentation rates.
de Courcy S. J.
Ely J. O.
Ross M. H.
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