Showing papers by "University of Saskatchewan published in 1993"

Airway Responsiveness. Standardized Challenge Testing With Pharmacological, Physical and Sensitizing Stimuli in Adults. Report Working Party Standardization of Lung Function Tests, European Community for Steel and Coal. Official Statement of the European Respiratory Society

Abstract: Asthma and chronic obstructive pulmonary disease (COPD, also called chronic airflow limitation (CAL)) are the most frequent diagnoses in patients with intrathoracic airways obstruction [1]. Often these patients show a spontaneous variability in the degree of airways obstruction, which can be documented by serial lung function measurements. Large variability in the degree of airways obstruction is indicative of an increased susceptibility of the patient to environmental stimuli that cause acute airway narrowing. Knowledge of the potential severity of these episodes of acute airways obstruction is of clinical interest. Therefore, several quantitative measures of the response of the airways to bronchoconstrictors in vivo have been advocated over the past two decades. The objective of the present guidelines is to address the methodological issues of the various available techniques, and to provide up-to-date international guidelines on standardization. The present recommendations might not represent the potentially best methodologies. However, they do represent the currently validated techniques, by which interchangeable results can be obtained among laboratories. Variable airways obstruction can be mimicked in the laboratory by challenge tests with bronchoconstrictive stimuli (fig. 1) [2]. This enables one to measure the degree of the so-called «airway responsiveness» of the subject to a particular agent. Since the bronchoconstrictive response varies from one stimulus to another, one needs to specify the challenging agent. Therefore, the term «nonspecific» airway responsiveness should be abandoned. Figure 1– Dose-response curves to inhaled methacholine using the dosimeter method in 3 subjects. Airway hyperresponsiveness in asthma is characterised by a leftward shift of the curve (hypersensitivity), a steeper slope (hyperreactivity), and an increase in maximal response (excessive airway narrowing). Modified from de Pee et al. [243] with permission. Airway hyperresponsiveness refers to an exaggerated response to the bronchoconstrictor. This is reflected by an increased sensitivity to the stimulus, which …

Stable-Nitrogen Isotope Enrichment in Avian Tissues Due to Fasting and Nutritional Stress: Implications for Isotopic Analyses of Diet

Abstract: Studies using measurements of61'5N to delineate diet or trophic level in natural ecosystems are based on the premise that 6'5N values in consumer tissues can be reliably correlated with those in the diet. However, juvenile Japanese Quail (Coturnixjaponica) fed a rationed diet designed to maintain, but not increase, body mass showed significantly enriched tissue 6'5N values over a control group fed the same diet ad libitum. We tested the hypothesis that fasting or nutritional stress can also cause elevated 6'5N values in tissues of wild birds by examining tissues of Arctic-nesting female Ross' Geese (Chen rossii) before and after their period of fasting during egg laying and incubation. Significant declines in body, pectoral muscle, liver and abdominal fat mass occurred from arrival through incubation. Post-incubating geese showed significantly higher pectoral muscle and liver 6'5N values compared to geese taken before clutch initiation but 6a3C values in these tissues were unchanged. We hypothesize a mechanism of tissue 6'5N enrichment due to reduced nutrient intake and discuss the implications of these results to ecosystem studies using stable-nitrogen isotope analysis.

Measuring Social Desirability: Short Forms of the Marlowe-Crowne Social Desirability Scale

Abstract: A practical difficulty with the Marlowe-Crowne Social Desirability Scale (SDS) is its length. Preferring a shorter measure of social desirability, researchers have devised a number of short forms o...

The Design of Replicated Studies

Abstract: Replication is little discussed in the statistical literature nor practiced widely by statistically minded researchers It is needed not merely to validate one's findings, but more importantly, to establish the increasing range of radically different conditions under which the findings hold, and the predictable exceptions This article describes how to design highly differentiated replications The irrelevance and/or impossibility of identical replications are also discussed Practical illustrations of the success and failure of replicated studies are given

Reproducibility of random amplified polymorphic DNA (RAPD) analysis among laboratories

Abstract: Random amplified polymorphic DNA (RAPD) analysis appears to offer a cost- and time-effective alternative to restriction fragment-length polymorphism (RFLP) analysis. However, concerns about the ability to compare RAPD results from one laboratory to another have not been addressed effectively. DNA fragments that were amplified by five primers and shown to be reproducibly polymorphic between two oat cultivars (within the Ottawa laboratory) were tested in six other laboratories in North America. Four of the six participants amplified very few or no fragments using the Ottawa protocol. These same participants were able to generate a considerable number of amplified fragments by using their own protocols. The reproducibility of results among laboratories was affected by two factors. First, different laboratories amplified different size ranges of DNA fragments, and, consequently, small and large polymorphic fragments were not always reproduced. Second, although reproducible results were obtained with four of the primers, reproducible results were not obtained with the fifth primer, using the same reaction conditions. It is suggested that if the overall temperature profiles (especially the annealing temperature) inside the tubes are identical among the laboratories, then RAPD fragments are likely to be reproducible.

Bovine herpesvirus 1: immune responses in mice and cattle injected with plasmid DNA.

Abstract: Mice and cattle injected with plasmids encoding bovine herpesvirus 1 (BHV-1) glycoproteins developed gene-specific antibody responses capable of neutralizing BHV-1. The ability of animals to respond serologically to DNA injections was in part dependent on the quantity of DNA injected and was also negatively affected by carrier DNA. Calves injected with a plasmid encoding BHV-1 gIV developed significant antibody titers to gIV and shed less virus than did the control calf after challenge. This report indicates the potential of DNA injection as a method of vaccination. Images

Embryogeny of gymnosperms: advances in synthetic seed technology of conifers

Abstract: Synthetic seed technology requires the inexpensive production of large numbers of high-quality somatic embryos. Proliferating embryogenic cultures from conifers consist of immature embryos, which undergo synchronous maturation in the presence of abscisic acid and elevated osmoticum. Improvements in conifer somatic embryo quality have been achieved by identifying the conditions in vitro that resemble the conditions during in ovulo development of zygotic embryos. One normal aspect of zygotic embryo development for conifers is maturation drying, which allows seeds to be stored and promotes normal germination. Conditions of culture are described that yield mature conifer somatic embryos that possess normal storage proteins and fatty acids and which survive either partial drying, or full drying to moisture contents similar to those achieved by mature dehydrated zygotic embryos. Large numbers of quiescent somatic embryos can be produced throughout the year and stored for germination in the spring, which simplifies production and provides plants of uniform size. This review focuses on recent advances in conifer somatic embryogenesis and synthetic seed technology, particularly in areas of embryo development, maturation drying, encapsulation and germination. Comparisons of conifer embryogeny are made with other gymnosperms and angiosperms.

Microstrip patch designs that do not excite surface waves

Abstract: Two variations of a circular microstrip patch design are presented which excite very little surface wave power. Both of the designs are based on the principle that a ring of magnetic current in a substrate (which models the patches) will not excite the dominant TM/sub 0/ surface wave if the radius of the ring is a particular critical value. Numerical results for radiation efficiency and radiated field strength from a ring of magnetic current are shown to verify this basic design principle. The proposed patch designs are chosen to have a radius equal to this critical value, while maintaining resonance at the design frequency. The designs excite very little surface-wave power, and thus have smoother radiation patterns when mounted on finite-size ground planes, due to reduced surface-wave diffraction. They also have reduced mutual coupling, due to the reduced surface-wave excitation. Measured results for radiation patterns and field strength within the substrate are presented to verify the theoretical concepts. >

Body weight and weight gain related to pulmonary function decline in adults: a six year follow up study.

Abstract: BACKGROUND--Obesity increases the risk of cardiovascular disease, hypertension, diabetes, digestive diseases, and some cancers. Several studies have shown that excess weight or weight gain is related to pulmonary dysfunction, but this issue needs to be further clarified. METHODS--The analysis was based on data of the Humboldt cohort study which was conducted in the town of Humboldt, Saskatchewan, Canada. The baseline survey in 1977 included 1202 adults, comprising 94% of all residents aged 25-59 years. Of these, 709 (59%) were followed up in 1983. Pulmonary function (forced vital capacity (FVC), forced expiratory volume in one second (FEV1) and maximal mid expiratory flow rate (MMFR) and weight were measured in both surveys. Weight gain was determined by subtracting weight at baseline from weight at follow up. A residual analysis was used to examine the relationship between body mass index (BMI) at baseline, weight gain, and pulmonary function decline. RESULTS--Both BMI at baseline and weight gain were significantly related to pulmonary function at follow up. The effect of weight gain during the study period, however, was more prominent. The results showed that both mean residual FVC and FEV1 were highest in the group that gained or = 4.0 kg, and intermediate in the group that gained 1.0-3.9 kg in both men and women after taking age, BMI at baseline, and smoking into account. The effect of weight gain on pulmonary function was greater in men than in women. Multiple regression analysis showed that each kilogram of weight gain was associated with an excess loss of 26 ml in FVC and 23 ml in FEV1 in men, and 14 ml and 9 ml respectively in women. CONCLUSIONS--Weight gain is significantly related to lung dysfunction. The effect of weight gain on pulmonary function is greater in men than in women.

Application of static VAr compensators to increase power system damping

Abstract: A theory for analyzing power system damping enhancement by application of static VAr compensators (SVCs) has been developed using the equal area criterion. Some fundamental issues, such as the effect of SVCs on a power system, how to control an SVC to improve system damping, and the differences between continuous and discontinuous control of SVC reactive power to achieve the maximum damping improvement, are discussed. A discontinuous SVC reactive power output at discrete points is determined from the power deviation on a transmission line. Time-domain simulations of the application of this approach to a one-machine system to increase swing oscillation damping and to a four-machine system to increase the damping of an interarea oscillation mode demonstrate that the theory and method can be applied to solve practical power system damping problems. >

Crop insurance and crop production: an empirical study of moral hazard and adverse selection

Abstract: Multiple risk crop insurance has not been very successful in the United States or elsewhere. As has been shown in other chapters in this book, no multiple risk crop insurance scheme has consistently earned enough premium income to cover payouts, much less administrative costs. The standard explanations for the failure of multiple risk crop insurance relate to problems of adverse selection and moral hazard. A number of theoretical models of these problems have been proposed (for example, Ahsan, Ali, and Kurian 1982, Quiggin 1986, Nelson and Loehman 1987, and Chambers 1989). However, there has been comparatively little empirical study of the problem. One reason may be that it is difficult, in practice, to distinguish between adverse selection and moral hazard.

Muon spin rotation study of the correlation between Tc and ns/m* in overdoped Tl2Ba2CuO6+ delta.

Abstract: The muon spin depolarization rate \ensuremath{\sigma} was measured in overdoped ${\mathrm{Tl}}_{2}$${\mathrm{Ba}}_{3}$${\mathrm{CuO}}_{6+\mathrm{\ensuremath{\delta}}}$. \ensuremath{\sigma}(T\ensuremath{\rightarrow}0) was found to decrease proportional to the superconducting transition temperature ${\mathit{T}}_{\mathit{c}}$ as doping \ensuremath{\delta} is increased. In the framework of the clean-limit London model, \ensuremath{\sigma}(0)\ensuremath{\sim}${\ensuremath{\lambda}}^{\mathrm{\ensuremath{-}}2}$\ensuremath{\sim}${\mathit{n}}_{\mathit{s}}$/${\mathit{m}}^{\mathrm{*}}$, this implies that the depression of ${\mathit{T}}_{\mathit{c}}$ by overdoping is associated with a decrease of the superconducting condensate density ${\mathit{n}}_{\mathit{s}}$ in spite of the increasing normal-state carrier density. This can be largely accounted for in terms of strong pair breaking, which depresses both the condensate density and ${\mathit{T}}_{\mathit{c}}$ with increased doping.

Extracellular ATP activates a cation conductance and a K+ conductance in cultured microglial cells from mouse brain

Abstract: Microglial cells have important functions during regenerative processes after brain injury. It is well established that they rapidly respond to damage to the brain tissue. Stages of activation are associated with changes of cellular properties such as proliferation rate or expression of surface antigens. Yet, nothing is known about signal substances leading to the rapid changes of membrane properties, which may be required to initiate the transition from one cell stage into another. From our present study, using the patch-clamp technique, we report that cultured microglial cells obtained from mouse or rat brain respond to extracellularly applied ATP with the activation of a cation conductance. Additionally, in the majority of cells an outwardly directed K+ conductance was activated with some delay. Since ADP, AMP, and adenosine (in descending order) were less potent or ineffective in inducing the cation conductance, the involvement of a P2 purinergic receptor is proposed. The receptor activation is accompanied by an increase of cytosolic Ca2+ as determined by a fura-2-based Ca(2+)- imaging system. This ATP receptor could enable microglial cells to respond to transmitter release from nerve endings with ATP as a transmitter or cotransmitter or to the death of cells with resulting leakage of ATP.

Free Radicals in the Genesis of Alzheimer's Diseasea

Abstract: As part of an ongoing investigation of the role of oxygen free radicals in Alzheimer's disease (AD), the formation of peroxidation products, the activities of free radical defense enzymes, and the level of total iron were determined in autopsy brain tissue from donors with AD and from age-matched non-demented donors. Calcium uptake was also investigated in mitochondria harvested from fibroblasts grown in tissue culture from skin samples taken from brain donors. Compared to controls, homogenates of AD frontal cortex produced elevated levels of peroxidation products and this difference was amplified in a dose-dependent manner by iron (1 to 200 microM). Peroxidation produced by 200 microM iron was reduced dose dependently by the lazaroid U-74500A. The IC50 was 10 microM in AD cortex and 2.5 microM in controls. Superoxide dismutase (SOD), one of the free radical defensive enzymes, was reduced by 25 to 35% in AD frontal cortex, hippocampus and cerebellum. In other brain areas, SOD did not differ between AD and control. The activities of catalase and glutathione peroxidase were the same in AD and control samples. Endogenous iron levels were higher in AD frontal cortex (2.5 nmol/mg protein) than in controls (1.5 nmol/mg protein). Calcium uptake by AD fibroblast mitochondria is 50% lower than in controls under basal conditions. Following exposure to 200 microM iron, mitochondrial calcium uptake is increased by 58% in AD and by 38% in controls. Pretreatment with 200 microM U-74500A or 1 mM deferoxamine, prior to exposure to 200 microM iron, gave complete protection to control mitochondria but gave only partial protection to AD mitochondria. These studies indicate that in AD, both CNS and peripheral cells show increased sensitivity to oxygen free radicals. The source of this increased sensitivity has not yet been identified but could reflect either reduced free radical defenses or increased free radical formation or both. Work is underway using electron paramagnetic resonance spectrometry to determine in vivo, premortem free radical activity in AD patients.

Factors affecting the oxidation of elemental sulfur in soils

Abstract: The use of elemental sulfur (S0) to alleviate widespread S deficiencies in agricultural soils is limited by the unpredictability of its oxidation to plant available sulfate. Here we review the biological, fertilizer and soil-related factors that control S0 oxidation. Sulfur oxidation in soil is mediated primarily by microorganisms, and thus it is the size, composition and activity of the microbial community which dictate oxidation rates. Because S0 oxidation is a biological process, it is strongly influenced by factors directly affecting microbial activity including soil temperature, water potential, and aeration. In many soils these factors represent the primary constraints to S0 oxidation. Oxidation is also influenced by the effective surface area of the S exposed to microbial activity. Thus oxidation is favored by reducing the particle size and abundant populations of heterotrophic bacteria and fungi capable of oxidizing S0, thus the availability of organic substrates from residue additions or root exudates may also affect S oxidation. Previous application of S0 may increase oxidation rates in many soils, presumably by stimulating S0 oxidizing populations. The large number of factors that govern S0 oxidation account for the variability in oxidation rates among soils, climatic regions, and agronomic practices. Many of these factors are subject to agronomic control, however, and it should be possible to devise S fertilizer strategies that exploit the slow release characteristics of S0 to meet crop demands efficiently in a variety of conditions.

Oxidative Deamination of Methylamine by Semicarbazide-Sensitive Amine Oxidase Leads to Cytotoxic Damage in Endothelial Cells: Possible Consequences for Diabetes

Abstract: Methylamine was observed to be deaminated by several semicarbazide-sensitive amine oxidases, which were prepared from blood and vascular tissues of various species, including humans. Although methylamine itself is relatively nontoxic toward endothelial cells obtained from both human umbilical vein and calf pulmonary artery, it becomes very toxic in the presence of SSAO. SSAO inhibitors (i.e., MDL-72974A) effectively protected the cells from methylamine-SSAO-induced damage. The cytotoxicity seems, therefore, to be a consequence of the deamination of methylamine. Our findings suggest that formaldehyde, the deaminated product of methylamine, may be responsible for these toxic effects. Human serum, which also contains SSAO, was also capable of deaminating methylamine and causing cytotoxicity to cultured endothelial cells. Both methylamine and SSAO circulate in human blood, and their concentrations in the blood of normal healthy subjects are quite close to those required to induce cytotoxicity in tissue-cultured cells. Both SSAO activity and methylamine levels have been reported to be increased in the blood of diabetic individuals. Blood SSAO activity also has been reported to be elevated in the blood of STZ-induced diabetic rats. It is possible, therefore, that an abnormal metabolism of methylamine may be involved in endothelial injury, and that it may subsequently induce atherosclerotic plaque formation and thus be involved in the cardiovascular disorders seen in diabetes.

Regional and total body bone mineral content, bone mineral density, and total body tissue composition in children 8-16 years of age.

Abstract: Normative values for total body bone mineral content (TBBM) and total body bone mineral density (TBMD) were derived from measurements on 234 children 8–16 years of age. In addition, bone mineral content (BMC) and bone mineral density (BMD) values for selected regions of interest and soft tissue (bone free lean and fat) for the total body are presented. Bone mineral and soft tissue values were determined by dual energy X-ray absorptiometry (DXA) using a Hologic QDR-2000 in the array mode. Results of a stepwise multiple regression analysis revealed a significant correlation between bone-free lean tissue (BFLT) and BMD (r2 = 0.80) in girls. Adding age to the equation accounted for an additional 2% of the variance (P < 0.05) and height accounted for another 1% of the variance (P < 0.05). Body weight and fat tissue (FT) did not account for any additional variance. In boys BFLT correlated significantly with BMD (r2 = 0.75;P < 0.05); none of the other predictor variables accounted for additional variance. No significant differences were found in TBBM or TBMD between boys and girls at any age. There was a significant overall gender effect for only three regions of interest. Boys had greater BMC in the head region and had greater BMD in the upper limbs, but post hoc analysis revealed no significant differences for any specific age groups. Girls had greater overall BMD in the pelvis, but this difference was only significant at the 15–6-year age group. The changes in BFLT and FT over the age ranges were consistent with the growth literature.

Nonlinear evolution of tearing modes in inhomogeneous plasmas

Abstract: The nonlinear behaviour of tearing modes in a plasma with density and temperature gradients is reviewed. The effects of inhomogeneities can essentially modify the evolution of small scale islands from that predicted by Rutherford theory. Plasma gradient effects provide the mechanism for island excitation even in situations when the linear tearing mode stability parameter Delta is negative. The magnetic islands are sustained by the differential response of electron and ion components of a plasma in a fluctuating electric field. Such nonlinear magnetic islands are not related to the linear instability of drift-tearing modes. The nonlinear equations describing the evolution of the width and frequency of the rotating islands are derived. In the framework of one-fluid MHD, the general equation for a neighbouring equilibrium in a finite pressure plasma is considered. The dynamics of unstable m=2 and m=1 magnetic islands based on this equation is described. The quasilinear saturation of island growth in a finite pressure plasma leads to the bifurcation of the island type equilibrium into states without islands. A new evolution equation of m=1 islands is derived. For monotonic safety factor and temperature profiles this equation predicts saturation of the m=1 island growth.

Influence of mild hypothermia on hypoxic-ischemic brain damage in the immature rat.

Abstract: Recent studies in adult animals have shown that even small decreases in brain or core temperature ameliorate the damage resulting from hypoxic-ischemic insults. To determine the effect of minor reductions in ambient temperature either during or after an hypoxic-ischemic insult on the brain of the immature rat, 7-d-postnatal rat pups underwent unilateral common carotid artery ligation followed by exposure to hypoxia in 8% oxygen for 3 h. Control animals were maintained at 37°C during hypoxia-ischemia. Intraischemic hypothermia was induced during the insult at temperatures of 34°C and 31°C. Postischemic hypothermia was induced by exposing rat pups that underwent hypoxia at 37°C to recovering environments of 34°C and 31°C. Temperatures were recorded every 15 min from thermistor probes placed in the ipsilateral hemisphere and rectally. Neuropathologic alterations were assessed at 30 postnatal d. During hypoxia, animals became poikilothermic. Brain damage occurred in 90% of rat pups exposed to hypoxia-ischemia at 37°C. Cerebral injury significantly decreased with decreasing temperatures during hypoxia-ischemia (p < 0.01). Only 30% of rats had brain damage when exposed to hypoxia-ischemia at 34°C, and none of the rats exposed at 31°C had brain damage. In contrast, there was no difference in the extent of cerebral injury between rat pups recovered under hypothermic conditions of either 34°C or 31°C compared with those recovered at 37°C. The results indicate that reductions in temperature of 3 to 6°C have a protective effect during but not immediately after hypoxia-ischemia. These findings have important implications about the thermoregulatory control of the sick newborn infant.

A cooperative conformational change in duplex DNA induced by Zn2+ and other divalent metal ions

Abstract: Zn2+ and some other divalent metal ions bind to duplex DNA at pHs above 8 and cause a conformational change. This new structure does not bind ethidium, allowing the development of a rapid fluoresce...