Fumonisin levels in Uruguayan corn products.

A survey was conducted to evaluate fumonisins FB1 and FB2 in Uruguayan corn products. Sixty-four samples of different local brands were purchased from retail stores during a 15-month period and analyzed for FB1 and FB2 by methanol-water extraction, cleanup with a 1 mL. strong-anion-exchange solid-phase extraction column, and liquid chromatography with o-pthaldialdehyde-2-mercaptoethanol derivatization and fluorescence detection. Contamination levels for FB1 varied from 50 ng/g (detection limit) to 6342 ng/g. Values were highest in feed samples (up to 6342 ng/g), unprocessed corn kernel (up to 3688 ng/g), and milled products, which included polenta (up to 427 ng/g). They were lowest in processed corn kernel (up to 155 ng/g) and snacks (up to 314 ng/g). FB2 was determined in one-fourth of the total samples and detected at trace levels in only one feed sample. The data demonstrated the natural occurrence of fumonisins in corn products in Uruguay. Feed and polenta that contain fumonisins could be of concern because they are consumed in large amounts and are often the main nutrient source in Uruguay.

Mycotoxin producing potential of Fusarium graminearum isolates from Uruguayan barley.

Twelve isolates of Fusarium graminearum were obtained from barely grains collected from different Uruguayan regions (harvest 1993-94). This was the predominant fungal species contaminating the crop due to a particular humid and warm season with cold nights conductive to toxin production The isolates were grown on moist, sterile rice, extracted with aqueous methanol, and examined for mycotoxin production. Zearalenone (ZEA) and the trichothecenes deoxynivalenol (DON), 3- and 15-acetyl-DON (AcDON), nivalenol (NIV), nivalenol (NIV), fusarenon-X (FX) and T-2 toxin (T-2) were analyzed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) and confirmed by gas chromatography-mass spectrometry (GC-MS). Eleven of the 12 strains were DON and/or ZEA producers and 9 were AcDON positive. No NIV, or FX were detected. One strain produced T-2. The predominant acetyl-DON isomer was 15-AcDON. Mass-spectral analysis yielded detectable levels of other mycotoxins, 13-OH-apotrichothecenes, 11-epiapotrichothecenes, culmorin, sambucinol, and isotrichodermol being the most numerous. From the metabolic profiles it is suggested that Uruguayan F. graminearum strains belong to the chemotype IB (DON/15-AcDON). The predominance of this chemotype is in accordance with data from Canada, United States, Mexico and Argentina which have similar climatic conditions that would favor F. graminearum growth and mycotoxin production.

Canine migration inhibitory factor: effect of Corynebacterium parvum administration.

Peripheral blood lymphocytes from dogs sensitized to streptolysin O (SLO) were assayed for migration inhibitory factor (MIF) production by the indirect MIF test, using guinea pig peritoneal exudate cells as the source of macrophages. A specific direct correlation was established between the degree of inhibition of migration and the concentration of SLO-stimulated supernatants from lymphocyte cultures (SLO-S) of untreated normal dogs. Undiluted SLO-S inhibited migration by 66.8%, whereas a dilution of 1:64 elicited a 3% inhibition. In parallel tests, purified protein derivative stimulation of lymphocytes from BCG-vaccinated dogs produced 92.6% inhibition. The effect of Corynebacterium parvum on SLO-specific MIF production was evaluated in three groups of dogs administered a single intramuscular injection of C. parvum at 5 or 50 mg/m(2) or 50 mg/m(2) in suspension with 10 mg of methylprednisolone. Inhibition of migration of macrophages exposed to a 1:4 dilution of SLO-S from dogs inoculated with C. parvum (5 mg/m(2)) was 33% greater (mean inhibition, 75%) than the same SLO-S dilution from uninoculated normal dogs (mean inhibition, 42%) (P < 0.0002). Similarly, lymphocytes from dogs administered 50 mg/m(2) caused an enhancement of migration inhibition, with a mean increase of 26% over controls (P < 0.002), whereas a dose of 50 mg/m(2) with methylprednisolone produced a 16% increase in migration inhibition (P < 0.05). The administration of C. parvum resulted in a three- to fourfold increase in the SLO-S dilution, which would reduce migration by 20% (MIF titer). This increase peaked between days 20 and 30 and lasted over 50 days post-C. parvum inoculation. These findings indicate that C. parvum specifically increases MIF production by canine lymphocytes in a linear correlation with SLO concentration and suggest its use as a stimulant of canine immunity.