The study of the structural basis of gas exchange function in the lung depends on the availability of quantitative information that concerns the structures establishing contact between the air in the ...alveoli and the blood in the alveolar capillaries, which can be entered into physiological equations for predicting oxygen uptake. This information is provided by morphometric studies involving stereological methods and allows estimates of the pulmonary diffusing capacity of the human lung that agree, in experimental studies, with the maximal oxygen consumption. The basis for this “machine lung” structure lies in the complex design of the cells building an extensive air-blood barrier with minimal cell mass.
With the new volume EM techniques, like serial block face scanning electron microscopy (SBF-SEM), new devices for three-dimensional (3D) reconstructions based on automated serial sectioning of tissue ...blocks and scanning their surfaces in between have become available (4). According to Crapo and colleagues (8) the mean AE1 cell volume in this lung was 1,996 mm3, and the mean basement membrane surface covered 4,053 mm2. Hannover Medical School Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease Hannover, Member of the German Center for Lung Research Hannover, Germany and REBIRTH Cluster of Excellence Hannover, Germany Ewald R. Weibel, Dr. med4 University of Bern Bern, Switzerland Christian Mühlfeld, Dr. med. Hannover Medical School Hannover, Germany Biomedical Research in Endstage and Obstructive Lung Disease Hannover, Member of the German Center for Lung Research Hannover, Germany REBIRTH Cluster of Excellence Hannover, Germany and Charite - Universitaetsmedizin Berlin‡ Berlin, Germany *Corresponding author (e-mail: schneider.jan@mh-hannover.de). †Ewald R. Weibel passed away February 19, 2019, at the age of 89.
1 Institute of Anatomy, University of Bern, Bern, Switzerland; ;
2 Stereology and Electron Microscopy Research Laboratory, University of Aarhus, Aarhus, Denmark; and ;
3 Institute of Functional and ...Applied Anatomy, Hannover Medical School, Hannover, Germany
Submitted 28 September 2009
; accepted in final form 1 December 2009
The mean linear intercept (chord) length ( L m ) is a useful parameter of peripheral lung structure as it describes the mean free distance in the air spaces. It is often misinterpreted as a measure of "alveolar size," and its estimation is fraught with a number of pitfalls. We present two methods for the accurate estimation of L m : 1 ) the indirect method, which derives L m from the volume-to-surface ratio of air spaces estimated by point counting methods, and 2 ) the direct method, which uses a set of random intercepts and calculates L m from their frequency distribution, for which we introduce a new and accurate method. Both methods are efficient and, with proper precautions, unbiased. The meaning of L m is assessed in two different examples. In a physiological study, the effect of different inflation levels is studied, showing that L m critically depends on lung inflation. In an experimental study on emphysema-like changes in a genetic mouse model, the effect of heterogeneity of air space size is assessed; these results are obtained partly because of differences in lung volume due to altered recoil in the emphysematous lungs. In conclusion, although L m is not a robust parameter of internal lung structure because it crucially depends on lung volume, it is still a valid measure for which accurate and efficient methods are available that yield additional parameters such as size distribution or alveolar surface area.
lung; alveoli; morphometry; stereology; mean linear intercept; emphysema; lung mechanics
Address for reprint requests and other correspondence: E. R. Weibel, Institute of Anatomy, Univ. of Bern, Baltzerstr. 2, CH-3000 Bern, Switzerland (e-mail: weibel{at}ana.unibe.ch ).
Establishing the 3D architecture and morphometry of the intact pulmonary acinus is an essential step toward a more complete understanding of the relationship of lung structure and function. We ...combined a special fixation method with a unique volumetric nondestructive imaging technique and image processing tools to separate individual acini in the mouse lung. Interior scans of the parenchyma at a resolution of 2 µm enabled the reconstruction and quantitative study of whole acini by image analysis and stereologic methods, yielding data characterizing the 3D morphometry of the pulmonary acinus. The 3D reconstructions compared well with the architecture of silicon rubber casts of mouse acini. The image-based segmentation of individual acini allowed the computation of acinar volume and surface area, as well as estimation of the number of alveoli per acinus using stereologic methods. The acinar morphometry of male C57BL/6 mice age 12 wk and 91 wk was compared. Significant increases in all parameters as a function of age suggest a continuous change of the lung morphometry, with an increase in alveoli beyond what has been previously viewed as the maturation phase of the animals. Our image analysis methods open up opportunities for defining and quantitatively assessing the acinar structure in healthy and diseased lungs. The methods applied here to mice can be adjusted for the study of similarly prepared human lungs.
This study compared the risk of a) clinically diagnosed eating disorders, and b) disordered eating behaviors, separately among three groups of United States college students, controlling for known ...covariates. These groups included college students self-identifying as: 1) gay/lesbian; 2) bisexual; and, 3) unsure, with self-identified heterosexuals as the reference. Data from the American College Health Association's National College Health Assessment II (2008–2009) were utilized (N=110,412). Adjusted logistic regression analyses, stratified by self-reported gender, examined the effect of self-identified sexual identity on clinical eating disorder diagnosis and disordered eating behaviors. Covariates included self-reported binge drinking (past 2weeks), stress (last 12months), smoking (past 30days), depression (past 12months), fraternity/sorority membership, college athletics participations, and race. Additional logistic regression sub-analyses examined sexual minorities only, with gay/lesbian as the referent. Gay, unsure, or bisexual men were at significantly increased odds to report both clinical eating disorders and disordered eating behaviors when compared to heterosexual men in both the unadjusted and adjusted models (p<.002). All sexual minority men and women were significantly more likely to report dieting to lose weight compared to heterosexual men and women (p<.002). Targeted disordered eating and eating disorder prevention efforts are needed for those who are sexual minorities, particularly for sexual minority men.
•Maladaptive eating behaviors among sexual minority college students was examined•Sexual minority men are at increased odds to report maladaptive eating behaviors•Sexual minority men and women were more likely to report dieting to lose weight•Targeted prevention efforts are needed, particularly for sexual minority men
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