Biomedical subjects

P Simonet

Publications and source records attributed to P Simonet.

At least 19 recordsLinked to original sources

PubMed2006

[Polylactic acid injections (Newfill) in the treatment of facial lipodystrophy in HIV-positive patients].

BACKGROUND: Lipodystrophy is a side-effect associated with treatment for human immunodeficiency virus (HIV) and is found chiefly on the face (disappearance of buccal fat pads) and is detrimental to self-esteem. PATIENTS AND METHODS: This was a retrospective study in HIV-positive patients with facial lipoatrophy treated between 1999 and 2004 by means of subcutaneous injections of polylactic acid (Newfill). We assessed the efficacy of treatment, the number of injections given, treatment methods and adverse effects. RESULTS: Eighty-three patients were treated between 1999 and 2004. Each patient received a mean of between 3 and 4 treatment sessions comprising subdermal injection of 1 ampoule of Newfill into each cheek. Ultrasound assessment of the dermis over the cheekbone was performed in 45 patients and showed an increase in dermal thickness of between 3 and 7 mm. Following injection, edema was observed in all cases and lasted between 1 and 2 days. Five patients presented bruising at the injection sites. Two patients presented asymmetry lasting 4 months and requiring correction. Four patients had non-inflammatory granulomas, which were not visible but were palpable in 2 cases; all nodules regressed after 4 months. DISCUSSION: Treatment of facial lipoatrophy in HIV patients by injection of polylactic acid (Newfill) was shown to be efficacious in the majority of subjects. Training in the administration of this treatment is needed to ensure optimal efficacy and safety. A number of technical difficulties led to changes in treatment methods, i.e. routine adoption of a mask and protective glasses and use of a Luer-lock syringe due to blockage of syringes in more than 20% of cases, with splashing; increase in dilution volume from 3 to 5 ml; use of a centrifuge to ensure greater homogeneity of the solution; use of lidocaine in place of water for injections in order to reduce pain for patients.

Adult↗

PubMed2002

Opportunistic colonization of Ralstonia solanacearum-infected plants by Acinetobacter sp. and its natural competence development.

The behavior of the soil bacterium Acinetobacter sp. BD413 was monitored in Ralstonia solanacearum-infected and non-infected tomato plants after direct injection into the stem or natural infection by roots. In healthy plants, Acinetobacter sp. BD413 failed to colonize plant tissue. In plants infected simultaneously by the pathogen R. solanacearum,the Acinetobacter population increased linearly to about 3.1 x 10(7) cells per gram plant material and was maintained at a high level until the death of the plant. Moreover, Acinetobacter sp. BD413 was found to develop a competent state when multiplying in planta, indicating it could possibly be transformed by bacterial or plant DNA.

Acinetobacter↗

PubMed2001

Quantification of bacterial subgroups in soil: comparison of DNA extracted directly from soil or from cells previously released by density gradient centrifugation.

All molecular analyses of soil bacterial diversity are based on the extraction of a representative fraction of cellular DNA. Methods of DNA extraction for this purpose are divided into two categories: those in which cells are lysed within the soil (direct extraction) and those in which cells are first removed from soil (cell extraction) and then lysed. The purpose of this study was to compare a method of direct extraction with a method in which cells were first separated from the soil matrix by Nycodenz gradient centrifugation in order to evaluate the effect of these different approaches on the analysis of the spectrum of diversity in a microbial community. We used a method based on polymerase chain reaction (PCR) amplification of a 16S rRNA gene fragment, followed by hybridization of the amplified fragments to a set of specific probes to assess the phylogenetic diversity of our samples. Control parameters, such as the relationship between amount of DNA template and amount of PCR product and the influence of competing DNA on PCR amplification, were first examined. Comparison between extraction methods showed that less DNA was extracted when cells were first separated from the soil matrix (0.4 microg g(-1) dry weight soil versus 38-93 microg g(-1) obtained by in situ lysis methods). However, with the exception of the gamma-subclass of Proteobacteria, there was no significant difference in the spectrum of diversity resulting from the two extraction strategies.

Bacteria↗

PubMed2001

Resistance of plastic ophthalmic lenses: the effect of base curve on different materials during static load testing.

PURPOSE: This study was designated to evaluate, through a static load test, the influence of lens base curve on the fracture resistance of three common plastic materials. METHODS: A JJ Lloyd load cell machine was used to test the fracture resistance of -4.00 D spherical lenses. The samples had a nominal center thickness of 2.0 mm and a base curve distributed in one of five groups (+0.50, +2.50, +4.50, +6.50, and +8.50 D). The lenses were manufactured in CR39, polycarbonate, and TL16, a high refractive index plastic (n = 1.599). RESULTS: The lens base curve influenced fracture resistance for all materials. For these materials, resistance increased as the base curve varied from +0.50 to +8.50 D. The resistance of CR39, TL16, and polycarbonate lenses was found to be linearly dependent on lens base curve. The effect is stronger for polycarbonate. Fracture resistance was higher for TL16 than for CR39, and polycarbonate was much more resistant to breakage than the two other materials. CONCLUSIONS: For a given power, the fracture resistance of an ophthalmic lens is reduced when its base curve has a low value. Consequently, the flattening of ophthalmic lenses for cosmetic purposes is not recommended as far as fracture resistance is concerned.

Eyeglasses↗

PubMed2001

Evaluation of biological and physical protection against nuclease degradation of clay-bound plasmid DNA.

In order to determine the mechanisms involved in the persistence of extracellular DNA in soils and to monitor whether bacterial transformation could occur in such an environment, we developed artificial models composed of plasmid DNA adsorbed on clay particles. We determined that clay-bound DNA submitted to an increasing range of nuclease concentrations was physically protected. The protection mechanism was mainly related to the adsorption of the nuclease on the clay mineral. The biological potential of the resulting DNA was monitored by transforming the naturally competent proteobacterium Acinetobacter sp. strain BD413, allowing us to demonstrate that adsorbed DNA was only partially available for transformation. This part of the clay-bound DNA which was available for bacteria, was also accessible to nucleases, while the remaining fraction escaped both transformation and degradation. Finally, transformation efficiency was related to the perpetuation mechanism, with homologous recombination being less sensitive to nucleases than autonomous replication, which requires intact molecules.

Acinetobacter↗

PubMed2001

Natural transformation of Pseudomonas fluorescens and Agrobacterium tumefaciens in soil.

Little information is available concerning the occurrence of natural transformation of bacteria in soil, the frequency of such events, and the actual role of this process on bacterial evolution. This is because few bacteria are known to possess the genes required to develop competence and because the tested bacteria are unable to reach this physiological state in situ. In this study we found that two soil bacteria, Agrobacterium tumefaciens and Pseudomonas fluorescens, can undergo transformation in soil microcosms without any specific physical or chemical treatment. Moreover, P. fluorescens produced transformants in both sterile and nonsterile soil microcosms but failed to do so in the various in vitro conditions we tested. A. tumefaciens could be transformed in vitro and in sterile soil samples. These results indicate that the number of transformable bacteria could be higher than previously thought and that these bacteria could find the conditions necessary for uptake of extracellular DNA in soil.

Agrobacterium tumefaciens↗

PubMed2001

Laboratory-scale evidence for lightning-mediated gene transfer in soil.

Electrical fields and current can permeabilize bacterial membranes, allowing for the penetration of naked DNA. Given that the environment is subjected to regular thunderstorms and lightning discharges that induce enormous electrical perturbations, the possibility of natural electrotransformation of bacteria was investigated. We demonstrated with soil microcosm experiments that the transformation of added bacteria could be increased locally via lightning-mediated current injection. The incorporation of three genes coding for antibiotic resistance (plasmid pBR328) into the Escherichia coli strain DH10B recipient previously added to soil was observed only after the soil had been subjected to laboratory-scale lightning. Laboratory-scale lightning had an electrical field gradient (700 versus 600 kV m(-1)) and current density (2.5 versus 12.6 kA m(-2)) similar to those of full-scale lightning. Controls handled identically except for not being subjected to lightning produced no detectable antibiotic-resistant clones. In addition, simulated storm cloud electrical fields (in the absence of current) did not produce detectable clones (transformation detection limit, 10(-9)). Natural electrotransformation might be a mechanism involved in bacterial evolution.

Culture Media↗

PubMed2000

Potential dissemination of antibiotic resistance genes from transgenic plants to microorganisms.

Evidence that genes were transferred during evolution from plants to bacteria was obtained from nucleotide and protein sequence analyses. However, the extent of such transfers among phylogenetically distant organisms is limited by various factors, including those related to complexity of the environment and those endogenous to the bacteria, designed to prevent a drift of the genome integrity. The goal of this article is to give an overview of the potentials and limits of natural interkingdom gene transfers, with a particular focus on prokaryote originating sequences fitting the nuclear genome of transgenic plants.

Drug Resistance, Microbial↗

PubMed2000

Plant genome complexity may be a factor limiting in situ the transfer of transgenic plant genes to the phytopathogen Ralstonia solanacearum.

The development of natural competence by bacteria in situ is considered one of the main factors limiting transformation-mediated gene exchanges in the environment. Ralstonia solanacearum is a plant pathogen that is also a naturally transformable bacterium that can develop the competence state during infection of its host. We have attempted to determine whether this bacterium could become the recipient of plant genes. We initially demonstrated that plant DNA was released close to the infecting bacteria. We constructed and tested various combinations of transgenic plants and recipient bacteria to show that the effectiveness of such transfers was directly related to the ratio of the complexity of the plant genome to the number of copies of the transgene.

Betaproteobacteria↗

PubMed2000

Transverse chromatic aberration and colour-defined motion.

A number of recent studies have explored the role of the chromatic system in motion processes using the isoluminance paradigm. A major concern when using such methodological procedures is potential artefacts produced by chromatic aberrations. In the present study we address the problem of optically induced luminance artefacts produced by transverse chromatic aberrations (TCA), which may contaminate the results obtained in chromatic motion-nulling experiments. Results show that different TCA levels artificially increase chromatic motion sensitivity values to varying degrees above 0.5 cpd for red/green gratings. The data also suggest the notion that naturally occurring TCA can decrease motion-nulling thresholds for chromatic gratings at high spatial frequencies. Furthermore, our data show that the motion-nulling paradigm for chromatic gratings may in fact be an efficient functional method for assessing the amount of TCA produced by optical factors.

Adult↗

PubMed1999

Drug-resistance genotyping in HIV-1 therapy: the VIRADAPT randomised controlled trial.

BACKGROUND: Growing evidence has linked HIV-1 resistance mutations and drug failure. The use of genotypic-resistance analysis to assist therapeutic decision-making in patients failing therapy has not been investigated. We assessed the virological and immunological impact of genotypic-resistance testing. METHODS: We did a prospective, open, randomised, controlled study of HIV-1-infected patients in whom combination therapy was not successful. We randomly assigned patients standard care (control, n=43) or treatment according to the resistance mutations in protease and reverse-transcriptase genes (genotypic group, n=65). The major endpoint was the change in HIV-1 RNA viral load. Analysis was by intention to treat. FINDINGS: 108 patients were enrolled. All patients were similar for risk factors, age, sex, previous treatment, CD4-cell count (214/microL [SD14]) and log HIV-1 RNA viral load at baseline (4.7 copies/mL [0.1]). At month 3, the mean change in HIV-1 RNA was -1.04 log (0.14) in the study group compared with -0.46 log (0.17) in the control group (mean difference 0.58 log [95% CI 0.14-1.02], p=0.01). At month 6, changes were -1.15 (0.15) log copies/mL, and -0.67 (0.19) log copies/mL in the genotypic group and the control group, respectively (mean difference 0.48 log [0.01-0.97], p=0.05). Difference in the drop in viral load combined at 3 months and 6 months was significant (p=0.015). At month 3, HIV-1 RNA was lower than detection level (200 copies/mL) in 29% (19/65) of patients in the genotypic group versus 14% (6/43) in the control group (p=0.017). At month 6, the values were 32% (21/65) and 14% (6/43) (p=0.067) for the genotypic group and the control group, respectively. Therapy was generally well tolerated, with ten patients (six in the genotypic group, four in the control group) requiring toxic-effect-related drug modification. INTERPRETATION: We found genotypic-resistance testing to have a significant benefit on the virological response when choosing a therapeutic alternative. Further study of the use of genotypic-resistance testing in assisting clinical decision-making is warranted.

Acquired Immunodeficiency Syndrome↗

PubMed1999

Distribution of gymnostoma spp. microsymbiotic frankia strains in new caledonia is related to soil type and to host-plant species

The diversity of the Frankia strains that are naturally in symbiosis with plants belonging to the Gymnostoma genus in New Caledonia was investigated. A direct molecular characterization of DNA extracted from nodules was performed, followed by characterization by restriction fragment length polymorphism (RFLP) of the ribosomal rrs-rrl (16S-23S) intergenic spacer (IGS) polymerase chain reaction (PCR)-amplified region. Seventeen different patterns were identified among the 358 microsymbiotic strains studied in the eight species of host plant present in New Caledonia. This genotypical approach permitted us to show that a large diversity existed among the patterns and that these did not exhibit a strict specificity to any host-plant species comparable with that previously found in the Casuarina and Allocasuarina symbioses in Australia. Despite this lack of specificity, a correspondence analysis nevertheless showed that the distribution of these patterns was related to soil type and to host-plant species. Furthermore, several Frankia strains were exclusively associated with the ultramafic soils.

Journal Article↗

PubMed1999

Co-evolution between Frankia populations and host plants in the family Casuarinaceae and consequent patterns of global dispersal.

Symbioses between the root nodule-forming, nitrogen-fixing actinomycete Frankia and its angiospermous host plants are important in the nitrogen economies of numerous terrestrial ecosystems. Molecular characterization of Frankia strains using polymerase chain reaction/restriction fragment length polymorphism (PCR/RFLP) analyses of the 16S rRNA-ITS gene and of the nifD-nifK spacer was conducted directly on root nodules collected worldwide from Casuarina and Allocasuarina trees. In their native habitats in Australia, host species contained seven distinctive sets of Frankia in seven different molecular phylogenetic groups. Where Casuarina and Allocasuarina trees are newly planted outside Australia, they do not normally nodulate unless Frankia is introduced with the host seedling. Nodules from Casuarina trees introduced outside Australia over the last two centuries were found to contain Frankia from only one of the seven phylogenetic groups associated with the host genus Casuarina in Australia. The phylogenetic group of Frankia found in Casuarina and Allocasuarina trees introduced outside Australia is the only group that has yielded isolates in pure culture, suggesting a greater ability to survive independently of a host. Furthermore, the Frankia species in this group are able to nodulate a wider range of host species than those in the other six groups. In baiting studies, Casuarina spp. are compatible with more Frankia microsymbiont groups than Allocasuarina host spp. adapted to drier soil conditions, and C. equisetifolia has broader microsymbiont compatibility than other Casuarina spp. Some Frankia associated with the nodular rhizosphere and rhizoplan, but not with the nodular tissue, of Australian hosts were able to nodulate cosmopolitan Myrica plants that have broad microsymbiont compatibility and, hence, are a potential host of Casuarinaceae-infective Frankia outside the hosts' native range. The results are consistent with the idea that Frankia symbiotic promiscuity and ease of isolation on organic substrates, suggesting saprophytic potential, are associated with increased microsymbiont ability to disperse and adapt to diverse new environments, and that both genetics and environment determine a host's nodular microsymbiont.

Actinomycetales↗

PubMed1999

Effects of induced transverse chromatic aberration from an afocal prismatic lens on spatio-temporal sensitivity.

The goal of this study was to evaluate the effect of ophthalmic lens-induced transverse chromatic aberrations (TCA) in natural viewing conditions on spatio-temporal thresholds. Three psychophysical experiments were performed; the first isolating the spatial component, the second isolating the temporal component and the third assessing spatio-temporal combinations. Taken together, the results show that TCA has profound effects on medium to high spatial frequencies (above 1 cpd) consistent with previous studies, and that the ratio of deficit TCA/blur can be higher than 2:1 for equivalent dioptric strengths. Furthermore, the results of Experiment 1 and 3 taken together show that the relative sensitivity loss caused by TCA can differ significantly between individuals and that a possible factor for this differential loss is the overall baseline spatio-temporal sensitivity profile of the individual.

Adult↗

PubMed1999

Rhodanobacter lindaniclasticus gen. nov., sp. nov., a lindane-degrading bacterium.

Lindane-degrading activity under aerobic conditions has been observed in two bacterial strains: UT26, phenotypically identified as Sphingomonas paucimobilis, and a new single unidentified isolate named RP5557T. The rrs (16S rDNA) sequences for both strains and the phenotypic characteristics for the unidentified isolate RP5557T were determined. RP5557T does not have high identity (less than 90% in all cases) with any sequence in the GenBank or RDP databases. A phylogenetic analysis based on rrs sequences indicated that RP5557T belongs to the gamma-Proteobacteria in a coherent phylum that includes the genera Xanthomonas and Xylella (100% bootstrap), whereas UT26 is clearly separate from the Xanthomonas cluster. Based on the phylogenetic analyses and on the phenotypic characteristics, a new genus, Rhodanobacter, containing a single species, Rhodanobacter lindaniclasticus, is proposed for strain RP5557T (= LMG 18385T), which becomes the type strain.

Bacteria, Aerobic↗

PubMed1999

Quantification of bias related to the extraction of DNA directly from soils.

In recent years, several protocols based on the extraction of nucleic acids directly from the soil matrix after lysis treatment have been developed for the detection of microorganisms in soil. Extraction efficiency has often been evaluated based on the recovery of a specific gene sequence from an organism inoculated into the soil. The aim of the present investigation was to improve the extraction, purification, and quantification of DNA derived from as large a portion of the soil microbial community as possible, with special emphasis placed on obtaining DNA from gram-positive bacteria, which form structures that are difficult to disrupt. Furthermore, we wanted to identify and minimize the biases related to each step in the procedure. Six soils, covering a range of pHs, clay contents, and organic matter contents, were studied. Lysis was carried out by soil grinding, sonication, thermal shocks, and chemical treatments. DNA was extracted from the indigenous microflora as well as from inoculated bacterial cells, spores, and hyphae, and the quality and quantity of the DNA were determined by gel electrophoresis and dot blot hybridization. Lysis efficiency was also estimated by microscopy and viable cell counts. Grinding increased the extracellular DNA yield compared with the yield obtained without any lysis treatment, but none of the subsequent treatments clearly increased the DNA yield. Phage lambda DNA was inoculated into the soils to mimic the fate of extracellular DNA. No more than 6% of this DNA could be recovered from the different soils. The clay content strongly influenced the recovery of DNA. The adsorption of DNA to clay particles decreased when the soil was pretreated with RNA in order to saturate the adsorption sites. We also investigated different purification techniques and optimized the PCR methods in order to develop a protocol based on hybridization of the PCR products and quantification by phosphorimaging.

Actinomycetales↗

PubMed1998

A review of available systems to investigate transfer of DNA to indigenous soil bacteria.

The deliberate or accidental release of genetically engineered microorganisms (GEMs) in the environment has led to some questions concerning microbial survival, transfer of DNA to the indigenous microflora and environmental consequences. Amongst horizontal gene transfer mechanisms, conjugation is probably the most frequent in the environment. With the aim of evaluating risks associated with environmental release of GEMs and their engineered DNA, studies of conjugative gene transfer between a donor strain and indigenous microflora have been conducted. Such studies required the development of a donor counterselection system to prevent growth of donor cells on transconjugant selective plates. This review summarizes the known and potential donor counterselection systems.

Bacteria↗

PubMed1997

Optical performance of aspheric concave ophthalmic lenses: the effect of vertex distance.

Variations of power errors in the periphery of concave aspheric lenses were assessed as a function of vertex distance. Comparisons were made between the performance of different types of spherical lenses and that of aspheric lenses (-6.00 and -8.00 D lenses were used). Off-axis measurements were made by means of a modified focimeter, which enabled rotation of the lens around the center of the vertex sphere. Reduction of the vertex sphere's radius from 27 to 23 mm simulated a 4-mm decrease in vertex distance. Results of the measurements are compared with a computed model. These results indicate that off-axis performance is more affected by a reduction of vertex distance in the case of aspheric lenses compared to spherical lenses. Resulting increases in oblique astigmatism (OA) and mean oblique error (MOE) are at the limit of clinical acceptance. The importance, for the practitioner, of respecting the vertex distance selected for a specific aspheric design when fitting this type of lens is emphasized.

Computer Graphics↗