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The properties and propagation of a cardiac-like impulse in the skin of young tadpoles (1971)

Roberts, Alan ; Stirling, Charles A.

Springer

Journal of comparative physiology 71 (1971), S. 295-310

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ISSN: 1432-1351

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The contact relationships of skin cells in late embryos and young larvae of Xenopus laevis are described. Superficial cells are joined by ‘tight’ or ‘gap’ junctions at their outer periphery but elsewhere ‘simple appositions’ are found. All-or-none impulses are evoked in the skin by electrical or mechanical stimuli (Fig. 3). Evidence is presented in favour of the view that these impulses are generated by the majority of skin cells and not by some neuronal element in the skin. The impulse propagates throughout the skin from any stimulated point (at average speed of 7.7 cm/sec) even when the animal is in distilled water. However, removal of Na+ from solutions bathing the inner skin surface or treatment with Tetrodotoxin abolishes the impulse indicating that it is Na+ dependent. Current injected into skin cells spreads to others so it is suggested that the impulse propagates by direct current flow from cell to cell. The ‘neuroid’ conduction system in the skin of Xenopus tadpoles is compared to similar systems in coelenterates and to the propagation of the vertebrate cardiac impulse.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00298141

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The ultrastructure of giant fibre and serial synapses in crayfish (1972)

Stirling, Charles A.

Springer

Cell & tissue research 131 (1972), S. 31-45

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ISSN: 1432-0878

Keywords: Synapse ; Ultrastructure ; Giant fibre ; Crayfish

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Medicine

Notes: Summary The ultrastructure of synapses between the cord giant fibres (lateral and medial) and the motor giant fibres in crayfish, Astacus pallipes, third abdominal ganglia have been examined. These electrotonic synapses are asymmetrical, they have synaptic vesicles only in the presynaptic fibre, and they have synaptic cleft widths normally of about 100 Å but narrowed to about 50 Å in restricted areas. Localized increases in density of the synaptic cleft and adjacent membranes also occur within a synapse, and synaptic vesicles are most tightly grouped at the membrane in such areas. Tight or gap junctions with 30 Å or narrower widths have not been found, but the junctions probably function in a similar way to gap junctions. Three small nerves are closely associated with the synapses between the giant fibres. One of these small nerves has round synaptic vesicles and is thought to be excitatory on morphological grounds; one has flattened vesicles and is thought to be inhibitory; and one is postsynaptic to the lateral giant and the two small presynaptic nerves. It is proposed that these small nerves modulate activity in the much larger giant fibre synapse.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00307199

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