Ultrastructure of nerve terminals and muscle fibers in denervated crayfish muscle

1973 ◽  
Vol 146 (2) ◽  
pp. 155-165 ◽  
Author(s):  
H. L. Atwood ◽  
C. K. Govind ◽  
G. D. Bittner
Keyword(s):  
Muscle Fibers ◽  
Nerve Terminals ◽  
Crayfish Muscle

Muscle Fibers in Regenerating Crayfish Motor Nerves

1997 ◽  
Vol 78 (6) ◽  
pp. 3498-3501 ◽  
Author(s):  
Joanne Pearce ◽  
Kristin M. Krause ◽  
C. K. Govind
Keyword(s):  
Signaling Pathway ◽  
Satellite Cells ◽  
Blood Cells ◽  
Axon Regeneration ◽  
Muscle Fibers ◽  
Nerve Terminals ◽  
Motor Axons ◽  
The Third ◽  
Motor Nerves ◽  
Regenerating Nerve

Pearce, Joanne, Kristin M. Krause, and C. K. Govind. Muscle fibers in regenerating crayfish motor nerves. J. Neurophysiol. 78: 3498–3501, 1997. Single discrete muscle fibers were found in regenerating motor nerves in adult crayfish. The regenerating nerves were from native or transplanted ganglia in the third abdominal segments and consisted of several motor axons. The proximal end of these motor axons showed numerous sprouts. Muscle fibers in these regenerating nerves appeared newly developed and were innervated by excitatory nerve terminals. A likely source of these novel muscle fibers may be blood cells in the nerve or satellite cells from neighboring muscle. Contacts made by axon sprouts with other axon sprouts, glia, and muscle fiber, in the form of a dense bar with clustered clear vesicles, characterized the regenerating nerve. These contacts may provide a possible signaling pathway for axon regeneration and myogenesis.

Fast BK-Type Channel Mediates the Ca2+-Activated K+ Current in Crayfish Muscle

1999 ◽  
Vol 82 (4) ◽  
pp. 1655-1661 ◽  
Author(s):  
Alfonso Araque ◽  
Washington Buño
Keyword(s):  
Electrical Activity ◽  
Single Channel ◽  
Muscle Fibers ◽  
Ionic Channels ◽  
Bk Channels ◽  
Intrinsic Properties ◽  
Open Probability ◽  
Crayfish Muscle ◽  
Fast Activation ◽  
Inside Out

The role of the Ca2+-activated K+ current ( I K(Ca)) in crayfish opener muscle fibers is functionally important because it regulates the graded electrical activity that is characteristic of these fibers. Using the cell-attached and inside-out configurations of the patch-clamp technique, we found three different classes of channels with properties that matched those expected of the three different ionic channels mediating the depolarization-activated macroscopic currents previously described (Ca2+, K+, and Ca2+-dependent K+ currents). We investigated the properties of the ionic channels mediating the extremely fast activating and persistent I K(Ca). These voltage- and Ca2+-activated channels had a mean single-channel conductance of ∼ 70 pS and showed a very fast activation. Both the single-channel open probability and the speed of activation increased with depolarization. Both parameters also increased in inside-out patches, i.e., in high Ca2+concentration. Intracellular loading with the Ca2+ chelator bis(2-aminophenoxy) ethane- N, N,N′,N′-tetraacetic acid gradually reduced and eventually prevented channel openings. The channels opened at very brief delays after the pulse depolarization onset (<5 ms), and the time-dependent open probability was constant during sustained depolarization (≤560 ms), matching both the extremely fast activation kinetics and the persistent nature of the macroscopic I K(Ca). However, the intrinsic properties of these single channels do not account for the partial apparent inactivation of the macroscopic I K(Ca), which probably reflects temporal Ca2+ variations in the whole muscle fiber. We conclude that the channels mediating I K(Ca) in crayfish muscle are voltage- and Ca2+-gated BK channels with relatively small conductance. The intrinsic properties of these channels allow them to act as precise Ca2+ sensors that supply the exact feedback current needed to control the graded electrical activity and therefore the contraction of opener muscle fibers.

scholarly journals Reinnervation of muscle fiber basal lamina after removal of myofibers. Differentiation of regenerating axons at original synaptic sites.

1978 ◽  
Vol 78 (1) ◽  
pp. 176-198 ◽  
Author(s):  
J R Sanes ◽  
L M Marshall ◽  
U J McMahan
Keyword(s):  
Skeletal Muscle ◽  
Basal Lamina ◽  
Muscle Fiber ◽  
Nerve Terminal ◽  
Synaptic Vesicles ◽  
Muscle Fibers ◽  
Nerve Terminals ◽  
Morphological Criteria ◽  
Histological Criteria ◽  
Active Zones

Axons regenerate to reinnervate denervated skeletal muscle fibers precisely at original synaptic sites, and they differentiate into nerve terminals where they contact muscle fibers. The aim of this study was to determine the location of factors that influence the growth and differentiation of the regenerating axons. We damaged and denervated frog muscles, causing myofibers and nerve terminals to degenerate, and then irradiated the animals to prevent regeneration of myofibers. The sheath of basal lamina (BL) that surrounds each myofiber survives these treatments, and original synaptic sites on BL can be recognized by several histological criteria after nerve terminals and muscle cells have been completely removed. Axons regenerate into the region of damage within 2 wk. They contact surviving BL almost exclusively at original synaptic sites; thus, factors that guide the axon's growth are present at synaptic sites and stably maintained outside of the myofiber. Portions of axons that contact the BL acquire active zones and accumulations of synaptic vesicles; thus by morphological criteria they differentiate into nerve terminals even though their postsynaptic targets, the myofibers, are absent. Within the terminals, the synaptic organelles line up opposite periodic specializations in the myofiber's BL, demonstrating that components associated with the BL play a role in organizing the differentiation of the nerve terminal.

scholarly journals Effects of Caffeine on Crayfish Muscle Fibers

1970 ◽  
Vol 55 (5) ◽  
pp. 665-687 ◽  
Author(s):  
Dante J. Chiarandini ◽  
John P. Reuben ◽  
Lucien Girardier ◽  
George M. Katz ◽  
Harry Grundfest
Keyword(s):  
Muscle Fibers ◽  
Bathing Medium ◽  
Contractile Responses ◽  
Crayfish Muscle ◽  
Contractile System ◽  
Mn Recovery

When caffeine evokes a contraction, and only then, crayfish muscle fibers become refractory to a second challenge with caffeine for up to 20 min in the standard saline (5 mM Ko). However, the fibers still respond with contraction to an increase in Ko, though with diminished tension. Addition of Mn slows recovery, but the latter is greatly accelerated during exposure of the fiber to high Ko, or after a brief challenge with high Ko. Neither the depolarization induced by the K, nor the repolarization after its removal accounts for the acceleration, which occurs only if the challenge with K had itself activated the contractile system; acceleration is blocked when contractile responses to K are blocked by reducing the Ca in the bath or by adding Mn. Recovery is accelerated by redistribution of intracellular Cl and by trains of intracellularly applied depolarizing pulses, but not by hyperpolarization. The findings indicate that two sources of Ca can be mobilized to activate the contractile system. Caffeine mobilizes principally the Ca store of the SR. Depolarizations that are induced by high Ko, by transient efflux of Cl, or by intracellularly applied currents mobilize another source of Ca which is strongly dependent upon the entry of Ca from the bathing medium. The sequestering mechanism of the SR apparently can utilize this second source of Ca to replenish its own store so as to accelerate recovery of responsiveness to a new challenge with caffeine.

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