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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
One of the most important and most numerous cells in the dermis is the fibroblast. They are usually found among the collagen fibers. Young fibroblasts have an abundance of cytoplasm while old fibroblasts (fibrocytes) have very little. In light microscopy, fibroblasts are spindle shaped with long cytoplasmic processes at each end. Their nucleus is oval and contains two to four nucleoli. Fibroblasts are motile and capable of mitosis. They are derived from mesenchymal cells. The fine structure of fibroblasts include elongated processes and the usual complement of organelles. The most characteristic feature in the cytoplasm is the abundance of rough endoplasmic reticulum. This is expected of cells that synthesize the collagen protein for export. Fine filaments, sometimes occurring in bundles, are usually seen in the cytoplasm of the fibroblasts. An active or young fibroblast showing extensive rough endoplasmic reticulum and several nucleoli indicates that it is synthesizing protein for secretion. Fibroblasts secrete procollagen, glycosaminoglycans, and proelastin. Secretory vesicles can be seen all along the cell membrane of the fibroblast. These vesicles fuse with the cell membrane and release their contents (procollagen) into the extracellular space where it will be enzymatically converted to collagen.38,199,204
Cell Components and Function
Published in Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal, Principles of Physiology for the Anaesthetist, 2020
Peter Kam, Ian Power, Michael J. Cousins, Philip J. Siddal
Exocytosis results in the secretion of large protein molecules synthesized by rough ER and stored in vesicles. These secretory vesicles migrate and fuse with the cell membrane. At the point of fusion, synapsins, special proteins, allow the secretion to be controlled by Ca+. Both endocytosis and exocytosis are energy-dependent processes.
Homeostasis of Dopamine
Published in Nira Ben-Jonathan, Dopamine, 2020
All cells possess a constitutive secretory pathway whereby vesicles that originate in the Golgi complex contain newly synthesized proteins (i.e., enzymes, growth factors, receptors, and extracellular matrix components) and carry them to the cell surface. Once there, the vesicles contact the plasma membrane and either release their content to the cell exterior (e.g., hormones or neurotransmitters), or their enclosed proteins become embedded within the plasma membrane (e.g., receptors). Neurons and endocrine/neuroendocrine cells are highly specialized cells that are dedicated to intercellular communication and store their chemical signals in committed secretory vesicles. Upon receiving appropriate stimuli, these cells release their content to the cell exterior by a calcium-regulated exocytosis.
Modulating insulin secretion and inflammation against sodium arsenite toxicity by levosimendan as a novel pancreatic islets’ protector
Published in Toxin Reviews, 2023
Marzieh Daniali, Mona Navaei-Nigjeh, Maryam Baeeri, Soheyl Mirzababaei, Mahdi Gholami, Mahban Rahimifard, Mohammad Abdollahi
Regarding the insulin secretion pathway, it should be noted that insulin is produced in the endoplasmic reticulum and stored and transported in vesicles. Insulin is released from β-cells by exocytosis involving the attachment of secretory vesicles to the plasma membrane by a group of proteins called SNARE. The interaction of these proteins with the plasma membrane forms a stable complex that prepares the membrane for attachment and fusion to the granule. The exocytosis of vesicles is also regulated by Ca2+ concentration. Some studies also showed that as insulin granules become acidic, structural changes occur in the SNARE protein, facilitating its attachment to the membrane. By acting on the insulin gene transcription promoter, NaAsO2 toxin causes the cell to lose sensitivity to extracellular glucose concentrations and alter the stability of insulin mRNA, which is typically affected by glucose concentrations (Meloni et al.2013).
Cancer-associated fibroblasts and the tumor microenvironment in non-small cell lung cancer
Published in Expert Review of Anticancer Therapy, 2022
Jun Suzuki, Masahiro Tsuboi, Genichiro Ishii
Exosomes are membrane-enclosed secretory vesicles that are considered to be important mediators of intercellular communication. Luga et al. first showed that CAF-secreted exosomes promote protrusion, migration, and metastasis of breast cancer cells via canonical Wnt signaling [61]. Miki et al. found that exosomes secreted by CAFs cause migration and invasion of cancer cells in only the scirrhous type of gastric cancer [62]. Interestingly, it was the CD9+ exosome that was involved in this process, not the CD81+ exosome reported by Luga et al. Therefore, the role of exosomes secreted by CAFs may vary depending on the organs and expressed proteins. Exosomes contribute to the increased malignancy of cancer cells through non-coding microRNAs (miRNAs), proteins, and metabolites [63].
Inverse association between systemic immune-inflammation index and bone mineral density in postmenopausal women
Published in Gynecological Endocrinology, 2021
Y. N. Du, Y. J. Chen, H. Y. Zhang, X. Wang, Z. F. Zhang
Neutrophils play a role in bone loss caused by inflammation. Riegel, Poubelle et al. reported that neutrophils contain pre-formed RANK, which is stored in secretory vesicles. When neutrophils are stimulated by inflammatory cytokines such as IL-4 and TNF-α, they express OPG and RANK, which are then transferred to cell membranes [14–16]. The expression of RANK by inflammatory neutrophils may be partly be related to the neutrophils’ ability to acquire functional phenotypes of active dendritic cells [17]. Neutrophils can secrete many chemokines, such as CCL2 and CCL20, that can summon Th17 cells [18], while Th17 cells lead to bone loss. However, a lack of neutrophils leads to localized inflammatory bone loss driven by IL-17 and may cause further damage to bone tissue [19].In summary, activated neutrophils are inducers of osteoclast production.