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Biomedical subjects

S Rousset

Publications and source records attributed to S Rousset.

At least 19 recordsLinked to original sources

Uniform magnetic properties for an ultrahigh-density lattice of noninteracting co nanostructures.

We report on the magnetic properties of two-dimensional Co nanoparticles arranged in macroscopically phase-coherent superlattices created by self-assembly on Au(788). Our particles have a density of 26 Tera/in2 (1 Tera=10(12)), are monodomain, and have uniaxial out-of-plane anisotropy. The distribution of the magnetic anisotropy energies has a half width at half maximum of 17%, a factor of 2 more narrow than the best results reported for superlattices of three-dimensional nanoparticles. Our data show the absence of magnetic interactions between the particles. Co/Au(788) thus constitutes an ideal model system to explore the ultimate density limit of magnetic recording.

Journal Article↗

Emotions generated by meat and other food products in women.

Eating behaviour depends partly on food preference, which is itself determined by different types of emotions. Among the emotions generated by food, disgust with red meat is common in women and can lead to reduced meat consumption. We tested the hypothesis that low meat intake is related to different negative emotions towards meat but does not affect the emotions expressed towards other food categories. Food intake of sixty women was followed throughout each day for 1 week and allowed us to assign women to two groups (low v. high meat-eating women). They were then invited to assess the intensity of twenty-six emotions described by words and induced by thirty food pictures. We determined the number of necessary dimensions to describe the space created by the twenty-six words. The results showed differences in emotions between the low and high meat-eating women. As expected, there were overall differences in the emotions generated by the thirty food pictures. Six clusters of emotions were necessary and sufficient to summarise the emotional space. These dimensions were described by 'disappointment', 'satisfaction', 'guilt', 'doubt', 'amused' and 'indifference'. As expected, the low meat-eating women felt more 'disappointment', 'indifference' and less 'satisfaction' towards meat than did the high meat-eating women. However, the low meat-eating women also stated other negative emotions such as 'doubt' towards some starchy foods. The only foods that they liked more than high meat-eating women were pears and French beans. In conclusion, low meat consumption was associated with specific negative emotions regarding meat and other foods.

Adolescent↗

Nutritional knowledge and concerns about meat of elderly French people in the aftermath of the crisis over BSE and foot-and-mouth.

The aim of this study was to compare elderly people with young adults in France for nutritional knowledge and concerns about meat in the aftermath of the rises with bovine spongiform encephalopathy and foot-and-mouth disease. Between March and April 2001, 99 healthy elderly people and 93 younger adults living in France were interviewed. Most of the elderly and young participants knew that meat contains proteins but were unaware of the role of proteins in body metabolism. The elderly knew that meat also contains iron and vitamins and is necessary for growth and for physical activity. However, elderly people had little awareness of the importance of consuming meat and were convinced that they had to reduce meat consumption because of their lower physical activity. On the other hand, they knew more than younger adults about animal diseases and were less worried about 'mad cow disease'. Thus, although the elderly people were confident about the safety of meat and recognised its nutritional properties, they did not consider it to be an essential food.

Adult↗

Protective role of uncoupling protein 2 in atherosclerosis.

BACKGROUND: Uncoupling protein 2 (UCP2) regulates the production of reactive oxygen species in macrophages. However, its role in atherosclerosis is unknown. METHODS AND RESULTS: Irradiated low-density lipoprotein receptor deficient mice (LDLR-/-) were transplanted with bone marrow from either UCP2 deficient mice (Ucp2-/-) or wild type mice (Ucp2+/+). Mice were fed an atherogenic diet for 7 weeks. Engraftment of bone marrow cells was confirmed by the presence of UCP2 protein expression in spleen cell mitochondria of Ucp2+/+ transplanted mice and its absence in Ucp2-/- transplanted mice. Leukocyte counts and plasma cholesterol levels were comparable in both groups. We found a marked increase in atherosclerotic lesion size in the thoracic aorta of Ucp2-/- transplanted mice compared with control Ucp2+/+ transplanted mice (8.3+/-0.9% versus 4.3+/-0.4%, respectively; P<0.005), as well as in the aortic sinus (150 066+/-12 388 microm2 versus 105 689+/-9 727 microm2, respectively; P<0.05). This was associated with increased nitrotyrosine staining, which suggests enhanced oxidative stress. Analysis of plaque composition revealed a significant increase in macrophage accumulation (P<0.05) and apoptosis (P<0.05), along with a decrease in collagen content (P<0.05), suggesting a potentially more vulnerable phenotype. CONCLUSION: These results suggest a protective role for UCP2 against atherosclerosis.

Animals↗

A new polymorphic site located in the human UCP1 gene controls the in vitro binding of CREB-like factor.

Uncoupling protein 1 (UCP1) is uniquely expressed in brown adipose tissue (BAT) and generates heat by uncoupling respiration from ATP synthesis. A defect in BAT thermogenesis has been described in different models of rodent obesity. In humans, the implication of BAT in energy expenditure is still under discussion. A BclI polymorphism associated with fat gain over time has been described in the upstream region of the human UCP1 (hUCP1) gene. In this study, a new polymorphic site linked to the BclI site is described which results in a C to A point mutation, 89 bp downstream of the BclI site, ie at position -3737 bp. This site is located in the recently analysed regulatory region of the hUCP1 gene. The mutation disrupts a consensus site for the binding of ATF/CREB transcription factor family and inhibits the factor binding in vitro. However, transient transfection of a rodent brown adipocyte cell line shows that the isoproterenol (ISO) stimulation of the hUCP1 gene transcription is not significantly affected by this mutation. However, we postulate that the C/A substitution, in human, may contribute to a minor defect in the regulation of hUCP1 transcription and that would explain fat gain over time.

Adipose Tissue, Brown↗

Electron confinement in surface states on a stepped gold surface revealed by angle-resolved photoemission.

STM images show that vicinal Au(788) surfaces are made up of a uniform array of (111)-oriented terraces of similar width ( approximately 3.8 nm). This uniformity makes it possible to study the electronic structure of the resulting step superlattice by angle-resolved photoemission. We show that for this terrace array the surface state appears to be broken up into one-dimensional quantum-well levels, indicating total electron confinement within the terraces. The angular resolution allows the probability density of the terrace quantum well state to be mapped in reciprocal space, complementing nicely the wave function measured in real space by STM.

Journal Article↗

Identification and synthesis of a kairomone mediating host location by two parasitoid species of the cassava mealybug Phenacoccus herreni.

Two encyrtid species, Acerophagus coccois and Aenasius vexans, parasitoids of the cassava mealybug Phenacoccus herreni use a contact kairomone from the body surface of their host as a host-location stimulant. The kairomone was synthesized and identified as O-caffeoylserine based on a combination of chromatographic methods. The synthetic compound was determined to be active.

Animals↗

Interplay between atomic and mesoscopic order on gold vicinal surfaces

Self-organization on Au(1,1,1) vicinal surfaces provides a unique opportunity to study the interplay between atomic and mesoscopic order. First, experimental results demonstrate the different interactions between steps and surface reconstruction on Au(1,1,1) vicinal surfaces. Depending on the step atomic structure, lines of discommensurations are found to be either parallel or perpendicular to the step edges. This leads to a complete understanding of the mesoscopic self-organization on theses surfaces, which drastically depends on the step structure. This points out the crucial role played by the edge energy cost which can monitor the faceting periodicity in a wide range of values.

Journal Article↗

Heavy ion-induced plasmid DNA damage in aerated or deaerated conditions.

Using the plasmid relaxation assay, the induction of single strand breaks (SSB) and base damages was investigated in air-dried plasmid DNA irradiated under air or under vacuum, with two high LET particles. We first observed that an irradiation with 12C5+ ion produced less of both damages when performed in a vacuum rather than in the presence of air. This could be due to the presence of O2 which increases the primary radicalar effects in the latter case. Another explanation is a difference in the degree of hydration of the DNA molecules. Indeed, under vacuum only the water molecules tightly bound to DNA will persist. In contrast, in the presence of air, the outer hydration shell enhances the amount of hydroxyl radicals available for the radiolytic attack. However, no difference in the SSB induction was observed when DNA was irradiated with 36S16+ ion in the presence of air or under vacuum. This is likely due to the LET effect which partly cancels the production of radicals by recombination and increases the formation of superoxide anions in the track. Similarly, the lower induction of damage by 36S16+ irradiation in comparison with the 12C5+ ion is a consequence of the higher ionizing density for 36S16+ than for 12C5+ ions. Meanwhile, for both ions, base damages are not detected when DNA is irradiated under vacuum, whereas they are as frequent as SSB when irradiation is performed in the presence of air. Altogether, these observations support the idea that SSB and base damage are not formed by the same mechanism.

Air↗

(E)-5-(Tributylstannylmethylidene)-5H-furan-2-ones: versatile synthons for the stereospecific elaboration of gamma-alkylidenebutenolide skeletons.

[reaction: see text] Stereoselective construction of (E)-gamma-tributylstannylmethylidene butenolides 1 was achieved through the palladium-catalyzed tandem cross-coupling/cyclization reactions of tributylstannyl 3-iodopropenoate derivatives with tributyltinacetylene. Iododestannylation of 1 occurs with inversion of the configuration of the exocyclic double bond while the observed selectivity in the Stille reaction was found to be dependent on the nature of the aryl halide.

4-Butyrolactone↗

The fidelity of double strand breaks processing is impaired in complementation groups B and D of Fanconi anemia, a genetic instability syndrome.

In mammalian cells, nonhomologous end-joining is the predominant mechanism to eliminate DNA double strand breaks. Such events are at the origin of deletion mutagenesis and chromosomal rearrangements. The hallmark of Fanconi anemia, an inherited cancer prone disorder, is increased chromosomal breakage associated to over-production of deletions. Knowing that double strand breaks are at the origin of deletion mutagenesis, the question arises whether their processing is affected in FA. We set up a "host cell end-joining assay" to analyze the fate of double strand breaks into extrachromosomal substrates transiently replicated in normal and FA-D lymphoblasts. Although no difference in plasmid survival was found, blunt-ended breaks were sealed with significantly lower fidelity in FA cells, resulting in a higher deletion frequency and a larger deletion size. The results suggest that FA-D and FA-B gene products are likely to play a role in end-joining fidelity of specific DNA double strand breaks.

Chromosome Breakage↗

6,4,4'-Trimethylangelicin photoadduct immunodetection in DNA: induction and repair in Fanconi's anemia and normal human fibroblasts.

6,4,4'-Trimethylangelicin (TMA)-photoinduced monoadducts (MAs) were detected and quantified on DNA of normal human and Fanconi's anemia (FA) fibroblasts (complementation groups A and D) by immuno-electron microscopy. TMA-modified DNA was extracted from the cells just after photoreaction, or after a subsequent 24 h repair period, for analysis of the MA processing capabilities of the different cell lines. Unmodified DNA was extracted from the control cells in parallel. The immunoreaction with antibody 7E3 was performed on single-stranded DNA fragments obtained by heat-formamide denaturation. On single-stranded DNA fragments scanned in the electron microscope, IgG-labeled MA sites appeared as isolated or clustered IgG molecules, which were not homogeneously distributed. The isolated IgG and the different clusters (doublets, triplets or near-neighbors (within a distance of 250 nucleotides)) were measured separately for induction frequency and removal. Few interstrand cross-links (CLs) were present on X-shape DNA fragments. At time zero, the distribution patterns of TMA-photoinduced IgG-labeled MA sites and CLs, and their amount per 10(6) nucleotides, were similar in the three cell lines. After the 24 h repair period, FA cells from two different genetic complementation groups demonstrated impaired incision-excision repair capabilities for both MAs (singlets or clusters) and CLs when compared with normal cells. In each cell line, the relative proportions of TMA-induced lesions remaining at time 24 h were similar to those initially induced. This implies analogous processing kinetics towards the TMA-photoinduced clusters of MAs and CLs in a given cell line.

Animals↗

Biochemical and electron microscope analyses of the DNA reverse transcripts present in the virus-like particles of the yeast transposon Ty1. Identification of a second origin of Ty1DNA plus strand synthesis.

Transposition of Saccharomyces cerevisiae Ty1 retroelements has been shown to involve reverse transcription in intracytoplasmic virus-like particles (Ty-VLPs). Ty DNA present in the particles specified by Ty1-H3 element was found to consist of the full-length genomic DNA as well as incomplete cDNAs mainly of plus polarity. Our results indicate that identical sequences (TGGGTGGTA) are used as primers for the synthesis of plus strand cDNA, generating cDNAs of 0.345 kb (analogous to the retroviral strong-stop plus cDNA) and of 2.1 kb. Electron microscopic analyses of Ty1-VLP DNA revealed two distinct classes, one full-length and the other corresponding to 0.34 kbp molecules, the size of a LTR sequence. The full-length molecules are either completely double-stranded or only partially double- stranded at one end or at both ends. These double-stranded regions are of a length corresponding to those of incomplete plus strands detected by biochemical techniques. Double-stranded circular molecules mainly of a length corresponding to that of two-LTR circles were also detected on electron micrographs. These analyses allowed us to propose a scheme for reverse transcription in Ty particles.

Base Sequence↗

Immunological probing of induction and repair of 8-methoxypsoralen photoadducts in DNA from Fanconi anemia and normal human fibroblasts: quantitative analysis by electron microscopy.

A direct method of immuno-electron microscopy has been employed to simultaneously determine 8-methoxypsoralen (8-MOP) photoinduced monoadducts (MA) and interstrand cross-links (CL), their relative localization along the DNA molecule, and their removal. It has been applied to DNA from cultures of Fanconi anemia (FA) fibroblasts (complementation groups A and D), and of normal human fibroblasts, following treatment by 8-MOP and 365 nm radiation. The immuno-reaction with monoclonal antibody 8G1 was performed on DNA extracted from the cells just after photoreaction, or after a 24 h repair period, and then denatured. Furan-side MA and also a significant proportion of pyrone-side MA were very efficiently immuno-detected. Only 1-2% CL were IgG-labeled. This is why CL were directly visualized and quantified on denatured DNA from the same cellular samples as used for immuno-detection. Results demonstrate that FA group A cells are not only impaired in the incision of CL, but also of MA. The response of FA group D cells is intermediate between normal and FA group A cells.

Cell Line↗

Linear mitochondrial DNAs of yeasts: frequency of occurrence and general features.

In most yeast species, the mitochondrial DNA (mtDNA) has been reported to be a circular molecule. However, two cases of linear mtDNA with specific termini have previously been described. We examined the frequency of occurrence of linear forms of mtDNA among yeasts by pulsed-field gel electrophoresis. Among the 58 species from the genera Pichia and Williopsis that we examined, linear mtDNA was found with unexpectedly high frequency. Thirteen species contained a linear mtDNA, as confirmed by restriction mapping, and labeling, and electron microscopy. The mtDNAs from Pichia pijperi, Williopsis mrakii, and P. jadinii were studied in detail. In each case, the left and right terminal fragments shared homologous sequences. Between the terminal repeats, the order of mitochondrial genes was the same in all of the linear mtDNAs examined, despite a large variation of the genome size. This constancy of gene order is in contrast with the great variation of gene arrangement in circular mitochondrial genomes of yeasts. The coding sequences determined on several genes were highly homologous to those of the circular mtDNAs, suggesting that these two forms of mtDNA are not of distant origins.

Base Sequence↗

Linear mitochondrial DNAs of yeasts: closed-loop structure of the termini and possible linear-circular conversion mechanisms.

The terminal structure of the linear mitochondrial DNA (mtDNA) from three yeast species has been examined. By enzymatic digestion, alkali denaturation, and sequencing of cloned termini, it was shown that in Pichia pijperi and P. jadinii, both termini of the linear mtDNA were made of a single-stranded loop covalently joining the two strands, as in the case of vaccinia virus DNA. The left and right loop sequences were in either of two orientations, suggesting the existence of a flip-flop inversion mechanism. Contiguous to the terminal loops, inverted terminal repeats were present. The mtDNA from Williopsis mrakii seems to have an analogous structure, although terminal loops could not be directly demonstrated. Electron microscopy revealed the presence, among linear molecules, of a small number of circular DNAs, mostly of monomer length. Linear and circular models of replication are considered, and possible conversion mechanisms between linear and circular forms are discussed. A flip-flop inversion mechanism between the inverted repeat sequences within a circular intermediate may be involved in the generation of the linear form of mtDNA.

Base Sequence↗

Repair of 8-methoxypsoralen photoinduced cross-links in yeast. Analysis by alkaline step-elution and electron microscopy.

The repair of interstrand cross-links induced by 8-methoxypsoralen plus UVA (365 nm) radiation DNA was analyzed in diploid strains of the yeast Saccharomyces cerevisiae. The strains employed were the wild-type D7 and derivatives homozygous for the rad18-1 or the rad3-12 mutation. Alkaline step-elution and electron microscopy were performed to follow the process of induction and removal of photoinduced cross-links. In accordance with previous reports, the D7 rad3-12 strain failed to remove the induced lesions and could not incise cross-links. The strain D7 rad18-1 was nearly as efficient in the removal of 8-MOP photoadducts after 2 h of post-treatment incubation as the D7 RAD+ wild-type strain. However, as demonstrated by alkaline step-elution and electron microscopic analysis, the first incision step at DNA cross-links was three times more effective in D7 rad18-1 than in D7 RAD+. This is consistent with the hypothesis that the RAD18 gene product is involved in the filling of gaps resulting from persistent non-informational DNA lesions generated by the endonucleolytic processing of DNA cross-links. Absence of this gene product may lead to extensive strand breakage and decreased recognition of such lesions by structural repair systems.

Cross-Linking Reagents↗