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We studied the neural control of goblet cell secretion in the lower airways of anesthetized guinea pigs using a semiquantitative morphometric technique. The magnitude of discharge of intracellular mucus was determined in histological sections of the trachea and main bronchi stained for mucus glycoproteins. Bilateral electrical stimulation of the cervical vagus nerves induced goblet cell secretion. The magnitude of the effect was dependent on the frequency, voltage, and pulse width of the stimulus, and the duration of stimulation. At 10 Hz, 5 V, and 5 ms for 3 min, there was a 62% decrease in the amount of intracellular mucus below that with sham stimulation. The secretion was blocked either by atropine or by pretreatment with capsaicin but was not significantly inhibited by idazoxan, an alpha-adrenoceptor antagonist. The magnitude of goblet cell discharge in animals pretreated with propranolol was intermediate between that in controls and that with nerve stimulation, although not significant to either. These results demonstrate that goblet cell secretion is under neural control in guinea pig airways and suggest that cholinergic, nonadrenergic-noncholinergic, and possibly adrenergic neural pathways, may contribute to the secretion.
Many neuropeptides have recently been identified in human and animal airways. These peptides have potent effects on airway caliber, blood vessels, and secretions, raising the possibility that they may be involved in airway diseases such as asthma. Vasoactive intestinal peptide andpeptide histidine methionine are potent bronchodilators and may be neurotransmitters of nonadrenergic bronchodilator nerves. In asthma, if these peptides are broken down more rapidly by enzymes from inflammatory cells, this might contribute to exaggerated bronchial responsiveness. Neuropeptides that are found in sensory nerves, such as substance P, neurokinin A, and calcitonin generelated peptide, have inflammatory effects and might also contribute to the pathology of asthma if released from sensory nerve endings by an axon reflex. These findings may have important therapeutic implications for the future.
Airway caliber is determined by a balance between many constrictor and dilator agents, which bring about their effects on the various target cells of the airway by activating specific cell surface receptors. Asthma and bronchial hyperresponsiveness may be viewed as an imbalance between excitatory and inhibitory receptor-mediated effects on the various target cells in the airway. Airway receptors can be grouped into those mediating the effects of the autonomic nervous system on the airways or those mediating the effects of the various mediators which may be generated in asthma. There is no convincing evidence that a fundamental defect in receptor function is involved in the pathogenesis of asthma, although minor abnormalities have been described. Recently there has been a considerable increase in our understanding of receptor function and control, which should throw light on the pathogenesis of airway obstruction and may lead to advances in asthma therapy. This may also lead to the development of novel drugs for treating asthma in the future.
Aims:The indication for transcatheter aortic valve implantation (TAVI) has evolved from inoperable patients to patients at increased surgical risk.In low-risk patients, surgical aortic valve replacement (SAVR) remains the standard of care.The aim of this study was to explore the outcomes of TAVI and SAVR in patients with a Society of Thoracic Surgeons (STS) predicted risk of mortality (PROM) score below 3% in the SURTAVI trial. Methods and results:In SURTAVI, patients at intermediate surgical risk based on Heart Team consensus were randomised to TAVI or SAVR.We stratified the overall patient population into quintiles based on the STS PROM score; the one-year mortality was correlated with the mean STS PROM score in each quintile.The quintiles were regrouped into three clinically relevant categories of STS score: less than 3%, 3 to <5%, and >5%.All-cause mortality or disabling stroke in each risk stratum was compared between TAVI and SAVR.Linear regressions between mean values of STS PROM in each quintile and observed allcause mortality at one year showed great association for the global population (r 2 =0.92),TAVI (r 2 =0.89) and SAVR cohorts (r 2 = 0.73).All-cause mortality or disabling stroke of TAVI vs. SAVR was 1.5% vs. 6.5% (p=0.04),6.5% vs. 7.6% (p=0.52) and 13.5% vs. 11.0%(p=0.40) in the <3%, 3-5%, and ≥5% STS score strata, respectively.Conclusions: Among patients at intermediate surgical risk but with an STS PROM <3%, TAVI may achieve superior clinical outcomes compared to SAVR.These findings support the need for an adequately powered randomised trial to compare TAVI with SAVR in patients at low operative risk.