Continuous lines of basophil/mast cells derived from normal mouse bone marrow.

Nonadherent tissue culture cell lines were established from normal bone marrow of a variety of mouse strains. The lines possessed morphological and histochemical markers of the basophil/mast cell and contained committed stem cells for metachromatic cells. Their derivation from normal marrow and their lack of tumorigenicity despite long-term culture makes these cell lines potentially important for studies of the mechanisms of allergic reactions and inflammation as well as the differentiation pathways involving this subset of hematopoietic cells.

Mechanism of suppression of the long terminal repeat of Moloney leukemia virus in mouse embryonal carcinoma cells.

Sequence-specific DNA-binding proteins that bind to the long terminal repeat (LTR) of Moloney leukemia virus in undifferentiated and differentiated mouse embryonal carcinoma (EC) cells were identified by gel retardation assay. The proteins that bind to the CCAAT box were present in both undifferentiated and differentiated EC cells. The amounts and the number of species of the proteins that bind to the enhancer and the GC-rich region were far lower in undifferentiated EC cells than in the differentiated counterparts. These proteins were supposed to be transcriptional activators. Proteins that bind upstream of the enhancer, namely, the -352 to -346 region and the -407 to -404 region, were identified. These proteins were designated the embryonic LTR-binding protein (ELP) and the LTR-binding protein, respectively. The ELP was present only in undifferentiated EC cell lines. The LTR-binding protein was detected in all cell lines tested. The mechanism of suppression of the LTR was investigated by the chloramphenicol acetyltransferase assay. The enhancer and the GC-rich region of the LTR functioned poorly in undifferentiated cells. When eight copies of ELP-binding sequences were inserted upstream of the enhancer region, expression of the chloramphenicol acetyltransferase gene was reduced about threefold in ECA2 cells. From these data, we concluded that two mechanisms, the shortage of activator proteins and the presence of a negative regulatory protein (ELP), are involved in the suppression of the LTR in undifferentiated EC cells.

A small nuclear RNA, U5, can transform cells in vitro.

Low-molecular-weight RNA exhibiting transforming potential was identified in chemically induced lymphoma cells by the transformation of mink lung cells after transfection. The RNA was sequenced by the direct chemical method and was shown to be a small nuclear RNA, U5. The transforming potential of the RNA was further studied in quantitative transformation assays using 3Y1, a rat fibroblastic cell line. Transformed foci appeared with a latency of 3 to 4 weeks after transfection. U5-transformed 3Y1 cells frequently carried an amplified c-myc oncogene. In addition, U5 induced chromosome aberrations in transfected cells, indicating that the RNA acts as a clastogen. Transforming and clastogenic potentials were specifically inactivated when U5 was incubated with RNase H in the presence of a complementary oligonucleotide. We discuss a possible mechanism of U5-induced cell transformation.

Inhibition by 3-amino-1H-1,2,4-triazole of hepatic tumorigenesis induced by diethylstilbestrol alone or combined with N-nitrosobutylurea in WF rats.

Six groups of inbred male WF rats were castrated at 40 days of age. Group 1 was given no further treatment; groups 3-6 received sc implantations of 5.0 mg diethylstilbestrol [(DES) CAS: 56-53-1]. At 50-55 days of age, groups 5 and 6 were given drinking water containing 5.0 mg N-nitrosobutylurea [(NBU) CAS: 869-01-2] per day for 30 days. After the termination of NBU treatment, groups 2, 4, and 6 were given 3-amino-1H-1,2,4-triazole (AT), considered an inhibitor of hydroperoxidases, in the drinking water throughout the experiment. Castrated male rats or rats castrated and treated with AT alone developed neither hepatic tumors nor pituitary tumors. The hepatic tumor incidence, the size and total number of hepatic tumors, and the mean liver weight were significantly reduced in rats given the DES-NBU combination and slightly reduced in rats given DES alone when AT was administered. In contrast, AT treatment did not change the pituitary tumor incidence and the mean pituitary weight. The thyroid gland weights were approximately 7-44 times greater in AT-treated groups than those in each corresponding control group. These data indicate that AT inhibited hepatic but not pituitary tumorigenesis and caused enlargement of the thyroid gland. The present study, therefore, provides evidence that the metabolic activation of DES by oxidation is involved in rat liver carcinogenesis.

Induction of hepatic tumors by diethylstilbestrol alone or in synergism with n-nitrosobutylurea in castrated male WF rats.

Inbred male WF rats were castrated at 40 days of age and divided into 5 groups. Group I was given no further treatment. Groups III, IV, and V received pellet implants of 5.0 mg diethylstilbestrol (DES) concurrently with castration. At 50-55 days of age, groups II, IV, and V were given drinking water containing 5.0 mg N-nitrosobutylurea (NBU) per day for 30 days (subthreshold dose). At the termination of NBU treatment, group V further received daily sc injections of 2-bromoergocryptine (CB-154; 0.4 mg/100 g body wt) four times a week throughout the experiment. None of castrated rats or rats castrated and treated with NBU alone developed hepatic tumors (HT) and pituitary tumors (PT). Incidences of HT and PT in groups III, IV, and V were 4/9 (44%) and 7/9 (78%), 15/17 (88%) and 12/17 (71%), and 17/20 (85%) and 4/20 (20%), respectively. The treatment of DES alone resulted in the concurrent development of HT and PT in castrated male rats (group III), and further NBU treatment significantly increased the incidence of HT (group IV). CB-154 treatment did not change the incidence of HT, the number of HT per rat, and the liver weight, although it significantly reduced the incidence of PT, the pituitary weight, and the serum prolactin level in castrated male rats given DES and NBU (group V). These results indicate that DES itself had a direct carcinogenic effect on the liver; this effect was not mediated by prolactin, and NBU increased the effect of DES in this process.

Effects of 17 beta-estradiol and diethylstilbestrol on concurrent development of hepatic, mammary, and pituitary tumors in WF rats: evidence for differential effect on liver.

17 beta-Estradiol [(E2) CAS: 50-28-2; estradiol] and diethylstilbestrol [(DES) CAS: 56-53-1; alpha-alpha'-diethyl-4,4'-stilbenediol] were compared to determine their tumor-inducing abilities in tissue. After castration at 40 days of age, inbred male WF rats received a pellet of either 5.0 mg DES or 5.0 mg E2. Approximately half of the rats that had been given DES or E2 were further given at 50-55 days of age 5.0 mg N-nitrosobutylurea [(NBU) CAS: 869-01-2; 1-butyl-1-nitrosourea] in their drinking water each day for 30 days. None of the castrated rats given E2 alone developed hepatic tumors (HT). Even further addition of NBU did not elicit any HT. Conversely, E2 treatment as well as DES treatment, whether administrated alone or in combination with NBU, resulted in an increase in the incidence of pituitary tumors (PT) and in the mean pituitary weight. The data indicate that E2 was ineffective in inducing HT in castrated male rats, whereas E2 showed an ability to induce PT similar to that of DES. In addition, E2 was not as able to induce as many mammary tumors as DES was able to induce. There was no significant synergism between E2 and NBU in contrast to that between DES and NBU in mammary tumorigenesis, whereas these two estrogens had a similar effect in causing an increase in the pituitary weight. This study, therefore, suggests that the carcinogenic effect of estrogens may not always correlate with their estrogenic effect and further confirms the noninvolvement of prolactin in hepatic tumorigenesis.

Inhibitory effect of antiestrogen on hepatic tumorigenesis in WF rats treated with diethylstilbestrol alone or in combination with N-nitrosobutylurea.

Four groups of inbred male WF rats were castrated and received sc implantations of diethylstilbestrol [(DES) CAS: 56-53-1; alpha,alpha'-diethyl-4,4'-stilbenediol] at 40 days of age. Group I was given no further treatment; groups II and IV were treated with antiestrogen (AntiE) clomiphene citrate simultaneously with DES treatment. At 50-55 days of age, groups III and IV were given drinking water containing N-nitrosobutylurea [(NBU) CAS: 869-01-2; 1-butyl-1-nitrosourea] for 30 days. Castrated male rats or rats castrated and treated with NBU alone developed neither hepatic tumors (HT) nor pituitary tumors (PT). When AntiE was administered, incidences of HT and PT, size and the total number of HT, and mean pituitary weight were significantly reduced in rats given DES alone and in rats given DES with NBU. AntiE treatment changed the distribution in the histologic classification of hepatocellular lesions: Neoplastic nodules, instead of hepatocellular carcinomas, were predominant. The results indicate that AntiE was effective in the inhibition of hepatic and pituitary tumorigenesis associated with DES treatment. Our previous study has shown that prolactin was not involved in this hepatic tumorigenesis. Therefore, these studies provide evidence that the carcinogenic effect of DES on the liver cell is direct and that HT are regulated in development and growth by AntiE treatment.

Synergism of diethylstilbestrol and other carcinogens in concurrent development of hepatic, mammary, and pituitary tumors in castrated male rats.

Castrated male WF rats, given implants of pellets containing 5.0 mg diethylstilbestrol (DES), were given N-butyl-N-nitrosourea (NBU) in small amounts, which alone produced no mammary tumors in intact female rats. Treatment resulted in the high yield of hepatic tumors (HT), mammary tumors (MT), and pituitary tumors (PT) concurrently in each rat. If animals were further treated with prolactin, the development of HT and MT was accelerated, whereas that of PT was suppressed. None of the intact or castrated rats receiving NBU and/or prolactin developed tumors in any tissues if DES treatment was omitted. Exposure of male rats, preconditioned similarly to NBU treatment, to 200 rads of 14.1-MeV fast-neutron radiation also elicited HT, MT, and PT with an efficiency comparable to that of NBU-treated rats. These findings indicate that DES played an essential role in the whole carcinogenic process in each tissue and that castrated male rats, if conditioned properly with estrogens, are useful for the study of the carcinogenesis mechanism in these tissues.

Establishment and immunologic characterization of 3-methylcholanthrene-induced sarcoma cell lines metastasizing widely in mice and exhibiting distinct and selective propensities for the mode of metastasis.

Successive transplantations of metastatic secondary tumors of a 3-methylcholanthrene-induced sarcoma in (C57BL/Ka X C3H/He)F1 male and female syngeneic mice resulted in the establishment of two unique tumor cell lines with enhanced metastatic potential. Moreover, each line showed distinct and selective propensities for the mode of metastasis. The 1101Pn tumor line, obtained by successive transplantations of metastatic pulmonary nodules, metastasized to many visceral organs via the bloodstream. Another tumor line, 1101Ln, selected by repeated transplantations of lymph node metastases, metastasized to almost all lymph nodes and to the lungs. When the metastatic pulmonary tumor of mice bearing 1101Ln was subcutaneously implanted on the backs of syngeneic mice, the tumor grew locally and eventually metastasized via the lymphatics, with systemic involvement of the lymph nodes. This finding is an indication that the intrinsic properties of tumor cells that form pulmonary metastases in 1101Ln tumor-bearing mice are distinct from those in 1101Pn tumor-bearing mice in terms of metastatic mode. The 1101Pn and 1101Ln tumor lines were nonimmunogenic or less immunogenic than the 505 tumor (the parental, nonselected tumor line). The growth and metastatic action of 505 tumors were enhanced by 400 R whole-body X-radiation, but no such effect was seen with 1101Pn tumors. Pretreatment of mice with OK-432, an immunopotentiator, retarded the growth and metastasis of 505 tumors but exerted little or no effect on 1101Pn tumors. The experimental results suggest that a tumor is composed of a heterogeneous cell population with respect to metastatic potential, metastatic mode, and tumor immunogenicity and that some intrinsic properties of the tumor cell have a primary role in the determination of the mode of cancer metastasis.

Prolactin and aging: X-irradiated and estrogen-induced rat mammary tumorigenesis.

Both sexes of inbred WF rats at either 8 or 28-60 weeks of age were exposed to 200 rad whole-body radiation, 2.5 or 5.0 mg 17 beta-estradiol (E2), or both agents The female rats treated with E2 alone or with both X-rays and E2 at 8 weeks of age showed a high incidence of mammary carcinomas (MCA), a large increase in pituitary weight, and a rise in serum prolactin (PRL) levels. However, the same treatments to males did not induce MCA despite a moderate increase in both pituitary weight and serum PRL. Ovariectomy prior to E2 treatment failed to modify the occurrence of MCA or pituitary tumors. When X-rays and E2 were given to female rats at 28-60 weeks of age, pituitary weight, serum PRL levels, and the incidence of MCA were unaffected. When the E2 pellet was kept for the first 24 weeks and withdrawn during the last 12 weeks, the incidence of MCA, pituitary weight, and serum PRL was low. It was concluded that: 1) the pituitary glands of young female rats were susceptible to E2 treatment but were insensitive in older females, and 2) the occurrence of MCA in female rats appeared to be promoted by elevated PRL levels secreted by E2-induced pituitary tumors. Mammary tissue of male rats was less sensitive to PRL levels in the development of MCA.

Mammary carcinogenic effect of low-dose fission radiation in Wistar/Furth rats and its dependency on prolactin.

The mammary carcinogenic effect in rats of low-dose fission radiation and its dependency on prolactin were studied. A total of 141 female W/Fu rats were exposed to 4.8, 8.9, or 19.5 rads of fission radiation that had both fision neutrons of 2.0 million electron volts (MeV) and gamma ray components similar to those produced by the Hiroshima bomb. Only 1 of 48 rats (2.0%) developed mammary tumor (MT) after irradiation alone, whereas 20 of 48 rats (41.6%) developed MT's if prolactin was supplied shortly after irradiation by means of grafting of the prolactin-secreting pituitary tumor. Furthermore, MT's occurred in 11 of 45 rats (24.4%) treated with prolactin as late as 12 months after irradiation, which suggested the long-term survival of radiation-induced dormant MT cells. A correlation was found between the development of MT and the elevation of serum prolactin level; most MT's appeared shortly after the grafted mammotropic pituitary tumor became palpable. The growth of MT's appeared to be promoted by prolactin in collaboration with ovarian hormones; the growth of adenocarcinomas was dependent on prolactin and ovarian hormones, whereas the growth of fibroadenomas appeared to be less hormone-dependent. Much higher biologic effectiveness, especially in the low-dose range, was found with 2.0-MeV fission neutrons compared with 14.1-MeV fast neutrons or 180-kilovolt peak X-rays in rat mammary carcinogenesis.

Role of prolactin in rat mammary carcinogenesis: detection of carcinogenicity of low-dose carcinogens and of persisting dormant cancer cells.

PIP: Rats used were W/Fu strain with a reported incidence of spontaneous mammary tumors (MTs) of 17%. Most of these have been benign fibroadenomas in older females. X-ray or fast neutron irradiations were given in subthreshold doses, some as low as 10 rads. Also, low doses (150 mg) of a chemical carcinogen (N-nitroso-N-butylurea; NBU) prolactin (MtH). The prolactin was provided by grafting a syngeneic mammatropic pituitary tumor (MtT.W95 or MtT.W98). Tumors developing at the implantation site were chormophobe adenomas. The latent period of tumor induction decreased after the 4th generation of animal passage of the tumors. In some rats, ovariectomy was done 1 week before X-irradiation. No MT was found in 18 untreated controls during 1 year of observation. No MT developed in 32 rats having only the grafts for 9-12 months. Total-body-X-irradiation with 25 or 50 rads alone elicited no MT for 1 year. Among 27 rats exposed to 200 rads of X-rays 2 developed MT fibroadenomas after 5 and 7 months. The supplemental administration of prolactin greatly increased and accelerated the occurrence of MTs in irradiated rats. Most of these were adenocarcinomas. Ovariectomized rats had fewer MTs than intact females. A correlation was found between dose and MT incidence. The persistence of chemically transformed MT cells was shown by the addition of prolactin several months after NBU therapy. MTs developed in 8 of 10 rats within 3 months after the MTT graft became palpable. All but 1 of these were adenocarcinomas. Apparently there had been no repair or elimination of damaged cells in the dormant state. It is suggested that progressive growth of MTs may depend on the hormonal milieu of the host.^ieng

Suppression of diethylstilbestrol and N-nitrosobutylurea-induced mammary and pituitary tumorigenesis in rats by prolonged treatment with 2-bromoergocryptine.

Inbred male W/Fu rats were castrated at 40 days of age (24) and divided into five groups. Group I was given no further treatment. Groups II, IV, and V received pellet implants of 5.0 mg diethylstilbestrol (DES) concurrently with the castration. At 50 to 55 days of age, Groups II, IV, and V were given drinking water containing 5.0 mg N-nitrosobutylurea (NBU)/day for 30 days. This amount does not induce mammary tumors (MTs) in castrated male rats (24) or in female rats (31). At the termination of NBU treatment, Group V received further daily s.c. injections of 2-bromoergocryptine (CB-154; 0.4 mg/100 g body weight) four times/week throughout the experiment. None of the castrated rats or rats castrated and treated with NBU alone developed MT or pituitary tumors (PTs). Incidences of MT and PT in Groups III, IV, and V were three of nine (33%) and seven of nine (78%), 15 of 17 (88%) and 12 of 17 (17%), and three of 20 (15%) and four of 20 (20%), respectively. The treatment with DES alone resulted in the concurrent development of MT and PT in castrated male rats (Group III), and further NBU treatment markedly accelerated the development and growth of MT (Group IV). CB-154 treatment profoundly reduced the incidences of both MT and PT in castrated male rats given DES and NBU (Group V). This treatment also depressed the increase in the number of MT per rat with MT, the pituitary and epididymis weights, and the serum prolactin levels caused by DES treatment. These results indicate that prolonged treatment with CB-154 was effective in the suppression of the concurrent tumorigenesis of mammary and pituitary glands, and the elevation of circulating prolactin levels, by counteracting the continuous stimulatory action of DES. In addition, CB-154 was able to reverse DES-enhanced growth of the epididymis in castrated male rats, suggesting a direct action of prolactin.

Establishment and characterization of human signet ring cell gastric carcinoma cell lines with amplification of the c-myc oncogene.

Two unique human signet ring cell gastric carcinoma cell lines (designated HSC-39 and HSC-40A) were established in vitro from the ascites of a 54-year-old male patient. Both cell lines were biologically quite similar, grew in vitro in suspension with a population doubling time of 28-30 h, and had cytological features of mucinous epithelial tumor cells. They formed colonies in soft agar, with a cloning efficiency of 0.8-1.0%. Ultrastructurally, numerous granules were observed in the cytoplasm, suggesting secretory activity. The frequent presence of desmosome and the tight junction at the cell boundary certifies the epithelial origin of the lines. Immunocytochemistry and radioimmunoassay showed production of tumor marker antigens (carcinoembryonic antigen, CA 19-9, and sialyl-Lex-i) and gastrin in both lines. These lines were transplantable in athymic BALB/c nude mice. The histopathology of each line growing in athymic BALB/c nude mice was similar to that of the original tumor. The karyotype of the cells was highly aberrant with structural and numerical changes. The presence of numerous double minute chromosomes and loss of the 13 chromosome and Y-chromosome characterize these lines. In addition, the amplified c-myc oncogene (16-32-fold) was found in both cell lines and original ascitic tumor cells. Overexpression of the c-myc mRNA was noted. These cell lines may be a useful tool, providing both in vivo and in vitro systems for further studies of the biology and therapy of human signet ring cell (or Borrmann's type IV carcinoma) gastric carcinoma.

Clonogenic cells and rat mammary cancer: effects of hormones, X rays, and fission neutrons.

On Day 0, young adult female F344 rats were adrenalectomized and intrasplenically implanted with a pituitary gland and capsule containing estrone. All were thereafter given 2.5 mg deoxycorticosterone per week and the choice of saline or tap water. This treatment yields high prolactin levels and glucocorticoid deficiency (Prl+/Glc-). On Day +48, total recoverable mammary DNA was increased by more than sevenfold, tritiated thymidine uptake by nearly fourfold, and total mammary clonogens by about fivefold. Irradiation with 4, 40, and 80 cGy X rays on Day +48 increased total mammary carcinomas per rat day at risk linearly with dose, and 40 and 80 cGy significantly decreased first carcinoma latency. A dose of 40 cGy X rays on Day -1 yielded tumor latencies and frequencies insignificantly different from unirradiated controls and significantly different from the dose on Day +48. Total carcinomas per rat day at risk were better fit by a function of dose to the power 0.4 than by a linear function after exposure to 1, 10, and 20 cGy fission neutrons, and 10 and 20 cGy significantly shortened the time to appearance of the first cancer. In contrast to results with X rays, 10 cGy neutrons on Day -1 yielded tumor frequencies and latencies insignificantly different from 10 cGy neutrons on Day +48. The carcinogenic action of X rays was thus influenced by total clonogen numbers and/or proliferation rates; that of neutrons was not.

Lack of evidence for the involvement of type-C and type-B retroviruses in radiation leukemogenesis of NFS mice.

Southern blot analysis revealed no difference between the DNA from radiation-induced thymic lymphomas and DNA from normal NFS mice. The probes used in the Southern blot analyses used a murine leukemia virus (MuLV) env DNA probe (pXenv), which specifically hybridizes with xenotropic and recombinant viral env genes, and mouse mammary tumor virus (MMTV) DNA probes (MMTV gag-pol, MMTV env, and MMTV LTR). This suggests that radiation leukemogenesis was not associated with gross alteration of the organization of these retroviral genomes. In DNA from radiation-induced thymic lymphoma, there was no indication of gross rearrangement in the common integration site of MuLV, pim-1, or in the common integration sites of MMTV, int-1 and int-2. Dot blot analysis of RNA from radiation-induced thymic lymphomas and normal thymuses demonstrated that there was no substantial difference between them in the expression of retroviral sequences, pim-1, pvt-1, int-1, or int-2, although transcripts that could be hybridized to the retroviral sequences were slightly elevated in some radiation-induced thymic lymphomas. These results show that radiation leukemogenesis does not appear to involve the activation of endogenous type-C and type-B retroviruses.

HTO oral administration in mice. I: Threshold dose rate for haematopoietic death.

Tritiated water in various concentrations was orally administered continuously to (C57BL/6N and C3H/He)F1 female mice in a closed animal chamber. Tritium radioactivity in various organ tissues was measured periodically after initiating tritiated water intake using an automatic sample combustion system and a liquid scintillation counter. After 7 days the specific radioactivity reached a plateau. These data allowed absorbed organ doses to be estimated. Within a range of 1.48 x 10(11) to 5.92 x 10(11) Bq/dm3 as the concentration of tritiated water in drinking water, the time of death after initiating the administration was about 2 weeks, a typical time for haematopoietic death. A linear relationship of times of death with tritiated water concentrations in drinking water was observed, on a log-log scale, between 1.85 x 10(10) Bq/dm3 and 1.48 x 10(11) Bq/dm3. At concentrations lower than 9.25 x 10(9) Bq/dm3, mice no longer died from haematopoietic failure. We conclude, therefore, that there should be a threshold dose rate for haematopoietic death.

Blocking of DNA synthesis in vitro by a guanosine 2',3'-cyclic phosphate: a possible mechanism of chromosome aberrations induced by U5 snRNA.

U5 snRNA can induce both transformation and chromosome aberrations of cells. The polypurine tract, GGAGAGGAA, of the RNA has been suggested to participate in both phenomena. In vitro transcription expected to give this polypurine oligoribonucleotide was associated with cleavage of transcripts, generating 5'-terminal hydroxyl and 3'-terminal 2',3'-cyclic phosphate groups. The cleavage was further studied by making use of a Mg(2+)-catalyzed reaction and RNase T1 and RNase U2 digestion. The cleavage was found to generate highly reactive RNA molecules, participating in subsequent ligation of RNAs. Such a reactive molecule, guanosine-2',3'-cyclic phosphate, was capable of blocking DNA synthesis in vitro. The results may provide a possible mechanism of the chromosome aberrations induced by U5.

Studies of radioactivity produced by the Hiroshima atomic bomb: 1. Neutron-induced radioactivity measurements for dose evaluation.

This review summarizes measurements made of 152Eu and 60Co radioactivity induced by neutron radiation from the Hiroshima atomic bomb (A-bomb) with the goal of estimating the neutron dose released by the bomb. Prior to these measurements, A-bomb-irradiated specimens such as rocks and pieces of concrete, which had not been shielded were collected. The specific radioactivity obtained (in bequerels per gram of Eu or Co) were compared with those calculated from DS86 neutrons. Findings of usefulness of 152Eu data within 700 m ground range are reported and systematic differences between measured activities and calculations are discussed. The 152Eu data were also useful for the discussion of circular asymmetry, and there was no asymmetry within the experimental errors. This review also covers the similar difference found in 32P data, which were measured immediately after the A-bomb, along with the other 152Eu and 60Co data. The need for more measurements of 152Eu activity in samples farther away from the hypocenter in order to verify the DS86 calculations is also discussed.

Studies of radioactivity produced by the Hiroshima atomic bomb: 2. Measurements of fallout radioactivity.

Three studies of fallout measurements were reviewed for the discussion of possible radioactivity intake from the Hiroshima atomic bomb. The first study discussed correlations between enriched 234U and 137Cs specific activities from the measurement of soil samples collected in the "black rain" area. The second study measured 137Cs activity on the rock and roof tile samples collected in the hypocenter area immediately after the explosion. Some of the rock and roof tile samples collected near the hypocenter had a small but detectable amount of 137Cs activity. However, it has been determined that 137Cs exposure, for example, was negligible compared with DS86 dose estimates, since these activity levels were low. The third study detected 90Sr activity in some of the specimens of human bones exhumed on Ninoshima Island. This study compared the difference in activity between the bone head and shaft, with higher activities obtained in the bone head. This fact suggests a short intake period for this activity, however, the levels of 90Sr contamination were too low to allow a discussion of the exposure risks.