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Biomedical subjects

S Maurice

Publications and source records attributed to S Maurice.

At least 19 recordsLinked to original sources
PubMed2005

Composition and dynamics of plasma in Saturn's magnetosphere.

During Cassini's initial orbit, we observed a dynamic magnetosphere composed primarily of a complex mixture of water-derived atomic and molecular ions. We have identified four distinct regions characterized by differences in both bulk plasma properties and ion composition. Protons are the dominant species outside about 9 RS (where RS is the radial distance from the center of Saturn), whereas inside, the plasma consists primarily of a corotating comet-like mix of water-derived ions with approximately 3% N+. Over the A and B rings, we found an ionosphere in which O2+ and O+ are dominant, which suggests the possible existence of a layer of O2 gas similar to the atmospheres of Europa and Ganymede.

Atmosphere↗
PubMed2005

Microscopy analysis of bone marrow-derived osteoprogenitor cells cultured on hydrogel 3-D scaffold.

Bone marrow contains progenitor cells that are able to differentiate into several mesenchymal lineages, including bone. These cells may also provide a potential therapy for bone repair. The purpose of this study was to select the osteoprogenitor cell subpopulation from bone marrow-derived mesenchymal stem cells (MSCs) and to test the ability of a hydrogel scaffold to support growth and osteogenic differentiation. MSCs isolated from rat femur bone marrow were cultured in DMEM medium supplemented with antibiotics, FCS, and L-glutamine. Osteogenic supplements (dexamethasone, sodium beta-glycerophosphate, and ascorbic acid) were added for one, two or three weeks. A selective subpopulation of osteoprogenitor cells was identified by immunohistochemistry, general morphology, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Committed osteogenic cells were transferred to a 3-D hydrogel scaffold and cultured for an additional week. In standard culture, the osteoprogenitor cells formed cell clusters identified by Alizarin red S staining and by positive osteocalcin immunostaining. The number of osteoprogenitor cells, matrix synthesis, and mineralization increased gradually up to three weeks in culture. Mineral deposition in the matrix analyzed by EDS revealed the presence of calcium and phosphate ions at a Ca/P molar ratio of 1.73 in both the osteogenic cultures and the scaffold osteoprogenitor culture. Histological preparations revealed cell clusters within the hydrogel scaffold and SEM analysis revealed cell clusters attached to the scaffold surface. It is concluded that the hydrogel scaffold can support growth and differentiation of osteogenic cultures including mineralization and can potentially serve as a bone graft substitute containing committed osteoprogenitor cells.

Animals↗
PubMed2005

Serum vascular endothelial growth factor as a significant marker of treatment response in pediatric malignancies.

The aim of this pilot study was to determine VEGF serum levels (S-VEGF) at diagnosis and at restaging in children diagnosed with cancer, and to investigate whether this parameter provides prognostic information for remission after induction therapy and response to treatment. S-VEGF levels of 35 consecutive pediatric patients with various types of cancer were assayed at diagnosis and at restaging. Levels of VEGF were determined using a commercially available ELISA anti-human VEGF immunoassay kit. Thirty-one children went into complete remission or had a very good partial response to first-line therapy; 4 patients developed tumor progression. At diagnosis average S-VEGF level was 495 pg/mL (range, 0.89--2220 pg/mL) and at restaging it decreased to 118.36 pg/mL (range, 7.44--487 pg/mL). (p=.0039). The 4 patients with tumor progression had increased S-VEGF levels at restaging. The comparison between the levels of S-VEGF at diagnosis and at restaging showed a significant difference for the patients who responded to treatment with decreased S-VEGF and the patients who developed tumor progression with increased S-VEGF (p=.0019). One child with metastatic Ewing sarcoma developed progressive disease after several weeks, with significantly progressively higher S-VEGF levels. One child with Hodgkin disease, who had a higher level at first restaging and developed progressive disease, responded to reinduction therapy and had a significantly lower level at the second restaging. The child with metastatic hepatoblastoma responded to first-line chemotherapy with concomitant decrease in S-VEGF and alpha-fetoprotein levels, but developed local recurrence with elevation in both parameters. Changes in S-VEGF levels correlated with response to treatment for most of the children diagnosed with cancer. This provides a rationale for exploring clinical interest in S-VEGF measurements of a larger group of children with malignancies, and using the test for clinical trials of antiangiogenic therapies.

Adolescent↗
PubMed2004

MEP (Mars Environment Package): toward a package for studying environmental conditions at the surface of Mars from future lander/rover missions.

In view to prepare Mars human exploration, it is necessary to promote and lead, at the international level, a highly interdisciplinary program, involving specialists of geochemistry, geophysics, atmospheric science, space weather, and biology. The goal of this program will be to elaborate concepts of individual instruments, then of integrated instrumental packages, able to collect exhaustive data sets of environmental parameters from future landers and rovers of Mars, and to favour the conditions of their implementation. Such a program is one of the most urgent need for preparing human exploration, in order to develop mitigation strategies aimed at ensuring the safety of human explorers, and minimizing risk for surface operations. A few main areas of investigation may be listed: particle and radiation environment, chemical composition of atmosphere, meteorology, chemical composition of dust, surface and subsurface material, water in the subsurface, physical properties of the soil, search for an hypothesized microbial activity, characterization of radio-electric properties of the Martian ionosphere. Scientists at the origin of the present paper, already involved at a high degree of responsibility in several Mars missions, and actively preparing in situ instrumentation for future landed platforms (Netlander--now cancelled, MSL-09), express their readiness to participate in both ESA/AURORA and NASA programs of Mars human exploration. They think that the formation of a Mars Environment working group at ESA, in the course of the AURORA definition phase, could act positively in favour of the program, by increasing its scientific cross-section and making it still more focused on human exploration.

Atmosphere↗
PubMed2004

An experimental evaluation of self-interference in Narcissus assoanus: functional and evolutionary implications.

Floral traits that reduce self-pollination in hermaphroditic plants have usually been interpreted as mechanisms that limit the genetic consequences of self-fertilization. However, the avoidance of sexual conflict between female and male function (self-interference) may also represent an important selection pressure for the evolution of floral traits, particularly in self-incompatible species. Here, we use experimental manipulations to investigate self-interference in Narcissus assoanus, a self-incompatible species with a stigma-height dimorphism in which the degree of spatial separation between sex organs (herkogamy) differs strikingly between the long- and short-styled morphs (hereafter L- and S-morphs). We predicted that weak herkogamy in the L-morph would cause greater self-pollination and hence self-interference. Experimental self-pollination reduced seed set when it occurred prior to, or simultaneously with, cross-pollination in the L-morph, but only if it occurred prior to cross-pollination in the S-morph. In the field, autonomous self-pollination was greater in the L-morph than the S-morph, but we found no evidence that self-interference reduced maternal or paternal fitness in either morph. One-day-old flowers of the L-morph have reduced stigma receptivity and hence exhibit protandry, whereas stigma receptivity and anther dehiscence are concurrent in the S-morph. This suggests that the two style morphs have alternative strategies for reducing self-interference: dichogamy in the L-morph and herkogamy in the S-morph. These results provide insight into the mechanisms that reduce sexual conflict in hermaphrodite plants and are of significance for understanding the evolution and maintenance of sexual polymorphisms.

Analysis of Variance↗
PubMed2003

Mars analysis by laser-induced breakdown spectroscopy (MALIS): influence of mars atmosphere on plasma emission and study of factors influencing plasma emission with the use of doehlert designs.

A project called MALIS (Mars Analysis by Laser-Induced breakdown Spectroscopy) is under progress to perform in situ analysis of Mars soils and rocks. This paper reports on the behavior of plasma in Martian conditions, i.e., in a CO2 atmosphere at pressures between 5 and 12 mbar. Plasma expansion and lifetime have been studied in order to compare plasma evolution under standard conditions (air at atmospheric pressure) and in a Mars atmosphere. We have shown that the Mars environment favors plasma expansion and lifetime. The second part of the study concerns optimization of the emission signal from the plasma. An original approach has been chosen, as we used a Doehlert design for the first time in laser-induced breakdown spectroscopy (LIBS). The best conditions obtained are for a laser wavelength of 1064 nm with the maximum energy available due to space limitations, which is 40 mJ at 15 Hz. The other factors studied are delay, angle of incidence, and CO2 pressure. We have shown that these factors do not have the same influence depending on which spectroscopic line is used, i.e., the atomic line or the ionic line.

Atmosphere↗
PubMed2002

Global distribution of neutrons from Mars: results from Mars odyssey.

Global distributions of thermal, epithermal, and fast neutron fluxes have been mapped during late southern summer/northern winter using the Mars Odyssey Neutron Spectrometer. These fluxes are selectively sensitive to the vertical and lateral spatial distributions of H and CO2 in the uppermost meter of the martian surface. Poleward of +/-60 degrees latitude is terrain rich in hydrogen, probably H2O ice buried beneath tens of centimeter-thick hydrogen-poor soil. The central portion of the north polar cap is covered by a thick CO2 layer, as is the residual south polar cap. Portions of the low to middle latitudes indicate subsurface deposits of chemically and/or physically bound H2O and/or OH.

Dry Ice↗
PubMed2002

Distribution of hydrogen in the near surface of Mars: evidence for subsurface ice deposits.

Using the Gamma-Ray Spectrometer on the Mars Odyssey, we have identified two regions near the poles that are enriched in hydrogen. The data indicate the presence of a subsurface layer enriched in hydrogen overlain by a hydrogen-poor layer. The thickness of the upper layer decreases with decreasing distance to the pole, ranging from a column density of about 150 grams per square centimeter at -42 degrees latitude to about 40 grams per square centimeter at -77 degrees. The hydrogen-rich regions correlate with regions of predicted ice stability. We suggest that the host of the hydrogen in the subsurface layer is ice, which constitutes 35 +/- 15% of the layer by weight.

Atmosphere↗
PubMed2001

Methylation of HpaII site at the human DXS16 locus on Xp22 as an assay for abnormal patterns of X inactivation.

The highly polymorphic human DXS16 locus on Xp22 contains a BglII restriction fragment length polymorphism with 33% heterozygosity. We report that methylation of the HpaII site, 3.1 kb away from this restriction fragment length polymorphism, correlates with X-inactivation. The BglII polymorphism distinguishes between the maternal and paternal alleles, and HpaII digestion identifies their methylation status. The accuracy of this assay was tested on more than 30 control females and some patients with known patterns of X-inactivation. The data obtained from this assay agree substantially with those obtained using the androgen receptor assay, which is widely used for detecting patterns of X-inactivation. This is the first marker on Xp22 found to be suitable for clonal analysis. Of additional significance is this marker's proximity to the pseudoautosomal boundary on the X chromosome and its potential use in identifying rare events occurring in this region, which lead to escape from normal X-inactivation.

Alleles↗
PubMed1999

Preparation of recombinant gilthead seabream (Sparus aurata) growth hormone and its use for stimulation of larvae growth by oral administration.

Gilthead seabream (Sparus aurata) growth hormone (gsGH) cDNA coding for the mature protein was cloned in a pGEM-T vector and then transferred into prokaryotic expression vector pET-8 and expressed in E. coli BL21 (DE3) cells upon induction with IPTG. The expressed protein, contained within the inclusion-body pellet, was solubilized in 4.5 M urea, refolded at pH 11.3 in the presence of catalytic amounts of cysteine, and purified to over 98% purity, as evidenced by SDS-PAGE. Gel-filtration on a Superdex column under nondenaturing conditions and partial amino acid N-terminal sequence showed the purified protein to be a monomeric alanyl-gsGH. Over 90% pure bacterial beta-lactamase was copurified as a by-product. Binding assays of the [125I]gsGH to gs liver microsomal fraction resulted in high specific binding characterized by a Kd = 1.93 nM. Recombinant gsGH, like ovine placental lactogen, exhibited growth-stimulating activity when applied orally to S. aurata larvae or intraperitoneally to juvenile fish.

Administration, Oral↗
PubMed1999

A-protein from achromogenic atypical Aeromonas salmonicida: molecular cloning, expression, purification, and characterization.

Achromogenic atypical Aeromonas salmonicida is the causative agent of goldfish ulcer disease. Virulence of this bacterium is associated with the production of a paracrystalline outer membrane A-layer protein. The species-specific structural gene for the monomeric form of A-protein was cloned into a pET-3d plasmid in order to express and produce a recombinant form of the protein in Escherichia coli BL21(DE3). The induced protein was isolated from inclusion bodies by a simple solubilization-renaturation procedure and purified by ion exchange chromatography on Q-Sepharose to over 95% pure monomeric protein. Recombinant A-protein was compared by biochemical, immunological, and molecular methods with the A-protein isolated from atypical A. salmonicida bacterial cells by the glycine and the membrane extraction methods. The recombinant form was found to be undistinguishable from the wild type when examined by SDS-PAGE and gel filtration chromatography. The immunological similarity of the protein samples was demonstrated by employing polyclonal and monoclonal antibodies in ELISA and Western blot techniques. All forms of A-protein were found to activate the secretion of tumor necrosis factor alpha from murine macrophage. To date, this represents the first large-scale production of biologically active recombinant A-protein.

Aeromonas↗
PubMed1998

Global elemental maps of the moon: the Lunar Prospector gamma-Ray spectrometer.

Lunar Prospector gamma-ray spectrometer spectra along with counting rate maps of thorium, potassium, and iron delineate large compositional variations over the lunar surface. Thorium and potassium are highly concentrated in and around the nearside western maria and less so in the South Pole-Aitken basin. Counting rate maps of iron gamma-rays show a surface iron distribution that is in general agreement with other measurements from Clementine and the Lunar Prospector neutron detectors.

Elements↗
PubMed1998

Major compositional units of the moon: lunar prospector thermal and fast neutrons

Global maps of thermal and fast neutron fluxes from the moon suggest three end-member compositional units. A high thermal and low fast neutron flux unit correlates with the lunar highlands and is consistent with feldspathic rocks. The South Pole-Aitken basin and a strip that surrounds the nearside maria have intermediate thermal and fast neutron flux levels, consistent with more mafic rocks. There appears to be a smooth transition between the most mafic and feldspathic compositions, which correspond to low and high surface altitudes, respectively. The maria show low thermal and high fast neutron fluxes, consistent with basaltic rocks.

Journal Article↗
PubMed1998

Lunar Fe and Ti abundances: comparison of lunar prospector and clementine data

The Lunar Prospector neutron spectrometer data correlate well with iron and titanium abundances obtained through analysis of Clementine spectral reflectance data. With the iron and titanium dependence removed, the neutron spectrometer data also reveal regions with enhanced amounts of gadolinium and samarium, incompatible rare earth elements that are enriched in the final phases of magma crystallization. These regions are found mainly around the ramparts of the Imbrium impact basin but not around the other basins, including the much larger and deeper South Pole-Aitken basin. This result confirms the compositional uniqueness of the surface and interior of the Imbrium region.

Journal Article↗
PubMed1998

Fluxes of fast and epithermal neutrons from Lunar Prospector: evidence for water ice at the lunar poles.

Maps of epithermal- and fast-neutron fluxes measured by Lunar Prospector were used to search for deposits enriched in hydrogen at both lunar poles. Depressions in epithermal fluxes were observed close to permanently shaded areas at both poles. The peak depression at the North Pole is 4.6 percent below the average epithermal flux intensity at lower latitudes, and that at the South Pole is 3.0 percent below the low-latitude average. No measurable depression in fast neutrons is seen at either pole. These data are consistent with deposits of hydrogen in the form of water ice that are covered by as much as 40 centimeters of desiccated regolith within permanently shaded craters near both poles.

Extraterrestrial Environment↗