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A Brunet

Publications and source records attributed to A Brunet.

At least 19 recordsLinked to original sources
PubMed2002

Class II transactivator-induced expression of HLA-DO(beta) in HeLa cells.

HLA-DO is an intracellular nonclassical MHC class II molecule expressed in the endocytic pathway of B lymphocytes. It shapes the repertoire of peptides bound to classical class II molecules such as HLA-DR by regulating the activity of HLA-DM. Using a peptide corresponding to the cytoplasmic tail of HLA-DO(beta), we have developed a mouse monoclonal antibody, HKC5. Immunofluorescence microscopy revealed that HKC5 recognizes HLA-DO molecules present in the endoplasmic reticulum as well as those in vesicular compartments of the endocytic pathway. In addition, the antibody detects the isolated beta chain on Western blots. Using mutants of the DO(beta) cytoplasmic tail fused to a reporter molecule and expressed in epithelial cells, we showed by flow cytometry that the antibody epitope includes one or both of the leucine residues forming the lysosomal sorting signal. Finally, we have used HKC5 to evaluate the presence of the HLA-DO(beta) chain in HeLa cells expressing the class II transactivator protein CIITA. Our flow cytometry and confocal microscopy analyses showed a marked expression of DO(beta) suggesting that HLA-DO could accumulate under the influence of CIITA in non-B cells.

Animals↗
PubMed2002

[Remodelling the aortic root by resection of the ascending aorta and non-coronary sinus in annular dilatation of the aorta and acute dissection of the descending aorta. 29 observations].

The first conservative surgical procedures of the native aortic valve in annular dilatation were performed by Yacoub and David [1, 2]. These so-called remodelling and inclusion procedures provided hope for a normal life without long-term anticoagulant therapy for patients with Marfan's syndrome, with protection from the complication of an acute dissection of the ascending aorta. The authors reported their experience in the Archives des Maladies du Coeur et des Vaisseaux in 1999, with excellent results [3]. However, a certain number of cases are encountered in which the Yacoub and David procedures cannot be performed because of the presence of a pseudo-bicuspid valve, isolated asymmetrical dilatation of the non-coronary sinus or acute dissection of the aorta without dilatation of the aortic root. In these forms, the authors have developed a technique of remodelling the aortic root with conservation of the native valve by resecting the ascending aorta and non-coronary sinus, rather than carrying out a Bentall procedure. Twenty-nine cases of this type have been treated in this way for three different indications: aneurysm of the ascending aorta with bicuspid aortic valve, aneurysm of the ascending aorta with aortic insufficiency and extension to the posterior sinus, and type A acute dissection of the aorta.

Adult↗
PubMed2001

[Transition metals and nitric oxide production in human endothelial cells].

The bioavailability of endothelial nitric oxide (NO) is regulated by transition metals but their mechanisms of action on NO synthesis and degradation are not clearly understood. Using differential pulse amperometry and NO microelectrodes, local NO concentration was measured at the surface of cultured human umbilical vein endothelial cells (HUVECs) stimulated by histamine or thrombin in the presence of transition metal chelators. The agonist-activated NO release required both extracellular Ca2+ and transition metals. In the presence of 1 mM external Ca2+, a low concentration of EGTA (5 microM) inhibited by 40% the NO release from stimulated HUVECs. In the presence of extracellular L-arginine, the inhibitory effect of EGTA was even more marked and, in its absence, it was suppressed by adding exogenous superoxide dismutase. The decrease in NO release induced by the copper chelators, cuprizone and DETC, suggests that extracellular traces of Cu2+ could regulate NO availability.

Arginine↗
PubMed2001

Transcription-dependent and -independent control of neuronal survival by the PI3K-Akt signaling pathway.

The PI3K-Akt signaling pathway plays a critical role in mediating survival signals in a wide range of neuronal cell types. The recent identification of a number of substrates for the serine/threonine kinase Akt suggests that it blocks cell death by both impinging on the cytoplasmic cell death machinery and by regulating the expression of genes involved in cell death and survival. In addition, recent experiments suggest that Akt may also use metabolic pathways to regulate cell survival.

Animals↗
PubMed2001

Analysis of agonist-evoked nitric oxide release from human endothelial cells: role of superoxide anion.

1. Dichlorofluorescein oxidation and electrochemical monitoring of in situ nitric oxide (NO) release from cultured human endothelial cells reveals that agonists such as thrombin and histamine simultaneously stimulate transient superoxide production. 2. The duration of *NO release was increased only in the simultaneous presence of extracellular L-arginine and exogenous superoxide dismutase. In contrast, the inhibition of membrane reduced nicotinamide adenine dinucleotide (phosphate) oxidases, the major source of *O2- in endothelial cells, did not prolong *NO release, although extracellular L-arginine was also present. Comparison of these two experimental conditions suggested that H2O2 was involved in the extension of the *NO signal. 3. The present study demonstrates that, in the absence of external L-arginine, *O2- production does not constitute the major pathway controlling the duration of agonist-induced *NO signal. These results suggest that L-arginine and H2O2 act jointly to maintain nitric oxide synthase in an activated form.

Arginine↗
PubMed2001

Transforming growth factor beta enhances epithelial cell survival via Akt-dependent regulation of FKHRL1.

The Forkhead family of transcription factors participates in the induction of death-related genes. In NMuMG and 4T1 mammary epithelial cells, transforming growth factor beta (TGF beta) induced phosphorylation and cytoplasmic retention of the Forkhead factor FKHRL1, while reducing FHKRL1-dependent transcriptional activity. TGF beta-induced FKHRL1 phosphorylation and nuclear exclusion were inhibited by LY294002, an inhibitor of phosphatidylinositol-3 kinase. A triple mutant of FKHRL1, in which all three Akt phosphorylation sites have been mutated (TM-FKHRL1), did not translocate to the cytoplasm in response to TGF beta. In HaCaT keratinocytes, expression of dominant-negative Akt prevented TGF beta-induced 1) reduction of Forkhead-dependent transcription, 2) FKHRL1 phosphorylation, and 3) nuclear exclusion of FKRHL1. Forced expression of either wild-type (WT) or TM-FKHRL1, but not a FKHRL1 mutant with deletion of the transactivation domain, resulted in NMuMG mammary cell apoptosis. Evidence of nuclear fragmentation colocalized to cells with expression of WT- or TM-FKHRL1. The apoptotic effect of WT-FKHRL1 but not TM-FKHRL1 was prevented by exogenous TGF beta. Serum starvation-induced apoptosis was also inhibited by TGF beta in NMuMG and HaCaT cells. Finally, dominant-negative Akt abrogated the antiapoptotic effect of TGF beta. Taken together, these data suggest that TGF beta may play a role in epithelial cell survival via Akt-dependent regulation of FKHRL1.

Active Transport, Cell Nucleus↗
PubMed2001

Protein kinase SGK mediates survival signals by phosphorylating the forkhead transcription factor FKHRL1 (FOXO3a).

Serum- and glucocorticoid-inducible kinases (SGKs) form a novel family of serine/threonine kinases that are activated in response to a variety of extracellular stimuli. SGKs are related to Akt (also called PKB), a serine/threonine kinase that plays a crucial role in promoting cell survival. Like Akt, SGKs are activated by the phosphoinositide-3 kinase (PI3K) and translocate to the nucleus upon growth factor stimulation. However the physiological substrates and cellular functions of SGKs remained to be identified. We hypothesized that SGKs regulate cellular functions in concert with Akt by phosphorylating common targets within the nucleus. The best-characterized nuclear substrates of Akt are transcription factors of the Forkhead family. Akt phosphorylates Forkhead transcription factors such as FKHRL1, leading to FKHRL1's exit from the nucleus and the consequent shutoff of FKHRL1 target genes. We show here that SGK1, like Akt, promotes cell survival and that it does so in part by phosphorylating and inactivating FKHRL1. However, SGK and Akt display differences with respect to the efficacy with which they phosphorylate the three regulatory sites on FKHRL1. While both kinases can phosphorylate Thr-32, SGK displays a marked preference for Ser-315 whereas Akt favors Ser-253. These findings suggest that SGK and Akt may coordinately regulate the function of FKHRL1 by phosphorylating this transcription factor at distinct sites. The efficient phosphorylation of these three sites on FKHRL1 by SGK and Akt appears to be critical to the ability of growth factors to suppress FKHRL1-dependent transcription, thereby preventing FKHRL1 from inducing cell cycle arrest and apoptosis. These findings indicate that SGK acts in concert with Akt to propagate the effects of PI3K activation within the nucleus and to mediate the biological outputs of PI3K signaling, including cell survival and cell cycle progression.

Animals↗
PubMed2001

The Peritraumatic Distress Inventory: a proposed measure of PTSD criterion A2.

OBJECTIVE: Meeting criterion A2 for the diagnosis of posttraumatic stress disorder (PTSD) in DSM-IV requires that an individual have high levels of distress during or after the traumatic event. Because of the paucity of valid and reliable instruments for assessing such responses, the authors developed a 13-item self-report measure, the Peritraumatic Distress Inventory, to obtain a quantitative measure of the level of distress experienced during and immediately after a traumatic event. METHOD: The cross-sectional study group comprised 702 police officers and 301 matched nonpolice comparison subjects varying in ethnicity and gender who were exposed to a wide range of critical incidents. RESULTS: The Peritraumatic Distress Inventory was found to be internally consistent, with good test-retest reliability and good convergent and divergent validity. Even after controlling for peritraumatic dissociation and for general psychopathology, the authors found that Peritraumatic Distress Inventory scores correlated with two measures of posttraumatic stress symptoms. CONCLUSIONS: The Peritraumatic Distress Inventory holds promise as a measure of PTSD criterion A2. Future studies should prospectively examine the ability of the Peritraumatic Distress Inventory to predict PTSD and its associated biological and cognitive correlates in other trauma-exposed groups.

Adult↗
PubMed2001

Posttraumatic stress disorder, trauma exposure, and the current health of Canadian bus drivers.

OBJECTIVE: Previous studies of veterans have linked posttraumatic stress disorder (PTSD) after combat-related trauma to increased reports of health problems. It is unclear whether this association between PTSD and increased health problems generalizes to civilians who are exposed to a broader array of traumatic events. We also do not know whether trauma exposure is associated with increased health problems in individuals who do not develop PTSD. Using a non-treatment-seeking civilian sample, we examined whether lifetime PTSD or trauma exposure by itself was associated with current health problems. METHODS: Using a cross-sectional design and self-report measures, we evaluated urban Canadian bus drivers (n = 342) on trauma exposure, lifetime PTSD, and current health problems. Based on their responses, we divided our sample into individuals who had never experienced trauma (n = 91), trauma-exposed individuals who had never developed PTSD (n = 218), and persons who developed PTSD at some point after trauma (n = 33). We compared these groups on health problems, treatment service use, and health assessment measures. RESULTS: The PTSD group reported increased health complaints, more frequent use of health treatments, and poorer health self-ratings compared with the exposed non-PTSD and nonexposed groups. Trauma-exposed drivers without PTSD did not differ from unexposed drivers on any health measure. Controlling for sex and trauma frequency did not alter our findings. CONCLUSIONS: Trauma exposure that leads to PTSD is associated with increased health problems, while trauma exposure alone is not. Our results extend previous findings to a broader civilian context and clarify associations between trauma exposure and health.

Adult↗
PubMed2001

Developing a training program to improve supervisor-resident relationships, step 1: defining the types of issues.

BACKGROUND: By some estimates, the teacher-learner relationship explains roughly half of the variance attributed to the effectiveness of teaching. Despite this, relationships largely have been ignored in the educational literature. PURPOSE: This qualitative pilot study sought to identify factors in the supervisor-resident relationship that hinder learning among University of Toronto psychiatry residents. METHOD: Thirteen postgraduate-year residents in Years 2-5 and their supervisors were interviewed regarding interactions that either assisted or adversely affected learning. RESULTS: Qualitative analysis of the interview data led to the identification of 5 types of issues affecting the supervisory relationship: goals and individual differences, communication and feedback, power and rivalry, support and collegiality, and role modeling and expertise. Face validity was supported when typed anonymous written feedback obtained from annual supervisor evaluations also could be organized into the 5 categories. CONCLUSIONS: Recognition of the types of interpersonal interactions that assist or hinder learning may contribute to enhanced teaching effectiveness.

Canada↗
PubMed2000

Functional characterization of a lysosomal sorting motif in the cytoplasmic tail of HLA-DObeta.

HLA-DO is an intracellular non-classical class II major histocompatibility complex molecule expressed in the endocytic pathway of B lymphocytes, which regulates the loading of antigenic peptides onto classical class II molecules such as HLA-DR. The activity of HLA-DO is mediated through its interaction with the peptide editor HLA-DM. Here, our results demonstrate that although HLA-DO is absolutely dependent on its association with DM to egress the endoplasmic reticulum, the cytoplasmic portion of its beta chain encodes a functional lysosomal sorting signal. By confocal microscopy and flow cytometry analysis, we show that reporter transmembrane molecules fused to the cytoplasmic tail of HLA-DObeta accumulated in Lamp-1(+) vesicles of transfected HeLa cells. Mutagenesis of a leucine-leucine motif abrogated lysosomal accumulation and resulted in cell surface redistribution of reporter molecules. Finally, we show that mutation of the di-leucine sequence in DObeta did not alter its lysosomal sorting when associated with DM molecules. Taken together, these results demonstrate that lysosomal expression of the DO-DM complex is mediated primarily by the tyrosine-based motif of HLA-DM and suggest that the DObeta-encoded motif is involved in the fine-tuning of the intracellular sorting.

Amino Acid Sequence↗
PubMed2000

Substrate recognition domains within extracellular signal-regulated kinase mediate binding and catalytic activation of mitogen-activated protein kinase phosphatase-3.

Mitogen-activated protein (MAP) kinase phosphatase-3 (MKP-3) is a dual specificity phosphatase that inactivates extracellular signal-regulated kinase (ERK) MAP kinases. This reflects tight and specific binding between ERK and the MKP-3 amino terminus with consequent phosphatase activation and dephosphorylation of the bound MAP kinase. We have used a series of p38/ERK chimeric molecules to identify domains within ERK necessary for binding and catalytic activation of MKP-3. These studies demonstrate that ERK kinase subdomains V-XI are necessary and sufficient for binding and catalytic activation of MKP-3. These domains constitute the major COOH-terminal structural lobe of ERK. p38/ERK chimeras possessing these regions display increased sensitivity to inactivation by MKP-3. These data also reveal an overlap between ERK domains interacting with MKP-3 and those known to confer substrate specificity on the ERK MAP kinase. Consistent with this, we show that peptides representing docking sites within the target substrates Elk-1 and p90(rsk) inhibit ERK-dependent activation of MKP-3. In addition, abolition of ERK-dependent phosphatase activation following mutation of a putative kinase interaction motif (KIM) within the MKP-3 NH(2) terminus suggests that key sites of contact for the ERK COOH-terminal structural lobe include residues localized between the Cdc25 homology domains (CH2) found conserved between members of the DSP gene family.

Amino Acid Sequence↗
PubMed2000

Differential regulation of the translation and the stability of two maternal transcripts in preimplantation rabbit embryos.

In most species, transcription is essentially silent during the first mitotic cell cycles that follow fertilization. This means that the regulation of gene expression in early embryos heavily relies on the translational activation or inactivation of maternal mRNAs. In mammals, the mechanisms that control the translation of maternal mRNAs have been mainly studied in the mouse when maternal to zygotic transition occurs after the first mitotic division. In other mammalian species, however, this transition occurs later after several cell cycles, and little is known concerning the regulation of maternal information during this period. To address this question, we have used rabbit pre-implantation embryos to analyze the translational activation and stability of two maternal mRNAs, mm 41 and mm61. During the cleavage period, these mRNAs exhibit distinct kinetics for both their translational activation and degradation. In addition, these mRNAs both undergo cytoplasmic polyadenylation but with different efficiencies. This polyadenylation was functionally correlated with the translational activation of these mRNAs; inhibiting polyadenylation prevented translational activation. The differential efficiency of cytoplasmic polyadenylation, driven by cis-elements in the 3' untranslated region of these mRNAs, was also observed in Xenopus laevis embryos, which emphasizes the high conservation of this mechanism between species.

3' Untranslated Regions↗
PubMed2000

Dose-finding study of paclitaxel and carboplatin in patients with advanced non-small cell lung cancer.

This dose-finding study was designed to determine the maximum tolerated dose (MTD), efficacy and toxicity of combined paclitaxel and carboplatin in 35 previously untreated patients with advanced non-small cell lung cancer (NSCLC). Paclitaxel was given as a 3-h infusion at escalating dose levels (100-250 mg/m2) immediately followed by carboplatin as a 30-min infusion (325 or 350 mg/m2) every 3 weeks. The dose-limiting toxicity, paresthesia, occurred at the highest dose level, therefore the recommended dose was established one level below (paclitaxel 225 mg/m2 with carboplatin 325 mg/m2). Neutropenia was the most common hematotoxicity; dose dependency was not apparent. Two patients, at different dose levels, had febrile neutropenia. Thrombocytopenia was rare. Non-hematological toxicities grade 3 or higher included infection, anorexia, alopecia and paresthesia. One patient had a hypersensitivity reaction (transient hypotension). The overall response rate was 23% and median survival time was 7.5 months. Promising activity and acceptable toxicity supports the development of this combination as a useful chemotherapeutic option in advanced NSCLC.

Adult↗
PubMed2000

Influence of SIN-1 on platelet Ca2+ handling in patients with suspected coronary artery disease: ex vivo and in vitro studies.

The 3-morpholinosydnonimine (SIN-1) generates both nitric oxide (NO) and superoxide anion (O2-). It elicits dose-dependent vasodilation in vivo, in spite of the opposite effects of its breakdown products on vascular tone and platelet aggregation. This study was designed to investigate the influence of intravenous SIN-1 injection on platelet Ca2+ handling in patients undergoing coronary angiography. SIN-1 administration reduced cytosolic [Ca2+] in unstimulated platelets by decreasing Ca2+ influx. It attenuated Ca2+ mobilization from internal stores evoked by thrombin or thapsigargin. In vitro studies were used as an approach to investigate how simultaneous productions of NO and O2- from SIN-1 modify thrombin- or thapsigargin-induced platelet Ca2+ mobilization. Superoxide dismutase, the O2- scavenger, enhanced the capacity of SIN-1 to inhibit Ca2+ mobilization but catalase had no effect. This suggests that the effects of SIN-1 on platelet Ca2+ handling resemble those of NO, but are modulated by simultaneous O2- release, independently of H2O2 formation.

Angina Pectoris↗
PubMed1999

Cell survival promoted by the Ras-MAPK signaling pathway by transcription-dependent and -independent mechanisms.

A mechanism by which the Ras-mitogen-activated protein kinase (MAPK) signaling pathway mediates growth factor-dependent cell survival was characterized. The MAPK-activated kinases, the Rsks, catalyzed the phosphorylation of the pro-apoptotic protein BAD at serine 112 both in vitro and in vivo. The Rsk-induced phosphorylation of BAD at serine 112 suppressed BAD-mediated apoptosis in neurons. Rsks also are known to phosphorylate the transcription factor CREB (cAMP response element-binding protein) at serine 133. Activated CREB promoted cell survival, and inhibition of CREB phosphorylation at serine 133 triggered apoptosis. These findings suggest that the MAPK signaling pathway promotes cell survival by a dual mechanism comprising the posttranslational modification and inactivation of a component of the cell death machinery and the increased transcription of pro-survival genes.

Animals↗