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Biomedical subjects

M Dubé

Publications and source records attributed to M Dubé.

At least 19 recordsLinked to original sources
PubMed2002

Interface dynamics and kinetic roughening in fractals.

We consider the dynamics and kinetic roughening of single-valued interfaces in two-dimensional fractal media. Assuming that the local height difference distribution function of the fronts obeys Levý statistics with a well-defined power-law decay exponent, we derive analytic expressions for the local scaling exponents. We also show that the kinetic roughening of the interfaces displays anomalous scaling and multiscaling in the relevant correlation functions. For invasion percolation models, the exponents can be obtained from the fractal geometry of percolation clusters. Our predictions are in excellent agreement with numerical simulations.

Journal Article↗
PubMed2001

Interface pinning in spontaneous imbibition.

Evaporation and gravity induced pinning in spontaneous imbibition are examined within a phase field formalism. Evaporation is introduced via a nonconserving term and gravity through a convective term that constrains the influx of liquid. Their effects are described by dimensionless coupling constants epsilon and g, respectively. From liquid conservation, the early time behavior of the average interface position follows H(t) approximately t1/2 until a crossover time t*(g,epsilon). After that the pinning height Hp(g,epsilon) is approached exponentially in time, in accordance with mean field theory. The statistical roughness of the interface is described by an exponent chi approximately 1.25 at all stages of the rise, but the dynamic length scale controlling roughness crosses over from xi(x) approximately H1/2 to a time independent pinning length scale xi(p)(epsilon,g).

Journal Article↗
PubMed2001

Thermal effects on atomic friction.

We model friction acting on the tip of an atomic force microscope as it is dragged across a surface at nonzero temperatures. We find that stick-slip motion occurs and that the average frictional force follows (absolute value lnv)(2/3), where v is the tip velocity. This compares well to recent experimental work, permitting the quantitative extraction of all microscopic parameters. We calculate the scaled form of the average frictional force's dependence on both temperature and tip speed as well as the form of the friction-force distribution function.

Journal Article↗
PubMed2001

Suicidal ideation and self-determination in institutionalized elderly.

The right to self-determination is central to the current debate on rational suicide in old age. The goal of this exploratory study was to assess the presence of self-determination in suicidal institutionalized elderly persons. Eleven elderly persons with serious suicidal ideations were matched according to age, sex, and civil status with 11 nonsuicidal persons. The results indicated that suicidal persons did not differ from nonsuicidal persons in level of self-determination. There was, however, a significant difference between groups on the social subscale. Suicidal elderly persons did not seem to take others into account when making a decision or taking action. The results are discussed from a suicide-prevention perspective.

Aged↗
PubMed2001

Analysis of ubiquitination in vivo using a transgenic mouse model.

The primary pathway for the proteolytic destruction of cellular proteins is through ubiquitin-mediated targeting to the proteasome. This pathway is pivotal not only in the elimination of damaged or misfolded proteins but also in the temporal, developmental, or signal-mediated destruction of normal cellular substrates. The list of known substrates of the ubiquitin/proteasome pathway is long, but most substrates have been identified in yeast or, more recently, in cultured mammalian cells. It is likely that many mammalian substrates with developmental or disease relevance have yet to be identified because their ubiquitination occurs in tissue or organ systems that cannot be adequately modeled in vitro. We have developed a transgenic mouse model that will allow the isolation and identification of these substrates. The human UbC promoter was used to drive expression of a hexahistidine-tagged version of human ubiquitin in a variety of mouse tissues from early embryonic stages, as assessed by a green fluorescent protein marker. Cleavage of the fusion protein by endogenous enzymes produced epitope-tagged ubiquitin that was detected both in monomeric form and conjugated to cellular proteins. This mouse model should facilitate in the analysis of normal and disease-related ubiquitination events in vivo.

Animals↗
PubMed2000

Muscle specific fragile X related protein 1 isoforms are sequestered in the nucleus of undifferentiated myoblast.

BACKGROUND: The family of Fragile X Mental Retardation Proteins is composed of three members: Fragile Mental Retardation 1, Fragile X Related 1 and X Related 2 proteins. These proteins are associated with mRNPs within translating ribosomes and have the capacity to shuttle between the nucleus and the cytoplasm. Great attention has been given to FMRP due to its implication in human hereditary mental retardation while FXR1P and FXR2P have only recently been studied. RESULTS: Using antibodies directed against several epitopes of FXR1P, we have detected protein isoforms generated by small peptides pocket inserts. Four isoforms of MW 70, 74, 78, 80 kDa are widely distributed in mouse organs, while in striated muscles these isoforms are replaced by proteins of 82 and 84 kDa containing an extra pocket of 27 aa. Expression of these muscle isoforms is an early event during in vitro differentiation of myoblasts into myotubes and correlates with the activation of muscle-specific genes. However, while FXR1P82,84 are associated with cytoplasmic mRNPs in myotubes, they are sequestered in the nuclei of undifferentiated myoblasts. These observations suggest that, in addition to a cytoplasmic function yet to be defined, FXR1P82,84 may play a nuclear role in pre-mRNA metabolism. CONCLUSIONS: The pattern of subcellular partitioning of FXR1P isoforms during myogenesis is unique among the family of the FXR proteins. The model system described here should be considered as a powerful tool for ongoing attempts to unravel structure-function relationships of the different FMR family members since the potential role(s) of FXR1P as a compensatory factor in Fragile X syndrome is still elusive.

Amino Acid Sequence↗
PubMed2000

Interaction structure of husbands' and wives' disclosure of marital conflict to their respective best friend.

Husbands' and wives' conversations with their respective best friend (N = 88) were coded to assess spouses' and friends' mutual influence in regulating support and interference with regard to spouses' marriage and to assess the impact of spouses' sex and marital satisfaction on the conversation processes. Dissatisfied husbands and wives expressed fewer positive and more negative views of marriage than satisfied husbands and wives and the friends in the 2 groups. There were no group and no sex differences in interference sequences. There were group and sex differences in support sequences. Friends of satisfied wives and those of dissatisfied husbands were more likely than satisfied wives and dissatisfied husbands to get support for their positive views of marriage. The findings are discussed with reference to the specific effects of outsiders' support and interference on satisfied and dissatisfied spouses.

Adult↗
PubMed2000

[Incidence of the onset of disability and recovery of functional autonomy among the very old after one year].

BACKGROUND: This article measures the survival rate and explores the changes in functional autonomy among both men and women over a one-year period in a sample of 272 subjects aged 80-85. METHODS: Data were taken from the Quebec Longitudinal Study on Aging, a multi-cohort prospective study focusing on health and quality of life. The sample comprises two sub-groups, namely disabled and autonomous subjects. Eligible participants were selected from the Quebec Health Insurance Plan (QHIP) file. However, to obtain the required number of participants, the sample was completed from eligible subjects who volunteered in response to TV, billboard and newspaper advertising about the project. The Functional Autonomy Measurement System (SMAF) was used to assess disability. The SMAF assesses functional disability in 5 domains: activities of daily living (ADL), mobility, instrumental activities (IADL), communication, and mental functioning. RESULTS: After one year, nearly 5% of the subjects had died and 72.5% were still autonomous, i.e., they had a score under 4.5 on the SMAF. The annual incidence of the onset of disability (including death, lengthy hospitalization, functional incapacities and cognitive deficits) was 20%. However, no difference was found between the sexes in regard to the risk of losing autonomy. The main areas where disability occurred among the previously autonomous subjects were, in order of importance, domestic tasks, mobility and communication. The study confirmed that it is possible to recover autonomy, even at this advanced age, particularly for women (11.2%), but less so for men (3.6%). CONCLUSION: This phenomenon of recovering functional autonomy suggests that octogenarians have a residual potential and confirms the effectiveness of preventive and curative measures and the benefits of interventions by community and family networks.

Activities of Daily Living↗
PubMed1999

Characterization of transgenic mice with targeted disruption of the catalytic domain of the double-stranded RNA-dependent protein kinase, PKR.

The interferon-inducible, double-stranded RNA-dependent protein kinase PKR has been implicated in anti-viral, anti-tumor, and apoptotic responses. Others have attempted to examine the requirement of PKR in these roles by targeted disruption at the amino terminal-encoding region of the Pkr gene. By using a strategy that aims at disruption of the catalytic domain of PKR, we have generated mice that are genetically ablated for functional PKR. Similar to the other mouse model of Pkr disruption, we have observed no consequences of loss of PKR on tumor suppression. Anti-viral response to influenza and vaccinia also appeared to be normal in mice and in cells lacking PKR. Cytokine signaling in the type I interferon pathway is normal but may be compromised in the erythropoietin pathway in erythroid bone marrow precursors. Contrary to the amino-terminal targeted Pkr mouse, tumor necrosis factor alpha-induced apoptosis and the anti-viral apoptosis response to influenza is not impaired in catalytic domain-targeted Pkr-null cells. The observation of intact eukaryotic initiation factor-2alpha phosphorylation in these Pkr-null cells provides proof of rescue by another eukaryotic initiation factor-2alpha kinase(s).

Animals↗
PubMed1999

Criterion validity of a new measure of self-actualization.

Many authors have questioned the validity of the major existing measures of self-actualization (the Personal Orientation Inventory, the Personal Orientation Dimensions, and the Short Index of Self-actualization), given their serious theoretical and methodological limitations. A new inventory was developed, the Measure of Actualization of Potential, and various studies were conducted to assess its theoretical and empirical content as well as its construct validity, internal consistency, and temporal reliability. The present aim was to estimate the criterion validity of the new measure using humanistic clinical psychologists' assessments as the criterion. The results show that eight clinical psychologists' rankings of 73 individuals are positively and highly correlated with the scores obtained by the same individuals on the Measure of Actualization of Potential.

Adolescent↗
PubMed1997

Hormonally regulated expression and alternative splicing of kit ligand may regulate kit-induced inhibition of meiosis in rat oocytes.

Mutations in the genes encoding the Kit tyrosine kinase receptor or kit ligand (KL) cause numerous phenotypic defects, including sterility. In the postnatal ovary, Kit is expressed on the oocyte surface and KL is produced by the surrounding granulosa cells, but its function in these cells is still unknown. The purpose of this study was to determine the role KL/Kit interactions play in the regulation of oocyte meiosis. Here, we demonstrate that meiotically arrested rat oocytes that are microinjected with Kit antisense oligonucleotides have decreased Kit expression. This decreased expression is associated with an increased ability of these oocytes to resume meiosis compared with those microinjected with missense oligonucleotides or buffer alone. In addition, oocytes cultured in the presence of KL were delayed in their resumption of meiosis, but KL could not enhance the meiosis inhibitory effects of dibutyryl cAMP, suggesting that KL operates through a mechanism that is independent of cAMP. Human chorionic gonadotropin-induced meiotic resumption in oocytes was accompanied by a shift in follicular granulosa cell KL expression from membrane-bound to soluble forms and a loss of expression of both forms of KL in cumulus cells. Thus, KL-activated Kit inhibits meiotic progression, and the in vivo luteinizing hormone-stimulated resumption of meiosis may negate Kit activity by a localized decrease in KL expression and by altering the form of KL produced within the follicle.

Alternative Splicing↗
PubMed1996

Spinal metastases as a first presentation of malignant astrocytoma.

A 46-year-old man presented with low dorsal pain and paresthesia. Computed tomography showed an osteolytic lesion involving most of the vertebral body and the left pedicle of the 12th thoracic vertebra (T12). Contrast-enhanced magnetic resonance imaging (MRI) of the spine showed an enhancing soft-tissue mass that involved the T11 and T12 vertebral bodies, as well as that of the first lumbar vertebra; the mass caused cord compression. Another lesion was identified at T9. The findings of percutaneous needle aspiration biopsy of the lesion were consistent with metastatic astrocytoma, a diagnosis confirmed at surgery. MRI of the brain showed an asymptomatic lesion of the left temporal lobe; histologic confirmation of malignant astrocytoma was obtained by stereotactic biopsy. This report shows that metastatic bone disease secondary to malignant astrocytoma may manifest itself before the primary lesion becomes symptomatic. This presentation of astrocytoma was unusual because there were no symptoms of the intracranial tumour and because metastatic disease to the bones is less common than to the chest and the lymph nodes.

Astrocytoma↗
PubMed1994

Replication of a Moloney murine leukemia virus mutant lacking the ELP binding site.

A mutant Moloney murine leukemia virus was created in which the binding site for the embryonal long terminal repeat binding protein had been replaced with a synthetic linker sequence. The virus was found to replicate normally in murine 3T3 fibroblasts, and the mutation was stably transmitted throughout repeated passages. The binding site is therefore dispensable with respect to viral replication. Titers of the mutant virus were comparable to those of wild-type preparations, even when supernatants were prepared from undifferentiated P19 embryonal carcinoma cells. Elimination of the repressor binding site therefore had little effect on viral replication in embryonal carcinoma cells. Elimination of the repressor binding site therefore had little effect on viral replication in embryonal cells, an unexpected result in light of the reported activity of the binding protein as a transcriptional repressor.

3T3 Cells↗
PubMed1994

The individual microbiologic effect of three antimycobacterial agents, clofazimine, ethambutol, and rifampin, on Mycobacterium avium complex bacteremia in patients with AIDS.

The individual antibacterial activities of clofazimine, ethambutol, and rifampin in the treatment of Mycobacterium avium complex bacteremia in patients with AIDS were determined. Sixty human immunodeficiency virus 1-infected patients who had at least one blood culture positive for M. avium complex were randomized to receive either clofazimine (200 mg), ethambutol (15 mg/kg), or rifampin (600 mg) once daily for 4 weeks. Only ethambutol resulted in a statistically significant reduction in the level of mycobacteremia. The median change in individual baseline colony counts was -0.60 log10 cfu/mL after 4 weeks of ethambutol (P = .046). In contrast, median changes in individual baseline colony counts were -0.2 log10 cfu/mL and +0.2 log10 cfu/mL for clofazimine and rifampin, respectively (both, P > .4). Ethambutol had greater antibacterial activity, as determined by changes in the level of mycobacteremia, than either rifampin or clofazimine, supporting its continued use in combination with other agents in the treatment of M. avium infection.

AIDS-Related Opportunistic Infections↗
PubMedDate not supplied

Comparison of streptokinase and urokinase in local thrombolysis of peripheral arterial occlusions for lower limb salvage.

PURPOSE: To compare the efficacy and safety of streptokinase (SK) and urokinase (UK) in the treatment of local thrombolysis. PATIENTS AND METHODS: Over a 24-month period, 40 patients with 45 lower limb arterial occlusions of less than 45 days duration underwent intraarterial fibrinolysis. Twenty occlusions were treated with recombinant UK and tissue culture-derived UK, and 25 occlusions were treated with SK. The study was retrospective, but the two groups were very homogeneous in terms of vascular surgical history, medical risk factors, and occlusion characteristics. RESULTS: Complete lysis (95% or more) was achieved in 84% of SK infusions and 89% of UK infusions. Endoluminal and surgical interventions as well as clinical outcomes of SK and UK treatment were comparable. However, infusion time was significantly longer for SK treatment: 28.5 hours versus 19.1 hours for UK treatment (P = .035). Complication rates were not statistically significantly different. Average length of stay in the intensive care unit was identical (2.2 days) for both groups, and the difference in hospital stay was not statistically significant (7.7 days for SK vs 8.7 days for UK). CONCLUSION: At the concentrations and doses used, the efficacy and safety of SK and UK were comparable, despite longer SK infusion time.

Arterial Occlusive Diseases↗