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S Clément

Publications and source records attributed to S Clément.

36 records · Page 2Linked to original sources
PubMed1997

The perception of frequency peaks and troughs in wide frequency modulations. IV. Effects of modulation waveform.

This work extends previous studies on the perceptual asymmetry between the local maxima and minima of wide frequency modulations (FMs) [L. Demany and K. I. McAnally, J. Acoust. Soc. Am. 96, 706-715 (1994); L. Demany and S. Clément, J. Acoust. Soc. Am. 97, 2454-2459 (1995); L. Demany and S. Clément, J. Acoust. Soc. Am. 98, 2515-2523 (1995)]. In experiment 1, subjects had to discriminate frequency shifts in the temporally central vertex of V- and A-shaped FMs imposed on 200-ms sinusoidal tone bursts. The precise shapes of these FMs varied in eight steps from quasi-triangles (with a durationless central vertex) to quasi-squares (with a long-duration central vertex). The central vertex was either a minimum or a maximum, but in each case the corresponding frequency was near 1000 Hz and the FM span was about 0.5 oct. For each FM shape, the discrimination threshold was lower when the vertex was a maximum than when it was a minimum, but (in four subjects out of five) this difference decreased monotonically as the FM became less and less triangular. FM shape had a remarkably small effect on the discrimination of the maxima, and the thresholds measured for the sharpest maxima were unexpectedly low. In subsequent experiments, subjects had to discriminate frequency shifts in the starting point or the final point of unidirectional FMs (tone glides) that spanned about 0.5 oct in 100 ms. The relevant frequency extremum was near 1000 Hz in each condition. At the final point of the glides, discrimination was better for rising glides than for falling glides. At the starting point of the glides, discrimination was better for falling glides than for rising glides. Thus discrimination was always better when the relevant frequency extremum was a maximum than when it was a minimum, and this effect was produced both "forward" and "backward." The latter fact suggests that the perceptual asymmetry of FM originates at least partly from central factors.

Differential Threshold↗
PubMed1997

Signalling functions of alpha-tocopherol in smooth muscle cells.

alpha-Tocopherol but not beta-tocopherol, activates protein phosphatase 2A, decreases protein kinase C activity and attenuates smooth muscle cell proliferation at physiological concentrations. beta-Tocopherol prevents the effects of alpha-tocopherol. Inhibition of protein kinase C alpha, but not of the other isoforms, by the inhibitor Gö6976 prevents the effect of alpha-tocopherol. Protein kinase C alpha, immunoprecipitated from alpha-tocopherol treated cells, is less phosphorylated and inactive. It is proposed that the specific activation of protein phosphatase 2A by alpha-tocopherol results in dephosphorylation and inactivation of protein kinase C alpha. Finally, this cascade of events leads to smooth muscle cell proliferation inhibition.

Animals↗
PubMed1996

Molecular requirements for polyamines binding to the antispermine monoclonal antibody Spm8-2.

The monoclonal antispermine antibody Spm8-2 was obtained by immunizing mice with a thyroglobulin-spermine conjugate. The molecular requirements for polyamines binding to this antibody were investigated by ELISA binding and inhibition tests, using a variety of natural polyamines and synthetic polyamine analogs. Four major structural determinants are important for the binding of polyamines by the antibody: (1) terminal amino groups: N-alkylation of both terminal amino groups of the polyamines leads to an important drop in the affinity for the antibody; (2) number of methylene groups spacing the amino groups: the four carbon chains appear to present the optimum length since the antibody binds polyamines with repeats of the aminobutyl moiety more actively than their homologues with shorter or longer carbon chains; (3) number of amino groups: the affinity of Spm8-2 for free homologous polyamines varied in the following order: pentamines > tetramines > triamines > diamines, showing the importance of the number of positive charges of the polyamines in the antibody-antigen reaction; the importance of charges is further emphasized by the dependence of antibody binding on the ionic strength of the medium; (4) N-acylation of one terminal amino group: the antibody binds more actively N1-acetylspermidine than spermidine or spermine. The binding properties of Spm8-2 suggest the presence of two recognition sequences, one selective for N-acylaminopropyl moieties, the second for the aminobutyl moiety.

Acetylation↗
PubMed1995

Spermine uptake is necessary to induce haemoglobin synthesis in murine erythroleukaemia cells.

To determine whether intracellular uptake of spermine is necessary to induce haemoglobin synthesis in murine erythroleukaemia (MEL) DS 19 cells, we used single-step selection for resistance to N1,N12-bis(ethyl)spermine (BESM), a cytotoxic spermine analogue, to isolate clones deficient in polyamine transport. The cells were approximately 500-fold more resistant to BESM than parental cells and were unable to accumulate BESM, putrescine, spermidine or spermine. Addition of spermine to the polyamine-transport-deficient cells failed to induce haemoglobin synthesis. Hexamethylene-1,6-bisacetamide, a well-known differentiating agent, induced haemoglobin synthesis in both parental and resistant cells. Polyamine-transport-deficient cells transfected with DNA purified from the parental cell line were further selected for their ability to grow in the presence of alpha-difluoromethylornithine and putrescine. The transfectants had an active transport system for polyamines, and spermine added to their culture medium accumulated inside the cells and induced haemoglobin production. These findings indicate that intracellular spermine uptake is required to induce haemoglobin production in MEL cells.

Animals↗
PubMed1995

Spermine induces haemoglobin synthesis in murine erythroleukaemia cells.

The naturally occurring polyamine spermine induces haemoglobin synthesis in murine erythroleukaemia (MEL) cells. Haemoglobin production was accompanied by accumulation of cytoplasmic beta-globin mRNA and growth inhibition, but not by cell-cycle block or changes in cell volume. Hexamethylene-bisacetamide (HMBA), a well known differentiating agent, also induces haemoglobin production, but causes a G1 block and decreases cell volume. These findings indicate that HMBA and spermine affect MEL cells differently, even though both induce haemoglobin production.

Acetamides↗
PubMed1995

The structure of polyamine analogues determines haemoglobin production and cytotoxicity in murine erythroleukaemia cells.

The naturally occurring polyamine spermine induces haemoglobin synthesis in murine erythroleukaemia (MEL) cells. We have studied the ability of various polyamine analogues to inhibit cell growth and induce haemoglobin production. Polyamine analogues with free terminal amino groups were good inducers of haemoglobin production in MEL cells. Haemoglobin levels correlated with the number of positive charges: pentamines (five positive charges) were stronger inducers than tetramines (four positive charges). Compounds ethylated at their terminal amines were poor inducers of haemoglobin production but good inhibitors of MEL cell growth. These results provide evidence that polyamine analogues support specific biological functions of polyamines in MEL cells and suggest relationships between polyamine structure and function.

Animals↗
PubMed1995

The perception of frequency peaks and troughs in wide frequency modulations. II. Effects of frequency register, stimulus uncertainty, and intensity.

In widely frequency modulated sine tones, frequency maxima are perceived more accurately than frequency minima: A shift in a local frequency extremum is better detected when the extremum is a maximum than when it is a minimum, even within the same spectral region [L. Demany and K. I. McAnally, J. Acoust. Soc. Am. 96, 706-715 (1994)]. It is reported here that this perceptual asymmetry is about equally strong for frequency extrema near 250 and 1000 Hz, but weaker near 4000 Hz. It was also found that near 1000 Hz, the asymmetry is about equally strong for stimuli with an SPL of 35 and 70 dB, although the neural excitation patterns of a 1000-Hz tone probably have a different shape--and more specifically a different asymmetry--at these two levels. Finally, stimulus uncertainty was found to reduce the perceptual asymmetry: A weaker asymmetry was measured when the standard frequency extremum varied randomly from trial to trial than when it was fixed. The latter result, and the fact that the asymmetry did not decrease with training in the discrimination task, suggest that the asymmetry cannot be counteracted by "top-down" attentional processes and may be a preattentional phenomenon.

Auditory Perception↗
PubMed1995

The perception of frequency peaks and troughs in wide frequency modulations. III. Complex carriers.

In widely frequency-modulated (FM) sine tones, local frequency maxima are perceived more accurately than local frequency minima [L. Demany and K. I. McAnally, J. Acoust. Soc. Am. 96, 706-715 (1994); L. Demany and S. Clément, J. Acoust. Soc. Am. 97, 2454-2459 (1995)]. The aim of the present work was to determine if a similar perceptual asymmetry exists for nonsinusoidal FM carriers. Within each stimulus, the logarithm of instantaneous frequency followed one cycle of a (2.5- or 5-Hz) cosine function, starting at phase pi in the "peak" condition and phase 0 in the "trough" condition. In each condition, subjects had to detect shifts in the frequency apex occurring at the temporal center of the stimuli. In experiment 1, the FM functions were imposed on complex tones consisting of a series of consecutive harmonics. Some of the stimuli were bandpass filtered in a 1-oct window with fixed edges. The measured thresholds were about four times lower in the peak condition than in the trough condition, which suggests that the asymmetry previously observed for "spectral" pitches also exists for "virtual" pitches. In experiment 2, the FM carriers were Shepard tones. With such carriers, the standard peak and trough stimuli could be made identical at both the apex and the end points. In spite of these local identities, the results were similar to those of experiment 1, which suggests that the perceptual asymmetry is not determined by local differences between the stimuli and is instead a genuine "motion" effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Auditory Perception↗
PubMed1994

[Medical secrecy].

Explore the source record for details and available documents.

Confidentiality↗
PubMed1993

[Children for the aged. Sibling configuration and support for aged parents in the rural south-western area of France].

The support of the dependent elderly is conditioned by the availability of the family, particularly of children, even when assistance services help the elderly stay at home. But it is difficult to tell if the elderly will have descendants capable of providing for them. A survey carried out in the rural South-Western area of France shows the importance of taking into account sibling configuration when seeking support for the old and disabled. The analyses presented here result from the joint utilization of an epidemiological study based on a questionnaire (N = 405) and a sociological survey on family history: 74 elderly people from the initial sample as well as several of their relatives and friends were interviewed at length on the conditions of support at home. Three main sibling configurations have been established: the only child, several children of the same gender, several children of different genders. They were related to three types of distances between parents and children: co-habitation, vicinity, remoteness. If one finds as many children co-habitating with at least one parent in one-child families as in the whole sample (33%), it means that family support mostly depends on the transfer of property for farmers and tradesmen: in this area, the heir must provide for his ageing parents. But there are marked differences according to the gender of the children: a boy is only likely to stay with his parents if he inherits their professional activity. On a qualitative level, the question dealt with in this article is the following: how can one plan for one's old age according to the rigidity of the number, the order and the gender of the children?

Adult↗
PubMedDate not supplied

Analytical findings in a suicide involving sodium azide.

A 47-year-old laboratory assistant ingested approximately 9 g of sodium azide powder and died 4 h later at a hospital. A high-performance liquid chromatographic method using diode-array detection has been developed for the determination of an azide benzoyl derivative in blood (after a simple deproteinization) and in several tissues (after homogenization in a neutral buffer and deproteinization of the supernatant). The blood concentration in this case was lower than those previously published. The highest azide concentration was found in lung tissue. A complete toxicological screening revealed the presence of cyanide in blood, which has been previously reported twice, but for the first time, it was confirmed by mass spectrometry. Whether the production of cyanide in the presence of azide took place in vivo or postmortem remains unknown; the nature of the metabolic pathway involved also remains unknown.

Azides↗
PubMedDate not supplied

[Sulfasalazine or salazosulfapyridine in the treatment of rheumatoid polyarthritis. An open study of 46 patients. Review of the literature].

The SASP was studied in 46 patients with rheumatoid arthritis. The efficacy criteria which were selected (decrease of the sed rate by more than 50 p. cent during the first hour, morning stiffness under 20 minutes, Ritchie's index inferior to 10 and decreased cortisone and NSAID doses), explain that 25 p. cent of the patients are considered as satisfied after 12 months of trial. The patients selected, present severe forms of the disease or forms resistant to other treatments. The improvement appears significant after the first month. Half of the patients left the trial either because of ineffectiveness, or evolutive relapse (21.73 p. cent) or because of side-effects (28.26 p. cent). The most frequently observed disorders and intolerances are of digestive nature. No serious accident is to be deplored. Such results are in accordance with the data from the literature. The SASP must therefore be considered as the fundamental treatment of rheumatoid arthritis. The new galenic forms, dissolving in the gastro-intestinal tract, have enabled to markedly improve the digestive tolerance.

Arthritis, Rheumatoid↗