6,963 publications from this institution
Goblet cell secretion in guinea‐pig airways is under neural control. Opioids have previously been shown to inhibit neurogenic plasma exudation and bronchoconstriction in guinea‐pig airways. We have now examined the effects of morphine and opioid peptides on tracheal goblet cell secretion induced by either electrical stimulation of the cervical vagus nerves, exogenous capsaicin, or acute inhalation of cigarette smoke. The degree of goblet cell secretion was determined by a morphometric method and expressed as a mucus score which is inversely related to mucus discharge. Morphine, 1 mg kg −1 , completely blocked goblet cell secretion induced by electrical stimulation of the vagus nerves. Morphine also inhibited the response to cigarette smoke given either at a low dose (10 breaths of 1:10 diluted in air), which principally activates cholinergic nerves, or at a high dose (20 breaths of undiluted), which activates capsaicin‐sensitive sensory nerves, by 100% and 73% respectively. In contrast, morphine had no significant inhibitory effect on capsaicin‐induced goblet cell secretion. The inhibitory effect of morphine was reversed by naloxone. Selective μ‐ or δ‐opioid receptor agonists, [ d ‐Ala 2 , NMePhe 4 , Glyol 5 ]enkephalin (DAMGO) or [ d ‐Pen 2 , d ‐Pen 5 ]enkephalin (DPDPE) respectively, caused a dose‐related inhibition of low dose cigarette smoke‐induced goblet cell discharge, with DPDPE more potent than DAMGO. A κ‐receptor agonist, trans ‐3,4‐dichloro‐ N ‐methyl‐ N ‐(2‐(1‐pyrollidinyl)cyclohexyl) benzeneacetamine (U‐50,488H), had no inhibitory effect. DPDPE had no inhibitory effect on goblet cell secretion induced by exogenous methacholine. DAMGO dose‐dependently blocked the response to high dose cigarette smoke with a maximal inhibition of 95% at 2 × 10 −7 mol kg −1 . Neither DPDPE nor U‐50,488H had any significant inhibitory effect. The increase in goblet cell secretion induced by exogenous substance P was not affected by DAMGO. We conclude that opioids inhibit neurally‐mediated goblet cell secretion via actions at prejunctional δ‐ and μ‐receptors on cholinergic nerves and at μ‐receptors on sensory nerve endings, and that capsaicin activation of sensory nerves is via a different mechanism from that of electrical or cigarette smoke activation.
Adenosine 5′-triphiosphate (ATP) is released from cells under physiologic and pathophysiologic conditions. Extracellular ATP acts as an autocrine and paracrine agent affecting various cell types by activating cell surface P2 receptors (P2R), which include trans-cell membrane cationic channels, P2XR, and G protein coupled receptors, P2YR. We have previously shown that ATP stimulates vagal afferent nerve terminals in the lungs by activating P2X2/3R. This action could lead to bronchoconstriction, cough and the local release of pro-inflammatory neuropeptides. In addition, ATP markedly enhances the IgE-dependent histamine release from human lung mast cells. Thus, we have proposed for the first time that extracellular ATP plays a mechanistic role in pulmonary pathophysiology in general and chronic obstructive pulmonary disease (COPD), and acute bronchoconstriction in asthma in particular. The present review examines whether ATP could also play a role in bradycardia and syncope in a subset of patients with pulmonary embolism.
The elastic local post-buckling behaviour of elliptical tubes under compression is analysed in this paper. A brief outline of the local, distortional and global buckling behaviour of EHS tubes is firstly provided, where it is shown that local buckling modes govern the stability of short to intermediate length tubes while distortional modes control the stability of intermediate length to moderately long tubes and global buckling dominates the behaviour of longer tubes. Following this, an in-depth numerical study employing shell finite element modelling, of the elastic local post-buckling behaviour of compressed elliptical hollow section (EHS) tubes is presented. It is concluded that EHS tubes with a low to moderate aspect ratio can support loads up to their limit loads but are imperfection sensitive (shell-type behaviour), while EHS tubes with a moderate to high aspect ratio can carry loads higher than their limit loads (plate-type behaviour) and are imperfection insensitive. The slope of the ascending post-buckling path increases with the EHS aspect ratio and can reach values up to 40% of the slope of the linear primary path. The bound imperfection amplitude concept, separating the imperfection amplitude ranges where the EHS tube is sensitive and insensitive, is proposed. It is also found that, for increasing EHS aspect ratio, the compressive stresses grow and accumulate near the zones of minimum radius of curvature while the zones of maximum radius of curvature possess an approximately uniform and relatively low compressive stress level. Therefore, it is expected that an approach based on the effective width concept widely used for the evaluation of the strength of flat plates may be adapted to the design of EHS tubes with moderate to high aspect ratios.
No abstract is provided for this article.
Of 652 consecutive patients referred for coronary angioplasty between September 1980 and March 1984, 49 patients presented with total or functional 'occlusion' of the involved vessel. Total vessel occlusion was defined as absent anterograde filling beyond the lesion. Functional occlusion was defined as faint, late anterograde opacification of the distal segment in the absence of a discernible luminal continuity. In 39 patients, the total or functional occlusion represented a progression, without acute myocardial infarction, of a previously diagnosed stenotic lesion. The maximal potential duration of occlusion was estimated to be 4 weeks or less in 21 patients, more than 4 to 8 weeks in 12, and more than 8 weeks in 16. Dilation of the occluded artery was attempted in the left anterior descending coronary artery in 30 patients, in the right coronary artery in 8, in the circumflex coronary in 7 and in 4 jumpgrafts. For the whole group, angioplasty was successful in 28 patients (57%). The primary success rate with the functionally occluded vessel (81%) was significantly higher than with the total occlusion (45%). In 33 patients with an occlusion estimated to be of 8 weeks or less, angioplasty was successful in 65%. In the 16 patients with an occlusion estimated to be of more than 8 weeks duration, dilation was successful in 44%. Of the 21 patients in whom angioplasty was unsuccessful, 11 required surgery (1 urgent with persistent pain and ST elevation and 10 elective). Ten patients were maintained on medical treatment. Of the 28 patients in whom angioplasty was successful, 10 patients had recurrence of symptoms during follow-up (1–42 months). Four were kept on medical therapy, three required bypass surgery and three underwent repeat percutaneous transluminal coronary angioplasty (PTCA). After primary success, late angiographic studies obtained in 20 out of 28 patients showed reocclusion in 8. In conclusion, elective PTCA of totally occluded coronary arteries is feasible but the primary success rate is lower (57%) than that associated with conventional lesions. the long-term clinical results following successful angioplasty are satisfactory (64%), but the incidence of reocclusion is higher (40%).
