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PubMed2000

Fern spore extracts can damage DNA.

The carcinogenicity of the vegetative tissues of bracken fern (Pteridium) has long been established. More recently, the carcinogenic effects of the spores of bracken have also been recognized. Both vegetative tissues and spores of bracken can induce adducts in DNA in animal tissues, but the possible genotoxic or carcinogenic effects of spores from fern species other than bracken are unknown. The single-cell gel electrophoresis ('comet') assay was used to investigate whether fern spores can cause DNA damage in vitro. Extracts of spores from six fern species were administered to cultured human premyeloid leukaemia (K562) cells. Spore extracts of five fern species: Anemia phyllitidis, Dicksonia antarctica, Pteridium aquilinum, Pteris vittata and Sadleria pallida, induced significantly more DNA strand breaks than those in the control groups. Only in one species, Osmunda regalis, was the effect no different from that in the control groups. Using extracts from A. phyllitidis and P. vittata, the extent of DNA damage was increased by increasing the original dose 10 times, whereas an experiment in which exposure times were varied suggested that the highest levels of strand breaks appear after 2 h exposure. Simultaneous incubation with human S9 liver enzyme mix ablated the damaging effect of the extracts. Our data show that fern spore extracts can cause DNA damage in human cells in vitro. Considering the strong correlation between DNA damage and carcinogenic events, the observations made in this report may well have some implications for human health.

Comet Assay↗
PubMed2000

Carcinogenic effects of ptaquiloside in bracken fern and related compounds.

Consumption of the bracken fern Pteridium aquilinum by cattle has been shown to induce bladder and intestinal carcinomas in cattle and to cause a number of diseases in other farm animals. An unstable glucoside named ptaquiloside, containing a reactive cyclopropane ring, has been isolated from the fern and its potent carcinogenicity proven. Nineteen of 31 ferns tested by chemotaxonomic methods in Japan have been found to contain potentially carcinogenic ptaquilosides as have Cheilanthes sieberi and Pteridium esculentum. Hydrolysis of ptaquilosides leads to pterosins; under milder conditions a dienone which is believed to be the primary carcinogen is obtained. Hypacrone, a sesquiterpine containing a reactive cyclopropane ring, has been isolated from Hypolepis punctata and its structure proved by synthesis. Illudins, structurally similar to ptaquiloside, have been isolated from the basidiomycete Omphalotus illudens. These give anti-tumour activity and similar reactivity with nucleophiles to ptaquiloside. Compound CC-1065, a highly toxic antibiotic also containing a cyclopropane ring, has been isolated from Streptomyces zelensis. The mechanism of its reactivity with DNA has been compared to that of ptaquiloside and the small structural differences between carcinogenic and anti-tumour activity discussed. Both CC-1065 and adozelesin, a synthetic analogue with anti-tumour activity, have been shown to alkylate the N-3 atom of adenine in a certain sequence of DNA. The reactivity of cysteine with ptaquilosides and illudins is discussed, as is the role of cysteine alkylating agents in apoptosis.

Animals↗
PubMed1975

[Distribution of endogenous inhibitors of the respiratory chain in plants].

70 phosphate buffer extracts of various plant tissues of 40 species as well as of 2 bacteria were tested for the presence of endogenous inhibitors of the respiratory chain. Electron transfer particles (ETP) from beef heart mitochondria served as test object. The NADH oxidase (spectrophotometrically) and the succinate oxidase activity (manometrically) were measured. Inhibitory activities could be detected in all the plant species tested, but there were quantitative differences by orders of magnitude. The inhibitory effects were more frequent and higher in the NADH oxidase system than those in the succinate oxidase system. The highest inhibitory activities were observed with blossoms of Forsynthia intermedia, male blossoms of Corylus avellana, inflorescences of Brassica oleracea, fronds of Pteridium aquilinum and gallnuts of Quercus. The specific inhibitory activities (related to the dry mass of the extracts) suggest very efficient inhibitors having concentrations of half-inhibition in the muM-range. With 6 extracts the inhibitory activity on the NADH oxidase system was completely destroyed by boiling (Brassica oleracea, Amoracia rusticana, leaves of Digitalis purpurea, roots of Allium cepa, fruit pips of Malus domestica and mushrooms of Lactarius vellereus). The results with some plant species (Bryophyllum daigremonteanum, Allium cepa, male blossoms of Corylus avellana, Pteridium aquilinum) suggest a biological dynamics of the inhibitory activity. The inhibitor from Bryophyllum was partially characterized with regard to its mode of action. The following supposed biological functions of endogenous respiratory inhibitors of plants are discussed: 1. Involvement in the degradation of mitochondria in the course of differentiation, maturation and involution processes as well as in biologically controlled senescence processes; 2. A switch-over to the alternative mitochondrial respiratory pathway; 3. Induction and maintenance of a resting metabolism, e.g. in dormancy, by action as growth inhibitors; 4. Action as phytoncides (phytoallexines) for the defense against parasites.

NADH, NADPH Oxidoreductases↗
PubMed2006

Microbial degradation and impact of Bracken toxin ptaquiloside on microbial communities in soil.

The carcinogenic and toxic ptaquiloside (PTA) is a major secondary metabolite in Bracken fern (Pteridium aquilinum (L.) Kuhn) and was hypothesized to influence microbial communities in soil below Bracken stands. Soil and Bracken tissue were sampled at field sites in Denmark (DK) and New Zealand (NZ). PTA contents of 2.1 +/- 0.5 mg g(-1) and 37.0 +/- 8.7 mg g(-1) tissue were measured in Bracken fronds from DK and NZ, respectively. In the two soils the PTA levels were similar (0-5 microg g(-1) soil); a decrease with depth could be discerned in the deeper B and C horizons of the DK soil (weak acid sandy Spodosol), but not in the NZ soil (weak acid loamy Entisol). In the DK soil PTA turnover was predominantly due to microbial degradation (biodegradation); chemical hydrolysis was occurring mainly in the uppermost A horizon where pH was very low (3.4). Microbial activity (basal respiration) and growth ([3H]leucine incorporation assay) increased after PTA exposure, indicating that the Bracken toxin served as a C substrate for the organotrophic microorganisms. On the other hand, there was no apparent impact of PTA on community size as measured by substrate-induced respiration or composition as indicated by community-level physiological profiles. Our results demonstrate that PTA stimulates microbial activity and that microorganisms play a predominant role for rapid PTA degradation in Bracken-impacted soils.

Biodegradation, Environmental↗
PubMed2006

Bracken-fern extracts can be clastogenic or aneugenic depending on the tissue cell assay.

The consumption of bracken fern (Pteridium aquilinum) as food is associated with a high incidence of cancer in humans and animals. We investigated the cytogenetic effects of bracken-fern extracts (hexane extract-HE, ethanol extract-EE, hot water extract-HWE and cold water extract-CWE) on chromosomes of peritoneal and bone-marrow cells of Swiss mice. In peritoneal cells, all four treatments (HE, EE, HWE and CWE) induced structural chromosome aberrations, but the EE also induced numerical chromosome aberrations. In bone-marrow cells both HE and CWE induced structural chromosome aberrations; additionally, the number of abnormal metaphases was higher in peritoneum than in bone marrow. We suggest that bracken fern induces cytogenetic damage through DNA strand breaks and affects chromosome segregation.

Aneuploidy↗
PubMedDate not supplied

H-ras immunohistochemical expression and molecular analysis of urinary bladder lesions in grazing adult cattle exposed to bracken fern.

Chronic ingestion of bracken fern (Pteridium spp.) by cattle produces upper alimentary tract and urinary bladder tumours causing a syndrome called bovine enzootic haematuria (BEH). Previous studies demonstrated ptaquiloside-DNA adducts and mutations in the h-ras gene in ileal epithelial cells of bracken fern-fed calves. Systematic inspection of the bladder mucosa of grazing cattle (n=126) from bracken-fern areas was carried out in a slaughterhouse. Of the 126 slaughterhouse cattle, 46 showed macroscopical lesions of the bladder. These bladders, together with six others known to have BEH, were examined histopathologically and by H-ras immunohistochemistry. Thirteen affected bladders were also examined by H-ras molecular analysis to detect mutations. Macroscopical and histological study of urinary bladder lesions found at the slaughterhouse revealed chronic cystitis (34.1%) and tumours (2.4%). There was significantly increased immunohistochemical expression of H-ras (P<0.05) in chronic cystitis (H-ras=53.24%) and bladder tumours (H-ras=63.60%) as compared with normal urinary bladders (H-ras=4.32%). A silent mutation (D38D) was detected in one animal with a mixed bladder tumour. The prevalence of urinary bladder lesions (chronic cystitis and tumours) obtained at the slaughterhouse was higher than expected. This study demonstrates that close inspection of urinary bladders of adult grazing cows is necessary to prevent possible human exposure to bracken-fern carcinogens. The absence of mutations in the codons of h-ras studied did not exclude the presence of polymorphisms in other regions of the gene (promoter or regulation sequences) or in other genes (belonging or not to the ras family) that significantly affect the H-ras protein.

Animals↗
PubMed2006

Urinary bladder lesions in bovine enzootic haematuria.

In cattle, bracken fern chronic toxicity is characterized by the presence of multiple tumours in the bladder (bovine enzootic haematuria). From October 1999 to March 2003, 433 urinary bladders with macroscopical lesions were collected in the slaughterhouse of São Miguel Island (Azores, Portugal), an endemic area where Pteridium aquilinum infestation in pastures is high. Bladder lesions were divided into three main categories (inflammatory lesions, non-neoplastic epithelial abnormalities and tumours) and described in detail. In some cases, neoplastic growth was confined to a single site, but in most cases multiple tumours developed within the same bladder. Epithelial tumours alone were present in 51.2% of the affected bladders, mesenchymal tumours alone in 17.4%, and both epithelial and mesenchymal tumours in the remaining 31.4%. The large number of tumours examined (870) revealed new categories not yet included in other veterinary classification systems, namely, inverted papilloma, papillary neoplasm of apparent low malignant potential, and haemangioendothelioma.

Animals↗
PubMed2007

Competing conservation goals, biodiversity or ecosystem services: element losses and species recruitment in a managed moorland-bracken model system.

Conservation management in Europe is often geared towards restoring semi-natural ecosystems, where the objective is to reverse succession and re-establish early-successional communities, to comply with national and international conservation targets. At the same time, it is increasingly recognised that ecosystems provide services that contribute to other, possibly conflicting policy requirements. Few attempts have been made to define these conflicts. Here, we assess some potential conflicts using a Calluna vulgaris-dominated moorland invaded by bracken (Pteridium aquilinum) as a model system, where the current policy is to reverse this process and restore moorland. We examined impacts of bracken control treatments on services (stocks and losses of C and mineral nutrients), litter turnover and biodiversity within a designed experiment over 7 years. Bracken litter was >2000 g m(-2) in untreated plots, and treatments reduced this quantity, and its element content, to varying degrees. Cutting twice per year was the most successful treatment in reducing bracken litter and its element content, increasing litter turnover, and increasing both mass and diversity of non-bracken vegetation. Diversity was greatest where bracken litter had been reduced, but species composition was also influenced by light sheep grazing. There was a significant loss of some chemical elements from bracken that could not be accounted for in other pools, and hence potentially lost from the system. In absolute terms large amounts of C and N were lost, but when expressed as a percentage of the total amount in the system, Mg was potentially more important with losses of almost a third of the Mg in the surface soil-vegetation system. There is, therefore, a potential dilemma between controlling a mid-successional invasive species for conservation policy objectives, especially when that species has evolved to sequester nutrients, and the negative effect of increasing environmental costs in terms of carbon accounting required, the potential input of nutrients to aquatic systems, and long-term nutrient loss. There is, therefore, a need to balance conservation goals against potential damage to biogeochemical structure and function.

Biodiversity↗
PubMed2002

Quantifying 137Cs aggregated transfer coefficients in a semi-natural woodland ecosystem adjacent to a nuclear reprocessing facility.

Radiocaesium (137Cs) activity concentrations and aggregated transfer factors (Tag values) were calculated for vascular plants, fungal fruiting bodies and invertebrates in a semi-natural Picea sitchensis woodland (Lady Wood) adjacent to the British Nuclear Fuels plc. reprocessing facility at Sellafield, Cumbria, UK. The Tag values for vascular plants ranged from 7.1 x 10(-4) - 1.9 x 10(-2) m2 kg(-1), the maximum value being for Pteridium aquilinum. Fungal fruiting bodies had higher Tag values (1.9 x 10(-3) - 1.8 x 10(-1) m2 kg(-1)) than vascular plants, with a maximum value for Mycena galericulata. None of the activity concentrations for edible foodstuffs collected within this study (fungi and berries) exceeded the EC recommended limits of 137Cs in foodstuffs grown within the UK. The invertebrate community sampled during the study had Tag values ranging from 3.4 x 10(-4) to 1.3 x 10(-2) m2 kg(-1). There were no systematic differences in 137Cs activity concentration between invertebrate guilds, or between seasonal cohorts within guilds. The invertebrates in Lady Wood were exposed to a dose from 137Cs (internal gamma + beta and external gamma) ranging between 4.37 x 10(-4) and 6.40 x 10(-4) mGy day(-1). Including dose from radionuclides other than 137Cs and accounting for uncertainties due to the relative biological effectiveness of differing radionuclides could increase total dose by approximately an order of magnitude. These dose rates are at least three orders of magnitude lower than the 1 mGy d(-1) level at which harm may be caused to terrestrial biota, hence the risk to the invertebrate community from the effects of ionising radiation in Lady Wood is low.

Cesium Radioisotopes↗
PubMed2003

Quercetin elevates p27(Kip1) and arrests both primary and HPV16 E6/E7 transformed human keratinocytes in G1.

Our previous work with primary bovine fibroblasts demonstrated that quercetin, a potent mutagen found in high levels in bracken fern (Pteridium aquilinum), arrested cells in G1 and G2/M, in correlation with p53 activation. The expression of bovine papillomavirus type 4 (BPV-4) E7 overcame this arrest and lead to the development of tumorigenic cells lines (Beniston et al., 2001). Given the possible link between papillomavirus infection, bracken fern in the diet and cancer of the upper gastrointestinal (GI) tract in humans, we investigated whether a similar situation would occur in human cells transformed by human papillomavirus type 16 (HPV-16) oncoproteins. Quercetin arrested primary human foreskin keratinocytes in G1. Arrest was linked to an elevation of the cyclin-dependent kinase inhibitor (cdki) p27(Kip1). Expression of the HPV16 E6 and E7 oncoproteins in transformed cells failed to abrogate cell cycle arrest. G1 arrest in the transformed cells was also linked to an increase of p27(Kip1) with a concomitant reduction of cyclin E-associated kinase activity. This elevation of p27(Kip1) was due not only to increased protein half-life, but also to increased mRNA transcription.

Cell Cycle Proteins↗
PubMed2026

Co-option of stomata in the convergent evolution of fern nectaries.

Understanding the origin of new structures is a central goal of evolutionary biology. In many instances, novel phenotypes arise through heterotopy: the expression of a structure in a new location. Using bracken fern (Pteridium aquilinum) as a model, we combine genomics, transcriptomics and metabolomics to begin to explore the origin and developmental routes in the convergent evolution of ant-enticing nectaries. We observe that P. aquilinum does not exclusively express flowering plant 'nectary genes' during nectary development. Rather, this fern builds nectaries through co-option of stomata. Specifically, P. aquilinum heterotopically expresses canonical angiosperm stomatal regulatory genes, leading to stomatal development in novel positions along the petiole. These non-laminar stomata were co-opted for nectar secretion through the expression of putative sugar transport genes, forming secretory nectarostomata. This work provides two advances in our understanding of nectary evolution and the origin of complex structures. First, heterotopic expression of stomata, and later exaptation, represents one realized developmental mechanism for the evolution of nectar glands. Second, while there are many routes to nectary evolution, nectarostomata development is a repeatable path that has evolved in ferns and flowering plants, representing an impressive case of convergent evolution through the same developmental mechanism, despite over 400 million years of divergent history.

Plant Stomata↗
PubMed2005

Genotoxic activity and inhibition of soil respiration by ptaquiloside, a bracken fern carcinogen.

Ptaquiloside (PTA) is a natural toxin produced by bracken (Pteridium aquilinum [L.] Kuhn). Assessment of PTA toxicity is needed because PTA deposited from bracken to soil may leach to surface and groundwater. Inhibition of soil respiration and genotoxic activity of PTA was determined by a soil microbial carbon transformation test and an umu test, respectively. In the carbon transformation test, sandy loam soil was incubated at five different initial concentrations of PTA for a period of 28 d, after which glucose was added and respiration measured for 12 consecutive hours. The tests were performed at 20 degrees C and soil moisture content of approximately 15%. For soil material sampled in the autumn, initial PTA concentrations ranging from 0.008 to 40.6 microg PTA/g dry soil were tested. From fitting of data by a sigmoidal function, a 10% effect dose (ED10) was estimated to 13 microg PTA/ g dry soil, with an upper 95% confidence limit of 43 microg PTA/g dry soil and a 95% lower confidence limit of -infinity microg PTA/g dry soil. For soil material sampled in late winter, initial PTA concentrations ranging from 1.56 to 212 microg PTA/g dry soil were tested, resulting in an ED10 value of 55 microg PTA/g dry soil, with an upper 95% confidence limit of 70 microg PTA/g dry soil and a 95% lower confidence limit of 40 microg PTA/g dry soil. The genotoxic activity of PTA was determined using the umu test without and with metabolic activation (addition of S9 rat liver homogenate). In tests with addition of S9, the induction ratio exceeded the critical ratio of 1.5 at a PTA concentration of 46 +/- 16 microg/ml and, in tests without S9, the critical ratio was exceeded at a PTA concentration of 279 +/- 22 microg/ml. The genotoxicity of PTA is comparable to that of quercetin, another bracken constituent. The toxicity of PTA toward microorganisms prolongs the persistence of PTA in terrestrial environments, increasing the risk of PTA leaching to drainage and groundwater.

Carbon↗
PubMed1996

Mechanism of bracken fern carcinogenesis: evidence for H-ras activation via initial adenine alkylation by ptaquiloside.

Bracken fern (Pteridium spp.) causes cancer of the oesophagus and the urinary bladder in cattle and sheep. Ptaquiloside (PT) is believed to be the carcinogenic principle which alkylates DNA when activated to its unstable dienone form (APT) under alkaline conditions. In this report we present evidence for the presence of PT-DNA adducts in the ileum of bracken fem-fed calves using the 32P-postlabelling assay. H-ras mutations were also observed in the ileum using single strand conformation polymorphism (SSCP) technique. Mutations corresponding to adenine to pyrimidine transversions in the codon 61 of H-ras were identified by the cycle sequencing method. In vitro DNA alkylation studies showed that APT alkylated H-ras primarily at the adenines. In addition, the rate of depurination of alkylated adenine was sequence dependent. Investigation of DNA template activity using a plasmid DNA showed that DNA synthesis by T7 DNA polymerase was terminated by the presence of all alkylated bases but certain apurinic sites allowed the DNA synthesis to continue. These results suggest that initial alkylation of adenine by PT in codon 61 followed by depurination and error in DNA synthesis lead to activation of H-ras proto-oncogene.

Adenine↗
PubMed1998

H-ras activation is an early event in the ptaquiloside-induced carcinogenesis: comparison of acute and chronic toxicity in rats.

Bracken fern (Pteridium spp.) produces cancer of the urinary bladder and oesophagus in grazing animals and is a suspected human carcinogen. The carcinogenic principle ptaquiloside (PT), when activated to a dienone (APT), forms DNA adducts which eventually leads to tumor. Two groups of female Sprague-Dawley rats were given a chronic dose of 3 mg APT weekly for 10 weeks either by intravenous (i.v.) tail vein or by intragastric (i.g.) route. A third group was given a weekly dose of 6 mg of APT for 3 weeks by the i.g. route corresponding to acute dosing. Both chronic i.v. and i.g. dosed animals showed ischemic tubular necrosis in the kidney but only i.v. dosed animals developed adenocarcinomas of the mammary glands. Acutely dosed i.g. animals produced apoptotic bodies in the liver, necrosis of blood cell precursors in the bone marrow and ischemic tubular necrosis in the kidney but they did not develop tumors. No mutations were found in the H-ras and p53 genes in the mammary glands of either the i.g. rats or the tumor-bearing i.v. rats. However, the mammary glands of a fourth group of rats, which received APT by i.v. and killed before tumor development, carried Pu to Pu and Pu to Py double mutations in codons 58 and 59 of H-ras. This study indicates that the route of administration plays a role in the nature of the disease expression from ptaquiloside exposure. In addition to confirming the role of APT in the PT-induced carcinogenesis our finding suggests that activation of H-ras is an early event in the PT-carcinogenesis model.

Animals↗
PubMed1988

Chromosome aberrations in cattle raised on bracken fern pasture.

Thirteen cows maintained on natural bracken fern (Pteridium aquilinum) were analyzed cytogenetically. The frequency of structural chromosome aberrations detected in peripheral blood cells was significantly higher when compared to that detected in animals raised on pasture containing no bracken fern. We discuss the clastogenic action of fern and its synergistic action with infection by type 2 and 4 papilloma virus in the same animals.

Animal Feed↗
PubMed1987

Enzootic haematuria in Nepal.

Haematuria of cattle has been recognised in the Nepal hills for many years where it is of local economic importance. The aetiology has been thought to be babesiosis. The disease was investigated in East Nepal over a nine month period. Affected animals exhibited a chronic, intermittent haematuria and an associated polyuria and dysuria. The average age of onset of clinical signs was 7.3 years and duration 1.5 years. Investigation revealed that urine samples contained intact red blood cells, protein and white blood cells. Red blood cell counts, packed cell volume and haemoglobin concentration were not significantly reduced compared to unaffected cattle. Histopathological examination of abnormal bladder tissue revealed epithelial proliferation and mononuclear infiltration and large, blood filled cavities in the lamina propria. Pteridium aquilinum, bracken fern, is common in this area. Blood smears were negative for Babesia spp. These findings conform to the classical description of enzootic haematuria. This is the first recorded occurrence for Nepal.

Animals↗
PubMed2005

Lead tolerance and accumulation in the gametophytes of the fern Athyrium yokoscense.

The fern Athyrium yokoscense is known to be highly tolerant to lead toxicity, and is a lead hyperaccumulator that can accumulate over 1,000 microg g(-1) of lead in its dry matter. In this work, we examined whether the gametophytic generation of A. yokoscense also resists lead toxicity like the sporophytic generation. Spore germination in A. yokoscense was more tolerant to Pb2+, compared to that in other fern species, such as Pteridium aquilinum, Lygodium japonicum and Pteris vittata. In addition, the early gametophyte development of A. yokoscense was not much affected by 10 microM Pb2+, as evaluated from the prothallial growth and rhizoid development. We also showed that Athyrium gametophytes could accumulate more than 10,000 microg g(-1) of lead, and that the lead was localized in the cytosol and vacuole of rhizoidal cells, as determined by a transmission electron micrograph. These results indicate that Athyrium gametophytes have the ability to accumulate lead in the rhizoids. Furthermore, the gametophytes were found to include a large amount of proanthocyanidins (condensed tannins). Because proanthocyanidins have a latent ability to complex with lead ions, the possible roles of proanthocyanidins in the lead tolerance and accumulation of Athyrium gametophytes are discussed.

Biological Transport↗
PubMed2005

Concentrations of arsenic and heavy metals in vegetation at two abandoned mine tailings in South Korea.

Untreated abandoned mines may result in hazards to ecosystems due to dispersion of various toxic elements such as arsenic (As) and lead (Pb). Phytoremediation is an alternative of remediation for large scale mine dumps. Plant species were sampled from two abandoned gold (Au) mines in South Korea. Plant samples were digested following the guidelines of US EPA Method 3050 (US-EPA, 1996) and analyzed by inductively coupled plasma mass spectrometry (ICP-MS). Concentrations and bioaccumulation factors of plants are reported and out-performing species are summarized. Poplar trees (Populus davidiana) growing on the Myoungbong tailings were suggested to be a potential species for revegetation of large scale Au mine tailings. Arsenic accumulations of bracken ferns (Pteridium aquilinum) sampled from the Duckum tailings were far lower than those of the reported hyperaccumulators, but the possible chronic adverse effects on residents through daily diet are of concern.

Agriculture↗