Pathological studies on Bovine papilloma virus-fern interaction in hamsters

Early pathological changes of Bovine papilloma virus (BPV-2)-fern (Pteridium aquilinum and Onychium contiguum fern) interaction in hamsters were studied. In bracken-exposed cattle, BPV induces malignancy in gastrointestinal and urinary bladder mucosa. Cutaneous warts were transmitted successfully in hamsters approximately after 3 months post inoculation while urinary bladder tumour of enzootic bovine haematuria cases were not transmitted. Histologically, tumour was diagnosed as fibroma. Onychium produced more pronounced effects than bracken fern which was characterized by significant reduction in body weight and testicular atrophy. BPV-fern interaction was not appreciable during early period of tumour induction and requires long-term studies for 12 to 18 months.     

Chemotaxonomy and phytochemical ecology of bracken

Variations in flavonoids extracted from fronds suggest that Pteridium aquilinum (L.) Kuhn is a monospecific genus. A wide range of secondary plant substances also occur in bracken including sesquiterpenoids, echydones, cyanogenic glycosides, tannins and phenolic acids.     

Bracken (Pteridium aquilinum)-induced DNA adducts in mouse tissues are different from the adduct induced by the activated form of the Bracken carcinogen ptaquiloside

Following treatment with bracken fern (Pteridium aquilinum) extract and bracken spores a number of DNA adducts were detected by (32)P-postlabeling. Three of these adducts have been described previously (Povey et al., Br. J. Cancer (1996) 74, 1342-1348) and in this study, using a slightly different protocol, four new adducts, with higher chromatographic mobility, were detected at levels ranging from 50 to 230% of those previously described. When DNA was treated in vitro with activated ptaquiloside (APT) and analysed by butanol extraction or nuclease P1 treatment, only one adduct was detected by (32)P-postlabeling. This adduct was not present in the DNA from mice treated with bracken fern or spores, suggesting either that bracken contains genotoxins other than ptaquiloside or that the metabolism of ptaquiloside produces genotoxins not reflected by activated ptaquiloside. However, as the ATP-derived adduct has been detected previously in ileal DNA of bracken-fed calves, species-specific differences in the metabolism of bracken genotoxins may exist, thereby leading to differences in their biological outcomes.     

Relationship between bracken and cancer

The production of tumours in animals by the carcinogenic action of bracken fern ( Pteridium aquilinum (L.) Kuhn) is described. One of the substances responsible has been identified as shikimic acid, and evidence is presented that it is a powerful mutagen. The isolation of another toxin which gives rise to malignancies is nearing completion. The possibility of an environmental human hazard is considered.     

Evidence for bracken fern as a food for aboriginal peoples of western washington

The aboriginal culture of the Northwest Coast is well known for its elaboration of cultural forms and reliance on the prolific fisheries of the region. Less well understood is the role indigenous plants played in the subsistence of the native peoples. A search of the historical and ethnographic literature indicates that bracken (Pteridium aquilinum Kuhn) was a major item in the dietary of the peoples of western Washington contributing both starch and fiber. This fern was collected and prepared by native women as a form of “flour” and baked or dried into cakes or bread. The record also indicates plant management by burning which has not previously been considered as a systematic method of production for the foraging societies of western Washington.     

Global chloroplast phylogeny and biogeography of bracken (Pteridium; Dennstaedtiaceae)

Bracken ferns (genus Pteridium) represent an ancient species complex with a natural worldwide distribution. Pteridium has historically been treated as comprising a single species, but recent treatments have recognized several related species. Phenotypic plasticity, geographically structured morphological variation, and geographically biased sampling have all contributed to taxonomic confusion in the genus. We sampled bracken specimens worldwide and used variable regions of the chloroplast genome to investigate phylogeography and reticulate evolution within the genus. Our results distinguish two major clades within Pteridium, a primarily northern hemisphere Laurasian/African clade, which includes all taxa currently assigned to P. aquilinum, and a primarily southern hemisphere Austral/South American clade, which includes P. esculentum and P. arachnoideum. All European accessions of P. aquilinum subsp. aquilinum appear in a monophyletic group and are nested within a clade containing the African P. aquilinum taxa (P. aquilinum subsp. capense and P. aquilinum subsp. centrali-africanum). Our results allow us to hypothesize the maternal progenitors of two allotetraploid bracken species, P. caudatum and P. semihastatum. We also discuss the biogeography of bracken in the context of the chloroplast phylogeny. Our study is one of the first to take a worldwide perspective in addressing variation in a broadly distributed species complex.     

The ecological status of bracken

Information about the morphology of bracken ( Pteridium aquilinum (L.) Kuhn var. aquilinum ) and the chief nutrients in the frond at different times of the year introduce an account of litter production and its accumulation in relation to the behaviour of frond, root and rhizome systems.
Where litter gain exceeds loss there is a correlation between the thickness and/or kind of litter and the level of the root and rhizome systems in relation to the mineral soil surface: with increase of litter the bracken becomes progressively more dependent for its physical and chemical soil environment on its own débris and less on the underlying mineral soil. An example of the limit of complete dependence has not been examined, but degeneration of the community can take place before that stage is reached.
From a review of the chief factors affecting bracken the conclusion is reached that the woodland habitat is both favourable and restrictive: in it bracken is in equilibrium with its environment, at a high social status. The relationship with other plant communities depends largely on the degree of human interference to which each is subject. Dominant bracken when left alone, and where gain of litter exceeds loss, becomes the victim of its own success; local degeneration opens the way for entry by other species.     

The taxonomy and phytogeography of bracken—a review

Some of the biological problems presented by bracken, Pteridium aquilinum (L.) Kuhn, are posed. Its taxonomic position within the Pteridophyta and the delimitation of entities within the genus are discussed on the basis of morphological and cytological evidence. The geographical ranges of the various brackens world-wide are described and mapped in outline, and emphasis placed on reviewing the natural ecological role of bracken in plant communities throughout the world. Further geographic areas where taxonomic investigation of Pteridium is most needed are indicated, and evidence of the reproductive, dispersal, establishment, colonizing ability and vegetative persistence of bracken is reviewed. Its palaeobiological spread, with associated vegetational history, and the effects on this of anthropogenic influences—better known than are comparable details for any other pteridophyte—are detailed, and the present magnitude of the resulting bracken problem in Britain (and especially in upland Britain) indicated.     

The taxonomic status and relationships of bracken ferns (Pteridium: Dennstaedtiaceae) from sub-Saharan Africa

Two morphotypes of bracken fern in the genus Pteridium Gled. ex Scop. occur in sub-Saharan Africa. The more common and widespread of these is assigned in contemporary systematic treatments to the European subspecies, P. aquilinum (L.) Kuhn ssp. aquilinum . We show that this African form is separable morphometrically and genomically from the European subspecies, and reinstate its earlier name P. aquilinum ssp. capense (Thunb.) C.Chr. The second African bracken, with a more localized tropical distribution mainly in the drainage basins of the Congo and Zambezi River systems, is confirmed as P. aquilinum ssp. centrali-africanum Hieron. ex R.E. Fr. We reject suggestions that this taxon be treated as a full species. Phenetic cluster analysis based on use of Arbitrarily Primed Polymerase Chain Reaction (A-P PCR) and Inter Simple Sequence Repeat (ISSR) fingerprinting of the nuclear genome provides evidence that the two African brackens are more closely related to each other than to other taxa, and sister to a grouping of the European sspp. aquilinum and pinetorum . The two African subspecies share solely with ssp. aquilinum a distinctive chloroplast haplotype carrying a 5-base direct repeat in the rps 4 –trn S region, confirming the close phyletic relationship between sspp. aquilinum , capense and centrali-africanum .  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 148 , 311–321.     

Effects of Sodium Selenite on the Growth of Bracken Fern Root Callus

Sodium selenite promotes the growth of bracken fern root callusgrowth over a narrow, low range of concentrations, while higherconcentrations are strongly inhibitory. Pteridium aquilinum, bracken fern, sodium selenite, selenium, callus     

Bracken carcinogens in the human diet.

The ubiquitous bracken fern (genus Pteridium) is the only higher plant known to cause cancer naturally in animals. In addition to the well-recognized syndromes of thiamine deficiency, acute haemorrhage associated with myeloid aplasia and blindness due to retinal degeneration, it causes neoplasia of the urinary bladder and in some circumstances, of the upper gut. In addition, it has been shown to cause neoplasia in a wide range of tissues in many experimental species. The major carcinogen (and the cause of the retinal degeneration and the myeloid aplasia) has been shown to be ptaquiloside (PT), a norsesquiterpene glucoside that can be present in bracken in extraordinary concentrations, up to 13 000 ppm. The highest concentrations were found in the crosiers and young unfolding fronds. The mutagenicity, clastogenicity, teratogenicity and carcinogenicity have been convincingly demonstrated. Under alkaline conditions the loss of the glucose gives rise to the formation of a dienone intermediate which possesses a highly reactive cyclopropyl ring capable of reacting with cellular macromolecules. PT has been shown to alkylate DNA at N3 of adenines in the minor groove, preferentially in 5'-TAG and 3'-A in 5'-AA-3' sequences. It also alkylates N7 guanines in the major groove occurring in 5'-TG sequences. It is believed that these alkylations lead to mismatch repair and subsequent mutations in particular proto-oncogenes. Recently a rat model of carcinogenesis has been established using intravenously (iv) administered PT. Some epidemiological evidence has indicated higher risk of cancer in people who consume bracken crosiers, people who consume milk of cows feeding on bracken and those who live in bracken-infested areas. PT has been found in the milk of cows fed on bracken fern experimentally and the milk of bracken-fed cows has been shown to cause cancer in rats. PT carcinogenesis presents an excellent model of environmental and experimental carcinogenesis.     

Bracken fern-induced malignant tumors in rats: absence of mutations in p53, H-ras and K-ras and no microsatellite instability

Bracken fern (genus Pteridium) has been shown to induce tumors in domestic and experimental animals. Epidemiological studies have also shown an association between human exposure to bracken toxins and increased risk for the development of upper gastrointestinal tract tumors. Our aim in this study was to investigate possible genomic alterations in bracken fern-induced tumors of experimental animals searching for molecular markers that might be used for human epidemiological studies. Using human colorectal carcinogenesis as a molecular model, we examined eight malignant bracken fern-induced tumors of rats for mutations in the genes associated with the "classic pathway" of colorectal cancer, i.e. p53 and ras, and also in the "mutator pathway" by evaluating microsatellite instability. Exons 5-9 of the p53 gene and exons 1 and 2 of the K-ras and H-ras genes were examined by DNA sequencing and no mutations were found in any of the eight tumors. Amplification of five previously validated microsatellite loci (one with mono-, three with di- and one with tetra-nucleotide repeat motifs) in the malignant tumors and in the surrounding normal tissue did not reveal any instability. The involvement of epigenetic alterations or of mutations in other tumor suppressor genes or oncogenes should be further investigated in the search for human epidemiological markers.     

Bracken thiaminase-mediated neurotoxic syndromes

The toxicity of bracken ( Pteridium aquilinum (L.) Kuhn) to animals is complicated because this plant elaborates more than one type of agent harmful to livestock. An enzyme, thiaminase I, which destroys thiamine, is responsible for the neurotoxic syndrome. Using a radiochemical assay, the distribution of thiaminase I activity in bracken throughout the growing season has been ascertained: levels are high in the rhizome and young buds, but fall sharply in the fronds as the aerial parts of the plant unfold.
The so-called thermostable 'antithiamine' factors present in bracken and other plant species are discussed.
The biochemical lesions of thiamine deficiency in animals are briefly outlined, and the clinical syndrome caused by the inclusion of bracken fronds or rhizomes in the diet for simple-stomached animals (rat, horse, pig) and a ruminant (sheep) are described.
All these neurotoxic syndromes respond to thiamine therapy in a dramatic way, if administered during the early stages of the disease.     

Fern constituents: Including occurrence,chemotaxonomy and physiological activity

A comprehensive survey of the 1966–1984 literature of the chemical constituents in ferns is presented. A table of fern constituents listed by species arranged according to Crabbe et al. (1975) is included. Advances in flavonoid, terpenoid and xanthone fern phytochemistry, including chemosystematics, are summarized. The taxonomic, chemical and pharmaceutical aspects of the phloroglucinols found in ferns are discussed. Developments in the investigation into the structure of the toxic principles of bracken (Pteridium aquilinum), whose consumption leads to cancer in domestic stock and to bracken cattle poisoning, are presented.     

Antigenic Mimicry Between Helicobacter pylori and Gastric Mucosa: Failure to Implicate Heat-Shock Protein Hsp60 Using Immunoelectron Microscopy

Background. Helicobacter pylori infection induces autoantibodies that cross-react with human gastric mucosa from infected individuals. Candidates for the antigens responsible for molecular mimicry causing autoreactivity include the heat-shock protein HspB (Hsp60, sometimes called Hsp54) or Lewis x and Lewis y carbohydrate antigens.
Objective. Our goal was to investigate the involvement of HspB (Hsp60) in autoreactivity between H. pylori and gastric biopsy tissue.
Materials and Methods. Immunoelectron microscopy was used to study cross-reactivity among biopsy tissues from a patient with gastritis, gastric ulcer, and duodenal ulcer and his own serum as well as reactivity with serum raised against HspB from H. pylori and monoclonal antibodies against Lewis antigens.
Results. The patient serum reacted with gastric mucosa, and the antibodies involved were predominantly IgG. Antibody raised to H. pylori HspB (Hsp60) reacted only with H. pylori cells but not with gastric mucosal tissue. In contrast, monoclonal antibodies specific for Lewis x and Lewis y antigens reacted with both H. pylori and human gastric epithelial tissue.
Conclusions. Hsp60 (Hsp54) is unlikely to be involved in autoreactivity seen in individuals infected with H. pylori. In contrast, we could not rule out the role of Lewis x and Lewis y carbohydrate antigens, expressed as a component of H. pylori lipopolysaccharides, in molecular mimicry and autoantibody production.     

Genetic and epigenetic alterations of tumor suppressor and tumor-related genes in gastric cancer

Both genetic and epigenetic alterations of tumor suppressor and tumor-related genes involved in the pathogenesis of gastric cancer are reviewed here, and molecular pathways of gastric carcinogenesis are proposed. Gastric carcinomas are believed to evolve from native gastric mucosa or intestinal metaplastic mucosa that undergoes genetic and epigenetic alterations involving either the suppressor pathway (defects in tumor suppressor genes) or mutator pathway (defects in DNA mismatch repair genes). Methylation of E-cadherin in native gastric mucosa results in undifferentiated carcinomas (suppressor pathway), while methylation of hMLHI results in differentiated foveolar-type carcinomas (mutator pathway). The majority of differentiated gastric carcinomas however, arise from intestinal metaplastic mucosa and exhibit structural alterations of tumor suppressor genes, especially p53. They appear to be related to chronic injury, perhaps due to Helicobacter pylori infection. Approximately 20% of differentiated carcinomas (ordinary-type) have evidence of mutator pathway tumorigenesis. Mutations of E-cadherin are mainly involved in the progression of differentiated carcinomas to undifferentiated tumors. The molecular pathways of gastric carcinogenesis depend on the histological background, and gastric carcinomas show distinct biological behaviors as a result of discernible cellular genetic and epigenetic alterations.     

Lewis antigens in Helicobacter pylori: biosynthesis and phase variation

The lipopolysaccharides (LPS) of most Helicobacter pylori strains contain complex carbohydrates known as Lewis antigens that are structurally related to the human blood group antigens. Investigations on the genetic determinants involved in the biosynthesis of Lewis antigens have led to the identification of the fucosyltransferases of H. pylori, which have substrate specificities distinct from the mammalian fucosyltransferases. Compared with its human host, H. pylori utilizes a different pathway to synthesize the difucosylated Lewis antigens, Lewis y. and Lewis b. Unique features in the H. pylori fucosyltransferase genes, including homopolymeric tracts mediating slipped-strand mispairing and the elements regulating translational frameshifting, enable H. pylori to produce variable LPS epitopes on its surface. These new findings have provided us with a basis to further examine the roles of molecular mimicry and phase variation of H. pylori Lewis antigen expression in both persistent infection and pathogenesis of this important human gastric pathogen.     

Studies on Phytoremediation of Copper Using Pteridium Aquilinum (Bracken Fern) In the Presence of Biostimulants and Bioassay Using Clarias Gariepinus Juveniles

A study was carried out to evaluate the uptake of copper from water containing 10 mg/L copper by Pteridium aquilinum (bracken fern) and Clarias gariepinus in the presence of five plant growth stimulants: Nitrogen: phosphorus: potassium (15-15-15: an inorganic fertilizer), pig, cattle, poultry, and a mixture of pig/cattle manures. A plant growth stimulant differentiated each treatment. A 96-hour bioassay using C. gariepinus was carried out at the end of the experiment to test the efficacy of the clean up by P. aquilinum. The control experiment contained no copper or plant growth stimulant. Fish survival, uptake of copper by P. aquilinum, C. gariepinus, concentration of copper in water, hematology and histopathology of the fish were assessed. Higher concentrations of copper were reported in P. aquilinum than in water or C. gariepinus. Low fish mortality was reported with the highest being 20% in the cattle manure–containing treatment.