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N Van Larebeke

Publications and source records attributed to N Van Larebeke.

17 recordsLinked to original sources
PubMed2005

Genotoxic and mutagenic activity of environmental air samples from different rural, urban and industrial sites in Flanders, Belgium.

The present study reports mutagenic and genotoxic activities associated with ambient air collected at 15 sites characteristic for urban, industrial or rural conditions in Flanders. Airborne particulates (PM10) and semi-volatile compounds were collected on quartz filters (QF) and polyurethane foam (PUF) cartridges using a high-volume sampling device. The mutagenic and genotoxic potency of the organic extracts--Soxhlet extraction with acetone--was determined by use of the Salmonella mutagenicity standard plate-incorporation assay and the Vitotox assay, respectively. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC). Ambient air samples contained significant PAH levels and mutagenic activities at all 15 sites: direct mutagenicity of up to 47 revertants per cubic meter was found in the QF extracts and more limited activity of up to 11 rev m(-3) in the PUF extracts. Metabolic activation of PUF extracts resulted in an important increase in mutagenic activity, up to 30 rev m(-3), but no such increase was observed for QF extracts. The highest values were observed outside large cities at industrial sites and at a rural site contaminated by pollution from a chemical plant at a distance of 4 km. Also at the background location near the North Sea a significant mutagenic activity was measured in the QF extracts (+S9: 9 rev m(-3); -S9: 7 rev m(-3)). Apparently, there is in Flanders a significant background exposure level to airborne mutagenicity, even in areas with limited or no nearby pollution sources. Based on the concentrations of 10 mutagenic PAHs and supposing additivity of their specific mutagenicities, only a few percent (mean 3%) of the observed indirect mutagenic activity could be explained. This implies that most mutagenic activity originated from other substances that were not identified or measured in our chemical analysis. This underscores the importance of bio-monitoring measurements.

Air Pollutants↗
PubMed2004

Genotoxic and mutagenic activity of environmental air samples in Flanders, Belgium.

Atmospheric pollution is assumed to play a role in the incidence of respiratory diseases and cancers. Airborne particles are able to penetrate deep into the lung and are composed of complex chemical mixtures, including mutagens and carcinogens such as polycyclic aromatic compounds (PACs). The present study reports mutagenic and genotoxic activities associated with ambient air collected near a busy street in Borgerhout, at an industrial site in Hoboken and in Peer, a rural community 70 km east of Antwerp in Flanders, Belgium. Airborne particulates (PM10) and semi-volatile organic compounds were sampled during winter and summer. Samples were collected with a high-volume sampler using quartz filters (QF) and polyurethane foam (PUF) cartridges. The mutagenic and genotoxic activity of the organic extracts was determined using the Salmonella test/standard plate-incorporation assay and the Vitotox assay. Concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) in the extracts were determined by reversed-phase high-performance liquid chromatography (HPLC). The mutagenicity assay, using Salmonella typhimurium strain TA98, demonstrated direct mutagenicity of up to 58 revertants/m3 for the QF extracts and low or no mutagenic activity in the PUF extracts. Metabolic activation of the samples resulted in high indirect mutagenicity for both QF and PUF extracts: up to 96 revertants/m3 were found in QF samples and 62 revertants/m3 in PUF samples. Genotoxic effects of the filter extracts were assessed with the Vitotox assay: some direct genotoxic effects were noted, i.e. without metabolic activation, but almost no effects were observed after metabolic activation. Without activation, most PUF extracts were bacteriotoxic. With metabolic activation this toxicity disappeared, but genotoxic effects were not observed. Statistical analysis showed that the observed biological effects correlated well with the PAH concentrations.

Air Pollutants↗
PubMed2002

Food contamination with polychlorinated biphenyls and dioxins in Belgium. Effects on the body burden.

The core paper of this debate shows that persistent organic pollutant residues of the 12 chemicals targeted for a phase out under the Stockholm Convention are present in almost all categories of food in the US food supply. For dioxins, the study does not use measured data, but is based upon potential dioxin residues in selected food items. Polychlorinated biphenyls are not included in the study. In this paper we discuss selected data of polychlorinated biphenyl and dioxin concentrations in Belgian food. Some of these exposures are chronic, others are attributable to incidents. Both result in high body burdens in Belgium. The paper also compares the current concentrations in food with the recent standards launched by the EU for dioxins in food, and discusses whether these values adequately protect European citizens.

Belgium↗
PubMed1984

A new model for the quantitative analysis of cell movements in vitro: definition of a shape change factor.

Changes in shape, in addition to translocations, are an important aspect of cell motility. We propose a simple geometrical model for the quantitative analysis of shape changes undergone by cultured cells. The extent to which images of a given cell do not overlap at the beginning and end of a time interval is used as a measure of motility, and a translation step included to eliminate translocation effects. Initial findings suggest that the method is widely applicable.

Animals↗
PubMed1983

Effects of dipyridamole (Persantin R) on morphology and motility of mouse embryo cells.

DPD inactivates the edges of cultured mouse embryo cells. Pseudopodal activity is inhibited and spreading is reduced. Concomitantly, the growth rate of the cells is reduced. The interference reflection image shows very large close contacts under DPD treated cells. The translocation speed of the cells is unaffected. DPD penetrates into the cytoplasm, but less or not into the nucleus.

Animals↗
PubMedDate not supplied

Effect of dipyridamole on invasion of five types of malignant cells in organ culture.

Dipyridamole (DPD) has been shown to inhibit the motility of cells in culture. We have tested the effect of DPD on the invasion in confronting organ culture of the following malignant cell lines: mouse MO4 cells; rat NBT II bladder tumor cells; human SA4 glioblastoma cells; mouse LLC H61 lung carcinoma cells; and mouse F87 C1.6T2 melanoma x lymphocyte hybrid cells. At concentrations of 20 micrograms/ml or higher, DPD inhibited the invasion of all cell types into embryonic chick heart. In serum-free culture medium the anti-invasive concentration of DPD was about ten times lower. Anti-invasive concentrations of DPD also inhibited proliferation of the malignant cells. Both inhibition of invasion and of proliferation were reversible.

Actin Cytoskeleton↗
PubMedDate not supplied

Carcinogenesis: mutations and mutagens.

In normal human cells there is a steady accumulation of mutations with time. We argue that the great majority of these mutations arise spontaneously and are due to endogenous factors or processes that damage DNA. A small fraction of these mutations converts a normal cell into a cell that is initiated towards the development of cancer. We propose that, in general, these initiated cells are more susceptible to the mutagenic effects of exogenous carcinogenic agents than to the mutagenic effects of endogenous factors. Indeed, it can be assumed that in most instances the initiation event is due to a mutation which causes inactivation or loss of a mutation avoidance gene, such as the p53 gene, or a gene which is involved in the repair of damaged DNA. Recent studies have shown that most of such mutations lead to a considerable enhancement in the mutagenicity of many exogenous agents, whereas the mutagenicity of endogenous factors is less affected. Furthermore, the progressive accumulation of mutations with increasing age implies that more initiated cells are likely to be found in older individuals. Therefore, sensitivity to the carcinogenic effect of exogenous mutagens can generally be assumed to increase in older people.

Age Factors↗
PubMedDate not supplied

Inhibition of invasion of MCF-7/6 human breast carcinoma cells in vitro by Methanobacterium thermoautotrophicum extract.

Precultured embryonic chick heart fragments were confronted in vitro with various invasive tumor cell lines (MCF-7/6 human breast carcinoma variant, BW-O-LiI mouse T-cell lymphoma cells and MO4 virally transformed fetal mouse carcass cells) and with a non-invasive cell line (MCF-7/AZ human breast carcinoma variant). Confronting cultures were incubated in the presence of various methanogenic cofactors: Methanobacterium thermoautotrophicum extract, coenzyme F420, FO (7,8-didemethyl-8-hydroxy-5-deazariboflavin), F+ (5'-phosphate derivative of FO), or methanopterin. Histological analysis revealed that the Methanobacterium thermoautotrophicum extract inhibits invasion of MCF-7/6 human cells. At the moment it is not known which factor in the extract is responsible for this inhibition.

Breast Neoplasms↗
PubMedDate not supplied

Action mechanisms of anti-invasive agents.

An anti-invasive activity has been observed with a number of agents in confronting cultures between invasive cell populations and embryonic chick heart fragments. Cytochalasins, microtubule inhibitors and dipyridamole act via intracellular targets. Inhibition of glycosylation of proteins, low temperature and alkyl lysophospholipids alter the plasma membrane. Flavonoids aim at extracellular targets. In a unifying hypothesis we postulate that invasion is due to lack of responsiveness to stop signals that normally retain cells within their tissue boundaries. Some of the anti-invasive agents act on cellular activities that are necessary for invasion; others might act on the stop signal, the perception of and/or the response to this signal.

Animals↗