Laboratory experiments using radiotracer of americium (²⁴¹Am) and humic acid isolated from natural surface soil have been conducted to evaluate the effect of added humic acid on the behavior of Am(III) in aqueous solution and the stability constant of the complex formed between Am(III) and humic acid. The former experiments were performed in the synthetic aqueous medium containing Ca or in fresh rain water at pH 6.5 and 4.5. At pH 6.5 in the absence of humic acid, Am(III) in both solutions [(Ca: 10 ppm) or rain water] was almostly adsorbed on the wall of the polyethylene vial used, and the major fraction of Am left in the solution was retained on the filter of 0.45μm pore size. On the other hand, in the presence of humic acid (100 ppm), the adsorption of Am on the vail was not observed, and the decrease of the retention of Am on the same filter suggests its complex formation with humic acid. At pH 4.5, the behavior of Am(III) in the solution (Ca: 10 ppm) was not influenced by the addition of humic acid (100 ppm). When the quantities of Ca were increased in the solution at a constant amount of humic acid, insoluble complexes were formed according to the increase of Ca to humic acid, and Am was scavenged over 90% as the insoluble complexes. The study of stability constant indicated that Am(III) had the strong interaction with humic acid.

View full abstract

Taking advantage of having assay techniques for various functions located in nucleocapside (infectivity) and in the envelope (hemagglutination, neuraminidase activity and hemolysis), effects of vacuum-uv radiation on Sendai virus were investigated. Monochromatic 163-nm photons from a bromine discharge lamp and polychromatic synchrotron radiation with wavelengths longer than 115 nm from the electron storage ring were used as the vacuum-uv sources. Irradiation was performed in vacuum (dry) and in aqueous suspension (wet)..For comparison the viruses were irradiated with far-uv radiation (254 nm). While the far-uv radiation affected only infectivity, the vacuum-uv radiation affected the infectivity and other virus functions as well. SDS-electrophoretic behaviors after irradiation in dry state indicated that vacuum-uv radiation caused uniform damage over several polypeptide components. The pattern was more similar to that of γ-rays previously studied. These results may be related to the fact that faruv photons are absorbed predominantly in viral nucleic acids while vacuum-uv photons are absorbed more or less uniformly by various virus components. In the irradiation in suspension some difference was noted between vacuum-uv and γ-radiations.

View full abstract

Environmental samples of ditch soil, ditch water, sea water, and sands were taken from a 280-MWe coal-fired power plant with a daily coal consumption of 2800 tons. Fly and bottom ashes were also taken from the same power plant. A 30 cm³ Ge(Li) detector coupled with a well-shielded and computer-aided multichannel analyzer was used to determine the radionuclides in environmental samples and ashes. Coal samples of North Taiwan with an ash to coal ratio of 1:4 were also investigated. Four major radionuclides of ²³²Th, ²³⁸U, ²³⁵U, and ⁴⁰K were reported assuming the secular equilibrium exists in thorium and uranium series. The annual release of ²³²Th, ²³⁸U, and ²³⁵U into atmosphere is 240, 210, and 30 mCi, respectively. Both fly and bottom ashes have highest activity per gram. On the other hand, the ²³⁵U content in Taiwan coals, ditch water at the plant site, and sands along the seashore off the plant site is below the detection limit.

View full abstract

The present study was designed to investigate the carcinogenic effects of fetal and postnatal irradiation in female mice. The C57BL/6J mice were subjected to whole-body exposure to 1-Gy or 4-Gy ¹³⁷Cs γ-ray irradiation on the 15th fetal day or the 30th postnatal day. Following this, all mice were observed throughout their respective life spans under conventional rearing conditions. The tumor incidence rate, average latent period and distributions of various tumors were used as the quantitative parameters of radiation-induced carcinogenesis. The following conclusions can be draw: (1) The mean life span of mice that underwent 4-Gy irradiation at the age of 30 days was shorter than that of non-irradiated control mice. (2) In control mice, the tumor incidence was 75.7%. (3) In order to estimate the mean age and tumor incidence, an adjustment for competing death is necessary. (4) The adjusted tumor incidences of thymic lymphoma and breast tumor of the irradiated groups were not different from those of control group. On the other hand, there was a significant difference between the two in the adjusted incidence of reticular tissue neoplasm.

View full abstract

Rate constants for the reactions of dichloride anion radicals with aliphatic peptides were determined by a conventional flash photolysis of 1 M solutions of potassium chloride containing aliphatic peptides. The rate constants were found to increase with increasing number of C-H bond. Partial rate constants were assigned to each C-H bond of the aliphatic peptides, as estimated for the reactions of hydroxyl radicals with the same substrates.
Trend in the partial rate constants and the effect of a protonated amino group on the reactivity indicate a reaction mechanism, hydrogen atom abstraction, similar to hydroxyl radicals.

View full abstract

Adult virgin female Swiss albino mice were irradiated with 2.5, 5 and 10 Gy of gamma radiation in the presence and absence of the drug MPG and changes in the ovarian follicular population were scored at various post irradiation intervals of 3 hours to 14 days. The results indicate that the drug has partially prevented the rapid reduction in the follicular number. Primordial follicles are protected to a greater extent than the growing and large follicles. The difference between the number of follicles of drug treated and non-drug treated animals is greater at low dose group.

View full abstract

Mouse legs were exposed to ¹³⁷Cs gamma rays with single or multiple fractions (up to 32) at various intervals of time between doses. Levels of skin shrinkage were measured 50 to 70 days after irradiation. Neither the formula of Ellis (Ellis, 1971) nor Moulder et al. (Moulder et al., 1975) for the time-dose relationship provided a reasonable fit to the data presented in this paper for skin shrinkage on mouse legs. The results were discussed in terms of cell survival curve models. The single-dose response curve for target cells relating to the early skin shrinkage seemed to be simple exponential until 250 rads, and then downward bending on a semilogarithmic scale.

View full abstract

To study the recovery from sublethal damage and the repopulation kinetics of skin during multifractionated exposures, mouse legs were exposed to ¹³⁷Cs γ rays. Levels of skin shrinkage were measured 50 to 70 days after either single or multiple fractions (up to 32) with various intervals of time between doses. The higher the dose per fraction, the later the surviving cells started to repopulate after irradiation. When the dose per fraction was 370 to 490 rads, and the number of fractions 8 to 32, the regeneration rate per day was almost constant from day 7 to day 31 after the first exposure. It was calculated that the number of skin stem cells increased an average of 1.3 fold per day. When the dose per fraction was more than 1000 rads, the average repopulation rate between day 15 and day 31 was lower than that between day 6 and day 15.

View full abstract

Gamma irradiation of two-day old pea seedlings with growth inhibiting doses of 1-4 Gy increased the number of the ³H-thymidine labelled cells in root meristem. This phenomenon can be explained by the induction of unscheduled DNA synthesis by irradiation.

View full abstract

As part of a series of studies designed to evaluate the relative radiotoxicity of various tritiated compounds, tritiated water, leucine, glucose and thymidine were singly ingested to rat and the metabolic fate of tritium was studied in various tissues over more than 100 days. The distribution and retention of tritium varied widely, depending on the chemical form in which tritium was administered. Tritium introduced as tritiated water behaved essentially as body water and distributed uniformly among the tissues. However, tritium administered as organic compounds resulted in relatively high incorporation into organic tissue constituents and its distribution differed among the various tissues. Moreover, the excretion rate of tritium from tissues was slower for tritiated organic compounds than for tritiated water. Administration of tritiated organic compounds results in higher radiation doses to the tissues than does administration of tritiated water. Among the tritiated compounds examined, for equal radioactivity administered, leucine gave the highest radiation dose, followed in turn by tritiated thymidine, glucose, and water.

View full abstract

A dose of 2.74 kBq of carrier-free ¹³¹I (NaI) was given orally to 2 male adults (A and B) in their routine works under a limitation of iodine intake for A and a fairly free access to iodine intake for B for 2 weeks predose. In both the thyroid and the whole-body, the retentions were expressed with a 2 term-exponential function. The metabolic data for subjects A and B are as follows: (1) a peak thyroidal uptake; 28.9 and 10.3% at 24 hours postdose (2) an effective half-time in the thyroid; 6.4 and 6.1 days (3) an effective half-time in the thighs; 0.2 and 0.3 day (4) excretion of ¹³¹I in the first 24-hr urine; 72 and 88% of the given dose (5) an amount of stable iodine in 24-hr urine before ¹³¹I administration; 0.29 and 2.0 to 5.4 mg. The dose commitments were estimated 1.19 and 0.39 mGy to the thyroid and 1 and 0.5 μGy to the total body for subjects A and B, respectively. The same results were obtained using the “S”, by MIRD.

View full abstract

Phospholipids of the membranes of spleen lymphosarcoma cells were radioactively labelled with the radioresistant fatty acid palmitic acid (16:0) and the radiosensitive fatty acid arachidonic acid (20:4). The effect of irradiation on the specific radioactivity of the phospholipids was studied. For the in vivo experiments trace amounts of radioactive palmitate or arachidonate were injected intraperitoneally into lymphosarcoma-bearing mice. Incorporation of label into the lipids of the tumorous spleen cells was monitored in control animals and in mice that were whole body irradiated after injection of the label. In both groups of animals the label was detected in the blood within minutes after injection and was found to be efficiently incorporated into the phospholipids of the tumor cells. In the irradiated animals a marked transient increase in label incorporation was observed as compared to control animals. The radiation effect was observed in the lipids of the total homogenate, purified nuclei, the mitochondriallysosomal fraction and in the microsomal fraction. Most experiments were performed with nuclei, which are known for their high radiosensitivity. The levels of label incorporation for palmitate and arachidonate were increased to the same extents and found to be dose dependent. For a dose of 5 Gy the increased label incorporation started immediately after irradiation and lasted for a period of about 50 minutes.
The increase in label incorporation into the phospholipids was preceded by an increase in the concentration of fatty acids in the cytosol of the tumors. Our experiments point to the occurrence of a transient increase in the flux of fatty acids through the plasma membrane as a result of irradiation and suggest that under normal physiological conditions fatty acid uptake through the plasma membrane is the rate-limiting step in the incorporation of acyl groups into the phospholipids.
Experiments with isolated tumor cells also showed an increased incorporation of fatty acids into the phospholipids after irradiation. Again the incorporation patterns of both types of fatty acids (16:0) and (20:4) were very similar. A hypotonic treatment of the cells also resulted in a similar increase in fatty acid incorporation as irradiation did; the effects of hypotonic treatment and irradiation were not additive.

View full abstract

Application of electrophoresis to the analysis of DNA strand breaks was studied comparing with the sedimentation analysis. A BRL gel electrophoresis system (Type V16) was used for this study. Calf thymus DNA (1 mg/ml) irradiated with ⁶⁰Co gamma-rays in SSC solution was applied to both the electrophoretic analysis and the sedimentation analysis. Lamda phage DNA and its fragments were employed as the standard size molecules. In a range from 1 k base pairs to 6 k base pairs in length for double stranded DNA or from 2 k bases to 12 k bases for single stranded DNA, the calculated average molecular weight from the electrophoresis coincided with that from the sedimentation. Number of single strand breaks and double strand breaks were 1.34 × 10¹¹ breaks/mg/rad (G = 0.215) and 0.48 × 10⁵ breaks/mg/rad², respectively.

View full abstract