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Biomedical subjects

R A Lewis

Publications and source records attributed to R A Lewis.

At least 307 records · Page 17Linked to original sources
PubMed1984

Specific binding of leukotriene C4 to ileal segments and subcellular fractions of ileal smooth muscle cells.

A specific high-affinity receptor for leukotriene C4 (LTC4) has been identified on segments of longitudinal smooth muscle from guinea pig ileum, in disrupted cells obtained from the ileal segments, and in subcellular fractions enriched for mitochondrial membranes and plasma membranes, respectively. Specific [3H]LTC4 binding at a fixed input at 4 degrees C reached a plateau at 60 min with each of the four preparations and was greater than 80% reversible after binding reached equilibrium by the introduction of excess unlabeled homoligand. LIGAND analysis demonstrated a single high-affinity receptor on the smooth muscle segments, the disrupted cells, and the subcellular fractions enriched for mitochondrial membranes and for plasma membranes with respective Kd values of 7.6 nM, 1.3 nM, 13 nM, and 8.5 nM. These Kd values overlap with the concentration of LTC4 known to elicit a spasmogenic response in the ileal muscle, indicating that the radioligand recognizes a receptor that mediates the biological response. Competition analysis with disrupted ileal cells and subcellular fractions with a fixed input of LTC4 radioligand and incremental concentrations of the natural sulfidopeptide leukotrienes demonstrated leukotriene D4 (LTD4) to be 1-3 logarithms less active than LTC4 and leukotriene E4 (LTE4) to be essentially inactive. Thus, ileal longitudinal smooth muscle cells possess a high-affinity receptor that is selective for LTC4 and that receptor exhibits both a plasma membrane and subcellular distribution.

Animals↗
PubMed1984

Leukotriene B4 action on endothelium mediates augmented neutrophil/endothelial adhesion.

The attachment of human polymorphonuclear leukocytes (PMN) to bovine endothelial monolayers is increased by pretreatment of the endothelial cells with leukotriene B4 (LTB4). The response is dose dependent with a maximum at 10(-6) M, requires no more than 1 min of preincubation for the maximal effect, and decays linearly over 30 min once the LTB4 is removed. Preincubation of PMN with LTB4 does not augment subsequent adhesion to a plastic substratum or an untreated monolayer of endothelial cells and eliminates the augmented attachment to LTB4-pretreated endothelial cells. The simultaneous exposure of both cell types during the adhesion interaction gives a biphasic dose-related increment, suggesting that the inhibition of the neutrophil adherence is less marked than with a pretreatment interval. Thus, the LTB4-dependent adherence of PMN to endothelial cells is selectively mediated by endothelial cells, is dose related, is reversible upon removal of the agonist from the endothelial cells, and is opposed by the direct action of LTB4 on the PMN.

Animals↗
PubMed1984

A comparison of visual field loss in primary open-angle glaucoma and the secondary glaucomas.

We compared the pattern of visual field loss in 148 patients with primary open-angle glaucoma and 63 patients with secondary glaucoma. The frequency with which each location in the visual field was defective was similar in the two conditions. The most common visual field defects in both varieties of glaucoma were superior arcuate scotomas and superior nasal steps. The similar distribution of visual field defects in primary and secondary glaucomas is consistent with a common mechanism for optic disc damage.

Computers↗
PubMed1984

Renal and systemic hemodynamic responses to intravenous infusion of leukotriene C4 in the rat.

We studied the systemic and renal hemodynamic effects of leukotriene C4 (2 micrograms/kg per min for 5 minutes, iv) in the rat. During the period of its infusion, leukotriene C4 produced a significant elevation of mean arterial pressure and reductions in cardiac output and renal blood flow, as measured by electromagnetic flow probes. These effects were abolished by FPL55712 , a putative antagonist of sulfidopeptide leukotrienes, but not by saralasin or indomethacin. Leukotriene C4 also resulted in an average loss of 20% in plasma volume which, during the postinfusion period, perpetuated the low cardiac output state and thus provoked the release of angiotensin II. This vasoactive peptide sustained the elevation in systemic vascular resistance and the reduction in renal blood flow over a 70-minute postinfusion observation period. Consequently, glomerular filtration rate fell by approximately 50%. These angiotensin II-mediated effects were abolished by saralasin. Indomethacin prevented the leukotriene C4-induced loss of plasma volume and, thus, allowed for the significant recovery of cardiac output and renal blood flow during the post-infusion period, thereby preserving glomerular filtration rate. We conclude that leukotriene C4 exerts direct systemic and renal vasoconstrictor, as well as cardiodepressant effects, during the period of its infusion. By virtue of its vasopermeability enhancing effect, leukotriene C4 also results in an immediate loss of plasma volume, an effect which requires the presence of secondarily generated cyclooxygenase products and which perpetuates the hemodynamic abnormalities observed beyond the period of leukotriene C4 infusion.

Animals↗
PubMed1984

Asthma induced by suggestion: is it due to airway cooling?

The effect of suggestion on the airway response to 10 inhalations of normal saline followed by doubling concentrations of isoproterenol was assessed in 12 normal and 30 asthmatic subjects. It was suggested that the first 5 saline solutions contained a bronchoconstrictor and that the second 5 contained a bronchodilator, or vice versa, and that the first 4 isoproterenol solutions were inert, whereas the last was a bronchodilator. Nine asthmatic, but no normal subjects, bronchoconstricted after saline inhalation, with a mean fall in specific airway conductance (SGaw) of 40%. This was dose-dependent and was abolished when inhalations were carried out at 37 degrees C 100% relative humidity. Suggestion did not affect the airway response to saline or isoproterenol in either group, but it did influence the subjective impression of airway caliber recorded on a visual analogue scale. In this study, the bronchoconstriction after saline inhalation, previously attributed to the effect of suggestion, was caused by airway cooling.

Adolescent↗
PubMed1984

Effects of exogenous arachidonic, eicosapentaenoic, and docosahexaenoic acids on the generation of 5-lipoxygenase pathway products by ionophore-activated human neutrophils.

Exogenous eicosapentaenoic acid (EPA) and docosahexaenoic acid (DCHA) have been compared with exogenous arachidonic acid for their capacity to modulate the oxidative metabolism of membrane-derived arachidonic acid by the 5-lipoxygenase pathway in ionophore-activated human neutrophils and for their suitability as parallel substrates in this pathway. The products from specific 14C- or 3H-labeled substrates were isolated by reverse phase high performance liquid chromatography (RP-HPLC) and were identified by elution of radiolabel at the retention times of the appropriate synthetic standards. Each product was also characterized by its ultraviolet (UV) absorption spectrum, and 7-hydroxy-DCHA was defined in addition by analysis of its mass spectrum. The metabolites, 5-hydroxyeicosatetraenoic acid, leukotriene B4 (LTB4), 6-trans-LTB4 diastereoisomers, 5-hydroxyeicosapentaenoic acid, 6-trans-leukotriene B5 diastereoisomers, leukotriene B5 (LTB5), and 7-hydroxy-DCHA were quantitated by integrated UV absorbance during resolution by RP-HPLC. LTB4 and LTB5 were also quantitated by radioimmunoassay of the eluate fractions, and leukotrienes C4 and C5 (LTC4 and LTC5, respectively) were quantitated by radioimmunoassay alone. None of the unlabeled exogenous fatty acids (5-40 micrograms/ml) altered the release of radioactivity from [14C]arachidonic acid-labeled, ionophore-activated neutrophils. The metabolism of 5 and 10 micrograms/ml of exogenous EPA by ionophore-activated, [14C]arachidonic acid-labeled neutrophils not only generated 5-hydroxyeicosapentaenoic acid, 6-trans-LTB5, LTB5, and LTC5, but also stimulated the formation of 5-hydroxyeicosatetraenoic acid, 6-trans-LTB4 diastereoisomers, and LTC4 from membrane-derived arachidonic acid. In contrast, LTB4 production was diminished throughout the EPA dose-response, beginning at 5 micrograms/ml EPA and reaching 50% suppression at 10 micrograms/ml and 84% suppression at 40 micrograms/ml. The selective decrease in extracellular LTB4 concentrations in the presence of EPA was not due to a change in the kinetic appearance of LTB4 or to an increase in conversion to its omega-oxidation metabolites. DCHA was metabolized to 7-hydroxy-DCHA, did not stimulate metabolism of membrane-derived arachidonic acid, did not appreciably inhibit LTB4 formation, and was not a substrate for leukotriene formation. Incremental doses of exogenous arachidonic acid resulted in increased production of 5-hydroxyeicosatetraenoic acid and 6-trans-LTB4 by ionophore-activated, [14C]arachidonic acid-labeled neutrophils without any change in LTB4 production. 5-hydroxyeicosapentaenoic acid and 7-hydroxy DCHA were inactive as chemotactic factors whereas 5-hydroxyeicosatetraenoic acid exhibited 2% of the potency of LBT4. Thus, exogenous DCHA does not appreciably interfere with the metabolism of membrane-derived arachidonic acid by ionophore-activated, [14C]arachidonic acid-labeled neutrophils and is converted only to a monohydroxy derivative. In contrast, exogenous EPA attenuates the generation of LTB4 and is converted to LTB5, which is a weak and partial agonist as compared with LTB4.

Arachidonate Lipoxygenases↗
PubMed1984

Kappa opioid analgesia is dependent on serotonergic mechanisms.

The serotonergic dependence of mu and kappa opioid analgesia was compared in the mouse tail-flick and hot-plate assays using morphine and the selective kappa agonist, U-50, 488H, respectively. Depletion of serotonin with p-chlorophenylalanine resulted in a marked antagonism of U-50,488H analgesic potency in both assays, as did reserpine pretreatment. Both of these effects were dose-related and the latter was reversed by treatment with the serotonin precursor, 5-hydroxytryptophan. Several reputed serotonin antagonists (cyproheptadine, ketanserin and pirenperone) also antagonized U-50,488H analgesia. In contrast, the analgesic potency of morphine was only decreased slightly by p-chlorophenylalanine and reserpine, and not at all by the serotonin antagonists. Thus, kappa, but not mu, analgesia is strongly dependent upon serotonergic mechanisms in these assays. However 5-hydroxytryptophan did not enhance U-50,488H analgesia in nonpretreated mice or in mice made tolerant to U-50,488H. Likewise, it did not alter the development of U-50,488H tolerance. On this basis it appears that kappa opioid tolerance is not due to serotonergic hypofunction.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗
PubMed1984

Immunologically induced generation of tetraene and pentaene leukotrienes in the peritoneal cavities of menhaden-fed rats.

The generation of sulfidopeptide leukotrienes and leukotriene B (LTB) in response to an IgG-mediated immune complex reaction in the peritoneal cavities of rats fed either a menhaden oil-supplemented diet or a beef tallow-supplemented diet for 9 to 10 wk was determined with the combined techniques of radioimmunoassay (RIA) and reverse-phase high performance liquid chromatography. Rats on the fish fat diet (FFD) incorporated eicosapentaenoic acid (EPA) into pulmonary and splenic tissues with an EPA:arachidonic acid ratio of approximately 2:1, whereas rats on the beef fat diet (BFD) showed no detectable EPA. The estimated total quantities of immunoreactive sulfidopeptide leukotrienes generated by each group of rats were similar, ranging from 70 to 99 ng/ rat in the FFD groups and 65 to 109 ng/rat in the BFD groups; for rats on the FFD this total included the pentaene products LTC5, LTD5, and LTE5 in quantities ranging from 24 to 39 ng/rat. The total quantities of immunoreactive LTB generated in the two groups of rats were similar, being 6 to 29 ng LTB4/rat for the BFD groups and the sum of LTB4 and LTB5 of 8 to 36 ng/rat for the FFD groups. There was a two- to seven-fold preferential generation of immunoreactive LTB5 over LTB4 in the FFD rats. LTC5 was equipotent with LTC4 in contracting guinea pig pulmonary parenchymal strips and ileal tissues. In contrast, LTB5 was 1/30 to 1/60 as potent and did not reach the same maximum as LTB4 in eliciting neutrophil chemotaxis. The finding that FFD favors the immunologic generation of LTB5, which has attenuated biologic activity when compared to LTB4, suggests that EPA-enriched tissues may produce less pro-inflammatory activity than tissues that are EPA-poor.

Animals↗
PubMed1984

An analysis of the relationship between 5-lipoxygenase product generation and the secretion of preformed mediators from mouse bone marrow-derived mast cells.

The quantitative relationships between the secretion of a granule-associated mediator, beta-hexosaminidase, and the oxidative metabolism of arachidonic acid by the 5-lipoxygenase pathway were analyzed for a homogeneous population of T cell-dependent, bone marrow-derived, murine mast cells. The mast cells were either sensitized with a monoclonal IgE and challenged with specific antigen, or to bypass a transmembrane signal, were stimulated with calcium ionophore A23187. The released products of the 5-lipoxygenase pathway were quantitated by integrated ultraviolet absorbance after resolution by reverse phase-high performance liquid chromatography in the case of 5-hydroxy-eicosatetraenoic acid (5-HETE), and by separate radioimmunoassays for leukotriene C4 (LTC4) and leukotriene B4 (LTB4). The activation-release response of the cells was perturbated by the introduction of three pharmacologic agents, each directed to different steps in the 5-lipoxygenase pathway of arachidonic acid metabolism, and the action of each agent was determined for separate cell samples while present and after its removal by washing. 5,6-Dehydroarachidonic acid (5,6-DHA), an irreversible inhibitor of 5-lipoxygenase, prevented formation of 5-HETE from exogenous [14C]arachidonic acid and from membrane-derived arachidonic acid in a dose-related fashion when sensitized mast cells, preincubated with drug, were washed before antigen activation. Release of 5-HETE, LTC4, and LTB4 was inhibited by 5,6-DHA in a corresponding dose-related fashion, with a minimal preincubation period of 1 to 5 min before the cells were washed and subjected to antigen-dependent activation. In contrast, the inhibitory effect of 5,6-DHA on beta-hexosaminidase release was lost after three washes and was not evident after one wash unless the preincubation period was extended to 15 min. The capacity of 5,6-DHA to prevent leukotriene generation without altering beta-hexosaminidase release was also observed with ionophore-activated mast cells. Preincubation of sensitized cells with diethylcarbamazine (DEC), followed by a wash before antigen-dependent activation, produced inhibition of leukotriene generation, no effect on beta-hexosaminidase release, and augmentation of 5-HETE release at the maximum dose studied; thus, DEC interrupts the pathway distal to the formation of 5-hydroperoxy-eicosatetraenoic acid (5-HPETE) from arachidonic acid by 5-lipoxygenase. Preincubation of sensitized cells with incremental amounts of the prostacyclin analog U-60,257, followed by washing and antigen challenge, inhibited LTC4 release without altering the release of LTB4 or beta-hexosaminidase.(ABSTRACT TRUNCATED AT 400 WORDS)

8,11,14-Eicosatrienoic Acid↗
PubMed1983

The myeloperoxidase-dependent metabolism of leukotrienes C4, D4, and E4 to 6-trans-leukotriene B4 diastereoisomers and the subclass-specific S-diastereoisomeric sulfoxides.

The mechanism of the metabolic inactivation of leukotrienes C4, D4, and E4 by human polymorphonuclear leukocytes activated by phorbol myristate acetate has been analyzed with the use of activated cells, their supernatants, the isolated components of the myeloperoxidase system, and chemically synthesized hypochlorous acid (HOC1). The metabolic products were resolved by reverse-phase high performance liquid chromatography in one or more solvent systems, and each product was characterized relative to chemically synthesized standards by its reverse-phase high performance liquid chromatography retention time, UV absorption spectrum, nonvascular smooth muscle spasmogenic activity, and immunoreactivity. The phorbol myristate acetate-activated human polymorphonuclear leukocytes converted each of the sulfidopeptide leukotrienes to products identical with synthetic diastereoisomers of 6-trans-leukotriene B4 by the following criteria: retention times in two solvent systems, lambda max of 269 nm with shoulders at 259 and 279 nm, and mass spectral analysis. Each of the sulfidopeptide leukotrienes was simultaneously converted to subclass-specific S-diastereoisomeric sulfoxides which co-chromatographed with synthetic standards, exhibited a bathochromic shift to a lambda max at 284 nm, were fully immunoreactive, and possessed less than 5% spasmogenic activity of the corresponding sulfidopeptide leukotrienes. When the sulfidopeptide leukotrienes were incubated with supernatants of phorbol myristate acetate-activated cells in the presence of 0.1 mM H2O2, with a mixture of 100 milliunits of myeloperoxidase, 0.1 mM H2O2, and 10 mM Cl-, or with chemically prepared HOCl, the metabolic products formed were the same as those obtained with the activated cells, indicating that extracellular inactivation was due to HOCl produced by the action of released myeloperoxidase.

Cell-Free System↗
PubMed1983

Airway constriction in normal humans produced by inhalation of leukotriene D. Potency, time course, and effect of aspirin therapy.

Five normal human subjects inhaled aerosols generated from solutions of leukotriene D (LTD) to determine the bronchoconstrictor potency and the time course of airway obstruction produced by this constituent of slow-reacting substance of anaphylaxis. The dose-effect and time-effect curves were compared with curves similarly generated for the well-characterized airway constrictor histamine. Leukotriene D was, on average, 5,900 times more potent than histamine on a molar basis in producing an identical decrement in maximal expiratory flow rate at 30% of control vital capacity above residual volume. In addition, although LTD had a rapid onset of effect, similar to that of histamine, the airway obstruction produced by LTD was longer lasting, thereby reflecting more closely the response of asthmatic allergic individuals to antigen inhalation. The response of these subjects to inhalation of LTD was not altered by ingestion of aspirin, suggesting that the airway obstruction was not mediated by cyclooxygenase products of arachidonic acid.

Adult↗
PubMed1983

IgE-mediated release of leukotriene C4, chondroitin sulfate E proteoglycan, beta-hexosaminidase, and histamine from cultured bone marrow-derived mouse mast cells.

Mouse bone marrow-derived mast cells differentiated in vitro and sensitized with monoclonal IgE respond to antigen-initiated activation with the release of histamine, beta-hexosaminidase, chondroitin sulfate E proteoglycan, and leukotriene C4 (LTC4). The chondroitin sulfate E nature of the glycosaminoglycan side chain was established by demonstrating that the chondroitinase ABC disaccharide digestion products were composed of equal quantities of 4-sulfated and 4,6-disulfated N-acetyl-galactosamine. The single immunoreactive sulfidopeptide leukotriene, released and quantitated with a class-specific antibody, was identified as LTC4 by its retention time on reverse-phase high-performance liquid chromatography and by its specific spasmogenic activity on the guinea pig ileum. The release of the preformed mediators, as well as of LTC4, was related in a dose-response fashion to the concentration of monoclonal IgE used during the sensitization step and to the concentration of specific antigen used to initiate the activation-secretion response. The optimal concentrations of IgE for sensitization and of antigen for challenge were the same for the release of preformed mediators and of LTC4. In addition, the time courses of their release were superimposable, with a plateau at 5 min after antigen challenge. The release of three preformed mediators and of LTC4 after fixation of IgE, washing of the sensitized cells, and antigen challenge unequivocally indicates a bone marrow-derived mast cell origin for these products. Linear regression analyses of the net percent release of beta-hexosaminidase to histamine and of 35S-chondroitin sulfate E to beta-hexosaminidase yielded straight lines that intersected at the origin, which indicates that the three preformed mediators are localized in the secretory granules of the bone marrow-derived mast cells. The concomitant generation of 23 ng of LTC4/10(6) sensitized bone marrow-derived mast cells represents the first example of IgE-dependent release of substantial amounts of LTC4, a component of slow reacting substance of anaphylaxis, from a mast cell population of greater than 95% purity. The IgE-dependent generation of LTC4, rather than prostaglandin D2, by the chondroitin sulfate E proteoglycan-containing bone marrow-derived mast cells contrasts with the predominant generation of prostaglandin D2 by heparin proteoglycan-containing mast cells. These differences together support the existence of two phenotypically different mast cell subclasses.

Animals↗
PubMed1983

Ethmozine suppression of single and repetitive ventricular premature depolarizations during therapy: documentation of efficacy and long-term safety.

This study reports a total of 1677 patient days' experience with the use of Ethmozine to suppress ventricular premature depolarizations. A total of 39 patients were studied on three placebo-controlled protocols. Ethmozine, given at a mean total daily dose of 830 mg +/- 318 mg on a dosing schedule of every 8 hours, resulted in a mean plasma Ethmozine level of 0.42 micrograms/ml +/- 0.28 micrograms/ml. In addition to reducing ventricular premature depolarizations from 11,049/24 hr during placebo to 2231/24 hr during Ethmozine therapy (80% reduction), the drug also resulted in a 95% reduction in paired forms and a 99% reduction in total runs of ventricular tachycardia. Ethmozine is extraordinarily well tolerated with only mild side effects of dizziness, perioral tingling, and euphoria, with no serious toxicity requiring discontinuation of therapy. Ethmozine demonstrates great potential as an effective drug in suppressing ventricular premature depolarizations with minimal side effects or toxicity.

Adult↗
PubMed1983

Identification and quantitation of arachidonic-acid metabolic products in rabbit, rat and human saliva.

Arachidonic-acid metabolites were identified in salivary secretions of rabbits, rats and man and in homogenates of rabbit parotid and submandibular glands. The following levels were determined in mixed saliva of healthy volunteers: PGE2, 0.65 +/- 0.8 ng/ml; PGF2 alpha, 0.41 +/- 0.06 ng/ml; serologically active hydroxyeicosatetraenoic acids (HETE) 319.6 +/- 36.6 ng/ml; serologically active 6-sulphidopeptide-containing leukotrienes 1.72 +/- 0.21 ng/ml (all values mean +/- SEM). In all instances, HETE markedly predominated over all other arachidonic-acid metabolites.

12-Hydroxy-5,8,10,14-eicosatetraenoic Acid↗
PubMed1983

Effects of leukotrienes C4 and D4 on glycoprotein and lysozyme secretion by human bronchial mucosa.

The effects of leukotrienes C4 (LTC4) and D4 (LTD4) on the secretion by human bronchial mucosa of [14C]glucosamine-labeled, trichloro-acetic acid/phosphotungstic acid-precipitable glycoprotein and lysozyme were evaluated in vitro. LTC4 and LTD4, in the concentration range of 0.16 to 1600 nM, induced a dose-related increase in the release of radiolabeled glycoprotein, but not of lysozyme. This secretagogue effect was selective for high molecular weight glycoproteins of about 2-5 x 10(6) daltons, and the median effective concentrations (EC50) of LTC4 of 9.4 x 10(-9) M and of LTD4 of 2.44 x 10(-8) M, indicate that these leukotrienes are approximately 100-fold more potent than the cholinergic agonist methacholine. Incubation of [14C]glucosamine-labeled bronchial mucosal explants with LTC4 or LTD4 for six sequential 15-min periods revealed a rapid, progressive decrement in glycoprotein release, compatible with stimulatory action on secretion rather than augmentation of the rate of glycoprotein synthesis. This interpretation is also consistent with the finding that the specific activity (ratio of bound radiolabel: protein content) of the macromolecular glycoprotein secreted by the explants is not changed with stimulation of release by the leukotrienes. Based upon the activity of synthetic leukotriene analogs, the specific C-6 chirality of the sulfidopeptide of LTD4, the presence of a hydroxyl at C-5 and the presence of eicosanoid carbons 9-20 were of no importance for secretagogue activity. These findings contrast with the stereochemical requirements for the spasmogenic response to sulfidopeptide leukotrienes and suggest that leukotriene-induced secretion is not likely to be mediated via a specific receptor.

Bronchi↗
PubMed1983

A withdrawal hyperalgesia test for physical dependence: evaluation of mu and mixed-partial opioid agonists.

The physical dependence-inducing properties of analgesics are commonly assessed by the appearance of typical narcotic withdrawal signs (weight loss, jumping, etc.) upon cessation of administration or treatment with a narcotic antagonist. We sought to develop a simple model of physical dependence based upon withdrawal hyperalgesia. The test compound was injected seven times over a period of three days. At various times after the last injection, 6% aqueous NaCl was injected i.p. and the mice were observed for stereotyped writhing. To assess the magnitude of hyperalgesia, the animals were also challenged with several concentrations of saline administered at the time of peak sensitivity and a saline EC50 was thereby derived. In this manner, it was demonstrated that morphine causes a marked, dose-related physical dependence. Other mixed opioids, pentazocine, ethylketocyclazocine, nalbuphine, and butorphanol (in decreasing order of effectiveness) were also active. In nonpretreated mice, naloxone caused a dose-related appearance of saline-induced writhing, suggestive of a blockade of endogenous analgesic mechanisms. Writhing in response to low concentrations of i.p. saline provides a sensitive test of analgesic physical dependence.

Analgesics, Opioid↗