ABSTRACT Following the detection of formaldehyde in cultivated mushrooms, an evaluation was carri... more ABSTRACT Following the detection of formaldehyde in cultivated mushrooms, an evaluation was carried out to assess whether its presence in food poses a risk to public health. Formaldehyde, a carcinogenic chemical, has a broad range of industrial applications and, hence, exposure to formaldehyde is ubiquitous through diverse consumer goods, food, the air, etc. The observed levels of formaldehyde in mushrooms are lower than the levels reported for vegetables, fruit, meat, fish and dairy products. On the basis of available data, a rough estimate of the dietary exposure to formaldehyde was performed. The exposure through the consumption of cultivated mushrooms (approximately 0.19 µg kg body weight day on average, consumers only) appeared to be small compared with the total dietary intake of formaldehyde (approximately 99.0 µg kg body weight day, total population). Based on comparison with toxicological safety limits for chronic exposure and given that formaldehyde is carcinogenic only through inhalation and not by ingestion, it can be concluded that the dietary exposure to formaldehyde is not a cause for concern.
Objective: Norpropoxyphene (NP) is a major metabolite of propoxyphene (P), a relatively weak m-op... more Objective: Norpropoxyphene (NP) is a major metabolite of propoxyphene (P), a relatively weak m-opioid receptor agonist. Toxic blood concentrations ranging from 3 to 180 mmol / l have been reported and the accumulation of NP in cardiac tissue leads to naloxone-insensitive cardiotoxicity. Since several lines of evidence suggest that not only block of I but also I block may contribute
... After spraying, the plates were heated at 100 "C in an oven for 5 min. Simmondsin an... more ... After spraying, the plates were heated at 100 "C in an oven for 5 min. Simmondsin and analogous compounds showed as violet spots. HPLC. ... The structure was solved by direct methods and refined using the NRCVAX system (Gabe et al., 1989). ...
ABSTRACT A method was developed for the isolation and identification of phytosterols and fatty al... more ABSTRACT A method was developed for the isolation and identification of phytosterols and fatty alcohols in jojoba oil. The method consists in the separation of these compounds from wax esters in the oil by means of an aluminum oxide column followed by further fractionation of the minor components by column chromatography on silica gel. The 4-demethylsterols, 4-methylsterols, triterpene alcohols (4,4-dimethylsterols), and fatty alcohols are identified by means of their gas chromatographic and mass spectrometric data. The present paper includes a method for the quantitation of the free sterols in jojoba oil. Keywords: Plant; alcohol; sterol; lipid; Simmondsia
... Samples were injected into a Rheodyne injector (Model 7125) (Berkeley, CA) supplied with a 20... more ... Samples were injected into a Rheodyne injector (Model 7125) (Berkeley, CA) supplied with a 20-pL injector loop. A stainless steel Cla (7-pm particle size) column was used (25 cm X 0.4-cm id) (E. Merck, Darmstadt, Germany). ...
A gas chromatographic procedure for the determination of carboxyhaemoglobin in blood was improved... more A gas chromatographic procedure for the determination of carboxyhaemoglobin in blood was improved by using a capillary system in combination with a micro thermal conductivity detector. This system is very sensitive with high resolutions. The analytical time is reduced to approximately two minutes. Using sulphuric acid as the liberating agent of carbon monoxide, a gradual and reproducible release of carbon monoxide was seen. This shortens the time in emergency cases for sample preparation.
A survey was conducted to check the toxicological impact of ethylene glycol present in a thermal ... more A survey was conducted to check the toxicological impact of ethylene glycol present in a thermal decomposition mixture of type C hydraulic fluid on laboratory animals submitted to an inhalation test. The target organs, i.e. kidneys, of exposed rats were evaluated histologically and oxalic acid--the ethylene glycol metabolite thought to cause renal failure--was quantified in urine samples. The results show that the low ethylene glycol concentrations present in the inhalation chamber produce only a temporarily increased oxalic acid excretion, at levels that are not significant. These findings are supported by the histological evaluation of the kidneys showing no calcium oxalate deposits or other abnormalities.
Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion s... more Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion species occurring in southern Africa which can cause severe envenoming among people. In contrast to many other genera, no data is available on the venom composition of scorpions belonging to the genus Parabuthus. Here we have investigated the components which may contribute to the venomous potential. The constancy of venom composition within each of the three species and between the three species was investigated by means of gel filtration chromatography. The venoms of the three species each were characterized by a constant and typical elution pattern, resulting in a 'gel filtration fingerprint' which allows distinction between each species. It appears that certain components in the venoms are common to either all three species, or to two of the three species. This points to a clear interspecies relationship within the genus. We also describe the isolation and characterization of some of the polypeptide toxins present in the venoms of P. villosus, P. transvaalicus and P. granulatus by means of reversed phase chromatography and screening of the toxic components on voltage-activated potassium and sodium channels. Our results confirm that toxins which inhibit potassium channels and alter sodium channel gating are present in the venoms studied.
The development of a specific and sensitive radioimmunoassay for the detection of N-desmethylzopi... more The development of a specific and sensitive radioimmunoassay for the detection of N-desmethylzopiclone in urine samples is described. The assay will be used to pre-screen for N-desmethylzopiclone as an indication of zopiclone intake in a forensic and emergency context. N-Hemisuccinyldesmethylzopiclone has been prepared as a hapten. The immunization of rabbits with the hapten-bovine serum albumin conjugate resulted in the production of highly specific antibodies, showing no significant cross-reactivities with existing drugs. The four-parameter logistic model was used to process the calibration data into a fitting curve (r2 = 0.9979). Intra- and inter-assay relative standard deviations were < 9.1 and < 19.1%, respectively. The minimum detectable dose of the immunoassay was calculated to be 0.1 ng ml-1 (Pooled-variance t-distribution, p = 0.01, degrees of freedom = 14).
Neurotoxins have highly specific actions on molecular targets, and thus offer an effective means ... more Neurotoxins have highly specific actions on molecular targets, and thus offer an effective means of characterizing the growing number of identified ion channels and receptors in the nervous system. Separation procedures leading to the identification of neurotoxins almost always include gel filtration chromatography, combined with ion-exchange and/or reversed phase chromatography. We present here an improved fractionation method based on the use of a new Superdex 30 prep grade HiLoad 16/60 FPLC gel filtration column. This single-step gel filtration protocol results in a shortening of the purification process and allows a superior qualitative separation of (neuro-)peptides in crude venoms as compared to any other type of gel filtration column used thus far. Screening of the collected fractions for potential ion channel blocking properties was performed by means of the whole-cell voltage clamp technique. To increase both the amount and speed of expression in Xenopus laevis oocytes of cloned ion channels, we employed a high-expression vector, pGEMHE, wherein the cDNA encoding a neuronal voltage-dependent potassium channel (RCK1) was subcloned. The combination of these techniques represents a fast and efficient identification procedure in the quest for new and selective neurotoxins for cloned channels and receptors.
The effect of RGS4, a GTPase-activating protein, on the deactivation kinetics and basal activity ... more The effect of RGS4, a GTPase-activating protein, on the deactivation kinetics and basal activity of GIRK1/GIRK2 channels activated by the human kappa-opioid receptor (hKOR) was investigated. Co-expression in Xenopus oocytes of RGS4 reduces the basal GIRK1/GIRK2 current and strongly increases the percentage agonist-evoked K+ conductance. RGS4 reconstitutes the native gating kinetics by accelerating GIRK1/GIRK2 channel deactivation, a phenomenon also seen after activation with other 7 TM receptors (e.g. muscarine type). In the absence of RGS4, the GIRK1/GIRK2 conductance was increased by approx. 50% after hKOR stimulation with the kappa-selective opioid receptor ligand, U69593; however more importantly, at the end of the washout period it was dramatically reduced to about 60% of the basal conductance as measured before receptor stimulation. Furthermore, we found that repeated receptor stimulation causes an increase of the agonist-gated deactivation kinetics, without affecting the maximal and minimal conductance levels of GIRK1/GIRK2 channels during and after agonist application. Unlike in the absence of RGS4, coexpression with RGS4 completely abolished the reduction of basal conductance after agonist washout and the deactivation kinetics remained unaffected upon repeated agonist application. The results presented here clearly indicate that previous stimulation by agonists activating G protein-coupled receptors may have long-lasting, strong consequences on the following responses. Therefore, our study provides evidence for a novel modulation of deactivation kinetics of GIRK1/GIRK2 currents in the absence of RGS4.
ABSTRACT Following the detection of formaldehyde in cultivated mushrooms, an evaluation was carri... more ABSTRACT Following the detection of formaldehyde in cultivated mushrooms, an evaluation was carried out to assess whether its presence in food poses a risk to public health. Formaldehyde, a carcinogenic chemical, has a broad range of industrial applications and, hence, exposure to formaldehyde is ubiquitous through diverse consumer goods, food, the air, etc. The observed levels of formaldehyde in mushrooms are lower than the levels reported for vegetables, fruit, meat, fish and dairy products. On the basis of available data, a rough estimate of the dietary exposure to formaldehyde was performed. The exposure through the consumption of cultivated mushrooms (approximately 0.19 µg kg body weight day on average, consumers only) appeared to be small compared with the total dietary intake of formaldehyde (approximately 99.0 µg kg body weight day, total population). Based on comparison with toxicological safety limits for chronic exposure and given that formaldehyde is carcinogenic only through inhalation and not by ingestion, it can be concluded that the dietary exposure to formaldehyde is not a cause for concern.
Objective: Norpropoxyphene (NP) is a major metabolite of propoxyphene (P), a relatively weak m-op... more Objective: Norpropoxyphene (NP) is a major metabolite of propoxyphene (P), a relatively weak m-opioid receptor agonist. Toxic blood concentrations ranging from 3 to 180 mmol / l have been reported and the accumulation of NP in cardiac tissue leads to naloxone-insensitive cardiotoxicity. Since several lines of evidence suggest that not only block of I but also I block may contribute
... After spraying, the plates were heated at 100 "C in an oven for 5 min. Simmondsin an... more ... After spraying, the plates were heated at 100 "C in an oven for 5 min. Simmondsin and analogous compounds showed as violet spots. HPLC. ... The structure was solved by direct methods and refined using the NRCVAX system (Gabe et al., 1989). ...
ABSTRACT A method was developed for the isolation and identification of phytosterols and fatty al... more ABSTRACT A method was developed for the isolation and identification of phytosterols and fatty alcohols in jojoba oil. The method consists in the separation of these compounds from wax esters in the oil by means of an aluminum oxide column followed by further fractionation of the minor components by column chromatography on silica gel. The 4-demethylsterols, 4-methylsterols, triterpene alcohols (4,4-dimethylsterols), and fatty alcohols are identified by means of their gas chromatographic and mass spectrometric data. The present paper includes a method for the quantitation of the free sterols in jojoba oil. Keywords: Plant; alcohol; sterol; lipid; Simmondsia
... Samples were injected into a Rheodyne injector (Model 7125) (Berkeley, CA) supplied with a 20... more ... Samples were injected into a Rheodyne injector (Model 7125) (Berkeley, CA) supplied with a 20-pL injector loop. A stainless steel Cla (7-pm particle size) column was used (25 cm X 0.4-cm id) (E. Merck, Darmstadt, Germany). ...
A gas chromatographic procedure for the determination of carboxyhaemoglobin in blood was improved... more A gas chromatographic procedure for the determination of carboxyhaemoglobin in blood was improved by using a capillary system in combination with a micro thermal conductivity detector. This system is very sensitive with high resolutions. The analytical time is reduced to approximately two minutes. Using sulphuric acid as the liberating agent of carbon monoxide, a gradual and reproducible release of carbon monoxide was seen. This shortens the time in emergency cases for sample preparation.
A survey was conducted to check the toxicological impact of ethylene glycol present in a thermal ... more A survey was conducted to check the toxicological impact of ethylene glycol present in a thermal decomposition mixture of type C hydraulic fluid on laboratory animals submitted to an inhalation test. The target organs, i.e. kidneys, of exposed rats were evaluated histologically and oxalic acid--the ethylene glycol metabolite thought to cause renal failure--was quantified in urine samples. The results show that the low ethylene glycol concentrations present in the inhalation chamber produce only a temporarily increased oxalic acid excretion, at levels that are not significant. These findings are supported by the histological evaluation of the kidneys showing no calcium oxalate deposits or other abnormalities.
Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion s... more Parabuthus transvaalicus, P. granulatus, and P. villosus are three medically important scorpion species occurring in southern Africa which can cause severe envenoming among people. In contrast to many other genera, no data is available on the venom composition of scorpions belonging to the genus Parabuthus. Here we have investigated the components which may contribute to the venomous potential. The constancy of venom composition within each of the three species and between the three species was investigated by means of gel filtration chromatography. The venoms of the three species each were characterized by a constant and typical elution pattern, resulting in a 'gel filtration fingerprint' which allows distinction between each species. It appears that certain components in the venoms are common to either all three species, or to two of the three species. This points to a clear interspecies relationship within the genus. We also describe the isolation and characterization of some of the polypeptide toxins present in the venoms of P. villosus, P. transvaalicus and P. granulatus by means of reversed phase chromatography and screening of the toxic components on voltage-activated potassium and sodium channels. Our results confirm that toxins which inhibit potassium channels and alter sodium channel gating are present in the venoms studied.
The development of a specific and sensitive radioimmunoassay for the detection of N-desmethylzopi... more The development of a specific and sensitive radioimmunoassay for the detection of N-desmethylzopiclone in urine samples is described. The assay will be used to pre-screen for N-desmethylzopiclone as an indication of zopiclone intake in a forensic and emergency context. N-Hemisuccinyldesmethylzopiclone has been prepared as a hapten. The immunization of rabbits with the hapten-bovine serum albumin conjugate resulted in the production of highly specific antibodies, showing no significant cross-reactivities with existing drugs. The four-parameter logistic model was used to process the calibration data into a fitting curve (r2 = 0.9979). Intra- and inter-assay relative standard deviations were < 9.1 and < 19.1%, respectively. The minimum detectable dose of the immunoassay was calculated to be 0.1 ng ml-1 (Pooled-variance t-distribution, p = 0.01, degrees of freedom = 14).
Neurotoxins have highly specific actions on molecular targets, and thus offer an effective means ... more Neurotoxins have highly specific actions on molecular targets, and thus offer an effective means of characterizing the growing number of identified ion channels and receptors in the nervous system. Separation procedures leading to the identification of neurotoxins almost always include gel filtration chromatography, combined with ion-exchange and/or reversed phase chromatography. We present here an improved fractionation method based on the use of a new Superdex 30 prep grade HiLoad 16/60 FPLC gel filtration column. This single-step gel filtration protocol results in a shortening of the purification process and allows a superior qualitative separation of (neuro-)peptides in crude venoms as compared to any other type of gel filtration column used thus far. Screening of the collected fractions for potential ion channel blocking properties was performed by means of the whole-cell voltage clamp technique. To increase both the amount and speed of expression in Xenopus laevis oocytes of cloned ion channels, we employed a high-expression vector, pGEMHE, wherein the cDNA encoding a neuronal voltage-dependent potassium channel (RCK1) was subcloned. The combination of these techniques represents a fast and efficient identification procedure in the quest for new and selective neurotoxins for cloned channels and receptors.
The effect of RGS4, a GTPase-activating protein, on the deactivation kinetics and basal activity ... more The effect of RGS4, a GTPase-activating protein, on the deactivation kinetics and basal activity of GIRK1/GIRK2 channels activated by the human kappa-opioid receptor (hKOR) was investigated. Co-expression in Xenopus oocytes of RGS4 reduces the basal GIRK1/GIRK2 current and strongly increases the percentage agonist-evoked K+ conductance. RGS4 reconstitutes the native gating kinetics by accelerating GIRK1/GIRK2 channel deactivation, a phenomenon also seen after activation with other 7 TM receptors (e.g. muscarine type). In the absence of RGS4, the GIRK1/GIRK2 conductance was increased by approx. 50% after hKOR stimulation with the kappa-selective opioid receptor ligand, U69593; however more importantly, at the end of the washout period it was dramatically reduced to about 60% of the basal conductance as measured before receptor stimulation. Furthermore, we found that repeated receptor stimulation causes an increase of the agonist-gated deactivation kinetics, without affecting the maximal and minimal conductance levels of GIRK1/GIRK2 channels during and after agonist application. Unlike in the absence of RGS4, coexpression with RGS4 completely abolished the reduction of basal conductance after agonist washout and the deactivation kinetics remained unaffected upon repeated agonist application. The results presented here clearly indicate that previous stimulation by agonists activating G protein-coupled receptors may have long-lasting, strong consequences on the following responses. Therefore, our study provides evidence for a novel modulation of deactivation kinetics of GIRK1/GIRK2 currents in the absence of RGS4.
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Papers by Paul Daenens