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Biomedical subjects

G Masson

Publications and source records attributed to G Masson.

At least 19 recordsLinked to original sources
PubMed2006

[Episiotomy and prevention of perineal and pelvic floor injuries].

OBJECTIVES: The objective of this review was to assess the efficacy of episiotomy to prevent severe perineal tears, urinary incontinence, faecal incontinence and genital prolapse. MATERIAL AND METHODS: A systematic review on Medline database was performed between 1980 and 2005. One hundred seventy seven articles were selected. Trial quality was assessed on the following parameters: design (prospective, randomized, meta-analysis), sample size (>50) and relevant results. Finally, 43 articles were analysed. RESULTS: The routine use of episiotomy did not prevent severe perineal tears. It decreased the risk of moderate anterior perineal lacerations. The risk of severe perineal tears during episiotomy increased in the following circumstances: primiparity, Asian women, perineal length<or=3cm, forceps or vacuum-assisted deliveries and macrosomia. Relevant studies were consistent in demonstrating no benefit for routine episiotomy to prevent urinary or faecal incontinence or pelvic floor relaxation, even if there is a lack of data concerning long-term effects on pelvic floor support. CONCLUSION: The routine use of episiotomy to prevent severe perineal tears, urinary incontinence, faecal incontinence and genital prolapse should be abandoned.

Adult↗
PubMed2005

Perinatal care regionalization and acceptability by professionals in France.

BACKGROUND: For twenty years, most of industrial countries developed recommendations on regionalization of perinatal care. Perinatal regionalization is particularly aimed at improving morbidity and mortality outcomes of low birth weight newborns by transferring pregnant women to the maternity units having a medical or neonatal environment suited to the risks incurred by mothers or babies. Perinatal regionalization cannot be effective without being well accepted by the majority of professionals. The objectives of this study were then to identify professionals'expectations and objections to perinatal regionalisation and to compare them from a professional group to another one. METHODS: Professionals of 3 French perinatal networks were under consideration: the Rhône, the Auvergne and the Gard-Lozère networks. The study included two stages: 1) a psychosociological qualitative study, based on professionals'interviews, aimed at identifying main concerns of professionals and developing a questionnaire; then 2) an epidemiological quantitative study, using this questionnaire within French networks. In the questionnaire, 8 dimensions explored the professionals'views: constraints related to regulation aspects and to the setting up of maternity units care levels, risk of loss of professionals' competence and prestige, consequences on medical practices, on inter-professional relationship, on work organization and financial aspects, and related to the new role of 'private practice'professionals, legal consequences. RESULTS: The response rate of the epidemiological study was 80%. The results permitted to construct 8 dimension scores describing the reasons of poor acceptability of regionalization. After taking into account the age, the sex, the network and the juridical status of the institution, the study revealed a significant poorer acceptability of regionalization by most of medical specialty groups (anesthetists, obstetricians, midwives and "private practice" professionals) compared with neonatologists, or by "private" professionals (professionals working in private clinics and "private practice" professionals) compared with professionals working in university or community hospitals. The study described also network setting up conditions related to its functioning. CONCLUSION: By identifying clearly professionals 'objections and expectations, this study should facilitate improvement in the organization of studied perinatal networks.

Attitude of Health Personnel↗
PubMed2005

[Neonatal consequences of maternal smoking during pregnancy].

In utero tobacco consumption is a serious public health problem in France; it is very frequent and the long term consequences are not only numerous but also misinterpreted by our population. 25 to 29% of women arrive at the end of their pregnancy without stopping smoking and 50% of non smoking mothers live in an environment polluted by tobacco during pregnancy. The authors would like to stress the gravity of this situation. At the maternity hospital in Nîmes, 358 women who gave birth at term and after a normal pregnancy were enrolled in a survey and monitored with thiocyanate for their tobacco consumption. Birth weight, height, and cranial perimeter of the infants were noted at birth. Results confirmed earlier work on this subject: the three variables studied were consistently weakened by the mother's addiction to tobacco. The authors recall previous medical literature on the pathophysiology and other consequences on the brain: such as I.Q. behavior, sudden infant death syndrome, vascular alterations with possible long-term complications, as well as pulmonary alterations on which there has recently been much research. The question is raised as to why this problem is so neglected in our society and what could be done to change this state of affairs.

Child Development↗
PubMed1997

Visual perception modifies goal-directed movement control: supporting evidence from a visual perturbation paradigm.

It is well known that dynamic visual information influences movement control, whereas the role played by background visual information is still largely unknown. Evidence coming mainly from eye movement and manual tracking studies indicates that background visual information modifies motion perception and might influence movement control. The goal of the present study was to test this hypothesis. Subjects had to apply pressure on a strain gauge to displace in a single action a cursor shown on a video display and to immobilize it on a target shown on the same display. In some instances, the visual background against which the cursor moved was unexpectedly perturbed in a direction opposite to (Experiment 1), or in the same direction as (Experiment 2) the cursor controlled by the subject. The results of both experiments indicated that the introduction of a visual perturbation significantly affected aiming accuracy. These results suggest that background visual information is used to evaluate the velocity of the aiming cursor, and that this perceived velocity is fed back to the control system, which uses it for on-line corrections.

Adult↗
PubMed1995

Postural effects of motion vision in young autistic children.

We present the first assessment of motion vision in childhood autism. Postural reactivity to visually perceived motion was measured in five autistic children and 12 normal controls of the same chronological age. Anteroposterior as well as total body sway occurring on a force platform in response to movements in the visual environment were compared. Autistic children were posturally more unstable than normal children and quite insensitive to visually perceived environmental motion. Some implications of this impairment for sensorimotor and social communication development in infantile autism are discussed.

Autistic Disorder↗
PubMed1995

Effects of the spatio-temporal structure of optical flow on postural readjustments in man.

How does the spatio-temporal structure of an oscillating radial optical flow affect postural stability? In order to investigate this problem, two different types of stimulus pattern were presented to human subjects. These stimuli were generated either with a constant spatial frequency or with a spatial frequency gradient providing monocular depth cues. When the stimulation was set in motion, the gain response of the antero-posterior postural changes depended upon the oscillation frequency of the visual scene. The amplitude of the postural response did not change with the amplitude of the visual scene motion. The spatial orientation of the postural sway (major axis of sway) depended strictly and solely on the structure of the visual scene. In static conditions, depth information resulting from the presence of a spatial frequency gradient enhanced postural stability. When set in motion, a visual scene with a spatial frequency gradient induced an organization of postural sway in the direction of the visual motion. Considering visual dynamic cues, postural instability depended linearly both on the logarithm of the velocity and on the logarithm of the temporal frequency. A nonlinear relationship existed between the amplitude of the fore-aft postural sway at the driving frequency and the temporal frequency, with a peak around 2-4 Hz. These results are discussed in terms of their implications for the separation of visual and biomechanical factors influencing visuo-postural control.

Adult↗
PubMed1995

Effects of stationary and moving textured backgrounds on the visuo-oculo-manual tracking in humans.

We investigated the effects of stationary and moving textured backgrounds on ocular and manual pursuit of a discrete target that suddenly starts to move at constant speed (ramp motion). When a stationary textured background was superimposed to the target displacement, the gain of the steady-state eye smooth pursuit velocity was significantly reduced, while the latency of pursuit initiation did not vary significantly, as compared to a dark background condition. The initial velocity of the eye smooth pursuit was also lowered. Both the initial acceleration and the steady-state manual tracking angular velocity were slightly, but not significantly, lowered when compared to a dark background condition. Detrimental effects of the stationary textured background were of comparable amplitude (approximately 10%) for ocular and manual pursuit. In a second condition, we compared ocular and manual pursuit when the textured background was either stationary or drifting. Initial and steady-state eye velocities increased when the textured background moved in the same direction as the target. Conversely, when the background moved in the opposite direction, both velocities were decreased. Eye displacement gain remained however close to unity due to an increase in the occurrence of catch-up corrective saccades. The effects of the moving backgrounds on the initial and steady-state forearm velocities were inverse to that reported for smooth pursuit eye movements. Neither manual nor ocular smooth pursuit latencies were affected.

Adult↗
PubMed1994

Low luminance contrast sensitivity: effects of training on psychophysical and optokinetic nystagmus thresholds in man.

We compared psychophysical contrast sensitivity function (psi-CSF) and optokinetic contrast sensitivity function (OKN-CSF) in man, for the combination of three spatial and three temporal frequencies. psi-CSF was defined as the inverse of the contrast threshold, that is the contrast value of a sinusoidal grating for which a subject was able to identify the width of a drifting grating. OKN-CSF was defined as the inverse of the contrast value of the grating which triggered an involuntary optokinetic nystagmus. In highly experienced subjects, OKN-CSF was overall higher than psi-CSF. More precisely, differences between both contrast sensitivity functions occurred mainly in the low spatio-temporal frequency range (below 4 c/deg and 9 Hz). In naive subjects, psi-CSF reached the level of OKN-CSF after two consecutive test sessions. OKN-CSF did not change with training. Similarly, high spatio-temporal frequency psychophysical thresholds did not change with training and, moreover, approximated OKN-CSF thresholds. Low spatio-temporal frequency psychophysical sensitivity was initially lower than corresponding OKN-CSF sensitivity; however, after only two training sessions, the two functions were indistinguishable due to a selective increase in psychophysical low spatio-temporal frequency sensitivity.

Adult↗
PubMed1994

Modulations of the optical flow did not induce locomotor pattern fluctuations in treadmill walking in man.

We report an analysis of gait during human treadmill walking when visual information from the self-displacement velocity was modulated. Removing or sinusoidally modulating the frequency edge information in the optical flow did not induce significant changes in the walking velocity as analyzed using Fast Fourier Transform or in the spatiotemporal gait parameters. While low-frequency fluctuations in displacement speed increased, there was no significant change in locomotor cycle stability, When a constant frequency edge was provided, i.e., when a backward optical flow was added, stride length decreased as compared to the no-optical-flow condition and instantaneous fluctuations in stride amplitude increased. Temporal gait parameters did not change. These partial effects might be better explained by modifications in trunk balance. In humans, modulation of velocity information on self-motion cannot induce unintentional modulation of walking velocity and did not enhance fluctuations in the locomotor pattern. These results argue against the proprioceptive role of sagittal visual-motion information in control of stability of rhythmic leg movement, at least when other proprioceptive feedback sources are available.

Acceleration↗
PubMed1993

Rabies RNA synthesis, detected with cDNA probes, as a marker for virus transport in the rat nervous system.

The kinetics of viral RNA synthesis in different parts of the rat brain, infected with fixed or street rabies virus strains, is correlated with their anatomical neuronal connections with the masseter muscles, using hybridization with rabies cDNA probes. Viral RNA synthesis is first detected in the brain-stem and in the pons where the direct anatomical projection of the masseter muscle nervous arborization into the sensory and motor nuclei is located, through the trigeminus nerve. Rabies RNA detection is delayed in the other regions of the rat brain depending on the time course of virus transport from the trigeminal nuclei through multiple nervous connections.

Afferent Pathways↗
PubMed1993

Dopaminergic modulation of visual sensitivity in man.

A large body of experimental evidence supports the hypothesis that dopamine is a functional neuromodulator at many levels of the visual system. Intrinsic dopaminergic neurons were characterized in most mammalian retina, including man. These neurons give rise to a dendritic plexus covering the retina. Thus, dopamine seems to be involved in the organization of the ganglion cell and the bipolar cell receptive fields and modulates physiological activity of photoreceptors, both processes which underlie sensitivity and spatial selectivity of visual processing in the early stage of the visual system. Moreover, few data are now available concerning the functional significance of dopaminergic modulation of visual sensitivity in man. Parkinson's disease is a specific disorder of central dopaminergic systems. Abnormalities in the pattern-evoked potentials and electroretinogram have been found in parkinsonian patients. Contrast sensitivity, a useful tool for measuring visual spatio-temporal sensitivity in man, has also been shown to be modified due to this affection. Dynamic contrast sensitivity is primarily decreased in these patients, distinguishing them from the normal aging process. Because these modifications in shape of the contrast sensitivity function are reversed by L-Dopa, and that neuroleptic administration could reproduce them in schizophrenia patients, it was suggested that dopamine might tune the contrast sensitivity function in man. We have recently shown that subcutaneous apomorphine induces changes in contrast sensitivity in healthy volunteers, which preferentially affect motion sensitivity. These dopaminergic sensitive modifications in the shape of the contrast sensitivity function might reflect a change in the range of sensitivity of the visual system, both in dynamic and spatial properties. This could be explained by a modification in the spatial and dynamic properties of the ganglion cell responses in the retina. Moreover, we suggest both from our results and from the review of the literature that human psychophysical data confirm the hypothesis that dopamine may be involved in light retinal adaptation, as light-induced and dopamine-induced modifications in the shape in the contrast sensitivity function are quite similar.

Contrast Sensitivity↗
PubMed1992

[Rademaker and Garcin syndrome associated with pallidal calcifications].

We report gait abnormalities with exaggerated support against gravity in a 76 year-old woman. This exaggeration, and its demonstration by ankle dorsiflexion in supine position, was first described by Rademaker and Garcin (1933) as probably resulting from cerebellar and brainstem lesions. In the present case, quantitative analysis of locomotion showed a strong reduction in both stride duration and stride length. There was an increased variability between two consecutive locomotor cycles and a large increase in both stance duration and relative double-support duration. Electromyography clearly showed leg hypertension following ankle dorsiflexion, contrasting with normal leg mobility in the supine patient. This suggested that reflexive antigravity support abnormalities could explain this pattern of locomotor disabilities, differentiating them from other kinds of "marche à petits pas". The present case was associated with bilateral pallidal calcifications, suggesting an involvement of the basal ganglia in support reaction against gravity and in control of adequate postural muscle tone necessary for locomotion.

Aged↗
PubMed1991

Apomorphine-induced yawning in migraine patients: enhanced responsiveness.

Migraine patients usually exhibit hypersensitivity to dopaminergic agonists, but the tests used (such as the so called "piribedil test") preferentially assess the sensitivity of the peripheral dopaminergic receptors. Apomorphine-induced yawning may be useful in the evaluation of central dopaminergic receptor sensitivity. Nine migraine patients were included in an age- and sex-matched control study. They had been without treatment for 1 month and free of a migraine attack for at least 7 days. Apomorphine hydrochloride (5 micrograms/kg) was administered subcutaneously, and yawning was recorded by two observers. The cumulative number of yawns as a function of time was studied. The comparison of the regression graphs showed a significant difference between migraine patients and controls. Migraine patients exhibited enhanced responsiveness to apomorphine challenge. This finding supports the hypothesis of a constant central dopaminergic hypersensitivity.

Adult↗
PubMed1991

Selective effects of low doses of apomorphine on spatiotemporal contrast sensitivity in healthy volunteers: a double-blind placebo-controlled study.

1. Apomorphine (1 and 5 micrograms kg-1) and placebo were given to nine normal volunteers, using a Latin-square design and double-blind procedures. The visual perception of static and moving patterns (static and motion contrast sensitivity) was evaluated before and 15 min after the dose administration. 2. Apomorphine (1 and 5 micrograms kg-1), as compared with placebo, led to a significant overall reduction of the visual perception of movement. This effect was dose-related, and apomorphine (5 micrograms kg-1) induced a more pronounced decrease in the visual perception of movement than apomorphine (1 microgram kg-1). With apomorphine (5 micrograms kg-1), the reduction was more pronounced for low spatial frequencies, and was linearly inversely correlated to the spatial frequency for a temporal frequency of 3 Hz. Finally, no significant effect of apomorphine was observed for sensitivity to static patterns. 3. Several non exclusive hypotheses may be suggested: The effects of apomorphine may result from stimulation of retinal D1- and/or D2-dopaminergic receptors. Apomorphine may increase the surround inhibition of ganglion cells' receptive-fields. This modification of the centre-surround balance may explain the decrease in contrast sensitivity for low spatial frequencies. The specific effects of apomorphine on the visual perception of movement support the hypothesis that apomorphine preferentially affects the magnocellular pathway which mediates sensitivity to moving patterns.

Adult↗