31 iallese boys who 15 years in the other two. That the latent period may be longer is supported by Goolden’s observa- tion of the developmentof thyroid cancer 40 years nts years after after radiation exposure.38 It may be that we are just reachingthecritical period in the post-radiation observations. es. * exposuresof the nt from those of e their thyroids ied, at least part ‘shorter half-life complicated by ‘atment schedule ‘tory growth and of these exposed ill be essential in for the develop- ART. 1 malignant thy- mancies, tules in the Mar‘in females than s 1s similar to the rted by Toyooka oping in persons n infancy. How. f the thyroid the securred.26 growth retardachildren before ormality or defiites the apparent ment processes to d deficiency. Ail help the children Se cin the children y might indicate zed nodular der developed thyiple pregnancies latent period be-very varied only ‘be argued that vas independent 1itis noteworthy oe clipe fie aller ct mene rit readetinlleees dari - enim dillon lation exposure imentof thyroid ie deficiency or ear to be among cresses ofpuberty a role in the de- ace, the develop- ture aging in the exposed groupthat mightbeassociated with radiation exposure. During the past 3 years these studies have been extendedto include examination of someaspectsof the immunestatus in the exposed and unexposed Marshallese populations which might be indicative of aging and/or radiation exposure. The studies reported here include measuringtransformation and replication of circulating lymphocytes from phytohemagglutinin (PHA) stimulation in culture, quantification of the various serum proteins by electrophoresis, immunodiffusion studies for immunoglobulin levels, and routine enumeration of peripheral blood elements. In contrast to results of previous studies, some of the present tests showed differences between the exposed and unexposed groups that might be interpreted as radiation effects. Therefore the results on the unexposed population are treated separately here in order to determinethe correlation ofthese criteria with aging in a normal Marshallese population. The results on the exposed group are compared with those on the unexposed group to evaluate possible radiation effects. ment of cancer was 7 years in one case and 14 and y of the thyroid ar development cases of hypo- SOME STUDIES OF IMMUNOLOGICAL ASPECTS OF AGING AND FALLOUT RADIATION EXPOSURE Among the many studies on the Rongelap people, the investigation of the possibility that radiation causes premature aging has been ofcontinuing interest, particularly because such findings have been reportedin irradiated animals.39 The 200 unexposed Marshallese people have served as an excellent comparison population for these studies since they are closely related and live in the same environment. For aging studies, during physical examinations measurements were made on characteristics considered to be criteria of aging.*0 Among these were skin elasticity and looseness and hair grayness; accommodation, visual acuity, and arcus senilis of the eyes; hearing Materials and Methods loss; nerve and neuromuscularfunction, vibratory sense, and handstrength; response to light extinction test and rapid movementtest; systolic blood pressure; and levels of blood cholesterol and body potassium (40K). Most of these criteria showed varying degrees of correlation with age and afforded a meansofarriving at a “biological age” In Table 15 the numbers of subjects on whom the various tests were done arelisted according to age decades. Lymphocyte Cultures. Blood cultures were set up as follows. The buffy coat was separated from 5 ml! of heparinized blood by sedimentation and centrifugation. The culture medium consisted of Eagle’s minimum essential medium supplemented score for each individual. However, none of the tests showed anysignificant indication of prema- Table 15 Numbers of Marshallese Subjects Tested in Various Studies (Since the results for males and females showed no significant difference, they were combined ) Lymphocyte A transformation (1968) ge group Blood elements (1967) ee ee, Exposed Unexposed Exposed 11 tH 25 19 15 11 9 10 4 6 12 11 26 19 17 11 10 10 4 6 6 9 9 11 11 4 2 2 2 3 99 16 20 11 5 15 7 7 8 5 9 102 1 44 8 105 1 45 7 65 1 16 6 1 61-70 Total 9000268 Immuno- globulins (1968) Unexposed 13~20 21-30. 31-40 41-50 31-60 71-80 Serum proteins (1968) 12 3 12 3 Unexposed Exposed 12 2 Unexposed Exposed i 98 3 46