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Biomedical subjects

A Dufour

Publications and source records attributed to A Dufour.

At least 19 recordsLinked to original sources
PubMed2006

Rightward shift of the auditory subjective straight ahead in right- and left-handed subjects.

While spatial asymmetries have been extensively investigated in the visual modality and to a lesser degree in the tactile modality, there are no reports on auditory spatial asymmetries in neurologically normal subjects. The subjects in this study performed an auditory midline task in which they had to adjust the level of two sounds that were presented simultaneously in different hemispaces so as to make the perceived fused sound appear to emanate from the midsagittal plane. The results showed that subjects reported a sound to be central when it was lateralized to the left (i.e., more intense at the left ear), as if there were a rightward shift in the perceived location. This rightward shift was more pronounced in left-handed than in right-handed subjects, even though all the subjects had to use both hands to adjust the sound level. Gaze direction significantly modulated the shift of the perceived auditory midline: the rightward shift was maximal when the subjects' gaze direction was central and 30 degrees to the right, while it disappeared when the gaze was directed 30 degrees to the left side. These results are compared with data obtained from neglect patients in previous studies and are discussed in terms of the interaction between asymmetrical hemispheric activations in auditory spatial tasks and an asymmetrical allocation of attention between the left and right hemispaces.

Acoustic Stimulation↗
PubMed2005

Enhanced self-localization by auditory cues in blind humans.

PURPOSE: Investigate the involvement of auditory spatial compensation, which is observed in blind humans, in self-localization processes. METHOD: Sighted and early-blind subjects had to indicate, on a two-dimensional view of the experimental room, the position where they previously sat and had passively listened to auditory spatial cues. Two different environments were distinguished. In a first session, auditory cues (i.e., white broadband sounds) were displayed successively in a dark anechoic room. This condition was defined as a simple acoustic environment. In a second session, four different auditory cues were displayed simultaneously at regular intervals in an experimental room, where echo cues were salient. This condition, which is more reminiscent of the natural situation, was described as a complex acoustic environment. RESULTS: Self-localization capacities were significantly better in early-blind individuals than in sighted subjects, whatever the type of acoustic environment. CONCLUSIONS: Auditory compensation leads to improved self-localization capacities in early-blind humans and indicates that prior visual experience is not essential for the development of spatial competence.

Adolescent↗
PubMed2005

Auditory compensation in myopic humans: involvement of binaural, monaural, or echo cues?

The purpose of this paper is to investigate the involvement of various auditory localization mechanisms in the improvement of auditory spatial sensitivity in the case of partial visual deprivation. We compared sensitivity to binaural, monaural, and echo cues between normal-sighted and myopic subjects. In an auditory task, which depended solely upon binaural processing, myopic and normal-sighted subjects showed an almost equal localization performance. We also found that myopic subjects were no more disturbed than normal-sighted subjects when spectral shape cues were removed. On the other hand, near-sighted subjects exhibited better echolocation skills and a higher sensitivity to echo cues than normal-sighted subjects. We can therefore conclude that an improved auditory spatial sensitivity in myopic subjects may result from the increased use of echo information.

Acoustic Stimulation↗
PubMed2005

Spatial auditory compensation in early-blind humans: involvement of eye movements and/or attention orienting?

Several studies have reported that the early-blind displays higher auditory spatial abilities than the sighted. Although many studies have attempted to delineate the cortical structures that undergo functional reorganization in blind people, few have tried to determine which auditory or non-auditory processes mediate these increased auditory spatial abilities. The aim of this paper is to investigate the role of eye movements and orientation of attention in auditory localization in blind humans. Although we found, in a first experiment, that the influence of eye movements on auditory spatial localization is preserved in spite of congenital visual deprivation, the saccade influence on spatial hearing is not more pronounced in the blind than in the sighted. In a second experiment, early-blind and sighted subjects undertook a task involving discrimination of sound elevation in which auditory targets followed uninformative auditory cues on either side with an intermediate elevation. When sounds were emitted from the frontal hemifield, both groups showed similar auditory localization performance. Although the auditory cue did not affect discrimination accuracy in both groups, early-blind subjects exhibited shorter reaction times than sighted subjects when sound sources were placed at far-lateral locations. Attentional cues, however, had similar effects on both groups of subjects, suggesting that improved auditory spatial abilities are not mediated by attention orienting mechanisms.

Adaptation, Physiological↗
PubMed2005

Anterior and non-anterior ruptured aneurysms: memory and frontal lobe function performance following coiling.

Our aim was to compare memory and frontal function performance between two groups of patients treated with Guglielmi detachable coil (GDC) following intracranial ruptured aneurysm. The subgroups drawn following the localization of the aneurysm consisted of 19 patients presenting with anterior communicating artery aneurysms and 16 patients exhibiting middle cerebral artery and posterior communicating artery aneurysms. The 35 patients and 35 normal controls were administered extensive neuropsychological assessment. Additionally, a scale of qualitative changes of mood was presented to the patients and patients' relatives. The patients showed a better general performance on memory compared with the executive function performance, which was similarly impaired in both groups. We suggest that executive functions are more vulnerable to differently located lesions than memory functions.

Adult↗
PubMed2002

Estimating the distribution of usual dietary intake by short-term measurements.

OBJECTIVE: To estimate the habitual dietary intake distribution in a population on the basis of repeated short-term measurements, especially of multiple 24 h diet recalls. METHODS: Six different statistical methods were evaluated and compared. The comparison referred to theoretical assumptions, admitted data transformations, statistical foundations, available software packages, and applications to real data of dietary intake. RESULTS: The Nusser method and a simplified version of it proposed in the paper have proved to be universally applicable methods for estimating the usual intake distribution for food groups and nutrients. Also, the Buck method seemed to be a robust estimation procedure suitable for the description of food consumption data, whereas the other considered methods were only applicable for log-normally distributed intake data or required a comprehensive data simulation. Characteristics of the estimated usual intake distribution were a decreased standard deviation, increased lower percentiles, and decreased upper percentiles compared to the observed sample distribution of individual means. Empirical results concerning total fat and vegetable intake in three different European consumption surveys showed that the estimated percentiles of the usual intake distribution did not depend markedly on the number of sampling days. CONCLUSIONS: Repeated short-term measurements like 24 h diet recalls can be used to describe the habitual dietary intake distribution in food consumption surveys. Recommended is a sampling design of two non-consecutive sampling days. The sampling days of all participants should be selected in such a way that they cover all seasons and days of the week.

Data Interpretation, Statistical↗
PubMed2001

Bacterial swarming: a biochemical time-resolved FTIR-ATR study of Proteus mirabilis swarm-cell differentiation.

Fourier transform infrared spectroscopy was applied to the study of the differentiation process undergone by Proteus mirabilis. This bacterium exhibits a remarkable dimorphism, allowing the cells to migrate on a solid substratum in a concerted manner yielding characteristic ring patterns. We performed an in situ noninvasive analysis of biochemical events occurring as vegetative cells differentiate into elongated, multinucleate, nonseptate, and hyperflagellated swarm cells. The major findings arising from this study are (i) the real-time monitoring of flagellar filament assembly, (ii) the evidence for de novo synthesis of qualitatively different lipopolysaccharides (LPS) and/or exopolysaccharides (EPS) constituting the slime into which bacteria swarm, and (iii) the alteration in the membrane fatty acid composition with a concomitant 10 degrees C decrease in the gel/liquid crystal phase transition resulting in an elevated membrane fluidity in swarm cells at the growth temperature. The time course of events shows that the EPS-LPS syntheses are synchronous with membrane fatty acid alterations and occur about 1 h before massive flagellar filament assembly is detected. This study not only provided a time sketch of biochemical events involved in the differentiation process but also led to the identification of the major spectral markers of both vegetative and swarm cells. This identification will allow to resolve the time-space structure of P. mirabilis colonies by using infrared microscopy.

Kinetics↗
PubMed2001

Transmigration of PBMNCs from beta-IFN-1b-treated MS patients: a one-year longitudinal study.

To evaluate the effects of in vivo beta-IFN-1b treatment on transmigration of mononuclear cells, we monitored for one year in vitro mononuclear cells trafficking through HUVECs monolayers stratified over a collagen gel during beta-IFN-1b treatment of 7 RR MS patients. The number of transmigrated cells was analysed before treatment (T0) and after 3 (T3), 6 (T6) and 12 months (T12); at the same time, levels of serum MMP-9 were quantified. The number of transmigrated cells decreased during treatment compared to pre-treatment values: the lowest number of transmigrated cells was detected at T3, and, although transmigration was still lower at T12, there was a trend to a return to pre-treatment levels over time. The amount of MMP-9 also decreased during therapy, although we could not find an absolute correlation between transmigration and levels of MMP-9, nor between either parameter and the clinical course of patients.

Adult↗
PubMed2001

In vitro modulation of adhesion molecules, adhesion phenomena, and fluid phase endocytosis on human umbilical vein endothelial cells and brain-derived microvascular endothelium by IFN-beta 1a.

Administration of interferon-beta (IFN-beta) in multiple sclerosis (MS) patients provides clinical benefits, although its mechanism(s) of action are not completely understood. We addressed the issue of whether concentrations of IFN-beta1a close to those reached in the serum of treated MS patients could modulate either adhesion molecules or adhesion of peripheral blood mononuclear cells (PBMC) as well as fluid phase endocytosis (FPE) in human umbilical vein endothelial cells (HUVEC) and in brain-derived microvascular endothelial cells (HBMEC). Adhesion was assessed by flow cytometry, and FPE was evaluated by peroxidase uptake. In our study, 200 U/ml IFN-beta1a induced a reduction in adhesion of PBMC to HUVEC. The information reported herein may contribute to further elucidating some of the mechanisms of action of IFN-beta on vascular endothelium.

Adjuvants, Immunologic↗
PubMed2000

Correlates of risky behaviors among young and older men having sexual relations with men in Montréal, Québec, Canada. Omega Study Group.

OBJECTIVE: To assess characteristics associated with 1) age and 2) recent unprotected anal sex with casual partners among men having sexual relations with men (MSM) participating in the Omega Cohort, Montréal, Québec, Canada. METHODS: The Omega Cohort is a study of the incidence and psychosocial determinants of HIV infection among MSM living in Montréal. MSM complete a questionnaire and are tested for HIV every 6 months. RESULTS: Thirteen percent of young MSM (< 30 years of age, n = 355) and 12% of older MSM (> or = 30 years of age, n = 455) reported recent unprotected anal sex with casual partners. The predictors of this latter behavior were: not living with a male sexual partner, unprotected anal sex with regular partner, > 5 casual partners, alcohol/drug use before anal sex, and having difficulties with procedures needed for safe sex. Among young MSM, additional predictors were: to have been living in Montreal for less than 1 year and to have exchanged money for sex. Among older MSM, additional predictors were: female sexual partners, unprotected anal sex with an HIV-infected partner, and feeling invulnerable to AIDS. CONCLUSION: Young Omega participants do not have more risky behaviors than older participants. Some predictors of recent risk behaviors with casual partners were different between the two groups. Prevention programs should be adapted consequently.

Adolescent↗
PubMed2000

Long-term immunological changes in azathioprine-treated MS patients.

The long-term immunological effects of azathioprine treatment have been investigated in 8 multiple sclerosis patients with different course of disease, chronic progressive (CP) or relapsing progressive (RP). We studied fluctuations in peripheral blood mononuclear cell subsets, IgG, IgM and soluble vascular cell adhesion molecule-1 (sVCAM-1), before and after 2 (T24) and 3 (T36) years of therapy. We observed a significant decrease in CD8+ cells over time and a trend to lower percentage of CD3-CD56+ cells at T24 and T36. CD4+CD45RA+ cells in MS patients were lower than in healthy controls before therapy and reached values similar to those of healthy controls at T24 and T36. The remaining immunological parameters did not show any significant fluctuations.

Adult↗
PubMed2000

Improved auditory spatial sensitivity in near-sighted subjects.

There is a great deal of anecdotal and empirical evidence in favor of compensatory plasticity of the sensorial modalities when one of them undergoes a total deficit. Yet, while most research has focused on the development of spatial hearing in totally blind individuals, there are few works dealing with auditory compensation in the case of a partial visual deprivation. In the present study, three experiments show that subjects undergoing a visual deficit like myopia are more accurate at localizing sounds than normal-sighted subjects.

Acoustic Stimulation↗
PubMed2000

High-dose methylprednisolone reduces cytokine-induced adhesion molecules on human brain endothelium.

OBJECTIVE: We investigated the in vitro effects of low- and high-dose methylprednisolone (MP) on the cytokine-induced expression of HLA-DR, ICAM-1 and VCAM-1 on human brain microvessel endothelial cells (HBMECs). METHODS: Brain endothelium was obtained from microvessels included in the apparently normal white matter of surgical specimens of nine patients. Cells were stained with monoclonal antibodies anti-HLA-DR, anti-ICAM-1 and anti-VCAM-1 and analysed by flow cytometry as fluorescence histograms. The mean fluorescence intensity (MFI) of HBMECs treated with different stimuli was calculated. RESULTS: gamma-IFN-induced HLA-DR was down-regulated in a dose-dependent manner by MP. High-dose MP reduced the TNF-alpha-induced ICAM-1 and VCAM-1 expression. CONCLUSIONS: The down-regulation of adhesion molecules on cerebral endothelial cells could decrease mononuclear cell transmigration through the blood brain barrier and consequently the perivascular infiltrates. The results add support to the rationale for high-dose MP treatment in multiple sclerosis relapses.

Adult↗
PubMed2000

Lantibiotic biosynthesis: interactions between prelacticin 481 and its putative modification enzyme, LctM.

Class AII and AIII lantibiotics and mersacidin are antibacterial peptides containing unusual residues obtained by posttranslational modifications of prepeptides, presumably catalyzed by LanM. LctM, the LanM for lacticin 481, is essential for the production of this class AII lantibiotic. Using the yeast two-hybrid system, we showed direct contact between the prelacticin 481 and LctM, supporting the proposed LctM function. Sixteen domains are conserved between the 10 known LanM proteins, whereas three additional domains were found only in class AII LanM proteins and in MrsM, the LanM for mersacidin. All the truncated LctM proteins that we tested presented impaired LctA-binding activity.

Amino Acid Sequence↗
PubMed2000

IS1675, a novel lactococcal insertion element, forms a transposon-like structure including the lacticin 481 lantibiotic operon.

Two copies of IS1675, a novel lactococcal insertion element from the IS4 family, are present on a 70-kb plasmid, where they frame the lantibiotic lacticin 481 operon. The whole structure could be a composite transposon designated Tn5721. This study shows that the lacticin 481 operon does not include any regulatory gene and provides a new example of a transposon-associated bacteriocin determinant. We identified five other IS1675 copies not associated with the lacticin 481 operon. The conservation of IS1675 flanking sequences suggested a 24-bp target site.

Amino Acid Sequence↗
PubMed2000

Association of hepatitis B virus infection with other sexually transmitted infections in homosexual men. Omega Study Group.

OBJECTIVES: This study determined the prevalence and factors associated with hepatitis B virus (HBV) infection among men who have sex with men. METHODS: At the baseline visit of an HIV study among men who have sex with men, we asked about HBV vaccination status and tested for HBV markers. RESULTS: Of 625 subjects, 48% had received at least 1 dose of HBV vaccine. Of 328 unvaccinated men, 41% had 1 or more HBV markers. HBV prevalence increased markedly with age and was associated with many sexual and drug-related behaviors. In a multivariate model, 7 variables were independently associated with HBV infection: ulcerative sexually transmitted diseases (odds ratio [OR] = 10.1; 95% confidence interval [CI] = 2.6, 54); injection drug use (OR = 5.2; 95% CI = 1.2, 26); gonorrhea or chlamydia (OR = 4.0; 95% CI = 1.9, 8.9); sexual partner with HIV/AIDS (OR = 3.6; 95% CI = 1.8, 7.1); 50 or more casual partners (OR = 3.4; 95% CI = 1.6, 7.1); received money for sex (OR = 3.0; 95% CI = 1.2, 7.8); and 20 or more regular partners (OR = 2.5; 95% CI = 1.1, 6.1). CONCLUSIONS: In Montreal, men who have sex with men are at risk for HBV infection, but a substantial proportion remain unvaccinated; new strategies are required to improve coverage. Men who have sex with men and who have a sexually transmitted infection, especially a genito-ulcerative infection, appear to be at particularly high risk for HBV infection.

Adult↗
PubMed1999

Importance of attentional mechanisms in audiovisual links.

The effect of auditory cues at different levels of visual processing was examined by using a visual "conjunction of features" discrimination task (experiment 1) and a "feature" discrimination task (experiment 2). In both experiments the visual target, appearing either on the left or the right of Ss' midline, was preceded by a brief tone either spatially proximal or distal to the target. In the "conjunction" task, subjects had to discriminate the orientation of a T flanked with T distractors of different orientations. In this task, assumed to require focused attention, discrimination accuracy was increased when the sound cue occurred at the subsequent visual target location and was decreased when it occurred at its alternative location. In the "feature" experiment, subjects had to discriminate the orientation of a line segment (+/-45 degrees) presented among line segment distractors. Accuracy was not affected, either when the sound was proximal or when it was distal to the location of the visual target. Results suggest that the early processing of sensory information is modality specific and that interference of auditory stimulation with visual stimuli is more pronounced as the processing of visual stimuli requires focused attention.

Acoustic Stimulation↗