scholarly journals A STUDY OF THE T SYSTEM IN RAT HEART

1970 ◽  
Vol 44 (1) ◽  
pp. 1-19 ◽  
Author(s):  
W. G. Forssmann ◽  
L. Girardier
Keyword(s):  
Rat Heart ◽  
Photometric Method ◽  
Ventricular Muscle ◽  
Transverse Tubular System ◽  
System A ◽  
L System ◽  
Line Region ◽  
Specific Granules ◽  
Sizable Proportion ◽  
T System

The technique of extracellular space tracing with horseradish peroxidase is adapted for labeling the transverse tubular system (T system) in rat heart. In rat ventricular muscle the T system shows extensive branching and remarkable tortuosity. The T system can only be defined operationally, since it does not display specific morphological features throughout its entire structure. Owing to branching of the T system, a sizable proportion of the apposition between the T system and L system (or closed system) occurs at the level of longitudinal branches of the T system and is not restricted to the Z line region. The regions of apposition between the T system and L system are analyzed in rat ventricular muscle and skeletal muscle (diaphragm) and compared with the intercellular tight junctions (nexuses) of heart muscle by the use of a photometric method. The over-all thickness of the nexus is significantly smaller than that of T-L junctions in both cardiac and skeletal muscles. The thickness of the membranes of the T and L systems are not significantly different in the two muscles, but the gap between both membranes is larger in the heart. In atrial muscle the following two types of cells are found: (a) those cells with a well-developed T system in which the tubular diameter is quite uniform and the orientation predominantly longitudinal and, (b) cells with no T system, but with a well-developed L system. Atrial cells possessing a T system are richly provided with specific granules and show little micropinocytotic activity, whereas cells devoid of T system show intense micropinocytotic activity and few specific granules. The possible functional implications of these findings are discussed.

scholarly journals Delayed rectification in the transverse tubules: origin of the late after-potential in frog skeletal muscle.

1977 ◽  
Vol 70 (1) ◽  
pp. 1-21 ◽  
Author(s):  
G E Kirsch ◽  
R A Nichols ◽  
S Nakajima
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Tetanic Stimulation ◽  
Potassium Accumulation ◽  
Transverse Tubular System ◽  
System A ◽  
Delayed Rectification ◽  
Wide Range ◽  
Time Courses ◽  
T System

Tetanic stimulation of skeletal muscle fibers elicits a train of spikes followed by a long-lasting depolarization called the late after-potential (LAP). We have conducted experiments to determine the origin of the LAP. Isolated single muscle fibers were treated with a high potassium solution (5 mM or 10 mM K) followed by a sudden reduction of potassium concentration to 2.5 mM. This procedure produced a slow repolarization (K repolarization), which reflects a diffusional outflow of potassium from inside the lumen of the transverse tubular system (T system). Tetanic stimulation was then applied to the same fiber and the LAP was recorded. The time courses of K repolarization and LAP decay were compared and found to be roughly the same. This approximate equality held under various conditions that changed the time courses of both events over a wide range. Both K repolarization and the LAP became slower as fiber radius increased. These results suggest that LAP decay and K repolarization represent the same process. Thus, we conclude that the LAP is caused by potassium accumulation in the T system. A consequence of this conclusion is that delayed rectification channels exist in the T system. A rough estimation suggests that the density of delayed rectification channels is less in the T system than in the surface membrane.

Three-Dimensional Visualization of the T-System of Frog Muscle Using High Voltage Electron Microscopy and a Lanthanum Stain

1977 ◽  
Vol 35 ◽  
pp. 570-571 ◽  
Author(s):  
Lee D. Peachey ◽  
Clara Franzini-Armstrong
Keyword(s):  
Electron Microscopy ◽  
High Voltage ◽  
Three Dimensional ◽  
Biological Tissues ◽  
High Voltage Electron Microscopy ◽  
Transverse Tubular System ◽  
Peroxidase Reaction ◽  
Voltage Electron ◽  
High Voltage Electron ◽  
T System

The effective study of biological tissues in thick slices of embedded material by high voltage electron microscopy (HVEM) requires highly selective staining of those structures to be visualized so that they are not hidden or obscured by other structures in the image. A tilt pair of micrographs with subsequent stereoscopic viewing can be an important aid in three-dimensional visualization of these images, once an appropriate stain has been found. The peroxidase reaction has been used for this purpose in visualizing the T-system (transverse tubular system) of frog skeletal muscle by HVEM (1). We have found infiltration with lanthanum hydroxide to be particularly useful for three-dimensional visualization of certain aspects of the structure of the T- system in skeletal muscles of the frog. Specifically, lanthanum more completely fills the lumen of the tubules and is denser than the peroxidase reaction product.

scholarly journals Remodeling of t-system and proteins underlying excitation-contraction coupling in aging versus failing human heart

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yankun Lyu ◽  
Vipin K. Verma ◽  
Younjee Lee ◽  
Iosif Taleb ◽  
Rachit Badolia ◽  
...  
Keyword(s):  
Heart Function ◽  
Ventricular Myocardium ◽  
Left Ventricular ◽  
Left Ventricular Myocardium ◽  
Excitation Contraction Coupling ◽  
Transverse Tubular System ◽  
Contraction Coupling ◽  
Senescent Phenotype ◽  
Cellular Microstructure ◽  
T System

AbstractIt is well established that the aging heart progressively remodels towards a senescent phenotype, but alterations of cellular microstructure and their differences to chronic heart failure (HF) associated remodeling remain ill-defined. Here, we show that the transverse tubular system (t-system) and proteins underlying excitation-contraction coupling in cardiomyocytes are characteristically remodeled with age. We shed light on mechanisms of this remodeling and identified similarities and differences to chronic HF. Using left ventricular myocardium from donors and HF patients with ages between 19 and 75 years, we established a library of 3D reconstructions of the t-system as well as ryanodine receptor (RyR) and junctophilin 2 (JPH2) clusters. Aging was characterized by t-system alterations and sarcolemmal dissociation of RyR clusters. This remodeling was less pronounced than in HF and accompanied by major alterations of JPH2 arrangement. Our study indicates that targeting sarcolemmal association of JPH2 might ameliorate age-associated deficiencies of heart function.

scholarly journals A Highly Selective Turn-On Fluorescent Probe for the Detection of Zinc

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 3825
Author(s):  
Ling-Yi Shen ◽  
Xiao-Li Chen ◽  
Xian-Jiong Yang ◽  
Hong Xu ◽  
Ya-Li Huang ◽  
...  
Keyword(s):  
High Selectivity ◽  
Fluorescence Probe ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Turn On ◽  
Imine Nitrogen ◽  
System A ◽  
Plot Analysis ◽  
L System

A novel turn-on fluorescence probe L has been designed that exhibits high selectivity and sensitivity with a detection limit of 9.53 × 10−8 mol/L for the quantification of Zn2+. 1H-NMR spectroscopy and single crystal X-ray diffraction analysis revealed the unsymmetrical nature of the structure of the Schiff base probe L. An emission titration experiment in the presence of different molar fractions of Zn2+ was used to perform a Job’s plot analysis. The results showed that the stoichiometric ratio of the complex formed by L and Zn2+ was 1:1. Moreover, the molecular structure of the mononuclear Cu complex reveals one ligand L coordinates with one Cu atom in the asymmetric unit. On adding CuCl2 to the ZnCl2/L system, a Cu-Zn complex was formed and a strong quenching behavior was observed, which inferred that the Cu2+ displaced Zn2+ to coordinate with the imine nitrogen atoms and hydroxyl oxygen atoms of probe L.

The FL-system: a functional L-system for procedural geometric modeling

2005 ◽  
Vol 21 (5) ◽  
pp. 329-339 ◽  
Author(s):  
Jean-Eudes Marvie ◽  
Julien Perret ◽  
Kadi Bouatouch
Keyword(s):  
Geometric Modeling ◽  
System A ◽  
L System

Faba bean canopy modelling with a parametric open L-system: a comparison with the Monsi and Saeki model

1998 ◽  
Vol 58 (1) ◽  
pp. 1-13 ◽  
Author(s):  
Carlos H. Dı́az-Ambrona ◽  
Ana M. Tarquis ◽  
M. lnés Mı́nguez
Keyword(s):  
Faba Bean ◽  
System A ◽  
L System

Na+-K+ pumps in the transverse tubular system of skeletal muscle fibers preferentially use ATP from glycolysis

2007 ◽  
Vol 293 (3) ◽  
pp. C967-C977 ◽  
Author(s):  
T. L. Dutka ◽  
G. D. Lamb
Keyword(s):  
Creatine Phosphate ◽  
Vital Role ◽  
Bathing Solution ◽  
Transverse Tubular System ◽  
Pump Function ◽  
Ec Coupling ◽  
Substrate Diffusion ◽  
Intracellular Ca ◽  
Triad Junction ◽  
T System

The Na+-K+ pumps in the transverse tubular (T) system of a muscle fiber play a vital role keeping K+ concentration in the T-system sufficiently low during activity to prevent chronic depolarization and consequent loss of excitability. These Na+-K+ pumps are located in the triad junction, the key transduction zone controlling excitation-contraction (EC) coupling, a region rich in glycolytic enzymes and likely having high localized ATP usage and limited substrate diffusion. This study examined whether Na+-K+ pump function is dependent on ATP derived via the glycolytic pathway locally within the triad region. Single fibers from rat fast-twitch muscle were mechanically skinned, sealing off the T-system but retaining normal EC coupling. Intracellular composition was set by the bathing solution and action potentials (APs) triggered in the T-system, eliciting intracellular Ca2+ release and twitch and tetanic force responses. Conditions were selected such that increased Na+-K+ pump function could be detected from the consequent increase in T-system polarization and resultant faster rate of AP repriming. Na+-K+ pump function was not adequately supported by maintaining cytoplasmic ATP concentration at its normal resting level (∼8 mM), even with 10 or 40 mM creatine phosphate present. Addition of as little as 1 mM phospho(enol)pyruvate resulted in a marked increase in Na+-K+ pump function, supported by endogenous pyruvate kinase bound within the triad. These results demonstrate that the triad junction is a highly restricted microenvironment, where glycolytic resynthesis of ATP is critical to meet the high demand of the Na+-K+ pump and maintain muscle excitability.

scholarly journals Severe T-System Remodeling in Pediatric Viral Myocarditis

2021 ◽  
Vol 7 ◽  
Author(s):  
Dominik J. Fiegle ◽  
Martin Schöber ◽  
Sven Dittrich ◽  
Robert Cesnjevar ◽  
Karin Klingel ◽  
...  
Keyword(s):  
Heart Failure ◽  
Chronic Heart Failure ◽  
Acute Myocarditis ◽  
Viral Myocarditis ◽  
Left Ventricular ◽  
Length Ratio ◽  
Transverse Tubular System ◽  
Ec Coupling ◽  
T Tubules ◽  
T System

Chronic heart failure (HF) in adults causes remodeling of the cardiomyocyte transverse tubular system (t-system), which contributes to disease progression by impairing excitation-contraction (EC) coupling. However, it is unknown if t-system remodeling occurs in pediatric heart failure. This study investigated the t-system in pediatric viral myocarditis. The t-system and integrity of EC coupling junctions (co-localization of L-type Ca2+ channels with ryanodine receptors and junctophilin-2) were analyzed by 3D confocal microscopy in left-ventricular (LV) samples from 5 children with myocarditis (age 14 ± 3 months), undergoing ventricular assist device (VAD) implantation, and 5 children with atrioventricular septum defect (AVSD, age 17 ± 3 months), undergoing corrective surgery. LV ejection fraction (EF) was 58.4 ± 2.3% in AVSD and 12.2 ± 2.4% in acute myocarditis. Cardiomyocytes from myocarditis samples showed increased t-tubule distance (1.27 ± 0.05 μm, n = 34 cells) and dilation of t-tubules (volume-length ratio: 0.64 ± 0.02 μm2) when compared with AVSD (0.90 ± 0.02 μm, p < 0.001; 0.52 ± 0.02 μm2, n = 61, p < 0.01). Intriguingly, 4 out of 5 myocarditis samples exhibited sheet-like t-tubules (t-sheets), a characteristic feature of adult chronic heart failure. The fraction of extracellular matrix was slightly higher in myocarditis (26.6 ± 1.4%) than in AVSD samples (24.4 ± 0.8%, p < 0.05). In one case of myocarditis, a second biopsy was taken and analyzed at VAD explantation after extensive cardiac recovery (EF from 7 to 56%) and clinical remission. When compared with pre-VAD, t-tubule distance and density were unchanged, as well as volume-length ratio (0.67 ± 0.04 μm2 vs. 0.72 ± 0.05 μm2, p = 0.5), reflecting extant t-sheets. However, junctophilin-2 cluster density was considerably higher (0.12 ± 0.02 μm−3 vs. 0.05 ± 0.01 μm−3, n = 9/10, p < 0.001), approaching values of AVSD (0.13 ± 0.05 μm−3, n = 56), and the measure of intact EC coupling junctions showed a distinct increase (20.2 ± 5.0% vs. 6.8 ± 2.2%, p < 0.001). Severe t-system loss and remodeling to t-sheets can occur in acute HF in young children, resembling the structural changes of chronically failing adult hearts. T-system remodeling might contribute to cardiac dysfunction in viral myocarditis. Although t-system recovery remains elusive, recovery of EC coupling junctions may be possible and deserves further investigation.

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