Amino-Termination of Silicon Carbide Nanoparticles.

Silicon carbide nanoparticles (SiC NPs) are promising inorganic molecular-sized fluorescent biomarkers. It is imperative to develop methods to functionalize SiC NPs for certain biological applications. One possible route is to form amino groups on the surface, which can be readily used to attach target biomolecules.

Transient delay of radiation-induced apoptosis by phorbol acetate.

The mechanisms of interference of a model tumour promoter 12-O-tetra-decanoylphorbol-13-acetate (TPA) with radiation-induced apoptosis in human peripheral lymphocytes have been investigated. The cells were treated with TPA under various conditions and thereafter exposed to a single lethal dose of gamma radiation. Morphological and biochemical changes characteristic of apoptosis were followed up to 72 h of post-irradiation time.

Intracellular deoxyribonucleotide pool imbalance and DNA damage in cells treated with hydroxyurea, an inhibitor of ribonucleotide reductase.

Imbalance in the nucleotide pool of mammalian cells has been shown to result in genotoxic damage. The goal of this study was to devise a sensitive, reproducible and simple method for detection of nucleotide pool changes in mammalian cells that could be used for problem-solving activities in drug development, e.g.

Evidence for different mechanisms of action behind the mutagenic effects of 4-NOPD and OPD: the role of DNA damage, oxidative stress and an imbalanced nucleotide pool.

The mutagenicity of 4-nitro-o-phenylenediamine (4-NOPD) and o-phenylenediamine (OPD) was compared using the Mouse Lymphoma Assay (MLA) with or without metabolic activation (S9). As expected, OPD was found to be a more potent mutagen than 4-NOPD. To evaluate possible mechanisms behind their mutagenic effects, the following end points were also monitored in cells that had been exposed to similar concentrations of the compounds as in the MLA: general DNA damage (using a standard protocol for the Comet assay); oxidative DNA damage (using a modified procedure for the Comet assay in combination with the enzyme hOGG1); reactive oxygen species (ROS; using the CM-H2DCFDA assay); and the balance of the nucleotide pool (measured after conversion to the corresponding nucleosides dC, dT, dG and dA using high-performance liquid chromatography).

Metabolic profiling of TRPV1 antagonists of the benzothiazole amide series: implications for in vitro genotoxicity assessment.

In vitro metabolic profiling and in vitro genotoxicity assessment are important aspects of the drug discovery program as they eliminate harmful compounds from further development. In standard in vitro genotoxicity testing, induced rat liver S9 is used as an exogenous bio-activation system for detecting promutagens. In this study we show that rat liver S9 is an insufficient system regarding the conversion of TRPV1 antagonists of the benzothiazole amide series into relevant in vivo metabolites.

Elevated serum 8-oxo-dG in hemodialysis patients: a marker of systemic inflammation?

Does inflammation, as assessed by high sensitivity C-reactive protein (hs-CRP), in patients with end-stage renal disease (ESRD) tightly associate with increased serum levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8- oxo-dG)? Increased oxidative stress and inflammation have both been highlighted among several nontraditional risk factors for cardiovascular disease, which is the main cause of mortality in ESRD patients. In contrast to oxidative stress effects on proteins and lipids, DNA base damage has not been well demonstrated in ESRD. Two groups of hemodialysis patients were studied, one group with persistent inflammation (n = 13, with constant elevation of CRP > 10 mg/L for 6 months) and one group of noninflamed patients (n = 19, with constant CRP < 10 mg/L for 6 months).

The nucleotide pool is a significant target for oxidative stress.

Oxidative stress is considered to be one of the most important phenomena involved in the process of aging and age-related diseases. 8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) has been frequently used as a marker for oxidative stress. However, the origin of extracellular 8-oxo-dG is not well understood.

Studies on radiation-induced apoptosis in G0 human lymphocytes.

Purpose: To determine the relationships between the frequencies of radiation-induced chromosomal alterations and the extent of apoptosis in G0 human lymphocytes.

Material And Methods: G0 human peripheral blood lymphocytes (HPBL) were X or gamma-irradiated, in the presence or absence of the repair inhibitor cytosine arabinoside (Ara-C). Directly after irradiation, a part of the lymphocytes were stimulated to grow while the rest were stimulated 48 h after irradiation.

Extracellular 8-oxo-dG as a sensitive parameter for oxidative stress in vivo and in vitro.

8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) is one of the mutagenic base modifications produced in DNA by the reaction of reactive oxygen species. The biological significance of 8-oxo-dG is shown by the existence of repair pathways that are able to recognize and remove this lesion from both DNA and the nucleotide pool. The final outcome of these evolutionarily conserved repair mechanisms in man is excretion of 8-oxo-dG/8-oxo-Gua from the intracellular to extracellular milieu including the blood plasma and urine.

Induction of homologous recombination in the hprt gene of V79 Chinese hamster cells in response to low- and high-LET irradiation.

Dense ionization tracks from high linear energy transfer (LET) radiations form multiple damaged sites (MDS), which involve several types of DNA lesions in close vicinity. The primary DNA damage triggers sensor proteins that activate repair processes, cell cycle control or eventually apoptosis in subsequent cellular responses. The question how homologous recombination (HR) and non-homologous end joining (NHEJ) interact in the repair of radiation-induced DNA damage of MDS type has been addressed in different model systems but several questions remain to be answered.

DNA fragmentation and morphological changes in apoptotic human lymphocytes.

Cell suspensions enriched in cells at various stages of apoptosis were obtained by separation of irradiated human peripheral blood lymphocytes on density gradients at different post-irradiation times. The state of DNA fragmentation in the cells was determined by comet assay and pulsed field gel electrophoresis. The morphologically distinguishable features of apoptosis such as chromatin condensation and cell shrinkage correlated with discrete stages of DNA fragmentation.

Changes in chromatin conformation during radiation-induced apoptosis in human lymphocytes.

Human peripheral lymphocytes in G(0) phase were irradiated with 1-5 Gy of gamma rays. The biochemical and morphological changes characteristic of apoptosis were examined for 72 h after irradiation. In parallel, changes in chromatin conformation were studied by the method of anomalous viscosity time dependence (AVTD) and by measurements of nuclear halo size.

Influence of dose-rate, post-irradiation incubation time and growth factors on interphase cell death by apoptosis and clonogenic survival of human peripheral lymphocytes.

Purpose: To investigate the effects of dose-rate, post-irradiation incubation time and growth factors on radiation-induced interphase cell death by apoptosis and reproductive cell death in human peripheral lymphocytes.

Materials And Methods: Lymphocytes in G0-phase were exposed in vitro to 1-3Gy 137Cs gamma-radiation at a high- (HDR, 45Gy/h) or a low dose-rate (LDR, 0.024Gy/h).

pH-dependent DNA cleavage in permeabilized human fibroblasts.

In several cell types, apoptosis is associated with intracellular acidification and activation of a pH-dependent endonuclease. We have examined the effect of acidic pH on the DNA of permeabilized human fibroblasts, and observed cleavage of DNA into high-molecular-mass fragments. This pH-dependent DNA breakage was modulated by temperature, the presence of histones and diethyl pyrocarbonate.

Detection of single-strand breaks and formamidopyrimidine-DNA glycosylase-sensitive sites in DNA of cultured human fibroblasts.

Under oxidative stress 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxodG), a damaged base with mutagenic potential, and single-strand breaks (SSB) are formed in DNA. Both lesions are frequently used as a parameter for oxidative damage of DNA. Here we report on results from the evaluation of a modified nick translation assay, where 8-oxodG and SSB formation in cellular DNA of cultured human fibroblasts were simultaneously detected.

Mapping of sequential epitopes recognized by monoclonal antibodies on the bovine leukaemia virus external glycoproteins expressed in Escherichia coli by means of antipeptide antibodies.

A lambda gt11 cDNA library prepared from bovine leukaemia virus (BLV)-producing ovine cells was screened with a cocktail of anti-BLV gp51 monoclonal antibodies (MAbs). Four recombinant phages with inserts of about 2-5 kbp were isolated. One, lambda BLV-gp51-1, was sequenced and shown to encode the C-terminal part of gp51 and all of gp30.