Fusarium head blight of cereals in Denmark: species complex and related mycotoxins

Quantitative real-time polymerase chain reaction differentiating 10 Fusarium spp. and Microdochium nivale or M. majus was applied to a total of 396 grain samples of wheat, barley, triticale, oat, and rye sampled across Denmark from 2003 to 2007, along with selected samples of wheat and barley from 1957 to 2000, to determine incidence and abundance of individual Fusarium spp. The mycotoxins deoxynivalenol (DON), nivalenol, zearalenone, T-2, and HT-2 were quantified using liquid chromatography-double mass spectrometry. Major differences in the Fusarium species complex among the five cereals as well as great yearly variation were seen. Fusarium graminearum, F. culmorum, and F. avenaceum were dominant in wheat, with DON as the dominant mycotoxin. F. langsethiae, F. culmorum, and F. avenaceum were dominant in barley and oat, leading to relatively high levels of the mycotoxins T-2 and HT-2. F. graminearum, F. culmorum, and F. avenaceum dominated in triticale and rye. The nontoxigenic M. nivale/majus were present in significant amounts in all cereal species. Wheat and barley samples from 1957 to 1996 exhibited no or very low amounts of F. graminearum, indicating a recent increase of this pathogen. Biomass and mycotoxin data exhibited good correlations between Fusarium spp. and their corresponding mycotoxins under field conditions.     

A general model of prion strains and their pathogenicity

Prions are lethal mammalian pathogens composed of aggregated conformational isomers of a host-encoded glycoprotein and which appear to lack nucleic acids. Their unique biology, allied with the public-health risks posed by prion zoonoses such as bovine spongiform encephalopathy, has focused much attention on the molecular basis of prion propagation and the "species barrier" that controls cross-species transmission. Both are intimately linked to understanding how multiple prion "strains" are encoded by a protein-only agent. The underlying mechanisms are clearly of much wider importance, and analogous protein-based inheritance mechanisms are recognized in yeast and fungi. Recent advances suggest that prions themselves are not directly neurotoxic, but rather their propagation involves production of toxic species, which may be uncoupled from infectivity.     

Roles of reactive oxygen species in interactions between plants and pathogens

The production of reactive oxygen species (ROS) by the consumption of molecular oxygen during host–pathogen interactions is termed the oxidative burst. The most important ROS are singlet oxygen (¹O₂), the hydroxyperoxyl radical (HO₂·), the superoxide anion , hydrogen peroxide (H₂O₂), the hydroxyl radical (OH^-) and the closely related reactive nitrogen species, nitric oxide (NO). These ROS are highly reactive, and therefore toxic, and participate in several important processes related to defence and infection. Furthermore, ROS also play important roles in plant biology both as toxic by-products of aerobic metabolism and as key regulators of growth, development and defence pathways. In this review, we will assess the different roles of ROS in host–pathogen interactions with special emphasis on fungal and Oomycete pathogens.     

Inhibited development of trichostrongylid worms in grazing cattle

Inhibition of development of gastro-intestinal trichostrongylid worms was studied using successive groups of tracer calves and groups of continuously grazed calves over one year in the Tully area of North Queensland lowland wet tropics. The results, assessed by means of worms from these calves recovered at necropsy 3 weeks after their removal from pastures, showed inhibition in the development of Haemonchus placei and Cooperia punctata at the early fourth stage at the approach to and during the relatively dry period in the area. Inhibition was however minor and inhibited larvae formed but only a small percentage of worm burdens in both categories of calves, indicating that they were not in any way of major epidemiological importance. It was suggested that the minor nature of inhibition was due to the mild climatic conditions which could not produce appropriate conditioning treatment, or caused only mild selection pressure for inhibition in the area.     

草酸氧化酶基因在受白粉菌侵染大麦叶片中的诱导表达

大麦受白粉菌侵染后,抗病品种和感病品种中草酸氧化酶ＲＮＡ转录物诱导表达,并伴随着酶活性的增加和蛋白质的积累。抗病品种Ｓｕｌｔａｎ－５在接种后２４ｈ酶活性开始明显增加,而感病品种在接种后３６ｈ才开始增加。接种４８ｈ后所有品种酶活性增加达到了高峰,酶活性大约为对照的４倍。ＳＤＳ－ＰＡＧＥ酶活性染色及Ｗｅｓｔｅｒｎ杂交表明受白粉菌侵染后酶活性上升,蛋白质积累增多。草酸氧化酶有２条活性带,分子量分别为９５     

A cultivation independent,PCR-based protocol for the direct identification of plant pathogens in infected plant material

A protocol involving PCR, shot-gun cloning and sequencing was developed as a pre-diagnostic screening tool working directly on disease symptoms. The method was used to show the presence of biotrophic and non-biotrophic eukaryotic plant pathogens in leaves and fruits.     

Balancing selection at the prion protein gene consistent with prehistoric kurulike epidemics

Kuru is an acquired prion disease largely restricted to the Fore linguistic group of the Papua New Guinea Highlands, which was transmitted during endocannibalistic feasts. Heterozygosity for a common polymorphism in the human prion protein gene (PRNP) confers relative resistance to prion diseases. Elderly survivors of the kuru epidemic, who had multiple exposures at mortuary feasts, are, in marked contrast to younger unexposed Fore, predominantly PRNP 129 heterozygotes. Kuru imposed strong balancing selection on the Fore, essentially eliminating PRNP 129 homozygotes. Worldwide PRNP haplotype diversity and coding allele frequencies suggest that strong balancing selection at this locus occurred during the evolution of modern humans.     

Benign cranial mediastinal lesions in three cats

Cranial mediastinal lesions were detected in three cats, associated with respiratory impairment (case one), spontaneous pneumothorax (case two) and myasthenia gravis (case three), respectively. On gross and histological examination, the first case was considered either a lymphangioma or a branchial cystic mass of the thymic region of the mediastinum; a cystic lesion was suggested by sonographic detection of multiple anechoic cavitations within a circumscribed mass, while fine needle aspiration cytology excluded lymphosarcoma. The second case was diagnosed histologically as a cystic thymoma, but the third case was not examined microscopically. The masses were amenable to surgical excision in the first two cats, while this proved unnecessary in the third case because of resolution following treatment with dexamethasone. Corticosteroid responsiveness was unhelpful in distinguishing between these benign lesions and lymphosarcoma, as in two cases there was a partial or complete response to dosing with prednisolone or dexamethasone. These cases are presented to emphasise that conditions other than lymphosarcoma can produce cranial mediastinal lesions in cats, and that the prognosis for surgical treatment of lymphangiomas, multilocular thymic cysts and cystic thymomas can be excellent.