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Biomedical subjects

E C Sleyster

Publications and source records attributed to E C Sleyster.

13 recordsLinked to original sources
PubMed1985

Designing a datacommunications network to support decentral computer facilities within the Eurotransplant organization.

For Eurotransplant the main aspects in processing the data are time, quality and volumes. The present trends appear to hand us the right opportunity to reconsider the existing information system. New scientific developments, renewal of the software, a fast growth of quantities and an increasing demand for decentralization have created the pre-condition for a project, in which a main task is fulfilled by a data-communications system. Here a dynamic new field is entered in a decade of growing user-awareness and interest. Public Telecommunication Companies and manufacturers, although having just established the first agreements in numerous standardization committees, are now being pushed to speed up. Eurotransplant, however, needs a professional system now which takes care of network management, data security, availability and so on. Specifications for a network are investigated and a pilot study is undertaken to show that international data communication is possible.

Computers↗
PubMed1982

Relation between localization and function of rat liver Kupffer cells.

Kupffer cells were found to be distributed over zone 1 (periportal), zone 2 (midzonal), and zone 3 (perivenous) of the rat liver acinus in a ratio of 4:3:2. After pronase digestion of the liver, two purified tractions of Kupffer cells could be obtained by centrifugal elutriation. Liver zone marking with methylene blue prior to cell isolation revealed that one fraction contained Kupffer cells from the periportal area; the other consisted mainly of such cells from the midzonal and perivenous areas. Periportal Kupffer cells were larger and showed higher lysosomal enzyme activities on a per cell basis as compared with midzonal and perivenous Kupffer cells. The immediate uptake of 0.31-micrometer. latex particles during a 2-minute perfusion of the liver was mainly accomplished by periportal Kupffer cells. The higher phagocytic activity of these cells was independent of the direction which latex was flushed through the liver. Seven days after in vivo administration of latex particles, at least 80 per cent of all Kupffer cells contained latex, but again periportal Kupffer cells showed a higher phagocytic activity in that they accumulated a relatively larger number of particles per cell. Latex phagocytosis increased the activity of cathepsin D in all Kupffer cells. Titration with pepstatin revealed that periportal Kupffer cells contained many more cathepsin D molecules than pepstatin revealed that periportal Kupffer cells contained many more cathepsin D molecules than midzonal and perivenous Kupffer cells. Latex particle uptake stimulated an increase in the molecular activity of cathepsin D in periportal cells as well as in the number of cathepsin D molecules in perivenous and midzonal cells. Kupffer cells show a functional heterogeneity that is related to their position in the liver acinus. Kupffer cells with a high endocytic activity, large and heterogeneous lysosomes, and high lysosomal enzyme activities are found in the periportal zone. This zonal heterogeneity can be reduced after phagocytosis of a triggering dose of latex.

Animals↗
PubMed1980

High activity of glucose-6-phosphate dehydrogenase in Kupffer cells isolated from rat liver.

Sinusoidal cells in the rat liver react intensively for G6DPH activity after appropriate incubation (Rieder et al. 1978). After isolation and purification of the sinusoidal Kupffer and endothelial cells, it was demonstrated that Kupffer cells exhibit a 5-8 times higher G6PDH activity on a per cell basis by comparison with endothelial cells, while the specific G6PDH activity was 3-4 times higher in Kupffer cells. The Kupffer cells can be divided into two groups which differ significantly in G6PDH activity calculated on a per cell basis. In histochemical studies, G6PDH can be used as a marker for Kupffer cell identification.

Animals↗
PubMed1978

Surface morphology and ultrastructure of isolated hepatic Kupffer and endothelial cells.

Isolated non-parenchymal cells from the rat liver were separated by centrifugal elutriation into two fractions containing structurally intact Kupffer and endothelial cells with purities of over 90% in both fractions. These two cell types were then examined by transmission and scanning electron microscopy. It is concluded that Kupffer and endothelial cells are readily distinguished under the scanning electron microscope on the basis of their different surface features. Kupffer cells show ridges and ruffles while endothelial cells have microvilli and blebs and lack ruffles. As in earlier studies, transmission electron micrographs show that Kupffer cells are larger, have a smaller nucleus--cytoplasm ratio and contain lysosomes while endothelial cells are smaller, have a higher nucleus-cytoplasm ratio and show extensive sieve-plates and fenestrations.

Animals↗
PubMed1976

Lysosomal enzyme activities in parenchymal and nonparenchymal liver cells isolated from young, adult and old rats.

Parenchymal and nonparenchymal cells were isolated from the livers of female BN/BiRij rats, aged 3, 12, 24 and 30-35 months, by means of enzymatic techniques. About 70% of the cells in the nonparenchymal cell suspensions were endothelial cells and 25% were Kupffer cells. More than 90% of the isolated parenchymal, Kupffer and endothelial cells were viable as judged by trypan blue exclusion and ultrastructural appearance. The age-related changes in the specific activities of the lysosomal enzymes acid phosphatase, beta-galactosidase, cathepsin D and arylsulphatase B in parenchymal and nonparenchymal cells showed no correlated behavior. The most prominent change was observed for the cathepsin D activity in parenchymal cells, which nearly triples during the lifespan of the rat. A comparison of the activities obtained with homogenates of the whole liver and with parenchymal and nonparenchymal cells revealed that aging changes in lysosomal enzyme activities in homogenates should be carefully interpreted, since opposite patterns of change were often observed in the activities in parenchymal cells and in nonparenchymal cells.

Acid Phosphatase↗
PubMed1975

Changes in lysosomes during ageing of parenchymal and nonparenchymal liver cells.

Intact and viable parenchymal and non-parenchymal liver cell preparations were isolated by enzyme perfusion techniques from young and old rats. The distribution of the lysosomal enzymes acid phosphatase, beta-galactosidase, cathepsin D, acid DNAse, and arylsulphatase B over parenchymal and non-parenchymal cells was determined. In addition, morphological and morphometric changes which occur in parenchymal cells with age were investigated. All lysosomal enzymes studied are present in both cell classes, but non-parenchymal cells possess much ligher activities per mg protein than do parenchymal cells. This phenomenon is most pronounced for cathepsin D with a 13-times higher specific activity in non-parenchymal cells. Electron microscopic observations demonstrated that the lysosomal activities in non-parenchymal cells can be attributed mainly to the large and numerous lysosomal structures in Kupffer cells. Parenchymal cells from old rats have higher lysosomal enzyme activities per mg protein than do hepatocytes from young rats. This observation is in agreement with the general increase with age in the cytoplasmic volume fraction occupied by lysosomal structures in parenchymal cells. In general, non-parenchymal cells show no increase in specific enzyme activities with age. The results obtained suggest an increase in the heterogeneity--in both appearance and enzyme content--of the lysosomal structures in parenchymal cells with age.

Acid Phosphatase↗
PubMedDate not supplied

Aging and multiple forms of acid phosphatase in isolated rat liver cells.

Purified suspensions of highly viable parenchymal, endothelial and Kupffer cells were prepared from the livers of young (3 months of age) and old (33-34 months of age) female rats. In the cell suspensions, the activities of the multiple forms of acid phosphatase were determined with the substrates 4-methylumbelliferyl phosphate, 1-naphthyl phosphate and p-nitrophenyl phosphate. Most specific enzyme activities increased during aging, but the preference to hydrolyse any of the three substrates did not change. The small age-related changes in effects of the inhibitors fluoride and alloxan were not uniform for the the three liver cell types. The pattern for multiple forms of acid phosphatase obtained after isoelectric focusing did not change with age for Kupffer cells, while one of the two major forms of the enzyme almost disappeared in endothelial cells from old rats. With age, a very pronounced heterogeneous pattern was observed for the enzyme forms in the long-lived parenchymal cells. The increase in heterogeneity in multiple forms of acid phosphatase in aging parenchymal cells may be the result of post-translational modifications.

Acid Phosphatase↗