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Biomedical subjects

J W Dorner

Publications and source records attributed to J W Dorner.

At least 19 recordsLinked to original sources
PubMed2001

Conidial movement of nontoxigenic Aspergillus flavus and A. parasiticus in peanut fields following application to soil.

The use of nontoxigenic strains of Aspergillus flavus and A. parasiticus in biological control effectively reduces aflatoxin in peanuts when conidium- producing inoculum is applied to the soil surface. In this study, the movement of conidia in soil was examined following natural rainfall and controlled precipitation from a sprinkler irrigation system. Conidia of nontoxigenic A. flavus and A. parasiticus remained near the soil surface despite repeated rainfall and varying amounts of applied water from irrigation. In addition, rainfall washed the conidia along the peanut furrows for up to 100 meters downstream from the experimental plot boundary. The dispersal gradient was otherwise very steep upstream along the furrows and in directions perpendicular to the peanut rows. The retention of biocontrol conidia in the upper soil layers is likely important in reducing aflatoxin contamination of peanuts and aerial crops such as corn and cottonseed.

Aflatoxins↗
PubMed2000

The phylogenetics of mycotoxin and sclerotium production in Aspergillus flavus and Aspergillus oryzae.

Aspergillus flavus is a common filamentous fungus that produces aflatoxins and presents a major threat to agriculture and human health. Previous phylogenetic studies of A. flavus have shown that it consists of two subgroups, called groups I and II, and morphological studies indicated that it consists of two morphological groups based on sclerotium size, called "S" and "L." The industrially important non-aflatoxin-producing fungus A. oryzae is nested within group I. Three different gene regions, including part of a gene involved in aflatoxin biosynthesis (omt12), were sequenced in 33 S and L strains of A. flavus collected from various regions around the world, along with three isolates of A. oryzae and two isolates of A. parasiticus that were used as outgroups. The production of B and G aflatoxins and cyclopiazonic acid was analyzed in the A. flavus isolates, and each isolate was identified as "S" or "L" based on sclerotium size. Phylogenetic analysis of all three genes confirmed the inference that group I and group II represent a deep divergence within A. flavus. Most group I strains produced B aflatoxins to some degree, and none produced G aflatoxins. Four of six group II strains produced both B and G aflatoxins. All group II isolates were of the "S" sclerotium phenotype, whereas group I strains consisted of both "S" and "L" isolates. Based on the omt12 gene region, phylogenetic structure in sclerotium phenotype and aflatoxin production was evident within group I. Some non-aflatoxin-producing isolates of group I had an omt12 allele that was identical to that found in isolates of A. oryzae.

Aflatoxins↗
PubMed1999

Regional differences in production of aflatoxin B1 and cyclopiazonic acid by soil isolates of aspergillus flavus along a transect within the United States.

Soil isolates of Aspergillus flavus from a transect extending from eastern New Mexico through Georgia to eastern Virginia were examined for production of aflatoxin B1 and cyclopiazonic acid in a liquid medium. Peanut fields from major peanut-growing regions (western Texas; central Texas; Georgia and Alabama; and Virginia and North Carolina) were sampled, and fields with other crops were sampled in regions where peanuts are not commonly grown. The A. flavus isolates were identified as members of either the L strain (n = 774), which produces sclerotia that are >400 micrometer in diameter, or the S strain (n = 309), which produces numerous small sclerotia that are <400 micrometer in diameter. The S-strain isolates generally produced high levels of aflatoxin B1, whereas the L-strain isolates were more variable in aflatoxin production; variation in cyclopiazonic acid production also was greater in the L strain than in the S strain. There was a positive correlation between aflatoxin B1 production and cyclopiazonic acid production in both strains, although 12% of the L-strain isolates produced only cyclopiazonic acid. Significant differences in production of aflatoxin B1 and cyclopiazonic acid by the L-strain isolates were detected among regions. In the western half of Texas and the peanut-growing region of Georgia and Alabama, 62 to 94% of the isolates produced >10 microgram of aflatoxin B1 per ml. The percentages of isolates producing >10 microgram of aflatoxin B1 per ml ranged from 0 to 52% in the remaining regions of the transect; other isolates were often nonaflatoxigenic. A total of 53 of the 126 L-strain isolates that did not produce aflatoxin B1 or cyclopiazonic acid were placed in 17 vegetative compatibility groups. Several of these groups contained isolates from widely separated regions of the transect.

Aflatoxin B1↗
PubMed1999

Aflatoxin reduction in corn through field application of competitive fungi.

Soil in corn plots was inoculated with nonaflatoxigenic strains of Aspergillus flavus and A. parasiticus during crop years 1994 to 1997 to determine the effect of application of the nontoxigenic strains on preharvest aflatoxin contamination of corn. Corn plots in a separate part of the field were not inoculated and served as controls. Inoculation resulted in significant increases in the total A. flavus/parasiticus soil population in treated plots, and that population was dominated by the applied strain of A. parasiticus (NRRL 21369). In the years when weather conditions favored aflatoxin contamination (1996 and 1997), corn was predominately colonized by A. flavus as opposed to A. parasiticus. In 1996, colonization by wild-type A. flavus was significantly reduced in treated plots compared with control plots, but total A. flavus/parasiticus colonization was not different between the two groups. A change to a more aggressive strain of A. flavus (NRRL 21882) as part of the biocontrol inoculum in 1997 resulted in a significantly (P < 0.001) higher colonization of corn by the applied strain. Weather conditions did not favor aflatoxin contamination in 1994 and 1995. In 1996, the aflatoxin concentration in corn from treated plots averaged 24.0 ppb, a reduction of 87% compared with the aflatoxin in control plots that averaged 188.4 ppb. In 1997, aflatoxin was reduced by 66% in treated corn (29.8 ppb) compared with control corn (87.5 ppb). Together, the data indicated that although the applied strain of A. parasiticus dominated in the soil, the nonaflatoxigenic strains of A. flavus were more responsible for the observed reductions in aflatoxin contamination. Inclusion of a nonaflatoxigenic strain of A. parasiticus in a biological control formulation for aflatoxin contamination may not be as important for airborne crops, such as corn, as for soilborne crops, such as peanuts.

Aflatoxins↗
PubMed1995

Effect of corn and peanut cultivation on soil populations of Aspergillus flavus and A. parasiticus in southwestern Georgia.

The effect of corn and peanut cultivation on the proportion of Aspergillus flavus to A. parasiticus in soil was examined. Soil populations were monitored in three fields during three different years in southwestern Georgia. Each field was planted in both peanuts and corn, and soil was sampled within plots for each crop. A. flavus and A. parasiticus were present in similar proportions in plots from all fields at the beginning of the growing season. A. terreus, A. niger, and A. fumigatus were the other dominant aspergilli in soil. Fields A and B did not show drought stress in peanut or corn plants, and soil populations of A. flavus and A. parasiticus remained stable during the course of the year. In field C, drought stress in corn plants with associated A. flavus infection and aflatoxin contamination greatly increased soil populations of A. flavus relative to A. parasiticus upon dispersal of corn debris to the soil surface by a combine harvester. Colonization of organic debris after it has been added to the soil may maintain soil populations of A. parasiticus despite lower crop infection.

Arachis↗
PubMed1994

Effect of Aspergillus parasiticus soil inoculum on invasion of peanut seeds.

Environmental control plots adjusted to late season drought and elevated soil temperatures were inoculated at peanut planting with low and high levels of conidia, sclerotia, and mycelium from a brown conidial mutant of Aspergillus parasiticus. Percentage infection of peanut seeds from undamaged pods was greatest for the subplot containing the high sclerotial inoculum (15/cm2 soil surface). Sclerotia did not germinate sporogenically and may have invaded seeds through mycelium. In contrast, the mycelial inoculum (colonized peanut seed particles) released large numbers of conidia into soil. Soil conidial populations of brown A. parasiticus from treatments with conidia and mycelium were positively correlated with the incidence of seed infection in undamaged pods. The ratio of A. flavus to wild-type A. parasiticus in soil shifted from 7:3 to 1:1 in the uninoculated subplot after instigation of drought, whereas in all subplots treated with brown A. parasiticus, the ratio of the two species became approximately 8:2. Despite high levels of brown A. parasiticus populations in soil, native A. flavus often dominated peanut seeds, suggesting that it is a more aggressive species. Sclerotia of wild-type A. parasiticus formed infrequently on preharvest peanut seeds from insect-damaged pods.

Aflatoxins↗
PubMed1990

Subchronic oral toxicity of cyclopiazonic acid (CPA) in male Sprague-Dawley rats.

The mycotoxin cyclopiazonic acid (CPA) is a potential contaminant of processed foods, grain and poultry. Twelve male Sprague-Dawley rats were given oral doses of 0, 0.2, 0.6, 2.0 or 4.0 mg CPA/kg body weight/day for 13 consecutive weeks to study its potential subchronic toxicity. No dose-related mortality or morbidity occurred. General appearance, behavior, body weight gain and food consumption of all groups were similar. CPA had no definite adverse hematologic or serum chemistry effects, although serum creatinine concentrations of rats given 2.0 and 4.0 mg CPA/kg BW were increased after seven and 13 weeks. Mild to focally moderate acute inflammation of the lamina propria and submucosa of the gastric epithelium was found in animals given less than or equal to 0.6 mg CPA/kg BW. No other dose-related microscopic lesions were found. Ultrastructural examination of the livers revealed subtle disruption of the cisternal pattern of the endoplasmic reticulum with ribosomal detachment in animals receiving 4.0, but not 2.0, mg CPA/kg BW. These data suggest that the toxic effects in rats of repeated, daily oral exposure to CPA may be less than previously reported. The possible relationship between toxicity and CPA epimerization is considered.

Administration, Oral↗
PubMed1989

Interrelationship of kernel water activity, soil temperature, maturity, and phytoalexin production in preharvest aflatoxin contamination of drought-stressed peanuts.

Samples of Florunner peanuts were collected throughout a period of late-season drought stress with mean geocarposphere temperatures of 29 and 25 degrees C, and determinations of maturity, kernel water activity (aw), percent moisture, capacity for phytoalexin production, and aflatoxin contamination were made. Results showed an association between the loss of the capacity of kernels to produce phytoalexins and the appearance of aflatoxin contamination. Kernel aw appeared to be the most important factor controlling the capacity of kernels to produce phytoalexins. Mature peanuts possessed additional resistance to contamination that could not be attributed solely to phytoalexin production. Kernel moisture loss was accelerated in the 29 degrees C treatment compared to the 25 degrees C treatment, and data indicated that the higher soil temperature also favored growth and aflatoxin production by Aspergillus flavus in peanuts susceptible to contamination.

Aflatoxins↗
PubMed1989

Fusarium mycotoxins from peanuts suspected as a cause of sandhill crane mortality.

An estimated 9,500 sandhill cranes (Grus canadensis) died in Gaines County, Texas and Roosevelt County, New Mexico between 1982 and 1987. The predominant clinical sign observed in sick cranes was their inability to hold their heads erect, both while standing and flying. Multiple muscle hemorrhages and submandibular edema were the most common lesions seen at necropsy. Mycotoxins produced by Fusarium sp. growing during cold, wet weather on peanuts left in the field after harvest, the predominant foods of the dead cranes at the time of these mortality events, were identified as the most likely cause of this mortality. Rendering moldy peanuts inaccessible to the cranes by conventional tillage resulted in reduced crane mortality in these areas.

Animals↗
PubMed1988

Neurochemical effects of cyclopiazonic acid in chickens.

Chickens dosed (per os) with cyclopiazonic acid (CPA) at 0.5, 5.0, and 10 mg/kg body weight showed significant (P less than or equal to 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.

Animals↗
PubMed1988

Toxicity of citreoviridin.

The mycotoxin citreoviridin (CIT) isolated from Penicillium citreoviride was studied to elucidate the mechanism of its toxic actions. In CF#1 mice, near lethal doses of CIT decreased motor activities, body temperature and had cataleptic effects. Male mice appeared to be more susceptible to CIT and had lower subcutaneous (sc) LD50 values and longer CIT-induced hypothermia and hypokinesia. In CIT-treated mice the weights and histology of liver, kidneys and adrenals were normal one week after sc treatment, except for the increased adrenal weights in female mice. Single doses of CIT (sc), given on either day 4 or 5 of pregnancy (perinidation period), had no adverse effect on the rates of pregnancy, implantation of ova and embryonal resorptions in those mice examined on day 12 of pregnancy. CIT (40 mg/kg ip) produced a brief electro-encephalographic (EEG) activation, cardiac sinus arrhythmias and tachypnea in the rabbit. Intravenous (iv) lethal doses of CIT (greater than or equal to 5 mg/kg) caused an EEG activation followed by high voltage delta waves, increased the T wave in the electrocardiogram (ECG) and depressed the respiratory amplitude. The death caused by iv CIT started with the respiratory arrest, followed by isoelectric EEG and ECG was the last to stop. In urethane-anesthetized rabbits CIT decreased the blood pressure, and in succession it lowered, flattened and inverted the T wave of ECG suggesting heart ischemia. These observations indicated that the toxic effects of CIT resulted from respiratory and cardiovascular failures (apnea, delta EEG waves, sinus arrhythmia, hypotension) leading to central nervous system depression due to systemic hypoxia.

Adrenal Glands↗
PubMed1987

Combined effects of the mycotoxins aflatoxin B1 and cyclopiazonic acid on Sprague-Dawley rats.

This study was conducted to determine whether exposure to cyclopiazonic acid (CPA) and aflatoxin B1 (AFB1) would alter the toxicity associated with exposure to either toxin individually. Groups of male rats were administered 0, 0.1 or 4.0 mg CPA/kg body weight/day intragastrically (three groups per dose level) for three consecutive days and 30 min after each of these CPA doses the rats were dosed by gavage with 0, 0.1 or 2.0 mg AFB1/kg body weight/day. Six of the 12 rats given each of these nine treatments were killed on day 4 after the initial dosing, and the rest were allowed a recovery period of 4 days prior to being killed. Weight loss in the three groups receiving 2.0 mg AFB1/kg/day occurred within 24 hr of the first doses. Feed consumption by these rats was about 60% of that in the other groups. By the end of the recovery period, rats in these three groups had lost an average of 31-38 g. Feed consumption throughout the recovery period by rats in the 2.0-mg AFB1 groups was about 50% of the control value, except in the group that also received the high dose of CPA, in which it was 75%. Gross pathological findings were primarily limited to rats in the high AFB1 group, and included icterus, shrunken liver and lesions in the kidney at the cortico-medullary junction. Microscopic changes were characteristic of aflatoxicosis in rats. Glycocholic acid assays indicated liver damage only in those groups that received the high AFB1 dose. We conclude that neither toxin potentiates the action of the other at the dose levels used in this study.

Aflatoxin B1↗
PubMed1987

Toxic effects of cyclopiazonic acid in the early phase of pregnancy in mice.

The reproductive toxicity of a single oral dose/mouse (15-50 mg/kg) of cyclopiazonic acid (CPA) in the early phase of pregnancy (day 2-8) was investigated. Male mice used in this study were untreated. A limited number of pregnant mice were treated with 66 mg/kg ergonovine maleate (po, sc) to compare its effect with that of an equivalent dose of CPA (50 mg/kg). Among control sperm-positive mice treated with po NaHCO3 solution, 97.5% were gravid on necropsy day (pregnancy day 12). A single dose of CPA (15-50 mg/kg, po) given on days 2 to 8, decreased the pregnancy rates significantly. In groups treated with a single dose of CPA on pregnancy day 4 to 8, vaginal hemorrhage was observed 1 to 7 days after treatment, and it usually resulted in termination of pregnancy (abortion). Fetal resorption rates were higher than the control rate only in the groups treated with 30 mg/kg CPA po on day 4 or 8. CPA decreased body weight gains and the weights of uteri with fetuses. The ovary weights were generally not changed. Ergonovine maleate (66 mg/kg, sc, po) had no significant effect on all of the parameters examined. The estrous cycle returned without any delay in sperm-positive mice in which nidation of fertilized eggs had been inhibited by CPA, and also in nonpregnant mice (used for the LD50 determination) surviving near lethal doses of CPA (50-70 mg/kg, po). The oral LD50 value for CPA in nonpregnant mice was 64 +/- 4.4 mg/kg, and the toxicity signs were ptosis, hypokinesia, hypothermia, action tremor, cessation of food and water intake and resulting cachexia. The duration and intensity of these toxic signs were dose dependent.

Aging↗
PubMed1986

Effects of cyclopiazonic acid on the contractility of organs with smooth muscles, and on frog ventricles.

The mycotoxins cyclopiazonic acid (CPA) and ergotamine, and the neurotransmitter serotonin all have the beta-aminoethylindole moiety in common. These compounds enhanced the peristaltic movements of the jejunum, ileum and estrous uterus and produced broncho-constriction in vitro. Atropine and cyproheptadine were able to counter the CPA-induced peristaltic movements of the ileum and jejunum. L-epinephrine was able to stop the contractions induced by CPA on both estrous and pregnant rat uteri. Unlike chlorpromazine, CPA did not block the inotropic effects of dopamine, epinephrine and serotonin in vas deferens. This indicated that the previously reported toxic effects of CPA (hypothermia, catalepsy, hypokinesia, tremor) which resembled the effects of anti-psychotic drugs (chlorpromazine, reserpine) probably were not due to the blocking of the neurotransmitter-receptors. In contrast to ergotamine, which decreased the inotropic effects of serotonin on the uterus, CPA had no anti-serotonin effects. The uterotonic effect of CPA (similar to that of ergotamine) suggested that CPA also might have an adverse effect on the reproductive function of humans and animals consuming CPA-contaminated foods.

Animals↗
PubMed1986

Toxicologic and immunologic effects of sublethal doses of cyclopiazonic acid in rats.

Effects of cyclopiazonic acid (CPA) on humoral immunity, cell-mediated immunity, weight gain, organ weights, clinical chemical and hematologic values, and gross and microscopic lesions were evaluated. Four groups of rats, each containing 3 males and 3 females, were given 0, 0.1, 1, and 5 mg of CPA/kg of body weight intraperitoneally for 28 days. A dosage level of 5 mg/kg produced a significant (P less than 0.05) decrease in weight gain. Rats given 0.1 or 1 mg of CPA/kg had a significant (P less than 0.05) reduction in antibody titer against sheep RBC 5 days after injection. The 0.1 mg/kg group also had a significant reduction in antibody titer 7 days after injection. Microscopic lesions were limited to liver, and kidneys and were characterized by vacuolated to granular hepatocyte cytoplasm and dilated renal convoluted tubules, many having pyknotic nuclei and scattered hyaline casts.

Animals↗