Polyimide foams derived from a high Tg polyimide with grafted poly(α-methylstyrene)

in Polymer (1996), 37(23), 5229-5236

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a ... [more ▼]

A new route to high-Tg, thermally stable polyimide foams has been developed. Foams were prepared by casting microphase-separated graft copolymers comprising a thermally stable main chain, polyimide, and a thermally labile graft, poly(α-methylstyrene). The copolymer compositions were designed so that the thermally labile block would be the dispersed phase. This can unzip to its monomer upon heating, and the decomposition product diffuses out of the film, leaving pores embedded in a matrix of the thermally stable component. The copolymers were synthesized through either the poly(amic acid) precursor, followed by chemical cyclodehydration to the imide form, or the poly(amic alkyl ester) precursor followed by thermal imidization. The decomposition of the α-methylstyrene in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild decomposition conditions were required to avoid rapid depolymerization of the α-methylstyrene and excessive plasticization of the polyimide matrix. The foams showed pore sizes with diameters ranging from less than 20 nm to over 1 µm, depending upon the synthetic route employed, and the reduction in the mass density was generally consistent with the starting composition. [less ▲]

The Role of Glycoproteins gC, gE, gI and gG in the Induction of Cell-Mediated Immune Responses to Bovine Herpesvirus 1

in Veterinary Microbiology (1996), 53(1-2), 121-32

Mutant viruses with deletions in genes encoding non-essential glycoproteins are considered as promising bovine herpesvirus 1 (BHV1) vaccine candidates. The present study compared the influence of various ... [more ▼]

Mutant viruses with deletions in genes encoding non-essential glycoproteins are considered as promising bovine herpesvirus 1 (BHV1) vaccine candidates. The present study compared the influence of various gene deletions (gC, gE, gI, gG) on the induction of cell-mediated immune responses against the virus. The highest BHV1 specific lymphoproliferative response was observed in the group of calves inoculated with the gC- mutant. However, in all groups of inoculated calves, limiting dilution analysis showed marked individual variability in the number of BHV1 specific T lymphocytes that were stimulated. The same animals were then challenged with wild-type BHV1. In these animals, limiting dilution analysis did not reveal gE, gI nor gG as a major T lymphocyte antigen. However, further analysis suggested the T cell antigenicity of gE in a low number of BHV1 hyperimmunized calves. Stimulation of MHC unrestricted cytotoxicity was also evaluated after inoculation with the various deletion mutants. Cytotoxicity in gC- inoculated calves was as high as in BHV1 inoculated calves. In conclusion, among the BHV1 deletion mutants that were tested, the gC- mutant stimulated the best cell-mediated immune responses. [less ▲]

Narrowband versus broadband for tele-education : a critical evaluation

in International Conference on Technology Supported Learning, Proceedings (1996, November)

"Pour une didactique de la textualité"

Scientific conference (1996, November)

Samuel Beckett

in Voir (1996), 12-13(novembre), 30-40

Subset-Specific Analysis of Calcium Fluxes in Murine Aids

in International Immunology (1996), 8(11), 1715-27

Infection of susceptible strains of mice with the Duplan strain of murine leukemia viruses induces a syndrome called MAIDS (murine acquired immunodeficiency syndrome) characterized by immunodeficiency and ... [more ▼]

Infection of susceptible strains of mice with the Duplan strain of murine leukemia viruses induces a syndrome called MAIDS (murine acquired immunodeficiency syndrome) characterized by immunodeficiency and lymphoproliferation. In addition to a complete refractoriness of most subsets of lymphocytes to mitogen stimulation, the development of phenotypic abnormalities occurs such as the appearance of an abnormal CD4+ T cell subset lacking membranes Thy-1. This study was performed to compare the calcium responses during the early stages of MAIDS (week 9 or earlier) between T cells and B cells and between CD4+Thy-1- and CD4+Thy-1+ T cells. B cells were strikingly less affected than T cells: their baseline [Ca2+]i did not significantly increase, and their calcium response to anti-IgM antibody and concanavalin A (Con A) was partially maintained. In contrast, the response to Con A was completely abolished in T cells. Interestingly, calcium mobilization in response to membrane receptor-independent stimuli such as ionophores and thapsigargin was strongly inhibited in T cells, while no such inhibition was found in B cells. In comparison with their CD4+Thy-1+ counterparts, CD4+Thy-1- T cells had blunted calcium responses in controls, as well as in infected mice. However, CD4+Thy-1+ T cells were also strikingly altered, suggesting that the loss of membrane Thy-1 could be associated with, but not directly responsible for abnormalities of calcium responses in CD4+ T cells from RadLV-Rs-infected mice. [less ▲]

Production et conditionnement des bactéries lactiques isolées du Lben Tunisien.

Poster (1996, November)

Les prions, aspects moleculaires

in Revue Médicale de Liège (1996), 51(11), 700-705

Influence de l'association du nomegestrol acetate sur l'amélioration de la qualité de vie induite par une estrogenotherapie chez la femme ménopausée

in Contraception, Fertilite, Sexualité (1992) (1996), 24(11), 847-51

Estrogen replacement therapy in postmenopausal women is followed by several benefits including a prompt improvement of quality of life. Due to uterine proliferation induced by prolonged estrogen intake ... [more ▼]

Estrogen replacement therapy in postmenopausal women is followed by several benefits including a prompt improvement of quality of life. Due to uterine proliferation induced by prolonged estrogen intake, progestogens are usually associated, on a cyclical basis, in hormonal replacement therapy prescribed to non-hysterectomized women. Persistence of the beneficial effect of estrogen on quality of life, during progestogens intake, was never investigated. We evaluated, through a specific and previously validated questionnaire, the changes in quality of life observed in 351 women recently menopaused, after 6 months of hormonal replacement therapy associating 24 days of estrogens and 12 days of administration of a non androgenic progestogen: nomegestrol acetate. Patients were randomized within two therapeutic groups in which evaluation of quality of life was performed either during the administration of estrogen alone or during administration of estrogen and progestogen. In the two groups, hormonal replacement therapy was followed by a significant improvement (P < 0,001) in quality of life and no significant difference was observed between the changes observed during estrogen or estrogen-progestogen administration. Quality of life indices measured after 6 months of hormonal replacement therapy are within the same range than values previously described in eugonadal women. We conclude that improvement of quality of life induced by estrogen replacement therapy remains unchanged during cyclical administration of nomegestrol acetate. [less ▲]

Automated Determination of Verapamil and Norverapamil in Human Plasma with on-Line Coupling of Dialysis to High-Performance Liquid Chromatography and Fluorometric Detection

in Journal of Chromatography. A (1996), 750(1-2), 351-60

A fully automated method for the simultaneous determination of verapamil and its main metabolite norverapamil in human plasma is described. This method is based on on-line sample preparation using ... [more ▼]

A fully automated method for the simultaneous determination of verapamil and its main metabolite norverapamil in human plasma is described. This method is based on on-line sample preparation using dialysis followed by clean-up and enrichment of the dialysate on a precolumn and subsequent HPLC analysis with fluorometric detection. All sample handling operations were performed automatically by a sample processor equipped with a robotic arm (ASTED system). The plasma samples were dialysed on a cellulose acetate membrane (cut-off: 15 kD) and the dialysate was purified and enriched on a short pre-column filled with cyanopropyl silica. Before starting dialysis, this trace enrichment column (TEC) was first conditioned with the HPLC mobile phase and then with pH 3.0 acetate buffer. 370 microliters of plasma sample spiked with the internal standard (gallopamil) were dialysed in the static-pulsed mode. The solution at the donor side was pH 3.0 acetate buffer containing Triton X-100 while the acceptor solution was made of the same acetate buffer. When dialysis was discontinued, the analytes were desorbed from the TEC by the HPLC mobile phase and transferred to the C18 analytical column by means of a switching valve. This mobile phase consisted of a mixture of acetonitrile, pH 3.0 acetate buffer and 2-aminoheptane. The influence of different parameters of the dialysis process on the recovery of verapamil and norverapamil has been studied. The effect of the volume, the aspirating and dispensing flow-rates of the dialysis solution has been investigated. The recoveries of verapamil and norverapamil in plasma were close to 75% and the limits of quantification were 5 ng/ml for both analytes. The method was found to be linear in the concentration range from 5 to 500 ng/ml (r2: 0.9996 for both analytes). The intra-day and inter-day reproducibilities at a concentration of 100 ng/ml were 2.3% and 5.6% for verapamil and 1.7% and 5.1% for norverapamil, respectively. [less ▲]