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Biomedical subjects

R A Lewis

Publications and source records attributed to R A Lewis.

At least 361 records · Page 20Linked to original sources
PubMed1982

Prostaglandin D2 generation after activation of rat and human mast cells with anti-IgE.

Anti-IgE-dependent activation of rat and human mast cells resulted in the preferential generation of the cyclooxygenase products prostaglandin D2 (PGD2) and prostaglandin I2 (PGI2) in the rat and PGD2 in the human. The average net generation of PGD2, determined by gas chromatography-mass spectrometry, was 13.1 ng/10(6) purified rat mast cells and 39.5 ng/10(6) dispersed, enriched human mast cells. After IgE-dependent activation, there was a linear relationship between the net quantities of PGD2 generated and of histamine secreted from dispersed human pulmonary cells when the number of mast cells was varied but the total number of cells was held constant, indicating that it is the number of mast cells participating in IgE-dependent activation, rather than total mast cell number, that determines PGD2 generation. A linear relationship was also shown between PGD2 generation, determined by radioimmunoassay, and the release of the granule marker beta-hexosaminidase from purified rat mast cells on the dose-response portion of the plot of their response to anti-IgE challenge. With higher concentrations of anti-IgE, PGD2 generation from rat mast cells plateaued, whereas net percent beta-hexosaminidase release increased further. In kinetic studies of rat mast cells activated with anti-IgE, the onset (1 to 2 min) and time of maximum generation (5 to 10 min) for PGD2 were delayed relative to the onset (15 to 30 sec) and completion (1 to 2 min) of beta-hexosaminidase release. Thus, the extracellular appearance of PGD2 during IgE-dependent mast cell activation represents a response additional to the secretion of granule-associated mediators.

Animals↗
PubMed1982

Corneal sensitivity after percutaneous radiofrequency trigeminal rhizotomy: a quantitative study.

Using the Cochet-Bonnet esthesiometer, we evaluated the corneal sensation in 13 patients with trigeminal neuralgia. We compared the preoperative and postoperative results after the trigeminal rhizotomy in a quantitative study. Of 13 patients who underwent operation, a decrease in corneal sensation developed compared with the eye that was not operated on in five patients. This decrease in sensitivity was not suggested by clinical symptoms or signs, and up to 23 months of follow-up failed to reveal any clinical symptoms. The failure to manifested clinical corneal symptoms in the follow-up period may result from the selective fiber destruction technique employed in radiofrequency rhizotomy with preservation of other myelinated nerves maintaining corneal nutrition.

Adult↗
PubMed1981

Tryptase from human pulmonary mast cells. Purification and characterization.

Tryptase, the predominant neutral protease in human mast cell secretory granules, was purified to homogeneity from dissociated and concentrated pulmonary mast cells by sequential chromatography on Dowex 1-X2, DEAE-Sephadex, and heparin-agarose. Purified tryptase gave a single stained protein band on polyacrylamide gels after electrophoresis at pH 4.3 in the presence of 4 M urea. The enzyme has an apparent molecular weight of 120,000 to 140,000 by gel filtration chromatography. Electrophoresis of purified tryptase under denaturing conditions revealed subunits with molecular weights of 37,000 and 35,000 in a molar ratio of 1:1, consistent with a tetrameric subunit structure for the holoenzyme of Mr = 144,000. Both subunits bind [3H]diisopropyl fluorophosphate as assessed by the correspondence of radioactivity with the two stained protein bands in a polyacrylamide gel after electrophoresis of purified tryptase under denaturing conditions, indicating that all four subunits of the holoenzyme may have active site capacity. Purified tryptase has a specific activity for tosyl-L-arginine methyl ester of 97 units/mg (1 unit = 1 mumol of substrate cleaved/min at 22 degrees C). Human pulmonary mast cells contain tosyl-L-arginine methyl ester-esterase at levels more than 100-fold higher than those of human neutrophils, eosinophils, and monocytes. One million mast cells contain about 1.1 units, or 6 to 19 micrograms of tryptase, and have the capacity to contribute dominant levels of this enzyme at tissue sites of mast cell degranulation.

Amino Acids↗
PubMed1981

Mast cell mediator release as a function of cyclic AMP-dependent protein kinase activation.

Stereo-specific perturbation of the IgE-receptor (shown in previous studies) produces a monophasic rise in cyclic AMP that peaks at 15 s and a depletion of cyclic AMP-dependent protein kinase that plateaus at 30-60 s. The previously observed linear relationship between the attenuation in the monophasic rise in cyclic AMP and the quantity of mediator release in the presence of incremental concentrations of the adenosine analogue 2',5',-dideoxyadenosine, DDA, which is known to inhibit adenylate cyclase, indicated a direct relationship between receptor perturbation, transmembrane activation of adenylate cyclase, and granule secretion. The role of cyclic AMP as a second messenger in this sequence is now apparent from the linear relationship between net percent mediator release and net percent activation of cyclic AMP-dependent protein kinase isoenzyme when IgE-dependent activation of adenylate cyclase is suppressed by incremental quantities of DDA. There was a comparable percent activation of both types I and II mast cell cyclic AMP-dependent protein kinase isoenzymes with anti-IgE-induced activation and secretion, and there was a parallel suppression of the activation of both isoenzymes in the presence of DDA. Although these studies firmly link the activation of cytoplasmic cyclic AMP-dependent protein kinase to the IgE receptor-initiated transmembrane activation of adenylate cyclase. they do not discriminate among the functions of the two isoenzymes.

Animals↗
PubMed1981

Functional characterization of synthetic leukotriene B and its stereochemical isomers.

Leukotriene B (LTB), a potent lipid chemotactic factor for neutrophils, is 5S,12R-dihydroxy-6,14-cis,8,10-trans-eicosatetraenoic acid (Fig 1), based upon direct comparison of natural LTB with synthetic 5S,12R-dihydroxy-6,8,10,14-eicosatetraenoic acid (5,12-di-HETE) stereoisomers in three biological assays. Of the six synthetic stereoisomers evaluated, only the 5S,12R,6,14-cis,8,10-trans compound had chemotactic potency for human neutrophils in vitro that was comparable to that of natural LTB, with a concentration of 3 X 10(9-9) M eliciting a one-half maximum response. In contrast, the racemic mixture of 5R,12R- and 5S,12S-6,10-trans,8,14-cis, the racemic mixture of 5S,12R- and 5R,12S-6,10-trans,8,14-cis, the 5S,12R-6,8-trans,10,14-cis, the 5S,12R-6,8,10-trans,14-cis, and the 5S,12S-6,8,10-trans,14-cis stereoisomers required concentrations of 3 X 10(-7) to 1 X 10(-6) M to elicit comparable responses. Only natural LTB and its synthetic counterpart elicited a local neutrophil infiltration when injected into the skin of the rhesus monkey at 10 ng and 100 ng per site. Natural and synthetic LTB at a concentration of 3 X 10(-8) M each provoked an EC25 contractile response of guinea pig pulmonary parenchymal strips in vitro, whereas the other four tested stereoisomers of 5,12-di-HETE were inactive at this concentration. Structure-function analyses suggest that the neutrophil chemotactic activity depends critically upon the C-1 to C-12 domain, including the stereochemistry of the 6-,8-,and 10-olefinic bonds and the presence of both hydroxyl groups.

Animals↗
PubMed1981

Deoxyguanosine kinase of neonatal mouse skin tissue.

Deoxyguanosine kinase (ATP: deoxyguanosine 5'-phosphotransferase) activity has been identified in neonatal mouse skin tissue. This activity which has a molecular weight of 44 000 was shown to be highly specific for deoxyguanosine as a substrate. Unique to deoxynucleoside kinases was the observation that this enzyme possessed a pH optimum of 5.2. In dilute solutions catalytic activity is lost, however the enzymatic activity can be stabilized by the addition of 20 micrometer MgATP or ATP. Kinetic analysis gave an apparent Km for deoxyguanosine of 7 micrometer. Double-reciprocal plots of activity vs. MgATP concentration produced a broken line with the break occurring at 0.5 mM MgATP. Below this concentration an apparent Km for MgATP of 23 micrometer was measured; above 0.5 mM MgATP an apparent Km of 265 micrometer was calculated. Mouse skin deoxyguanosine kinase was strongly inhibited by dGTP, dGDP and UDp. dGTP was a competitive inhibitor of deoxyguanisine with an apparent Ki of 1.9 micrometer. UPD (K1,app = 3 micrometer), dGDP = 0.7 micrometer) (Ki,app = 0.07 micrometer] were competitive inhibitors of MgATP and dGTP ki,app = 0.07 micrometer) were competitive inhibitors of MGATP when the concentration of MgATRP was greater than 0.5 mM.

Adenosine Triphosphate↗
PubMed1981

Von Recklinghausen neurofibromatosis. Incidence of iris hamartomata.

The results of a prospective survey of the ophthalmic manifestations of neurofibromatosis (NFT) have never been published. We studied the ocular features of NFT in 77 patients (ages 5 weeks to 69 years) among whom the diagnosis was made by nonophthalmic parameters. Of subjects ages 6 years and older, 92% had hamartomatous lesions of the iris, termed Lisch nodules, as distinguished from common iris nevi in nonaffected individuals. The presence of Lisch nodules is correlated to age, but not to number of café-au-lait spots, number of neurofibromata, or severity of disease. Lisch nodules appear among prepubertal children and are apparently unique to NFT. They are a valuable criterion by which to diagnose NFT in problematic cases.

Adolescent↗
PubMed1981

Radioimmunoassay of the leukotrienes of slow reacting substance of anaphylaxis.

A rabbit immunized with a conjugate of leukotriene D4 (LTD4) and bovine albumin via the icosanoid carboxyl produced antibodies with comparable affinities for leukotrienes C4, D4, and E4 (LTC4, LTD4, and LTE4) and their 11-trans stereoisomers. The antibodies bound 3H-labeled 11-trans-LTC4 and 11-trans-LTC4 with the same average association constant (Ka) of 2.8 x 10(9) M-1 at 37 degrees C and were present at a concentration of 0.32 microgram/ml of the immune rabbit plasma. When 9.5 microliter of anti-LTD4 and 108 pmol of 11-trans-[3H]LTC4 (40 Ci/mmol) were incubated in a volume of 300 microliter with LTC4, LTD4, LTE4, or their 11-trans stereoisomers, 50% inhibition of 11-trans-[3H]LTC4 binding was achieved at levels varying between 0.3 and 0.7 ng. As assessed with synthetic analogs of the natural leukotrienes, the antibodies recognized neither those changes within the 6-sulfidopeptide unit of LTD4 produced by deamination or modest peptide lengthening nor the specific stereochemistry of the delta 14-cis double bond. However, the antibodies did recognize the triene lipid domain and the position and spatial orientation of the glutathione or cysteinylglycine function. Binding of 11-trans-[3H]LTC4 by anti-LTD4 was not inhibited by glutathione, cystinylbisglycine, arachidonic acid, or 5-hydroxy-6,8,11,14-icosatetraenoic acid, and leukotriene B4 (LTB4) was about 1/1000th as active as LTC4, LTD4, or LTE4. Mouse lymphoma (WEHI-5) and rat basophil leukemia (RBL-1) cells, when stimulated with calcium ionophore A23187, each produced immunoreactive leukotrienes; and LTC4, LTD4, and LTE4 from RBL-1 cells were individually quantitated by radioimmunoassay after resolution by high-performance liquid chromatography.

Animals↗
PubMed1981

Contractile activities of structural analogs of leukotrienes C and D: necessity of a hydrophobic region.

Sixteen structural analogs of leukotrienes C and D were tested for their contractile activities on guinea pig pulmonary parenchymal strip and ileum. The analogs differed from the native structures in the position of either the thioether-linked peptide side chain or the hydroxyl group (or both) or in the number and positions of ethylenic bonds. Analogs in which the thioether-linked peptide chain was attached other than at the C-6 position had substantial reductions in activity on both smooth muscle preparations, whereas analogs in which the various ethylenic bonds were saturated retained substantial contractile activity in both assays. These observations demonstrate that, although a hydrophobic region of the eicosinoid is necessary for contractile activity, the length of this segment is more critical than its precise stereochemistry. Analogs of leukotrienes based on the possibility of parallel biosynthetic routes deriving from 8-, 11-, and 15-hydroperoxyeicosatetraenoic acid as precursors were found to effect a comparatively weak contractile response so that their role as biological agents in this respect seems unlikely.

Animals↗
PubMed1981

Contractile activities of structural analogs of leukotrienes C and D: role of the polar substituents.

Twenty-three structural analogs of the leukotriene components of slow reacting substance of anaphylaxis (SRS-A), in which the polar regions of the leukotriene were systematically modified, were tested for their contractile activities on guinea pig pulmonary parenchymal strips and guinea pig ileum. The structural modifications allowed evaluation of the separate contributions of the four polar units in the C-1 to C-6 region of the SRS-A leukotrienes to smooth muscle spasmogenic activity. The free NH2-terminal amino group of the S-linked peptide was necessary for full activity, and its deletion or substitution reduced activity by more than one but less than two orders of magnitude. A similar level of importance was apparent for the free glycine carboxyl group. In contrast, a free eicosanoid carboxyl at C-1 is not required for full activity on the airway and for substantial activity on the ileum. A role for the C-5 hydroxyl is indicated by the inactivity of the one available 5-desoxy analog. Nucleophilic, divalent sulfur is not critical to leukotriene D (LTD) activity, in that one sulfoxide had substantial function. The conformational relationship between the eicosanoid and peptide moieties of LTD is of considerable importance in that epimers at the C-5 or C-6 position were less active than LTD by more than two orders of magnitude. Several lines of evidence suggest that the relative geometrical arrangement of the C20 chain and the peptide unit is important to activity, consistent with the existence of a true receptor for LTD.

Animals↗
PubMed1981

Effect of propranolol on the airway response to prostaglandin E2 in normal man.

1 The airway response to inhaled prostaglandin E2 (PGE2) and the effect of oral propranolol on this response was studied in eight normal subjects in a double-blind randomised trial. The airway response was measured as specific airway conductance (sGaw). 2 Inhalation of PGE2 caused retrosternal soreness, coughing and an awareness of mucus production. Despite this, PGE2 caused bronchodilatation and reproducible dose-response curves were obtained, with a maximum increase in sGaw of 53%. 3 Inhalation of the diluent of PGE2, an ethanol/saline mixture, did not cause irritation nor did it alter sGaw. 4 Prior administration of propranolol 80 mg did not alter baseline sGAW, nor the response to PGE2, indicating that the action of PGE2 in vivo is unaffected by bronchial beta-adrenoceptor blockade. 5 This technique should be of value in studying bronchodilator prostaglandins and their interaction with other drugs.

Adult↗
PubMed1981

Effects of prostaglandin D2 and theophylline on rat serosal mast cells: discordance between increased cellular levels of cyclic AMP and activation of cyclic AMP-dependent protein kinase.

Previous studies have shown that perturbation of the mast cell IgE-Fc receptor activates adenylate cyclase so as to raise cellular levels of cyclic AMP and to activate cyclic AMP-dependent protein kinase. Theophylline, an inhibitor of cytoplasmic cyclic nucleotide phosphodiesterase, raises cellular cyclic AMP levels, activates Type I and Type II cytoplasmic cyclic AMP-dependent protein kinase isoenzymes, and inhibits immunologic mediator release in a dose-dependent fashion. Since the EC50 values for each of these effects are similar (8 to 9.5 mM), it seems likely that a relationship exists between the activation of cyclic AMP-dependent protein kinase and the inhibition of mediator release. Such inhibition could be due to either to the uncovering of an inhibitory protein by phosphorylation or to the depletion of cyclic AMP-dependent protein kinase holoenzyme, which is essential for productive IgE-Fc receptor-induced activation-secretion coupling. PGD2, which also raises mast cell cyclic AMP levels in a dose-dependent fashion and interacts synergistically with theophylline in this regard, fails to suppress mediator release alone or to add to the inhibitory effect of theophylline. The finding that PGD2 also fails to activate cyclic AMP-dependent protein kinase suggests that the adenylate cyclase stimulated by this agonist is not linked to the mast cell activation-secretion response.

Animals↗