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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Sebaceous glands contain cells in various stages of differentiation. Morphologically, the gland consists of a group of lobes or acini. Three types of acinar cells have been described ultrastructurally. The structure of these cells changes progressively from the periphery to the center of each gland. The peripheral cell lies on the basement membrane that surrounds the acinus of the sebaceous gland. The second cell type is the partially differentiated cell which is actively synthesizing lipid. The third cell type is the fully differentiated cell which is large and full of lipid droplets. It is at this stage that the cell will rupture and release its entire secretion (lipid) into the sebaceous duct and then onto the surface of the skin. This process is termed holocrine secretion. The function of sebum, a complex mixture of lipids, is that of acting as an antibacterial agent. Also, in hairy mammals it may act as a waterproofing agent and may prevent moisture loss from the human epidermis.217,219,229,230 As noted by Strauss et al.,230a differences can occur in sebum composition among mammals.
ExperimentaL Oral Medicine
Published in Samuel Dreizen, Barnet M. Levy, Handbook of Experimental Stomatology, 2020
Samuel Dreizen, Barnet M. Levy
Leake et al.78 detailed the ultrastructural changes in the rat parotid gland after ligation of Stensen’s duct. The duct was ligated unilaterally in 18 mature Sprague-Dawley rats, and the parotid gland was examined by electron microscopy at intervals up to 90 days. The course ran from swelling and engorgement lasting 4 to 6 days to progressive atrophy. At 3 months, the number of identifiable acini was greatly decreased. Nuclei in the few remaining acinar cells were prominent because of the lack of secretory granules in the cytoplasm. Endoplasmic reticulum was severely disorganized and sometimes absent. Golgi apparatus was markedly decreased. Microvilli were truncated with blunt ends. Cell borders remained distinct with well-demarcated desmosomes. There was an increase in collagen and infiltration of some inflammatory cells in the areas formerly occupied by the acini.
Pancreatitis and pancreatic insufficiency
Published in Michael JG Farthing, Anne B Ballinger, Drug Therapy for Gastrointestinal and Liver Diseases, 2019
Stefan Kahl, Peter Malfertheiner
The initial events of acute pancreatitis are still incompletely elucidated (Fig. 10.1). Basic knowledge, which is still evolving, is derived from animal experiments.8 Acinar cells of the pancreas are extremely active in the synthesis of digestive enzymes, which are delivered as inactive proenzymes into the duodenal lumen where they are activated by enterokinases. In acute pancreatitis, acinar cell injury leads to co-localization of digestive enzyme zymogens and lysosomes and, in this way, lysosomal hydrolase cathepsin-B activates trypsinogen to trypsin within the cell compartment. This intracellular digestive enzyme activation produces a local inflammatory process that may extend to a generalized phenomenon, with release of cytokines and tissue damaging factors including the platelet aggregating factor (PAF). This series of events results in systemic inflammatory response syndrome (SIRS), which may progress into individual or multiple organ failure (MOF).
Stem cell therapy for salivary gland regeneration after radiation injury
Published in Expert Opinion on Biological Therapy, 2023
Akshaya Upadhyay, Simon D Tran
SGs are composed of oral epithelium-derived acinar and ductal cells arranged in a complex invaginated pattern within the mesenchyme to maximize the surface area for the production and secretion of saliva (Figure 1). Physiologically, acinar cells have been considered post-mitotic, quiescent, and highly differentiated. Thus, it was an enigma when they were found to be radio-sensitive, given that radiation affects actively dividing cells. However, recent evidence shows that acinar cells might regain their division potential and be actively involved in repair and regeneration when needed [2]]. Given the crucial role of acinar cells in saliva production and their sensitivity to damaging agents, SG regeneration can be considered synonymous with acinar cell regeneration. Hence, we call them the ‘delicate darlings’ of SG researchers.
Chronic jetlag accelerates pancreatic neoplasia in conditional Kras-mutant mice
Published in Chronobiology International, 2023
Patrick B. Schwartz, Morgan T. Walcheck, Manabu Nukaya, Derek M. Pavelec, Kristina A. Matkowskyj, Sean M. Ronnekleiv-Kelly
Prior work in the liver revealed that cell-autonomous knock-out of the clock in liver hepatocytes (Albumin-Cre; Bmal1fx/fx) drove a nearly identical phenotype compared to chronic jetlag mice (non-alcoholic fatty liver disease progressing to HCC) (Kettner et al. 2016). However, we found that in the pancreas of KC mice, this was not evident. We expected that this was a consequence of non-cell autonomous changes to the circadian clock (i.e. not acinar cells or PanINs) – whether by loss of clock function or by misalignment – are responsible for accelerating the neoplastic progression. To examine further, we tested the hypothesis that misalignment of the clock in an alternative cell population caused the accelerated PanIN formation and progression; this was done by evaluating the expression of individual cells in the tumor microenvironment over time. We performed single-cell RNA sequencing (scRNAseq) from pooled pancreatic samples (1 male/female) from both normal circadian and chronic jetlag KC mice at 5 and 9 months (Figure 6a-b). Notably, male and female mice were pooled because we consistently demonstrated no sex-specific effect within either the normal circadian or the chronic jetlag group of KC mice at 5 months or 9 months. After filtering and dimensionality reduction, a total of 14 different heterogeneous cell types were annotated using the ScType package comprising 42 211 cells (Figure 6a-b & Supplemental Data 2–3) (Ianevski et al. 2022). These included acinar cells, several classes of immune cells, endothelial cells, and fibroblast populations.
Long-term changes of pancreatic function in patients with complicated walled-off necrosis
Published in Scandinavian Journal of Gastroenterology, 2022
Camilla Nøjgaard, Mikkel Werge, Astrid Naver, Anne Wilkens Knudsen, Nicolai J. Wewer Albrechtsen, Søren Møller, Lise Lotte Gluud, Srdan Novovic
Eighty-five percent of the pancreatic tissue is represented by the exocrine pancreas whereas only 2% is comprised of endocrine tissue [24]. Approximately, 40 acinar cells constitute an acinus which is connected by centroacinar cells to the pancreatic duct system lined by pancreatic duct cells. Nearly one million islets of Langerhans are scattered throughout the pancreas. As the acinar and Langerhans cells are closely allocated it is understandable if necrosis in the pancreas leads to both exocrine and endocrine insufficiency. In line with this, we found that the four patients with new-onset diabetes also had exocrine insufficiency. This is usually not the case in chronic pancreatitis, as these patients can either have diabetes without PEI or the opposite or both. This confirm that acute necrotizing pancreatitis and chronic pancreatitis are two different diseases with different pathogenesis.