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
Spinal processing: anatomy and physiology of spinal nociceptive mechanisms.
The processing of nociceptive input that occurs at the spinal level represents the first stage of effective control over its access to higher regions of the central nervous system. Recent developments in both the anatomy and physiology of nociceptive processing pathways at this level are beginning to yield an integrated understanding of structure and function. Most small afferent axons terminate in the more superficial laminae of dorsal horn, but technical difficulties have, until recently, prevented analysis of the functional properties of identified small fibres. ⋯ The mechanisms of such descending controls and the importance of their interaction with segmental control systems, such as those involving the dynorphin opioids, are just beginning to be understood. Many somatosensory neurons in dorsal horn, both the large cells, some of which project supraspinally, and the small cells of superficial laminae, receive convergent nociceptive and non-nociceptive inputs. Although solely nociresponsive neurons are clearly likely to fill a role in the processing and signalling of pain in the conscious central nervous system, the way in which such useful specificity could be conveyed by multireceptive neurons is difficult to appreciate.(ABSTRACT TRUNCATED AT 400 WORDS)
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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.