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Accueil > Publications > Recherche par années > Années 1990 > 1991

1991

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A mutation in the human lipoprotein-lipase gene as the most common cause of familial chylomicronemia in french-canadians

Background. Lipoprotein lipase hydrolyzes the triglyceride core of chylomicrons and very-low-density lipoproteins and has a crucial role in regulating plasma lipoprotein levels. Deficiencies of lipoprotein lipase activity lead to aberrations in lipoprotein levels. Worldwide, the frequency of lipoprotein lipase deficiency is highest among French Canadians. We sought to determine the molecular basis of the disorder in this population. Methods. The entire coding sequence of the lipoprotein lipase gene from one French Canadian patient was amplified by the polymerase chain reaction and sequenced. Exon 5 from 36 other French Canadian patients was amplified and analyzed by dot blot hybridization with allele-specific oligonucleotides. Results.

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Accumulation of acyl-enzyme in DD-peptidase-catalyzed reactions with analogs of peptide-substrates

Thioester substrates can be used to study the hydrolysis and transfer reactions catalysed by ß-lactamases and DD-peptidases. With the latter enzymes, accumulation of the acyl-enzyme can be detected directly. The efficiency of various amines as acceptor substrates was in excellent agreement with previous results obtained with peptide substrates of the DD-peptidases. The results indicated the presence of a specific binding site for the acceptor substrates, Although most of the results agreed well with a simple partition model, more elaborate hypotheses will be needed to account for all the data presented.

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Acyltransferase activities of the high-molecular-mass essential penicillin-binding proteins

The high-molecular-mass penicillin-binding proteins (HMM-PBPs), present in the cytoplasmic membranes of all eubacteria, are involved in important physiological events such as cell elongation, septation or shape determination. Up to now it has, however, been very difficult or impossible to study the catalytic properties of the HMM-PBPs in vitro. With simple substrates, we could demonstrate that several of these proteins could catalyse the hydrolysis of some thioesters or the transfer of their acyl moiety on the amino group of a suitable acceptor nucleophile. Many of the acyl-donor substrates were hippuric acid or benzoyl-D-alanine derivatives, and their spectroscopic properties enabled a direct monitoring of the enzymic reaction. In their presence, the binding of radioactive penicillin to the PBPs was also inhibited.

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Altered o-glycan synthesis in lymphocytes from patients with wiskott-aldrich syndrome

The only molecular defect reported for the X-linked immunodeficiency Wiskott-Aldrich syndrome (WAS) is the abnormal electrophoretic behavior of the major T lymphocyte sialoglycoprotein CD43. Since the 70 to 80 O-linked carbohydrate chains of CD43 are known to influence markedly its electrophoretic mobility, we analyzed the structure and the biosynthesis of O-glycans of CD43 in lymphocytes from patients with WAS. Immunofluorescence analysis with the carbohydrate dependent anti-CD43 antibody T305 revealed that in 10 out of the 12 WAS patients tested increased numbers of T lymphocytes carry on CD43 an epitope which on normal lymphocytes is expressed only after activation.

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An automated method for the assessment of spontaneous and stereotyped climbing behavior in mice : effects of the selective D(1)- and D(2)- dopamine receptor agonists SKF-38393 and RU-24926 and their association

A video-tracking technique has been used for the evaluation of climbing behavior in mice. An automated image analysis system, the Videotrack 512 (Electronique Lyonnaise), was adapted for this specific application. This allowed distinguishing between spontaneous climbing and stereotyped climbing. The activity duration of mice was simultaneously measured. In order to validate this method, in the present study the ability of apomorphine to induce climbing in mice, and the effects of the D1-dopamine receptor agonist SKF-38393 and the D2-dopamine agonist RU-24926 and their association were investigated.

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Bis(pyrrolecarboxamide) linked to intercalating chromophore oxazolopyridocarbazole (OPC) - selective binding to DNA and polynucleotides

We have investigated some properties related to interaction with DNA and recognition of AT-rich sequences of netropsin-oxazolopyridocarbazole (Net-OPC) (Mrani et al., 1990), which is a hybrid groove-binder-intercalator. The hybrid molecule Net-OPC binds to poly[d(A-T)] at two different sites with K(app) values close to 7 X 10(6) and 6 X 10(8) M-1 (100 mM NaCl, pH 7.0). Data obtained from melting experiments are in agreement with these values and indicate that Net-OPC displays a higher binding constant to poly[d(A-T)] than does netropsin. On the basis of viscometric and energy transfer data, the binding of Net-OPC to poly[d(A-T)] is suggested to involve both intercalation and external binding of the OPC chromophore.

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Brownian dynamics in a confined geometry - experiments and numerical simulations

The Brownian dynamics of a colloidal suspension is measured in the immediate vicinity of a rigid surface by the Evanescent Quasielastic Light Scattering Technique. A net decrease of the measured diffusion coefficient is observed, due to the hydrodynamic slowing down of the particles very close to the wall. This effect is all the more important when the particles are allowed to get closer to the wall, i.e. when the range of the static wall/particle repulsive interaction decreases. It thus provides a mean for testing the particle/wall static interactions via a dynamic light scattering measurement. The data are analysed by a Brownian dynamic simulation which is proven to be quite valuable to interpret light scattering data from

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