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Biomedical subjects

Bernard Rousseau

Publications and source records attributed to Bernard Rousseau.

31 records · Page 2Linked to original sources
PubMed2004

Functional outcomes of reduced hyaluronan in acute vocal fold scar.

To examine the functional effects of hyaluronan and collagen alterations in acute vocal fold scar, we injured 15 pig larynges by vocal fold mucosa stripping. At 3, 10, and 15 days after operation, we performed excised larynx experiments to measure phonation threshold pressure (PTP) and vocal economy (an acoustic output-cost ratio; OCR), and then performed hyaluronan and collagen assays. Five uninjured larynges were used as excised controls. Hyaluronan was reduced in the scarred vocal folds through 15 days of wound healing. Collagen was increased at day 15. The PTP was increased and OCR was decreased in scarred larynges, indicating decreased vocal efficiency and ease of phonation. Thus, PTP and OCR were sensitive to the biomolecular changes in acute vocal fold scar. Hyaluronan was more susceptible than collagen to acute tissue ultrastructural alterations. These findings may provide a rationale for increasing hyaluronan in acute vocal fold scar to improve postoperative vocal outcomes.

Acoustics↗
PubMed2004

Growth factor therapy for vocal fold scarring in a canine model.

Vocal fold scarring remains a therapeutic challenge. Hepatocyte growth factor (HGF) has strong antifibrotic activity and has proved to have therapeutic potential in restoration of scar tissues such as liver cirrhosis and lung fibrosis. The present study aimed to clarify the effects of HGF injection into scarred vocal folds in a canine model. Canine vocal folds were stripped unilaterally and treated with intracordal injection of saline solution (sham group), HGF (HGF group), or HGF with cultured autologous normal vocal fold fibroblasts (Fb/HGF group) 1 month after injury. The larynges were harvested 6 months after the initial injury and then subjected to vibratory and histologic examination. The results of vibratory examinations in the excised larynx setup revealed that phonation threshold pressure significantly increased and vocal efficiency was significantly reduced in all treated groups as compared to normal data obtained from normal canine larynges. However, the HGF group presented much better results than both the sham and Fb/HGF groups in terms of mucosal wave amplitude and incidence of vocal fold bowing, glottal incompetence, and phase asymmetry. The histologic data indicated a significant increase of collagen in both the sham and Fb/HGF groups, while normal levels of collagen were found in the HGF group. Tissue contraction of the lamina propria was also observed in both the sham and Fb/HGF groups, but was barely detectable in the HGF group. Although the HGF-treated vocal folds appeared to require more driving forces for vibration, HGF might prevent excessive collagen deposition and tissue contraction and thus reduce the effects of scarring on the vibratory properties of the vocal folds. From these data it is concluded that HGF has considerable potential in the treatment of vocal fold scarring.

Animals↗
PubMed2003

Enrichment of the light-harvesting complex in diadinoxanthin and implications for the nonphotochemical fluorescence quenching in diatoms.

The pigment composition of diatoms differs from that of green algae and plants. Diatoms contain chlorophyll (Chl(1)) c, fucoxanthin, and diadinoxanthin (DD). An intermittent light regime during growth induced a large increase in the DD content in the marine planktonic diatom Phaeodactylum tricornutum. Light-harvesting complex containing fucoxanthin (LHCF) subunits were purified on a sucrose gradient after treatment of thylakoid membranes with a mild detergent. DD was found in all the LHCF fractions: a "major" composite LHCF fraction and the two fractions where some LHCF was associated with photosystem centers. For cells enriched in DD, most of the additional DD molecules were bound to the major LHCF fraction. The DD enrichment of the major LHCF fraction was accompanied by a decrease in the fucoxanthin to Chl a ratio. Either some fucoxanthin molecules were replaced by DD or there could be a relative enrichment of subunits rich in DD at the expense of fucoxanthin/Chl c rich subunits. Under high light illumination, a higher degree of de-epoxidation of DD into DT was observed for the major LHCF of cells enriched in DD. This fraction has the higher DD content and the higher degree of de-epoxidation. These results show that the distal antennae, probably mostly isolated as the major LHCF fraction, play a crucial role in the formation of NPQ, its amplitude depending on the amount of DD bound and on the degree of de-epoxidation (Lavaud et al. (2002) Plant Physiol. 129, 1398-1406).

Darkness↗
PubMed2003

Tracking outcomes after phonosurgery for sulcus vocalis: a case report.

Outcomes data after a surgical or behavioral intervention should be tracked until stability is reached. Often it is unclear how long patients should be followed and at what point an outcome can be considered stable. These issues have implications for treatment decision making, efficacy measurement, and the design of research studies. Vocal function data were collected 24 hours before and at 1, 6, and 12 months after phonosurgery for sulcus vocalis. One data series was collected daily during the first month after surgery, providing a unique opportunity to study voice changes in the immediate postoperative period. The different vocal function indices (acoustic, perceptual, videostroboscopic, aerodynamic, psychosocial) demonstrated a general pattern of improvement after intervention; however, they appeared to reach stability at different times. This report reinforces the value of following patients until complete outcome stability.

Adult↗
PubMed2003

Characterization of vocal fold scarring in a canine model.

OBJECTIVE: The objective was to assess the histological and viscoelastic shear tissue properties of the scarred vocal fold lamina propria at 2 and 6 months postoperatively in a canine model. STUDY DESIGN: Experimental, nonrandomized prospective study. METHODS: Six canine larynges were injured using a vocal fold stripping procedure. At 2 and 6 months postoperatively, histological analyses of the scarred and control lamina propria samples were completed for collagen, procollagen, elastin, and hyaluronic acid. RESULTS: In canines killed at 2 months, scarred tissue samples contained increased procollagen and decreased elastin. Elastin fibers in the scarred lamina propria were characteristically tangled and disorganized. In canines killed at 6 months, scarred tissue samples showed decreased elastin and increased collagen. Collagen fibers formed thick, disorganized bundles, and elastin fibers were disorganized throughout the entire scarred vocal fold lamina propria. Viscoelastic shear tissue measurements revealed increased stiffness and viscosity in one of three cases at 2 months and in all three cases at 6 months, indicating increased stiffness and resistance to shear flow during oscillatory shear deformation for scarred tissue samples. No differences were observed between the two postoperative times. CONCLUSIONS: Results indicated that viscoelastic tissue changes may take place before scar maturation in the scarred vocal fold lamina propria and that, although abundant collagen deposition may influence viscoelastic shear tissue properties, disorganization of collagen and elastin fibers, thick bundle collagen formation, or the interplay of several of these factors might also play a contributing role.

Animals↗
PubMed2003

Fibronectin and adhesion molecules on canine scarred vocal folds.

OBJECTIVE: To examine the expressions of fibronectin and other adhesion molecules on the scarred vocal folds in a short- and long-term animal model. STUDY DESIGN: Animal model. METHODS: Six beagles' vocal folds were stripped unilaterally and left untreated. After wounding the vocal folds were harvested from three dogs at 2 months and three dogs at 6 months. The untouched vocal fold was used as a control, and the stripped vocal fold as scarred. Subsequently, the expressions of fibronectin, cadherin, syndecan-1 and syndecan-4 on both vocal folds were examined by immunohistochemical and image analysis. RESULTS: Compared with the control vocal folds, fibronectin significantly increased in the superficial layer of the lamina propria on the scarred vocal folds at both 2 and 6 months. Co-deposition of collagen was observed only at 6 months. Syndecan-4 was significantly overexpressed at the basal layer cells of the epithelium at both 2 and 6 months. No significant expression of either cadherin or syndecan-1 was detected. CONCLUSIONS: Scar characteristics at 2 and 6 months are not identical, suggesting that a 2-month period may not be a sufficient to study vocal fold scarring. Adhesion molecules are important in reorganization of extracellular matrix during wound healing because of their binding and adhesion characteristics. The results indicate that fibronectin might be important in providing a scaffold for the deposition of other proteins such as collagen, and the binding characteristics might affect the stiffness of the scarred vocal fold. Prolonged expression of syndecan-4 may reflect the role of focal adhesion during the assembly of scar structure. Ultimately, better understanding of the histological features of the scarred vocal fold might lead to new approaches to treatment.

Animals↗
PubMed2002

Regioselective photolabeling of glycoprotein A in membranes.

We have developed a chemical method for directly identifying the amino acid residues of the transmembrane domain of a protein that are located right in the center of the membrane. Glycophorin A (GPA), the major sialoglycoprotein of human erythrocytes, was the first membrane protein whose primary sequence was elucidated, but its three-dimensional structure is still not known. GPA has been reconstituted into liposomes formed from dimyristoylphosphatidylcholine, dimyristoylphosphatidylserine, cholesterol, and a bola-amphiphilic phospholipidic photoactivatable probe (radioactive probe 1) by a detergent-mediated method. Electron microscopy confirmed the formation of spherical vesicular structures, and sucrose-density gradients revealed that the proteoliposomes comprised only one membrane fraction. Proteinase-K digestion of GPA in the proteoliposomes suggested that the orientation of GPA in reconstituted proteoliposomes was virtually identical to that observed in natural erythrocyte membranes. After photo-irradiation of the reconstituted proteoliposomes and in situ tryptic digestion, the photolabeled amino acid residues were analyzed by Edman degradation and their radioactivity was measured. Val80 and Met81, which had been assumed to be located near the center of the transmembrane domain of GPA, were indeed highly selectively photolabeled by probe 1. The new method might be applied to analyze the three-dimensional arrangement of the transmembrane domain of protein complexes that are made up from several subunits.

Amino Acid Sequence↗
PubMed2002

Concise synthesis of anhydrovinblastine from leurosine.

[reaction: see text] The Cp(2)TiCl-mediated deoxygenation of leurosine (1) afforded anhydrovinblastine (4) in good yield. Furthermore, as the reaction proceeded via a carbon-centered radical intermediate, this transient was also trapped by a hydrogen-atom donor to afford selectively reduced alkaloid 10.

Antineoplastic Agents↗
PubMed2002

Highly chemoselective hydrogenolysis of iodoarenes.

The catalytic hydrodehalogenation reaction using molecular hydrogen and Pd/C has been revisited. It is shown that the speed of removal of halogen increases with increasing electronegativity I < Br < Cl. Nevertheless, selective dehydrohalogenation in compounds containing other reducible functions can be achieved only with iodine and not with bromine or chlorine. Selective deiodination of iodobenzophenone could be accomplished without reducing the carbonyl group. Hydrogenolysis of azidoiodoaromatic compounds to the corresponding azido compounds is high yielding. This selectivity was exploited for the labeling of benzophenone- and azido-containing compounds by deuterium and tritium.

Journal Article↗
PubMed2002

Influence of the diadinoxanthin pool size on photoprotection in the marine planktonic diatom Phaeodactylum tricornutum.

The pool size of the xanthophyll cycle pigment diadinoxanthin (DD) in the diatom Phaeodactylum tricornutum depends on illumination conditions during culture. Intermittent light caused a doubling of the DD pool without significant change in other pigment contents and photosynthetic parameters, including the photosystem II (PSII) antenna size. On exposure to high-light intensity, extensive de-epoxidation of DD to diatoxanthin (DT) rapidly caused a very strong quenching of the maximum chlorophyll fluorescence yield (F(m), PSII reaction centers closed), which was fully reversed in the dark. The non-photochemical quenching of the minimum fluorescence yield (F(o), PSII centers open) decreased the quantum efficiency of PSII proportionally. For both F(m) and F(o), the non-photochemical quenching expressed as F/F' - 1 (with F' the quenched level) was proportional to the DT concentration. However, the quenching of F(o) relative to that of F(m) was much stronger than random quenching in a homogeneous antenna could explain, showing that the rate of photochemical excitation trapping was limited by energy transfer to the reaction center rather than by charge separation. The cells can increase not only the amount of DT they can produce, but also its efficiency in competing with the PSII reaction center for excitation. The combined effect allowed intermittent light grown cells to down-regulate PSII by 90% and virtually eliminated photoinhibition by saturating light. The unusually rapid and effective photoprotection by the xanthophyll cycle in diatoms may help to explain their dominance in turbulent waters.

Algorithms↗
PubMed2001

Mid-Membrane Photolabeling of the Transmembrane Domain of Glycophorin A in Phospholipid Vesicles This work was supported in part by the Japan Science and Technology Corporation (JST), the Université Louis Pasteur (ULP) "Supermolecules" Joint Research Project, and the European Union (DG-XII, contract PL 950990). We are grateful for support granted by JST to N.H., by the Herrmann-Schlosser Stiftung and the Stiftung zur Förderung Körperbehinderter to W.H., and by the "Société des Amis des Sciences" of France to P.G. We also thank Dr. F. Pattus, Dr. G. Crémel, Dr. P. Hubert, Dr. A. Van Dorsselaer (Strasbourg), Dr. J. L. Rigaud, and Dr. J. L. Popot (Paris) for stimulating discussions.

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Journal Article↗