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Biomedical subjects

G S Shephard

Publications and source records attributed to G S Shephard.

At least 19 recordsLinked to original sources
PubMed2006

Human dietary exposure to fumonisin B1 from Iranian maize harvested during 1998-2000.

Fumonisin B(1) (FB(1)) is the most abundant of the fumonisin mycotoxins, mainly produced in maize by F. verticillioides and F. proliferatum. A previous study on the FB1 contamination of maize harvested in Mazandaran and Isfahan Provinces of Iran in 1998 and 1999 demonstrated contamination in both provinces. This present study was undertaken to further investigate the variation in levels of contamination and to estimate possible levels of human exposure to fumonisins in Iran. The mean level of FB(1) in 49 visually healthy maize samples collected from Mazandaran Province during 2000 was 6.14 mg/kg, which is higher than that found during 1998 and 1999 (2.27 and 3.18 mg/kg, respectively). Although these levels are higher than the Iranian legislative limits for fumonisins in maize intended for humans, the relatively low estimated consumption of maize in Iran (3.3 g/person/day) implies that average exposures (0.011 and 0.215 microg/kg body weight/day in Isfahan and Mazandaran, respectively) are within the provisional maximum tolerable daily intake of 2 microg/kg body weight/day set by the Joint FAO/WHO Expert Committee on Food Additives. Nevertheless, certain sections of the population who may consume higher amounts of maize or who may replace all or some of their consumption of other cereals with maize, could well exceed this limit.

Food Contamination↗
PubMed2005

The simultaneous determination of selected flavonol glycosides and aglycones in Ginkgo biloba oral dosage forms by high-performance liquid chromatography-electrospray ionisation-mass spectrometry.

An accurate, precise and sensitive liquid chromatography-tandem mass spectrometric (LC-MS-MS) method was developed for the determination of two flavonol glycosides, rutin and quercitrin, together with the algycone markers, quercetin, kaempferol and isorhamnetin in several Ginkgo biloba solid oral dosage forms. In addition, a novel quercetin glycoside, not yet reported in Ginkgo extracts, was identified. Liquid chromatography was performed using a minibore high-performance liquid chromatography (HPLC) column (150 mm x 2.0mm i.d.) and a one step gradient of acetonitrile-formic acid (0.3%) at a flow rate of 0.5 ml/min. Baseline separation of the five selected flavonol marker compounds was achieved within 20 min at 45 degrees C. Tandem mass spectrometry was performed using electrospray ionisation (ESI) in the negative ion mode. The marker compounds exhibited linearity over the range of 3-26 microg/ml and intra- and inter-day standard deviations were better than 7% and 16%, respectively. All Ginkgo products investigated were found to contain varying amounts of target analytes.

Calibration↗
PubMed2004

Fumonisin contamination of a corn sample associated with the induction of hepatocarcinogenesis in rats-role of dietary deficiencies.

A corn sample associated with a field outbreak of equine leukoencephalomalacia in Pennsylvania, USA, during 1983/1984 and induced hepatotoxic and hepatocarcinogenic effects when fed to male Fischer rats was analyzed mycologically and chemically for the presence of fumonisins (FB), hydrolysed FB derivatives and aflatoxins (AFB). Fusarium verticillioides was found to be the predominant fungal contaminant in the corn sample but Aspergillus flavus was also present. Trace amounts (0.1 microg/kg) of AFB(1) and AFB(2) and a total FB level of 33.5 mg/kg (FB(1):FB(2):FB(3) ratio of 9:2.3:1) were found. No hydrolysed FB derivatives or AFG(1) and AFG(2) were detected. Based on the chemical stability of the fumonisins in different corn cultures of F. verticillioides kept at 4 degrees C over a period of 13-20 years, a level of approximately 55 mg/kg of total FB is estimated in the original corn sample. A possible role of certain dietary constituents such as the high protein content and deficiencies in certain micronutrients is evaluated to address differences in the organ-specific toxicity of FB(1) in rats using commercial, semi-purified, purified and corn-only diets.

Animals↗
PubMed2004

Determination of the mycotoxin fumonisin B1 in maize by reversed-phase thin-layer chromatography: a collaborative study.

A simple and cost-effective method using thin-layer chromatography for the determination of the mycotoxin fumonisin B1 in maize is described. The analytical method consisted of the extraction of ground maize by shaking with methanol/water (75:25) for 60 min and clean-up of the resultant extract by means of strong anion exchange solid-phase extraction. The purified residue, formed by evaporation of the elution solvent, was reacted with fluorescamine and the fumonisin B1-derivative was separated by reversed-phase thin-layer chromatography using a developing solution of methanol/aqueous 4% potassium chloride (70:30). The derivatized FB1 was readily visualized as a greenish-yellow spot under long wavelength ultraviolet light and quantified by visual comparison with a set of similarly derivatized standards in the range 20-300 ng FB1 spotted on plate. Based on visual comparison, levels down to 0.5 mg kg(-1) were successfully estimated. The method was collaboratively studied in 14 laboratories using four duplicate maize meal samples (including a blank) and a spiked sample for determination of recovery. No significant difference was observed between mean FB1 levels by high-performance liquid chromatography or thin-layer chromatography. Based on within-laboratory relative standard deviations of 27.1-41.7% and between-laboratory relative standard deviations of 35.0-63.3%, the method can be considered semiquantitative. The mean recovery achieved by participants at a spiking level of 2.00 mg kg(-1) was 74.5%.

Carcinogens↗
PubMed2004

Fumonisins in Brazilian corn-based foods for infant consumption.

A survey of 196 samples of corn-based infant foods from 13 cities of Sao Paulo State, Brazil, was carried out to investigate the fumonisin contamination in the products. Based on their ingredients, the products were divided into seven groups: infant cereal designated as types A-D, corn meal, corn starch and instant cereal baby food. Although certain infant food samples were free of fumonisin contamination (<20 microg kg(-1); corn starch and infant cereals of type A, B and D), contamination levels in the other products (corn meal, instant corn-based baby food and cereal type C) were of concern, particularly those in corn meal. All samples in these categories contained fumonisins. The mean level for total fumonisins (FB1 + FB2 + FB3) in corn meal was 2242 microg kg(-1) (maximum 8039 microg kg(-1)), in instant corn-based baby food was 437 (maximum 1096) microg kg(-1) and in infant cereal type C was 664 (maximum 1753) microg kg(-1).

Brazil↗
PubMed2002

Fumonisin B(1) in maize harvested in Iran during 1999.

The fumonisin B(1) (FB(1)) contamination of maize collected in two areas of Iran during 1999 was determined. The 20 maize samples from Mazandaran Province, situated on the Caspian littoral of Iran, consisted of random samples of farmers' lots and were all contaminated with FB(1) at a mean level of 3.18 mg kg(-1) (range 0.68-7.66 mg kg(-1)). The 10 samples (of the same maize cultivar) from Isfahan Province in central Iran were purchased as maize cobs in local retail markets and had mean FB levels of 0.22 mg kg(-1) (mean of all samples, 6/10 samples positive, range <0.01-0.88 mg kg(-1)). The FB levels in Mazandaran, an area of high oesophageal cancer, were significantly (p < 0.0001) higher than the FB levels found in maize from Isfahan, an area of low oesophageal cancer in Iran.

Carboxylic Acids↗
PubMed2001

Toxicokinetics of ochratoxin A in vervet monkeys (Cercopithecus aethiops).

The toxicokinetics of ochratoxin A were investigated in vervet monkeys (Cercopithecus aethiops). Three female monkeys were treated intravenously with ochratoxin A at doses, respectively, of 0.8, 1.5 and 2 mg/ kg body weight (BW). Blood and urine samples were collected over a period of 21 days. Plasma and urine extracts were analysed by high-performance liquid chromatography (HPLC) with either fluorescence or negative ion electrospray ionization mass spectrometric detection. The clearance of ochratoxin A from plasma followed a two-compartment model. The elimination half-life of ochratoxin A in the monkeys was determined to be 19-21 days and the average total body clearance was 0.22 +/- 0.07 ml/h per kg and the average apparent distribution volume of the central compartment was 59 +/- 9 ml/kg and the peripheral compartment was 59 +/- 20 ml/kg. No evidence was found for any metabolic conversion of ochratoxin A.

Animals↗
PubMed2001

The effect of repeated gavage doses of fumonisin B1 on the sphinganine and sphingosine levels in vervet monkeys.

Fumonisins occur widely around the world in maize products intended for human and animal consumption posing a health hazard. Direct measurement of fumonisins in physiological fluids as a biomarker of exposure is not practicable, however fumonisins disrupt sphingoid metabolism by inhibition of sphinganine N-acyltransferase. In this study the disruption in sphinganine (Sa) and sphingosine (So) levels in plasma and urine was measured in vervet monkeys (Cercopithecus aethiops) dosed with repeated gavages of 1mg fumonisin B1 (FB1)/kg body weight three times/week continuously over a 51-day period. The plasma Sa/So ratio reached a maximum (mean of 4.3) after 30 days in the dosed monkeys with a three-fold increase above the ratio of the control monkeys and then declined slowly to double the value in controls after 51 days. The lack of a clear elevation in urinary Sa/So ratios after 51 days of multiple exposure in the dosed monkeys indicates that the plasma ratio is more sensitive than urinary changes in monkeys. This is confirmed by the plasma levels of liver function enzymes of which aspartate transaminase, glutamyl-transferase and lactate dehydrogenase were increased in the dosed monkeys, while the plasma indicators of renal function were not increased above the levels in the control monkeys. Thus repeated low doses of FB1 can cause sustained disruption of sphingoid metabolism.

Animals↗
PubMed2001

The effect of a single gavage dose of fumonisin B(2) on the sphinganine and sphingosine concentrations in vervet monkeys.

The disruption in sphinganine (Sa) and sphingosine (So) concentrations in plasma and urine of vervet monkeys (Cercopithecus aethiops) was measured following a single gavage dose of either 1 (low dose) or 10 mg (high dose) fumonisin B(2) (FB(2))/kg body weight. Blood and urine were collected over a 51-day period. In the low-dose monkeys, none of the parameters measured increased significantly above the control values. In the high-dose monkeys the plasma Sa/So ratios were significantly increased (P< 0.05) above the corresponding control ratios after 3 days and continued to be significantly raised for another 27 days, whereafter the ratios declined to control values after 51 days. The plasma aspartate transaminase (AST) activities increased significantly above their control values from day 5 to day 23 and the gamma-glutamyl transferase (GGT) activities from day 7 until the end of the study period. The plasma cholesterol concentration and alanine transaminase (ALT) and lactate dehydrogenase (LDH) activities increased transiently, but not significantly, and returned to control values within the study period. The urinary Sa/So ratio, plasma creatinine and urea values in both groups of monkeys did not increase above the control values. This study demonstrated that a single large dose of FB(2) can cause transient disruption of sphingoid metabolism in vervet monkeys.

Animals↗
PubMed2001

The reduction of patulin in apple juice by three different types of activated carbon.

Three types of activated carbon (NORIT SA 4, NORIT SX 4 and NORIT CA 1) were investigated for their ability to reduce patulin levels in apple juice at various Brix levels and temperatures. The steam-activated carbons (NORIT SA 4 and NORIT SX 4) exhibited similar adsorption isotherms at a dosage level of 1 g/l. They achieved patulin reductions of 80% and 70% respectively in 12(o) Brix juice at 55 degrees C. The similarity in performance between the steam-activated carbons implies that the purity and the surface acidity does not influence the adsorption of patulin. Chemically-activated carbon (NORIT CA 1) was less effective in removing patulin and achieved only a 45% reduction at a dose of 1 g/l. Patulin removal was influenced by juice Brix in that higher carbon doses were required at higher Brix levels for equivalent removal efficiency. At a dose of 1 g/l, NORIT SA 4 removed only 45% patulin from a 20(o) Brix juice. The removal of patulin from either 12 or 20(o) Brix juice by NORIT SA 4 at 1 g/l was not influenced by temperature changes in the range 30 to 65 degrees C.

Beverages↗
PubMed2001

Assessing chronic exposure to fumonisin mycotoxins: the use of hair as a suitable noninvasive matrix.

This study describes for the first time the accumulation of measurable levels of fumonisin mycotoxins in the hair of nonhuman primates (vervet monkeys, Cercopithecus aethiops) and rats exposed to contaminated feed. Hair was subjected to reflux with methanol, and the resulting extract was cleaned up on strong anion exchange (SAX) and C18 solid-phase sorbents. Fumonisins FB1, FB2, and FB3 as well as their hydrolysis products commonly known as aminopolyols, AP1 and AP2, were detected in monkey hair using high-performance liquid chromatography coupled to electrospray ionization mass spectrometry (HPLC-ESI-MS). Despite matrix interferences, the two-stage mass spectrometric process (MS-MS) yielded product ion mass spectra, which served as diagnostic indicators thus providing unequivocal identification of FB1, FB2, and FB3 as well as AP1 and AP2. In vervet monkeys, the levels of exposure related well to the levels of toxin detected in hair, and levels as high as 5.98 mg FB1, 33.77 mg FB1, and 65.93 mg FB1/kg of hair were found in monkeys receiving control, low-dose, and high-dose contaminated diets, respectively. Hair was also analyzed from rats given either single gavage doses of 1 and 10 mg FB1/kg body weight or contaminated feed (50 mg FB1/kg), resulting in an exposure of approximately 4.25 mg FB1/kg body weight/day based on the measured daily feed intake. Analysis of rat hair over a four-week period indicated that mean levels up to 34.50 mg/kg and 42.20 mg/kg were detectable by the fourth week in the rats treated by gavage (10 mg FB1/kg body weight) and those receiving contaminated feed, respectively. This relationship indicates that hair can provide an easily applicable non-invasive matrix for assessing chronic exposure to fumonisin mycotoxins.

Administration, Oral↗
PubMed2001

Toxicity of culture material of Fusarium verticillioides strain MRC 826 to nonhuman primates.

We conducted a chronic feeding study in vervet monkeys (Cercopithecus aethiops) over 13.5 years. The experimental design consisted of two dietary treatment groups, each including males and females, fed varying levels of culture material of Fusarium verticillioides (Sacc.) Nirenberg (= F. moniliforme Sheldon) strain MRC 826 mixed into their daily food ration. Two females were included as treatment controls. We conducted blood chemical analyses bimonthly and recorded all clinical signs during the course of the experiment. We took liver biopsies at various stages during the initial phase of the experiment. Several monkeys were terminated in extremis during the experiment. Detailed feed intake profiles were determined 5 years after the experiment began, and the fumonisin B (FB) mycotoxin content of the feed was determined during the final stages of the experiment. The apparent FB consumption patterns were related to changes observed in the biochemical parameters in the blood and urine, including the liver function enzymes and creatinine clearance as well as differential blood counts and sphingolipid levels in the serum and urine. An apparent no-effect threshold for kidney and liver damage is estimated to be between 0.11 and 0.18 mg FB/kg body weight (bw)/day, which corresponds to a feed contamination level of between 8.21 and 13.25 mg FB/kg bw diet. Apart from the effects on the liver and kidney, a wide variety of parameters, including cholesterol and creatine kinase, were also adversely affected. Several blood parameters, including white and red blood cells, also significantly decreased in the treated animals. The serum sphinganine level and the sphingosine/sphinganine ratio, monitored toward the end of the experiment, significantly increased in both the low-dose and high-dose animals. The present study provides important information about the diversity of lesions induced by culture material of F. verticillioides in vervet monkeys and the dosage levels of fumonisins to be used in long-term studies in nonhuman primates.

Animal Feed↗
PubMed2000

Determination of patulin in apple juice by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

An HPLC-MS-MS method with selected reaction monitoring (SRM) for the determination of patulin in apple juice samples is described. Mass spectrometric detection was accomplished following atmospheric pressure chemical ionization (APCI) in both positive and negative ion modes. Collision induced dissociation (CID) of the protonated molecular ion led initially to the loss of H2O (fragment m/z 137). At higher energies CO is lost from both the protonated parent molecule (fragment m/z 127) and the dehydrated molecular ion (fragment m/z 109). In contrast, CID of the deprotonated molecular ion led initially to the fragment at m/z 109 corresponding to the loss of either CO2 or acetaldehyde, followed at higher CID energy by the loss of H2O (fragment m/z 135) and CO (fragment m/z 125) from the deprotonated molecular ion. Detection in the negative ion mode proved superior and a linear response was observed over the injected range from 6 to 200 ng patulin. Apple juice samples spiked with patulin between 10 and 135 microg/l were analyzed following liquid-liquid extraction with ethyl acetate and clean up with sodium carbonate. Utilizing reversed-phase HPLC with acetonitrile-water (10:90) at 0.5 ml/min, levels down to 10 microg/l were readily quantified and a detection limit of 4 microg/l was attainable at a signal-to-noise (SIN) ratio of 4. The MS data for the spiked samples compared well to the UV data and when plotted against each other displayed a correlation coefficient (R) of 0.99.

Atmospheric Pressure↗
PubMed2000

Chromatographic determination of the mycotoxin patulin in fruit and fruit juices.

Patulin is a mycotoxin produced by several fungal species of the genera Penicillium and Aspergillus, but principally by Penicillium expansum on fruit such as apples. The occurrence of patulin as a natural contaminant of apple juice is a worldwide problem and international recommendations and regulations have been made for maximum levels permitted in consumer products. This paper reviews currently available analytical methods for its determination in fruit and fruit juices. Of these, HPLC with ultraviolet or, preferably, photodiode array detection is most widely used, although GC and TLC methods have also been described.

Beverages↗
PubMed2000

Natural occurrence of fumonisins in corn from Iran.

Corn collected in the Mazandaran and Isfahan Provinces of Iran was analyzed for fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)), and fumonisin B(3) (FB(3)). The samples from Mazandaran Province, situated on the Caspian littoral of Iran, were random samples from farmers' corn lots collected in September 1998, whereas those from Isfahan Province, situated further south in the center of Iran, were bought as corn cobs in the local retail market during October 1998. All 11 samples from Mazandaran showed high levels of fumonisin contamination with FB(1) levels between 1.270 and 3.980 microg/g, FB(2) levels between 0.190 and 1.175 microg/g, and FB(3) levels between 0.155 and 0.960 microg/g. Samples from Isfahan showed lower levels of contamination with eight of eight samples having detectable FB(1) (0.010-0.590 microg/g), two of eight samples having detectable FB(2) (0.050-0.075 microg/g), and two of eight samples having detectable FB(3) (0.050-0.075 microg/g). This is the first report of fumonisin contamination of corn from Iran, in which samples from the area of high esophageal cancer on the Caspian littoral have been shown to contain high levels of fumonisins.

Carboxylic Acids↗
PubMed1999

Determination of the Fusarium mycotoxins, fusaproliferin and beauvericin by high-performance liquid chromatography-electrospray ionization mass spectrometry.

A method is described using LC-MS for the detection of the mycotoxins fusaproliferin (FUS) and beauvericin (BEA) in cultures of Fusarium subglutinans and in naturally contaminated maize. Protonated molecular ion signals for FUS and BEA were observed at m/z 445 and m/z 784, respectively. Collision induced dissociation of the readily dehydrated protonated molecular ion of the sesterterpene FUS (m/z 427) led to the loss of another water molecule (m/z 409) and acetic acid (m/z 385), while the cyclic lactone trimer BEA fragmented to yield the protonated dimer (m/z 523) and monomer (m/z 262), respectively. Detection of FUS was best performed in the MS-MS mode while BEA displayed a stronger signal in the MS mode. The on-column instrumental detection limits for pure FUS and BEA were found to be 2 ng and 20 pg (S/N=2) while those in naturally contaminated maize were 1 microg/kg and 0.5 microg/kg, respectively. Five South African strains of F. subglutinans were analyzed following methanol extraction of which four produced FUS at levels between 330 mg/kg and 2630 mg/kg while only three produced BEA at levels between 140 mg/kg and 700 mg/kg. Application of this method to naturally contaminated maize samples from the Transkei region of South Africa showed FUS at levels of 8.8-39.6 microg/kg and BEA at 7.6-238.8 microg/kg.

Anti-Bacterial Agents↗
PubMed1999

Determination of the mycotoxin moniliformin in cultures of Fusarium subglutinans and in naturally contaminated maize by high-performance liquid chromatography-atmospheric pressure chemical ionization mass spectrometry.

A LC-MS method employing triethylamine as ion-pairing reagent for the determination of moniliformin in culture material and naturally contaminated maize samples is described. Mass spectrometric detection of moniliformin was accomplished following atmospheric pressure chemical ionization to yield the deprotonated molecular ion [M-H]- at m/z 97. The moniliformin response was found to be linear over the injected range 10 ng to 700 ng and a detection limit of 10 ng was attainable at a signal-to-noise (S/N) ratio of 4. Five South African strains of Fusarium subglutinans were grown on maize kernels and moniliformin extracted with an acetonitrile-water (95:5) mixture. Following sample clean up with reversed-phase (C18) solid-phase extraction cartridges, the extracts were subjected to LC-MS analysis. Triethylamine was used as an ion-pair reagent and found to improve the retention characteristics of moniliformin without any detrimental effects to the instrument. Moniliformin concentrations ranged between 130 mg/kg and 1460 mg/kg culture. Application of this method to naturally contaminated maize samples from Transkei showed that it was capable of measuring moniliformin levels down to 10 micrograms/kg in selected moldy maize cobs. This is the first report on the application of LC-MS to the analysis of moniliformin in cultures of F. subglutinans and in naturally contaminated maize.

Atmospheric Pressure↗