BACKGROUND: The trachea is the main air passages which is important for taxonomic reasons. The structure of trachea varies considerably in different avian species. OBJECTIVES: This study has been carried out in order to determine the histological and histochemical structure of the trachea in ostriches. METHODS: Sixteen tracheas of 8 female and 8 male nine-month-old healthy blue-necked African ostriches in slaughterhouse of Isfahan were selected. Each trachea divided into cranial, middle and caudal portions and fixed in 10% neutral buffered formalin. Tissues sections were stained with H&E and special stains included Masson’s trichrome, Verhoeff’s, Foot’s, Van Gieson’s, Periodic acid-Schiff, and Alcian blue. RESULTS: The trachea of blue-neck ostriches was composed of tunica mucosa-submucosa, cartilaginous, muscular and serosa. The epithelium was ciliated pseudostratified columnar contained simple alveolar goblet mucous glands. These glands reacted negatively to Periodic acid-Schiff but positively to Alcian blue. The propria-submucosa was composed of dense connective tissue. The muscularis mucosa was absent. Tunica cartilaginous and muscular was made up of sternotrachealis muscle and cartilaginous rings. The rings were only composed of hyaline cartilage. There is no osseous tissue in the tracheal rings. Tunica serosa was composed of loose tissue contained parasympathetic ganglia, adipose tissues, vessels, and all the connective fibers. Three final cartilage rings were shaped tympanum of the syrinx. The histological structure of the trachea showed no significant differences between the male and female ostriches. Except for the decreased number of mucous glands in caudal portion of the trachea, the histological structures of the trachea showed no considerably differences among various portions. CONCLUSIONS: Based on this study, it can be concluded that although the histological and histochemical structure of the trachea in ostrich was similar to those of some other species, but that there were also some differences.

Effects of furosemide, exercise, and atropine on tracheal mucus transport rate (TMTR) in horses were investigated. Atropine (0.02 mg/kg of body weight) administered IV or by aerosolization significantly (P < 0.05) decreased TMTR at 60, but not at 30 minutes after its administration in standing horses. Furosemide (1.0 mg/kg, IV) did not have any significant effect on TMTR when measured at 2 or 4 hours after its administration in standing horses. Exercise alone or furosemide (1.0 mg/kg, IV) administration followed 4 hours later by exercise did not alter TMTR, compared with values for standing control or exercised horses administered saline solution. Atropine (0.02 mg/kg, IV) administered after exercise significantly (P < 0.05) decreased TMTR, compared with values for no exercise standing controls, for exercise after administration of saline solution, and for furosemide and exercise.

Thirty-eight tracheobronchial aspirates (TBA) were collected from twenty 1 to 6-month-old foals, which were free of clinical signs of respiratory tract or other infectious disease. We collected TBA from 9 of the foals 3 times when they were approximately 8, 16, and 24 weeks old. Aspirates were examined cytologically after staining with modified Wright-Giemsa, Gram, toluidine blue, and prussian blue stains. Aerobic bacterial culturing was performed on all aspirates. Of the 20 initial TBA, 4 (20%) were normal cytologically on the basis of previously defined criteria for TBA from clinically normal horses, 6 (30%) had a high percentage of eosinophils (> 5%), 8 (40%) were classified as indicative of subacute inflammation, and 2 (10%) were classified as indicative of acute inflammation. Nine (45%) were positive for mast cells and none were positive for hemosiderin-laden macrophages (hemosiderophages). Of the 9 foals from which samples were collected at 16 and 24 weeks of age, results were similar, except for an increase in the number of TBA classified as indicative of chronic inflammation (33% and 22% respectively) and the number positive for hemosiderophages (33% and 88%, respectively). One TBA was considered nondiagnostic because of pharyngeal contamination. Culturing of 12 of the 37 aspirates (32%) yielded a potential microbial pathogen. Only 2 were positive cultures from the same foal. The following organisms were isolated: beta-hemolytic Streptococci spp (4), Actinobacillus/Pasteurella spp (4), Rhodococcus equi (2), unidentified nonenteric Gram-negative rod (1), and Escherichia coli (1). Thirty-four of the 37 aspirates (92%) yielded light growth of various organisms considered to be nonpathogenic and normal inhabitants of the upper respiratory tract. It was concluded that the presence of inflammatory cells, eosinophils, and mast cells in the tracheobronchial aspirates from clinically normal foals is a common finding. These cytologic findings were consistent in the samples collected from foals at 8, 16, and 24 weeks of age. It was also concluded that bacteria with recognized pathogenicity can be isolated from TBA from clinically normal foals and were most frequently isolated from 1- to 2-month-old foals or those with cytologic evidence of inflammation, even in the absence of clinical signs of respiratory tract disease.

The thiamylal sparing effect of midazolam was studied in 30 healthy Beagle and mixed-breed dogs. Using a replicated Latin square design, all dogs were given placebo (saline solution) and 0.025, 0.05, 0.1, and 0.2 mg of midazolam/kg of body weight prior to IV administration of thiamylal sodium. The 0.1 and 0.2 mg/kg dosages significantly decreased the amount of thiamylal required to obtund swallowing reflex and easily achieve endotracheal intubation. Midazolam at 0.1 and 0.2 mg/kg reduced thiamylal requirement by 16.4% and 18.9%, respectively, whereas the 0.05 mg/kg dosage decreased thiamylal requirement by only 6.8%. The 0.2 mg/kg dosage did not further decrease thiamylal requirement beyond that achieved with the 0.1 mg/kg dosage of midazolam. This study demonstrates that the preanesthetic IV administration of midazolam reduces the thiamylal dose necessary to accomplish intubation. The optimal preanesthetic dosage (lowest dosage with significant effect) was 0.1 mg/kg.

The role of endotoxin in the pathogenesis of acute pneumonic pasteurellosis is uncertain. Recently, we reported that Escherichia coli-derived endotoxin given by airway inoculation fails to induce lung injury in calves. Because Pasteurella haemolytica-derived endotoxin may differ substantially from E coli in its pathogenicity, we repeated these studies with Pasteurella endotoxin. Intratracheal inoculation of P haemolytica endotoxin caused hypoxemia and increased the alveolar-arterial oxygen differences without causing hypercarbia or changes in lung mechanical properties and volumes. In contrast, IV inoculation of endotoxin caused systemic hypotension, leukopenia, gas exchange impairment, increased total pulmonary resistance, and decreased dynamic compliance. Both routes of inoculation increased serum endotoxin concentrations and were associated with areas of pulmonary hemorrhage, edema, and acute inflammation. We concluded that P haemolytica-derived endotoxin is pathogenic by IV and airway routes of inoculation, and therefore differs from E coli endotoxin in its ability to induce lung lesions in calves.

During acute bouts of recurrent airway obstruction (heaves) in horses, neutrophils that are capable of increased production of reactive oxygen species accumulate in the airways. In the study reported here, the effect of hydrogen peroxide (H2O2; 1 micromolar to 0.1M), one of these reactive oxygen species products, on the responses of isolated trachealis muscle of horses was determined. Before and after incubation with H2O2, contractile responses to acetylcholine, electrical field stimulation (EFS), 127 mM KCl, and relaxation responses to isoproterenol and activation of the nonadrenergic noncholinergic inhibitory response (iNANC) were evaluated. Beginning at 1 mM, H2O2 contracted trachealis muscle in a concentration-dependent manner. This contraction was unaffected by atropine (1 micromolar), tetrodotoxin (1 micromolar), or 1 micromolar meclofenamate. Contraction of trachealis muscle in response to H2O2 is, therefore, not attributable to release of prostaglandins, acetylcholine, or other neurotransmitters. Above a concentration of 0.1 mM, H2O2 depressed the responses to EFS. acetylcholine, and KCl in a concentration-dependent manner. At 0.1M, H2O2 decreased the maximal responses to EFS, acetylcholine, and KCl by 62.7 +/- 7.2, 60.58 +/- 6.12, and 37.8 +/- 9.54%, respectively. In the presence of meclofenamate (1 micromolar), partial but significant protection against 1 to 100 mM H2O2 was observed. In tracheal strips contracted with 0.3 micromolar methacholine, H2O2 had no effect on the isoproterenol concentration-response curve. Up to a concentration of 100 mM, H2O2 had no effect on iNANC response. However, in the presence of 100 mM H2O2, this response was abolished in 2 of 4 horses. We conclude that high concentrations of H2O2 affected the responses of airway smooth muscle by actions on neurotransmission, muscarinic receptors, and downstream from receptors; some of the H2O2 effects were in part mediated by cyclooxygenase products; and H2O2 had no effect on beta-adrenergic- or iNANC-induced relaxation.

To measure tracheal mucociliary transport rate (TMTR) in awake dogs, restrained in dorsal recumbency, 99mtechnetium-labeled macroaggregated albumin was administered by tracheal injection, and the cephalic movement of boluses containing the radiopharmaceutical was detected by a gamma camera positioned lateral to the dog's head and neck. The distance traveled by each bolus was measured, relative to external markers placed a known distance apart. Tracheal mucociliary transport rates were calculated by dividing the measured distance of radiopharmaceutical movement by elapsed time. The technique was efficient and well tolerated. Mean (+/- SD) TMTR was 35.3 +/- 15.9 mm/min. Significant (P = 0.029) difference in TMTR was found between males and females, but significant difference attributable to age of the dog was not detected. This method of measuring TMTR in awake dogs has potential for evaluation of clinical animal patients with suspected tracheal mucociliary abnormalities.

A protected catheter brush introduced by fiberoptic bronchoscopy was used to sample the tracheal and bronchial mucosa in 28 horses with small airway disease. Tracheal and bronchial brushings were examined for the presence of fungi, aerobic and anaerobic bacteria, and a cytoiogical evaluation was also done on fluid collected by the bronchoalveolar lavage (BAL) technique. Microorganisms (bacteria and fungi) were isolated more often in tracheal brushings (53.6%) than in bronchial brushings (10.7%). Anaerobic bacteria were not isolated. Results of this study indicate that fiberoptic bronchoscopy using a protected catheter brush is an easy and practical technique to obtain minimally contaminated samples for isolation of microorganisms from the lower respiratory tract of horses. However, no association was observed between isolation of high numbers of microorganisms from the bronchi and severity of small airway disease.

Strips of trachealis muscle were dissected from the mid-cervical portion of the trachea from horses that were free of respiratory tract disease. The epithelium and mucosa were removed from one group of tissues and were left intact in a second group of tissues. Each tissue was suspended in a bath filled with Krebs-bicarbonate solution that was aerated with 5% CO2 in oxygen and maintained at 37 C. Isometric tension was continuously recorded. The contractile response to square-wave electrical stimulations increased as frequency (3, 5, 10, 15, 20, 25, and 30 Hz), voltage (10, 15, 18, and 25 V), and pulse duration (0.2, 0.5, 1.0, 1.5, and 2.0 ms) increased in tissues with the epithelium and mucosa intact. A stimulus of 18 V, 20 Hz, and 0.5 ms induced maximal contraction. Atropine (10(-6) M) abolished the response to 18 V and 0.5 ms at all frequencies. The increase in active isometric tension was concentration dependent when acetylcholine (10(-9) to 10(-4) M) was added to the baths in 0.5-logarithmic increments. Tissues that were contracted in response to acetylcholine (10(-5) M) had a concentration-dependent decrease in active isometric tension when isoproterenol was added to the baths in 0.5-logarithmic increments (10(-9) to 10(-4) M). The contraction and relaxation curves were qualitatively similar, but quantitatively different in tissues with and without the epithelium and mucosa. Removing the epithelium and mucosa increased the contractile response to acetylcholine at bath concentrations of 3.1 X 10(-7) M and 10(-6) M. The presence of epithelium and mucosa enhanced the magnitude of isoproterenol-induced relaxations. We concluded that electrical stimulation released acetylcholine from isolated equine trachealis muscle, that isoproterenol induced relaxation of the trachealis muscle, and that the magnitude of the responses to exogenous agonists depended on the presence of epithelium and mucosa.