scholarly journals Conserved Mechanisms in the Formation of the Airways and Alveoli of the Lung

2021 ◽  
Vol 9 ◽  
Author(s):  
David Warburton
Keyword(s):  
Airway Epithelium ◽  
Alveolar Epithelium ◽  
Upper Airway ◽  
Intrinsic Property ◽  
Branching Morphogenesis ◽  
Radial Symmetry ◽  
Respiratory Epithelium ◽  
Lower Airway ◽  
Upper Airways ◽  
Alveolar Duct

Branching is an intrinsic property of respiratory epithelium that can be induced and modified by signals emerging from the mesenchyme. However, during stereotypic branching morphogenesis of the airway, the relatively thick upper respiratory epithelium extrudes through a mesenchymal orifice to form a new branch, whereas during alveologenesis the relatively thin lower respiratory epithelium extrudes to form sacs or bubbles. Thus, both branching morphogenesis of the upper airway and alveolarization in the lower airway seem to rely on the same fundamental physical process: epithelial extrusion through an orifice. Here I propose that it is the orientation and relative stiffness of the orifice boundary that determines the stereotypy of upper airway branching as well as the orientation of individual alveolar components of the gas exchange surface. The previously accepted dogma of the process of alveologenesis, largely based on 2D microscopy, is that alveoli arise by erection of finger-like interalveolar septae to form septal clefts that subdivide pre-existing saccules, a process for which the contractile properties of specialized alveolar myofibroblasts are necessary. Here I suggest that airway tip splitting and stereotypical side domain branching are actually conserved processes, but modified somewhat by evolution to achieve both airway tip splitting and side branching of the upper airway epithelium, as well as alveologenesis. Viewed in 3D it is clear that alveolar “septal tips” are in fact ring or purse string structures containing elastin and collagen that only appear as finger like projections in cross section. Therefore, I propose that airway branch orifices as well as alveolar mouth rings serve to delineate and stabilize the budding of both airway and alveolar epithelium, from the tips and sides of upper airways as well as from the sides and tips of alveolar ducts. Certainly, in the case of alveoli arising laterally and with radial symmetry from the sides of alveolar ducts, the mouth of each alveolus remains within the plane of the side of the ductal lumen. This suggests that the thin epithelium lining these lateral alveolar duct buds may extrude or “pop out” from the duct lumen through rings rather like soap or gum bubbles, whereas the thicker upper airway epithelium extrudes through a ring like toothpaste from a tube to form a new branch.

Comparison of upper and lower airway responses of two sensitized rat strains to inhaled antigen

1992 ◽  
Vol 73 (4) ◽  
pp. 1608-1613 ◽  
Author(s):  
L. J. Xu ◽  
S. Sapienza ◽  
T. Du ◽  
S. Waserman ◽  
J. G. Martin
Keyword(s):  
Upper Airway ◽  
Brown Norway ◽  
Lower Airway ◽  
Sprague Dawley ◽  
Pulmonary Resistance ◽  
Upper Airways ◽  
Tracheal Pressure ◽  
Airway Response ◽  
Airway Responses ◽  
Inbred Rat

The purpose of the study was to investigate the relationships between upper airways responses and pulmonary responses of two strains of highly inbred rats to inhaled antigen. To do this we measured the upper and lower airways resistance for 60 min after challenge of Brown-Norway rats (BN; n = 13) and an inbred rat strain (MF; n = 11), derived from Sprague-Dawley, with aerosolized ovalbumin (OA). Rats were actively sensitized with OA (1 mg sc) using Bordetella pertussis as an adjuvant. Two weeks later the animals were anesthetized and challenged. Tracheal pressure, esophageal pressure, and airflow were measured, from which total pulmonary resistance was partitioned into upper airway and lower pulmonary resistance (RL). The peak upper airway response to inhaled OA was similar in BN (1.89 +/- 0.66 cmH2O.ml-1.s; n = 7) and MF (2.85 +/- 0.68 cmH2O.ml-1.s; n = 6). The lower airway response to OA challenge was substantially greater in BN, and RL changed from 0.07 +/- 0.01 to 0.34 +/- 0.13 (n = 6; P < 0.05). The MF did not have any significant increase in RL after challenge; the baseline RL was 0.12 +/- 0.02 and only reached a peak value of 0.15 +/- 0.05 (n = 5; P = NS). Lower airway responsiveness of BN (n = 10) to serotonin, an important mediator early allergic airway responses, was similar to MF (n = 7).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhalation injury in the ICU

2016 ◽  
Author(s):  
Silvia Coppola ◽  
Franco Valenza
Keyword(s):  
Imaging Techniques ◽  
Carbon Monoxide Poisoning ◽  
Significant Risk ◽  
Upper Airway ◽  
Injured Patient ◽  
Inhalation Injury ◽  
Smoke Inhalation ◽  
Lower Airway ◽  
Upper Airways ◽  
Chemical Injury

Inhalation injury represents one of the most serious associated injuries complicating the care of thermally-injured patient. It can result in severe respiratory failure and acute respiratory distress syndrome (ARDS) by three mechanisms—thermal or chemical injury, and impairment of systemic oxygen supply. Thermal injury can cause erythema, ulceration, and progressive, life-threatening oedema, particularly of the upper airways. Chemical injury is due to irritants or cytotoxic compounds, and depends on the material burned, the temperature of the fire, and the amount of oxygen present in the fire environment. It is responsible for irritation, ulceration, and oedema of the mucosal surface, and the initiation of a lung inflammatory reaction when small particles reach the alveoli. Moreover, the increased vascular permeability, and the reduced surfactant production carry a significant risk in the development of pneumonia and ARDS. Bronchospasm and upper airway oedema can occur rapidly, while lower airway oedema can be asymptomatic for up to 24 hours. Lung imaging techniques may not reveal injured areas for the first 24–48 hours. Fibre optic bronchoscopy is considered to be the most direct diagnostic method for the definitive diagnosis of inhalation injury. The patient management includes airways assessment, adequate fluid resuscitation, and mechanical ventilation when required. All victims of smoke inhalation should be always evaluated for cyanide and carbon monoxide poisoning.

scholarly journals Role of Aquaporin Water Channels in Airway Fluid Transport, Humidification, and Surface Liquid Hydration

2001 ◽  
Vol 117 (6) ◽  
pp. 573-582 ◽  
Author(s):  
Yuanlin Song ◽  
Sujatha Jayaraman ◽  
Baoxue Yang ◽  
Michael A. Matthay ◽  
A.S. Verkman
Keyword(s):  
Knockout Mice ◽  
Fluid Transport ◽  
Upper Airway ◽  
Lower Airway ◽  
Wild Type ◽  
Upper Airways ◽  
Airway Epithelia ◽  
Airway Humidification ◽  
Surface Liquid

Several aquaporin-type water channels are expressed in mammalian airways and lung: AQP1 in microvascular endothelia, AQP3 in upper airway epithelia, AQP4 in upper and lower airway epithelia, and AQP5 in alveolar epithelia. Novel quantitative methods were developed to compare airway fluid transport–related functions in wild-type mice and knockout mice deficient in these aquaporins. Lower airway humidification, measured from the moisture content of expired air during mechanical ventilation with dry air through a tracheotomy, was 54–56% efficient in wild-type mice, and reduced by only 3–4% in AQP1/AQP5 or AQP3/AQP4 double knockout mice. Upper airway humidification, measured from the moisture gained by dry air passed through the upper airways in mice breathing through a tracheotomy, decreased from 91 to 50% with increasing ventilation from 20 to 220 ml/min, and reduced by 3–5% in AQP3/AQP4 knockout mice. The depth and salt concentration of the airway surface liquid in trachea was measured in vivo using fluorescent probes and confocal and ratio imaging microscopy. Airway surface liquid depth was 45 ± 5 μm and [Na+] was 115 ± 4 mM in wild-type mice, and not significantly different in AQP3/AQP4 knockout mice. Osmotic water permeability in upper airways, measured by an in vivo instillation/sample method, was reduced by ∼40% by AQP3/AQP4 deletion. In doing these measurements, we discovered a novel amiloride-sensitive isosmolar fluid absorption process in upper airways (13% in 5 min) that was not affected by aquaporin deletion. These results establish the fluid transporting properties of mouse airways, and indicate that aquaporins play at most a minor role in airway humidification, ASL hydration, and isosmolar fluid absorption.

scholarly journals Human rhinovirus serotypes induces different immune responses

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Ji Heui Kim ◽  
Jung Yeon Jang ◽  
Yong Ju Jang
Keyword(s):  
Immune Responses ◽  
Airway Epithelium ◽  
Inflammatory Responses ◽  
Low Density Lipoprotein ◽  
Density Lipoprotein ◽  
Upper Airway ◽  
Human Rhinovirus ◽  
Lower Airway ◽  
Mrna Levels ◽  
Human Nasal Epithelial Cells

Abstract Background Different species of human rhinovirus (HRV) can induce varied antiviral and inflammatory responses in human blood macrophages and lower airway epithelium. Although human nasal epithelial cells (HNECs) are a primary infection route of HRV, differences between major and minor groups of HRV in the upper airway epithelium have not been studied in detail. In this study, we investigated viral replications and immune responses of major and minor groups of HRV in the HNECs. Methods Viral replication, immune responses of IFN-β, IFN-λ, proinflammatory cytokines, and viral receptors, and mRNA expression of transcription factors of HRV16 (major group) and HRV1B (minor group) in the HNECs were assessed. Results Compared with HRV16, HRV1B replicated more actively without excessive cell death and produced higher IFN-β, IFN-λ1/3, CXCL10, IL-6, IL-8, and IL-18 levels. Furthermore, low-density lipoprotein receptor (LDLR), TLR3, MDA5, NF-κB, STAT1, and STAT2 mRNA levels increased in HRV1B-infected HNECs. Conclusion HRV1B induces a stronger antiviral and inflammatory response from cell entry to downstream signaling compared with HRV16.

Motor responses to positive-pressure breathing in the developing opossum

1985 ◽  
Vol 58 (5) ◽  
pp. 1489-1495 ◽  
Author(s):  
J. P. Farber
Keyword(s):  
Airway Resistance ◽  
Upper Airway ◽  
Abdominal Muscle ◽  
Positive Pressure ◽  
Postnatal Life ◽  
Abdominal Muscles ◽  
Upper Airways ◽  
Motor Responses ◽  
Upper Airway Resistance ◽  
Upper Airway Muscles

The suckling opossum exhibits an expiration-phased discharge in abdominal muscles during positive-pressure breathing (PPB); the response becomes apparent, however, only after the 3rd-5th wk of postnatal life. The purpose of this study was to determine whether the early lack of activation represented a deficiency of segmental outflow to abdominal muscles or whether comparable effects were observed in cranial outflows to muscles of the upper airways due to immaturity of afferent and/or supraspinal pathways. Anesthetized suckling opossums between 15 and 50 days of age were exposed to PPB; electromyogram (EMG) responses in diaphragm and abdominal muscles were measured, along with EMG of larynx dilator muscles and/or upper airway resistance. In animals older than approximately 30 days of age, the onset of PPB was associated with a prolonged expiration-phased EMG activation of larynx dilator muscles and/or decreased upper airway resistance, along with expiratory recruitment of the abdominal muscle EMG. These effects persisted as long as the load was maintained. Younger animals showed only those responses related to the upper airway; in fact, activation of upper airway muscles during PPB could be associated with suppression of the abdominal motor outflow. After unilateral vagotomy, abdominal and upper airway motor responses to PPB were reduced. The balance between PPB-induced excitatory and inhibitory or disfacilitory influences from the supraspinal level on abdominal motoneurons and/or spinal processing of information from higher centers may shift toward net excitation as the opossum matures.

scholarly journals Changes in the Upper and Lower Pharyngeal Airway Spaces Associated with Rapid Maxillary Expansion

2012 ◽  
Vol 2012 ◽  
pp. 1-5 ◽  
Author(s):  
Fitin Aloufi ◽  
Charles B. Preston ◽  
Khalid H. Zawawi
Keyword(s):  
Orthodontic Treatment ◽  
Upper Airway ◽  
Rapid Maxillary Expansion ◽  
Lower Airway ◽  
Control Group ◽  
Maxillary Expansion ◽  
Pharyngeal Airway ◽  
Significant Difference ◽  
And Gender ◽  
Maxillary Constriction

Objectives. The primary objectives of this retrospective study were first to compare the upper and lower pharyngeal airway spaces between orthodontic patients with and without maxillary constriction and second to evaluate the effect of rapid maxillary expansion (RME) on these airway spaces. A secondary objective was to compare the mode of breathing between groups. Materials and Methods. The experimental (RME) group consisted of 30 patients (mean age, years, 16 boys and 14 girls) with maxillary constriction who were treated with hyrax-type RME. The control group comprised the records of age- and gender matched patients (mean age, years, 16 boys and 14 girls) with no maxillary constriction but requiring nonextraction comprehensive orthodontic treatment. Cephalometric measurements in the sagittal dimension of upper and lower airway spaces for the initial and final records were recorded. Mode of breathing and length of treatment were also compared. Results. The sagittal dimension of the upper airway increased significantly in the RME group ( mm) compared to the control group ( mm), . However, there was no significant difference in the lower pharyngeal airway measurement between the RME group () and the control group (), . There was no significant difference with respect to mode of breathing between the two groups (). Conclusion. Rapid maxillary expansion (RME) during orthodontic treatment may have a positive effect on the upper pharyngeal airway, with no significant change on the lower pharyngeal airway.

Effects of pharyngeal lubrication on the opening of obstructed upper airway

1992 ◽  
Vol 72 (6) ◽  
pp. 2311-2316 ◽  
Author(s):  
H. Miki ◽  
W. Hida ◽  
Y. Kikuchi ◽  
T. Chonan ◽  
M. Satoh ◽  
...  
Keyword(s):  
Hypoglossal Nerve ◽  
Muscle Tone ◽  
Upper Airway ◽  
Intraluminal Pressure ◽  
Lower Airway ◽  
Before And After ◽  
Airway Opening ◽  
Cervical Trachea ◽  
Artificial Surfactant ◽  
Stimulation Of

We examined the effect of electrical stimulation of the hypoglossal nerve and pharyngeal lubrication with artificial surfactant (Surfactant T-A) on the opening of obstructed upper airway in nine anesthetized supine dogs. The upper airway was isolated from the lower airway by transecting the cervical trachea. Upper airway obstruction was induced by applying constant negative pressures (5, 10, 20, and 30 cmH2O) on the rostral cut end of the trachea. Peripheral cut ends of the hypoglossal nerves were electrically stimulated by square-wave pulses at various frequencies from 10 to 30 Hz (0.2-ms duration, 5–7 V), and the critical stimulating frequency necessary for opening the obstructed upper airway was measured at each driving pressure before and after pharyngeal lubrication with artificial surfactant. The critical stimulation frequency for upper airway opening significantly increased as upper airway pressure became more negative and significantly decreased with lubrication of the upper airway. These findings suggest that greater muscle tone of the genioglossus is needed to open the occluded upper airway with larger negative intraluminal pressure and that lubrication of the pharyngeal mucosa with artificial surfactant facilitates reopening of the upper airway.

scholarly journals Role of Taste Receptors as Sentinels of Innate Immunity in the Upper Airway

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Neil N. Patel ◽  
Alan D. Workman ◽  
Noam A. Cohen
Keyword(s):  
Airway Epithelium ◽  
Taste Receptor ◽  
Upper Airway ◽  
Airway Disease ◽  
G Protein Coupled Receptors ◽  
Innate Immune ◽  
Taste Receptors ◽  
Taste Sensation ◽  
G Protein Coupled

Evidence is emerging that shows taste receptors serve functions outside of taste sensation of the tongue. Taste receptors have been found in tissue across the human body, including the gastrointestinal tract, bladder, brain, and airway. These extraoral taste receptors appear to be important in modulating the innate immune response through detection of pathogens. This review discusses taste receptor signaling, focusing on the G-protein–coupled receptors that detect bitter and sweet compounds in the upper airway epithelium. Emphasis is given to recent studies which link the physiology of sinonasal taste receptors to clinical manifestation of upper airway disease.

Inspiratory coactivation of the genioglossus enlarges retroglossal space in laryngectomized humans

1996 ◽  
Vol 80 (5) ◽  
pp. 1595-1604 ◽  
Author(s):  
I. Kobayashi ◽  
A. Perry ◽  
J. Rhymer ◽  
B. Wuyam ◽  
P. Hughes ◽  
...  
Keyword(s):  
Upper Airway ◽  
Dependent Manner ◽  
Tongue Movement ◽  
Forward Movement ◽  
Upper Airways ◽  
Posterior Aspect ◽  
Airway Patency ◽  
Significant Movement ◽  
Tongue Position ◽  
Tracheal Stoma

To investigate the relationship between the electrical activity of the genioglossus (GG-EMG) and associated tongue movement, seven laryngectomized subjects breathing through a tracheal stoma (without pressure or flow change in the upper airway) were studied in the supine position. Tongue movement, with the use of lateral fluoroscopy, and GG-EMG expressed as a percentage of maximum voluntary genioglossal activation were monitored simultaneously during 1) spontaneous inspiration (SI), 2) resistive loaded inspiration (LI), and 3) rapid inspiration (RI). Tongue position during each maneuver was compared with its position during spontaneous expiration. Peak GG-EMG during the three maneuvers was significantly different from each other (SI: 5.4 +/- 1.6, LI: 11.9 +/- 1.8, and RI: 51.6 +/- 9.4 (SE) %, respectively). Associated forward movement of the posterior aspect of the tongue was minimum during SI; however, significant movement was observed during LI, and this was increased during RI. Significant covariance existed between peak GG-EMG and this movement. Genioglossal coactivation with inspiration enlarges the glossopharyngeal airway, particularly in its caudal part. In subjects with intact upper airways, this activation may protect or enhance upper airway patency in an effort-dependent manner.

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