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Anatomy of an Alveolar Type II Cell Diagram


Marian L. Miller University of Cincinnati , Department of Environmental Health , 160 Panzeca Way , College of Medicine , Cincinnati , OH 45267-0056 millermn@ucmail.uc.edu


Editor’s note: T is article should be read whether or not you are a cell biologist. T e author uses a specifi c example to make an important point: drawn images matter, must be done correctly, and details are essential. T ink of similar situations in your own fi eld.


Abstract: Graphical display of data is an important tool for all scientifi c disciplines, requiring as much thought as communication with words. Misrepresentation of data in images and diagrams can nullify the accompanying text, confuse the reader, as well as oversell unimportant facts. Suitable diagrams in science reinforce new data on a backdrop of known information. Creation of these diagrams is a task requiring skill and knowledge.


Introduction Translating complicated hypotheses and conclusions into


useful scientifi c information for students, colleagues, and the public at large is diffi cult. Illustrations improve communication in scientifi c reporting [ 1 , 2 ]. Pictures predate writing for this purpose, and using both text and graphics increases impact and understanding. Microscopists, for example, oſt en “know” biological cells pictorially and are able to visualize them, and their organelles, spatially. Others “know” cells diff erently and produce copious verbiage about them, but they may never really “see” them dimensionally. T us, occasionally some degree of hardwired or environmentally reinforced bias toward language versus image-based thinking creeps into scientifi c communica- tions. Unrecognized, such biases can foster serious errors in text and diagrams and cause missed opportunities in teaching. Scholars more adept at transmitting knowledge with language seem to predominate over those who communicate through the visual sense; thus, publications occasionally contain outright erroneous graphics. Pictures are powerful communicators of information, and errors in them undermine the scientifi c message.


What Makes a Good Diagram? Information . When knowledge is accurate and communi- cation between scientist and artist is eff ective, then good diagrams follow. Review papers are excellent places for compre- hensive descriptions to bolster knowledge [ 3 ]. Where data are not known and questions abound, communication may be poor, and erroneous diagrams may result.


Alveolar cells line the alveoli of the lungs, and alveolar type


II cells, 5–7 µm in diameter, comprise a small percent of the alveolar surface area. But these cells secrete surfactant that is critical in lowering surface tension in the alveoli. Much detailed information about these cells comes from transmission electron microscopy (TEM). To demonstrate the problem of creating good diagrams of these cells, two diagrams of alveolar type II cells are presented here, both based on the same data. Figure 1 is a diagram of an alveolar type II cell with misinformation, which is similar to diagrams actually published in prestigious journals [ 4 ]. Figure 2 shows that diagram edited to provide more accurate visual data.


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T e cell . In general, it is preferable to list the name of the cell type before any sub-classifi cation, for example, rather than “type II alveolar cell”, use “alveolar type II cell”. Alveolar type II cells are acceptably drawn as cuboidal, but a single solid outline implies that all portions of the cell membrane (plasmalemma) function similarly ( Figure 1 ), which is not always true. In Figure 2 the cell has polarity: microvilli defi ne the apical membrane at the right-hand side of the cell, hatch marks at top and bottom of the plasmalemma represent junctional complexes on lateral plasmalemma, and a gray band on the leſt indicates the basement membrane adjacent to basal plasmalemma. A light gray bounding box (right side, Figure 1 ) is presumed to represent the alveolar space. But, the “white space” between the alveolar type II cell and gray box becomes confusing. Does it represent surfactant hypophase? Figure 2 depicts the entire alveolar space without color. It also permits a logical positioning of an alveolar macrophage ( Figure 2 ). T e text “alveolus” now is aligned with the text “alveolar type II cell” to show a division from cellular to extracellular. Organelle placement . T e alveolar type II cell in Figure 1 shows a single lamellar body (LB), depicted as an oval, positioned close to what is assumed to be lateral plasmalemma (an arrow points to the apical membrane in Figure 1 , and there is the word “secretions”). Because exocytosis of LBs occurs at the apical membrane, this organelle is better placed just beneath the apical plasmalemma as shown in Figure 2 . In addition to placement, relative size and numerical density are extremely important in diagrams, so using a single oversized LB as seen in Figure 1 , misinforms. Figure 2 uses smaller LB to indicate that there are many in each type II cell. T e vast majority of electron micrographs from many species show LBs with distinctive, electron-dense, parallel or concentric lipid leafl ets, a morphology not noted in Figure 1 , but shown in Figure 2 . Two mitochondria were added to Fig. 2 for completeness. Nucleus . The ratio of nucleus to cytoplasm in a generic cell is about 0.45. A random selection of 50 alveolar type II cells imaged by TEM produced a ratio of about 0.37, much larger than the ratio of 0.1 (determined morphometrically) depicted in Figure 1 . This ratio was corrected in Figure 2 . The inner and outer nuclear membranes in Figure 1 show breaks, which in reality should not be “breaks” but should be nuclear pore complexes spanning both the inner and outer nuclear membranes. Uneven and out-of-position profiles of the nuclear membrane in Figure 1 (blue) were careless and have been redrawn in Figure 2 . Anatomical icons . Figure 1 used icons based on electron microscopic structures, but then it depicted DNA as a double helix rather than the nuclear structure that would be consistent with that genre: areas of euchromatin, condensed chromatin, and a nucleolus. In addition, the double helix was shown at the center of the nucleus in Figure 1 but labeled with the word “telomerase,” probably in an attempt to bring


doi: 10.1017/S1551929517000803 www.microscopy-today.com • 2017 September


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