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Biomedical subjects

A M Dosne

Publications and source records attributed to A M Dosne.

17 recordsLinked to original sources
PubMed1991

Importance of plasminogen activator inhibitor type 1 (PAI-1) for preventing single chain urokinase plasminogen activator (scu-PA) conversion into two chain urokinase plasminogen activator (tcu-PA) in plasma in vitro.

We have studied the effects of PAI-1 on the conversion of scu-PA into tcu-PA in vitro in plasma containing or not a 125I-fibrin clot by determining tcu-PA activity on S2444. Two preparations of PAI-1 have been used, a fraction of medium conditioned with the monkey Vero cells (Vero-Prep), the antiurokinase activity of which is inhibited at 83% by anti PAI-1 IgG, or purified human PAI-1 from HT 1080 fibrosarcoma cells. Scu-PA purified from human kidney cells has been treated with diisopropylfluorophosphate before use. In plasma, conversion of scu-PA into the tc form is accelerated by addition of anti PAI-1 IgG. In plasma containing a clot, generation of tcu-PA, is considerably delayed after addition of the Vero-Prep or human PAI-1. Clot lysis is also decreased but to a lesser extent than it would be expected from the level of tcu-PA activity. Addition of anti PAI-1 antibodies shortens the lag phase before tcu-PA appears and moderatly accelerates clot lysis. These results demonstrate the importance of PAI-1 for the stability of scu-PA in plasma in vitro by delaying its conversion into tcu-PA.

Animals↗
PubMed1989

Effect of standard heparin and a low molecular weight heparin on thrombolytic and fibrinolytic activity of single-chain urokinase plasminogen activator in vitro.

The effect of unfractioned heparin (UH) and low molecular weight heparin (LMWH) (Kabi 2165 - Fragmin) on in vitro scu-PA thrombolytic and fibrinogenolytic activity was investigated. Thrombolytic activity was evaluated by following lysis of radiolabeled plasma clot immersed in plasma in presence of scu-PA alone or with either form of heparin. A 200 IU/ml scu-PA concentration produced clot lysis within 7 hr. UH or LMWH led to a slightly faster clot lysis which was statistically significant only at the 2nd and 3rd hour. No significant difference could be evidenced between UH and LMWH effect. During clot lysis, plasmin, generated within the clot led to a gradual transformation of scu-PA to tcu-PA, specially after a 4-hr incubation. Appearance of tcu-PA activity in the plasma surrounding the clot was significantly inhibited by either form of heparin. This finding contrasts with results observed in purified systems and suggests the presence of heparin-dependent plasma factor(s) inhibiting tcu-PA formation or its activity. Possible candidates might be anti-thrombin III and PAI-3. No fibrinogen breakdown was observed when plasma was incubated for 7 hr at 37 degrees C in presence of scu-PA alone (200 IU/ml) or with either form of heparin. However, in presence of a plasma clot, an important fibrinogen breakdown was observed during clot lysis reflecting the action of plasmin and/or tcu-PA generated within the clot, in the surrounding plasma. Fibrinogenolysis was less pronounced in the presence of both heparin preparations possibly as a consequence of the reduction in the tcu-PA level. These results underline the importance of plasma factors in the interaction of heparin with plasminogen activators such as scu-PA.

Fibrinogen↗
PubMed1988

Tumor necrosis factor (TNF) stimulates plasminogen activator inhibitor (PAI) production by endothelial cells and decreases blood fibrinolytic activity in the rat.

The effect of human recombinant tumor necrosis factor (TNF) was studied in vitro on human endothelial cells. TNF (1-1000 pg/ml) induced a dose-dependent increase in PAI level in the supernatant from 6 to 25 U/ml as estimated against urokinase. This effect was time-dependent. It was not suppressed by Polymyxin B thus excluding a possible contribution of an endotoxin contamination. Fibrinoenzymography performed after SDS-PAGE showed that this inhibitor neutralized urokinase and tissue plasminogen activator and gave rise to high molecular weight complexes. TNF (30 micrograms/kg) was also injected in rat. Blood fibrinolytic activity determined 4 hr later was decreased as estimated by the prolongation of the euglobulin clot lysis time from 37 to 188 min. Fibrinoenzymographic profile of the plasma was then characterized by a fainting of the tPA lysis band but the capacity of plasma to neutralize urokinase was not significantly modified. These results suggest that TNF could alter the fibrinolytic balance by stimulating PAI production at the endothelial level. This might be of importance in synergy with the TNF-induced procoagulant activity for promoting vascular occlusion of tumor capillaries.

Animals↗
PubMed1986

Effect of polymyxin B and colimycin on induction of plasminogen antiactivator by lipopolysaccharide in human endothelial cell culture.

The effect of lipopolysaccharide (LPS) on the production of fibrinolytic inhibitor by human endothelial cells was determined because results of previous experiments have shown us that it is possible to stimulate this synthesis with muramyl dipeptide. Treatment of these cells with LPS resulted in a marked enhancement of fibrinolytic inhibitor, as estimated in a urokinase-induced fibrinolysis assay. A dose-response curve was obtained for LPS concentrations ranging from 10 to 1,000 ng/ml, thus demonstrating the great sensitivity of these cells. This inhibitor did not reduce plasmin activity and formed complexes with high- and low-molecular-weight urokinase as visualized by fibrin enzymography on sodium dodecyl sulfate-polyacrylamide electrophoretic gels. The molecular weight of this inhibitor was estimated to be 54 to 58 kilodaltons. These findings led us to conclude that LPS stimulates formation of a plasminogen antiactivator. This LPS effect could be suppressed by polymyxin B and colimycin. The stimulatory effect of muramyl dipeptide required doses which were at least 1,000 times greater than those of LPS and was not decreased by polymyxin B. These results show the possibility of independent modulation of plasminogen antiactivator production at the endothelial level, which could be important in endotoxemia. Under these conditions colimycin might have an additional advantage for clinical use because of its ability to prevent fibrinolytic inhibition.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1979

[Vascular endothelium (author's transl)].

Studies during recent years have shown the importance of the vascular endothelium in several physiological and pathological circumstances. The culture of endothelial cells has permitted the direct study of endothelial functions. The endothelium is a selective barrier between blood and tissues: the molecules cross it, according to their size, either through the intercellular junctions or through the cells by pinocytotic vesicles. The permeability is modulated by vasomotor agents and modified during endothelial regeneration, especially for the lipids. The endothelium plays a prominent part in the maintenance of the blood flow through its nonthrombogenic properties. It metabolizes circulating thrombogenic substances (arachidonic acid, adenosine diphosphate) and produces potent antiaggregating agents (prostacyclin and adenosine). It may also release a plasminogen activator promoting thrombolysis. The endothelial cells contribute to the formation of the basement membrane by synthesizing collagen and fibronectin, which are involved in platelet adhesion and aggregation to exposed subendothelium. On the other hand, the endothelium has a modulating influence on the local blood flow by producing vasoconstrictors (angiotensin II and III) and vasodilating agents (adenosine and prostacyclin). It is not necessary to elucidate the coordination of these functions and their relationship to the endothelial disorders in vascular diseases.

Actins↗
PubMed1976

[Vascular subendothehlium: structure and functions (author's transl)].

Two subendothelial structures, glomerular basement membrane and arterial subendothelium, were compared regarding their biochemistry and ultrastructure and their role in physiology and pathology. Filtration function of the glomerular basement membrane can be related to the presence of three layers which are superimposed on each other and which differ regarding the orientation and density of the microfibrils. The arterial subendothelium which is a mixture of amorphous material, microfibrilis, elastin and collagen, with a still unknown orientation of these components, limits the transport of many blood molecules and reinforces the endothelial barrier. A striking difference is observed in the thrombogenicity of these two structures, especially in their reactivity towards platelets. This can be related to the presence of collagen IV in the glomerular basement membrane and of collagen III in the arterial subendothelium: in both cases adhesion of platelets can be observed. The presence of platelet aggregates on the subendothelial surface may also be seen. This is probably due to the presence of collagen III which is known to be able to induce the platelet release reaction and thereby promotes aggregation.

Animals↗