A trial for chemotaxonomic analysis of toxigenic Fusarium species was performed by an introduction of restriction fragment length polymorphisms based on the selected DNA probes of Fusarium sp. Fn 2B strain, a well-known producer of trichothecene mycotoxins nivalenol and fusarenon-X. A total DNA of F. Fn 2B was prepared from the protoplast suspension of mycelia, digested with BamHI, and ligated into BamHI site of plasmid vector pUC19. Two clones harboring inserts in sizes of approximately 1.1 and 1.7 kb were randomly selected for probes. Hybridization patterns of 32P-labeled 1.1 and 1.7 kb fragments of Fn 2B with BamHI, EcoRI or HindIII-digested DNAs from F, sporotrichioides (4 isolates), F, graminearum (6 isolates), F, tricinctum (4 isolates), F. poae (4 isolates), F. crookwellense (3 isolates) and others, were compared by Southern blots. The data obtained with the 1.1 kb fragment have revealed a similar pattern of restriction fragment profiles among the isolates of same Fusarium species such as F. sporotrichioides, F, tricinctum or F. graminearum. While, the fragment profile of Fn 2B strain did not correspond to that of all the other Fusarium spp. tested. This suggested that F. sp. Fn 2B, originally reported as F. nivale by Dr. Tsunoda and later cited as F. tricinctum at NRRL by J. J. Ellis and to F. sporotrichioides at the Medical Research Council Collection (MRC, Tygerberg, South Africa) by Marasas et al., may be unidentified Fusarium species.
Aspergillus nomius, an aflatoxigenic species in Aspergillus section Flavi was first reported by Kurtzman et al. in 1987, but this fungus in Japan has never been reported. Several aflatoxigenic fungi were isolated from Japanese tea-field soil and silkworm excrements that display characteristics consistent with A. nomius. In order to identify these isolates we examined their colony color, micromorphological characters, mycotoxin production and DNA sequences. These fungi have light olive to moss green colony color, the conidia are spherical to subspherical having very rough surface ornamentation and their diameter is about 4.6μm. They produce aflatoxins B1, B2, G1, and G2 but do not produce detectable amounts of cyclopiazonic acid. The DNA sequences from the ITS and large subunit rDNA are identical with the sequence of an ex type strain of A. nomius. On the basis of these data we determined that two of these isolates are A. nomius.
To test the hypothesis that the toxicity of rubratoxin B is a consequence of apoptosis, we investigated fragmentation of nuclei and internucleosomal fragmentation (DNA ladder). Exposure to rubratoxin B caused HL-60 cells to condense their chromatin and fragment their nuclei, showing that rubratoxin B induces apoptosis. We observed DNA ladder in HL-60 cells treated with rubratoxin B for 24 hr. Cycloheximide did not affect rubratoxin B-induced DNA ladder. Therefore, rubratoxin B-induced apoptosis is considered not to require protein synthe-sis. Twenty four-hr treatment of rubratoxin B or ethylene glycol-bis (β-aminoethyl ether)-tetraacetic acid (EGTA) alone resulted in DNA ladder, but no DNA ladder treated with both chemicals for 24 hr. Eight-hr treatment of rubratoxin B and EGTA resulted in DNA ladder, suggesting that long exposure to both chemicals led to post-apoptotic DNA degradation. Since the addition of Ca2+ inhibited the effect of EGTA, the reduction of extracellular Ca2+ concentra-tion by EGTA appears to cause an enhancement of rubratoxin B-induced DNA degradation.
The purpose of this study was to investigate the enhancement of Salmonella typhimurium colonization and changes in the intestinal tract in chickens administered with ochratoxin A. Eleven-day old chickens received 108 colony-forming units S. typhimurium orally for 2 consecutive days. The 13-old-day chickens were administered a dose of ochratoxin A (2.0mg/kg/bird) orally. The number of S. typhimurium in both the duodenal and cecal contents of chickens administered with this dose of ochratoxin A increased significantly when compared with control birds. There were no significant differences in chickens administered doses of ochratoxin A below this level. There were significant differences in pH value, oxidation-reduction potential, and amount of acetic acid in duodenal and cecal contents between ochratoxin A-administered chickens and control ones. Number of feces were counted and decreased in chickens administered with ochratoxin A. Feed intake decreased by administration of ochratoxin A. Experi-mental evidence indicated that S. typhimurium colonization enhanced in the duodena and ceca of ochratoxin A-administered chickens and that fecal counts of chickens administrated with the ochratoxin A decreased.
A new metabolite named emecorrugatin A, which caused lethal paralysis in mice, and its analogue named emecorrugatin B were isolated from an Ascomycete, Emericella corrugata, together with two known toxic metabolites, sterigmatocystin and norsolorinic acid.