Showing papers by "Université de Sherbrooke published in 1994"

L’analyse par théorisation ancrée

Abstract: Cet article presente en detail les etapes d’une methode d’analyse qualitative, l’analyse par theorisation ancree, qui est une adaptation-transformation de la grounded theory approach. La methode permet de theoriser un phenomene empirique a travers la codification, la categorisation, la mise en relation, l’integration, la modelisation et la theorisation. La presentation de la methode est illustree par des exemples de recherches menees par l’auteur.

Human monocytes/macrophages: NO or no NO?

Abstract: The production of nitric oxide (NO) and other reactive nitrogen intermediates by cytokine- activated rodent cells is an important component of an- timicrobial and/or antineoplasic activity of these cells. This pathway involves the oxidation of arginine to citrul- line, with the concomitant release of NO by an inducible form of NO synthase (iNOS). Numerous cell types express iNOS after stimulation with bacterial products and/or cytokines. The role of NO and its derivatives in host resistance is a subject of intense investigation in mouse models of infections or neoplasia. Although human cells such as hepatocytes and endothelial cells have been shown to express an inducible NO synthase, the presence of such a pathway in human monocytes/macrophages has been questioned by many investigators and is a subject of great controversy. In this short review, we discuss some salient points of this debate.J. Leukoc. Biol. 55: 682-684; 1994.

The A1 and A1B proteins of heterogeneous nuclear ribonucleoparticles modulate 5' splice site selection in vivo.

Abstract: Recent in vitro results suggest that the heterogeneous nuclear ribonucleoparticle (hnRNP) A1 protein modulates alternative splicing by favoring distal 5' splice site (5'SS) selection and exon skipping. We used a mouse erythroleukemia (MEL) cell line (CB3C7) deficient in the expression of hnRNP A1 to test whether variations in hnRNP A1 and AlB protein levels affected alternative splicing in vivo. In contrast to A1-expressing MEL cell lines, CB3C7 cells preferentially selected the proximal 13S and 12S 5'SS on the adenovirus E1A pre-mRNA. Transiently expressing the A1 or A1B cDNA in CB3C7 cells shifted 5'SS selection toward the more distal 9S donor site. A1 protein synthesis was required for this effect since the expression of a mutated A1 cDNA did not affect 5'SS selection. These results demonstrate that in vivo variations in hnRNP A1 protein levels can influence 5'SS selection.

Charged spin-texture excitations and the Hartree-Fock approximation in the quantum Hall effect

Abstract: We develop a Hartree-Fock approach to the charged spin-texture excitations (CSTE's) of the ferromagnetic incompressible ground state, which occurs in the quantum Hall effect at Landau-level filling factor [nu]=1. The CSTE's are the appropriate generalization of skyrmions to the situation when there is a nonzero Zeeman coupling. We find for Coulomb interactions that the charged spin-texture excitation energies are always smaller than the excitation energies of localized spin 1/2 quasiparticles and quasiholes. However, the amount by which the energy is lowered is quite small for typical experimental situations. The net spin of the CSTE's is always much larger than 1/2, suggesting that adding or removing charge from a filled Landau level rapidly degrades its spin polarization.

Management of occupational back pain: the Sherbrooke model. Results of a pilot and feasibility study.

Abstract: OBJECTIVES--The aim was to combat occurrence of chronic occupational back pain. METHODS--A multidisciplinary model to manage back pain that includes both clinical and ergonomic approaches has been developed. Early detection, early clinical and ergonomic evaluations, and early active treatment make up the cornerstone of management. Detection of cases starts after four weeks of absence from work. An ergonomic intervention is implemented at six weeks. A medical specialist is involved at eight weeks. If return to work is not possible after 12 weeks, a functional recovery therapy followed by a therapeutic return to work is implemented. A multidisciplinary team decides if return to original or modified work is possible or if vocational rehabilitation is necessary. This model has been implemented by the investigators in the Sherbrooke (Quebec, Canada) area, and is presently being evaluated through a randomised trial in 31 industrial settlements (about 20,000 workers). A cluster randomisation of industries and workers will allow separate testing of ergonomic and clinical interventions. RESULTS--One year after implementation, 31 of 35 of the eligible industrial sites participated in the study and 79 of 88 of the eligible workers affected by recent back pain had agreed to participate. Ergonomic and clinical interventions have been implemented as planned. Only three workers dropped out. Hence this global clinical and ergonomic management programme has been shown to be feasible in a general population. CONCLUSION--A global management programme of back pain joining ergonomic and clinical intervention with a multidisciplinary approach has not been tested yet. Linking these two strategies in a same multidisciplinary team represents a systemic approach to this multifactorial ailment. During the first year of this trial we did not find any conflict between these two interventions from the employer's or worker's point of view.

Glibenclamide vs gliclazide in type 2 diabetes of the elderly.

Abstract: The objective of this study was to compare the effect of two sulphonylureas on the frequency of hypoglycaemic events and glycaemic control in elderly patients with Type 2 diabetes. Twenty-two untreated elderly patients were treated with glibenclamide or gliclazide in a randomized double-blind fashion. Prior to treatment, a biochemical profile, an oral glucose tolerance test, and a 2-h hyperglycaemic glucose clamp (glucose 5.4 mmol l-zs-1 above baseline) were performed. Patients were seen regularly over 6 months to assess glycaemic control and the frequency of hypoglycaemic reactions. Hyperglycaemic clamp studies and oral glucose tolerance tests were repeated at 1 and 6 months. The area under the curve for the oral glucose tolerance test (glibenclamide: 15.5 +/- 0.7; gliclazide: 14.9 +/- 0.8 mmol l-1 (p = NS)) and the haemoglobin A1C (glibenclamide: 7.4 +/- 0.2%; gliclazide: 7.9 +/- 0.5% (p = NS)) were similar at 6 months. Hypoglycaemic reactions were significantly more frequent with glibenclamide than with gliclazide: 17 vs 4 (p < 0.01). Insulin sensitivity index (ml kg-1 min-1 pmol-1 x 100) was increased significantly by glibenclamide but not gliclazide (glibenclamide: 0.284 +/- 0.116 (baseline) vs 0.518 +/- 0.102 (6 months) (p < 0.05), gliclazide: 0.260 +/- 0.048 (baseline) vs 0.358 +/- 0.048 (6 months) (p = NS)). We conclude that glycaemic control was equivalent with the two drugs but the incidence of hypoglycaemic reactions was significantly greater with glibenclamide probably because this drug increases insulin sensitivity to a greater degree.

A toll quality 8 kb/s speech codec for the personal communications system (PCS)

Abstract: A toll quality speech codec at 8 kb/s suitable for the future personal communications system is presented. The codec is currently under standardization by the ITU-T (successor of CCITT) where the codec terms of reference were mainly determined considering PCS application. The encoding algorithm is based on algebraic code-excited linear prediction (ACELP) and has a speech frame of 10 ms. Efficient pitch and codebook search strategies, along with efficient quantization procedures, have been developed to achieve toll quality encoded speech with a complexity implementable on current fixed-point DSP chips. Formal subjective listening tests, performed by ITU-T SG 12, showed that the codec quality is equivalent to that of G.726 ADPCM at 32 kb/s in error-free conditions and it outperforms G.726 under error conditions. The codec performs adequately under tandeming conditions, and can support a frame erasure rate up to 3% with a degradation in its performance that is still worse than the ITU-T requirements, and this is one subject of study for the next phase. The algorithm has been implemented on a single fixed-point DSP for the ITU-T subjective rest, and required about 29 MIPS. An optimized version, however, requires 24 MIPS without any speech quality degradation. >

Design and engineering aspects of a high resolution positron tomograph for small animal imaging

Abstract: Describes the Sherbrooke positron emission tomograph, a very high resolution device dedicated to dynamic imaging of small laboratory animals. Its distinctive features are: small discrete scintillation detectors based on avalanche photodiodes (APD) to achieve uniform, isotropic, very high spatial resolution; parallel processing for low deadtime and high count rate capability; multispectral data acquisition hardware to improve sensitivity and scatter correction; modularity to allow design flexibility and upgradability. The system implements the "clam-shell" sampling scheme and a rotating rod transmission source. All acquisition parameters can be adjusted under computer control. Temperature stability at the detector site is ensured by the use of thermoelectric modules. The initial system consists of one layer of 256 modules (two rings of detectors) defining 3 image slices in a 118 mm diameter by 10.5 mm thick field. The axial field can be extended to 50 mm using 4 layers of modules (8 rings of detectors). The design constraints and engineering aspects of an APD-based PET scanner are reviewed and preliminary results are reported. >

Dysregulation of interleukin 8, interleukin 10, and interleukin 12 release by alveolar macrophages from HIV type 1-infected subjects.

Abstract: We examined the in vitro release of interleukin 8 (IL-8), interleukin 10 (IL-10), and interleukin 12 (IL-12) by alveolar macrophages from normal volunteers and HIV-1-infected subjects. Normal volunteers had very low levels of IL-8 and IL-10 and undetectable IL-12 in the cell-free bronchoalveolar lavage fluid (BALF). Asymptomatic HIV-1-infected subjects had elevated levels of IL-8 and IL-10 in their BALF, and HIV-1-infected subjects with nonspecific interstitial pneumonitis (NIP) or infected with Pneumocystis carinii had the highest BALF levels of IL-10 and IL-8. It was found that alveolar macrophages from asymptomatic HIV-1 subjects and from NIP subjects spontaneously released elevated IL-8, IL-10, and IL-12. However, AIDS subjects infected with P. carinii had cells that released elevated levels of IL-10 and IL-8, but low levels of IL-12. When alveolar macrophages were stimulated with Staphylococcus aureus Cowan (SAC), cells from normal volunteers responded with a considerably increased release of IL-8, IL-10, and IL-12; cells from HIV-1-infected subjects without P. carinii infection responded with a moderate increase in release of all three monokines. SAC stimulation did not enhance the release of monokines by cells from AIDS subjects with P. carinii infection, and IL-12 levels remained low. There was no strict relationship between spontaneous cytokine release and p24 HIV-1 antigen expression by alveolar macrophages. Finally, we showed that neutralizing IL-10 production by alveolar macrophages from AIDS subjects substantially increased IL-12 releasability.(ABSTRACT TRUNCATED AT 250 WORDS)

High quality coding of wideband audio signals using transform coded excitation (TCX)

Abstract: This paper describes the application of transform coded excitation (TCX) coding to encoding wideband speech and audio signals in the bit rate range of 16 kbits/s to 32 kbits/s. The approach uses a combination of time domain (linear prediction; pitch prediction) and frequency domain (transform coding; dynamic bit allocation) techniques, and utilizes a synthesis model similar to that of linear prediction coders such as CELP. However, at the encoder, the high complexity analysis-by-synthesis technique is bypassed by directly quantizing the so-called target signal in the frequency domain. The innovative excitation is derived at the decoder by inverse filtering the quantized target signal. The algorithm is intended for applications whereby a large number of bits is available for the innovative excitation. The TCX algorithm is utilized to encode wideband speech and audio signals with a 50-7000 Hz bandwidth. Novel quantization procedures including inter-frame prediction in the frequency domain are proposed to encode the target signal. The proposed algorithm achieves very high quality for speech at 16 kbits/s, and for music at 24 kbits/s. >

High-Resolution PET Imaging and Quantitation of Pharmaceutical Biodistributions in a Small Animal Using Avalanche Photodiode Detectors

Abstract: UNLABELLED The feasibility of high-resolution PET using BGO-avalanche photodiode detectors for in vivo imaging and quantitation of the biodistribution of radiopharmaceuticals in small animals is demonstrated. A prototype PET camera consisting of two scanning arrays of eight EG&G C30994 solid-state scintillation detectors was used to simulate a 310-mm diameter dual-ring animal tomograph having a 130-mm port and three imaging slices, each about 3.5 mm thick. The spatial resolution (FWHM) is 3 mm or less, isotropic and uniform throughout the 120-mm diameter field of view. METHODS Female Fischer 344/CRBL rats implanted with subcutaneous mammary adenocarcinoma tumors were injected with copper-tetrasulfophthalocyanine (CuPcS4), a potential sensitizer for the photodynamic therapy of cancer, labeled with 64Cu (T1/2 = 12.7 hr, beta +:19%). RESULTS In spite of the low specific radioactivity of 64Cu and other inherent limitations, organs such as the liver, kidneys and the tumor could be resolved with sufficient detail for their separation and quantitation. Apart from the tumor, agreement was obtained between the biodistributions measured by PET and by scintillation counting. The discrepancy for the tumor measurement results from averaging the radioactivity over the entire tumor volume when, in fact, CuPcS4 does not completely penetrate the tumor. This incomplete penetration is noted on the PET images. CONCLUSIONS PET based on avalanche photodiode detectors provides an accurate measurement of target organ and tumor tissue concentrations. These preliminary results demonstrate the potential of very high resolution PET for biodistribution studies in small animals.

Quantitative structure-activity relationships/comparative molecular field analysis (QSAR/CoMFA) for receptor-binding properties of halogenated estradiol derivatives.

Abstract: interactions. The model with the best predictive performance (r2 = 0.895) was used to visualize steric and electrostatic features of the QSAR (standard deviation*coefficient contour maps) and to predict receptor-binding affinities (RBA) of substituted estradiols other than those included in the original database. Twenty-seven test molecules were selected, including five which had previously been reported by other investigators. For the latter, a very good correlation with literature RBA values was obtained, which together with the high crossvalidated r2 provides evidence for the high predictive capacity of the model. Among the unknown structures, the model suggests several new substitutions to derive at reasonable affinity ligands for the estrogen receptor.

Synthesis and photodynamic activities of silicon 2,3-naphthalocyanine derivatives.

Abstract: Bis(tert-butyldimethylsiloxy)- (7), bis(dimethylthexylsiloxy)- (8), bis(tri-n-hexylsiloxy)- (9), and bis(dimethyloctadecylsiloxy)silicon 2,3-naphthalocyanines (10) were prepared via substitution of the bis(hydroxy) precursor with the corresponding chlorosilane ligands and characterized by spectroscopic and combustion analyses. They show strong absorption around 780 nm where tissues exhibit optimal transparency. Compounds 7-10 are capable of producing singlet oxygen. They are relatively photostable although less stable than the analogous phthalocyanine, i.e., the bis-(dimethylthexylsiloxy)silicon phthalocyanine (12). They were evaluated as potential photosensitizers for the photodynamic therapy (PDT) of cancer in vitro against V-79 cells and in vivo against the EMT-6 tumor in Balb/c mice. In vitro all four dyes showed limited phototoxicity combined with substantial dark toxicity. Surprisingly, in vivo (i.v., 0.1 mumol/kg, 24 h prior to the photoirradiation of the tumor with 780-nm light, 190 mW/cm2, 400 J/cm2) all dyes induced tumor regression in at least 50% of mice whereas compound 8 gave a complete tumor response in 80% of mice without apparent systemic toxicity at doses as high as 10 mumol/kg. At 24 h postinjection, compound 8 showed a favorable tumor to muscle ratio of 7, assuring minimal damage to the healthy tissue surrounding the tumor during PDT. Our data confirm the potential of silicon naphthalocyanines as far-red-shifted photosensitizers for the PDT of cancer and indicate the importance of the selection of the two axial silicon ligands for optimal photodynamic efficacy.

Rheological properties of structured fluids

Abstract: The kinetic theory proposed by Soong and Liu for describing the rheological properties of structured fluids has been extended to predict shear-thinning, shear-thickening, thixotropy, and antithixotropy in different ranges of shear rates. Viscoelastic properties, as given by the Gordon-Schowalter Maxwell model, with a non-constant modulus, have also been considered. The theoretical predictions are compared with the predictions of a model used by Ait-Kadi, et al. (1988), for a hydrolyzed polyacrylamide solution containing 20 g/1 of NaCl. the predictions and experimental data for the viscosity and primary normal stress coefficient are in reasonably good agreement. The stress growth functions have also been calculated and have been found to be consistent with experimental observations.

Polyionic Hydrogels Obtained by Complexation between Xanthan and Chitosan: Their Properties as Supports for Enzyme Immobilization

Abstract: A method for the preparation of hydrogels from the complexation of chitosan and xanthan is reported. Stable hydrogels capable of retaining be tween 65 and 95% weight water were prepared. The water retention and prop erties of the hydrogels were studied as a function of the degree of acetylation of chitosan and the ratio chitosan/xanthan used in the preparation of the gel. Spectroscopic FTIR was used to confirm complexation between the amine (chi tosan) and carboxylic (xanthan) groups. Electron micrographs (SEM and TEM) show the formation of a fibrillar structure with characteristic pore sizes be tween 100 and 1000 nm and fibril diameters between 50 and 100 nm. The diffu sion coefficient of 4-O-methyl-d-glucurono-D-xylan Remazol Brilliant Blue R (RBB-xylan) in the complex chitosan-xanthan was 2.02 × 10-12 m 2s-1 at 30°C. The chitosan-xanthan complex was used to immobilize two enzymes (endo-1,4- β-xylanase and protease) either as single enzymes or as a binary system. Immo bilization varied between 85 and 98...

Suspension plasma spray

Abstract: The plasma spray method produces a material deposit on a substrate to form either a protective coating of a near net shape body, or produces a powder of a given material. The material is supplied to a plasma discharge in the form of a suspension comprising small solid particles of that material dispersed into a liquid or semi-liquid carrier substance. The suspension is brought into the plasma discharge by an atomizing probe using a pressurized gas to shear the suspension and thus atomize it into a stream of fine droplets. The plasma discharge vaporizes the carrier substance and agglomerate the small solid particles into partially or totally melted drops which are accelerated to hit the substrate and form thereon the coating or near net shape body. Alternatively, the molten drops can be solidified in-flight and collected into a vessel to produce a powder of that material.

Finite-size scaling of the frustrated Heisenberg model on a hexagonal lattice

Abstract: We investigate through Monte Carlo simulations the critical behavior of the antiferromagnetic Heisenberg model on a hexagonal lattice. Critical exponents associated with both magnetic and chiral orderings were estimated. The transition temperatures of these two kinds of order were found to be the same within error margins, in agreement with previous results. The calculation of the Binder parameter also demonstrates that the transition is most likely continuous. The exponents obtained agree, for the most part, with those of Kawamura and thus provide further support for the existence of a new universality class.

Gambiense trypanosomiasis: Frequency of, and risk factors for, failure of melarsoprol therapy

Abstract: 1083 patients with late-stage Trypanosoma brucei gambiense sleeping sickness were treated with melarsoprol in Nioki hospital, Zaire, between 1983 and 1990. Sixty-two (5.7%) died during treatment. Of the 1021 patients who survived the treatment, 63 (6.2%) subsequently relapsed, 58 (92%) of whom were diagnosed within 2 years of melarsoprol treatment. There was no evidence of an increase in the frequency of treatment failures during the study period, and the rate of relapses that we documented is comparable to that reported from Zaire more than 30 years ago. Relapses were more frequent among patients who had trypanosomes seen in the cerebrospinal fluid (CSF) at the time of the initial diagnosis (odds ratio [OR] = 2.76, 95% confidence interval [CI] = 1.65-4.63, P = 0.0001). Male patients had twice as many relapses as females (OR = 2.00, 95% CI = 1.19-3.36, P = 0.009), which was partly explained by males having trypanosomes in the CSF more often than females. There were important geographical variations in the frequency of relapses within the territory of the Nioki rural health zone, suggesting that the circulation of trypanosomes was geographically limited. Prednisolone treatment did not increase the risk of treatment failure, nor did decreasing the total dose of melarsoprol from 12 to 9 injections for patients with > or = 100 white blood cells/mm3 of CSF. Since patients with trypanosomes in the CSF are also those who are at the highest risk of melarsoprol-induced encephalopathy, more aggressive treatment regimens cannot be recommended.(ABSTRACT TRUNCATED AT 250 WORDS)

Limit Relative Category and Critical Point Theory

Abstract: Let X be a Finsler manifold of classC 1 and letf ∈C 1 (X,ℝ). Acritical point off is a pointu ∈X such thatdf(u) = 0. The corresponding valuef(u)is called acritical value. In many applications, the critical points of a functional are the weak solutions of a boundary value problem. For example, the critical points of $$f(u) = \int_{0}^{T} {[ - \frac{1}{2}(Ju,u) - H(t,u)]dt}$$ (1) on an appropriate space of T-periodic functions are the T-periodic solutions of the Hamiltonian system \(Ju + abla H(t,u) = 0,\)where ▽ denotes the gradient with respect tou.

High-order split-step exponential methods for solving coupled nonlinear Schrodinger equations

Abstract: Numerical integration schemes for coupled time-dependent nonlinear Schrodinger equations are examined using exponential splitting step methods. Exponentiation of the nonlinear potential term is reduced to the exponential of a kinetic energy term which can be calculated by fast Fourier transforms. High-order iteration schemes involving a minimum number of product operators are shown to yield highly accurate amplitude and phase. These new splitting methods are shown to be highly efficient both with respect to accuracy and integration time.