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Biomedical subjects

J Collet

Publications and source records attributed to J Collet.

At least 19 recordsLinked to original sources
PubMed2002

Compact disc with both numeric and genomic information as DNA microarray platform.

The compact disc (CD) is an ideal toolfor reading, writing, and storing numeric information. It was used in this work as a support for constructing DNA microarrays suited for genomic analysis. The CD was divided into two functional areas: the external ring of the CD was used for multiparametric DNA analysis on arrays, and the inner portion was usedfor storing numeric information. Because polycarbonate and CD resins autofluoresce, a colorimetric method for DNA microarray detection was used that is well adaptedfor the fast detection necessary when using a CD reader. A double-sided CD reader was developed for the simultaneous analysis of both array and numeric data. The numeric data are engraved as pits in the CD tracks and result in the succession of 0/1, which results from the modulation of the laser reflection when one reads the edges of the pits. Another diffraction-based laser was placed above the CD for the detection of the DNA targets on the microarrays. Both readersfit easily in a PC tower. Both numeric and genomic information data were simultaneously acquired, and each array was reconstituted, analyzed, and processed for quantification by the appropriate software.

Compact Disks↗
PubMed2001

Colorimetric silver detection of DNA microarrays.

Development of microarrays has revolutionized gene expression analysis and molecular diagnosis through miniaturization and the multiparametric features. Critical factors affecting detection efficiency of targets hybridization on microarray are the design of capture probes, the way they are attached to the support, and the sensitivity of the detection method. Microarrays are currently detected in fluorescence using a sophisticated confocal laser-based scanner. In this work, we present a new colorimetric detection method which is intented to make the use of microarray a powerful procedure and a low-cost tool in research and clinical settings. The signal generated with this method results from the precipitation of silver onto nanogold particles bound to streptavidin, the latter being used for detecting biotinylated DNA. This colorimetric method has been compared to the Cy-3 fluorescence method. The detection limit of both methods was equivalent and corresponds to 1 amol of biotinylated DNA attached on an array. Scanning and data analysis of the array were obtained with a colorimetric-based workstation.

Bacterial Proteins↗
PubMed2001

Serum insulin-like growth factor-I (IGF-I) does not correlate positively with isometric strength, fatigue, and quality of life in post-polio syndrome.

OBJECTIVES AND BACKGROUND: To determine if serum insulin-like growth factor-I (IGF-I) levels are associated with strength, body mass index (BMI), fatigue, or quality of life in post-poliomyelitis syndrome (PPS). PPS is likely due to a distal disintegration of enlarged post-polio motor units as a result of terminal axonal sprouting. Age-related decline in growth hormone and IGF-I (which support terminal axonal sprouts) is proposed as a contributing factor. METHODS: As part of the North American Post-Poliomyelitis Pyridostigmine Study (NAPPS), baseline data on maximum voluntary isometric contraction (MVIC), BMI, subjective fatigue (fatigue severity scale, Hare fatigue symptom scale), health-related quality of life (short form health survey-36; SF-36), and serum IGF-I levels were gathered on 112 PPS patients. Pearson correlation coefficients were calculated to evaluate the association between serum IGF-I and MVIC in 12 muscles, BMI, two fatigue scales, and SF-36 scale scores. RESULTS: There is a significant inverse correlation of IGF-I levels with MVIC in left ankle dorsiflexors (r=-0.30, P<0.01), and left and right knee extensors (r=-0.22, -0.25, P=<0.01, 0.01), but no significant correlations in other muscles. When men and women were evaluated separately, inverse correlations of IGF-I levels with MVIC were found only in men. IGF-I correlated inversely with BMI (r=-0.32, P=0006) and age (r=-0.32, P=0.0005). IGF-I did not correlate with the fatigue or SF-36 scales. CONCLUSIONS: In this exploratory study, we found that contrary to our expectations, IGF-I did not correlate positively with strength. IGF-I correlated negatively with strength in several lower extremity muscles, BMI, and age. IGF-I is likely not an important factor in the pathogenesis of fatigue and in determining quality of life in PPS, but its role on strength should be studied further.

Adult↗
PubMed2000

Effect of prior exposure to Chlamydia pneumoniae, Helicobacter pylori, or cytomegalovirus on the degree of inflammation and one-year prognosis of patients with unstable angina pectoris or non-Q-wave acute myocardial infarction.

Inflammation and chronic infections may be important features in the pathogenesis of acute coronary syndromes. We describe 6 systemic markers of inflammation in patients with unstable angina or non-Q-wave myocardial infarction and the relations between these markers, seropositivity to chronic infections, and prognosis. C-reactive protein (CRP), serum amyloid A protein (SAA), fibrinogen, interleukin-6 (IL-6), neopterin, procalcitonin, and serum antibody levels to Chlamydia pneumoniae, Helicobacter pylori, and cytomegalovirus were measured on admission and 48 hours later. One-year clinical follow-up was performed. Plasma levels of acute phase reactants were all elevated on admission and increased further at 48 hours: CRP from 10.1 +/- 2.1 mg/L at baseline to 26.6 +/- 5.1 mg/L at 48 hours (p <0.001); SAA from 27.3 +/- 8.5 to 93.1 +/- 23.2 mg/dl (p <0.005); fibrinogen from 3.2 +/- 0.1 to 3.8 +/- 0.1 g/L (p <0.0001); whereas initial high levels of IL-6 tended also to increase from 9.8 +/- 2 to 15.3 +/- 3.1 pg/ml (p = NS). In contrast, neopterin and procalcitonin remained unchanged. We found no association between levels of each inflammatory marker and the serologic status. Furthermore, levels of inflammatory proteins in patients seronegative to all 3 agents were comparable to those of patients seropositive to 2 or 3 infectious agents. The composite end points of death, myocardial infarction, recurrent angina, or revascularization at 1-year follow-up did not differ according to the serologic status. Thus, in patients with acute coronary syndromes, the acute phase proteins increased over the first 2 days of hospitalization. This initial inflammatory reaction as well as the 1-year clinical outcome did not differ according to the initial serologic status of Chlamydia pneumoniae, Helicobacter pylori, or cytomegalovirus.

Acute-Phase Proteins↗
PubMed1999

Gene expression in developing rat hippocampal pyramidal neurons appears independent of mossy fiber innervation.

In the rat, neonatal gamma-irradiation of the hippocampus induces a selective destruction of dentate granule cells and prevents the development of the mossy fiber-CA3 pyramidal cell connection. In the absence of mossy fiber input, the CA3 pyramidal neurons exhibit morphological alterations and rats deprived of dentate granule cells fail to develop kainate-induced epileptic activity in the CA3 pyramidal neurons. Neonatal elimination of the granule cells also impairs learning and memory tasks in adult rats. In the present work, we assessed by in situ hybridization and semi-quantitative RT-PCR, whether in the pyramidal layers, the absence of mossy fiber input alters the expression of a number of genes involved in activity-dependent signal transduction, in GABAergic neurotransmitter signaling and in neurite development via microtubule organization. Surprisingly, we show that the expression and the developmentally regulated alternative splicing of the genes we examined in the developing hippocampus are not altered in the pyramidal neurons, whether the dentate granule afferents are present or absent. Our results suggest that in the CA3 pyramidal layer, the developmental expression patterns of the mRNAs we studied are independent of extrinsic cues provided by mossy fiber input.

Alternative Splicing↗
PubMed1998

Analysis of osm-6, a gene that affects sensory cilium structure and sensory neuron function in Caenorhabditis elegans.

Mutation in the Caenorhabditis elegans gene osm-6 was previously shown to result in defects in the ultrastructure of sensory cilia and defects in chemosensory and mechanosensory behaviors. We have cloned osm-6 by transposon tagging and transformation rescue and have identified molecular lesions associated with five osm-6 mutations. The osm-6 gene encodes a protein that is 40% identical in amino acid sequence to a predicted mammalian protein of unknown function. We fused osm-6 with the gene for green fluorescent protein (GFP); the fusion gene rescued the osm-6 mutant phenotype and showed accumulation of GFP in ciliated sensory neurons exclusively. The OSM-6::GFP protein was localized to cytoplasm, including processes and dendritic endings where sensory cilia are situated. Mutations in other genes known to cause ciliary defects led to changes in the appearance of OSM-6::GFP in dendritic endings or, in the case of daf-19, reduced OSM-6::GFP accumulation. We conclude from an analysis of genetic mosaics that osm-6 acts cell autonomously in affecting cilium structure.

Alleles↗
PubMed1997

Developmentally regulated alternative splicing of mRNAs encoding N-terminal tau variants in the rat hippocampus: structural and functional implications.

Tau protein variants are axonal microtubule-associated phosphoproteins whose expression correlates with developmentally regulated neurite outgrowth. A single gene encodes multiple tau transcripts via complex alternative splicing. We studied the expression of the mRNAs encoding N-terminal variants of tau, and we showed distinct alternative splicing of exons 2 and 3 in nervous tissues of the adult rat, including the inner ear, hippocampus, cortex, striatum, brainstem, cerebellum, olfactory bulb and retina. Using the reverse transcriptase-coupled polymerase chain reaction and in situ hybridization, we then focused our developmental study on hippocampal neurons, both in vivo and in vitro, to address the developmental and spatial expression of the alternatively spliced mRNAs encoding N-terminal variants of tau. Tau mRNAs devoid of exons 2 and 3 were present throughout development, although their levels decreased in adults. Those containing exon 2 but not exon 3 were already present in the hippocampus of newborn rats and their levels increased during the first postnatal week, mainly in the pyramidal cell layer. Tau RNAs containing exons 2 and 3 appeared at the end of this period in the pyramidal cell layer and in the dentate granule cells. Exon 2-containing mRNAs seemed to be associated with cells undergoing axonal sprouting, while exon 3-containing RNAs were expressed in mature neurons that had established their connections. The timing and pattern of tau alternative splicing were maintained in cultured hippocampal neurons, suggesting that splicing processes are independent of the organized connectivity and of the environmental cues provided in vivo. Secondary structure predictions of tau variants revealed that the insertion of the exon 3-encoded domain substantially modifies the secondary structure of the N-terminal region of tau. This N-terminal heterogeneity may confer distinct regulatory roles on the tau variants during ontogeny and may contribute to plasticity in the adult rat brain.

Alternative Splicing↗
PubMed1996

Use of neutral surfactants for the capillary electrophoretic separation of hydrophobically modified poly(acrylic acids).

Hydrophobically modified poly(acrylic acids) (HMPAs) are random copolymers of sodium acrylate and dodecyl acrylamide, containing 0-10% mol/mol of dodecyl grafts. The hydrophobic character of different HMPAs of average molecular weight 150,000 was studied by capillary electrophoresis (CE), using neutral surfactants as buffer additives. The differentiation of the electrophoretic mobilities of HMPAs with their hydrophobicity was achieved through the use of nonionic Brij 35 and zwitterionic DAPS surfactants. A nearly baseline separation of the precursor and three HMPAs derivatives was obtained in a poly(ethylene glycol)-coated capillary with a background electrolyte containing 10 mM N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (DAPS) and 10 mM borax (pH 9.2). In addition to CE experiments, the polymer-surfactant interactions were also investigated by means of quasi-elastic light scattering (QELS) and viscosimetric measurements. According to the latter results, the separation mechanism was interpreted as an expansion of the polymer coil in the presence of micelles and subsequent change of its frictional properties. A true micellar electrokinetic capillary chromatography (MEKC) partitioning model was discarded on the basis of the relative sizes of the macromolecule and the micelles.

Acrylates↗
PubMed1995

Mutations affecting the chemosensory neurons of Caenorhabditis elegans.

We have identified and characterized 95 mutations that reduce or abolish dye filling of amphid and phasmid neurons and that have little effect on viability, fertility or movement. Twenty-seven mutations occurred spontaneously in strains with a high frequency of transposon insertion. Sixty-eight were isolated after treatment with EMS. All of the mutations result in defects in one or more chemosensory responses, such as chemotaxis to ammonium chloride or formation of dauer larvae under conditions of starvation and overcrowding. Seventy-five of the mutations are alleles of 12 previously defined genes, mutations which were previously shown to lead to defects in amphid ultrastructure. We have assigned 20 mutations to 13 new genes, called dyf-1 through dyf-13. We expect that the genes represented by dye-filing defective mutants are important for the differentiation of amphid and phasmid chemosensilla.

Animals↗
PubMed1993

Optimizing a method of protein extraction for two-dimensional electrophoretic separation of proteins from planarians (Platyhelminthes, Turbellaria).

Different procedures for microscale extraction of proteins from small amounts of tissue of planarians (Platyhelminthes, Turbellaria) to be analyzed by two-dimensional gel electrophoresis (2-D PAGE) are compared. Three extraction methods were assessed: (i) extraction of soluble proteins with nondenaturing Tris buffers, (ii) extraction with Tris buffer containing the anionic detergent sodium dodecyl sulfate (SDS), and (iii) denaturing extraction under reducing conditions in the presence of urea and Nonidet P-40 (NP-40) with or without SDS. Buffers combining minute concentrations of SDS (0.01%), denaturing concentrations of urea (8M) and alkaline pH solubilized the greatest number of proteins without detectable proteolysis. Neither the presence of protease inhibitors nor higher concentrations of SDS improved protein extraction. We have applied this method to planarians to detect proteins specific to the pharynx. The resulting two-dimensional pattern shows a larger number of specific spots than in previous extraction methods.

Animals↗
PubMed1993

The first European simulation of a long-duration manned space mission.

Europe's space flight ambitions will involve long-duration manned space missions in the next century. This objective has given rise to several studies being undertaken in "space-analogous" environments during the last few years. The first wholly space-oriented manned simulation study undertaken in Europe took place during 1990. It involved a crew of six isolated for 4 weeks in a hyperbaric chamber complex. The resources available for the study were primarily devoted to obtaining scientific data on the psychological and physiological effects of long-duration isolation and confinement on crew performance. Fundamental lessons were also learned on the operational side, and these will be fully exploited in setting up future simulation campaigns.

Humans↗
PubMed1993

European isolation and confinement study. Blood pressure, volume-regulating hormones, and electrolytes.

In the ISEMSI confinement experiment we observed three main reactions concerning blood volume regulation: first, a stress activation produced by the high workload that the subjects had to accomplish, both before the isolation period and during the two first weeks of isolation; second, a typical defense reaction to the environment occurred, at least during the two initial days of isolation and later perhaps between crew members themselves; and third, a change in blood volume regulating hormone levels may have been the result of the increase of sympathetic system activity and of dehydration. Confinement is certainly a good and valid method to simulate space station life (with the absence of weightlessness). So, it is interesting to use these confinement studies to perform biological and physiological experiments to obtain greater knowledge, but also to prepare and validate new scientific protocols or new scientific equipment suitable for spaceflights. Even more so, confinement is a good way to prepare and train crew members for long-term space missions. It would seem desirable to confirm the scientific results obtained during the ISEMSI campaign, and especially those for the regulation of the blood volume. This will be done during the next confinement experiment, called EXEMSI, in which four subjects will be subjected to 60 days of confinement.

Adult↗
PubMed1992

Global approach to simulation: a gateway to long-term human presence in space.

The establishment of an autonomous European manned space capability is an objective set up by the ESA Council Meeting at the ministerial level, in 1985/1987. ESA's Long-Term Programme Office (LTPO), charged of the preparation of the programme for a European Manned Space Infrastructure (EMSI), started during 1988 to build up an intellectual framework in the domain of long-duration manned space missions. EMSI scope was eventually extended to embrace Moon/Mars missions and bases. Several exploratory studies on problems related to human factors in long-duration space missions were initiated by LTPO. The work of an ad-hoc group of experts (SIMIS Group) has been focused during 1989/1990 on the planning for simulation of such missions with a broad mandate, covering the physiological, psychological and operational aspects of long-duration exposure to microgravity and isolation/confinement. Preliminary results of SIMIS activities are reported. The HYDREMSI experiment, carried out in a terrestrial, analogous environment for 72 days during 1989, is described as an example of the envisaged simulations.

Astronauts↗
PubMed1990

Presence in invertebrate genomes of sequences characterized by the repetition of the triplet CCPurine.

In Drosophila melanogaster (Dm), polypeptidic domains have been found in different morphogenetic genes. Two types of them are characterized by the repetition of nucleotidic triplets: the M repeat (CAX) and the paired repeat (CAXCCX). In this paper we described a third type of repeat isolated from the genome of a Polychaete annelid: Owenia fusiformis. This repeat is characterized by the repetition of the triplet CCPurine. Phylogenetic studies showed the presence of this repeat in all the invertebrate genomes tested (eight copies in Dm genome) while we failed to detect it in vertebrate genomes.

Amino Acid Sequence↗