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Biomedical subjects

R W Bonser

Publications and source records attributed to R W Bonser.

30 records · Page 2Linked to original sources
PubMed1986

Inhibition of phorbol ester stimulated superoxide production by 1-oleoyl-2-acetyl-sn-glycerol (OAG); fact or artefact?

OAG-stimulated superoxide (O2) production by HL-60 granulocytes showed enantiomeric specificity but reached a maximum of only 5% of that produced by either phorbol myristate acetate (PMA) or phorbol dibutyrate (PDBu). At 10-100 microM, OAG displaced specifically-bound [3H]PDBu from intact HL-60 cells by only 25%, suggesting limited cell penetration. OAG (10-100 microM) also inhibited PDBu-stimulated O2 production by 25%; this inhibition was enantiomerically specific. However, at a lower concentration (3 microM), both enantiomers of OAG fully blocked O2 production stimulated by PMA (0.5 microM). This inhibition is probably artefactual, due to the hydrophobic PMA physically associating with OAG in the extracellular fluid.

Animals↗
PubMed1985

Stimulation and inhibition of secretion by phorbol myristate acetate in different cell types.

In washed human platelets and in HL60 granulocytes phorbol myristate acetate (PMA, 1-2000nM) synergised with threshold concentrations of secretogogues to induce a sustained maximum secretory response. Likewise, superoxide production from HL60 cells maintained a maximal response at PMA concentrations between 30-300nM. At concentrations up to 10nM PMA also augmented calcium ionophore, A23187, stimulated histamine release from rat peritoneal mast cells. However, in the mast cell PMA concentrations above 10nM reduced maximum histamine release in a dose-dependent manner.

Animals↗
PubMed1981

Esterification of an endogenously synthesized lipoxygenase product into granulocyte cellular lipids.

The human promyelocytic leukemia cell line HL60 can be induced to differentiate into mature granulocytes by exposure to Me2SO. [1-14C]Arachidonic acid incubated overnight with these cells was incorporated mainly into membrane phospholipids. Stimulation of these cells with the calcium ionophore, A23187, resulted in a rapid release of esterified arachidonic acid from phosphatidylethanolamine and phosphatidylcholine. The released arachidonic acid was metabolized via both the cyclooxygenase and lipoxygenase pathways into three major hydroxylated products, 12-L-hydroxy-5,8,10-heptadecatrienoic acid (HHT), 5(S)-hydroxy-6,8,11,14-icosatetraenoic acid (5-HETE), and 5-(S),12(R)-dihydroxy-6,8,10,14-icosatetraenoic acid (leukotriene B). Arachidonic acid was also incorporated into triacylglycerols and phosphatidylinositol. The lipoxygenase product, 5-HETE, was rapidly esterified into cellular lipids. Thirty minutes after ionophore stimulation, 55% of the total 5-HETE synthesized was esterified into phospholipids and 35% incorporated into acylglycerols. In contrast, the other hydroxylated derivatives of arachidonic acid (HHT and leukotriene B) were not incorporated into acylglycerols or phospholipids. Esterification of hydroxylated metabolites of arachidonic acid into membrane phospholipids may serve to regulate a number of granulocyte functions.

Arachidonic Acid↗
PubMed1981

The production of 5-HETE and leukotriene B in rat neutrophils from carrageenan pleural exudates.

Rat neutrophils isolated from three-hour carrageenan pleural exudates actively metabolize arachidonic acid into three major metabolites, HHT, 11-HETE and 15-HETE. However, in the presence of the calcium ionophore, A23187, or the non-ionic detergent, BRIJ 56, these cells also produce 5-HETE and LTB. The production of these lipoxygenase products is calcium dependent. While non-steroidal anti-inflammatory drugs do not affect 5-HETE or LTB production, BW 755C and ETYA inhibit formation of these metabolites from exogenously added arachidonic acid.

Animals↗
PubMed1980

Thrombin and bradykinin modulate prostaglandin synthetase independently of phospholipase.

Thrombin and bardykinin stimulate prostaglandin production from exogenous arachidonic acid in 3T3 cells. The increase in PG production cannot be explained simply by the contribution from endogenous AA metabolism. The rates of stimulated PG production from exogenous and endogenous AA both remain linear fro 3 min, then fall rapidly. It is suggested that BK and Th may act by directly stimulating cyclooxygenase independently of phospholipase.

Animals↗
PubMed1980

Role of extracellular arachidonate in regulation of prostaglandin biosynthesis in cultured 3T3 fibroblasts.

The stimuli that activate phospholipase releasing substrate fatty acids for PG biosynthesis also activates the reuptake of liberated fatty acids by the cell. The substrate released by these stimuli is accessible to albumin in 3T3 cells, and it is therefore presumably released into the extracellular space before it undergoes enzymatic conversion. Added exogenous arachidonate competes freely with endogenous arachidonate released by a stimulus, suggesting no apparent coupling mechanism between phospholipase and cyclooxygenase enzyme systems.

Animals↗