Showing papers by "Université du Québec à Montréal published in 2002"

Motivation and dropout in female handballers: a 21‐month prospective study

Abstract: The purpose of this study was to test a motivational model of sport dropout that integrates the 4 stage-causal sequence proposed by the Hierarchical Model of Vallerand (1997) and elements from achievement goal theory (Nicholls, 1989). The model posits that a task involving motivational climate facilitates, while an ego-involving climate undermines, perceptions of competence, autonomy, and relatedness. In turn, feeling incompetent, non autonomous, and unrelated to others undermines self-determined motivation toward handball which leads to the intention of dropping out of handball. Finally, such intentions are implemented later on. Three-hundred and thirty-five females handballers completed a motivation questionnaire and were followed for 21-months. Results from structural equation modeling analyses provided basic support for the model. Findings are discussed in light of their theoretical and applied implications.

Potential disadvantages of using socially acquired information

Abstract: The acquisition and use of socially acquired information is commonly assumed to be profitable. We challenge this assumption by exploring hypothetical scenarios where the use of such information either provides no benefit or can actually be costly. First, we show that the level of incompatibility between the acquisition of personal and socially acquired information will directly affect the extent to which the use of socially acquired information can be profitable. When these two sources of information cannot be acquired simultaneously, there may be no benefit to socially acquired information. Second, we assume that a solitary individual's behavioural decisions will be based on cues revealed by its own interactions with the environment. However, in many cases, for social animals the only socially acquired information available to individuals is the behavioural actions of others that expose their decisions, rather than the cues on which these decisions were based. We argue that in such a situation the use of socially acquired information can lead to informational cascades that sometimes result in sub-optimal behaviour. From this theory of informational cascades, we predict that when erroneous cascades are costly, individuals should pay attention only to socially generated cues and not behavioural decisions. We suggest three scenarios that might be examples of informational cascades in nature.

Respiration in the open ocean

Abstract: A key question when trying to understand the global carbon cycle is whether the oceans are net sources or sinks of carbon. This will depend on the production of organic matter relative to the decomposition due to biological respiration. Estimates of respiration are available for the top layers, the mesopelagic layer, and the abyssal waters and sediments of various ocean regions. Although the total open ocean respiration is uncertain, it is probably substantially greater than most current estimates of particulate organic matter production. Nevertheless, whether the biota act as a net source or sink of carbon remains an open question.

Natural fire regime : a guide for sustainable management of the Canadian boreal forest

Abstract: The combination of certain features of fi re disturbance, notably fi re frequency, size and severity, may be used to characterize the disturbance regime in any region of the boreal forest. As some consequences of fi re resemble the effects of industrial forest harvesting, conventional forest management is often considered as a disturbance that has effects similar to those of natural disturbances. Although the analogy between forest management and fi re disturbance in boreal ecosystems has some merit, it is important to recognise that it also has its limitations. Short fi re cycles generally described for boreal ecosystems do not appear to be universal; rather, important spatial and temporal variations have been observed in Canada. These variations in the fi re cycle have an important infl uence on forest composition and structure at the landscape and regional levels. Size and severity of fi res also show a large range of variability. In regions where the natural matrix of the boreal forest remains relatively intact, maintenance of this natural variability should be targeted by forest managers concerned with biodiversity conservation. Current forest management tends to reduce this variability: for example, fully regulated, even-aged management will tend to truncate the natural forest age distribution and eliminate over-mature and old-growth forests from the landscape. We suggest that the development of strategic-level forest management planning approaches and silvicultural techniques designed to maintain a spectrum of forest compositions and structures at different scales in the landscape is one avenue to maintain this variability. Although we use the boreal forest of Quebec for our examples, it is possible to apply the approach to those portions of the boreal forest where the fi re regime favours the development of even-aged stands in burns.

Relationship between changes in hemoglobin level and quality of life during chemotherapy in anemic cancer patients receiving epoetin alfa therapy

Abstract: BACKGROUND Hemoglobin increases have been associated with quality of life (QOL) improvements in anemic cancer patients treated with epoetin alfa, but intervention generally has been reserved for symptomatic anemia or hemoglobin < 10 g/dL. Relationships among hemoglobin, functional status, and patient reported QOL have not been well characterized. METHODS Data from two open-label, community-based trials of epoetin alfa therapy that enrolled 4382 anemic cancer patients undergoing chemotherapy were used to evaluate the relationship between hemoglobin changes and QOL changes. The authors measured QOL using the Linear Analog Scale Assessment (LASA) and the more detailed, disease-specific Functional Assessment of Cancer Therapy-Anemia (FACT-An) instrument. Analyses were performed to determine the incremental change in QOL associated with hemoglobin increases (1 g/dL increments). RESULTS Cross-sectional analyses showed a nonlinear relationship and significant positive correlation between high hemoglobin levels and high LASA and FACT-An scores (r = 0.25 and 0.29, respectively, P < 0.01). Patients with hemoglobin increases of ≥ 2 g/dL reported statistically significant improvements in five FACT-An items selected a priori specifically to reflect functional capacity. An incremental analysis used regression methods to identify the longitudinal relationship between incremental changes in hemoglobin and QOL scores. This relationship was found to be nonlinear, with the maximum QOL gain occurring at a hemoglobin level of 12 g/dL (range, 11–13 g/dL). Patients with low baseline QOL scores and longer time periods between baseline and final QOL assessments experienced significantly (P < 0.05) greater increases in overall QOL. Progressive disease at baseline, change in disease status from baseline to end of study, and increase in self-reported pain or nausea all had significant (P < 0.05) negative effects on QOL scores. CONCLUSIONS A direct relationship exists between hemoglobin increases during epoetin alfa therapy and corresponding QOL improvements in cancer patients receiving chemotherapy across the clinically relevant hemoglobin range of 8–14 g/dL. These data suggest that the maximal incremental gain in QOL occurs when hemoglobin is in the range of 11–13 g/dL. Cancer 2002;95:888–95. © 2002 American Cancer Society. DOI 10.1002/cncr.10763

A Motivational Model of Work Turnover

Abstract: The purpose of this article was to propose and test a motivational model of work turnover. The model posits that feelings of relatedness toward work colleagues and feelings of competence jointly and positively affect self-determined work motivation, which in turn facilitates work satisfaction but prevents emotional exhaustion. Moreover, work satisfaction and emotional exhaustion respectively lead to negative and positive effects on turnover intentions. Finally, over time, turnover intentions translate into turnover behavior. A total of 490 alumni from a school of administration completed a questionnaire assessing the various components of the motivational model. Results from structural equation modeling analyses (with EQS; Bentler, 1992) supported the motivational model. Results are discussed in light of the relevant literature, and future research directions are proposed.

Downscaling ability of one-way nested regional climate models: the Big-Brother Experiment

Abstract: A methodology is developed for testing the downscaling ability of nested regional climate models (RCMs). The proposed methodology, nick-named the Big-Brother Experiment (BBE), is based on a "perfect-prognosis" approach and hence does not suffer from model errors nor from limitations in observed climatologies. The BBE consists in first establishing a reference climate by performing a large-domain high-resolution RCM simulation: this simulation is called the Big Brother. This reference simulation is then degraded by filtering short scales that are unresolved in today's global objective analyses (OA) and/or global climate models (GCMs) when integrated for climate projections. This filtered reference is then used to drive the same nested RCM (called the Little Brother), integrated at the same high-resolution as the Big Brother, but over a smaller domain that is embedded in the Big-Brother domain. The climate statistics of the Little Brother are then compared with those of the Big Brother over the Little-Brother domain. Differences can thus be attributed unambiguously to errors associated with the nesting and downscaling technique, and not to model errors nor to observation limitations. The results of the BBE applied to a one-winter-month simulation over eastern North America at 45-km grid-spacing resolution show that the one-way nesting strategy has skill in downscaling large-scale information to the regional scales. The time mean and variability of fine-scale features in a number of fields, such as sea level pressure, 975-hPa temperature and precipitation are successfully reproduced, particularly over regions where small-scale surface forcings are strong. Over other regions such as the ocean and away from the surface, the small-scale reproducibility is more difficult to achieve.

Oxytocin induces differentiation of P19 embryonic stem cells to cardiomyocytes.

Abstract: We recently discovered the existence of the oxytocin/oxytocin receptor (OT/OTR) system in the heart. Activation of cardiac OTR stimulates the release of atrial natriuretic peptide (ANP), which is involved in regulation of blood pressure and cell growth. Having observed elevated OT levels in the fetal and newborn heart at a stage of intense cardiomyocyte hyperplasia, we hypothesized a role for OT in cardiomyocyte differentiation. We used mouse P19 embryonic stem cells to substantiate this potential role. P19 cells give rise to the formation of cell derivatives of all germ layers. Treatment of P19 cell aggregates with dimethyl sulfoxide (DMSO) induces differentiation to cardiomyocytes. In this work, P19 cells were allowed to aggregate from day 0 to day 4 in the presence of 0.5% DMSO, 10(-7) M OT and/or 10(-7) M OT antagonist (OTA), and then cultured in the absence of these factors until day 14. OT alone stimulated the production of beating cell colonies in all 24 independently growing cultures by day 8 of the differentiation protocol, whereas the same result was obtained in cells induced by DMSO only after 12 days. Cells induced with OT exhibited increased ANP mRNA, had abundant mitochondria (i.e., they strongly absorbed rhodamine 123), and expressed sarcomeric myosin heavy chain and dihydropyridine receptor-alpha 1, confirming a cardiomyocyte phenotype. In addition, OT as well as DMSO increased OTR protein and OTR mRNA, and OTA completely inhibited the formation of cardiomyocytes in OT- and DMSO-supplemented cultures. These results suggest that the OT/OTR system plays an important role in cardiogenesis by promoting cardiomyocyte differentiation.

Polytopal realizations of generalized associahedra

Abstract: On demontre que les eventails simpliciaux complets associes aux systemes de racines cristallographiques dans "Y-systems and generalized associahedra" sont projectifs au sens de la geometrie torique (les polytopes simples associes sont des associaedres generalises). On obtient ce resultat en explicitant une famille de fonctions supports strictement convexes.

High transcytosis of melanotransferrin (P97) across the blood-brain barrier.

Abstract: The blood-brain barrier (BBB) performs a neuroprotective function by tightly controlling access to the brain; consequently it also impedes access of proteins as well as pharmacological agents to cerebral tissues. We demonstrate here that recombinant human melanotransferrin (P97) is highly accumulated into the mouse brain following intravenous injection and in situ brain perfusion. Moreover, P97 transcytosis across bovine brain capillary endothelial cell (BBCEC) monolayers is at least 14-fold higher than that of holo-transferrin, with no apparent intra-endothelial degradation. This high transcytosis of P97 was not related to changes in the BBCEC monolayer integrity. In addition, the transendothelial transport of P97 was sensitive to temperature and was both concentration- and conformation-dependent, suggesting that the transport of P97 is due to receptor-mediated endocytosis. In spite of the high degree of sequence identity between P97 and transferrin, a different receptor than the one for transferrin is involved in P97 transendothelial transport. A member of the low-density lipoprotein receptor protein family, likely LRP, seems to be involved in P97 transendothelial transport. The brain accumulation, high rate of P97 transcytosis and its very low level in the blood suggest that P97 could be advantageously employed as a new delivery system to target drugs directly to the brain.

The summer metabolic balance in the epilimnion of southeastern Quebec lakes

Abstract: On the basis of data collected in Quebec lakes, del Giorgio and Peters (1994) and Carignan et al. (2000) have come to opposite conclusions regarding the metabolic balance between heterotrophy and autotrophy in lakes in general. In the present study, epilimnetic oxygen and carbon dioxide saturation was measured in 33 lakes from the St. Lawrence Lowlands region of Quebec to examine the extent of epilimnetic net heterotrophy (i.e., O2:CO2 balance) in lakes of different characteristics. We found that ~75% of the lakes were undersaturated with oxygen and supersaturated with CO2. There was a strong negative relationship between the departures of O2 and CO2 from saturation. What has not been noted elsewhere is that oxygen concentrations were negatively related to dissolved organic carbon (DOC) concentration, and, therefore, metabolic gas balances could be predicted from DOC; a value between 4 and 6 mg L−1 DOC corresponds to metabolic equilibrium. Because most of the lakes in del Giorgio and Peters (1994) had DOC concentrations above this threshold and most lakes in Carignan et al. (2000) were below, their apparently contradictory conclusions can be reconciled within a larger general theory. Contrary to studies elsewhere, however, we found that the degree of oxygen undersaturation increased with lake trophic status, expressed either as total phosphorus or nitrogen concentrations.

Green Tea Catechins Inhibit Vascular Endothelial Growth Factor Receptor Phosphorylation

Abstract: Vascular endothelial growth factor (VEGF) receptors (VEGFR) play a major role in tumor angiogenesis and, thus, represent attractive targets for the development of novel anticancer therapeutics. In this work, we report that green tea catechins are novel inhibitors of VEGFR-2 activity. Physiological concentrations (0.01–1 μm) of epigallocatechin-3 gallate, catechin-3 gallate, and, to a lesser extent, epicatechin-3 gallate induce a rapid and potent inhibition of VEGF-dependent tyrosine phosphorylation of VEGFR-2. The inhibition of VEGFR-2 by epigallocatechin-3 gallate was similar to that induced by Semaxanib (SU5416), a specific VEGFR-2 inhibitor. The inhibition of VEGFR-2 activity by the catechins displayed positive correlation with the suppression of in vitro angiogenesis. These observations suggest that the anticancer properties of green tea extracts may be related to their inhibition of VEGF-dependent angiogenesis.

Spectral Decomposition of Two-Dimensional Atmospheric Fields on Limited-Area Domains Using the Discrete Cosine Transform (DCT)

Abstract: For most atmospheric fields, the larger part of the spatial variance is contained in the planetary scales. When examined over a limited area, these atmospheric fields exhibit an aperiodic structure, with large trends across the domain. Trying to use a standard (periodic) Fourier transform on regional domains results in the aliasing of largescale variance into shorter scales, thus destroying all usefulness of spectra at large wavenumbers. With the objective of solving this particular problem, the authors have evaluated and adopted a spectral transform called the discrete cosine transform (DCT). The DCT is a widely used transform for compression of digital images such as MPEG and JPEG, but its use for atmospheric spectral analysis has not yet received widespread attention. First, it is shown how the DCT can be employed for producing power spectra from two-dimensional atmospheric fields and how this technique compares favorably with the more conventional technique that consists of detrending the data before applying a periodic Fourier transform. Second, it is shown that the DCT can be used advantageously for extracting information at specific spatial scales by spectrally filtering the atmospheric fields. Examples of applications using data produced by a regional climate model are displayed. In particular, it is demonstrated how the 2D-DCT spectral decomposition is successfully used for calculating kinetic energy spectra and for separating mesoscale features from large scales.

Cold-regulated cereal chloroplast late embryogenesis abundant-like proteins. Molecular characterization and functional analyses.

Abstract: Cold acclimation and freezing tolerance are the result of complex interaction between low temperature, light, and photosystem II (PSII) excitation pressure. Previous results have shown that expression of the Wcs19 gene is correlated with PSII excitation pressure measured in vivo as the relative reduction state of PSII. Using cDNA library screening and data mining, we have identified three different groups of proteins, late embryogenesis abundant (LEA) 3-L1, LEA3-L2, and LEA3-L3, sharing identities with WCS19. These groups represent a new class of proteins in cereals related to group 3 LEA proteins. They share important characteristics such as a sorting signal that is predicted to target them to either the chloroplast or mitochondria and a C-terminal sequence that may be involved in oligomerization. The results of subcellular fractionation, immunolocalization by electron microscopy and the analyses of target sequences within the Wcs19 gene are consistent with the localization of WCS19 within the chloroplast stroma of wheat (Triticum aestivum) and rye (Secale cereale). Western analysis showed that the accumulation of chloroplastic LEA3-L2 proteins is correlated with the capacity of different wheat and rye cultivars to develop freezing tolerance. Arabidopsis was transformed with the Wcs19 gene and the transgenic plants showed a significant increase in their freezing tolerance. This increase was only evident in cold-acclimated plants. The putative function of this protein in the enhancement of freezing tolerance is discussed.

Balancing work and family with telework? Organizational issues and challenges for women and managers

Abstract: This article presents a research on telework and deals with the following questions: Who are the teleworkers (sex, age, main socio‐occupational categories)? What are the impacts of telework on work organization and working conditions, particularly for women, and in terms of work‐family balance, since telework is sometimes presented as a solution to problems of reconciling work and family responsibilities? Finally, what is the level of satisfaction among teleworkers and why are they satisfied or dissatisfied with this system? Are there differences between various groups on this regard? We insist on the dimensions of working conditions and autonomy in telework and highlight the fact that there is a risk of polarization according to gender, women being more frequently in a situation where they have less autonomy than men in telework, although many also see telework in a positive way, as an “escape” from a bureaucratic work environment.

Shared predators and indirect trophic interactions: lemming cycles and arctic-nesting geese

Abstract: Summary 1 We investigated the hypothesis that cyclic lemming populations indirectly affect arctic-nesting greater snow geese (Anser caerulescens atlanticus L.) through the behavioural and numerical responses of shared predators. 2 The study took place on Bylot Island in the Canadian High Arctic during two lemming cycles. We recorded changes in foraging behaviour and activity rate of arctic foxes, parasitic jaegers, glaucous gulls and common ravens in a goose colony during one lemming cycle and we monitored denning activity of foxes for 7 years. We also evaluated the total response of predators (i.e. number of eggs depredated). 3 Arctic foxes were more successful in attacking lemmings than goose nests because predators were constrained by goose nest defence. Predators increased their foraging effort on goose eggs following a lemming decline. 4 Activity rates in the goose colony varied 3·5-fold in arctic foxes and 4·8-fold in parasitic jaegers, and were highest 2 and 3 years after the lemming peak, respectively. The breeding output of arctic foxes appeared to be driven primarily by lemming numbers. 5 Predators consumed 19–88% of the annual goose nesting production and egg predation intensity varied 2·7-fold, being lowest during peak lemming years. Arctic foxes and parasitic jaegers were the key predators generating marked annual variation in egg predation. 6 Our study provides strong support for short-term, positive indirect effects and long-term, negative indirect effects of lemming populations on arctic-nesting geese. The outcome between these opposing indirect effects is probably an apparent competition between rodents and many terrestrial arctic-nesting birds.

L'approche collaborative de recherche en éducation: un rapport nouveau à établir entre recherche et formation

Abstract: Les auteurs exposent les composantes d'un modele de recherche collaborative lie a une certaine facon de faire de la recherche «avec» plutot que «sur» les praticiens. C'est sous l'angle de la double fonction de recherche et de formation, a concilier dans la demarche collaborative, que leur modele est aborde. Le texte situe historiquement l'emergence de l'idee de collaboration de recherche en education et presente les trois facettes complementaires du modele: a) une definition conceptuelle du modele conduit a preciser le sens donne aux notions de recherche et de formation; b) le modele est illustre par une description de cinq projets differents bases sur une demarche collaborative commune; c) une lecture transversale des cinq projets conduit a discuter des composantes du modele.

Phosphorylation states of Cdc42 and RhoA regulate their interactions with Rho GDP dissociation inhibitor and their extraction from biological membranes.

Abstract: The Rho GDP dissociation inhibitor (RhoGDI) regulates the activation-inactivation cycle of Rho small GTPases, such as Cdc42 and RhoA, by extracting them from the membrane. To study the roles of Mg(2+), phosphatidylinositol 4,5-bisphosphate (PIP(2)), ionic strength and phosphorylation on the interactions of RhoGDI with Cdc42 and RhoA, we developed a new, efficient and reliable method to produce prenylated Rho proteins using the yeast Saccharomyces cerevisiae. It has been previously reported that protein kinase A (PKA)-treatment of isolated membranes increased RhoA extraction from membranes by RhoGDI [Lang, Gesbert, Delespine-Carmagnat, Stancou, Pouchelet and Bertoglio (1996) EMBO J. 16, 510-519]. In the present study, we used an in vitro affinity chromatography system to show that phosphorylation of RhoA and Cdc42 significantly increased their interaction with RhoGDI under physiological conditions of ionic strength. This increase was independent of the nucleotide (GDP or guanosine 5'-[gamma-thio]triphosphate) loaded on to the Rho proteins, as well as of Mg(2+) and PIP(2). Moreover, dephosphorylation of rat brain membranes by alkaline phosphatase significantly decreased the extraction of RhoA and Cdc42 by RhoGDI. Subsequent re-phosphorylation by PKA restored the extraction levels, indicating the reversibility of this process. These results clearly demonstrate that the phosphorylation states of Cdc42 and RhoA regulate their interactions with RhoGDI and, consequently, their extraction from rat brain membranes. We therefore suggest that phosphorylation is a mechanism of regulation of Cdc42 and RhoA activity that is independent of GDP-GTP cycling.

Passion and gambling: on the validation of the Gambling Passion Scale (GPS).

Abstract: Vallerand and his colleagues (Vallerand & Blanchard, 1999; Vallerand, Blanchard, Koestner, & Gagne, 2001) have recently proposed a new concept of passion. According to these authors, passion refers to a strong inclination toward an activity that we like, find important, and in which we invest time. Vallerand et al. have identified two types of passion: obsessive and harmonious. Obsessive passion refers to an internal pressure that forces an individual to engage in the activity. Harmonious passion, on the other hand, refers to an internal force that leads an individual to choose freely to engage in an activity. While obsessive passion has been shown in some circumstances to lead to negative psychological and physical consequences, harmonious passion generally leads to positive psychological and physical consequences. The purpose of the present research was to validate a measure of passion toward gambling: the Gambling Passion Scale (GPS). The GPS consists of two subscales (obsessive passion and harmonious passion) comprising five items each. Results from two studies involving a total of 340 participants revealed satisfactory internal consistency and temporal stability indices, as well as a two-factor structure supported by exploratory and confirmatory factor analyses. Finally, a series of partial correlational analyses between the two subscales and scales assessing behavioral measures related to gambling supported the construct validity of the GPS. The present results suggest that the GPS is a useful scale for research on gambling.

Increased Levels of Apolipoprotein D in Cerebrospinal Fluid and Hippocampus of Alzheimer's Patients

Abstract: Apolipoprotein D (apoD) is a member of the lipocalin family of proteins. Most members of this family are transporters of small hydrophobic ligands, although in the case of apoD, neither its physiological function(s) nor its putative ligand(s) have been unequivocally identified. In humans, apoD is expressed in several tissues, including the CNS, and its synthesis is greatly increased during regeneration of rat peripheral nerves. As apoD may have an important function in the nervous system and, particularly, in nerve regeneration, we measured immunoreactive apoD levels in the hippocampus and in CSF of patients with either Alzheimer's disease (AD) or other neuropathologies. In parallel, we determined the concentrations of apolipoprotein E (apoE), another apolipoprotein also implicated in nerve regeneration and in the etiology of AD. Levels of apoD but not apoE were increased in the hippocampus of AD patients compared with controls. ApoD concentrations, as determined by radioimmunoassay, were significantly increased in the CSF of AD patients (4.23 +/- 1.58 microg/ml) and patients with other pathologies (3.29 +/- 1.35 microg/ml) compared with those in the CSF of normal subjects (1.15 +/- 0.71 microg/ml). Although the differences were smaller than for apoD, the mean apoE concentrations in the CSF of both groups of patients were also significantly higher than those of controls. In AD patients, apoD, but not apoE, levels in CSF and hippocampus increased as a function of inheritance of the epsilon4 apoE allele. This study therefore demonstrates that increased apoD levels in the hippocampus and in CSF are a marker of neuropathology, including that associated with AD, and are independent of apoE concentrations.

Assessing aggressive and depressed children's social relations with classmates and friends: a matter of perspective.

Abstract: This study examined aggressive, depressed, and aggressive–depressed childrenr's peer relations from the children's own and from their peers' perspective. Participants were 819 fourth through sixth graders (50.2% girls) who were assessed twice during the same school year. Measures included children's aggression and depression, self-rated and peer-rated social acceptance, number of reciprocal friends, and self-rated and friend-rated friendship quality. Analyses revealed different patterns, depending on the perspective considered. Depression but not aggression was significantly related to difficulties with the peer group and with dyadic friends from the children's own perspective, whereas the opposite pattern was found according to the peers' view. The co-occurrence of aggression and depression entailed significant difficulties with peers regardless of perspective. The implications of these results for the links between children's aggression and depression and their interpersonal relationships are discussed.

Evolution of the fine structure constant driven by dark matter and the cosmological constant

Abstract: Bekenstein's model of a scalar field $\ensuremath{\varphi}$ that affects the electromagnetic permeability (usually identified with ``changing $\ensuremath{\alpha}'')$ predicts tiny variations of the effective fine structure constant up to very high redshifts, $|\ensuremath{\alpha}(z=3.5)/{\ensuremath{\alpha}}_{0}\ensuremath{-}1|l{10}^{\ensuremath{-}10},$ when the constraints from E\"otv\"os-Dicke-Braginsky types of experiments are imposed. We generalize this model by allowing additional couplings of $\ensuremath{\varphi}$ to both a dark matter candidate and to the cosmological constant. We show that in a supersymmetric generalization of Bekenstein's model, the coupling to the LSP, which is assumed to contribute significantly to the dark matter density, can be up to six orders of magnitude stronger than the coupling to the baryon energy density. This allows one to evade the present limits on the nonuniversality of the gravitational attraction due to $\ensuremath{\varphi}$ exchange and at the same time accommodate the effective shift in $\ensuremath{\alpha}$ at the level of $\ensuremath{\alpha}(z=3.5)/{\ensuremath{\alpha}}_{0}\ensuremath{-}1\ensuremath{\sim}{10}^{\ensuremath{-}5},$ reported recently from observations of quasar absorption spectra.