Tracheal Muscle Research Articles

Effect of Drying on the Quantity and Composition of Artemisia monosperma Essential Oil and Exploring the Bronchodilator Effect Using Guinea Pig Tracheal Muscles

Effect of Drying on the Quantity and Composition of Artemisia monosperma Essential Oil and Exploring the Bronchodilator Effect Using Guinea Pig Tracheal Muscles

Iatrogenic Full-length Rupture of Posterior Trachea: A Multidsciplinary Management

Iatrogenic trachealis muscle rupture (ITR) following elective intubation is a potentially fatal complication with a low incidence of 0.05-0.37%. Tears involving the whole length has not been reported. We report a case of a 26-year-old lady with seropositive rheumatoid arthritis who underwent total thyroidectomy for Hashimoto Thyroiditis. Intraoperatively, a complete linear trachealis muscle rupture from the carina to the first tracheal ring was diagnosed by the Otorhinolaryngology (ORL) team by tracheoscopy through the endotracheal tube (ETT). Unlike the common presentation of subcutaneous emphysema or pneumomediastinum, the surgeon noticed the ETT cuff in the left operative field. Initial repair of the lateral defect was performed immediately by opposing the sternocleidomastoid muscle to the adjacent infrahyoid muscles. However, serial computed tomography and flexible tracheoscopy showed complete tear of the trachealis muscle with presence of pneumomediastinum and dynamic changes of the injury. We illustrate a concerted effort of multidisciplinary teams of ORL, Cardiothoracic Surgery, Intensivist, Anaesthetist, Radiologist and Speech Therapist in the steps of management which involved series of tracheoscopy and imaging prior to extubation. In view of extensive trachealis muscle tear with hemodynamically stable patient, conservative management was opted for this patient as it outweighs the benefit of the surgery. We include the outpatient management until the patient’s trachea fully healed 6 months after the injury. The management is compared to the management review in the literature. This case has taught multiple new important lessons in the management of challenging tracheal rupture in a patient.International Journal of Human and Health Sciences Supplementary Issue 01: 2024 Page: S54

Tissue-engineered tracheal implants: Advancements, challenges, and clinical considerations.

Restoration of extensive tracheal damage remains a significant challenge in respiratory medicine, particularly in instances stemming from conditions like infection, congenital anomalies, or stenosis. The trachea, an essential element of the lower respiratory tract, constitutes a fibrocartilaginous tube spanning approximately 10-12 cm in length. It is characterized by 18 ± 2 tracheal cartilages distributed anterolaterally with the dynamic trachealis muscle located posteriorly. While tracheotomy is a common approach for patients with short-length defects, situations requiring replacement arise when the extent of lesion exceeds 1/2 of the length in adults (or 1/3 in children). Tissue engineering (TE) holds promise in developing biocompatible airway grafts for addressing challenges in tracheal regeneration. Despite the potential, the extensive clinical application of tissue-engineered tracheal substitutes encounters obstacles, including insufficient revascularization, inadequate re-epithelialization, suboptimal mechanical properties, and insufficient durability. These limitations have led to limited success in implementing tissue-engineered tracheal implants in clinical settings. This review provides a comprehensive exploration of historical attempts and lessons learned in the field of tracheal TE, contextualizing the clinical prerequisites and vital criteria for effective tracheal grafts. The manufacturing approaches employed in TE, along with the clinical application of both tissue-engineered and non-tissue-engineered approaches for tracheal reconstruction, are discussed in detail. By offering a holistic view on TE substitutes and their implications for the clinical management of long-segment tracheal lesions, this review aims to contribute to the understanding and advancement of strategies in this critical area of respiratory medicine.

Comparative Macro- and Micro-morphological Study on the Syrinx of Three Avian Species

This study aimed to explain and compare the anatomical, histological, histochemical & histomorphometric analyses of the syrinx in different species of birds. This study includes 21 healthy birds from geese (Anser Anser Domesticus), cattle egrets (Bublucus ibis) & house sparrows (Passer domesticus), seven from each species. Results: Anatomically, the syrinx of the three studied species was tracheobronchial type composed of 2 different cartilaginous groups arranged in three parts: Tracheo-Syringeal cartilage in (cranial, intermediate part (tympanum)) and broncho-syringeal cartilage; as well as the trachea's muscles were once thought to be the syrinx's extrinsic muscles. Histologically, the lamina epithelialis of the Tracheo-Syringeal part was represented by pseudostratified ciliated columnar epithelium in the three investigated species with goblet cells in geese, house sparrows and lack goblet cells in cattle egrets. The pessulus in all three investigated species was triangular and positioned at the tip of the tracheal bifurcation. The bulla of house sparrow was considered the intrinsic syringeal muscles and these muscles in sparrows are not only present in geese or cattle egrets.

Wnt signaling regulates ion channel expression to promote smooth muscle and cartilage formation in developing mouse trachea.

Ion channels play critical roles in the physiology and function of the nervous system and contractile tissue; however, their role in noncontractile tissue and embryonic development has yet to be understood. Tracheobronchomalacia (TBM) and complete tracheal rings (CTR) are disorders affecting the muscle and cartilage of the trachea and bronchi, whose etiology remains poorly understood. We demonstrated that trachealis muscle organization and polarity are disrupted after epithelial ablation of Wntless (Wls), a cargo receptor critical for the Wnt signaling pathway, in developing trachea. The phenotype resembles the anomalous trachealis muscle observed after deletion of ion channel encoding genes in developing mouse trachea. We sought to investigate whether and how the deletion of Wls affects ion channels during tracheal development. We hypothesize that Wnt signaling influences the expression of ion channels to promote trachealis muscle cell assembly and patterning. Deleting Wls in developing trachea causes differential regulation of genes mediating actin binding, cytoskeleton organization, and potassium ion channel activity. Wnt signaling regulates the expression of Kcnj13, Kcnd3, Kcnj8, and Abcc9 as demonstrated by in vitro studies and in vivo analysis in Wnt5a and β-catenin-deficient tracheas. Pharmacological inhibition of potassium ion channels and Wnt signaling impaired contractility of developing trachealis smooth muscle and formation of cartilaginous mesenchymal condensation. Thus, in mice, epithelial-induced Wnt/β-catenin signaling mediates trachealis muscle and cartilage development via modulation of ion channel expression, promoting trachealis muscle architecture, contractility, and cartilaginous extracellular matrix. In turn, ion channel activity may influence tracheal morphogenesis underlying TBM and CTR.NEW & NOTEWORTHY Ion channels play critical roles in the physiology and function of the nervous system and contractile tissue; however, their role in noncontractile tissue and embryonic development has yet to be understood. In this study, we focused on the role of ion channels in the differentiation and patterning of the large airways of the developing respiratory tract. We identify a mechanism by which Wnt-beta-catenin signaling controls levels of ion channel-encoding genes to promote tracheal differentiation.

The impact of endotracheal intubation on oxygen delivery, trachea pressure and wall deformation

This paper concerns improving endotracheal tube (ETT) insertion through advanced computational science modelling. The study aims to better understand endotracheal intubation (ETI) and reduce medical errors in intensive and critical care units since ETT insertion is unique for each patient, depending on age, gender, size, physiology, and underlying health conditions. We have employed computational fluid dynamics and biomechanics modelling to investigate the effect of ETT for three ventilation modes on (a) local oxygen delivery to the lungs, (b) air pressure and wall shear stress at the tracheal walls, and (c) oscillatory elastic deformation of the tracheal tissues and muscle. For the first time, we reveal how the ventilation mode and ETT insertion in the trachea may induce major complications, especially in long periods of ETT. We show that rotating the ETT or displacing it by 2 mm only can induce a significant rise in the tracheal pressure up to 177 cmH2O. This study, for the first time, shows the vital role of computers in biology and medicine to provide enhanced decision-making-support to clinicians and medical doctors dealing with ETI.

Molecular docking analysis of selected bioactive components of Glycyrrhiza glabra against bronchial asthma

Bronchial asthma is a chronic inflammatory disease of the lung by the combined action of various cytokines. As a result of the strong inflammatory response increased infiltration of cytokines result, damages respiratory epithelium, Hyperplasia of the trachealis muscle, and increased mucous production. Athimathura choornam is a promising drug used in all inflammatory conditions. Objective: To explore the efficacy of the Siddha formulation Athimathura choornam, an anti asthmatic drug using computational molecular docking analysis. Method: Based on the phytochemical study the active principles present in the plant Athimathuram were retrieved. 3D structure of the targets were retrieved from the repository and purified before the initiation of docking using the software. The potency of the drug was screened based on the binding of the ligands Asparagine, Liquiritin, and Glabridin with targets mentioned. These results were compared with the standard drugs such as Cetirizine, Salicylic acid, Diclofenac, Ibuprofen, and Celecoxib. Results and Conclusion: Liquiritin has 9 interactions (90%) similar to that of Ibuprofen, 14 interactions (90%) similar to that of Citrazinehence , 5 interactions (100%) similar to that of salicylic acid hence it has promising COX 1 inhibition ,Histamine 1 blocking activity and Prostaglandin Synthase inhibition activity. Asparagine has 3 interactions (60%) similar to Celecoxib, has promising COX 2 inhibition activity. Glabridin has 2 interactions (50%) similar to that of Diclofenac hence it has promising IL6 inhibition activity.

Wet adhesive hydrogels to correct malacic trachea (tracheomalacia) A proof of concept

Tracheomalacia (TM) is a condition characterized by a weak tracheal cartilage and/or muscle, resulting in excessive collapse of the airway in the newborns. Current treatments including tracheal reconstruction, tracheoplasty, endo- and extra-luminal stents have limitations. To address these limitations, this work proposes a new strategy by wrapping an adhesive hydrogel patch around a malacic trachea. Through a numerical model, first it was demonstrated that a hydrogel patch with sufficient mechanical and adhesion strength can preserve the trachea's physiological shape. Accordingly, a new hydrogel providing robust adhesionon wet tracheal surfaces was synthesized employing the hydroxyethyl acrylamide (HEAam) and polyethylene glycol methacrylate (PEGDMA) as main polymer network and crosslinker, respectively. Exvivo experiments revealed that the adhesive hydrogel patches can restrain the collapsing of malacic trachea under negative pressure. This study may open the possibility of using an adhesive hydrogel as a new approach in the difficult clinical situation of tracheomalacia.

2023 TERMIS – AMERICAS Conference & Exhibition Boston Marriott Copley Place April 11–14, 2023

2023 TERMIS – AMERICAS Conference & Exhibition Boston Marriott Copley Place April 11–14, 2023

Comparative GC Analysis, Bronchodilator Effect and the Detailed Mechanism of Their Main Component—Cinnamaldehyde of Three Cinnamon Species

Cinnamon is one of the most commonly used spices worldwide. In some Arab countries, cinnamon is used with other ingredients to relieve bronchospasm and treatment of airways-related disorders. In the current study, GC, GC-MS and tracheal relaxant effect comparison were performed using the three available types in Saudi Arabia, Cinnamomum verum (Ceylon cinnamon), C. cassia (Chinese cinnamon) and C. loureiroi (Vietnamese cinnamon). The essential oil of C. verum was the most potent in the relaxation of guinea pig isolated tracheal muscles against carbachol (CCh, 1 uM)-evoked bronchospasm at the concentration range from 0.03 to 3 mg/mL followed by C. bureiroi at 0.03 to 5 mg/mL; whereas, C. cassia was the least potent oil. Cinnamaldehyde (1), isolated as the main component of the three oils induced complete relaxation of low K+ (25 mM)-evoked contractions, with mild effect on the contractions evoked by high K+ (80 mM). Pre-incubation of the tracheal tissues with glibenclamide (10 μM) significantly opposed the relaxation of low K+ by cinnamaldehyde. The standard drug, cromakalim also inserted glibenclamide-sensitive inhibition of low K+ without relaxing high K+. These results indicate that cinnamaldehyde acts predominantly by ATP-specific K+ channel opening followed by weak Ca++ antagonistic effects. The obtained results justify the medicinal value of cinnamon oil in respiratory disorders.

Emergency Tracheostomy: Indications, Techniques and Complications in 67 Cases at the Omar Bongo Ondimba Army Training Hospital

Introduction: Tracheotomy is the temporary or permanent surgical opening of the cervical trachea followed by the placement of a cannula. Objective : to recall the indications, techniques and complications of emergency tracheotomy. Materials and method : This was a retrospective descriptive study conducted in the ENT and CCF department of HIAOBO, involving 67 medical records of hospitalized patients in whom a tracheostomy was performed in emergency from January 2010. to December 2019. Results : The study involved 51 men (76%) and 16 women (24%), a ratio of 3.18 . The average age was 45.85 years with extremes of 5 and 78 years. Laryngeal dyspnea was the reason for consultation in 86.57% of cases. The indications were malignant tumors of the upper aero-digestive tract in 54% of cases, difficult extubation in intensive care patients in 12% of cases, laryngeal papillomatosis in 12% of cases, inflammatory pathology in 7 cases, traumatic pathology 4 cases, extrinsic tracheal compression, muscle disease and laryngo -tracheal stenosis in 1 case each. Tracheotomy was performed under general anesthesia in 73% of cases and under local anesthesia in 27% of cases. Complications were observed in (16.42%). Conclusion : Emergency tracheotomy is a survival gesture. Mastery of the technique, the right choice of equipment, perfect knowledge of the anatomical relationships of the trachea, and postoperative care help to minimize complications.

Distribution of proteins for synaptic release in nerve endings associated with the trachealis muscle of rats.

The immunohistochemical localization of proteins for synaptic release was examined in smooth muscle-associated sensory nerve endings using whole-mount preparations of the rat trachea. Plant-like smooth muscle-associated nerve endings with immunoreactivity for Na+-K+-ATPase, α3-subunit were identified in the trachealis muscle. VGLUT1, synapsin1, t-SNARE proteins (SNAP25 and syntaxin1), v-SNARE proteins (VAMP1 and VAMP2), and a presynaptic active zone-related protein (piccolo) were detected in the terminal parts of these endings. These results suggest that smooth muscle-associated nerve endings secrete glutamate to modulate sensorimotor functions in the lung deflation reflex.

Bronchodilator Secondary Metabolites from Rhazya stricta Decne Aerial Parts

The plant kingdom comprises medicinally useful plants that have provided many new drugs used to treat various diseases. In our search for bronchodilator secondary metabolites from plants growing in Saudi Arabia, the total extract of Rhazya stricta showed activity against carbamylcholine- (CCh) induced bronchoconstriction in guinea pig tracheal muscles used as an ex vivo model. The fractions obtained from liquid–liquid extraction process were tested for bronchodilator effects. The most active ethyl acetate fraction (RS-E) and aqueous fraction (RS-H) were subjected to biologically guided phytochemical study using different stationary phases and chromatographic techniques to isolate the pure secondary metabolites. Five known compounds were isolated from the active fractions. Three alkaloids namely; (-)-quebrachamine (1), (+)-eburenine (2), (+)-stemmadenine (3) as well as the two iridoid glycosides loganic acid (4) and loganine (5) were identified by various spectroscopic methods. Among the isolated compounds 1 and 5 were the only active as bronchodilators in the plant. It is worth to mention that iridoid glycosides are isolated for the first time from R. stricta.

Biaxial mechanical properties of the bronchial tree: Characterization of elasticity, extensibility, and energetics, including the effect of strain rate and preconditioning

Distal airways commonly obstruct in lung disease and despite their importance, their mechanical properties are vastly underexplored. The lack of bronchial experiments restricts current airway models to either assume rigid structures, or extrapolate the material properties of the trachea to represent the small airways. Furthermore, past works are exclusively limited to uniaxial testing; investigating the multidirectional tensile loads of both the proximal and distal pulmonary airways is long overdue. Here we present comprehensive mechanical and viscoelastic properties of the porcine airway tree, including the trachea, trachealis muscle, large bronchi, and small bronchi, via measures of elasticity, extensibility, and energetics to explore regional and directional dependencies, cross-examining strain rate and preconditioning effects using planar equibiaxial tensile tests for the first time. We find bronchial regions are notably heterogeneous, where the trachea exhibits greater stiffness, energy loss, and preconditioning sensitivity than the smaller airways. Interestingly, the trachealis muscle is similar to the distal bronchi, despite being anatomically located adjacent to the proximal ring. Tissues are anisotropic and axially stiffer under initial loading, losing more energy with greater stress relaxation circumferentially. Strain rate dependency is also noted, where tissues are more energetically efficient at the faster strain rate, likely attributable to the microstructure. Findings highlight assumptions of homogeneity and isotropy are inadequate, and enable the improvement of aerosol flow and dynamic airway deformation computational predictive models. These results provide much needed fundamental material properties for future explorations contrasting healthy versus diseased pulmonary airway mechanics to better understand the relationship between structure and lung function. Statement of significanceWe present comprehensive multiaxial mechanical tensile experiments of the proximal and distal airways via measures of maximum stress, initial and ultimate moduli, strain and stress transitions, hysteresis, energy loss, and stress relaxation, and further assess preconditioning and strain rate dependencies to examine the relationship between lung function and structure. The mechanical response of the bronchial tree demonstrates significant anisotropy and heterogeneity, even within the tracheal ring, and emphasizes that contrary to past studies, the behavior of the proximal airways cannot be extended to distal bronchial tree analyses. Establishing these material properties is critical to advancing our understanding of airway function and in developing accurate computational simulations to help diagnose and monitor pulmonary diseases.

Detection of morphometrical, histological and histochemical characteristics of lung and trachea in adult local squirrel (Sciurus anomalus)

The present study aimed to identify the topography, morphology, histochemistry and histology of lung structures, bronchial divisions and trachea in adult local Squirrel (Sciurus anomalus) as a species inhabited in Iraqi environments. This work was conducted on thirty local Squirrel of both sexes (15) males and (15) females were divided into three equal groups, first for http://wsx5customurl.comanatomical perceptions, second to resin cast technique and the third for histological study. Anatomically, in both sexes, the trachea appeared as a cartilaginous structure consisting of flexible cartilaginous rings, C-like, connected by annular ligaments. It begins at the end of the cricoid cartilage from the level of the second cervical vertebra to the fourth thoracic vertebral plane; eventually, it splits into the right and left main bronchi. Count tracheal rings, the entire weight of the lung, full length, the diameter of the trachea and right and left bronchi. The trachea in females was slightly less than in males but not significantly. The bronchial tree was detected in resin cast, which was constructed of the trachea divided into left and right primary bronchi (Main bronchi), the right one was split into four secondary bronchi to enter the right lobes and two secondary bronchi to the left one. The left lung contains one lobe, whereas four lobes were observed in the right. Histologically, the wall of the trachea consists of four layers. Epithelial cells of ciliated pseudostratified columnar and goblet cells that reacted positively with PAS were covered in the mucosa. Submucosa was devoid of the tracheal glands. The Trachealis muscle is connected from the outer aspect of rings. Similarly to the trachea, the primary bronchi are structured but smaller in diameter; they break up within the lung into primary, secondary and tertiary bronchi, then it terminates in respiratory bronchioles that contain Clara cells and open at the end in the sacs of alveoli. Two types of pneumocystis were observed lining the alveoli. The current study concluded anatomically and histologically that there were no significant differences between males and females of local squirrels. The lobulation of the lung in squirrels is different from other animals. The trachea and lung histologically resembled numerous animals, however, the wall had micro morphometric changes. But, the surface lining cells of the tracheal and bronchi mucosa secrete neutral mucin, with no submucosal glands in the tracheal wall. Keywords: Trachea, Local Squirrel, Bronchial Tree, Histochemical, Lung.

Biomechanical analysis of tracheal stent during cough reflex.

Tracheal stenting is a common method which is widely used to cure different tracheal disorders including airways stenosis, chronic coughs, and accidents. In this study, we aimed to analyze the reaction of the trachea wall to exhale in three phases of light, moderate, and vigorous activities at air flows of 15 L/min (light), 26 L/min (medium), and 30 L/min (vigorous). Fluid structure interaction (FSI) was used for the numerical analysis using computed tomography (CT) images. The flow was assumed incompressible and turbulent. The stent is silicone with a Young's modulus equal to 1 MPa, Poisson's ratio 0.28, and density of 2330 kg/m3. The stent length was 60 mm and fix support boundary condition was applied for all inputs and outputs. Numerical simulation was performed using ANSYS software. The induced stresses, strains, wall deformation, flow pressure, and the flow velocity were obtained. The results showed that the stent prevented the local deformation of the wall of trachea and it reduced the induced strain in the position. But the stenting could lead to stress concentration. Finally, the stent prevented the damage to the trachea muscles during coughs in row.

Microstructure and mechanics of the bovine trachea: Layer specific investigations through SHG imaging and biaxial testing

The trachea is a complex tissue made up of hyaline cartilage, fibrous tissue, and muscle fibers. Currently, the knowledge of microscopic structural organization of these components and their role in determining the tissue’s mechanical response is very limited. The purpose of this study is to provide data on the microstructure of the tracheal components and its influence on tissue’s mechanical response. Five bovine tracheae were used in this study. Adventitia, cartilage, mucosa/submucosa, and trachealis muscle layers were methodically cut out from the whole tissue. Second-harmonic generation(SHG) via multi-photon microscopy (MPM) enabled imaging of collagen fibers and muscle fibers. Simultaneously, a planar biaxial test rig was used to record the mechanical behavior of each layer. In total 60 samples were tested and analyzed. Fiber architecture in the adventitia and mucosa/submucosa layer showed high degree of anisotropy with the mean fiber angle varying from sample to sample. The trachealis muscle displayed neat layers of fibers organized in the longitudinal direction. The cartilage also displayed a structure of thick mesh-work of collagen type II organized predominantly towards the circumferential direction. Further, mechanical testing demonstrated the anisotropic nature of the tissue components. The cartilage was identified as the stiffest component for strain level < 20% and hence the primary load bearing component. The other three layers displayed a non-linear mechanical response which could be explained by the structure and organization of their fibers. This study is useful in enhancing the utilization of structurally motivated material models for predicting tracheal overall mechanical response.

The macroscopical and microscopical characters of the trachea in different avian species: A comparative study

This study aimed to explain and compare the anatomical, histological, histochemical and histomorphometrical analyses of the trachea in different species of birds. This study includes 21 healthy birds from geese (Anser anser domesticus), cattle egrets (Bublucus ibis) and house sparrows (Passer domesticus), 7 seven from each species. Anatomically, the trachea of the goose (the proximal and distal parts) was the longest of all the studied species, yet it had fewer cartilaginous rings than those of the cattle egret. Also, the tracheal length, beside the tracheal muscle in geese plays an important role in the phonation process. Histologically, the trachea is composed of four distinct tunicae: mucosa, propria submucosa, fibrocartilaginous, and adventitia. The epithelium that lined the trachea was ciliated, pseudostratified columnar epithelium (respiratory epithelium) with simple mucous tubuloalveolar glands in either proximal or distal parts depending on the species. The proximal part is made up of overlapped hyaline cartilaginous rings that partially ossified in geese and cattle egrets but did not ossify in sparrows. In the distal part, the overlapping faded in three investigated species.

Brachycephalic Syndrome in Dogs - Endoscopic Findings in the Airways

Background: Brachycephalic dogs have several abnormalities in the airways, which generate clinical manifestations that impair the quality of life of these animals. Primary alterations promote airflow obstruction and increase intraluminal negative pressure, causing secondary alterations due to a cycle of inflammation with consequent obstruction. With the onset of inflammation and other alterations in the airways, clinical manifestations can be observed, such as snoring, reverse sneezing, coughing, dyspnea, cyanosis, syncope, and vomiting. Endoscopic examination of the airways allows visualization and diagnosis of morphological changes in these animals. This study aimed to evaluate the endoscopic findings of the airways and determine the quantitative and qualitative assessment of the severity of clinical manifestations in 14 dogs with brachycephalic syndrome (BS). Materials, Methods &amp; Results: Historical and anamnesis data and clinical, respiratory, and digestive manifestations were collected from the owners’ reports. The clinical manifestations were classified as mild, moderate, or severe. All animals were subjected to endoscopy of the airways, and image findings were grouped according to the anatomical site where they were observed, then the abnormalities were correlated with the severity of the clinical manifestations. When comparing the frequency of endoscopic abnormalities with the severity of clinical manifestations, it is interesting to observe that animals with severe disease more frequently presented the following alterations: prolongation and thickening of the soft palate, laryngeal changes, presence of hyperemia, lymphoid hyperplasia and polyps in the nasopharynx, hypoplasia and presence of tracheal secretion and thickening of the dorsal tracheal muscle; bronchial collapse, hypoplasia of the main bronchi and bronchial hyperemia and the presence of aberrant nasal turbinates. Comparison between the means of nonparametric variables was performed using the Mann-Whitney test, with a 5% significance level. Discussion: A higher frequency of French Bulldog dogs included in the study was observed, probably due to their greater popularity, although any brachycephalic dog may be affected by BS. Considering that nostril stenosis is a congenital alteration, which is usually diagnosed early, and since the animals included in the study were dogs referred for the rhinoplasty procedure the higher frequency of young dogs in the study was not surprising. The results revealed a significant difference in the endoscopic findings with the severity of the clinical manifestations in different variables, such as prolongation and thickening of the soft palate, eversion of the laryngeal saccules, presence of laryngeal inflammation and collapse, presence of polyps or lymphoid hyperplasia in the nasopharynx, thickening of the dorsal muscle of the trachea, polyps in the trachea and hypoplasia in addition to bronchial hyperemia. The larynx was the most affected anatomical site, with alterations present in 92.8% of the evaluated dogs. Based on these findings, it can be concluded that airway obstruction caused by primary alterations can cause secondary alterations, with consequent clinical manifestations in brachycephalic dogs it is possible to suggest that dogs with this syndrome may present severe manifestations of the disease, regardless of age. Furthermore, it can be concluded that in this study, dogs with BS had frequent laryngeal alterations and that alterations in the main bronchi were present in all animals with severe manifestations of the disease. Keywords: airway obstruction, bronchial collapse, endoscopy, larynx.

Regional Differences in Mucociliary Clearance in the Upper and Lower Airways.

As the nasal cavity is the portal of entry for inspired air in mammals, this region is exposed to the highest concentration of inhaled particulate matter and pathogens, which must be removed to keep the lower airways sterile. Thus, one might expect vigorous removal of these substances via mucociliary clearance (MCC) in this region. We have investigated the rate of MCC in the murine nasal cavity compared to the more distal airways (trachea). The rate of MCC in the nasal cavity (posterior nasopharynx, PNP) was ∼3–4× greater than on the tracheal wall. This appeared to be due to a more abundant population of ciliated cells in the nasal cavity (∼80%) compared to the more sparsely ciliated trachea (∼40%). Interestingly, the tracheal ventral wall exhibited a significantly lower rate of MCC than the tracheal posterior membrane. The trachealis muscle underlying the ciliated epithelium on the posterior membrane appeared to control the surface architecture and likely in part the rate of MCC in this tracheal region. In one of our mouse models (Bpifb1 KO) exhibiting a 3-fold increase in MUC5B protein in lavage fluid, MCC particle transport on the tracheal walls was severely compromised, yet normal MCC occurred on the tracheal posterior membrane. While a blanket of mucus covered the surface of both the PNP and trachea, this mucus appeared to be transported as a blanket by MCC only in the PNP. In contrast, particles appeared to be transported as discrete patches or streams of mucus in the trachea. In addition, particle transport in the PNP was fairly linear, in contrast transport of particles in the trachea often followed a more non-linear route. The thick, viscoelastic mucus blanket that covered the PNP, which exhibited ∼10-fold greater mass of mucus than did the blanket covering the surface of the trachea, could be transported over large areas completely devoid of cells (made by a breach in the epithelial layer). In contrast, particles could not be transported over even a small epithelial breach in the trachea. The thick mucus blanket in the PNP likely aids in particle transport over the non-ciliated olfactory cells in the nasal cavity and likely contributes to humidification and more efficient particle trapping in this upper airway region.