Mercury-Dependent Inhibition of Selenoenzymes and Mercury Toxicity

2012 ◽  
pp. 91-99 ◽  
Author(s):  
Nicholas V. C. Ralston ◽  
Alexander Azenkeng ◽  
Laura J. Raymond
Keyword(s):  
Mercury Toxicity ◽  
Dependent Inhibition

The Roles of α2-Antiplasmin and Plasminogen Activator Inhibitor 1 (PAI-1) in the Inhibition of Clot Lysis

1993 ◽  
Vol 70 (02) ◽  
pp. 301-306 ◽  
Author(s):  
Linda A Robbie ◽  
Nuala A Booth ◽  
Alison M Croll ◽  
Bruce Bennett
Keyword(s):  
Plasminogen Activator ◽  
Plasminogen Activator Inhibitor ◽  
Fibrin Clot ◽  
Clot Lysis ◽  
Plasminogen Activator Inhibitor 1 ◽  
Dependent Inhibition ◽  
Activator Inhibitor ◽  
Pai 1

SummaryThe relative importance of the two major inhibitors of fibrinolysis, α2-antiplasmin (α2-AP) and plasminogen activator inhibitor (PAI-1), were investigated using a simple microtitre plate system to study fibrin clot lysis in vitro. Cross-linked fibrin clots contained plasminogen and tissue plasminogen activator (t-PA) at concentrations close to physiological. Purified α2-AP and PAI-1 caused dose-dependent inhibition. All the inhibition due to normal plasma, either platelet-rich or poor, was neutralised only by antibodies to α2-AP. Isolated platelets, at a final concentration similar to that in blood, 2.5 × 108/ml, markedly inhibited clot lysis. This inhibition was neutralised only by antibodies to PAI-1. At the normal circulating ratio of plasma to platelets, α2-AP was the dominant inhibitor. When the platelet:plasma ratio was raised some 20-fold, platelet PAI-1 provided a significant contribution. High local concentrations of PAI-1 do occur in thrombi in vivo, indicating a role for PAI-1, complementary to that of α2-AP, in such situations.

Inhibition of the Activities of α2-Plasmin inhibitor (PI) and CI inhibitor (CI-Inh) by the Synthetic Fibrinolytic Agent, 3-Hydroxypropyl Flufenamide (Flu-HPA)

1979 ◽  
Author(s):  
L Miles ◽  
J Burnier ◽  
M Verlander ◽  
M Goodman ◽  
A Kleiss ◽  
...  
Keyword(s):  
Plasminogen Activators ◽  
Inhibitory Effect ◽  
Mechanisms Of Action ◽  
Flufenamic Acid ◽  
Clot Lysis ◽  
Factor Xiia ◽  
Dependent Inhibition ◽  
Normal Human ◽  
Plasmin Inhibitor

Flu-HPA is one of a series of flufenamic acid derivations that enhances plasminogen-dependent clot lysis in vitro. Studies of possible mechanisms of action of Flu-HPA were undertaken. The influence of Flu-HPA on the inhibition of purified plasmin by purified PI was studied. PI activity was assessed by its inhibition of the clevage of the tripeptide S-2251 (H-D-Val-Leu-Lys-pNA) by plasmin. Flu-HPA was dissolved in DMF or in methonol and preincubated with PI before addition of plasmin. At Flu-HPA concentrations greater than 1mM and up to 60mM, the inhibitory activity of PI was totally lost. The inhibitory effect of normal human plasma on plasmin was also completely abolished at concentrations of Flu-HPA between 2.5 and 40mM. The effect of Flu-HPA on the inhibition of purified plasma kallikrein by purified CI-Inh was also studied. CI-Inh activity was measured by its inhibition of cleavage of the tripeptide Bz-Pro-Phe-Arg-pNA by kallikrein. When Flu-HPA, dissolved in DMF or in methonol, was preincubated with CI-Inh, a concentration dependent inhibition of CI-Inh activity was observed. CI-Inh activity was abolished by concentrations of Flu-HPA greater than 1mM. Flu-HPA also inhibited the activity of CI-Inh on purified Factor XIIa. These observations suggest that this flufenamic acid derivative may enhance fibrinolysis not only by inhibiting PI activity but also by decreasing the inactivation of plasminogen activators by CI-Inh.

Modulation of Arachidonic Acid Metabolism in Human Endothelial Cells by Glucocorticoids

1986 ◽  
Vol 55 (03) ◽  
pp. 369-374 ◽  
Author(s):  
Raffaele De Caterina ◽  
Babette B Weksler
Keyword(s):  
Endothelial Cells ◽  
Vascular Endothelial Cells ◽  
Umbilical Vein ◽  
Arachidonic Acid Metabolism ◽  
Protein Synthesis Inhibitor ◽  
Synthesis Inhibitor ◽  
Prolonged Incubation ◽  
Dependent Inhibition ◽  
Human Thrombin ◽  
Umbilical Vein Endothelial Cells

SummaryTo learn whether glucocorticoids inhibit prostaglandin (PG) production in vascular endothelial cells, we investigated the effects of glucocorticoids on PG synthesis by cultured human umbilical vein endothelial cells (EC). Pretreatment of EC with dexamethasone (DX, 10-9 to 5 x 10-5 M) caused a dose-dependent inhibition of PGI2 production when PG synthesis from endogenous arachidonate was stimulated by human thrombin (0.25-2 U/ml) or ionophore A 23187 (1-5 μM). The inhibition was detectable at 10-7 M DX and maximal at 10-5 M (4.0 ± 0.7 vs. control: 7.7 ± 1.9 ng/ml, mean ± S.D., P <0.01). The production of PGE2 and the release of radiolabelled arachidonate (AA) from prelabelled cells were similarly inhibited. Prolonged incubation of EC with glucocorticoids was required to inhibit PG production or arachidonate release: ranging from 8% inhibition at 5 h to 44% at 38 h. In contrast, prostaglandin formation from exogenous AA was not altered by DX treatment. When thrombin or ionophore-stimulated EC were restimulated with exogenous AA (25 μM), DX-treated cells released more PGI2 than control cells (5.7 ± 0.5 vs. 4.1 ± 0.6 ng/ml, P <0.01). Both the decrease in PGI2 production after thrombin/ionophore and the increase after re-stimulation with AA were blunted in the presence of the protein synthesis inhibitor cycloheximide (0.1-0.2 μg/ml). Thus, incubation of EC with glucocorticoids inhibits PG production at the step of phospholipase activation. The time requirement for these steroid effects and their blunting by cycloheximide are consistent with the induction of regulatory proteins, possibly lipocortins, in endothelial cells.

Differences between antigenic determinants of pig and cat zona pellucida proteins

Reproduction ◽  
2000 ◽  
pp. 15-23 ◽  
Author(s):  
K Jewgenow ◽  
M Rohleder ◽  
I Wegner
Keyword(s):  
In Vitro Fertilization ◽  
Zona Pellucida ◽  
Antigenic Determinants ◽  
Vitro Fertilization ◽  
Contraceptive Vaccine ◽  
Sperm Binding ◽  
Dependent Inhibition ◽  
Dose Dependent Inhibition ◽  
Dose Dependent

Despite many efforts, the control of reproduction in feral cat populations is still a problem in urban regions around the world. Immunocontraception is a promising approach; thus the present study examined the suitability of the widely used pig zona pellucida proteins (pZP) for contraception in feral domestic cats. Purified zona pellucida proteins obtained from pig and cat ovaries were used to produce highly specific antisera in rabbits. Antibodies against pZP raised in rabbits or lions were not effective inhibitors of either in vitro sperm binding (cat spermatozoa to cat oocytes) or in vitro fertilization in cats, whereas antibodies against feline zona pellucida proteins (fZP) raised in rabbits showed a dose-dependent inhibition of in vitro fertilization. Immunoelectrophoresis, ELISA and immunohistology of ovaries confirmed these results, showing crossreactivity of anti-fZP sera to fZP and to a lesser extent to pZP, but no interaction of anti-pZP sera with fZP. It is concluded that cat and pig zonae pellucidae express a very small number of shared antigenic determinants, making the use of pZP vaccine in cats questionable. A contraceptive vaccine based on feline zona pellucida determinants will be a better choice for the control of reproduction in feral cats if immunogenity can be achieved.

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