PubMed Health⌕ Search

Biomedical subjects

C Gosse

Publications and source records attributed to C Gosse.

At least 19 recordsLinked to original sources
PubMed2006

Quadruplex-based molecular beacons as tunable DNA probes.

Molecular beacons (MBs) are fluorescent nucleic acid probes with a hairpin-shaped structure in which the 5' and 3' ends are self-complementary. Due to a change in their emissive properties upon recognition with complementary sequences, MBs allow the diagnosis of single-stranded DNA or RNA with high mismatch discrimination, in vitro and in vivo. Whereas the stems of MB hairpins usually rely on the formation of a Watson-Crick duplex, we demonstrate in this report that the preceding structure can be replaced by a G-quadruplex motif (G4). Intramolecular quadruplexes may still be formed with a central loop composed of 12 to 21 bases, therefore extending the sequence repertoire of quadruplex formation. G4-MB can efficiently be used for oligonucleotide discrimination: in the presence of a complementary sequence, the central loop hybridizes and forms a duplex that causes opening of the quadruplex stem. The corresponding G4-MB unfolding can be detected by a change in its fluorescence emission. We discuss the thermodynamic and kinetic opportunities that are provided by using G4-MB instead of traditional MB. In particular, the intrinsic feature of the quadruplex motif facilitates the design of functional molecular beacons by independently varying the concentration of monovalent or divalent cations in the medium.

DNA Probes↗
PubMed2005

Magnetic force probe for nanoscale biomolecules.

We present a new technique to measure the mechanical properties of small biomolecules. This technique uses long range repulsive colloidal forces together with magnetic attraction as a force probing tool. The biomolecules are grafted between superparamagnetic particles, which are regularly spaced within long chains maintained by an external magnetic field. Varying the magnetic field results in compression or extension of the molecules between the particles. In order to demonstrate this technique we use, as a size controlled model molecule, a short double stranded DNA (151 base pairs) for which the force-extension law is determined and found in agreement with existing predictions.

Biopolymers↗
PubMed2000

Catalytic action of fuculose 1-phosphate aldolase (class II) as derived from structure-directed mutagenesis.

Previous analyses established the structures of unligated L-fuculose 1-phosphate aldolase and of the enzyme ligated with an inhibitor mimicking the substrate dihydroxyacetone phosphate. These data allowed us to suggest a catalytic mechanism. On the basis of this proposal, numerous mutations were now introduced at the active center and tested with respect to their catalytic rates and their product distributions. For several mutants, the structures were determined. The results demonstrate the catalytic importance of some particular residues in defined conformations and in the mobile C-terminal chain end. Moreover, they led to a modification of the proposed mechanism. The effect of some mutations on enantioselectivity and on the ratio of diastereomer formation indicates clearly the binding site of the aldehyde moiety in relation to the other substrate dihydroxyacetone phosphate.

Aldehyde-Lyases↗
PubMed1991

Chemical stability of ecomustine, a new antitumor agent in aqueous and biological media as assessed by high-performance liquid chromatography.

Ecomustine, or CY233 (NSC-609224), is a new water-soluble nitrosoureido sugar derived from acosamine. A high-performance liquid chromatographic assay (HPLC) developed to quantify the unchanged drug in aqueous solutions and biological specimens enabled us to study the chemical stability as a function of pH, light, and temperature. In buffered aqueous solutions, the kinetics of degradation of CY233 is a first-order process. The log k-pH profile demonstrated hydroxide ion-catalyzed solvolysis. The drug is most stable at pH 4, more stable than some other nitrosoureas in 5% glucose (t1/2, 62-67 h) and in 0.9% isotonic saline (t1/2, 25-37 h) solutions. Based on these findings, blood samples should be collected in cold tubes (4 degrees C) containing citrate buffer (pH 4) and all manipulations should be protected from heat and light.

Antineoplastic Agents↗
PubMed1990

Intra-arterial hepatic chemotherapy with pirarubicin. Preclinical and clinical studies.

Intra-arterial hepatic chemotherapy (IAHC) with adriamycin (ADM) has not increased its therapeutic index. For our preclinical studies, we selected pirarubicin (THP), an ADM derivative with faster cellular uptake. In rabbits with VX2 tumor in the liver we compared plasmatic and cellular pharmacokinetics of ADM and THP after i.v. and IAH therapy. For ADM, there were no differences in plasma and heart concentrations, with only a slight increase in tumoral levels after IAH compared to i.v. administration; on the other hand, with IAH THP, there was important reduction in systemic exposure with a major increase in tumoral drug distribution. In the phase I study, involving nine patients with implanted catheters, the starting dose of THP was 30 mg/m2 with a 10 mg/m2 intrapatient escalation every 3 weeks in the absence of toxicity. Pharmacokinetics were compared for i.v. and IAH administration in seven patients. The limiting toxicity was neutropenia and the maximal tolerated dose (MTD) ranged from 50 to 110 mg/m2. Moderate nausea-vomiting (grade 1-2) and alopecia (grade 1) occurred at the MTD. No arterial occlusion, gastroduodenal ulcer, hepatitis, or sclerosing cholangitis were seen. In the phase II study, in colorectal cancer patients (CRC) with metastasis confined to the liver, patients were enrolled until June 1990. THP (40 min infusion every 3 weeks) was initiated at 60 mg/m2 with 10 mg/m2 increment until grade 2 hematotoxicity. The median MTD was 85 mg/m2 (range of 60-120 mg/m2), and the median number of cycles was 7 (range of 2-11) with cumulated doses from 180 to 1,030 mg/m2. Grade 2-4 neutropenia was reached in 15 patients. Other toxicities included two arterial occlusions, one episode of gastritis, but no hepatic toxicity and no heart failure. Antitumor effect (in 18 patients) included 1 CR, 5 PR, 3 MR, 6 NC, and 3 PD. The median survival was 18+ months and 1-year survival was 73% +/- 12%. Seven patients had extrahepatic progression at this time. In conclusion, besides 5-FU or Fudr, THP is active in IAHC (probably in relation with high local extraction) on CRC liver metastases usually unresponsive to ADM. It can be given in an outpatient setting with minimal toxicity.

Animals↗
PubMed1989

Characterization of the anti-tumour activity against solid tumours of a new nitrosoureido sugar: Cy 233.

The anti-tumour properties of Cy 233, a new nitrosoureido sugar, were investigated in two murine solid tumours: B16 melanoma and subcutaneously implanted colon adenocarcinoma. Injected i.v., Cy 233 exerted a strong anti-tumour effect against the established B16 melanoma: long-term survivors were recorded with all schedules of treatment. The drug was even more effective against advanced colon 38 adenocarcinoma: it produced a high percentage of total tumour regression, regardless of the route of administration (i.p., i.v., p.o.). The marked in vivo activity of Cy 233 against advanced colon 38 adenocarcinoma, which is known to be resistant to such major anti-cancer drugs as BCNU and chlorozotocin, its water solubility and its stability in aqueous media are further elements warranting toxicological and clinical studies of this agent.

Adenocarcinoma↗
PubMed1989

Rationale for the synthesis and preliminary biological evaluation of highly active new antitumor nitrosoureido sugars.

Various new nitrosoureido derivatives of di- or trideoxy sugars were synthesized. The influence of the hydroxyl substitution pattern, the configuration at the anomeric center, and the absolute configuration of the sugar moiety on the antitumor activity of a series of nitrosoureido derivatives of di- and trideoxy sugars was studied. All compounds showed a very significant activity in vivo against L1210 leukemia, B16 melanocarcinoma, and Lewis lung carcinoma. Methyl 3-[3-(2-chloroethyl)-3-nitrosoureido]-2,3-dideoxy-alpha-D-arabino- hexopyranoside, 24 (NSC 609224), was found to be the most active compound. When treated with 24 (NSC 609224) at 20 mg/kg on day 1, at least 90% of the L1210 leukemia and B16 melanocarcinoma bearing mice showed a survival of over 60 days for a LD50 value for this compound of 42 mg/kg.

Amino Sugars↗
PubMed1982

[Fall in the levels of circulating lymphoblasts caused by intravenous administration of the A50 monoclonal antibody in a patient with acute T-cell lymphoblastic leukemia. A step in the demonstration of serotherapy with monoclonal antibodies].

In an 8-year-old boy with acute lymphoblastic leukaemia not previously treated intravenous administration of a single 8 mg dose of a monoclonal antibody that recognizes an epitope restricted to the surface of mature T-cells resulted, within 20 hours, in a fall in circulating lymphoblasts from 200 000 to 70 000. No adverse clinical or biological reaction was detected and no antigenic modulation occurred at lymphoblast surface. This observation constitutes a first step in the complex development of effective serotherapy for malignant diseases, using monoclonal antibodies.

Animals↗
PubMed1982

Phenomenon of human T cells rosetting with sheep erythrocytes analyzed with monoclonal antibodies. "Modulation" of a partially hidden epitope determining the conditions of interaction between T cells and erythrocytes.

Anti-D66 is a monoclonal antibody able to inhibit E-rosette formation of T cells both at 4 degrees C and at 37 degree C but that does not inhibit T cell rosette formation with neuraminidase or 2-amino-ethylisothiouronium bromide (AET)-pretreated E. As demonstrated by capping experiments, it defines an epitope, D66, that is directly involved in E-rosette formation. D66 is distinct from the epitope defined by 9.6 because 9.6, a previously defined "pan-T" monoclonal antibody, inhibits E(AET) rosette formation and because no cross-blocking occurred between both antibodies fixation. However, 9.6 and D66 are carried by the same molecule, as demonstrated by sequential immunoprecipitation assays performed on two different T cell lines. On the thymocyte surface, also, 9.6 and D66 are most probably carried by the same molecule, as indicated by cocapping and colysostripping experiments. D66 is present at higher densities on thymocytes and activated T cells than on peripheral blood T cells. Investigation of numerous T cell populations, both normal and malignant, showed a straightforward correlation between elevated D66 density and ability to form 37 degrees C stable E-rosettes. Neuraminidase treatment of thymocytes and peripheral blood lymphocytes forming E-rosettes unmasked a large fraction of D66 not readily accessible on their surface. These hidden D66 epitopes appear to be responsible for a surprising observation: the ability of anti-D66 to inhibit E-rosette formation could be totally reversed by fixation on anti-D66 of an antibody to mouse immunoglobulin or an Fab fragment anti-mouse immunoglobulin. This would induce microdisplacement with emergence of hidden D66, as documented by fluorometric studies. Finally, malignant T cells with a differentiative status of mature T cells, but forming no (or low numbers of) E-rosettes, could be induced both to display D66 and to form E-rosettes by neuraminidase treatment.

Animals↗
PubMed1977

Survival curve of a human melanoma in nude mice.

Using cells from our tissue culture of human melanoma cell line Na 11, we transplanted 1 X 10)6) tumor cells sc into athymic nude mice. Tumors appeared after a latent period of 4-10 days; when they reached a mean volume of 100 mm3 we irradiated them with various doses of X-rays. Some tumors were irradiated while the mice were still alive; others were treated 10 minutes after the animals had been asphyxiated with nitrogen. All irradiation was done in the presence of oxygen. These tumors were excised, and cell suspensions were prepared; the cells formed colonies with a mean plating efficiency of 29%. In another series of experiments, we irradiated tumor cells in vitro 2 hours after excision, when most cells were fixed and presumably oxygenated. We then calculated survival curves for the tumor cells irradiated under these three conditions and found an average anoxic cell fraction of 85%, which was much higher than that reported in many other tumor systems. We explored several possible explanations for this phenomenon.

Animals↗
PubMed1976

Antitumor activity of 9-hydroxyellipticine (NSC 210717) ON L1210 mouse leukemia and the effect of route of injection.

The antitumor activity of a new derivative of ellipticine, 9-hydroxyellipticine (NSC 210717), was studied using L1210 mouse leukemia. Low doses of this drug have a high antileukemic activity, whereas high doses have less activity than expected because of a leveling off in the antitumor activity-dose relationship, as if a few cells were resistant to the treatment. The possible causes of this apparent resistance were investigated. It is suggested that this apparent resistance is related to the sequestration of a small number of cells in compartments inaccessible to the drug. A model was developed which takes into account the distribution of cells in various compartments and their drug sensitivity therein. It was predicted and observed that the activity of drugs acting on cells in the small compartments can be observed only in conjunction with the presence of drugs acting on the cells in the major compartment. The importance of this observation in the screening procedures of new drugs, the clinical trial of new chemotherapeutic agents, and the association of anticancer drugs are discussed within this context. 9-Hydroxyellipticine is of interest because it acts on leukemic cells in the brain.

Alkaloids↗
PubMed1975

[2 new antineoplastic derivatives: 9-hydroxy-2-methyl-ellipticinium (acetate) and 9-hydroxy-2,6-dimethyl-ellipticinium (chloride). Effect on mouse L 1210 leukemia].

The antitumoral activity of two new derivatives of ellipticine, 9-hydroxy-2-methyl ellipticinium and 9-hydroxy-2,6-dimethyl-ellipticinium, has been determined using L 1210 mouse leukemia. The first compound elicits a therapeutic index similar to that of 9-hydroxy-ellipticine but is active at doses ten times smaller. The second compound elicits an exceptionally high therapeutic index. It is still active when used at one hundredth of the sublethal dose.

Alkaloids↗