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Biomedical subjects

L Couture

Publications and source records attributed to L Couture.

At least 19 recordsLinked to original sources
PubMed2004

Induction of infertility in adult male bonnet monkeys by immunization with phage-expressed peptides of the extracellular domain of FSH receptor.

Active immunization of proven fertile adult male bonnet monkeys (Macaca radiata) with phage-expressed follicle-stimulating hormone receptor (FSHR)-specific peptides from the extracellular domain resulted in a progressive drop in sperm count with all animals becoming azoospermic by day 100. However, serum testosterone concentrations were unaltered during the entire course of study and animals exhibited normal mating behaviour. Breeding studies with proven fertile female monkeys revealed that all the immunized males were infertile. Following interruption of immunization on day 225, sperm counts returned to normal with restoration of fertility. These results indicate that infertility can be induced in adult male monkeys by interfering with the action of FSH using specific peptides of the extracellular domain of FSHR as antigens, without the risk of producing cross-reacting antibodies to the other glycoprotein hormones.

Animals↗
PubMed2001

Effect of antidepressants on ATP-dependent calcium uptake by neuronal endoplasmic reticulum.

This study investigated the effect of tricyclic and atypical antidepressants on adenosine triphosphate (ATP) dependent calcium uptake by the endoplasmic reticulum of lysed synaptosomes from rat brain cortex. Tricyclic antidepressants (imipramine, desipramine, clomipramine, amitriptyline) exhibited no effect in the lower range (0.06 to 2 microM) of drug concentrations, and a concentration-dependent inhibition of calcium uptake in the upper range (6 to 200 microM). A concentration-dependent inhibition was observed for atypical antidepressants (mianserin, desmethylmianserin, venlafaxine, desmethylvenlafaxine, fluoxetine) in both the lower and the upper range of drug concentrations. Since no stimulation of calcium uptake was observed in either concentration range, it appears that the tricyclic and atypical antidepressants tested are not capable of normalizing, through their effect on the endoplasmic reticulum, an overactive calcium signal. which is possibly implicated in the etiology of affective disorders. Also, although only marginal inhibition of calcium uptake is expected at brain concentrations of tricyclics and mianserin-desmethylmianserin that are likely to be encountered during clinical use, a more substantial inhibition could occur with fluoxetine.

Adenosine Triphosphate↗
PubMed2000

Purification and structural analysis of a soluble human chorionogonadotropin hormone-receptor complex.

Receptors for the luteotropin/human chorionogonadotropin hormone belong to the G-protein-coupled receptor family by their membrane-anchoring domains. They also possess a large extracellular domain (ECD) responsible for most of the hormone-receptor interactions. Structure-function studies identified several contacts between hormone and receptor ECD, but the precise topology of the complex is still unknown because of the lack of suitable heterologous expression means. Receptor ECDs exhibit leucine repeats and have been modelized on the basis of the three-dimensional structure of the porcine ribonuclease inhibitor, the first structurally known leucine-rich repeats protein. Here we report overexpression (up to 20 mg per liter) and purification to homogeneity of a soluble human chorionogonadotropin-ECD receptor complex secreted by stably cotransfected Chinese hamster ovary cells. Biochemical analysis and surface plasmon resonance data were in favor of a unique dimer with a 1:1 ligand-receptor stoichiometry. Immunopurified complex was submitted to circular dichroism characterization; CD spectra deconvolution indicated more than 25% alpha helices contributed by the receptor, in agreement with the porcine ribonuclease inhibitor-based modelization.

Base Sequence↗
PubMed1999

Inhibition of human immunodeficiency virus type 1 by Tat/Rev-regulated expression of cytosine deaminase, interferon alpha2, or diphtheria toxin compared with inhibition by transdominant Rev.

A retroviral vector was designed to express toxic proteins only in the presence of the HIV-1 Rev and/or Tat protein(s). The design of this vector incorporates an HIV-specific expression cassette that consists of three elements: the U3R region of the HIV-1 IIIB LTR provides the promoter and Tat-responsive element, a modified intron derived from the human c-src gene facilitates the splicing of inserted genes, and the HIV-1 RRE region enhances the transport of unspliced mRNAs. To further limit potential readthrough transcription, the expression cassette was inserted in the reverse transcriptional orientation relative to the retroviral vector LTR. Three different genes, interferon alpha2, diphtheria toxin (DT-A), and cytosine deaminase, were inserted into this vector. Tat and Rev inducibility was demonstrated directly by a >300-fold induction of interferon production and functionally by a decrease in colony-forming units when a Tat and Rev expression vector was titered on HeLa cells harboring the inducible DT-A cassette. The Tat-inducible cytosine deaminase gene was tested in the Sup-T1 T cell line and shown to inhibit HIV-1 production only when engineered cells were grown in the presence of 5-fluorocytosine. To test the ability of this system to inhibit HIV-1 infection in bulk PBL cultures, a series of transduction and challenge experiments was initiated with both the interferon and DT-A vectors. Protection against infection was documented against three HIV strains in PBLs. Last, the interferon and DT-A vectors were compared with a vector encoding a transdominant Rev protein and were shown to mediate equal or greater inhibition of HIV-1.

Blotting, Northern↗
PubMed1999

Chitosan treatment of wheat seeds induces resistance to Fusarium graminearum and improves seed quality.

Chitosan treatment (2-8 mg/mL) of wheat seeds significantly improved seed germination to recommended seed certification standards (>85%) and vigor at concentrations >4 mg/mL, in two cultivars of spring wheat (Norseman and Max), by controlling seed-borne Fusarium graminearum infection. The germination was <80% in the control and >85% in benomyl- and chitosan-treated seeds. Seed-borne F. graminearum was reduced to >50% at higher chitosan treatments compared to the control. Synthesis of phenolic acids was stimulated in primary leaves following chitosan treatment, and levels of these phenolic acids, especially ferulic acid, increased significantly with increasing chitosan concentration. Lignin content of primary leaves also showed a similar pattern. The synthesis of precursors of lignin such as p-coumaric, ferulic, and sinapic acids and phenolic acids having antimicrobial activity such as benzoic, p-coumaric, caffeic, protocatechuic, chlorogenic, ferulic, and gallic acids was also stimulated by chitosan treatment. The induction of phenolic acids and lignin was significantly lower in cv. Max compared to Norseman. Chitosan also inhibited fungal transmission to the primary roots of germinating seedlings. Results suggest that chitosan controlled seed-borne F. graminearum infection and increased the resistance in seedlings by stimulating the accumulation of phenolics and lignin. Thus, chitosan has a potential for improvement of seed quality and enhancement of crop yields as well as increased value of stored grains for food and feed.

Benomyl↗
PubMed1999

Critical relationship between glycosylation of recombinant lutropin receptor ectodomain and its secretion from baculovirus-infected insect cells.

The lutropin receptor ectodomain overexpressed under the control of the powerful polyhedrin promoter in baculovirus-infected Sf9 insect cells, is mainly found in an inactive, intracellularly-aggregated form. It is secreted in an active form under the control of the P10 promoter, a somewhat weaker and earlier promoter, at the price of a lower production. The apparent molecular masses of the two species encoded by the same cDNA are 48 kDa and 60-68 kDa, respectively. The relationship between the extent and type of glycosylation and the extracellular targeting for the recombinant lutropin receptor ectodomains was investigated precisely with endoglycosidases, lectins of various specificities, and a glycosylation inhibitor, and tested with monoclonal and polyclonal antibodies. The results indicate that the strong polyhedrin promoter probably overwhelms the processing capacity of the ER in Sf9 cells, so that only a high-mannose precursor is expressed in large amounts. Only a minute amount of protein is secreted, which has been processed by Sf9 exoglycosidases/glycosyltransferases and bears complex/hybrid oligosaccharides. The weaker P10 promoter allows secretion of a mature and active receptor ectodomain, bearing complex glycosylation. An important O-linked glycosylation is also added post-translationally on this species. In particular, beta-galactose and sialic acid residues were specifically detected in the secreted species, evidence of the induction of the corresponding glycosyltransferases or of their genes. These results suggest that Sf9 cells should eventually be engineered with chaperones and glycosyltransferases in order to improve the production of demanding glycoproteins such as the porcine lutropin ectodomain, so as to open the way to resolution of the three-dimensional structures of these receptors.

Amino Acid Sequence↗
PubMed1999

Adenovirus-mediated expression of a ribozyme to c-myb mRNA inhibits smooth muscle cell proliferation and neointima formation in vivo.

Smooth muscle cell (SMC) proliferation is an important component of restenosis in response to injury after balloon angioplasty. Inhibition of proliferation in vivo can limit neointima hyperplasia in animal models of restenosis. Ribozymes against c-myb mRNA have been shown to be effective inhibitors of SMC proliferation in vitro. The effectiveness of adenovirus as a gene therapy vector in animal models of restenosis is well documented. In order to test the utility of ribozymes to inhibit SMC proliferation by a gene therapy approach, recombinant adenovirus expressing ribozymes against c-myb mRNA was generated and tested both in vitro and in vivo. This adenovirus ribozyme vector is shown to inhibit SMC proliferation in culture and neointima formation in a rat carotid artery balloon injury model of restenosis.

Adenoviridae↗
PubMed1999

Generating FSH antagonists and agonists through immunization against FSH receptor N-terminal decapeptides.

Follicle-stimulating hormone (FSH) via interaction with G-protein coupled specific receptors plays a central role in the control of gametogenesis in mammals of both sexes. In females, FSH is crucial for follicle growth, follicle maturation and ovulation. FSH receptors, together with luteinizing hormone-chorionic gonadotropin and thyrotropin receptors belong to a subfamily of structurally related receptors within the seven transmembrane receptor family. Among several other regions, the N-terminus of these receptors is believed to be responsible for important specific hormone-receptor contact sites. Recombinant filamentous phages displaying at their surface three overlapping N-terminal decapeptides of the FSH receptor, peptides A18-27, B25-34 and C29-38 were constructed. Ewes and female mice were immunized against the three FSH receptor (FSHR) recombinant phages. Immunoglobulins purified from immunized animals were analyzed for their biochemical properties on a Chinese hamster ovary cell line expressing the porcine FSH receptor. AntiA and antiB immunoglobulins (IgGs) behave as antagonists for 125I-FSH binding and for FSH-dependent cAMP production, while antiC IgGs did not compete for hormone binding. By contrast, antibodies against the C29-38 peptide displayed FSH agonist activity and stimulated the FSH receptor, whereas antiA and antiB IgGs did not. Furthermore, when the FSHR phages were used as peptidic vaccines, they induced a reversible inhibition of ovulation rate in ewes, and impaired fertility in female mice.

Amino Acid Sequence↗
PubMed1998

Type I protein C deficiency in French Canadians: evidence of a founder effect and association of specific protein C gene mutations with plasma protein C levels.

Protein C (PROC) deficiency is one of the most common autosomal codominant diseases. Although more than 150 germline mutations in the PROC gene have been described around the world, the spectrum of mutations among French Canadians is unknown. We have identified one frameshift (3363 ins C) and two missense mutations (R178Q and T298M) in 7 French Canadian families with type I PROC deficiency. In order to demonstrate a possible founder effect for the 3363 ins C mutation, we have constructed a high-resolution genetic map to locate several highly polymorphic markers close to PROC locus. We have then genotyped five markers in 36 heterozygotes for the 3363 ins C mutation. Our data suggest that these patients carry a common haplotype at the PROC locus. Immunologic plasma PROC levels of heterozygotes and genetically normal relatives were also correlated with the nature of the mutation in the coding sequence and with the genotype of three polymorphisms in the PROC promoter. We found that the mean immunologic plasma PROC levels were lower in heterozygotes for the frameshift mutation 3363 ins C compared to heterozygotes for one of the two missense mutations R178Q and T298M (0.46 vs 0.61; P = 0.0004). Moreover, this difference cannot be explained by the genetic variation of the three polymorphisms in the PROC promoter which accounts for only 10.4% of the variation of immunologic PROC levels in non-deficient subjects. These results suggest that the nature of the mutation in the coding sequence of PROC gene may modulate immunologic plasma PROC levels.

Adult↗
PubMed1997

Temperature during cardiopulmonary bypass for coronary artery operations does not influence postoperative cognitive function: a prospective, randomized trial.

OBJECTIVE: The objective was to examine the effect of temperature (28 degrees vs 36 degrees C) during cardiopulmonary bypass on postoperative cognitive functions in a prospective, double-blind, and randomized manner. METHODS: Sixty-two patients scheduled for coronary operations were randomized to warm or cold cardiopulmonary bypass. Preoperative and postoperative (7 days) neuropsychologic evaluations were performed by an observer unaware of cardiopulmonary bypass temperature. RESULTS: Fifty-four patients completed the study (cold bypass, n = 24; warm bypass, n = 30). Significant (p < 0.01) postoperative deterioration for tests of psychomotor coordination and verbal memory was noted in both warm and cold groups, but no differences were observed between groups. CONCLUSION: Temperature during cardiopulmonary bypass for coronary operations does not influence postoperative cognitive function.

Adult↗
PubMed1996

Mapping of HCG-receptor complexes.

Molecular forms of the porcine LH/CG receptor (pLHR) and complexes between hCG and either the full-length pLHR or its extracellular domain (ectodomain) have been produced in various recombinant systems. In COS cells and in the baculovirus insect cells system, the co-expression of the ecto- and endo-domains reconstituted a functional receptor where the association of the two domains seems to depend upon the presence of disulfide bridges. According to previous observations [39], synthetic peptides mimicking three regions of the ectodomain (21-38, 100-115, 250-272) were found to inhibit hormone binding and stimulation of cAMP production. Antisera raised against these peptides contained anti-peptide antibodies (Ab) able to interfere with hormone signalling. Moreover, the results of peptide mapping indicated that some peptides stretches may be more involved in signalling rather than in binding. Immunochemical mapping based on monoclonal antibodies (mAbs) was used to probe the hCG-ectodomain complex. It appeared that mAbs directed to epitopes present on the 'beta-tip' of hCG (assembled from the beta subunit loops 3 and 1, and previously designated site IIIb) and on the 'alpha-tip' (alpha subunit loops 1 and 3, site IIIa) bound to hCG-receptor complexes, whereas a conformational epitope (defined by the alpha-beta interface between beta seat belt C-terminus and alpha loop 2, site II) was masked. Interestingly, we and others previously reported that, in the hCG-full length receptor complex, site IIIa was shielded to mAb binding. A peptide mimicking the second extracellular loop (EL2) of the receptor endodomain was found to prevent the binding of a mAb directed to site IIIa, suggesting that this region of the endodomain may be interacting with the 'alpha-tip'. In the full-length, membrane anchored pLHR, the EL2 peptide inhibited hCG-induced cAMP production, but not binding. The possibility of inhibiting stimulation without inhibition of binding gives support to the 'negative specificity' hypothesis [6]. Thus, the ectodomain of the glycoprotein hormone receptors might be considered as a screening device preventing access of any glycoprotein hormone to the signalling peptide keys of the endodomain, which otherwise would be sensitive to any alpha subunit stimulation. Finally, antibody binding to site IIIa on the hCG-ectodomain complex was also hindered by an anti-peptide mAb directed against a peptide encoded by the eighth exon (pE x 8) of the LHR. This suggests that pEx8 is vicinal to the alpha-tip of hCG and to EL2 in the hCG-full length receptor complex. Altogether, these observations help to build up a topological model of the hCG-receptor complex.

Amino Acid Sequence↗
PubMed1996

A defined epitope on the human choriogonadotropin alpha-subunit interacts with the second extracellular loop of the transmembrane domain of the lutropin/choriogonadotropin receptor.

The monoclonal antibody, HT13 recognizes human choriogonadotropin (CG) bound to the extracellular domain of its receptor, but not to the full-length receptor. The HT13 epitope is located in the regions of residues 15-17 and 73-75 of the human CG alpha-subunit. Only one synthetic peptide, lutropin (LH)/CG-receptor-(481-497)-peptide (EL2 peptide), which spans the second putative extracellular loop of the LH/CG-receptor endodomain, prevents recognition of human CG by HT13 mAb. EL2 peptide decreases hormone-induced cAMP production, but not high-affinity binding. An anti-EL2 serum also displays the capacity to inhibit human CG-stimulated cAMP production. These results suggest that the second extracellular loop of the receptor is in contact with the HT13 epitope of human CG alpha-subunit and is involved in signal transduction. A relative orientation of the hormone versus the endodomain is proposed.

Amino Acid Sequence↗
PubMed1996

Immunization against exon 1 decapeptides from the lutropin/choriogonadotropin receptor or the follitropin receptor as potential male contraceptive.

Pituitary gonadotropin hormones lutropin (LH) and follitropin (FSH) control steroidogenesis and gametogenesis in male and female gonads through interaction with G protein-coupled receptors, LHR and FSHR. In the male, LH acts on leydig cells and is mostly responsible for the acquisition of puberty and the production of androgens while FSH, together with androgens, regulates spermatogenesis within Sertoli cells. We have engineered filamentous phages displaying mouse LHR and human FSHR decapeptides chosen in hormone binding regions. Peptides from both receptors displayed on phages belong either to the receptor specific exon 1 (amino acids 18-27) or to the homologous exon 4 (amino acids 98-107). Vaccination of prepubertal BALB/c male mice with hybrid phages using sub-cutaneous or intraperitoneal injections induced immunity against receptors. Anti-receptor immunization produced agonist or antagonist effects depending only on the circulating levels of the antibodies. Both anti-LHR and anti-FSHR vaccines induced efficient as well as reversible male contraception, through different mechanisms: targeting LH receptors inhibited or hyperstimulated Leydig cell testosterone production while targeting FSH receptors did not affect testosterone levels.

Amino Acid Sequence↗
PubMed1996

Peptide and immunochemical mapping of the ectodomain of the porcine LH receptor.

The LH/hCG receptor is a G protein-coupled receptor with an N-terminal extracellular domain involved in hormone-receptor interaction. The recombinant porcine receptor, stably expressed in Chinese hamster ovary (CHO) cells, has the same characteristics (Kd and cAMP production) as in Leydig cells. Six synthetic peptides derived from the receptor ectodomain and two polyclonal anti-peptide sera were tested in the homologous system porcine LH and porcine LH receptor. Their ability to inhibit hormone binding and signal transduction on CHO cells expressing the recombinant receptor was evaluated. Peptides 25-40 and 107-121 exhibited a high transduction inhibition as compared with hormone binding, peptides 21-36, 102-111, and 102-121 inhibited hormone binding more efficiently than signal transduction, and peptide 7-24 exhibited inhibition of both hormone binding and hormone-induced cAMP production. Immunoglobulins against peptides 21-36 and 102-111 inhibited both hormone binding and receptor activation suggesting that these sequences are located on the receptor surface. The data suggest that multiple, discontinuous regions of the extracellular domain of porcine LH receptor are involved in hormone binding and signal transduction. Two minimum critical sequences, 21-24 and 102-107, are involved in hormone binding and vicinal segments may be implicated in signal transduction.

Amino Acid Sequence↗
PubMed1995

The porcine follitropin receptor: cDNA cloning, functional expression and chromosomal localization of the gene.

The porcine follitropin receptor-encoding cDNA (pFSHR) was cloned using reverse transcription-polymerase chain reaction (RT-PCR). Total RNA from porcine granulosa cells was used as template. Two overlapping cDNA fragments encoding, respectively, aa 1 to 290 and aa 191 to 694 of the pFSHR were obtained. Taken together, the two fragments represented the whole coding sequence, assuming a comparable length for the FSHR from the porcine, rat and human species. Functionality of the cloned receptor was assessed by expression experiments; COS cells transfected with the pFSHR cDNA exhibited high-affinity specific binding for [125I]hFSH and FSH-dependent cAMP production. The primary sequence of the porcine FSHR N-terminal hormone-binding domain showed high percentages of identity with the sequences from ovine, human, and rat origins. A truncated form of the pFSHR cDNA, lacking aa 75 to 124 in the N-terminal domain, was also cloned and sequenced. A PCR-derived cDNA fragment of 1.45 kb was used as gene-specific hybridisation probe to map the pFSHR-encoding gene by radioactive in situ hybridization. This gene was found co-localized (as in human) with the porcine lutropin hormone receptor (pLHR)-encoding gene on the q2.2-q2.3 region of pig chromosome 3.

Amino Acid Sequence↗
PubMed1995

Improved accumulation and activity of ribozymes expressed from a tRNA-based RNA polymerase III promoter.

RNA polymerase III (pol III) transcripts are abundant in all cells. Therefore, pol III promoters may be ideal for expressing high levels of exogenous RNAs, such as antisense RNAs, decoy RNAs and ribozymes, in many different cell types. We have improved accumulation of recombinant RNAs expressed from a human meti tRNA-derived pol III promoter > 100-fold by modifying the 3' terminus of the transcripts to hybridize to the 5' terminus. This terminal duplex includes the 8 nt leader sequence present in the primary wild-type meti tRNA transcript that is normally removed during processing to the mature tRNA. Expression of an anti-HIV ribozyme was analyzed in cells stably transduced with retroviral vectors encoding pol III transcription units containing this modification. High accumulation of recombinant pol III ribozyme transcripts was observed in all cell lines tested. Due to the enhanced transcript accumulation, ribozyme cleavage activity was readily detectable in total RNA extracted from stably transduced human T cell lines. One pol III transcription unit, termed 'TRZ', was optimized further for ribozyme cleavage activity. The improved pol III transcription units reported here may be useful for expressing a variety of functional and therapeutic RNAs.

Base Sequence↗
PubMed1995

Adenoviral-mediated gene transfer to fetal pulmonary epithelia in vitro and in vivo.

Vector-mediated gene transfer offers a direct method of correcting genetic pulmonary diseases and might also be used to correct temporary abnormalities associated with acquired, nongenetic disorders. Because the fetus or newborn may be a more immune tolerant host for gene transfer using viral vectors, we used replication defective recombinant adenoviral vectors to test the feasibility of gene transfer to the fetal pulmonary epithelium in vitro and in vivo. Both proximal and distal epithelial cells in cultured fetal lung tissues from rodents and humans diffusely expressed the lacZ transgene 3 d after viral infection. In vivo gene delivery experiments were performed in fetal mice and lambs. Delivery of Ad2/CMV-beta Gal to the amniotic fluid in mice produced intense transgene expression in the fetal epidermis and amniotic membranes, some gastrointestinal expression, but no significant airway epithelial expression. When we introduced the adenoviral vector directly into the trachea of fetal lambs, the lacZ gene was expressed in the tracheal, bronchial, and distal pulmonary epithelial cells 3 d after viral infection. Unexpectedly, reactive hyperplasia and squamous metaplasia were noted in epithelia expressing lacZ in the trachea, but not in the distal lung of fetal lambs. 1 wk after infection, adenovirus-treated fetuses developed inflammatory cell infiltrates in the lung tissue with CD4, CD8, IgM, and granulocyte/macrophage positive immune effector cells. Transgene expression faded coincident with inflammation and serologic evidence of antiadenoviral antibody production. While these studies document the feasibility of viral-mediated gene transfer in the prenatal lung, they indicate that immunologic responses to E1-deleted recombinant adenoviruses limit the duration of transgene expression.

Adenoviruses, Human↗