Search PubMed⌕ Search

Biomedical subjects

C Tetta

Publications and source records attributed to C Tetta.

At least 163 records · Page 9Linked to original sources
PubMed1983

Biosynthesis and release of platelet-activating factor from human monocytes.

The aim of the present study was to investigate the pathways of platelet-activating factor (PAF) production and release from human monocytes. For this purpose, both phagocytic stimuli and stimuli induced by soluble agents were used. The phagocytic stimuli exerted their effect in a receptor-specific mechanism related to surface Fc, C3b and C3d receptors. Stimuli induced by soluble agents, such as A23187 and pH 10.6, which do not require interaction with specific receptors, were also effective in inducing PAF release. In contrast, C5a, a soluble agent which induces a receptor-mediated release of PAF from neutrophils, failed to induce PAF release from monocytes. PAF release from monocytes could be dissociated from phagocytosis and from release of lysozyme. The PAF release required the presence of extracellular cations, the activation of membrane esterase and phospholipase A2 and the integrity of the microfilament system. Moreover, PAF release was modulated by lipoxygenase and intracellular cAMP levels. The relevance of an acetylation process in the biosynthesis of PAF was suggested by the increase of PAF yields in the presence of sodium acetate and by the incorporation of 14C-sodium acetate into molecules of active PAF.

Acetates↗
PubMed1983

Effect of prostacyclin (PGI2) on immune-complex-induced neutropenia.

This study reports the results of in vitro and in vivo investigations on the effect of prostacyclin (PGI2) on polymorphonuclear neutrophils (PMN) challenged with immune complexes (IC). In vitro, PGI2 does not affect the interaction of IC with PMN membrane receptors, but prevents the ensuing PMN aggregation and secretion of platelet-activating factor, a lipid mediator responsible for immune-induced PMN aggregation. In vivo, the infusion of PGI2 in New Zealand white rabbits injected with IC prevents IC-induced neutropenia and thrombocytopenia as well as the embolization of PMN into the pulmonary peripheral capillary network. These results suggest a physiological role for PGI2 in modulating the interaction between IC and PMN.

Agranulocytosis↗
PubMed1983

The release of platelet-activating factor from human endothelial cells in culture.

The release of platelet-activating factor (PAF) from stimulated human endothelial cells (HEC) cultured from normal term, umbilical cord veins is described. HEC in primary cultures released PAF after challenge with A23187, rabbit anti-human factor VIII (RaHu/FVIII), angiotensin II, and vasopressin. HEC subcultures maintained the ability to release PAF in the presence of A23187 and RaHu/FVIII, whereas the release of PAF in response to angiotensin II and vasopressin was not constant and was reduced. Control cultured, smooth muscle cells derived from umbilical cord veins, previously depleted of endothelial cells, did not release PAF under the above-mentioned stimulation. Plastic-adherent or cultured monocytes released PAF with A23187, but not with RaHu/FVIII, angiotensin II, and vasopressin. The release of PAF from HEC in primary cultures required the presence of extracellular cations and the activation of membrane phospholipase A2. PAF release induced by A23187, RaHu/FVIII, angiotensin II, and vasopressin was unaffected by indomethacin, an inhibitor of cyclooxygenase, which, however, favored the release of PAF from HEC stimulated with thrombin, a stimulus that did not affect HEC in the absence of indomethacin. PGI2 inhibited PAF release from stimulated HEC. The relevance of an acetylation process in the biosynthesis of PAF and HEC was supported by the following evidence: 1) the increase in PAF yield in the presence of sodium acetate and, particularly, of acetyl-CoA; 2) the incorporation of [14C]acetate into PAF molecules; 3) the loss of radioactivity and of biologic activity after treatment with phospholipase A2. These results indicate that HEC in culture are able to release PAF and that metabolic pathways similar to those described for leukocytes are involved.

Angiotensin II↗
PubMed1983

Acute lung inflammation induced in the rabbit by local instillation of 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine or of native platelet-activating factor.

The intratracheal instillation into rabbits of 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC) or native platelet-activating factor (PAF) was shown to induce a dose-dependent acute pulmonary inflammation characterized by accumulation of macrophages in the alveolar space, degenerative and necrotic changes of alveolar epithelium, and accumulation of polymorphonuclear leukocytes (PMNs) and platelets in the alveolar capillary lumens with degenerative changes of endothelial cells. Infiltration of alveolar septa by inflammatory cells and, in a later stage, pulmonary fibrosis were also observed. Intrabronchial instillation of lysoglyceryl ether phosphorylcholine (lyso-GEPC) produced no inflammatory changes or only mild ones. In comparison with acute inflammation induced by intratracheal instillation of C5a des Arg, which is mainly characterized by the presence of neutrophils, red blood cells, and fibrin in the alveolar space, AGEPC and native PAF seem to induce a more severe accumulation of macrophages in the alveolar space and septa and of platelet and PMNs in the lumens of alveolar capillaries. These results are compatible with the concept that during inflammatory reaction an intraalveolar release of PAF contributes to the development of pulmonary injury.

Acute Disease↗
PubMed1982

Detection of basophil sensitization by IgE antibodies to nuclear antigens in connective tissue diseases.

Responses of the IgE type to various nuclear antigens have been explored using the human basophil degranulation test (HBDT) to single (SS) and double-stranded (DS) deoxyribonucleic acid (DNA), nuclear ribonucleoprotein (nRNP), and Sm antigens. This study was conducted on systemic lupus erythematosus (SLE) patients as compared to rheumatoid arthritis (RA) polymyositis (PM), scleroderma (SCL) and mixed connective tissue disease (MCTD). SLE and MCTD patients showed a high level of basophil degranulation to the four antigens. Degranulation to nRNP protein was higher in MCTD than in SLE cases. HBDT to the four antigens were constantly negative in control donors and in RA, PM and SCL. Basophil degranulation to DS-DNA in SLE was blocked by previous exposure of the blood to anti-human-IgE antiserum. These results exemplify the specificity of the HBDT, making this simple and fast test a useful tool in the diagnosis of connective tissue diseases.

Antigens↗
PubMed1981

Neutropenia induced by platelet-activating factor (PAF-acether) released from neutrophils: the inhibitory effect of prostacyclin (PGI2).

Soluble and phagocytic stimuli released PAF-acether from PMN leucocytes, as determined by chromatography and bioassay by platelet aggregation. The same material caused aggregation of human and rabbit PMN leucocytes in vitro which was inhibited by ETYA and PGI2. PGI2 also inhibited PAF-acether release by PMN leucocytes and, in vivo, PGI2 abolished not only PAF-acether-induced, but also immune complex or C5a-induced thrombocytopenia and neutropenia in rabbits. These data suggest that PAF-acether may be involved in activation of both platelets and PMN leucocytes in vivo.

Agranulocytosis↗
PubMed1981

Mediators of immune-complex-induced aggregation of polymorphonuclear neutrophils. II. Platelet-activating factor as the effector substance of immune-induced aggregation.

Platelet-activating factor (PAF) is released in vitro during human and rabbit polymorphonuclear neutrophil (PMN) aggregation induced by C5a anaphylatoxin, neutrophil cationic proteins (CP) and their carboxypeptidase-B-derived fragments, C5a des Arg and CP des Arg, as well as phagocytosis of opsonized baker's yeast particles and immune complexes (IC). Purified PAF itself is able to cause in vitro PMN aggregation. By using selective inhibitors, we show that PMN aggregation, induced either by PAF or by other soluble stimuli such as C5a, CP and their des Arg products, follows a similar metabolic pathway, which is both adenosine-diphosphate-(ADP)- and arachidonic acid (AA)- independent. The in vivo injection of purified PAF into rabbits leads both to formation of intravascular PMN aggregates and to development of acute neutropenia, which has the same features as those observed after challenge with IC, C5a and CP. In this respect, electron-microscopic studies of intravascular PMN aggregates in the pulmonary capillary network and glomeruli show identical ultrastructural patterns. Moreover, the intravascular release of PAF is demonstrated after the intravenous injection of IC and temporally correlated with the development of neutropenia. We suggest that PAF is probably the final, common, effector substance of IC-, C5a-, C5a-des-Arg-, CP-, CP-des-Arg-mediated PMN aggregation.

Adenosine Diphosphate↗
PubMed1981

Release of platelet-activating factor (PAF) and histamine. II. The cellular origin of human PAF: monocytes, polymorphonuclear neutrophils and basophils.

The origin of platelet activating factor (PAF) from human leucocytes was investigated. Purified monocytes release PAF passively at pH 10.6, when challenged with Ionophore A 23187 or under phagocytic stimuli. Pure preparations of polymorphonuclear neutrophils liberate PAF passively, when challenged with C5a, neutrophil cationic proteins (CP), their carboxypeptidase B derived products (C5a des Arg, CP des Arg) or under phagocytic stimuli. Basophil rich buffy coat cells release PAF when challenged with C5a, CP, anti-IgE (in low amount) or Synacthen concomitantly with basophil degranulation and histamine release. Electron microscopy studies, carried out on Synacthen-stimulated basophil rich buffy coat, provide morphological evidence for platelet-basophil interaction. In conclusion our data demonstrate that PAF can be released from different leucocyte populations. However, the stimuli able to trigger such release appear to have some specificity for the cell target.

Antigen-Antibody Complex↗
PubMed1981

Heparin is unable to prevent contact activation by three different membranes.

In spite of the anticoagulant activity of heparin platelet deposition and contact activation of coagulation occurs during dialysis. We have studied platelet counts, fibrinogen, platelet factor 4, beta-thromboglobulin, thromboxane B2, FRA, C3d and kallikrein values, whole blood and euglobulin lysis times and membrane areas in haemodialysis using cuprophan and cellulose acetate and in haemofiltration with polyacrilonitrile. Deposits on all the three membranes included leucocytes, platelets and fibrin. The coagulation and fibrinolytic systems are activated more intensively with cellulose acetate and more prolongedly with polyacrilonitrile. Platelet factor 4 and beta-thromboglobulin increases suggest platelet activation, only partially dependent on arachidonic acid-mediated pathway as thromboxane B2 is not increased. The complement system is activated whereas serum kallikrein does not alter, suggesting that platelets rather than factor XII are crucial in contact activation.

Adolescent↗
PubMed1981

Release of platelet-activating factor in human pathology. I. Evidence for the occurrence of basophil degranulation and release of platelet-activating factor in systemic lupus erythematosus.

Basophil degranulation and release of platelet-activating factor (PAF acether) have been implicated in enhanced vascular permeability and immune complex deposition in rabbit acute serum sickness. PAF-acether is a phospholipid mediator of anaphylaxis, released from leukocytes of several mammalian species, including man, that aggregates platelets and releases their vasoactive amines. In this article, we evaluated the occurrence of basophil degranulation and release of PAF-acether in patients with systemic lupus erythematosus. In the acute phases of the disease, basophils were in vivo degranulated, and the amount of PAF-acether releasable from leukocytes was markedly reduced. During remission or in the latent phases of the disease, when the number of metachromatically staining basophils increased. in an vitro degranulation and release of PAF-acether were observed after DNA challenge. Electron microscopy studies demonstrated that basophils indeed degranulated in response to DNA. These studies also showed the interaction between degranulating basophils and human platelets which aggregated even if the other two pathways of human platelet aggregation, i.e., the ADP- and the arachidonic acid-dependent pathways, were blocked. The concomitance of basophil degranulation and release of PAF-acether, together with the morphologic evidence of the interaction between degranulating basophils and aggregated platelets, was strongly suggestive of release of PAF-acether from basophils in systemic lupus erythematosus.

Animals↗
PubMed1980

[Immune complex monitoring in Echinococcus infections].

In two patients with hepatic echinococcosis, we studied the in vivo interaction between circulating immune complexes and polymorphonuclear neutrophil surface receptors according to our previously described technique and quantitated the amount of circulating immune complexes by the C1q binding assay. Both tests were positive prior to surgical removal of the cysts, to gradually become negative to weeks later, and are persistently negative at two months after complete asportation. The application of the two tests may be of value in assessing surgical radicality and consequently the prompt disappearance of circulating parasite antigens. In particular, failure of these two tests two turn negative or the occurrence of further, new positivities may suggest either uncomplete eradication of the cyst or reinfection. These immunologic techniques appear to provide a better monitoring of echinococcosis than all the other well-known immunological tests which detect specific immunoglobulins present in serum for a long time and therefore unable to indicate the persistence or the new appearance of the parasite antigens.

Adult↗
PubMed1980

Mediators of immune complex-induced aggregation of polymorphonuclear neutrophils. I. C5a anaphylatoxin, neutrophil cationic proteins and their cleavage fragments.

This study reports the results of in vitro investigations on the aggregation of polymorphonuclear neutrophils (PMN) induced by the C5a anaphylatoxin complement component as well as the cationic proteins (CP), which are released by challenging PMN with immune complexes (IC). The carboxy-peptidase-derived des-Arg fragments of CP and C5a; CPi and C5ai, inactive in terms of anaphylactic and chemotactic activity, nevertheless showed a more potent ability to aggregate PMN than CP and C5a. The process of PMN aggregation required metabolic energy and divalent cations, Ca++ and Mg++. The microtubular system and the subplasmalemmal microfilaments appeared to be of critical importance. Electron microscopic studies on aggregates of PMN obtained on stimulation with CP, C5a, CPi and C5ai showed parallel tracts of variable length of cell membranes at the points where cells were in contact with each other.

Anaphylatoxins↗
PubMed1979

Detection of immune complexes on the surface of polymorphonuclear neutrophils.

A simple immunohistological test has been developed to detect and to quantitate the presence of immune complexes (IC) on the surface of human polymorphonuclear neutrophils (PMN). The interaction between IC and PMN has been evaluated in several human IC diseases. High amounts of immunoglobulins (Ig) and C3 were detected on the PMN surface from these patients. The deposits of Ig and C3 were inversely related to the percentage of membrane-free receptors for Fc and C3.

Acid Phosphatase↗