1983年 · 第03卷第06期

Xizang (Tibet) has long been known as "the roof of the world" with a mean elevation of 4, 000 metres. Based on the results of epidemiological survey of mortalities from malignant tumors in1974~1976 (about 2.5×10⁶person-years), the possibility of the correlations between the cosmic radiation levels and the death rate of cancer was analysed.

The results show that although the mean annual dose equivalent (about 180 mrem) is 6 times as high as that of the sea level, the death rate (56.26×10^-5) of cancer seems to be lower than the average value (66.92×10^-5) of the whole country, and so does the mortality from leukemia. Moreover, it appears that elevation (ranging from 1, 680 to 4, 750 metres) is irrelevant to the death rate of cancer, which drops markedly when the altitude exceeds 4, 000 metres.

In situ measurements of natural terrestrialγ-radiation were conducted in Hebei Province in 1982. A Reuter-Stokes RSS-111 high pressure ionization chamber and a FD-71 scintillation surveymeter were used. The range of the terrestrial γ-radiation level was from 5 to 15.7μR/h. The terrestrial γ-radiation population-weighted mean absorbed dose rate in the air was found to be 6.6μrad/h in Hebei Province.

It is theoretically assumed that radiation induced asymmetric and symmetric chromosome cxchanges occur with equal frequency. With G-banding technique the present study of human lymphocytes irradiated in vitro with ⁶⁰Coγ-rays showed that the ratios between symmetric and asymmetric exchanges for 150 and 200 rads were 1: 0.75 and 1: 0.67 respectively. An excess of asymmetric exchanges was apparent. This may be due to the fact that although the introduction of banding techniques has greatly improved the detection of symmetric exchanges, some of the trsnalocations and deletions still remain overlooked, thus making the number of symmetric exchanges underestimated.

Mucopolysaccharide is an important component of the hemopoietic micro-environment and has various biological functions. This paper reports the changes of the contents of mucopolysaccharide and the number of nucleated cells of bone marrow in irradiated rats.

A group of animals were irradiated with 600 rads of ⁶⁰Co γ-rays, and the level of mucopolysaccharide in bone marrow was measured at various intervals (3 hours to 7 days) after irradiation. Another group of animals were irradiated with various doses (50~500 rad of γ-rays). Beside mucopolysaccharide, the number of marrow nucleated cells were also observed 3 days after irradiation.

The results in the first group showed that the level of mucopolysaccharide decreased significantly 3 hours after irradiation and reached the mininum after 3 days. It began to recover after 7 days and reached approximately to normal level after 25 days. The results in the second group showed that the decrease of the level of mucopolysaccharide and the number of marrow nucleated cells were in accord with the increase of the radiation doses. A good linear relationship between radiation doses and both indicators was obtained.

Four alkaloids were isolated from Thermopsis lanceolata. Three of them were identified as thermopsine, cytisine, and anagyrine. These 3 alkaloids and the semi-synthesized N-methylcytisine had been tested for antiradiation activity. LD₅₀ of these alkaloids were 190±8.2, 12.0, 46.7, and 58±2mg/kg respectively. It brought about an increase in survival rate when mice were treated with thermopsine before exposure to 900 rad of γ-rays. 75mg/kg of thermopsine given intraperitoneally or intravenously 15 min before exposure increased survival rates by 27.5% and 42.5% respectively as compared with control mice. When the drug was administered 100mg/kg subcutaneously survival rate increased by 35%, and the maximum survival rate reached 62% when it was given intraperitoneally at the same dose.

Thermopsine improved hematopoietic function. It increased the weight of mouse spleen and the count of CFU-S on 8th day after 800 rad exposure, but had no effect on the reduction of bone marrow cells after 300 rad exposure and on the incorporation of ³H-TdR into DNA of bone marrow cells.

Anagyrine also raised survival rate of mice when it was administered intraperitoneally in dosage of 15mg/kg 60 min before exposure.