Teruie Sumino

The relationship between cell killing effect and number of lanthanide atoms bound to DNA molecules in cultured HeLa cells treated with rare earth elements

HeLa S-3 cells were treated with several rare earth elements, Ce, La, and Sm, at 37 °C for 1 hour and the relationship between the lethal effects of these elements and the number of the atoms bound to DNA, RNA, and proteins was examined. Among the 3 element, only Ce gave an exponential dose-survival relationship from which the value of mean lethal concentration (D0) was determined to be 6.75 mM. By using identically treated cells, the number of Ce atoms combined with DNA, RNA and protein molecules in HeLa cells were determined after fractionation of the cells using neutron activation analysis. In this way, theD0 value given as the Ce concentration was replaced by the number of Ce atoms combined with each fraction, then the target volumes, viz., cell killing efficiency, expressed as the reciprocal ofD0 value was calculated for each fraction. The results suggested that DNA and RNA could stochiometrically be the primary target molecule for cell killing by Ce.

DETERMINATION OF RARE EARTH ELEMENTS IN FERN LEAVES USING INSTRUMENTAL NEUTRON ACTIVATION ANALYSIS

The lanthanides (REE) in 142 fern leaves collected from several sampling sites in Japan have been determined by neutron activation analysis, and the correlations between any two REEs in the logarithmic scattering diagram were examined. The relationship was expressed by the general formula, Y=aX+b with a correlation coefficient R. A strong positive correlation was seen between any two REEs in the diagram with a regression coefficient and a correlation coefficient close to unity. However, between Eu or Tb and other REEs the relationship was split into two lines with the same correlation coefficient. From the intercept b, the relative abundance of the two elements was determined for each REE and compared with those in hickory and tobacco leaves. These findings indicated that the abundance pattern of fern leaves is quite different from those of hickory and tobacco leaves. Namely, the relative abundance of La and Ce was quite similar in the three plants, but the abundance of the other REEs (Nd, Sm, Gd, Dy and Lu) was considerably lower in ferns than in hickory and tobacco leaves. For Eu and Tb the higher values obtained in fern leaves coincided with those of the two plants.

CORRELATION BETWEEN LANTHANIDE CONTENTS IN FERN LEAVES

The lanthanides (REE) in 142 fern leaves collected from several sampling sites in Japan were analyzed by neutron activation analysis. In most cases, between two REE a strong positive correlation was seen in the logarithmic scattering diagram with a correlation coefficient and a regression coefficient close to unity, suggesting neither selective accumulation by plants nor different availability by soil take place between the two elements. However, between Eu or Tb and another REE the relationship showed two lines with the same correlation coefficient. This suggested that there must be a difference in the availability of REEs or in the absorption characteristics of plants. Further analysis revealed that the 142 ferns could be separated into three groups, and the splitting was attributable to some difference in the environmental factors where the fern was grown. However the REE contents in the soil collected together with the corresponding fern did not reflect the concentration of the REE in the fern leaves.

Unusual interrelationship between care earth element and calcium contents in fern leaves

Since the rare earth elements (REE) are most informative as isomorphic replacements of Ca2+ in organisms, we analyzed these elements in 142 fern leaves collected from several sampling sites in Japan by instrumental neutron activation analysis (INAA), and the correlation between the REE and Ca contents was examined. In most cases, between any particular REE and the Ca contents, the correlation in the logarithmic scattering diagram was expressed as a single line parallel to the vertical (Y) axis. However, the detailed analysis of the diagrams characterized with respect to the sampling site revealed that the 142 ferns could be separated into two or three groups on the basis of their different REE/Ca ratios. The sampling sites where the different REE/Ca ratios were observed completely agreed with those found in the preceding report, i.e., regarding the unusual correlation between Eu and the other REEs.

Correlation between terbium and the other rare earth element contents in fern leaves

The lanthanides (REEs) in 142 fern leaves collected from 9 sampling sites in Japan were analyzed by instrumental neutron activation analysis. Between two REEs a strong positive correlation was found in the logarithmic scattering diagram with correlation and regression coefficients close to unity, suggesting neither selective accumulation by plants nor different availability from soil between the two elements. However, between Tb and the other REEs the relationship showed two lines with the same correlation coefficient. This suggested that there must be a difference in the availability of REEs or in their absorption characteristics by plants. Further analysis revealed that the splitting was due to some difference in the environmental factors where the fern grew. However, the amount of REE in the soil collected together with the corresponding fern did not reflect the REE concentration in the fern leaves.

Cell-killing efficiency and number of platinum atoms binding to DNA, RNA and protein molecules of HeLa cells treated with combinations of hyperthermia and carboplatin

The effect of hyperthermia on the cell killing efficiency of Pt atoms binding to DNA, RNA and protein molecules of HeLa cells treated withcis-diamine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA) was examined. HeLa S-3 cells were treated with195mPt-radiolabeled CBDCA for 60 minutes at various temperatures, and the relationship between the lethal effect and the number of Pt atoms binding to DNA, RNA and proteins was examined. The mean lethal concentration (D0) of carboplatin for a 60 min-treatment at 0, 25, 37, 40, 42 and 44°C was 671.2, 201.5, 67.3, 33.4, 20.2 and 15.6 μM, respectively. By using identically treated cells, the number of Pt-atoms combined with DNA, RNA and protein molecules were determined in the subcellular fractions. Thus, the D0s given as the drug concentrations were replaced with the number of Pt-atoms combined in each fraction. Then, the cell-killing efficiency of the Pt atom was expressed as the reciprocal of the number of Pt-atoms combined and was calculated for each molecule. The efficiency for DNA molecules was 0.699, 1.42, 2.65, 4.84, 7.74 and 8.28·104 nucleotides, respectively, for the conditions described above. From 0 to 44°C, the cell-killing efficiency of Pt atoms increased by a factor of 11.9.

Determination of rare earth and other elements in algae by ICP-MS and neutron activation analysis

Several rare earth elements (REEs) and other elements in algae were investigated by ICP-MS and INAA. Algae materials were supplied from an IAEA Intercomparison Study:Chlorella vulg. grown under reduced levels of toxic elements (IAEA-391) and IAEA-393 algae was grown in a medium to which certain toxic elements were added. 34–691 mg of algae samples were dissolved in conc, nitric acid using a microwave sampleppreparation system. REEs could be detected in the order of magnitude of 10−3 ng/g by ICP-MS. Activation analysis failed to detect any REEs because of a strong interference due mainly to24Na and32P. The distriubtion patterns of these REEs in algae slightly differed from those ofCarya sp. and tobacco leaves, and differed significantly from that of fern leaves. The distribution pattern was rather similar to that found in the North American shale composite (NASC).

Determination of the target volume of HeLa cells treated with platinum-195 m radiolabeled cis-diammine(1,1-cyclobutane-dicarboxylato)-platinum(II); comparison with cis- and trans-diamminedichloroplatinums(II)

HeLa S-3 cells were treated with 195mPt-radiolabeled cis-diammine(1, 1-cyclobutane-dicarboxylato)platinum(II) (carboplatin) under various conditions, and the relationship between lethal effect and the number of Pt atoms binding to DNA, RNA and proteins was examined. The mean lethal concentrations for the cells treated with carboplatin at 37 degrees C for 1, 2 and 3 h were 553.4, 194.3 and 68.7 microM, respectively. By using identically treated cells, the numbers of Pt-atoms combined with DNA, RNA and protein molecules were determined after fractionation of the cells. In this way the D0 values (D0, dose that would give an average of one lethal event per member of the population), expressed as the drug concentration, were substituted for the number of Pt atoms combined with each fraction. The target volumes, the efficiency of Pt atom to kill cells expressed as the reciprocals of the D0 values, were then calculated with each fraction. The results suggested that DNA was the primary target for cell killing by carboplatin. The target volumes for DNA were 0.891 x 10(4), 2.01 x 10(4) and 3.96 x 10(4) nucleotides for 1, 2 and 3 h treated cells, respectively. The cell killing effects of carboplatin were lower than those of cis-diamminedichloroplatinum(II) (CDDP) by factors of 6.0, 2.8 and 2.6 for 1, 2 and 3 h treatments at 37 degrees C, respectively, in terms of the target volume, while those in terms of the mean lethal dose (D0) were 59.5, 29.0 and 21.5, respectively.

Enhanced cell-killing action of cisplatin in the presence of terbium chloride

The literature indicates that the interaction of Tb3+ with DNA modified by the antitumour drug cis-diaminedichloroplatinum(II) (CDDP) results in substantial enhancement of the fluorescence of this cation, while no enhancement is observed in the case of DNA modified by irradiation with ionizing radiation. This study investigates the effect of Tb3+ on the survival of cultured mammalian cells treated with CDDP. HeLa cells were treated with a combination of195mPt-CDDP and TbCl3, and the relationship between lethal effect and the numbers of Tb and/or Pt atoms binding to DNA, RNA and proteins was examined. The Tb content in each fraction was determined using instrumental neutron activation analysis. It was found that the cytotoxic effect of CDDP was greatly enhanced by the presence of Tb ions (D0 of CDDP fell from 8.3 μM without Tb to 3.2 μM with 0.75 mM Tb), while no such effect was found in radiation-induced cell-killing. The number of Tb atoms bound to DNA molecules in a cell was calculated to be about 4.5·107, namely 1 per 1.400 nucleotides, under that situation.

The effect of 60Co‐γ‐irradiation on potassium Tetrachloroplatinum(ii) in NH4Cl solution: Enhanced cell killing effect

Abstract The effect of 60Co‐γ‐irradiation on aqueous solutions of potassium tetrachloroplatinum(II) K2(PtCl4) under various conditions was examined by using high performance liquid chromatography (HPLC). After short irradiation times at a dose rate of 1.6 x 104 Gy/h, cis‐diamminedichloroplatinum(II) (CDDP), after longer irradiation times trans‐diamminedichloroplatinum(II) (TDDP) was produced. The cell killing effect of the irradiated K2 (PtCl4) solutions was compared with that of the theoretically expected from the concentrations of various Pt‐compounds after irradiation. The observed cell‐killing effect compared with the theoretical one increased with increasing radiation dose. Thus, the present results revealed that some very cytotoxic substance, besides CDDP was synthesized in 60Co‐γ‐irradiated K2 (PtCl4) solution.