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Biomedical subjects

H Prydz

Publications and source records attributed to H Prydz.

At least 127 records · Page 7Linked to original sources
PubMed1983

Regulation of thromboplastin synthesis in mouse placental cells in vitro.

Mouse placental cells are probably constitutive producers of the thromboplastin apoprotein in vitro. The effect of cyclic AMP-elevating compounds on their expression of thromboplastin activity has been studied. Dibutyryl cyclic AMP, the phosphodiesterase inhibitor Ro 20-1724 and the adenyl cyclase stimulator forskolin all decrease the synthesis of thromboplastin. Prostaglandin E2 and the phosphodiesterase inhibitor butyl-methyl-xanthine have a biphasic dose dependent effect. A stimulation was observed at low concentrations, whereas higher doses decreased the synthesis of thromboplastin. Adrenaline had no effect. Combination of two compounds, each at maximally inhibiting concentration gave no significant additive inhibitory effect, showing that they probably act via the same pathway.

1-Methyl-3-isobutylxanthine↗
PubMed1983

Monocytes and platelets share the glycoproteins IIb and IIIa that are absent from both cells in Glanzmann's thrombasthenia type I.

By means of an antiserum specific to the complex of the platelet membrane glycoproteins IIb and IIIa we demonstrate here that monocytes and purified monocyte membranes share these glycoproteins with platelets. The monocyte glycoprotein IIb-IIIa complex showed complete immunological identity with the platelet counterpart and, furthermore, dissociated after EDTA treatment exactly as did the platelet complex. In Glanzmann's thrombasthenia type I, monocytes as well as platelets lack this antigen completely.

Antigens, Surface↗
PubMed1983

Inflammatory particles stimulate thromboplastin production by human monocytes.

Several inflammatory particles (zymosan, two forms of asbestos, carrageenan) and the soluble inflammatory agent dextran sulphate induced a dose- and time-dependent increase in thromboplastin activity of cultured human monocytes. Two weakly inflammatory particles (latex and anatase) had little effect. The increase largely depended on protein synthesis; was slow, reaching a peak at about 18 h; and was not due to endotoxin. This procoagulant may contribute to the fibrin deposition frequently seen in inflammatory lesions.

Asbestos↗
PubMed1983

Platelets stimulate thromboplastin synthesis in human endothelial cells.

Human umbilical vein endothelial cells in culture synthesize thromboplastin upon stimulation with phytohaemagglutinin (PHA) or the tumor promotor 12-O-tetradecanoyl-phorbol-13-acetate (TPA). The thromboplastin activity is further strongly enhanced in a time dependent reaction by the presence of gel-filtered platelets or platelet aggregates. This effect was demonstrable at platelet concentrations lower than those normally found in plasma, it may thus be of pathophysiological relevance. The thromboplastin activity increased with increasing number of platelets added. Cycloheximide inhibited the increase, suggesting that de novo synthesis of the protein component of thromboplastin, apoprotein III, is necessary. When care was taken to remove monocytes no thromboplastin activity and no apoprotein III antigen could be demonstrated in suspensions of gel-filtered platelets, platelets aggregated with thrombin or homogenized platelets when studied with a coagulation assay and an antibody neutralization technique.

Blood Platelets↗
PubMed1983

Amines induce increased thromboplastin activity in human monocytes.

A variety of amines induced a dose-dependent and time-dependent increase in thromboplastin activity of cultured human monocytes. The increase required protein synthesis, and reached a peak after about 18 h. Some inhibitory effects were noted at low concentrations of NH4Cl. It is suggested that the amines act by raising the pH of acidic intracellular compartments.

Amines↗
PubMed1983

Cellular cooperation in endothelial cell thromboplastin synthesis.

Endothelial cells from human umbilical veins produce a procoagulant identified as thromboplastin (tissue factor, factor III) when stimulated with the phorbol ester 12-0-tetradecanoyl-phorbol-13-acetate (TPA), phytohaemagglutinin (PHA) or endotoxin, Inducible thromboplastin synthesis (i.e. synthesis of the protein component of thromboplastin, apoprotein III) was totally inhibited by cycloheximide and actinomycin D, indicating that de novo protein and RNA syntheses are necessary. Serum enhanced the induced apoprotein synthesis. Of the total thromboplastin activity in homogenates of stimulated endothelial cells, about 50--70% was available on the cell surface for interaction with other coagulation factors, inactivation by trypsin and neutralization with antiserum against apoprotein III. Induced synthesis of thromboplastin in endothelial cells was 2--7-fold enhanced by the presence of several other cell types in optimal ratio 4--10 cells per endothelial cell. Some of these cell types were themselves thromboplstin producers (U-937, U-937-4), some were not inducible (lymphocytes, granulocytes and the lymphoblast lines Daudi and Molt 4). This enhancing effect was also seen with cell-free culture supernatants, but these were generally somewhat less effective than the intact cells. Supernatants derived from cells cultured in the presence of TPA, PHA or endotoxin were in most cases more effective than supernatants from unstimulated cells.

Cell-Free System↗
PubMed1983

Thromboplastin as a marker for monocyte differentiation.

The thromboplastin synthesis of the human monocytoid cell line U-937 and its two subclones designated U-937-3 and U-937-4 has been studied. U-937-4 seems by several functional criteria to represent a more advanced stage of monocyte differentiation than the original U-937. U-937-3 appears to be arrested at an even more immature stage than the original population. The basal thromboplastin activity was higher in U-937-4 than in U-937-3 or U-937 cells (7.0 +/- 1.9 (SEM), 1.0 +/- 0.2 and 1.6 +/- 0.6 units/mg protein, respectively) although not as high as in human normal monocytes (14.1 +/- 2.4). The thromboplastic expression of the two clones was maximal when cells were in logarithmic growth. Both clones responded with a weak to moderate thromboplastin synthesis upon addition of stimulants like phytohaemagglutinin (PHA), immune complexes or endotoxin. Thromboplastin production was also potentiated in the presence of lymphocytes. The supporting effect of lymphocytes was strong in the case of U-937-3 as well as in U-937 cells, but less pronounced in U-937-4 cells as it also is in human monocytes. The thromboplastin response after PHA stimulation was more rapid in U-937-4 cells (maximal after 4-8 h) than in U-937 or U-937-3 cells (12-16 h). Human monocytes also responds quickly to PHA (maximally 4 h). Total phospholipid content and the relative distribution of individual phospholipids were essentially similar in U-937-3, U-937-4 and U-937. With regard to thromboplastin production, U-937-4 cells seem to be more monocyte-like than the more immature cells U-937-3 and U-937. It is concluded that thromboplastin seems to be a useful marker for monocyte differentiation.

Antigen-Antibody Complex↗
PubMed1983

Macrophage heterogeneity in thromboplastin response.

The procoagulant activities of non-elicited mouse monocytes/macrophages from four anatomical localizations were compared. These cell populations were further examined for their ability to increase their procoagulant activity on exposure to endotoxin or phytohaemagglutinin (PHA). Peritoneal macrophages exhibited the highest basal procoagulant activity. Their activity was further enhanced by stimulation with endotoxin and PHA, but marked strain differences were noted. This procoagulant has been identified as tissue thromboplastin. Isolated adherent spleen cells, peripheral blood monocytes or lung alveolar macrophages had a low basal procoagulant activity that did not increase on exposure to PHA or endotoxin. The identity of the weak procoagulant in these cells is uncertain. The presence of lymphocytes in the macrophage cultures (4:1 ratio) enhanced slightly (1.3 to 1.5-fold) the response of peritoneal macrophages to endotoxin or PHA but did not significantly influence the procoagulant activity of the other macrophage subpopulations under the conditions tested. These results demonstrate heterogeneity among different macrophage subpopulations with regard to cellular procoagulant expression.

Animals↗
PubMed1983

Synthesis of thromboplastin (factor III) in mouse placental cells in vitro.

Mouse placental cells have been isolated and grown in cultures. These cells produce a procoagulant which is identical to thromboplastin (factor III) by two criteria. The procoagulant activity increases with time, culminating on the 5th day of culture. The increase is inhibited by cycloheximide, alpha-amanitin, and actinomycin D, showing that de novo synthesis of protein and RNA is necessary. About 90-95% of the total cellular thromboplastin activity in whole cells is available for inactivation by particle-bound trypsin and thus present on the cell surface. Endotoxin and phytohaemagglutinin did not further increase the procoagulant activity.

Amanitins↗
PubMed1983

The role of cellular cooperation in thromboplastin synthesis.

Increasing evidence [1, 2, 3] demonstrates the clinical importance of monocyte thromboplastin synthesis in the pathogenesis of thrombosis and disseminated intravascular coagulation. Among the first to describe this was the group of the late F Josso [4, 5]. In addition, monocytes and macrophages appear to contribute to fibrin deposition in inflammatory lesions [6, 7]. Several procoagulant substances have been reported to appear in monocyte cultures. Among these, thromboplastin is the most potent and probably also the most important and well studied. Based as it is on our own work, this brief review will deal only with thromboplastin. It is a phospholipid-protein complex, consisting in human material of one species of protein (apoprotein III) mol. wt. approximately 52,000 surrounded by phospholipids [8] in an optimal molecular ratio of apoprotein:phospholipids of approximately 1:80 [9]. Apoprotein III is an integral membrane glycoprotein which apparently is located mainly on the outside of the plasma membrane. The molecular weight has recently been confirmed in our laboratory by Western blotting, using a monoclonal antibody to apoprotein III developed here (Johnsen, unpublished).

Animals↗
PubMed1983

Intravenous injections of tissue thromboplastin and phospholipase C in rabbits.

Previous experiments (Gollub et al. [10]. Giercksky et al.) have shown that phospholipase C (PLC) has a protective effect on rats and rabbits receiving thromboplastin infusions. As a step towards the possible use of PLC in humans, we have investigated further the use of PLC in rabbits. Infusions of human or rabbit thromboplastin caused a rapid fall in factors V and VIII. LD50 for our standard human thromboplastin preparation was estimated to be 1.5--1.8 ml/kg. Highly purified PLC was given as an intravenous bolus immediately before thromboplastin. No improvement of survival and only a slight difference in factors V and VIII were observed, in contrast to earlier observations in the rat. This may in part be due to differences in the susceptibility to PLC of the thromboplastins used. PLC was also more toxic in rabbits than in rats.

Animals↗
PubMed1983

Is lymphocyte co-operation necessary for thromboplastin synthesis by human monocytes?

Human monocytes synthesize the protein component of thromboplastin and express increased procoagulant activity when appropriately stimulated in vitro. The activity reached maximum between 2 and 20 h depending on the stimulant used. The presence of lymphocytes (lymphocyte: monocyte ratio 4:1) enhanced this activity only very slightly (up to 1.3-fold) at the time of maximal monocyte thromboplastin expression. Lymphocytes had a marked potentiating effect on PHA stimulation that became clearly evident after 12 h, at which time the thromboplastin response of monocytes alone to PHA had subsided. The thromboplastin activity of monocytes remained at a high level for 24-40 h in the presence of PHA or endotoxin and lymphocytes, but lymphocytes did not influence the early (4-8 h) thromboplastin response. Neither did lymphocytes alter the magnitude or the time course of the response when monocytes were stimulated with PPD, TPA or immune complexes. The lymphoblastoid cell line Molt 4 (T cell like) was as effective as lymphocytes, Daudi cells (B cell like) were slightly less effective. The enhancement of thromboplastin activity in PHA-stimulated monocytes could be induced also by conditioned medium from PHA stimulated lymphocytes. We conclude that freshly isolated monocytes synthesize thromboplastin directly upon interaction with a stimulant, and are not dependent on a helper effect of lymphocytes or lymphocyte products. Such help, however, will prolong the ability of the monocytes to respond.

Antigen-Antibody Complex↗
PubMed1982

Synthesis of thromboplastin protein by a murine macrophage-like cell line.

The established murine macrophage cell line J-774.1 responds to endotoxin with synthesis of thromboplastin apoprotein. The response develops in the absence of added lymphocytes and there is no increased responsiveness in cocultures of J-774.1 cells and BALB/c lymphocytes. J-774.1 cells therefore do not depend on lymphocyte cooperation for their response to endotoxin.

Animals↗
PubMed1982

Effect of immune complex-containing sera from patients with rheumatic diseases on thromboplastin activity of monocytes.

Monocytes isolated from peripheral blood of patients with various rheumatic diseases and circulating immune complexes (IC) developed a significantly higher thromboplastin (tissue factor) activity than normal cells when cultured in vitro without inducers, but normal cells responded more strongly with thromboplastin production upon stimulation with IC or phytohaemagglutinin (PHA). Sera from patients with rheumatic diseases and circulating IC induced a significant increase in the thromboplastin activity of normal monocytes. Lysozyme release from patient monocytes was significantly lower than the release from control cells when stimulated with IC. Patient sera contained higher amounts of lysozyme than normal sera, indicating lysozyme release in vivo. These data suggest that activation of monocytes in vivo by IC may take place. The increased expression of thromboplastin in monocytes/tissue macrophages may be important for the development of microvascular thrombosis and fibrin deposition seen in chronic inflammatory lesions.

Adolescent↗
PubMed1982

Phospholipase C from Bacillus cereus has sphingomyelinase activity.

Purified, electrophoretically homogeneous phospholipase C (PLC) preparations can be separated into two peaks by isoelectric focusing in sucrose gradients. The main peak has an isoelectric pH of 6.6-6.8 and contains two Zn2+ per molecule. The more acid peak (isoelectric pH about 6.2) contains about one Zn2+ per molecule and has a markedly reduced specific activity which can be raised by adding Zn2+. The purified enzyme has a low sphingomyelinase activity which coincides completely with the lecithinase activity in fractions from isoelectric focusing. The sphingomyelinase activity was greatly enhanced by substitution of Co2+ for Zn2+ but remained essentially unaltered when the levels of Ca2+ and Mg2+ were changed. These findings provide evidence that the sphingomyelinase activity is a true endogenous activity of PLC and not caused by contaminating sphingomyelinase.

Bacillus cereus↗
PubMed1982

Synthesis of thromboplastin by U-937 cells.

A human monocytoid cell line (U-937) produces a procoagulant identified as thromboplastin when stimulated with phytohaemagglutinin (PHA), endotoxin, immune complexes, the phorbol ester 12-O-tetradecanoyl-phorbol 13-acetate (TPA) or the divalent ionophore A 23187. The basal thromboplastin expression of these cells and the increased activity induced by the stimulants were dependent on supply of fresh medium suggesting that the synthetic rate was highest when the cells were in logarithmic growth. Inducible thromboplastin synthesis was inhibited by actinomycin D or cycloheximide, indicating dependence on messenger RNA and protein synthesis. Differentiation of the cells in the macrophage direction by TPA did not make the cells more responsive to PHA. Thromboplastin induction in U-937 cells was potentiated by the presence of lymphocytes, especially when stimulated with PHA or endotoxin. This supporting effect was also obtained by conditioned medium from lymphocyte cultures, suggesting a role for a soluble lymphocyte product.

Antigen-Antibody Complex↗