Aged skin commonly is afflicted by inflammatory skin diseases or xerosis/eczema that can be triggered or exacerbated by impaired epidermal permeability barrier homeostasis. It has been previously described a permeability barrier defect in humans of advanced age (> 75 years), which in a murine analog >18 mos, could be attributed to reduced lipid synthesis synthesis. However, the functional abnormality in moderately aged mice is due not to decreased lipid synthesis, but rather to a specific defect in stratum corneum (SC) acidification causing impaired lipid processing processing. Endogenous Na+/H+ antiporter (NHE1) level was found declined in moderately aged mouse epidermis. This acidification defect leads to perturbed permeability barrier homeostasis through more than one pathways, we addressed suboptimal activation of the essential, lipid-processing enzyme, β-glucocerebrosidase (BGC) is linked to elevated SC pH. Finally, the importance of the epidermis acidity is shown by the normalization of barrier function after exogenous acidification of moderately aged skin.
We report the two photon luminescence (TPL) and second harmonic generation (SHG) characteristics of Zinc Oxide (ZnO) in ceramic, thick film and nano-rod. All samples were prepared from commercially available analytical pure ZnO powder. Sintering, physical vapour deposition (PVD), and hydrothermal methods were used in preparing the three types of samples respectively. The comparison among the three showed, while a degree of similarities between the ceramic and the nano-rod, a significant difference in the film. Possible reasons for the wavelength downshift in the film sample are discussed. Images acquired by TPL and SHG microscopy are presented, both ceramic and film samples show granular structure and a reverse bright-dark contract was observed from TPF to SHG image between the grain region and the granular boundaries.
Second harmonic generation (SHG) results from molecules being polarized by an external electric field, often provided by an intense laser beam. The polarizability depends on firstly the intrinsic structural properties of the substance and hence the second order nonlinear susceptibility, and secondly the intensity and polarization direction of the incident light. The polarization characteristics of the beam are therefore of interest. In this paper, we discuss some considerations in SHG microscopy when the incoming beam is circularly polarized, and present some supporting results as well as a question for future work.
The polarization dependence of the second harmonic emission of purified in-vitro reconstituted fibrils of collagen has been examined. The results confirmed the quasi-hexagonal crystalline structure within the fibrils. Interesting different polarization behaviours were seen between collagen types I and II, which can be utilized as an experimental technique for differentiation.
Collagen is known to be a very effective generator of the second harmonic of incident light from 700 to 1100nm, and second harmonic generation (SHG) microscopy is coming into use as a tool for studying the distribution of collagen in tissue. It also shows promise as a technique for characterizing collagen - both in distinguishing different collagen types and their packing and in identifying degradation of collagen in pathologic conditions. However many aspects of image formation in SHG microscopy of collagen remain imperfectly understood, and we have commenced a rigorous study of these factors. The present paper presents the first results from this program.