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Human umbilical vein endothelial cells (HUVECs) are primary cells isolated from the vein of an umbilical cord, extensively used in cardiovascular studies and medical research. These cells, retaining the characteristics of endothelial cells in vivo, serve as a valuable cellular model system for understanding vascular biology, endothelial dysfunction, pathophysiology of diseases such as atherosclerosis, and responses to different drugs or treatments. Transmission electron microscopy (TEM) has been a cornerstone in revealing the detailed architecture of multiple cellular model systems including HUVECs, allowing researchers to visualize subcellular organelles, membrane structures, and cytoskeletal elements. Among them, the endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus can be meticulously examined to recognize alterations indicative of cellular responses to various stimuli. Importantly, Weibel-Palade bodies are characteristic secretory organelles found in HUVECs, which can be easily distinguished in the TEM. These distinctive structures also dynamically react to different factors through regulated exocytosis, resulting in complete or selective release of their contents. This detailed review summarizes the ultrastructural features of HUVECs and highlights the utility of TEM as a pivotal tool for analyzing HUVECs in diverse research frameworks, contributing valuable insights into the comprehension of HUVEC behavior and enriching our knowledge into the complexity of vascular biology.

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Morchella sextelata, a highly sought-after edible mushroom worldwide, is evaluated based on its cap color as an essential commercial property indicator. In the present study, the effects of blue light on cap pigmentation in M. sextelata, as well as the synthesis and structural characteristics of melanin pigments within the cap were examined. The results showed that an increase in the proportion of blue light within the lighting environment promoted melanin synthesis and melanization of the cap. Transmission and scanning electron microscopy revealed the localization of melanin within the mycelium and its ultrastructural characteristics. The UV-visible analysis demonstrated that melanin exhibited a maximum absorption peak at 220 nm and possessed high alkaline solubility as well as acid precipitability. The structural characteristics of melanin were analyzed using FTIR, NMR, HPLC, and elemental analysis, which confirmed the presence of eumelanin, pheomelanin, and allomelanin in both brown and black caps. Furthermore, blue light can stimulate the synthesis of both eumelanin and pheomelanin. The obtained results can serve as the foundation for comprehending the mechanism by which light regulates color formation in mushrooms.

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Jirovecia species primarily infect oligochaetes and are typically characterized by large rod-shaped spores with a tail-like posterior prolongation. Presently, seven Jirovecia spp. are reported worldwide with only one described in China. Here, a new species, Jirovecia branchilis n. sp. was discovered in glands of oligochaetes Branchiura sowerybi Beddard, 1892 in China. Jirovecia branchilis n. sp. elicited the formation of numerous opaque xenomas of 0.12 to 0.20 mm (n = 30) in diameter. Electron microscopic observations demonstrated that the earliest developmental stages observed were uninucleate meronts residing directly with the host cytoplasm. Mature spores were rod-shaped with blunt ends and possessed a collar-like anchoring disk, a manubrium-type polar filament, a bipartite polarplast, and a three-layered spore wall. A tail-like prolongation was distinctly observed in the posterior of spores and measured 13.2-28.6 µm long (n = 30). Jirovecia branchilis n. sp. showed 98.54% sequence similarity with Janacekia tainunus isolated from the fat body of chironomidae larvae Kiefferulus tainanus based on obtained partial SSU rDNA gene sequence, but was significantly different in morphology, host, and infection sites. SSU rDNA-based phylogenetic analysis indicated Jirovecia branchilis n. sp. clustered with Janacekia tainanus within the Jirovecia-Bacillidium-Janacekia clade. In conclusion, a new species within Jirovecia, Jirovecia branchilis n. sp. is erected herein based mainly on its morphological, ecological, and to a lesser degree on its molecular characteristics. The whole relationship between Jirovecia spp., Janacekia spp., and Bacillidium spp. is in need of revision and could potentially be elucidated by using additional makers and sequencing a broader diversity of the already described species.

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The article presents the main electron microscopic signs of the main histological variants of renal cell carcinoma. The ultrastructural profiles of rare forms of renal cell carcinoma included in the latest International Histological Classification of Kidney Tumors (WHO, 2016) are considered.

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The vanilloid receptor TRPV1 has been suggested to play an important role in thermal nociception and inflammatory hyperalgesia. In our previous study, we examined the expression of TRPV1 and colocalization of TRPV1 with substance P (SP) and calcitonin gene related peptide (CGRP) through fluorescence immunocytochemistry. Here, we investigated ultrastructural characteristics of TRPV1 immunoreactive fibers in the human tooth pulp through preembedding immunocytochemistry. TRPV1 immunoreactivity was present in the unmyelinated nerve fibers in the tooth pulp. There were two types of TRPV1 IR nerve fibers identified in the human tooth pulp: one containing clear round vesicles and many dense-cored vesicles, the other containing clear round vesicles and few dense-cored vesicles. TRPV1 immunoreactive fibers were constant in diameter without swellings along the length. Boutons en passant and boutons terminaux usually observed in the CNS were not observed in the TRPV1 immunoreactive fibers. Many vesicles were accumulated in the TRPV1 immunoreactive fibers, however synaptic structure was not found. It is known that dense-cored vesicles contain neuropeptides such as SP and CGRP and clear round vesicles contain neurotransmitter such as glutamate. Taken together, our results suggest that TRPV1 immunoreactive fibers showing distinct ultrastructructural features may be involved in inflammatory hyperalgesia and thermal nociception in the tooth pulp.

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