Tracheal Muscle Research Articles

Human trachealis and main bronchi smooth muscle are normoresponsive in asthma.

Airway smooth muscle (ASM) plays a key role in airway hyperresponsiveness (AHR) but it is unclear whether its contractility is intrinsically changed in asthma. To investigate whether key parameters of ASM contractility are altered in subjects with asthma. Human trachea and main bronchi were dissected free of epithelium and connective tissues and suspended in a force-length measurement set-up. After equilibration each tissue underwent a series of protocols to assess its methacholine dose-response relationship, shortening velocity, and response to length oscillations equivalent to tidal breathing and deep inspirations. Main bronchi and tracheal ASM were significantly hyposensitive in subjects with asthma compared with control subjects. Trachea and main bronchi did not show significant differences in reactivity to methacholine and unloaded tissue shortening velocity (Vmax) compared with control subjects. There were no significant differences in responses to deep inspiration, with or without superimposed tidal breathing oscillations. No significant correlations were found between age, body mass index, or sex and sensitivity, reactivity, or Vmax. Our data show that, in contrast to some animal models of AHR, human tracheal and main bronchial smooth muscle contractility is not increased in asthma. Specifically, our results indicate that it is highly unlikely that ASM half-maximum effective concentration (EC50) or Vmax contribute to AHR in asthma, but, because of high variability, we cannot conclude whether or not asthmatic ASM is hyperreactive.

Histology and Scanning Electron Microscopy of the Lower Respiratory Tract in the Adult Red Fox (Vulpes vulpes)

MOUSSA, E. A. & HASSAN, S. A. Histology and scanning electron microscopy of the lower respiratory tract in the adult red fox(Vulpes vulpes). Int. J. Morphol., 33(1):267-274, 2015.SUMMARY: The study was conducted on a total of three adult healthy freshly killed red foxes of both sexes weighing about 4-6 kg collected from Abou Rawwash, Giza, Egypt. The wall of trachea and bronchi formed of mucosa, submucosa and adventitia. Themucosa formed of pseudostratified columnar epithelium and lamina propria. The respiratory epithelium composed of tall columnarciliated, goblet cells, basal cells, and neuroendocrine cells. Goblet cells account for about 20 to 30% of cells in the more proximal. Basalcells are relatively small triangular cells whose bases are attached to the basement membrane. The primary bronchiole is lined by simplecolumnar nonciliated to cuboidal epithelium containing some bronchiolar exocrine cells and some goblet cells. Neuroendocrine cellsconstitute about 4 to 5% of bronchial epithelial cells, attached at their bases to the basement membrane and have tapering apic es. The laminapropria consists principally of a network of capillaries, a meshwork of connective tissue fibers continuous with the basement membrane.The submucosa formed of connective tissue elements and blood vessels and devoid of Tracheobronchial glands in red fox. The adventitiacontain tracheal cartilage and muscle in trachea and bronchial cartilages and muscles in bronchi. Tracheal muscle is transverse bundlesattached to the outer perichondrium. In the bronchi, muscle is organized in transverse bundles close to the epithelium adjacent to the laminapropria and longitudinal bundles close to the cartilages. Alveoli are demarcated by septa composed of a continuous layer of epi thelial cellsoverlying a thin interstitium. The epithelial cells consist principally of type I and type II pneumocytes. SEM revealed that, the mucosalsurface of both trachea and bronchi was completely covered by cilia. There were few glandular openings or goblet cell.KEY WORDS: Scanning; Fox; Respiratory; Histology.

Bronchial but not Tracheal Smooth Muscle is Hypercontractile in an Equine Model of Severe Asthma

Asthma is an inflammatory disease of the airways characterized by airway hyperresponsiveness, an exaggerated bronchoconstrictive response of airway smooth muscle (ASM) to stimuli. However, whether asthmatic ASM is mechanically different from non-asthmatic ASM is still unclear. Most studies so far have been performed on the trachealis muscle but it might not be representative of smooth muscle in the more peripheral airways. Thus, we addressed this question in an equine model of asthma (horse with heaves) and compared the trachealis (TSM) and peripheral bronchial (BSM) airway smooth muscle mechanics.Muscle strips from de-epithelialized TSM and BSM (less than 10 mm in diameter) were mounted horizontally in an experimental chamber between a length controller and a force transducer (Aurora Scientific Inc.). Maximal velocity of shortening (Vmax), methacholine dose response and stress were measured.We found no difference in Vmax between TSM from control horses and horses with heaves (0.124±0.01vs. 0.119±0.01; control vs. heaves; P=0.8), whereas the BSM exhibited a significantly higher Vmax (0.114±0.01 vs. 0.239±0.02; P=0.03). Western blot analysis showed a significant increase of the (+)insert fast smooth muscle myosin heavy chain (SMMHC) isoform in BSM of heaves-affected horses (0.78±0.04 vs. 1.0±0.05, P=0.0092), while no such difference was found in TSM (0.91±0.05 vs.0.97±0.08;P=0.54). The expression of calponin was significantly increased in TSM of heaves-affected horses (0.92±0.15 vs. 2.5±0.57, P=0.037; but this was not observed in BSM (0.37±0.14 vs. 0.49±0.18; P=0.62). There were no differences detected in the expression of MLCK, total SMMHC and transgelin. Peripheral airways may have a greater exposure to inflammatory cells than the trachealis which may explain their differences in mechanics. Further studies await to determine the mechanism underlying in observed effect.Supported by: CIHR(MOP102718), NIH(RO1HL103405), RFBR(12-04-0076)

Relaxant action mechanism of essential oil of Agastache mexicana aereal parts on guinea-pig trachea smooth muscle

In this study was investigated the relaxant action mechanism of essential oil of Agastache mexicana (EOAM) in guinea-pig isolated trachea model. The major components of this oil were estragole (80.28%) and D-limonene (17.55%). EOAM relaxed the carbachol (3µM, EC50 =18.25 ± 1.026 µg/mL) or histamine (3µM, EC50 =13.3 ± 1.026 µg/mL)-induced contractions in tracheal muscle. The relaxant effect of EOAM was not modified by the presence of propranolol (3µM), glibenclamide (10µM) or 2',5'-dideoxyadenosine (10µM), suggesting that relaxant effect of this essential oil is not related to β2-adrenergic receptors, ATP-sensitive potassium channels or adenylate cyclase activation. EOAM was more potent to antagonize histamine, whit pA'2 of -1.507 ±.122 (32.13 ± 1.32 µg/mL) than carbachol, with pA'2 of -2.180 ± 0.357 (151.35 ± 2.27 µg/mL). Also, EOAM antagonized the calcium chloride-induced contractions. These results suggest that relaxant effect of EOAM is due to an antihistaminic and anticholinergic effect in addition to the blockade of calcium influx in the guinea-pig trachea smooth muscle. It is possible that estragole and D-limonene are the responsible compounds of the relaxant effect of the essential oil of Agastache mexicana.

Preventive effects of ipratropium and salbutamol against insulin induced tracheal smooth muscle contraction in guinea pig model

Inhalational insulin was withdrawn from the market due to its potential to produce airway hyper-reactivity and bronchoconstriction. So the present study was designed to explore the acute effects of insulin on airway reactivity of guinea pigs and protective effects of salbutamol and ipratropium against insulin induced airway hyper-responsiveness on isolated tracheal smooth muscle of guinea pig. The tracheal muscle contractions were recorded with transducer on four channel oscillograph. The mean ± SEM of maximum amplitude of contraction with increasing concentrations of insulin (10-7- 10-3 M ), insulin pretreated with fixed concentration of salbutamol (10-7 M) and ipratropium (10-6 M) were 35 ± 1.13 mm, 14.55 ± 0.62 mm and 27.8 ± 1.27 mm respectively. Salbutamol inhibited the contractile response of insulin greater than ipratropium on isolated tracheal muscle of guinea pig. So we suggest that pretreatment of inhaled insulin with salbutamol may be preferred over ipratropium in amelioration of its potential respiratory adverse effects such as bronchoconstriction.

Simulation of swallowing dysfunction and mechanical ventilation after a Montgomery T-tube insertion

The Montgomery T-tube is used as a combined tracheal stent and airway after laryngotracheoplasty, to keep the lumen open and prevent mucosal laceration from scarring. It is valuable in the management of upper and mid-tracheal lesions, while invaluable in long and multisegmental stenting lesions. Numerical simulations based on real-patient-tracheal geometry, experimental tissue characterization, and previous numerical estimation of the physiological swallowing force are performed to estimate the consequences of Montgomery T-tube implantation on swallowing and assisted ventilation: structural analysis of swallowing is performed to evaluate patient swallowing capacity, and computational fluid dynamics simulation is carried out to analyze related mechanical ventilation. With an inserted Montgomery T-tube, vertical displacement (Z-axis) reaches 8.01 mm, whereas in the Y-axis, it reaches 6.63 mm. The maximal principal stress obtained during swallowing was 1.6 MPa surrounding the hole and in the upper contact with the tracheal wall. Fluid flow simulation of the mechanical ventilation revealed positive pressure for both inhalation and exhalation, being higher for inspiration. The muscular deflections, considerable during normal breathing, are nonphysiological, and this aspect results in a constant overload of the tracheal muscle. During swallowing, the trachea ascends producing a nonhomogeneous elongation. This movement can be compromised when prosthesis is inserted, which explains the high incidence of glottis close inefficiency. Fluid simulations showed that nonphysiological pressure is established inside the trachea due to mechanical ventilation. This may lead to an overload of the tracheal muscle, explaining several related problems as muscle thinning or decrease in contractile function.

CD4+ T cells enhance the unloaded shortening velocity of airway smooth muscle by altering the contractile protein expression

Abundant data indicate that pathogenesis in allergic airways disease is orchestrated by an aberrant T-helper 2 (Th2) inflammatory response. CD4(+) T cells have been localized to airway smooth muscle (ASM) in both human asthmatics and in rodent models of allergic airways disease, where they have been implicated in proliferative responses of ASM. Whether CD4(+) T cells also alter ASM contractility has not been addressed. We established an in vitro system to assess the ability of antigen-stimulated CD4(+) T cells to modify contractile responses of the Brown Norway rat trachealis muscle. Our data demonstrated that the unloaded velocity of shortening (Vmax) of ASM was significantly increased upon 24 h co-incubation with antigen-stimulated CD4(+) T cells, while stress did not change. Enhanced Vmax was dependent upon contact between the CD4(+) T cells and the ASM and correlated with increased levels of the fast (+)insert smooth muscle myosin heavy chain isoform. The levels of myosin light chain kinase and myosin light chain phosphorylation were also increased within the muscle. The alterations in mechanics and in the levels of contractile proteins were transient, both declining to control levels after 48 h of co-incubation. More permanent alterations in muscle phenotype might be attainable when several inflammatory cells and mediators interact together or after repeated antigenic challenges. Further studies will await new tissue culture methodologies that preserve the muscle properties over longer periods of time. In conclusion, our data suggest that inflammatory cells promote ASM hypercontractility in airway hyper-responsiveness and asthma.

Insulin causes airway hyper-reactivity

Background: We explored the acute effects of insulin and one possible mechanism underlying the acute contractile effects of insulin on isolated tracheal smooth muscle of guinea pig in vitro. Methods: Effects of increasing concentrations of histamine (10 −7 -10 −3 M), insulin (10 −7 -10 −3 M), insulin pretreated with a fixed concentration of indomethacin (10 −6 M) were studied on isolated tracheal tissue of guinea pig in vitro by constructing cumulative concentration response curves. The tracheal smooth muscle contractions were recorded with transducer on four channel oscillograph. Results: Histamine and insulin produced a concentration-dependent reversible contraction of isolated tracheal muscle of guinea pig. The mean±standard error of the mean of maximum amplitudes of contraction with histamine, insulin and insulin pretreated with indomethacin were 92.5±1.20 mm, 35±1.13 mm and 14.55±0.62 mm respectively. Indomethacin shifted the concentration-response curve of insulin to the right and downwards. Conclusions: Insulin has acute contractile effects on guinea pig airways, which were significantly inhibited by prostaglandin synthesis inhibitor indomethacin confirming the involvement of contractile prostaglandins in insulin-induced airway hyper-responsiveness.

A Quantitative Study on the Trachea of the Red Sokoto (Maradi) Goat (Capra hircus)

The trachea forms the part of the conducting system which transports air from the external environment to the lungs. The aim of this study was to provide quantitative dimensions of the trachea of Red Sokoto goat (Capra hircus). Quantitative analysis was conducted on nine tracheas from goats (ages were ranged between eight months and three years) without sex variation in this study. The results showed that tracheas were extended from the cricoid cartilage of larynx to the hilus of the lungs, where they were divided into the right and left bronchi. They were structurally composed of the cartilaginous rings that were incomplete dorsally but bridged by tracheal muscles at the ends of the tracheal cartilages. The mean length of the trachea from the first to the last ring was 257 ± 7.11 mm and the number of tracheal rings varied from 35 to 57, with a mean value of 49.33 ± 2.78. The left bronchial mean length (19.78 ± 2.66 mm) was significantly longer than the right (10.44 ± 1.79 mm). The cross-sectional area (CSA) was wider at the intrathoracic area (221.5 ± 0.2 mm2) than cervical area (176 ± 0.1 mm2).

Response of smooth bronchial musculature in bronchoconstrictor substances in newborn with lung atelectasis at the respiratory distress syndrome (RDS).

ABSTRACTObjective:Role of the atelectasis (hypoxia) in the respiratory system of the live and exited newborn (250 up to 3000 g. of body weight), which has died due to different causes was studied in this work.Methods:Response of tracheal rings to dopamine, serotonine and ethanol in the different molar concentrations (dopamine: 0,05 mg/ml, 0,5 mg/ml, 5 mg/ml; serotonine (5-HT): 10-4, 10-3, 10-2, 10-1 mol/dm3; ethanol: 0,2 ml, 0,5 ml, 1,0 ml; 96%) was followed up. Study of the smooth tracheal musculature tone (STM) was elaborated in 16 tracheal preparations taken following the newborn death due to different causes.Results:Based on functional researches of tracheal isolated preparations, it was ascertained as follows: atelectasis (cases born with lung hypoxia) has changed the response of STM to dopamine, serotonine and ethanol in a significant manner (p<0,01) in comparison to cases of controlling group, which has died due to lung inflammatory processes (e.g. pneumonia, bronchopneumonia, cerebral hemorrhage), which have also caused significant response (p<0,05).Conclusion:Results suggest that exited cases from lung atelectasis and cases of controlling group reacts to above mentioned substances by causing significant constrictor action of tracheobronchial system.

Cholinergic control of the murine trachealis muscle via non-vesicular acetylcholine release involving NK1 receptor activation

In addition to quantal, vesicular release of acetylcholine (ACh), there is also non-quantal release at the motor endplate which is insufficient to evoke postsynaptic responses unless acetylcholinesterase (AChE) is inhibited. We here addressed potential non-quantal release in the mouse trachea by organ bath experiments and (immuno)histochemical methods. Electrical field stimulation (EFS) of nerve terminals elicited tracheal constriction that is largely due to ACh release (atropine-sensitive) and is not significantly affected by AChE or butyrylcholinesterase (BChE) gene-deficiency.

&lt;em&gt;Ex vivo&lt;/em&gt; Method for High Resolution Imaging of Cilia Motility in Rodent Airway Epithelia

An ex vivo technique for imaging mouse airway epithelia for quantitative analysis of motile cilia function important for insight into mucociliary clearance function has been established. Freshly harvested mouse trachea is cut longitudinally through the trachealis muscle and mounted in a shallow walled chamber on a glass-bottomed dish. The trachea sample is positioned along its long axis to take advantage of the trachealis muscle to curl longitudinally. This allows imaging of ciliary motion in the profile view along the entire tracheal length. Videos at 200 frames/sec are obtained using differential interference contrast microscopy and a high speed digital camera to allow quantitative analysis of cilia beat frequency and ciliary waveform. With the addition of fluorescent beads during imaging, cilia generated fluid flow also can be determined. The protocol time spans approximately 30 min, with 5 min for chamber preparation, 5-10 min for sample mounting, and 10-15 min for videomicroscopy.

&lt;em&gt;Ex vivo&lt;/em&gt; Method for High Resolution Imaging of Cilia Motility in Rodent Airway Epithelia

An ex vivo technique for imaging mouse airway epithelia for quantitative analysis of motile cilia function important for insight into mucociliary clearance function has been established. Freshly harvested mouse trachea is cut longitudinally through the trachealis muscle and mounted in a shallow walled chamber on a glass-bottomed dish. The trachea sample is positioned along its long axis to take advantage of the trachealis muscle to curl longitudinally. This allows imaging of ciliary motion in the profile view along the entire tracheal length. Videos at 200 frames/sec are obtained using differential interference contrast microscopy and a high speed digital camera to allow quantitative analysis of cilia beat frequency and ciliary waveform. With the addition of fluorescent beads during imaging, cilia generated fluid flow also can be determined. The protocol time spans approximately 30 min, with 5 min for chamber preparation, 5-10 min for sample mounting, and 10-15 min for videomicroscopy.

Effects of Dexmedetomidine on the Isolated Rat Tracheal Smooth Muscle

Background/Purpose Intranasally administered dexmedetomidine, a highly selective α2-adrenoceptor agonist, has been found to an effective premedication in children. However, the effect of delivering dexmedetomidine directly into the tracheal smooth muscle through inhalation has not been adequately explored. The objective of this study was to determine the effects of dexmedetomidine on the isolated rat tracheal smooth muscle in vitro. Methods A portion of rat trachea (5 mm in length) was mounted in a muscle bath filled with 30 mL of Krebs solution at 37°C. The following effects of dexmedetomidine were assessed: (1) effect on the tracheal smooth muscle resting tension, (2) effect on contraction caused by 10−6 M methacholine, and (3) effect on electrically induced tracheal smooth muscle contractions. Results Dexmedetomidine elicited a negligible effect on the basal tension of the trachea as its concentration was increased. Dexmedetomidine caused a concentration-dependent relaxation in the trachealis muscle precontracted with 10−6 M methacholine, but did not affect the contractile response to electrical field stimulation. Conclusion The results of this study suggest that high concentrations of dexmedetomidine might have an antispasmodic effect on the tracheal smooth muscle.

Neurotransmitters in parasympathetic ganglionic neurons and nerves in mouse lower airway smooth muscle

In most species, including humans, lower airway smooth muscle (ASM) contains nerve terminals from two distinct populations of parasympathetic ganglionic neurons based on neurotransmitter phenotype: cholinergic and non-adrenergic non-cholinergic (NANC), causing contraction and relaxation, respectively, of ASM. Using immunohistological staining, the density and distribution of NANC-associated neurotransmitters, vasoactive intestinal peptide (VIP) and nitric oxide synthase were 6% of total nerve profiles compared to 19% cholinergic nerves in ASM in mouse (C57BL/6) central airways. The location of the NANC parasympathetic neurons innervating the tracheal ASM, as determined by retrograde neuronal tracer from the trachealis muscle, was the myenteric plexus of the esophagus, closely associated with the outer striated longitudinal muscle layers; the majority of the retrograde-labeled neurons were VIP- and NOS-IR. The results of these experiments provide the first direct evidence that VIP-IR and NOS-IR neurons intrinsic to the mouse esophagus project axons to the adjacent trachealis muscle.

The effect of hydroethanol extract of Achillea millefolium on β-adrenoceptors of guinea pig tracheal smooth muscle

Different pharmacological effects of Achillea millefolium including its relaxant effect on smooth muscle have been shown previously. In the present study the stimulatory effect of the plant extract on β-adrenoceptor of tracheal muscle was examined in order to investigate one possible mechanism for its observed relaxant effect. Effect of three concentrations of hydroethanol extract, 10 nM propranolol, and saline on β-adrenoceptor was tested in two experimental groups including; nonincubated tracheal smooth muscles (group 1) and incubated tracheal smooth muscle with chlorpheniramine (group 2). Concentration response curves to isoprenaline were performed in precontracted tracheal smooth muscle in the presence of the extract, propranolol and saline. Values of EC50 and CR-1 were measured. Leftward shifts in isoprenaline curves were observed in the presence of medium and high concentrations of the extract compared with saline in both groups. The values of EC50 obtained in the presence of medium and high concentrations of the extract only in group 1 were nonsignificantly lower than that of saline. The values of CR-1 obtained in the presence of all concentrations of the extract in both groups were negative and significantly different with that of propranolol. The results indicated a small stimulatory effect of the extract on ß2-adrenoceptors.

Isolation and Spasmolytic Evaluation of New Alkaloids from &amp;lt;i&amp;gt;Dichrostachys cinerea&amp;lt;/i&amp;gt; (L.) Wight et Arn. (Fabaceae)

Dichrostachys cinerea (L.) Wight et Arn. (Fabaceae) root bark is used in Ivorian Traditional Medicine to treat asthma, which is a respiratory disorder characterized by inflammation and the restriction of tracheal muscles obstructing the air circulation. The tracheal relaxant effect of a crude aqueous-alcoholic extract of the plant root bark was previously shown. For the present study, alkaloids were isolated from the same extract and investigated ex vivo in C57Bl/6j mice isolated trachea contracted with carbachol 1 μM, in comparison with a reference bronchodilatator, i.e. salbutamol. Two extraction procedures allowed isolating 2 Alkaloids that monodimensional and bi-dimensional nuclear magnetic resonance (NMR) and mass specters allowed identifying a pyrolidine structure type nucleus with a long bi-hydroxyled alkyl chain. Alkaloid 1, carrier of a sugar, is a glycoside of Alkaloid 2. Both alkaloids induced similar spasmolytic effects, but Alkaloid 1 was more effective than Alkaloid 2 at 9 × 10-6 M (p ＜ 0.01), 3 × 10-5 M, and 9 × 10-5 M (p ＜0.001). Salbutamol induced its spasmolytic effect in a different way, and its maximal effect Emax (less than 30%) was obtained at 9 × 10-6 M, while Emax of both alkaloids (100%) was obtained at 3 × 10-4 M.

Effect of inhaled fluticasone and salmeterol on tracheal responsiveness and lung inflammation: Influence of administration time and allergen-free period

The effect of inhaled fluticasone propionate (FP) and salmeterol (SM) on tracheal responsiveness (TR) to methacholine and lung pathology of sensitized guinea pig was examined. Six groups of guinea pigs (n = 7) were sensitized to ovalbumin (OA). Three groups were subjected to inhaled FP and SM, one group during (A), one group after sensitization (for 18 days, B) and other group during sensitization but with 18-days delay before measurements (C). Other three groups were treated with placebo. The TR to methacholine and tracheal muscle contractility were significantly higher than those of control group (P < 0.001 for all cases). The lungs of placebo groups showed variable pathological changes (nonsignificant to P < 0.001) compared to control group. TR, intra-alveolar and interabronchoal hemorrhagie (P < 0.001 in only group A) in treated groups with FP and SM were significantly decreased compared to placebo groups. The improvement in all variables in treatment groups A and C were more pronounced than group B. These results showed a protective effect of FP and SM on tracheal responsiveness and lung pathology during sensitization which was more effective than after sensitization.

Blebbistatin, a myosin II inhibitor, suppresses Ca&lt;sup&gt;2+&lt;/sup&gt;-induced and “sensitized”-contraction of skinned tracheal muscles from guinea pig

Blebbistatin, a potent inhibitor of myosin II, has inhibiting effects on Ca2+-induced contraction and contractile filament organization without affecting the Ca2+-sensitivity to the force and phosphorylation level of myosin regulatory light chain (MLC20) in skinned (cell membrane permeabilized) taenia cecum from the guinea pig (Watanabe et al., Am J Physiol Cell Physiol. 2010; 298: C1118–26). In the present study, we investigated blebbistatin effects on the contractile force of skinned tracheal muscle, in which myosin filaments organization is more labile than that in the taenia cecum. Blebbistatin at 10 μM or higher suppressed Ca2+-induced tension development at any given Ca2+ concentration, but had little effects on the Ca2+- induced myosin light chain phosphorylation. Also blebbistatin at 10 μM and higher significantly suppressed GTP-γS-induced "sensitized" force development. Since the force inhibiting effects of blebbistatin on the skinned trachea were much stronger than those in skinned taenia cecum, blebbistatin might directly affect myosin filaments organization.

Avian infectious bronchitis and deep pectoral myopathy—A case control study

Infectious bronchitis is caused by a coronavirus, infectious bronchitis virus (IBV). Infectious bronchitis is an acute and highly contagious disease of economic importance due to the reduction in weight gain observed with infected broilers and the drop in egg quality and production associated with infected laying hens. The presence of deep pectoral myopathy has been associated with IBV variants. This lesion is detected at slaughterhouses and is characterized by paleness and atrophy of the deep pectoral muscle, including necrosis of the region, leading to condemnations of the breast muscle, a valuable meat cut in the market. This work aimed to study the relationship between deep pectoral myopathy and IBV by describing tracheal and muscle lesions and comparing the frequency of IBV detection via reverse-transcription (RT) PCR in muscle, tracheal, and cecal tonsil samples from broilers with and without myopathy. A case-control study was conducted in 40 broiler flocks vaccinated with the Massachusetts strain. The case group consisted of 23 flocks that presented myopathic lesions under sanitary inspection and a control group of 17 flocks without myopathic lesions. The tracheal, cecal tonsil, and supracoracoid muscle (with and without lesions) samples from the 40 broiler flocks were screened by RT-PCR to detect IBV. Histopathology of muscle and tracheal tissue was carried out. Upon microscopic examination, the muscle samples from the case group presented extensive necrosis, intense mononuclear inflammatory infiltration, muscle fiber fragmentation, and fibrotic tissue, confirming myopathy, whereas muscles from the control group showed no alterations. The tracheal samples presented a large number of infiltrated mononuclear inflammatory cells that in some areas formed submucosal nodules. A total of 25 flocks tested IBV positive by RT-PCR: 14 from the case group and 11 from the control group. The IBV was detected by RT-PCR directly in muscle samples. Despite that, the relationship between deep pectoral myopathy and IBV was not established. The higher positive IBV RT-PCR percentage noted in the cecal tonsil samples demonstrates how important the choice of organs is for diagnostic purposes.