Biomedical subjects

Isabelle Boutet

Publications and source records attributed to Isabelle Boutet.

15 recordsLinked to original sources

PubMed2005

Molecular characterization and expression of the gene encoding aspartate aminotransferase from the Pacific oyster Crassostrea gigas exposed to environmental stressors.

A partial cDNA encoding cytosolic aspartate aminotransferase (AST) (EC 2.6.1.1) was isolated from a Crassostrea gigas digestive gland library. This sequence was used to design specific primers to amplify the AST genomic sequence. We obtained a complete gene, 5054 bp in length, encoding cytosolic AST and containing a 404 amino acid open reading frame. Phylogenetic analysis showed that C. gigas AST sequence constitutes a branch distinct from homologous sequences from other invertebrate groups. We also investigated AST mRNA expression in different tissues of oysters exposed to hydrocarbons, pesticides, hypoxia and hypo-salinity stress. The results showed that AST expression responds to hydrocarbon exposure, hypoxia and salinity stress, but not to pesticide exposure in an organ and time-specific manner. Use of AST as a potential molecular biomarker for monitoring of disturbed ecosystems is discussed.

Amino Acid Sequence↗

PubMed2005

Stress response in Cu2+ and Cd2+ exposed oysters (Crassostrea gigas): an immunohistochemical approach.

Localization of heat shock proteins (HSPs) and metallothioneins (MTs) was investigated in a marine bivalve (Crassostrea gigas) by immunohistochemical methods. Differential protein expression was demonstrated in digestive gland, gonad and gills, using a polyclonal antibody against C. gigas proteins. Application of this technique showed the cellular and tissue immunolabelling specificity of the two proteins. HSPs and MTs were localized in the epithelium of the digestive gland and gills in contact with the palleal compartment. For the first time, localization of MTs was observed in mature gametes of bivalve molluscs. Our results establish a basis for the use of immmunodetection techniques to study the tissue-specific localization of stress proteins in marine bivalves exposed to metal stress.

Animals↗

PubMed2005

A novel method for assessing contrast sensitivity in the beagle dog is sensitive to age and an antioxidant enriched food.

Tasks requiring visual discrimination are commonly used in assessment of canine cognitive function. However, little is known about canine visual processing, and virtually nothing is known about the effects of age on canine visual function. This study describes a novel behavioural method developed to assess one aspect of canine visual function, namely contrast sensitivity. Four age groups (young, middle aged, old, and senior) were studied. We also included a group of middle aged to old animals that had been maintained for at least 4 years on a specially formulated food containing a broad spectrum of antioxidants and mitochondrial cofactors. Performance of this group was compared with a group in the same age range maintained on a control diet. In the first phase, all animals were trained to discriminate between two high contrast shapes. In the second phase, contrast was progressively reduced by increasing the luminance of the shapes. Performance decreased as a function of age, but the differences did not achieve statistical significance, possibly because of a small sample size in the young group. All age groups were able to acquire the initial discrimination, although the two older age groups showed slower learning. Errors increased with decreasing contrast with the maximal number of errors for the 1% contrast shape. Also, all animals on the antioxidant diet learned the task and had significantly fewer errors at the high contrast compared with the animals on the control diet. The initial results suggest that contrast sensitivity deteriorates with age in the canine while form perception is largely unaffected by age.

Aging↗

PubMed2005

Age-associated cognitive deficits in humans and dogs: a comparative neuropsychological approach.

We compared performance of younger and older human participants to that of younger and older dogs on tasks that evaluate object discrimination, egocentric spatial ability, object recognition, spatial memory, and cognitive flexibility. Our goal was to determine whether (i) tasks sensitive to advanced age in dogs are also age-sensitive in humans; (ii) the pattern of task difficulty observed in dogs mirrors that observed in humans; (iii) dogs and humans use similar strategies to solve equivalent tasks. Dogs performed more poorly than humans on reversal tasks that evaluate cognitive flexibility. We suggest that dogs, most notably older dogs, use different strategies than healthy humans when solving these tasks. Humans appear to test a priori hypotheses to solve the task at hand. As a consequence, expectations about the complexity of the task being tested can impair human performance. By contrast, dogs appear to rely more heavily on either simpler hypotheses, or associative trial and error learning, which probably accounts for their difficulty in learning non-matching tasks. Dogs also show perseverative responding, which hinders the acquisition of reversal tasks.

Adult↗

PubMed2005

Molecular identification and expression study of differentially regulated genes in the Pacific oyster Crassostrea gigas in response to pesticide exposure.

The effects of pesticide contamination on the metabolism of marine molluscs are poorly documented. We investigated the response of a marine bivalve, the Pacific oyster, Crassostrea gigas, using a suppression subtractive hybridization method to identify up- and down-regulated genes after a 30-day exposure period to herbicides (a cocktail of atrazine, diuron and isoproturon, and to the single herbicide glyphosate). A total of 137 unique differentially expressed gene sequences was identified, as well as their associated physiological process. The expression of 18 of these genes was analyzed by RT-PCR under laboratory experimental conditions. The metabolic functions they are associated with include xenobiotic detoxification, energy production, immune system response and transcription. This study provides a preliminary basis for studying the response of marine bivalves to long-term herbicide exposure in terms of regulated gene expression and characterizes new potential genetic markers of herbicide contamination.

Acetylcholinesterase↗

PubMed2004

Molecular characterization of the glutamine synthetase gene in the Pacific oyster Crassostrea gigas: expression study in response to xenobiotic exposure and developmental stage.

In this study, we characterized the full-length cDNA and genomic sequence of the gene encoding cytosolic glutamine synthetase (CgGSII) in the Pacific oyster, Crassostrea gigas. A phylogenetic analysis of GS sequences showed that CgGS clustered with the invertebrate group as expected. We analyzed the expression of mRNA CgGSII using RT-PCR to follow the expression of this gene in gills and digestive gland of oysters exposed, under experimental conditions, to hypoxia and to several contaminants (hydrocarbons and two pesticide treatments, glyphosate and a mixture of atrazine, diuron and isoproturon). We also investigated the expression of CgGSII in different developmental stages of C. gigas. Our results show that CgGSII expression was highly regulated in xenobiotic-exposed oysters compared to the control for all the treatments. Likewise, CgGSII expression was highly regulated according to the developmental stage of C. gigas. Finally, use of CgGSII as a possible marker to monitor xenobiotic exposure in disturbed ecosystems is discussed.

Amino Acid Sequence↗

PubMed2004

Molecular identification and expression of two non-P450 enzymes, monoamine oxidase A and flavin-containing monooxygenase 2, involved in phase I of xenobiotic biotransformation in the Pacific oyster, Crassostrea gigas.

Marine bivalve metabolism can be perturbed by hydrocarbon and pesticide pollution in coastal ecosystems. In this study, in the Pacific oyster, Crassostrea gigas, full-length cDNAs encoding two non-P450 phase I enzymes, flavin-containing monooxygenase 2 (FMO-2) and monamine oxidase A (MAO A), were characterized. Both sequences contained the co-factor fixation motifs characteristic of their respective enzyme families. Using reverse transcription polymerase chain reaction (RT-PCR), the messenger RNA (mRNA) transcription levels of these two enzymes in tissues of oysters exposed, under experimental conditions, to hydrocarbons and two pesticide treatments were investigated. The pesticide treatments were exposure to either glyphosate or to a mixture composed of atrazine, diuron and isoproturon. The results showed a strong differential expression of FMO-2 and MAO A that was both tissue-specific as well as time- and treatment-dependent. It was also clearly demonstrated that the transcription levels of MAO A (generally considered a constitutive enzyme without external regulation) were induced by hydrocarbons and pesticides in digestive gland and inhibited by pesticides in gill tissue. Furthermore, the transcription levels of FMO-2 and MAO A mRNA in digestive gland might be useful as a marker of hydrocarbon or pesticide exposure in monitoring programs.

Amino Acid Sequence↗

PubMed2004

Response of the Pacific oyster Crassostrea gigas to hydrocarbon contamination under experimental conditions.

Hydrocarbon contamination perturbs the metabolism of the marine bivalve Crassostrea gigas. To understand the response of this organism to hydrocarbon exposure, a suppression subtractive hybridisation method was employed to characterise up- and down-regulated genes during hydrocarbon exposure. The number of differentially expressed gene sequences obtained via this method was 258. The expression of genes involved in hydrocarbon detoxification (cytochrome p4501A1-like protein, cytochrome b(5), flavin-containing monooxygenase 2 and glutathione S-transferase omega class), protection against oxidative stress (copper/zinc superoxide dismutase) and cell protection (heat shock protein 70 family) was analysed by RT-PCR. An increase in the mRNA level of all genes studied was observed. A quantification of HSP70 by Enzyme Linked Immunosorbent Assay (ELISA) showed a significant increase of this protein during exposure. This study provides a basis for studying hydrocarbon detoxification processes in marine bivalves, especially C. gigas.

Animals↗

PubMed2004

Differential impact of the FMR1 gene on visual processing in fragile X syndrome.

Fragile X syndrome (FXS) is the most common form of heritable mental retardation, affecting approximately 1 in 4000 males. The syndrome arises from expansion of a trinucleotide repeat in the 5'-untranslated region of the fragile X mental retardation 1 (FMR1) gene, leading to methylation of the promoter sequence and lack of the fragile X mental retardation protein (FMRP). Affected individuals display a unique neurobehavioural phenotype that includes striking visual-motor deficits. Here we provide neurobiological and behavioural evidence that supports the hypothesis that these visual-motor deficits are attributable to a magnocellular (M) visual pathway impairment. Immunohistochemical staining of a lateral geniculate nucleus (LGN) of a normal human male revealed high FMRP basal expression selectively within the M layers, suggesting an increased susceptibility of these neurons to the lack of FMRP as occurs in FXS. Similar staining of monkey LGNs for quantification purposes revealed that the difference is not an artefact of cell size differences between M and parvocellular (P) neurons. Further, Nissl staining of the LGNs of a male FXS patient revealed alaminar nuclei comprised of a homogenous population of small sized neurons, providing anatomical and morphological support for the idea that an M pathway pathology exists in FXS. Consistent with these neurobiological data, we have found that male patients with FXS have reduced sensitivity for psychophysical stimuli that probe the M pathway but not for those that probe the P pathway, a complementary visual stream that performs a separate set of early visual operations. Finally, male patients with FXS performed poorly on a global motion task but not on a form perception task, suggesting that the M pathway thalamic deficit may have a selective impact on cortical visual functioning in the parietal lobe, which is known to be a major recipient of M pathway afferents via the primary visual cortex. Together, these findings provide the first evidence that the loss of a single gene product, FMRP, in humans leads to abnormal neuroanatomical morphology of the LGN and a concomitant selective visual deficit of the M pathway.

Adolescent↗

PubMed2003

Organization and nucleotide sequence of the European flat oyster Ostrea edulis heat shock cognate 70 (hsc70) and heat shock protein 70 (hsp70) genes.

The heat shock protein 70 family is composed of both environmentally inducible (Hsp) and constitutively expressed (Hsc) members. We sequenced two genes encoding Hsp70 and Hsc70 in the European flat oyster Ostrea edulis. The Oehsc70 gene contained introns, while the Oehsp70 gene did not. The corresponding amino acid sequences contained the characteristic motifs of the HSP70 family.

Amino Acid Sequence↗

PubMed2003

Molecular identification and expression of heat shock cognate 70 (hsc70) and heat shock protein 70 (hsp70) genes in the Pacific oyster Crassostrea gigas.

The 70-kDa heat shock protein (Hsp) family is composed of both environmentally inducible (Hsp) and constitutively expressed (Hsc) family members. We sequenced 2 genes encoding an Hsp70 and an Hsc70 in the Pacific oyster Crassostrea gigas. The Cghsc70 gene contained introns, whereas the Cghsp70 gene did not. Moreover, the corresponding amino acid sequences of the 2 genes presented all the characteristic motifs of the Hsp70 family. We also investigated the expression of Hsp70 in tissues of oysters experimentally exposed to metal. A recombinant Hsc72 was used as an antigen to produce a polyclonal antibody to quantify soluble Hsp70 by enzyme-linked immunosorbent assay in protein samples extracted from oysters. Our results showed that metals (copper and cadmium) induced a decrease in cytosolic Hsp70 level in gills and digestive gland of oysters experimentally exposed to metal. These data suggest that metals may inhibit stress protein synthesis.

Amino Acid Sequence↗

PubMed2003

Configural face encoding and spatial frequency information.

Configural relations and a critical band of spatial frequencies (SFs) in the middle range are particularly important for face recognition. We report the results of four experiments in which the relationship between these two types of information was examined. In Experiments 1, 2A, and 2B, the face inversion effect (FIE) was used to probe configural face encoding. Recognition of upright and inverted faces and nonface objects was measured in four conditions: a no-filter condition and three SF conditions (low, medium, and high frequency). We found significant FIEs of comparable magnitudes for all frequency conditions. In Experiment 3, discrimination of faces on the basis of either configural or featural modifications was measured under the same four conditions. Although the ability to discriminate configural modifications was superior in the medium-frequency condition, so was the ability to discriminate featural modifications. We conclude that the band of SF that is critical for face recognition does not contribute preferentially to configural encoding.

Adolescent↗

PubMed2002

The influence of attention on holistic face encoding.

We examined the influence of attention on the formation of holistic face representations using the composite effect (Perception 16 (1987) 747). In Experiment 1, stimuli composed of a face superimposed on a house were shown during encoding. Subjects delineated either the face or the house, thus manipulating attention away or toward the face. In Experiment 2, an intact face image was presented with letters scrolling from top to bottom. Subjects were asked to either ignore the letters or read them and decipher the words that they formed. Aligned and misaligned composites were shown at testing. Recognition performance was consistently better for misaligned than aligned stimuli, regardless of the allocation of attention during encoding. In Experiment 3, we show that the composite effect can be eliminated by a disruption in holistic processing at the time of encoding. We conclude that holistic encoding is one aspect of face analysis that occurs equally well with or without attention.

Adolescent↗

PubMed2002

Immunochemical quantification of metallothioneins in marine mollusks: characterization of a metal exposure bioindicator.

A recombinant metallothionein CgMT1, from the Pacific oyster Crassostrea gigas, was synthesized and used as antigen in the development of antibodies and a specific enzyme-linked immunosorbent assay (ELISA). The ELISA showed that rabbit anti-CgMT1 IgG reacted with purified CgMT1 and MTs from other marine bivalves, indicating its suitability as a reagent to quantify MTs and for monitoring of metal contamination in field animals. Application of this assay to tissues excised from metal exposed C. gigas, showed that MT induction reached a saturation level in gills that was not observed in digestive gland. Quantification of MTs in gills and digestive gland of field-collected C. gigas showed that the MT level depended on the metal concentrations at the collection sites and may have been influenced by salinity variations at estuarine sites. Oysters from metal-contaminated estuarine sites showed lower MT concentrations than those from nonestuarine contaminated sites.

Animals↗

PubMedDate not supplied

Polymorphism of metallothionein genes in the Pacific oyster Crassostrea gigas as a biomarker of response to metal exposure.

Quantification of metallothioneins (MTs) is classically associated with a cellular response to heavy metal contamination and is used in the monitoring of disturbed ecosystems. Despite the characterization of several MT genes in marine bivalves, only a few genetic studies have used MT genes as potential biomarkers of pollution. The aim of this study was to assess whether MT gene polymorphism could be used to monitor exposure of the Pacific oyster Crassostrea gigas to heavy metals and to develop specific genetic markers for population genetic studies in relation to environmental stress. The polymorphism of two exons of the C. gigas MT gene CgMT1 were studied using polymerase chain reaction single-strand conformation polymorphism (PCR-SSCP) in both field populations exposed to various metals concentrations and in experimentally exposed populations. High frequencies of two SSCP types in exons 2 and 3 of the CgMT1 gene have found to be significantly associated with tolerance to metals in experimental and field oyster populations. The use of MT1 gene polymorphism in C. gigas as in the present study should therefore be of high ecological relevance. In conclusion, the analysis of the types in these two CgMT1 gene exons, which can confer a greater tolerance to heavy metals, can constitute a good biomarker of effect of the presence of heavy metals in ecosystems.

Animals↗