scholarly journals Ca2+-ATPase Molecules as a Calcium-Sensitive Membrane-Endoskeleton of Sarcoplasmic Reticulum

2021 ◽  
Vol 22 (5) ◽  
pp. 2624
Author(s):  
Jun Nakamura ◽  
Yuusuke Maruyama ◽  
Genichi Tajima ◽  
Yuto Komeiji ◽  
Makiko Suwa ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Muscle Contraction ◽  
Morphological Changes ◽  
Transmembrane Protein ◽  
Muscle Relaxation ◽  
Transmission Electron ◽  
Almost All ◽  
Induced Crystallization ◽  
Sensitive Membrane

The Ca2+-transport ATPase of sarcoplasmic reticulum (SR) is an integral, transmembrane protein. It sequesters cytoplasmic calcium ions released from SR during muscle contraction, and causes muscle relaxation. Based on negative staining and transmission electron microscopy of SR vesicles isolated from rabbit skeletal muscle, we propose that the ATPase molecules might also be a calcium-sensitive membrane-endoskeleton. Under conditions when the ATPase molecules scarcely transport Ca2+, i.e., in the presence of ATP and ≤ 0.9 nM Ca2+, some of the ATPase particles on the SR vesicle surface gathered to form tetramers. The tetramers crystallized into a cylindrical helical array in some vesicles and probably resulted in the elongated protrusion that extended from some round SRs. As the Ca2+ concentration increased to 0.2 µM, i.e., under conditions when the transporter molecules fully carry out their activities, the ATPase crystal arrays disappeared, but the SR protrusions remained. In the absence of ATP, almost all of the SR vesicles were round and no crystal arrays were evident, independent of the calcium concentration. This suggests that ATP induced crystallization at low Ca2+ concentrations. From the observed morphological changes, the role of the proposed ATPase membrane-endoskeleton is discussed in the context of calcium regulation during muscle contraction.

The Sarcoplasmic Reticulum in Muscle Fatigue and Disease: Role of the Sarco(endo)plasmic Reticulum Ca2+-ATPase

2004 ◽  
Vol 29 (3) ◽  
pp. 308-329 ◽  
Author(s):  
A. Russell Tupling
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Calcium Release ◽  
Contractile Activity ◽  
Muscle Relaxation ◽  
Low Frequency ◽  
Free Calcium ◽  
Cellular Mechanisms ◽  
Plasmic Reticulum ◽  
Low Frequency Fatigue

Skeletal muscles induced to contract repeatedly respond with a progressive loss in their ability to generate a target force or power. This condition is known simply as fatigue. Commonly, fatigue may persist for prolonged periods of time, particularly at low activation frequencies, which is called low-frequency fatigue. Failure to activate the contractile apparatus with the appropriate intracellular free calcium ([Ca2+]f) signal contributes to fatigue but the precise mechanisms involved are unknown. The sarcoplasmic reticulum (SR) is the major organelle in muscle that is responsible for the regulation of [Ca2+]f, and numerous studies have shown that SR function, both Ca2+ release and Ca2+ uptake, is impaired following fatiguing contractile activity. The major aim of this review is to provide insight into the various cellular mechanisms underlying the alterations in SR Ca2+ cycling and cytosolic [Ca2+]f that are associated both with the development of fatigue during repeated muscle contraction and with low-frequency or long-lasting fatigue. The primary focus will be on the role of the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) in normal muscle function, fatigue, and disease. Key words: calcium release, calcium uptake, muscle relaxation, low-frequency fatigue, Brody disease

scholarly journals LONG-TERM ORGAN CULTURE OF THE SALAMANDER HEART

1971 ◽  
Vol 48 (1) ◽  
pp. 1-14 ◽  
Author(s):  
Edward W. Millhouse ◽  
John J. Chiakulas ◽  
Lawrence E. Scheving
Keyword(s):  
Electron Microscopy ◽  
Morphological Changes ◽  
Heart Beat ◽  
Normal Pattern ◽  
Contraction Mechanism ◽  
Filamentous Material ◽  
Almost All ◽  
T System

Beating salamander hearts were maintained in tissue culture for periods ranging from 1 to 6 months. After 1, 3, or 6 months of culture, six hearts, along with six control hearts, were fixed for electron microscopy. In control tissue, the sarcoplasmic reticulum usually demonstrated the normal pattern of paired, linearly arranged membranes, although in some cases, the reticulum showed a variation from these membranes to a series of small vesicles. There was no evidence of a T-system of tubules in any of the material examined. Desmosome-Z band complexes were observed in almost all sections of both control and experimental material. A possible role of these complexes in the excitation-contraction mechanism is discussed. In 3 month cultured material, alterations in normal myofibrillar pattern occurred. Small segments of myofibrils branched from one Z band to join the Z band of an adjacent myofibril, or appeared to be fraying out into the sarcoplasm. In 6 month cultured material, myofibrils were fragmented into short segments from which myofilaments frayed out into the sarcoplasm. This filamentous material may be remnants of myofilaments. Despite the morphological changes in myofibrils, the heart pulsation rate, established at the beginning, was maintained throughout the culture period. It is suggested that the alterations, observed in the experimental material, occurred in elements not essential for heart beat maintenance, or that these alterations have not yet progressed to a critical point of affecting the heart beat.

scholarly journals ssgA Is Essential for Sporulation ofStreptomyces coelicolor A3(2) and Affects Hyphal Development by Stimulating Septum Formation

2000 ◽  
Vol 182 (20) ◽  
pp. 5653-5662 ◽  
Author(s):  
Gilles P. van Wezel ◽  
Jannes van der Meulen ◽  
Shinichi Kawamoto ◽  
Ruud G. M. Luiten ◽  
Henk K. Koerten ◽  
...  
Keyword(s):  
Cell Division ◽  
Morphological Changes ◽  
Antibiotic Production ◽  
Streptomyces Coelicolor ◽  
Wild Type ◽  
Septum Formation ◽  
Transmission Electron ◽  
In The Wild ◽  
Regulator Genes

ABSTRACT The role of ssgA in cell division and development of streptomycetes was analyzed. An ssgA null mutant ofStreptomyces coelicolor produced aerial hyphae but failed to sporulate, and ssgA can therefore be regarded as a novelwhi gene. In addition to the morphological changes, antibiotic production was also disturbed, with strongly reduced actinorhodin production. These defects could be complemented by plasmid-borne ssgA. In the wild-type strain, transcription of ssgA was induced by nutritional shift-down and was shown to be linked to that of the upstream-located gene ssgR, which belongs to the family of iclR-type transcriptional regulator genes. Analysis of mycelium harvested from liquid-grown cultures by transmission electron microscopy showed that septum formation had strongly increased in ssgA-overexpressing strains in comparison to wild-type S. coelicolor and that spore-like compartments were produced at high frequency. Furthermore, the hyphae were significantly wider and contained irregular and often extremely thick septa. These data underline the important role forssgA in Streptomyces cell division.

scholarly journals CaMKII activation in early diabetic hearts induces altered sarcoplasmic reticulum-mitochondria signaling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Marilen Federico ◽  
Maite Zavala ◽  
Tamara Vico ◽  
Sofía López ◽  
Enrique Portiansky ◽  
...  
Keyword(s):  
Sarcoplasmic Reticulum ◽  
Control Diet ◽  
Respiratory Control ◽  
Retention Capacity ◽  
Transmission Electron ◽  
Intracellular Ca ◽  
Confocal Images ◽  
Increased Activity ◽  
Camkii Activation

AbstractPrediabetic myocardium, induced by fructose-rich diet (FRD), is prone to increased sarcoplasmic reticulum (SR)-Ca2+ leak and arrhythmias due to increased activity of the Ca2+/calmodulin protein kinase II (CaMKII). However, little is known about the role of SR-mitochondria microdomains, mitochondrial structure, and mitochondrial metabolisms. To address this knowledge gap we measured SR-mitochondrial proximity, intracellular Ca2+, and mitochondrial metabolism in wild type (WT) and AC3-I transgenic mice, with myocardial-targeted CaMKII inhibition, fed with control diet (CD) or with FRD. Confocal images showed significantly increased spontaneous Ca2+ release events in FRD vs. CD WT cardiomyocytes. [3H]-Ryanodine binding assay revealed higher [3H]Ry binding in FRD than CD WT hearts. O2 consumption at State 4 and hydrogen peroxide (H2O2) production rate were increased, while respiratory control rate (RCR) and Ca2+ retention capacity (CRC) were decreased in FRD vs. CD WT isolated mitochondria. Transmission Electron Microscopy (TEM) images showed increased proximity at the SR-mitochondria microdomains, associated with increased tethering proteins, Mfn2, Grp75, and VDAC in FRD vs. CD WT. Mitochondria diameter was decrease and roundness and density were increased in FRD vs. CD WT specimens. The fission protein, Drp1 was significantly increased while the fusion protein, Opa1 was unchanged in FRD vs. CD WT hearts. These differences were prevented in AC3-I mice. We conclude that SR-mitochondria microdomains are subject to CaMKII-dependent remodeling, involving SR-Ca2+ leak and mitochondria fission, in prediabetic mice induced by FRD. We speculate that CaMKII hyperactivity induces SR-Ca2+ leak by RyR2 activation which in turn increases mitochondria Ca2+ content due to the enhanced SR-mitochondria tethering, decreasing CRC.

Nanoparticles of Metastable Copper Nitride Grown by Ar Ion Beam Irradiation

2006 ◽  
Vol 11-12 ◽  
pp. 567-570 ◽  
Author(s):  
Ki Wan Jang ◽  
Shun Ichiro Tanaka
Keyword(s):  
Thin Film ◽  
Morphological Changes ◽  
Irradiation Time ◽  
Ion Beam ◽  
Ion Beam Irradiation ◽  
Polycrystalline Thin Film ◽  
Copper Nitride ◽  
Transmission Electron ◽  
Average Size

Nanoparticles of metastable copper nitride(Cu3N) have been successfully fabricated from Cu mask using Ar ion ‘transcription method’ which is firstly invented by B.-S. Xu, C. Iwamoto and S.-I. Tanaka in 1996 [1]. The structural and morphological changes with irradiation time are studied by transmission electron microscopy (TEM). The thin film-like crystalline Cu3N which is covered with amorphous or polycrystalline cuprite (Cu2O) layer in the as-received Cu mask plays a role of target. Polycrystalline Cu3N nanoparticles nucleate and grow up to the average size of 15nm after 30 sec-irradiation. Coalesence of 50nm-sized grown Cu3N nanoparticles forms polycrystalline thin film after 2min-irradiation and its growth behavior follows Volmer-Weber mode. As irradiation time increases from 30 sec to 15 min, Cu3N nanoparticles are thought to be grown preferentially along the [111] and [100] directions. Cu2O still remain with Cu3N after 15 min.-irradiation.

Crystallization under 1 MeV Electron Beam Irradiation of Nanometer-Sized W-Dendrites Fabricated on Alumina Substrates with Electron-Beam-Induced Deposition

2005 ◽  
Vol 475-479 ◽  
pp. 4035-4038 ◽  
Author(s):  
Ming Hui Song ◽  
Kazutaka Mitsuishi ◽  
Kazuo Furuya
Keyword(s):  
Electron Beam ◽  
Electron Microscope ◽  
Transmission Electron Microscope ◽  
Electron Beam Irradiation ◽  
Transmission Electron ◽  
Electron Beam Induced Deposition ◽  
Dendritic Form ◽  
Almost All ◽  
Induced Crystallization ◽  
Amorphous Part

Nanometer-sized W-dendritic form structure was fabricated with electron-beam-induced deposition (EBID) in a 200 kV transmission electron microscope. The as-prepared nanodendrites are composed of W-nanocrystals and amorphous. The as-prepared nanodendrites were then irradiated with 1 MeV electron beam in a high voltage transmission electron microscope. The effect of the irradiation is investigated. The irradiation transformed effectively almost all the amorphous part to crystalline state. Morphology of the nanodendrite also changes. The irradiation induced crystallization and morphology change are discussed.

A Reproducible Selective Stain for Cardiac Sarcoplasmic Reticulum

1974 ◽  
Vol 32 ◽  
pp. 214-215
Author(s):  
R. A. Waugh ◽  
J. R. Sommer
Keyword(s):  
Complex System ◽  
Electron Microscope ◽  
Sarcoplasmic Reticulum ◽  
Transmission Electron Microscope ◽  
Electron Microscopic ◽  
Cardiac Sarcoplasmic Reticulum ◽  
Transmission Electron

Cardiac sarcoplasmic reticulum (SR) is a complex system of intracellular tubules that, due to their small size and juxtaposition to such electron-dense structures as mitochondria and myofibrils, are often inconspicuous in conventionally prepared electron microscopic material. This study reports a method with which the SR is selectively “stained” which facilitates visualizationwith the transmission electron microscope.

On Future Directions in Pathology

1982 ◽  
Vol 40 ◽  
pp. 274-277
Author(s):  
Benjamin F. Trump ◽  
Irene K. Berezesky ◽  
Raymond T. Jones
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Clinical Pathology ◽  
Future Directions ◽  
Diagnostic Pathology ◽  
The Past ◽  
Transmission Electron ◽  
Organ Systems ◽  
The Many

The role of electron microscopy and associated techniques is assured in diagnostic pathology. At the present time, most of the progress has been made on tissues examined by transmission electron microscopy (TEM) and correlated with light microscopy (LM) and by cytochemistry using both plastic and paraffin-embedded materials. As mentioned elsewhere in this symposium, this has revolutionized many fields of pathology including diagnostic, anatomic and clinical pathology. It began with the kidney; however, it has now been extended to most other organ systems and to tumor diagnosis in general. The results of the past few years tend to indicate the future directions and needs of this expanding field. Now, in addition to routine EM, pathologists have access to the many newly developed methods and instruments mentioned below which should aid considerably not only in diagnostic pathology but in investigative pathology as well.

Transmission Electron Microscopy studies of texture of Cr underlayer of magnetic recording hard disk

1991 ◽  
Vol 49 ◽  
pp. 580-581
Author(s):  
L. Tang ◽  
G. Thomas ◽  
M. R. Khan ◽  
S. L. Duan
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Transmission Electron Microscopy ◽  
Magnetic Recording ◽  
Magnetic Thin Films ◽  
Magnetic Films ◽  
Substrate Bias ◽  
Epitaxial Relationship ◽  
Transmission Electron

Cr thin films are often used as underlayers for Co alloy magnetic thin films, such as Co1, CoNi2, and CoNiCr3, for high density longitudinal magnetic recording. It is belived that the role of the Cr underlayer is to control the growth and texture of the Co alloy magnetic thin films, and, then, to increase the in plane coercivity of the films. Although many epitaxial relationship between the Cr underlayer and the magnetic films, such as ﹛1010﹜Co/ {110﹜Cr4, ﹛2110﹜Co/ ﹛001﹜Cr5, ﹛0002﹜Co/﹛110﹜Cr6, have been suggested and appear to be related to the Cr thickness, the texture of the Cr underlayer itself is still not understood very well. In this study, the texture of a 2000 Å thick Cr underlayer on Nip/Al substrate for thin films of (Co75Ni25)1-xTix dc-sputtered with - 200 V substrate bias is investigated by electron microscopy.

Ultrastructural Study of Rat Colon Following Psyllium Ingestion

1985 ◽  
Vol 43 ◽  
pp. 580-581
Author(s):  
F.G. Lightfoot ◽  
L.E. Grau ◽  
M.M. Cassidy ◽  
G.R. Tadvalkar ◽  
G.V. Vahouny
Keyword(s):  
Electron Microscopy ◽  
Morphological Changes ◽  
Large Population ◽  
Rat Colon ◽  
Gastrointestinal Disorders ◽  
Luminal Surface ◽  
Fecal Material ◽  
Transmission Electron ◽  
Morphologic Analysis ◽  
Irritable Bowel

Psyllium hydrophillic mucilloid is a natural gelling fiber consumed by a large population of our society. It is used as a bulk-producing laxative and in the treatment of gastrointestinal disorders such as “Irritable Bowel Syndrome”. The literature pertaining to the ultrastructural effects of this agent is sparse.This study documents morphological changes induced by psyllium. Animals fed a diet containing 2% psyllium for four weeks were subsequently sacrificed and processed for scanning and transmission electron microscopy. The colon contained fecal material combined with psyllium which conformed to the contour of the luminal surface. This mixture formed surface replicas of the intestinal mucosa. These replicas and their related colonic sites were processed for morphologic analysis.

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