No description available.

No description available.

Percentage in-vitro conidial germination of inaequalis was inversely related to the log conidial concentration. The filtrate from a conidial suspension of inaequalis was shown to inhibit conidial germination. Ferrous iron was shown to reduce conidial germination. Anthranillic acid reversed the inhibitory action of ferrous iron and enhanced germination of conidial suspensions not containing additional iron. Continuous rolling or ''pre-treatment" of conidial suspensions of V. inaequalis used for inoculum increased levels of infection. It was suggested that this improvement may be a result of higher numbers of germinated conidia present on the leaf surface. Pre-treatment of inocula was adopted as a standard inoculation technique. Symptom expression was studied under two categories :- i) Effect on seedling growth (stunting/promotion) ii) Foliar symptoms (total disease expression score - TDE) Stunting and TDE values were correlated to lesion number and positively correlated to inoculum concentration. High inoculum concentrations caused stunting and low ones resulted in growth promotion. Similar responses were found with all apple varieties tested. Experimental evidence was presented to support the hypotheses :- 1) Conidia only produce stunting. 2) The filtrate from a pre-treated conidial suspension of V. inaequalis contained a factor which induced growth promotion of apple seedlings. Washing pre-treated conidia with GDW immediately before inoculation enhanced stunting of apple seedlings. Foliar sprays of the pre-treatment filtrate promoted seedling growth, concentrating it further enhanced promotion. The factor responsible was resistant to boiling, suggesting it to be non-protein but after standing for 24 h lost its ability to promote growth. Bioassays of the filtrate for IAA and cytokinins were negative. A dock leaf disk test was positive for gibberellins. Analysis of the filtrate using mass spectrometry indicated the presence of high molecular weight ions but it was not possible to identify any particular fragment or conclude whether these could be responsible for growth enhancement. It is suggested that the filtrate acts by increasing cell elongation rather than cellular proliferation. Use of the fungicides dodine and captan produced a host response to infections by inaequalis ranging from stunting to growth promotion. The potential of pre-treatment and symptom assessment for use as a fungicide screening technique was demonstrated. It was suggested that summation of the ranked scores for TDE and phytotoxic stunting provided an accurate assessment of a chemical's suitability for further testing.

In six, healthy, adult horses, the origin of the left internal carotid artery was isolated via a modified hyovertebrotomy approach. Normograde blood flow was occluded by placement of a tourniquet on the artery near its origin. Lumenal access was gained through placement of a distally directed introducer sheath and retrograde blood flow from the cerebral arterial circle was confirmed. An 8.5 mm diameter detachable latex balloon loaded onto a carrier catheter and placed within a guiding catheter was introduced into the internal carotid artery through the introducer sheath and advanced to the target occlusion site (the proximal curve of the sigmoid flexure of the internal carotid artery). The balloon was inflated with 0.5 ml of a radiopaque solution. Correct placement and inflation of the balloon were confirmed by intraoperative radiography. The balloon was then released and the guiding and carrier catheters withdrawn. Immediate embolization of the distal internal carotid artery was determined by lack of retrograde blood flow through the introducer sheath. The introducer sheath was withdrawn from the vessel and the proximal tourniquet was replaced with two ligatures. Horses were euthanized on day 30 and detailed gross and histopathologic examinations were performed. The balloons were easily placed into the target site and produced immediate occlusion of retrograde flow from the cerebral arterial circle. All balloons remained inflated in their original position throughout the study period. Mature thrombus formation and absence of clinically significant inflammation were consistent findings in all occluded internal carotid arteries at gross necropsy and histologic examination. / Master of Science

No description available.

Cell surface mannan oligosaccharides have been implicated in die pathogenesis of C. albicans through roles such as adhesion to host cells and modulation of the immune system (Calderone, 1993, Chaffin, 1998). Understanding the molecular biology of glycosylation is therefore critical to elucidating host-fungus interactions. The CaMNTI gene, responsible for adding the second mannose on 0-linked mannan has previously been shown to be important for adhesion and virulence in C. albicans (Buurman et ai, 1998). In this project, the CaMNT1 gene family was studied as a means to understand more about the roles of oligosaccharide synthesis in Candida-host interactions. The Camntlp enzyme was expressed heterologously in P. pastoris and its cofactor and acceptor specificities were determined. The key residues for the retaining mechanism of CaMntlp catalysis and for cofactor binding were determined by site-directed mutagenesis as Asp350, Glu-318, His-377 and His377. This knowledge may aid in the rational design of antifungals against the MNT1 family of Candida mannosyltransferases. Two further members of the gene fainily; CaMNT3 and CaMNT5 were disrupted using the ura-blaster technique. Deletion of CaMNT3 and to a lesser extent CaMNT5 led to strains unable to form hyphae on solid Spider medium. This phenotype is distinct from that reported for CaMNT1 and suggests a role for these genes upstream or downstream of the Cphlp MAP Itinase cascade that regulates yeast-hypha morphogenesis. The Camnt3 and CamntS nuU mutants were attenuated in virulence in a systemic mouse model of candidosis. The heterozygous mutants were more attenuated in virulence than the nuU mutants indicating that a compensation mechanism may upregulate expression of other MNT genes when both copies of CaMNTS or CaMNT3 are disrupted. This study has shown that glycan synthesis affects morphogenesis in C. albicans and indicates many cell wall proteins require to be glycosylated to perform their function.

The dependency of maize (Zea mays L.) and bambara groundnut (Vigna subterranea) grown in acid tropical soils, on the mycorrhizal condition for improved growth and nutrient uptake, and the effects of various management practices on root infection by vesicular-arbuscular mycorrhizal fungi in maize plants were investigated. The effect of soil pH on mycorrhiza formation in perennial ryegrass and maize was also investigated using a temperate soil in which pH levels had been maintained in the field over a long period. Infection of roots of maize and bambara groundnut plants by vesicular-arbuscular mycorrhizal (VAM) fungi indigenous to the tropical soils, resulted in increased plant dry weights as well as increased uptake of nutrients. The population of VAM fungi in the soils consisted of several species in the genera Glomus and Gigaspora. The foliar application of two systemic fungicides (Triforine and calixin) to maize plants resulted in reduced infection with the application of calixin compared to control plants. Root infection by VAM fungi was not different from that of control plants when triforine was applied. Two phosphorus sources (triple superphosphate and Ghafsa phosphate rock) applied to soils at rates equivalent to 22kg ha-1 and 44kg ha-1 had varied effects on VAM fungal infection in maize roots. Phosphate rock applied at both rates and triple superphosphate applied at the lower rate (22kg ha -1) increased root infection compared to that for triple superphosphate at the higher rate. It was suggested that the increased availability of the relatively soluble triple superphosphate was responsible for the reduced infection. The effect of lime application on VAM fungal infection was dependent on the type of phosphorus fertilizer applied to the soils. Increased root infection occurred when lime was applied in addition to triple superphosphate in comparison to phosphate rock. Without lime application, increased infection occurred when phosphate rock was applied compared to triple superphosphate. In the temperate soil with pH maintained over a long period, no VAM fungal infection was found at pH values below 5.0 when ryegrass was the host, although infection occurred when maize was the host plant. There was an effect of host plant on the infectivity of the fungi present in the soils with low pH but infection was low in comparison with that in soil at pH values above 5.0 indicating that management practices which result in soil pH changes may influence mycorrhizal associations in different plant species to different extents. The application of phosphate rock was beneficial to mycorrhiza formation and it was suggested that fertilizer practices which involve the use of phosphate rock could confer additional benefits that can be derived from increased mycorrhiza formation.

Pulses are a major source of human protein intake nowadays and will continue to be so because of their high protein content. Pulse crops are members of the family Leguminosae. The five major pulse crops grown in Canada are chick peas, green peas, lentils, pinto bean and kidney beans. Over the past 20 years, Canada has emerged as the world’s largest exporter of lentils and one of world’s top five exporters of beans. These contribute more than $2 billion income to the Canadian economy. The major causes of fungal infection in these pulses are Aspergillus flavus and Penicillium commune. Early stages of fungal infections in pulses are not detectable with human eyes. Near infrared (NIR) hyperspectral imaging system is an advanced technique widely used for detection of insect infestation and fungal infection in cereal grains and oil seeds. A typical NIR instrument captures images across the electromagnetic spectrum at evenly spaced wavelengths from 700 to 2500 nm (a system at the University of Manitoba captures images in the 960 nm to 1700 nm range). From the captured images, the spatial relationships for different spectra in the neighborhood can be found allowing more elaborate spectral-spatial methods for a more accurate classification of the images. The primary objective of this study was to assess the feasibility of the NIR hyperspectral system to identify fungal infections in pulses. Hyperspectral images of healthy and fungal infected chick peas, green peas, lentils, pinto bean and kidney beans were acquired and features (statistical and histogram) were used to develop classification models to identify fungal infection caused by Aspergillus flavus and Penicillium commune. Images of healthy and fungal infected kernels were acquired at 2 week intervals (0, 2, 4, 6, 8 and 10 weeks from artificial inoculation). Six-way (healthy vs the five different stages of infection) and two-way (healthy vs every stage of infection) models were developed and classifications were done using linear discriminant analysis (LDA) and quadratic discriminant analysis (QDA) classifiers. The LDA classifier identified with 90-94% accuracy while using the six-way model, and with 98-100% accuracy when using the two-way models for all five types of pulses and for both types of fungal infections. The QDA classifier also showed promising results as it identified 85-90% while using the six-way model and 96-100% when using the two-way models. Hence, hyperspectral imaging is a promising and non-destructive method for the rapid detection of fungal infections in pulses, which cannot be detected using human eyes. / October 2015

The fungus Ascosphaera apis causes the disease chalk brood in larvae of the honey bee, Apis mellifera. Ascospores were recognised as the agents of disease, but the site of their germination to initiate infection had not been established. In this study larval surface cuticle was initially investigated as a possible site, but spores did not even activate here. Therefore, potential inhibitors of spore germination were studied, including water and chloroform washings of larval cuticle; 4 larval food constituents - pollen, honey, brood food, royal jelly; and a variety of medium-chain fatty acids a t concentrations of 1, 0.1 and 0. 01%. Royal jelly exhibited a severe inhibitory effect on all germination stages. Larvae were successfully infected by feeding them food Containing A. apis spores, both in vitro and in vivo. A histological study of infected larvae demonstrated germination of spores in the mid-gut lumen, followed by penetration of the peritrophic membrane and gut epithelium by developing hyphae; and subsequent invasion of larval tissues by mycelia. Various aspects of spore physiology were investigated. Spore activation and enlargement were shown to be independent of temperature within the ranges of 10 to 40°C and 25 to 40°C respectively, while germ-tube production was closely temperature related, only occurring between 25 and 37°C - with an optimum between 31 and 35°C . However, all 3 germination stages were found to be independent of environmental pH within the range of pH 5 to 7.8. Studies on the nutritional requirements for germination revealed the need for exogenous supplies of both a carbon and nitrogen source to support germ-tube production. The ‘spore-ball phenomenon’ was investigated and a supplementary amino acid source was identified . The etiology of chalk brood is discussed in the light of these findings.

Occidiofungin is a novel glycolipopeptide, synthesized and secreted by Burkholderia contaminans MS14, demonstrating broad-spectrum antifungal activity and potential for successful clinical applications. Its mechanism of action has not yet been determined but is known to exhibit fungicidal activity via the induction of apoptosis in a manner unique from that of currently approved antifungals. As an early investigation into occidiofungin’s mechanism of action, we aimed to identify environmental and cellular factors that significantly alter the susceptibility of the model organism, Saccharomyces cerevisiae. To that end, we have demonstrated that occidiofungin’s bioactivity requires active cellular growth, that new protein synthesis is necessary to adequately respond to occidiofungin exposure, and that alterations in transcriptional regulation in response to glucose and phosphate deprivation have synergistic and antagonist consequences, respectively, on occidiofungin’s effectiveness. Together, this data provides a foundation on which occidiofungin’s mechanism of action can be illuminated.