Aquatic Centre Walls

Construction of the concrete walls and pillars for the Aquatic Centre progress.

The effect of age on the structure and compostition of the cell walls of Choanephora cucurbitarum

The effect of age on the structure and composition of isolated and purified cell walls from cultures of Choanephora cucurbitarum was investigated by microchemical analyses, visible and infrared spectrophotometry, x-ray diffractometry and electron microscopy. Qualitative evaluation revealed the presence of lipids, proteins, neutral sugars, strong alkali soluble sugars, chitin, chitosan and uronic acids in the cell walls of both the 1 and 7 day old cultures. As the mycelium aged, there was a slight but statistically significant increase in the protein content, and a pronounced rise in the chitin and neutral sugar constituents of the cell walls. Conversely, the decrease in the chitosan content during this period had the net effect of altering the chitin: chitosan ratio from near unity in the younger cultures, to a 2:1 ratio in the 7 day old cell wall samples. Glutaraldehyde-osmium fixed thin sections of the 1 day old vegetative hyphae of £. curbitarum revealed the presence of a monolayered cell wall, which upon aging became bilayered. Replicas of acid hydrolysed cell walls demonstrated that both the 1 and 7 day old samples possessed an outer layer which was composed of finely granular amorphous material and randomly distributed microfibrils. The deposition of an inner secondary layer composed of parallel oriented microfibrils in the older hypha was correlated with an increase in the chitin content in the cell wall. The significance of these results with respect to the intimate relationship between composition and structure is discussed.

Receipt from Allan and Bro. of St. Catharines for work done on walls

Receipt from Allan and Bro. of St. Catharines for work done on walls, Oct. 31, 1876.

Structural Work

Construction on the Aquatic Centre progresses and concrete walls go up.

Concrete Forms

Forms and reinforcing steel bars used in the walls of the Aquatic Centre.

Steel Reinforcing Bars

Steel reinforcing bars used in the construction of the walls for the Aquatic Centre.

Wall Construction

Pouring the concrete during the construction of the walls for the Aquatic Centre.

Wall and Pillar Construction

Construction of the concrete walls and pillars for the Aquatic Centre.

Thistle Complex Construction

This picture shows construction work underway on the Thistle Complex. The groundwork, supporting pillars, and preliminary work on the concrete walls can be seen. The most notable feature is the exposed foundation of the Thistle Theatre to the left. The adjacent lecture halls are also taking form to the right.

Thistle Complex Construction

This picture shows construction work underway on the Thistle Complex. The groundwork, supporting pillars, and concrete walls can be seen. The most notable feature is the exposed foundation of the Thistle Theatre to the left. The adjacent lecture halls are also taking form to the right.

Armourstone revetments : will standard design criteria prevent failure? /

Bank stabilization structures are used to prevent the loss of valuable land within the urban environment and the decision for the type of structure used depends on the properties of the stream. In the urban areas of Southern Ontario there is a preference for the use of armourstone blocks as bank stabilization. The armourstone revetment is a free standing stone structure with large blocks of stone layered vertically and offset from one another. During fieldwork at Forty Mile Creek in Grimsby, Ontario armourstone failure was identified by the removal of two stones within one column from the wall. Since the footer stones were still in place, toe scour was eliminated as a cause of failure. Through theoretical, field, and experimental work the process of suction has been identified as a mode of failure for the armourstone wall and the process of suction works similarly to quarrying large blocks of rock off bedrock streambeds. The theory of lateral suction has previously not been taken into consideration for the design of these walls. The physical and hydraulic evidence found in the field and studied during experimental work indicate that the armourstone wall is vulnerable to the process of suction. The forces exerted by the flow and the resistance of the block determine the stability of the armourstone block within the wall. The design of the armourstone wall, high surface velocities, and short pulses of faster flowing water within the profile could contribute to armourstone failure by providing the forces needed for suction to occur, therefore adjustments to the design of the wall should be made in order to limit the effect.

Immuno-cytochemical localization of glycoproteins involved in recognition and attachment in a mycoparatism

Polyclonal antibodies prepared against the two glycoproteins (Mr 100 and 85 kDa) involved in recognition and attachment of the mycoparasite, Piptocephalis virginiana, to its hosts, Mortierella pusilla and Phascolomyces articulosus, susceptible and resistant, respectively, were employed to localize the antigens at their cell surfaces. Indirect immunocytochemical technique using secondary antibodies labelled with either FITC or gold particles as probes, were used. FITC-Iabelled antibodies revealed a discontinous pattern of fluorescence on the hyphae of MortlerelLa pusilla and no fluorescence on the hyphae of Phascolomyces articulosus. Intensity of fluorescence was high in the germinating spores of both the fungi. Fluoresence could be observed on P. articulosus hyphae pretreated with a commercial proteinase. Fluorescence was not observed on either hyphae or germinating spores of the nonhost M0 r tie re11 a ca ndelabrum and the mycoparasite P. virginiana. Antibodies labelled with gold conjugate showed a different pattern of antigen localization on the hyphal walls of the susceptible and resistant hosts. Patches of gold particles were observed allover the whole cell wall of the susceptible host but only on the inner cell wall layer of the resistant host. Cell wall fragments of the susceptible host but not those of the resistant host, previously incubated with the antibodies inhibited attachment of the mycoparasite. Implications of preferential localization of the antigen in the resistant host and its absence in the nonhost are described.

Isolation and partial characterization of host cell wall surface glycoproteins: their involvement in agglutination, attachment and appressorium formation by piptocephalis virginiana

Cell surface proteins obtained by alkaline extraction from isolated cell walls of Mortierella pusilla and M. candelabrum, host and nonhost, respectively, to the mycoparasite, Piptocephalis virginiana, were tested for their ability to agglutinate mycoparasite spores. The host cell wall protein extract had a high agglutinating activity (788 a.u. mg- t ) as compared with the nonhost extract (21 a.li. mg- t ). SDS-polyacrylamide gel electrophoresis of the cell wall proteins revealed four protein bands, a, b, c, and d (Mr 117, 100, 85 and 64 kd, respectively) at the host surface, but not at the nonhost surface, except for the faint band c. Deletion of proteins b or c from the host cell wall protein extract significantly reduced its agglutinating activity. Proteins band c, obtained as purified preparations by a series of procedures, were shown to be two glycoproteins. Carbohydrate analysis by gas chromatography demonstrated that glucose and Nacetylglucosamine were the major carbohydrate components of the glycoproteins. It was further shown that the agglutinating activity of the pure preparation containing both band c was 500-850 times that of the single glycoproteins, suggesting the involvement of both glycoproteins in agglutination. The results suggest that the glycoproteins band c are the two subunits of agglutinin present at the host cell surface. The two glycoproteins band c purified from the host cell wall protein extract were further examined after various treatments for their possible role in agglutination, attachment and appressorium formation by the mycoparasite. Results obtained by agglutination and attachment tests showed: (1) the two glycoprotein-s are not only an agglutinin responsible for the mycoparasite spore agglutination, but may also serve as a receptor for the specific recognition, attachment and appressorium formation by the mycoparasite; (2) treatment of the rnycoparasite spores with various sugars revealed that arabinose, glucose and N-acetylglucosamine inhibited the agglutination and attachment activity of the glycoproteins, however, the relative percentage of appressorium formation was not affected by the above sugars; (3) the two glycoproteins are relatively stable with respect to their agglutinin and receptor functions. The present results suggest that the agglutination and attachment may be mediated directly by certain sugars present at the host and mycoparasite cell surfaces while the appressorlum formation may be the response of complementary combinations of both sugar and protein, the two parts of the glycoproteins at the interacting surfaces of two fungi.

Probing cell surfaces of host and nonhost species of a mycoparasite, using FITC-labeled lectins

Cell surfaces of susceptible host species (Mortierella pusllla and Cboanepilora cucurbitarum ), resistant host (Pilascolomyces articulosus ), nonhost (Mortierella candelabrum ) and the mycoparasite (Piptocepilalis virginiana) were examined for sugar distribution patterns using light and fluorescent microscopy techniques. The susceptible host, resistant host and the mycoparasite species exhibited a similar sugar distribution profile; they all showed N-acetyl glucosamine and D-glucose on their cell wall surfaces. The nonhost cell wall surface showed a positive binding reaction to FITClectins specific for N-acetyl glucosamine and also for OI.-fucose, N-acetyl galactosamine and galactose. Treatment of these fungi with mild concentrations of proteinases (both commercial as well as the mycoparasiteproteinase) resulted in the revelation of additional sugars on the fungal cell walls. The susceptible host treated with proteinase expressed higher levels of N-acetyl glucosamine and D-glucose. The susceptible host also showed the presence of OI.-fucose, N-acetyl galactosamine and galactose. The proteinasetreated susceptible host cell walls also showed an increase in the levels of attachment with the mycoparasite. Treatment of the resistant host with proteinases revealed OI.-fucose in addition to N-acetyl glucosamine and D-glucose. Treatment of the nonhost cell wall with proteinase resulted in the exposure of low levels of D-glucose, in addition to sugars found on the untreated nonhost cell wall surface. The mycoparasite treated with proteinase revealed OI.-fucose, N-acetyl galactosamine and galactose on its cell surface in addition to the sugars N-acetyl glucosamine and D-glucose. Protoplasts were isolated from hosts and nonhost fungi and their surfaces were examined for sugar distribution patterns. The susceptible host and nonhost protoplast membranes showed all the sugars (N-acetyl glucosamine, D-glucose, (It.-fucose, N-acetyl galactosamine and galactose) tested for. The resistant host protoplast membrane however, had only N-acetyl glucosamine and D-glucose exposed. This sugar distribution profile resembles that exhibited by the untreated resistant host cell wall, as well as that shown by the untreated mycoparasite cell surface. Only susceptible host protoplasts were successful in attaching to the mycoparasite surface. Resistant host protoplasts did not show any interaction with the i mycoparasite cell surface. Both susceptible as well as resistant host protoplasts were incapable of attaching to agarose beads surface-coated with specific carbohydrates. The mycoparasite however, did attach to agarose beads surface-coated with either N-acetyl glucosamine, D-glucose/Dmannose or o:,- methyl-D-mannose. The relevance of the cell wall and the protoplast membrane in the light of the present results, in reacting appropriately to bring about either a susceptible, a resistant or a nonhost response has been discussed.

Investigations on the host-parasite interface of a mycoparasite system /

The cell wall composition of Choanephora cucur - bitarum and the host-parasite interface, after infection with Piptocephalis virginiana , were examined in detail. The cell walls of C_. cucurbitarum were determined to be composed of chitin (17%), chitosan (28.4%), neutral sugars (7.2%),uronic acid (2.4%), proteins (8.2%) and lipids (13.8%). The structure of hyphal walls investigated by electron microscopy of shadowed replicas before and after alkali-acid hydrolysis, showed two distinct regions: microfibrillar and amorphous. The microfibrils which were composed of mainly chitin, were organized into two distinct layers: an outer, thicker layer of randomly orientated microfibrils and an inner, thin layer of parallel microfibrils.Electronmicrographs of the host-parasite interface of C_. cucurbitarum and the mycoparasite , P_. virginiana , 30 h following inoculation, showed that the sheath zone has a similar electron density to that of the host cell wall. The sheath was not present around the young (18 h old) haustorium. High-resolution autoradiographs of infected host hyphae showed that radioactive N-acetyl-D-glucosamine , a precursor of chitin, was incorporated preferentially in the host cell wall and sheath zone. Cell fractionation of label fed hyphae showed that 84% of the label was present in the cell wall and specifically in the chitin portion of the wall. The antifungal antibiotic, Polyoxin D, a specific inhibitor of the enzyme, chitin synthetase, suppressed the incorporation of the label in the cell wall and sheath zone and resulted in a decrease in electron density of the developing sheath. The significance of these results is discussed in the light of host resistance.