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Biomedical subjects

C Merle

Publications and source records attributed to C Merle.

At least 19 recordsLinked to original sources
PubMed2003

Compactibility study of calcium phosphate biomaterials.

This study investigated the micromechanism responsible for the densification and consolidation of powders during dynamic compaction, an experimental process in which ceramic is formed without heating. Three calcium-deficient apatites (CDA: two powders and a fibrous compound) and a biphasic calcium phosphate (BCP) were studied to determine their aptitude (rheological and physical properties) for compactibility under various dynamic compaction pressures. Powders were investigated for their physicochemistry, particle size, and flow time, and compacts for their compaction rate, density, specific area, mechanical characteristics, and disintegration time. Powder particles showed different morphological features depending on the synthesis protocol used, specific area and rheological behaviour. Compacts were not obtained with BCP, regardless of the gas pressure used, whereas CDA produced compacts with good mechanical properties (high hardness and compression stress), particularly for the fibrous compound. The poor compressibility and compactibility of BCP powders were confirmed, whereas fibrous CDA powders showed good compactibility conducive to high-quality filling of biomaterials.

Biocompatible Materials↗
PubMed2003

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles for bone implantation. Influence of the formulation process on size, drug loading, in vitro release and cytocompatibility.

Vancomycin encapsulation in biodegradable poly(epsilon-caprolactone) microparticles (200 microm mean diameter) was most efficient with a simple emulsion technique that dispersed 122.5 mg/g of polymer. Scanning electron micrographs showed smooth or pitted particles. Dissolution studies were correlated with microparticle morphology, indicating higher release with pitted particles when vancomycin was encapsulated in a dissolved state. The cytocompatibility of these poly(epsilon-caprolactone) microparticles was demonstrated by a direct contact cytotoxic assay. This material can be considered as an efficient drug delivery system for bone implantation.

Absorbable Implants↗
PubMed2003

Purification and characterization of a membrane glycoprotein from the fish pathogen Flavobacterium psychrophilum.

AIMS: The cell envelope of the fish pathogen Flavobacterium psychrophilum contains more than 50 polypeptides resolved by sodium dodecyl sulphate-polyacrylaminde gel electrophoresis analysis including a major component named P60. Here, we have developed a simple and efficient procedure for the purification of P60 and therefore permitting its biochemical characterization. METHODS AND RESULTS: Membrane proteins were selectively extracted from isolated cell envelopes with the mild non-ionic detergent Triton X-100. About 10 polypeptides were identified from the detergent fraction, including P60. The P60-enriched fraction was thereafter subjected to an anion exchange chromatographic step in the presence of Triton X-100. The molecule was purified at the milligram level (yield, about 75%; purification factor, 6.2). Analyses performed by charge shift electrophoresis, Triton X-114 phase separation and by detection of sugar-modified components showed that P60 is a true amphiphilic membrane-associated glycoprotein. CONCLUSIONS: The method described in this paper provides pure and non-denaturated P60 and should prove to be easily scaled-up. As sugar-modified protein, P60 should be included in the growing list of glycosylated prokaryotic proteins. SIGNIFICANCE AND IMPACT OF THE STUDY: It offers the possibility of obtaining P60 in amounts allowing the testing of the potential of P60 as a candidate for anti-flavobacteria subunit vaccines, as P60 is one of the major antigens.

Animals↗
PubMed2002

Hydroxylated human homotrimeric collagen I in Agrobacterium tumefaciens-mediated transient expression and in transgenic tobacco plant.

Potential contamination of animal-derived collagen with pathogens has led to the demand for safe recombinant sources of this complex molecule. In continuation of our previous work [Ruggiero et al. (2000) FEBS Lett. 469, 132-136], here we show that it is possible to produce recombinant hydroxylated homotrimeric collagen in tobacco plants that are co-transformed with a human type I collagen and a chimeric proline-4-hydroxylase (P4H). This is to our knowledge the first time that transient expression in tobacco was used to improve the quality of a recombinant protein produced in plants through co-expression with an animal cell-derived modifying enzyme. We demonstrated the functionality of the new chimeric P4H and thus improved the thermal stability of recombinant collagen I from plants to 37 degrees C.

Agrobacterium tumefaciens↗
PubMed2001

Unhydroxylated triple helical collagen I produced in transgenic plants provides new clues on the role of hydroxyproline in collagen folding and fibril formation.

Human unhydroxylated homotrimeric triple-helical collagen I produced in transgenic plants was used as an experimental model to provide insights into the role of hydroxyproline in molecular folding and fibril formation. By using chemically cross-linked molecules, we show here that the absence of hydroxyproline residues does not prevent correct folding of the recombinant collagen although it markedly slows down the propagation rate compared with bovine fully hydroxylated homotrimeric collagen I. Relatively slow cis-trans-isomerization in the absence of hydroxyproline likely represents the rate-limiting factor in the propagation of the unhydroxylated collagen helix. Because of the lack of hydroxylation, recombinant collagen molecules showed increased flexibility as well as a reduced melting temperature compared with native homotrimers and heterotrimers, whereas the distribution of charged amino acids was unchanged. However, unlike with bovine collagen I, the recombinant collagen did not self-assemble into banded fibrils in physiological ionic strength buffer at 20 degrees C. Striated fibrils were only obtained with low ionic strength buffer. We propose that, under physiological ionic strength conditions, the hydroxyl groups in the native molecule retain water more efficiently thus favoring correct fibril formation. The importance of hydroxyproline in collagen self-assembly suggested by others from the crystal structures of collagen model peptides is thus confirmed experimentally on the entire collagen molecule.

Animals↗
PubMed2001

[Thrombotic microangiopathy during HIV infection. A retrospective study performed in infectious diseases units in southern France].

OBJECTIVES: To describe and analyze the clinical and biological manifestations of thrombotic microangiopathy (TMA) and evaluate the therapeutic strategies. METHODS: A retrospective study was performed in 14 infectious diseases units of southern France. All HIV patients presenting TMA during the last decade were selected (n = 14). RESULTS: The principle signs observed, aside from defining TMA (association of microangiopathic hemolytic anemia, thrombocytopenia and renal failure), were diarrhea (n = 9) and a high level of lacticodehydrogenase (LDH). Patients were at an advanced stage of HIV infection (median of CD4+ cells counts = 70/mm3). Specific etiology was identified in 7 cases: bacterial infection (n = 5), CMV retinitis associated with Kaposi's sarcoma (n = 1) and intravenous drug use (n = 1). Various treatments were used: plasmatic exchange (5 cases), fresh frozen plasma (6 cases), steroid therapy (4 cases), acetyl salicylic acid (3 cases), adaptation of antiretroviral treatment (3 cases). The global prognostic was poor with 50% mortality within 2 months. A high level of LDH (> 2500 UI/L) was associated with premature death in 5 of the 6 cases observed. CONCLUSION: Our data confirm the severity of TMA in case of HIV infection. The common treatment remains the use of plasmatic exchange and fresh frozen plasma; an optimal antiretroviral therapy must be associated.

AIDS-Related Opportunistic Infections↗
PubMed2001

Nursing considerations of the neonate with congenital heart disease.

Nursing care of the neonate with CHD incorporates a knowledge base of the anatomy and physiology of congenital heart defects, surgical repair, complications associated with CHD, diagnostic testing, medical therapy, and psychosocial support. The neonatal nurse is a vital member of the cardiac team in providing accurate assessments, implementing medical therapies, and supporting the family.

Algorithms↗
PubMed2001

Association of vancomycin and calcium phosphate by dynamic compaction: in vitro characterization and microbiological activity.

Dynamic compaction has rarely been used to produce drug-delivery devices in granule form. This report considered four processes associating vancomycin and compared dynamic compaction with wet granulation, a classical method. In the wet granulation study, vancomycin was associated with biphasic calcium-phosphate (BCP) granules either by adsorption or incorporation with a new granulation. In the dynamic compaction study, BCP powder was compacted at 1.1, 1.5 and 1.9 MPa. The compacts obtained were crushed and sieved (200-500 microm), and the vancomycin solution was adsorbed on the resulting granules. After crushing and sieving, the compaction of BCP and vancomycin powders produced vancomycin-loaded granules. In each study, 4.76% of vancomycin was associated with BCP. Granules were characterized in terms of porosity, vancomycin release and vancomycin biological activity. Physicochemical studies of BCP and vancomycin showed their structural integrity after dynamic compaction, which prolonged vancomycin release time from 1 to 6 days. However, a microbiological assay indicated that vancomycin had been altered since only 27.7% was found to be active.

Anti-Bacterial Agents↗
PubMed2001

A new injectable bone substitute combining poly(epsilon-caprolactone) microparticles with biphasic calcium phosphate granules.

Previous studies have shown the effectiveness of an injectable bone substitute (IBS) composed of biphasic calcium phosphate in 2% hydroxypropyl methylcellulose gel (50/50 w/w). A therapeutic agent in the form of a drug can be added to the biomaterial by encapsulation into microparticles to protect the active agent, control its release and preserve the material rheological properties. Poly(epsilon-caprolactone) was used in this study because of its biocompatibility and resorbability, as tested in orthopaedic implants and surgical sutures. Particles (80-200 microm) were manufactured by a solvent evaporation-extraction process (1 g of polymer, 11-15 ml methylene chloride, with a stirring speed of 400-600 rpm) and introduced into the IBS in a 5-50% (V/V) range. Injectability was evaluated by texture analysis. With less than 45% of particles, the material had rheological properties similar to those of the reference IBS, whereas injectability decreased markedly with more than 45% of particles. A preliminary in vitro release study showed that this type of triphasic IBS could be efficient for drug delivery systems with osteoconduction properties.

Anti-Bacterial Agents↗
PubMed2001

Bleeding reflux esophagitis: a prospective 1-year study in a university hospital.

OBJECTIVES: The prevalence of bleeding from reflux esophagitis has not been studied. The aim of the study was to evaluate the 1-yr prevalence of bleeding from reflux esophagitis, as well as the independent factors associated with bleeding. METHODS: All patients with reflux esophagitis diagnosed with upper digestive tract endoscopy in Reims Hospital in 1996 were included. Studied parameters were prospectively recorded and compared between patients with bleeding and nonbleeding reflux esophagitis. RESULTS: Endoscopy was performed in 1983 patients of whom 219 (11.0%) had overt upper digestive tract hemorrhage. Reflux esophagitis was the cause of bleeding in 32 patients (14.6%). Reflux esophagitis was diagnosed in 391 patients during the same period of time. Bleeding reflux esophagitis accounted for 8.2% of them. Independent factors associated with bleeding were grade 3 or 4 (Savary-Miller) esophagitis (odds ratio [OR]: 25.5, 95% confidence interval [CI]: 9.6-67.9), cirrhosis (OR: 5.7, 95% CI: 1.7-18.9), Eastern Cooperative Oncology Group performance status > or = 3 (OR: 4.6, 95% CI: 1.5-14.2), and anticoagulant therapy (OR: 3.9, 95% CI: 1.2-12.5). A history of reflux esophagitis or heartburn was noted in only 28.1% or 37.5% of the patients with bleeding reflux esophagitis, respectively. CONCLUSIONS: In this population of patients with reflux esophagitis, the prevalence of bleeding esophagitis was high (8.2%). Bleeding esophagitis occurred primarily in patients with severe esophagitis and was the revealing clinical form of gastroesophageal reflux disease in the majority of cases, suggesting that bleeding prevention would hardly be effective.

Adult↗
PubMed2000

Influence of isostatic compression on the stability of vancomycin loaded with a calcium phosphate-implantable drug delivery device.

It is essential to prevent microbial infections after osteoarticular trauma or prosthesis implantation. As an alternative to antibiotic parenteral administration, antibiotic-loaded biomaterials allow high concentrations to be obtained in situ without systemic toxicity. Although the formulation of biphasic calcium-phosphate (BCP)-vancomycin granules by isostatic compression has recently been used to produce drug-delivery devices, the stability of vancomycin needs to be proven. In this study, vancomycin was associated with BCP powders by isostatic compression at 100, 140, or 200 MPa and then extracted or released by a rotating paddle system for 24 h. Vancomycin assays were performed by spectrophotometric and microbiological methods. The results show that all vancomycin associated with the material was recovered after extraction without degradation. Thus, vancomycin was not denaturated after application of 100, 140, or 200 MPa of isostatic compression. The results for vancomycin released from granules compressed at the three pressures were not significantly different (p =.01) whether assays were performed microbiologically or spectrophotometrically, indicating a good correlation between the two methods. This process involving high pressure appears to be a good means of developing drug delivery devices loaded with therapeutic agents without denaturating the components.

Anti-Bacterial Agents↗
PubMed2000

Isostatic compression, a new process for incorporating vancomycin into biphasic calcium phosphate: comparison with a classical method.

Isostatic compression has rarely been used to load calcium-phosphate biomaterials with therapeutic agents. This report, concerning four processes associating vancomycin, compares isostatic compression with wet granulation, a classical method. In the wet granulation study, vancomycin was associated with biphasic calcium-phosphate (BCP) granules either by adsorption or incorporation with a new granulation. In the isostatic compression study, BCP powder was compressed at 100, 140 and 200 MPa. The blocks obtained were crushed and 200-500 microm, sieved; thus, the vancomycin solution was absorbed on these granules. Compaction of BCP and vancomycin powders gave, after crushing and sieving, granules loaded with vancomycin. In each study, 5% vancomycin was associated with BCP. Vancomycin release profiles were assessed by an in vitro culture chamber dissolution test. Physicochemical studies of BCP and vancomycin showed their structural integrity after isostatic compression. Isostatic compression prolonged vancomycin release time from 3 to 7 days and the release time became greater as isostatic pressure increased, probably because of the porosity decrease of the granules during compression.

Calcium Phosphates↗
PubMed2000

[First confirmed case of laryngeal diphtheria in Djibouti].

The first bacteriologically confirmed case of laryngeal diphtheria in Djibouti was reported in 1998. It involved a three-year-old native-born infant who had been vaccinated during the first year of life with three doses of a combined vaccine against diphtheria, tetanus, poliomyelitis, and pertussis. A rapid clinical improvement was observed under erythromycin treatment. Other cases of laryngeal diphtheria have been observed. It is important to reverse decreasing vaccinal coverage in Djibouti and to warn incoming travelers of the need to be adequate immunized against diphtheria. Enhanced epidemiologic surveillance of this disease is also needed.

Child, Preschool↗
PubMed1999

Development of a "continuous-flow adhesion cell" for the assessment of hydrogel adhesion.

The purpose of this study was to develop an in vitro perfusion technique or "continuous-flow adhesion cell" model to predict the in vivo performances of different mucoadhesive drug delivery systems based on hydrogels. Two studies were performed, either using a rabbit small intestine or a polyethylene surface; the adhesion of four gels--two poly(acrylic acid)s (PAAs) (carbomer [CM] and polycarbophil [PC]), an ethyleneoxide-propyleneoxide block copolymer (Poloxamer 407 [PM]), and a polysaccharide (scleroglucane [SG])--were evaluated. In this respect, scleroglucane was used as a control. The adhesiveness of the different gels for both supports is in accordance with that described in the literature, that is, polycarbophil adhered more strongly than carbomer, which itself adhered more strongly than poloxamer. This study proved that the gels adhere more strongly to the polyethylene tube than to the rabbit small intestine, thus indicating that evidence for adhesion properties does not need any presence of mucus. Therefore, our in vitro model could be a good method, more precise and more simple than an ex vivo technique, to predict the bioadhesion of gelified devices.

Adhesiveness↗
PubMed1999

[Discovery of a focus of intestinal bilharziasis in te Republic of Djibouti].

An unprecedented pocket of intestinal schistosomiasis was discovered in the Republic of Djibouti in 1997. The first cases were diagnosed in French and Djiboutian tourists who presented initial symptoms of bilharzian infection after bathing in the fresh-water basin under Hassan Gari Bira Falls, near Randa. Seventeen cases were subsequently confirmed by detection of anti-schistosome antibodies using indirect hemagglutination (IH) and indirect immunofluorescence (IIF) and/or detection of Schistosoma mansoni eggs in the stool. Further testing was performed in 35 village inhabitants, mostly children, who had been exposed by bathing in the basin. The IH reaction was positive in 28 patients (80 p. 100) including 17 (49 p. 100) with levels greater than 1/64. In 92 p. 100 of cases, IH findings were confirmed by IIF which indicated that association with hypereosinophilia was common. Schistosoma mansoni eggs were found in stools from 7 patients (19 p. 100) who generally displayed mild hypereosinophilia. Information concerning the zone of risk was distributed and control measures were undertaken as widely as possible in Djibouti and abroad.

Adolescent↗
PubMed1998

In vitro influence of apatite-granule-specific area on human growth hormone loading and release.

Although calcium phosphate biomaterials often are used as drug delivery systems (DDS) at bone sites, the conditions affecting the loading of the therapeutic agent (TA) have not been well documented. A human growth hormone (hGH) adsorption method was used in this study to investigate the influence of the formulated apatite (AP)-specific area on loading and release. AP powders were formulated with a 200-500 microm granulometry and various specific areas. Two milligrams of hGH in solution were deposited for 24 h at 37 degrees C on 100 mg of AP with different specific areas. The amount of hGH loaded was determined by immunoradiometric assay (IRMA) and eluted stain bioassay (ESTA) using Nb2 lymphoma rat cells. Although loading was not greatly influenced by a specific area between 3 and 25 m2/g, dependency was noted for higher specific areas. Human GH release was measured by IRMA and ESTA over a 33-day period, with half-time release between 25 and 79 h. Comparison of IRMA and ESTA measurements for the hGH amounts loaded showed that hGH biologic activity was conserved. Results indicate that it is feasible to control the quantity of TA loading on AP by modifying specific areas for in vivo applications.

Animals↗
PubMed1998

Idiopathic hypersomnia.

Identification of idiopathic hypersomnia dates back 20 years only. It typically consists of prolonged nocturnal sleep, great difficulty waking up in the morning or at the end of a nap, and constant or recurrent excessive daytime sleepiness. Complete and incomplete forms are encountered. Twenty-three subjects fulfilling ICSD criteria are reported with clinical, polysomnographic and immunogenetic data. Considering differential diagnosis is an important step in the diagnosis of idiopathic hypersomnia. Idiopathic hypersomnia is much less frequent than narcolepsy. A strong genetic component is suggested by the high proportion of familial cases. No association with HLA has been evidenced to date.

Adolescent↗