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R N Young

Publications and source records attributed to R N Young.

13 recordsLinked to original sources
PubMed1992

Development of 2,3-dihydro-6-(3-phenoxypropyl)-2-(2-phenylethyl)-5-benzofuranol (L-670,630) as a potent and orally active inhibitor of 5-lipoxygenase.

Leukotrienes are potent biological mediators of allergic and inflammatory diseases and are derived from arachidonic acid through the action of the 5-lipoxygenase. In this study, the syntheses and comparative biological activities of three series of 2,3-dihydro-2,6-disubstituted-5-benzofuranols with various substituents on position 3 are described. Compounds from each series were evaluated for their ability to inhibit the production of leukotriene B4 (LTB4) in human peripheral blood polymorphonuclear (PMN) leukocytes and the 5-lipoxygenase reaction in cell-free preparations from rat PMN leukocytes. The structure-activity relationships of each series in vitro and in vivo are presented. The bioavailability, metabolism, and toxicity profile of each series are discussed. The series with no substituent at position 3 was the most potent and among the compounds in that series 2,3-dihydro-6-(3-phenoxypropyl)-2-(2-phenylethyl)-5-benzofuranol (46, L-670,630) was chosen for further development.

Animals↗
PubMed1992

Mouse monoclonal antibody to a latent epitope of leucocyte receptors for leukotriene B4.

Human blood polymorphonuclear (PMN) leucocytes and human leucocytes of the HL-60 line, which were induced to differentiate by 1,25-dihydroxyvitamin D3, express stereospecific receptors for the potent chemotactic mediator, leukotriene B4 (LTB4), that is derived by 5-lipoxygenation from arachidonic acid. Monoclonal antibodies to LTB4 receptors (LTB4-R) were generated by immunizing BALB/c mice with partially purified PMN leucocyte membrane proteins, and fusing their splenocytes with P3X63Ag8 mouse myeloma cells. Hybridoma supernatants were screened initially by binding to PMN leucocyte LTB4-R protein, which had been affinity cross-linked with aminopropylamide (APA)-LTB4 and immobilized in plastic wells through attachment of the linked APA-LTB4 to adherent Fab of monoclonal anti-LTB4. Of the three clones producing antibodies which bound to LTB4-R, 0.5 mg/ml of one IgG3k antibody, termed E2, precipitated over 90% of the [3H]LTB4-binding activity of solubilized PMN leucocyte membrane proteins. E2 also bound to a radiolabelled protein of 70,000-80,000 MW from 125I-labelled PMN leucocyte membranes [35S]-labelled HL-60 cell membranes, and PMN leucocyte membranes affinity-labelled with [3H]APA-LTB4, that was identical in size to the LTB4-R precipitated by the rabbit IgG anti-idiotypic antibodies. E2 did not bind to intact PMN leucocytes or modify the binding of [3H]LTB4 by PMN leucocytes. The binding of E2 to LTB4-R in purified membranes of PMN leucocytes was less than one-fourth of that observed for the anti-idiotypic antibodies, but increased substantially after solubilization of the LTB4-R. The E2 monoclonal antibody thus recognizes a partially latent substituent of LTB4-R, which does not contribute to combining site function.

Animals↗
PubMed1991

Affinity labeling of the membrane protein-binding component of human polymorphonuclear leukocyte receptors for leukotriene B4.

A radiolabeled N-(3-aminopropyl)-leukotriene B4 amide ([3H]LTB4-APA) analog of the potent leukocyte chemotactic factor leukotriene B4 (LTB4) binds to receptors for LTB4 in plasma membrane-enriched preparations from human blood polymorphonuclear leukocytes (PMNL) and intact PMNL with respective mean dissociation constants of 2.3 nM and 69 nM at 4 degrees C. The [3H]LTB4-APA bound to plasma membrane-enriched preparations from PMNL was covalently cross-linked to membrane proteins with disuccinimidyl suberate. Solubilization and resolution by SDS-PAGE of proteins from [3H]LTB4-APA-labeled PMNL membranes revealed predominant labeling of a 60-kDa protein. Labeling of the PMNL membrane protein was inhibited by LTB4 and its analogs at concentrations similar to those inhibiting the binding of [3H]LTB4 to its receptor, with an identical rank order of potency of LTB4 greater than 20-hydroxy-LTB4 greater than LTB4-APA = 5(S),12(R)-dihydroxy-eicosa-14-cis-6,8,10-trans-tetraenoic acid much greater than LTD4 = LTC4. GTP suppressed the labeling of the 60-kDa PMNL membrane protein to an extent consistent with the decrease in receptor affinity for LTB4 induced by GTP. The stereospecificity of the affinity cross-linking reaction and the regulation by GTP support the identification of an approximately 60-kDa protein as the binding component of the PMNL receptor for LTB4.

Affinity Labels↗
PubMed1991

Development of novel leukotriene--based anti-asthma drugs: MK-886 and MK-571.

A potent, selective and orally active receptor antagonist of leukotriene D4, MK-571, was discovered and developed from a styrylquinoline lead structure based on a hypothetical model of the leukotriene D4 receptor. MK-571 blocks the action of LTD4 in animals and man, and is effective in a number of animal models of antigen-induced bronchoconstriction at plasma concentration at or below 2 micrograms/mL. MK-571 also blocks antigen-induced asthmatic responses in man. In addition a series of 2-indolealkanoic acids was discovered to be inhibitors of leukotriene biosynthesis. From this series, MK-886, a nanomolar inhibitor of leukotriene biosynthesis was developed. The mechanism of action of MK-886 has been found to be the inhibition of activation of the 5-lipoxygenase enzyme. This inhibition is mediated by interaction with a specific 18 kD protein termed 5-lipoxygenase activating protein (FLAP). MK-886 is an inhibitor of leukotriene biosynthesis and of antigen-induced bronchoconstriction in animal models and in asthmatic men.

Animals↗
PubMed1989

Preparation of leukotriene B4 antibodies in sheep.

The antibody response of eight sheep immunised against leukotriene B4-keyhold limpet haemocyanin (LTB4-KLH) was investigated. Four Suffolk x Mule sheep and two Soay sheep received subcutaneous injections of conjugate over a period of 11-21 weeks, and two Suffolk x Mule sheep received intramuscular and subcutaneous injections for 11 weeks. All eight animals reacted successfully to immunisation and produced antibodies of high affinity and specificity for LTB4. The antiplasma could be used for radioimmunoassay at dilutions of 1/10(5)-1/10(6) and the highest titres were obtained in Soay sheep. Intramuscular immunisation produced a faster but less sustained response than subcutaneous injections. The uniformity of response between animals in relation to the immunisation regime and the physico-chemical similarity of the antibodies suggest that the quality of the conjugate is the most important factor for successful antibody production.

Animals↗
PubMed1988

L-648,051, a potent and specific aerosol active leukotriene D4 antagonist.

L-648,051 (I) is a potent, competitive and selective antagonist of the leukotriene D4 receptor in guinea pig and human lung tissue. Its activity on isolated smooth muscle preparations and its superiority relative to other agents (L-649,923 (II) or FPL 55712) in reversing ongoing contraction to LTD4 was somewhat unexpected in light of the results of receptor binding studies (Ki = 6.2 microM for L-648,051 versus 0.4 microM for L-649,923 and 2.0 microM for FPL 55712 on guinea pig lung membranes). The reasons for this observed superiority are unknown but may relate to the rate at which various antagonists equilibrate with the leukotriene receptors on various tissues. The physical properties (polarity) of L-648,051 may contribute to this enhanced rate of equilibration. The rapid metabolism and elimination of L-648,051 in vivo should be an advantage for a topical agent by minimizing systemic exposure. The potential role for L-648,051 as a novel aerosol therapy for asthma is now being investigated.

Animals↗
PubMed1987

Stereoselective determination of (beta S,gamma R and beta R,gamma S)-4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy) propylthio]-gamma-hydroxy-beta-methylbenzenebutanoic acid in human and rat plasma by normal-phase high-performance liquid chromatography.

A stereoselective high-performance liquid chromatographic method was developed for the determination of the enantiomeric composition comprising (beta S,gamma R and beta R,gamma S)-4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy) propylthio]-gamma-hydroxy-beta-methylbenzenebutanoic acid in human and rat plasma. Both enantiomers, (beta S,gamma R)- and (beta R,gamma S)-1, were isolated from the plasma by liquid-liquid extraction, the organic phase was evaporated to dryness, and the residue was lactonized with p-toluenesulfonic acid followed by derivatization with R(+)-alpha-methylbenzylamine to form diastereomeric Schiff base adducts. Separation was performed on a silica column (Supelcosil) with a mobile phase composed of 97.8% hexane, 2% isopropyl alcohol, and 0.2% triethylamine. The column eluant was monitored with a variable wavelength UV detector set at 280 nm (0.005 AUFS). Based on the peak area ratios, the method shows excellent linear relationships with their corresponding concentrations and satisfactory intraday and interday assay precision and accuracy. The detection limit of this method is 25 ng/mL in plasma for each enantiomer. The method has been applied to the assay of plasma obtained from human subjects administered 1 in safety and tolerability studies and from rats administered 1 intravenously or per os.

Animals↗
PubMed1985

Development of enzyme-linked immunosorbent assays for measurement of leukotrienes and prostaglandins.

Enzyme-linked immunosorbent assays (ELISAs) were developed for the leukotrienes LTC4 and LTB4 and the prostaglandins 6-keto PGF1 alpha and thromboxane (TxB2). In an indirect assay procedure for all 4 eicosanoids a BSA conjugate of the leukotrienes or an ovalbumin conjugate of the prostaglandins was absorbed to polystyrene microtiter plates. Samples containing the respective eicosanoids were incubated in the coated wells with specific rabbit antisera. The wells were then incubated successively with a goat anti-rabbit antibody linked to fluorescein and a rabbit anti-fluorescein antibody linked to alkaline phosphatase. The resultant assays for LTC4, LTB4, 6-keto PGF1 alpha, and TxB2, gave steep, sensitive inhibition curves; IC50s were 0.2, 10, 1, and 0.4 pmol respectively with minimal cross-reactivity to other eicosanoids. The sensitivities and specificities were comparable to those found in the RIA, and the levels determined in this assay correlate well with those determined in non-immunological assays.

6-Ketoprostaglandin F1 alpha↗
PubMed1978

Multichannel electrochemical microbial detection unit.

A compact multichannel unit for electrochemical detection of microorganisms that automatically displays detection time length is described. This unit was successfully tested with various members of the Enterobacteriaceae group.

Bacteriological Techniques↗