1983年 · 第03卷第04期

This paper was given by Dr. Hiroo Kato at a seminar in the Laboratory of Industrial Hygiene, Ministry of Public Health, China. The author summarized the late effects of A-bomb radiation according to the data collected in Hiroshima and Nagasaki up to date. Radiation effects are limited to an increase in some malignant tumors (leukemia, cancers of thyroid, breast, lung, and stomach, and multiple myeloma), as well as an excess of cataracts, small head size and mental retardation in the exposed in utero, chromosomal aberrations and delay in growth and development.

No relationship to radiation can be established for chronic lymphatic leukemia and osteosarcoma, as well as mortality from disease other than malignant tumor, accelerated aging, infertility and birth defects so far.

Since the risk of radiation-induced malignant tumors other than leukemia has increased with age, and since those who were young ATB and who have shown the highest values for both relative and absolute risks have just entered the cancer age, careful long-term follow-up should be continued.

LACA and CFW strain mice at age of 10 weeks received whole-body irradiation with 9 to 15 Gy of ⁶⁰Coy-rays. Syngeneic bone marrow cells were injected intravenously two to three hours after irradiation to some irradiated mice, while others were not injected.

The manifestations of radiosensitivity in these two strains of mice were similar, and the protective effects of bone marrow transplantation in them were also alike. After irradiation with 9 and 9.5 Gy, the mortalities of transplanted groups were 0 to 26.7% in comparison with 70 to 100% in non-transplanted groups.

The protective effect of bone marrow transplantation decreased gradually with the increase of radiation doses, and the upper limit dose of its protection was 12 Gy. Therefore, bone marrow transplantation can protect mice not only from acute radiation sickness of severe hematopoietic type, but also from that of mild gastrointestinal type.

According to the results of this paper and the data in the literature concerning experiments in large animals and clinical observation, bone marrow transplantation is probably able to protect human beings from acute radiation sickness of mild gastrointestinal type.

The radioprotective effect of WR-2721 on the intestinal epithelium in mice was observed on the 3rd day after exposure to different doses of γ-rays or at different intervals after a single dose of 1000 rad. The results showed that the dose-effect curves of various intestinal parameters in mice receiving 1200～2400 rads of radiation and treated with WR-2721 apparently shifted to the right. The doses required to produce an effect on the same parameters in the protected group equivalent to 50% of the normal values were 549～1307 rads higher than those in the controls. After irradiation with 1000 rad the injury of intestinal epithelium of protected group was less serious and the repairing process was 2～4 days earlier than that of the control. Since WR-2721 could increase hte number of cycling cryptal cells in S and M phase, it may be inferred that cells with low radiosensitivity are increased during exposure and that is the underlying mechanism of radioprotection of this compound.

Allogeneic bone marrow cells treated by crude extracts from soybean and peanut were used to reconstitute lethally irradiated mice. Transplantation of mouse bone marrow cells agglutinated by these lectins (PNA and SBA) resulted in high survival rate of the irradiated recipients, whereas transplantation of unagglutinated fraction or whole bone marrow cells resulted in high mortalities. The percentage of Thy-1 bearing cells in each fraction was tested by the cytotoxic assay and ANAE stain.

The number of T-cells in both PNA and SBA agglutinated fractions was less than that of the unagglutinated ones. About 1.3% of T-cells were found in twice agglutinated fraction, in which yield of CFU-C/10⁵ was enriched by 5.77 times in comparison with that in non-agglutinated fraction.

The approach described in this paper for extraction of lectins from soybean and peanut and the isolation of hemopoietic stem cells can offer many advantages over other techniques: it is inexpensive, simple, and efficient for processing of large number of cells.

The effect of repeated and fractionated irradiation is one of the important subjects in the radiobiological research. On the basis of 30 day survival rate and hematological changes of mice receiving ⁶⁰Coγ-ray irradiation, factors influencing the biological effect of repeated and fractionated irradiation were studied. The results indicate that the injury caused by fractionated irradiation may be milder than or similar to that induced by single irradiation. The severity of the former depends mainly on the accumulated dose, fractionated dose, the interval between two doses and the first dose of the fractionated irradiation. It was found in this experiment that a 50% bone marrow inhibition dose (BMID) given 1~2 days after a preliminary dose of 10% BMID would produce a maximal hematological effect.