Biomedical subjects

S Michaud

Publications and source records attributed to S Michaud.

17 recordsLinked to original sources

PubMed2002

Particle size fractionation of paralytic shellfish toxins (PSTs): seasonal distribution and bacterial production in the St Lawrence estuary, Canada.

We determined the seasonal distribution of paralytic shellfish toxins (PSTs) and PST producing bacteria in > 15, 5-15, and 0.22-5 microm size fractions in the St Lawrence. We also measured PSTs in a local population of Mytilus edulis. PST concentrations were determined in each size fraction and in laboratory incubations of sub-samples by high performance liquid chromatography (HPLC), including the rigorous elimination of suspected toxin 'imposter' peaks. Mussel toxin levels were determined by mouse bioassay and HPLC. PSTs were detected in all size fractions during the summer sampling season, with 47% of the water column toxin levels associated with particles smaller than Alexandrium tamarense (< 15 microm). Even in the > 15 microm size fraction, we estimated that as much as 92% of PSTs could be associated with particles other than A. tamarense. Our results stress the importance of taking into account the potential presence of PSTs in size fractions other than that containing the known algal producer when attempting to model shellfish intoxication, especially during years of low cell abundance. Finally, our HPLC results confirmed the presence of bacteria capable of autonomous PST production in the St Lawrence as well as demonstrating their regular presence and apparent diversity in the plankton.

Animals↗

PubMed2001

Scanning of estrogen receptor alpha (ERalpha) and thyroid hormone receptor alpha (TRalpha) genes in patients with psychiatric diseases: four missense mutations identified in ERalpha gene.

Estrogen and thyroid hormones exert effects on growth, development, and differentiation of the nervous system. Hormone administration can lead to changes in behavior, suggesting that genetic variants of the estrogen receptor alpha (ERalpha) and the thyroid hormone receptor alpha (TRalpha) genes may predispose to psychiatric diseases. To investigate this possibility, regions of likely functional significance (all coding exons and flanking splice junctions) of the ERalpha and TRalpha genes were scanned in patients with schizophrenia (113), along with pilot studies in patients with bipolar illness (BPI), puerperal psychosis, autism, attention-deficit hyperactivity disorder (ADHD), and alcoholism. A total of 1.18 megabases of the ERalpha gene and 1.16 megabases of the TRalpha gene were scanned with Detection of Virtually All Mutations-SSCP (DOVAM-S), a method that detects virtually all mutations. Four missense mutations, seven silent mutations and one deletion were identified in the ERalpha gene, while only four silent mutations were present in the TRalpha gene. Two of the missense mutations in ERalpha are conserved in the six available mammalian and bird species (H6Y, K299R) and a third sequence variant (P146Q) is conserved in mammals, birds, and Xenopus laevis, hinting that these sequence changes will be of functional significance. These changes were found in one patient each with BPI, puerperal psychosis, and alcoholism, respectively. Analysis of the ERalpha and TRalpha genes in 240 subjects reveals that missense changes and splice site variants are uncommon (1.7% and 0%, respectively). Further analyses are necessary to determine if the missense mutations identified in this study are associated with predisposition or outcome for either psychiatric or nonpsychiatric diseases.

Alleles↗

PubMed2001

Molecular strain typing of Campylobacter jejuni by pulsed-field gel electrophoresis in a single day.

Rapid molecular strain typing is critical for effective outbreak investigation and implementation of infection control measures. Pulsed-field gel electrophoresis is a highly discriminatory technique for Campylobacter jejuni, but generally requires 3-5 days. We describe a simplified protocol for pulsed-field gel electrophoresis that provides high quality typing of C. jejuni isolates in a single day.

Adult↗

PubMed2000

Female adolescents and their sexuality: notions of honour, shame, purity and pollution during the floods.

This paper explores the experiences of female adolescents during the 1998 floods in Bangladesh, focusing on the implications of socio-cultural norms related to notions of honour, shame, purity and pollution. These cultural notions are reinforced with greater emphasis as girls enter their adolescence, regulating their sexuality and gender relationships. In Bangladeshi society, adolescent girls are expected to maintain their virginity until marriage. Contact is limited to one's family and extended relations. Particularly among poorer families, adolescent girls tend to have limited mobility to safeguard their 'purity'. This is to ensure that the girl's reputation does not suffer, thus making it difficult for the girl to get married. For female adolescents in Bangladesh, a disaster situation is a uniquely vulnerable time. Exposure to the unfamiliar environment of flood shelters and relief camps, and unable to maintain their 'space' and privacy from male strangers, a number of the girls were vulnerable to sexual and mental harassment. With the floods, it became difficult for most of the girls to be appropriately 'secluded'. Many were unable to sleep, bathe or get access to latrines in privacy because so many houses and latrines were under the water. Some of the girls who had begun menstruation were distressed at not being able to keep themselves clean. Strong social taboos associated with menstruation and the dirty water that surrounded them made it difficult for the girls to wash their menstrual cloths or change them frequently enough. Many of them became separated from their social network of relations, which caused them a great deal of anxiety and stress. Their difficulty in trying to follow social norms have had far-reaching implications on their health, identity, family and community relations.

Adaptation, Psychological↗

PubMed1999

The nuclear chronicles: gene transcription and molecular traveling.

The transfer and processing of an RNA transcript from its locus of transcription on chromatin through the nuclear membrane to its site of translation on cytoplasmic ribosomes is a long and complex journey involving numerous processes and interactions with various macromolecules. These various steps that regulate gene expression were the subject of the 9th Winternational Symposium of the Canadian Society of Biochemistry and Molecular & Cell Biology held at Manoir du Lac Delage, a small resort centre north of Quebec City on February 12-15, 1999.

Animals↗

PubMed1997

Regulation of heat shock gene induction and expression during Drosophila development.

Some heat shock genes are expressed in the absence of stress during embryogenesis and metamorphosis in the fruit fly Drosophila melanogaster. Their functions in these processes are unknown. During development, each of the four members of the small heat shock protein family (Hsp27, Hsp26 Hsp23 and Hsp22), which are coordinately induced in response to a heat stress, shows a specific pattern of expression in diverse tissues and cells. This expression is driven through cell-specific enhancers in the promoter regions of their genes. In addition, some of the Hsps show cell-specific induction by heat shock. Hsp23, for example, is only inducible in a single cell type (cone cells) of the eye ommatidium, while the other small Hsps are inducible in all cells of the eye unit. In germ line tissues such as testes, Hsp23 and 27 are both readily expressed in the absence of stress (albeit in distinct cell lineages) and cannot be further induced by heat shock. Hsp27 is expressed throughout oogenesis, but its intracellular localization is stage-specific, being nuclear from germarium to stage 6 and cytoplasmic from stage 8 onwards. Finally the small Hsps show tissue-specific post-translational modifications. Thus the function(s) of the small Hsps may be modulated by different cell and developmental stage-specific mechanisms operating either on their expression, their cellular localization or their structure by post-translational modifications.

Animals↗

PubMed1997

Cell-specific expression and heat-shock induction of Hsps during spermatogenesis in Drosophila melanogaster.

The developmental and heat-shock-induced expression of two small heat-shock proteins (Hsp23 and Hsp27) was investigated during spermatogenesis in Drosophila melanogaster. Both of these Hsps were expressed in unstressed and stressed male gonads as shown by immunoblotting. Immunostaining of whole-mount organs and thin sections of testes showed that an anti-Hsp23 antibody specifically decorated cells of the somatic lineage, such as the cyst cells and the epithelial cells of the testis and of the seminal vesicle. Hsp27 was expressed in some somatic cells (cyst cells and epithelial cells of the accessory glands) and, in addition, was also visible in the maturing spermatocytes of the germline. The same cell-specific pattern of expression was observed after heat shock, and cells which did not express Hsp23 and Hsp27 in the absence of stress were similarly unable to mount a heat shock response for these s-Hsps. However other Hsps such as Hsp70 and Hsp22 were induced under heat-shock conditions in testes. Actinomycin D prevented the heat-induced accumulation of these Hsps indicating that the induction of Hsps was regulated at the transcriptional level. The heat shock transcriptional factor of Drosophila (DmHSF), present in significantly lower amount in testes when compared to other tissues such as the head, was shown to be required for the heat activation of Hsp22 and Hsp70. Immunostaining revealed that HSF expression was restricted to specific cells such as cyst cells, epithelial pigment cells, spermatogonia and spermatids but not the primary spermatocytes. These data show that the expression and induction of the different small Hsps is regulated in a cell-specific manner under both normal and heat shock conditions and suggest that factors other than the DmHSF are involved in this regulation in male gonads.

Animals↗

PubMed1996

Atomic spectroscopy with surface wave plasmas.

The use of microwave induced plasmas, particularly of surface wave plasmas, as detectors in atomic emission spectrometry for elemental analysis is reviewed. Surface wave plasmas have been produced at low HF power and used as gas chromatographic detectors. The analytical performances for the detection of non-metals with a Fourier transform spectrometer and a two-channel filter unit are reported. The excitation behavior of non-metals in helium-based mixed gas-plasmas has also be studied. In particular, the effect of power and of nitrogen concentration on the bromine emission has been systematically investigated. A nine-fold improvement of the detection limits for bromine can be obtained in a high power (900 W) helium-nitrogen (0.1-0.2%) plasma.

Journal Article↗

PubMed1993

A functional association between the 5' and 3' splice site is established in the earliest prespliceosome complex (E) in mammals.

The earliest detectable mammalian prespliceosome complex (E) contains the non-snRNP splicing factor U2AF, U1 snRNP, and several spliceosome-associated proteins (SAPs). We show that specific complexes, designated E3' and E5', assemble independently on RNAs containing only a 3' or 5' splice site, respectively. U2AF is enriched in E3', whereas U1 snRNP is enriched in E5'. Using a highly sensitive substrate-competition assay, we show that both the 5' splice site and the pyrimidine tract at the 3' splice site are required for efficient E complex assembly on intact pre-mRNA. We conclude that the 5' and 3' splice sites are associated functionally as early as E complex by either direct or indirect interactions between U1 snRNP and U2AF. Our observations predict that E complex assembly is a major control point for establishing splice site selection in both constitutively and alternatively spliced pre-mRNAs.

Animals↗

PubMed1992

Protein components specifically associated with prespliceosome and spliceosome complexes.

We have carried out a systematic analysis of the protein composition of highly purified mammalian spliceosomes. We show that > 30 distinct proteins, including 20 previously unidentified components [designated spliceosome-associated proteins (SAPs)], are specifically associated with the spliceosome in a salt-resistant complex. In contrast to these spliceosome-specific proteins, we show that hnRNP proteins are not tightly associated with purified prespliceosome and spliceosome complexes. The splicing factor U2AF65, U1 snRNP-specific proteins, and several SAPs are present in the earliest prespliceosome complex (E). A set of 10 proteins is then added to the first ATP-dependent prespliceosome complex (A), and concomitantly, a significant decrease in the level of U2AF65 is observed. The fully assembled spliceosome is formed by the addition of 12 proteins in a reaction that requires ATP and both the 5' and 3' splice sites.

Adenosine Triphosphate↗

PubMed1991

An ATP-independent complex commits pre-mRNA to the mammalian spliceosome assembly pathway.

Previous studies have identified five distinct mammalian splicing complexes that assemble on pre-mRNA in vitro. Of these complexes, which include H, E, A, B, and C, only the B and C complexes have been isolated and shown directly to be functional intermediates in the splicing pathway. In this report we carried out a systematic analysis of the temporal and functional relationships among the H, E, A, and B complexes. Using gel filtration to isolate each complex, we show that H complex, which consists primarily of hnRNP proteins, assembles first in either the presence or absence of ATP. Subsequently, E complex, which contains stably bound U1 snRNP, is detected in reactions lacking ATP, whereas A complex, which contains stably bound U1 and U2 snRNPs, is detected in reactions containing ATP. We show that E complex can be chased into A and B complexes and that A complex can be chased into B complex. Both E and A complexes can also be chased into spliced products. In contrast, H complex cannot be chased into A or B complexes or spliced products under the same conditions. We conclude that in addition to the two spliceosome complexes (B and C), two distinct pre-splicesome complexes (E and A) are functional intermediates in the splicing pathway. Comparison of the efficiency of splicesome assembly on different pre-mRNAs has revealed dramatic differences. We show that these differences are first apparent at the time of E complex assembly. Thus, we conclude that E complex commits pre-mRNA to the splicing pathway and that this step is critical in determining the efficiency of mammalian spliceosome assembly.

Adenosine Triphosphate↗

PubMed1985

Detection of false-positives among total and fecal coliform counts by factorial analysis of correspondence.

Application of an analysis of correspondence to the biochemical characteristics of total and fecal coliforms isolated in the Ivory Coast permitted us to separate two small clusters of isolates different from the main clusters, which included isolates from human and animal feces. The isolates grouped in the small clusters were from water samples. An analysis of the biochemical characteristics which permitted the segregation of the "water-specific" isolates from the main clusters indicates that water-specific total coliforms were citrate positive, indole negative, and amygdaline positive. Water-specific fecal coliforms were either citrate positive, indole negative, amygdaline positive, and inositol negative or indole negative, amygdaline positive, and inositol positive. Any isolates not fitting the above patterns could be considered of fecal origin. If this observation is confirmed under temperate climates and for a greater number of isolates, these simple tests could be used to confirm the fecal origin of coliforms.

Animals↗

PubMed1983

Binding and effects of 5 alpha-androstane-3 beta,17 beta-diol in the male rat pituitary.

5 alpha-androstane-3 beta,17 beta-diol (Adiol) binds to cytosol proteins from male rat pituitary with a relatively high affinity (KD = 15 +/- 6 nM) and a low capacity (n = 92 +/- 8 fmol/mg protein). These saturable proteins which bind Adiol are characterized as estrogen receptor. This conclusion was based on the binding characteristics, the binding stereospecificity and the sedimentation coefficient in sucrose linear gradients. Moreover. Adiol induces, in vivo, the nuclear translocation of estrogen receptor and some effects of estrogen action. It is efficient to induce progesterone receptor and to increase pituitary protein content but inefficient to increase DNA synthesis. Results suggest a mechanism of Adiol action in the male rat pituitary similar to that observed with androgens in other target tissues. Moreover, the study of Adiol and 17 beta-estradiol binding suggests two forms of estrogen receptor in the cytosol from male rat pituitary. The maximal concentration of binding sites was observed at 22-30 days of age for E2 and at 37-42 days of age for Adiol. On the other hand, the nuclear ontogenic pattern suggested a single class of binding sites for E2 and Adiol in the pituitary nuclei.

Androstane-3,17-diol↗

PubMedDate not supplied

Epidemiology of enterococcal bacteremia in a referral center for hepatobiliary diseases.

BACKGROUND: Enterococcus faecium (EFM) and Enterococcus faecalis (EFL) account for most infections which predominantly originate in the abdomen or the urinary tract. The objectives of this study were to compare the risk factors associated with EFM and EFL bacteremia Patients and Method: Retrospective study of 64 EFL and 27 EFM bacteremia cases that occurred between January 1993 and December 1996 in a referral center for hepatobiliary diseases. RESULTS: Univariate predictors of EFM bacteremia, compared to EFL, were an orthoptic liver transplantation (OLT), use of steroids, admission in the hepatology service, a central vascular catheter and an abdominal source. Forward regression models identified OLT as the only independent risk factor for EFM bacteremia (odds ratio, OR = 4.320; p = 0.0064), and septic shock as the only predictor of a fatal enterococcal bacteremia (OR = 13.152; p = 0.0003). Molecular typing of EFM isolates identified four small nosocomial clusters (of two to seven patients each) of EFM bacteremia, involving primarily patients admitted to the intensive care unit or on the hepatology ward. CONCLUSION: Strategies are needed to prevent enterococcal bacteremia in patients with severe liver disease, especially those undergoing OLT.

Adult↗

PubMedDate not supplied

The development of a database for payment card embossing machines.

In order to meet increasing operational demands involving the forensic examination of payment cards, a software program was created to enable the cards to be linked by identifying characteristics found on characters embossed on their plastic surfaces. In doing so, a database was developed, reducing an otherwise insurmountable task into an orderly and efficient process. Counterfeit cards as well as altered genuine cards, from across Canada, can be accurately correlated and linked to the specific embossing machines responsible for their production.

Commerce↗

PubMedDate not supplied

Influence of hydrodynamic conditions on biofilm behavior in a methanogenic inverse turbulent bed reactor.

This paper presents a study about the influence of gas velocity on a methanogenic biofilm in an inverse turbulent bed reactor. Experimental results indicate a dynamic response of the growing attached biomass to the changes of hydrodynamic conditions, mainly attrition constraints. Short but intensive increases of gas velocity (U(g)) are shown to induce more detachment than a high but constant gas flow rate. Hydrodynamic conditions control the composition of the growing biofilm in terms of cells and exocellular polymeric substances (EPS). The cell fraction within the biofilm (R(cell)) was found to be inversely proportional to the gas velocity. The specific activity expressed in methane production rate or COD removal rate is higher in biofilms formed under high hydrodynamic constraints. The control of the hydrodynamic conditions in a biofilm reactor should make it possible to obtain a resistant and active biofilm.

Bacteria, Anaerobic↗

PubMedDate not supplied

External tibial torsion and the effectiveness of the solid ankle-foot orthoses.

The aims of this study were to determine the influence of external tibial torsion on the effectiveness of the ankle-foot orthoses (AFO) in children with lumbosacral myelomeningocele. Forty patients with normal tibial rotation and 18 patients with excessive external tibial torsion were evaluated with three-dimensional gait analysis at their comfortable walking speed. The group with normal tibial rotation showed significantly greater knee extension and lower mean extension moment compared with the group with external tibial torsion (p < 0.05). The posteriorly and laterally deviated ground-reaction force relative to the knee-flexion axis compromises the ability of this force to facilitate knee extension. Patients with torsional magnitudes >20 degrees demand close inspection as candidates for derotation osteotomy. The AFO will continue to stabilize the ankle-foot complex, but improved knee motion, knee-extensor activity, and ultimately walking efficiency may be compromised.

Adolescent↗