Potassium inactivation in single myelinated nerve fibres of Xenopus laevis

1971 ◽  
Vol 330 (1) ◽  
pp. 61-73 ◽  
Author(s):  
J�rgen R. Schwarz ◽  
Werner Vogel
Keyword(s):  
Xenopus Laevis ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Potassium Inactivation

Potassium inactivation in myelinated nerve fibres

1971 ◽  
Vol 27 (4) ◽  
pp. 397-398 ◽  
Author(s):  
J. R. Schwarz ◽  
W. Vogel
Keyword(s):  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Potassium Inactivation

scholarly journals The Structure of Myelin Sheaths in the Central Nervous System of Xenopus laevis (Daudin)

1960 ◽  
Vol 7 (1) ◽  
pp. 121-126 ◽  
Author(s):  
A. Peters
Keyword(s):  
Xenopus Laevis ◽  
Myelin Sheath ◽  
Cytoplasmic Process ◽  
Nerve Fibres ◽  
Myelinated Nerve ◽  
Outer Line ◽  
Myelin Sheaths ◽  
Dense Line ◽  
Central Myelin ◽  
The Central Nervous System

The structure of myelinated nerve fibres has been studied in the spinal cord and optic nerve of the tadpoles of Xenopus laevis. Potassium permanganate-fixed material was examined with the electron microscope. The myelin sheath itself is made up of spirally arranged lamellae in which the intraperiod and dense lines alternate. Inside the myelin sheath an inner cytoplasmic process surrounds the axon and where the external surfaces of its bounding membrane come together an internal mesaxon is formed. The intraperiod line begins within the mesaxon and the dense line usually begins in the same region by apposition of the cytoplasmic surfaces of the membrane. The width of each lamella is 140 A. The outer line in the sheath is the dense line and this terminates in a tongue where the cytoplasmic surfaces of the myelin-forming glial cell separate. Thus, central myelin in Xenopus tadpoles is arranged in the same way as peripheral myelin, the only difference being that in central fibres, cytoplasm on the outside of the sheath is confined to that present in the tongue. For this reason adjacent central sheaths come into apposition without any intervening material being present. When this occurs an intraperiod line is formed between them.

Extracellular Receptor Potentials from the Lateral-Line Organ of Xenopus Laevis

1980 ◽  
Vol 86 (1) ◽  
pp. 63-77
Author(s):  
ALFONS B. A. KROESE ◽  
JOHAN M. VAN DER ZALM ◽  
JOEP VAN DEN BERCKEN
Keyword(s):  
Xenopus Laevis ◽  
Lateral Line ◽  
Hair Cells ◽  
Water Displacement ◽  
Stimulus Amplitude ◽  
Nerve Fibres ◽  
Large Stimulus ◽  
Sensory Hair ◽  
Lateral Line Organ ◽  
Line Organ

1. The response of the epidermal lateral-line organ of Xenopus laevis to stimulation was studied by recording extracellular receptor potentials from the hair cells in single neuromasts in isolated preparations. One neuromast was stimulated by local, sinusoidal water movements induced by a glass sphere positioned at a short distance from the neuromast. 2. The amplitudes of the extracellular receptor potentials were proportional to the stimulus amplitude over a range of 20 dB. The phase of the extracellular receptor potentials with respect to water displacement was independent of the stimulus amplitude. 3. With large stimulus amplitude, and stimulus frequencies between 0.5 Hz and 2 Hz, the extracellular receptor potentials, and responses of single afferent nerve fibres, showed a phase lead of 1.2 π radians with respect to water displacement, i.e. they were almost in phase with water acceleration. 4. It is concluded that under conditions of stimulation with small-amplitude water movements, the hair cells respond to sensory hair displacement, whereas under conditions of stimulation with large-amplitude water movements they respond to sensory hair velocity.

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