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Biomedical subjects

C Laurent

Publications and source records attributed to C Laurent.

At least 163 records · Page 9Linked to original sources
PubMed1989

Hyaluronan in experimental serous and purulent otitis media.

The concentration of hyaluronan (hyaluronic acid; sodium hyaluronate; HA), a major component of connective tissue, was analyzed by a specific radioassay in tissue samples from normal rat middle ears and in tissue and effusions from middle ears affected by experimentally induced otitis media. In normal ears the pars flaccida of the tympanic membrane contained a considerably higher concentration of HA (60 to 200 micrograms/g) than the pars tensa and areas of the medial wall (2 to 7 micrograms/g). In purulent otitis media the pars flaccida contained less HA than in normal ears. The HA concentrations were lower in purulent (3 to 40 micrograms/mL) than in serous (20 to 190 micrograms/mL) effusions. The weight average molecular weight of HA in serous fluid was high (greater than 10(6] and comparable to that in lymph. It is inferred from the study that the subepithelial tissue and its matrix components, eg, HA, must be considered when attempting to understand the function of the middle ear normally and in otitis media.

Animals↗
PubMed1988

Hyaluronan improves the healing of experimental tympanic membrane perforations. A comparison of preparations with different rheologic properties.

Preparations of hyaluronan at various concentrations and molecular weights were topically applied to experimental tympanic membrane (TM), perforations in the rat and their ability to improve the healing pattern was elucidated. The perforation occupied the upper posterior quadrant of the TM. Alterations in healing rate and quality of the healed TM were examined by otomicroscopy and in histologic sections. Hyaluronan enhanced the healing rate and resulted in less opacity and structural alteration of the scar area. Closure time for the TM perforation was correlated to the concentration of hyaluronan but not to its molecular weight or viscosity. Improved scar quality was obtained in the presence of hyaluronan irrespective of its rheologic properties. Hyaluronan improved the restoration of the fibrous connective tissue layer. Treatment of TM perforation in man with hyaluronan at high concentrations should be considered as an alternative to myringoplasty.

Administration, Topical↗
PubMed1988

Adult human masseter muscle fibers express myosin isozymes characteristic of development.

Masseter muscle biopsies were obtained from nine patients undergoing orthognatic surgery or surgery for parotid tumors. A detailed enzyme-histochemical and immunocytochemical study of these muscles was performed using antibodies specific to the various isozymes of the myosin heavy chain (MHC) in order to identify the MHC isozymes that were present in the different fiber types. The contractile proteins in these same biopsies were analyzed by two-dimensional gel electrophoresis, native pyrophosphate gel electrophoresis, and by an immunopolypeptide mapping approach. These studies have shown that there is a very heterogeneous distribution of the myosin isozymes, with many fibers containing more than one myosin type. We also present evidence that in addition to adult fast and slow myosin, the human masseter muscle contains two proteins, neonatal MHC and embryonic myosin light chain, that are characteristic of developing muscle.

Electrophoresis↗
PubMed1988

SCE increases after an accidental acute inhalation exposure to EtO and recovery to normal after 2 years.

Sister-chromatid exchanges (SCEs) were studied in 3 workers accidentally exposed for about half an hour to high levels of ethylene oxide (more than 700 ppm) during a sterilizing process. The 3 workers had clinical symptoms of exposure and were tested for SCE frequencies 5 days and 2 years after the accident: 2 had also been tested 6 months earlier. All 3 showed a similar increase in SCEs after the accident, to a mean of 13.8 SCEs/cell compared with 8.6 for a control group. The incidence of 'high-frequency cells' was markedly elevated but decreased over 2 years, when the mean SCE frequencies had also returned to pre-accident levels.

Accidents↗
PubMed1988

Budesonide nasal spray as prophylactic treatment after polypectomy (a double blind clinical trial).

This double-blind parallel-group study compared the effect of budesonide with placebo, in the prophylaxis of nasal polyp recurrence after evulsion. Seventy-three patients with first time or recurrent polypectomy were enrolled. At revisits 3 and 6 months after evulsion, the budesonide-treated patients had significantly lower polyp scores than the placebo-treated patients. Only patients with recurrent nasal polyposis benefited from the budesonide treatment, whereas no effect was evident in patients with first time evulsion.

Administration, Intranasal↗
PubMed1988

Control of myogenesis in the mouse myogenic C2 cell line by medium composition and by insulin: characterization of permissive and inducible C2 myoblasts.

Using subcloning and manipulations of culture conditions we have isolated from the mouse myogenic cell line C2 a variant cell line that we named inducible. Unlike the progenitor cells that are referred to as permissive, inducible myoblasts differentiate poorly in Dulbecco modified Eagle medium plus fetal calf serum (FCS) and require the presence of insulin at a high concentration (1.6 10(-6) M) or insulin-like growth factor I (IGFI) at a lower concentration (2.5 10(-8) M) to differentiate. Permissive and inducible myoblasts fail to differentiate when grown in MCDB202 medium plus 20% FCS, even after a prolonged arrest in G1 phase. This shows that an arrest in G1 is in itself insufficient to trigger terminal differentiation. Both cell types also exhibit distinct patterns of accumulation of muscle mRNAs corresponding to sarcomeric actins and myosin light chain MLC1A. The possibility that these two cell lines might represent two different stages of the progression of myoblasts toward terminal differentiation is discussed.

Actins↗
PubMed1987

Hyaluronan in the middle ear of the rat. The normal distribution of hyaluronan and the clearance of exogenously administered hyaluronan from the middle ear.

The content of hyaluronan (HA), a common connective tissue component, was determined in well defined areas of the rat middle ear. The HA concentration in the pars flaccida of the tympanic membrane was considerably greater than in the pars tensa and areas on the medial wall of the middle ear cavity. The fate of exogenous HA introduced into the middle ear was also studied in rats. Tritium-labelled HA disappeared through the Eustachian tube (ET) and was followed by analysis of the nasopharyngeal secretion. The radioactivity in the secretion reached a peak at 3 h and decreased to almost zero within 12 h, indicating that most of the HA was removed. By autoradiography and direct analysis of the HA concentration and molecular weight distribution the fate of HA after obstruction of the ET was followed. Radioactive HA was confined to the middle ear and no uptake into surrounding tissues could be traced by autoradiography 4 days after application. The amount of HA that could be recovered from the middle ear was constant for up to 6 days. Analysis of the molecular weight distribution of the deposited HA indicated only slow degradation during these 6 days.

Animals↗
PubMed1987

Hyaluronan and healing of tympanic membrane perforations. An experimental study.

Hyaluronan, an extracellular high molecular weight polysaccharide, was applied onto experimentally performed tympanic membrane (TM) perforations in the rat. The hyaluronan-treated perforations closed faster than the untreated controls and showed less scar tissue. Initially the perforation became covered by a sheet of keratin and hyaluronan, which appeared to relax and orientate the retracted collagen fibres at the margin of the perforation. The hypertrophic stratified keratinizing squamous epithelium advanced within the hyaluronan-keratin cover and closed the perforation ahead of an approaching connective tissue. Three months after the closure, the hyaluronan-treated TMs appeared transparent in comparison to the opaque untreated controls. In histological sections the hyaluronan-treated TM was comparably thin and an organized collagen fibre layer was discernible. Hyaluronan of various concentrations (0.75, 1.0, 1.75 and 1.9%) and molecular weights (4 x 10(6) and 6 x 10(6)) were tested. The healing rate and degree of scar tissue was dependent on the concentration, but not on the molecular weight of the hyaluronan. Hyaluronan, at the higher concentration, healed the perforations faster and produced a less opaque TM than hyaluronan at low concentration. The number of applications of hyaluronan also influenced the healing rate; fewer applications resulted in a reduced rate. However, the quality of the healed TM was influenced to a lesser extent by the number of hyaluronan applications. Even single applications caused less scar tissue in comparison with untreated TMs. It is inferred from the study that hyaluronan, exogenously applied, might be valuable also in the clinical situation to enhance the healing of different types of TM perforation.

Animals↗
PubMed1987

Reversible changes in inner ear function following hyaluronan application in the middle ear.

A safety study regarding the potential ototoxicity of 1.9% hyaluronan was performed in 20 rats. In all animals the middle ear was completely filled with hyaluronan three times at 2-day intervals between the administrations. Inner ear function was evaluated by computerized auditory brainstem response (ABR) measurements. ABR recordings were performed prior to exposure, after myringotomy (but prior to administration of hyaluronan), 5 days after the last administration (n = 15; these animals were then sacrificed for analysis of the middle ear), one month and 3 months later (n = 5). The hearing thresholds were improved in animals 5 days after the last administration of hyaluronan at 6-8 kHz, whereas the hearing thresholds were impaired at 12 and 20 kHz. After one month, ABR thresholds were even better than precontrol levels at 2, 4 and 6 kHz, whereas at all other frequencies the ABR threshold was normal. Three months after hyaluronan exposure, all ABR thresholds were normal, but viscous material was present in the middle ear in 3 of 5 animals. It is concluded that hyaluronan causes reversible changes in inner ear function but lacks ototoxic adverse effects.

Animals↗
PubMed1987

Hyaluronan applied to the middle ear mucosa prior to fixation improves the morphological quality.

In a previous study, it was noted that immersion-fixed middle ear mucosa appeared better preserved if treated with hyaluronan (hyaluronic acid, HA) prior to fixation. The present study showed that HA instilled into the middle ear caused the epithelial cells to emerge more brilliant--when stained with toluidine blue--but did not hinder minor autolytic changes from occurring. The precise molecular or biochemical event or events that cause the brilliance are not known at present. HA did not cause any severe structural alterations of the mucosa.

Animals↗
PubMed1987

[In vitro action of fosfomycin combined with rifampicin, pefloxacin and imipenem on staphylococci (checkerboard method in a liquid medium)].

The combined activity of fosfomycin with rifampin, pefloxacin and imipenem was investigated, by the checkerboard method performed in liquid medium, against 50 clinical isolates of staphylococci (25 Staphylococcus aureus and 25 coagulase-negative staphylococci). The combination of fosfomycin plus rifampin had an additive bacteriostatic effect and an antagonistic bactericidal effect. Fosfomycin combined with pefloxacin was found to be additive or moderately synergistic. Fosfomycin in combination with imipenem was generally highly synergistic, especially against meticillin-resistant strains; however the bactericidal effect was occasionally antagonistic.

Anti-Bacterial Agents↗
PubMed1986

The catabolic fate of hyaluronic acid.

Part of the hyaluronic acid (HA) synthesized in peripheral tissues enters the blood circulation through the lymph. It is rapidly taken up by the endothelial cells in the liver (half-life in blood is 2.5-5.5 minutes) and degraded. Pure primary cultures of liver endothelial cells were obtained by a newly developed technique and used to follow the metabolism of the polysaccharide on the cell surface. At 37 degrees C the HA is effectively endocytosed and degraded to acetate and lactate. A radioassay specific for HA and sensitive in the nanogram range has been developed to follow the concentration of HA in serum. The normal level in man is 10 to 100 micrograms/l. Elevated serum levels of HA are seen in liver cirrhosis, rheumatoid arthritis and scleroderma indicating that both an impaired catabolism in the liver and an increased synthesis in the peripheral tissues can modify the HA level.

Animals↗