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This series aims at the measurement of flame generated nanoparticles and an assessment of their biological effects. In the present part a brief review is given on previous papers dealing with nanoparticles with emphasis on detection through various methods. A more detailed account is provided of own measurements using photo ionization mass spectrometry. This includes photo fragmentation, spectra of low pressure flames, coagulation effects, and nanoparticle measurements in the exhaust gas of a sooting normal pressure premixed flame well outside of the visible zone. A model on nanoparticle formation is discussed as are its implications on emissions of vehicle engines.

Generation of Chinese Hamster Ovary (CHO) cell lines stably expressing green fluorescent protein (GFP) was achieved using a plasmid vector that encoded the red-shifted pCX-xGFP under the control of a strong hybrid promoter composed of a CMV enhancer and a β-actin/β-globin gene promoter. Cotransfection of the promoter-less pSV2-Neo helper plasmid transmitting neomycin resistance was followed by selection with the antibiotic G418. Constitutive GFP expression could be visualized in living and fixed cells using fluorescence spectroscopy, fluorescence microscopy, and flow cytometry. DNA repair-proficient (AA8) and deficient (UV5) CHO strains were used for survival tests after UVC irradiation. Cells carrying the GFP construct (AA8-pGFP, UV5-pGFP) show the same response to UV irradiation (colony forming ability) as their nontransformed parental cell lines (AA8, UV5). Using GFP as a marker for cell viability, cells were harvested after certain postirradiation growth periods and the numbers of GFP expressing cells and fluorescence intensities were determined by FACS analysis. Generally, GFP fluorescence in irradiated cells is not seen when cell membranes are damaged (leak-out of the soluble GFP). Irradiated cells without membrane damage express GFP continuously (leading to a dose-dependent increase in GFP contents).

The effect of aphidicolin, a specific inhibitor of DNA polymerases α and δ, was studied on DNA synthesis, PLD-recovery and DNA double-strand break rejoining in X-irradiated human fibroblasts. In unirradiated, exponentially growing cells, aphidicolin (0·5-5 µg ml) inhibited DNA synthesis almost completely. This effect depended not only on aphidicolin concentration but also on the duration of pre-incubation. The action of aphidicolin was found to be reversible. When aphidicolin had been removed, colony forming ability was not affected in aphidicolin pretreated cells. Aphidicolin pretreated and irradiated cells showed a reduction in PLD-recovery, dependent on aphidicolin concentration and duration of pretreatment. The initial number of DNA double-strand breaks (calibrated by 125I decay) was not affected by aphidicolin. However, after incubation for 90 min in the presence of aphidicolin there was a large reduction in double-strand break rejoining. With long incubation periods in aphidicolin rejoining was almost completely inhibited.

Calibration of the non-denaturing (pH 9·6) filter elution technique by 125I decays has been used to examine the relationship between X-ray-induced DNA double-strand breaks (dsb) and cellular survival of CHO cells and human fibroblasts. DNA dsb induction varies markedly between the two cell lines, reflecting the different survival levels. The relationships between lethal lesions (- ln S) and DNA dsb are also significantly different for CHO cells and human fibroblasts, suggesting either different probabilities of dsb conversion into lethal lesions or different repair capacities.

Summary X-irradiated (1.0 kGy) yeast cells (Saccharomyces uvarum, ATCC 9080), grown in liquid medium stop their mitotic activities and form giant cells by development of several buds which do not separate from mother cells. Depending on the time in culture, wet and dry weights per cell, protein- RNA- and DNA- contents per cell as well as incorporation rates of14C-leucine per cell and per hour and patterns (isoelectric focussing) of water soluble proteins were studied. Weights per cell, RNA and protein contents per cell and14C-leucine incorporation rates increase markedly in giant cells, whereas DNA content per cell is only duplicated. Protein patterns in isoelectric focusing show one interesting difference. In samples from giant cells one protein band (IP=6.63) decreases after 8 h in culture and later on disappears completely. This finding is not due to primary damage in X-irradiated DNA but seems to be related to the control of cell cycle events.