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J Doucet

Publications and source records attributed to J Doucet.

At least 19 recordsLinked to original sources
PubMed2001

Coactosin-like protein, a human F-actin-binding protein: critical role of lysine-75.

Coactosin-like protein (CLP) was recently identified in a yeast two-hybrid screen using 5-lipoxygenase as bait. In the present study, we report the functional characterization of CLP as a human filamentous actin (F-actin)-binding protein. CLP mRNA shows a wide tissue distribution and is predominantly expressed in placenta, lung, kidney and peripheral-blood leucocytes. Endogenous CLP is localized in the cytosol of myeloid cells. Using a two-hybrid approach, actin was identified as a CLP-interacting protein. Binding experiments indicated that CLP associates with F-actin, but does not form a stable complex with globular actin. In transfected mammalian cells, CLP co-localized with actin stress fibres. CLP bound to actin filaments with a stoichiometry of 1:2 (CLP: actin subunits), but could be cross-linked to only one subunit of actin. Site-directed mutagenesis revealed the involvement of Lys(75) of CLP in actin binding, a residue highly conserved in related proteins and supposed to be exposed on the surface of the CLP protein. Our results identify CLP as a new human protein that binds F-actin in vitro and in vivo, and indicate that Lys(75) is essential for this interaction.

Actins↗
PubMed2001

Investigation of human hair cuticle structure by microdiffraction: direct observation of cell membrane complex swelling.

The cuticle of mammalian hair fibres protects the core of the fibre against physical and chemical stress. The structure and some of the properties of the cuticle have been extensively studied by electron microscopy. However, there is still a need for a less invasive structural probe. For this purpose, microdiffraction experiments have been carried out on human hair samples showing a characteristic small-angle X-ray scattering pattern for the cuticle. This pattern has been assigned to the cell membrane complex (CMC) between each cuticle scale. Using a simple model of the electron density within the CMC, values have been derived for the average thickness of the beta- and delta-layers which are close to those obtained by electron microscopy. In order to illustrate the potentialities of microdiffraction in studying the properties of the cuticle, the effect of water sorption has been monitored. Using the intensity modelling described above, a 10% swelling of the delta-layer's thickness has been observed. This study shows that structural modifications of the CMC by physical or chemical stress can be followed directly on the cuticle of human hair fibres by microdiffraction analysis.

Cell Membrane↗
PubMed2001

Unraveling double stranded alpha-helical coiled coils: an x-ray diffraction study on hard alpha-keratin fibers.

Transformations of proteins secondary and tertiary structures are generally studied in globular proteins in solution. In fibrous proteins, such as hard alpha-keratin, that contain long and well-defined double stranded alpha-helical coiled coil domains, such study can be directly done on the native fibrous tissue. In order to assess the structural behavior of the coiled coil domains under an axial mechanical stress, wide angle x-ray scattering and small angle x-ray scattering experiments have been carried out on stretched horse hair fibers at relative humidity around 30%. Our observations of the three major axial spacings as a function of the applied macroscopic strain have shown two rates. Up to 4% macroscopic strain the coiled coils were slightly distorted but retained their overall conformation. Above 4% the proportion of coiled coil domains progressively decreased. The main and new result of our study is the observation of the transition from alpha-helical coiled coils to disordered chains instead of the alpha-helical coiled coil to beta-sheet transition that occurs in wet fibers.

Animals↗
PubMed2001

5-Lipoxygenase interacts with coactosin-like protein.

We have recently identified coactosin-like protein (CLP) in a yeast two-hybrid screen using 5-lipoxygenase (5LO) as a bait. In this report, we demonstrate a direct interaction between 5LO and CLP. 5LO associated with CLP, which was expressed as a glutathione S-transferase fusion protein, in a dose-dependent manner. Coimmunoprecipitation experiments using epitope-tagged 5LO and CLP proteins transiently expressed in human embryonic kidney 293 cells revealed the presence of CLP in 5LO immunoprecipitates. In reciprocal experiments, 5LO was detected in CLP immunoprecipitates. Non-denaturing polyacrylamide gel electrophoresis and cross-linking experiments showed that 5LO binds CLP in a 1:1 molar stoichiometry in a Ca(2+)-independent manner. Site-directed mutagenesis suggested an important role for lysine 131 of CLP in mediating 5LO binding. In view of the ability of CLP to bind 5LO and filamentous actin (F-actin), we determined whether CLP could physically link 5LO to actin filaments. However, no F-actin-CLP.5LO ternary complex was observed. In contrast, 5LO appeared to compete with F-actin for the binding of CLP. Moreover, 5LO was found to interfere with actin polymerization. Our results indicate that the 5LO-CLP and CLP-F-actin interactions are mutually exclusive and suggest a modulatory role for 5LO in actin dynamics.

Actins↗
PubMed2001

Cardiac malignant lymphoma successfully treated with chemotherapy.

We report the case of an 83-year-old woman with diffuse large B-cell lymphoma located in the right cardiac ventricle revealed by acute congestive heart failure. Complete and long-lasting disappearance of the cardiac tumor was observed with monochemotherapy (cyclophosphamide).

Journal Article↗
PubMed2001

Does age play a role in mylohyoideus muscle function?

Because swallowing disorders are frequent in the elderly, we assessed the relationship between age and mylohyoideus muscle contraction, which is an important component of the initial step in swallowing. In a prospective study, 120 subjects without any personal history of diseases associated with swallowing disorders underwent electromyographic recording (EMG) of mylohyoideus muscle activity. Four groups of equal size (n = 30) were defined according to age (< or = 50, 51-70, 71-85, >85 years). The frequency and duration of mylohyoideus muscle asynchronisms were compared among the four groups. The comparison of mylohyoideus muscle EMG among groups did not show a significant difference in the mean number of asynchronisms, in duration per subject or in the frequency of long-lasting asynchronisms. Asynchronisms were a very frequent event, observed in 98% of subjects, and were mostly short, lasting less than 0.1 s in 90% of subjects. In healthy elderly patients, there was no linear relationship between the mean duration of asynchronisms and ageing. The occurrence of one or more long-lasting asynchronisms or of at least six asynchronisms during a sequence of 10 successive swallows should be considered to be abnormal.

Aged↗
PubMed2000

Aberrant expression of active leukotriene C(4) synthase in CD16(+) neutrophils from patients with chronic myeloid leukemia.

Elevated leukotriene (LT)C(4) synthase activity was observed in peripheral blood granulocyte suspensions from patients with chronic myeloid leukemia (CML). Magnetic cell sorting (MACS) with CD16 monoclonal antibodies (mAbs), which were used to fractionate granulocytes from CML patients and healthy individuals, yielded highly purified suspensions of CD16(+) neutrophils. The purity of these cell fractions was verified by extensive morphologic examination. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses, demonstrating the absence of interleukin-4 messenger RNA (IL-4 mRNA), further confirmed the negligible contamination of eosinophils in these fractions. Notably, purified CML CD16(+) neutrophils from all tested patients transformed exogenous LTA(4) to LTC(4). These cells also produced LTC(4 )after activation with ionophore A23187 or the chemotactic peptide fMet-LeuPhe (N-formylmethionyl-leucyl-phenylalanine). Subcellular fractionation revealed that the enzyme activity was exclusively distributed to the microsomal fraction. Expression of LTC(4) synthase mRNA in CML CD16(+) neutrophils was confirmed by RT-PCR. Furthermore, Western blot analyses consistently demonstrated expression of LTC(4) synthase at the protein level in CML CD16(+) neutrophils, whereas expression of microsomal glutathione S-transferase 2 occurred occasionally. Expectedly, LTC(4) synthase activity or expression of the protein could not be demonstrated in CD16(+) neutrophil suspensions from any of the healthy individuals. Instead, these cells, as well as CML CD16(+) neutrophils, transformed LTA(4) to LTB(4). The results indicate that aberrant expression of LTC(4) synthase is a regular feature of morphologically mature CML CD16(+) neutrophils. This abnormality, possibly associated with malignant transformation, can lead to increased LTC(4) synthesis in vivo. Such overproduction may be of pathophysiological relevance because LTC(4 )has been demonstrated to stimulate proliferation of human bone marrow-derived myeloid progenitor cells. (Blood. 2000;95:1456-1464)

Antigens, CD↗
PubMed2000

[Is cognitive change related to hypothyroidism reversible with replacement therapy?].

PURPOSE: Although cognitive impairment related to hypothyroidism has been investigated, issues regarding treatment have been less extensively studied. The aim of this study was to assess cognitive function in patients with hypothyroidism just before treatment and after hypothyroidism had resolved. METHODS: Standardized psychometric assessment (including ten tests) was done in 30 outpatients with biochemical evidence of hypothyroidism (TSH = 92.1 mU/L, range: 11.4-400) and in 30 control subjects matched for age and gender with normal thyroid function. These tests were repeated twice before treatment and after hypothyroidism had been cured. Statistical analysis was done using the Mann-Whitney U test. RESULTS: The baseline characteristic of patients with hypothyroidism showed that attention, motor speed, memory and visual-spatial organization were significantly impaired. Cognitive decline was significantly greater with increasing age. Cognitive impairment significantly decreased after hypothyroidism had been cured, reaching values obtained in age-matched control subjects. CONCLUSION: Attention, motor speed, memory and visual-spatial organization are significantly impaired in hypothyroidism, particularly in the elderly, suggesting that ageing could have potential effects on cognitive functions. Hormone-replacement therapy leads to normalization of the cognitive functions.

Age Factors↗
PubMed2000

Pesticide residues in the Canadian Market Basket Survey--1992 to 1996.

Market basket food samples from six Canadian cities collected from 1992 to 1996 were analysed for pesticide residues. One hundred and thirty-six composites were prepared for each city, representing 99% of the Canadian diet. Residues were found most frequently in peanut butter and butter. DDE, malathion and captan occurred most frequently, while the fungicides chlorothalonil, dicloran and captan were present in the highest concentrations. Processed commodities contained fewer residues and at lower concentrations than the raw products. No residues were detected in either milk or soy-based infant formula. Of the infant foods sampled, fruit contained both the greatest number and highest concentrations of pesticides.

Arachis↗
PubMed2000

Does treatment of constipation improve faecal incontinence in institutionalized elderly patients?

OBJECTIVE: to evaluate whether faecal incontinence can be improved by treatment of constipation in elderly patients with faecal incontinence associated with impairment of rectal emptying. DESIGN: a prospective randomized study with a 2-month follow-up. SETTING: five long-term care units. SUBJECTS: 206 patients with daily faecal incontinence associated with chronic rectal emptying impairments such as faecal impaction received either a single osmotic laxative (group I) or an osmotic agent along with a rectal stimulant and weekly enemas (group II). MEASUREMENTS: episodes of faecal incontinence and associated details of soiled laundry (used as indicators of the workload for caregivers). We performed periodic digital rectal examinations on group II patients to evaluate whether treatment resulted in complete and long-lasting rectal emptying. We compared data between groups and in group II between persistently constipated patients and patients with complete rectal emptying. RESULTS: the frequency of faecal incontinence did not significantly differ between the two groups. The 23 patients in group II who had complete rectal emptying had 35% fewer episodes of faecal incontinence and 42% fewer incidents of soiled laundry than the rest of the group. CONCLUSIONS: when long-lasting and complete rectal emptying is achieved by laxatives, the number of episodes of faecal incontinence as well as the workload for caregivers is reduced.

Aged↗
PubMed2000

trans-Nonachlor and cis-nonachlor toxicity in Sprague-Dawley rats: comparison with technical chlordane.

cis-Nonachlor and trans-nonachlor are bioaccumulating components of the pesticide chlordane, which can be detected in various environmental biota and in humans. Existing studies have focused on the potential adverse health effects of the parent chlordane mixture. Comparable toxicity data are nonexistent for individual chlordane constituents such as trans-nonachlor, cis-nonachlor, or oxychlordane, which are among the most common chlordane-related environmental contaminants and tissue residues. In this study, rats were administered cis-nonachlor, trans-nonachlor, or technical chlordane by gavage for 28 days at doses of 0.25 to 25 mg/kg body weight. Residue analyses indicated that trans-nonachlor accumulation in adipose was greater than cis-nonachlor when rats were administered each chemical under identical conditions of dose and exposure. For all test chemicals, the major metabolite oxychlordane accumulated in adipose tissue. Adipose tissue residue levels of all test chemicals and the major metabolite were higher in female rats. The liver was a target organ in male and female rats, indicated by increased liver weight and histopathological changes consistent with microsomal enzyme induction. Hepatic changes were most pronounced in rats treated with trans-nonachlor. Elevated kidney weights and depressed organic ion transport were observed in males treated with trans-nonachlor and chlordane. Although in general, changes in target organs and clinical chemistry endpoints were similar for all 3 test chemicals, the approximate toxicity ranking from most to least toxic was trans-nonachlor > technical chlordane > cis-nonachlor.

Animals↗
PubMed2000

Distribution and interference functions for two-dimensional hexagonal paracrystals.

The notion of a paracrystal is particularly well adapted to the calculation of the scattering interference function of distorted crystallographic lattices in which the long-range order does not exist. However, classical paracrystal modelling cannot be used directly for hexagonal lattices because it does not respect the hexagonal symmetry. Here an analytical determination of the distribution and interference functions for two-dimensional hexagonal paracrystals is presented.

Journal Article↗
PubMed2000

Initial experience of an objective structured clinical examination in evaluating urology residents.

OBJECTIVES: Objective Structured Clinical Examination (OSCE) is now generally considered as the new gold standard for evaluating clinical competence. The objective of this study was to assess the feasibility of OSCE in evaluating urology residents. MATERIAL AND METHODS: 20 urology residents rotated through a circuit of five standardized patient-based OSCE stations of 10 min duration. The selection of problems was based on educational objectives of urology residency programs. Written questionnaires based on Likert-type scales were used to measure OSCE feasibility. The mean score was arbitrarily used as a passing score. Student t test was only used to compare the performance between junior and senior residents. RESULTS: Senior residents performed globally better, but without significant differences (51.3+/-7.8 vs. 45.03+/-5.1, p>0.05). Senior resident scores regarding outpatient problems were significantly higher (p = 0.04), more senior residents reached the passing score (75 vs. 16% junior residents). All the participants agreed that the clinical situations were realistic and that the simulated patients were believable. Most participants agreed that the sampling of cases were representative of urology practice. CONCLUSIONS: This is the first reported OSCE applied to urology residency. The results of this pilot study support the feasibility of an OSCE in assessing the performance of urology residents. Our data raises questions regarding the training of outpatient consultation skills to residents. This experiment warrants further series to explore the study's psychometrics features.

Clinical Competence↗
PubMed2000

Exploring a biological tissue from atomic to macroscopic scale using synchrotron radiation: example of hair.

A combined approach, using synchrotron radiation-based diffraction and infrared microspectrometry, has been used to study the structure and molecular composition of hair samples. These methods allowed us to get an insight at different structural scales into the composition and structure of hair. Firstly, information about the configuration of amino-acid residues was obtained at atomic scale, secondly, a model was presented for the geometry and the packing of the microfibrils at medium scale and finally different structural zones were evidenced by microdiffraction at macroscopic scale. We also showed that the two main components of hair--proteins and lipids--are not evenly distributed within the fiber. In addition, these two components exhibit different structure, depending upon their location. Moreover, diffraction and microdiffraction data indicate that the cuticle zone is mainly composed of lipid granules, whereas the cortex and the medulla zones are composed primarily of alpha-keratin. Infrared microspectroscopy, using an enhanced lateral resolution thanks to synchrotron radiation, indicates, on one hand, that the protein structure between the cuticle and cortex are different, and on the other hand, that the concentration of lipids, inside the medulla, is much higher than everywhere else. This work emphasizes the complementarity between both techniques, and highlights the potentialities they can offer in the case of various other studies in biology.

Hair↗
PubMed2000

Study of the keratinization process in human hair follicle by X-ray microdiffraction.

Synchrotron X-ray micro-diffraction studies along the follicle and the hair fibre allowed us to follow the keratinization process and the progressive organization of the keratin: i) molecular organization appeared progressively in the follicle; the formation of alpha-helices was completed inside the follicle. ii) supramolecular organization appeared only outside the follicle, far from the bulb; filament structure was observed far from the follicle. Comparisons between structures observed for in vitro and in vivo grown hair, whatever in the bulb or in the fibre, indicate there is no evidence of any structural difference. More, no variation in the transition in vivo/in vitro zone has been observed. In vitro and in vivo fibres exhibited the same structure.

Hair↗