[en] The results of investigations aimed at the elucidation of nature and mechanism of radiation-induced collagen aggregation are briefly reviewed. Collagen solution irradiated in air is more susceptible to the action of proteinases. This effect is most probably responsible for the increased degradation of collagen in the irradiated animals. Tropocollagen irradiated under nitrogen tends to aggregate into dimers and tetramers. These aggregates are branched type polymers. Irradiation in nitrogen induces in collagen three new aldehyde compounds which are probably identical with the three new components reducible with borohydride. Involvement of these components in the formation of intermolecular cross-links seems to be of importance in the mechanism of radiation-induced aggregation and fibrilogenesis of collagen. (author)

[en] Gamma- or X-irradiation of tyrosine solutions, pH 4.0 and 8.6 was performed and the products of radiolysis were analyzed by fluorescence and column chromatography and thin-layer chromatography. Dityrosine was found in oxygen-free solutions. The radiation yield of dityrosine formation was estimated and the mechanism of radiolytic dimerization of tyrosine is proposed. (author)

[en] Aqueous solutions of phenylalanine, pH 5.0, saturated with air, nitrogen or N₂O were irradiated with 100 to 1.000 Gy doses of gamma radiation. In all samples irradiated fluorescence analysis revealed the presence of dityrosine. Its yield depended on the radiation dose, pH of the solution and the gaseous phase present during irradiation. The maximum Gsub(dityrosine) value was attained in an air saturated solution. It is assumed that dityrosine is formed from tyrosine, the one of the main radiolytic products of phenylalanine. (author)

[en] Tropocollagen shows higher ultraviolet fluorescence (emission max. about 305 nm) and lower blue fluorescence (emission max. about 420 nm) than the dimers and tetramers isolated from irradiated collagen. This indicates dityrosine structures in the radiation-induced collagen aggregates. (author)

[en] Products of radiolysis of tyrosine and glycyl-L-tyrosine in oxygen-free nitrogen, N₂O or air saturated water solution, pH 4.0 or 8.6 were analysed in an amino acid analyser and upon separation on DEAE cellulose or BioGel P-2 column with spectrofluorimetry. Apart from dihydroxyphenylalanine tyrosine solution irradiated in nitrogen or N₂O contained dityrosine, while that of irradiated glycyl-L-tyrosine contained glycyl-dityrosine-glycine. Both dimeric products were formed with radiation yields, of about 0.15 at low pH value. In addition an unknown, nonfluorescent but ninhydrin positive product was found in irradiated tyrosine solution. Another, unidentified product of radiolysis was detected in N₂O or air saturated solutions of tyrosine. The product had a blue-green fluorescence and a molecular weight of about 500. (author)

[en] The effect of hypoxic (10% of oxygen) conditions during irradiation of rats with 9.0 Gy dose of X-rays on determined in lung homogenate concentration of DNA, protein and collagen (as hydroxyproline) and on the activity of cathepsin, β-glucuronidase, acid phosphatase and plasminogen activator was studied. Assays were made from 1 day to 15 months after exposure. It was found that regardless of hypoxic conditions of irradiation, collagen content in rat lungs was increasing with time after exposure. However, hypoxic conditions resulted in partial decrease during later periods after exposure of other biochemical indices of irradiation. It was particularly evident in the case of the fibrinolytic activity which in hypoxic rats was increased during the first several days only, while in rats irradiated under normal conditions this increase persisted for more than one year after exposure. (author)

[en] The secondary structure of tropocollagen molecules and its dimer and tetramer, both isolated from tropocollagen irradiated with X-rays in solution under nitrogen was studied by measuring ORD, CD and UV spectra, kinetics of tritium-hydrogen exchange and kinetics of renaturation of thermally denatured collagen materials. The results have demonstrated that aggregates of tropocollagen contain less helical structure than native, non-aggregated molecules. (author)

[en] Blue fluorescence characteristic of dityrosine appeared in γ-irradiated solutions of tyrosine, glycyl-L-tyrosine or polytyrosine (MW 110,000). The intensity of fluorescence was used for the determination of the dityrosine concentration in hydrolysed samples. The radiation-induced formation of dityrosine depended on pH and on the presence of oxygen during radiolysis carried out with a total dose of the order of 1000 Gy. The presence of oxygen in the system suppressed the formation of dityrosine in solution at low or neutral pH but had no effect on this process in alkaline solutions. Except for the radiolysis of air-saturated poly-L-tyrosine solutions, where G(Dityrosine) = 0.35, the yields of dityrosine at high pH were lower than the yields obtained during radiolysis at low pH and in the absence of oxygen. (author)

[en] Young Wistar rats were exposed to 650 R of whole body X-rays then sacrificed at different times after exposure up to one year, and various biochemical parameters in lung tissue were determined. Decrease in protein and elastin content and elevation in fibrinolytic and catheptic activity lasted during the whole observation period. In other parameters a fluctuation, mostly decrease followed by an increase, was seen only during the acute phase of radiation disease. (author)

[en] Short communication. 1 ref., 3 figs, 1 tab