Biomedical subjects

C Simoneau

Publications and source records attributed to C Simoneau.

At least 19 recordsLinked to original sources

PubMed2006

Solid-phase microextraction method for the determination of hexanal in hazelnuts as an indicator of the interaction of active packaging materials with food aroma compounds.

Fatty foods are susceptible to lipid oxidation resulting in deterioration of product quality due to the generation of off-flavours. Hexanal is a good indicator of rancidity. Therefore, a method based on solid-phase microextraction (SPME) coupled to gas chromatograph with flame ionization detection was developed to determine hexanal formation in hazelnuts during storage. Optimum conditions were as follows: carboxen-polydimethylsiloxane 75 microm fibre, extraction time 10 min, equilibrium time 10 min and equilibrium temperature 60 degrees C. The effect of oxygen scavengers on the oxidation process was also evaluated by measuring hexanal formation in hazelnuts stored with/without oxygen absorber sachets. Oxygen scavengers were shown to reduce oxidation; however, analysis of the sachet revealed that other volatile compounds from the headspace were also absorbed.

Aldehydes↗

PubMed2003

Evaluation of some screening methods for the analysis of contaminants in recycled polyethylene terephthalate flakes.

A range of different analytical techniques were used to test recycled polyethylene terephthalate (PET) flakes for potential chemical contaminants. The techniques used were headspace gas chromatography coupled to mass spectrometry (GC-MS), liquid extraction followed by GC-MS, supercritical-fluid extraction followed by GC-MS, and migration testing followed by elemental analysis using inductively coupled plasma mass spectroscopy (ICP-MS). The PET samples were 50 representative samples taken from 600 that had been collected throughout Europe and which had been screened for potential contaminants using a single technique of high-temperature GC-MS. Six of the 50 samples tested had been spiked with a selection of model contaminants, three samples were virgin PET flakes and two of the samples were from supercleaning processes. All samples were analysed 'blind' in this exercise. The qualitative results showed that most of the contaminants came from the first use, being flavour-aroma compounds from soft drinks. The quantitative analysis found concentrations under a few mg kg(-1) in the polymer, except for the spiked samples. Element migrations were low and only calcium, silicon and sodium had median migrations above 50 microg l(-1). This in-depth analysis of recycled PET flakes did not identify any significant contaminants that had not already been detected by the high-temperature static GC-MS screening method, thus demonstrating its utility.

Beverages↗

PubMed2003

European survey of contamination of homogenized baby food by epoxidized soybean oil migration from plasticized PVC gaskets.

The results are reported of a European survey of the contamination of baby food with epoxidized soyabean oil (ESBO). Fat from the sample was extracted, transmethylated and derivatized for analysis by gas chromatography/mass spectrometry (GC/MS). Analysis was carried out of 248 samples of various types of foodstuffs from the 15 European Union Member States as well as Switzerland. ESBO was found in 95 of 248 samples analysed at levels from 1.5 to 135.2 mg kg(-1). The highest concentrations were found in main dish mixed foods such as vegetables and meat or carbohydrate- and vegetable-based mixes. Levels exceeded 30 mg kg(-1) in 15% of the samples, and 4% exceeded the overall migration limit fixed for plastics in the European Union of 60 mg kg(-1). This level of contamination is significant, confirming results from previous surveys and indicating a risk for the tolerable daily intake to be exceeded. These results suggest that an emphasis must be placed for more systematic research with a focus on the parameters for migration.

Dietary Carbohydrates↗

PubMed2002

Creation of on-line solutions in support of the dissemination of legislative and analytical information on food-contact materials.

To facilitate access to European Commission (EC) documentation and provide a public service resource of relevant information an Internet site dedicated to food-contact materials was created (http://cpf.jrc.it/webpack/) in 1998. The site contains legislative information in downloadable format, information on contacts for authorities and organizations in the field of food-contact materials, as well as information on methods for overall and specific migration. A satellite site (http://cpf.jrc.it/smt/) is dedicated to physicochemical and spectral information (FT-IR, GC-MS, NMR) as well as analytical methods on an increasing number of regulated substances. Many of these, as well as substances submitted for evaluation, are held in a centralized databank at the JRC in Ispra and aliquots can be made available to the public upon request. The site also recently expanded to provide an incentive for analytical networking between institutions by including information pages on current EC-funded and national projects and conference announcements.

Databases, Factual↗

PubMed2002

Time-temperature study of the kinetics of migration of BADGE (bisphenol-A-diglycidyl-ether) into a fatty medium.

The migration kinetics of bisphenol-A-diglycidyl-ether (BADGE) from processed and non-processed model cans into vegetable oil was investigated as a function of the process treatment and the temperature of storage. Cans were either not heat-treated at all or were processed at 115 degrees C for 30 min or for 1 h after filling with oil. Each series of experiments comprised 30 samples and was further divided into three groups to be stored at different temperatures (20, 40 and 60 degrees C). Aliquots from the samples were taken at regular intervals for > 1 year. Samples were analysed for BADGE by high-performance liquid chromatography with fluorescence detection. The results showed that temperature processing had the largest effect on migration of BADGE. Storage temperature also significantly influenced migration from non-processed cans, in particular at higher storage temperatures such as 60 degrees C. Some samples were Subjected to 60 degrees C storage after an initial period at 20 degrees C and an effect on migration was also noted, although to a much lesser extent than from processing. The results of migration at higher temperatures were also correlated to the potential degradation of BADGE from oxidation products.

Benzhydryl Compounds↗

PubMed2000

Occurrence of bisphenol-F-diglycidyl ether (BFDGE) in fish canned in oil.

The levels of bisphenol-F-diglycidyl ether (BFDGE) were quantified as part of a European survey on the migration of residues of epoxy resins into oil from canned fish. The contents of BFDGE in cans, lids and fish collected from all 15 Member States of the European Union and Switzerland were analysed in 382 samples. Cans and lids were separately extracted with acetonitrile. The extraction from fish was carried out with hexane followed by re-extraction with acetonitrile. The analysis was performed by reverse phase HPLC with fluorescence detection. BFDGE could be detected in 12% of the fish, 24% of the cans and 18% of the lids. Only 3% of the fish contained BFDGE in concentrations considerably above 1 mg/kg. In addition to the presented data, a comparison was made with the levels of BADGE (bisphenol-A-diglycidyl ether) analysed in the same products in the context of a previous study.

Animals↗

PubMed2000

An Internet compendium of analytical methods and spectroscopic information for monomers and additives used in food packaging plastics.

An internet website (http:¿cpf.jrc.it/smt/) has been produced as a means of dissemination of methods of analysis and supporting spectroscopic information on monomers and additives used for food contact materials (principally packaging). The site which is aimed primarily at assisting food control laboratories in the European Union contains analytical information on monomers, starting substances and additives used in the manufacture of plastics materials. A searchable index is provided giving PM and CAS numbers for each of 255 substances. For each substance a data sheet gives regulatory information, chemical structures, physico-chemical information and background information on the use of the substance in particular plastics, and the food packaging applications. For monomers and starting substances (155 compounds) the infra-red and mass spectra are provided, and for additives (100 compounds); additionally proton NMR are available for about 50% of the entries. Where analytical methods have been developed for determining these substances as residual amounts in plastics or as trace amounts in food simulants these methods are also on the website. All information is provided in portable document file (PDF) format which means that high quality copies can be readily printed, using freely available Adobe Acrobat Reader software. The website will in future be maintained and up-dated by the European Commission's Joint Research Centre (JRC) as new substances are authorized for use by the European Commission (DG-ENTR formerly DGIII). Where analytical laboratories (food control or other) require reference substances these can be obtained free-of-charge from a reference collection housed at the JRC and maintained in conjunction with this website compendium.

Data Display↗

PubMed1999

Estimation of intake of bisphenol-A-diglycidyl-ether (BADGE) from canned fish consumption in Europe and migration survey.

The exposure to bisphenol-A-diglycidyl-ether (BADGE) from canned fish in oil was assessed from consumption data collected for each Member State of the European Union and Switzerland, and migration data from a European survey on 382 samples. Trade figures were used when no consumption data were available. The average consumption of canned fish in Europe was 2.3 kg per person per year, with values ranging from 0.2 kg per person per year in the United Kingdom to 5.1 kg per person per year in Denmark. The exposure to BADGE was calculated as microgram per person per day. The data indicated that exposure to BADGE was in the range below 4 mg per person per year, i.e. 9 micrograms per person per day, hence a fairly low exposure in part due to the fact that canned fish is a relatively minor dietary item. An approximation assuming the general figure of a 60 kg adult, would thus be 0.15 microgram/kg body weight per day. This is a fairly limited exposure considering the provisional limit in food had been set a 1 mg/kg and assumed 1 kg of food ingested. In countries for which increased exposure was found, the reason was mainly caused by one individual sample exhibiting a high concentration rather than a larger number of samples with mildly elevated concentrations.

Animals↗

PubMed1999

Monitoring of bisphenol-A-diglycidyl-ether (BADGE) in canned fish in oil.

A survey at the European levels was initiated on the quantification of bisphenol-A-diglycidyl-ether (BADGE) in canned fish in oil in order to assess the exposure of BADGE. A total of 382 canned fish sample were collected from all 15 Member States and Switzerland and analysed for BADGE in fish. The fish was extracted first with hexane and reextracted with acetonitrile, followed by a membrane filtration and reverse phase HPLC analysis with fluorescence detection. The analysis of the fish showed that about 3% of the samples contained BADGE at a level above 1 mg/kg. The samples exceeding the limit by a larger margin were mostly from anchovy cans and cans manufactured in 1991-1995.

Animals↗

PubMed1999

Stability testing of selected plastics additives for food contact in EU aqueous, fatty and alternative simulants.

Within the framework of the AIR3-CT94-2360 EU-project, the stability of three plastics additives in three EU aqueous and fatty food simulants and in two alternative simulants was studied under various time-temperature conditions. The additives tested were bis(2-ethylhexyl) adipate (DEHA), bis(2-ethylhexyl) phthalate (DEHP) and octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl) propionate (Irganox 1076). The various test conditions included exposures of 10 days at 40 degrees C, 1 h at reflux temperature for all aqueous simulants, 10 days at 40 degrees C and 1 h 175 degrees C for the olive oil and 2 days at 20 degrees C and 3 h at 60 degrees C for the isooctane simulant. Following the exposure, the additive samples were extracted from aqueous simulants with hexane. A sonication step was necessary to ensure maximum extraction of control samples. In the case of the isooctane simulant, the samples were analyzed directly from the simulant. The oil samples were extracted by acetonitrile. The extracts of samples exposed to various heat conditions as well as unexposed spiked controls and blanks were analysed by gas chromatography (GC) on a non-polar (5%--phenyl)-methylpolysiloxane capillary column with high temperature capabilities. The results showed that DEHA, DEHP and Irganox 1076 were stable at 40 degrees C and at reflux temperature in ethanolic or acidic aqueous simulants. The various additives were also stable in the organic isooctane simulant as well as in the fatty simulant olive oil. Studies on the stability of such additives used in food packaging are designed for regulatory purposes as an aid to decide whether the legislation should regulate limits for plasticizers based on a quantity in the food packaging itself or based on an ingested dose by the consumer.

Chromatography, Gas↗

PubMed1996

Effects of halothane and isoflurane on bradykinin-evoked Ca2+ influx inbovine aortic endothelial cells.

BACKGROUND: Volatile anesthetics, such as halothane and isoflurane, have been reported to affect the endothelium mediated relaxation of vascular smooth muscle cells. Because the activity of the constitutive nitric oxide synthase in endothelial cells depends on the availability of intracellular Ca2+, there is a definite possibility that the observed inhibitory effect of volatile anesthetics involves an action on the agonist-evoked internal Ca2+ mobilization and/or Ca2+ influx in these cells. Therefore, a study was undertaken to determine how halothane and isoflurane affect the Ca2+ signalling process in vascular endothelial cells. METHODS: The effect of halothane and isoflurane on the Ca2+ response to bradykinin of bovine aortic endothelial (BAE) cells was investigated using the fluorescent Ca2+ indicator fura-2. Halothane or isoflurane was applied either to resting cells or after bradykinin stimulation. The agonist-evoked Ca2+ influx in BAE cells was estimated by measuring either the rate of fura-2 quenching induced by Mn2+ or the increase in cytosolic Ca2+ concentration initiated after readmission of external Ca2+ after a brief exposure of the cells to a Ca(2+)-free external medium. The effects of halothane on cell potential and intracellular Ca2+ concentration were measured in cell-attached patch-clamp experiments in which a calcium-activated K+ channel and an inward rectifying Ca(2+)-independent K+ channel were used as probes to simultaneously monitor the intracellular Ca2+ concentration and the cell transmembrane potential. In addition, combined fura-2 and patch-clamp cell-attached recordings were carried out, to correlate the variations in internal Ca2+ caused by halothane and the activity of the Ca(2+)-dependent K+ channels, which are known in BAE cells to regulate intracellular potential. Finally, a direct action of halothane and isoflurane on the gating properties of the Ca(2+)-activated K+ channel present in these cells was investigated in patch-excised inside-out experiments. RESULTS: The results of the current study indicate that the initial Ca2+ increase in response to bradykinin stimulation is not affected by halothane, but that pulse applications of halothane (0.4-2 mM) or isoflurane (0.5-1 mM) reversibly reduce the sustained cytosolic Ca2+ increase initiated either by bradykinin or by the Ca2+ pump inhibitor thapsigargin. In addition, halothane appeared to dose-dependently inhibit the Ca2+ influx evoked by bradykinin, and to cause, concomitant to a decrease in cytosolic Ca2+ concentration, a depolarization of the cell potential. Halothane failed, however, to affect internal Ca2+ concentration in thapsigargin-treated endothelial cells, which were depolarized using a high K+ external solution. Finally, halothane and isoflurane decreased the open probability of the Ca(2+)-dependent K+ channel present in these cells. CONCLUSIONS: These observations suggest that the effects of halothane and isoflurane on Ca2+ homeostasis in BAE cells reflect, for the most part, a reduction of the thapsigargin- or bradykinin-evoked Ca2+ influx, which would be consequent to a cellular depolarization caused by an inhibition of the Ca(2+)-dependent K+ channel activity initiated after cell stimulation.

Anesthetics, Inhalation↗

PubMed1995

Measurement of mevalonic acid in human urine by bench top gas chromatography-mass spectrometry.

Urinary excretion of mevalonate was reported to be correlated with endogenous cholesterol biosynthesis. A method is described whereby mevalonate (MVA) concentration in urine is determined by bench top gas chromatography-mass spectrometry after extraction as mevalonalactone (MVL) and conversion to mevalonolactone mono-TMS derivative. Within- and between-assay coefficients of variation were 4.02% and 8%, respectively. The mean concentration of MVA in 24-h urine collections from ten normolipidemic urinary subjects was 203 +/- 49.6 ng/ml (range: 44-576 ng/ml). Administration of 40 mg of Pravastatin (an HMG-CoA reductase inhibitor) significantly decreased (approximately 50%) the night concentration of MVA in five healthy volunteers. This assay could be useful for investigation of endogenous cholesterol synthesis rate in various dyslipidemias and in response to drug treatment.

Adult↗

PubMed1995

Effect of acetate and propionate on fasting hepatic glucose production in humans.

OBJECTIVE: Short chain fatty acids (SCFA, e.g. acetate and propionate) produced from bacterial colonic fermentation may be involved in the improvement of fasting glucose concentration observed with high dietary fibre diets. Because fasting blood glucose is related to hepatic glucose production, we have tested the effect of propionate and acetate on hepatic glucose production. SETTING: The study was carried out in the Clinical Research Center for Human Nutrition. SUBJECTS: Six healthy young volunteers. INTERVENTIONS: The subjects received, in a random order: acetate (12 mmol/h), or propionate (4 mmol/h), or acetate+propionate (12 mmol/h + 4 mmol/h), or an isotonic sodium salt solution (saline) in 3 h gastric infusions. Blood glucose and plasma insulin was monitored. Hepatic glucose production was measured with an isotopic method using [6,6-2H2] glucose. RESULTS: No changes were observed in blood glucose, plasma insulin concentrations or hepatic glucose production with any of the infused solutions. An increase in free fatty acid (FFA) plasma concentration related to the fasting state was observed with the saline solution, but not with the SCFA infusions (P < 0.05). There was also an increase in beta-hydroxybutyrate concentration with the saline and the acetate solutions, but not with the propionate or acetate+propionate solutions. CONCLUSIONS: SCFA, administered at a rate calculated on the basis of a continuous daily fermentation of 30 g dietary fibres, do not change hepatic glucose production or fasting blood glucose. Propionate and acetate decrease plasma FFA, and further studies are needed to explore this effect on glucose tolerance and insulin sensitivity.

Acetates↗

PubMed1994

Measurement of whole body acetate turnover in healthy subjects with stable isotopes.

Colonic fermentation of dietary fibres produces short-chain fatty acids (e.g. acetate, propionate). Measurements of whole body acetate turnover was used in order to estimate the production of colonic short-chain fatty acids in human subjects. However, higher flux rates for acetate have been reported in human studies with stable isotopes as compared to radioactive tracers. The reasons for this discrepancy are unclear. In this study, the stable isotope (1-13C)acetate was used and a method was developed to measure its enrichment in plasma. Variations between and within assays were less than 5%. The standard curve was linear from 0.5% to 10% enrichment. When this tracer was infused for 160 min in six healthy volunteers, acetate turnover was found to be 7.5 +/- 1 mumol kg-1 min-1, which is similar to data reported with radioactive tracers. We assumed that the higher flux rate previously observed with stable isotope tracers was related to differences in the physiological status of the subjects involved in these studies.

Acetates↗

PubMed1990

Single-channel and Fura-2 analysis of internal Ca2+ oscillations in HeLa cells: contribution of the receptor-evoked Ca2+ influx and effect of internal pH.

Patch-clamp and Fura-2 experiments were performed in order to investigate the calcium oscillations due to H1 receptor stimulation in HeLa cells. The cytosolic calcium fluctuations occurring directly at the plasma membrane inner face were detected by measuring the activity of calcium-dependent potassium channels. This method also allowed measurement of changes in intracellular potential using as indicator the amplitude of the channel current jump. The average internal calcium concentration was obtained from Fura-2 experiments carried out at either the single-cell level or from a small population of cells in monolayer. The results indicate that the internal calcium oscillations in HeLa cells arise from a biphasic process with an initial phase independent of the presence of external calcium. External calcium was found, however, to become essential once the regular oscillatory process has been established. Removing external calcium after this initial phase produced a rapid decay in the burst frequency and eventually a complete abolition of the oscillations. In addition, the calcium oscillations occurring during the external-calcium-dependent phase could be blocked by calcium entry blockers such as Co2+ or La3+, or abolished by perfusing the external medium with a high-K+ solution. Experiments were also performed in which the cell internal pH (pHi) was changed by removing the external bicarbonate or by adding NH4Cl to the bathing solution. The results obtained under these conditions indicate that an increase in internal pH abolishes selectively the appearance of calcium spikes without increasing the basal calcium level, while a cellular acidification maintains or stimulates the calcium oscillatory process. It was also observed that the inhibitory effect of alkaline pH was independent of external calcium, and that calcium oscillations could always be seen at alkaline pH during the initial phase of histamine stimulation. On the basis of these results, it is proposed that the internal calcium oscillations in HeLa cells depend on the release of calcium from internal pools, which are reloaded via a pH-dependent mechanism. Part of the calcium sequestration occurring during the oscillatory process would be carried out, however, by pH-insensitive calcium compartments.

Benzofurans↗

PubMed1988

External ATP triggers a biphasic activation process of a calcium-dependent K+ channel in cultured bovine aortic endothelial cells.

We have used the patch-clamp method in order to investigate the single-channel events underlying the effect of external ATP on the potassium permeability of bovine aortic endothelial cells (BAE). The results obtained from cell-attached and inside-out experiments led first to conclude that BAE cells possess an inward rectifying potassium channel activated by internal calcium at micromolar concentrations. The channel conductance for inward currents was estimated at 40 pS in symmetrical 200 mM KCl and the open-channel probability was found to be voltage insensitive within the membrane voltage range -50 to -100 mV. Based on results obtained in the cell-attached configuration, it could next be established that external ATP and ADP at micromolar concentrations could trigger, via the stimulation of P2 purinergic receptors, a time variable activation process of the observed calcium-dependent potassium channel. This activation process was found to occur in a biphasic manner with an initial phase independent of the presence of calcium in the cell bathing medium. The second phase which could be blocked by calcium channel blockers such as Co2+ or La3+ required, however, the presence of external calcium and could be abolished by depolarizing the cells using high K+ external solutions. Another important aspect related to this phenomenon was the observation that removing ATP from the external medium during the second phase led to a complete abolition of the associated calcium-dependent potassium channel activation process. It is suggested from these results that the action of ATP on the potassium permeability of BAE cells is related to a second messenger mediated release of calcium from internal calcium stores coupled to an ATP-dependent calcium influx abolished at depolarizing voltages.

Adenosine Triphosphate↗

PubMed1988

Effects of litter size and light regimen imposed during lactation on ovarian follicular population at weaning in third-parity sows.

Sixteen third-parity sows maintained under two photoperiod treatments (16 h light: 8 h dark [16 h] or 4 h light: 20 h dark [4 h]) were assigned to be unilaterally ovariectomized (left ovary) at weaning on d 28 after farrowing a small litter (12 or fewer piglets; S) or a large litter (more than 12 piglets; L). Antral follicles were classified as atretic or nonatretic and divided into six size classes. The right ovary was obtained at slaughter, 16 d after estrus was detected. Number of antral follicles in the left ovary was greater (P less than .05) for L sows (540) than for S sows (427). Sows exposed to 16 h of light with large litters had a higher number of atretic follicles than all other groups (litter size x photoperiod interaction, P less than .05). Number of nonatretic follicles were similar between groups. However, when nonatretic follicles were classed by size (1 = smallest; 6 = largest), their distribution differed. In Class 1, L sows had more follicles than S sows (P less than .05). For Classes 3 and 4, photoperiod interacted with litter size to decrease the number of follicles in L 16 h sows (litter size x photoperiod interaction, P less than .05). These lower numbers of nonatretic follicles were related to a higher rate of follicular atresia in L 16 h sows. In Classes 2, 3 and 4, L 16 h sows had more atretic follicles than any other group (litter size x photoperiod interaction, P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1987

Oscillatory activation of calcium-dependent potassium channels in HeLa cells induced by histamine H1 receptor stimulation: a single-channel study.

We have used the patch-clamp method (O.P. Hamill et al., Pfluegers Arch., 391:85-100, 1981) in order to investigate the activation pattern of a calcium-dependent potassium channel following H1 receptor stimulation in HeLa cells. Our results essentially indicate that the stimulation of H1 receptors by exogenous histamine at concentrations greater than 1 microM induces an oscillatory activation pattern of calcium-dependent potassium channels characterized by the occurrence of channel current bursts separated by long silent periods. It was also found that the occurrence of these bursts could be directly correlated with transmembrane potential oscillations, the latter being the resulting effect of the calcium-dependent potassium channel synchronous openings. In addition, the cyclic activation of the calcium-dependent potassium channels could be initiated by the addition of histamine to a calcium-free external medium, indicating that the stimulation of the H1 receptors in HeLa cells is mainly related to the release of calcium from internal stores. Finally, the membrane-permeable cyclic AMP analog dibutyryl cyclic AMP was found to be ineffective in initiating single-channel events such as those triggered by exogenous histamine. It is proposed that the oscillatory activation of the calcium-dependent potassium channels in HeLa cells results from a repetitive transient increase in cytosolic free calcium concentration consequent to the H1 receptor stimulation.

Adenylyl Cyclases↗