Maximal forced expiratory maneuver to measure airway obstruction in allergen challenged mice

Combined forced oscillation and forced expiration measurements in mice for the assessment of airway hyperresponsiveness

Background

Pulmonary function has been reported in mice using negative pressure-driven forced expiratory manoeuvres (NPFE) and the forced oscillation technique (FOT). However, both techniques have always been studied using separate cohorts of animals or systems. The objective of this study was to obtain NPFE and FOT measurements at baseline and following bronchoconstriction from a single cohort of mice using a combined system in order to assess both techniques through a refined approach.

Methods

Groups of allergen- or sham-challenged ovalbumin-sensitized mice that were either vehicle (saline) or drug (dexamethasone 1 mg/kg ip)-treated were studied. Surgically prepared animals were connected to an extended flexiVent system (SCIREQ Inc., Montreal, Canada) permitting NPFE and FOT measurements. Lung function was assessed concomitantly by both techniques at baseline and following doubling concentrations of aerosolized methacholine (MCh; 31.25 - 250 mg/ml). The effect of the NPFE manoeuvre on respiratory mechanics was also studied.

Results

The expected exaggerated MCh airway response of allergic mice and its inhibition by dexamethasone were detected by both techniques. We observed significant changes in FOT parameters at either the highest (Ers, H) or the two highest (Rrs, R_N, G) MCh concentrations. The flow-volume (F-V) curves obtained following NPFE manoeuvres demonstrated similar MCh concentration-dependent changes. A dexamethasone-sensitive decrease in the area under the flow-volume curve at the highest MCh concentration was observed in the allergic mice. Two of the four NPFE parameters calculated from the F-V curves, FEV_0.1 and FEF50, also captured the expected changes but only at the highest MCh concentration. Normalization to baseline improved the sensitivity of NPFE parameters at detecting the exaggerated MCh airway response of allergic mice but had minimal impact on FOT responses. Finally, the combination with FOT allowed us to demonstrate that NPFE induced persistent airway closure that was reversible by deep lung inflation.

Conclusions

We conclude that FOT and NPFE can be concurrently assessed in the same cohort of animals to determine airway mechanics and expiratory flow limitation during methacholine responses, and that the combination of the two techniques offers a refined control and an improved reproducibility of the NPFE.

Histologic analysis of zafirlukast's effect on capsule formation around silicone implants

BACKGROUND

The most common complication experienced by patients who have undergone mammary implant surgery is capsular contracture. This matter concerns physicians and patients, but to date, there is no effective way to avoid this complication. Surgical intervention usually is required. In 2002, the use of zafirlukast, a leukotriene inhibitor (a drug used for asthma treatment), was reported for the treatment of capsular contracture, with good results.

METHODS

For this study, 30 female Wistar rats were used. These animals received two silicone implants each: one with a smooth surface and one with a textured surface. All the animals received daily intraperitoneal injections for 90 days and were divided as follows: control group (C) receiving only saline solution, experimental group 1 (E-I) receiving 1.25 mg/kg/day of zafirlukast, and experimental group 2 (E-II) receiving 5 mg/kg/day of zafirlukast. Histologic analysis used hematoxilin and eosin to verify vessels, capsule thickness, and inflammatory cells. Immunoistochemical analysis with smooth muscle anti-actin antibody was used for myofibroblast verification. Picro-Sirius under polarized light was used for collagen analysis.

RESULTS

Textured implant experimental groups presented smaller numbers of vessels, thinner capsules, lower collagen density, and smaller numbers of mastocytes and eosinophils than the control group. No significant differences were found in smooth surface implants, as compared with the control group.

CONCLUSION

Zafirlukast reduced the occurrence of factors directly and indirectly connected with capsular contracture.

Small airway changes in healthy and ovalbumin-treated mice during quasi-static lung inflation

Previously, we developed a synchrotron radiation CT system to evaluate the morphometric changes (length and diameter, D) and small airway compliance (sC(aw)) of euthanized mice under quasi-static inflation [Sera, T., Uesugi, K., Yagi, N., 2005. Localized morphometric deformations of small airways and alveoli in intact mouse lungs under quasi-static inflation. Respir. Physiol. Neurobiol. 147, 51-63). Using this system, this study compared normal and asthmatic small airways. Ovalbumin-treated mice were used as an asthma model. Compared with the values at functional residual capacity, D of normal and asthmatic small airways (D<200microm) increased by 48% and 36% at the end of tidal inspiration. For larger airways (D>500microm), the increases were 23% and 20%, respectively. The ratio of the sC(aw) of asthmatic small airways to that of healthy small airways was 0.57, and the ratio was 0.70 for larger airways. The morphometric changes and sC(aw) in asthma model mice were significantly lower than those of healthy mice. The differences in sC(aw) between healthy and asthma model mice were greater for smaller airways.