Tetrazolium salts have become some of the most widely used tools in cell biology for measuring the metabolic activity of cells ranging from mammalian to microbial origin. With mammalian cells, fractionation studies indicate that the reduced pyridine nucleotide cofactor, NADH, is responsible for most MTT reduction and this is supported by studies with whole cells. MTT reduction is associated not only with mitochondria, but also with the cytoplasm and with non-mitochondrial membranes including the endosome/lysosome compartment and the plasma membrane. The net positive charge on tetrazolium salts like MTT and NBT appears to be the predominant factor involved in their cellular uptake via the plasma membrane potential. However, second generation tetrazolium dyes that form water-soluble formazans and require an intermediate electron acceptor for reduction (XTT, WST-1 and to some extent, MTS), are characterised by a net negative charge and are therefore largely cell-impermeable. Considerable evidence indicates that their reduction occurs at the cell surface, or at the level of the plasma membrane via trans-plasma membrane electron transport. The implications of these new findings are discussed in terms of the use of tetrazolium dyes as indicators of cell metabolism and their applications in cell biology.

Tetrazolium dyes as tools in cell biology: new insights into their cellular reduction.

The text consists of two sections, one for those studying or practicing diagnostic radiology, nuclear medicine and radiation oncology; the other for those engaged in the study or clinical practice of radiation oncology--a new chapter, on radiologic terrorism, is specifically for those in the radiation sciences who would manage exposed individuals in the event of a terrorist event. The 17 chapters in Section I represent a general introduction to radiation biology and a complete, self-contained course especially for residents in diagnostic radiology and nuclear medicine that follows the Syllabus in Radiation Biology of the RSNA. The 11 chapters in Section II address more in-depth topics in radiation oncology, such as cancer biology, retreatment after radiotherapy, chemotherapeutic agents and hyperthermia.

Radiobiology for the Radiologist

Ionizing radiation-induced metabolic oxidative stress and prolonged cell injury

Fluorescent and luminescent probes for measurement of oxidative and nitrosative species in cells and tissues: progress, pitfalls, and prospects.

Reactive oxygen species (ROS) are critically important chemical intermediates in biological studies, due to their multiple physiologically essential functions and their often pathologically deleterious effects. Consequently, it is vital that their presence in biological samples has to be quantifiable. However, their high activity, very short life span and extremely low concentrations make ROS measurement a scientifically challenging subject for researchers. One of the widespread methods for ROS detection, based on the oxidation of the non-fluorescent probe 2',7'-dichlorodihydrofluorescein (DCFH(2)) to yield the highly fluorescent 2',7'-dichlorofluorescein (DCF), was developed more than 40 years ago. However, from its initial application, argumentative questions have arisen regarding its action mechanisms, reaction principles and especially its specificity. Herein, the authors attempt to undertake a comprehensive review: to describe the basic characteristics of DCFH(2); to discuss the present views of the mechanisms of its fluorescence formation; to summarize the fluorescence formation interferents; to outline its application in biological research; and to underline its advantages and disadvantages in ROS detection as well as for the methodological considerations that arise during analysis.

2′,7′-Dichlorodihydrofluorescein as a fluorescent probe for reactive oxygen species measurement: Forty years of application and controversy

Spectrofluorometric determination of intracellular levels of reactive oxygen species in drug-sensitive and drug-resistant cancer cells using the 2′,7′-dichlorofluorescein diacetate assay ☆

Meesungnoen, J., Jay-Gerin, J-P., Filali-Mouhim, A. and Mankhetkorn, S. Low-Energy Electron Penetration Range in Liquid Water. Radiat. Res. 158, 657–660 (2002). Monte Carlo simulations of electron tracks in liquid water are performed to calculate the energy dependence of the electron penetration range at initial electron energies between 0.2 eV and 150 keV, including the subexcitation electron region (<7.3 eV). Our calculated electron penetration distances are compared with available experimental data and earlier calculations as well as with the results of simulations using newly reported amorphous ice electron scattering cross sections in the range ∼1–100 eV.

Low-Energy Electron Penetration Range in Liquid Water

Abstract Meesungnoen, J., Jay-Gerin, J-P., Filali-Mouhim, A. and Mankhetkorn, S. Low-Energy Electron Penetration Range in Liquid Water. Radiat. Res. 158, 657–660 (2002). Monte Carlo simulations of electron tracks in liquid water are performed to calculate the energy dependence of the electron penetration range at initial electron energies between 0.2 eV and 150 keV, including the subexcitation electron region (<7.3 eV). Our calculated electron penetration distances are compared with available experimental data and earlier calculations as well as with the results of simulations using newly reported amorphous ice electron scattering cross sections in the range ∼1–100 eV.

SHORT COMMUNICATION Low-Energy Electron Penetration Range in Liquid Water

Rhodamine B as a mitochondrial probe for measurement and monitoring of mitochondrial membrane potential in drug-sensitive and -resistant cells.

Monte Carlo simulations are used to investigate the effects of multiple ionization of water molecules on the yields of formation of free radical and molecular species, including molecular oxygen, in the radiolysis of pure, deaerated liquid water by using different types of radiation (1H+, 4He2+, 12C6+, and 20Ne9+ ions) up to ∼900 keV/μm, at neutral pH and 25 °C. Taking into account the double, triple, and quadruple ionizations of water, the primary (or “escape”) yields (at 10-6 s) of the various radiolytic species (G , GH•, GH2, G•OH, GHO2•/O2•-, and GH2O2) are calculated as a function of the linear energy transfer (LET) of the radiation. Our results quantitatively reproduce the large increase observed in GHO2•/O2•- at high LET. Under the conditions of this study, the mechanisms of triple and quadruple ionizations contribute only weakly to the production of HO2•/O2•-. With the exception of protons, our calculations also simultaneously predict a maximum in GH2O2 corresponding to the LET of ∼4.5-MeV helium ...

Jintana Meesungnoen

Papers

Spectrofluorometric determination of intracellular levels of reactive oxygen species in drug-sensitive and drug-resistant cancer cells using the 2′,7′-dichlorofluorescein diacetate assay ☆

Low-Energy Electron Penetration Range in Liquid Water

SHORT COMMUNICATION Low-Energy Electron Penetration Range in Liquid Water

Rhodamine B as a mitochondrial probe for measurement and monitoring of mitochondrial membrane potential in drug-sensitive and -resistant cells.

High-LET radiolysis of liquid water with 1H+, 4He2+, 12C6+, and 20Ne9+ ions: effects of multiple ionization.