James K. Porter

In vitro auxin production by Balansia epichloë

Abstract Balansia epichloe , a systemic plant pathogen isolated from Sporobolus poiretii , was shown to produce the plant growth regulators 3-indole acetic acid, 3-indole ethanol, 3-indole acetamide and methyl-3-indole carboxylate when grown on a medium containing tryptophan. When grown on a tryptophan deficient medium 3-substituted indole derivatives were not detected. However, extracts of the medium in lower doses increased and in higher doses inhibited the growth of wheat coleoptiles.

Inhibition of protein synthesis in rat primary hepatocytes by extracts of Fusarium moniliforme-contaminated corn

Mycological screening of two separate lots of corn samples that caused field cases of equine leukoencephalomalacia (ELEM) revealed heavy contamination with the fungus Fusarium moniliforme. Neutral and acidic fractions of a chloroform-methanol (1:1, v/v) extract of the corn were evaluated for toxicity using rat primary hepatocytes. The extracts had little effect on the release of lactate dehydrogenase from the hepatocytes, and were without effect on unscheduled DNA synthesis, indicating low cell lethality and lack of genotoxicity. However, neutral extracts of the corn were found to contain potent inhibitor(s) of protein synthesis as measured by incorporation of [3H]valine into the hepatocytes. When an isolate of F. moniliforme obtained from the corn samples or an isolate of F. moniliforme from South Africa that had previously been shown to cause ELEM (MRC 826) were grown on autoclaved seed corn, neutral extracts of the culture materials similarly inhibited protein synthesis. Whether the compound(s) responsible for inhibition of protein synthesis is associated with any of the toxic syndromes associated with F. moniliforme remains to be determined. The use of primary hepatocytes may be a useful bioassay for elucidating biologically active secondary metabolites of fungi.

Fusaric Acid and Modification of the Subchronic Toxicity to Rats of Fumonisins in F. moniliforme Culture Material

Fumonisins and fusaric acid (FA) are mycotoxins produced by Fusarium moniliforme and other Fusarium which grow on corn. Fumonisins cause animal toxicities associated with F. moniliforme and, like F. monliforme, they are suspected human oesophageal carcinogens. Toxic synergism was obtained by simultaneous administration of FA and fumonisin B1 to chicks in ovo. To determine the effect of FA on in vivo toxicity of F. moniliforme culture material (CM), male rats (12 groups, n = 5/ group) were fed diets containing 0.025, 0.10 or 2.5% CM (providing dietary levels of 3.4, 18.4 or 437 ppm fumonisins, respectively) to which, at each CM level, 0, 20, 100 or 400 ppm FA were added. Additionally, an FA control group was fed 400 ppm FA only and an untreated control group was given neither FA nor culture material. Apoptosis and other effects consistent with those caused by fumonisins were present in the kidneys of animals fed 0.025% or more CM and in the livers of animals fed 2.5% CM. FA was without effect. No differences between the untreated and FA control groups were noted and no differences among the four groups (0-400 ppm FA) fed 0.025% CM, the four groups fed 0.10% CM or the four groups fed 2.5% CM were apparent. Thus, FA exerted no synergistic, additive or antagonistic effects on the subchronic in vivo toxicity of fumonisin-producing F. moniliforme.

Effects of Fusarium moniliforme and Corn Associated with Equine Leukoencephalomalacia on Rat Neurotransmitters and Metabolites

Abstract Fusarium moniliforme (FM) is associated with equine leukoencephalomalacia (ELEM) and hepatotoxicities in horses and rats. The neurochemical effects of ELEM-associated corn naturally infected with FM and FM strain MRC 826 were studied in rats. Increases in brain 5-hydroxyindoleacetic acid (5-HIAA, major metabolite of serotonin, 5-HT) and 5-HIAA/5-HT ratios were observed in rats fed the ELEM-FM corn. These rats had reduced body weights (17%, P < 0.01) and increased brain weight/body weight ratios (14%, P < 0.01) as compared with controls that were fed commercial corn. Rats fed a rodent chow supplemented (16%, w/w) with corn cultures of FM (MRC 826) had brain 5-HT and 5-HIAA increased (11% and 60%, P < 0.01, respectively). At 20% FM (MRC 826)-chow diet, the 5-HIAA levels were increased (18%, P < 0.01). In both the 16% and 20% diets, brain 5-HIAA/5-HT ratios were increased (45%, P < 0.01 and 10%, P < 0.05), body weights reduced (30% and 18%, P < 0.01) and brain weight/body weight ratios increased (40% and 16%, P < 0.01), respectively. The incidences of microscopic liver lesions (particularly bile duct proliferations, hepatocellular hyperplasia, and focal necrosis) were consistent with rats fed the FM contaminated and FM-fortified diets. These results suggest a possible FM (ELEM-associated)-induced dysfunction in either 5-HT metabolism or 5-HIAA elimination in rat brains.

Neurochemical effects of cyclopiazonic acid in chickens.

Abstract Chickens dosed (per os) with cyclopiazonic acid (CPA) at 0.5, 5.0, and 10 mg/kg body weight showed significant (P ≤ 0.05) increases in brain dopamine and serotonin concentrations 96 hr after dosing. The increases coincide with significant decreases in homovanillic acid and subtle increases of dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid concentrations. The elevated dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid concentrations may be related to the elevated concentrations of dopamine and serotonin, respectively. The observed changes in neurotransmitter/metabolite concentrations 96 hr after dosing parallel elimination of CPA from the birds skeletal muscles; however, they do not correlate with the significant weight losses in these birds at 48 and 96 hr after dosing. The brain weights of the treated birds were statistically insignificant from their respective controls, although increases in brain weight-body weight ratio within treatments and with time correlated with CPA toxicity. No significant changes were observed in dopamine, dihydroxyphenylacetic acid, homovanillic acid, serotonin, and 5-hydroxyindoleacetic acid concentrations among the treatments at 3, 24, and/or 48 hr after dosing.

Occurrence and clinical manifestations of ergot and fescue toxicoses

Historically, ergotism in animals has been defined as a disease of livestock consuming the sclerotia of Claviceps sp. infected grasses. The gangrenous form of ergot toxicity most frequently occurs when animals are exposed to Claviceps purpurea on feed grains and pasture grasses. This type of ergotism is a great risk to livestock, especially cattle. The convulsive form of ergotism, a nervous disorder ranging from mild tremors to severe tetany, is observed in cattle grazed on Paspalum grasses infected with Claviceps paspali [24, 45, 49, 50, 57].

Isolation and characterization of three self-inhibitors of germination from aeciospores of Cronartium fusiforme

The germination inhibition activity of a crude aqueous extract from aeciospores of Cronartium fusiforme was tested against seven rust species and three spore types and found to be aeciospore specific but not species specific. Inhibition was assessed by a germination bioassay. Three self-inhibitors were isolated and purified from the aqueous extract. The ED 100 values of the self-inhibitors were 12.0–30.0, 2.3–7.2, and 3.1–11.9 μ g/ml. The activity of the combined self-inhibitors was 0.81–1.25 μ g/ml, indicating a synergistic effect. The self-inhibitors were structurally similar molecules containing only carbon, hydrogen, and oxygen, with no aromatic rings or unusual bonding.