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H P Kertscher

Publications and source records attributed to H P Kertscher.

At least 19 recordsLinked to original sources
PubMed2001

Separation, analyses and syntheses of trimethoprim impurities.

The analysis of several impurities of the chemotherapeutic agent trimethoprim with various methods, including thin layer chromatography, gas chromatography, capillary electrophoresis as well as nuclear magnetic resonance is described. These methods were used to identify new impurities in trimethoprim batches. The main impurities were separated by column chromatography. To ensure the identity of the impurities, de novo syntheses were successfully carried out. With the methods described, it was possible to detect, separate and identify new impurities in trimethoprim batches.

Anti-Infective Agents, Urinary↗
PubMed1997

[PAF-antagonists with lipid structure. 6. Alkylpropandiol lipids with acyl- and ether- structures at the C-3 position and heterocyclic head groups; synthesis, characterization and structure-activity relationship].

A series of 14 PAF-analogues with simple lipid structure and heterocyclic head groups were synthesized, and the PAF-inhibitory potencies on human blood platelets was evaluated in vitro. Structure-activity relationships revealed that the PAF-antagonist activity is strongly influenced by the distance between position C-3 of the backbone and onium center and the structure of the heterocyclus. The best activity showed the 3,5-dimethylpyridinium derivative with a distance of 5 methylene groups (IC50 = 0.8 mumol/l).

Blood Platelets↗
PubMed1993

[PAF-antagonists with a phospholipid structure. 5. Propanediol phospholipids with various substituted pyridinium and quinuclidinium head groups and variations of the phosphorus-nitrogen distance;synthesis, characterization and structure activity relationship].

A series of 10 PAF-analogues, structurally modified in position C-2 (n-propyl) and position C-3 (polar head group) were synthesized, and the PAF-inhibitory potencies was evaluated using PAF-induced aggregation of human blood platelets in vitro. Structure-activity relationships revealed, that the PAF-inhibitory activity is strongly influenced by the distance between phosphate and onium center and the structure of the substituted heterocyclus. The best activity was observed by 3,5-dimethylpyridinium- and 4-ethylpyridinium derivative with a P-N-distance of 6 methylene groups (IC50 = 1.9 x 10(-6) mol/l and 2.7 x 10(-6) mol/l).

Blood Platelets↗
PubMed1992

[PAF-antagonists with phospholipid structure. 4. Alkylcarbamoylphospholipids with heteroarene and heterocyclase head groups and variation of the P-N-distance; synthesis, characterization and structure-activity relationship].

A series of 11 PAF-analogues, structurally modified in position 1 (alkylcarbamoyloxy), position 2 (n-propyl), and position 3 (polar head group) were synthesized, and the inhibitory potencies on human blood platelets in vitro was evaluated. Investigations of structure-activity relationships revealed, that the PAF antagonist activity is strongly influenced by the chain length of the alkylcarbamoyl residue and the structure of the polar head group. Derivatives with pentadecyl and octadecylcarbamoyl structure emerged effective inhibitors. The best activity was observed by dimethylaminopyridinium, analogues with a P-N distance of 3 or 4 methylene groups and pentadecyl or octadecylcarbamoyl structure (IC50 = 1.0-1.6 mumol/l).

Blood Platelets↗
PubMed1991

Inhibition of PAF-induced human platelet responses by newly synthesized ether phospholipids.

A series of 10 analogues of platelet-activating factor (PAF) was evaluated for proaggregatory and inhibitory behaviour on human blood platelets in vitro. Most of the compounds did not activate platelets but inhibited the PAF-induced aggregation. The inhibition was concentration-dependent and selective for PAF. Platelet responses to ADP and collagen were not suppressed. Schild analysis of the aggregation data was consistent with a simple competitive antagonism. The pA2 of the most effective antagonist (1-O-hexadecyl-2-O-ethylglycero-3-phosphoric acid-6'-(1-chinuclidinium)-hexylester) was 5.96. There is also evidence for its ability to inhibit the high affinity binding of [3H]PAF to the platelet receptors.

Adenosine Diphosphate↗
PubMed1991

Synthesis and proaggregatory activity of 1-O-(2-methyloctadecyl)-2-O-acetyl-rac-glycero-3-phosphocholine.

Racemic 1-O-(2-methyloctadecyl)-2-O-acetyl-glycero-3-phosphocholine, a branched chain PAF species, was prepared by chemical synthesis and investigated for biological activity on human blood platelets in vitro. The synthesis started from 2-O-benzylglycerol and 2-methyloctadecyl-1-methyl sulfonate and was accomplished in five reaction steps. A comparison with 'octadecyl-rich' PAF showed that the PAF species described here exerts a 22-fold weaker proaggregatory activity. Based on [3H]PAF-binding studies, an obstruction of PAF-binding or the signal transduction by the branched alkyl chain in C-1 position of the glycerol backbone is suggested.

Humans↗
PubMed1991

Effects of the synthetic ether phospholipid KO-286011 on cells and components of rabbit blood.

The ether phospholipid KO-286011, which is related to platelet-activating factor (PAF), was examined for PAF-antagonistic action on rabbit platelets both in vitro and ex vivo. It inhibited the aggregation of washed platelets induced by PAF (5 nmol/l) concentration dependently (IC50 = 6.5 X 10(-7) mol/l). After injecting 0.5 mg/kg to rabbits, the ex vivo PAF-mediated aggregation in heparinized platelet-rich plasma was influenced selectively. The inhibition was short and maximal after 5 min. In contrast, hematocrit, counts of peripheral platelets and leukocytes, hemoglobin content, partial thromboplastin time, prothrombin time, and fibrinolytic activity in plasma were not affected. However, the therapeutic range of KO-286011 is limited because of membranolytic activity at higher dosages, leading to hemolysis and drop of circulating platelet counts.

Animals↗
PubMed1991

Species-dependent differences of high affinity [3H]PAF-binding to platelets from humans and pigs and its inhibition by selected antagonists.

The sensitivity of blood platelets towards PAF (1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine) strongly varies with species and is primarily responsible for different pathophysiological effects after its administration to experimental animals. Platelets from domestic pigs were shown to possess one single class of high-affinity PAF-binding sites. Receptor density and sensitivity of pig platelets towards PAF were distinctly higher than those from humans. Preincubation of platelets from both species with PAF-specific antagonists diminished the high affinity [3H]PAF-binding concentration-dependently. Eight PAF-related antagonists, the ginkgolide BN 52021, as well as the hetrazepine WEB 2086 were included and mean inhibitory concentrations (IC50) between 0.09 and 124 mumol/l ascertained. Comparing the rank order of inhibitory potency considerable differences became evident between both species. The quotients of the IC50 values obtained with human and pig platelets differed for about two orders of magnitude. Moreover, the inhibitory profile of the PAF-related antagonists was found to be highly sensitive to small structural changes. Based on these findings a species-dependent difference at the PAF receptor level of platelets from pigs and humans is suggested.

Animals↗
PubMed1991

[PAF-antagonists with a phospholipid structure. 1. Phospholipids with hetero-arene head groups: synthesis, characterization and determination of the action of structural elements].

A series of analogues of platelet-activating factor (PAF) with heteroarene head groups have been synthesized, and tested for biological activities on blood platelets in vitro. In comparison with PAF most of the structural modifications exerted weak proaggregatory effects. The 4-(dimethylamino)pyridinium compound did not activate platelets but inhibited selectively PAF-induced platelet responses. These results point to a crucial role of the distance between the phosphoryl group and polar head for expression of PAF-antagonistic properties. Structural features of PAF-antagonist have been investigated by two-dimensional proton NMR spectroscopy, and proposed a model with three-dimensional structure.

Blood Platelets↗
PubMed1991

[PAF-antagonists with phospholipid structure. 2. Phospholipids with heteroarene head groups and variations of the phosphorus-nitrogen distance; synthesis, characterization and structure-activity relationships].

A series of 27 PAF-analogues with heteroarene head groups and variation of the P-N-distance on the C-3-position of the backbone were synthesized, and the PAF-antagonistic activity on human blood platelets in vitro was evaluated. Investigation of structure-activity relationships revealed that PAF-antagonistic activity is strongly influenced by the 4-(Dimethylamino)-pyridine as polar head base and the distance between phosphate group and onium center. Maximal activity was observed with a chain length of 3 or 4 methylene groups. Among the compounds tested, 1-O-Hexadecyl-2-n-propylpropan-1,3-diol-3-phosphoric acid-4'-[4-(dimethylamino)pyridinium]butylester was the most effective inhibitor in the in vitro assay (KB = 0.3 mumol/l).

Chromatography, Thin Layer↗
PubMed1991

[PAF-antagonists with phospholipid structure. 3. Phospholipids with heterocyclane head groups and variations of the phosphorus-nitrogen distance; synthesis, characterization and structure-activity relationship].

A series of 13 PAF-analogues with heterocyclane head groups and variation of the P-N-distance on the C-3-position of the backbone were synthesized. The proaggregatory and inhibitory potencies on rabbit and human blood platelets in vitro was evaluated. Investigations of structure-activity relationship revealed that the PAF-inhibitory potency is strongly influenced by the distance between phosphate and onium center and the structure of the heterocyclane. Derivatives with a P-N-distance of 4 or more methylene groups emerged effective inhibitors. The best activity was observed by chinuclidine- and N-methylpiperidine analogues with a chain length of 6 methylene groups (KB = 1.1 to 2.3 mumol/l).

Animals↗
PubMed1990

Platelet-activating factor (PAF) inhibitory profile of KO-286011 on blood platelets in vitro and in vivo.

A newly synthesised structural analogue of PAF, coded KO-286011 (1-O-hexadecyl-2-O-ethyl-rac-glycero-3-phosphoric acid 4-(N,N-dimethylamino)pyridinium butylester), was proved for its ability to inhibit PAF-mediated platelet responses in vitro and in vivo. The compound inhibited effectively the PAF-induced aggregation and secretion of human and rabbit platelets. In contrast, there was little influence on ADP-, collagen-, and arachidonic acid-triggered platelet responses. Schild-analysis of aggregation data ascertained in human platelet-rich plasma was consistent with a simple competitive antagonism and yielded a pA2 of 6.44. Proaggregatory activity of KO-286011 was excluded turbidimetrically as well as by means of a single cell counting technique. [3H]PAF binding studies provided evidence that KO-286011 exerts its inhibitory action at the PAF-receptor level. A significant inhibition of the ex vivo PAF-induced platelet aggregation was found after i.v. administration of 0.5 mg/kg KO-286011 to rabbits. The effect was most pronounced 5 min after dosing the inhibitor and detectable over a period of 30 min. Intravenous administration of 10 and 25 micrograms/kg KO-286011 to guinea pigs prevented dose-dependently the PAF-induced formation of thromboxane A2. The PAF-inhibitory action of KO-286011 was more potent than that of the ginkgolide BN 52021.

Animals↗
PubMed1988

Proaggregatory and inhibitory effects of 2-O-ethyl analogues of platelet-activating factor (PAF) on human and rabbit platelets.

A series of 8 analogues of platelet-activating factor (PAF) in which both the acetyl group and the polar head are changed, were tested for biological activities on human and rabbit platelets in plasma. Two of these compounds, 1-O-hexadecyl-2-O-ethyl-rac-glycero-3-phosphoric acid-5'-trimethylammoniumpentyl ester and 1-O-hexadecyl-2-O-ethyl-rac-glycero-3-phosphoric acid-6'-trimethylammoniumhexyl ester inhibit selectively the PAF-induced aggregation response without showing any agonistic activity. Schild analysis revealed a competitive antagonism and KB values of 4.4 and 10.5 mumol/l, respectively. These results point to a crucial role of the distance between the phosphoryl group and the polar head for expression of PAF-antagonistic properties. Moreover, the substituent at the 2-position was found to influence predominantly the agonistic behaviour.

Animals↗
PubMed1988

Effect of specific antagonists on PAF-induced platelet aggregation and release of plasminogen activator.

We investigated the inhibitory effects of two synthetic phospholipids KO-286,001 and KO-286,006 on the platelet-activating factor (PAF) induced release of plasminogen activator (PA) in the isolated pig ear preparation as well as aggregation of pig platelets. The action was compared with that of the natural PAF antagonist BN 52021. The activator release induced by 5 x 10(-9) mol/l PAF was inhibited by 10(-6) mol/l KO-286,006, whereas BN 52021 and KO-286,001 had no effect. All three PAF antagonists tested inhibited the aggregation in a dose-dependent manner. Comparison of the IC50 values confirmed the considerably lower inhibitory action of BN 52021 and KO-286,001. Our results suggested that similar receptor sites are involved in both PAF activities tested and furthermore, that are species differences in the inhibition of PAF effects.

Animals↗
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↗