The plasminogen-dependent fibrinolytic activity of several human tumours has been studied. The following neoplastic tissues, which were obtained from cancer patients by either surgery or biopsies, were examined: cervical, mammary. prostatic, ovarian, lung carcinomas, melanoma, basalioma. Fibrinolysis was measured in lysates either of tumour tissue specimens or of respective cell cultures. This measurement was based on release of radioactivity from '2s1-fibrin-coated Petri dishes. All examined tumours showed elevated levels of plasminogen-dependent fibrinoiytic activity. However, normal control tissues had little or no activity. These results indicate that the fibrinolyds might be useful in differentiating between malignant and normal tissues, Les auteurs ont Btudi6 I'activit6 fibrinolytique plasminogbe-dependante de plusieurs tumeurs humaines. 11s ont examine les tissus n6oplasiques suivants, obtenus h la suite d'interventions chirurgicales ou de biopsies effectuees sur des sujets cancireux: cancers du col uterin, du sein, de la prostate, de I'ovaire, du poumon, m6lanome, basaliome. La fibrinolyse a i t 6 mesuree dans les lysats des sp6cimens de tissus tumoraux ou des cultures respectives. Cette mesure 6tait fondQe sur la radioactivit6 d6gagie par les boites de Petri enduites de fibrine-'251. Pour toutes les tumeurs examinees, I'activit6 fibrinolytique plasminoghedipendante etait 6lev6e. Par contre, pour lei tissus normaux, elle Ctait faible ou nulle. Ces r6sultats indiquent que la fibrinolyse pourrait servir a distinguer les tissus canchreux des tissus normaux.

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The U.V.-induced DNA-to-protein cross-linking in synchronously growing HeLa cells exhibits age-dependent variations. The maximum yield of cross-linking is observed during S-phase and exposure of mid-S cells to 250 ergs/mm2 renders about 22 per cent of DNA unextractable owing to cross-linking with proteins. Cells irradiated in G1 or G2 exhibit much smaller amount of cross-linking. The unextracted DNA was recovered from the protein fraction, and the addition of 0-5 per cent trypsin solution rendered all the DNA extractable. Fluctuations in the age-response pattern for the yield of DNA-protein cross-links varies throughout the cell-cycle in the same way as the efficiency for cell-killing, i.e. cells are resistant in G1, sensitive as they move into and through the S phase, and resistant again in G2. Dose-response curves determined at different times in the cycle reveal that up to about 500 ergs/mm2 the amount of DNA recovered from S cells decreased for about 8 per cent for every 100 ergs/mm2 of U.V. light. The amount of recovered DNA remained unchanged for cells exposed to 500 ergs/mm2 in the middle of S, for as long as 8 hours after exposure, i.e. for as long as the experiments were carried out no recovery from this damage was observed.

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