1Heart Research Center Goettingen, 2Clinic of Cardiology & Pulmonology, University Medical Center Goettingen, 3German Center for Cardiovascular Research (DZHK) partner site Goettingen, 4BioMET, Center for Biomedical Engineering & Technology, University of Maryland School of Medicine
1Anhui Province Key Laboratory of Hepatopancreatobiliary Surgery, The First Affiliated Hospital of USTC, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, Anhui, China, 2Central Nodal (Anhui) Bioscience and Technology Research Center, Hefei, Anhui, China, 3Pediatric Cardiac and Thoracic Surgery, University Hospitals Cleveland Medical Center
Methods for the Isolation, Culture, and Functional Characterization of Sinoatrial Node Myocytes from Adult Mice
1Department of Physiology and Biophysics, University of Colorado Anschutz Medical Campus, 2Department of Bioengineering, University of Colorado Anschutz Medical Campus, 3Department of Medicine, Division of Cardiology, University of Colorado Anschutz Medical Campus
Skeletal muscle is the most abundant type of muscle in the body. Tendons are the connective tissue that attaches skeletal muscle to bones. Skeletal muscles pull on tendons, which in turn pull on bones to carry out voluntary movements.
Skeletal muscles are surrounded by a layer of connective tissue called epimysium, which helps protect the muscle. Beneath the epimysium, an additional layer of connective tissue, called perimysium, surrounds and groups together subunits of skeletal muscle called fasciculi. Each fascicle is a bundle of skeletal muscle cells, or myocytes, which are often called skeletal muscle fibers due to their size and cylindrical appearance. Between the muscle fibers is an additional layer of connective tissue called endomysium. The muscle fiber membrane is called the sarcolemma. Each muscle fiber is made up of multiple rod-like chains called myofibrils, which extend across the length of the muscle fiber and contract. Myofibrils contain subunits called sarcomeres, which are made up of actin and myosin in thin and thick filaments, respectively. Actin contains myosin-binding sites that allow thin and thick filaments to connect, forming cross bridges. For a muscle to contract, accessory proteins that cover myosin-binding sites on thin filaments must be displaced to enable the formation of cross bridges. During muscle contracti…
The Endoplasmic Reticulum (ER) in eukaryotic cells is a substantial network of interconnected membranes with diverse functions, from calcium storage to biomolecule synthesis. A primary component of the endomembrane system, the ER manufactures phospholipids critical for membrane function throughout the cell. Additionally, the two distinct regions of the ER specialize in the manufacture of specific lipids and proteins. The rough ER is characterized by the presence of microscopically-visible ribosomes on its surface. As a ribosome begins translation of an mRNA in the cytosol, the presence of a signal sequence directs the ribosome to the surface of the rough ER. A receptor in the membrane of the ER recognizes this sequence and facilitates the entry of the growing polypeptide into the ER lumen through a transmembrane protein complex. With the assistance of chaperones, nascent proteins fold and undergo other functional modifications, including glycosylation, disulfide bond formation, and oligomerization. Properly folded and modified proteins are then packaged into vesicles to be shipped to the Golgi apparatus and other locations in the cell. Chaperones identify improperly folded proteins and facilitate degradation in the cytosol by proteasomes. Lacking ribosomes, the smooth ER is the cellular location of lipid and steroid synthesis, cellular detoxification, …