Biomedical subjects

J Sainte-Marie

Publications and source records attributed to J Sainte-Marie.

28 records · Page 2Linked to original sources

PubMed1987

The influence of coupling transferrin to liposomes or minibeads on its uptake and fate in leukemic L2C cells.

Coupling transferrin to liposomes or minibeads did not affect its uptake by L2C lymphocytes via the Tf specific receptors. The uptake kinetics of Tf conjugated with particles about 50 nm in diameter was as rapid as in the case of native Tf, and the receptors were recycled with a similar turnover time (about 15 min). Contrary to the generally accepted scheme, we found some Tf degradation provoked by cellular uptake. The degradation represented about 10% of the amount of ligand taken up by the cells. It occurred when transferrin was coupled to liposomes, but not when coupled to minibeads.

Biological Transport↗

PubMed1986

Internalization of low-density-lipoprotein-specific receptors in leukemic guinea pig lymphocytes.

Leukemic guinea pig lymphocytes (L2C) have ten times as many low-density lipoprotein (LDL) receptors as healthy lymphocytes, but LDL accounts for only 38% of the cholesterol in L2C cells, compared to more than 95% in normal cells. Our data show that LDL fails to regulate cholesterol biosynthesis and that there is a defect in LDL internalization and receptor turnover in L2C cells. We also demonstrate that the degradation of LDL is not a limiting process. By discriminating between binding and internalization, we show that internalization in L2C is much slower than in normal cells and that the decrease in metabolism is related to the slow turnover of the LDL receptors.

Animals↗

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

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

Raman studies of structural rearrangements induced in human plasma lipoprotein carotenoids by malondialdehyde.

Raman and resonance Raman spectra of plasma lipoproteins +/- malondialdehyde were studied at concentrations which block the normal receptor-mediated uptake by cells. The strong resonance Raman bands at about 1010, 1162 and 1530 cm-1, due to the presence of carotenoids in the lipoproteins, are envisaged as structural probes. High resolution resonance Raman spectra of the 1500-1600 cm-1 region reveal multiple features suggesting the coexistence of several structural populations of beta-carotene whose precise assignment is complex. When plasma lipoproteins are reacted with malondialdehyde, a complex change occurs in the resonance Raman banding of beta-carotene in the 1500-1600 cm-1 region. Malonaldehyde (MDA) also modifies the acoustical region (70-200 cm-1 of low density lipoprotein (LDL) lipids. We suggest that malondialdehyde association with plasma lipoproteins alters the lipid structure via apoprotein or apoprotein/lipid associations.

Apolipoproteins↗

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↗

PubMed1984

Resonance Raman spectra of beta-carotene in native and modified low-density lipoprotein.

Low-density lipoproteins isolated between density 1.02 and 1.063 g/cm3 from normal fasting human plasma, show strong resonance Raman spectra due to the presence of beta-carotene. Three intense bands, at 1010, 1160 and 1530 cm-1, are assigned to the stretching vibrations of -C-CH3, = C-C = and -C = C- bonds, respectively, of beta-carotene. High-resolution spectra of the 1500-1600 cm-1 region reveal multiple features, suggesting the coexistence of several structural populations of beta-carotene. The modifications of lipoproteins with pH and temperature (30 degrees-42 degrees) change the resonance Raman spectra of beta-carotene. The specific binding of LDL at pH 7.0 by fibroblast cells is suppressed. Our experiments thus suggest that physical and chemical perturbations of plasma lipoproteins modify the lipid-protein interactions and thereby alter the configurational distribution of beta-carotene molecules within these particles.

Carotenoids↗

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↗