China
Africa
Explore chapters and articles related to this topic
Muscle and Nerve Histology
Published in Maher Kurdi, Neuromuscular Pathology Made Easy, 2021
The plasmalemma extends deeps into the muscle fibers, forming T-tubules that carry the depolarization of action potential inside the fibers. Hence, a T-tubule with two terminal cisterns forms a triad. The triad has a voltage-gated calcium channel and ryanodine receptor. T-tubules and sarcoplasmic reticulum are essential components involved in muscle contraction.
Skeletal Muscle
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
Myofibrils are surrounded by two distinctive structures (Figure 9.5). One is a system of transverse tubules, or T tubules, that encircle each myofibril at regular intervals. In mammals, the T tubules are found near the junction of the A bands and the I bands. The T tubules have a lumen, 2–5 nm across, that is open to the external medium at the surface of the fiber. They are therefore filled with extracellular fluid, and their membrane lining is a continuation of the sarcolemma, thereby allowing the muscle AP to propagate deep into the muscle fiber. Because of their extensive nature, the T tubules increase the effective capacitance per unit area of the muscle fiber to more than 5 µF/cm2, compared to about 0.8 µF/cm2 for the membranes of other cells.
Ultrastructure of The Myometrium and The role of Gap Junctions in Myometrial Function
Published in Gabor Huszar, The Physiology and Biochemistry of the Uterus in Pregnancy and Labor, 2020
Arie Verhoeff, Robert E. Garfield
Although these vesicles have been suggested to be sites for ion transport and binding,34,35 their function is not known. It is suggested that they perform a similar function as the T-tubules in striated muscle. The vesicles are often seen in close association to mitochondria and sarcoplasmic reticulum (SR) (Figure 3).31,32,36 The vesicles are not likely to participate in any pinocytotic or endocytotic function as they have never been shown to be interiorized. Electron-dense tracers readily penetrate into the vesicles when added either before or after fixation,30 suggesting that they are all open to the exterior.
The roles of human induced pluripotent stem cell-derived cardiomyocytes in drug discovery: managing in vitro safety study expectations
Published in Expert Opinion on Drug Discovery, 2020
Adult cardiomyocytes display a high length-to-width ratio, may be bi-nucleated, and form sophisticated internal structures such as T-tubules and the sarcoplasmic reticulum within the sarcomere’s Z-line. T-tubules are significant due to their role in contraction propagation [7]. Adult cardiomyocytes display Z-discs, I-, H-, A- and M- bands. In addition, adult cardiomyocytes have sarcomeres that are long (2.2 μm) and highly organized. These cells also possess large numbers of mitochondria due to the heart’s ceaseless energetic demands. Myocardial mitochondria tend to be evenly distributed throughout the cell and account for 20%-40% of cell size. In contrast, immature hiPSC-CMs tend to be round, usually mono-nucleated, and the sarcomere is disorganized and shorter (1.6 μm). Typical 2-dimensional cell constructs also do not possess T-tubules and only have disorganized Z-discs and I- bands and the sarcomeres appear to be organized but in a more isotropic fashion [8].
Coenzyme Q10 protects against doxorubicin-induced cardiomyopathy via antioxidant and anti-apoptotic pathway
Published in Tissue Barriers, 2023
Dalia A. Shabaan, Nora Mostafa, Manal M. El-Desoky, Eetmad A. Arafat
Intercalated discs play a vital role in the transmission of action potentials and Ca2+ during muscle contraction, where the Gap junction channels of the intercalated discs are responsible for direct cell-to-cell communication. Therefore, heart disease causes modification of gap junction organization.49 In the present study, we demonstrated ultrastructure changes in the intercalated disk and its gap junctions’ contents. TEM examination revealed substantially damaged intercalated discs. they appeared hazy, uneven, or interrupted. Our results are in accordance with previous studies.50,51 They attributed the contractility dysregulation in dox. induced heart failure to intercalated disc damage and uncoupling between T tubule and sarcoplasmic reticulum
Motor activity and Becker’s muscular dystrophy: lights and shadows
Published in The Physician and Sportsmedicine, 2020
Giuseppe Lanza, Marcello Pino, Francesco Fisicaro, Carla Vagli, Mariagiovanna Cantone, Manuela Pennisi, Rita Bella, Maria Bellomo
During relaxation, the myofilaments of these sarcomeres would no longer be able to overlap and interact, so that, in the course of repeated eccentric contractions, these sarcomeres will be lengthened instantly. Eventually, this would lead to a rapid increase in tension of the adjacent sarcomeres that leads to a structural damage. If sufficient, the damage of the T-tubules together with the opening of cationic channels which are activated by mechanical stimuli, will lead to the release of intracellular calcium. The increase in sarcoplasmic calcium levels, in turn, causes the activation of proteolytic enzymes associated with destruction and subsequent repair process of the muscle fiber [12–15].