Interalveolar Pores Research Articles

A novel technique proposition for determining the resection margins in lung resection by using a thermal camera.

Determination of resection margins is very important in anatomical lung resections for both oncologic outcomes and postoperative complications. Absence of intersegmental plans naturally in segmentectomy surgeries and presence of incomplete fissure variationally in pulmonary lobectomy procedures constitute a challenge for surgeons in determining resection margins. Thoracic surgeons can prefer various techniques such as inflation deflation method, indocyanine green imaging, and three-dimensional segment modeling to cope with this problem. These techniques have some disadvantages such as high cost, the necessity of intravenous drug administration, need for an additional imaging system and ineffectiveness due to emphysema, anthracotic lung surface or interalveolar pores. Here we studied an alternative method for the solution of these disadvantages and aimed to demonstrate the correctness of a hypothesis based on detecting the cooling of the ischemic lung portion by a thermal camera after dividing the related pulmonary artery. We planned determining margins of resection with a thermal camera in patients scheduled for pulmonary lobectomy or segmentectomy. We made some measurements and mapping with a thermal camera before and after the dividing of pulmonary artery of related lobe or segment then processed the images taken with a software on the computer. We detected a significant decrease in temperature in the ischemic lung area and demonstrated mapping the demarcation line between ischemic and perfused areas effectively by thermography in a total of 32 patients underwent lung resection. Pulmonary resection margins can be detected effectively by thermography in patients.

Evaluation of the Effects of the Correction of Hydroelectrolytic Disorders during Prolonged Ex-Vivo Lung Perfusion

Purpose During ex-vivo lung perfusion (EVLP), the ionic concentrations and pH of perfusion liquid are modified. In the course of this study, we evaluated whether these ionic disruptions have an impact on the lung graft during 12 hours of EVLP and whether the correction of these disruptions can avoid any lung lesions. If this were confirmed, it would allow longer EVLP time. Methods Twelve pigs' lungs were conventionally retrieved, cold preserved, perfused normothermically ex vivo for 12 hours, cold preserved for a second time and transplanted and reperfused for 4 hours. Ionic analysis and arterial and venous gas analysis were performed every hour during EVLP. Every 2 hours, 100mL of Steen solution were replaced with new Steen solution in the Steen N group and with modified Steen solution in the Steen + group. After 12 hours of EVLP, the right lung was harvested for structural, biological, cellular and histological analysis. The left lung was transplanted to a healthy swine and blood ionic and gas analysis were performed every hour during the left lung reperfusion. Results During EVLP, ∆PO2, compliance and pulmonary vascular resistance were similar in both groups. The ionic concentrations and pH were corrected in the Steen + group. After the left lung transplant, physiological and biological parameters were similar in both groups. Structural analysis by scanning electron microscopy showed a rise of interalveolar pores in the Steen + group. Conclusion The correction of hydroelectrolytic disorders during 12 hours of EVLP is feasible but does not improve lung function during EVLP and after the left lung transplant.

Congenital Segmental Emphysema: An Evolving Lesion

Congenital segmental emphysema (CSE) is a newly-recognised sub-type of congenital parenchymal lung anomaly. It is characterised by antenatal detection and post-natal evolution from an initially solid segmental appearance to a hyperlucent and hyperinflated segment. A retrospective review of a single-centre tertiary referral database between Jan 1994 and Dec 2007 was performed. 130 infants had antenatally detected lung anomalies, and of these 12 (9.2%) infants (initially labelled as congenital cystic adenomatoid malformation (CCAM)), showed features better defined as CSE. The lesions were described antenatally as non-progressive microcystic (n=6), hyperechogenic (n=2) or both (n=2). Early post-natal CT scans showed areas of solid segmental parenchyma, initial hyperlucency or microcysts. Subsequent CT imaging, however, showed evolution to segmental hyperlucency in areas previously solid and in 2 cases a central bronchocele was noted. Ten children underwent resectional surgery (segmentectomy n=4, lobectomy n=6) at a median age of 1 (range 0.4-5.2) year and the gross appearance of the resected specimen confirmed hyperinflated (not cystic) segments. Histological review showed localised abnormally dilated alveolar spaces in 7 cases. Adjacent areas consistent with type 2 CCAM were also seen (n=3). CSE lies within the spectrum of both CCAM and sequestration but there is a definite post-natal evolution and volume change which presage symptoms. This may be associated with segmental bronchial atresia and progressive air trapping via collateral airways such as the interalveolar pores of Kohn.

The gloved finger sign.

The branching tubular or fingerlike opacities extending out from the hila represent dilated bronchi filled with mucus (mucoid impaction). The mucoid impaction within a bronchus creates the appearance of a gloved finger. Once bronchial obstruction has occurred, the mucous glands continue to secrete until the bronchial pressure exceeds the secretory pressure. Mucous secretions are transported by ciliary action up to the site of the obstruction (2). The secretions become inspissated, and the mucus and inflammatory debris accumulate distal to the bronchial obstruction, thus causing bronchial dilatation (3). The dilated, mucus-filled bronchi are not visible at radiography if the surrounding lung is collapsed and airless. In patients with the gloved finger sign, the lung distal to the mucoid impaction remains aerated by collateral air drift through the interalveolar pores and the canals of Lambert, which allows the dilated bronchi to be seen as tubular branching opacities (4). The gloved finger sign can also be seen in conditions that do not involve bronchial obstruction, provided that the bronchi are dilated with secretions.

Ultrastructural study of the alveolar lining and the bronchial mucus layer by block staining with oolong tea extract: the role of various surfactant materials.

To investigate the roles of various surfactant materials in the lung, we examined rat lung fixed with a mixture of 0.2% oolong tea extract (which contains various polyphenols) and 2.5% glutaraldehyde by electron microscopy. We also measured the surface tension of various isolated surfactant fractions, with a Wilhelm balance. A fraction containing lamellar bodies and a fraction containing lattice-like structures were obtained by discontinuous sucrose gradient centrifugation. From the 15 000 g supernatant, a fraction containing electron-dense amorphous materials was obtained as the 105 g precipitate. The fraction containing lamellar bodies and the fraction containing electron-dense amorphous materials displayed surfactant activity, but the fraction containing lattice-like structures did not. The lamellar bodies were found to be gradually secreted from type II epithelial cells while self-decomposition occurred. The alveolar lining layer had the form of a thin film consisting of electron-dense amorphous materials. These electron-dense amorphous materials may be precursors of the phospholipid film, which exhibits surfactant activity, on the alveolar surface. Lattice-like structures and lamellar bodies were found to be located in the interalveolar pores. The interalveolar pores were filled with surfactant, and this indicated that they do not play a role in the collateral ventilation of the alveoli. It may be that the lattice-like structures serve to connect lung epithelial cells in the interalveolar pores, as well as serving as the basis for the formation of the alveolar ducts. The bronchial mucus layer, which consisted of fibrillar mucous materials, was not divided into an epiphase and a hypophase. A surfactant, in the form of an osmiophilic surface film and some trilaminar materials, was found to cover the mucus layer. Thus, it is possible that the lamellar bodies could be transformed into various surfactant materials, which then serve bronchial or alveolar mechanical and physiological functions.

Formation of interalveolar pores in the rat lung.

The aim of this morphological investigation was to obtain more information about the structural and cellular mechanisms of interalveolar pore formation in postnatal lung development. Assuming that alveolar pore formation is related to the general thinning of interalveolar walls observed in the postnatal period, we have focused our attention on the topographical relationship between epithelial cells and connective tissue in the septum. Thereby we tried to formulate a uniform concept of pore formation. After fixation with glutaraldehyde and osmiumtetroxide, tissue blocks of rat lungs aged 44 days were embedded in Epon. Serial sections were obtained in order to analyse precisely pores and supposed sites of pore formation (type II cells and thin spots in transsections of interalveolar walls). We made the following observations: there are pores with or without type II cells in the neighbourhood, and "pre-pores" with either fully transseptal granular pneumocytes, or thin spots in the interalveolar wall consisting of one or two layers of type I cell epithelium or of type II and type I cells without intervening connective tissue. From these findings we deduce that there is a general principle of interalveolar pore formation which consists in the formation of transseptal interepithelial cell contacts (i.e., between cells of type II and type I or type I and type I), promoted by the thinning of interalveolar walls in the stage of microvascular maturation. Within the zone of contact the cells thin out and give way to form an interalveolar opening.

Morphological Evidence for Migration of Particle-Laden Macrophages through the Interalveolar Pores of Kohn in the Murine Lung

We have investigated the topography of particle-laden macrophages in the pulmonary tissue of CD-1 mice after intratracheal instillation of a suspension of 250 micrograms of calcium tungstate. The mice were sacrificed 1, 3, 7 and 14 days after the particle deposition. Lung fragments were studied by scanning electron microscopy (SEM) coupled with X-ray microanalysis that allowed in situ elemental identification of tungsten in the lungs. Tungsten-positive macrophages were distinctly located in the lungs of mice sacrificed at 1-3 days when compared with samples from mice killed 7-14 days after the calcium tungstate instillation. At 1-3 days, the tungsten-carrying macrophages were accumulated near the terminal bronchioles whereas they were seen predominantly in the alveolar ducts and sacs in the 7- to 14-day groups of mice. This suggests that during pulmonary inflammation there is a redistribution of the particle-containing macrophages throughout the deep lung tissue. In high-magnification SEM views, we observed that the tungsten-positive macrophages presented numerous surface microvilli. Tungsten-laden phagocytes were detected in interalveolar fenestrae, at the so-called Kohn pores. This finding documents that the Kohn pores may be used by inflammatory cells as a pathway for the migration of phagocytes in between adjacent alveolar sacs.

Pores of Kohn are filled in normal lungs: low-temperature scanning electron microscopy

Interalveolar pores of Kohn, small uniform-sized epithelium-lined openings in alveolar walls of normal lung, have historically been demonstrated with electron-microscopic techniques that remove water. We show these pores to be present but almost invariably filled with material when water and surfactant are preserved in frozen hydrated lung examined with low-temperature scanning electron microscopy. In the normal mouse, 16 open empty pores per alveolus were found in instillation-fixed dried lung vs. less than 1 per alveolus in frozen hydrated lungs (P less than 0.001). In the normal rat, 13 pores were seen per alveolus in instillation-fixed dried lung vs. less than 1 per alveolus in frozen hydrated lungs (P less than 0.001). We suggest that pores of Kohn 1) function primarily as conduits for interalveolar movement of alveolar liquid, surfactant components, and macrophages, 2) provide distributed sites for tubular myelin storage without increasing gas diffusion pathway thickness in the alveolar subphase itself, and 3) do not function as pathways for collateral ventilation during normal breathing in the absence of atelectasis or obstruction.

Scanning electron microscopic approach to the co-localization of type-II pneumocytes with alveolar brush cells and interalveolar pores

Scanning electron microscopic approach to the co-localization of type-II pneumocytes with alveolar brush cells and interalveolar pores

An ultrastructural study of the equine lower respiratory tract

The surface features of the lower respiratory tract of 20 clinically normal horses of different ages and types were studied with scanning electron microscopy. Parallel light microscopical and transmission electron microscopical studies were also carried out. The ciliary carpet was virtually complete from the trachea to the lobar bronchi. In small bronchi, ciliation was less complete allowing numerous non-ciliated mucous cells to become obvious. The terminal bronchioles, populated mainly by non-ciliated bronchiolar epithelial cells, had an abrupt junction with alveolar ducts. Interalveolar pores were common particularly in older horses.

Development of Alveolar Septa and Formation of Alveolar Pores during the Early Postnatal Period in the Rat Lung

In order to investigate the formation of alveolar pores, lungs of rats, after intratracheal perfusion of glutaraldehyde, are processed at postnatal days 1, 7, 14, 16 and 21 for light and transmission electron microscopy and at days 7 and 16 for scanning electron microscopy. The initial low secondary crests of day 1 rapidly elongate to pleats subdividing the primary saccules. The ledges of some pleats partly grow toward each other as ring like diaphragms, leaving openings whose boundary is composed of alveolar epithelium separated by a basal lamina from a connective tissue sheath with capillaries. At day 7, in scanning electron microscopy the lumina of some rudimentary alveoli communicate by apertures of different sizes, as a result of the outgrowth of curved alveolar pleats which narrow to a ring-like aperture. The interalveolar openings observed in scanning electron microscopy resemble those investigated by light and transmission electron microscopy. The number of interalveolar pores increases from day 7 on; they become more and more frequent at days 14, 16 and 21, respectively. It appears that alveolar multiplication in newborn rats proceeds not only by segmentation of terminal respiratory units but also by compoundment of septa. The difference between genuine pores and transsections of folds in transmission electron microscopy will be given closer attention in this study. Also, the incidence and location of type II pneumocytes during rapid enlargement of the alveolar surface area is discussed.

Distribution of pores within alveoli in the human lung.

Usually the wall opposite the orifice of alveoli has been used to study interalveolar pores by scanning electron microscopy. To ascertain whether biased results may be obtained from this, the distribution of pores within alveoli was studied in human lungs. By the use of scanning electron photomicrographs, the number, major axes of pores, and proportional area of pores to the alveolar wall were estimated. The alveolar wall seen opposite the orifice was defined as the bottom wall. Average number of pores per alveolus was 13-21, and one-half of them was located in the bottom walls. The average length of major axes was 7-19 micron, and average area fractions were 0.8-5%. The distribution of the numerical density, area fraction, and size of pores was uniform regardless of their location within the alveolus and the size of alveoli. Thus pores can be compared using the bottom walls of alveoli. This will facilitate the study of the effects of age, smoking, and topography on pore size and frequency in humans.

Anatomical relationships between type II pneumonocytes and alveolar septal gaps in the human lung.

This report describes a relationship between type II pneumonocytes and breaks in continuity in the alveolar septum of the human lung. Breaks in continuity of the septum are defined as gaps in the connective tissue matrix of the alveolar septum, with or without discontinuity of the accompanying alveolar epithelium. Septal connective tissue gaps accompanied by epithelial discontinuity are recognized as interalveolar pores of Kohn. When the discontinuity is confined to the connective tissue matrix, epithelial continuity may be maintained by either a single or a double layer of type I epithelium, by a type II cell, or by both type I and type II epithelial cells. Alveolar septal gaps were studied by electron microscopy on random sections in 26 adult human lung specimens and by serially sectioning and montaging the entire circumference of one alveolus to a depth of 103 microns (approximately one-half a normal alveolus) from one of the specimens. Fixation was by way of the airways in most specimens, but by vascular perfusion in the serially sectioned specimen and in seven others. In lungs studied by random sections, we found that the incidence of septal connective tissue gaps with epithelial continuity per specimen correlated with the incidence of pores (r = .468, P less than .016), and also with the incidence of type II cells (r = .422, P less than .025) in the specimen. Five percent of all type II cells observed in the random sections in the 26 specimens (103/1,955) occupied septal gaps, and 2.5% (49/1,955) were located at the rim of a pore. In contrast, in the single serially sectioned montaged alveolus, 69% of all type II cells occupied some type of septal gap, with 24% of all type II cells forming part of the rim of a pore. Over half of all pores in this alveolus were associated with a type II cell. We concluded that a relationship between the incidence of type II cells and gaps in the alveolar septum could be demonstrated on random sections in normal human lungs, which was much more obvious in a single serially sectioned hemialveolus. Serial section techniques of whole alveoli may be necessary to establish relationships that may not be apparent on random sections and that require the study of whole cells in continuity with their environment in order to be identified. The findings may be significant in suggesting a possible role of the type II cell in alveolar septal repair.

The effect of age on lung structure in male BALB/cNNia inbred mice.

Morphometric examination using light, scanning electron, and transmission electron microscopy was performed on the lungs from 32 inbred male BALB/ cNNia mice between 38 days and 28 months of age. Between 38 days and 9 months of age the changes were primarily those of growth. Alveolar multiplication and total elastic-fiber length appeared complete by 38 days of age. The major increase in the number of interalveolar pores occurred by 68 days, but there was a significant further increase from 68 days to 9 months of age. At 9 months, approximately 10% of the alveolar wall was formed by pores. Alveolar ducts, the cylindrical core of air central to alveolar mouths, increased more in diameter than length. Between 9 and 28 months the changes were attributed to aging and were different from those reported in humans and other species. Lung volume, alveolar surface area, and total volume of alveolar wall increased with age; there was no change in mean linear intercept and volume proportion of alveolar and alveolar duct air. Total area of pores increased with age, but their number and area fraction of the alveolar wall did not change. No transmission electron microscopic changes were seen in the alveolar walls. We speculate that the morphometric differences between our animals and those studied in other reports may reflect the fact that our animals were specific-pathogen-free animals and kept under protected circumstances.

Emphysema-like changes in the lungs of starved rats.

We examined the effects of starvation on lung structure in rats allowed only one fifth of their measured daily food consumption until they lost 40% of their initial body weight, and evaluated volume-pressure relationships in saline-filled lungs, lung morphometric and connective tissue morphologic features and lung ultrastructure by scanning electron microscopy. Compared with rats fed full rations, the volume-pressure curve was shifted upward and to the left and the chord compliance was significantly increased. In the starved rats, enlargement of air spaces and alveolar wall destruction was associated with a significant increase in mean linear intercept and a decrease in internal surface area. Elastic fibers appeared short, irregular, and fewer in number in starved lungs. Scanning electron microscopy showed enlarged air spaces, thin, irregular, and effaced alveolar walls, and an increased number and size of interalveolar pores in the starved group. We concluded that starvation results in mechanical and morphologic changes in the lung similar to those seen in emphysema, and that starved lung may be a useful experimental model for the study of emphysema.

Alterations in stress distributions around interalveolar pores after exposure to papain in dogs.

Electron microscopic examination of dog lungs after exposure to papain for as little as 30 min showed removal of surfactant material from the pores of Kohn, and significant enlargement of the pores. We analyzed these early events in terms of structural mechanics, and concluded that: (1) The approximate doubling of the average diameter indicates a lowering of the effective modulus of elasticity in the vicinity of the pores to less than 50% of its original value, which is consistent with the destruction of elastin. (2) The removal of the surfactant material, which normally occludes the pores, results in the loss of the force caused by surface tension, which normally acts at the rim of the pore, and alleviates maximal tissue stress. This lost force can result in a stress increase on the elastin by as much as 20 to 30% of its strength. (3) The whole lung volume pressure deflation curves obtained in hamsters after exposure to papain show a significant increase in compliance associated with papain treatment. Degradation in the elastic modulus of the tissue, caused by the papain, contributes to such an increase. On the other hand, surface tension measurements from canine lung extracts after exposure to papain yield results that should contribute to a decrease in compliance. Because papain treatment destroys the continuity of the lining layer, this contribution is minimized, and the effect on the tissue dominates, resulting in a net increase in compliance.

Interalveolar pores in mouse lung. Regional distribution and alterations with age.

Quantitative analysis of the regional distribution of interalveolar pores in the lungs of BALB/c mice 1 to 28 months of age (n = 25) was performed by scanning electron microscopy. In all the age groups examined, the subpleural and peribronchiolar alveoli had significantly more pores than the midzonal region (p < 0.01). No significant changes were noted in the number of pores per alveolus between 3 and 26 months of age in the midzonal, peribronchiolar, and subpleural alveoli. We concluded that (1) intralevolar pores are regionally distributed in the lungs of BALB/c mice by 3 months of age, and (2) the number of pores do not significantly change with increasing age during the first 26 months.

Collateral ventilation.

Ventilation may bypass obstructed airways through collateral channels, including interalveolar pores of Kohn, bronchiole-alveolar communications of Lambert, and interbronchiolar pathways of Martin. Resistance through these channels, like resistance through small airways, increases with decreasing lung volume and with hypocapnia. But whereas the distention of collateral channels and small airways by a variety of factors is similar, the efficiency of ventilation through collateral channels is less than the efficiency through airways. Gas inspired through collateral channels is contaminated with alveolar gas from surrounding lung so that the dead space for collateral ventilation is increased. When one part of the lung ventilates out of phase with the surrounding lung, pulmonary interdependence promotes more homogeneous ventilation. In the presence of airways obstruction, interdependence may be a primary factor governing the rate of collateral ventilation. In man, collateral ventilation is unimportant in normal lungs. However, with disease, it may be critical in producing or compensating for abnormalities. For example, the long time constant for collateral ventilation in the middle lobe may be responsible for atelectasis, which results in the middle lobe syndrome. On the other hand, the short time constant for collateral ventilation in emphysema may be essential for the distribution of ventilation beyond obstructed airways.