Biomedical subjects

D L Park

Publications and source records attributed to D L Park.

50 records · Page 3Linked to original sources

PubMedDate not supplied

Distribution of ammonia/aflatoxin reaction products in corn following exposure to ammonia decontamination procedure.

The distribution of aflatoxin decontamination reaction products in corn following ammonia decontamination treatment was determined. The parameters of the ammoniation procedure used to decontaminate aflatoxin contaminated corn were 2% NH3, 16% moisture, 55 psi, 40-45 degrees C, and 60 min duration. Uniformly ring-labelled 14C-aflatoxin B1 was added to corn (1.0 microCi/kg) containing 7500 micrograms naturally-incurred aflatoxin B1 (AFB1)/kg. Aflatoxin levels were reduced by ca 93% after ammonia treatment. Distribution of radiolabelled AFB1 was used to follow the modification of AFB1 and the ammonia/aflatoxin reaction products were separated and isolated through a series of chemical extraction/partition procedures. Samples of the ammoniated product were fractionated through sequential extraction with methylene chloride and methanol, then either treated with acetic acid and sodium hydroxide or exposed to proteolytic enzyme digestion followed by methylene chloride extraction. Approximately 88% of the added radioactivity was detected in the corn after treatment (i.e. 12% of aflatoxin reaction products were volatile), ca 20% was extracted with methylene chloride and ca 13% was extracted with methanol. Treatment with acid and base released 18.8% of the added radioactivity. Similar amounts (19.1%) of aflatoxin-related compounds were liberated after enzymatic digestion with Pronase E. The remaining corn matrix after acid-base treatment or Pronase digestion contained ca 37.0% of the original radioactivity. A fluorescent spot on the TLC plate represented 6.1% of the CH2Cl2-extractable compounds and contained a compound which reacts chromatographically similarly to AFB2a.

Aflatoxins↗

PubMedDate not supplied

Surveillance programmes for managing risks from naturally occurring toxicants.

Aflatoxins are potent carcinogenic, mutagenic and teratogenic metabolites produced by moulds that grow on food and feed. Their toxicity has caused severe health and economic problems worldwide. Other mycotoxins which have been associated with human health risks include ergot alkaloids, citreoviridin, trichothecenes, ochratoxins, citrinin, tremorgenic mycotoxins and the fumonisins. Many phycotoxins have also been associated with human illnesses; these phycotoxins include paralytic shellfish poisons, diarrhoeic shellfish poisons, ciguatera-related toxins, neurotoxic shellfish poisons, tetrodotoxin and, the more recently discovered, domoic acid which is associated with amnesic shellfish poisoning. Human exposure to these naturally occurring toxins can be from direct consumption of contaminated commodities or from foods derived from animals previously exposed to these toxins in their feed. Food safety monitoring programmes for selected toxins have been established for raw and finished products susceptible to contamination. Components of these control programme include the establishment of regulatory limits or guidelines, monitoring susceptible products for specific compounds, and the diversion of the contaminated products to lower-risk uses and/or decontamination procedures.

Consumer Product Safety↗

PubMedDate not supplied

Isolation and identification of dihydrocitrinone, a urinary metabolite of citrinin in rats.

Dihydrocitrinone, 3,4-dihydro-6,8-dihydroxy-3,4,5-trimethylisocoumarin-7-carboxylic acid, was isolated and identified as a urinary metabolite after oral administration of citrinin to rats. Male and female Osborne-Mendel rats received 30 mg citrinin/kg body weight by oral intubation. The metabolite dihydrocitrinone was present in urine collected at 0-2, 2-4, 4-6, 6-8, and 8-24 h after treatment. Only unchanged citrinin was found in blood collected 24 h after administration of the compound. The metabolite had a blue fluorescence and the same Rf on thin-layer chromatography, the same retention time on reverse-phase high-pressure liquid chromatography, and the same mass spectrum as an authentic sample of dihydrocitrinone.

Animals↗

PubMedDate not supplied

Performance of three pneumatic probe samplers and four analytical methods used to estimate aflatoxins in bulk cottonseed.

The requirement by the U.S. Food and Drug Administration that agricultural products susceptible to aflatoxin contamination contain aflatoxin at levels < or =20 parts per billion for consumer-ready products has led to the establishment of inspection programs by various industries. In Arizona, cottonseed samples from 100 ton piles are collected by an accumulation of 3 or more probings with a pneumatic probe. When sampling compacted cottonseed piles, the large official pneumatic probe (7.6 x 127 cm) decreases in efficiency. Two smaller probes (1.9 x 127 cm and 1.9 x 254 cm ) were therefore developed and tested for their suitability for sampling cottonseed piles. Three rapid analytical methods (one thin-layer chromatographic and 2 immunochemical) were tested for suitability as on-site assay systems. An analysis of variance of the analytical test results showed no differences between the various probes tested. Of the rapid methods, however, only the AflaTest-P immunoaffinity column gave results similar to those of the official AOAC thin-layer chromatography method. In terms of safety, however, all methods prevent material contaminated above regulatory limits from reaching the consumer.

Aflatoxins↗

PubMedDate not supplied

Liquid chromatographic method for determination of aflatoxins B1, B2, G1, and G2 in corn and peanut products: collaborative study.

A collaborative study of a liquid chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, Canada, South Africa, and Switzerland. Twenty-one artificially contaminated raw peanuts, peanut butter, and corn samples containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The test portion was extracted with methanol-0.1N HCl (4 + 1), filtered, defatted with hexane, and then partitioned with methylene chloride. The concentrated extract was passed through a silica gel column. Aflatoxins B1 and G1 were derivatized with trifluoroacetic acid, and the individual aflatoxins were determined by reverse-phase liquid chromatography with fluorescence detection. Statistical analysis of the data was performed to determine or confirm outliers, and to compute repeatability and reproducibility of the method. For corn, relative standard deviations for repeatability (RSDr) for aflatoxin B1 ranged from 27.2 to 8.3% for contamination levels from 5 through 50 ng/g. For raw peanuts and peanut butter, RSDr values for aflatoxin B1 were 35.0 to 41.2% and 11.2 to 19.1%, respectively, for contamination levels from 5 through 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. Relative standard deviations for reproducibility (RSDr) for aflatoxin B1 ranged from 15.8 to 38.4%, 24.4 to 33.4%, and 43.9 to 54.0% for corn, peanut butter, and raw peanuts, respectively. The method has been adopted official first action for the determination of aflatoxins B1, B2, G1, and G2 in peanut butter and corn at concentrations greater than or equal to 13 ng total aflatoxins/g.

Aflatoxin B1↗

PubMedDate not supplied

Enzyme-linked immunosorbent assay for screening aflatoxin B1 in cottonseed products and mixed feed: collaborative study.

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, South Africa, Switzerland, The Netherlands, Tunisia, and the United States. Twenty-eight samples of raw and roasted peanuts, corn, whole cottonseed, cottonseed meal, ammoniated cottonseed meal, and poultry feed containing various quantities of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on conjugation of pure aflatoxin B1 to an enzyme and the competition between this conjugate and (free) aflatoxins in the product for aflatoxin-specific antibodies coated onto microtiter well walls. After a wash step to remove all unbound aflatoxins, a substrate, added to each well, is catalyzed from a colorless to a green solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the product increases. Overall correlation was good between ELISA and thin-layer chromatographic (TLC) results for cottonseed products and mixed feed. Variable results were reported for corn and peanut product samples. Although some positive samples (greater than 15 ng/g) of cottonseed products and mixed feed were reported to contain less than 15 ng/g by visual determination, a review of data for absorbance measurements showed that the contamination level was close to the greater than or equal to 15 ng/g standard and would not have been reported as negative under routine screening.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxin B1↗

PubMedDate not supplied

Visual and semiquantitative spectrophotometric ELISA screening method for aflatoxin B1 in corn and peanut products: follow-up collaborative study.

A joint AOAC/IUPAC (International Union of Pure and Applied Chemistry) interlaboratory study of an enzyme-linked immunosorbent screening assay (ELISA) for aflatoxins was conducted in laboratories in Canada, France, Japan, The Netherlands, Switzerland, Tunisia, and the United States. Twelve raw and roasted peanut and corn portions containing various concentrations of natural aflatoxins and supplemented when appropriate with aflatoxin B1 were distributed to participating laboratories for testing. The assay is based on competition between an enzyme-conjugated aflatoxin B1 and (free) aflatoxins in the test sample for aflatoxin-specific antibodies coated onto interior surfaces of microtiter wells. After a wash step to remove all unbound aflatoxins, a substrate added to each well is catalyzed from a colorless to a blue solution by any bound enzyme-conjugated aflatoxin B1 present. The intensity of the color decreases as the amount of free aflatoxin B1 in the test portion increases. Final determination of aflatoxin concentrations can be made by either visual comparison with standard solutions or spectrophotometric comparisons (at 650 nm) to knowns. Overall correlation was good between ELISA and thin-layer chromatographic results for corn and roasted peanut products, with 93 and 98% correct responses for visual and instrumental determinations, respectively. For instrumental determinations of aflatoxin in corn and roasted peanuts in the less than or equal to 20 ng/g range, the relative standard deviations for repeatability (RSDr) were 14.9 and 41.4%, respectively, and the relative standard deviations for reproducibility (RSDR) were 45.7 and 43.5%, respectively. For instrumental determination of greater than 20 ng/g, the respective RSDr and RSDR values were 19.4 and 52.7% for corn and 23.3 and 23.3% for roasted peanuts.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxin B1↗

PubMedDate not supplied

Enzyme-linked immunosorbent assay of aflatoxins B1, B2, and G1 in corn, cottonseed, peanuts, peanut butter, and poultry feed: collaborative study.

A direct competitive enzyme-linked immunosorbent assay (ELISA) screening method for aflatoxins at 20 ng/g was studied by 12 collaborators. Test samples of peanut butter were extracted by blending with methanol-water-hexane (55 + 45 + 100) and heating the test extracts on a steam bath; test samples of the other commodities were extracted by blending with methanol-water (80 + 20). All test extracts were filtered and the filtrates were diluted with buffer to a final methanol concentration of less than 30%. Each diluted filtrate was applied to a cup containing a filter with immobilized polyclonal antibodies specific to aflatoxins B1, B2, and G1. Aflatoxin B1-peroxidase conjugate was added, the cup was washed with water, and a mixture of hydrogen peroxide and tetramethylbenzidine was added. The test sample was judged to contain greater than or equal to 20 ng aflatoxins/g when, after exactly 1 min, no color was observed on the filter; when a blue or gray color developed, the test sample was judged to contain less than 20 ng aflatoxins/g. All collaborators correctly identified naturally contaminated corn and raw peanut positive test samples. No false positives were found for controls containing less than 2 ng aflatoxins/g. The correct responses for positive test samples spiked at levels of 10, 20, and greater than or equal to 30 ng aflatoxins/g (the ratio of B1:B2:G1 was 10:1:3) were 52, 86, and 96%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aflatoxin B1↗

PubMedDate not supplied

Sampling and sample preparation for detection and quantitation of natural toxicants in food and feed.

The primary goal of a sampling plan for natural toxins, i.e., mycotoxins and seafood toxins, is to obtain a sample that accurately represents the concentrations of individual components of a given lot. Factors affecting the ability of the sampling plan to accomplish this goal include: (1) nature of the analyte of interest; (2) distribution of the analyte throughout the lot, (3) physical characteristics of the product, (4) accessibility of the product to random representative sampling, (5) sampling procedure, and (6) size of sample. Sampling plans are composed of 3 distinct components: (a) sampling, (b) sample preparation, and (c) analysis. Normally, sampling contributes the largest relative error while analysis comprises the least. Automatic, continuous stream samplers provide the most representative samples for commodities such as nuts, cottonseed, and cereal grains. Good sample preparation equipment is currently available for these commodities; the use of this equipment to obtain a representative test sample is discussed.

Animal Feed↗

PubMedDate not supplied

Review of the decontamination of aflatoxins by ammoniation: current status and regulation.

Ammoniation of corn, peanuts, cottonseed, and meals to alter the toxic and carcinogenic effects of aflatoxin contamination has been the subject of intense research effort by scientists in various government agencies and universities, both in the United States and abroad. Results of these studies have been well documented over the last 20 years. Engineers have devised workable systems of treatment of whole seeds, kernels, or meals; chemists have identified and characterized products formed from the reaction of aflatoxin B1 with ammonia with and without a meal matrix; biochemists have studied the biological effects of these compounds in model systems; and nutritionists have studied animal responses to rations containing ammoniated or non-ammoniated components. This review describes these studies. Results demonstrate overwhelming support for the efficacy and safety of ammoniation as a practical solution to aflatoxin detoxification in animal feeds.

Aflatoxins↗

PubMedDate not supplied

Evaluation of enzyme-linked immunosorbent assay of cleanup for thin-layer chromatography of aflatoxin B1 in corn, peanuts, and peanut butter.

A simple, rapid enzyme-linked immunoassay (ELISA) was used to evaluate the performance of each step (extraction, filtration, solvent partition, and silica gel column chromatography) of a solvent-efficient thin-layer chromatographic (TLC) method which is undergoing interlaboratory collaborative study for the determination of aflatoxin B1 in corn, raw peanuts, and peanut butter. The apparent average recoveries using the ELISA method were about 30 to 50% higher than those using the TLC method if only the amount of B1 added to the samples was used in the calculations. After the cross-reaction of the antibody with other aflatoxins added to the samples was considered, the amounts recovered approached the levels of aflatoxins added in all 3 commodities tested. With no cleanup treatment, ELISA recoveries at aflatoxin B1 levels above 7.5 ng/g were 84, 79, and 103% for corn, raw peanuts, and peanut butter, respectively. The coefficients of variation were between 5.2 and 25.2%. With each cleanup step in the TLC method, ELISA detected a progressive decrease in recovery from 150.5 to 105.3% (before correction for the presence of other aflatoxins) or from 93.5 to 65.4% (after correction for other aflatoxins) of B1 added to the samples. The ELISA data support the conclusion obtained from previous studies that cleanup treatments were not necessary in the ELISA. When large amounts of other aflatoxins are present, an understanding of the cross-reactivity of antibody with other aflatoxins in the ELISA is essential for final interpretation of the data.

Aflatoxin B1↗

PubMedDate not supplied

Variability of mouse bioassay for determination of paralytic shellfish poisoning toxins.

Toxic shellfish extracts and paralytic shellfish poison (PSP) standard solutions, tested over a range of pH levels, storage conditions, and temperatures, were monitored for toxin concentration, using the mouse bioassay and thin layer chromatography (TLC). A comparison of PSP toxin concentrations in toxic shellfish extracts and PSP standard solutions when dilution was varied suggests that other factors in the shellfish extracts contribute to the toxicity in mice; the closet agreement was at the death time range of 5-8 min. The toxicities of PSP standard solutions at pH levels ranging from 2 to 6 and held at 4 degrees C for various times were relatively constant; however, there was a gradual decrease in toxicity with pH 6 solutions. Also, standard solutions (pH 6) held at 4 degrees C for 28 days showed a 50% decrease in toxicity when the pH was adjusted to 2. TLC analyses of PSP standard solutions and toxic shellfish extracts revealed multiple spots at the Rf ranges of saxitoxin/neosaxitoxin and gonyaulax toxins I-IV. PSP standard solutions usually had a single spot in the saxitoxin/neosaxitoxin area. No attempt was made to confirm the identity of these compounds. Previously tested toxic shellfish extracts with subsequent pH adjustment to 1.5 and additional heat treatment (100 degrees C for 5 min) showed no appreciable difference in mouse toxicity. The use of antifoaming agents during the acid extraction step did not affect the final amounts of PSP obtained.

Animals↗

PubMedDate not supplied

Negative ion chemical ionization mass spectrometric method for confirmation of identity of aflatoxin B1: collaborative study.

An interlaboratory study of a negative ion chemical ionization mass spectrometric (MS) confirmation procedure for aflatoxin B1 was conducted in laboratories in the United States, England, and West Germany. Twelve partially purified, dry film extracts from naturally and artificially contaminated roasted peanuts, cottonseed, and ginger root containing varying quantities of aflatoxin B1 were distributed to the participating laboratories. The extracts required additional cleanup before MS analysis, using either an acidic alumina column and preparative thin layer chromatography (TLC) or a 2-dimensional TLC procedure. Recovery of purified aflatoxin B1 was influenced by the degree of recovery of sample from acid alumina and/or the TLC plate and incomplete elution of aflatoxin B1 from silica gel. Factors affecting MS confirmation included the purity and recovery of aflatoxin and MS instrument sensitivity. Aflatoxin B1 identity was confirmed in 19.5, 90.9, and 100% of samples containing less than 5, 5-10, and greater than 10 ng aflatoxin B1/g product, respectively, by solid probe introduction using full mass scans. The MS method has been adopted official first action.

Aflatoxin B1↗

PubMedDate not supplied

Solvent-efficient thin-layer chromatographic method for the determination of aflatoxins B1, B2, G1, and G2 in corn and peanut products: collaborative study.

An interlaboratory study of a solvent-efficient thin-layer chromatographic (TLC) method for the determination of aflatoxins B1, B2, G1, and G2 was conducted in laboratories located in the United States, France, Tunisia, and Denmark. Eighteen artificially contaminated samples plus blanks of raw peanuts and peanut butter and corn containing varying amounts of aflatoxins B1, B2, G1, and G2 were distributed to participating laboratories. The method consists of elements of the U.S. Food and Drug Administration (FDA), Contaminants Branch (CB) (AOAC Method 968.22) and FDA, Best Foods (BF) (AOAC Method 970.45) methods with reduced requirements for solvents. Participating laboratories used either visual or densitometric techniques during the final determinative step. Statistical analysis of the data was performed to determine or confirm outliers and to compute repeatability and reproducibility of the method using either visual or densitometric techniques for the determinative step. Reported results from laboratories using a densitometer showed that, for corn, the relative standard deviation for repeatability (RSDr) for aflatoxin B1 ranged from 56.6 to 41.7% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 ranged from 21.3 to 37.3% and 65.9 to 42.1%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr ranges for aflatoxins B2, G1, and G2 were similar. For reproducibility (R), the RSDR ranges for aflatoxin B1 were 41.7-56.6%, 56.6-84.8%, and 26.4-37.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 95.3, 139.0, and 95.6% for corn, peanut butter, and raw peanuts, respectively. When analysts determined aflatoxin concentrations in corn by visual comparison to standards, the RSDr values for aflatoxin B1 were 47.8-11.4% for contamination levels ranging from 5 to 50 ng/g. For raw peanuts and peanut butter, the RSDr values for aflatoxin B1 were 76.3-12.6% and 33.4-8.8%, respectively, for the contamination levels ranging from 5 to 25 ng/g. RSDr values for aflatoxins B2, G1, and G2 were similar. The RSDR values for aflatoxin B1 were 34.6-90.2%, 45.5-59.3%, and 31.8-78.3% for corn, peanut butter, and raw peanuts, respectively. Average recoveries for all aflatoxins at all levels were 111.0, 157.6, and 92.3% for corn, peanut butter, and raw peanuts, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)

Aflatoxin B1↗