To enhance our understanding of cholinergic mechanisms and muscarinic receptors in bronchoconstriction, we have characterized the muscarinic receptor subtypes in rabbit tracheal smooth muscle using radioligand binding and functional assays. The Kd for [3H]quinuclidinyl benzilate ([3H](−)QNB) binding determined from saturation isotherms was 12.6 ×/÷ 1.1 pM (geometric mean ×/÷ SEM), and the Bmax was 269 ± 7 fmol/mg protein (arithmetic mean ± SEM). Competitive inhibition studies with the muscarinic antagonists pirenzepine (PZ), 11[[2-[(diethylamino)-methyl]1-piperidinyl]acetyl]-5,11-dihydro-6H-pyrido-[2,3-b][1,4]benzodiazepine-6-one (AF-DX116), 4-diphenylacetoxy-N-methylpiperidine methobromide (4-DAMP), and hexahydrosiladifenidol (HHSiD) demonstrated heterogeneity of muscarinic receptor sub-types in rabbit tracheal smooth muscle. PZ bound with low affinity to a single receptor site, indicative of an absence of M1 receptors. AF-DX116 (M2 selective) bound with high affinity to approximately 83% of muscarinic binding sites, and 4-DAMP and HHSiD (M3 antagonists) bound with high affinity to approximately 24 and 28% of muscarinic binding sites, respectively. Additionally, direct binding studies with [3H]4-DAMP demonstrated high-affinity binding with 23% of muscarinic binding sites. Thus, the majority of muscarinic receptors in rabbit tracheal smooth muscle bound with high affinity to an M2-selective antagonist, and the remaining receptor sites bound with high affinity to M3 antagonists. The inhibitory effects of atropine, PZ, AF-DX116, and 4-DAMP on methacholine-induced contraction of rabbit tracheal rings were compared. 4-DAMP was a potent inhibitor of methacholine-induced contraction, but PZ and AF-DX116 demonstrated low potency. Our data suggest that methacholine-induced contraction in rabbit tracheal smooth muscle is mediated by the relative minority of receptors (17 to 28%) that bind with high affinity to the M3 muscarinic antagonists, 4-DAMP and HHSiD.
Rationale: The use of neuromuscular blocking agents (NMBAs) has been shown to be valuable in improving successful tracheal intubation in the operating room and emergency department. However, data on NMBA use in critically ill intensive care unit (ICU) patients are lacking. Furthermore, there are no data on NMBA use with video laryngoscopy.Objectives: To evaluate the effect of NMBA use on first-attempt success (FAS) with tracheal intubation in the ICU.Methods: Single-center observational study of 709 consecutive patients intubated in the medical ICU of a university medical center from January 1, 2012 to June 30, 2014. Data were collected prospectively through a continuous quality improvement program on all patients intubated in the ICU over the study period. Data relating to patient demographics, intubation, and complications were analyzed. We used propensity score (propensity to use an NMBA) matching to generate 5,000 data sets of cases (failed first intubation attempts) matched to controls (successful first attempts) and conditional logistic regression to analyze the results.Measurements and Main Results: There were no significant differences in patient demographics, except median total difficult airway characteristics were higher in the non–NMBA group (2 vs. 1, P < 0.001). There were significant differences in the sedative used between groups and the operator level of training. More patients who were given NMBAs received etomidate (83 vs. 35%) and more patients in the non–NMBA group received ketamine (39 vs. 9%) (P < 0.001). The FAS for NMBA use was 80.9% (401/496) compared with 69.6% (117/168) for non–NMBA use (P = 0.003). The summary odds ratio for FAS when an NMBA was used from the propensity matched analyses was 2.37 (95% confidence interval, 1.36–4.88). In the subgroup of patients intubated with a video laryngoscope, propensity-adjusted odds of FAS with the use of an NMBA was 2.50 (1.43–4.37; P < 0.001). There were no differences in procedurally related complications between groups.Conclusions: After controlling for potential confounders, this propensity-adjusted analysis demonstrates improved odds of FAS at intubation in the ICU with the use of an NMBA. This improvement in FAS is seen even with the use of a video laryngoscope.
Glucocorticoids are an effective anti-inflammatory therapy for the treatment of asthma. The anti-inflammatory effects of glucocorticoids may be due to the inhibition of transcription factors that regulate cytokine synthesis. Because of the potential role of the bronchial epithelium in asthmatic inflammation and the possibility that this cell may be the main target of inhaled glucocorticoids, we have characterized glucocorticoid receptors (GR) and GR signaling in the human bronchial epithelial cell line BEAS-2B. Western blot analysis and radioligand binding studies demonstrated that BEAS-2B cells have functional GR that bind to dexamethasone (Dex) (dissociation constant = 5.6 nM and maximal density of binding sites = 228 +/- 3.3 fmol/mg protein). GR were activated by Dex as assessed using a glucocorticoid-responsive reporter plasmid. Transfection of BEAS-2B cells with an activator protein-1 (AP-1) reporter construct followed by 12-O-tetradecanoylphorbol-13-acetate (TPA) treatment resulted in a fivefold induction of reporter gene activity. Transfection with a nuclear factor (NF)-kappa B reporter construct followed by tumor necrosis factor-alpha (TNF-alpha) treatment resulted in a 10-fold induction of reporter gene activity. Dex (10(-7) M) markedly repressed both the induced AP-1 and NF-kappa B activity. The GR antagonist RU-486 inhibited the repressive effect of Dex on TNF-alpha-induced NF-kappa B activity by 81% but only counteracted the repressive effect of Dex on TPA-induced AP-1 activity by 43%. These studies demonstrate that cross-signaling between AP-1 and NF-kappa B with GR may explain the anti-inflammatory properties of glucocorticoids in airway epithelial cells.
THE CAMBRIDGE COMPANION TO BASEBALL, LEONARD CASSUTO AND STEPHEN PARTRIDGE (EDS) (2011) Cambridge: CUP, 280 pp., ISBN-10: 0521145759, ISBN-13: 978-0521145756 (pbk), £17.99 DREAMING OF DIXIE: HOW THE SOUTH WAS CREATED IN AMERICAN POPULAR CULTURE, KAREN L. COX (2011) Chapel Hill: University of North Carolina Press, 224 pp., ISBN-10: 0807834718, ISBN-13: 978-0807834718 (hbk), £30.50
A series of transgenic mice was produced by microinjection of a segment of DNA, containing 460 base pairs of the phosphoenolpyruvate (P-enolpyruvate) carboxykinase promoter-regulatory region ligated to the bovine growth hormone structural gene, into the male pronucleus of fertilized mouse eggs. Founder animals which contained the gene were selected for further analysis and for breeding. The concentration of bovine growth hormone in the serum of animals which were shown to contain the gene ranged from a low of 5 ng/ml serum to approximately 2300 ng/ml serum. Mice with high levels of bovine growth hormone had growth rates double that of their litter mates which did not contain the transgene. The transgene was expressed only in the liver and kidney of the animals studied, and the level of specific mRNA for bovine growth hormone in these tissues could be regulated by diet in a manner similar to the endogenous P-enolpyruvate carboxykinase gene. Feeding the animals a diet high in carbohydrate for 1 week caused a 90% decrease in the concentration of bovine growth hormone in the blood, suggesting that the expression of the chimeric P-enolpyruvate carboxykinase/bovine growth hormone gene is sensitive to insulin. When the same animals were then refed a diet high in protein, but devoid of carbohydrate, the concentration of bovine growth hormone in their blood was induced 30-fold within a week. The administration of dibutyryl cyclic AMP to the transgenic mice caused a 2-fold induction in the level of bovine growth hormone in the serum within 90 min. Thus the region between -460/+73 in the P-enolpyruvate carboxykinase promoter-regulatory region contains sequences which can direct the tissue-specific expression, as well as hormonal and dietary responsiveness, of a linked structural gene.
