T E Cleveland

United States Department of Agriculture, Washington, Washington, D.C., United States

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Publications (215)475.72 Total impact

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    ABSTRACT: The persistent occurrence of aflatoxins in food and feed remains a problem for producers of commodities subject to colonization with toxigenic molds. Aflatoxins are secondary metabolites of fungi of the Aspergillus spp. associated with deleterious health effects. Because current screening methods for these toxins are lengthy, destructive, and costly, there is a continuous search for a more rapid, noninvasive, and cost-effective technology. The present study utilized a fluorescence excitation–emission matrix (EEM) of aflatoxin as well as two additional secondary metabolites (kojic acid and the bright greenish-yellow fluorescence (BGYF) compound) of Aspergillus flavus measured with a fluorescence spectrophotometer. The results were compared to image data acquired with a fluorescence hyperspectral sensor in order to evaluate the potential of image-based technology for detecting aflatoxin in grain. The excitation–emission matrix of aflatoxin B1 standard produced overlapping peaks in 340–400 nm of excitation range emitting in the blue range at around 450 nm. The spectral signature extracted from the hyperspectral image was also in the blue range, emitting blue fluorescence. Because the results from both systems were comparable, where all fluorescence peaks were in the blue range, the present study validates the feasibility of image-based technology for nondestructive detection of aflatoxin in corn. Additional peaks were revealed in the aflatoxin EEM in the 260-nm excitation range that were not present in the kojic acid and BGYF compound mixture. This new information allows for the separation of the aflatoxin signature from the potentially confounding overlap of other secondary metabolites occurring in the blue and blue-green spectral ranges.
    Food and Bioprocess Technology 04/2014; 7(4). · 4.12 Impact Factor
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    ABSTRACT: A currently utilized pre-harvest biocontrol method involves field inoculations with non-aflatoxigenic Aspergillus flavus strains, a tactic shown to strategically suppress native aflatoxin-producing strains and effectively decrease aflatoxin contamination in corn. The present in situ study focuses on tracking the invasion and colonization of an aflatoxigenic A. flavus strain (AF70), labeled with green fluorescent protein (GFP), in the presence of a non-aflatoxigenic A. flavus biocontrol strain (AF36), to better understand the competitive interaction between these two strains in seed tissue of corn (Zea mays). Corn kernels that had been co-inoculated with GFP-labeled AF70 and wild-type AF36 were cross-sectioned and observed under UV and blue light to determine the outcome of competition between these strains. After imaging, all kernels were analyzed for aflatoxin levels. There appeared to be a population difference between the co-inoculated AF70-GFP+AF36 and the individual AF70-GFP tests, both visually and with pixel count analysis. The GFP allowed us to observe that AF70-GFP inside the kernels was suppressed up to 82% when co-inoculated with AF36 indicating that AF36 inhibited progression of AF70-GFP. This was in agreement with images taken of whole kernels where AF36 exhibited a more robust external growth compared to AF70-GFP. The suppressed growth of AF70-GFP was reflected in a corresponding (upto 73%) suppression in aflatoxin levels. Our results indicate that the decrease in aflatoxin production correlated with population depression of the aflatoxigenic fungus by the biocontrol strain supporting the theory of competitive exclusion through robust propagation and fast colonization by the non-aflatoxigenic fungus.
    Frontiers in Microbiology 01/2014; 5:122. · 3.90 Impact Factor
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    ABSTRACT: In an effort to address the problem of rapid detection of aflatoxin in grain, particularly oilseeds, the current study assessed the spectral differences of aflatoxin production in kernels from a cornfield inoculated with spores from 2 different strains of toxigenic Aspergillus flavus. Aflatoxin production in corn from the same field due to natural infestation was also assessed. A small corn plot in Baton Rouge, La., U.S.A., was used during the 2008-growing season. Two groups of 400 plants were inoculated with 2 different inocula and 1 group of 400 plants was designated as controls. Any contamination detected in the controls was attributed to natural infestation. A subset of each group was imaged with a visible near infra red (VNIR) hyperspectral system under ultra violet (UV) excitation and subsequently analyzed for aflatoxin using affinity column fluorometry. Group differences were statistically analyzed. Results indicate that when all the spectral data across all groups were averaged, any potential differences between groups (treated and untreated) were obscured. However, spectral analysis based on contaminated "hot" pixel classification showed a distinct spectral shift/separation between contaminated and clean ears with fluorescence peaks at 501 and 478 nm, respectively. All inoculated and naturally infected control ears had fluorescence peaks at 501 nm that differed from uninfected corn ears. Results from this study may be useful in evaluating rapid, noninvasive instrumentation and/or methodology for aflatoxin detection in grain.
    Journal of Food Science 08/2013; 78(8):T1313-20. · 1.78 Impact Factor
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    ABSTRACT: Aflatoxin contamination caused by Aspergillus flavus infection of corn is a significant and chronic threat to corn being used as food or feed. Contamination of crops at levels of 20 ng g(-1) or higher (as regulated by the USFDA) by this toxin and potent carcinogen makes the crop unsalable, resulting in a significant economic burden on the producer. This review focuses on elimination of this contamination in corn which is a major US crop and the basis of many products. Corn is also "nature's example" of a crop containing heritable resistance to aflatoxin contamination, thereby serving as a model for achieving resistance to aflatoxin contamination in other crops as well. This crop is the largest production grain crop worldwide, providing food for billions of people and livestock and critical feedstock for production of biofuels. In 2011, the economic value of the US corn crop was US$76 billion, with US growers producing an estimated 12 billion bushels, more than one-third of the world's supply. Thus, the economics and significance of corn as a food crop and the threat to food safety due to aflatoxin contamination of this major food crop have prompted the many research efforts in many parts of the world to identify resistance in corn to aflatoxin contamination. Plant breeding and varietal selection has been used as a tool to develop varieties resistance to disease. This methodology has been employed in defining a few corn lines that show resistance to A. flavus invasion; however, no commercial lines have been marketed. With the new tools of proteomics and genomics, identification of resistance mechanisms, and rapid resistance marker selection methodologies, there is an increasing possibility of finding significant resistance in corn, and in understanding the mechanism of this resistance.
    Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment 07/2013;
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    ABSTRACT: Highlights ► Used fluorescence hyperspectral imagery to study Aspergillus flavus inoculated maize. ► Toxigenic and atoxigenic strains of fungi were compared in the study. ► The actual aflatoxin of each maize kernel was chemically measured. ► The best results for separation were achieved with the germ side of the maize kernels. ► The study showed potential of imaging for aflatoxin contamination detection in maize.
    Biosystems Engineering. 06/2013; 115(2):125–135.
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    ABSTRACT: Naturally occurring Aspergillus flavus strains can be either toxigenic or atoxigenic, indicating their ability to produce aflatoxin or not, under specific conditions. Corn contaminated with toxigenic strains of A. flavus can result in great losses to the agricultural industry and pose threats to public health. Past research showed that fluorescence hyperspectral imaging could be a potential tool for rapid and non-invasive detection of aflatoxin contaminated corn. The objective of the current study was to assess, with the use of a hyperspectral sensor, the difference in fluorescence emission between corn kernels inoculated with toxigenic and atoxigenic inoculums of A. flavus. Corn ears were inoculated with AF13, a toxigenic strain of A. flavus, and AF38, an atoxigenic strain of A. flavus, at dough stage of development and harvested 8 weeks after inoculation. After harvest, single corn kernels were divided into three groups prior to imaging: control, adjacent, and glowing. Both sides of the kernel, germplasm and endosperm, were imaged separately using a fluorescence hyperspectral imaging system. It was found that the classification accuracies of the three manually designated groups were not promising. However, the separation of corn kernels based on different fungal inoculums yielded better results. The best result was achieved with the germplasm side of the corn kernels. Results are expected to enhance the potential of fluorescence hyperspectral imaging for the detection of aflatoxin contaminated corn.
    Proc SPIE 05/2012;
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    ABSTRACT: The genomic study of filamentous fungi has made significant advances in recent years, and the genomes of several species in the genus Aspergillus have been sequenced, including Aspergillus flavus. This ubiquitous mold is present as a saprobe in a wide range of agricultural and natural habits, and can function as an opportunistic animal and plant pathogen. A. flavus produces many secondary metabolites including aflatoxins, aflatrem and cyclopiazonic acid. In this chapter, our main focus is on the current status of the genomics of A. flavus as well as on the potential applications of genomics-based approaches to understanding mycotoxin production and fungal pathogenicity. It is hoped that the results of A. flavus genomics and functional genomics studies will empower researchers to find effective controlling strategies to eliminate mycotoxin contamination and to yield a safer and more abundant food and feed supply.
    Mycology. 09/2011; 2(3):218-236.
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    ABSTRACT: To better understand the effect of temperature on mycotoxin biosynthesis, RNA-Seq technology was used to profile the Aspergillus flavus transcriptome under different temperature conditions. This approach allowed us to quantify transcript abundance for over 80% of fungal genes including 1153 genes that were differentially expressed at 30 and 37 °C. Eleven of the 55 secondary metabolite clusters were upregulated at the lower temperature, including aflatoxin biosynthesis genes, which were among the most highly upexpressed genes. On average, transcript abundance for the 30 aflatoxin biosynthesis genes was 3300 times greater at 30 °C as compared with 37 °C. The results are consistent with the view that high temperature negatively affects aflatoxin production by turning down transcription of the two key transcriptional regulators, aflR and aflS. Subtle changes in the expression levels of aflS to aflR appear to control transcription activation of the aflatoxin cluster.
    FEMS Microbiology Letters 06/2011; 322(2):145-9. · 2.05 Impact Factor
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    ABSTRACT: A 14-step biomimetic synthetic route to glyceollin I (1.5% overall yield) was developed and deployed to produce the natural enantiomeric form in soy, its unnatural stereoisomer, and a racemic mixture. Enantiomeric excess was assessed by asymmetric NMR shift reagents and chiral HPLC. Antiproliferative effects were measured in human breast, ovarian, and prostate cancer cell lines, with all three chiral forms exhibiting growth inhibition (GI) in the low to mid μM range for all cells. The natural enantiomer, and in some cases the racemate, gave significantly greater GI than the unnatural stereoisomer for estrogen receptor positive (ER(+)) versus ER(-) breast/ovarian cell lines as well as for androgen receptor positive (AR(+)) versus AR(-) prostate cancer cells. Surprisingly, differences between ER(+) and ER(-) cell lines were not altered by media estrogen conditions. These results suggest the antiproliferative mechanism of glyceollin I stereoisomers may be more complicated than strictly ER interactions.
    Journal of Medicinal Chemistry 05/2011; 54(10):3506-23. · 5.61 Impact Factor
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    ABSTRACT: Aspergillus flavus is the most infamous species among the over 185 known species within the genus Aspergillus. It is not only one of the most abundant and widely distributed soil-borne molds that can be found anywhere on earth but,also produces aflatoxins, among the most carcinogenic natural products ever discovered (Jelinek et al., 1989). A. flavus is a saprobe capable of surviving on many organic nutrient sources like plant debris, tree leaves, decaying wood, animal fodder, cotton, compost piles, dead insects and animal carcasses, stored grains, and even human and animal patients (Klich, 1998). Its optimal range for growth is between 25 – 37°C, but it can grow in a wide range of temperatures from 12 to 48°C. The ability of the fimgus to grow at relatively high temperatures of the fungus contributes to its pathogenicity in humans and other warm blooded animals. For most of its life-cycle, the fungus exists in the form of mycelia or asexual spores known as conidia. Stress from adverse conditions such as lack of adequate nutrients or water, causes the mycelia to form resistant structures called sclerotia. The fungus over-winters either as spores, as scierotia or as mycelia in debris. Under favorable conditions scierotia germinate directly to produce new colonies or conidiophores with conidia (Bennett et al., 1986; Cotty, 1988; Chang et al., 2002)
    02/2011: pages 51-73;
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    ABSTRACT: Selective principal component regression analysis (SPCR) uses a subset of the original image bands for principal component transformation and regression. For optimal band selection before the transformation, this paper used genetic algorithms (GA). In this case, the GA process used the regression correlation as its fitness function. This algorithm was used for analyzing fluorescence hyperspectral images of aflatoxin contaminated corn kernels. The results showed that SPCR could produce results similar to the standard PCR approach. However, the data dimension was much less for the SPCR process. The SPCR correlation coefficient was 0.8 when 33 of the original 74 bands were used for the SPCR transformation. The results demonstrated that SPCR could be used as a combined dimension reduction and data analysis tool for high dimensionality data processing.
    Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2011 3rd Workshop on; 01/2011
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    ABSTRACT: Toxigenic and atoxigenic strains of Aspergillus flavus were grown on potato dextrose agar (PDA) and wetted (23% moisture) sterile, cracked corn for 14 and 21 days, respectively. Volatile compounds produced by A. flavus, as well as those present in the PDA controls and sterile cracked maize, were collected using solid-phase micro-extraction (SPME) and identified by gas chromatography/mass spectrometry. Results show that growth substrate had a major impact on the number and type of volatiles detected. Growth on sterile cracked maize produced many more volatiles than did potato dextrose agar. There were also differences observed in the type of volatiles produced between toxigenic and non-toxigenic isolates, as well as between isolates of the same toxigenic grouping.
    Annals of agricultural and environmental medicine: AAEM 12/2010; 17(2):301-8. · 3.06 Impact Factor
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    ABSTRACT: Glyceollins are pterocarpan phytoalexins elicited in high concentrations when soybeans are stressed. We have previously reported that the three glyceollin isomers (GLY I-III) exhibit antiestrogenic properties, which may have significant biological effects upon human exposure. Of the three isomers, we have recently shown that glyceollin I is the most potent antiestrogen. Natural (-)-glyceollin I recently was synthesized along with its racemate and unnatural (+) enantiomer. In this study, we compared the glyceollin I enantiomers' ER binding affinity, ability to inhibit estrogen responsive element transcriptional (ERE) activity and endogenous gene expression in MCF-7 cells. The results demonstrated similar binding affinities for both ERalpha and ERbeta. Reporter gene assays in MCF-7 cells revealed that while (+)-glyceollin I slightly stimulated ERE transcriptional activity, (-)-glyceollin I decreased activity induced by estrogen. Co-transfection reporter assays performed in HEK 293 cells demonstrated that (+)-glyceollin I increased ERE transcriptional activity of ERalpha and ERbeta with and without estrogen with no antiestrogenic activity observed. Conversely, (-)-glyceollin I decreased the activity of both ER subtypes stimulated by estradiol demonstrating potent antiestrogenic properties. Additionally, each Gly I enantiomer induced unique gene expression profiles in a PCR array panel of genes commonly altered in breast cancer.
    Steroids 12/2010; 75(12):870-8. · 2.80 Impact Factor
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    ABSTRACT: Aflatoxin contamination in corn is a serious problem for both producers and consumers. The present study applied the Spectral Angle Mapper classification technique to classify single corn kernels into contaminated and healthy groups. Fluorescence hyperspectral images were used in the classification. Actual corn aflatoxin concentration was chemically determined using the VICAM analytical method for quantification purpose. An obvious fluorescence peak shift was observed to be associated with the aflatoxin contaminated corn. Aflatoxin classification levels were based on Food and Drug Administration's regulation, including 20 ppb (parts per billion) for human consumption and 100 ppb for feed. Classification accuracy for the 20 ppb level is 86% with a false positive rate of 15%. For the 100 ppb level, the accuracy is 88% with a false positive rate of 16%. The results indicate that the Spectral Angle Mapper method and fluorescence hyperspectral imagery have the potential to classify aflatoxin contaminated corn kernels.
    Hyperspectral Image and Signal Processing: Evolution in Remote Sensing (WHISPERS), 2010 2nd Workshop on; 07/2010
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    ABSTRACT: Aflatoxins are toxic secondary metabolites of the fungi Aspergillus flavus and Aspergillus parasiticus, among others. Aflatoxin contaminated corn is toxic to domestic animals when ingested in feed and is a known carcinogen associated with liver and lung cancer in humans. Consequently, aflatoxin levels in food and feed are regulated by the Food and Drug Administration (FDA) in the US, allowing 20 ppb (parts per billion) limits in food and 100 ppb in feed for interstate commerce. Currently, aflatoxin detection and quantification methods are based on analytical tests including thin-layer chromatography (TCL) and high performance liquid chromatography (HPLC). These analytical tests require the destruction of samples, and are costly and time consuming. Thus, the ability to detect aflatoxin in a rapid, nondestructive way is crucial to the grain industry, particularly to corn industry. Hyperspectral imaging technology offers a non-invasive approach toward screening for food safety inspection and quality control based on its spectral signature. The focus of this paper is to classify aflatoxin contaminated single corn kernels using fluorescence hyperspectral imagery. Field inoculated corn kernels were used in the study. Contaminated and control kernels under long wavelength ultraviolet excitation were imaged using a visible near-infrared (VNIR) hyperspectral camera. The imaged kernels were chemically analyzed to provide reference information for image analysis. This paper describes a procedure to process corn kernels located in different images for statistical training and classification. Two classification algorithms, Maximum Likelihood and Binary Encoding, were used to classify each corn kernel into "control" or "contaminated" through pixel classification. The Binary Encoding approach had a slightly better performance with accuracy equals to 87% or 88% when 20 ppb or 100 ppb was used as classification threshold, respectively.
    Proc SPIE 04/2010;
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    ABSTRACT: The objective of this study was to examine the relationship between fluorescence emissions of corn kernels inoculated with Aspergillus flavus and aflatoxin contamination levels within the kernels. Aflatoxin contamination in corn has been a long-standing problem plaguing the grain industry with potentially devastating consequences to corn growers. In this study, aflatoxin-contaminated corn kernels were produced through artificial inoculation of corn ears in the field with toxigenic A. flavus spores. The kernel fluorescence emission data were taken with a fluorescence hyperspectral imaging system when corn kernels were excited with ultraviolet light. Raw fluorescence image data were preprocessed and regions of interest in each image were created for all kernels. The regions of interest were used to extract spectral signatures and statistical information. The aflatoxin contamination level of single corn kernels was then chemically measured using affinity column chromatography. A fluorescence peak shift phenomenon was noted among different groups of kernels with different aflatoxin contamination levels. The fluorescence peak shift was found to move more toward the longer wavelength in the blue region for the highly contaminated kernels and toward the shorter wavelengths for the clean kernels. Highly contaminated kernels were also found to have a lower fluorescence peak magnitude compared with the less contaminated kernels. It was also noted that a general negative correlation exists between measured aflatoxin and the fluorescence image bands in the blue and green regions. The correlation coefficients of determination, r(2), was 0.72 for the multiple linear regression model. The multivariate analysis of variance found that the fluorescence means of four aflatoxin groups, <1, 1-20, 20-100, and >or=100 ng g(-1) (parts per billion), were significantly different from each other at the 0.01 level of alpha. Classification accuracy under a two-class schema ranged from 0.84 to 0.91 when a threshold of either 20 or 100 ng g(-1) was used. Overall, the results indicate that fluorescence hyperspectral imaging may be applicable in estimating aflatoxin content in individual corn kernels.
    Food Additives and Contaminants - Part A Chemistry, Analysis, Control, Exposure and Risk Assessment 03/2010; 27(5):701-9.
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    ABSTRACT: Maize (Zea mays L.) is a major crop susceptible to Aspergillus flavus infection and subsequent contamination with aflatoxins, the potent carcinogenic secondary metabolites of the fungus. Protein profiles of maize genotypes resistant and susceptible to A. flavus infection and/or aflatoxin contamination have been compared, and several resistance-associated proteins have been found, including a pathogenesis-related protein 10 (PR10). In this study, RNA interference (RNAi) gene silencing technology was employed to further investigate the importance of PR10. An RNAi gene silencing vector was constructed and introduced into immature Hi II maize embryos through both bombardment and Agrobacterium infection procedures. PR10 expression was reduced by 65% to more than 99% in transgenic callus lines from bombardment. The RNAi-silenced callus lines also showed increased sensitivity to heat stress treatment. A similar reduction in PR10 transcript levels was observed in seedling leaf and root tissues developed from transgenic kernels. When inoculated with A. flavus, RNAi-silenced mature kernels produced from Agrobacterium-mediated transformation showed a significant increase in fungal colonization and aflatoxin production in 10 and six, respectively, of 11 RNAi lines compared with the non-silenced control. Further proteomic analysis of RNAi-silenced kernels revealed a significant reduction in PR10 production in eight of 11 RNAi lines that showed positive for transformation. A significant negative correlation between PR10 expression at either transcript or protein level and kernel aflatoxin production was observed. The results indicate a major role for PR10 expression in maize aflatoxin resistance.
    Molecular Plant Pathology 01/2010; 11(1):69-81. · 3.88 Impact Factor
  • Chapter: Aflatoxins
    12/2009; , ISBN: 9780470054581
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    ABSTRACT: The fungicidal properties of purified CAY-1, dissolved silver ion and ethylenediamine tetraacetic acid (EDTA) separately were studied in vitro as were the abilities of silver and EDTA to enhance CAY-1 fungicidal properties. Non-germinated and germinating conidia of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium verticillioides (Fusarium moniliforme), Fusarium oxysporum and Fusarium solani were incubated separately with CAY-1 (0-24.8 μg ml(-1)), silver (0-111.1 μg ml(-1)), and EDTA (0-2400 μg ml(-1)). Controls consisted of non-germinated or germinated conidia in test medium. To assess combined activity, compounds, based on the sub-lethal doses of each as defined in the initial experiments, were combined and tested in bioassays. Controls for the mixed sets consisted of non-germinated or germinated conidia only or with the sub-lethal CAY-1 test concentrations. The minimum inhibitory concentrations (MICs) for CAY-1 and silver, both separate and combined, were determined. Viability assays showed CAY-1 activity only against the germinating conidia of A. flavus, A. niger and F. solani. Silver was active against the germinating conidia of all fungi and the non-germinated conidia of F. oxysporum and F. solani. Combined silver and CAY-1 produced significant viability loss at concentrations not effective separately. EDTA was not fungicidal separately and did not enhance CAY-1 fungicidal properties. MIC data showed that CAY-1 plus silver had an additive effect. Results indicate that dissolved silver was fungicidal in vitro and enhanced the fungicidal properties of CAY-1 at concentrations ineffective when tested separately.
    Mycoses 11/2009; 54(4):e1-9. · 1.28 Impact Factor

Publication Stats

6k Citations
475.72 Total Impact Points

Institutions

  • 1988–2014
    • United States Department of Agriculture
      • Agricultural Research Service (ARS)
      Washington, Washington, D.C., United States
  • 2007–2013
    • Mississippi State University
      • Department of Biochemistry and Molecular Biology
      Mississippi, United States
    • Vanderbilt University
      • Department of Biological Sciences
      Nashville, MI, United States
    • North Carolina State University
      • Department of Plant Pathology
      Raleigh, NC, United States
  • 1988–2013
    • Southern Regional Medical Center
      Georgia, United States
  • 2010
    • Louisiana State University Health Sciences Center New Orleans
      • Section of Hematology / Oncology
      New Orleans, LA, United States
  • 1996–2010
    • Louisiana State University
      • Department of Plant Pathology and Crop Physiology
      Baton Rouge, LA, United States
  • 2009
    • Rutgers, The State University of New Jersey
      • School of Environmental and Biological Sciences
      New Brunswick, New Jersey, United States
  • 2008
    • National Institute of Advanced Industrial Science and Technology
      Tsukuba, Ibaraki, Japan
  • 1993–2007
    • Tulane University
      • • Section of Hematology and Medical Oncology
      • • Department of Cell and Molecular Biology
      New Orleans, LA, United States
  • 2006
    • Houston Zoo
      Houston, Texas, United States
  • 1999–2006
    • Louisiana State University Agricultural Center
      Baton Rouge, Louisiana, United States
  • 2005
    • Government Arts College, Coimbatore
      Koyambattūr, Tamil Nādu, India
  • 2002
    • American University Washington D.C.
      Washington, Washington, D.C., United States
    • Saint Louis University
      • Geriatric Research, Education and Clinical Center
      Saint Louis, MI, United States
  • 1998–1999
    • University System of Georgia
      Atlanta, Georgia, United States
  • 1997
    • National Institutes of Health
      Maryland, United States
  • 1995–1997
    • Clemson University
      Clemson, South Carolina, United States
  • 1994
    • Purdue University
      • Department of Botany and Plant Pathology
      West Lafayette, IN, United States