When motile swarmer cells of Caulobacter crescentus differentiate into sessile stalked cells, the flagellum is ejected. To elucidate the molecular mechanism of the flagellar ejection, flagellar hook-basal body (HBB) complexes from C. crescentus were purified and characterized. The purified HBBs were less stable against acidic pH or protease treatment than HBBs of Salmonella typhimurium, supporting the view that flagellar ejection from C. crescentus is initiated by destruction of the fragile basal structures. In addition, protease treatment of the purified flagella resulted in the specific digestion of the MS ring complex, revealing for the first time the intact structure of the whole rod.

the stratum corneum plays a crucial role in epidermal barrier function. Various changes occur in granular cells at the uppermost stratum granulosum during cornification. To understand the temporal details of this process, we visualized the cell shape and organelles of cornifying keratinocytes in a living human epidermal equivalent model. three-dimensional time-lapse imaging with a two-photon microscope revealed that the granular cells did not simply flatten but first temporarily expanded in thickness just before flattening during cornification. Moreover, before expansion, intracellular vesicles abruptly stopped moving, and mitochondria were depolarized. When mitochondrial morphology and quantity were assessed, granular cells with fewer, mostly punctate mitochondria tended to transition to corneocytes. Several minutes after flattening, DNA leakage from the nucleus was visualized. We also observed extension of the cell-flattening time induced by the suppression of filaggrin expression. Overall, we successfully visualized the time-course of cornification, which describes temporal relationships between alterations in the transition from granular cells to corneocytes. The human epidermis is a heterogeneous, multilayered structure constructed from keratinocytes 1. All keratinocytes are originally produced at the lowest layer of the epidermis, the stratum basale (SB), following which they move towards the skin surface while differentiating through the stratum spinosum (SS) and stratum granulosum (SG) and finally transform into corneocytes at the border between the SG and the most outer layer, the stratum corneum (SC). Due to the robust hydrophobic features of the SC and tight junctions that form at the second layer of the SG, these factors play a crucial role in protection against physical damage and harmful factors outside the body as well as the prevention of water loss from inside the body 2-4. The terminal differentiation of the uppermost granular cells to corneocytes, the cells of the SC, is called cornification, which is a kind of programmed cell death. During cornification, a variety of phenomena occur in granular cells 3. One of the most obvious changes is in their thickness. Corneocytes are very thin with a thickness of approximately 0.2-0.5 μm 5. Furthermore, corneocytes do not contain nuclei and other organelles but rather are filled with densely packed keratin filaments throughout their cytoplasm 3,6. The condensation of keratin filaments is induced by interaction with filaggrin monomers 7,8. At the cell periphery, the cornified envelope, a structure consisting of various cross-linked intracellular proteins such as involucrin and loricrin, is formed 9. Adjacent corneocytes are interconnected by corneodesmosomes, which are modified desmosomes, and their intercellular space is filled with lipids 2. Several recent reports have elucidated that autophagy is involved in the elimination of nuclei and mitochondria during terminal differentiation 10,11. It has also been reported that DNA is degraded by both DNase1L2 ...

No abstract

Improvement of the water‐impermeable barrier function of skin is clinically important, because barrier abnormality is associated with various skin diseases, such as psoriasis or atopic dermatitis. We have shown that topical application of fatty acids, sex hormones, hexoses, polyols and polymers influences barrier homeostasis, but the effects are highly dependent on even small variations of molecular structure. Moreover, the effects appear within one hour after application and thus are likely to be non‐genomic (physicochemical) phenomena. Secretion of lipids from lamellar bodies into the intercellular space between stratum granulosum and stratum corneum is a crucial step in epidermal water‐impermeable barrier homeostasis, especially at the early stage of barrier recovery after damage, and phase transition of the lipid lamellar structure in the epidermis is an important part of this process. Therefore, we evaluated the effects of the above molecules on the physicochemical properties of phospholipid monolayers and liposomes as models of the lamellar body membrane and cell membrane. Molecules that influenced the barrier recovery process also altered the stability of liposomes and the air‐water surface pressure of phospholipid monolayers. Studies using attenuated total reflection Fourier‐transform infrared spectroscopy (ATR FT‐IR), differential scanning calorimetry (DSC) and 13C nuclear magnetic resonance (NMR) spectrometry suggested that molecules influencing barrier recovery interact specifically with phospholipids. The idea that molecules interacting with phospholipids may influence barrier homeostasis should open up new approaches to the treatment of a variety of skin diseases.

Background/Purpose: Topical application of polyoxyethylene/polyoxypropylene dimethyl ether (EPDME) random copolymer improves the barrier function of skin, whereas polyethylene glycol (PEG) and polypropylene glycol (PPG) are ineffective.The aim of this work was to examine the interaction between these polymers and lipid molecules in the stratum corneum in order to establish whether EPDME-specific changes in the structural ordering of lipids might account for the improvement of barrier function. Methods:We used two-photon microscopy to evaluate the effects of EPDME, PEG, and PPG on the structural ordering of lipids in an epidermal-equivalent model in terms of the fluorescence changes of Laurdan, a fluorescent dye that responds to changes of membrane fluidity. The generalized polarization (GP) value, a parameter that reflects lipid ordering, was measured at various depths from the surface of the stratum corneum.Results: EPDME increased the GP value to a depth of about 3 µm from the surface, indicating that lipid ordering was increased in this region, while PEG and PPG of the same molecular weight had no effect. Diffusion of Lucifer yellow into the epidermis was reduced after application of EPDME, indicating that the barrier function was improved. Conclusion:These results support the view that EPDME improves barrier function by increasing the ordering of lipid structures in the stratum corneum. The methodology described here could be useful for screening new compounds that would improve the structural ordering of lipids. K E Y W O R D Sepidermal barrier homeostasis, keratinocyte, Laurdan, lipid ordering, two-photon microscope | 633 UMINO et al.