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M Vidal

Publications and source records attributed to M Vidal.

At least 181 records · Page 10Linked to original sources
PubMed1986

Comparison of the internalization efficiency of LDL and transferrin receptors on L2C guinea pig lymphocytes.

We demonstrate that L2C lymphocytes have about 10-times more receptors for transferrin (Tf) than healthy lymphocytes, as has been shown in the case of LDL receptors. The dissociation constant is the same in the two cell types (about 4 X 10(-7) M). In contrast to LDL, Tf enters L2C lymphocytes with very rapid kinetics. It is shown by cross-reaction that each receptor is internalized independently of the other.

Animals↗
PubMed1986

Mathematical model of the metabolism of 123I-16-iodo-9-hexadecenoic acid in an isolated rat heart. Validation by comparison with experimental measurements.

The aim of the present study was to demonstrate that it is possible to estimate the intracellular metabolism of a fatty acid labelled with iodine using external radioactivity measurements. 123I-16-iodo-9-hexadecenoic acid (IHA) was injected close to the coronary arteries of isolated rat hearts perfused according to the Langendorff technique. The time course of the cardiac radioactivity was measured using an INa crystal coupled to an analyser. The obtained curves were analysed using a four-compartment mathematical model, with the compartments corresponding to the vascular-IHA (O), intramyocardial free-IHA (1), esterified-IHA (2) and iodide (3) pools. Curve analysis using this model demonstrated that, as compared to substrate-free perfusion, the presence of glucose (11 mM) increased IHA storage and decreased its oxidation. These changes were enhanced by the presence of insulin. A comparison of these results with measurements of the radioactivity levels within the various cellular fractions validated our proposed mathematical model. Thus, using only a mathematical analysis of a cardiac time-activity curve, it is possible to obtain quantitative information about IHA distribution in the different intracellular metabolic pathways. This technique is potentially useful for the study of metabolic effects of ischaemia or anoxia, as well as for the study of the influence of various substrates or drugs on IHA metabolism in isolated rat hearts.

Animals↗
PubMed1986

Salla disease in one non-Finnish patient.

In a 5-year-old boy, an early onset psychomotor retardation with non-progressive ataxia and without dysmorphic features, associated with lysosomal storage disease found on ultrastructural examination of the conjunctiva, led to the diagnosis of Salla disease. This was supported by a tenfold excretion of urinary free sialic acid, without abnormal oligosacchariduria or anomaly in lysosomal enzymes. This boy is a native of Southern France. Screening of urinary sialic acid has to be introduced in aetiological investigations of patients with apparently non-progressive psychomotor retardation associated with ataxia or dystonic movements.

Child↗
PubMed1986

Possible involvement of presynaptic alpha 1-adrenoceptors in the effects of idazoxan and prazosin on 3H-noradrenaline release from tail arteries of SHR.

The effects of several alpha-adrenoceptor antagonists have been examined on tritium release elicited by electrical stimulation from isolated perfused SHR tail artery preparations prelabelled with 3H-noradrenaline (3H-NA). Phentolamine and yohimbine potently facilitated the stimulation evoked release of tritium at low frequencies of stimulation, but the alpha 2-adrenoceptor antagonist idazoxan was only weakly active at 1 mumol/l, despite antagonising the clonidine-evoked inhibition of 3H-release at a lower concentration of 0.1 mumol/l. The alpha 1-adrenoceptor antagonists prazosin and corynanthine also increased stimulation evoked tritium release in this preparation, suggesting the presence of prejunctional alpha 1-adrenoceptors. Furthermore, the alpha 1-adrenoceptor agonist methoxamine (3 mumol/l) caused a significant inhibition of tritium-evoked release, an effect which was blocked by prazosin (10 nmol/l). When alpha 1-adrenoceptors were blocked in the presence of prazosin, idazoxan (0.1 mumol/l) produced a significant facilitatory effect on the electrically-evoked release of 3H-transmitter. On the other hand, when alpha 2-adrenoceptors were blocked in the presence of yohimbine, exposure to idazoxan (0.1 mumol/l) reduced significantly the stimulation-evoked release of tritium elicited by electrical stimulation. The results indicate that in the SHR tail arteries, idazoxan has a partial agonist inhibitory activity on transmitter release, which can mask the facilitatory effects due to blockade of presynaptic alpha 2-adrenoceptors. The inhibitory effects of idazoxan appear to involve presynaptic alpha 1-adrenoceptors, which when stimulated, reduce 3H-NA release in SHR tail arteries.

Adrenergic alpha-Antagonists↗
PubMed1986

Differential effects of alpha-beta-methylene ATP on responses to nerve stimulation in SHR and WKY tail arteries.

The effects of alpha,beta-,methylene-adenosine triphosphate, (alpha,beta-methylene ATP, a P2-receptor desensitising agent) have been evaluated on vasoconstrictor responses elicited by exogenous agonists or electrical field stimulation in isolated perfused SHR or WKY tail arteries and on tritium release elicited by electrical field stimulation in SHR-tail arteries pre-labeled with 3H-noradrenaline. Exposure to alpha,beta-methylene ATP (0.1 mumol/l) significantly inhibited vasoconstrictor responses to electrical field stimulation in SHR tail arteries. These inhibitory effects were not further increased at a higher concentration of alpha,beta-methylene ATP (1 mumol/l). In WKY tail arteries, alpha,beta-methylene ATP (1 mumol/l) failed to significantly inhibit vasoconstrictor responses to electrical stimulation. In SHR tail arteries prelabelled with 3H-noradrenaline, alpha,beta-methylene ATP (1 mumol/l) did not inhibit the stimulation evoked release of tritium. However, at this concentration, alpha,beta-methylene ATP significantly antagonized the vasoconstrictor responses of SHR tail arteries induced by exogenous ATP (1 mumol/l), beta,gamma-methylene ATP (30 mumol/l), a stable agonist at P2-receptors, or 60 mmol/l KCl. These effects of alpha,beta-methylene ATP on contractile responses to KCl were not observed in WKY-tail arteries. In tail arteries obtained from reserpine pretreated SHR, despite a 85-95% decrease in endogenous noradrenaline tissue content, the vasoconstrictor responses induced by periarterial field stimulation were greatly diminished, but not abolished. These residual responses to periarterial field stimulation were not antagonized by prazosin (0.1 mumol/l), but were practically abolished by the addition of alpha,beta-methylene ATP (1 mumol/l). In tail arteries from WKY rats pretreated with reserpine, exposure to prazosin (0.1 mumol/l) further reduced the residual responses elicited by electrical field stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1986

Thiolation of low-density lipoproteins and their interaction with L2C leukemic lymphocytes.

We present here, a new method for coupling sulfhydryl groups (SH) to low-density lipoprotein (LDL) surface. This method uses homocysteine thiolactone (HCTL) which reacts with lysine residues in a very mild manner, and permits the selection of the number of SH bound per LDL. Under our experimental conditions (8 SH/LDL), the affinity of thiolated LDL for the specific receptors and their further internalization by L2C lymphocytes are preserved.

Animals↗
PubMed1985

Kinetics of phospholipid transfer between liposomes (neutral or negatively charged) and high-density lipoproteins: a spin-label study of early events.

The kinetics of spin-labeled phosphatidylcholine transfer between vesicles and HDL particles exhibited a two-phase process, as seen by ESR spectroscopy. The results were analyzed by considering several possible steps in the overall transfer, whose aspects were also studied: (i) micellar complex formation after HDL apolipoprotein-vesicle mixture, (ii) the rate of PC transfer from the micellar complex to HDL, (iii) the rate of the reverse reaction between overloaded HDL particles and other particles such as HDLs, LDLs, and lipid vesicles. The results agree most convincingly with a mechanism in which the diffusion of phospholipids into the HDL-endogenous lipids is the limiting step, occurring as a two-step process. In addition, we observed a negative charge effect on the lipid transfer rates and yields.

Electron Spin Resonance Spectroscopy↗
PubMed1985

LDL-mediated targeting of liposomes to leukemic lymphocytes in vitro.

We describe a method for the covalent coupling of low-density lipoproteins (LDL) to the surface of small unilamellar vesicles, and the delivery of the liposome content to leukemic L2C lymphocytes in vitro. We demonstrate the stability of the linkage between LDL and liposomes, the preservation of vesicle integrity and the affinity of the LDL for their specific receptors after the coupling reaction. Hygromycin B, an impermeant inhibitor of protein synthesis, was encapsulated in the targeted liposomes, and delivered into the cytoplasm of leukemic L2C lymphocytes by the LDL pathway, as demonstrated by the lethal effect on cells measured by 51chromium-release assay.

Animals↗
PubMed1985

Do iodinated fatty acids undergo a nonspecific deiodination in the myocardium?

The intracellular and subcellular distribution of 16-(123I)-iodo-9-hexadecenoic acid were studied in isolated rat hearts, perfused with or without glucose. At various time intervals after injection, cardiac lipids were extracted and the activity was determined for all fractions and all lipid classes. The total cardiac activity was maximal within 1 min postinjection and most of the activity was in the aqueous phase. The presence of glucose in the perfusion medium induced an increase of total cardiac and organic fraction activities. In the latter fraction, activity was very low for FFA, but high for triglycerides (TG), and especially polar lipids. The presence of an exogenous substrate, led to a more active esterification of fatty acids. Coronary effluent analysis showed, in the hydrophilic phase, a lower activity spike in the presence than in the absence of glucose. In the mitochondrial fraction most activity occurred in the organic phase, especially as polar lipids. In the nonmitochondrial fraction, activity was much higher in the aqueous phase. At 90 s postinjection of 1-14C-palmitic acid, over 80% of the myocardial activity was found in the hydrophilic fraction, which indicates, as for the iodo-fatty acid (IFA), an immediate and important oxidation, especially without glucose. These data seem to prove that IFA is taken up by the myocardial cell, subsequently enters the mitochondria and, without an early deiodination, is oxidized with iodide release. Changes in IFA metabolism, consecutive to modifications of glucose concentration in the perfusion medium can be observed by external detection of the myocardial activity curve. Omega-Iodinated fatty acids do not undergo a nonspecific deiodination and are therefore well suited for an external study of myocardial metabolism.

Animals↗
PubMed1985

The anatomy of the dysplastic hip in cerebral palsy related to prognosis and treatment.

The development of dysplasia of the hip in cerebral palsy has been studied in 292 hips in children. The rate of migration of the hip has been defined, and gave a very early indication of the prognosis for the dysplasia. A close relationship was also found between the early radiographic changes and the functional locomotor anatomy. By reviewing the initial radiographs the need for early treatment and its adaptation to the future locomotor potential of the child can be assessed. Treatment is usually by musculotendinous releases and is especially effective in early recentering of the femoral head, but this method is ineffective in correcting bone dysplasia, particularly acetabular obliquity, which starts at around the age of 30 months. It is preferable to anticipate its development by early tenotomies which are much better tolerated than pelvic osteotomy in spastic children.

Cerebral Palsy↗
PubMed1985

Controlled binding of liposomes to cultured cells by means of lectins.

Lectin-mediated binding of liposomes to Hela cells was analyzed as a function of different parameters. We show that the amount of lectin covalently bound to liposomes can be accurately controlled. We chose to work with 500 - to 1 000 molecules of WGA bound per liposome of 1 micron diameter. These liposomes bound very efficiently to Hela cells as demonstrated by fluorescent microscopy, and fluorescent cell-sorting. We show that the number of liposomes bound is proportional to the input, over a wide range of concentrations. The liposomes bound very tightly to cells and could not be removed by trypsin or N-acetylglucosamine, which competes with WGA binding.

Acetylglucosamine↗
PubMed1985

Influence on the myocardial and blood activity course of the characteristics of the labelled fatty acid injected i.v. into mice.

In order to choose a labelled fatty acid (FA) for the external study of myocardial metabolism, FAs that are different in chain length, saturation, nature and position of the radioactive label, are injected i.v. into mice. Myocardial and blood activities are measured at various times p.i. It appears that hexadecanoic and hexadecenoic acids, iodine labelled in omega position, have the highest maximal myocardial activity among all the FAs studied. Furthermore, the myocardial and blood time-activity course is similar for both FAs. As unsaturated FAs have apparently a higher myocardial fixation in man than the saturated ones, 123I 16 iodo-9 hexadecenoic acid has been selected and seems well suited for the study of myocardial metabolism.

Animals↗
PubMed1985

Kinetics of (16 123I) iodohexadecenoic acid metabolism in the rat myocardium, influence of glucose concentration in the perfusate and comparison with (1 14C) palmitate.

External counting, intracellular and subcellular distribution of (16 123I) iodohexadecenoic acid are studied on isolated rat hearts perfused with or without glucose. The presence of an exogenous substrate reduces the fatty acid oxidation and induces an increase of total cardiac and organic fraction activities. In this fraction, activity is very low for free fatty acids, but high for triglycerides and especially for polar lipids. The presence of an exogenous substrate leads to a more active esterification of fatty acids. Coronary effluents analysis shows, in the hydrophilic phase, a lower activity rebound in the presence of glucose. In the mitochondrial fraction, activity is mostly in the organic phase, as polar lipids especially. In the non-mitochondrial fraction, activity is much higher in the aqueous phase. 90 s p.i. of (l 14C) palmitic acid, over 80% of the myocardial activity is found in the hydrophilic fraction, which indicates--as for the iodo fatty acid (IHA)--an immediate and important oxidation, especially without glucose. These data seem to prove that IHA is taken up by the myocardial cells, enters the mitochondria where it is, without an early deiodination, oxidized with iodide release. IHA metabolic changes can be seen on the external detection myocardial activity curve. Omega iodinated fatty acids do not undergo a nonspecific important deiodination and are therefore well adapted to an external study of myocardial metabolism.

Animals↗
PubMed1985

Characterization of low density lipoprotein receptors in freshly isolated leukemic guinea pig lymphocytes (L2C).

The present study shows that L2C leukemic guinea pig lymphocytes have 10 times as many low density lipoprotein (LDL) receptors per cell as normal lymphocytes. The affinity of these receptors is higher for guinea pig LDL than for human LDL. In contrast to normal cells, in which the degradation of the receptor-bound LDL is quite efficient, the leukemic cells only degraded a small fraction of these same receptor-bound LDL. Thus, the internalization index was nearly 4 times higher in the normal cells than in the leukemic cells. In L2C cells, cholesterol homeostasis derived 38% of its cholesterol input from receptor-mediated degradation of LDL and 62% from cholesterol synthesis, whereas in normal cells, these fractions were 97% and 3% respectively.

Animals↗
PubMed1985

Kinetics of iodomethylated hexadecanoic acid metabolism in the rat myocardium: influence of the number and the position of methyl radicals.

The methyl-branched fatty acids, if radioiodine labelled in alpha position, are potentially adapted to a selective study of FA myocardial uptake. To determine the position and the number of methyl radicals that are necessary to obtain a maximal uptake and a minimal degradation, we measured time-activity evolution of isolated and perfused rat hearts after an injection of iodinated fatty acids which are mono- or dimethylated in alpha or beta position. Except for dimethyl fatty acid, the uptake is similar for all fatty acids studied to that of the straight chain analogue; beta mono- or dimethyl fatty acids seem best adapted to a study of the uptake because alpha monomethyl fatty acids undergo a metabolic degradation and alpha mono- and dimethyl fatty acids induce ventricular fibrillations.

Animals↗
PubMed1984

The influence of the internal content of negatively charged liposomes on their interaction with high-density lipoprotein.

The release of the internal content of negatively charged phosphatidylcholine/phosphatidylserine vesicles under the influence of high density lipoprotein was studied. Under standard conditions (the same composition outside and inside the compartment) the leakage of negative liposomes increased significantly. However, a high internal concentration of calcein provoked a sealing effect, exhibited both in sucrose and in calcein release. This sealing effect is not related to the size of vesicles, the fluidity of the membrane, the distribution of phosphatidylserine molecules, or the membrane potential. Our data indicate that surface potential influences this effect, probably in addition to a lateral pressure effect such as with cholesterol. The surface potential, as measured by the water-lipid partition coefficient of fatty acids, is strongly affected by internal ionic strength when liposomes contain calcein as well as other polyanions (6-carboxyfluorescein, sodium citrate).

Anions↗