~ Y 4 1 woe |. t i CHAPTER 4 HEMATOLOGY 4.1 INTRODUCTION Since it is generally agreed that a depression in the formed elements of the peripheral] blood is the most useful practical clinical index of the degree of exposure to ionizing radiation, a systematic study of the leukocytes and platelets was relied upon as a major aid in evaluating the clinical status, severity of the radiation injury, and prognosis of the exposed individuals. Animal experimentation had previously shown that the rate of development and magnitude of the depression were equally important in evaluating the severity of radiation injury. Since there had been no previous exposure of human beingsto significant amounts of fallout radiation, no hematological data known to be strictly applicable* were available for use as a guide in the evaluation of the exposed Americans and Marshallese. Accordingly emphasis was placed on — systematic serial studies, utilizing a few highly standardized hematologic determinationsto insure that individual and group trends would have maximum validity. Since it was known that the Utirik group had received a very small dose of radiation compared to the other exposure _ BSag . froups, less extensive determinations were carried out on these people. - 4.2 GENERAL METHODS Hematological examinations included total leukocyte, neutrophile, lymphocyte and platelet counts, and hematocrit determinations. Whenever possible an entire exposure group was studied in a single day. Occasionally two days were required to complete the larger groups. Capillary blood was used, usually obtained from the finger but occasionally from the heel or ear. Twopipettes each for total leukocyte and platelet counts were filled. From each pipette a single hemocytometer chamber wasfilled. All pipettes were rotated for 10 minutes, and the cells were allowed to settle for 10 minutes in the hemocytometer chamber before counting. A 3 per cent acetic acid diluting fluid was used for total leukocyte counts. The blood was diluted with I per cent ammonium oxalate for platelet counts and counted in flat bottom hemocytometers using a dark phase contrast microscope. * Two blood smears were made with each ex- amination, using a beveled end glass slide for spreading. One blood smear was fixed in methy! alcohol. The other was stained by Wright’s method, from which a 100 cell differential count was made. Hematocrits were performed using heparinized capillary tubes. One end of the capillary tube was heat sealed and the tube was centrifuged in an ALOE centrifuge at 12,500 rpm for 5 minutes. A large literature on the hematologic effects of radiation exists; however, these data were not relied upon for direct comparison and evaluation of the exposed individuals for reasons that will be indicated later in the discussion.