Landmann unit

FIGURE 28.1 Normal structure ofthe lipid lamellae in the intercellular space. Shown are three Landmann units... 

The Landmann-unit structure of intercellular lipid lamellae is illustrated in Figure 28.1. This structure is found throughout nearly all of the normal SC. Swartzendruber et al. proposed a plausible molecular model that accounts for the electron-lucent and electron-dense lamellar structure of the Landmann unit.10 These Landmann units are dynamic in nature. At least in the inner and middle SC they are altered by age,19 disease,8 11 20-22 and hormonal status23,24 by experimental solvent treatment25-27 and topical inhibitor treatment.28,29 They are known to reform spontaneously following solvent extraction,5,26 and topical application of certain lipids is also reported to effect lamellar repair and barrier improvement.29-33... 

FIGURE 28.2 (a) Landmann units from the outer SC of a person 24-years old, skin grade 0.5. (b) A mixture... 

FIGURE 28.5 (a)Control, nontreated site from a 42-year-old male. The outermost (right) layers contain darkly staining globules in an amorphous matrix. Lamellae are present in deeper corneocyte layers, but Landmann units are rare, (b) Treatment with mineral oil results in the formation of large amorphous phases containing some darkly staining material. Bar = 200 nm. 

FIGURE 28.6 (a) Neat petrolatum site from a 42-year-old male. Flocculent/fibrous material existing as streamers or bands is present within an otherwise empty-appearing intercellular space, (b) Formulated (10%) petrolatum site. Lamellae, occasionally forming Landmann units, are sometimes separated by a thin layer of more darkly staining amorphous material. Bar = 200 nm. 

The streamer phase observed with neat petrolatum (Figure 28.6[a]) was not observed, but amorphous material was common (data not shown). Reasonable lamellae were occasionally encountered, as shown in Figure 28.6(b). Often these lamellae were separated by thin expanses of amorphous material, as shown in the center of Figure 28.6(b). In general, treatment with formulated petrolatum resulted in an appearance of the intercellular lipids that was much improved over that of neat petrolatum or mineral oil. The corneocytes were more closely apposed, and Landmann units were more common. 

The structure of the lipids in the intercellular space is overwhelmingly the SEFA look for both the 2 and 10% concentrations, as shown in Figure 28.8(a). With the 10% concentration, extra Landmann units within the SEFA phase were occasionally seen, as shown in Figure 28.8(b). 

FIGURE 28.7 Neat SEFA site from a 42-year-old male, (a) Comeocytes are closely apposed, with well-formed lamellae at the corneocyte surface. Between the lamellae is a relatively uniform layer of an amorphous material. This pattern is referred to as the SEFA look. (b) Occasional multiple Landmann units are present in the intercellular space. The length of the double Landmann units is always relatively short. Bar = 100 nm. 

FIGURE 28.13 Tape strips from a 48-year-old female, (a) Site of application of a commercial moisturizing body wash containing petrolatum. The appearance is typical of a person over age 40 with good skin condition. The corneocytes are closely apposed and lamellae are frequent, but the lamellae appear somewhat disorganized and amorphous/fibrous material is present between lamellae. Landmann units are nevertheless easy to find, as shown in the left intercellular space, (b) Site of application of a mild synthetic bar followed by a glycerin-based moisturizing lotion. The intercellular spaces contain amorphous and fibrous material as well as prominent wavy lamellae without a Landmann pattern. Bar =100 nm. 

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