Image analysis method for heterogeneity and porosity characterization of biomimetic hydrogels

This work presents an image processing procedure for characterization of porosity and heterogeneity of hydrogels network mainly based on the analysis of cryogenic scanning electron microscopy (cryo-SEM) images and can be extended to any other type of microscopy images of hydrogel porous network. An algorithm consisting of different filtering, morphological transformation, and thresholding steps to denoise the image whilst emphasizing the edges of the hydrogel walls for extracting either the pores or hydrogel walls features is explained. Finally, the information of hydrogel porosity and heterogeneity is presented in form of pore size distribution, spatial contours maps and kernel density dot plots. The obtained results reveal that a non-parametric kernel density plot effectively determines the spatial heterogeneity and porosity of the hydrogel.

Image analysis method for heterogeneity and porosity characterization of biomimetic hydrogels

This work presents an image processing procedure for characterization of porosity and heterogeneity of fully hydrated hydrogels based on the analysis of cryogenic scanning electron microscopy (cryo-SEM) images. An algorithm consisting of different filtering, morphological transformation, and thresholding steps to denoise the image whilst emphasizing the hydrogel fibres edges for extracting the pores features is explained. Finally, the information of hydrogel porosity and heterogeneity is presented in form of pore size distribution, spatial contours maps and kernel density dot plots. The obtained results reveal that a non-parametric kernel density plot effectively determines the spatial heterogeneity and porosity of the hydrogel.

In situ differentiation of iridophore crystallotypes underlies zebrafish stripe patterning

Skin color patterns are ubiquitous in nature, impact social behavior, predator avoidance, and protection from ultraviolet irradiation. A leading model system for vertebrate skin patterning is the zebrafish; its alternating blue stripes and yellow interstripes depend on light-reflecting cells called iridophores. It was suggested that the zebrafish’s color pattern arises from a single type of iridophore migrating differentially to stripes and interstripes. However, here we find that iridophores do not migrate between stripes and interstripes but instead differentiate and proliferate in-place, based on their micro-environment. RNA-sequencing analysis further reveals that stripe and interstripe iridophores have different transcriptomic states, while cryogenic-scanning-electron-microscopy and micro-X-ray diffraction identify different crystal-arrays architectures, indicating that stripe and interstripe iridophores are different cell types. Based on these results, we present an alternative model of skin patterning in zebrafish in which distinct iridophore crystallotypes containing specialized, physiologically responsive, organelles arise in stripe and interstripe by in-situ differentiation.

In situ differentiation of iridophore crystallotypes underlies zebrafish stripe patterning

Skin color patterns are ubiquitous in nature, evolve rapidly, and impact social behavior1, predator avoidance2, and protection from ultraviolet irradiation3. A leading model system for vertebrate skin patterning is the zebrafish4-7; its alternating blue stripes and yellow interstripes depend on guanine crystal-containing cells called iridophores that reflect light. It was suggested that the zebrafish’s alternating color pattern arises from a single type of iridophore migrating differentially to stripes and interstripes7-9. When we tracked iridophores, however, we found they did not migrate between stripes and interstripes but instead differentiated and proliferated in place based on their micro-environment. RNA seq analysis further revealed stripe and interstripe iridophores had different transcriptomic states, while cryogenic scanning electron microscopy and micro-X-ray diffraction showed they had different guanine crystal organizations and responsiveness to norepinephrine, all indicating that stripe and interstripe iridophores are different cell types. Based on these results, we present a new model of skin patterning in zebrafish in which distinct iridophore crystallotypes containing specialized, physiologically responsive, subcellular organelles arise in stripe and interstripe zones by in situ differentiation. In this model, pattern phenotype depends not only on interactions among pigment cells that affect their arrangements, but also on factors that specify subcellular organization and physiological responsiveness of specialized organelles.

The rice BZ1 locus is required for glycosylation of arabinogalactan proteins and galactolipid and plays a role in both mechanical strength and leaf color

Background: The cell wall and chloroplast are two fundamental structures determining plant mechanical strength and grain yield. Therefore, understanding mechanisms that improve plants’ ability to develop a robust cell wall and well-developed chloroplast is of upmost importance for agricultural activities. Results: In this study, we report the functional characterization of a novel rice mutant, brittle stem and zebra leaf ( bz1 ), which displays altered cell wall composition and collapsed chloroplast membrane. Molecular and biochemical analysis revealed that BZ1 encodes a functional UDP-galactose/glucose epimerase (UGE) and is ubiquitously expressed with higher expression in stem and leaf tissues. Multiple techniques analyses, including immunoblots, immuno-gold, and cryogenic scanning electron microscopy, demonstrated a significantly impaired glycosylation of arabinogalactan proteins (AGPs) and disordered cellulose microfibril deposition in bz1 . Lipid profiling assay showed that the amount of monogalactosyldiacylglycerols (MDGD), a major chloroplast membrane glycolipid, was significantly decreased in bz1 . Taken together, these results strongly demonstrate that BZ1 participates in UDP-galactose supply for the sidechain biosynthesis of AGPs and MDGD, which thereby, respectively, results in altered cell wall and abnormal chloroplast development. Due to inferior mechanical strength and reduced photosynthesis, bz1 plants displayed detrimental agronomic traits, whereas BZ1 overexpressing lines showed enhanced plant growth. Transcriptome analysis of stems and leaves further showed that numerous key genes involved in AGPs biosynthesis and photosynthesis metabolism were substantially suppressed in bz1 . Conclusions: Our finding identifies BZ1 as a dual-targeting UGE protein for glycosylation of AGPs and MDGD and suggests a strategy for breeding robust elite crops.

Polyamide fabric coated with a dihydroxyacetone-loaded chitosan hydrogel for a cosmeto-textile application

Cosmeto-textiles, which allow the administration of molecules when in contact with the skin, are increasingly being developed by cosmetic industries. We have designed an innovative approach for cosmeto-textile products, based on the impregnation of textile fibers with chitosan hydrogels, which have been cross-linked with genipin and loaded with dihydroxyacetone, which is an active component that induces sunless tanning. Dihydroxyacetone-loaded chitosan hydrogels have been prepared and characterized by means of cryogenic scanning electron microscopy (cryo-SEM). The images showed that genipin cross-linking decreases the mesh distance of hydrogels. The release of dihydroxyacetone from these cross-linked genipin chitosan hydrogels has been studied by a dialysis membrane method. These dihydroxyacetone-loaded chitosan hydrogels have been incorporated to polyamide textiles by a simple padding technique. The presence of dihydroxyacetone on these textiles has been detected by hyperspectral imaging on a dark field high resolution optical microscope. Finally, the performance of fabrics as cosmeto-textiles, with a tanning effect, has been evaluated by skin-colorimetry measured with an evaluation panel of 10 people. The results have demonstrated that dihydroxyacetone-loaded textiles produce a tanning effect on skin, and incorporation of dihydroxyacetone-loaded chitosan hydrogels into polyamide fabrics represents a friendly and appropriate strategy to obtain a cosmeto-textile with tanning effect.

Microscopic measurements on the decomposition behaviour of methane hydrates formed in natural sands

In this work, the decomposition behaviour of methane hydrate in porous media was investigated microscopically using powder X-ray diffraction, cryogenic scanning electron microscopy and in situ Raman spectroscopy.