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S Lacour

Publications and source records attributed to S Lacour.

6 recordsLinked to original sources
PubMed2006

Charon's size and an upper limit on its atmosphere from a stellar occultation.

Pluto and its satellite, Charon (discovered in 1978; ref. 1), appear to form a double planet, rather than a hierarchical planet/satellite couple. Charon is about half Pluto's size and about one-eighth its mass. The precise radii of Pluto and Charon have remained uncertain, leading to large uncertainties on their densities. Although stellar occultations by Charon are in principle a powerful way of measuring its size, they are rare, as the satellite subtends less than 0.3 microradians (0.06 arcsec) on the sky. One occultation (in 1980) yielded a lower limit of 600 km for the satellite's radius, which was later refined to 601.5 km (ref. 4). Here we report observations from a multi-station stellar occultation by Charon, which we use to derive a radius, R(C) = 603.6 +/- 1.4 km (1sigma), and a density of rho = 1.71 +/- 0.08 g cm(-3). This occultation also provides upper limits of 110 and 15 (3sigma) nanobar for an atmosphere around Charon, assuming respectively a pure nitrogen or pure methane atmosphere.

Journal Article↗
PubMed2001

Anticancer agents sensitize tumor cells to tumor necrosis factor-related apoptosis-inducing ligand-mediated caspase-8 activation and apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a new cytokine that was proposed to specifically induce apoptosis of cancer cells. In tumor cells that are resistant to the cytokine, subtoxic concentrations of chemotherapeutic drugs can restore the response to TRAIL. The present study further explores the mechanisms that determine tumor cell sensitivity to TRAIL by comparing four human colon carcinoma cell lines We show that colon cancer cell sensitivity to TRAIL-induced apoptosis and cytotoxicity correlates with the expression of the death receptors TRAIL-R1 and TRAIL-R2 at the cell surface, as determined by now cytometry, whereas the two decoy receptors TRAIL-R3 and TRAIL-R4 can be detected only in permeabilized cells. Clinically relevant concentrations of cisplatin and doxorubicin sensitize the most resistant colon cancer cell lines to TRAIL-induced cell death without modifying the expression nor the localization of TRAIL receptors in these cells. TRAIL induces the activation of procaspase-8 and triggers caspase-dependent apoptosis off colon cancer cells. Cytotoxic drugs lower the signaling threshold required for TRAIL-induced procaspase-8 activation. In turn, caspase-8 cleaves Bid, a BH3 domain-containing proapoptotic molecule of the Bcl-2 family and activates effector caspases. Together, these data indicate that chemotherapeutic drugs sensitize colon tumor cells to TRAIL-mediated caspase-8 activation and apoptosis.

Antibiotics, Antineoplastic↗
PubMed1993

[Perforated and pre-perforated ulcer in rheumatoid polyarthritis].

The authors report a case about relapsing corneal ulceration in a patient with rheumatoid arthritis. Treatment of such perforated and preperforated corneal ulcers is a difficult task. The poor visual outcome of an emergency penetrating keratoplasty leads to the use of other methods (conjunctival flaps, corneal graft, keratopatch, tissue adhesive). This case report stresses the importance of preserving the anatomy of the eye allowing in a record time the performance of corneal graft. The use of immunosuppressive drugs is also discussed because of the existence of a rheumatoid arthritis with eye involvement.

Arthritis, Rheumatoid↗
PubMed1991

[Mucoepidermoid carcinoma of the conjunctiva with intraocular invasion. Apropos of a case].

One case of mucoepidermoid carcinoma of the conjunctiva with intraocular invasion is described. Review of literature retrieve 15 cases of conjunctival localisation of mucoepidermoid carcinoma. These tumors appear to be locally aggressive, they all invade the intraocular or intraorbital structures. They require always a radical surgery with wide excision. Histopathologically, histochemical stains for glycoproteins confirm the diagnosis with admixture of squamous and mucus secreting cells.

Aged↗