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Biomedical subjects

L Dupuy

Publications and source records attributed to L Dupuy.

9 recordsLinked to original sources
PubMed2005

A density-based approach for the modelling of root architecture: application to Maritime pine (Pinus pinaster Ait.) root systems.

Root morphology influences strongly plant/soil interactions. However, the complexity of root architecture is a major barrier when analysing many phenomena, e.g. anchorage, water or nutrient uptake. Therefore, we have developed a new approach for the representation and modelling of root architecture based on branching density. A general root branching density in a space of finite dimension was used and enabled us to consider various morphological properties. A root system model was then constructed which minimizes the difference between measured and simulated root systems, expressed with functions which map root density in the soil. The model was tested in 2D using data from Maritime pine Pinus pinaster Ait. structural roots as input. We showed that simulated and real root systems had similar root distributions in terms of radial distance, depth, branching angle and branching order. These results indicate that general density functions are not only a powerful basis for constructing models of architecture, but can also be used to represent such structures when considering root/soil interaction. These models are particularly useful in that they provide a local morphological characterization which is aggregated in a given unit of soil volume.

Models, Biological↗
PubMed2004

Reproducibility of the respiratory dead space measurements in mechanically ventilated children using the CO2SMO monitor.

OBJECTIVES: To assess the reproducibility of respiratory dead space measurements in ventilated children. DESIGN: Prospective study. SETTING: University pediatric intensive care unit. PATIENTS: Thirty-two mechanically ventilated children (0.13-15.4 years) who were clinically stable. METHODS: The single-breath CO(2) test (SBT-CO(2)) was recorded using the CO(2)SMO Plus from the mean of 30 ventilatory cycles during 1 h (at T0, T15, T30, T45, and T60). Airway dead space was determined automatically (Novametrix Medical Systems, USA), and manually by Bohr- Enghoff equations using data obtained by SBT-CO(2). At the end of the study period, arterial blood gas was sampled in order to calculate alveolar and physiologic dead space. Intrasubject reproducibility of measurements was evaluated by the intraclass correlation coefficient. Two-way analysis of variance was used to evaluate the relationships between time and measurements. The two methods for calculating airway dead space were compared by using two-tailed Student's t-test and Bland-Altman analysis. RESULTS: Airway dead space measurement had a good reproducibility during the 1-h period, whatever the method used (intraclass correlation coefficient: 0.84 to 0.87). No significant difference was observed with time. Airway dead space values from the SBT-CO(2) method were smaller than those from Bohr-Enghoff equations. Physiologic dead space values from the SBT-CO2 method were similar to those from Bohr-Enghoff equations. CONCLUSION: The measurement of airway dead space by the CO(2)SMO Plus was reproducible over a 1-h period in children requiring mechanical ventilation, provided ventilatory parameters were constant throughout the study. SBT-CO(2) analysis may provide a bedside non-invasive monitoring of volumetric capnography.

Adolescent↗
PubMed1998

Role of cellular actin in the gene expression and morphogenesis of human respiratory syncytial virus.

Cytoskeletal protein actin and nonactin cellular proteins were essential for human respiratory syncytial virus (RSV) gene expression. In vitro, specific antibodies against actin inhibited RSV transcription, whereas antibodies against other cytoskeletal proteins had little or no effect. Affinity purified cellular actin or bacterially expressed recombinant actin activated RSV transcription. However, optimal transcription required additional cellular protein(s) that appeared to function as accessory factor(s) for actin. In the absence of actin, these proteins did not activate viral transcription. Purified viral nucleocapsids contained actin, but no cytokeratin, tubulin, or vimentin. Cytochalasin D or DNasel--agents that destabilize actin polymers--had little effect on RSV transcription. RSV infection itself seemed to alter the structure of the cellular actin filaments. Treatment of infected cells with cytochalasin D produced a more severe disruption of the filaments and drastically reduced the production of infectious virus particles but still had little effect on intracellular synthesis of viral macromolecules. Thus actin seems to serve a dual role in RSV life cycle: its monomeric form as well as polymeric form activate viral transcription, while only the microfilament form may take part in viral morphogenesis and/or budding.

Actin Cytoskeleton↗
PubMed1983

Cefotetan: comparative study in vitro against 226 Gram-negative clinical isolates.

The activity in vitro of the new cephamycin, cefotetan, was compared with that of cephalothin, cefoxitin, cefuroxime and cefotaxime against 226 recently isolated Gram-negative pathogens (207 Enterobacteriaceae and 19 Acinetobacter). Cefotetan was consistently more potent than cephalothin, cefoxitin and cefuroxime. Cefotaxime and cefotetan were essentially similar in activity against the Enterobacteriaceae with the singular exception of Enterobacter spp. which were markedly more susceptible to the former drug. None of the five agents was especially active against acinetobacter but cefotaxime was the best. Limited tests of bactericidal activity showed that the MBC differed from the MIC by a factor of 4 at most. Increasing the inoculum tested from 10(2) to 10(8) per ml had little adverse effect on the MIC of cefotetan. If the recommendations of the National Committee for Clinical Laboratory Standards for susceptibility to cephalosporins are applicable to cefotetan and the breakpoint criteria of less than or equal to 10 mg/l (sensitive) and greater than or equal to 32 mg/l (resistant) are acceptable, then only a few of the Enterobacteriaceae in this study were resistant. These resistant organisms were amongst Enterobacter spp. and Citrobacter spp.

Anti-Bacterial Agents↗
PubMed1982

[Dibekacin: diffusion in bronchial mucus].

The study of the bronchial concentration of dibekacin has shown a different degree of activity than that of gentamicin. This activity resembles that of amikacin with a three hour time lag from the appearance of the bronchial peak in relationship to the serum peak. In addition there seems to be a special passage mechanism for the antibiotic from the blood into the bronchial secretions since we observed an increase in the mucus/serum ratio through time.

Adult↗