Showing papers by "McGill University published in 1993"

Contribution of central neuroplasticity to pathological pain: review of clinical and experimental evidence

Abstract: Peripheral tissue damage or nerve injury often leads to pathological pain processes, such as spontaneous pain, hyperalgesia and allodynia, that persist for years or decades after all possible tissue healing has occurred. Although peripheral neural mechanisms, such as nociceptor sensitization and neuroma formation, contribute to these pathological pain processes, recent evidence indicates that changes in central neural function may also play a significant role. In this review, we examine the clinical and experimental evidence which points to a contribution of central neural plasticity to the development of pathological pain. We also assess the physiological, biochemical, cellular and molecular mechanisms that underlie plasticity induced in the central nervous system (CNS) in response to noxious peripheral stimulation. Finally, we examine theories which have been proposed to explain how injury or noxious stimulation lead to alterations in CNS function which influence subsequent pain experience.

Expression of Endothelin-1 in the Lungs of Patients with Pulmonary Hypertension

Abstract: Background Pulmonary hypertension is characterized by an increase in vascular tone or an abnormal proliferation of muscle cells in the walls of small pulmonary arteries. Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide with important mitogenic properties. It has therefore been suggested that endothelin-1 may contribute to increases in pulmonary arterial tone or smooth-muscle proliferation in patients with pulmonary hypertension. We studied the sites and magnitude of endothelin-1 production in the lungs of patients with various causes of pulmonary hypertension. Methods We studied the distribution of endothelin-1-like immunoreactivity (by immunocytochemical analysis) and endothelin-1 messenger RNA (by in situ hybridization) in lung specimens from 15 control subjects, 11 patients with plexogenic pulmonary arteriopathy (grades 4 through 6), and 17 patients with secondary pulmonary hypertension and pulmonary arteriopathy of grades 1 through 3. Results In the controls, endothelin-1-like immu...

Suggestibility of the child witness: A historical review and synthesis.

Abstract: The field of children's testimony is in turmoil, but a resolution to seemingly intractable debates now appears attainable. In this review, we place the current disagreement in historical context and describe psychological and legal views of child witnesses held by scholars since the turn of the 20th century. Although there has been consistent interest in children's suggestibility over the past century, the past 15 years have been the most active in terms of the number of published studies and novel theorizing about the causal mechanisms that underpin the observed findings. A synthesis of this research posits three "families" of factors--cognitive, social, and biological--that must be considered if one is to understand seemingly contradictory interpretations of the findings. We conclude that there are reliable age differences in suggestibility but that even very young children are capable of recalling much that is forensically relevant. Findings are discussed in terms of the role of expert witnesses.

Robust receding horizon control of constrained nonlinear systems

Abstract: We present a method for the construction of a robust dual-mode, receding horizon controller which can be employed for a wide class of nonlinear systems with state and control constraints and model error. The controller is dual-mode. In a neighborhood of the origin, the control action is generated by a linear feedback controller designed for the linearized system. Outside this neighborhood, receding horizon control is employed. Existing receding horizon controllers for nonlinear, continuous time systems, which are guaranteed to stabilize the nonlinear system to which they are applied, require the exact solution, at every instant, of an optimal control problem with terminal equality constraints. These requirements are considerably relaxed in the dual-mode receding horizon controller presented in this paper. Stability is achieved by imposing a terminal inequality, rather than an equality, constraint. Only approximate minimization is required. A variable time horizon is permitted. Robustness is achieved by employing conservative state and stability constraint sets, thereby permitting a margin of error. The resultant dual-mode controller requires considerably less online computation than existing receding horizon controllers for nonlinear, constrained systems. >

The role of the medial prefrontal cortex (cingulate gyrus) in the regulation of hypothalamic-pituitary-adrenal responses to stress

Abstract: In the studies reported here we have examined the role of the medial prefrontal cortex (MpFC) in regulating hypothalamic-pituitary-adrenal (HPA) activity under basal and stressful conditions. In preliminary studies we characterized corticosteroid receptor binding in the rat MpFC. The results revealed high-affinity (Kd approximately 1 nM) binding with a moderate capacity (42.9 +/- 3 fmol/mg) for 3H- aldosterone (with a 50-fold excess of cold RU28362; mineralocorticoid receptor) and high-affinity (Kd approximately 0.5–1.0 nM) binding with higher capacity (183.2 +/- 22 fmol/mg) for 3H-RU 28362 (glucocorticoid receptor). Lesions of the MpFC (cingulate gyrus) significantly increased plasma levels of both adrenocorticotropin (ACTH) and corticosterone (CORT) in response to a 20 min restraint stress. The same lesions had no effect on hormone levels following a 2.5 min exposure to ether. Implants of crystalline CORT into the same region of the MpFC produced a significant decrease in plasma levels of both ACTH and CORT with restraint stress, but again, there was no effect with ether stress. Neither MpFC lesions nor CORT implants had any consistent effect on A.M. or P.M. levels of plasma ACTH or CORT. Manipulations of MpFC function were not associated with changes in the clearance rate for CORT or in corticosteroid receptor densities in the pituitary, hypothalamus, hippocampus, or amygdala. Taken together, these findings suggest that MpFC is a target site for the negative-feedback effects of glucocorticoids on stress-induced HPA activity, and that this effect is dependent upon the nature of the stress.

Incidence of and Risk Factors for Falls and Injurious Falls among the Community-dwelling Elderly

Abstract: To determine the frequency of and risk factors for falls and injurious falls in the noninstitutionalized elderly, the authors conducted a follow-up study of 409 community-dwelling persons aged 65 years or more in west-central Montreal, Quebec, Canada, from May 1987 to October 1988. Following an initial at-home interview, each subject was telephoned every 4 weeks for 48 weeks for collection of data on falls experienced since the last contact. Each of the 12 follow-up interviews was completed by at least 90% of the subjects eligible for interview. Data were also collected in the follow-up interviews on time-varying exposures. Twenty-nine percent of the subjects fell during follow-up; 17.6% fell once, and 11.5% fell two or more times. The incidence rate for falls was 41.4 falls per 1,000 person-months. The majority of falls resulted in no injury or in minor injury only. Potential risk factors investigated included sociodemographic variables, physical activity, alcohol consumption, acute and chronic health problems, dizziness, mobility, and medications. Multivariate analyses showed that the following factors were statistically significantly associated with an increased rate of falls: dizziness (incidence rate ratio (IRR) = 2.0), frequent physical activity (IRR = 2.0), having days on which activities were limited because of a health problem (IRR = 1.8), having trouble walking 400 m (IRR = 1.6), and having trouble bending down (IRR = 1.4). Factors which were protective included diversity of physical activities (IRR = 0.6), daily alcohol consumption (IRR = 0.5), having days spent in bed because of a health problem (IRR = 0.5), and taking heart medication (IRR = 0.6). Risk factors for injurious falls were similar.

A triple dissociation of memory systems: hippocampus, amygdala, and dorsal striatum

Abstract: This study investigated the respective roles of the hippocampus, the amygdala, and the dorsal striatum in learning and memory. A standard set of experimental conditions for studying the effects of lesions to the three brain areas using an 8-arm radial maze was used: a win-shift version, a conditioned cue preference (CCP) version, and a win-stay version. Damage to the hippocampal system impaired acquisition of the win-shift task but not the CCP or win-stay tasks. Damage to the lateral amygdala impaired acquisition of the CCP task but not the win-shift or win-stay tasks. Damage to the dorsal striatum impaired acquisition of the win-stay task but not the win-shift or CCP tasks. These results are consistent with the hypothesis that the mammalian brain may be capable of acquiring different kinds of information with different, more-or-less independent neural systems. A neural system that includes the hippocampus may acquire information about the relationships among stimuli and events. A neural system that includes the amygdala may mediate the rapid acquisition of behaviors based on biologically significant events with affective properties. A neural system that includes the dorsal striatum may mediate the formation of reinforced stimulus-response associations.

The Architecture of Simplicity

Abstract: This article argues that over time the world views, goals, strategies, cultures, and processes of successful organizations will become more pure or “simple”: They will come to focus more narrowly on a single theme, activity, or issue at the expense of all others. This is explained by managerial, cultural, structural, and process factors within the organization. It is also attributed to both the complementary way in which these factors configure and the paradox that although simplicity may trigger ultimate failure, it can bring about Initial success. The article offers some illustrative propositions concerning the nature, causes, moderating factors, and consequences of simplicity, and it makes suggestions for conducting further research.

Postoperative Chemotherapy and Delayed Radiation in Children Less Than Three Years of Age With Malignant Brain Tumors

Abstract: Background Among patients with malignant brain tumors, infants and very young children have the worst prognosis and the most severe treatment-related neurotoxic effects. Therefore, in 1986, the Pediatric Oncology Group began a study in which postoperative chemotherapy was given in order to permit a delay in the delivery of radiation to the developing brain. Methods Children under 36 months of age with biopsy-proved malignant brain tumors were treated postoperatively with two 28-day cycles of cyclophosphamide plus vincristine, followed by one 28-day cycle of cisplatin plus etoposide. This sequence was repeated until the disease progressed or for two years in 132 children under 24 months of age at diagnosis and for one year in 66 children 24 to 36 months of age at diagnosis. After this, the patients received radiation therapy. The response to the first two cycles of chemotherapy was measured in 102 patients with residual postoperative disease. Results The first two cycles of cyclophosphamide and vincristine...

Methane production and consumption in temperate and subarctic peat soils: Response to temperature and pH

Abstract: Rates of methane (CH4) production under anaerobic conditions and CH4 consumption under aerobic conditions were studied in slurries of peat samples kept at different temperatures (0–35°C) and pH values (buffered at pH 3.5–8). Apparent Xn, CH4 for consumption was 1 μm. Optimum temperatures for both processes were about 25°C but CH4 production showed much more temperature-dependence (activation energies 123–271 kJ mol−1, Q10 values 5.3–16) than did CH4 consumption (activation energies 202−80 kJ mol−1 values 1.4–2.1). In the 0–10°C range, CH4 production was negligible but CH4 consumption was 13–38% of maximum. Both processes showed optimum pH values which were about 2 pH units higher than the native peat pH in acidic peats and only 0–1 pH unit higher in the more alkaline peats. We conclude that the microflora involved in CH4 metabolism is not well adapted to either low temperatures or low pH values.

Tracking deformable objects in the plane using an active contour model

Abstract: The problems of segmenting a noisy intensity image and tracking a nonrigid object in the plane are discussed. In evaluating these problems, a technique based on an active contour model commonly called a snake is examined. The technique is applied to cell locomotion and tracking studies. The snake permits both the segmentation and tracking problems to be simultaneously solved in constrained cases. A detailed analysis of the snake model, emphasizing its limitations and shortcomings, is presented, and improvements to the original description of the model are proposed. Problems of convergence of the optimization scheme are considered. In particular, an improved terminating criterion for the optimization scheme that is based on topographic features of the graph of the intensity image is proposed. Hierarchical filtering methods, as well as a continuation method based on a discrete sale-space representation, are discussed. Results for both segmentation and tracking are presented. Possible failures of the method are discussed. >

Radiation therapy oncology group: Radiosurgery quality assurance guidelines

Abstract: A multidisciplinary Radiation Therapy Oncology Group (RTOG) task force has developed quality assurance guidelines for radiosurgery. The purpose of the guidelines are fourfold: (1) To ensure that participating institutions have the proper equipment and appropriate technique(s) to administer radiosurgery; (2) to outline a standard data set for each treated patient to assess protocol compliance; (3) to define minor and major deviations in protocol treatment; and (4) to set forth clinical data necessary to determine treatment efficacy, including failure patterns, and treatment toxicity. These guidelines are being implemented into active and developing radiosurgery protocols.

Characterization of a functional NF-kappa B site in the human interleukin 1 beta promoter: evidence for a positive autoregulatory loop.

Abstract: The -300 region of the interleukin 1 beta (IL-1 beta) promoter contains a functional NF-kappa B binding site composed of the decamer sequence 5'-GGGAAAATCC-3'. Probes representing the -300 region or the NF-kappa B site alone interacted with NF-kappa B proteins present in phorbol myristate acetate-, lipopolysaccharide-, or Sendai virus-induced myeloid cell extracts as well as recombinant NFKB1 (p50) and RelA (p65); furthermore, NF-kappa B protein-DNA complex formation was dissociated in vitro by the addition of recombinant I kappa B alpha. Mutation of the NF-kappa B site in the context of the IL-1 beta promoter reduced the responsiveness of the IL-1 beta promoter to various inducers, including phorbol ester, Sendai virus, poly(rI-rC), and IL-1 beta. A 4.4-kb IL-1 beta promoter fragment linked to a chloramphenicol acetyltransferase reporter gene was also preferentially inducible by coexpression of individual NF-kappa B subunits compared with a mutated IL-1 beta promoter fragment. When multiple copies of the IL-1 beta NF-kappa B site were linked to an enhancerless simian virus 40 promoter, this element was able to mediate phorbol ester- or lipopolysaccharide-inducible gene expression. In cotransfection experiments, RelA (p65) and c-Rel (p85) were identified as the main subunits responsible for the activation of the IL-1 beta NF-kappa B site; also, combinations of NFKB1 (p50) and RelA (p65) or c-Rel and RelA were strong transcriptional activators of reporter gene activity. The presence of a functional NF-kappa B binding site in the IL-1 beta promoter suggests that IL-1 positively autoregulates its own synthesis, since IL-1 is a strong inducer of NF-kappa B binding activity. Thus, the IL-1 beta gene may be considered as an important additional member of the family of cytokine genes regulated in part by the NF-kappa B/rel family of transcription factors.

Hyperactive Children Grown Up: ADHD in Children, Adolescents, and Adults

Abstract: This second edition of a classic volume demonstrates that fifty percent of hyperactive children continue to face problems of impulsivity, restlessness, low self-esteem, and social skill deficits when they become adults. Providing a complete developmental analysis of the symptoms evinced from infancy through adolescence, the authors show how the disorder is manifested and what happens during treatment at different ages. The authors attempt to distinguish patterns that can be linked to early hyperactivity and examine predictive factoRs related to adult outcome. Clinical vignettes present psychotherapy sessions with children and a poignant rendering of one individual's experience of growing up hyperactive. The new section of the second edition begins with a postscript by this same individual where he relays how he has met the various challenges posed by ADHD. This section also contains a summary of recent research on genetic transmission, neurobiological aspects, and the importance of coexistance of other conditions in ADHD. An extensive update of the treatment for both children and adults has been added to the second edition to present a summary of recent findings regarding the use of medications and various psychosocial treatments.

An unambiguous nomenclature for xyloglucan‐derived oligosaccharides

Abstract: A revised system of abbreviated names is proposed for xyloglucan-derived oligosaccharides. Each (1→4)-linked β-D-glucosyl residue (and the reducing terminal n-glucose moiety) of the backbone is given a one-letter code according to its substituents. The name of the oligosaccharide consists of these code letters listed in sequence from non-reducing to reducing terminus of the backbone

Association of folding intermediates of glycoproteins with calnexin during protein maturation

Abstract: Calnexin, an endoplasmic reticulum transmembrane protein, represents a new type of molecular chaperone that selectively associates in a transient fashion with newly synthesized monomeric glycoproteins in HepG2 cells. Calnexin only recognizes glycoproteins when they are incompletely folded. Dissociation of glycoproteins from calnexin occurs at different rates and is related to the time taken for their folding, which may then initiate their differential transport rates from the endoplasmic reticulum.

The influence of temperature and water table position on carbon dioxide and methane emissions from laboratory columns of peatland soils

Abstract: SUMMARY Laboratory columns (80 cm long, 10 cm diameter) of peat were constructed from samples collected from a subarctic fen, a temperate bog and a temperate swamp. Temperature and water table position were manipulated to establish their influence on emissions of CO2 and CH4 from the columns. A factorial design experiment revealed significant (P rising limb) was very pronounced for CH4 emissions, attributed to a release of CH4 stored in porewater and a lag in the development of anaerobic conditions and methanogenesis on the rising limb. Decreases in atmospheric pressure were correlated with abnormally large emissions of CO2 and CH4 on the falling limb. Peat slurries incubated in flasks revealed few differences between the three peat types in the rates of CO2 production under aerobic and anaerobic conditions. There were, however, major differences between peat types in the rates of CH4 consumption under aerobic incubation conditions and CH4 production under anaerobic conditions (bog > fen > swamp), which explain the differences in response of the peat types in the column experiment.

Biosorption of cadmium by biomass of marine algae

Abstract: Biomass of nonliving, dried brown marine algae Sargassum natans, Fucus vesiculosus, and Ascophyllum nodosum demonstrated high equilibrium uptake of cadmium from aqueous solutions. The metal uptake by these materials was quantitatively evaluated using sorption isotherms. Biomass of A. nodosum accumulated the highest amount of cadmium exceeding 100 mg Cd[sup 2+]/g (at the residual concentration of 100 mg Cd/L and pH 3.5), outperforming a commercial ion exchange resin DUOLITE GT-73. A new biosorbent material based on A. nodosum biomass was obtained by reinforcing the algal biomass by formaldehyde cross-linking. The prepared sorbent possessed good mechanical properties, chemical stability of the cell wall polysaccharides and low swelling volume. Desorption of deposited cadmium with 0.1-0.5 M HCl resulted in no changes of the biosorbent metal uptake capacity through five subsequent adsorption/desorption cycles. There was no damage to the biosorbent which retained its macroscopic appearance and performance in repeated metal uptake/elution cycles.

Glycoprotein biosynthesis in yeast

Abstract: Many proteins in the yeast Saccharomyces cerevisiae are modified by the attachment of N-linked saccharides to asparagine, of O-linked mannose glycans to serine or threonine, and of glycosylphosphoinositol membrane anchors. The biosynthetic events leading to these modifications are coupled to the secretory pathway. Early stages of N-linked glycosylation and the formation of glycosylphosphoinositol anchors have been conserved through evolution of eukaryotes. Studies of yeast offer a variety of genetic and molecular biological approaches, which have led to the isolation of different glycosylation mutants and of genes for enzymes involved in glycosylation. Yeast mutants are useful to identify biosynthetic intermediates, to establish whether a given enzyme is essential for viability, and to determine how cellular functions are affected when glycosylation is perturbed. Yeast glycosylation mutants and genes can be used to identify their counterparts in other eukaryotes.

La autoantigen enhances and corrects aberrant translation of poliovirus RNA in reticulocyte lysate.

Abstract: Translation initiation on poliovirus RNA occurs by internal binding of ribosomes to a sequence within the 5' untranslated region. We have previously characterized a HeLa cell protein, p52, that binds to a fragment of the poliovirus 5' untranslated region (K. Meerovitch, J. Pelletier, and N. Sonenberg, Genes Dev. 3:1026-1034, 1989). Here we report the purification of the HeLa p52. Protein microsequencing identified p52 as La autoantigen. The La protein is a human antigen that is recognized by antibodies from patients with autoimmune disorders such as systemic lupus erythematosus and Sjogren's syndrome. We show that the La protein stimulates translation of poliovirus RNA, but not brome mosaic virus, tobacco mosaic virus, and alfalfa mosaic virus 4 RNA, translation in a reticulocyte lysate. In addition, La corrects aberrant translation of poliovirus RNA in a reticulocyte lysate. Subcellular immunolocalization showed that La protein is mainly nuclear, but after poliovirus infection, La is redistributed to the cytoplasm. Our results suggest that La protein is involved in poliovirus internal initiation of translation and might function through a similar mechanism in the translation of cellular mRNAs.

Magnitude and patterns of herbivory in aquatic and terrestrial ecosystems

Abstract: HERBIVORES can consume a sufficiently large proportion of primary production to regulate plant biomass in some environments1–3. Little is known, however, about how rates of herbivory vary among ecosystems and how herbivores influence the global distribution of vegetation. Patterns of herbivory in terrestrial ecosystems have been summarized recently4,5, but comparisons with aquatic systems are uncertain because past generalizations about herbivory in aquatic systems are based on surprisingly few data6–8. Herbivory is thought to be higher in aquatic than in terrestrial ecosystems9–11 and the impact of herbivores in aquatic systems is believed to decrease with increasing primary productivity12–15, a pattern opposite to that in terrestrial systems4,5. Here we examine these hypotheses using data from 44 aquatic sites. Herbivore biomass and herbivory rates increase at similar rates with increasing primary productivity in aquatic and in terrestrial systems. For a given level of primary productivity, aquatic and terrestrial herbivores reach similar biomass, but aquatic herbivores remove on average 51% of annual primary production, three times more than terrestrial herbivores. Mass-specific rates of herbivory are greater in aquatic than in terrestrial systems.

Rapid and protracted phases of retinal ganglion cell loss follow axotomy in the optic nerve of adult rats

Abstract: To investigate the short- and long-term effects of axotomy on the survival of central nervous system (CNS) neurons in adult rats, retinal ganglion cells (RGCs) were labelled retrogradely with the persistent marker diI and their axons interrupted in the optic nerve (ON) by intracranial crush 8 or 10 mm from the eye or intraorbital cut 0.5 or 3 mm from the eye. Labelled RGCs were counted in flat-mounted retinas at intervals from 2 weeks to 20 months after axotomy. Two major patterns of RGC loss were observed: (1) an initial abrupt loss that was confined to the first 2 weeks after injury and was more severe when the ON was cut close to the eye; (2) a slower, persistent decline in RGC densities with one-half survival times that ranged from approximately 1 month after intraorbital ON cut to 6 months after intracranial ON crush. A small population of RGCs (approximately 5%) survived for as long as 20 months after intraorbital axotomy. The initial loss of axotomized RGCs presumably results from time-limited perturbations related to the position of the ON injury. A persistent lack of terminal connectivity between RGCs and their targets in the brain may contribute to the subsequent, more protracted RGC loss, but the differences between intraorbital cut and intracranial crush suggest that additional mechanisms are involved. It is unclear whether the various injury-related processes set in motion in both the ON and the retina exert random effects on all RGCs or act preferentially on subpopulations of these neurons.

Black hole entropy and higher curvature interactions.

Abstract: A general formula for the entropy of stationary black holes in Lovelock higher-curvature gravity theories is obtained by integrating the first law of black hole mechanics, which is derived by Hamiltonian methods. The entropy is not simply one quarter of the surface area of the horizon, but also includes a sum of intrinsic curvature invariants integrated over a cross section of the horizon.

MRI volumetric measurement of amygdala and hippocampus in temporal lobe epilepsy

Abstract: We performed MRI volumetric measurements of the amygdala (AM), the hippocampal formation (HF), and the anterior temporal lobe in a group of 30 patients with intractable temporal lobe epilepsy (TLE) and in seven patients with extratemporal lobe foci. Measurements were analyzed with a semiautomated software program and the results compared with those of normal controls and correlated with the findings of all other investigations. In particular, we compared the results with the lateralization of epileptic abnormalities in the EEG. Volumetric studies of AM and HF showed lateralization of measurable atrophy consistent with that derived from extracranial and intracranial EEG examinations. The HF volumes were more sensitive and provided a lateralization in 87%. Combined measurements of AM and HF showed lateralization in 93%, always congruent with the results of EEG lateralization. This slight but important additional improvement in discrimination justifies using AM measurements in MRI volumetric studies of mesial temporal structures. Volumetric studies combined with other currently employed noninvasive techniques may diminish the need for invasive methods of investigation in patients with TLE.