Biomedical subjects

P V Bellier

Publications and source records attributed to P V Bellier.

14 recordsLinked to original sources

PubMed2007

Evaluating the biological effects of intermittent 1.9 GHz pulse-modulated radiofrequency fields in a series of human-derived cell lines.

Several recent studies have suggested that radiofrequency (RF) fields may cause changes in a variety of cellular functions that may eventually lead to potential long-term health effects. In the present study, we have assessed the ability of non-thermal RF-field exposure to affect a variety of biological processes (including apoptosis, cell cycle progression, viability and cytokine production) in a series of human-derived cell lines (TK6, HL60 and Mono-Mac-6). Exponentially growing cells were exposed to intermittent (5 min on, 10 min off) 1.9 GHz pulse-modulated RF fields for 6 h at mean specific absorption rates (SARs) of 0, 1 and 10 W/kg. Concurrent negative (incubator) and positive (heat shock for 1 h at 43 degrees C) controls were included in each experiment. Immediately after the 6-h exposure period and 18 h after exposure, cell pellets were collected and analyzed for cell viability, the incidence of apoptosis, and alterations in cell cycle kinetics. The cell culture supernatants were assessed for the presence of a series of human inflammatory cytokines (TNFA, IL1B, IL6, IL8, IL10, IL12) using a cytometric bead array assay. No detectable changes in cell viability, cell cycle kinetics, incidence of apoptosis, or cytokine expression were observed in any of RF-field-exposed groups in any of the cell lines tested, relative to the sham controls. However, the positive (heat-shock) control samples displayed a significant decrease in cell viability, increase in apoptosis, and alteration in cell cycle kinetics (G(2)/M block). Overall, we found no evidence that non-thermal RF-field exposure could elicit any detectable biological effect in three human-derived cell lines.

Apoptosis↗

PubMed2006

Increased FITC fluorescence on LPS stimulated neutrophils cultured in whole blood.

Recently, it has been observed that Annexin V labelling of phosphatidylserine (PS) on non-apoptotic cells can vary in different leukocyte populations and with the activation of cells, due to differences in the absolute level of exposed PS. We have also observed changes in the absolute level of Annexin V-FITC intensity, but under conditions where absolute PS expression did not change. In the present study, we have explored the effect of neutrophil cell activation on Annexin V-FITC fluorescence intensity by comparing alternatively labelled matched antibodies against Annexin V. Human venous whole blood was cultured with and without stimulation with lipopolysaccharide (LPS). Apoptosis in the neutrophil and lymphocyte populations was analyzed by flow cytometry and the intensity of FITC labelling was compared to matched fluorochromes conjugated to the same cell surface markers. There was an increase in the intensity of Annexin V-FITC in non-apoptotic neutrophils when stimulated with LPS, which did not correlate with increased apoptosis. Furthermore, CD65-FITC intensity also increased on activated neutrophils. Activated neutrophils exhibited higher amounts of FITC fluorescence that were not associated with changes in extracellular PS expression. This effect appears to be fluorochrome related, likely due to an increase in the pH surrounding activated neutrophils.

Adult↗

PubMed2006

Gene expression analysis of a human lymphoblastoma cell line exposed in vitro to an intermittent 1.9 GHz pulse-modulated radiofrequency field.

This study was designed to determine whether radiofrequency (RF) fields of the type used for wireless communications could elicit a cellular stress response. As general indicators of a cellular stress response, we monitored changes in proto-oncogene and heat-shock protein expression. Exponentially growing human lymphoblastoma cells (TK6) were exposed to 1.9 GHz pulse-modulated RF fields at average specific absorption rates (SARs) of 1 and 10 W/kg. Perturbations in the expression levels of the proto-oncogenes FOS, JUN and MYC after exposure to sham and RF fields were assessed by real-time RT-PCR. In addition, the transcript levels of the cellular stress proteins HSP27 and inducible HSP70 were also monitored. We demonstrated that transcript levels of these genes in RF-field-exposed cells showed no significant difference in relation to the sham treatment group. However, concurrent positive (heat-shock) control samples displayed a significant elevation in the expression of HSP27, HSP70, FOS and JUN. Conversely, the levels of MYC mRNA were found to decline in the positive (heat-shock) control. In conclusion, our study found no evidence that the 1.9 GHz RF-field exposure caused a general stress response in TK6 cells under our experimental conditions.

Cell Line, Tumor↗

PubMed2006

Microarray gene expression profiling of a human glioblastoma cell line exposed in vitro to a 1.9 GHz pulse-modulated radiofrequency field.

The widespread use of mobile phones has led to public concerns about the health effects associated with exposure to radiofrequency (RF) fields. The paramount concern of most persons relates to the potential of these fields to cause cancer. Unlike ionizing radiation, RF fields used for mobile telecommunications (800-1900 MHz) do not possess sufficient energy to directly damage DNA. Most rodent bioassay and in vitro genotoxicity/mutation studies have reported that RF fields at non-thermal levels have no direct mutagenic, genotoxic or carcinogenic effects. However, some evidence has suggested that RF fields may cause detectable postexposure changes in gene expression. Therefore, the purpose of this study was to assess the ability of exposure to a 1.9 GHz pulse-modulated RF field for 4 h at specific absorption rates (SARs) of 0.1, 1.0 and 10.0 W/kg to affect global gene expression in U87MG glioblastoma cells. We found no evidence that non-thermal RF fields can affect gene expression in cultured U87MG cells relative to the nonirradiated control groups, whereas exposure to heat shock at 43 degrees C for 1 h up-regulated a number of typical stress-responsive genes in the positive control group. Future studies will assess the effect of RF fields on other cell lines and on gene expression in the mouse brain after in vivo exposure.

Cell Line, Tumor↗

PubMed2005

Effect of pro-inflammatory cytokines on spontaneous apoptosis in leukocyte sub-sets within a whole blood culture.

Pro-inflammatory cytokines are known to affect apoptosis in human peripheral blood cells. Neutrophils, which are an essential component of the immune response and usually undergo apoptosis rapidly, are greatly affected by these cytokines. In this study, the effect of varying concentrations of TNF-alpha, IL-1beta and IL-6 on the apoptotic response of leukocytes and their sub-sets in cultured whole blood were studied over a 48 h culture period. At clinically relevant concentrations, it was found that these pro-inflammatory cytokines reduced the amount of spontaneous apoptosis in neutrophils in culture, but had little effect on the lymphocyte population. Distinct differences in the sensitivity of neutrophils to cytokine-mediated protection against spontaneous apoptosis were apparent when compared to previous studies conducted using purified or enriched neutrophil cultures. IL-1beta, at a dose of 0.01 pg/mL, was observed to significantly inhibit spontaneous neutrophil apoptosis by approximately 90% and 65% at 24 and 48 h of culturing, respectively. This concentration used in whole blood is dramatically lower than that required to elicit similar protection in neutrophil-enriched cell cultures. Higher concentrations of TNF-alpha (1.0 pg/mL) and IL-6 (125 pg/mL) were also found to significantly inhibit neutrophil apoptosis, at levels much lower than previously published using neutrophil-enriched cultures. Furthermore, each cytokine displayed a unique signature with respect to the optimal applied doses required to elicit maximal protection against spontaneous neutrophil apoptosis. These results demonstrate the dramatic differences in cellular responses that exist between neutrophil-enriched cultures and whole blood culture systems, where multiple blood cell types provide a much more complex environment.

Apoptosis↗

PubMed2005

Evaluating DNA damage in rodent brain after acute 60 Hz magnetic-field exposure.

In recent years, numerous studies have reported a weak association between 60 Hz magnetic-field exposure and the incidence of certain cancers. To date, no mechanism to explain these findings has been identified. The objective of the current study was to investigate whether acute magnetic-field exposure could elicit DNA damage within brain cells from both whole brain and cerebellar homogenates from adult rats, adult mice and immature mice. Rodents were exposed to a 60 Hz magnetic field (0, 0.1, 1 or 2 mT) for 2 h. Then, at 0, 2 and 4 h after exposure, animals were killed humanely, their brains were rapidly removed and homogenized, and cells were cast into agarose gels for processing by the alkaline comet assay. Four parameters (tail ratio, tail moment, comet length and tail length) were used to assess DNA damage for each comet. For each species, a significant increase in DNA damage was detected by each of the four parameters in the positive control (2 Gy X rays) relative to the concurrent nonirradiated negative and sham controls. However, none of the four parameters detected a significant increase in DNA damage in brain cell homogenates from any magnetic-field exposure (0- 2 mT) at any time after exposure. The dose-response and time-course data from the multiple animal groups tested in this study provide no evidence of magnetic-field-induced DNA damage.

Aging↗

PubMed2003

No evidence for genotoxic effects from 24 h exposure of human leukocytes to 1.9 GHz radiofrequency fields.

The current study extends our previous investigations of 2-h radiofrequency (RF)-field exposures on genotoxicity in human blood cell cultures by examining the effect of 24-h continuous-wave (CW) and pulsed-wave (PW) 1.9 GHz RF-field exposures on both primary DNA damage and micronucleus induction in human leukocyte cultures. Mean specific absorption rates (SARs) ranged from 0 to 10 W/kg, and the temperature within the cultures was maintained at 37.0 +/- 1.0 degrees C for the duration of the 24-h exposure period. No significant differences in primary DNA damage were observed between the sham-treated controls and any of the CW or PW 1.9 GHz RF-field-exposed cultures when processed immediately after the exposure period by the alkaline comet assay. Similarly, no significant differences were observed in the incidence of micronuclei, incidence of micronucleated binucleated cells, frequency of binucleated cells, or proliferation index between the sham-treated controls and any of the CW or PW 1.9 GHz RF-field-exposed cultures. In conclusion, the current study found no evidence of 1.9 GHz RF-field-induced genotoxicity in human blood cell cultures after a 24-h exposure period.

Adult↗

PubMed2002

Differential apoptotic response to ionizing radiation in subpopulations of human white blood cells.

The purpose of this paper is to characterize the apoptotic response of various subpopulations of human white blood cells after in vitro exposure to ionizing radiation using the modified neutral comet assay (MNCA). White blood cells, isolated from human whole blood, were fractionated into granulocytes and mononuclear cells which were further separated into B-cells, natural killer (NK) cells, and CD4(+) and CD8(+) T-cells. The separated fractions were exposed to low doses of X-rays and then MNCA was used to measure the apoptotic fraction (AF) at different time points in irradiated and unirradiated aliquots of sorted cultures. The spontaneous AF in unirradiated control cells was the most critical determinant of whether an apoptotic response could be detected in irradiated cells. When cultured in isolation granulocytes and B-cells had the highest background AF, with NK cells having the next highest. CD4(+) and CD8(+) T-cells had a low, stable, spontaneous AF which gave them the highest signal-to-noise ratio. Although B-cells demonstrated the highest radiation-induced apoptotic response to 1Gy of X-rays, CD8(+) T-cells were the most radiation-responsive lymphocytes due to their low spontaneous AF. By generating dose response curves for CD4(+) and CD8(+) T-cells, the sensitivity of the MNCA for detecting apoptosis in these two cell types was also examined.

Apoptosis↗

PubMed2002

DNA damage and apoptosis in the immature mouse cerebellum after acute exposure to a 1 mT, 60 Hz magnetic field.

Several recent studies have reported that whole-body exposure of rodents to power frequency magnetic fields (MFs) can result in DNA single- and double-strand breaks in the brains of these animals. The current study was undertaken to investigate whether an acute 2h exposure of a 1 mT, 60 Hz MF could elicit DNA damage, and subsequently apoptosis, in the brains of immature (10-day-old) mice. DNA damage was quantitated at 0, 2, 4, and 24h after exposure using the alkaline comet assay. Apoptosis was quantitated in the external granule cell layer (EGCL) of the immature mouse cerebellum at 0 and 24h after exposure to MF by the TdT-mediated dUTP nick-end labeling (TUNEL) assay. Four parameters (tail ratio, tail moment, comet length and tail length) were used to assess DNA damage for each comet. While increased DNA damage was detected by tail ratio at 2h after MF exposure, no supporting evidence of increased DNA damage was detected by the other parameters. In addition, no similar differences were observed using these parameters at any of the other post-exposure times. No increase in apoptosis was observed in the EGCL of MF-exposed mice, when compared to sham mice. Taken together, these results do not support the hypothesis that acute MF exposure causes DNA damage in the cerebellums of immature mice.

Animals↗

PubMed2002

Cylindrical waveguide applicator for in vitro exposure of cell culture samples to 1.9-GHz radiofrequency fields.

An applicator for in vitro cell culture exposure was developed based on a circularly polarized, cylindrical waveguide for the 1.9-GHz frequency band used by Personal Communications Services (PCS) in Canada. The applicator consists of two coaxial Petri dishes that sit on the open end of the cylindrical waveguide. The inner 60-mm Petri dish contains the cell culture while the outer 150-mm dish contains coolant water, which is circulated from a pump. A dosimetric evaluation was made using thermometric and E-field probe techniques. The latter allowed the entire inner dish to be scanned to determine the range of specific absorption rates (SARs) pertinent to the expected position of the cells. A representative SAR rate (SAR per unit of input power) of 8.6 +/- 2.1 W/kg/W (95th percentile) was determined 1 mm from the bottom, for a 10 ml sample volume of standard medium. Evaluation of the cooling system demonstrated that following an initial 0.3 degrees C temperature increase, a constant temperature was maintained for 24 h when the waveguide was energized to achieve an average sample SAR of 10 W/kg. These properties enable both acute and sub-acute in vitro bio-effect studies to be performed on a variety of cell culture samples.

Blood↗

PubMed2002

DNA damage and micronucleus induction in human leukocytes after acute in vitro exposure to a 1.9 GHz continuous-wave radiofrequency field.

Human blood cultures were exposed to a 1.9 GHz continuous-wave (CW) radiofrequency (RF) field for 2 h using a series of six circularly polarized, cylindrical waveguides. Mean specific absorption rates (SARs) of 0.0, 0.1, 0.26, 0.92, 2.4 and 10 W/kg were achieved, and the temperature within the cultures during a 2-h exposure was maintained at 37.0 +/- 0.5 degrees C. Concurrent negative (incubator) and positive (1.5 Gy (137)Cs gamma radiation) control cultures were run for each experiment. DNA damage was quantified immediately after RF-field exposure using the alkaline comet assay, and four parameters (tail ratio, tail moment, comet length and tail length) were used to assess DNA damage for each comet. No evidence of increased primary DNA damage was detected by any parameter for RF-field-exposed cultures at any SAR tested. The formation of micronuclei in the RF-field-exposed blood cell cultures was assessed using the cytokinesis-block micronucleus assay. There was no significant difference in the binucleated cell frequency, incidence of micronucleated binucleated cells, or total incidence of micronuclei between any of the RF-field-exposed cultures and the sham-exposed controls at any SAR tested. These results do not support the hypothesis that acute, nonthermalizing 1.9 GHz CW RF-field exposure causes DNA damage in cultured human leukocytes.

Adult↗

PubMed2002

DNA damage in human leukocytes after acute in vitro exposure to a 1.9 GHz pulse-modulated radiofrequency field.

Blood cultures from human volunteers were exposed to an acute 1.9 GHz pulse-modulated radiofrequency (RF) field for 2 h using a series of six circularly polarized, cylindrical waveguides. Mean specific absorption rates (SARs) ranged from 0 to 10 W/kg, and the temperature within the cultures during the exposure was maintained at 37.0 +/- 0.5 degrees C. DNA damage was quantified in leukocytes by the alkaline comet assay and the cytokinesis-block micronucleus assay. When compared to the sham-treated controls, no evidence of increased primary DNA damage was detected by any parameter for any of the RF-field-exposed cultures when evaluated using the alkaline comet assay. Furthermore, no significant differences in the frequency of binucleated cells, incidence of micronucleated binucleated cells, or total incidence of micronuclei were detected between any of the RF-field-exposed cultures and the sham-treated control at any SAR tested. These results do not support the hypothesis that acute, nonthermalizing 1.9 GHz pulse-modulated RF-field exposure causes DNA damage in cultured human leukocytes.

Cells, Cultured↗

PubMed2001

Differential rates of cytokine production and apoptosis in venipuncture and finger-stab derived blood cultures.

The collection of finger-stab (FS) blood is a convenient and non-invasive method of rapidly acquiring human blood and is becoming increasingly popular for use in human biomonitoring studies. This study compared whole blood (WB) and peripheral blood mononuclear cell (PBMC) cultures derived from venipuncture (VP) and FS blood, to determine whether they respond similarly under culture conditions. The rates of spontaneous- and radiation-induced apoptosis and pro-inflammatory cytokine production were monitored over 72 h in each of four culture conditions. In non-irradiated WB cultures, the spontaneous rate of apoptosis was significantly lower in cultures from FS-derived blood than from VP-derived blood. However, FS- and VP-derived cultures responded similarly to radiation-induced apoptosis. PBMC cultures, regardless of the source, were the most responsive to radiation. When the levels of pro-inflammatory cytokines were measured, a significant time-dependent increase in TNF-alpha, IL-6 and IL-1beta production was observed in FS-derived cultures, but not in VP-derived cultures. While VP and FS blood cultures were found to respond similarly to radiation-induced apoptosis, there was a significant difference in the rate of spontaneous apoptosis in non-irradiated WB cultures and in the in situ production of pro-inflammatory cytokines between VP- and FS-derived blood cultures.

Apoptosis↗

PubMed2000

Comet assay: rapid processing of multiple samples.

The present study describes modifications to the basic comet protocol that increase productivity and efficiency without sacrificing assay reliability. A simple technique is described for rapidly preparing up to 96 comet assay samples simultaneously. The sample preparation technique allows thin layers of agarose-embedded cells to be prepared in multiple wells attached to a flexible film of Gelbond, which improves the ease of manipulating and processing samples. To evaluate the effect of these modifications on assay sensitivity, dose-response curves are presented for DNA damage induced by exposure of TK6 cells to low concentrations of hydrogen peroxide (0-10 microM) and for exposure of human lymphocytes to X-irradiation (0-100 cGy). The limit of detection of DNA damage induced by hydrogen peroxide in TK6 cells was observed to be 1 uM for all parameters (tail ratio, tail moment, tail length and comet length) while the limit of detection of DNA damage in human lymphocytes was 10 cGy for tail and comet length parameters, but 50 cGy for tail ratio and tail moment parameters. These results are similar to those previously reported using the conventional alkaline comet assay. The application of SYBR Gold for detection of DNA damage was compared to that of propidium iodide. Measurements of matching samples for tail length and comet length were similar using both stains. However, comets stained with SYBR Gold persisted longer and were much brighter than those obtained with propidium iodide. SYBR Gold was found to be ideal for measuring tail length and comet length but, under present assay conditions, impractical for measuring tail ratio or tail moment due to saturation of staining in the head region of the comets.

Cell Line↗