Philosophical transactions of the Royal Society of London. Series B, Biological sciences
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Mar 1996
ReviewNGF as a mediator of inflammatory pain.
The chapter reviews some of recent evidence which suggests that one neurotrophin, nerve growth factor (NGF), is a peripherally produced mediator of some persistent pain states, notably those associated with inflammation. The evidence for this proposal is as follows. 1. The endogenous production of NGF regulates the sensitivity of nociceptive systems. ⋯ In a number of animal models, much of the hyperalgesia associated with experimental inflammation is blocked by pharmacological "antagonism' of NGF. The mechanisms by which NGF up-regulation in inflamed tissues might lead to sensory abnormalities is also discussed. In particular, evidence is reviewed which suggests that increased NGF levels leads to both peripheral sensitization of nociceptors and central sensitization of dorsal horn neurons responding to noxious stimuli.
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Aug 1995
Proprioceptive hair cells on the neck of the squid Lolliguncula brevis: a sense organ in cephalopods for the control of head-to-body position.
Decapod cephalopods, such as cuttlefishes and squids, have a distinct neck region that allows movements (roll, pitch and yaw) of the head relative to the body. This paper describes the structure, innervation and central pathways of proprioceptive hair cells on the neck of the squid Lolliguncula brevis that sense such movements and control head-to-body position. These hair cells exist on the dorsal side of the neck underneath the nuchal cartilage, close to the animal's midline on either side of the nuchal crest. ⋯ Bilateral deafferentation of the cells elicited a downward head pitch offset. This offset was superimposed on the compensatory head pitch response during imposed body pitch. These morphological and behavioural findings show that the neck hair cells and the associated nuchal cartilage structures of Lolliguncula brevis form a neck receptor organ that, together with statocyst and visual inputs, controls the position of the animal's head and body.
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Jul 1991
The long-term effectiveness of different regimens of occlusion on recovery from early monocular deprivation in kittens.
Although the behavioural effects of an early period of monocular deprivation imposed on kittens can be very severe, resembling an extreme form of the human clinical condition deprivation amblyopia, they are not necessarily irreversible. Considerable behavioural as well as physiological recovery can occur if normal visual input is restored to the deprived eye sufficiently early, particularly if the other (initially non-deprived) eye is occluded at the same time (reverse occlusion). However, past work has shown that in many situations the improvement in the vision of the initially deprived eye that occurs during reverse occlusion is not retained following the subsequent introduction of binocular visual input. ⋯ Experiments were done to establish some of the factors that contributed to the successful outcome associated with certain of the regimens of part-time reverse occlusion. It was established that recovery was just as good in animals in which the visual axes were vertically misaligned by means of prisms during the daily period of binocular visual exposure, thereby indicating that the visual input to the two eyes need not be concordant. However, animals that received equivalent visual exposure of the two eyes each day, but successively rather than simultaneously, all developed very severe bilateral amblyopia.(ABSTRACT TRUNCATED AT 400 WORDS)
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Philos. Trans. R. Soc. Lond., B, Biol. Sci. · Apr 1990
The contribution of latent human failures to the breakdown of complex systems.
Several recent accidents in complex high-risk technologies had their primary origins in a variety of delayed-action human failures committed long before an emergency state could be recognized. These disasters were due to the adverse conjunction of a large number of causal factors, each one necessary but singly insufficient to achieve the catastrophic outcome. Although the errors and violations of those at the immediate human-system interface often feature large in the post-accident investigations, it is evident that these 'front-line' operators are rarely the principal instigators of system breakdown. ⋯ New methods of risk assessment and risk management are needed if we are to achieve any significant improvements in the safety of complex, well-defended, socio-technical systems. This paper distinguishes between active and latent human failures and proposes a general framework for understanding the dynamics of accident causation. It also suggests ways in which current methods of protection may be enhanced, and concludes by discussing the unusual structural features of 'high-reliability' organizations.
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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)