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C Tetta

Publications and source records attributed to C Tetta.

At least 127 records · Page 7Linked to original sources
PubMed1987

Release of platelet-activating factor from rabbit heart perfused in vitro by sera with transplantation alloantibodies.

During "hyperacute rejection" of rabbit heart perfused with transplantation alloantibodies, platelet activating factor (PAF) was released into the coronary effluent, which appeared to have physicochemical and functional properties similar to the 1-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (synthetic PAF) and to PAF obtained from IgE-sensitized rabbit basophils. The release of PAF was associated with an early tachycardia, followed by increasing bradycardia and conduction arrhythmias, as well as decrease of coronary flow and of amplitude of electrogram. The heart stopped beating within 30 min. The release of PAF as well as the "rejection" required the presence of fresh rabbit serum as a source of complement. The PAF receptor antagonist SRI 63-072 in a dose of 0.6 mg, reversed by 70% the reduction of coronary flow within 2-4 min after its addition to the perfusate; ED50 was 0.4 mg. Bradycardia and arrhythmia were reduced; however, the normal electrical activity was only occasionally restored. The cessation of heart action was delayed up to 50 min after the beginning of perfusion with transplantation alloantibodies and complement, but it was not prevented. These results suggest that PAF is released during "rejection" of the heart perfused in vitro with serum containing transplantation alloantibodies in the absence of inflammatory cells and that this mediator is at least in part responsible for the deterioration of cardiac function.

Animals↗
PubMed1987

In vitro complement-independent activation of human neutrophils by hemodialysis membranes: role of the net electric charge.

Polymethylmethacrylate (PMMA) membranes with different net electric charges and percentage water contents (anionic 71%, neutral 70%, cationic 75%) were evaluated for their ability to stimulate plasma-free human polymorphonuclear neutrophils (PMN), and compared for potency to cuprophan (Cu), already described as being a potent trigger of PMN. The release of lysozyme, beta-glucuronidase, lactic dehydrogenase (LDH), and the generation of a platelet aggregating activity were studied in the supernatants from plasma-free human PMN incubated with different membranes. The PMN intracellular content of neutrophil cationic proteins (NCP), elastase, and cathepsin G were also studied by immunofluorescence using specific antisera on smears of PMN before and after incubation with each membrane. Only cationic, but not anionic or neutral PMMA induced a marked release of lysozyme (range 20-25% of the sonicated control, assumed as 100%), and beta-glucuronidase (40-43%), and marked depletion of the intracellular content of NCP, elastase, and cathepsin G, suggesting a degranulation process. Platelet aggregating activity was generated and referred to the release of platelet activating factor (PAF) only in the supernatants from PMN incubated with cationic, but not with anionic, or neutral PMMA membranes. These results indicate that modification of the net electric charge can per se turn PMMA, commonly recognized as inert, into a material with marked PMN activating effects, comparable to those of Cu, a highly reactive polymer.

Cations↗
PubMed1986

Production of platelet-activating factor by chick retina.

In the present study it is demonstrated that platelet-activating factor (PAF) was produced by chick retinas, upon stimulation with neurotransmitters such as acetylcholine (ACh), dopamine, or with calcium ionophore A23187, but not upon stimulation with gamma-amino-n-butyric acid, L-glycine, L-glutamate, epinephrine, or histamine. PAF produced in response to ACh, dopamine, or A23187 was not released into supernatants but was extractable from retinas. The amounts of extractable PAF increased after sonication of stimulated retinas. While no PAF activity could be recovered from unstimulated retinas, small amounts of this lipid can be detected following sonication of the tissue. The amount of extractable PAF from ACh-, dopamine-, or A23187-stimulated retinas was dependent upon the incubation time and concentration of the agonists. PAF was identified on the basis of chemical and lipase treatments, biological activity with washed rabbit platelets, behavior on thin layer chromatography, and high pressure liquid chromatography. Control cell preparations (leukocytes, erythrocytes, and embryogenic fibroblasts) did not produce PAF upon neurotransmitter stimulation. ACh and dopamine promoted PAF production by increasing dithiothreitol-insensitive cholinephosphotransferase activity, without affecting the acetyltransferase activity. In contrast, the A23187 ionophore stimulated the acetyltransferase activity but did not affect the dithiothreitol-insensitive cholinephosphotransferase.

Acetylcholine↗
PubMed1986

Interleukin 1 stimulates platelet activating factor production in cultured human endothelial cells.

Monocyte-derived interleukin 1 (IL 1) induced the platelet activating factor (PAF) production in cultured human endothelial cells (HEC). The product was identified as PAF by the chemical properties, the susceptibility to phospholipase A2 and C and to lipase A1, its behaviour in thin layer chromatography and in high pressure liquid chromatography and the recovery of biological activity tested on rabbit platelets. The action of IL 1 was concentration-dependent and took more than 2 hours to became apparent. Most of the PAF produced was cell-associated and only the 25% of the total was released.

Cells, Cultured↗
PubMed1986

In vitro contractile effect of platelet-activating factor on guinea-pig myometrium.

Platelet-activating factor (PAF) evoked myometrial contractions in two different patterns, depending on whether spontaneous activity was present. In spontaneously active myometrial strips (58%), both PAF and oxytocin enhanced the amplitude of myometrial contractions. In quiescent myometrial strips, PAF induced contractions characterized by a prompt development of tension, a plateau, and a final, rapid relaxation. In 54% of these strips, PAF-induced contraction was followed by rhythmic activity. PAF contractile response was dependent upon the concentration (0.1-100 nM); the minimal effective concentration of PAF was 0.1 nM and the EC50 was 1 nM. The response to oxytocin (0.01-10 mU/ml), assumed as reference stimulus, was characterized by a prompt development of tension, which was followed by a sustained, slow contraction and relaxation. PAF response was almost completely dependent on cyclooxygenase and partially on lipoxygenase pathways, as inferred from studies with indomethacin and FPL 55712, respectively. A receptor mediated mechanism of PAF action was suggested by specific desensitization of the myometrium to a second challenge with an equimolar concentration of PAF (but not with oxytocin) and the blocking effect of CV 3988, a specific PAF receptor antagonist.

Animals↗
PubMed1986

Platelet cationic proteins are present in glomeruli of lupus nephritis patients.

Synthetic polycations have been shown to bind and neutralize glomerular polyanions (GPA), thereby increasing the permeability of the glomerular capillary wall (GCW). In the present study it is demonstrated that human platelet-derived cationic proteins (HuPlt CP), which are able to increase cutaneous vascular permeability, bind in vitro to the GCW following incubation of normal human kidney sections with purified HuPlt CP or with washed human platelets stimulated with thrombin, immune complexes (IC) and platelet-activating factor (PAF), or stimulated with a suspension of washed human platelets and polymorphonuclear leukocytes in the presence of phagocytable substrate. The antiserum used in immunofluorescence test to detect the binding of HuPlt CP was specific for two different molecular types of HuPlt CP, both with an isoelectric point (pI) of 10.5. Glomerular deposits of HuPlt CP were also detectable by immunofluorescence microscopy in renal glomeruli present in tissue obtained by biopsy from patients with systemic lupus erythematosus (SLE), a disease in which platelets have been implicated as mediator of glomerular injury. These data indicate that when activated platelets release HuPlt CP in vivo, these proteins bind to glomerular structures. The binding of HuPlt CP to GCW appears to be ionic in nature since heparin, a polyanion, prevents this binding in vitro. In addition, heparin, as well as a high molarity buffer, removed deposits of HuPlt CP bound in vitro to normal GCW or bound in vivo to glomeruli of patients with SLE. The binding of HuPlt CP to GCW is associated with loss of colloidal iron staining, a qualitative technique that demonstrates primarily epithelial cell surface anionic sialoglycoproteins. In experiments of in vitro binding of purified HuPlt CP to section of normal kidney treatment with heparin completely restores the normal pattern of colloidal iron staining suggesting ionic neutralization of GPA. In contrast, heparin is only partially effective in restoring colloidal iron staining in normal kidney sections treated with platelets directly stimulated with IC or PAF or in kidney sections of patients with SLE. These observations indicate that under these conditions the ionic interaction of HuPlt CP with GCW is only partially responsible for the loss of colloidal iron staining. The results of the present study suggest that biologically active polycationic mediators released from stimulated platelets localize in GCW and participate in the induction of glomerular injury.

Adult↗
PubMed1986

Fc receptor triggering induces expression of surface activation antigens and release of platelet-activating factor in large granular lymphocytes.

Triggering of large granular lymphocyte (LGL) Fc receptor with a specific monoclonal antibody (AB8.28) linked to an insoluble matrix induces cell activation, as witnessed by expression of HLA class II (DR and DQ) molecules and interleukin 2 receptor. Moreover, this event is accompanied by a concomitant release of platelet-activating factor by LGL. We conclude that the Fc receptor molecule identified by mAb AB8.28 represents a trigger for LGL activation.

Antibodies, Monoclonal↗
PubMed1986

Effect of platelet-activating factor (PAF) on human cardiac muscle.

The effect of platelet activating factor (PAF) on three mechanical [maximal mechanical tension (Pmax); time to peak tension; maximal rate of rise of tension (+dP/dt)] and four electrical [action potential duration (APD); resting membrane potential; overshoot; maximum rate of depolarization] parameters of cardiac function was studied on fragments of isolated human cardiac papillary muscle. 20 specimens of small tissue fragments excised from the left ventricle by open heart surgery were challenged with various doses of synthetic PAF (10(-10)-10(-6) M). PAF, but not its biologically inactive 2-lyso-derivative (lyso-PAF), induced a biphasic dose-dependent effect, characterized by a transient positive effect on inotropism (increased Pmax, +dP/dt) and of APD, followed by a marked, prolonged negative effect on both inotropism (decreased Pmax, time to peak tension, +dP/dt) and APD. No changes in resting membrane potential, overshoot and maximum rate of depolarization were detected after PAF challenge. Propranolol (2 X 10(-7) M) completely prevented the positive inotropic effect suggesting a stimulation of beta-receptors, possibly exerted by endogenous catecholamines. Indomethacin (1 X 10(-4) M) did not modify the initial positive effect, but markedly reduced the subsequent negative effect induced by PAF on inotropism. These findings are consistent with the interpretation that the effect of PAF on the inotropism is related to liberation of cyclooxygenase-derived metabolites.

Action Potentials↗
PubMed1986

Interleukin 1 stimulates platelet-activating factor production in cultured human endothelial cells.

Monocyte-derived interleukin 1 (IL-1) was found to be a potent inducer of platelet-activating factor (PAF) in cultured human vascular endothelial cells (HEC). The product was identified as PAF by its behavior in chromatographic systems, its recovery of biological activity, and its physico-chemical properties and susceptibility to lipases. The response of HEC to IL-1 was concentration-dependent, took more than 2 h to become apparent, and decreased after 18 h of incubation. Most of the PAF produced was cell-associated and only a small amount (about 25% of the total) was released in the culture medium. To study the mechanism of IL-1-induced HEC-PAF production we tested the activity of 1-O-alkyl-sn-glycero-3-phosphocholine:acetyl/coenzyme A acetyltransferase in HEC. Acetyltransferase activity measured in IL-1-stimulated HEC lysates showed a three to five times greater maximum velocity, but the same Michaelis constant, as untreated cells. The regulation of PAF generation in HEC by IL-1 may be an important aspect of the two-way interaction between immunocompetent cells and vascular tissue.

Acetyl Coenzyme A↗
PubMed1986

Platelet-activating factor contracts human myometrium in vitro.

The myometrial contractile responses to synthetic 1-0-octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (platelet-activating factor, PAF) and to oxytocin were evaluated in vitro on uterine (lower segment) strips obtained from pregnant women at term (39th week), undergoing elective cesarean section. Contractility was measured isometrically in an isolated organ bath using a superfusion technique. PAF in a concentration range between 5 and 100 nM as well as oxytocin (0.1-10 mU/ml) induced a dose-dependent contraction which could be categorized in two patterns, depending on whether spontaneous activity was present. In resting strips, oxytocin induced a prompt (0.5-1 min) development of active tension, followed by a prolonged (6-18 min), slow contraction and a final relaxation. However, at variance with oxytocin, PAF-induced contractions were rhythmic (3-8/hr), and characterized by a prompt (0.5-2 min) development of tension, followed by a brief (0.5-2 min) plateau, and a final, rapid relaxation. In spontaneously active strips, both stimuli induced a marked potentiation of the contractile activity. PAF response was dependent on both cyclooxygenase- and lipoxygenase-derived products as inferred from the abrogating effects of indomethacin and FPL 55712. A receptor-mediated mechanism of action was inferred from the occurrence of specific desensitization to PAF (but not to oxytocin), and from the blocking effect of CV 3988, a specific PAF receptor antagonist. The present study indicates that PAF stimulates the contraction of human myometrium in vitro and suggests that this mediator may have a role in labor.

Adult↗
PubMed1986

Cardiovascular alterations in the rabbit infused with platelet activating factor (PAF): effect of kadsurenone, a PAF-receptor antagonist.

The ECG and haemodynamic alterations caused by the i.v. infusion of platelet-activating factor (PAF) in the rabbit were studied after pretreatment with Kadsurenone, a specific PAF-receptor antagonist. Infusion of PAF at 0.8 microgram/kg in the rabbit caused important ECG changes, such as ST-segment depression and conduction arrhythmias, concomitantly with a marked reduction in left ventricular systolic pressure, mean arterial pressure and cardiac output, with a rise in total peripheral resistances and mean right atrial pressure. These physiological parameters became maximal at 75-120 seconds after PAF challenge, and returned to near prechallenge values within 25-60 minutes. Pretreatment with Kadsurenone, administered either intravenously (0.014 M, 1 ml/kg) or intraperitoneally (0.14 M, 1 ml/kg), exerted a quite complete protective effect in regard to the ECG changes and caused a significant reduction in the magnitude of all the haemodynamic alterations observed after intravenous infusion of PAF (0.8 microgram/kg). These results suggest that Kadsurenone is an effective inhibitor of PAF-induced cardiovascular changes in the rabbit, probably due to its competitive antagonism against PAF binding to specific receptors.

Animals↗
PubMed1986

Localization of cationic proteins derived from platelets and polymorphonuclear neutrophils and local loss of anionic sites in glomeruli of rabbits with experimentally-induced acute serum sickness.

The localization of cationic proteins (CP) derived from platelets and from polymorphonuclear neutrophils (PMN) in glomeruli of 42 rabbits injected i.v. with a large amount of bovine serum albumin, was investigated in sequential biopsies by immunofluorescence, using goat-anti-platelet CP and anti-PMN CP sera. Platelet CP deposits became detectable within 7 to 8 days after the i.v. injection of bovine serum albumin, before or coincident with the onset of proteinuria. The intensity and the extent of linear and segmental deposits of platelet CP along the glomerular capillary walls reached a peak at day 9 to 10, when proteinuria was maximal. The anti PMN-CP serum stained the cytoplasm of the few PMN present in glomeruli and only occasionally at day 11 and 12 identified focal deposits of PMN-CP along the glomerular capillary walls. The kinetic study of glomerular immune deposits showed that the first appearance of immune deposits in antigen excess was preceded by, or was concomitant, with the detection of platelet-CP in glomeruli. In the later stages of serum sickness, the immune deposits showed a progressive increase in rabbit IgG and C3. The glomerular polyanions were studied by light microscopy, using the colloidal iron technique, and by electron microscopy using polyethyleneimine as a cationic probe. The glomerular deposits of platelet-CP were associated with a reduction of colloidal iron staining, which was maximal 9 to 11 days after the i.v. injection of bovine serum albumin. At day 15, colloidal iron staining was almost completely restored. At day 9 in rabbits with acute serum sickness the anionic sites of glomerular basement membrane evidenced by polyethyleneimine, were segmentally decreased, mainly in the lamina rara interna. In rabbit studied at day 15 the anionic sites were decreased only at the base of the subepithelial electron dense deposits (humps). These results suggest that in rabbits with experimentally-induced acute serum sickness, during the early stages of glomerular immune deposit formation endogenous CP, released mainly from platelets, bind to glomerular capillary walls and possibly contribute to the neutralization of glomerular polyanions.

Acute Disease↗
PubMed1985

Immune complexes in preeclampsia and normal pregnancy.

We determined in normal nonpregnant (group I) and normal pregnant (group II) women and in patients with preeclampsia (group III): (1) immunoglobulins and complement C3b associated with polymorphonuclear leukocytes and platelet surfaces in an attempt to evaluate the interaction in vivo of immune complexes with the membranes of these cells; (2) the occurrence of circulating immune complexes; (3) the serum levels of immunoglobulins, C3, and C4; and (4) the plasma levels of complement C3d. In patients with preeclampsia (group III), the percentages of polymorphonuclear leukocytes and platelets positive for membrane-bound IgG, IgM, IgA, and C3 were significantly higher than the percentages in groups I and II. In group III, there also was a significant increase in circulating immune complexes, as compared to groups I and II. However, circulating immune complexes were also present in significant amounts in normal pregnancy (group II). The plasma levels of complement C3d were markedly increased in the most severe cases of preeclampsia.

Adult↗
PubMed1985

Functional and molecular characterization by the CB04 monoclonal antibody of a cell surface structure exerting C3-complement receptor activity.

CB04 monoclonal antibody which reacts with an epitope of a surface molecule expressed on human monocytes has been elicited using peripheral blood lymphocytes as immunizer. The characterization of the monoclonal antibody examined at the phenotypic, molecular, and functional levels indicates that the CB04 antibody defines a structure present on monocytes, tissue macrophages, B cells, polymorphonucleates, and erythrocytes. The molecular weight (220 kD), the tissue distribution in health and disease conditions, and the involvement in relevant biological processes indicate that the CB04 structure is the receptor for the C3b fragment of the complement. The binding of the antibody to the cell surface induces inhibition of the C3bi receptorial function.

Animals↗
PubMed1985

Human platelet cationic proteins bind to rat glomeruli, induce loss of anionic charges and increase glomerular permeability.

The binding of human platelet cationic proteins (HuPlt CP) to rat renal cortex in vitro and in vivo, the loss of glomerular polyanions (GPA) and the increase in glomerular permeability were studied. HuPlt CP were purified by sequential cation-exchange chromatography and chromatofocusing, by which these proteins were shown to be highly cationic in nature (pI 10.5) and mainly composed of three molecular species of 55.60 kD, 40.45 kD, and 10 kD as studied by gel permeation in high pressure liquid chromatography and SDS-polyacrylamide gel electrophoresis. Binding of HuPlt CP to glomerular capillary walls (GCW), mesangium and to peritubular capillaries of the rat renal cortex was demonstrated by immunofluorescence, using a specific goat anti-HuPlt CP antiserum, after incubation of the sections with HuPlt CP in vitro and after injection of HuPlt CP in vivo. This interaction was ionic in nature, since treatment of sections with heparin abrogated the binding of HuPlt CP to glomerular structures. The glomerular deposits of HuPlt CP were associated with the loss of GPA as revealed by colloidal iron staining (light microscopy) in both in vitro and in vivo experiments and by ruthenium red staining (electron microscopy) in in vivo studies. After the injection of native ferritin, the increase in glomerular permeability produced by an infusion of HuPlt CP was observed by the increased ratio of counted particles within the glomerular basement membrane with respect to controls. The binding of HuPlt CP to GCW and the loss of GPA was consistent with the interpretation that HuPlt CP may increase glomerular permeability due to the neutralization of GPA.

Animals↗