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Biomedical subjects

S Nicolas

Publications and source records attributed to S Nicolas.

29 records · Page 2Linked to original sources
PubMed1997

The psychophysics of J-R-L Delboeuf (1831-1896).

Delboeuf's writings on psychophysics are little known nowadays. The object of this paper is to describe the psychological contributions of this eminent Belgian psychologist of the second half of the 19th century. A true pioneer of experimental psychology, his work on psychophysics began in 1865 at the University of Gand (Ghent) but was not published until 1873 and following years. His work in this area is characterised on the one hand by the adoption of a logarithmic law relating sensation strength to stimulus strength, but which differed from that of Fechner; and on the other hand by the utilisation of a psychophysical technique based on brightness contrast (now called the 'bisection method'). Even though, Delboeuf was classified by Fechner in his later writings as an opponent of his beliefs. Delboeuf was nevertheless one of his least-virulent critics and the only psychologist of that era to have adopted a logarithmic law. Delboeuf's work is not only of historic interest; his original ideas possess sufficient interest for present-day psychophysicists to reexamine them.

Belgium↗
PubMed1997

The post-discharge prophylactic management of the orthopedic patient with low-molecular-weight heparin: enoxaparin.

This prospective, double-blind trial was performed to determine whether 4 weeks' prophylaxis with enoxaparin after total hip replacement (THR) is more effective in protecting against deep vein thrombosis (DVT) than prophylaxis during hospitalization. Two hundred sixty-two patients undergoing THR were given enoxaparin 40 mg once daily during hospitalization (9 +/- 2 days) before being randomized at discharge to continue enoxaparin (N = 131) or receive placebo (N = 131) for a total of 1 month (30 +/- 4 days). According to intention-to-treat analysis, 43 DVT and 2 pulmonary emboli (PE) occurred in the placebo group (34.4%) versus 21 DVT and no PE in the enoxaparin group (P < 0.001). The reduction in proximal DVT was also significant (21.4 vs 6.1%; P < 0.001). No major bleeding complications developed. Prophylaxis with enoxaparin for one month significantly reduces venous thromboembolic disease in patients undergoing THR compared to conventional prophylaxis during hospitalization.

Adult↗
PubMed1996

Low-molecular-weight heparin (enoxaparin) as prophylaxis against venous thromboembolism after total hip replacement.

BACKGROUND: The risk of venous thromboembolism in patients undergoing total hip replacement is known to be high. However, the optimal duration of prophylaxis with anticoagulant agents after this procedure is unknown. We sought to determine whether one month of anticoagulant therapy with the low-molecular-weight heparin enoxaparin is more effective than enoxaparin therapy given only during the hospitalization for surgery. METHODS: Two hundred sixty-two patients undergoing total hip replacement received enoxaparin during their hospitalizations (average stay, 10 to 11 days). They were then randomly assigned to receive enoxaparin or placebo (131 patients each). Blinded outpatient therapy (or placebo) was continued long enough that the total treatment period, inpatient plus outpatient, was one month for each patient. Bilateral ascending phlebography was performed 19 to 23 days after discharge, with deep-vein thrombosis as the primary end point. Distal and proximal thrombosis, pulmonary embolism, and hemorrhage were also recorded, as were deaths. RESULTS: Venography was adequate in 116 patients in the placebo group and 117 in the enoxaparin group. We observed 43 episodes of deep-vein thrombosis and 2 episodes of pulmonary embolism in the placebo group, but only 21 episodes of deep-vein thrombosis and no episodes of pulmonary embolism in the enoxaparin group (incidence of thromboembolism, 39 percent and 18 percent, respectively; P<0.001). The difference in the incidence of proximal deep-vein thrombosis was also significant (24 percent and 7 percent in the placebo and enoxaparin groups, respectively; P<0.001). Six enoxaparin groups, respectively; P<0.001). Six patients in the enoxaparin group and one patient in the placebo group had hematomas at their injection sites. No patients died or had major complications. CONCLUSIONS: There were significantly fewer venous thromboembolic complications in patients undergoing elective hip replacement when prophylaxis with enoxaparin was given for a total of one month, rather than only during the hospitalization.

Adult↗
PubMed1996

Clonal cell cultures from adult spinal cord of the amphibian urodele Pleurodeles waltl to study the identity and potentialities of cells during tail regeneration.

The urodele amphibians are nearly the only adult vertebrates able to regenerate their missing or amputated tail. The most striking feature of this model lies in the ability of the spinal cord (SC) to differentiate, within the regenerating tail, a new ependymal tube from which the SC and the peripheral nervous system originate. A fundamental question is whether, in response to tail excision, the ependymoglia of the old SC stump behaves as an embryonic neuroepithelium. To evaluate this possibility, cell lines from primary cell cultures of adult SC were established for the first time in newts, and two cell clones, immunochemically characterized as ependymoglial cell populations, could be obtained. To analyze the potentialities of these clonal cells, after transplantation in tail regenerates, cell-marking experiments, using either in vitro transfection with lacZ gene or the lineage tracer lysinated rhodamine dextran (LRD), were performed. One to 2 weeks postimplantation, most of labeled derivatives were identified as melanocytes. Interestingly, labeled cells were also seen integrated in the ependymoglia of the regenerating SC. Two to 6 weeks after implantation in young regenerates, we also observed LRD-labeled elongated cells close to nerves or myofibers which were unambiguously identified as Schwann cells by galactocerebroside staining. Taken together, these findings showed that clonal cells derived from adult newt SC cultures could largely find, in regenerate mesenchyme, suitable environmental conditions to differentiate into melanocytes or Schwann cells. Because these two cells types arise from neural crest cells during embryo-genesis, this supports the interesting view that multipotent cells are still present in the SC of adult urodeles.

Animals↗
PubMed1996

A Distal-less-like gene is induced in the regenerating central nervous system of the urodele Pleurodeles waltl.

We report the cloning of a Distal-less-like gene (PwDlx-3) and its pattern of expression during embryonic development and adult tail regeneration in the urodele Pleurodeles waltl. Using RT-PCR and in situ hybridization experiments we determined that, during regeneration, PwDlx-3 is expressed in the epidermis, the cells associated with muscle masses and in the ventrolateral parts of the ependymal tube. PwDlx-3 localization in the muscle masses and in cells of the ependymal tube, which give rise during regeneration to the ventral roots and the spinal ganglia, suggests that this gene might be expressed in cells which have some neural crest cell potentialities. PwDlx-3 is the first homeobox gene shown to be expressed in the regenerating spinal cord but not in the adult one and could thus be involved in the regeneration of the nervous system.

Amino Acid Sequence↗
PubMed1993

Fulminant hepatic failure after Lepiota mushroom poisoning.

We present ten patients who suffered from a cyclopeptide syndrome from two different foci, one caused by Lepiota helveola (seven cases) and the other by Lepiota brunneoincarnata (three cases). Of the ten victims, five recovered completely after the intestinal stage and the other five developed a phase of visceral involvement with alterations of liver function. In two patients, hepatic function became normal after the 7th day after ingestion. Three patients developed fulminant hepatitis and two of these died of adult respiratory distress syndrome. The fulminant hepatitis patient who later improved developed active chronic hepatitis 1 year later. Finally, five patients developed mixed polyneuropathy. In this paper the indications for orthotopic liver transplant (OLTx) are discussed and the development of late complications such as active chronic hepatitis and mixed polyneuropathy are considered.

Adult↗
PubMed1990

Three point mutations in the CFTR gene in French cystic fibrosis patients: identification by denaturing gradient gel electrophoresis.

The cystic fibrosis (CF) gene was recently identified as a gene spanning 250 kilobases (kbp) and coding for a 1480 amino acid protein, cystic fibrosis transmembrane conductance regulator (CFTR). Approximately 70% of CF mutations involve a three-base-pair deletion in CFTR exon 10, resulting in the loss of a phenylalanine at position 508 in the gene product (delta F508). In order to screen for other molecular defects, we have used a strategy based on denaturing gradient gel electrophoresis (DGGE) of polymerase chain reaction (PCR)-amplified gene segments. This method, which permits rapid detection of any sequence change in a given DNA stretch, was used successfully to analyse 61 non-delta F508 CF chromosomes from French CF patients. A study of CFTR exons 10, 11, 14a, 15 and 20 detected three mutations located in exons 14a, 15 and 20, along with several nucleotide sequence polymorphisms. These nucleotide changes were identified by direct sequencing of PCR fragments displaying altered electrophoretic behaviour, together with some of the polymorphisms and mutations previously characterized by others. The strategy presented here constitutes a valuable tool for the development of carrier testing for individuals or couples with a family history of cystic fibrosis, and will contribute to deciphering the functionally important regions of the CFTR gene.

Cystic Fibrosis↗
PubMed1989

Residue determination of two co-administered antibacterial agents--cephalexin and colistin--in calf tissues using high-performance liquid chromatography and microbiological methods.

Residues of two antibacterial agents, cephalexin and colistin, co-administered by intramuscular injection to calves, were quantified in four different tissues (muscle, fat, liver and kidney) by column switching HPLC and by a microbiological method. For cephalexin assay, tissue samples with cephradin as internal standard were homogenized in a 5% trichloroacetic acid solution and filtrates were injected onto a concentration precolumn filled with LiChroprep RP-18 (25-40 microns). A clean-up step was incorporated by flowing a mobile phase (methanol-0.01 M phosphate buffer (pH 3.0); 15:85, v/v) through the enrichment column before elution on a LiChrospher RP-18e (5 microns) column with a methanol-phosphate buffer (30:70, v/v) at a flow rate of 1 ml min-1. Spectrometric detection was at 260 nm. An additional "off-line" washing step of extracts with methylene chloride was operated to achieve higher selectivity in the case of liver and kidney samples. The limit for quantitative assay was 0.045 micrograms g-1 with relative standard deviations in the range 5-8% and recoveries within 70%. For microbiological assay of colistin, samples were homogenized in 0.1 M hydrochloric acid-acetonitrile mixtures (3:1, v/v, for kidney and liver; 3:2, v/v, for fat and muscle). The supernatants were assayed by the cylinder plate method after evaporation to dryness under vacuum. Bordetella bronchiseptica ATCC 4617 was chosen as test organism. After a 3-h diffusion step at room temperature, the medium was incubated at 37 degrees C for 18 h and then the diameter of the growth inhibition zones was measured. Sensitivity reached 0.10-0.15 micrograms g-1. Results from the analysed samples over a 7-28 day period after drug administration show that no cephalexin was found at concentrations higher than the quantitation limit in the four test tissues and that colistin was found in muscle (injection site only) for 15 days and in kidney for 21 days.

Adipose Tissue↗
PubMed1988

Oxolinic acid in the trout: bioavailability and tissue residues.

A study was performed on the serum bioavailability and tissue elimination of oxolinic acid in the trout. The compound was added to the diet and administered at a dosage-level of 12 mg/kg/day for 7 consecutive days. The study utilized an analytical technique, high performance liquid chromatography, which has been described in detail here. The results obtained demonstrate that serum concentrations higher than the MIC for the control of the target pathogens (Aeromonas and Yersinia) can by sustained throughout the treatment period. The same positive results were observed in the tissues. Besides, on the base of a tolerance level of 0.05 ppm for the residue levels of oxolinic acid in the edible tissues (muscle mass and skin), a withdrawal time of six days after interruption of the prescribed treatment can be proposed.

Animals↗