Lung stiffness of C57BL/6 versus BALB/c mice

Figures

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  Figure 1. Body weight of mice (A) and total lung wet weight (B) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. N = 9 per group.

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  Figure 2. Respiratory mechanics measured through oscillometry by the flexiVent. Respiratory system resistance (Rrs) (A), respiratory system elastance (Ers) (B), tissue resistance (G) (C), tissue elastance (H) (D) and hysteresivity (η) (E) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. Significant differences are indicated by asterisks (*, ** and *** p < 0.05, 0.01 and 0.001 respectively). N = 9 per group.

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  Figure 3. FlexiVent readouts from the deep inflation (DI) maneuver and the stepwise, pressure-controlled, partial pressure–volume (P–V) maneuver. Inspiratory capacity (IC) (A), quasi-static elastance (Est) (B) and the parameter K of Salazar-Knowles equation (C) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. Significant differences are indicated by asterisks (**** is p < 0.0001). N = 9 per group.

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  Figure 4. FlexiVent readouts from the ramp-style, full-range, pressure–volume (P–V) maneuver and the excised lung volume measured by liquid displacement. Total lung capacity (TLC) (A), vital capacity (VC) (B), residual volume (RV) (C), expiratory reserve volume (ERV) (D), functional residual capacity (FRC) (E), lung volume at 10 cmH2O expressed in percentage of TLC (V10_TLC) (F), lung compliance (G) and excised lung volume (H) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. Significant differences are indicated by asterisks (*, ** and **** are p < 0.05, 0.01 and 0.0001, respectively). N = 9 per group.

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  Figure 5. Protocol to measure lung tissue mechanics of the right inferior lobe in vitro. Each lobe was subjected to 3 consecutive sequences of sinusoidal small-amplitude strain oscillations for 2 min followed by a half-sine stretch of 30%. A representative strain trace is shown in (A). The green section prior to the second and the third 30% stretches are locations where the mechanical properties of the lobe (i.e., elastance, resistance and hysteresivity) were calculated during the small-amplitude oscillations. They were selected to be away (i.e., 1 min) from the large 30% stretch, where the mechanical properties had nearly reached a steady-state. The blue and red sections are locations of the second and third half-sine stretches of 30%, where the mechanical properties of the lobe were calculated during the large-amplitude oscillations. They were selected because they were the first 30% stretches where the mechanical properties of the lobe had reached a near steady-state. The corresponding force trace before, during, and after the second 30% stretch is shown in (B). The corresponding force-strain trace is shown in (C). The blue and red lines are actual data fits during the 30% stretch and…

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  Figure 6. Lung tissue mechanics measured in vitro on the right inferior lobe. Resistance, elastance and hysteresivity measured during either small-amplitude oscillations (A) or large-amplitude oscillation (B) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. Significant differences are indicated by asterisks (* is p < 0.05). N = 8 per group.

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  Figure 7. The content of airway smooth muscle and lung collagen. Representative histological images (A), histological determinations of the airway smooth muscle content (unitless; because it was calculated for each airway as the area of smooth muscle divided by the square of the basement membrane perimeter) (B) and the lung collagen fractional area (C), and the determination of the lung hydroxyproline content (D) are shown for BALB/c (open circles) and C57BL/6 (solid squares) mice. Data are individual results, together with means ± SD. Significant differences are indicated by asterisks (* is p < 0.05). N = 9 per group.