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The Scientific Basis of Medicine
Published in John S. Axford, Chris A. O'Callaghan, Medicine for Finals and Beyond, 2023
Chris O'Callaghan, Rachel Allen
The membrane-bound nucleus acts as a store for genetic information. Nuclear pores facilitate exchange of protein and RNA between the nucleus and the rest of the cell. Newly formed proteins destined for transport to lysosomes or the cell surface are inserted into the endoplasmic reticulum (ER), a system of folded membranes. Initial protein glycosylation may also occur within the ER. From the ER, proteins progress through a related system of compartments known as the Golgi complex, where further modifications take place. The Golgi complex sorts macromolecules for onward transport and, on leaving it, proteins progress through a system of vesicles until they reach their ultimate location.
Structural Organization of the Liver
Published in Robert G. Meeks, Steadman D. Harrison, Richard J. Bull, Hepatotoxicology, 2020
Morphologically, the Golgi complex consists of a stack of 4–6 dis-shaped cisternae, each with a diameter of 1 μm and a 30-nm lumen and associated small vesicles (20–30 nm in diameter) (Figure 18). The closely stacked cisternae (the Golgi stack) have two distinct faces: a convex, dis or forming face and a concave, trans or maturing face. The cis face is closely associated with the ER. The trans face is the face closest to the cell surface. The vesicles associated with the trans face include those containing protein or lipoprotein destined for secretion into the sinusoid after vesicular fusion with plasma membrane. Some of the vesicles in this region are primary lysosomes that recycle between the Golgi complex and secondary lysosomes (see section on Vasicular Transport System). In addition, an elaborate trans-tubular reticular membrane system has been demonstrated. This system is thought to be involved in terminal glycosylation, and in the sorting of endocytic and exocytic constituents of lysomosomes and plasma membrane (Griffiths and Simons, 1986; Farequhar, 1985). The Golgi complex are relatively numerous in the hepatocytes, and their number is estimated to be as many as 50 per cell. They tend to be more numerous in the proximity of the bile canaliculi. The membrane of the Golgi complex comprises approximate 2% of total cellular membrane surface area, or approximately 0.185 m2 per gram of liver (Blouin, 1983).
The Immune System and its Function
Published in Istvan Berczi, Pituitary Function and Immunity, 2019
The heavy and light chains of immunoglobulins are produced in the rough endoplasmic reticulum of B lymphocytes, and assembly begins in the cysternae. Carbohydrate is added in the Golgi complex, after which the molecules are packed in secretory vesicles that fuse with the plasma membrane and become externalized and shed, or remain membrane-bound in order to function as an antigen receptor.
Mitochondrial organization and structure are compromised in fibroblasts from patients with Huntington’s disease
Published in Ultrastructural Pathology, 2022
Marie Vanisova, Hana Stufkova, Michaela Kohoutova, Tereza Rakosnikova, Jana Krizova, Jiri Klempir, Irena Rysankova, Jan Roth, Jiri Zeman, Hana Hansikova
Similarly to the mitochondrial network, structural changes of the Golgi apparatus during physiological/pathological processes like cell cycle,59 neurodegeneration60 or cellular ATP production42 were described. Research in the last decade has shown that the Golgi complex is responsible not only for the protein secretory pathway, but is also a highly dynamic organelle influenced by various cellular stimuli and also playing a role in HD pathogenesis. Dysfunctional mHtt disrupts vesicular transport from Golgi along microtubules and prevents the fusion of vesicles with the plasma membrane.61 Lower ATP production or increased cellular stress lead to modulation of steroidogenesis or membrane lipid homeostasis via the Golgi protein ACBD3.62 In HD, increased levels of the ACBD3 protein raise the levels of the ACBD3/mHtt/Rhes complex (Rhes, Ras homolog enriched in striatum, is a small GTPase), causing a higher cytotoxicity in HD via Rhes-induced sumoylation of mHtt.63 We suggest that the observed changes in Golgi architecture in fibroblasts complement the ultrastructural and functional alteration of mitochondria caused by HD pathogenesis.
Ultrastructural evidence for presenсe of gap junctions in rare case of pleomorphic xanthoastrocytoma
Published in Ultrastructural Pathology, 2020
Evgeniya Yu. Kirichenko, Sehweil Salah M. M., Zoya A. Goncharova, Aleksei G. Nikitin, Svetlana Yu. Filippova, Sergey S. Todorov, Marina A. Akimenko, Alexander K. Logvinov
Tumor cells of PXA were represented by large polygonal mononuclear or multinuclear xanthastrocytes, with dark cytoplasm due to the presence of multiple gliofibrills. The nuclei of these cells had dark karyoplasm, irregular shape with deepenings and invaginations, sometimes without clear boundaries of the karyolemma. The longitudinal processes of such cells were filled with bundles of gliofibrills and could contact the bodies of other cells. Among the cellular organelles, the Golgi complex, RER, mitochondria, and intermediate filaments, which often displace other organelles, were noted. Also, the cytoplasm of such cells contained various inclusions: multiple lipid drops, not limited by the membrane, primary and secondary lysosomes of various calibers, as well as lipofuscin granules (Figure 2a). Another type of PXA cells had less dark cytoplasm due to the lower content of gliofibrils: as a rule, they have elongated bodies with elongated nuclei, light karyolemma and invaginations. The presence of a basal lamina surrounding single cells as well as small groups of cells was noted (Figure 1h). The tumor intercellular space consisted of predominantly small processes of various caliber containing gliofibrills.
Early photoreceptor outer segment loss and retinoschisis in Cohen syndrome
Published in Ophthalmic Genetics, 2018
Katherine E. Uyhazi, Gil Binenbaum, Nicholas Carducci, Elaine H. Zackai, Tomas S. Aleman
Cohen syndrome is an infrequent, autosomal recessive disease characterized by a distinctive facial appearance, microcephaly, mental retardation, benign neutropenia, and pigmentary retinopathy (1–3). The condition has been associated with functionally null mutations in COH1 (VPS13B), a gene located at 8q22-q23 that encodes a member of a group (VPS13) of evolutionarily conserved proteins involved in maintaining mitochondrial integrity and protein sorting (4–9). COH1 is ubiquitously expressed, although brain- and retinal-specific splicing variants have been identified (10). The protein localizes to the Golgi complex and there is evidence in support for a role of COH1 in maintaining the structural and functional integrity of this organelle through its involvement in protein glycosylation reactions and lysosomal/endosomal function (10–14). The syndrome is considered a congenital disorder of glycosylation that disrupts neuronal outgrowth (10,13).