Search PubMed⌕ Search

Biomedical subjects

R N Pinckard

Publications and source records attributed to R N Pinckard.

At least 73 records · Page 4Linked to original sources
PubMed1979

Platelet-activating factor. Evidence for 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine as the active component (a new class of lipid chemical mediators).

A glyceryl ether containing phosphoglyceride, 1-O-alkyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (Ac-GEPC), has been shown to have a biological activity indistinguishable from that of naturally generated (rabbit) platelet activating factor (PAF). Its biochemical and biological properties so closely parallel those of naturally occurring PAF that we propose they are one and the same compound. Both PAF and AcGEPC could be converted to an inactive form through base-catalyzed methanolysis and restored to 100% functional activity by reaction with acetic anhydride. The synthetic lipid, AcGEPC, elicited 50% secretion of serotonin from rabbit platelets at a level of 10(-10) M (based on phosphorus). A propionyl derivative had somewhat comparable activity towards platelets, whereas the butyryl homologue was some 7-fold less active and the stearoyl derivative was inactive. These short chain acylglyceryl ether phosphoglycerides represent an entirely new, potent and unique class of lipid chemical mediators. 1-Acyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AcLL) also exhibited activity towards platelets but was some 200-fold less active than AcGepc. the propionyl lysolecithin behaved quite similarly to AcLL, but butyryl and stearoyl lysolecithins showed no activity.

Animals↗
PubMed1979

In vitro activation of complement by isolated human heart subcellular membranes.

Activation of human complement (C) occurred in vitro when mitochondrial membranes isolated from normal human heart tissue were incubated with normal human serum. This activation, as measured by C3 depletion, was not completely inhibited by blocking classical pathway activity in serum treated with EGTA, in C2-deficient serum, or in C1-depleted serum, nor in serum heated at 50 degrees C for 30 min to block the alternative pathway, but it could be prevented by blocking the classical and the alternative pathway simultaneously with EDTA, or by treating heated serum (50 degrees C. 30 min) with EGTA. Factor B was converted in normal serum as well as in EGTA-treated serum, but not in EDTA-treated serum. Mitochondrial membranes had no direct enzymatic or other activity that could inactivate functionally or highly purified C4 or C3, but the membranes could bind and activate C1 either in serum or in functionally pure C1 preparations. C4 also bound to the mitochondrial membranes only in the presence of C1. These data suggest that the activation of C by heart subcellular membranes involved both the classical and the alternative pathways, that the mitochondrial membrane preparations were capable of forming stabel complexes with C1 and C4, but not C3, and that the mitochondrial membrane preparations did not contain enzymes or have inherent properties that could directly cause C3 conversion.

Adsorption↗
PubMed1977

Platelet activating factor (PAF). A possible direct mediator of anaphylaxis in the rabbit and a trigger for the vascular deposition of circulating immune complexes.

Evidence is presented that IgE-induced, basophil-derived, platelet-activating factor (PAF) causes sequestration of rabbit platelets during sublethal IgE-induced anaphylaxis, and produces a state of specific desensitization in the platelets upon their subsequent return to the circulation. Moreover, depletion of platelets from rabbits undergoing lethal anaphylaxis abrogated the mortality and markedly reduced other parameters of the anaphylaxis. It was suggested that PAF may represent a major mediator of this reaction. A number of lines of evidence have suggested in addition that PAF may play a role in acute experimental immune complex disen that PAF may play a role in acute experimental immune complex disease in rabbits by causing release of vasoactive amines from platelets, lase in rabbits by causing release of vasoactive amines from platelets, leading to increased vascular permeability and deposition of circulating immune complexes along filtering vascular membranes. This data, providing evidence for the action of PAF in vivo and implicating this action in two allergic reactions, supports the contention that PAF is an important mediator of acute allergic reactions.

Anaphylaxis↗
PubMed1977

Basophil-derived platelet-activating factor (PAF) as an in vivo mediator of acute allergic reactions: demonstration of specific desensitization of platelets to PAF during IgE-induced anaphylaxis in the rabbit.

The anaphylactic response to an i.v. injection of antigen into rabbits making only IgE antibody against the antigen was shown to be preceded by a disappearance of the metachromatic staining properties of the circulating basophils and was accompanied by marked but transient thrombocytopenia. The platelets which returned to the circulation 1 hr after the anaphylaxis were shown to be unresponsive to the secretion-inducing activity of basophil-derived platelet-activating factor (PAF) when compared with platelets examined before antigen challenge. By contrast, platelet responsiveness to other stimuli such as collagen, thrombin, and C3b was unchanged. The specific desensitization to PAF provides strong evidence for the action of this mediator on platelets in vivo during IgE-mediated anaphylaxis and provides a useful tool for detecting the effects of particular cell activators in inflammatory reactions.

Acute Disease↗
PubMed1977

Intravascular aggregation and pulmonary sequestration of platelets during IgE-induced systemic anaphylaxis in the rabbit: abrogation of lethal anaphylactic shock by platelet depletion.

Significant alterations in the circulatory properties of platelets have been documented during IgE-induced systemic anaphylactic shock in the rabbit. Within 30 to 60 sec after i.v. antigen challenge, platelet aggregation occurs in both the venous and arterial circulations. The platelet aggregates then sequester in small blood vessels of various organs, particularly in the lung. The organ sequestration results in the development of a profound thrombocytopenia within 3 to 5 min after antigen challenge. Fifteen min later deaggregation of platelets occurs and the platelets return to the peripheral circulation within normal, prechallenge levels by 60 min. Additional experiments demonstrated that platelet depletion before antigen challenge abrogates the lethal effects and significantly reduces the pathophysiologic manifestations of IgE-induced systemic anaphylaxis. We conclude that the IgE-induced platelet alterations, probably induced by the intravascular release of basophil and perhaps mast cell-derived platelet-activating factor (PAF), play a major role in the pathogenesis of systemic anaphylaxis in the rabbit.

Anaphylaxis↗
PubMed1976

IgE-induced respiratory and circulatory changes during systemic anaphylaxis in the rabbit.

We studied systemic anaphylaxis induced by the administration of 200 mug of horseradish peroxidase into 11 anesthetized rabbits known to be producing anti-horseradish peroxidase antibodies only of the IgE class. Ventilatory changes included a transient, abrupt decrease in breathing frequency followed by increased minute ventilation; lung mechanical changes included decreased dynamic lung compliance and increased total pulmonary resistance; cardiovascular changes included pulmonary hypertension, systemic hypotension, and, frequently, a transient bradycardia. Recovery from these physiologic changes took place within 60 min. After recovery, the administration of 2 mg of horseradish peroxidase into 6 of the rabbits induced a second reaction indistinguishable from the first with respect to ventilatory and circulatory alterations; however, lung mechanical changes were less prominent. No histologic evidence of pulmonary edema or intraluminal plugging of the pulmonary edema or intraluminal plugging of the pulmonary circulation was observed by light microscopy. Although the first anaphylactic reaction was accompanied by disappearance of stainable basophils from the circulating blood, the second reaction occurred despite the absence of circulating basophils. These studies characterize further the effects of antigen challenge in rabbits producing detectable concentrations of IgE, but not other classes of antibody to the antigen.

Airway Resistance↗
PubMed1975

Characterization of autoantigenic sites on isolated dog heart mitochondria.

1. Anti-heart mitochondria autoantibodies were developed in serum from dogs following experimental myocardial infarction. 2. Heart mitochondria frozen and thawed repeatedly in a sucrose/Tris-chloride buffer retained both their functional integrity as measured by the respiratory control ratio and their ability to serve as an antigen in a complement fixation test. Mitochondria frozen and thawed in a potassium chloride/Tris-chloride buffer lost both their functional integrity and their autoantigenic activity after one freeze-thaw cycle. 3. Extraction of the heart mitochondria with acetone/water mixtures to remove phospholipids from the membrane led to a complete loss of the ability of the mitochondria to react in the complement fixation test but did not affect the ability of the membranes to bind autoantibody in absorption experiments. 4. Treatment of the mitochondrial membranes with increasing concentrations of trypsin caused a loss of up to approximately 50% of the membrane protein with a gradual decrease in the autoantigenic activity of the membrane without impairment of the ability of the membrane to bind autoantibody. 5. Removal of up to 90% of the sialic acid of the mitochondrial membrane with neuraminidase resulted in a considerable increase in the complement-fixing autoantigenic activity of the membrane without changing the apparent ability of the membrane to bind autoantibody in absorption experiments. 6. Exposure of mitochondrial membranes to autoantibody and complement caused an inhibition of both an inner mitochondrial membrane enzyme, i.e. cytochrome oxidase (48%) and an outer mitochondrial membrane enzyme, i.e. NADH cytochrome c reductase (rotenone insensitive) (37%).

Animals↗
PubMed1975

Consumption of classical complement components by heart subcellular membranes in vitro and in patients after acute myocardial infarction.

Experiments were conducted to characterize the antibody-independent activation of complement in human serum by isolated human heart mitochondrial membranes in vitro and to determine whether similar patterns of complement consumption occurred in patients after acute myocardial infarction. Direct evidence for the interaction of C1 and heart mitochondrial membranes was obtained by mitochondria-C1 binding and elution experiments. Exposure of normal human sera to isolated human heart mitochondria at 37 degrees C resulted in the consumption of C1, C4, C2, and C3 without significant consumption of the terminal components of the complement system (C6 through C9). The consumption occurred in the absence of detectable anti-heart mitochondria autoantibody, was demonstrated to be calcium dependent, and was inhibited by either 0.01 M EDTA or ethylene glycol bis(bets-aminoethyl ether) N,N,N',N',-tetraacetic acid (EDTA). Although specific absorption of C1q from human sera inhibited the mitochondria-dependent activation of C4, C3 donsumption was not affected. These data indicate that the consumption of C4 and C2 likely occurred due to the mitochondrial membrane-mediated activation of C1, but that the consumption of the C3 did not necessarily involve either the classical or alternative complement pathways. After the in vitro characterization of the mitochondria-dependent activation of the complement system, additional studies were performed to determine whether similar consumption occurred in patients after acute myocaridal infarction. During a 72-h period after hospital admission significant decreases in C1, C4, and C3 occurred in six patients with recent chest pain but no evidence of acute myocardial infarction. These studies suggest that myocardial cell necrosis results in the release of subcellular membrane constituents capable of activating the complement system in the absence of detectable anti-heart autoantibodies; such activation may be responsible in part for the development of acute inflammation and evolution of the infarct size following coronary artery occulusion.

Autoantibodies↗
PubMed1975

Intravascular effects of IgE antibody upon basophils,, neutrophils, platelets and blood coagulation in the rabbit.

Rabbits synthesizing only IgE antibody to BSA were challenged intravenously with 50 mg BSA and the associated blood cell and coagulation alterations were examined. Basophils decreased by 90% within 1 min of challenge. This was followed by a 70% decrease in neutrophils and a 50% decrease in platelets by 15 min. These changes were found to be highly significant when compared to control unimmunized rabbits similarly challenged. By 60 min, the neutrophils and platelets in the experimental rabbits had returned to 50 and 80% of their prechallenge levels respectively, but no basophils were demonstrable by toluidine blue staining. Lymphocyte counts in the experimental rabbits did not differ from controls at 0, 1, 15, or 60 min after challenge. Blood coagulation alterations also occurred after BSA challenge in the rabbits synthesizing IgE. A significant shortening of the whole blood clotting time in plastic tubes at 25 degrees C occurred in blood samples taken at 30 sec after antigen challenge. Similarly, in vitro addition of BSA to blood samples taken prior to challenge significantly shortened the whole blood clotting time. In addition, significant prolongation of whole blood clotting times was observed in blood obtained 60 min after challenge, but only among the rabbits positive for systemic anaphylaxis. This in vivo study corroborated the known in vitro effects of IgE upon the rabbit blood basophil and platelet. In addition, the results indicate that the intravascular interaction of antigen with specific IgE antibody induced neutrophil and blood coagulation alterations.

Animals↗
PubMed1975

IgE-induced blood coagulation alterations in the rabbit: consumption of coagulation factors XII, XI, and IX in vivo.

Intravenous administration of BSA into 3-month-old rabbits producing detectable anti-BSA antibody only of the IgE class of immunoglobulin induced a variety of intravascular blood coagulation alterations observed in the plasma 15 min after antigen challenge included: a) the intravascular consumption of intrinsic blood coagulation factors XII, XI, and IX and possibly the reduction in clottable fibrinogen; b) a significant prolongation of the activated partial thromboplastin time but not the prothrombin time; and c) the production of an inhibitor affecting the last stage of blood coagulation. The observed blood coagulation alterations were not caused by the manipulative procedures utilized, the presence of anti-BSA, IgG or IgM antibody, histamine-induced alterations in the vascular endothelium or the development of hypotensive shock. It is proposed that specific IgE antibody can induce directly or indirectly the activation of intrinsic blood coagulation in vivo.

Aminocaproates↗
PubMed1974

Characterization of rat liver subcellular membranes. Demonstration of membrane-specific autoantigens.

The induction of acute hepatocellular necrosis in rats resulted in the production of complement fixing, IgM autoantibodies directed toward inner and outer mitochondrial membranes, microsomal membrane, lysosomal membrane, nuclear membrane, cytosol, but not to plasma membrane. Utilizing selective absorption procedures it was demonstrated that each subcellular membrane fraction possessed unique autoantigenic activity with little or no cross-reactivity between the various membrane fractions. It is proposed that the development of membrane-specific autoantibodies may provide an immunological marker useful in the differential characterization of various subcellular membranes.

Animals↗