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.     

Toward numerical simulations of fluid–structure interactions for investigation of obstructive sleep apnea

Obstructive sleep apnea (OSA) is a medical condition characterized by repetitive partial or complete occlusion of the airway during sleep. The soft tissues in the airway of OSA patients are prone to collapse under the low-pressure loads incurred during breathing. This paper describes efforts toward the development of a numerical tool for simulation of air–tissue interactions in the upper airway of patients with sleep apnea. A procedure by which patient-specific airway geometries are segmented and processed from dental cone-beam CT scans into signed distance fields is presented. A sharp-interface embedded boundary method based on the signed distance field is used on Cartesian grids for resolving the airflow in the airway geometries. For simulation of structure mechanics with large expected displacements, a cut-cell finite element method with nonlinear Green strains is used. The fluid and structure solvers are strongly coupled with a partitioned iterative algorithm. Preliminary results are shown for flow simulation inside the three-dimensional rigid upper airway of patients with obstructive sleep apnea. Two validation cases for the fluid–structure coupling problem are also presented.     

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.     

Shock Processing of Amino Acids Leading to Complex Structures—Implications to the Origin of Life

The building blocks of life, amino acids, are believed to have been synthesized in the extreme conditions that prevail in space, starting from simple molecules containing hydrogen, carbon, oxygen and nitrogen. However, the fate and role of amino acids when they are subjected to similar processes largely remain unexplored. Here we report, for the first time, that shock processed amino acids tend to form complex agglomerate structures. Such structures are formed on timescales of about 2 ms due to impact induced shock heating and subsequent cooling. This discovery suggests that the building blocks of life could have self-assembled not just on Earth but on other planetary bodies as a result of impact events. Our study also provides further experimental evidence for the ‘threads’ observed in meteorites being due to assemblages of (bio)molecules arising from impact-induced shocks.     

Time dependence of electrical resistance at high pressure in some tellurium based amorphous alloys

Electrical resistance measurements are reported for amorphous In₂₀Te₈₀ and Cu₂₅Au₅Te₇₀ alloys up to a pressure of 80 Kbar using a Bridgman anvil apparatus and a four lead arrangement to measure resistances. The amorphous samples are produced by liquisol quenching. The resistance shows time dependent changes which are analysed in detail. The contention that there is a pressure-induced transformation from the amorphous to the crystalline phase is confirmed by X-ray diffraction of samples recovered after they were pressurised to 35 Kbar in a hydrostatic environment.     

Reactivity with hydrogen of pure iron oxide and of iron oxides doped with oxides of Mn,Co, Ni and Cu

Using dynamic TG in H₂, X-ray powder diffraction and Mössbauer Spectroscopy the reactivities fot hydrogen reduction of Fe₂O₃ prepared at different temperatures, Fe₂O₃ doped with oxides of Mn, Co, Ni and Cu prepared at 300C from nitrate precursors and intermediate spinels derived from above samples during reduction have been explored. The reactivity is higher for finely divided Fe₂O₃ prepared at 250C. The reduction is retarded by Mn, marginally affected by Co and accelerated by Ni and Cu, especially at higher (5 at.%) dopant concentration. These reactivities confirmed also by isothermal experiments, are ascribed to the nature of disorder in the metastable intermediate spinels and to hydrogen spill over effects.

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Zusammenfassung Mittels Debye-Scherrer-Aufnahmen, Mössbauer-Spektroskopie und DTG in WasserstoffatmosphÄre wurde die ReaktivitÄt bezüglich der Reduktion mit Wasserstoff von Fe₂O₃, versetztem Fe₂O₃ und von intermediÄren Spinellen aus der Reduktion obiger Proben untersucht. Die reinen Fe₂O₃-Proben wurden bei verschiedenen Temperaturen hergestellt. Mit Oxiden von Mn, Co, Ni und Cu versetzte Fe₂O₃-Proben wurden bei 300C aus Nitrat-VorlÄufern hergestellt. Eine höhere AktivitÄt besteht für fein zerkleinertes, bei 250C hergestelltes Fe₂)O₃. Die Reduktion wird durch Mn verzögert, durch Co unwesentlich beeinflu\t und durch Ni und Cu beschleunigt, besonders bei höheren Konzentrationen (5 mol%). Diese ReaktivitÄten, die auch durch isotherme Experimente bestÄtigt werden konnten, wurden der Ungeordnetheit in den metastabilen intermediÄren Spinellen sowie Wasserstoff-überschu\-Effekten zugeschrieben.

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The authors thank Dr. Chitra Sankar for her help and useful discussions on the Mössbauer studies carried out. They also thank A. V. Narayan and D. Molliah for their assistance with the figures.     

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.