Quantitative variation in effector activity of ToxA isoforms from Stagonospora nodorum and Pyrenophora tritici-repentis.

ToxA is a proteinaceous necrotrophic effector produced by Stagonospora nodorum and Pyrenophora tritici-repentis. In this study, all eight mature isoforms of the ToxA protein were purified and compared. Circular dichroism spectra indicated that all isoforms were structurally intact and had indistinguishable secondary structural features. ToxA isoforms were infiltrated into wheat lines that carry the sensitivity gene Tsn1. It was observed that different wheat lines carrying identical Tsn1 alleles varied in sensitivity to ToxA. All ToxA isoforms induced necrosis when introduced into any Tsn1 wheat line but we observed quantitative variation in effector activity, with the least-active version found in isolates of P. tritici-repentis. Pathogen sporulation increased with higher doses of ToxA. The isoforms that induced the most rapid necrosis also induced the most sporulation, indicating that pathogen fitness is affected by differences in ToxA activity. We show that differences in toxin activity encoded by a single gene can contribute to the quantitative inheritance of necrotrophic virulence. Our findings support the hypothesis that the variation at ToxA results from selection that favors increased toxin activity.

Metabolomics protocols for filamentous fungi.

Proteomics and transcriptomics are established functional genomics tools commonly used to study filamentous fungi. Metabolomics has recently emerged as another option to complement existing techniques and provide detailed information on metabolic regulation and secondary metabolism. Here, we describe broad generic protocols that can be used to undertake metabolomics studies in filamentous fungi.

Gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS): a new autosomal dominant syndrome.

OBJECTIVE: The purpose of this study was the clinical and pathological characterisation of a new autosomal dominant gastric polyposis syndrome, gastric adenocarcinoma and proximal polyposis of the stomach (GAPPS). METHODS: Case series were examined, documenting GAPPS in three families from Australia, the USA and Canada. The affected families were identified through referral to centralised clinical genetics centres. RESULTS: The report identifies the clinical and pathological features of this syndrome, including the predominant dysplastic fundic gland polyp histology, the exclusive involvement of the gastric body and fundus, the apparent inverse association with current Helicobacter pylori infection and the autosomal dominant mode of inheritance. CONCLUSIONS: GAPPS is a unique gastric polyposis syndrome with a significant risk of gastric adenocarcinoma. It is characterised by the autosomal dominant transmission of fundic gland polyposis, including areas of dysplasia or intestinal-type gastric adenocarcinoma, restricted to the proximal stomach, and with no evidence of colorectal or duodenal polyposis or other heritable gastrointestinal cancer syndromes.

Decoding the mannitol enigma in filamentous fungi.

Mannitol is a 6-carbon polyol that is among the most abundant biochemical compounds in the biosphere. Mannitol has been ascribed a multitude of roles in filamentous fungi including carbohydrate storage, reservoir of reducing power, stress tolerance and spore dislodgement and/or dispersal. The advancement of genetic manipulation techniques in filamentous fungi has rapidly accelerated our understanding of the roles and metabolism of mannitol. The targeted deletion of genes encoding proteins of mannitol metabolism in several fungi, including phytopathogens, has proven that the metabolism of mannitol does not exist as a cycle and that many of the postulated roles are unsupported. These recent studies have provided a much needed focus on this mysterious metabolite and make this a fitting time to review the roles and metabolism of mannitol in filamentous fungi.

Mannitol is required for asexual sporulation in the wheat pathogen Stagonospora nodorum (glume blotch).

The physiological role of the mannitol cycle in the wheat pathogen Stagonospora nodorum (glume blotch) has been investigated by reverse genetics and metabolite profiling. A putative mannitol 2-dehydrogenase gene (Mdh1) was cloned by degenerate PCR and disrupted. The resulting mutated mdh1 strains lacked all detectable NADPH-dependent mannitol dehydrogenase activity. The mdh1 strains were unaffected for mannitol production but, surprisingly, were still able to utilize mannitol as a sole carbon source, suggesting a hitherto unknown mechanism for mannitol catabolism. The mutant strains were not compromised in their ability to cause disease or sporulate. To further our understanding of mannitol metabolism, a previously developed mannitol-1-phosphate dehydrogenase (gene mpd1) disruption construct [Solomon, Tan and Oliver (2005) Mol. Plant-Microbe Interact. 18, 110-115] was introduced into the mutated mdh1 background, resulting in a strain lacking both enzyme activities. The mpd1mdh1 strains were unable to grow on mannitol and produced only trace levels of mannitol. The double-mutant strains were unable to sporulate in vitro when grown on minimal medium for extended periods. Deficiency in sporulation was correlated with the depletion of intracellular mannitol pools. Significantly sporulation could be restored with the addition of mannitol. Pathogenicity of the double mutant was not compromised, although, like the previously characterized mpd1 mutants, the strains were unable to sporulate in planta. These findings not only question the currently hypothesized pathways of mannitol metabolism, but also identify for the first time that mannitol is required for sporulation of a filamentous fungus.

Stagonospora nodorum: cause of stagonospora nodorum blotch of wheat.

UNLABELLED: SUMMARY Stagonospora nodorum is an important pathogen of wheat and related cereals, causing both a leaf and glume blotch. This review summarizes recent advances in our understanding of taxonomy, control and pathogenicity of this species. TAXONOMY: Stagonospora (syn. Septoria) nodorum (Berk.) Castell. and Germano [teleomorph: Phaeosphaeria (syn. Leptosphaeria) nodorum (Müll.) Hedjar.], kingdom Fungi, phylum Ascomycota, subphylum Euascomycota, class Dothideomycetes, order Pleosporales, family Phaeosphaeriaceae, genus Phaeosphaeria, species nodorum. HOST RANGE: Wheat, Triticum aestivum, T. durum, Triticale, are the main hosts but other cereals and wild grasses have been reported to harbour S. nodorum. Disease symptoms are lens-shaped necrotic lesions on leaves, girdling necrosis on stems (especially the nodes, hence 'nodorum') and lesions on glumes. Mature lesions produce pycnidia scattered throughout the lesions, especially as tissue senesces. USEFUL WEBSITES: http://ocid.nacse.org/research/deephyphae/htmls/asco_taxlist_spat.html (taxonomic information), http://ohioline.osu.edu/ac-fact/0002.html (disease information), http://wwwacnfp.murdoch.edu.au/ (ACNFP homepage), http://www.broad.mit.edu/annotation/fungi/stagonospora_nodorum/index.html (genome sequence homepage), http://cogeme.ex.ac.uk/efungi/ (genome sequence annotation and analysis).

The Mak2 MAP kinase signal transduction pathway is required for pathogenicity in Stagonospora nodorum.

A gene encoding a mitogen-activated protein kinase (MAPK) putatively orthologous to Pmk1 from Magnaporthe grisea was cloned and characterised from the wheat glume blotch pathogen Stagonospora nodorum. Protein sequence alignments showed the cloned gene, Mak2, is closely related to homologues from other dothideomycete fungi. Expression studies revealed Mak2 is up-regulated during in vitro growth upon nitrogen starvation but is not sensitive to carbon starvation or osmotic stress. Transcript analysis in planta showed Mak2 to be expressed throughout infection and up-regulated during the sporulation phase of the infection cycle. Fungal strains harbouring a disrupted Mak2 gene were created by homologous gene recombination. The mutant strains had a severely altered phenotype in vitro with reduced growth rate and failure to sporulate. Further phenotypic analysis revealed that the mutants had near-normal levels of secreted protease activity, were not hypersensitive to osmotic stress and appeared to have melanin synthesis intact. The mak2 strains were essentially non-pathogenic to wheat leaves. No penetration structures formed and although entry was observed through stomates, the infection rarely continued. The results within this study are discussed within the context of the differences in downstream regulation of the Mak2 MAPK pathway and the cAMP signal transduction pathway in S. nodorum; and differences are compared to mak2 mutant strains in other pathogenic fungi.

Argon plasma coagulation for treatment of watermelon stomach.

BACKGROUND AND STUDY AIMS: Watermelon stomach or gastric antral vascular ectasia (GAVE) is a rare but well-recognized cause of gastrointestinal blood loss, which typically affects elderly women. Historically patients were treated with antrectomy but this has been largely replaced by endoscopic therapy such as Nd:YAG laser. Argon plasma coagulation (APC) is a new noncontact electocoagulation technique which has several theoretical advantages over laser. The objective of this study was to assess the efficacy of APC in treating GAVE. PATIENTS AND METHODS: We retrospectively reviewed the case-records of five patients (four women, one man) with iron deficiency anaemia or gastrointestinal blood loss due to GAVE who were treated with APC and for whom a follow-up of more than 12 months was available. Four patients were transfusion-dependent. Their mean age was 71 years (range 58 - 83). The mode of presentation, number of treatment sessions, response to therapy and recurrence (if any) were recorded. RESULTS: A mean of 2.6 treatment sessions per patient were required. All patients had an endoscopically observed response to therapy and all patients had a sustained rise in hemoglobin level after treatment. Transfusion dependence ceased in all patients. After a mean follow-up of 20 months GAVE recurred in two patients (40 %). Both patients responded to further APC treatment. No major complications were recorded. CONCLUSION: APC is a safe and effective short-term treatment for GAVE. The natural history of the condition is uncertain, and at medium-term follow-up GAVE is found to recur in a substantial number of patients treated with APC. Re-treatment with APC is an option in these patients.

Management of biliary tract complications following liver transplantation.

BACKGROUND: A review of biliary tract complications was performed in 32 patients who underwent liver transplantation by the Western Australian Liver Transplantation Service during a 2-year period. METHODS: A review was made of patient data collected prospectively, and confirmed by retrospective casenote review. RESULTS: A total of 30 patients (31 grafts) survived more than 2 days after transplantation, and of these 28 had an end-to-end biliary anastomosis. Analysis of these 28 patients found that eight of 17 patients with T-tubes had complications: three leaks at T-tube removal; two strictures and leaks; and three strictures. Six of 11 patients without a T-tube had complications: one leak; three strictures and leaks; and two strictures. Predisposing factors were present in eight of the 14 patients with biliary tract complications: hepatic artery stenosis in three; and one each with hepatic artery thrombosis; biliary calculi; donor-recipient bile duct mismatch; severe cellular rejection: and prolonged postoperative hypotension. Acute rejection, steroid-resistant rejection and cytomegalovirus infection were all significantly more common in those patients with biliary tract complications compared with those without. There was no difference in cold ischaemic time or donor age. Twelve of the 14 patients with biliary complications required endoscopic stenting with or without balloon dilation, and eight patients required radiological percutaneous drainage of bile collections. Only one patient required biliary reconstruction and two patients required re-transplantation. One patient died of uncontrolled infection. Of three patients who underwent choledochojejunostomy, biliary leak developed in two patients, both of whom required operative biliary and hepatic repair. One of the three patients died from disseminated Aspergillus infection. The median total hospital stay of patients with biliary complications was 61 days (range: 30-180 days) compared with 33.5 days (range: 22-70 days) for patients without. Of patients with end-to-end biliary anastomosis, 50% had biliary tract complications and more than half of these had predisposing factors. The majority of biliary complications were managed without the need for surgery. CONCLUSION: A total of 50% of patients with end-to-end biliary anastomosis had biliary tract complications. Biliary strictures presented later than leaks, and the majority of these complications were managed without the need for surgery.

Banff schema for grading liver allograft rejection: utility in clinical practice.

An accurate and functional system for grading acute liver allograft rejection is important for patient management, research, and communication. The Banff schema is a consensus document designed to provide an internationally accepted standard for this purpose. The aim of this study is to determine if application of the Banff schema would significantly alter the grading of acute liver allograft rejection compared with the Birmingham system. One hundred twenty-four post-liver transplantation biopsies performed by the Western Australian Liver Transplantation Service between 1992 and 1997 were retrospectively analyzed by a pathologist and a hepatologist. Each was supplied with a brief clinical history before applying the Banff and Birmingham criteria. Results were compared with each other and to the diagnosis made at the time of the biopsy, which was based on the European grading system. Rejection was diagnosed by the reviewers in 61 of 124 biopsy specimens according to the criteria of Snover. The Banff schema and Birmingham system agreed on the grade of rejection in 22 of the 61 biopsy specimens. The Banff schema elevated the grade of rejection in 39 specimens by an increment of one. In no instance did the Banff schema reduce the grade. Comparison between the Banff schema and diagnosis made at the time of biopsy showed agreement in 39 specimens, whereas the Banff schema elevated the grade in 15 specimens and reduced the grade in 23 specimens. In comparison to the Birmingham system, the Banff schema elevated the grade of liver allograft rejection in the majority of biopsy specimens, and this has the potential to alter clinical management with the adoption of the Banff schema or if the systems are used interchangeably.

Liver transplantation in Western Australia: improved services to an isolated population.

OBJECTIVE: To assess performance of the Western Australian Liver Transplantation Service in the light of debate about whether small transplant centres can produce optimal outcomes. DESIGN: Review of patient data collected prospectively and confirmed by retrospective casenote review. SUBJECTS: All patients referred to the Western Australian Liver Transplantation Assessment Panel. Those who underwent transplantation at the Western Australian Liver Transplantation Service (to June 1996) were compared with those referred to other transplant centres before the elective service was established in July 1994. OUTCOME MEASURES: Numbers of referrals and transplants; characteristics of the transplantation procedure; and patient outcomes. RESULTS: Annual referrals for liver transplant in Western Australia (WA) increased from 12 (1985-1993) to 41 (July 1994-June 1996), with five deaths on the "activated" list before July 1994, but none after. To June 1996, 30 patients had received 31 transplants by the Western Australian Liver Transplantation Service (two emergency transplants in 1992 and 1993, respectively, and 28 elective transplants and one retransplant after June 1994), with median operation time of 5.5 hours (range, 3-10.5), median red cell transfusion of 4 units (range, 0-55) and median hospital stay of 24 days (range, 12-128). There was no severe primary graft dysfunction. Major complications included hepatic artery thrombosis or stenosis (5 patients, one requiring retransplant), biliary stricture not associated with hepatic artery pathology, bile leak and perihepatic abscess (4 each), and cytomegalovirus infection (3). Patient survival was 83% and graft survival 81% at a mean follow-up of 13 months, compared with 86% and 83%, respectively, at one year for WA patients who received transplants elsewhere before July 1994. CONCLUSIONS: Performance of the Western Australian Liver Transplantation Service compares favourably with national and international standards, and WA patients receiving liver transplants have increased dramatically since the service was established. This supports the viability of committed liver transplantation centres with only 10-15 patients a year and argues the need for nationally decentralised services.

Intra-abdominal fluid collections after liver transplantation.

Fluid collections are commonly seen following orthotopic liver transplantation. The majority of these collections are not infected and resolve spontaneously. However, infected collections are associated with significant morbidity and mortality and usually require drainage. Clinical signs of infection are frequently masked following transplantation due to immunosuppression. Intrahepatic collections usually represent abscesses or bilomas and invariably require intervention. Altered anatomical relationships result in signs that frequently help to differentiate these from loculated fluid within hepatic fissures. Other imaging features indicating infection include the presence of gas where none was seen previously, the development of a discrete wall and changes in the surrounding liver.

Anomalously high concentrations of brain extracellular uric acid detected with chronically implanted probes: implications for in vivo sampling techniques.

The height of peak 2, h2, recorded using linear sweep voltammetry with 350-micron-diameter carbon paste electrodes in rat striatum was measured from the day of implantation (day 0) to 4 months after surgery. The value of h2 was at a minimum on day 0 (0.6 +/- 0.2 nA; n = 20), rose sharply to a maximum on day 2 (6.3 +/- 0.9 nA; n = 12), and decreased to a stable level by day 7 (3.3 +/- 0.7 nA; n = 16), which lasted for 4 months (3.2 +/- 0.6 nA; n = 9). These changes were shown by microinfusion of uricase to be due to variations in the concentrations of extracellular uric acid, although h2 appears to have a small baseline contribution of approximately 0.3 nA from 5-hydroxyindoleacetic acid. The stable value of h2 recorded under chronic conditions was estimated to correspond to a minimal uric acid concentration of 50 mumol/L, which represents a 10-fold increase in the extracellular level of this purine metabolite compared with the initial (acute) value. Very similar results were obtained using a microdialysis technique that detected uric acid directly. These estimates of striatal uric acid concentration are in marked contrast to those obtained using 40-micron diameter carbon fiber electrodes, which showed a decrease from the acute preparation to less than 1 mumol/L under chronic conditions. Large values of h2 were also recorded with chronically implanted paste electrodes in the hippocampus and frontal cortex.(ABSTRACT TRUNCATED AT 250 WORDS)