Healthy Rat Lungs Research Articles

The effects of different lung parts, age, and batches on the lung microbiota of healthy rats

Background Rat models are valuable tools to study the lung microbiota in diseases. Yet the impacts of different lung parts, young and mature adult stages, and the different batches of the same conditions on the healthy rat lung microbiome have not been investigated. Methods The rat lung microbiome was analyzed to clarify the lung part-dependent and age-dependent differences and to evaluate the effects of several ‘batch environmental factors’ on normal rats, after eliminating potential contamination. Results The results showed that the contamination could be identified and excluded. The lung microbiome from left and right lung parts was very similar so one representative part could be used in the microbiome study. There were significantly different lung microbial communities between the young and mature adult groups, and also between the different feeding batches groups of the same repetitive feeding conditions, but a common lung microbiota characterized by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria as the most dominant phyla were present in all adult rats. It indicated that the experiment under the same condition of the same rats batch was needed to compare the difference in the lung microbiota and repeated experiments were necessary to confirm the results. Conclusion These data represented that the lung bacterial communities were dynamic and rapidly susceptible to environmental influence, clustered strongly by age or different feeding batches but similar in the different lung tissue parts. This study improved the basic understanding of the potential effects on the lung microbiome of healthy rats.

A Rodent Model of Human-Dose-Equivalent 5-Fluorouracil: Toxicity in the Liver, Kidneys, and Lungs.

5-Fluorouracil (5-FU) is a chemotherapy drug widely used to treat a range of cancer types, despite the recurrence of adverse reactions. Therefore, information on its side effects when administered at a clinically recommended dose is relevant. On this basis, we examined the effects of the 5-FU clinical treatment on the integrity of the liver, kidneys, and lungs of rats. For this purpose, 14 male Wistar rats were divided into treated and control groups and 5-FU was administered at 15 mg/kg (4 consecutive days), 6 mg/kg (4 alternate days), and 15 mg/kg on the 14th day. On the 15th day, blood, liver, kidney, and lung samples were collected for histological, oxidative stress, and inflammatory evaluations. We observed a reduction in the antioxidant markers and an increase in lipid hydroperoxides (LOOH) in the liver of treated animals. We also detected elevated levels of inflammatory markers, histological lesions, apoptotic cells, and aspartate aminotransferase. Clinical treatment with 5-FU did not promote inflammatory or oxidative alterations in the kidney samples; however, histological and biochemical changes were observed, including increased serum urea and uric acid. 5-FU reduces endogenous antioxidant defenses and increases LOOH levels in the lungs, suggesting oxidative stress. Inflammation and histopathological alterations were also detected. The clinical protocol of 5-FU promotes toxicity in the liver, kidneys, and lungs of healthy rats, resulting in different levels of histological and biochemical alterations. These results will be useful in the search for new adjuvants to attenuate the adverse effects of 5-FU in such organs.

Т1 mappingofratlungsin19 FMRIusing octafluorocyclobutane.

To demonstrate the feasibility of using octafluorocyclobutane (OFCB, c-C4 F8 ) for T1 mapping of lungs in 19 F MRI. The study was performed at 7 T in three healthy rats and three rats with pulmonary hypertension. To increase the sensitivity of 19 F MRI, a bent-shaped RF coil with periodic metal strips structure was used. The double flip angle method was used to calculate normalized transmitting RF field (B1n + ) maps and for correcting T1 maps built with the variable flip angle (VFA) method. The ultrashort TE pulse sequence was applied for acquiring MR images throughout the study. The dependencies of OFCB relaxation times on its partial pressure in mixtures with oxygen, air, helium, and argon were obtained. T1 of OFCB linearly depended on its partial pressure with the slope of about 0.35 ms/kPa in the case of free diffusion. RF field inhomogeneity leads to distortion of T1 maps built with the VFA method, and therefore to high standard deviation of T1 in these maps. To improve the accuracy of the T1 maps, the B1n + maps were applied for VFA correction. This contributed to a 2-3-fold decrease in the SD of T1 values in the corresponding maps compared with T1 maps calculated without the correction. Three-dimensional T1 maps were obtained, and the mean T1 in healthy rat lungs was 35 ± 10 ms, and in rat lungs with pulmonary hypertension-41 ± 9 ms. OFCB has a spin-rotational relaxation mechanism and can be used for 19 F T1 mapping of lungs. The calculated OFCB maps captured ventilation defects induced by edema.

Effect of inhaled oxygen concentration on 129 Xe chemical shift of red blood cells in rat lungs.

To investigate the dependence of dissolved 129 Xe chemical shift on the fraction of inhaled oxygen, Fi O2 , in the lungs of healthy rats. The chemical shifts of 129 Xe dissolved in red blood cells, δRBC , and blood plasma and/or tissue, δPlasma , were measured using MRS in 12 Sprague Dawley rats mechanically ventilated at Fi O2 values of 0.14, 0.19, and 0.22. Regional effects on the chemical shifts were controlled using a chemical shift saturation recovery sequence with a fixed delay time. MRS was also performed at an Fi CO2 value of 0.085 to investigate the potential effect of the vascular response on δRBC and δPlasma . δRBC increased with decreasing Fi O2 (P = .0002), and δPlasma showed no dependence on Fi O2 (P = .23). δRBC at Fi CO2 = 0 (210.7 ppm ± 0.1) and at Fi CO2 = 0.085 (210.6 ppm ± 0.2) were not significantly different (P = .67). δPlasma at Fi CO2 = 0 (196.9 ppm ± 0.3) and at Fi CO2 = 0.085 (197.0 ppm ± 0.1) were also not significantly different (P = .81). Rat lung δRBC showed an inverse relationship to Fi O2 , opposite to the relationship previously demonstrated for in vitro human blood. Rat lung δRBC did not depend on Fi CO2 .

A Preclinical Safety Study of Thyroid Hormone Instilled into the Lungs of Healthy Rats-an Investigational Therapy for ARDS.

Acute respiratory distress syndrome (ARDS) is a severe, life-threatening form of respiratory failure characterized by pulmonary edema, inflammation, and hypoxemia due to reduced alveolar fluid clearance (AFC). Alveolar fluid clearance is required for recovery and effective gas exchange, and higher rates of AFC are associated with reduced mortality. Thyroid hormones play multiple roles in lung function, and L-3,5,3'-triiodothyronine (T3) has multiple effects on lung alveolar type II cells. T3 enhances AFC in normal adult rat lungs when administered intramuscularly and in normal or hypoxia-injured lungs when given intratracheally. The safety of a commercially available formulation of liothyronine sodium (synthetic T3) administered intratracheally was assessed in an Investigational New Drug Application-enabling toxicology study in healthy rats. Instillation of the commercial formulation of T3 without modification rapidly caused tracheal injury and often mortality. Intratracheal instillation of T3 that was reformulated and brought to a neutral pH at the maximum feasible dose of 2.73 µg T3 in 300 µl for 5 consecutive days had no clinically relevant T3-related adverse clinical, histopathologic, or clinical pathology findings. There were no unscheduled deaths that could be attributed to the reformulated T3 or control articles, no differences in the lung weights, and no macroscopic or microscopic findings considered to be related to treatment with T3. This preclinical safety study has paved the way for a phase I/II study to determine the safety and tolerability of a T3 formulation delivered into the lungs of patients with ARDS, including coronavirus disease 2019-associated ARDS, and to measure the effect on extravascular lung water in these patients. SIGNIFICANCE STATEMENT: There is growing interest in treating lung disease with thyroid hormone [triiodothyronine (T3)] in pulmonary edema and acute respiratory distress syndrome (ARDS). However, there is not any published experience on the impact of direct administration of T3 into the lung. An essential step is to determine the safety of multiple doses of T3 administered in a relevant animal species. This study enabled Food and Drug Administration approval of a phase I/II clinical trial of T3 instillation in patients with ARDS, including coronavirus disease 2019-associated ARDS (T3-ARDS ClinicalTrials.gov Identifier NCT04115514).

Mapping regional strain in anesthetised healthy subjects during spontaneous ventilation

IntroductionBreathing produces a phenomenon of cyclic deformation throughout life. Biomechanically, deformation of the lung is measured as strain. Regional strain recently started to be recognised as a tool in the...

Applying Positive End-Expiratory Pressure During Mechanical Ventilation Causes Pulmonary Redox Imbalance and Inflammation in Rats.

Mechanical ventilation (MV) may induce or aggravate lung injury through the production of cytokines, inflammatory infiltration of neutrophils, and changes in the permeability of the alveolar-capillary barrier. The use of positive end-expiratory pressure (PEEP) helps improve gas exchanges avoiding alveolar collapse at the end of expiration. The present study aimed to analyze inflammatory response and redox imbalance in lungs of rats submitted to MV with and without PEEP. Eighteen Wistar rats were divided into three groups: control (CG), PEEP group (PG), and zero PEEP (ZEEP) group (ZG). PG and ZG were submitted to MV for 60 min with or without PEEP, respectively. Subsequently, the animals were euthanized, and blood, bronchoalveolar lavage fluid, and lungs were collected for analyses. The number of neutrophils was higher in PG compared with CG. Leucocyte and neutrophil influx in bronchoalveolar lavage fluid was higher in PG compared with CG. PG showed an increase in alveolar area compared with the other groups. There were increases in the levels of chemokines, CCL3 and CCL5, in PG compared with CG. There were increases in oxidation of lipids and proteins in PG compared with other groups. There were increases in the activity of superoxide dismutase and catalase in PG compared with CG and ZG. However, there was a decrease in the ratio of glutathione to glutathione disulfide in PG compared with other groups. MV with PEEP caused redox imbalance and inflammation in lungs of healthy rats.

Salvianolic acid B as an anti-emphysema agent I: In vitro stimulation of lung cell proliferation and migration, and protection against lung cell death, and in vivo lung STAT3 activation and VEGF elevation

Emphysema causes progressive and life-threatening alveolar structural destruction/loss, yet remains irreversible and incurable to date. Impaired vascular endothelial growth factor (VEGF) signaling has been proposed as a new pathogenic mechanism, and if so, VEGF recovery may enable reversal of emphysema. Thus, we hypothesized that salvianolic acid B (Sal-B), a polyphenol in traditional Chinese herbal danshen, is an alveolar structural recovery agent for emphysema by virtue of VEGF stimulation/elevation via activation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3), as stimulating lung cell proliferation and migration, and protecting against lung cell death. Using in vitro human lung microvascular endothelial (HMVEC-L) and alveolar epithelial (A549) cell systems, Sal-B was examined for 1) stimulation of cell proliferation by the MTT and BrdU assays; 2) promotion of cell migration by the scratch wound closure assay; 3) protection against emphysema-like induced cell death by the trypan blue exclusion and flow cytometry assays; and 4) mechanistic involvement of JAK2/STAT3/VEGF in these activities. Sal-B was also spray-dosed to the lungs of healthy rats for two weeks to verify the lung's STAT3 activation and VEGF elevation by western blot, as well as the absence of functional and morphological abnormalities. All the in vitro cell-based activities were concentration-dependent. At 25 μM, Sal-B 1) stimulated cell proliferation by 1.4–2.6-fold; 2) promoted migratory cell wound closure by 1.5–1.7-fold; and 3) protected against cell death induced with H2O2 (oxidative stress) and SU5416 (VEGF receptor blockade) by 49–86%. JAK2 and STAT3 inhibitors and VEGF receptor antagonist each opposed these Sal-B's activities by over 65%, suggesting the mechanistic involvement of JAK2/STAT3 activation and VEGF stimulation/elevation. In rats, Sal-B at 0.2 mg/kg enabled 1.9 and 1.5-fold increased STAT3 phosphorylation and VEGF elevation in the lungs, respectively, while causing no functional and morphological abnormalities. Hence, Sal-B was projected to be a new class of anti-emphysema agent capable of reversing alveolar structural destruction/loss via JAK2/STAT3/VEGF-dependent stimulation of lung cell proliferation and migration, and inhibition of induced lung cell death.

Anatomic Characterization of Intrapulmonary Bronchopulmonary Anastomoses in Healthy Rat Lungs

Many neonates with pulmonary hypertension die from right‐to‐left shunt and hypoxemia soon after birth. Intrapulmonary bronchopulmonary anastomotic pathways (IBAPs) have been observed in the lungs of these infants. We indirectly characterized right‐to‐left shunt recruitment by hypoxia (12% O2) in healthy humans and animals that can be reversed by 100% O2. We hypothesized that IBAPs are a normal lung feature whose recruitment is induced by hypoxia. Anesthetized rats were ventilated with 21% or 12% O2 for 20 minutes. Lungs were then immediately removed, airway fixed with 10% formalin, sectioned, and stained for the histological evaluation of IBAPs. The direction of blood flow through these pathways was evaluated by injecting red and green fluorescent microspheres into the right (RV) and left (LV) ventricles of rats ventilated with 12% or 100% O2 and determining their abundance in the lung. Histological sections demonstrated abundant IBAPs in 12% O2‐ventilated lungs, connecting the pulmonary and bronchial arterial trees, but not 21% O2‐ventilated lungs. Consistent with right‐to‐left shunt through these pathways, microspheres injected into the right ventricle were found in the pleural and bronchial vascular beds, but LV‐injected spheres were not found in the pleura. In 100% O2‐ventilated lungs, both RV‐ and LV‐injected microspheres were found coincidentally in pleural vessels, suggesting a possible left‐to‐right shunt. Future studies will aim to anatomically determine the vessel type containing co‐localized red and green microspheres and further characterize IBAPs, including describing their receptor expression.Support or Funding InformationUniversity of Iowa Start‐Up Fund

Aerosol transport throughout inspiration and expiration in the pulmonary airways.

Little is known about transport throughout the respiration cycle in the conducting airways. It is challenging to appropriately describe the time-dependent number of particles entering back into the model during exhalation. Modeling the entire lung is not feasible; therefore, multidomain methods must be used. Here, we present a new framework that is designed to simulate particles throughout the respiration cycle, incorporating realistic airway geometry and respiration. This framework is applied for a healthy rat lung exposed to ∼1μm diameter particles, chosen to facilitate parameterization and validation. The flow field is calculated in the conducting airways (3D domain) by solving the incompressible Navier-Stokes equations with experimentally derived boundary conditions. Particles are tracked throughout inspiration by solving a modified Maxey-Riley equation. Next, we pass the time-dependent particle concentrations exiting the 3D model to the 1D volume conservation and advection-diffusion models (1D domain). Once the 1D models are solved, we prescribe the time-dependent number of particles entering back into the 3D airways to again solve for 3D transport. The coupled simulations highlight that about twice as many particles deposit during inhalation compared to exhalation for the entire lung. In contrast to inhalation, where most particles deposit at the bifurcation zones, particles deposit relatively uniformly on the gravitationally dependent side of the 3D airways during exhalation. Strong agreement to previously collected regional experimental data is shown, as the 1D models account for lobe-dependent morphology. This framework may be applied to investigate dosimetry in other species and pathological lungs.

The differential effects of inspiratory, expiratory, and combined resistive breathing on healthy lung.

Combined resistive breathing (CRB) is the hallmark of obstructive airway disease pathophysiology. We have previously shown that severe inspiratory resistive breathing (IRB) induces acute lung injury in healthy rats. The role of expiratory resistance is unknown. The possibility of a load-dependent type of resistive breathing-induced lung injury also remains elusive. Our aim was to investigate the differential effects of IRB, expiratory resistive breathing (ERB), and CRB on healthy rat lung and establish the lowest loads required to induce injury. Anesthetized tracheostomized rats breathed through a two-way valve. Varying resistances were connected to the inspiratory, expiratory, or both ports, so that the peak inspiratory pressure (IRB) was 20%–40% or peak expiratory (ERB) was 40%–70% of maximum. CRB was assessed in inspiratory/expiratory pressures of 30%/50%, 40%/50%, and 40%/60% of maximum. Quietly breathing animals served as controls. At 6 hours, respiratory system mechanics were measured, and bronchoalveolar lavage was performed for measurement of cell and protein concentration. Lung tissue interleukin-6 and interleukin-1β levels were estimated, and a lung injury histological score was determined. ERB produced significant, load-independent neutrophilia, without mechanical or permeability derangements. IRB 30% was the lowest inspiratory load that provoked lung injury. CRB increased tissue elasticity, bronchoalveolar lavage total cell, macrophage and neutrophil counts, protein and cytokine levels, and lung injury score in a dose-dependent manner. In conclusion, CRB load dependently deranges mechanics, increases permeability, and induces inflammation in healthy rats. ERB is a putative inflammatory stimulus for the lung.

Soluble form of the receptor for advanced glycation end-products attenuates inflammatory pathogenesis in a rat model of lipopolysaccharide-induced lung injury

Acute respiratory distress syndrome (ARDS) is a severe respiratory failure caused by acute lung inflammation. Recently, the receptor for advanced glycation end-products (RAGE) has attracted attention in the lung inflammatory response. However, the function of soluble form of RAGE (sRAGE), which is composed of an extracellular domain of RAGE, in ARDS remains elusive. Therefore, we investigated the dynamics of pulmonary sRAGE and the effects of exogenous recombinant human sRAGE (rsRAGE) under intratracheal lipopolysaccharide (LPS)-induced lung inflammation. Our result revealed that RAGE was highly expressed on the alveolar type I epithelial cells in the healthy rat lung including sRAGE isoform sized 45 kDa. Under LPS-induced injured lung, the release of sRAGE into the alveolar space was increased, whereas the expression of RAGE was decreased with alveolar disruption. Treatment of the injured lung with rsRAGE significantly suppressed the lung edema, the neutrophils infiltration, the release of high mobility group box-1 (HMGB1), and the expressions of TNF-α, IL-1β and iNOS. These results suggest that the alveolar release of sRAGE may play a protective role against HMGB1 as well as exogenous pathogen-associated molecular patterns. Supplementary therapy with sRAGE may be an effective therapeutic strategy for ARDS.

Distribution of aerosolized particles in healthy and emphysematous rat lungs: Comparison between experimental and numerical studies

In silico models of airflow and particle deposition in the lungs are increasingly used to determine the therapeutic or toxic effects of inhaled aerosols. While computational methods have advanced significantly, relatively few studies have directly compared model predictions to experimental data. Furthermore, few prior studies have examined the influence of emphysema on particle deposition. In this work we performed airflow and particle simulations to compare numerical predictions to data from our previous aerosol exposure experiments. Employing an image-based 3D rat airway geometry, we first compared steady flow simulations to coupled 3D–0D unsteady simulations in the healthy rat lung. Then, in 3D–0D simulations, the influence of emphysema was investigated by matching disease location to the experimental study. In both the healthy unsteady and steady simulations, good agreement was found between numerical predictions of aerosol delivery and experimental deposition data. However, deposition patterns in the 3D geometry differed between the unsteady and steady cases. On the contrary, satisfactory agreement was not found between the numerical predictions and experimental data for the emphysematous lungs. This indicates that the deposition rate downstream of the 3D geometry is likely proportional to airflow delivery in the healthy lungs, but not in the emphysematous lungs. Including small airway collapse, variations in downstream airway size and tissue properties, and tracking particles throughout expiration may result in a more favorable agreement in future studies.

Sci—Thur PM: YIS — 05: Hyperpolarized Noble Gas Magnetic Resonance Imaging and Dynamic Spectroscopy of Rat Lungs

Magnetic Resonance (MR) imaging using hyperpolarized noble gases (HNG's), 3He and 129Xe, provide non‐invasive approaches for probing lung function and structure. In particular, measurement of HNG ventilated lung volumes (e.g., ventilation defects) and apparent diffusion coefficients (ADC) are useful for characterizing chronic obstructive pulmonary disease (COPD) and emphysema. Of particular interest, hyperpolarized 129Xe also dissolves in the lung parenchyma and blood compartments, offering an interesting palette of potential biomarkers of pulmonary disease, including quantifying xenon diffusing capacity in inflammatory disease and may be useful for assessing pulmonary perfusion. 129Xe dissolved in tissue and blood experience large chemical shifts and can be selectively saturated and allowed to recover as a function of delay time as in the chemically selective saturation recovery (CSSR) technique. CSSR has previously been used to study surface‐to‐volume ratio (S/V) and diffusing capacity of xenon (DXe) in the lung which is analogous to diffusing capacity of carbon monoxide. In this work, the 129Xe CSSR technique is used to measure S/V ratios and Dxelp in whole healthy rat lungs as a function of ventilated lung volume assessed with 3He MR imaging. The data follow theoretically predicted trends for Ttr, S/V and DXeLP. In parallel to this study, 3D 129Xe imaging was also investigated and compared to 3He for lung volume assessment in an effort to remove the reliance on 3He which is costly and scarce. Absolute ventilated volumes (|VLV|) derived from preliminary results for 3He and 129Xe were 9.74 mL and 9.14 mL respectively for a pressure of 9.1cmH2O.

Sci-Fri AM: Imaging - 01: Measurement of Ultra-Short and Long-Range 3 He Apparent Diffusion Coefficients in an Elastase-Induced Rat Model of Emphysema

Hyperpolarized Helium‐3 (3He) Magnetic Resonance(MR)imaging is a novel technique used for investigating structural and functional properties of the lungin vivo. In particular, 3He diffusionmeasurements have shown remarkable sensitivity for diagnosing Chronic Obstructive Pulmonary Disease (COPD), particularly emphysema. Restricted diffusion reduces the free diffusion coefficient, thus resulting in a measured apparent diffusion coefficient (ADC) related to the size of the acinus and alveoli. ADC has been predicted to behave anisotropically, and can be described by two components: (i) a longitudinal component along the acinus and (ii) a transverse component perpendicular to the acinus which depend on the diffusion time (δ). We measured3He ADC at both ultra short (< 1 ms) and long (δ=50 ms ‐ 1 s) diffusion times in both healthy rat lungs and rat lungs instilled with elastase to simulate emphysema. Ultra‐short domain ADC maps were measured using a 3.0 T MRimaging system, where the transverse ADC component was found to be most sensitive to elastase damage for diffusion times near 360 μs, consistent with theoretical models. Whole‐lung long‐range ADC measurements were acquired using a 74 mT MRimaging system, since the low magnetic field has the advantage of longer T2* from reduced susceptibility differences at the air‐tissue interfaces. Measured ADC correlated well with histology (i.e. mean linear intercept). Possible extension of this work to hyperpolarized Xenon‐129 (129Xe) anisotropic ADC measurements at low field is discussed, as an optimal diffusion time of 20.8 ms has been predicted, more favorable for clinical studies

Redox Balance and Cellular Inflammation in the Diaphragm, Limb Muscles, and Lungs of Mechanically Ventilated Rats

High tidal volume (VT) mechanical ventilation was shown to induce organ injury other than lung injury and systemic inflammation in animal models of ventilator-induced lung injury. The authors aimed to explore whether high VT mechanical ventilation per se induces early oxidative stress and inflammation in the diaphragm, limb muscles, and lungs of healthy rats exposed to ventilator-induced lung injury. Protein carbonylation and nitration, antioxidants (immunoblotting), and inflammation (immunohistochemistry) were evaluated in the diaphragm, gastrocnemius, soleus, tibialis anterior, and lungs of mechanically ventilated healthy rats and in nonventilated control animals (n = 8/group) for 1 h, using two different strategies (moderate VT [VT = 9 ml/kg] and high VT [VT = 35 ml/kg]). The main findings are summarized as follows: compared with controls, (1) the diaphragms and gastrocnemius of high-VT rats exhibited a decrease in reactive carbonyls, (2) the soleus and tibialis of high- and moderate-VT rodents showed a reduction in reactive carbonyls and malondialdehyde-protein adducts, (3) the lungs of high-VT rats exhibited a significant rise in malondialdehyde-protein adducts, (4) the soleus and tibialis of both high- and moderate-VT rats showed a reduction in protein nitration, (5) the lungs of high- and moderate-VT rats showed a reduction in antioxidant enzyme levels, but not in the muscles, and (6) the diaphragms and gastrocnemius of all groups exhibited very low inflammatory cell counts, whereas the lungs of high-VT rats exhibited a significant increase in inflammatory infiltrates. Although oxidative stress and inflammation increased in the lungs of rats exposed to high VT, the diaphragm and limb muscles exhibited a decline in oxidative stress markers and very low levels of cellular inflammation.

Improved technique for measurement of regional fractional ventilation by hyperpolarized 3He MRI

Quantitative measurement of regional lung ventilation is of great significance in assessment of lung function in many obstructive and restrictive pulmonary diseases. A new technique for regional measurement of fractional ventilation using hyperpolarized 3He MRI is proposed, addressing the shortcomings of an earlier approach that limited its use to small animals. The new approach allows for the acquisition of similar quantitative maps over a shortened period and requires substantially less 3He gas. This technique is therefore a better platform for implementation in large species, including humans. The measurements using the two approaches were comparable to a great degree, as verified in a healthy rat lung, and are very reproducible. Preliminary validation is performed in a lung phantom system. Volume dependency of measurements was assessed both in vivo and in vitro. A scheme for selecting an optimum flip angle is proposed. In addition, a dead space modeling approach is proposed to yield more accurate measurements of regional fractional ventilation using either method. Finally, sensitivity of the new technique to model parameters, noise, and number of included images were assessed numerically. As a prelude to application in humans, the technique was implemented in a large animal study successfully.

Blockade of leucocyte function-associated antigen-1 (LFA-1) decreases lymphocyte trapping in the normal pulmonary vasculature: studies in the isolated buffer-perfused rat lung.

Adhesion molecules regulate the migration of lymphocytes in lymphoid and non-lymphoid organs. In the lung, little is known about lymphocyte sticking and migration through the pulmonary vascular endothelium in physiological or pathological situations. Therefore the isolated buffer-perfused rat lung was used to investigate the mobilization of lymphocytes out of the normal lung into the venous effluent and to the bronchoalveolar space. The lymphocyte subset composition was characterized in the venous effluent, the lung tissue and the bronchoalveolar lavage (BAL) using immunocytology. Lymphocytes continuously left the normal lung at a total of 5.0 +/- 0.7 x 106 cells within the first hour of perfusion. The injection of 200 x 106 lymphocytes via the pulmonary trunk increased the venous release of lymphocytes by 170%. To investigate the effect of LFA-1 and CD44 on the adhesion of lymphocytes to the pulmonary endothelium, lymphocytes preincubated with an anti-LFA-1 MoAb, which blocks the interaction of LFA-1 and intercellular adhesion molecule-1 (ICAM-1), or lymphocytes preincubated with an anti-CD44 MoAb, were injected. The injection of LFA-1-blocked lymphocytes led to an increase by 70% of injected cells recovered in the perfusate within the first hour, whereas anti-CD44 treatment of injected lymphocytes had no effect. The LFA-1-blocked lymphocytes showed higher numbers of T and B cells in the effluent. Thus, the present experiments demonstrate that LFA-1 influences the trapping of lymphocytes in the vasculature of the healthy rat lung.

3D MRI of non-Gaussian 3He gas diffusion in the rat lung

In 3He magnetic resonance images of pulmonary air spaces, the confining architecture of the parenchymal tissue results in a non-Gaussian distribution of signal phase that non-exponentially attenuates image intensity as diffusion weighting is increased. Here, two approaches previously used for the analysis of non-Gaussian effects in the lung are compared and related using diffusion-weighted 3He MR images of mechanically ventilated rats. One approach is model-based and was presented by Yablonskiy et al., while the other approach utilizes the second order decay contribution that is predicted from the cumulant expansion theorem. Total lung coverage is achieved using a hybrid 3D pulse sequence that combines conventional phase encoding with sparse radial sampling for efficient gas usage. This enables the acquisition of nine 3D images using a total of only ∼1 L of hyperpolarized 3He gas. Diffusion weighting ranges from 0 s/cm 2 to 40 s/cm 2. Results show that the non-Gaussian effects of 3He gas diffusion in healthy rat lungs are directly attributed to the anisotropic geometry of lung microstructure as predicted by the Yablonskiy model, and that quantitative analysis over the entire lung can be reliably repeated in time-course studies of the same animal.

Oxygen tension modulates transpulmonary passage of 50μm solid microspheres under physiologic conditions in healthy rat lungs

Oxygen tension modulates transpulmonary passage of 50μm solid microspheres under physiologic conditions in healthy rat lungs