This study focused on the water distribution in human stratum corneum and on the swelling of the corneocytes. For this purpose stratum corneum was hydrated to various levels and used either for Fourier transform infrared spectroscopy or for cryo-scanning electron microscopy. The images were analyzed with respect to water localization and cell shape. The Fourier transform infrared spectra were measured to study the water-lipid interactions. The results show that water only slightly changes the lipid transitions in the stratum corneum even at a hydration level of 300% wt/wt compared to stratum corneum and that water is inhomogeneously distributed in the stratum corneum. No gradual increase in water level was observed in depth. At 57%-87% wt/wt water content the hydration level in the central part of stratum corneum is higher than in the superficial and deeper cell layers. Water domains are mainly present within the corneocytes and not in the intercellular regions. At a very high hydration level (300% wt/wt), the corneocytes are strongly swollen except for the deepest cell layers adjacent to the viable epidermis. The corneocytes in these layers are not swollen. At 300% wt/wt hydration level water domains are also present in intercellular regions. Between 17% wt/wt and 300% wt/wt the cell thickness increases linearly with the hydration level suggesting that swelling of cells mainly occurs in the direction perpendicular to the skin surface. At an increased hydration level, the corneocyte envelope more efficiently surrounds the cell content compensating for the increased cell volume. The changes in stratum corneum morphology with increasing water level have also been observed in dermatomed skin.

Based on the type of vegetable, the different processes applied led to microstructures with different rheological properties. This study shows that particle size distribution, morphology and phase volume are important parameters to explain the complex relationship between rheology and microstructure for these types of systems.

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Ascospores of the fungus Talaromyces macrosporus are dormant and extremely stress resistant, whereas fungal conidia-the main airborne vehicles of distribution-are not. Here, physical parameters of the cytoplasm of these types of spores were compared. Cytoplasmic viscosity and level of anisotropy as judged by spin probe studies (electron spin resonance) were extremely high in dormant ascospores and during early germination and decreased only partly after trehalose degradation and glucose efflux. Upon prosilition (ejection of the spore), these parameters fell sharply to values characteristic of vegetative cells. These changes occurred without major volume changes that suggest dramatic changes in cytoplasmic organization. Azide reversibly inhibited prosilition as well as the decline in cytoplasmic parameters. No organelle structures were observed in etched, cryoplaned specimens of ascospores by low-temperature scanning electron microscopy (LTSEM), confirming the high cytoplasmic viscosity. However, cell structures became visible upon prosilition, indicating reduced viscosity. The viscosity of fresh conidia of different Penicillium species was lower, namely, 3.5 to 4.8 cP, than that of ascospores, near 15 cP. In addition the level of anisotropic motion was markedly lower in these cells (h 0 /h ؉1 ‫؍‬ 1.16 versus 1.4). This was confirmed by LTSEM images showing cell structures. The decline of cytoplasmic viscosity in conidia during germination was linked with a gradual increase in cell volume. These data show that mechanisms of cytoplasm conservation during germination differ markedly between ascospores and conidia.Ascospores of the fungus Talaromyces macrosporus are sexual structures that exhibit extreme resistance to heat, high pressure, drought, and freezing (14, 15). They contain an extremely high level of trehalose (13) and have relatively low amounts of water in an aqueous environment. The spores show constitutive dormancy in rich media, and germination is triggered and synchronized by a short heat treatment at 85°C. Ascospores of T. macrosporus can germinate after 17 years of storage (40) and belong to the most resilient eucaryotic structures described hitherto. They can survive a heat treatment at 85°C for 100 min or high pressurization at 1,000 MPa for 5 min (14). Upon heat activation, the spores degrade their trehalose within 100 min, followed by a rapid release of glucose into the bathing medium up to 10% of the cell wet weight. After 2.5 h, the outer cell wall opens, and the protoplast encompassed by the inner cell wall is ejected in a fast process (seconds) termed prosilition. The ejected cell then swells and forms a germ tube, resembling events that occur in other fungal spores. Conner et al. (10) studied the cellular basis of heat resistance in relatively young (11-day) and older (25-day) ascospores of Neosartorya fischeri exhibiting different heat resistance levels (D 82 of approximately 23 and Ͼ60 min, respectively). The ascospores showed differences in the inner cell wall region at the lateral ridge...

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