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There have been many studies about the formation, storage, transport and degradation of melanosomes in epidermal melanocytes but studies of melanocytes and melanosomes in fetal hair follicles (HFs) have been limited and ambiguous. The goal of this study was to investigate the distribution of melanocytes and the degradation of melanosomes in fetal HFs. After obtaining approval and informed consent for the study, a scalp specimen from a 5 month gestational age fetus was obtained and was divided into two parts. One part was subjected to immunohistochemical staining with the melanocyte-specific marker HMB-45 and was then observed by light microscopy to detect the distribution of melanocytes in HFs. The other part underwent conventional processing for transmission electron microcopy (TEM). Subsequently, the morphology of melanosomes in HF melanocytes and their degradation in cortical keratinocytes were observed. Immunohistochemically, scattered round melanocytes lacking dendrites were mainly observed along the outer root sheath of the lower part of the HF. A few fusiform or tri-dendritic melanocytes were located at the bottom of the hair bulbs. Significantly melanized melanocytes with multiple dendrites were concentrated in the pigmented area in the center of the hair bulbs, only above the dermal papilla. Analysis by TEM revealed melanocytes containing melanosomes at all stages of development. Autophagosomes containing stage mature IV melanosomes were observed in some melanocytes. Many phagolysosomes containing numerous melanosomes were observed in the cortical keratinocytes. Some phagolysosomes were concentrically surrounded by 3-5 layers of endoplasmic reticulum. Melanosomes that had been degraded or were being degraded in phagolysosomes in keratinocytes had lost their integrity and had become an ill-defined melanosomal dust that were arranged irregularly. Partial melanin particles were released into the cytosol. Melanocytes in different regions of fetal HFs had different morphologies and were at various stages of differentiation. Fetal HF melanocytes contained not only melanosomes at different developmental stages, but autophagosomes were seen occasionally. Melanosomes were degraded into irregular pigment particles in the phagolysosomes of cortical keratinocytes. These results provide important clues to elucidate the mechanism of melanosome biodegradation.

The biosynthetic pathway of l -methionine in microorganisms was complex and regulated at multiple levels. In this study, a two-step method for l -methionine production combined fermentation and biocatalysis was realized in one pot. The O-succinyl- l -homoserine (OSH) producing strain Escherichia coli W3110(DE3) ΔIJB∗TrcmetL/pTrc-metAfbr-Trc-thrAfbr-yjeH (ΔIJB) was constructed initially. OSH in the fermentation supernatant was then converted to l -methionine in the presence of O-succinyl- l -homoserine sulfhydrylase (OSHS) and sodium methanethiol. The titer of l -methionine could reach 21.1 g/L after 88 h (84 h fermentation and 4 h catalysis) in a two-step method (process 1). In a one-pot two-strain system (process 2), two strains ΔIJB and E. coli BL21(DE3)/pET28b–OSHS–cutinase were co-cultured, and 8.24 g/L l -methionine was obtained. In another one-pot one-strain system (process 3), strain E. coli ΔIJB/pET28b–OSHS–cutinase could co-express OSHS and cutinase during ΔIJB fermentation at the same time, obtaining 13.6 g/L l -methionine in a 5 L fermentor after 84 h. By comparing the three processes for l -methionine production based on the process 1, the simplified process in process 3 provided in this study showed potent in the large-scale production of l -methionine with convenient handling and production efficiency, but further works still need to be carried out to improve the l -methionine production.

Aims Constructing a strain with high yield of O-succinyl-l-homoserine (OSH) and improving the titre through multilevel fermentation optimization. Methods and results OSH high-yielding strain was first constructed by deleting the thrB gene to block the threonine biosynthesis. Single-factor experiment was carried out, where a Plackett-Burman design was used to screen out three factors (glucose, yeast and threonine) from the original 11 factors that affected the titre of OSH. The Box-Behnken response surface method was used to optimize the fermentation conditions. Through gene editing and medium optimization, the titre of OSH increased from 7·20 to 8·70 g l-1 in 500 ml flask. Furthermore, the fermentation process and fed-batch fermentation conditions including pH, temperature, feeding strategy and feeding medium were investigated and optimized. Under the optimal conditions, the titre of OSH reached 102·5 g l-1 , which is 5·6 times higher than before (15·6 g l-1 ). Conclusions O-succinyl-l-homoserine fermentation process was established and the combination of response surface methodology and metabolic pathway analysis effectively improved the titre of OSH. Significance and impact of the study In this study, the titre of OSH reached the needs for industrial production and the metabolic pathway of OSH was demonstrated for further optimization.

O-Succinyl- l -homoserine (OSH) is an important platform chemical in production of C4 chemicals such as succinic acid, homoserine lactone, γ‑butyrolactone, and 1,4‑butanediol. The production of OSH through chemical method or the current engineering strain is difficult and not optimal, and thereby there remains a need to develop new engineering strategy. Here, we engineered an OSH overproducing Escherichia coli strain through deleting the degradation and competitive pathways, overexpressing thrA and metL to enhance the metabolic flux from l -asparate to l -homoserine. Additionally, increasing the precursor succinyl-CoA supply through simultaneously knocking out sucD and overexpressing sucA further increased the yield of OSH. The engineered strain OSH9/pTrc-metA11-yjeH with above strategies produced OSH at the concentration of 24.1 g/L (0.609 g/g glucose) in batch fermentation. To gain detailed insight into metabolism of the engineered strain, comparative metabolic profiling was performed between the engineered and wide-type strain. The metabolomics data deciphered that the carbon was directed toward the OSH biosynthesis resulting in less flexibility of the genetically modified strain than the wide-type strain.

The skin is especially vulnerable to many physical triggering factors, causing many distinctive clinical features as shown in this chapter: erythema ab igne, actinic lichen planus, phytophotodermatitis, colloid milium, and dermatitis artefacta.

Skin tumor is the most intriguing topic for the clinicians. This chapter covers a wide range of issues and provides with informative clues and tips associated with clinical features and pathological presentations and keeps pace with the latest development in molecular biology and immunohistochemistry to assist the readers in the establishment of accurate diagnosis. These following disorders are elaborately selected and arranged from a histopathological perspective.

Defects of dermal elastic fibers are relatively uncommon. This chapter touches upon disseminated elastosis perforans serpiginosa, papular elastorrhexis, congenital cutis laxa, cutis laxa, blepharochalasis, pseudoxanthoma elasticum, cutis hyperelastica complicated by the abnormity in immunoassay, giant connective tissue nevus, eruptive collagenoma, white fibrous papulosis of the neck, and pseudoainhum.

This chapter presents with granulosis rubra nasi, Fox-Fordyce disease, ophiasis and sisaipho hair regrowth pattern, pseudopelade of Brocq, alopecia areata sparing white hairs within lesion, coexistence of acquired hypertrichosis and scalp alopecia, woolly hair, monilethrix, pili annulati, trichonodosis, hair cast, trichostasis spinulosa, cutaneous pili migrans, red hair, permanent poliosis after plucking, congenital leukonychia totalis, hyperpigmentation of the nail from lead deposition, longitudinal erythronychia, chromonychias, subungual splinter hemorrhage, sebaceous gland hyperplasia, as well as sebaceous hyperplasia within epidermis after scald.

This chapter deals with a heterogeneous group of skin disorders caused by parasitic infection, sting, and bites and consists of cutaneous leishmaniasis, cutaneous paragonimiasis, cutaneous larva migrans, cerebral and subcutaneous cysticercosis, cutaneous myiasis caused by larvae of Hypoderma bovis, phthiriasis palpebrarum, tick bite, Norwegian scabies, infant Pyemotes dermatitis, and jellyfish dermatitis.

In Real-Time Bidding (RTB) advertising, estimating the winning price is an important task in evaluating the bid cost of bid requests in Demand-Side Platforms (DSPs). The prior works utilize censored linear regression for winning price estimation by considering both winning and losing bid records. In the traditional regression models, the winning price of each bid request is based on Gaussian distribution. However, the property of Gaussian distribution is not suitable for the winning price of each bid request, and it is hard to link the physical meaning of Gaussian distribution and the winning price. Therefore, in this paper, based on our observation and analysis, the winning price of each bid request is modeled by a unique gamma distribution with respect to its features. Then we propose a gamma-based censored linear regression with regularization for winning price estimation. To derive the parameters of our proposed complicated model based on bid records, our approach is to divide this hard problem into two sub-problems, which are easier to solve. In practice, we also provide four heuristic initial parameter settings that are able to greatly reduce the computation cost when deriving the parameters. The experimental results demonstrate that our approach is highly effective for estimating the winning price compared with the state-of-the-art approaches in three real datasets.