HE NATURE OF PLEURAL EFFUSIONS has been
T extensively explored by means of biochemical, bacteriological, and histological methods, and all are currently employed to distinguish their benign or malignant character. Criteria for differentiation moreover are based upon certain definitive clinical and laboratory features, such as age of the patient, location of the effusion, its specific gravity, its cellular and protein content, as well as the roentgen-ray appearance of the underlying lung. Cytological techniques, while of established value, often have definite limitations because rapid enzymatic digestion of cells renders microscopic interpretation difficult.
With the availability of radioactive phosphorus (P37, suitable for use as a tracer vehicle, a new approach became possible, notably, the exploration of alterations in intracellular chemical relationships.
Marshakl2, l 3 demonstrated that the uptake of radioactive phosphorus (P37 by the cell nucleus and cytoplasm was greater in malignant than in normal tissues. Furthermore, a n increase in nuclear concentration of this r a d i e active isotope was detected in certain rapidly multiplying normal cells such as are seen in regenerating liver. hlarshak14 noted that this alteration in metabolic activity was intimately associated with the movement of radioactive phosphorus into the nucleoprotein fraction, largely as desoxyribonucleic acid (DNA). DNA synthesis is recognized as an index of the rapidity of cellular division and is highest in conditions associated with acute inflammatory and neoplastic processes.
Lawrence, Erf, Tuttle, and others detected an increase in the retention of radioactive phosphorus in tissues of leukemic mice when compared with retention by similar tissues in