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Biomedical subjects

C Lefevre

Publications and source records attributed to C Lefevre.

68 records · Page 4Linked to original sources
PubMedDate not supplied

Processing of vasoactive intestinal peptide and transferrin in human cancerous colonic cells.

Endocytosis of vasoactive intestinal peptide (VIP) and of transferrin (Tf) was comparatively studied in human cancerous colonic HT-29 cells. Cellular depletion in potassium inhibits the internalization of VIP (23%) and to a greater extent (42%) that of Tf. This indicates that clathrin-coated pits are also involved, at least in part, in VIP uptake. The distribution of 125I-Tf- or 125I-VIP-containing vesicles in sucrose gradients revealed low and high density vesicle subpopulations. The low density vesicle subpopulation represented a transient compartment from which incoming vesicles containing N-leucyl-beta naphthylamidase were recycled back to the membrane while those containing beta-hexosaminidase (HA) and ligand were mostly transferred into the high density compartment. Subsequent fusion of the latter with heavy vesicles was demonstrated by the shift of HA and ligand with vesicles that had been prelabeled with horseradish peroxidase (HRP). Simultaneous internalization of Tf-HRP and 125I-VIP showed that both the low and high density vesicle subpopulations comprised of two types of VIP-containing vesicle, as confirmed by the density shift reaction: two-thirds of VIP shifted with the Tf-HRP-containing vesicles to denser fractions and the remaining was found with unshifted vesicles. These findings indicate that the VIP-receptor complex processing in HT-29 cells follows two routes, the major route being common with Tf endocytosis.

Coated Pits, Cell-Membrane↗
PubMedDate not supplied

Texas Res-X and rhodamine Red-X, new derivatives of sulforhodamine 101 and lissamine rhodamine B with improved labeling and fluorescence properties.

Texas Red sulfonyl chloride (TR-SC) and Lissamine rhodamine B sulfonyl chloride (LRB-SC) are popular dyes often used to prepare red fluorescent conjugates that are useful second labels in combination with fluorescein. Unfortunately, being sulfonyl chloride derivatives, both are unstable to moisture during storage and prone to hydrolysis in the conjugation reaction. Their instability causes the percentage of reactive dye to vary from lot to lot and requires use of low temperatures and a relatively high pH to optimize conjugation efficiency. Succinimidyl esters of the aminohexanoic acid sulfonamides of both dyes have been prepared, which are designated Texas Red-X succinimidyl ester (TR-X-SE) and Rhodamine Red-X succinimidyl ester, respectively. Their spectral properties are similar to those of their sulfonyl chloride analogs; moreover, incorporation of the succinimidyl ester at the end of the aliphatic chain spacer facilitates conjugation, decreases precipitation of proteins during conjugation and storage, and usually increases the fluorescence yield of the conjugate. Comparison of the rate of hydrolysis of TR-SC with that of TR-X-SE shows that, while the former was completely hydrolyzed within 5 min by exposure to water, TR-X-SE retains most of its reactivity for more than an hour. The reactivity of both new derivatives is high between pH 7.5 and 8.5, allowing conjugation of proteins that do not tolerate the high pH required for reaction with sulfonyl chlorides. In addition, Texas Red maleimides and haloacetamides containing spacer groups were prepared for labeling sulfhydryl groups. A Texas Red-X derivative of phalloidin has also been prepared, and its use for labeling F-actin has been characterized.

Chemical Phenomena↗
PubMedDate not supplied

Optimal control of a birth and death epidemic process.

We employ a birth and death process to describe the spread of an infectious disease through a closed population. Control of the epidemic can be effected at any instant by varying the birth and death rates to represent quarantine and medical care programs. An optimal strategy is one which minimizes the expected discounted losses and costs resulting from the epidemic process and the control programs over an infinite horizon. We formulate the problem as a continuous-time Markov decision model. Then we present conditions ensuring that optimal quarantine and medical care program levels are nonincreasing functions of the number of infectives in the population. We also analyze the dependence of the optimal strategy on the model parameters. Finally, we present an application of the model to the control of a rumor.

Communicable Disease Control↗
PubMedDate not supplied

The Lefevre ulnar nail.

The Lefevre nail applies the principles of locked intramedullary nailing in the treatment of fractures of the ulna. It is made up of two segments which slide telescopically, so that assembly may be in compression, distraction or neutral. Fixation at the two ends of the ulna is guaranteed by two transverse screws. It may be used in pseudarthrosis and osteotomies for lengthening and shortening, as well as in simple or complex fractures. The cases presented provide an overview of the use of the nail at the Brest Center, where the nail was invented and developed, and at the Rizzoli Institute. The study includes 22 fractures, 1 pseudarthrosis and 1 osteotomy. Consolidation was obtained in all of the cases after an average of 2.5 months. Immobilization in plaster was required only in cases with associated lesion of radius. The functional results obtained were satisfactory.

Adolescent↗
PubMedDate not supplied

[Comparative study of 3 therapeutic methods for Pouteau Colles' fracture. Apropos of 97 cases].

Results of three therapeutic modalities used for the treatment of a homogeneous series of patients with a Pouteau Colles fracture are analyzed. Orthopedic treatment provided deceiving results. Pinning was, on the contrary, very effective, intrafocal pinning with immediate mobilization of the wrist appearing perfectly effective. Few complications were reported in contrast to plastered immobilizations. Good results were obtained in 80% of cases and functional recovery was rapid, indicating that this method represents undoubted progress when compared with conventional therapies.

Adult↗
PubMedDate not supplied

[Kirner's deformity. Apropos of 3 new cases. Review of the literature].

Three cases of Kirner's deformity in siblings are reported. Kirner's deformity consists in a palmar bending of the terminal phalanx of the 5th finger. The deformity is usually bilateral; the condition is congenital but the deformity is recognized in later childhood and has to be classified as osteochondrodysplasia.

Child↗
PubMedDate not supplied

[Latarjet's operation in recurrent antero-internal luxation of the shoulder].

Latarjet's operations as single therapy was performed in 52 patients admitted since 1976 with recurrent antero-internal dislocation of shoulder. There were no recurrences but three patients (6%) complained of residual instability. Effectiveness of results depends on use of a perfect technique : the bony ridge playing both an active and passive role should be level with the antero-internal border of the glenoid.

Adolescent↗