scholarly journals THE STRUCTURE OF INSECT FIBRILLAR FLIGHT MUSCLE

1961 ◽  
Vol 10 (4) ◽  
pp. 123-158 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Flight Muscle ◽  
Close Association ◽  
High Rate ◽  
Maximum Plasma ◽  
Very High Frequency ◽  
Mature Adult ◽  
Functional Homology ◽  
A Value

The fine structure of fibrillar flight muscle of the mature adult beetle Tenebrio molitor is described. Although the very high frequency of contraction of fibrillar muscle has previously been in part accounted for as the result of mechanical specialization of the wing-bearing segment rather than of a correspondingly high rate of motor impulse supply, the problem of the nature of the pathway by which excitation is conducted into these large fibers remained. Therefore, particular attention has been given to the disposition and relationships of the plasma membrane and sarcoplasmic reticulum in this tissue. The invading tracheoles draw with them a sheath of plasma membrane from the surface to all depths in the fiber, and it is suggested that these sheaths, together with the extensive tubular arborisations arising from them, reduce the maximum plasma membrane-to-fibril distance from the radius of the fiber to a value of less than 2 µ. The evidence presented here confirms Veratti's contention that in fibrillar muscle the "reticulum" is associated with, though entirely distinct from the fibrils. Unlike other muscles so far examined, these flight muscle fibers contain a plasma membrane reticulum only, but it is possible that elsewhere the general "sarcoplasmic reticulum" includes a component derived from the plasma membrane, likewise acting as the pathway for inward conduction of excitation. Profiles of the internalised plasma membrane in Tenebrio showing the usual triple-layered 25-25-25 A organization are frequently seen, in sections, in close association with isolated vesicles (defined by "simple" 50 A membranes) which are here considered to represent, in vestigial form, the portion of the sarcoplasmic reticulum which in other types of muscle is complex and highly developed. Such associations, in Tenebrio, between these two dissimilar elements are here termed "dyads" and the possible morphological and functional homology between these and the "triads" of other types of fiber is considered.

scholarly journals THE ORGANIZATION OF FLIGHT MUSCLE IN AN APHID, MEGOURA VICIAE (HOMOPTERA)

1965 ◽  
Vol 27 (2) ◽  
pp. 379-393 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Cell Surface ◽  
Flight Muscle ◽  
Muscle Cells ◽  
Indirect Flight Muscle ◽  
Megoura Viciae ◽  
Flight Muscles ◽  
High Degree ◽  
T System

The organization of the indirect flight muscle of an aphid (Hemiptera-Homoptera) is described. The fibers of this muscle contain an extensive though irregularly disposed complement of T system tubules, derived as open invaginations from the cell surface and from the plasma membrane sheaths accompanying the tracheoles within the fiber. The sarcoplasmic reticulum is reduced to small vesicles applied to the T system surfaces, the intermembrane gap being traversed by blocks of electron-opaque material resembling that of septate desmosomes. The form and distribution of the T system and sarcoplasmic reticulum membranes in flight muscles of representatives of the major insect orders is described, and the extreme reduction of the reticulum cisternae in all asynchronous fibers (to which group the aphid flight muscle probably belongs), and the high degree of their development in synchronous fibers is documented and discussed in terms of the contraction physiology of these muscle cells.

scholarly journals THE ORGANIZATION OF THE FLIGHT MUSCLE IN A DRAGONFLY, AESHNA SP. (ODONATA)

1961 ◽  
Vol 11 (1) ◽  
pp. 119-145 ◽  
Author(s):  
David S. Smith
Keyword(s):  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Muscle Fiber ◽  
Flight Muscle ◽  
The Face ◽  
Electron Microscopes ◽  
Great Development

The structure of the flight muscle of a dragonfly (Aeshna sp.) has been studied with the light and electron microscopes, and the organization of this specialized tubular muscle is described. This tissue is characterized by the great development of the sarcosomes, which are slab-like and are arranged within the fiber opposite each sarcomere of the radially oriented lamellar myofibrils. A well developed and highly ordered sarcoplasmic reticulum is present, consisting of perforated curtain-like cisternae extending across the face of each fibril, together with tubular invaginations of the fiber plasma membrane situated within indentations in the sarcosomes and traversing the fibril surface midway between the Z and M levels. The structure of these fibers, and notably the organization of the reticulum, is compared with that of other types of muscle, and the possible role of the two components of the sarcoplasmic reticulum in the contraction physiology of the dragonfly muscle fiber is discussed.

An Electron Microscopical Study of the Innervation and Sarcoplasmic Reticulum of the Fibrillar Flight Muscle of Drosophila Melanogaster

1964 ◽  
Vol s3-105 (69) ◽  
pp. 1-6 ◽  
Author(s):  
S. AHMAD SHAFIQ
Keyword(s):  
Drosophila Melanogaster ◽  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Peripheral Nerves ◽  
Plasma Membranes ◽  
Flight Muscle ◽  
Microscopical Study ◽  
Electron Microscopical Study ◽  
Electron Microscopical

The peripheral nerves of Drosophila are of the ‘tunicated’ type; their mesaxons are derived from several independent invaginations of the lemnoblast plasma membrane and possess septate desmosomes. Fine branches of the nerves and tracheoles penetrate deeply into the fibres of the flight muscle and draw the sarcolemma in with them. The myoneural junctions occur on the invaginated portions of the sarcolemma. The axons shed their lemnoblastic elements and become closely apposed to the muscle plasma membranes at the junctions. The sarcoplasmic reticulum of the flight muscle seems to consist mainly of the extensive infoldings of the sarcolemma and their processes, as in Tenebrio. ‘Dyads’ formed by the association of isolated vesicles with the membranous infoldings are present in Drosophila. Most of these ‘dyads’ seem to be in register with the myofibrils, two pairs being associated with each sarcomere.

High Rate Deposition of Stable Hydrogenated Amorphous Silicon in Transition from Amorphous to Microcrystalline Silicon

2003 ◽  
Vol 762 ◽  
Author(s):  
Guofu Hou ◽  
Xinhua Geng ◽  
Xiaodan Zhang ◽  
Ying Zhao ◽  
Junming Xue ◽  
...  
Keyword(s):  
Phase Transition ◽  
Amorphous Silicon ◽  
Hydrogenated Amorphous Silicon ◽  
Chemical Vapor ◽  
High Rate ◽  
Very High Frequency ◽  
High Quality ◽  
Working Pressure ◽  
Hydrogen Dilution ◽  
Hydrogenated Amorphous

AbstractHigh rate deposition of high quality and stable hydrogenated amorphous silicon (a-Si:H) films were performed near the threshold of amorphous to microcrystalline phase transition using a very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) method. The effect of hydrogen dilution on optic-electronic and structural properties of these films was investigated by Fourier-transform infrared (FTIR) spectroscopy, Raman scattering and constant photocurrent method (CPM). Experiment showed that although the phase transition was much influenced by hydrogen dilution, it also strongly depended on substrate temperature, working pressure and plasma power. With optimized condition high quality and high stable a-Si:H films, which exhibit σph/σd of 4.4×106 and deposition rate of 28.8Å/s, have been obtained.

Changes in phosphorus metabolism of sheep in response to the increased demands for P associated with an intravenous infusion of calcium

1984 ◽  
Vol 102 (1) ◽  
pp. 135-139 ◽  
Author(s):  
G. D. Braithwaite
Keyword(s):  
Intravenous Infusion ◽  
Calcium Metabolism ◽  
Research Council ◽  
Agricultural Research ◽  
Close Association ◽  
High Rate ◽  
Phosphorus Metabolism ◽  
Agricultural Research Council ◽  
P Absorption ◽  
P Retention

SummaryThe effect on phosphorus and calcium metabolism of a high rate of Ca infused directly into the blood of 10-month-old sheep, already receiving an adequate Ca and P intake, has been studied by a combination of balance and radioisotope techniques. Ca retention was significantly increased during the infusion and most of the extra Ca was retained in bone. Urinary Ca excretion also showed a small but significant increase and the efficiency of Ca absorption a small but significant decrease. Because of the close association of Ca and P in bone, the increased skeletal retention of Ca resulted in an increased skeletal P retention and hence an increased demand for P. This increased P demand was met partly by a decrease in the rate of endogenous faecal loss of P and partly by an increase in the rate and efficiency of P absorption. Because the increase in P demand was relatively small, it was not possible to decide whether the endogenous faecal loss of P can be reduced in response to increased demands to the level found at zero P intake as suggested by the Agricultural Research Council (1980) or whether higher losses at normal P intakes are inevitable.

Abstract 274: Spatiotemporal Regulation of β Adrenergic Signaling In Heart failure

2014 ◽  
Vol 115 (suppl_1) ◽  
Author(s):  
Yang K Xiang ◽  
Federica Barbagallo ◽  
Bing Xu ◽  
Qin Fu
Keyword(s):  
Heart Failure ◽  
Plasma Membrane ◽  
Sarcoplasmic Reticulum ◽  
Cardiac Myocytes ◽  
Cardiac Disease ◽  
Spatiotemporal Regulation ◽  
Disease Therapy ◽  
Functional Implications ◽  
Underlying Mechanisms

Our long-term goal is to understand mechanisms that govern spatiotemporal regulation of cAMP/PKA signaling in cardiac myocytes under physiological and pathophysiological conditions, and their implication in cardiac disease therapy. Here we use a series of biosensors to measure cAMP/PKA activity under βAR subtype regulation. In failing cardiac myocytes, the cAMP and PKA activity are shifted from the plasma membrane to the intracellular sarcoplasmic reticulum and the myofilaments. Meanwhile, β2AR displays an increased role in signaling to the myofilaments in failing myocytes when compared to the control myocytes. Moreover, we show that an increased βAR association with phosphodiesterases promotes the alteration in spatiotemporal propagation of cAMP/PKA signaling in failing myocytes. These observations and the underlying mechanisms and functional implications will be discussed.

Microtubules and associated microfilaments in the tentacles of the suctorian Heliophrya erhardi Matthes

1976 ◽  
Vol 20 (3) ◽  
pp. 589-617
Author(s):  
M. Hauser ◽  
H. Van Eys
Keyword(s):  
Plasma Membrane ◽  
Resting State ◽  
Close Association ◽  
Ultrastructural Level ◽  
Peritrophic Membrane ◽  
Electron Microscopic ◽  
Helical Wave ◽  
Length Changes ◽  
Microscopic Findings

At the ultrastructural level length changes accompanying linear movements of resting (non-feeding) tentacles of the suctorian Heliophrya involve not only altered microtubule numbers, but also marked changes in the specific microtubule pattern of cross-sectioned tentacles. These changes in number and pattern indicate a sliding between axonemal microtubules. The visualization of microfilaments in the cytoplasm at the tentacle base and in the knob region could shed new light on the problem of whether microtubular sliding is an active or passive process. At the tentacle base, microfilaments are either arranged in a ring-shaped configuration around the axoneme, or they run parallel to the axonemal microtubules, whereas at the tentacle tip during the resting state, microfilaments are closely associated with the plasma membrane of the knob. They form a filamentous reticular layer, which is continuous at the anchorage site of axonemal microtubules with the dense epiplasmic layer of the tentacle shaft. Obiously, this filamentous layer is engaged in positioning the haptocysts at the plasma membrane and in holding the membrane itself under tension. The putative contractile nature of microfilaments and the epiplasmic layer is argued from ATP-sensitive glycerol models of tentacles and from the results of halothane treatment of native tentacles. Halothane treatment of resting tentacles also gave indications of the presence of differentially stable intermicrotubule-bridges. The role of micro-filaments and halothane-resistant dynein-like inter-row bridges in tentacle movement is discussed. As soon as the plasma membrane of the knob is ‘sealed’ with the prey pellicle during feeding, the microtubules of the sleeve region slide into the knob where they bend back and outwards. The microtubules now appear decorated and sometimes cross-connected by microfilaments which adhere closely to the plasma membrane- now acting as a peritrophic membrane-lining the prey cytoplasm against the microtubules of the inner tube. These microfilaments which show a close association with the microtubules of the active knob area, are thought to be engaged in microtubular bending and stretching during feeding. They may also be involved in the transport of the peritrophic membrane in distal tentacle regions. Microinematographically recorded oscillations in tentacle diameter in these regions are in agreement with the electron-microscopic findings of various states of collapsed tentacle axonemes. These observations, as well as the occurrence of helically twisted tentacles during feeding, suggest microfilament mediated sequential back and forth movements of sleeve microtubules in the knob region which generate a proximally migrating helical wave.

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