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Biomedical subjects

R Legros

Publications and source records attributed to R Legros.

At least 19 recordsLinked to original sources
PubMed2006

A high-rate perfusion bioreactor for plant cells.

A perfusion bioreactor allowing continuous extraction of secondary metabolites was designed and challenged for Eschscholtzia californica plant cell suspensions. Four sedimentation columns mounted inside a 2.5-L bioreactor separated single cells and cell aggregates from the culture medium. Cells were elicited with chitin at day 4 and the liquid medium free of cells and debris was then continuously pumped to the extraction columns containing fluidized XAD-7 resins, and then recirculated back to the cell suspension. A medium upward velocity corresponding to cell sedimentation velocity maintained a stable cell/medium separation front in the columns for sedimented cell volume (SCV) of 90% (70% packed cell volume, PCV). Two perfusion bioreactor cultures of 10 and 14 days were performed. A maximum dilution rate of 20.4/day was reached from day 4 to day 6, and was then reduced to 5/day at day 9 for 55% SCV. Control cultures were performed without and with free extraction resins into the cell suspension. Perfusion cultures showed similar specific growth rates of 0.24 +/- 0.04/day before and after elicitation. However, production level in the perfusion cultures was similar to that from the culture without resins with a maximum of 2.06 micromole/gDW total alkaloids, with 1.54 micromole/gDW in the resins. Cultures with free resins resulted in 30.94 micromole/gDW with 28.4 +/- 8.8 micromole/gDW in the resins. Difference in the cells nutritional state from elicitation was identified as a major cause in the production reduction. However, pathway to chelilutine was favored in the continuous extraction culture.

Adsorption↗
PubMed2006

Optimization and scale-up of a fluid bed tangential spray rotogranulation process.

The production of pellets in the pharmaceutical industry generally involves multi-step processing: (1) mixing, (2) wet granulation, (3) spheronization and (4) drying. While extrusion-spheronization processes have been popular because of their simplicity, fluid-bed rotogranulation (FBRG) is now being considered as an alternative, since it offers the advantages of combining the different steps into one processing unit, thus reducing processing time and material handling. This work aimed at the development of a FBRG process for the production of pellets in a 4.5-l Glatt GCPG1 tangential spray rotoprocessor and its optimization using factorial design. The factors considered were: (1) rotor disc velocity, (2) gap air pressure, (3) air flow rate, (4) binder spray rate and (5) atomization pressure. The pellets were characterized for their physical properties by measuring size distribution, roundness and flow properties. The results indicated that: pellet mean particle size is negatively affected by air flow rate and rotor plate speed, while binder spray rate has a positive effect on size; pellet flow properties are enhanced by operating with increased air flow rate and worsened with increased binder spray rate. Multiple regression analysis enabled the identification of an optimal operating window for production of acceptable pellets. Scale-up of these operating conditions was tested in a 30-l Glatt GPCG15 FBRG.

Acetaminophen↗
PubMed2005

In situ extraction strategy affects benzophenanthridine alkaloid production fluxes in suspension cultures of Eschscholtzia californica.

The effect of contact between cells and extractive phase on secondary metabolite production was investigated in two-phase suspension cultures of Eschscholtzia californica. A system was designed to extract benzophenanthridine alkaloids from the cell culture, without contact between XAD-7 resins and the cells: only medium was recirculated through a column packed with the extractive phase. This strategy was compared to the classic method of addition of resins directly into the cell suspension. Removal of the product directly from the medium enabled important increases in production of alkaloids, namely a 20-fold increase in sanguinarine production and a 10-fold increase in chelerythrine, with high recovery in the resin. The recirculation strategy greatly simplified the production process since the resins are easily recovered from the cell culture and enable harvest of product without termination of culture. However, due to limited flow rate, the recirculation strategy was slightly less effective than direct addition of resins into the cell suspension. In addition to enabling increased production, removal of secondary metabolites from the medium changed metabolic flux distribution, testifying to a complex control mechanism of production.

Acrylic Resins↗
PubMed2001

Enhancing pyrene mineralization in contaminated soil by the addition of humic acids or composted contaminated soil.

The addition of composted PAH-contaminated soil to PAH-contaminated soil spiked with 14C-labeled pyrene resulted in rapid mineralization of pyrene (more than 57% after 21 days compared with 3.4% in un-amended soil). The addition of the humic acid fraction of the composted soil also increased the mineralization potential of the soil significantly, but to a lesser extent (37.5% mineralization after 106 days compared with 20.6% in unamended soil). Increasing the humic acid concentration increased mineralization up to a maximum of more than three times the unamended rate, after which the rate of pyrene mineralization decreased, possibly due to inhibitory pH or concentrations of salts. The amendment of PAH-contaminated soil with materials containing humic acids or humic acid extracts is suggested as a method of bioremediation.

Bacteria↗
PubMed1999

The design and use of aerated microcosms in mineralization studies.

The need for aeration of microcosms during mineralization of 14C-labeled compounds in high oxygen demand environments was assessed using active compost-soil mixtures as the model system. Rapid mineralization of 14C-hexadecane occurred in continuously aerated microcosms while no mineralization occurred in unaerated microcosms. Daily flushing with air also yielded no mineralization. Mineralization of 14C-glucose was much less dependent on aeration. The alkaline solution volume and number of CO2 traps required for continuous aeration were calculated and tested experimentally.

Aerobiosis↗
PubMed1998

[Magnetic resonance imaging of tibial periostitis].

Tibial periostitis frequently occurs in athletes. We present our experience with MRI in a series of 7 patients (11 legs) with this condition. The clinical presentation and scintigraphic scanning suggested the diagnosis. MRI exploration of 11 legs demonstrated a high band-like juxta-osseous signal enhancement of SE and IR T2 weighted sequences in 6 cases, a signal enhancement after i.v. contrast administration in 4. Tibial periostitis is a clinical diagnosis and MRI and scintigraphic findings can be used to assure the differential diagnosis in difficult cases with stress fracture. MRI can visualize juxta-osseous edematous and inflammatory reactions and an increased signal would appear to be characteristic when the band-like image is fixed to the periosteum.

Adult↗
PubMed1996

[Unilateral adrenal hematoma in adults. Contribution of MRI in follow-up].

We describe a case of unilateral and spontaneous adrenal hematoma. Initial and follow up MRI examinations showed serial modifications typical of hematoma and allowed to exclude a preexisting non hyperfunctioning tumor. MRI findings modified the therapeutic attitude, a voiding surgery.

Adrenal Gland Diseases↗
PubMed1995

[Parathyroid adenoma as an ectopic carotid mass. Apropos of a case].

Authors report a case of parathyroid adenoma as lateral palpable cervical mass, with serious hypercalcemia. MRI and ultrasound investigations were performed preoperatively. No other pathological parathyroid gland was found. Surgical treatment did not include the exploration of the four parathyroid glands. Long term follow-up is necessary.

Adenoma↗
PubMed1991

[Pneumatosis cystoides intestinalis. Apropos of a case].

Pneumatosis cystoides intestinalis is most frequently characterised by the presence of gaseous cysts, in the intra-parietal, subserous or sub-mucous zones of the colon. This complaint, with symptoms of non specific colic and the cause of chronic pain, generally progresses favourably but can be responsible for surgical complications. Characteristic signs are detected on an plain abdominal X-ray and by colonoscopy. The diagnosis can be established by CT or by ultrasonography but needs carefully trained operators. CT remains the most successful technique for the initial diagnosis and subsequent follow-up. Ultrasonography can also be used for follow-up. As the lesions regress rapidly, the diagnosis must established rapidly, otherwise the disorder might easily be incorrectly diagnosed.

Female↗
PubMed1990

Inflammatory reactions induced by various calcium pyrophosphate crystals.

Various inflammatory reactions can be induced by different crystals responsible for various arthropathies. The aim of this work was to study modifications induced in the rat, locally and at distance, by intrapleural injection of 3 forms of pyrophosphate crystals (CaPP dihydrated monoclinic (M), CaPP dihydrated triclinic (T) and CaPP anhydrous (beta]. The data presented here show that the structure of irritants plays a decisive role in the kinetics of inflammatory reactions from a local and systemic point of view.

Acute-Phase Reaction↗
PubMed1987

Age-related changes in mineral of rat and bovine cortical bone.

The mineral of cortical bones has been studied in newborn, growing, and adult rats and in the calf and cow, using X-ray diffraction and infrared spectroscopy during the thermal decomposition of bones and by microassay of carbonate. The mineral of all the bone samples, regardless of species or age, was found to be a calcium-deficient apatite containing both CO3(2-) and HPCO4(2-) ions in the crystal lattice. The crystal size, Ca/P molar ratio, and CO3(2-) ion content of cortical bone all increased with increasing age in both the rat and the bovine. The Ca/P ratio varied from 1.51 in newborn rats to 1.69 in adults but remained that of Ca-deficient apatite even though its value was close to that of stoichiometric hydroxyapatite (1.67). Both the carbonate ion and the hydrogenophosphate ion contents varied from one animal species to another and with age within a given species. Maturation was correlated with an increase in carbonate ion content, which replaced the HPO4(2-) ions. In contrast, the calcium ion number per unit formula did not vary during maturation. Cortical bone mineral, in both species, regardless of age, can therefore be represented by the following formula: Ca8.3 (PO4)4.3 (CO3)x(HPO4)y(OH)0.3; y decreased and x increased with increasing age, (x + y) being constant, equal to 1.7.

Age Determination by Skeleton↗
PubMed1986

Crystallographic identification of a calcium deposit in calcified pericarditis associated with articular chondrocalcinosis.

In a case of CPPD crystal deposition disease of the pseudorheumatoid type and of long duration, calcified constrictive pericarditis developed and was surgically treated. Analysis of the calcium deposit in the pericardium was carefully made by infrared absorption, x-ray diffraction, and thermogravimetry. It revealed that the deposit was composed of B-type carbonated apatite. Previously, both calcium pyrophosphate dihydrate (CPPD) and apatite crystals, either in the same place or in different tissues, have been reported in the same patient. These observations raise the possibility that the same metabolic error might lead to both types of crystal deposition.

Apatites↗
PubMed1986

[Physicochemical analysis of subcutaneous calcifications in a case of Thibierge-Weissenbach syndrome].

A physicochemical study of subcutaneous calcium deposits was performed in a patient with typical Thibierge-Weissenbach syndrome which had begun, ten years previously, with Raynaud's phenomenon and sclerodactylia. Calcium deposits had progressively developed, forming large plates on the arms, flanks and thighs. In the course of the disease they had become ulcerated, exuding a white, chalky material. X-ray films and xerograms demonstrated the extent of these deposits. The calcium-phosphorus balance was normal, and the other clinical and laboratory examinations were concordant with a diagnosis of Thibierge-Weissenbach syndrome (calcinosis). Only systemic corticosteroid therapy slowed down the pathological process; calcium chelating agents (diphosphonate) proved ineffective. The physicochemical study showed that the deposits consisted of carbonated apatite type B with the following formula: Ca8.0(PO4)4.1(CO3)1.2(HPO4)0.8 The mineral substance seemed to be less reactive and more stable than normal bone. This would account for the total lack of effectiveness of all treatments, notably calcium chelating agents, on the course of the deposits. Treatments usually produce bone demineralization before they influence the calcium deposits. This study provides much more detailed information than was hitherto available on calcium deposits and on carbonate ion contents in the apatite phase. The presence of carbonates increases the solubility and reactivity of calcium apatite.

Calcinosis↗
PubMed1982

X-ray diffraction of calcined bone tissue: a reliable method for the determination of bone Ca/P molar ratio.

A method is proposed which allows direct measurement by X-ray diffraction of the Ca/P molar ratio in bone tissue after calcination at 900 degrees C. It is based on the construction of a standard curve from known mixtures of hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TP), since these are the only two crystallized mineral phases in the bone ash after its calcination at 900 degrees C. This method, based on physical analysis, may also be used to calculate the respective proportions of calcium and phosphorus after the Ca/P molar ratio has been obtained. It is more sensitive than and at least as accurate as the usual chemical techniques, even though it can be applied to minute samples of bone tissue. Furthermore, the method permits simultaneous determination of lattice parameters and provides additional information about bone mineral structure.

Animals↗
PubMed1982

[Thermal stability of carbonates in bone tissue].

The analysis shows that carbonate ions present in the mineral phases of calcified tissues are decomposed in two steps during their ignition. These carbonate ions might be all localised in the phosphate sites of the apatitic structure (B type carbonate apatite). The loss of one important part of carbonate ions at a abnormally low temperature (250 degrees C) might result from an intracristalline reaction between these ions and HPO4(2-) or P2O7(4-) ions present in the apatitic structure.

Animals↗