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There has been an ongoing controversy over how to decide whether the distribution of species is “random” — i.e., whether it is not greatly different from what it would be if species did not interact. We recently showed (Roberts and Stone (1990)) that in the case of the Vanuatu (formerly New Hebrides) avifauna, the number of islands shared by species pairs(More)
Competitive athletes completed two studies of 2-h steady-state (SS) cycling at 70% peak O(2) uptake followed by 7 kJ/kg time trial (TT) with carbohydrate (CHO) intake before (2 g/kg) and during (6% CHO drink) exercise. In Study A, 12 subjects received either 6 mg/kg caffeine 1 h preexercise (Precaf), 6 x 1 mg/kg caffeine every 20 min throughout SS (Durcaf),(More)
Rohon-Beard neurones show substance P-like immunoactivity in their somas and in their centrally projecting axons. Peripherally, the morphology of their free nerve endings within the trunk skin has been shown using horseradish peroxidase staining. The excitation of Rohon-Beard neurones by natural and electrical stimulation of the skin has been examined using(More)
The spinal neurons in the embryos and young larvae of two amphibians (Xenopus and Triturus) and two fish (Oryzias and Brachydanio) are described and compared. They can be placed into a limited number of common neuron classes: Rohon-Beard sensory, dorsolateral and dorsolateral commissural sensory interneurons, inhibitory ascending interneurons, two classes(More)
Motor networks typically generate several related output patterns or gaits where individual neurons may be shared or recruited between patterns. We investigate how a vertebrate locomotor network is reconfigured to produce a second rhythmic motor pattern, defining the detailed pattern of neuronal recruitment and consequent changes in the mechanism for rhythm(More)
The response of the foot to touch during walking depends on whether it is in the air or on the ground. In most animals, reflex responses to external stimuli are similarly adapted to their timing in the locomotor cycle, but there is only fragmentary information about the neural mechanisms involved. In arthropods, reflex modulation can occur in the sensory(More)
Neurobiotin was injected into individual spinal interneurons in the Xenopus tadpole to discern their anatomical features and complete axonal projection patterns. Four classes of interneuron are described, with names defining their primary axon projection: Dorsolateral ascending and commissural interneurons are predominantly multipolar cells with somata and(More)
Glycine and gamma-aminobutyric acid (GABA) are inhibitory transmitters of major importance. Whereas neurones using GABA as the transmitter can be visualized by immunocytochemical methods for glutamate decarboxylase (GAD) or GABA, no comparable techniques have been available for the selective visualization of glycinergic neurones. We have now produced(More)
The neuronal basis of the excitation received by motoneurones during swimming in curarized Xenopus embryos has been investigated further. Extracellular stimulation of axons in the fibre tracts of the spinal cord has been used to evoke unitary excitatory post-synaptic potentials (p.s.p.s) in motoneurones. The p.s.p.s. had a rise time of 3-5 ms and a long(More)