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Biomedical subjects

E Bastida

Publications and source records attributed to E Bastida.

At least 73 records · Page 4Linked to original sources
PubMed1985

Inhibitory effects of dipyridamole on growth, nucleoside incorporation, and platelet-activating capability in the U87MG and SKNMC human tumor cell lines.

The effects of dipyridamole on tumor cell function were examined in cultures of two lines of human origin, the SKNMC neuroblastoma line that activates platelets by a mechanism which is dependent on the release of adenosine 5'-diphosphate and the U87MG glioblastoma line that induces platelet activation by the generation of thrombin. Cells grown in the presence of dipyridamole at 1 microM showed greater than 80% inhibition of uptake of adenosine, thymidine, and uridine with both lines. At 5 microM tumor cell growth was inhibited by 70% (U87MG) and 90% (SKNMC) but without concomitant cytotoxicity as determined by clonogenic assay (50% inhibitory concentration approximately 20 microM). At 10 microM dipyridamole cyclic adenosine 3':5'-monophosphate levels increased 150% with both cell lines but no changes above baseline values were seen at 2.5 microM. The two cell lines showed different responses to being cultured in the presence of dipyridamole in terms of their ability to subsequently activate platelets. U87MG cells cultured in 10 microM dipyridamole showed a doubling of the lag time as compared with cells grown in the absence of dipyridamole but with full aggregation; with SKNMC cells the aggregation rate was reduced and cells grown in 10 microM dipyridamole showed no reversible first wave, a 5-fold increase in lag time and a 75% inhibition in total aggregation. Since therapeutic doses of dipyridamole result in plasma concentrations of approximately 3.5 microM these results suggest that potential antimetastatic effects of dipyridamole could be direct arising from inhibition of important steps in tumor cell metabolism or indirect by suppressing one or more of the mechanisms involved in the ability of tumor cells to activate platelets.

Cell Division↗
PubMed1985

Effects of divalent cations on the interaction of platelets with tumor cells: aggregation and perfusion studies with two homologous human systems.

The effects of chelation of divalent cations in the interaction of platelets and tumor cells has been studied in a homologous human system using human platelet-rich plasma and two tumor cell lines of human origin: SKNMC (neuroblastoma) cells, which cause platelet aggregation by an adenosine diphosphate-dependent mechanism, and U87MG (glioblastoma) cells, which function by a thrombin-dependent mechanism. When added at zero time, citrate 14 mmol/L completely abolished aggregation in heparinized (5 U/ml) platelet-rich plasma by either cell line, but the degree of inhibition was reduced by later addition of the chelating agent. Calcium citrate 8 mmol/L reduced by only 10%, indicating that citrate anion was not responsible for the inhibition. Addition of Ca++ or Mg++ alone or in combination at concentrations up to 1.5 mmol/L did not reverse the inhibition. Addition of higher concentrations of Ca++ (2 mmol/L) caused immediate clotting, whereas concentrations of Mg++ up to 6 mmol/L were without effect. Inhibition could be reversed by washing the platelets free of citrate and resuspending in heparinized platelet-rich plasma. Aggregation by either cell line was inhibited by EDTA and EGTA. In the Baumgartner perfusion apparatus, platelet interaction with subendothelium was increased about 50-fold in the presence of SKNMC cells, but this effect was also abolished after addition of citrate. After addition of U87MG cells to heparinized PRP, there was a 400-fold increase in platelet interaction with subendothelium, and complex thrombi containing red cells, white cells, and fibrin were formed. This stimulation was reduced to control levels by addition of citrate.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1984

Tissue factor in microvesicles shed from U87MG human glioblastoma cells induces coagulation, platelet aggregation, and thrombogenesis.

Microvesicles (diameter ca 200 nm) from the cell-free supernatant of U87MG human glioblastoma cell caused platelet aggregation and coagulation in a manner identical with that previously shown for the intact cells. Both activities were inhibited by dansylarginine -N-(3-ethyl-1,5-pentanediyl) amide (DAPA), confirming the thrombin-dependent nature of both activities. The specific activities per microgram of protein were 2-10 times greater in the microvesicles than in the plasma membrane fraction, suggesting localization in specific membrane domains. Sucrose density centrifugation gave a single protein peak (density 1.14) with congruent procoagulant and platelet aggregating activities. Both activities required the extrinsic pathway, as shown by studies with factor-deficient plasmas, and both were inhibited by heating (60 min/100 degrees C), by reduction and alkylation, and by incubation of the microvesicles with rabbit anti-bovine brain tissue factor antibody. These observations were confirmed using microvesicles from the HL-60 human promyelocytic leukemia cells, which are known to contain tissue factor activity. The results suggest that both procoagulant and proaggregating activities are causally related through the presence of tissue factor in the microvesicles. Studies with the Baumgartner perfusion apparatus showed that U87MG microvesicles increased the size of adherent thrombi nearly tenfold and that these thrombi were associated with nucleated cells from the blood. The increase in adherent thrombi did not occur if perfusion was carried out in the presence of DAPA, confirming the role of thrombin in their formation.

Antibodies↗
PubMed1982

The use of a perfusion model for studying aggregation and attachment of platelets and tumor cells at subendothelial surfaces.

The Baumgartner perfusion apparatus has been applied to the study of the interaction of platelets and tumor cells and their attachment to subendothelial structures. Cells derived from an anaplastic murine tumor (Hut 20 line) induced platelet aggregation and were included in platelet thrombi that deposited on vascular subendothelium in perfusion experiments with heparinized human blood. In contrast, perfusion of blood samples containing cells from a line derived from a human epithelial carcinoma of the lung (A549 line), which did not interact with platelets, resulted in the deposition of platelets alone, with no tumor cells or blood cells other than platelets being observed in the thrombus. Extremely large platelet-tumor cell thrombi were found at the vascular surface in Hut 20 perfusions using vessel segments which had been treated with alpha-chymotrypsin. These large heterogeneous thrombi perturbed blood flow through the system and entrapped both erythrocytes and white cells. In order to quantitate the deposition of tumor cells, Hut 20 cells were labeled with 125I-deoxyuridine and perfused in whole blood at a concentration of 3.7x10(5)/ml. Tumor cell incorporation into platelet-tumor cell thrombi on chymotrypsinized segments yielded about 30,000 cpm/mg of vascular tissue but this value was reduced some 2 orders of magnitude by the inclusion of PGE1 (1 ng/ml of perfusing blood; 2.8 microM) in parallel samples. Aspirin at 100 microM reduced tumor cell-dependent platelet aggregation but did not decrease the platelet-dependent deposition of radiolabeled Hut 20 cells on vascular subendothelium, suggesting the release reaction may not be of major significance in this interaction. Tumor cell-induced platelet aggregation was not observed in a perfusion experiment using blood from a patient with severe von Willebrand's disease. However addition of 0.1 vol of ABO-compatible, heterologous plasma as a source of factor VIII to the von Willebrand blood sample restored the platelet-dependent deposition of radiolabeled tumor cells to control values.

Animals↗
PubMed1981

Differing platelet aggregating effects by two tumor cell lines: absence of role for platelet-derived ADP.

Two different mechanisms of aggregation of heparinized human platelet-rich plasma have been identified with two tumor cell lines: In neither case are these mechanisms dependent on platelet-derived ADP. U87MG cells from a glioblastoma line of human origin caused a single irreversible wave of aggregation simultaneously with the onset of platelet secretion, and this was inhibited by heparin and hirudin but not by apyrase or phospholipase D. In contrast, Hut 20 cells from an undifferentiated tumor cell line of murine origin gave an initial reversible wave followed by a second irreversible wave, which then led to secretion. The first wave of platelet aggregation was unaffected by heparin or hirudin but was inhibited by apyrase, and the second wave was inhibited by phospholipase D. Citrate caused irreversible inhibition with either cell line, and aggregation did not occur with gel filtered platelets. These results suggest that platelet aggregation by the Hut 20 line is initially dependent on ADP released from the tumor cells, whereas aggregation induced by the U87MG line is dependent on a procoagulant activity of the tumor cell surface.

Adenosine Diphosphate↗