H NMR spectroscopy-based metabolomic assessment of uremic toxicity, with toxicological outcomes, in male rats following an acute, mid-life insult from ochratoxin a

Overt response to a single 6.25 mg dose of ochratoxin A (OTA) by oral gavage to 15 months male rats was progressive loss of weight during the following four days. Lost weight was restored within one month and animals had a normal life-span without OTA-related terminal disease. Decline in plasma OTA concentration only commenced four days after dosing, while urinary excretion of OTA and ochratoxin alpha was ongoing. During a temporary period of acute polyuria, a linear relationship between urine output and creatinine concentration persisted. Elimination of other common urinary solutes relative to creatinine was generally maintained during the polyuria phase, except that phosphate excretion increased temporarily. ¹H NMR metabolomic analysis of urine revealed a progressive cyclic shift in the group principal components data cluster from before dosing, throughout the acute insult phase, and returning almost completely to normality when tested six months later. Renal insult by OTA was detected by ¹H NMR within a day of dosing, as the most sensitive early indicator. Notable biomarkers were trimethylamine N-oxide and an aromatic urinary profile dominated by phenylacetylglycine. Tolerance of such a large acute insult by OTA, assessed by rat natural lifetime outcomes, adds a new dimension to toxicology of this xenobiotic.

Comments on "Ochratoxin A: In utero Exposure in Mice Induces Adducts in Testicular DNA. Toxins 2010, 2, 1428-1444"-Mis-Citation of Rat Literature to Justify a Hypothetical Role for Ochratoxin A in Testicular Cancer

A manuscript in the journal recently cited experimental rat data from two manuscripts to support plausibility of a thesis that ochratoxin A might be a cause of human testicular cancer. I believe that there is no experimental evidence that ochratoxin A produces testicular cancer in rats or mice.

Effects of fasting and gender on ochratoxin A toxicokinetics in F344 rats

Ochratoxin A (OTA) is a mycotoxin that causes renal tumors in rats, particularly in males. In previous kinetic studies performed in fed conditions (Vettorazzi et al., 2008), mature F344 male rats presented a significantly lower OTA bioavailability than females and young animals. The objective of the present study was to evaluate two factors which could explain this different kinetic profile: the presence of food and the male-specific protein alpha-2u-globulin. Therefore, a 24h kinetic study has been performed in rats under fasting conditions. Food ingestion has been controlled in both sexes during two months. The presence of alpha-2u-globulin in the urine has been analyzed with SDS-gradient mini-gel electrophoresis. Fasting tends to increase the maximum OTA plasma concentrations and the rate of absorption. The relative bioavailability is significantly increased under fasting conditions only in males. Mature males consumed a higher amount of food but, as the OTA dose administered, it was proportional to body weight. The reason why the OTA bioavailability is more affected in presence of food only in males is unclear. Several possibilities, such as differences in gastric emptying, OTA-food interactions and the involvement of alpha-2u-globulin are discussed.

Contrasting nephropathic responses to oral administration of extract of cultured Penicillium polonicum in rat and primate

Liquid- or solid substrate-cultured Penicillium polonicum administered in feed to rats over several days evokes a histopathological response in kidney involving apoptosis and abnormal mitosis in proximal tubules. The amphoteric toxin is yet only partly characterized, but can be isolated from cultured sporulating biomass in a fraction that is soluble in water and ethanol, and exchangeable on either anion- or cation-exchange resins. After several weeks of treatment renal proximal tubule distortion became striking on account of karyocytomegaly, but even treatment for nearly two years remained asymptomatic. Extract from a batch of solid substrate fermentation of P. polonicum on shredded wheat was incorporated into feed for rats during four consecutive days, and also given as an aqueous solution by oral gavage to a vervet monkey daily for 10 days. Treatment was asymptomatic for both types of animal. Rat response was evident as the typical renal apoptosis and karyomegaly. In contrast there was no such response in the primate; and neither creatinine clearance nor any haematological characteristic or serum component concentration deviated from a control or from historical data for this primate. The contrast is discussed concerning other negative findings for P. polonicum in pigs and hamsters. Renal karyomegaly, as a common rat response to persistent exposure to ochratoxin A, is not known in humans suspected as being exposed to more than the usual trace amounts of dietary ochratoxin A. Therefore the present findings question assumptions that human response to ochratoxin A conforms to that in the rat.

Pathological outcomes in kidney and brain in male Fischer rats given dietary ochratoxin A, commencing at one year of age

Malignant renal carcinoma, manifest in morbid ageing rats, is the striking component of an otherwise silent response after about nine months of exposure to ochratoxin A in the first year of life (daily intake ~100-250 µg/kg body weight). Reasons for the long latency are unclear, as is whether there would be a similar carcinogenic response if toxin exposure started at one year of age. Therefore, 24 male Fischer rats were given 100 µg ochratoxin A as a daily dietary contaminant for 35 weeks from age 50 weeks. Plasma ochratoxin A concentration reached a maximum value of ~8 µg/mL within one month of starting the toxin regimen. No renal carcinomas occurred. Four renal adenomas, two of which were only microscopic, were found among the six rats surviving for 110 weeks. The findings raise new questions about a difference between young adults and mature adults in sensitivity of male rats to the ochratoxin A-induced DNA damage necessary for renal carcinogenesis. A pilot histological study of perfuse-fixed brains of the toxin-treated rats showed no gross abnormalities, correlating with the consistent absence of behavioral or neurological disorders from chronic ochratoxin A exposure regimens in the range 100-250 µg/kg/day during the second half of life. Reasoned questioning concerning ochratoxin A as a neurotoxic mycotoxin is made.

Oncological outcomes in rats given nephrocarcinogenic exposure to dietary ochratoxin a, followed by the tumour promoter sodium barbital for life: a pilot study

The potent experimental renal carcinogenesis of ochratoxin A (OTA) in male rats makes the dietary contaminant a potential factor in human oncology. We explored whether the tumour promoter sodium barbitate could shorten the otherwise long latency between exposure to toxin and tumourigenesis. Young rats, of a hybrid in which mononuclear leukaemia was rare, were given feed contaminated (5 ppm) with OTA for 36 weeks to initiate renal tumourigenesis. Some individuals were thereafter given sodium barbitate (500 ppm in drinking water) for life. Pathological outcomes were studied at or near the end of natural life. Renal tumours in males given barbitate became evident after latency of one year, but only slightly before those without barbitate. In contrast, female mammary tumourigenesis was advanced by at least 6 months synchronously in all rats given the OTA-barbitate regimen compared to tumourigenesis in controls. Diagnosis of malignant mammary angiosarcoma in a female given the OTA-barbitate regimen is a new finding in the rat. The long latency of OTA-induced renal tumourigenesis was not notably susceptible to accelerated promotion by barbitate, contrasting with an apparently marked effect of barbitate on development of mammary tumours.

Structures of covalent adducts between DNA and ochratoxin a: a new factor in debate about genotoxicity and human risk assessment

The potent renal carcinogenicity of ochratoxin A (OTA) in rats, principally in the male, raises questions about mechanism. Chromatographic evidence of DNA adducts after (32)P-postlabeling analysis contrasts with experimental attempts to demonstrate the absence of OTA in such adducts. Proffered schemes for alternative epigenetic mechanisms in OTA carcinogenicity remain unsatisfying, while structural data substantiating DNA-OTA adducts has also been lacking. We report refined (32)P-postlabeling methodology revealing one principal adduct isolated in small amounts from the kidneys of all five Fischer and five Dark Agouti rats to which OTA had been given on four consecutive days. We also describe structural data for the principal adduct from OTA/DNA interaction in vitro and its subsequent preparative isolation by the postlabeling methodology (as C-C8 OTA 3'dGMP), essentially creating an ochratoxin B-guanine adduct. Reasoning for the unsuitability of experimental protocols in published evidence claiming nongenotoxicity of OTA is given. In vivo exposure of renal DNA to cycles of adduction with OTA, necessarily protracted for carcinogenesis to occur, can reasonably explain an occasional focal neoplasm from which metastasizing carcinoma could develop.

A pilot study of nuclear instability in archived renal and upper urinary tract tumours with putative ochratoxin aetiology

DNA ploidy measurement has been applied uniquely to wax-embedded tissue of primary renal cell and metastatic tumours of a key experimental researcher on porcine ochratoxicosis, a control, and four transitional cell carcinomas from cases of Balkan endemic nephropathy. Primary renal tumour was diploid, and hyperdiploid metastasis was within the lower ploidy range for typical renal cell carcinoma. Three Balkan primary tumours showed extensive aneuploidy indicating marked nuclear instability, similar to model rat renal carcinoma caused by ochratoxin A. In contrast, much less nuclear instability in the putative occupational ochratoxicosis case fitted poorly with the ochratoxin A model.

Minimum tolerable exposure period and maximum threshold dietary intake of ochratoxin A for causing renal cancer in male Dark Agouti rats

In rats fed dietary ochratoxin A (5 ppm for 3, 6 or 9 months) no renal tumours occurred throughout natural life of the group treated for 3 months, during which the ochratoxin dose was 3 times that in the high dose group of the NTP study. Bilateral renal carcinoma occurred in one rat in the 6 month group. Four rats treated for 9 months developed unilateral renal carcinoma. Overall latency between ceasing toxin exposure and discovering tumours was 35-97 weeks. Experimental verification of a 'no observable effect level' was made for feed containing 400 ppb, equivalent to approximately 7 microg ochratoxin A/day for Dark Agouti rats for up to 2 years, during which mean daily dose commenced at approximately 50 microg/kg, but later for adults was in the range 30-20 microg/kg. This data doubles the daily in vivo threshold dose from the NTP study ( approximately 15 microg/kg), and could influence human risk assessment. An at least 3 month threshold period for exposure to exceptionally high daily OTA intake (90 microg; 640-450 microg/kg) raises doubts over interpretation of experimental molecular data for OTA exposure at lower dose for up to 3 months in studies aimed at understanding carcinogenic mechanism.

The role of tryptophan as a biosynthetic precursor of indole-diterpenoid fungal metabolites: continuing a debate

Studies in the 1980s and 1990s on the origin of the indole moiety in fungal indole-diterpenoids using (14)C-labelled tryptophan consistently showed autoradiographic evidence but gave low % incorporation of the probe. Recent studies on a member of the group (nodulisporic acid A), using more specific (13)C methodology, demonstrated a role of the tryptophan biosynthetic pathway but, in failing to show involvement of end-product, concluded that the indole was derived from indole-3-glycerol phosphate and suggested that the previous (14)C data arose via metabolic scrambling of label. In considering the protocol for the (13)C studies, there is concern that the fungal material was starved of an exogenous nitrogen source and thus could have degraded added labelled tryptophan. Consequently, synthesis of the serine necessary for anabolic formation of tryptophan may have been constrained. It is suggested that (13)C studies on appropriate fungi early in the idiophase of submerged or surface fermentation should be made before the biosynthesis of indole-diterpenoids can become clearer.

Biosynthesis of scorpinone, a 2-azaanthraquinone from Amorosia littoralis, a fungus from marine sediment

The biogenetic origin of the carbon atoms in the 2-azaanthraquinone scorpinone ( 1), produced by the rare fungus Amorosia littoralis isolated from marine sediment, was explored through isotopic enrichment studies utilizing [2- (13)C]-acetate and [1,2- (13)C]-acetate. The labeling results reveal a heptaketide precursor is involved in the biosynthesis of 1, as has been found for the structurally related naphthoquinone dihydrofusarubin. The previously identified naphthoquinone herbarin ( 2) was also isolated and appears to bear the same biogenetic relationship to 1 as the fusarubins do to the fungal 2-azaanthraquinone bostrycoidins.

DNA ploidy distribution in renal tumours induced in male rats by dietary ochratoxin A

DNA ploidy distribution, measured in experimental renal tumours that occurred in twelve ageing male Fischer rats derived from carcinogenicity experiments on ochratoxin A (OTA) in response to chronic dietary exposure, was diploid in all renal adenomas and aneuploid in all carcinomas, correlating with their typical organised and disorganised histopathology, respectively. Aneuploidy was also detected in renal tissue in which karyomegaly, induced by OTA, was analogous to that caused by the fungus Penicillium polonicum. Thus, the experimental rat renal carcinoma could arise within an adenoma directly from certain persistent karyomegalic tubular epithelial cells long after their particular genetic damage has been caused during a protracted period of OTA insult.

Amorosia littoralis gen. sp. nov., a new genus and species name for the scorpinone and caffeine-producing hyphomycete from the littoral zone in The Bahamas

The new generic and species name Amorosia littoralis gen. sp. nov. is introduced for the conidial dematiaceous hyphomycete isolated from the littoral zone in The Bahamas and reported in 2001 to produce the novel aza-anthraquinone scorpinone, and also caffeine. No satisfactory generic placement was found at the time, but subsequent morphological and molecular investigations reveal that a new generic name is required. The new genus has some similarity to several fungi described in Trichocladium, but differs substantially from the type species of that genus in the form of the conidia and the lack of ornamentation. BLAST studies using the 18S and 28S rDNA gene sequences place the new genus in the Sporormiaceae. In addition to the morphological studies, an ultrastructural examination of the conspicuous porate septa of hyphae showed that they do not belong to a basidiomycete.

Natural and directed biosynthesis of communesin alkaloids

A role for tryptophan, acetate, mevalonate and methionine in the biosynthesis of communesins A and B, novel structurally-related and biologically-active Penicillium metabolites, has been established by isotopic labelling techniques. The incorporation of (14)C-tryptamine has also been demonstrated. dl-2-(13)C-tryptophan specifically enriched two carbon atoms in the (13)C NMR spectrum, thereby defining the intra-molecular arrangement of the two tryptophan-derived moieties. Feeding differentially labelled precursors during communesin production showed that tryptophan and methionine are involved early in the biosynthesis and that mevalonate provides an isoprene which is added later. A biosynthetic pathway involving an early precursor based on tryptophan is proposed. Indole-N-((13)C-methyl) tryptophan was not incorporated into communesins implying that N-methylation of tryptophan is not the first step of the communesin biosynthetic pathway. During deamination of indole-N-((13)C-methyl) tryptophan to 1-(13)C-methylindole-3-carboxylic acid communesin biosynthesis was inhibited. Of several halogenated indoles tested for directed biosynthesis, only dl-6-fluoro-tryptophan and 6-fluoro-tryptamine caused accumulation of the corresponding monofluoro-analogues of communesins A and B.

Deuterium NMR used to indicate a common mechanism for the biosynthesis of ricinoleic acid by Ricinus communis and Claviceps purpurea

Previous studies have shown that ricinoleic acid from castor bean oil of Ricinus communis is synthesized by the direct hydroxyl substitution of oleate, while it has been proposed that ricinoleate is formed by hydration of linoleate in the ergot fungus Claviceps purpurea. The mechanism of the enzymes specific to ricinoleate synthesis has not yet been established, but hydroxylation and desaturation of fatty acids in plants apparently involve closely related mechanisms. As mechanistic differences in the enzymes involved in the biosynthesis of natural products can lead to different isotopic distributions in the product, we could expect ricinoleate isolated from castor or ergot oil to show distinct (2)H distribution patterns. To obtain information concerning the substrate and isotope effects that occur during the biosynthesis of ricinoleate, the site-specific natural deuterium distributions in methyl ricinoleate isolated from castor oil and in methyl ricinoleate and methyl linoleate isolated from ergot oils have been measured by quantitative (2)H NMR. First, the deuterium profiles for methyl ricinoleate from the plant and fungus are equivalent. Second, the deuterium profile for methyl linoleate from ergot is incompatible with this chemical species being the precursor of methyl ricinoleate. Hence, it is apparent that 12-hydroxylation in C. purpurea is consistent with the biosynthetic mechanisms proposed for R. communis and is compatible with the general fundamental mechanistic similarities between hydroxylation and desaturation previously proposed for plant fatty acid biosynthesis.

Screening of sweet sorghum accessions for inhibition of secondary sporulation and saccharide measurements in honeydew of Claviceps africana

Certain sweet sorghums (Sorghum bicolor) inhibit the secondary sporulation of Claviceps africana, which occurs on exuded ergot honeydew when the parasite is supplied with excess sucrose, which is then transformed to unique free oligosaccharides fructosyl - mannitol and difructosyl - mannitol with spore germination inhibiting properties. Five accessions (BRA-035726-SUGAR DRIP, BRA-035696-THEIS, BRA-036013-MN-4578, BRA-035947-MN-4418 and CMSXS-633) of sweet sorghum were selected among 50 evaluated. These five accessions failed to support secondary sporulation on the "honeydew" exuded from infected florets. There was a higher concentration (%w/v) of the free oligosaccharides on the honeydew of these accessions when compared to a hybrid male-sterile grain sorghum. Therefore, a possible strategy would be seek to incorporate a sweet character into "A" lines for hybrid seed production in order to restrict secondary disease spread.

Comparative responses to mode of oral administration and dose of ochratoxin A or nephrotoxic extract of Penicillium polonicum in rats

Administration of Penicillium polonicum extract to male Sprague-Dawley rats (200 g), either mixed in feed or given daily by gavage, for 5 days, had no clinical effects. However, at necropsy on day 6 marked histopathological changes occurred in renal tubule epithelia, including mitotic figures, karyomegalic nuclei, and frequent apoptosis identified specifically by TUNEL methodology and confocal microscopy. Ochratoxin A given similarly to rats (daily, 1 mg or 0.2 mg) was also clinically asymptomatic except for the 1 mg dose given by gavage; rats in this group lost weight. Marked renal tubular necrosis, though even without any significant accompanying apoptosis, was evident only at this higher dose by gavage; it was associated also with the highest incidence of renal DNA adducts and a disproportionately high concentration of ochratoxin A in plasma on day 6. Significantly fewer renal DNA adducts were detected in rats given 1 mg ochratoxin A in feed. The study demonstrates the potential for exaggerated toxicological responses to ochratoxin A administered by gavage through predicted consequential surges in the circulating concentration of the mycotoxin.

Clinicomorphological studies in chicks fed ochratoxin A while simultaneously developing coccidiosis

The progression of coccidiosis and the resultant mortality were followed in chicks fed a OTA-contaminated diet. More complex and rapid progress of coccidiosis occurred in OTA-treated chicks than in chicks fed a OTA-free diet. The concentration of total protein in the serum was significantly decreased in the chicks in the OTA-treated group, whereas this was significantly increased in chicks infected with Eimeria tenella, irrespective of additional treatment with OTA. The serum glucose concentration was significantly increased in all the chicks exposed to OTA and/or suffering from coccidiosis, as was serum retention of uric acid in all groups, most notably in those consuming OTA. OTA induced degenerative changes in, and an increase in the weight of the kidneys, liver, heart and ventriculum; there was depletion of lymphoid tissue and a decrease in the lymphoid organs' weight and body weight. Coccidiosis induced only a slight growth depression and a slight increase in the relative weight of the kidneys and liver. The intensity of the clinical signs, the impairment of kidney function, macroscopic and histopathological changes, deviations in the weight of some organs and general depression in growth were greater when chicks infected with E. tenella were also given OTA.

Experimental one year ochratoxin A toxicosis in pigs

Mild mycotoxic nephropathy was induced in 6 pigs by a diet containing ochratoxin A at 800 ppb, several times higher than that naturally encountered in some feed for pig production in Bulgaria. The nephropathy was expressed only as slightly hypertrophied kidneys with a faintly mottled surface, discernible at the end of the experiment to a skilled observer but probably not recognisable in routine slaughterhouse processing. Histological examination showed two types of changes: degenerative - affecting epithelial cells in some proximal tubules of pigs after 6 months, and proliferative changes in the interstitium which predominated after 1 year of exposure to ochratoxin A. Telangiectasis and lymph stasis were rarely seen. The renal lesions were similar to those described for classical mycotoxic porcine nephropathy formerly encountered in Denmark, but they were rather different from the porcine nephropathy which occurs spontaneously in Bulgaria. Measurement of ochratoxin A in serum provided analytical values complementary to feed intake and with similar concentration values. It also showed both accumulation with time, from 3 months to 6 months (approximately 1 ppm), and a 2-fold range of values within a group eating from a common feed source, as in commercial pig production. Mild symptomatology in this long, single-mycotoxin experiment serves to lessen somewhat the current perception of the direct renal toxicity of ochratoxin A alone, though a role in multi-toxin contexts is unquestioned.

Biosynthesis of ochratoxins by Aspergillus ochraceus

Shaken liquid fermentation of an isolate of Aspergillus ochraceus showed growth-associated production of ochratoxins A and B, followed by production of a related polyketide diaporthin. Later, between 150 and 250 h, mellein accumulated transitorily. In contrast, shaken solid substrate (shredded wheat) fermentation over 14 days produced mainly ochratoxins A and B (ratio ca. 5:1) in very high yield (up to 10 mg/g). In these systems experiments with 14C-labelled precursors and putative intermediates revealed temporal separation of early and late stages of the ochratoxin biosynthetic pathway, but did not support an intermediary role for mellein. The pentaketide intermediate ochratoxin beta was biotransformed very efficiently into both ochratoxins A and B, 14 and 19%, respectively. The already chlorinated ochratoxin alpha was only biotransformed significantly (4.85%) into ochratoxin A, indicating that chlorination is mainly a penultimate biosynthetic step in the biosynthesis of ochratoxin A. This was supported by poor (1.5%) conversion of radiolabelled ochratoxin B into ochratoxin A. Experiments implied that some ochratoxin B may arise by dechlorination of ochratoxin A.

Scorpinone: a new natural azaanthraquinone produced by a Bispora-like tropical fungus

Scorpinone (1), 3-methyl-6,8-methoxy-2-aza-9,10-anthraquinone, has been isolated from the mycelium of a cultured sterile fungus of Caribbean origin. The structure was elucidated by X-ray crystallography, and 2D NMR spectral data have been assigned. The compound is one of very few known fungal azaanthraquinones.

Biosynthesis of diaporthin and orthosporin by Aspergillus ochraceus

Diaporthin and orthosporin were characterised from the fungus Aspergillus ochraceus D2306. Diaporthin was identified by high-resolution electron impact mass spectrometry and 1H and 13C NMR spectroscopy, from which new spectroscopic assignments were made. Orthosporin was also identified by mass spectrometry and both fungal metabolites are reported for the first time as co-metabolites and also as products of A. ochraceus. The methylation inhibitor ethionine affected production of both diaporthin and orthosporin in spite of no obvious methylation step in the biosynthesis of orthosporin, implying that extracellular orthosporin may arise by de-O-methylation of diaporthin. The biosynthetic origin of diaporthin was demonstrated by incorporation of [1-14C]acetate and [methyl-14C]methionine administered in early idiophase.

Differentiating the biosynthesis of pseudomonic acids A and B

Pseudomonic acid A (1) has been the dominant commercial pseudomonate antibiotic produced by Pseudomonas fluorescens. In specific shaken flask conditions initial fermentation accumulation of 1 is followed by preferential accumulation of the 8-hydroxy derivative, pseudomonic acid B (2). Biosynthetic probing with a pulse of [1-14C] acetate or L-[methyl-14C] methionine at early, mid and late stages of the fermentation gave relative patterns of radioactivity in 1 and 2 that are inconsistent with an assumption that 2 arises by oxidation of 1, or that 1 is formed by reduction of 2. Since [methyl-14C] methionine only labels carbons in the 12-carbon part of the pseudomonate molecule that is thought to be an early biosynthetic moiety, the evidence from radiolabelling experiments implies that preferential early oxidation of this biosynthetic intermediate causes the pathway diversion to accumulate 2 instead of 1.

Caffeine: also a fungal metabolite

Caffeine has been found to occur as a fungal metabolite and to be the principal alkaloid in sclerotia of Claviceps sorghicola, a Japanese ergot pathogen of Sorghum spp.

Susceptibility to secondary bacterial infections in growing pigs as an early response in ochratoxicosis

Mycotoxic nephropathy was induced in twelve 14 kg pigs fed a dietary component, moulded by Aspergillus ochraceus and contributing ochratoxin A at 1 or 3 ppm for up to 3 weeks. Concurrently, salmonellosis arose spontaneously in all six animals treated at 3 ppm and all died between days 15 and 17. Two of the six pigs in the 1 ppm group died similarly but the rest, and all of six control animals, were unaffected. Clinical biochemistry and histology revealed changes typical of renal ochratoxicosis in all ochratoxin-treated pigs. Clinical and pathomorphological changes typical of salmonellosis were evident in all those that died and Salmonella choleraesuis was consistently isolated from their faeces and liver. In a further experiment at 1 ppm ochratoxin A in animals immunised against S. choleraesuis haemorrhagic diarrhoea resulted instead, associated with Serpulina hyodysenteriae and Campylobacter coli. There was concomitant evidence of immunosuppression and delayed response to immunization. For the first time, susceptibility to natural infectious disease has been demonstrated in pigs exposed to the immunotoxicity of ochratoxin A. Differentiation of biochemical and histological changes attributable to ochratoxicosis or to secondary disease may require reinterpretation of a classical description of experimental porcine ochratoxicosis.

Ochratoxin formation in Aspergillus ochraceus with particular reference to spoilage of coffee

Production of ochratoxin on media by eight isolates of Aspergillus ochraceus from coffee or its processing environment in India, Indonesia, Kenya, and Brazil, and seven Brazilian isolates from other commodities, has been compared with yields in shaken fermentation on shredded wheat and coffee (Coffea arabica). Shredded wheat most consistently allowed expression of biosynthesis of ochratoxins A and B in yields up to 3.5% of the dry product. Culture on artificial media was an unreliable predictor of ochratoxin yield on both shredded wheat and coffee. Coffee was a relatively poor substrate for ochratoxin production particularly when sterilised. Notably, two Asian coffee isolates produced 400 mg kg(-1) ochratoxin A on unsterilised ground green coffee, showing this to be a preferred substrate for further experimentation. The study focused on isolates of A. ochraceus, which from evidence of culture on media would not be expected to be suitable fungi for future studies to establish both the fact of spoilage of coffee by A. ochraceus and the dynamics of ochratoxin formation by isolates of this species.

Influence of halogen salts on the production of the ochratoxins by Aspergillus ochraceus Wilh

The first report of the biological production of bromo ochratoxin B by Aspergillus ochraceus Wilh. is presented as well as a study of the influence of potassium bromide, potassium iodide, potassium fluoride, and potassium chloride on the production of ochratoxin A and ochratoxin B. Potassium fluoride and potassium iodide inhibited the growth of the fungus, whereas potassium chloride substantially stimulated the production of ochratoxin A in shaken solid substrate fermentation on whole wheat or shredded wheat, generally giving a high yield of ochratoxins. Increasing levels of potassium bromide led to a decline in ochratoxin A production and an increase in bromo-ochratoxin B, ochratoxin B, and 4-hydroxy ochratoxin B. Nevertheless, A. ochraceus was much less versatile in the bromo analogues than other fungi, which produce metabolites containing chlorine. Analysis included aminopropyl solid-phase extraction column cleanup followed by quantitative analysis on reversed-phase HPLC using fluorescence detection and employing N-(5-chloro-2-hydroxybenzoyl)phenylalanine as an internal standard.

Relations Among Sorghum Ergot Isolates from the Americas, Africa, India, and Australia

Sorghum ergot, initially restricted to Asia and Africa, was recently found in the Americas and Australia. Three species causing the disease have been reported: Claviceps sorghi in India, C. sorghicola in Japan, and C. africana in all ergot-positive countries. The objective of our study was to study the intraspecific variation in C. africana isolates in the Americas, Africa, India, and Australia. We confirmed C. africana, C. sorghi, and C. sorghicola as different species using differences in nucleotide sequences of internal transcribed spacer 1 and 5.8S rDNA regions. Sequences of this region obtained from the representative American, Indian, and Australian isolates of C. africana were identical. In addition, random amplified polymorphic DNA (RAPD) banding patterns of sorghum ergot pathogen isolates from the United States, Mexico, Puerto Rico, Bolivia, Australia, and India were evaluated with nearly 100 primers. A total of 65 primers gave identical patterns for all isolates, which confirmed that all were C. africana. The identity of RAPD pattern and rDNA sequence of Indian isolates with those of C. africana confirmed that the species is now present in India. Only 20 primers gave small pattern differences and 7 of them were used for routine testing. All of the American isolates were identical and three isolates of the same type were also found in South Africa, suggesting Africa as the origin of the invasion clone in the Americas. Australian and Indian isolates were distinguishable by a single band difference; therefore, migration from the Asian region to Australia is suspected. Another distinct group was found in Africa. Cluster analysis of the informative bands revealed that the American and African group are on the same moderately (69%) supported clade. Isolates from Australia and India belonged to another clade.

Isolation and characterization of 3-methoxy-2(5H)-furanone as the principal nephrotoxin from Narthecium ossifragum (L.) Huds

The principal substance in Narthecium ossifragum (L.) Huds, responsible for the nephrotoxic effects on cattle, moose, goats and other ruminants has been isolated and identified by X-ray crystallography as 3-methoxy-2(5H)-furanone. The Fourier-transform infra-red, 1H and 13C nuclear magnetic resonance, and mass spectra are also given. The concentration in four different batches of plant material varied from 113 to 344 microg g(-1) (wet weight). Extracts of N. ossifragum and fractions derived from them, including purified 3-methoxy-2(5H)-furanone, were each dosed intraruminally, to young goats. 3-Methoxy-2(5H)-furanone of 99.9% purity (15 mg kg(-1) live weight) caused increased concentration of creatinine in serum within 2-3 days, typical of kidney damage caused by N. ossifragum, while toxic effect was obtained down to 4 mg kg(-1) live weight with less purified material (> or = 95%). Toxic effect was also obtained with synthesized 3-methoxy-2(5H)-furanone (30 mg kg(-1) live weight). The isomer 4-methoxy-2(5H)-furanone, detected in some of the batches of the plant material, was not toxic when dosed at 60 mg kg(-1) live weight.

Uptake of radiolabelled ochratoxin A from soil by coffee plants

[3H, 14C] Ochratoxin A, prepared biosynthetically, was applied in dilute NaHCO3 solution to the soil in which coffee plants had grown to four pairs of leaves. Three weeks later the compound, isolated from dilute NaHCO3 extract of leaves by immunoaffinity chromatography, was detected by scintillation counting as a 1-2 ppm component of leaf dry weight, greatly exceeding the trace (ppb) occurrence of ochratoxin A in some green coffees, which therefore might arise in the field directly from fungal activity in soil rather than from fungal infection of cherries or processed green coffee.

Claviceps africana Discovered in India

The African ergot pathogen (Claviceps africana Frederickson, Mantle, & de Milliano) of sorghum (Sorghum bicolor (L.) Moench) was recently discovered in the Americas (4) and Australia, having previously only been recognized outside Africa in Thailand and Japan (3). The fungus provides a striking example of intercontinental epiphytotics of uncertain origins. Another fungus (C. sorghi Kulkarni, Seshadri & Hegde), the anamorph of which (Sphacelia sorghi McRae) is morphologically similar to that of C. africana and also causes ergot disease of sorghum, is considered to be the pathogen endemic to the Indian subcontinent (1,2). Five isolates of endemic ergot pathogen of sorghum from different locations in Southern India were provided as C. sorghi by ICRISAT, Hyderabad. The isolates were morphologically indistinguishable when cultivated on an asparagine-sucrose-salts agar, producing a white mycelium but no spores. Suspensions of hyphal fragments of each isolate were inoculated into gaping florets of a male-sterile sorghum grown at the Chelsea Physic Garden, London, in 1998. Infection of a few florets occurred with difficulty (<0.1% efficiency) by two of the isolates (from Andhra Pradesh and Madhya Pradesh states) to give a pathology typical of C. africana (2), especially with respect to the prominent young sphacelium forcing the glumes apart before first exudation of honeydew, the low concentration of honeydew oligosaccharides, and the white cascade of secondary sporulation on honeydew. This sphacelial fructification functioned as highly infective inoculum in other inflorescences, readily producing similar pathology leading to the formation of persistently small, roughly spherical "sclerotia" that were typical of C. africana in the recent American epiphytotics, but bearing none of the sclerotial characteristics of C. sorghi. Analysis of ergot tissue from near-mature inflorescences revealed dihydroergosine, an alkaloid that differentiates C. africana from C. sorghi, together with festuclavine, the identity of which was shown by GCMS (gas chromatography-mass spectrometry) (2). This evidence from pathogen isolates was complemented by analysis of a sample of small, spherical "sclerotia" from ICRISAT that also had a similar alkaloid composition. It is therefore clear that C. africana is now in India and this influences not only the interpretation of data on sorghum ergot disease published in recent years from that region, where the identity of the pathogen may not have been rigorously monitored, but also future phytopathological strategies for sorghum more widely in Asia. References: (1) R. Bandyopadhyay et al. Plant Dis. 82:356, 1998. (2) D. E. Frederickson et al. Mycol. Res. 95:1101, 1991. (3) P. G. Mantle and H. A.-G. Hassan. Int. Sorghum Millets Newsl. 35:97, 1994. (4) E. M. Reis et al. Plant Dis. 80:463, 1996.

Porcine nephropathy in Bulgaria: a progressive syndrome of complex or uncertain (mycotoxin) aetiology

Macroscopic nephropathy was observed in 506 pigs at slaughter in Bulgaria in 1993/94. Histopathological changes were mainly degenerative and proliferative, and were linked with kidney hypertrophy similar to that of the classical Danish Syndrome. Retention cysts formed by dilated tubules, activation or proliferation of capillary and vascular endothelium, and the development of neoplastic tissue were also observed. The most advanced pathology took the form of extensive interstitial fibrosis. Traces of ochratoxin A were found in the kidneys of the majority of 96 cases examined, and in some feed samples taken retrospectively from farms or commercial sources. The dietary ochratoxin concentration (100 micrograms/kg), calculated from serum analyses, closely matched the average of individually analysed feeds. In other feeds no ochratoxin A was detected and the cosmopolitan mycobiota isolated did not include the ochratoxinogenic Penicillium verrucosum that caused the Danish syndrome. Aspergillus ochraceus was rare and the isolates did not synthesise ochratoxin in laboratory culture. The unconfirmed diagnosis of ochratoxicosis suggests a complex or multi-toxin aetiology for this rather common chronic disease in Bulgaria.

The effects of the tremorgenic mycotoxin penitrem A on the rat cerebellum

Within 10 minutes of intraperitoneal injection of penitrem A (3 mg/kg), rats develop severe generalized tremors and ataxia that persist for up to 48 hours. These are accompanied by a three- to fourfold increase in cerebellar cortical blood flow. Mitochondrial swelling occurs in cerebellar stellate and basket cells within 30 minutes of dosing and persists for more than 12 hours without leading to cell death. From 2 hours, Purkinje cell dendrites show early cytoplasmic condensation accompanied by fine vacuolation of smooth endoplasmic reticulum and enlargement of perikaryal mitochondria. From 6 hours, many Purkinje cells develop intense cytoplasmic condensation with eosinophilia that resembles "ischemic cell change," and from 12 hours, many other Purkinje cells show marked watery swelling. Astrocytes begin to swell from 0.5 hours after injection and show hypertrophy of organelles from 6 hours. Also from 6 hours onward, discrete foci of necrosis appear in the granule cell layer, while permeability of overlying meningeal vessels to horseradish peroxidase becomes evident at 8 hours. All changes are more severe in vermis and paravermis. Despite widespread loss of Purkinje cells, the animals' behavior becomes almost normal within a week. While tremor occurs with doses of 1.5 and 0.5 mg/kg, cellular damage is minimal. The tremor mechanism differs from that of harmaline since destruction of inferior olivary nuclei abolishes neither the tremor response to penitrem A nor the cellular damage. No morphological changes are found in other brain regions. The affinities of penitrem A for high-conductance calcium-dependent potassium channels and for gamma-aminobutyric acid receptors with the probability of resultant excitotoxity are considered to be important underlying factors for these changes.

Nephrotoxicity in goats caused by dosing with a water extract from the stems of Narthecium ossifragum plants

Seven goats were given a single dose of an aqueous extract derived from 30 g (wet weight) of Narthecium ossifragum per kg liveweight. Their serum creatinine and urea concentrations increased to day 5 but then fell to normal by day 10. Serum magnesium increased to day 4 and decreased to normal by day 9. Their serum calcium concentration was lower than normal on days 4, 5 and 6. Histopathological examination of the kidneys of goats killed or found dead 2, 4, 6, 8, 11 or 16 days after dosing revealed tubular epithelial cell degeneration and necrosis. Regeneration of the tubular epithelium and signs of interstitial fibroplast proliferation and fibrosis could be seen in animals killed on days 8, 11, 16 and 42. No signs of liver damage were observed in 3 goats dosed with the insoluble plant material from 40 g (wet weight) Narthecium ossifragum per kg liveweight. The total dose was divided into three doses, which were given intraruminally within 7 h. The activities of aspartate aminotransferase, gamma-glutamyltransferase and glutamate dehydrogenase remained within the normal range in all 10 goats after dosing.

Further studies on the presence, qualities and effects of the toxic principles from Narthecium ossifragum plants

One calf was dosed during one day with an aqueous extract from 3.0 kg (wet weight) of Narthecium ossifragum and another was dosed on the same day with the insoluble plant residue. The concentrations of serum creatinine and magnesium increased only in the calf dosed with the aqueous extract, while the activity of glutamate dehydrogenase increased only in the serum of the calf dosed with the plant residue, so differentiating the nephrotoxic and hepatotoxic principles as water-soluble and water-insoluble compounds, respectively. One calf was dosed with 30 g (wet weight) N. ossifragum flower stems per kg live weight during one day and another was dosed with 30 g (wet weight) N. ossifragum leaves per kg live weight on the same day. The serum creatinine and urea concentrations and also the activities of glutamate dehydrogenase, aspartate aminotransferase and gamma-glutamyltransferase in the serum increased in the calf dosed with the flower stems, whereas there was only a slight temporary increase in the creatinine concentration in serum from the calf dosed with the leaves. However, histopathological examination of the kidneys of the calf dosed with the flower stems revealed severe tubular necrosis and degeneration. It therefore appears that both the toxic principles are present in the flower stems of N. ossifragum rather than in its leaves. The serum creatinine concentration was significantly increased in a non-ruminating calf dosed with an aqueous extract from 32 g (wet weight) N. ossifragum per kg liveweight during one day, showing the intrinsic nephrotoxicity of the plant.

Detection of ergot (Claviceps purpurea) in a dairy feed component by gas chromatography and mass spectrometry

A dairy feed that contained barley malt screenings caused hyperthermia in dairy cattle. The feed was suspected of containing ergot and was subsequently analyzed to determine the ricinoleate component, a special and prominent feature of oil-rich ergot tissue. Triglyceride oil was extracted by organic solvents from the dairy feed, and the oil was saponified to release fatty acids. Ricinoleate, as a methyl ester, was selectively resolved from other fatty acids by silica gel chromatography and was analyzed by capillary gas chromatography coupled with chemical ionization mass spectrometry, which demonstrated the presence of the methyl ricinoleate molecule and proved that the feed contained ergot. The methodology may be refined to monitor for ergot in powdered dairy feed more routinely.

Nephrotoxicity of Narthecium ossifragum in cattle in Norway

During the summer of 1992 renal failure was diagnosed in 232 grazing cattle in 85 herds on the west coast of Norway. The salient clinical signs were depression, anorexia and melaena or fresh blood in the faeces; diarrhoea was also commonly observed. The serum concentrations of creatinine, urea, magnesium and phosphorus, and the activities of glutamate dehydrogenase, aspartate aminotransferase and creatine kinase were above normal and the serum calcium concentration was below normal. Post mortem examinations consistently revealed renal tubular necrosis. In some cases there was liver necrosis and also erosions at the base of the tongue, in the oesophagus and in the jejunum and colon. The toxicity was probably caused by the plant Narthecium ossifragum (bog asphodel).

Renal histopathological responses to nephrotoxic Penicillium aurantiogriseum in the rat during pregnancy, lactation and after weaning

The typical renal histopathological changes in proximal tubules of rats consuming food containing shredded wheat moulded by Penicillium aurantiogriseum did not occur in neonates of rats ingesting the nephrotoxic diet during pregnancy nor in pups fed only by lactation from a treated dam. In contrast, weanlings consuming the moulded diet consistently showed within a few days densely staining mitosis-like structures in the proximal tubules which was the first step leading to development of the prominent tubular cytomegaly and karyomegaly seen when 16 weeks old. Karyomegaly and cytomegaly became evident also when mouldy shredded wheat constituted only 1% of a diet consumed on 45 days during the first 8 weeks after weaning, demonstrating the potency of the active component. Relevance to the putative involvement of nephrotoxic mycotoxins in human renal disease is discussed, as is the apparent absence of a renal histopathological response in adult rats during pregnancy and lactation.

Biosynthesis of glyantrypine by Aspergillus clavatus

The biosynthesis of glyantrypine from radiolabelled amino acid precursors has been shown experimentally to involve anthranilic acid, tryptophan and glycine. Low values for percentage incorporation of radiolabel into glyantrypine were partly influenced by a complex array of other novel alkaloids shown by the radiolabelling experiments to be related to glyantrypine. Interpretation of radiolabel incorporation from [14C-carboxyl]-anthranilic acid into microbial metabolites seen to contain an anthranilyl moiety in various biosynthetic arrangements is discussed. The possibility of diversion of anthranilic acid from the kynurenine pathway to glyantrypine biosynthesis is recognised.