Biomedical subjects

F Cardinaux

Publications and source records attributed to F Cardinaux.

17 recordsLinked to original sources

PubMed2006

Multispeckle diffusing-wave spectroscopy with a single-mode detection scheme.

We present a detection scheme for diffusing-wave spectroscopy (DWS) based on a two-cell geometry that allows efficient ensemble averaging. This is achieved by putting a fast rotating diffuser in the optical path between laser and sample. We show that the recorded (multispeckle) correlation echoes provide an ensemble averaged signal that does not require additional time averaging. Furthermore, combined with traditional two-cell DWS, the full intensity autocorrelation function can be measured with a single experimental setup. The scheme provides access to a large range of correlation times thus opening an experimental window for the study of slowly relaxing and arrested systems, such as viscoelastic complex fluids, colloidal glasses, and gels.

Journal Article↗

PubMed1992

N-terminal truncation of salmon calcitonin leads to calcitonin antagonists. Structure activity relationship of N-terminally truncated salmon calcitonin fragments in vitro and in vivo.

Structural requirements for binding to the bone calcitonin (CT) receptor and for CT bioactivity both in vitro and in vivo were assessed for a series of N-terminally truncated, N alpha-acetylated, fragments of salmon calcitonin (sCT). Sequential deletion of amino acid residues from the amino-terminus of [Ala7]sCT-(2-32) peptide amide first led to partial agonists and, upon deletion of residues 1 to 7, to a high affinity antagonist, N alpha-acetyl-sCT-(8-32)-NH2. The presence of two separate domains within the sCT sequence is proposed: (I) a binding domain comprising residues 9-32 and (II) an activation domain requiring residues 3 to 6. N alpha-acetyl-sCT-(8-32)-NH2, in several bioassays including plasminogen activator release from LLC-PK1 cells (pA2 = 7.31), cAMP production in UMR-106-06 cells (pA2 = 7.81) and in the fetal rat long bone resorption assay showed potent antagonistic properties.

Acetylation↗

PubMed1991

Amylin or CGRP (8-37) fragments reverse amylin-induced inhibition of 14C-glycogen accumulation.

The peptides amylin and calcitonin-gene related peptide (CGRP) have been shown to have similar effects on glycogen metabolism in vivo and in vitro. However, it is not clear whether they act via separate receptors. Peptide fragments based on the amino acid sequence of amylin or CGRP were evaluated for their ability to inhibit the action of the peptides in vitro. Insulin-stimulated glycogen turnover, as measured by 14C-glycogen accumulation, was inhibited about 70% by amylin (10nM) and 85% by CGRP (10nM). In the absence of exogenous peptide, peptide fragments based on the 8-37 and 10-37 amino acid sequences of rat amylin (10 uM) had no affect on 14C-glycogen accumulation. In the presence of amylin (10nM), the 8-37 and 10-37 fragments blocked amylin-induced inhibition of 14C-glycogen accumulation 100% and 11.4%, respectively. The 8-37 and 10-37 amylin fragments blocked CGRP inhibition of 14C-glycogen accumulation by 23.2% or 28.6%, respectively. The CGRP 8-37 fragment was equally effective as the amylin 8-37 reversing the effects of amylin than at reversing the effects of CGRP. These results demonstrate that amylin (8-37) completely antagonizes the effects of amylin with limited ability to block CGRP. Removing the eighth and ninth amino acids reduced the effectiveness of the inhibitor by about 90%.

Amyloid↗

PubMed1989

Competition for antigen presentation in living cells involves exchange of peptides bound by class II MHC molecules.

T cells recognize foreign proteins as peptides bound to self molecules encoded by the major histocompatibility complex (MHC). The kinetics of interaction between purified class II MHC molecules and peptides is unusual, in that the rate of association is very slow, but once formed, the complexes are extremely stable. This raises the question of how the antigen-presenting cell provides a sufficient number of free MHC binding sites to ensure T cell immunity. We present results suggesting that an exchange of peptide in MHC binding sites may take place under physiological conditions.

Ammonium Chloride↗

PubMed1989

Inhibition of T cell response with peptides is influenced by both peptide-binding specificity of major histocompatibility complex molecules and susceptibility of T cells to blocking.

Synthetic peptides corresponding to sequences 46-62 and 51-62 of mouse lysozyme and 46-61 of hen egg-white lysozyme (HEL) were used as competitors in a variety of T cell responses. The competitors, according to their binding specificity for major histocompatibility complex (MHC) were expected to inhibit T cell responses restricted to I-Ak, but not those restricted to I-Ad, I-Ek molecules. In competition experiments with T cell hybridomas, the poor binder I-Ed molecule required 10- to 15-fold higher competitor concentrations than the good binder I-Ak molecule to achieve 50% inhibition of antigen presentation. Similarly, the nonresponder state of H-2d mice to HEL peptide 46-61 could be overcome by increasing the immunizing dose, and proliferative T cell responses to different antigens in association with a variety of class II MHC molecules could be blocked by the mouse lysozyme and HEL peptides. Thus, the capability of some and failure of other MHC molecules to bind certain peptides appeared quantitative, rather than of an all or none nature, in these experimental systems. The susceptibility of uncloned T cell lines to peptide competitors was found to decrease with time. Lines maintained by repeated restimulation with antigen and APC, but without exogenous interleukin 2, acquired resistance within weeks. In contrast, T cell clones retained their susceptibility to peptide competitors over a long period of time. The latter data raise the possibility that a competition between ubiquitous (self) peptides and foreign antigen may result in the selection of T cells that have high avidity for the activating antigen-MHC complex, and are thus relatively resistant to competition at the level of antigen presentation.

Amino Acid Sequence↗

PubMed1989

Major histocompatibility complex--dependent T cell epitopes of lymphocytic choriomeningitis virus nucleoprotein and their protective capacity against viral disease.

In mice the immune response to infection with lymphocytic choriomeningitis virus (LCMV), a member of the arenavirus family, is mainly based on the activity of cytotoxic T cells. The immunogenic epitopes of the viral nucleoprotein recognized by cytotoxic T cells in various inbred strains of mice were defined. These epitopes were located in H-2d and H-2q mice in the amino-terminal region and in H-2b mice in the carboxy-terminal region of the nucleoprotein. A detailed analysis with synthetic peptides allowed the definition of a common epitope of 9 amino acids in H-2d and H-2q mice and of about 15 amino acids in H-2b mice. These T cell epitopes were all recognized in association with H-2 D or L transplantation antigen. The protective capacity of recombinant vaccinia viruses expressing these epitopes was documented by assaying prevention of virus replication, protection against LCM and prevention of the local footpad swelling reaction. Thus, distinct T cell epitopes on the same internal viral protein mediate protection in a major histocompatibility complex-restricted manner.

Amino Acid Sequence↗

PubMed1988

In vivo competition between self peptides and foreign antigens in T-cell activation.

Cytotoxic and helper T lymphocytes recognize foreign antigen in the form of short peptides associated with class I and class II major histocompatibility complex (MHC) molecules, respectively. A recent study of the three-dimensional structure of a class I MHC molecule revealed a cleft formed by the amino-terminal half of the protein, which could serve as the binding site for these peptides. Because an individual possesses only a limited set of different MHC molecules, each molecule of this set must have the ability to bind a large number of different peptides in order to ensure full immunocompetence. Thus, it can be anticipated that peptides with unrelated sequences compete for binding to the same MHC molecule, and, indeed, this has been shown to occur in vitro. We therefore decided to see whether such competition could also regulate the cell responses in vivo. We have found that a synthetic peptide corresponding to residues 46-62 of mouse lysozyme, although not immunogenic itself, effectively inhibits the priming for T-cell responses when injected into mice together with foreign protein or peptide antigens. The inhibition observed strictly correlates with the capacity of the competitor to bind to the particular MHC molecule presenting the foreign antigen, and its extent depends on the molar ratio between antigen and competitor.

Animals↗

PubMed1977