Showing papers by "University of Guelph published in 1991"

Rhodococcus equi: an animal and human pathogen.

Abstract: Recent isolations of Rhodococcus equi from cavitatory pulmonary disease in patients with AIDS have aroused interest among medical microbiologists in this unusual organism. Earlier isolations from humans had also been in immunosuppressed patients following hemolymphatic tumors or renal transplantation. This organism has been recognized for many years as a cause of a serious pyogranulomatous pneumonia of young foals and is occasionally isolated from granulomatous lesions in several other species, in some cases following immunosuppression. The last decade has seen many advances in understanding of the epidemiology, pathogenesis, diagnosis, treatment, and immunity to infection in foals. The particular susceptibility of the foal is not understood but can be explained in part by a combination of heavy challenge through the respiratory route coinciding with declining maternally derived antibody in the absence of fully competent foal cellular immune mechanisms. R. equi is largely a soil organism but is widespread in the feces of herbivores. Its growth in soil is considerably improved by simple nutrients it obtains from herbivore manure. About one-third of human patients who have developed R. equi infections had contact in some way with herbivores or their manure. Others may have acquired infection from contact with soil or wild bird manure. R. equi is an intracellular parasite, which explains the typical pyogranulomatous nature of R. equi infections, the predisposition to infection in human patients with defective cell-mediated immune mechanisms, and the efficacy of antimicrobial drugs that penetrate phagocytic cells.

Group Cohesion and Performance: A Meta-Analysis

Abstract: Past research examining group cohesion and performance was reviewed using metaanalysis. The results indicated a positive relationship with the average cohesive group performing 18 percentile points above the average noncohesive group. Given the nature of the studies used here (all studies had been previously published), caution is suggested in generalizing these results to "real" work groups.

Performance and metabolic responses to a high caffeine dose during prolonged exercise

Abstract: The present study examined whether a high caffeine dose improved running and cycling performance and altered substrate metabolism in well-trained runners. Seven trained competitive runners [maximal O2 uptake (VO2max) 72.6 +/- 1.5 ml.kg-1.min-1] completed four randomized and double-blind exercise trials at approximately 85% VO2max; two trials running to exhaustion and two trials cycling to exhaustion. Subjects ingested either placebo (PL, 9 mg/kg dextrose) or caffeine (CAF, 9 mg/kg) 1 h before exercise. Endurance times were increased (P less than 0.05) after CAF ingestion during running (PL 49.2 +/- 7.2 min, CAF 71.0 +/- 11.0 min) and cycling (PL 39.2 +/- 6.5 min, CAF 59.3 +/- 9.9 min). Plasma epinephrine concentration [EPI] was increased (P less than 0.05) with CAF before running (0.22 +/- 0.02 vs. 0.44 +/- 0.08 nM) and cycling (0.31 +/- 0.06 vs. 0.45 +/- 0.06 nM). CAF ingestion also increased [EPI] (P less than 0.05) during exercise; PL and CAF values at 15 min were 1.23 +/- 0.13 and 2.51 +/- 0.33 nM for...

The Ah receptor and the mechanism of dioxin toxicity.

Abstract: Over the last several decades, dioxins have become the subject of intense public and scientific scrutiny. This is the result of not only their widespread presence in the environment but also their great toxicity. The environmental issue has been addressed through the study of the production, release and fate of dioxins and related substances, as well as the development of analytical techniques to detect and quantify these compounds in environmental matrices. The toxicology of dioxins has been addressed principally through studies of their mechanism of toxic action using animal models and is the focus of this review. In addition, the potential threat that dioxins present to human health has been addressed in a limited manner through epidemiological studies of populations known to have been exposed to dioxins.

Fertilizing capacity of bovine sperm may be maintained by binding of oviductal epithelial cells.

Abstract: The ability of the bovine oviduct to maintain the motility and fertilizing capacity of bovine sperm was investigated by incubating frozen-thawed sperm with endosalpingeal epithelial cells cultured on either tissue culture plastic (nonpolarizing) or Matrigel.coated Millicell (polarizing) substrata, Sperm were also incubated in medium alone or with cultured bovine tracheal epithelial cells, Motility was determined at 6-h intervals over a 48-h period. The fertilizing capacity of sperm was evaluated after 0, 24, and 30 h of incubation by adding oocytes to the culture and determining the incidences of fertilization and polyspermy. Motility was maintained for 48 h in sperm that bound to endosalpingeal epithelial cells, but to a greater extent with polarized cells (38.4% motile) than with nonpolarized cells (0.8%). Fertilizing capacity was maintained for 30 h in sperm incubated with endosalpingeal epithelial cells on Matrigel/Millicell, but not in sperm incubated in medium alone or with tracheal cells. Only sperm incubated with oviductal cells developed hyperactivated motility. Scanning electron micrographs revealed that sperm were bound by the rostral portion of the intact acrosome to the apical surface of polarized endosalpingeal cells, These results suggest that the oviduct may not only store sperm but may also maintain sperm viability and fertilizing capacity during the preovulatory period,

Properties of P-wave mesons with one heavy quark.

Abstract: We present the results of a quark model study of $L=1$ mesons with one heavy quark. We give the masses of these states as predicted by the relativized quark model and the decay properties as calculated using both the pseudoscalar emission model and the flux-tube-breaking model. We examine the idealized limit of one infinitely massive quark and one light quark and discuss our results in this context as a guide to what can be learned from the study of these states. We find that, even for $B$ mesons, the tensor interactions play an important role in the spectroscopy and the ${m}_{Q}\ensuremath{\rightarrow}\ensuremath{\infty}$ has not yet been reached. We conclude that further experimental study of the decay properties of the ${D}_{1}$ mesons is important to the understanding of the $^{3}P_{1}\ensuremath{-}^{1}P_{1}$ mixing mechanism.

Impact of Country-of-Origin Cues on Consumer Judgments in Multi-Cue Situations: a Covariance Analysis

Abstract: The effect of country-of-origin labelling on consumers’ assessments of product quality, risk to purchase, perceived value and likelihood of purchasing was tested experimentally in a multi-product, multi-cue setting. Country-of-origin information was found to be more important in affecting product quality assessments than were price and brand information. Price was important in value assessment while brand was significant in a few product specific cases. Age, education, sex, and perceptions of ability to judge products were variously related to consumers’ ratings of quality, risk, value and likelihood of purchase especially when the product was more complex and difficult to judge. However, much of the variation in consumer judgments was not accounted for by the variables employed in this study, suggesting that future research should include more detailed studies of information processing whereby intrinsic and extrinsic product cues and a wide range of consumer characteristics are taken into consideration.

Biology of the exotic zebra mussel, Dreissena polymorpha, in relation to native bivalves and its potential impact in Lake St. Clair

Abstract: The zebra mussel, Dreissena polymorpha, is a new exotic species that was introduced into the Great Lakes as early as the fall of 1985. It differs markedly from native species of bivalves in its: (i) shell form; (ii) mode of life; (iii) reproductive potential; (iv) larval life cycle; (v) population dynamics; (vi) distribution, (vii) dispersal mechanisms; (viii) physiology; (ix) potential impact on the ecosystem; and (x) impact on society and the economy. In body form, it has an anterior umbone, a flat ventral surface with permanent aperature for the byssal apparatus and a shape that together make the animal well adapted for life on a hard surface. The shell has a zebra-stripe pattern, a heteromyarian muscle condition and lacks hinge teeth which make it easily identifiable from native bivalves. The zebra mussel is strongly byssate and has an epifaunal mode of life not seen in native bivalves. The species is dioecious and has external fertilization, the eggs developing into pelagic veligers which remains planktonic for approximately 4 weeks. Gametogenesis begins in late winter to early spring, veligers appear in the water column in late May to early June and disappear in mid to late October in Lake St. Clair. Adults live for about 2 years and have very rapid growth rates. Maximum shell lengths average 2.3 to 2.5 cm. Standing crops as high as 200 000 m-2 are present in the 1-m depths of the Ontario shores. Infestations may be interfering with the normal metabolism of native unionid clams and there is potential of the unionid clam populations being reduced or even eliminated from Lake St. Clair.

Effects of a sudden increase in natural mortality of adults on a population of the common snapping turtle (Chelydra serpentina)

Abstract: A northern population of snapping turtles (Chelydra serpentina) centred around Lake Sasajewun in the Wildlife Research Area in Algonquin Park, Ontario, has been studied and individually marked sinc...

Free radicals may contribute to oxidative skeletal muscle fatigue

Abstract: We used mouse soleus in vitro (n = 30) and canine gastrocnemius-plantaris preparations (n = 20) pump-perfused at the animal's blood pressure to establish if free radicals contribute to fatigue in oxidative skeletal muscle. The soleus from each leg contracted for 200 ms (70 Hz) once every minute for 60 min in Hepes buffer gassed with 100% oxygen at 27 degrees C. When contracting in Hepes alone, both muscles fatigued at 0.9 mN/mm2.min over the 60 min. The addition of purines to the bath increased the rate to 1.4 mN/mm2.min and the addition of xanthine oxidase to generate free radicals increased the rate again to 1.9 mN/mm2.min. Thus free radicals appeared to attenuate oxidative skeletal muscle function. Each canine muscle contracted isometrically at 4 Hz for 30 min and then rested for 45 min before contracting for a second 30 min at 4 Hz. In each experiment, we infused saline at 0.76 mL/min into resting muscle and at 1.91 mL/min during the first contraction period. During the remainder of the experiment, we infused, at the same rates, saline (n = 4), 10 microM dimethyl sulfoxide (DMSO) (n = 4) to identify the effect of scavenging hydroxyl radicals, 1 mM allopurinol to establish the effect of blocking xanthine oxidase (n = 4), or 200 microM desferoxamine to determine the effect of chelating iron (n = 4). With saline, the fatigue rate over the 30 min of contractions increased from 5.0 +/- 0.2 to 6.3 +/- 0.5 N/kg.min from the first to the second stimulation period. The fatigue rate was slower in the second period with each of the three experimental substances (DMSO, 5.9 +/- 0.8 to 3.2 +/- 0.3; allopurinol, 7.3 +/- 1.1 to 4.6 +/- 0.6; desferoxamine, 6.8 +/- 0.8 to 4.4 +/- 0.8 N/kg.min). The fatigue rate was the same as control when DMSO was infused only during the second contraction period. Therefore, free radicals appeared to contribute to fatigue in oxidative skeletal muscle.

Rapid identification of genetic variation and pathotype of Leptosphaeria maculans by random amplified polymorphic DNA assay.

Abstract: Canadian isolates of Leptosphaeria maculans, the causal agent of blackleg of crucifers, were examined for genetic relatedness by the random amplified polymorphic DNA assay. DNA polymorphisms amplified with random decamer primers were used to distinguish three groups of isolates. Group 1 contained all isolates of the virulent pathotype, group 2 contained isolates of the avirulent pathotype from western Canada, and group 3 contained avirulent pathotype isolates from Ontario. These results agreed with other reports which showed many genetic differences between pathotypes and were consistent with the hypothesis that the virulent pathotype was recently introduced into Canada and has diverged relatively little. In contrast, the avirulent pathotype has probably been present in Canada for a longer time and has diverged with geographic isolation. In addition to establishing genetic relationships, DNA fingerprints generated by the random amplified polymorphic DNA assay have potential applications in pathotype identification and blackleg disease management.

The implications of cognitive processes for animal welfare

Abstract: In general, codes that have been designed to safeguard the welfare of animals emphasize the importance of providing an environment that will ensure good health and a normal physiological and physical state, that is, they emphasize the animals' physical needs. If mental needs are mentioned, they are always relegated to secondary importance. The argument is put forward here that animal welfare is dependent solely on the cognitive needs of the animals concerned. In general, if these cognitive needs are met, they will protect the animals' physical needs. It is contended that in the few cases in which they do not safeguard the physical needs, it does not matter from a welfare point of view. The human example is given of being ill. It is argued that welfare is only adversely affected when a person feels ill, knows that he or she is ill, or even thinks that he or she is ill, all of which processes are cognitive ones. The implications for welfare of animals possessing certain cognitive abilities are discussed. For example, the extent to which animals are aware of their internal state while performing behavior known to be indicative of so-called states of suffering, such as fear, frustration, and pain, will determine how much they are actually suffering. With careful experimentation it may be possible to determine how negative they feel these states to be. Similarly, the extent to which animals think about items or events absent from their immediate environment will determine how frustrated they are in the absence of the real item or event but in the presence of the cognitive representation.

Biological membrane deterioration and associated quality losses in food tissues

Abstract: Biological membranes are rarely considered by food scientists when the deteriorative reactions that take place during the processing or storage of food tissues are studied. Yet, membranes and their deterioration play a major but underestimated role in food losses, and recent biochemical information indicates that at least some of these reactions can be controlled by procedures suited to food materials. Much of the present information available on membrane degradation in food systems is incomplete and speculative. It is known, however, that in order to accomplish their many indispensable functions in cells, membranes are constituted mainly of phospholipids, protein, and some carbohydrates arranged in thin, bimo‐lecular sheet‐like structures that serve to compartmentalize cells and their organelles. Membranes have embedded in their asymmetric surfaces complements of catalytic and cytoskeletal proteins that serve permeability and structural functions. Membrane surfaces exhibit fluidity, due partiall...

Glucose and glutamine metabolism in pre-attachment cattle embryos in relation to sex and stage of development.

Abstract: Individual Day-7 embryos (morulae to expanded blastocysts) were incubated with radiolabelled substrates and karyotyped to determine the sex. In Exp. 1, embryos were incubated for 3 h with D-[1-14C]glucose, as a measure of the activity of the pentose-phosphate pathway (PPP) and D-[5-3H]glucose, as a measure of total glucose metabolism. The labelled products 14CO2 and 3H2O were collected throughout the measurement period. Total glucose metabolism in male embryos was twice that in female embryos and increased between the morula and expanded-blastocyst stages. Relative to total glucose metabolism, PPP activity was four times greater in female than in male embryos. In Exp. 2, embryos were cultured with D-[1-14C]glucose, and L-[3,4-3H(N)]glutamine (a measure of Krebs cycle activity) in the presence of brilliant cresyl blue, a stimulator of the PPP. Glutamine metabolism increased from the morula to expanded-blastocyst stages. Relative to the metabolism of glutamine, the activity of the PPP was one-third greater in female than in male embryos.

Multiple Discrepancies Theory

Abstract: The three remaining sections of this chapter are devoted to a detailed account of MDT. The substance of the theory has changed very little since it was originally explained in Michalos (1985), but the version presented here has a bit more precision. In the next section I review the seven discrepancies employed in the theory, and provide more information about research and developments related to the specific theories connected to these discrepancies. Section 2.3 gives an overview of research on the social and personal construction of knowledge, perception and value. It seemed worthwhile to include this material in the context of a discussion of the notoriously low correlations people have found between objective and subjective indicators because there are still researchers who imagine that the correlations are between things that are wholly independent and rigorously measurable on the one hand and things that are equally independent but only roughly measurable on the other hand. In fact, there is apparently much more inter-dependence, interaction and similarity in measurement problems than such researchers suppose. In the final section I review the literature on the role of background conditions and conditioners on perceived well-being.

Workplace variables, affective responses, and intention to leave among women managers

Abstract: This study investigated workplace variables and affective responses as precursors of intentions to leave organizations via a survey of 306 women managers. The contribution of workplace variables typically included in turnover studies was assessed, as well as that of additional variables thought to be particularly pertinent to professional women's organizational experiences. The results of a canonical correlation analysis indicated that women who felt that their expectations had not been met, who described their jobs as limited in leadership, responsibility, variety, time flexibility and autonomy and who cited office politics and being in a male dominated environment as potential factors in a leave decision, expressed low job satisfaction and organizational commitment and had a greater intention to leave. Implications for organizations are discussed and directions for further research are suggested.

Comparative fecundity of decapod crustaceans i. the fecundity of thirty-three species of nine families of caridean shrimp

Abstract: Etude de la fecondite de trente-trois especes de crevettes carides tropicales et subtropicales appartenant a neuf familles. Les masses externes d'oeufs ont ete classees en precoces (yeux non apparents) et tardives (yeux bien visibles). Pour chaque femelle ovigere, les oeufs, de forme ovale, ont ete preleves, comptes et mesures. Le volume d'un oeuf et, a partir de ce volume, celui de la masse d'oeufs ont ete calcules. Les resultats pour les oeufs precoces et pour les oeufs tardifs ont ete statistiquement compares pour chaque espece puis entre especes. Le volume de l'oeuf a un stade donne etait constant a l'interieur de l'espece. Le nombre d'oeufs precoces par masse d'oeufs (EN) et le volume de la masse d'oeufs (EMV) pour les femelles d'une meme espece provenant de localites eloignees ne presentaient pas de differences significatives. EN en EMV offraient une relation lineaire positive en fonction de la taille des femelles. En retenant seulement les donnees relatives aux oeufs precoces, la relation lineaire entre EMV et le volume de la carapace (CV) etait beaucoup plus forte que la relation entre EN et la longueur de la carapace (CL). La regression du volume de la masse d'oeufs (EMV) par rapport au volume moyen de la carapace a ete etablie pour toutes les especes (r2 = 0,644). La tranformation logarithmique des donnees avant la regression donne une relation beaucoup plus etroite (r2 = 0,943). La fecondite des femelles a oeufs precoces d'une espece peut-etre evaluee en termes de EMV si le CV d'un echantillon est determine, d'apres l'equation: log EMV = 0,89 (log CV) - 0,34. La fecondite peut aussi etre evaluee en termes de nombre d'oeufs par masse d'oeufs (EN), en divisant le EMV calcule par le volume de l'oeuf (EV) determine d'apres le meme echantillon utilise pour deriver CV (EN = EMV/EV). On evite ainsi le processus long et fastidieux de comptage des masses d'oeufs entieres. Cependant, quand les equations de fecondite sont disponibles pour des familles particulieres, comme ils ont ete etablis ici pour les Hippolytidae, les Alpheidae et les Palaemonidae, il est recommande de les utiliser de preference a l'equation presentee ici.

Crop Rotation and Tillage Effects on Corn Growth and Soil Structural Stability

Abstract: Increasing concerns about soil degradation with continuous corn (Zea mays L.) production and a scarcity of scientific information regarding corn grown in rotation with the diversity of crops produced in Ontario, prompted a long term study on the effect of various crop rotations and their interaction with two tillage systems on corn growth and soil structure. Eight rotations were established in 1980 which included continuous corn, six rotations comprised of 2 yr of corn following 2 yr of another crop or crop sequence, and continuous alfalfa (Medicago sativa L.). Each rotation was divided into either conventional tillage (fall moldboard plow) or minimum tillage (fall chisel plow) (...)

Turnover of carbon through the microbial biomass in soils with different texture

Abstract: Ten soils, with the same type of clay and under the same management but having different clay contents, were amended with 14C-labelled glucose and incubated for 90 days to determine the influence of texture on the turnover of C through the microbial biomass. After 90 days, there was little difference among the soils in residual 14C. However, rates of CO2 evolution and mineralization indicated that during the first day of incubation, the rate of decomposition of substrate C was greater in soils with more clay. From 1 to 5 days the turnover of C through the biomass was relatively slower in these soils. Total biomass C (labelled + unlabelled C) contents reached maximal amounts after 1.25 days and were maintained at higher quantities in soils with greater amounts of clay until the end of the incubation. Biomass 14C was maintained at higher amounts in soils with more clay but only until 45 days. The proportion of C derived from the labelled glucose and incorporated in the biomass ranged from 59 to 73% after 1.25 days and from 16 to 20% after 90 days. The unlabelled biomass was significantly correlated with the amount of clay at all sampling dates and appeared to be qualitatively different than the labelled biomass in the heavy tcxturcd soils. After 1.25 days of incubation, the non-living 14C accounted for 12 to 23% of added to glucose 14C; after 90 days it ranged from 11 to 20%. The ratio of living to non-living 14C was consistently higher in soils with more clay. This was attributed to adsorption of non-living C by clay and to product utilization by a secondary population.

Inferring consensus structure from nucleic acid sequences

Abstract: This paper presents an unsupervised inference method for determining the higher-order structure from sequence data. The method is general, but in this paper it is applied to nucleic acid sequences in determining the secondary (2-D) and tertiary (3-D) structure of the macromolecule. The method evaluates position - position interdependence of the sequence using an information measure known as expected mutual information. The expected mutual information is calculated for each pair of positions and the chi-square test is used to screen statistically significant position pairs. In the calculation of expected mutual information, an unbiased probability estimator is used to overcome the problem associated with zero observation in conserved sites. A selection criterion based on known structural constraints of the strongest interdependent position pairs is applied yielding position pairs most indicative of secondary and tertiary interactions. The method has been tested using tRNA and 5S rRNA sequences with very good results.