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Biomedical subjects

S Garnier

Publications and source records attributed to S Garnier.

15 recordsLinked to original sources

[Post-traumatic necrotizing fasciitis].

We are reporting the case of a 39-year-old male, without notable previous history except for an important alcoholic and tobacco consumption, who suffered a bicycle accident resulting in a minor wound on the left elbow. The neglected wound evolved extremely rapidly towards a necrotizing fasciitis, which underwent further complications consisting of a heat shock and multivisceral failure that necessitated reanimation procedures. The patient benefited a triple antibiotic therapy (amoxicillin-clavulanic acid, ornidazole and levofloxacin) and an extensive surgical debridement. The progression was then slow but favourable. The patient is now in functional reeducation. This observation illustrates the rate of evolution of the lesions caused by necrotizing fasciitis and reminds on the importance of prompt therapy.

Adult↗

When morphometry meets genetics: inferring the phylogeography of Carabus solieri using Fourier analyses of pronotum and male genitalia.

Population differentiation is a crucial step in the speciation process and is therefore a central subject in studies of microevolution. Assessing divergence and inferring its dynamics in space and time generally require a wide array of markers. Until now however, most studies of population structure are based on molecular markers and those concerning morphological traits are more scarce. In the present work, we studied morphological differentiation among populations of the ground beetle Carabus solieri, and tested its congruence with genetic population structure. The shape of pronotum and aedeagus was assessed using Dual Axis Fourier Shape Analysis. manova on Fourier coefficients revealed highly significant morphological variation between populations and a similar geographical pattern of differentiation for both structures. On the whole, morphological and genetic patterns were also found to be congruent. Our analysis confirms the phylogeographical scenario proposing that two entities of C. solieri differentiated during the last glaciation events before recolonizing the actual range of the species. It also indicates a large introgression between the two differentiated entities in the centre of the range.

Analysis of Variance↗

[Low dose helical CT pelvimetry: evaluation of radiation dose and image processing].

PURPOSE: to estimate from phantom measurements the radiation dose and the accuracy of helical ct pelvimetry. MATERIALS AND METHODS: Eight helical CT acquisitions using different tube current (100, 50, 25 or 10mAs) and pitch factor (1.125 or 1.375) settings but identical collimation (2mm) and kilovoltage (120 kVp) were evaluated using a four-channel MDCT scanner and compared with conventional CT pelvimetry including a single scout and two transverse images. A plexiglas phantom combined with an ionization chamber was used to calculate the CTDIw and DLP for each acquisition. Then, an ex vivo phantom of bony pelvis was used to evaluate the accuracy of helical acquisitions for the measurement of pelvic diameters (i.e. the antero-posterior inlet, the transverse inlet and the interspinous distance). Reconstructions of helical acquisitions were performed using 2D MPR, 3D MIP and 3D SSD algorithms. RESULTS: CTDIw and DLP of conventional pelvimetry were 26 mGy and 42 mGy.cm respectively. The radiation dose of helical acquisitions decreased linearly with tube current (CTDIw: from 13 to 1.3 mGy, DLP: from 218.3 to 18.7 mGy.cm). Compared to conventional CT, the dose was nearly similar at 25 mAs and reduced at 10 mAs. Helical acquisitions provided accurate measurements of pelvic diameters with a pitch of 1.125 and a 2D MPR algorithm to evaluate the AP inlet and a 3D MIP algorithm to evaluate the transverse inlet and the interspinous distance. Variations of tube current did not influence the accuracy of pelvic diameter measurement. CONCLUSION: Our results suggest that accurate low-dose helical CT pelvimetry using 10-25 mAs and a pitch factor of 1.125 combined with 2D MPR and 3D MIP reconstructions is possible.

Algorithms↗

Isolation by distance and sharp discontinuities in gene frequencies: implications for the phylogeography of an alpine insect species, Carabus solieri.

Analysis of genetic isolation by distance (IBD) is of prime importance for the study of processes responsible for spatial population genetic structure and is thus frequently used in case studies. However, the identification of a significant IBD pattern does not necessarily imply the absence of sharp discontinuities in gene frequencies. Therefore, identifying barriers to gene flow and/or secondary contact between differentiated entities remains a major challenge in population biology. Geographical genetic structure of 41 populations (1080 individuals) of an alpine insect species, Carabus solieri, was studied using 10 microsatellite loci. All populations were significantly differentiated and spatially structured according to IBD over the entire range. However, clustering analyses clearly identified three main clusters of populations, which correspond to geographical entities. Whereas IBD also occurs within each cluster, population structure was different according to which group of populations was considered. The southernmost cluster corresponds to the most fragmented part of the range. Consistently, it was characterized by relatively high levels of differentiation associated with low genetic diversity, and the slope of the regression of genetic differentiation against geographical distances was threefold those of the two other clusters. Comparisons of within-cluster and between-cluster IBD patterns revealed barriers to gene flow. A comparison of the two approaches, IBD and clustering analyses, provided us with valuable information with which to infer the phylogeography of the species, and in particular to propose postglacial colonization routes from two potential refugia located in Italy and in southeastern France. Our study highlights strongly the possible confounding contribution of barriers to gene flow to IBD pattern and emphasizes the utility of the model-based clustering analysis to identify such barriers.

Analysis of Variance↗

Tetanus in developing countries: an update on the Maternal and Neonatal Tetanus Elimination Initiative.

Tetanus is a vaccine-preventable disease that yearly causes a total of 309,000 deaths. Of particular concern is maternal and neonatal tetanus (MNT), which can be prevented through immunization of the mother in pregnancy. In 2000, neonatal tetanus alone was responsible for an estimated 200,000 deaths. While the focus is on 57 priority countries, 90% of the neonatal tetanus deaths occur in 27 countries. UNICEF is spearheading the effort to eliminate MNT by the year 2005, with the support of numerous partners. MNT elimination is defined as less than one case of neonatal tetanus per 1000 live births at district level. The main strategies consist of promotion of clean delivery practices, immunization of women with a tetanus toxoid (TT) containing vaccine, and surveillance. Maternal tetanus immunization is, in most developing countries, implemented as part of the routine immunization program. However, large areas remain underserved, due to logistical, cultural, economical or other reasons. In order to achieve the target of MNT elimination by 2005, and to offer protection to women and children otherwise deprived from regular immunization services, countries are encouraged to adopt the "high risk approach". This approach implies that, in addition to routine immunization of pregnant women, all women of child bearing age living in high risk areas are targeted for immunization with three doses of a tetanus toxoid containing vaccine (TT or Td), implemented as "supplemental immunization activities" (SIAs). Through SIAs, about 17 million women have been reached with at least two doses of TT vaccine in the past 3 years, and it is estimated that another 200 million need to be targeted in the years to come. SIAs should substantially reduce the burden of disease. Countries will also have to improve their existing immunization and clean delivery programs to ensure that the elimination of maternal and neonatal tetanus is maintained.

Adult↗

Medial olivocochlear bundle activation and perceived auditory intensity in humans.

In order to test the hypothesis of a role of cochlear efferent activity in intensity perception in humans, loudness functions, loudness integration, and loudness summation were measured in the absence and in the presence of contralateral noise in normal-hearing subjects. Additionally, relationships with the effect of the noise on evoked otoacoustic emissions (EOAEs) were tested, and comparisons with vestibular neurotomy patients were performed. Overall, the results failed to demonstrate significant effects of contralateral noise stimulation on loudness functions and loudness integration. Furthermore, no significant differences were found in vestibular neurotomy patients. A significant effect of contralateral noise on loudness summation was noted, but was not related to the effect on otoacoustic emissions. The present results fail to support the notion that efferent influences onto the cochlear compression have a significant perceptual effect.

Acoustic Stimulation↗

Measurement of first- and second-order modulation detection thresholds in listeners with cochlear hearing loss.

First- and second-order modulation detection thresholds were measured in normal hearing and hearing-impaired listeners. 'First-order' modulation detection thresholds correspond to the ability of listeners to detect sinusoidal amplitude modulation (SAM); they are measured as a function of the frequency of that modulation, f(m). 'Second-order' modulation detection thresholds correspond to the ability to detect sinusoidal modulation applied to the modulation depth of a SAM signal; they are measured as a function of the frequency of the modulation applied to the modulation depth (referred to as f(m)'). In this case, the SAM signal acts as a 'carrier' stimulus of frequency f(m) and sinusoidal modulation of the SAM-signal's modulation depth (at rate f(m)') generates two additional components in the modulation spectrum at f(m)-f(m)' and f(m)+f(m)'. In both groups of listeners, first-order modulation detection thresholds were measured for modulation frequencies f(m) ranging between 4 Hz and 32 Hz, and second-order modulation detection thresholds were measured for second-order modulation frequencies f(m)' ranging between 1 Hz and 11 Hz, using a fixed first-order modulation frequency f(m) of 16 Hz. The results showed that, in hearing-impaired listeners: first-order modulation detection thresholds were within the normal range up to f(m) = 16 Hz and poorer than normal at f(m) = 32 Hz; second-order modulation detection thresholds were within the normal range at f(m)' = 3, 5 and 11 Hz, and poorer than normal at f(m)' = 1 Hz and 7 Hz. These results suggest that cochlear damage has little effect on the detection of both sinusoidal and complex temporal envelopes.

Adult↗

Differential expression of apoptosis-associated genes post-hepatectomy in cirrhotic vs. normal rats.

Liver regeneration after partial hepatectomy or liver injury is controlled by a wide variety of growth factors that are proven activators or inhibitors of hepatocyte proliferation. Liver regeneration post-hepatectomy has been proven to be decreased and delayed in cirrhotic vs. normal liver. Apoptosis seems to play an important role in cellular proliferation and in liver regeneration. Therefore, this study has analyzed the expression of apoptosis-associated genes following 2/3 hepatectomy in cirrhotic vs. normal rats. Cirrhosis was induced by a weekly intragastric administration of CCl4 for 16 weeks followed by hepatectomy and histological examination of the resected liver. Rats were sacrificed at 6 h, 12 h, 24 h, or 72 h after liver resection. The expression of proapoptotic (Bad, Bak, Bax) and antiapoptotic (Bcl-2, Bcl-XL) genes was analyzed by quantitative RT-PCR. We have observed an early increase in antiapoptotic mRNA levels and a delayed increase in proapoptotic mRNA levels in normal liver following hepatectomy. Before resection, proapoptotic mRNA levels were significantly higher in cirrhotic vs. normal liver. After hepatectomy, apoptotic mRNA levels were decreased and delayed as compared with that observed following hepatectomy in normal liver. These results indicate that apoptosis takes place in liver during CCl4-induced cirrhosis and could participate in the impaired regenerative response observed in cirrhotic liver.

Animals↗

Effect of frequency content on categorical loudness normalization.

In this study, increases in loudness with increases in bandwidth, termed loudness summation, were derived from loudness growth functions estimated using a loudness-scaling procedure. The results revealed that at equal loudness category, categorical loudness summation was generally larger in normal-hearing than in hearing-impaired subjects; furthermore, the increase in loudness summation at intermediate loudness levels observed in the former, was absent in the latter. These results, in broad agreement with recent data from the literature, can be explained in the light of physiological data on cochlear compression. One implication of these results regarding hearing aid fitting was that channel-by-channel loudness normalization was effective only when the incoming sound was closed in bandwidth to one of the test stimuli.

Adult↗

Temporal loudness integration and spectral loudness summation in normal-hearing and hearing-impaired listeners.

The aim of this study was to test for differences between normal-hearing and hearing-impaired listeners regarding two fundamental aspects of intensity perception: loudness integration and loudness summation. Loudness functions for three different stimuli were measured using categorical loudness scaling in 8 normal-hearing and 12 hearing-impaired subjects. The results indicated that temporal loudness integration, defined as the difference in SPL between 16.25-ms and 300-ms noise bursts of equal loudness, was larger in the hearing-impaired than in the normal-hearing listeners. Loudness summation, defined as the difference in SPL between a 300-ms, 1,600-Hz tone pip and a white noise burst of the same duration and loudness, did not differ between the two groups. Implications of these results for hearing aid fitting strategies based on loudness normalization are discussed.

Adult↗

Loudness growth functions and EABR characteristics in Digisonic cochlear implantees.

Electrically evoked auditory brainstem responses (EABRs) and loudness functions were measured in 14 subjects equipped with an MXM Digisonic cochlear implant. EABRs were evoked by 75-Hz pulse trains presented on the apical electrode. Loudness functions at the same rate and at a rate more conventional for psychoacoustic measurements (300 Hz) were measured using a categorical loudness-scaling procedure. The results revealed a significant difference in the loudness functions measured at 75 and 300 Hz, loudness increasing more steeply with stimulus intensity for the latter rate. Significant correlations between EABR wave V thresholds and perceptual thresholds measured at both 75 and 300 Hz were observed. Furthermore, in 8 out of the 14 patients, EABR wave V saturated at a stimulus level corresponding precisely to the loudest bearable, i.e. "Too loud" level for the 300-Hz stimulation rate; this same level corresponded to the "Comfortable" loudness level for the 75-Hz stimulation rate. On average, an almost linear relationship was observed over the first half of the loudness range between the stimulus intensity, expressed as a pulse duration in log units, and wave V amplitude in dB. Although further investigation is required before maximum comfort levels can be predicted reliably from EABR measures in individual subjects, these results indicate new directions regarding the estimation of perceptual dynamic range limits on the basis of EABR measures in cochlear implantees.

Adult↗

Action of tropoelastin and synthetic elastin sequences on vascular tone and on free Ca2+ level in human vascular endothelial cells.

The elastic properties of extensible tissues such as arteries and skin are mainly due to the presence of elastic fibers whose major component is the extracellular matrix protein elastin. Pathophysiological degradation of this protein leads to the generation of elastin peptides that have been identified in the circulation in the ng/mL to microg/mL range. Similar concentrations of an elastin peptide preparation (kappa-elastin) were previously demonstrated to induce, among other biological actions, a dose- and endothelium-dependent vasorelaxation mediated by the elastin/laminin receptor and by endothelial NO production. To determine the elastin sequence(s) responsible for vasomotor activity and to learn more about possible signaling pathways, we have compared the action of different concentrations (10(-13) to 10(-7) mol/L) of recombinant human tropoelastin, eight synthetic elastin peptides, and a control peptide (VPVGGA) on both rat aortic ring tension and [Ca2+]i of cultured human umbilical vein endothelial cells. No vasoactivity could be detected for VPVGGA and for the elastin-related sequences VGVGVA, PGVGVA, and GVGVA. Tropoelastin, VGV, PGV, and VGVAPG were found to induce an endothelium- and dose-dependent vasorelaxation and to increase endothelial [Ca2+]i, whereas PVGV and VGVA produced these effects only at low concentration (10(-11) mol/L). A likely candidate for mediating the elastin peptide-related effects is the elastin/laminin receptor, since the presence of lactose strongly inhibited the vasoactivity associated with these compounds. Our results show that although the flanking amino acids modulate its activity, VGV seems to be the core sequence recognized by the elastin receptor.

Animals↗

Auditory efferents involved in speech-in-noise intelligibility.

Following studies proposing that medial olivocochlear efferents might be involved in the processing of complex signals in noise, we tested the involvement of efferent feedback in speech-in-noise intelligibility. Two approaches were used: measures of speech-in-noise intelligibility in vestibular neurotomized patients with cut efferents and comparison with normal hearing subjects; and correlations between effectiveness of olivocochlear feedback, assessed by contralateral suppression of otoacoustic emissions and speech-in-noise intelligibility in normal subjects. Contralateral noise improved speech-in-noise intelligibility in normal ears. This improvement, which was almost absent in de-efferented ears of vestibular neurotomized patients, was correlated with the strength of the olivocochlear feedback. Together, these results suggest that olivocochlear efferents play an antimasking role in speech perception in noisy environments.

Adult↗

Spectral and cepstral properties of vowels as a means for characterizing velopharyngeal impairment in children.

This study investigated spectral differences in the phonation of vowels between a group of 21 children with velopharyngeal impairment and a paired control group of 42 subjects. The speech material was composed of the isolated vowels /a/, /i/, and /u/, a sustained vowel /a/, and four vowels included in spoken words: two nasals /in/ and /on/ in "dindon," and two orals /a/ and /o/ in "gâteau." A bottom-up discriminant function analysis indicated that the cepstrum coefficients and the linear-FFT were the most efficient tools in the test to classify the set of children. They were superior to the results obtained with the formant-representation of the vowels. The use of a perceptive scale (barks) did not improve the results. Discrimination over the total group showed percentages lower than those obtained when boys and girls were assessed separately. The best discriminating results were obtained with the /a/ of "gâteau" for the girls and with the isolated /i/ for the boys.

Case-Control Studies↗

Effect of signal duration on categorical loudness scaling in normal and in hearing-impaired listeners.

The present study sought to determine whether the duration of white-noise bursts affects their loudness category rating in the same way for hearing-impaired as for normally-hearing subjects. Twelve normally-hearing and 12 hearing-impaired subjects took part. Categorical loudness growth functions were obtained for 16.25 ms, 32.5 ms, 75 ms, 150 ms and 300 ms white noise bursts. Temporal integration of loudness was defined as the intensity difference needed for stimuli of different durations to result in identical category ratings. In normally-hearing subjects, temporal integration of loudness occurred mainly with the short-duration (16.25 ms and 32.5 ms) stimuli, whereas it was found with almost every stimulus duration in hearing-impaired subjects. In other words, temporal integration of loudness between 16.25 ms and 300 ms stimulus duration was greater in hearing-impaired listeners and there was a difference between normal and hearing-impaired subjects regarding change in loudness perception with stimulus duration. Consequently, the use of fixed-duration stimuli hinders loudness normalization.

Adolescent↗