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Biomedical subjects

G Ostermann

Publications and source records attributed to G Ostermann.

At least 55 records · Page 3Linked to original sources
PubMed1987

Plasma from atherosclerotic patients exerts an increased degradation of platelet-activating factor.

Platelet-activating factor (PAF) is a naturally occurring phospholipid that exerts diverse biological activities. In the present study the degradation of PAF as well as lipid concentrations were measured both in plasma from 28 patients suffering from peripheral vascular disease and 18 healthy volunteers of comparable age. Beside some changes of the lipoprotein pattern it was also found that the capacity to degrade PAF is significantly elevated in the patient group. In view of this finding the question arises whether there is any link between the degradation of PAF and the development of atherosclerosis.

Aged↗
PubMed1987

Modification of the polar head group of platelet-activating factor: influence on the biological activity.

Racemic analogues of platelet-activating factor and its lyso derivatives have been prepared in which one methyl of the trimethylammonium group has been replaced by ethyl, propyl, allyl, or carboxymethylene. The influence of chemical modification on the biological activity was assessed by measuring platelet aggregation and desensitization. The results point to a crucial role of a positively charged polar head group for the expression of biological activity of platelet-activating factor. There are also some indications of a more non-specific interaction of the polar head group of platelet-activating factor with its platelet binding sites.

Humans↗
PubMed1987

[Synthesis and platelet aggregating activity of structural analogs of platelet-activating factor with a heterocyclic head group].

Structural analogues of platelet-activating factor (PAF, 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine) containing an imidazole or thiazole residue as polar head group have been prepared and tested for platelet aggregating properties. Compared with PAF all analogues exert considerably lower platelet-stimulating activities. The agonistic behaviour is shown to depend primary on the presence of a positively charged polar head group.

Animals↗
PubMed1986

The role of lipoproteins in the degradation of platelet-activating factor.

Measuring both platelet-stimulating activity and liberation of acetate, the capacity of serum and individual lipoproteins to degrade the platelet-activating factor (PAF) was studied. The highest degrading effect relative to the protein content was found in very low density lipoproteins (VLDL) and in low density lipoproteins (LDL). The effect is about 10- and 100-fold higher than that of high density lipoproteins (HDL) and serum, respectively. In lipoprotein deficient serum (LPDS) less than 5% of serum activity is detectable. Considerable individual variations are observed measuring the degradation of PAF under standard conditions in plasma from 37 healthy volunteers. Moreover, this activity is shown to correlate strongly with the plasma concentration of LDL. On the other hand, a significant negative correlation was found between the PAF-degrading capacity and the plasma concentration of HDL. In contrast, the PAF-degradation is unrelated to the concentration of plasma triglycerides. The results point to a possible role of plasma lipoproteins in regulating the degradation of PAF released into the circulation.

Humans↗
PubMed1985

Platelet-stimulating and membranolytic properties of racemic PAF-acether and analogues.

Three synthetic 1-O-hexadecyl-rac-glycero-3-phosphocholines and the corresponding 1-O-hexadecyl-rac-glycero-3-phosphoric acid methyl esters were tested for platelet-aggregatory and membranolytic properties. Nanomolar concentrations of both the 2-O-acetyl and the 2-O-propionyl derivative of 1-O-hexadecyl-rac-glycero-3-phosphocholine were shown to activate platelets in human platelet-rich plasma. About 625-fold higher concentrations of the corresponding phosphoric acid methyl esters are required to produce the same platelet-stimulating effect. The 1-O-hexadecyl-rac-glycero-3-phosphocholine and the 1-O-hexadecyl-rac-glycero-3-phosphoric acid methyl ester are both nearly ineffective up to final concentrations of 0.1 to 0.2 mM. All tested compounds also cause a graduated lysis of red cells in the range of micromolar concentrations.

Blood Platelets↗
PubMed1985

[Synthesis and biologic activity of some stable structure analogs of platelet activating factor].

Physiologically stable structure analogues of the platelet-activating factor (PAF-acether), the acetyl group of which had been substituted by short-chain alkyl rests, had been synthesized and been tested with regard to their biological activity against thrombocytes. Five differently substituted 2-alkylmalonic acid esters with methyl rest up to n-pentyl rest had been applied the basic products. The n-propyl compound exhibits the most intense biological activity, which is, however, essentially reduced against the PAF-acether. With conditions of the examination, all the other derivatives possess a more decreased activity.

Chemical Phenomena↗
PubMed1984

[Possible regulatory importance of cellular sulfhydryl groups and reduction metabolic pathways for the activation of human blood platelets].

The activation of the blood platelets is the prerequisite for their participation in physiological and pathological intravasal processes. An aimed influence on the distinct functions of the blood platelets presumes an exact knowledge about course and regulation of the activation of the platelets. Investigations on glucose-6-phosphate-dehydrogenase-deficient platelets and on the effect of glutathione-oxidizing substances on normal platelets showed references to a regulatory significance of the cellular thiol/disulphide state in the process of activation. In this case particularly the arachidonic acid balance and the SH/SS-state of platelet proteins seem to be in close connection with reductive ways of metabolism.

Arachidonic Acids↗
PubMed1984

Cooperative effects of 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine (PAF-acether) and exogenous arachidonic acid in stimulation of human blood platelets.

Cooperative effects of PAF-acether and arachidonic acid in blood platelet activation were studied in human platelet-rich plasma. Using a combination of low concentrations of PAF-acether and subthreshold amounts of exogenous arachidonic acid an enhancement of aggregation and an increased formation of malondialdehyde are obtained. Both effects are completely suppressed either by acetylsalicylic acid or by use of PAF-acether desensitized platelets, indicating that cyclooxygenase products and intact receptors for PAF-acether are of primary importance in the observed synergism. Stimulating activity of PAF-acether on the formation of cyclooxygenase products is also seen with use of higher concentrations of arachidonic acid during mild stimulation of human platelets. This effect of PAF-acether is dependent on the concentration used and is obviously due to changes in the platelet membrane as derived from experiments with lysed platelets. Enhanced capacity of platelets to synthesize endoperoxides and thromboxane in consequence of an in vivo release of PAF-acether into the circulation might be of pathobiochemical relevance in some circumstances.

Arachidonic Acids↗
PubMed1984

The influence of PAF on the metabolization of arachidonic acid by human blood platelets.

The cooperative action of PAF and arachidonic acid, collagen or the divalent cation ionophore A 23 187 was studied in human platelet-rich plasma. Besides an augmentation of the platelet aggregation also increased amounts of thromboxane B2 and malondialdehyde are generated. Both effects are inhibited by aspirin indicating that the cyclooxygenase pathway plays a major role in the synergistic platelet activation.

Arachidonic Acid↗
PubMed1984

Halo lipids. VI. Stimulation of human and rabbit blood platelets by racemic halo analogues of O-alkyl-glycerophosphocholine.

Halo analogues of O-alkyl- glycerophosphocholines are shown to stimulate human and rabbit blood platelets. Using 50-500 microM, a concentration dependent platelet aggregation is triggered in human platelet-rich plasma. Distinctly lower concentrations up to 10 microM activate the platelets in rabbit platelet-rich plasma. Moreover, the halo analogues enhance aggregation and release reaction triggered by suboptimal concentrations of ADP. In protein poor mediums the halo lipids in a concentration of 50 microM or higher cause a complete lysis of platelets. These results indicate that the halo lipids tested show the typical behaviour reported on lysophosphatidic acids which has to be taken into account using these compounds for other purposes.

Adenosine Diphosphate↗