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Biomedical subjects

D J Hanahan

Publications and source records attributed to D J Hanahan.

At least 109 records · Page 6Linked to original sources
PubMed1981

Human platelet stimulation by acetyl glyceryl ether phosphorylcholine.

Acetyl glyceryl ether phosphorylcholine (AGEPC) induced dose-dependent platelet aggregation and release of [3H]serotonin and platelet factor 4 in citrated human platelet-rich plasma. ADP scavengers or indomethacin prevented irreversible platelet aggregation responses induced by 0.2 microM AGEPC but had no effect upon platelet secretion; prostacyclin inhibited AGEPC-induced aggregation and secretion. EDTA or EGTA inhibited AGEPC-induced aggregation but had no effect on platelet secretion.

Blood Coagulation Factors↗
PubMed1981

Activation of human neutrophils with 1-O-hexadecyl/octadecyl-2-acetyl-sn-glycerol-3-phosphorylcholine (platelet activating factor).

1-O-Hexadecyl/octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC), the acetylated alkyl phosphoglyceride known as platelet-activating factor, stimulated human neutrophil (PMN) exocytosis, migration, superoxide production and aggregation over a concentration range of 10(-10) to 10(-5) M. AGEPC-induced PMN exocytosis of azurophilic (myeloperoxidase and beta-glucuronidase) and specific (lactoferrin and lysozyme) lysosomal granules was rapid (T 1/2 = 20 sec), dependent on the presence of cytochalasin B, but was not associated with release of cytoplasmic LDH. As seen with the complement-derived peptide stimulus, C5a, AGEPC-initiated PMN enzyme release was dependent on temperature and cellular glycolysis but not on the presence of extracellular Ca++. When analyzed by gradient analysis, PMN migration caused by AGEPC was primarily chemotactic in nature. An unusual feature for both enzyme secretion and migration was a decrease in response between 10(-6) M and 10(-5) M AGEPC. This decreased responsiveness could be explained by rapid PMN desensitization occurring at high AGEPC concentrations, limiting the overall cellular response. Rapid desensitization for exocytosis was demonstrated in PMN stimulated with AGEPC in the absence of cytochalasin B. When cytochalasin B was added subsequently and PMN challenged with AGEPC or C5a, stimulus-specific desensitization to AGEPC but not C5a-induced lysosomal enzyme release occurred. PMN desensitized to C5a responded normally to a subsequent AGEPC challenge. Stimulation of all the PMN functions examined was markedly attenuated with removal of the 2-acetyl group from AGEPC (lyso GEPC). These results suggest that AGEPC stimulates a wide variety of human PMN responses by a receptor-like mechanism, dependent on the short chain fatty acid ester in the 2-position of the alkyl phosphoglyceride.

Animals↗
PubMed1981

Acetyl glyceryl ether phosphorylcholine. Intravascular alterations following intravenous infusion into the baboon.

The intravenous infusion of 1-O-hexadecyl/octadecyl-2-acetyl-sn-glyceryl-3-phosphorylcholine (AGEPC) in baboons (28 micrograms per kg.) induced acute, but reversible, thrombocytopenia and neutropenia and the intravascular release of platelet factor 4 and thromboxane B2. Maximal depression of circulating platelets and neutrophils occurred within 30 seconds after AGEPC infusion and was accompanied by significant elevations in plasma platelet factor 4 and thromboxane B2 levels (p less than 0.02). Hematocrit values increased after AGEPC infusion, but this increase was delayed relative to the other intravascular alterations, i.e., maximal hematocrit values occurred at 10 to 20 minutes after AGEPC infusion.. The thrombocytopenia induced by AGEPC was reversed within 2 to 3 minutes; in contrast, circulating neutrophils did not return to preinfusion levels until 30 minutes after AGEPC infusion. Plasma platelet factor 4 and thromboxane B2 elevations gradually decreased and returned to preinfusion levels within 30 to 60 minutes. The deacetylated derivative of AGEPC, lyso-glyceryl ether phosphorylcholine, had no effect when similarly infused into baboons. These studies demonstrate that the intravenous administration of AGEPC into baboons initiated significant but reversible intravascular alterations; thus, this unusual acetylated alkyl phosphoglyceride may be an important mediator of inflammation in primates, including man.

Animals↗
PubMed1980

The isolation and characterization of a third or neutral phospholipase A2 in the venom of Agkistrodon halys blomhoffii. An improved fractionation procedure for all three enzymes.

The isolation of a new, third phospholipase A2 from Agkistrodon halys blomhoffi is described. On the basis of a pI value of 6.9, it is termed a neutral phospholipase A2. It was characterized as to its amino acid content, activity towards phosphatidylcholine, heat stability, and hemolytic behavior on human erythrocytes. A comparison of these characteristics with those of the acidic and basic phospholipases A2 established the uniqueness of the neutral enzyme. Two particularly important observations were concerned with the complete stability of the three phospholipases on heating at 100 degrees C at pH 6.0 in the presence of 10 mM Ca2+, but variable stability in the absence of Ca2+, and the significant lack of hemolytic activity by the acidic (pI 4.9) phospholipase A2 as compared to the neutral (pI 6.9) and basic (pI 8.7) enzyme which produced extensive hemolysis of human erythrocytes. Other facets of the characteristics of these phospholipases are discussed.

Animals↗
PubMed1980

Identification of platelet activating factor isolated from rabbit basophils as acetyl glyceryl ether phosphorylcholine.

Platelet activating factor obtained from antigen-stimulated rabbit buffy coat leukocytes containing 10% IgE-sensitized basophils was shown by gas-liquid chromatographic and mass spectrometric analysis of products after acetolysis and by base and acid hydrolysis to be acetyl-alkylglyceryl phosphorylcholine. The alkyl side chains were composed of octadecyl (greater than 90%) and hexadecyl (less than 10%) residues.

Animals↗
PubMed1980

Physical and chemical properties of platelet-activating factor obtained from human neutrophils and monocytes and rabbit neutrophils and basophils.

Platelet-activating factor secreted by stimulated human neutrophils and monocytes and rabbit neutrophils and basophils was isolated, purified and chemically and physically characterized. All four preparations had identical thin layer chromatographic behavior in a variety of solvent systems, identical solubility behavior in various organic and aqueous solvents and responded comparably to a variety of chemical and physical agents designed to reveal the presence functional groups. These findings indicate that human neutrophil and monocyte, and rabbit neutrophil and basophil derived platelet-activating factor preparations are indistinguishable, and support the conclusion that platelet-activating factor is a neutral, polar lipid molecule whose functional activity is dependent upon the presence of a carboxylic acid ester.

Animals↗
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↗
PubMed1978

Insensitivity of factor V and factor Va to diisopropylfluorophosphate and antithrombin III.

Bovine plasma Factor V and Factor Va, the latter prepared by thrombin or venom activator action on Factor V, are not inactivated by diisopropylfluorophosphate or antithrombin III nor do they form identifiable complexes with either of these reagents. On the basis of these data, it is concluded that bovine Factor V and Factor Va are not serine proteases.

Antithrombins↗
PubMed1977

Characterization of the alkyl ether species of phosphatidylcholine in bovine heart.

The molecular types of lecithin in beef heart lipids were investigated by a combination of mild hydrolytic procedures and silicic acid chromatography. The major species of sn-glycero-3-phosphorylcholine (GPC) were found to be: diacyl-GPC (57%), alk-l-enyl, acyl-GPC (39%), alkyl acyl-GPC (3%), and dialkyl-GPC ( less than 1%). No di-alk-l-enyl-GPC or alk-l-enyl alkyl-GPC were detected. The derived monoalkyl-and dialkyl-glycerols were characterized by their infrared spectra and alkyl chain compositions.

Animals↗