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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Phospholipases (PL) A-2 and C stimulated the outputs of prostaglandin (PG) F-2 alpha, PGE-2 and 6-keto-PGF-1 alpha from the Day-7 and Day-15 guinea-pig uterus superfused in vitro. PLC had a more pronounced effect than PLA-2, particularly on the output of PGE-2. The ratios of the outputs of PGF-2 alpha and PGE-2 were similar after stimulation by A23187 and PLA-2, but this ratio was lower after stimulation by PLC. It appears that the stimulation of endometrial PGF-2 alpha synthesis by Ca2+ is via activation of PLA-2 rather than via activation of PLC, although the PLC used was of bacterial origin (which uses phosphatidylcholine as substrate) rather than of mammalian origin (which uses phosphatidylcholine as substrate). Forskolin (which increased endometrial and myometrial cyclic AMP levels) and phorbol 12-myristate-13-acetate had no effect on uterine PG output, indicating that cyclic AMP and protein kinase C are not involved in the stimulation of endometrial PGF-2 alpha synthesis in the guinea-pig. Uterine PG output was not stimulated by 54 mM-KCl, which shows that the pulsatile nature of endometrial PGF-2 alpha synthesis and release is not due to an intermittent, synchronous depolarization of the endometrial cells.
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PMID:Effects of various factors on prostaglandin synthesis by the guinea-pig uterus. 311 14

In anesthetized rats the intravenous infusion (15-120 min) of the prostacyclin analogue CG 4203 (0.215-2.15 micrograms.kg-1.min-1) resulted in a time and dose dependent shortening of the ex vivo euglobulin clot lysis time (ECLT). This effect that appeared to be significant already in the non-hypotensive dose range of CG 4203, was still existing at 2 hours after cessation of the infusion. The phosphodiesterase inhibitor theophylline (4.64 mg.kg-1 i.v.) potentiated the ECLT shortening effect of CG 4203. Even the highest dose of CG 4203 did not change the plasma fibrinogen levels. In contrast to low molecular weight urokinase (100 PU/ml) CG 4203 (10 microM) did not shorten the in vitro lysis of preformed euglobulin clots from untreated rats nor did it reduce the 125J-fibrin content of human thrombi in the Chandler loop system. From these results it is concluded that intravenously infused CG 4203 increases the plasma fibrinolytic activity in rats by a c-AMP dependent mechanism, probably by release of plasminogen activator. Direct urokinase like activation of plasminogen does not occur with CG 4203. The relevance of this activity is discussed with respect to the CG 4203 treatment of occlusive vascular diseases.
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PMID:Stimulation of the plasma fibrinolytic activity in rats by the prostacyclin analogue CG 4203. 332 46

Macrophages incubated with complexed or aggregated IgE released beta-glucuronidase (beta-G) within 30 min. In contrast in the presence of aggregated or complexed IgG, macrophages liberated equivalent amount of beta-G only after 6 h incubation. In addition the rapid macrophage stimulation induced by aggregated IgE was also followed by a faster 3H-glucosamine incorporation when compared to the delayed activation caused by aggregated IgG. However, macrophages stimulated either by IgG or by IgE oligomers produced the same percentage of plasminogen activator at 24 h. In contrast, while the interaction between macrophages and aggregated IgE was only followed by a peak of cyclic GMP and a beta-G release during the first 30 min of incubation, the interaction between macrophages and IgG oligomers was accompanied by a simultaneous increase of cyclic GMP and AMP nucleotides and by an absence of beta-G exocytosis. Moreover, the beta-G release induced by aggregated IgE was increased when macrophages were preincubated with aggregated IgG. This additive effect was not observed in the reverse situation. Finally macrophages activated by IgG oligomers were demonstrated to exert a cytotoxic effect on tumour cells and to kill schistosomula in the presence of a low level of complement. Taken together these results underline the peculiar ability of aggregated or complexed IgE to trigger rapidly the macrophage activation compared to aggregated IgG and can explain the important role of complexed IgE in some macrophage dependent cytotoxicity mechanisms (i.e. in parasitic diseases).
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PMID:Macrophage triggering by aggregated immunoglobulins. II. Comparison of IgE and IgG aggregates or immune complexes. 608 35

F9 mouse teratocarcinoma stem cells differentiate into parietal endoderm cells in the presence of retinoic acid, dibutyryl cyclic AMP, and theophylline (RACT). When F9 cells are exposed to 2-5 mM sodium butyrate plus RACT, they fail to differentiate. Differentiation is assessed by induction of laminin and collagen IV mRNA, the synthesis of laminin, collagen IV and plasminogen activator proteins, and alterations in cell morphology. Butyrate inhibits differentiation only when added within 8 hr after retinoic acid addition. Thus an early event in retinoid action on F9 cells is butyrate-sensitive. The population doubling time and cell cycle distribution of F9 cells are not altered within the first 24 hr after butyrate addition, suggesting that butyrate does not inhibit differentiation by inhibition of growth or normal cycling. However, butyrate does inhibit histone deacetylation in F9 cells, and this could be the mechanism by which butyrate inhibits differentiation.
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PMID:Butyrate inhibits the retinoic acid-induced differentiation of F9 teratocarcinoma stem cells. 609 Feb 44

Y1 mouse adrenal tumor cells and mutants of Y1 cells (Kin 2 and Kin 8), with defects in regulatory subunit of type 1 protein kinase (R1), were assayed for steroid, growth, and plasminogen activator after application of the tumor promoter 12-O-Tetradecanoylphorbol-13-acetate (TPA). TPA, like ACTH, caused an increase in steroid production and a decrease in growth in Y1 cells. The effects on steroidogenesis were diminished in Kin 2 and markedly diminished in Kin 8. TPA induced plasminogen activator in Y1 but not Kin 2 or Kin 8 while ACTH induced the enzyme in both Y1 and Kin 2 but not Kin 8. TPA did not produce a measurable increase in cyclic nucleotides in Y1 cells. Unlike Cytochalasin E, another agent that causes steroidogenesis without changes in cyclic AMP concentration, TPA and ACTH did not require serum for its effect on steroid production. Cytochalasin E also caused induction of plasminogen activation in Y1, but not in Kin 2 or Kin 8 cells. TPA however produced growth inhibition in both mutant cell types while ACTH produced a progressively diminishing growth inhibitory effect in Kin 2 and Kin 8. The results suggest that a portion of TPA action on Y1 cells requires R1.
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PMID:Action of 12-O-tetradecanoylphorbol-13-acetate on Y1 adrenal cells apparently requires the regulatory subunit of type 1 cyclic AMP dependent protein kinase. 610 Sep 78

An epithelioid clone of Chinese hamster (CHO) cells which is spontaneously transformed was exposed to the mutagen N-methyl-N-Nitro-N-Nitrosoguanidine (MNNG), and a fibroblastic variant, clone CHO-F2, was isolated. This clone is partially reverted in several of the in vitro properties characteristic of transformed cells. When compared to wild type CHO, CHO-F2 has a longer doubling time, a lower saturation density and less piling up at high cell density, and a higher serum requirement. CHO-F2 also elaborates less plasminogen activator and has more abundant microtubules and actin cables. On the other hand, both CHO and CHO-F2 grow in agar suspension (although CHO-F2 grows with a lower efficiency), both lack detectable LETS protein, and both are tumorigenic in nude mice. Thus, expression of the individual properties frequently associated with transformation and tumorigenicity can be dissociated. The most critical biochemical change in CHO-F2 appears to be an increase in the intracellular level of cyclic AMP, when compared to CHO, and several growth and morphological properties of CHO-F2 resemble those induced in wild type CHO exposed to exogenous dibutyryl cyclic AMP. The role of cyclic AMP in expression of the transformed phenotype and the significance of individual in vitro parameters of transformation with respect to tumorigenicity are discussed.
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PMID:Isolation and characterization of a morphologic variant of Chinese hamster (CHO) cells. 624 27

Macrophages from various sources can be stimulated by a variety of substances to secrete a range of inflammatory mediators and degradative enzymes. The mechanisms involved in the activation and secretory processes are unknown, However, recent evidence suggests that cyclic AMP may play a role in the regulation of neutral protease secretion. Thus, it has been shown that agents known to increase intracellular cyclic AMP levels (cyclic AMP analogues, phosphodiesterase inhibitors, prostaglandin E1 and E2, catecholamines, cholera toxin and, indirectly, glucocorticosteroids) inhibit the secretion of the neutral protease plasminogen activator. It is speculated that macrophage activation may also initiated by changes in the steady-state levels of cyclic nucleotides. A decrease in intracellular cyclic AMP and/or an increase in cyclic GMP levels would favour secretion. It is possible that these changes could be brought about by the action of various stimuli to modify the capacity of the macrophage to synthetize or degrade cyclic nucleotides.
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PMID:Cyclic nucleotides, possible intracellular mediators of macrophage activation and secretory processes. 626 14

Levels of plasminogen activator activity were determined in testes obtained from normal and irradiated rats in various ages. During normal development, plasminogen activator activity per g testis increased rapidly between 40 and 60 days of age, but a comparable rise did not occur in germ-cell depleted testes of irradiated rats. Levels of enzyme in various populations of testicular cells were highest in Sertoli (varying between 1800 and 6300 units/mg protein in cell maintained under different culture conditions), and lowest in peritubular myoid cells (about 1 unit/mg protein), with intermediate levels in germinal cells (ranging between 147 and 560 units/Mg protein in residual bodies, spermatocytes and spermatids). No protease inhibitor could be detected in germ-cell extracts. The addition to the medium in which Sertoli cells were in culture of particles which can be phagocytosed (autoclaved E. coli) resulted in an increased formation of plasminogen activator activity by Sertoli cells. A synergistic enhancement of enzyme production resulted following the addition of submaximal quantities of dibutyryl cyclic AMP and autoclaved bacteria to sertoli cells in culture. On the basis of these data, we suggest that the presence of advanced germinal cells during gonadal development may stimulate the synthesis of plasminogen activator by Sertoli cells, mediated in part by the phagocytosis of residual bodies by sertoli cells which occurs prior to spermiation.
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PMID:Changes in levels of plasminogen activator activity in normal and germ-cell-depleted testes during development. 628 Oct 97

The main emphasis of this paper is on the changes in function of granulosa cells as they undergo cytodifferentiation in follicles developing from the preantral to the antral stage, and on the hormones present in the milieu of gonadotrophins and steroids which are essential for these events to proceed normally. We found that FSH alone could induce aromatase activity in cultures of immature granulosa cells and that this effect could be duplicated by dibutyryl cyclic AMP. Incubation of cell sonicates under optimal conditions indicated that FSH acted on granulosa cells to increase the cellular concentration of active aromatase. Prior treatment with androgens augmented the FSH effect. Progesterone synthesis is another differentiated function which can be induced in culture by FSH alone and augmented in the presence of androgens. In assessing the enzymes involved in progesterone synthesis we found that cholesterol side-chain cleavage activity had similar hormonal requirements whereas 3 beta-hydroxysteroid dehydrogenase activity was stimulated by FSH alone. FSH also stimulates cyclic AMP binding activity in cultured granulosa cells during cytodifferentiation. These proteins represent another class of intracellular proteins, quite distinct from the steroidogenic enzymes, which increase as the granulosa cells mature. The ability of FSH to induce the appearance of LH and prolactin receptors, and stimulate the secretion of plasminogen activator and proteoglycans is reviewed. It is concluded that the appearance of steroidogenic enzymes and other intracellular proteins, cell-surface and secreted proteins as well as morphological maturation of granulosa cells require the presence of FSH. In the "turning-on" of some of these differentiated functions androgens play a permissive role. Having established events which occur during normal development of the follicle, we considered ways by which this overall process could be interrupted and fertility controlled. Here we describe the ways by which prolactin and LHRH interfere with the normal process of granulosa cell cytodifferentiation.
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PMID:Hormonal interactions in the control of granulosa cell differentiation. 631 Feb 32

The influence of hypoxia and acidosis on the release of vascular plasminogen activator was studied in the isolated perfused pig ear. Perfusion with deoxygenated or acid solutions led to significant increases in plasminogen activator release (p less than 0.001); acid solutions of pH 6.7 were more effective than those of pH 6.9. Perfusions with lactate and AMP, two metabolic products which might act as mediators of fibrinolytic stimulation during hypoxia, resulted in moderate increases of plasminogen activator in the effluent (p less than 0.01).
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PMID:Effects of hypoxia and acidosis on vascular plasminogen activator release in the pig ear perfusion system. 653 46


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