DNA LESIONS AND DNA DEGRADATION IN MOUSE LYMPHOMA L5178Y CELLS AFTER PHOTODYNAMIC TREATMENT SENSITIZED BY CHLOROALUMINUM PHTHALOCYANINE

Two closely related strains of mouse lymphoma L5178Y cells, LY-R and LY-S, have been found to differ in their sensitivity to the cytotoxic effects of photodynamic treatment (PDT) with chloroaluminum phthalocyanine (CAPC) and red light. Strain LY-R is more sensitive to photodynamic cell killing than strain LY-S. Differences in uptake of CAPC could not account for the differences in cytotoxic effects. There was no marked difference between the two strains in the induction of single-strand breaks (which includes frank single-strand breaks and alkali-labile lesions), but substantially more DNA-protein cross-links were formed in strain LY-R by CAPC and light. Repair of single-strand breaks proceeded with similar kinetics in both strains for the first 30 min post-irradiation, suggesting that these lesions are not responsible for the differential sensitivity of the two strains to the lethal effects of photodynamic treatment. Thereafter, alkaline elution revealed the presence of increasing DNA strand breakage in strain LY-R. DNA degradation, as measured by the conversion of prelabeled [14C] DNA to acid-soluble radioactivity, was more rapid and extensive in strain LY-R.     

INDUCTION OF DNA-PROTEIN CROSS-LINKS IN CHINESE HAMSTER CELLS BY THE PHOTODYNAMIC ACTION OF CHLOROALUMINUM PHTHALOCYANINE AND VISIBLE LIGHT

Abstract— Chloroaluminum phthalocyanine (CAPC) is an efficient photosensitizer for the inactivation of Chinese hamster V79 cells. In order to investigate possible molecular mechanisms in the photo-dynamic action of CAPC and visible light, the induction and repair rate of two classes of DNA lesions have been determined, i.e. DNA single-strand breaks and DNA-protein cross-links. In cells pretreated with 1 μ.M CAPC, a fluence of 12 kJ/m² of red light (>600 nm) kills approximately 50% of the cells and induces 3 to 3.5 Gy-equivalents of single-strand breaks. The repair of these breaks was slower than the repair of single-strand breaks induced by -irradiation. The photodynamic action of CAPC also induces a large number of DNA-protein cross-links which, in contrast to -radiation-induced DNA-protein cross-links, do not appear to be repaired during 4 h of post-treatment incubation in fresh medium. These studies suggest that DNA may be an important target for the cytotoxicity of CAPC + red light.     

Application of simulated standard spectra for the analysis of complex sample spectra from NaI(Tl) detectors

The most accurate method for the analysis of complex gamma ray spectra from scintillation detectors is least squares method. The major requirement of this method is individual standard spectra of all nuclides expected in the complex spectrum which is not possible and feasible for some nuclides. In the present work, an approach of using simulated standard spectrum of the radionuclides for the least squares analysis is studied. The paper describes the methodology used for the generation of simulated spectrum which is the main objective, and validation of results using standard sources in the Sodium Iodide (NaI(Tl)) based gamma ray spectrometer.     

OCCURRENCE OF PYRIMIDINE-RICH TRACTS IN ASCITES TUMOR DNA AND THE FORMATION OF UV-INDUCED THYMINE DIMERS

Abstract— Analysis of the distribution of pyrimidine-rich tracts (up to decanucleotides) in ascites tumor DNA revealed that these tracts occur predominantly in repetitive sequence of DNA. UV irradiation of ascites DNA resulted in preferential formation of thymine dimers in the pyrimidine-rich tracts as compared to other regions of DNA.     

Determination of plutonium in sediments by solvent extraction and α-spectrometry

A simple technique for the determination of environmental levels of plutonium in a highly complex matrix (sediments containing very high amounts of iron and other metals) is reported. The sediments, collected from the Hudson River Estuary with an Emory dredge, were hand-homogenized before a sample aliquot was taken. Samples were airdried, weighed, spiked with ²⁴²Pu tracer, and heated at 400°C for 24 h. Plutonium was leached from the sediment with an acid mixture. The leachate was filtered, and plutonium coprecipitated with iron by adding ammonia solution. After dissolution, plutonium was extracted with 20% trilaurylamine in xylene, the extracts were thoroughly acid-washed to remove uranium and thorium traces, and plutonium was then back-extracted with 2 M sulfuric acid prior to electrodeposition onto a platinum planchet. The isotopic composition of plutonium was determined by α-spectrometry. Tracer yield and plutonium concentrations determined on aliquots of the same samples by this method and by an ion-exchange technique were not significantly different.     

Thorium,uranium and plutonium in human tissues of world-wide general population

The results on the concentrations of thorium, uranium, and plutonium in human tissues of world-wide general populations are summarized. The majority of thorium and uranium are accumulated in the skeleton, whereas, plutonium is divided between two major organs; the liver and skeleton. However, there is a wide variation in the fractions of plutonium in the liver and the skeleton of the different populations.     

Natural radioactivity studies of Bidar soil samples using gamma spectrometry

The activity of the terrestrial primordial radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K are measured for Bidar soil samples. The collected soil samples are analyzed using HPGe detector based on high resolution gamma spectrometric system. The activity of the three radionuclides ²²⁶Ra, ²³²Th and ⁴⁰K were found to be in the range of BDL–47.68, 7.65–59.08 and BDL–260.65 Bq kg^?1 respectively. The mean gamma absorbed dose rate in air above 1 m from ground is estimated to be 34.47 nGy h^?1. Annual effective dose equivalent and the radium equivalent activity were within the limits in the present study and it is found that the activity of the radionuclides are comparable with the worldwide literature values. Also the external hazard indices for the soil samples of Bidar district were within the limit of unity.     

Angular distribution XPS studies on recoil-implanted substrates: Au in Al2O3

Angular distribution XPS has been employed for the first time to follow the changes in the electronic structure of gold as it is implanted into Al₂O₃ overlayers on aluminium by recoil. The rudimentary aspects of the implantation process may be followed by observing the Au 4f_{$\text{7}\text{2}$} intensity as a function of primary ion dose for discrete values of θ. Intensity versus primary ion dose curves show three distinct regions — a continuous-film region, an island and cluster region, and an implanted-atom region. For this system, while only gold atoms are introduced into the substrate, the surface contains clusters of gold even for very low gold concentrations. The valence-band density of states shows good agreement with a theoretical spectrum calculated using a unity polarizability model previously described.     

Gamma spectrometric analysis of ore samples from Sandur of Bellary, Karnataka, India

In the present paper the gamma spectrometric technique has been used to study the natural radioactivity levels present in the iron ore samples collected from the Sandur of Karnataka, India. This region, a member of Dharwar craton, known as Sandur schist belt is rich in Manganese and Hematite ore (Fe). The entire belt is characterized by numerous bands of banded magnetite and hematite quartzite. The ore samples were collected and prepared as per the ASTM standard procedures. The gamma spectrometric measurements were performed using a HPGe detector (Eurosys) based high-resolution 8k multi channel analyzer. The detector has a relative efficiency of 50% and resolution of 2.0?keV for 1.332?MeV gamma energy of ⁶⁰Co. The output of the detector was analyzed using a PC based 8k channel analyzer system. The mean activity concentrations of the ²³⁸U, ²³²Th and ⁴⁰K in the ore samples were found to be 14.59, 16.54 and 25.29?Bq/kg, respectively. The mean absorbed dose rate and the annual dose equivalent were estimated to be 18.97?nGy?h^?1 and 24.93???Sv?y^?1, respectively, which is lower than the world recommended average of 1?mSv?y^?1. The present work concludes that the natural radioactivity levels in ore samples of this region is within the natural limits and pose no health hazard to the public.     

Determination of the activity ratios of 231Pa to 235U and 227 Th to 235U in ore samples using gamma-spectrometry

Summary Elérhetoség