Peribronchovascular Interstitium Research Articles

Malária pulmonar: aspectos na tomografia computadorizada de alta resolução - relato de caso

Neste trabalho é relatado o caso de paciente do sexo masculino, de 38 anos de idade, que desenvolveu quadro de malária com comprometimento pulmonar. A tomografia computadorizada de alta resolução evidenciou espessamento de septos interlobulares e de bainhas peribroncovasculares, com áreas esparsas de atenuação em vidro fosco e de consolidações, além de derrame pleural bilateral, aspectos compatíveis com edema pulmonar. O paciente recebeu tratamento específico, evoluindo bem e tendo alta 11 dias após a internação.

Alterations in the immunohistochemical distribution patterns of vascular endothelial growth factor receptors Flk1 and Flt1 in bleomycin-induced rat lung fibrosis.

To investigate the role of vascular endothelial growth factor (VEGF) in fibrogenesis, the distribution patterns of the VEGF receptors Flt1 and Flk1 were studied by immunohistochemistry, double immunofluorescence, and immunoelectron microscopy in normal (n=2) and bleomycin-treated (n=21) adult rats. Lungs were studied at 5, 24, 28, 35, and 42 days after treatment (p.t.). Flt1, Flk1, and VEGF immunoreactivity localised predominantly to the pulmonary epithelium. In control lungs, Flt1 immunoreactivity was present in ciliated bronchial epithelium and type 2 pneumocytes, Flk1 in Clara cells, and VEGF in Clara cells and type 2 pneumocytes. Flk1 localised to mast cells, present in the peribronchovascular and pleural interstitium only. Flt1- and Flk1-mRNAs were observed in Clara cells and type 2 pneumocytes. Bleomycin-induced fibrogenesis was characterised by a decrease in Flk1 immunoreactivity of Clara cells, and an increase in VEGF-immunoreactive myofibroblasts and type 2 pneumocytes by day 5 p.t., followed by a progressive accumulation of Flk1-immunoreactive mast cells by day 24 p.t. in fibrotic lesions containing VEGF-immunoreactive myofibroblasts. After 42 days, fibrotic regions were densely populated by mast cells. Since mast cells are known to be chemotactically attracted by VEGF, we suggest that VEGF/Flk1 represents the molecular link between proliferation of myofibroblasts, accumulation of mast cells, and the burst of fibrosis at sites of initial lesions in bleomycin-induced fibrosis.

Peribronchovascular interstitium of the pulmonary hilum: normal and abnormal findings on thin-section electron-beam CT.

The peribronchovascular interstitium, including bronchial vessels and lymphatic channels, is an important anatomic component of the lung, especially the pulmonary hilum [1-3] (Fig.1). Various pathologic processes involve and spread along this interstitium [4, 5]. Although it has been difficult to accurately evaluate the morphologic changes occurring in the peribronchovascular interstitium with conventional CT or MR imaging [6], spiral CT and electron-beam CT can show these changes clearly and consistently [7, 8]. A judgement as to whether the peribronchovascular interstitium is normal or abnormal is necessary for the CT diagnosis of pulmonary hilar lesions. In this assay, the normal peribronchovascular interstitium and various pathologic processes involving this interstitium are shown as they appear on thin-section electron-beam CT scans.

RESPIRATORY BRONCHIOLITIS-ASSOCIATED INTERSTITIAL LUNG DISEASE

Respiratory bronchiolitis-associated interstitial lung disease is a distinct clinical syndrome found in current or former cigarette smokers. The disease often is confused with other interstitial lung diseases, especially idiopathic pulmonary fibrosis. The clinical presentation resembles those of patients with other interstitial lung diseases--cough and dyspnea, with coarse rales on physical examination. Diffuse fine reticulonodular interstitial opacities are found on chest radiograph, usually with normal-appearing lung volumes. Bronchial wall thickening, prominence of peribronchovascular interstitium, small regular and irregular opacities, and small peripheral ring shadows are distinctive features. Pulmonary function testing may be normal but usually demonstrates mild to moderate restriction and normal or slightly reduced diffusing capacity. A mixed obstructive-restrictive pattern is common. Respiratory bronchiolitis-associated interstitial lung disease is characterized histologically by an inflammatory process involving the membranous and respiratory bronchioles. The pathologic findings are dominated by the finding of tan-brown pigmented macrophages within respiratory bronchioles and neighboring alveolar ducts and alveoli. The pulmonary parenchyma away from the airway usually is normal or may demonstrate mild hyperinflation. The clinical course and prognosis of respiratory bronchiolitis-associated interstitial lung disease are unknown. Most patients respond favorably to corticosteroids, with documented improvement in lung function and chest radiographs. Smoking appears to play a role in the pathogenesis, so smoking cessation is important in the resolution of this syndrome.

Airway level at which edema liquid enters the air space of isolated dog lungs.

To identify lung units associated with liquid leakage into the air space in high-pressure pulmonary edema, we perfused air-inflated dog lung lobes with albumin solution to fill the loose peribronchovascular interstitium. Next, we perfused the lobes for 90 s with fluorescent albumin solution then froze the lobes in liquid nitrogen. This procedure confined the fluorescent perfusate to the liquid flux pathway between the circulation and the air space and eliminated the previously filled peribronchovascular cuffs as a source of the fluorescence that entered the air space. We divided each frozen lobe into three horizontal layers and prepared fluorescence-microscopic sections of each layer. In the most apical layers where alveolar flooding was minimal, 10.6 +/- 21.0% (SD) of alveolar ducts were either fluorescence filled or air filled and continuous with fluorescence-filled alveoli. In the same layers, 11.0 +/- 19.0% of respiratory bronchioles were similarly labeled. No terminal bronchioles in these layers were fluorescence labeled. This suggested that the fluorescent albumin entered the air space across the epithelium of respiratory bronchioles, alveolar ducts, or their associated alveoli. To simulate an alternative explanation, i.e., that fluorescence first entered central airways then flowed into peripheral air spaces, we prepared two additional lobes that we first partially inflated with fluorescent albumin then filled to capacity with air. This pushed the fluorescent solution along the airways into the lung periphery. In these lobes the ciliary lining of bronchi and terminal bronchioles was fluorescence coated. By comparison, cilia in fluorescence-perfused lobes were not coated. We conclude that alveolar flooding in hydrostatic pulmonary edema occurs across the epithelium of alveolar ducts, respiratory bronchioles, or their associated alveoli.(ABSTRACT TRUNCATED AT 250 WORDS)

Growth rate of perivascular cuffs in liquid-inflated dog lung lobes.

In the early stages of pulmonary edema, excess liquid leaving the pulmonary exchange vessels accumulates in the peribronchovascular interstitium where it forms large peribronchovascular cuffs. The peribronchovascular interstitium therefore acts as a reservoir to protect the air spaces from alveolar flooding. The rate of liquid accumulation and the liquid storage capacity of the cuffs determine how quickly alveolar flooding is likely to follow once edema formation has begun. To measure the rate and capacity of interstitial filling we inflated 11 isolated degassed dog lung lobes with liquid to an inflation pressure of 14 cmH2O (total lung capacity) for 1-300 min, then froze the lobes in liquid N2. We made photographs of 20 randomly selected 12 X 8-mm cross sections from each lobe and measured cuff volume from the photographs by point-counting. We found that cuff volume increased from 2.2% of air-space volume after 1 min of inflation to 9.3% after 300 min. To measure the driving pressure responsible for cuff formation we used micropipettes to measure subpleural interstitial liquid pressure at the hilum of three additional lobes. With liquid inflation pressure set to 14 cmH2O interstitial pressure rose exponentially to 11.5 cmH2O. Interstitial compliance calculated from our volume and pressure measurements equaled 0.09 ml X cmH2O-1 X g wet wt-1, a value similar to that measured in air-inflated lungs. Goldberg [Am. J. Physiol. 239 (Heart Circ. Physiol. 8): H189-H198, 1980] has likened interstitial filling to the charging of a capacitor, a process that follows a monoexponential time course.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence of perivascular liquid accumulation in liquid-inflated dog lung lobes.

The peribronchovascular interstitium of the lung is a potential space that expands in pulmonary edema with the formation of large liquid cuffs. To study the time course of cuff formation we inflated nine isolated dog lung lobes with liquid to total lung capacity, rapidly froze them in liquid N2 after inflation periods of 1-300 min, then photographed 20 blocks of each lobe at X3 magnification. From the photographs we measured the ratio of cuff area to vessel area for arteries and veins of 0.05-8 mm diam. We found that the cuff-to-vessel area ratio attained a maximum value of 3-4, which was independent of vessel size. However, the first cuffs to reach maximum size were those around vessels of 0.1-0.5 mm diam, whereas cuffs around larger vessels filled more slowly. No cuffs were visible around vessels smaller than 0.1 mm diam. After 45 min cuffs had formed around 99% of all vessels larger than 0.5 mm diam but had formed around only 38% of veins and 91% of arteries of smaller diameter. We simulated the observed rate and pattern of cuff growth using electrical analog models. The filling pattern and model analyses suggest that liquid entered the interstitium from an air space site associated with arteries of approximately 0.1-1.0 mm diam, spread to adjacent sites, and eventually reached the lobe hilum. The estimated perivascular interstitial flow resistance decreased approximately 100-fold with cuff expansion.