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Biomedical subjects

J Dijkstra

Publications and source records attributed to J Dijkstra.

At least 91 records · Page 5Linked to original sources
PubMed1985

Influence of liposome charge on the association of liposomes with Kupffer cells in vitro. Effects of divalent cations and competition with latex particles.

We studied the interaction of large unilamellar liposomes carrying different surface charges with rat Kupffer cells in maintenance culture. In addition to 14C-labeled phosphatidylcholine, all liposome preparations contained either 3H-labeled inulin or 125I-labeled bovine serum albumin as a non-degradable or a degradable aqueous space marker, respectively. With vesicles carrying no net charge, intracellular processing of internalized liposomes caused nearly complete release of protein label into the medium in acid-soluble form, while phospholipid label was predominantly retained by the cells, only about one third being released. The presence of the lysosomotropic agent, ammonia, inhibited the release of both labels from the cells. At 4 degrees C, the association and degradation of the vesicles were strongly reduced. These results are very similar to what we reported on negatively charged liposomes (Dijkstra, J., Van Galen, W.J.M., Hulstaert, C.E., Kalicharan, D., Roerdink, F.H. and Scherphof, G.L. (1984) Exp. Cell Res. 150, 161-176). The interaction of both types of vesicles apparently proceeds by adsorption to the cell surface followed by virtually complete internalization by endocytosis. Similar experiments with positively charged vesicles indicated that only about half of the liposomes were taken up by the endocytic route, the other half remaining adsorbed to the cell-surface. Attachment of all types of liposomes to the cells was strongly dependent on the presence of divalent cations; Ca2+ appeared to be required for optimal binding. Neutral liposomes only slightly competed with the uptake of negatively charged vesicles, both at 4 degrees and 37 degrees C, whereas negatively charged small unilamellar vesicles and negatively charged latex beads were found to compete very effectively with the large negatively charged liposomes. Neutral vesicles competed effectively for uptake with positively charged ones. These results suggest that neutral and positively charged liposomes are largely bound by the same cell-surface binding sites, while negatively charged vesicles attach mainly to other binding sites.

Adsorption↗
PubMed1985

Rheumatoid arthritis of the shoulder. Description and standard radiographs.

The course of rheumatoid arthritis in the shoulder is evaluated in 143 patients. In a period of 29 years, 630 x-rays were taken of 286 shoulders. In this series 2 or more x-rays per shoulder were taken of 89 patients (29 male, 60 female). The various changes in the glenohumeral and acromioclavicular joints are described. Gross destruction appears to be rare, compared to the more frequently seen minor cystic changes. The progress of the disease is often slow or halting. One or both of the shoulders in some of the patients (15 male and 29 female) did not have any detectable x-ray changes, although some of them were followed up for more than 20 years. During our follow-up it became apparent that the acromioclavicular and glenohumeral joints do not follow the same course neither in time nor in severity of joint destruction. Therefore, we divided the shoulder joint into the acromioclavicular and glenohumeral joint. One normal stage and 5 stages of pathology are recognised to fit into previously published schemes of the other joints. Stage 5 appears to be a new phenomenon of neojoint formation, under the previous humeral head with the inferior glenoid rim. Joint disease in the acromioclavicular joint could be divided only into 3 stages.

Acromioclavicular Joint↗
PubMed1984

Effects of ammonium chloride and chloroquine on endocytic uptake of liposomes by Kupffer cells in vitro.

In this study we investigated the interaction of liposomes with rat Kupffer cells in maintenance culture by using the lysosomotropic amines ammonium chloride and chloroquine as inhibitors of intralysosomal degradation. The liposomes (large unilamellar vesicles) contained either the metabolically inert 3H-labeled inulin or the degradable 125I-labeled bovine serum albumin. In control incubations, the cells released nearly all accumulated protein label and about 30% of the lipid label when they were incubated in the absence of liposomes, after an initial uptake period of 1 h in the presence of liposomes. This release of label was, for the greater part, suppressed in the presence of ammonia or chloroquine. When the inhibitors were present during the initial uptake period, a several-fold increase in the amount of protein label accumulating in the cells and a smaller, but still marked, increase in lipid label accumulation were observed. The effect of ammonia when present during uptake was readily reversible in contrast to that of chloroquine. Experiments with encapsulated inulin revealed that both lysosomotropic agents also affected the uptake process per se to some extent, probably as a result of impaired membrane/receptor recycling. Labeled liposomes adsorbed to the cells at 4 degrees C were effectively internalized and processed intracellulary after shifting the temperature to 37 degrees C, even when a 500-fold excess of unlabeled liposomes was present in the medium during the 37 degrees C incubation. The observed effects of ammonia and chloroquine indicate that, after uptake, the liposomes are degraded within lysosomes, thus confirming our previous conclusion that endocytosis is the major uptake mechanism at 37 degrees C. From the temperature-change experiments we conclude that, at 4 degrees C, the liposomes are bound with high affinity to the cells, remaining firmly attached to the cell-surface structures which initiate their internalization when the temperature is raised to 37 degrees C.

Albumins↗
PubMed1984

Interaction of liposomes with Kupffer cells in vitro.

We investigated the interaction of liposomes with rat Kupffer cells in monolayer maintenance culture. The liposomes (large unilamellar vesicles, LUV) were composed of 14C-labelled phosphatidylcholine, cholesterol and phosphatidylserine (molar ratio 4:5:1) and contained either 3H-labelled inulin or 125I-labelled bovine serum albumin as a non-degradable or a degradable aqueous space marker, respectively. After 2-3 days in culture the cells exhibited optimal uptake capacity. The uptake process showed saturation kinetics, maximal uptake values amounting to 2 nmol of total liposomal lipid/h/10(6) cells. This is equivalent to 1500 vesicles per cell. The presence of fetal calf serum (FCS) during incubation increased uptake nearly two-fold, whereas freshly isolated rat serum had no effect. The binding of the liposomes to the cells caused partial release of liposomal contents (about 15-20%) both at 4 degrees C and at 37 degrees C. In the presence of metabolic inhibitors the uptake at 37 degrees C was reduced to about 20% of the control values. Inulin and lipid label became cell-associated at similar rates and extents, whereas the association of albumin label gradually decreased after attaining a maximum at relatively low values. When, after 1 h incubation, the liposomes were removed continued incubation for another 2 h in absence of liposomes led to an approx. 30% release of cell-associated lipid label into the medium in water-soluble form. Under identical conditions as much as 90% of the cell-associated albumin label was released in acid-soluble form. Contrarily, the inulin label remained firmly cell-associated under these conditions. From these results we conclude that Kupffer cells in monolayer culture take up liposomes primarily by way of an adsorptive endocytic mechanism. This conclusion was confirmed by morphological observations on cells incubated with liposomes containing fluorescein isothiocyanate (FITC) dextran or horseradish peroxidase as markers for fluorescence microscopy and electron microscopy, respectively.

Adsorption↗
PubMed1983

Targeted and nontargeted liposomes for in vivo transfer to rat liver cells of a plasmid containing the preproinsulin I gene.

A plasmid containing the rat preproinsulin I gene was entrapped in large liposomes and intravenously administered to rats. Four hours after inoculation, the livers were processed for the isolation of hepatocytes. Kupffer cells, and endothelial cells, DNA was purified, and the exogenous DNA was detected in the different cell DNA preparations by Southern blotting. By using liposomes consisting of phospholipids and cholesterol, Kupffer cells were shown to be, on a per cell basis, the primary target for gene incorporation. In an attempt to target the liposomes to other liver cells, a glycolipid, lactosylceramide, was included in the lipid bilayer of the liposomes; this resulted in a substantial increase in the proportion of the exogenous gene in the hepatocytes and mainly in the endothelial cells, with a simultaneous decrease of this proportion in the Kupffer cells. Thus, it is shown that inclusion of a specific glycolipid within the bilayer of the liposomes may direct the DNA-containing vesicles to specific cell types in the liver.

Animals↗
PubMed1981

The involvement of parenchymal, Kupffer and endothelial liver cells in the hepatic uptake of intravenously injected liposomes. Effects of lanthanum and gadolinium salts.

125I-labeled albumin or poly(vinyl pyrrolidone) encapsulated in intermediate size multilamellar or unilamellar liposomes with 30-40% of cholesterol were injected intravenously into rats. In other experiments liposomes containing phosphatidyl[Me-14C]choline was injected. 1 h after injection parenchymal or non-parenchymal cells were isolated. Non-parenchymal cells were separated by elutriation centrifugation into a Kupffer cell fraction and an endothelial cell fraction. From the measurements of radioactivities in the various cell fractions it was concluded that the liposomes are almost exclusively taken up by the Kupffer cells. Endothelial cells did not contribute at all and hepatocytes only to a very low extent to total hepatic uptake of the 125I-labels. Of the 14C-label, which orginates from the phosphatidylcholine moiety of the liposomes, much larger proportions were recovered in the hepatocytes. A time-dependence study suggested that besides the involvement of phosphatidylcholine exchange between liposomes and high density lipoprotein, a process of intercellular transfer of lipid label from Kupffer cells to the hepatocytes may be involved in this phenomenon. Lanthanum or gadolinium salts, which effectively block Kupffer cell activity, failed to accomplish an increase in the fraction of liposomal material recovered in the parenchymal cells. This is compatible with the notion that liposomes of the type used in these experiments have no, or at most very limited, access to the liver parenchyma following their intravenous administration to rats.

Animals↗
PubMed1980

Effect of lipoprotein-free plasma on the interaction of human plasma high density lipoprotein with egg yolk phosphatidylcholine liposomes.

Liposomes consisting of 14C-labeled egg yolk phosphatidylcholine were incubated with whole human plasma or plasma subfractions. The transfer of liposomal phospholipid to plasma high density lipoprotein was determined by gel filtration. Whole plasma degraded the liposomes considerably faster than isolated high density lipoprotein. The phospholipid-transferring activity of whole plasma could be recovered in an equivalent mixture of isolated high density lipoprotein and lipoprotein-free plasma. The transfer stimulating activity in lipoprotein-free plasma was not associated with albumin but with a component of higher molecular weight. Upon incubation of lipoprotein-free plasma with liposomes this component appeared to be adsorbed to the liposomes and could thus be separated from the bulk protein by gel filtration. This binding to liposomes is taken as an indication that the component acts by modifying the lipid-water interface thus facilitating the insertion of the lipoprotein into the liposomal bilayer.

Biological Transport↗
PubMed1978

Estradiol-induced synthesis of vitellogenin. IV. The isolation of non-degraded polysomes from avian liver using an endogenous ribonuclease inhibitor.

A procedure allowing the isolation of intact polysomes from rooster liver is described. Good recovery of polysomes is achieved by the presence of Triton X-100 in the homogenization and centrifugation steps since the detergent prevents the sedimentation of microsomes with the nuclear fraction. This sedimentation of microsomes leads to considerable losses of polysomes, especially the larger ones. In the detergent-treated homogenate the integrity of the polysomes is threatened by various ribonucleases, some of which can be effectively inhibited by the addition of both heparin and yeast RNA. The remaining nuclease activity is counteracted by the endogenous ribonuclease inhibitor of the liver. In estradiol-treated roosters, sufficient endogenous inhibitor is present to inhibit its specific ribonuclease, but in control roosters there is not. This difference is due to a hormone-mediated increase in inhibitor level and decrease in nuclease level. Consequently, for an estrogenized rooster, the addition of both heparin and yeast RNA to the homogenate suffices to stabilize the polysomes, whereas control rooster liver homogenate needs supplementation with endogenous ribonuclease inhibitor. The cytosol of estrogenized rooster liver can be used as a crude inhibitor preparation. Rat liver cytosol is only partially effective; this may indicate a certain degree of species specificity of the inhibitor. The isolation procedure described also yields large polysomes from the livers of duck and Xenopus.

Animals↗
PubMed1976

Estradiol-induced synthesis of vitellogenin. III. The isolation and characterization of vitellogenin messenger RNA from avian liver.

The messenger RNA of the hormone-induced protein vitellogenin was isolated from the liver of estrogen-treated roosters. Starting from total polysomal RNA, the vitellogenin messenger was purified 67-fold by oligo (dT)-cellulose chromatography and sizing on a sucrose gradient. The messenger was translated in vitro into a 170 000 dalton polypeptide chain, having the immunochemical characteristics of vitellogenin. From electrophoretic and immunochemical analysis of the in vitro product of translation at least 63% of the messenger activity of the RNA preparation could be attributed to vitellogenin mRNA. Gel electrophoresis of the most purified fraction revealed residual contamination with the larger ribosomal RNA species. The molecular weight of the messenger RNA molecule, obtained by contour length measurements in the electron microscope, lies between 2.5 - 10(6) and 2.8 - 10(6).

Animals↗
PubMed1975

In vitro reaction of beta-propiolactone and gamma-butyrolactone with glutathione and cysteine.

The in vitro reaction of the carcinogenic beta-propiolactone (BPL) and the non-carcinogenic gamma-butyrolactone (GBL) with glutathione (GSH) and cysteine (CySH) was examined spectrophotometrically. The characteristic absorbance of thioesters in the region of 233 nm appeared when BPL and GSH reacted but not when BPL and CySH reacted or when GBL was mixed with GSH or CySH. The absorbance disappeared when hydroxylamine was added. The results are in striking contrast to the notion that all carcinogenic lactones alkylate nucleophiles and that all inactive lactones acylate nucleophiles. The reaction between BPL and GSH produced about equal quantities of thioester and thioether, which could be separated chromatographically.

Binding Sites↗