Quantitative Measurement of Hematopoietic Cells of the Marrow1

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Abstract
Details of a method originally proposed by Suit for the measurement of the total cellularity of hematopoietic tissue of the marrow are presented. A known amount of Fe59 was injected intravenously. At the time of maximum clearance of the isotope from the plasma, an aliquot of marrow was obtained and the radioactive counts due to Fe59 and number of marrow cells contained therein were enumerated. In animals the amount of radioactivity localized in the entire skeleton was determined. The total marrow cells could then be calculated by simple proportions. The reliability of the method in animals was established by showing that 2 other marrow tags, hemoglobin and porphyrin, gave comparable values. By comparison with data in 3 animal species including the monkey it was estimated that 2/3 of a dose of intravenously injected radioiron localizes in the marrow in normal humans. Detailed studies of marrow aliquots for cell counting established that about 50% of the cells were lost in preparation. Data in normal animals indicated that there were 12 to 39 x 109 nucleated marrow cells per kg body weight in the various species studied. These figures agree well with those of other investigators. A subsequent paper presents a detailed analysis of the results obtained.