Organic acids, including L- and D-lactate, explain most but not the entire elevated anion gap in diarrhea-associated metabolic acidosis. Also, D-lactate has been implicated in the neurological symptoms associated with this condition. Less-common organic compounds may influence the anion gap and neurological symptoms. This research aimed to characterize and attempt to identify a previously unidentified compound, Compound X, first noted in diarrheic acidotic calves with elevated anion gap (Omole, 1999).<p> High performance liquid chromatography (HPLC) was used to measure Compound X in biological fluids from diarrheic and healthy calves; diarrheic piglets, foals, and human infants; and calves experimentally infused with saline or acid. Attempts were made to identify Compound X using HPLC with tandem and Fourier-transform mass spectrometry.<p> Compound X was significantly higher in diarrheic calf serum (p<0.001) and lower in feces (p<0.001) and rumen fluid (p<0.001) than those fluids from healthy calves. Compound X in serum from acid-infused calves (median peak area ratio = 1.5 1.9) was lower than that of diarrheic calves (median = 4.8) and only slightly greater than that of healthy calves (median = 1.2). Serum Compound X correlated with serum D-lactate in diarrheic and healthy calves combined; however, no such correlation was observed in acid-infused calves. Conversely, a relationship between Compound X and neurological disturbance was present in acid-infused calves, but not in diarrheic calves. In other species, Compound X was highest in diarrheic infants and lowest in diarrheic piglets. Although mass spectrometry and database library searches revealed several compounds as putative matches for Compound X, none of the compounds made sense within the context of acidosis and mammalian biological fluids. Therefore, the identity of Compound X remains unknown.<p> Compound X has been established as a ubiquitous compound(s) present in the biological fluids of mammals. Compound X may be a normal intestinal compound or bacterial metabolite that crosses the intestinal epithelium during diarrhea. In spite of this, Compound X was associated with the neurological manifestations of D-lactic acidosis. Compound X`s identity was not determined, and some reasons for this and future directions are discussed.

Organic acids, including L- and D-lactate, explain most but not the entire elevated anion gap in diarrhea-associated metabolic acidosis. Also, D-lactate has been implicated in the neurological symptoms associated with this condition. Less-common organic compounds may influence the anion gap and neurological symptoms. This research aimed to characterize and attempt to identify a previously unidentified compound, Compound X, first noted in diarrheic acidotic calves with elevated anion gap (Omole, 1999).<p> High performance liquid chromatography (HPLC) was used to measure Compound X in biological fluids from diarrheic and healthy calves; diarrheic piglets, foals, and human infants; and calves experimentally infused with saline or acid. Attempts were made to identify Compound X using HPLC with tandem and Fourier-transform mass spectrometry.<p> Compound X was significantly higher in diarrheic calf serum (p<0.001) and lower in feces (p<0.001) and rumen fluid (p<0.001) than those fluids from healthy calves. Compound X in serum from acid-infused calves (median peak area ratio = 1.5 1.9) was lower than that of diarrheic calves (median = 4.8) and only slightly greater than that of healthy calves (median = 1.2). Serum Compound X correlated with serum D-lactate in diarrheic and healthy calves combined; however, no such correlation was observed in acid-infused calves. Conversely, a relationship between Compound X and neurological disturbance was present in acid-infused calves, but not in diarrheic calves. In other species, Compound X was highest in diarrheic infants and lowest in diarrheic piglets. Although mass spectrometry and database library searches revealed several compounds as putative matches for Compound X, none of the compounds made sense within the context of acidosis and mammalian biological fluids. Therefore, the identity of Compound X remains unknown.<p> Compound X has been established as a ubiquitous compound(s) present in the biological fluids of mammals. Compound X may be a normal intestinal compound or bacterial metabolite that crosses the intestinal epithelium during diarrhea. In spite of this, Compound X was associated with the neurological manifestations of D-lactic acidosis. Compound X`s identity was not determined, and some reasons for this and future directions are discussed.

Lactic acid, which induces pH depression, leads to ATP efflux from muscle to extracellular space: it was reported that CFTR was involved in this process. However, the mechanism by which lactic acid activated CFTR and brought about the ATP release is still unknown. This study was performed to investigate (1) what channels may be involved or even conduct ATP release, and (2) how lactic acid activated CFTR. Expression of the possible channels that may conduct ATP release in L6 cells was investigated using RT-PCR: ClC-2, ClC-3, ClC-7, CACC, VDAC, connexin 40, connexin 43 and pannexin 3 were expressed in L6. Incubation of cultured L6 cells with lactic acid (10 mM) increased the extracellular ATP from 0.6 ± 0.06 to 1.1 ± 0.09 nM (P ? 0.05), indicating that lactic acid stimulated ATP efflux in vitro. The non-specific chloride channel inhibitor, DIDS, failed to abolish the lactic-acid-induced ATP release, suggesting that DIDS-sensitive chloride channels were not involved in the ATP efflux. Among the non-specific inhibitors of connexin channels, gadolinium inhibited acidosis-induced ATP efflux, but carbenoxolone failed to inhibit it, and so the role of connexins remains uncertain. The specific inhibitor of CFTR, CFTRinh-172, and the non-specific open-channel blocker of CFTR, glibenclamide, both abolished the acidosis-induced ATP release, but another specific inhibitor of CFTR, GlyH-101, which blocks CFTR from the external side, failed to abolish the ATP release, suggesting that acidosis-induced ATP is dependent on CFTR-activation, but does not involve ATP moving through the CFTR chloride channel. We hypothesize that, at low pH, the Na+/H+ exchanger (NHX) extruded H+ out of the cell and the resulting intracellular Na+ was transported out by Ca2+/Na+ exchanger (NCX); the localized increase in Ca2+ activated adenyl cyclase (AC), thus elevating intracellular cAMP; cAMP-activated-PKA then phosphorylated CFTR, which regulated an ATP release channel. KT-5720, an inhibitor of PKA, abolished the acidosis-induced ATP release, and forskolin, an agent that elevates cAMP, stimulated it, suggesting that the cAMP/PKA pathway was involved. The specific inhibitor of NCX, SN-6 and KB-R7943, both abolished the acidosis-induced ATP release, supporting a role for NCX in mediating this process. However, amiloride, the non-specific inhibitor of NHX failed to abolish ATP efflux. The whole cell Cl- currents were studied in L6 cells: lactic acid increased the whole cell currents from 2.33 ± 0.10 to 3.54 ± 0.34 nA (P ? 0.05), and this lactic-acid-induced increase in Cl- current could be inhibited by CFTRinh-172, suggesting that the CFTR Cl- channel was opened at low pH. Moreover, forskolin increased whole cell Cl- currents, which supported a role for the cAMP/PKA pathway in the lactic-acid-induced increase in CFTR current. These data confirm that CFTR is involved in the lactic-acid-induced ATP release from L6 cells. The roles of the NCX and cAMP/PKA pathway in activating CFTR at low pH are supported, but further studies are required to determine whether the NHX is involved in CFTR activation and whether connexins participate in ATP release. / published_or_final_version / Physiology / Master / Master of Philosophy

Successfully inducing malolactic fermentation in the production of grape wines can be challenging, especially in wines after finishing alcoholic fermentation with limited energy sources, low pH values and high ethanol concentrations. In this thesis, the kinetics of several chemicals of enological relevance were studied in a white wine (Chardonnay) and a red wine (Cab Franc) vinified by traditional, consecutive alcoholic (AF) and malolactic fermentations (MLF), and simultaneous AF/MLF, where bacteria were co-inoculated with yeast. The Chardonnay must was adjusted to four pH values (3.20, 3.35, 3.50 or 3.65), the cab Franc was kept as original pH value (3.56) and the concentrations of sugars, organic acids as well as acetaldehyde were followed throughout the fermentations. For Chardonnay the degradation of glucose and fructose was slower at the lowest must pH value (3.20) and independent from the time of bacterial inoculation. In all cases, malolactic conversion was faster after yeast-bacterial co-inoculation and was completed in simultaneous treatments at pH values of 3.35-3.65, and consecutive treatments at pH 3.50 and 3.65. No statistically significant difference was observed among the final acetic acid concentration, in all inoculation and pH treatments. For Cab Franc, it confirmed that co-inoculation shortened the fermentation periods while having minor effects on other parameters. Overall, simultaneous AF/MLF allowed for greatly reduced fermentation times, while the must pH remained a strong factor for fermentation success and determined the final concentration of various wine components. The time of inoculation influenced formation and degradation kinetics of organic acids and acetaldehyde significantly.

The polymer materials industry is heavily dependent on the use of petroleum based plastics. This poses a problem, as the world is facing ongoing petroleum supply problems. A need exists for a bio-carbon based polymer material that has the performance and cost of currently used petroleum plastics. However, the overall performance of current bio-based plastics indicate that they must be somehow supplemented to achieve the properties of that of petroleum-based polymers. The low impact strength and thermal stability of poly(lactic acid), PLA are targets for improvement. One option is for development is through blending with acrylonitrile butadiene styrene (ABS). The viability and efficacy of using these two polymers as blending partners is investigated. The PLA used in these studies has unique and interesting crystallization properties. These have been examined and detailed in part 1. The second part of study includes neat polymer properties, miscibility analysis, and large scale process results. This results in an optimized blending ratio on which to go forward with development. The mechanical, thermal, and morphological properties are investigated in these studies. Significance of this research and development is widespread, as the material developed has the potential to reduce the use of petroleum-based carbon in plastics. / The financial support from the 2010 Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph -Bioeconomy for Industrial Uses Research Program, Natural Sciences and Engineering Research Council (NSERC) AUTO21 NCE project and Grain Farmers of Ontario (GFO), to carry out this research is gratefully acknowledged.

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Cheese ripening is a costly and lengthy process. Increasing the enzyme pool in the cheese curd has been shown to accelerate the cheese ageing process, enhance flavour and texture. The characteristics of two lactic acid bacteria attenuated by pulsed electric fields were studied in a milk system and in cheese slurry. The potential of accelerating cheese ripening via the addition of starter cultures attenuated by pulsed electric fields (PEF) was studied. / Pulsed electric field treatment was performed in a static treatment chamber using bi-polar waveform with a field intensity of 20 kV and 2 mus pulse width. The number of pulses ranged from 10 to 500. Evaluation of the starter cultures was assessed through the analysis of acidifying abilities, survival fractions, enzymatic activities and proteolysis (RP-HPLC and Cd-ninhydrin) in water soluble nitrogen extracts following the different attenuation treatments. / Pulsed electric fields significantly affected the general viability of the cells through a delayed acidification and an inhibition of enzymatic activity. A study in cheese slurry systems showed that the cultures under investigation were not able to provide an increased proteolysis levels following PEF treatment. The results of this study also suggest that optimal PEF treatment varies for each LAB strain and that the Lactococcus strains do not possess high enough proteinase and peptidase activities to be beneficial for the acceleration of cheese ripening.

The metabolic activity of bacterial microorganisms may influence the growth and metabolic activities of other microbes that are present in any specific niche. Lactic acid bacteria (LAB) are antagonistic to some microbial pathogens by the metabolic production of compounds with antimicrobial activity. Consequently, investigators have measured the effects of those antimicrobials to inhibit specific pathogens. However, the mode(s) of action of LAB against foodborne pathogens on products and/or in broth is not completely understood. Therefore, the objectives of this research were to (i) determine the LAB dose required for inhibition of Escherichia coli O157:H7 and Salmonella enterica in vitro and on spinach, and (ii) identify and quantify the major antimicrobial substances synthesized by LAB as a function of postinoculation storage conditions. Assays were performed at 7 degrees C under aerobic conditions. The foodborne pathogens dose responses were assessed in a liquid microbiological medium (in vitro) and on spinach leaf surfaces. Different levels of foodborne pathogens and LAB cultures were used. The addition of LAB cultures did not reduce E. coli O157:H7 or Salmonella enterica populations when performed in vitro. However, when LAB cultures were sprayed on the surfaces of spinach leaves at 8.0 log10 CFU/g, there were significant reductions on E. coli O157:H7 of 1.62 and 0.73 log10 CFU/g (after 3 days) and on Salmonella enterica of 1.85 and 0.71 log10 CFU/g (after 6 days) for treatments inoculated with an initial level of 2.0 and 4.0 log10 CFU/g, respectively. After quantification of the antimicrobial compounds synthesized by LAB cultures, they were correlated against the population growth of targeted pathogens. The highest Llactic acid (3.71 plus/minus 0.14 micromoles/ml, day 12) and hydrogen peroxide (3.72 plus/minus 3.34 microM, day 6) production were obtained from the in vitro sample inoculated with 8.0 log10 CFU/ml of LAB and 0.0 log10 CFU/ml of pathogens. The highest bacteriocin production (0.1 plus/minus 0.01 mg/ml) was obtained from the in vitro sample with 8.0 log10 CFU/ml of LAB and 2.0 log10 CFU/ml of pathogens. In conclusion, the LAB cultures were able to produce detectable amounts of antimicrobials that may be used as intervention and/or sciencebased practice against foodborne pathogens by producers and the industry.

Eleven male triathletes were studied to determine the relationships between selected metabolic measurements and triathlon performance. Measurements were made for oxygen consumption (V02), pulmonary ventilation (Ve) and heart rate (HR) during submaximal and maximal 400-yd freestyle swimming (FS), cycle ergometry (CE) and treadmill running (TR). Submaximal workloads were 1 m/sec for swimming, 200 watts for cycling and 7.5 mph for running. The mean (1/min) was significantly (P<0.05) lower during 1/min) than CE (4.68 1/sin) or TR (4.81 1/min). cycling and running performance times during the (1.2 mile swim, 56 mile cycle, 13.1 mile run) were to have a low relationship to V0z max (ml/kg/min) -0.32 and -0.55, respectively. The V0z max when expressed as 1/min was found to significantly (P<0.05) related to cycling time (r=-0.70). However, at a selected workload the %VO2 max was found to be highly related to swimming (0.91), cycling (0.78) and running (0.86) performance times. Maximal HR (bts/min) was also observed to be significantly (P<0.05) lower during FS (163) than CE (176) or TR (183). Running and cycling times in the triathlon were highly correlated (P<0.05) to overall triathlon performance times, 0.97 and 0.81, respectively, whereas swimming was found to be less a contributor to the athlete's final time, r=0.30. This study suggests that economy of effort is of greater importance to a triathlete's performance than their maximal oxygen uptake.