Biomedical subjects

R C Schothorst

Publications and source records attributed to R C Schothorst.

10 recordsLinked to original sources

PubMed2006

Effects of Fusarium toxin-contaminated wheat and feed intake level on the biotransformation and carry-over of deoxynivalenol in dairy cows.

An experiment was carried out to examine the effects of feeding Fusarium toxin-contaminated wheat (8.21 mg deoxynivalenol (DON) and 0.09 mg zearalenone (ZON) per kg dry matter) at different feed intake levels on the biotransformation and carry-over of DON in dairy cows. For this purpose, 14 ruminal and duodenal fistulated dairy cows were fed a diet containing 60% concentrate with a wheat portion of 55% (Fusarium toxin-contaminated wheat (mycotoxin period) or control wheat (control period)) and the ration was completed with maize- and grass silage (50 : 50) on a dry matter basis. Daily DON intakes ranged from 16.6 to 75.6 mg in the mycotoxin period at dry matter intakes of 5.6-20.5 kg. DON was almost completely biotransformed to de-epoxy DON (94-99%) independent of the DON/feed intake, and the flow of DON and de-epoxy DON at the duodenum related to DON intake ranged from 12 to 77% when the Fusarium toxin-contaminated wheat was fed. In the serum samples, de-epoxy DON was detected in the range of 4-28 ng ml-1 in the mycotoxin period, while concentrations of DON were all below the detection limit. The daily excretion of DON and de-epoxy DON in the milk of cows fed the contaminated wheat varied between 1 and 10 microg and between 14 and 104 microg, respectively. The total carry-over rates as the ratio between the daily excretion of DON and de-epoxy DON into milk and DON intake were in the ranges of 0.0001-0.0002 and 0.0004-0.0024, respectively. Total carry-over rates of DON as DON and de-epoxy DON into the milk increased significantly with increasing milk yield. In the urine samples, de-epoxy DON was the predominant substance as compared with DON with a portion of the total DON plus de-epoxy DON concentration to 96% when the Fusarium toxin-contaminated wheat was fed, whereas the total residues of DON plus de-epoxy DON in faeces ranged between 2 and 18% of DON intake in the mycotoxin period. The degree of glucuronidation of de-epoxy DON was found to be approximately 100% in serum. From 33 to 80% of DON and from 73 to 92% of de-epoxy DON, and from 21 to 92% of DON and from 86 to 100% of de-epoxy DON were glucuronidated in the milk and urine, respectively. It is concluded that DON is very rapidly biotransformed to de-epoxy DON in the rumen and only negligible amounts of DON and de-epoxy DON were transmitted into the milk within the range of 5.6-20.5 kg day-1 dry matter intake and milk yields (fat corrected milk) between 10 and 42 kg day-1.

Animal Feed↗

PubMed2005

Processing and purity assessment of standards for the analysis of type-B trichothecene mycotoxins.

The lack of reliable, certified calibrant solutions for the Fusarium mycotoxins deoxynivalenol (DON), 3-acetyl-DON (3-Ac-DON), 15-acetyl-DON (15-Ac-DON) and nivalenol (NIV) is a serious drawback in the already problematic area of trichothecene analysis. For this reason, purified DON, 3-Ac-DON, 15-Ac-DON and NIV standards were processed, the conditions required for their isolation and purification were optimised, and the crystalline toxins were thoroughly characterised. Several complimentary analytical methods were used to evaluate the identities of the mycotoxins and the types and amounts of impurities; results obtained from 1H and 13C NMR spectra, as well as from IR-spectra, were in agreement with the literature. Elemental analysis revealed that the isolated NIV occurs as monohydrate. If this is not known it results in a weighing error of approximately 5%. Differential scanning calorimetry (DSC) was only successful for 15-Ac-DON, as the other trichothecenes decomposed during measurements. No traces of chloride, nitrate and sulphate were found by means of ion chromatography (IC). As expected UV absorption spectra for DON, NIV, 3-Ac-DON and 15-Ac-DON yielded lambda(max) values of 216, 217, 217 and 219 nm, respectively. Minor peaks due to impurities were observed by high performance liquid chromatography (HPLC) with UV detection. The main impurity peak in the DON sample was identified by LC-tandem mass spectroscopy (LC-MS/MS) as 4,7-dideoxy-NIV (7-deoxy-DON), which occurs at levels of approximately 1.4%. Gas chromatography (GC) was performed, coupled with either an electron capture detector (ECD), a flame ionisation detector (FID), or a mass spectrometric detector (MS); however, derivatisation prior to GC analysis makes the estimation of impurities difficult. LC-MS/MS was found to be unsuitable for quantifying levels of impurities. It can be concluded that high-purity (>97%) B-trichothecene standards were successfully processed and fully characterised for the first time.

Chromatography, High Pressure Liquid↗

PubMed2005

Determination of N-nitrosodiethanolamine in cosmetic products by LC-MS-MS.

We have developed and validated in-house a liquid chromatography and mass spectrometry (LC-MS-MS) method for determination of N-nitrosodiethanolamine (NDELA) in cosmetics. The sample is diluted with water and then a C18 clean-up is performed. The average recovery of NDELA is 88.3%, range 48.3-112.7%, and the limit of detection is 22.8 microg kg-1. The repeatability is 7.6%, and the intermediate precision is 8.7%. Surveys were carried out in the Netherlands in September and October 2002 to determine the quantities of NDELA in cosmetics marketed in the Netherlands. The LC-MS-MS method was used to determine the NDELA content of 140 cosmetic products including shower gels, hair oils, shampoos and conditioners, cream and foam baths, mud baths, scrubs, creme and other soaps, and body washes. NDELA at levels ranging from 23 to 992 microg kg-1 was found in 35 cosmetic products.

Chromatography, Liquid↗

PubMed2005

Determination of trichothecenes in duplicate diets of young children by capillary gas chromatography with mass spectrometric detection.

Trichothecenes are mycotoxins produced by several fungal genera, mainly Fusarium species, that can contaminate a wide range of cereals used for human and animal consumption. They are associated with various adverse health effects in animals and humans such as feed refusal, vomiting and immunotoxic effects. A method based on capillary gas chromatography with mass spectrometric detection was developed and validated in-house for the determination of nine trichothecenes in duplicate diets of young children. The trichothecenes were extracted from the sample matrix by water/ethanol (90/10). The extracts were cleaned by means of ChemElut and Mycosep columns. The cleaned extracts were evaporated to dryness and derivatized to trimethylsilyl ethers at room temperature. The residues were dissolved in iso-octane and washed with water. The final extracts were analysed for trichothecenes by GC-MS. The response was linear in the range tested (1-10 microg kg(-1)). Recoveries for the trichothecenes were between 70 and 111%, with the exception of nivalenol, which had a low recovery (34%). The limit of quantification for all trichothecenes was below 0.4 microg kg(-1). Seventy-four food samples from young children collected by 74 respondents in a duplicate diet study were analysed for trichothecenes with the developed method. The mean levels of deoxynivalenol, nivalenol, HT-2 toxin and T-2 toxin were 5.8, 0.3, 0.3 and 0.1 microg kg(-1), respectively. Based on the individual results, dietary intake calculations were made. For deoxynivalenol, the tolerable daily intake of 1 microg kg(-1) body weight was exceeded by nine respondents. For the combined intake of T-2 and HT-2 toxin, the temporary tolerable daily intake of 0.06 microg kg(-1) body weight was exceeded by nine respondents.

Body Weight↗

PubMed2003

Identification of extractable substances from rubber nettings used to package meat products.

Ten meat nettings were sampled from four different suppliers in the Netherlands. These meat nettings consisted both of natural rubber and of vegetable fibres. Nitrosamines were extractable up to 2 mg x kg(-1) netting, the nitrosamine being N-nitrosodibenzylamine. The nitrosatable substances found were precursors of N-nitrosodimethylamine and N-nitrosodibenzylamine and were extracted up to 0.4 mg x kg(-1) nettings. Considering the ratio of meat netting and foodstuff, the extractable amount of nitrosamines and nitrosatable substances does not raise concern for public health. The meat nettings were also screened for other potential migrants. Extractable amounts of several alkanes, alkenes, acids, antioxidants, plasticizers and sterols were found. Several of these extracted substances are not allowed in the Netherlands, although some are authorized in other countries. Several substances, however, have not been evaluated for use in food-contact materials and therefore the possible risk to public health is unknown.

Animals↗

PubMed2003

Migration of N-nitrosamines, N-nitrosatable substances and 2-mercaptobenzthiazol from baby bottle teats and soothers: a Dutch retail survey.

In 2001, a retail market survey of 19 samples of teats and soothers was performed in the Netherlands. The migration of 2-mercaptobenzthiazol (MBT), N-nitrosamines and nitrosatable substances was measured. A screening was also performed for other potential migrants. Of the soothers, shield size and yield strength were determined. Most of the teats and soothers on the Dutch market were made of silicone rubber, although a few were made of natural rubber. The migration of N-nitrosamines and nitrosatable substances was far below the migration limit of 0.01 and 0.1 mg kg(-1) teat, respectively, with the exception of one natural rubber soother. For this soother, the migration of nitrosatable substances was 0.23 mg kg(-1) and measures were therefore taken against the supplier. MBT was detected in only one natural rubber sample, migration being well below the limit of 0.3 mg/teat. The extractable substances in the silicone teats and soothers are siloxanes. From the two natural rubber products, substances were extracted that were not on the positive list of the Dutch Packaging and Food-Utensils Regulation. Most of these substances are allowed in other countries, or authorized for plastic food contact materials. The size of the shields of all soothers and yield strengths were in compliance with the Regulation.

Benzothiazoles↗

PubMed2001

Determination of N-nitrosodimethylamine in artificial gastric juice by gas chromatography-mass spectrometry and by gas chromatography-thermal energy analysis.

The thermal energy analyser (TEA) is considered to be the gold standard for the determination of nitrosamines. However, since many laboratories cannot justify the use of such a very specific detection system, alternative detection methods are useful. While standard gas chromatography (GC) detectors lack the selectivity of the TEA detector, mass spectrometry (MS) seems to be the method of choice to combine GC separation with mass selective detection. Moreover, the detection limits of the GC-MS assay in general use are about 4 times lower than those of the GC-TEA assay. A comparison of GC-MS and GC-TEA data on N-nitrosodimethylamine determinations showed a strong correlation between the two assays (R2 = 0.86), demonstrating the exchangeability of these methods.

Carcinogens↗

PubMed1999

The oral nitrate and nitrite intake in The Netherlands: evaluation of the results obtained by HPIC analysis of duplicate 24-hour diet samples collected in 1994.

In spring and autumn of 1994 duplicates of 24-h diets were collected from 123 respondents. One of the goals of this study was to determine the amount of nitrite and nitrate in the duplicates of 24-h diets to establish the oral daily intake of these analytes. For this purpose an HPIC/UV method for the determination of nitrate and nitrite in duplicate diets was developed and validated. The sample preparation procedure was derived from the in-house method used for the determination of nitrate and nitrite in human blood plasma. The sample is diluted with water, deproteinized with Carrez reagent, followed by chromatographic clean-up on an SPE C18-column. Both the nitrate and the nitrite results are quantitative. The recovery for nitrite was on average 104% (n = 21, spiking levels: 0.84-95 mg/kg) and for nitrate on average 103% (N = 21, spiking levels: 1.8-404 mg/kg). Samples of duplicates of 24-h diets were analysed according to the method developed. The median intake of nitrite calculated from the samples collected in spring 1994 was 0.6 mg/person day (range < 0.1-6.1 mg/person/day). For the samples collected in autumn 1994 these figures were < 0.2 mg/person/day (range < 0.1-16 mg/person/day). The mean intake of nitrate was 73 mg/person/day (range 7-322 mg/person/day) in spring 1994 and 87 mg/person/day (range 1-310 mg/person/day) in autumn 1994. The overall mean intake of nitrate in 1994 was 80 mg/person/day. The daily intake for nitrate was higher than that found in the duplicate diet study carried out in 1984/1985, when an average daily intake of 52 mg/person was measured. The intake of nitrite was also higher than found in the duplicate diets collected in 1984/1985. The findings of the study are discussed in the context of the ADI for nitrate and nitrite as well as the outcome of other recent European intake studies.

Adolescent↗

PubMed1998

Results of the second inventory on quality assurance/quality control (QA/QC) and good laboratory practice (GLP) for European Union National Reference Laboratories for residue analyses.

In February 1996 the "Second inventory on QA/QC and GLP for EU-NRLs" was submitted to all European Union National Reference Laboratories (EU-NRLs) for residue analyses. This second inventory was a follow up on the "Inventory on QA/QC" (1993) which was used for the organisation of the first workshop on "GLP for EC-NRLs". In February 1997 a response on the second inventory of 100% was achieved. From the completed inventories it became evident that almost all EU-NRLs for residue analyses now have a described quality program based on an international standard. However only 33% of the EU-NRLs are officially accredited, certified or in compliance with good laboratory practice (GLP) principles. Most of the accredited EU-NRLs have a quality program based on the European Standard EN45001. Seven of the EU-NRLs still do not have a described quality program or have not appointed a quality officer and for 12 of the EU-NRLs the independence of the QA officer is not formally arranged. Only about 50% of the EU-NRLs have a standard operating protocol (SOP) to handle complaints. Almost all of the EU-NRLs have SOPs available and a system to control them. In comparison with the results of the first inventory it is evident that most of the EU-NRLs have made considerable progress in the implementation of quality systems. However it is also evident that a substantial number of EU-NRLs still lack some critical QA facilities. The new deadline for the full implementation of all relevant QA facilities is January 2002.

Animals↗

PubMed1997

Twenty-four-hour duplicate diet study 1994; nitrate and nitrite: method development and intake per person per day.

In spring and autumn of 1994 duplicates of 24-h diets were collected from 123 consumers (respondents). One goal of this study is to determine the amount of nitrite and nitrate in the duplicates of 24-h diets in order to establish the oral daily intake of these analytes. For this purpose a HPIC/UV method for the determination of nitrate and nitrite in duplicate diets was developed and validated. The mean intake of nitrate is 80 mg NO3- ion/person per day and the median intake of nitrite is 0.1 mg NO2- ion/person per day. The daily intake for nitrate as well nitrite is higher than found in the duplicate diets collected in the 1984/1985 study.

Adolescent↗