Biomedical subjects

Frédéric Marin

Publications and source records attributed to Frédéric Marin.

7 recordsLinked to original sources

PubMed2006

Toxoplasmic chorioretinitis and antitumor necrosis factor treatment in rheumatoid arthritis.

OBJECTIVES: To present the data supporting the possible relationship of ocular toxoplasmosis to antitumor necrosis factor-alpha (TNF-alpha) therapy in patients with rheumatoid arthritis (RA). METHODS: A Medline search was performed using the words "toxoplasmosis, anti-TNF-alpha antagonists, chorioretinitis." We report 2 RA patients who developed ocular toxoplasmosis while receiving anti-TNF-alpha therapy. RESULTS: In addition to our patients with toxoplasmic chorioretinitis, there are 2 published cases of cerebral toxoplasmosis during treatment with anti-TNF-alpha agents. CONCLUSION: The risk of serious toxoplasmic infection during anti-TNF-alpha therapy for RA should be recognized.

Adult↗

PubMed2006

Sagittal curvature of total knee replacements predicts in vivo kinematics.

BACKGROUND: It is known that in vivo kinematics after total knee replacement is influenced by the design of the implant. The goal of this study was to show that the sagittal curvature of two different knee prostheses differing in geometric design predicts their in vivo motion behavior. METHODS: Three-dimensional tibio-femoral displacements of two prosthesis designs (single radius vs. dual radius) were measured during knee extension under weight bearing conditions by in vivo video fluoroscopy. Finite helical axes were computed to represent the tibio-femoral motions. Angular deviation alpha and the spatial localization deviation delta were used to characterize the motions. Angular deviation is the angle between each incremental finite helical axis and the medio-lateral axis of the femoral component of the prosthesis. The spatial localization deviation is the distance between each finite helical axis and the center of the femoral component of the prosthesis. Statistical comparisons were performed using the median and the interquartile range of the angular deviation and the spatial localization deviation. FINDINGS: The single-radius design showed finite helical axes concentrated at a single axis near to the medio-lateral axis of the femoral component. The angular and spatial localization deviation of the dual radius design were larger compared to the single radius design, exhibiting finite helical axes varying between two axes. INTERPRETATION: Video fluoroscopy in combination with finite helical axis analysis proved to be suitable methods to evaluate the in vivo kinematical behavior of total knee arthroplasty, which can be useful for implant designers. Knowledge of in vivo kinematics can also provide surgeons with more background information about the total knee arthroplasty models they implant.

Arthroplasty, Replacement, Knee↗

PubMed2005

Caspartin and calprismin, two proteins of the shell calcitic prisms of the Mediterranean fan mussel Pinna nobilis.

We used the combination of preparative electrophoresis and immunological detection to isolate two new proteins from the shell calcitic prisms of Pinna nobilis, the Mediterranean fan mussel. The amino acid composition of these proteins was determined. Both proteins are soluble, intracrystalline, and acidic. The 38-kDa protein is glycosylated; the 17-kDa one is not. Ala, Asx, Thr, and Pro represent the dominant residues of the 38-kDa protein, named calprismin. An N-terminal sequence was obtained from calprismin. This sequence, which comprises a pattern of 4 cysteine residues, is not related to any known protein. The second protein, named caspartin, exhibits an unusual amino acid composition, since Asx constitutes by far the main amino acid residue. Preliminary sequencing surprisingly suggests that the first 75 N-terminal residues are all Asp. Caspartin self-aggregates spontaneously into multimers. In vitro tests show that it inhibits the precipitation of calcium carbonate. Furthermore, it strongly interferes with the growth of calcite crystals. A polyclonal antiserum raised against caspartin was used to localize this protein in the shell by immunogold. The immunolocalization demonstrates that caspartin is distributed within the prisms and makes a continuous film at the interface between the prisms and the surrounding insoluble sheets. Our finding emphasizes the prominent role of aspartic acid-rich proteins for the building of calcitic prisms among molluscs.

Amino Acid Sequence↗

PubMed2003

Molluscan shell matrix characterization by preparative SDS-PAGE.

The glycoproteinaceous constituents of molluscan shell matrices usually resist chromatographical fractionation. We describe a protocol that overcomes this difficulty and permits collection of a large amount of shell proteins for further in vitro characterization. After dissolution of the mineral phase, the glycoproteins are fractionated "blind" on a preparative electrophoresis. They are subsequently detected with a polyclonal antibody raised against the whole matrix.

Animals↗

PubMed2003

Phosphorylation of serine residues is fundamental for the calcium-binding ability of Orchestin, a soluble matrix protein from crustacean calcium storage structures.

Orchestia cavimana is a terrestrial crustacean, which cyclically stores calcium in diverticula of the midgut, in the form of calcified amorphous concretions. These concretions are associated with a proteinaceous matrix, the main constituent of the soluble matrix is Orchestin, an acidic calcium-binding protein [Testenière et al., Biochem. J. 361 (2002) 327-335]. In the present paper, we clearly demonstrate that Orchestin is phosphorylated on serine and tyrosine residues, but that calcium binding only occurs via the phosphoserine residues. To our knowledge, this is the first example of an invertebrate mineralization for which a post-translational modification is clearly related to an important function of a calcifying protein.

Amino Acid Sequence↗

PubMed2003

Screening molluscan cDNA expression libraries with anti-shell matrix antibodies.

In a previous paper [Marin et al., Protein Expr. Purif. 23 (2001) 175], we showed that polyclonal antibodies raised against molluscan shell matrices could be useful tools for visualizing shell proteins after a preparative fractionation of the shell matrix. In this paper, we have used the same antibodies for screening a cDNA library constructed from mantle tissues of the nacro-prismatic bivalve Pinna nobilis. The immunoscreening led to the identification of a new protein, mucoperlin [Marin et al., J. Biol. Chem. 275 (2000) 20667], which was subsequently overexpressed. A polyclonal antibody was obtained from the recombinant mucoperlin. In a control assay, we unambiguously demonstrated that this antibody and one of the sera used for the initial screening hybridize with the same clones. We assess that screening cDNA libraries with antibodies elicited against unfractionated calcifying matrices is a good alternative to oligonucleotide screening techniques, particularly in the field of molluscan biomineralization where only few gene sequences are known.

Animals↗

PubMed2003

Accurate determination of a joint rotation center based on the minimal amplitude point method.

In many computer-assisted surgery procedures in the field of joint replacement a joint rotation center must be located. To this end, joints such as the hip or the shoulder are approximated as spherical joints, and the most commonly used numerical method is the sphere-fitting algorithm. However, this method has a numerical instability where there is a limited range of motion caused by, for example, joint impingement. The aim of the present study was to develop an alternative kinematic method called the minimal amplitude point method. This method estimates the localization of the rotation center and can easily be integrated into program codes of computer-assisted surgery modules. It mainly consists of identifying the point of a mobile segment that moves least in the reference coordinate system of an immobile segment using an optimization procedure (genetic algorithm). The point determined can then be assumed to be the rotation center of the joint. To compare results of the two methods, an experimental set-up of two rigid solids linked by a spherical joint with known geometry was used to compute the rotation center. In contrast to the sphere-fitting method, the minimal amplitude point method permits the evaluation of the rotation center with an error of less than 4.1 mm, having a range of motion (ROM) of 5 degrees. An equivalent accuracy for the sphere-fitting method requires an ROM of 45 degrees.

Algorithms↗