Philosophical transactions of the Royal Society of London. Series B, Biological sciences
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Feb 1985
Visceral nociception: peripheral and central aspects of visceral nociceptive systems.
Discomfort and pain are the sensations most commonly evoked from viscera. Most nociceptive signals that originate from visceral organs reach the central nervous system (c.n.s.) via afferent fibres in sympathetic nerves, whereas parasympathetic nerves contain mainly those visceral afferent fibres concerned with the non-sensory aspects of visceral afferent function. Noxious stimulation of viscera activates a variety of specific and non-specific receptors, the vast majority of which are connected to unmyelinated afferent fibres. ⋯ Visceral pain is the consequence of the diffuse activation of somato-sensory nociceptive systems in a manner that prevents accurate spatial discrimination or localization of the stimuli. Noxious stimulation of visceral receptors triggers general reactions of alertness and arousal and evokes unpleasant and poorly localized sensory experiences. This type of response may be a feature of sensory systems dominated by unmyelinated afferent inputs.
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A role for thalamic structures in the processing of signals of nociception and pain has been suggested on the basis of clinical data since the turn of the century. Searches for a 'pain centre' by lesion or stimulation were often disappointing and the electrophysiological data were rare and usually contradictory. ⋯ The eventual respective roles of these thalamic structures are considered. Electrophysiological recordings from thalamic structures in a model of experimental pain, arthritic rats, are also presented.
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Jun 1982
Memory disorders following focal neocortical damage.
Two aspects of memory defects following circumscribed neocortical lesionare considered. First, the selective impairment involving one category of stimuli (e.g. faces, colours) or a specific mnestic ability (spatial orientation). ⋯ Short-term memory tests are performed poorly by aphasics. In long-term memory tests, the performance depends on the nature of the task; in the early stages of paired-associate learning aphasics are impaired, on recurring figure recognition no hemispheric difference emerges, on sequential memory right brain-damaged patients have the poorest scores.
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Mar 1977
Meiosis in a temperature-sensitive DNA-synthesis mutant and in an apomictic yeast strain (Saccharomyces cerevisiae).
It is shown that in the temperature-sensitive yeast mutant (Saccharomyces cerevisiae) spo 11 at the restrictive temperature of 34 degrees C. (1) premeiotic DNA synthesis is nearly completely blocked; (2) the nucleus enters meiotic prophase indicated by the formation of axial cores and polysynaptonemal complexes; (3) the kinetic apparatus functions normally at meiosis I and II; (4) early spore formation occurs in nearly all cells but it is variable and all spores eventually degenerate. It is concluded that chromosome replication is not a prerequisite for the functions listed above. ⋯ It is shown that a diploid which produces 2-spored asci, synthesized from 4117, no. 5, and an adenine requiring strain (1) has a normal meiotic prophase with abundant synaptonemal complexes; (2) has only one meiotic spindle; (3) has spores which form red clones more frequently than normal or u.v.-treated vegetative cells form ade/ade red sectors through mitotic recombination. It is concluded that this apomictic yeast has maintained meiotic prophase, but that one of the two meiotic divisions is suppressed.