Relative importance of cellular uptake and reactive oxygen species for the toxicity of alloxan and dialuric acid to insulin-producing cells.

The diabetogenic agent alloxan is selectively accumulated in insulin-producing cells through uptake via the GLUT2 glucose transporter in the plasma membrane. In the presence of intracellular thiols, especially glutathione, alloxan generates "reactive oxygen species" (ROS) in a cyclic reaction between this substance and its reduction product, dialuric acid. The cytotoxic action of alloxan is initiated by free radicals formed in this redox reaction. Autoxidation of dialuric acid generates superoxide radicals (O(2)(*-)) and hydrogen peroxide (H(2)O(2)), and finally hydroxyl radicals ((*)OH). Thus, while superoxide dismutase (SOD) only reduced the toxicity, catalase, in particular in the presence of SOD, provided complete protection of insulin-producing cells against the cytotoxic action of alloxan and dialuric acid due to H(2)O(2) destruction and the prevention of hydroxyl radical ((*)OH) formation, indicating that it is the hydroxyl radical ((*)OH) which is the ROS ultimately responsible for cell death. After selective accumulation in pancreatic beta cells, which are weakly protected against oxidative stress, the cytotoxic glucose analogue alloxan destroys these insulin-producing cells and causes a state of insulin-dependent diabetes mellitus through ROS-mediated toxicity in rodents and in other animal species, which express this glucose transporter isoform in their beta cells.

Comparative study of membrane potential-sensitive fluorescent probes and their use in ion channel screening assays.

In this study, the authors compared and evaluated 4 membrane potential probes in the same cellular assay: the oxonol dye DiBAC(4)(3), the FLIPR membrane potential (FMP) dye (Molecular Devices), and 2 novel fluorescence resonance energy transfer (FRET) dye systems from PanVera [CC2-DMPE/DiSBAC(2)(3)] and Axiom [DiSBAC(1)(3)/DiSBAC(1)(5)]. The kinetic parameters of each membrane probe were investigated in RBL-2H3 cells expressing an endogenous inward rectifier potassium channel (IRK1). The FMP dye presented the highest signal over background ratio whereas the FRET dyes from PanVera gave the fastest response. The determination of IC(50) values for 8 different channel modulators indicated a good correlation between the 4 membrane probe systems. The compound-dye interaction was evaluated in the presence of compounds at 10 muM and clearly indicated no effect on the FMP or the PanVera donor dye, whereas some major interference with the oxonol probes was observed. Using a cell permeabilization assay in the presence of gramicidin, the authors concluded that the FRET dyes from PanVera and the FMP dye are unable to measure the gramicidin-induced cell membrane hyperpolarizations. The 4 dye systems were investigated under high-throughput screening (HTS) conditions, and their respective Z' parameter was determined. The characteristics of each dye system and its potential use in HTS assays is discussed.

Molecular complexes of iron violurate with donor amines.

The acceptor character of iron violurate complex was studied by examining the electronic, vibrational and 1H-nmr spectra of the charge transfer molecular complexes formed between the iron violurate as pi-acceptor and some amines as n-donors. Elemental analysis and spectral results establishes 1:2 stoichiometry of the adducts. The study has been conducted at different temperatures. Values of delta G degree, delta H degree and delta S degree have been calculated from the self-consistent values of the formation constants (KCT). Ionization potentials of the donors have been calculated and the solvent effect on the KCT values is discussed. The antibacterial and antifungal effects of the molecular complexes were studied.

Barbiturate and nonbarbiturate sedative hypnotic intoxication in children.

This article reviews the pharmacology, toxicology, and treatment of both barbiturate and nonbarbiturate sedative hypnotic overdose. Although poisoning with these agents has declined over recent years, intoxication with them can still result in a life-threatening situation requiring immediate assessment and treatment.

Long-lasting effects of early barbiturates on central nervous system and behavior.

Forty years of prescribing barbiturates to pregnant women and infants, and thirty years of animal research have shown that barbiturates affect the developing central nervous system (CNS) and behavior. This paper compiles and reviews animal and selected human literature in this research area. Early barbiturate exposure in animals reduces brain weight with related changes in brain biochemistry and neuromorphology. Significant changes may be found in surviving adult offspring. Evidence of CNS and behavioral damage in human beings due to early barbiturate exposure is not clearcut, however, confounded by the conditions for which the drugs are prescribed. In animals, early drug exposure significantly reduces levels of hormones, vitamins, and other biologically active macromolecules via (long-lasting) induction of hepatic metabolizing enzymes. Whether or not in humans treated with barbiturates, hormone levels remain within the normal range (by-feed-back regulation) and, also, if vitamin deficiencies can be simply corrected by supplements is still being debated. Early barbiturates administered to animals is associated with long-lasting disturbances in activity, learning performance, sexual behavior, and reproductive function, but not in a simple dose-exposure related manner. Animal studies show that long-lasting functional tolerance to drugs develops following early barbiturate exposure. Although infants become "passively addicted" following in utero exposure, there is as yet no data on subsequent development of human adult tolerance. Drug related damage must, in any case, be weighed against therapeutic benefits of drug administration and the results of failure to treat.