Biomedical subjects

C A Kohler

Publications and source records attributed to C A Kohler.

8 recordsLinked to original sources

PubMed1992

Analogues of platelet activating factor. 7. Bis-aryl amide and bis-aryl urea receptor antagonists of PAF.

A series of bis-aryl amide (13-57 and 66-81) and bis-aryl urea (58 and 85) antagonists of platelet-activating factor (PAF) was prepared that contain, separating the two aromatic rings, linear amide linkages of the form -(CH2)nCONH- (n = 0-2), -OCH2CONH-, and -(CH2)nNHCO- (n = 0-1), branched amide linkages of the form -(CH2)nN(COR)- (n = 1-3, R = CH3 or n-C3H7), and -N(COCH3)CH2-, and urea linkages of the form -NHCONH- and -CH2N(CONHCH3)-. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in the mouse, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Best activity was observed for compounds having linkages of the type -CH2CONH-, -CH2N(COR)-, and -CH2NHCO-. Many of these compounds inhibit PAF-induced platelet aggregation with IC50's under 1 microM.

Amides↗

PubMed1992

Analogues of platelet activating factor. 6. Mono- and bis-aryl phosphate antagonists of platelet activating factor.

A series of aryl phosphoglyceride (3, 19-61) and bis-aryl phosphate (67-135) antagonists of platelet activating factor (PAF) were prepared. A group of four bifunctional phosphorus reagents (5a-c and 7) were developed that allowed the preparation of these aryl phosphates in which the position of aromatic substitution can be varied. These compounds were examined for their ability to inhibit PAF-induced platelet aggregation of rabbit platelets. Selected compounds were also evaluated for their ability to displace [3H]PAF from its receptor on rabbit platelets. These in vitro data were compared to similar data obtained for a number of known PAF antagonists. The compounds were evaluated in vivo, in both the mouse and rabbit, for their ability to prevent death induced by a lethal challenge of PAF. The relationships between the biological activity and the nature, lipophilicity, and position of substituents of the aromatic rings were studied. Compound 105 (CL 184005) has been selected to undergo further development as a potential therapeutic agent for the treatment of septic shock in man.

Animals↗

PubMed1992

Studies of the effect of a platelet-activating factor antagonist, CL 184,005, in animal models of gram-negative bacterial sepsis.

The effect of CL 184,005, a potent and specific platelet-activating factor antagonist, has been examined in a variety of animal models relevant to gram-negative bacterial sepsis. Pretreatment of mice with CL 184,005 protected them from the lethal effects of platelet-activating factor. When rats or primates rendered hypotensive with endotoxin were treated with CL 184,005, blood pressure was normalized. Pretreatment of rats with CL 184,005 protected them from the gastrointestinal lesions induced by endotoxin. Pretreatment of rats and mice with CL 184,005 protected them from the lethal effects of endotoxin. Plasma tumor necrosis factor levels in endotoxin-treated mice were lower when the mice were pretreated with CL 184,005. These observations suggest that CL 184,005 may be potentially useful in the treatment of gram-negative bacterial sepsis, and the agent is undergoing clinical evaluation.

Animals↗

PubMed1986

A computerized multichannel platelet aggregometer system.

Commercially available instrumentation for conducting platelet aggregation studies in clinical and research laboratories consists of one-, two-, or four-channel aggregometers used in conjunction with strip chart recorders. These instruments have limited utility in large-scale drug screening and evaluation of the mode of action of drugs or in the clinical diagnosis of platelet disorders. A new instrument, a computerized multichannel aggregometer system (CMPAS) has been developed to collect, display, and analyze platelet aggregation data. The system is comprised of a 24-channel Born-type aggregometer, interfaced to a Rockwell AIM-65 microcomputer through an analogue-to-digital converter and an Epson dot-matrix printer. Each channel is individually calibrated, and aggregation data can be collected on up to 24 different platelet-rich plasma samples simultaneously. Conversational programs written in BASIC prompt the user for the addition of agonists and inhibitors. The tracings for each channel are displayed simultaneously, and a program automatically analyzes the data to generate the following parameters: baseline optical density, maximum aggregation response, positive and negative slopes, time to peak aggregation, and percentage response. Computerized multichannel aggregometer system data outputs are comparable to data generated by a standard Chronolog aggregometer unit. The advantages of the system include multichannel capability, simultaneous display of all channels allowing relative comparisons between control and experimental groups, and time savings and improved efficiency in conducting and analyzing aggregation experiments.

Animals↗

PubMed1986

Analogues of platelet activating factor. 4. Some modifications of the phosphocholine moiety.

Racemic analogues of platelet activating factor (PAF) in which the methylene bridge separating the phosphate and trimethylammonium moieties is altered in length (7a-f) have been prepared. Increasing the length of this bridge results in a progressive decrease in the hypotensive and platelet aggregation responses. Analogues in which the phosphocholine group is substituted with a methyl group (7h and 7i) or a phenyl group (5j) or in which the methylene bridge is replaced with a meta-substituted benzyl group (5k) have been prepared. With respect to both the blood pressure and platelet aggregation responses, 7i and 5k showed little if any changes in potency compared to racemic C16-PAF (1a). While 7h is more potent than 1a with respect to both the hypotensive and platelet aggregation properties, 5j is less potent. Replacement of the phosphate moiety of C18-PAF (1b) with a phosphonate group (7g) leads to decreased activity in both assays. Analogue 11, in which the phosphocholine group has been replaced with a 4-(trimethylammonio)butoxy group, exhibited no detectable hypotensive or platelet aggregating activity. None of the analogues exhibited a separation of the blood pressure and platelet aggregation activities.

Animals↗

PubMed1986

Analogues of platelet activating factor. 5. Multiple oxygen substitution of the alkoxy chain.

Racemic analogues of platelet activating factor (PAF) in which the alkoxy chain (R = -O(CH2)15CH3) has been replaced with a chain containing multiple ether linkages near the end (17, R = -O(CH2)8O(CH2)2O(CH2)2OCH3) or at the beginning (18, R = -O(CH2)2O(CH2)2O(CH2)9CH3) of the chain have been prepared. Both compounds exhibit reduced hypotensive and platelet aggregation responses compared to racemic C16-PAF (1a). This reduction in the biological activities is more apparent when the new oxygen atoms are located near the end of the chain. This substitution of additional oxygen atoms into the alkoxy chain does not result in any dramatic gains in selectivity of the biological responses.

Animals↗

PubMed1985

Analogues of platelet activating factor (PAF). 2. Some modifications of the glycerine backbone.

Racemic analogues of platelet activating factor (PAF) that contain a methylene group between the C2 and C3 carbon atoms (39) or between the C1 and C2 carbon atoms (40) have been synthesized. These compounds show reduced platelet aggregation and hypotensive activity as measured against racemic C16 PAF. Compounds in which the C1 carbon atom of PAF is substituted with one or two methyl groups (41 and 42, respectively) or the C3 carbon is substituted with a single methyl group (43) have been synthesized. Platelet aggregation and hypotensive responses produced by these compounds are significantly less than those obtained with racemic C16 PAF. None of the above compounds exhibit a separation of the platelet aggregation and hypotensive activities.

Animals↗

PubMed1985

Analogues of platelet activating factor. 3. Replacement of the phosphate moiety with a sulfonylbismethylene group.

An analogue of platelet activating factor (PAF) in which the phosphate moiety has been replaced with a sulfonylbismethylene group has been prepared. A key step in the synthetic sequence is the preparation of 4-[[3-(dimethylamino)propyl]thio]-1-(hexadecyloxy)-2-butanol via a one-pot reaction involving a sequential Michael addition and reduction. In comparison to racemic C16-PAF, 8 showed no platelet aggregating activity and substantially reduced hypotensive activity.

Animals↗