Biomedical subjects

S Charron

Publications and source records attributed to S Charron.

4 recordsLinked to original sources

PubMed2006

Individual QTLs controlling quantitative variation in blood pressure inherited in a Mendelian mode.

We studied three possible genotypes at 10 well-defined blood pressure (BP) QTLs using congenic rat lines. The central question was whether the hypertensive or normotensive allele is dominant, or whether there is partial dominance. The congenic strains were employed to investigate the BP effects of alleles originating from normotensive rats in the background of hypertensive Dahl salt-sensitive (DSS) rats. The normotensive alleles at eight QTLs were fully dominant over DSS alleles, which we tentatively interpreted as indicating that DSS rats incurred a loss of function at these loci and that the QTLs produced BP-reducing agents. In contrast, the normotensive allele of only one QTL was recessive over its DSS counterpart, implying a gain of function at this QTL or a null allele involved in generating a BP-elevating agent. Only one locus, C17QTL, had alleles exhibiting partial dominance. These estimates of dominance differ considerably from those obtained by QTL analysis in a F2 cross. This disagreement demonstrates the importance of establishing a cause-effect relationship between a QTL and its phenotypic effect via congenic strains. The dominance relationships suggest pertinent strategies for gene identification and pharmaceutical intervention.

Alleles↗

PubMed1993

Temporary threshold and loudness shifts: frequency patterns and correlations.

Two experiments studied the frequency pattern of TLS (temporary loudness shift) as a function of the level and frequency of the fatiguing sound. In experiment 1, the fatiguing tones were intermittent 375-, 1500-, or 3000-Hz tones (10 s on/10 s off) at 75, 80, 85, 90, or 95 dB SPL. The TLS patterns were established for a continuous, 60-phon test tone at different frequencies presented simultaneously with the intermittent fatiguing tone. In experiment 2, a 1000-Hz exposure tone with an intermittency of 10 s on/20 s off was used with a continuous 60-dB test tone at different frequencies. In both experiments, the total exposure duration was 60 s; TLS was measured 5 s after the exposure ended. For the lowest two exposure levels, the TLS pattern had one peak centered on the exposure frequency. As the exposure level increased, a two-peak pattern became evident, with the second peak at higher test frequencies. This finding could be interpreted as psychoacoustical evidence for the double (passive and active) mode of displacement of the basilar membrane. In experiment 2, a TTS (temporary threshold shift) measurement after exposure to a 45-min, 1000-Hz tone at 90 dB was added to the TLS sessions. The correlations between maximum TTS after a 45-min exposure and the TLS obtained after a 60-s exposure were calculated for each of the exposure levels and test frequencies used in TLS measurements. The correlation reached as high as 0.9 for TLSs measured at 1120 Hz after a 90-dB exposure; it was smaller but significant for TLSs at the exposure frequency. Despite these correlations, differences in the overall patterns of TTS and TLS suggest that they stem from two different mechanisms.

Acoustic Stimulation↗

PubMed1988

Frequency selectivity in loudness adaptation and auditory fatigue.

An intermittent monaural tone may induce a decline in the loudness of a continuous tone presented to the same ear [Canévet et al., Br. J. Audiol. 17, 49-57 (1983)]. Two experiments studied the frequency selectivity of loudness adaptation induced in this manner. The method of successive magnitude estimations was used to measure the loudness of a monaural 84-s test tone before and after a single presentation of a 24-s inducer tone in the same ear. The first experiment shows that, for an inducing tone (500, 1000, or 3000 Hz) approximately 15 dB more intense than a test tone set to one of 21 different frequencies, adaptation is greatest when the two tones have the same frequency; with increasing difference between the test-tone and inducer frequencies, adaptation progressively declines. The second experiment measured frequency selectivity in the loudness reduction caused by a 1000-Hz inducer as a function of its level. As inducer level went from 75 to 95 dB (with test tone constant at 60 phons), selectivity passes progressively from the type seen in short-term or low-level fatigue (maximal for the 1000-Hz test tone) to a type seen in long-term or high-level fatigue (maximal for the 1000-Hz test tone) to a type seen in long-term or high-level fatigue (maximal at frequencies higher than that of the inducer or fatiguing tone). A common cochlear origin and a continuity between the mechanisms of ipsilaterally induced adaptation and high-level fatigue are suggested by the data.

Adaptation, Physiological↗

PubMedDate not supplied

[Breast feeding and birth spacing in Burundi: an approach].

Breast-feeding (BFD), post-partum amenorrhea (PPA), and birth interval (BI) were studied in 247 mothers from Burundi (159 rural and 88 urban). BFD was higher in rural than in urban areas (23.8 +/- 6.8 vs 16.5 +/- 7.2 mths, p less than 0.001), as for PPA (16.9 +/- 8.5 vs 8.9 +/- 8 mths, p less than 0.001) and Bl (29 +/- 11 vs 25.7 +/- 10.7 mths, p less than 0.01). PPA of non exclusively breast-feeding (NEB) mothers was lower than that of the other mothers (5.7 +/- 6.5 vs 13.9 +/- 9 mths, p less than 0.001). The proportion of mothers with PPA less than or equal to 12 months was higher in NEB mothers (88.9% vs 49%, p less than 0.001). The relative risk of pregnancy 9 to 12 mths after a birth was 4 times higher for these mothers (28% vs 9%, RR = 3.9, p less than 0.001). PPA and BI were correlated with BFD (respectively r = 0.644 and r = 0.21, p less than 0.001). A multivariate analysis showed that PPA is lowered when BFD and frequency of sucking are reduced in urban high socio-economic levels (R = 56%, p less than 0.01). BI was not so lowered in urban area than expected with a lower BFD and PPA. These data suggest that post-partum infertility period lowered in urban area would be partially counterbalanced by cultural taboo inhibiting sexual intercourse during breast-feeding. Deep modification in sexual behavior accelerated by use of contraceptives should lead to be careful in their spread in family planning programmes where breast-feeding promotion is more than ever a priority.

Adult↗