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Comparative Anatomy, Physiology, and Biochemistry of Mammalian Skin
Published in David W. Hobson, Dermal and Ocular Toxicology, 2020
Apocrine glands are large, simple coiled tubular structures. The name apocrine is inappropriate because it was once thought that the apical portion of the cell was lost during secretion; however, electron microscopy has shown that the secretion is actually a product of the cell and that no cytoplasm is lost during the secretory process. The secretory portion of this gland consists of cuboidal to columnar cells which rest on the myoepithelial cells or on the basement membrane. In areas of the basement membrane which are devoid of myoepithelial cells, the plasmalemma of the secretory cell is highly convoluted. This folded area could provide for an exchange of metabolites. The apical portion of this cell has microvilli on its surface. Organelles are prominent, especially the Golgi apparatus which is usually located on the apical side of the nucleus. Mitochondria are located both on the basal side and apical side of the nucleus. They are greatly enlarged and have a homogeneous granular matrix. Large, dense granules are located on the apical side of the Golgi region and vary in size, density, and homogeneity. Rough endoplasmic reticulum and tonofilaments are abundant. Adjacent secretory cells are connected by junctional complexes.229
Cellular Components of Blood
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
Within the platelet are numerous granules, the α-granules and the dense granules (DG). The α-granules contain β-thromboglobulin, fibronectin, fibrinogen, platelet factor 4, platelet-derived growth factor (PDGF), thrombospondin (TSP) and vWF (Figure 51.13b). The platelet DG has an electron-dense core and stores serotonin, ADP, ATP and pyrophosphate. Other organelles include lysosomes containing hydrolytic enzymes, and peroxisomes containing catalase. Anaerobic glycolysis in the mitochondria is the main source of ATP, although some aerobic metabolism occurs through the Krebs citric acid cycle.
PRP in Vitiligo
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
These cytokines play important roles in cell proliferation, chemotaxis, cell differentiation, and angiogenesis. Platelet-derived growth factor has a significant role in the formation of blood vessels (angiogenesis) that induces proliferation of various cells as epithelial cells, collagen tissue, and smooth muscle cells. VEGF is another chemical signal stimulating the growth of new blood vessels and tissue growth. Dense granules of platelet contain serotonin, histamine, dopamine, calcium, and adenosine. These bioactive factors have fundamental effects on the biologic aspects of wound healing [6].
Platelets for advanced drug delivery in cancer
Published in Expert Opinion on Drug Delivery, 2023
Daniel Cacic, Tor Hervig, Håkon Reikvam
Although platelets are anucleate cell fragments with a rapid mRNA time decay [23], limited protein synthesis persists [24]. However, most platelet proteins are inherited by parental MKs, and a recent analysis of the platelet proteome identified over 5,000 unique proteins [25]. Some proteins are packed in granules, mainly alpha granules and dense granules, which are released upon platelet activation, yielding a complex releasate [26]. Furthermore, the composition of the platelet releasate differs depending on the activation stimuli [27,28]. Platelet alpha granules contain several hundred proteins, including growth factors and chemokines [29,30]. Conversely, dense granules primarily contain small coagulation-active substances such as ADP, serotonin, and calcium. However, mass spectrometry analysis has also revealed a minor selection of cell signaling proteins [31].
A new case with Hermansky-Pudlak syndrome type 9, a rare cause of syndromic albinism with severe defect of platelets dense bodies
Published in Platelets, 2021
Vincent Michaud, Mathieu Fiore, Valentine Coste, Yoann Huguenin, Jean-Claude Bordet, Claudio Plaisant, Eulalie Lasseaux, Fanny Morice-Picard, Benoit Arveiler
The present report describes the fourth HPS-9 patient in the literature. Skin and hair hypopigmentation seems to be a constant feature since all cases reported have light skin or hair (Table I). Ocular albinism is constant since all HPS-9 patients show at least a nystagmus and two of them have iris transillumination and retinal hypopigmentation. Hematological features are also frequent. Although patients with HPS usually have a normal platelet count, the three previously described HPS-9 patients have thrombopenia and our patient has a platelet number in the lower limit of the normal range. Platelet aggregation is described as abnormal for three patients but detailed information is lacking for the two patients published. Absence of dense granules has only been studied for two patients included one from Okamura et al. without detail of the method used. Platelet study by electron microscopy is important to support the molecular diagnosis of HPS. To note, leukopenia and recurrent infections were noted in two patients. Neutropenia has only been described for HPS-2 and HPS-10 and is not found in our patient. Extensive NK-cell function studies allowed Badolato et al. to conclude to a defect in NK-cell degranulation [2]. Our case is the only one with delayed psychomotor development and dextrocardia. Due to the limited number of cases reported we cannot yet conclude that these findings are features of HPS-9, or if they occurred fortuitously.
96-well plate-based aggregometry
Published in Platelets, 2018
Melissa V. Chan, Paul C. Armstrong, Timothy D. Warner
Coupled with the study of platelet aggregation, other measures of platelet activation can also readily be assessed. For example, ATP release from dense granules after agonist stimulation can be detected using CHRONO-LUME® (Chronolog, Labmedics, UK) reagent. The firefly luciferase enzyme found in this reagent converts ATP to light which can be readily measured with standard laboratory equipment (30). In simple terms, the reagents can be added to a white-walled 96-well plate before mixing for a shorter period of time (2–3 minutes) and placing into a luminescent plate reader. This assay allows both laboratory-based studies into the mechanisms of granule release and the effects of drug therapies, as well as the clinical characterization of platelets from patients with suspected abnormal dense granule release.