Showing papers by "University of Ottawa published in 1996"

Learning in the presence of concept drift and hidden contexts

Abstract: On-line learning in domains where the target concept depends on some hidden context poses serious problems. A changing context can induce changes in the target concepts, producing what is known as concept drift. We describe a family of learning algorithms that flexibly react to concept drift and can take advantage of situations where contexts reappear. The general approach underlying all these algorithms consists of (1) keeping only a window of currently trusted examples and hypotheses; (2) storing concept descriptions and reusing them when a previous context re-appears; and (3) controlling both of these functions by a heuristic that constantly monitors the system's behavior. The paper reports on experiments that test the systems' perfomance under various conditions such as different levels of noise and different extent and rate of concept drift.

Regulation of cell adhesion and anchorage-dependent growth by a new β1-integrin-linked protein kinase

Abstract: THE interaction of cells with the extracellular matrix regulates cell shape, motility, growth, survival, differentiation and gene expression, through integrin-mediated signal transduction1–3. We used a two-hybrid screen to isolate genes encoding proteins that interact with the β1-integrin cytoplasmic domain. The most frequently isolated complementary DNA encoded a new, 59K serine/threonine protein kinase, containing four ankyrin-like repeats. We report here that this integrin-linked kinase (ILK) phosphorylated a β1-integrin cytoplasmic domain peptide in vitro and coimmunoprecipitated with β1 in lysates of mammalian cells. Endogenous ILK kinase activity was reduced in response to fibronectin. Overexpression of p59ILK disrupted epithelial cell architecture and inhibited adhesion to integrin substrates, while inducing anchorage-independent growth. We propose that ILK is a receptor-proximal protein kinase regulating integrin-mediated signal transduction.

Suppression of apoptosis in mammalian cells by NAIP and a related family of IAP genes

Abstract: DYSREGULATION of apoptosis can result in inappropriate suppression of cell death, as occurs in the development of some cancers1, or in failure to control the extent of cell death, as is believed to occur in acquired immunodeficiency and certain neurodegenera-tive disorders, such as spinal muscular atrophy (SMA). Recently, we isolated a candidate gene, encoding neuronal apoptosis inhibitor protein (NAIP)2, for SMA. This gene is homologous to two baculovirus inhibitor of apoptosis proteins3,4(Cp-IAP and Op-IAP) and is partly deleted in individuals with type I SMA. A second SMA candidate gene encoding survival motor neuron (SMN), which is contiguous with the NAIP locus on 5ql3.1, was also reported5. Here we demonstrate a NAIP-mediated inhibition of apoptosis induced by a variety of signals, and have identified three additional human complementary DNAs and a Drosophila melanogaster sequence that are also homologous to the baculovirus lAPs. The four open reading frames (ORFs) possess three baculoviral inhibition of apoptosis protein repeat (BIR) domains and a carboxy-terminal RING zinc-finger. The human iap genes have a distinct but overlapping pattern of expression in fetal and adult tissues. These proteins significantly increase the number of known apoptotic suppressors.

Apoptosis in Ischemic and Reperfused Rat Myocardium

Abstract: Apoptosis has been observed previously in hearts subjected to either continuous ischemia or ischemia followed by reperfusion. The purpose of this study was to compare the timing and extent of apoptosis in both continuously ischemic and reperfused myocardium. We show that rats subjected to continuous coronary artery occlusion display characteristic signs of apoptosis solely in the ischemic myocardium after only 2.25 hours of ischemia, as illustrated by positive in situ end labeling (ISEL) of apoptotic cardiomyocyte nuclei in tissue sections and/or the presence of DNA "ladders" in agarose gels. In contrast, reperfusion after a 45-minute occlusion accelerated the process, with apoptosis becoming evident solely in the reperfused myocardium after only 1 hour of reperfusion. ISEL and DNA ladder intensity increased with duration of ischemia or reperfusion. The volume of myocardium in which ISEL was observed was smaller in the reperfused hearts, and the ISEL-stained nuclei represented 23% and 33% of the total nuclei in the reperfused and permanently occluded myocardium, respectively. Therefore, the data suggest that reperfusion lowers the extent of apoptosis in ischemic myocardium but, paradoxically, accelerates the residual apoptosis, possibly because of reperfusion injury. A large accumulation of neutrophils was observed in both the permanently occluded and reperfused myocardium, suggesting that the inflammatory response may have contributed to apoptosis in both settings. This study therefore confirms that both ischemic and reperfused rat myocardium can undergo apoptotic cell death. However, the data suggest that although reperfusion lowers the number of myocytes undergoing apoptosis, it accelerates apoptosis in the nonsalvageable cells.

A full genome search in multiple sclerosis

Abstract: The aetiology of multiple sclerosis (MS) is uncertain. There is strong circumstantial evidence to indicate it is an autoimmune complex trait. Risks for first degree relatives are increased some 20 fold over the general population. Twin studies have shown monozygotic concordance rates of 25-30% compared to 4% for dizygotic twins and siblings. Studies of adoptees and half sibs show that familial risk is determined by genes, but environmental factors strongly influence observed geographic differences. Studies of candidate genes have been largely unrewarding. We report a genome search using 257 microsatellite markers with average spacing of 15.2 cM in 100 sibling pairs (Table 1, data set 1 - DS1). A locus of lambda>3 was excluded from 88% of the genome. Five loci with maximum lod scores (MLS) of >1 were identified on chromosomes 2, 3, 5, 11 and X. Two additional data sets containing 44 (Table 1, DS2) and 78 sib pairs (Table 1, DS3) respectively, were used to further evaluate the HLA region on 6p21 and a locus on chromosome 5 with an MLS of 4.24. Markers within 6p21 gave MLS of 0.65 (non-significant, NS). However, D6S461, just outside the HLA region, showed significant evidence for linkage disequilibrium by the transmission disequilibrium test (TDT), in all three data sets (for DS1 chi2 = 10.8, adjusted P < 0.01)(DS2 and DS3 chi2 = 10.9, P < 0.0005), suggesting a modest susceptibility locus in this region. On chromosome 5p results from all three data sets (222 sib pairs) yielded a multipoint MLS of 1.6. The results support genetic epidemiological evidence that several genes interact epistatically to determine heritable susceptibility.

A randomized trial to assess the efficacy of surgery in addition to radiotherapy in patients with a single cerebral metastasis

Abstract: BACKGROUND Cerebral metastasis is a common oncologic problem that occurs in 15–30% of cancer patients; approximately half such metastases are single. Previous retrospective studies and two randomized trials reported that the addition of surgical extirpation prior to radiation therapy increased survival, neurologic function, and quality of life compared with radiation alone in patients with a single brain metastasis. METHODS A randomized controlled trial was conducted in which patients with a single brain metastasis were allocated to undergo radiation alone or surgery plus radiation. Radiation consisted of 3000 centigray to the whole brain in 10 fractions. RESULTS Forty-three patients received radiation alone and 41 patients surgery plus radiation. All but two of the study patients died. No difference in survival was detected between the groups; the median survival for the radiation group was 6.3 months (95% confidence interval, 3–11.4) compared with 5.6 months for the surgery plus radiation group (95% confidence interval, 3.9–7.2) (P = 0.24). Most patients died within the first year (69.8% in the radiation arm vs. 87.8% in the surgery plus radiation arm). There were no significant differences in the 30-day mortality, morbidity, or causes of death. Extracranial metastases was an important predictor of mortality (relative risk, 2.3). The mean proportion of days that the Karnofsky performance status was; ce70% did not differ between the 2 groups. CONCLUSIONS This trial failed to demonstrate that the addition of surgery to radiation therapy improved outcome of patients with a single brain metastasis. Thus, the efficacy of surgery plus radiation compared with radiation alone needs to be addressed by further clinical trials and/or a meta-analysis. Cancer 1996;78:1470-6.

Measuring Self-Concept Across the Life Span: Issues and Instrumentation

Abstract: Measuring Self-Concept: The Conceptual Issues Measuring Self-Concept: The Psychometric Issues Search for and Selection of Self-Concept Measures Measures of Self-Concept for Young Children: Measurement of General Self-Concept: Joseph Pre-School and Primary Self-Concept Screening Test Measurement of Multidimensional Self-Concepts: The Pictoral Scale of Perceived Competence and Social Acceptance Measures of Self-Concept for Preadolescents: Measurement of Specific Self-Concepts: Academic Self Description Questionnaire I Perception of Ability Scale for Students Measurement of Multidimensional Self-Concepts Multidimensional Self-Concept Scale Pier-Harris Children's Self-Concept Scale Self Description Questionnaire I Self-Perception Profile for Children Measures of Self-Concept for Adolescents: Measurement of Specific Self-Concepts: Academic Self Description Questionnaire II Dimensions of Self-Concept Physical Self Description Questionnaire Self-Esteem Scale Measurement of Multidimensional Self-Concepts: Multidimensional Self-Concept Scale Pier-Harris Children's Self-Concept Scale Self Description Questionnaire II Self-Perception Profile for Adolescents Tennessee Self-Concept Scale Measures of Self-Concept for Adults: Measurement of Specific Self-Concepts: Dimension of Self-Concept Body Esteem Scale Physical Self-Perception Profile Self-Esteem Scale Measurement of Multidimensional Self-Concepts: Adult Self-Perception Profile Self Description Questionnaire III Self-Perception Profile for College Students Tennessee Self-Concept Scale The Self-Perception Genesis Method Measures of Self-Concept for Special Populations The Learning Disabled Self-Perception Profile for Learning Disabled Students Perception of Ability Scale for Students The Hearing Impaired: Self-Concept Scale for the Hearing-Impaired Tennessee Self-Concept Scale (Revised) Self-Concept Measurement: State-of-the-Art and Future Directions Arts Self-Perception Inventory Music Self-Perception Inventory Reading Self-Concept Scale.

Values and Organizational Structure

Abstract: Recent developments in organizational theory emphasize the need to examine the relationship between organizational values and structure. Values underpin organizational structure and give it meaning. Drawing on concepts of culture, institutional theory, and archetypes, this paper tests hypotheses on the value/structure relationship. The sample used for the study was a set of Canadian amateur sport organizations undergoing institutional change. This test shows that there is a fit between elite values and the nature of the institutionally prescribed organizational archetype.

Assessing the quality of randomized controlled trials. Current issues and future directions

Abstract: Assessing the quality of randomized controlled trials is a relatively new and important development. Three approaches have been developed: component, checklist, and scale assessment. Component approaches evaluate selected aspects of trials, such as masking. Checklists and scales involve lists of items thought to be integral to study quality. Scales, unlike the other methods, provide a summary numeric score of quality, which can be formally incorporated into a systematic review. Most scales to date have not been developed with sufficient rigor, however. Empirical evidence indicates that differences in scale development can lead to important differences in quality assessment. Several methods for including quality scores in systematic reviews have been proposed, but since little empirical evidence supports any given method, results must be interpreted cautiously. Future efforts may be best focused on gathering more empirical evidence to identify trial characteristics directly related to bias in the estimates of intervention effects and on improving the way in which trials are reported.

Mechanical and neuroendocrine regulation of the endocrine heart

Abstract: The cardiac natriuretic peptides (NP) -- atrial natriuretic factor (ANF) and brain natriuretic peptide (BNP) -- are polypeptide hormones produced by cardiocytes in the atria of mammals. ANF and BNP are continuously released from the heart, but appropriate mechanical or neuroendocrine stimuli increase their rate of release with or without a concomitant increase in synthesis. The results of our investigations lead us to propose that the endocrine response of the heart to pressure or volume load varies in relation to whether the challenge is acute, subacute or chronic. The acute response to stretch is based on a phenomenon referred to as "stretch-secretion coupling" which results in enhanced secretion of NP stored in the atria. NP release following stretch is made at the expense of a depletable NP pool with no apparent effect on synthesis. The stimulation of NP production that is seen during mineralcorticoid escape is referred to as "subacute" and is characterized by stimulation of atrial ANF and BNP gene transcription secondary to volume overload in which plasma ANF, but not plasma BNP, is significantly elevated. With chronic stimulation, as seen in DOCA-salt treatment at the hypertensive stage, activation of the cardiac fetal program in ventricle is seen together with a stimulation of ANF and BNP production in both atria and ventricles. However, the activation of NP gene expression in the atria is not necessarily associated with fetal isogene expression even though the ventricular hypertrophic process is characterized by the expression of fetal isogenes, including ANF and BNP, that are normally expressed in the fetal ventricle. It seems likely that the acute stimulation of NP release is based on an electromechanical coupling. However, protracted stimulation of release is seen in situations in which profound neuroendocrine changes have taken place, thus suggesting that the primary stimulus for chronically enhanced NP gene expression and NP release is based on changes in the hormonal environment of the atrial cardiocyte. It is concluded that the endocrine heart responds to changes in hemodynamic load with specific changes in translational, post-translational and storage processes for ANF and BNP following acute or chronic stimulation. As a result, plasma levels of ANF and BNP may be used as indicators of the degree of atrial hemodynamic overload and ventricular hypertrophy, respectively. It may be advanced that the endocrine heart differentiates and responds to different hemodynamic challenges in either acute or chronic conditions with specific changes in transcription, translation, post-translational processing, storage, and release of ANF and BNP. We propose that this differentiation is part of the reason for the heart to produce two hormones with similar spectra of activity. This paradigm warrants further investigation.

Oscillatory zoning in minerals; a common phenomenon

Abstract: Crystals characterized by oscillatory zoning show evidence for a quasi-cyclic alternation in the chemical composition of discrete growth-shells from tens of nanometers to tens of micrometers in thickness. Oscillatory zoning is most commonly observed and studied in crystals of magmatic plagioclase, but sensitive imaging techniques (e.g., Nomarski interference contrast microscopy, cathodoluminescence, back-scattered electron imaging, X-ray topographs) reveal its presence in many other minerals. Through the application of these techniques and an exhaustive review of the literature, oscillatory zoning is shown to occur in at least 75 rock-forming and accessory minerals comprising most major mineral classes: silicates (hydrous and anhydrous), sulfides, oxides, halides, carbonates, phosphates, and sulfates. Such mineral zoning is a common but often well-concealed phenomenon in magmatic rocks (particularly alkaline ones), hydrothermally altered rocks, mineralized rocks, and carbonate sequences. Mechanisms of oscillatory zoning are discussed, including the less-studied effects of adsorption and elastic stress in near-surface growth-layers. Its "non-equilibrium chemistry" makes oscillatory zoning a rich subject for further research.

Factors regulating phytoplankton and zooplankton biomass in temperate rivers

Abstract: By measuring Chl a, zooplankton biomass, nutrient concentrations, and water residence time in 31 rivers in eastern Canada, we tested the following hypotheses: Chl a is positively related to nutrient concentrations and water residence time, and zooplankton biomass is positively related to Chl a and water residence time. Chl a ranged from 1.8 to 27.6 μg liter -1 , total phosphorus (TP) from 7.3 3 to 212.3 μg liter -1 and water residence time from 3.3 to 19.4 d. There was a positive relationship between Chl a and TP (R 2 = 0.76) and no relationship between Chl a and residence time. In contrast, zooplankton biomass was positively related to water residence time (R 2 = 0.33). There was only a weak positive relationship between Chl a and zooplankton biomass. Mean river zooplankton biomass was low (11.3 μg liter -1 dry mass) compared to lakes of similar Chl a concentration.

Multistability and delayed recurrent loops.

Abstract: Multistable dynamical systems have important applications as pattern recognition and memory storage devices. Conditions under which time-delayed recurrent loops of spiking neurons exhibit multistability are presented. Our results are illustrated on both a simple integrate-and-fire neuron and a Hodgkin-Huxley-type neuron, whose recurrent inputs are delayed versions of their output spike trains. Two kinds of multistability with respect to initial spiking functions are found, depending on whether the neuron is excitable or repetitively firing in the absence of feedback.

Low-dose ionizing radiation decreases the frequency of neoplastic transformation to a level below the spontaneous rate in C3H 10T1/2 cells.

Abstract: We have previously shown that chronic exposure of plateau-phase C3H 10 T1/2 cells to (60)Co gamma radiation at doses as low as 10 cGy protected the cells against neoplastic transformation by a subsequent large acute radiation exposure. We have also shown that this induced resistance to neoplastic transformation correlated with an increased ability to repair radiation-induced chromosome breaks. We now show that a single exposure of quiescent cells to doses as low as 0.1 cGy also reduces the risk of neoplastic transformation, from the spontaneous level to a rate three- to fourfold below that level. Higher doses, up to 10 cGy at the same dose rate (0.24 cGy/min), did not reduce the neoplastic transformation frequency further. This protective effect was seen only in irradiated cells that were allowed to incubate at 37 degrees C before release from contact inhibition. Cells released into low-density subcultures immediately after irradiation had unchanged neoplastic transformation frequencies. These results demonstrate that low or chronic exposure to radiation can induce processes which protect the cell against naturally occurring as well as radiation-induced alterations that lead to cell transformation. If similar processes are induced in human cells, the results also suggest that a single low dose, at background or occupational exposure levels, may in some circumstances reduce rather than increase cancer risk, a conclusion inconsistent with the linear no-threshold model of cancer risk from radiation.

Antioxidant compound responses to chilling stress in differentially sensitive inbred maize lines

Abstract: Chilling temperatures increase the amounts of potentially lethal toxic oxygen compounds present within plants. These toxic oxygen compounds can be scavenged by antioxidant compounds such as ascorbate and β-carotene. Three developmental stages (first, third and fifth leaf) of four inbred lines of maize (Zea mays L.) exhibiting differential sensitivity to chilling were examined in order to determine if the chilling-sensitive line had lower concentrations of antioxidant compounds than did the tolerant lines. Plants were exposed to one of three treatments: (1) control (25°C constant), (2) control treatment plus a short-term chilling exposure of 11°C one day prior to harvesting, and (3) long-term (11°C constant) chilling exposure. Total ascorbate, total glutathione, β-carotene, α-tocopherol and chlorophyll contents were quantified, and ratios of dehydroascorbate/ascorbate and reduced/oxidized glutathione were determined. Lower concentrations of β-carotene were found in the chilling-sensitive relative to those in the chilling-tolerant lines for the first-leaf stage under both short- and long-term chilling treatments. Concentrations of total ascorbate and glutathione and β-carotene in the chilling-sensitive line increased as the chilling treatment progressed and as the plants developed until they ultimately became either significantly higher or no different relative to the tolerant lines. Results suggest that this sensitive line became less sensitive to chilling-induced oxidative stress with development.

Language, Identity, and Adjustment The Role of Linguistic Self-Confidence in the Acculturation Process

Abstract: Research in both cross-cultural psychology and the social psychology of language has examined the changes in identity and language behavior that occur when two ethnolinguistic groups come into contact. This study attempted to integrate these two fields of inquiry through an investigation of the relations between identity, interethnic contact, linguistic self-confidence, and psychological adjustment in 179 Chinese university students. The findings indicated that exclusive identification with either the first or second language group was the most commonly endorsed identity. Correlational and path analyses of the relations between interethnic contact, self-confidence in using the English and Chinese languages, Chinese and Canadian identities, and adjustment variables supported the proposed model in which communication variables mediate the influence of interethnic contact on identity and adjustment. The results are interpreted within the context of current formulations of acculturation and intercultural comm...

Individual transferable quotas: theory and practice

Abstract: The paper examines the theory and practice of individual transferable quotas (ITQs) in fisheries. Using the experience of several countries, a number of ITQ programmes are examined with respect to fisher compliance and their effect upon economic efficiency, employment, the harvesting shares of fishers, cost recovery and rent capture.1

BDNF and NT‐3, but not NGF, Prevent Axotomy‐induced Death of Rat Corticospinal Neurons In Vivo

Abstract: Brain-derived neurotrophic factor (BDNF) and neurotrophin-3 (NT-3) have been identified as survival factors for adult axotomized rat corticospinal neurons (CSN) in vivo. Axotomy of corticospinal neurons at the level of the internal capsule induced death of 46% of the CSN within the first week after axotomy. The surviving population of CSN displayed severe atrophy with mean cross-sectional area 49% of their unlesioned contralateral counterparts 7 days after axotomy. Using in situ hybridization to assess the expression of the receptors for the family of neurotrophins, we found trkB and trkC but not trkA mRNA expression in CSN. Intraparenchymal application of BDNF or NT-3 at doses of 12 microg/day for 7 days via an osmotic minipump fully prevented the axotomy-induced death of CSN. Interestingly, no neuronal atrophy was seen after BDNF application while NT-3 had only a partial effect on the size of the axotomized CSN. Nerve growth factor did not prevent death or cell atrophy, consistent with lack of trkA mRNA expression in these neurons. These findings show that BDNF and NT-3 are survival factors for adult rat CSN in vivo, and may contribute to the development of therapeutic strategies aiming at the prevention of CSN degeneration in human motor neuron diseases.

The palliative care quiz for nursing (PCQN): the development of an instrument to measure nurses' knowledge of palliative care

Abstract: This paper descrihes the process and outcomes of a study to develop a tool to measure nurses' knowledge of palhative care The development of the palhative care quiz for nursing (PCQN) entailed the convening of an advisory committee, a wide process of consultation, the development of a conceptual firamework, determination of format, generating of items and pre-testing, piloting and further testing of the quiz The PCQN is a 20-item true, false and 'I don't know' test of knowledge that is easily administered and has utility for assessing knowledge, stimulating discussion and identifying misconceptions ahout palliative care nursing

Prospective validation of a decision rule for the use of radiography in acute knee injuries.

Abstract: Objective. —To validate a previously derived decision rule for the use of radiography in patients with acute knee injury. Design. —Prospectively administered survey. Setting. —Emergency departments of two university hospitals serving adults. Patients. —Convenience sample of 1096 of 1251 eligible adults with acute knee injuries; 124 patients were examined by two physicians. Main Outcome Measures. —Attending emergency physicians assessed each patient for standardized clinical variables and determined the need for radiography according to the decision rule. Patients who did not have radiography underwent a structured telephone interview at day 14 to determine the possibility of a fracture. The rule was assessed for ability to correctly identify the criterion standard, fracture of the knee. An attempt was made to refine the rule by means of univariate and recursive partitioning analyses. Results. —The decision rule had a sensitivity of 1.0 (95% confidence interval [CI], 0.94 to 1.0) for identifying 63 clinically important fractures. Physicians correctly interpreted the rule in 96% of cases, and the κ value for interpretation was 0.77 (95% CI, 0.65 to 0.89). The potential relative reduction in use of radiography was estimated to be 28%. The probability of fracture, if the decision rule were "negative," is estimated to be 0% (95% CI, 0% to 0.4%). Attempts to refine the rule led to a model with improved specificity but with an unacceptable loss of sensitivity. Conclusion. —Prospective validation has shown this decision rule to be 100% sensitive for identifying fractures of the knee, to be reliable and acceptable, and to have the potential to allow physicians to reduce the use of radiography in patients with acute knee injury. ( JAMA . 1996;275:611-615)

Electrical percolation phenomena in cement composites containing conductive fibres

Abstract: Electrical conductivity measurements on cement composites containing carbon fibres or steel fibres were conducted. Percolation phenomena associated with electrical conductivity were observed. The conductivity of the systems studied increased by several orders of magnitude, at a specific concentration of conductive fibre, i.e. the percolation concentration. The percolation concentration is shown to be dependent on conductive fibre geometry instead of system composition. The results provide an important guide for the manufacture of conductive cement composites containing conductive fibres.