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Biomedical subjects

W F Kwolek

Publications and source records attributed to W F Kwolek.

At least 19 recordsLinked to original sources
PubMed1984

Aflatoxin contamination of maize kernels before harvest. Interaction of Aspergillus flavus spores, corn earworm larvae and fungicide applications.

Two maize (Zea mays L.) hybrids with varying degrees of resistance to damage by corn earworm (CEW) (Heliothis zea Boddie) were grown in Iowa, Georgia, and Missouri. Treatments included: introduction of Aspergillus flavus Link ex. Fr. spores onto newly-emerged silks, application of a fungicide as an aqueous spray onto test ears during the first three weeks after flowering, infestation of ears with CEW eggs, and combinations of these variables. CEW larvae were collected from developing ears and examined for the presence of internal A. flavus group propagules. Aflatoxin levels were determined in mature kernels. Toxin concentrations exhibited a distinct regional variation with relatively high levels in Georgia samples, intermediate concentrations in Missouri kernels and low levels in Iowa samples. No treatment effects were noted in Georgia samples but introduction of A. flavus and CEW increased toxin accumulation in Missouri kernels. Although the CEW-susceptible hybrid exhibited a trend towards increased damage by the insect, no treatment-related differences were observed in the presence of the fungus in larvae or in aflatoxin contamination. Fungicide applications did not significantly reduce aflatoxin levels in mature kernels.

Aflatoxins↗
PubMed1983

Variability of bright, greenish-yellow fluorescent particles and aflatoxin in ground blends of Zea mays.

Developing corn (Zea mays) kernels of single cross B73 X Mo17 grown near Columbia, MO, were inoculated with conidia of Aspergillus flavus or A. parasiticus. After harvest bright greenish-yellow fluorescing (BGYF) kernels were selected under ultraviolet black light (365 nm); they contained 3696 ng/g (A. parasiticus strain NRRL 3145) and 6666 ng/g (A. flavus strain UGA 5337) aflatoxins, respectively. The BGYF-free kernels were obtained from the same hybrid grown in northern Iowa. No BGYF kernels nor aflatoxins were found in 10 assays. To assess the variability in detection of BGYF particles and aflatoxin in ground corn blends, a series was developed by mixing BGYF kernels with BGYF-free kernels in various ratios. In the finely ground samples, standard deviations decreased significantly (P = 0.05) among blends for aflatoxin values in mixtures with higher levels of BGYF particles. Strain 3145 (A. parasiticus) was significantly (P = 0.01) different from strain 5337 (A. flavus) for aflatoxins concentration and the number of grams of BGYF in the blends (r greater than 0.99). The percent fines (passed a 40-mesh screen) in ground, 100% BGYF kernels was significantly (P = 0.01) higher for strain 3145 (A. parasiticus) inoculated samples than for strain 5337 (A. flavus) in spite of equivalent grinding procedures. This observation showed that the relationship between aflatoxin levels determined for a sample and the fraction of BGYF material in the blend was dependent on the fungal-strain source of the BGYF kernels used in the blend.

Aflatoxins↗
PubMed1983

Extraction and thin layer chromatography of aflatoxin B1 in mixed feeds.

A method was developed for the determination of aflatoxin B1 in commercially prepared feeds. The method incorporates methylene chloride and citric acid solution extraction, cleanup on a small silica gel column, and thin layer chromatography for quantitation. Commercial turkey starter, catfish chow, medicated pig starter, broiler finisher, rabbit chow, horse feed, rat chow, and dog chow were investigated. The feeds were spiked with naturally contaminated corn at 4 different levels of aflatoxin B1 (16-130 microgram/kg). Three assays were run on each of the 32 combinations of feed and levels of aflatoxin. Mean recoveries were 85.9-92.8% at levels of 16.5, 32.9, 65.8, and 131.6 micrograms/kg. The relative standard deviation per assay was 18.6%. This method is more rapid and less involved than most previously published methods for mixed feeds.

Aflatoxin B1↗
PubMed1983

Treatment of freshly harvested 1980 Georgia dent corn samples collected for aflatoxin analysis.

In 1980, corn was harvested from six 15-ft rows in each of 67 fields in Georgia for aflatoxin analysis. Every sixth ear from each field was placed in a sample bag to be dried the day of collection. The rest of the corn was husked and shipped to Peoria in cardboard boxes. When undried ear samples arrived in Peoria, each sample was randomly separated into 5 equivalent subsamples. One set of 67 subsamples was shelled and dried as soon as possible to avoid further aflatoxin formation. Two other sets of 67 subsamples were stored 3 and 6 weeks before shelling and drying. The remaining 2 sets of ear samples were placed in plastic bags with 5% Monoprop (1 part propionic acid plus 1 part versite) and stored 3 and 6 weeks before shelling and drying. The samples dried in Georgia before shipping had an average total aflatoxin level of 217 ng/g. Samples shelled and dried immediately after arrival had an average level of 202 ng/g. Samples shelled and dried after 3 and 6 weeks of storage had average total aflatoxin levels of 417 and 387 ng/g, respectively. Samples stored 3 and 6 weeks in the presence of 5% Monoprop (2.5% propionic acid) had average total aflatoxin levels of 120 and 157 ng/g, respectively.

Aflatoxins↗
PubMed1982

Production of vomitoxin on corn by Fusarium graminearum NRRL 5883 and Fusarium roseum NRRL 6101.

Two vomitoxin-producing isolates of Fusarium spp. were grown on cracked corn for 1 to 8 weeks at 15, 20, 25, 28, and 32 degrees C. Maximum production of vomitoxin by Fusarium graminearum Schw. NRRL 5883 occurred at 30 degrees C and 40 days, and that by Fusarium roseum Schw. NRRL 6101 occurred at 26 degrees C and 41 days. These optimum production points were determined from response surface contour graphs in relation to temperature and time. Only small amounts of vomitoxin were produced at 15 and 20 degrees C by each strain. A 133-microgram quantity of vomitoxin, with an indicated purity of 95%, was isolated per gram of corn fermented with F. graminearum NRRL 5883.

Fusarium↗
PubMed1982

Determination and thin layer chromatographic confirmation of identity of aflatoxins B1 and M1 in artificially contaminated beef livers: collaborative study.

An international collaborative study involving 13 laboratories was conducted to test methods for the determination and thin layer chromatographic (TLC) confirmation of identity of aflatoxins B1 and M1 in beef liver. For the determination, each collaborator furnished fresh or frozen beef liver. Samples were artificially contaminated by adding solutions containing various concentrations of aflatoxins B1 and M1 (0.032-0.69 ng/g). Two TLC confirmation methods were tested with extracts obtained from the determination. Two measurement methods using 2-dimensional TLC were evaluated. In the first, sample extracts were compared directly with B1 and M1 standards on TLC plates; in the second, internal standards plus sample extracts were compared with B1 and M1 standards on the plates. Average within-laboratory coefficients of variation (CV) for the direct method were 26% for B1 and 26% for M1 compared with 24 and 26%, respectively, for the internal standard method. The average between-laboratory CV values were 39% for B1 and 41% for M1 by the direct method and 36% for B1 and 39% for M1 by the internal method and 36% for B1 and 39% for M1 by the internal standard method. Recoveries ranged from 64 to 90% for B1 and from 72 to 86% for M1. These data indicate that the more convenient direct method was sufficient, and internal standards were unnecessary. An analysis of variance was calculated from combined sample data to determine components of variance. The within-laboratory CV values were 27.0 and 32.3% for B1 and M1, respectively, and the between-laboratory CV values were 47.1 and 53.2%, respectively. Both TLC confirmation methods gave satisfactory results and have been adopted official first action, along with the determination method.

Aflatoxin B1↗
PubMed1981

Thermal inactivation of eight Salmonella serotypes on dry corn flour.

Dry heat was used to inactivate Salmonella newington, Salmonella typhimurium, Salmonella anatum, Salmonella kentucky, Salmonella cubana, Salmonella seftenberg, Salmonella thompson, and Salmonella tennessee in corn flour at 10 and 15% moisture. The flour was spray inoculated at 10(5) Salmonella cells per g and then stored at 49 degrees C (120 degrees F); viable Salmonella cells were counted on Trypticase (BBL Microbiology Systems) soy agar plates every 30 min for the first 4 h and then at 4-h intervals for 20 additional h of storage. After 24 h, 99.9% of all Salmonella cells were killed. S. thompson and S. tennessee were more resistant to heat inactivation than the other serotypes. Naturally occurring contamination by Salmonella spp. in dry food products could be significantly reduced with this treatment.

Flour↗
PubMed1980

Mouse bioassay for Fusarium metabolites: rejection or acceptance when dissolved in drinking water.

Ten metabolites of Fusarium species (butenolide, diacetoxyscirpenol, equisetin, fusaric acid, gibberellic acid, moniliformin, NRRL 6227 peptide, T-2 toxin, vomitoxin, and zearalenone) were added to the drinking water of mice to determine whether they were consumed or refused. Of the 10, only the trichothecenes--diacetoxyscirpenol, T-2 toxin, and vomitoxin--were refused. Refusal of 2 mg of the trichothecenes per liter was not enhanced by adding 100 mg of zearalenone per liter.

Animals↗
PubMed1979

Tissue distribution of radioactivity from ochratoxin A-14C in rats.

Examination of the distribution of radioactivity in rat tissues during the first 24 hr after administration of ochratoxin A-14C demonstrated maximum accumulation in stomach and kidney. The highest counts were observed in stomach, lung, kidney, thymus, spleen and heart during the first 6 hr after treatment, whereas the brain, liver muscle, duodenum, jejunum, ileum, and cecum exhibited the greatest counts at 18 hr after toxin exposure.

Animals↗
PubMed1979

Mass spectrometric analysis of deuterium dual labeled blood lipids.

A gas chromatography selected ion monitoring mass spectrometer technique was developed to analyze deuterium dual labeled blood lipid samples from a human feeding experiment. In the metabolism experiment, described elsewhere. [2H2] labeled cis and [2H4] labeled trans fatty acids were fed to a human sujbect as a single pulse in order to determine whether the human body differentiates between cis and trans fatty acids in the diet. The analytical method described here was developed to accurately measure the ratio of [2H2]methyl oleate to [2H4]methyl elaidate in the presence of large amounts of [2H0] methyl oleate in samples derived from separated fractions of blood lipids. The technique is different from most selected ion monitoring methods in that the internal standard was fed to the subject along with the experimental material; the samples contained large amounts of unlabeled material chemically identical to the labeled material and the ratio of [2H2] to [2H4] fatty esters was of principal interest rather than the absolute value. Nine standards were analyzed eight or more times to form a basis for statistical evaluation of the method. Analysis of the plasma phosphatidyl ethanolamine fraction from the metabolic experiment is given as an example.

Analog-Digital Conversion↗
PubMed1979

Aflatoxin variation among corn samples with varying ratios of Aspergillus flavus-inoculated/noninoculated kernels.

Aflatoxin levels and physical properties of corn kernels inoculated with Aspergillus flavus during development and noninoculated kernels were compared in samples with various proportions of the 2 kernel types. The relationship between mean toxin levels and associated standard deviations of 5 samples demonstrated a linear association from the lowest toxin in noninoculated corn through a mixture of 60% inoculated/40% noninoculated. However, at the highest toxin level in the 100% inoculated material, a reduction in sample variation was observed. Examination of individual kernal weights showed that inoculated kernels were distinctly lighter than noninoculated seed. A uniform grinding procedure of the samples yielded heterogeneous particle sizes based on the starting corn. The large particle fraction (greater than 500 micrometers) decreased from 100% noninoculated kernels through the mixtures to the 100% inoculated seed; particles below 150 micrometers were most abundant in the ground samples from inoculated kernels. In addition, the density of particles within a size category varied; lower densities were observed in samples obtained from A. flavus-inoculated kernels.

Aflatoxins↗
PubMed1977

Aflatoxin in corn: evaluation of filter fluorometer reading of minicolumns.

A minicolumn method using a filter fluorometer was compared with thin layer chromatography for determining aflatoxin in corn. The minicolumn-fluorometer method identified many more samples as aflatoxin-positive than the AOAC CB method. Some corn samples contain a blue-fluorescing substance that interferes with minicolumn chromatography of aflatoxins. Aflatoxin levels measured by the minicolumn-fluorometer method did not correspond to those obtained by the CB method.

Aflatoxins↗
PubMed1976

Aspergilus flavus and aflatoxin in Iowa corn before harvest.

Aspergillus flavus and aflatoxin were detected in ears of Iowa corn on plants before harvest in 1975. Presence of the fungus was associated with kernel injury caused by the second generation European corn borer. Amounts of aflatoxin B1 in corn from a limited number of selected ears ranged from 1 part per billion to 1560 parts per billion with a mean of 430 parts per billion.

Aflatoxins↗