Correlates of electrical activity inXenopus laevis embryos

Macklin, Martin; Wojtkowski, Wita

doi:10.1007/bf00694146

Cited by 8 publications

(5 citation statements)

References 16 publications

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“…During the pre metamorphic stages (XI-X-VII), the hindlimb becomes progressively larger and of more use to the animal for swimming. During metamorphosis, when the tail and gills disappear and limbs and lungs develop, roughly three, overlapping, phases of locomotion can be distinguished (Muntz 1964(Muntz , 1975Macklin and Wojtkowski 1973;): (a) the immobile phase (stages 1-24); (b) the phase of tail locomotion (approximately stages 20-60), including non-motile (stages 20-22), pre-motile (stages 22-24), early flexure (stages 24-28), early swimming (stages 28-33) and free swimming (from stage 33 on) phases; and (c) the phase of limb locomotion (approximately stages 46-66), including non-motile (stages 46-53), pre-motile (stages 53-55), motile (stages 55-59) and fully functional (from stage 59 onwards) stages. The forelimbs emerge at stage XX, and the tail undergoes progressive degeneration until it is completely resorbed at stage XXV.…”

Section: (C)mentioning

confidence: 99%

“…Stages XVIII -XXv, the metamorphic stages, begin with degeneration of the cloacal tailpiece. The development of the tail starts with the segregation of the first myotomes at stage 17 (Nieuwkoop and Faber 1967;Muntz 1964Muntz , 1975Macklin and Wojtkowski 1973;Elsdale and Davidson 1983;. Gosner (1960) presented another system for staging the development of Rana pipiens, and Manelli and Margaritora (1961) for R. esculenta.…”

Section: (C)mentioning

confidence: 99%

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Anurans

Donkelaar¹

1998

The Central Nervous System of Vertebrates

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Section: (C)mentioning

confidence: 99%

Section: (C)mentioning

confidence: 99%

Anurans

Donkelaar¹

1998

The Central Nervous System of Vertebrates

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“…2). The 'S-reflex' of the amphibian tadpole has been misunderstood also (as was suggested by Macklin & Wojtkowski, 1973).…”

Section: Museular Control Of Vertebrate Swimming Nwvenmtsmentioning

confidence: 99%

“…This cannot be so, for locomotion is brought about against external resistance by the application of suitable forces to the environment. The 'S-reflex' of the amphibian tadpole has been misunderstood also (as was suggested by Macklin & Wojtkowski, 1973). If it is to maintain a position while stationary which is similar in form to a position passed through in locomotion, the animal itself must provide an analogue of any unbalanced environmental force of resistance which applies when it is moving through that position in locomotion.…”

Section: Museular Control Of Vertebrate Swimming Nwvenmtsmentioning

confidence: 99%

The Muscular Control of Vertebrate Swimming Movements

Blight

1977

Biological Reviews

139

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SUMMARY The succession of hypotheses on the role of myotomal muscle in the generation of swimming movements is described and the conventional concept of ‘waves of contraction’ is shown to be based on a number of misinterpretations. The form of undulatory movements in vertebrate swimmers is characterized by the properties of the sinusoidal oscillation of parts of the body about the axis of progression. An important variable is the relative amplitude of the lateral oscillation of the head end, which can be large in some animals though usually small in most adult aquatic vertebrates. Cinematographic records of swimming animals are examined to determine the forces involved in the generation of waves of bending. A simplified analysis suggests that undulation can be produced by alternation of tension development from side to side without ‘waves of contraction’ passing down the body. Model systems which are able to flex from side to side are considered and two types distinguished ‐ the ‘resistance‐dominated’ which propagates waves of bending from centre to extremities, and the ‘stiffness‐dominated’ which does not. The type to which a model belongs is determined by the interrelationship of its stiffness and resistance, and the power with which it flexes. A model homogeneous in its properties along its length cannot generate longitudinal movement by flexing from side to side. Some degree of unevenness from one end to the other is required for propulsion. Observations of the movements of an ‘ostraciiform model’ are shown to discount previous theories of the hydromechanics of swimming by the oscillation of a stiff tail about a single pivot. A new interpretation is provided. The majority of vertebrate swimmers behave like ‘hybrid oscillators’ which flex from side to side, ‘resistance‐dominated’ posteriorly and ‘stiffness‐dominated’ anteriorly. The origin of the ‘waves of contraction’ suggested by electromyograms of swimming animals is traced to the requirement for a tail of variable stiffness for variable frequency of oscillation and to the need to reduce lateral oscillation of the head. Delayed contraction posteriorly and early contraction anteriorly contribute to these functions. The ability of amphioxus to swim backwards and the inability of most vertebrates to do so is related to their structural organization in the form of ‘hybrid oscillators’. Electromyograms are examined in the light of these mechanical models. A developmental sequence is described for the newt which illustrates the organization of the muscular control of swimming movements and may throw light upon the development of the neural mechanism.

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“…This link probably accounts for the behavioural observation of a contralateral flexion response which is most readily demonstrated in early embryos which cannot swim. Stroking the trunk skin of stage 27-31 embryos will elicit a single flexion of the body which only involves the contraction of muscles on the side of the body contralateral to the stimulus (Macklin & Wojtkowski, 1973;Roberts & Smyth, 1974). This response is retained in stage 37-38 embryos but becomes less obvious because skin stimulation is usually quickly followed by swimming movements.…”

Section: Possible Post-synaptic Effects Of Dorsolateral Interneuronesmentioning

confidence: 99%

Interneurones in the Xenopus embryo spinal cord: sensory excitation and activity during swimming.

Clarke¹,

Roberts²

1984

The Journal of Physiology

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The dorsolateral spinal cord of embryonic Xenopus laevis has previously been shown to contain two anatomical classes of interneurones with dendrites in the dorsal tract where they could be contacted by the central axons of Rohon‐Beard cells (Roberts & Clarke, 1982). The activity of these neurones within the dorsolateral spinal cord has been examined using intracellular micro‐electrodes. Following electrical stimulation of Rohon‐Beard neurites within the ipsilateral skin, dorsolateral neurones receive a short‐latency, compound, excitatory post‐synaptic potential (e.p.s.p.). The amplitude of the e.p.s.p. depends upon the number of Rohon‐Beard cells stimulated. The e.p.s.p. consists of early and later components. The early components may result from monosynaptic connexions from Rohon‐Beard cells, the later components from some unidentified interposed neurones. During episodes of fictive swimming the dorsolateral neurones are inhibited by rhythmic inhibitory post‐synaptic potentials. Following Rohon‐Beard neurite stimulation, neurones in the contralateral spinal cord receive e.p.s.p.s. These contralateral e.p.s.p.s are probably one of the post‐synaptic effects of one of the dorsolateral neurone classes. The results suggest that the dorsolateral neurones are responsible for amplifying and distributing the primary afferent signals of Rohon‐Beard cells, and may be involved in the initiation of swimming and reflex movements.

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Correlates of electrical activity inXenopus laevis embryos

Cited by 8 publications

References 16 publications

Anurans

Anurans

The Muscular Control of Vertebrate Swimming Movements

Interneurones in the Xenopus embryo spinal cord: sensory excitation and activity during swimming.

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