N. D. Davis

Bio: N. D. Davis is an academic researcher from Auburn University. The author has contributed to research in topics: Aflatoxin & Aspergillus ochraceus. The author has an hindex of 22, co-authored 41 publications receiving 1585 citations. Previous affiliations of N. D. Davis include United States Department of Agriculture.

Production of aflatoxins B1 and G1 by Aspergillus flavus in a semisynthetic medium.

Abstract: Isolates of Aspergillus flavus produced 0.2 to 63 mg of aflatoxins B1 and G1 per 100 ml in a nutrient solution consisting of 20% sucrose and 2% yeast extract. Various factors influencing the fermentation were studied. The maximal amount of toxin was produced by ATCC culture 15548 in 1-liter flasks containing 100 ml of medium incubated as stationary cultures for 6 days at 25 C.

Association of an endophytic fungus with fescue toxicity in steers fed Kentucky 31 tall fescue seed or hay.

Abstract: Previous research has implicated an endophytic fungus as being associated with fescue toxicity (summer syndrome) in cattle grazing Kentucky 31 tall fescue (Festuca arundinacea Schreb.) pastures. Hay and seed were harvested from Kentucky 31 pastures known to be either fungus-free or heavily infested with an endophytic fungus identified as Acremonium coenophialum Morgan-Jones and Gams. Four diets containing either 60% fungus-free seed, 60% fungus-infested seed, 85% fungus-free hay or 85% fungus-infested hay were group-fed to three steers each (avg wt 239 kg) in a 53-d feeding trial. Presence of the fungus reduced (P less than .05) daily gains (kg/d) in steers fed either the seed diets (.96 vs .20) or the hay diets (.66 vs .28). Feed intake was depressed 36% for the seed diets and 8% for the hay diets when the fungus was present. Rectal temperatures were elevated .6 C (P less than .05) for both groups receiving diets containing the fungus, but respiration rate was elevated only in the fungus-infested seed group. In vitro dry matter disappearance was not decreased by presence of the fungus. Steers receiving fungus from either seed or hay were nervous and highly excitable, which resulted in large variations in plasma epinephrine and norepinephrine concentrations. The results of this experiment further implicate an endophytic fungus as being associated with fescue toxicity.

Limiting temperature and relative humidity for growth and production of aflatoxin and free fatty acids byAspergillus flavus in sterile peanuts

Abstract: Sound mature kernels, broken mature kernels, immature kernels, and unshelled Early Runner peanuts were heat-treated in controlled environment cabinets and inoculated with spores ofAspergillus flavus Treatments were incubated at 97–99% relative humidity at different temperatures ranging from 5 to 55C and also at 30C with relative humidities ranging from 55 to 99% Samples were removed after 7 and 21 days and assayed for aflatoxin, free fatty acids, and peanut kernel moisture The limiting relative humidity for aflatoxin production byA flavus was 85±1% relative humidity for 21 days at 30C The limiting low temperature for visible growth and aflatoxin production by the fungus was 13±1C for 21 days at 97–99% relative humidity Damaged kernels, however, developed some afllatoxin in 21 days at 12C The maximum temperature for aflatoxin production was 415±15C for 21 days at 97–99% relative humidity Fungus growth and sporulation at 43C were equal to that at 40C, but no aflatoxin was produced Moisture content of immature kernels was higher at equilibrium with the same relative humidity than the moisture content of sound mature kernels, damaged kernels, or kernels from unshelled peanuts There appeared to be no proportional quantitative correlation between synthesis of aflatoxin and production of free fatty acids in nonliving peanuts, but no aflatoxin was produced without a simultaneous increase in free fatty acids

Penitrem A and Roquefortine Production by Penicillium commune.

Abstract: Extracts of Penicillium commune, a fungus isolated from cottonseed, showed biological activity in day-old cockerels. Two neurotoxic metabolites were isolated and identified as penitrem A and roquefortine. This is the first report of roquefortine being produced by a fungus other than Penicillium roqueforti as well as the first report of penitrem A and roquefortine being produced in the same culture. Production of these toxins on liquid media and cottonseed was determined.

Tremorgenic Toxin from Penicillium verruculosum

Abstract: A new mycotoxin that produces severe tremors and acute toxicity when administered orally or intraperitoneally (ip) to mice and 1-day-old cockerels was obtained from a strain of Penicillium verruculosum Peyronel isolated from peanuts. The ip 50% lethal dose (LD(50)) of this tremorgen was 2.4 mg/kg in mice and 15.2 mg/kg in chickens. Orally administered LD(50) values for the toxin were 126.7 mg/kg in mice and 365.5 mg/kg in chickens. The trivial name "verruculogen" is proposed for this tremorgenic mycotoxin. Physical and chemical characteristics of the mycotoxin are described.

Genetic Inhibition by Double-Stranded RNA

Abstract: A process is provided of introducing an RNA into a living cell to inhibit gene expression of a target gene in that cell. The process may be practiced ex vivo or in vivo. The RNA has a region with double-stranded structure. Inhibition is sequence-specific in that the nucleotide sequences of the duplex region of the RNA and of a portion of the target gene are identical. The present invention is distinguished from prior art interference in gene expression by antisense or triple-strand methods.

Methods and means for obtaining modified phenotypes

Abstract: Methods and means are provided for reducing the phenotypic expression of a nucleic acid of interest in eucaryotic cells, particularly in plant cells, by introducing chimeric genes encoding sense and antisense RNA molecules directed towards the target nucleic acid, which are capable of forming a double stranded RNA region by base-pairing between the regions with sense and antisense nucleotide sequence or by introducing the RNA molecules themselves. Preferably, the RNA molecules comprises simultaneously both sense and antisense nucleotide sequence.

Alternaria mycotoxins: an overview of chemical characterization, producers, toxicity, analysis and occurrence in foodstuffs

Abstract: Microfungi of the genus Alternaria are ubiquitous pathogens and saprophytes. Many species of the genus Alternaria commonly cause spoilage of various food crops in the field or post-harvest decay. Due to their growth even at low temperatures, they are also responsible for spoilage of these commodities during refrigerated transport and storage. Several Alternaria species are known producers of toxic secondary metabolites - Alternaria mycotoxins. A. alternata produces a number of mycotoxins, including alternariol, alternariol monomethyl ether, altenuene, altertoxins I, II, III, tenuazonic acid and other less toxic metabolites. Tenuazonic acid is toxic to several animal species, e.g. mice, chicken, dogs. Alternariol, alternariol monomethyl ether, altenuene and altertoxin I are not very acutely toxic. There are several reports on the mutagenicity and genotoxicity of alternariol, and alternariol monomethyl ether. Alternariol has been identified as a topoisomerase I and II poison which might contribute to the impairment of DNA integrity in human colon carcinoma cells. Analytical methods to determine Alternaria toxins are largely based on procedures, involving cleanup by solvent partitioning or solid phase extraction, followed by chromatographic separation techniques, in combination with ultraviolet, fluorescence, electrochemical and mass spectroscopic detection. A large number of Alternaria metabolites has been reported to occur naturally in food commodities (e.g. fruit, vegetables, cereals and oil plants). Alternariol, alternariol monomethyl ether and tenuazonic acid were frequently detected in apples, apple products, mandarins, olives, pepper, red pepper, tomatoes, tomato products, oilseed rape meal, sunflower seeds, sorghum, wheat and edible oils. Alternariol and alternariol monomethyl ether were detected in citrus fruit, Japanese pears, prune nectar, raspberries, red currant, carrots, barley and oats. Alternariol monomethyl ether and tenuazonic acid were detected in melon. Natural occurrence of alternariol has been reported in apple juice, cranberry juice, grape juice, prune nectar, raspberry juice, red wine and lentils.