Showing papers by "Dalhousie University published in 1994"
1,000 citations
TL;DR: This study demonstrates that fatigue is a very prevalent and severe problem in MS, fatigue impact cannot be predicted by clinical measures of neurologic impairment, and fatigue has a significant effect on the mental health and general health status of MS patients.
Abstract: Although fatigue is recognized as a symptom of MS, there have been insufficient methods for evaluating this symptom We administered the Fatigue Impact Scale to 85 MS patients and 20 hypertensive patients Neurologic impairment, mental health, and general health status were also assessed MS patients reported significantly higher fatigue impact than hypertensive patients Most MS patients reported fatigue as either their worst (14%), or one of their worst (55%) symptoms Disease classification and neurologic impairment had little bearing on Fatigue Impact Scale scores in the MS sample The best predictive models for mental health and general health status in the MS sample both included the Fatigue Impact Scale as a significant factor This study demonstrates that: 1) fatigue is a very prevalent and severe problem in MS, 2) fatigue impact cannot be predicted by clinical measures of neurologic impairment, 3) fatigue has a significant effect on the mental health and general health status of MS patients
921 citations
Journal Article•
TL;DR: Existing definitions of frailty are reviewed and an alternative working definition is examined to discover if this understanding offers any useful insights.
Abstract: T he terms "frail" and "frailty" are now part of the language of geriatric medicine and gerontology.'` Characterizing the physiologic basis of frailty has been described as one of the most important research endeavours in medical gerontology.2'5 However, "frail" and "frailty" are often undefined.5 As the concept of frailty is increasingly invoked (a MEDLINE search revealed that citations with the MeSH term "frailty" increased from 13 in 1986 to 80 in the first 9 months of 1992), it is important to understand what is meant by the term and to discover if this understanding offers any useful insights. In this article we review existing definitions of frailty and examine an alternative working definition that en-
597 citations
TL;DR: Three-dimensional maps representing the local atomic densities are presented for several water models and provide a picture of the short-range order in liquid water which reveals specific details of its local structure that are important in the understanding of its properties.
Abstract: Liquid state structure has traditionally been characterized with the radial distribution functions between atoms. Although these functions are routinely available from x-ray diffraction and neutron scattering experiments or from computer simulations, they cannot be interpreted unambiguously to provide the spatial order in a molecular liquid. A direct approach to determining the spatial structure in the liquid state is demonstrated here. Three-dimensional maps representing the local atomic densities are presented for several water models. These spatial maps provide a picture of the short-range order in liquid water which reveals specific details of its local structure that are important in the understanding of its properties.
483 citations
TL;DR: An event-related brain potential reflecting the acoustic-phonetic process in the phonological stage of word processing was recorded to the terminal words of spoken sentences and the independence of this response from the ERP component known to be sensitive to semantic violations (N400) was demonstrated.
Abstract: An event-related brain potential (ERP) reflecting the acoustic-phonetic process in the phonological stage of word processing was recorded to the terminal words of spoken sentences. The peak latency of this negative-going response occurred between 270 and 300 msec after the onset of the terminal word. The independence of this response (the phonological mismatch negativity, PMN) from the ERP component known to be sensitive to semantic violations (N400) was demonstrated by manipulating sentence endings so that phonemic and semantic violations occurred together or separately. Four conditions used sentences that ended with (1) the highest Cloze probability word (e.g., “The piano was out of tune.”), (2) a word having the same initial phoneme of the highest Cloze probability word but that was, in fact, semantically anomalous (e.g., “The gambler had a streak of bad luggage.”), (3) a word having an initial phoneme different from that of the highest Cloze probability word but that was, in fact, semantically appropriate (e.g., “Don caught the ball with his glove.”), or (4) a word that was semantically anomalous and, therefore, had an initial phoneme that was totally unexpected given the sentence's context (e.g., “The dog chased our cat up the queen”). Neither the PMN nor the N400 was found in the first condition. Only an N400 was observed in the second condition while only a PMN was seen in the third. Both responses were elicited in the last condition. Finally, a delayed N400 occurred to semantic violations in the second condition where the initial phoneme was identical to that of the highest Cloze probability ending. Results are discussed with regard to the Cohort model of word recognition.
447 citations
TL;DR: While failure rates decreased with increasing implant length, failure rates for each implant length were consistently higher in smokers than in nonsmokers.
Abstract: This paper reviews the outcome of 2,194 Branemark implants placed in 540 patients by one of the authors over a 6-year period. The overall failure rate of 5.92% is consistent with other studies; however, when patients were subdivided into smokers and nonsmokers, it was found that a significantly greater percentage of failures occurred in smokers (11.28%) than in nonsmokers (4.76%) (P < .001). These differences were significant for all areas except the posterior mandible. While failure rates decreased with increasing implant length, failure rates for each implant length were consistently higher in smokers than in nonsmokers. The possible mechanisms of failure in smokers are discussed, and a protocol for cessation of smoking around the time of surgery is proposed.
417 citations
TL;DR: Although treatment was not associated with any improvement in symptoms, ursodeoxycholic acid therapy caused the bilirubin to fall significantly within the first 3 mo of therapy (p<0.001), which led to an improvement in serum markers of cholestasis.
414 citations
TL;DR: Direct evidence is presented that sex and mtDNA inheritance are coupled in mussels of the genus Mytilus, establishing a newly discovered type of cytoplasmic DNA transmission.
Abstract: In animals, mitochondrial DNA (mtDNA) inheritance is predominantly maternal. In a few cases incidental transmission of paternal mtDNA was observed and estimated to account for only 10(-4)-10(-3) of an individual's mtDNA content. In contrast, biparental inheritance is common in mussels of the genus Mytilus. Here we present direct evidence that sex and mtDNA inheritance are coupled in Mytilus. Females inherit mtDNA only from their mother, but they transmit it to both daughters and sons. Males inherit mtDNA from both parents, but they transmit to sons only the mtDNA they inherited from their father. In pair matings, this mtDNA inheritance pattern is associated with a strong sex-ratio bias. These findings establish a newly discovered type of cytoplasmic DNA transmission. We also present evidence that the phenomenon breaks down in interspecific hybrids.
400 citations
TL;DR: In this article, a surface processes model of large-scale erosional denudation is used to establish the controls on the evolution of a model escarpment that is related to the rifting of a continent.
Abstract: Experiments with a surface processes model of large-scale (1-1000 km) long-term (1-100 my) erosional denudation are used to establish the controls on the evolution of a model escarpment that is related to the rifting of a continent The mdoel describes changes in topographic form as a result of sumultaneous short- and long-range mass transport representing hillslope (diffusive) processes and fluvial transport (advection), repsectively Fluvial entrainment is modeled as a first-order kinetic reaction which reflects the erodibility of the substrate, and therefore the fluvial system is not necessarily carrying at capacity One dimensional and planform models demonstrate that the principal controls on the evolution of an initially steep model escarpment are (1) antecedent topography/drainage; (2) the timesale (or equivalently a length scale) in the fluvial entrainment reaction; (3) the flexural response of the lithosphere to denudation; and (4) the relative efficiencies of the short- and long-range transport processes When rainfall and substrate lithology are uniform, a significant amount of discharge draining over the escarpment top causes it to degrade Only when the top of the model escarpment coincides with a drainage divide can escarpment retreat occur for these conditions An additional requirement for retreat of a model escarpment without decline is a long reaction time scale for fluvial entrainment This corresponds to a substrate that is hard to detach by flucial erosion, and therefore to fluvial erosion that is not transport limited Coninuous backtilting of an escarpment due ot flexural isostatic uplift in response to denudational unloading helps maintain the scarp top as a divide It is essntial if the escarpment gradient is to be preserved during retreat in a uniform lithology Low flexural rigidieties propote steep and slowly retreating escarpments For given rainfall and substrate conditions, the morphology of a retraeating model escarpment is determined by the ratio of hte short-range diffusive and long range advective transport efficiencies A low ration (which is interpreted to correspond to a more humid, temperate climate) produces a convex upper slope, and concave lower slope morphology and only major escarpments are predicted to preserve a high scarp gradient Lithological contrasts in hte model produce more complex morphologies and predict the formation of scarps crowned by an erosionaly resistant caprock However, resistant caprocks are not an essential requirement for model scarps to retreat We conclude that the inferred controls and model behavior are both consistent with the present-day morphology of rifted continental margins and with modern conceptual models of landscape evolution
370 citations
TL;DR: The evidence for an imitative deficit in autism and for the possible role of deficiencies in the representation of actions are considered and an argument is developed for the claim that the imitation problem is diagnostic of a basic information-processing rather than a social dysfunction.
Abstract: This article considers the evidence for an imitative deficit in autism and for the possible role of deficiencies in the representation of actions. An argument is developed for the claim that the imitation problem is diagnostic of a basic information-processing rather than a social dysfunction. Reviews are offered of the empirical literature on gestural imitation in autism (and other developmental disorders) and the more anecdotal evidence for problems in the domain of action development in autism. An account that may help to integrate these areas is suggested, as are directions for future research.
362 citations
TL;DR: In this article, the authors identify the theoretical assumptions that this "commonsense view" entails and argue against this view of these behaviors by suggesting that the phenomena are entirely compatible with an account which does not attribute to the infant an understanding that others have psychological relations to objects or that self and others are equivalent in their potential for such psychological relations.
TL;DR: Surgical denervation of the chromaffin tissue, and the inhibition of cortisol synthesis by implantation of cortisol-laden pellets within the forebrain nuceli or by the administration of metopirone, hold the most promise for eliminating the release of catecholamines and cortisol respectively.
Abstract: We have attempted to critically review the methods used to experimentally controlin vivo levels of circulating stress hormones (cortisol, epinephrine, norepinephrine) in fish, and to suggest which of them are most suitable for future studies (Table 4). From the discussion it is evident that there are numerous choices for achieving elevated hormone concentrations. However, the method chosen should match the temporal pattern and the degree of hormone elevation that is concordant with the type of stress one is trying to simulate; in other words be physiological. With regard to inhibition of hormone release as a tool forin vivo physiological investigations, it appears that few of these methods are suitable for widespread usage. However, surgical denervation of the chromaffin tissue, and the inhibition of cortisol synthesis by implantation of cortisol-laden pellets within the forebrain nuceli or by the administration of metopirone, hold the most promise for eliminating the release of catecholamines and cortisol respectively.
TL;DR: The general utility of microsatellite VNTRs to fisheries and aquaculture research is highlighted, and the merits of a particular class of nuclear markers, variable numbers of tandem repeats (VNTR) loci are argued.
Abstract: In the four accompanying reviews of this issue (Carvalho and Hauser, 1994; Ferguson, 1994; Park and Moran, 1994; Ward and Grewe, 1994), the authors have provided a thorough assessment of the molecular basis and utility of various genetic markers currently available to researchers in aquaculture and fisheries research. These reviews emphasize the pre-eminent roles of isozymes and mitochondrial DNA (mtDNA) in fisheries genetic research, with a rather more limited discussion of nuclear DNA markers and technologies. This emphasis is understandable, given the large volume of data and the established technology that prevail for allozymes, and to a lesser, but still significant extent, mtDNA. In this article we look to the future, and in doing so, take a more radical view. Here we argue the merits of a particular class of nuclear markers, variable numbers of tandem repeats (VNTR) loci. VNTRs themselves comprise two (probably related) classes of loci, the minisatellites and microsatellites (Wright, 1993, 1994; Park and Moran, 1994). Our intent in this commentary is to highlight the general utility of microsatellite VNTRs to fisheries and aquaculture research. In expounding our view, we draw primarily on the experience we have gained with microsatellites in the Marine Gene Probe Laboratory (MGPL) at Dalhousie University.
TL;DR: A review of approaches to detecting cytokines in normal and diseased tissue and in various general contexts of epithelial cell function to establish cytokine synthesis by different epithelia is examined.
Abstract: The epithelium has long been regarded as a passive barrier intended to protect the underlying tissues. Many regulatory signals, including cytokines, that control epithelial cell proliferation and differentiation and cell function during inflammation were thought to be nonepithelial-derived. Now there is a growing appreciation that epithelial cells provide some of the impetus for their own growth and differentiation, and may also regulate the function of other cells through the elaboration of certain cytokines. Moreover, because epithelial cells serve as the interface between the organism and environment, they are in a position to signal changes in the environment. It is now clear that epithelial cells respond to injury or infection with cytokine secretion. Various approaches to detecting cytokines in normal and diseased tissue have been undertaken during the past few years to establish cytokine synthesis by different epithelial. This review will examine these recent investigations in various general contexts of epithelial cell function.
TL;DR: A review of explanations for natural succession suggests a strong, common basis for theoretical understanding, but also suggests that several well known models are incomplete as explanations of succession as mentioned in this paper, since numerous aspects of historical and environmental circumstances will impinge on the process in a unique manner.
Abstract: Critical review of explanations for patterns of natural succession suggests a strong, common basis for theoretical understanding, but also suggests that several well known models are incomplete as explanations of succession. A universal, general cause for succession is unlikely, since numerous aspects of historical and environmental circumstances will impinge on the process in a unique manner. However, after disturbance, occupation of a site by any species causes changes in the conditions at the site. Sorting of species may result, since different species are adapted to different regions of environmental gradients. Such sorting can generate several patterns of species abundance in time, but commonly results in sequential replacements of species adapted to the varying conditions. This may be due to constraints on species' strategies, or life history traits, placed by the limited resources available to the organism. These constraints often result in inverse correlation between traits which confer success during early and late stages of succession. Facilitatory or inhibitory effects of species on each other are best understood in terms of these life history interactions, perhaps as restrictions on, or as moderation of, these processes. Strong support for the importance of correlations in life history traits stems from comparisons of simulated succession with and without these correlations. These simulations are reviewed in some detail, and followed by brief reviews of other prominent models for succession. Several aspects of the confusion and controversies in the successional literature are then discussed, with a view to a more optimistic synthesis and direction for successional ecology.
01 Jan 1994
TL;DR: A three‐dimensional description of the distribution and organization of the canine intrinsic cardiac nervous system was developed in order to characterize its full extent physiologically.
Abstract: Background: A three-dimensional description of the distribution and organization of the canine intrinsic cardiac nervous system was developed in order to characterize its full extent physiologically.
Methods: The anatomy of the canine intrinsic cardiac nervous system was investigated in 67 mongrel dogs by means of visulization following methylene blue staining as well as by light and electron microscopic analyses.
Results: Collections of ganglia associated with nerves, i.e., ganglionated plexuses, were identified in specific locations in epicardial fat and cardiac tissue. Distinct epicardial ganglionated plexuses were consistently observed in four atrial and three ventricular regions, with occasional neurons being located throughout atrial and ventricular tissues. One ganglionated plexus extended from the ventral to dorsal surfaces of the right atrium. Another ganglionated plexus, with three components, was identified in fat on the left atrial ventral surface. A ganglionated plexus was located on the mid-dorsal surface of the two atria, extending ventrally in the interatrial septum. A fourth atrial ganglionated plexus was located at the origin of the inferior vena cava extending to the dorsal caudal surface of the two atria. On the cranial surface of the ventricles a ganglionated plexus that surrounded the aortic root was identified. This plexus extended to the right and left main coronary arteries and origins of the ventral descending and circumflex coronary arteries. Two other ventricular ganglionated plexuses were identified adjacent to the origins of the right and left marginal coronary arteries. Intrinsic cardiac ganglia ranged in size from ones comprising one or a few neurons along the course of a nerve to ones as large as 1 × 3 mm estimated to contain a few hundred neurons. Intrinsic cardiac neuronal somata varied in size and shape, up to 36% containing multiple nucleoli. Electron microscopic examination demonstrated typical autonomic neurons and satellite cells in intrinsic cardiac ganglia. Many of their axon profiles contained large numbers of clear, round, and dense-core vesicles. Asymmetrical axodendritic synapses were common.
Conclusions: The canine intrinsic cardiac nervous system contains a variety of neurons interconnected via plexuses of nerves, the distribution of which is wider than previously assumed. © 1994 Wiley-Liss, Inc.
TL;DR: Copyright to the above-listed unpublished and original article submitted by the above author(s), the abstract forming part thereof, and any subsequent errata is hereby transferred to the American Physical Society (APS) for the full term thereof throughout the world, subject to the Author Rights.
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TL;DR: In this paper, the authors explain the close association of chromitites, regardless of compositions, with dunites and harzburgites can be explained by interaction between melts and depleted lherzolites in the upper mantle, where continuous reaction between melt and wallrock modifies the compositions of the magmas towards the precipitation of chromite alone under upper mantle conditions.
Abstract: High-Cr and high-Al podiform chromitites are derived from melts formed by high and low degrees of partial melting in the upper mantle, respectively. The close association of the chromitites, regardless of compositions, with dunites and harzburgites can be explained by interaction between melts and harzburgites or depleted lherzolites in the upper mantle. Continuous reaction between melt and wallrock modifies the compositions of the magmas towards the precipitation of chromite alone under upper mantle conditions. The modified magmas would have higher silica and lower magnesia and would be extracted into the crust or erupted, leaving chromite pods in situ with dunite rinds that grade to harzburgites or lherzolites.
01 Jan 1994
TL;DR: In this paper, a nonlinear regression of existing data with a power law produces a statistically significant correlation between biological mixing coefficient, D B, and burial velocity, ω, with a worldwide mean of 98 ± 45 cm.
TL;DR: The evidence for an increase as well as a decrease in aggression during domestication in fish is critically evaluated, the various mechanisms by which competitive behavior in fish can affect individual growth rates under natural or artificial conditions are described, and the direction and intensity of any phenotypic change in food-related agonistic behavior following natural orificial selection for rapid growth will depend on the relationship between agonism and access to food.
Journal Article•
TL;DR: There was strong evidence that H. pylori is the main cause of duodenal ulcers not induced by nonsteroidal anti-inflammatory drugs, but all of Koch's postulates were not fulfilled, and a moderate relation between such infection and gastric cancer.
Abstract: OBJECTIVE: To evaluate current evidence for a causal relation between Helicobacter pylori infection and gastritis, duodenal ulcer, gastric cancer and nonulcer dyspepsia. DATA SOURCES: A MEDLINE search for articles published in English between January 1983 and December 1992 with the use of MeSH terms Helicobacter pylori, gastritis, duodenal ulcer, gastric cancer, dyspepsia and clinical trial; abstracts were excluded. Six journals and Current Contents were searched manually for pertinent articles published in that time frame. STUDY SELECTION: Original studies with at least 25 patients, case reports and reviews that examined the relation between H. pylori and the four gastrointestinal disorders; 350 articles were on gastritis, 122 on duodenal ulcer, 44 on gastric cancer and 96 on nonulcer dyspepsia. DATA EXTRACTION: The quality of the studies was rated independently on a four-point scale. The strength of the evidence was assessed using a six-point scale for each of the eight established guidelines for determining a causal relation. DATA SYNTHESIS: There was conclusive evidence of a causal relation between H. pylori infection and histologic gastritis. Koch9s postulates for the identification of a microorganism as the causative agent of a disease were fulfilled for H. pylori as a causative agent of gastritis. There was strong evidence that H. pylori is the main cause of duodenal ulcers not induced by nonsteroidal anti-inflammatory drugs, but all of Koch9s postulates were not fulfilled. There was moderate epidemiologic evidence of an association between chronic H. pylori infection and gastric cancer. There was a lack of convincing evidence of a causal association between H. pylori and nonulcer dyspepsia. CONCLUSIONS: The evidence supports a strong causal relation between H. pylori infection and gastritis and duodenal ulcer and a moderate relation between such infection and gastric cancer. Further studies are needed to clarify the role of H. pylori in these disorders. Thus far, there is no evidence of a causal relation between H. pylori and nonulcer dyspepsia.
TL;DR: There was wide variability in the number of pain hours/week reported with 17.6% of the sample reporting continuous pain for the month preceding assessment, and patients with pain reported poorer mental health and more social‐role handicap.
Abstract: Previous studies have reported variable prevalence of pain in multiple sclerosis (MS) and have not documented the impact of pain on daily living. In this consecutive series, we report on data collected from structured interviews with 85 patients seen within a 16-month period at a regional referral clinic. The prevalence of pain for the month preceding assessment was 53%. There were no significant differences between patients who did and those who did not report pain on the basis of patient demographics (age, gender) and disease characteristics (disease subtype, duration and neurologic symptom severity). Disease duration and neurologic symptom severity were significantly correlated with the number of hours of pain per week but were not correlated with pain severity, the number of pain sites or pain-related distress. There was wide variability in the number of pain hours/week reported with 17.6% of the sample reporting continuous pain for the month preceding assessment. Sixty-five percent of patients with pain reported taking medications for pain and 90% of these patients evaluated their medication(s) as 50% effective or better. Nevertheless, patients with pain reported poorer mental health and more social-role handicap. Discussion focuses on the need for routine assessment of pain and the comprehensive evaluation of the effectiveness of pain interventions in the therapeutic management of patients with MS.
TL;DR: In this paper, no significant correspondence between exons and units of protein structure was detected, suggesting that the putative correspondence does not exist and that the exon theory of genes is untenable.
Abstract: A tendency for exons to correspond to discrete units of protein structure in protein-coding genes of ancient origin would provide clear evidence in favor of the exon theory of genes, which proposes that split genes arose not by insertion of introns into unsplit genes, but from combinations of primordial mini-genes (exons) separated by spacers (introns). Although putative examples of such correspondence have strongly influenced previous debate on the origin of introns, a general correspondence has not been rigorously proved. Objective methods for detecting correspondences were developed and applied to four examples that have been cited previously as evidence of the exon theory of genes. No significant correspondence between exons and units of protein structure was detected, suggesting that the putative correspondence does not exist and that the exon theory of genes is untenable.
TL;DR: Results show that although UVB photons are more damaging than UVA (320–400 nm), the greater fluxes of UVA in the ocean cause more UV inhibition, and models can be used to analyze the sensitivity of water column productivity to UVB and ozone depletion.
Abstract: Concerns about stratospheric ozone depletion have stimulated interest in the effects of UVB radiation (280–320 nm) on marine phytoplankton. Research has shown that phytoplankton photosynthesis can be severely inhibited by surface irradiance and that much of the effect is due to UV radiation. Quantitative generalization of these results requires a biological weighting function (BWF) to quantify UV exposure appropriately. Different methods have been employed to infer the general shape of the BWF for photoinhibition in natural phytoplankton, and recently, detailed BWFs have been determined for phytoplankton cultures and natural samples. Results show that although UVB photons are more damaging than UVA (320–400 nm), the greater fluxes of UVA in the ocean cause more UV inhibition. Models can be used to analyze the sensitivity of water column productivity to UVB and ozone depletion. Assumptions about linearity and time-dependence strongly influence the extrapolation of results. Laboratory measurements suggest that UV inhibition can reach a steady-state consistent with a balance between damage and recovery processes, leading to a non-linear relationship between weighted fluence rate and inhibition. More testing for natural phytoplankton is required, however. The relationship between photoinhibition of photosynthesis and decreases in growth rate is poorly understood, so long-term effects of ozone depletion are hard to predict. However, the wide variety of sensitivities between species suggests that some changes in species composition are likely. Predicted effects of ozone depletion on marine photosynthesis cannot be equated to changes in carbon flux between the atmosphere and ocean. Nonetheless, properly designed studies on the effects of UVB can help identify which physiological and ecological processes are most likely to dominate the responses of marine ecosystems to ozone depletion.
TL;DR: The authors proposed an alternative model in which subduction of the Asian lithospheric mantle develops following the collision of India, which is supported by numerical calculations of crustal deformation and thickening, and is consistent with available geological and geophysical data.
Abstract: THE relative northward motion of the Indian subcontinent that followed the onset of continental collision with Asia has produced extensive deformation of the Earth's crust, giving rise to the world's highest mountains in the Himalayan chain and the world's largest high-elevation region, the Tibetan plateau. The formation of the broad mountain belt implies that, contrary to the original tenets of plate tectonics, the lithospheric plates have experienced widespread deformation far from the plate boundary1. Several models have been proposed2–6 to explain the manner in which this post-collisional deformation is distributed within the continental lithosphere of the Indian and Asian plates. Here we propose an alternative model in which subduction of the Asian lithospheric mantle develops following the collision of India. Our model is supported by numerical calculations of crustal deformation and thickening, and is consistent with available geological and geophysical data7–9. This picture suggests that lithospheric mantle is not deformed along with the crust, and would imply that continental collision zones are more analogous to oceanic subduction zones than was previously believed.
TL;DR: A symposium devoted to classic and new approaches in the use of liposomal systems was organized and chaired by M. Mezei and E. Touitou and focused on liposomes as tools in the mechanistic study of absorption promoters and interaction with the human skin.